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Stormwater Roundtable Presenation 01/10


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This Powerpoint was compiled by Sandeep Mehrotra, Chair of the Hastings Environmental Commission and Vice President, Hazen & Sawyer P.C., Environmental Engineers and Scientists. It covers Low Impact Development/Better Site Design Principles & Techniques - What they are, Why they matter in flooding and water quality. It was presented at a Stormwater Management Roundtable organized by Groundwork Hudson Valley/Saw Mill River Coalition, Greenburgh Environmental Forum, and Federated Conservationists of Westchester.

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Stormwater Roundtable Presenation 01/10

  1. 1. Overview of Sustainable Stormwater Management/Low Impact Development Presented by Sandeep Mehrotra Vice President Hazen and Sawyer P.C. Sponsored by
  2. 2. What is Stormwater Management? <ul><li>To Control, Capture, Detain, Retain, Recharge and Convey Rain Water (and snow) effectively without adversely affecting life, property and natural resources. </li></ul>
  3. 3. Why is Stormwater Management so Important? <ul><li>Water is an essential resource for sustaining all forms of life on Earth </li></ul>
  4. 4. The Blue Planet <ul><li>80% of the earths surface is water </li></ul><ul><ul><li>Oceans and seas </li></ul></ul><ul><ul><li>Lakes, rivers, and streams </li></ul></ul><ul><ul><li>Ground water and aquifers </li></ul></ul><ul><ul><li>Atmospheric moisture (rain) </li></ul></ul>
  5. 5. Types of Water <ul><li>Salt water – 97 % </li></ul><ul><li>Glaciers - 2 % </li></ul><ul><li>Fresh water – 1 % </li></ul>
  6. 6. Sources of our Water <ul><li>Today we have approximately the same amount of water as when the Earth was formed. </li></ul><ul><li>Earth will not get any more water. </li></ul><ul><li>Sources of our freshwater </li></ul><ul><ul><li>Lakes and Reservoirs </li></ul></ul><ul><ul><li>Rivers and streams </li></ul></ul><ul><ul><li>Groundwater and aquifers </li></ul></ul><ul><ul><li>Rainwater </li></ul></ul>
  7. 7. Water moves in a never ending cycle <ul><li>Nature recycles it over and over again </li></ul><ul><li>The water you drink may have been drunk by a dinosaur </li></ul>
  8. 8. Water and Humans <ul><li>Water is an essential resource for our existence </li></ul><ul><li>Humans use water for </li></ul><ul><ul><li>Drinking </li></ul></ul><ul><ul><li>Washing </li></ul></ul><ul><ul><li>Recreation </li></ul></ul>
  9. 9. How Much Water Do We Use <ul><li>Typical water usage is 150 gpd per person </li></ul><ul><li>Typical suburban household uses 450 gpd </li></ul><ul><li>Total Westchester usage is 122 gpd </li></ul><ul><li>Total NY tri-state area usage is 1.4 bgd </li></ul>
  10. 10. Need for Effective Stormwater Management <ul><li>Earth's fresh water supply is limited and threatened by pollution. </li></ul><ul><li>We are using our fresh water faster then we are recharging our groundwater. </li></ul><ul><li>The more water we use the more energy we use for water and wastewater treatment. </li></ul>
  11. 11. Comparison of Pre-Development and Developed Hydrologic Cycles <ul><li>Developed </li></ul>Pre-Development
  12. 12. Comparison of Pre- and Post-Development Hydrographs, CSP 1992
  13. 13. Evolution of Paradigms for Storm Water Management Run it in the Ditches
