LOW IMPACT DESIGN: WHY WHEN HOW

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LOW IMPACT DESIGNWHY? WHEN? HOW?

• Eric H. Livingston
• Bureau of Watershed Management
• Florida Dept. of Env. Protection
• Tallahassee, Florida
• 850/245-8430
• eric.livingston_at_dep.state.fl.us
• http//dep.state.fl.us/water/watershed

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EVOLUTION OF STORMWATER MANAGEMENT LID WHY?

• Drainage
• Erosion and sediment control
• Stormwater treatment
• Stormwater retrofitting

BUT We are still not achieving our goal
of protecting or enhancing aquatic ecosystems

• Watershed management

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Loss of designated uses
IMPAIRED WATERS
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CURRENT STATUS OF IMPAIRED WATERS(Through Group
3)
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IMPAIRED WATERS PROBLEMS AND POLLUTION SOURCES

• MAJOR POLLUTANTS OF CONCERN
• Nutrients, nutrients, nutrients!
• Oxygen demanding substances
• Bacteria
• MAJOR SOURCES OF POLLUTANTS
• Stormwater existing development
• Stormwater future development
• Stormwater agricultural
• Leaching agriculture, landscape, OSDS

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Phosphorus Trends in Florida Waters 1970 -2005
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Caloosahatchee River October 15, 2005
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GREATER FOCUS ONWATER QUALITY/AQUATIC ECOLOGY

• TMDL/NPDES rules
• FWRA of 1999
• Beach monitoring
• Nutrient criteria
• Biological criteria
• Sediment quality
• Source water protection

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Maintaining Ecological Integrity
Impact Mitigation or Function Restoration /
Preservation?

• Hydrology
• Volume, Frequency, Recharge,
• Velocity
• Habitat Structure
• Physical, Biological
• Water Quality
• Chemical Pollutants, Temperature Energy Sources
• Nutrients / Food Chain
• Biotic Interactions
• Competition / Disease

Stressor Impacts Are Cumulative, Temporal and
Individually Variable.
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Loss of Hydrologic Functions Caused By Cumulative
Impacts
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Preserving the Natural Hydrologic Cycle
Volume, Frequency, Timing, Recharge,
Evaporation
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INCREASING IMPERVIOUSNESSINCREASES RUNOFF
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STORMFLOW IMPACTS

• 100 year peak flow increases 2 X
• 15 year peak flow increases 3 X
• 2 year peak flow increases 57 X

• 2-yr peak flow occurs 3 X per year (res dev)
• 2-yr peak flow occurs 6 X per year (comm.)

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• Channel erosion destroys ecological habitat
• Sedimentation smothers biota
• Changed hydroperiod affects estuary ecology

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Stormwater Mgmt Must Address the Entire Flow
Frequency Curve
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RELATIONSHIP OF IMPERVIOUSNESS TO BIOLOGICAL
COMMUNITY HEALTH
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EFFECTS OF STORMWATER AND STORMWATER BMPs ON
SMALL STREAMS

• Study sites in Montgomery County, MD Austin,
  TX Vail, CO Puget Sound,WA
• Major effects on biota are caused by hydrologic
  changes
• No impervious threshold effect
• Minimize impervious surfaces
• Retain forests and wetlands
• Maintain 100 riparian buffer
• BMPs more important as urbanization increases

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FLORIDAS STORMWATER RULES

• 1979 Chapter 17- 4.248, F.A.C.
• 1982 Chapter 17- 25, F.A.C.
• 1994 Chapter 62- 25, F.A.C.
• Water management district ERP rules

• TECHNOLOGY BASED
• Performance Standard
• BMP Design Criteria
• Presumption of compliance

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Performance Standard for New Stormwater Discharges

• Erosion and sediment control
• Retain sediment on-site
• Not violate turbidity standard
• Stormwater quantity
• Discharge rate WMD or local standards
• Volume control
• Stormwater quality
• 80 average annual load reduction
• 95 average annual load reduction
• Basin specific requirements

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COMPARISON OF TREATMENT EFFICIENCIES
ESTIMATED REMOVAL EFFICIENCIES TYPE OF
BMP ( LOAD REDUCTION) TN TP
TSS BOD DRY RETENTION 0.50 VOLUME 80 80
80 80 0.75 VOLUME 90 90 90
90 1.00 VOLUME 95 95 95
95 1.25 VOLUME 98 98 98
98 OFF-LINE RET/DET 60 85 90
80 WET RETENTION 40 50 85 40 WET
DETENTION 30 65 90 65 WET
DET/FILTER 0-10 50 85 75 DRY
DETENTION 10-20 20-40
20-60 20-50 DRY DET/FILTER 0-20 0-20
40-60 0-50 ALUM INJECTION 50 gt90
gt95 60
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EXAMPLE PROJECT
Assume BMPs are wet detention
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LID WHY?KEY ALLOCATION ISSUEHow allocate
loadings from future growth?

