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GREEN STORMWATER PRACTICES
Mark D. Heinzer, P.E., LEED AP, CPESC
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PR
ESENTATIONOUTLINE
AGENDA
o Benefits of green stormwaterpractices
o General Information
o Advantages/Disadvantages
o Evaluating green practiceso Disconnecting impervious
area/vegetated swales
o Bioretention cells, Bioswales
o Bioretention basics
o Soil amendmentso Sustainable landscaping
o Permeable pavers/perviousconcrete
o Level Spreaders
o Rain water Harvesting
o Green roofs
o Constructed Wetlands
o LEED and other green
designations
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GREEN SUSTAINABLE
SROI Sustainable Return on Investment
Design LifeGreen Infrastructure = Strategically planned and managed networks of naturallands, working landscapes and other open spaces that conserve ecosystem values
and functions and provide associated benefits to human populations. -
www.greeninfrastructure.net
Sustainable Infrastructure = "The design of new infrastructure, and the re-design,rehabilitation, re-use or optimization of existing infrastructure, which is consistent
with the principles of urban sustainability and global sustainable development"
University of Toronto
GENERAL INFORMATIONST
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REDUCE VOLUME OF STORMWATER RUNOFF / PEAK FLOWS
IMPROVE RUNOFF QUALITY
COMPLIANCE!
PUBLIC RELATIONS
AESTHETICS
COST??
Benefits of green stormwater practicesST
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Disconnecting impervious area/vegetated swales
The effectiveness of grass swales was also quite good for both pollutant removal
and runoff volume reduction.USEPA and LID Center, Low Impact Development, A
Literature Review
DISCONNECTING IMPERVIOUS AREAS:
BUFFER STRIPS
LANDSCAPING
VEGETATED SWALES:
USE CHECK DAMS
MAINTENANCE MOWING, SEDIMENT REMOVAL
EROSION
CHEAPER THAN CURB AND GUTTERVelocity < 1fps for Peak Flow
Residence Time = 5 minutes
ST
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THE BIG DISCONNECT
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ST
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THE BIG DISCONNECT
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USE WHEN DRAINING AREAS LESS THAN 5 ACRES.(Larger areas create higher flows and volumes of runoff which do not lend
themselves to filtration and infiltration)
The following steps are recommended for completing a grass swale design:
Determine design flow rate to the system (Qwq)
Determine the slope of the system
Select a swale shape
Determine required channel widthCalculate the cross sectional area of flow
Calculate the velocity of channel flow
Calculate swale length
Select swale location based on the design parameters
Select a vegetation cover for the swale
Check for swale stability
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THE BIG DISCONNECT
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FLAT SLOPES OF LESS THAN 4%, CHANNEL SLOPES BETWEEN 1-2% ARERECOMMENDED.
RUNOFF VELOCITIES MUST BE NON-EROSIVE. Velocity < 1fps for Peak Flow
A MINIMUM FIVE-MINUTE RESIDENCE TIME IS RECOMMENDED FOR THE WATERQUALITY PEAK FLOW. Residence Time = 5 minutes
SELECT A GRASS THAT CAN WITHSTAND RELATIVELY HIGH-VELOCITY FLOWS AT THEENTRANCES, AND BOTH WET AND DRY PERIODS.
SIDESLOPES SHOULD BE 4:1 OR FLATTER WHERE SPACE PERMITS.
NOT TO EXCEED 3:1
MAXIMUM FLOW DEPTH FOR WATER QUALITY = +/-4
MANNINGS n = 0.15 FOR FLOW DEPTHS HEIGHT OF VEGETATION, DECREASES ASDEPTH INCREASES
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THE BIG DISCONNECT
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STORMWATER
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THE BIG DISCONNECT
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BIORETENTION
Bioretention is the process in which contaminants and sedimentation are removedfrom stormwater runoff. Stormwater is collected into the treatment area whichconsists of a grass buffer strip, sand bed, ponding area, organic layer or mulch layer,planting soil, and plants. - USEPA
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BIORETENTION
When to use Bioretention:
When you have shallow grades that allow for sheet flow
conditions over level entrance areas.
Commercial or Residential areas 1-3 acres in size.
(Where practical, place proposed impervious surfaces on hydrologic soil groups C &
D and preserve soil groups A & B to reduce the net change in the CN value.)
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BIORETENTION SOIL MEDIA
85 to 88 percent sand. A washed, medium sand is sufficient.
8 to 12 percent fines. Fines include both clay and silt.
