Low Impact Development Principles, Techniques, and Implementation M A S SA C H U SETTS LO W IM PA C T D EV ELO PM EN T TO O LKIT Slide show prepared by: In coordination with:
Transcript
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Low Impact Development Principles, Techniques, and
Implementation Slide show prepared by: In coordination with:
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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 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
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What is Low Impact Development? NOT rocket science NOT
formulaic NOT the answer to everychallenge 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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Typical pre-development conditions: Runoff = 10% Infiltration =
50% WHY DO WE NEED LOW IMPACT DEVELOPMENT?
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Typical post-development conditions: Runoff = 55% Infiltration
= 15% WHY DO WE NEED LOW IMPACT DEVELOPMENT?
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Social and ecological impacts of too much asphalt WHY DO WE
NEED LOW IMPACT DEVELOPMENT?
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High cost and low effectiveness of conventional pipe and pond
strategies WHY DO WE NEED LOW IMPACT DEVELOPMENT?
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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
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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
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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
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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
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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
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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
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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
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LID STRATEGIES Low Impact Site Design Open Space Residential
Design 1. Identify Conservation Areas
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LID STRATEGIES Low Impact Site Design Open Space Residential
Design 1. Identify Conservation Areas 2. Locate House Sites
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LID STRATEGIES Low Impact Site Design Open Space Residential
Design 1. Identify Conservation Areas 2. Locate House Sites 3.
Align Roads & Trails
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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
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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
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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
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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.
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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.
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LID STRATEGIES Low Impact Site Design
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LID STRATEGIES Roadways and Parking Areas Road Profile Narrower
roadways (18- 24 feet) Permeable parking lanes Open section
roadways Alternative curb designs
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LID STRATEGIES Roadways and Parking Areas Alternative
Turnarounds Smaller cul-de-sacs Bioretention islands One-way-loops
Hammerhead turnarounds
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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
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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 Parking stalls Overflow parking
Driveways Walkways and plazas Applications
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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
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LID STRATEGIES Bioretention 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 STRATEGIES Bioretention Parking lot islands Median strips
Rooftop runoff Applications
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LID STRATEGIES Bioretention Applications Urban retrofits
High-density areas
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LID STRATEGIES Vegetated Swales Roadside swales country
drainage Parking lots Low-angle slopes only Opportunity for snow
storage Conveyance, treatment, infiltration
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LID STRATEGIES Vegetated Swales Conveyance, treatment,
infiltration
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LID STRATEGIES Grassed Filter Strips Pretreatment and
Attenuation Low-angle vegetated slopes Adjacent to parking lots and
roadways Opportunity for snow storage
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LID STRATEGIES Grassed Filter Strips
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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
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Infiltration and Volume Reduction LID STRATEGIES Infiltration
Trenches / Dry Wells
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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
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Runoff Reduction and Water Conservation LID STRATEGIES Rain
Barrels and Cisterns
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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
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LID STRATEGIES Green Roof Systems
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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 BENEFITS Improved Water Quality Increased Aquifer
Recharge
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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
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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
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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
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LID IMPLEMENTATION Review 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 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
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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
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For more information, visit: www.mapc.org/lid www.mapc.org/lid
home of the Fact sheets Brochures Local codes checklist Frequently
asked questions Internet links and resources