1. low impact development robb lukes low impact development center june 2008 analysis and design

3. Q T Developed Condition, Conventional CN (Higher Peak, More Volume, and Earlier Peak Time) Existing Condition Hydrograpgh Pre/ Post Development Losses

4. Q T Developed Condition, with Conventional CN and Controls Existing Additional Runoff Volume Developed Existing Peak Runoff Rate Detention Peak Shaving

5. Q T Developed Condition, with LID- CN no Controls. Existing Reduced Runoff Volume Developed- No Controls Reduced Q p Minimize Change in Curve Number

6. Q T Developed, LID- CN no controls same Tc as existing condition. Existing More Runoff Volume than the existing condition. Developed, no controls Reduced Q p Maintain Time of Concentration

7. Q T Provide Retention storage so that the runoff volume will be the same as Predevelopment Retention storage needed to reduce the CN to the existing condition = A 2 + A 3 A 3 A 2 A1 Reducing Volume

8. Q T Provide additional detention storage to reduce peak discharge to be equal to that of the existing condition. Existing Predevelopment Peak Discharge Detention Storage

9. Q T Comparison of Hydrographs A 2 A 3 LID Concepts Conventional Controls Existing Increased Volume w/ Conventional

10. design storm approaches single event vs. continuous simulation - peak flows / - volume / hydromodification flooding - water quality

13. EPA Stormwater Management Model (EPA SWMM) Developer US EPA; Oregon State U.; Camp, Dresser and McKee (CDM) Rainfall Modeled Single Event and Continuous Watershed Size Large to Small Watersheds Primary Use Flooding, Quantity, and Quality Land Use & Source Area User defined land uses and source areas Application to LID Can be adapted to simulate LID controls, models storage and infiltration processes

14. Source Loading and Management Model (SLAMM) Developer Dr. Robert Pitt, U of Alabama; John Voorhees Rainfall Continuous Watershed Size Large to Small Watersheds Land Uses Residential, Commercial, Industrial, Highway, Institutional, and other Urban Source Areas Roofs, Sidewalks, Parking, Landscaped, Streets, Driveways, Alleys, etc. Primary Use Runoff Quantity and Quality Application to LID Infiltration, Wet Ponds, Porous Pavement, Street Sweeping, Biofiltration, Vegetated Swales, Other Urban Control Device

15. Prince George’s County BMP Evaluation Model Developer Tetra Tech Inc.; Prince George’s County Rainfall Continuous Watershed Size Site Level to Small Watersheds Land Uses Low-Medium-High Density Residential, Commercial, Industrial, Forest, and Agriculture Source Areas Impervious or Pervious Primary Use Runoff Quantity and Quality Application to LID Retention and conveyance options can be adapted to simulate various LID practices

16. Western Washington Hydrology Model (WWHM3) / *Bay Area Hydrology Model (BAHM) *Model to be released in July 2007 Developer Washington State Dept. of Ecology; AQUA TERRA Consultants; and Clear Creek Solutions, Inc. Rainfall Continuous Watershed Size Large to Small sites in 19 Counties of Western Washington Primary Use Runoff Quantity (Evapotranspiration, Surface Flow, Interflow, Groundwater Flow) Application to LID Ponds, Infiltration Trenches/Basins, Wetlands, Sand Filter, Gravel Trench Beds, Vaults/Tanks, Swales, Green

17. Contra Costa Integrated Management Practice Sizing Calculator Developer Contra Costa Clean Water Program; Dan Cloak Environmental Consulting Rainfall 35 years of continuous Contra Costa rainfall used to sizing factors Watershed Size Small Sites in Contra Costa County Primary Use Simplified method for IMP sizing Application to LID Limited sizing options are available for permeable pavement, dry wells, infiltration trenches/basins, vegetated or grassy swales, bioretention, and in-ground planters

18. National LID Manual Technique Developer US EPA; Prince George’s County Rainfall Single Event Watershed Size Small Sites in Contra Costa County Primary Use Estimates a developed sites retention and detention storage requirements Application to LID Applies to any IMP with retention storage: bioretention, infiltration, porous pavement, swales, and planters