12% to obtain 1 in/hr infiltration rate for nitrogen removal
8% to obtain 2 in/hr infiltration rate for phosphorus, metal, and otherpollutant removal
3 to 5 percent organic matter. pine bark fines has been successfully used.
Or
50 percent sand
20 to 30 percent topsoil
20 to 30 percent compost
And
Underdrain gravel should be clean, double-washed #57 stone.
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BIORETENTION BASIC DESIGN PROCEDURE NRCS METHOD
Determine depth of runoff using the following equation from the Natural
Resources Conservation Service:
Runoff Depth in Inches = (P-0.2*S)^2 / (P+0.8*S)P = Precipitation (typically use 1 inch)
S = 1,000 / CN - 10
CN = Curve Number
Calculate volume of runoff to be treated
Runoff Volume (ft) = Watershed Area (ft) * Runoff Depth (ft)
Remember to convert runoff depth from inches to feet (1 foot = 12 inches)
Calculate required surface area
Bioretention Surface Area (ft) = Runoff Volume (ft) / Avg. Depth of
Water (ft)
Average depth of water is typically 6-9 inches
Source: USDA. 1986. Urban Hydrology for Small Watersheds. Washington, D.C.: U.S.
Department of Agriculture. Technical Release No. 55.
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BIORETENTION BASIC DESIGN PROCEDURE RATIONAL METHOD
Flow Based Sizing
Qtreat= C ItreatA Itreat= 0.2 in/hour
Infiltration rate = 5 in/hour
Area = C * (0.2 in/hr) * A (varies per project)5 in/hour
Area = C*A* 4%
Volume Based Sizing
Vtreat= C P85thA P85th= Rainfall in inches (varies per region)
Store the Treatment Volume
Determine Depth Requirement based on Available Surface Area
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Soil Chemistry To support plant growth while removing phosphorus fromrunoff, the fill soil must have a P-index between 10 and 30. If thebioretention area is not designed to reduce phosphorus in runoff, a P-Indexfor the fill soil of 25 to 40 is recommended.
When Constructing Bioretention
Use teeth on bucket to scarify the bottom as you excavate the
last 9-12 of the basin to avoid smearing the subgrade soil.
Excavate when subgrade soils are relatively dry.
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Permeable pavers/pervious pavement
WHEN TO USE PERVIOUS
SURFACES:LOW TRAFFIC AREASLOW SPEED
LIGHT LOADSFLAT GRADE
MINIMIZE TURNINGMOVEMENTSAESTHETICS
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PERVIOUS PAVEMENTS
CONCRETE
STRENGTH?
DURABILITY?
CONSTRUCTABILITY?
COST?
AESTHETICS?
ASPHALT
STRENGTH?
DURABILITY?
CONSTRUCTABILITY?
COST? AESTHETICS?
MECHANISTIC IMPERICAL DESIGN METHODOLOGY???
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PERVIOUS PAVEMENTS
CONCRETE
STRENGTH?
DURABILITY?
CONSTRUCTABILITY?
COST?
AESTHETICS?
ASPHALT
STRENGTH?
DURABILITY?
CONSTRUCTABILITY?
COST? AESTHETICS?
MECHANISTIC IMPERICAL DESIGN METHODOLOGY???
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PERVIOUS CONCRETE
PORTLAND CEMENT ASSOCIATION CONCRETE THINKING FOR A SUSTAINABLE WORLD
NATIONAL READYMIX CONCRETE ASSOCIATION
AMERICAN CONCRETE PAVING ASSOCIATION
DESIGN TOOL FOR HYDRAULIC CALCULATIONS (EXCEL SPREADSHEET)
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PERVIOUS PAVEMENT
DESIGN TOOL
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PERVIOUS ASPHALT VOID SPACE ~20%
OPEN GRADED RICTION COURSE
HIGHER INFILTRATION RATES OVER THE WINTER (UP TO 100%)*
WATER QUALITY
*Dr. Robert Roseen, director of the University of New Hampshire Stormwater Center(UNHSC)
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PERVIOUS PAVERS
Flow occurs through gaps between the blocksTypically 1/8 to 1 in size depending on block used
Maintenance:
Sweeping; regenerative air or pure vacuum sweeper
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CAN DESIGN ASFLEXIBLE PAVEMENTIN SOME CASES
TEST PERMEABILITYUSING DOUBLE ORSINGLE RINGINFILTROMETER
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PAVERS PLANTED WITH GRASS
PLANTABLE CONCRETE SYSTEMS
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PAVERS PLANTED WITH GRASS
PERVIOUS PAVING GRIDS
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LEVEL SPREADERS
BMP designed to take a concentrated flow and spread it out toinduce sheet flow across a buffer strip or into another BMP such as a
bioretention area.
