CVC Head Office - Credit Valley Conservation

Transcription

Low Impact Development Infrastructure
Performance and Risk Assessment
May 2016
Technical
Report
CVC Head Office
Business and Multi-Residential Retrofit
CVC HEAD OFFICE, CITY OF MISSISSAUGA
LOW IMPACT DEVELOPMENT INFRASTRUCTURE PERFORMANCE
AND RISK ASSESSMENT
TECHNICAL REPORT
MONITORING RESULTS (2014-2015)
CREDIT VALLEY CONSERVATION
NOTICE
The contents of this report do not necessarily represent the policies of the supporting
agencies. Although every reasonable effort has been made to ensure the integrity of the
report, the supporting agencies do not make any warranty or representation, expressed
or implied, with respect to the accuracy or completeness of the information contained
herein. Mention of trade names or commercial products does not constitute
endorsement or recommendation of those products.
Acknowledgements
Program Team
CVC Water and Climate Change Science Division
Andrea Bradford, University of Guelph
Program Partners
Ontario Ministry of the Environment and Climate
Change
Building Industry and Land Development
Association
Region of Peel
Peel District School Board
Maxxam Analytics
City of Mississauga
Environment and Climate Change Canada
Grand River Conservation Authority
University of Guelph
City of Toronto
Town of Orangeville
Town of Halton Hills
Polis Project on Ecological Governance
Unilock
Imbrium
Aquafor Beech Limited
Sequoia Grove Homes
Rattray Marsh Protection Association
Freeman and Associates
Ontario Centres of Excellence
Intra-Corp
City of Waterloo
Mattamy Homes
Premont Homes
Rossma Developments
This report was created with funding support from the Government of Ontario
Expert Advisory Committee
John Antoszek, MOECC
Hans Schreier, UBC
Geosyntec Consultants
Wright Water Engineers, Inc
Andrea Bradford, University of Guelph
Bill Snodgrass, City of Toronto
James Li, Ryerson University
Darko Joksimovic, Ryerson University
Celia Fan, Ryerson University
Trevor Dickinson, University of Guelph
Jiri Marsalek, ECCC, National Water Research
Institute
Advisory Committee
Aaron Law, MOECC
Don Cross, MOECC
Sabrina Ternier, MOECC
Barb McMurray, MOECC
Les Stanfield, MNRF
John Nemeth, Region of Peel
Dagmar Breuer, City of Mississauga
Muneef Ahmad, City of Mississauga
Maggie Lu, City of Brampton
Tim Van Seters, TRCA
Chris Denich, Aquafor Beech
Will Cowlin, Aquafor Beech
Bill Dainty, Calder Engineering
David Ashfield, TMIG
Steve Auger, LSRCA
Brian Greck, Trout Unlimited
Steve Schaeffer, SCS Consulting Group
Harold Reinthaler, Schaeffers Cons.Eng.
Jason Thistlewaite, University of Waterloo
Jenn Drake, University of Guelph, and University of
Toronto
The success of CVC’s LID program is attributed to the leadership, vision, and
commitment of:
•
Infrastructure Performance and Risk Assessment (MOECC)
•
Showcasing Water Innovation (MOECC)
•
Nando Iannicca, City of Mississauga Councillor and CVC Chair
•
Jim Tovey, City of Mississauga Councillor and CVC Board Member
•
City of Mississauga Green Development Standards and Water Quality Strategy
•
CVC Board of Directors
•
Region of Peel’s Term of Council Priorities
•
Janet McDougald, Peel District School Board Ward 7 Trustee
Comments or questions on this document should be directed to:
Christine Zimmer, P.Eng, MSc (Eng)
Jennifer Dougherty, P.Eng, M.A.Sc.
Senior Manager, Water and Climate Change
Science
Manager, Water Quality Protection
Credit Valley Conservation
1255 Old Derry Road
Mississauga, Ontario L5N 6R4
905-670-1615 x229
[email protected]
1255 Old Derry Road
Mississauga, Ontario L5N 6R4
905-670-1615 x262
[email protected]
CVC LID Demonstration Monitoring Projects:
Performance Evaluation of the CVC Head Office
i
TABLE OF CONTENTS
TABLE OF CONTENTS ................................................................................................................................. I
APPENDICES ............................................................................................................................................... II
LIST OF TABLES ......................................................................................................................................... III
LIST OF FIGURES ....................................................................................................................................... IV
EXECUTIVE SUMMARY ............................................................................................................................ VII
1
INTRODUCTION ................................................................................................................................. 1
1.1
The State of Stormwater Infrastructure in Ontario .............................................................. 1
1.2
The Need for Long-Term Performance Assessment of LID in Ontario ............................... 2
1.3
Mississauga Stormwater Charge and Credit ...................................................................... 2
1.4
CVC Office Expansion ........................................................................................................ 3
2
SITE DESIGN...................................................................................................................................... 6
2.1
LID Design .......................................................................................................................... 6
2.2
Permeable Pavement.......................................................................................................... 8
2.3
Grass Swales .................................................................................................................... 10
2.4
Rainwater Harvesting ........................................................................................................ 11
3
MONITORING RESULTS AND INTERPRETATIONS...................................................................... 12
3.1
Precipitation ...................................................................................................................... 13
3.2
Hydrology .......................................................................................................................... 16
3.2.1
CVC Head Office Hydrology ............................................................................. 17
3.2.2
Lag Time............................................................................................................ 22
3.2.3
Influence of Precipitation Intensity on Performance .......................................... 22
3.3
Water Quality .................................................................................................................... 25
3.3.1
Pollutant Load Reduction .................................................................................. 26
3.3.2
Event Mean Concentrations and Comparisons to the BMPDB......................... 28
3.4
Reclaimed Water Usage ................................................................................................... 30
3.5
CVC Head Office Site Water Balance............................................................................... 32
4
MAINTENANCE ................................................................................................................................ 34
5
DISCUSSION – MONITORING OBJECTIVE ASSESSMENT ......................................................... 37
6
SUMMARY OF OBSERVATIONS .................................................................................................... 41
6.1
Water Quantity .................................................................................................................. 41
6.2
Water Quality .................................................................................................................... 41
6.3
Rainwater Harvesting System ........................................................................................... 41
7
REFERENCES .................................................................................................................................. 42
© Credit Valley Conservation 2016
APPENDICES
APPENDIX
APPENDIX
APPENDIX
APPENDIX
APPENDIX
APPENDIX
A
B
C
D
E
F
CVC Head Office Monitoring Plan
Infrastructure Performance Assessment Protocol
Data Management and Analytical Methodology
Data Analysis Summaries
Intensification of Urban Water Cycle
Site Maintenance and Inspection Log
ii
iii
LIST OF TABLES
Table 1-1: Stormwater Credit Criteria (City of Mississauga, 2015)............................................................... 3
Table 2-1: Components of the permeable pavement ................................................................................... 9
Table 3-1: A summary of the measurement objectives, measurement types, monitoring locations,
monitoring equipment and frequency utilized at the CVC Head Office monitoring site ..................... 13
Table 3-2: Precipitation comparison between EC Toronto Lester B. Pearson Int’l A weather station and
CVC Head Office. ............................................................................................................................... 13
Table 3-3: Statistical analysis of all precipitation events during the monitoring period at CVC Head Office
............................................................................................................................................................ 19
Table 3-4: Comparison of low-intensity and high-intensity rain events at CVC Head Office ..................... 23
Table 3-5: Provincial Water Quality Objectives (PWQOs) for selected parameters of interest .................. 26
Table 3-6: CVC Head Office estimated water quality treatment performance summary for zero-effluent
and sampled events between July 2014 to September 2015 ............................................................ 27
Table 3-7: Estimated total load reduction for each precipitation bin ........................................................... 28
Table 3-8: Water quality summary statistics for sampled events at CVC Head Office with comparisons to
the NSQD and water quality guidelines.............................................................................................. 29
Table 3-9: Comparison of CVC Head Office Median Sampled Effluent EMC to different BMPs from
BMPDB ............................................................................................................................................... 30
Table 6-1: SWM criteria and preliminary observations. .............................................................................. 38
iv
LIST OF FIGURES
Figure 1-1: The CVC Head Office site location in the Credit Valley WatershedLID Monitoring Objectives 4
Figure 2-1: Stakeholders at the monitoring objectives meeting .................................................................... 6
Figure 2-2: Drainage areas of the different features at CVC Head Office. Drainage is indicated by the blue
lines, with the dotted blue lines signifying underground drainage. ....................................................... 7
Figure 2-3: Cross section of the permeable pavement, showing the 1 Pavers, 2 Bedding layer, 3
Geotextile fabric, and 4 Base layer. The underdrain is located in the base layer. ............................. 10
Figure 2-4: Grass swale at CVC Head Office ............................................................................................. 10
Figure 2-5: Rainwater storage tank, located in the basement of CVC’s head office .................................. 11
Figure 3-1: Monitoring equipment that is used at CVC Head Office ........................................................... 12
Figure 3-2: Rainfall frequency distribution graph between EC Toronto Pearson International Airport station
and CVC Head Office ......................................................................................................................... 14
Figure 3-3: Percentage of events falling at or below a given precipitation depth at ECCC Toronto Pearson
International Airport using hourly weather records from 1950-2005. ................................................. 15
Figure 3-4: Development conditions; urban water cycle with stormwater management ponds and LID
(adapted from FISRWG, 1998)........................................................................................................... 16
Figure 3-5: Changes in stream flow hydrograph as a result of urbanization (adapted from Schueler, 1987)
............................................................................................................................................................ 17
Figure 3-6: Runoff volume reduction during monitoring period at CVC Head Office .................................. 20
Figure 3-7: Peak flow rate reduction during monitoring period at CVC Head Office .................................. 20
Figure 3-8: Comparison of CVC Head Office with retention pond .............................................................. 21
Figure 3-9: Hydrologic summary of the rain event on October 3 and 4, 2014 ............................................ 21
Figure 3-10: Lag time statistics by storm depth .......................................................................................... 22
Figure 3-11: Volume reductions at different precipitation depths and peak intensities for all events at CVC
Head Office ......................................................................................................................................... 23
Figure 3-12: Hydrologic summary of a low-intensity rain event on April 19 and 20, 2015. ........................ 24
Figure 3-13: Hydrologic summary of a high-intensity rain event on June 22 and 23, 2015. ...................... 24
th
Figure 3-14: Monthly 75 Per centile Total Suspended Solids concentration compared at an urban vs.
rural catchment ................................................................................................................................... 25
Figure 3-15: Estimated total load reduction by event size for TSS. Black bars show the range in load
reductions for individual storm events. ............................................................................................... 28
Figure 3-16: Reclaimed water used from a 12-week period in mid-2015. The orange line indicates the
overall median recaimed water usage of 1300 L for workdays. ......................................................... 31
Figure 3-17: CVC’s water usage for May 2015. .......................................................................................... 32
Figure 3-18: CVC Head Office water balance for a 4.6 mm rain event on October 20, 2014 .................... 33
Figure 3-19: CVC Head Office water balance for a 43.3 mm rain event on May 30, 2015 ........................ 33
Figure 4-1: Infiltration test results for both permeable parking lots ............................................................. 35
Figure 4-2: Accumulated sediment and debris in the rainwater storage tank ............................................ 36
GLOSSARY OF ACRONYMS AND ABBREVIATIONS
BMP
Best Management Practices
BMPDB
International Stormwater Best Management Practices Database
Cd
Cadmium
CCME
Canadian Council of Ministers of the Environment
cm
centimetre
Cl
Chloride
Cu
copper
CVC
EC
Environment Canada
EMC
Event Mean Concentration
FCM
Federation of Canadian Municipalities
g
gram
GTA
Greater Toronto Area
hr
hour
Fe
Iron
kg
kilogram
Pb
Lead
L
litre
L/min
litre per minute
L/s
litres per second
LID
Low Impact Development
LGRA
Low Volume Groundwater Recharge Areas
MDL
Method Detection Limit
m
metre
m
2
square metre
m
3
cubic metre
MEDEI
Ministry of Economic Development, Employment and Infrastructure
mg
milligram
mg/L
milligrams per litre
µg/L
micrograms per litre
mm
millimetre
min
minute
Ni
Nickel
N
Nitrogen
NO2 + NO3
Nitrite and Nitrate
v
NSQD
National Stormwater Quality Database
MOE
Ontario Ministry of Environment
MOECC
Ontario Ministry of the Environment and Climate Change
PoC
Parameters of Concerns
P
Phosphorus
PAH
polycyclic aromatic hydrocarbon
PO4
Orthophosphate
PWQO
Provincial Water Quality Objectives
QA
Quality Assurance
QC
Quality Control
RWH
Rainwater Harvesting
RL
reporting limit
s
second
SWM
Stormwater Management
TDS
Total Dissolved Solids
TKN
Total Kjeldahl Nitrogen
TN
Total Nitrogen
TP
Total Phosphorus
TSS
Total Suspended Solids
US EPA
United States Environmental Protection Agency
yr
year
Zn
Zinc
vi
vii
EXECUTIVE SUMMARY
Stormwater management has been headline news given the flooding in Alberta and the Greater Toronto
Area (GTA) in recent years. The 2016 Canadian Infrastructure Report Card documented 671 occurrences
that resulted in flood damages since 2009. More than 66,000 private properties were affected, with more
than $500 million in damages. The replacement value for stormwater infrastructure in very poor, poor or
fair condition was estimated at $31 billion (Canadian Infrastructure Report Card, 2016). This estimate
does not take into consideration the need for infrastructure within existing urban areas that do not
currently have systems for flood control or stormwater treatment. For example, it is estimated that only 35
per cent of the GTA has stormwater management controls (TRCA, 2013). In addition to flood control,
stormwater management is needed to protect streams from erosion and water quality deterioration
In an attempt to mitigate risk, the Ministry of the Environment and Climate Change (MOECC), the City of
Mississauga and Credit Valley Conservation (CVC) have partnered with over twenty-five (25) public and
private-sector organizations over the past several years to implement a number of innovative SWM retrofit
sites spanning both public and private properties. CVC’s Head Office includes two permeable parking lots
and a rainwater harvesting system, and demonstrates the type of low impact development (LID) that can
be installed at a typical office building. LID is an innovative SWM practice that consists of green
infrastructure, and source and conveyance controls. The LID practices at CVC’s Head Office treat
stormwater runoff, promote infiltration and retention, and slow the release of stormwater runoff. In
addition, the rainwater harvesting system allows rainwater to be retained and used as a non-potable
water source instead using treated water.
CVC has conducted comprehensive performance assessment to evaluate its ability to control runoff
volume and remove pollutants. For water quantity control, CVC Head Office provides a median volume
reduction of 70 per cent and a median peak flow reduction of 81 per cent. This significantly reduces the
runoff and pollutants entering the receiving creek, the Credit River, and Lake Ontario. Furthermore, the
LID practice at CVC Head Office is able to replicate a more natural water balance in a highly urbanized
setting, providing improved water quality and protection of aquatic habitat.
From a water quality perspective, there is significant pollutant reduction from stormwater runoff entering
the Credit River. Throughout the study period, the site has been found to provide 81 per cent total
suspended solids (TSS) removal for all events, and providing a total load reduction of at least 69 per cent
for all parameters but nitrate + nitrite for all events.
The rainwater harvesting system has allowed the organization to significantly reduce its municipal water
usage, with about 26 per cent of total water usage being reclaimed water while this system was online.
The total reclaimed water usage, and therefore municipally-treated water saved, from August 2013 to
December 2015 was about 400 000 L.
The City of Mississauga has introduced a stormwater charge and an associated credit program, and this
site demonstrates the types of features that may be eligible for a stormwater charge rebate if installed on
business and multi-residential properties. CVC is developing an application for this credit, and the results
from this study along with the maintenance documentation may be used to assist in the application.
This performance evaluation would suggest that wide-spread adoption of LID would yield significant
benefits to receiving streams as well as the Great Lakes. Results from the CVC Head Office project will
provide municipalities with the tools to make improvements to address pressures due to growth, infill,
redevelopment and at the same time protect and enhance the environment (in keeping with the MOECC’s
proposed Great Lakes Protection Act; the Ministry of Economic Development, Employment and
Infrastructure’s (MEDEI’s) Building Together: Municipal Infrastructure Strategy; and the Ministry of
Municipal Affairs and Housing’s Go Green: Ontario’s Action Plan on Climate Change).
1
1 INTRODUCTION
1.1
The State of Stormwater Infrastructure in Ontario
Canada’s aging infrastructure is receiving a great deal of attention due, in part, to the frequency of flood
events such as the 2013 floods in southern Alberta and Greater Toronto Area (GTA). The 2016 Canadian
Infrastructure Report Card documented 671 occurrences that resulted in flood damages since 2009. More
than 66,000 private properties were affected, with more than $500 million in damages. The replacement
value for stormwater infrastructure in very poor, poor or fair condition was estimated at $31 billion
(Canadian Infrastructure Report Card, 2016). This estimate does not take into consideration the need for
infrastructure within existing urban areas that do not currently have systems for flood control or
stormwater treatment. For example, it is estimated that only 35 percent of the GTA has stormwater
management controls (TRCA, 2013). To bring older developments across the nation to today’s standards,
Federation of Canadian Municipalities (FCM) estimated it would cost an additional $56.6 billion (FCM,
2007). This figure assumes conventional practices are feasible and does not include land acquisition
costs, which, in growth areas around Toronto, can be three or four times that of infrastructure costs
(Reinthaler, Partner, Schaeffers & Associates Limited, 2012). Building cost-effective resiliency into
stormwater infrastructure requires an alternate solution.
The estimated damage of the
July 8, 2013 storm event is
almost $1 billion, and is now
the most expensive storm in
Ontario’s history (IBC, 2014)
Both nationally and locally,
water damage is the largest
single component of insured
loss with claims tallying $1.7
billion per year (IBC, 2012).
In the United States, Europe and Australia there has been a growing movement towards green
infrastructure for stormwater management. Green infrastructure for stormwater management, also
referred to as low impact development (LID), is an integrated approach to stormwater management that
uses site planning and small engineered controls to capture runoff as close as possible to where it is
generated. LID controls can be incorporated within urban environments where space is a constraint. They
can be implemented in infill, redevelopment and greenfield sites to meet stormwater management
objectives.
Flood control is not the primary purpose of low impact development, but LID has the ability to reduce
runoff volumes and delay runoff thereby reducing pressures on downstream stormwater infrastructure
and receiving waters. A recent report generated estimates of the monetary value of flood loss avoidance
that could be achieved by green infrastructure implemented watershed-wide, in new development and
redevelopment, in the United States (Atkins, 2015). The present value of flood losses avoided between
2020 and 2040 for the conterminous United States, assuming no damages within the 10 year floodplain
and a 3 per cent discount rate, was estimated at $0.8 billion dollars (Atkins, 2015). If green infrastructure
was also used to retrofit existing imperviousness, the flood loss avoidance benefits would be even higher.
The primary benefits of green infrastructure are water quality and stream protection. Practices such as
permeable pavements and bioretention systems can retain the water from events that occur relatively
often. This helps to mimic pre-development hydrological conditions and reduce stream erosion. Stream
erosion is a common response to high flows that occur more often and for longer durations after
urbanization. Most of the pollutants that accumulate in urban areas are carried to streams and other
receiving waters by the moderate sized events that occur more frequently. Therefore, capturing and
treating the runoff from these events can play a large role in protecting water quality.
2
Business and multi-residential properties constitute a large portion of urban land use areas. Much of
these properties consist of impervious surfaces, such as roofs, parking lots, driveways, and sidewalks.
These impervious surfaces cause stress on the municipal stormwater system, and impair the water
quality of receiving water bodies such as the Credit River and Lake Ontario (CVC, 2009). Using the
principles of LID to re-establish natural processes, it can help to reverse the impacts of urban
development on downstream water quality and quantity. For more information on CVC’s LID sites and
Showcasing Water Innovation project, visit http://www.creditvalleyca.ca/low-impact-development/.
1.2
The Need for Long-Term Performance Assessment of LID in Ontario
The Ministry of Economic Development, Employment and Infrastructure (MEDEI) (through Sustainability
Planning) requires Ontario municipalities to develop asset management plans when requesting provincial
infrastructure funding. Asset management is an integrated life-cycle approach to effective stewardship of
infrastructure assets to maximize benefits, manage risk, and provide satisfactory levels of service to the
public in a sustainable and environmentally responsible manner.
One of the barriers to widespread adoption of LID in Ontario is the limited local, long-term performance
data available to conduct the integrated life-cycle analysis required for asset management. The lack of
data for practices, individually and in combination, makes it difficult for designers to select and size
stormwater infrastructure, for municipalities and landowners to budget for maintenance costs and for
approval agencies to permit these innovative techniques in varied land-use applications.
To build confidence in sizing and long-term performance of stormwater infrastructure, CVC and its
partners have implemented a series of demonstration sites within various land-use settings and are
delivering a LID Infrastructure Performance and Risk Assessment (IPRA) program. The multi-year IPRA
program will evaluate LID effectiveness in flood control, erosion protection, nutrient removal, and
mimicking the pre-development water balance. This program will produce performance data addressing
the outstanding knowledge gaps and priority objectives identified by multiple stakeholders within CVC’s
Stormwater Management Monitoring Strategy (2012). Section 2 of this report discusses the 19 objectives
identified for CVC’s overall stormwater management monitoring program.
LID performance data inherently supports Ontario’s Water Opportunities Act, the Great Lakes Protection
Act, and recommendations from MOECC’s Policy Review of Municipal Stormwater Management in the
Light of Climate Change by providing information on innovative water technologies. Building on the
findings of existing research, CVC’s program will also advance the understanding of maintenance
requirements for optimal LID performance and life-cycle cost analysis for asset management to meet
provincial requirements for sustainability planning.
The knowledge gained through performance evaluation will strengthen existing tools and be used to
create new tools to support the promotion of voluntary efforts. This research directly supports the
protection of the Great Lakes by providing elected officials, municipal engineering and operations
personnel, developers, contractors, consultants and businesses and residential landowners with the tools
they need to successfully implement LID in their communities.
1.3
Mississauga Stormwater Charge and Credit
Stormwater management in the City of Mississauga is a responsibility of the municipality, and was
traditionally funded solely from property taxes and development charges. Due to ageing infrastructure and
increased pressures because of climate change, this funding is no longer sufficient to maintain current
levels of service. After a stormwater financing study and consultation with stakeholders and the general
public, the city decided to implement a Stormwater Charge. This option was considered the more
sustainable and equitable source of funding (AECOM, 2013). This charge will be based on the amount of
impervious surfaces of a property, as these put the most strain on the stormwater infrastructure. The
2
charge for 2016 will be $100 per 267 m of impervious surface. Stormwater rates such as this are
relatively new to Ontario but have been implemented in many municipalities throughout the United States.
3
Some of the ﬁrst Ontario municipalities to introduce stormwater rates include the City of Waterloo and the
City of Kitchener, which established stormwater utilities in 2010 (CVC, 2014).
Mississauga is also establishing a stormwater credit program to recognize property owners that
implement stormwater best management practices that benefit the city’s stormwater infrastructure. The
total credit, as a percentage of stormwater charge for the property, will be calculated based on the criteria
in Table 1-1. The maximum credit given will be 50 per cent.
Table 1-1: Stormwater Credit Criteria (City of Mississauga, 2015)
Category
Peak
Reduction
Flow
Water
Treatment
Runoff
Reduction
Evaluation Criteria
Total Credit (50%
Maximum)
Percent reduction of the 100-year post development flow to predevelopment conditions of the site
Up to 40%
Quality
Consistent with Provincial criteria for enhanced treatment
Up to 10%
Volume
Percent capture of first 15 mm of rainfall during a single rainfall
event
Up to 15%
Develop and implement a pollution prevention plan
Up to 5%
Pollution Prevention
LID, such as permeable pavement, enhanced vegetated swales, and rainwater harvesting can be eligible
for credit in one or more of the above categories.
1.4
CVC Office Expansion
From 2009 to 2012, Credit Valley Conservation (CVC) undertook renovations to their head office location
in Mississauga, Ontario. In 2010, a new parking lot utilizing permeable pavement and grass swales was
constructed, in preparation for the addition of a new building. This building is registered with the Canada
Green Building Council, and is certified LEED Gold. It includes many green features, including daylighting
and a high-efficiency HVAC system. It also includes a rainwater harvesting system, where rainwater that
falls on the roof is routed to a basement rainwater storage tank. An additional permeable pavement lot
was constructed in 2012. CVC’s head office site is ideal as a demonstration site for visitors, and shows an
example of LID features that could be installed in a typical municipal or commercial office building. The
site is located adjacent to the Credit River, and the surrounding area is primarily residential with pockets
of agricultural and natural areas.
The first permeable pavement parking lot, the grass swales, and the rainwater harvesting system are
being monitored to assist in the development and refinement of LID guidance documents and retrofit
guides available at http://www.creditvalleyca.ca/low-impact-development/. These documents assist
stakeholders in protecting and managing water resources through development of sustainable stormwater
management practices in existing and new developments.
CVC is currently developing an application for the Mississauga Stormwater Charge Credit, with a focus on
the LID installed at the site. Options for future LID features are also being considered. The monitoring
program results may be used in the application for the categories of Water Quality Treatment and Runoff
Volume Reduction, and for verification and maintenance documentation.
4
CVC
Head
Office
Figure 1-1: The CVC Head Office site location in the Credit Valley WatershedLID Monitoring Objectives
Working with project partners and stakeholders, CVC has defined 19 objectives for CVC’s overall
stormwater management monitoring program. CVC held several meetings to collect input from
