Municipal stormwater general permits
Municipal stormwater general permits regulate discharges from municipal stormwater systems. These drainage systems are separated from sanitary sewer systems and are owned or operated by cities, counties, and other public entities.
Stormwater is rain and snow melt that runs off surfaces such as rooftops, paved streets, highways, and parking lots. As water runs off these surfaces, it can pick up pollutants that contaminate local water bodies.
There are four municipal stormwater general permits in Washington.
The Phase I Municipal Stormwater Permit regulates discharges from municipal separate storm sewer systems (MS4s) owned or operated by the state's largest cities and counties.
The Phase II Municipal Stormwater Permits regulate discharges from certain "small" MS4s in Washington.
We issue two Phase II permits:
- Eastern Washington Phase II Municipal Stormwater Permit
- Western Washington Phase II Municipal Stormwater Permit
- The permits also apply to public separate storm sewer systems operated by other types of public entities located in a Phase I or II city or county. Examples include ports, prison complexes, park districts, universities, or diking and drainage districts.
- See secondary permittee guidance to determine who should apply for permit coverage.
The WSDOT municipal stormwater permit regulates discharges from state highways, rest areas, park-and-ride lots, ferry terminals, and maintenance facilities within the urbanized areas of the state.
The 1990 Phase I regulation requires medium and large cities or certain counties with populations of 100,000 or more to obtain NPDES permit coverage for their stormwater discharges.
The 1999 Phase II regulation requires small MS4s in U.S. Census Bureau defined urbanized areas, as well as MS4s designated by the permitting authority, to obtain NPDES permit coverage for their stormwater discharges.
Lake Forest Park
Bainbridge Island School District #303
|Eastmont Metropolitan Park District
Port of Benton
Central Washington University
Sunnyside Valley Irrigation District
Yakima Valley Community College
Washington State University Tri-Cities
Washington State University Pullman
Washington State University Spokane
Selah School District #19
Apply for permit coverage
- Review print version of online application (pdf) - For reference only
For guidance about applying, changing, or implementing and complying with your municipal stormwater permit see the municipal stormwater guidance page. 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.
Are our permits successful at preventing or reducing pollution from stormwater runoff? Check out the Stormwater Action Monitoring program and our other results on the stormwater monitoring page.
Keep in touch with us
Join our municipal stormwater permit email list to receive updates about our permits.