Transcript LID Toolkit Presentation

M AS SACHUSETTS
LO W I M PACT DEV ELO PM EN T TO O LKI T
Low Impact Development
Principles, Techniques, and Implementation
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Presentation Outline
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What is Low Impact Development?
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Why do we need LID?
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Low Impact Development Principles
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Low Impact Development Techniques
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Benefits of LID
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Local Implementation & Considerations
What is
Low Impact Development?
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Comprehensive, landscape-based
approach to sustainable development
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Set of strategies to maintain existing
natural systems, hydrology, ecology
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Cost-effective, flexible approach based
on a toolkit of simple techniques
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Collection of practices that have been
implemented nationwide
What is
Low Impact Development?
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NOT rocket science
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NOT formulaic
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NOT the answer to every challenge
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NOT yet finished evolving
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NOT common in Massachusetts
WHY DO WE NEED LOW IMPACT DEVELOPMENT?
Conventional strategies
aren’t working
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Increased runoff & decreased recharge
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Loss of vegetation and wildlife habitat
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Loss of community character
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Polluted waterways
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Cost of development
WHY DO WE NEED LOW IMPACT 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
LID PRINCIPLES
1. Use existing natural systems as the
integrating framework for site planning
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Land use planning and
watershed planning
Identify environmentally
sensitive resources:
wetlands, mature trees, slopes,
drainageways, permeable soils,
waterway buffers
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Assess existing hydrology
Define a development
envelope
LID PRINCIPLES
2. Focus on prevention
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Minimize clearing and
grading
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Cluster buildings and
reduce building footprints
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Reduce road widths,
use shared driveways,
reduce parking area
Align roads to minimize
impact
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Use green rooftops
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Use permeable paving
LID PRINCIPLES
3. Treat stormwater close to the source
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Create subwatersheds and
“micromanage” runoff in a
treatment train of small
structures
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Flatten slopes, lengthen
flow paths, maximize
sheet flow
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Maintain natural flow
paths, use open drainage
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Use LID techniques to
manage frequent,
low-intensity storms
LID PRINCIPLES
4. Emphasize simple, nonstructural,
low-tech, low-cost methods
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Open drainage systems
and filter strips
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Disconnection of roof
runoff
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Rain barrels
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Street sweeping
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Public education
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Reduce construction
disturbance
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Minimize lawn area
LID PRINCIPLES
5. Create a multifunctional landscape
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Use stormwater
management components
that provide filtration,
treatment, and
infiltration.
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Provide open space and
wildlife habitat.
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Store water for landscape
use
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Reduce heat island effect
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Enhance site aesthetics
LID PRINCIPLES
6. Maintain and sustain
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Reduce use of pesticides
and fertilizers.
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Use drought-resistant
plants.
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Maintain rain gardens and
bioretention areas.
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Provide adequate funding
for public works
departments
LID STRATEGIES
Low Impact Site Design
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Conservation of
natural hydrology, trees,
vegetation
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Stream & wetland
buffers
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Minimize impervious
surfaces
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Stormwater
micromanagement
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Ecological landscaping
Conservation
Typical
Subdivision
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
LID STRATEGIES
Low 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
Low Impact Site Design
Buildings and Roadways
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Cluster buildings within
the development
envelope
Design buildings with
smaller footprints
Roadways should follow
existing grades.
Use parking structures
Separate parking areas
LID STRATEGIES
Low Impact Site Design
Buildings and Roadways
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Cluster buildings within
the development
envelope
Design buildings with
smaller footprints
Roadways should follow
existing grades.
Use parking structures
Separate parking areas
LID STRATEGIES
Low 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, lowintensity storms.
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LID STRATEGIES
Low 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, lowintensity storms.