stakeholders including municipal decision makers, provincial and federal environmental agencies,
engineering and planning professionals, conservation authorities, academia, and watershed advocate
groups.
5
The stakeholder group identified the below listed objectives for the program, listed in order of stakeholder
priority. The objectives specific to the CVC Head Office program include objectives # 1, 2, 5, 9, 13, 14,
15, 16, and 18 (in bold). To assess these nine objectives, a monitoring plan was developed for this site
(see Appendix A) and the resulting analysis and discussion evaluates the site’s performance according
to these objectives.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
Evaluate how a site with multiple LID practices treats stormwater runoff and manages
stormwater quantity as a whole.
Evaluate long-term maintenance needs and maintenance programs, and the impact of
maintenance on performance.
Determine the life-cycle costs for LID practices.
Assess the water quality and quantity performance of LID designs in clay or low infiltration soils.
Evaluate whether LID SWM systems are providing flood control, erosion control, water
quality, recharge, and natural heritage protection per the design standard.
Assess the potential for groundwater contamination in the short- and long-term.
Assess the performance of LID designs in reducing pollutants that are dissolved or not associated
with suspended solids (i.e. nutrients, oils/grease, and bacteria).
Demonstrate the degree to which LID mitigates urban thermal impacts on receiving waters.
Assess the water quality and quantity performance of LID technologies.
Evaluate how SWM ponds perform with LID upstream. Can the wet pond component be reduced or
eliminated by meeting the erosion and water quality objectives with LID?
Assess the potential for soil contamination for practices that infiltrate.
Evaluate effectiveness of soil amendments and increased topsoil depth for water balance and longterm reliability.
Evaluate and refine construction methods and practices for LID projects.
Develop and calibrate event mean concentrations (EMCs) for various land uses and
pollutants.
Assess performance of measures to determine potential rebates on development charges,
credits on municipal stormwater rates and/or reductions in flood insurance premiums (i.e.
can LID reduce infrastructure demand?).
Assess the ancillary benefits, or non-SWM benefits.
Assess the potential for groundwater mounding in localized areas.
Improve and refine the designs for individual LID practices.
Assess the overall performance of LID technologies under winter conditions.
6
2 SITE DESIGN
2.1
LID Design
The CVC Head Office incorporates a variety of LID
features including permeable pavement parking lots and a
rainwater harvesting system supplying non-potable water
to toilets, urinals and outdoor hose taps. These LID
features filter and store stormwater before discharging to
Credit River and Lake Ontario. Prior to the LID
construction, this site drained directly into a tributary of the
Credit River with no opportunity for pre-treatment. There is
also a grass swale that drains the asphalt roadway. This
swale is not enhanced with bioretention features. The site
area is shown in Figure 2-2, and the total drainage area is
2
about 4500 m . All of the LID features drain to a
monitoring catchbasin, where water quality and quantity
are measured to assess their effectiveness. The water
then travels to an outfall, where it is drained by an existing
swale to the Credit River.
Figure 2-1: Stakeholders at the monitoring
objectives meeting
7
Figure 2-2: Drainage areas of the different features at CVC Head Office. Drainage is indicated by the blue lines, with
the dotted blue lines signifying underground drainage.
The CVC Head Office is designed to provide water quality benefits, while at the same time improving
runoff quantity control. During relatively small and frequently occurring runoff events, stormwater will
infiltrate into the permeable pavement parking lot. The site is designed to reduce the amount of surface
ponding during and after these events. During higher-volume events, the LID features provide a degree of
attenuation for flood flows. Since the site is a retrofit, detention is limited by space constraints of the LID
features. The environmental level of service is improved by protecting downstream waterways from
contaminants and as well as providing volume retention.
2.2
8
Permeable Pavement
Permeable pavement allows for the filtration, storage, and infiltration of stormwater, which can reduce
flows compared to traditional impervious paving surfaces such as concrete and asphalt. The area of first
2
permeable parking lot, installed in 2010, is roughly 1,462 m . This lot provides a total of 52 spaces for
visitors and staff. This feature primarily handles the rainfall that falls directly on the lot, as only a small
portion of the surrounding asphalt roadway runoff is being directed towards the permeable pavers. The
underdrain for the permeable pavement drains to the monitoring catchbasin.
The different components of the permeable pavement are shown in Table 2-1 while a cross section is
given in Figure 2-3.
Table 2-1: Components of the permeable pavement
Paver:
The 80 mm thick permeable interlocking
concrete paver used was Uni Eco-Stone,
manufactured by Unilock. The L shaped
pavers have nubs around them which
leave a consistent 1 cm space around each
paver.
Bedding and Geotextile:
The bedding layer is 25 mm thick and
provides a level surface for the pavers. It is
composed of 1.18 to 4.75 mm diameter
chip stone. This stone is also used as a
filler stone for the pavers.
A geotextile drainage fabric separates the
bedding and base layers.
Base and Underdrain:
A base layer of Granular A 22 mm
diameter crushed recycled, locally sourced
concrete (450 mm depth) provides
structural support to the pavement and a
storage reservoir for the stormwater.
The underdrain is located in this layer, a
100 mm diameter corrugated PVC pipe
placed 300 mm below grade.
Edging Restraints:
A concrete curb or rigid metal edging
restraint is required to keep the pavers in
place and tightly packed. Concrete curbing
is preferred, but a metal edging restraint
can be used due to cost constraints, as
they are significantly cheaper.
Subgrade:
The soils in this area are predominantly
sandy silt glacial till of low permeability
embedded with permeable sand lenses.
The boreholes taken in the location of the
parking lot found both sand and gravel fill
and sandy silt glacial till.
9
10
Figure 2-3: Cross section of the permeable pavement, showing the 1 Pavers, 2 Bedding layer, 3 Geotextile fabric,
and 4 Base layer. The underdrain is located in the base layer.
The use of the locally-sourced recycled concrete for the base materials is not typical for permeable
pavement, but was used for this lot to attain LEED certification. The second permeable pavement lot was
2
installed in 2012, and has an area of about 2400 m .This lot has several differences from the older lot, as
it uses a 475 mm depth base, does not use the recycled concrete for the base, has concrete curbs
instead of edging restraint, and uses a darker coloured stone to help melt snow and ice in the winter. This
lot is not part of the monitoring program, and the results given in this report only apply to the older lot, the
swales adjacent to that lot, and the rainwater harvesting system.
2.3
Grass Swales
Grass swales were installed between the older permeable paver parking lot and the asphalt roadway
serving the building (Figure 2-4). These swales are not enhanced bioretention features, and primarily
collect and convey runoff from the asphalt roadway, as there is typically little to no runoff from the
2
permeable pavement. The total swale area is 378 m .
Figure 2-4: Grass swale at CVC Head Office
2.4
11
Rainwater Harvesting
Rainwater Harvesting (RWH) Systems can reduce rooftop runoff as rainwater is collected by roof
downspouts and directed to a cistern for future non-potable water use. Rainwater is collected from the
roof of the new CVC building to a 5,000 litre rainwater storage tank located in the basement of the
2
building. The drainage area of this roof is 536 m . The roof runoff is directed through 75 mm diameter
ABS piping to the tank. When the tank is full, excess water is drained to a grass swale catchbasin. A
picture of the tank is shown in Figure 2-5. The tank is also frequently filled with water that was collected in
the building’s sump. A high water table surrounds the building resulting in a small amount of water
continuously collected in a sump.
The collected water is used to supply non-potable water to toilets and urinals in the building addition as
well as supply water to outdoor hose bibs. To supply this water to the connected fixtures, the system uses
a standard constant-speed style pump and pressure tank. The multi-stage pump provides a flow rate of
40 litres per minute, while the pressure tank stores 100 litres.
Rainwater is treated by a 100-micron particle filter (model JUDO JFXL-T). Maintenance of the filtration
system is minimized by using this type of filter because it includes an automatic timer-based self-cleaning
backwash system. One potential long-term performance issue associated with the design of the treatment
system is the filter location. The filter is located upstream of the pump (on the suction line), which tends to
increase the amount of wear on the pump due to increased strain. When designing RWH systems, it is
recommended that all treatment components (filters, Ultraviolet lamps, etc.) be installed downstream of
the pump, on the discharge line of piping. If intake of debris into the pump is a concern, a line strainer
filter can be used to protect the pump from large debris while minimizing wear.
During periods when the tank is nearly empty (from insufficient rainfall or excess demands from indoor or
outdoor use) a ‘top-up’ system is used to supply the tank with potable municipal water. The RWH system
uses a rod-style mechanical float to determine a low level, at which time a normally-closed solenoid valve
opens to permit potable water to enter the tank. The building’s potable water system is protected from
contamination by the non-potable rainwater by using a backflow prevention device.
Figure 2-5: Rainwater storage tank, located in the basement of CVC’s head office
12
3 MONITORING RESULTS AND INTERPRETATIONS
This section presents results from the analysis of data from the monitoring program at CVC Head Office
from July 2014 to September 2015.
The monitoring program at CVC Head Office includes a variety of elements such as precipitation,
hydrology, water quality monitoring, and water usage monitoring. Table 3-1 summarizes these activities
and their locations. A more detailed discussion is included in the following subsections. This report
contains the analyses of a range of precipitation and flow events during the study period. The monitoring
protocols, comprehensive data management and analysis for this site are discussed in Appendices B, C
and D respectively.
Figure 3-1: Monitoring equipment that is used at CVC Head Office
13
Table 3-1: A summary of the measurement objectives, measurement types, monitoring locations, monitoring
equipment and frequency utilized at the CVC Head Office monitoring site
Measurement Type
Monitoring Equipment
Location / Description
Level and Flow
ISCO 2150 area
velocity flow and level
meter
At the monitoring location
shown in Figure 2-2
Stormwater Quality Sampling
ISCO 6712 automatic
sampler
At the monitoring location show
in Figure 2-2
Rainfall Depth
City of Mississauga rain
gauge
CVC Office rooftop, newer
building
Raintank Usage and Level
Hobo U20 level logger,
OM-CP-PULSE101A
pulse loggers
CVC Office basement
Note: Specific protocols are discussed in Appendices B and C.
3.1
Precipitation
Precipitation at CVC Head Office has been monitored continuously between July 3, 2014 and September
30, 2015 excluding January 1, 2015 to March 29, 2015. This data was collected using a heated tippingbucket rain gauge which was installed on the roof of the CVC Head Office building on the site. The
records are used to describe the rainfall distribution in the study area. For comparison, the rainfall record
from the Environment and Climate Change Canada (ECCC) weather station, Toronto Pearson
International Airport (climate ID: 6158733), is used to provide a long-term regional context for
understanding regional “normal” or average precipitation values. This weather station is located about 10
km northeast of CVC Head Office. Table 3-2 compares the monthly and annual precipitation normals
between Toronto Pearson International Airport weather station (1981 – 2010) and the precipitation
recorded at CVC Head Office during the monitoring period. Knowledge of the event sizes that contribute
to the majority of annual rainfall is helpful for understanding pre-development conditions and performance
results. Additional gauges maintained by the City of Mississauga and CVC are used as references if any
data from the primary gauge on site seems unusual.
Table 3-2: Precipitation comparison between EC Toronto Lester B. Pearson Int’l A weather station and CVC Head
Office.
Parameters
Jan
Feb
Mar
Apr
May June July
Aug
Sept
Oct
Nov
Dec Annual
74.5
Station : Toronto Pearson International Airport (1981-2010)
Precipitation (mm)
51.8 47.7
Station : CVC Head Office
a
2014 Precipitation
n/a
(mm)
b
2015 Precipitation
n/a
(mm)
49.8
68.5
74.3
71.5
75.7
78.1
61.1
75.1
57.9
785.9
n/a
n/a
n/a
n/a
n/a
90.0
24.6 108.6 56.8
37.4
25.4
N/A
n/a
n/a
72.2
69.8 172.5 31.8
65.2
n/a
n/a
N/A
67.4
n/a
a
Notes: Data starts on July 3, 2014 at 8:00
b
Data starts on March 30, 2015 at 9:10 and ends on September 30, 2015 at 23:50
The average annual precipitation at Toronto Pearson International Airport weather station from 1981 –
2010 is 786 mm. The precipitation normals indicate that between May and September are typically the
rainiest months since each month exceeds 70 mm of precipitation. Moreover, the monthly precipitation of
CVC Head Office in Sept 2014 and June 2015 exceed 100 mm.
14
Figure 3-2 provides a summary table and illustrates the typical annual rainfall distribution for Toronto
Pearson International Airport weather station between 1960 and 2012 and the actual number of
precipitation events that were recorded at CVC Head Office during the monitoring period between July
2014 and September 2015. An event is considered to occur when 2 mm or greater precipitation is
recorded, with a dry period of at least 6 hours between events (Appendix C). The pattern of captured
rainfall events at CVC Head Office is very similar to that at Toronto Pearson International Airport weather
station, with the exception of the 2-5 mm and 5-10 mm. CVC Head Office had a larger proportion of
events in the 2-5 mm range, and a smaller proportion in the 5-10 mm range. The percentage differences
among the remaining frequency distribution groups between the two stations are within ±3 per cent.
50%
45%
Percentage of Events
40%
35%
30%
25%
20%
15%
10%
5%
0%
2 to 5
5 to 10
10 to 15
15 to 20
20 to 25
25 to 30
30 to 35
35+
Precipitation Event Depth (mm)
Toronto Pearson International Airport
CVC Head Office
Figure 3-2: Rainfall frequency distribution graph between EC Toronto Pearson International Airport station and CVC
Head Office
The frequency of events for a given size from ECCC Toronto Pearson International Airport station is
presented in Figure 3-3. In this chart, hourly weather records from 1950-2005 have been analyzed with
WQ-COSM software. This software is designed for determining and maximizing the ‘water quality capture
volume’ for a BMP based on local historical rainfall data. This volume is used to adequately design and
size BMPs for improved water quality and quantity control based on historical rainfall. At Toronto Pearson
International Airport, events with a depth of 25 mm or less account for 90 per cent of all events annually.
At CVC Head Office, these events accounted for 87 per cent of the events over the study period.
Figure 3-3: Percentage of events falling at or below a given precipitation depth at ECCC Toronto Pearson
International Airport using hourly weather records from 1950-2005.
15
3.2
16
Hydrology
In natural and rural environments with vegetated soils,
surface runoff is generally low and represents a
small fraction (10 per cent to 20 per cent) of the
total fallen precipitation (Prince George’s County,
1999). Water either percolates into the ground or is
returned to the atmosphere by evaporation and
transpiration. A considerable percentage of the
rainfall infiltrates into the soil and contributes to the
groundwater. The local water table is often
connected to nearby streams, providing infiltration
to streams and wetlands during dry periods and
maintaining base flow essential to the biological
and habitat integrity of streams.
Land development converts permeable land into
impermeable surfaces. During urbanization, natural
channels are replaced by artificial drainage pipes
and channels that decrease the amount of water
infiltration and storage within the soil column. This
alters the hydrologic regime by allowing less
infiltration and more channeled runoff through the
urban infrastructure.
As a much larger percentage of rainwater hits
impervious surfaces including roofs, sidewalks,
parking lots, driveways, and streets, it must be
controlled through SWM techniques. Traditional
approaches have focused on collection and
conveyance to quickly transport stormwater to the
nearest watercourse to prevent property damage.
Current SWM has taken an “end-of-pipe”
approach, using gutters and piping systems to
carry rainwater into ponds or detention basin. This
approach does not mitigate or alter the runoff
volume component of the water cycle which is the
driving force of erosion, pollution and lower dry
weather stream flows due to changes in hydrology.
Cook and Dickinson (1986) examined the impacts
of urbanization, including the installation of a
stormwater conveyance system near Guelph,
Ontario.
Comparing
the
pre-development
conditions of the area with ongoing development,
the researchers noted several changes in the
hydrologic response. Changes included an
increase in annual runoff, a change in the time of Figure 3-4: Development conditions; urban water cycle
peak flow, a reduction in hydrograph lag time, and with stormwater management ponds and LID (adapted
an increase in hydrograph peak discharge. Urban from FISRWG, 1998)
development produces runoff for events where
pre-development conditions produced no runoff, such as during the summer months outside of the
snowmelt or spring runoff period.
A robust SWM system that meets all environmental and economic goals must include both conventional
SWM facilities and source-based LID practices. Conventional facilities typically lack the ability to provide
17
water balance benefits or reduce the volume of runoff from heavily urbanized areas. As a result they offer
fewer benefits with respect to infiltration, water quality and erosion mitigation. LID practices excel where
conventional systems fail by allowing for natural hydrologic processes including infiltration and
evapotranspiration as close to the source as possible. A greater discussion of the urban water cycle can
be found in Appendix E.
Figure 3-5 shows a hydrograph comparing stream discharge before, during, and after a storm under preand post-development conditions (Schueler, 1987). As indicated, streams with developed watersheds
have substantially higher peak flows which occur more quickly than under pre-development conditions.
Impervious surface coverage as low as 10 per cent can destabilize a stream channel, raise water
temperatures, and reduce water quality and biodiversity (Schueler, 1995).
Figure 3-5: Changes in stream flow hydrograph as a result of urbanization (adapted from Schueler, 1987)
LID practices are designed to mitigate the rapidly changing water cycle by mimicking the predevelopment hydrology within the urban environment. LID strategies strive to allow natural or predevelopment infiltration to occur as close as possible to the original area of rainfall. By engineering
terrain, vegetation, and soil features to perform this function, the landscape can retain more of its natural
hydrological function. Although most effective when implemented on a community-wide basis, using LID
practices on a smaller scale can also have a positive impact.
3.2.1 CVC Head Office Hydrology
LID at CVC Head Office include permeable pavement parking lots and a rainwater harvesting system.
The monitoring program involves both the older permeable pavement lot and the rainwater harvesting
system, along with grass swales that drain the asphalt roadway. The project team assessed the
performance of the LID features determining the reduction in runoff volume and the reduction in peak
flow. Inflows were estimated using the Simple Method, which calculates flow according to drainage area,
amount of precipitation, and a runoff coefficient based on level of imperviousness. Effluent flow is
measured through level measurements at a catchbasin located downstream of underdrains draining the
permeable pavement lot, the grass swales, and the rooftop when the rainwater harvesting tank is full
(Monitoring location HO-1 on Figure 2-2). Due to a locally high water table, there is a near constant of
baseflow in the monitoring catchbasin. Baseflow separation is used to determine the amount of flow in
18
catchbasin that is stormflow. Appendix C contains a thorough discussion of the data management and
analytical methodology, including baseflow separation. Table 3-3 presents the hydrologic summary for 62
events over the monitoring period (July 2014 – September 2015). Influent runoff volume and influent peak
flow rate were estimated using the Simple Method (Appendix C). Peak precipitation intensity and peak
effluent flow rate were measured over ten minute time periods.
Increasing the amount of water that infiltrates and does not produce stormwater effluent from the site (i.e.
volume reduction) is important to reduce pressure on local stormwater infrastructure and receiving water
bodies. Runoff volume reduction reflects higher groundwater recharge, smaller flows to the storm sewer
network, and reduction in pollutant loading. The mean estimated event runoff volume reduction for all
events at CVC Head Office is 72 per cent. The mean event peak flow rate reduction for all events is 78
per cent.
Figure 3-6 and Figure 3-7 show runoff volume reduction and peak flow rate reduction, respectively, for
events of different magnitude. Events are binned into six categories: 2-5 mm, 5-10 mm, 10-15 mm, 15-20
mm, 20-25 mm, and greater than 25 mm. Runoff volume and peak flow rate is reduced for events of all
sizes, with a general pattern of lower reductions with larger precipitation events. The CVC Head Office
site retains on average 74 per cent of runoff for all events smaller than 25 mm. The site also provides on
average 79 per cent peak flow rate reduction for all events less than 25 mm.
The permeable pavement works by infiltrating a portion of the runoff generated by the site, therefore
reducing total runoff leaving the site as well as the rate at which runoff leaves the site.
Figure 3-8 compares the event influent volume versus effluent volume at CVC Head Office to retention
ponds or wet ponds in units of watershed-millimetres (data from the BMPDB, 2011). Retention ponds are
typically designed to manage runoff to prevent flooding and downstream erosion while improving water
quality. The central 1:1 line, on Figure 3-8, represents effluent equal to influent (no volume reduction).
As the outflow volume of retention ponds depend on the available storage (i.e. the pre-event pond water
levels), retention ponds can not always provide volume reduction. When comparing CVC Head Office to a
retention pond, the CVC Head Office permeable pavement shows greater volume reduction capabilities
than many retention ponds because the data point cloud from CVC Head Office is concentrated below the
1:1 line (i.e. more inflow than outflow). The graph qualitatively supports that the CVC Head Office LID
site provides greater volume reduction benefits when compared to a retention pond. This alleviates the
impact on the downstream water bodies, allowing the site to mimic a more natural hydrology.
2.50
6.25
12.92
46.50
9.11
3.65
7.30
16.40
73.75
12.23
25% Percentile
Standard
Deviation
Mean
Maximum
75% Percentile
9.34
0.17
2.00
Minimum
13.07
62
62
Count
Median
Event
Duration
(hr)
Event
Precipitation
(mm)
Statistic
15.09
20.4
60
15.36
9.6
4.8
1.2
62
Peak
Precipitation
Intensity
(mm/hr)
3.74
4.64
18.45
3.59
2.40
1.27
0.32
62
Antecedent
Dry Period
(days)
6.57
3.85
32.51
3.98
1.45
0.61
0
62
42771
51472
241015
38581
22510
10755
5574
62
19732
20798
91097
14446
6496
1987
0
62
19%
90%
100%
78%
81%
70%
7%
62
Measured Estimated
Peak
Estimated
Effluent Peak Flow
Effluent
Inflow
Flow Rate
Volume Reduction
Volume (L)
(L/s)
(L)
(%)
Table 3-3: Statistical analysis of all precipitation events during the monitoring period at CVC Head Office
18%
84%
100%
72%
70%
59%
28%
62
Estimated
Event
Runoff
Volume
Reduction
(%)
19
1,600
Total volume (m3)
1,400
1,200
1,000
800
600
400
200
0
Count
Event size
28
2 - 5 mm
8
8
6
4
54
8
5 - 10 mm 10 - 15 mm 15 - 20 mm 20 - 25 mm All Events All Events
<25 mm
>25 mm
Volume reduction 81%
75%
61%
61%
57%
67%
57%
Uncontrolled Urban Runoff (Estimated)
LID Treated Effluent (Measured)
Figure 3-6: Runoff volume reduction during monitoring period at CVC Head Office
Average Peak Flow Rate (L/s)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
Count
Event size
28
2 - 5 mm
8
8
6
4
54
8
5 - 10 mm 10 - 15 mm 15 - 20 mm 20 - 25 mm All Events All Events
<25 mm
>25 mm
77%
66%
75%
66%
74%
57%
Peak Flow Rate 83%
Reduction
Figure 3-7: Peak flow rate reduction during monitoring period at CVC Head Office
20
21
Outflow (watershed-mm)
25.00
20.00
15.00
10.00
5.00
0.00
0
5
10
15
20
25
Inflow (watershed-mm)
Retention Pond Events < 25 watershed-mm
(Source: BMPDB, 2011)
CVC Head Office Events < 25 watershed-mm
Figure 3-8: Comparison of CVC Head Office with retention pond
28
0
24
4
Flow (L/s)
20
8
16
12
12
90 per cent
peak flow rate
reduction
8
16
71 per cent
reduction
4
0
2014-10-03 12:00
2014-10-03 20:00
2014-10-04 04:00
volume
Figure 3-9: Hydrologic summary of the rain event on October 3 and 4, 2014
20
24
2014-10-04 12:00
Precipitation (mm)
Precipitation (mm)
Figure 3-9 shows an example of a hydrologic event summary of a storm event, illustrating hydrograph
response with reduced peak and total runoff volume. This storm event occurred on October 3 and 4 2014,
and had a precipitation depth of 17.4 mm over 14 hours, with a peak rainfall intensity of 27.6 mm/hr.
Volume reduction for this event was estimated to be about 71 per cent and peak flow rate reduction was
estimated to be about 90 per cent. These estimates are affected by many variables including normal
variability in measurements, rainfall-runoff assumptions, etc.
22
Overall, CVC Head Office is reducing the voume of urban runoff entering the Credit River. The site has
demonstrated its ability to provide runoff volume reduction and peak flow rate reduction for events of all
sizes.
3.2.2 Lag Time
An additional benefit of LID features over conventional stormwater infrastructure is the delayed
hydrograph response time. While paved surfaces produce runoff almost instantaneously with
precipitation, LIDs provide some lag time between rainfall and runoff as a result of their ability to capture
the first few millimeters of rainfall for storage and infiltration/evaporation.
Hydrologic lag time statistics computed from precipitation and effluent peaks are presented in Figure
3-10. Error bars represent +/- 5 per cent of error at the given precipitation range. Longer lag times mimic
pre-development conditions and give greater opportunity for surface runoff to infiltrate and delays contact
with the receiving water body.
The median lag time for all events with observed effluent is 0.33 hours, as represented by the horizontal
line in Figure 3-10, which presents the median lag time of all storms with observed effluent. The delay
between precipitation and effluent provides relief and resilience to receiving water bodies already
burdened by high volume of storm water.
0.7
Lag time (hours)
0.6
0.5
0.4
0.3
0.2
0.1
0
Event size
Count (n)
<5 mm
21
5-10 mm
7
10-15 mm
8
15-20 mm
6
20-25 mm
4
≥25 mm
8
median peak lag time
Blackline represents the overall median lag time. Error bars represent +/- 5 percent error at the given precipitation range.
Figure 3-10: Lag time statistics by storm depth
3.2.3 Influence of Precipitation Intensity on Performance
Figure 3-6 shows that both the volume reduction reduction generally decreases with increasing total
precipitation. Another factor that affects the performance of the LID system is rainfall intensity, with more
intense storms generally having lower volume reductions. Figure 3-11 shows volume reduction vs
precipitation depth and peak intensity. Larger, darker data points represent a lower reduction. Figure
3-11 shows that generally, volume reduction decreases with increasing precipitation depth and increasing
peak intensity. 77 per cent of events with a total precipitation over 25 mm or peak precipitation intensity
over 40 mm/h have a volume reduction under 55 per cent, while only 14 per cent of the events with a total
precipitation under 25 mm and with a peak intensity under 40 mm/h have a volume reduction under 55
per cent. As more intense events are expected in Canada due to climate change, further understanding
of how storm intensity drives water quantity performance can help improve future LID designs.
23
80.0
Total Precipitation Depth (mm)
70.0
60.0
Volume
Reduction
under 55
50.0
55-70
40.0
70-85
30.0
85-100
20.0
100
10.0
0.0
0
10
20
30
40
50
60
Peak Intensity (mm/h)
Figure 3-11: Volume reductions at different precipitation depths and peak intensities for all events at CVC Head
Office
Table 3-4, Figure 3-12 and Figure 3-13 present hydrologic summaries of a low intensity rain event on
April 19 and 20, 2015 and a high-intensity rain event on June 22 to 23, 2015. Both of these rain events
had a similar total precipitatio, with 21 mm for the first event and 20.8 mm for the second. The second
event had a peak intensity ten times higher than the first, and had almost two thirds of the total
precipitation fall in a 20-minute period. The low-intensity event had a greater volume reduction, at 69 per
cent compared to 52 per cent, and a greater peak flow reduction, at 73 per cent compared to 60 per cent.
Table 3-4: Comparison of low-intensity and high-intensity rain events at CVC Head Office
April 19-20, 2015
(low intensity)
June 22-23, 2015
(high intensity)
Event Precipitation (mm)
21
20.8
Event Duration (hr)
18.5
12.8
Peak Precipitation Intensity (mm/hr)
4.8
48
Antecedent Dry Period (days)
2.7
6.4
Peak Effluent Flow Rate (L/s)
1.2
17.3
Estimated Inflow Volume (L)
68,436
67,090
Measured Effluent Volume (L)
20,931
31,916
Estimated Peak Flow Reduction (%)
73
60
Estimated Event Runoff Volume Reduction (%)
69
52
Event
24
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
2015-04-20 16:00
Precipitation (mm)
Flow (L/s)
50.0
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
2015-04-19 16:00
2015-04-20 00:00
2015-04-20 08:00
Precipitation (mm)
Figure 3-12: Hydrologic summary of a low-intensity rain event on April 19 and 20, 2015.
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
2015-06-23 19:00
Precipitation (mm)
Flow (L/s)
50.0
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
2015-06-22 19:00
2015-06-23 03:00
2015-06-23 11:00
Precipitation (mm)
Figure 3-13: Hydrologic summary of a high-intensity rain event on June 22 and 23, 2015.
3.3
25
Water Quality
TSS Concentration (mg/L)
Monthly 75th Percentile (1975-2013)
The project team compared CVC
Head Office data with reference
45
Urban Stream (60-65%
sources, including comparisons
Impervious)
Rural Stream (10-20%
40
with water quality data from similar
Impervious)
CWQG
LID practices within the region and
35
with
other
North
American
30
locations.
This
includes
25
comparisons to the PWQOs,
BMPDB,
and
NSQD.
This
20
comparison
provides
an
15
understanding of CVC Head Office
LID practice performance to other
10
locations including cold weather
5
climates in North America. These
0
