stormwater roundtable presenation 01/10

Overview ofOverview ofSustainable Stormwater Sustainable Stormwater Management/Low Impact Development Management/Low Impact Development

Presented by

Sandeep MehrotraVice President

Hazen and Sawyer P.C.www.hazenandsawyer.com

Sponsored by

What is Stormwater Management?What is Stormwater Management?

To Control, Capture, Detain, Retain, Recharge and Convey Rain Water (and snow) effectively without adversely affecting life, property and natural resources.

Why is Stormwater Management so Why is Stormwater Management so Important?Important?

Water is an essential resource for sustaining all forms of life on Earth

The Blue PlanetThe Blue Planet

80% of the earths surface is water

Oceans and seas

Lakes, rivers, and streams

Ground water and aquifers

Atmospheric moisture (rain)

Types of WaterTypes of Water

Salt water – 97 %

Glaciers - 2 %

Fresh water – 1 %

Sources of our WaterSources of our Water

Today we have approximately the same amount of water as when the Earth was formed.

Earth will not get any more water.

Sources of our freshwater

Lakes and Reservoirs

Rivers and streams

Groundwater and aquifers

Rainwater

Water moves in a never ending cycleWater moves in a never ending cycle

Nature recycles it over and over again

The water you drink may have been drunk by a dinosaur

Water and HumansWater and Humans

Water is an essential resource for our existence

Humans use water for

Drinking

Washing

Recreation

How Much Water Do We UseHow Much Water Do We Use

Typical water usage is 150 gpd per person

Typical suburban household uses 450 gpd

Total Westchester usage is 122 gpd

Total NY tri-state area usage is 1.4 bgd

Need for Effective Stormwater Need for Effective Stormwater ManagementManagement

Earth's fresh water supply is limited and threatened by pollution.

We are using our fresh water faster then we are recharging our groundwater.

The more water we use the more energy we use for water and wastewater treatment.

Comparison of Pre-Development and Comparison of Pre-Development and Developed Hydrologic CyclesDeveloped Hydrologic Cycles

Developed

Pre-Development

Comparison of Pre- and Post-Comparison of Pre- and Post-Development Hydrographs, CSP 1992Development Hydrographs, CSP 1992

Large Storm

Higher Baseflow

Changes in stream hydro logy as a result of urban ization (Schueler, 1992)

Low er and LessRapid Peak

Higher and M oreRapid PeakDischarge

M ore R unoff Vo lum e

G radualRecession

Pre-developm ent

Post-developm ent

Sm all Storm

Evolution of Paradigms for Storm Water Evolution of Paradigms for Storm Water ManagementManagement

Run it

in the

Ditches

Paradigm Shift # 1Paradigm Shift # 1

Run it in the Combined Sewers

Run it in Separate Sewers

…Oh, and Control Downstream Flooding

Storm Water Pond

Also... Don’t Pollute and Protect Natural Resources

BMP for Quantity and Quality Control

Protected Stream Side Buffer

Green Infrastructure

Soft Path for Storm Water

Use BMP’s to Achieve Source Control

Rain Barrels, Typ.

Bioretention CellReforestation

Amended Soils

Green RoofGreen Roof

InfiltrationTrench

PorousPavement

No Curb & Gutter

ReducedStreet Widths

GrassySwale

ConcaveMedian

Rain Gardens, Typ.

TreeConservation

Paradigm # 6Paradigm # 6Hybrid Design

LID practices for infiltration and control of small storms

BMP’s for peak rate and quantity control

Rain Barrels, Typ.

Bioretention CellReforestation

Amended Soils

Green RoofGreen Roof

InfiltrationTrench

PorousPavement

No Curb & Gutter

ReducedStreet Widths

GrassySwale

ConcaveMedian

Rain Gardens, Typ.

TreeConservation

Stable Stream in Natural

Riparian Corridor

BMP for Large Storm Events

So What is Low Impact Development? So What is Low Impact Development?

