LID Toolkit Presentation

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

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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

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What isLow Impact Development?

• NOT rocket science
• NOT formulaic
• NOT the answer to every challenge
• NOT yet finished evolving
• NOT common in Massachusetts

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WHY DO WE NEED LOW IMPACT DEVELOPMENT?
Conventional strategies arent working

• Increased runoff decreased recharge
• Loss of vegetation and wildlife habitat
• Loss of community character
• Polluted waterways
• Cost of development

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WHY DO WE NEED LOW IMPACT DEVELOPMENT?

• Typical pre-development conditions
• Runoff 10 Infiltration 50

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WHY DO WE NEED LOW IMPACT DEVELOPMENT?

• Typical post-development conditions
• Runoff 55 Infiltration 15

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WHY DO WE NEED LOW IMPACT DEVELOPMENT?

• Impacts of too much asphalt

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WHY DO WE NEED LOW IMPACT DEVELOPMENT?

• High cost and low effectiveness of conventional
  pipe and pond strategies

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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

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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

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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

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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

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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

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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

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LID STRATEGIESLow Impact Site Design

• Conservation of natural hydrology, trees,
  vegetation
• Stream wetland buffers
• Minimize impervious surfaces
• Stormwater micromanagement
• Ecological landscaping

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

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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

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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.

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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.

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LID STRATEGIESLow Impact Site Design
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LID STRATEGIESRoadways and Parking Areas
Road Profile

• Narrower roadways (18-24 feet)
• Permeable parking lanes
• Open section roadways
• Alternative curb designs

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LID STRATEGIESRoadways and Parking Areas
Alternative Turnarounds

• Smaller cul-de-sacs
• Bioretention islands
• One-way-loops
• Hammerhead turnarounds

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LID STRATEGIESRoadways and Parking Areas
Parking Lots

• Create multiple small lots
• Allow shared parking
• Reduce requirements near transit
• Require compact spaces
• Set parking maximums

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LID STRATEGIESRoadways and Parking Areas
Parking Lots

• Create multiple small lots
• Allow shared parking
• Reduce requirements near transit
• Require compact spaces
• Set parking maximums

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LID STRATEGIESPermeable Paving
Runoff reduction

• Grass pavers
• Paving stones
• Porous asphalt
• Pervious concrete

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LID STRATEGIESPermeable Paving
Applications

• Parking stalls
• Overflow parking
• Driveways
• Walkways and plazas

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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

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LID STRATEGIESBioretention

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

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LID STRATEGIESBioretention
Applications

• Parking lot islands
• Median strips
• Rooftop runoff

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LID STRATEGIESBioretention
Applications

• Urban retrofits
• High-density areas

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LID STRATEGIESVegetated Swales
Conveyance, treatment, infiltration

• Roadside swales country drainage
• Parking lots
• Low-angle slopes only
• Opportunity for snow storage

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LID STRATEGIESVegetated Swales
Conveyance, treatment, infiltration
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LID STRATEGIESGrassed Filter Strips
Pretreatment and Attenuation

• Low-angle vegetated slopes
• Adjacent to parking lots and roadways
• Opportunity for snow storage

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LID STRATEGIESGrassed Filter Strips
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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

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LID STRATEGIESInfiltration Trenches / Dry Wells
Infiltration and Volume Reduction
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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

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LID STRATEGIESRain Barrels and Cisterns
Runoff Reduction and Water Conservation
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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

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LID STRATEGIESGreen Roof Systems
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LID STRATEGIESGreen Roof Systems
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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

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LID STRATEGIESStormwater Planters
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LID BENEFITSA Hydrologically Functional Lot
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LID BENEFITSLower Peak Discharge Rates Reduced
Runoff Volume
0 4 8 12
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LID BENEFITSReduced Combined Sewer Overflows
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LID BENEFITSImproved Water QualityIncreased
Aquifer Recharge
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LID BENEFITSLower Construction Costs Higher
Lot Yield
  Conventional Low 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 Yield 74 81
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LID IMPLEMENTATIONImportant 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

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LID IMPLEMENTATIONLong-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

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LID IMPLEMENTATIONReview of Local Codes

• Zoning Bylaw and Site Plan Review
• Subdivision Rules and Regulations
• Board of Health Regulations
• Wetland Regulations
• Building Codes

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LID IMPLEMENTATIONStormwater/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

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LID IMPLEMENTATIONCollaboration 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

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For more information, visit

• www.mapc.org/lid home of the
• Fact sheets
• Brochures
• Local codes checklist
• Frequently asked questions
• Internet links and resources