comparisons are useful in order to
Dec.
Sept.
Oct.
Nov.
May
June
July
Aug.
Feb.
Mar.
April
Jan.
understand whether there is a
th
Figure 3-14: Monthly 75 Per centile Total Suspended Solids
need to improve on design or
concentration compared at an urban vs. rural catchment
consider alternate sizing approaches for
these control measures and to assure
regulators that the CVC Head Office LID features do provide adequate performance to meet PWQOs. The
results in this section demonstrate the water quality performance of the parking lot LID that was
implemented at CVC Head Office.
Installing stormwater quality controls is important so that development or urbanization does not degrade
the water quality of receiving water bodies. CVC’s Stormwater Management Criteria (CVC, 2012)
stipulates that all watercourses and water bodies such as Lake Ontario within CVC’s jurisdiction are
classified as requiring, at a minimum, an enhanced level of protection with 80 per cent TSS removal.
For the last three decades, Ontario developers and municipalities have been achieving enhanced water
quality control by constructing end-of-pipe wet facilities (i.e. wet ponds, wetlands and hybrid ponds). In
conventional end-of-pipe wet stormwater management infrastructure, the main treatment mechanism for
reduction in particulates is through settling. This mechanism is less effective in removing smaller particles
for shorter time frames. Similarly, other dissolved pollutants often go untreated through conventional
stormwater infrastructure. Nutrients as well as many hydrocarbons are often associated with fine particles
(Appendix E).
Figure 3-14 shows the difference in TSS concentration between an urban (impervious cover between 6065 per cent) stream that receives stormwater from upland developments (with conventional end-of-pipe
wet facilities) as the dark blue line and a rural stream (pink line) with 10-20 per cent impervious cover
during dry ambient conditions in the Credit River watershed. The comparison demonstrates that there are
higher levels of TSS in the stream draining the developed area with conventional stormwater
management wet facilities than in the rural area. This result is due to the lack of water quality control in
the stormwater management ponds. To further support these conclusions, a USGS study (USGS 2008)
conducted in Wisconsin, showed that during a 7 year of study, LID on average yielded 20 per cent less
sediment per acre (39 lb/acre) when compared to a conventional development with a traditional
stormwater management basin (49 lb/acre).
CVC’s Water Quality Strategy (CVC, 2009) further identifies parameters of concern (PoC) in Table 3-5
that must meet the respective provincial or federal water quality objectives. Table 3-5 summarizes
PWQOs for many of the parameters that are being monitored at the CVC Head Office site. Although
these objectives were not specifically developed for stormwater discharges, Environment Canada,
26
MOECC, and the U.S. EPA have long recognized that urban stormwater is a major contributor to pollutant
loading to our creeks, rivers and Great Lakes. The guidelines listed in the table provide context for
planning and water resource management. These guidelines will be used as a basis for assessing water
quality performance of LID practices and indicate which pollutants are particularly well controlled.
Table 3-5: Provincial Water Quality Objectives (PWQOs) for selected parameters of interest
Parameter
Unit
PWQO
Water Quality
Cadmium (Cd)
μg/L
0.2
Copper (Cu)
μg/L
5
Iron (Fe)
μg/L
300
Lead (Pb)
μg/L
1 – 5 depending on hardness (Interim)
Nickel (Ni)
μg/L
25
Zinc (Zn)
μg/L
20 (Interim revised)
Total Phosphorus (TP)
μg/L
30
Nitrate-Nitrogen (NO3 as N)
mg/L
3.0 (CCME)
Nitrite + Nitrate (NO2 + NO3)
mg/L
N/A
Total Suspended Solids (TSS)
mg/L
25 (CCME)
Other
Temperature
°C
Narrative standard, with some numeric components
Sources: Water Management Policies, Guidelines, Provincial Water Quality Objectives of the Ministry of the Environment (July
1994, Reprinted February 1999); Canadian Environmental Quality Guidelines. Canadian Council of Ministers of the Environment.
(2015).
CVC proposes stringent measures to control the discharge of PoCs to
water courses. Implementing best management practices such as
treatment trains that incorporate LID can help achieve control so the
quality of the receiving water bodies is protected or improved.
Water quality control of LID practices is best measured as load
reduction, which takes into account all volume and pollutant reduction
mechanisms. Load reduction in LID practices is influenced by several
mechanisms:
volume
reduction
(e.g.,
infiltration
and
evapotranspiration), filtration, settling, and adsorption. While infiltration
decreases pollutant loadings to surface water, it provides a pathway for
water-soluble pollutants (e.g., nitrates and chlorides) to reach
groundwater. Filtration, settling, and adsorption removes pollutants
from surface water by retaining them in the filter media.
Event mean concentrations
(EMCs)
are
the
flowproportional
average
concentrations
of
water
quality parameters during a
storm event.
The EMCs and the runoff
volume
determine
the
pollutant loads from a site
and are representative of
average
pollutant
concentrations over a runoff
event.
3.3.1 Pollutant Load Reduction
Pollutant load removal was determined in the following manner: influent load to the LID device was
estimated by multiplying the predicted influent volume by the NSQD median influent concentration for
commercial, institutional, and industrial land uses in EPA Rain Zone 1. For several parameters, there was
insufficient data available in the NSQD to estimate influent loads. The estimated influent load was
compared with the monitored effluent load. Where influent volume was predicted but no effluent volume
27
was recorded, the estimated pollutant load reduction was 100 per cent. For events where effluent
discharge was recorded but no water quality sample was collected, loads were computed with the median
effluent value from the collected CVC Head Office water quality samples.
Based on representative influent data from the NSQD, CVC Head Office achieved a total estimated load
reduction for TSS of 81 per cent, as shown in Table 3-6. This achieves provincial standards for enhanced
water quality treatment of 80 per cent TSS removal. These results show that for all parameters there is an
estimated load reduction of at least 69 per cent with the exception of NO2 + NO3.
Parameter
b
Table 3-6: CVC Head Office estimated water quality treatment performance summary for zero-effluent and sampled
events between July 2014 to September 2015
a
TSS
TP
NO2+NO3
TKNc
Cu
Zn
Sampled Events
Unsampled Events
Zero-outflow events
(n = 12)
(n = 42)
(n = 8)
Total
Estimated
Influent
a
Load (g)
Total
Effluent
Load (g)
Total
Estimated
Influent
a
Load (g)
Total
Estimated
Effluent
Load (g)
Total
Estimated
Influent
a
Load (g)
Total
Effluent
Load (g)
Estimated
Total
Load
Reduction
(%)
105274
136
560
612
20.38
138
30714
59.54
461
189
7.41
35.51
181181
234
964
2160
35.07
237
26075
60
619
441
7.36
44
10153
13.10
54.04
98.26
1.97
13.26
0
0
0
0
0
0
81
69
32
78
74
80
Used data from the NSQD to estimate influent concentrations, using medians after filtering for USEPA Rain Zone 1 and
Commercial, Industrial, and Institutional land uses. Used the Simple Method to estimate influent volume (Appendix C)
For OP, Cd, Fe, Ni, and Cl-, there was insufficient data available in NSQD to estimate influent concentration
c
Only 7 sampled events for TKN and 47 unsampled events
b
For monitored events, the total load reductions for TSS and other water quality parameters, sorted by 5
mm precipitation event size increments, are compared in Table 3-7. Figure 3-15 shows the range of load
reductions for individual events along with the total load reduction for TSS in each precipitation bin.
Similar figures for the other parameters can be found in Appendix D. The total estimated load reduction
generally decreases with increasing precipitation event size, and the >25 mm range has the lowest
reduction for all parameters but NO2 + NO3 and Zn. The CVC Head Office LID site performs well for
events of 25 mm and under, with an 86 per cent TSS reduction and a reduction of at least 74 per cent for
the other parameters other than NO2 + NO3. These events constitute 90 per cent of all precipitation events
in Ontario. For events over 25 mm, the TSS reduction is considerably lower at 73 per cent. Statistical
tests (Mann-Whitney U test and Student’s t-test) show the TSS reduction for these storms is significantly
different than the TSS reduction for storms under 25 mm. Of the measured parameters, NO2 + NO3 and
the other nutrients show the greatest inconsistently in load reduction for individual events.
28
Table 3-7: Estimated total load reduction for each precipitation bin
Storm Size
TSS
TP
(mm)
(%)
(%)
NO2 +
NO3
(%)
<5
92
86
5 - 10
92
10 - 20
TKN
Cu
Zn
(%)
(%)
(%)
64
89
88
90
81
47
87
86
87
84
72
27
78
75
80
15 - 20
84
72
28
80
77
79
20 - 25
81
62
15
76
74
76
All events <25
86
74
35
82
80
82
All events >25
73
61
26
73
67
76
100
90
Load Reduction (%)
80
70
60
50
40
30
20
10
0
2-5
5 - 10
10 - 15
15 - 20
20 - 25
>25
Rain Event Size (mm)
Figure 3-15: Estimated total load reduction by event size for TSS. Black bars show the range in load reductions for
individual storm events.
3.3.2 Event Mean Concentrations and Comparisons to the BMPDB
While loading comparisons are preferred, EMCs also demonstrate the reduction in concentration with
treatment of the LID system. The median effluent EMC information for sampled events at CVC Head
Office and the estimated influent EMCs from the NSQD are provided in Table 3-8 with PWQOs (from
Table 3-5) as a comparison. It shows that several of the median effluent concentrations for most
parameters sampled at CVC Head Office exceed the PWQOs, except for Fe, Ni, and NO2 + NO3. For all
parameters but NO2 + NO3, the median effluent concentration is higher than the estimated influent
concentration. This indicates that although many of the effluent EMCs exceed guidelines, they would
likely be even higher if not for the LID treatment. As discussed before, the major benefit for LID features
with respect to water quality is the load reductions. In addition, the PWQOs were developed for
freshwater waterbodies and not specifically developed for stormwater discharges.
29
Table 3-8: Water quality summary statistics for sampled events at CVC Head Office with comparisons to the NSQD
and water quality guidelines
CVC Head Office EMCs and PWQOs
Statistic
Median
Effluent
EMC (n=12)
Estimated
Influent
EMC (from
d,e
NSQD)
PWQO
/CCME
Cd
µg/L
Cu
µg/L
Fe
µg/L
Pb
µg/L
Ni
µg/L
Zn
µg/L
NO2 +
NO3
mg/L
1.03
14.75
193.5
NDa
0.09
87.2
-
24
-
-
-
0.2
5
300
1-5
25
TKN
mg/L
PO4
mg/L
TP
mg/L
TSS
mg/L
Cl
mg/L
1.24
b
0.67c
0.08
0.12
52
231.5
162
0.66
1.12
-
0.16
124
-
20
3d
N/A
N/A
0.03
25
120
a
The median EMC value for Pb was below the detection limit
Guideline value for NO3 is used.
Only 7 samples for TKN.
d
Used data from the NSQD to estimate influent concentrations, using the median values after filtering for USEPA Rain Zone 1 and
Commercial, Industrial, and Institutional land uses.
e
Insufficient data available in NSQD to estimate influent concentration for some parameters
b
c
The median effluent EMC for CVC Head Office is compared to the discharge from five other BMP types
within the same EPA rainfall zone (Zone 1) (Table 3-9) from the BMPDB, including bioretention, detention
basins, manufactured devices, retention pond and wetland channel. While the performance is not
available for every parameter, relating median effluent EMC within the same precipitation zone reduces
variability in climate pattern differences. The CVC Head Office median effluent EMCs are either lower or
within the range of values for PO4, Fe, TKN, Ni, and TP, and higher than the range of values for NO2 +
NO3, Cd, Cu, TSS, and Zn. The difference in design for this lot compared to typical permeable pavement
with the use of locally-sourced, recycled concrete for the base may be a contributor to the difference in
performance between this lot and those in the BMPDB. The presence of baseflow at this site may also
contribute to the EMC concentrations, although for most events the volume of the stormflow is much
higher than the baseflow. Water chemistry testing of this baseflow is planned to help quantify any
potential contribution to the effluent concentrations.
30
Table 3-9: Comparison of CVC Head Office Median Sampled Effluent EMC to different BMPs from BMPDB
Parameter
(units)
NO2 + NO3
(mg/L)
PO4
(mg/L)
Cd (µg/L)
Cu (µg/L)
Fe (µg/L)
TKN
(mg/L)
Pb (µg/L)
Ni (µg/L)
TP (mg/L)
TSS
(mg/L)
Zn (µg/L)
CVC Head
Office
Median
Effluent
EMC*
BMP Typea
Bioretention
Porous
Pavement
Detention
Basin
Manufactured
Devices
Retention
Pond
Wetland
Channel
1.24
0.21
0.65
-
0.44
0.19
0.17
0.08
-
-
-
-
0.09
-
1.03
-
-
-
0.11
0.40
-
14.75
193.5
-
-
-
7.00
5.74
-
-
-
-
-
360
-
0.67
-
-
-
0.57
1.10
1.50
ND
0.09
b
-
-
-
3.58
5.00
1.90
-
-
-
-
2.00
-
0.12
0.18
0.06
0.14
0.07
0.18
0.22
52
6.20
-
22.6
26.0
14.4
12.0
87.2
-
-
-
30.5
18.8
-
*Bold numbers represent values which are less than all given BMP effluent EMCs.
a
Values represent BMPs in USEPA rainfall zone 1
b
Median EMC value for Pb was lower than the detection limit
Overall CVC Head Office water quality analysis indicates that the LID performance is improving water
quality by reducing the total load of parameters of concern entering the Credit River. In addition, there is
an estimated reduction in concentration of most of the parameters. Other summaries and comparisons
including time series plots and graphical statistical summary plots can be found in Appendix D.
3.4
Reclaimed Water Usage
The rainwater harvesting system allows the use of reclaimed water at CVC’s Head Office. Daily use from
a twelve week period from April to July 2015 is shown in Figure 3-16. The median daily usage of the
reclaimed water during workdays is 1300 L. Due to maintenance and a sump pump failure, there were
time periods where the rainwater harvesting system was left offline and reclaimed water was not used in
the building. For details of how this system was monitored, please see Appendix B.
31
Daily Reclaimed Water Usage
(L)
2500
2000
1500
1000
500
0
25-Apr-15
16-May-15
6-Jun-15
27-Jun-15
18-Jul-15
Date
Figure 3-16: Reclaimed water used from a 12-week period in mid-2015. The orange line indicates the overall median
recaimed water usage of 1300 L for workdays.
The reclaimed water usage was compared to the total municipal water usage to determine the relative
usage percentages of each. Total reclaimed water usage varied by month, with a total reclaimed water
usage of 26 per cent for the time periods it was online. The maximum reclaimed water usage as a per
cent of total water usage during this time period in May 2015, where 32 per cent of the total water usage
was reclaimed water (Figure 3-17). The total amount of reclaimed water used from August 2013 to
December 2015, and thus municipal water saved, was 441 820 L, or over 150 000 L/year. The total cost
savings from not using municipal water over this period was approximately $845, although this does not
take into account the cost of installing and maintaining the system. As the reclaimed water is only used
for toilets and garden hoses for one of the two main buildings at CVC’s main office, the water savings
would likely be considerably higher if reclaimed water was used for both buildings. Additionally, the
presence of an environmental laboratory and staff shower may also increase the amount of municipal
water used relative to a normal office building.
The addition of the sump pump water allows a consistent input of water to the storage tank, allowing the
consistent daily water demand to be met. If only rainwater from the rooftop was used to fill the storage
tank, only about half of the current reclaimed water usage demand could be met. A full rain tank only has
capacity for about a week’s worth of reclaimed water usage if there is no additional input during that time.
32
CVC Water Use, May 2015
31750, 32%
66370, 68%
Reclaimed Water Used (L)
Treated Water Used (L)
Figure 3-17: CVC’s water usage for May 2015.
3.5
CVC Head Office Site Water Balance
The addition of a rainwater harvesting system allowed rainwater that falls on the rooftop of one of the
buildings at CVC Head Office to be retained and reused as non-potable water. As the storage tank holds
about 5000 L of water, this allows it to store up to about 9 mm of rainfall for each event, assuming no
reclaimed water usage, and up to 11 mm of each event assuming median daily water usage. However, as
the storage tank is also periodically filled with water from the sump pump, in practice only 2000 L or less
of space is available during rain events, representing a rainfall depth of 3.7 mm falling on the roof. The
volume of water that is retained is dependent on this empty space. As the tank fills up during the early
parts of large rain events, the percentage of the total water that falls on the monitoring site that is retained
is reduced. Total site water balances for both a smaller and larger storm event are shown in Figure 3-18
and Figure 3-19. While the volume retained by the rainwater storage tank is similar for both events, the
percentage of the total rainwater retained is much smaller for the 43.3 mm event than the 4.6 mm event
(2 per cent vs 13 per cent).
Directing water from the sump pump to the rainwater harvesting system lowers the available volume for
the retention of rooftop rainwater, but is still a benefit to the local stormwater system as this sump pump
water would otherwise have been directed to a storm sewer. Installing a larger stormwater tank would
allow an increased volume of rooftop rainwater to be retained.
Water Balance for October 20 2014 Storm
521, 4%
1721,
13%
Water discharged to
stormwater system (L)
Water collected by
raintank (L)
11058, 83%
Water retained by LID (L)
Figure 3-18: CVC Head Office water balance for a 4.6 mm rain event on October 20, 2014
Water Balance for May 30 2015 Storm
Water discharged to
stormwater system (L)
57472.8, 41%
78800.2, 57%
Water collected by
raintank (L)
Water retained by LID (L)
2182, 2%
Figure 3-19: CVC Head Office water balance for a 43.3 mm rain event on May 30, 2015
33
34
4 MAINTENANCE
The stormwater facilities at CVC Head Office are designed to trap debris, sediments and other
stormwater pollutants that will accumulate and will need to be removed periodically through maintenance.
Understanding maintenance needs of these systems is a priority for the program and property owners to
assess if these technologies are feasible from a city wide perspective. Traditional stormwater ponds need
to be maintained as well but there is less monitoring data on these activities, making it unclear in terms of
frequency and extent of maintenance at different intervals.
Long term infrastructure assessment is needed (both quality and quantity performance) to capture when a
decline in performance occurs and how performance is restored once maintenance work has been
completed. Therefore maintenance documentation in concert with long term performance assessment is
required in order to link maintenance activities to changes in performance. Some maintenance
requirements may only be detectable through long term performance.
A maintenance checklist was developed to quantitatively record site conditions and maintenance needs
as accurately as possible. The goal of the checklist format is to make inspections easy and
straightforward for anyone to complete. There is a corresponding legend to accompany the checklist to
give guidance to someone who may not be familiar with LID, such as maintenance and landscaping staff.
The same information is collected each time in the same format, ensuring proper documentation and
making it easier to track changes over time which gives consistency to the monitoring. By reviewing the
checklist data over time you can determine the frequency of maintenance needed for each site and
provide insight into future designs and planning of LID features. Developing a maintenance schedule
based on data gathered at the site, allows for the establishment of maintenance costs, which are
important to the functionality and life cycle of LID and other stormwater features. The maintenance and
inspection checklist can be found in Appendix F.
Several issues were identified from these maintenance checklists. Due to the amount of deciduous trees
surrounding the grass swales, the swales become filled with fallen leaves in the autumn months, which
may decrease infiltration into these swales. Erosion has also been identified in these swales. There is
evidence of clogging in sections of the older permeable pavement lot, which has only been vacuumed
once (in 2012) as of the end of 2015.
In November 2015, infiltration tests were completed for both permeable parking lots (Figure 4-1), using
ASTM method C1781 (ASTM, 2015). The results showed that the newer lot had high infiltration rates,
suggesting that no maintenance is required. The older lot had lower infiltration rates, and the tests
provided further evidence that there are areas of clogging. This indicates the need for maintenance, such
as vacuuming, at the older permeable lot.
While age may be one of the reasons for the poor performance of the older lot relative to the newer lot,
the use of recycled concrete as opposed to standard materials for the base layer may also be a factor.
Vacuuming is being planning for the older lot in 2016, followed by another round of infiltration tests. The
results of the monitoring program before and after this maintenance will be compared. Further
maintenance may be completed based on the requirements of CVC’s application for Mississauga’s
Stormwater Charge Credit Program
35
Figure 4-1: Infiltration test results for both permeable parking lots
Maintenance inspections have also shown that the edging restraints used for the old permeable parking
lot are not providing the necessary support for the pavers in certain sections of the lot. Some spreading of
the pavers at the edge of the lot has been observed. As part of the one-year construction warranty
between the contractor and CVC, the pavers that had moved out of alignment were adjusted by the
contractor. CVC has now taken over management of the parking lot and is monitoring the status of the
pavers for any further issues. These initial issues with the edging restraint were one of the factors
influencing CVC to specify a concrete curb for the expansion lot.
Cleaning of the rainwater storage tank is one of the major maintenance tasks associated with the
rainwater harvesting system. The frequency of tank cleaning for the CVC system could have been
mitigated by installing a screen mesh or “sock”-style filter on the piping conveying rainwater to the tank
from the roof. The use of a pre-storage filter is highly recommended with rainwater harvesting systems as
it prevents large amounts of debris from entering the tank. It also provides other benefits such as
reducing potential wear on the pump and pressure system.
In the summer of 2015, the CVC’s rainwater storage tank was cleaned for the first time in several years.
Sediment and some larger debris had accumulated in the tank (Figure 4-2). It is suspected that the
sediment is largely from the sump pump and the large debris from the roof. This cleaning was done inhouse, using a wet/dry shop-vac and a pressure washer. It took about 2 hours, and required two staff
members. Due to a sump pump failure in the fall of 2015, the tank required additional cleaning. An
outside contractor was used at a cost of about $200 for half a day of work. Moving forward, the use of an
outside contractor is considered preferable to cleaning the tank using CVC staff as it is cleaned much
more thoroughly for a competitive price. Starting in 2016, the raintank is expected to be cleaned in this
manner once per year.
Figure 4-2: Accumulated sediment and debris in the rainwater storage tank
36
37
5 DISCUSSION – MONITORING OBJECTIVE ASSESSMENT
To advance the use of LID designs and practices, CVC has worked with partners and stakeholders to
address their questions about performance, operations, and implementation. Stakeholders identified top
priorities to help maximize the benefits of investments in LID, and provide the data that is needed to
develop long-term solutions for SWM plans. CVC has consulted the expert advisory committee to develop
and implement a robust monitoring program to better understand LID performance and address
information gaps. This list assesses each objective relevant to the monitoring program conducted at CVC
Head Office between 2014 and 2015.
1. Evaluate how a site with multiple LID practices treats stormwater runoff and manages stormwater
quantity as a whole.
 CVC Head Office features permeable pavement along with a rainwater harvesting system.
The site provided volume reduction and peak flow reduction for storm events. The median
volume reduction for all storm events was 70 per cent and the median peak flow reduction
was 81 per cent. The total volume reduction for storms with a depth of 25 mm or less was 67
per cent.
2. Evaluate long-term maintenance needs and maintenance programs and the impact of
 Areas of clogging have been identified on the permeable parking lot. Maintenance of this lot,
including vacuuming, is planned in 2016. Once this has been completed the performance of
the site before and after this maintenance will be compared.
 The rainwater storage tank collects some sediment and debris from the roof and sump
pump, and is expected to be cleaned about once per year for a cost of about $200
3. Determine the life-cycle costs of LID practices.
 This objective was not part of the CVC Head Office monitoring program so was not
evaluated at this location. Please see the Lakeview or Elm Drive reports for additional
information on life-cycle costs of LID practices.
4. Assess the water quality and quantity performance of LID designs in clay or low infiltration soils.
evaluated at this location. Please see the Riverwood report for additional information on the
performance of LID in clay or low-infiltration soils.
5. Evaluate whether the LID SWM systems are providing flood control, erosion control, water
quality, recharge and natural heritage protection per the design standard.
 See Table 5-1 below.
38
Table 5-1: SWM criteria and preliminary observations.
SWM
Criteria
Water
quality
CVC SWM Criteria for New
Development
Level 1 (enhanced) level of
protection (80% TSS removal) as
per the SWM design criteria
At a minimum detain 5 mm.
Erosion
control
Flood
control
For sites with SWM ponds, detain
25 mm for 48 hrs.
Post- to pre-control of peak flows
for the 2- to 100-year design
storms to the appropriate
Watershed Flood Control Criteria.
Observed Performance
CVC Head Office had a total TSS
reduction of 81% over all events. This
exceeds Level 1 (enhanced) protection.
For all events under 25 mm,
representing 90% of precipitation
events annually, the total TSS
reduction was 86%.
While not specifically monitored for
detention rates, CVC Head Office has
achieved a median 81% peak flow
reduction and 70% volume reduction,
therefore allowing the site to mimic a
more natural hydrologic cycle and likely
reduce the impacts of erosion on the
downstream receiving creek.
CVC Head Office has achieved a
median 81% peak flow reduction.
During the monitoring period, there was
insufficient data to compare with the 2and 100- year design storms. A longer
monitoring period is necessary.
6. Assess the potential for groundwater contamination in the short- and long-term.
evaluated at this location. Please see the IMAX or Meadows in the Glen reports for
additional information on the potential for groundwater contamination at LID sites.
7. Assess the performance of LID designs in reducing pollutants that are dissolved or not associated
with suspended solids.
 Nitrate is in a dissolved state and is partly sequestered in the vadose zone and could travel
with the movement of groundwater. Monitoring results show a 32 per cent load reduction for
NO2 + NO3.
8. Demonstrate the degree to which LID mitigates urban thermal impacts on receiving waters.
evaluated at this location. Please see the Elm Drive report for additional information on
thermal benefits of LID.
9. Assess the water quality and quantity performance of LID technologies, which currently do not
receive credits or are only given limited credit in the 2003 MOE SWM Planning and Design
Manual.
 Permeable/porous pavement is not eligible for credit towards the water quality criteria as
shown in Table 3.2 of the 2003 MOE SWM Planning and Design Manual. Based on the
findings during the monitoring period the LID at CVC Head Office provides a median 81 per
cent peak flow reduction and a median 70 per cent volume reduction over all events. The
overall TSS reduction was 81 per cent. However, LID benefits for peak flow reduction are
39
often overlooked. The sizing of SWM features downstream will need to take this into
account, as these reductions minimize pressure on stormwater infrastructure.
10. Evaluate how SWM ponds perform with LID upstream. Can the wet pond component be reduced
or eliminated by meeting erosion and water quality objectives with LID?
 While this objective was not part of the CVC Head Office monitoring program, this site
demonstrates water quality control of about 81 per cent TSS removal, achieving the Level 1
enhanced water quality objective of 80 per cent TSS removal
11. Assess the potential for soil contamination for practices that infiltrate.
evaluated at this location. Please see the Elm Drive and Riverwood reports for additional
information on the potential for soil contamination for practices that infiltrate.
12. Evaluate effectiveness of soil amendments and increased topsoil depth for water balance and
long-term reliability.
evaluated at this location.
13. Evaluate and refine construction methods and practices for LID projects.
 Photo logs of construction activities were taken as the LID was installed, and ongoing
inspections and maintenance is occurring.
 Initial evidence that the edging restraints are not providing the necessary support for the
pavers in certain sections of the lot. Some spreading of the pavers at the edge of the lot was
observed. As part of the one-year construction warranty between the contractor and CVC,
the pavers that had moved out of alignment were adjusted by the contractor. CVC has now
taken over management of the parking lot and is monitoring the status of the pavers for any
further issues. These initial issues with the edging restraint were one of the factors
influencing CVC to specify a concrete curb for the expansion lot constructed approximately
one year after the first lot.
 The frequency of tank cleaning for the CVC rainwater harvesting system (approximately
once per year) could have been mitigated by installing a screen mesh or “sock”-style filter on
the piping conveying rainwater to the tank from the roof. The use of a pre-storage filter is
highly recommended with RWH systems as it prevents large amounts of debris from
entering the tank. It also provides other benefits such as reducing potential wear on the
pump and pressure system.
 Infiltration testing completed on both permeable lots indicate that the older lot has much
slower infiltration rates. This may be due to the use of locally sourced bedding materials to
achieve LEED certification.
14. Develop and calibrate EMCs for various land uses and pollutants.
 Influent runoff sampling must be collected from numerous sites to develop robust land-use
EMCs. The effluent characteristics of CVC Head Office are being compared to land-use
EMCs developed through the NSQD. To date, the NSQD land-use EMC data is providing a
valuable reference and its use is recommended for future studies. EMC values have been
developed for several parameters listed in Error! Reference source not found. based on the
2014 to 2015 water quality data.
15. Assess performance of measures to determine potential rebates on development charges, credits
on municipal stormwater rates and/or reductions in flood insurance premiums.
 CVC is currently developing an application for the Mississauga stormwater charge credit
program. These monitoring results may be used to assist in the application process.


