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Title: LOW IMPACT DESIGN: WHY WHEN HOW


1
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

2
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

3
Loss of designated uses
IMPAIRED WATERS
4
CURRENT STATUS OF IMPAIRED WATERS(Through Group
3)
5
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

6
Phosphorus Trends in Florida Waters 1970 -2005
7
Caloosahatchee River October 15, 2005
8
GREATER FOCUS ONWATER QUALITY/AQUATIC ECOLOGY
  • TMDL/NPDES rules
  • FWRA of 1999
  • Beach monitoring
  • Nutrient criteria
  • Biological criteria
  • Sediment quality
  • Source water protection

9
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.
10
Loss of Hydrologic Functions Caused By Cumulative
Impacts
11
Preserving the Natural Hydrologic Cycle
Volume, Frequency, Timing, Recharge,
Evaporation
12
INCREASING IMPERVIOUSNESSINCREASES RUNOFF
13
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.)

14
  • Channel erosion destroys ecological habitat
  • Sedimentation smothers biota
  • Changed hydroperiod affects estuary ecology

15
Stormwater Mgmt Must Address the Entire Flow
Frequency Curve
16
RELATIONSHIP OF IMPERVIOUSNESS TO BIOLOGICAL
COMMUNITY HEALTH
17
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

18
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

19
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

20
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
21
EXAMPLE PROJECT
Assume BMPs are wet detention
22
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

23
EVOLUTION FOR STORMWATER/WATERSHED MANAGERS
  • Its the volume!
  • Secondary treatment inadequate
  • Structural BMPs have limitations
  • Return to basics
  • Multiple objectives
  • Stormwater is an asset

24
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
25
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

26
BEST MANAGEMENT PRACTICES
Nonstructural prevention
Structural mitigation
27
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

28
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

29
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

30
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

31
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

32
FLORIDA LID PROJECTSLID HOW?
  • Bonita Bay Bonita Springs
  • Mederra Gainesville
  • River Forest Bradenton
  • Baldwin Park - Orlando

33
  • The Problem Conventional Site Design
  • Efficiency
  • Collect
  • Concentrate
  • Convey

Good Drainage Approach
34
Tree Conservation Rain Gardens Vegetated swales
35
WATERSHED TREATMENT TRAIN
  • Filter strips, buffers
  • Lawn chemical mgmt.
  • Pervious pavement
  • Rain barrels, vegetation

36
Low Impact Development Preserving Hydrology
Think Small
37
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

38
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
39
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

40
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)

41
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42
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

43
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
44
Runoff coefficients for basins in parking lot
45
Flowrain0.84,F2345cf,F8196,F4138cf,F623cf
46
Comparison between basinsLead (ug/l)
47
PERVIOUS CONCRETE INFORMATION
  • Florida Concrete Products Assn
  • http//www.fcpa.org/
  • Manuals
  • Training classes certification of contractors
  • Training videos

48
Field Test Results
Age of concrete varies from 10 to 20 years
(except for Site 4 Area 1).
49
PERVIOUS CONCRETEPITFALLS TO AVOID
  • Pervious concrete is different
  • Batching
  • Pouring/finishing
  • Maintenance
  • Contractor training is essential
  • Use a certified contractor

50
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51
TURF BLOCKPERVIOUS PAVERS
  • Difficult to install
  • Difficult to maintain
  • May not be socially acceptable
  • Good for overflow parking

52
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53
REDUCING IMPERVIOUSNESSWHATS IT COST?
  • Asphalt 1.00/sf
  • Pervious concrete 3.50/sf
  • Pavers 3.85/sf
  • Pervious pavers 4.00/sf

54
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
55
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56
TALLAHASSEE PARKING LOT TREATMENT TRAIN
57
TALLAHASSEE PARKING LOT TREATMENT TRAIN
Sod over Geoweb
58
TALLAHASSEE PARKING LOT TREATMENT TRAIN
59
TALLAHASSEE PARKING LOT TREATMENT TRAIN
60
TALLAHASSEE PARKING LOT TREATMENT TRAIN
61
Parking Lot Bioretention Landscaping
62
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63
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64
The benefits provided by vegetation
65
Biological Pollutant RemovalPlant / Soil Flora /
Soil Chemistry
  • Phytoremediation
  • Translocate
  • Accumulate
  • Metabolize
  • Volatilize
  • Detoxify
  • Degrade
  • Bioremediation

66
TREES ARE STORMWATER BMPs!
  • Urban Ecosystem Analysis, Jax (2005)
  • American Forests (www.americanforests.org)

67
Tree Box Filter
Tree
Side Walk
Inlet
Curb
Street
High Rate Biofilter
Storm Drain
68
Street tree stormwater filters
69
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70
Three Zone Riparian Forest Buffer Zone
71
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72
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73
  • 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
74
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75
Buckman Heights courtyard with infiltration
garden
76
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77
Flatter Wider
Smaller Culverts Detention Bioretention
Infiltration Filtration
Multifunctional Swales
78
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79
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80
Scuppers into Stormwater Planter
81
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82
Ritzdorf Stormwater Flow Through Planter
83
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84
BES Lab Vegetative Filter
85
Runoff Storage Below Sidewalks Or Depressed
Green Space.
Incorporate micro-scale BMPs into maintenance
activities and revitalization programs
86
Orlando Streetscape Exfiltration System
87
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91
August 2003
Shadow Wood Preserve Green Roof, Bonita Springs
92
UCF Student Union Green Roof
93
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

94
Runoff Use Consumption Reduction Save 100 / yr.
95
South Bay Utilities Inc.
  • Upscale residential
  • Some Commercial
  • No CUP
  • No FPSC
  • 50/1,000 gallons
  • Shallow horizontal wells
  • Customer agreements 900 homes - HOA

96
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

97
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)

98
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

99
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

100
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

101
CASE STUDY90 SF lots on 50 acresCOMPARISON OF
HYDROLOGY
102
CASE STUDYCOMPARISON OF COSTS
103
Water is the lifeblood of our Planet
104
A Water Quality Street waiting to happen
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