PREPARED UNDER. The 319 Nonpoint Source Pollution Grant Program FUNDED BY. MA Department of Environmental Protection Boston, MA PREPARED BY

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1 PREPARED UNDER The 319 Nonpoint Source Pollution Grant Program FUNDED BY MA Department of Environmental Protection Boston, MA PREPARED BY Vanasse Hangen Brustlin, Inc. Watertown, MA Horsley Witten Group, Inc. Sandwich, MA The Center for Watershed Protection Ellicott City, MD Stacey DePasquale Engineering, Inc. Lawrence, MA

2 Month XX, 2011 Location here

3 Selecting the Right Practice for the Site

4 Session Overview Overview of Practice Options Design Considerations for Practice Groups BMP Sl Selection Mti Matrices and Special lcold ldclimate Considerations Example Selection Exercise

5 Primary Practice Groups* WVTSs (Wet Vegetated Treatment Systems) Permeable Paving Infiltration ti Practices Filtering Practices Green Roofs Open Channels *As identified in the Rhode Island Stormwater Design and Installation Standards Manual

6 WVTSs Design Options Option 1: Shallow WVTS Option 2: Gravel WVTS Photo Source: Horsley Witten Source: UNH Stormwater Center

7 Selection Considerations for WVTSs Need to maintain a permanent pool, so a water balance is required (especially for Option 1). Consider ongoing maintenance of vegetation within the practice. Depending on the design, there may be some groundwater influence. Excellent pollutant removal, and can provide detention for largestorm events. Can be a community amenity and provide habitat, but also may raise safety concerns.

8 Infiltration Practice Design Options Infiltration Basin Infiltration Trench Underground Infiltration Chambers Dry Well Dry Well Underground Infiltration Chamber

9 Selection Considerations for Infiltration Practices Infiltrates to groundwater, so need to consider contaminants in the drainage area carefully Soils are critical!!! Typically out of sight so aesthetics are not a concern High cost for construction and maintenance Great pollutant removal, and provides infiltration; some designs can provide flood control as well

10 Permeable Pavement Design Options Porous Concrete/ Asphalt Pavers Source: Rob Roseen Source: MA EOEA

11 Selection Considerations for Permeable Pavement Depending on the design, may need to consider groundwater issues/soils (similar to infiltration practices) High maintenance and cost Limit in high traffic areas

12 Filtering System Design Options Sand Filter Organic Filter Bioretention ti Tree Filter Tree Filter: Source, CWP Bioretention: Source, CWP

13 Selection Considerations for Filtering Systems Good pollutant removal, except for phosphorus Moderate to high cost Available head dis a constraint tfor many filter designs May be designed as an exfilter to recharge groundwater Bioretention and tree filters can be a property amenity Vegetation offers supplemental benefits

14 Green Roof Design Options Extensive Green Roof: Source, Sierra Club Intensive Green Roof: Source, Sierra Club

15 Selection Considerations for Green Roofs Very high initial cost Roof slope and structural stability Good pollutant t removal except for phosphorus h Can provide channel protection but not flood control Offers manyother amenities (aesthetics, reduce energy required for heating and cooling; reduce heat island effect)

16 Open Channel Design Options Dry Swale: Source, CWP Wet Swale: Source, CWP

17 Selection Considerations for Open Channel Practices Wet swale option intercepts groundwater Site slope is important Requires significant ifi space (difficult to apply in high h density developments) Good removal except for pathogens Wet swale may create nuisances (e.g., mosquito habitat)

18 Five Step Process to BMP Screening Land Use Physical Feasibility Watershed Factors Stormwater Management Capability Community and Environmental lfactors

19 Step 1 Land duse Rural BMPsfor lowdensity areas Residential BMPs for med. to high density residential Roads & Highways BMPs for major roads Commercial BMPs suitable for new commercial areas LUHPPL BMPs for Land Uses with Higher Potential Pollutant Loads Ultra Urban Sites BMPs for space limited areas

20 Rural/ Residential Land Often have open space Can utilize a combination of on site and larger drainage area practices Some small site practices limited due to cost or maintenance concerns

21 Rural and Residential Land Residential lland uses ranging from Low to High Density Applicability Best Options Sometimes Options Practices WVTSs, Bioretention (for Rural), Dry Wells, Infiltration Trench (for Rural Land), Open Channels (for Rural Land), Permeable Pavement Shallow Infiltration Basin Infiltration Trench (forresidential) Most Filters Green Roof Open O Channels (for Residential) i

