Regulatory Requirements for Stormwater Systems

King County, Pierce County, Tacoma, Port of Seattle, City of Seattle, Everett are the “big 6” for NPDES. These are ‘phase 1’.

Every city that is over 10,000 people or projected to be over 10,000 within 5 years is considered ‘phase 2’.

NPDES stormwater page

King County 2015 Stormwater Management Program (SWMP), set to comply with 2013-2018 NPDES Phase 1

Additional information:

“The State Department of Ecology combined the federal requirements of the Clean Water Act with the State requirements of the State Waste Discharge Act and initiated the first stormwater NPDES permit program in 1995 for jurisdictions having populations greater than 250,000. King, Pierce, Clark, and Snohomish Counties, as well as the Cities of Tacoma and Seattle, became the first Phase I permittees, along with the Washington State Department of Transportation.

In 2007, Ecology issued the Phase II permits to jurisdictions that owned or operated municipal separated storm sewer systems (MS4s). Today there are more than one hundred MS4 permits issued statewide. These permits are on a five-year renewal cycle. The State legislature acted in the 2011 session to set the next issuance date of MS4s in 2013.

The permits include requirements for inventorying stormwater facilities, inspecting and maintaining facilities, reducing pollutants at their sources, public education, reporting NPDES permit compliance, and applying protective design standards to new development of impervious surfaces. The protective design standards are found in the State Stormwater Manual, first adopted in 1992 and updated in 2005 for western and eastern Washington. Phase I permits contain additional requirements for water quality monitoring and retrofits.”