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Federal and Washington State Surface and Stormwater Regulations

This page provides a brief overview of the Clean Water Act and state laws related to surface water and stormwater.

It is part of MRSC's series on Storm and Surface Water Management.


Under the federal Clean Water Act, the National Pollutant Discharge Elimination System (NPDES) permit program controls water pollution by regulating point sources that discharge pollutants into waters of the United States.

The NPDES Stormwater Program requires the implementation of stormwater programs. For jurisdictions in Washington State, Phase I of the NPDES stormwater permit program applied to only six local governments. Phase II of the NPDES rules extended coverage to operators of regulated small municipal separate storm sewer systems (MS4s) serving less than 100,000.

The Washington State Department of Ecology develops and administers National Pollutant Discharge Elimination System (NPDES) municipal stormwater permits in Washington State. See the Department of Ecology's Municipal Stormwater General Permit Information webpage.

Federal Regulations

Washington State Regulations

Last Modified: April 02, 2021