  14. 14. Paradigm Shift # 1 <ul><li>Run it in the Combined Sewers </li></ul>
  15. 15. Paradigm Shift # 2 <ul><li>Run it in Separate Sewers </li></ul>
  16. 16. Paradigm Shift # 3 <ul><li>… Oh, and Control Downstream Flooding </li></ul>Storm Water Pond
  17. 17. Paradigm Shift # 4 <ul><li>Also... Don’t Pollute and Protect Natural Resources </li></ul>BMP for Quantity and Quality Control Protected Stream Side Buffer
  18. 18. Paradigm Shift # 5 <ul><li>LID </li></ul><ul><li>Green Infrastructure </li></ul><ul><li>Soft Path for Storm Water </li></ul>Use BMP’s to Achieve Source Control
  19. 19. Paradigm # 6 <ul><li>Hybrid Design </li></ul><ul><li>LID practices for infiltration and control of small storms </li></ul><ul><li>BMP’s for peak rate and quantity control </li></ul>Stable Stream in Natural Riparian Corridor BMP for Large Storm Events
  20. 20. So What is Low Impact Development? <ul><li>New Philosophy </li></ul><ul><ul><li>Maintaining Functional Relationships Between Terrestrial and Aquatic Ecosystems </li></ul></ul><ul><ul><li>Keep Water Where it Falls </li></ul></ul><ul><li>New Principles </li></ul><ul><ul><li>Decentralized / Source Control </li></ul></ul><ul><ul><li>Distributed / Multi-functional / Multi-beneficial </li></ul></ul><ul><li>New Approaches to Old Ideas </li></ul><ul><ul><li>Prevent / Retain / Detain / Filter / Infiltrate / Treat / Use / Conserve </li></ul></ul>
  21. 21. Low Impact Development <ul><li>Storm Water Management Strategy </li></ul><ul><ul><li>Mimic natural flows, source control </li></ul></ul><ul><ul><li>Emphasize conservation, use existing natural features </li></ul></ul><ul><ul><li>Integrate with distributed, small-scale storm water controls </li></ul></ul><ul><ul><li>BMP’s employ natural processes – infiltration, soil storage, filtration, evaporation, and uptake by vegetation </li></ul></ul>Large Storm Higher Baseflow Lower and Less Rapid Peak Higher and More Rapid Peak Discharge More Runoff Volume I S T R E A M F L O W R A T E Gradual Recession Pre-development Post-development Small Storm
  22. 22. Low Impact Development <ul><li>Don’t rely on conventional end-of-pipe structural solutions </li></ul><ul><li>Instead use conservation practices and BMP’s to mimic pre-development hydrology </li></ul><ul><ul><li>Apply at parcel and subdivision scale </li></ul></ul><ul><ul><li>Detain, retain, store, infiltrate, evaporate run-off </li></ul></ul><ul><ul><li>Reduce volume of storm water discharge, pollutants </li></ul></ul>
  23. 23. Functional Drainage
  24. 24. Conventional Development Centralized Pipe and Pond Control
  25. 25. LID Development Conservation Minimization Soil Amendments Open Drainage Rain Gardens Rain Barrels Pollution Prevention Disconnected Decentralized Distributed Multi-functional Water Use Multiple Systems
  26. 26. Good Drainage Paradigm The Problem: Conventional Site Design Collect Concentrate Convey Centralized Control
  27. 27. Hydrologically Connected Ecologically Dysfunctional
  28. 28. Get the water away as fast as possible!
  29. 29. Conventional vs. LID Storm Water Approach
  30. 30. Lot Level Source Controls LID Site Create a Hydrologically Functional Lot Conservation Open Drainage Rain Gardens Amended Soils Rain Barrel Porous Pavement Narrower Streets
  31. 31. Cumulative Beneficial Impacts of LID Techniques LID rebuilds ecological functions piece by piece.
