Puget Sound Olympia

Municipal Stormwater


Water Quality > Stormwater > Municipal Stormwater General Permit

Municipal Stormwater General Permits

Urban areas that collect stormwater runoff in municipal separate storm sewers (MS4s) and discharge it to surface waters are required to have a permit under the federal Clean Water Act.

The Environmental Protection Agency (EPA) stormwater regulations established two phases--Phase I and Phase II--for the municipal stormwater permit program. (See our Municipal Stormwater Permittee Lists for a listing of the permittees covered by the Municipal Stormwater Permits.)

The Department of Ecology develops and administers National Pollutant Discharge Elimination System (NPDES) municipal stormwater permits in Washington State.

The Municipal General Permit stormwater program requirements include the following:

  • Public Education & Outreach.

  • Public Involvement.

  • Illicit Discharge Detection & Elimination (IDDE).

  • Construction Site Stormwater Runoff Control.

  • Pollution Prevention, Good Housekeeping, and Operation and Maintenance.

  • Post Construction Stormwater Management for New Development & Redevelopment, including Low Impact Development (LID).

  • Monitoring.

  • Structural Stormwater Controls (Phase I only).

  • Source Control (Phase I only).


New item 2012 Permit Appeals

Regional Stormwater Monitoring Program (RSMP)

Ecology's LID Resources webpage