22 Roads and Highways Focus on linear practices Can use wetland practices inthe mediansand and cloverleafs Permeable pavement options may be limited in high traffic areas Photo Source: Panoramio.com

23 Roads and Highways Applicability Best Options Sometimes Options Infiltration Trench Practices Organic Filter and Bioretention Open Channels WVTS Other Infiltration Practices Sand Filters Permeable Pavement Never Options Green Roof

24 Commercial/ High Density Land is limited and at a premium Infiltration may be a challenge depending on locations of nearby utilities and buildings Rooftop can represent a high fraction of the total impervious cover

25 Commercial/ High Density Applicability Best Options Sometimes Options Never Options Infiltration Trench All Filters Open Channels Extensive Green Roof Practices WVTS Other Infiltration Practices Permeable Pavement Sand Filters Intensive Green Roof Dry Swale Wet Swale

26 LUHPPL Watch out for infiltration!! Highly contaminated runoff Small llda practices have a real advantage, as they can be placed to capture runoff from the areas generating the highest pollutant load and used in combination with downstream practices

27 LUHPPL Applicability Best Options Yes, but require a liner, and cannot infiltrate Never Options Green Roofs Practices WVTS Permeable Pavement Filters Dry Swale InfiltrationPractices Wet Swale

28 Ultra Urban Space is at a premium Focus on practices that can be integrated intothe the landscape, or perhaps underground Rooftops represent a high fraction of the total impervious cover

29 Ultra Urban Applicability Best Options Sometimes Options Never Options Filters Green G Roofs Infiltration Practices Dry Swales Wet Swales WVTSs Practices

30 Step 2. Physical Feasibility Soils Water Table Drainage Area Slope Head

31 Soils/ Water Table WVTSs (Wet Vegetated Treatment Systems) Permeable Paving Infiltration ti Practices Filtering Practices Green Roofs Open Channels

32 Key Soil/ Water Table Concerns for Practice Groups Practices WVTSs Infiltration Practices Filtering Practices Open Channels Concerns Need WT separation for LUHPPL In A soils, may need a liner Photos from Bill Hunt, NCSU 2 3 feet WT separation Need sufficient permeability to infiltrate Keep filter above WT No soils concerns unless exfilter design Dry swale needs to be above WT Wet swale intercepts GW

33 Drainage Area WVTSs are Large Drainage Area practices to retain the permanent pool Filters and most infiltration practices are small drainage area to limit clogging Some limits on drainage area to individual inlets of open channel practices to prevent rill formation

34 Slope/ Available Head

35 Site Slope and Head Concerns for Practice Groups Practices Head Slope WVTSs 3 5 feet <8% Infiltration 1 3 Feet <6% Practices Filtering Practices 2 6 Feet <5 6% Open Channels 1 5 Feet 1 4% unless check dams

36 Step 3. Watershed (Receiving Waters) Groundwater Freshwater Streams and Rivers Other Fresh Waters (e.g., lakes, ponds) Coastal Waters

37 Groundwater Photo source: For all practices, be careful with regard to LUHPPL infiltration Infiltration practices need setbacks from drinking wells For open channels, pretreat LUHPPL Filters are an excellent first line practice to treat LUHPPLs

38 Freshwater Streams and Rivers Need to consider temperature in cold water streams, so WVTSs maybe restricted Providing channel protection and flood protection is critical; may need to pair water quality practices with detention practices to meet this goal

39 Other Fresh Waters (Lakes and Ponds) Often Phosphorus limited, so focus on practices with high P removal WVTSs and infiltration provide the best P removal For open channels, the wet swale is a great option Filters have moderate to high removal Flood control/ channel is less important

40 Coastal Waters Nitrogen and bacteria are key pollutants Design modifications improve pollutant removals: Long detention times in WVTSs for bacteria die off Infiltration in A orb soil horizon for N removal Swales need to be combined with pollution prevention for bacteria removal Dry swales better than wet swales for TN removal

41 Step 4. Stormwater Management Capability Water Quality Recharge Channel Protection Quantity Control

42 Management Capability Summary Only infiltration practices and exfilter filter designs meet recharge criteria, but LID practices also contribute toward this goal. All practices meet Water Quality goals, except infiltration practices with little separation from groundwater. Channel protection can be met by WVTSs and detention practices, but filters, infiltration practices and wet swales can help meet this goal. Flood control is only provided by WVTSs, detention practices, or infiltration practices in highly permeable soils.