24. Suburban Commercial Site LID Options Selected Source Areas Best Management Practice Roof (20000 sf) Sidewalk (2700 sf) Bioretention Cell w/ Underdrain -Contra Costa Sizing Tool: 1800 sf -3 ft of media depth -0.5 ft of surface storage depth Parking Lot and Loading Area (70,000 sf) Permeable Pavement -15000 sf, located in outer parking spaces -2.5 ft of aggregate depth Grassed Swale -420 linear ft -4 ft bottom width Landscaping Maintain Native Soil Structure Avoid Compaction Deep Soil Aeration

25. Suburban Commercial Site Modeling Results Rainfall: 1997 Continuous Historical Rainfall for Los Angeles CA. SWMM SLAMM Evapotrans. (acre-ft) Infiltration (acre-ft) Runoff (acre-ft) Runoff (acre-ft) Pre-Developed 0.11 4.29 0.08 0.25 Post-Developed 0.37 1.57 3.01 1.77 Post-Developed w/ LID 0.31 3.65 0.62 0.44 Reduction in Runoff w/ LID --- --- 79% 75%

29. Suburban Commercial Site LID Options Selected Source Areas Best Management Practice Roof (0.5 acres) Bioretention Cell w/ Underdrain -2.5 ft of media depth -0.5 ft of surface storage depth Parking Lot and Loading Area (1.6 ac) Permeable Pavement -1.5 ft of aggregate base/subbase Sidewalk (0.1 ac) Landscaping (1.25 ac) Native Landscaping - sidewalk drains to landscaped area - amend soils - avoid compaction - deep soil aeration

31. Suburban Commercial Site Pre-Developed Condition

33. Suburban Commercial Site Peak Flow Results 2 yr-24 hr (cfs) 10 yr-24 hr (cfs) 100 yr-24 hr (cfs) Pre-Developed – Forest Condition 0.17 0.33 0.55 Developed – No Mitigation 0.89 1.28 1.77 Half Permeable Parking Lot 0.57 0.87 1.28 Full Permeable Parking Lot 0.51 0.71 0.96 Half Permeable Parking Lot & Landscaping Amended Soils 0.41 0.58 0.81 Half Permeable Parking Lot & Bioretention Cell for Roof Runoff 0.38 0.46 0.55

34. Suburban Commercial Site Peak Runoff Results

35. Suburban Commercial Site Yearly Peak Runoff Results (1948-1998)

36. WWHM3: Water Balance Comparison

37. Suburban Commercial Site Modeling Results Rainfall Data Used: Los Angeles 1997 SWMM SLAMM Evapotrans. (acre-ft) Infiltration (acre-ft) Runoff (acre-ft) Runoff (acre-ft) Pre-Developed 0.11 4.29 0.08 0.25 Post-Developed 0.37 1.57 3.01 1.77 Post-Developed w/ Per. Parking Lot and Bio. Cell 0.31 3.65 0.62 0.44 Reduction in Runoff w/ LID --- --- 79% 75%

41. Metro West SWMM Model Results Rainfall Data Used: 1992 Washington Dulles Intl. Rain Gage (total of 41.26”) Runoff (acre-ft) Pre-Developed 6.2 Existing 24.2 Post-Developed w/ SWM 76.4 Post-Developed w/ SWM & LID 58.5 Reduction in Runoff w/ LID 77%

42. Metro West SWMM Peak Discharge Results for a 2yr-24hr storm Condition Areas A & B (cfs) Area C (cfs) Area D (cfs) Without LID Inflow 100.5 74.4 48.8 Outflow 9.5 20.8 11.6 With LID Inflow 84.0 61.0 36.7 Outflow 8.5 16.8 6.6 % Reduction in Outflow w/ LID 11% 19% 43%

43. Metro West SWMM Peak Discharge Results for a 10yr-24hr storm Condition Areas A & B (cfs) Area C (cfs) Area D (cfs) Without LID Inflow 178.7 130.7 85.8 Outflow 60.9 69.7 24.1 With LID Inflow 147.6 112.4 62.7 Outflow 47.8 42.4 21.3 % Reduction in Outflow w/ LID 22% 39% 12%

45. Village at Watt’s Creek SLAMM Analysis Scenario Catchbasin With Sumps Residential Downspout Disconnection Residential Bioretention Cells Residential Rain Barrels Permeable Pavement for Alleys and Driveways Street Bioretention Planters No BMPs  #1 – All BMPs       #2 – Bio. Cells    #3 – Rain Barrels    #4 – Permeable Pvt.    #5 – Street Planters   

