West Virginia Stormwater Management Manual: Methods.

Transcription

1 West Virginia Stormwater Management Manual: Methods Created to deliver targeted training on new tools and practices to improve the quality of stormwater runoff.

2 Chesapeake Bay Stormwater Training Partnership 2

3 Things That Go Together Well Stormwater Manual Design Compliance Spreadsheet Cistern Design, Checklists, other Tools Chesapeake Bay Stormwater Training Partnership 3

4 Performance Standards for Site and Neighborhood Design 5.a.ii.A.1.:... require management measures that keep and manage on site the first one-inch of rainfall... Means: require stormwater practices that are designed and sized to capture and treat the runoff from a 1-inch rain event. Chesapeake Bay Stormwater Training Partnership 4

5 Performance Standards for Site and Neighborhood Design 5.a.ii.A.1. (continued): Runoff volume reduction can be achieved by canopy interception, soil amendments, evaporation, rainfall harvesting, engineered infiltration, extended filtration and/or evapotranspiration and any combination of the aforementioned practices. Means: The permit establishes that a wide array of runoff reduction pathways are considered acceptable Chesapeake Bay Stormwater Training Partnership 5

6 Manual Outline Chapter 1: Introduction Chapter 2: WV Stormwater Regulations Chapter 3: BMP Selection & Design Methodology Chapter 4: BMP Specifications Chapter 5: Stormwater Hotspots Chapter 6: Design Examples Chesapeake Bay Stormwater Training Partnership 6

7 Manual Outline Appendix A: Checklists Appendix B: Infiltration Testing Appendix C: Stormwater Design in Karst Appendix D: Soil Amendments Appendix E: Treatment Volume Peak Flow Rate Appendix F: BMP Landscaping & Plant Lists Appendix G: Resources for Dry & Wet Ponds Appendix H: Considerations for Impaired Waters Chesapeake Bay Stormwater Training Partnership 7

8 Chapter 4: BMP Specifications 4.1. Better Site Design Sheet Flow to Filter Strip or Conservation Area Impervious Disconnection Bioretention Water Quality Swale Urban Bioretention Residential Rain Garden Permeable Pavement Grass Swale Chesapeake Bay Stormwater Training Partnership 8

9 Chapter 4: BMP Specifications Infiltration Regenerative Stormwater Conveyance Rainwater Harvesting Vegetated Roofs Filtration Practices Stormwater Wetlands Chesapeake Bay Stormwater Training Partnership 9

10 Methods 1. Runoff Reduction 2. Treatment Volume 3. BMPs in Series 4. Design Volume 5. Level 1 & Level 2 Design Chesapeake Bay Stormwater Training Partnership 10

11 1. Runoff Reduction Runoff Reduction processes & capabilities vary by practice Infiltration Canopy Interception Evaporation Transpiration Rainwater Harvesting Extended Filtration Chesapeake Center Bay for Stormwater Watershed Training Protection Partnership 11

12 Typical Extended Filtration Chesapeake Bay Stormwater Training Partnership 12

13 Chesapeake Bay Stormwater Training Partnership 13

14 2. Treatment Volume: Runoff Coefficient for Land Cover Types Chesapeake Bay Stormwater Training Partnership 14

15 Treatment Volume Calculation Chesapeake Bay Stormwater Training Partnership 15

16 Treatment Volume Achieve Treatment Volume reduction at site scale Plan BMPs for each drainage area on the site 15 Acres, 25, 0.6 acre lots Impervious = 3 ac. Managed Turf = 11 ac. Forest/Open Space = 1 ac. Treatment Volume (Tv) = 19,130 cubic feet Chesapeake Bay Stormwater Training Partnership 16

17 3. Practices in Series Chesapeake Bay Stormwater Training Partnership 17

18 Treatment Volume = 18,100 cubic feet BMP 3 BMP 2 BMP 1 Chesapeake Bay Stormwater Training Partnership 18

19 4. Design Volume (Dv) For Treatment Volume = 18,100 cubic feet Dv = 5,100 cf Dv = 5,500 cf Dv = 7,500 cf Chesapeake Bay Stormwater Training Partnership 19

