Stormwater Roundtable Presenation 01/10

Overview of Sustainable Stormwater Management/Low Impact Development Presented by Sandeep Mehrotra Vice President Hazen and Sawyer P.C. www.hazenandsawyer.com Sponsored by

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

The 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 Water
Salt water – 97 %
Glaciers - 2 %
Fresh water – 1 %

Sources 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 cycle
Nature recycles it over and over again
The water you drink may have been drunk by a dinosaur

Water and Humans
Water is an essential resource for our existence
Humans use water for
Drinking
Washing
Recreation

How 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 Management
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 Developed Hydrologic Cycles
Developed
Pre-Development

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

Evolution of Paradigms for Storm Water Management Run it in the Ditches

Paradigm Shift # 1
Run it in the Combined Sewers

Paradigm Shift # 2
Run it in Separate Sewers

Paradigm Shift # 3
… Oh, and Control Downstream Flooding
Storm Water Pond

Paradigm Shift # 4
Also... Don’t Pollute and Protect Natural Resources
BMP for Quantity and Quality Control Protected Stream Side Buffer

Paradigm Shift # 5
LID
Green Infrastructure
Soft Path for Storm Water
Use BMP’s to Achieve Source Control

Paradigm # 6
Hybrid Design
LID practices for infiltration and control of small storms
BMP’s for peak rate and quantity control
Stable Stream in Natural Riparian Corridor BMP for Large Storm Events

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 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 Less Rapid Peak Higher and More Rapid Peak Discharge More Runoff Volume I S T R E A M F L O W R A T E Gradual Recession Pre-development Post-development Small Storm

Low 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

Functional Drainage

Conventional Development Centralized Pipe and Pond Control

LID Development Conservation Minimization Soil Amendments Open Drainage Rain Gardens Rain Barrels Pollution Prevention Disconnected Decentralized Distributed Multi-functional Water Use Multiple Systems

Good Drainage Paradigm The Problem: Conventional Site Design Collect Concentrate Convey Centralized Control

Hydrologically Connected Ecologically Dysfunctional

Get the water away as fast as possible!

Conventional vs. LID Storm Water Approach

Lot Level Source Controls LID Site Create a Hydrologically Functional Lot Conservation Open Drainage Rain Gardens Amended Soils Rain Barrel Porous Pavement Narrower Streets

Cumulative Beneficial Impacts of LID Techniques LID rebuilds ecological functions piece by piece.

How Does LID Maintain or Restore The Hydrologic Regime?
Creative ways to:
Maintain / Restore Storage Volume
interception, depression, channel
Maintain / Restore Infiltration Volume
Maintain / Restore Evaporation Volume
Maintain / Restore Runoff Volume
Maintain Flow Paths
Engineer a site to mimic the natural water cycle functions / relationships

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 Bioretention

Rain Garden Treatment Train Approach Bioretention Cell Storm Drain System Bioretention Cell Grass Filter Strip Flow Path Grass Swale

Large Lot Composite Site Analysis

LID 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

Staten Island Bluebelt Program Ongoing Accomplishments
Ecologically sound and cost-effective storm water management for 1/3 of Staten Island
Preservation of natural drainage corridors
Water quality improvements by attenuating storm flows, reducing erosion, and treating storm water in BMP’s
Expansion of open space inventory
Better wildlife habitat through habitat enhancement structures and native paintings
Infrastructure cost savings (tens of millions of dollars)

Basic Components of LID Approach
Conservation Measures
Site Planning
Maintain Pre-development Time of Concentration
Provide Multiple Redundant BMP’s
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 storage / evaporation / recharge / detention
Storing Cycling Nutrients (bacteria / fungi) phosphorous / nitrogen / carbon
3. Plant Productivity (vigor)
4. Water Quality filter / buffer / degrade / immobilize detoxify organic and inorganic materials
“ 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 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

IMP Effect or Function Slow Runoff Filtration Infiltration Retention Detention Evaporation Water Quality Control Soil Amendments X X x 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 X X X Rock Beds X X X X

The Bioretention Concept Original Design P.G County 1993

Vegetated Conveyance

Rain is Resource
Capture & Use
Toilet Flushing
Car washing
Irrigation
Mixing
Washing
Gardening
Recharge
Benefits
Reduce Demand
Self-sufficiency
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 Lot Level
Bioretention
Infiltration
Street Trees
Green roofs
Site Planning
Proprietary Devices

Bioretention 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’ 2” Mulch Infiltration System Highly Pervious Soils Existing Ground

2’ 2” Mulch Drain Pipe Filtration System Existing Ground Highly Pervious Soils

2’ 2” Mulch Drain Pipe Combination Filtration / Infiltration Moderately Pervious Soils Gravel Sandy Organic Soil Existing Ground

Bioretention
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

Low Flow Media 2 to 10 inches / hour Peat / Sand / Aggregate Matrix - PSD
Peat 15 to 20% by volume
Clay <5% (<0.002 mm)
Silt <5% (0.002-0.05 mm)
Very Fine Sand 5-10% (0.05-0.15 mm)
Fine Sand 15-20% (0.15-0.25 mm)
Medium to Coarse Sand 60-70% (0.25-1.0 mm)
Coarse Sand 5-10% (1.0-2.0 mm)
Fine Gravel <5% (2.0-3.4 mm)

High Flow Media 10 to 50 inches / hour Peat Sand / Aggregate Matrix - PSD
Peat 5 to 10% by volume
Clay <2% (<0.002 mm)
Silt <2% (0.002-0.05 mm)
Very Fine Sand 5% (0.05-0.15 mm)
Fine Sand 10% (0.15-0.25 mm)
Medium to Coarse Sand 70% (0.25-1.0 mm)
Coarse Sand 10-15% (1.0-2.0 mm)
Fine Gravel 5-10% (2.0-3.4 mm)

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 Areas

Bioretention 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 Considerations
Off line vs. Flow-through
Inlet
Surface Storage
Underdrain – Dewater media

Off-line 2005 Lake County, OH

Flow-through 2005 lake County, OH

Porous Pavers Capturing Roof Runoff

Urban Canopy
Multiple Benefits
Reduce Stormwater Runoff
Improve Air Quality
Reduce Energy Consumption
Reduce Urban Heat Island
Carbon Storage
Habitat Value

Portland Oregon Bureau of Environmental Services Building

Street Tree / Shrub Filters

Proprietary Devices

Typical Layouts - Office Building

Typical Layouts - Big Box Design

Needed Paradigms Shifts to Address 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.
Sources

Thank You

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Stormwater Roundtable Presenation 01/10

by Emily Eder on Mar 03, 2010

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Stormwater Roundtable Presenation 01/10 — Presentation Transcript