Presentation is loading. Please wait.

Presentation is loading. Please wait.

Pond and Wetland BMPs, Retrofitting Detention Basins.

Similar presentations


Presentation on theme: "Pond and Wetland BMPs, Retrofitting Detention Basins."— Presentation transcript:

1 Pond and Wetland BMPs, Retrofitting Detention Basins

2 WET PONDS

3

4 Wet Pond Treatment Processes Settling Plant Uptake and Adsorption Infiltration Evaporation

5 Wet Ponds - Criteria Provide Quantity and Quality Control (not volume control) Drainage Area: Minimum of 10 Acres (>25 Acres Preferred) Treat Water Quality Volume Retrofit Opportunities Maintenance sediment removal Inlet & outlet vegetation

6 Wet Ponds – Primary Design Parameters Storage Volume Channel Protection & Flood Control Detention Time (24-48 Hours) Water Quality Release Rate Channel Protection & Flood Control

7 Wet Pond – Other Design Criteria Treat Up to 75 Acres Include Forebay Depth: 4-6 Feet Geometry Affects Performance dead storage short circuiting

8

9

10

11 Extended Detention Pond

12 Wet Pond

13 Multiple Pond System

14 Pocket Pond

15 Wet Pond – Hydraulic Design Design Pond Using Acceptable Methodology –NRCS…TR55…TR20 –Penn State Runoff Model (PSRM) –Modified Rational Method –Other Hydrograph Routing Is Necessary

16

17 Wet Pond – Area Ratio Area Ratio = Drainage Area Pond Area Should Be Less Than 100 For Maximum Efficiency

18 Wet Ponds – Pollutant Removal Sediment…………..50-90% Total Phosphorus…30-90% Soluble Nutrients….40-80% Lead………………..70-80% Zinc…………………40-50%

19

20

21

22

23

24

25

26 Wet Pond Criteria 1.Minimum Contributory Area: 10 Acres 2.Pretreatment: Sediment Forebay Sized to Contain 0.1 inches per impervious area 3.Design to Treat Water Quality Volume 4.Multiple Treatment Pathways Increase Performance …Multiple Cells …Pond-Wetland Train

27 Wet Pond Criteria 5.Pond Benches A. Safety Bench – 6%Maximum Slope B. Aquatic Bench – Maximum Depth 18” Below Normal Pool 6.Provide for Maintenance Access

28

29

30

31

32

33

34

35

36

37

38

39 Types of Wetlands Shallow Wetland Extended Detention Wetland Pond-Wetland System Pocket Wetland

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55 Component Design Outlet Structure

56

57

58

59

60

61

62

63

64 Wetland Treatment Criteria 1.Surface Area: At least 1% of total Drainage Area 2.25% of WQ v Should Be In Deep Water Zones (4’) 3.Minimum of 35% of Area: Depth of 6” or less 4.At least 65% of Area: Shallower than 18”

65

66

67

68

69

70

71

72

73

74 Existing Conditions – (Pre-Construction)

75 Proposed Conditions (Post-construction)

76

77

78

79

80

81

82

83

84 Retrofitting Detention Basins

85 Conventional Detention Basins Designed For Flood Control & Channel Protection large storm events (50 year…100 year) Do Not Control: runoff volume water quality Do Not Provide aesthetics wildlife habitat

86 Retrofitting Detention Basins - Benefits Pollutant Removal Water Quality Improvement Wildlife Habitat Creation Aesthetic Improvement Reduced Maintenance

87 Retrofitting Detention Basins - Modifications Modify Outfall Structure create two-stage release treat small storms for water quality Eliminate Paved Low-Flow Channels use meandering vegetated swales increase detention time for small storms

88 Retrofitting Detention Basins - Modificatons Use Stilling and Settling Basins at Inlets & Outlets remove sediment & attached pollutants plant with wetland plants Regrade to Provide Micro-Habitats Create Wetland - Pond Areas

89 Extended Detention Basin Conversion

90 Wet Pond Conversion

91

92

93

94

95

96

97

98

99 Proposed Conditions – Post Construction Construction

100


Download ppt "Pond and Wetland BMPs, Retrofitting Detention Basins."

Similar presentations


Ads by Google