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Part 4 Stormwater BMP Toolbox September 26, 2013. Community Innovation Challenge Grant 2013. Objective of the Task. Encourage small property owners and developers to use on-site treatment and management of stormwater. Format existing materials to be understood by the general public.
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Part 4 Stormwater BMP Toolbox September 26, 2013 Community Innovation Challenge Grant 2013
Objective of the Task Encourage small property owners and developers to use on-site treatment and management of stormwater. Format existing materials to be understood by the general public. Create “Mini-Spec” sheets for property owner to hand to developer or contractor. Encourage good construction and pollution prevention practices. Not “reinvent the wheel”
Small-Site Stormwater Management Improve Water Quality • Increase groundwater/aquifer recharge • Improve surface water quality • Reuse stormwater for watering • Protect private property • Reduce adverse impacts to stream channels • Show the importance of BMP maintenance • Reduce erosion and sedimentation during construction Hiwassee River Watershed Coalition, Inc.
Site Characteristics • Identify Site Characteristics • Building Locations • Impervious and Pervious Areas • Types of Impervious Area • Slopes and Contours • Wetlands or Drinking Water Sources
Pervious and Impervious Area • Determine Pervious and Impervious Areas • Design treatment and infiltration based on the surface area of all existing or proposed impervious area. • Minimize Impervious Area • Pervious areas are more cost effective to maintain and construct.
Soil Permeability Soil Permeability: ability of soil to allow water to pass through it. For Infiltration BMP’s • Soils with high permeability are desirable. • Design requires calculating the correct area and volume of water to be stored and/or infiltrated to prevent BMP surcharging. • Maintenance is important to maintain soil permeability and overall effectiveness.
Total Suspended Solids (TSS) Removal Rates • BMPs minimize volume of TSS entering surface waters and/or aquifers • MassDEP Stormwater Handbook is not required for single family homes or small development, but guides effective BMP design. • Requires 80% TSS removal. • Requires 44% TSS removal prior to infiltration, if BMP is located within a critical area.
Site Limitations and Setbacks Natural site limitations include: steep slopes, wetlands, surface waters, and seasonal high groundwater. Massachusetts Stormwater Handbook
Minimize BMP Space Requirements • Minimize stormwater runoff by maximizing onsite treatment, storage, and infiltration. • Retain stormwater at small sites with the following design principles: • Reduce building footprints; • Cluster buildings; • Slope impervious surfaces toward stormwater BMP’s; • Install vegetated filter strips or rain gardens at the end of driveways and parking lots; • Utilize rain barrels or cisterns.
For Each BMP Description Benefits Applicability Limitations Level of Treatment Provided Costs Common Applications Maintenance Schedule Resources
BMPs Included in the Toolbox Pretreatment BMPs Street Sweeping Deep Sump Catch Basins Treatment BMPs Bioretention Areas (Rain gardens) Subsurface infiltration systems (Cultech, Stormtech) Tree box filters Lance Landscape
BMPs Included in the Toolbox (cont) Infiltration BMPs Porous pavement Dry wells Infiltration Trenches Conveyance BMPs Drainage Channels Water quality swales/grassed channels
BMP “Accessories” • Level Spreaders • Catch Basin Inserts • Rip rap • Rain barrels • Cisterns • Erosion control measures • Mulching • Hay bales • Silt fencing • Biodegradable mesh Photo: University of Southern Alabama Photo: BMP Supplies
Erosion Prevention BMPs: Mulching Increase stormwater infiltration, reduce runoff velocity, and provide more suitable habitat for seedling germination.
Construction Management Practices Construction activities can contribute sediment to surface water bodies, provide the opportunity for spills from equipment to occur and for nuisance dust to be generated. Best management practices can reduce the potential for these issues to occur. NPDES Construction General Permit vs. Local Construction Requirements
Construction Management Practices Small Site SWPPPPreventing sediment transport is the primary goal of a SWPPP. Development: * Owner, Designer Contractor Considerations: * Existing Site Conditions * Limit and Stabilize Site Disturbances * Keep Runoff Velocities Low * Protect Disturbed Areas * Retain Sediment Onsite * Include an Operation, Inspection and Maintenance Plan. Complete a site walk with all parties prior to construction. GatorGuard Environmental Products
Site Staging • Minimize Disturbance • Avoid Steep Slopes and Excessive Grading • Stockpile Stabilization • Using Vegetation for Stabilization • Dust Prevention
Equipment and Waste Management • Cleaning Vehicles Leaving the Site • Fueling Operations • Construction Waste Management Photo: Hong Kong EPD