• Provide an allocation
• Must reduce more loads from existing sources
• Dont provide an allocation
• Increased stormwater treatment for new development

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EVOLUTION FOR STORMWATER/WATERSHED MANAGERS

• Its the volume!
• Secondary treatment inadequate
• Structural BMPs have limitations
• Return to basics
• Multiple objectives
• Stormwater is an asset

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CHAPTER 62-40, FACSTORMWATER GOALFUTURE
STORMWATER PERFORMANCE STANDARD?
POST lt PRE

• Peak discharge rate
• Volume
• Recharge
• Pollutant loading (nutrients)

In effect in Lake Apopka, Lake Okeechobee, and
SW Florida
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LIMITS OF STRUCTURAL STORMWATER MANAGEMENT

• Inability to treat to high levels
• Lack of flexibility in site design
• Loss of useable land area
• Connection of impervious areas
• Disregard site resource benefits
• Altered site hydrology/pollutant loads
• Cost
• Maintenance obligations

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BEST MANAGEMENT PRACTICES
Nonstructural prevention
Structural mitigation
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PREVENTING STORMWATER POLLUTION USING
NONSTRUCTURAL BMPs

• LAND USE MANAGEMENT PROMOTE LID
• Protect natural SWM system
• Protect natural areas, wetlands, riparian buffers
• Minimize impervious surfaces, veg clearing
• SOURCE CONTROLS
• Street sweeping, litter control
• Minimize fertilizer pesticide use
• Natural landscaping (FYN Program)
• Prevent illicit connections discharges
• PUBLIC EDUCATION
• Storm sewer stenciling
• Roof runoff to pervious areas
• Aquascaping littoral areas
• Maintaining their stormwater system

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RETURN TO BASICSFOCUSING ON POLLUTION PREVENTION

• Reduce stormwater volume
• Conservation or Low Impact Design
• Reduce Directly Connected Imp. Area
• Stormwater reuse

• Reduce stormwater pollutants
• Source controls (FYN, street sweeping)
• Operation and maintenance

• Retain/enhance natural stormwater system
• Riparian buffers, reforestation
• Wetland and floodplain protection
• Protect and plant forests, vegetation

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LID WHEN? UNIFIED STATEWIDE STORMWATER RULE
Governor Bush Its time to kick it up with
respect to the level of stormwater treatment in
Florida

• Harper Report April 2006
• DEP-WMD draft rule Summer 2006
• Create TAC September 2006
• TAC Meetings Sept Dec 2006
• Rule Workshops Jan June 2007
• Rule Adoption - July 2007

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LID IMPEDIMENTS IN FLORIDA

• Local land development regulations
• Save the Swales
• Reduce imperviousness
• Landscaping based on FYN/Green Industries BMP
  Program
• Time to permit approval
• Effectiveness data
• FYN, green roofs
• Swales, rain gardens
• Pervious pavement

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URBAN STORMWATER BMP RESEARCH

• UCF Stormwater Management Academy
• Managed stormwater is good water
• http//stormwater.ucf.edu/
• FDEP stormwater research projects
• Effectiveness of littoral zones
• Effectiveness of proprietary BMPs
• Improving nitrogen removal in BMPs
• Stormwater reuse design/health risks
• Evaluation of pervious concrete
• Evaluation of green roofs
• Turf grass fertilization/irrigation needs
• Florida Urban BMP Data Base

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FLORIDA LID PROJECTSLID HOW?