New Philosophy Maintaining Functional Relationships

Between Terrestrial and Aquatic Ecosystems Keep Water Where it Falls

New Principles Decentralized / Source Control Distributed / Multi-functional / Multi-beneficial

New Approaches to Old Ideas Prevent / Retain / Detain / Filter / Infiltrate /

Treat / Use / Conserve

Low Impact DevelopmentLow Impact Development

Storm Water Management Strategy

Mimic natural flows, source control

Emphasize conservation, use existing natural features

Integrate with distributed, small-scale storm water controls

BMP’s employ natural processes – infiltration, soil storage, filtration, evaporation, and uptake by vegetation

Large Storm

Higher Baseflow

Lower and LessRapid Peak

Higher and MoreRapid PeakDischarge

More Runoff Volume

GradualRecession

Pre-development

Post-development

Small Storm

Low Impact DevelopmentLow Impact Development

Don’t rely on conventional end-of-pipe structural solutions

Instead use conservation practices and BMP’s to mimic pre-development hydrology

Apply at parcel and subdivision scale

Detain, retain, store, infiltrate, evaporate run-off

Reduce volume of storm water discharge, pollutants

Conventional Low Impact

Good Drainage Functional Drainage

Conventional Conventional DevelopmentDevelopment

Centralized Centralized Pipe and Pond Pipe and Pond ControlControl

LID DevelopmentLID Development

Conservation Conservation Minimization Minimization Soil Amendments Soil Amendments Open Drainage Open Drainage Rain Gardens Rain Gardens Rain Barrels Rain Barrels Pollution PreventionPollution Prevention

Disconnected Disconnected Decentralized Decentralized Distributed Distributed Multi-functional Multi-functional Water UseWater Use

Multiple SystemsMultiple Systems

Good Drainage ParadigmGood Drainage Paradigm

The Problem: Conventional Site DesignThe Problem: Conventional Site Design

Collect Collect Concentrate Concentrate Convey Convey Centralized Centralized ControlControl

HydrologicallyHydrologically ConnectedConnected

Ecologically Ecologically DysfunctionalDysfunctional

Get the water away as fast as possible!

Conventional vs. LID Storm Water ApproachConventional vs. LID Storm Water Approach

Lot Level Source Controls

LID Site LID Site

Create a Hydrologically Create a Hydrologically Functional LotFunctional Lot

Conservation

Open DrainageRain Gardens

Amended Soils

Rain Barrel

Porous Pavement

Narrower Streets

Cumulative Cumulative Beneficial Impacts Beneficial Impacts of LID Techniquesof LID Techniques

LID rebuilds LID rebuilds ecological ecological functions functions piece by piece by piece. piece.

How Does LID Maintain or Restore The How Does LID Maintain or Restore The Hydrologic Regime?Hydrologic Regime?

Creative ways to:Creative ways to:

Maintain / Restore Storage Volume Maintain / Restore Storage Volume

interception, depression, channel interception, depression, channel

Maintain / Restore Infiltration Volume Maintain / Restore Infiltration Volume

Maintain / Restore Evaporation VolumeMaintain / Restore Evaporation Volume

Maintain / Restore Runoff Volume Maintain / Restore Runoff Volume

Maintain Flow PathsMaintain Flow Paths

Engineer a site to mimic the natural water cycle functions / relationships

Why is LID so Attractive ?Why is LID so Attractive ?

Universally Applicable (Arid, Clays, Karst, Cold, Coastal… . )

Economically Sustainable

Ecologically Sustainable

Added Values

Lower Costs (Construction, Maintenance & Operation)

Multiple Benefits (air / water / energy / property values)

Silent on Growth Management

Ideal for Urban Retrofit

Common Sense Approach

Public Acceptance

“Rain Gardens”

View of Lot with Storage and BioretentionView of Lot with Storage and Bioretention

Rain Garden Rain Garden

Treatment Train ApproachTreatment Train Approach

Bioretention CellStorm Drain System

Bioretention Cell

Flow Path

Grass Swale Grass Filter Strip

Large Lot Composite Site AnalysisLarge Lot Composite Site Analysis

LID ApproachLID Approach

Multiple functions/benefits Drainage Aesthetics Real estate values Privacy Reduced costs Greater lot yield

