Design Principles
for Stormwater Management on Compacted,
Contaminated Soils in Dense Urban Areas
EPA's Brown fields Program is designed to empower states, communities, and other stakeholders in economic
redevelopment to work together in a timely manner to prevent, assess, safely clean up, and sustainably reuse brownfields,
A brownfield is a property, the expansion, redevelopment, or reuse of which may be complicated by the presence or
potential presence of a hazardous substance, pollutant, or contaminant, EPA's Brownfields Program provides financial and
technical assistance for brownfield revitalization, including grants for environmental assessment, cleanup, and job training.
What is Green Infrastructure?
Most development and redevelopment practices
cover large areas of the ground with impervious
surfaces such as roads, driveways, sidewalks, and
new buildings themselves, which then prevent
rainwater from soaking into the ground. These
hard surfaces increase the speed and amount of
Stormwater that runs into nearby waterways,
carrying pollutants and sediment each time it rains.
Green infrastructure seeks to reduce or divert
Stormwater from the sewer system and direct
it to areas where it can be infiltrated, reused or
evapotranspirated. Soil and vegetation are used
instead of, or in conjunction with, traditional
drains, gutters, pipes and centralized treatment
areas. In many new and redevelopment projects,
green infrastructure is implemented to manage and
mitigate the polluted runoff created by precipitation
that falls on rooftops, streets, sidewalks, parking
lots and other impervious surfaces.
How can Green Infrastructure be Applied to
Brownfield Sites?
Preparing brownfields for redevelopment often
requires capping of contaminated soils, creating
even larger impervious surfaces. The challenge
for managing Stormwater on brownfield sites
is allowing this capping while mitigating the
impervious surface conditions that can negatively
impact local waterways.
Unlike many conventional developments,
impervious footprints on brownfields cannot
always be minimized through site designs that
incorporate more porous surfaces to allow for
infiltration. Direct infiltration on a brownfield
site may introduce additional pollutant loads to
groundwater and nearby surface waters. However,
green infrastructure practices exist that can retain,
treat and then release Stormwater without it ever
coming in contact with contaminated soils.
A bioswale in Wilmington,
Delaware, designed to absorb
and retain Stormwater runoff.
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Blue arrows represent flows
of surface and groundwater
onto brownfield site
The University of Michigan's
School of Natural Resources
and Environment developed
design guidelines that use
low impact development
techniques on contaminated
sites. Using a former industrial
site in Flint, Michigan, called
Chevy in the Hole, graduate
students considered and refined
methods to prevent residual
contamination from moving
with stormwater.
Design Considerations
A key component of using
green infrastructure for brownfield sites is treatment and storage of stormwater, rather than complete
infiltration. Most brownfields that have residual contamination need caps, so vegetated areas need to
be located above caps and fitted with underdrain systems to remove overflow stormwater.
Development and redevelopment projects should start with keeping existing trees onsite, minimizing
compaction of earth that inhibits water infiltration, and planting trees and other vegetation in
areas where none exists. Retaining existing tree cover and vegetated areas helps infiltrate and
evapotranspirate stormwater runoff while intercepting large amounts of rainfall that would otherwise
enter waterways as runoff.
Buildings and other impervious surfaces can be strategically located to act as caps over areas with
known contamination. Areas with fill caps can include soils and vegetation above the cap in the
form of swales or rain gardens. If fitted with an under-drain system to release treated stormwater off
site, these planted areas can safely allow filtration and evapotranspiration of stormwater. Additional
features like impermeable liners or gravel filter blankets can be coupled with modified low impact
development (LID) practices that safely filter stormwater without exposing the water to contaminated
soils.
Green roofs are an ideal way to reduce the runoff from building roofs by encouraging
evapotranspiration of rainwater. Another option for brownfield sites is the capture and reuse of
stormwater for non-potable uses; this can include runoff storage in rain barrels for irrigation of green
roofs or landscaped areas, or in cisterns that store rainwater for toilet flushing and other uses.
Site location within the watershed is very important. In particular, projects in groundwater recharge
areas should avoid low impact development practices
that promote infiltration, and use techniques that directly
discharge treated stormwater instead. Furthermore, new
and redeveloped sites near brownfields should use green
infrastructure practices to prevent additional runoff from
flowing onto potentially contaminated areas.
Overall, when developing a stormwater management plan
on a brownfield, surrounding sites must be considered.
(Source: Flint Futures: Alternative Futures for Brownfield
Redevelopment in Flint, Michigan.)
The Matthew Henson Conservation Center
in Washington, DC, utilizes a green roof.
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General Principles for Using Green Infrastructure on Brownfield Sites
Guideline #1: Differentiate between groups of contaminants as a way to better minimize risks.
Guideline #2: Keep non-contaminated stormwater separate from contaminated soils and water to
prevent leaching and spreading of contaminants.
Guideline #3: Prevent soil erosion using vegetation, such as existing trees, and structural practices like
swales or sediment basins.
Guideline #4: Include measures that minimize runoff on all new development within and adjacent to a
brownfield. These measures include green roofs, green walls, large trees, and rainwater cisterns.
Definitions
Bioswales are open channels with a dense cover of vegetation where runoff is directed or retained to
evapotranspirate and filter.