46. Village at Watt’s Creek SLAMM Runoff Reduction

51. 8% BMP Determining LID BMP Size

54. Initial BMP Input Values BMP-A Calculation BMP-B Calculation Evaluation Factor Calculation Routing Sequence Cost Calculation BMP Model Runner Initial Run Results: Evaluation Factor & Cost Values New changeable variable values BMP Optimizer Solution Changeable Variables (C810) (num, min, max, increment) Control Target (C830) Input File Loader Evaluation Factor & Cost Values feed new possible solution to runner based on previous simulation result ArcGIS Map Interface BMP Simulation/Optimization DLL Prince George’s County LID Model BMP Model Input File

55. PG BMP Evaluation Model HSPF LAND SIMULATION – Unit-Area Output by Landuse – Existing Flow & Pollutant Loads Simulated Flow/Water Quality Improvement Cost/Benefit Assessment of LID design BMP Module BMP DESIGN – Site Level Design – SITE-LEVEL LAND/BMP ROUTING Simulated Surface Runoff

56. HSPF Land Use Representation

58. BMP Class A: Storage/Detention Overflow Spillway Bottom Orifice Evapotranspiration Infiltration Outflow : Inflow : Modified Flow & Water Quality From Land Surface Storage Underdrain Outflow

59. BMP Class B: Open Channel Outflow : Inflow : From Land Surface Overflow at Max Design Depth Open Channel Flow Evapotranspiration Infiltration Underdrain Outflow Modified Flow & Water Quality Modified Flow & Water Quality

60. Holtan Infiltration Model veg. parameter void fraction soil porosity soil f c D u (A) background f c D s

61. Phosphorus Lead Calibrated BMPs!!!

62. General Water Quality First Order Decay Representation Mass 2 = Mass 1 x e – k t Pollutant Removal is a function of the detention time

63. Underdrain Water Quality Percent Removal Mass out = Mass in x (1 - PCTREM) Underdrain percent removal is a function of the soil media Mass in = Surface conc * underdrain flow

65. Pre-Development Developed, No BMPs Developed, LID

67. Government Center Plan

69. Model Screenshot

70. Government Center Results

74. Construction

75. Maintenance

77. Q T 2 3 4 5 6 7 Hydrograph Summary 2 3 4 1 Existing Developed, conventional CN, no control. Developed, conventional CN and control. Developed, LID-CN, no control. Developed, LID-CN, same Tc. Developed, LID-CN, same Tc, same CN with retention. Same as , with additional detention to maintain Q. 6 5 6 7 Pre-development Peak Runoff Rate 1

83. Metro West SWMM and SLAMM Model Results Rainfall: 1997 Continuous Historical Rainfall for Los Angeles CA. SWMM SLAMM Evapotrans. (acre-ft) Infiltration (acre-ft) Runoff (acre-ft) Runoff (acre-ft) Pre-Developed 1.45 56.59 0.30 0.16 Existing 2.61 33.84 21.87 14.31 Post-Developed 4.67 15.87 37.70 27.04 Post-Developed w/ LID 4.78 42.45 11.03 6.53 Reduction in Runoff w/ LID --- --- 78% 76%

85. Metro West SLAMM Pollutant Load Results Sediment (ton) Phosphorous (lbs) Zinc (lbs) Post-Developed 2.05 20.10 12.07 Post-Developed w/ LID 1.36 16.04 3.11 % Reduction w/ LID 34% 20% 74%

89. Village at Watt’s Creek SLAMM Runoff Reduction

90. CA Spreadsheet Total Site Area (acres) 5.74 Proposed Impervious Area (acres) 2.13 Required Area for Non-Structural Treatment (acres) 2.02 Required Volume for Structural Treatment (acre-ft) 2.09 Credit Options Tree Planting 0.30 Disconnect Rooftop Runoff 0.46 Disconnect Non-Rooftop runoff 0.06 Use of Grass Swales 0 Sheet flow to streamway or setback 0 Pervious pavers 0.60 Green Roof 0 Final Area (acres) 0.60 Final Volume (acre-ft) 0.62

92. California Volume Runoff Calculator Developer California State Water Resources Control Board Rainfall Uses Annual Rainfall Volume and 24 hr – 85th Percentile Storm Event Watershed Size Small Sites Primary Use Uses NRCS Method to calculate area required for non-structural and the required volume for structural treatment Application to LID Options limited to disconnected impervious surfaces, tree planting, pervious pavers, green roofs, stream buffer