Phase I Municipal Stormwater Permit
On August 1, 2012, Ecology issued an updated 2013-2018 Phase I permit, that became effective on August 1, 2013.
The National Pollutant Discharge Elimination System (NPDES) and State Waste Discharge General Permits cover discharges from municipal separate storm sewer systems (MS4s). The Phase I Municipal Stormwater Permit regulates the discharges from MS4s owned or operated by Clark, King, Pierce and Snohomish Counties; and the cities of Seattle and Tacoma (incorporated cities with a population over 100,000 and unincorporated counties with populations of more than 250,000 according to the 1990 census). The permit also applies to MS4s owned by public entities located in a Phase I city or county; including the Ports of Seattle and Tacoma.
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