1996 Terra Nova Environmental Impact Statement - C

Transcription

Preface
The Development Application for the Terra Nova Development has been prepared pursuant to the CanadaNewfoundland Atlantic Accord Implementation Act and the Canada-Newfoundland Atlantic Accord
Implementation (Newfoundland) Act. These Acts require that plans for development of the Terra Nova Field be
approved by the Canada-Newfoundland Offshore Petroleum Board.
This Development Application has been prepared by Petro-Canada on behalf of and in cooperation with all the
development Proponents: Petro-Canada, Mobil Oil Canada Properties, Husky Oil Operations Limited, Murphy Oil
Company Ltd. and Mosbacher Operating Limited.
This application consists of five main documents:
1.
2.
3.
4.
5.
Development Application Summary
Development Plan - Part I
Canada-Newfoundland Benefits Plan
Environmental Impact Statement
Socio-Economic Impact Statement
As well, Development Plan - Part II, which consists of the numerous reports used to prepare the development plan,
has been filed with the Board. In the future Project Phase, a Safety Plan and an Environmental Protection Plan will
also be prepared.
Each of the five main documents is described below:
Development Plan Summary - an overview of all aspects of the plans to develop the Terra Nova
Field engineering, economic, environmental and social
Development Plan - Part I - the details of the engineering, reservoir and economic plans for the Terra Nova Field
Canada-Newfoundland Benefits Plan - a description of the Proponents' commitments and plans for the
participation of Canadian, in particular Newfoundland and Labrador businesses, and the employment of
Canadians, in particular Newfoundland and Labrador residents, during the development.
Environmental Impact Statement - a description of the physical and biological environments of the Terra Nova
area and the impacts of the development on them
Socio-Economic Impact Statement - a description of the baseline conditions for, and the effects of the Terra Nova
Development on industry, employment, demography, housing, social infrastructure and services, public
infrastructure, municipal government and the fishery
The Development Application for the Terra Nova Development is based on preliminary information and design
work available to March 31, 1996. As further information becomes available, the plans described in this
Development Application may be modified or refined. Furthermore, submission of this Development Application
does not necessarily commit the Proponents to proceed with the Terra Nova Development.
Any requests for Development Application documents should be sent to:
Petro-Canada
Suite 504, Scotia Centre
235 Water Street
St. John's, Newfoundland A1C 1B5
The Development Application documents were printed in Newfoundland.
Telephone: (709) 576-2681
Facsimile: (709) 576-2685
The Authors
Petro-Canada contracted the following firms to research the environmental impacts of the Terra Nova
Development:
LGL Limited - St. John's, Newfoundland
ASL Environmental Sciences Inc. - Sidney, British Columbia
S.L. Ross Environmental Research Ltd. - Ottawa, Ontario
The technical content of this Environmental Impact Statement is the result of that assessment.
Master Table of Contents
1.
2.
Introduction
1-1
1.1
1.2
1.3
1.4
1.5
1-1
1-9
1-11
1-13
1-13
Environmental Management
2-1
2.1
Total Loss Management
2-2
2.1.1
2.1.2
2.1.3
2.1.4
2.1.5
2.1.6
2-2
2-2
2-4
2-4
2-5
2-6
2.2
3.
Scope of the Development
History of the Field
Participants in the Development
Schedule
Management
Leadership
Organization
Issue Management
Evaluation
Stewardship
Operating Practice
Application of Total Loss Management
2-6
Physical Environmental Setting
3-1
3.1
Atmospheric Environment
3-1
3.1.1
3.1.2
3.1.3
3.1.4
3.1.5
3-1
3-6
3-11
3-13
3-22
3.2
Database
Air Masses and Circulation Patterns
Climatic Controls and Variations
Regional Climatology
Severe Conditions
Oceanic Environment
3-37
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
3.2.6
3.2.7
3-37
3-40
3-42
3-60
3-81
3-84
3-84
Database
Bathymetry
Water Masses
Ocean Currents
Tides and Other Short-Term Sea-Level Variations
Oceanic Fronts
Upwelling Areas
Document #95032-0-EI-GM-00010.0 Rev.0
iv
3.2.8
3.3
3.4
3.5
3.6
4.
Wave Climate
3-88
Sea Ice and Icebergs
3-111
3.3.1
3.3.2
3.3.3
3-111
3-113
3-135
Database
Sea Ice
Icebergs
Geology
3-157
3.4.1
3.4.2
3.4.3
3.4.4
3-157
3-163
3-166
3-166
Bedrock Geology
Physiography and Surficial Sediments
Hydrocarbon Occurrence and Production
Seismicity
Shoreline Environment
3-172
3.5.1
3.5.2
3-172
3-173
Coastal Geomorphology
Hydrology, Oceanography and Ice
Chemical Environment
3-176
3.6.1
3.6.2
3-176
3-179
Water Quality
Marine Sediment Chemistry
Biological Environmental Setting
4-1
4.1
Grand Banks Ecosystem
4-1
4.1.1
4.1.2
4.1.3
4.1.4
4-4
4-4
4-6
4-6
Plankton
Benthos
Fish
Marine-Related Birds and Mammals
4.2
Phytoplankton
4-9
4.3
Other Microbiota
4-14
4.4
Invertebrate Zooplankton
4-16
4.4.1
4.4.2
4.4.3
4.4.4
4.4.5
4-17
4-18
4-20
4-21
4-25
Species Composition
Geographic Distribution
Vertical Distribution
Seasonal and Annual Variability
Importance in Food Web
v
4.5
4.6
Ichthyoplankton
4-26
4.5.1
4.5.2
4.5.3
4.5.4
4.5.5
4.5.6
4-27
4-33
4-33
4-35
4-36
4-36
Geographic and Seasonal Distribution
Recent Ichthyoplankton Research
Interannual Variability
Flemish Cap
Benthos
4-38
4.6.1
4.6.2
4-38
4-39
Macrophytes and Associated Microscopic Algae
Benthic Fauna
4.7
Biofouling
4-45
4.8
Fish and Fisheries
4-48
4.8.1
4.8.2
4.8.3
4.8.4
4.8.5
4.8.6
4.8.7
4.8.8
4.8.9
4.8.10
4.8.11
4.8.12
4.8.13
4.8.14
4.8.15
4.8.16
4-53
4-55
4-55
4-57
4-57
4-59
4-62
4-65
4-68
4-70
4-72
4-76
4-76
4-77
4-78
4-78
4.9
Iceland Scallop
Snow Crab
Stimpson Surf Clam
Skates
Redfish
Capelin
Atlantic Herring
Atlantic Cod
Greenland Halibut
Witch Flounder
American Plaice
Pollock
Haddock
Yellowtail Flounder
Northern Shrimp
Other Notable Species
Marine-Related Birds
4-85
4.9.1
4.9.2
4.9.3
4.9.4
4.9.5
4-85
4-85
4-93
4-93
4-93
Database
Breeding Biology and Nesting Populations
Foods and Feeding Habits
Geographic and Seasonal Distributions
Important Species and Areas
vi
4.10
4.11
5.
Marine Mammals
4-97
4.10.1
4.10.2
4.10.3
4.10.4
4-97
4-97
4-100
4-101
Database
Populations and Stocks
Food and Feeding Habits
Predevelopment Pollutant Concentrations - Biota
4-103
4.11.1 Hydrocarbons
4.11.2 Trace Elements
4-103
4-107
Impact Assessment
5-1
5.1
Impact Assessment Methodology
5-3
5.1.1
5.1.2
5-3
5-3
Types of Impacts
Impact Analysis Methods
5.2
Evaluation of Alternatives
5-10
5.3
Normal Operations During Drilling and Construction
5-11
5.3.1
5.3.2
5.3.3
5.3.4
Description of Physical Facilities and Activities
Presence of Structures
Lights and Beacons
Installation of Seabed Components and Underwater
Construction
5.3.5 Discharge of Drilling Muds and Cuttings
5.3.6 Discharge of Other Fluids and Solids
5.3.7 Atmospheric Emissions
5.3.8 Effects of Ships and Boats
5.3.9 Effects of Helicopters
5.3.10 Effects of Noise
5.3.11 Shore-Based Facilities
5-11
5-13
5-16
Normal Production and Maintenance Operations
5-46
5.4.1
5.4.2
5.4.3
5.4.4
5.4.5
5.4.6
5.4.7
5-46
5-48
5-48
5-49
5-49
5-55
5-58
5.4
Lights and Beacons
Maintenance of Subsea Structures
Injection Water
Produced Water
Other Operational Discharges
Atmospheric Emissions
5-16
5-16
5-28
5-33
5-33
5-34
5-34
5-42
vii
5.4.8
5.4.9
5.4.10
5.4.11
5-59
5-59
5-60
5-61
5.5
Transportation
5-62
5.6
Decommissioning
5-64
5.6.1
5.6.2
5-64
5-66
5.7
5.8
Terra Nova Development Area
Shore-Based Facilities
Oil Spills
5-67
5.7.1
5.7.2
5.7.3
5.7.4
5.7.5
5.7.6
5.7.7
5.7.8
5-68
5-85
5-90
5-100
5-108
5-114
5-121
5-125
Oil Spill Probability Analysis
Selection of Oil Spill Scenarios
Terra Nova Oil Properties and General Spill Behaviour
Modelling and Description of Selected Oil Spill Scenarios
Terra Nova Spill Trajectories
Environmental Impact Assessment
Assessment of Oil-Spill Countermeasures
Residual Impacts
Cumulative Impacts
5-127
5.8.1
5.8.2
5.8.3
5-127
5-134
5.8.4
6.
Effects of Ships and Boats
Effects of Helicopters
Effects of Noise
Impact Summary
Cumulative Development Impacts
Cumulative Impacts of the Development and Other
Activities on the Grand Banks
Cumulative Impacts and Climatic Change
5-135
5-136
Mitigation Measures and Contingency Planning
6-1
6.1
Drilling Mud
6-1
6.2
Well Treatment Fluids
6-2
6.3
Produced Water
6-2
6.4
Storage Displacement Water
6-2
6.5
Deck Drainage
6-2
6.6
Garbage and Sewage
6-3
viii
6.7
Ship and Boat Noise
6-3
6.8
Helicopters
6-3
6.9
6-4
6.10
Chronic and Accidental Spills
6-4
6.11
Oil-Spill Mitigation and Contingency Planning
6-5
6.11.1
6.11.2
6.11.3
6.11.4
6.11.5
6-6
6-6
6-16
6-18
6-21
Spill Prevention
Countermeasure Techniques
Contingency Planning
External Response Capability
Future Research and Development
7.
Environmental Protection Plan
7-1
8.
Monitoring and Reporting
8-1
8.1
Physical Environmental Monitoring
8-1
8.2
Compliance Monitoring
8-2
8.2.1
8.2.2
8.2.3
8.2.4
8.2.5
8.2.6
8-2
8-3
8-3
8-3
8-3
8-3
8.3
Drilling Muds and Cuttings
Produced Water
Cooling Water
Deck Drainage
Air Emissions
Environmental Effects Monitoring
8-4
8.3.1
8.3.2
8.3.3
8-4
8-4
8-4
Effects and Zone of Influence of Drilling Muds and Cuttings
Zone of Influence of Produced Water
Effects of Oily Water on Fish
Glossary
Bibliography
ix
Chapter 1
Table of Contents
1.
Introduction
1.1
1.2
1.3
1.4
1.5
Schedule
Management
1-1
1-1
1-9
1-11
1-12
1-12
Tables
1.2-1
1.2-2
1.3-1
1.4-1
Discovery and Other Exploratory Well Results
Delineation Well Results
Proponents' Predevelopment Cost Sharing
Major Milestone Dates
1-9
1-11
1-13
1-13
Figures
1.1-1
1.1-2
1.1-3
1.1-4
1.1-5
1.1-6
1.1-7
1.3-1
1.4-1
1.5-1
Location Map
Field Map
Significant Discovery Area
Proposed Development - Monohull Alternative
Proposed Development - Semisubmersible with Dynamic
Storage Alternative
Proposed Development - Semisubmersible with Storage
Vessel Alternative
Preliminary Seafloor Layout, Wells, Manifolds, and Flowlines
Significant Discovery Area Ownership
Preliminary Development Schedule
Organizational Structure
Document #95032-0-SE-GM-00001.0, Rev.0
1-2
1-3
1-4
1-6
1-7
1-8
1-10
1-12
1-14
1-15
1.
Introduction
The Socio-Economic Impact Statement (SEIS) discusses the socio-economic effects of
the Terra Nova Development. The SEIS deals with the following areas:
·
·
·
·
·
·
·
·
·
Industry and employment
Demography
Housing
Social infrastructure and services
Public infrastructure and services
Municipal government
The fishery
Land and resource use
Socio-cultural issues
Particular attention is given to issues of most concern to local residents and issues
arising from the Hibernia project or other significant events. The geographic scope is
primarily provincial, with regions most likely to be directly affected by the Terra Nova
Development covered in detail.
The SEIS covers the period from project engineering through construction, installation
and operations to decommissioning and abandonment. The main socio-economic
impacts will be associated with construction, installation and the early years of
operations. Subsequent operations, however, will see the cessation of economic
benefits.
1.1
The Terra Nova Oil Field is situated on the Grand Banks, about 350 km east-southeast
of St. John's, Newfoundland, and 35 km southeast of the Hibernia Oil Field (Figure
1.1-1). The field encompasses four geological structural fault blocks (Figure 1.1-2):
West Flank, Graben, East Flank and Far East. A Significant Discovery Area (SDA)
covers the four blocks (Figure 1.1-3).
It is expected that oil reserves of approximately 47 x 106 m3 will be recovered from the
Jeanne d'Arc Formation in two of the blocks, the Graben and the East Flank. The
reservoir consists of a sequence of medium- to coarse-grained sandstones deposited
about 140 million years ago in the Late Jurassic age. While the Far East block has not
yet been tested by drilling, it may yield oil reserves of up to 16 x 106 m3. It is
contemplated that a well will be drilled in the Far East block early in the life of the field
to evaluate the presence of hydrocarbons. Following successful results, the Far East
will be brought into production. The West Flank block has low potential for
commercial oil production. Produced gas will be conserved by reinjection into the field.
95032-0-SE-GM-00001.0, Rev.0
1-1
Development of the Terra Nova Field will include development drilling, and the
engineering, procurement, construction or modification, installation, commissioning
and operation of a floating production system and associated facilities. The crude oil
will be delivered directly to market using shuttle tankers or via a transshipment facility.
Since the discovery of the Terra Nova field in 1984, studies have been conducted on
various production systems, including a floating production system and a gravity base
structure (GBS). The clear conclusion is that a floating production system is the only
viable alternative for economic development of the Terra Nova Field. The amount of
oil that can be recovered is insufficient to warrant using a GBS platform, which has
higher capital cost.
Pre-Engineering will be undertaken in 1996 to determine the optimum type of floating
production system for Terra Nova. The following floating production facility (FPF)
alternatives will be considered:
·
·
New or converted monohull (Figure 1.1-4)
New or converted semisubmersible with:
Dynamic storage (Figure 1.1-5)
Storage vessel (Figure 1.1-6)
Pre-Engineering will also determine if the hull of the FPF will be made of steel or
concrete.
Water depth in the area is about 95 m. Physical environmental conditions are similar to
the northern areas of the North Sea except for the seasonal presence of icebergs and
sea ice at the Terra Nova location.
Reliable systems for the detection, monitoring and management of icebergs, including
towing techniques, have been developed. An ice management plan will give operations
personnel sufficient early warning of any need to disconnect the FPF or drilling units
from their moorings and risers. This would provide an orderly and controlled move off
location, in the event an unmanageable iceberg that presents a hazard approaches too
close to the facilities.
The depletion strategy is based on pressure maintenance of the reservoir. This will be
accomplished by waterflood for most of the field with the option of gas flooding in the
southern portion of the reservoir.
Initial development plans for the Graben and East Flank blocks foresee about 32 wells,
including production wells, water injection wells and gas injection wells. Five of the
existing delineation wells will be assessed for possible use as development wells. As the
FPF will not have a drilling capability, new wells will be drilled and completed using
one or more semisubmersible drilling units. Wells will be tied into subsea manifolds
95032-0-SE-GM-00001.0, Rev.0
1-5
with flowlines and connected to the FPF through flexible marine risers.
An additional 12 wells could be required to exploit the potential oil reserves of the Far
East block. Figure 1.1-7 shows a preliminary layout of the planned wells, field
manifolds and riser manifolds.
The production facilities will have the capacity to handle full field development. They
will be designed for 20 x 103 m3/d of oil with a 32 x 103 m3/d limit on total fluid
handling. Gas injection of 2.6 x 106 m3/d and water injection of 38 x 103 m3/d are
anticipated. A full field production life of about 18 years is anticipated.
1.2
The Terra Nova K-08 discovery well was drilled in 1984. The well had 58 m of net oil
pay and flowed a total of 1430 m3/d of oil from four drillstem tests (DST). Two
additional wells were drilled during the exploration phase. Table 1.2-1 summarizes the
results of these exploratory wells.
Table 1.2-1
Discovery and Other Exploratory Well Results
Well Number
Description
Results
Year
Drilled
Terra Nova
K-08
Drilled into a keystone
graben of a northwestplunging rollover anticline
Discovery well; 58 m of net pay; flowed
1430 m 3/d of oil from four DSTs
1984
Beothuk
M-05
Drilled updip of the K-08
discovery well
Pay not encountered in the Terra Nova
equivalent sands; demonstrated the
southern depositional limit of the field
1985
Drilled as an updip step-out
from K-18
Encountered water-bearing reservoir
sands
1985
Terra Nova
K-17
Six additional delineation wells were drilled in the field. Table 1.2-2 summarizes the
results of the delineation wells.
Of the nine wells drilled in the field, six are located within the Graben and East Flank
blocks. Five major and two minor oil-bearing sands have been identified.
95032-0-SE-GM-00001.0, Rev.0
1-9
Table 1.2-2
Delineation Well Results
Well
Number
Description
Year
Drilled
Results
Terra Nova
K-18
Drilled on the western flank of the
structure outside the Graben
Encountered water-bearing reservoir sands
1984
Terra Nova
K-07
Drilled updip and across the east-west
fault from the discovery well
Encountered 28 m of net oil pay; flowed a
total of 1260 m 3/d of oil from two DSTs
1985
Terra Nova
I-97
Drilled to evaluate the updip edge of the
east flank
Encountered 11 m of net oil pay and flowed a
total of 640 m 3/d of oil; defined the southern
field boundary
1986
Terra Nova
H-99
Drilled to confirm additional reserves on
the east flank of the structure
Encountered 43 m of net oil pay and flowed
1200 m 3/d of oil
1987
Terra Nova
C-09
Drilled downdip from the K-08 discovery
well to encounter the oil-water transition
and identify the northern extent of the
field
Oil-water contact not encountered; 64 m of
net oil pay penetrated with a total flow of
1330 m 3/d of oil
1988
Terra Nova
E-79
Drilled on the easternmost extremity of
the H-99 fault block to test sand
development on this fault block and the
far east portion of the structure
74 m of net oil pay penetrated with a total of
3650 m 3/d of oil from three DSTs
1988
1.3
The Terra Nova Significant Discovery Area (SDA) incorporates five Significant
Discovery Licences (SDL) with ownership varying in each SDL.
The owners of interests in the four SDL blocks covering the West Flank, Graben and
East Flank currently share costs through a pre-development agreement. These owners
and their predevelopment cost-sharing interests are shown in Table 1.3-1.
Table 1.3-1
Proponents' Predevelopment Cost Sharing
Owner
Petro-Canada
Mobil Oil Canada Properties
Husky Oil Operations Limited
Murphy Oil Company Ltd.
Mosbacher Operating Limited
95032-0-SE-GM-00001.0, Rev.0
Share (%)
49.2
20.7
15.8
10.7
3.6
1-11
The fifth SDL, 1034, is operated by Husky (Figure 1.3-1). The varying ownership
across Terra Nova requires unitization of the field. This process is underway and when
complete, the equity interest of individual owners will be established.
1.4
Schedule
The development schedule (Figure 1.4-1) reflects the approach that will be taken for
the construction or modification, installation and operation of a production system at
Terra Nova. Major milestones are listed in Table 1.4-1.
1.5
Management
The Terra Nova Proponents will appoint Petro-Canada as the Operator, acting on their
behalf (Figure 1.5-1).
The Operator's authority, role, responsibility and reporting requirements will be
outlined in the Unit agreement and Construction, Ownership and Operating agreements
that will be in place for the execution of the development. Proponents' rights,
responsibilities and dispute resolution mechanisms will be included in the agreement.
Table 1.4-1
Major Milestone Dates
Milestone Description
Public announcement regarding Development Application preparation
File Development Application
Obtain all regulatory approvals
Proponents approve execution of the development
First Oil
Finish Production (includes Far East)
Decommissioning and Abandonment
Scheduled
Completion Date
Quarter
Year
4
2
2
4
4
3
4
1995
1996
1997
1997
2001
2019
2019
Technical and management committees will establish overall Proponents' requirements
and budgetary approvals for the Operator's implementation. Petro-Canada will review
on a regular basis the development status with the Proponents who will provide advice
and guidance. Petro-Canada will manage and direct all aspects of the development
within the authority and approval parameters of the agreements.
95032-0-SE-GM-00001.0, Rev.0
1-12
A safe, environmentally sound, quality-controlled, fit-for-purpose and cost-effective oil producing
system will be developed using an alliance contracting strategy.
The alliance philosophy involves establishing long-term relationships between the
Operator, contractors and possibly key suppliers to collectively achieve mutual
objectives in a more effective and efficient way than traditional contracting methods.
The alliance approach focusses on maximizing the efficiency of the design, construction
and production start-up.
The current trend in the industry is to adopt the alliance approach in implementing
major oil and gas projects, particularly in high-cost areas such as the North Sea and the
East Coast of Canada. Using the alliance approach, companies are lowering costs while
sustaining high levels of safety, quality and protection of the environment. This is
enabling industry to remain competitive in the global marketplace.
The alliance approach will allow for the:
-
Elimination of unproductive organizational layers
Use of functional specifications
Use of standardized equipment
Reduction of documentation requirements to an optimum level
Clarification and simplification of contracts with contractors and suppliers and
the minimization of adversarial clauses
Streamlining of the procurement processes
Rationalization of design, materials and construction standards
Simplification of maintenance requirements and creation of an inherently safe
workplace
For the Project Phase, Petro-Canada will establish an alliance with a group of
contractors and key suppliers to execute the core work up to First Oil production (i.e.,
engineering, procurement, construction or modification, installation, commissioning
and possibly pre-development drilling). Other companies, contractors and suppliers will
be engaged in the development through the normal procurement-of-goods-and-services
process.
Petro-Canada and other alliance companies will establish a single alliance-based
Integrated Management Team (IMT). Petro-Canada and other Proponents' personnel
will be represented in the IMT and in the alliance organization as a whole. Each
member company of the alliance will participate in a risk-reward commercial
arrangement with established targets aimed at meeting the functional, quality, safety,
environmental, cost and schedule requirements.
95032-0-SE-GM-00001.0, Rev.0
1-16
In the Project Phase an alliance board will be formed from members of alliance
companies (including Petro-Canada) to monitor work status and ensure the alliance
objectives are being met.
The mission of the Project Phase alliance will be completed when First Oil is delivered.
Petro-Canada intends to lead the Operations Phase and will use contracting strategies,
such as alliancing, partnering and sub-contracting, to enhance the safety and efficiency
of the operations.
95032-0-SE-GM-00001.0, Rev.0
1-17
Chapter 2
Table of Contents
2.
2.1
2.2
2.1.1 Leadership
2.1.2 Organization
2.1.3 Issue Management
2.1.4 Evaluation
2.1.5 Stewardship
2.1.6 Operating Practice
2-1
2-2
2-2
2-2
2-4
2-4
2-5
2-6
2-6
Figures
2.1-1
Total Loss Management Fishbone Diagram
Appendices
2A
Petro-Canada Environmental Protection and Occupational
Health and Safety Policies
Document #95032-0-EI-GM-00002.0, Rev.0
2-3
2.
Environmental protection, and occupational health and safety are fundamental PetroCanada values. The management of these issues is conducted within a larger system,
the Total Loss Management (TLM) framework.
At Petro-Canada, loss management systems have been developed over many years.
Processes have been adapted to reflect both internal developments and changing
expectations of Canadian society. In 1992, specialists within the company, divisional
management teams and external experts reviewed loss management performance and
processes. This evaluation led, over time, to the development of the TLM approach.
TLM encompasses all programs and activities associated with health, safety,
environment, reliability, process hazard management, risk assessment and loss
prevention. It is a systematic and continuous approach toward the elimination or
reduction of risks to people, the environment, assets and production. TLM means
doing the right thing, for the right reason, in the right way, and at the right time.
In the broadest sense, TLM ensures that loss management is an integral part of how
business is conducted. TLM is being pursued as a company-wide means of managing
the review and integration of all existing loss management programs and practices.
TLM is designed so that the lessons of the past assist in shaping the future. It identifies
the elements and activities that must be incorporated into all operations. TLM was built
upon the strengths of existing programs. Petro-Canada's vision of success includes:
-
Running operations effectively and reliably with a focus on prevention
-
Making Petro-Canada a leader in the industry
This chapter discusses the TLM approach and how it will be applied during the Project
and Operations phases of the development. Copies of the Petro-Canada Environmental
Protection and Occupational Health and Safety policies can be found in Appendix 2A.
Petro-Canada will prepare a Safety Plan and an Environmental Protection Plan, in
accordance with the regulations, that will be submitted to the C-NOPB for approval
during the Project Phase.
2-1
2.1
The following key elements make up the TLM framework:
·
·
·
·
·
·
Leadership
Organization
Issue Management
Evaluation
Stewardship
Operating Practice
Figure 2.1-1 illustrates how each of the six elements has been subdivided into a number
of discrete initiatives.
Combining initiatives from within these elements produces the health, safety,
environment, reliability, risk assessment and loss prevention programs. Petro-Canada is
best positioned to deliver the appropriate standard of care, and meet its loss
management targets, when these programs include some or all of the initiatives
associated with each of the six elements.
2.1.1
Leadership
Leadership in TLM comes from all levels within the company Senior Management
through to front-line personnel are all accountable for various activities. Exemplary
loss management performance requires the commitment of every employee, through
continuous striving, to incorporate sound loss management philosophies and practices
into business activities.
Statements with respect to or demonstrating leadership provide documented
performance expectations to the public, the regulators and the courts. This is especially
true of formal statements that are widely distributed. They may be used to assess the
adequacy of actual actions and performance. It is essential that these communications
be reasonable and relevant to the business operating environment, that they are
developed with the input and buy-in of those directly affected, that the application is
equitable and that they are reviewed and updated on a regular basis.
2.1.2
Organization
The quality and commitment of its employees is one of Petro-Canada's most important
competitive advantages. The contributions of individuals is the largest single factor in
achieving TLM goals.
2-2
Superior loss management performance requires:
-
Highly competent employees focussed on loss management
-
Maintaining the expertise of health, safety, environment, reliability and loss
prevention professionals
-
Senior managers and management teams capable of creating a business
environment where loss management is valued
-
The identification and resolution of functional boundaries that impair the flow
of information and coordination
All four components are essential to properly manage current issues and anticipate
future challenges.
Continuing employee performance requires organizational support through
considerations such as hiring (and retaining) capable individuals, workplace setting
(conditions and aesthetics), training, site health and safety factors and employee
assistance programs.
2.1.3
Issue Management
Issue management involves the identification, assessment and management of the
opportunities and liabilities associated with present and anticipated loss management
issues. Issues that could influence strategic direction, involve unique (and significant)
change or affect the viability of key assets, are candidates for referral to the issue
management process.
The support and participation of all levels of management and a timely reporting
process is critical in meeting the objectives of this element. Management participation
and support provide the impetus and strategic direction required for effective
integration with operations. Timely communication ensures that all stakeholders
(management teams, issue owners and operations personnel) affected by the issue can
act with the knowledge that there is consensus and support for the resulting action
plans.
2.1.4
Evaluation
Evaluations of both physical assets and operational performance have a wide range of
applications in TLM by helping to identify and manage the extent to which individuals,
the environment and the company are exposed to hazard and risk. Such evaluations
are viewed by regulators and the courts as fundamental to the concept of due diligence
and have recently been employed as a key consideration by financial markets and
lending institutions.
2-4
The objective of both internal and external evaluation is to recognize and promote the
achievement and maintenance of loss management performance by:
-
Identifying liabilities or potential problems associated with operations
Determining whether appropriate and effective operating and management
systems are in place
Providing a feedback mechanism for continuous improvement
Ensuring compliance with regulator and corporate requirements
Verifying conformance and positioning with industry practice
Improving and integrating processes for identifying, planning for and communicating
acceptable risks, appropriate responses and accurate costs will assist in developing cost
effective liability management tools.
2.1.5
Stewardship
Petro-Canada cannot define success simply in terms of having a clean regulatory
record; responsible management must be demonstrated. Proper stewardship allows all
employees with loss management responsibilities, not just those associated with day-today operations, an opportunity to improve the company's loss management
performance.
Integration of TLM issues into the company's business operations and strategy relies
upon proactive and comprehensive reporting and feedback processes. These reporting
processes help the company take all reasonable steps to prevent or mitigate
unacceptable impacts resulting from business activities.
Stewardship includes information on the ongoing cycle of setting loss management
expectations and comparing those expectations to actual performance. These
performance measures and targets are designed to reflect past performance and the
impact of proactive initiatives. They are an important tool in the effort to continuously
improve loss management performance.
Compliance with regulator requirements and accident statistics have been used as
indicators of loss management performance. Scientific uncertainty and long lag times
between an event and its consequences can complicate the selection and measurement
of other environmental and health indices. However, simply because the economic
benefits associated with superior loss management performance may not be
immediately determinable does not mean they do not confer benefit or that the issues
can, or should be set aside.
2.1.6
Operating Practice
Risks can be minimized through appropriate loss management procedures, programs
and standards coupled with sound management practices. Loss management
2-5
considerations must be addressed from project inception and evaluation through
design, construction, start-up, routine operations and eventual decommissioning and
reclamation.
The other five TLM elements provide the building blocks for effective management of
loss by operations. The operating practice element describes a range of initiatives and
relationships unique to the operating environment at the field and facility level.
There are serious loss implications associated with failure to adequately design,
construct, commission and operate facilities. Improved reliability, efficiency and
prevention are all achievable goals if operating practices incorporate an aggressive loss
management focus.
On-going effort to maximize production involves changes to processes, equipment,
materials and operational parameters. Each of these changes can lead to accidents and
incidents if the changes are not discussed and communicated to all stakeholders.
Many operations rely on the availability of experienced contractors to provide a range
of services; many of these services involve safety-sensitive tasks. It is imperative that
contractor selection include evaluation of loss management programs and performance
and that open and honest communications be maintained with the contractors before
and during the conduct of their duties.
Planning, exercising and evaluating emergency response programs are essential for
minimizing impacts associated with unplanned events. Maintaining an effective
emergency response capability requires extra effort and constant support from all
employees.
Many loss management programs are concerned with the health and safety of the
individuals and communities close to the operations. The best means of achieving
community support and trust is through communication, consultation and frank
disclosure on issues affecting their health and safety.
2.2
Table 2.2-1 summarizes how TLM will be applied to Terra Nova activities during the
Project and Operations phases.
2-6
Corporate policies for environmental protection and health and
safety apply
Vice President Frontier and International
Will be developed to apply policies to the Terra Nova
Development; includes participation of alliance contractors
Developed with alliance contractors to meet corporate, regulatory
and classification society requirements
Ensure alliance contractors understand and accept loss
management philosophies; management participation (hands-onleadership); audit to verify application of systems and programs
A clear definition of goals and expectations will be
communicated in a formal, written and widely distributed
fashion; employee contributions to loss management will be
recognized
· Policy
· Accountability
· Procedures
· Standards
· Commitment
· Communication
Contractor evaluation and selection process
Contractor evaluation and selection process
Contractor will address decision-making authority; will report
processes and management responsibilities for routine and
emergency conditions
· Key Skills
· Training
· Roles and Responsibilities
Organization
Vision for the Terra Nova Development will be generated to
communicate a sense of future performance
Project Phase
· Vision
Leadership
Element and Initiatives
Operations Phase
Operations manuals will address onshore and offshore
roles and responsibilities, and the reporting process for
routine and emergency conditions
Job and task analysis will assess training needs and
priorities
Terra Nova staffing program will establish positionspecific loss management skills and prerequisites for
hiring, promotions and transfers
A clear definition of goals and expectations will be
communicated in a formal, written and widely distributed
fashion; employee contributions to loss management will
be recognized
Continuous reinforcement through daily activities; support
by verification of the understanding of the intent and
application of policies and procedures
Expected to be similar but may be modified to meet
specific requirements
Those not in place for Project Phase will be developed for
this phase
Vice President Frontier and International
Corporate policies for environmental protection and health
and safety apply
Vision for the Terra Nova Development will be generated
to communicate a sense of future performance
Total Loss Management Application to Environmental Management
Table 2.2-1
Terra Nova management will regularly consider current or
anticipated loss management issues, such as compliance,
safety records, regulatory change loss statistics, and take
action as appropriate; senior management, owners or other
stakeholders will be notified as appropriate
Petro-Canada will monitor contractor progress and performance
for indication of short- and longer-term loss management issues;
actions as dictated by issue and stakeholders
Issue Management
Rights of Proponents to audit contractor sites and performance
will be addressed in contract, consistent with alliance principles
Same actions as for audits
Contractor scope of work includes risk assessment for design,
construction, installation and operations; cooperative activity
between Proponents and contractor risk assessment are integral
components of the safety management system
Contractors will be required to investigate serious (to be defined
in contract) loss incidents
· Audits
· Inspections
· Risk Assessment
· Investigation
Evaluation
Variable compensation or value-sharing programs to
incorporate TLM expectations and performance
Performance measures for loss management could be negotiated
into contracts
· Performance Management
Programs, incidents and operations-specific problems will
be investigated (sampling and analysis as required).
Includes down-grading accident and near-hits
Facilities delivered should have addressed risk assessment
at every stage. Risk assessment is ongoing for change in
facility, operation or operating environment
Inspections will be used between audits or as a follow-up;
used in place of audit at less complex facilities
Rigorous, scheduled and objective appraisals by internal or
external teams will be planned and conducted; Significant
audit findings will be reported to higher levels of
management. Implementation of recommendations will be
tracked, and resourcing for audit programs given priority in
planning cycle
Key loss management positions will be identified; potential
candidates will be inventoried and training and
assignments arranged
Contractors will have sufficient qualified personnel for all aspects
of alliance activity
· Succession Planning
Loss management issues will be integrated into business
decisions, planning and budgeting
Operations Phase
Loss management issues will be addressed in contracts
Project Phase
· Business Integration
Table 2.2-1
Consistent with alliance concept. Contractors will be required to
provide information to Petro-Canada for inclusion in stewardship
report; as a minimum compliance, safety statistics, analysis of
variance from expectations and (as necessary) plans for
improvement
Contractors may be required to submit benchmarking data during
evaluation phase, or at other times as necessary
Performance measures can be built into the alliance contract risk
and reward compensation program
Timely feedback will be provided to the contractor
· Benchmarking
· Performance Measures
· Reporting
Contractors will be required to report within specified times for
serious loss events, including details, basic causes and measures
to prevent recurrence
Project Phase
· Analysis and Assessment
Stewardship
· Event Reporting
Operations Phase
Appropriate and effective communication at and between
all levels of the Terra Nova Development; actions and
measures will be appropriate and aligned with corporate
strategy; timely feedback will be provided to those
preparing the information
Loss management performance targets could be a
component for individual or team performance
Terra Nova management will benchmark procedures,
activities, programs, performance and achievement against
other offshore operators as part of the development's
continuous improvement cycle
Consistent with corporate stewardship reporting procedure,
Terra Nova management will report on current and future
compliance issues, analyze the differences between
expectations and results and provide evidence of
measureable improvement
Event-reporting procedures will be developed; as a
minimum, reports will include details of events' basic
causes, and systems and measures to prevent recurrence
Table 2.2-1
Contractor will:
· Conduct activities in accordance with engineering controls
and procedures
· Incorporate input from operations and maintenance into
design
· Design for equipment reliability, energy efficiency, minimum
environmental impact, and operating safety
· Document pre start-up and inspection procedures for routine
and emergency conditions
Specific procedures will be developed between the contracting
parties
Manuals will be developed to support the latter part of the Project
Phase. As a minimum, contractors will be required to:
· Ensure programs are in place and in use that verify the
reliability of piping, vessels and equipment
· Provide fundamental safety, health and hygiene contracts for
the workplace
· Document compliance requirements and performance
In addition to the evaluation and selection process discussed
above, an open and honest dialogue before and during the term of
the contract will be maintained
Contractors will be responsible for emergency preparedness at
onshore sites; their preparedness will be reviewed during audits
and inspections. Offshore emergency preparedness plans will be
prepared and implemented jointly with the Operator
· Design, Construction, Startup
· Management of Change
· Operations and Maintenance
· Third Party Services
· Emergency Preparedness
Operating Practice
All changes made to facilities, equipment, materials
and operating parameters will be discussed before
implementation, documented and transmitted to other
operating personnel
Environmental, safety, health and operating risks and
compliance implications arising out of any changes
made to facilities, equipment, materials and operational
parameters will be communicated
Petro-Canada will comply with pertinent regulations in the
development of all emergency preparedness plans PetroCanada will:
· Maintain emergency response plans that are available
to, and discussed with, employees, government
agencies and the public
Contractors will play a significant role in operations,
therefore Petro-Canada will:
· Evaluate the safety program and performance of
contractors during the award process
· Conduct site orientations including facility layout and
loss management philosophy and procedures
· Maintain open and honest dialogue with contractors
before and during the term of the contract
Manuals prepared for the Project Phase will be used as the
basis for the Operations Phase; these documents will be
updated as necessary
·
·
During operations, should new equipment be added, the
same procedures would apply; startup after turnaround will
go through a process similar to that for the Project Phase;
this will be described in the operations manuals
· Community Relations
Contractors will be expected to deal openly and honestly with the
public respecting their operations and activities
Conduct periodic emergency response simulations and
drills to validate training and procedures
Ensure initial responders have the necessary financial
and operational authorities
Petro-Canada will:
· Develop and maintain a relationship with the public
that facilitates the investigation of complaints, responds
to concerns and provides information on loss
management issues that may be of interest
·
·
Appendix 2A
Petro-Canada Environmental Protection and
Occupational Health and Safety Policies
Chapter 3
Table of Contents
3.
3.1
3.2
3.3
3.4
3.5
3.6
3.1.1 Database
3.1.2 Air Masses and Circulation Patterns
3.1.3 Climatic Controls and Variations
3.1.4 Regional Climatology
3.1.5 Severe Conditions
Oceanic Environment
3.2.1 Database
3.2.2 Bathymetry
3.2.3 Water Masses
3.2.4 Ocean Currents
3.2.5 Tides and Other Short-Term Sea-Level Variations
3.2.6 Oceanic Fronts
3.2.7 Upwelling Areas
3.2.8 Wave Climate
3.3.1 Database
3.3.2 Sea Ice
3.3.3 Icebergs
Geology
3.4.1 Bedrock Geology
3.4.2 Physiography and Surficial Sediments
3.4.3 Hydrocarbon Occurrence and Production
3.4.4 Seismicity
3.5.1 Coastal Geomorphology
3.5.2 Hydrology, Oceanography and Ice
3.6.1 Water Quality
3.6.2 Marine Sediment Chemistry
3-1
3-1
3-1
3-6
3-11
3-13
3-22
3-37
3-37
3-40
3-42
3-60
3-81
3-84
3-84
3-88
3-111
3-111
3-113
3-135
3-157
3-157
3-163
3-166
3-166
3-172
3-172
3-173
3-176
3-176
3-179
Tables
3.1-1
3.1-2
3.1-3
3.1-4
Expected Extreme Wind Speeds at Terra Nova
Occurrence of Restricted Ceiling Height Based on Rig Data
Occurrence of Restricted Ceiling Height Based on Ship Data
Occurrence of Freezing Precipitation
95032-0-EI-GM-00003.0, Rev.0
3-24
3-31
3-32
3-35
3.1-5
3.2-1
3.2-2
3.2-3
3.2-4
3.2-5
3.2-6
3.2-7
3.2-8
3.2-9
3.2-10
3.2-11
3.2-12
3.2-13
3.2-14
3.2-15
3.3-1
3.3-2
3.4-1
3.4-2
3.4-3
3.6-1
3.6-2
3.6-3
Computed Extreme Values for Superstructure Icing at Terra Nova
Satellite-Based Remote Sensors
Monthly Temperature and Salinity Statistics from Historical Bottle
Data in the Terra Nova Area, Surface, 1900-1987
Data in the Terra Nova Area, 20 m Depth, 1900-1987
Data in the Terra Nova Area, 50 m Depth, 1900-1987
Data in the Terra Nova Area, Within 10 m of Bottom, 1900-1987
Summary of Moored Current Meter Data Sets Available for Terra
Nova and the Immediate Vicinity
Extreme Currents at Terra Nova Computed for Various Return
Periods
Significant Wave Height Versus Peak Period at Terra Nova, 1980 to
1988 and 1990 Observations
Joint Distribution of Wave Height and Wind Direction at Terra Nova,
1980 to 1986
Wave Height Persistence for Terra Nova, February, 1980 to 1986
Wave Height Persistence for Terra Nova, May, 1980 to 1986
Wave Height Persistence for Terra Nova, August, 1980 to 1986
Wave Height Persistence for Terra Nova, November, 1980 to 1986
Wave Groupiness Factor for Significant Wave Height Classes
Extreme Significant Wave Height and Associated Periods for Terra
Nova
Characterization of Sea Ice by Type, Thickness and Age
Descriptive Statistics for Iceberg Scour at Terra Nova
Geological Timetable
Lithology of Pre-Mesozoic Basement Rocks of the Study Area
Stratigraphy of Surficial Sediments Overlying Tertiary Bedrock
Trace Metal Concentrations in Grand Banks and the Gulf of St.
Lawrence Seawater
Concentrations of Organic Compound Residues in Marine Sediments
Trace Metals in Marine Sediments in Eastern Canada
3-35
3-40
3-56
3-57
3-58
3-59
3-62
3-79
3-94
3-95
3-96
3-97
3-98
3-99
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3-105
3-115
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3-161
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3-179
3-181
Figures
3.1
3.1-1
3.1-2
Environmental Study Area
Climatological Database Area
Mean Sea-Level Pressures
95032-0-EI-GM-00003.0, Rev.0
3-2
3-5
3-7
3.1-3
3.1-4
3.1-5
3.1-6
3.1-7
3.1-8
3.1-9
3.1-10
3.1-11
3.1-12
3.1-13
3.1-14
3.1-15
3.1-16
3.1-17
3.1-18
3.1-19
3.2-1
3.2-2
3.2-3
3.2-4
3.2-5
3.2-6
3.2-7
3.2-8
3.2-9
3.2-10
3.2-11
3.2-12
3.2-13
3.2-14
3.2-15
3.2-16
3.2-17
3.2-18
3.2-19
3.2-20
3.2-21
3.2-22
3.2-23
3.2-24
3.2-25
NAO Index Anomaly and Northwesterly Winds
Areal Distribution of Cyclonic Activity - Number of
Events and Genesis
Flow Field Within a Split-Frontal System Storm
Monthly Air Temperatures
Weekly Air Temperatures
Mean Monthly Precipitation, St. John's
Maximum Daily Precipitation, St. John's
Monthly Occurrence of Precipitation
Seasonal Wind Roses
Average Monthly Wind Speeds, St. John's and Terra Nova
Maximum Monthly Wind Speeds
Average Number of Days with Fog, St. John's
Visibility Statistics from Ship Data
Visibility Statistics from Drilling Rigs
Ceiling Statistics from Drilling Rigs
Limited Flying Weather Statistics
Superstructure Icing
Bathymetric Chart of the Grand Banks
Bathymetric Chart of the Terra Nova Area
Location and Distribution - Temperature and Salinity Measurements
Distribution of Water Masses in the Area
Average Distribution of Temperature and Salinity
Contours of Temperature, Salinity and Dissolved Oxygen
Average Annual Temperature, Salinity and Sigma-T, Station 27
Temperature and Salinity Values for all Years,
Central Grand Banks Region
Temperature Profiles Based on Monthly Means,
Terra Nova Area
Time Series of Temperature and Salinity Anomalies, Station 27
Time Series of the Summer Cold Intermediate Layer Parameters
Location of Long-Term Current Meter Mooring Data
Tracks of 144 Drifting Buoys
Major Ocean Circulation Features
Computed Currents From Drifting Buoy Data
Comparison of Mean Velocity Vectors
Model-Derived Depth-Averaged Currents
Model-Derived Summer Currents
Composite Map of Mean Near-Surface Currents
Selected Drifting Buoy Tracks Showing Eddies and Meanders
Inertial Oscillations in Currents
Vertical Distribution of North-South Current Components
Cotidal Charts for Newfoundland Waters
Locations of Bottom-Pressure Moorings
Eastern and Western Boundaries of the Labrador Current
95032-0-EI-GM-00003.0, Rev.0
3-8
3-10
3-12
3-14
3-15
3-16
3-18
3-19
3-20
3-21
3-23
3-25
3-26
3-27
3-29
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3-54
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3-61
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3-67
3-69
3-71
3-72
3-73
3-74
3-76
3-78
3-80
3-82
3-83
3-85
3.2-26
3.2-27
3.2-28
3.2-29
3.2-30
3.2-31
3.2-32
3.2-33
3.2-34
3.2-35
3.3-1
3.3-2
3.3-3
3.3-4
3.3-5
3.3-6
3.3-7
3.3-8
3.3-9
3.3-10
3.3-11
3.3-12
3.3-13
3.3-14
3.3-15
3.3-16
3.3-17
3.3-18
3.3-19
3.3-20
3.3-21
3.3-22
3.3-23
3.3-24
3.3-25
3.3-26
3.3-27
3.3-28
3.4-1
3.4-2
3.4-3
3.4-4
Northern Boundary of the Gulf Stream
SAR Features Merged with Sea Surface Temperature and Wind Data
Distribution of WRIPS and WAVEC Buoy Data
Percent Exceedance of Significant Wave Height by Season
Distribution of Peak Periods by Season
Directional Wave Spectra
Sea Surface Elevations of the Wave Record, Largest Individual Wave
Seasonal Variability of Storms
Distribution of Storm Wave Heights
Interannual Variability of Storms
Average Composition and Total Concentration of Sea Ice
Median and Maximum Sea-Ice Limits, Week of January 15, 1959-1995
Median and Maximum Sea-Ice Limits, Week of February 12, 1959-1995
Median and Maximum Sea-Ice Limits, Week of March 19, 1959-1995
Median and Maximum Sea-Ice Limits, Week of April 16, 1959-1995
Median and Maximum Sea-Ice Limits, Week of May 14, 1959-1995
Median and Maximum Sea-Ice Limits, Week of June 4, 1959-1995
Spatial Extent of Sea Ice
Occurrence of Sea Ice
Percentage Distribution of All Ice
Mean Ice Velocity (Derivation Imagery) Satellite
Percent Exceedance of Mean Daily Drift Speed and
Distribution of Draft Directionality
Average Ice Thickness in 1° Grid Centred on Terra Nova
Estimate of Average Occurrence Probabilities - Ice Thickness
Sea Ice Deformation Type
Iceberg Circulation
Annual Counts of Iceberg Crossings at 48°N
Annual Counts of Icebergs South of 48°N Versus
South Labrador - Newfoundland Ice Extent
Iceberg Speed Exceedance and Velocity Direction Distributions
Observed and Modelled Hourly Iceberg Positions
Number of Icebergs Crossing 48°N by Month
Annual Number of Iceberg Sightings in the Terra Nova 1° Grid
Maximum and Mean Annual Numbers of Icebergs Observed
Exceedance for Waterline Lengths for On-Shelf and Off-Shelf Icebergs
Exceedance for Iceberg Draft On-Shelf and Off-Shelf Areas
Exceedance for Iceberg Sail Height
Exceedance for Iceberg Mass
Contours of Observed Scour Areal Densities
Sedimentary Basins Offshore Eastern Canada
Bedrock Geology Map
Time Stratigraphic Section of the Jeanne d'Arc Basin
Hydrocarbon Traps Recognized on the Grand Banks
95032-0-EI-GM-00003.0, Rev.0
3-86
3-87
3-90
3-92
3-93
3-101
3-102
3-106
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3-117
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3-119
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3-121
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3-132
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3-143
3-145
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3-148
3-149
3-150
3-151
3-155
3-158
3-159
3-162
3-167
3.4-5
3.4-6
3.4-7
3.5-1
Fault Structures of the Jeanne d'Arc Basin
Seismotectonic Setting of the Grand Banks
Earthquake Epicenters and Magnitudes
Major Drainage Basins
95032-0-EI-GM-00003.0, Rev.0
3-168
3-169
3-171
3-174
3.
This chapter of the Terra Nova Environmental Impact Statement describes the physical
and chemical environment of the Grand Banks, with emphasis on the area for the Terra
Nova Development.
The physical environment, particularly the atmospheric, oceanic, and ice regimes, is
discussed in detail because of its importance to operational and environmental risk
issues. In addition, the physical databases are most extensive.
The Hibernia Environmental Impact Statement (Mobil, 1985), which was based upon
studies in the early 1980s and earlier, has provided the foundation information for this
document. This information has been updated with all new information available. The
study area in the following subsections is identical to that described in Mobil (1985).
Figure 3-1 shows the study area.
3.1
3.1.1
Database
Routine recording of climatological data at Newfoundland land stations began over
120 years ago with the establishment of weather stations at St. John's and Bell Island.
Several additional weather stations were established in the 1930s and 1940s because of
the need for better meteorological data and forecasts to support aviation. Other
stations were added from the 1950s to the early 1970s. In 1990, 41 weather stations
were in operation in Newfoundland, from which at least 20 years of data were
available. Ten of these weather stations were providing complete synoptic and hourly
measurements of temperature, precipitation, sunshine, moisture and winds, and subsets
of these measurements were being collected at the other stations.
Weather measurements from ships operating on the high seas have been collected for
many decades. Ship-based measurements are subject to biases in that ships tend to
avoid severe weather conditions, if possible, and follow established shipping routes.
Nevertheless, the availability of direct measurements far offshore is invaluable for
climatological descriptions and studies. Over the past 20 years, the national weather
services of the U.S. and Canada have developed and implemented archival and display
systems for ship-based observations.
An important addition to the climatological database for the Northeast Grand Banks
are the synoptic marine weather observations collected at three-hour intervals from
offshore drilling rigs. Compilations of these marine weather observations from the
Hibernia region and adjoining areas were presented by Mobil (1985) for the period
1975 to 1983. From 1984 to 1991, marine weather observations were also collected at
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the Terra Nova and adjoining wellsite areas. These data have been incorporated into
Petro-Canada's Terra Nova Environmental Database.
The major climatological databases used in this report are:
1.
Archives of Canadian Climatological Data. Regional climatological data
sets for Atlantic Canada are available from the Atmospheric Environment
Service (AES) of Environment Canada, at AES, Atlantic Weather Centre,
Bedford, Nova Scotia and at AES national headquarters in Downsview,
Ontario. This database includes hourly weather, rainfall, temperature, sunshine
solar radiation, soil temperature, pan evaporation, wind speed and direction.
Data sets are available for land stations through to early 1995.
2.
Marine Climatological Data - Hydrometeorology and Marine Division,
Canadian Climate Centre, AES, Downsview, Ontario. The extent of
climatological data from the Canadian Climate Centre depends on each
individual data set; some start in the early 1800s. The data sets are updated
approximately every five years; the most recent update includes data from the
late 1980s. This database includes waves, winds, ice cover, air and water
temperature, air pressure, storm tracks, and present weather codes. For data
collected up to the mid-1980s, the marine climatological summaries were
obtained through the MAST (Marine Statistics) system, which provided
summaries of marine and coastal station meteorological reports.
3.
Comprehensive Ocean-Atmosphere Data Set (COADS). The COADS
database is archived at AES Downsview, Ontario (1957-1988) and at the U.S.
Pacific Marine Environmental Laboratory (PMEL), Seattle, Washington. This
is a worldwide database for marine climatic and oceanographic data and is up
to date. Unfortunately, some Canadian marine observations have not been
included in this database since late 1988. The range of output parameters
readily accessible for data collected since the late 1980s (through PMEL) are
limited to monthly means.
4.
Petro-Canada's Terra Nova Environmental Database. Petro-Canada's
Wellsite Environmental Database consists of data collected by the oil industry
and government agencies operating in and passing through the Terra Nova
region. It includes observations of air temperatures, wind speed, wind
direction, atmospheric pressure and visibility. Historical observations dating
back to 1868 from ships of opportunity have also been included.
Caution is necessary when comparing data from land, ship and well sites. While the
ship-based data spans many years, the sampling effort varies considerably with the year,
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and the quality of data varies with the type of measuring instrument and the level of
personnel training. By contrast, the sampling effort at land and rig stations is more
uniform over time. Land station data sets typically span 30 years or more and rig
station data sets span just over 10 years. Also, both the instrumentation and personnel
training at land and rig stations are governed by standards set by AES.
As well, the standard measurement level varies with data type. At land stations, the
measurements are obtained at the standard 10 m level. Ship- and rig-based
measurements of winds are usually obtained at higher elevations, usually 20 and 80 m,
respectively; they are then corrected to a height of 19.5 m above mean sea level using
the marine boundary layer approach (Cardonne, 1978).
Figure 3.1-1 shows the areas encompassed by each of the climatological databases
used in this document. The two coastal stations are St. John's, Newfoundland and
Cartwright, Labrador, just north of the upper end of the map.
An important part of the information base on atmospheric sciences are the research
programs conducted over the past decade on major East Coast storms. These
programs include the:
-
Canadian Atlantic Storms Program (CASP), Phase I in 1986 (Stewart, 1991)
-
CASP, Phase II in 1992 (Smith et al., 1994; Hudak et al., 1995; Stewart et al.,
in press)
-
Genesis of Atlantic Lows Experiment (GALE) in 1986 (Dirks et al., 1988)
-
Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA) in
1989 (Halock and Kreitzber, 1988)
In all these programs, extensive field experiments were conducted. Based on the
analyses of the field data, combined with numerical modelling studies, descriptions of
key attributes of East Coast storms (severe wind shear, precipitation types, and severe
icing) have improved and the physical processes and controlling factors for the major
storms are better understood. As understanding increases, operational forecasting is
improved, including recent upgrades to the Canadian Meteorological Centres Regional
Finite Element (RFE) operational weather prediction model (Mailhot et al., 1995).
95032-0-EI-GM-00003.0, Rev.0
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3.1.2
Air Masses and Circulation Patterns
Pressure and Circulation Patterns
The overall atmospheric circulation of the study region can be characterized by the
large-scale seasonal distribution of sea-level pressure (Figure 3.1-2). In the fall and
winter, low pressures occur in the northernmost portions of the North Atlantic
(Icelandic Low) and high pressures occur over a broad region of the tropical portions
of the North Atlantic Ocean (the Azores High). The difference in winter sea-level air
pressure between the Azores High and Icelandic Low, known as the North Atlantic
Oscillation (NAO) (Rogers, 1984), is a convenient index representing the strength of
the winter circulation over the northern portion of the North Atlantic Ocean.
A strong mean airflow occurs from west to east across the North Atlantic Ocean at
mid-latitudes, as indicated by a band of closely spaced pressure contours (isobars)
extending from the Canadian East Coast to the United Kingdom. The Icelandic Low
weakens in the spring, and by summer it no longer appears as a distinct feature in the
mean surface pressure maps. This is a reflection of the less frequent and less intense
storms occurring during spring and summer.
Over the past 25 years, the NAO index has exhibited strong positive anomalies in the
early 1970s, mid-1980s and early 1990s. This indicates above normal occurrences of
stronger than normal cyclonic weather disturbances over the Northwest Atlantic Ocean
(Figure 3.1-3). The positive NAO anomalies coincide with more frequent
northwesterly winds during the early 1970s and early 1990s, with a less pronounced
increase in the mid-1980s (Colbourne et al., 1994). The more frequent northwesterly
winds are associated with colder air and ocean temperatures, and more sea ice in the
study area.
Air Masses and Fronts
The climate of the Terra Nova study area is very dynamic, being largely governed by
the influence of the weather systems passing through the area. These weather systems
are often intense, and include strong winds and a wide range of precipitation types,
particularly in the fall and winter.
The passing storms, and other weather systems, can be characterized by the airmass
type associated with the weather systems. Maritime air mass is present most of the
time, occurring as generally cool and moist conditions. At times, arctic air (originating
over the northern continental regions of North America, Greenland and the Arctic
Ocean) will reach the study area in a modified form. This results in relatively cold and
dry winters, and cool and moist summers. In winter, arctic air moving from the
northwest is rapidly warmed by the relatively warm ocean temperatures, producing low
temperatures, variable cloudiness and snow squalls in the study area. Tropical air
95032-0-EI-GM-00003.0, Rev.0
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masses, characterized by warm and humid conditions originating in the Gulf of Mexico
and mid-Atlantic areas, also influence the study area, although they occur there only in
a highly modified form. Surface conditions include low clouds, fog and drizzle, all of
which reduce visibility.
Different air masses are often associated with moving weather systems. The air masses
are separated by fronts, occurring as strong gradients in temperature, moisture and
winds conditions. Fronts generally represent the most variable and intense weather
elements of passing storms. In frontal areas, the weather systems are most rapidly
modified and intensified.
Storms
Newfoundland and its adjoining waters have a well-deserved reputation as one of the
stormiest parts of North America. Many of the storms that traverse North America
from west to east at mid-latitudes pass near Newfoundland and the Terra Nova area as
they move out into the North Atlantic. As shown in Figure 3.1-4, the area just to the
south of Newfoundland is the most active area of cyclonic activity in North America
and the adjoining oceans (Zishka and Smith, 1980). Another favoured track for storm
movements is located just to north of Newfoundland, along the north shore of the St.
Lawrence River extending through Southern Labrador. In summer (July), cyclonic
activity is much decreased in the area south of Newfoundland, but is just as frequent in
the southern Quebec and Labrador region (Piccolo and El-Sabh, 1993).
Winter cyclones are considerably more intense and frequent than those in the summer.
The associated winds reach gale force several times in a typical year, and sometimes
attain hurricane force. Winter storms generally produce snow, ice pellets or freezing
precipitation, near or below a surface temperature of 0°C, although many also contain
regions where rain reaches the surface. Winds, precipitation and superstructure icing
are discussed in more detail below.
Formation of cyclones ("cyclogenesis") tends to be concentrated in fairly distinct areas
(Figure 3.1-4), primarily the lee-side of major mountain ranges such as the Rocky and
Appalachian ranges, and east coastal regions. On the East Coast, there are particularly
high levels of activity off the northeastern coast of the United States.
The cyclonic activity in winter and spring is always caused by storms originating at
comparable latitudes to those of the Terra Nova region. Such storms are known as
"extra-tropical" cyclones. In late summer and fall, tropical storms, sometimes reaching
hurricane status, that originate in equatorial regions and develop in the Caribbean, can
bring windy, wet weather as they pass within 300 km of Newfoundland. Such storms
usually greatly diminish in strength as they move far from the warm-water sources that
provide their energy.
95032-0-EI-GM-00003.0, Rev.0
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Over a period of 35 years, an average of one tropical storm per year has passed within
300 km of Newfoundland (Phillips, 1990). There are rare occurrences when violent
tropical storms approach Newfoundland, such as in 1978 when Hurricane Ella passed
south of Cape Race producing winds of more than 117 km/h in St. John's. More
recently, on September 10 and 11, 1995, Hurricane Luis travelled northeastward
directly over southeastern Newfoundland with wind speeds of 83 km/h (one-minute
mean) gusting to 111 km/h (Bigio, 1995).
3.1.3
Climatic Controls and Variations
The most common Canadian East Coast winter storms, the extra-tropical cyclones, are
complex systems characterized by cold and warm fronts that can exhibit a wide range
of surface manifestations along with precipitation bands that vary considerably among
the various storms. A typical East Coast storm (Figure 3.1-5) can be described as a
split-frontal system with the upper cold front oriented parallel to but generally moving
faster than the surface cold front (Stewart and MacPherson, 1989).
A great deal of effort has been directed at understanding the explosive deepening of
extra-tropical cyclones through atmospheric research programs conducted within the
past decade (CASP-I and II, GALE and ERICA). This most intense form of
extra-tropical cyclones is a rapid (greater than 0.1 kPa/h) and sustained fall of the
central pressure of a winter storm, which results in greatly intensified winds often with
increased precipitation (Sanders and Gyakum, 1980; Kuo et al., 1991).
In the Atlantic Canada region, such storms occur about once per week (Stewart et al.,
1995b). Recent research shows the cause of the rapid decrease in pressure as strong,
large-scale, vertical gradients in the atmosphere ("baroclinic" conditions) associated
with strong, upper-layer forcing or tropopause folding. Low-pressure centres located
over a very warm ocean surface, such as the Gulf Stream, can induce very intense
convection because of:
-
The large surface moisture and heat fluxes from the ocean to the atmosphere
-
Low-pressure centres over land, sea ice or cold water, where the forcing from
above in the atmosphere is sufficient to rapidly deepen a storm
Over the past decade, much has been learned about the processes occurring within
storms through the CASP-I and II, GALE and ERICA research programs. As well as
leading to better understanding of the physical processes, these ongoing research
programs are inducing improvements in observational and forecasting skills (Stewart,
1991).
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In particular, forecasting of intense winter storms arising from explosive deepening is
being improved by the early identification of such storms from surface observations,
remote sensing by satellite, and numerical weather models (Mailhot and Chouinard,
1989; Mailhot et al., 1995).
However, further improvements in the operational forecasting of severe weather are
needed. For example, spatially detailed wind fields in severe storms are needed to
better forecast extreme waves (Desjardins, 1995). Research and development activities
addressing these requirements are underway at the RPN division of AES (Mailhot,
1995, pers. comm.) and further improvements, including higher resolution wind field
forecasts, are anticipated soon.
3.1.4
Regional Climatology
Temperature
The annual mean daily temperatures in the Terra Nova area and at St. John's are 5.0°C
and 4.7°C, respectively. February is the coldest month and August is the warmest
month both onshore and offshore (Figure 3.1-6). Daily maxima are lower and minima
are higher offshore (except from November to January) because of the greater
influence of the ocean at the offshore location. In particular, the Terra Nova area is
located nearer the warm waters of the Gulf Stream and further from the continental air
masses, which are comparatively cold in winter and warm in summer. The lowest
recorded temperature in the Terra Nova area is -17.3°C and the highest is 26.8°C. The
comparable values for St. John's are -23.8°C and 31.5°C. The extreme values of air
temperature in the Terra Nova area are derived from observations taken by passing
ships since 1856; the accuracy of any individual measurement is difficult to assess.
Three cold periods have occurred over the past 25 years at coastal stations along the
eastern Newfoundland and Labrador shelves (Figure 3.1-7). These periods were in the
early 1970s, the mid-1980s and the early 1990s. The negative air temperature
anomalies of the third event began in the late 1980s and have continued through 1994,
making this period the longest cold period in the latter half of this century.
Precipitation
As part of its wet, mild climate, southeast Newfoundland receives annual precipitation
of over 1000 mm. This makes this region the wettest area in Eastern Canada. Total
precipitation in St. John's is 1482 mm per year on average, with 78 percent of this
falling as rain and the remainder as snow. Rain occurs throughout the year (Figure 3.18), and is reported an average of 161 days each year. Snowfall has been reported in St.
John's in all months except July and August, but 95 percent of the total annual snowfall
occurs from November to April. Throughout the year, snowfall is reported 87 days on
95032-0-EI-GM-00003.0, Rev.0
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average, with measurable snowfall occurring on about half of the days from December
to March.
The monthly extremes for precipitation at St. John's are uniformly high throughout the
year (Figure 3.1-9), with maximum daily rainfalls exceeding 50 mm having occurred in
every month. The largest one-day rainfall of 121.2 mm occurred on October 4, 1942.
Daily snowfalls of 25 cm or more have been reported for all months from November to
May, with the maximum total snowfall in one day of 54.9 cm occurring on February
15, 1959.
Precipitation measurements available for the Terra Nova study area do not include
volumetric data on precipitation. However, data on the occurrence of precipitation are
available from ship reports collected since 1856, and from the offshore oil rigs
operating in the area since 1972.
According to rig observations between 1972 and 1985 (Figure 3.1-10) the occurrence
of precipitation in the Terra Nova study area is lowest in July (12 percent) and highest
in January (42 percent). Rainfall is most likely in autumn, with moderate to heavy
rainfall occurring most frequently from September to January, when average
occurrence levels exceed 3.5 percent. Snowfall is seasonal, with the earliest important
occurrences being observed in November and December. Snow is most likely to occur
in January through March. Moderate to heavy snowfall is most likely to occur in
January and February, with mean occurrences of 2.4 and 3.3 percent, respectively.
Wind
Wind is a very important attribute of the weather for planning and conducting offshore
operations, primarily because it generates waves and currents. Wind data in the Terra
Nova area has been collected from offshore drilling platforms since 1972, and from
observations from passing ships dating back for over 100 years. A strong annual cycle
is evident in both wind direction and speed. In winter, spring and fall, the dominant
winds are from the westerly quadrant, while in summer the dominant wind direction is
the southwesterly quadrant (Figure 3.1-11). Wind speeds are much lower in summer
compared to winter. Winds of gale force or greater (greater than 61 km/h) are
observed in 22 percent of the January observations, 11 percent of the October
observations, 9 percent of the April observations and only 3 percent of the July
observations.
The average monthly wind speeds in the Terra Nova area and at St. John's are greatest
in the fall and winter and lowest in the summer (Figure 3.1-12). Terra Nova monthly
mean wind speeds are higher than those measured at St. John's in all months. The
overall annual mean wind speed in the Terra Nova area is 35 km/h as compared to
24 km/h at St. John's. The higher winds at Terra Nova arise, in part, because
measurements are taken at higher levels above the surface (typically 80 m above sea
95032-0-EI-GM-00003.0, Rev.0
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level from drilling rigs and 20 m above sea level from passing ships as compared to the
standard 10 m measurement height at the St. John's weather station). When allowances
are made for comparing the onshore and offshore winds at a common measurement
elevation, the winds at the offshore Terra Nova location are still larger than those
onshore, although the difference is reduced.
Winds vary over distances that are small (a few to several kilometres) relative to the
scale size of the passing storms generally associated with strong winds. This variability
in the winds, called mesoscale variability, has been studied over the northern Grand
Banks in the recent CASP II project (discussed in more general terms in Section 3.1.3).
Strong lateral variations were observed in the wind fields over the ocean, and some of
the wind gradients were associated with changes in surface conditions such as the
presence of ice edges (Smith and MacPherson, 1996). Improved understanding of the
mesoscale variability within the surface wind field, from CASP II and other studies, is
leading to ongoing improvements in high spatial resolution of wind fields from
operational weather forecasting services (Mailhot et al., 1995) These improvements
are particularly important for forecasting of ocean waves generated by intense storm
systems. Ocean wave models, as discussed in Section 3.2.8, require inputs adequate to
resolve fronts and rapidly evolving jet streak features (Graber et al., 1995).
3.1.5
Severe Conditions
Winds
The maximum hourly wind speeds (as measured from a one-minute average at hourly
intervals at 80 m elevation) are also higher at Terra Nova than at St. John's with the
largest value at both locations being measured in February (145 km/h at Terra NovaHibernia and 140 km/h at St. John's) (Figure 3.1-13) . Even larger winds have been
reported from ship observations dating back to 1856 in the Terra-Nova area, with the
largest value of 175 km/h being reported in January. The ship-based observations,
especially those from long ago, are less reliable.
The estimated extreme values of wind speed in the Terra Nova area for various
recurrence intervals and at the 80 m level elevation are given in Table 3.1-1
(Seaconsult, 1988). The results for the 10-year and 25-year recurrence intervals for
one-minute means agree reasonably well with the observed maximum winds in the
Terra Nova/Hibernia area (maximum measured wind speed of 145 km/h over an 11year period). Computation of the vertical wind profiles and wind gust values make use
of the standard Det Norske Veritas (1977) tabulated values. The corresponding
extremal value results for the standard 10 m level are (for various return periods): 91
km/h (1 year), 102 km/h (10 years), 106 km/h (25 years), 109 km/h (50 years) and 113
km/h (100 years) for the 1 hour mean measurement values. The expected 100-year
return period values at the standard 10 m elevation for mean gusts (at various
95032-0-EI-GM-00003.0, Rev.0
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durations) are: 119 km/h (10 minute mean values), 133 km/h (1 minute means), 143
km/h (15 second means) and 150 km/h (3 second means). The Det Norske Veritas
(1977) gust factors, as applied in the Seaconsult (1988) analyses reported here, appear
to be generally consistent with more recent studies of over-water gust factors of Smith
and Chandler (1987) derived from extended wind turbulence measurements collected
off the coast of Nova Scotia. More recently, Brown and Swail (1991) have evaluated
different models of gust factors using extensive over-water data sets collected at
various locations, including those of Smith and Chandler (1987).
Table 3.1-1
Expected Extreme Wind Speeds at Terra Nova (km/h)
Recurrence
Interval
(a)
1
10
25
50
100
1-Hour
Mean
10-Minute
Mean
1-Minute
Mean
15-Second
Gust
3-Second
Gust
124
139
144
148
154
126
141
146
150
156
135
152
157
161
168
143
159
167
170
176
148
167
172
178
183
Visibility
The waters off the Avalon Peninsula and the Grand Banks are noted for frequent fog.
Fog develops when warm, humid air from the south contacts the cold, sometimes
ice-infested waters influenced by the cold Labrador Current. Fog occurs in all seasons,
but most frequently in spring and summer, when the air temperatures are warming after
winter (typically 5 to 15°C, while the sea surface temperatures remain near 0°C). The
fogs are often accompanied by moderate to strong winds. In other seasons and at other
places, fog disperses under strong winds, but here the fog is sufficiently dense and
widespread that winds have little clearing effect (Phillips, 1990). The mean number of
days with fog at St. John's (Figure 3.1-14) are at a pronounced maximum from April to
July.
The monthly frequencies of various visibilities are shown in Figures 3.1-15 and 3.1-16
for ship data and for drilling platform data, respectively. Ship data are taken in the
lower 10 m of the atmosphere, while the drilling rig data are taken at 20 to 30 m
elevation above the sea. Fog occurs frequently from May to July.
95032-0-EI-GM-00003.0, Rev.0
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In July, the foggiest month, visibility is reduced to less than 1 km 52 percent of the
time. By contrast, from September through March, visibility is reduced to less than 1
km 7 to 15 percent of the time. In the spring and summer fog is thick on the Grand
Banks, and most fog severely restricts visibility (Seaconsult, 1988).
The persistence of low visibility events, derived from only the drilling-rig data from
1972 to 1985, also is seasonal. Severely restricted visibilities (< 0.9 km) lasted longer
than 48 hours only 2.2 percent in January and 13.3 percent in July, the foggiest month.
In July, 4.7 percent of the events exceeded 96 hours in duration.
Ceiling Height
Ceiling height, the height of the lowest cloud layer when cloud cover is more than one
half of the sky, is also an important meteorological variable affecting aircraft
movements to and from offshore drilling platforms. The seasonal pattern of low ceiling
occurrence (Figure 3.1-17) is similar to that of restricted visibility.
The lowest ceiling class (0 to 49 m) occurs 53.1 percent in July (Tables 3.1-2 and 3.13) based on rig data and 50.2 percent, based on ship data. In contrast, in winter
(October to March) the lowest ceiling classes occur routinely less than 20 percent of
the time in both rig and ship analyses. Duration or persistence statistics for ceiling are
very similar to those of restricted visibility (Seaconsult, 1988).
"Flying weather" statistics can be derived from a combination of limited visibility and
limited ceiling statistics. The mean monthly occurrences of the two categories "severe"
and "restricted" flying weather are shown in Figure 3.1-18. The effect of the fog season
on flight operations is clearly evident in the severe (i.e., most restrictive) category. In
July, severe flying weather occurs more than 50 percent of the time while from
September to January it occurs less that 17 percent of the time. In February to June and
August, severe weather occurs at intermediate levels of 21 to 40 percent.
Thunderstorms
Thunderstorms develop under unstable atmospheric conditions, and are caused by
heating of the air column by the underlying surface. Thunderstorms are not common,
especially in fall, winter and spring because of the generally cool regional climate. On
average, fewer than one thunderstorm per month occurs at St. John's, except for July
and August, when one thunderstorm per month occurs (Environment Canada, 1993).
The occurrence of thunderstorms over the Northeast Grand Banks is even lower
(Mobil, 1985).
95032-0-EI-GM-00003.0, Rev.0
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14.7
21.2
19.1
27.2
31.4
35.7
50.2
22.8
12.9
8.6
13.6
13.3
0-49
95032-0-EI-GM-00003.0, Rev.0
Note: Data from 1972 to 1985.
January
February
March
April
May
June
July
August
September
October
November
December
Month
0.4
0.4
0.4
0.9
1.8
2.2
1.5
1.4
1.7
1.2
0.9
0.9
50-99
4.4
5.7
4.8
4.2
7.4
9.0
6.0
8.0
8.2
5.4
4.7
4.2
100199
7.5
8.1
7.9
6.7
7.6
7.3
4.0
8.6
7.5
8.2
7.4
6.6
200299
35.4
32.7
24.3
17.9
14.2
13.1
9.2
17.5
17.9
26.8
32.5
39.5
300-599
13.9
9.1
12.3
8.6
5.8
4.7
3.3
6.6
7.5
14.3
12.3
12.1
600999
0.6
1.2
1.5
1.1
0.9
0.8
0.9
0.8
1.0
1.3
0.6
0.8
10001499
Ceiling Height (m)
1.5
0.6
1.1
1.2
1.1
0.9
0.8
0.7
0.9
0.9
0.8
0.8
15001999
2.5
3.2
3.5
3.7
4.1
2.4
2.4
2.4
3.5
3.6
1.6
2.0
20002499
Occurrence of Restricted Ceiling Height Based on Rig Data
Table 3.1-2
19.1
17.8
25.2
28.5
25.7
23.9
21.8
31.2
38.9
29.6
25.6
19.7
>2500
4565
2486
2711
3259
4216
4205
4572
4714
4543
4538
5049
5441
3-31
Number of
Observations
10.7
10.4
14.0
20.5
30.6
40.0
53.1
28.4
16.1
15.5
13.8
14.6
January
February
March
April
May
June
July
August
September
October
November
December
Note: Data from 1886 to 1979.
0-49
Month
0.9
0.8
0.7
0.7
1.0
0.7
1.5
0.7
0.8
1.4
0.8
0.4
50-99
4.9
3.7
4.9
3.5
4.2
3.0
2.4
3.1
4.0
4.7
5.0
3.5
100199
15.9
15.6
10.3
9.9
9.6
6.6
5.2
7.3
9.3
10.6
12.4
13.9
200299
27.0
26.7
21.8
15.8
12.9
10.4
9.4
13.2
13.7
18.9
21.7
22.0
300-599
10.9
11.9
12.4
10.0
8.5
6.9
5.9
11.6
11.6
9.9
11.8
12.4
600999
3.7
2.7
3.8
2.5
2.8
3.1
0.9
1.9
2.0
2.1
2.7
4.6
10001499
Ceiling Height (m)
1.5
1.1
1.1
1.2
1.3
0.6
0.3
0.8
0.4
0.4
0.8
1.3
15001999
0.9
0.5
0.4
0.8
1.1
0.6
0.4
1.0
0.8
1.0
1.0
0.5
20002499
Occurrence of Restricted Ceiling Height Based on Ship Data
Table 3.1-3
24.6
26.6
30.7
25.1
28.1
28.2
20.9
31.9
41.2
35.4
29.9
26.7
>2500
1053
1045
1007
1215
1601
1066
1099
1177
1167
1103
1072
1216
Number of
Observations
Even in July and August, the months in which thunderstorms are most likely to occur,
only four were observed at Hibernia during July for the five-year period 1979 to 1983,
and only two were observed during August.
Freezing Precipitation
Freezing precipitation occurs when rain or drizzle falls through a layer of cold air,
causing it to freeze on impact with a surface. Freezing precipitation is common in
winters in Newfoundland. At St. John's, freezing precipitation occurs most often in
March, but is nearly as likely to occur from January to April (Table 3.1-4). In the Terra
Nova-Hibernia region, freezing precipitation is also most likely to occur in the winter
months, December to March. However, the historical data (1868 to 1981) derived
from ship observations indicate the frequency of freezing precipitation is only 0.2 to 0.4
percent for December to March, considerably lower than the corresponding values for
St. John's of 4 to 5 percent (Mobil, 1985).
Superstructure and Spray Icing
Offshore operations off Newfoundland can be disrupted by accumulations of ice on
superstructures of vessels and production platforms. Such accumulations interfere with
equipment functioning and pose safety hazards to personnel through potential falls and,
in the case of extreme accumulations, by affecting vessel stability.
Offshore icing can occur in two ways. In the first, condensation freezes on the
superstructures being cooled by cold air moving seaward over marine areas.
Accumulations are strongly dependent on air temperature and wind speed, which
control cooling rates, and on other factors such as the diameter of the cooled surfaces
(Figure 3.1-19). The second way for offshore icing to occur is by instantaneous
freezing of sea spray on superstructures. Such ice accumulations depend on sea state
and height above mean sea level as well as wind speed and air temperature. Early
documentation of icing characteristics in Canadian waters was provided by Brown and
Agnew (1985) and Brown and Mitten (1988).
Quantitative estimates of extreme superstructure ice accumulations have been obtained
(Seaconsult, 1988) using two different models (Lozowski et al., 1979 and Makkonen,
1984) in conjunction with a 30-year time series of meteorological data recorded at St.
John's Torbay Airport. These models, which differ in their treatment of alternative
glaze- and rime-ice deposition forms, produced significantly different estimates of
accumulated thicknesses on a common 5 cm cylinder for standard return periods (Table
3.1-5).
95032-0-EI-GM-00003.0, Rev.0
Table 3.1-4
Occurrence of Freezing Precipitation
Month
Jan
Feb
Mar
7
7
9
3.8
5.1
5
0.4
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
8
1
0
0
0
0
0
1
4
4.9
4.6
0.1
0
0
0
0
0
0.2
0.1
22
17
0
0
0
0
0
0
0
1
2
0.4
0.2
0.1
0
0
0
0
0
0
0
0.2
St. John's, Newfoundland
Days per month
with freezing
precip.1
Percentage of
hourly obs. with
freezing
precipitation 2
Terra Nova-Hibernia
No. of days with
freezing precip.
observed3
Percentage of
synoptic obs. with
freezing
precipitation 4
Sources:
Climate Normals, 1961-1990 (Environment Canada, 1993).
Transport Canada, 1953-1976 Hourly Data Summary (Mobil, 1985).
Wellsite Data, 1979-1983 (Mobil, 1985).
Environment Canada, 1868-1981 (Mobil, 1985).
Table 3.1-5
Computed Extreme Values for Superstructure Icing at Terra Nova
Return Period TR
(a)
10
25
50
100
Glaze Ice Thickness
(Lozowski's model)
(mm)
56
72
84
95
Combined Glaze of Rime Ice
Thickness (Makkonen's model)
(mm)
72
113
141
169
Notes:
1. Values apply to a 5 cm diame ter cylinder.
2. Ice thickness is interpreted as the maximum radial dimension accreted onto the cylinder.
3.
Ice accretion is generally not symmetrical about the cylinder. This must be taken into account when
loads are calculated.
95032-0-EI-GM-00003.0, Rev.0
Unfortunately, neither of the models has been verified in any detail. Additional
uncertainties were introduced by the use of terrestrial meteorological data to provide
an adequate duration of data for meaningful estimates of return periods. Use of actual
marine meteorological data would, largely because of the warmer air temperatures,
produce lower accumulation estimates. Data are available (T. Yip, pers. comm.) which
would allow extension of estimated accumulation rates to other curvatures and
configurations.
Runs of an early spray ice model developed by Stallabrass (1979, 1980), using seven
years of hydrometeorlogical data recorded on the Grand Banks estimated spray ice
accumulations of 316 mm and 514 mm, respectively for 10- and 100-year return
periods (Seaconsult, 1988). These estimates must be regarded as, at best, upper limits
of corresponding extreme accumulation values, as the model tends to predict icing
events that were not observed.
All available icing models have been evaluated (Brown and Horjen, 1989) for their
ability to produce accumulation rates comparable to those observed (Brown and
Roebber, 1985; Roebber and Mitten, 1987). Model refinements needed for reliable
design load estimates were identified. Many of these refinements have been
implemented in an enhanced version of the RIGICE superstructure icing model
(Compusult, 1994), but its application to the offshore Newfoundland region is still
required.
95032-0-EI-GM-00003.0, Rev.0
3.2
Oceanic Environment
3.2.1
Database
The oceanographic database for the study area consists of large quantities of ship-based
measurements on water properties (temperature, salinity, dissolved oxygen and
nutrients). The data collection started in the 19th century, with the first systematic
oceanographic studies of the Grand Banks begun in 1913 by Matthews (1914). Coastal
water level data extend back to the early part of this century. The databases on direct
measurements of ocean currents, which are of key importance to the Terra Nova
Development, are more limited in duration, as routine current meter and drifter
trajectory data collection only became feasible in the early 1970s. Circulation estimates
derived from water property data using the geostrophic method extend back to the
1920s (see Petrie and Anderson, 1983 for a review of the early ocean current data sets
off the Newfoundland Shelf).
The key oceanographic databases are maintained by three Fisheries and Oceans
agencies: Marine Environmental Data Services (MEDS) Branch in Ottawa, the
Bedford Institute of Oceanography (BIO) in Dartmouth and the Northwest Atlantic
Fisheries Centre (NAFC) in St. John's. Other important data sets are held by the
Northwest Atlantic Fisheries Organization (NAFO) in Dartmouth and the departments
of oceanography of both Dalhousie and Memorial universities.
Wave climate data are archived by MEDS. Scientific studies of wave climate are the
responsibility of the AES of Environment Canada. As well, groups at BIO and the
Canada Centre for Remote Sensing (CCRS), in collaboration with AES, are involved
in scientific research on the development of improved wave monitoring and forecast
systems.
Since the early 1980s, oceanographic research has focussed on new areas, including
studies of the ice and ocean dynamics, and the use of numerical modelling for
oceanographic research. Considerable funding has been provided by the Panel on
Energy Research and Development (PERD) of the Government of Canada. Major
programs supported, in part, by PERD funding include:
Labrador Ice Margin Experiment. The Labrador Ice Margin Experiment (LIMEX)
was an ice and oceanographic study of the southern marginal ice zone of the Labrador
pack ice at the time of its maximum advance in early spring (Tang and Manore, 1992).
A pilot study was carried out in March 1987, followed by the main multi-disciplinary
program conducted in March 1989. A followup study was conducted in March and
April 1990.
Labrador Sea Extreme Waves Experiment. The Labrador Sea Extreme Waves
Experiment (LEWEX) was an international effort to assess methods of measuring and
modelling the directional properties of wind-generated ocean waves, especially their
95032-0-EI-GM-00003.0, Rev.0
evolution in the presence of rapidly changing wind directions (Beal, 1991). The main
data-gathering period was in March 1987 off the northeast Newfoundland Shelf,
northeast of the Grand Banks. Aircraft observations were carried out in conjunction
with the LIMEX 1987 pilot study.
Grand Banks ERS-1 SAR Validation Experiment. The Grand Banks ERS-1 SAR
Validation Experiment was an international research study to obtain a calibrated set of
wave measurements in a high sea-state environment. This study:
-
Assessed the accuracy of sensors aboard the European Space Agencies' ERS-1
satellite
-
Investigated coupling of wind and wave fields (Dobson and Vachon, 1994)
An extensive array of satellite-, aircraft-, buoy- and ship-based data were collected in
November 1991 on the Grand Banks.
Canadian Atlantic Storms Program II. The Canadian Atlantic Storms Program II
(CASP) was an interdisciplinary Canadian project to study of the mature stages of
explosive cyclogenesis in East Coast winter storms. Its purpose was to investigate the
storms' influence on the circulation and sea-ice properties of the Newfoundland
Continental Shelf and Grand Banks (Smith et al., 1994). Extensive meteorological,
oceanographic and sea-ice data were collected from February to April 1992 over the
northeastern Newfoundland shelf and northern and eastern portions of the Grand
Banks. Results from the meteorological component of CASP II are given in Section
3.1.5.
More recently, oceanographic studies have been important components of major
fisheries research studies of the troubled fisheries of the Canadian East Coast waters.
The two major programs are:
Northern Cod Science Program. The Northern Cod Science Program (NCSP) was
established in 1990 and operated from NAFC to:
-
Improve understanding of cod ecosystem dynamics on the Labrador and
Newfoundland shelves
-
Identify environmental influences on fisheries
Major initiatives include data collection, modelling and analysis of historical data. The
results of these oceanographic studies are now being published.
Ocean Production Enhancement Network. The Ocean Production Enhancement
Network (OPEN) was funded under Canada's Networks of Centres of Excellence
program. OPEN's mission was to investigate the processes controlling the survival,
95032-0-EI-GM-00003.0, Rev.0
growth, reproduction and distribution of fish and shellfish, specifically Atlantic Cod and
sea scallops. A total of 38 projects, organized into nine modules, were funded under
OPEN from 1990 to 1995 (Ocean Production Enhancement Network, 1995). The
oceanographic projects of direct interest to this EIS include studies of:
-
The circulation and density field on the Newfoundland-Labrador shelf and
slope
-
Particle trajectories and ocean diffusion
Advances in remote-sensing measurement have been incorporated into many of the
major studies. Over the past ten years, remote-sensing techniques have become better
at and increasingly available for measuring oceanographic, sea ice and meterological
(wind) variables. Several remote-sensing platforms are currently operational, and
others will be put into place in the near future, including systems operating in the
visible, infra-red and microwave wavelengths. Measurements derived from these
sensors are available in near real-time from:
-
Public and private sector archives dating to the early 1970s in the case of the
optical visible and infrared wavelengths
-
Public and private sector archives dating to 1992 in the case of microwave
systems
Optical systems repeat coverage of a given area at an interval of less than 24 hours,
subject to atmospheric conditions, while the all-weather microwave systems repeat
coverage at intervals in excess of one day, depending on the observation mode.
Remote-sensing data sets have made important contributions to knowledge of the
oceanographic environment. These same remote-sensing techniques will be evaluated
for application to the environmental monitoring and forecast systems for the Terra
Nova Development. The all-weather microwave systems are particularly suited to
weather and wave forecasting. They contribute to ice management through provision
of near real-time data and in allowing updates of ice and wave climate from archival
data. Table 3.2-1 shows a summary of the capabilities of the satellite-based remote
sensors.
Also available are aerial sensors, including:
-
Airborne spectrophotometers, capable of intertidal and nearshore habitat
mapping
-
Airborne ultraviolet and infrared sensors for use in tracking oil and chemical
slicks
95032-0-EI-GM-00003.0, Rev.0
Table 3.2-1
Satellite-Based Remote Sensors
Sensor
Date of First Data
Availability
Type
Relevant Oceanographic
Parameters Measured
NOAA AVHRR
1974
Optical imager
Sea surface temperature
Sea ice
Cloud cover
Ocean current location
Sea WIFS
operational 1996
Optical imager
Ocean colour (productivity and
turbidity)
Sea ice
Cloud cover
RadarSat SAR
operational 1996
Microwave imager
Sea ice
Wave spectra
Surface slicks
ERS-1 SAR
1992
Microwave imager
Sea ice
Wave spectra
Slicks and fronts
ERS-1
Scatterometer
1992
Microwave
Wind speed and direction type
ERS-1 Alimeter
1992
Microwave
Significant wave height
Ocean currents
Wind speed
Topex/Poseidon
Altimeter
1994
Microwave
Significant wave height
Ocean currents
Wind speed
Finally, remote-sensing advances have also been realized with acoustic instrumentation
used within the ocean itself. Of particular significance is the Acoustic Doppler CurrentProfiling (ADCP) technology, by which moving vessels can measure and record in real
time ocean current profiles throughout the water column. ADCP technology can also
be used in bottom-mounted units for continuously recording currents from near-bottom
to near-surface levels for weeks and months. This provides the equivalent of an
extensive chain of current meters.
3.2.2
Bathymetry
Main Bathymetric Features
The major bathymetric feature of the southern Newfoundland shelf is the Grand Banks
(Figure 3.2-1). It consists of four banks (St. Pierre, Green, Whale and Central Grand)
95032-0-EI-GM-00003.0, Rev.0
separated by three channels (Halibut, Haddock and Avalon). The Grand Banks extends
almost 500 km offshore and covers an area of about 270 000 km 2. Each of the banks is
relatively flat with typical water depths of 100 m or less. Farther east, the Flemish Pass
separates the Grand Banks from the Flemish Cap, another major bank-like feature with
water depths as shallow as 140 m.
Terra Nova is located on the northeast sector of the Central Grand Bank in
approximately 95 m water depth. The bottom relief in the area is relatively featureless
(Figure 3.2-2), although steep slopes occur to the north and the east at the edge of the
Central Grand Bank.
Effect of Bathymetry on Oceanographic Parameters
The Grand Banks-Flemish Cap bathymetric features exert a major influence on the
regional oceanic circulation. A major characteristic of ocean currents along the eastern
margin of North America is their tendency to follow local and regional underwater
topographic features (Smith and Schwing, 1991).
The major circulation feature of the area, the offshore branch of the Labrador Current,
is trapped over the Continental Slope at the edge of the banks (see Section 3.2.4 for
more information on ocean circulation). In the Flemish Pass area, the slope divides into
two parts, a southward component passing through the Flemish Pass and an eastward
part rounding the Flemish Cap.
The Labrador Current splits in a similar manner. The inner branch of the Labrador
Current, found on the shoreward portion of the Continental Shelf, is also steered by
local topographic features, and is concentrated by the bottom troughs which define the
Avalon and Haddock channels. Over the comparatively flat and featureless banks, the
ocean circulation is generally weak and variable.
3.2.3
Water Masses
Temperature and salinity are the most important physical properties of seawater, and
together determine its density. The distribution of these properties is closely linked to:
-
Ocean circulation and mixing
Sea-ice distributions
Air-sea interaction processes
Marine biological distributions
Database
Temperature and salinity data have been collected for many years in the study area, as
far back as the early part of this century. Up until the late 1970s, temperature and
salinity were measured in bottle samples collected at discrete depths through the water
95032-0-EI-GM-00003.0, Rev.0
column. Thermometers mounted to the bottles provided the temperature data while
ship- or land-based salinometers were used to measure salinity from the water samples
collected in the bottles. Since the late 1970s, highly accurate, continuous measurement
devices, known as conductivity-temperature-depth (CTD) profilers have become
routinely used in oceanographic studies.
Using bottle data collected from 1910 to 1982 inclusive, Drinkwater and Trites (1986)
analyzed temperature and salinity distributions in the Grand Banks area by discrete
subregions. They used over 17 500 sets of profile data, each consisting on average of
11 depths per station. The key data sets used, locations of which are shown in Figure
3.2-3, were:
1.
NAFO standard oceanographic lines off Bonavista and the Grand Banks (or
the Flemish Cap), which have been occupied routinely since the early 1930s
2.
Station 27, the first hydrographic monitoring station on the standard Grand
Banks line (from St. John's to Flemish Cap), established in 1946. This station
has been occupied regularly, two to four times each month, mainly by
oceanographic and fisheries research vessels.
There are more data collected over a longer time span at this one station than
anywhere else in the Grand Banks area (approximately 1360 profiles in total to
1993; Colbourne and Fitzpatrick, 1994).
3.
The immediate vicinity of Terra Nova, where available temperature and salinity
data sets were assembled using the national data archive (data from 1900 to
1987; MEDS, Ottawa) and the measurements made from drilling rigs 1983 to
1985 (Seaconsult, 1988)
Water Mass Types, Origin and Distribution
The water in the Grand Banks area is largely a mixture of:
-
Cold, comparatively fresh water originating on the Continental Shelf off
Labrador and further north, and carried into the area by the Labrador Current
-
The Slope Water found immediately to the south and east of the Grand Banks
area (Figure 3.2-4)
95032-0-EI-GM-00003.0, Rev.0
The actual range of observed values in the study area reflects the mixture of these two
water masses, as well as the effects of local exchanges of the ocean with the
atmosphere and the formation and melt cycle of sea ice (Prinsenberg and Ingram,
1991).
Temperatures and salinities at the Terra Nova area are frequently influenced by
Labrador Current water through lateral mixing with, and intrusions from the offshore
branch of the Labrador Current. The Labrador Current is found over the inner portion
of the Continental Slope located within 60 km of the Terra Nova site (Section 3.2.4). A
dominant feature of the vertical temperature structure of the east coast of
Newfoundland shelf is the cold intermediate layer (CIL) (Petrie et al., 1988). The layer
is formed in winter through heat losses at the surface to the atmosphere, followed by
rejection of salt through the formation of sea ice at the surface. In spring and summer,
the upper layer becomes stratified because of warming and melt of the sea ice; this
stratification reduces transfer of heat to the deeper waters. As a result, the CIL is
present over the Continental Shelf through much of the summer with temperatures
ranging from 0.0 to -1.8°C (the freezing point of seawater). The CIL is located
between the warm upper layer and the warmer Slope Water near the bottom and at the
shelf edge.
The regional distribution of water properties over the full study area is presented for
early May and July from all available data sets (Figure 3.2-5 after Colbourne, 1994;
Colbourne and Narayanan, 1994) to 1994 for the surface and at 75 m depth (near
bottom on much of the Grand Banks). The warmer, high-salinity Slope Water can be
seen to the south and east of the Grand Banks at both the surface and at 75 m depth.
Large horizontal gradients mark the outer branch of the Labrador Current, which
separates the Slope Water from the waters on the Banks and northeast Shelf, and
which carries colder, less saline water from the north.