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LID STRATEGIES
Low Impact Site Design
LID STRATEGIES
Roadways and Parking Areas
Road Profile
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Narrower roadways (1824 feet)
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Permeable
parking lanes
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Open section roadways
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Alternative curb designs
LID STRATEGIES
Roadways and Parking Areas
Alternative Turnarounds
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Smaller cul-de-sacs
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Bioretention islands
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One-way-loops
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Hammerhead
turnarounds
LID STRATEGIES
Roadways and Parking Areas
Parking Lots
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Create multiple small
lots
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Allow shared parking
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Reduce requirements
near transit
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Require compact spaces
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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
Runoff reduction
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Grass pavers
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Paving stones
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Porous asphalt
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Pervious concrete
LID STRATEGIES
Permeable Paving
Applications
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Parking stalls
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Overflow parking
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Driveways
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Walkways and plazas
LID STRATEGIES
Bioretention
Treatment, retention, infiltration, landscaping
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Excavation filled with
engineered soil mix
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Herbaceous perennials,
shrubs, trees
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Ponded water infiltrates
within 72 hours
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Overflow outlet and
optional underdrain
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
Applications
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Parking lot islands
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Median strips
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Rooftop runoff
LID STRATEGIES
Bioretention
Applications
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Urban retrofits
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High-density areas
LID STRATEGIES
Vegetated Swales
Conveyance, treatment, infiltration
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Roadside swales
“country drainage”
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Parking lots
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Low-angle slopes only
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Opportunity for snow
storage
LID STRATEGIES
Vegetated Swales
Conveyance, treatment, infiltration
LID STRATEGIES
Grassed Filter Strips
Pretreatment and Attenuation
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Low-angle vegetated
slopes
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Adjacent to parking lots
and roadways
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Opportunity for snow
storage
LID STRATEGIES
Grassed Filter Strips
LID STRATEGIES
Infiltration Trenches / Dry Wells
Infiltration and Volume Reduction
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Runoff stored in void
space; slowly
percolates into the
ground
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Excellent for rooftop
runoff
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Pretreatment is
critical for surface
runoff
LID STRATEGIES
Infiltration Trenches / Dry Wells
Infiltration and Volume Reduction
LID STRATEGIES
Rain Barrels and Cisterns
Runoff Reduction and Water Conservation
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Downspouts directed
to tanks or barrels
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50 – 50,000 gallons
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Excess diverted to
drywell or rain
garden
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Landscaping, car
washing, other
nonpotable uses
LID STRATEGIES
Rain Barrels and Cisterns
Runoff Reduction and Water Conservation
LID STRATEGIES
Green Roof Systems
Runoff Reduction, Reduce Heating/Cooling Costs
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Rainwater stored in a
lightweight
engineered soil
medium
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Hardy, droughtresistant vegetation
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Reduce runoff by 50%
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Not for use in
stressed basins
LID STRATEGIES
Green Roof Systems
LID STRATEGIES
Green Roof Systems
LID STRATEGIES
Stormwater 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 STRATEGIES
Stormwater Planters
LID BENEFITS
A Hydrologically Functional Lot
LID BENEFITS
Lower Peak Discharge Rates
Reduced Runoff Volume
Rainfall / Runoff LID vs Conventional
0.8
Flow
0.6
Conventional
LID
Rainfall
0.4
0.2
0
0
4
8
Hours
12
16
LID BENEFITS
Reduced Combined
Sewer Overflows
LID BENEFITS
Improved Water Quality
Increased Aquifer Recharge
LID BENEFITS
Lower Construction Costs
Higher Lot Yield
Grading/Roads
Storm Drains
SWM Pond/Fees
Bioretention/Micro
Total
Unit Cost
Lot Yield
Conventional
$569,698
$225,721
$260,858
—
Low Impact
$426,575
$132,558
$ 10,530
$175,000
$1,086,277
$14,679
74
$744,663
$9,193
81
LID IMPLEMENTATION
Important Considerations
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Select appropriate cold climate techniques
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Ensure adequate emergency access
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Prioritize pedestrian safety
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Define ownership: public, private, mix?
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Require monitoring and inspection
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Assign maintenance responsibilities
LID IMPLEMENTATION
Long-Term Maintenance
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All stormwater systems require
maintenance
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LID maintenance often simple, low cost
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Ensure adequate funding for DPWs
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Homeowner/landscaper education
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Consider requiring permanent sureties
LID IMPLEMENTATION
Review of Local Codes
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Zoning Bylaw and Site Plan Review
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Subdivision Rules and Regulations
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Board of Health Regulations
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Wetland Regulations
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Building Codes
LID IMPLEMENTATION
Stormwater/LID Bylaw
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Replace the “patchwork” of stormwater
codes with a single set of local standards
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Establish Stormwater Permitting Authority
to review all projects over a certain size
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Specify performance standards
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Utilize expert review when necessary
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Permit/promote the use of LID techniques
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Require a maintenance plan
LID IMPLEMENTATION
Collaboration is Critical!
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Local boards
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Public works officials
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Fire department and emergency response
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Developers and builders
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Consultants and engineers
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Business interests and property owners
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Environmental advocates
For more information, visit:
www.mapc.org/lid
home of the
M AS SACHUSETTS
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LO W I M PACT DEV ELO PM EN T TO O LKI T
Fact sheets
Brochures
Local codes checklist
Frequently asked questions
Internet links and resources