new england grows february 8, 2013 england grows february 8, 2013 (c) 2013, ... example project...

New England Grows February 8, 2013

(c) 2013, Chris Webb & Associates, Inc., PS 1

Emerging Trends in Stormwater ManagementEmerging Trends in Stormwater ManagementNew England Grows 2013New England Grows 2013

Christopher J. Webb, PE, LEED-FellowChris Webb & Associates, Inc., PS, Bellingham, WA

www.chriswebbpe.com

1. Grey to Green

STORMWATER MANAGEMENTEmerging Big Picture Design Trends

2. Centralized to Distributed 3. Linear to Circular

STORMWATER MANAGEMENTEmerging Big Picture Design Trends

4. LID / GSI emerging as “Best Available Technology”

“Best available science suggests that a broad category of new stormwater management practices that come under the heading of lowpractices that come under the heading of low impact development (LID) or green stormwater infrastructure (GSI) can improve flow control, water quality treatment and protection of receiving waters. Accordingly, many states across the U.S. are considering adoption of LID practices. The use of LID practices will be required for managing stormwater in western Washington over the next few years as the new NPDES permit is phased in.”

--Washington Stormwater Center

Is there a Problem here?



New England Land Cover, USGS, 2006

L.I.D. Site Design Techniques: Planning (clustering, maximize density where appropriate, preserve

ecologically sensitive areas, site selection, etc.) Street Geometrics (skinny streets, interconnected street grid, etc.)

Di ti i i f ( bl t t d t t

LOW IMPACT DEVELOPMENTIntroduction

Disconnecting impervious surfaces (curbless streets, downspouts to splash blocks and not connected to a piped stormwater system, sheet flow to greatest extent possible, grass filter strips, etc.)

Soil Amendments (Compost amended soils to increase water retention and reduce irrigation needs)

Bioretention (or “Raingardens”) Porous Pavements Rainwater Collection and Reuse Green Roofs (vegetated roof systems)

Minimize concentrating stormwater

Sheet flow

Small drainage basins

LOW IMPACT DEVELOPMENTGoals

Surface conveyance

Work with the soil

Amended soil with compost

Bioretention / raingardens

Pervious pavements

Use smaller decentralized solutions at the source…

Decentralized Approach(S ll S l S t )

LOW IMPACT DEVELOPMENTApproach

(Small Scale Systems)vs.

Centralized Approach(Large Scale System)

Use smaller infiltration rates over larger areas…

LOW IMPACT DEVELOPMENTApproach Summary

“Create a hydraulically functional landscape.”

LOW IMPACT DEVELOPMENTValue Created

Multi-purpose infrastructure is inherently more efficient use of land and resources than single purpose infrastructure

Decentralized infrastructure can be more effective because it can exploit synergies with other systems and maximize the utilization of a site’s latent capacity for infiltration



LOW IMPACT DEVELOPMENTPredicting future Challenges / Opportunities

The future of stormwater management will…

Require civil/site contractors to become more like landscape contractors and vice versa…

Ch ll /O t iti T i i t d dChallenges/Opportunities: Training, standards, new business models to build these systems

Stormwater practices will be increasingly made up of a network of smaller green interventions at the beginning of the pipe vs. larger grey end of pipe solutions…

Challenges/Opportunities: Post Construction Operations, Maintenance & Management, new business models needed to perform the service

Bioretention swales adjacent to roads and within right of way.

Application of bioretention cells on single family lots increasing…in the Northwest region and nationally

LOW IMPACT DEVELOPMENTApplication Trends in Puget Sound

Northwest region and nationally.

Under-drains vs. overflows may be the most misunderstood & challenging design element.

Construction in dense settings requires careful sequencing, staging, and TESC.

Photo by City of Maplewood MN

Hydrologic performance tending to exceed design expectations.

LOW IMPACT DEVELOPMENTApplication Trends in Puget Sound

Approximately 98% stormwater volume reduction compared to pre-existing street design.

Last recorded discharges on 12/14/02 and 12/07.

SEA Street project, 2nd Ave NW, from NW 117th to NW 120th

Why build healthy soil? More marketable buildings and

landscapes Better site erosion control Reduced need for water and

LOW-IMPACT DEVELOPMENTCompost Amended Soil

Reduced need for water and chemicals

Less stormwater runoff, better water quality

Healthy landscapes = satisfied customers

www.buildingsoil.org

LOW-IMPACT DEVELOPMENTCompost Amended Soil

5 Construction Practices: Retain and protect native topsoil &

vegetation where practical Restore disturbed soils, to restore healthy

soil functions, by: stockpiling & reusing good quality site• stockpiling & reusing good quality site soil, or

• tilling 2-3" of compost into poor site soils, or

• bringing in 8" of compost- amended topsoil

Loosen compacted subsoil, if needed, by ripping to 12" depth

Mulch landscape beds after planting Protect restored soils from erosion or re-

compaction by heavy equipment

LOW-IMPACT DEVELOPMENTBioretention / Raingardens

What is Bioretention?