  32. 32. How Does LID Maintain or Restore The Hydrologic Regime? <ul><li>Creative ways to: </li></ul><ul><ul><li>Maintain / Restore Storage Volume </li></ul></ul><ul><ul><ul><li>interception, depression, channel </li></ul></ul></ul><ul><ul><li>Maintain / Restore Infiltration Volume </li></ul></ul><ul><ul><li>Maintain / Restore Evaporation Volume </li></ul></ul><ul><ul><li>Maintain / Restore Runoff Volume </li></ul></ul><ul><ul><li>Maintain Flow Paths </li></ul></ul><ul><li>Engineer a site to mimic the natural water cycle functions / relationships </li></ul>
  33. 33. Why is LID so Attractive ? <ul><li>Universally Applicable (Arid, Clays, Karst, Cold, Coastal… . ) </li></ul><ul><li>Economically Sustainable </li></ul><ul><li>Ecologically Sustainable </li></ul><ul><li>Added Values </li></ul><ul><li>Lower Costs (Construction, Maintenance & Operation) </li></ul><ul><li>Multiple Benefits (air / water / energy / property values) </li></ul><ul><li>Silent on Growth Management </li></ul><ul><li>Ideal for Urban Retrofit </li></ul><ul><li>Common Sense Approach </li></ul><ul><li>Public Acceptance </li></ul>
  34. 36. “ Rain Gardens”
  35. 37. View of Lot with Storage and Bioretention
  36. 38. Rain Garden Treatment Train Approach Bioretention Cell Storm Drain System Bioretention Cell Grass Filter Strip Flow Path Grass Swale
  37. 39. Large Lot Composite Site Analysis
  38. 40. LID Approach <ul><li>Multiple functions/benefits </li></ul><ul><ul><li>Drainage </li></ul></ul><ul><ul><li>Aesthetics </li></ul></ul><ul><ul><li>Real estate values </li></ul></ul><ul><ul><li>Privacy </li></ul></ul><ul><ul><li>Reduced costs </li></ul></ul><ul><ul><li>Greater lot yield </li></ul></ul><ul><li>Long term benefits inspired long-term maintenance </li></ul><ul><li>Gardening: # 1 hobby </li></ul><ul><li>Success of LID depends on lot-by-lot responsibility for maintenance </li></ul><ul><li>Issues of acceptance by regulatory agencies </li></ul>
  39. 41. Staten Island Bluebelt Program Ongoing Accomplishments <ul><li>Ecologically sound and cost-effective storm water management for 1/3 of Staten Island </li></ul><ul><li>Preservation of natural drainage corridors </li></ul><ul><li>Water quality improvements by attenuating storm flows, reducing erosion, and treating storm water in BMP’s </li></ul><ul><li>Expansion of open space inventory </li></ul><ul><li>Better wildlife habitat through habitat enhancement structures and native paintings </li></ul><ul><li>Infrastructure cost savings (tens of millions of dollars) </li></ul>
  40. 42. Basic Components of LID Approach <ul><li>Conservation Measures </li></ul><ul><li>Site Planning </li></ul><ul><li>Maintain Pre-development Time of Concentration </li></ul><ul><li>Provide Multiple Redundant BMP’s </li></ul><ul><li>Maintenance and Education </li></ul>
  41. 43. Basic Components of LID Approach <ul><li>1) Conservation Measures </li></ul><ul><ul><li>Forest cover to intercept, evaporate, transpire rainfall </li></ul></ul><ul><ul><li>Preserved soils, amend as needed for enhanced porosity </li></ul></ul><ul><ul><li>Topographic features that slow store infiltration rain... “don’t do this, do this” </li></ul></ul><ul><ul><li>Natural drainage features </li></ul></ul>
