Costa Rica Sewage Collection and Treatment System – Final

Transcription

Analysis of Infrastructure Vulnerability to Climate Change
Limon Underwater Outfall, Costa Rica
March 2011
ACKNOWLEDGEMENTS
Executive Summary
March 2011
The success of this Project was made possible thanks to the following people:
Instituto Costarricense de Acueductos y Alcantarillados (AyA):
Ing. Alejandro Rodríguez Vindas
Ing. Hernán Villalobos Slon
Ing. Patricia Zamora Cordero
Ing. Álvaro Araya García M.Sc.
Ing. Luis Carlos Vargas Fallas, Dr.Sc. -- Coordinador
Instituto Meteorológico Nacional (IMN):
Ing. Nazareth Rojas Morales
Ing. Roberto Villalobos Flores
Colegio Federado de Ingenieros y de Arquitectos (CFIA):
Lic. Marcela Matarrita Zeledón
Lic. Cristina Carmona Lopéz
Ing. Laura Solera Bonilla
Ing. Freddy Bolanos Cespedes
Ing. Olman Vargas Zeledón
Unión Panamericana de Asociaciones de Ingeniería (UPADI):
Ing. Irene Campos - Presidenta de UPADI
Engineers Canada:
Jeff O´Driscoll, P.Eng.
Guy Felio, P.Eng.
Roger Rempel, P.Eng.
Darrel Danyluk, P.Eng
Heather Auld
David Lapp, P.Eng
Without the hard work and voluntary efforts of this group of professionals, the completion
of this important project would not have been possible.
This project was supported through a financial contribution from the Government of
Canada.
Substantial in-kind professional days were contributed by the members of the Costa Rica
Project Team (Colegio, Aya and IMN) and from the Canadian Project Team from Engineers
Canada.
Executive Summary
March 2011
Introduction
The Instituto Costarricense de Acueductos y
Alcantarillados de Costa Rica (AyA), the Instituto
Meteorológico Nacional de Costa Rica (IMN) and the
Colegio Federado de Ingenieros y de Arquitectos de
Costa Rica (CFIA), under the guidance of Engineers
Canada, developed a vulnerability analysis to climate
change of the Underwater Outfall of the city of Limon,
Costa Rica. The analysis, conducted using the PIEVC
Engineering Vulnerability Protocol, integrated the
sewer system, pumping system, wastewater preconditioning plant and the controlled outlet system
into the sea (underwater outfall).
The infrastructure under analysis is located on the
Caribbean coast of Costa Rica, it provides service to the
central area of the city of Limon and it is between 10 and 20 years old (outfall – 10 years and
sewers - 20 years).
The main purpose of this study was to perform a risk assessment of the Wastewater
Treatment System of Limón (Costa Rica) to climate change starting from the selection of
parameters describing the climate and meteorological events typical of the geographical area
where the infrastructure is. The result of this analysis was the prioritisation of the actions to be
carried out by the entity in charge of this infrastructure (AyA) taking into consideration climate
change based risks (nature and intensity of events).
The analysis was made using the PIEVC Engineering Protocol, Version of April 9 2009 as
guideline.
The project was carried out from August 2010 to March 2011 and it considered climate change
effects up to year 2040.
This project involved a multidisciplinary team which involved about 13 engineering and
meteorology professionals. IMN provided support related to meteorological information,
analysis, modelling and projection of climate behaviour. Since AyA was the original designer of
the project and it is at present the system owner and manager, it provided support regarding
engineering design and specific operational aspects. . The local implementation of the PIEVC
Engineering Protocol and general coordinator of the project was CFIA. Engineers Canada
worked as an external advisor in the use of the Protocol and on meteorological aspects.
Executive Summary
March 2011
Page 2 of 17
Definition of the Project
The infrastructure for the project was chosen because
of the availability of information and social
considerations. The combination of these factors made
the vulnerability analysis to climate change of the
Limon underwater outfall a high priority project.