20 Drainage Area (DA) BMP 1 BMP 2 Treatment Volume (Tv) = DA size x runoff coefficient x 1.0 inch BMP 3 Tv = Design Volume BMP 1 + Design Volume BMP 2 + Design Volume BMP 3 Chesapeake Bay Stormwater Training Partnership 20

21 5. Level 1 and Level 2 Design Specifications Level 1 -- Standard Design Features (included in all designs) needed to maintain proper BMP: Function Safety Appearance Safe conveyance Performance longevity Maintenance Level 2 -- Enhanced Design Features include specific design features to improve the BMP s Total Performance Chesapeake Bay Stormwater Training Partnership 21

22 Chesapeake Bay Stormwater Training Partnership 22

23 Chesapeake Bay Stormwater Training Partnership 23

24 Methods 1. Runoff Reduction 2. Treatment Volume 3. BMPs in Series 4. Design Volume 5. Level 1 & Level 2 Design Chesapeake Bay Stormwater Training Partnership 24

25 Chesapeake Bay Stormwater Training Partnership 25

26 West Virginia Stormwater Management Manual: Practices Created to deliver targeted training on new tools and practices to improve the quality of stormwater runoff.

27 Chapter 4: BMP Specifications 4.1. Better Site Design Sheet Flow to Filter Strip or Conservation Area Impervious Disconnection Bioretention Water Quality Swale Urban Bioretention Residential Rain Garden Permeable Pavement Grass Swale Infiltration Regenerative Stormwater Conveyance Rainwater Harvesting Vegetated Roofs Filtration Practices Stormwater Wetlands Chesapeake Bay Stormwater Training Partnership 2

28 Chapter 4: BMP Specifications: Site Design 4.1. Better Site Design Sheet Flow to Filter Strip or Conservation Area Impervious Disconnection Chesapeake Bay Stormwater Training Partnership 3

29 Chapter 4: BMP Specifications: Runoff Reduction Bioretention Water Quality Swale Urban Bioretention Residential Rain Garden Permeable Pavement Grass Swale Infiltration Regenerative Stormwater Conveyance Rainwater Harvesting Vegetated Roofs Chesapeake Bay Stormwater Training Partnership 4

30 Chapter 4: BMP Specifications: Pollutant Removal Filtration Practices Stormwater Wetlands Chesapeake Bay Stormwater Training Partnership 5

31 Chapter 4: BMP Specifications: Site Design 4.1. Better Site Design Sheet Flow to Filter Strip or Conservation Area Impervious Disconnection Chesapeake Bay Stormwater Training Partnership 6

32 4.1. Self-Crediting Better Site Design Chesapeake Bay Stormwater Training Partnership 7

33 Site Design is First Slice of Salami Reduce Impervious Cover Reduce Site Distrubance Reduce Managed Turf Chesapeake Bay Stormwater Training Partnership 8

34 Reduce Impacts By Design Chesapeake Bay Stormwater Training Partnership 9

35 Not So Good Good Chesapeake Bay Stormwater Training Partnership 10

36 Watershed Protection Elements (Part 2C5.i.A.) 1. Minimize Impervious surfaces 2. Preserve, protect, create and restore ecologically sensitive areas 3. Prevent or reduce thermal impacts to streams 4. Avoid or prevent hydromodification of streams and other waterbodies 5. Protect trees and other vegetation 6. Protect native soils Chesapeake Bay Stormwater Training Partnership 11

37 Checklist Format Chesapeake Bay Stormwater Training Partnership 12

38 Sheet Flow to Vegetated Filter Strip or Conservation Area Chesapeake Bay Stormwater Training Partnership 13

39 Sheetflow to Conservation Area or Vegetated Filter Strip Re-Engineering the Filter Strip: Two Filter Designs Vegetated Filter Strip Sheet Flow to Conserved Open Space Chesapeake Bay Stormwater Training Partnership 14