The large gradients, both horizontal and vertical, that occur at the eastern edge of the
Grand Banks can be seen in a routine oceanographic transect of the Grand Banks
(Flemish Cap) standard line of May 7 to 8, 1994 (Figure 3.2-6). Over the broad
expanse of the Grand Banks, the water column is characterized by cold water (less than
0.5°C) with nearly vertically uniform salinity, and hence density. Over the steep, inner
portion of the Continental Slope in water depths of 200 m or more, comparatively
saline and warmer water of Slope Water influence is present at depth. This water also
occurs much nearer the surface farther offshore as indicated by the steeply sloping
contours of temperature and salinity. The strong gradients in temperature and salinity in
waters deeper than 200 m mark the core of the offshore branch of the Labrador
Current.
Even though warmer, more saline Slope Water is present within 150 km of the Terra
Nova site, this water is confined to the Continental Slope areas by the strong offshore
branch of the Labrador Current.
95032-0-EI-GM-00003.0, Rev.0
The Slope Water only indirectly affects the Terra Nova site through mixing within the
Labrador Current; it does not itself occur at the Terra Nova site.
Seasonal Variations
Seasonal variations of temperature, salinity and density (sigma-t) for the inner portion
of the Newfoundland Shelf are well represented in monthly means computed from the
extended data sets (1946 to 1993) collected at Station 27, located about 8 km east of
St. John's. The largest seasonal cycles (Figure 3.2.7 from Colbourne and Fitzpatrick,
1994) occur at the surface, where maximum temperatures (greater than 12°C), and
minimum salinities (31.1) and densities occur in late August. The annual minimum in
temperature (less than -1°C), and maxima in salinity (32.3) and density occur in March.
At increasing depths, the amplitude of the annual cycle decreases. Also, the annual
cycle in temperature lags behind that at the surface as depth increases. This variation of
the annual temperature cycle with depth can be explained primarily as vertical mixing of
heat input caused by accumulated heating at the surface during the spring and summer
(Petrie et al., 1991). The annual cycle in salinity and density also lags behind that at
surface with increasing depth, but Petrie et al. (1991) show this annual cycle cannot be
explained by vertical mixing alone. This is because the amplitudes in the annual cycles
are larger as one proceeds north and the annual minima occur increasingly early. For
salinity and density, southward advection of fresh, low-salinity waters, originating as
melting sea ice and river runoff, drive the annual cycle along with vertical mixing
processes.
The development of a stratified water column in spring and summer is evident in the
monthly temperature, salinity and density values at Station 27 (Figure 3.2-7). The
upper portion of the water column is most stratified in August at the time of maximum
temperatures, minimum salinities and minimum densities, with the thickness of the
upper mixed layer typically limited to depths of 15 m or less. Below the upper layer,
the CIL occupies most of the water column, as indicated by the subzero temperatures
persisting at 50 and 75 m depths through the summer months. Vertical mixing in the
fall results from increasing wind speeds that progressively deepen the upper mixed
layer to about 50 m depth by December. Through the winter, stratification throughout
the water column is low. This is because:
-
Ice formation at upstream locations further mixes the water column through
extrusion of dense salt brine into the ocean
-
There is ongoing wind-induced mixing
The seasonal variability of the waters over the central portions of the Grand Banks
(Figure 3.2-8 [for location see shaded zone in Figure 3.2-3]) reveal a similar pattern to
95032-0-EI-GM-00003.0, Rev.0
that at Station 27. Like Station 27, the annual cycle is largest at the surface and
decreases in amplitude with depth. However, the decrease in amplitude with depth is
larger, and at 75 m depth there is no significant annual cycle in either temperature or
salinity. Also, salinities are generally higher in the mid-Grand Banks region, as the
direct influence of the Labrador Current is diminished because of the greater distance
to either the inshore or offshore branches of the current.
For the Terra Nova area, the monthly mean temperatures and salinities at depths of 0
m, 20 m, 50 m and within 10 m of the bottom are shown in Tables 3.2-2 to 3.2-5.
Figure 3.2-9 shows profile plots of temperature for February, May, July and
November. Salinities are generally higher than those measured at Station 27, while the
seasonal cycle in temperature is very similar to that of Station 27. The vertical profiles
(Figure 3.2-9) show that the water column at Terra Nova is a two-layer system over
most of the year, except in winter when the water column is uniformly cold. With the
onset of spring, increased solar radiation heats the upper layer and the reduced winds
are not capable of mixing the warmed water to the bottom.
By August and September, a warm surface layer is present and the surface
temperatures are the warmest of the year. From October to December, the surface
layer erodes because of decreased surface heating and the increased vertical mixing
caused by the stronger winds.
The extended time series record (1946 to 1993) available at Station 27 can be analyzed
for interannual variability of oceanographic conditions on the East Newfoundland
Shelf. Keeley (1981) computed the temperature and salinity anomalies at this location
for the period 1946 to 1977. Colbourne et al. (1994) examined the anomalies in the
Station 27 data for the period 1970 to 1993 (Figure 3.2-10).
Interannual variations are evident throughout the full record over a wide range of time
scales from one to several years, with considerable variability at periods of three to four
years in the upper to mid-depth levels. The amplitude of interannual variations was
approximately 1°C at the surface, increasing to 3°C in mid-water column, then
decreasing to less than 1°C at depths of 100 m or more. The amplitude of interannual
variability in salinity was approximately 1 to 1.5 psu from the surface to 50 m depth,
then decreasing to levels of approximately 0.5 psu at 150 m depth.
95032-0-EI-GM-00003.0, Rev.0
Table 3.2-2
Monthly Temperature and Salinity Statistics from Historical
Bottle Data in the Terra Nova Area
Surface, 1900-1987
Temperature (°°C)
Mon
N
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
1
2
Mean
28
28
10
88
111
72
73
18
14
70
35
4
0.68
-0.36
-0.08
0.53
2.29
5.03
10.84
12.52
11.68
6.90
6.28
2.43
Min3
Max4
-0.77
-1.69
-1.61
-1.30
-0.39
2.10
5.60
10.30
7.80
4.10
2.62
0.02
STD5
95% Limits6
2.10
0.64
1.20
2.40
6.80
13.41
13.80
14.60
15.40
11.30
8.95
4.82
0.71
0.51
0.90
0.90
1.65
2.05
1.66
1.49
2.17
1.15
1.59
2.05
0.40
-0.56
-0.72
0.34
1.98
4.56
10.46
11.78
10.43
6.62
5.75
-0.83
0.95
-0.16
0.57
0.72
2.60
5.50
11.23
13.26
12.94
7.17
6.80
5.70
33.09
33.16
33.24
33.30
33.87
33.30
32.77
32.74
32.18
32.50
32.19
-
0.22
0.29
0.20
0.21
0.30
0.24
0.30
0.45
0.21
0.09
0.13
-
32.63
32.46
32.76
32.82
32.67
32.67
32.27
31.93
31.49
31.99
31.87
-
32.88
33.20
33.18
32.92
32.83
32.80
32.45
32.57
32.54
32.04
32.18
-
Salinity (ppt)
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
14
5
6
72
50
50
44
10
3
55
5
1
32.76
32.83
32.97
32.87
32.75
32.74
32.36
32.25
32.02
32.01
32.03
32.23
32.37
32.36
32.83
32.36
32.24
32.17
31.70
31.55
31.78
31.87
31.85
-
Source: Seaconsult (1988).
Notes:
1. N - number of observations. Each observation was assumed to be independent for calculating the 95% confidence
limits of the population mean.
2. Mean - sample mean.
3. Min - minimum observed value.
4. Max - maximum observed value.
5. STD - sample standard deviation
6. 95% limits - the lower and upper limits of the 95% confidence limits of the population mean. There is a 2.5% chance
the true monthly mean will lie below the smaller value and a 2.5% chance it will lie above the larger value.
95032-0-EI-GM-00003.0, Rev.0
Table 3.2-3
20 m Depth, 1900-1987
Temperature ( °C)
Mon
N1
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Mean 2
20
28
10
88
111
68
73
18
10
70
35
4
0.53
-0.46
-0.16
0.37
1.75
3.84
7.99
10.02
10.37
6.76
5.97
2.54
Min3
Max4
-0.90
-1.66
-1.67
-1.30
-0.53
1.11
2.98
5.74
6.54
3.50
2.61
0.02
STD5
95% Limits 6
1.97
0.58
1.11
2.01
4.87
7.49
11.99
13.64
14.30
11.85
8.70
4.85
0.77
0.49
0.89
0.79
1.35
1.51
2.08
1.92
2.41
1.17
1.45
2.07
0.17
-0.65
-0.80
0.21
1.50
3.49
7.51
9.07
8.65
6.48
5.49
-0.75
0.89
-0.26
0.48
0.54
2.00
4.20
8.46
10.98
12.10
7.03
6.45
5.83
33.12
33.16
33.21
33.34
33.29
33.12
32.12
32.76
32.21
32.43
32.21
-
0.23
0.29
0.18
0.20
0.26
0.18
0.28
0.29
0.13
0.07
0.11
-
32.67
32.47
32.77
32.83
32.70
32.70
32.42
32.25
31.76
32.01
31.92
-
33.00
33.20
33.16
32.93
32.84
32.80
32.58
32.66
32.40
32.05
32.18
-
Salinity (ppt)
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
10
5
6
72
50
46
44
10
3
55
5
1
32.84
32.83
32.96
32.88
32.77
32.75
32.50
32.45
32.08
32.03
32.05
32.23
32.54
32.36
32.81
32.37
32.09
32.28
31.89
31.92
31.95
31.91
31.92
-
Notes:
1. N - number of observations. Each observation was assumed to be independent for calculating the 95% confidence limits of the
population mean.
5. STD - sample standard deviation.
6. 95% limits - the lower and upper limits of the 95% confidence limits of the population mean. There is a 2.5% chance the true
monthly mean will lie below the smaller value and a 2.5% chance it will lie above the larger value.
95032-0-EI-GM-00003.0, Rev.0
Table 3.2-4
50 m Depth, 1900-1987
Temperature ( °C)
Mon
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
N1
Mean 2
20
28
10
88
113
69
73
18
10
70
35
4
0.35
-0.50
-0.22
-0.03
0.35
0.86
0.72
0.65
0.73
2.44
1.87
2.20
Min3
Max4
-0.93
-1.55
-1.66
-1.40
-1.29
-1.50
-1.40
-0.95
-0.70
-1.07
-1.00
0.01
STD5
95% Limits 6
1.30
0.49
0.99
1.50
2.70
3.50
3.90
2.40
3.46
5.58
5.59
4.80
0.63
0.47
0.88
0.71
0.93
1.02
1.15
0.93
1.21
1.58
1.79
2.13
0.05
-0.68
-0.85
-0.17
0.18
0.61
0.46
0.19
-0.14
2.07
1.27
-1.19
0.64
-0.32
0.42
0.12
0.52
1.10
0.99
1.11
1.60
2.81
2.46
5.59
33.14
33.17
33.22
33.36
33.35
33.32
33.49
33.19
33.15
33.24
33.10
-
.20
.27
.19
.20
.21
.20
.16
.19
.18
.22
.31
-
32.73
32.54
32.78
32.88
32.82
32.85
32.86
32.78
32.54
32.40
32.36
-
33.02
33.20
33.17
32.97
32.94
32.96
32.96
33.05
33.42
32.52
33.14
-
Salinity (ppt)
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
10
5
6
72
51
47
44
10
3
55
5
1
32.88
32.87
32.97
32.92
32.88
32.91
32.91
32.92
32.98
32.46
32.75
32.23
32.58
32.45
32.82
32.39
32.36
32.57
32.56
32.65
32.79
32.13
32.34
-
Notes:
population mean.
95032-0-EI-GM-00003.0, Rev.0
Table 3.2-5
Within 10 m of Bottom, 1900-1987
Temperature ( °C)
Mon
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
N1
Mean 2
18
27
7
39
79
39
66
14
6
20
26
2
0.04
-0.61
-0.27
-0.44
-0.54
-0.23
-0.30
-0.49
-0.25
-0.70
-0.41
-0.45
Min3
Max4
-1.20
-1.56
-1.68
-1.40
-1.42
-1.60
-1.60
-1.35
-0.98
-1.30
-1.19
-1.00
STD5
95% Limits 6
0.90
0.34
0.60
0.74
0.80
2.00
3.00
1.00
0.60
1.10
0.60
0.10
0.54
0.35
0.78
0.54
0.55
0.69
0.77
0.70
0.67
0.64
0.51
0.78
-0.23
-0.75
-0.99
-0.61
-0.66
-0.44
-0.48
-0.89
-0.95
-1.00
-0.62
-1.70
0.30
-0.47
0.45
-0.26
-0.42
-0.01
-0.11
-0.09
0.46
-0.40
-0.21
6.54
33.19
33.19
33.19
33.68
33.62
33.58
34.86
33.49
33.14
33.30
-
0.14
0.23
0.18
0.26
0.28
0.19
0.33
0.22
0.09
0.12
-
32.95
32.62
32.55
33.00
32.95
33.04
33.10
32.89
32.92
32.85
-
33.18
33.20
33.43
33.21
33.18
33.21
33.31
33.26
33.11
33.46
-
Salinity (ppt)
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
8
5
3
24
25
21
37
8
6
3
-
33.06
32.91
32.99
33.10
33.07
33.13
33.20
33.08
33.02
33.16
-
32.81
32.57
32.86
32.78
32.24
32.71
32.84
32.87
32.95
33.08
-
Notes:
population mean.
95032-0-EI-GM-00003.0, Rev.0
From 1970 to 1993, there were three major cold periods at all standard depths: in the
early 1970s, mid-1980s and early 1990s (Figure 3.2-10). These cold periods are all
associated with severe meterological and sea-ice conditions on the Labrador and
Newfoundland shelfs during these same periods. For all three periods, the cold
anomalies at the bottom were established first and lasted the longest. The largest
anomalies occurred in the upper 100 m in mid-1991, reaching peak values of -4.0°C. In
the deeper waters, the early 1990s peak was less pronounced, but negative temperature
anomalies persisted from 1983 to 1993 with only a few very minor positive anomalies
interrupting nearly uniform negative values.
The anomalies in salinity follow a generally similar pattern with negative anomalies
occurring in the cold periods mentioned above. However, the events appear to be of
shorter duration and less consistent with depth. The cooling events experienced since
the early 1970s are evident in the yearly time series of the CIL column, with subzero
temperatures during summer (Figure 3.2-11).
The time series of the CIL cross-sectional areas and minimum temperatures for the
Bonavista and Grand Banks (Flemish Cap) standard transects since 1950 reveal four
major cold periods. The minimum temperatures and maximum areas occur in the early
1950s, early to mid-1970s, mid-1980s and early 1990s (Colbourne et al., 1994;
Colbourne, 1995). The CIL parameters are consistent with a gradual warming trend
starting in the early 1950s and attaining greatest warming in the mid-1960s. This period
was followed by the cooler conditions caused by the three major cold periods (with
peaks in 1972, 1984 and 1991). Overall, the northern Grand Banks area has
experienced unusually low water temperatures during spring and summer from 1972 to
1974, and then another much longer period of low water temperatures from 1983 to
1994.
3.2.4
Ocean Currents
Ocean currents are inherently highly variable, making measurement difficult.
Ocean currents are of interest over two areas:
1.
The portion of the northeast Grand Bank encompassing the Terra Nova and
Hibernia oilfields
2.
The much larger study area encompassing the entire eastern Newfoundland
Shelf region, from the northern margins of the Grand Banks southward
Over the larger area of interest for this project, the quantity of direct observations of
ocean currents remains limited, although major data-collection programs have been
carried out over the past 15 years.
95032-0-EI-GM-00003.0, Rev.0
Estimation of Ocean Currents from Density Profile Data
The earliest type of ocean current estimates were derived by indirect means, using the
geostrophic method to derive the velocity field from the internal pressure and density
distribution within the ocean (Smith, 1937; Petrie and Anderson, 1983). The internal
pressure data were determined from vertical profiles of temperature and salinity, and
hence density. This approach, which accounted for virtually all estimates of regional
ocean circulation until the early 1970s, has significant limitations for the comparatively
shallow shelf waters.
Moored Current Meter Data
With the advent of internally recording current meters in the late 1960s, followed by
satellite-tracked drifting buoys in the late 1970s, oceanographers acquired the
capability to obtain many data sets of direct ocean current observations spanning
extended periods (greater than one month). The most recent technological advance, the
bottom-mounted acoustic dopplier current profiler (ADCP) provides profiles of the
ocean currents throughout nearly all the water column. Only a few such data sets,
offering high vertical resolution, presently exist (Tang and Belliveau, 1994; DeTracey
et al., 1995).
For the immediate area around Terra Nova, extensive sets of moored current meter
data sets, each spanning several weeks of continuous data, have been collected, mostly
in support of offshore drilling operations. These moored current meter data sets are
summarized in Table 3.2-6.
Table 3.2-6
Summary of Moored Current Meter Data Sets
Available for Terra Nova and the Immediate Vicinity
Near Surface
(approx. 20 m)
Mid-Depth
(approx. 40-50 m)
Near Bottom
(> 60 m)
Period
Jan. 1980 - Feb. 1986
(Seaconsult, 1988)
Mar. 1986 - May 1992 a,b
a
b
No.
Sites
No.
Data Sets
No.
Sites
No.
Data Sets
No.
Sites
No.
Data Sets
11
16
18
28
8
11
12
14
12
15
12
14
Data compilation provided by Gregory (1995).
Includes moored current meter data from the CASP II oceanographic program, December 1991 May 1992 (Lively, 1994).
95032-0-EI-GM-00003.0, Rev.0
Within the larger study area, current meter measurements, obtained from 1980 to
1992, are available for extended durations (82 to 603 days) at 28 locations (Figure 3.212) on the Continental Shelf and Slope areas east of Newfoundland (Narayanan et al.,
1995). Other important current meter data sets, albeit of shorter duration, are also
available for the study area. One example is current meter data collected at eight sites in
1986 and 1987 on the southeast shoal of the Grand Banks (Ross et al., 1988).
Drifting Buoy Measurements of Ocean Currents
Drifting buoy data have been collected for many years. In the 1960s and 1970s, drifter
information was limited to tagged units (released and then returned by anyone
recovering them) and ship-drift data. Beginning in the late 1970s, satellite-tracked
drifters came into use, which reported positions several times each day. These drifter
data sets are particularly useful for estimation of surface currents, since the drifting
buoys operate in the surface layer. Major drifter studies in the eastern Newfoundland
region include the following:
· BIO program of 1981 to 1985 (Petrie and Isenor, 1984; Petrie and Warnell, 1988)
· The ongoing drifting buoy program operated since 1976 by the International Ice
Patrol of the U.S. Coast Guard during the spring iceberg season (Murphy et al.,
1991)
· More recent NCSP drifter studies conducted in 1992 and 1994 (Pepin and Helbig,
1995; Helbig and Brett, 1995)
A composite of some 144 drifter tracks from these programs is shown in Figure 3.2-13
(Helbig and Brett, 1995).
Numerical Modelling of Ocean Circulation
Another increasingly useful source of ocean current information is available from
numerical model studies. Recent modelling studies (Greenburg and Petrie, 1988;
Hukuda et al., 1989; Tang and Yao, 1992; Ikeda, 1990; Tang and Gui, 1995; de
Young, Lu and Greatbach, 1995) agree reasonably well with the major circulation
features. Models offer the advantage of spatially gridded outputs and the potential for
operating in near-real-time if suitable input fields (e.g., winds or sea levels) can be
provided. However, more development is required to adequately model the subtidal
variability of the ocean and to validate the model output against independent
observations.
An updated approach to computing surface shelf circulation, using vertical density
profiles combined with numerical modelling, has been developed by Sheng and
95032-0-EI-GM-00003.0, Rev.0
Thompson (1995). In this approach, the currents initially computed from the vertical
density profiles relative to fixed depth levels are compared with observations. From the
comparisons, optimal inflow boundary conditions are estimated, which are then used to
drive the northern boundary of a limited-area numerical model. The superposition of
currents attributable to the local density field, combined with the currents caused by
remote forcing, constitute the detailed ocean current field.
Major (Long-Term) Current Systems
The ocean circulation off Eastern Canada (Figure 3.2-14) is dominated by large-scale
currents flowing over the continental margins of the northwest Atlantic Ocean. These
Continental Shelf currents, specifically the West Greenland, Baffin, Labrador and Nova
Scotia currents, have been identified by Chapman and Beardsley (1989) as individual
features of an interconnected coastal current system that extends over 5000 km and
represents the largest known coastal current system in the world. As well as these coldwater coastal currents, two major, deep-basin currents are present:
· The warm Gulf Stream
· The North Atlantic Current, which combines waters from the Gulf Stream and the
Labrador Current
Within the extended study area, the Labrador Current consists of two major branches
(Figure 3.2-12). The inner branch is located on the inner half of the shelf, and its core is
steered by the local underwater topography. For example, this inner branch follows the
trough feature separating the Avalon Peninsula coastline from the western edge of the
Grand Bank. The stronger offshore branch of the Labrador Current flows primarily
along the shelf break over the upper portion of the Continental Slope, at water depths
of 300 to 1500 m. The flows in this outer branch are stronger than the inner branch.
Mean near-surface speeds of the core of the outer branch are normally 25 to 40 cm/s;
those of the inner branch are 10 to 20 cm/s (Fissel and Lemon, 1991).
In areas outside the direct influence of either branch of the Labrador Current, the flows
are generally weaker, more variable, and tend to be aligned with the local bathymetry.
Winds are the major driving force for ocean currents, but non-wind-driven flow
variations at subtidal time scales are also evident.
The Labrador Current outer branch exhibits a distinct seasonal variation in flow speeds
(Lazier and Wright, 1993; Narayanan et al., 1995), in which the mean flows from
September to October are nearly twice as large as the mean flows in March and April.
This annual cycle is the result of the large annual variation in the steric height (derived
from the vertical integral of the internal density distribution) over the Continental Shelf
in relation to the much less variable internal density characteristics of the adjoining deep
95032-0-EI-GM-00003.0, Rev.0
waters. The large variation in density conditions on the shelf results from increased
freshwater input (e.g., from melting ice upstream in the spring and summer) which is
referred to as buoyancy flux. Wind stress provides the major driving force of currents
on the Continental Shelf, with a distinct annual cycle (Section 3.1.4) of comparatively
strong winds in winter, and weaker, more variable winds in summer. Extended current
meter data records obtained on the Northeast Newfoundland shelf off White Bay (site
23 in Figure 3.2-12) indicate that the annual cycle of Labrador Current inner branch is
wind driven, with the strongest flows occurring in late winter.
Surface Circulation
Near-surface circulation, as measured from drifting buoy data sets collected on the
eastern Newfoundland Shelf to 1994 is presented as the mean and variability computed
over 50 km squares (Figure 3.2-15; Helbig and Brett, 1995). The eastward flow along
the northern flank of the Grand Banks transports water from the inner shelf out to the
vicinity of the offshore branch. In this same area, the outer branch of the Labrador
Current bifurcates into an eastward flow directed to the north of Flemish Cap and a
southward flow passing in the deep-water trough (Flemish Pass) separating the
Northeast Grand Banks from the Flemish Cap. The two branches of the Labrador
Current are readily apparent in these drifter measurements; in these areas, the mean
near-surface currents are relatively large, and tend to exceed the variability in the flows
(after low-pass filtering to remove fluctuations with periods of less than 30 h, i.e., tidal
currents and inertial oscillations). Elsewhere over the northeast Newfoundland Shelf,
the mean currents are relatively weak (a few to 10 cm/s), and the fluctuations about the
means have comparable values.
Over the comparatively shallow Grand Banks, the mean currents are very weak (a few
centimetres per second or less) with a variability (5 to 15 cm/s) much larger than the
mean values. The extensive array of current meter data on the northeast segment of the
Grand Banks, extending outward from the Terra Nova region and collected from
January to May 1992, shows that local winds drive the currents in the interior of the
banks where Terra Nova is situated (DeTracy et al., 1995). However, direct
wind-driven forcing is not dominant over the outer margin of the Grand Banks and into
deeper water. At the shelf break, subtidal variability is greater because of a combination
of:
- Meandering of the Labrador Current core
- Eddy formation
- Propagation of continental shelf waves generated far to the north in the Labrador
Sea
95032-0-EI-GM-00003.0, Rev.0
The average flow speeds measured from drifter tracks (with attached drogues spanning
depths of 15 to 25 m) tend to be considerably larger than those measured from moored
current meters (at 40 m depth). This difference is shown in a comparison of these two
types of data on the northeast Newfoundland Shelf obtained from NCSP programs of
1990 to 1993 (Figure 3.2-16, from Colbourne et al., 1995). The magnitudes differ by a
factor of about 1.7 (Narayanan et al., 1995).
The numerical modelling results of Greenburg and Petrie (1988) provide a detailed,
high-resolution presentation of the circulation. This barotropic model (vertically
uniform currents) is driven by a sea-level slope across the northern boundary (Hamilton
Bank on the south-central portion of the Labrador Shelf), and appears to reasonably
depict the main circulation features of the eastern Newfoundland shelf (Figure 3.2-17).
The vertical uniformity used in the model results in the surface currents being
consistently underestimated. Recent comparisons of the model results with extended
current meter data sets obtained between 1980 and 1993 (Narayanan et al., 1995),
show that the model predictions more or less agree with the observations. In particular,
the cross-shelf flows on the northeast Newfoundland Shelf (e.g., north of Funk Island
Bank) from the offshore to inshore branches of the Labrador Current are confirmed in
the observations. The model, even after allowing for the uniformity through the water
column, underestimates the actual magnitude of the offshore branch of the Labrador
Current along the northeast Newfoundland Shelf. Similar underestimates are apparent
in the magnitude of the flow in the inner branch of the Labrador Current from the
mouth of Bonavista Bay to the coast off the Avalon Peninsula.
The hybrid numerical modelling results of Sheng and Thompson (1995), which
represent the summer surface circulation (Figure 3.2-18) in terms of the local internal
density field and remote forcing at the upstream model boundary (off southern
Labrador), also agree well with observations and the Greenburg and Petrie (1988)
model results. These model results present a high-resolution representation of:
- Strong topographically influenced flows of the inner branch of the Labrador Current
within the major embayments of the Avalon Peninsula
- The anticyclonic (clockwise) gyre centred on the crest of Flemish Cap
In the first case, the results agree qualitatively with the recent measurement program in
Conception Bay (deYoung and Sanderson, 1995).
These recent observation and modelling results are generally consistent with the
modified International Ice Patrol (IIP) gridded surface current field (Figure 3.2-19).
This information was derived by Murphy et al. (1991), primarily from drifting buoy
data of 1976 to 1989, and updated by Yao et al. (1992) using more recent current
meter and drifter data obtained to 1991. However, further modifications to the IIP
95032-0-EI-GM-00003.0, Rev.0
gridded surface current field appear to be warranted, based on comparisons with the
extensive observational data sets collected in recent years, as well as numerical model
studies.
The model modifications could include examination of the inshore branch of the
northeast Newfoundland Shelf through to the inner side of the Grand Banks as this
may be too broad. Also, the surface currents on the northeast Newfoundland Shelf
appear to be too large, in general. The IIP currents on the eastern part of the Grand
Bank (within the 200 m isobath) are similarly overestimated and are more spatially
variable than observed. IIP has recently announced forthcoming revisions to their
gridded surface current field (D.L. Murphy, IIP, pers. comm., 1995), which address
these points.
Mesoscale Circulation Features
Mesoscale currents include eddies and meanders, which have typical time scales of 2 to
50 days and typical spatial scales of 10 to 100 km. Mesoscale eddies and meanders are
evident in the drifter tracks (Figure 3.2-13), especially in the areas immediately adjacent
to the offshore branch of the Labrador Current and on the northeast Newfoundland
Shelf. Voorheis et al. (1973) have identified over 30 eddies on the central part of the
Continental Slope along the eastern margin of the Grand Banks from an analysis of
historical oceanographic data sets dating back to the 1920s. The eddies are mostly
cyclonic (counterclockwise), have typical speeds of 25 to 30 cm/s and have an average
size of 102 km in diameter. Meanders had typical lengths of 275 km in the along stream
direction, and about half this in the cross-stream direction.
Meanders and eddies occur on the Grand Bank proper, as seen in selected drifter tracks
(Figure 3.2-20) from 1980, 1984 and 1985. Eddies were observed in the tracks of
drifters that were resident on the banks for an extended period of time (tracks A and G)
and in the tracks of drifters following the offshore branch of the Labrador Current
which "spins-off" over the bank itself (Figure 3.2-20b).
There are various underlying causes of the eddies and meanders. Over the shallowwater banks, they may be a consequence of mesoscale features in the wind-forcing
field, which produce similar patterns in the surface drift. Mesoscale eddies can also be
generated by depth-varying instabilities in the main core of the offshore branch of the
Labrador Current. Using satellite imagery obtained off the Labrador Shelf, eddies and
meanders in the offshore branch of the Labrador Current have been shown to have
characteristic periods of four days and wavelengths of 75 km (LeBlond, 1982). Once
formed, such features can be advected from the main core of the current into shallower
or deeper waters.
95032-0-EI-GM-00003.0, Rev.0
Wind-Driven Currents
Wind blowing over the ocean surface produces two different types of responses in
ocean currents. In one case, the upper layer of the ocean drifts with the wind, usually at
about 3 percent of the wind speed and 20 to 45° to the right of the wind direction. This
response occurs over synoptic periods of 2 to 10 days, comparable to the periods of
the storm related (or synoptic scale) wind variations. In the other case, during passing
storms, the ocean responds through strong inertial motions. Such motions, generally
called inertial oscillations, occur in a fluid when it is suddenly disturbed, for example,
when an intense wind front passes over the ocean surface. Because of the earth's
rotation, the resulting water motion is circular clockwise in the northern hemisphere.
The time to complete a full circle, called the inertial period, is 16.5 hours over the
northern Grand Banks.
Over the Grand Banks, typical amplitudes of inertial oscillations range from 10 to 30
cm/s (de Young and Tang, 1990; Tang and Belliveau, 1994). In the interior of the
Grand Banks away from strong large-scale currents, inertial oscillations can account
for more of the total variance than either low-frequency, synoptic-scale variability or
tidal currents. Inertial currents are characterized by large variations in amplitude with
depth (Figure 3.2-21) which are related, in part, to the stratification of the water
column. Under more stratified conditions prevalent in spring and summer (Section
3.2.3), more of the energy of the inertial oscillations can be confined to the upper layer
of the water column. An example of two episodes at Terra Nova of strong inertial
oscillations, when speeds exceeded 30 cm/s, are August 31, 1983 and Sept. 11, 1983
(Figure 3.3-21). Typically, inertial oscillations persist for two to six days following the
triggering event.
Tidal Currents
Tidal flows are the movements within the water column associated with the regular
predictable changes in sea level driven by the gravitational attraction of the moon and
the sun. Tidal currents on the Grand Banks are dominantly semidiurnal (highs and lows
twice daily). The largest tide, the lunar semidiurnal (M2), has amplitudes ranging from
less than 1 to 9 cm/s (Petrie et al., 1987).
An analysis of six years of current meter records, collected from 1980 to 1986 in the
vicinity of Terra Nova, shows that the mean amplitude of the diurnal tidal currents is 3
cm/s while that of semidiurnal tidal currents is 8 cm/s (Seaconsult, 1988). The analysis
results were also used to predict tidal currents over a 20-year period, from which an
extreme value for total tidal currents of 20 cm/s was computed.
Internal tides, in which the astronomical tidal flows interact with a stratified water
column, can also result in significant flows at tidal periods in localized areas. The
phenomenon is generally most important at the shelf edge where the tides can enhance
95032-0-EI-GM-00003.0, Rev.0
vertical mixing of deep, nutrient-rich water found over the Continental Slope into shelf
areas (Smith and Sandström, 1988).
Mean and Extreme Currents at Terra Nova
The major offshore branch of the Labrador Current is located 50 to 60 km to the east
of the Terra Nova site, and is confined to areas where water depths exceed 200 m.
Over the broad expanse of the relatively shallow (less than 100 m depth) and
comparatively flat portions of the Grand Banks, currents are generally weak and
variable (Figure 3.2-22).
As discussed above, the flows are dominated by wind forcing along with tidal currents.
Intrusions of cold Labrador Current water onto the northeast Grand Banks have been
observed (Kudlo et al., 1972). These intrusions are associated with generally lowamplitude flows of about 5 cm/s and last five to ten days. The weak speeds make it
difficult to extract such events from residual current variations caused by wind forcing.
The extended moored-current-meter data sets available for Terra Nova (1980 to 1986,
Table 3.2-3) show the mean flow speeds are low: 3.6 cm/s at the surface to the
southwest, 1.8 cm/s at mid-depth to the northwest, and 0.3 cm/s near the bottom to the
northwest (Seaconsult, 1988). Variations of the actual currents are much larger than
the mean current values, by a factor of 5 or more.
The current meter data sets obtained in the Terra Nova area from 1980 to 1986 were
analyzed using the Weibull function to determine expected extreme values (Seaconsult,
1988). Table 3.2-7 shows these extreme current values.
Table 3.2-7
Extreme Currents at Terra Nova
Computed for Various Return Periods
Depth Level
95032-0-EI-GM-00003.0, Rev.0
Return Period (a)
1
10
100
Near-surface (20 m)
Current speed (cm/s)
Direction
75
W
79
W
96
W
Mid-depth (45 m)
Direction
76
SW
87
SW
99
SW
Near-bottom (70 m)
Direction
61
SE
74
SE
87
SE
3.2.5
Tides and Other Short-Term Sea-Level Variations
Tides are highly predictable. From extended measurements at tide stations along the
coast of Canada, and at a few selected offshore locations, the major astronomical
constituents of tides can be determined and used to accurately predict tidal heights.
Along the east coast of Newfoundland and over the Grand Banks, the largest tidal
constituent is the lunar semidiurnal (M2) with an amplitude of approximately 40 cm.
The three other major semidiurnal and diurnal constituents are lower in amplitude (10
to 15 cm; Figure 3.2-23).
The tides along the east coast of Newfoundland are mixed, mainly semidiurnal in
nature, with two high tides and two low tides occurring each day. One of the sets of
tides is higher (and lower) than the other daily set. A typical tidal range each day is 1 m.
To provide better data for tidal predictions for the region, a set of eight bottommounted gauges were installed and operated around the periphery of the Grand Banks
(Figure 3.2-24) for a six-month period in 1983 and 1984 (Petrie et al., 1987). As well
as conventional tidal or harmonic analyses, a numerical model of the Grand Banks was
also developed (Petrie et al. 1987). Tides were analyzed for site 2, at Terra Nova and
site 6, over the slope area at the edge of the Grand Bank (Seaconsult, 1988). The
maximum tidal amplitude above mean water level, computed over a 20-year period,
was 53 cm at site 2 and 37 cm at site 6. The minimums below mean water level were
-51 cm and -34 cm, respectively.
Storm surges cause sea levels to rise as a result of the wind stress on the surface of the
ocean (Murty et al., 1995). Murty and Greenburg (1987) described a storm surge that
resulted from a storm passing through the Newfoundland area on January 10, 1982 and
causing damage along the eastern part of the southern shore of Newfoundland. The
high water level at Argentia was about 2 m, of which about 1.3 m was attributed to the
storm surge (Murty and Greenburg, 1987). This water-level height at Argentia was
exceeded only once in this century, by the November 1929 earthquake on the Grand
Banks. Such large storm surges are rare, in terms of the requisite wind-stress forcing
conditions. Moreover, they produce important effects only when the storm surge
occurs during high tides. The amplitudes of storm surges are generally much smaller in
deeper water away from the coastline.
Storm surges for the Terra Nova area were analyzed (Seaconsult, 1988) using the
extended water-level data sets of 1983 to 1984 at sites 2, 3, 6 and 7 (Figure 3.2-24),
after removing the tidal variations. The maximum computed displacement amplitude
was 36 cm for site 2. Using a Weibull extreme value analysis on these data, extreme
storm surge levels at Terra Nova have been estimated as amplitudes of 54 cm for a
one-year return period, 66 cm for a 10-year return period and 79 cm for a 100-year
return period. In the worst case of combined tide and storm surge, the expected
95032-0-EI-GM-00003.0, Rev.0
100-year elevation would be approximately 1.26 m (Seaconsult, 1988).
3.2.6
Oceanic Fronts
Oceanic fronts are narrow boundary zones separating dissimilar water types. They are
defined by large horizontal gradients in water properties, including temperature and
salinity. Fronts often coincide with areas of strong current shears. Water is turbulently
mixed in fronts, enhancing vertical exchanges of momentum, heat, salt and dissolved
gases. Fronts are commonly associated with surface zones of enhanced biological
productivity.
Fronts are widely observed within the larger study area, and have particularly
prominent amplitudes and commonly occur at the shelf edge (Narayanan et al., 1991).
Satellite imagery has been used extensively to monitor the variability in location of the
offshore branch of the Labrador Current. This dominant regional circulation feature
(Section 3.2.4) is associated with a large surface gradient in temperature and salinity.
Using the visible band, the advanced very high resolution radiometer on the NOAA
series of satellites has proven effective for these studies (Figure 3.2-25) (Isenor, 1988;
Isenor et al., 1992).
An even longer record of the location of the northern boundary of the Gulf Steam in
the waters south of the Grand Banks has been developed using satellite imagery
(Figure 3.2-26; Drinkwater and Myers, 1993). The variability in the location of this
major, large-scale front influences the ocean climate of the Continental Shelf through
the Slope Water found to the south and east of the Grand Banks.
The ability to routinely detect and monitor frontal features and eddies is being
increasingly enhanced by new remote-sensing technologies, particularly synthetic
aperture radar (SAR) sensors, which have all-weather sensing capabilities. Figure 3.227 shows an example of such results obtained over the interior of the Grand Banks in
November 1991.
3.2.7
Upwelling Areas
Upwelling is the process in which deeper ocean waters move upward and mix with
surface waters. The upwelled waters usually have higher concentrations of nutrients,
which may be depleted in the upper layers by phytoplankton uptake. As the biological
food web is based on phytoplankton, areas where upwelling occurs are commonly
biologically productive.
Classical wind-driven coastal upwelling occurs at coastlines or the outer limits of
continental shelfs, where winds transport the surface layer offshore and these waters
are replaced by water upwelled from below. For a shelf edge of uniform orientation
and slope characteristics, wind-driven upwelling is determined by the strength of the
wind forcing, the slope of the bottom at the shelf break, local friction and the degree of
95032-0-EI-GM-00003.0, Rev.0
stratification in the water column (Smith and Sandström, 1988). Studies conducted at
the edge of the Scotian Shelf (Petrie, 1983) show that while upwelling from depths of
400 m does occur at the shelf break, the upwelled waters appear to be confined within
about 10 km of the slope. Moreover, the response to wind forcing is three dimensional
in that upwelling is favoured in certain areas where the complex shelf edge topography
is particularly amenable to the process, and less likely to occur at other locations with
different topographic features. The Newfoundland Shelf, like the Scotian Shelf, has a
very complex underwater topography at the shelf edge (Section 3.1.2), and upwelling
may be a localized process in this area as well (Smith and Sandström, 1988).
Primary biological productivity is enhanced by a sequence of biophysical factors.
Upwelling from below replenishes nutrients into the surface layer where these may
have been depleted and limited primary production. Once the nutrient levels have been
replenished, then stratification of the water column causes the phytoplankton to remain
within the upper ocean where the energy from the sun promotes growth (Mann, 1991).
Thus, episodic events of strong winds over stratified waters may be effective in causing
bursts of plankton production. Such events may be important on the Grand Banks in
spring and summer, when the stratified upper layer is underlain by the nutrient-rich
CIL.
3.2.8
Wave Climate
A sound understanding of the mean and extreme wave climate at the Terra Nova site is
required to support system design and operational planning.
The main parameters for describing wave conditions are the significant and the
maximum wave height. The significant wave height, Hs, is defined as the average of the
highest one-third of the individual waves. It represents the height an experienced
observer will visually estimate for a given seastate (Khandekhar and Swail, 1995). The
maximum wave height, Hm, is the greatest vertical distance between a wave crest and
adjacent trough. Other wave parameters of interest are:
Wave period. The peak spectral period, Tp, associated with the largest energy levels
(or spectral densities) in a time series of continuous wave data (typically of 20 minutes
duration).
Wave direction. The directional sector containing the waves of greatest energy.
Wave grouping. A tendency for large waves to travel together. There is ample
evidence in wave data collected on the Grand Banks that groups of large waves do
occur (Seaconsult, 1988).
95032-0-EI-GM-00003.0, Rev.0
Wave Data
Wave data can be collected visually from ships or by direct measurements using
moored buoys. Visual estimates of wave heights from passing ships do not provide
continuous data at a given site, and are prone to biases and errors that preclude use in
statistical analyses of mean and extreme conditions. Nearly all direct measurements of
waves on the Grand Banks have been made using waverider buoys. These instruments
monitor sea-surface elevation using a vertical accelerometer sensor, which is integrated
twice to determine vertical displacement measurements. These measurements are
relayed by radio link to drilling rigs or other nearby platforms. The WAVEC buoy, a
directional version of the waverider buoy, measures the components of the surface
elevations needed for determining wave direction. This buoy has been used
occasionally for wave monitoring, but it has contributed less than 10 percent of the
direct measurement database.
Waverider data collection began on the Grand Banks in 1973, but the first data sets
were generally of short duration and obtained at widely separated successive sites. The
earliest data sets collected in conjunction with offshore drilling in the Hibernia and
Terra Nova areas were obtained in June 1979. Subsequent monitoring provided nearly
continuous direct measurements of waves at or near Terra Nova from 1980 to early
1986 followed by less frequent measurements from 1986 to 1990 (Figure 3.2-28).
Wave Models
Wave models, driven by surface winds, were first developed for operational wave
predictions in the 1950s and have improved steadily over the past three decades.
Second- and third-generation wave models rely on representations of wave processes
in the frequency domain, using the spectral energy balance equation (Khandekhar and
Swail, 1995). A state-of-the-art global operational model, WAM, developed by the
Wave Modelling (WAM) group has recently been used by weather forecast centres in
Europe and North America. Operational wave-modelling is being improved by research
on the assimilation of near-real-time, remote-sensing data from all-weather, radarsatellite sensors. These sensors include:
- Scatterometers for wind measurements
- Radar altimeters for wave height estimation
- SAR for determining two-dimensional wave spectra for initializing wind and wave
fields in the operational models (Khandekhar and Swail, 1995; Wilson et al., 1995)
95032-0-EI-GM-00003.0, Rev.0
Gridded wind data sets are available at standard synoptic intervals from the mid-1950s
to the present. This 40-year span of data is several times the duration of continuous,
direct wave measurements available for any subregion of offshore waters on the
Canadian East Coast. Consequently, wave hindcast models can be used to provide
extended data sets for estimating the extremes of wave climate (Eid et al., 1991;
Canadian Climate Centre, 1991).
Normal Conditions
Table 3.2-8 shows the annual distribution of measured significant wave heights and
peak periods as determined from the 1980 to 1990 measurements at Terra Nova
including the nearly continuous data spanning 1980 to 1986 (five years and 10 months
of data). The maximum significant wave height, Hs, is between 11 and 12 m, as
computed from 3-hourly average values. The associated peak period, T p, ranges from
13 to 17 s. Roughly half the periods exceed 10 s and only 1 percent of the measured
wave heights exceed 7 m.
The same extended data set can be used to derive the distribution of H s by mean wind
direction (Table 3.2-9) (measured wave directions were only rarely available). The
largest waves are associated with winds blowing from the north and west; these are
also the directions of the largest winds (Section 3.1.5).
The wave climate has a marked seasonal distribution, as seen in the distributions of
observed significant wave heights and peak periods (Figures 3.2-29 and 3.2-30). The
highest waves occur in December and February with an Hs of 11 to 12 m. The
measured waves have a tendency to be steeper in February (i.e., shorter periods) than
in December. Wave climate is much reduced in magnitude in May through August,
with the lowest mean waves in August and May (maximum Hs less than 5 m). The
most common peak period of waves in fall and winter is 10 to 11 s, as compared to 7
to 8 s in summer. Observed peak periods of up to 18 s occur in the fall and winter.
Tables 3.2-10 to 3.2-13 show persistences for various wave height categories for
February, May, August and November. Wave height persistence has been computed
from the six-year data set for individual months. The longest measured persistence of
Hs greater than 5 m was 84 h in March.
In terms of maximum sea state, Hs greater than 11 m occurred once and lasted for 6
hours. However, the statistics for seas between 6 and 10 m indicate that sea states are
generally more persistent in February than in any other month.
95032-0-EI-GM-00003.0, Rev.0
539
3.0
3.0
97.0
12
11
39
100
151
99
76
35
9
2
4
1
0-1
95032-0-EI-GM-00003.0, Rev.0
7
80
365
575
792
1149
1284
574
197
157
60
5
5
1
2-3
5811
5251
32.1
29.0
35.1 64.135.9
64.9
1
11
122
322
724
1125
1448
1030
591
222
78
59
29
2
7
1-2
Note:
1. Sampling interval - 3 hours.
No. obs.
% Total
Cum. %
% Exceed.
2-3
3-4
4-5
5-6
6-7
7-8
8-9
9-10
10-11
11-12
12-13
13-14
14-15
15-16
16-17
17-18
Peak Period
(s)
3623
20.0
84.2
15.8
3
47
177
445
668
979
620
316
206
138
20
4
3-4
1629
9.0
93.2
6.8
6
32
151
265
439
314
163
147
67
26
15
4
4-5
744
4.1
97.3
2.7
1
2
17
110
193
156
98
98
44
17
5
3
5-6
294
1.6
98.9
1.1
1
4
30
70
92
50
22
12
12
1
6-7
110
0.6
99.5
0.5
1
7
18
24
19
18
13
7
3
7-8
55
0.3
99.8
0.2
1
1
4
11
19
15
4
8-9
15
0.1
99.9
0.1
1
1
11
2
9 - 10
Significant Wave Height (m)
14
0.1
100.0
0.0
5
5
2
1
1
3
0.0
100.0
0.0
2
1
10 - 11 11 - 12
Significant Wave Height Versus Peak Period
at Terra Nova, 1980 to 1988 and 1990 Observations
Table 3.2-8
3-94
100.0
99.9
99.1
96.4
89.4
78.1
61.8
43.3
23.4
12.2
6.9
2.8
0.8
0.3
0.0
0.0
0.0
0.1
0.9
3.6
10.5
21.4
38.2
56.7
76.6
87.8
93.1
97.2
99.2
99.7
100.0
100.0
0.0
0.1
0.8
2.7
6.9
11.4
16.3
18.4
20.0
11.2
5.2
4.1
2.1
0.5
0.2
0.0
1
23
140
484
1243
2064
2957
3336
3613
2023
948
743
372
90
43
8
17062
%
Exceed.
Cum. %
%
Total
No. of
Obs.
495
3.1
3.1
96.9
No. obs.
% Total
Cum. %
% Exceed.
Source: Seaconsult (1988)
Note:
1. Sampling interval - 3 hours.
30
24
25
56
123
114
99
24
0-1
N
NE
E
SE
S
SW
W
NW
Wind
Direction
5198
32.7
35.8
64.2
415
271
439
497
1170
1227
860
319
1-2
4662
29.4
65.2
34.8
464
237
438
434
798
792
901
598
2-3
3216
20.2
85.4
14.6
343
133
180
223
439
503
796
599
3-4
1358
8.6
94.0
6.0
120
54
53
59
158
213
408
293
4-5
584
3.7
97.7
2.3
73
44
22
11
50
61
167
156
5-6
225
1.4
99.1
0.9
24
3
1
3
13
32
75
74
6-7
42
0.3
99.8
0.2
1
5
21
8
2
8
32
19
79
0.5
99.6
0.4
7
8-9
18
7-8
Significant Wave Height (m)
1
5
5
1
12
0.1
99.9
0.1
9 - 10
Joint Distribution of Wave Height and Wind Direction
at Terra Nova, 1980 to 1986
Table 3.2-9
1
1
3
3
1
9
0.1
100.0
0.0
10 -11
1
2
3
0.0
100.0
0.0
11 -12
15883
1498
766
1158
1283
2756
2961
3367
2094
9.4
4.8
7.3
8.1
17.4
18.6
21.2
13.2
No. of Obs. % Total
Table 3.2-10
Wave Height Persistence for Terra Nova
February, 1980 to 1986
Wave Height Threshold (m)
Duration
(h)
1
0-6
6-12
12-48
24-48
48-96
96-168
168-360
360-744
744-1464
Sum
Min. duration
Mean duration
Max. duration
% Exceedence
of wave height
2
4
2
1
6
5
5
1
4
1
4
7
453
1112
1140
100
26
3
239
1416
92
Notes:
1. Sample interval - 3 h.
95032-0-EI-GM-00003.0, Rev.0
3
4
5
6
7
8
9
23
10
16
15
8
3
17
9
10
10
2
11
5
6
5
6
6
1
2
2
2
2
1
1
75
3
25
147
46
48
3
17
72
21
27
3
14
48
10
15
3
12
45
4
6
3
16
39
2
5
3
12
27
1
3
10
11
Sum
1
1
1
2
1
1
70
36
35
40
15
4
4
2
10
3
3
10
18
1
3
3
7
12
1
1
3
3
3
0
216
Table 3.2-11
May, 1980 to 1986
Duration (h)
0-6
6-12
12-24
24-48
48-96
96-168
168-360
360-744
744-1464
Sum
Min. duration
Mean duration
Max. duration
% Exceedence of wave height
Notes:
1. Sample interval - 3 h.
95032-0-EI-GM-00003.0, Rev.0
1
2
3
2
1
5
4
3
18
3
340
1029
96
3
4
Sum
14
4
7
7
10
3
2
16
5
9
2
8
47
3
44
321
47
37
3
15
63
13
9
3
4
15
1
1
41
9
19
12
13
3
7
4
3
111
Table 3.2-12
August, 1980 to 1986
Duration (h)
0-6
6-12
12-24
24-48
48-96
96-168
168-360
360-744
744-1464
Sum
Min. duration
Mean duration
Max. duration
Notes:
1. Sample interval- 3 h.
95032-0-EI-GM-00003.0, Rev.0
1
2
3
4
Sum
8
2
2
4
3
5
3
3
4
15
6
10
10
6
1
1
7
3
7
2
1
8
2
1
38
13
20
16
10
6
4
3
4
34
3
211
1143
89
49
3
31
321243
32
20
3
15
51
7
11
3
6
24
2
114
Table 3.2-13
November, 1980 to 1986
Duration (h)
0-6
6-12
12-48
24-48
48-96
96-168
168-360
360-744
744-1464
Sum
Min. duration
Mean duration
Max. duration
Notes:
1. Sample interval- 3 h.
95032-0-EI-GM-00003.0, Rev.0
1
2
1
1
6
8
75
1095
1464
100
3
4
5
6
7
8
2
3
2
4
6
4
4
5
18
5
7
13
13
3
1
1
20
6
11
13
3
2
14
10
9
4
1
4
4
2
1
4
30
3
166
702
89
61
3
43
492
57
55
3
22
156
26
38
3
12
54
11
11
3
12
42
3
6
3
8
21
1
Sum
2
1
70
36
35
40
15
4
4
2
10
3
3
5
9
0
212
2
Directional wave measurements are much less available than non-directional data for
the Terra Nova area (Table 3.2-8). However, such data obtained in December 1985 are
instructive in showing the presence of crossing seas. For example, on December 3,
1985 (Figure 3.2-31), in the aftermath of the storm of December 1 and 2 (H s of 7.8 m),
swell heights of 4 to 6 m were measured travelling to the southwest, following the
storm. A growing sea was also evident propagating to the northeast, which resulted in
a combined wave height of 5.8 m almost equally divided in energy between the two
opposing wave trains.
Maximum Observed Waves
The largest recorded wave in the Terra Nova area over the 1980-1986 period of data
collection was 24.8 m in crest-to-trough height (see Figure 3.2-32), measured on
December 22, 1983. During this same storm, the largest H s value of 13.8 m was
measured, although not from the same 20 min measurement sample. The ratio of
maximum wave height to significant wave height (Hm/Hs) is 1.8 for this particular
storm.
Based on the measurements of the 23 most severe storms during the six-year period of
measurements (Seaconsult, 1988), the average Hm/Hs ratio is 1.9 and ranges from 1.3
to 2.4. For peak storm conditions, where Hs is greater than 10 m, the ratio Hm/Hs is
always less than or equal to 1.9.
Peak periods measured during the maximum wave heights, from the 23 Grand Banks
storms of 1980 to 1986, range from 9.8 s (Hs = 4.6, Hm = 6.4 m) to 19.5 s (Hs = 13.5,
Hm = 24.8 m).
Wave groupiness can also be characterized from the 1980-1986 Grand Banks storm
data (Seaconsult, 1988). A value of 0.8 to 1.2 for the groupiness factor GF (Funke
and Mansard, 1979) indicates several groups of large waves separated by a period of
low-amplitude waves. GF values of 0.4 to 0.6, on the other hand, indicate small
numbers of grouped waves. The GF parameter does not directly provide information
on the maximum sea surface set-down, or the number of waves in particular groups.
The bivariate distribution of GF versus Hs (Table 3.2-14) indicates GF ranges from 0.3
to 1.3 with a median value of 0.63. For the largest waves in which H s is greater than 9
m, wave groupiness is somewhat higher with a median value of 0.7, ranging from 0.4
to 1.1. Overall, wave groupiness is important (GF greater than 0.8) in about 3 percent
of the storm records, and in 13 percent of the larger data records where H s is greater
than 9 m.
95032-0-EI-GM-00003.0, Rev.0
3
0.0
0.0
100.0
3
0.3-0.4
81
1.3
1.4
98.6
95032-0-EI-GM-00003.0, Rev.0
1001
16.5
17.9
82.1
1
1
1
9
38
96
286
242
83
35
13
6
7
0.5-0.6
3
9
17
35
9
5
1
0.4-0.5
Note: 1. Sample period - Storms 1 through 23.
No. OBS.
% Total
Cum. %
% Exceed.
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
9-10
10-11
11-12
12-13
13-14
Significant
Wave
Height
1765
29.0
89.3
10.7
4
45
112
340
476
416
181
102
54
13
13
8
1
5
69
178
604
681
573
263
98
62
21
9
12
3
2578
42.4
60.3
39.7
0.7-0.8
0.6-0.7
505
8.3
97.6
2.4
6
31
70
143
133
65
31
12
12
1
1
0.8-0.9
Groupiness Factor
116
1.9
99.5
0.5
4
5
17
28
24
21
10
6
1
0.9-1.0
21
0.3
99.9
0.1
1
1
4
8
5
2
1.0-1.1
5
0.1
100.0
0.0
1
1
1
1
1
1.1-1.2
Wave Groupiness Factor for Significant
Wave Height Classes
Table 3.2-14
2
0.0
100.0
0.0
1
1
1.2-1.3
0.3
2.9
7.3
22.3
26.1
22.1
10.2
4.5
2.4
0.9
0.5
0.3
0.1
21
174
441
1357
1589
1342
618
276
147
54
31
21
6
6077
%
Total
No. of
Obs.
99.7
96.8
89.5
67.2
41.1
19.0
8.8
4.3
1.8
1.0
0.4
0.1
0.0
0.3
3.2
10.5
32.8
58.9
81.0
91.2
95.7
98.2
99.0
99.6
99.9
100.0
3-103
%
Exceed.
Cum.
%
Extreme Wave Values Computed from Observations
Extreme values for ocean waves have been computed (Seaconsult, 1988) using the
continuously measured wave data set assembled for the Terra Nova area, spanning a
period of nearly six years from 1980-1986. The continuous measurements were fitted
to a three-parameter Weibull distribution, a computational technique that has compared
well with extremal analysis of waves derived from hindcast studies for the N.E. Grand
Banks region (Bolen et. al., 1989).
The extreme wave value results (Table 3.2-15) indicate the expected extreme
significant wave height (as a 3-hourly average value) is 15.0 m over a 100-year
recurrence interval. Associated values for other wave parameters, including peak
periods, largest individual wave height and its expected period, are also provided in
Table 3.2-15. Considerable statistical uncertainties are inherent in extrapolating from a
measurement period of six years to recurrence intervals of up to 100 years. Using the
standard statistical methodology (Seaconsult, 1988), the upper prediction limits for the
extreme wave heights are estimated. For the 100-year recurrence interval, the 50percent level of the upper limit of significant wave height is computed as 15.4 m, while
the corresponding value at the 90-percent level is 17.1 m.
Beyond the statistical uncertainties, other uncertainties arise from the possibility of
omission of maximal storm events in the period considered, and the effects of
significant levels of interannual variability. The likelihood of an omission of major storm
events is very low, given that the general area around Terra Nova was closely
monitored throughout the six-year period used in the analyses. The effects of
interannual variability are more difficult to assess. Interannual variability is determined
as the change in the distribution of maximum wave events over a long return period
(e.g., 100 years) relative to a comparatively short period over which data were
available. This source of uncertainty is discussed in more detail below.
Extreme Wave Values from Hindcast Studies
Because the return period of 100 years duration is much greater than the duration of
continuously recorded wave data, wave hindcast modelling studies have been widely
used to estimate the extreme wave conditions. An extreme storm-wave hindcasting
study for the Hibernia area (Cardone et al., 1989) computed estimated extreme wave
conditions from the wave hindcast results for 26 large wave-producing storms over the
34-year period, 1950 to 1984. The results for significant wave height are in good
agreement with those computed from direct observations (Table 3.2-15). By fitting the
hindcast results using the FT-1 (or Gumbel) distribution, the computed 100-year return
period for H is 15.0 m, with a 90 percent upper confidence limit value of 17.1 m.
95032-0-EI-GM-00003.0, Rev.0
Table 3.2-15
Extreme Significant Wave Height and Associated Periods for Terra Nova
Return
Period TR
(a)
Sign. Wave Height Hs (m)
Upper Prediction Limit
Confidence Level
Expected
1
10
25
50
100
10.5
12.8
13.7
14.3
15.0
50%
10.9
13.2
14.1
14.7
15.4
Expected
Peak
Period TP
(s)
Period
Range Wave
Ht. TP
(s)
Individual
Wve Hm
(m)
Expected
Period
THm
(s)
90%
12.7
14.9
15.8
16.4
17.1
14.1
15.5
16.0
16.3
16.7
12.1 - 17.4
13.3 - 19.1
13.8 - 19.8
14.1 - 20.2
14.4 - 20.7
20.7
25.1
26.8
27.9
29.3
12.5
13.5
14.5
14.6
14.7
Sample Period: 26 storms from 1980-1986.
Extreme wave conditions have been analyzed on a regional basis for the East Coast of
Canada (Canadian Climate Centre 1991). Wave hindcasting of 68 severe storms was
carried out from 1957 to 1988. The selected storms all occurred in the fall and winter
months (Figure 3.2-33) as would be expected given the very pronounced seasonal
cycle in storm wave events in the North Atlantic Ocean. The wave hindcasts were
derived with a spectral wave model adapted to the North Atlantic basin on a highresolution nested grid, with a temporal resolution of 2 h and spatial resolution of about
85 km. The wave model output was validated for all 68 of the storms (Environment
Canada, 1995). The distribution of storm wave heights by direction for the Terra Nova
area (Figure 3.2-34) indicates that the primary direction of storm waves was from the
southwest. Other large (Hs greater than 6 m) wave events were associated with arrivals
from the northwest.
The Canadian Climate Centre (1991) study provides the foundation for a database and
analysis system that can be used for updating estimated extreme wave values as the
data record of major events expands with time. As shown in Figure 3.2-35, there is
considerable interannual variability in the occurrence of storms on the Canadian East
Coast.
Since the completion of the regional hindcasting of extreme waves (Canadian Climate
Centre, 1991) using events up to 1988, three severe storms have occurred off the East
Coast of Canada:
· October 31, 1991 (the "storm of the century")
· March 15, 1993 (Cardone and Swail, 1995)
· The Hurricane Luis storm of September 10 to 11, 1995 (Bigio, 1995)
95032-0-EI-GM-00003.0, Rev.0
For each of these storms, very large significant wave heights, exceeding 15 m, were
measured by instrumented buoy platforms located in deep water to the south of Nova
Scotia and Newfoundland (no measurements were made during these events in the
Terra Nova area). The very high waves were measured at deep-water buoys, installed
in the mid- to late 1980s, in areas where few direct wave measurements had previously
been collected.
In view of the large wave events recently measured off the East Coast, 12 large waveproducing storms during the 1988 to early 1995 period have been selected for
additional wave hindcasting, using the third-generation wave model with shallow water
capabilities. The results from the expanded wave hindcast data set, now comprising 80
storms in total, reveal little change in the estimated 100-year return period for H s in the
Terra Nova-Hibernia area (Oceanweather, 1996) from the earlier results to 1988
(Swail, 1995). For the model grid point near 46.9N, 48.9W, the expected 100-year
return period for Hs, is 15.5 m (for the years 1957 to early 1995) as compared to 15.4
m (for the years 1957 to 1988). The corresponding Hs values for the grid points
encompassing the Terra Nova field are 15.4 m and 16.0 m (Oceanweather, 1996). The
very modest change in the estimated 100-year extreme values of H s, with the 1988 1995 storms included, arises from the reductions in the wave fields reaching the N.E.
Grand Banks by comparison to the larger waves present along the main storm tracks
well south of Nova Scotia and Newfoundland (e.g., the largest hindcast waves from the
Storm of the Century and the Halloween storms in the Terra Nova area were 6.7 m
and 5.7 m, respectively). Only one of the recently added 12 storms, occurring on
January 12, 1991 with peak Hs of 12.8 m, was among the 10 largest wave-producing
storms for the Terra Nova area of the 80 events now in the wave hindcast database.
Recent studies of possible changes in wave climate in the North Atlantic Ocean provide
empirical evidence that there has been a trend toward increased wave heights and
storminess in the eastern North Atlantic Ocean (Bacon and Carter, 1991; Kushnir et
al., 1995) since the early 1960s. However, there is no evidence for a similar trend for
the western North Atlantic Ocean, including the northeast Grand Banks, over this same
period (Kushnir et al., 1995).
The amplitude of the computed trend in increasing mean wave heights in the eastern
North Atlantic is modest (about 0.3 m wave height per decade). This trend in mean
wave heights does not mean that a similar trend will occur in extreme values, given the
statistical difference between mean and extreme wave sample populations.
There is a hypothesis that wave climate trends reflect climate changes caused by the
anthropogenic effects of greenhouse gases in the atmosphere, but this is not supported
by the preliminary scientific studies conducted to date. The most recent research
indicates that atmospheric fields, specifically winds and sea-level pressure gradients,
95032-0-EI-GM-00003.0, Rev.0
which cause ocean waves, vary periodically over multi-decadal time scales (WASA
Group, 1995; Kushnir et al., 1995) rather than as an upward trend of the type that may
be expected for effects associated with greenhouse gases in the atmosphere. However,
Resio et al (1995) carried out an analysis of the variability in the weather patterns in the
North Atlantic Ocean, which generate the ocean waves, for an extended period
spanning nearly 100 years. From the atmospheric pressure field analyses, a large degree
of variability in extreme wave values can be expected at time scales of decades and
longer, which supports the value of the ongoing updating of wave hindcast databases.
95032-0-EI-GM-00003.0, Rev.0
3.3
Two different forms of floating ice, sea ice and icebergs, are present in the marine
environment. Sea ice, produced by freezing of the ocean's surface layer, is usually
loosely packed and pressure-free in the vicinity of the Terra Nova site. Small floe sizes
and the prevalence of advanced stages of deterioration generally allow for easy
navigation, albeit with reduced vessel speeds. The primary operational significance of
sea ice lies in its tendency to suppress higher sea states and to interfere with iceberg
detection and towing operations.
Icebergs are generated by fragmentation or “calving” of freshwater ice into the marine
environment at the termini of glaciers. They are the primary focus of ice management
efforts because of the hazards posed by their potential physical contact with all major
components of offshore production facilities.
Although strong connections between icebergs and surrounding sea ice have long been
recognized (Smith, 1931), only recently has it been convincingly shown that regional
sea ice conditions largely determine iceberg severity off Newfoundland (Marko et al.,
1994a). Consequently, description of the ice environment begins with a summary of the
characteristics of the regional and local sea-ice cover before presentation of basic and
critical information on icebergs. In all instances, extreme conditions are included as part
of the spatial and temporal variability issues central to assessment of potential impacts
on offshore development.
3.3.1
Database
The most abundant regional sea-ice data are available from approximately 40 years of
ice observations carried out by Canadian and, to a lesser extent, by U.S. government
agencies. Initially, such observations were almost exclusively obtained from airborne
reconnaissance. Since the 1970s, however, images from polar-orbiting satellites have
strongly augmented and, in some cases, replaced airborne observing as principal data
sources for daily and (approximately) weekly composite-ice charts produced by the
AES Ice Centre. These charts, directly or indirectly, through results from compilations
of Sowden and Geddes (1980), Seaconsult (1988), and Cote (1989), underlie the
description of sea ice in this EIS. Supplementary information on ice movements,
thicknesses and floe sizes, and their linkages to environmental factors have been
obtained from:
- Observations made by the offshore oil exploration industry in the 1970s and 1980s
- PERD-supported DFO and AES research programs
Data on icebergs have been available for an even longer period, dating back to the
second decade of this century. Consequent formation of the IIP led to the routine
compilation of iceberg sighting data in areas south of Labrador initially using marine
95032-0-EI-GM-00003.0, Rev.0
vessel reports as basic data sources. Beginning in the 1950s, fixed-wing aircraft
gradually assumed major responsibilities for iceberg surveillance, with important
additional data being obtained since the 1970s from observations made during oil
exploration activities.
Since its inception, the IIP has collated and cross-indexed sighting data from all sources
to provide updated position mappings and estimates of numbers of icebergs crossing
48°N on annual and shorter time frames. Additional coverage beyond the 52°N limit of
IIP interests, and in inshore areas, also has been available for more than two decades
from the AES Ice Centre.
IIP data have been the basis of most efforts to quantify and understand iceberg
behaviour off eastern North America. These data include daily charts of iceberg
positions prepared from recent sightings and radar target positions. Iceberg positions
and sizes are deduced using very simple and imprecise models of iceberg drift and
deterioration. Unfortunately, the database is not internally consistent because of
changes over time in production procedures and detection technologies, and large
variations in levels of effort. This has constrained analyses of spatial and temporal
trends, and characteristic variations.
Since 1989, iceberg data have also been available from almost daily regional aerial
surveys of East Coast offshore areas between 45°N and 55°N by Provincial Airlines
Ltd. (PAL). These surveys have obtained detailed data in inshore areas generally
neglected in IIP efforts and are particularly notable in that they visually confirm the
identity of icebergs after initial detection with imaging radar. The survey frequency, on
average every five days, allows estimation of iceberg numbers in defined counting areas
without the complex procedures used by IIP. Thus, icebergs passing through a given
area, i.e., a 1° grid (1° latitude by 1° longitude), are estimated as simple sums of local
counts obtained in all surveys during the time period of interest.
The accuracies of such estimates are sensitive to the extent to which drift and
deterioration result in all traversing icebergs to be detected once and only once in the
counting area. Average drift speeds of 20 km/d on the Grand Banks and 30 km/d just
off the Grand Banks (Section 3.2.4) approximately satisfy the counting criterion for
iceberg numbers in the 110 km x 75 km areas associated with 1° grids.
Comparisons of annual total numbers of icebergs south of 48°N indicate that IIP
estimates are significantly larger than PAL iceberg counts in all but the first two years
of the common 1989-1995 survey period. This difference is contrary to expectations,
given the IIP's neglect of inshore icebergs routinely included in PAL surveys. This
difference likely reflects a combination of the uncertainties associated with each survey
and estimation procedures. For example, there is significant possibility of confusion
between ships and icebergs in heavily SLAR-based IIP surveys. In this EIS, the
95032-0-EI-GM-00003.0, Rev.0
description of the regional iceberg environment is based on both the key long-duration
IIP database and PAL data obtained for the years 1989 to 1995.
Other iceberg data, largely consisting of the results of measurements of physical
dimensions and velocities, are available as a consequence of numerous monitoring and
study programs carried out by the oil industry during exploration activities and in
preparation for eventual offshore oil production. These data, together with results
obtained from related PERD- and ESRF- supported research efforts, have contributed
important elements of the existing iceberg knowledge base.
The sea-ice database is not as uncertain as the iceberg database just described. Instead,
sea-ice data support relatively unambiguous and detailed cross-comparisons dating
back to the late 1950s and even, with lesser precision, to the second decade of this
century (Hill and Jones, 1990).
3.3.2
Sea Ice
Formation and Growth
Seawater cooled through atmospheric heat exchange increases in density, and sinks to
a depth determined by the vertical, largely salinity-sensitive, vertical density profile of
the upper ocean. In polar and subpolar regions, this process eventually produces a
relatively well-defined surface layer of water at the freezing temperature. Further loss
of heat to the atmosphere initiates ice growth in forms and at rates strongly dependent
on air temperature, wind speed and sea state. Additional important factors in
determining local ice thicknesses are:
- Levels of snow accumulation
- Magnitudes of heat fluxes from deeper, warmer ocean layers
- Ice deformation driven by winds and current, often acting within constraints
imposed by nearby land masses
Major categories of sea-ice age and thickness are listed in Table 3.3-1. Almost all the
ice near Terra Nova consists of young ice, thinner than 30 cm, or thicker first-year ice.
Local ice thicknesses significantly greater than 1.0 m are, in most cases, associated with
deformed first-year ice (see "Deformation" in this section). Old ice, with densities
elevated by refreezing after survival of one or more spring and summer melt seasons,
appears only very rarely in the region. Figure 3.3-1 shows a typical annual cycle of
change in the composition and overall concentration of sea ice off Newfoundland.
The higher density, crushing strength and thickness of this ice make it an exceptional, if
rare and highly localized, navigational obstacle. In practical terms, its primary
operational significance is that it introduces hard-to-detect vessel collision hazards
95032-0-EI-GM-00003.0, Rev.0
roughly equivalent to the growler- and bergy bit-sized iceberg fragments.
Table 3.3-1
Characterization of Sea Ice by Type, Thickness and Age
Description
New ice
Grey ice
Grey-white ice
White ice
Old ice
Thickness
(cm)
10
10-15
15-30
30-200
-
Age
Earliest stage of development
Early season first year
Mid-season first year
First year
Second and multi-year ice
Areal Distribution
The Terra Nova site lies close to the extreme southern limit of the regional pack ice. In
this area warmer water temperatures dissipate the last remnants of ice that have drifted
south from original ice growth areas in Baffin Bay, Davis Strait and the Labrador Sea.
The annual regional ice cycle begins in September with the growth of new ice in
Northwest Baffin Bay following the nearly complete clearance of ice from all areas
between Canada and Greenland south of about 78°N. A combination of growth and
predominantly southward drift, driven by the prevailing northerly winds and the strong,
cold Baffin Current, advances the ice southward beginning in October. Coverage
increases most rapidly in western areas off the North American continent. By
December, on average, the leading edge of the advancing ice pack lies off Northern
Labrador. Simple modelling estimates (Marko et al., 1994b) suggest that, in April, 60
to 80 percent of the ice off Labrador south of 55° has grown in areas north of 60°N. In
typical years, the ice edge reaches the northern tip of Newfoundland in early January
and the Grand Banks in mid-February (Navoc, 1986). The pack ice off Newfoundland
generally reaches annual peak coverage in March but can remain at high levels through
May and, occasionally, well into June. Figure 3.3-1 shows that thicker first year or
white ice becomes the dominant ice form in areas off Newfoundland beginning in
March just before water temperatures seasonally rise above the freezing level.
Subsequently the ice pack retreats rapidly northward with significant ice concentrations
confined north of Labrador by the end of July, except in extremely severe ice seasons.
Occasionally, first-year ice remnants remain at the end of the summer season off the
east coast of Baffin Island near 70°N. These remnants, together with late discharges of
first year and older ice from Lancaster, Jones and Smith sounds, are the source of the
95032-0-EI-GM-00003.0, Rev.0
thicker, fresher old ice which can appear off Labrador and, in smaller amounts, off
Newfoundland (Markham, 1980).
Seasonal ice coverage in Newfoundland waters is shown by plots of extreme and
median positions of the ice edge midway though each of the months January through
June in Figures 3.3-2 to 3.3-7 . The minimum, or least-advanced, ice-edge positions are
not shown because, in all months, the region was ice-free in at least one year of the
study period. The maximum ice positions shown are composites of the most advanced
ice-edge positions recorded in each compass direction over the period of record. The
years associated with the constituent individual sections of these maximum ice edge
boundaries are indicated.
Figures 3.3-2 to 3.3-7 show two different median ice-edge boundaries. One of these
boundaries was derived by identifying the 0.5° latitude x 1° longitude grid cells where
sea ice has a 50 percent probability of occurring, based on ice charts for the period
1963 to 1987 (Seaconsult, 1988). The second median ice edge was obtained with
identical procedures applied to ice charts from 1988 to 1995. The 1988 to 1995 data
were included to illustrate the possibility of very substantial changes in ice conditions
generally attributed to decadal and even longer term regional climate variability. The
substantially more southerly and easterly positions of the post-1987 median ice edges
reflect the more extensive ice coverages that have been observed off Eastern Canada
waters since 1983. These coverages, as well as those observed between roughly 1910
and 1930, are maximal for the present century (Miles, 1974; Hill and Jones, 1983;
Marko et al., 1992).
Ice conditions in the preceding two decades are shown in Figure 3.3-8 by plots of
annual mid-April ice extents, both for a sum of three latitude bands (45° to 47°N, 49°
to 51°N and 53° to 55°N) and for 45° to 47°N alone as this includes the Terra Nova
site. The ice extents for the three latitude bands are closely correlated with mid-winter
upstream (Davis Strait) air temperatures and ice extents (Marko et al., 1994a) and with
annual iceberg numbers south of 48°N. These data show that, on average, ice coverage
has increased by 56 percent since 1983 relative to the earlier 1963 to 1982 period.
Moreover, even the lowest post-1982 level of ice coverage, observed in 1988, was 30
percent larger than the 1963 - 1982 mean.
The ice data for latitudes 45°N to 47°N (Figure 3.3-8) show that ice is appearing more
frequently at latitudes encompassing the Terra Nova site. Figure 3.3-9 shows
directional quadrant displays of statistics on annual occurrences of sea ice over the
period 1959 - 1995. Data are included for areas:
- Within 5 km of the Terra Nova site
- Within 5 to 25 km of the Terra Nova site
- Within 25 to 50 km of the Terra Nova site
95032-0-EI-GM-00003.0, Rev.0
The first of each pair of numbers in the upper panel of Figure 3.3-9 denotes the
fractional probability of ice appearances at some time within a given year. The second
entry in each case denotes the corresponding average number of weeks associated with
annual ice incursions.
Ice concentration data are summarized in the lower panel of the same figure, with the
paired entries denoting the average values of total and first year ice concentrations,
respectively, associated with ice incursions. Figure 3.3-10 shows the annual timings of
all 1960-1995 ice incursions within 50 km of Terra Nova. These data show the onset in
roughly 1983 of higher incursion probabilities together with the ice incursions centred
broadly around mid-March. This is when ice coverage around Newfoundland usually
peaks (see Figures 3.3-2 to 3.3-7).
Ice Movement
The position of Terra Nova in the vicinity of the extreme southern limit of the regional
pack ice has limited collection of ice drift data to areas at least 50 km north of the
proposed oil production site (Figure 3.3-11). Although the accuracies of the individual
vectors in Figure 3.3-11 are lowest in the Grand Banks region, the fields of motion
shown in Figure 3.3-11 are very similar to those of the regional surface currents
(Section 3.2.9) because of the paucity of repeat observations of individual ice features.
The principal circulation features are strong easterly and southerly movements
associated with the outer branch of the Labrador Current regimes on the northern and
eastern slopes, respectively, of the Grand Banks. A weaker, but still substantial,
southerly drift, evident in the Avalon Channel, is associated with a continuation of the
inner branch of the Labrador Current. Over the mass of the Grand Banks, the mean
flow is weaker and less definitive in direction.
The velocities of ice and surface currents are extremely variable. Their standard
deviations are comparable to or larger than their corresponding long-term temporal
averages. This extreme variability greatly complicates ice movement prediction and
contributes to large short- and long-term variabilities in areal ice distributions.
Drift speed and direction distribution are shown in Figure 3.3-12 as derived
(Seaconsult, 1988) from satellite-tracked, ice-mounted, drift buoy data from 1984 to
1987. The original buoy deployments, (Fissel et al., 1985) on ice floes at approximately
49°N, just north of the northern edge of the Grand Banks, were more or less
immediately swept up in the Labrador Current. They then followed trajectories
overlying the strong currents that follow the slope regions at the edge of the Banks. As
a consequence the indicated velocities are not representative of Terra Nova or adjacent
bank areas but of the adjacent slope regions (Figure 3.3-11).
95032-0-EI-GM-00003.0, Rev.0
While ice movements and surface currents on the Grand Banks are largely wind-driven
(De Tracy et. al., 1995), models using wind field inputs have not yet been able to
predict ice velocities with average errors significantly less than mean drift velocities.
Models that derive surface currents from either long-term means or "coupled"
ice-ocean models (Marko et al., 1994c) have produced similar results.
Even simpler treatments based on empirical linear relationships between ice velocity
and the contemporary local wind (Fissel and Tang, 1991) have produced uncertainties
of a factor of two in ice-to-wind speed ratios and turning angles.
More recent hindcast analyses (Marko and Fissel, submitted) have explained close to
75 percent of the variance in observed daily ice velocities through use of
bathymetrically specific, non-linear neural networks operating on inputs of
contemporary local- and time-lagged, non-local winds. These results presumably reflect
dependencies of local, bathymetrically controlled surface currents on temporal and
spatial details of regional wind fields. This suggests that more sophisticated empirical
methods could improve prediction of daily ice movements off Labrador and
Newfoundland.
Floe Size
The horizontal dimensions of individual ice floes are complicated functions of ice
history, concentration and thickness. As well, they are sensitive to water temperature,
sea state and proximity to ice pack and land. In Newfoundland waters, distinctions are
made between the size characteristics of floes located within roughly 100 km of the
coastline and in areas north and south of the 49°N northern boundary of the Grand
Banks. Physical confinement, colder air and water temperatures and the more effective
damping of wave amplitudes by seaward ice generally restrict the largest floes at the
inshore area. In the two offshore areas, floe sizes are smaller south of 49°N because of
melting, and fracturing is enhanced by typically lower ice concentrations and higher
water temperatures and sea states. In both offshore regimes, floe size decreased from
west to east because of progressive decreases in wave amplitudes propagating into the
pack ice from the open ocean.
Floes with diameters larger than 0.5 km are usually confined to the inshore regime and
areas north of 49°N. SLAR data from 1978 to 1982 (Carrier, 1982) show that such
floes can have diameters as large as 5 km and can comprise at least 2 percent of the
pack ice in March and April. Unfortunately, because the ice edge did not move
significantly south during the study period, these data contribute little to knowledge of
floe characteristics near Terra Nova.
Nevertheless, AES composite ice chart data for 1964 to 1987 indicate that floes had
diameters larger than 0.1 km in only 10 percent of reported occurrences of ice within
95032-0-EI-GM-00003.0, Rev.0
50 km of Terra Nova. Estimates made in several earlier studies (Blenkarn and Knapp,
1969; Nolte and Trethart, 1971; Convey, 1972; LeDrew and Culshaw, 1977;
Dobrocky Seatech, 1985) indicate that mean floe diameters in offshore areas south of
49°N are less than 30 m. Few observations of floes with diameters larger than 60 m
were reported. A northwest-to-southeast size gradient was also identified (Dobrocky
Seatech, 1985), with mean and maximum floe diameters decreasing from 8 m and 37
m, respectively, at 49°N, 51°W to 1 m and 3 m in the vicinity of Terra Nova
(Seaconsult, 1988). Mean and maximum diameters may exceed these values by an
order of magnitude or more (Seaconsult, 1988) when ice extent is close to its seasonal
maximum in years of exceptionally severe ice conditions. There is evidence that many
of the larger floes recorded in the cited studies and commonly observed on coarse
resolution (1 km) satellite images are conglomerates of smaller floes bound at their
peripheries by newly-grown, thinner ice.
Thickness
Physical growth of sea ice on the Grand Banks is largely confined to new ice formation
south of the main regional icepack during early winter outbreaks of cold air and, later
in the winter, in leads and irregular patches of open water interior to the pack ice
(Table 3.3-1). This new ice is usually short-lived as a distinct entity because of:
- Melting in later warmer periods and dispersal by wave action
- Incorporation into adjacent floes and deformed ice structures
Most of the sea ice on the Grand Banks is initially formed in upstream areas and
increases in thickness during subsequent southward drift (Figure 3.3-13) late in the ice
season. Figure 3.3-9 shows that slightly less than half of the ice coverage within 50 km
of Terra Nova is thicker than 30 cm. Figure 3.3-14 shows a more detailed thickness
probabilities in undeformed sea ice within 5 km of Terra Nova. This data was derived
subjectively (Seaconsult, 1988) from the 1959 to 1987 AES ice chart data used to
construct Figure 3.3-9 and is probably least reliable at the upper extreme of the
thickness range. The absence of ice significantly thicker than 1 m shown in Figure 3.314 agrees with most field observations.
Exceptional reports of first-year floes with thicknesses of 2 m in an area several tens of
kilometres northwest of Terra Nova (Dobrocky Seatech, 1985) have been attributed to
high upstream growth rates in the presence of heavy seasonal snow accumulations. The
occasional presence of even thicker, up to 6 m, multi-year ice is also possible; however,
sightings of such ice are so unusual as to preclude meaningful frequency or
concentration estimates.
95032-0-EI-GM-00003.0, Rev.0
Deformation
The maximum thickness of undeformed sea ice is largely determined by the flow of
heat from the ocean at the ice undersurface and the rate of heat loss at the ice surface.
Ice is thicker than approximately 0.5 m on the northern Grand Banks because of ice
from colder, more northern areas, as noted earlier, and ice deformation.
Sea ice deformation occurs in highly concentrated (approximately 10/10) pack ice
typically near land or landfast ice, which mechanically restricts ice responses to currents
and winds. Sea ice is deformed when it fails under the resulting compressive and, in
some cases, shear stresses; this produces the rough surface topography associated with
portions of the East Coast ice pack.
Deformations are generally classified as rafting, ridging or hummocking
(Figure 3.3.15). Rafting occurs when one sheet of ice overrides an adjacent sheet.
Ridging is associated with linear pileups and consolidation of ice blocks produced by
repeated local failures at a common boundary between two sections of relatively
undeformed ice. The third category, hummocking, refers to a much wider spatial
distribution of randomly scattered broken and upturned ice blocks.
Quantitative data on deformed ice are usually confined to ridge-type deformations
because of relatively easy characterization of frequency (number of ridges/km), length,
width and maximum top-to-bottom thickness (sail height plus keel depth).
Nevertheless, few quantitative data are available for the Grand Banks region, in part
because linear ridge formations of the type commonly observed in Arctic areas are
relatively rare. Instead, the deformed pack ice consists of fields of confused jumbles of
uplifted and broken floes (Figure 3.3-15b). Observation indicates that maximum sail
heights, corresponding to local peak heights in such fields, are approximately 2 m
(Dobrocky Seatech, 1985). This estimate is reasonably consistent with airborne
electromagnetic sensor measurements in Newfoundland areas farther inshore (Rossiter
and Holliday, 1989).
Ridge thicknesses near Terra Nova also have been estimated from data gathered off
southern Labrador during February and early March and extrapolated to the Grand
Banks and Terra Nova region (Seaconsult, 1988). With this approach, which neglects
the considerable meltdown and disintegration that accompanies additional drift,
indications are that ridges or rubble fields with sails as large as 3.5 m could form on the
Grand Banks (Bradford, 1972; Nordco, 1977; Nordco/C-CORE, 1978). Nolte and
Trethart (1972) calculated average ridge heights of approximately 1 m. Assuming
typical keel-to-sail ratios of 3:1 and allowing for meltdown during additional southward
drift south, these results suggest that 3 m and 15 m would be appropriate estimates for
the average and maximum thicknesses, respectively, of ridges in deformed ice
approaching the Terra Nova site.
95032-0-EI-GM-00003.0, Rev.0
It is important to note that, except in the case of early seasonal ice incursion (i.e.,
January or February) (Figure 3.3-10), when ice thicker than 30 cm is rare on the Grand
Banks, the hazards of even maximally thick deformed ice are greatly reduced by
melting of its constituent rafted and upturned floes and its interstitial, binding ice. These
changes increase structural fragility and ice porosity, reducing the operational hazards
of surviving ridge or rubble field fragments well below those associated with smaller
pieces of denser old or glacial ice.
3.3.3
Icebergs
Origins and Controlling Factors
The icebergs that appear seasonally each year off Newfoundland are originally
generated by marine glaciers located primarily (Feazel and Kollmeyer, 1972; Marko, in
prep.) north of 68°N on the west coast of Greenland. Newly created icebergs move
away from such source areas with the spring and summer clearance of sea ice and enter
the basic regional circulation shown in Figure 3.3-16. The pattern of movement reflects
both the predominant regional wind patterns and the strong cyclonic ocean currents
centred on the continental slopes (Section 3.2.4).
Recent evidence (Marko, in prep.) suggests that most icebergs reaching Newfoundland
initially move northward, taking a year or so to reach northwestern Baffin Bay. In the
interim, the icebergs melt, fracture and subdivide, reducing their linear dimensions, on
average, by a factor of about two. Many icebergs never reach northwestern Baffin Bay
because of long-term or repeated groundings accompanied by in situ meltdown during
the ice-free season in shallow West Greenland waters. Similar iceberg losses during
subsequent ice-free segments of the circulation adjacent to Baffin Island and Labrador
further reduce the number of drifting icebergs.
In fact, there is considerable evidence (Marko et al., 1994a; Marko, in prep.) that most
icebergs reaching Newfoundland each spring and summer have drifted southward
across 75°N from September to November of the previous year. This timing allows
these icebergs to avoid significant depletion during subsequent winter drift past the
Baffin Island and Labrador coastlines. Avoidance depends on the seasonal presence of
impenetrable fast ice in adjacent shelf areas, as it prevents iceberg entry and grounding.
Elimination of losses to groundings, together with the apparent absence of substantial
deterioration during the southerly winter drift accounts for the essentially identical size
distributions associated with iceberg populations observed in Northwest Baffin Bay
each fall and off southern Labrador the following spring (Marko, in prep.).
Deterioration of icebergs during subsequent southward drift determines seasonal
iceberg severities off Newfoundland. At most, only about 0.5 percent of the glacial ice
calved into West Greenland waters each year (Reeh, 1985) reaches 48°N off
95032-0-EI-GM-00003.0, Rev.0
Newfoundland in the form of icebergs. Actual annual numbers of icebergs appearing
south of 48°N (Figure 3.3-17) (IIP and PAL data), have little correspondence with
annual production rates in the West Greenland source area.
Instead these numbers are largely determined by sea ice conditions off and to the south
of southern Labrador, which control mass losses to wave action and meltdown.
Figure 3.3-18 shows a roughly bilinear empirical relationship between annual iceberg
numbers south of 48°N and mid-April spatial extents of sea ice off Labrador and
Newfoundland. The breakdown of this relationship occurs roughly at ice extents at the
1000 m bathymetric contour. This contour is usually associated with the main axis of
the outer branch of the Labrador Current and peak southward iceberg fluxes.
Additional sea ice in areas on and beyond the iceberg flow axis increase the probability
for iceberg survival to 48°N. Additional offshore extensions of the pack ice shorten the
length of subsequent drift through open, wave-exposed, warm water.
The horizontal movements of free-floating icebergs (i.e., ungrounded icebergs in open
water or in low concentrations of sea ice) are largely determined by local winds and
currents. When embedded in extensive fields of first year or older sea ice, iceberg
movements follow those of the adjacent ice, except, perhaps, when such ice is in an
advanced state of decay. In the vicinity of Terra Nova, generally characterized by lowto-moderate concentrations of relatively thin, structurally weak sea ice, icebergs tend to
move independently of the sea ice, reflecting the influence of deeper currents.
Nevertheless, iceberg speeds and drift directions on the Grand Banks (Figure 3.3-19)
as measured over one- to three-hour time intervals in the years 1983 to 1985
(Seaconsult, 1988) are qualitatively similar to mean sea ice velocity fields (Figure 3.311). About 65 percent of the measured speeds were less than 40 cm/s and 47 percent
were directed toward the southwest.
Equivalent plots (Figure 3.3-19) of off-shelf drift data (Seaconsult, 1988) show the
greater prevalence of higher speeds and easterly through southerly drift. This indicates
the dominance of the strong Labrador Current on the northern and eastern slopes of
the Grand Banks.
Several studies (Murphy and Anderson, 1985; Smith, 1993) show that, when
reasonably accurate contemporary wind and current data are available, observed
iceberg trajectories can readily be reproduced with simple physically based models of
iceberg drift. Results (Figure 3.3-20) are relatively insensitive to model parameters such
as air and water drag coefficients and, to some extent, to iceberg dimensions and shape
(Smith, 1993).
95032-0-EI-GM-00003.0, Rev.0
At present predictive model performances comparable to that indicated in Figure 3.320 are attained (Marko et al., 1987) only with near-real-time wind and current data
from locations within a few kilometres of the iceberg. Use of observed and forecast
winds accuracies which are, at best, comparable to those for physically-based sea-ice
drift models. Improvements in forecasts, which reduce average prediction errors to
levels comparable to corresponding drift magnitudes over daily or shorter periods,
have, thus far, only been obtained with mixed deterministic-statistical methodology (de
Margerie et al., 1986). However, given the growing abundance of regional iceberg
data, empirical approaches will enhance forecasting capabilities.
Variations in Local and Regional Iceberg Numbers
The numbers of icebergs crossing any given latitude off Eastern Canada vary
considerably both annually (Figure 3.3-17) and monthly. At 48°N, on the approaches
to the Terra Nova site, long-term averages of data compiled by the IIP over 1955 to
1985 (Figure 3.3-21) show that numbers of arriving icebergs peak in April but are at
high levels from April to June. Nevertheless, maximum monthly iceberg arrivals for the
year have been recorded in each of the months March through June and, in 1993, about
20 percent of the icebergs that year crossed 48°N in February.
Variations in the timing of iceberg influxes reflect annual differences in southward ice
and iceberg drift rates, and the wind fields. Winds heavily influence drift rates, and the
offshore position and extent of the ice pack.
The average number of icebergs crossing 48°N each month, over the full period of
iceberg count records, would be expected to be higher than shown in Figure 3.3-21,
given that iceberg totals (Figure 3.3-17) for most of 1955 to 1985 are lower than both
earlier and, particularly, subsequent periods. Most of the higher iceberg numbers
post-1982 have been suggested (Seaconsult, 1988) to be associated with the initiation
of routine use of imaging radar in 1983. As noted previously, this technological
advance allowed more efficient and, presumably, more complete survey capabilities.
However, the annual counts obtained from PAL surveys, also plotted along with IIP
data in Figure 3.3-17, show peaks of comparable magnitude to those pre-1983.
Therefore difficulties in comparing different portions of the full annual iceberg count
record may be primarily limited by remaining uncertainties in data extraction and
evaluation procedures necessitated by current usage of radar technologies.
In any case, for 1989 to 1995, the close correspondences between reliable Labrador
spring ice extent data (Figure 3.3-18) and the numbers of icebergs south of 48°N
appear to be relatively independent of the use of alternative IIP and PAL data. These
correspondences allow use of the time-series data of Figure 3.3-8 to confirm the
exceptionally high numbers of icebergs off Newfoundland since 1983. The ice extent
95032-0-EI-GM-00003.0, Rev.0
data indicate that 8 out of the 13 subsequent years show iceberg numbers in excess of
600, the threshold of the high seasonal iceberg severity category (Marko et al., 1987).
The iceberg count data show the same results for 9 out of the 13 years. In terms of
mean annual numbers of icebergs south of 48°N, the post-1982 numbers (701 with
PAL data and 838 without) are approximately three times larger than the mean annual
count (269) estimated for the previous 23 years.
The impact of such an increase in icebergs near the Terra Nova site is shown by plots
of occurrence percentages for different ranges of iceberg numbers observed annually in
the 1° grids containing the site (Figure 3.3-22). Comparisons of data from 1960 to
1982 (Figure 3.3-17) with the corresponding post-1982 results of Figure 3.3-17
(obtained using PAL data for the 1989-1995) period show a pronounced shift toward
more iceberg per year iceberg numbers. The counts suggest that iceberg numbers
larger than, alternatively, 50 and 100 icebergs were approximately twice as probable as
in the earlier survey period. Iceberg-free conditions, corresponding to less than 10
icebergs per year were almost three times as rare, with an occurrence percentage
declining from 56 percent to 23 percent.
A plot of annual iceberg numbers in other 1° grids between 45°N and 53°N (Figure
3.3-23) using 1989-1995 PAL data shows the regional iceberg distribution. The upper
and lower numbers in each rectangle denote, respectively, sums of the maximum and
mean numbers of icebergs observed each month of the year. The maximum numbers
provide a worst-case representation of local annual iceberg severities as not all
maximum monthly iceberg numbers actually were recorded in the same year.
These data show that icebergs are most frequent in the Avalon Channel adjacent to
Newfoundland and over the northern and eastern slopes of the Grand Banks. These are
regions associated with the strong flowing branches of the Labrador Current. The
largest numbers of icebergs immediately adjacent to the Terra Nova 1° grid tend to
appear in the 1° grid immediately to the north, northeast and east. These areas are
traversed by the 200 m contour associated with the approximate inshore edge of the
outer branch of the Labrador Current.
Iceberg Size Distributions
The accuracy of information on the physical dimensions of Grand Banks icebergs is
limited by measurement uncertainties, varying selection criteria and often unspecified
selection criteria. Recent work (Crocker, 1993; Crocker and Cammaert, 1994; Marko,
in prep.) has distinguished between iceberg lengths greater and smaller than
approximately 20 m.
