Low Impact Development Principles, Techniques, and Implementation

1. Low Impact DevelopmentPrinciples, Techniques, and Implementation In coordination with: Slide show prepared by:

2. What is Low Impact Development? Why do we need LID? Low Impact Development Principles Low Impact Development Techniques Benefits of LID Local Implementation & Considerations Presentation Outline

3. 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 What isLow Impact Development?

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

5. 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

6. Typical pre-development conditions: Runoff = 10% Infiltration = 50% WHY DO WE NEED LOW IMPACT DEVELOPMENT?

7. Typical post-development conditions: Runoff = 55% Infiltration = 15% WHY DO WE NEED LOW IMPACT DEVELOPMENT?

8. Social and ecological impacts of too much asphalt WHY DO WE NEED LOW IMPACT DEVELOPMENT?

9. High cost and low effectiveness of conventional “pipe and pond” strategies WHY DO WE NEED LOW IMPACT DEVELOPMENT?

10. 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 LID PRINCIPLES1. Use existing natural systems as the integrating framework for site planning

11. 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 LID PRINCIPLES2. Focus on prevention

12. 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

13. 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

14. 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

15. 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

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

17. LID STRATEGIESLow Impact Site Design Open Space Residential Design 1. Identify Conservation Areas

18. LID STRATEGIESLow Impact Site Design Open Space Residential Design 1. Identify Conservation Areas 2. Locate House Sites

19. LID STRATEGIESLow Impact Site Design Open Space Residential Design 1. Identify Conservation Areas 2. Locate House Sites 3. Align Roads & Trails

20. LID STRATEGIESLow Impact Site Design Open Space Residential Design 1. Identify Conservation Areas 2. Locate House Sites 3. Align Roads & Trails 4. Draw the Lot Lines

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 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

23. 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.

24. 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.

25. LID STRATEGIESLow Impact Site Design

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

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

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

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

30. LID STRATEGIESPermeable Paving Runoff reduction • Grass pavers • Paving stones • Porous asphalt • Pervious concrete

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

32. 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

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

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

35. LID STRATEGIESBioretention Applications • Urban retrofits • High-density areas

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

37. LID STRATEGIESVegetated Swales Conveyance, treatment, infiltration

38. LID STRATEGIESGrassed Filter Strips Pretreatment and Attenuation • Low-angle vegetated slopes • Adjacent to parking lots and roadways • Opportunity for snow storage

39. LID STRATEGIESGrassed Filter Strips

40. LID STRATEGIESInfiltration Trenches / Dry Wells Infiltration and Volume Reduction • Runoff stored in void space; slowly percolates into the ground • Excellent for rooftop runoff • Pretreatment is critical for surface runoff

41. LID STRATEGIESInfiltration Trenches / Dry Wells Infiltration and Volume Reduction

42. 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

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

44. LID STRATEGIESGreen Roof Systems Runoff Reduction, Reduce Heating/Cooling Costs • Rainwater stored in a lightweight engineered soil medium • Hardy, drought-resistant vegetation • Reducerunoffby50% • Not for use in stressed basins

45. LID STRATEGIESGreen Roof Systems

46. LID STRATEGIESGreen Roof Systems

47. LID STRATEGIESStormwater Planters Runoff Reduction, Treatment, Attenuation • “Bioretention in a Box” • Vegetative uptake of stormwater pollutants • Pretreatment for suspended solids • Aesthetically pleasing • Reduction of peak discharge rate

48. LID STRATEGIESStormwater Planters

49. LID BENEFITSA Hydrologically Functional Lot

50. LID BENEFITSLower Peak Discharge Rates Reduced Runoff Volume 0 4 8 12 16