40
The water quality monitoring indicates that the older parking lot is achieving 81 per cent TSS
reduction, qualifying it for a credit for the water quality category
As the LID is located at CVC’s Head Office, it acts a demonstration site for examples of LID
that can be eligible for the Mississauga stormwater charge credit program
16. Assess the ancillary benefits, or non-SWM benefits.
 CVC’s rainwater harvesting system has led to a total reclaimed water usage of over 400 000
L, reducing strain on municipal water supplies. Up to 32 per cent of CVC’s monthly water
usage has been reclaimed water.
 As the LID is located at CVC’s Head Office, it has allowed for various education and
community learning opportunities for municipal representatives or members of the public
visiting CVC.
 Refer to CVC’s Grey to Green Road Retrofits: Business and Multi-Residential Properties
(CVC, 2014) for more indirect benefits, such as a healthier and safer work environment.
17. Assess the potential for groundwater mounding in localized areas.
evaluated at this location.
18. Improve and refine the designs for individual LID practices.
 LID landscapes should conform to typical urban landscaping principles, unlike stormwater
ponds or stream restorations which follow natural landscaping approaches. There are many
options for design depending on the LID practice. It is important to determine the right
design for the right location. The performance results from this location can help to inform
future permeable pavement and rainwater harvesting system designs.
 Refer to CVC’s Landscape Design Guide for Low Impact Development for a complete
discussion of landscaping principles for successful LID design.
19. Assess the overall performance of LID technologies under winter conditions.
evaluated at this location. Please refer for the Elm Drive and IMAX reports for additional
information on winter performance of LID.
41
6 SUMMARY OF OBSERVATIONS
These findings focus on the short-term performance assessment of LID at CVC Head Office. Discussed
below is a summary of findings from the assessment conducted during the monitoring period from July
2014 to September 2015.
6.1
Water Quantity
The precipitation events captured at CVC Head Office matched well with the event frequency distribution
published for the Toronto region (Figure 3-2), with the exception of events from 2 to 5 mm and 5 to 10
mm. Among all events captured during the monitoring period (Appendix D), 87 per cent were a depth
less than 25 mm, indicating that the preliminary conditions at CVC Head Office are representative of the
GTA.
CVC’s design priorities are to manage water quantity and enhance water quality. For water quantity, the
performance of CVC Head Office is as follows:
•
•
•
•
•
6.2
The median runoff reduction for all hydrologic events observed during the monitoring period was
70 per cent (Table 3-3).
Storm events with depths < 25 mm were attenuated with 67 per cent volume reduction
During the monitoring period, the median peak flow reduction was found to be 81 per cent
(Table 3-3)
While CVC Head Office was not designed for flood mitigation, estimated inflow and measured
outflow show considerable reduction in peak flow.
Volume reduction decreases with total precipitation depth and/or peak precipitation intensity
Water Quality
The performance results have demonstrated that the LID at CVC Head Office is providing water quality
benefits:
•
•
•
•
6.3
When stormwater effluent was discharged from CVC Head Office during rain events, it achieved
about 81 per cent TSS load reduction (Table 3-6).
The CVC Head Office LID site performs well for events of 25 mm and under, with an 86 per cent
TSS reduction and a reduction of at least 74 per cent for the other parameters aside from NO2 +
NO3. These events constitute 90 per cent of all precipitation events in Ontario.
Nutrient loadings from stormwater runoff are a concern as they feed algae growth which can in
turn lead to beach closures. TP and nitrate are typical nutrients that are monitored to assess the
effectiveness of stormwater practices to reduce algae growth. The performance assessment at
CVC Head Office showed a total of 69 per cent load reduction in TP and a 32 per cent load
reduction in NO2 + NO3 over the monitored period.
The CVC Head Office median effluent EMCs are either lower or within the range of values PO4,
Fe, TKN, Ni, and TP when compared to five other BMP types within the same EPA rainfall zone
(Zone 1) (Table 3-9) from the BMPDB, including bioretention, detention basins, manufactured
devices, retention pond and wetland channel
Rainwater Harvesting System
•
•
The total reclaimed water usage from August 2013 to December 2015 was 400 000 L
The reclaimed water usage represented 26 per cent of CVC’s total water usage during the
months the raintank was online
42
7 REFERENCES
ASTM, 2015. ASTM C1781 / C1781M-15, Standard Test Method for Surface Infiltration Rate of
Permeable Unit Pavement Systems, ASTM International, West Conshohocken, PA
AECOM, 2013. City of Mississauga Stormwater Financing Study.
http://www.mississauga.ca/portal/residents/stormwaterfinancingstudy Retrieved February 12,
2016
Canadian Construction Association (CCA), Canadian Public Works Association, Canadian Society for
Civil Engineers and Federation of Canadian Municipalities. 2012. Municipal Roads and Water
System. Volume 1. ISBN 978-1-897150-45-0
Canadian Council of Ministers of the Environment (CCME). 2015. Canadian Environmental Quality
Guidelines. http://ceqg-rcqe.ccme.ca/en/index.html#void
City of Mississauga, 2015. Stormwater Charge Credit Application Guidance Manual.
http://www7.mississauga.ca/Departments/Marketing/stormwater/stormwatercharge/img/stormwater-credits-manual-0.1.pdf Retrieved February 12, 2016
Cook, D.J. and Dickinson, W.T. 1986. “The Impact of Urbanization on the Hydrologic Response of a
Small Ontario Watershed.” Canadian Journal of Civil Engineering, 13: 620-630.
Credit Valley Conservation (CVC). 2009. Water Quality Strategy. http://www.creditvalleyca.ca/wpcontent/uploads/2011/07/Final-PII-WQSModelingReport.pdf
Credit Valley Conservation (CVC). and Toronto and Region Conservation Authority (TRCA). 2011. Low
impact development stormwater management planning and design guide. Version 1.0.1.
http://www.creditvalleyca.ca/low-impact-development/low-impact-developmentsupport/stormwater-management-lid-guidance-documents/low-impact-development-stormwatermanagement-planning-and-design-guide/
Credit Valley Conservation (CVC). 2012. Stormwater Management Criteria.
http://www.creditvalleyca.ca/wp-content/uploads/2012/09/CVC-SWM-Criteria-AppendicesAugust-2012.pdf
Credit Valley Conservation (CVC). 2014. Grey to Green Business & Multi-Residential Retrofits: Optimizing
Your Bottom Line through Low Impact Development. http://www.creditvalleyca.ca/wpcontent/uploads/2015/01/Grey-to-Green-Business-and-Multiresidential-Guide1.pdf
EBNFLO Environmental and AquaResource Inc. (2010). Guide for Assessment of Hydrologic Effects of
Climate Change in Ontario. Prepared for The Ontario Ministry of Natural Resources and Ministry
of the Environment in partnership with Credit Valley Conservation
Federal Interagency Stream Restoration Working Group (FISRWG). 1998. Stream Corridor Restoration:
Principles, Processes, and Practices. PB98-158348LUW.
Federation of Canadian Municipalities (FCM). 2007. Danger Ahead: The Coming Collapse of Canada’s
Municipal Infrastructure.
Insurance Bureau of Canada (IBC). 2012a. Water Damage is on the Rise: Are you Protected?
http://www.ibc.ca/en/home_insurance/documents/brochures/water_damage_on_rise_en_web.pdf
Insurance Bureau of Canada (IBC). 2012b. Factsheet: Water Damage is on the Rise: Are you Protected?
43
Insurance Bureau of Canada (IBC). 2014. FACTS of the Property and Casualty Insurance Industry. 36th
edition, ISSN 1197 3404.
International Stormwater Best Management Practices Database (BMPDB). 2011. Technical Summary:
Volume Reduction.
http://bmpdatabase.org/Docs/Volume%20Reduction%20Technical%20Summary%20Jan%20201
1.pdf
International Stormwater Best Management Practices Database (BMPDB). Retrieved on Mar 15, 2015:
http://www.bmpdatabase.org/index.htm
Intergovernmental Panel on Climate Change (IPCC). 2014: Climate Change 2014: Synthesis Report.
Contribution of Working Groups I, II and III to the Fifth Assessment Report of the
Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer
(eds.)]. IPCC, Geneva, Switzerland, 151 pp.
Ontario Ministry of Environment (MOE). 1999. Water Management Policies, Guidelines, Provincial Water
Quality Objectives of the Ministry of the Environment. July 1994, Reprinted: Feb 1999.
http://www.ene.gov.on.ca/stdprodconsume/groups/lr/@ene/@resources/documents/resource/std
01_079681.pdf
Ontario Ministry of Infrastructure (MEDEI). 2015. Building Together: Jobs and Prosperity for Ontarians.
Executive Summary. Retrieved on January 2015:
http://www.moi.gov.on.ca/en/infrastructure/building_together/summary.asp
Personal Communication with Harold Reinthaler, Partner, Schaeffers & Associates, Ltd., Concord,
Ontario. October 2012
Prince George’s Country, Maryland Department of Environmental Resources Programs and Planning
Division. 1999. Low-Impact Development Hydrologic Analysis.
Royal Bank of Canada (RBC). 2015. RBC Canadian Water Attitudes Webinar: A Discussion with
stakeholders. March 25, 2015. Lynn Patterson, Chris Coulter and Bob Sandford.
Schueler, T. 1987. Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban
BMPs. Metropolitan Washington Council of Governments, Washington, DC.
Schueler, T. 1995. Environmental Land Planning Series: Site Planning for Urban Stream Protection.
Prepared by the Metropolitan Washington Council of Governments and the Center for Watershed
Protection, Silver Spring, Maryland.
Toronto and Region Conservation Authority (TRCA). 2013. Toronto and Region Watersheds Report Card
2013. http://trca.on.ca/dotAsset/157180.pdf
United States Geological Survey (USGS). 2008. A Comparison of Runoff Quantity and Quality from Two
Small Basins Undergoing Implementation of Conventional and Low-Impact-Development (LID)
Strategies: Cross Plains, Wisconsin, Water Years 1999–2005.
http://pubs.usgs.gov/sir/2008/5008/pdf/sir_2008-5008.pdf.
Workplace Safety and Insurance Board (WSIB). 2011. High-impact claims. Fact Sheet.
http://www.wsib.on.ca/files/Content/FactSheetEnglishHigh-impactclaims0921A/0921A.pdf
LOW IMPACT DEVELOPMENT INFRASTRUCTURE
PERFORMANCE AND RISK MANAGEMENT ASSESSMENT
Appendix A
Monitoring Plan
NOTICE
FINAL REPORT
CVC Head Office Monitoring Plan – Work Strategy Plan v2.1
Credit Valley Conservation Head Office Monitoring Plan Executive Summary: Monitoring of a Low
Impact Green Office Building
_____________________________________________________________________________________
BACKGROUND
Municipalities across Canada are struggling to address a number of issues surrounding stormwater
management; from aging infrastructure to insufficient stormwater management. To prevent the
degradation of receiving streams and the Great Lakes, and damage to property and infrastructure from
erosion and flooding, innovative stormwater management techniques and technologies will need to be
implemented.
The purpose of the study is to evaluate the effectiveness of a rainwater harvesting system, permeable
paving, and bioswales, with respect to: reducing stormwater effluent volume, reducing total loadings of
parameters of concern, and reducing the use of municipally treated water. This project will help
educate urban municipalities on how to balance growth, redevelopment, stormwater infrastructure, and
the environment in light of climate change; providing a template that municipalities can employ to costeffectively address environmental and development issues.
PROJECT OBJECTIVES
1.
“Innovative” stormwater management demonstration site:
This treatment approach is “above and beyond” the standard practices in place pertaining to
stormwater management in Ontario, using a rainwater harvesting system, permeable
pavement, and bioretention trenches as source control for treatment and management.
This project will also add much needed performance data to support design initiatives of
such practices.
2.
To support initiatives such as source protection and municipal stormwater management in
light of climate change.
3.
Template for Municipalities Across Ontario:
Comprehensive effectiveness monitoring of performance data will be conducted to provide
municipalities across Ontario with a template for LID implementation.
PROJECT SCHEDULE
1.
2.
Initiation of Environmental Monitoring – Summer 2013
End of Project – Late Fall 2021
1
CVC Head Office Monitoring
Work Strategy Plan
1.0
PURPOSE & OBJECTIVES
2.0
BACKGROUND
3.0
LID INITIATIVES
4.0
STUDY AREA
5.0
MONITORING SITE
6.0
WORK PLAN
7.0
DATA MANAGEMENT & ANALYSIS
8.0
REPORTING
9.0
INTENTIONS TO PUBLISH
10.0
COSTING
11.0
ADAPTIVE PROGRAM
12.0
REFERENCES
1
1. Monitoring Purpose and Objectives
The purpose of the study is to evaluate the overall stormwater runoff reductions and pollutant removals
for a typical office building and parking lot when multiple Low Impact Development (LID) practices are
employed.
The following monitoring objectives are based on the nineteen objectives identified for CVC’s overall
stormwater management program and are relevant for CVC’s Head Office site:
1.
Evaluate how a site with multiple LID practices treats stormwater runoff and manages
stormwater quantity as a whole.
2.
Evaluate long-term maintenance needs and maintenance programs, and the impact of
5.
Evaluate whether LID SWM systems are providing flood control, erosion control, water quality,
recharge, and natural heritage protection per the design standard.
9.
13.
14.
Develop and calibrate event mean concentrations (EMCs) for various land uses and pollutants.
15.
Assess performance of measures to determine potential rebates on development charges,
credits on municipal stormwater rates and/or reductions in flood insurance premiums (i.e. can
LID reduce infrastructure demand?).
16.
18.
Improve and refine the designs for individual LID practices.
This monitoring plan is based on the protocols and practices being used in other CVC monitoring
programs.
2. Background
Our communities are supported by functions provided by our environment such as abundant, safe
drinking water, and clean air. Studies conducted on the Credit River Watershed have found that we
need to integrate how we build our communities with how we manage our stormwater to support a
sustainable environment. This is known as Low Impact Development (LID). The design of the new CVC
head office building includes LID measures such as a rainwater harvesting system and a permeable
pavement parking lot with perimeter grass swales, which will help to reduce the buildings
environmental impact.
LID attempts to mimic natural processes by reducing surface runoff and increasing infiltration.
Therefore, its performance depends on local conditions including, climate, soils, and drainage.
2
Individual LID measures should be examined with respect to basic hydrological cycle components:
evapotranspiration, infiltration, and runoff. Stormwater infiltration occurs on natural soils with pervious
cover and at special facilities (bioretention and swales) located throughout the catchment area. At the
CVC Head Office site, it is expected that infiltration will occur in the permeable parking lot and the grass
swale areas. Long-term sustainable infiltration depends on soil cover, soils, hydrology, risk of clogging of
infiltration sites, and infiltration facility maintenance. Mimicking a natural water balance also supports
the enhancement of runoff quality and ecological integrity in receiving streams (J. Marsalek and Q.
Rochfort 2008). CVC will assess if the LID practices put in place provide runoff control, improved water
quality, and increased groundwater recharge leading to more natural site hydrology and water quality
when compared to conventional stormwater management practices.
This monitoring project can act as a model to other sites contemplating LID stormwater management
ideas and a point of comparison to other locations with similar systems already in place.
3. LID Initiatives
The most commonly used method of stormwater conveyance from streets in urban areas is curb and
gutter. With this method, storm water is quickly brought to receiving watercourses in underground
pipes. Very little of the water therefore soaks into the ground to be naturally filtered before it reaches
these watercourses. This can lead to a number of problems in local streams including flash flooding, a
decline water quality, and a reduction of stream baseflow and groundwater levels.
Through a combination of swale drainage and permeable paving stones, outlined in table 1, the
hydrology and water quality leaving the CVC Head Office site will be improved over conventional
stormwater practices.
Table 1: Swale and LID practices located at the CVC head office
LID Practice
Picture
Swale drainage can reduce pollutant
and sediment concentrations, and
can have significant reduction time of
flow to local creeks and storm drain
systems. Open drainage also has the
ability to reduce mosquito breeding
areas through the reduction of areas
with standing water.
3
Permeable Paving Stones increase
stormwater infiltration by allowing
water to soak into the joints between
the paving stones and into the
ground.
Rainwater Harvesting Systems can
reduce rooftop runoff as rainwater is
collected by roof downspouts and
directed to a cistern. At the CVC
building, water collected in the
cistern will be used for flushing
toilets and landscape watering.
4. Study Area
The subject site for the study is located in the City of Mississauga, within the Credit River Watershed,
and drain directly to the Credit River (Figure 1). The surrounding area is primarily residential with
pockets of agricultural and natural areas. A catchbasin has been installed in a location after the
permeable parking lot and the perimeter swales underdrains come together and leave the site providing
a location that will be ideal for installing monitoring equipment located. Since the monitoring station
will drain an area of 4469m2, 33% of which is impervious, it will be possible to calculate a water balance
by equipping it with monitoring equipment to measure flow and take water samples during rainfall
events. A rain gauge is located on top of the CVC Office Building to provide precipitation data.
4
Study
Area
Figure 1: Study area located in the Credit River Watershed
5
Figure 2: Areal View of Project Area
6
Figure 3: New CVC Office Building
5. Monitoring Site
Existing site plans were reviewed followed by a site walk to gain an understanding of the existing
drainage system for the study area. One monitoring station is proposed to monitoring stormwater
leaving the site, located in the southernmost grass swale and shown on Figure 2.
6. Work Plan
6.1
Instrumentation
A site visit was conducted to review the existing drainage infrastructure and assess suitable
types of equipment for the monitoring program.
The equipment located in the catchbasin is as follows:





