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Washington: Seattle
Green Infrastructure Type: Green Municipalities
Types of Green Infrastructure Used: Green Roofs, Rain Gardens, Vegetated Swales & Landscaping, Downspout Disconnections, and Rain Barrels.
Summary:
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Vegetated swales are an integral part of Seattle's
"SEA Street" design. |
Description:
Like a number of other cities in the United States, Seattle is using green infrastructure as a means of controlling the frequency of its combined sewer overflow (CSO) events. In the late 1990s, the city launched a series of high-profile green infrastructure pilot projects. The first of these, known as the Viewlands Cascade project, consisted of a series of 16 stepped, vegetated cells that were built to collect stormwater runoff from approximately 72 acres. The results of the project exceeded even the highest expectations, with monitoring results showing a 75-80% reduction in total runoff volume, and as much as a 60% reduction in peak flows. In another undertaking, the city retrofitted an entire 660-foot block of 2nd Avenue with an array of green infrastructure techniques, including vegetated swales on both sides of the street that were designed to infiltrate and treat stormwater runoff. All told, the final construction design (known as the Street Edge Alternative, or SEA street design) reduced the amount of impervious cover by more than 18% while adding nearly 100 trees and 1,100 shrubs. Further, hydrologic modeling has indicated a 99% reduction in total potential surface runoff, and the project was so successful that local residents have requested that their own streets be retrofitted in a similar fashion. In addition to these projects, Seattle has launched a subsidized rain barrel and cistern program to encourage rainwater harvesting, has installed several green roofs throughout the city for testing and monitoring purposes, and has begun an urban forestry initiative with a goal of increasing the city’s tree canopy from 27% to 40% of the city’s surface area.
For more information, visit: Seattle Public Utilities Natural Drainage System  .
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