What is the difference between a Phase I and a Phase II Municipal Stormwater Permit?
The Phase I Municipal Stormwater Permit regulates releases 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. The Department of Ecology issues two Phase II permits:
- Eastern Washington Phase II Municipal Stormwater Permit
- Western Washington Phase II Municipal Stormwater Permit
The Western Washington Phase II permit requires local governments to manage and control stormwater runoff so that it does not pollute downstream waters. The Stormwater Management Program Plan (Plan) describes the cityβs planned actions and activities for the year to meet the requirements of the permit.
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