Stormwater quality in California is regulated under a layered framework that begins with the federal Clean Water Act and is implemented locally through individual agency stormwater ordinances and stormwater management plans.
Clean Water Act
The federal Clean Water Act establishes the basic structure for regulating discharges of pollutants into waters of the United States. Under the Act, the U.S. Environmental Protection Agency administers the National Pollutant Discharge Elimination System (NPDES) permit program.
State Permits
In California, the State Water Resources Control Board and the nine Regional Water Quality Control Boards implement the NPDES program for stormwater. Municipal Separate Storm Sewer Systems (MS4s) are regulated under two general permits:
- Phase I MS4 Permit — applies to medium and large municipalities (typically populations over 100,000) and certain counties.
- Phase II MS4 Permit — applies to small MS4s in urbanized areas. Most SJVSWQP members fall under Phase II.
Each member agency has adopted a local stormwater ordinance and a Stormwater Management Plan (SWMP) that detail the Best Management Practices (BMPs) used to meet permit conditions.