Low Impact Development Principles, Techniques, and Implementation Slide show prepared by: In coordination with:

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

What is Low 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

What is Low Impact Development? NOT rocket science NOT formulaic NOT the answer to everychallenge NOT yet finished evolving NOT common in Massachusetts

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

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

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

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

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

LID PRINCIPLES 1.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

LID PRINCIPLES 2.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

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 LID PRINCIPLES 3.Treat stormwater close to the source

Open drainage systems and filter strips Disconnection of roof runoff Rain barrels Street sweeping Public education Reduce construction disturbance Minimize lawn area LID PRINCIPLES 4. Emphasize simple, nonstructural, low-tech, low-cost methods

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 LID PRINCIPLES 5.Create a multifunctional landscape

Reduce use of pesticides and fertilizers. Use drought-resistant plants. Maintain rain gardens and bioretention areas. Provide adequate funding for public works departments LID PRINCIPLES 6.Maintain and sustain

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

LID STRATEGIES Low Impact Site Design Open Space Residential Design 1. Identify Conservation Areas

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

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

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

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

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

Stormwater Management LID STRATEGIES Low Impact Site Design 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.

Stormwater Management LID STRATEGIES Low Impact Site Design 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.

LID STRATEGIES Low Impact Site Design

LID STRATEGIES Roadways and Parking Areas Road Profile Narrower roadways ( feet) Permeable parking lanes Open section roadways Alternative curb designs

LID STRATEGIES Roadways and Parking Areas Alternative Turnarounds Smaller cul-de-sacs Bioretention islands One-way-loops Hammerhead turnarounds

LID STRATEGIES Roadways and Parking Areas Parking Lots Create multiple small lots Allow shared parking Reduce requirements near transit Require compact spaces Set parking maximums

LID STRATEGIES Roadways and Parking Areas Parking Lots Create multiple small lots Allow shared parking Reduce requirements near transit Require compact spaces Set parking maximums

LID STRATEGIES Permeable Paving Grass pavers Paving stones Porous asphalt Pervious concrete Runoff reduction

LID STRATEGIES Permeable Paving Parking stalls Overflow parking Driveways Walkways and plazas Applications

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

LID STRATEGIES Bioretention Excavation filled with engineered soil mix Herbaceous perennials, shrubs, trees Ponded water infiltrates within 72 hours Overflow outlet and optional underdrain

LID STRATEGIES Bioretention Parking lot islands Median strips Rooftop runoff Applications

LID STRATEGIES Bioretention Applications Urban retrofits High-density areas

LID STRATEGIES Vegetated Swales Roadside swales “country drainage” Parking lots Low-angle slopes only Opportunity for snow storage Conveyance, treatment, infiltration

LID STRATEGIES Vegetated Swales Conveyance, treatment, infiltration

LID STRATEGIES Grassed Filter Strips Pretreatment and Attenuation Low-angle vegetated slopes Adjacent to parking lots and roadways Opportunity for snow storage

LID STRATEGIES Grassed Filter Strips

LID STRATEGIES Infiltration 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

Infiltration and Volume Reduction LID STRATEGIES Infiltration Trenches / Dry Wells

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

Runoff Reduction and Water Conservation LID STRATEGIES Rain Barrels and Cisterns

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

LID STRATEGIES Green Roof Systems

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

LID STRATEGIES Stormwater Planters

LID BENEFITS A Hydrologically Functional Lot

LID BENEFITS Lower Peak Discharge Rates Reduced Runoff Volume

LID BENEFITS Reduced Combined Sewer Overflows

LID BENEFITS Improved Water Quality Increased Aquifer Recharge

ConventionalLow Impact Grading/Roads $569,698$426,575 Storm Drains $225,721$132,558 SWM Pond/Fees $260,858$ 10,530 Bioretention/Micro —$175,000 Total$1,086,277$744,663 Unit Cost$14,679$9,193 Lot Yield7481 LID BENEFITS Lower Construction Costs Higher Lot Yield

LID IMPLEMENTATION Important Considerations Select appropriate cold climate techniques Ensure adequate emergency access Prioritize pedestrian safety Define ownership: public, private, mix? Require monitoring and inspection Assign maintenance responsibilities

LID IMPLEMENTATION Long-Term Maintenance All stormwater systems require maintenance LID maintenance often simple, low cost Ensure adequate funding for DPWs Homeowner/landscaper education Consider requiring permanent sureties

LID IMPLEMENTATION Review of Local Codes Zoning Bylaw and Site Plan Review Subdivision Rules and Regulations Board of Health Regulations Wetland Regulations Building Codes

LID IMPLEMENTATION Stormwater/LID Bylaw Replace the “patchwork” of stormwater codes with a single set of local standards Establish Stormwater Permitting Authority to review all projects over a certain size Specify performance standards Utilize expert review when necessary Permit/promote the use of LID techniques Require a maintenance plan

LID IMPLEMENTATION Collaboration is Critical! Local boards Public works officials Fire department and emergency response Developers and builders Consultants and engineers Business interests and property owners Environmental advocates

For more information, visit: home of the Fact sheets Brochures Local codes checklist Frequently asked questions Internet links and resources