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.

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

• Phase I Municipal Stormwater Permit
• Phase II Eastern Washington Municipal Stormwater Permit
• Phase II Western Washington Municipal Stormwater Permit
• Washington State Department of Transportation Municipal Stormwater Permit

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).