Isco 6712 sampler
Isco 2150 area velocity flow meter
Hobo UA-002-64K temperature logger
Hobo U20 level logger located in the perimeter grass swale to determine the
presence of overland flow contributing to outflow
Steel box for secure onsite equipment storage
The equipment located for the rainwater harvesting system is proposed as follows:
7



Hobo U20 level logger located in the rainwater storage tank to measure water
depth
Water meter located on the outflow pipe from the tank to calculate water
outflow
OM-CP-PULSE101A pulse loggers located on the water meter to log outflow
from and municipal water top-up to the rainwater harvesting system
All equipment, except the OM-CP-PULSE101A pulse loggers, will be set to log every 10 minutes.
The pulse loggers will log every hour. Data will be stored in the logger’s memory and
downloaded in person biweekly as a minimum using ISCO Flowlink 5, Hoboware, and OMEGA
software. The software will automatically summarize and plot the data together graphically,
which can then easily be exported to a program like Microsoft Excel.
The site will be visited at a minimum of every two weeks to check battery power, inspect
equipment, and make sure everything is operational.
6.2
Hydrology
A compound weir is installed in the monitoring catchbasin to ensure accurate level and flow
measurements. An area velocity level and flow meter is installed and set to record water level
and flow at 10-minute intervals. The rain gauge currently installed on the roof of the CVC office
building will supply precipitation data. In addition, a water level meter located in the rainwater
storage tank will be used to calculate water inflow, a water meter located on the outflow pipe
from the tank will calculate water outflow, and a pressure transducer is located in the rainwater
storage tank will measure rainwater level. This data will help determine how much roof runoff is
diverted from the stormwater infrastructure and repurposed for use in toilets and irrigation.
Figure 7: Monitoring station in the catchbasin
8
6.3
Water Quality
A minimum of five (5) precipitation events will be sampled per year from the monitoring
catchbasin with the Isco Auto sampler. A wet event will be defined as any rainfall event greater
than 2 mm or snowfall event greater than 5 cm. In addition, five (5) samples will be collected
from the rainwater harvesting system during various conditions through out the first year of the
monitoring program.
Samples will be analysed for:
 Chloride
 Conductivity
 pH
 Total Suspended Solids (TSS)
 Nutrients:
o Total Phosphorus
o Orthophosphate
o Total Ammonia
o Nitrate & Nitrite
 Metals
 PAH (only in the first year of sampling)
The sampler holds twenty-four (24) one (1) litre bottles. Event sampling will be conducted as
follows:
 One (1) sample will be submitted per monitoring station per event.
 The 24 bottles will then be filled 500 mL every 20 minutes. Therefore, 1 bottle will
be filled every 40 minutes and the program will last for 16 hours. The timing may be
changed to 500 mL every 10, 30 or 40 minutes based on the forecasted event.
 Using the flow data, water from the ISCO bottles will then be mixed into 1 flow
weighted composite sample at the time of collection.
 Samples will be brought to an accredited Canadian Laboratory such as the MOE
Laboratory Services Branch in Etobicoke for laboratory analysis.
9
Figure 8: Data logger and autosampler used at HO-1
7. Data Management & Analysis
CVC will manage water level, water usage, water flow, and water quality data sets, and provide data
analysis for the study. Water quantity and quality data will be organised into hydrological events so that
analysis can be performed on an event by event basis. Table 2 summarises the conditions which define
the beginning and end of a hydrological event. Parameters which will be calculated for each hydrological
event are outlined in Table 3. Flow weighted composite water quality samples will provide event-mean
concentrations (EMC) for parameters of interest and continuously monitored water quality parameters,
like temperature, can be processed to calculate event mean temperature (EMT). A hydrologic summary
will be prepared for each event and a water quality summary will be prepared for each sampled event.
Table 2: Defining hydrological events
Event Type
Beginning
Precipitation
Precipitation observed
Thaw
Outflow observed, no
precipitation observed
End
Outflow from monitoring site
returns to baseflow for a period
of 6 hours
Outflow from monitoring site
returns to baseflow for a period
10
No outflow
Precipitation observed, outflow
does not exceed baseflow
Table 3: Hydrologic and water quality parameters
Precipitation
Outflow
 Event type
 Presence/absence of
outflow
 Precipitation
depth
 Outflow volume
 Antecedent dry
 Peak flow rate
period
 Duration
 Duration
 Intensity
of 6 hours
No precipitation observed for a
period of 6 hours
Hydrologic evaluation
 Volume reduction
(using simple
method to calculate
inflow)
 Peak flow reduction
 Lag time
Water quality
Composite samples:
 EMC
 Pollutant loads
Continuously
monitored:
 Temperature
Table 4: How objectives will be monitored
Objective How objective will be monitored
1.
 Precipitation data collection and outflow data collection.
 The precipitation data will be used to calculate a total volume of water that is entering
the site; this is determined by the total precipitation depth and drainage area.
 The outflow data will be calculated using continuous water level measurements and a
rating curve created for the installed weir.
 The total volume of water entering the site will then be compared to the total volume of
water leaving the site giving a total volume reduction.
2.
 Performing site inspections on an ongoing basis along with logging the timing and details
of maintenance activities will provide data to evaluate long term maintenance needs of
LID systems.
 Periodic infiltration testing of the paver surface can be used to determine the rate of
clogging and to evaluate the effectiveness of maintenance activities.
 Performance data, such as discharge quantity and quality, will be compared to
maintenance schedules and actions to determine the impact of maintenance on
performance.
5.
 The CVC head office is not designed for flood control, however, the total volume of
reductions can be used to help evaluate whether the LID SWM system is reducing surface
runoff thus providing flood control.
 Calculating peak flow reductions will assist in this evaluation as well as be used to
evaluate erosion control.
 The water quality of the of the LID’s discharge will be evaluated by collecting flow
weighted water samples using an autosampler providing EMCs of targeted water quality
parameters. The water quality results will be compared to typical EMCs from similar land
uses to determine if the LID system provides an improvement in water quality.
 Load reductions of selected water quality parameters will be calculated
9.
 The water quality and quantity performance will be assessed through collecting water
samples from precipitation events and through the collection of discharge data
respectively.
11
 Water quality and quantity results from the CVC head office site will be compared to EMC
data available in literature to assess the performance of the LID technology
 The total volume of water entering the site will then be compared to the total volume of
water leaving the site giving a total volume reduction.
 The reduction in volume will quantify reduction in demand on stormwater management
infrastructure allowing for potential rebates on development charges, credits on
municipal stormwater rates and reductions in flood insurance premiums.
 Creating photo logs of construction activities while construction is taking place
performing site inspections after the construction is completed will help evaluate and
refine construction methods and practices for LID projects.
 Collecting flow weighted composite samples will provide EMCs from precipitation events
of different sizes and intensities will help develop and calibrate EMCs of pollutants for
commercial and institutional land uses.
 Monitoring the amount of water saved, through the use of a rainwater harvesting
system, will help assess the non-SWM benefits of LID
 The amount of water that is harvested and used through the use of a rainwater
harvesting system is the amount of treated water that is not used reducing the amount
of money spent on utilities.
 The completion of site inspections and through observations taken during rain events.
 These activities will demonstrate how the LID system works at managing stormwater as
well as highlight any deficiencies either in the construction or the design. This will allow
for improvements on LID systems to better capture and treat stormwater.
10.
13.
14.
16.
18.
1.
2.
5.
9.
13.
14.
15.
16.
18.
Evaluate how a site with multiple LID practices treats stormwater runoff and manages stormwater quantity as a
whole.
Evaluate long-term maintenance needs and maintenance programs, and the impact of maintenance on performance.
Evaluate whether LID SWM systems are providing flood control, erosion control, water quality, recharge, and natural
heritage protection per the design standard.
Develop and calibrate event mean concentrations (EMCs) for various land uses and pollutants.
Assess performance of measures to determine potential rebates on development charges, credits on municipal
stormwater rates and/or reductions in flood insurance premiums (i.e. can LID reduce infrastructure demand?).
Improve and refine the designs for individual LID practices
8. Reporting
CVC will develop a draft report outline, author a draft report, and submit a final report detailing the
entire study and results. CVC will also develop interpretive signage to be erected at the study site. CVC
will develop a public information strategy and identify information to communicate to the public.
9. Intentions to Publish
While the study is underway, information collected is confidential and not to be shared with personnel
outside the study team. Once the monitoring data has undergone a thorough internal review, the
intention is for the information to enter into the public domain.
10. Costing
12
A table outlining monitoring costs for the research project is summarized in appendix 1.
The cost estimate provides the following breakdown:

Cost to purchase equipment;

Cost of equipment installation;

Cost to trigger samplers and collect samples;

Cost of monthly data acquisition, equipment maintenance and calibration;

Cost of laboratory analysis.

Cost of data analysis and reporting

Cost of staff time
These costs are based on hiring a consultant to install the equipment. Since some of the equipment will
be installed within the catchbasins, personnel certified in confined space entry will be required. In
addition, staff may need to trigger and collect samples outside of typical business hours as precipitation
events may occur during evenings and weekends.
11. Adaptive Program
The program is intended to be adaptive in nature, implying that the program will be continually
reviewed and changes may be made to the sampling protocols, methods, and locations as needed. Data
will need to be collected for multiple years in order to make accurate conclusions about the site’s
performance. The program will continue until enough data is collected to make conclusions based on
the monitoring objectives.
12. References
CVC (Credit Valley Conservation Authority). (2008). Cooksville Creek Watershed Study and Impact
Monitoring: Background Report Draft. Not Published.
CVC (Credit Valley Conservation Authority). (2009). Cooksville Creek Watershed Study and Impact
Monitoring: Characterization Report. Not Published.
J. Marsalek and Q. Rochfort. 2008. Observations on Monitoring the LID Project “Meadows in the Glen”.
Memo to Credit Valley Conservation & Intercorp.
13
Appendix B
Infrastructure Performance
and Risk Assessment Protocol
NOTICE
FINAL REPORT
APPENDIX B: Infrastructure Performance and Risk Assessment Protocol
INFRASTRUCTURE PERFORMANCE AND RISK ASSESSMENT
PROTOCOL
This section of the document presents the monitoring protocol prepared by CVC. The section also
includes information relevant to potential monitoring refinements on the site. This section of the report will
evolve as monitoring methods are refined.
1.1
Hydrology
An ISCO 2150 area velocity level and flow module was installed in an overflow catch basin with the probe
secured to the bottom of the outlet pipe to ensure accurate water level measurements. The flow meter
records water levels at 10-minute intervals. The monitoring station is equipped with an ISCO 6712
automatic sampler for collection of water quality samples. The automatic sampler is set to trigger based
on levels measured at the monitoring station.
A rain gauge maintained by the City of Mississauga is installed on the roof of CVC’s Head Office to
provide precipitation data. An additional rain gauge maintained by CVC was installed at the monitoring
location HO-1 on August 19, 2015 to be used as a backup. A precipitation event is considered to occur
when 2 mm or more precipitation is recorded. If more than 6 hours elapse between precipitation and/or
flow events, they are considered to be separate events.
1.2
Surface Water Quality
CVC’s surface water quality sampling goal is to sample a minimum of five precipitation events per year
from the monitoring location with an ISCO 6712 automatic sampler. The sampler is connected to the flow
logger and triggers when the logger records a predetermined level.
The automatic sampler is programmed to collect samples that allows for a composite sample to be
compiled for water quality analysis for each event at the outflow monitoring station. The sampler holds 24
1-litre bottles. When the sampler is triggered, all bottles are filled provided there is sufficient runoff.
Bottles that are sampled while outflow was observed are used to generate a flow-weighted composite
sample. The sampler is programmed to collect samples at a fixed time interval. The length of time
between when the bottle is filled was lengthened or reduced depending on the event forecasted. This
either shortened or lengthened the sampling program in order to provide a flow-weighted composite
sample that is representative of the event and that provided adequate sample volume to perform
laboratory analyses. CVC has developed program lengths of 8, 16, 24, and 32 hours, with associated
sample collection intervals of 10, 20, 30, and 40 minutes, respectively. Depending on the expected
duration of the storm event forecasted, the program length is adjusted to collect samples over the entire
storm hydrograph. Once the sample program is completed, CVC staff downloads the data and creates a
flow-weighted composite sample for EMC and load analysis.
Samples are analyzed for:
•
Chloride
•
Turbidity
•
Conductivity
•
pH
•
•
Nutrients:

Total Phosphorus

Orthophosphate
© Credit Valley Conservation 2016 – Watershed Knowledge

Total Kjehldahl Nitrogen (TKN)