40 Chesapeake Bay Stormwater Training Partnership 15

41 Design Considerations Sheet Flow Boundary Spreaders Level Spreaders for concentrated flow Maximum slopes Chesapeake Bay Stormwater Training Partnership 16

42 Stream Buffers Designated during initial lot recordation/subdivision; Protected with legal instrument to prevent alteration of the land or vegetation; Width varies (35. ft to 150 ft.); Must establish sheet flow into buffer Chesapeake Bay Stormwater Training Partnership 17

43 Level Spreader Applicable to filter strips, buffers, and conserved open space with concentrated inflow. Henrico County, VA Level Spreader 30 to 40 ft in length; 50 ft width at level lip Chesapeake Bay Stormwater Training Partnership 18

44 How Big A Slice? 4 9 cf/each 100 square foot of conservation area Chesapeake Bay Stormwater Training Partnership 19

45 Impervious Surface Disconnection Chesapeake Bay Stormwater Training Partnership 20

46 Impervious Surface Disconnection Rooftop/Small Impervious Area Disconnection Simple disconnection Soil amended filter path Disconnection to small-scale runoff reduction practice: rain garden, infiltration, rainwater harvesting COMPENSATORY PRACTICE Chesapeake Bay Stormwater Training Partnership 21

47 Simple Disconnection Filter corridors from the downspout to the street Level spreader to distribute runoff over width Criteria for: Contributing IC area Length Width Slope of receiving area Chesapeake Bay Stormwater Training Partnership 22

48 Appendix D: Soil Amendments Chesapeake Bay Stormwater Training Partnership 23

49 Soil Amended Filter Path Enhanced runoff reduction in C/D soils Can Be Use for Multiple Practices Chesapeake Bay Stormwater Training Partnership 24

50 Soil Amendments for Other Practices Chesapeake Bay Stormwater Training Partnership 25

51 How Big A Slice? 2 4 cf/each 100 square foot of pervious receiving area* Runoff reduction for compensatory practices varies based on the practice: see bioretention, infiltration, rainwater harvesting specs Chesapeake Bay Stormwater Training Partnership 26

52 Design Example Chesapeake Bay Stormwater Training Partnership 27

53 Treatment Volume -- Typical Layout 15 Acres, 25, 0.6 acre lots Impervious = 3 ac. Managed Turf = 11 ac. Forest/Open Space = 1 ac. Treatment Volume (Tv) = 19,130 cubic feet Tv applies to each drainage area + site Chesapeake Bay Stormwater Training Partnership 28

54 Treatment Volume Site Design Measures 15 Acres, 25, 1/4 acre lots Impervious = 2 ac. Managed Turf = 5 ac. Forest/Open Space = 8 ac. Treatment Volume (Tv) = 10,890 cubic feet 19,130 10,890 = 8,240 cubic feet Chesapeake Bay Stormwater Training Partnership 29

55 Treatment Volume Additional RR Practices 13 lots = rain gardens = 0.65 ac. 12 lots = sheetflow to conservation (½ roof + ½ yard) = 0.30 ac. IC ac. turf Remaining Treatment Volume (Tv) = 7,608 cubic feet Total Reduction from Site Design = 11,522 Chesapeake Bay Stormwater Training Partnership 30

56 Chapter 4: BMP Specifications: Runoff Reduction Bioretention Water Quality Swale Urban Bioretention Residential Rain Garden Permeable Pavement Grass Swale Infiltration Regenerative Stormwater Conveyance Rainwater Harvesting Vegetated Roofs Chesapeake Bay Stormwater Training Partnership 31

57 Bioretention Chesapeake Bay Stormwater Training Partnership 32

58 Bioretention Bioretention Water Quality Swale Urban Bioretention Residential Rain Garden Chesapeake Bay Stormwater Training Partnership 33

