pp/y Clean Water State Revolving Fund
Green Project Reserve
Clean Water
Case Study: Spokane Urban Runoff Green ways Ecosystem
Innovative Stormwater Management
The City of Spokane, Washington has developed a demonstration program to construct street-side rain
gardens to control pollution from stormwater runoff. Polluted stormwater and combined sewer
overflows have been identified as some of the leading causes of urban water pollution and have
significantly contributed to pollutant loadings of the Spokane River, affecting downstream drinking
water resources and water quality for threatened and endangered salmon species. The Spokane River is
a tributary of the Columbia River and runs through the city. The Spokane Urban Runoff Greenway
Ecosystem (SURGE) program will retrofit the existing urban landscape of curb and gutter systems in
several places around the city using low-impact and green infrastructure strategies to mimic the natural
hydrologic process by capturing, treating, and infiltrating stormwater runoff, to study the impact on
water quality.
This project was selected by Spokane over gray infrastructure approaches to municipal stormwater
management for its alignment with the goals and policies laid out in the city's Comprehensive Plan to
restore, protect and enhance features of the natural environment. The policies included in the
Comprehensive Plan call for watershed studies, the reduction of impervious surface areas, and the
maintenance of natural areas within the urban environment. With this project Spokane was able to
implement innovative stormwater techniques to protect both surface water and groundwater from
contamination as well as to utilize and protect areas of natural drainage.
Spokane received a $599,000 American Recovery and Reinvestment Act (ARRA) loan from the
Washington State Department of Ecology's Water Pollution Control Revolving Fund, 50 percent of which
was in the form of principal forgiveness. The city used these funds to construct the West Broadway
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SURGE project, which was included as part of the city's Sustainability Action Plan. The plan describes
Spokane's ongoing commitment toward adopting green practices that support a more sustainable
approach towards publicly owned treatment works and the urban environment.
"The Broadway Avenue Spokane Urban Runoff Greenways Ecosystem or SURGE project is a low cost
solution to capture, treat, and infiltrate runoff as close to where it falls as possible/' says Mayor Mary
Verner. "The storm gardens will enhance the beauty of Broadway Avenue and improve water quality by
reducing the contaminants going to the Spokane River."
The city constructed a network of rain gardens between the curbs and sidewalks to intercept
stormwater runoff on either side of Broadway Avenue, extending from Elm to Oak Streets. Rain gardens
are an example of green infrastructure design particularly suited for the inland Northwest as they are
capable of properly treating stormwater runoff flows from both rain and snow events. Street-side
depressions, planted with native vegetation, are designed to capture runoff from impervious areas like
roofs, streets, and parking lots, allowing it to naturally be absorbed into the ground. In all, 37 rain
gardens were constructed along with five drainage structures and over 1,200 square yards of pervious
sidewalk.
The project makes use of different plant palettes, or planting schemes, based upon specific criteria
including drought tolerance, low maintenance, aesthetic appeal and local availability. Native species
grown in the local area were selected for the 37 rain gardens not only for their aesthetic appeal but also
for their ability to thrive during the long, dry summers and cold, snowy winters of the inland Northwest.
Vegetative cover was not the only design consideration given to the rain gardens. Careful selection of
the proper soils to augment the treatment and infiltration process was another specific planning
element in the creation of the greenway ecosystem. An innovative approach used on the West
Broadway SURGE was the utilization of the "tree zone" concept, which addresses multiple site
conditions such as building set-back distances and amounts of available sunlight. Such varied conditions
make selecting one species of tree impossible, so planners selected five different tree varieties suitable
for each of the existing site conditions.
Native plant species used in the rain gardens
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Each rain garden is comprised of a layer of structural soil, which includes a mix of gravel, topsoil, and
moisture retaining gel to support the growth of tree roots; a layer of treatment soil consisting of topsoil,
sand, and organic matter to provide biological treatment to stormwater; and a layer of composted
mulch at the surface to regulate moisture, minimize weed growth, and further enhance biological
treatment cleansing.
The West Broadway SURGE project has numerous
environmental, economic, and social benefits,
including improving the operation of Spokane's
combined sewer system, providing a low-cost
alternative to treating and managing stormwater
runoff, and increasing urban green space that
provides an enhanced aesthetic environment and
improves water quality. This project won EPA's
Performance and Innovation in the SRF Creating
Environmental Success (PISCES) award in 2010.
BROADWAY AVENUE
For more information please contact the Washington Clean Water State Revolving Fund Loan Program
http://www.ecy.wa.gov/programs/wq/funding/FundingPrograms/CWSRF/cwsrf.html
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