Background and Overview Stormwater NPDES Compliance For New Developments.
Stormwater Compliance
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Transcript of Stormwater Compliance
Stormwater Management Green Building Festival
October 11 2012
Sameer Dhalla, P.Eng.
Toronto and Region Conservation Authority
TRCA Jurisdiction
• Rouge River
• Petticoat Creek
• Duffins Creek
• Carruthers Creek
The TRCA's area of jurisdiction includes:
• 3,467 sq. km: 2,506 on land and 961 water-based.
This area is comprised of nine watersheds including:
The TRCA’s jurisdiction also extends into Lake Ontario to a point defined by the Territorial Divisions Act, R.S.O. 1980
• Etobicoke Creek
• Mimico Creek
• Humber River
• Don River
• Highland Creek
The population in 2004 within TRCA’s jurisdiction is approximately 4,300,000
(37% of Ontario’s population).
Impacts of Urbanization on Hydrologic Cycle
Up to 500% more runoff
Stream bank erosion and bed
degradation
Increased peak flows - flooding
Increase pollutant loading
(including thermal impacts)
Reduction of groundwater and
baseflow
Loss of aquatic habitat and
natural features
Risk to Infrastructure
Consequences of Poor
Stormwater Management
Evolution of Stormwater Management
Stormwater Management Practices
Impacts are mitigated through the implementation of
Stormwater Management Practices consisting of:
Source Controls
Porous Pavers
CWC / Infiltration Systems
Conveyance Controls
Wet Pond
End-of-Pipe Controls
Treatment Train Approach
TRCA Stormwater Management WHERE WE ARE TODAY
77% of urban areas do
not have adequate
stormwater controls (mostly
older areas that were
developed prior to the
required implementation of
stormwater management
controls)
Over 800 SWM Ponds
have been constructed
Very few Source and
Conveyance Controls (LID
sites)
The Solution to Stormwater Pollution
1. Implement Municipal Stormwater
Retrofit Projects (e.g. Toronto Wet Weather
Flow Management Plan and Municipal SWM
Pond Retrofits such as Pioneer Park and Earl
Bales Park)
2. Maintain existing stormwater
management infrastructure (e.g. pond
clean-outs)
3. Encourage existing communities to
implement lot level controls on private
property (e.g. rain gardens/barrels, SNAP,
PPG)
4. Ensure that all new developments
(including redevelopments) are
designed to comply with the
updated Stormwater Management
Criteria
New Development
End of Pipe Controls (SWM Ponds)
Mitigates increased peak flows from urban areas (no volume control)
Reduces pollutant loadings (does not provide thermal benefits)
Currently the standard practice for stormwater treatment (usually the
only practice employed in the “treatment train”)
Post (no
SWM)
Pre-
Development
Post (w/
Detention)
Time
Dis
ch
arg
e
WHY DO WE NEED TO IMPROVE CURRENT PRACTICES?
Conventional strategies don’t address all impacts
Changes to water balance (increased runoff
volume & decreased recharge & ET)
• Accelerated stream channel erosion and/or
sedimentation;
• Risk of damage to infrastructure &
property;
• Degraded aquatic and terrestrial habitats;
• Degraded water quality (increased
temperature and pollutant loads);
• Less diverse aquatic and terrestrial
communities.
Goal: That stormwater management effectively mitigate the impacts of
urbanization on the natural water cycle (Water Balance Approach)
Objectives:
To prevent increases in flood risk;
To prevent undesirable
geomorphic changes in
watercourses;
To protect water quality;
To preserve groundwater and
baseflow characteristics;
To maintain an appropriate
diversity of terrestrial and aquatic
life and opportunities for human
use.
Stormwater Management Criteria Document
Stormwater Management Criteria Overview
SWM Objective SWM Criteria What’s New
1. Flood Protection Control Peak Flows to Pre-
Development Levels
Need to assess impacts to Regulatory
Storm as well as the 2-100 year design
storms
2. Erosion Protection Mitigate increases in flow rates
and volumes to protect
watercourses from stream bank
erosion
Need for volume control (site retention
of stormwater through infiltration,
evapo-transpiration and/or reuse -
LID). Minimum 5mm for small sites
that do not require a detailed analysis
3. Water Quality
Control
Enhanced level of protection
(80% TSS Removal MOE, 2003)
Need for thermal protection for
coldwater species and the need for
clean water (eg. Roof drainage) to
wetlands. Credit for LID
4. Water Balance Maintain Water Balance for
Significant Recharge Areas and
Ecologically Significant Areas
(sensitive wetlands and
woodlots)
This is a new criteria, need for LID in
environmentally sensitive areas
Conventional “end-of-pipe” strategy Low Impact Development strategy
Need to Move Towards a Water Balance Approach
(Low Impact Development)
• Mitigates impacts to hydrologic cycle
• Reduces generation of excess runoff
volume
• Restores natural flow pathways and
patterns
• Reduces temperature impacts
1. Integrate Stormwater into Planning
(Multi Disciplinary Approach)
2. Focus on runoff prevention
(innovative planning, LID practices)
3. Treat stormwater close to the source
(respect natural flow paths,
stormwater is a resource)
4. Create multifunctional landscapes
(site aesthetics, energy, conserve
potable water, wildlife, parks)
5. Educate and maintain (maintenance
plans)
SWM and LID PRACTICES and DESIGN PRINCIPLES
Stormwater Management – Water Balance Approach
“Integrated design teams and the treatment train approach are essential ingredients
for the implementation of successful stormwater management strategies, where the
environment and our communities are soundly protected by infrastructure that is
integrated within the urban fabric.” (TRCA SWM Criteria Document, 2012)
Contact Information
Sameer Dhalla, P.Eng.
Phone: 416 661 6600 x 5350
Email: [email protected]
TRCA website:
www.trca.on.ca
STEP website:
www.sustainabletechnologies.ca
Key Recommendations –
Resolution 4 – 2012M
WHEREAS, stormwater has been recognized by the International Joint
Commission (IJC) and Canadian and US regulatory authorities as the
leading non-point sources of pollutants to nearshore water quality in
the Great Lakes and St. Lawrence; and
WHEREAS, the volume and frequency of untreated stormwater
discharged to the nearshore can only be expected to increase in the
foreseeable future – due to more severe and numerous weather events and
climate change, compounded in urban areas by planned growth and
intensification – unless more proactive stormwater planning and
management is applied and implemented in urban and rural areas; and
WHEREAS, support for naturalized infrastructure in the management of rural
stormwater run-off also helps landowners and municipalities adapt to the
impacts of climate change in ways that help to mitigate climate change
because natural infrastructure takes carbon out of the atmosphere and
locks it up in plant material.
LOW IMPACT DEVELOPMENT BENEFITS
Lower Construction Costs
Higher Lot Yield Project Conventional Low Impact Difference
2nd Avenue SEA
Street (Wash.)
$868,803 $651,548 25%
Auburn Hills
(Wisconsin)
$2,360,385 $1,598,989 32%
Gap Creek
(Arkansas)
$4,620,600 $3,942,100 15%
Somerset
(Maryland)
$2,456,843 $1,671,461 32%
Tellabs Campus
(Illinois)
$3,162,160 $2,700,650 15%
Source: US EPA, 2007, Reducing Stormwater Costs Through Low Impact Development Strategies and Practices
(in US dollars)