• Bonita Bay Bonita Springs
• Mederra Gainesville
• River Forest Bradenton
• Baldwin Park - Orlando

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• The Problem Conventional Site Design
• Efficiency
• Collect
• Concentrate
• Convey

Good Drainage Approach
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Tree Conservation Rain Gardens Vegetated swales
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WATERSHED TREATMENT TRAIN

• Filter strips, buffers
• Lawn chemical mgmt.
• Pervious pavement
• Rain barrels, vegetation

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Low Impact Development Preserving Hydrology
Think Small
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REFERENCES

• Conservation Design for Stormwater Management
  (1997). Delaware DNREC and Brandywine
  Conservancy.
• Low Impact Development Design Strategies (2000).
  Prince Georges Co., Md. EPA 841-B-00-003.
• Low Impact Hydrologic Analysis (2000). Prince
  Georges Co., Md. EPA 841-B-00-002.
• http//lowimpactdevelopment.org/
• http//www.greenroofs.ca/grhcc/index.html

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Low Impact Development

• Comprehensive approach
• Hydrology is integrating framework
• Micro-scale or precession management
• Control stormwater at the source
• Use simple, nonstructural methods
• Decentralized / disbursed flows
• Create multifunctional landscape and
  infrastructure

Pollution and Hydrologic Prevention
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LOW IMPACT DESIGN

• APPROACHES - Preventive
• Watershed planning
• Local planning
• Site (lot) planning
• Concurrency!
• Reduce imperviousness
• Min. disturbance
• Protect vegetation, trees
• Reduce soil compaction

• PRACTICES - Mitigation
• Infiltration basins
• Bioretention
• Biofiltration
• Swales
• Filter strips
• Terraforming
• Natural areas
• Wetlands
• Wet detention

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LOW IMPACT/CONSERVATION DESIGN PRINCIPLES

• Protect/avoid sensitive areas
• Minimize disturbed areas, compaction
• Minimize loss of vegetation
• Minimize imperviousness, especially DCIA
• Maximize infiltration
• Reduce setbacks
• Cluster development
• Use innovative planning tools (TDR)

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LOW IMPACT DESIGNREDUCING IMPERVIOUSNESS

• Tailor and decrease road width
• Minimize road length
• Use pervious pavements for parking
• Reduce required parking spaces
• Reduce parking space size
• Use one way angled parking
• Minimize paved driveways/size
• Side walks on one side only

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REDUCING IMPERVIOUSNESSIN PARKING LOTS

• Nonstructural tools
• Reduce required parking spaces
• Reduce parking space size
• Use one way angled parking

• Structural tools
• Use pervious pavements for parking
• Pervious concrete
• Turf block/pavers
• Geoweb and sod

BUT, THIS MAY REQUIRE CODE OR CULTURAL CHANGE
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Runoff coefficients for basins in parking lot
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Flowrain0.84,F2345cf,F8196,F4138cf,F623cf
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Comparison between basinsLead (ug/l)
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PERVIOUS CONCRETE INFORMATION

• Florida Concrete Products Assn
• http//www.fcpa.org/
• Manuals
• Training classes certification of contractors
• Training videos

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Field Test Results
Age of concrete varies from 10 to 20 years
(except for Site 4 Area 1).
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PERVIOUS CONCRETEPITFALLS TO AVOID

• Pervious concrete is different
• Batching
• Pouring/finishing
• Maintenance
• Contractor training is essential
• Use a certified contractor

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TURF BLOCKPERVIOUS PAVERS

• Difficult to install
• Difficult to maintain
• May not be socially acceptable
• Good for overflow parking

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REDUCING IMPERVIOUSNESSWHATS IT COST?

• Asphalt 1.00/sf
• Pervious concrete 3.50/sf
• Pavers 3.85/sf
• Pervious pavers 4.00/sf

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BMP TREATMENT TRAIN

Final Treatment and Attenuation
Runoff Load Generation
Additional Treatment Attenuation
Source controls Public ed Erosion control Roof
runoff Florida Yards LID
Storage tank Sediment sump Alum/PAM
Swales Catch basins Filter inlets Oil/water
separators
Retention Detention Wetlands
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TALLAHASSEE PARKING LOT TREATMENT TRAIN
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TALLAHASSEE PARKING LOT TREATMENT TRAIN
Sod over Geoweb
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TALLAHASSEE PARKING LOT TREATMENT TRAIN
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TALLAHASSEE PARKING LOT TREATMENT TRAIN
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TALLAHASSEE PARKING LOT TREATMENT TRAIN
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Parking Lot Bioretention Landscaping
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The benefits provided by vegetation
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Biological Pollutant RemovalPlant / Soil Flora /
Soil Chemistry

• Phytoremediation
• Translocate
• Accumulate
• Metabolize
• Volatilize
• Detoxify
• Degrade
• Bioremediation

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TREES ARE STORMWATER BMPs!

