green infrastructure 2

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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

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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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T.COM

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

[email protected]

Hunt Engineering LLC

16521 Hunt Road

Laurelville, Ohio 43135

740-332-HUNT

www.HuntEngineeringLLC.com

[email protected]

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