A CAse study of How Green InfrAstruCture Is HelpInG MAnAGe urbAn storMwAter CHAllenGes typeS of gReen InfRaStRuctuRe uSed: Green roofs, rain barrels/cisterns, permeable pavement, rain gardens, vegetated swales, street trees, green streets

seattle has been working at green infrastructure for over a decade, and its commitment over many years has resulted in a serious overall program. the city does not yet have a comprehensive citywide green infrastructure plan; its Comprehensive drainage plan is generally supportive of green infrastructure (which it dubs “natural drainage strategies”), but does not spell out an overall vision of its implementation. on the other hand, seattle contains broadly-applicable requirements to use green infrastructure “to the maximum extent feasible,” for both new and redevelopment projects and the city requires certain projects to achieve specific numeric targets for peak runoff following development. seattle has strong resources to assist private parties to implement green infrastructure and an equally major investment in implementing green infrastructure in practice to achieve stormwater and Cso reduction goals. specifically, the city has stormwater and right-of-way improvement design manuals laying out stormwater design strategies for different kinds of projects, and it has demonstrated green infrastructure via numerous roadway improvement projects and green roofs. these initiatives now are accompanied by regulatory green infrastructure programs—Green factor—which demands that development projects achieve minimum scores based on landscaping features that promote the use of green infrastructure, as well as the stormwater code, which requires for most projects the use of green stormwater infrastructure best management practices (bMps) to mitigate stormwater where feasible. As a complement to these resources, seattle also provides green infrastructure incentives— rebates for installing rain barrels and cisterns to capture stormwater in a particular basin served by the combined sewer system. other incentives are integrated into the city’s stormwater fees, which help pay for the implementation of stormwater control strategies; non-residential properties’ fee is directly related to the amount of on-site impervious area, and all property owners in the city can receive a parcel credit for installing green infrastructure features as well as other flow control and treatment bMps. Additionally, city officials report that the Cso reduction strategy is committing to using green infrastructure, which will be formalized through the long term Control plan efforts currently underway.