Concept originated in Prince George’s County, MD in early 1990’s

Image by AHBL from the PSAT LID technical manual

Small depressions in the ground that receive stormwater from small basins

Provide stormwater treatment and/or retention

Soil, plants, and soil microbes work as a system to break down pollutants



LOW IMPACT DEVELOPMENTBioretention Water Quality Treatment pathways

Stormwater volume reduction

Sedimentation Filtration Phytoremediation

water quality treatment

Phytoremediation Thermal attenuation Adsorption Volatilization

LOW IMPACT DEVELOPMENTBioretention Myths

Bioretention is not and effective flow control practice on till Bioretention can not be used for water quality treatment in

pollutant hot spots Geotextiles necessary at the soil mix and native soil

interfaceStormwater Reduction (%) for Seattle Soils

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0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

Ratio of Rain Garden Area to Impervious Area

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uctio

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Till Outwash

Stormwater Reduction (%) for Seattle Soils

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10%

20%

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0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

Ratio of Rain Garden Area to Impervious Area

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Till Outwash

LOW-IMPACT DEVELOPMENTBioretention / Raingarden Public ROW Example(First in City of Bellingham, WA)

LOW-IMPACT DEVELOPMENTBioretention integrated into site & building design

LOW-IMPACT DEVELOPMENTUrban design example

LOW-IMPACT DEVELOPMENTUrban design example



LOW-IMPACT DEVELOPMENTBioretention / Raingarden in Urban setting (Portland, OR)

Permeable (Porous) Surfaces

Hardscapes Porous Concrete / Asphalt Pavements

POROUS PAVEMENTSImpervious Surface Reduction Strategies

Porous Concrete / Asphalt Pavements Interlocking Concrete Pavers Gravel Cellular Confinement Systems

Softscapes Reinforced Grass Surfaces

Grass Cellular Confinement Systems

REINFORCED GRASS PAVEMENTExample Project

Boundary Bay Brewery, Bellingham, WA

POROUS GRAVEL PAVEMENT

ADA Assessible Trail

POROUS CONCRETE PAVEMENT Impervious Surface Reduction Strategies

REINFORCED GRASS / PERVIOUS CONCRETE PAVEMENTHybrid Pervious Pavement Example Project (2006)

Dan Godwin Center, Bellingham, WA



Pervious Concrete

LOW-IMPACT DEVELOPMENTExample Project (Municipal Community Center)

Firstenburg Community Center, City of Vancouver, WAPervious Concrete

Pervious Concrete Raingarden Strip

Raingarden Strip

Full Depth Permeable Asphalt Pavement vs. what has been used for years in noise and safety mitigation (friction course)

PERMEABLE ASPHALT PAVEMENTSummary

Lower cost than pervious concrete

More frequent replacements (i.e. less durable)

Pervious ATB is available

INTERLOCKING CONCRETE PAVERSTypes of Pavers

UNI ECOSTONESF-RIMA TURFSTONE

Seattle, WA, 2007 Rainwater for flushing 1 toilet in new studio 480 gallon HDPE cistern In-line upstream filter (1 mm mesh)

RAINWATER HARVESTINGSingle Family Residential Non-Potable Water Example Project

No water system back-up (hose of needed) No pump, only gravity flow only (elevated

tank 4.5’) No downstream filtration

Swinomish Indian Reservation, Skagit County, WA, built 1999

Rainwater as sole source of potable water

RAINWATER HARVESTINGResidential Potable Water Example Project

water 1,600 sf metal roof, 5,600 gal. Storage,

2 people, 20/5 micron cartridge filtration, 1/0.5 micron carbon at taps, UV disinfection

Composting toilets & small greywater re-use system



RAINWATER HARVESTINGResidential Potable Water Example Project

14-Units Zero Net Energy, Lopez Island, WA

Rainwater for non-potable uses(toilet flushing clothes washers and

RAINWATER HARVESTINGMulti-Unit Residential Non-Potable Water Example Project

(toilet flushing, clothes washers, and irrigation)

34,000 gallon central cistern Water System back-up Many green building strategies 5 micron sand filter filtration Water Right Acquired

RAINWATER HARVESTINGSports Stadium Example Project

RAINWATER HARVESTINGAs Green Stormwater Infrastructure

LOW-IMPACT DEVELOPMENTGreen Roofs

Residential

Commercial

Key LID Benefits…

Water Quality

Greater levels of stormwater quality are achieved than conventional treatment practices

LOW IMPACT DEVELOPMENTSummary

Water Quantity

Greater amounts of infiltration and groundwater recharge

Addresses stormwater run-off volume and not just rate

Reduced potable water use via rainwater collection and re-use & using soil amendments

More natural site hydrology benefits stream habitats and wetlands



Key LID Benefits…

Aesthetics

More attractive when integrated into the design

E i l

LOW IMPACT DEVELOPMENTSummary

Economical

Efficient use of land by reduce or eliminate ponds and vaults

Skinny streets are less expensive to build

Stormwater treatment with bioretention is the least expensive method of stormwater treatment when used in place of landscaping

On soils that infiltrate more than about 1/4” /hr. LID will typically be less expensive to build than traditional systems

new england grows february 8, 2013 england grows february 8, 2013 (c) 2013, ... example project...

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