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Metro Boston Stormwater / Low Impact Development Capacity Building Project

Metro Boston Stormwater / Low Impact Development Capacity Building Project. Lexington & Wakefield 1 st Workshop - February 7, 2007 Wakefield Town Hall. Slide show prepared by: Metropolitan Area Planning Council. With funding provided by Massachusetts Office of Coastal Zone Management.

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Metro Boston Stormwater / Low Impact Development Capacity Building Project

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  1. Metro Boston Stormwater / Low Impact Development Capacity Building Project Lexington & Wakefield 1st Workshop - February 7, 2007 Wakefield Town Hall Slide show prepared by: Metropolitan Area Planning Council With funding provided by Massachusetts Office of Coastal Zone Management

  2. Reasons for Stormwater Management:IMPACT OF DEVELOPMENT Typical pre-development conditions: Runoff = 10% Infiltration = 50%

  3. Reasons for Stormwater Management:IMPACT OF DEVELOPMENT Typical post-development conditions: Runoff = 55% Infiltration = 15%

  4. Reasons for Stormwater Management: • Stormwater quality • Stormwater quantity – flooding • Groundwater – recharge • National Pollution Discharge Elimination System (NPDES) requirements

  5. STORMWATER MANAGEMENT POLICY • Clean Water Act (CWA) – Phase II • National Pollution Discharge Elimination System (NPDES) - Phase II Objectives

  6. STORMWATER MANAGEMENT PROGRAM(Phase II): • Public Education & Outreach • Public Involvement • Illicit Discharge Detection & Elimination • Construction Site Stormwater Runoff Control • Post Construction Stormwater Management For New Development and Redevelopment • Pollution Prevention / Good Housekeeping For Municipal Operations

  7. STORMWATER MANAGEMENT PROGRAM(Phase II): • Zoning, subdivision, site plan review, and other existing permitting processes • Stormwater bylaws / ordinances and regulations • Inspection and enforcement activities • System inventory / mapping • Operations and maintenance • Capital projects • Project administration • Funding (e.g. Stormwater Utility)

  8. What isLow Impact Development? • Comprehensive, landscape-based approach to sustainable development • Set of strategies to maintain existing natural systems, hydrology, ecology • Cost-effective, flexible approach based on a toolkit of simple techniques • Collection of practices that have been implemented nationwide

  9. What isLow Impact Development? • NOT rocket science • NOT formulaic • NOT the answer to every challenge • NOT yet finished evolving • NOT common in Massachusetts

  10. WHY DO WE NEED LOW IMPACT DEVELOPMENT?Conventional strategies aren’t working • Increased runoff & decreased recharge • Loss of vegetation and wildlife habitat • Loss of community character • Polluted waterways • Cost of development

  11. LID PRINCIPLES • Work with the existing landscape • Focus on prevention • Practice micromanagement • Emphasize simplicity • Practice multi-tasking • Maintain and sustain

  12. LID PRINCIPLES1. Use existing natural systems as the integrating framework for site planning • Land use planning and watershed planning • Identify environmentally sensitive resources: wetlands, mature trees, slopes, drainageways, permeable soils, waterway buffers • Assess existing hydrology • Define a development envelope

  13. LID PRINCIPLES2. Focus on prevention • Minimize clearing and grading • Cluster buildings and reduce building footprints • Reduce road widths, use shared driveways, reduce parking area • Align roads to minimize impact • Use green rooftops • Use permeable paving

  14. LID PRINCIPLES3. Treat stormwater close to the source • Create subwatersheds and “micromanage” runoff in a treatment train of small structures • Flatten slopes, lengthen flow paths, maximize sheet flow • Maintain natural flow paths, use open drainage • Use LID techniques to manage frequent, low-intensity storms

  15. LID PRINCIPLES4. Emphasize simple, nonstructural, low-tech, low-cost methods • Open drainage systems and filter strips • Disconnection of roof runoff • Rain barrels • Street sweeping • Public education • Reduce construction disturbance • Minimize lawn area

  16. LID PRINCIPLES5. Create a multifunctional landscape • Use stormwater management components that provide filtration, treatment, and infiltration. • Provide open space and wildlife habitat. • Store water for landscape use • Reduce heat island effect • Enhance site aesthetics

  17. LID PRINCIPLES6. Maintain and sustain • Reduce use of pesticides and fertilizers. • Use drought-resistant plants. • Maintain rain gardens and bioretention areas. • Provide adequate funding for public works departments

  18. LID STRATEGIES • Low impact site design • Stormwater Management • Buildings and Roadways • Roadways and Parking Areas • Permeable paving • Bioretention • Vegetated Swales • Rain Barrels and Cisterns • Green Roof Systems

  19. LID STRATEGIESLow Impact Site Design • Conservation of natural hydrology, trees, vegetation • Stream & wetland buffers • Minimize impervious surfaces • Stormwater micromanagement • Ecological landscaping Conservation Typical Subdivision

  20. LID STRATEGIESLow Impact Site Design Stormwater Management • Minimize directly connected impervious area • Create multiple sub-watersheds • Increase time of concentration • Use a “treatment train” of LID techniques to deal with frequent, low-intensity storms.

  21. LID STRATEGIESLow Impact Site Design Buildings and Roadways • Cluster buildings within the development envelope • Design buildings with smaller footprints • Roadways should follow existing grades. • Use parking structures • Separate parking areas

  22. LID STRATEGIESRoadways and Parking Areas Road Profile • Narrower roadways (18-24 feet) • Permeable parking lanes • Open section roadways • Alternative curb designs

  23. LID STRATEGIESRoadways and Parking Areas Alternative Turnarounds • Smaller cul-de-sacs • Bioretention islands • One-way-loops • Hammerhead turnarounds

  24. LID STRATEGIESRoadways and Parking Areas Parking Lots • Create multiple small lots • Allow shared parking • Reduce requirements near transit • Require compact spaces • Set parking maximums

  25. LID STRATEGIESPermeable Paving Applications • Parking stalls • Overflow parking • Driveways • Walkways and plazas

  26. LID STRATEGIESBioretention Treatment, retention, infiltration, landscaping • Excavation filled with engineered soil mix • Herbaceous perennials, shrubs, trees • Ponded water infiltrates within 72 hours • Overflow outlet and optional underdrain

  27. LID STRATEGIESBioretention Applications • Parking lot islands • Median strips • Rooftop runoff

  28. LID STRATEGIESVegetated Swales Conveyance, treatment, infiltration • Roadside swales “country drainage” • Parking lots • Low-angle slopes only • Opportunity for snow storage

  29. LID STRATEGIESVegetated Swales Conveyance, treatment, infiltration

  30. LID STRATEGIESRain Barrels and Cisterns Runoff Reduction and Water Conservation • Downspouts directed to tanks or barrels • 50 – 50,000 gallons • Excess diverted to drywell or rain garden • Landscaping, car washing, other nonpotable uses

  31. LID STRATEGIESRain Barrels and Cisterns Runoff Reduction and Water Conservation

  32. LID STRATEGIESGreen Roof Systems Runoff Reduction, Reduce Heating/Cooling Costs • Rainwater stored in a lightweight engineered soil medium • Hardy, drought-resistant vegetation • Reduce runoff by 50% • Not for use in stressed basins

  33. LID STRATEGIESGreen Roof Systems Applications

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