59 Chesapeake Bay Stormwater Training Partnership 34

60 Level 1 Chesapeake Bay Stormwater Training Partnership 35

61 Level 2 -- Infiltration Chesapeake Bay Stormwater Training Partnership 36

62 Level 2 Extended Filtration Chesapeake Bay Stormwater Training Partnership 37

63 Level 2 -- Infiltration Sump Chesapeake Bay Stormwater Training Partnership 38

64 Level 2 Upturned Elbow (Internal Water Storage Zone) Chesapeake Bay Stormwater Training Partnership 39

65 How Big A Slice? % (55% for Level 1 WQS) Chesapeake Bay Stormwater Training Partnership 40

66 Permeable Pavement Chesapeake Bay Stormwater Training Partnership 41

67 Chesapeake Bay Stormwater Training Partnership 42

68 Level 1 Chesapeake Bay Stormwater Training Partnership 43

69 Level 2 -- Infiltration Chesapeake Bay Stormwater Training Partnership 44

70 Level 2 Infiltration Sump 45% RR 100% RR Chesapeake Bay Stormwater Training Partnership 45

71 How Big A Slice? % Level 2: 45% above UD; 100% for sump Chesapeake Bay Stormwater Training Partnership 46

72 Grass Swale Chesapeake Bay Stormwater Training Partnership 47

73 Chesapeake Bay Stormwater Training Partnership 48

74 One Design Level: Depends on Soil Types, Soil Amendments Chesapeake Bay Stormwater Training Partnership 49

75 Check Dams Chesapeake Bay Stormwater Training Partnership 50

76 How Big A Slice? inches per CDA Chesapeake Bay Stormwater Training Partnership 51

77 Infiltration Chesapeake Bay Stormwater Training Partnership 52

78 Chesapeake Bay Stormwater Training Partnership 53

79 One Design Level Chesapeake Bay Stormwater Training Partnership 54

80 Additional Pipe/Arch Storage Chesapeake Bay Stormwater Training Partnership 55

81 How Big A Slice? 100% for Design Volume Chesapeake Bay Stormwater Training Partnership 56

82 Regenerative Conveyance Chesapeake Bay Stormwater Training Partnership 57

83 Chesapeake Bay Stormwater Training Partnership 58

84 Riffles, Pools, Sand/Woodchip Bed Chesapeake Bay Stormwater Training Partnership 59

85 How Big A Slice? 100% for Design Volume Chesapeake Bay Stormwater Training Partnership 60

86 Rainwater Harvesting Chesapeake Bay Stormwater Training Partnership 61

87 Chesapeake Bay Stormwater Training Partnership 62

88 Year-Round Use OR Chesapeake Bay Stormwater Training Partnership 63

89 Secondary On-site Runoff Reduction Practices Grass Filter Strip Grass Channel Bioretention (micro, small) Dry Swale Infiltration Rooftop Disconnection Storage & Release in Foundation Planter BMP Clearinghouse Chesapeake Bay Stormwater Training Partnership 64

90 Cistern Design Spreadsheet - INPUT 1.) Drop Down Menu to select 1 of 4 regions 2.) Enter Area of Rooftop to be Captured in SF 3.) Enter Area to be Irrigated (if any). Also Enter inches/week (1 /SF assumed) and start and end day of year of application 4.) Enter Internal demand usage for flushing of toilets and urinals (if any) based on per Person or designer estimate. Also enter day of week to begin & end Chesapeake Bay Stormwater Training Partnership 66

91 Enter Runoff Reduction from Cistern Spreadsheet in Design Compliance Spreadsheet Runoff Reduction Practice 1. Vegetated Roof (4.2.9) Vegetated Roof 2. Impervious Surface Disconnection/Rooftop Practices Simple Disconnection to A/B Soils or Soil-Amended Filter Path in C/D Soils (4.2.2, Appendix D) Simple Disconnection to C/D Soils (4.2.2) To Residential Rain Garden (4.2.3.C) To Rainwater Harvesting (4.2.8) Impervious Cover in Contributing Drainage Area (acres) Managed Turf in Contributing Drainage Area (acres) Volume Received by Practice (cubic feet) N/A 0 N/A 0 N/A 0 N/A 0 N/A 0 Description of Credit 100% volume reduction for the Design Volume of the practice Reduce volume conveyed to conservation area by 4 cu. ft per each 100 sq. ft. of pervious receiving area. Reduce volume conveyed to conservation area by 2 cu. ft per each 100 sq. ft. of pervious receiving area. 60% volume reduction for the Design Volume of the practice Subtract a variable % of the provided Design Volume based on annual beneficial use (see Cistern Design Spreadsheet). % Credit 100% N/A N/A 60% To Urban Bioretention (4.2.3.B) N/A 0 60% volume reduction for the Design Volume of the practice 60% Chesapeake Bay Stormwater Training Partnership 67

