Western Washington Phase II Municipal Stormwater Permit
Final Permits and Manuals Released
Ecology has reissued the Phase I, Western WA Phase II, and Eastern WA Phase II Municipal Stormwater General Permits, and updated the Stormwater Management Manuals.
Visit the permit pages linked above for the current permit or the Municipal Stormwater Permit Reissuance webpage to view the draft documents and learn more about the process.
We develop and administer Clean Water Act National Pollutant Discharge Elimination System (NPDES) municipal stormwater permits in Washington. The Western Washington Phase II permit requires local governments to manage and control stormwater runoff so that it does not pollute downstream waters.
The current permit is effective Aug. 1, 2024, and expires on July 31, 2029.
Overview of permit timelines
View permit timelines for new and continuing permittees will be provided here. These timelines provide an overview of major deadlines for implementing permit requirements.
Annual reports for the calendar year are due by March 31 the following year.
Am I covered by a MS4 permit?
The Phase II permit for Western Washington covers over 80 cities and portions of six counties.
Find a list of cities and counties covered by this permit.
Municipal stormwater permit guidance
For guidance about applying, changing, or implementing and complying with your municipal stormwater permit see municipal stormwater guidance. Stormwater manuals provide stormwater permit implementation and management guidance. For more general stormwater permit guidance, see the stormwater guidance page.
Frequently asked questions
Have a question? Check out our frequently asked questions page.Permit history
Keep in touch with us
Join our municipal stormwater permit email list to receive updates about this permit.