Long term benefits inspired long-term maintenance

Gardening: # 1 hobby

Success of LID depends on lot-by-lot responsibility for maintenance

Issues of acceptance by regulatory agencies

Basic Components of LID ApproachBasic Components of LID Approach

1. Conservation Measures

2. Site Planning

3. Maintain Pre-development Time of Concentration

4. Provide Multiple Redundant BMP’s

5. Maintenance and Education

1) Conservation Measures

Forest cover to intercept, evaporate, transpire rainfall

Preserved soils, amend as needed for enhanced porosity

Topographic features that slow store infiltration rain... “don’t do this, do this”

Natural drainage features

Use the Soil Ecosystem Functions

1. Hydrology 1. Hydrology storage / evaporation / recharge / detention storage / evaporation / recharge / detention

2.2. Storing Cycling Nutrients (bacteria / fungi) Storing Cycling Nutrients (bacteria / fungi) phosphorous phosphorous / nitrogen / carbon/ nitrogen / carbon

3. Plant Productivity (vigor)3. Plant Productivity (vigor)

4. Water Quality 4. Water Quality filter / buffer / degrade / immobilize filter / buffer / degrade / immobilize detoxify organic and inorganic materialsdetoxify organic and inorganic materials

““Most diverse ecosystem in the world”Most diverse ecosystem in the world”

2) Site Planning

Multidisciplinary team

Located development away from critical areas, A & B soils

Street system that minimizes impervious surface

Reduce pipes, curb and gutters

Green parking lot design

Hydrologic Soil GroupsHydrologic Soil Groups

Group A: High rate of infiltration, low, rate of runoff potential

Group B: Moderate infiltration rates when fully wet, moderately coarse textured

Group C: Slow infiltration rates when thoroughly wet, have layer impeding downward movement or moderately fine to fine textured.

Groups D: Very slow infiltration rates when thoroughly wet, clays with high shrink/swell potential; high permanent water table or have clay pan or clay layer near to surface or shallow over nearly imperious surface.

*adopted from San Diego LID manual

3) Maintain Pre-Development Time of Concentration

Hydrologically rough landscape

Open drainage system

Flatten slopes

Disperse drainage

Lengthen flow paths

Maintain natural flow paths

Increase distance from streams

Maximize street flow

4) Provide multiple redundant BMP’s

Biorentention cells Vegetated swales Rain gardens Green roofs Blue roofs Green street lay-out

Porous Pavement Infiltration planters Infiltration trench Rain barrels Dry wells Storage vaults

Effect or Function

Slow Runoff

Filtration Infiltration Retention Detention Evaporation Water Quality Control

Soil Amendments

Bioretention X X X X X X

Vegetated Buffers

X X X X

Grassed Swales

X X X X

Rock Swales X X X X

Rain Barrels X

Street Trees X

Vegetated Roofs

X X X X

Permeable Materials

Rock Beds X X X X

Vegetated ConveyanceVegetated Conveyance

Rain is ResourceRain is Resource

Capture & UseCapture & UseToilet FlushingToilet FlushingCar washingCar washingIrrigation Irrigation Mixing Mixing Washing Washing GardeningGardeningRechargeRecharge

BenefitsBenefitsReduce DemandReduce DemandSelf-sufficiency Self-sufficiency Save Money Save Money

5) Maintenance and Education

Storm water controls as amenities that property owners will want to maintain

Educate home owners, landscapers about proper operation and maintenance

Promote pollution prevention through proper lawn and car care, hazmat handling, good home keeping

Applicability of LID to Urban Settings at Applicability of LID to Urban Settings at Lot LevelLot Level

Bioretention

Infiltration

Street Trees

Green roofs

Site Planning

Proprietary Devices

Bioretention Design ObjectivesBioretention Design Objectives

Peak Discharge Control 1-, 2-, 10-, 15-, 100-year storms Bioretention may provide part or all of this

control

Water Quality Control ½”, 1” or 2” rainfall most frequently used Bioretention can provide 100% control

Ground water recharge Many jurisdictions now require recharge

( e.g., MD, PA, NJ, VA)