95032-0-EI-GM-00003.0, Rev.0
The dimensions of the larger icebergs have been reasonably well described by
lognormal or gamma distributions in upstream areas such as Labrador, Baffin Bay and,
to a slightly lesser extent, off Newfoundland. Figure 3.3-24 shows representative
distributions of exceedance percentages for the waterline lengths of icebergs in this
category (Seaconsult, 1988). This information is based on data gathered from surface
vessel surveys in Newfoundland waters south of 49°N and east of 51°W. The on- and
off-shelf data, corresponding to local water depths less than and greater than 100 m,
respectively show the effects of bathymetry on iceberg distribution. The restriction of
draft in the shallower waters introduces similar limitations on other, draft-correlated
dimensions.
Figure 3.3-24 shows:
- Negligible probability in on-shelf areas of icebergs longer than about 180 m
- Mean onshelf iceberg lengths of 68.9 m
- Mean iceberg lengths of 80.7 m
The 8 percent probability of on-shelf icebergs longer than 120 m is comparable to a 6
percent figure obtained from 1989-1995 PAL data (PAL, 1995) for the Terra Nova 1°
grid. However, since two-thirds of the latter icebergs were observed in a single year,
1989, the considerable spatial and temporal averaging in the distributions of Figure 3.324 should be recognized. There has been little systematic study of the spatial and
temporal scales of variations in such distributions beyond basic distinctions between
the on- and off-shelf regimes.
Figure 3.3-25 shows the draft restrictions of on-shelf and off-shelf areas as derived
from side-scan sonar measurements on subsets of the icebergs represented in Figure
3.3-24. In off-shelf areas, icebergs have drafts larger than 150 m and in on-shelf areas,
iceberg drafts are in the 20 m to 100 m range. Mean on-shelf and off-shelf drafts are
59.8 m and 68.5 m, respectively.
Fewer data are available on above-water iceberg heights and on the overall masses of
Grand Banks icebergs. Measurements of 113 icebergs on the northern Grand Banks
(Ice Engineering, 1981a; 1981b; 1982; 1983) (Figure 3.3-26) show median heights of
about 20 m. Only about 4 percent of the icebergs have heights in each of the extreme
categories (less than 10 m or greater than 50 m).
Figure 3.3-27 shows a representative mass distribution derived for on-shelf regions
from the data of Figure 3.3-24 using an empirically established connection between the
mass and 30 percent of the cube of the waterline length (G.B. Crocker, pers. comm.).
This approach to estimating the distribution of iceberg mass avoids the statistical
problems posed by the small sample sizes used in most previous estimates. It also
reproduces observations that only a few percent of the on-shelf icebergs have masses in
excess of 1 million tons (Seaconsult, 1988).
95032-0-EI-GM-00003.0, Rev.0
Figure 3.3-27 shows that three-quarters of the icebergs appearing inside the 100 m
contour on the Grand Banks have masses smaller than 250 000 tons.
Only in recent years has significant effort been given to systematic study of the bergy
bits and growlers which comprise, respectively, most of the lower and upper ends of
the smaller iceberg regime (lengths less than 20 m). Bergy bits and growlers must also
be managed to ensure transport vessel and support vessel safety. Even though they are
smaller than icebergs they are still of substantial size, and they are more difficult to
detect, particularly in high seas. Consequently, high operational priority has been given
(Croasdale and Associates, 1994) to the acquisition of detailed knowledge of these
smaller members of the regional and local iceberg populations. Measurements on
several recently disintegrated icebergs (Crocker, 1993) over a large, intensively
surveyed area (Crocker and Cammaert, 1994) indicate (Marko, in prep.) that relative
numbers of iceberg fragments are a function of length by a common negative
exponential probability law. Additional data and study are required to assess the
universality and the physical origins of the latter law as well as to establish the nature of
its connections with adjacent distributions of larger icebergs.
Iceberg Deterioration
As discussed earlier, the iceberg conditions at Terra Nova and on the Grand Banks
represent the net effects of advection and accumulated deterioration on icebergs calved
at least two years previously, primarily in West Greenland waters. Iceberg mass is lost
all along individual drift trajectories, particularly where waves are strong and water
temperatures are above freezing. These conditions tend to occur in areas and at times
when sea ice is not present.
At present, iceberg deterioration can be quantified only by estimation (Anderson, 1983)
of drifting iceberg lifetimes using highly idealized mass dissipation algorithms (White et
al., 1980). These algorithms are based on wave-driven erosion at iceberg waterlines,
but are limited in accuracy by multiple, factor-of-two uncertainties in key energy
transfer- and iceberg characterization-parameters. They are even less accurate when
applied to realistically shaped icebergs containing naturally occurring and
erosion-generated structural defects.
Algorithm simplification has included attempts to represent the complex process of
iceberg fragmentation in terms of idealized failure in the overhanging ice ledges, which
are generated by the waterline erosion process (White et al., 1980; Venkatesh et al.,
1994). This approach has limitations (Marko and Fissel, 1994). Crude estimates of
overall floating iceberg mass loss rates have been made in model studies (Marko et al.,
1994a) by scaling-up the White et al. (1980) wave erosion algorithm to reproduce
losses inferred from repeated estimates of individual iceberg dimensions (Robe et al.,
1977; Venkatesh, 1986).
95032-0-EI-GM-00003.0, Rev.0
More recent work (Marko, in prep.) suggests that the observed, approximately
lognormal character of size distributions in populations of larger icebergs all along the
main iceberg trajectories (Figure 3.3-16) cannot be explained solely in terms of the
mechanisms considered by White et al. (1980). Instead, the work suggests the
observed size distributions indicate the presence of important modes of flexural failure
driven by ocean waves. The proposed failure modes preferentially fracture icebergs into
two or more comparably sized fragments at naturally occurring or erosion-induced
structural defects. It was shown that this mechanism decreases in effectiveness when
iceberg lengths become smaller than, roughly, one half of the prevailing ocean
wavelength. This decreased effectiveness is consistent with the appearance of a
different, negative exponential size distribution law in icebergs smaller than 20 m.
Marko (in prep.) suggests the latter size distribution is most consistent with the
predominance, in small icebergs, of fracture processes which occur with equal
probability at randomly distributed structural defects.
Iceberg Scouring
Icebergs with drafts exceeding local water depths disturb the sea floor, resulting in
continuous or interrupted linear gouges and pits. These are called iceberg scours. The
dimensions and frequencies of scours can be used to assess probabilities for unwanted
interactions between icebergs and oil production infrastructure on or below the sea
floor.
Details of the scouring process are only incompletely known and undoubtedly depend
on the following:
· Sea bottom slope and composition
· Iceberg shape and stability
· Strength and directionality of the current-, wind- and sea ice-forces acting on the
iceberg
Evidence accumulated off Labrador suggests that long, continuous ice scours are most
often generated by icebergs stabilized by adjacent dense sea ice (Geonautics Ltd.,
1989). Such icebergs, particularly in the thicker ice found north of the Grand Banks,
have limited rotation about both vertical and horizontal axes, which are important
determinants of scour characteristics (Woodward-Lynas et al., 1985). These rotations,
along with, presumably, fracture and breakage of bottom-embedded keels, eventually
reorient icebergs into shallower draft configurations. In other circumstances, rotations
about horizontal axes of free-floating icebergs increase iceberg draft and initiate
scouring.
Scouring probabilities and depths have been assessed using a variety of techniques and
various mixtures of data:
· Sedimentation rates
95032-0-EI-GM-00003.0, Rev.0
· Incident iceberg numbers, drafts, velocities, depths and areal densities
· Ages of existing scours
Table 3.3-2 lists basic existing scour data characteristics, as determined from sidescan
sonar surveys of the region between 46° to 47.5°N and 48.2° to 50W°. The observed
scours began and ended in similar water depths and did not penetrate more than 1.5 m
into the seafloor. Figure 3.3-28 shows the frequencies of scouring near Terra Nova
relative to other Newfoundland offshore regions in the form of contours of scouring
density.
Table 3.3-2
Descriptive Statistics for Iceberg Scour at Terra Nova
Coordinates for Northwest Corner
47.457°°N 49.988°°W
Parameter
No. of records
Maximum
Minimum
Average
Std. Dev.
Scour Length
m
62
3370
60
566.3
623.2
Coordinates for Southeast Corner
46.01°°N 48.203°°W
Scour Width
m
Sour Depth
m
53
85
7
24.8
4.0
53
1.5
0.0
0.6
0.3
Change in Water Depth
m
1.0
0.0
0.8
0.4
Note: These scour statistics are for water depths between 80 and 100 m.
Highest scouring densities tend to be concentrated, in spite of the deeper water, in
strong current regimes associated with the Avalon Channel, the outer slopes of the
Grand Banks and areas off southern Labrador.
Conversion of the approximately 100 scours/100 km2 density indicated for Terra Nova
and surrounding Grand Banks regions into annual scouring probabilities require use of
an estimated (Scott et al., 1984) age of 2500 years for the oldest scours in the vicinity.
The simplest estimation procedures neglect the possibility that sedimentation has
obliterated a substantial fraction of the scours. As a consequence, the resulting
probability estimate of 0.04 scours/100 km2 per year (Lewis et al., 1987) represents a
minimum value for the true local scouring probability. Initial attempts to refine this
estimate by allowing for scour infilling by sediment transport yielded a probability of
about 0.1 scours/100 km2 per year (Lewis et al., 1987). Still higher probability
estimates of 0.35 scours/100 km2 per year were obtained by calculating scour
frequencies from iceberg flux and draft statistics (d'Apollonia and Lewis, 1986). These
calculations used iceberg fluxes derived from IIP data for the period 1960 to 1984 and
draft statistics obtained from Labrador data. The IIP data should underestimate recent
95032-0-EI-GM-00003.0, Rev.0
Grand Banks scouring probabilities because of the notably higher post-1984 regional
iceberg fluxes; the Labrador data should produce the opposite effect because
deterioration reduces iceberg draft during the additional drift from Labrador to the
Grand Banks. Approximate cancellation of these opposing estimation tendencies is
assumed, leaving the d'Appollonia and Lewis (1986) estimate as a tentative upper limit
for local scouring probabilities.
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3.4
Geology
Canada's eastern continental margin offers clues to understanding the geological setting
of the Grand Banks and its hydrocarbon-rich zones. In broad terms, the geological
history represented by the bedrock and overlying surface sediments of Newfoundland's
Continental Shelf are the result of two long-term plate tectonic processes.
The first tectonic process took place during the Paleozoic era and involved the initial
rifting of a primordial continental land mass. This was followed by the opening and
closing of an old ocean (Iapetus Ocean) and ended with the collision of the continents
on either side of the Iapetus to form a super-continent (Pangea). The colliding
continents juxtaposed older Proterozoic crustal fragments and created the Paleozoic
sequence of rocks which today are expressed topographically by the Appalachian
Mountains.
The second tectonic process, which occurred during the Mesozoic and Cenozoic and
which is of primary interest with respect to oil exploration and development, involved
the birth and growth of the North Atlantic Ocean. This involved at least two periods of
initial rifting that eventually separated the present-day land masses of North America,
Greenland, Europe, and Western Africa. During these periods, thick sedimentary
sequences were deposited along the western margin of the Atlantic in various
sedimentary basins such as those shown in Figure 3.4-1.
The Jeanne D’Arc Basin has been the focus of oil exploration activity since 1964 and
contains the Terra Nova and Hibernia fields. Sedimentological processes related
primarily to ocean waves and currents, sea ice movement, global sea level changes,
sediment slides and slumping, and glaciation during the Tertiary and Quaternary
periods have resulted in the physiography of the seabed that exists today.
3.4.1
Bedrock Geology
The bedrock geology of the study area can be grouped into two principal complexes
associated with the tectonic processes described above:
· A basement complex represented by pre-Mesozoic rocks
· A thick, mainly sedimentary sequence of Mesozoic and Cenozoic age
Figure 3.4-2 shows the distribution of basement and sedimentary rocks in the study
area. Table 3.4-1 is a geological time scale that defines the terminology used in
describing the age of the various bedrock units.
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Pre-Mesozoic basement rocks (consisting of sedimentary, igneous, and
metasedimentary rocks) have been encountered in shallow exploratory holes, and
detected by geophysical methods, in various parts of the study area. They are exposed
on the continental margin around Newfoundland as well as on the Flemish Cap,
Eastern Shoals and Virgin Rocks. Elsewhere, erosional surfaces of the basement
underlie the younger Mesozoic-Cenozoic sedimentary sequences. Table 3.4-2 shows
the lithology of the exposed basement rocks and their location.
Mesozoic-Cenozoic Complex
The tectonic and stratigraphic framework in which the Mesozoic-Cenozoic rocks occur
has been described by numerous authors (Grant and McAlpine, 1990; Tankard et al.,
1989; Enachescu, 1987; and others). This complex of sedimentary and, to a lesser
extent, igneous rocks represents the initial rifting and spreading of the continents to
form the North Atlantic Ocean. Grant and McAlpine (1990) have grouped the various
lithological units of the Grand Banks into six depositional sequences and have provided
tectonic interpretations for each (Figure 3.4-3). These sequences are described below.
The lithologies forming Sequence 1 were deposited in the Late Triassic to Early
Jurassic upon erosional basement surfaces. These rocks consist of red beds, evaporites,
carbonates and volcanics. They represent arid continental depositional environments
characterized by a succession of evaporite basins, coastal sabkhas, tidal flats, restricted
lagoons and a neritic sea. These lithologies suggest an early continental rifting episode
that failed.
Table 3.4-2
Lithology of Pre-Mesozoic Basement Rocks of the Study Area
Location
Lithology
Nearshore band paralleling the
Avalon Peninsula westward to
Fortune Bay
Tightly folded metasedimentary and
metavolcanic rocks with a low grade of
metamorphism
Virgin Rocks
Diabase and a tillite with distinctive granitic
inclusions
Eastern Shoals
Pink and white quartzites
Flemish Cap
Granodiorite intruding dacite and volcanogenic
siltstone
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Sequence 2 lithologies were deposited during the Early to Late Jurassic within a
shallow inland sea (or epeiric basin) that flooded the land. The lithologies
characterizing this sequence consist mainly of shallow-marine shales and limestones,
with siltstones and sandstones to a lesser extent. The Upper Jurassic Rankin Formation
contains a 75 to 150 m thick, carbon-rich shale unit known as the Egret Member. This
unit, which was laid down in a restricted, shallow, neritic sea and brackish lagoon
environment, is the source rock from which oil in the Jeanne D’Arc Basin is derived.
From the Late Jurassic to Early Cretaceous, Sequence 3 lithologies resulting from
continental uplift and rifting were deposited. These rocks, consisting of sandstones,
siltstones and to a lesser extent, shales and limestones were deposited in fluvial fans,
deltas, interdistributary bays, estuaries, tidal flats and shallow-marine environments.
Oil-bearing reservoir rocks found in the Jeanne D’Arc Basin were deposited within this
sequence.
Depositional Sequence 4 was created during the tectonic transition from continental
rifting to oceanic spreading between the Grand Banks and Europe that spanned the
Early to Late Cretaceous. This sequence is characterized by fine-grained estuarine
sandstones, and lagoonal and tidal flat shales of the Avalon Formation, followed by
sands of the Ben Nevis Formation deposited in shallow estuarine channels and tidal
flats. Both formations are also recognized as oil- bearing reservoir rocks of the Jeanne
D’Arc Basin.
Sequence 5 represents continental drifting between Labrador-Greenland and
Greenland-Northern Europe from the Late Cretaceous to the Paleocene. Sedimentation
was intermittent and produced deltaic deposits, chalky limestones, and transgressive
marine shales with minor siltstones and sandstones deposited in a sub-littoral
environment.
By the Eocene, sediment deposition over the Grand Banks had dwindled substantially.
Subsidence and seaward tilting of the continental margin in the Tertiary resulted in the
formation of semiconsolidated neritic sandstones, siltstones, and shales belonging to the
Banquereau Formation (Sequence 6). A lowering of the sea level about 15 000 years
ago exposed much of the Grand Banks, allowing subaerial and glacial erosion of the
top of the Banquereau Formation.
3.4.2
Physiography and Surficial Sediments
The Continental Shelf of Newfoundland can be described in terms of three major
physiographic zones (Fader and Miller, 1986; Fader and Piper, 1990):
1. An inner shelf of undulating relief underlain by Pre-Mesozoic basement with incised
channels filled by glacial sediment
95032-0-EI-GM-00003.0, Rev.0
2. An inner-central zone of broad, longitudinal depressions (e.g., the Avalon Channel)
3. An outer shelf of large, shallow banks separated by transverse troughs (such as the
Grand Banks)
Surficial sediments refer here to those sediments deposited during the Quaternary
above erosional surfaces of the Tertiary Banquereau Formation. The main geological
features that control the occurrence and distribution of surficial sediments on the
continental shelf are as follows (Fader and Miller, 1986):
· The lithology and morphology of the bedrock
· The advance and recession of Pleistocene continental ice sheets that extended over
the shelf
· A Late Pleistocene-Holocene low sea-level stand at about 100 m below today’s sea
level
· An oceanic regime persisting since the Holocene that reworks the sediments
In general, the thickness of these sediments above the Tertiary semi-consolidated
bedrock is believed to be between 10 and 18 m on the Grand Banks (Fader and Miller,
1986; Seaconsult, 1988). Table 3.4-3 describes the stratigraphy of the five main units.
Of these, only the basal Grand Banks Drift and overlying Grand Banks Sand and
Gravel occur in the Terra Nova development area (Seaconsult, 1988; Moran and
Mosher, 1988).
The Grand Banks Drift is a formation of glacial till (or diamicton) that was deposited
over Tertiary bedrock directly beneath the glacier. The Grand Banks Sand and Gravels
are sediments consisting of lag gravels (including pebble-to-boulder sized fragments)
and sands that represent most of the seafloor in the Terra Nova Development area.
The most common bedforms identified on the Grand Banks are sand ridges, sand
ribbons, megaripples, and wave-formed ripples. Of these, the largest are the sand
ripples which can be up to 15 m thick, 60 km long, and with a wavelength of 4 km
(Seaconsult, 1988). Of interest are the numerous W-shaped bedforms up to 200 m in
size that characterize the Terra Nova area. Their origin is unknown (G. Fader, Atlantic
Geoscience Centre, pers. comm.).
95032-0-EI-GM-00003.0, Rev.0
Strongly to weakly laminated, sandy to silty,
marine clay
Rounded to subrounded lag gravels (pebble to
boulder range) overlain by clean, well-sorted,
coarse to medium grained sand. Many clasts
have an Avalonian affinity.
Fine-grained, clean to muddy sand with some
gravel
Rhythmically banded, silty clay of
glaciomarine origin. May contain dropstones.
Normal and overconsolidated, poorly-sorted,
gravelly and sandy muds. May contain shell
fragments. Coarse fraction often shows an
Avalonian affinity.
Siltstone, mudstone and sandstone
Grand Banks Sand and
Gravel
Adolphus Sand
Downing Silt
Grand Banks Drift
Tertiary
Lithology
Placentia Clay
Formation
0 to 60
0 to 10
0 to 10
(generally a
veneer)
0 to 20
(generally a
veneer)
0 to 30
Thickness
(m)
Remarks
Unconformity at surface probably formed by subaerial and glacial
erosion
Normal consolidated facies is restricted to basinal areas, underlying and
interbedded with Downing Silt. Overconsolidated facies occurs over
large areas of Grand Bank and underlies the normal consolidated facies.
The two facies are thought to be separated by a glacial erosional surface
(intraformational erosional surface). Much of the till is thought to have
been deposited proximal to the buoyancy line of an ice sheet.
Unconformable with underlying bedrock surface.
Overlying and interbedded with normally consolidated Grand Banks
Drift. Most frequently occurs in basin areas, and probably deposited
from sediment plumes and rainout from ice shelves.
Sub-littoral deposits formed seaward of the Late Wisconsinan shoreline.
Occurs in water depths greater than 100 m.
Basal transgressive deposits across bank areas (above 100 m water
depth), formed during Late Wisconsinian-Holocene transgression. Much
of the sand is presently undergoing reworking in various bedforms such
as sand ridges, sand ribbons, megaripples and wave-formed ripples. The
thickest deposits are associated with sand ridges. Unconformable with
Grand Banks Drift and Downing Silt.
In part a time equivalent of Grand Banks Sand and Gravel; basinal
deposits conformable with Downing Silt
Stratigraphy of Surficial Sediments Overlying Tertiary Bedrock
Table 3.4-3
3.4.3
Hydrocarbon Occurrence and Production
During much of the Mesozoic-Cenozoic, an overall extensional tectonic regime
combined with crustal subsidence, periods of rapid sediment loading, and development
of salt structures resulted in the production of numerous faults (Enachescu, 1987;
Tankard et al., 1989). These faults both define the margins of and dissect the
sedimentary basins. To a large extent, they also have contributed to the migration and
structural entrapment of hydrocarbons in the reservoir rocks. Figure 3.4-4 shows a
variety of hydrocarbon traps that characterize the Jeanne D’Arc Basin, many of which
are fault controlled. Figure 3.4-5 is a plan of the Jeanne D’Arc Basin showing the
complex fault structure of the bedrock units.
Oil was first discovered in the Terra Nova Field in 1984 when Petro-Canada penetrated
the Jurassic Jeanne D’Arc sandstone with its K-08 well. Following this success, eight
additional wells were drilled to define and delineate the extent of oil reserves in the
field. Terra Nova is the second-largest reservoir discovered in the Jeanne d'Arc Basin
with recoverable oil reserves estimated at 48 x 106 m3 of light, sweet crude with API
gravity of 32 to 34° (Petro-Canada, unpublished report).
The Terra Nova reservoir is subdivided into four major structural blocks: the West
Flank, the Graben, the East Flank and the Far East. Drilling results have identified five
major and two minor oil-bearing sands in The Graben and East Flank. Although the Far
East block has not been tested by drilling, geophysical data suggest that it may contain
up to 16 x 106m3 million barrels of recoverable oil. There are no plans to develop the
West Flank at this time.
3.4.4
Seismicity
Nolan-Ertec (1989) has defined the Grand Banks seismotectonic province as a
triangular area bounded by the Glooscap-Newfoundland Fracture Zone to the south;
the Charlie Fracture Zone-Hermitage Flexure-Long Range Fault to the north and west;
and the edge of the Continental Shelf to the east (Figure 3.4-6).
This area is one of relatively low seismic activity. Based on geological characteristics
and information from historic events, earthquakes with magnitudes of less than M=5.5
are expected to occur in the Grand Banks province (Nolan-Ertec, 1989). However,
past seismic events are not well documented for the offshore, particularly for
earthquakes with magnitudes less than M=5 (Seaconsult, 1988).
The most seismically active portion of the Newfoundland Continental Shelf is the
Laurentian Channel (along the Newfoundland Fracture Zone). Here an earthquake with
a magnitude M=7.2 occurred in 1929, with aftershocks as high as M=6.
95032-0-EI-GM-00003.0, Rev.0
Earthquakes with magnitudes of about M=6 occurred in the same area in 1951, 1954
and 1987. Figure 3.4-7 shows the epicentres and magnitudes of earthquakes recorded
between 1929 and 1980.
In terms of relative seismicity, the Terra Nova site is comparable to the Hibernia
development area (Seaconsult, 1988) and both are ranked as Zone 1 areas out of a
range of 0 as the low to 5 as the high (Mobil, 1985). Zone 0 is well represented by the
aseismic Gulf of Mexico, while Zone 5 represents areas of severe seismic risk such as
in the Gulf of Alaska (Mobil, 1985).
95032-0-EI-GM-00003.0, Rev.0
3.5
3.5.1
Coastal Geomorphology
Shoreline sensitivity data have been collected by aerial video surveys in the early 1980s
for southeastern Newfoundland by Mobil Oil. Northeastern Newfoundland shorelines
from St. Anthony to Trinity Bay were surveyed by Petro-Canada.
The portion of the Newfoundland coastline described in this section extends from
Cape St. Francis on the northeast tip of the Avalon Peninsula to Point Crewe at the tip
of the Burin Peninsula. Based on the predicted movement of oil in the water, this is the
shoreline area that could be impacted by a spill should one occur in the offshore
development area (Mobil, 1985).
Newfoundland’s eastern coastline is generally characterized by rocky headlands and
steep cliffs with few, discontinuous pocket beaches and baymouth bars, or barachoix.
The shoreline varies from being deeply indented (the result of preferential erosion along
unresistant faults, folds and erosive bedrock), to straight with few embayments (as
along the Cape Shore of Placentia Bay where bedrock structure parallels the coast)
(Catto, 1994).
To a large extent, the development of this coastline has been strongly influenced by the
effects of the last glaciation. This influence is reflected by the predominantly
pebble-gravel beaches that occupy 53 percent of the coastal backshore areas, and the
rarity of sand-dominated beaches that occupy less than one percent of the shoreline
(Forbes, 1984; Shaw and Forbes, 1987; Catto, 1994; Liverman et al., 1994; Mobil,
1985; Newfoundland Geological Survey Branch, unpublished data).
In an effort to characterize the beaches of Newfoundland’s eastern shoreline, Catto
(1994) has grouped these areas into three categories:
1. Exposed systems
2. Low- to moderate-energy coves
3. High-energy coves
Exposed systems are those beaches that have developed along open coastlines where
both shore-normal and shore-parallel (or longshore) currents govern sediment
deposition and erosion. These beaches, typically found in Placentia Bay, derive their
sediment from glacial till deposits located upcurrent.
Low-to-moderate and high-energy cove systems are well represented along the eastern
coast of the Avalon (i.e., the “Southern Shore”). These beaches are typically
characterized by dominantly shore-normal sediment transport and derive their sediment
from nearby cliffs of bedrock or glacial till. This pattern of sediment transport implies
95032-0-EI-GM-00003.0, Rev.0
that sediment and contaminants, once introduced into a beach system, will remain
within the cove for a considerable period and will be less likely to migrate laterally
along the shoreline (Catto, 1994).
A number of studies have shown that sea level is progressively rising around the
Avalon Peninsula at rates of up to 7 mm/a. This is manifested by coastal erosion rates
approaching 1 m/a year at some beaches. To some degree, this erosion is the result of
historic anthropogenic influences such as aggregate quarrying and construction near
the shoreline; however, coastal areas relatively untouched by humans have also shown
this pattern (Taylor et al., 1990; Catto, 1994; Liverman et al., 1994). A joint coastal
monitoring program has recently been initiated by the Newfoundland Geological
Survey Branch and the Geological Survey of Canada to measure the changing nature
of this shoreline.
3.5.2
Hydrology, Oceanography and Ice
Rivers in the study area are typically small in total volume discharge, with a strong
seasonal variation resulting from the annual cycle in precipitation. The most significant
rivers (i.e., those rivers with drainage areas > 50 km2), and the water bodies into which
they drain, are shown in Figure 3.5-1. Overall, the amount of freshwater input into
shoreline waters is modest, given the comparatively low area of land drainage relative
to the large lengths of shoreline around the Avalon and Burin peninsulas. Generally,
local freshwater runoff is small in comparison to that arising from the melting of sea ice
in spring in coastal areas, and on the northeast Newfoundland Shelf.
The tides experienced along the coastlines are moderate in size, with normal tidal
heights of approximately 1 m (Section 3.2.5). Along the south coast, including
Placentia Bay, the tide is predominant semidiurnal (two highs and two lows each day).
Off the east coast of Newfoundland, the tide can be characterized as mixed, mainly
semidiurnal (Godin, 1980).
Ocean currents in the exposed outer coastal areas are dominated by the southward
flowing inner branch of the Labrador Current (Petrie and Anderson, 1983; Petrie,
1991; Narayanan et al., 1995). The inner branch of the Labrador Current has typical
speeds of 20 cm/s, and is centred over the Avalon Channel, an underwater trough
separating the coastline from the western side of the Grand Banks (see Section 3.2).
Southward flows along the exposed portions of the shoreline, such as headlands, can
be expected to be considerably larger than the mean flows at times. This results from
the combination of the longshore drift, tidal currents and undertows induced by waves
breaking along the coast. The Labrador Current turns westward after rounding Cape
Race, and a branch of this current exhibits a cyclonic, re-entrant pattern in the mouth of
Placentia Bay.
95032-0-EI-GM-00003.0, Rev.0
Within the major bays along the coastline, the local circulation can be markedly
different than that on the outer coast. The circulation within Trinity Bay (Yao et al.,
1988) and Conception Bay (deYoung et al., 1993; deYoung and Anderson, 1995) has
recently been studied. Generally, the mean current speeds are lower (2 cm/s) in these
two large bays than those along the outer coastlines. In most of the area, the flow
speeds are controlled by the local underwater topography, with the basin shape playing
a significant role in defining the characteristics of the flow field. Tidal flows in the bays
are also weak, with typical speeds of a few centimetres per second or less for the
dominant semidiurnal (M2) tidal constituent. Given the generally weak and variable
circulation, the residence time for water, and any drifting matter including pollutants is
much longer than for the offshore regions, DeYoung and Anderson (1995) estimate
residence times in Conception Bay as about 40 days.
Exposure to ocean waves is a major determinant of shoreline characteristics as
discussed above. The large ocean waves that occur in the offshore area (Section 3.2-8)
have very high energy levels as they impinge on and break along the exposed outer
shoreline. Again, within the larger embayments, and in areas sheltered by offshore
islands, the exposure to ocean waves is much reduced, resulting in much different
beach types in these areas.
Sea ice is also a seasonal factor in the shoreline environment. It can disturb the
shoreline during break-up (through bottom scouring), or in more sheltered locations
where it can be a landfast ice cover, it can protect the shoreline from waves and strong
currents. Pack ice often covers the shoreline from mid-March to late April. In the major
bays, the pack ice tends to remain in place for extended periods, while along the
exposed offshore shorelines, it is moved quickly through the area by local winds and
currents.
95032-0-EI-GM-00003.0, Rev.0
3.6
3.6.1
Water Quality
Trace Metals
Large concentrations of essential metals (e.g., Cu, Zn, Fe, V, Cr), and low
concentrations of other non-essential metals (e.g., Hg, Cd, Pb) may be toxic to living
organisms. Table 3.6-1 shows the results of two studies measuring the levels of trace
metals in seawater from the Grand Banks and the Gulf of St. Lawrence. There are no
data available since 1985 on trace metal levels in seawater from the Grand Banks. In
general, metal concentrations in marine waters of the North Atlantic and in coastal
areas do not vary widely except for some coastal regions with localized metal
contamination (Eaton et al., 1986).
Table 3.6-1
Trace Metal Concentrations in Grand Banks and
the Gulf of St. Lawrence Seawater
Grand Banks
Element
Concentration
March
(ug/kg)
Arsenic (As)
Cadmium (Cd)
Chromium C)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Mercury (Hg)
Molybdenum (Md)
Nickel (Ni)
Vanadium (Va)
Zinc (Zn)
1.89
0.20
0.31
1.85
3.50
0.39
0.004
0.086
1.36
0.16
3.79
Concentration
November
(ug/kg)
1.89
0.26
0.37
1.97
1.40
0.41
0.002
0.460
0.91
0.13
2.01
Palegic NW
Atlantic
(ug/kg)
1.5
0.04
0.23
0.11
0.45
0.003
0.001
10.0
0.23
N/A
0.35
Central
St. Lawrence
Estuary
(ug/kg)
N/A
0.093
N/A
0.84
5.5
N/A
N/A
N/A
0.52
N/A
2.11
Source: Data for Grand Banks is from MacKnight et al. (1981) in Mobil (1985).
Hydrocarbons
Detailed water quality studies of the Grand Banks by Levy (1983); and MacKnight et
al. (1981) were presented in the Hibernia Development Project EIS (Mobil, 1985).
There are no additional Grand Banks water quality data available since 1985.
95032-0-EI-GM-00003.0, Rev.0
A study by Levy (1986) documented background water quality hydrocarbon values
from the Labrador shelf area. Samples were collected from both the surface of the
ocean (referred to as the surface microlayer in Levy, 1986) and at numerous depths
(referred to collectively as water column samples). Floating particulate petroleum
residues were also measured.
Background water quality data for the Hudson Strait-Labrador Shelf show:
- No appreciable amounts of particulate petroleum residues
- Extractable petroleum residues in the surface microlayer ranging from 4.5 to 20.9
ug/L (general background level of 8.13 ug/L)
- An overall background level in the water column of 0.51 ug/L
Levy (1986) also compared the results to hydrocarbon levels for the Grand Banks
(Levy, 1983) since the Labrador Shelf is the source water of the Labrador Current
which project south to the Grand Banks. The background level in the surface
microlayer for the Labrador Shelf is substantially lower than that (28.9 ug/L) of the
Grand Banks (Levy, 1983). Water column background levels are similar to reported
values for the Grand Banks (0.17 ug/L; Levy, 1983); both are considerably lower than
1 ug/L. Levy (1986) noted that the background extractable petroleum residues in the
water columns throughout the East Coast of Canada are well below the concentrations
of petroleum-related substances known to have toxic or sublethal effects on marine life
(Kiceniuk and Khan, 1983 in Levy, 1986). This study concluded that very low
extractable hydrocarbon values are evident in the surface waters and throughout the
water column. The primary source was suggested to be more likely from atmospheric
fallout of aromatic compounds than from point-source emissions dispersed by
oceanographic processes.
Dissolved Oxygen
There are two major sources of oxygen dissolved in ocean water:
· Photosynthesis by marine plants including phytoplankton
· Gaseous exchange with the air environment
Oxygen is consumed in the marine environment during chemical oxidation of organic
matter, called chemical oxygen demand, and plant and animal respiration, called
biological oxygen demand. Dissolved oxygen (DO) is essential for natural water
systems and its concentration is indicative of the ability of the aquatic system to sustain
life.
DO concentrations often vary seasonally as a result of changes in water temperature,
salinity and mixing. The DO concentrations in the Grand Banks water column have
95032-0-EI-GM-00003.0, Rev.0
been reported as uniform with mean surface values of 8 ml/L decreasing to 7 ml/L near
the bottom substrate (Levy, 1983).
Recent oceanographic surveys report similar data. During a mid-spring 1993 survey of
the Grand Banks, DO concentrations of 9.5 ml/L were recorded in the surface and 7.5
ml/L near the bottom (Colbourne, 1993). Oxygen saturations ranged from 100 percent
at the surface to 90 m depth and to 90 percent in deeper water (Colbourne and
Narasyanan, 1994). The high DO values were explained by the annual plankton bloom,
which usually starts in late March - early April on the Grand Banks (Colbourne, 1993).
Data collected during a July 1994 survey report very similar DO concentrations and
saturation data as in 1993, with no evidence of oxygen depletion.
Suspended Particulate Matter
Microscopic biota, clay, silt, organic and inorganic nutrients that are held in suspension
by currents and flow make up the suspended particulate matter and affect water clarity.
Water clarity partly determines the amount of light scattering that occurs in an aquatic
system and is an important factor of overall water quality.
Many of the suspended particulate components occur naturally and their concentrations
will vary seasonally depending on mixing and primary productivity by phytoplankton.
Anthropogenic sources of suspended solids (primarily silts, clays and nutrients via
sewage) may increase the levels of suspended particulate matter to the point where
primary productivity is adversely affected.
The level of suspended particulate matter for the Grand Banks region is in the range of
0.01 to 2.77 mL/L and is within normal ocean levels (MacKnight et al., 1981 in Mobil,
1985). There have been no recent data on suspended particulate matter levels in the
water column.
Inorganic Nutrients
Inorganic nutrients such as silicates, nitrates and phosphates occur naturally in aquatic
systems and are essential nutrients for phytoplankton. Nutrient concentrations in the
water column vary seasonally and are affected by currents and phytoplankton
concentration. In general, during phytoplankton blooms, such as in spring, nutrient
concentrations decrease. During recent oceanographic surveys of the Grand Banks,
inorganic nutrient concentrations were low in surface waters during summer (M.A.
Paranjape and E. Colbourne, unpublished report, 1994). Concentrations increased in
the fall because of mixing within the water column.
95032-0-EI-GM-00003.0, Rev.0
3.6.2
Marine Sediment Chemistry
Trace elements, inorganic and organic compounds may occur in seafloor sediments as
a result of various natural processes. In addition, sediments can be contaminated by
these compounds by human activities such as fishing, shipping, oil exploration and
atmospheric emissions. For example, the byproducts of petroleum combustion are
known to be a major contributor of petroleum residues, heavy metals, and trace
elements to the seafloor (Hellou et al., 1992). Contamination, both natural and
anthropogenic, can result in a wide range of adverse affects on marine organisms
(Macdonald et al., 1992).
Organics
Concentrations of hydrocarbons and petroleum residues have been measured in
surficial bottom sediments taken from the Grand Banks (Levy, 1983; MDS, 1995).
Table 3.6-2 shows the results of Levy's study in 1983 for the Hibernia EIS. A more
recent study by MDS (1995) indicated no detectable levels of total petroleum
hydrocarbons (TPHs) in any of 164 sediment samples recently taken from the Hibernia
gravity base structure site (Table 3.6-2). This study also reported no detectable levels
of polynuclear aromatic hydrocarbons in the samples.
Table 3.6-2
Concentrations of Organic Compound Residues in Marine Sediments
Location
Proposed Hibernia gravity base
structure site
Grand Banks
Grand Banks
Scotian Shelf
Offshore N. Atlantic
North Sea
Coastal Nfld.
Hudson Strait/Labrador Shelf
a
b
c
Petroleum Residue
(ppm)
N/A
0-4.7b
0-7.3b
0.01-2.3 b
1.0-5.9b
1.0-26.0 b
1.0-25.0 b
2.29 geometric mean c
TPH
(ppm)
PAHs
(ppm)
< 30.2a
<0.1a
-
-
MDS (1985).
Levy (1983) in Mobil (1985).
Levy (1986).
Petroleum residues in surficial bottom sediments farther north in the Hudson Strait and
Labrador Shelf have been studied in detail and are known to be relatively low (2.29
µg/g) (Levy, 1986).
95032-0-EI-GM-00003.0, Rev.0
Trace Elements
The trace element content of Grand Bank surficial bottom sediments were studied in
detail in the early 1980s for the Hibernia Development Project EIS as well as in 1995
(Table 3.6-3). The recent work, which was done by MDS Environmental Services Ltd.
on 164 samples, focused on the proposed site for the Hibernia gravity base structure.
In Canada, there are no nationally accepted marine sediment quality guidelines.
However, the criteria in the Ocean Dumping Guidelines can be used to define the
nature of marine sediments to be disposed at an open-water site (JWE, 1995). In
addition, measured concentrations from other marine areas in Eastern Canada can also
be used for comparison (Table 3.6-3).
Trace element levels in Grand Banks sediments are generally either below the Ocean
Dumping Guideline levels or within the range of values for other marine areas of
Atlantic Canada. An exception exists for one MDS sediment sample which has 3000
ppm of barium and 212 ppm of lead. Mr. R. McCubbin with Hibernia Management
Development Company indicates that these elevated values are likely localized and the
result of past drilling activities located near the sampling station.
95032-0-EI-GM-00003.0, Rev.0
Table 3.6-3
Trace Metals in Marine Sediments in Eastern Canada
Grand Banks
Concentration
(ppm)
Weak Acid
Leachable
Concentration
(ppm)
Arsenic
Barium
N/A
15-690
N/A
N/A
<1.0-2.7
60-3000
-
310
-
Cadmium
0.02-0.43
<0.05-0.04
<0.05-0.35
0.04-.087
0.22
0.6
Chromium
1.48-39.00
<1.0
2.0-8.5
8-241
57
-
Cobalt
Copper
Iron
Lead
Lithium
Mercury
1.29-9.59
3.0-25.6
N/A
0.7-15.3
N/A
0.01-0.02
N/A
<1.0
N/A
<0.5-219
N/A
N/A
N/A
<1.0-8.8
800-11 000
1.2-212
<2.0-3.9
<0.01-0.03
3-76
8-66
0.1-12.3
15
20
0.03
45
45
0.75
Molybdenum
Nickel
1.30-6.09
0.1-28.0
N/A
N/A
N/A
N/A
Vanadium
Zinc
10.0-22.8
0.30-3.77
<1-39.5
N/A
2.0-55
8-215
51
165
Element
95032-0-EI-GM-00003.0, Rev.0
Total
Concentration
(ppm)
Gulf of St.
Lawrence
(ppm)
Bay of
Fundy
(ppm)
Ocean
Dumping
Guidelines
(ppm)
Chapter 4
Table of Contents
4.
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.1.1 Plankton
4.1.2 Benthos
4.1.3 Fish
4.1.4 Marine-Related Birds and Mammals
Phytoplankton
Other Microbiota
4.4.1 Species Composition
4.4.2 Geographic Distribution
4.4.3 Vertical Distribution
4.4.4 Seasonal and Annual Variability
4.4.5 Importance in Food Web
Ichthyoplankton
4.5.1 Geographic and Seasonal Distribution
4.5.2 Recent Ichthyoplankton Research
4.5.3 Geographic and Seasonal Distribution
4.5.4 Vertical Distribution
4.5.5 Interannual Variability
4.5.6 Flemish Cap
Benthos
4.6.1 Macrophytes and Associated Microscopic Algae
4.6.2 Benthic Fauna
Biofouling
Fish and Fisheries
4.8.1 Iceland Scallop
4.8.2 Snow Crab
4.8.3 Stimpson Surf Clam
4.8.4 Skates
4.8.5 Redfish
4.8.6 Capelin
4.8.7 Atlantic Herring
4.8.8 Atlantic Cod
4.8.9 Greenland Halibut
4.8.10 Witch Flounder
4.8.11 American Plaice
4.8.12 Pollock
4.8.13 Haddock
4-1
4-1
4-4
4-4
4-6
4-6
4-9
4-14
4-16
4-17
4-18
4-20
4-21
4-25
4-26
4-27
4-33
4-33
4-35
4-36
4-36
4-38
4-38
4-39
4-45
4-48
4-53
4-55
4-55
4-57
4-57
4-59
4-62
4-65
4-68
4-70
4-72
4-76
4-76
4.9
4.10
4.11
4.8.14 Yellowtail Flounder
4.8.15 Northern Shrimp
4.8.16 Other Notable Species
4.9.1 Database
4.9.2 Breeding Biology and Nesting Populations
4.9.3 Foods and Feeding Habits
4.9.4 Geographic and Seasonal Distributions
4.9.5 Important Species and Areas
Marine Mammals
4.10.1 Database
4.10.2 Populations and Stocks
4.10.3 Food and Feeding Habits
4.10.4 Geographic and Seasonal Distributions
4.11.1 Hydrocarbons
4.11.2 Trace Elements
4-77
4-78
4-78
4-85
4-85
4-85
4-93
4-93
4-93
4-97
4-97
4-97
4-100
4-101
4-103
4-103
4-107
Tables
4.1-1
4.1-2
4.4-1
4.4-2
4.5-1
4.6-1
4.6-2
4.8-1
4.8-2
4.9-1
4.9-2
4.9-3
4.9-4
4.9-5
4.9-6
4.10-1
4.10-2
4.10-3
Feeding Relationships of Commercially and Ecologically Important
Finfish and Shellfish of the Study Area
Feeding Relationships of Important Marine-Related Birds
and Marine Mammals of the Study Area
Zooplankton Biomass on the Grand Banks
Seasonal Peaks in Abundance of Major Zooplankton Species
on the Grand Banks
Dominant Fish Larvae on the Grand Banks
Relationship of Standing Crop of Infaunal Animals to Depth
Stomach Contents of Common Fish Species as Percentage Volume
Species Caught Commercially in Grand Banks Study Area
and Landed at Newfoundland Ports, 1992-94
Past and Recent Biomass Estimates in the Grand Banks Study Area
Marine Birds Recorded in the Study Area
Reproduction Parameters of Seabirds Nesting in the Study Area
Summary of Seabird Nesting, Hatching and Fledging in the
Study Area
Estimates of the Numbers of Nesting Seabirds Within the
Study Area and at Major Colonies in or Near the Study Area
Feeding Behaviour and Foods of Marine Birds in the Hibernia Study Are4
Summary of Bird Distributions in the Study Area
Marine Mammals Observed in the Study Area
Population Estimates of Marine Mammals in the Terra
Nova Study Area
Food of Marine Mammals Occurring in the Study Area
4-7
4-8
4-22
4-23
4-27
4-41
4-43
4-51
4-52
4-87
4-89
4-90
4-92
4-90
4-95
4-98
4-99
4-101
4.11-1
4.11-2
4.11-3
Concentrations of PAH in Muscle of Cod from Three Locations
in the Newfoundland Offshore (ug/g. dry wt.)
Concentration of Aromatics in Muscle Tissue (ug/g. dry wt.)
Range of Concentrations of Trace Elements and Metals in Biota
Sampled from the Hibernia Site
4-104
4-105
4-108
Figures
4-1
4.1-1
4.1-2
4.2-1
4.2-2
4.4-1
4.5-1
4.5-2
4.8-1
4.8-2
4.8-3
4.8-4
4.8-5
4.8-6
4.8-7
4.8-8
4.8-9
4.8-10
4.8-11
4.8-12
4.8-13
4.9-1
Environmental Study Area
The Ocean Ecosystem
Energy Flow Pathways in the Grand Banks - Flemish Cap Ecosystem
Mean 0 to 50 m Phytoplankton Chlorophyll Concentration and
Primary Production Rate on the Grand Banks: 1980-81
Distribution of Chlorophyll-a and Nitrate-N in the Hibernia Area
Mean Zooplankton Displacement Volume in the Upper 70 m
on the Grand Banks
Geographic Subareas of the Grand Banks Relevant to
Ichthyoplankton
Seasonal Distribution of Dominant Ichthyoplankton Species
on the Grand Banks: 1980-81
Major Offshore Plateaus on the Grand Banks
Distribution of Icelandic Scallops
General Distribution of Snow Crab Commercial Catches in 1994
Major Areas of Capelin Feeding on the Grand Banks, 1987-1990
Capelin Stocks and Spawning Migration Routes of Capelin
Capelin Catches Random Depth-Stratified Bottom-Trawl Surveys
- Spring 1991
Capelin Catches Random Depth-Stratified Bottom-Trawl Surveys
- Autumn 1993
Cod Catches From Fall Surveys 1990-1992
Inshore and Offshore Locations of Spawning Atlantic Cod
Distribution of Greenland Halibut Catches, Autumn Surveys,
1978-1992
Distribution of American Plaice Catches, 1992 Juvenile
Flatfish Surveys
Distribution of American Plaice Catches 1990-1993 RV Surveys
Distribution of Yellowtail Flounder, Spring, 1978, 1990 and 1992
Seabird Colonies on the Southeast Coast of Newfoundland
4-2
4-3
4-5
4-10
4-12
4-24
4-28
4-30
4-49
4-54
4-56
4-60
4-61
4-63
4-64
4-67
4-69
4-71
4-73
4-75
4-79
4-86
4.
This chapter describes the biological environment of the Grand Banks, with emphasis
on the area for the Terra Nova Development.
The Hibernia Environmental Impact Statement (EIS) (Mobil, 1985), which was based
on studies carried out in the early 1980s and earlier, provided the foundation for this
document. The significant environmental changes since the publication of the Hibernia
EIS, such as the decline in populations of many species of fish and the concomitant
collapse of the East Coast fisheries, as well as the significant increases in knowledge of
the Grand Banks environment, have been added and interpreted for the Terra Nova
Development.
The study area for this assessment (Figure 4-1) is identical to that described in Mobil
(1985). The extent to which certain topics are discussed in this section reflects the
amount of literature published since 1985 and not their relative importance for the
impact assessment that follows.
4.1
Since the preparation of the Hibernia EIS (Mobil, 1985), a number of environmental
and human-induced changes have occurred that are affecting the Grand Banks
ecosystem. These changes include the collapse of many fish populations, primarily due
to overfishing; water mass changes as evidenced by temperature and salinity
characteristics over the last ten years; and the closing of most major ground fisheries. In
addition there has been an increase in the harvests of other normally less-fished species
such as crab, shrimp, scallops and clams. All these factors can potentially impact the
Grand Banks at the ecosystem level and likely preclude the possibility of detecting any
oil development-induced changes at the population level.
The Grand Banks ecosystem is a complex and dynamic system composed of and
controlled by numerous physical, chemical, biological and human factors (Figure 4.11). This ecosystem is not fully understood and it is not the intent of this document to
investigate any of these factors in detail. The following description provides a general
indication of some of the important relationships on the Grand Banks, and an idea of
the impacts that may occur on those components of most significance (e.g.,
commercially important fish, seabirds).
The major components of the Grand Banks ecosystem and some of the key
relationships are described briefly below and in more detail in Sections 4.2 to 4.10.
4-1
4.1.1
Plankton
The term plankton is derived from the Greek for ‘floater’ and refers to those plant and
animal organisms that drift more or less with water currents. Plankton includes
microbes, algae, juvenile and adult invertebrates, and many species of fish eggs and
larvae. Many plankters are capable of significant vertical movement within the water
column in response to light and other environmental factors. Their distribution and
abundance is determined by oceanographic conditions and season. In the North
Atlantic, plankton abundance generally peaks in the spring and to a lesser extent in the
fall. Plankton commonly occurs in aggregations caused by oceanographic conditions
such as vertical or horizontal fronts (Sections 3.2.6 and 4.4.2) or behaviourial
mechanisms that create "swarms." These aggregations are exploited by feeding sea
birds, baleen whales and other predators.
In the Grand Banks ecosystem, primary production (the conversion of water and
carbon dioxide into organic matter in the presence of sunlight) is accomplished
primarily by phytoplankton in the upper 50 m or so of the water column. Important
nutrients used by the phytoplankton during this process include various forms of
nitrate, silicate and phosphate. Nutrients are recycled into the upper water column by
upwelling, microbial activity and animal excretion. The resulting biomass forms the
base of the food web that supports higher life forms. Important energy pathways on the
Grand Banks are shown in Figure 4.1-2.
The phytoplankton biomass is used primarily by zooplankton grazers, which in turn are
eaten by predators such as other species of zooplankton, fish, birds and marine
mammals. It is likely that plankton populations have responded in some unknown and
possibly unmeasurable manner to water mass changes over the last ten years. For a
discussion of water masses, refer to Section 3.2.3.
4.1.2
Benthos
Benthos is another Greek term that refers to plants and animals that live in or on the
sea bottom. The group is diverse in form and function and includes attached micro- and
macro-algae, and invertebrates such as polychaete worms, molluscs and crustaceans.
Commercially important members include lobster, scallop, shrimp and crab. Some
species of fish spend most of their time on or near the sea floor and may use the
substrate for cover, feeding and deposition of eggs. The composition of the benthic
community is directly related to substrate type and water depth.
Benthic animals have a variety of feeding behaviours, including filtering, scraping,
boring, scavenging, engulfing and seizing. They form an important food resource for
many species of fish, including flatfish and cod.
4-4
Changing conditions on the Grand Banks over the last ten years have probably affected
the benthic community to some extent. Changing oceanographic conditions, if severe
enough, can affect distributions. With the decrease in bottom trawler activity, mortality
rates have decreased, but this may be offset by increased predation.
4.1.3
Fish
Fish species that occur in the Terra Nova area are not unique to the area and occur in
many other parts of the banks. Both pelagic (e.g., capelin, mackerel, tuna) and
demersal (skate, flatfish cod) are found. Table 4.1-1 lists commercially important
species and their common food items. Fish are important not only as food for humans
but also ecologically as predators and food for other species.
There appears to have been a recent shift in the species composition on the Grand
Banks with a decrease in many species in addition to the much-publicized northern cod
(Gomes, 1993).
4.1.4
Marine-Related Birds and Mammals
Marine-related birds and mammals are important predators of zooplankton, benthos
and fish. They in turn serve as food for other species and recycle nutrients into the
upper water column through excretion (Table 4.1-2).
4-6
Table 4.1-1
Feeding Relationships of Commercially and Ecologically Important Fin Fish and Shellfish of the Study Area
X
X
X
X
X
Polychaetes, Nematodes
X
X
X
X
X
Gastropods
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sea Urchins
X
X
X
Sea Cucumbers
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Cumaceans
X
X
Hyperiids
X
X
X
Amphipods, Isopods
X
X
X
X
X
Pandalus
X
X
Pagurus
X
X
Ostracods
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Homarus
X
X
X
X
Chaetognaths
X
X
X
X
X
X
X
X
Invert. Eggs, Larvae
X
X
X
Appendicularia
X
X
X
X
X
X
Misc. Small Invert.
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Small Fish, Larvae
X
X
X
X
X
X
X
X
X
X
X
X
X
Redfish
X
X
X
Flounders
X
X
X
X
X
X
X
Sand Lance
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Pout
X
X
Wolffish
X
Skate
X
X
X
Haddock
X
Capelin
X
Herring
X
X
Mackerel
X
X
Lanternfish
X
X
Misc. Fish
X
X
Source: Mobil (1985)
X
X
Particulate Detritus
Hake
X
X
X
Insects
Cod
X
X
Decapod Larvae
Fish Eggs
X
X
X
Cancer
X
X
Chionoecetes
X
X
X
X
X
Hyas
X
X
X
X
X
X
X
Crabs
X
X
X
X
Shrimp
X
X
X
X
Scall ops
X
X
X
X
Lobster
X
X
X
X
Sand Lance
X
X
X
X
X
Thorney Skate
X
X
X
X
X
Wolffish
Lumpfish
Atlantic Cod
X
X
X
Decapod Crustaceans
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sea Stars
Phytoplankton
Haddock
White Hake
X
Silver Hake
X
Red Hake
X
X
Sand Dollars
X
X
X
X
X
Brittlestars
Mysids/Euphausiids
American Plaico
Medusae, Ctenophores
Copepods
Winter Flounder
X
Cephalopods
X
Shell Fish
X
Bryrozoans, Sponges, Tunicates
Bivalves
Yellowtail Flounder
Pollock
Eel Pout
Witch Flounder
Redfish
Turbot
Dogfish
Porbeagle Shark
Bluefin Tuna
Atlantic Salmon
Demersal
Swordfish
Lanternfish
Atlantic Saury
Squid
X
Capelin
X
Herring
Mackerel
Foraminifera, Protists
Larval Fish
Pelagic
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Table 4.1-2
Feeding Relationships of Important Marine-Related Birds and Marine Mammals of the Study Area
Sea Urchines
X
X
X
Seals
Toothed Whales
Fin, Sei
Blue
Minke
Baleen Whales
Humpback
Cormorants, Loons, Grebes
Coastal Birds
Waterfowl
Terns
Kittiwakes
X
Seals
X
Porpoises, Dolphins
X
Northern Bottlenose
X
X
Killer
X
X
X
Sperm
Cephalopods
X
Pilot
Bivalves
Gulls
Phalaropes
Storm-Petrels
X
Gastropods
Jaegars, Skuas
Klepto-Parasites
Mammals
Surface Feeders
Polychaetes, Nematodes
Fulmars
Gannets
Shearwaters
Razorbills
Puffins
Murres
Dovekies
Food
Black Guillemots
Plunging
Pursuit Divers
Birds
X
X
X
X
X
X
X
X
X
X
X
X
Sand Dollars
X
Sea Stars
X
X
Sea Cucumbers
X
Copepods
X
Mysids/Euphausiids
X
Hyperiids
X
Amphipods, Isopods
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Decapod, Crustaceans
Pandalus
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Cancer
X
Insects
X
Misc. Small Invertebrates
X
X
X
Algae
X
Small Fish Larvae
X
X
X
X
Fish Eggs
X
X
X
Redfish
Cod
X
X
X
X
X
X
Flounders
X
X
X
Hake
Sand Lance
X
X
X
X
X
X
Pout, Gunnels
X
Tomcod
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Skate
X
X
X
Haddock
Capelin
X
X
Herring
X
X
X
X
X
X
Mackerel
X
Offal
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Vegetation, Seeds, Berries
X
Bird Eggs, Young
X
Seals, Birds
X
X
X
Lanternfish
Misc. Fish
X
X
X
X
X
X
X
X
X
4.2
Phytoplankton
In the marine ecosystem, primary production is mainly accomplished by two groups of
plants:
·
·
The phytoplanktonic organisms found floating in the water column
The macrophytic seaweeds and vascular plants
A third group, microscopic algae, which live on the surface of macrophytes and on
bottom sediments, can be important primary producers as well, and often provide rich
grazing areas for marine fauna in coastal areas. This section describes phytoplankton on
the Grand Banks. Macrophytes and other attached algae are described in Section 4.6.
The following description of the phytoplankton of the study area is summarized from
Mobil (1985) and the results of the Mobil-sponsored cruises of 1980 and 1981
described by Hollibaugh (1981) and Hollibaugh and Booth (1981).
The phytoplankton, composed of microscopic free-floating plants, are responsible for
most of the primary production in the open ocean areas. In order to photosynthesize,
these cells must remain in the upper lighted portion of the water column known as the
euphotic zone. Phytoplankters cannot move themselves great distances; thus their
distribution is heavily dependent on vertical and horizontal water movements (Section
3.2) and other physical processes. Their growth depends on the amount of sunlight
(season) and the concentration of nutrients (e.g., nitrates, phosphates, silicates) in the
water.
In response to the changing light regime and nutrient concentrations over the year, the
phytoplankton community varies in abundance, growth rates and species composition
in a relatively predictable pattern. In the northwestern Atlantic, the highest standing
crops (as measured by chlorophyll a concentrations or cell counts) and growth rates (as
measured by the amount of primary production) are usually found in the spring. This is
known as the spring bloom, and is generally dominated by diatoms. After the spring
bloom, the standing crop and growth rates drop back to near minimal levels, and then
rise again to a second, generally smaller peak in late summer or early fall. This fall
bloom is generally much smaller than the spring bloom and is dominated by
dinoflagellates and other microflagellates. After the fall bloom, standing crop and
production drop to a winter minimum.
The annual seasonal cycles of chlorophyll and primary production for the study area,
averaged for all areas sampled in the Mobil-sponsored cruises in 1980 and 1981, are
shown in Figure 4.2-1. In general, they follow the seasonal cycle described above.
Before the spring bloom, production was limited by water column instability except at
the frontal zone along the shelf break. At this time the phytoplankton crop was light-
4-9
but not nutrient-limited. In March, chlorophyll concentrations averaged 24 mg/m 2 and
primary production averaged 300 mg C per m2/d. As the season progressed, water
column stratification and stabilization intensified and light levels increased. This was
accompanied by a rapid increase in standing crop and production to a peak in May
when typical spring bloom diatoms such as Chaetoceros and Thalassiosira dominated
the phytoplankton. The peak average chlorophyll concentration was 130 mg/m 2; at the
same time production rates averaged 1710 mg C per m2/d. The spring bloom quickly
dissipated and from July to September average chlorophyll concentrations varied
between 11 and 18 mg/m2, while production rates varied between 238 and 299 mg C
per m2/d. Chlorophyll concentrations were slightly higher in November (average of 31
mg/m2) but no samples were taken in October, and the full fall bloom may have been
missed. The standing crop then dropped to its winter minimum in January (average
chlorophyll concentration of 12 mg/m2 and production of 72 mg C per m2/d).
Data collected on the Mobil-sponsored cruises were used to plot the vertical
distribution of chlorophyll and nitrate (the most limiting nutrient) on the northeast
Grand Banks (Figure 4.2-2). In the winter months, the chlorophyll and nitrate
concentrations are distributed fairly evenly throughout the water column. At the height
of the spring bloom in May, chlorophyll levels are high in the surface waters, where
nitrate has become depleted. During the summer, standing crop is again more evenly
distributed throughout the water column and nitrate levels remain depleted in the
surface waters. With the breakdown of stratification in the fall, nitrate levels are
replenished in the surface waters while chlorophyll levels remain low.
The results of the Mobil-sponsored cruises clearly showed geographic variations in
phytoplankton biomass and productivity. In particular, productivity appeared to be high
in a frontal zone along the shelf break of the Grand Banks. It was also high in the
Avalon Channel, in a patch south of the Avalon Peninsula, and to the west of St. Pierre
Bank.
Since the Mobil-sponsored work in the early 1980s, no other comprehensive study of
the phytoplankton has been conducted in the study area. Nevertheless, several smaller
studies have provided some additional information. Anderson and Gardner (1986)
confirmed that the shelf break was an upwelling area and an area of high productivity.
Pomeroy et al. (1991), in studies carried out in 1986, 1988 and 1990, showed that the
duration and size of the spring bloom in Conception Bay and on the Grand Banks was
characterized by considerable interannual variability that depended on weather
conditions. It could be short-lived and intense or drawn out over a two or three month
period between March and June.
4-11
There is growing evidence that very small phytoplankton species, the "ultraplankton"
play a much larger role in the spring bloom than was previously known (Murphy and
Haugen, 1985; Li et al., 1993). Ultraplankton are cells smaller than 5 to 10 μm, and are
composed of both prokaryotic chroococcoid cyanobacteria and a diverse assemblage
of eucaryotic phototrophic species (e.g., prymnesiophytes, prasinophytes,
chrysophytes, and cryptophytes). In more northerly waters, such as within the present
study area, the cyanobacteria appear to be less important than in more southerly
waters. Brown and Yoder (1993), using satellite imagery, observed large blooms of
coccolithophorids (Prymnesiophyceae) over the Grand Banks, and speculated that
these blooms seasonally impact the region's carbon and sulphur cycles. Prasad and
Haedrich (1993), again using satellite imagery, demonstrated the spatial variability (i.e.,
patchiness) in chlorophyll concentrations over the Grand Banks. They found small
patches of elevated chlorophyll concentrations in February off the Avalon Channel and
in Bonavista and Trinity bays, and speculated that these may indicate production that
sustains winter fisheries in these areas. Prasad and Hollibaugh (1992) and Prasad et al.
(1992) used data from the Mobil-sponsored cruises to tune remote-sensing algorithms
used to estimate primary production.
4-13
4.3
Other Microbiota
In this EIS, microbiota are defined as the non-primary producing microscopic marine
organisms, and include viruses, bacteria, yeasts and fungi. This description of the
microbiota of the study area is summarized from Mobil (1985) and Bédard and Bunch
(1983) who conducted microbiological investigations as part of the Mobil-sponsored
oceanographic cruises of 1980 and 1981.
Relatively little is known about marine viruses, yeasts and fungi; this is particularly true
in the northwestern Atlantic. Yeasts and fungi are generally more common in estuarine
and coastal environments than in the high seas. They degrade organic matter, including
petroleum hydrocarbons, but their role in the marine ecosystem may be relatively
unimportant.
Much more work has been done on marine bacteria, and they probably play a more
important role in the marine ecosystem. Most marine bacteria are heterotrophs,
consuming organic substances for carbon and energy, and occur in both the water
column and in benthic sediments. They play a vital role in converting dissolved organic
carbon (DOC) exuded by phytoplankton into particulate bacterial biomass that is then
available to other trophic levels. Estimates of the portion of primary production that
passes through bacteria range from 10 to 50 percent. Some marine bacteria are able to
degrade petroleum oil products; these are known as "oleoclasts". Oleoclastic bacteria
are found as natural components of virtually all marine aquatic communities, although
their activity may be low in pristine non-oil-polluted areas. This section describes the
general bacterial community of the Grand Banks area, with some specific information
on oleoclast activity.
Bédard and Bunch (1983) found that the activity of heterotrophic bacteria correlated
directly with the biomass and activity of phytoplankton, although other factors
modified the relationship. Microheterotrophs were responsible for maintaining DOC
levels at fairly constant levels, and their activity increased when DOC input presumably
increased during the spring phytoplankton bloom. Bacterial abundance did not vary
much over time, however, this may be as a result of heavier grazing by nanoflagellates
during bloom periods. The abundance and activity of microheterotrophs in the water
column on the Grand Banks were comparable to those of other marine areas of similar
trophic status.
Far more bacterial activity was taking place on the bottom sediments than in the water
column. As much as half the bacterial mineralization on the Grand Banks may take
place on the bottom. Again, bacterial activity in the sediments appears to exhibit little
variation over time, apparently unaffected by the supply of organic matter from the
water column. Activity and abundance was related to the organic carbon content of the
sediments.
4-14
The potential activity and abundance of oleoclasts in both the water column and the
sediments were judged to be low. This was particularly true in July. Other evidence
suggests that the natural populations of oleoclasts in the water column of the Grand
Banks is an order of magnitude lower than most other uncontaminated marine
environments (Mobil, 1985). Bédard and Bunch (1983) speculated that interactions
between temperature, nutrients and naturally occurring cycles of oleoclastic
populations will determine the rate of biodegradation of any petroleum released on the
Grand Bank. Lee and Levy (1989) noted that microbes in the sea are able to increase
and decrease their activity over a wider range than any other group of organisms, and
that they remain dormant until conditions become favourable.
Since 1985, considerable work on the role of bacteria in the spring bloom of North
Atlantic waters has been conducted as part of the Cold Ocean Productivity Experiment
(e.g., Pomeroy and Deibel, 1986; Pomeroy et al., 1991) and the North Atlantic Bloom
Experiment (e.g., Li et al., 1993). While the role of bacteria and the controlling
mechanisms of bacterial production are not yet fully understood, their role in the bloom
can be significant, depending on environmental conditions.
Pomeroy et al. (1991) found that the numbers of free-living heterotrophic bacteria in
Conception Bay and Newfoundland coastal waters during the spring phytoplankton
bloom were at the low end of the range reported in the ocean. Growth rates varied
considerably with depth, suggesting layers of normal microbial activity in an otherwise
microbially sluggish system. Bacterial numbers are normally high in eutrophic systems,
but this was not the case for Conception Bay in April and May where both chlorophyll
and photosynthetic rates were high. Pomeroy et al. (1991) concluded that microbial
metabolism and production in cold waters are limited by both the ability of bacteria to
transport and assimilate substrates at the low temperatures, and low concentrations of
substrate normally present.
4-15
4.4
The term zooplankton refers to those weak-swimming or floating animals that more or
less drift with the ocean currents (although some species are capable of extensive
vertical migrations in the water column). The group is composed of a wide variety of
organisms (from protozoans to vertebrates) with sizes ranging from tiny microbes to
jellyfish with tentacles 10s of metres long. Many bottom-dwelling invertebrates (e.g.,
crabs) and fish have planktonic eggs or larvae. Zooplankters have diverse feeding
modes that may involve the absorption of nutrients from DOC, the filtering of relatively
vast quantities of water, the use of large mucus nets or stinging apparatus to trap prey,
or various types of devices to seize prey. They play an important role in nutrient
recycling and in the transfer of energy from the lower trophic levels (e.g.,
phytoplankton) to the important higher trophic levels of commercial fish, seabirds and
marine mammals.
In predicting the impacts of chemical or petroleum hydrocarbon spills on marine
zooplankton, information on the following is needed:
·
·
·
·
·
Species composition, particularly dominant species
Abundance and biomass
Distribution in time, geographic space and water column
Position and importance in the food web
Variability on all of the above
The following sections briefly describe what is known about the invertebrate
zooplankton on the Grand Banks in terms of the above topics up to and including the
Hibernia EIS (Mobil, 1985). The background study by Strong (1981) was the major
source of relevant information up to that point. Since the preparation of the Hibernia
EIS in 1983 and 1984, there have been several studies relevant to invertebrate
zooplankton populations on the Grand Banks. These works include the studies of
communities and water masses (Anderson and Gardner (1986)), seasonal development
(Anderson (1990)), microzooplankton herbivory (Paranjape (1990)), capelin feeding
(Gerasimova (1994)), and distribution and abundance (Myers et al. (1994)). Relevant
information from these later studies is highlighted where appropriate. Constraints on
these recent data sources in terms of applicability to Terra Nova are discussed briefly
below.
The results of Anderson and Gardner (1986) and Paranjape (1990) are based on work
conducted on the Southeast Shoal. Information from this part of the Banks may not be
directly applicable to the Terra Nova area because the Southeast Shoal is physically
unique. An anti-cyclonic gyre centred over the shoal (see Section 3.2 for a complete
description of the physical oceanography of the area) probably has important influence
on the plankton community. The study of Anderson (1990) provides valuable
information on the seasonal development of zooplankton, but it is limited to the
Flemish Cap, another area unique in terms of physical oceanography. The approach of
4-16
Gerasimova (1994) and Myers et al. (1994) is broad scale and thus of some general
applicability to Terra Nova. The continuous plankton recording (CPR) data contained
in Myers et al. (1994) is of particular interest because it is derived from a large number
of samples (17 000) over a long period of time (1959-1992). However, it suffers from
somewhat sporadic coverage, particularly in the Terra Nova region of the Grand
Banks, presumably because Terra Nova is somewhat off the normal shipping routes.
4.4.1
Species Composition
During the Mobil-sponsored oceanographic field program from March 1980 to
February 1981, at least 86 species of invertebrate zooplankton from 11 phyla were
collected on the Grand Banks (Strong, 1981). The dominant species varied according
to collection method as well as location and time of sampling. In the 333 µm mesh
bongo samplers, calanoid copepods predominated; the Atlantic cold water species,
Calanus finmarchicus, was dominant in terms of overall abundance (1 to 1000/m3). C.
finmarchicus is known to be the dominant calanoid in the Northwest Atlantic,
including the Flemish Cap (Akenhead, 1980). Other abundant species included the
copepods Calanus glacialis and Calanus hyperboreus (two arctic species that were
particularly evident beyond the 200-m isobath and during May and June), Temora
longicornis, Pseudocalanus minutus and Centropages harmatus. Barnacle larvae were
abundant at certain stations and times.
In the smaller mesh (80 µm) ring nets, the samples were dominated numerically by the
small cyclopoid copepod Oithona similis in concentrations commonly higher than
100 000/m3. Other numerous small-sized species included the cyclopoid Oncaea
minuta and the hapacticoid copepod Microsetella norvegica.
The neuston net (333 µm mesh) sampled only surface waters (approximately the upper
10 cm). In these collections, the copepods C. finmarchicus, C. glacialis, P. minutus, T.
longicornis, the amphipod Parathemisto gaudichaudi, the larvacean Frittilaria
borealis, barnacle nauplii and crab zoea dominated at various times and locations.
Since 1985, analysis of the continuous plankton recorder data has confirmed what
many other authors have concluded: namely that zooplankton in North Atlantic surface
waters are dominated by calanoid copepods (Myers et al., 1994).
Several recent plankton studies have been conducted on the Southeast Shoal of the
Grand Banks, but it is not entirely clear if species composition on the Southeast Shoal
is directly comparable to the Terra Nova area. It likely is to some extent because some
of the same water masses occur in both areas. Anderson and Gardner (1986) found a
total of 56 taxa in samples collected in mid-May on the eastern boundary of the
Southeast Shoal. Thirty-five of these were identified to species level. Thirteen shallowwater stations were dominated by the ctenephore Pleurobrachia pileus. Shelf-break
4-17
and deepwater stations were dominated by copepods, primarily 5th and 6th copepodite
stages of C. finmarchicus and Pseudocalanus spp. Paranjape (1990) found the microzooplankton to be dominated by the oligotrichs of the genera Lohmanniella and
Strombidium during three seasons based upon April, July and October sampling.
There have been a few new reports on abundance and biomass of some of the major
species occurring in the area. Anderson and Gardner (1986) reported densities in the
Southeast Shoal area for the most common species P. pileus, C. finmarchicus and
Pseudocalanus spp. In the same area, these authors found the highest calanoid
copepod biomass to be associated with Labrador Current water at the shelf break.
Anderson (1990) reported total invertebrate plankton volume (an indicator of biomass)
seasonally for the Flemish Cap from 1978 to 1983. In addition, that publication
contains density data for C. finmarchicus by copepodite stage and by depth (≤200 m;
201-400; ≤400; >400).
The most extensive data on abundance are contained in Myers et al. (1994). Monthly
counts for the 10 m sampling depth are presented for about 50 taxa, including about 25
invertebrate taxa. In North Atlantic Fisheries Organization (NAFO) Division 3L, which
contains Terra Nova, the highest counts are usually due to copepods, particularly C.
finmarchicus, Pseudocalanus spp., T. longicornis, Acartia spp., O. similis, and a few
others. While other groups such as hyperiid amphipods, euphausiids, and chaetognaths
may not be as abundant as copepods, they may be extremely important in terms of
biomass, at least at certain times and locations.
4.4.2
Geographic Distribution
Some of the major factors influencing the temporal and spatial distribution of
zooplankton in the North Atlantic (Colebrook, 1982) are:
-
The locations of main overwintering stocks
Water currents
Temperature
In general, water circulation in the Grand Banks and Flemish Cap areas is dominated
by the cold, southward-flowing Labrador Current. The Labrador
Current branches near the northern part of the banks into relatively strong inshore
(Avalon Channel) and offshore components. Currents over the banks, other than winddriven surface currents, tend to be weak and variable with a possible anticyclonic gyre
on the southeastern area of the banks (Petrie and Anderson, 1983). South of the Grand
Banks, the southward flow is bounded and turned eastward by the warm water of the
North Atlantic Drift.
4-18
Oceanographic fronts, boundary zones between adjacent water masses of dissimilar
characteristics, may also affect the distribution of zooplankton by concentrating the
free-drifting plankton. Of the six main types of fronts defined in a review by Bowman
(1978), the ones most likely to be important in the Grand Banks region are:
-
Fronts at the edges of western boundary currents
Shelf break fronts
Shallow-sea fronts formed around banks and shoals
If a gyre exists on the Southeast Shoal, it also may concentrate plankton. Although a
number of fronts probably exist in the Grand Banks area and at least several expected
ones (i.e., shelf-break front and a front south of the Grand Banks between the Labrador
Current water and the North Atlantic Drift) may be relatively extensive and semipermanent, no one has clearly demonstrated a "concentrating effect" on zooplankton
populations in this area. This is probably due to the sampling locations being too far
apart rather than a real lack of effect. Most large-scale studies in the western North
Atlantic (IGY and CPR programs) have shown that total plankton (or at least the
dominant species C. finmarchicus), as measured by total numbers or biomass, is higher
on the Grand Banks than in the oceanic water farther offshore (Kusmorskaya, 1959;
Robinson et al., 1975).
Most plankton researchers attempt to relate particular species or groups of species to
specific water masses. This approach is often more useful than simply describing
species composition relative to fixed geographic points, since the planktonic
environment is extremely dynamic, particularly on the Grand Banks. Species that
appear particularly useful as indicators of water types in the area of interest include C.
glacialis (water of arctic origin), C. finmarchicus (mixed arctic and Atlantic water) and
C. helgolandicus (subtropical Atlantic water (Matthews, 1969; Jaschnov, 1970). Other
species and groups have also been used as indicators at various times (e.g., large
number of ctenophores for cold Labrador Current water (Pinhey, 1926); seven species
of euphausiids for various water types and geographical areas near the Grand Banks
and Flemish Cap (Drobysheva, 1964).
In general, the zooplankton of the Flemish Cap and the Grand Banks is dominated by
cold-water (i.e., arctic or boreal) species (Pavshtiks et al., 1962; Semenova, 1963;
Strong, 1981; and others). However, warm-water species may occur as "strays".
Bainbridge (1961) and Pavshtiks et al. (1962) have reported patches of warm-water
species in late winter just northeast of the Grand Banks; these species may enter the
area in eddies or counter currents from the North Atlantic Drift.
During the Mobil oceanographic program (1980-1981), none of the regions (five
representative subareas) examined demonstrated significant differences in zooplankton
biomass, although during the spring the biomass at a few stations appeared to be
consistently high. These high biomass areas included the northern shelf break, the
4-19
central part of the southeast bank, and nearshore stations near the Avalon Peninsula
(Strong, 1981). No species, or groups of species, are reported by Strong (1981) to be
more common or unique to specific geographic areas. There was, however,
considerable variation between stations, caused primarily by the patchy nature of
zooplankton distributions.
Zooplankton may be highly aggregated, by 100 to more than 1000 times the average
density of the population as estimated by net sampling. This may be a result of the
swarming behaviour of such animals as mysids and euphausiids and others (Omori and
Hamner, 1982; Sameoto, 1983) or physical concentrating mechanisms such as eddies
and fronts (Longhurst, 1980, 1981; Owen, 1981)). All of these concentrating
mechanisms are known to occur in the Grand Banks and Flemish Cap area; however,
their effects on the distribution and abundance of Grand Banks zooplankton
populations has yet to be discovered.
The spatial and temporal scale of the sampling design utilized by Strong (1981) was
too large to adequately demonstrate any concentrating effects. Farther south, Herman
et al. (1981), used continuous sampling equipment, show a much higher estimated
plankton production and copepod abundance at the shelf-break front off Nova Scotia
than in the shelf and slope waters. There is likely also some shelf-break effect at the
edges of the Grand Banks; Longhurst (1980) shows the approximate expected position
of a semipermanent front (as composed from several satellite infrared images) and its
presence was suggested in the data collected during the Mobil Grand Banks study.
There have been no broad-scale plankton surveys since the Mobil studies were
completed. Anderson (1990) reports maximum calanoid copepod spawning, as
evidenced by egg and nauplii densities, occurred in the shallow water over the Flemish
Cap. However, this author also found evidence of spawning in deep water off the cap.
4.4.3
Little information is available concerning the vertical distribution of invertebrate
zooplankton in the Grand Banks area. The dominant species, C. finmarchicus,
although found over the banks during winter, may overwinter in deep water off the
banks. Semenova (1963), sampling during early spring, found much higher numbers
(36 to 220/m3) in deep water off the banks and off Flemish Cap as opposed to 0-16/m 3
in the shallow waters on the banks. Kusmorskaya (1959) sampled during early spring
and late fall with closing nets and found that C. finmarchicus was distributed from
surface to bottom over the banks but was more or less restricted to deep water (200 to
500 m) farther east. Kusmorskaya (1959) also found that total plankton was greatest in
the upper 200 m near the banks and that during spring spawning the highest numbers
of C. finmarchicus occurred in the upper 50 m.
4-20
In general, the highest numbers of zooplankters are likely found in the upper 50 m of
the water column, particularly during the spring bloom. This is true for eastern
Canadian arctic waters (Buchanan and Sekerak, 1982) and Labrador waters (Buchanan
and Browne, 1981), and is likely for the Grand Banks, which is heavily influenced by
the Labrador Current.
Strong's (1981) study was not designed to collect vertical distribution information.
However, the data based on surface (neuston) net collections suggest that four species
of important copepods (including C. finmarchicus and P. minutus) were much more
(by a factor of six) numerous at the surface at night than they were during the day. In
addition, the surface-dwelling copepod Anomalocera patersoni and the amphipods
Parathemisto spp. appeared to be much more numerous at the surface (i.e., upper 10
cm). This vertical migratory behaviour by some species (both invertebrates and fish)
has been observed for many years. Invertebrate vertical migration generally involves
four phases, mostly in response to light conditions (LaRow, 1976):
1.
2.
3.
4.
Ascent from day depth
Midnight sinking
Dawn rise
Descent to day depth
There have been no recent studies specifically addressing vertical distribution of
invertebrate zooplankton on the Grand Banks. The CPR data are constrained by
sampling horizontally at one depth (nominally 10 m but actually 6.7 ± 1.7 m; Myers et
al., 1994).
Anderson (1990) provided valuable data on the vertical distribution of copepod eggs
and nauplii, C. finmarchicus, and other copepods on the Flemish Cap. However, these
data are constrained by the relatively coarse sampling strata used (≤200 m; 201-400;
≤400; >400 m) and by the fact that Flemish Cap is a unique area.
4.4.4
Seasonal and Annual Variability
The dominant seasonal feature of zooplankton populations in the North Atlantic is the
massive development of herbivorous species (e.g., some copepods, including C.
finmarchicus) either during the spring phytoplankton bloom or shortly after.
Carnivorous species such as medusae, some amphipods and chaetognaths also develop
rapidly at this time of abundant food. A lesser fall bloom may occur in some areas
under certain conditions.
4-21
Colebrook (1982) examined CPR data from the North Sea and North Atlantic since
1948 for four phytoplankton and five zooplankton taxa. He concluded that seasonal
variations appear to be controlled by the distribution of main overwintering stocks,
currents, and in some instances, temperature control of the rate of population increase.
C. finmarchicus undergoes massive spawning on the Grand Banks during the spring
(Kusmorskaya, 1959; Pavshtiks et al., 1962). Vladimirskaya (1967), analyzed 810
samples collected from 194 oceanographic stations in the northwest Atlantic between
1958 and 1961 and found the greatest spring abundance of C. finmarchicus (3.5-7.5 x
105/m2) occurred in those areas most influenced by the Labrador Current (i.e., northern
and northeastern Grand Banks). Mass development seemed to proceed earliest in the
warmer water of the southern and eastern Grand Banks. Matthews (1969) also
observed this from CPR data. Vladimirskaya found that during the summer C.
finmarchicus was most abundant on the northeastern Grand Bank (5.0-7.0 x 105/m2)
and the northeastern Flemish Cap (4.5 x 105/m2). During early autumn, the greatest
abundance was on the eastern (3.2 x 105/m2) and southwestern (1.1 x 105/m2) slopes of
the Grand Banks; in late autumn the greatest abundance was on the northern slope.
Most C. finmarchicus were at overwintering depths (greater than 100 m or below 200
to 500 m where possible) by early October (Vladimirskaya, 1967). However, there may
be a lack of discrimination between the possible species of Calanus (i.e., C.
finmarchicus vs. C. glacialis) in Vladimirskaya's data, so the results must be used
carefully. Vladimirskaya's (1965) data on total zooplankton biomass are probably of
more use in impact prediction than the number of C. finmarchicus (Table 4.4-1).
Table 4.4-1
Zooplankton Biomass on the Grand Banks
Season
Spring
Summer
Autumn
Depth
0-100 m
0-200 m
0-100 m
0-100 m
Mean Biomass
(mg/m3)
130-350
≤ 900
≥ 1000
100-300
Source: Vladimirskaya (1965).
Mean total zooplankton biomass (as measured by displacement volumes) on the Grand
Banks as determined by Strong (1981) appears to follow the classical pattern of great
increases in the spring in conjunction with the spring phytoplankton bloom, a decrease
in the summer, probably caused by predation and overgrazing of phytoplankton, and a
4-22
slight increase in the fall, possibly as a response to a fall phytoplankton bloom (Figure
4.4-1).
In contrast, Kendaris (1980), in an inshore study conducted from April to September,
found that although copepod larval stages were at their greatest abundance in May,
total zooplankton abundance was low until August, when it increased by a factor of
five. Overall, the copepods P. minutus and Oithona nana dominated the zooplankton,
with the copepod T. longicornis replacing O. nana in September.
C. finmarchicus dominates the zooplankton community of the Flemish Cap in terms of
both abundance and biomass. Times of maximum spawning appear to be controlled by
water temperature and occur in mid-April. They may be a month earlier on the shelf to
the west and south of the Cap (the Terra Nova area) (Anderson, 1990). Spawning
times of C. finmarchicus are known to be closely linked to the spring phytoplankton
bloom. Maximum numbers of C. finmarchicus at the 10 m depth occur in August in
NAFO Division 3L, which encompasses the Terra Nova area (Myers et al., 1994).
Peaks in abundance of some other major species at the 10 m depth are shown in Table
4.4-2.
Table 4.4-2
Seasonal Peaks in Abundance of Major Zooplankton Species on the Grand
Banks
Timing
January
January-February
March
July
August
November
Species
Pleuromanna robusta, Pleuromamma borealis,
Pleuromamma gracilis
Metridia lucens
Clione limacina
Eucheata norvegica
C. finmarchicus, T. longicornis, Acartia spp., Podon,
spp., Evadne spp., euphausiids
Oithona spp., chaetognaths
Sources:
Myers et al., (1994).
CPR data.
4-23
One of the characteristics of plankton communities is their variability in time and space.
While plankton are more or less ubiquitous, patchiness in community structure,
abundance and biomass may vary on scales from several metres to many kilometres.
There also may be considerable interannual variability, something recognized by recent
researchers. For example, Myers et al. (1994), using the 1959-1992 CPR data, found a
decline over the long term in both diatom and copepod abundances. Anderson (1990)
found significant yearly differences in the development rates and abundance of C.
finmarchicus. Anderson and Gardner (1986) noted the interannual variability in
abundance of the predatory combjelly P. pileus, a potentially important determinant of
larval fish abundance. Gerasimova (1994) remarked on the interannual variability in the
location of capelin feeding areas on the Grand Banks and a shift from euphausiids to
larval fish prey when euphausiids were scarce.
4.4.5
Importance in Food Web
Zooplankton play key roles in the world’s oceans. Herbivorous species such as
copepods feed on phytoplankton and in turn are fed upon by predaceous invertebrates,
fish, birds and marine mammals. Their grazing on phytoplankton is great enough to
provide a significant pathway for nutrient regeneration as well as to influence
phytoplankton species composition and biomass. Farther up the food chain,
invertebrate zooplankton such as young copepods can influence fish abundance,
because copepods are an important food source for young fish.
Conversely, predaceous zooplankton species such as jellyfish can influence the
abundance of fish by predation upon fish eggs and larvae.
Recent research on the Grand Banks and Flemish Cap have provided further evidence
of the importance of invertebrate zooplankton to the ecosystem. Plankton-grazing
experiments on the Southeast Shoal have demonstrated the importance of microzooplankton in limiting phytoplankton and bacterial populations (Paranjape, 1990).
Anderson's (1990) Flemish Cap work supports the hypothesis of Runge (1988) that
copepods act as a direct link between phytoplankton and fisheries variability in
temperate marine ecosystems dominated by larger copepods. On the other hand, Myers
et al. (1994) suggest there is no obvious evidence of this in the CPR data.
Copepods (mainly C. finmarchicus, C. hyperboreus, Metridia longa) euphausiids
(mostly Thysanoessa raschii but also some Meganyctiphanes norvegica) and juvenile
sandeels and capelin form the bulk of the capelin’s diet on the Grand Banks
(Gerasimova, 1994). The slopes to the north and northeast of Terra Nova have been
reported to be important feeding areas for immature capelin in spring (Campbell and
Winters, 1973; Jangaard, 1974). Copepods are the most important food item for
capelin in NAFO Division 3L (Gerasimova, 1994).
4-25
4.5
Ichthyoplankton
The Hibernia EIS provides information on the Flemish Cap as well as the Grand Banks.
Given the strong southerly flow of the eastern branch of the Labrador Current along
the shelf break between the Grand Banks and the Flemish Cap, it is only in very
unusual circumstances that the activities at the Terra Nova site could affect the Flemish
Cap. At the same time the ecosystem of the Flemish Cap is unique (Anderson, 1984),
and is not likely representative of the processes that occur on the Grand Bank. For
these reasons, discussion of the Flemish Cap ecosystem is de-emphasized in this
document.
At least 45 species of fish have been identified as early life stages (i.e., eggs, larvae or
pelagic juveniles) in the ichthyoplankton of the Grand Banks and inshore waters of
Newfoundland. The most frequently reported of these have been:
-
Atlantic herring (Clupea harengus harengus)
Capelin (Mallotus villosus)
Atlantic cod (Gadus morhua)
Sand lance (Ammodytes sp.)
Redfish (Sebastes sp.)
Seasnail (Liparis atlanticus)
Witch flounder (Glyptocephalus cynoglossus)
American plaice (Hippoglossoides platessoides)
Yellowtail flounder (Pleuronectes ferruginea)
With the exception of the sand lance and seasnail, these are all, or have been in the past,
commercially important species in the fishery on the Grand Banks or inshore
Newfoundland. On the Flemish Cap a number of additional species have been found,
but usually in low numbers. Here redfish (probably Sebastes mentella and Sebastes
fasciatus) completely dominate the ichthyoplankton.
Bonnyman (1981) found that seven of the nine species listed for the Grand Banks
above comprised 87 percent of the total number of fish larvae taken throughout the
Mobil-sponsored oceanographic cruises in 1980 and 1981 (Table 4.5-1).
The most striking feature of the ichthyoplankton on the Grand Banks is the complete
dominance of the sand lance. Its average abundance was 188 fish/1000 m3, or nine
times the abundance of capelin, the next most abundant species (Mobil, 1985). The
sand lance is a small, slender fish generally considered to be pelagic but which is often
found buried in bottom sands and which has benthic attached eggs. Commercially, the
sand lance is not an important species, but other commercially important fish feed on
them extensively, and in coastal regions they are an important food item for seabirds.
4-26
Table 4.5-1
Dominant Fish Larvae on the Grand Banks
Species
Sand lance
Capelin
Redfish
Witch flounder
Yellowtail flounder
American plaice
Atlantic cod
Mean No./1000 m 3
188
21
12
8
6
4
2
Percent of Total
65
9
6
3
2
1
1
The other six species are all commercially important. All but capelin are considered to
be demersal (groundfish), although redfish may rise from the bottom, particularly at
night. Capelin are pelagic and, aside from their commercial importance, are a key item
in the food web, being a principal food item of whales, seals, seabirds and other fish.
Capelin spawn inshore on gravel beaches where the adhesive eggs take about two
weeks (depending on temperature) to hatch. In addition to these inshore spawners, an
offshore spawning population is located on the Southeast Shoal area.
Redfish eggs are retained within the body of the female and the young are "extruded"
when fully developed. The remaining species
cod, witch flounder, yellowtail
flounder and American plaice
have pelagic eggs that float near the surface during
incubation. Consequently, their distribution is affected by ocean currents.
4.5.1
The following description of the geographic and seasonal distribution of
ichthyoplankton in the continental shelf area off the east coast of Newfoundland is
based largely on the Mobil-sponsored oceanographic cruises of 1980 and 1981. A
description such as this, based on one year's work, cannot address variations in the
ichthyoplankton that occur from year to year (see Section 3.1.3). The description is
based on seven geographic subdivisions of the Grand Banks (Figure 4.5-1):
1.
2.
3.
4.
5.
The Inshore area
The Avalon Channel-St. Pierre Bank area
Central Grand Bank
North and East slopes
The Southeast Shoal and Tail of the Bank
4-27
6.
7.
The Southwest Slope
The deep water off the banks
The seasonal distribution of the dominant ichthyoplankton species within these
subareas for the years 1980 to 1981 is shown in Figure 4.5-2. "Mean numbers" in the
following descriptions refer to the average for a number of samples collected in a
particular subarea (Figure 4.5-1) or over a specific time period. Maximal mean
numbers refer to a specific subarea or time where average densities were highest.
January
In January, the ichthyoplankton community was sparse. However, newly hatched sand
lance larvae (6-10 mm in length) could be found on the Southeast Shoal, as well as a
few scattered juvenile capelin (hatched the previous year).
March
In March, sand lance larvae increased in number and were more widely distributed
across the Banks. American plaice and cod-type eggs (cod, haddock or witch flounder
(CHW) eggs) were present on the Banks and on the slopes in low numbers.
April
In April, sand lance larvae were widely distributed on the Banks and appeared to be at
their maximum concentration in some areas; the mean concentration of sand lance in
the Southeast Shoal-Tail area was 7801 fish/1000 m3. In the deep waters off the slopes
and along the slopes (but not on the banks), redfish larvae appeared in the
ichthyoplankton. Plaice eggs were the dominant egg component of the ichthyoplankton
in April, and were fairly widespread in inshore areas and on the Banks. CHW eggs
were found in small numbers in all areas.
May
In May, sand lance larvae were still widely distributed, and cod and plaice larvae
appeared in small numbers on the Central Grand Bank and the Northeast Slope.
Redfish were found in close to maximal mean numbers and were still largely confined
to the shelf slope and deep waters off the shelf. Maximum mean numbers of both plaice
(464/1000 m3) and CHW (121/1000 m3) eggs were found in May in the Inshore
region. While plaice eggs were found over most of the shelf, CHW eggs were largely
confined to the north half of the Grand Banks. Yellowtail eggs were present in small
numbers in all areas but the deep water off the shelf.
4-29
June
In June, yellowtail eggs reached a maximal mean of 170/1000 m 3 on the Southeast
Shoal-Tail area of the Banks, and were abundant on the Central Grand Bank. CHW
eggs were still relatively abundant, particularly in the Avalon Channel-St. Pierre Bank,
the Central Grand Bank and the Southeast Shoal-Tail areas. The number of plaice eggs
had declined, but moderate numbers were still found on the Central Grand Bank and
the Southeast Shoal-Tail areas. In most areas, the number of sand lance larvae was
declining in June; however, the mean number of sand lance larvae was high in the
Inshore region (1717/1000 m3), primarily because of high numbers in the mouths of
Placentia and St. Mary's bays. These larvae averaged 25 to 31 mm in length, and so
had not been newly hatched. Redfish larvae were still found along the shelf break and in
deep water, while relatively small numbers of plaice were found everywhere but the
deep water off the Banks. Cod larvae were confined to the Central Grand Bank and the
Northeast Slope areas. Witch flounder larvae made their first appearance of the year in
June in the Avalon Channel-St. Pierre Bank, Southeast Shoal and Tail, and Northeast
Slope areas.
July
In July, there was an increased dominance of flatfish eggs and larvae, and a decrease in
other species, particularly sand lance. The number of plaice eggs continued to decline,
while CHW eggs maintained relatively high concentrations, particularly in the Inshore,
Avalon Channel-St Pierre Bank, Central Grand Bank and Southeast Shoal-Tail areas.
In most areas, numbers of redfish larvae continued to decline; however, high numbers
of newly extruded larvae were found at two stations close to the shelf break in the
Southeast Shoal-Tail area. This resulted in the highest mean concentration of redfish
for this area (126/1000 m3). It appears that a second spawning of redfish occurs on the
slope of the Banks, as is thought to occur on the Flemish Cap.
Cod larvae were found in small numbers in all areas except the deep water off the shelf
and the Southwest Slope; American plaice larvae were similarly widely distributed.
Yellowtail larvae were relatively abundant in the Inshore region, on the Central Grand
Bank and in the Southeast Shoal-Tail region. Witch flounder were found in most areas
(except for the deep water off the shelf), but were most abundant in the Inshore and
Avalon Channel-St. Pierre Bank regions. Capelin larvae made an appearance for the
first time of the year in the Inshore and Avalon Channel-St. Pierre regions.