Evapotranspiration is the return of water to the atmosphere either through evaporation or by plants.
Green Infrastructure and Low Impact Development (LID) both refer to systems and practices that use
or mimic natural processes to infiltrate, evapotranspirate or reuse stormwater or runoff on the site where
it is generated.
Green roofs can be used to effectively reduce or eliminate runoff from small and medium sized storms.
A soil mixture is placed over a waterproof membrane and drainage system and then planted with
water absorbent and drought tolerant plants. Most systems also have root barriers. These roofs soak up
stormwater and release it back into the atmosphere through evaporation and plant respiration, while
draining excess runoff.
Rain gardens serve the same purpose as stormwater planters and are appropriate where there is more
area to plant vegetation. Sizing is dependent on the area of impervious surfaces draining to the rain
garden, but they can be designed to only treat a portion of the runoff so they can be placed in most
situations.
Stormwater harvest and reuse.
Rainwater harvested in cisterns,
rain barrels, or other devices may
be used to reduce potable water
used for landscape irrigation,
fire suppression, toilet and urinal
flushing, and custodial uses.
Storage and reuse techniques
range from small-scale systems
(e.g., rain barrels) to underground
cisterns that may hold large
volumes of water.
Stormwater planters.
Downspouts can be directed
into stormwater planters. These
planters are used to temporarily
detain, filter and evapotranspirate
stormwater using plant uptake.
Flow-through planter
QVEXFLOW
DOWNSPOUT OUTFALL
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CONCRETE WALL
SLOTTED UNDERDRAW
KL~NS LENGTH OF .TJLYIH?
CLEAN SOIL
LWLRMEABLE LINER
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OUTTLOW TO STORM SEWER
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Additional Resources
The Emeryville, California Stormwater Guidelines for Green, Dense Redevelopment provides guidance on
using vegetative stormwater treatment measures for this dense, brownfield-laden city:
www.ci.emeryville.ca.us/planning/stormwater.html.
EPA's Green Infrastructure Web site (www.epa.gov/npdes/greeninfrastructure) provides definitions, case studies
and performance data for various practices that might be applicable to brownfield sites.
The Low Impact Development Center is dedicated to research, development, and training for water resource and
natural resource protection issues. The Center focuses specifically on furthering the advancement of Low Impact
Development technology: www.lowimpactdevelopment.org.
Green Roofs for Healthy Cities collects and publishes technical information on green roof products and services:
www. greenroofs.org.
The Center for Watershed Protection's Better Site Design Tools provide links to various better site design
resources and publications: www.cwp.org/PublicationStore/bsd.htm.
American Rivers' Catching the Rain: A Great Lakes Resource Guide for Natural Stormwater Management
describes a variety of low impact development strategies that can be implemented in a wide range of built
environments. Available at: www.americanrivers.org/site/DocServer/CatchingTheRain.pdf?docID=163
NRDC's Rooftops to Rivers: Green Strategies for Controlling Stormwater and Combined Sewer Overflows is
a policy guide for decision makers looking to implement green strategies in their own area, including nine case
studies of cities that have successfully used green techniques to create a healthier urban environment.
Available at: www.nrdc.org/water/pollution/rooftops/contents.asp
Portland's (Oregon) Trees for Green Streets: An Illustrated Guide is a guidebook that helps communities select
street trees that reduce stormwater runoff from streets and improve water quality.
Available at: www.metro-region.org/article.cfm?articleID=263
Seattle's pilot Street Edge Alternatives Project (SEA Streets) is designed to provide drainage that more closely
mimics the natural landscape prior to development than traditional piped systems. Good information can be found
at: www.seattle.gov/util/About_SPU/Drainage_&_Sewer_System/Natural_Drainage_Systems/Street_Edge_
Alternatives/index.asp
EPA's Protecting Water Resources with Higher-Density Development report helps communities better
understand the impacts of higher and lower density development on water resources. The findings indicate that
low-density development may not always be the preferred strategy for protecting water resources.
Available at: www.epa.gov/dced/water_density.htm.
Portland Metro's (Oregon) Green Streets: Innovative Solutions for Stormwater and Stream Crossings is a
handbook that describes stormwater management strategies and includes detailed illustrations of "green" street
designs that allow infiltration and limit stormwater runoff.
Available at www.metro-region.org/article.cfm?articleID=262
EPA's Protecting Water Resources with Smart Growth is a report intended for audiences already familiar with
smart growth concepts who seek specific ideas on how techniques for smarter growth can be used to protect water
resources. The report describes 75 policies that communities can use to grow in the way that they want while
protecting their water quality. Available at: www.epa.gov/dced/water_resource.htm
EPA's Using Smart Growth Techniques as Stormwater Best Management Practices reviews nine common smart
growth techniques and examines how they can be used to prevent or manage stormwater runoff. Available at:
www.epa.gov/dced/stormwater.htm
EPA's Brownfields Program Website (www.epa.gov/brownfields) provides information on and resources for
assessing, cleaning up and redeveloping brownfields, including grant funding opportunities.
&EPA
Design Principles for Stormwater Solid Waste EPA-560-F-07-231
Management on Compacted, and Emergency April 2008
Contaminated Soils in Dense Urban Areas Response (5105T) www.epa.gov/brownfields
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