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Low Impact DevelopmentPrinciples, Techniques, and Implementation

In coordination with:

Slide show prepared by:


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

Presentation Outline


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 isLow Impact Development?


What is low impact development1

NOT rocket science development

NOT formulaic

NOT the answer to every challenge

NOT yet finished evolving

NOT common in Massachusetts

What isLow Impact Development?


Why do we need low impact development conventional strategies aren t working
WHY DO WE NEED LOW IMPACT DEVELOPMENT? developmentConventional strategies aren’t working

  • Increased runoff & decreased recharge

  • Loss of vegetation and wildlife habitat

  • Loss of community character

  • Polluted waterways

  • Cost of development


Why do we need low impact development

Typical pre-development conditions: development

Runoff = 10% Infiltration = 50%

WHY DO WE NEED LOW IMPACT DEVELOPMENT?


Why do we need low impact development1

Typical post-development conditions: development

Runoff = 55% Infiltration = 15%

WHY DO WE NEED LOW IMPACT DEVELOPMENT?


Why do we need low impact development2

Social and ecological impacts of too much asphalt development

WHY DO WE NEED LOW IMPACT DEVELOPMENT?


Why do we need low impact development3

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 pond” strategies

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


Lid principles 2 focus on prevention

Minimize clearing and grading pond” strategies

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


Lid principles 3 treat stormwater close to the source
LID PRINCIPLES pond” strategies3. 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


LID PRINCIPLES pond” strategies4. 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


LID PRINCIPLES pond” strategies5. 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


LID PRINCIPLES pond” strategies6. 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


Lid strategies low impact site design

Conservation of pond” strategiesnatural hydrology, trees, vegetation

Stream & wetland buffers

Minimize impervious surfaces

Stormwater micromanagement

Ecological landscaping

LID STRATEGIESLow Impact Site Design

Conservation

Typical Subdivision


LID STRATEGIES pond” strategiesLow Impact Site Design

Open Space Residential Design

1. Identify Conservation Areas


LID STRATEGIES pond” strategiesLow Impact Site Design

Open Space Residential Design

1. Identify Conservation Areas

2. Locate House Sites


LID STRATEGIES pond” strategiesLow Impact Site Design

Open Space Residential Design

1. Identify Conservation Areas

2. Locate House Sites

3. Align Roads & Trails


LID STRATEGIES pond” 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


LID STRATEGIES pond” 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


LID STRATEGIES pond” 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


LID STRATEGIES pond” 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.


LID STRATEGIES pond” 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.


LID STRATEGIES pond” strategiesLow Impact Site Design


LID STRATEGIES pond” strategiesRoadways and Parking Areas

Road Profile

  • Narrower roadways (18-24 feet)

  • Permeable parking lanes

  • Open section roadways

  • Alternative curb designs


LID STRATEGIES pond” strategiesRoadways and Parking Areas

Alternative Turnarounds

  • Smaller cul-de-sacs

  • Bioretention islands

  • One-way-loops

  • Hammerhead turnarounds


LID STRATEGIES pond” strategiesRoadways and Parking Areas

Parking Lots

  • Create multiple small lots

  • Allow shared parking

  • Reduce requirements near transit

  • Require compact spaces

  • Set parking maximums


LID STRATEGIES pond” strategiesRoadways and Parking Areas

Parking Lots

  • Create multiple small lots

  • Allow shared parking

  • Reduce requirements near transit

  • Require compact spaces

  • Set parking maximums


LID STRATEGIES pond” strategiesPermeable Paving

Runoff reduction

  • Grass pavers

  • Paving stones

  • Porous asphalt

  • Pervious concrete


LID STRATEGIES pond” strategiesPermeable Paving

Applications

  • Parking stalls

  • Overflow parking

  • Driveways

  • Walkways and plazas


LID STRATEGIES pond” 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


LID STRATEGIES pond” strategiesBioretention

  • Excavation filled with engineered soil mix

  • Herbaceous perennials, shrubs, trees

  • Ponded water infiltrates within 72 hours

  • Overflow outlet and optional underdrain


LID STRATEGIES pond” strategiesBioretention

Applications

  • Parking lot islands

  • Median strips

  • Rooftop runoff


LID STRATEGIES pond” strategiesBioretention

Applications

  • Urban retrofits

  • High-density areas


LID STRATEGIES pond” strategiesVegetated Swales

Conveyance, treatment, infiltration

  • Roadside swales “country drainage”

  • Parking lots

  • Low-angle slopes only

  • Opportunity for snow storage


LID STRATEGIES pond” strategiesVegetated Swales

Conveyance, treatment, infiltration


LID STRATEGIES pond” strategiesGrassed Filter Strips

Pretreatment and Attenuation

  • Low-angle vegetated slopes

  • Adjacent to parking lots and roadways

  • Opportunity for snow storage


LID STRATEGIES pond” strategiesGrassed Filter Strips


LID STRATEGIES pond” 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


LID STRATEGIES pond” strategiesInfiltration Trenches / Dry Wells

Infiltration and Volume Reduction


LID STRATEGIES pond” 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


LID STRATEGIES pond” strategiesRain Barrels and Cisterns

Runoff Reduction and Water Conservation


LID STRATEGIES pond” 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


LID STRATEGIES pond” strategiesGreen Roof Systems


LID STRATEGIES pond” strategiesGreen Roof Systems


LID STRATEGIES pond” 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


LID STRATEGIES pond” strategiesStormwater Planters


LID BENEFITS pond” strategiesA Hydrologically Functional Lot


LID BENEFITS pond” strategiesLower Peak Discharge Rates Reduced Runoff Volume

0 4 8 12 16


LID BENEFITS pond” strategiesReduced Combined Sewer Overflows


LID BENEFITS pond” strategiesImproved Water QualityIncreased Aquifer Recharge


LID BENEFITS pond” strategiesLower Construction Costs Higher Lot Yield


LID IMPLEMENTATION pond” strategiesImportant 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 pond” strategiesLong-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 pond” strategiesReview of Local Codes

  • Zoning Bylaw and Site Plan Review

  • Subdivision Rules and Regulations

  • Board of Health Regulations

  • Wetland Regulations

  • Building Codes


LID IMPLEMENTATION pond” strategiesStormwater/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 pond” strategiesCollaboration 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: pond” strategies

www.mapc.org/lidhome of the

  • Fact sheets

  • Brochures

  • Local codes checklist

  • Frequently asked questions

  • Internet links and resources


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