August
In August, the Inshore region appeared to be important for ichthyoplankton. Capelin
larvae in maximal numbers dominated the plankton in this region (1731/1000 m 3), but
4-31
American plaice (44/1000 m3), cod (30/1000 m3), and witch flounder (225/1000 m3) all
exhibited their maximal mean numbers at this location and time. Yellowtail larvae were
also abundant in the Inshore region, and reached maximal mean numbers of 82/1000
m3 on the Central Grand Bank in August. Capelin, American plaice, cod and witch
flounder were abundant on the Central Grand Bank as well. Sand lance and redfish
larvae had declined in importance as components of the ichthyoplankton in August, as
had plaice, CHW and yellowtail eggs.
September
In September, capelin, cod, witch flounder, plaice and yellowtail larvae were still
important components of the ichthyoplankton in the Avalon Channel-St. Pierre Bank
and Central Grand Bank areas. They were likely important in the Inshore region as
well, but no sampling was done in this area in September. CHW and yellowtail eggs
were still found in small numbers on the Continental Shelf but not in the slope areas or
off the shelf. Redfish and sand lance had almost completely disappeared from the
plankton by this time.
November
In November, the ichthyoplankton were severely impoverished; only low numbers of
capelin and occasional specimens of sand lance and plaice were found.
Summary
The ichthyoplankton of the Grand Banks can be described as having two peaks. The
first occurs in April and May, and is dominated by sand lance on the Continental Shelf,
and redfish on the slopes and in the deep water off the slope. The second, which takes
place in August primarily in waters close to shore (and in the Central Grand Bank and
Southeast Shoal areas for yellowtail) is characterized by the emergence of capelin
larvae associated with peak numbers of cod and flatfish larvae.
Of obvious importance in examining the potential impacts of a pollutant such as oil,
which is concentrated on or near the sea surface, is the vertical distribution of fish eggs
and larvae in the plankton. Data from the Mobil-sponsored cruises in 1980 and 1981
indicate that the overall concentration of fish eggs in the surface waters (as determined
from Neuston surface samplers) was approximately 100 times greater than an average
concentration through the water column to 70 m (as determined from oblique BONGO
tows). The concentrations of CHW, American plaice, and yellowtail flounder eggs all
were significantly higher in the surface samples than in the depth-integrated samples.
The depth distribution of larvae was less distinct. While plaice, cod, redfish and witch
4-32
flounder larvae were all in lower concentrations in the surface samples than in the
depth-integrated samples, the concentrations of capelin and sand lance larvae in surface
and depth-integrated samples were not significantly different. Vertical distribution is
discussed further in Section 4.5.4.
4.5.2
Recent Ichthyoplankton Research
Helbig et al. (1992), in an investigation of the environmental influences on the
recruitment of Newfoundland/Labrador cod, state that very little information is
available on the temporal and spatial distribution of cod eggs, larvae, and juveniles on
the Newfoundland and Labrador shelves.
Given the economic importance of the northern cod stock in the past, and the
resources expended on research related to this stock in recent years (Northern Cod
Science Program), it is not surprising that even less is known about the early life stages
of other fish species (with the possible exceptions of capelin and yellowtail flounder) on
the Grand Banks, and in other Newfoundland and Labrador waters.
The Mobil Oil Canada Ltd. work of 1980 and 1981 remains the single most
comprehensive plankton survey carried out on the Grand Banks. The work published
since 1984 has mostly been done by researchers of Fisheries and Oceans Canada or
Memorial University. This information tends to focus on particular species or on
particular subareas of the Grand Banks. Virtually nothing more has been reported on
the ichthyoplankton of the Northeast Grand Bank, in the vicinity of the Hibernia and
Terra Nova oil fields.
Much of the recent work has focussed on testing two hypotheses related to the
importance of egg and larval survival success (deYoung and Davidson, 1994):
4.5.3
1.
The match-mismatch hypothesis that larval survival is dependent on the timing
of larval emergence in relation to the timing of peak numbers of zooplankton
food items
2.
Larval survival depends on the larvae remaining in zones favourable for their
development
There is growing evidence in support of Bonnyman's (1981) observation that the drift
of eggs and larvae onto the Grand Banks from the northeast Newfoundland shelf did
not contribute greatly to the development of the ichthyoplankton community on the
Grand Banks in 1980 and 1981. Recent evidence suggests that the retention of eggs
and larvae in the general area where they are spawned is an important determinant of
year-class strength (deYoung and Davidson, 1994; Davidson and deYoung, 1995), and
4-33
that cod, at least, spawn in areas where their eggs and larvae are likely to be retained
(Hutchings et al., 1993). Helbig et al. (1992), using particle drift simulation modelling,
conclude that Labrador Shelf cod eggs and larvae are segregated from Grand Banks
eggs and larvae. They also found that drift rates over the Grand Banks appeared to be
slow enough to ensure that eggs and larvae are retained, and that special retention
mechanisms, such as are thought to occur on the Southeast Shoal, are not necessary.
Drift of eggs and larvae off the Grand Banks into water of unfavourable rearing
conditions is not thought to be a significant problem (Myers and Drinkwater, 1988).
In modelling simulations of cod egg and larval drift, deYoung and Davidson (1994)
and Davidson and deYoung (1995) found that the northern Grand Banks was the most
favourable spawning location from a "retention on the Grand Banks" perspective. This
is consistent with the conclusion of Hutchings et al. (1993) who found that cod
spawned all over the Grand Banks, but particularly on the northern half, and not
exclusively on the shelf slopes as had previously been thought. It is also consistent with
the findings of Bonnyman (1981) reported above, that cod eggs and larvae were often
found in greatest concentrations on the northern half of the Grand Banks.
It has been hypothesized that the bays of northeast Newfoundland are important
juvenile nursery areas for the northern cod stock, after eggs and larvae drift into the
bays northeast from the shelf. However, Helbig et al. (1992), using particle drift
simulation modelling, concluded that storm tracks had to be extremely favourable to
cause drift into these bays, and that the Newfoundland northeast shelf was a far more
likely juvenile-rearing area. This conclusion was supported by the work of Anderson et
al. (1995), who found that cod eggs spawned offshore remained offshore, and that
pelagic juveniles found in the inshore bays had probably been spawned inshore. These
conclusions support those of Hutchings et al. (1993) who, in a review of information
on cod-spawning locations, concluded that local, inshore populations of cod may make
a larger contribution to recruitment than was previously thought.
Frank et al. (1992) infer spawning locations for three flatfish species from larval and
juvenile distribution on the southern Grand Banks in 1986, 1987 and 1988, assuming
passive advection in conjunction with measured currents in the area. The Southeast
Shoal is inferred as a spawning location for yellowtail in two of the three years. For
plaice, a spawning location along the northern or northeastern Grand Banks with
southward drift in the Labrador current is inferred. There was little evidence that witch
flounder had been spawned on the slopes of the Grand Banks, as had been assumed in
the past.
Capelin larvae, on the other hand, are rapidly dispersed to the Grand Banks after
hatching on beaches in Newfoundland bays. Using an advection-diffusion model,
deYoung et al. (1994) conclude that the residence time for capelin larvae hatched at the
4-34
head of Conception Bay was approximately 20 to 40 days. Larvae that were hatched
on beaches closer to the mouth of the bay had a residency time as short as a few days.
Other recent studies have examined the timing of the onset of larval feeding in relation
to the timing of the zooplankton bloom (the match-mismatch hypothesis). Anderson
and Gardner (1986), in an examination of the biological oceanography of the Southeast
Shoal and shelf-break area that confirmed the higher productivity along the shelf found
by Hollibaugh and Booth (1981), found high densities of sand lance and snail fish over
the shallow area of the Southeast Shoal at a time when prey items (i.e., early stages of
copepods) were in low supply and ctenophore predators were abundant. This was a
somewhat paradoxical finding, inconsistent with the match-mismatch hypothesis.
In a study of the spatial distribution of capelin larvae on the Southeast Shoal, Frank et
al. (1993) conclude that behavioural responses in older larvae enabled them to remain
within patches of zooplankton prey, and that the importance of the match-mismatch
hypothesis as a regulator of larval survival and recruitment may be less universal than
previously hypothesized. On the other hand, Myers et al. (1993) note that cod
spawning in all areas always occurs before the peak of the main zooplankter food item
for cod larvae. They conclude, in support of the match hypothesis, that the timing of
cod spawning is coupled to the timing of plankton production, but only in a general
way; recruitment will not be strongly influenced by changes in the timing of the
plankton peak, contrary to the assertions of the full match-mismatch hypothesis.
4.5.4
Several recent studies have provided information on the vertical distribution of fish
eggs and larvae. Frank et al. (1992) examined larval flatfish distribution on the southern
Grand Banks based on ichthyoplankton surveys in 1986, 1987 and 1988. Yellowtail
larvae and juveniles reach peak concentrations between 18 and 28 m, at or near the
thermocline, with only small numbers being found at the surface. Plaice larvae appear
to be predominantly subthermocline, and none were found in the surface 5 m. Witch
flounder larvae were also centred around the thermocline (around 23 m) with only
small numbers in the surface 5 m. All three flatfish species exhibit some daily vertical
migration. However, the vertical range of diel migration in yellowtail is small, as it is
for plaice and witch, providing little support for the theory of retention via daily vertical
migrations.
DeYoung et al. (1994) found peak densities of capelin larvae within the top 40 m in
Conception Bay, with smaller larvae at shallower depths than larger larvae. Frank et al.
(1993) examined larval capelin on the Southeast Shoal and found that all size classes
exhibited diel vertical migration. The vertical range increased with larval size; for yolk-
4-35
sac larvae, the range was about 15 m, whereas for large post yolk-sac larvae, the range
was greater than 40 m.
Anderson and deYoung (1994) found that the density of healthy cod eggs decreased
with age and development, ensuring a positive buoyancy and that hatching would take
place in conditions favourable for larval feeding and growth. Dead eggs sank rapidly
and were lost to the bottom, and eggs increased in density when exposed to
unfavourable water conditions (e.g., low oxygen levels).
4.5.5
The concentration of fish eggs and larvae in the water column is subject to considerable
interannual variability, by orders of magnitude in various fish species (Frank et al.,
1992; Anderson, 1994). Myers and Cadigan (1993a,b) conclude that variability in
relative year-class strength of groundfish is usually determined at the larval stage, but
that this can change as a result of juvenile mortality. A variety of factors probably
contribute to the interannual variability in egg and larval populations, including:
4.5.6
-
Parent stock size in some instances (northern cod stock in recent years)
-
The timing of spawning in relation to environmental factors (capelin and
onshore wind frequency; Leggett et al., 1984)
-
Strength and direction of currents (flatfish on Southeast Shoal; Walsh, 1992)
-
Freezing in cold, low-salinity water (2J3KL cod; Myers et al., 1993)
-
Spawning at the "right site" in relation to water temperature, spawning location
and resulting retention time (cod; deYoung and Rose, 1993)
-
Storm conditions and related degree of offshelf transport (Myers and
Drinkwater, 1988)
-
Abundance of prey and predators, water temperature and salinity
Flemish Cap
In an examination of the early life history of redfish on the Flemish Cap, Anderson
(1984) determined that redfish constituted at least 90 percent of all fish larvae. Samples
were taken in 12 surveys from 1978 to 1982, all conducted between March and
August. Anderson confirmed that two species-specific peaks in larval extrusion
occurred, one in early April, and a second, smaller peak in mid June (the early peak
was Sebastes mentella and the later peak S. fasciatus). In the early extrusion, larval
4-36
abundances reached as high as 733 larvae/m2. Anderson also noted that interannual
variability could be high, and that larvae greater than 13 mm were an order of
magnitude more abundant in 1982 than in 1981. Anderson (1984) stated that the
bimodal pattern of larval extrusion was unique to redfish populations in North America
and the Mobil data indicate a similar pattern on the Southeast Slope (Section 3.12.1),
with two periods of peak extrusion, May and July. Finally, Anderson (1990) examined
the timing of the peak in copepod spawning in relation to the peak redfish extrusion
period. He hypothesized that while the time of spring calanoid spawning did not vary
much (mid- to late April), the interannual variations in the rate of copepod
development would have significant effects on larval fish feeding, growth and survival.
Myers et al. (1993) report that cod spawn about two months earlier on the Flemish
Cap than on the Grand Banks at similar latitudes, adding support to observations that
the Flemish Cap ecosystem is distinct from that of the Grand Bank.
4-37
4.6
Benthos
4.6.1
Macrophytes and Associated Microscopic Algae
The term "macrophytes" encompasses both large algal species such as kelps, and large
vascular plants such as eelgrass. A flora of microscopic algae, often benthic diatoms, is
usually found growing on these macrophytic plants and on bottom substrates where
light conditions are suitable.
Mobil (1985) summarizes information on the macrophytes of the study area. About
300 species of macrophytic algae occur in coastal areas. Their spatial distribution is
controlled by substrate type (macrophytic algae require solid, stable surfaces for
attachment), exposure, light penetration, ice scour, and water temperature. The
macrophyte zone is highly productive in Atlantic Canada, and provides important
habitat for many fish species. Four distinct communities can be identified on the basis of
location:
1.
The community growing in shallow waters and intertidal areas of coastal
Newfoundland
2.
The community growing in the shallow waters of the Virgin Rocks-Eastern
Shoals region
3.
Coralline algal communities growing in deeper waters to depths of 50 m
4.
Communities that have developed as part of the biofouling community on
drilling rigs
Communities can be defined based on species composition as well. Generally speaking,
two such seaweed algal communities are found in the study area:
1.
An open Atlantic association of the north and east coasts that occurs in deeper
cold water, mainly below 25 m
2.
A community associated with the more protected waters of the south and west
coasts that includes species at the northern or southern limits of their ranges
Within these two communities are species that exhibit winter-spring growth, and those
that exhibit summer-autumn growth. Three reproductive periods have been identified:
winter (December-April), spring (March-July), and summer-autumn (June-November).
The reproductive gametes are planktonic, allowing ready dispersal to other suitable
areas. Thus, drilling rigs that provide hard substrates at optimum depths and light
conditions are readily colonized. Macrophytic algal communities exhibit zonation
patterns with different species growing at different depths or at different elevations of
4-38
the intertidal zone. This zonation is evident on the artificial substrates of the drilling rigs
as well.
Marine vascular plants, primarily eelgrass and cord grass of salt marshes are found only
on fine-grained, soft bottoms in shallow, protected embayments.
Microalgae and coraline algae are important components of the benthos in water
depths shallower than 30 to 50 m. Macrophytes (seaweed) are important at water
depths shallower than 30 m.
It is unlikely that extensive macrophyte beds are located in the Terra Nova area where
the depth is too great to allow development of macrophytic algal species. However,
macrophytic communities will undoubtedly develop on drilling or production structures
located in this area.
Since the summary of information on macrophytes provided by Mobil (1985), there has
been little work of any significant relevance to the environmental implications of drilling
for oil at Terra Nova (R. Hooper, Memorial University, pers. comm.).
4.6.2
Benthic Fauna
Benthic animals live in, on, or attached to the sea bottom. Infaunal animals live within
the sediment and can include bivalves (clams), polychaete worms, some crustaceans
such as amphipods and cumaceans, and other kinds of animals. Filter feeding infaunal
animals feed directly on plankton, while detritovores feed on the bacteria associated
with detritus. Detritovores may feed on the sediment surface or ingest sediment and
extract whatever nutritive value it contains. In offshore waters, the source of this
detritus is phytoplankton that sinks to the bottom, zooplankton faecal pellets and other
organic matter of pelagic origin. In nearshore waters, marine algae and detritus in
terrestrial runoff can also contribute to the detritus pool. Some benthic animals are
carnivores and feed on other benthic animals. Hyperbenthic animals live in or on the
substrate but are also active swimmers in the layer above the bottom. Epibenthic
animals live attached to hard substrates.
Benthic community structure, animal and plant distributions and the standing crop of
benthic animals are related to:
-
Temperature
Water depth
Food supply
Predation within the benthos by fish and other pelagic predators
Disturbance
The passage of time
4-39
Benthic communities are not static. A community that has sustained heavy predation or
disturbance from fishing gear may be very different from the pre-disturbed community
and the communities that represent stages in succession from the disturbed state to a
climax state. Because of predation, disturbance, differences in microhabitat over short
distances and the dynamics of benthic communities, abundances of benthic animals are
highly variable even within small areas (Vezina, 1988; Downing, 1989; Schneider and
Haedrich, 1991; Schneider et al., 1987). Because of the high variance, differences
among locations or over time can be demonstrated only if there are large differences in
animal abundances, species composition, or both.
Historically, benthic studies have included the following:
·
Taxonomic descriptions of the animals present
·
Descriptions of the communities present
·
Investigations of the relationships between animals and communities and the
physical attributes of their environment
·
Reproductive studies that include long-term population dynamics
·
Investigations of the relationships between standing crop, community structure
and food supply
·
Trophic dynamic studies of the relationships between and among benthic
animals, including studies of the effects of predation and disturbance
Over the years, predation by fish and disruption by fishing gear has been intense on the
Grand Banks benthos. Studies of benthic communities or even individual species on the
Grand Banks have not been conducted beyond the third level described above. Thus,
there are insufficient data to explain the observed distribution of animals and to relate
apparently different communities to the stages of succession within communities.
Grand Bank benthic communities that have been classified as different may represent
different stages of succession of the same community and there may be fewer basic
community types than described by Nesis (1965) and Hutcheson et al. (1981).
Because of the decline in fish stocks and concomitant decline in fishing intensity, one
would expect that some major changes in benthic community structure could have
occurred since the last comprehensive study, conducted in 1980. The causes of the
decline in fish stocks may have also caused changes in benthic community structure
apart from changes related to predation and disturbance from fishing gear. Long-term
cycles in benthos and plankton related to cyclical changes in hydrography have been
4-40
noted in other parts of the North Atlantic (Gray and Christie, 1983).
Species Composition
At least 370 species of polychaete, echinoderm, crustacean and mollusc occur on the
Grand Banks. Numerically, polychaetes are the most abundant infaunal taxa, and
echinoderms and bivalves are dominant in terms of biomass (Hutcheson et al., 1981).
Crustaceans are the dominant hyperbenthic animal. Deep water and northern areas of
the banks contain arctic/sub-arctic assemblages. Temperate species are characteristic of
shallow water and southerly portions of the banks.
Standing Crop and Productivity
Infaunal benthos appears to decrease with increasing depth (Table 4.6-1). Hutcheson et
al. (1981) estimated the average standing crop of infaunal benthic animals on the Grand
Banks at depths between 51 and 421 m to be at 481 g/m2 wet weight. The highest
standing crops are found in areas dominated by the bivalve Mesodema. Nesis (1965)
recorded a biomass of 4.6 kg/m2 (wet weight) in one of these areas. At one of
Hutcheson's stations dominated by this bivalve, standing crop averaged 7.3 kg/m 2 wet
weight (17 replicates over 5 sampling periods).
Hutcheson et al. (1981) estimated average annual infaunal productivity on the Grand
Banks to be about 368 g/m2 wet weight (536 J/m2). The overall production- tobiomass ratio was 0.9 on a wet weight basis. These high standing crop and productivity
estimates reflect the high primary production on the Grand Banks.
Table 4.6-1
Relationship of Standing Crop of Infaunal Animals to Depth
Depth
(m)
Standing Crop
(g/m2)
0-50
1573
50-100
449
100-200
168
200-300
47
300-500
47
500-1000
64
1000-1500
32
Source: Nesis, (1965).
4-41
Filter feeding and surface deposit feeding are the most common modes of feeding
(Hutcheson et al., 1981). Hutcheson et al. (1981) suggest that this reflects a direct link
between plankton production and benthic communities.
Based on the combined work of Nesis (1965) and Hutcheson et al. (1981), the
Hibernia EIS identified 12 benthic communities on the Grand Banks. Each community
was associated with specific substrate, depth, geographic location and water mass
characteristics.
Hutcheson et al. (1981) found no evidence of major seasonal changes in the structure
of benthic communities during a period of less than one year; however, they did find
seasonal changes in the abundance of some individual species.
Interactions with Fish
The feeding habits (as indicated by their stomach contents) of 14 of the most common
fish species on the Grand Banks are shown in Table 4.6-2. Infaunal and hyperbenthic
animals make up a significant proportion of the diets of these common fish species, and
decapods and echinoderms are especially important. Polychaetes and crustaceans are
important food items for young cod (Paz et al., 1993).
Interactions with Fishing
In 1985, approximately 236 100 hours were spent trawling on and near the Grand
Banks (Messieh et al., 1991). This represents about 1 300 000 km of trawling effort.
The total area swept by bottom fishing gear could be as much 9 000 km 2 (estimated
from data in Messieh et al., 1991). The effects on the benthos can include direct
mortality of individuals, indirect mortality through exposure of animals to increased
predation by fish attracted to the area, and long-term changes in benthic community
structure (Messieh et al., 1991).
An ongoing (1990-97) collaborative research project on the impacts of trawling on the
Grand Banks is being conducted by the Bedford Institute of Oceanography (BIO) and
Fisheries and Oceans Canada (St. John's). The research is being conducted in an area
about 60 km northeast of Hibernia that has been closed to trawling since 1987 (centre
position at 47°10_ N, 48°17_ W) (D. Gordon, BIO, pers. comm.). The project
involves assessing the impacts of one type of bottom trawl on a relatively
homogeneous, sandy environment. Extensive, video-guided sampling of the sediment,
and the infaunal and epibenthic communities has been conducted. There is preliminary
evidence of impacts on sediments and some epibenthic species such as crab (Fisheries
and Oceans Canada, 1995).
4-42
Gammarid Amphipods
Cumacea
Decapods
Isopods
Echinoderms
Molluscs
Anthozoa
Polychaetes
Sponges
Tunicates
Sipunculids
Total fish and pelagic
Total benthic animals
28.6
30.3
0.3
0.2
0.3
2.0
38.3
61.7
28.8
2.2
1.0
0.5
63.8
36.2
Spotted
Wolffish
3.7
Atlantic
Wolffish
89.1
10.9
46.8
53.2
22.3
0.4
3.5
0.2
24.5
Common
Grenadier
1.0
1.7
46.3
53.7
53.7
Longfin
Hake
1.3
9.1
0.1
Atlantic
Cod
57.7
42.3
0.1
5.4
1.9
0.3
4.8
29.6
0.2
Roughhead
Grenadier
11.3
88.7
84.8
15.2
0.1
0.8
80.1
1.8
0.5
99.5
0.2
1.7
13.2
86.3
0.4
1.2
0.0
American Greenland
Plaice
Halibut
0.1
5.7
4.6
6.7
0.5
Witch
Flounder
Stomach Contents of Common Fish Species
as Percentage Volume
Table 4.6-2
0.2
9.4
90.6
3.4
52.8
0.8
33.4
56.6
43.4
2.2
35.7
0.0
0.1
4.2
1.2
89.0
11.0
11.0
Arctic Thorny Acadian
Eelpout Skate Redfish
96.3
3.7
3.7
Golden
Redfish
60.3
39.7
0.2
4.1
35.4
Deepwater
Redfish
Intertidal and Nearshore Benthic Communities
Coastlines adjacent to the Grand Banks consist of rocky cliffs, with fjord-like inlets and
pebble-cobble beaches. Some sand beaches and salt marshes are also present.
Substrate, wave exposure and ice conditions are important determinants of the
abundance and distribution of intertidal animals (Steele, 1983).
The intertidal biota of Newfoundland is typical of that of the northwestern Atlantic.
Barnacles, limpets, mussels, amphipods, and the predatory gastropod Thais are
commonly encountered in the intertidal zone. Most intertidal and subtidal animals feed
directly on plant material thorough grazing or suspension feeding. Gastropods, limpets
and chitons are the dominant grazers in the intertidal zone. The sea urchin is probably
the dominant grazer in rocky sublittoral environments. At depths below that occupied
by the urchins, chitons are the dominant grazer.
4.7
Biofouling
Fouling of offshore structures by marine plants and animals can affect the safe
operation of those structures (Hardy, 1981). Fouling organisms increase friction
between the structure's surface and the water and affect maneuvreability, wave loading,
and weight (Evans, 1981; Hardy, 1981). Fouling organisms, by their presence or
through release of chemicals, can cause or increase corrosion. A dense cover of fouling
organisms can also interfere with inspections. In situ cleaning of structures can be both
dangerous and expensive.
The fouling potential of the Hibernia site has been assessed by Welaptega (1993). This
report was limited by the lack of site-specific information but made the following points
that are also relevant to Terra Nova:
·
Microfouling, by bacteria, diatoms, protocoans, etc., if not properly controlled,
can create operational problems such as blockage, dangerous H 2S production,
and corrosion of steel structures. In addition, microfouling prepares the surface
for macrofouling.
·
Macrofouling can cause operational problems such as blockage and excessive
loadings.
Welaptega (1993) also modelled the amount of potential buildup based upon
information from other areas. The riser, the floating platform and other subsea
structures will likely be subject to colonization by fouling organisms. Offshore
structures act as artificial reefs and are colonized by a wide variety of plants and
animals (Forteath et al., 1982). Colonizing organisms can include attached forms such
as seaweeds, hydroids, byozoans, barnacles, sea anemones, sea cucumbers, tunicates,
tube-dwelling polychaetes and mussels (Forteath et al., 1982). Mobile grazers and
predators such as starfish, urchins, limpets, gastropods, amphipods and chitons can also
colonize structures (Forteath et al., 1982).
Availability of spat, competition for space and illumination are the dominant factors
shaping the species composition of a fouling community on the Grand Banks.
Sessile animals produce pelagic larvae with a fixed life span. If the larvae do not find
suitable substrate within a fixed time period, they die. Current patterns are an important
determinant of the kinds of animals found on offshore structures. If currents carry live
spat from breeding coastal populations to offshore structures, then intertidal biota will
have an opportunity to colonize. The source for intertidal animal larvae that could
settle on structures at the Terra Nova site could only be the north shore of
Newfoundland. The inshore branch of the Labrador Current passes along the north
shore of Newfoundland then divides southward and eastward. The eastward-flowing
branch flows along the northern Grand Banks to its northeast corner where it joins the
southward-flowing, offshore branch of the Labrador current. The core of this
southward-flowing current passes within 40 to 50 km of the Terra Nova site (Section
3.2.4). Eddies or wind could bring larvae onto the Terra Nova site.
Because of ice scour, attached intertidal life is sparse along exposed areas on the north
coast of Newfoundland (South, 1983). In sheltered areas, intertidal life is comparable
to that found in other parts of the island. Barnacles, mussels, Chondrus, and the
rockweed Fucus, are common (South, 1983; Steele, 1983). The pattern of zonation in
the subtidal zone is determined by grazing of the sea urchin Strongylocentrotus
droebachiensis (Steele, 1983). In the absence of grazing, competition for space would
determine zonation on production facilities. The kelps, Laminaria, Agarum and Alaria,
the red algae, Ptilota, encrusting red coraline algae and Desmarestia are common
subtidal plants (Steele, 1983). These could all be considered potential fouling
organisms.
Desmarestia is a particularly noxious fouling plant because, when damaged (by, for
example, wave action) it releases free sulphuric acid, which can accelerate corrosion
(Hardy, 1981). The filamentous algae, Enteromorpha, can withstand wide fluctuations
in environmental conditions and so is considered a cosmopolitan fouling plant (Evans,
1981). Enteromorpha is found on the north shore of Newfoundland (South, 1983).
In the North Sea, kelps have colonized platforms a hundred or more miles from shore
(Moss et al., 1981). Zoospores can live for up to 80 days; millions are released by each
plant. Young plants can be free floating and then attach themselves to solid structures.
Viable fertile barnacles, mussels, kelp and filamentous algae on supply boats and oiltransfer ships could also be a source of fouling organisms.
Starfish are not usually able to reach shallow regions of platforms that are anchored to
the bottom (Forteath et al., 1983). Starfish and other predators and urchins may be
unable to reach a floating production platform or the top parts of the riser pipe and so
predation may be minimal. A lack of grazing by urchins could allow extensive fouling
by large macrophytes.
In time, a clear pattern of zonation related to water depth and illumination would be
evident on offshore structures. There would also be changes in species composition
over time. Early colonizers might not be able to compete for space with other animals
and would subsequently diminish in importance or be excluded altogether.
Growth of fouling organisms may be quite rapid. Animals that normally inhabit the
intertidal zone are always immersed in water when attached to offshore structures and
so can feed continuously (Forteath et al., 1983).
Animals that normally live in the intertidal zone may not have restricted depth
distribution in offshore waters. In the north sea, the barnacle Balanus crenatus can be
found between mean low water and 60 m depth, and the mussel Mytilus edulis can
dominate the fouling community on oil and gas platforms from mean low water to
depths of 30 m (Forteath et al., 1983).
4.8
Fish and Fisheries
This section is based on published literature (primary publications and government
publications) and unpublished data provided by Fisheries and Oceans Canada. Data
regarding commercial fisheries statistics came primarily from Fisheries and Oceans
Canada and NAFO sources as compiled by Canning & Pitt Associates, Inc. Figure 4.81 shows the NAFO divisions offshore Newfoundland, and the major offshore plateaus
of the Grand Banks. The Terra Nova site is located in Division 3L.
Major finfish and invertebrate stocks have changed drastically in the past eleven years.
Cod have traditionally dominated catches in Newfoundland waters but in recent years,
cod stocks have declined drastically, and other species have become more
commercially important. Almost without exception, the traditional groundfish
resources in the waters around Newfoundland are presently at or very near historical
low levels. For Canadian-managed stocks with total allowable catches still in place,
information suggests that they may still be in decline. For the NAFO-managed
resources, excluding those of the Flemish Cap, directed fisheries remain open only for
Greenland halibut and 3LN redfish.
Based on Canadian and foreign catch size (Mobil, 1985), the five most important
species on the Grand Banks in 1982 (the base year described in the Hibernia EIS) were
Atlantic cod, redfish, American plaice, capelin and yellowtail flounder. Approximate
total landings of each species in the study area in 1982 (NAFO, 1995) were as follows:
·
·
·
·
·
Atlantic cod (3LMNO) - 137 000 t
Redfish (3LMN) - 36 000 t
American plaice (3LMNO) - 51 000 t
Capelin (3NO) - 0 t
Yellowtail flounder (3LNO) - 12 000 t
By 1994, NAFO catch statistics pertaining to these species in the same Divisions had
changed appreciably:
·
·
·
·
·
Atlantic cod - 40 000 t
Redfish - 18 000 t
American plaice - 8100 t
Capelin - 0 t
Yellowtail flounder - 2000 t
There was no offshore capelin fishery in either 1982 or 1994. However, capelin was an
important inshore commercial species in 1982.
The five most important species in the study area in 1994 (excluding 3M), based on
total landings at Newfoundland ports (Canning & Pitt, 1995), were Stimpson surf clam
(11 092 t), snow crab (4742 t), Iceland scallops (4033 t), skate (mainly thorny skate)
(1940 t), and redfish (1495 t). Catches of all other species were less than 1100 t. Table
4.8-1 lists commercial species landed at Newfoundland ports from 1992 to 1994 and
indicates in which NAFO Divisions catches were made (data did not include Division
3M). These rankings provide some indication of present relative importance of each
species to Newfoundland.
Trawlable biomass is an estimate of biomass derived from research vessel surveys. It
does not represent the total stock biomass but instead is some proportion of this
acknowledging that the catchability of the research trawl is not 100 percent. By the
1990s, the trawlable biomass estimates of various species had declined precipitously
compared to those of the mid-1980s (Table 4.8-2). The biomass estimates of Atlantic
cod and American plaice dropped most dramatically.
The principal commercial pelagic species in the study area in the early 1980s were
capelin, squid, herring and mackerel, which, on the list of the 15 most heavily caught
species on the Grand Banks, ranked fourth, seventh, ninth and tenth, respectively. In
1994, the total Newfoundland port landings of these species from the study area were
as follows (Canning & Pitt, 1995):
·
·
·
·
Capelin - 1037 t
Squid - 95 t
Herring - 973 t
Mackerel - 5 t
Groundfish stocks present within the Terra Nova study area include the following:
·
·
·
·
·
·
·
·
Cod (2J3KL, 3M, 3NO, 3Ps)
Redfish (3LN, 3M, 3O)
American plaice (3LNO, 3M, 3Ps)
Witch flounder (2J3KL, 3NO, 3Ps)
Greenland halibut (management areas SA2 + 3KLMN)
Haddock (3LNO, 3Ps)
Yellowtail flounder (3LNO)
Pollock stock (3Ps)
In addition, there are fisheries for lumpfish and skate (Fisheries and Oceans Canada,
1995).
Pelagic stocks present in the area include capelin (part of 3L, 3NO) and herring.
Important invertebrates include northern shrimp, snow crab and Iceland scallops
(Fisheries and Oceans Canada, 1995).
Mactromeris polynyma
Chionecetes opilio
Chlamys islandica (predom.)
Raja radiata (predom.)
Sebastes spp.
Mallotus villosus
Clupea harengus
Pleuronectes americanus
Gadus morhua
Mercenaria mercenaria
Lophius americanus
Rheinhardtius hippoglossoides
Homarus americanus
Xiphias gladius
Glytocephalus cynoglossus
Hippoglossoides platessoides
Illex illecebrosus
Urophycis tenuis
Hippoglossus hippoglossus
Pollachius virens
Melanogrammus aeglefinus
Anarchichas lupus (predom.)
Anguilla rostrata
Scomber scombrus
Thunnus thynnus
Coryphaenoides rupestris
Mytilus edulis
Gadus ogac
Limanda ferruginea
Merluccius bilinearis
Cyclopterus lumpus
Squalus acanthias
Salmo trutta, Salvelinus fontinalis
Various
Scientific Name
Source: Canning and Pitt (1995).
Notes:
1. Flemish Cap in 3 M is not included.
2. Indicated divisions refer to both directed and incidental catches.
3. Species are listed in descending order according to catch weight in 1994.
Stimpson surf clam
Snow crab
Scallops
Skate
Redfish
Capelin
Herring
Winter flounder
Atlantic cod
Quahogs
Monkfish
Turbot (Greenland halibut)
Lobster
Swordfish
Witch flounder
American plaice
Squid
White hake
Halibut
Pollock
Haddock
Wolffish
Eels
Mackerel
Bluefin tuna
Roundnose grenadier
Mussels
Rock cod
Yellowtail flounder
Silver hake
Lumpfish
Dogfishes
Trout
Bar clams
Common Name
3N
3L, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3O, 3Ps
3L, 3Ps
3L, 3Ps
3L, 3N, 3Ps
3L 3O, 3Ps
3N
3N, 3O, 3Ps
3L, 3O, 3Ps
3L, 3Ps
3N, 3O
3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3Ps
3O, 3Ps
3L, 3N, 3O, 3Ps
3O, 3Ps
3O, 3Ps
3O, 3Ps
3L, 3Ps
3L, 3Ps
3L, 3N, 3O
3O, 3Ps
3L, 3Ps
3L, 3Ps
3L, 3Ps
3Ps
3Ps
3Ps
3L, 3Ps
3Ps
1994
3N, 3O
3L, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3Ps
3L, 3Ps
3L, 3Ps
3L, 3N, 3O, 3Ps
3N
3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3Ps
3L, 3N, 3O, 3Ps
3L, 3N, 30, 3Ps
3L, 3N, 3O, 3Ps
3L, 3Ps
3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3Ps
3L, 3Ps
3L,3N, 3O
3LM 3N, 3O, 3Ps
3Ps
3Ps
3L, 3N, 3OM 3Ps
-3O, 3Ps
3O
3L, 3Ps
3Ps
1993
NAFO Divisions of Catch
Species Caught Commercially in Grand Banks Study Area
and Landed at Newfoundland Ports, 1992-94
Table 4.8-1
3N
3L, 3Ps
3L, 3N, 3Ps
3L, 3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3Ps
3L, 3Ps
3L, 3Ps
3L, 3N, 3O, 3Ps
3N
3L, 3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3Ps
3N, 3O
3L, 3N, 3L, 3Ps
3L, 3N, 3L, 3Ps
3L, 3Ps
3L, 3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3N, 3O, 3Ps
3L, 3Ps
3L, 3Ps
3L, 3N, 3O
3L, 3N, 3O
3Ps
3Ps
3L, 3N, 3O, 3Ps
--3Ps
3L, 3Ps
--
1992
Table 4.8-2
Past and Recent Biomass Estimates in the Grand Banks Study Area
Species
a
b
NAFO
Division
Exploitable Biomass
In Early 1980sa
(t)
Trawlable Biomass in
Early 1990sb
Biomass (t)
Year
Atlantic cod
2J3KL
3NO
100 000 - 150 000
130 000 - 220 000
< 5000
10 000
1994
1994
American plaice
3LNO
350 000 - 400 000
25 000 - 50 000
1994
Yellowtail flounder
3NO
80 000 - 90 000
35 000 - 70 000
1994
Redfish
3LN
3O
3M
190 000
150 000
150 000
21 000 (average)
30 000 - 75 000
126 000
Greenland halibut
23KL
10 000 - 12 000
35 000
1994
Witch flounder
2J3KL
7000
2000
1994
1992-94
1994
1994
Mobil (1985).
Fisheries and Oceans Canada (1995) and NAFO (1995).
The proposed Terra Nova development area is located in the fisheries statistical unit
area or subdivision 3Lt. Adjacent subdivisions include 3Lh, 3Li, 3Ma, 3Mc, 3Nb, 3Na
3Lr (Figure 4.8-1). Landings at Newfoundland ports (Canning & Pitt, 1995) from
1992 to 1994 of catches from these unit areas (excluding the 3M areas), give some
indication of particular species that deserve attention. Within 3Lt, Iceland scallops (4.9
to 23.1 t, 1993-94), American plaice (143.4 t, 1992), Atlantic cod (25.4 t, 1992), and
Greenland halibut (3.1 t, 1992) have been taken at levels worth considering.
Examination of catches in 3Lt and all adjacent areas between 1992 and 1994 reveals
the importance of other species in addition to these four. Based on 1994 landings, the
most heavily exploited species in these seven areas were Iceland scallops (2350 t),
snow crab (441 t), Stimpson surf clam (16 t) and bluefin tuna (4 t). All four of these
species accounted for relatively substantial catches in all three years. Other species
caught in 3Lt and adjacent areas at some time between 1992 to 1994 include American
plaice, Atlantic cod, yellowtail flounder, redfish, haddock, witch flounder, wolffish and
roundnose grenadier.
Most past research has been done on the species that have been commercially
important for many years (i.e., certain groundfish). As a result, less information is
available on population dynamics and biology of some of the species which have just
recently become commercially important (i.e., Stimpson surf clam, snow crab, Iceland
scallop, shrimp and thorny skate).
The following sections discuss those species presently important in 3Lt and adjacent
units.
4.8.1
Iceland Scallop
The Iceland scallop, a suspension feeder, filters water immediately above the sediment
surface. Scallops are preyed upon by Atlantic cod, American plaice, yellowtail flounder
and wolffish (Gilkinson and Gagnon, 1991).
Spawning intensity is greatest in the fall after which the fertilized eggs float at or near
the water’s surface. Hatching occurs at the upper water column and the larvae remain
planktonic for approximately two months before settling to the bottom where
remaining development takes place.
On the northeastern Grand Banks, there is a definite association between Iceland
scallops and gravelly, cobbly substrata (Gilkinson and Gagnon, 1991). This is probably
a result of the scallop's need to attach itself to a stable substratum. A strong attachment
keeps the animal from being swept away by the strong currents.
In July and August, 1982, a survey was conducted to investigate the distribution of the
Iceland scallop in Divisions 3L, 3N, and 3O (Naidu and Cahill, 1989). The majority of
the fishing stations used in the survey were located on the central and western Banks
(Figure 4.8-2). While they were commonly found throughout the Grand Banks in
depths ranging from 49 m in 3N to 220 m in 3L, their abundance was extremely
variable. Of the three broad areas, 3N yielded the best catches, followed by 3L and 3O.
In 1989, another exploratory survey was made in Division 3N (Naidu and Cahill,
1990). Scallops were most abundant in two restricted areas: one just southwest of
Carson Canyon between 57 and 91 m, and the other in the slope area straddling the 5791 m and 92-183 m isobaths off the Lilly Canyon (Figure 4.8-2). Generally, Iceland
scallops were found unevenly distributed over Division 3N although abundance was
higher north of 44° 30'. Despite the occurrence of these aggregations, average densities
within the aggregations were low (0.33 to 2.0 scallops/m2).
In spring 1991, a research survey was conducted on Green Bank in Division 3Ps but no
extensive beds of Iceland scallops were found. Prospect for commercialization of the
Green Bank scallops was deemed minimal (Naidu and Cahill, 1992).
As of 1995, there are only a few locations on the Grand Banks where Iceland scallops
are found in commercial quantities. Research data indicate that the scallop beds in
Division 3N are possibly being depleted (Fisheries and Oceans Canada, 1995).
4.8.2
Snow Crab
Snow crabs are commonly found in association with mud or sand-mud bottoms at
temperatures ranging from 0 to 4.5°C. Young crabs are often found in shallower areas
where the substrate is more gravelly. No seasonal changes in distribution occur as this
species is essentially non-migratory. Hatching takes place in the summer and the larvae
spend about three months swimming freely at or near the surface. Toward the end of
the third larval stage, snow crab descend to the bottom where they remain (Marine
Research Associates Ltd., 1980).
This omnivorous shellfish commonly eats bivalves, worms, small crustaceans and brittle
stars (Marine Research Associates Ltd., 1980).
Landings data from 1994 (Canning & Pitt, 1995) suggest a wide distribution of snow
crab. However, surveys covering part of the total area indicate a declining trend in the
catches of pre-recruits, which could translate to a widespread biomass reduction
(Fisheries and Oceans Canada, 1995) (Figure 4.8-3).
Taylor and O'Keefe (1994) reported that snow crab landings in 3L between the mid1980s (~ 3000 t) and 1994 (~12 000 t) have steadily increased while those in 3Ps have
remained relatively constant (< 2000 t). The majority of the landings within the study
area have occurred within 150 to 200 km of the Newfoundland coast from Cape St.
Francis to the tip of the Burin Peninsula.
4.8.3
Stimpson Surf Clam
Remarkably, this species accounted for the highest landings at Newfoundland ports
from study-area regions fished in 1994 (Canning & Pitt, 1995). Aside from some data
regarding its distribution and abundance on the Grand Banks, essentially no
information is available on the Stimpson surf clam, especially its general biology and
ecology. Based on data for catches landed at Newfoundland ports (Canning & Pitt,
1995), concentrations of this shallow-burrowing species (within 15 cm of substrate
surface) appear to occur in the south-central and southeastern portions of the Grand
Banks, on both the plateau and slope regions, somewhat south of the Terra Nova area.
4.8.4
Skates
Of the eight to 10 species of skate in waters around Newfoundland, the thorny skate
(Raja radiata) is by far the most common, making up about 90 percent of all caught
during research surveys.
Thorny skate are widely distributed throughout the Grand Banks (3LNOPs). They
have been found in depths ranging from 18 to over 1000 m and in temperatures
ranging from -1.4 to 14°C. This sedentary species has been caught on both hard and
soft substrates (McEachran and Musick, 1975).
Limited information indicates that thorny skate reproduction occurs year round on the
Grand Banks (Templeman, 1982a). The species is essentially non-migratory and
spawning occurs throughout the general area of distribution. They deposit egg cases (6
to 40 per year) each containing a single embryo.
Thorny skates feed on a variety of items including polychaetes, amphipods, decapods
and fish, proportions of each being dependent on the size of the skate (Scott and Scott,
1988). Redfish, sand lance and small haddock appear to be important fish prey.
Templeman (1982b) found that crabs were the most important food item to thorny
skate found between 17 and 200 m, and fish dominated at greater depths.
Canadian test fisheries for this species were initiated in 1994. According to data
collected in research surveys between 1986 and 1994 in Divisions 3LNOPs, the
biomass of thorny skate in 3O and 3Ps remained relatively stable until the early 1990s
when declines were observed. In Divisions 3L and 3N, the estimated biomass of this
species has declined steadily since 1986. Divisional estimates of biomass in 1994
ranged from under 5000 to just over 10 000 t, the highest occurring in 3O (Fisheries
and Oceans Canada, 1995).
4.8.5
Redfish
Three species of redfish occur in the area, roughly segregated by depth. Acadian
redfish (Sebastes fasiatus) is a shallow-water (~0-600 m) species compared to the
other two. Golden redfish (S. marinus) is found at intermediate depths (< 300-750 m)
and beaked redfish (S. mentella) is a deep-water (350-1100 m) species.
Redfish are ovoviviparous (i.e., give birth to living young) and generally spawn in the
March to July period. An estimated 15 000 to 20 000 larvae are released by female
redfish. Spawning on the Flemish Cap apparently commences in early spring (deeper
water). Similar activity on the northeastern, eastern, and southeastern slopes of the
Grand Bank occurs at different times in later spring and early summer, depending on
the water depth and temperature.
Redfish feed on a variety of small invertebrates and small fish. Between 1981 and 1988,
beaked redfish on the Flemish Cap (3M) intensified their feeding during the summer,
coinciding with the increase in zooplankton biomass (Albikovskaya and Gerasimova,
1993). Their primary prey was the copepod, Calanus finmarchicus; other food items
included hyperiids, euphausiids and shrimp. Rodriguez-Marin et al. (1994) also
investigated the feeding habits of redfish on the Flemish Cap. Redfish collected by them
during the summer of 1993 were divided by species. The beaked redfish had a wider
prey spectrum than either the golden or American redfish. Crustaceans made up 64
percent of its diet by volume; fish essentially accounted for the remainder. The other
two redfish species fed predominantly on crustaceans such as copepods, hyperiids,
shrimp, mysids and euphausiids. Atlantic halibut, Atlantic cod and swordfish are active
redfish predators.
Based on data collected from 1990 to 1993, redfish were most concentrated along the
slope of the _Nose of the Bank_ (Flemish Pass) (3L) and along the eastern slope of the
_Tail of the Bank_ (3N) (Power, 1994). Results of bottom trawl surveys have
demonstrated considerable variability between consecutive seasons and years. Despite
this, the data from Canadian surveys in 3L suggest that the mean estimated trawlable
biomass since 1992 (5000 t) is the lowest it has ever been. Spring and autumn surveys
conducted in 3N from 1991 to 1994 indicated a mean estimated trawlable biomass of
16 000 t. However, variability between tows was much greater in 3N than in 3L,
perhaps a function of seasonal changes in distribution or catchability (NAFO, 1995).
Prognosis of the resource in 3NL is not positive. The resource in 3L appears to be very
low with no good sign of recruitment and, while the 3N resource presently contains a
recruiting component of unknown abundance, there are no signs from the surveys to
indicate good year classes to follow (NAFO, 1995).
Results of European Union (EU) trawl surveys between 1988 and 1993 have shown
gradual declines in the stock. The 1993 estimated biomass of beaked redfish, which
account for the greatest proportion of redfish catch in this area, was one-third of that in
1992 (Gorchinsky and Power, 1994). Vazquez (1995) reports the main concentrations
of redfish on the northern, western and southern slopes of the Flemish Cap.
Surveys for redfish in Division 3O have been conducted in the spring and fall since
1991. Biomass estimates from the spring surveys show an increasing trend between
1991 (~ 10 000 t) and 1995 (84 000 t). It is still unclear as to whether redfish of 3O are
resident or migrants from another area. A low proportion of fish collected during these
surveys exceeded 30 cm length but significant amounts of larger fish have been found
in the past in the deeper, hard-to-fish regions (Fisheries and Oceans Canada, 1995).
4.8.6
Capelin
Capelin play a significant role as food for other fishes, marine birds and marine
mammals. Their chief predator in the past has been the Atlantic cod, and seasonal
migrations of these two species have been closely associated. Other fish predators of
adult capelin include haddock and Atlantic salmon. Larval and juvenile capelin are
important to the diets of Atlantic herring, flounders, dogfish, sculpins and eelpout.
Bailey et al. (1977) identifies five species of marine mammals and nine marine bird
species known to forage extensively on capelin.
Capelin eat planktonic organisms such as euphausiids, copepods and amphipods.
Feeding is seasonal (Figure 4.8-4) and intensifies in late winter and early spring in the
prespawning period. Feeding intensity declines as spawning season approaches and
virtually ceases during spawning. Several weeks after spawning, the surviving fish start
feeding again and continue to do so until early winter (Scott and Scott, 1988).
Capelin are demersal spawners and their eggs adhere to the spawning substrate. Two
physical factors, water temperature and gravel size, have been identified as important
factors for capelin spawning. Interestingly, there is a co-occurrence of beach- and
offshore bottom-spawning populations of capelin in the study area (Figure 4.8-5)
(Carscadden et al., 1989). With the exception of the Southeast Shoal stock, the stocks
within the study area are beach spawners. Mature capelin undertake extensive
migrations during the spring from the offshore banks to the inshore spawning beaches.
The distribution and movements of capelin have been linked to upwelling along the east
coast of Newfoundland (Schneider, 1994). The favourable temperature range reported
for intensive beach spawning on the east and south coasts of Newfoundland is 5.5 to
8.5°C (Templeman, 1948). Templeman also reported that the best spawning beaches
had gravel of 2 - 15 mm diameter. Once spawning and hatching have occurred, the
larvae are advected from embayments into the open bays in as little as 6 to 8 h. Within
a few weeks, they have been displaced by the current from the nearshore waters onto
the Grand Banks where the maturation process continues. Initially, the dispersal of
capelin larvae is passive but it is later moderated by vertical migrations which bring the
larvae in contact with different current regimes.
As mentioned, the Southeast Shoal capelin are not beach spawners. Carscadden (1978)
found that the bottom temperature at the Shoal during spawning ranged from 0.1 to
6.3°C. Sand grains from the Southeast Shoal range from 0.5 to 2.2 mm in diameter.
Carscadden et al. (1989) suggested that spawning on the Southeast Shoal is controlled
by suitable substrate and that bottom temperature determines the final spawning
location.
In the Northwest Atlantic, five stocks of capelin have been identified on the basis of
spawning times, patterns of fishery, and their biological traits. The three that fall within
the boundaries of the study area include those Northern Grand Bank and Avalon in 3L;
those of the South Grand Bank and Southeast Shoal in 3NO; and those of the St.
Pierre Bank in 3Ps.
In 1987, capelin were readily caught in eastern, northern and western 3L, northwestern
3O and toward the shelf break in both 3O and 3N. Only rarely were large catches taken
on the plateau of the Grand Banks in 3O, 3N and southern 3L. In 1991, capelin were
caught at numerous stations in eastern and northern 3L and at numerous stations near
the shelf break in southern 3NO (Figure 4.8-6). The most notable difference from 1987
was the absence of large capelin catches in southwestern 3L (Lilly, 1992).
Fall surveys from 1980 to 1989 showed moderate to good catches on the northern and
northeastern slopes of the Grand Banks (3L) (Lilly and Davis, 1993) as well as in the
northwestern 2J3K, with a break in the distribution occurring between these two areas.
By 1992, this break had disappeared resulting in a continuous capelin distribution from
south-central 3K to northern 3L. Some suggest that this southward migration of the
Northern Grand Bank and Avalon stock may be associated with cold water
temperature although other years with similar coldwater trends were not
characterized by a shift in capelin distribution.
Surveys in the fall of 1993 showed the highest concentrations at the north and
northeastern slopes of the Grand Banks (3L) with far smaller catches on the western
Whale Bank and in north-central 3O (Figure 4.8-7) (Lilly, 1994).
In 1993, by-catches of capelin were reported from a new shrimp fishery that had
developed on the Flemish Cap (3M), an area in which capelin were reported to be rare
(Carscadden, 1994). There is speculation that the sudden presence of capelin at the
Cap might be due to an eastward shift in the distribution of capelin in Division 3K.
4.8.7
Atlantic Herring
Atlantic herring is a pelagic species occurring both in shallow inshore waters and
offshore waters. In offshore waters, they can be found at depths ranging from surface
to 200 m (Scott and Scott, 1988). As of 1995, herring stocks off the east coast of
Newfoundland are estimated to be low with biomasses of only about 10 percent of
observed maxima. Low temperatures are thought to be having negative effects. Stocks
off the Southeast coast are also at low levels but appear to be less depressed than those
off the east coast (Fisheries and Oceans Canada, 1995).
Generally, spring spawning takes place in inshore shallows while summer and fall
spawning occurs in deeper, offshore areas. Eggs remain on the bottom until hatching
when the larvae move into the water column.
Herring larvae are light sensitive and therefore commonly migrate vertically depending
on the ambient light levels (Scott and Scott, 1988).
Atlantic herring are daytime visual feeders and use their long, well-developed gill rakers
to filter out plankton (Blaxter, 1966). Young herring feed primarily on phytoplankton
and then switch to zooplankton and ichthyoplankton as they grow. Copepods,
euphausiids, pteropods, mollusc larvae, fish eggs and larvae of sand lance, capelin and
herring are identified prey of adult herring. This species serves as an important prey
item for many fishes (e.g., skates, salmon, cod, hake), marine birds and marine
mammals.
4.8.8
Atlantic Cod
Atlantic cod inhabit cool-temperate to subarctic waters from inshore regions to the
edge of the Continental Shelf. Although adapted to bottom feeding, they may also
spend much time off bottom and be found from the surface to depths of greater than
400 m. (Scott and Scott, 1988). Numerous separate stocks of this species exist
throughout the Canadian Atlantic region, four of which occur in the study area.
As fry, cod feed on copepods, amphipods, barnacle larvae and other small crustaceans.
Juvenile and young adult cod continue to feed on crustaceans such as euphausiids,
mysids, shrimp, small lobsters and crabs. Once cod reach a length of approximately 50
cm, their diet switches almost entirely to fish. Depending on feeding locality and prey
availability, capelin, sand lance, redfish and herring can be very important food species.
Cod, being voracious eaters, may significantly influence the population sizes of these
species. Other fish species that are taken by Atlantic cod include alewives, Atlantic and
Arctic cod, cunner, flounders, haddock, hake, mackerel, shannies, snakeblenny,
sculpins and silversides (Scott and Scott, 1988).
Casas and Paz (1994) described the food and feeding of Flemish Cap cod during
summers between 1988 and 1993. Feeding intensity was high and the prey spectrum
was narrow in all years, with hyperiids and small redfish appearing to be the most
important prey.
Total reported commercial landings by all Canadian and Newfoundland fleets and gear
in the Newfoundland region (NAFO Divisions 2GHJ, 3KLMNO and 3Ps) increased
from less than 2 x 105 t in 1978 to approximately 3.5 x 105 t in 1988, paralleling the
introduction and increased exploitation by the Canadian offshore trawler fleet. After
1988, landings dropped sharply to less than 1 x 105 t in 1992 (Taggart et al., 1994).
Estimates of spawners in the Newfoundland region follow a temporal pattern similar to
that seen in the total landings. Between 1987 and 1993, population estimates of
spawners in 2J + 3KL have declined from greater than 3 x 108 to less than 1 x 108. This
pattern is also apparent in the 3NO and 3Ps estimates (Taggart et al., 1994).
Abundance distributions of adult cod in the study area, derived from annual research
surveys in the early 1980s, show frequent, widespread catches of age 5+ cod (Bishop
et al., 1993). During the late 1980s and early 1990s, high catches of age 5+ cod were
more common farther south and were closer to the offshore shelf break. By 1992, the
survey catch rates were severely reduced in the majority of sets throughout the region,
except for one large aggregation along the shelf break at the border between 3K and
3L and two smaller aggregations near the shelf break in 3Ps (Figure 4.8-8).
Anderson (1993), through investigations of the distributions of demersal juvenile cod
between 1981 and 1992, showed that age 1+ juveniles are concentrated primarily along
the coastal regions of northern Newfoundland and Labrador and farther offshore on the
Grand Banks. During the study period, juveniles of increasing age were found
progressively farther offshore on the shelf, a pattern similar to that seen for older age
groups during the 1980s.
The 2J + 3KL cod stock has displayed an apparent southerly shift in distribution since
1989 (deYoung and Rose, 1993; Rose et al., 1994). Reasons for this apparent shift
might include the following (NAFO, 1995):
·
·
·
·
Colder ocean conditions
Southerly shift in capelin distribution
Combination of fishing mortality and ocean climate factors
High fishing mortality in the northern areas (changing pattern not actually a
"shift")
As of 1995, the stock remains at a very low level, probably in the order of 1 percent of
that in the early 1980s. It consists of mainly young fish.
The 3M cod stock on the Flemish Cap is considered to be a discrete population.
Results of a bottom trawl survey in this area by the Spanish in July 1994 indicated
highest concentrations in the central to northwestern region of the Cap (Vazquez,
1995). Total biomass estimates from research vessel surveys have been low compared
to levels in the mid-1980s (except for 1989 when an increase in biomass was produced
by the relatively abundant 1985 and 1986 year classes).
The 3NO cod stock occupies the southern part of the Grand Banks. Cod are found
over the shallower parts in the summer, particularly in the Southeast Shoal area (3N)
and on the slopes of the Bank in winter as water temperatures drop. This stock was at
an all time low in 1994 and was represented mainly by 2 year classes, 1989 and 1990.
The 3Ps cod stock abundance and biomass decreased between 1989 and 1994.
Biomass and abundance from the 1995 survey were substantially higher than those of
recent years but this was a result of one large cod catch in a small part of the entire
survey area. Therefore, the 1995 estimates must be treated with caution (Canning &
Pitt, 1995).
Myers et al. (1993) conclude that cod spawning throughout Divisions 3KL lasts three
to four months; generally beginning and ending earlier in the north (January to June)
and later in the south (February to September). Spawning in the more southerly
Divisions 3NO and 3Ps peaks in April and May with no significant latitudinal trend in
the average spawning time. Historically, cod eggs and early- stage larvae in the
offshore have been concentrated on and along the shelf break of the Grand Banks,
particularly in the more northern regions (Taggart et al., 1994). Fitzpatrick and Miller
(1979) indicated that spawning was concentrated along the southern shelf break of the
Flemish Cap (3M), the southwest and SE shelf break of the Grand Banks (3NO), and
the shelf break of the St. Pierre Bank in Division 3Ps. More recent analysis (Hutchings
et al., 1993) of cod maturity data collected from 1946 to 1992 suggests that spawning
may be more prevalent in inshore regions, along western (landward) edges of offshore
banks, as well as the interior of the Grand Banks (Figure 4.8-9). Spawning on the shelf
in Division 3L was documented in 1991 and 1992 (Rose, 1993).
4.8.9
Greenland Halibut
Spawning of this species is thought to occur primarily in Davis Strait in winter and
early spring at depths of 650 to 1000 m. There is now some evidence that Greenland
halibut also spawn in the Flemish Cap region. Junquera and Zamarro (1994) report that
between May 1990 and December 1991, spawning in the Flemish Pass area (3LM)
peaked in the summer months with a secondary peak occurring in December.
Spawning activity was observed throughout the year but at much lower levels. All
observed spawning occurred at depths in the 800 to 1700 m range.
Soon after hatching, the larvae rise to about 30 m from the surface where they remain
until they are approximately 70 mm long. They then descend to greater depth as they
grow. They do not become as closely associated with bottom living as other flatfish
(Scott and Scott, 1988).
Greenland halibut are bathypelagic predators with a wide prey spectrum. Peak feeding
appears to occur in summer and fall when the major species eaten include capelin,
Atlantic cod, polar cod, roundnose grenadier, redfishes, sand lance, crustaceans
(especially Pandalus borealis) and cephalopods. Small amounts of benthic
invertebrates are also consumed (Scott and Scott, 1988).
No research survey covers the entire geographical range of the Greenland halibut
stock; therefore the abundance and biomass of the total stock remains underestimated
(NAFO, 1995).
Winter deepwater surveys of Divisions 3LMN in 1994 and 1995 resulted in extremely
variable biomass estimates. Despite the lack of data, it is believed the stock has declined
significantly in recent years (Bowering et al., 1994).
Canadian fall surveys from 1978 to 1992 had no large catches in Division 3L (Figure
4.8-10). Most catches in this division occurred on the ‘Nose of the Bank’ in an area
known as the Sackville Spur. The highest catches of Greenland halibut in 3L were
made during the earlier surveys when coverage was only to 366 m. Coverage in 1991
and 1992 was to over 700 m and catches were negligible (Bowering and Power, 1993).
4.8.10
Witch Flounder
Witch flounder spawn in 3L from March to July, with the highest intensity from March
to May. Spawning in 3Ps occurs at highest intensity between January and March.
During the winter and spring months, witch flounder can be found in spawning
concentrations along the continental slope of St. Pierre Bank. Spawning in 3NO occurs
principally in July and August. All spawning generally occurs along the continental
slopes and deepwater channels at depths exceeding 500 m where water temperatures
are likely to be most appropriate (Scott and Scott, 1988). This species is considered
non-migratory.
The principal diet of the witch flounder includes polychaetes, amphipods, small fish and
molluscs such as small bivalves and snails.
Gorchinsky et al. (1995) report that the estimated biomass of witch flounder in
Division 3L has been at a low level since the mid-1980s. Since then, estimates have
been within the 1000 to 2000 t range, very similar to the biomass estimates in Division
3N.
Trawlable biomass in Division 3N has been at very low levels throughout 1971 to
1993, usually at less than 1000 t. In 3O during the same period, biomass estimates have
shown considerable annual fluctuations (between 6000 and 12 000 t). The preliminary
estimate for 1993 was near the lowest ever observed, despite the fact that areal
coverage during the surveys was highest between 1991 and 1993 (Bowering et al.,
1993). Witch flounder are most concentrated on the southwest edge of the Grand
Banks in Division 3O.
Relatively complete surveys have been conducted in winter on St. Pierre Bank (3Ps)
since 1976. Since 1980, the biomass estimates have ranged between 2000 to 6000 t.
Survey data do not indicate any increases in recruitment in recent years (Fisheries and
Oceans Canada, 1995).
4.8.11
American Plaice
Using juvenile flatfish surveys carried out in the summer and fall between 1985 and
1989 on the Grand Banks, Divisions 3LNO, Walsh (1991) showed that the distribution
of juveniles and adults overlaps extensively. Walsh identified three oceanic nursery
areas on the Grand Banks:
·
·
·
The northern slope of the Banks (3L)
The southern end of the Banks (3NO)
Whale Deep area of Division 3O
Since then, survey coverage has been extended into deep water along the edge of the
Banks and has revealed new information with respect to nursery areas. In addition to
the areas identified from the 1985-1989 surveys, concentrations of juvenile American
plaice were found on the northeastern and southwestern slopes of the Grand Banks and
east of Whale Deep (Figure 4.8-11). These juveniles appeared to show fidelity to their
nursery areas (Walsh, 1994).
The discontinuity in the distributions of juvenile and adult American plaice may suggest
that for the northern Grand Banks and the ‘Tail of the Bank’, there are two distinct
stocks that recruit from separate nursery areas. More synchrony in year-class strength
was found between 3O and 3L but not 3N, which may indicate the effect of different
oceanographic regimes in these areas (Walsh, 1994). Spawning occurs in spring, a little
earlier on the Flemish Cap than on the Grand Banks. Females 40 to 70 cm in length
may produce 250 000 to 1.5 million eggs. The eggs float near the surface and usually
hatch within 11 to 14 days when water temperature is approximately 5°C (Scott and
Scott, 1988).
The most frequent prey of American plaice reported on the southern Grand Bank are
fish and benthic invertebrates. Zamarro (1992) found that the diet of 40 to 55 cm long
American plaice collected in this region throughout all seasons (1987-1989) consists
mainly of sand lance and brittlestars, and some capelin. Pitt (1973) reports that on the
Grand Banks, fish (capelin, sand lance and mailed sculpin) accounted for 85 percent of
the total weight of plaice stomach contents. Invertebrates accounted for the remainder.
Analysis of plaice stomachs collected in the summer of 1993 on the Flemish Cap
indicated benthic prey such as brittlestars, polychaetes, bivalve molluscs, and small
pelagic crustaceans such as hyperiids (Rodriguez-Marin et al., 1994). This species
appears to feed most intensely during late spring and summer, after which feeding
drops to almost nil in January. Zamarro (1992) concluded that the American plaice is a
species with a capacity to feed on a wide variety of prey and the flexibility to feed when
prey is more accessible.
Between 1989 and 1993, late summer and fall surveys for flatfish covered the Grand
Banks out to a maximum of 274 m depth. The surveys during this period represent the
most extensive overall coverage of the population on the Grand Banks (Figure 4.8-12).
The northern population (3L) of American plaice was concentrated in colder and
deeper waters than the southeastern (3N) and southwestern (3O) populations, which
were concentrated in shallower and slightly warmer waters (greater than 0°C) (Walsh,
1994).
In Division 3L American plaice were distributed across the Banks in a depth range of
62 to 250 m and a temperature range of -1.6 to 1.7°C, but the population was
concentrated in the north and northeast in a mean depth range of 115 to 135 m and a
mean temperature range of -1.1 to 0.6°C (Walsh, 1994). Although the estimated
abundance of American plaice was fairly stable between 1989 and 1993 (2013 x 10 6 to
2413 x 106), the estimated biomass in 1993 (160 000 t) was down from the 1989
estimated biomass of 254 000 t.
Surveys in Division 3L in 1985 indicated seasonal variation in the distribution of
American plaice (Morgan and Brodie, 1991). In spring, plaice were more abundant in
depths of less than 100 m than in other seasons, but during the winter, plaice were
under-represented in depths of less than 150 m.
In Division 3N, the population was distributed in a depth range of 42 to 223 m and a
temperature range of -1.6 to 7.5°C. The main concentrations were found on the _Tail
of the Bank_ in a mean depth range of 64 to 71 m and a mean temperature range of 0.1
to 1.7°C (Walsh, 1994). The estimated abundance from the 1993 survey (760 x 10 6)
was substantially lower than that for 1989 (1205 x 106) but estimated biomass was
higher in 1993 (119 000 t) than it was in 1989 (100 000 t).
In Division 3O, the population was distributed over the bank in a depth range of 63 to
218 m and a temperature range of -1.5 to 8.0°C. Plaice were concentrated in the Whale
Deep area, a deepwater basin on the western side, along the southwest slope near the
_Tail._ These concentrations were found in a mean depth and temperature range of 84
to 94 m and 0.6 to 1.3°C (Walsh, 1994). The estimated abundance from the 1993
survey (1113 x 106) was higher than that for 1989 (855 x 106). The estimated biomass
was lower in 1993 (124 000 t) than in 1989 (147 000 t).
Fall surveys conducted in 3LNO between 1990 to 1994 show a severe decline in
abundance and biomass of older (7+) American plaice. With respect to juvenile fish, the
1988 and 1989 year-classes show some promise but there have been no large yearclasses since. Variability in abundance and biomass of American plaice during the
period between 1989 and 1993 was higher in Division 3L than in Divisions 3N and 3O.
Although the stock in 3M appears to be stable at a low level, the abundance estimate is
only about 40 percent of that of 1988. According to EEC surveys, the estimated
biomass of 3M plaice has decreased from the 1988 level of 8500 t to 3600 t in 1992
(Godinho and de Cardenas, 1993). American plaice on the Flemish Cap between 1978
and 1985 were distributed mainly in the shallower central, southern and southwestern
areas (Bowering and Brodie, 1994).
According to research vessel survey information up to 1995, the American plaice stock
in Division 3Ps is at a very low level. The biomass index has declined to 10 percent of
its mid-1980s level.
4.8.12
Pollock
Pollock in waters of the south coast of Newfoundland are thought to be at the northern
limit of their Northwest Atlantic range. Cold waters throughout the region in recent
years have probably been restricted their distribution and behaviour (Fisheries and
Oceans Canada, 1995).
Research has shown that mature pollock occur along the slopes of St. Pierre Bank and
the southern Grand Banks (Fisheries and Oceans Canada, 1995). In summer months,
schools of young fish are occasionally found in harbours along Newfoundland's south
coast, but this species generally does not occur in Newfoundland waters in sufficient
numbers to support a commercial fishery. Research surveys have indicated a decline in
the 3Ps pollock since 1987 to an estimated level under 1000 t.
4.8.13
Haddock
There is speculation that cold waters throughout the area in recent years have probably
restricted haddock distribution and behaviour. Deep waters to the south and low
bottom temperatures to the north restrict young haddock development to the slopes of
St. Pierre Bank and the southern part of the Grand Banks. In some years, bank waters
remain on the bank, resulting in haddock larvae settling in suitable conditions,
However, in other years, the bank water is caught up in eddies of the Gulf Stream and
the pelagic larvae settle in waters too deep for survival. Temperatures on St. Pierre
Bank have also been below normal for a number of years (Fisheries and Oceans
Canada, 1995).
Haddock are primarily bottom feeders and their food varies with their size. Those
under 50 cm length prefer crustaceans such as amphipods, pandalid shrimp and hermit
crabs. Other prey include echinoderms, molluscs and annelid worms. The diets of
haddock greater than 50 cm include more small fish (approximately 30 percent). These
include sand lance, capelin, silver hake, herring and argentines. Herring and capelin
eggs are also eaten when available (Scott and Scott, 1988).
Research surveys in Divisions 3LNO have been conducted since the early 1970s, with
more extensive coverage in recent years. Abundance and biomass indices from the
spring surveys were low through to the early 1980s from which time they gradually
increased until 1988 (1984 estimates were the highest of the period between 1982 and
1988). The indices have been low since 1988. Spring surveys in Division 3L have never
found many haddock (Fisheries and Oceans Canada, 1995).
Surveys in 3Ps since 1972 have shown low abundance and biomass indices up to 1982
but both peaked in 1985. However, since 1985, both indices have declined to very low
levels (Fisheries and Oceans Canada, 1995).
Haddock in 3LNO and 3Ps show considerable variation in recruitment but the
mechanisms are poorly understood. There have been no signs of improved recruitment
in recent years, indicating poor prospects for stock improvement in the near future
(Fisheries and Oceans Canada, 1995).
4.8.14
Yellowtail Flounder
Yellowtail flounder commonly prefer sandy bottoms and feed upon surficial and
interstitial benthic macrofauna such as amphipods and polychaetes, but they also eat
smaller quantities of other crustaceans such as shrimp, cumaceans and isopods, as well
as occasional sand lance and capelin (Scott and Scott, 1988).
Spawning takes place on the Grand Banks from May to September, peaking in mid to
late June in areas adjacent to the Labrador Current in depths of less than 100 m and
bottom temperatures exceeding 2°C (Walsh, 1992). No documented spawning
migration or spawning concentrations have been reported for this sedentary species.
Yellowtail are serial-batch bottom spawners. Egg hatching times vary with temperature
(4 to 15 days). The pelagic larvae, which appear to have a short residence time in the
water layers, have been caught in Grand Banks surveys from June to September.
Juveniles (ages 1 to 4) concentrate on the Southeast Shoal and adjacent areas, which
are thought to be oceanic nursery sites for yellowtail flounder (Walsh, 1992).
Three series of Canadian research vessel surveys on the Grand Banks have been
examined to determine any changes in the distribution of yellowtail flounder during the
late 1980s and early 1990s (Brodie and Walsh, 1994). Abundance estimates declined
sharply in the mid to late 1980s from over 300 x 106 to under 150 x 106 in 1993. Plots
of spring survey data between 1978 and 1992 clearly show the contraction of a fairly
wide distribution over the southern and central Grand Banks to one concentrated
around the western side of the Southeast Shoal in Division 3N (Figure 4.8-13).
Yellowtail have virtually disappeared from Division 3L where they were once relatively
abundant. Data also indicate a southern shift in the northern limit of this species. In
1992 and 1993, the apparent northern limits were about 93 km to the south of the
1971-1991 mean value and almost 185 km south of the maximum in 1978. Morozova
(1993) concluded that temperature was not a factor contributing to the change in
distribution but that stock abundance was. Contraction of distribution may simply
reflect movement of parts of the population from marginal habitats to areas with more
suitable substrate and associated benthic food items.
Estimated biomass of yellowtail in 3LNO dropped substantially between 1984
(135 000 t) and 1993 (60 000 t). The most severe biomass declines have been seen in
Divisions 3L and 3N. There has been relative stability in 3O (Brodie et al., 1993).
4.8.15
Northern Shrimp
Northern shrimp at the Flemish Cap and _Nose of the Bank_ spawn in August and
females are thought to migrate to shallower areas to release the larvae (Nicolajsen,
1994). The circulation on the Cap is characterized by an anticyclonic gyre, which likely
contributes to shrimp larvae retention in the area.
Northern shrimp appear to be concentrated in the western, northern and northeastern
areas of the Flemish Cap (Parsons, 1994). The biomass of this species on the Cap has
declined continuously since 1992 (Sainza, 1994). The Canadian fishery in this region
only began in 1993 and it appears the high exploitation in that year had strong effects
on the population. Lower catch rates coupled with changes in fishing patterns were
evident in 1994 (Parsons and Veitch, 1994), resulting in a less than optimistic outlook
for the population in 1995.
High commercial catch rates and high estimated spawning biomass indicate shrimp
stocks off the east coast of Newfoundland within the 200-mile limit appear to remain
very healthy.
4.8.16
Other Notable Species
Short-Finned Squid
The short-finned squid (Illex illecebrosus) is a pelagic cephalopod with a lifespan of
only 1 to 1.5 years. Its inshore migration to and over the Continental Shelf appears to
be linked to food availability. Crustaceans are the dominant component in the diet of
smaller juvenile squid while fish (e.g., cod, capelin, herring, redfish and squid) are more
important to the larger adults. Squid predators include pilot whales, cod, haddock,
pollock, red hake and silver hake (Black et al., 1987).
Short-finned squid are believed to spawn only once before death, in the area of Blake
Plateau south of Cape Hatteras in late autumn and early winter. Egg masses, and
eventually larvae and juveniles, passively drift northward in the Gulf Stream, sometimes
reaching the Grand Banks by late spring or early summer (Black et al., 1987). By
summer, the juvenile squid start to move inshore into shallow waters off
Newfoundland. The inshore migration routes are commonly over the southwest slope
of the Grand Banks. The number of individuals and the timing of inshore migration is
most possibly a function of local water temperature and stock size (Mobil, 1985). By
November, the squid leave the inshore waters and move south to spawn.
Black et al. (1987) present squid distribution maps based on research surveys. Between
1978 and 1982, the highest concentrations of squid were found on the southwest slope
of the Grand Bank. In 1979, they were also numerous on the northeast slope and
central Grand Bank.
Generally, short-finned squid abundance off Newfoundland has remained low from
1983 to 1993 (Beck et al., 1994).
Atlantic Salmon
Sea movements of the anadromous Atlantic salmon (Salmo salar) are not well
understood although the main function of sea migration is known to be feeding. Small
Atlantic salmon eat mainly euphausiids, amphipods and decapods while larger salmon
feed on herring, alewives, smelt, capelin, small mackerel, sand lance and small cod.
While salmon are at sea their predators include seals, sharks, pollock, tuna and various
birds (e.g., gulls, cormorants, bald eagles, and ospreys) (Scott and Scott, 1988).
Salmon may move in three ways (Mobil, 1985):
1.
2.
3.
Migration to study-area rivers
Migration through coastal areas to rivers in other parts of eastern Canada
Feeding, overwintering and migration in offshore areas
Salmon migration in offshore areas is generally a clockwise coastal migration over the
northeast Newfoundland shelf and southern Grand Banks. Research suggests an
extensive spring migration in surface waters along the slope regions (approximately
180 m). Some scientists believe large numbers of salmon may overwinter in deep water
east of the Grand Banks (Mobil, 1985).
Thirty-three scheduled salmon rivers empty into the coastal waters of the study area.
Between 1986 and 1991, only four of them averaged total catches that exceeded 200
fish per year (Buchanan et al., 1994).
Atlantic Mackerel
Atlantic mackerel (Scomber scombrus) are pelagic inhabitants of temperate waters of
the open sea and are regarded as some of the most active and migratory fishes (Scott
and Scott, 1988).
This species feeds by both filter feeding and individual selection of organisms. In
Newfoundland waters, the mackerel’s most probable method of feeding involves
pursuit and capture. Prey of Atlantic mackerel include amphipods, euphausiids,
shrimps, crab larvae, small squid, fish eggs, and young fish such as capelin and herring.
Feeding is most intense during springtime. Predators of mackerel include Atlantic cod,
dogfish, bluefin tuna, swordfish, porpoises and seals (Scott and Scott, 1988).
Mackerel are present in Canadian coastal waters during the summer and fall. During
the winter they are usually found in moderately deep water along the Continental Shelf
south of Sable Island where water temperatures exceed 7°C. In spring, there is a
general inshore and northeast migration resulting, in some of the fish spawning in areas
of the Gulf of St. Lawrence. After spawning, some adult mackerel continue a
clockwise migration through the Strait of Belle Isle to waters off eastern
Newfoundland. There seems to also be a minor migration to south and eastern
Newfoundland waters in late spring rather than migration to the Gulf of St. Lawrence
(Mobil, 1985).
Grégoire (1993) reported commercial catches between 1983 to 1991 in NAFO
Divisions 3K, 3L, and 3Ps, mostly in inshore areas. Scott and Scott (1988) reported
mackerel distribution extending to the eastern slope of the Grand Banks and as far
south as the Southeast Shoal region.
Lumpfish
Lumpfish are primarily bottom dwelling but have been reported to be semipelagic
during early life. Off Newfoundland, adult fish have been caught by commercial
trawlers in winter in depths of 180 to 330 m. Spawning takes place during the spring
and early summer in Newfoundland waters. Preferred spawning sites are shallow rocky
shore areas with abundant seaweed growth. The eggs remain attached to the substrate
until they hatch in late summer. The adults return to deeper water in late summer to
early fall. Young lumpfish remain in the upper 1 m of the water column for the first
year of life and then migrate to the bottom (Scott and Scott, 1988).
Lumpfish diet consists of a variety of invertebrates (euphausiids, pelagic amphipods,
copepods, combjellies) as well as small fishes such as herring and sand lance. Feeding
intensity of adult lumpfish is highest during the winter (Scott and Scott, 1988).
There is little knowledge about lumpfish stock. Survey biomass estimates have been
made for Division 3L between 1981 and 1994 and Division 3Ps between 1981 and
1995 (Fisheries and Oceans Canada, 1995). Fall survey estimates for 3L have generally
been less than 2000 t. In 3Ps, surveys conducted between January and June showed an
order of magnitude decline in biomass estimate from 1985 to 1995. The proportion of
female fish in the survey catches also declined steadily from the mid-1980s to 1995.
Between 1984 and 1987, landings of lumpfish in Divisions 3KLP increased from 500
to 3000 t. Landings averaged 2000 t until 1993. The fishery was predominantly in
Division 3K in the late 1980s (Fisheries and Oceans Canada, 1995).
Sand Lance
Sand lance are small, semipelagic fishes of the genus Ammodytes. Two species have
been reported in the northwest Atlantic, A. americanus and A. dubius, the latter being
more common the outer Grand Banks. Certain fish species, including Atlantic cod,
American plaice and thorny skate, depend on sand lance during certain times of the
year as an important food resource. The sand lance therefore plays an important role in
linking planktonic production to some fish in higher trophic levels. Despite its
important ecological role, its behaviour, distribution and feeding habits on the Grand
Banks remain poorly understood (Gomes, 1993).
Sand lance have been reported in close association with sandy bottom areas. They are
most abundant on the eastern Grand Banks at depths shallower than 100 m in
temperatures ranging from -1.0 to 2.0°C (Winters, 1983). They appear to be important
in the food chain of the southern part of the Banks (3N), where they made up the bulk
of American plaice diet; to the east of the Virgin Rocks, where they are prey for cod;
and on the _Nose of the Bank,_ where once again they constitute a substantial part of
cod diet.
Sand lance on the Grand Banks are thought to eat copepods, Calanus finmarchicus,
and euphausiids.
Bluefin Tuna
Bluefin tuna may be present in Canadian waters from early summer to early fall,
feeding at depths of 25 to 180 m. During this time, they are eating primarily pelagic
species such as herring, capelin, mackerel and squid. Other prey include saury,
lanternfishes and hake (Scott and Scott, 1988). Because of their size, bluefin tuna
predators are few, but include certain whales, sharks and man.
Wolffish
The wolffish (predominantly Atlantic wolffish) is commonly found in deeper water
along slope areas. In the Newfoundland region, it tends to occur over hard clay bottom
in a depth range of 100 to 350 m. Keats et al. (1985) reported an inshore movement of
Atlantic wolffish during the spring, presumably in preparation for August spawning,
which generally occurs at depths of 5 to 15 m. Hatching occurs in the fall and the
larvae remain on or near the bottom close to the hatching area. Larvae seldom swim to
the surface waters.
This wolffish feeds primarily on a variety of bottom invertebrates, including
echinoderms, molluscs and crustaceans. Redfish has been a prey item in certain areas.
Feeding activity is reduced at spawning time and remains at a low level until hatching.
Juvenile wolffish have been found in cod stomachs (Scott and Scott, 1988).
Roundnose Grenadier
The roundnose grenadier generally inhabits the deep waters of the North Atlantic
Continental Slopes and Shelf. In the northwest Atlantic, it is commonly found in 400 to
1000 m of water. It is thought that this species spawns near Iceland and the eggs and
larvae are carried to the Grand Banks by water currents (Scott and Scott, 1988).
The roundnose grenadier undertakes diurnal vertical feeding migrations, as is evidenced
by the pelagic food organisms found in their stomachs. Prey of this species varies
widely. On the northeastern slope of the Grand Banks, myctophids (lanternfish) are the
main component of the diet while in other areas, amphipods and mysids are the primary
prey. Feeding is seasonal and the peak intensity occurs in fall and winter. Roundnose
grenadier are prey to Greenland halibut and redfish (Scott and Scott, 1988).
Roughhead Grenadier
The roughhead grenadier is an important bycatch in the Spanish Greenland halibut
fishery on the Flemish Cap (Casas, 1994). The greatest catches taken during research
surveys in the eastern Grand Banks were in waters at 2.0 to 3.5°C at depths of 180 to
500 m. Spawning of the eastern Grand Bank population is thought to occur on the
southern and southeastern slopes of the Banks (Scott and Scott, 1988).
Roughhead grenadier eat a variety of benthic invertebrates including bivalve molluscs,
shrimp and starfishes. Longline catches on the Grand Banks showed that larger
grenadier prefer bivalves, shrimp and fishes while smaller ones eat mainly bivalves,
starfish, shrimp and polychaetes. This species is no doubt prey for larger fish inhabiting
the same areas. Grenadier have been found in Atlantic cod taken from the Grand Banks
(Scott and Scott, 1988).
4.9
Marine-related birds and mammals are important predators of zooplankton, benthos
and fish. Major feeding relationships are shown in Table 4.1-2. Birds and mammals, in
turn, serve as food for other species and recycle nutrients into the upper water column
through excretion.
Over 60 species of birds have been recorded in the study area (Table 4.9-1) and
millions of individual birds use the area annually. Of the 60 species, approximately 18
are pelagic, 9 of which nest in the study area. A wide variety of waterbirds use the
coastal and shore zones as well, including gulls, terns, cormorants, waterfowl and
shorebirds.
4.9.1
Database
In the ten-year period since the publication of the Hibernia EIS, the results of some
additional pertinent studies have become available. These include updates on the size
and species composition of seabird nesting colonies in southeastern Newfoundland,
additional data on coastal and offshore distribution, and several investigations into the
response of seabird populations to the significant changes that have occurred in fish
stocks and other prey species. The specific sources are described in the following
sections.
Other recent studies on seabirds of the area cover chronic low-level oil pollution and its
effects on seabirds, particularly in Placentia Bay (Chardine and Pelly, 1994); and the
energetics of seabirds and their role in the marine ecosystems of eastern Canada
(Diamond et al., 1993).
4.9.2
Breeding Biology and Nesting Populations
Most seabirds nesting in eastern Canada have low fecundity, deferred maturity, and
high survival rates. Many species lay only one egg per year and do not begin to breed
until several years old. They are long-lived, however, and continue to nest each year for
many years. Data on various aspects of the reproductive biology of the species nesting
in the study area are presented in Tables 4.9-2 and 4.9-3.
Since the publication of the Hibernia EIS, Cairns et al. (1989) summarized the available
census data for seabird colonies around Newfoundland. Census data for the study area,
and for major colonies in or near the study area, are presented in Table 4.9-4. The
major seabird colonies are mapped in Figure 4.9-1. Over ten million seabirds nest in or
near the study area, along the southeast coast of Newfoundland.
Table 4.9-1
Common Name
Scientific Name
Distribution in Study Area
Red-throated loon
Common loon
Pied-billed grebe
Red-necked grebe
Northern fulmar 1
Cory's shearwater
Greater shearwater
Sooty shearwater
Manx shearwater 1
Little shearwater
Wilson's storm-petrel
Leach's storm-petrel 1
Northern gannet 1
Great cormorant
Double-crested cormorant 1
Canada goose
American black duck
Ring-necked duck
Greater scaup
Common eider
King eider
Harlequin duck
Oldsquaw
Black scoter
Surf scoter
White-winged scoter
Common goldeneye
Bufflehead
Common merganser
Red-breasted merganser
Gavia stellata
Gavia immer
Podilymbus podiceps
Podiceps grisegena
Fulmarus glacialis
Colonectris diomedea
Puffinus gravis
Puffinus griseus
Puffinus puffinus
Puffinus assimilis
Oceanites oceanicus
Oceanodroma leucorhoa
Sula bassanus
Phalacrocorax carbo
Phalacrocorax auritus
Branta canadensis
Anas rubripes
Aythya collaris
Aythya marila
Somateria mollissima
Somateria spectabilis
Histrionicus histrionicus
Clangula hyemalis
Melanitta nigra
Melanitta perspicillata
Melanitta fusca
Bucephala clangula
Bucephala albeola
Mergus merganser
Mergus serrator
coastal
coastal
coastal
coastal
offshore, coastal
offshore
offshore, nearshore
offshore, nearshore
offshore, nearshore
offshore
offshore
offshore
offshore, coastal
coastal
coastal
coastal
coastal
coastal
coastal
coastal
coastal
coastal
coastal
coastal
coastal
coastal
coastal
coastal
coastal
coastal
Black-bellied plover
Semipalmated plover
Greater yellowlegs
Spotted sandpiper 1
Semipalmated sandpiper
White-rumped sandpiper
Purple sandpiper
Red-necked phalarope
Red phalarope
Pomarine jaeger
Parasitic jaeger
Long-tailed jaeger
Great skua
Common black-headed gull
Ring-billed gull
Herring gull 1
Iceland gull
Lesser black-backed gull
Glaucous gull
Great black-backed gull 1
Black-legged kittiwake 1
Pluvialis squatarola
Charadrius semipalmatus
Tringa melanoleuca
Actitis macularia
Calidris pusilla
Calidris fuscicollis
Calidris maritima
Phalaropus lobatus
Phalaropus fulicaria
Stercorarius pomarinus
Stercorarius parasiticus
Stercorarius longicaudus
Catharacta skua
Larus ridibundus
Larus delawarensis
Larus argentatus
Larus glaucoides
Larus fuscus
Larus hyperboreus
Larus marinus
Rissa tridactyla
littoral
littoral
littoral
littoral
littoral
littoral
littoral
offshore
offshore
offshore
offshore
offshore
offshore
coastal
coastal
coastal, offshore
coastal, offshore
coastal, offshore
coastal, offshore
coastal, offshore
coastal, offshore
Table 4.9-1
Common Name
Sabine's gull
Ivory gull
Common tern 1
Arctic tern 1
Dovekie
Common murre 1
Thick-billed murre 1
Razorbill 1
Black guillemot 1
Atlantic puffin 1
Scientific Name
Xema sabini
Pagophila eburnea
Sterna hirundo
Sterna paradisaea
Alle alle
Uria aalge
Uria lomvia
Alca torda
Cepphus grylle
Fratercula arctica
Source: Mobil (1985).
1
Indicates species that nest along coast in study area.
Distribution in Study Area
offshore
offshore
coastal, offshore
coastal, offshore
offshore, coastal
coastal, offshore
coastal, offshore
coastal, offshore
coastal
coastal, offshore
Table 4.9-2
Reproduction Parameters of Seabirds Nesting in the Study Area
Mean Adult
Survival Rate
Species
Age of First
Breeding
(years)
Clutch
Size
Breeding
Success1
Sources
Northern fulmar
0.97
6-12
1
0.55
Dunnet et al. (1963); Dunnet and
Ollason (1978)
Leach's storm-petrel
>0.70
3-5
1
0.79-0.94
Huntington (1963); Wilbur
(1969); Morse and Buchheister
(1977)
Manx shearwater
0.90
5-6
1
0.69
Perrins et al. (1973)
Northern gannet
0.95
4-7
1
0.81
Nelson (1966); Montevecchi and
Porter (1980)
Herring gull
0.80-0.85
3-7
2-3
1.03-1.58
Haycock and Threlfall (1975);
Kadlec (1976); Pierotti (1982)
Great black-backed gull
-
4-5
3
0.50-2.11
Butler and Trivelpiece (1981)
Black-legged kittiwake
0.81-0.86
3-7
2
0.54-0.58
Maunder and Threlfall (1972);
Wooler and Coulson (1977)
Common and arctic terns
0.86
2-4
1-3
0.59-0.77
Cullen (1956); Kirkham (1984)
Common murre
0.92
4-5
1
0.72
Birkhead and Hudson (1977)
Thick-billed murre
0.91
3-5
1
0.68
0.76
Birkhead and Hudson (1977);
Gaston and Nettleship (1981)
Razorbill
0.89-0.92
4-6
1
0.55-0.71
Bedard (1969); Lloyd and
Perrins (1977); Hudson (1982)
Black guillemot
0.77-0.89
2
1-2
0.12-0.78
Asbirk (1979); Cairns (1981)
Atlantic puffin
0.95
4-6
1
0.60-0.66
Ashcroft (1979); Harris (1983)
Notes: 1 Numbers of chicks fledged per breeding pair of adults.
Table 4.9-3
Summary of Seabird Nesting, Hatching and Fledging in the Study Area
Species
Egg Laying
Incubation
Northern
fulmar
2nd half May(1)
47-51 days(2)
observed
July 10(1)
47-51 days(2)
late Aug-early
Sept(2)
Canadian breeding
population is 360
000 pairs (3); Nfld.
colony may represent
new colonization (2).
Manx
shearwater
-
-
-
-
-
Information on
breeding activity in
coastal Nfld. is
lacking. One colony
has been identified
on Middle Lawn
Island(4).
Leach's
storm-petrel
mid May to mid
August (5,6,7) peak:
first half of June
41-42
days (5,6,7)
peak: last half
of July(5,6,7)
63-70
until mid Nov.
peak: late Sept.
Baccalieu colony is
probably largest in
the world. (8,9)
Northern
gannet
mid to late
May(10,11)
42 days (10,11)
late June to
early July
91 days(10,11)
late Sept. to
early Oct.(9,10)
Nfld. breeding
population represents
17% of the eastern
Canadian population.
Nfld.'s population is
stable and
increasing(12)
Herring gulls;
Great blackbacked gulls
mid to late
May(13,14,15)
26-29 days
mid-late June
45 days(13)
50-55 days (13,15)
late July - early
August
Nest singly or in
colonies at many
locations along Nfld.
East Coast (16). Study
area breeding
population is only a
small proportion of
total Canadian (3).
Black- legged
kittiwake
late May-early
June(18)
27 days(18)
late June(18)
42 days(18)
early Aug.(18)
Three major colonies
along Avalon
Peninsula (17). Nfld.
group represents
approx. 33% total
Canadian breeding
population.
Common
terns;
Arctic terns
first half June(19,20)
22 days (19,20)
mid July
21-26 days(19,20)
late July-early
Aug.(19,20)
Occur singly or in
small colonies along
the Avalon
Peninsula (17)
Common
murres
mid May(21,22)
32 days(21,22)
23 days(21,22)
mid-late July(20)
Breeding population
in study areas
represents 17% total
Canadian breeding
population (3).
Hatching
(13,14,15)
Nesting
Fledging
Comments
Table 4.9-3
Summary of Seabird Nesting, Hatching and Fledging in the Study Area
Species
Egg Laying
Incubation
Hatching
Thickbilled
murres
early June(21,22)
Razorbill
early June
34-39 days
early-mid July
Atlantic
puffins
mid-late May(24)
42 days(24)
Black
guillemots
mid May - early
June(24)
28-33
days(24)
Nesting
Fledging
Comments
late July-early
August(20)
Nesting population
in study area
represents <1% of
Canadian breeding
population (23)
24 days
late July - early
August
Nesting population
in study area
represents 3% of
the North American
population (3).
Information
extrapolated from
data for
Labrador (22).
early July(24)
40-45 days(24)
mid to late
August(24)
Most abundant
alcids in study
area(3). Includes
approx. 72% of the
N. American
population (3).
mid June - mid
July(24)
34-39 days(24)
early - late
August(24)
No estimate of the
number of breeding
birds in the study
area but considered
to be low (3,26).
(1)
(10)
(19)
(2)
(11)
(20)
Montevecchi et al. (1978)
Cramp and Simmons (1977)
(3)
Nettleship (1980)
(4)
Lien and Grimmer (1978)
(5)
Grimmer (1980)
(6)
Huntingdon (1963)
(7)
Wilbur (1969)
(8)
Maccarone and Montevecchi (1981)
(9)
Pitocchelli et al. (1981)
Kirkham (1980)
Montevecchi and Porter (1980)
(12)
Montevecchi (pers. comm.)
(13)
Haycock and Threlfall (1975)
(14)
Pierotti (1982)
(15)
Butler and Trivelpiece (1981)
(16)
Erwin (1971)
(17)
Brown et al. (1975)
(18)
Maunder and Threlfall (1972)
Hawksley (1950)
Kirkham (1984)
(21)
Tuck (1961)
(22)
Birkhead and Nettleship (1982)
(23)
Gaston (1980)
(24)
Cairns (1981)
(25)
Renaud and Bradsteet (1980).
(26)
Nettleship (1972)
149
Total # sites
Total # nesting pairs
916 682
92 775
87 544
59 705 +
30 175 +
5 485
1 839
1 735 +
1 600
592
467 +
100
40
20
17
2 812 +
No.
Nesting
Pairs
>1 001 684
17
246
600
330
20 +
?
780 020
92 600
77 487
43 369
6 995
WBI
Source: Cairns et al. (1989).
