The Basics
The problem:
As rain runs off streets, rooftops, and parking lots, it picks up oil, grease, metals, and other pollutants, carrying them to our lakes, creeks, the Duwamish River, and the Puget Sound. In many parts of Seattle, rain also flows into the sewer system. During storms, this rain can cause sewage overflows into local waterways. Recent scientific studies have determined that polluted runoff is the biggest threat to water quality in the Puget Sound.
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- raingardens
- bioretention
- green roofs
- permeable pavement
- cisterns
- trees
GSI in Seattle

Seattle is a national leader in using GSI. We have been building GSI for nearly two decades. This picture shows a High Point rain garden (in the West Seattle neighborhood) that helps keep polluted runoff out of Longfellow Creek. Seattle has a goal to manage 700 million gallons of polluted runoff by 2025.
Partners & Contributors
Thanks to the contributions of many community partners, philanthropies, private developers, and Seattle Public Utilities and King County Wastewater Treatment Division, nearly 100 million gallons of polluted runoff are managed by green stormwater infrastructure in Seattle.
Below are links to organizations that have been involved with building GSI in Seattle. If your organization would like to be added to this list, contact us.