Storm Water Management and Mitigation in California

California has issued four types of storm water discharge permits. They are the Phase I and Phase II Municipal Separate Storm Sewer System (MS4) permits for operators of storm drain systems in large urbanized areas (Phase I) and for operators of small municipal separate storm sewer systems (Small MS4s), which includes University of California campuses, California State University Campuses, various utility-owned sites and other non-traditional operators, such as fairgrounds, the Construction General Permit, which covers all construction projects that disturb one acre or more of land, the Industrial General Permit and the California Department of Transportation Statewide Storm Discharge Permit.

Coverage under each of these permits is obtained by filing a Notice of Intent, required registration documents and filing fees. Each permit order includes conditions for mandated coverage. Copies of the permit orders, fact sheets and assistance can be found at the following links: