Stormwater Discharges from Municipal Sources in Region 10

General Information

Under the National Pollutant Discharge Elimination System (NPDES) stormwater program, operators of large, medium and regulated small municipal separate storm sewer systems (MS4s) require authorization to discharge pollutants under an NPDES permit.

In Region 10, EPA is the NPDES stormwater permitting authority for facilities on Indian Country lands in Idaho, Oregon and Washington; and federal operators in Washington.

If EPA is not the permitting authority for your facility, contact your state's stormwater program:

• Alaska MS4 Program
• Idaho Stormwater Permits
• Oregon Municipal Stormwater Permits
• Washington Stormwater General Permits

• NPDES Stormwater Program in Region 10
• NPDES Stormwater Final MS4 General Permit Remand Rule

MS4 Permits in Washington

EPA Region 10 is the NPDES permitting authority for MS4 discharges operated by federal entities in Washington, regulated MS4s located in Indian Country, and/or regulated MS4s discharging to waters subject to tribal water quality standards.

If your facility is not within one of these categories, visit Washington Stormwater General Permits for permitting information.