  42. 44. Use the Soil Ecosystem Functions <ul><li>1. Hydrology storage / evaporation / recharge / detention </li></ul><ul><li>Storing Cycling Nutrients (bacteria / fungi) phosphorous / nitrogen / carbon </li></ul><ul><li>3. Plant Productivity (vigor) </li></ul><ul><li>4. Water Quality filter / buffer / degrade / immobilize detoxify organic and inorganic materials </li></ul><ul><ul><li>“ Most diverse ecosystem in the world” </li></ul></ul>
  43. 45. Basic Components of LID Approach <ul><li>2) Site Planning </li></ul><ul><ul><li>Multidisciplinary team </li></ul></ul><ul><ul><li>Located development away from critical areas, A & B soils </li></ul></ul><ul><ul><li>Street system that minimizes impervious surface </li></ul></ul><ul><ul><li>Reduce pipes, curb and gutters </li></ul></ul><ul><ul><li>Green parking lot design </li></ul></ul>
  44. 46. Hydrologic Soil Groups <ul><li>Group A: High rate of infiltration, low, rate of runoff potential </li></ul><ul><li>Group B: Moderate infiltration rates when fully wet, moderately coarse textured </li></ul><ul><li>Group C: Slow infiltration rates when thoroughly wet, have layer impeding downward movement or moderately fine to fine textured. </li></ul><ul><li>Groups D: Very slow infiltration rates when thoroughly wet, clays with high shrink/swell potential; high permanent water table or have clay pan or clay layer near to surface or shallow over nearly imperious surface. </li></ul><ul><li>*adopted from San Diego LID manual </li></ul>
  45. 47. Basic Components of LID Approach <ul><li>3) Maintain Pre-Development Time of Concentration </li></ul><ul><ul><li>Hydrologically rough landscape </li></ul></ul><ul><ul><li>Open drainage system </li></ul></ul><ul><ul><li>Flatten slopes </li></ul></ul><ul><ul><li>Disperse drainage </li></ul></ul><ul><ul><li>Lengthen flow paths </li></ul></ul><ul><ul><li>Maintain natural flow paths </li></ul></ul><ul><ul><li>Increase distance from streams </li></ul></ul><ul><ul><li>Maximize street flow </li></ul></ul>
  46. 48. Basic Components of LID Approach <ul><li>4) Provide multiple redundant BMP’s </li></ul><ul><ul><li>Biorentention cells </li></ul></ul><ul><ul><li>Vegetated swales </li></ul></ul><ul><ul><li>Rain gardens </li></ul></ul><ul><ul><li>Green roofs </li></ul></ul><ul><ul><li>Blue roofs </li></ul></ul><ul><ul><li>Green street lay-out </li></ul></ul><ul><ul><li>Porous Pavement </li></ul></ul><ul><ul><li>Infiltration planters </li></ul></ul><ul><ul><li>Infiltration trench </li></ul></ul><ul><ul><li>Rain barrels </li></ul></ul><ul><ul><li>Dry wells </li></ul></ul><ul><ul><li>Storage vaults </li></ul></ul>
  47. 49. IMP Effect or Function Slow Runoff Filtration Infiltration Retention Detention Evaporation Water Quality Control Soil Amendments X X x Bioretention X X X X X X Vegetated Buffers X X X X Grassed Swales X X X X Rock Swales X X X X Rain Barrels X Street Trees X Vegetated Roofs X X X X Permeable Materials X X X Rock Beds X X X X
  48. 50. The Bioretention Concept Original Design P.G County 1993
  49. 51. Vegetated Conveyance
  50. 53. Rain is Resource <ul><li>Capture & Use </li></ul><ul><li>Toilet Flushing </li></ul><ul><li>Car washing </li></ul><ul><li>Irrigation </li></ul><ul><li>Mixing </li></ul><ul><li>Washing </li></ul><ul><li>Gardening </li></ul><ul><li>Recharge </li></ul><ul><li>Benefits </li></ul><ul><li>Reduce Demand </li></ul><ul><li>Self-sufficiency </li></ul><ul><li>Save Money </li></ul>
