1. STEP 3: SITING AND SIZING STORM WATER CONTROLS Section 6

4. Runoff Conveyance / Diversion Storage Detention Retention Treatment Physical Chemical Biological Peak Attenuation Discharge Infiltration Evapotranspiration Pollutants (to Disposal) Control Systems What are Best Practices? Runoff Source Control Precipitation Pollutant Source Control Impervious Infiltration Evapotranspiration Pervious Source Controls Preservation Restoration Resource Protection

5. Best Local Land Use Practices to Illustrate through Case Studies u Imperviousness control (e.g., reduce, disconnect, permeable materials) u Vegetated filter strips and swales u Infiltration practices (e.g., rain gardens, trenches, dry wells) u Filters / underdrains (bioretention, soil amendments, sand, other) u Basins (wet, dry, wetland, vaults) u Stream, floodplain, and wetland enhancements / setbacks u Integrated Combinations of Practices

6. Rain Barrel/Cistern Green Roof Rain Garden Pocket Park Bioretention DecentralizedApproach

7. Opportunities and Barriers : Less Imperviousness Source Controls

8. Opportunities and Barriers : Permeable Pavements Source Controls

9. Opportunities and Barriers : Disconnected Downspouts Source Controls

10. Opportunities and Barriers : Rain Barrels and Cisterns Source Controls

11. Opportunities and Barriers : Filter Strips and Swales Conveyance / Treatment Systems for Yards / Roads / Parking

12. Opportunities and Barriers : Rain Gardens Control Systems for Yards

13. Opportunities and Barriers : Pocket Wetlands Control Systems for Yards

14. Opportunities and Barriers : Bioretention drain Not sogood Good – Run-off from the parking lotcan be absorbed by the plants and soil Center for Watershed Protection Control Systems for Roads / Parking

15. Opportunities and Barriers : Bioretention Control Systems for Roads / Parking

16. Semi-DecentralizedApproach Rain Barrel Green Roof Rain Garden Pocket Park Bioretention

17. Opportunities and Barriers : Bioretention Before After Control Systems for Roads / Parking

18. CentralizedApproach Rain Barrel Green Roof Rain Garden Pocket Park Bioretention

19. Opportunities and Barriers : Pocket Park with Best Practices Control Systems for Sites/Regions

20. Dry Extended Detention Basin Wet Pond - Solids Settling Wet Pond - Eutrophication Wetland Photo Copyright 1999, Center for Watershed Protection Opportunities and Barriers : Basins for Water Quality / Quantity Control Control Systems for Sites/Regions

21. Multi-use Storm Water Basin Runoff Park & Recreation Treatment and Stream Erosion Control Park Facilities & Parking Pretreatment & Additional Flood Control (Ballfields, Hiking Jogging, Biking) Recharge where Possible Flood Control

22. Bruns Ave. Elementary School Wetland and BMP Demonstration Project; Charlotte, NC Opportunities and Barriers : Integrated Water Quality / Quantity Control Control Systems for Sites/Regions

24. Step 3.a.1: Area Information

25. Drainage areas and flow paths are measured from site plan

26. A R = 3 ac A R = 0.6 ac = 0.6 ac = 0.3 ac

27. Step 3.a.1: Area Information 2.3 ac 0.5 ac 1.8 ac 10 min

28. Step 3.a.1 (cont.): Characteristics of Soils at BMP Site

29. 1.0 0.75 0.50 0.25 0.0 Soil Column Porosity = Total Void Space in Soil Water Balance within Soil Column Field Capacity = Limit of Gravity Drainage Saturation Wilting Point = Moisture available to plants Ponding Available to Groundwater Available to Plants Evaporation Only Infiltration = Saturated Hydraulic Conductivity (in/hr) Precipitation (in/hr) Ponding

31. Table 3.a.1. Infiltration Properties of Typical Soil Types

32. Clay Loam 0.04 0.464 0.310 0.187 5 2.32 1.55 0.935 Step 3.a.1 (cont.): Characteristics of Soils at BMP Site

33. Unified Stormwater Sizing Criteria (Minnesota, 2005)

34. Time Flow Small storm and large storm control strategies differ Water Quality: First Flush Capture Volume e.g., 10-yr 1-hr = 2.03 in/hr WQv = 0.75 in in 1hr Downstream Pipe/Channel Capacity = 1.4 in/hr Water Quantity: Peak Shaving Volume Extended Detention = 0.016 in/hr Note: 1 in/hr ~ 1 cfs/ac

