City of Seattle — Stormwater Low Impact Development Practices

As part of the City of Seattle's commitment to sustainable development, the City is implementing Stormwater Low Impact Development (LID) practices using numerous approaches. Two approaches are presented within this paper. First, the existing City of Seattle Stormwater, Grading and Drainage Control Code provides a variety of stormwater LID guidance to be used on various projects. Second, the City is also redeveloping a 129-acre housing project using an entirely new approach towards stormwater management. The existing stormwater code implements both flow control and water quality treatment LID practices. This existing LID guidance will be updated as part of revisions to the stormwater code to meet the revised Municipal Stormwater National Pollutant Discharge Elimination System (NPDES) permit. The High Point redevelopment project is currently incorporating stormwater LID drainage practices. The High Point area was a low-income housing development that is now being redeveloped as a mixed-income housing development. This project redefines the stormwater management design approach to be used for infrastructure and site development. The collaboration for this project produced an unprecedented effort between the Seattle Housing Authority, Seattle Public Utilities, and other City agencies. As a result of this innovative design approach, a traditional low-income housing development was enhanced by a more livable green space. The City stormwater code and the High Point project confirm Seattle's environmental commitment for sustainable development to maintain a high quality of life.