Notes:
1. Major colony names are:
WBI = Witless Bay Islands BI = Baccalieu Island
CSM = Cape St.Mary's
GREEN = Green Island
IRON = Iron Island
GC = St. Pierre Grand Columbier
MLI = Middle Lawn Island CORBIN = Corbin Island
2. Symbols are:
x = present but number nesting unknown
8
6
7
25
77
1
6
51
2
7
22
1
3
2
1
51
No.
Nesting
Sites
Nesting Population
Leach's storm-petrel
Atlantic puffin
Common murre
Herring gull
Northern gannet
Ring-billed gull
Thick-billed murre
Razorbill
Black guillemot
Manx shearwater
Double-crested cormorant
Great cormorant
Northern Fulmar
Common and Arctic tern
Species
Study Area
>26 585
x
1 000
100
10 000
10 000
x
5 485
CSM
>105 075
x
x
>10 650
25
50
5 000
100 000
CORBIN
50
600
10 000
IRON
In the Study Area
26 447
8
100
6
20
26 313
MLI
Major Colonies
Estimates of the Numbers of Nesting Seabirds Within the Study Area
and at Major Colonies in or Near the Study Area
Table 4.9-4
>3 384 033
x
181
100
100
3 336 000
30 000
4 000
12 975
x
677
BI
72 001
?
1
72 000
GREEN
Near the Study Area
100 718
?
5
200
113
100 000
400
GC
? = possibly nesting
4-93
4.9.3
Foods and Feeding Habits
Fish, crustaceans, and cephalopods are the major categories of prey eaten by seabirds
in the study area. In particular, capelin, copepods, amphipods, and short-finned squid
are eaten by many species. Offal from fishing vessels is used as a food source by several
species as well. Prey are obtained by a variety of feeding methods. Different species
specialize in foraging at the surface, at shallow depths, and by diving deep underwater.
Food and feeding habits are summarized in Table 4.9-5.
The dramatic changes that have occurred in the fish stocks of the Grand Banks
undoubtedly have had significant consequences on the numbers, distribution, breeding
success and feeding habits of seabirds in the area. A number of recent studies have
investigated this. Nettleship (1991) found that the productivity of Atlantic puffins was
lower when capelin were scarce and the puffins switched to other prey. Montevecchi et
al. (1987) found a significant association between failures of the human and avian
fisheries for squid and mackerel.
4.9.4
The basic distributional data presented in the Hibernia EIS (and summarized in Table
4.9-6) remain true, although seasonal and annual variations are poorly known. There
are also few data regarding the effects of the fisheries collapse on the distribution of
birds in the study area. Additional data on the offshore distribution of seabirds are
available in Brown (1986).
4.9.5
Important Species and Areas
The southeastern coast of Newfoundland and the Grand Banks are very important
areas for many species of marine-related birds. There are several million nesting birds,
and millions more annual visitors from areas as disparate as the Canadian and European
arctics, and the south Atlantic Ocean. Following is a list of some of the significant
features of this area, summarized principally from Lock et al. (1994):
·
The northern gannet nests at only six sites in North America; two of those sites
are in or near the study area.
·
Almost 3.5 million pairs of Leach's storm-petrels nest on Baccalieu Island, near
the study area. This is the majority of the entire Atlantic Ocean population of
this species.
·
Some of the largest seabird nesting colonies in eastern North America south of
Hudson
Strait
are
located
on
the
Avalon
Peninsula.
Table 4.9-5
Feeding Behaviour and Foods of Marine Birds in the Hibernia Study Area
Species
(Species-group)
Feeding Behaviour
Food Taken
Source
Seabirds
Northern fulmar
Greater shearwater
Sooty shearwater
Storm-petrels
Northern gannet
Phalaropes
Jaegers and skuas
Herring gull
Iceland gull
Glaucous gull
Terns
Surface feeding
Pursuit plunging
Pursuit plunging
Surface feeding
Deep plunging
Surface feeding
Kleptoparasitism
Surface feeding
Surface feeding
Surface feeding
Surface feeding
Surface feeding
Surface and pursuit
plunging
Fish, cephalopods, crustaceans, offal
Capelin, squid, crustaceans, offal
Capelin, squid, crustaceans, offal
Myctophid fish, amphipods
Mackerel, capelin, squid
Copepods
Fish
Fish, crustaceans, cephalopods, offal
Fish, crustaceans
Brown (1970)
Brown et al. (1981)
Brown et al. (1981)
Linton (1978)
Kirkham (1980)
Brown (1980)
Hoffman et al. (1981)
Threlfall (1968)
Threlfall (1968)
Threlfall (1968)
Braune and Gaskin (1982)
Dovekie
Common murre
Thick-billed murre
Black guillemot
Razorbill
Atlantic puffin
Pursuit diving
Pursuit diving
Pursuit diving
Pursuit diving
Pursuit diving
Pursuit diving
Amphipods, copepods
Fish, invertebrates
Fish, invertebrates
Fish, invertebrates
Fish, invertebrates
Fish, invertebrates
Bradstreet (1982)
Bradstreet (1983)
Tuck (1961)
Cairns (1981)
Bradstreet (1983)
Bradstreet (1983)
Waterfowl (eiders)
Bottom feeding
Molluscs, crustaceans
Cantin et al. (1974)
Loons
Surface diving
Fish, molluscs, crustaceans
Cormorants
Surface diving
Fish
Palmer (1962)
Shorebirds
Intertidal probing
Invertebrates
Palmer (1967)
Alcids
Table 4.9-6
Summary of Bird Distributions in the Study Area
Area
Subarea
Birds Commonly Observed
Flemish Cap
Northern fulmar, shearwaters, black-legged kittiwake, storm-petrels, and
dovekie
Coastal waters of
Newfoundland
Summer: Large numbers of northern gannet, herring gull, black-legged
kittiwake, common murre, and Atlantic puffin. Small numbers of
northern fulmar, great black-backed gull, terns, thick-billed murre,
razorbill, and black guillemot. Large numbers of Leach's storm-petrels
are present but rarely observed.
Winter: Large numbers of ducks (primarily common eiders), shorebirds,
gulls, murres and dovekie
Grand Banks
Southeast Shoal
Summer: Northern fulmar, greater shearwater, sooty shearwater, storm
petrels, jaegers and skuas
Winter: Northern fulmar and black-legged kittiwake
"Tail of the
Bank"
Spring and Summer: Northern fulmar and shearwaters common; stormpetrels, jaegers, black-legged kittiwake and murres also present
Winter: Large numbers of black-legged kittiwake, murres and dovekie
Shelf Edge
Spring and Summer: Northern fulmar, shearwaters, storm-petrels,
jaegers and black-legged kittiwake common; phalaropes also present
Winter: Large numbers of northern fulmar, black-legged kittiwake,
glaucous gull, Iceland gull, skuas and dovekie
·
Almost four million thick-billed murres winter on the Grand Banks
over
half of the 5 to 6 million that breed in western Greenland and the eastern
Canadian arctic.
·
Most of the world population of greater shearwaters, estimated at 5 million
birds, spends the summer on the Grand Banks, wintering from their nesting
grounds in the south Atlantic Ocean.
·
The Grand Banks are the chief wintering area for the approximately 14 million
dovekies that nest along northwest Greenland.
Aside from the overall importance of the Grand Banks to seabird populations, certain
key sites are of particular note. These are the large seabird colonies at Baccalieu Island
to the north of the study area and, within the study area, the Witless Bay Islands and
Cape St. Mary's (see Table 4.9-4 and Figure 4.9-1).
Several endangered or threatened bird species occur in the inshore area. The most
important of these are the harlequin duck, a small coastal species, and the piping
plover, which nests locally on Miquelon and at Big Barasway on the south coast of
Newfoundland. These species are listed by the Committee on the Status of Endangered
Wildlife in Canada as endangered. Manx shearwaters and common black-headed gulls
have small nesting populations in southern and eastern Newfoundland but are primarily
European species.
4.10
Marine Mammals
The 18 species of marine mammals listed in the Hibernia EIS still make up the marine
mammal community in the study area. The Hibernia EIS list, with updated species
names, is reproduced here as Table 4.10-1. A few additional species may occur, but
because of their rarity are not considered important components of the ecosystem. The
18 species include baleen whales, toothed whales, and seals. Most marine mammals
that occur in the waters of the Grand Banks and the southeast coast of Newfoundland
are transients, occurring typically in spring and summer. Nevertheless, despite only
seasonal occurrence, the study area is an important feeding area for these species.
4.10.1
Database
The 1980 to 1981 marine mammal surveys conducted for the Hibernia EIS (Parsons
and Brownlie, 1981) resulted in what is still the single most comprehensive data set on
the occurrence of marine mammals in the study area. Some additional studies have
been published since the Hibernia EIS, but these have focussed on particular locations
within the study area or elsewhere around the northwest Atlantic rather than on the
study area as a whole. These new studies provide additional data on distribution,
numbers and feeding, and are discussed in the following subsections.
4.10.2
Populations and Stocks
Reliable population estimates for most of the marine mammals in the study area are not
available. The summary table from the Hibernia EIS, reproduced here, with a few
additional sources, as Table 4.10-2, is still the best source of information. Some
additional information is available on the local numbers and relative abundance of
several species.
Whitehead and Glass (1985) estimated that 900 humpback whales used the Southeast
Shoal of the Grand Bank in June and July of 1982 and 1983. This was estimated to be
about 15 to 30 percent of the northwest Atlantic population.
Piatt et al. (1989), concluded that about 50 to 100 different humpbacks passed through
the Witless Bay area during their northward feeding migration each year of their study
(May to August, 1982 to 1985). Minke and fin whales also occurred in Witless Bay, in
the ratio of 10 humpback: 1 fin: 3.5 minke.
Table 4.10-1
Marine Mammals Observed in the Study Area (Updated from Mobil 1985)
Species
Status in Study Area
Baleen Whales
Minke whale (Balaenoptera acutorostrata)
Fin whale (B. physalus)
Blue whale (B. musculus)
Sei whale (B. borealis)
Humpback whale (Megaptera novaeangliae)
Right whale (Eubalaena glacialis)
transient and summer resident
late winter, spring and summer visitor
late summer visitor
unknown
Toothed Whales
Sperm whale (Physeter macrocephalus)
Atlantic pilot whale (Globicephala melaena)
Killer whale (Orcinus orca)
Northern bottlenose whale (Hyperoodon ampullatus)
Harbour porpoise (Phocoena phocoena)
Atlantic white-sided dolphin (Lagenorhynchus acutus)
White-beaked dolphin (L. albirostris)
Common dolphin (Delphinus delphis)
permanent resident
summer resident
summer resident
summer resident
Seals
Grey seal (Halichoerus grypus)
Harbour seal (Phoca vitulina)
Harp seal (Phoca groenlandica)
Hooded seal (Cystophora cristata)
summer resident
permanent resident
rare visitor
rare visitor
Sources:
Sergeant (1966); Leatherwood et al. (1976); Mansfield (1967); Mansfield and Beck (1977);
Boulva and McLaren (1979).
Mobil (1985).
Table 4.10-2
Population Estimates of Marine Mammals
in the Terra Nova Study Area
Population Occurring in the Study Area
NW Atlantic Pop.
Size
Species
Estimated
Number
Stock
Sources
Baleen Whales
Minke whale
?
Cdn. east coast
?
Fin whale
Blue whale
8000-13 000
low hundreds
Nfld. - N.S.
?
6250 - 11600
?
Sergeant (1977)
Mitchell (1974)
(1) Labrador Sea
965
Sei whale
2078
Mitchell &
Chapman (1977)
(2) Nova Scotia
870
Mitchell &
Chapman (1977)
Humpback whale
Right whale
2300-4100
?
Nfld.-Labrador
?
1700 - 3200
?
Whitehead (1982)
Toothed Whales
Sperm whale
Atlantic pilot whale
22 000?
?
?
?
?
abundant
Mitchell (1973a)
Mercer (1975)
Killer whale
Northern bottlenose whale
?
?
?
?
Mitchell (1974)
Harbour porpoise
Atlantic white-sided dolphin
> 4000
?
Gaskin (1977)
?
?
?
White-beaked dolphin
?
?
?
Common dolphin
?
?
?
Seals
Grey seal
30 000
?
Bonner (1981)
Harbour seal
40 000 - 100 000
930
Boulva and
McLaren (1979);
Bigg (1981)
Harp seal
1.7 - 4.3 million
Roff and Bowen
(1983); Stenson
(1993)
Hooded seal
400 000 - 450 000
Stenson (1993)
Source: Mobil (1985) with updates
In general, it seems likely that populations of the large baleen whales, especially
humpbacks, have increased since the end of commercial whaling in the northwest
Atlantic over 20 years ago. Humpback whales are certainly the most common large
whale in the waters around Newfoundland during the summer (Lynch and Whitehead,
1984). Data collected by Lynch and Whitehead (1984) and Whitehead and Carscadden
(1985), however, suggest that numbers of fin whales in the area may be declining.
Minke whale populations appear to be stable in Newfoundland (Whitehead and
Carscadden, 1985).
The population of harp seals in the northwest Atlantic has increased since the late
1970s coincident with the large reduction in the commercial harvest of this species
(Roff and Bowen, 1986; Stenson, 1993). Pup production is estimated to be increasing
as well (Stenson et al., 1995). Similarly, the population and pup production of hooded
seals may be increasing (Stenson et al., 1994). It is not known whether the growing
populations of these two seals have expanded their ranges south into the study area to
any ecologically meaningful extent. Historically, harp and hooded seals have been
uncommon to rare winter and spring visitors to the study area; they have occurred
primarily north of the Grand Banks. They are species of concern presently, however,
because of questions of the role of seals in the decline of fish stocks in Newfoundland
waters. There are numerous anecdotal accounts of harp seals becoming more
numerous in Newfoundland waters, and fishers commonly believe that seals have
contributed to declines in cod populations.
4.10.3
Food and Feeding Habits
Fish provide food for baleen whales (small fish), toothed whales (larger fish), and seals.
Baleen whales also consume vast quantities of zooplankton, while toothed whales feed
also on squid. Seals and other whales are included in the diet of killer whales as well.
Diet data are summarized for each species in Table 4.10-3, reproduced from the
Hibernia EIS.
Data available since 1985 have not shown large-scale shifts in the diets of the marine
mammals in the study area. Recent studies have, in general, confirmed the earlier
findings and provided more specific information and indications of variability. Capelin
remain the key prey for humpback, fin and minke whales in the study area, and shortfinned squid are the primary prey of Atlantic pilot whales. The large-scale incursion of
humpback whales inshore along the northeast coast of Newfoundland in the summers
from 1977 to 1980 has not occurred on the same scale since. Whitehead and
Carscadden (1985) suggested that the large-scale inshore incursion was related to the
low abundance of immature capelin offshore in those years.
Table 4.10-3
Food of Marine Mammals Occurring in the Study Area
Species
Foods Taken
Source
Baleen Whales
Minke whale
Fin whale
Blue whale
Sei whale
Humpback whale
Fish (mainly capelin), squid, euphausiids
Fish (capelin, herring), euphausiids
Euphausiids
Copepods, euphausiids, some fish
Capelin, euphausiids
Sergeant (1963)
Sergeant (1977)
Gaskin (1982)
Gaskin (1982)
Mitchell (1973b), Gaskin (1982)
Squid, fish
Primarily short-finned squid, also cod
Fish, squid, seals, dolphins, other whales
Primarily squid, also fish
Schooling fish, (capelin, cod, herring, mackerel)
Short-finned squid, herring, small pelagic fish
Fish (cod, capelin, herring), squid
Squid, fish
Sergeant (1966), Roe (1969)
Sergeant (1962), Mercer (1975)
Gaskin (1982), Leatherwood et al. (1976)
Mitchell (1975b)
Smith and Gaskin (1974)
Sergeant et al. (1980)
Leatherwood et al. (1976), Gaskin (1982)
Leatherwood et al. (1976)
Fish (primarily herring, cod) squid, shrimp
Fish (primarily herring, flounder), squid, shrimp
Fish, squid, shrimp, molluscs
Fish, crustaceans
Mansfield and Beck (1977)
Boulva and McLaren (1979)
Reeves and Ling (1981)
Foy et al. (1981), Ronald and Healey (1981)
Toothed Whales
Sperm whale
Atlantic pilot whale
Killer whale
Northern bottlenose whale
Harbour porpoise
Atlantic white-sided dolphin
White-beaked dolphin
Common dolphin
Seals
Grey seal
Harbour seal
Hooded seal
Harp seal
Other recent studies
Whitehead and Glass (1985) on the Southeast Shoal of the
Grand Bank, and Piatt et al. (1989) in Witless Bay on the Avalon Peninsula
also
show the importance of capelin as food for humpbacks and other cetaceans.
4.10.4
The report by Parsons and Brownlie (1981) remains the most comprehensive data set
on the spatial and temporal occurrence of marine mammals in the study area. However,
the degree of annual variability in the occurrence of marine mammals in the study area
is still poorly known. Also, few data are available concerning the offshore occurrence
of marine mammals in winter. There may be small numbers of the large whales in the
study area during this season.
Ice conditions, water temperatures, and prey distribution vary annually and the
occurrence and distribution of seals and whales vary accordingly. Weekly and even
daily distributions of baleen whales, particularly humpback, fin and minke whales are
strongly correlated with changing capelin abundance (Whitehead et al., 1980; Piatt et
al., 1989).
The Atlantic pilot whale and the harbour seal are the only marine mammals known to
be resident year-round in the study area. The 16 other species of marine mammals
recorded in the study area occur seasonally, primarily spring through autumn.
Although harp and hooded seals are rare in the study area, occurring in greatest
numbers to the north of the Grand Banks, they occur in at least the northern portions
of the Grand Banks in winter (February) and spring (April) (Stenson and Kavanagh,
1993).
4.11
The Terra Nova Field is near the outer edge of the Continental Shelf, an area which,
although not pristine, presumably receives less pollutants from anthropogenic sources
than inshore coastal regions. This offshore area has been used by fishing vessels as part
of trans-Atlantic shipping lanes and receives currents from the Gulf of St. Lawrence.
All of these are potential sources of pollutants.
Numerous substances may reduce the health or value of a biological community or
species. The two most important groups in terms of Terra Nova development,
hydrocarbons and trace elements, are discussed below.
4.11.1
Hydrocarbons
Polycyclic aromatic hydrocarbons (PAH) are ubiquitous in the marine environment
and, although they can be produced biologically, originate primarily from
anthropogenic sources (Hellou et al., 1994c). PAH may enter the environment directly
from a release of crude oil and petroleum products during exploration, production and
transport, and indirectly from atmospheric deposition following the incomplete
combustion of organic material (Canadian Council of Resource and Environment
Ministries, 1985; Hellou et al., 1994c).
PAH belong to a group of chemical compounds containing two or more fused
aromatic ring structures. These chemicals are unsaturated and are composed of carbon
and hydrogen atoms. Many of these compounds are potential carcinogens and
mutagens, 16 individual PAHs have been recognized as priority pollutants by The
World Health Organization, the European Economic Community, and the US
Environmental Protection Agency.
The scientific literature reviewed on hydrocarbon concentrations in marine biota
discusses both PAH and the broader group of chemicals, polycyclic aromatic
compounds (PAC). PAC include PAH, heterocyclic aromatic compounds and
organochlorines. While PAH concentrations are primarily associated with only
petroleum products and releases, PAC concentrations reflect petroleum and other types
of contamination (PCBs, many pesticides, surfactants).
Mobil (1985) reported that no data or research were available for petroleum
hydrocarbon pollutants in organisms on the Grand Banks. Since 1985, considerable
research has been completed and there are several detailed studies on hydrocarbon
concentrations in marine vertebrate and invertebrate populations in the study area.
Finfish
Two detailed studies of hydrocarbons in Atlantic cod (Gadus morhua) (Hellou et al.,
1994a,b) have indicated that low, but detectable, concentrations of PAH were found in
cod muscle samples collected from the Grand Banks. Hellou et al. (1994b) compared
PAH concentrations in cod sampled from sites in the Gulf of St. Lawrence (a more
coastal marine area) to cod collected from offshore Newfoundland. Although overall
concentrations were low, NAFO Division 3K showed the highest levels of PAH (Table
4.11-1).
In another research study of hydrocarbon concentrations in cod from the Grand Banks,
only acenophthene (18 ng/g, dry weight), fluorene (28 ng/g) and chrysene (22 ng/g)
were detected, once each in two liver samples. Fluorene (72 ng/g) was detected in an
ovary sample (Hellou et al., 1994a).
Primary data are available for PAH levels in three other species of finfish: American
plaice (Hippoglossoides platessoides), Greenland halibut or turbot (Reinhardtius
hippoglossoides), and yellowtail flounder (Pleuronectes ferruginea).
Table 4.11-1
Concentrations of PAH in Muscle of Cod
from Three Locations in the Newfoundland Offshore
(ug/g. dry wt.)
Sample Number
1
2
3
4
5
6
7
8
9
10
Mean
S.D.
Source: Hellou et al. (1994b).
Note:
1. Chrysene was used as a standard
2. ND - non detectable
2J
3K
3Ps
CH
ND
0.01
ND
0.01
0.01
ND
ND
ND
0.04
ND
0.01
0.01
CH
CH
0.58
0.19
0.11
0.05
0.21
0.09
0.07
0.55
0.05
0.12
0.20
0.20
ND
0.05
ND
0.01
ND
ND
ND
ND
ND
0.04
0.01
0.02
Hellou et al. (1995) measured aromatic hydrocarbon levels in muscle of plaice and
halibut from the St. Lawrence Estuary and the Northwest Atlantic (NAFO Divisions 2J
and 3K). Using a chrysene standard, PAH contaminants were detected in both areas,
although samples from the offshore Northwest Atlantic were the lowest (Table 4.11-2).
In 1995, MDS Environmental Services Limited, under contract from the Hibernia
Management and Development Company Limited, completed an analytical study of
trace metals, mercury, total petroleum hydrocarbons and polycyclic aromatic
hydrocarbon content in scallops and American plaice collected from the proposed
Hibernia gravity base structure site. Both liver and dorsal fillets of American plaice
were collected and analyzed for numerous PAH including the 16 recommended priority
pollutants. No PAH levels were measured above the detection limit (0.05 mg/kg or
ppm) for any of the liver or muscle samples (samples were measured using both dry
and wet weight basis).
Table 4.11-2
Concentration of Aromatics in Muscle Tissue
(ug/g dry wt.)
Species
Site
No. of
Samples
Chrysene units
mean
Plaice
Northwest Atlantic
Site 1 - St. Lawrence open coast
Site 2 - St. Lawrence Estuary
Site 6 - Saguenay River
13
5
4
7
ND (ND - 0.06)
0.02 (ND - 0.06)
0.04 (ND - 0.14)
0.13 (ND - 0.39)
Halibut
Northwest Atlantic
Site 2 - St. Lawrence Estuary
Site 4 - Saguenay Fiord in the
vicinity of an aluminum smelter
Site 6 - Saguenay River
10
4
4
0.08 (ND - 0.27)
0.76 (0.48 - 1.1)
0.93 (0.19 - 1.5)
7
2.9 (0.77 - 5.3)
Halibut
Source: Hellou et al. (1995).
Note: ND - non detectable.
In a study to determine baseline levels of hydrocarbons in offshore flatfish, Hellou and
Warren (1995a), using detection limits between 0.01 and 0.09 ng/g (ppb) wet weight,
detected PAH levels indicating petroleum hydrocarbons in flatfish from the Grand
Banks. Out of the three NAFO divisions sampled (3L, 3Ps, 3O), the highest levels of
specific PAH (primarily naphthalene) were detected in samples from 3L.
PAC concentrations in liver probably represent short-term exposure, while
concentrations in muscle may represent long-term bioaccumulation. The results for
yellowtail flounder are similar to those for cod with low, but detectable concentrations
of PAH priority pollutants. Underwater seeps of crude oil were proposed as a possible
source of hydrocarbons, although there was no variation in concentration with location.
Sampling was not conducted in NAFO Division 3Lt, the division that includes the
Terra Nova Field.
Marine Mammals
There are few studies on hydrocarbon (PAH) concentrations in marine mammals.
Hellou et al. (1990) measured PAH concentrations in four species of seal and six
species of whale from waters around Newfoundland and Labrador, including two
samples from northeast Newfoundland. Low, but detectable concentrations of PAH
(0.02-0.45 ug/g chrysene equivalent) were measured in all ten species and relatively
high values were recorded for the two samples (white sided dolphin; and harbour
porpoise) collected off the northeast coast. The PAH source was not explained beyond
the theory that higher hydrocarbon levels might occur in areas of fishing activity.
Invertebrates
One study of hydrocarbons in two crab species (Chionoecetes opilio and Hyas
coartatus) identified PAH contaminants and biologically derived hydrocarbons in both
species (Hellou et al. 1994c). The 16 recommended PAH priority pollutants were
measured and some of them were identified (concentrations in the range of 30 to 560
ng/g dry wt. of prominent PAH) in both species of crab. Sample locations for the study
included both inshore (i.e., Conception Bay) and offshore sites (i.e., western edge of
Grand Banks in the Avalon Channel).
A study of hydrocarbons in several species of molluscs collected primarily from inshore
waters of Newfoundland with one offshore sampling station on the St. Pierre Bank
(NAFO 3Ps), detected some recommended PAH priority pollutants (Hellou et al.,
1993). Mollusc species studies included:
-
Scallops (Placopecten magellanicus)
Mussels (Mytilus edulis)
Periwinkles (Nucella lapillus)
Clams (Mya arenaria)
Whelks (Buccinum undatum)
Propeller clams (Crytoderia siliqua)
The results showed low hydrocarbon levels (e.g., the range for hydrocarbon
concentrations in mussels was 0.21 to 1.80 ug/g chrysene).
MDS Environmental Services Limited (1985) reported no TPH or PAH levels above
the detection limit of 0.05 mg/kg for any of the viscera or muscle samples (both dry
and wet weight basis) collected from Icelandic scallops.
4.11.2
Trace Elements
Finfish
Data on concentrations of trace elements in Atlantic cod in NAFO Divisions 2J and
3Ps were reported for the first time by Hellou et al. (1992). The trace elements
measured included the priority heavy metals mercury, cadmium and lead.
Concentrations of these heavy metals were comparable to levels reported in cod from
the Northeast Atlantic, the North Sea and the Baltic Sea. Of all the elements measured,
mercury was elevated in muscle, silver in liver, and zinc and selenium in ovaries.
Concentrations of the priority heavy metal pollutants were all well below the levels
permissible in food.
Hellou et al. (1995b) measured certain heavy metal and trace element content in
muscle, liver and gonad of yellowtail flounder collected from NAFO divisions 3Ps, 3N
and 3O. In general, arsenic, boron, cadmium, iron, lead, selenium, silica and zinc were
detected in all tissues at concentrations above 1 ug/g. The concentration of Pb was
below 0.3 ug/g in all tissues. The study concludes the detected values were low and
represent pristine conditions.
MDS Environmental Services Limited (1995) measured 10 trace elements and heavy
metals in American plaice muscle and liver samples from the Hibernia site (Table 4.113). The measured levels were considered low. Mercury levels in dorsal fillets ranged
from 0.19 - 0.32 ug/g, well below the guidelines for chemical contaminants in fish and
fish products.
Invertebrates
MDS Environmental Services Limited (1995) measured 10 trace elements and heavy
metals in Icelandic scallop muscle and viscera samples (Table 4.11-3). The Canadian
Journal of Fisheries and Aquatic Sciences measured levels were considered low except
for cadmium and copper values in several of the samples.
Table 4.11-3
Range of Concentrations of Trace Elements and Metals
in Biota Sampled from the Hibernia Site
American Plaice
(mg/kg) dry wt.
Elements
Arsenic (As)
Chromium (Cr)
Barium (Ba)
Cadmium (Cd)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Zinc (Zn)
Lithium (Li)
Mercury (Hg)
Liver
4.2 - 9.8
<5
1.1 - 1.9
<1
6.2 - 1.3
77 - 180
< 0.5 - 0.7
53 - 80
<2
0.05 - 0.1
Fillet
9.1 - 1.7
<5
< 0.05 - 0.79
< 1 - 3.4
2.3 - 100
< 10 - 26
< 0.5 -12
19 - 170
<2
0.19 - 0.32
Icelandic Scallop
(mg/kg) dry wt.
Viscera
2.6 - 5.8
5.5 - 7.6
22 - 59
9.3 - 7/2
10 - 25
440 - 650
0.8 - 2.1
58 - 180
<2
< 10
Muscle
2.2 - 2.5
<5
2-4.8
< 1 -2.3
2.2 - 15
14 - 52
< 0.5
52 - 61
<2
< 10
Source: MDS Environmental Services Limited (1995).
Marine Mammals
Certain organochlorine chemical and heavy metal contaminants were measured in
white-beaked dolphins (Lagenorhynchus albirostris) and pilot whales (Globicephala
melaena) that were either stranded or became trapped in inshore coastal waters of
Newfoundland (Muir et al., 1988). Both species are migratory and frequent the inshore
and offshore waters of Newfoundland, including portions of the Grand Banks. The
results of this study indicate that cadmium levels in both species were much higher than
reported for other cetaceans from East Coast Canadian waters. Relatively high levels of
lead and PCBs were reported in dolphins. The Gulf of St. Lawrence was proposed as a
possible source of contaminants.
Chapter 5
Table of Contents
5.
Impact Assessment
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.1.1 Types of Impacts
5.1.2 Impact Analysis Methods
5.3.1 Description of Physical Facilities and Activities
5.3.2 Presence of Structures
5.3.3 Lights and Beacons
5.3.4 Installation of Seabed Components and Underwater
Construction
5.3.5 Discharge of Drilling Muds and Cuttings
5.3.6 Discharge of Other Fluids and Solids
5.4.1 Presence of Structures
5.4.2 Lights and Beacons
5.4.3 Maintenance of Subsea Structures
5.4.4 Injection Water
5.4.5 Produced Water
5.4.6 Other Operational Discharges
Transportation
Decommissioning
5.6.1 Terra Nova Development Area
Oil Spills
5.7.1 Oil Spill Probability Analysis
5.7.2 Selection of Oil Spill Scenarios
5.7.3 Terra Nova Oil Properties and General Spill Behaviour
5-1
5-3
5-3
5-3
5-10
5-11
5-11
5-13
5-16
5-16
5-16
5-28
5-33
5-33
5-34
5-34
5-42
5-46
5-46
5-48
5-48
5-49
5-49
5-55
5-58
5-59
5-59
5-60
5-61
5-62
5-64
5-64
5-66
5-67
5-68
5-85
5-90
5.7.4
5.8
Modelling and Description of Selected Oil Spill
Scenarios
5.7.5 Terra Nova Spill Trajectories
5.7.6 Environmental Impact Assessment
5.7.7 Assessment of Oil-Spill Countermeasures
5.7.8 Residual Impacts
Cumulative Impacts
5.8.1 Impact Summary
5.8.2 Cumulative Development Impacts
5.8.3 Cumulative Impacts of the Development and Other
Activities on the Grand Banks
5.8.4 Cumulative Impacts and Climatic Change
5-100
5-108
5-114
5-121
5-125
5-127
5-127
5-134
5-135
5-136
Tables
5.3-1
5.3-2
5.3-3
5.3-4
5.3-5
5.3-6
5.4-1
5.4-2
5.4-3
5.4-4
5.6-1
5.7-1
5.7-2
5.7-3
5.7-4
5.7-5
5.7-6
5.7-7
5.7-8
Level I Matrix: Interactions Between Development Activities
and Ecosystem Elements
Volume of Cuttings and Mud Discharged from One Well
Toxicity of Drilling Muds
Concentration and Toxicity of Components in Gel and WaterBased Drilling Muds
Typical Concentration of Components in PHPA Polymer and WaterBased Muds
Natural and Development-Related Underwater Noise Levels
Level I Matrix: Interactions Between Operational Activities
and Ecosystem Elements
Injection Water Additives
Production and Injection Forecast Waterflood in the Graben and
East Flank
Flowline Dimensions and Hydrocarbon Inventories
Level I Matrix: Interactions Between Abandonment Activities and
Ecosystem Elements
Input of Petroleum Hydrocarbons into the Marine Environment
Terra Nova Development Statistics of Importance to Study
Offshore Petroleum Industry Statistics
Spill Classification Categories
Historical Large Oil Spills from Offshore Oil-Well Blowouts
Blowouts and Spillage from U.S. Federal Offshore Wells
Compared to Crude Oil and Condensate Production on
Federal OCS Leases, 1971 to 1993
Oil Spills of 1000 Barrels or More from Platforms on the
U.S. OCS, 1964 to 1993
Spill Frequency from Platforms for Spills in the Size Ranges
of 1-50 Barrels and > 50 Barrels (U.S. OCS 1970 - 1993)
5-12
5-17
5-18
5-21
5-22
5-35
5-47
5-50
5-51
5-57
5-65
5-70
5-73
5-74
5-75
5-75
5-78
5-81
5-81
5.7-9
5.7-10
5.7-11
5.7-12
5.7-13
5.7-14
5.7-15
5.7-16
5.7-17
5.7-18
5.7-19
5.7-20
5.7-21
5.7-22
5.7-23
5.7-24
5.8-1
5.8-2
5.8-3
Spills Larger than 240 Barrels that Occurred at SBM
Facilities, 1982 to 1985
Predicted Number of Blowouts and Spills for the Terra Nova
Development over its 20-Year Lifetime
Summary of Hibernia Spill Scenarios
Summary of Terra Nova Spill Scenarios
Terra Nova Spill Scenario Environmental Data
Properties of Terra Nova Crude and Hibernia Crude
Evaporation of Conventional Crude Oil Slicks as a Function
of Sea State (%)
7150 m3/d Platform Blowout Scenario Summary
7150 m3/d Subsea Blowout Scenario Summary
4800 m3/d Subsea Blowout Scenario Summary
800 m3/d Batch Spill Scenario Summary
Impact and Closest Point of Approach of Hibernia Oil
Slicks to Shoreline
Trajectories Reaching Land
Summary of Worst-Case Potential Impacts of Accidental
Spills at Hibernia
Summary of Worst-Case Potential Impacts of Accidental
Spills at Terra Nova
Spill Scenario Environmental Data
Level II Matrix for Development Drilling
Level II Matrix for Production
Matrix for Worst-Case Accidental Oil Spills
5-83
5-86
5-87
5-88
5-90
5-92
5-94
5-101
5-104
5-105
5-107
5-109
5-111
5-115
5-117
5-126
5-128
5-131
5-133
Figures
5.3-1
5.5-1
5.7-1
5.7-2
Aliphatic Hydrocarbons in Beatrice Oil Field Sediments
Transportation Routes Relevant to Terra Nova
Terra Nova Trajectories (February 1st: 1946 to 1989)
Terra Nova Trajectories (August 1st: 1946 to 1989)
Appendices
5.A
5.B
5.C
5.D
5.E
Historical Statistics on Blowouts
Using the Most Appropriate Exposure When Comparing the Terra Nova
Development and Operations in the U.S. Gulf of Mexico
Statistics on Blowout-Related Oil Spills and Canadian Experiences
Offshore Production and Transportation Activities: Important Accidental Events
Brief Description of S.L. Ross Oil Spill Model
5-24
5-63
5-112
5-113
5.
Impact Assessment
This section assesses the impacts on the Grand Banks environment of the development,
operation and eventual abandonment of the Terra Nova Field. The estimated life of the
field is 15 to 18 years.
Most impacts of normal drilling and production operations are rated as not significant.
This would not have been the case 30 years ago. Today, the project design and
operational procedures routinely include mitigation measures such as the following:
·
Low-toxicity drilling muds have replaced toxic diesel-based muds.
·
Oil-water separators are used to treat discharges.
·
More stringent regulations respecting the quality of discharges have been put in
place.
·
Sophisticated blowout preventers and subsea safety valves are standard
equipment in wells.
·
Tankers are built with double-sided hulls, double-bottomed, ice-strengthened at
the waterline with dual propulsion and segregated and ballast.
The Terra Nova Development, for the most part, will use existing technology. Floating
production systems have been successfully used in both the North Sea and the Gulf of
Mexico. Petro-Canada is highly experienced with operations on the Grand Banks,
including ice management.
In this assessment, additional mitigation measures to further reduce impacts are
recommended. The Terra Nova Development will involve the participation of
numerous contractors who will provide goods and services throughout the life of the
development. The process associated with contractor selection will include evaluation
of loss management practices and compliance records.
In assessing the potential impacts of the Terra Nova Development, extensive use was
made of the Hibernia EIS biophysical and impact assessment documents. The Hibernia
EIS presented the pertinent regional biophysical information and oil and gas impact
assessment literature available to 1985. Details of the Hibernia related studies are not
repeated. Rather this EIS:
-
Summarizes the results and conclusions found in the Hibernia-related reports
and the Hibernia EIS
5-1
-
Revises recent literature on the environmental impacts associated with offshore
oil and gas development and regional biophysics
-
Updates databases and compares the more recent information with that of
1985
There are some notable differences between Hibernia and Terra Nova that may
influence the impact assessment:
·
Terra Nova is roughly one-half the size of Hibernia in terms of reserves and
numbers of wells.
·
The Terra Nova floating production facility (FPF) can be moved to avoid
collisions whereas Hibernia is fixed and built to withstand ice and other
potential threats.
·
Terra Nova wells will be drilled from a number of locations around the field
whereas Hibernia will drill from one central location.
·
The water depth at Terra Nova is about 15 m deeper than at Hibernia.
·
Terra Nova is using an alliance contractor approach for design engineering.
This section presents the impacts for drilling and field development, normal production
operations, transportation of oil from Terra Nova and decommissioning at project end.
The impacts of large accidental spills are considered separately, as are cumulative
impacts of the development along with the other activities in the area.
5-2
5.1
5.1.1
Types of Impacts
Two general types of impacts are considered in this document:
1.
Impacts of the project on the environment, particularly the biological
environment
2.
Impacts of the environment, particularly the physical environment, on the
project, discussed in more detail in Chapter 3 and Section 5.7 of this document,
and chapters 5 and 8 of the Development Plan.
The biological environment is emphasized because the fish, marine mammals and birds
of the Grand Banks area are of great interest and value to society. These vertebrates
are also good indicators of the health of the marine system upon which they depend.
Social impacts, including those on the commercial fisheries, are considered in a
separate report, the Socio-Economic Impact Statement (SEIS). Social and economic
benefits of the development are also contained in the SEIS.
5.1.2
Impact Analysis Methods
Methods of impact assessment are described in the Hibernia EIS, the C-NOPB
guidelines (1988), and the Canadian Environmental Assessment Act (CEAA) and its
associated Responsible Authorities Guide (1994). Detailed methods are described in
the following subsections. The specifications and spirit of these documents have been
followed in preparation of this EIS.
Scoping
Scoping for the EIS was based on the documents referenced in the previous section,
discussions with consultants, government and industry, and by public consultations,
including key informant workshops.
The public and key informant consultations focussed on the four study areas. In the
case of the Marystown, Isthmus of Avalon and Argentia areas, comments and impacts
were solicited through:
-
A six-hour public open house
A key informant workshop with local citizens knowledgeable about socioeconomic and environmental issues in the area
5-3
Given its larger population base, three open houses were held in St. John's.
Furthermore, the St. John's area workshop was supplemented by three others dealing
with province-wide issues related to fisheries, the environment and socio-economic
effects.
Province-wide public consultations involved the holding of additional open houses in
Carbonear, Gander, Grand Falls, Corner Brook, Stephenville and Port aux Basques; a
telephone survey; and a general solicitation of input through the use of advertisements
and a 1-800 number.
For further details of the public consultation process, see the SEIS.
The following issues were raised during the public consultations:
·
The project's environmental impacts
Environmental protection and safety
Environmental monitoring programs
Iceberg management
Potential impacts of pollution
·
The fishery
Fish taint testing
Migratory fish stocks in the vicinity of the Terra Nova Field
Sediment impacts on spawning and breeding grounds
·
Oil spills
Prevention, management and cleanup
Fishery compensation
The impacts on St. Mary's bird sanctuary
Effects on the coastline
·
Waste disposal management and treatment
Management and monitoring - the regulatory body responsible?
Discharge at the facility
A treatment facility in the province?
Drilling muds - use and handling
·
Impacts of the physical environment
Climate trends - impacts on design criteria for production facility
Impacts of storms and seas seem to have been overlooked
The issue of earthquakes offshore
5-4
Valued Ecosystem Components
It is not possible to address the potential interactions between every project activity and
every component of the natural and human environment. Thus, the EIS focusses on
important valued ecosystem components (VECs). However, impacts are assessed on
other elements of the ecosystem such as water quality, plankton and benthos, where
relevant. VECs are discussed extensively in Beanlands and Duinker (1983).
VECs include the following groups:
·
Rare or threatened species or habitats
·
Species or habitats that are unique to an area, or are valued for their aesthetic
properties
·
Species that are harvested by people
VECs were identified in the Hibernia EIS (Mobil 1985) and through research by the
Terra Nova environmental assessment team. The VECs considered in this EIS include:
·
·
·
·
Commercial fish species
The fishery
Seabirds
Marine mammals
Several subsections also discuss effects on benthic animals. Benthic animals are not
VECs. However, as they are not mobile, they can be more readily assessed than the
mobile VECs listed above. Benthic animals are good indicators of possible
development effects at, in or on the seabed, and also can indicate the likelihood of
effects on VECs. The commercial aspects of the fishery are detailed in Chapter 9 of the
Socio-Economic Impact Statement.
Boundaries
Impacts are assessed for the 15 to 18 year lifespan of the Project and Operations
phases of the Terra Nova Development. Effects that could continue after
decommissioning are also considered. The spatial boundaries of the assessment include
the Grand Banks and nearshore areas being considered for onshore facilities. For
accidental oil spills, the impacts were assessed for all areas that could be affected by a
spill or loss of well control at Terra Nova, as determined through oil spill modelling.
5-5
Impact Assessment Procedures
Procedures were according to the Canadian Environmental Assessment Agency
(CEAA, 1994), Duffy (1986) and the Federal Environmental Assessment and Review
Office (FEARO) (1976, 1978). Assessment of the potential impacts of each project
phase involved five steps:
1.
2.
3.
4.
5.
Preparation of interaction matrices (Level I)
Identification and evaluation of potential impacts
Description of mitigation measures and residual impacts
Preparation of impact summary tables (Level II matrices)
Evaluation of cumulative impacts
Preparation of Interaction Matrices
Interaction matrices (Level I) were prepared for the development, production and
decommissioning components of the project, as well as for transport of crude oil and
onshore facilities. A Level I interaction matrix identifies all possible project activities
that could interact with any of the VECs. The matrices include times and places where
interactions could occur. Level I matrices are used only to identify potential
interactions; they make no assumptions about the potential impacts of the interactions.
Identification and Evaluation of Impacts
Interactions identified in the Level I matrices were then evaluated for their potential to
cause impacts. The potential for impact of many interactions was deemed impossible or
extremely remote; thus these interactions were not considered further. In this way, the
assessment could focus on key issues and the more significant environmental effects
specified in C-NOPB guidelines (1988).
An interaction was considered to be a potential impact if it could change the abundance
or distribution of VECs, change the prey species or habitats used by VECs, or affect
fishing activities. The potential for impact was assessed by a discipline expert who
considered:
-
The location and timing of the interaction
The literature on similar interactions and associated impacts
The Hibernia EIS
When necessary, consultation with other experts
Results of similar impact assessments and especially monitoring studies done in
other areas
When data were insufficient to allow certain or precise impact evaluations, tentative
predictions were made based on professional judgement. In such cases, the uncertainty
5-6
is documented in the EIS. For the most part, the potential effects of offshore oil
developments are reasonably well known.
The impacts are presented as predictions based on the literature. In some cases, the
predictions will be tested by modelling. Information on monitoring programs are
presented in Chapters 7 and 8 of this document.
Impacts were evaluated for the proposed development design, which includes many
mitigation measures that are mandatory or have become standard operating procedure
in the industry. However, the impacts were evaluated before implementation of
development-specific mitigation measures.
Description of Mitigation Measures and Residual Impacts
Most significant impacts can be mitigated by additions to or changes in equipment,
operational procedures, timing of activities, or other measures. Mitigation measures
appropriate for each impact predicted in the matrix were identified and the impacts of
various project activities were then evaluated assuming that appropriate mitigation
measures are applied. Any impacts remaining after the implementation of mitigation
measures, termed residual impacts, were then identified.
In this EIS, mitigation measures were identified in a generic way. Details necessary for
the implementation of mitigation measures will be contained in the EPP.
Preparation of Impact Summary Tables
Impact tables (Level II matrices) were prepared summarizing the predicted impacts
before and after mitigation measures. Each interaction identified in the Level I
interaction matrix is addressed in the impact summary tables (Level II matrices).
The following information is included for each interaction:
·
·
·
·
·
·
·
·
The project activity
Important ecosystem components
The potential interaction (e.g., noise disturbance)
Ranking of the magnitude of the potential impact before mitigation
Direction (positive or negative), scale and duration of impact
Likelihood of occurrence
A brief description of the mitigation measures (e.g., scheduling, use of
equipment)
Ranking of the predicted residual impacts after mitigation
Impacts unlikely to occur are also listed.
5-7
Evaluation of Cumulative Impacts
The final step was determining the cumulative effects of the development. Cumulative
effects are the combined effects of all phases of the development plus the effects of
other projects existing or planned for the area. Cumulative effects may be additive or
synergistic.
Levels of Potential Impacts
The terminology used to describe potential impacts must be clear, objective and easily
understood. Precise definitions for the ranking of potential impacts are used in this EIS,
as follows:
Major Impact. An impact resulting in a 10 percent, or greater, change in the carrying
capacity of the environment, size of an animal population, size of a resource harvest or
a commercial fishery, or attribute of another VEC.
Moderate Impact. An impact resulting in a 1 to 10 percent change in the carrying
capacity of the environment, size of an animal population, size of a resource harvest or
commercial fishery, or attribute of another VEC.
Minor Impact. An impact resulting in a less than 1 percent change in the carrying
capacity of the environment, animal population size, resource harvest or commercial
fishery, or attribute of another VEC.
Negligible Impact. Impacts with essentially no effects.
Regional Impact. An impact that affects the region, defined for this EIS as the Grand
Banks and the entire nearshore area adjacent to the Grand Banks and the onshore
facilities.
Local Impact. An impact at the local level, defined here as the areas within 1 to 10 km
from development activities.
Sublocal Impact. An impact on the biophysical environment within 1 km of
development activities.
Long-Term Impact. An impact that lasts for more than five years.
Medium-Term Impact. An impact that lasts for one to five years.
Short-Term Impact. An impact that lasts for less than one year.
5-8
Significance of Potential Impacts
The terms defined above can be combined, as appropriate, to define the level of
potential impact. For example, a potential impact can be rated positive, long term and
regional. The most serious impact (positive or negative) in this rating system is major,
regional and long term; the least serious is negligible. However, it is also necessary to
define what level of impact constitutes a significant impact. Impact significance is
defined as follows:
Not Significant Impact. Means that an impact is negligible or is minor, short term,
and local or sublocal in nature.
Significant Impact. Means that the impact rating is major or moderate or that it is
minor with a medium- or long-term and a regional impact.
The above definitions are based on Duffy (1978), Canadian Environmental Assessment
Guidelines and FEARO Guidelines, and have been used in numerous EISs since 1985.
It is recognized there is an apparent "geographic gap" between a regional impact and a
local impact. However, it was felt that inventing new impact categories would render
the assessment incomparable with other recent EISs. For this EIS, the gap is not an
issue for routine operations because all of the impacts were ultimately considered to be
sublocal or local. It may be an issue for large oil spills but the assessment of these
events was handled somewhat differently (see Section 5.7).
5-9
5.2
The FPF for the Terra Nova Development will be a new or converted monohull or
semisubmersible vessel supporting a topsides deck. The hull of the vessel can be built
of steel or reinforced, prestressed and post-tensioned concrete.
For more information on the alternatives considered, refer to Chapter 6 of the
Development Plan.
The potential impacts on the offshore environment of a monohull or a semisubmersible
are virtually the same. The development and decommissioning scenarios are the same,
as are the anticipated emissions and discharges. The discussion of potential impacts in
the following sections is based upon a generic floating production system.
5-10
5.3
Potential interactions between development activities and ecosystem elements are
shown in Table 5.3-1. These interactions are discussed in the following subsections.
5.3.1
Description of Physical Facilities and Activities
Chapter 1 of the EIS provides an overview of the Terra Nova Development. This
subsection provides the details on the drilling and construction components of the
development necessary to the assessment of environmental impacts.
In order to meet the 2001 schedule for First Oil, drilling will begin in 1999 and may
continue throughout the development's life. The Terra Nova Field, including the Far
East block, will involve drilling up to 39 new wells.
Current plans call for re-entering five of the nine exploratory wells that have already
been drilled. The remaining 39 production and injection wells will be drilled
sequentially. Wells will be drilled in clusters of up to six. The subsea structures will be
installed once a year for the first two or three years, and about every second year
thereafter.
Flowlines lying on the substrate will connect the well clusters to up to eight field
manifolds. Oil production, water injection and gas injection flowlines will connect these
field manifolds to a subsea riser-base manifold. Flexible risers will carry oil from the
riser-base manifold up to the FPF, and water and gas from the FPF down to the riserbase manifold for distribution to the field manifolds and the injection wells (see Figure
1.1-7).
Wells will be drilled by one, and sometimes two semisubmersible drilling rigs at a rate
of two to six wells per year. Each drilling rig will be supported by a number of supply
vessels. One of these vessels will be on standby while the others will carry material
from the supply base to the drilling rig. On average, there will be about two round trips
per week between the supply base and drilling rig. When two drilling rigs are operating,
four to six supply vessels may be used. Helicopters will make an average of one round
trip per day to each drilling rig.
The FPF will be brought to the field and will begin to operate two years after the start
of drilling; thus production and drilling will occur simultaneously for at least nine years.
Production facilities are described in Section 5.4.
There will be an onshore supply base in the vicinity of St. John's. Drilling pipe, subsea
pipe, manifolds, cement, drilling muds, chemicals and all the other materials required
for drilling and FPF operation will be stored at the site. Coordination of some
operations with the Hibernia shore base is possible, and will be investigated. Personnel
5-11
x
x
x
x
Shore facilities
Atmospheric emissions
Liquid and solid releases
Garbage and waste
Noise
Lights and beacons
Vessel traffic
Accidents
Ships and boats
Helicopters
Noise
Drillings rigs
Support Vessels
Helicopters
Other fluids and solids
Completion, packer and workover
Cement
BOP fluid
Hydrostatic testing fluid
Cooling water
Deck drainage
Bilge water
Sanitary and domestic waste
Garbage
Other waste
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Fish
Fouling Pelagic
Terrestrial
Plankton Larvae Infauna Organisms Fish Groundfish Fishery Seabirds
Birds
Whales Seals
Drilling mud
Oil-based mud
Water-based mud
Glycol-based mud
x
x
x
Air
Water
Quality Quality
Lights and beacons
Underwater construction
Presence of structures
Safety zone
Artificial reef effect
Subsea structures
Surface structures
Project Component
Ecosystem Components
Table 5.3-1
Level I Matrix: Interactions Between Development Activities and Ecosystem Elements
will travel to and from the offshore site by helicopter via St. John's Airport.
5.3.2
The environmental effects of the presence of the drilling rigs and subsea structures at
the Terra Nova site are assessed below.
Effects on Fish
The subsea structures and associated safety zone have the potential to alter the local
abundance and distribution of fish.
Generally, anything that adds to the relief or structural diversity of soft-bottom marine
habitats will attract fish (Polovina, 1991). Production structures, pipes, mounds of
cement and debris will create artificial reefs that will be colonized by epifaunal animals
and will attract fish (Stanley and Wilson 1990; Dustan et al., 1991; Black et al., 1994).
Pelagic fish are also attracted to the structures but are generally found around and near
structures, not within them (Gallaway et al., 1981). The fish community found within,
very near and around offshore oil and gas structures, to some extent, depends on the
nature of the structure (Stanley and Wilson, 1991). Holes in the bottom, such as glory
holes, would also be inhabited by fish (Dustan et al., 1991). Studies conducted in the
North Sea show that cod, haddock and other commercially important species are
attracted to and concentrate around production facilities (Picken and McIntyre, 1989).
The Newfoundland Offshore Area Petroleum Production and Conservation
Regulations define a safety zone as the zone at and under sea level that covers the
greater of the area comprised within 500 m of a production installation, and the area
comprised within 50 m of the anchor pattern of a production installation. A production
installation is a facility and an associated platform, artificial island, subsea production
system, offshore loading system, drilling equipment, facilities related to marine
activities and dependent diving systems. The subsea system comprises equipment and
structures that are located on or below, or buried in, the seafloor for the production of
petroleum from, or for the injection of fluids into, a field under an offshore production
site, and includes production riser, flowlines and associated production control systems.
Flowlines are pipelines used to transport fluids from a well to a production facility or
vice versa, and include intrafield export and all gathering lines.
As wells are completed, and subsea pipe and manifolds are laid, the size of the safety
zone will be increased as required. The total area closed to fishing could be about
10 km2 in 2001 increasing to 56 km2 (assuming 12 wells in the Far East) by years 2006
to 2009.
5-12
Even with the resumption of a groundfish fishery, the negative impacts of the safety
zone on fisheries would be minor, local and long term. On the other hand, the 56-km 2
closed area could create a refuge, where fish, including commercially important
species, could be attracted to the subsea structures and become concentrated.
Therefore, on fish populations, the reef effect and the safety zone together could have a
positive, long-term, minor-to-moderate, local, significant impact. This refuge and
enhancement of local populations, which could move outside the development area,
may offset the negative impact of the safety zone on fisheries.
Biofouling
The subsea structures will create habitat for biofouling organisms. In the North Sea,
most of the fouling biomass in the upper 50 m is composed of seaweeds, hydroids,
mussels, soft corals and anemones. Below that depth, hydroids, soft corals, anemones
and tubeworms are the most common animals (Welaptega, 1993).
Colonization of subsea structures by fouling epifaunal animals and plants is considered
a nuisance and eventually a hazard. Epifaunal animals make visual inspections more
difficult, increase hydrodynamic loading, contribute to fatigue and corrosion, and may
interfere with corrosion protection systems (Edyvean et al., 1985). Biofouling could
cause minor-to-moderate, sublocal and long-term negative impacts on subsea
structures.
Fouling organisms will be periodically removed as necessary using diver- or
ROV-deployed brushes or high-pressure water jets (Welaptega, 1993). Removal of
fouling organisms will reduce impacts to negligible. The accumulation of removed
fouling organisms on the bottom may attract invertebrate and fish predators (Dicks,
1982).
Effects on Benthic Animals
The presence of structures can modify the substrate characteristics of the adjacent
seabed and infaunal community (Davis et al., 1982). Changes in benthic communities
are also related to increased predation by fish, such as cod, which are attracted to
environment around the structures (see "Effects on Fish" above), and by invertebrate
predators, such as starfish, which are attracted to the area by the presence of fouling
organisms (Davis et al., 1982). Scavengers are attracted to the area by the presence of
removed fouling organisms on the bottom (Dicks, 1982).
There has been much concern over the long-term effects of trawling on the benthos.
Some studies have shown effects and some have not (see review by Messieh et al.,
1991). Some authors have concluded that extensive trawling can produce long-term
changes in sediment characteristics and the structure of the benthic community
5-13
(deGroot, 1984 and references cited therein). At present, the Bedford Institute of
Oceanography (BIO) and the Northwest Atlantic Fisheries Centre, St. John's are
conducting a collaborative research project on the impacts of trawling on the Grand
Banks. The research is being conducted in an area about 75 km northeast of Hibernia
that has been closed to trawling since 1987 (the centre position is 47°10_N, 48°17_W)
(D. Gordon, BIO, pers. comm.). The project involves assessing the impacts of one type
of bottom trawl on a relatively homogeneous, sandy environment through extensive,
video-guided, sediment, infaunal and epibenthic sampling. Samples and data are still
being analyzed, but there is preliminary evidence of negative impacts of trawling on
sediments and some epibenthic species, such as crab (Fisheries and Oceans Canada,
1995).
A safety zone will allow recovery of the benthos in the zone, and will also provide an
indirect benefit in that another test area where comparative data for trawl effects
studies could be available.
Impacts of the presence of structures on benthos would depend on the state of the
fisheries. If the fishery does not recover, and present low levels of fishing are
maintained, then the relative impacts of a fishery closure on the benthos are likely to be
negligible. On the other hand, if the fishery recovers, then the relative effects of a safety
zone on the benthos are quite likely to be positive, minor, long term and local.
Effects on Birds and Marine Mammals
Migrating birds nearing the end of their migration could be attracted to the drilling
platforms and supply boats. In the past, some concern has been expressed that birds
nearing the end of their migration could land on structures and die of exhaustion and
lack of food and water, and that if the structures had not been present, the birds would
have made a landfall.
The Buccaneer oil and gas field is 45 km offshore of the northeastern Gulf of Mexico
and within a major migration corridor used by birds migrating across the Gulf of
Mexico. Northbound birds that had died of exhaustion were found on the platforms
during spring migration (Aumann 1980). If the structures had not been present, the
birds might have made it to land in one hour, but could have died on arrival or before
reaching land. Fall migrants were not found on the Buccaneer platforms, which were
near the start of the autumn trans-Gulf flights. The Terra Nova Development area is
not within a major migration corridor for passerine birds (songbirds and perching
birds). Any passerines in the area would be very much off course.
Gulls and terns are known to make extensive use of offshore structures for resting and
feeding (Aumann, 1980). However, many ships can be found on the Grand Banks, and
many of these are more attractive than offshore structures to seabirds because they
5-14
provide potential food in the form of fish refuse. The passive use of Terra Nova vessels
by resting gulls and terns would have negligible effects on the birds.
Overall, impacts on marine and terrestrial birds caused by the presence of structures
would be negligible. Potential effects on marine mammals are mainly related to the
effects of noise produced by the facilities. (Section 5.3.10).
5.3.3
Lights and Beacons
The drilling rigs and supply and standby ships will carry navigation lights and warning
lights. Working areas will be illuminated with floodlights. The helideck on the drilling
units and the FPF will be floodlit and have omnidirectional guidance lights.
Fish and squid may be attracted to illuminated surface waters near the vessels (Hurley,
1980); however, the impacts on fish and squid would be negligible.
Night-migrating birds are attracted to light sources during foggy or overcast
conditions, and may collide with structures (Avery et al., 1978) or be incinerated by the
flare (Bourne, 1979; Sage, 1979). There are no quantitative data describing the
frequency of collisions, but anecdotal information suggests they are rare. The small
numbers of birds involved and infrequent periods of flaring would result in these
collisions having a negligible impact on bird populations.
5.3.4
Installation of Seabed Components and Underwater Construction
Completion of wells, and installation of manifolds and pipe may require excavation and
some other form of bottom preparation. No underwater blasting is anticipated. During
any one year, disturbance will occur over relatively small areas. Recolonization by
opportunistic species can be quite rapid, even in cold water (e.g., Thomson and Martin,
1984); therefore, impacts on the benthos are likely to be negligible.
The underwater construction may displace fish by approximately 100 m but these
impacts would be negligible.
Marine mammals and fish could potentially be affected by the associated noise (see
Section 5.3.10).
5.3.5
Discharge of Drilling Muds and Cuttings
The design of the development requires directional drilling of the wells from cluster
locations. This will significantly minimize the number and length of subsea flowlines
and associated risks. On directional wells, the shales will be exposed for longer periods
5-15
of time and hole stability is of greater concern than with vertical wells. The shale
intervals are longer and subject to greater risk of hole collapse because of wellbore
inclination. Oil-based muds are the most reliable method of managing hole stability,
lubricity, and lower drill string hole torque and drag.
Drilling cuttings will be discharged over a wide area within the 56 km2 development
area, and not at one central site in the field as is the case at Hibernia. Wells will be
drilled in clusters, each cluster consisting of up to six wells. Wells within clusters will be
drilled about 25 m apart along the circumference of a circle.
The current plans are to drill the upper 1500 m of each well using water-based drilling
muds. Use of low-toxicity, oil- or inhibited water-based muds is planned for depths of
1500 m, measured depth, to total depth.
The effects of discharged cuttings depend on the type of drilling mud used. Table 5.3-2
shows estimates of the volumes of mud and cuttings that could be discharged from an
average well drilled directionally to a depth of 4440 m with a horizontal reach of 2000
m from the vertical.
Table 5.3-2
Volume of Cuttings and Mud Discharged From One Well
Depth
Subsea
(m)
Volume of
Dry Rock
(m3)
Mud Type
Discharge
0-176
110
Gel and
seawater
175 m3 to seafloor
176-500
160
Gel and
seawater
450 m3 to seafloor
500-1500
170
PHPA polymer
and seawater
450 m3 return to rig for discharge from solids
control and 450 m 3 to seafloor
1500-3940
220
Oil or glycol
Recycle - max. oil content of 15 g/100 g dry
cuttings
3940-4440
18.3
Oil or glycol
Recycle - max. oil content of 15 g/100 g dry
cuttings
Note: Volumes are for a 4440 m ss well with a horizontal reach of 2000 m from the vertical.
The inhibited water-based fluid muds (glycol, PHPA and KCl polymer) and lowtoxicity, oil-based drilling muds to be used for the Terra Nova Development are of
5-16
relatively low toxicity (Addy et al., 1984; GESAMP, 1993; Hinwood et al., 1994). The
96-h LC50 (concentration of a compound that kills 50 percent of the organisms after 96
hours exposure) for a variety of fish and invertebrates is in the 2000 to 100 000+ ppm
range as shown in Table 5.3-3.
Table 5.3-3
Toxicity of Drilling Muds
Mud Type
1
96-h LC50
Reference
Low-toxicity oil
2000 - > 90 000
GESAMP, 1993
Glycol
6300 - 9500
ANCO Product Sheet
Gel and seawater
~100 000
Thomas et al., 1984
PHPA polymer and seawater
10 000 - 100 000+
Thomas et al., 1984
Diesel oil1
< 100 ppm
GESAMP, 1993
Not to be used at Terra Nova; included for comparative purposes only.
The characteristics and potential effects of the three mud types are discussed below.
Oil-Based Muds
Oil-based muds may be used when drilling at substrate depths greater than 1500 m.
The oil-based mud will be recovered, recycled or transferred to shore in a manner
approved by the Chief Conservation Officer, and disposed in a manner approved by
local authorities. The EPP will provide details on mud handling, storage and disposal.
The aromatic content of the base oil will be as specified in the National Energy Board,
Canada-Newfoundland Offshore Petroleum Board and Canada-Nova Scotia Offshore
Petroleum Board's Offshore Waste Treatment Guidelines, which currently call for a
maximum aromatic content of 5 percent. Cuttings also will be treated to meet the
Offshore Waste Treatment Guidelines in effect at the time of drilling; these guidelines
currently specify:
-
A maximum of oil content 15 g/100 g dry cuttings averaged over a 48-hour
period
5-17
-
Measurement of oil concentrations in solids every 12 hours using specified
methods
-
Calculation of a rolling 48-hour average concentration
-
Reporting of oil concentrations 30 g/100 g or greater within 24 hours to the
Chief Conservation Officer
After treatment to reduce oil content, the cuttings will then be discharged from the
drilling rig at a depth of at least 10 m below the surface. Most cuttings will rapidly fall
to the bottom because cuttings mixed with oil adhere to each other, inhibiting
dispersion. As the drilling rig will be positioned over each well, cuttings will be
discharged at the various well locations within the development area.
Oil content of the cuttings discharged from C-09 and E-79 exploratory wells was about
12 to 18 percent on a dry weight basis. Drilling at E-79 at substrate depths greater than
1200 m generated about 127 to 191 m3 of cuttings per well (wet volume; about 114 to
172 m3 dry volume). Thus, about 21 m3 of oil were released with the cuttings.
Production wells, which will be partly drilled with oil-based muds, could release on
average about 238 m3 of cuttings, containing a maximum of 36 m3 of low-toxicity oil.
Cuttings discharged from the drilling of all 27 new wells in the Graben and East Flank
will contain about 972 m3 of oil, which will be released over an approximate 11-year
drilling period. The Far East may discharge another 432 m3 if 12 wells are developed
there.
Much of the information on effects of oil-based muds and cuttings available at the time
of the Hibernia EIS (Mobil 1985) was collected in the North Sea, where many wells
were drilled from single stationary platforms and the relatively more toxic diesel-based
muds were used. In the North Sea, cuttings from the drilling of multiple wells with
low-toxicity oil-based muds formed a plume of debris on the bottom with
concentrations of oil highest within 250 m of the platform (Addy et al., 1984).
Concentrations of oil up to 13 times background levels could be detected at distances
of up to 750 m downstream of the platform and at shorter distances in other directions
(Addy et al., 1984). Biological effects on the benthos were evident near a platform,
minimal but present at 250 to 500 m from a platform, and undetectable at 800 to 4000
m from a platform (Addy et al., 1984).
Direct smothering of the benthos was the main effect observed near drilling platforms
(Davies et al., 1984). Beyond this area, the effects were consistent with those expected
from organic enrichment of the sediment or toxicity; the two effects could not be
distinguished (Addy et al., 1984; Davies et al., 1984). The major localized effects on
the benthos were a reduction in species diversity, and elevated numbers and biomass
close to the platform (Kingston, 1992). The elevated biomass and numbers indicate a
high level of biological activity and degradation of the oil (Kingston, 1992). On
5-18
average, biological effects were noted at concentrations of 60 ppm oil in sediment with
effects on sensitive species noted at 25 ppm (GESAMP, 1993). Some benthic animals,
including those found on the Grand Banks, are sensitive to organic enrichment or
effects of oil.
Generally, organic enrichment or oil pollution eliminates or reduces the number of
sensitive species and increases the numbers of tolerant species. Elevated hydrocarbon
concentrations were detected beyond the area of biological effects (Davies et al.,
1984).
Low-toxicity oil-based drilling muds to be used at the Terra Nova Development will
have a lower percentage of aromatic compounds than the diesel-based drilling muds
commonly used before 1985 (Addy et al., 1984). Low-toxicity oil-based muds are
similar in toxicity to water-based muds (GESAMP, 1993). Low-toxicity oil-based
muds have a 96-h LC50 for most fish at concentrations of about 20 000 to greater than
90 000 ppm (GESAMP, 1993). For the most sensitive species low-toxicity oil-based
muds are toxic at 2000 to 3000 ppm. By comparison, the most sensitive species have
an LC50 of < 100 ppm for diesel-based, drilling mud (GESAMP, 1993).
Glycol Water-Based Muds
Glycol water-based muds are considered an alternative for drilling the deeper portions
of the production wells. Glycols, in general, are less toxic than oil (Hinwood et al.,
1994). The threshold for harmful effects of oil are concentrations of less than
1000 ppm (Davies et al., 1984), whereas 96-h LC50s for glycols are in the 20 000 to
100 000 ppm range (Environment Canada, 1994). EC50s for ANCO 4000 glycol-based
formulated drilling fluid is 9487 ppm for a benthic animal (Abra alba) and 6303 ppm
for a marine algae (ANCO product sheet).
Glycols are not volatile and do not evaporate from surface waters. Photo-oxidation is a
minor fate of glycols in water. Di-ethylene glycol hydrolyzes and has a half-life of less
than 25 days in water. In fresh water, aerobic biodegradation by bacteria is the most
important fate process for glycols. The half-life for glycols in fresh water is between 2
and 20 days. However, in fresh water, the process is temperature-dependent, and little
biodegradation occurs at temperatures of 8°C or less. Hydrocarbons are biodegradable
in cold temperate marine waters (Minas and Gunkel, 1995); a slow biodegradation of
glycols could occur.
Glycols, unlike oil, readily dissolve in water. Most of the glycol associated with
cuttings would dissolve while settling through the water column or soon after settling
on the bottom. As the other components of glycol-based mud are similar to those of
water-based mud, the impacts of glycol-based mud and cuttings would be essentially
the same as those of water-based muds.
5-19
Inhibited Water-Based Muds
The upper 1500 m of each well will be drilled using gel and water and PHPA polymer
and seawater-based muds. The spent mud will be discharged at a depth below 10 m. A
well drilled at an angle with a reach of 2000 m from the vertical will release about 625
m3 of the gel and seawater and 900 m3 of the PHPA polymer and seawater muds to the
seabed (Table 5.3-2).
Gel and water-based muds are relatively nontoxic (Table 5.3-4). The mud components
are mixed with water before use, resulting in concentrations of approximately the 96-h
LC50 values for rainbow trout. This type of water-based mud has 96-h LC50s for fish
and invertebrates that are in the 100 000 ppm (10 percent) range (Thomas et al., 1984).
Table 5.3.4
Concentration and Toxicity of Components in
Gel and Water-Based Drilling Muds
Concentration
g/L
Amount per Well
(x 103 t)
Toxicity1
(g/L)
Bentonite
57-114
36-71
50
Caustic soda
0.7-1.4
0.4-0.9
0.1
Soda ash
0.7-1.4
0.4-0.9
--
Barite
228-342
143-214
100
Mud Component
1
96 h LC50 for rainbow trout (from Mobil, 1985).
Components of PHPA polymer and water-based muds are shown in Table 5.3-5.
Typical 96 h LC50 values for fish and invertebrates exposed to polymer-based muds
range from 10 000 ppm to hundreds of thousands ppm (Thomas et al., 1984). They are
slightly more toxic than the gel and seawater-based muds. The PHPA polymer and
water-based muds will be diluted to nontoxic levels close to the discharge point.
Heavy Metal Contamination
Both the drilling muds and the cuttings can contain heavy metals. The kinds and
quantities of metals can be quite variable and depend on the composition of the mud
and the cuttings. In the Gulf of Mexico, contamination by heavy metals was
5-20
Table 5.3-5
Typical Concentration of Components in PHPA
Polymer and Water-Based Muds
Trade
Name
Function
Chemical
Concentration
(g/L)
Total Amount
Per Well
(x 10-3t)
Barium sulphate
As required
As required
Barite
Increase hard
density
Various
Primary
viscosities
Organic
viscosifier
2.9
2.6
Caustic soda
pH control
NaOH
4.3
3.9
Soda ash
Treatout Ca ion
contamination
Sodium
carbonate
0.7
0.6
Sodium
bicarbonate
Treatout cement
contamination
Sodium
bicarbonate
As required
As required
Various
Primary fluid loss
reducer
Sodium
polyacrylate
5.7
5.1
Various
Secondary fluid
loss reducer
(nonviscosifying)
Polyanionic
cellulose
5.7
5.1
Sodium
sulphite
Biocide
Sodium sulphite
0.7
0.6
PHPA
Shale incapsulator
Partially
hydrolized
Poly acrylamide
11.4
10.3
limited to an area within 100 m of the production platforms; however, some of the
trace elements were believed to have been deposited by produced water rather than by
cuttings (Wheeler, et al. 1980). The field had been in operation for 20 years at the time
of sampling.
High concentrations of heavy metals are toxic, bioaccumulate, can pass through the
food chain, and harm marine biota (Forstner and Wittmann, 1983). The uptake of
metals by marine animals depends on the bioavailability of the metals; therefore, total
concentrations do not always reflect the availability of metals to animals (Forstner and
Wittmann, 1983). Metals bioavailability is generally low when the metals are absorbed
onto particles or complexed with organic molecules (Forstner and Wittmann, 1983;
Leland and Kuwabara, 1985; Hinwood et al., 1994), as generally happens in natural
waters. Drilling activities are unlikely to produce concentrations of heavy metals that
5-21
are harmful to marine animals (Neff et al., 1980 in Hinwood et al., 1994).
Zone of Influence
The zone of influence can be defined by chemical or biological "markers", or both. The
boundary of the zone is defined by the points at which the measured variables reach
background levels. Chemical markers can include metal or hydrocarbon concentrations
in sediments. The measurement of contaminants in sediments is difficult and results can
vary widely depending upon the sampling and analysis techniques used and other
factors. Many authors refer to the chemically-defined zone of influence as the
"contaminated area". The term contaminated in the present context means simply that
measured values are above some previously determined background level. The
chemical contamination (i.e. elevated levels) may not have any biological significance
unless the contaminants are bioavailable and at high enough levels to impact natural
processes.
A zone of influence as determined by biological markers is normally smaller than one
determined by chemical ones. Biological markers can include changes in species
composition, biomass, contaminant body burdens, histology, genetics and enzyme
induction. A zone of influence determined by biological effects monitoring is the one
that is most relevant in determining environmental impact.
In the North Sea, cuttings contaminated with low-toxicity oil-based muds from five
wells were discharged at one location and affected benthos only to a limited extent.
Biological effects were noted only in the immediate vicinity of the platform and were
comparatively weak at 250 m and undetectable 750 m from the platform. Aliphatic
hydrocarbon distributions for one well and five wells together are shown in Figure 5.31 (Addy et al., 1984).
At the Venture Field off Sable Island, concentrations of low-toxicity oil in sediments
were three to four orders of magnitude higher than background levels within 200 m of
the drilling site, and dropped to 10 times background levels within 200 to 1500 m of
the drilling site (Yunker and Drinnan, 1987). Note that this area is shallow, sandy, and
the sediments are very mobile. As such, these observations may not be relevant to
Terra Nova.
Data from approximately 380 single wells sites in the North Sea show that sediments
are contaminated along the axis of the prevailing current, but to distances about 25
percent or less of those at multi-well sites (GESAMP, 1993). The zone of biological
effects would be about 250 to 500 m from a single drilling site (GESAMP, 1993).
Within this zone, benthic animals were affected only in the immediate vicinity of the
platform and minimally affected at 250 m. Effects were undetectable at 750 m from the
platform (Addy et al., 1984). It is possible that minor biological effects from single
wells could be noted up to 1 km from a single well and oil could be present at distances
5-22
N
900
800
700
600
500
400
300
200
100
0
Platform
50
250
750
1500
3000
Distance (m)
3000
1500
750
250
50
5 Wells
1 Well
Distance (m)
of 1 to 8 km from the well, depending on prevailing currents (GESAMP, 1993).
However, as discussed below, in practice, effects may be undetectable.
Recent investigations in the Norwegian sector of the North Sea show the zone of
effects could be much larger than those described above. Olsgard and Gray (1995)
have shown that the zone of influence increases with time and that after 6 to 9 years
effects were noted up to 6 km away from the platform. The expansion of affected areas
continued after cessation of discharge of cuttings contaminated with oil-based muds.
The area of effects was only slightly smaller than the contaminated area. An analysis of
benthos at 10 platforms showed that the zone of effects was not directly related to the
amount of oil discharged with cuttings. For 10 platforms, the zone of effects ranged
from < 1 to 6 km. The quantities of oil discharged at seven of the 10 platforms were 5
to 20 times that which will be discharged from the Terra Nova field. Unfortunately,
Olsgard and Gray (1995) do not identify the type of oil-based mud used nor do they
identify the kinds of hydrocarbons found in the sediments. Relatively large volumes of
diesel-based mud have been used in the North Sea. The high toxicity of diesel and low
biodegradability of oil below the surface could explain the large and expanding zones
of influence around the platforms. However, because the type of oil used was nowhere
identified in the study, its applicability to Terra Nova is questionable.
Duration of Effects and Recovery of the Benthos
In areas of the North Sea, benthos on sediments initially contaminated with up to 4300
ppm of diesel-based mud from multiple wells, partially recovered one to two years after
drilling (Mair et al., 1987; GESAMP, 1993). Opportunistic species colonized the
substrates within a few months (Kingston, 1992). North Sea data indicate biological
effects and contamination from single wells may not last beyond one season of winter
storms (GESAMP, 1993).
Low-toxicity oil-based muds are biodegradable under aerobic conditions, but not under
anaerobic conditions (Steber et al., 1995). In the upper centimetre of sediment, oil will
biodegrade in approximately 150 days (Petersen et al., 1991), but oil within a pile of
cuttings or at depths greater than 1 cm remains unchanged for long periods of time
(Yunker and Drinnan 1987; Petersen et al., 1991; Steber et al., 1995). At the Terra
Nova site, two or three wells may be drilled within a cluster in any one year, and would
be close enough for their cuttings piles to overlap. For one well the cuttings pile could
be a up to 10 cm thick, decreasing to 5 cm within 30 m, and 1 cm within 50 to 100 m
of the release site, if Scotian Shelf observations can be applied to Terra Nova (Yunker
and Drinnan, 1987). For two or three wells drilled close to each other, the pile could be
deeper; however, outside the immediate vicinity of the drill site, the cuttings would be
exposed to aerobic conditions that facilitate oil biodegradation.
5-24
Yunker and Drinnan (1987) found decreasing concentrations of low-toxicity oil with
increasing core depth, suggesting that at least part of the oil floated to the top of the
cuttings pile. They found little or no oil biodegradation below the sediment surface.
Wave action and weathering significantly reduced hydrocarbon content in the
sediments near the drill site within three months.
Dustan et al. (1991) examined seven individual exploratory drill sites off the Florida
Keys. They found no cuttings piles near two exploration wells drilled 30 years
previously to over 2000 m in 20 m of water; however, there were pieces of cuttings in
the sediments. Coverage by living organisms of the bottom and an abandoned pipe, the
only visible sign of drilling activity, was the same and biological communities appeared
typical. At another site, where a well had been drilled seven years previously to 3464 m
in 53 m of water, signs of drilling activity were limited to an area less than 50 m in
diameter. In this area, the biological community appeared unaffected and cuttings and
mud were not visible. At an exploration well drilled two years previously in 70 m of
water to 3200 m, Dustan et al. (1991) found a mound 10 to 15 m in diameter and 2 m
high that consisted mainly of casing cement with some cuttings. The expected cuttings
pile could not be found. Benthic communities were disturbed within a radius of 25 m
around the mound. All the debris created artificial reefs, which attracted fish and
provided substrate for epifaunal animals. Similarly, examination of three exploratory
well sites drilled with water-based muds in the Hibernia field revealed only slight
accumulations of drilling materials (NORDCO, 1983). Dustan et al. (1991) conclude
that with modern technology and anti-dumping regulations, exploratory wells could
probably be drilled without leaving a trace. They caution that these results cannot be
extrapolated to the effects of production well groups.
At Terra Nova, a maximum of six closely spaced wells will be drilled over two or more
years at each of the manifolds. This is not similar to production drilling at Hibernia or
the North Sea, where many wells are drilled from a single platform and all cuttings are
discharged in the same place. At each of the manifolds, the zone of influence and
effects of drilling will be smaller than that around fixed production platforms and
slightly larger than at single well sites.
Effects on Fish
Because only two or three wells will be drilled per site in any one year, low-toxicity
oil-based drilling mud will be used, and discharges will be strictly controlled,
concentrations of any oil released from cuttings are unlikely to be high enough to cause
fish mortality. Bioaccumulation of oil in tissue and subsequent tainting of fish flesh has
been identified as a potential problem associated with the use of oil-based muds
(GESAMP, 1993). Tainting imparts an oily taste to fish, rendering them unpalatable
and unmarketable. Tainting is usually associated with lipid-soluble hydrocarbons in the
C22-C30 range, with a maximum at C26 (Tidmarsh et al., 1985). Phenols,
dibenzothiophenes, naphalenic acids, mercaptans, tetradecanes and methylated
5-25
naphalenes may be the principal components causing tainting. As low-toxicity drilling
muds contain highly refined paraffinic and naphthenic oils, there is a small potential for
tainting by these components.
Flatfish near offshore platforms may become tainted if hydrocarbon concentrations in
sediments exceed 200 ppm dry weight (S.L. Ross and LFA, 1993). Although flatfish
can bioaccumulate hydrocarbons from drill cuttings in their livers, it is unclear whether
they would accumulate enough hydrocarbons in muscle tissue to cause tainting (S.L.
Ross and LFA, 1993). The authors speculate that cuttings discharged from platforms in
deep water would lose the lighter fractions of oil, known to cause tainting, while falling
through the water column.
Impacts
Much of the literature on the impacts of drilling muds may not be directly applicable to
Terra Nova because low-toxicity muds will be used and because the discharges are
subject to more stringent regulation than in the past.
In the Terra Nova Development, low-toxicity, oil-based drilling muds will be used,
recovered and recycled. The 48-hour average concentration of oil in released cuttings
will be 15 g/100 g dry cuttings. This amount is likely considerably lower than that
released by the fields discussed in previous sections. Some of the oil on discharged
cuttings will dissolve while the cuttings pass though the water column. Oil that remains
adhered to cuttings will probably aerobically degrade. Because only small numbers of
wells will be drilled per year in the development area, the concentration of oil in
sediments will remain low and will affect benthos in only a very limited area.
Glycol-based muds will also be recovered and recycled but spent mud will be released
at the site. The glycol that adheres to cuttings will quickly disperse. The components of
water-based muds are relatively nontoxic. The effects of the discharge of muds and
cuttings are unlikely to persist beyond one storm season.
Impacts on benthic animals could be minor to major and medium-term within a few
hundred metres of the drilling sites and minor and short-term within the development
area. Overall, impacts on the benthos in the development area are likely to be minor
and short-term with small areas experiencing minor to major impacts on benthic
animals. A monitoring program will be implemented to determine the extent and
duration of contamination of the sediments and the extent and duration of effects on
benthic animals.
Only a few wells will be drilled each year. Drilling will likely only take place for part of
the year. Impacts on fish and the fishery would be negligible. Fish that may become
tainted are likely to be those that are attracted to the subsea structures and reside in the
safety zone. Highly mobile fish are unlikely to remain near oiled cuttings long enough
to become tainted. The Environmental Effects Monitoring Program (EEM) will track
5-26
fish tainting by all sources of hydrocarbons, including oil-based drilling muds that could
be released during development and production. If tainted fish are found, the source of
tainting will be investigated and further mitigation measures implemented.
Cuttings, and the oil or glycol discharged with them will have negligible impacts on
birds or marine mammals. Cuttings fall to the seafloor; therefore, there is little chance
of interaction. Effects on plankton are likely to be transitory and sublethal in only a
small area; therefore, impacts will be negligible. Small amounts of oil could enter the
water and turbidity will increase in the immediate vicinity of the discharge site. Impacts
on water quality will be minor, sublocal and short-term.
Mitigation measures for the Terra Nova Development include the use of low-toxicity,
oil-based drilling muds, inhibited water-based muds (glycol), recovery and recycling of
oil, and treating oil-contaminated cuttings to meet the Offshore Waste Treatment
Guidelines.
5.3.6
Discharge of Other Fluids and Solids
In addition to drilling muds and cuttings, many other materials and liquids will be used
on the Terra Nova Development, some of which will be released into the environment.
Other Fluids Associated With Drilling
Other fluids associated with the drilling and completion of wells include completion,
packer and workover fluids; cement slurry; and blowout preventer (BOP) fluid.
Completion and workover fluids are pumped into wells after drilling to prepare them
for production, and are similar in composition. About 200 m3 of fluids containing
corrosion inhibitors, biocide and about 0.7 tons of calcium chloride are used per well.
After completion and workover operations, wells are cleaned and the fluids are
pumped into a tank. If the used fluids are highly acidic, the acid is neutralized before
discharge. The fluids are also processed in an oil-water separator to reduce the level of
hydrocarbons to below the guideline level of 40 mg/L specified by the Offshore Waste
Treatment Guidelines.
Effluents are usually diluted 1000-fold within 50 m of the discharge point (Sommerville
et al., 1987). Sommerville et al. (1987) estimated dispersion based on numerical
modelling and laboratory experiments using a 1:120 scale model to simulate flume
dispersion and verified results with actual field measurements of the dispersion of
rhodamine B. Concentration of discharged fluid in seawater beyond this distance will
be 0.1 percent, the concentration of oil in water less than 40 μg/L and concentrations
of aromatic hydrocarbons about 7 to 13 μg/L. The small amounts of these completion,
5-27
packer and workover fluids would result in negligible impacts on marine biota.
Based on experience with the exploratory wells, about 33 t (26.4 m 3) of excess cement
will be released to the seabed per well, and will kill some benthos locally. If the cement
remains in a pile, it will act as an artificial reef, be colonized by epifaunal animals and
attract fish. The impacts (either negative or positive) of the cement would be negligible.
Blowout preventer fluid is used in the blowout preventer stacks during drilling. The
fluids are usually glycol-water mixes, but oil can also be used. Glycol-water mixes will
be used at Terra Nova and will have a low toxicity. Periodic testing of the blowout
preventer is required by regulations. The approximate 1 m3 of the fluid released per test
will be quickly dispersed. Periodic releases of this small amount of glycol will have
negligible impact on marine biota.
Well treatment fluids recovered from operations will be treated to reduce oil
concentrations to levels specified by the Offshore Waste Treatment Guidelines
(maximum of 40 mg/L). Time series of raw and averaged data from analysis of treated
and discharged fluids will be submitted to the Chief Conservation Officer on an
approved schedule.
Well treatment fluids containing diesel oil or oil with a high aromatic content will not
be used unless recovered and recycled, or transferred to shore. Strongly acidic fluids
will be neutralized before discharge. A chemical management plan will be developed
with the chemical suppliers and submitted to the C-NOPB as part of the EPP.
Small volumes of treated effluent will affect water quality in the immediate vicinity of
the discharge; these impacts will be minor, sublocal and short-term. Any major impact
on plankton is of concern because it forms the base of food chains leading to the VECs.
Effects on plankton of the release of other drilling fluids will likely be transitory and
sublethal because small volumes will be released and toxicity levels will be low. This
will result in negligible impacts.
Direct impacts on fish from the release of other drilling fluids are unlikely. A major
concern related to the release of oily water is the potential to taint fish. As described
earlier, fish tainting will be monitored and all sources of hydrocarbons that could be
released during field development and production will be considered. If tainted fish are
found, the source(s) will be investigated and further mitigation measures will be
implemented.
Treated oily-water discharge from other drilling fluids could affect seabirds and marine
mammals. Small amounts of oil (a few millilitres) on the plumage of a seabird can kill it
within a few days (Peakall et al., 1987). Seabirds may survive external oiling with 0.1
5-28
ml of oil, but have less reproductive success (Butler et al., 1988). In the Terra Nova
Development, oily water will be treated before discharge to reduce oil concentrations
in the discharge to no more than 40 mg/L. These discharges would be diluted 1000fold within 50 m downstream of the discharge (Sommerville et al., 1987). In addition,
the oily water will be discharged below the surface. Thus, it is very unlikely that birds
will be impacted.
The marine mammals of the Newfoundland region rely on blubber rather than fur for
insulation. They can withstand some degree of external oiling with no serious damage
(see Englehardt, 1985; Richardson et al., 1989; and Geraci and St. Aubin, 1990 for
reviews). Eye irritation from surface oil may be the only surface effect of exposure to
small concentrations of oil (Geraci and Smith, 1976). However, a marine mammal
would have to be in the immediate vicinity of the discharge for some period to
experience this type of effect. Eye irritation is transitory and disappears after animals
move to clean water.
Releases of treated oily water are likely to have negligible impacts on birds and marine
mammals.
Deck Drainage
Deck drainage, other than that of the supply boats will be isolated from the main
sources of oily waste. For example, the deck drainage system will not collect
discharges from drip pans under machinery. Wastes and fluids from drip pans will be
recovered and recycled, or transferred to shore for disposal in an approved manner.
A closed drain system will collect leakage and drainage of hydrocarbons from mudhandling operations. An open water drain will collect drainage from machinery spaces
and working areas. Liquids will pass through an oily-water separator and the oily
effluent from the separator will be collected for disposal. The clear water will be
discharged over the side. Deck drainage will be processed to meet the Offshore Waste
Treatment Guidelines, which currently call for no more oil than 15 mg /L of discharged
water. Concentrations greater than this are considered to exceed normal operating
practice and must be reported within 24 hours to the Chief Conservation Officer.
Impacts on water quality from treated deck drainage will be minor, sublocal and short
term.
Deck drainage is unlikely to have any direct effects on fish. As discussed earlier, fish
tainting will be monitored.
Releases of treated oily water are likely to have negligible impacts on birds and marine
mammals.
5-29
Hydrostatic Testing Fluids
Subsea flowlines will be hydrostatically tested to ensure their integrity. Normally, this is
only done once. The test fluid will be seawater with additives to prevent corrosion and
microbial growth in the lines. Hydrostatic testing fluids typically include:
-
Oxygen scavenger (sodium or ammonium bisulphite at 50 to 100 mg/L)
Biocide
Corrosion inhibitor (amines or imidazolines at 100 to 500 mg/L)
Glycol
Dye
After testing, the test fluid in the flowlines will be discharged to the sea and any unused
fluid will be shipped to shore for disposal. The volume discharge will equal the volume
of the flowlines.
Using the current subsea layout (see Figure 1.1-7), the volume of fluids would be
approximately 4000 m3. Ammonium bisulphite has a 96-h LC50 for mysids of 750 000
ppm; the biocides that control bacterial and fungal growth have an LC50 of 450 000
ppm; and amine oil has an LC50 of 780 000 (Hinwood et al., 1994). Clorination is
another possible biocide. New biocides, corrosion inhibitors and oxygen scavengers
with reportedly low toxicities will be investigated. The toxicity of the testing fluid will
depend on the kinds and quantities of chemicals used in its formulation. In addition,
when released, the test fluids are immediately diluted; if this occurs rapidly, none of its
component chemicals are hazardous to marine life (Black et al. 1994). Impacts on
marine biota would be negligible. Impacts on water quality will be negligible to minor,
sublocal and short term.
Cooling Water
Development drilling will require about 10 000 m3/d of seawater, most of which will be
used as cooling water (estimate in Mobil, 1985). Cooling water will be chlorinated to a
level of 1 or 2 mg chlorine. This water will be discharged at temperatures of about
30°C above ambient. Small numbers of zooplankton and fish larvae would be entrained
in the intakes and some would be killed by the heated effluent. Impacts will be
negligible because the volume of entrainment will be low and the area of thermal effects
will be small.
As specified in the Offshore Waste Treatment Guidelines, any intent to use biocides
other than chlorine will be submitted to the Chief Conservation Officer for approval
before use.
5-30
Sanitary and Domestic Waste
Grey water from showers, sinks and washers will be discharged without treatment.
Sewage and other domestic effluents from the drill rigs will be treated to meet the
EPS (1990) and the Offshore Waste Treatment Guidelines for operations in offshore
deep waters. Domestic wastes will be macerated to a particle size of 6 mm or smaller
before discharge. Sanitary wastes will be treated before disposal. Mobil (1985)
estimated 11 m3/d of sewage and 21 m3/d domestic waste per rig.
Organic matter will be quickly dispersed and degraded by bacteria. The impacts on
receiving waters of this small amount of organic matter and nutrients will be negligible.
Garbage and Other Waste
Sludges from oil-water separators, spent lubricants, all plastic material, glass and metal
wastes will be transferred to shore for appropriate handling, including reuse and
recycling where possible. Garbage and other wastes will not come into contact with
marine biota.
Small Spills
Fuel, drilling muds and other chemicals will be transported by supply vessel from the
onshore facilities to the drilling rig. Small amounts of these materials could be spilled
during transit, during transfer to the drilling rig or while in storage on the drilling rigs.
Spillage of concentrated chemicals or drilling muds would cause a greater impact than
spillage of diluted chemicals.
All fuel, chemicals and wastes will be handled in a manner that minimizes or eliminates
routine spillage and accidents. The EPP will provide details of safe fuel, chemical,
waste handling and storage procedures. Workers will be trained in these procedures.
The EPP will also contain detailed measures for preparing for and responding to spills,
including the use of cleanup equipment, training of personnel and identification of
personnel to direct cleanup efforts, lines of communications and organizations that
could assist cleanup operations. All cleanup measures and procedures will be specified
in the EPP. More detailed information on spills is included in Section 5.7.
5-31
5.3.7
During development drilling, there will be four sources of atmospheric emissions:
1.
Burning of well fluids during production tests (burner boom emissions)
2.
Engine, generator and heating exhausts from the drill rigs, supply vessels and
multipurpose vessels
3.
Mud, degassing and other mudroom exhausts
4.
Fugitive emissions
Production testing of the wells is critical to the determination of the initial reservoir
conditions. On average, two individual reservoir units will be tested per well. Each test
will produce less than 1000 m3 of mixed hydrocarbon liquids per unit (J. Katay,
Petro-Canada, pers. comm.). The hydrocarbons produced by the tests and some mud
will be burned with burner booms. The fires from these booms will emit relatively large
amounts of carbonaceous particles, and a visible fire and smoke plume. In addition to
the smoke and particulate matter, emissions will also contain unburned hydrocarbons,
and traces of nitrous oxides, carbon monoxide and sulphur dioxide.
Exhaust gases will also be emitted from generators, engines and heaters on board the
drill rigs and the support vessels. Exhaust gases will contain traces of nitrous oxides,
carbon monoxide and sulphur dioxide and burned hydrocarbons. Fuel (normally diesel)
and equipment will be carefully selected and maintained to optimize combustion
efficiency. It is estimated that engine exhausts from drilling and workover will be about
5 x 106 m3/d per rig (Mobil, 1985).
Small amounts of gas will also be vented through flame arresters on storage tanks on
the drill rig. In addition, there will be some small and unquantifiable amounts of fugitive
emissions such as hydrocarbon losses at valves and seals, and particulate matter from
cement and chemical powders.
In general, the impacts of atmospheric emissions will be negligible because small
amounts will be released and they will rapidly disperse to undetectable levels.
Emissions are discussed in more detail in Section 5.4.
5.3.8
Each drilling rig will be supported by several vessels of up to 12 000 HP. These will be
supply vessels commonly used to support offshore oil field development. They will
transport pipe, liners, casing cement, drilling muds, chemicals, fresh water, food and all
5-32
the other material necessary for drilling. One vessel will remain near each rig on
standby. This type of vessel will be used to redirect icebergs that pose a threat to the
drilling rig(s).
Discharges from the vessels are discussed in Section 5.3.6. All discharges from vessels,
including sanitary and domestic waste and bilge water, will be treated as described
above. Overall, impacts of vessel discharges would be negligible. Potential impacts
related to noise are discussed in Section 5.3.10.
5.3.9
Helicopters will be used to transport personnel and materials to and from the work site.