On one hand, the application of the Protocol requires
broad information on the design and operations of the
infrastructure to be analyzed. The underwater outfall,
pumping and sewer system, all together, were recently
built (no more than 20 years ago). Technical and design
specifications of the main infrastructure elements
were therefore available, which was not the case in
other project identified.. In addition, the system
operational logs were available for the outfall, which
provided essential information to determine the
performance of the system regarding certain climate
events.
Likewise, regarding meteorological information, there was data available from a
meteorological station near the study site. Furthermore, global and regional models were also
available - which, together with local information, represented enough data to carry out the
respective analysis.
Limon is one of the most socially depressed cities in Costa Rica; the central Government has
defined a series of important projects for this area with the purpose of investing capital and
thus create jobs and social welfare. However, these projects of national importance (Limon
Project – City – Port and New Port of Limon) require a wastewater management infrastructure
able to handle the new loads they will be subjected to. This is the strategic aspect of the
underwater outfall system and which forces to take into consideration climate change aspects
so that its service level reaches optimal conditions for future development.
Finally, as previously mentioned, the city of Limon has critical social conditions that make it
susceptible to climate impacts (coastal city and high criminality index). Therefore the
identification of infrastructure elements vulnerable to climate change provided by the
application of the Protocol will allow limiting the negative social effects that would occur in
case of extreme climate events.
Executive Summary
March 2011
Page 3 of 17
Climate Factors
The project team originally defined thirteen climate factors to be considered in the analysis.
However, upon extended analysis and discussions, it was concluded to use a reduced group of
factors. The final list of climate factors is as follows:
Application in the analysis
Relevant effect
infrastructure
Determine variation in
water consumption given
that higher per capita water
consumption
involves
higher returns to the
collection system.
Reduce
the
system
treatment capacity upon
early reaching the design
value.
Impact on the work
conditions in the EPA.
Risks of accidents and
operation shutdown of EPA.
Sea breeze
The breeze contains salinity
that may damage the
equipment and electric,
telemetric, control and
communication installations
because
of
increased
corrosion.
Failure of control system
resulting
in
operation
shutdown of EPA and of
underwater outfall.
Intense rain
Intake flow to EPA increases
due
to
storm
drain
connections.
Operation shutdown of EPA
and of underwater outfall.
Flooding rain
Flooding of urban area
when hydraulic capacity of
the storm drain system is
exceeded and damage
caused from flooding of
EPA.
Operation shutdown of the
EPA and of the underwater
outfall. Risk of damage to
the
equipment,
infrastructure
and
operators.
Lightning
Damage
to
electromechanical
equipment and possible
effects on the personnel of
EPA.
Failure of the control
system
resulting
from
operation shutdown of EPA
and of the underwater
outfall.
Parameter
High temperature
on
the
Executive Summary
March 2011
Page 4 of 17
Power supply failure at EPA
and at the pumping
stations.
Wind: speed
direction
Tidal waves
Hurricane
and
Wind speed and direction
component determines the
direction of sea currents in
the discharge area of the
outfall diffusers.
Possibility
of
extreme
hurricane winds and waves
in the study area where the
EPA and the underwater
outfall are.
Determine the possible
infrastructure damage and
overcharge– heavy rain and
effect of wind and waves.
They jointly determine the
spreading of the outfall
plume in accordance with
the design taking it far from
the shore or towards the
shoreline.
Operation shutdown caused
by waves reaching the EPA
level and flooding the
operation area. Damage to
the building infrastructure.
Stability of the underwater
outfall
piping
and
anchoring.
Possible
damage
to
infrastructure under poor
urban drainage conditions,
elevation of stations and
equipment considering the
effects of additional loads.
Analysis period
The work team defined the assessment term in
30 years (2040). This is based on the remaining
useful life of the sewerage system, the preconditioning station and the underwater outfall
without significant rehabilitation work.
