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SEA Streets Project Seattle, Washington from the Fall 2006 Building Better Report In response to the high mortality of the endangered Coho salmon in Puget Sound estuaries, likely caused by toxic stormwater runoff, Seattle and Seattle Public Utilities (SPU) have developed an innovative plan requiring any new development or street to incorporate better stormwater management when redevelopment occurs. Consideration must be given to expansion of basic drainage systems, flood protection, protecting ditch drainage systems, coordination of landslide mitigation and expanding water quality monitoring. Street Edge Alternatives (SEA Streets) Project SPU initiated Street Edge Alternative (SEA Streets), its first Natural Drainage System project, with the goal of catching, detaining and filtering runoff from a 2.3 acre area near Pipers Creek. Instead of installing a "traditional" stormwater system exclusively involving culverts, drains and pipes, SPU created a drainage system along streets and sidewalks which incorporated native plantings and swales with soils that catch, hold and filter water. In the process of creating more natural drainage systems, SEA Streets reduced the impervious surface area of city streets by 11 percent, helping to rein in the pavement that contributes to high velocity, toxic rainwater runoff. (1) The impressive results of the SEA Streets project - a decrease in the volume of stormwater runoff by 98 percent for a 2-year storm event - have led the way for other Natural Drainage System projects, such as the 110th Street Cascade project. (2) 110th Street Cascade Project The Cascade project contains and filters runoff from a steeply sloped, 21 acre area by employing a system of pools that step down through a series of mini-waterfalls that mimic nature (3), slowing the velocity of the water. Vegetation and swales that form part of the system help to filter out and break down polluted runoff, before the water reaches Pipers Creek. Seattle's Green Future As the Natural Drainage System project continues to grow, areas like the Broadview Green Grid, a 32 acre, 15 square block area are incorporating techniques from both the SEA Streets and Cascade projects, using vegetated swales and tiered water pools to control stormwater. Ambitious projects are planned for the Thornton Creek watershed and are underway for the 129 acre High Point Housing project, where SPU is partnering with the Seattle Public Housing Authority to improve stormwater management in this project that comprises 10 percent of the Longfellow Creek watershed. (4) Working in conjunction with the Seattle Department of Transportation, Seattle Public Utilities has started a path toward a cleaner, better way of building residential streets. Already, university researchers and other local government officials have made Seattle's streets a destination to learn about these good models of stormwater stewardship. Footnotes: Seattle Public Utilities, Street Edge Alternatives (SEA Streets) Project. Ibid. Seattle Public Utilities, 110th Cascade Project. Seattle Public Utilities, High Point Project. Up to Top HOME | Email Signup | About Us | Contact Us | Terms of Use | © 2008 Sierra Club