92 How Big A Slice?? % Chesapeake Bay Stormwater Training Partnership 68

93 Vegetated Roof Chesapeake Bay Stormwater Training Partnership 69

94 Chesapeake Bay Stormwater Training Partnership 70

95 Extensive Green Roof Chesapeake Bay Stormwater Training Partnership 71

96 Intensive Green Roof Chesapeake Bay Stormwater Training Partnership 72

97 How Big A Slice? 100% for Design Volume Chesapeake Bay Stormwater Training Partnership 73

98 Chapter 4: BMP Specifications: Pollutant Removal Filtration Practices Stormwater Wetlands Chesapeake Bay Stormwater Training Partnership 74

99 Filtration Practice Chesapeake Bay Stormwater Training Partnership 75

100 Surface Sand Filter Underground/Vault Sand Filter Perimeter Sand Filter Chesapeake Bay Stormwater Training Partnership 76

101 How Big A Slice? 0% Chesapeake Bay Stormwater Training Partnership 77

102 Stormwater Wetland Chesapeake Bay Stormwater Training Partnership 78

103 Wetland Basin Multi-Cell or Pond/Wetland Subsurface Gravel Wetland Chesapeake Bay Stormwater Training Partnership 79

104 How Big A Slice? 0% Chesapeake Bay Stormwater Training Partnership 80

105 Chapter 4: BMP Specifications 4.1. Better Site Design Sheet Flow to Filter Strip or Conservation Area Impervious Disconnection Bioretention Water Quality Swale Urban Bioretention Residential Rain Garden Permeable Pavement Grass Swale Infiltration Regenerative Stormwater Conveyance Rainwater Harvesting Vegetated Roofs Filtration Practices Stormwater Wetlands Chesapeake Bay Stormwater Training Partnership 81

106 Design Compliance Spreadsheet West Virginia Design Compliance Spreadsheet Drainage Area A Drainage Area A Post-Development Land Cover (acres) Land Cover Type HSG A soils HSG B Soils HSG C Soils HSG D Soils Totals Forest/Preserved Open Space Managed Turf Impervious Cover Total 0.00 Rv(turf) 0.00 Rv(impervious) 0.95 Apply Runoff Reduction Practices Runoff Reduction Practice 1. Vegetated Roof (4.2.9) Vegetated Roof 2. Impervious Surface Disconnection/Rooftop Practices Simple Disconnection to A/B Soils or Soil-Amended Filter Path in C/D Soils (4.2.2, Appendix D) Simple Disconnection to C/D Soils (4.2.2) To Residential Rain Garden (4.2.3.C) To Rainwater Harvesting (4.2.8) To Urban Bioretention (4.2.3.B) Impervious Cover in Contributing Drainage Area (acres) Managed Turf in Contributing Drainage Area (acres) Volume Received by Practice (cubic feet) N/A 0 N/A 0 N/A 0 N/A 0 N/A 0 N/A 0 Description of Credit 100% volume reduction for the Design Volume of the practice Reduce volume conveyed to conservation area by 4 cu. ft per each 100 sq. ft. of pervious receiving area. Reduce volume conveyed to conservation area by 2 cu. ft per each 100 sq. ft. of pervious receiving area. 60% volume reduction for the Design Volume of the practice Subtract a variable % of the provided Design Volume based on annual beneficial use (see Cistern Design Spreadsheet). 60% volume reduction for the Design Volume of the practice Chesapeake Bay Stormwater Training Partnership 82