  51. 54. Basic Components of LID Approach <ul><li>5) Maintenance and Education </li></ul><ul><ul><li>Storm water controls as amenities that property owners will want to maintain </li></ul></ul><ul><ul><li>Educate home owners, landscapers about proper operation and maintenance </li></ul></ul><ul><ul><li>Promote pollution prevention through proper lawn and car care, hazmat handling, good home keeping </li></ul></ul>
  52. 57. Applicability of LID to Urban Settings at Lot Level <ul><li>Bioretention </li></ul><ul><li>Infiltration </li></ul><ul><li>Street Trees </li></ul><ul><li>Green roofs </li></ul><ul><li>Site Planning </li></ul><ul><li>Proprietary Devices </li></ul>
  53. 58. Bioretention Design Objectives <ul><li>Peak Discharge Control </li></ul><ul><ul><li>1-, 2-, 10-, 15-, 100-year storms </li></ul></ul><ul><ul><li>Bioretention may provide part or all of this control </li></ul></ul><ul><li>Water Quality Control </li></ul><ul><ul><li>½”, 1” or 2” rainfall most frequently used </li></ul></ul><ul><ul><li>Bioretention can provide 100% control </li></ul></ul><ul><li>Ground water recharge </li></ul><ul><ul><li>Many jurisdictions now require recharge </li></ul></ul><ul><ul><li>( e.g., MD, PA, NJ, VA) </li></ul></ul>
  54. 59. 2’ 2” Mulch Infiltration System Highly Pervious Soils Existing Ground
  55. 60. 2’ 2” Mulch Drain Pipe Filtration System Existing Ground Highly Pervious Soils
  56. 61. 2’ 2” Mulch Drain Pipe Combination Filtration / Infiltration Moderately Pervious Soils Gravel Sandy Organic Soil Existing Ground
  57. 63. <ul><li>Bioretention </li></ul><ul><li>Shallow Ponding - 4” to 6” </li></ul><ul><li>Mulch 3” </li></ul><ul><li>Soil Depth 2’ - 2.5’ </li></ul><ul><li>Sandy Top Soil </li></ul><ul><ul><li>65% Sand </li></ul></ul><ul><ul><li>20% Sandy Loam </li></ul></ul><ul><ul><li>15% Compost </li></ul></ul><ul><li>Under Drain System </li></ul><ul><li>Plants </li></ul>X 2’ Under Drain
  58. 64. Low Flow Media 2 to 10 inches / hour Peat / Sand / Aggregate Matrix - PSD <ul><li>Peat 15 to 20% by volume </li></ul><ul><li>Clay <5% (<0.002 mm) </li></ul><ul><li>Silt <5% (0.002-0.05 mm) </li></ul><ul><li>Very Fine Sand 5-10% (0.05-0.15 mm) </li></ul><ul><li>Fine Sand 15-20% (0.15-0.25 mm) </li></ul><ul><li>Medium to Coarse Sand 60-70% (0.25-1.0 mm) </li></ul><ul><li>Coarse Sand 5-10% (1.0-2.0 mm) </li></ul><ul><li>Fine Gravel <5% (2.0-3.4 mm) </li></ul>
  59. 65. High Flow Media 10 to 50 inches / hour Peat Sand / Aggregate Matrix - PSD <ul><li>Peat 5 to 10% by volume </li></ul><ul><li>Clay <2% (<0.002 mm) </li></ul><ul><li>Silt <2% (0.002-0.05 mm) </li></ul><ul><li>Very Fine Sand 5% (0.05-0.15 mm) </li></ul><ul><li>Fine Sand 10% (0.15-0.25 mm) </li></ul><ul><li>Medium to Coarse Sand 70% (0.25-1.0 mm) </li></ul><ul><li>Coarse Sand 10-15% (1.0-2.0 mm) </li></ul><ul><li>Fine Gravel 5-10% (2.0-3.4 mm) </li></ul>
  60. 66. Plants Considerations <ul><li>Pollutant uptake </li></ul><ul><li>Evapotranspiration </li></ul><ul><li>Soil ecology / structure / function </li></ul><ul><li>Number & type of plantings may vary, </li></ul><ul><ul><li>Aesthetics </li></ul></ul><ul><ul><li>Morphology (root structure trees, shrubs and herbaceous) </li></ul></ul><ul><ul><li>Native plants materials </li></ul></ul><ul><ul><li>Trees 2 in. caliper / shrubs 2 gal. size / herbaceous 1 gal size. </li></ul></ul><ul><ul><li>landscape plan will be required as part of the plan. </li></ul></ul><ul><ul><li>Sealed by a registered landscape architect. </li></ul></ul><ul><ul><li>Plants are an integral part no changes unless approved </li></ul></ul><ul><ul><li>Plant survival </li></ul></ul><ul><li>Irrigation – Typical / customary </li></ul>