Total Ammonia

Nitrate & Nitrite
•
Total Metals (Cadmium, Chromium, Copper, Iron, Lead, Nickel and Zinc)
•
Polycyclic Aromatic Hydrocarbons (PAH’s)
Figure 1-1: Typical sampling turbidity at a curb and
gutter site
Figure 1-2:Typical sampling turbidity at Riverwood
All water quality samples were taken to the Ministry of Environment and Climate Change lab, for analysis.
Table 1-1 summarizes water quality parameters and associated analytical methods.
1
Table 1-1: Quality parameters of interest and MOECC method number
3
Water Quality Parameter
Units
MOECC Method Number
Total Cadmium (Cd)
ug/L
E3497
Total Copper (Cu)
ug/L
E3497
Total Iron (Fe)
ug/L
E3497
Total Lead (Pb)
ug/L
E3497
Total Nickel (Ni)
ug/L
E3497
Total Zinc (Zn)
ug/L
E3497
Dissolved Chloride (Cl)
mg/L
E3016A
Nitrate (NO 3 )
mg/L
E3364A
Nitrate + Nitrite (NO 3 + (NO 2 )
mg/L
E3364A
Total Kjeldahl Nitrogen (TKN)
mg/L
E3364A
Orthophosphate (PO 4 )
mg/L
E3364A
Total Phosphorus (TP)
mg/L
E3516
mg/L
E3188B
1 The water quality parameters listed are recommended parameters of interest; CVC has performed a broad screening of over 27 parameters.
2 Monitoring of parameter may not be feasible using automated sampling and/or composite sampling techniques due to hold time constraints
3 Method numbers are dated to time of lab analysis (2015)
1.3
Rainwater Harvesting System
Continuous water level and usage information is collected for the rainwater harvesting system. An Onset
HOBO U20 level logger is installed in the cistern to monitor level, along one is installed at the top of the
cistern, above the overflow level, for barometric compensation. Omega OM-CP-PULSE101A pulse
loggers are installed at both the outlet of the cistern and the municipal “top-up” inlet. These record a pulse
3
for every time 0.01 m of water, and are used to determine recycled water usage.
1.4
Site Visits
CVC staff visits the site at least once every other week to check battery power, inspect equipment, and
make sure the site is operating properly. Data is downloaded in person from each piece of equipment biweekly or more frequently using ISCO Flowlink 5 software or equivalent. The software automatically
summarized and plotted the data graphically, which was easily exported to a program like Microsoft
Excel. During site visits, CVC staff also noted any changes that have occurred on the site and any
equipment adjustments/maintenance.
Appendix C
Data Management and
Analytical Methodology
NOTICE
FINAL REPORT
APPENDIX C: Data Management and Analytical Methodology
DATA MANAGEMENT AND ANALYTICAL METHODOLOGY
CVC compiled monitoring data consisting of water level, flow and water quality at CVC Head Office. The
processes for the collection of water level, flow, precipitation and water quality data is laid out in
Appendix B. Provided here is a description on the data management and analysis activities for this site.
Analyses for this site summarize available performance data and compare these data to other applicable
BMP performance data sources. These analyses summarize the water quantity and quality effectiveness
of the implemented BMPs, which can be used to guide CVC decision-making processes with respect to
stormwater management and LID design.
1.1
Data Management
The collected site data include time series of precipitation and flow and composite water quality sample
data. Data management includes initial processing and organizing, including identifying the site and
reference input data to be analyzed and organization of the site data for event-based analysis.
1.1.1
Input Data Processing
The data analyses were completed with the CVC Head Office monitoring data set collected by CVC.
Hydrologic and water quality data dates from July 2014 - September 2015.
Reference data included the following data sources:
1.1.2
•
National Stormwater Quality Database (NSQD)
•
International Stormwater BMP Database (BMPDB)
•
Ontario Provincial Water Quality Objectives (PWQO) or Canadian Councils of Ministers of the
Environment (CCME) Canadian Water Quality Guidelines for the Protection of Aquatic Life,
whichever is more restrictive.
Input Data Organization
The flow and precipitation data were divided into hydrologic events associated with the collected water
quality samples to provide meaningful, event-based analyses. Hydrologic events were defined using the
time series of both flow and precipitation as defined in Table 1-1.
Table 1-1: Hydrologic Event Definition for CVC Data Analyses
Event Type
Hydrologic Event
1.2
Beginning
Precipitation > 2 mm
End
Stormflow and Precipitation = 0 for 6 consecutive hours
Data Analysis
Data analysis involved identifying appropriate evaluation and presentation (graphical) methods, and the
data analysis tools and work flow as described in the following sections.
1.2.1
Data Analysis Evaluation Methods
The CVC Head Office site was evaluated using event-based analysis, with the event defined as
previously indicated in Table 1-1. The site was evaluated for both water quantity and water quality
performance. The site was not monitored for inflow; it receives inflow as sheet flow and interflow from the
permeable pavement and swales, making it difficult to measure inflow directly. Because of this, the
1
Simple Method was selected to estimate influent volume as a product of a calculated runoff coefficient,
the drainage area, and the event precipitation. Estimated influent volume was compared to actual effluent
volume to evaluate BMP estimated volume reduction. It is recommended that this method for calculating
2
runoff could be improved through the development of a calibrated SWMM model . Substantial existing
flow and rainfall monitoring data could be used to calibrate and verify a hydrologic model.
Simple Method
The standard method for evaluating stormwater BMPs is to compare untreated inflows to treated
outflows. This method is used in comparing both water quality and quantity parameters such as volume
reduction, peak flow or contaminate loading. Using water quality and quantity monitoring equipment can
be useful for monitoring inflows however; it can be impractical due to possible disruption in the intended
design of the practice in diverting runoff into the LID. Additionally, many BMPs have multiple inflow points
into the practice making inflow monitoring expensive and complex and may still require some form of flow
estimation.
The Simple Method is a spreadsheet based runoff estimation procedure that is used for determining
stormwater runoff and pollutant loading for urban areas. The Simple Method determines estimated inflow
based on drainage area, amount of precipitation, and a runoff coefficient. This information is used to
1
determine a runoff coefficient . While the Simple Method is typically used to calculate annual runoff, CVC
has modified the formula to determine runoff on an event-by-event basis. CVC has also added a BMP
component to account for LID areas. Note that the BMP area is not considered in the runoff coefficient
calculation since complete infiltration into the practice is assumed for BMP areas.
The drainage area for CVC Head Office was derived using orthographic imagery and site visits. This
process allows the catchment area to be divided into impervious, pervious and BMP surfaces, which are
used in the equation below to determine the runoff coefficient. Precipitation data was obtained from the
rain gauge on site maintained by the City of Mississauga. This data is used with the drainage area to
determine event inflow runoff volume. As part of this rooftop is connected to the rainwater harvesting
system, this rooftop is considered an impervious surface when the rainwater storage tank is full, and is
considered a pervious surface when the rainwater storage tank is not full. Table 1-2 and Table 1-3
present the drainage area and use of the Simple Method at CVC Head Office when the rainwater storage
tank is full and when the rainwater storage tank is not full, respectively. A level logger located in the
rainwater storage system is used to determine which equation is used to determine inflow volume.
The runoff coefficient is defined as:
Rv = 0.05 + 0.9 * la
Where:
Rv is the runoff coefficient
0.9 is the fraction of rainfall events that produce runoff
la is the impervious fraction (Impervious Area/Drainage Area to the BMP)
The modified Simple Method formula used is:
2
2
Event inflow volume (L): Drainage Area to the BMP (m ) * Rv + BMP area (m ) * Event
Precipitation (mm)
Note: the BMP area is added since precipitation on the BMP area is considered to fully infiltrate into the practice.
1 Schueler, T. 1987. Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban BMPs. Metropolitan Washington Council of Governments.
Washington, DC
2 EPA. (2010). "Storm Water Management Model (SWMM)." Water Supply and Water Resources Division, National Risk Management Research Laboratory, CDM.
Table 1-2: Drainage area and application of the Simple Method at CVC Head Office when the rainwater
storage tank is full
2
Land Use
Area (m )
Total impervious area
1439
Total pervious area
1235
Total drainage area to the BMP (impervious area + pervious area)
2674
1840
Total BMP area
Ia= impervious fraction (total impervious area/total drainage area to the BMP)
0.538
Rv= 0.05 + 0.9 * Ia
0.534
Total drainage area to the BMP * Rv + total BMP area:
Multiply this number by event precipitation (mm) to get event inflow volume (L)
3268
Table 1-3: Drainage area and application of the Simple Method at CVC Head Office when the rainwater
storage tank is not full
2
Land Use
Area (m )
Total impervious area
903
Total pervious area
1771
Total drainage area to the BMP (impervious area + pervious area)
2674
1840
Total BMP area
Ia= impervious fraction (total impervious area/total drainage area to the BMP)
0.338
Rv= 0.05 + 0.9 * Ia
0.354
Total drainage area to the BMP * Rv + total BMP area:
Multiply this number by event precipitation (mm) to get event inflow volume (L)
2787
Best results are produced when the method is used for smaller catchments at a development site scale.
Further modeling would be required for determining runoff for a large watershed. Additionally, the Simple
Method only provides estimates for the storm event itself and does not consider pollutant contribution
from baseflow generated within the catchment.
section.
3
Baseflow separation is further described in the following
Lastly, the Simple Method can overestimate inflow volume for smaller events where rainfall depths would
be used up by catchment wetting and surface depression storage. This occurs because the Simple
Method applies the same runoff coefficient to storms of all magnitudes.
Baseflow Separation
Flow is almost constantly measured at the monitoring location at CVC Head Office due to baseflow.
Baseflow separation is needed during storm events to separate baseflow and stormflow. The constant
slope method is used, which assumes the baseflow changes in a linear fashion from the start of stormflow
to the return to baseflow (i.e. a linear interpolation between the baseflow immediately prior to and
immediately after stormflow). Per Linsley et al (1975), the time of the end of stormflow can be estimated
using the following equation:
0.2
N= 0.83A
Where:
N is number of days after the final peak of the storm hydrograph
2
A is the total drainage area of the site in km .
2
Using the drainage area of 0.004514 km , the time of return to baseflow is 0.2818 days, or 6 hours and 46
minutes after the final peak of the storm hydrograph. This is then rounded to 6 hours and 50 minutes, as
the data is summarized in 10 minute intervals.
As the baseflow naturally fluctuates by 1-2 mm, the start of stormflow was generally considered to be the
first increase of 3 mm in a 10 minute period during precipitation. However, if the baseflow was steadily
increasing by 1 or 2 mm during precipitation and the level was not fluctuating to these values prior to the
precipitation, the start of stormflow was changed accordingly. For consistency, the final peak of the
hydrograph was considered to occur at the highest level after which there were no further decreases and
then increases of at least 5 mm. The reported stormflow will therefore be the measured flow minus the
estimated baseflow.
While each stormflow period ends 6 hours and 50 minutes after the final peak of the storm hydrograph,
for our purposes for LID monitoring projects if there is less than 6 hours between precipitation and/or
stormflow, it is considered the same storm event. Therefore, one storm event can have multiple periods of
stormflow starting and stopping (e.g. if additional rain causes stormflow less than 6 hours after the return
to baseflow from previous precipitation). The stormflow events will still be interpolated separately, but are
considered part of the same storm event for water balance purposes.
Water Quality
Both contaminant loadings and discharge concentrations have been evaluated for CVC Head Office.
Loading reduction is the best way to evaluate water quality performance. However, to understand the
filtration mechanism only discharge concentration was compared to reference water quality guidelines,
runoff EMCs from similar land uses, and effluent concentrations for similar BMPs. An estimated total
influent load was calculated as a product of the estimated influent volume and the NSQD Commercial,
Industrial, and Institutional median EMC for evaluation purposes. Effluent EMCs are derived from the lab
3 Centre for Watershed Protection, (2010). Stormwater Management Design Manual. New York State Department of Environmental Conservation. Albany New
York
reported value of the flow proportional samples collected on site for several parameters listed below. The
statistical summaries have been organized by pollutant. Data set summary statistics are presented in
both tabular and graphical formats.
The recommended parameters of interest analyzed are:
1.2.2
•
Cadmium
•
Copper
•
Iron
•
Lead
•
Nickel
•
Zinc
•
Dissolved Chloride
•
Nitrate + Nitrite
•
Total Kjeldahl Nitrogen
•
Orthophosphate
•
Total Phosphorus
•
Total Suspended Solids
Data Analysis Presentation Methods
The summary tables include both parametric and non-parametric statistics. Parametric statistics operate
under the assumption that data arise from a single theoretical statistical distribution that can be described
mathematically using coefficients, or parameters, of that distribution. The mean and standard deviation
are example parameters of the normal, or Gaussian, distribution. Non-parametric statistics, including the
4
median, are fundamentally based on the ranks of the data with no need to assume an underlying
distribution. Non-parametric statistics do not depend on the magnitude of the data and are therefore
resistant to the occurrence of a few extreme values (i.e., high or low values relative to other data points
5
do not significantly alter the statistic). Time series plots of the sampled EMC values are also provided. A
box plot is provided to compare CVC Head Office TSS values with those from the NSQD sorted by land
use. Figure 1-2 is a key for the box plots provided in Appendix D.
4 In this context, ranks refer to the positions of the data after being sorted by magnitude.
5 Helsel, D.R. and R. M. Hirsch, 2002. Statistical Methods in Water Resources Techniques of Water Resources Investigations, Book 4, chapter A3. U.S. Geological Survey. 522
pages.
Figure 1-2: Explanation of box and whisker diagram
1.2.3
Data Analysis
Most of the data analysis was done using Microsoft Excel. Total influent volumes due to rainfall were
estimated from a storm event’s total precipitation by using the Simple Method as discussed in Section
1.2.1 Data Analysis Evaluation Methods. Volume reductions were then computed as the difference
between the estimated influent volume and measured effluent volume. Hydrologic lag times were then
computed using the peak of precipitation hyetograph to the peak of effluent event hydrograph. Influent
loads are calculated using the estimated influent EMC multiplied by the influent volume. For events
sampled for water quality, effluent loads are calculated using the measured effluent volume multiplied by
the measured EMC, and for events that were not sampled for water quality, the median of the sampled
EMCs is multiplied by the measured effluent volume. The freely available, open source statistical analysis
program R is used to calculate some of the statistics and create box-whisper plots.
1.3
Table and Figure Definitions
Definitions for information found in the tables and figures presented in this report are included below for
guidance.
Tables include a combination of the following results, listed in alphabetical order:
•
Antecedent Dry Period - The amount of time with no rain or flow preceding the event.
•
Effluent EMC - The event mean concentration of the effluent for the event.
•
Estimated Pollutant Load Reduction - The estimated mass of a pollutant passing through the
BMP; what has been removed from the system.
•
Estimated Total Influent Load - The estimated total pollutant load carried by influent for the event,
as calculated by multiplying the Estimated Total Influent Volume by the NSQD Residential EMC.
•
Estimated Total Influent Volume - The estimated total volume of influent for the event based on
an application of the Simple Method with the measured rainfall depth.
•
Estimated Volume Reduction - The estimated amount of volume removed as calculated by the
difference between the Estimated Total Influent Volume and the Total Effluent Volume.
•
Event Duration - The total length of time for the event.
•
Lag Time - The time as calculated from the peak of precipitation event hyetograph to the peak of
effluent event hydrograph.
•
Peak Effluent Flow - The maximum effluent flow rate for the event based on measured effluent.
•
Peak Precipitation Intensity - The maximum rate of precipitation for the event.
•
Sample Date - The date the water quality sample was collected.
•
Storm Date - The start date of the hydrologic event.
•
Total Effluent Load - The total pollutant load carried by the effluent out of the BMP for the event,
as calculated by multiplying the Total Effluent Volume by the Effluent EMC.
•
Total Effluent Volume - The total measured volume effluent for the event.
•
Total Precipitation - The total depth of rainfall for the event.
•
WQ Guideline - The applicable PWQO or CCME water quality guideline for the pollutant.
Hydrologic Summary Figures presented in this report include the following results:
•
Flow - The rate of flow for the estimated influent hydrograph and measured effluent hydrograph
with corresponding flow rates increasing upwards along the left chart axis.
•
10-min Precipitation Depth - The depth of precipitation per 10-minute intervals with corresponding
depths increasing downward along the right chart axis.
Tables and Comparative BMP Box Plots include the following BMPs represented in the BMPDB:
•
Bioretention - Vegetated, shallow depressions used to temporarily store stormwater prior to
infiltration, evapotranspiration, or discharge via an underdrain or surface outlet structure.
Treatment is achieved through filtration, sedimentation, sorption, infiltration, biochemical
processes and plant uptake.
•
Detention Basin (a.k.a. Dry Pond) - Grass-lined basins that, while fully drainable between storm
events, temporarily detain water through outlet controls to reduce peak stormwater runoff release
rates and provide sedimentation treatment. Volume losses and load reductions through infiltration
may also be significant.
•
Green Roof - Vegetated roofs that provide stormwater treatment via filtration, sorption,
biochemical processes and plant uptake.
•
Biofilter - Vegetated swales or strips that provide treatment via filtration, sedimentation, infiltration,
biochemical processes and plant uptake.
•
LID - low-impact development (LID) monitored at a site-scale basis; green infrastructure.
•
1.4
Manufactured Device - Devices that are designed to provide various treatment processes such as
sedimentation, skimming, filtration, sorption, and disinfection. Treatment process subcategories
within the BMPDP include biological filtration, filtration, inlet insert, multi-process, physical (with
volume control), physical (manufactured device), and oil/grit separators. The last two treatment
process subcategories, which are of primary interest to CVC, are further described below:
o
Physical (manufactured device) are hydrodynamic devices that provide treatment via
®
6
settling and includes proprietary devices like Stormceptors . A performance summary
found statistically significant reductions for Zn and TP for physical (manufactured device)
treatment processes. It was hypothesized that TSS results, showing no significant
reductions, were affected by unusually low influent TSS concentrations.
o
Oil/grit separators are designed for removing floatables and coarse solids. The
performance summary found statistically significant reductions for only TSS for oil/grit
separators treatment processes.
•
Media Filter - A constructed bed of filtration media that receives water at the surface and allows it
to pond on the surface if inflows exceed the rate of percolation through the bed. Outflow from the
media bed can be through underdrains or infiltration. Depending on the media used, treatment is
provided via filtration, sorption, precipitation, ion exchange and biochemical processes.
•
Porous Pavement - Pavement that allows for infiltration through surface void spaces into
underlying material. Subcategories of porous pavement include modular block, pervious concrete,
porous aggregate, porous asphalt, and porous turf. Treatment is provided via infiltration, filtration,
sorption, and biodegradation.
•
Retention Pond (a.k.a. Wet Pond) - Basins that feature a permanent pool of water (dead storage)
below flood control (live storage) that is outlet controlled. Treatment is provided primarily through
sedimentation; other treatment processes may include sorption and biochemical processes.
•
Wetland Basin - Shallow basins typically designed with inflow energy dissipation and variable
depths and vegetation types to promote interactions between runoff, aquatic vegetation, and
wetland soils. Treatment is provided via sedimentation, sorption, biochemical processes,
coagulation, flocculation, plant uptake and microbial transformations.
•
Wetland Channel - Densely vegetated waterways used to treat and convey runoff. Treatment is
provided via filtration, sedimentation, microbial transformations and plant uptake.
Statistical Significance and Hypothesis Testing Considerations
Statistical hypothesis testing is a powerful approach for evaluating
stormwater BMP performance data. The most common type of
statistical hypothesis testing involves comparisons of paired inflow
and outflow EMC data to determine if the means significantly differ
given an acceptable level of statistical confidence. This technique,
which includes the paired t-Test, is commonly employed as a part of
the analysis of the International Stormwater BMP Database and is a
valuable statistical test for large, normally-distributed data sets.
Nonparametric hypothesis testing, such as the Wilcoxon signed-rank
test, can also be conducted (on medians rather than means);
however, the statistical test generally is more powerful for parametric
At least 35 paired events are
needed to verify that a
statistically significant difference
in concentration of 80% has
been
achieved.
Long-term
assessment is needed to gain
this confidence.
6 Leisenring, M., Clary, J., Hobson, P. 2012. International Stormwater Best Management Practices (BMP) Database, Manufactured Devices Performance
Summary. Prepared by Geosyntec Consultants, Inc. and Wright Water Engineers, Inc. July.
data when the normality assumptions hold (rare for stormwater). While statistical hypothesis testing is
most commonly used for inflow/outflow analysis, it can be applied to any two data sets to determine if
there is a statistically significant difference between the mean or median values of the two data
distributions. In this case, tests on independent data sets are used (e.g., standard t-Test (parametric) and
Mann-Whitney rank-sum test (non-parametric)) instead of matched pairs.
For the CVC Head Office site, the ability to conduct such testing is limited by the lack of measured inflow
data. However, even if inflow EMCs had been measured or estimated from the initiation of monitoring, it is
unlikely that the data set would be large enough for meaningful statistical hypothesis testing. To gain a
sense of the size of the data set needed, consider hypothesis testing designed to detect a 75% difference
7
between inflow and outflow mean EMC values for TSS (see Pitt and Parmer 1985 ). Assuming a
coefficient of variation of 1.5 (on the low end of variability for most stormwater parameters), a power of
80% (standard for this type of analysis) and a confidence level of 90%, more than 35 paired samples
would need to be collected.
