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 permit was first modified on December 17, 2014 and the first modification went into effect on January 16, 2015. The permit was modified a second time on July 20, 2016 and the second modification will go into effect on August 19, 2016.
See the permit history page for redlined versions of the permit issued August 1, 2012.
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.
The files below are the permit as modified in July 2016.
*This clean version corrects a minor formatting error where the citation to the Structural Stormwater Control was missing. No changes to permit requirements/language.
2018 Western Washington Permit Reissuance
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