2” Mulch2” Mulch

Infiltration System

Highly Pervious Soils

Existing Existing GroundGround

Drain Pipe

Filtration System Filtration System

Existing Existing GroundGround

Highly Pervious Soils

Drain Pipe

Combination Filtration / InfiltrationCombination Filtration / Infiltration

Moderately Pervious Soils

Gravel

Sandy Organic Soil

Existing Ground

BioretentionBioretention Shallow Ponding - 4” to 6”

• Mulch 3”

• Soil Depth 2’ - 2.5’

• Sandy Top Soil

• 65% Sand

• 20% Sandy Loam

• 15% Compost

• Under Drain System

• Plants

X 2’

Under Drain

Plants Considerations Plants Considerations

Pollutant uptake

Evapotranspiration

Soil ecology / structure / function

Number & type of plantings may vary, Aesthetics Morphology (root structure trees, shrubs and herbaceous) Native plants materials Trees 2 in. caliper / shrubs 2 gal. size / herbaceous 1 gal size. landscape plan will be required as part of the plan. Sealed by a registered landscape architect. Plants are an integral part no changes unless approved Plant survival

Irrigation – Typical / customary

Residential Rain Gardens

Example Bioretention AreasExample Bioretention Areas

Bioretention Construction CostsBioretention Construction Costs

Excavation (assume no hauling)

$3 - $5 / cy

Fill Media $15 - $20 / cy

Vegetation/ Mulch $1.00 - $1.50 / sf

Underdrains /Gravel & Outlet

$0.50 - $1.50 / sf

Total $10 - $14 / sf

Design Configuration ConsiderationsDesign Configuration Considerations

Off line vs. Flow-through

Surface Storage

Underdrain – Dewater media

Off-line

2005 Lake County, OH

Flow-through

2005 lake County, OH

Porous Pavers Capturing Roof Runoff

Urban CanopyUrban Canopy

Multiple BenefitsReduce Stormwater Runoff Improve Air Quality Reduce Energy Consumption Reduce Urban Heat Island Carbon StorageHabitat Value

Portland Oregon Bureau of Portland Oregon Bureau of Environmental Services BuildingEnvironmental Services Building

Street Tree / Street Tree / Shrub FiltersShrub Filters

Proprietary DevicesProprietary Devices

2” Mulch

Sandy Filter Media

Drain Pipe

Storm Drain

Roadway

A Grow ing Idea in Stormwater Filt ration.

Optional Infiltration Storage

Volatilization

BioretentionClean-out

Rip-Rap

Biodegradation

Root Uptake

Drains to infiltration storage

Tree Grate

Typical Layouts - Office BuildingTypical Layouts - Office Building

Typical Layouts - Big Box DesignTypical Layouts - Big Box Design

Needed Paradigms Shifts to Address Needed Paradigms Shifts to Address Urbanization Urbanization

Watersheds to Ecosystems

Impact Reduction to Functional Restoration

Political Solutions to Scientific Solutions

Rhetoric to Reality

Larry Coffman, President, Stormwater Services, LLP, Presentations at StormCon New Jersey Conference, October 2007.

Bay Area Stormwater Management Agencies Association, “Start at the Source: Design Guidance Manual for Stormwater Quality Protection,” 1999 Edition.

Prince George’s County, Maryland, Department of Environmental Resources, “Low Impact Development Design Strategies: An Integrated Design Approach,” June 1999.

Puget Sound Action Team. Olympia, WA, “Natural Approaches to Stormwater Management: Low Impact Development in Puget Sound,” March 2007.

Larry Coffman, “Low-Impact Development Design: A New Paradigm for Stormwater Management Mimicking and Restoring the Natural Hydrologic Regime,” undated.

New Hanover County, City of Wilmington, North Carolina, “Joint Low Impact Development Guidance Manual - - Draft,” July 2007.

County of San Diego, “Low Impact Development Handbook: Stormwater Management Strategies - - Public Review Draft,” July 20, 2007.

Puget Sound Action Team, Washington State University Pierce County Extension, “Low Impact Development: Technical Guidance Manual for Puget Sound,” January 2005.

Andy Reese and Charlene Johnston, “Stormwater Funding and Utility Development,” Presentation at StormCon New Jersey Conference, October 2007.

Low Impact Development Center, Washington D.C.

SourcesSources

Thank YouThank You

stormwater roundtable presenation 01/10

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