7 R. Pitt and K. Parmer. Quality Assurance Project Plan (QAPP) for EPA Sponsored Study on Control of Stormwater Toxicants. Department of Civil and
Environmental Engineering, University of Alabama at Birmingham. 1995. Reprinted in Burton, G.A. Jr., and R. Pitt. Stormwater Effects Handbook: A Tool
Box for Watershed Managers, Scientists, and Engineers. ISBN 0-87371-924-7. CRC Press, Inc., Boca Raton, FL. 2002. 911 pages.
Figure 1-3: Statistical Hypothesis testing paired samples required to detect 75% difference in population
means for power of 80% (Pitt and Parmer 1985)
Therefore, eventually it may be possible for CVC to conduct hypothesis testing if inflow EMCs can be
estimated and/or measured and paired with outflow data; however, it will take at least several years to
build a data set that is sizeable enough, and will not be conducted at this stage for the CVC Head Office
site. Furthermore, if differences between inflow and outflow EMC distribution means are smaller (e.g. 20%
reduction or even 50% reduction), greater numbers of paired samples will be needed to detect differences
with confidence. While a large number of events are needed for statistical hypothesis testing, the site
nonetheless is currently providing useful data that can be used to calculate annual outflow loads with
some associated uncertainty. CVC is evaluating methods for estimating inflow loads based on land use
and EMC data from the NSQD at other monitoring locations. This will permit calculation of an annual load
reduction for the facility. As the data sets grow and if inflow EMC data can be collected from land uses
within the watershed or entering the LID features at other sites, the uncertainty of the comparison will
decrease, permitting more accurate, and eventually statistically meaningful comparison.
If CVC is able to collect data for and/or estimate inflow EMCs, it should still be feasible to estimate inflow
and outflow loads and calculate reductions on an annual basis to compare with the MOECC 80% TSS
removal requirement, whether or not statistical significance holds (for small data sets, the conclusion
often is that there is not a statistically significant difference; however, this finding may be reflective of the
limited size of the data set rather than the lack of a true difference in population means/medians.
Appendix D
Data Analysis Summaries
NOTICE
FINAL REPORT
APPENDIX D: Data Analysis Summaries
1
RAINFALL EVENTS ANALYSIS
Table D-1: Summary of Rainfall Events
Starting Date and
Time
2014-07-07 02:10
2014-07-08 11:30
2014-07-13 05:00
2014-07-15 01:30
2014-07-19 16:10
2014-07-20 13:20
2014-07-27 18:50
2014-08-11 22:40
2014-08-20 19:20
2014-09-01 20:50
2014-09-02 12:10
2014-09-05 18:30
2014-09-10 15:40
2014-09-15 14:50
2014-09-21 05:50
2014-10-03 13:00
2014-10-06 21:50
2014-10-14 22:50
2014-10-16 17:20
2014-10-20 06:30
2014-10-24 05:10
2014-10-27 22:00
2014-10-31 01:30
2014-11-04 13:20
2014-11-06 16:40
2014-11-17 09:40
2014-11-23 23:50
2014-12-11 04:20
2014-12-16 05:40
2015-04-02 18:10
2015-04-03 17:40
2015-04-04 19:10
2015-04-08 10:10
2015-04-09 14:40
Ending Date and Time
Event Duration
(hrs)
Precipitation
Depth (mm)
07-Jul-2014 13:10
08-Jul-2014 18:20
13-Jul-2014 16:00
15-Jul-2014 08:00
20-Jul-2014 01:10
20-Jul-2014 18:20
28-Jul-2014 12:50
12-Aug-2014 10:00
20-Aug-2014 22:00
02-Sep-2014 04:30
02-Sep-2014 20:00
06-Sep-2014 12:30
11-Sep-2014 10:10
16-Sep-2014 05:50
22-Sep-2014 08:10
04-Oct-2014 12:00
08-Oct-2014 00:20
15-Oct-2014 05:50
16-Oct-2014 22:20
20-Oct-2014 19:50
24-Oct-2014 07:50
28-Oct-2014 03:50
01-Nov-2014 04:40
04-Nov-2014 20:10
07-Nov-2014 00:20
17-Nov-2014 14:00
24-Nov-2014 09:00
11-Dec-2014 20:00
17-Dec-2014 07:40
02-Apr-2015 19:00
03-Apr-2015 23:50
04-Apr-2015 21:40
09-Apr-2015 04:50
10-Apr-2015 11:40
11.00
6.83
11.00
6.50
9.00
5.00
18.00
11.33
2.67
7.67
7.83
18.00
18.50
15.00
26.33
23.00
26.50
7.00
5.00
13.33
2.67
5.83
27.17
6.83
7.67
4.33
9.17
15.67
26.00
0.83
6.17
2.50
18.67
21.00
6.8
5.8
10.8
2.4
8.6
3.6
46.4
17.2
4.2
3.4
21.0
27.8
40.2
4.6
9.4
17.4
9.8
2.8
4.6
4.6
2.6
2.0
10.8
3.8
3.8
2.4
20.8
9.2
3.2
3.0
3.6
2.2
19.6
12.0
Starting Date and
Time
2015-04-13 16:30
2015-04-19 22:30
2015-04-21 09:10
2015-05-09 22:20
2015-05-10 16:50
2015-05-11 19:40
2015-05-30 11:40
2015-06-07 20:40
2015-06-10 16:50
2015-06-12 04:00
2015-06-14 07:30
2015-06-22 20:50
2015-06-27 10:50
2015-07-07 12:30
2015-07-14 07:50
2015-07-17 10:00
2015-07-19 14:50
2015-07-31 21:20
2015-08-02 16:30
2015-08-04 13:30
2015-08-10 11:50
2015-08-19 21:50
2015-08-24 01:50
2015-09-08 04:10
2015-09-09 07:20
2015-09-11 18:10
2015-09-19 13:40
2015-09-29 11:50
Ending Date and Time
Event Duration
(hrs)
Precipitation
Depth (mm)
14-Apr-2015 01:20
20-Apr-2015 17:00
22-Apr-2015 03:30
10-May-2015 04:50
11-May-2015 00:00
12-May-2015 00:50
01-Jun-2015 02:00
08-Jun-2015 15:50
11-Jun-2015 00:00
13-Jun-2015 00:40
14-Jun-2015 19:20
23-Jun-2015 09:40
28-Jun-2015 21:50
08-Jul-2015 02:50
15-Jul-2015 00:20
17-Jul-2015 14:30
19-Jul-2015 21:40
01-Aug-2015 04:20
03-Aug-2015 06:00
04-Aug-2015 21:50
11-Aug-2015 00:00
20-Aug-2015 15:50
24-Aug-2015 06:40
08-Sep-2015 12:10
09-Sep-2015 14:10
13-Sep-2015 21:40
19-Sep-2015 20:50
29-Sep-2015 22:40
8.83
18.50
18.33
6.50
7.17
5.17
38.33
19.17
7.17
20.67
11.83
12.83
35.00
14.33
16.50
4.50
6.83
7.00
13.50
8.33
12.17
18.00
4.83
8.00
6.83
51.50
7.17
10.83
4.6
21.0
5.0
12.0
6.8
7.8
43.3
27.8
4.3
14.5
5.0
20.8
73.8
15.6
4.8
4.4
3.4
2.6
16.4
2.8
29.2
12.4
2.2
12.6
2.4
25.6
16.4
10.4
2
HYDROLOGIC ANALYSIS
Table D-2: Hydrologic Summary of Rainfall Events
Starting Date and
Time
Antecedent
Dry Period
(Days)
Total
Inflow
Volume
(L)
Peak
Inflow
(L/s)
Total
Outflow
Volume
(L)
Peak
Outflow
(L/s)
Peak
Reduction
(%)
Estimated
Volume
Reduction
(L)
(%)
2014-07-07 02:10
3.3
20,000
4.9
7,625
1.2
75%
12,375
62%
2014-07-08 11:30
0.9
17,059
5.9
3,620
0.8
87%
13,439
79%
2014-07-13 05:00
4.4
31,765
26.5
10,826
6.4
76%
20,939
66%
2014-07-15 01:30
1.4
7,059
2.9
839
0.3
89%
6,219
88%
2014-07-19 16:10
2.9
25,208
4.9
7,208
1.1
78%
17,999
71%
2014-07-20 13:20
0.51
9,636
9.2
3,320
1.7
81%
6,316
66%
2014-07-27 18:50
4.7
136,472
45.1
91,097
32.2
29%
45,374
33%
2014-08-11 22:40
6.5
49,030
13.7
14,001
3.0
78%
35,029
71%
2014-08-20 19:20
0.8
10,535
10.0
526
0.3
97%
10,009
95%
2014-09-01 20:50
2.2
10,000
3.9
2,166
0.7
82%
7,834
78%
2014-09-02 12:10
0.32
61,765
49.0
34,574
15.2
69%
27,191
44%
2014-09-05 18:30
2.7
81,419
7.8
37,069
2.4
70%
44,350
54%
2014-09-10 15:40
4.1
118,236
40.2
80,072
32.5
19%
38,164
32%
83%
2014-09-15 14:50
2.0
12,750
2.5
2,191
0.4
85%
10,560
2014-09-21 05:50
5.0
26,608
9.8
9,758
3.2
67%
16,850
63%
2014-10-03 13:00
1.8
46,761
19.2
14,808
2.1
89%
31,953
68%
2014-10-06 21:50
0.6
25,620
14.2
5,813
1.3
91%
19,808
77%
2014-10-14 22:50
6.1
7,543
1.7
841
0.2
89%
6,702
89%
2014-10-16 17:20
0.5
11,798
5.0
1,279
0.9
83%
10,519
89%
2014-10-20 06:30
3.3
11,971
3.3
522
0.2
95%
11,449
96%
2014-10-24 05:10
2.4
6,522
1.7
0
0.0
100%
6,522
100%
2014-10-27 22:00
1.6
5,017
2.5
0
0.0
100%
5,017
100%
2014-10-31 01:30
2.4
28,042
2.0
18,547
0.9
52%
9,495
34%
2014-11-04 13:20
3.4
9,532
0.8
0
0.0
100%
9,532
100%
2014-11-06 16:40
1.9
9,532
1.7
0
0.0
100%
9,532
100%
2014-11-17 09:40
5.5
6,020
0.8
0
0.0
100%
6,020
100%
2014-11-23 23:50
1.0
60,744
7.8
28,277
3.8
52%
32,467
53%
Starting Date and
Time
2014-12-11 04:20
Antecedent
Dry Period
(Days)
1.3
Total
Inflow
Volume
(L)
Peak
Inflow
(L/s)
23,076
1.7
Total
Outflow
Volume
(L)
Peak
Outflow
(L/s)
0
0.0
Peak
Reduction
(%)
Estimated
Volume
Reduction
(L)
(%)
100%
23,076
100%
82%
2014-12-16 05:40
3.5
8,719
2.0
1,588
0.4
80%
7,131
2015-04-02 18:10
3.2
7,525
5.0
0
0.0
100%
7,525
100%
2015-04-03 17:40
0.94
9,809
4.2
2,636
0.6
86%
7,173
73%
2015-04-04 19:10
0.8
6,471
2.0
0
0.0
100%
6,471
100%
2015-04-08 10:10
3.5
57,128
7.8
26,478
3.4
57%
30,650
54%
2015-04-09 14:40
0.41
34,775
4.9
16,095
1.9
62%
18,680
54%
2015-04-13 16:30
3.2
12,577
5.9
4,722
1.6
72%
7,855
62%
2015-04-19 22:30
2.7
61,592
3.9
20,931
1.2
70%
40,661
66%
2015-04-21 09:10
0.67
14,100
3.9
4,680
1.2
68%
9,420
67%
66%
2015-05-09 22:20
17.8
31,052
37.6
10,574
10.5
72%
20,478
2015-05-10 16:50
0.50
19,654
14.7
7,683
5.5
63%
11,971
61%
2015-05-11 19:40
0.8
20,517
11.7
7,180
3.9
67%
13,338
65%
2015-05-30 11:40
18.5
124,610
19.6
57,473
4.2
78%
67,137
54%
2015-06-07 20:40
6.8
79,887
19.6
37,171
6.7
66%
42,716
53%
20%
2015-06-10 16:50
1.5
10,660
15.7
8,543
9.0
43%
2,117
2015-06-12 04:00
1.2
40,483
18.8
9,176
2.4
87%
31,307
77%
2015-06-14 07:30
1.3
14,706
2.9
5,735
0.8
73%
8,971
61%
2015-06-22 20:50
6.4
60,381
39.2
31,916
17.3
56%
28,465
47%
2015-06-27 10:50
4.0
216,914
25.7
70,932
1.6
94%
145,982
67%
2015-07-07 12:30
8.1
45,017
33.3
23,544
10.8
67%
21,473
48%
2015-07-14 07:50
6.2
12,386
7.5
3,421
1.1
86%
8,966
72%
2015-07-17 10:00
2.4
11,989
3.3
1,451
0.6
81%
10,538
88%
2015-07-19 14:50
1.5
8,701
12.5
3,174
1.6
88%
5,527
64%
2015-07-31 21:20
6.3
7,647
10.8
2,165
1.3
88%
5,482
72%
2015-08-02 16:30
1.5
48,236
17.6
20,398
3.3
81%
27,838
58%
2015-08-04 13:30
1.3
8,235
10.8
2,299
1.5
86%
5,936
72%
2015-08-10 11:50
2.1
85,883
16.7
40,192
4.7
72%
45,691
53%
2015-08-19 21:50
5.1
33,700
12.7
25,911
13.2
-3%
7,789
23%
80%
4,543
70%
2015-08-24 01:50
3.4
6,471
6.9
1,928
1.4
Starting Date and
Time
2015-09-08 04:10
Antecedent
Dry Period
(Days)
14.9
Total
Inflow
Volume
(L)
Peak
Inflow
(L/s)
36,280
11.8
Total
Outflow
Volume
(L)
Peak
Outflow
(L/s)
19,899
8.9
Peak
Reduction
(%)
Estimated
Volume
Reduction
(L)
(%)
24%
16,381
45%
68%
2015-09-09 07:20
0.8
7,059
4.9
2,249
1.1
77%
4,810
2015-09-11 18:10
2.2
72,351
5.9
23,999
1.9
67%
48,352
67%
2015-09-19 13:40
5.7
41,482
33.4
24,081
12.0
64%
17,401
42%
2015-09-29 11:50
9.6
26,086
3.3
2,421
0.3
91%
23,665
91%
3
WATER QUALITY PERFORMANCE
Table D-3: EMC Summary for All Events
Starting Date and
time
TSS
(mg/L)
TP
(mg/L)
PO4
(mg/L)
NO2+NO3
(mg/L)
TKN
(mg/L)
Cd
(µg/L)
Cu
(µg/L)
Fe
(µg/L)
1
Pb
(µg/L)
1
Ni
(µg/L)
Zn
(µg/L)
Dissolved
Cl (mg/L)
27-Jul-2014 18:50
46.4
116
0.206
0.143
1.08
1.07
1.77
29.5
174
-3.24
2.77
103
168
11-Aug-2014 22:40
17.2
18.6
0.063
0.0349
1.56
0.42
1.82
18.1
96.8
-0.719
0.377
110
247
10-Sep-2014 15:40
40.2
98.4
0.177
0.0914
0.921
0.67
1.79
16.4
242
-1.72
0.659
87.9
84.3
21-Sep-2014 05:50
9.4
15.4
0.137
0.0993
1.67
0.45
1.89
10.7
88
-4.12
-0.603
81.7
207
03-Oct-2014 13:00
17.4
48.6
0.04
0.0393
1.24
0.54
2.11
12.7
141
-3.22
0.248
123
170
19-Apr-2015 22:30
21.0
9.7
0.039
0.0201
1.89
0.69
1.11
11.3
51.1
0.29
-0.19
155
375
11-May-2015 19:40
7.8
30.5
0.121
0.0622
1.86
0.69
0.644
13.8
370
-3.79
-0.998
100
394
07-Jun-2015 20:40
27.8
77.8
0.068
0.0641
1.35
0.67
0.475
20.7
270
0.0443
-0.155
75.2
282
22-Jun-2015 20:50
20.8
96.2
0.252
0.174
1.11
0.67
0.302
15.7
418
-1.56
0.55
60.2
237
07-Jul-2015 12:30
15.6
61.9
0.181
0.115
1.04
0.67
0.951
12.1
300
-1.41
-0.0118
50.9
226
10-Aug-2015 11:50
29.2
55.9
0.119
0.0714
0.931
0.67
0.223
12.9
213
-2.5
0.208
86.5
132
19-Aug-2015 21:50
12.4
40.5
0.096
0.0815
1.24
0.67
0.584
17.5
141
0.791
-0.377
60.9
345
Count
1
Precipitation
Depth
(mm)
12
12
12
12
12
12
12
12
12
12
12
12
12
Minimum
7.80
9.70
0.04
0.02
0.92
0.42
0.22
10.70
51.10
-4.12
-1.00
50.90
84.30
25 Percentile
14.80
27.53
0.07
0.06
1.07
0.64
0.56
12.55
129.95
-3.23
-0.24
71.63
169.50
Median
19.08
52.25
0.12
0.08
1.24
0.67
1.03
14.75
193.50
-1.64
0.10
87.20
231.50
75 Percentile
28.11
82.40
0.18
0.10
1.59
0.68
1.80
17.65
277.50
-0.53
0.42
104.75
297.75
Maximum
46.40
116.00
0.25
0.17
1.89
1.07
2.11
29.50
418.00
0.79
2.77
155.00
394.00
Mean
22.09
55.79
0.12
0.08
1.32
0.66
1.14
15.95
208.74
-1.76
0.21
91.19
238.94
Standard Deviation
11.88
35.24
0.07
0.05
0.34
0.16
0.70
5.24
114.95
1.65
0.94
29.44
96.32
Analytical method used by MOECC produced negative concentrations. These values are to be treated as non-detects.
Table D-4: Water Quality Performance for Total Suspended Solids (TSS)
Starting Date and Time
Effluent EMC
(mg/L)
Precipitation Depth
(mm)
Total Estimated Total Estimated
Influent
Influent Load
3
Volume (m )
(g)
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
Estimated Pollutant
Load Reduction
27-Jul-2014 18:50
11-Aug-2014 22:40
116.0
18.6
46.4
17.2
136.47
49.03
16,922
6,080
91.10
14.00
10,567
260
(g)
6,355
5,819
10-Sep-2014 15:40
98.4
40.2
118.24
14,661
80.07
7,879
6,782
46%
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
15.4
48.6
9.7
30.5
77.8
96.2
61.9
55.9
40.5
12
9.7
27.5
52.3
82.4
116.0
55.8
35.2
25
124
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.80
14.80
19.08
28.11
46.40
22.09
11.88
N/A
N/A
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
3,299
5,798
7,637
2,544
9,906
7,487
5,582
10,649
4,179
12
2544
5231
6783
10092
16922
7896
4429
N/A
N/A
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
150
720
203
219
2,892
3,070
1,457
2,247
1,049
12
150
250
1253
2936
10567
2560
3329
N/A
N/A
3,149
5,079
7,434
2,325
7,014
4,417
4,125
8,403
3,129
12
2325
3881
5449
6840
8403
5336
1933
N/A
N/A
95%
88%
97%
91%
71%
59%
74%
79%
75%
12
38%
68%
77%
92%
97%
76%
20%
N/A
N/A
(%)
38%
96%
Table D-5: Water Quality Performance for Total Phosphorus (TP)
27-Jul-2014 18:50
11-Aug-2014 22:40
10-Sep-2014 15:40
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
Effluent EMC
(mg/L)
0.21
0.06
0.18
0.14
0.04
0.04
0.12
0.07
0.25
0.18
0.12
0.10
12
0.04
0.07
0.12
0.18
0.25
0.12
0.07
0.03
0.16
Precipitation Depth
(mm)
46.4
17.2
40.2
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.80
14.80
19.08
28.11
46.40
22.09
11.88
N/A
N/A
Influent
Influent Load
3
Volume (m )
(g)
136.47
49.03
118.24
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
21.84
7.84
18.92
4.26
7.48
9.85
3.28
12.78
9.66
7.20
13.74
5.39
12
3.28
6.75
8.75
13.02
21.84
10.19
5.71
N/A
N/A
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
91.10
14.00
80.07
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
18.77
0.88
14.17
1.34
0.59
0.82
0.87
2.53
8.04
4.26
4.78
2.49
12
0.59
0.88
2.51
5.60
18.77
4.96
5.88
N/A
N/A
Estimated Pollutant
Load Reduction
(g)
3.07
6.96
4.75
2.92
6.89
9.04
2.41
10.25
1.62
2.94
8.96
2.90
12
1.62
2.92
3.91
7.46
10.25
5.23
3.03
N/A
N/A
(%)
14%
89%
25%
69%
92%
92%
74%
80%
17%
41%
65%
54%
12
14%
37%
67%
82%
92%
59%
29%
N/A
N/A
Table D-6: Water Quality Performance for Phosphate (PO 4 )
27-Jul-2014 18:50
11-Aug-2014 22:40
10-Sep-2014 15:40
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
Effluent EMC
(mg/L)
0.14
0.03
0.09
0.10
0.04
0.02
0.06
0.06
0.17
0.12
0.07
0.08
12
0.02
0.06
0.08
0.10
0.17
0.08
0.05
N/A
N/A
Precipitation Depth
(mm)
46.4
17.2
40.2
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.80
14.80
19.08
28.11
46.40
22.09
11.88
N/A
N/A
Influent
Influent Load
Volume (m3)
(g)
136.47
49.03
118.24
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
91.10
14.00
80.07
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
13.03
0.49
7.32
0.97
0.58
0.42
0.45
2.38
5.55
2.71
2.87
2.11
12
0.42
0.56
2.25
3.54
13.03
3.24
3.76
N/A
N/A
Estimated Pollutant
Load Reduction
(g)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
(%)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Table D-7: Water Quality Performance for Nitrite + Nitrate (NO 2 + NO 3 ).
Effluent EMC
(mg/L)
27-Jul-2014 18:50
11-Aug-2014 22:40
10-Sep-2014 15:40
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
1.08
1.56
0.92
1.67
1.24
1.89
1.86
1.35
1.11
1.04
0.93
1.24
12
0.92
1.07
1.24
1.59
1.89
1.32
0.34
3a
0.66
Precipitation Depth
(mm)
46.4
17.2
40.2
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.80
14.80
19.08
28.11
46.40
22.09
11.88
N/A
N/A
Influent
Influent Load
Volume (m3)
(g)
136.47
49.03
118.24
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
90.07
32.36
78.04
17.56
30.86
40.65
13.54
52.73
39.85
29.71
56.68
22.24
12
13.54
27.84
36.11
53.71
90.07
42.02
23.57
N/A
N/A
a
Water quality guideline for Nitrate used
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
91.10
14.00
80.07
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
98.39
21.84
73.75
16.30
18.36
39.56
13.35
50.18
35.43
24.49
37.42
32.13
12
13.35
20.97
33.78
42.21
98.39
38.43
25.27
N/A
N/A
Estimated Pollutant
Load Reduction
(g)
-8.31
10.52
4.29
1.26
12.50
1.09
0.19
2.55
4.42
5.23
19.26
-9.89
12
-9.89
0.87
3.42
6.55
19.26
3.59
8.12
N/A
N/A
(%)
-9%
33%
5%
7%
41%
3%
1%
5%
11%
18%
34%
-44%
12
-44%
2%
6%
21%
41%
9%
22%
N/A
N/A
Table D-8: Water Quality Performance for Total Kjeldahl Nitrogen (TKN)
27-Jul-2014 18:50
11-Aug-2014 22:40
10-Sep-2014 15:40
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
Effluent EMC
(mg/L)
1.07
0.42
0.67
0.45
0.54
0.69
0.69
N/A
N/A
N/A
N/A
N/A
7
0.42
0.50
0.67
0.69
1.07
0.65
0.22
N/A
1.2
Precipitation Depth
(mm)
46.4
17.2
40.2
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.80
14.80
19.08
28.11
46.40
22.09
11.88
N/A
N/A
Influent
Influent Load
Volume (m3)
(g)
136.47
49.03
118.24
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
163.77
58.84
141.88
31.93
56.11
73.91
24.62
95.86
72.46
54.02
103.06
40.44
12
24.62
50.63
65.65
97.66
163.77
76.41
42.86
N/A
N/A
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
91.10
14.00
80.07
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
97.47
5.88
53.65
4.39
8.00
14.44
4.95
N/A
N/A
N/A
N/A
N/A
7
4.39
5.42
8.00
34.05
97.47
26.97
35.68
N/A
N/A
Estimated Pollutant
Load Reduction
(g)
66.29
52.96
88.24
27.54
48.12
59.47
19.67
N/A
N/A
N/A
N/A
N/A
7
19.67
37.83
52.96
62.88
88.24
51.75
23.21
N/A
N/A
(%)
40%
90%
62%
86%
86%
80%
80%
N/A
N/A
N/A
N/A
N/A
7
40%
71%
80%
86%
90%
75%
18%
N/A
N/A
Table D-9: Water Quality Performance for Cadmium (Cd)
27-Jul-2014 18:50
11-Aug-2014 22:40
10-Sep-2014 15:40
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
Effluent EMC (µg/L)
1.77
1.82
1.79
1.89
2.11
1.11
0.64
0.48
0.30
0.95
0.22
0.58
12
0.22
0.56
1.03
1.80
2.11
1.14
0.70
0.2
N/A
Precipitation
Depth (mm)
46.4
17.2
40.2
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.80
14.80
19.08
28.11
46.40
22.09
11.88
N/A
N/A
Total
Estimated
Influent
Volume (m3)
Total
Estimated
Influent Load
(g)
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
136.47
49.03
118.24
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
91.10
14.00
80.07
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
0.161
0.025
0.143
0.018
0.031
0.023
0.005
0.018
0.010
0.022
0.009
0.015
12
0.005
0.014
0.020
0.027
0.161
0.040
0.053
N/A
N/A
Estimated Pollutant
Load Reduction
(g)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
(%)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Table D-10: Water Quality Performance for Copper (Cu)
27-Jul-2014 18:50
11-Aug-2014 22:40
10-Sep-2014 15:40
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
29.5
18.1
16.4
10.7
12.7
11.3
13.8
20.7
15.7
12.1
12.9
17.5
12
10.7
12.6
14.8
17.7
29.5
16.0
5.2
5
24
Precipitation
Depth (mm)
46.4
17.2
40.2
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.80
14.80
19.08
28.11
46.40
22.09
11.88
N/A
N/A
Total
Estimated
Influent
Volume (m3)
Total
Estimated
Influent Load
(g)
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
136.47
49.03
118.24
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
3.28
1.18
2.84
0.64
1.12
1.48
0.49
1.92
1.45
1.08
2.06
0.81
12
0.49
1.01
1.31
1.95
3.28
1.53
0.86
N/A
N/A
91.10
14.00
80.07
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
2.69
0.25
1.31
0.10
0.19
0.24
0.10
0.77
0.50
0.28
0.52
0.45
12
0.10
0.22
0.37
0.58
2.69
0.62
0.74
N/A
N/A
Estimated Pollutant
Load Reduction
(g)
0.59
0.92
1.52
0.53
0.93
1.24
0.39
1.15
0.95
0.80
1.54
0.36
12
0.36
0.57
0.93
1.17
1.54
0.91
0.40
N/A
N/A
(%)
18%
78%
54%
84%
83%
84%
80%
60%
65%
74%
75%
44%
12
18%
58%
74%
81%
84%
67%
20%
N/A
N/A
Table D-11: Water Quality Performance for Iron (Fe)
27-Jul-2014 18:50
11-Aug-2014 22:40
10-Sep-2014 15:40
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
174
97
242
88
141
51
370
270
418
300
213
141
12
51
130
194
278
418
209
115
300
N/A
Precipitation
Depth (mm)
46.4
17.2
40.2
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.80
14.80
19.08
28.11
46.40
22.09
11.88
N/A
N/A
Total
Estimated
Influent
Volume (m3)
Total
Estimated
Influent Load
(g)
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
136.47
49.03
118.24
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
91.10
14.00
80.07
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
15.85
1.36
19.38
0.86
2.09
1.07
2.66
10.04
13.34
7.06
8.56
3.65
12
0.86
1.90
5.36
10.86
19.38
7.16
6.34
N/A
N/A
Estimated Pollutant
Load Reduction
(g)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
(%)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Table D-12: Water Quality Performance for Lead (Pb)
27-Jul-2014 18:50
11-Aug-2014 22:40
10-Sep-2014 15:40
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
a
-3.24
-0.72a
-1.72a
-4.12a
-3.22a
0.29
-3.79a
0.04
-1.56a
-1.41a
-2.50a
0.79
12
-4.12
-3.23
-1.64
-0.53
0.79
-1.76
1.65
1
N/A
Precipitation
Depth (mm)
46.4
17.2
40.2
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.80
14.80
19.08
28.11
46.40
22.09
11.88
N/A
N/A
Total
Estimated
Influent
Volume (m3)
Total
Estimated
Influent Load
(g)
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
136.47
49.03
118.24
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
91.10
14.00
80.07
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
-0.30
-0.01
-0.14
-0.04
-0.05
0.01
-0.03
0.00
-0.05
-0.03
-0.10
0.02
12
-0.30
-0.06
-0.04
-0.01
0.02
-0.06
0.09
N/A
N/A
a
Estimated Pollutant
Load Reduction
(g)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
(%)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Table D-13: Water Quality Performance for Nickel (Ni)
27-Jul-2014 18:50
11-Aug-2014 22:40
10-Sep-2014 15:40
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
2.77
0.38
0.66
-0.60a
0.25
-0.19a
-1.00a
-0.16a
0.55
-0.01a
0.21
-0.38a
12
-1.00
-0.24
0.10
0.42
2.77
0.21
0.94
25
N/A
Precipitation
Depth (mm)
46.4
17.2
40.2
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.80
14.80
19.08
28.11
46.40
22.09
11.88
N/A
N/A
Total
Estimated
Influent
Volume (m3)
Total
Estimated
Influent Load
(g)
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
136.47
49.03
118.24
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
91.10
14.00
80.07
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
0.252
0.005
0.053
-0.006
0.004
-0.004
-0.007
-0.006
0.018
0.000
0.008
-0.010
12
-0.010
-0.006
0.002
0.011
0.252
0.026
0.073
N/A
N/A
a
Estimated Pollutant
Load Reduction
(g)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
(%)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Table D-14: Water Quality Performance for Zinc (Zn)
27-Jul-2014 18:50
11-Aug-2014 22:40
10-Sep-2014 15:40
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
103
110
88
82
123
155
100
75
60
51
87
61
12
50.9
71.6
87.2
104.8
155.0
91.2
29.4
20
162
Precipitation
Depth (mm)
46.4
17.2
40.2
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.80
14.80
19.08
28.11
46.40
22.09
11.88
N/A
N/A
Total
Estimated
Influent
Volume (m3)
Total
Estimated
Influent Load
(g)
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
136.47
49.03
118.24
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
22.11
7.94
19.15
4.31
7.58
9.98
3.32
12.94
9.78
7.29
13.91
5.46
12
3.32
6.83
8.86
13.18
22.11
10.32
5.79
N/A
N/A
91.10
14.00
80.07
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
9.38
1.54
7.04
0.80
1.82
3.24
0.72
2.80
1.92
1.20
3.48
1.58
12
0.72
1.45
1.87
3.30
9.38
2.96
2.65
N/A
N/A
Estimated Pollutant
Load Reduction
(g)
12.73
6.40
12.12
3.51
5.75
6.73
2.61
10.15
7.86
6.09
10.44
3.88
12
2.61
5.29
6.57
10.22
12.73
7.36
3.36
N/A
N/A
(%)
58%
81%
63%
82%
76%
67%
78%
78%
80%
84%
75%
71%
12
58%
70%
77%
80%
84%
74%
8%
N/A
N/A
Table D-15: Water Quality Performance for Dissolved Chloride (Dissolved Cl-)
27-Jul-2014 18:50
11-Aug-2014 22:40
10-Sep-2014 15:40
21-Sep-2014 05:50
03-Oct-2014 13:00
19-Apr-2015 22:30
11-May-2015 19:40
07-Jun-2015 20:40
22-Jun-2015 20:50
07-Jul-2015 12:30
10-Aug-2015 11:50
19-Aug-2015 21:50
Count
Minimum
25 Percentile
Median
75 Percentile
Maximum
Mean
Standard Deviation
WQ Guideline
Median Influent
Effluent EMC
(mg/L)
168
247
84
207
170
375
394
282
237
226
132
345
12
84.30
169.50
231.50
297.75
394.00
238.94
96.32
128
N/A
Precipitation Depth
(mm)
46.4
17.2
40.2
9.4
17.4
21.0
7.8
27.8
20.8
15.6
29.2
12.4
12
7.8
14.8
19.1
28.1
46.4
22.1
11.9
N/A
N/A
Influent
Influent Load
Volume (m3)
(g)
136.47
49.03
118.24
26.61
46.76
61.59
20.52
79.89
60.38
45.02
85.88
33.70
12
20.52
42.19
54.71
81.39
136.47
63.67
35.72
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Total
Measured
Effluent
Volume (m3)
Total
Measured
Effluent Load
(g)
91.10
14.00
80.07
9.76
14.81
20.93
7.18
37.17
31.92
23.54
40.19
25.91
12
7.18
14.61
24.73
37.93
91.10
33.05
26.71
N/A
N/A
15304
3458
6750
2020
2517
7849
2829
10482
7564
5321
5305
8939
12
2020
3301
6035
8122
15304
6528
3859
N/A
N/A
Estimated Pollutant
Load Reduction
(g)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
(%)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
140.0
Effluent EMC
120.0
Total Suspended Solids (mg/L)
Guideline
100.0
80.0
60.0
40.0
20.0
0.0
Sampling Dates
Figure D-1: Time Series Plot of Effluent Concentrations of Total Suspended Solids from Sampling Events.
0.3
Effluent EMC
Total Phosphorus (mg/L)
0.3
Guideline
0.2
0.2
0.1
0.1
0.0
Sampling Dates
