City of Seattle Public Utilities, Combined Sewer System
National Pollutant Discharge Elimination System (NPDES) Wastewater Discharge Permit
June 27, 2025, 12 a.m. - July 31, 2025, 11:59 p.m. PT
We invite your comments on the draft NPDES permit no. WA0031682.
The Department of Ecology invites public comment on the resissuance of NPDES permit no. WA0031682. The proposed permit authorizes the intermittent discharge of combined wastewater and stormwater into Lake Washington, Lake Washington Ship Canal, Lake Union, Union Bay, Portage Bay, Salmon Bay, Elliot Bay, Duwamish Waterwater, Longfellow Creek and Puget Sound.
You may view the Draft Permit and Fact Sheet
Background
We regulate wastewater released from municipalities and industries using the National Pollutant Discharge Elimination System (NPDES) Wastewater Discharge Permit. This permit regulates wastewater that goes directly into lakes, rivers, Puget Sound, or the ocean (surface water). All wastewater must be treated before it goes into surface water to protect human health and aquatic life. Learn more about water quality individual permits.
Questions
To request ADA accommodation, contact Ecology's ADA Coordinator by email at ecyadacoordinator@ecy.wa.gov, or call 360-407-6831, 711 (relay service), or 877-833-6341 (TTY). More about our accessibility services.