Executive Summary
March 2011
Page 5 of 17
Infrastructure components
The infrastructure elements for this project are defined in the following table.
Element
Sewage collection system
Pumping stations
Pre-conditioning station
Underwater outfall
Subelements
Connections
Siphons
Networks
Local sewers
Main collectors
Manholes
Coastal mini-stations
Land mini-stations
Centrifugal stations
Submersible stations
Building
Ventilation system
Gates,
screens,
Parshal
channel,
interconnection channel
Milli-screens
Worm screw, baskets, hoisting system,
transportation
Water tank
Pumps
Overflowing structure
Accessories in pumping line
Control board
Electrical plant
Piping
Diffusers
Closing valve
Anchoring
Wave retaining wall
Personnel
Telecommunication equipment
Wastewater collection system
Pre-conditioning station
Underwater outfall
Telephones at the pre-conditioning station
Telemetry
Radios
Internet text messaging
Executive Summary
March 2011
Page 6 of 17
Climate change considerations and modelling performed
In order to forecast potential climate changes, a series
of studies were carried out based on the following
aspects:
•
•
•
•
•
Climate description of the area
Definition of climate and meteorological
factors giving rise to the present vulnerability
of the infrastructure
Present occurrence probability according to
historic records
Future occurrence probability by means of
model-generated projections for the 20112040 period
Critical analysis of climate projections for those
parameters with missing records to allow
modelling
The following information sources for the climate change vulnerability analysis of the
infrastructure were used:
•
•
•
•
•
•
•
•
•
•
Limon meteorological station record (81-003)
Flooding records (database of the Sistema de Inventario de Efectos de Desastres –
System of Inventory of Disaster Effects)
Records of Hurricanes (Central American Probabilistic Risk Assessment)
Wave modelling: WAVEWATCH III Model, version 2.22 of NOAA
Meteorological reports of IMN
Operation Log of the sewage treatment and collection system (AyA)
Climate related literature produced and edited by IMN
Scientific publications
Regional climate models (MCR) and application to local conditions by means of
dynamic Downscaling Model using special and temporal high resolution MR PRECIS.
Results used were those of MG HAdAM3H and sea surface anomalies of model
HadCM3. (space resolutions– 50 km, temporal resolutions – annual)
Global models generated by CCCSN, based on the results of the 4th report of IPCC.
For the cases where modelling was not available, the analysis used correlations and trend
analysis, scientific publications, information on the web related to climate change and
publications of IPCC.
Executive Summary
March 2011
Page 7 of 17
Occurrence probability
Based on the analysis described above, and
as a result of discussions held with the work
team, the following group of present and
future probabilities were established for the
different climate factors considered. It
should be noted here that, besides this
general analysis, an alternate methodology
of
probability
determination
was
developed. Events were therefore divided in
extreme and recurrent events.
Parameter
Present
probability
Future probability
High
temperature
5
6
Sea breeze
7
7
Intense rain
1
2
Flooding rain
1
2
Lightning
2
2
Wind:
speed
and direction
1
2
Tides (wave)
1
2
Hurricanes
0
1
Executive Summary
March 2011
Page 8 of 17
The following are the tables of modified probability (present and future) for extreme (Ext) and
recurrent (Rec) events:
Probability
Type
Parameter
present
future
Rec
High temperature
4
5
Rec
Wave
1
2
Rec
Sea breeze
2
3
Rec
Lightning
2
2
Probability
Type
Parameter
present
future
Ext
Flooding rain
4
5
Ext
Intense rain
6
7
Ext
Hurricane
1
2
Ext
Wind
3
3
Executive Summary
March 2011
Page 9 of 17
Training, discussion and follow-up workshops for the application of the PIEVC Engineering
Protocol.
For the implementation of the project under consideration, three workshops were held. The
first one, in August 2010 (three days), was the initial training for the Costa Rican work team.
This workshop also included a visit to the project site.