The helicopters will make an average of one trip per day to each drilling rig.
Potential impacts of helicopters on the marine environment are mainly related to noise,
which is discussed in the following subsection.
5.3.10
Effects of Noise
Marine animals, particularly mammals, depend on the underwater acoustic
environment. Thus, potential negative effects caused by human-made noise within the
marine environment is a concern. The reactions of marine animals to underwater noise
can be variable, depending on the characteristics of the noise source, the species
involved and the behaviour of the animal at the time of disturbance. Because
underwater noise propagates for long distances, the potential zone of influence around
a particular vessel can be many tens of kilometres in radius. The zone of influence of
underwater noise at Terra Nova includes zones around the development area, shipping
routes between the supply base and the drilling rig or FPF, and the helicopter flight
routes between St. John's Airport and the Terra Nova Field.
This subsection presents information on the reactions of marine animals to noises of the
kind associated with the Terra Nova Development. The subject matter is complicated
and reactions of marine animals to underwater noise are extremely variable. Thus,
much background material must be evaluated and presented to justify impact
predictions.
The sea is a naturally noisy environment. Natural ambient noise is often related to sea
state. Ambient noise tends to increase with increasing wind speed and wave height
(Table 5.3-6). In many areas, shipping is a major contributor to ambient noise.
5-33
Table 5.3-6
Natural and Development-Related Underwater Noise Levels
Source
Broadband
Noise Level
(dB rel 1μ
μPa1)
Source Levels at Dominant
Frequencies
Hz
Ambient Noise
Wind < 1.8 km/h
Wind 20.4 to 29.7 km/h
Wind 40.8 to 50.0 km/h
Heavy shipping
Light shipping
Remote shipping
-
Noise Level
dB rel 1μ
μPa1
100
100
100
50
50
50
60
97
102
105
86
81
TNT explosion
0.5 kg at 60 m
267
21
-
Seismic airguns
216-259
50-100
-
Depth sounder
180+
12,000+
-
Semisubmersible drilling rig (working)
154
7-14, 29, 70
-
Drillship (working in 20 m water depth)
174-185
to 600
-
Supply boats
with propeller nozzles
with bow thrusters operating
-10
+11
-
-
Large Tanker
186
100+, 125
177
Supertanker
190->205
70
175
Super Puma Helicopter at 300 m above sea level
Received level at sea surface
Received level at 3 to 18 m depth
-
20, 50
-
105-110
65-70
Source: Richardson et al. (1995)
1
3rd octave band level
Drilling Rigs
Generally, semisubmersible drill rigs produce less noise than do drillships (Richardson
et al., 1995; Table 5.3-6). Noise from a semisubmersible drilling rig working in 114 m
water depth in the Bering Sea did not exceed ambient noise levels beyond a range of 1
km (Greene 1986). Support boats were also present at the time these measurements
were taken. In contrast, noise produced by working drillships declined to ambient
5-34
levels only at distances beyond 10 km from the source (Richardson et al., 1995).
Marine Mammals
Development activities may produce intermittent low-frequency sounds. Specific
information about the reactions of some baleen whales to low-frequency noise pulses
has been obtained by observing their responses to pulses from airguns and other
non-explosive methods of marine seismic exploration. Humpback, gray and bowhead
whales all seem quite tolerant of noise pulses from marine seismic exploration (Malme
et al., 1984, 1985, 1988; Richardson et al., 1986; Ljungblad et al., 1988; Richardson
and Malme, 1993). The same may be true of fin and blue whales (Ljungblad et al.,
1982; McDonald et al., 1993). These species usually continue their normal activities
when exposed to pulses with peak received pressures as high as 150 to 160 dB
(relative to 1 μPa), and sometimes even higher. Such levels are 50 to 60 dB or more
above typical 1/3-octave ambient noise levels. However, subtle behavioral effects are
suspected at least some of the time at lower received levels, at least in bowheads and
possibly gray whales.
When exposed to sounds from a drillship, some beluga whales altered course to swim
around the source, increased swimming speed, or reversed direction of travel (Stewart
et al., 1982). Reactions to semisubmersible drillship noise were less severe than were
reactions to motorboats with outboards. Dolphins and other toothed whales show
considerable tolerance of drill rigs and their support vessels.
Bowhead whales did react to drillship noises within 4 to 8 km of a drillship when the
received levels were 20 dB above ambient or about 118 dB (relative to 1μPa) (Greene
1985, 1987a; Richardson et al., 1985a,c, 1990). Reaction was greater at the onset of
the sound (Richardson et al., 1995). Thus, bowhead whales migrating in the Beaufort
Sea avoided an area with a radius of 10 km around a drillship where received noise
levels were 115 dB (relative to 1μPa) (Richardson et al., 1990). Some individual
whales are less responsive and may become habituated sufficiently to be seen within 4
to 8 km of a drillship (Richardson et al., 1985a,c, 1990).
Sound attenuates less rapidly in the shallow Beaufort Sea where these experiments
were conducted than in temperate waters of greater depth. Off California, the reaction
zone (120 dB (relative to 1μPa)) around a semisubmersible drill rig was much less than
1 km for grey whales (Malme et al., 1983, 1984). Humpback whales showed no clear
avoidance response to received drillship broadband noises of 116 dB (relative to 1μPa)
(Malme et al., 1985). Baleen whales may show behavioral changes to received
broadband drillship noises of 120 dB (relative to 1μPa) or greater. Broadband source
levels produced by a working semisubmersible drilling rig may be about 154 dB
(relative to 1μPa) at 1 m (Table 5.3-4). Assuming spherical spreading, received levels
at 100 m distance would be about 114 dB (relative to 1μPa). Thus, behavioral
5-35
reactions could be limited to a very small area around the drilling rig.
Impacts of drilling operations on whales may be negligible to minor, sublocal, and short
term. Although the effects of each well location would be short term, the effects of all
drilling is considered long term since drilling in the fairly restricted field area will
continue for 11 years or more. However, because the drilling activities will continue for
several years, habituation may occur, thereby reducing impacts to negligible.
Semisubmersible drilling rigs are quieter than drillships, and this type of MODU will
likely be used in the Terra Nova Field. Mitigation is not warranted because predicted
impacts are small.
Fish
Seismic exploration with airguns can reduce the catch per unit effort in some fisheries
and the abundance or availability of fish (Dalen and Raknes, 1985; Dalen and Knutsen,
1986; Skalski et al., 1992; Engas et al., 1993). Fish are not necessarily driven from the
area by a loud sound, but they may sometimes change their behaviour and activity
patterns.
Chapman and Hawkins (1969) and Pearson et al. (1992) conducted experiments to
determine the effects of strong noise pulses on fish. They used airguns with source
levels of 220 to 223 dB (relative to 1μPa). They noted startle responses at received
levels of 200 to 205 dB (relative to 1μPa), alarm responses at 177 to 199 dB, an
overall threshold for the above behavioral response at about 180 dB, and an
extrapolated threshold of about 161 dB for subtle changes in the behaviour. In both
tests, fish returned to pre-exposure behaviours within 20 to 60 minutes after exposure.
However, habituation lasts only as long as a continuous disturbance, and resumption of
the disturbing activity after a quiet period may again elicit disturbance responses from
the same fish.
Noises emitted by a semisubmersible drilling rig are much lower in magnitude, but
more continuous, than those discussed above. The fact that fish are well-known to be
attracted to offshore drilling and production platforms (see Section 5.3.2) indicates that
fish adapt well to noises associated with offshore development activities. Impacts on
fish of noise from the Terra Nova Development would probably be negligible.
Support and Supply Vessels
Broadband source levels (at 1 m) for most small ships are in the 170 to 180 dB
(relative to 1μPa) range (Richardson et al., 1995). Broadband underwater sounds from
the supply ship Robert Lemeur were 130 dB (relative to 1μPa) at a distance of 0.56 km
(Greene, 1987a). Some ships use bow thrusters to aid in manoeuvering. Broadband
underwater sounds from the Robert Lemeur were 11 dB higher when bow thrusters
were operating than when they were not (Greene 1985, 1987a). The Robert Lemeur
5-36
has nozzles around the propellers. Broadband noise levels from ships lacking nozzles or
cowlings around the propellers can be about 10 dB higher than those from ships with
the nozzles (Greene, 1987a).
Marine Mammals
Reactions of baleen whales to boat and other noises include changes in swimming
direction and speed, blow rate, and the frequency and kinds of vocalizations
(Richardson et al., 1995). Baleen whales may approach or avoid boats (Watkins,
1986). Avoidance was strongest when boats approached directly or vessel noise
changed abruptly (Watkins, 1986; Beach and Weinrich, 1989). Humpback whales
responded to boats at distances of at least 0.5 to 1 km, and avoidance and other
reactions have been noted in several areas at distances of several kilometres (Jurasz and
Jurasz, 1979; Bauer, 1986; Dean et al., 1985; Bauer and Herman, 1986). During some
activities and at some locations, humpbacks exhibit little or no reaction to boats
(Watkins, 1986).
Right whales also respond variably to boats. There may be an initial orientation away
from a boat, followed by a lack of observable reaction (Atkins and Swartz, 1989). A
slowly moving boat can approach a right whale, but an abrupt change in course or
engine speed will elicit a reaction (Goodyear, 1989; Mayo and Marx, 1989; Gaskin,
1991). When approached by a boat, right whale mothers will interpose themselves
between the vessel and calf, and will maintain a low profile (Richardson et al., 1995).
The closely related bowhead whale will begin avoiding diesel-powered boats at
distances of 4 km. They first attempt to flee and then swim perpendicular to the boat
(Richardson et al., 1985b,c; Koski and Johnson, 1987). They may be displaced by a
few kilometres when fleeing, although some bowheads may return to the area within a
day. Effects are transitory.
In summary, whales may show little reaction or gradually move away from boats
travelling slowly on a steady course. If the vessel changes course or speed, whales
likely will swim rapidly away. Avoidance is strongest when the boat travels directly
towards the whale.
Dolphins may tolerate and often approach boats of all sizes, and ride the bow and stern
waves (Shane et al., 1986). At other times, dolphin species known to be attracted to
boats will avoid them, often because of previous boat-based harassment (Richardson et
al., 1995). Other species avoid boats. Generally, small cetaceans avoid boats when they
are approached within 0.5 km to 1.5 km, with some species showing avoidance at
distances of 12 km (Richardson et al., 1995).
The potential impacts on baleen whales of individual passages by supply vessels during
field development are likely to be minor, short term, and sublocal. However, as there
will be repeated passages, the impacts from supply vessels are likely to be minor, long
5-37
term and sublocal to local. Impacts on toothed whales may be similar; that is, minor,
long term and sublocal to local. Impacts on mammals can be reduced if the boats
maintain a steady course and speed, whenever possible.
Birds
The normal offshore activities of ships are likely to have inconsequential effects on
sea-associated birds. Some species will be attracted to drill rigs and boats. Direct
effects on other species are unlikely because seabirds are highly mobile and can easily
avoid ships by flying or diving. Energy expended in these infrequent evasive
movements would be trivial and would have no effect on an individual bird's daily
energy budget.
Noise and disturbance from ships are unlikely to affect birds in the area. Birds have
adapted to ship traffic throughout the world. Some species, such as northern fulmar
and gulls, are attracted to ships and often follow them for extended periods (Wahl and
Heinemann, 1979; Brown, 1986). Thus, noise and disturbance from normal offshore
ship operations will not affect sea-associated birds in offshore waters. Impacts would
be negligible.
There is a concern that passing ships could disturb seabird colonies. Cliff-nesting
species are susceptible to panic caused by human activities. Temporary abandonment
of colonies by adult birds can increase predation by gulls and ravens of unguarded eggs
and young. Helicopter traffic is the main concern, but the ships themselves could cause
minor to moderate, local, medium-term impacts when the colonies are occupied. The
EPP will identify colonies and the timing of their use by birds. Avoidance of colonies
will lead to negligible impacts.
Fish
The noise made by fishing boats can scare some target fish. Sudden changes in noise
level can cause fish to dive or change direction. The time of year, whether the fish have
eaten recently, and the nature of the sound all determine whether the fish will react to
noise. Short, sharp sounds can startle herring. In one study, the fish changed direction
and moved away from the source, but schooling behaviour was not affected (Blaxter et
al., 1981). Schwarz and Greer (1984) studied the responses of herring within a 3.3-m
square pen to vessel sounds. The following kinds of responses were noted:
·
Avoidance - the fish moving slowly away from the sound source
·
Startle - fish flexing their bodies powerfully and then swimming at high speed
without changing direction, or shuddering with each blast (the last noted by
Pearson et al., 1992)
5-38
·
Alarm - the school packing, fleeing at high speed, diving repeatedly, and
quickly changing directions
The sounds of large vessels or accelerating small vessels mainly caused avoidance
responses among the herring. The startle response was occasionally observed.
Avoidance ended within 10 seconds of the departure of the vessel. Twenty-five percent
of the fish groups habituated to the sound of the large vessel and 75 percent of the
responsive fish groups habituated to the sound of the small boat. Chapman and
Hawkins (1969) also note that fish adjust rapidly to high sound levels.
Underwater noise from supply vessels may cause minor, short-term and sublocal
impacts on fish behaviour. These behavioural changes are expected to have negligible
impacts on fish populations and fisheries.
Helicopters and Fixed-wing Aircraft
Helicopters will be used to ferry personnel to and from the development area.
Fixed-winged aircraft will be used for ice reconnaissance.
Helicopters are quite noisy compared to fixed-wing aircraft. Source levels in air for
helicopters can be about 150 dB (relative to 1 μPa) (Richardson et al., 1995).
Sound does not transfer well between air and water. In the upper water column (3 to
18 m water depth), received noise levels depend on the altitude of the aircraft above
the water (Richardson et al., 1995), as follows:
Aircraft Altitude
(m)
Received Noise Levels in Upper Water Column
(dB (relative 1 μPa))
152
305
610
109
107
101
At angles greater than 13° from the vertical, most sound is reflected from the sea
surface. Thus, noise from aircraft is audible mainly within a 13o cone under the aircraft.
The area of potential audibility increases with increasing depth, but the sound also
attenuates with increasing water depth. Thus, a Bell 214ST was audible to a
hydrophone at 3-m depth for 38 seconds, but only for 11 seconds at 8-m depth
(Richardson et al., 1995). Some airborne sounds will enter the water column at angles
greater than 13° from the vertical when seas are rough.
5-39
Marine Mammals
Pinnipeds hauled out for pupping or moulting are very sensitive to aircraft disturbance
(Richardson et al., 1995). Fixed-wing aircraft flying at low altitudes below 60 to 120 m
and helicopters flying below 305 m, may cause panic among adult harbour seals and
mortality of young at haul-out beaches (Johnson, 1977; Bowles and Stewart, 1980;
Osborn, 1985). Not all harbour seals react in this way. Seals that have become
habituated to aircraft may show little or no reaction (M. Bigg in Johnson et al., 1989).
There are few observations of the reactions of seals in the water to aircraft. Overflights
at low altitudes may cause some animals to dive (Richardson et al., 1995).
Toothed whales show variable reactions to aircraft. Some beluga whales ignored
aircraft flying at 500 m altitude but dove for longer periods and some times swam away
when aircraft was at 150 to 200 m (Bel'kovich, 1960; Kleinenberg et al., 1964). Lone
animals sometimes dove in response to flights at 500 m. Off Alaska, some belugas
showed no reaction to airplanes or helicopters at 100 to 200 m altitude, while others
dove abruptly or swam away in response to overflights at altitudes up to 460 m
(Richardson et al., 1991). Narwhals dove in response to helicopters flying at altitudes
below 244 m and, to a lesser degree, at 305 m (Kingsley et al., 1994). Some sperm
whales showed no reaction to helicopters and airplanes flying over at altitudes of
150 m, but some dove immediately (Clarke 1956; Mullin et al., 1991). Dall's porpoise
and spinner dolphins reacted abruptly to overflights at 215 to 300 m (Withrow et al.,
1985; B. Wursig in Richardson et al., 1995).
Minke, bowhead and right whales reacted to aircraft overflights at altitudes of 150 to
300 m by diving, changing dive patterns or leaving the area (Leatherwood et al., 1982;
Watkins and Moore, 1983; Payne et al., 1983; Richardson et al., 1985b,c). Helicopter
disturbance to humpbacks is a concern off Hawaii and helicopters are prohibited from
approaching humpbacks within a slant range of 305 m (Tinney, 1988; Atkins and
Swartz, 1989; NMFS, 1987).
Low-flying helicopters and fixed-wing aircraft could cause minor, short-term, and
sublocal impacts on marine mammals in the water and minor, long-term, local impacts
on seals at terrestrial haul-out sites. Helicopters will fly at a minimum altitude of 600 m
whenever possible. Haul-out beaches used by harbour seals will be identified in the
EPP and avoided by overflying project aircraft. Aircraft will be prohibited from flying
low over wildlife for viewing by passengers. These measures will reduce impacts on
marine mammals, including hauled-out seals, to negligible.
5-40
Birds
Most sea-associated birds flush or dive in response to low-flying aircraft (e.g., Polar
Gas Project, 1977; LGL Ltd., unpubl. data). The significance of these disturbances is
probably low, if the flights are infrequent. In one of the few systematic studies of
aircraft disturbance, Ward and Sharp (1974) found that moulting sea ducks in the
Beaufort Sea showed no detectable reactions to helicopter overflights at 300 m above
sea level. Overflights at 100 m had no apparent influence on overall feeding activity or
population size, although the ducks did show short-term avoidance reactions.
Studies of other species in other situations have shown a variety of responses to
overflying aircraft (Davis and Wisely 1974; Gollop et al., 1974a,b; Schweinsburg,
1974; Koski, 1975, 1977; Barry and Spencer, 1976; Fyfe and Oldenorff, 1976; Platt
and Tull, 1977; Fletcher and Busnel, 1978; Webb, 1980). In general, these studies
support the contention that birds respond most to low-level flights and the effects of
these responses are generally transitory. Nonetheless, project helicopters will be flown
at minimum altitudes and will have routing restrictions to minimize these responses.
Of most concern are the large colonies of nesting seabirds. An aircraft flying near a
seabird colony is capable of causing a panic response by the birds, which can result in
eggs and flightless young being accidentally pushed off cliff ledges when the adults
suddenly flush, or being unguarded and thus exposed to harsh weather and predators.
Impacts would be moderate to major, local and long term.
There are no colonies on the direct flight path between St. John's and the Terra Nova
development area. Helicopters and aircraft will fly at altitudes no lower than 600 m
whenever possible and pilots will be instructed to avoid repeated overflights of
concentrations of birds and important bird habitats. Impacts on birds in open water
would be negligible. Guidelines for avoiding major seabird colonies will be based on
Nettleship (1980). These Canadian Wildlife Service guidelines recommend that aircraft
not approach closer than 8 km seaward and 3 km landward of a seabird colony from
April 1 to November 1. The EPP will document the locations of seabird colonies and
other areas where sea-associated birds congregate. Use of these mitigation measures
will ensure potential impacts on birds will be negligible.
5.3.11
A site in or around St. John's will likely serve as the onshore support base for the Terra
Nova Development. The support base will comprise a marine base, warehousing and
lay-down yards. The location of the support base will be particularly dependent on the
available infrastructure, including multi-modal transport and other operational and
economic realities. While all viable options will be considered, coordination with other
5-41
offshore operators such as Hibernia Management Development Company will be
considered. The final site will have the necessary space and facilities to service and
supply offshore facilities. The site will likely be operated by an independent contractor.
The onshore support base will have to include the following:
·
·
·
·
·
·
·
Heliport
Wharves suitable for berthing, loading and unloading all project vessels
Laydown areas for material and equipment handling
Office facilities
Potable water and drill water source
Road access
Storage tanks for diesel fuel, drilling mud, cement and other fluids required for
field development
The Terra Nova Development could require the following facilities for construction
activities during the Project Phase:
·
·
·
·
A site for the fabrication or conversion of the FPF and topsides
A facility for the construction and some pre-assembly of subsea facilities
A heliport
A supply and service base with access for supply vessels, barges and other
construction equipment
These facilities will be operated by independent contractors who will be responsible for
meeting environmental regulations. Petro-Canada will strive to ensure, through
contracting procedures, that the contractor will have all of the required environmental
approvals and capabilities. The performance of these contractors will be verified
through inspection and audit (Chapter 2, Table 2.2-1)
Exhausts from helicopter turbines, marine diesel engines, and generators on board the
supply boats and other service vehicles will be emitted to the atmosphere.
The base will be located at an existing marine service centre. Impacts of emissions from
this relatively small number of vessel and aircraft movements at the base will be
negligible.
5-42
Routine Liquid and Solid Releases
The Operator will work with the contractors to ensure that no liquids or solids will be
released directly from the shore base. Sanitary sewage will enter the existing sewage
system of the selected operations centre. Depending on the site-specific drainage
facilities, storm and apron runoff may enter the local storm sewers or the harbour
directly. Drainage may contain small amounts of fuels, hydraulic fluids, drilling mud
and other chemicals from small spills.
Garbage and Wastes
Garbage will be transferred from the rigs to the supply boats and subsequently
offloaded at the shore base in secured containers. Nontoxic waste will be trucked to an
approved landfill by a licensed operator. Both landfill and transportation company will
operate under their own environmental permits. Their performance will also be subject
to inspection and audit. The overall impact of the additional garbage from the oil field
is likely to be negligible.
Oily wastes and hazardous wastes will be brought ashore by the supply boats and
handled in a safe manner as specified in the EPP and legislation and guidelines
governing the handling of the specific materials. They will be transferred to a licensed
operator for disposal at an approved facility.
Noise, Lights, Beacons and Human Presence
Noise, lights, beacons and human presence will be typical of those associated with an
existing harbour. Impacts will be negligible.
Aircraft Traffic
Aircraft traffic associated with the project will include scheduled flights into St. John's
for personnel and equipment, seasonal ice reconnaissance flights by a fixed-wing
aircraft, and helicopter transportation from St. John's Airport to the development area.
The rotary-wing flights will be conducted by two Super Puma (or equivalent)
helicopters, and will average about one per day.
The ice reconnaissance and helicopter flights will have negligible impacts on the
existing airport area.
Vessel Traffic
When two drilling rigs are operating, there could be up to four supply-boat round trips
per week. Noise impacts on marine mammals and fish from engine and propeller noise
within the harbour will be within the normal realm of shipping activity in the area; thus,
impacts will be negligible.
5-43
Small Spills
There is some potential for accidental releases of chemicals, drilling muds and diesel
fuel during the loading, unloading and storage of materials. Accidental releases would
likely be relatively small. The most likely spills would result from losing a sling load
during loading or unloading or fuel loss during a line rupture or faulty connection.
Because such spills would be at dockside, detection, response and containment of the
spills would be rapid. The EPP will contain safe-handling procedures for minimizing
the risk of spills and detailed response measures for dealing with them.
Potential impacts of these small spills on phytoplankton and zooplankton would be
minor, short term, and sublocal. In the absence of spill countermeasures, the potential
impacts on benthos, fish, birds and possibly, seals could be minor, short term to
medium term, and sublocal. Emergency response measures would reduce impacts to
negligible or minor, short term and sublocal.
5-44
5.4
Potential interactions between production and maintenance activities and ecosystem
elements are shown in Table 5.4-1 and discussed in the following subsections.
Production and maintenance activities will be continuous throughout the 15 to 18 year
lifespan of the development. This section deals with impacts of normal production
operations and maintenance, including loading of crude oil onto tankers.
Transportation of crude oil is discussed briefly in the following section.
The FPF will be either a monohull, ice-strengthened, ship-shaped vessel with a doublesided hull and integral crude oil storage or a semisubmersible vessel with separate field
storage tankers. The FPF will contain equipment for:
-
Receiving and processing crude oil
Injecting water
Treating produced water
Compressing gas for injection
Power generation
Safety and control systems
Communications
Accommodation
Laboratory
Workshops
Laydown facility
Fuel storage
Helideck
One or more double-sided-hulled, ice-reinforced shuttle tankers up to 120 000 t
deadweight will be used to transport the crude oil from the FPF to a transshipment
facility or direct to market. The type of crude oil transfer system to be used will depend
on the type of FPF selected. If a monohull FPF is used, the offloading hose will run
directly from the FPF to the shuttle tanker. If a semisubmersible FPF is used, then
crude oil will be transferred via subsea flowline to storage or export facilities.
The FPF will be supported by two or more supply and standby vessels. On average,
there will be one helicopter round trip to the FPF per day.
5.4.1
The FPF and supply vessels will be on site during the 15 to 18 year life of the
development. There will be a drill rig in the vicinity. During this time, subsea structures
will also be present on the sea bottom.
5-45
Shore facilities
Garbage and waste
Noise
Lights and beacons
Vessel traffic
Accidents
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Helicopters
Noise
FPF
Support vessels
Helicopters
x
x
x
x
x
x
x
x
x
Other waste
Ships and boats
x
x
x
x
x
x
x
x
x
Garbage
Cooling water
Deck drainage
x
x
x
x
x
x
Underwater maintenance
Injection water
Produced water
Storage displacement water
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Fish
Fouling Pelagic
Terrestrial
Plankton Larvae Infauna Organisms Fish Groundfish Fishery Seabirds
Birds
Whales Seals
Lights and beacons
Air
Water
Quality Quality
Safety zone
Artificial reef effect
Subsea structures
Surface structures
Development Component
Ecosystem Elements
Level I Matrix: Interactions Between Operational Activities and Ecosystem Elements
Table 5.4-1
Effects on Fish
Effects of subsea structures and the artificial reef effect have already been discussed in
Section 5.3-2.
Effects of the safety zone are also discussed in Section 5.3-2.
Biofouling
Biofouling has been previously discussed in Section 5.3-2.
Effects on Benthic Animals
The effects of trawling on the benthos were discussed in Section 5.3.2. It was
concluded that trawling may have negative effects on sediments and some species such
as crabs. Thus, the presence of a safety zone around the Terra Nova Development
could have positive effects by allowing recovery of the benthos in the zone.
The impacts of structures on benthos will depend on the state of the fisheries over the
development period. If the present low levels of fishing are maintained, then the safety
zone would produce negligible impacts on benthos. On the other hand, if the fisheries
recover, then the relative effects of the safety zone on the benthos are likely to be
positive, minor, long term and local.
Overall, impacts on marine and terrestrial birds caused by the presence of structures
will be negligible, as discussed in Section 5.3-2. Potential effects on marine mammals
are mainly related to the effects of noise produced by the facilities. These are discussed
in Section 5.4.10.
5.4.2
Lights and Beacons
The FPF, supply and standby ships, and tankers will carry navigation and warning
lights. Working areas will be illuminated with floodlights. The helideck on the FPF will
be floodlit and have omnidirectional guidance lights. Impacts would be negligible, as
discussed in Section 5.3.2.
5.4.3
Maintenance of Subsea Structures
Subsea structures will require periodic inspection, cleaning to remove fouling
organisms, repairs, and maintenance of corrosion-protection devices and coatings.
Impacts of removal of fouling organisms have been discussed in Section 5.3-2.
Maintenance activities will disturb a small area of the bottom and cause negligible
5-47
impacts on benthic communities. Some resident fish may be disturbed, but impacts will
be negligible. There will be no interaction with pelagic fish or marine mammals.
Potential effects on marine mammals and fish could be caused by the associated noise.
Effects of underwater noise are discussed in Section 5.4.10.
5.4.4
Injection Water
Water will be injected into the reservoir to enhance oil recovery by maintaining
reservoir pressure. Water will be processed and pressurized for injection on the FPF.
The FPF will be designed to inject up to 38 x 103 m3 of water into the reservoir or 6.4
x 103 m3/d per well. Water will be injected at a pressure of 20.7 MPa.
The injection water will be filtered, chlorinated, and treated with oxygen scavengers
and corrosion inhibitors, as shown in Table 5.4-2. Additives used in the treatment of
the injection water will be used in minimum amounts by utilizing sophisticated metering
equipment.
Removing this amount of seawater will have a negligible impact. Some zooplankters
and fish larvae will be entrained, but impacts on populations from entrainment will be
negligible.
Injected water will eventually be discharged as produced water.
5.4.5
Produced Water
There is little water in the producing formations at Terra Nova. Therefore, most of the
produced water will be water injected to enhance recovery. Estimates of the amounts
of produced water are based on full-field waterflood. Table 5.4-3 gives the maximum
estimates of produced water during the life of the field. Volumes, in the Graben and
East Flank, will be somewhat lower if other enhanced recovery methods are used in
conjunction with waterflood.
Composition of Produced Water
The produced oil will contain water. This water will be separated from the crude oil
during the production process. The produced water will be passed through a producedwater treatment system to reduce its oil content to meet the Offshore Waste Treatment
Guidelines before it is discharged into the sea (currently these guidelines call for 30-day
average concentrations of 40 mg/L or less). Over the life of the field, about 46.5 x 106
m3 of produced water, containing a total maximum of 1863 m3 of oil, will be
discharged. Another 832 m3 might be contributed by the Far East for a total of about
2695 m3.
5-48
Table 5.4-2
Injection Water Additives
Purpose
Additive
Concentration
(ppm)
Biocide
Chlorine
1-2
Oxygen scavenger
Sodium or ammonium bisulphite
5-10
Scale inhibitor
Surfactants
Inhibitor: organophosphate phosphino
polyacrylate; polyacrylate organic
phosphate esters
5-50
5-20
Corrosion inhibitors
Amines and imidazolines; aliphatic
diamines; quaternary nitrogen
compounds; poly-oxyalkylated amines;
nitrogen heterocyclics (alkylated
polymerized pyridine)
10-20
5-25
Zone of Influence
Because there will be little or no formation water in the produced water, its salinity will
be that of the injected water and the same as that of the receiving water. The reservoir
temperature is 96°C. The produced water will be warmer and less dense than the
receiving seawater and, if discharged at the surface, would form a plume. To enhance
dispersion of the produced water, it will be discharged 10 m or more below the sea
surface. When discharged at these depths, the water will tend to rise, but in so doing, it
will be mixed with the receiving water so that the temperature approaches that of the
receiving water within a few tens of metres of the discharge (Black et al., 1994). The
depth of discharge will be adjusted to ensure the plume does not reach the surface.
Modelling done for Hibernia for discharge above the thermocline, predicted dilution by
a factor of 170 near the discharge, a factor of 1000 at a distance of 500 m and a factor
of 1 x 104 five km downstream (Mobil, 1985). However, it must be noted that the
produced water from Hibernia will be compositionally different from that at Terra
Nova.
5-49
15.9
15.9
15.9
15.9
13.6
11.0
8.9
7.2
5.8
4.7
3.8
3.1
2.5
2.0
1.6
1.3
1.1
0.9
0.7
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
49.5
49.3
49.0
48.6
48.1
47.5
46.8
45.9
44.7
43.4
41.6
39.5
36.9
33.7
29.6
24.7
18.9
13.1
7.3
1.5
Cumulated
Oil
Production
(106m3)
34.9
34.7
34.5
34.2
33.9
33.5
32.9
32.3
31.5
30.5
29.3
27.8
26.0
23.7
20.9
17.4
13.3
9.2
5.1
1.0
Recovery
Factor
(%)
6587
93
114
142
173
216
266
330
408
505
624
774
956
1184
1461
1814
2114
2114
2114
2114
2114
Gas
Rate
(103m3/d)
2066
283
283
283
283
283
283
283
283
283
283
283
283
283
283
283
283
283
283
283
283
Fuel Gas
Used
(103m3/d)
Production
0.94
0.93
0.91
0.89
0.87
0.84
0.80
0.76
0.71
0.66
0.59
0.51
0.43
0.34
0.23
0.15
0.05
0.02
0.00
0.00
Water
Content
(fraction)
Notes:
1. The estimated development life is at year 2014.
2. Reservoir pressure is assumed to be maintained at 30 MPa throughout the development life.
Total
15.9
Oil Rate
(103m3/d)
2001
Year
50.4
11.0
10.9
10.8
10.7
10.5
10.3
10.1
9.7
9.3
8.9
8.3
7.5
6.6
5.5
4.1
2.8
0.8
0.3
0.0
0.0
Water
Rate
(103m3/d)
100
12
12
12
12
12
12
13
13
13
14
14
15
15
17
18
19
17
16
16
16
Total
Liquid
Rate
(103m3/d)
Production and Injection Forecast
Waterflood in the Graben and East Flank
Table 5.4-3
116
12
12
12
12
13
13
13
14
14
15
16
17
18
20
22
24
22
21
21
21
Water
Rate
(103m3/d)
-190
-169
-141
-110
-67
-17
47
125
222
341
491
673
901
1178
1531
1831
1831
1831
1831
1831
Gas
Reinjection
Rate
(103 m3/d)
2740
2725
2693
2664
2620
2572
2519
2429
2326
2226
2076
1870
1645
1384
1019
701
209
81
0
0
Gas
Lift
(103m3/d)
Injection
2833
2840
2834
2838
2836
2838
2849
2837
2831
2850
2850
2826
2829
2845
2833
2816
2324
2196
2114
2114
Total Gas
Compression
(103m3/d)
Produced-water plume dispersion models designed for the North Sea were verified
with scale modelling and field tests (Sommerville et al., 1987). Assuming a discharge of
1 x 104 m3 of produced water, which is slightly less dense than seawater (similar to the
Terra Nova situation), dilution by a factor of 1000 was predicted within 50 m
downstream of the discharge and by a factor of 3000 within 250 m. Given this rate of
dilution, the concentration of produced water in seawater would be less than 0.1
percent at distances greater than 50 m downstream of the discharge. Assuming that the
discharge is treated to current Offshore Waste Treatment Guidelines, which call for
concentrations of oil in discharge to be less than 40 mg/L (30-day average),
concentration of oil in water would be less than 40 μg/L (40 mg/L diluted by a factor
of 1000), and concentrations of aromatic hydrocarbons would be less than 13 μg/L at
distances of 50 m from the source. This dilution factor assumes the produced water
will be less dense than seawater and not neutrally buoyant.
In the North Sea, mussel monitoring studies showed that mussels on the platforms had
hydrocarbon concentrations 60 to 100 times that of controls (Sommerville et al.,
1987). At a site 6 km from the source, hydrocarbon levels in mussels were 6 to 10
times that of controls and at distances of 10 km, levels were close to those of
unexposed mussels. The maximum zone of influence may have been 6 to 10 km
downstream of the source. However, some of the oil accumulated in mussels may have
originated from diesel oil-based drilling muds (Sommerville et al., 1987).
Effects of Produced Water
The most toxic components of the produced water are the volatile hydrocarbon
aromatics: benzene, toluene, ethylbenzene, xylene and polycyclic aromatic
hydrocarbons (PAHs). All but the PAHs, evaporate quickly and pose only a very
localized threat to marine organisms (Black et al., 1994). The PAHs are more
persistent and are probably responsible for biological effects near produced water
outfalls (Black et al., 1994).
The LC50 levels for the injection water additives have been presented previously in
Section 5.3.6, Hydrostatic Testing Fluids. Produced water is generally considered to be
nonhazardous with 96-h LC50 values of 1000 to greater than 10 000 ppm (GESAMP,
1993). Acute toxicity is unlikely at dilutions of 100-fold (Sommerville et al., 1987),
which will occur near the discharge point.
As previously stated, injection water additive use will be minimized, therefore, it is
expected that any additives used will be neutralized while in the wells and formation.
Injection water could be contaminated by chemicals while in the formation. The
concentrations of these chemicals in most produced waters are less than the 96-h LC 50
levels for most species and are not of ecotoxicological concern (Sommerville et al.
1987; GESAMP 1993).
Water Quality
Produced water could affect water quality slightly downstream of the release point.
Impacts would be minor, sublocal and long term.
Plankton
The threshold level above which toxic effects on water-column organisms could be
expected may be about 10 μg/L of aromatic hydrocarbons (Black et al., 1994).
Assuming that aromatic hydrocarbons comprise 33 percent of the oil in produced
water, concentrations of 10 μg/L of aromatic hydrocarbons could be expected within
50 to 500 m of the discharge point. Cod and herring larvae and phytoplankton appear
to be unaffected by produced water (Sommerville et al., 1987). Copepods and larvae of
benthic animals may be sensitive to concentrations of aromatic hydrocarbons on the
order of 5 to 15 μg/L (Davies et al., 1981). Plankton in the plume of produced water
would be exposed to oil concentrations of 5 μg/L for a very short period of time
because dilution would occur rapidly. After treatment, impacts of produced water on
the plankton would be minor, short term and sublocal to local.
Benthos
Fouling organisms on structures within 10 to 20 m of the outfall will likely accumulate
oil and sustain some reduction in biomass and productivity (Gallaway et al., 1981;
Sommerville et al., 1987).
Because the plume will rise, it will not interact with benthos; therefore, impacts on the
benthos will be negligible.
Fish
Produced water diluted by a factor of 100 (> 60 μg/L) will induce the aryl hydrocarbon
hydroxylase (AHH) enzyme system in fish (Davies et al., 1981). Little or no AHH
activity was noted in fish exposed to produced water diluted by a factor of 500. Fish
exposed to various dilutions of produced water for 20 days showed little or no
histological damage while those exposed for 30 days did (Davies et al., 1981).
Sublethal effects on fish could be expected in the immediate vicinity of the platform and
would mainly affect resident fish.
Produced water can contain benzene, toluene, and zylene (Sommerville et al., 1987)
that could cause tainting in fish. However, the rapid dilution of produced water would
reduce the risk of tainting in fish to an insignificant level (GESAMP, 1993). Resident
fish attracted to the area by the reef effect would be most at risk from tainting;
however, because of the safety zone these fish would not be harvested. In general,
most of the compounds in produced water are of low acute toxicity and dispersion and
degradation should limit effects to the immediate vicinity of the discharge (Sommerville
et al., 1987). Sommerville et al., (1987) do caution that site-specific aspects must be
considered and the GESAMP (1993) study points out that few studies have been
conducted on sublethal or chronic effects on marine organisms.
Direct impacts on fish and impacts on the fishery are predicted to be negligible which
will be verified by a monitoring program for taint.
Birds and Marine Mammals
As discussed in Section 5.3.6, treated oily water is likely to have negligible impacts on
birds and marine mammals.
Mitigation and Monitoring
The FPF will be designed to treat 18.3 x 103 m3/d of produced water. The water
treatment system will reduce oil content of discharged produced water to levels
specified in the Offshore Waste Treatment Guidelines, which currently specify:
-
A 30-day average concentration of 40 mg/L or less
-
That oil concentrations greater than 80 mg/L during any 48-hour period of
production are considered to be in exceedance of normal operating practice
and are to be reported to the Chief Conservation Officer within 48 hours
-
That measurement of oil concentrations be taken every 12 hours
-
A daily calculation of a rolling 30-day average
-
The measurement methods to be used
Most of the oily water discharge will be produced water. A monitoring program will
determine oil concentrations at various distances from the discharge and will look at
pre-injection and produced water compositions. The extensive literature base on
models coupled with the final field layout will be used to design the monitoring
program.
A program to monitor potential tainting in fish has been described in Section 5.3.5.
5.4.6
Other Operational Discharges
In addition to produced water, there will be many other materials and liquids associated
with the Terra Nova Development. Some of these will be released into the
environment. They are discussed in the following sections.
A semisubmersible FPF will not have internal storage for oil. The oil may be pumped to
a storage unit, (or direct to shuttle tankers). All these vessels will have segregated
ballast tanks, so there will be no possibility of oil-contaminated ballast water being
discharged over the side.
A monohull FPF vessel will have crude storage capacity on board. It will also have
separate ballast tanks to prevent contamination of ballast water with oil, so again there
will be no possibility of oil-contaminated ballast water being discharged over the side.
Ballast water from tankers could contain larvae of epifaunal animals, which would
colonize the structures. However, fouling will occur without this additional source of
larvae.
The potential impacts of discharge of storage displacement water will be negligible.
Cooling Water
The cooling water system will be designed to be as closed as possible. It is possible
some of the water could be injected. The design has not yet been finalized.
Cooling water will be chlorinated to a level of 1 or 2 mg/L of chlorine. This water may
be discharged at temperatures of about 30°C above ambient. Some zooplankton and
fish entrained in the intakes would be killed by the heated effluent. Potential impacts
will be negligible because the volume of entrained water and the area of thermal effects
will both be small (Mobil, 1985)
Deck Drainage
Drainage from the decks of drill rigs and the FPF will be isolated from the main sources
of oily waste, and on the FPF, the water will be passed through an oil-water separator.
The oily effluent from the separator will be collected for disposal, and the clear water
discharged over the side. Deck drainage will be processed to meet the Offshore Waste
Treatment Guidelines of 15 mg/L. Oil concentrations of greater than 15 mg/L are
considered to have exceeded normal operating practice and are to be reported within
24 hours to the Chief Conservation Officer.
Small volumes of treated deck drainage containing small amounts of oil will cause
minor, sublocal and short-term impacts on water quality. The potential effects of deck
drainage on plankton are likely to be transitory and sublethal and will affect only a small
volume of water; impacts will be negligible. As shown in Section 5.4.5, the chronic
subsurface releases of treated oily water are likely to have negligible impacts on birds
and marine mammals. Fish tainting will be monitored.
Sanitary and Domestic Waste
The topside facility on the FPF will accommodate about 100 people. In addition, there
will be personnel crewing the drill rig(s), supply and standby boats.
Grey water from showers, sinks and washers will be discharged without treatment into
the sea. Sewage and other domestic effluents will be treated to meet the EPS (1990)
and the Offshore Waste Treatment Guidelines. Treatment will be as required for
operations in offshore deep waters. Domestic wastes will be macerated to a particle
size of 6 mm or smaller before discharge. Sanitary wastes will be treated and the
effluent discharged overboard. For an FPF, Mobil (1985) estimated 19 m 3/d of sewage
and 34 m3/d of domestic waste.
Organic matter will be quickly dispersed and degraded by bacteria. Impacts of this
small amount of organic matter and nutrients to receiving waters will be negligible.
Garbage and Other Waste
Solid nonhazardous waste will be compacted and transferred to shore. Sludges from
oil-water separation units or other process vessels, spent lubricants, all plastic material,
glass and metal wastes will be transferred to shore for appropriate handling. Toxic or
hazardous waste will be transported to shore for appropriate disposal. There will be no
interaction between garbage and marine biota.
Small Spills
Fuel and other chemicals will be transported to the FPF and drill rig(s) by supply boat
from onshore facilities. There could be routine spillage or small spills of these materials
while they are in transit, during transfer to the FPF, or while they are stored on the
FPF.
Table 5.4-4 provides information on the number of flowlines and oil volumes
associated with the layout in Figure 1.1-7. Spills from these lines are possible and
Table 5.4-4
Flowline Dimensions and Hydrocarbon Inventories
Location
Flowline
Reference
Length
(m)
Number of
Lines
Pipe
Diameter
(mm)
Hydrocarbon
Inventory
(m3)
Graben
P-R
R-G1
G1-G2
G2-G3
G1-H99
G2-C09
G3-K07
Cluster Wells
200
4440
2060
2060
1840
1450
1260
28
2 risers
2
2
2
1
1
1
1 per well
250
250
200
200
150
150
150
150
10
436
129
129
33
26
22
0.5
East Flank
P-R
R-E1
E1-E2
E2-E3
E2-E79
E3-I97
Cluster Wells
200
2750
2060
2190
1450
1400
28
2 risers
2
2
2
1
1
1 per well
250
250
200
200
200
150
150
10
270
129
138
46
25
0.5
Far East
P-R
R-F1
F1-F2
Cluster Wells
200
5630
2190
28
2 risers
2
2
1 per well
250
250
200
150
10
553
138
0.5
Water injection
R-W1
7200
2
200
0
Transfer (semisubmersible FPF
only)
P-CP1
P-CP2
2000
2000
1
1
600
600
565
565
could arise from corrosion, dropped objects, slipped anchors, damage from towed
fishing gear or scouring icebergs.
Crude oil will be transferred from the FPF to storage or to shuttle tankers. If a
monohull FPF is used, a tandem offloading system will be provided. Crude oil would
be pumped from the stern of the FPF to the shuttle tanker. If a semisubmersible FPF is
used, crude oil will flow though export pipelines to two subsea offloading systems
located approximately 2.5 km from the FPF. There is a potential for routine spillage
and small accidents during crude oil transfer operations.
Impacts of these spills are discussed in Section 5.7.
Mitigation
All crude oil transfers and fuel, chemical and waste-handling activities will be carried
out in a manner designed to minimize or eliminate chronic inputs and accidents. Details
about these activities will be provided in the EPP and operations manuals.
All subsea equipment will be routinely visually monitored by divers or ROV.
Procedures will be developed for simultaneous drilling and production operations that
will address anchoring and dropped objects protection. The safety zone will be
enforced by the standby vessel.
If a controlled disconnect is required because of storm conditions or as a result of a
perceived unavoidable collision (iceberg, other vessel), all subsea facilities, including
export lines, will be flushed and the oil circulated to the FPF, all systems will be shut
down and valves will be closed. Little, if any, crude oil would be released during a
controlled disconnect. However, if an emergency disconnect were required, there
would be an emergency shutdown and a loss of crude oil from the riser. The volume
contained in the riser would be about 64 barrels of oil.
The FPF will contain secondary containment systems and sumps designed to contain
spills. Shutdown systems and routines will minimize environmental effects from
accidental damage to the FPF by isolating systems and equipment. Shutdown routines
will be developed in the detailed design phase.
The EPP will contain detailed response measures for dealing with spills.
5.4.7
During production operations, there will be three sources of atmospheric emissions:
1.
Infrequent flaring of well fluids and gas (flare stack)
2.
Engine, generator, and heating exhausts from the FPF, supply and
multipurpose vessels
3.
Fugitive emissions
Occasionally, some crude oil and gas components may be burned with burner booms
that will emit relatively large amounts of carbonaceous particles and a visible fire and
smoke plume. In addition to the smoke and particulate matter, emissions will also
contain unburned hydrocarbons, and traces of nitrous oxides, carbon monoxide and
sulphur dioxide.
Exhaust gases will also be emitted from generators, engines, and heaters onboard the
FPF and the support vessels. Exhaust gases will contain traces of nitrous oxides,
carbon monoxide and sulphur dioxide and unburned hydrocarbons. Fuel and equipment
will be carefully selected and maintained to minimize the amount of noxious gases in
emissions.
Small amounts of gas will also be vented through flame arrestors on storage tanks on
the FPF. In addition, some small and unquantifiable amounts of fugitive emissions will
also occur. Examples are hydrocarbon losses at valves and seals, stripping gas, vented
vapours from storage tanks, and release gas from turbine start systems (Christensen,
1994).
It is anticipated that the volume of emission discharges from the FPF will be on the
order of 2.7 x 106 m3/d for flaring, 9 x 106 m3/d for engine exhausts, 8 x 103 m3/d from
venting during tanker loading (intermittent), and about 1 x 103 m3/d from fugitive
emissions (Petro-Canada and Mobil 1985 estimates).
Some information on emissions from burning crude are contained in Fingas et al.
(1994).
The impacts of atmospheric emissions are anticipated to be negligible because small
amounts will be released and they will rapidly disperse to undetectable levels.
5.4.8
The FPF will be supported by two or three vessels of up to 12 000 HP. These will be
standard supply vessels in common use for offshore support work. There will be about
two transits per week to the FPF. The supply vessels will transport fuel, chemicals,
fresh water, food and all the other material necessary for operation and maintenance of
the FPF. One vessel will remain near the FPF on standby. As well, there will be a drill
rig or two and attendant supply vessels on site.
Potential impacts of the presence of vessels are discussed in Section 5.4.1. Discharges
from the vessels are discussed in Section 5.4.6. All discharges from vessels, including
sanitary and domestic waste will be treated as described above. Overall, impacts of
vessel discharges would be negligible. Potential impacts related to underwater noise are
discussed in Sections 5.3.10 and 5.4.10.
5.4.9
Helicopters will be used to transport personnel and materials to and from the FPF and
the drill rig(s). There will be approximately one round-trip per day to the FPF. Impacts
of helicopters on the marine environment are mainly related to noise, discussed in the
following section.
5.4.10
Effects of Noise
Marine animals, particularly mammals, are dependent upon the underwater acoustic
environment. There is concern about potential negative effects caused by the
introduction of man-made noise into the marine environment. The potential effects of
underwater noise on marine mammals and fish were discussed in detail in Section
5.3.10. In that section, noise effects from stationary drilling rigs, from supply vessels,
and from aircraft were considered. The principal underwater noise sources during
production will be the same as those during project development. Thus, the reader
should read Section 5.3.10 in conjunction with the present section.
Floating Production Facility
Present development plans for Terra Nova call for a FPF. Most of the production
machinery will be above the waterline, but propulsion engines and some other
machinery will be below. Machinery will include diesel generators, thrusters for
propulsion, pumps, compressors, a crude oil separation and processing system, and
life-support systems.
Most studies on the effects of noise associated with production activities have been
done using sounds emitted by bottom-founded production platforms or artificial
islands. Production platforms supported by metal legs have all of the machinery above
the waterline and transmit very little sound to the water. Production platforms and
artificial islands are relatively quiet. Noise levels and characteristics of a
semisubmersible FPF or a ship-shaped monohull FPF may be similar to those emitted
by a semisubmersible drilling rig or a large drillship.
Marine Mammals
The potential effects of semisubmersible and ship-shaped drilling platforms were
discussed in Section 5.3.10. At Terra Nova, the FPF will be in the same position for 15
to 20 years. Hence, the effects on marine mammals are predicted to be very localized.
Habituation is likely, if the mammals find food in the vicinity. Overall, the effects of the
stationary FPF are likely to be negligible to minor, long-term and sub-local.
Fish
Fish in the immediate vicinity of the FPF may hear the sound, but, the well-known
attraction of fish to offshore production facilities (see 5.3.2) indicates that they do not
react strongly, if at all, to noises associated with offshore production activities. Impacts
of noise on fish would be negligible.
Supply and Standby Vessels
The supply and standby vessels will likely be the loudest sources of underwater noise
associated with the development. It has been well-established that mobile noise sources
have greater effects on marine mammals than do stationary sources. Also, the potential
effects of the supply vessels cover a much larger area because of their mobility. The
effects of underwater noise from the supply vessels are likely to be of more concern
than from the FPF or tankers.
The potential effects on marine mammals, birds and fish of underwater noise from
supply vessels were reviewed in Section 5.3.10.
Helicopters and Fixed-Wing Aircraft
Helicopters will be used to ferry personnel to and from the FPF and the drill rig(s).
Fixed-winged aircraft will be used for ice reconnaissance. These activities are the same
as those that occur during development drilling. The potential impacts of helicopter and
fixed-wing aircraft were fully discussed in Section 5.3.10.
5.4.11
Shore-based facilities similar to those required for development drilling activities will be
needed to support production at the Terra Nova Development.
Potential impacts of a shore-based facility from atmospheric emissions, routine liquid
and solid releases, garbage, wastes, noise, lights, beacons, human presence, vessel and
aircraft traffic are discussed in Section 5.3-11.
5.5
Transportation
Oil will be offloaded from the production facility to tankers for shipment. Up to three
Canadian flagged and crewed shuttle tankers of 80 000 to 120 000 t deadweight will
be required. The number and size will depend on a number of factors, including the
final design decision for the production facility and the location of markets for Terra
Nova crude. Other factors notwithstanding, these tankers will be ice-strengthened and
have double bottoms, double-sided hulls, dual propulsion and advanced navigation and
communication equipment. Each tanker will have a crew of 20 to 25.
The oil could be shipped directly to market or transshipped through an onshore storage
and loading terminal. Final decisions on these transportation options will be made on
the basis of a market analysis and consideration of other factors. General transportation
routes are shown in Figure 5.5-1.
5.6
Decommissioning
When the Terra Nova Field has been depleted to a level where further production is
uneconomic, the site will be abandoned and restored to minimize residual impact on the
environment. Approvals to abandon components of the Terra Nova Development will
be obtained in accordance with the Newfoundland Offshore Area Petroleum
Production and Conservation Regulations. The technology associated with
abandonment and removal procedures is expected to change over the next 15 to 18
years, resulting in refined and new techniques.
5.6.1
Terra Nova Development Area
Individual wells will be abandoned as they become unproductive or, in the case of
injection wells, when reservoir injection is no longer required. In general, well
abandonment will consist of the following procedures:
·
Cement plugs and mechanical bridge plugs will be installed in the wells to seal
the formation.
·
The caisson master valve assembly, upper tree structure, guide base, and
flowline support structure will be removed.
·
Production wells will be purged of hydrocarbons and abandoned in place.
Abandonment procedures will be prepared for the straightforward task of removing the
FPF and possibly a storage tanker. All hazardous topsides equipment will be
decommissioned offshore prior to towing inshore. All anchors, anchor lines, and
anchor chains will be retrieved.
Subsea facilities include the production manifolds, riser base manifolds, loading riser
manifold, flowlines and export lines. Any subsea facilities installed above the seafloor
will be purged of hydrocarbons and decommissioned in accordance with regulations in
place at the time. All umbilicals will be decommissioned, made safe, and then retrieved.
Any subsea facilities installed sub-seafloor will be purged of hydrocarbons and left in
place.
Effects on Benthos
There will be some disturbance to infaunal communities during abandonment and
decommissioning (see Table 5.6-1). Disturbance will be minor, short term and sublocal.
Onshore
Offshore
Decommissioning
Abandonment
Development
Component
Air
Water
Quality Quality
x
x
x
x
x
x
x
x
x
x
Fish
Fouling
Pelagic Ground
Terrestrial
Plankton Larvae Infauna Organisms Epibenthos Fish
-fish
Fishery Seabirds
Birds
Whales
Ecosystem Elements
Level I Matrix: Interactions Between Abandonment Activities and Ecosystem Elements
Table 5.6-1
x
Seals
Effects on Biofouling Community
Effects on the biofouling community will vary depending upon the options available at
the time of decommissioning. Where structures are removed the communities will be
lost. The benthic community will return to predevelopment conditions. There is no
associated impact. Where structures are not removed, biofouling communities will be
maintained on these hard substrates as long as the structures are intact. While this
impact will be long term, it will be minor at most.
Increased vessel activity during periods when facilities are being removed may cause
some disturbance to marine mammals over and above that associated with routine
production activities. However, this disturbance will occur within relatively short
periods of time. Impacts will be minor, short term and sublocal. After abandonment,
the Terra Nova site will have no effect on birds and marine mammals.
Effects on Fish
The most important effect on fish will be the termination of the safety zone if in fact it
constituted a refuge. Assuming a diverse commercial fishery operates in the area,
conditions should revert to those before development. Overall there would be no
impact.
If some structures remain projecting above the seabed, there will be a positive, minor
(at most), sublocal, long-term impact on fish populations due to the reef effect. Fish
will be slightly protected from predation by bottom trawlers. On the other hand, there
may be a negative impact (sublocal, negligible to minor but long term) on the
groundfish fish hery, if it resumes in the area.
5.6.2
The shore-based facilities will be located in an existing port. As a result, cessation of
Terra Nova activities is expected to have negligible impacts on the environment.
5.7
Oil Spills
In this part of the EIS, the environmental impacts of oil spills that might occur with the
Terra Nova Development are assessed and the countermeasures that might mitigate
these impacts evaluated. The goals are to:
-
Assess the probability of different types of marine spills from Terra Nova
Development operations
-
Predict their probable behaviour, movement and possible landing points on
shore
-
Assess their potential effects on the environment
-
Evaluate countermeasures available to mitigate the effects of such spills
The focus is on large oil spills because these are the primary environmental concern.
This section starts with an identification of potential spill sources and follows with a
quantitative assessment of the probabilities of large spills happening. This is followed
by a detailed analysis of the specific characteristics of hypothetical Terra Nova spills in
terms of their behaviour and fate. These spill scenarios, involving various spill types and
sizes, serve subsequently as the basis for the impact assessment and the
countermeasures analysis.
Terra Nova crude oils, like those at Hibernia, are waxy oils that behave in an unusual
manner when spilled in cold waters. Because of this unique behaviour and its influence
on both spill impact and cleanup potential, a description is given of laboratory analysis
of the oil and the implications for spill impact and persistence. This is followed by a
discussion of the results of computer modelling to estimate the behaviour and fate of
the selected hypothetical spills, both at source and away from source. Because Terra
Nova spills are likely to be highly persistent, lasting weeks and perhaps even months on
the water surface, an assessment is made of the chances of any spilled oil from Terra
Nova reaching shore.
In the hypothetical spill scenarios, succinct and definitive descriptions of Terra Nova
spill behaviour are made. It is emphasized that, although these descriptions are based
on many years of study of historical oil spills, they are also based on only limited data
on Terra Nova oils themselves and their spill behaviour. Some spill-related laboratory
testing of Terra Nova oils was done in 1985 (S.L. Ross, 1985) and more extensive
work was performed with similar Hibernia oils in 1988 (S.L. Ross, and D. Mackay
1988). These studies provide reasonable data for predicting the near-source behaviour
of Terra Nova spills, but not their behaviour far from source, after many weeks of
environmental exposure. The long-term spill descriptions in this analysis are therefore
based largely on professional judgements based on many years of experience in the oil
spill research business.
From an oil-spill perspective, the Terra Nova Development is similar to the Hibernia
project. Both oils are waxy, the locations are close to each other and subject to similar
climatic conditions, and the types and sizes of spills from each project can be expected
to be similar. Much of the research and analysis that went into the EIS for Hibernia 10
years ago is applicable to this study. There are two small differences in the oil-spill
situation today, mostly a result of new knowledge of offshore currents in the area
(affecting spill trajectory somewhat) and better oil-spill fate-and-behaviour models that
take into consideration the special waxy nature of Grand Banks crude oils (meaning
that spills will persist longer than was predicted 10 years ago). Everything else is
essentially the same.
In terms of spill cleanup, techniques and equipment for dealing with oil spills at the
Terra Nova site are ineffective most of the time because of the high sea states in the
area. On the other hand, the chances of oil coming ashore and causing serious damage
are negligible, as was the case in the Hibernia assessment. The only serious
environmental threat seems to be impacts on birds at sea from very large spills, and this
is balanced against the very low probability that such spills will ever happen over the
expected 15 to 18 year life of the project.
What was done 10 years ago regarding Hibernia oil spills is essentially valid today for
Terra Nova oil spills; therefore, the details of Hibernia-related studies need not be
repeated. Rather, for each oil spill subject discussed in the following sections, the
approach will be to:
5.7.1
-
Summarize the results and conclusions found in the relevant Hibernia-related
reports and the Hibernia EIS
-
Discuss the similarities and differences between the Terra Nova Development
spill situation and that of the previously analyzed Hibernia project
-
Describe any different situations in as much detail as is necessary for
assessment
-
Summarize the results and compare them with the results found in 1985 for
Hibernia
Oil Spill Probability Analysis
This section of the EIS assesses the probability of occurrence of the various kinds of oil
spills that could happen during the Terra Nova Development. The activities that can
lead to blowouts or spills are as follows:
·
·
Development drilling
Completion of wells drilled
·
·
·
Various production activities, including wirelining, coiled tubing and snubbing
operations
Workovers
Iceberg scours
Batch spills or instantaneous spills can occur from accidents on the FPF where oil is
stored or handled, or accidents during storage tanker or shuttle tanker loading or
flowline rupture.
The Hibernia EIS
The oil-spill probability discussion in the Hibernia EIS (Vol. IIIb, p. 69) and the 1984
S.L. Ross report to Mobil Oil Canada, Ltd. Hibernia Oil Spills and their Control (p.
43-84) is based mostly on a voluminous study by Gulf Research and Development
Company in 1981 that covers offshore oil activity from 1955 to 1980. In neither the
Hibernia EIS nor the S.L. Ross study was any attempt made to predict the frequency of
large spills from Hibernia operations, although statistics from offshore operations in the
U.S. Gulf of Mexico and the North Sea were used to suggest that spill frequencies
were likely to be low. Subsequently, a number of new statistical reports on spills from
offshore oil activities have been prepared, some analyzing operations to 1994. Simple
approaches have been developed by the United States Minerals Management Service
and others for predicting the occurrence of large spills from both offshore oil activities
and tanker accidents.
Oil Pollution Record of the Offshore Oil and Gas Industry
Compared with other industries with the potential for discharging petroleum oil into
the marine environment, the industry of exploring, developing and producing offshore
oil and gas is relatively clean. As noted in a study on oil pollution by the United States
National Academy of Sciences (1985) and as summarized in Table 5.7-1, the offshore
exploration and production industry contributes only 1.5 percent of the total petroleum
input to the world's oceans. The oil-spill prevention mechanisms built into offshore
activities are obviously effective. For example, on the U.S. Outer Continental Shelf
(OCS) where, from 1971 to 1993, more than 22 000 wells were drilled and eight billion
barrels1 of oil and condensate were produced, only five blowouts occurred that
involved any discharge of oil. The total oil discharged in these five events was only
about 1000 barrels.
Table 5.7-1
Input of Petroleum Hydrocarbons into the Marine Environment
Source of Contribution
Oil
Quality
(106 t/a)
Contribution to
Total Input
(%)
Natural sources
Marine seeps
Sediment erosion
0.2
0.05
6.2
1.5
Total natural sources
0.25
7.7
Offshore oil and gas production
0.05
1.5
Tanker operations
Dry docking
Marine terminals
Bilge and fuel oils
Tanker accidents
Nontanker accidents
0.7
0.03
0.02
0.3
0.4
0.02
21.5
0.9
0.6
9.2
12.3
0.6
Total
1.47
45.2
0.3
9.2
Atmosphere
Municipal and industrial wastes and runoff
Municipal wastes
Refineries
Nonrefining
Industrial wastes
Urban runoff
River runoff
Ocean dumping
0.7
0.1
21.5
3.1
0.2
0.12
0.04
0.02
6.2
3.7
1.2
0.6
Total wastes and runoff
1.18
36.3
Total
3.25
100.0
Source: NAS (1985).
Similarly, at Terra Nova, the chance of having large spills from offshore oil and gas
operations is low. This statement is based on the assumption that the practices and
technologies used for the Terra Nova Development will be at least as safe as those
used in other offshore oil and gas operations around the world and in accordance with
the accepted practices of the international petroleum industry. Because statistics on
U.S. offshore oil and gas operations are the best available and are used extensively in
this analysis, it is specifically assumed that Terra Nova Development operations are
comparable to operations in U.S. waters (U.S. statistics include operations in Alaska,
where ice is a factor).
Sources of Information
Statisticians of the U.S. Minerals Management Service (MMS) have produced a vast
body of literature on marine oil-spill probability in the Gulf of Mexico. These oil spill
statistics have been extensively peer-reviewed and are updated regularly, and will be
used as a primary source of information for this EIS.
In addition to MMS reports, four other key sources of information are referenced, all
focussing on blowouts and spills from offshore oil and gas activities. The first is the
study for Dome Petroleum Limited by Gulf (1981) entitled Analysis of Accidents in
Offshore Operations where Hydrocarbons were Lost. This study analyzes the causes of
accidents and spills particularly well.
The next two studies focus on blowouts. One study, conducted in 1985 by Manadrill
Drilling Management Inc., concentrates on the issue of relief- well drilling capability on
land in Canada, but also provides a good summary of previous studies on offshore
blowout probability. The other study was prepared by Adams Pearson Associates Inc.
(1991) for the former Canadian Petroleum Association (now the Canadian Association
of Petroleum Producers) on the subject of "worst case" blowouts, mostly in reference
to operations in the Canadian Beaufort Sea. This study explains in relatively simple
terms how blowouts happen and how they tend to stop naturally.
A recent reference source is a comprehensive report prepared in Europe by Technica
a.s. entitled Hydrocarbon Leak and Ignition Data Base (E&P Forum, 1992). This
study is based on oil company reports of spills and blowouts that have occurred during
offshore exploration and production activities from 1970 to 1981. Most (85 to 90
percent) of the blowout and spill statistics are derived from activities in the U.S. Gulf of
Mexico Outer Continental Shelf (USGOM-OCS), but data from the North Sea are also
included. This study is useful because blowout and spill statistics are neatly separated
into those involving gas-producing wells and those involving oil-producing wells. The
major problem with the Technica study is that its blowout frequencies seem to be lower
than those reported in recent government publications. For example, in MMS (1994)
25 blowouts during workovers are reported to have happened in USGOM-OCS from
1970 to 1989, but in the Technica study only 16 blowouts are reported for both the
USGOM-OCS and the North Sea. The difference is perhaps because Technica has
likely excluded blowouts that did not discharge hydrocarbons into the environment,
that were caused by disasters like acts of war or hurricanes, or that were "unfairly"
reported one way or the other. To be conservative, this assessment uses the higher
numbers from MMS in calculating blowout frequencies. This same "worst-case"
approach is used whenever different numbers are reported in the literature.
There is also a SINTEF database. However, 95 percent of the data are from operations
in the USOCS. This EIS covers USOCS activities for the period 1970 to 1993 using
the MMS (1994) report.
The Terra Nova Development and Worldwide Statistics
As this EIS refers to many statistics, it is convenient to summarize data related to the
development itself and data related to drilling, production and spills from similar
developments in other parts of the world. The statistics relevant to Terra Nova
Development are summarized in Table 5.7-2. Table 5.7-3 provides statistics from other
offshore oil and gas producing areas of the world that will be used throughout the
report.
Categories of Spill Size
For this EIS, four spill-size classifications are used. One is an "extremely large" spill
involving the loss of more than 150 000 of barrels of oil. Such disasters can cause
damage, especially when they occur close to land. They are also important because
whenever and wherever they occur they receive international media coverage and
influence the public's view of oil spills in general. The next two size ranges are for "very
large" spills, that is, spills larger than 10 000 barrels (sizes that MMS tracks) and
"large" spills, that is, spills larger than 1000 barrels.
"Large" spills are reasonably well documented, have the potential for serious local
damage if washed ashore, and occur with sufficient regularity to cause concern. The
next classification is "small" spills involving loss of fewer than 50 barrels, which may
not cause severe damage but nonetheless occur frequently and are regular reminders of
the threat of much larger and more damaging spills. Spill sizes are summarized in Table
5.7-4.
Blowouts
In the oil and gas industry, a distinction is made between two stages of petroleum field
drilling: exploration drilling (including delineation drilling), where knowledge of the
geological and depositional environment is speculative or limited; and development
drilling, where the structure is better defined and drilling better controlled. Exploration
drilling in the Terra Nova Development has been
Table 5.7.2
Terra Nova Development Statistics of Importance to Study
Parameter
Value
Number of development wells to be drilled in total, including
18 gas or water injection wells
39
Production wells (21 yet to be drilled plus 5 to be developed
from previously drilled delineation wells)
26
Production lifetime
15 to 20 a
Total crude oil produced during lifetime
47 to 64 x 106m3
Oil-producing well-years
312
completed, but 39 development wells have yet to be drilled. Blowouts, which are
generally defined as uncontrolled flows of well fluids (water, gas, oil and gas liquids)
from a wellhead or well-bore can happen during drilling operations, but also can occur
during production, workovers and well completion activities. The frequency of
blowouts involving releases of oil to the environment is very small when compared
with the frequency of all blowouts.
Significant Oil Spills from Blowouts
Historical Statistics. The main environmental concern with the Terra Nova
Development is the possibility of a well blowout discharging tens or even hundreds of
thousands of barrels of crude oil into the marine environment. An offshore well
blowout involving a discharge of crude oil has never been experienced in Canada 2. In
U.S. waters, only four very large spills from oil-well blowouts have occurred since
offshore drilling began in the mid-fifties. To show the data worldwide, Table 5.7-5 lists
all blowouts involving spills of more than 10,000 barrels each. Five extremely large
spills (150,000 barrels or more) have occurred in the history of offshore exploration
and production, two of these during development drilling.
Table 5.7-3
Offshore Petroleum Industry Statistics
Statistic
Worldwide Offshore
Exploratory wells drilled, 1955-1980
Development wells drilled , 1955-1980
Total wells drilled, 1955-1980
Approximate number exploration wells drilled to 1988
Approximate number develop and production wells drilled to 1988
Approximate cumulative offshore oil produced to January 1980
(excluding Lake Maricaibo)
Total blowouts of all kinds, 1955-1980
Blowouts during exploration drilling (incl. shallow gas), 1955-1980
Blowouts during development drilling (incl. shallow gas), 1955-1980
Blowouts during production and workovers
Total shallow-gas blowouts
Value
Data Source
11 737
24 896
36 633
20 000
51 000
Gulf, 1981
Gulf, 1981
Gulf, 1981
Sharples et al., 1989
Sharples et al., 1989
5.6 x 109 m3
214
96
66
52
54
Gulf, 1981
Gulf, 1981
Gulf, 1981
Gulf, 1981
Gulf, 1981
Gulf, 1981
United States, Gulf of Mexico (USGOM) and Outer Continental
Shelf (USOCS)
Exploratory wells drilled in USGOM, 1955-1980
Development wells drilled in USGOM, 1955-1980
Total wells drilled in USGOM, 1955-1980
Total wells drilled in USOCS (96% in GOM), 1971-1993
Total wells drilled in USOCS, 1955-1993
Approximate cumulative total oil produced in OCS to January 1980
Cumulative total oil produced in OCS, 1971 to end 1993
Total blowouts of all kinds, 1955-1980
Blowouts during exploration drill (incl. shallow gas), GOM, 1955-80
Blowouts during development drill (incl. shallow gas), GOM, 1955-80
Production and workover blowouts, GOM, 1955-1980
Total shallow-gas blowouts, USGOM, 1955-1980
Exploratory drilling blowouts, USOCS, 1971-1993
Development drilling blowouts, USOCS, 1971-1993
Production, workover and completion blowouts, OCS, 1971-1993
4 794
12 390
17 184
22 594
31 645
1.4 x 109 m3
1.2 x 109 m3
98
30
36
32
29
49
44
56
Gulf, 1981
Gulf, 1981
Gulf, 1981
MMS, 1994
MMS, 1994
Gulf, 1980
MMS, 1994
Gulf, 1980
Gulf, 1981
Gulf, 1981
Gulf, 1980
Gulf, 1981
MMS, 1994
MMS, 1994
MMS, 1994
Norwegian Offshore
Exploration wells drilled, 1976-1980
Development wells drilled, 1976-1980
Exploration drilling blowouts, 1976-1980
Development drilling blowouts, 1976-1980
4 175
6 941
32
14
Manadrill, 1985
Manadrill, 1985
Manadrill, 1985
Manadrill, 1985
UK North Sea
Exploration wells drilled, 1964-1980
Development wells drilled, 1964-1980
Blowouts during all stages, 1964-1980
838
721
6
Gulf, 1981
Gulf, 1981
Gulf, 1981
Table 5.7-4
Spill Classification Categories
Size
(bbl)
Category
Extremely large spill
> 150,000
Very large spill
> 10,000
Large spill
> 1000
Small spill
< 50
Table 5.7-5
Historical Large Oil Spills from Offshore Oil-Well Blowouts
Area
Reported Spill Size
(bbl)
Date
Operation Underway
Mexico (Ixtoc 1)
3,000,000
1979
Exploratory drilling
Dubai
2,000,000
1973
Mexico
247,000
1986
Workover
Nigeria
200,000
1980
North Sea and Norway
158,000
1977
Workover
Iran
100,000
1980
U.S., Santa Barbara
77,000
1969
Production
Saudi Arabia
60,000
1980
Mexico
56,000
1987
U.S., S. Timbalier 26
53,000
1970
?
U.S., Main Pass 41
30,000
1970
Production
U.S., Timbalier Bay and Greenhill
11,500
1992
Production
Trinidad
10,000
1973
Source: Gulf (1981), updated by reference to the Oil Spill Intelligence Report.
Blowouts During Drilling. Spill frequencies are best expressed in terms of a risk factor
such as the number of wells drilled. On a worldwide basis, approximately 51 000
offshore development wells were drilled from 1955 to 1988 (Table 5.7-3; Sharples et
al., 1989). Thus the frequency of extremely large spills from oil-well blowouts during
development drilling becomes 3.9 x 10-5 spills per well drilled or one such spill for
every 26 000 wells drilled. Similarly, up to 1988, four development drilling blowouts
have produced "very large" spills (Table 5.7-5), so the spill frequency for these is 7.8 x
10-5 spills per well drilled or one such spill for every 13 000 wells drilled.
There are two historical spills that can be considered to be "exceptionally large spills"
(greater than 1,000,000 bbl):
·
The Ixtoc-1 blowout in the Bay of Campeche, Mexico, which occurred in 1979
during exploratory drilling
·
A blowout in Dubai that occurred in 1973 during development drilling
Both were caused by drilling procedures not practised in Canadian waters and that are
totally contrary to Canadian regulations and accepted international oil and gas industry
practices. The probability of having this size of spill at Terra Nova because of a
development drilling accident is exceptionally low, much less than the worldwide
frequency of one development drilling blowout (Dubai) for every 51 000 development
wells drilled or 2.0 x 10-5 spills (greater than 1,000,000 bbl) per well drilled.
The number of wells drilled worldwide since 1988 is not readily available, but it is
known that only one oil-well blowout larger than 10,000 barrels has occurred since that
time, and it did not occur during drilling. (This was the Timbalier Bay production-well
blowout that occurred in state waters in the USGOM in September 1992.) This means
that estimates based on current statistics would be even lower than those noted above
because no drilling-related blowouts have occurred since 1988.
Blowouts During Production and Workovers. Table 5.7-5 shows the occurrence of
two extremely large (greater than 150,000 bbl) and five very large (greater than 10,000
bbl) oil spills from blowouts during production and workovers. Developing an exact
risk exposure for these events is not easy because of lack of data, but it is estimated
that the total oil produced offshore on a worldwide basis to the end of 1993 is about
100 billion barrels, and the total producing oil well-years is 200 000 (based on
information in Gulf, 1981; NAS, 1985; E&P Forum, 1992; and MMS, 1994) (see
Appendix 5.B).
Well-years was chosen as the more reasonable exposure parameter. The worldwide
frequency of extremely large oil spills (greater than 150,000 bbl) from oil-well
blowouts that occurred during production or workovers is 2/200 000 or 1.0 x 10-5
blowouts per well-year. For very large spills (greater than 10,000 bbl) the number is 2.5
x 10-5 blowouts per well-year.
Prediction for the Terra Nova Development. Thirty-nine wells will be drilled in the
Terra Nova Development, and the exposure for the project will be 312 well-years.
Using the above worldwide spill frequency statistics as a basis for prediction, the
estimated spill frequencies are:
·
Extremely large oil spills (greater than 150,000 bbl) from blowouts during a
drilling operation, based on an exposure of wells drilled: 39 x 3.9 x 10-5 = 1.5 x
10-3 or a 0.15 percent chance over the entire drilling period
·
Very large oil spills (greater than 10,000 bbl) from drilling blowouts based on
an exposure of wells drilled: 39 x 7.8 x 10-5 = 3.0 x 10-3 or a 0.30 percent
chance over the drilling period
·
Extremely large oil spills (greater than 150,000 bbl) from production and
workover blowouts, based on an exposure of well-years: 312 x 1.0 x 10-5 = 3.1
x 10-3 or a 0.31 percent chance over the project's lifetime (20 years)
·
Very large oil spills (greater than 10,000 bbl) from production and workover
blowouts, based on an exposure of well-years: 312 x 2.5 x 10-5 = 7.8 x 10-3 or a
0.78 percent chance over the project's lifetime (20 years)
Oil Well Blowouts Involving Any Discharge of Oil (Greater Than 1 bbl)
Historical Statistics. Historical statistics are used to estimate the chances of any
blowout occurring during Terra Nova Development operations, either during
development drilling, production operations, workovers or completions. Historical
statistics for blowouts involving small oil discharges are derived from American
sources because the MMS keeps track of spills down to one barrel in size.
The MMS statistics over the 23 year period from 1971 to 1993 provide the basis for
calculating probabilities and are found in Table 5.7-6. Note that there are no large spills
(greater than 1000 bbl) listed in the table.
Development Drilling and Well Completions. The total number of development wells
drilled in the U.S. Federal OCS is not shown in Table 5.7-6, but is approximately 16
000 (MMS, 1994; E&P Forum, 1992).
Table 5.7-6
Blowouts and Spillage from U.S. Federal Offshore Wells Compared to Crude Oil
and Condensate Production on Federal OCS Leases
1971 to 1993
Drilling Blowouts
Year
Nondrilling Blowouts
Well
Starts
Exploration
Development
Production
No.
No.
No.
bbl
bbl
Workover
bbl
No.
Completion
bbl
No.
bbl
No.
bbl
MMbbl
1971
851
1
0
1
0
2
450
1
0
0
0
5
450
407
1972
845
2
0
2
0
1
0
0
0
0
0
5
0
396
1973
820
2
0
1
0
0
0
0
0
0
0
3
0
385
1974
802
1
0
1
0
4
275
0
0
0
0
6
275
355
1975
842
4
0
1
0
0
0
1
0
1
0
7
0
325
1976
1 078
1
0
4
0
1
0
0
0
0
0
6
0
315
1977
1 240
3
0
1
0
1
0
3
0
1
0
9
0
296
1978
1 164
3
0
4
0
0
0
3
0
1
0
11
0
288
1979
1 140
4
0
1
0
0
0
0
0
0
0
5
0
274
1980
1 158
3
0
1
0
2
1
1
0
1
0
8
1
275
1981
1 208
1
0
2
0
1
0
3
64
3
0
10
64
283
1982
1 255
1
0
4
0
0
0
4
0
0
0
9
0
315
1983
1 180
5
0
5
0
0
0
2
0
0
0
12
0
351
1984
1 352
3
0
1
0
0
0
1
0
0
0
5
0
385
1985
1 169
3
0
1
0
0
0
2
40
0
0
6
40
380
1986
694
0
0
1
0
0
0
1
0
0
0
2
0
384
1987
845
2
0
0
0
3
0
1
0
2
60
8
60
359
1988
950
1
0
1
0
0
0
1
0
0
0
3
0
333
1989
947
2
0
51
0
32
0
1
0
0
0
11
0
314
1990
1 018
1
0
1
0
0
0
3
9
1
0
6
9
305
1991
726
3
0
33
0
0
0
0
0
0
0
6
0
326
1992
431
3
100
0
0
0
0
0
0
0
0
3
100
338
1993
879
0
0
3
0
0
0
0
0
0
0
4
604
353
Total
22 594
49
100
44
0
18
726
28
113
10
60
150
1059
7740
Source: MMS (1994).
Note: Only crude oil and condensate blowout spillage is given here for the 150 blowouts that occurred during the past 22 years.
1
Two of the drilling blowouts occurred during drilling for sulphur.
2
One blowout occurred during abandonment operations.
3
Two of the drilling blowouts occurred during drilling for sulphur.
4
OCS
Production
Total
Blowouts
.
The original reference (MMS, 1994) has a typographical error in this row, inasmuch as there is no source for this 60 barrel spill
The number of blowouts from development drilling is shown as 42 (the two blowouts
from sulphur drilling are removed); therefore, the blowout frequency is 42/16 000 or
2.6 x 10-3 blowouts per well drilled. No oil was spilled in any of these blowouts. This
suggests that all the blowouts occurred in gas prone fields, and would further suggest
that blowouts from development drilling in oil-prone fields are extremely improbable.
As a worst-case, however, it will be assumed that the above blowout frequency applies
to Terra Nova Development.
For blowouts during completions the equivalent statistic is 10/14 000 or 0.71 x 10 -3
blowouts per well. Note again that none of the blowouts during development drilling
discharged any oil, and only one during completion work involved an oil discharge (60
bbl). Combining both frequencies, the frequency for blowouts that occur during
development drilling and completion operations becomes (2.6 + 0.71) x 10-3 or 3.3 x
10-3 blowouts per well.
Blowouts During Production and Workovers. As discussed earlier, the best accident
exposure to use for the continuous operation of production is well-years, i.e., the
product of the number of oil production wells in operation and the number of years of
operation. The number of oil well-years for the population in Table 5.7-6 from 1971
through 1993 can be calculated from another table in MMS (1994) (page 40); the
number is 97 921 producing oil well-years. This exposure is also convenient to use for
workovers inasmuch as these maintenance activities, although not continuous, usually
occur with regularity, approximately every seven years or so during the lifetime of a
well.
For all the gas-producing and oil-producing areas of the U.S. Federal OCS, 46
blowouts occurred during production and workovers (Table 5.7-6). Forty-two
involved gas only and four involved oil. It was assumed the 42 gas blowouts occurred
in association with gas-producing wells and the remaining four occurred from
oil-producing wells.
The frequency of blowouts that produced a spill from oil-producing wells during a
production operation or workover was calculated to be 4/97 921 or 4.1 x 10 -5
blowouts per well-year. The four spills had an average size of only 200 barrels.
Predictions for Terra Nova Development. There will be about 39 development wells
drilled during the Terra Nova Development, resulting in a calculated oil-well blowout
frequency of 39 x 3.3 x 10-3 or 0.13, or a 13 percent chance of a blowout. According
to the statistics in Table 5.7-6, however, the chances of having an oil discharge
associated with the blowout is extremely low (actually zero according to the table). It is
known that large and even extremely large spills have occurred during development
drilling (Table 5.7-5), but the frequency of these has been very low.
For blowouts during production and workovers, the Terra Nova Development
statistics are 312 well-years x 4.1 x 10-5 blowouts per well-year or 1.3 x 10-2 blowouts
over the course of the entire development, equalling about a 1.3 percent chance.
Large Oil Spills (Greater Than 1000 bbl) From Platforms
Historical Record. There have been very few large spills from platforms operating in
U.S. OCS waters. In addition to the four from blowouts noted in Table 5.7-5, there
have been only six others (Table 5.7-7) to the end of 1994. These all occurred before
1980. MMS statisticians responsible for analyzing and predicting oil spill frequencies
associated with offshore oil and gas activities in the OCS have decreased the estimate
gradually over the past decade in recognition of a statistical trend towards lower spill
frequency. The latest estimate developed by Anderson and LaBelle (1994) is 0.45 spills
per billion barrels for spills equal or greater than 1000 barrels and 0.16 spills per billion
barrels for spills equal or greater than 10,000 barrels.
This is equivalent to 3.6 x 10-5 spills per well-year for spills greater than 1000 bbl and
1.3 x 10-5 spills per well-year for spills greater than 10,000 bbl3. The above statistic for
spills greater than 10,000 bbl is smaller than the statistic derived earlier for blowouts
greater than 10,000 bbl (i.e., 2.5 x 10-5). This is inconsistent because the first category
includes blowout spills. The reason for the anomaly is that the U.S. record was used for
the former and the worldwide record was used for the latter. The results mean that
spills occur less frequently in U.S. waters than they do world-wide.
Predictions for the Terra Nova Development. The total well-years for Terra Nova
Development is estimated to be 312. The estimated frequency of any spills larger than
1000 bbl and 10 000 bbl, respectively, is 312 x 3.6 x 10-5 = 1.1 x 10-2 (1.1 percent
chance) and 312 x 1.3 x 10-5 = 4.1 x 10-3 (0.41 percent chance).
Platform Spills Involving Small Discharges
Historical Record. Small spills occur regularly at offshore platforms. Table 5.7-8
summarizes frequency of spills larger than one barrel of all pollutants from facilities and
operations on Federal OCS leases from the period 1970 to 1993 (MMS, 1994). This
period involved the production of 8.0 billion barrels of oil and condensate and 103 486
well-years of production activity.
Table 5.7-7
Oil Spills of 1000 Barrels or More from Platforms on the U.S. OCS
1964 to 1993
Date
(yy-mm-dd)
64-04-08
64-10-03
65-07-19
69-01-28
69-03-16
70-02-10
70-12-01
73-01-09
79-11-23
80-11-13
92-09-29
Location
Size
(bbl)
Eugene Island Block 208
Eugene Island Ship Shoal
Ship Shoal Block 29
Santa Barbara Channel
Ship Shoal Block 72
Main Pass Block 41
South Timbalier Block 29
West Delta Block 79
Main Pass Block 151
High Island Block 206
Timbalier Bay and Greenhill
2,559
11,869
1,688
77,000a
2,500
30,000
53,000
9,935
1,500b
1,456
11,500c
Cause of Spill
Collision
Hurricane (7 platforms)
Blowout (condensate)
Blowout
Collision, weather
Blowout
Blowout
Storage tank rupture
Collision, weather, tank spill
Pump failure, hurricane, tank spill
Production well blowout
Sources: Anderson and LaBelle (1994).
a
Estimates vary between 10 000 to 77 000 bbl.
b
Refined product.
c
This spill was in Louisiana State waters and not OCS waters, but is included in table for interest
Table 5.7-8
Spill Frequency from Platforms
for Spills in the Size Ranges of 1-50 Barrels and > 50 Barrels
(U.S. OCS 1970 - 1993)
Spill Size Range
Number of
Spills
Probability of Occurrence
(spills/well-year)
-2
1 - 50 bbl
1806
1.7 x 10
> 50 bbl
81
7.8 x 10
Source: MMS (1994)
Note: Total volume of 1806 + 81 spills = 116 136 barrels.
-4
.
Predictions for Terra Nova Development. For the Terra Nova Development the
predictions are 312 x 1.7 x 10-2 = 5.3 spills less than fifty barrels over the course of the
development; and 312 x 7.8 x 10-4 = 0.24 spills greater than 50 barrels, or a 24 percent
chance of having one such spill over the course of the project.
Spills During Tanker Loading
Spills are possible when Terra Nova crude oil is transferred from the FPF to shuttle
tankers. Developing predictions of frequencies for these spills is difficult at this time
because the design of the loading system has not been finalized. As well, the
technologies involved in loading offshore tankers have changed significantly in the last
few years, making the use of historical spill statistics for predicting future spill
frequencies questionable. The literature seems to indicate a dramatic drop in spill
frequencies over the last few years as better technologies were adopted.
Experience in United Kingdom Sector of the North Sea, 1976-1979. Tankers have
been used in the U.K. sector of the North Sea since 1976 to transport oil from the
offshore production facilities to shore. Both single buoy mooring (SBM) and singlepoint mooring (SPM) systems are used. The breakdown of statistics from 1976 (when
production began) to 1979 is available in Gulf (1981). Of all spills during oil industry
exploration and production activities in the U.K. sector of the North Sea, 23 percent
(34 spills) involved offloading accidents and accounted for 73 percent of the total oil
spilled. Ninety-four percent of these 34 spills were less than 100 barrels each. Spill size
averaged 18 barrels.
There were two large spills (greater than 1000 barrels), each having a volume of 4000
barrels. The volume of oil produced during 1976 to 1979 inclusive was 870 million
barrels for the entire U.K. offshore; therefore, the frequency of large spills was 2/0.87
or 2.3 spills per billion barrels produced.
Shell Oil Experience, 1982 to 1985. Table 5.7-9 lists spills at various worldwide SBM
facilities. These were taken from summaries documented by the Oil Spill Intelligence
Report (June 24, 1983; October 5, 1984; and November 21, 1986) for the period from
1982 to 1985 inclusive. Only spills larger than 238 barrels are included. A statistical
analysis of these spills is not justified because the listing is likely not complete (only
Shell Oil facilities are included) and because oil production statistics at these facilities
are not readily available. Table 5.7-9 does show, however, that large spills from hose
ruptures can and do occur during offloading operations offshore. The average size of
the spills larger than 1000 barrels is 4700 barrels, which is similar to the two U.K.
North Sea SBM spills that occurred between 1976 and 1979 (4000 barrels each).
Table 5.7-9
Spills Larger Than 240 Barrels that Occurred at SBM Facilities
1982 to 1985
Date
(yy-mm-dd)
Location
Quantity Spilled
(bbl)
Cause
83-01-10
53°25_N, 04°20_W
Amlwch, Wales, UK
1 070
Hose failure
83-02-10
53°25_N, 04°20_W
Amlwch, Wales, UK
430
3-08-20
05°22_N, 06°45_E
Forcados, Nigeria
8 290
Hose rupture
83-10-12
05°22_N, 06°45_E
Forcados, Nigeria
4 690
Hose failure during
loading
83-11-11
04°30_N, 07°15_E
near Bonny, Nigeria
480
Hose failure during
pressure testing
Floating hose failure
Source: Oil Spill Intelligence Report SBM, Shell.
Statoil Experience in the North Sea, 1979 to 1995. Statoil, the national oil company of
Norway, has more than 15 years of experience with offshore loading in the North Sea,
starting with the Statfjord A platform in 1979. Initially, the operation was based on an
articulated loading platform and modified conventional tankers, but has evolved into
today's submerged turret loading system and a large fleet of specialized vessels. A
Statoil paper on the subject (Breivik, 1995) indicates that 5000 cargoes of crude oil,
involving about 4 billion barrels, have been lifted by Statoil-operated tankers up to May
1994. In that time only two large spills have occurred: a 4000-barrel spill in 1980 and a
5800-barrel spill in 19924. This gives a spill frequency of 2/4 x 109 or 0.5 large spills
per billion barrels transported.
Breivik (1995) indicates that only two smaller spills have occurred, each less than 150
barrels.
Predictions for Terra Nova Development. The existing data suggest that in the earlier
days of offloading, the frequency of large spills was relatively high (2.3 spills per billion
barrels produced) and very high for smaller spills, but has been reduced lately to 0.5
large spills per billion barrels produced as a result of better technologies. If Terra Nova
Development uses these latest technologies and systems, and operates them as well as
Statoil, then a predicted large-spill frequency of 0.5 spills per 109 bbl produced might
be reasonable. If not, the higher number of 2.3 spills per 109 bbl should be used. For
want of further information, an arithmetic average of the numbers will be used here;
specifically, 1.4 large spills (greater than 1000 bbl) for every billion barrels produced.
For a production of 400 million barrels produced, the spill frequency prediction for the
Terra Nova Development becomes 1.4 x 0.400 = 0.56 large spills over the course of
the 15 to 18 year development, or about a 50:50 chance of occurrence. As discussed
above, the size of an offloading spill is likely to be in the 4000-barrel range, which is
relatively small compared to other types of potential large spills.
Summary of Blowout and Spill Frequencies
Over the 15 to 18 year development period the chances of an extremely large (greater
than 150,000 bbl) and very large (greater than 10 000 bbl) oil-well blowout from
development drilling are about 0.15 and 0.30 percent, respectively. If four wells are
drilled per year for about 10 years (for a total of 39 wells), the spill frequencies become
1.6 x 10-4 extremely large spills (greater than 150 000 bbl) per year and 3.1 x 10-4 very
large spills (greater than 10 000 bbl) per year. This means that one extremely large spill
might occur every 6300 years of drilling at this rate and one very large spill every 3200
years. For similar blowouts from production activities and workovers the equivalent
numbers are one extremely large oil well blowout (greater than 150,000 bbl) for every
6400 years of production and one very large oil well blowout (greater than 10,000 bbl)
for every 2600 years of production. These predictions are based on worldwide blowout
data and are strongly influenced by blowouts that have occurred in Mexico, Africa and
the Middle East. Even lower frequencies could result for Terra Nova Development in
view of the fact that no development drilling blowout spills larger than 10,000 barrels
have occurred anywhere since 1980, suggesting significant improvement in technology
and practices over the past 15 years.
The chances of having a blowout of any kind are relatively high, perhaps as high as 11
percent, but historical data suggest a 95 percent chance that the blowout will discharge
no oil at all.
The probability of a scouring iceberg has not been addressed in this document. There
will be sufficient notification of such an event for all lines to be flushed with sea water.
Calculated oil-spill frequencies are summarized in Table 5.7-10. The highest
frequencies are for small spills. Spills of less than 50 barrels are predicted to occur
about once every five years. The chances of having a platform-based spill larger than
50 barrels over the life of the development are less than 25 percent.
Large platform-based spills (greater than 1000 bbl) have about a 1 percent chance of
occurring over the course of the development, and very large platform spills (greater
than 10,000 bbl) have a 0.4 percent chance. Tanker-loading spills of greater than 1000
barrels have a 50:50 chance of occurring over the project period, although the spill size
would likely be moderate, perhaps in the 5000-barrel range. This frequency could be
reduced if state-of-the-art offloading technologies are utilized in the project.
5.7.2
Selection of Oil Spill Scenarios
Hypothetical, large oil spills from oil-well blowouts and tanker-loading accidents are
used as a basis for describing the fate, behaviour, impact and control of Terra Nova
spills in the following subsections.
Recognizing that no two spills are alike, detailed spill-specific scenarios are used to
assess impacts and cleanup capability. These precisely defined oil-spill situations are
used as a benchmark in the evaluation process. The objective is to develop a
manageable number of detailed large-spill scenarios that illustrate what could be
expected if a major spill occurred during the Terra Nova Development. Scenarios are
selected to cover the range of spill types and sizes. The selection covered the two main
possibilities for large spills:
·
·
A continuous spill from an oil-well blowout involving a large discharge over a
relatively long period of time
A batch spill from a ruptured container or loading hose leading to a large
discharge of oil over a short period of time. This scenario also simulates a
similar-sized spill from the subsea system
Spills from tanker accidents are not considered.
The Hibernia EIS
Table 5.7-11 summarizes of the oil spill scenarios used in the Hibernia EIS.
The 4800 m3/d oil blowouts were calculated by Mobil Oil to be the highest flow
possible from the most prolific well discharging with no restriction, that is, with
1
4.1 x 10 -5/well-years
7.8 x 10 -5/wells drilled
2.5 x 10 -5/well-year
Blowout during production and workovers involving some
oil discharge > 1 bbl
Development drilling blowout with oil spill > 10,000 bbl
Development drilling blowout with oil spill > 150,000 bbl
Production/workover blowout with oil spill > 10,000 bbl
Production/workover blowout with oil spill > 150,000 bbl
7.8 x 10-4/well-year
Oil spill > 50 bbl
Oil Spill < 50 bbl
U.S. data only
Oil spill > 1000 bbl
1.4/109 bbl produced
Oil spill > 1000 bbl 1
TANKER LOADING SPILLS
Oil spill > 10,000 bbl 1
PLATFORM SPILLS (including blowouts)
Historical
Frequency
Blowout during development drilling and completions
BLOWOUTS
Event
0.40 x 10 9 bbl produced
312 well-years
312 well-years
312 well-years
312 well-years
312 well-years
312 well-years
39 wells drilled
39 wells drilled
312 well-years
39 wells drilled
Terra Nova
Development Exposure
Predicted Number of Blowouts and Spills for the Terra
Nova Development over its 20-Year Lifetime
Table 5.7-10
1.1 x 10 -3
4.1 x 10 -3
3.1 x 10 -3
7.8 x 10 -3
1.5 x 10 -3
3.0 x 10 -3
1.3 x 10 -2
1.3 x 10 -1
0.56
5.3
0.24
No. of Events
56
100
24
1.1
0.41
0.31
0.78
0.15
0.30
1.3
13
Probability
(%)
absolute open flow. As a worst case it was further assumed that this flow rate would
continue until a relief well were drilled that would stop the flow in 90 days. The
average size and duration of the smaller blowouts were simply calculated on the basis
of worldwide statistics of blowouts where some oil (greater than 2000 bbl) was
discharged (S.L. Ross 1984). The tanker spills were selected on similar grounds.