43 Step 5. Community and Environmental Benefit Ease of Maintenance Affordability Community Acceptance Safety Habitat

44 Ease of Maintenance Lowest Maintenance for Dry Well, Wet Swale, and Shallow WVTS Highest Maintenance for most infiltration Practices and Sand Filters

45 Affordability Dry wells and Wet Swales are the most affordable design options Gravel WVTS, Sand/Organic Filters, and Intensive Green Roofs the least affordable (most expensive) options

46 Community Acceptance/ Safety Photo source: Shallow Infiltration Basins, Sand Filters, Bioretention, and Wet Swales have some issues with regard to community acceptance due to temporary ponding Some safety concerns for Shallow WVTS and Wet Swales due to permanent ponding

47 Habitat WVTSs and Intensive Green Roofs provide the most habitat Organic Filters, Bioretention, Extensive Green Roofs and Wet Swales Provide Some Habitat

48 Climate Considerations: Cold Climates Snowmelt may carry a significant pollutant load Deicers can create environmental problems and design challenges Cold winter temperatures may reduce the effectiveness of many traditional practices

49 Regional Considerations: Cold Climate Design Challenges Freezing of the Permanent Pool Pipe Freezing/Frost Heave Decreased Biological Activity and Settling Velocities Lower Oxygen Levels in Bottom Sediment Reduced SoilInfiltration Shorter Growing Season

50 Flow with Ice Cover (Source: Oberts, 1990)

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53 When the drainage area to a pond system has significant pollutant sources, the load trapped in the ice or on its surface can be tremendous.

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56 Wetland Performance in Snowmelt and Rain on Snow (Source: Oberts, 1994) Snowmelt Rain After Snowmelt TSS VSS TP DP COD TKN NO3 TPB -40

57 Design Modifications: WVTSs/Treatment and Pretreatment Provide some portion of the water quality storage as extended detention. Provide additional treatment and pre treatment (forebay) volume. Consider seasonal operation to capture snowmelt. Emphasize Pond/Wetland d Systems where possible.

58 Dry ED Storage as Pretreatment

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60 Increase Total Volume

61 Seasonal Operation Pond

62 Design Modifications: WVTSs/Landscaping Use salt tolerant species, when practice receives road or parking area runoff Adjust the planting window to ensure establishment Consider winter planting with dormant rhizomes

63 WVTS with Level Spreader Pretreatment

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65 Design Modifications: WVTS Conveyance & Maintenance Avoid submerged inlets Consider using frost free outlets such as weirs Avoid small lldiameter outlets t Consider alternative trash rack or riser hood configurations Consider in line ponds where practical

66 Baffle Weir Near Outlet

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71 Design Modifications: Infiltration Systems Avoid Porous Pavement for sanded surfaces Ensure that infiltration practices do not create a groundwater concern, possibly by diverting winter snowmelt Consider seasonal operation Use a porous medium on infiltration basin floors, if possible

72 Infiltration Versus Soil Moisture Source: Granger et al. (1984)

73 Seasonal Operation Infiltration Basin

74 Design Modifications: Sand Filters Use a gravel layer at the base of the filter to prevent freezing Design underground filters to be below the frost line Use frost free inlets and outlets where possible Increase the slope of underdrain pipes to at least 1% to Increase the slope of underdrain pipes to at least % to ensure flow through the system

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77 Design Modifications: Open Channels When used as a roadside practice, mulch to restore moisture and soil structure lost due to deicer application Use salt tolerant plant species when used as a roadside did practice Incorporate open channel practices into a snow storage system

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80 Additional Resources Rhode Island Stormwater Design and Installation Standards Manual. Available at: State of Minnesota Stormwater Manual. Available at: types pca php/water/water typesand programs/stormwater/stormwatermanagement/minnesota s stormwater manual.html Design of Stormwater BMPs for Cold Climates. Available at

81 CONTACT INFORMATION Bethany E. Eisenberg Director of Stormwater Services VHB Vanasse Hangen Brustlin, Inc. 101 Walnut Street Watertown, MA Phone: x1229 Fax: Direct: Richard A. Claytor, Jr., P.E. Principal Engineer Horsley Witten Group 90 Route 6A, Sandwich, MA Deb Caraco Center for Watershed Protection Field Office: 606 N. Aurora St., Ithaca, NY Main Office: 8390 Main Street, 2nd Floor, Ellicott City, MD Stacey A. DePasquale, P.E. President SDE 354 Merrimack kstreet, Suite 200 Lawrence, MA inc.com inc.com/