35. Water Quality Volume WQ v = C * P * A / 12 where: WQ v = water quality volume in acre-feet C = runoff coefficient appropriate for storms less than 1 inch = 0.858i 3 - 0.78i 2 + 0.774i + 0.04 or 0.9i + 0.05 I = percent imperviousness P = rainfall in inches = 0.75 inches A = area draining into the facility in acres

36. Figure 8. Mean storm precipitation depth in the U.S (inches) – Source: “Urban Runoff Quality Control”, ASCE / WEF, 1997. Capture volume depends on local precipitation statistics

37. Orlando, Florida Cincinnati, Ohio Figure 9. Cumulative probability distribution of daily precipitation for two cities in the U.S. (Roesner, et. al., 1991)

38. Runoff Volume Captured and Controlled by BMP (acre-inch/acre) 10-yr, 1-hr event Capture volume depends on local precipitation statistics

39. Step 3.a.2: Calculating Water Quality Volume 0.4 0.28 = (0.5 ac * 1 + 1.8 ac * 0.28) / 2.3 ac = 0.44 0.0625 0.44 * 0.0625 ft = 0.028 ft 0.028 ft * 2.3 ac = 0.064 ac-ft

40. Step 3.a.3: Determine the Peak Flow Rate for the Water Quality Storm (Q WQ )

41. Figure 3.a.1 – Intensity-Duration-Frequency Curves for the Ohio Lake Erie Region (Section 02) Adapted from Huff and Angel, 1992 1.2 in/hr T C = 10 min

42. Step 3.a.3: Determine the Peak Flow Rate for the Water Quality Storm (Q WQ ) 10 min 1.2 in/hr 0.44 * 1.2 in/hr * 2.3 ac = 1.21 cfs

43. STEP 3.a.4. Determine Initial Soil Moisture Conditions 1.55 ft 2 days

45. Filter Strips and Swales Q WQ Q R-SW D R-SW I WQ LSTtLSTt

46. Backyard swales are common within many developments

47. Step 3.b.1: Swale Design Parameters

48. STEP 3.b.2: Evaluate Site Conditions to Determine if a Grass Filter Strip is a Feasible BMP Option.

49. Step 3.b.3: Sizing for Water Quality (Q WQ = [1.486* A*R 2/3 *S S 1/2 ] / n)

50. Step 3.b.4: Calculate the Swale Cross- Sectional Area at peak Q WQ

51. Look-up table for AR 2/3 Depth (ft) Width (ft)

52. Step 3.b.5&6: Calculate Flow, Travel Time in Swale

53. Step 3.b.7: Check major storm capacity

54. Step 3.b.8: Adjust WQ V for Infiltration within Swale

55. Group Discussion Topic #4a: Drainage Areas and Internal Drainage (Steps 3a & 3b)

57. Flow Rate (Discharge) Time Before Urbanization After Urbanization with No Detention After Urbanization with an Extended Detention After Urbanization with Volume Control (Detention) Rainstorm Extended drawdown times promote infiltration, control runoff volume <1-year design storm

58. Infiltration Basin

59. Step 3.c.1: BMP Site 1 Characteristics

60. Step 3.c.2: Determine Total Water Quality Volume Entering BMP site

61. Step 3.c.3: Native Soil Infiltration within BMP (pass 1)

62. Group Discussion Topic #4b: Native Soil Infiltration Capacity (Step 3c)

65. Combination Filter / Infiltrator

67. Step 3.a.1: Characteristics of Soils at BMP Site Clay Loam 0.04 0.464 0.310 0.187 5 2.32 1.55 0.935

68. Table 3.a.1. Infiltration Properties of Typical Soil Types

69. Clay Loam 0.04 0.464 0.310 0.187 5 2.32 1.55 0.935 Step 3.a.1: Characteristics of Soils at BMP Site - Enhanced Soil Infiltration Sandy Loam 0.43 0.453 0.190 0.085 2.0 0.906 0.380 0.170

70. Step 3.d.1: Amended Soil in BMP (pass 2)

71. Step 3.d.2: Determine Infiltration, Evaporation and Soil Moisture within BMP

72. STEP 3.e: Design Basin BMP (if soil moisture condition is Saturated or Ponded after Step 3.d.)

73. Extended Dry Detention Basin

74. Infiltration & Filter & Detention in a Single Facility

75. Group Discussion Topic #4c: Amended Soil Infiltration / Detention Facility (Steps 3c, d, e)

77. Group Discussion Topic #4d: Commercial Development Storm Water Management (Steps 3c, d, e)

78. Permeable Pavement

79. Permeable Pavement with Infiltration and Detention

80. Group Discussion Topic #4d: Commercial Development Storm Water Management (Steps 3c, d, e)