Finally, the volumes for the transfer and intrafield pipeline spills were calculated based
on flow rates and potential duration, the latter limited by the use of automatic shut-off
valves.
Table 5.7-11
Summary of Hibernia Spill Scenarios
Spill Type
Source
Blowout
Subsea
Duration
4800 m3/d
90 d
320 m3/d
5d
4800 m3/d
90 d
320 m3/d
5d
30 000 m3
1h
9000 m3
24 h
Transfer
800 m3
instantly
Pipeline
300 m3
1h
Platform
Batch
Flow
Tanker
Selection of Terra Nova Scenarios
Spill Type, Size and Duration
Table 5.7-12 shows the five scenarios selected for Terra Nova Development. The
concept of an average-size blowout based on historical data has been rejected, because
it has little instructional value. The transfer spill of 800 m3 is identical to that chosen for
Hibernia. Tanker spills are not considered at this time. The worst-case blowout
scenarios selected for Terra Nova are similar to those selected for Hibernia, but some
are more extreme. The reason is not that Terra Nova spills are expected to be larger
than those from the Hibernia project, but rather that the situation is analyzed
differently, as explained below.
Table 5.7-12
Summary of Terra Nova Spill Scenarios
Spill Type
Blowout
Batch
Source
Flow
Duration
4800 m3/d
90 d
4800 m3/d
45 d
7150 m3/d
7d
Surface
7150 m3/d
7d
Transfer
800 m3
Subsea
instantly
Blowouts. The method used to select and size the various Terra Nova blowout
scenarios was originally developed for use in the Beaufort Sea in the late 1980s and
early 1990s (Adams and Pearson Associates Inc., 1991). The specific techniques used
to calculate fluid escape paths, flow rates and incident durations are beyond the scope
of this EIS. Detailed engineering calculations using specific Terra Nova drilling and
production characteristics were used to determine the flow scenarios.
The blowout scenario occurs with no drill pipe in the hole and casing set down to near
the producing formation. Oil and gas flow into the hole and up the casing at rates of
9500 m3/d of oil with a gas-oil ratio of 134 m3/m3. The GOR is corrected to
atmospheric conditions. The flow rate of the blowout declines after one week to 4800
m3/d and finally reaches a steady-state value of about 3200 m3/d. The volumes used for
this scenario would make this hypothetical event the largest spill in history. The flow
rate declines because of the depletion of the reservoir pressure and choking of the flow
by debris breaking off the walls of the uncased section and falling into the bottom of the
hole.
It is quite likely, given the physical characteristics of the producing formations, and the
extremely high flow rates, that the uncased well bore would collapse in less than a day
after the blowout occurred, shutting off the flow. This is believed to be the case for a
blowout in the Beaufort Sea, an area with similar reservoir rock characteristics (Adams
and Pearson Associates Inc., 1991). Two short-duration flow rate scenarios have been
chosen that reflect seven days of high flow from the well. One is a subsea blowout
emanating from the blowout preventer on the seafloor; the other is a surface blowout,
where the oil sprays out of the riser at the drill floor. The oil production rate for these
scenarios was chosen as the average over the first week, or 7200 m 3/d. Two longer
term blowout scenarios were also developed. These involve oil flow rates of 4800 m 3/d
(representing a long-term average flow) lasting for 45 or 90 days. The shorter duration
represents the time estimated to drill a relief well using the rig involved in the blowout;
the longer duration is the estimated time to complete a relief well with a rig brought in
from elsewhere.
Both long-term blowouts are subsea release scenarios. To develop a realistic scenario
that lasts for a long duration and requires a relief well, it is necessary to envision a
blowout that escapes to the sea floor outside the casing. In this hypothetical situation,
the casing shoe (the cement annulus between the bottom portion of the casing and the
drilled rock hole) fails and allows reservoir fluids to escape to the surface via a fracture
in the rock. No well-control operations would kill this type of blowout; a relief well
would be required. The flow rates of oil and gas through such a leak are impossible to
estimate, but could be much less than the flow achievable through casing. For the sake
of this assessment it is assumed that the flow is 4800 m3/d.
No long-term surface blowout is included in the scenarios. If a platform blowout were
to occur it would likely be controlled quickly or kill itself because of reservoir rock
collapse in a short time (81 percent of all blowouts are controlled or die naturally in 7
days (Adams and Pearson Associates Inc., 1991); if the blowout were not controllable
from the surface, the rig would be pulled off the blowout well (converting the platform
blowout to a subsea blowout) and used to drill the relief well.
Batch Spills. The batch spill size was selected from the average, large batch spill size
determined in the previous section. The spill duration is assumed to be instantaneous
(or nearly so) since the cause of such spills historically has been a hose rupture or a
storage tank failure, both of which result in high oil release rates that rapidly drain the
affected system. The volumes associated with this scenario fit well with the volumes of
oil in flowlines as set out in Table 5.4-4.
Environmental Conditions Assumed for Scenarios
For each scenario, calculations of oil-slick behaviour and fate were made for two sets
of seasonal environmental conditions. The average temperatures and winds for the
Terra Nova site in December, January, February, June, July and August are reproduced
(from Chapter 3 of this EIS) in Table 5.7-13. For scenario purposes, a winter spill was
defined as occurring with air and water temperatures of 2°C and winds of 12 m/s; a
summer spill occurred with air and water temperatures of 11°C and winds of 9 m/s.
Table 5.7-13
Terra Nova Spill Scenario Environmental Data
Winter
Summer
Parameter
5.7.3
December
January
February
June
July
August
Average air
temperature (°C)
2
0
-1
7
11
13
Average water
temperature (°C)
2
1
0
5
11
12
Average wind speed
(m/s)
12
12
12
9
9
8
Terra Nova Oil Properties and General Spill Behaviour
There are many publications that describe the conventional behaviour of marine oil
spills, including the main processes of spreading, evaporation, water-in-oil
emulsification, and dispersion. However, Grand Banks crude oils, including those of
Hibernia and Terra Nova, do not behave like conventional oil because of their waxy
nature. In studies for the Hibernia EIS (S.L. Ross, 1984) and for early studies of Terra
Nova crudes (S.L. Ross, 1985) it was understood that these crude oils would behave in
an unusual manner and attempts were made to predict such behaviour, but it was not
until a comprehensive study was completed on the subject several years later (S.L.
Ross and D. Mackay Environmental Research Limited, 1988) that this peculiar spill
behaviour could be better appreciated and estimated mathematically. If the Hibernia
EIS were redone today with current knowledge and models, it would show spills
persisting on the water surface for a much longer time.
The main purpose of this subsection is to describe the spill-related properties of Terra
Nova crude oil and how it is likely to behave if spilled in the Grand Banks marine
environment. This discussion is set against a brief discussion of the behaviour of
"conventional" crude oil spills.
Spill-Related Properties of Terra Nova Crude Oils
Table 5.7-14 lists the important spill-related physical properties of the Terra Nova
crude used for spill scenario prediction in this EIS. The particular crude used is Terra
Nova K-08 DST. No. 4 (S.L. Ross, 1985). The oil properties of this crude oil are
considered representative although it is recognized that:
-
The Terra Nova area will produce oils with a range of properties
These oils will be blended as part of the production process
The oils produced by the individual wells will change over time
The key difference between Hibernia and Terra Nova crude is that the pour point of the
Terra Nova crude is higher, equalling the average summer water temperature. This has
significant implications, discussed in the next section, for the behaviour of Terra Nova
crude spills.
Another key spill-related property of Terra Nova crude is the fact that it will form very
stable water-in-oil emulsions when spilled, even when the oil is fresh. The Hibernia
crude is similar in this regard. The formation of stable emulsions also has implications
for spill behaviour, particularly survival time.
The remainder of the spill-related physical properties of the Terra Nova crude are
typical of a medium-gravity crude oil.
Comparison of Terra Nova Spill Behaviour to Conventional Oil Spill Behaviour
When oil is spilled at sea it is subject to several weathering processes. The major
weathering processes are:
-
Drifting (advection)
Spreading
Evaporation
Natural dispersion of oil in water
Water-in-oil emulsification
Table 5.7-14
Properties of Terra Nova Crude and Hibernia Crude
Parameter
Terra Nova Crudea
Hibernia Crudeb
API gravity
32.5°
30.4°
Density at 15°C
862.1 kg/m3
874 kg/m3
Viscosity
at 25°C
at 50°C
18.2 mm2/s
5.9 mm2/s
25 mm2/s
-
Interfacial tensions at 20°C
air to oil
oil to seawater
29.0 mN/m
29.6 mN/m
27.2 mN/m
21.0 mN/m
Pour point
12°C
9°C
Flash point
21°C
14°C
Emulsion formation tendency
and stability at 1°C and 15°C
Forms very stable emulsion
even when fresh
Forms very stable emulsion
even when fresh
Aqueous solubility in salt water
at 22°C
18.78 g/m3
17 g/m3
Weathering (see Stiver and
Mackay, 1983)
Equation 1c
Equation 2d
a K08 well DST No. 4; S.L. Ross (1985).
b B-27 well, S.L. Ross and DMER (1988), and S.L. Ross (1984). The properties of Hibernia crude given in Table 4.7-2 on
page 70 of the Hibernia EIS are actually those of fresh Avalon crude.
c FV = 1n(1 + 6404 Θ exp (6.3 - 4253/TK)/TK) (TK/6404)
d FV = 1n(1 + 5974 Θ exp (6.3 - 4141/TK)/TK) (TK/5974)
where:
FV = fraction of oil weathered by volume
1n = natural logarithm
Θ = evaporative exposure
exp = exponential base e
TK = environmental temperature ( °Kelvin = 273 + °C)
Drifting
Drifting or advection occurs when surface slicks are moved away from the spill site by
water currents. These currents usually combine residual current movement and
wind-induced surface movements. In nearshore marine waters, the movement of oil
slicks is also affected by tidal currents, river outflows and longshore currents.
The properties of the spilled oil do not greatly affect the drifting process; hence spills of
Terra Nova oil will move as any spilled oil would. The subject of oil spill drifting is
covered in more detail in a subsequent section on Terra Nova spill trajectories.
Oil Spreading
Numerous models of oil spreading behaviour and its dependence on oil properties and
environmental conditions have been developed over the last three decades. Recent
models relate the properties of the oil (density, viscosity and interfacial tension) to its
spreading on calm water. Most good models include an oceanic diffusion term to
describe spreading behaviour in more realistic sea conditions.
Conventional oils that flow easily on water (specifically, low pour point, low viscosity)
usually spread quickly. For example, a spill of 1000 m3 can result in a total slick area of
about 10 km2 in one or two days. This is equivalent to an average slick thickness of 0.1
mm. The surface oil is usually not a uniform, thin sheet of oil, but rather is composed of
thick patches (usually thicker than 1 mm) that contain most of the spill volume
surrounded by sheens (about 1 to 10 µm or 0.001 to 0.01 mm). The rule-of-thumb is
that 90 percent of an oil spill's volume is contained in 10 percent its area.
Terra Nova crude will not spread like a conventional oil for two reasons. First, the
pour point of the crude is equal to or above the average water temperature year-round.
This means that when Terra Nova crude is spilled it will gel. This will likely result in
blowouts generating streams of small gelled droplets of oil (S.L. Ross and DMER
1988) that do not coalesce to form a slick (as was the case at the IXTOC-1 subsea
blowout and the Uniacke platform blowout). These individual droplets may, however,
agglomerate to form larger particles. Batch spills of Terra Nova crude will likely form
into thick (1 or more cm) layers of gelled oil "fractured" into metre-sized mats of oil by
wave action (S.L. Ross and D. Mackay Environmental Research Limited, 1988; S.L.
Ross, 1986).
The second property of Terra Nova crude that will affect its spreading behaviour is its
interfacial tension with air and seawater. Oil will not generate a sheen on water if the
sum of its oil-to-air and oil-to-water interfacial tensions exceeds the interfacial tension
between the air and the water (about 70 mN/m). As can be seen from Table 5.7-14, the
sum of these interfacial tensions for fresh Terra Nova crude is nearly 60 mN/m.
Further, as Terra Nova oil evaporates both its air-to-oil and oil-to-water interfacial
tensions increase. After the oil has lost about 29 percent of its volume to evaporation
the sum of the interfacial tensions exceed 70 mN/m and the oil will stop generating a
sheen.
Evaporation
Evaporation is one of the most intensively studied and predictable processes. The
evaporation rate of an oil slick is controlled or affected by:
-
Temperature
The surface area of the oil in contact with air
The thickness of the oil
Wind speed
The concentration and vapour pressure of the individual components of the oil
Most good oil evaporation rates models follow an approach developed by Professor D.
Mackay at the University of Toronto (Stiver and Mackay, 1983) where an overall
"mass transfer coefficient" for evaporation is first determined experimentally. The
volume or mass fraction of oil evaporated is related to an exposure coefficient
(combining time, oil volume and area, and the mass transfer coefficient to the
atmosphere) and to the vapour pressure-concentration behaviour of the oil. The unique
aspect of this approach is that it permits the results from a variety of laboratory
evaporation experiments to be extrapolated to actual environmental conditions with a
relatively high degree of confidence. Table 5.7-15 illustrates the results of this approach
in predicting the evaporative loss from a 1 mm slick of crude oil (density = 0.84 g/cm3)
as a function of sea state.
Table 5.7-15
Evaporation of Conventional Crude Oil Slicks as a Function of Sea State
(%)
Exposure = 6 hrs
Exposure = 24 hrs
Sea State
5°°C
15°°C
5°°C
15°°C
Medium (2-3)
23
32
28
37
High (4-6)
26
35
29
38
For the Terra Nova oil, and all waxy, viscous oils, there are additional resistances to
mass transfer that curtail evaporation. These relate primarily to the development of
internal resistances to the movement of molecules to the surface of the slick and their
escape from the surface of the slick into the air. When a waxy oil evaporates and loses
volatiles, the wax molecules begin to precipitate from solution and the oil begins to gel;
once a certain resistance to flow is created by the precipitated waxes the oil reaches its
pour point. In other words evaporation raises the pour point of an oil until it equals,
then exceeds ambient temperature. At this point, it becomes more difficult for
molecules to migrate from the inside of the slick to the surface, and the surface and
near-surface of the slick begin to lose volatiles at a rate faster than the interior. This
eventually results in a "skin" of waxy-like material forming on the surface of slicks. This
"skin" further restricts the movement of molecules from the interior of the oil to the
atmosphere.
Experiments have indicated that when the pour point exceeds ambient temperature by
about 15°C, these resistances to evaporation become significant (S.L. Ross and D.
Mackay Environmental Research Limited, 1988).
Another significant feature of Terra Nova spills that relates to evaporation is the
formation of non-spreading droplets by blowouts. The surface-area-to-volume
relationship is different for a sphere than for a flat plate (specifically, a slick). For an
infinite flat plate the ratio of area to volume is the inverse of the thickness (as used in
Stiver and Mackay (1983) to develop evaporation rate of a slick); for a sphere (or
droplet) the ratio of area to volume is 6 divided by the diameter. Although the droplet
is floating in water and not suspended in air and thus its full surface area is not exposed
to air, the use of 6 divided by diameter adequately fits evaporation data from droplets
on water (S.L. Ross and D. Mackay Environmental Research Limited, 1988). This may
be because the volatiles can migrate from the droplet into water and from there into the
air nearly as fast as they can migrate directly into the air.
In summary, waxy oils evaporate more slowly than conventional oils and can form
waxy skins that virtually encapsulate fresher oil within.
Emulsification
When most crude oils are spilled at sea, they tend to form water-in-oil emulsions.
Emulsification occurs in the presence of mixing energy such as that provided by wave
action. During emulsification, seawater is incorporated into the oil in the form of
microscopic droplets. This water intake results in a significant increase in the bulk
volume of the oil (usually up to a four- or five-fold increase) and a marked increase in
fluid viscosity. Conventional crude oils will start to emulsify within a few minutes of
being spilled, and will form a highly viscous and stable emulsion within hours. Most
refined petroleum products do not emulsify. Many crude oils do not begin to emulsify
immediately; however, once some of their light ends have evaporated and their
asphaltenes and waxes concentrated to a certain degree, they will begin to emulsify.
Terra Nova crude will emulsify readily at ambient temperatures when it is fresh (Table
5.7-14). This is not true for gelled oil droplets generated by a blowout; these droplets
are too small to be penetrated by the mixing action of waves and do not readily
coalesce to form a slick. This coalescence process is one possible explanation for the
near-source emulsification observed at the IXTOC-1 blowout (Ross et al., 1979).
Natural Dispersion and Dissolution
The dispersion and dissolution of oil into the water column by natural forces is an
important process controlling the long-term fate of oil slicks at sea. In conjunction with
evaporation, this process reduces the volume of oil on the water surface, thereby
influencing the potential extent of surface and shoreline contamination. It is discussed
in more detail here than the other processes because of concern that the dispersion of a
Terra Nova spill might affect fish on the Grand Banks.
Dispersion and dissolution are physical processes by which oil and the more soluble
lower-molecular-weight hydrocarbons move from the slick into the water column.
Conventional crude oil droplets are dispersed relatively easily from the slick into the
water column by waves. The larger of these droplets, which are buoyant, resurface
quickly and rejoin the slick. The smaller droplets remain in suspension in the water
column. The lighter, more water-soluble hydrocarbons partition from these droplets
into the water phase. Clouds of the entrained dissolved and particulate oil then spread
horizontally and vertically by diffusion and other long-range transport processes. The
oil concentrations in the water column under the slick are the result of the competing
processes of entrainment of oil into the water column, which increases the
concentration, and horizontal and vertical diffusion and transport of hydrocarbons,
which decreases the oil concentration in the water column.
Although natural dispersion is a poorly understood process, it is known that oil to
water interfacial tension, oil viscosity, oil buoyancy and slick thickness each inversely
affect the ability of a particular oil to disperse naturally. Sea state is also an important
factor. Even light, non-viscous oils do not rapidly disperse under calm conditions. On
the other hand, over a period of time, even emulsified oils can disperse in heavy seas
with frequent breaking waves.
The net flux rate of oil from a slick (small particles and dissolved hydrocarbons) into
the water column will vary greatly depending on the properties of the spilled oil and
mixing energy (Delvigne, 1985, 1987; Mackay et al., 1980), but simulations (done with
the oil spill model discussed later in this report) suggest that the net entrainment rate of
oil from a thick slick of Arabian medium crude oil into the water column at average
wind speeds (20 km/h) would be on the order of 1 to 2 mg/cm2 per hour. In
experimental spills, oil concentrations measured in the water beneath the slicks have
ranged from several hundred parts per billion to as much as several parts per million
(McAuliffe et al., 1981; Lichtenthaler and Daling, 1985; Lunel and Lewis, 1993).
Thick slicks of Terra Nova crude will be particularly resistant to natural dispersion.
This is primarily because of the gelled nature of the crude at ambient temperatures
(particularly droplets from blowouts) and the strong tendency of mats of the oil to
emulsify. Modelling suggests that the only significant source of dispersed oil for Terra
Nova spills will be from the sheens generated by thicker slicks or droplets. Once the oil
reaches a level of evaporation that stops sheen formation, it will survive on the sea
surface for a very long time.
Sedimentation
Some of the oil that becomes entrained into the water column may become associated
with suspended particulate matter and may ultimately settle to the seabed. The amount
and concentrations of hydrocarbons that reach the seabed near a spill site appear to be
a function of:
-
The amount of oil entrained into the water column
The amount and nature of particulate matter suspended in the water column
Water depth
The speed of subsurface water movements
Historically, seabed contamination has been observed in spills in shallow nearshore
environments where suspended sediments loads are relatively high. In several historical
nearshore spills, levels of seabed contamination have been as great as several hundreds
of parts per million (S.L. Ross 1993). In deeper offshore waters it is unlikely that
significant levels of oil contamination would develop in seabed sediments near a spill
site because of the low suspended sediment load and the long settling times.
Once seabed sediments have become contaminated with spilled oil, decontamination
appears to require from several weeks to several years. The smaller lighter
hydrocarbons degrade more quickly than higher molecular weight molecules (S.L.
Ross 1993).
Considering the low rate of natural dispersion expected for spills of Terra Nova crude,
sedimentation is unlikely to occur to a measurable degree.
Near-Source Behaviour of Oil Well Blowouts
Marine oil spills resulting from offshore oil well blowouts behave very differently from
instantaneous batch spills. Spills from blowouts and batch spills are not produced in the
same way and their initial layouts and properties are subsequently different. Because
the selected hypothetical spills in this analysis are mostly blowout-related, it is useful to
explain this briefly with particular reference to the Terra Nova situation. For a more
detailed treatment of the subject see S.L. Ross (1984).
There are two basic kinds of offshore oil-well blowouts. The first is a subsea blowout,
in which the drilling platform moves off site or is destroyed during the blowout. In this
case the discharging oil emanates from a point on the sea bed and rises through the
water column to the water surface. The 1979 Ixtoc-1 blowout in the Bay of Campeche,
Mexico (Ross et al. 1979) is an example of this kind of oil-well blowout. The second
type of blowout occurs above-surface, the platform maintains its position during the
accident (because it is undamaged or bottom-founded) and the oil discharges into the
atmosphere from some point on the platform above the water surface, and
subsequently falls on the water surface some distance downwind. The 1977 Ekofisk
blowout in the North Sea (Audunson, 1980) and the Uniacke blowout off Nova Scotia
(Gill et al., 1985) are examples of this type.
Subsea Blowouts
Oil-well blowouts, both subsea and platform, generally involve crude oil and natural
gas. The volume ratios of these two fluids are a function of the characteristics of the
reservoir. The natural gas, being a compressible fluid under pressure at reservoir
conditions, provides the driving force for an uncontrolled blowout. As the well
products flow upward, the gas expands, finally exiting the well-head at extremely high
velocities. At this point the oil makes up only a small fraction of the total volumetric
flow.
The high velocity at the wellhead generates a highly turbulent zone that fragments of
the oil into droplets ranging from 0.5 to 2.0 mm in diameter (Dickins and Buist, 1981).
Because water is also entrained in this zone, a rapid loss of momentum occurs a few
metres from the discharge location. At this point buoyancy becomes the driving force
for the remainder of the plume. In this region the gas continues to expand because of
reduced hydrostatic pressures. As the gas rises, oil and water in its vicinity are
entrained in the flow and carried to the surface.
Although the terminal velocity of a gas bubble in stationary water is only about 0.3 m/s,
velocities in the centre of blowout plumes can reach 5 to 10 m /s as a result of the
pumping effect of the rising gas in the bulk liquid. That is, the water surrounding the
upward-moving gas is entrained and given an upward velocity, which is then increased
as more gas moves through at a relative velocity of 0.3 m/s. When the plume becomes
fully developed, a considerable quantity of water containing oil droplets is pumped to
the surface.
In the surface zone, the rising water and oil flow away from the centre of the plume in a
radial layer. At the surface the oil coalesces in this outward flow of water and spreads
at a rate much faster than ordinary spill spreading rates. The resulting slick takes on a
hyperbolic shape when subjected to a natural water current, with its apex pointed
up-current. The dimensions of the slick can be estimated using mathematical models,
briefly described in the next section.
The situation would be slightly different for a subsea blowout involving the Terra Nova
oil. In this case, the oil droplets would not recoalesce to form a slick, but remain a
discrete droplets because the pour point of the crude exceeds ambient water
temperatures. These fresh oil droplets would generate a sheen on the surface.
Above-Surface Blowouts
Oil released during a blowout from an offshore platform above the water's surface will
behave differently than that from a subsurface discharge. The gas and oil will exit at a
high velocity and will be fragmented into a jet of fine droplets. The height that this jet
rises above the release point will vary depending on the reservoir pressure, gas velocity,
oil particle size distribution, and the prevailing wind velocity. The fate of the oil and gas
at this point is determined by atmospheric dispersion and the settling velocity of the oil
particles. The oil will "rain" down, with the larger droplets falling closer to the release
point. If the gas is blowing through the derrick or some other obstruction, oil droplets
will agglomerate on the obstruction(s) and increase in diameter. During their time in the
air the droplets evaporate, generally quite quickly because of their high surface-area-tovolume ratio and the fact that the oil is warm.
For conventional oils a slick will form on the water surface. Slick dimensions can be
estimated with the use of a mathematical atmospheric deposition model. Generally,
slicks resulting from a platform or surface blowout are much thicker and narrower than
slicks from subsea blowouts (and thus are easier to control and recover using
conventional spill cleanup equipment).
In the case of a surface blowout at the Terra Nova Field, it has been assumed that the
oil spray hits the derrick and other structural steel on the rig and the fine oil mist
agglomerates to form 1 mm diameter droplets. These droplets rain down onto the
water surface and form a slick (the flow rate of the well and atmospheric deposition
calculations indicate that the droplets would fall on top of each other, as opposed to
discrete droplets as is the case for a subsea blowout). The degree of evaporation
experienced by the droplets during their time in the air is such that the oil slick will not
generate any sheen and is extremely viscous with a pour point well above ambient
temperatures.
5.7.4
Modelling and Description of Selected Oil Spill Scenarios
When referring to the fate and behaviour of marine oil spills, "fate" usually means the
movement of the spill as it is driven by winds and currents, and "behaviour" means the
processes that the spill is undergoing (spreading, evaporation, dispersion) that change
its properties (e.g., viscosity, density) and change its distribution in the environment
(air, water surface and water column). This section focusses on the behaviour of the
selected hypothetical spills. The following section concentrates on the fate or trajectory
of the spilled oil.
Of particular interest in this EIS is the behaviour of large blowout spills at and near the
platform, because it is here where spill control measures can be most effective. Also
important are the distribution and "stickiness" of the oil particles on the surface as a
function of time because these properties will influence estimates of impact on birds
that use the surface waters in the area.
The predictions used in this section were generated using a state-of-the-art spill
behaviour and fate model (S.L. Ross Model, Appendix 5.E). For the scenario
descriptions, average seasonal temperatures and winds were used; for the trajectory
analysis in the following section time-varying winds were used. The model used the
properties of Terra Nova crude (as listed in Table 5.7-14 and S.L. Ross, 1985) as
inputs. Five scenarios were developed (Table 5.7-12) and spill behaviour predictions
made for each in both summer and winter conditions. The model was configured to
plot trajectories for 30 days or until the remaining oil moved beyond the boundary of
the study area used for modelling (40° to 50°W, 42° 45_ to 51° 30_ N). The decision
to terminate at the study boundaries was based on the wide distribution of droplets and
the results of the S.L. Ross data report on adhesion characteristics of spilled Terra
Nova oil (S.L. Ross, 1996).
Blowout Scenarios
The near-source behaviour of the hypothetical surface blowout is described first,
followed by the descriptions for the various subsea blowouts.
Scenario 1a: 7150 m3/d Surface Blowout Lasting Seven Days in Summer
A blowout occurs on the MODU resulting in a discharge of 7150 m 3/d of Terra Nova
crude with a gas-oil ratio of 134 m3/m3. The MODU is not damaged and remains in
position throughout the seven-day blowout period. The gas exits at the drill floor (25 m
above the water surface) at a velocity of about 500 m/s, shattering the oil into 0.09 mm
diameter droplets, on average. These droplets are projected 26 m upward by the jet of
gas, impact on the derrick and agglomerate to a size of about 1 mm. These larger
droplets rain down on the water, beside the rig. Most of the droplets falls onto the
water surface within 355 m of the rig. Throughout the seven days required to kill the
well, the air and water temperatures average 11°C. The combined surface current is
0.29 m/s.
Table 5.7-16 shows the trends in spill behaviour in the early stages of this and the
following scenario. The slick at source is 75 m wide and 2.6 mm thick. The oil making
up the slick has lost 36 percent of its volume as a result of evaporation while the
droplets were in the air. As a result, it does not generate a sheen. The resulting oil has a
viscosity of 3300 mPas and a pour point of 34°C. Within the first hour of exposure to
the environment, the oil has formed an emulsion containing 40 percent water. The
water content increases to 74 percent after 6 hours and 75 percent in 24 hours. The
viscosity of the emulsion increases to 138 000 mPas in 24 hours.
As the slick drifts from the site, wave action breaks it into viscous mats of oil that move
away from each other under the influence of oceanic turbulence. Because the oil is
thick and viscous and does not generate a sheen, it survives for a very long time at sea.
After 24 days (the time it takes for the slick to reach the boundary of the study area) 58
percent of the oil discharged is still on the surface.
Scenario 1b: 7150 m3/d Surface Blowout Lasting Seven Days in Winter
This accident is identical to that of the first scenario except that it occurs in winter
(higher winds and colder temperatures). The higher winds result in a longer hang time
for the droplets (they fall out within 420 m of the rig) and thus, a slightly wider slick
(82 m). The colder temperatures result in slightly less initial evaporation (32 percent by
volume) but a higher initial viscosity (3400 mPas.). As with the summer scenario, the
oil will not generate a sheen and emulsifies rapidly (65 percent water in one hour) to
form extremely persistent mats. Even in the higher winter seas, 61 percent of the oil
discharged remains on the sea surface after 19 days.
Scenario 2a: 7150 m3/d Subsea Blowout Lasting Seven Days in Summer
In this scenario, the blowout occurs through the casing shoe and the oil and gas flow to
the seabed through a fracture in the rock. The oil flow rate is 7150 m 3/d and the gas-oil
ratio is 134 m3/m3. The fluids erupt from the seabed and the gas breaks the oil into 0.8
mm diameter droplets that are carried to the surface in the water being drawn up by the
gas. Throughout the seven days before the well-bore collapses, sealing off the flow, the
temperatures are 11°C and the wind speed is 9 m/s.
1
82
Winter
180
180
6h
925
925
24 h
1.9
2.6
At source
7.4
10.4
6h
7.3
10.4
24 h
Emulsion Mat Thickness
(mm)
3400
3300
At source
132 000
121 000
6h
Viscosity
(mPas)
157 000
138 000
24 h
58
40
1h
75
74
6h
75
75
24 h
Water Content of
Emulsion (% vol)
At source this is the width of the oil slick; farther downdrift, it is the diameter of the circle in which the separate oil mats may be found.
75
At source
Summer
Season
Slicklet1 Width
(m)
7150-m3/d Platform Blowout Scenario Summary
Table 5.7-16
39% gone in
19 days
42% gone in
24 days
Slicklet
Dissipation
At the surface the oil drops themselves do not spread but, because the oil is fresh they
do generate a thin sheen. The entrained water flow creates a hyperbolic-shaped slick
that extends 230 m up-current of the gas boil zone (located at the focus of the
hyperbole) and is 1460 m wide downstream. The oil droplets are widely scattered in
this zone. By the time the slick has spread to 1460 m the oil droplets have lost 13
percent of their volume to evaporation; this increases to 20 percent after six hours and
27 percent after 24 hours.
Table 5.7-17 illustrates the spill behaviour in the early stages of this and the next
scenario. The slick spreads slowly from its initial width, and reaches 1640 m after six
hours. By this time the droplets have evaporated to a point that they stop generating
sheen and oil spreading stops. After about 36 hours, oceanic turbulence begins to
spread the droplets out.
Evaporation raises the viscosity of the droplets, which do not emulsify, to 1900 mPas.
after six hours and 6900 mPas. after 24 hours. Evaporation also slightly reduces the
diameter of the droplets, from 0.83 mm initially to 0.77 mm after six hours and 0.75
mm after 24 hours. The droplets are very persistent, losing only 38 percent of their
volume after 24 days.
Scenario 2b: 7150 m3/d Subsea Blowout Lasting Seven Days in Winter
This scenario is identical to the previous one, except that it occurs in winter, with
higher wind speed (12 m/s) and colder temperatures (2°C). The upstream extent of the
slick from the gas boil is slightly less than in summer (180 m) and its downstream width
is also less (1120 m). This is caused by the higher wind-driven current. The colder
temperatures slow the evaporation rate of the droplets, even in higher winds, because
the pour point of the oil exceeds 2°C by a margin of 15° sooner. This means that
internal resistances to evaporation slow evaporation sooner than in summer. In the
winter spill, the oil droplets lose diameter slightly more slowly for the first day than in
summer and their viscosity increases more slowly. As with the summer spill the oil is
very persistent, with only 39 percent lost in 19 days at sea.
Scenario 3a: 4800 m3/d Subsea Blowout Lasting 45 Days in Summer
This scenario is almost the same as Scenario 2, except that the oil and gas flow rates
are lower. As a result, slightly larger oil droplets are generated at the seabed (1.25 mm)
and the upstream extent (200 m) and downstream width (1280 m) are less than for the
7150 m3/d situation.
The oil droplets lose 14 percent of their volume to evaporation in the first hour, 20.2
percent by six hours and 27.3 percent after 24 hours. The scenario results are
summarized in Table 5.7-18. The volume losses to evaporation from the droplets
146
1120
Winter
At source
1585
1640
6h
Slicklet Width
(m)
Summer
Season
1860
1640
24 h
0.83
0.83
At source
0.80
0.77
6h
0.75
0.75
24 h
Oil Droplet Diameter
(mm)
30
20
At source
750
1900
6h
Viscosity
(mPas)
6900
6900
24 h
7150-m3/d Subsea Blowout Scenario Summary
Table 5.7-17
0
0
1h
0
0
6h
0
0
24 h
Water Content of
Emulsion (% vol)
39% gone in
19 days
38% gone in
24 days
Slicklet
Dissipation
1280
980
Winter
At source
1430
1480
6h
Slicklet Width
(m)
Summer
Season
1650
1480
24 h
1.25
1.25
At source
1.19
1.16
6h
Oil Droplet Diameter
(mm)
1.13
1.12
24 h
30
20
At source
1000
1700
6h
Viscosity
(mPas)
6000
5700
24 h
4800-m3/d Subsea Blowout Scenario Summary
Table 5.7-18
0
0
1h
0
0
6h
0
0
24 h
Water Content of
Emulsion (% vol)
38% gone in
19 days
38% gone in
24 days
Slicklet
Dissipation
decreases their diameter to 1.19 m after 6 hours and 1.13 m after one day. The droplets
do not emulsify, but the evaporative loss increases their viscosity to 1700 mPas in 6
hours and 5700 mPas in 24 hours. The droplets are very persistent. Only 38 percent of
their volume is lost over 24 days.
Scenario 3b: 4800 m3/d Subsea Blowout Lasting 45 Days in Winter
The only difference between this scenario and the previous one (Table 5.7-18) is higher
winds (12 m/s) and lower temperatures (2°C). The higher winds generate faster surface
currents, which make for a narrower slick (980 m) with a smaller upstream extent (155
m). Because the winter spill evaporates more slowly as a result of the earlier onset of
internal resistances to evaporation, it generates a sheen for a longer period than in
summer, resulting in faster spreading. The reduced evaporation also results in a slower
decrease in oil droplet diameter and a lower oil viscosity after six hours. The colder
temperatures mean that after 24 hours at sea the oil is more viscous (6000 mPas) than
in summer. The oil droplets are very persistent. They lose only 38 percent of their
volume in 19 days.
Scenario 4a: 800 m3 Batch Spill in Summer
As a result of an transfer accident, 800 m3 of Terra Nova crude are spilled
instantaneously onto 11°C water in 9 m/s winds. The oil gels shortly after it enters the
water and begins to break up into mats but, because it is fresh, the mats generate a
sheen. The oil also begins to emulsify, reaching 32 percent water content in one hour.
At this point its viscosity is 1200 mPas and the mats are 32 mm thick. Evaporation,
mostly from the thick slick, proceeds to a 15 percent volume loss after six hours and 20
percent loss after 24 hours. Natural dispersion (entirely from the sheen) removes 0.3
percent of the oil in the first six hours and 0.7 percent in the first day. Dissipation of 95
percent of the surface slick takes 19 days.
Table 5.7-19 summarizes the early behaviour and characteristics of the slick.
Scenario 4b: 800 m3 Batch Spill in Winter
The main difference between this scenario and the previous one is the accelerated
natural dispersion rate of the sheen in the higher winter winds and the slower
evaporation, attributable to the onset of internal resistances in the colder temperatures
(Table 5.7-19). The slick is predicted to survive for 11 days.
760
780
Winter
1h
1100
1070
6h
2000
1760
24 h
Slick Diameter
(m)
Summer
Season
53
35
1h
61
67
6h
68
63
24 h
Emulsion Mat Thickness
(mm)
2540
1200
1h
7 200
10 100
6h
Viscosity
(mPas)
11 700
22 600
24 h
800 m3 Batch Spill Scenario Summary
Table 5.7-19
65
32
1h
75
75
6h
75
75
24 h
Water Content of
Emulsion (% vol)
95% gone in 11 days
95% gone in 19 days
Slick Dissipation
5.7.5
Terra Nova Spill Trajectories
Once the spilled oil escapes the Terra Nova site it will be swept by currents and wind
until it gradually disperses in the water, diffuses on the surface to low concentration, or
contacts land. As noted in the previous subsections, Terra Nova oil spills will be highly
persistent, and survival times of weeks and even months are conceivable. The
possibility of Terra Nova oil spills contacting and damaging Newfoundland shorelines
will be addressed in this section as will the effects Terra Nova will have on fishing
activities. Because Terra Nova spills are very resistant to dispersion, the impact on fish
will likely be low, as discussed in the next section, but oil on the surface might affect
the fishery.
The Hibernia EIS
For the Hibernia EIS, Seaconsult (1984) modelled potential slick movement at the
Hibernia site using 30 years (1945 to 1975) of meteorological and oceanographic data.
Results showed that a slick from a large surface blowout would move over substantial
portions of the Grand Banks during its calculated survival time. Trajectories generally
demonstrated that under the prevailing winds and currents, slicks would tend to move
offshore, to the east and northeast. Only during the winter (November, December,
January and March), would there be there any chance of shoreline contact (Table 5.720). Of the 11 000 trajectories run, only 12 involved some oil reaching land. The
volume of oil remaining on the sea surface at the time of landfall was not calculated for
trajectories in this study (Seaconsult, 1984), but can be approximated from results of
other modelling reported in the EIS (see Figure 4.7-5 in Hibernia EIS Volume IIIb). In
all scenarios the amount of oil reaching the shoreline from spills at the Hibernia site is
far less than the amount spilled because spills took a minimum of 9.8 days and an
average of 21.9 days to reach shore and by that time the oil was heavily weathered.
In most scenarios only negligible amounts of oil remained on the sea surface after 9.8
days at sea, except in the worst-case surface blowouts. In the worst-case surface
blowout in winter, approximately 25 percent of the 4800 m3/d discharged daily
persisted after 9.8 days and 10 percent after 21.9 days.
The following assumptions and methods were used by Seaconsult. Atmospheric
Environment Service (AES) geostrophic data were used for the years between 1946
and 1975. These data were adjusted to represent surface winds more accurately by
multiplying the wind speed by 0.88 and rotating the direction by 20° anticlockwise. The
water currents used were the International Ice Patrol (IIP) data set of 1979. Slick
trajectories were estimated by the vector addition of the IIP water currents and 3.5
percent of the adjusted AES wind speed rotated 10° to the right for coriolis effect.
Scenarios were run for a maximum of 180 days or until the slick left the study area or
hit land.
Table 5.7-20
Impact and Closest Point of Approach of Hibernia Oil Slicks to Shoreline
Closest
Approach
Impact
Month
Number of
Trajectories
On shore
Percent of
Trajectories
On shore
Earliest
Time to
Shore
(d)
January
4
0.43
9.8
February
0
-
-
March
2
0.22
29
April
0
-
-
May
0
-
June
0
July
Shoreline
Location
Southeast
Avalon
Time from
Start
of Spill
(d)
Distance
From
Shore
(km)
-
-
8.5
51
-
-
-
29
76
-
-
10.7
150
-
-
-
19
150
0
-
-
-
16
144
August
0
-
-
-
10.2
194
September
0
-
-
-
74
103
October
0
-
-
-
13.2
134
November
5
0.56
17.2
Southeast
Avalon
-
-
December
1
0.11
27.2
Southeast
Avalon
-
-
Southwest
Burin
Data Set and Initial Conditions
Since the Hibernia work, an updated IIP water current grid and additional AES wind
data have become available. The 1995 IIP water current data and AES's 1946 to 1989
wind data have been used for the trajectory analysis reported here. The AES wind data
have been adjusted as outlined above and combined with the water currents as
described for the previous Hibernia modelling.
The main difference between the 1995 IIP mapping and the old data set is the presence
of a weak current that moves towards southern Newfoundland from about 50°W
44°N. This is discussed in detail in Chapter 3. The large wind data set provides a more
representative historical wind sample. The trajectory modelling for this study is
intended to identify whether this new information alters the prediction reached in the
previous study
that there is minimal risk of shoreline impact from potential spills in
the Terra Nova-Hibernia vicinity.
The majority of the trajectories generated in this study originate at a point half way
between the Hibernia and Terra Nova fields. This site was selected to allow the new
analysis to be relevant to both production areas. Test scenarios were run to check the
sensitivity of the spill location to its ultimate path and end point. In areas of low
currents the trajectories were found to follow similar parallel paths because the winds
at these close sites are similar. If the spills enter a region of strong currents, their paths
could start to deviate.
The conditions that cause oil to approach Newfoundland must necessarily involve
persistent winds from the East. Oil moving to land is not generally influenced by strong
currents and as a result trajectories from the three sites that move toward land generally
follow parallel paths. Thus trajectories starting at the mid-point location can reasonably
be used to represent spills from both Terra Nova and Hibernia, for the present impact
assessment requirements and given the coarseness of the biological database and the
uncertainties present in the wind and water current data.
Trajectory Analysis Results
The primary objective of trajectory modelling is to identify the possible movement and
distribution of oil from representative spills. As in the Hibernia work, slick movements
have been modelled using historical wind data and the best available water current data.
Slicks released on every day for which appropriate wind data are available between
1946 and 1989 were tracked. The trajectories were run for 30 days, or until the slicks
hit land or moved out of the study area. The number of slicks predicted to hit land from
this modelling is presented in Table 5.7-21. In general, trajectories are in the offshore
direction, to the east. Only a very few trajectories, all occurring during winter months,
reach land. These results are very similar to those found in the previous work
completed for the Hibernia development. The percentage of the spills hitting land in
this assessment is about 0.15 percent; the Hibernia study indicated that 0.1 percent
would hit land. Some examples of trajectories are shown in Figures 5.7-1 and 5.7-2.
These figures each show the trajectories of 44 spills. The area covered by these figures
is somewhat larger than the "study area" referred to earlier.
Table 5.7-21
Trajectories Reaching Land
Month/Year
(Days Slicks Released)
Time to Shore
(h)
March 1951
25, 26, 27
342 to 474
January 1979
18, 19, 20, 21, 22, 23, 24
432 to 552
March 1987
9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23
492 to 702
Notes:
1. Total slicks hitting land = 24
2. Total scenarios run = 15 900
For each trajectory in the model, the spill is discharged on the first day (and then on
each successive day) of the month in question, February or August, each year from
1946 to 1989. Each spill is then moved by the historical winds and currents in that
month and year.
The potential for shoreline contamination arising from these hypothetical spills depends
not only on the fact that the predicted trajectory hits land, but also on the volume of oil
spilled initially and the weathering and spreading undergone by the oil while at sea. The
trajectory analyses summarized in Table 5.7-21 suggest that oil spilled at the Terra
Nova site would spend from 342 hours (14 days) to 702 hours (29 days) at sea before
contacting the Newfoundland shore. Despite the persistence of Terra Nova oil spills,
after this many days at sea the spilled oil would have spread to very low surface oil
concentrations, and would result in similarly low levels of shoreline contamination.
Study Area
Study Area
5.7.6
Environmental Impact Assessment
Potential impacts from accidental spill scenarios at the nearby Hibernia site were
assessed in the Hibernia EIS (Mobil 1985). These impact estimates were based on an
exhaustive assessment process using the best available knowledge of spills in 1985, and
of sensitivity and vulnerability of biological resources. Rather than repeating this
analysis for Terra Nova the earlier analyses were re-examined to determine the degree
to which they are applicable to the spill scenarios being considered at Terra Nova. The
analysis is divided into two parts: potential offshore biological impacts and shoreline
impacts.
Note that the impact definitions are not as precise as those used in the previous sections
for drilling and production activities. Accidental spills are treated in this manner to
allow direct comparison with the Hibernia EIS. Also, there is considerable uncertainty
as to the level of impacts that might be caused by the waxy Terra Nova crude,
particularly in regard to seabirds.
Potential Offshore Biological Impacts
Table 5.7-22, taken from the Hibernia EIS, summarizes the worst-case potential
impacts from possible spill scenarios associated with the project. The assessment
concluded that for most target groups, potential impact in all spill scenarios was either
no impact or negligible impact. Minor impacts were expected on microbiota and the
biofouling community. Fish and shellfish stocks were assessed to be at no risk or
negligible risk from spills. A minor impact rating was assigned for pelagic fish to
acknowledge that certain spill trajectories contacted an offshore feeding ground for
important salmon stocks in a deepwater area to the southeast of Hibernia. Only
offshore marine birds target group were assigned a major impact rating for large
blowout spills.
The purpose of this assessment is to re-evaluate the conclusions arrived at in the
Hibernia EIS and to determine their applicability to Terra Nova. In particular, four
potential situations have been considered that might invalidate the conclusions made in
the Hibernia EIS. These are:
-
Differences arising from the different location of the spill (spill site)
-
New knowledge developed since 1985 concerning the fate of spilled oil or
sensitivity of resources to spills
-
Changes in the abundance and spatial distribution of oil-sensitive resources as a
result of long-term changes on the Grand Banks
-
New knowledge concerning the abundance or distribution of oil-sensitive
resources or the movement of spilled oil
Table 5.7-22
Summary of Worst-Case Potential Impacts of Accidental Spills at Hibernia
Crude Oil
Transfer Spill1
Subsea Blowout2
Surface Blowout2
Marine plants
Phytoplankton
Macrophytes
0a
-
0
-
0
-
Microbiota
Water column
Sediments
1
1
1
1
1
1
Zooplankton
0
0
0
Ichthyoplankton
0
0
0
Macrobenthos
Hyperbenthos
Epibenthos, infauna
0
-
0
0
0
0
Biofouling community
1
1
1
Fish and commercial shellfish
Pelagic fish
Groundfish
Shellfish
0
-
1
0
0
1
-
Marine-related birds
Seabirds
Waterfowl
Other marine-related species
1
-
1-3
-
1-3
-
Marine mammals
Whales
Seals
0
-
0
-
0
-
Ecosystem
-
-
-
Environmental Components
Notes:
1
800 m3
4800 m 3/d for 90 days
a
Impacts Rating: - = No impact; 0 = Negligible; 1 = Minor; 2 = Moderate; 3 = Major
2
The results of detailed re-examinations of scenarios are summarized in Appendix 5.D,
Table 5.D1, and are further summarized in Table 5.7-23.
Benthos
If the benthos were affected by Terra Nova spills, it would be damaged indirectly
through oil contamination of the seabed. Sediments could become contaminated either
through direct contact between the spilled oil and sediments in a subsea blowout or
through sedimentation of hydrocarbons from the sea surface to the seabed following a
surface spill. The Hibernia EIS discounted the potential for impact of surface spills on
benthos regardless of the size of the spill and assessed the potential as no or negligible
impact. This reflects the generally accepted notion that the potential for sediment
contamination is low for spills in deeper, offshore waters. This is because of a
combination of very slow settling rates for oil-contaminated particles and
comparatively rapid rates of horizontal transport of these particles away from the spill
site. Some of the spilled oil will ultimately settle to the seabed, but only after the
surface oil has become widely dispersed over a large area. The spill-related research
published since 1985 agrees with these conclusions.
In a blowout on the seabed, sediments near the discharge site might become
contaminated with fresh oil. The Hibernia EIS recognizes this possibility and the
associated potential for adverse effects on benthic biota in the immediate vicinity of the
discharge. The EIS also recognizes that effects would be restricted to the immediate
vicinity of the blowout and as such the overall impact on the benthic community of the
Grand Banks would be negligible. There has been no new information concerning
effects of seabed blowouts published since 1985 that would indicate that the scale of
impact of a seabed blowout would be greater than indicated in the Hibernia EIS.
Spills at the Terra Nova site threaten the same benthic communities as do those at the
Hibernia site. All aspects of the fate and trajectories of Terra Nova spills are similar to
Hibernia spills. As well, the better knowledge of waxy crude oils that we have today
suggests that spills of either Hibernia or Terra Nova crude oil will persist on the water
surface for longer periods than suggested in the Hibernia EIS. This greater resistance to
dispersion leads to further reassurance that spills at Terra Nova would not contaminate
the seabed more heavily nor have greater impact on the benthic community than the
Hibernia EIS indicates.
Plankton
This subsection addresses risks to both plankton and juvenile fishes. The Hibernia EIS
concluded that for surface spills hydrocarbon contamination of the upper water column
would not be sufficient to cause lethal or sublethal effects to water column dwellers.
The potential impact on plankton would be negligible. It was
Table 5.7-23
Summary of Worst-Case Potential Impacts of Accidental Spills at Terra Nova
Crude Oil
Transfer
Spill1
Subsea
Blowout2
Subsea
Blowout3
Subsea
Blowout4
Surface
Blowout2
Marine Plants
Phytoplankton
Macrophytes
0a
-
0
-
0
-
0
-
0
-
Microbiota
Water Column
Sediments
1
1
1
1
1
1
1
1
1
1
Zooplankton
0
0
0
0
0
Ichthyoplankton
0
0
0
0
0
Macrobenthos
Hyperbenthos
Epibenthos, Infauna
0
-
0
0
0
0
0
0
0
0
Biofouling Community
1
1
1
1
1
Fish and Commercial Shellfish
Pelagic Fish
Groundfish
Shellfish
0
-
1
0
0
1
0
0
1
0
0
1
-
Seabirds
Waterfowl
Other Marine-Related Species
1
-
1-3
-
1-3
-
1-3
-
1-3
-
Marine Mammals
Whales
Seals
0
-
0
-
0
-
0
-
0
-
Ecosystem
-
-
-
-
-
Notes:
1
800 m3
3
4
Impacts Rating: - = No impact; 0 = Negligible; 1 = Minor; 2 = Moderate; 3 = Major
2
recognized that during a subsea blowout plankton, ichthyoplankton and juvenile fishes
might be entrained into the blowout
plume and be killed. In the latter case it was concluded that while the effects of the
blowout, even a major one, might be significant locally, the overall impact on Grand
Banks populations would be negligible. The assessment was that the overall impact of
spills on plankton and juvenile fishes would be negligible.
The concentrations of spill-generated hydrocarbons in the water-column upon which
the above assessments were made were probably low considering the two spill studies
on which they were based. In one case, water-column measurements were taken many
kilometres from the site of a blowout (the Ekofisk platform blowout in 1977) two days
after the blowout was stopped; in the other case involving a major tanker spill (the
Amoco Cadiz in 1978) measurements were taken as long as three weeks after the spill
happened. Neither case reflects exposure conditions under a fresh oil slick. The
Hibernia EIS does reasonably represent the potential exposure conditions in the upper
water column under slicks from Terra Nova spills because the Terra Nova oil is waxy
like the Hibernia oil. Because Terra Nova oil will likely form encrusted semi-solid mats
or fine droplets when spilled, the toxic fraction of the crude will probably be rendered
less available to plankton animals or juveniles, thus protecting them from effects.
The impact of the spills described in the Hibernia EIS apply equally well to
corresponding spills at Terra Nova (but for different reasons), indicating that
environmental risks to plankton and juveniles in the Terra Nova spill scenarios would
be negligible.
Fish
The Hibernia EIS concludes that neither surface spills nor subsea blowouts posed
significant risks to either pelagic or demersal fish stocks. Accounts of spill effects
published in recent years do not contradict this conclusion. However, a minor risk
rating was assigned to pelagic fishes in order to draw attention to the fact that some
calculated spill trajectories from hypothetical large spills entered the offshore feeding
areas of important salmon stocks in an area southeast of the production site. Although
no specific effects of this contact could be identified, this potential interaction should be
noted.
There is little information in the recent oil-spill literature to suggest that effects of spills
on fish in offshore areas might be greater than indicated in the Hibernia EIS. Neither is
there any information on the distributions of Grand Banks fish stocks to indicate that
the stocks might be more vulnerable to spill effects than indicated in the earlier analysis.
Overall there is nothing to indicate that risks from the hypothetical Terra Nova spill
scenarios would be greater than was indicated for corresponding scenarios at Hibernia.
As is implied in the Hibernia EIS, the risk to offshore salmon from Hibernia spills is
probably negligible and hence the risk to salmon from Terra Nova spills is similarly
negligible.
Seabirds
Seabirds are present in large numbers on the Grand Banks throughout the year,
although individual species are abundant only in certain seasons. The Hibernia EIS
stated that the impact of spills on bird populations in all seasons ranged from minor to
major, depending on the size of the spill. The predicted high level of impact was based
on several factors including:
-
Large spill volume and long persistence of the spilled oil
Movement of the oil slicks over considerable distances
High sensitivity of seabirds to oil slicks
Large proportions of the Atlantic stocks of certain species aggregating on the
Grand Banks at certain times of each year
Birds concentrating somewhat in certain areas around the Grand Banks
New information available since 1985 has confirmed the sensitivity and vulnerability of
seabirds to marine oil spills (Burger, 1993; Eppley et al., 1992; Patten, 1993; Piatt et
al, 1990; Williams et al., 1995; and Heubeck, in press). The information on Grand
Banks bird populations contained in this report confirms the vulnerability of those
populations to both Hibernia spills and Terra Nova spills.
It is important to recognize the waxiness of the Terra Nova oil and the possible
implications for impact on birds. One opinion is that Terra Nova oil spills will form
waxy particles rather than fluid slicks. These oil particles may not wet birds' feathers in
the same way as conventional, non-waxy oils. Major changes in the oil's spreading
behaviour and its ability to wet birds' feathers will certainly reduce the potential impact
of spills on birds. However, until the properties of Terra Nova oil spills are better
understood, especially the potential of the oil to lose its "stickiness" over time, it is
conservative to assume that the risks to birds from Terra Nova oil are similar to those
from a conventional oil; therefore the risks assessed for Hibernia spills would apply
equally to the corresponding spills at Terra Nova.
Marine Mammals
Whales, seals, dolphins and porpoises are the only marine mammals at risk from spills
at the Terra Nova site. Whales are present on the offshore portions of the Grand Banks
in low numbers at certain times of the year. The Hibernia EIS stated that potential
impacts even from major spills on whale populations would be negligible. This was
based on the following:
·
When present on the offshore portions of the Grand Banks, whales occur in
low numbers so that only small proportions of populations of are at risk at any
time.
·
Whales are relatively insensitive to oil slicks so that even when they are in
contact with oil they are not affected by it.
·
No new information concerning the sensitivity or vulnerability of whales has
become available within the past decade to change this assessment.
Seals are present on or near the Grand Banks for at least part of the year. The majority
of those present are associated with the edge of the pack ice. In average years, the ice
edge extends no nearer than several hundred kilometres to the north of the HiberniaTerra Nova area and then only for several months of the year. In the years of heaviest
ice, the pack ice extends southward as far as the Hibernia-Terra Nova area, but for only
a few weeks of the year. Some oil from a large Terra Nova spill might reach the ice
edge at least during a few weeks during years of average-to-heavy ice conditions.
The Hibernia EIS concluded that the risks to seal populations from oiling the
southernmost edge of the pack ice were limited because seals are less common on the
deteriorating southern extremities of the ice edge than they are farther north. There is
no new information concerning the distribution of seals that would alter this
assessment. Also, there is nothing in recently published oil-spill literature to indicate
that seals are more vulnerable or sensitive to spills than what was believed in 1985. In
short, there is no information available to refute the 1985 assessment that the risk to
seals from oil production activities at the Hibernia area would be negligible. Since the
information presented here indicates that the fates and movements of Terra Nova and
Hibernia oil spills would be similar, it is clear that the risks to regional seal stocks from
spills at the Terra Nova site are negligible.
Shorelines
The character of the Newfoundland shorelines that lie within the study area is described
in the Hibernia EIS, and the statements regarding the qualitative fate of stranded oil
from Hibernia spills apply equally well to Terra Nova spills. This information is
summarized as follows:
·
Much of the shoreline consists of steep, rocky shores exposed to high- energy
wave action. Oil stranded on these shores would be quickly dispersed by
waves.
·
A smaller proportion of the shoreline is made up of pocket cobble beaches.
Stranded oil would penetrate readily into this type of shore, and once it had
penetrated, weathering and dispersion rates would be low.
·
Sheltered sand beaches, salt marshes and lagoons make up a small fraction of
the shorelines in the study area. Oil stranded in these protected or low-energy
environments might weather, but would persist for a long time.
The probability of oil from a spill at Terra Nova reaching the coastal zone of
Newfoundland is very low, but it is important to consider the potential effects. The
degree of impact will depend on the amount of oil reaching the shoreline, the state of
weathering of the oil, the character of the shore, and the types of living natural
resources that inhabit the contaminated area. The Hibernia EIS suggested that coastal
zone impact from a spill at the Hibernia site could range from negligible to major,
depending on the conditions. It now appears this assessment was pessimistic. The
potential risks of shoreline impact for spills from either the Terra Nova or Hibernia sites
are more probably in the range of negligible to minor.
During most of the year, the probability of oil contacting any shoreline is very small.
Only under winter conditions might oil contact the shoreline and even then the
probability is very small. According to the results of the trajectory analysis in this EIS,
oil spilled at either the Hibernia site or Terra Nova site would require from 14 to 29
days to travel from the sites to the shoreline. As a result, any oil reaching the shoreline
would be heavily weathered, probably in the form of non-sticky tar balls. Most
importantly, however, the oil would be very widely dispersed so that the average
amount of oil stranding on any stretch of beach would be very small.
Because any given area would be contaminated with only small amounts of oil in the
form of small weathered fragments, the risks to the intertidal and subtidal benthic
communities would be negligible, as would the immediate effects on widely distributed
shoreline species of birds. Contrary to the Hibernia EIS the indirect risk from stranded
oil to birds that breed later in the year are probably minor at worst, as the small
amounts of oil that strand initially would be resuspended and further dispersed by
winter waves and storms before the birds arrived at their nesting sites in the spring. The
potential impact on marine mammals in coastal environments can also be expected to
be negligible, as indicated in the Hibernia EIS.
5.7.7
Assessment of Oil-Spill Countermeasures
In the report on Hibernia (S.L. Ross, 1984), oil-spill countermeasures were assessed
for various spill possibilities. The focus of the assessment was a quantitative evaluation
of the potential effectiveness of the containment and recovery, in-situ burning, and
dispersant-use. The assessment also included a discussion of the most applicable
specific equipment choices considering the properties of the Hibernia oil and the
climatic conditions offshore Newfoundland.
This section summarizes the findings of this earlier work, discusses the significance of
any differences between Hibernia and Terra Nova, and summarizes the
countermeasures implications for Terra Nova. The focus is on the countermeasures for
blowout spills, which represent the bulk of the scenarios considered.
Summary of Hibernia Findings
In the Hibernia study the purpose of the countermeasures analysis was to evaluate the
potential effectiveness of spill countermeasures against a range of hypothetical spill
scenarios (Table 5.7-11). This was done in a quantitative manner by calculating the
maximum likely fraction of oil removed from the environment using state-of-the-art
response techniques. By using spill scenarios, the evaluation process was able to
include realistic expectations of equipment performance with regard to expected oilslick properties and dimensions and typical environmental conditions.
Physical Recovery
Focussing on physical recovery techniques first, the premise was to use one or more
containment and recovery modules capable of concentrating and recovering oil at sea
on a steady, manageable basis. Each module included a given length of boom, one large
skimmer that would sit within the boom, and three ocean-going vessels, two being
required to handle the boom and one to act as a storage unit to receive collected oil
from the skimmer. In addition, two high-rate pumps were required for transfer
purposes. Added to the equipment requirements were personnel to staff the vessels,
tend booms, operate skimmers and transfer pumps, and manage the operation.
For each of the blowout spill scenarios, the total fraction of oil removed by physical
recovery was estimated by:
FR = FRT x FTRP x FSI x FSE
where
FR = overall fraction of oil spill removed
FRT = response time factor, which considers delays in the start of at-source operations
FTRP = fraction of time that recovery is possible considering the environmental
factors of daylight, visibility (fog) and sea state
FSI = fraction of slick width intercepted by booms
FSE = skimmer efficiency factor
These are determined as follows:
FRT: Response Time Factor. The response time factor depends on the distance
between the spill site and the location(s) of the response system, and equipment
mobilization and transit times. For the scenarios analyzed in the Hibernia report it was
assumed that two days would be required by a shore-based organization for response
and set-up at the spill site. Thus for a 90-day blowout: FRT = 88/90 = 0.98.
FTRP: Fraction of Time Recovery is Possible. Containment and recovery operations
are possible when there is daylight, visibility greater than 1000 m, and when waves are
less than 1 m high for all wave periods or when waves are between 1 and 2 m high but
have periods of greater than 6 s. There is some seasonal variation for three parameters
of interest; the FTRP values used in the analysis range from 0.03 in winter to 0.20 in
summer.
FSI: Fraction of Slick Intercepted by Booms. Assuming a boom-length to boomswath-width ratio of 3:1, the maximum swath width is, for each of the response
modules, 250 m. FSI is simply the applicable boom swath width divided by the slick
width close to the blowout source. For situations in which the slick width is less than
the swath width, the fraction is 1.0; that is, the best practicable booming arrangement
can intercept all oil flowing from the blowout.
FSE: Skimmer Efficiency Factor. This includes all factors associated with limitations of
the system such as actual pumping rates, and losses and downtime caused by
equipment breakdown and lack of temporary storage capacity. Recovery rates were
specified for three different skimming systems. In each case the rates were assumed to
decline with increasing viscosity. The rates ranged from 2400 m3/d per skimmer with
oil with viscosity less than 500 cp, to about 1000 m3/d per skimmer at 2000 cp, to
negligible amounts when the oil viscosity exceeded 10 000 cp. (Note that the specified
recovery rates are for total fluid; for emulsions the oil recovery rate was reduced
according to the estimated oil content.)
Chemical Dispersion
The approach for evaluating the potential effectiveness of chemical dispersion was
similar to that used for physical recovery, with consideration given to response time,
application efficiency, fraction of time that operations would be possible, and dispersant
effectiveness. Dispersant effectiveness was assumed to be a function of oil viscosity,
specifically, 60 percent effective for oils less than 2000 cp, and ineffective for
viscosities greater than this value.
In Situ Burning
For in situ burning it was assumed that similar constraints would apply with respect to
response time, fraction of slick intercepted by booms, and fraction of time that
response would be possible. The only difference was the assumption that if the oil
could be contained it could be burned with virtually 100 percent efficiency; thus the
total fraction of oil removed by burning was estimated using the same formula as for
recovery, with the "skimmer efficiency" (FSE) equal to 100 percent.
Mobile Recovery
For "instantaneous" or "batch-type" spills (i.e., those from tankers, pipelines, or transfer
operations), the evaluation scheme was modified somewhat to include mobile sweeping
operations with the containment and recovery equipment. Similar to the response to
blowout spills was the assumption that recovery operations would only be possible for
a fraction of the time according to climatic conditions (see FTRP above).
Evaluation Results
Countermeasures effectiveness was found to depend primarily on three factors:
·
·
·
Climatic conditions (FTRP)
Oil properties
Blowout slick widths
Climatic Conditions. Climatic conditions were found to be an overriding factor in
countermeasures effectiveness. The rough sea conditions offshore Newfoundland
would severely limit containment and recovery, or in-situ burning countermeasures to
an average of 20 percent of the time in summer months and 3 percent of the time in
winter. For the remaining 80 to 97 percent of the time, containment would be
impossible and oil would leave the vicinity of the spill source and be unavailable for
effective recovery or burning.
Oil Properties. The second key limitation was the effect of oil viscosity on both
skimmer performance and dispersant effectiveness. As noted previously, skimmer
performance was assumed to decline dramatically with increasing oil viscosity, meaning
that even when sea conditions allowed containment and recovery operations, skimmers
would be working at less than maximum effectiveness. For dispersant-use, the high
viscosity of the oil means that dispersants would likely be ineffective in all scenarios
except perhaps for those that occurred during the summer when warmer water
temperatures would lower oil viscosities. It should be noted that even for the summer
spill scenarios, viscosities low enough to allow dispersant-use occurred only for a short
period of time after the spill event, and only for one of the two oils originally
considered in the Hibernia EIS.
Blowout Slick Widths. The third key limitation for containment and recovery
effectiveness was the slick width for the large blowout spill scenarios. In these
scenarios the slick width was estimated to be 1500 m, or twice the maximum swath
width of a three-module containment and recovery operation, resulting in a slick
interception factor (FSI) of 50 percent.
Comparison of Terra Nova and Hibernia
In terms of oil spill countermeasures, there are no significant differences between
Hibernia and the Terra Nova. The potential effectiveness of response measures for
spills is extremely limited, because of a number of factors.
There have been no significant advances in response technology since 1984 that would
overcome the key limitations of containment in rough seas and recovery of viscous,
waxy oils. Large ship-based skimming systems have been improved since 1984, but
they still rely on the traditional technique of using a floating boom to contain and
concentrate the oil, a technique that is ineffective in high seas. Similarly, the ability to
recover and process viscous oils has been improved in the past decade, but still remains
limited for use in the offshore environment.
Similarly, there have been no major advances in dispersants for viscous waxy oils, and
given the properties of Terra Nova oil, dispersant-use can be ruled out as a potential
countermeasure.
There has been considerable research on in-situ burning over the last ten years, and it
continues to show promise as a technique for dealing with large oil spills. However, for
Terra Nova spills, the success of in-situ burning will continue to be limited by the need
to first contain the oil, which will itself be severely limited by the rough sea conditions.
Given their close proximity, the Terra Nova and Hibernia sites should experience
similar climatic conditions. Data were re-examined for Terra Nova to calculate a value
for FTRP, the fraction of time response would be possible. As summarized in Table 5.724, the only minor difference in FTRP is due to the use of updated wave data for this
study.
The response strategies and equipment, the oil properties, and the climatic conditions
are essentially the same for Terra Nova as they were in the 1984 evaluation of
countermeasures for Hibernia spills. The conclusion, as it was for Hibernia, is that the
response effectiveness will be 20 percent or less in summer months and 3 percent or
less in winter.
5.7.8
Residual Impacts
Residual impacts from spills are those that would result even after all possible
mitigation efforts have been made. As far as spills are concerned, mitigation efforts fall
into two categories:
Table 5.7-24
Spill Scenario Environmental Data
Winter
Parameter
Summer
Dec
Jan
10
10
14
35
50
22
Daylight (h)
8
9
10
16
15
14
Waves < 1 m (%)
0
0
0.3
5.5
10.3
11.6
Waves 1 to 2 m and period > 6 s (%)
3.4
6.1
8.5
52.3
46.4
42.4
Calculated F TRP
1.0
2.1
3.2
25.0
17.7
24.6
Average F TRP
-
2.1
-
-
22.2
-
FTRP used in Mobil (1984)
-
3
-
-
20
-
Visibility < 1 km (%)
1.
2.
Feb
Jun
Jul
Aug
Those devoted to preventing spills
Those intended to minimize environmental damage once a spill has taken place
The assessment for the Hibernia situation in 1985 applies equally well to Terra Nova.
The Operator will prepare for spills, focussing on safe operations because in most
instances no mitigation may be possible once oil is spilled. This lack of capability is
simply because no equipment or techniques exist to recover spills of waxy crude oil in
very rough marine environments such as the Grand Banks.
Since little mitigation will be possible once oil is spilled, the "residual spill effects" are
equal to the unmitigated effects described earlier. It must be remembered, however,
that the scenarios are based on several worst-case assumptions, including a blowout
scenario that would result in the worst oil spill in history.
The potential impact of spills on many resource groups is negligible. Nevertheless, the
minor risk assessed for salmon stocks, microbial and biofouling communities, as well as
the minor-to-major risks to bird populations will persist regardless of the best of
planning and mitigation efforts.
5.8
Cumulative Impacts
Cumulative environmental effects are defined by the Canadian Environmental
Assessment Agency (CEAA, 1995) as:
The effect on the environment which results from effects of a project when combined
with those of other past, existing and imminent projects and activities. These may
occur over a certain period of time and distance.
The intent of cumulative effect assessment is to describe those impacts of various
projects or activities that may be more than simply the sum of the individual parts.
Cumulative impacts and energy projects (mostly onshore) have been reviewed in
Hegmann and Yarranton (1995).
The concept of cumulative impact is difficult to address in the context of offshore oil
development. Unless the boundaries of individual project impacts overlap, cumulative
impacts are additive sums of the affected areas. The following discussion is general; it
focusses on the overall impacts of activities that will be occurring during the life of the
Terra Nova Development.
The discussion begins with a summary of impacts for the development, operation and
abandonment of the Terra Nova Field. This is followed by a cumulative assessment of
all project activities. An assessment of the overall impacts of Terra Nova development
and other projects planned for the Grand Banks area follows. The final subsection deals
with the effect of possible climatic changes on the assessment of impacts and
cumulative impacts.
5.8.1
Impact Summary
All possible interactions between the development and VECs were identified in the
Level I matrices (Tables 5.3-1, 5.4-1 and 5.6-1). The potential interactions were
described, evaluated and rated. Potential impacts, mitigation measures and residual
impacts of Terra Nova activities are summarized in the Level II matrices (Tables 5.8-1
and 5.8-2).
Routine Operations
Impacts were evaluated after consideration of mitigation measures that were designed
into the development and its operational procedures. Most development impacts were
rated as negligible. The few impacts rated as moderate or major involved potential
helicopter disturbance to seabird colonies. Development-specific mitigation measures
will reduce these impacts to negligible. There was some uncertainty about impact
predictions in the following instances:
·
The zone of influence of cuttings drilled with low-toxicity oil-based muds
Other drilling fluids
Water quality
Plankton
Fish
Seabirds
Seabirds
Deterioration
Mortality
Tainting
Mortality
Reproduction
Minor
Negligible
Negligible
Negligible
Negligible
Minor
Negligible
Minor
Negligible
Negligible
Negligible
Negligible
Negligible
Sublocal
Sublocal
-
-
Sublocal
Sublocal
Local
Local
Local
Scale
-
Disturbance
Disturbance
Disturbance
Underwater construction
Benthos
Fish
Marine mammals
Deterioration
Mortality
Mortality
Mortality
Tainting
No interaction
No interaction
Attraction
Attraction and mortality
Lights and beacons
Fish
Seabirds
Discharge of drilling muds and cuttings
Water quality
Plankton
Benthos
Fish
Fishery
Seabirds
Marine mammals
-
Negligible
Negligible
Negligible
Min.-Mod
Negligible
Negligible
Negligible
Protection
Refuge
Access
Structural integrity
Migration
Disturbance
Disturbance
Negligible
Negligible
+
+
-
+/-
Minor
Min.-Mod
Minor
Magnitude
Protection
Refuge
Access
Potential
Impact
Safety zone and fishery moratorium
lifted
Benthos
Fish (reef effect)
Fishery
not lifted
Benthos
Fish (reef effect)
Fishery
Fouling organisms
Terrestrial birds
Seabirds
Marine mammals
Field development - offshore
Development Activity/VEC
Short-term
Short-term
Short-term
Long-term
Long-term
Long-term
Long-term
Duration
Effluent treatment
Effluent treatment
Effluent treatment
Effluent treatment
Effluent treatment
Treatment or discharge at depth
Low-toxicity mud or treatment
Removal
None
None
None
Mitigation
Level II Matrix for Development Drilling and Construction
Table 5.8-1
Negligible
Magnitude
+/-
Scale
Duration
Sub-Lethal effects
Deterioration
Mortality
Tainting
Mortality
Reproduction
Sub-Lethal effects
Deterioration
All effects
All effects
All effects
All effects
All effects
Mortality
Mortality
Deterioration
No Interaction
See Accidents
Deterioration
Disturbance
Disturbance
Disturbance
Disturbance
Disturbance
Disturbance
Deck drainage
Water quality
Plankton
Fish
Seabirds
Seabirds
Marine mammals
Hydrostatic testing fluids
Water quality
Plankton
Benthos
Fish
Seabirds
Marine mammals
Cooling water
Zooplankton
Fish larvae
Sanitary and domestic water
Water quality
Garbage and other waste
Marine environment
Small spills
Marine environment and biota
Air quality
Noise - drilling rigs
Marine mammals
Fish
Noise - supply vessels
Marine Mammals
Seabirds
Seabird colonies
Fish and fisheries
Potential
Impact
Marine mammals
Minor
Negligible
Min.-Mod.
Negligible
Neg.-minor
Negligible
Negligible
Negligible
Negligible
Negligible
Neg.-Minor
Minor
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Magnitude
Sub to local
Local
-
Sublocal
Sublocal
Sublocal
Scale
-
-
-
-
+/-
Med.-term
Long-term
Long-term
Short-term
Short-term
Duration
Avoidance - EPP
Steady course and speed
Spill response - EPP
Waste brought ashore
None
Effluent treatment
Effluent treatment
Effluent treatment
Effluent treatment
Effluent treatment
Effluent treatment
Effluent treatment
Mitigation
Table 5.8-1
Negligible
Negligible
(If habituation)
Magnitude
+/-
Scale
Duration
Deterioration
Mortality
Deterioration
Mortality
Disturbance
Disturbance
Disturbance
Disturbance
Mortality
Water quality
Marine biota
Garbage and waste
Water quality
Marine biota
Noise, lights, beacons
Human presence
Wildlife
Aircraft traffic
People, wildlife
Vessel traffic
Wildlife
Small spills
Marine biota
Note: EPP means Environmental Protection Plan.
Deterioration
Disturbance
Disturbance
Disturbance
Disturbance
Potential
Impact
Air quality
Field development - shore facilities
Noise aircraft
Marine mammals
Seal haul-outs
Seabirds - open water
Seabirds - colonies
Minor
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Minor
Minor
Negligible
Mod.-Major
Magnitude
-
Sublocal
Short-med.
Avoidance - EPP
Long-term
Local
-
Response - EPP
Handling - EPP
Handling - EPP
Materials handling - EPP
Handling - EPP
Avoidance - EPP
Mitigation
Short-term
Long-term
Duration
Sublocal
Local
Scale
-
+/-
Table 5.8-1
Neg.-Min.
Negligible
Negligible
Magnitude
-
+/-
Shortterm
Scale
Short-term
Duration
Attraction
Attraction or mortality
Disturbance
Disturbance
Disturbance
Entrainment
Deterioration
Mortality
No interaction
Mortality
Tainting
Mortality
Sub-lethal effects
No Interaction
Lights and beacons
Fish
Seabirds
Maintenance of sub-facilities
Benthos
Fish
Marine mammals
Injection water
Zooplankton
Produced water
Water quality
Plankton
Benthos
Fish
Fishery
Seabirds
Marine mammals
Storage displacement water
Marine biota
Negligible
Negligible
Negligible
Negligible
Minor
Minor
Negligible
Negligible
Negligible
Negligible
-
-
Negligible
Negligible
Negligible
Min.-Mod
Negligible
Negligible
Negligible
Protection
Refuge
Access
Structural integrity
Migration
Disturbance
Disturbance
Negligible
Negligible
+
+
-
+/-
Minor
Min.-Mod
Minor
Magnitude
Protection
Refuge
Access
Potential
Impact
lifted
Benthos
Fish (reef effect)
Fishery
not lifted
Benthos
Fish (reef effect)
Fishery
Fouling organisms
Terrestrial birds
Seabirds
Marine mammals
Operations and maintenance
Development Activity/ Environmental
Component
Sublocal
Sublocal
Sublocal
Local
Local
Local
Scale
Long-term
Short-term
Long-term
Long-term
Long-term
Long-term
Duration
Table 5.8-2
Separate ballast tanks
Effluent treatment
Effluent treatment
Removal
None
None
None
Mitigation
Negligible
Magnitude
+/-
Scale
Duration
Deterioration
No Interaction
Water quality
Garbage and other waste
Marine environment
EPP means Environmental Protection Plan.
Disturbance
Noise - FP
Marine mammals
Note:
Deterioration
Air quality
See Accidents
Deterioration
Mortality
Tainting
Mortality
Reproduction
Sub-lethal effects
Deck drainage
Water quality
Plankton
Fish
Seabirds
Seabirds
Marine mammals
Small spills of crude oil
Marine environment and biota
Mortality
Mortality
Potential
Impact
Cooling water
Zooplankton
Fish larvae
Development Activity/ Environmental
Component
Neg.-minor
Negligible
Negligible
Minor
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Magnitude
-
-
+/-
Sublocal
Sublocal
Scale
Long-term
Short-term
Duration
Table 5.8-2
If habituation
Des. gr. Spill response - EPP
Waste brought ashore
Effluent treatment
Effluent treatment
Effluent treatment
Effluent treatment
Effluent treatment
Effluent treatment
Mitigation
Negligible
Magnitude
+/-
Scale
Duration
·
The zone of influence and impacts of produced water
Monitoring programs will be developed, and are discussed further in Chapter 7.
Oil Spills
The probability of oil spills involving more than a few barrels of oil is very low. A
potential impact summary for five worst-case scenarios is contained in Table 5.8-3. It is
based upon the S.L. Ross Model and the Hibernia EIS (Mobil 1985). The waxy nature
of the crude means it is relatively persistent in the modelling scenarios. On the other
hand, the anticipated behaviour of the oil from a blowout that results in small dispersed
droplets, coupled with its waxy nature, may result in lesser biological effects than those
found or predicted elsewhere.
Table 5.8-3
Matrix for Worst-Case Accidental Oil Spills
Crude Oil
Transfer
Spill1
Subsea
Blowout2
Subsea
Blowout3
Subsea
Blowout4
Surface
Blowout2
Negligible
Negligible
Negligible
Negligible
Negligible
Minor
Minor
Minor
Minor
Minor
Zooplankton
Negligible
Negligible
Negligible
Negligible
Negligible
Ichthyoplankton
Negligible
Negligible
Negligible
Negligible
Negligible
Benthos
Negligible
Negligible
Negligible
Negligible
Negligible
Minor
Minor
Minor
Minor
Minor
Negligible
Negligible
Negligible
Minor
Negligible
Negligible
Minor
Negligible
Negligible
Minor
Negligible
Negligible
Minor
Negligible
Negligible
Minor
Negligible
Negligible
Minor-Major
Negligible
Negligible
Minor-Major
Negligible
Negligible
Minor-Major
Negligible
Negligible
Minor-Major
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Phytoplankton
Microbiota
Biofouling community
Fish and commercial shellfish
Pelagic fish
Groundfish
Shellfish
Marine-related birds
Seabirds
Waterfowl
Other
marinerelated
species
Marine mammals
Notes:
1
800 m3
7150 m3/d for 7 days
3
4
2
Document #95032-0-EI-GM-00005.0, Rev.B3
5-130
In any event, oil spills and their potential impacts on the environment, particularly on
seabirds, are of concern. Great emphasis will be on prevention. Mitigations will include
spill cleanup and use of controlled burning if approved and feasible.
Decommissioning and Abandonment
The technology associated with abandonment and removal procedures is expected to
change over the next 15 to 18 years, resulting in refined and new techniques. All subsea
facilities will be purged of oil and decommissioned in accordance with regulations in
place at that time. Whichever procedures are used, it is anticipated that the site will
return to predevelopment conditions; therefore, impacts are expected to be negligible.
5.8.2
Cumulative Development Impacts
As shown above, after mitigation, most residual impacts are negligible. There are a few
minor, short-term, sublocal impacts. A few impacts are of greater magnitude. These are
minor in magnitude but are long term. They are:
-
Impacts of oily water discharges on water quality: negative, minor, sublocal
and long term
-
Impacts of oily cuttings on benthos: negative, minor, sublocal and long term
-
Effects of noise from vessels on marine mammals: negative, minor, local and
long term
-
Effects of the fish refuge on fish populations: positive, minor to moderate, local
and long term
-
Effects of the fishery closure on fishing: negative, minor, local and long term
The first two impacts on the above list do not affect VECs. The negative impacts of a
safety zone and the positive impacts of the fishery refuge are both relatively small scale
(see Chapter 9 of the SEIS).
The long-term impacts of vessel noise on the behaviour of marine mammals would
probably have a negligible impact on population levels.
5-131
Approximately 1404 m3 of oil will be discharged with cuttings, and approximately
2695 m3 of oil will be discharged with the produced water. These estimates are based
on the assumptions that 36 m3 of oil will be discharged with the cuttings from each well
and that produced water contains 40 mg/L of oil. Low levels of hydrocarbons will also
be discharged with processed deck drainage and other fluids used in drilling and
completion, as well as with atmospheric emissions.
In the North Sea, 7 percent of all hydrocarbon inputs were caused by flaring and small
accidental spills (Nihoul and Ducrotoy, 1994). Applying this percentage to Terra Nova
yields an estimated input of 308 m3 via accidents and flaring. Oil input could be about
0.6 m3/a for the FPF and perhaps half of that for the drilling rigs. Total input via deck
drainage, processed to contain no more than 15 mg/L of oil, could be 18 m 3. Inputs
from other drilling fluids and other sources would be minor in comparison. Total
regulated oil inputs over the lifespan of the development could be about 4425 m 3.
Produced water and other oily water inputs will affect the pelagic ecosystem, while oil
discharged with cuttings will affect the benthic ecosystem. Thus, impacts of the two
types of oily discharges are not cumulative. Impacts of oily water discharges on VECs
are rated as negligible.
Impacts of routine operations as summarized in Tables 5.8-1 and 5.8-2 are not
cumulative or additive. The magnitude of the predicted impacts does not increase when
all development activities are considered simultaneously.
The probability of large accidental oil spills is very low. The probability of small spills
such as loading spills is somewhat higher. Loading spills will occur at the surface and
oil from a blowout will be quickly driven to the surface. Because of the waxy, buoyant
nature of the crude, it will not become mixed with produced water or cuttings that are
discharged subsurface. As a result, it is not anticipated that impacts from a spill will be
cumulative.
5.8.3
Cumulative Impacts of the Development and Other Activities on the Grand
Banks
Other human activities that will be occurring on the Grand Banks when the Terra Nova
Development begins, include the Hibernia project, the commercial fishery, and
commercial shipping. This document does not consider the cumulative impacts of most
other potential development activities because there is inadequate information on their
likelihood, timing and scale. Potential activities that could occur during the life of the
project include seismic exploration and exploratory drilling (e.g., Amoco) or
development of other oil fields such as Whiterose and Ben Nevis to the northeast of
Terra Nova. Seabed mining is a possibility but is unlikely.
5-132
For the most part, cumulative impacts of the Terra Nova and Hibernia developments
involve an addition of the zones of influence of produced water, discharged oily
cuttings, transportation routes, the area affected by sound around the development, and
the safety zone. Present information suggests that the two projects are far enough apart
to avoid overlap. The proposed environmental monitoring program for the Hibernia
project considers a distance of 16 km adequate for a control sampling station. This
distance is less than halfway between the two fields. The safety zones for Hibernia and
Terra Nova will be about 0.01 and 0.2 percent, respectively, of NAFO 3Lt. The two
developments will cover approximately 0.04 percent of the total Grand Banks area.
After decommissioning and abandonment, depending upon the regulations in place at
the time, there still may be some equipment left on the seabed. The extent of the
affected area is expected to be somewhat smaller than the combined areas of the safety
zones.
The Terra Nova Development will investigate synergies with Hibernia. This may allow
some shared logistics that may minimize the numbers of aircraft and vessel trips and
reduce the area needed for a shore base. In addition, the potential for sharing resources
during an emergency situation will greatly improve response times.
To date, the greatest human impacts on the Grand Banks have been caused by
overfishing. The impacts have been so large that the fishery is much reduced and its
future is uncertain. While there is some potential for tainting small numbers of resident
fish, the net impact of the Terra Nova and Hibernia developments on the recovery of
fish stocks may be beneficial if the safety zones are large enough to provide a refuge. If
the fishery again approaches historical levels, fishing activity will create significant
impacts on the ecosystem, regardless of presence of the Terra Nova and Hibernia
developments.
Impacts of shipping associated with Terra Nova are insignificant when compared with
those associated with commercial shipping activity and transits by fishing boats. Thus,
the cumulative impacts associated with shipping will increase by a negligible amount.
5.8.4
Cumulative Impacts and Climatic Change
Atmospheric climatic change, whether of natural or anthropogenic causes, leads to
changes in the marine climate. Changes in marine climate could affect the nature of the
predicted impacts of the environment on the Terra Nova Development. Changes in ice,
wave or meteorological regime could necessitate changes in operational procedures.
These have been discussed in this document and appropriate monitoring programs are
proposed in Chapter 8.
Changes in the marine climate can affect species composition and abundance of marine
biota. For example, subarctic waters are especially susceptible to marine
5-133
climatic change when the relative influence of temperate and arctic waters changes over
periods ranging from a few years to millennia. The fish and marine mammals of West
Greenland have been particularly sensitive to these types of climatic change. During
some periods, the fauna of the West Greenland coast is typically arctic in nature and
during others it is more temperate (Dunbar and Thomson, 1979). Changes in the
species composition of the plankton and timing of the spring bloom caused by climatic
change have been documented in the North Sea (Bernal, 1991).
Long-time series of oceanographic and biological data collected in a standardized
fashion are necessary to document climate-induced changes (Southward, 1995). These
kinds of data are not available for the Grand Banks, in spite of the centuries-old
commercial fishery there. Conover et al. (1995) speculate that natural or anthropogenic
global warming has caused increased melting of glaciers and arctic ice which have
caused a lowering of temperature and salinity of the surface waters of the Grand
Banks. Through effects on plankton, changes in the physical regime may have had
negative effects on survival of cod larvae (Conover et al., 1995). The cod stocks of the
Grand Banks have survived numerous climatic cycles, but none during which fishing
pressure has been as intensive as in recent times. These types of climatic change can be
predicted (Conover et al., 1995) and explained, especially if long-time series of data are
available (Southward, 1995).
Changes in marine climate leading to ameliorating or deteriorating conditions for the
Grand Banks fisheries will not change the impact predictions made in this EIS. They
are independent. Changes in the physical or biological oceanographic regime of the
Grand Banks will not affect the zone of influence or effects of the discharge of drilling
muds and cuttings, produced water or other oily discharges, or the zone of noise
effects. The effects of presence of structures will depend on the future state of the
fisheries and this has been considered in our evaluation. With one exception,
cumulative impacts will also not change; a change in the cod stock will affect vessel
traffic on the Grand Banks.
5-134
Appendix 5.A
5.A
5.A.1
Introduction
The following analysis on blowouts of all kinds (gas only, gas and oil, and oil only) was
done for a first draft of this study. It was later rejected because the data did not make a
distinction between blowouts from oil-producing fields versus those from gasproducing fields, as is now done in the main text. Nevertheless, the analysis is still of
some interest, because it shows that blowout frequency is somewhat consistent around
the world (thus justifying the use of U.S. Gulf of Mexico data for this study) and that
development drilling is far less risky than exploration drilling, a phase that is now
finished at Terra Nova. Not shown in this analysis, however, is the fact that blowouts in
oil-producing fields are about three times less frequent than those in gas-producing
fields (E&P Forum, 1992). This fact is now reflected in the main text.
5.A.2
Historical Statistics on Blowouts of All Kinds
Several comprehensive studies have been made on offshore blowouts, as mentioned
earlier. The ones that were done for Canadian clients include Gulf (1981), Manadrill
(1985), and Adams Pearson (1991). The statistics in terms of exploration and
production in the U.S. Outer Continental Shelf (OCS), especially in the Gulf of
Mexico; in the U.K. and Norwegian sectors of the North Sea; and worldwide are
summarized in Table 5.A-1. Most data are taken from Table 5.7-3 in the main text.
Table 5.A-1 shows that blowout frequencies seem to be relatively consistent from area
to area. In terms of blowouts of any kind versus number of wells drilled, the chances
are on the order of one in 170. This includes not only blowouts during exploration and
development drilling, but also blowouts from production, workovers and completion
activities. Also included are so-called "shallow-gas" blowouts, which do not involve oil.
If these shallow-gas blowouts are removed from the equation, the blowout frequency
becomes about one in 240.
The frequency for the Canadian offshore (one in 96) seems to be twice as high as the
rest of the world, but, as explained in Adams Pearson Associates Inc. (1991), two of
the four blowouts (which occurred in the Beaufort Sea) were so-called "water"
blowouts that produced no gas or oil. The stringent classification standard in Canada
set by the federal regulators is the likely reason for the poorer statistic.
The next thing to notice is that development drilling is about two to three times as safe
as exploration drilling. The U.S. Gulf of Mexico record, which is considered the most
reliable, shows that exploration drilling blowouts (including shallow-gas blowouts)
have occurred at a frequency of one in 160, and development drilling blowouts have
occurred at a frequency of one in 344 (including shallow-gas
one in 122
one in 377
Blowout incidence:
exploration drilling only
Blowout incidence:
development drilling only
2.
Gulf (1981)
MMS (1994)
3.
Dahl et al (1983) as reported in Manadrill (1985)
4.
CPA (1989)
1.
one in 226
54
Shallow-gas blowouts
Blowout incidence:
exp. and dev. drilling only
214
Total blowouts incl. shallowgas and production
one in 171
52
Production/workover blowouts
Blow incidence:
total blowouts/total drilled
66
Development well blowouts
incl. shallow-gas blowouts
24,896
Development wells
96
11 737
Exploration wells
Exploration well blowouts incl.
shallow-gas blowouts
36 633
Wells drilled
Worldwide
1955-19801
one in 344
one in 160
one in 260
one in 175
29
98
32
36
30
12,390
4 794
17 184
US GOM
1955-19801
one in 243
-
-
56
44
49
149
one in 152
?
?
?
22 594
US OCS
1971-19932
one in 496
one in 130
one in 242
?
?
?
46
14
32
6 941
4 175
11 116
Norwegian Offshore
1976-19803
Frequency of Historical Offshore Blowouts
Table 5.A-1
-
-
one in 260
?
?
?
0
6
721
838
1 559
UK North Sea
1955-19801
zero
one in 95
one in 96
one in 96
1
4
0
0
4
5
380
385
Offshore Canada
1966-19884
blowouts). For predicting a gas-blowout-frequency for the Terra Nova Development, it
would be fair to eliminate the risk of blowouts from exploration drilling, this phase now
being essentially over; from the U.S. GOM record this would provide a blowout
frequency number of one blowout for every 344 development wells drilled, or 2.9 x
10-3 blowouts per well drilled.
A key environmental question about the blowouts listed in Table 5.A-1 is whether they
involved the discharge of oil. The historical database suggests there is a 95 percent
probability or greater that future blowouts will not contain oil in significant quantities.
This statistic is based on the record in the U.S. Gulf of Mexico (OCS), where from
1955 to 1980, 98 blowouts occurred but only five discharged oil in quantities greater
than 1000 barrels. The more recent record is similar. As shown in Table 5.7-6 (main
text), in the entire U.S. OCS from 1971 to 1993, although 150 blowouts in total
occurred, only eight involved oil in any amount. The total amount for all eight was only
about 1000 barrels.
One of the main reasons that oil spills from historical blowouts have been relatively
small is that most have been brought under control quickly, either through mechanical
procedures or because of the tendency of a blowing well to "self-bridge" and stop
naturally. This has been discussed in detail in Adams Pearson Associates Inc. (1991),
Manadrill (1985) and Gulf (1981). In the 145 blowouts in the U.S. Gulf of Mexico
from 1956 to 1986, 60 percent were controlled in less than one day, 81 percent were
controlled in less than a week, and 91 percent within one month (Adams Pearson
Associates Inc., 1991).
Appendix 5.B
Using the Most Appropriate Exposure when Comparing the
Terra Nova Development and Operations in
the U.S. Gulf of Mexico
5.B
Using the Most Appropriate Exposure when
Comparing the Terra Nova Development and
Operations in the U.S. Gulf of Mexico
In presenting and predicting spill frequencies for tanker operations in the U.S. and
exploration and production operations in Federal OCS water, the U.S. Mineral
Management Service (MMS) uses an exposure of "billion of barrels of crude oil"
produced or transported (Anderson and LaBelle 1994). For tanker spills, the
MMS-derived spill frequencies (e.g., 1.2 spills [>1000 bbl] for every billion barrels of
oil transported) are useful and appropriate for predicting tanker spill frequencies in
other parts of the world because tankers moving in U.S. waters are similar in size to
those moving elsewhere. One key advantage to MMS of using this kind of exposure
for both tanker operations and offshore exploration and production operations is that
spill frequencies associated with these two kinds of operations can be directly
compared.
The problem is the use of the MMS exploration and production spill frequencies for
other areas that do not produce similar amounts of oil per producing well. For
example, in the U.S. OCS, between the 1971 and 1993, 7.74 billion barrels were
produced in 97 921 well-years (MMS, 1994). This means that each oil-producing well
on average produced 79 000 barrels per year or (7.74 x 109/9.79 x 104). This is only
about 200 BOPD. However, for Terra Nova the equivalent number is over 20 (1.7
million barrels per year [400 x 106/240]).
It is seen that the more realistic risk exposure for comparing the Terra Nova operations
to those in the U.S. OCS is well-years and not billions of barrels of oil produced. To
convert the MMS spill frequency of spill per billion barrels of oil produced to spills per
well-years, the number should be multiplied by 7.9 x 10-5.
