Combined Sewer Overflow Reports & Requirements
Seattle must meet state and federal regulatory requirements in order to comply with the Clean Water Act. The program is regulated via a National Pollutant Discharge Elimination System (NPDES) permit.
- 2016-2021 NPDES Combined Sewer System Permit Fact Sheet (PDF)
- 2016-2021 NPDES Combined Sewer System Permit (PDF)
One requirement in the current permit is to provide realtime online reporting of overflows in Seattle.
Annual Reports
All reports in PDF format.
2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 | 2014 | 2013 | 2012
Consent Decree
As of July 2013, Seattle has entered into a historic agreement, a Consent Decree (PDF), with the Environmental Protection Agency, Department of Justice, and the Washington State Department of Ecology to reduce sewer overflows (SSOs) and combined sewer overflows (CSOs). Some key points about the history and desired outcome include:
- Long-Term Effort: Seattle has a long history of reducing CSOs since the 1960s and 70s. During the last two decades, Seattle has been implementing control systems to reduce these overflows even more.
- Landmark Agreement: The Consent Decree requires that we finish the job of reducing sewage overflows to protect public health and the environment. It was the first to provide a unique opportunity to integrate stormwater control into the plan for CSO control. We may implement stormwater control projects ahead of CSO projects, provided the stormwater projects provide greater environmental benefit.
- Commitment to Protect: We have committed to spend approximately $500 million on capital improvements between 2010 and 2025 to reduce CSOs to protect Seattle waterways and a quality environment. When completed, Seattle will have achieved greater than 95% reduction in all its CSOs.
For more information on our efforts to control stormwater and sewage overflows, see the Plan to Protect Seattle's Waterways.