The second workshop focused on the discussion of the risk analysis matrix and was held for
three days in December 2010.
The last workshop took place in March 2011 to review the results and global analysis of the
project. During this workshop, the analysis results were presented to government entities and
professionals from other organisations and it included a site visit. This was a five-day
workshop.
Furthermore, during the course of the project, 7 telephone conferences were held with the
specialized support team of Engineers Canada and the work team of Costa Rica.
Risk tolerance thresholds
The tolerance thresholds provided under the Protocol were used for this project. These
thresholds proved to be appropriate for risk rating. However, the system operator (AyA)
included in its recommendations a slight downward variation of the high risk threshold. Thus,
the following are the risk thresholds used:
Low Risk
Medium Risk
High Risk
•Less than 12
•Excluded for further
analysis
•From 12 to 35
•Kept for further
analysis
•More than 35
•Go directly to
recommendations
Risk calculation for main interactions found
Based on the probabilities obtained for the climate factors rated as recurrent and extreme,
severity (gravity of impact) values were assigned and the risk equation shown below was
applied:
R=PxS
Where:
R = risk
P = probability
S = severity (gravity of impact)
Executive Summary
March 2011
Page 10 of 17
The respective results were obtained after applying the risk equation for each one of the
defined interactions (climate event + infrastructure component). Risk rating was made using
the above established thresholds.
The following table shows the matrix of the main risks found. It must be noted here that the
matrix includes present and future risks (RA and RF).
PA
PF
G
RA
RF
4
5
7
28
35
4
5
7
28
35
Gates, grids, Parshall channel, interconnection channel
4
5
7
28
35
Networks, sub sewer, sewage system
6
7
5
30
35
6
7
5
30
35
6
7
5
30
35
6
7
5
30
35
4
5
6
24
30
4
5
6
24
30
6
7
4
24
28
6
7
4
24
28
6
7
4
24
28
Water tank
6
7
4
24
28
Land mini stations
4
5
5
20
25
4
5
5
20
25
4
5
5
20
25
4
5
5
20
25
3
3
7
21
21
6
7
3
18
21
6
7
3
18
21
4
5
4
16
20
Infrastructure Component
Climate Parameter
Asis Esna,
Pacuare 2
Land mini-stations
Asis Esna,
Flooding rain
Intense rain
Gates, grids, Parshall channel, interconnection channel
Networks, sub sewer, sewage system
Coastal mini stations
Flooding rain
Coastal mini stations
Pacuare 1
Pacuare 2
Pacuare 1
Water tank
Intense rain
Flooding rain
Overflow structure
Power plant
Pumps
Overflow structure
At EPA
Sea breeze
Intense rain
High temperature
It follows from the analysis performed that from the 138 interactions there is none of high risk.
There are 41 interactions that currently have a medium risk which will increase to 54 for future
risks. It follows from the above that there are presently 97 low risk interactions decreasing to
84 in the future. The charts below summarize present and future risks.
Executive Summary
March 2011
Page 11 of 17
Present risk
Future risk
Vulnerability Assessment
A series of calculations were made to determine the system wastewater collection, treatment
and disposal capacity in Limon.
The analysis of the intense rain shows that the maximum capacity of sewage is 91,1 l/s and
that there are illicit connections from houses roofs to the sanitary sewage system. Modelling,
using a light rain of 16 mm/hr of intensity, shows that the system will collapse with only 4% of
the houses’ roofs connected to the sewage the system. However, the sewage system does
have capacity to treat the wastewater presently generated and what will be generated in the
future if the illicit connections made from houses’ roofs to the sewage system are not
disconnected.
The flooding rain analysis shows that for an extreme event identified in the system log
(intensity of 106 mm/hr) the storm drainage system has enough capacity for the water flow
generated. However, in this specific event the analysis showed that many outlets were clogged
and this kept rain water from entering into the storm drainage system. It has been verified that
the storm drainage system has enough capacity to handle rain but it is vulnerable to future
conditions. It should be noted here that the analysis of the storm drainage system was done
because there are interconnections between the sanitary and the storm systems.