Appendix 5.C
Statistics on Blowout-Related Oil Spills and
Canadian Experiences
5.C
Statistics on Blowout-Related Oil Spills and
Canadian Experiences
Up to the end of 1989, about 400 offshore wells were drilled in Canada and, although
there was no blowout involving a large oil discharge, the Uniacke G-72 gas blowout
that happened off Sable Island in 1984 discharged about 1500 barrels of condensate
(Gill et al., 1985). This means that the frequency of blowouts in Canada where oil was
discharged has been one in 400 or so. This is a poor frequency compared to the
recorded U.S. OCS experience. Of the total 31 645 wells drilled in U.S. OCS waters
from 1955 to 1993, only two blowouts involved condensate discharges5. This
represents a frequency of one in 16 000, which is 40 times less than the
Canadian-equivalent statistic. It is possible that drilling in Canadian offshore waters is
far less safe than in U.S. waters as suggested by the above numbers, but this seems
unlikely because the companies that have been and are involved are international
organizations that use the same technologies and skills in their various ventures around
the world, and Canadian regulations are believed to be as tough as those that exist in
the U.S. and other countries. Three explanations for the anomaly are possible:
1.
Condensate spills from gas blowouts may be under-reported around the world
because they are highly volatile and only last as slicks for very short periods, in
the order of minutes.
2.
The probability of condensate spills from blowouts in Canada may be lower
than that suggested because the database for prediction is inadequate (only one
such event and only 400 wells compared to the 32 000 in the U.S.).
3.
Gas fields off Nova Scotia may be much more condensate-prone than the fields
in the U.S. Gulf of Mexico.
Appendix 5.D
Offshore Production and Transportation Activities:
Important Accidental Events
5.D
Offshore Production and Transportation Activities:
Important Accidental Events
This appendix summarizes the qualitative effects of important accidental events on
physical, chemical and biological environments.
The Hibernia EIS contained a table summarizing physical and chemical effects on a
scenario-by-scenario basis. The corresponding tables for Terra Nova would have been
very similar to Hibernia EIS Table H-2 Nos. 1, 7 and 9 with the following exception. In
both subsea and above sea discharges, spill behaviour would be influenced by the
combination of the waxiness of the oil and low temperatures of the seawater. In surface
spills, instead of the oil forming fluid slicks, the oil would form semi-solid mats that
would spread more slowly than slicks, and might simply break apart into smaller and
smaller mats. In the case of subsea blowouts, the oil rising in the blowout plume would
arrive at the sea surface in the form of semi-solid droplets, 1 to 3 mm in diameter, that
would not recoalesce into a thin slick.
The impacts of the transfer spill, subsea blowout and above-sea blowout are
summarized in Table 5.D-1.
Group Affected
Phytoplankton
Wat-Col. Microbiota
Oleclasts
Zooplankton
Ichthyoplankton
Biolfouling Comm.
Hyperbenthos
Benthos
Pelagic Fish
Capelin
Salmon
Demersal Fishes
Seabirds
Whales
Phytoplankton
Wat-Col. Microbiota
Oleclasts
Zooplankton
Ichthyoplankton
Biolfouling Comm.
Hyperbenthos
Benthos
Pelagic Fish
Capelin
Some water-soluble
hydrocarbons dissolved
Floating mats of semisolid oil, breaking up
into smaller mats and
fragments; ultimately
sedimented or tar balls
Liquid and Solid Releases
Batch Spill, 800 m 3, instantaneous
1. Transfer Spill
Project Component
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
Season
Location on or floating
past the platform at time
of spill within slick
dispersion zone;
sensitivity to toxic
components
Location on or floating
past the platform at time
of spill within slick
dispersion zone;
components
Lethal and sublethal
effects; enhancement
of oleclasts
Key Impact Attributes
Sublethal and
possibly lethal
of oleclasts
Nature of Impact
0
0
1
0
0
1
0
0
0
0
0
0
1
0
0
1
0
0
0
0
0
0
0
0
Impact
Rating
Mitigating
Measures
Operational safety
and accident
prevention; oil spill
response plan
Operational safety
and accident
response plan
Potential Impacts to the Biological Environment
during Offshore Production and Transportation Activities: Accidental Events
Table 5.D-1
0
0
1
0
0
1
0
0
0
0
0
0
1
0
0
1
0
0
0
0
0
0
0
0
Residual
Impact
Rating
Project Component
Salmon
Demersal Fishes
Seabirds
Whales
Group Affected
All
All
All
All
Season
Nature of Impact
Key Impact Attributes
0
0
1
0
Impact
Rating
Potential Impacts to the Biological Environment
during Offshore Production and Transportation Activities: Accidental Events
Table 5.D-1
Mitigating
Measures
0
0
1
0
Residual
Impact
Rating
Wat-Col. Microbiota
Oleclasts
Benthic Infauna
Benthic Epifauna
Shellfish
Hyperbenthos
Phytoplankton
Wat-Col. Microbiota
Oleclasts
Zooplankton
Ichthyoplankton
Biolfouling Comm.
Hyperbenthos
Benthos
Pelagic Fish
Capelin
Salmon
Demersal Fishes
Seabirds
Whales
Whales
Wat-Col. Microbiota
Oleclasts
Zooplankton
Ichthyoplankton
Hyperbenthos
Benthos
Pelagic Fish
Capelin
Salmon
Demersal Fishes
Crude oil and gas
release, percolating up
through sediments;
generates rising plume
at seabed surface; oilcontaminated settle to
seabed beyond range of
influence of plume
Some water-soluble
in upper water-column
Fluid oil arrives at the
sea surface in the form
of small droplets, 1 to 3
mm in diameter, which
weather to tar balls
Location relative to
release and plume;
components
of oleclasts
of oleclasts
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
release and plume;
components
effects;
contamination;
enhancement of
oleclasts
All
All
All
All
All
All
contaminated sediments
0
1
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
Operational safety
and accident
prevention;
contingency plan
Operational safety
and accident
contingency plan
0
1
0
0
0
0
Operational safety
and accident
prevention;
contingency plan
Turbulent plume of crude oil and gas rising from blowout point on or in seabed through the water-column to boil on sea surface; gas into the atmosphere; remainder
spreads as cloud of semi-solid oil droplets, 1 to 3 mm in diameter
2. Subsea Oil and Gas Blowout without Fire
All
All
3
0
3
0
Gas, oil aerosols, oil
droplets, volatile
hydrocarbons
Birds
Mammals
All
effects
airborne plume of gas or
droplets
0
Operational safety
and accident
prevention;
contingency plan
0
Plume of oil and gas shooting into the atmosphere from point of discharge falling back on the sea surface and on deck in the form of droplets; on decks, washing
system washes oil through drainage into the sea; airborne oil arrives at the sea surface in the form of droplets; runoff from; fluid runoff from rig forms mats of semisolid oil on sea surface
3. Surface Oil and Gas Blowout without Fire at the Production Facility
Seabirds
Whales
Phytoplankton
Wat-Col. Microbiota
Oleclasts
Zooplankton
Ichthyoplankton
Biolfouling Comm.
Hyperbenthos
Benthos
Pelagic Fish
Capelin
Salmon
Demersal Fishes
Seabirds
Whales
Wat-Col. Microbiota
Oleclasts
Zooplankton
Ichthyoplankton
Hyperbenthos
Benthos
Pelagic Fish
Capelin
Salmon
Demersal Fishes
Seabirds
Whales
Some water-soluble
in upper water-column
Floating mats of semisolid oil fragment to tar
balls; droplets remain
separate
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
release and plume;
components
release and plume;
components
of oleoclasts
of oleoclasts
0
1
0
0
0
0
0
0
0
0
3
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
Operational safety
and accident
contingency plan
Operational safety
and accident
prevention;
contingency plan
0
1
0
0
0
0
0
0
0
0
3
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
Appendix 5.E
Brief Description of S.L. Ross Oil Spill Model
Chapter 6
Table of Contents
6.
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
6.10
6.11
Drilling Mud
Produced Water
Deck Drainage
Garbage and Sewage
Ship and Boat Noise
Helicopters
Chronic and Accidental Spills
6.11.1 Spill Prevention
6.11.2 Countermeasure Techniques
6.11.3 Contingency Planning
6.11.4 External Response Capability
6.11.5 Future Research and Development
6-1
6-1
6-2
6-2
6-2
6-2
6-3
6-3
6-3
6-4
6-4
6-5
6-6
6-6
6-16
6-18
6-21
Tables
6.11.1
Major Boom and Skimmer Manufacturers and Their
Canadian Representatives
6-22
6.
All Terra Nova Development activities will be conducted in an environmentally safe
and responsible manner. Two approaches will be used to reduce impacts:
1.
Compliance with current industry standards, government legislation,
regulations and guidelines
2.
Site-specific measures, designed into all stages of the development, including
drilling, construction, installation, production, and abandonment and
decommissioning
The first approach, compliance, is best addressed at the design stage. Pertinent
standards, regulations and guidelines will be provided to the alliance contractors. The
second approach will be accomplished in the context of the Total Loss Management
framework (Chapter 2, Table 2.2-1).
The following sections briefly describe some of the important development mitigation
measures and the approach to contingency planning. The actual mitigation measures
will be described in more detail in the contingency plan and the environmental
protection plan (EPP).
6.1
Drilling Mud
Low-toxicity water-based muds will be used where practicable. In other cases,
low-toxicity oil-based muds or low-toxicity, inhibited water-based muds (glycol) will
be used.
Oil-based muds will be used according to the Offshore Waste Treatment Guidelines:
·
The aromatics content of the base oil used in formulation of oil-based drilling
mud will be less than 5 percent.
·
Oil-based muds will be recovered and recycled or transported to shore for
disposal.
·
Cuttings will be treated so that there is a maximum of 15 g oil/100 g dry solids,
averaged over a 48-hour period.
·
After treatment, cuttings will be discharged from the drilling rig at the lowest
level possible.
6-1
The use of oil-based muds will be addressed in the respective drilling program
approvals (DPA).
6.2
Well treatment fluids recovered from operations will be processed to reduce oil
concentration to 40 mg/L or less, as required by the Offshore Waste Treatment
Guidelines. Well treatment fluids with a high aromatic content will not be used unless
recovered and recycled or transferred to shore. Strongly acidic fluids will be neutralized
before discharge.
6.3
Produced Water
Produced water will be treated to reduce oil content before discharge into the sea. The
treatment will reduce the oil content of discharged produced water to 30-day average
concentrations of 40 mg/L or less, as specified in the Offshore Waste Treatment
Guidelines.
6.4
If a semisubmersible floating production facility (FPF) is selected, crude oil will be
pumped to a storage tanker or directly to shuttle tankers. All tankers will have
independent ballast tanks, so that there will be no possibility of the oil contaminating
the ballast water discharged over the side.
Alternatively, if a monohull FPF vessel is selected, it will have crude oil storage
capacity on board. The monohull would also have separate ballast tanks to prevent
contamination of ballast water with oil; thus, there will be no possibility of
oil-contaminated ballast water being discharged over the side.
6.5
Deck Drainage
Drainage from the decks of various project vessels will be isolated from the main
sources of oily waste. For example, the deck drainage system will not collect
discharges from drip pans under machinery. Wastes and fluids from drip pans will be
recovered and recycled, or transferred to shore for disposal in an approved manner.
A closed drain system will collect leakage and drainage of hydrocarbons from mudhandling operations. An open water drain will collect drainage from machinery spaces
and working areas (but not drip pans) and liquids will be passed through an oil-water
separator. The oily effluent from the separator will be collected for disposal. Deck
drainage will be processed to meet the Offshore Waste Treatment Guidelines of 15 mg
oil/L.
6-2
6.6
Garbage and Sewage
Grey water from showers, sinks and washers will be discharged without treatment.
Sewage and other domestic effluents from the FPF and drill rigs will be treated to meet
the Offshore Waste Treatment Guidelines. Domestic wastes will be macerated to a
particle size of 6 mm or smaller before discharge.
Sludges from oil-water separation units, spent lubricants, all plastic material, glass and
metal wastes will be transferred to shore for appropriate handling.
Garbage will be transferred in secured containers from the rigs to the supply boats and
offloaded at the shore base.
Oily and other hazardous wastes will be brought ashore in secured containers by the
supply boats. The containers will be liquid-tight to prevent spillage during transit and
transfer from the development area to the final disposal area.
6.7
Ship and Boat Noise
Impacts of ship and boat noise on marine mammals and fish can be reduced if the boats
maintain a steady course and speed, whenever possible.
Ships can disturb seabirds while passing near seabird colonies. The Environmental
Protection Plan (EPP) will identify bird colonies and their timing of use. Passage close
to colonies will be avoided.
6.8
Helicopters
Helicopters will fly at a minimum altitude of 600 m, unless safety concerns dictate
otherwise.
Helicopters can disturb harbour seals at haul-out sites. Haul-out beaches used by
harbour seals will be identified in the EPP and avoided.
Aircraft pilots will be instructed not to fly low over wildlife and to avoid repeated
overflights of concentrations of birds or important bird habitats.
Guidelines for avoiding major seabird colonies will be based on Nettleship (1980).
These Canadian Wildlife Service guidelines recommend that aircraft not approach
closer than 8 km seaward and 3 km landward of a seabird colony from 1 April to 1
November. The EPP will document the locations of seabird colonies and other areas
where sea-associated birds congregate.
6-3
6.9
All fuel, chemical and waste-handling activities will be carried out in a manner designed
to minimize or eliminate spillage and accidents. Workers at the facilities will be trained
in the proper procedures for handling these products and responding to spills.
Independent suppliers will handle fuel, chemicals and waste according to all applicable
regulations. Audits and inspections will be conducted at these facilities.
Drilling mud and cement will be stored at dockside in bulk tanks. Diesel fuel will be
supplied by an approved commercial supplier either via tanker truck or through
dockside fuelling facilities. Water will be obtained from a government-approved
drinking water source.
Garbage from the drilling rig and supply boats will be brought ashore and trucked to an
approved landfill. Waste oil and other waste fluids transported to shore by supply boats
will be transferred to an approved waste handler. Non-toxic waste will be trucked to an
approved landfill by a licensed operator.
Oily and other toxic wastes will be brought ashore by the supply boats in secured,
liquid-tight containers and transferred to a final disposal area. They will be transferred
to an operator licensed to process and dispose of these materials in an approved
manner.
Sanitary sewage will enter the existing sewage system of the selected centre.
Depending on the site-specific drainage facilities, storm and apron runoff may enter the
harbour directly, or via local storm sewers.
6.10
Small Spills
The EPP will provide details of safe fuel-, chemical-, and waste-handling and storage
procedures that are designed to minimize or eliminate spills and accidents.
The FPF will contain secondary containment systems and sumps designed to contain
spills. Shutdown systems and routines will minimize environmental effects by isolating
systems and equipment during upsets or incidents on the FPF. Shutdown routines will
be developed in the detailed design phase.
6-4
6.11
Chapter 5, Section 5.7, presents an evaluation of the effectiveness of various
countermeasures that would be useful in the event of an oil spill related to the Terra
Nova Development. In this section, an outline of the Terra Nova Development's
anticipated spill-response capability will be described. Mitigation will be discussed in
terms of spill prevention, contingency planning, and oil-spill countermeasures.
Petro-Canada's position with respect to emergency preparedness, including
contingency planning and spill response, is stated in the company's TLM framework. In
particular, the Environmental Protection Policy and the Occupational Health and Safety
Policy set out the company's commitments to protect the environment and the well
being of its employees and others proximate to company's operations. In accordance
with these directives, Petro-Canada intends, to the greatest extent possible, to prevent
all spills from occurring.
Although prevention of oil spills will be a primary focus, Petro-Canada will undertake
all the necessary planning, training, and exercising to ensure that the appropriate spillresponse capability is in place for all phases of the Terra Nova Development. The
capability will meet all regulatory standards applicable at the time offshore activities
begin.
In 1985, Mobil tabled the Hibernia Environmental Impact Statement (Mobil, 1985) in
which a review of appropriate offshore countermeasures of the time were described.
Petro-Canada considers the Hibernia EIS to be a good basis for planning for oil-spill
countermeasures at Terra Nova. In this chapter additional technologies, developed
since the Hibernia EIS, will be reviewed.
In November, 1989, the Canadian Petroleum Association (now the Canadian
Association of Petroleum Producers) and the Independent Petroleum Association of
Canada jointly published the report of the Task Force on Oil Spill Preparedness
(TFOSP) in the upstream petroleum industry. The report assessed the Canadian
upstream industry's (offshore and onshore) current state of preparedness for dealing
with oil spills resulting from exploration and production activities. Petro-Canada
participated in the development of the TFOSP report and endorsed the observations,
conclusions, and recommendations presented. These findings will be incorporated into
the development of contingency plans and response capability for the Terra Nova
Development.
6-5
6.11.1
Spill Prevention
Spill prevention will be addressed as a matter of policy and practice within the Terra
Nova Development. All offshore systems and structures, procedures, and programs
will be designed with due regard for the prevention of loss of any hydrocarbons.
Standard operating procedures that reduce or eliminate the chance of a spill, even in
the case of equipment failure, will be instituted for all oil-handling components. Routine
maintenance and testing schedules will be determined for all aspects of the production
program, with particular attention paid to well control, product storage and handling,
and fuel transfer systems. Guidelines for operating in poor weather, high sea state, or
sea ice or iceberg conditions will be established. Good communications and sound
marine practices for all vessels will also improve the ability to prevent spills.
Proper environmental operating practices will be assured through regular inspections
and audits of the offshore facilities. All spills, whether contained or not, will be
reported and investigated so that deficiencies in design or procedures can be identified
and corrected.
The general awareness of offshore workers will be increased through training,
seminars, and safety meetings. Personnel will be encouraged to report potential
problems and "near hit" incidents in an attempt to avoid a re-occurrence that could
result in a loss of containment or other release of oil.
6.11.2
Countermeasure Techniques
The Hibernia and Terra Nova production locations will be close to each other and will
experience the same difficult operating conditions. Furthermore, it is expected that the
oil produced at each will be generally a waxy crude oil that becomes quite viscous after
weathering and emulsification. Because of the difference in production systems, there
will be differences in spills caused by loss of well control at each site. There will be
similarities in other areas so that batch spills and the nature of the oil itself on water will
be similar.
In reviewing the proposed Hibernia countermeasures and technologies that may be
applicable to oil spills at Terra Nova, one must consider how poor weather will limit
the effectiveness of any technique, the safety of response personnel and how
weathering and emulsification will affect the use of skimmers and dispersants.
6-6
Contemporary countermeasure technologies were reviewed in 1984 by Hibernia (Ross,
1984) and in 1989 by the Canadian Petroleum Association (TFOSP, 1989). Since
1989, a number of individual techniques and equipment types have also been reviewed.
In this chapter, countermeasures technologies available in 1995 will be reviewed using
information presented in these reports where applicable.
Oil-Spill Surveillance
An offshore spill is likely to spread quickly and break up in rough weather conditions.
Countermeasure operations away from the spill source will be successful only if
accurate and up-to-date information on the oil's properties and behaviour, slick sizes,
and projected movement are known. Updated slick information for a Terra Nova oil
spill will be obtained through continuing surveillance activities.
In the 1984 Hibernia review (Ross, 1984), a section is dedicated to surveillance
techniques. Included in this review are:
-
A statement on the use of aircraft, including suggestions for developing search
patterns
-
Comments on visual observations of offshore oil slicks
-
A review of remote sensing techniques including Side Looking Airborne Radar
(SLAR), aerial photography, UV and infra-red spectral scanners, and satellite
applications
-
A description of spill-tracking drifting beacons
As a basis for airborne surveillance, all of the information presented in this report is
useful. New developments are described below.
RADARSAT, a satellite-borne Canadian synthetic aperture radar (SAR) system will be
operational in early 1996. This system has the potential of being a valuable surveillance
tool in the tracking of major spills, however the four day coverage cycle limits its use as
a real-time tool. The Proponents are currently investigating the potential of
groundwave radar as a slick-monitoring tool.
Environment Canada Emergency Science Branch continues in the development of an
airborne SLAR system that will be suitable for oil spill detection. In Newfoundland, the
Titan radar enhancement system provides digitization and signal processing compatible
with most marine or airborne scanning radars. This system should be capable of
identifying even small slicks by detecting the damping effects of oil on the sea surface.
6-7
A professional offshore surveillance capability is now resident in Newfoundland.
Provincial Airlines provides routine fisheries and ice surveillance to government and
industry and can provide the platforms, sensors, and trained personnel for any airborne
surveillance program.
On-Water Oil Collection and Recovery
On-water oil collection and recovery has evolved since the preparation of the Hibernia
EIS. The principle changes have been in the development of more seaworthy inflatable
offshore boom systems. Some skimming systems have been improved to work in
higher sea states and are capable of handling higher viscosity oil. Even with
improvements, this equipment is still limited by sea state and visibility. It would be
suitable for use in Grand Banks conditions for only a small part of the year. TFOSP
estimated the proportion of time that countermeasures can be attempted on the Grand
Banks to be about 5 percent in winter and 25 percent in summer (TFOSP, 1989).
Based on recent work (see Chapter 5), these estimates have been revised slightly to 3
percent in winter and 20 percent in summer.
Following is a review of selected equipment that may be considered for use at Terra
Nova. Criteria for inclusion here are the usefulness of the equipment in Grand Banks
conditions and the familiarity of the Canadian oil-spill-response community with the
gear. Other equipment can be found in industry spill-response catalogues such as the
International Oil Spill Control Directory (Oil Spill Intelligence Report, 1993) and the
World Catalogue of Oil Spill Response Products (Shulze, 1993).
Ro-Boom
The Roulands Ro-Boom is a popular and rugged offshore boom built in a variety of
sizes (freeboard 0.3 - 1.3 m). The boom is constructed of flexible inflatable chambers
with a chain ballast tension line at the base of the skirt. The deflated boom is stored on
a hydraulic reel and inflated in sections during deployment. The boom is typically used
in a two-vessel towed configuration.
Norwegian Boom Systems
Amongst the widely-used recent-generation offshore boom systems is the NOFI series
manufactured by All Maratim. The North Sea Operators Clean Seas Association
(NOFO), tests this boom annually in offshore conditions during the Norwegian
oil-on-water exercise.
In September, 1995, Petro-Canada participated in an operational exercise in British
Columbia in which a NOFI system was deployed.
6-8
The NOFI boom is inflatable and stored and recovered on a dedicated hydraulic reel. It
is used in mobile collection systems and is rated for significant wave heights of 2 to 3
m. The boom is constructed of flexible inflatable chambers with a chain ballast that
together provide good heave stiffness. This boom is available in different sizes
(freeboard 0.6 to 1.0 m). Available options include a guiding boom and the Oil Trawl,
a V-shaped collection pocket with netting underneath to prevent oil from going under
the boom. The Fully Integrated Oil Containment System (FIOCS) consists of the
guiding boom, Oil Trawl, adjustable cross bridle mechanism, and ISO shipping
containers. The NOFI V-Sweep is a smaller, single-vessel side sweep variation of the
FIOCS.
Vikoma Booms
The Vikoma Ocean Pack is the boom that has been used by both industry and
government since the early 1980s for Grand Banks spill response. It is an
older-generation offshore boom that consists of a single-chamber inflatable tube and
self-filling water ballast chamber. The boom has good sea-keeping qualities and is
quickly deployed but easily damaged.
The more recent Vikoma Hi Sprint offshore boom is similar to the Ro-Boom in
construction, having sequential inflation chambers and a chain ballast member.
Oil Stop Booms
The Oil Stop offshore boom is another inflatable boom suitable for offshore
applications. It is similar to the NOFI and Ro-Boom systems in that it can be stored on
a dedicated reel for ease of storage and recovery but uses a single-point inflation
technology and an integrated-chamber structure that allows for efficient uninterrupted
deployment with the security of modular construction.
Conventional Weir Skimmers
Floating weir skimmers are commonly used for recovery of oil on water. They are
quite efficient if the spilled oil has been thickened in a collection boom but are less so as
viscosity or sea state increases.
The Walosep W-2 weir skimmer was evaluated in the 1989 waxy and viscous oils
skimmer tests (S.L. Ross, 1989) and was found to be quite effective in the recovery of
weathered Terra Nova crude. Rated capacity for the W-2 is 45 m3/h. Measured
recovery rates for oil of viscosities up to 100 000 cSt were consistently in the order of
10 to 20 m3/h (S.L. Ross, 1989).
The GT-185 Skimmer was also evaluated in the 1989 CPA skimmer tests (S.L. Ross,
1989). This skimmer employs a self-adjusting weir and archimedes screw-type pump,
and is commonly used in Canada. Several units are owned by the Canadian Coast
6-9
Guard (CCG) and Eastern Canada Response Corporation (ECRC). The GT-260, a
larger, more robust model, is also used by these organizations and is considered more
suitable for offshore use because of its increased sea-keeping and pumping capacities.
Rated capacities for the GT-185 and GT-260 are 45 and 100 m3/h, respectively.
Measured GT-185 recovery rates for oil of viscosities up to 10 000 cSt were
consistently in the order of 25 to 30 m3/h but decreased to about 10 m3/h with
viscosities over 100 000 cSt (S.L. Ross, 1989).
The Desmi 250 and Desmi Ocean Skimmers are offshore weir skimmers that were
proven to be useful in the recovery of heavy emulsified oil during the Aragon spill. The
level of the weir in each of these two skimmers is hydraulically controlled, which allows
the operator to adjust the skimmer's efficiency. Rated capacities for the Desmi 250 and
Desmi Ocean skimmers are 80 and 100 m3/h, respectively.
Transrec Skimmer
Frank Mohn (Framo) has developed several skimmers for offshore use. The Framo
ACW-400 disc skimmer was formerly the standard for Grand Banks countermeasures
(industry and Canadian Coast Guard) and was evaluated in the 1989 waxy and viscous
oils skimmer tests (S.L. Ross, 1989). The performance of this skimmer is greatly
affected by wave action and increasing viscosity and is, therefore, not recommended
for use at Terra Nova. The more recent Framo Transrec skimmers are reviewed here as
candidates for offshore operations.
These skimmers were developed in cooperation with NOFO, and come in three
models: the 350, 250, and 200 (indicating rated capability in m3/h). The Transrec 250
and 350 skimmers are standard equipment on all Norwegian offshore spill- response
vessels. The CCG in St. John's has a Transrec 200. The basic Transrec skimmer design
consists of a conventional floating weir with centrifugal transfer pump. The complete
system includes an integrated reel and hose assembly. The Transrec can be modified to
include an emulsion-breaking attachment and a belt-skimmer cassette that fits into the
top of the weir. Both of these additions greatly improve the skimmer's capability in
high-viscosity oil conditions. In NOFO offshore tests, the skimmers were able to
maintain rated capacity in 2.5 m seas (oil type unknown) and reach a recovery
efficiency of 98 percent with the belt skimmer attachment (Shulze, 1993).
Sea Devil-Sea Wolf Skimmers
The Vikoma Sea Devil and Sea Wolf are toothed disc skimmers designed for use with
high-viscosity oils and floating debris. The discs are oleophilic and star-shaped to claw
heavy oil into a central hopper. Recovered oil is then transferred by a vertical
Archimedes screw pump. Transfer of recovered oil is enhanced by a film of lubricating
6-10
water introduced to the transfer hose via an annular ring injection system. Rated
capacity for the Sea Devil is 100 m3/h.
Rope Skimmers
There are several rope skimmers available, all of which employ one or more continuous
oleophilic bands that pass through floating oil and then are squeezed through a series of
rollers. Recognized models for offshore use are the Nor-Marine Foxtail and the Oil
Mop Mk IV-160DP. The ropes are easy to deploy and are less affected by sea state
than other skimmer types. These skimmers are best suited to very localized
concentrations of mid-viscosity oil. Rated capacities for the Foxtail and Oil Mop
skimmers are 100 and 32 m3/h, respectively. High water content can be expected with
these skimmers.
As part of the TFOSP program, the Foxtail was evaluated for collection of oil in ice
(Counterspil Research Inc., 1992). In cold water tests using weathered crude,
measured recovery rates were about 7 m3/h with about 59 percent efficiency. Recovery
rates for the same oil in ice were similar but with much higher water content.
Belt and Perforated-Drum Skimmers
Belt and drum skimmers are particularly useful in the recovery of heavy oils.
Unfortunately, vessel-mounted belt skimmers are affected by the action of sea state on
the deployment platform. Independent belt skimming devices, such as the optional
device available for the Framo Transrec skimmers, are expected to be much more
efficient.
The rough surface of a perforated drum skimmer acts like a belt skimmer in that it can
pull a viscous oil off the water and deposit it in a hopper for transfer. The Oil Recovery
Sweden WP-1-30 perforated drum skimmer, with a rated capacity of 70 m3/h, may be
quite useful for weathered Terra Nova crude.
Transfer Pumps
Once recovered from the sea surface, heavy oil must be transferred to temporary
storage at sea. High-viscosity pumps that have proven capability can be obtained from
Framo, Desmi, and Pharos.
In Situ Burning
Combustion of oil on the sea surface was identified in the 1984 Hibernia review as a
possible countermeasure technique for use on the Grand Banks. In situ burning of
floating oil on the ocean has been proven effective in the Newfoundland Offshore Burn
Experiment (NOBE) undertaken by Environment Canada and the CCG during August
6-11
1993. Burning of emulsified oil after treatment with an emulsion-breaking chemical was
also proved possible in tests conducted by Alaska Clean Seas in September, 1994.
Since the Hibernia EIS, the helitorch, a safe and reliable helicopter oil slick igniter, has
been developed. This device has been tested in NOBE, arctic spill experiments, and in
routine forest fire back-burning operations. Helitorches are readily available from CCG
in St. John's, from the Newfoundland Department of Forestry, and from Oil Spill
Response Ltd. (OSRL). Experienced pilots flying for CCG and forestry contractors are
also easily found in Newfoundland.
Due to the observed failure of fire-boom in the 1993 NOBE, it is clear that the use of in
situ burning will be limited unless methods of burning without a fire-boom can be
developed. Taking advantage of thickened, weathered oil in naturally-formed
windrows is one possible method that may have a potential future application.
Dispersion
Dispersion is a natural process in any oil spill. Eventually, oil on water will be broken
into small droplets through physical action and become available to bacteria for
biological breakdown. Intentional dispersion of oil can be a quick disposal option for
offshore spills. This is usually accomplished through the application of chemicals using
aircraft or vessel-based spray equipment. Chemical dispersion may present a potential
hazard to fisheries and the subsurface ecosystem but the dispersion of oil removes a
very real threat to seabirds on the surface.
Chapter 5 of this report concludes that dispersants will only be effective while the
viscosity of the spilled Terra Nova oil is low, shortly after release and before
weathering or emulsification.
In Canada, the use of dispersants on a marine oil spill is strictly controlled by
Environment Canada. In developing an oil spill contingency plan, Petro-Canada will
discuss the implications of using chemical dispersants with regulatory agencies.
In the contingency plan the decision-making process for the use of chemical dispersants
will include operational and environmental considerations. The application of chemicals
will be considered only if the probability of successful dispersion is high, if the benefits
of removing oil from the sea surface are clear, and if the possible impact to the
subsurface marine environment is acceptable.
6-12
Emulsion Breaking
Terra Nova crude is difficult to handle when emulsified as it becomes very viscous and
persistent. Emulsified oil has a very high water content making transfer and storage
inefficient. Finally, emulsified oil is resistant to in situ burning and both natural and
chemically induced dispersion. A possible solution to these problems is the application
of emulsion-breaking chemicals.
The Canadian Petroleum Association commissioned a review of emulsion-breaking
chemicals (Ross et al., 1992). One of the conclusions was that three off-the-shelf
products were found to be effective in de-emulsifying Grand Banks crude in laboratory
conditions. The use of emulsion-breaking chemicals, especially before on-water
recovery, or dispersion, or burning, will be considered by Petro-Canada in the
development of a countermeasures capability for Terra Nova.
Considerations in the decision to include emulsion-breaking chemicals in the Terra
Nova response strategy will include the high cost of maintaining an inventory and
application techniques. Given the anticipated high persistence of emulsified Terra Nova
crude, emulsion-breaking technology is a possible area for future research and
development.
Disposal
The progress of any oil-spill clean-up is ultimately limited by the ability to store and
dispose of the collected oil. In the field, temporary storage of oil, oily water, and
emulsified oil is an important issue. Storage on the collection platform, either in
portable deck tanks or permanent built-in tanks is an easy, temporary measure. As the
volume of collected oil increases with time, barges or tankers will be required to hold
the oil. An important study that will be used as a reference in sourcing tankage will be
Tanker Selection for Open Ocean Oil Spill Response Operations off the East Coast of
Canada commissioned by ESRI in 1990 (Coughlan, 1990).
Ultimately, the oil may be disposed of in a number of ways: through re-introduction to
the production stream on the platform, as fuel in the boilers of one the three
Newfoundland pulp mills, in the kiln at the North Star Cement plant in Corner Brook,
or through a refining or recycling process.
The environmental data required to run an oil-spill trajectory model will be provided by
the Terra Nova physical environment monitoring program. Synoptic current, weather,
and wave data will be collected routinely as part of this program and will be available at
any time to trajectory modellers.
6-13
Biological Environmental Monitoring
Biological and chemical sampling required during a spill will be addressed as part of the
Terra Nova EPP and will be undertaken as part of the Terra Nova environmental
effects monitoring (EEM) program. The protocols for sampling will be established
during the development of the EEM program. In preparing these protocols,
Petro-Canada will review the generic offshore scientific response plan developed with
Environment Studies Revolving Fund (ESRF) and Petroleum and Energy Research and
Development (PERD) funding.
With clear objectives and protocols in place for spill-related environmental monitoring,
a contractor will be able to mobilize quickly for field sampling in a spill event.
Terra Nova Spill-Response Capability
Consistent with past Petro-Canada commitments, the Terra Nova Development will be
supported by a dedicated spill-response capability. Trained personnel and response
equipment will be designated and positioned for quick mobilization in the event of a
spill. A clear and concise contingency plan will be developed to direct response
operations. Before beginning offshore operations, Petro-Canada will ensure that any
financial instruments required by governments to fund spill response, and legitimate
compensation for damage caused by a spill, are negotiated and in place.
Past Experience
Petro-Canada has been involved in east coast offshore exploration since the 1970s
having drilled on the Grand Banks, the Labrador Shelf, and the Scotian Shelf.
Petro-Canada was responsible for ensuring that an oil spill response capability was
available for all these programs. The company was a founding member of the Oil Spill
Service Centre cooperative, now OSRL in Southampton, England, an international
spill-response service provider. Petro-Canada was also a founding member of the East
Coast Spill Response Association (ESRA) in St. John's (later East Coast Spill
Response Inc. - ESRI), a cooperative formed to provide east coast Canadian operators
with an offshore spill-response capability. When ESRI was disbanded in 1993, the
assets were sold to a response organization which has now become the Eastern Canada
Response Corporation (ECRC).
Relief Well
In the event of an oil spill due to loss of well control, it may be necessary for a relief
well to be drilled. Relief wells will be discussed in the Drilling Program Approvals.
6-14
Response Personnel and Oil Spill Response Eq uipment
A spill-response technical service provider will be retained to support the Terra Nova
Development so that ongoing drilling and production operations will be generally
unaffected by a spill response effort. This provider will either be an existing commercial
oil- spill-response organization or a dedicated organization formed in the future to
support offshore activities.
The team that will manage the response will be identified in the oil-spill contingency
plan. Petro-Canada will consider the use of a dedicated team of Petro-Canada
personnel, a contracted team of recognized experts, or some combination thereof.
The dedicated oil-spill-response equipment and trained personnel assembled to support
the Terra Nova Development will be adequate for a timely response to small spills or as
a first response capability in a larger spill incident. Should additional equipment be
required to cope with a larger spill, Petro-Canada will draw on the resources of outside
organizations. Examples of some of the oil-spill-response organizations that may
provide additional equipment are given in Chapter 5.
Regardless of the technology employed, it is anticipated that equipment will be used in
discreet modules or systems. For instance, a mobile collection and recovery system
would include an offshore boom system, a skimmer, temporary tankage, transfer
pumps and auxiliary hoses, hydraulic power packs, tools, and rigging. Each system will
require a dedicated operating crew and one or more suitable vessels to tow equipment,
act as a platform for oil collection, or transport waste oil. As an offshore spill increases,
additional equipment will be mobilized on a system-by-system basis. In this way, the
spill management team will be able to delegate tasks to established, self-contained
working groups and assign the logistics resources efficiently.
Training
Petro-Canada presently has several employees who have received training in marine
oil-spill-response countermeasures from OSRL. Some of these individuals have also
received training from other institutions.
Petro-Canada is committed to ensuring that all Terra Nova oil-spill-response personnel
are properly trained and to enhancing this training through regular operational
exercises. Designated company personnel will continue to receive formal training and
be involved in regular exercises as required. Contractors' personnel will be screened for
past formal training and practical experience and will be required to describe what
efforts will be made for future training.
6-15
Trajectory Modelling
Petro-Canada will have an oil-spill dispersion-modelling capability that can be used at
the time of a spill to predict the trajectory of spilled oil offshore. In each past Grand
Banks drilling program, Petro-Canada has modelled the fate of oil spilled at the wellsite
using the best software and data available at the time. Since that time, trajectory
modelling capability has improved and more weather and current data for the Terra
Nova area are available. For the purposes of planning and for input to the Terra Nova
EIS (Chapter 5), Petro-Canada and the Hibernia Management and Development
Company (HMDC) have recently run an improved spill model that uses as inputs a
central release point, equidistant from the Terra Nova and Hibernia production
locations, a generic oil type (with worst-case weathering and persistence
characteristics), and updated historical seasonal weather and oceanographic conditions
to determine spill trajectories in representative scenarios.
Logistics
A logistics infrastructure will be employed to obtain materiel specified by response
managers and transport operations personnel to get equipment to and from the spill
site, and source additional operational platforms required.
One of the primary difficulties in mounting a large-scale offshore spill response
operation will be sourcing the vessels needed in the deployment of on-water
equipment. The type of vessel most suitable for this application is the standard offshore
supply vessel that will be used to support the Terra Nova Development offshore. At
the present time, there are no supply vessels available in Newfoundland and only a few
available in Atlantic Canada. In some cases, an offshore trawler could be used to fill
support roles. Some trawlers are presently available in Newfoundland. As offshore
drilling and production activity increases, some supply vessels will be stationed locally
and may be available for spill response. In a large-scale spill response, the number of
local vessels available may be insufficient and outside vessels may be needed. In
anticipation of this situation, Petro-Canada will maintain a list of available vessels that
may be useful for spill operations.
6.11.3
Contingency Planning
The key to the successful control of most oil spills is an efficient reaction, which
includes reporting, assessment, communication, and mobilization of response
resources. A Terra Nova oil-spill-response contingency plan will be developed to direct
personnel through a successful response operation. This plan will also be used in formal
response exercises to train personnel and to test the effectiveness of the spill response
system.
6-16
The oil-spill contingency plan will be a primary response document but will be one of
several emergency response plans developed for the Terra Nova Development.
Company operations manuals, policy directives, and guidelines will be used in the
development of the plan. In order to avoid duplication, other documents relating to
emergency oil spills will be cross-referenced. In its complete form, the oil spill
contingency plan will be a comprehensive manual and reference document that includes
detailed procedures and a considerable amount of background data. As in past drilling
programs, Petro-Canada will also produce concise and focussed tools such as wall
charts or wallet cards, which will serve as quick references for operations personnel in
the event of an oil-spill emergency.
Distribution
The contingency plan will be produced in limited numbers and distributed only to those
who will have a role to play in a response operation. The plan will be available on each
offshore facility, helicopter, flight-following service and in the shore-based offices of
the company and major contractors. Copies will also be distributed to federal and
provincial government regulatory agencies as required. Each page of the plan will be
dated and will be identified by a section and page reference. The plan will be kept
current through the issue of updates to registered plan holders. It will be the
responsibility of plan holders to ensure their copy of the plan is accurate and current.
Format
The format of the plan will be one that most clearly communicates the actions required
of all parties in a spill event. Past Petro-Canada plans have been based on the manual
prepared by the Canadian East Coast Offshore Safety Committee (CEOSC).
Regardless of the format chosen, the contingency plan will be organized for ease in
communicating situation details with other east coast operators and appropriate
government agencies.
Content
The contingency plan will consist of four basic sections:
·
·
·
·
Introduction
Response procedures
Contact information
Supporting data
The introduction will present the purpose of the plan and Petro-Canada's commitment
to the protection of human health and life, the environment, and corporate and
contractor property. The company's TLM framework specifically identifies contingency
planning within the contexts of Leadership (policy), Organization (training), and
6-17
Operating Practice (emergency preparedness) as an important part of loss management.
The response procedures section will describe the chain of command and key personnel
responsibilities within the Terra Nova organization. Notification and documentation
procedures and the prescribed interactions between development personnel,
government, and other operators will be specified. References will be made to
appropriate response strategies that detailed in the supporting data section of the plan.
Designated personnel and proper procedures for dealing with the public and the media
will be identified.
The plan will include contact lists for relevant company, government, and contractor
personnel. This section will include a listing of the Terra Nova oil-spill- response team
and will include contact information and relevant experience of each individual named
to the team.
The supporting data section will include an assessment of Terra Nova's response
capability and the expected effectiveness of countermeasure options, specific response
strategies for most likely scenarios, listings and sources of oil-spill countermeasures
equipment, descriptions of the predicted movement and fate of spilled oil in most likely
spill scenarios, environmental resource protection priorities and resource sensitivities to
be considered.
6.11.4
External Response Capability
Petro-Canada recognizes that, in the event of a larger spill, resources (equipment and
operators) additional to those dedicated by Petro-Canada to oil-spill response will be
required.
Eastern Canada Response Corporation
ECRC is a private-sector organization certified by the CCG under the regulations
resulting from recent amendments to the Canada Shipping Act. ECRC was formed by
a group of shareholder oil companies, including Petro-Canada, to provide a strong
private-sector response capability for a broad client base conducting marine operations
in eastern Canada.
ECRC is one of three such response organizations in Canada managed by the
CMRMC. Through a network of strategically positioned ECRC-owned equipment, a
core of permanent professional CMRMC response-management personnel, and a large
pool of standby, trained response technicians, CMRMC-ECRC has the capability of
responding to both nearshore and offshore spills throughout Canada. CMRMC-ECRC
is currently providing a dedicated oil-spill-response service to designated oil-handling
facilities and vessels throughout eastern Canada. At this time, Petro-Canada has had
preliminary discussions with ECRC concerning the provision of offshore oil-spillresponse services in support of the Terra Nova Development.
6-18
ECRC operates a series of facilities linked through common management in
Newfoundland (St. John's), Nova Scotia (Dartmouth), and Quebec (Sept Isles, Levis,
and Montreal). Each facility has experienced management with trained technical
personnel and at least enough equipment to respond to a 2500 t spill. ECRC also has
mutual aid arrangements with other response companies in Point Tupper, Nova Scotia,
and Saint John, New Brunswick. ECRC's Newfoundland Response Centre in St. John's
is strategically located close to both St. John's Harbour and Torbay Airport for quick
response to an offshore incident.
ECRC has over 2800 m of offshore boom configured for two-vessel sweep
applications. This inventory includes NOFI 1000 and 600 V-Sweep systems, Vikoma
Oceanpack and High Sprint systems, Roulands Ro-Boom, and a FIOCS V-Sweep.
ECRC also has Pharos Marine GT-185 and GT-260 weir skimmers with positive
displacement pumps for recovery of high-viscosity weathered crude in an offshore
environment.
Hibernia
HMDC will begin offshore activities in the summer of 1997, leading to production in
early 1998. It is Petro-Canada's understanding that HMDC intends to equip its two
purpose-built multi-use offshore supply vessels with NOFI sidesweep systems, onboard
skimming capability, and 700 t waste oil storage capacity. HMDC vessels will also be
equipped with fire monitors, which should be suitable for herding of oil on the surface,
mechanical dispersion of oil and breaking leads in pack ice in which spilled oil might
collect.
Petro-Canada is participating in ongoing discussions with HMDC concerning oil- spillresponse mutual aid.
Canadian Coast Guard
CCG operates a large oil-spill-response depot in St. John's, including five complete
offshore mobile collection and recovery systems. CCG also operates a fleet of vessels
from St. John's suitable for offshore spill response. The CCG offshore-response
capability is integrated so that each system is designated for use on a particular vessel
or vessels. Each of these five systems includes an offshore sidesweep boom system
(Vikoma Oceanpack, Norwegian Oil Trawl, Ro-Boom, or NOFI V-Sweep) and a large
heavy oil skimmer (Transrec 200, ACW 400, or GT-260). CCG also has
vessel-mounted dispersant application equipment and a helicopter-deployed helitorch
system in its Newfoundland inventory.
6-19
CCG offshore-response capability is being enhanced by the installation of permanent
onboard tankage for storage of waste oil on each of the vessels designated for offshore
spill-response duties.
Oil Spill Response Ltd.
OSRL is an international response organization based in Southampton, England.
OSRL operates the Oil Spill Service Centre in Southampton on behalf of a consortium
of major oil companies requiring a marine oil-spill-response capability. Petro-Canada
was a founding member of OSRL. OSRL has the capability to respond simultaneously
to two 30 000 t spills. Twenty-five percent of OSRL's equipment inventory is
appropriate for offshore applications. OSRL has its own dedicated Hercules and
Ilyushin transport aircraft and would be able to move equipment to St. John's for a
Grand Banks response operation in less than 24 hours.
Offshore boom systems include four 500 m Vikoma Ocean Boom and four 200 m
Roulands Hi-Seas Ro-Boom systems. Each of these systems are typically used in
two-vessel advancing-boom collection systems. Equipment appropriate for recovery of
a weathered Terra Nova crude include six Desmi 250 weir skimmers, two Vikoma Sea
Devil toothed disc skimmers, two WP 1-30 drum separator skimmers, and a variety of
rope mop skimmers. OSRL also has a helitorch system and a 20 m3 Aerial Dispersant
Delivery System (ADDS) for use with a Hercules aircraft.
International Response Organizations
International response organizations recognized as having an offshore response
capability that might be employed in a major spill at Terra Nova include NOFO, the
Norwegian North Sea Operators Clean Seas Association; Marine Spill Response
Corporation (MSRC), a nation-wide oil spill cooperative in the USA; and National
Response Corporation (NRC), an American commercial spill services provider. NOFO
and MSRC both have trained personnel and dedicated or designated offshore vessel
and equipment systems that would fit easily into the modular approach designated for
escalation of the countermeasures effort proposed for Terra Nova. Petro-Canada
recognizes that both of these organizations have strict national mandates and may only
be able to release limited resources to Terra Nova. NRC is less encumbered and may
be a more convenient source of equipment.
6-20
Equipment Suppliers
If additional equipment is required and is not available through established response
organizations, or if replacement parts are needed for equipment that has been
mobilized, Petro-Canada may have to deal directly with major equipment suppliers.
While most offshore spill response equipment is manufactured outside Canada, there
are reliable Canadian distributors for the equipment likely to be most useful to the
Terra Nova Development. Table 6.11-1 lists major boom and skimmer manufacturers
and their Canadian representatives.
6.11.5
Future Research and Development
Petro-Canada has supported offshore spill response research and development through
contributions to ESRF, PERD, and industry-sponsored task forces such as Canadian
Offshore Operators Spill Response Association (COOSRA). Meaningful research in
this area is usually very expensive and is best funded by a consortium of sponsors.
Petro-Canada will monitor ongoing research in areas directly applicable to the Terra
Nova Development. Of particular interest will be work relating to the handling of waxy
crude oil and in developments in emulsion-breaking technology.
6-21
Table 6.11-1
Major Boom and Skimmer Manufacturers
and Their Canadian Representatives
Manufacturer
Canadian Representative
Offshore Boom
Systems
All Maratim (NOFI boom)
Bergen Norway
Ro-Clean International
Odense, Denmark
Vikoma International
Isle of Wight, UK
Oil-Stop
Los Angeles, CA
Associated Marine
Dartmouth, NS
Navenco Marine
Chateauguay, PQ
Can Ross
Oakville, ON
PolE-Mar
Ottawa, ON
Skimmers
Frank Mohn
Bergen, Norway
Desmi
Norresundby, Denmark
Pharos Marine
Gothenburg, Sweden
H.Henriksen (Foxtail)
Tonsberg, Norway
Vikoma International
Isle of Wight, UK
PolE-Mar
Ottawa, ON
Associated Marine
Dartmouth, NS
Pol-E-Mar
Ottawa, ON
Can Ross
Oakville, ON
6-22
Chapter 7
Table of Contents
7.
7-1
7.
Environmental protection is a fundamental part of Petro-Canada's and the Proponents'
corporate policies. Petro-Canada's environmental protection policy contains the
following principles:
·
·
·
·
·
·
·
·
Compliance with applicable legislation and industry standards
Assessment and mitigation of impacts of all Project phases
Programs for management of waste and emissions
Prompt and effective response to emergencies
Awareness training for all employees
Use of all resources efficiently
Support of research on environmental effects
Open and fair dealings with the public regarding company activities
Petro-Canada and the Proponents will prepare an environmental protection plan (EPP)
for all phases of the Terra Nova Development. The plan will provide detailed guidance
to personnel on procedures for eliminating or minimizing adverse environmental
impacts. The EPP will be reviewed annually and updated as needed.
The EPP will contain the following components:
·
·
·
·
·
·
·
·
·
·
·
·
·
·
Corporate environmental policy
Standards and codes of practice
Mitigation procedures for development, production, decommissioning and
abandonment
Chain of command for environmental decision-making
Environmental education, training and orientation procedures
Environmental effects monitoring (EEM) procedures and reporting
Environmental compliance-monitoring (ECM) practices and reporting
Copies of applicable legislation, regulations, guidelines, licences, permits and
approvals
Management plans for waste, atmospheric emissions and effluent releases
Contingency plan for accidental discharges (see Chapter 6 for more details)
Environmental clauses for contractors
Environmental inspection and audit procedures
Fishing industry agreements and compensation procedures
Performance review practices
7-1
The core of the EPP will be the mitigation procedures, tailored for each stage of the
Terra Nova Development (development, production, decommissioning and
abandonment). An overview of some of these mitigation measures is found in Table
2.2-1. Industry standards and government legislation and guidelines in effect at the time
of the respective activities will be used. Some example components and activities
included or considered for mitigation will be:
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
Drilling muds
Well-treatment fluids
Produced water
Storage displacement waters
Deck drainage
Solid and sanitary wastes
Ship and boat noise
Routing of ships to minimize disturbance to wildlife
Routing, and minimum altitudes, for helicopters to minimize disturbance to
wildlife
An anti-harassment policy for wildlife
Onshore facilities
Regulated inputs of crude oil
Spills and response
Fuel and chemical handling
Compliance- and effects-monitoring programs will be integral parts of the EPP.
Compliance monitoring will be based on the Offshore Waste Treatment Guidelines.
Environmental effects monitoring may measure the effects and zone of influence of
drilling muds and cuttings, and produced water.
The sections of the EPP pertaining to each phase of the development will be submitted
to the Canada-Newfoundland Offshore Petroleum Board (C-NOPB) for approval at
least six months before beginning field development, production, or decommissioning
and abandonment.
7-2
Chapter 8
Table of Contents
8.
8.1
8.2
8.3
8.2.1 Drilling Muds and Cuttings
8.2.2 Well Treatment Fluids
8.2.3 Produced Water
8.2.4 Cooling Water
8.2.5 Deck Drainage
8.2.6 Air Emissions
8.3.1 Effects and Zone of Influence of Drilling Muds and
Cuttings
8.3.2 Zone of Influence of Produced Water
8.3.3 Effects of Oily Water on Fish
8-1
8-1
8-2
8-2
8-3
8-3
8-3
8-3
8-3
8-4
8-4
8-4
8-4
8.
Environmental monitoring will be included in the Terra Nova Development's
operations plan. Both the impact of the environment on the development and the
impact of the development on the environment will be monitored. There will be three
types of environmental monitoring:
1.
Physical environmental monitoring (weather, waves, ice) to help minimize risk
to facilities and personnel
2.
Compliance monitoring to ensure contaminant levels in regulated discharges
meet requirements
3.
Environmental effects monitoring to verify impact predictions
Monitoring programs will be evaluated for effectiveness on a regular basis. Reporting
procedures and a feedback loop will give early warning of environmental change or the
need to modify mitigation measures or the EPP.
The design for environmental effects monitoring at Terra Nova will differ somewhat
from that proposed for the Hibernia area. At the Hibernia site, discharges will emanate
from and activities will be centred at one place, whereas at Terra Nova, fluids will be
discharged and activities will occur over a larger area.
Environmental monitoring program designs have not been finalized. They will be
developed in concert with government agencies and submitted to the C-NOPB for
approval. In general, monitoring program strategy and design will be guided by the
Environmental Studies Research Funds (ESRF) East Coast and the Beaufort Sea
monitoring strategy studies (Thomas et al., 1984; Thomas, 1992) and consultations
with government. The monitoring study design will also consider the five years of
experience gained during the design and implementation of the EEM program for the
Hibernia project (e.g., Buchanan et al., 1990; Christian et al., in prep).
Some potential monitoring programs are discussed briefly in the following sections.
8.1
The physical environment monitoring program will help minimize the risk to personnel
and facilities. This program will support operational requirements, including:
8-1
-
Ensuring safe operations on site and in the movement of personnel and
equipment
-
Preventing damage to the environment
-
Optimizing production
The program will provide accurate and reliable real-time measurements to support
operational decisions on drilling, construction and production activities, and
movements of aircraft and vessels. The measurements are essential to the
meteorological forecasting program and are important to wave forecasting, the ice
management program and to real-time oil-spill trajectory modelling (if and when
required). Measurements made at Terra Nova will also contribute to the climatological
database available for future scientific and operational studies on local, regional and
global scales.
The proposed program will be discussed with the appropriate regulatory agencies prior
to submission to the C-NOPB for approval.
8.2
Compliance monitoring will be based on the final Offshore Waste Treatment
Guidelines. Effluent limits and monitoring regulations used in this EIS were based on
the draft guidelines. A compliance monitoring program will be submitted to the CNOPB for approval.
It should be noted that in addition to filing reports with the Chief Conservation Officer
respecting conditions that are considered to have exceeded normal operating practice,
Petro-Canada will investigate these exceedances for cause and corrective action.
8.2.1
Drilling Muds and Cuttings
Cuttings will be treated to meet Offshore Waste Treatment Guidelines, which currently
call for:
-
A maximum of 15 g oil/100 g dry cuttings averaged over a 48-hour period
-
Measurement of concentrations of oil in solids to be measured every 12 hours
using the specified methods
-
Calculation of a rolling 48-hour average concentration
-
Reporting of oil concentrations of 30 g/100 g or greater to the Chief
Conservation Officer within 24 hours
8-2
8.2.2
Well treatment fluids recovered from operations will be processed to an oil
concentration of 40 mg/L or less as required by the Offshore Waste Treatment
Guidelines. Time series of raw and averaged data from analysis of treated and
discharged fluids will be submitted to the Chief Conservation Officer on an approved
schedule.
A chemical management plan will be developed with the chemical suppliers and
submitted to the C-NOPB as part of the EPP.
8.2.3
Produced Water
Produced water will be treated to meet Offshore Waste Treatment Guidelines which
call for:
8.2.4
-
Treatment to reduce oil content of discharged produced water to 30-day
average concentrations of 40 mg/L or less
-
Reporting of oil concentrations of more than 80 mg/L during any 48-hour
period of production to the Chief Conservation Officer within 48 hours
-
Measurement of oil concentrations every 48 hours, and daily calculation of a
rolling 30-day average
-
Use of the specified test methods
Cooling Water
Any requirement to use biocides, other than chlorine, in cooling water will be
submitted to the Chief Conservation Officer for approval before use.
8.2.5
Deck Drainage
Deck drainage will be processed to meet the Offshore Waste Treatment Guidelines of
15 mg oil/L. Oil concentrations of greater than 15 mg/L in the discharge will be
considered to have exceeded normal operating practice and be reported within 24
hours to the Chief Conservation Officer.
8.2.6
Air Emissions
All emissions produced as a result of flaring or boom burning will meet any
government regulations in place at the time.
8-3
8.3
An environmental effects monitoring program (EEM), including collection of baseline
data, will be developed in conjunction with C-NOPB and other relevant government
agencies. The EEM program will be submitted to the C-NOPB for approval.
8.3.1
Effects and Zone of Influence of Drilling Muds and Cuttings
The EEM will monitor oil concentrations in sediments and effects on benthic animals.
8.3.2
Zone of Influence of Produced Water
Most of the oily water discharge will be produced water. The EEM will determine oil
concentrations at various distances from the discharge.
8.3.3
Effects of Oily Water on Fish
A program to monitor tainting in fish will be implemented. This monitoring program
will consider all sources of hydrocarbons that could be released during development
and production. If tainted fish are found, the source will be determined and further
mitigation measures will be implemented.
8-4
Glossary
abandonment. The decommissioning of facilities and removal of offshore structures following
exhaustion of reserves.
abiotic. Nonbiological; a process not mediated or resulting from the activity of organisms. Ocean
currents and weather are examples ofabiotic processes.
accretion. Growth by organic enlargement; growing of separate things into one.
ADCP. Acoustic Doppler-Current Profiling.
ADDS. Aerial Dispersant Delivery System.
advection. The process of, or referring to the transport of one fluid mass (air, water) by the
movement of another.
aerobic. A process requiring the presence of air or oxygen.
AES. Atmospheric Environment Service.
AHH. (Enzyme) Aryl hydrocarbonhydroxylase.
alcids. A group of shorebirds, predominantly of northern coasts, including auks, puffins,
murres
and guillemots.
anadromous. Used to describe fish that spawn in fresh water after spending most of their life in
the sea.
anaerobic. Not requiring the presence of oxygen.
anemones. Solitary or colonial jelly-like sessile animals with tentacles; taxonomically closely
related to stony corals.
annulus. The space between drill pipe and bore wall, pipe and casing, or concentric strings of
casing.
anomaly. A geological feature, especially in the subsurface, distinguished by geological,
geophysical orgeochemical means, which is different from the general
surroundings and is often of potential economic value, e.g., a magnetic anomaly.
anthropogenic. Derived or resulting from human activity.
Glossary-1
anticline. A fold, generally convex upward, whose core contains the
stratigraphically oldest
rocks.
anticyclone. An atmospheric pressure distribution in which there is a high central pressure related
to the surroundings. Resulting weather is usually quiet and settled.
API. American Petroleum Institute.
articulated loading platform (ALP).A column attached by means of an articulated joint to a
permanent base on the ocean floor. The column supports a loading head. Crude oil
is transferred by export lines to the base of the ALP, up through the column, and
through the loading head to shuttle tankers.
artificial reef. An underwater artificial structure that provides habitat similar to that provided by
a natural reef.
artificial reef effect.The effect generated by the placement of an undersea structure in an area
where previously there were no similar habitats.
Benthic organisms colonize the
structure, and subsequently fish and other organisms are attracted to it in search of
food.
astronomical tides.The alternate rise and fall of the surface of oceans, seas, and the bays, rivers,
etc., connected with them, caused by the gravitational attraction of the sun and
moon.
baleen. Comb-like semi-rigid plates with frayed edges that hang from the roof of a baleen whale's
mouth; used when feeding to filter prey from the water.
ballast water. Water carried in tanks on a vessel (e.g., tanker) to maintain sea-going stability.
barite. A common mineral (bariumsulphate) associated with lead ores; used as a weighting
material for drilling because of its high specific gravity.
basement. A series of igneous and metamorphic rocks, generally with complex structure, beneath
dominantly sedimentary rocks.
bathymetry. The measurement of depths of water in oceans, seas and lakes; also the information
derived from such measurements.
bbl. The abbreviation for barrel.
bedrock. A general term for the rock, usually solid, that underlies soil or other unconsolidated,
superficial material.
Glossary-2
benthos. Organisms living on, in, or attached to the sea bottom; includes both animals and plants.
bentonite. A clay material used to impart viscosity in drilling fluids; also referred to as gel.
bergy bit. A piece of floating glacier having a sail greater than 1.5
m but less than 5m and a
2
water plane area greater than 20m but less than 300 m2. Size approximates that
of a small house and mass is between 120 and 5400 t.
bilge. The nearly horizontal part of a ship's bottom.
BIO. Bedford Institute of Oceanography.
biocide. A chemical agent that destroys bacteria.
biodegradable. Refers to a substance that can be broken down by micro-organisms.
biodegradation. The biological conversion of organic material to inorganic nutrients.
biofouling. The encrustation of submerged structures by barnacles and mollusks,
seaweeds and
other marine life; also known as marine fouling.
biological oxygen demand.The amount of dissolved oxygen required to meet the metabolic
needs of anaerobic micro-organisms in water rich in organic matter such as
sewage.
biomass. The amount of living matter of a specified type given as a concentration per unit area or
volume.
biota. The flora and fauna of a region.
bloom. Rapid growth of a population ofplanktonic organisms.
blowout. A change in the gas or oil pressure of the well, which cannot be handled by the well's
control system, resulting in uncontrolled flow.
blowout preventer (BOP). A stack or an assembly of heavy duty valves attached to the top of
the casing to control well pressure.
BOP. blowout preventer.
boreal. Northern.
boulder. A rounded rock fragment greater than 256 mm in diameter.
Glossary-3
burner boom. A structure that supports necessary piping and apparatus for burning drilling mud,
produced oil, gas and other fluids; used to burn recovered fluids during well testing
operations on a drilling rig. Usually such burners are fueled by diesel.
C-NOPB. Canada-Newfoundland Offshore Petroleum Board.
caisson. A large-diameter pipe that houses asubmudlinewellhead.
calved. Icebergs broken off from a glacier that reaches the sea.
casing. Steel pipe used in oil and gas wells to seal off fluids from the
borehole and to prevent the
walls of the hole from sloughing or caving. There may be several strings of casing
in a well, one inside the other.
CASP. Canadian Atlantic Storms Program.
CCG. Canadian Coast Guard.
CCRS. Canada Centre for Remote Sensing.
CEAA. Canadian Environmental Assessment Agency.
Cenozoic. An era of geological time, from the beginning of the Tertiary period to the present.
(Some authors do not include the Quaternary, considering it a separate era.) It is
characterizedpaleontologically by the evolution and abundance of mammals,
advanced mollusks and birds. The Cenozoic is considered to have begun about 65
million years ago.
CEOSC. Canadian East Coast Offshore Safety Committee.
chemical oxygen demand (COD).The amount of dissolved oxygen required to allow the
abiotic
oxidation of chemical compounds.
chlorophyll. A green pigment found in all algae and higher plants. Responsible for light capture in
photosynthesis.
CHW. Cod, haddock and witch flounder eggs.
CIL. Cold intermediate layer.
clast. An individualdetrital constituent of a sediment.
Glossary-4
clay. A mineral fragment ordetrital particle of any composition (often a crystalline fragment of a
clay mineral), smaller than a very fine silt grain, having a diameter less than
μm.
4
climax. A community that has reached a steady-state under a particular set of environmental
conditions.
CMRMC. Canadian Marine Response Management Corporation.
COADS. Comprehensive Ocean-Atmosphere Data Set.
cobble. A rounded rock fragment between 64 and 256 mm in diameter.
completion. The activities necessary to prepare a well for the production of oil and gas.
condensate. Liquid hydrocarbons that are produced with natural gas and that separate from the
gas as a result of decreases in temperature and pressure; API gravity generally is
50 to 120° and colour varies from water white to straw blush.
Continental Shelf. Gently sloping, shallowly submerged marginal zone of the continents
extending from the shore to an abrupt increase in bottom inclination; greatest
average depth less than 183m, slope generally less than 1 to 1000, local relief less
than 18.3 m, width ranging from very narrow to more than 320
km.
Continental Slope. Continuously sloping portion of the continental margin with gradient of more
than 1 to 40, beginning at the outer edge of the Continental Shelf and bounded on
the outside by a rather abrupt decrease in slope where the continental rise begins at
depths ranging from about 1400 to 3000 m.
COOSRA. Canadian Offshore Operators Spill Response Association.
core. A cylindrical boring of rock from which composition and stratification may be determined.
CPA. Closest point of approach.
CPR. Continuous plankton recording.
crude oil. Unrefined petroleum.
crustaceans. Invertebrate animals, such as lobster, shrimps, crabs, copepods and
amphipods, with
at least five pairs of jointed legs.
CTD. Conductivity-temperature-depth.
Glossary-5
current shear. A tangent or plane of contact where two opposing currents collide and are
subsequently driven away from each other.
cuttings. Chips and small fragments of rock that are brought to the surface by the drilling mud as
it circulates.
cyclogenesis. The initiation ofcyclonic circulation, or strengthening around an existing depression
or cyclone.
cyclone. A circular or nearly circular area of low atmospheric pressure around which the winds
blow counterclockwise in the northern hemisphere and clockwise in the south. It
may cause precipitation and cloudiness over many thousands of square miles.
dB. Decibel.
deadweight. The maximum design weight of cargo, crew and effects for a ship (the "payload").
delineation well. See appraisal well.
deltaic. Pertaining to, or like a delta.
demersal. Referring to animals, usually fish, associated with, but not living on, the sea bottom.
detritus. Dead or decaying organic matter, and associated microorganisms that are responsible
for its decomposition.
Development (Terra Nova Development)."Development" refers to all phases of the project,
from the decision to go ahead with construction through to abandonment of the
field.
Development Application.The official title of the documentation submitted in support of Terra
Nova Development. The Development Application includes: Development Plan,
Parts 1 and 2; Canada-Newfoundland Benefits Plan; Development Application
Summary; Environmental Impact Statement;
Socio-Economic Impact Statement.
development drilling.Drilling and bringing into production additional wells on a lease following
the drilling of the discovery and appraisal wells.
development well.A well drilled in an area already proved to be productive.
Glossary-6
dewpoint (water). The temperature at which watervapour condenses out of a gas at a specified
pressure.
DFO. Fisheries and Oceans.
diatoms. Microscopic algae characterized by "pill-box like" cell walls containing silica.
diel. Daily.
dinoflagellate. A chiefly marine one-celled organism with
resemblances to both plants and
animals. Hard parts preserved asmicrofossils are important for dating and
correlating Mesozoic and Cenozoic deposits.
discovery well. An exploratory well that encounters a new and previously untapped petroleum
deposit; a successful wildcat well.
DO. Dissolved oxygen.
DOC. Dissolved organic carbon.
drill water. Water used as the liquid phase in water-based mud; usually denoting non-saline
water.
drilling mud. A special mixture of clay, water and chemical additives pumped down the wellbore
through the drill pipe and drill bit to cool the rapidly rotating bit, lubricate the drill
pipe as it turns in the wellbore, and carry rock cuttings to the surface; may have a
water base or oil base.
drilling platform.An offshore structure from which a number of wells are drilled. The legs of the
platform are anchored to the seabed and the platform is built on a large-diameter
pipe frame.
drilling rig. A ship-shaped or semisubmersible vessel, or a jackup platform, with equipment
suitable for offshore drilling.
drillstem test (DST). A short-term test of the productive capacity of a well through drillpipe.
dry dock. A dock that can be kept dry for use during the construction or repair of ships.
DST. Drillstem test.
echinoderms. Invertebrate animals with radial symmetry and high carbonate content; includes
starfish, brittlestars, sea urchins, sand dollars and sea cucumbers.
ECM. Environmental compliance monitoring.
Glossary-7
ecosystem. The complex of a community and its environment functioning as an ecological unit in
nature.
ECRC. Eastern Canada Response Corporation.
EEM. Environmental effects monitoring.
effluents. The liquid waste discharges of sewage and industrial processing.
EIS. Environmental Impact Statement.
emergency shutdown (ESD) system.A system that, when activated, shuts in producing wells
and isolates or depressures associated equipment.
endangered. Descriptive of a species that is in danger of extinction within all or part of its range
(the region to which it is native).
Environmental Impact Statement (EIS).A document that attempts to predict the effects a
major development might have on the human and natural environments of a given
geographic area. An EIS is prepared to enable industry, government and the public
to consider the environmental and socio-economic costs and benefits of a
development project. Based on the information contained in the EIS, decisions can
be made on whether to proceed with the development project.
epibenthos. Plants or animals that live on the sea bottom. Some of the animals are not attached,
but crawl about.
epifauna. Benthic animals living attached to or crawling over the bottom.
EPP. Environmental Protection Plan.
EPS. Environmental Protection Service.
ERICA. Experiment on Rapidly Intensifying Cyclones over the Atlantic.
ERS-1. European remote sensing satellite.
ESRA. East Coast Spill Response Association.
ESRF. Environmental Studies Research Fund.
ESRI. East Coast Spill Response Inc.
estuary. That area of a coastal embayment that is under the influence of both fresh water and sea
water.
Glossary-8
EU. European Union.
euphausiid. Small shrimp-like zooplankton commonly known as krill.
euphotic zone. The upper layers of the water column down to the limits of effective light
penetration for photosynthesis.
exploration well.A well drilled to find an oil- or gas-bearing formation.
facies (sedimentary).The appearance and characteristics of a rock unit reflecting the
depositional environment of its origin, as distingushed from adjacent units of
different origin.
FAO. (a) Financial Assistance Officer. (b) Food and Agriculture Organization.
fast ice. Ice attached to land or a permanent ice shelf excluding grounded ice or ice of land origin.
fault. A fracture or fracture zone along which there has been displacement of the sides relative to
each other parallel to the fracture. The displacement may be a few millimetres or
many kilometres.
FEARO. Federal Environmental Assessment and Review Office.
fecundity. Fertility.
filter feeder. Animals that strain suspended food particles from the surrounding water.
FIOCS. Fully Integrated Oil Containment System.
First Oil. Milestone achieved when the first shuttle tanker has been filled with oil from the Terra
Nova production system and the shuttle tanker disconnects from the offloading
system. The entire production system is handed over to operations personnel at
this point. This is the first quantity of oil to be delivered from the reservoir through
the complete production and offloading system, including fiscal metering.
flare. An arrangement of piping and burners used to dispose of surplus combustible vapours (by
burning).
flaring. Disposal of surplus combustible vapours by burning at the discharge of the flare tower.
flatfish. Fish with a flattened body and both eyes on one side of the head. Includes plaice,
flounder and halibut.
Glossary-9
fledge. To raise a young bird until it is able to fly.
floating production system.A monohull or semisubmersible vessel with equipment suitable for
producing hydrocarbons.
flowline. (a) A pipeline that takes fluids from a single well or a series of wells to a gathering
centre. (b) Seabed piping that connects field components such as wells, manifolds
and riser bases.
fluvial. Of or pertaining to a river.
formation water.See produced water.
FPF. Floating production facility.
freeboard. The height between normal water level and the deck of a vessel or structure in the
water.
front. A sloping transition zone between two water or air masses of different density and
temperature.
frontal zone. The three-dimensional zone or layer of large horizontal density gradient, bounded
by frontal surfaces and surface front.
GALE. Genesis of Atlantic Lows Experiment.
GBS. Gravity-base structure.
gel. A substance used in drilling that is in a liquid state when flowing and a semisolid gelled state
at rest. This allows the drill cuttings to stay in suspension when circulation has
stopped. See bentonite.
geology. The study of the structure, origin, history and development of the earth.
geostrophic. Pertaining to deflecting force resulting from the earth's rotation.
GESAMP. Joint Group of Experts on the Scientific Aspects of Marine Pollution.
GF. Groupiness factor.
glaciomarine. Marine sediments that contain glacial material.
GOR. Gas-oil ratio.
Glossary-10
graben. A fault-bounded elongate crustal block that is down-dropped relative to adjacent crustal
blocks, usually resulting in a topographic low.
grain. A general term for sedimentary particles of all sizes (from clay to boulders), as used in the
expressions "grain size," "fine-grained" and "coarse-grained."
gravity base structure (GBS).The base of an offshore drilling and production platform, usually
made of concrete, and of such tremendous weight that it is held securely on the
ocean bottom without the need for piling or anchors.
grey water. Water that has been used for washing, showers, laundry, or in the galley and contains
no hydrocarbons or high concentrations of chemicals.
groundfish. Species of fish that are collected by bottom gear (trawls); e.g., cod, haddock and
flounder.
gyre. Circular movement of water masses.
h. The abbreviation for hour.
habitat. The place where an animal or plant lives, often characterized by some physical condition
(e.g., stream habitat).
heterotrophs. Organisms that receive nourishment by ingesting and breaking down organic
matter from the surrounding water.
HF. High frequency radio.
HMDC. Hibernia Management and Development Company.
Holocene. An epoch of the Quaternary period extending from the end of the Pleistocene,
approximately eight thousand years ago, to the present time; also, the
corresponding series of rocks and deposits. When the Quaternary is designated as
an era, the Holocene is considered to be a period.
Hs The abbreviation for significant wave height.
hurricane. A tropical cyclone with wind speeds over 118 km/h, usually accompanied by rain,
thunder and lightning.
hydrography. The science of the waters of the earth's surface, particularly with reference to their
physical features, position, volume, etc., and the preparation of charts of seas,
lakes, rivers, contours of the seabed, shallows, deeps, currents, etc.
Glossary-11
hydroids. Typical colonial polyps with variously branched bushy or feathery growths. Each polyp
has a crown of tentacles around the mouth.
hyperbenthic. Benthic or bottom organisms that spend part of their time in the water column for
feeding or reproduction.
Hz. Hertz; unit of sound frequency equal to one cycle per second.
iceberg scour. Seafloor trench caused by the ploughing motion of an iceberg grounding on the
ocean floor.
ichthyoplankton. Collective term for fish eggs and larvae when planktonic.
IGY. International geophysical year.
IIP. International Ice Patrol.
impact. An observable and measurable response of a population, individual or abiotic factor to an
external source of disturbance.
IMT. Integrated Management Team.
inertial currents.Wind-driven currents that oscillate in horizontal circular paths.
inertial period. The amount of time required for an inertial current to complete a full circle.
infilling. A process of deposition by which sediment falls or is washed into depressions, cracks or
holes, as the filling in of crevasses upon the melting of glacier ice.
inhibitor. A substance that is capable of stopping or retarding a chemical reaction.
injection water. Water pumped into the formation to maintain reservoir pressure (secondary
recovery technique); offshore, injection water is filtered seawater treated with
biocides, oxygen scavenger and scale inhibitor.
inshore fishery. Refers to fishing using vessels 35 feet and under in length.
interannual. Year-to-year.
isobath. A line on a map or chart connecting points of equal water depth.
isopods. A group of crustaceans including wood lice and sow bugs.
Glossary-12
jackup drilling unit.An offshore drilling structure with tubular or derrick legs supporting the
deck and hull. A jackup rig is towed or propelled to a location with its legs up.
Once the legs are firmly positioned on the seafloor, the deck and hull heights are
adjusted and levelled.
juvenile. Fish past the larval stage of development, but not yet large enough to be caught in the
commercial fishery, e.g., cod remain juveniles for about four years.
JWE. Jacques, Whitford Environment.
keel. A steel beam or timber, or a series of steel beans and plates or timbers joined together,
extending along the centre of the bottom of a ship from stem to stern and often
projecting below the bottom, to which the frames and hull plating are attached.
kleptoparasite. A bird that steals food from other birds to feed its young; includes jaegars and
skuas.
km. The abbreviation for kilometre.
L. The abbreviation for litre.
larva. The first immature phases of many animals after hatching of eggs and before assuming the
adult form and habit.
LC50. The concentration of a toxicant necessary to kill 50 percent of the test organisms in a
standard time period.
LEWEX. Labrador Sea Extreme Waves Experiment.
LFA. LeDrew, Fudge and Associates.
LIMEX. Labrador Ice Margin Experiment.
liner. A length of casing used downhole to shut off a water or gas formation or prevent the loss
of drilling fluids in a porous formation.
lithology. The physical character of a rock.
m. (a) The abbreviation for metre. (b) The abbreviation for earthquake magnitude.
M2. Lunar semidiurnal component.
m3. The abbreviation for cubic metre.
macrophytes. Macroscopic attached aquatic plants.
Glossary-13
manifold. A multiple piping arrangement containing the valving to divide a flow into several
parts, combine several flows into one, or reroute a flow to one of several possible
destinations.
MANMAR. Manual of Marine Weather Observing.
marine riser. In an offshore drilling facility, a system of piping extending from the hole and
terminating at the rig.
MAST. Marine Statistics.
Md. Measured depth; the distance measured along the well-bore from the drill floor in a deviated
well.
MEDS. Canadian Marine Environment Data Service.
megaripple. A large, gentle, ripple-like feature composed of sand in subaqueous environments
having a wavelength grreater than 1 m or a ripple height greater than 10
cm.
Wavelengths reach 100 m and amplitude about 0.5 m; may be formed by tidal
currents.
Mesozoic. An era of geologic time, from the end of the Paleozoic to the beginning of the
Cenozoic, or from about 225 to 65 million years ago.
mg. The abbreviation for milligram.
microbiota, micro-organisms.Microscopic organisms, including animals, plants, bacteria,
yeasts, fungi, etc., which are primarily single-celled, although some colonial forms
and multi-celled organisms are included. Individuals range in size from about
0.0001 to 0.5 mm in diameter.
migration. In seismic processing, plotting of dipping reflections in their true spatial positions.
mitigating (mitigative) measure.A procedure designed to reduce or negate the possible harmful
effects of a substance or process on a species, habitat or environment.
mm. The abbreviation for millimetre.
MMS. Minerals Management Service (U.S.).
MODU. Mobile offshore drilling unit.
mollusc. An animal possessing an external or vestigial calcium carbonate shell; including clams,
snails and squid.
Glossary-14
monohull. A ship-shaped vessel.
MSRC. Marine Spill Response Corporation (U.S.).
NAFC. Northwest Atlantic Fisheries Centre.
NAFO. Northwest Atlantic Fisheries Organization.
NAO. North Atlantic Oscillation.
NCSP. Northern Cod Science Program.
NEB. National Energy Board.
neritic. The zone of the ocean inshore from the edge of the Continental Shelf, including coastal
bays and inlets and the Continental Shelf.
neuston. Planktonic organisms living in or near the surface film at the surface of the sea.
NMC. National Meteorological Center (U.S.).
NOAA. National Oceanic and Atmospheric Administration.
NOBE. Newfoundland Offshore Burn Experiment.
NOFO. North Sea Operators Clean Seas Association.
NRC. National Response Corporation (U.S.).
nursery area.An area that supports fish during their first year of life.
NWP. Numerical weather prediction.
offal. Refuse, garbage.
oleoclasts. Bacteria that have the ability to degrade hydrocarbons.
OPEN. Ocean Production Enhancement Network.
Operations Phase. The period following First Oil until cessation of all oil production from the
Terra Nova Field. Includes post First Oil development drilling, offshore installation
activities, production, operations, maintenance, well abandonment,
decommissioning and removal from the Terra Nova Field of all facilities,
equipment and vessels used in the production system.
Glossary-15
Operator. When capitalized in this document, refers to Petro-Canada.
OSRL. Oil Spill Response Ltd.
overconsolidation.Consolidation (of sedimentary material) that is greater than normal for the
existing overburden, e.g., consolidation resulting from desiccation or from
pressure of overburden that has since been removed by erosion.
ovoviviparous. Producing eggs that are hatched within the body, so that the young are born alive
but without placental attachment; as certain reptiles and fishes, etc.
PAC. Polycyclic aromatic compounds.
pack ice. Any area of sea ice, except fast ice, composed of a heterogeneous mixture of ice of
varying ages and sizes, and formed by the packing together of pieces of floating
ice.
packer. An expanding plug used near the bottom of a well to isolate the tubing-casing annulus.
PAH. Polycyclic aromatic hydrocarbons.
PAL. Provincial Airlines Ltd.
paleo. Ancient, old.
PCB. Polychlorinated biphenyls.
pebbles. Smooth rounded stones ranging in diameter from 2 to 64 mm.
pelagic. Living or feeding in the water column.
PERD. Panel on Energy Research and Development.
petroleum. Oil and natural gas.
photosynthesis. The utilization of the sun by plants to combine water and carbon dioxide into
simple sugars.
PHPA. An inhibited water-based drilling fluid.
physiography. The description and origin of landforms.
Glossary-16
phytoplankton. Planktonic (i.e., floating or swimming) photosynthesizing organisms that are
mostly single-celled, although some are colonial; some are capable of swimming,
while others are incapable of independent motion.
pile. A long, heavy wooden, steel or reinforced concrete post driven, jacked, jetted or drilled into
the ground to support a load.
plankton. Organisms living in water that are not capable of swimming vigorously enough to
move independently of water movements.
platform. A large structure used during the development and production phases to support such
facilities as the drilling rigs, living quarters, production equipment and helipads.
Pleistocene. An epoch of the Quaternary period, after the Pliocene of the Tertiary and before the
Holocene; also, the corresponding worldwide series of rocks. It began two to three
million years ago and lasted until the start of the Holocene some eight thousand
years ago. Where the Quaternary is designated as an era, the Pleistocene is
considered to be a period.
plume. A trail of oil.
PMEL. U.S. Pacific Marine Environmental Laboratory.
polychaete. A marine worm with true body segments and hard spines.
polymer mud. A drilling mud to which has been added a polymer (a chemical that consists of
large molecules that were formed from small molecules in repeating structural
units) to increase the viscosity of the mud.
porosity. The volume of the pore space expressed as a percentage of the total volume of the rock
mass.
ppb. Parts per billion.
ppm. Parts per million.
Pre-Engineering. All of the engineering work undertaken before the Project Phase to determine
the preferred floating production system for Terra Nova. Begins with the invitation
to submit Alliance qualification proposals through selection of the three Alliance
groups, through selection of the preferred production system and Alliance.
Includes further definition engineering work with the preferred Alliance up to the
commencement of the Project Phase.
Glossary-17
years
Precambrian Era.A division of geological time including time older than about 600 x610
ago.
pressure gradient.The rate of pressure increase with depth.
primary production.Carbon fixation during photosynthesis; includes
phytoplankton.
produced sand. Sand produced with oil and gas.
production manifold.A steel structure containing piping and valves located on the seabed,
remote from the surface producing facility. Flow from producing wells is combined
at the production manifold before moving to the riser base and then the surface
producing facility.
production platform.An offshore structure equipped to receive oil or gas from offshore wells
where primary processing, compression and pumping are carried out before
transportation of the oil or gas to shore.
production wellhead. The terminal point of a producing well, consisting of casing head, tubing
head, tubing string connection, and the complex known as the Christmas tree.
productivity. The rate of production of newbiomass by populations of organisms.
Project Phase. The period beginning with regulatory approval of the Development Application
and the proponents' authorization to execute Terra Nova Development, up to the
production and offloading of First Oil. Includes detail engineering, procurement,
construction, commissioning, installation and development drilling up to First Oil.
Does not include development drilling after First Oil.
Proponents. Those Terra Nova asset owners who are sharing in the predevelopment costs and
who have authorizedPetro-Canada to prepare a Development Application in its
capacity as Operator.
protozoa. A group of single-celled animals.
psu. The abbreviation for practical salinity unit.
Quaternary. The second period of the Cenozoic era, following the Tertiary; also, the
corresponding system of rocks. It began two to three million years ago and
extends to the present. It consists of two grossly unequal epochs: the Pleistocene,
up to about eight thousand years ago, and the Holocene since that time.
Glossary-18
recruitment. The addition of individuals to a population through reproduction and immigration.
reflection. The return of a wave or energy incident upon a surface to its original medium. Also, in
seismic prospecting, the indication on a record of such reflected energy.
Regulatory Phase.The period and activities associated with the regulatory review of the
Development Application. Commences with the filing of the Development
Application and ends upon receipt of approval.
reserves. That part of an identified resource from which a usable mineral or energy commodity
can be economically and legally extracted at the time of determination.
reservoir. A subsurface, porous, permeable rock body in which oil or gas has accumulated; most
reservoir rocks are limestones, dolomites,sandstones, or a combination of these.
residual impacts. Those impacts remaining after enhancement and
mitigative measures have been
applied.
RFE. Regional finite element.
rift. An elongate structural trough bounded by normal faults formed during
crustal extension.
rig. Refers to the combination of equipment used to drill wells.
riser. A flowline carrying oil or gas from the seabed to the deck of a production platform or a
tanker loading platform.
riser base manifold.A simple structure located on theseafloor to act as a termination point for
the production riser, satellite wells and transfer lines.
ROV. Remotely operated vehicle.
s. The abbreviation for second.
sand. A detrital particle smaller than a granule and larger than a coarse silt grain, having a
diameter in the range of 0.625 mm to 2 mm.
sandstone. Consolidated sediment composed primarily of sand-sized grains.
SAR. (a) Search and rescue. (b) Synthetic aperture radar.
Glossary-19
SAWRS. Supplementary aviation weather reporting service.
SBM. Single buoy mooring.
scour. (a) Seafloor trench caused by theploughing motion of an iceberg grounding on the ocean
floor. (b) Seafloor erosion caused by strong currents, resulting in the
redeployment
of bottom sediments and formation of holes and channels.
SDA. Significant Discovery Area.
SDL. Significant DiscoveryLicence.
sea ice. Any ice floating in the sea.
sediment. Solid material, both mineral and organic, that is being or has been transported from its
site of origin by air, water or ice, and has come to rest on the earth's surface either
above or below sea level.
sedimentary rock.Rocks formed by the accumulation of sediment in water or from air. The
sediment may consist of rock fragments or particles, the remains of animals or
plants, the product of chemical action or evaporation, or of mixtures of these
materials.
SEIS. Socio-Economic Impact Statement.
seismic. Pertaining to, characteristic of or produced by earthquakes or earth vibration.
seismicity. The phenomenon of earth movements; seismic activity.
seismotectonic. Pertaining to deformation of earth's crust from shocks not due to volcanic action.
semidiurnal tide. A tide having two high waters and two low waters during a tidal day.
semisubmersible.A drilling or production vessel that has the main buoyancy chambers
(pontoons) below the active wave zone to provide enhanced vessel stability.
separator. A cylindrical or spherical vessel used to separate the components in mixed streams of
fluids.
sequence. A succession of geological events, processes or rocks, arranged in chronological order
to show their relative position and age with respect to the geological history as a
whole.
sessile. Organisms that are fixed to substrate.
Glossary-20
shale. Sedimentary rock consisting dominantly of clay-sized particles, an appreciable amount of
which are clay minerals.
shear. A stress causing or tending to cause two adjacent parts of a solid to slide past one another
parallel to the plane of contact.
shelf break. An abrupt change in slope, marking the boundary between the Continental Shelf and
the Continental Slope.
shuttle tanker. A ship with large tanks in the hull for carrying oil or water back and forth over a
short route.
sidescan sonar. A sonar device used in seismic surveys to scan the seabed from the side of the
survey ship.
silt. A detrital particle smaller than a very fine sand grain and larger than coarse clay, having a
diameter in the range of 0.004 mm to 0.625 mm.
siltstone. Consolidated sediment consisting dominantly of silt-sized grains.
SLAR. Side-looking airborne radar.
snubbing. A procedure for servicing wells that are under pressure. Pipe and
downhole tools are
withdrawn from or lowered into the well through a stack of rams (valve-like
devices that close around pipe or tubing being withdrawn or lowered and seal off
the well pressure).
sorting. The degree of similarity in grain size of sedimentary particles in a sediment; a measure of
the spread or range of the particle-size distribution on either side of an average.
source rock. Sedimentary rock in which organic material under pressure, heat and time was
transformed into liquid or gaseous hydrocarbons (usually shale or limestone).
SPM. Single-point mooring.
ss. The abbreviation forsubsea.
stock. A species, group or population that maintains and sustains itself over time in a definable
area. A stock is characterized by constancy of the genetic information in the gene
pool, and constancy of expression of particular characters controlled either
genetically or environmentally. Examples include maintenancecolour
of
variations
or particular growth rates.
Glossary-21
storm surge. A rise above normal water level due to the action of wind on the water surface and
the rise in level because of atmospheric pressure reduction.
stratification. Division of the water column into layers, or strata, because of differences in
density, structure or temperature.
stratigraphy. A branch of geology concerned with the form, arrangement, geographic
distribution, chronological succession, composition, correlation and mutual
relationships of rock strata, especially sedimentary.
stratum. A tabular or sheet-like body or layer of sedimentary rock, visually separable from other
layers above and below; a bed. It has been defined asstratigraphic
a
unit that may
be composed of a number of beds, as a layer greater than 1 cm in thickness and
constituting a part of a bed, and as a general term that includes both "bed" and
"lamination." The term is more frequently used in its plural form, strata.
subaerial. Formed, existing or taking place on the land surface.
sublittoral. The area of the seafloor below the level of extreme low spring water.
submarine canyon.Steep valley-like submarine depression crossing the continental-margin
region. Common on the Continental Slope and Shelf, but some continue across the
Continental Rise.
submudline. Preparing a well for the production of oil and gas with the completion
wellhead
components installed below the sea floor.
surficial. Characteristic of, pertaining to, formed on, situated at, or occurring on the earth's
surface; especially, consisting of unconsolidated residual, alluvial or glacial
deposits lying on the bedrock.
synoptic. Atmospheric conditions existing at a given time over an extended region; e.g., a
synoptic weather map, which is drawn from observations taken simultaneously at a
network of stations over a large area, thus giving a general view of weather
conditions.
t. The abbreviation fortonne (a metric ton).
tectonic. Of, pertaining to, or designating the rock structure and external forms resulting from the
deformation of the earth's crust. As applied to earthquakes, it describes shocks not
due to volcanic action, collapse of caverns, or landslides.
Terra Nova Development."Development" refers to all phases of the project, from the decision
to go ahead with construction through to abandonment of the field.
Glossary-22
Tertiary. The first period of the Cenozoic era (after the Cretaceous of the Mesozoic era and
before the Quaternary), thought to have covered the span of time between 65 and
1.5 to 2.5 million years ago. It is divided into five epochs: the Paleocene, Eocene,
Oligocene, Miocene and Pliocene.
TFOSP. Task Force on Oil Spill Preparedness.
thermocline. A temperature gradient as in a layer of sea water, in which the temperature decrease
with depth is greater than that of the overlying and underlying water.
threatened species.In Canada, an indigenous species that is likely to become endangered if the
factors affecting its vulnerability are not reversed.
till. Nonsorted, nonstratified material (containing particles ranging in size from clay particles to
boulders) that has been carried or deposited by a glacier.
TLM. Total Loss Management.Petro-Canada's loss management framework.
topside (or topsides) facilities.The oil- and gas-producing and support equipment located on the
top of an offshore structure.
TPH. Total petroleum hydrocarbons.
transgressive (or transgression).Refers to the encroachment of the sea upon the land.
transport (or transportation).A phase of sedimentation that includes the movement by natural
agents (such as flowing water, ice, wind or gravity) of sediment or of any loose
material, either as solid particles or in solution, from one place to another on or
near the earth's surface, e.g., the drifting of sand along a seashore under the
influence of currents, the creeping movement of rocks on a glacier or the
conveyance of silt, clay and dissolved salts by a stream.
tree. (a) An arrangement of valves placed on top of a well to control flow from the well. (b)
An
arrangement of valves and fittings attached to the tubing head to control flow and
provide access to the tubing string.
trophic level. The position an organism occupies in the food web, determined by the number of
energy transfer steps needed to get to that point.
tropical storm. A tropical cyclone with wind speeds from 61 to 118 km/h.
tunicates. Globular or elongatedsaclike filter-feeding animals attached to the substrate at one
end, and with two openings,incurrent and excurrent, at the free end.
Glossary-23
turbidity. The state or condition of having the transparency or translucency of water disturbed,
as when sediment in water is stirred up.
turret. A low, tower-like structure capable of revolving horizontally within the hull of a ship and
connected to a number of mooring lines and risers. It allows the ship to rotate with
the weather while maintaining a fixed mooring system.
umbilical. A conduit or group of conduits providing communications for the purposes of power
and control from a floating production facility to a facility located on the
seafloor.
unconformity. The structural relationship between rock strata in contact, characterized by a lack
of continuity in deposition and corresponding to a period of
nondeposition,
weathering or especially erosion (eithersubaerial or subaqueous) before the
deposition of the younger beds.
upwelling. Light surface water transported away from a coast (by action of winds parallel to it)
and replaced near the coast by heavier subsurface water.
USGOM. U.S. Gulf of Mexico.
USGOM-OCS. U.S. Gulf of Mexico Outer Continental Shelf.
USOCS. U.S. Outer Continental Shelf.
VEC. Valued ecosystem component.
VHF. Very high frequency.
viscosity. The measure of the resistance of a fluid to flow; the lower the viscosity number, the
more readily the fluid will flow.
WAM. Wave Modelling Group.
water column. The vertical dimension of a body of water, i.e., the water between a reference
point or area on the surface and one located directly below it on the bottom.
water-based mud. A drilling mud in which the continuous phase is water. See
drilling mud.
wave hindcasting. Prediction of waves based on past meteorological conditions.
wave rider buoys.An instrumented buoy moored in a specific marine location; used to collect
oceanographic data.
well casing. See casing.
Glossary-24
well completion. The final sealing-off of a drilled well from the
borehole with valving, safety and
flow-control devices, following final cementing and perforation of the casing at the
producing zone and removal of the drilling apparatus from the
borehole.
well workover. A program of work performed on an existing well; may involve re-evaluating the
production formation, clearing sand from producing zones, jet lifting, replacing
downhole equipment, deepening the well,
acidizing or fracturing, or improving the
drive mechanism.
wireline. A rope composed of steel wires twisted into strands that are in turn twisted around a
central core of hemp or otherfibre to create a rope of great strength and flexibility;
used to lower and raise logging instruments and bottom line-pressure gauges.
Wisconsinan. Pertaining to the classical fourth glacial stage (and the last definitely ascertained,
although there appear to be others) of the Pleistocene Epoch in North America,
following theSagamonian interglacial stage and preceding the Holocene.
WMO. World Meteorological Organization.
zooplankton. The animal component of those organisms drifting or weakly swimming in the
ocean largely at the mercy of prevailing currents.
Glossary-25
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1996 Terra Nova Environmental Impact Statement - C

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