  61. 67. Residential Rain Gardens
  62. 68. Example Bioretention Areas
  63. 72. Bioretention Construction Costs Excavation (assume no hauling) $3 - $5 / cy Fill Media $15 - $20 / cy Vegetation/ Mulch $1.00 - $1.50 / sf Underdrains /Gravel & Outlet $0.50 - $1.50 / sf Total $10 - $14 / sf
  64. 73. Design Configuration Considerations <ul><li>Off line vs. Flow-through </li></ul><ul><li>Inlet </li></ul><ul><li>Surface Storage </li></ul><ul><li>Underdrain – Dewater media </li></ul>
  65. 74. Off-line 2005 Lake County, OH
  66. 75. Flow-through 2005 lake County, OH
  67. 78. Porous Pavers Capturing Roof Runoff
  68. 79. Urban Canopy <ul><li>Multiple Benefits </li></ul><ul><li>Reduce Stormwater Runoff </li></ul><ul><li>Improve Air Quality </li></ul><ul><li>Reduce Energy Consumption </li></ul><ul><li>Reduce Urban Heat Island </li></ul><ul><li>Carbon Storage </li></ul><ul><li>Habitat Value </li></ul>
  69. 80. Portland Oregon Bureau of Environmental Services Building
  70. 81. Street Tree / Shrub Filters
  71. 83. Proprietary Devices
  72. 84. Typical Layouts - Office Building
  73. 85. Typical Layouts - Big Box Design
  74. 86. Needed Paradigms Shifts to Address Urbanization <ul><li>Watersheds to Ecosystems </li></ul><ul><li>Impact Reduction to Functional Restoration </li></ul><ul><li>Political Solutions to Scientific Solutions </li></ul><ul><ul><li>Rhetoric to Reality </li></ul></ul>
  75. 87. <ul><li>Larry Coffman, President, Stormwater Services, LLP, Presentations at StormCon New Jersey Conference, October 2007. </li></ul><ul><li>Bay Area Stormwater Management Agencies Association, “Start at the Source: Design Guidance Manual for Stormwater Quality Protection,” 1999 Edition. </li></ul><ul><li>Prince George’s County, Maryland, Department of Environmental Resources, “Low Impact Development Design Strategies: An Integrated Design Approach,” June 1999. </li></ul><ul><li>Puget Sound Action Team. Olympia, WA, “Natural Approaches to Stormwater Management: Low Impact Development in Puget Sound,” March 2007. </li></ul><ul><li>Larry Coffman, “Low-Impact Development Design: A New Paradigm for Stormwater Management Mimicking and Restoring the Natural Hydrologic Regime,” undated. </li></ul><ul><li>New Hanover County, City of Wilmington, North Carolina, “Joint Low Impact Development Guidance Manual - - Draft,” July 2007. </li></ul><ul><li>County of San Diego, “Low Impact Development Handbook: Stormwater Management Strategies - - Public Review Draft,” July 20, 2007. </li></ul><ul><li>Puget Sound Action Team, Washington State University Pierce County Extension, “Low Impact Development: Technical Guidance Manual for Puget Sound,” January 2005. </li></ul><ul><li>Andy Reese and Charlene Johnston, “Stormwater Funding and Utility Development,” Presentation at StormCon New Jersey Conference, October 2007. </li></ul><ul><li>Low Impact Development Center, Washington D.C. </li></ul>Sources
  76. 88. Thank You