Stormwater ManagementGreen Building FestivalOctober 11 2012Sameer Dhalla, P.Eng.Toronto and Region Conservation Authority
TRCA Jurisdiction The TRCAs area of jurisdiction includes:• 3,467 sq. km: 2,506 on land and 961 water-based.This area is comprised of nine watersheds including:• Etobicoke Creek • Rouge River• Mimico Creek • Petticoat Creek• Humber River • Duffins Creek• Don River • Carruthers Creek• Highland CreekThe TRCA’s jurisdiction alsoextends into Lake Ontario to apoint defined by the TerritorialDivisions Act, R.S.O. 1980 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
Consequences of PoorStormwater Management 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
Stormwater Management Practices Impacts are mitigated through the implementation of Stormwater Management Practices consisting of:Source Controls Conveyance Controls End-of-Pipe Controls Porous Pavers CWC / Infiltration Systems Wet PondTreatment Train Approach
TRCA Stormwater ManagementWHERE WE ARE TODAY 77% of urban areas donot have adequatestormwater controls (mostlyolder areas that weredeveloped prior to therequired implementation ofstormwater managementcontrols) Over 800 SWM Pondshave been constructed Very few Source andConveyance Controls (LIDsites)
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
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) Discharge Post (w/ Detention) Pre- Development Time
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.
Stormwater Management Criteria DocumentGoal: That stormwater management effectively mitigate the impacts ofurbanization 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 OverviewSWM Objective SWM Criteria What’s New1. Flood Protection Control Peak Flows to Pre- Need to assess impacts to Regulatory Development Levels Storm as well as the 2-100 year design storms2. Erosion Protection Mitigate increases in flow rates Need for volume control (site retention and volumes to protect of stormwater through infiltration, watercourses from stream bank evapo-transpiration and/or reuse - erosion LID). Minimum 5mm for small sites that do not require a detailed analysis3. Water Quality Enhanced level of protection Need for thermal protection forControl (80% TSS Removal MOE, 2003) coldwater species and the need for clean water (eg. Roof drainage) to wetlands. Credit for LID4. Water Balance Maintain Water Balance for This is a new criteria, need for LID in Significant Recharge Areas and environmentally sensitive areas Ecologically Significant Areas (sensitive wetlands and woodlots)
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 Conventional “end-of-pipe” strategy Low Impact Development strategy
SWM and LID PRACTICES and DESIGN PRINCIPLES 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)
Stormwater Management – Water Balance Approach
“Integrated design teams and the treatment train approach are essential ingredientsfor the implementation of successful stormwater management strategies, where theenvironment and our communities are soundly protected by infrastructure that isintegrated within the urban fabric.” (TRCA SWM Criteria Document, 2012)
Contact Information TRCA website:Sameer Dhalla, P.Eng. www.trca.on.caPhone: 416 661 6600 x 5350Email: firstname.lastname@example.org 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 YieldProject Conventional Low Impact Difference2nd Avenue SEA $868,803 $651,548 25%Street (Wash.)Auburn Hills $2,360,385 $1,598,989 32%(Wisconsin)Gap Creek $4,620,600 $3,942,100 15%(Arkansas)Somerset $2,456,843 $1,671,461 32%(Maryland)Tellabs Campus $3,162,160 $2,700,650 15%(Illinois)Source: US EPA, 2007, Reducing Stormwater Costs Through Low Impact Development Strategies and Practices (in US dollars)