Seattle Public Utilities: Expanding the use of green stormwater infrastructure

Seattle Public Utilities: Expanding the use of green stormwater infrastructure

As we enter a new decade and our region experiences rapid growth and a changing climate, green stormwater infrastructure (GSI) is more important than ever. GSI uses plants, trees, soil and collection systems to slow and treat rain once it falls and becomes polluted runoff. Incorporating nature into the built environment helps developed urban areas work more like forests and natural areas. This, in turn, reduces flooding, prevents sewer overflows, and decreases other types of pollution from entering our streams, lakes, and Puget Sound. GSI also provides broader benefits including wildlife habitat, air quality improvements, reduced human health impacts from extreme heat events, and new economic development opportunities. 

Over the past 20 years, Seattle Public Utilities (SPU) has created three pipelines of GSI production. First, SPU-led construction projects in the right-of-way capture and manage dirty runoff from dozens of streets around Seattle. Second, the RainWise incentive program pays property owners to install rain gardens and cisterns on their land; so far this program has funded almost 2,000 projects, which together manage 25 million gallons of stormwater every year. Finally, Seattle’s Stormwater Code requires redevelopment projects to manage their own runoff, leading to thousands of new rain gardens, green roofs, rainwater harvesting systems, and permeable paving installations around Seattle.

Looking ahead, we’re building additional pipelines for GSI projects, so we can accelerate production of GSI to meet a 2025 goal of managing 700 million gallons of stormwater with GSI every year. New approaches we’re working on include:

  • “Beyond code” partnerships, in which SPU provides permitting support and/or project funding to help developers exceed their code requirements, managing extra runoff for downstream benefits.
  • Dozens of new roadside bioretention projects to improve water quality in the Longfellow, Thornton, and Piper’s Creek watersheds.
  • GSI to implement community priorities while improving system capacity in higher density, mixed-use urban village neighborhoods.
  • Co-development with Seattle Parks and Recreation to provide GSI and new parks in areas that lack open space and where GSI can strengthen the drainage and wastewater systems.
  • Creek floodplain restoration along urban streams to prevent downstream flooding, improve water quality, provide community green space, and improve aquatic habitat.

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