Washington Stormwater-Municipalities regulations & environmental compliance analysis

Washington Stormwater-Municipalities: What you need to know

Governing Law and Regulations

National Pollutant Discharge Elimination System (NPDES) permit program: Washington Administrative Code (WAC) 173-220-010 to 173-220-240

Regulatory Agencies
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Washington Department of Ecology (WDOE) Water Quality Program

U.S. Environmental Protection Agency (EPA) Region 10

See ADDRESSES & CONTACTS for addresses and telephone numbers.

See national section for basic information and federal regulations.

Comparison: State vs. Federal

Rules. Washington is authorized by the U.S. Environmental Protection Agency (EPA) to administer the federal National Pollutant Discharge Elimination System (NPDES) wastewater permit program, including permit authority for stormwater discharges associated with municipalities. The Washington Department of Ecology (WDOE) rules generally follow the federal permitting regulations for municipal stormwater discharges with additional requirements, and issues three municipal stormwater general permits. For more information on the federal municipal stormwater permitting program, see the national section STORMWATER—MUNICIPALITIES.

Administration and enforcement. WDOE's Water Quality Program is responsible for the administration and enforcement of the NPDES stormwater discharge permit regulations in Washington.

State Requirements


Washington issues permits for municipal separate storm sewer systems (MS4s) that are covered under EPA's Phase I and Phase II Municipal Stormwater NPDES permits for medium and large MS4s. The Phase I permit regulates discharges from MS4s owned or operated by Clark, King, Pierce, and Snohomish counties, and the cities of Seattle and Tacoma. The Phase II permits cover certain small MS4s. The WDOE offers a Western ...

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