GRAVEL FILLED TRENCH WITH LEVEL OVERLOW
-Dont use where you have highly erodible soils or little vegetation
-May be surface fed or via pipe
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PA Stormwater
BMP Manual
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NC-DENR BMP
Manual
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LEVEL SPREADERS
100 L.F. OF LEVEL SPREADER FOR 1 CFS OF FLOW
DONT DISCHARGE TO SLOPES GREATER THAN 8%
Break drainage area into small distributed catchment areas
Cannot handle large flows
Prone to short circuiting and small concentrated flows
Cannot handle sediment loads
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RAINWATER HARVESTING
Capturing rainfall for later use
FROM RAIN BARRELS
TO
LARGE UNDERGROUND STORAGE
FACILITIES
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Image Source: BuffaloNiagara River
Keeper.org
Image Source: HamiltonCo., OH
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SOURCES
ROOF RUNOFF
RUNOFF FROM PAVED AREAS
RUNOFF THROUGH PERVIOUS SURFACES
DISCHARGE FROM OTHER BMPS
Pretreatment is critical for success
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PRETREATMENT
Downspout Filtersfirst flush diverters
Hydrodynamic Separators
Sand Filters
Oil and Grease Traps
Disinfection
Level of Pretreatment corresponds to proposed uses
No pump Irrigation (rain barrel)
Irrigation System
Wash Water
Industrial uses
Non-potable indoor use
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GREEN ROOFS
INTENSIVE
SIMPLE INTENSIVE
EXTENSIVE
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GREEN ROOFS
INTENSIVE
SIMPLE INTENSIVE
EXTENSIVE
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Benefits of green roofs include:
attenuation of storm water run-off;
absorption of air pollutants and dust;
reduction in the 'urban heat island' effect;
provision of wildlife habitat;
attractive open space;
health benefits;
protecting the building fabric from sunlight and temperature fluctuations;
reducing costs, including drainage, heating, air conditioning;
eat CO2, give off Oxygen.
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Set specific goals to be achieved by the green roof:
Capture first 1 inch of rainfall;
Capture 85th Percentile storm;
provide XX% pervious surfaces;
Meet criteria for LEED Certification
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CONSIDERATIONS:
WHERE IS THE SUN? WHAT ARE THE NUMBER OF DAYLIGHT HOURS?
AVERAGE ROOFTOP TEMPERATURE?
RAINFALL CHARACTERISTICS?
MICROCLIMATE CONSIDERATIONS
IS IRRIGATION NEEDED?
STRUCTURAL ISSUES?
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CONSTRUCTED WETLANDS
PACKAGED MODULAR WETLAND
-Subsuface Flow
CONSTRUCTED WETLAND
-Open Water System
-Subsurface Flow Sysytem
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Source: SunTree Technologies
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LEED CERTIFICATION
SUSTAINABLE SITES
SSp1: Construction Activity Pollution prevention
SSc5.1: Protect or Restore Habitat
SSc6.1, 6.2: Quantity and Quality ControlSSc7.1: Heat Island Effect (Roof)
WATER EFFICIENCY
WEp1: Water Use Reduction, 20%
WEc1: Water Efficient Landscaping
WEc3: Water Use Reduction (30%-40%)
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ZOFNASS PROGRAM FOR SUSTAINABLE INFRASTRUCTURE
HARVARD UNIVERSITY GRADUATE SCHOOL OF DESIGN1.ENERGY
2.WATER
3.WASTE
4.TRANSPORTATION
5.LANDSCAPE
6.INFORMATION
SUSTAINABLE SITES INITIATIVE
ASLA, LADYBIRD JOHNSON WILDFLOWER CENTER, UT AUSTIN
1. Site Selection
2. Pre-Design Assessment and Planning
3. Site DesignWater
4. Site DesignSoil and Vegetation
5. Site DesignMaterials Selection
6. Site DesignHuman Health and Well-Being
7. Construction
8. Operations and Maintenance
9. Monitoring and Innovation
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Questions and Contact
Mark D. Heinzer, P.E., LEED AP, CPESC
Vice President and Chief Engineer of Southeast Operations
Hunt Engineering LLC
16521 Hunt Road
Laurelville, Ohio 43135
740-332-HUNT
www.HuntEngineeringLLC.com