Figure D-2: Time Series Plot of Effluent Concentrations of Total Phosphorus from Sampling Events.
0.2
0.2
Effluent EMC
0.2
Phosphate (mg/L)
0.1
0.1
0.1
0.1
0.1
0.0
0.0
0.0
Sampling Dates
Figure D-3: Time Series Plot of Effluent Concentrations of Phosphate from Sampling Events.
3.5
Effluent EMC
3.0
Nitrite + Nitrate (mg/L -N)
Guideline
2.5
2.0
1.5
1.0
0.5
0.0
Sampling Dates
Figure D-4: Time Series Plot of Effluent Concentrations of Nitrite + Nitrate from Sampling Events1.
1
Water quality guideline for Nitrate is used
1.2
Effluent EMC
Total Kjeldahl Nitrogen (mg/L)
1.0
0.8
0.6
0.4
0.2
0.0
Sampling Dates
Figure D-5: Time Series Plot of Effluent Concentrations of Total Kjeldahl Nitrogen from Sampling Events.
2.5
Effluent EMC
Guideline
Cadmium (µg/L)
2.0
1.5
1.0
0.5
0.0
Sampling Dates
Figure D-6: Time Series Plot of Effluent Concentrations of Cadmium from Sampling Events.
35.0
Effluent EMC
30.0
Guideline
Copper (µg/L)
25.0
20.0
15.0
10.0
5.0
0.0
Sampling Dates
Figure D-7: Time Series Plot of Effluent Concentrations of Copper from Sampling Events.
450.0
Effluent EMC
400.0
Guideline
350.0
Iron (µg/L)
300.0
250.0
200.0
150.0
100.0
50.0
0.0
Sampling Dates
Figure D-8: Time Series Plot of Effluent Concentrations of Iron from Sampling Events.
1.2
Effluent EMC
1.0
Guideline
Lead (µg/L)
0.8
0.6
0.4
0.2
0.0
Sampling Dates
Figure D-9: Time Series Plot of Effluent Concentrations of Lead from Sampling Events1.
1
Analytical method used by MOECC produced negative concentrations. These values are to be treated as non-detects and were assigned a value of 0 for this plot.
30.0
Effluent EMC
25.0
Guideline
Nickel (µg/L)
20.0
15.0
10.0
5.0
0.0
Sampling Dates
Figure D-10: Time Series Plot of Effluent Concentrations of Nickel from Sampling Events1.
1
Analytical method used by MOECC produced negative concentrations. These values are to be treated as non-detects and were assigned a value of 0 for this plot.
180
Effluent EMC
160
Guideline
140
Zinc (µg/L)
120
100
80
60
40
20
0
Sampling Dates
Figure D-11: Time Series Plot of Effluent Concentrations of Zinc from Sampling Events.
450
Effluent EMC
400
Guideline
Dissolved Chloride (mg/L)
350
300
250
200
150
100
50
0
Sampling Dates
Figure D-12: Time Series Plot of Effluent Concentrations of Dissolved Chloride from Sampling Events.
Figure D-13: Box plot of CVC Head Office TSS concentrations compared to NSQD concentrations by land use.
100
90
Load Reduction (%)
80
70
60
50
40
30
20
10
0
2-5
5 - 10
10 - 15
15 - 20
20 - 25
>25
TP
NO2+NO3
TKN
Figure D-14: Estimated total load reduction by event size for nutrients. Black bars show the range in load reductions for individual storm events.
100
90
Load Reduction (%)
80
70
60
50
40
30
20
10
0
2-5
5 - 10
10 - 15
15 - 20
20 - 25
>25
Cu
Zn
Figure D-15: Estimated total load reduction by event size for metals. Black bars show the range in load reductions for individual storm events.
Appendix E
Intensification of Urban
Water Cycle
NOTICE
FINAL REPORT
APPENDIX E: Intensification of Urban Water Cycle
1 INTENSIFICATION OF URBAN WATER CYCLE
It is expected that the population of the Greater Toronto Area
1
(GTA) will grow from 6.4 million in 2012 to 8.9 million by 2036 .
This ongoing urbanization of our environment by increasing
imperviousness results in a phenomenon commonly known as
2
the “urban stream syndrome” , where hydrographs become
flashier (i.e., increased flow variability), baseflow decline, water
quality is degraded, stream channels are eroded, water
temperatures rise, and biological richness declines. Figure 1
shows a hydrograph comparing stream flow rates before,
during, and after a storm under pre- and post-development
3
conditions . As indicated, streams with developed watersheds
have substantially higher peak flows, and these peak flows
occur more quickly than under predevelopment conditions. This
is reflective of typical urban conditions, where runoff moves
quickly over impervious surfaces and drains into a channel.
Impervious surfaces such as streets,
sidewalks and driveways contribute 6575% of total loadings of suspended
solids, total phosphorus, and metals to
our receiving streams and lakes
(Bannerman et al., 1992). Furthermore,
beach closures and reductions in
recreational fishing due to pollutant
loading from urban stormwater and
have resulted in up to $87 million a year
in lost revenue to local economies
(Marbek, 2010).
Figure 1: Changes in stream flow hydrograph as a result of urbanization (adapted from Schueler, 1987)
1
Ministry of Finance (MOF). 2013. Ontario Population Projections Update.
http://www.fin.gov.on.ca/en/economy/demographics/projections/projections2012-2036.pdf
2
Walsh CJ, Roy AH, Feminella JW, Cottingham PD, Groffman PM, Morgan RP II. 2005. The urban stream syndrome: Current
knowledge and the search for a cure. Journal of the North American Benthological Society 24(3):706-723
3
Schueler, T. 1987. Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban Best Management
Practices. Metropolitan Washington Council of Governments, Washington, DC.
This ongoing urbanization of our environment by increasing imperviousness also corresponds to a
significant alteration to the water cycle. Continued development with structured conveyance and
impervious pathways redistributes the water budget to favour runoff over evaporation, infiltration, and
recharge for streams and groundwater. The figures below illustrate how four important components in the
4
water cycle are affected by increasing levels of imperviousness .
In natural and rural environments with vegetated soils, surface runoff is generally low and represents a
5
low fraction (10 to 20%) of the total fallen precipitation . Water either percolates into the ground or is
returned to the atmosphere by evaporation and transpiration. A considerable percentage of the rainfall
infiltrates into the soil and contributes to the groundwater. The local water table is often connected to
nearby streams, providing seepage to streams and wetlands during dry periods and maintaining base
flow essential to the biological and habitat integrity of streams. Water that is evaporated into the
atmosphere behaves like an air conditioner for the urban atmosphere, thereby more water in the
atmosphere reduces the urban heat island effect, mitigating high air temperatures (Figure 2a).
Figure 2a: Hydrologic Cycle: Natural ground cover
Figure 2b: Hydrologic Cycle: 10-20% Impervious Predevelopment Conditions
cover - Predevelopment Conditions
(Adapted from FIRSWG, 1998)
Land development converts permeable land into increasing impermeable surfaces. During urbanization,
natural channels are replaced by artificial drainage pipes and channels that decrease the amount of water
infiltration and storage within the soil column. This alters the hydrologic regime by allowing less rainfall
infiltration into the ground, and more channeled runoff through the urban infrastructure. Alterations to site
runoff characteristics can cause an increase in the volume and frequency of runoff flows (discharge),
velocities that cause flooding, and accelerated erosion (Figure 3a). This also decreases the amount of
water available for evapotranspiration and infiltration. Evaporation decreases because there is less time
for it to occur when runoff moves quickly off impervious surfaces. Transpiration decreases because
vegetation has been removed. In addition, urban infrastructure removes water from shallow ponds and
wetlands that could have otherwise been used to replenish the water table and maintain low flow
conditions in local watercourses. Headwater streams, with small contributing drainage areas, are
especially sensitive to localized changes in groundwater recharge and base flow.
4
Adapted from Federal Interagency Stream Restoration Working Group (FISRWG). 1998. Stream CorridorRestoration:
Principles, Processes, and Practices. PB98-158348LUW.
5
Prince George's County, Maryland Department of Environmental Resources Programs and Planning Division. 1999. LowImpact Development Hydrologic Analysis
As a much larger percentage of rainwater hits impervious surfaces including roofs, sidewalks, parking
lots, driveways, and streets, it must be controlled through storm water management techniques.
Traditional approaches have focused on collection and conveyance to quickly transport stormwater to the
nearest watercourse to prevent property damage (Figure 3a). Current stormwater management has
taken an "end of pipe" approach, using gutters and piping systems to carry rainwater into ponds or
detention basins (Figure 3b). This approach does not mitigate or alter the runoff volume component of
the water cycle which is the driving force over flood risk and drought due to decreases in subsurface
flows.
Figure 3a: Stormwater Management with no
water quality control
Figure 3b: Stormwater management using
SWM ponds.
(Adapted from FIRSWG, 1998)
Urban areas are particularly susceptible to flooding
due to a high concentration of impervious surfaces
that channel precipitation runoff into the city’s
underground infrastructure. During rainfall events of
high intensity, duration and/or frequency, the runoff
component of the water balance will be overwhelmed
and not mitigated by infiltration, creating flood-prone
areas in urbanized zones (Figure 4).
As part of adaptive management, stormwater
management has evolved over time in Ontario, from
flood control requirements in the 1970s, to water
quality and erosion requirements in the 1980s, to
Figure 4: Flood prone area in Cooksville
water balance requirements in 2012. The cost and
Creek watershed
complexity of these engineered systems has
increased. In light of the current spot light on climate
change and aging infrastructure there is growing awareness that stormwater management has become
more than just treating a storm event it’s also about maintaining stream flows during dry weather periods
for wastewater assimilation, fisheries, and water takings.
Through the Great Lakes Protection Act,
Water Opportunities Act and Redside Dace legislation, stormwater is being recognized as a resource to
be treated at source, conveyance and prior to entering waterways.
A robust stormwater management system that meets all environmental and economic goals must include
both conventional stormwater management facilities and source based Low Impact Development (LID)
practices. Conventional facilities are typically effective at achieving flood control by providing large
volumes of stormwater detention. Conventional facilities however lack the ability to provide water balance
benefits or reduce the volume of runoff from heavily urbanized areas. As a result they offer little benefits
with respect to infiltration and erosion mitigation. LID practices excel where conventional systems fail by
allowing for natural hydrologic processes including infiltration and evapotranspiration as close to the
source as possible.
LID practices are designed to mitigate the rapidly changing water cycle by mimicking nature within the
urban environment. LID strategies strive to allow natural infiltration to occur as close as possible to the
original area of rainfall. By engineering terrain, vegetation, and soil features to perform this function, the
landscape can retain more of its natural hydrological function (Figure 5). Although most effective when
implemented on a community-wide basis, using LID practices on a smaller scale can also have a positive
impact.
Figure 5: Urban water cycle with Low Impact Development stormwater Management - (Adapted from
FIRSWG, 1998)
2 UNEXPECTED CONSEQUENCES OF URBAN DEVELOPMENT
As might be expected, there is a linear relationship between the amount of impervious surfaces in a given
area and the amount of runoff generated. What is unexpected is what this means in terms of both the
volume of water generated and the rate at which it exits the surface. Depending on the degree of
impervious cover, the annual volume of storm water runoff can increase to anywhere from 2 to 16 times
6
the predevelopment amount . Impervious surface coverage as low as 10% can destabilize a stream
7
channel, raise water temperatures, and reduce water quality and biodiversity .
This is consistent with monitoring data from the urbanizing subwatershed of Fletchers’ Creek which
shows increasing trends in peak flows downstream from developed catchments despite post to predevelopment control with conventional SWM facilities such as wet ponds. In fact, the flow of the creek has
on average increased by roughly two orders of magnitude despite the adoption of conventional
stormwater management (Figure 6).
Figure 6: Increasing trends in stream flow pre- and post-construction in Fletchers’ Creek
The longer duration of higher flows due to
increased volume combines with that from
downstream tributaries to increase the
downstream peaks. As a result, the portions of
Fletchers Creek is experiencing extensive bank
slumping and erosion (Figure 7).
In a natural setting, typically 6-9 events per year
produce runoff that enters the stream. With LID
stormwater management, very little to no runoff
is produced during precipitation events less
than 25 mm in depth, that is 90% of all
precipitation events. What this means is that
69% of all the rain to fall will not produce runoff.
6
Figure 7: High stream flow in Fletcher’s Creek
Schueler, T. 1994. The Importance of Imperviousness. Watershed Protection Techniques 1(3):1’00-111.
7
Schueler, T. 1995. Site Planning for Urban Stream Protection. Metropolitan WashingtonCouncil of Governments, Washington,
DC.
In fact, LID sites can prevent runoff for events up to 25 mm in depth (Figure 8). For rainfall events with a
depth greater than 25 mm, in which runoff is produced, it was previously thought that LID would have little
effect in mitigating flows. However, monitoring data has shown that there is runoff volume reductions and
peak flow reductions even for large storm events.
90% of Total 9vents
69 % of Total 5epth
20
18
18
16
Avg. # of Events/yr
16
0-25mm
14
12
10
9
8
6
6
4
3
2
2
2
25 to 30
30 to 35
35+
2
0
2 to 5
5 to 10
10 to 15
15 to 20
20 to 25
Rainfall Depth (mm)
Figure 8: Typical Annual Rainfall Frequency Distribution for Toronto Lester B. Pearson 1960-2012
3 CHANGES IN WATER QUALITY
Pollution from storm water runoff can also
be a major concern in urban areas.
Rainwater washing across streets and
sidewalks can pick up spilled oil,
detergents,
solvents,
de-icing
salt,
pesticides, fertilizer, and bacteria from pet
waste. Carried untreated into streams and
waterways, these materials become "nonpoint source pollutants" which can
increase water temperature, algae content,
impact aquatic habitats, cause beach
closures and require additional costly
treatment to make the water potable for
drinking water systems. Beach closures
and reductions in recreational fishing due
to pollutant loading from urban stormwater
Figure 9: Sediment Plume from Credit River to Lake
Ontario (Photo Credit: Aquafor Beech, 1990)
8
and have resulted in up to $87 million a year in lost revenue to local economies .
During last three decades, Ontario developers and municipalities have constructed end-of-pipe wet
facilities (i.e. wet ponds, wetlands and hybrid ponds) as standalone stormwater management facilities to
provide water quality control through the removal of total suspended solids. Conventional end-of-pipe wet
stormwater management ponds, in which the main treatment mechanism is capture of particulates
through settling, are not effective in removing the fine particles that carry most of the nutrients as well as
most of the dissolved pollutants and hydrocarbons. The increase in water temperature as result of the
increase in impervious surfaces is also a major water quality concern in urban streams. Retention of
stormwater in conventional wet ponds allows stormwater to warm up, causing thermal impacts on
receiving water bodies. Because temperature plays a central role in the rate and timing of instream biotic
and abiotic reactions, such increases have an adverse impact on streams. In some regions, summer
stream warming can irreversibly shift a cold-water stream to a cool-water or even warm-water stream,
resulting in deleterious effects on salmonids and other temperature-sensitive organisms.
There is also significant concern about
phosphorus loading from urban areas.
Phosphorus is one of main pollutants of
concern in urban drainage. Phosphorus and
other nutrients are transported by runoff in a
particulate-bound and dissolved phosphorus
form.
45
Impervious)
Impervious)
40
CWQG
35
TSS Concentration (mg/L)
In the Credit River Watershed, the
difference in the concentration of total
suspended solids (TSS) in an urban
stream that was receiving stormwater from
upland developments with conventional
end-of-pipe wet facilities and a rural
stream with only 10 - 20% impervious
cover during dry ambient condition is
shown in Figure 10. The comparison
demonstrated that there are higher levels
of TSS in the stream draining the
developed
area
with
conventional
stormwater management wet facilities than
in the rural area. This is due to the lack of
runoff volume control in the stormwater
management ponds.
30
25
20
15
10
5
0
Jan.
Feb.
Mar.
April
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
th
Figure 10: Monthly 75 Percentile Total Suspended
Solids concentration compared at an urban vs. rural
catchment
Note: Different urban/rural stream have unique
responses to development. The example graphs how
scenarios observed for one rural and one urban
watercourse in CVC’s jurisdiction.
The Total Phosphorus (TP) concentration in two monitored streams within CVC’s watershed showed
similar results to those observed for TSS. Higher phosphorous concentrations were observed in the urban
stream that was receiving stormwater from upland developments into a conventional end-of-pipe SWM
facility than in the rural stream that had only 10 - 20% impervious cover during the summer months. Peak
concentrations were seen in the rural stream during the spring season whereas peak concentrations were
seen in the urban stream during the summer season (Figure 11). This is due to the greater level of
impervious surfaces and lack of stormwater volume control in the urban stream. Elevated concentrations
8
Marbek (submitted to Ontario Ministry of Environment). 2010. Assessing the Economic Value of Protecting the Great Lakes:
Rouge River Case Study for Nutrient Reduction and Nearshore Health Protection.
http://www.greeninfrastructureontario.org/sites/greeninfrastructureontario.org/files/Final%20Rouge%20Report%20Nov%2030.p
df
of nutrients in the summer season is the major
factor contributing to excess algae growth and
depressed dissolved oxygen in receiving
9
streams .
Impervious)
Impervious)
0.160
PWQO
0.140
TP Concentration (mg/L)
Currently there is a significant concern about
phosphorus loading from urban areas.
Phosphorus is considered as one of main
pollutants of concern in urban drainage.
Phosphorus
and
other
nutrients
are
transported by runoff in a particulate-bound
and dissolved phosphorus form.
0.180
0.120
0.100
0.080
0.060
0.040
0.020
0.000
Jan.
Feb.
Mar.
April
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
New York State SWM Design Manual also
Figure 11: Monthly 75th Percentile Total Phosphorus
states that “Based on the best available
concentration compared at an urban vs. rural catchment
data, it has been observed that particles
less than 10 μm tend to have substantially
higher
associated
phosphorus
concentrations than larger particle sizes”. This raises concerns with respect to the ability of wet ponds to
10
remove particulate phosphorus as they are not efficient in removing particles less than 10 μm .
Moreover, treatment mechanisms focused on capture of particulates does not address dissolved
phosphorus removal. This is consistent with the 2003 MOE Stormwater Design Guidelines, which state
that while end-of-pipe facilities are typically designed to remove 60-80% suspended solids, the typical
removal efficiency for total phosphorus is 40-50%.
Section 4.4 of the 2003 MOE Stormwater Design Guidelines also recognize that the use of stormwater
ponds for water quantity and quality control can impair receiving stream habitat because of the heating of
the discharge water. Because a municipality may have hundreds of wet stormwater management facilities
within a single watershed, the cumulative impacts on aquatic systems can be significant.
In streams containing Redside Dace, Ministry
of Natural Resources requires that there be no
storm runoff from rainfall events in the range of
5 to 15 mm, considering the recommendations
of the subwatershed plans and soil
11
permeability . In such circumstances, low
impact development strategies to promote
infiltration and stormwater reuse should be
utilized to match post development water
balance with the pre-development condition.
Figure 12: High TSS from urban runoff in
Springbrook Creek habitat of Redside Dace
9
Aquafor Beech (for Conservation Halton). 2005. LOSAAAC Water Quality Study. Aquafor Beech reference 64353.
https://halton.ca/living_in_halton/water_wastewater/water_quality_protection/lake_ontario/LOSAAAC/
10
Greb, S. and Bannerman, R. 1997. Influence of particle size on wet pond effectiveness. Water Environment Research, 69 (6):
1134-1138.
Ministry of Natural Resources (MNR). 2011. DRAFT Guidance for Development Activities in Redside Dace Protected Habitat.
11
Ontario Ministry of Natural Resources, Peterborough, Ontario. ii+42 pp
4 RESOURCE INFORMATION
Literature reviews show that LID practices mitigate the impacts of urbanization by mimicking predevelopment hydrology. CVC/TRCA’s Low Impact Development Stormwater Management Planning and
Design Guide provides planning and design guidance on a wide range of stormwater management
practices such as bioretention, disconnection of downspouts, rain harvesting, swales, permeable
pavement, and green roofs.
Prevention of urban runoff is an effective means to achieve a broad range of stormwater management
objectives such as maintaining pre-development runoff volume, frequency and duration for frequent storm
events, reducing runoff temperature, reducing the concentration of TSS and reducing the loading of
phosphorus into surface waters. Reducing imperviousness and disconnection of impervious areas can be
achieved through alternative design standards for road widths, road right of ways, minimum numbers of
parking lot, varied front and rear lots, the use of pervious materials and the use of source controls as
discussed in the above document.
For detailed information on preventative and mitigation measures to address thermal impacts of urban
developments, refer to CVC’s Study Report: Thermal Impacts of Urbanization including Preventative and
Mitigation Techniques and CVC/TRCA Low Impact Development Stormwater Management Planning and
Design Guide.
Appendix F
Site Maintenance and
Inspection Logs
NOTICE
FINAL REPORT
Appendix F – Site Maintenance and Inspection Log
Site: CVC Head Office
Inspector:
Date:
Site Characteristics:
CVC Head Office
Road, parking lay-by and sidewalk
Engineered bioretention mix
Permeable pavement and grass swale
Online
Inlet pipes from parking lay-by and permeable
pavement sidewalk
Drainage Area
Soil Media
Pretreatment
Hydraulic Configuration
Inlet Type
Contributing Drainage
Area:
Category:
% of Trash/Debris Present
0% --- 5% --- 10% --- 15% --- 20% +
% of Sediment
Accumulation
0% --- 5% --- 10% --- 15% --- 20% +
Inlets:
0% --- 5% --- 10% --- 15% --- 20% +
% of Sediment
Accumulation
0% --- 5% --- 10% --- 15% --- 20% +
% of Erosion
0% --- 5% --- 10% --- 15% --- 20% +
Structural damage?
Yes
or
No
Is inlet clear and able to
accept incoming flow?
Yes
or
No
Grass Swale:
0% --- 5% --- 10% --- 15% --- 20% +
Evidence of Ponding
Yes
% of Area Ponding
0% --- 5% --- 10% --- 15% --- 20% +
Approximate Depth of
Ponding
___________________
or
No
Notes:
% of Bare/Exposed Soil
0% --- 5% --- 10% --- 15% --- 20% +
% of Sediment
Accumulation
0% --- 5% --- 10% --- 15% --- 20% +
% of Erosion
0% --- 5% --- 10% --- 15% --- 20% +
Permeable Pavement:
0% --- 5% --- 10% --- 15% --- 20% +
% of Sediment
Accumulation
0% --- 5% --- 10% --- 15% --- 20% +
Structural damage?
Yes
Area of broken/cracked/
heaving pavers or curbs?
0% --- 5% --- 10% --- 15% --- 20% +
Evidence of Clogging
Yes
or
or
No
No
Outlet:
0% --- 5% --- 10% --- 15% --- 20% +
% of Erosion
0% --- 5% --- 10% --- 15% --- 20% +
% of Sediment
Accumulation
0% --- 5% --- 10% --- 15% --- 20% +
Structural damage?
Yes
or
No
Is outlet clear and able to
accept overflow?
Yes
or
No
Is maintenance required?
Yes
or
No
What needs to be done?
___________________
How much time was spent
on maintenance?
____________________
Maintenance:
Regular maintenance, longterm maintenance or
emergency maintenance?
Who is responsible?
How often is regular
maintenance done?
____________________
____________________
____________________
Photos:
Number of Photo
Site Comments:
Description/Notes

CVC Head Office - Credit Valley Conservation

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