• Urban Ecosystem Analysis, Jax (2005)
• American Forests (www.americanforests.org)

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Tree Box Filter
Tree
Side Walk
Inlet
Curb
Street
High Rate Biofilter
Storm Drain
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Street tree stormwater filters
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Three Zone Riparian Forest Buffer Zone
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• Bioretention/Biofiltration
• Shallow Ponding
• Infiltration and/or filtration
• Volume control
• Multifunctional landscape
• Aesthetic value
• Habitat value
• Property value
• Low cost maintenance
• High pollutant removal
• Physical / chemical / biological

X
2
Under Drain
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Buckman Heights courtyard with infiltration
garden
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Flatter Wider
Smaller Culverts Detention Bioretention
Infiltration Filtration
Multifunctional Swales
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Scuppers into Stormwater Planter
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Ritzdorf Stormwater Flow Through Planter
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BES Lab Vegetative Filter
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Runoff Storage Below Sidewalks Or Depressed
Green Space.
Incorporate micro-scale BMPs into maintenance
activities and revitalization programs
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Orlando Streetscape Exfiltration System
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August 2003
Shadow Wood Preserve Green Roof, Bonita Springs
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UCF Student Union Green Roof
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BENEFITS OF ECOROOFS

• Economic benefit
• Stormwater management
• Improve air quality
• Moderate urban heat island effect
• Building insulation
• Reduce energy consumption
• Sound insulation
• Health and horticultural therapy
• Recreation
• Food supply
• Habitat and wildlife biodiversity
• Aesthetics

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Runoff Use Consumption Reduction Save 100 / yr.
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South Bay Utilities Inc.

• Upscale residential
• Some Commercial
• No CUP
• No FPSC

• 50/1,000 gallons
• Shallow horizontal wells
• Customer agreements 900 homes - HOA

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LOW IMPACT DESIGN WHY? COST SAVINGS

• Cost Savings
• Less ponds
• Less piping
• Fewer structures
• Less curb / gutters
• Less paving
• Less grading
• BMP maintenance
• Energy conservation

• Cost increases
• Design
• Grading
• Site Investigation
• Landscaping
• Maintenance

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BENEFITS OF LID Pembroke Woods,
Emmittsburg, MD

• Designed per LID Design Manual
• Original design (43 acre site)
• 68 1/4 acre lots, 2 wet ponds, clearing
• LID redesign
• 70 lots (increased by 2 90,000)
• Eliminated 2 wet ponds (saved 200,000)
• Added 2.5 acres of undisturbed open space and
  wetlands (less mitigation)
• Swales instead of curb/gutter (saved 60,000)
• Road width reduced 36 to 30 (17 savings)

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EXAMPLE CASE STUDYSITE CHARACTERISTICS

• Size 84 acres
• Veg Forests, cropland, grasses
• Soils HSG B D
• Hydrology Generally S N, 5 subbasins
• with natural swale conveyances
• Water Stream on northern border
• Critical areas Wetland, floodplain

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EXAMPLE CASE STUDYCONVENTIONAL DESIGN

• Lots 90 SF on 50 acres
• Lot size 18,975 ft2
• Natural area 34 acres, stream corridor
• Road length/width 7,579 feet/28 feet
• Imperviousness 26.2
• SWM Curb/gutter/storm sewers with 3 wet
  detention ponds

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EXAMPLE CASE STUDYCONSERVATION DESIGN

• Lots 90 SF on 35 acres
• Lot size 10,000 - 18,975 ft2
• Lot configuration around open space
• Natural area 49 acres, stream corridor, natural
  conveyances
• Road length/width 6,333 feet/20 feet
• Imperviousness 10.7
• SWM Open space swales, storm sewers, retention,
  reforestation

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CASE STUDY90 SF lots on 50 acresCOMPARISON OF
HYDROLOGY
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CASE STUDYCOMPARISON OF COSTS
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Water is the lifeblood of our Planet
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A Water Quality Street waiting to happen