Regarding wind effects, it was determinedthrough modelling of the contamination plume, that
the outfall has appropriate capacity and that it is unlikely low speed current conditions with
easterly winds will occur. This means that the underwater outfall has enough capacity to
handle wind effects.
Executive Summary
March 2011
Page 12 of 17
General discussion
The analysis performed to determine the vulnerability
of the infrastructure and the subsequent engineering
analysis show that the two main events that would
affect the wastewater collection, treatment and
disposal system of Limon are intense rain and flooding
rain.
The following are the systems that will be mainly
affected:
•
•
•
Pumping system (coastal and inland systems)
Gates, screens, Parshall channel and
interconnection channel (pre-conditioning
station)
Sewer systems (collectors and sub-collectors)
Recommendations
•
It is considered that the application of the PIEVC Engineering Protocol to the Sewage
System of the city of Limón has allowed addressing in a systematic way the climate
change issue, starting from a broad climate analysis.
•
The best results in the Protocol application were obtained for parameters in which
there were load thresholds validated by the occurrence of events (recorded in the
operation logs) with climate records.
•
For these thresholds, the infrastructure that at present is being affected in terms of
loss of capacity or operation shutdown was identified.
•
The adaptation measures that require immediate action, even without having the
extreme conditions resulting from climate change impacts were also identified.
•
Aspects that require more detailed study, improvements to be made in equipment and
better information records were also identified.
•
For future applications of the PIEVC Engineering Protocol to the national
infrastructure, institutions must ensure the participation of officials according to
workloads arising out of the protocol application, in order to secure an appropriate
process and optimum knowledge transfer.
Executive Summary
March 2011
Page 13 of 17
•
An alternative way of applying the protocol – through the retention of consulting
services (Case study of Claireville and G. Ross Lord Dams and Metro Vancouver
Sewerage) may result in time savings for the projects but will not achieve knowledge
transfer.
•
The Risk Management issue
must reach the level of
“National Project”, in order
to secure joint leadership
and participation of the
institutions in charge of the
infrastructure,
and
especially
those
that
generate climate related
data.
Final comments
Knowledge, management and application of the PIEVC Engineering Protocol
The CFIA, AyA and IMN, with the support of Engineers
Canada, carried out the project of applying the PIEVC
Engineering Protocol to a given infrastructure. The
three entities in Costa Rica reported that they had
never worked as a team before the project started and
this in itself is one of the milestone achievements of
the project. All along the application process the
general targets defined in the original proposal were
achieved. Thus:
•
•
•
•
•
•
It was determined the vulnerability to climate
change of the wastewater collection,
treatment and disposal system of the city of
Limon.
A better understanding was achieved of the
need for climate information, the form this information is requested to the
corresponding institution and the way it must be submitted to the technical team.
Expertise in the use and applicability of the PIEVC analysis process was acquired.
The direct or indirect effects of climate change to the infrastructure under study were
established through the establishment of interrelations between the infrastructure
components and the climate factors.
Priority actions to adapt the existing infrastructure to present and future climate
events were identified.
Climate information gaps that shall be filled in the future in order to carry out a second
cycle of engineering analysis for this project were identified.
Executive Summary
March 2011
Page 14 of 17
•
An operational structure that integrated all the parties involved (system operator,
owner of the system, meteorological specialist, project manager, among others) was
established and that, we hope, will be applicable to other projects.
Vulnerability to climate change of the wastewater collection, treatment and disposal system
of the city of Limón.
In accordance with the risk analysis performed of the City of Limon’s wastewater collection,
treatment and disposal system, it is determined that the system has enough capacity to handle
the projected effects of climate change over the 30 year assessment period.
Executive Summary
March 2011
Page 15 of 17

Costa Rica Sewage Collection and Treatment System – Final

Transcription

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