The NPDES permit program, including stormwater permitting, has been delegated from the EPA to the state in California (except for Indian). EPA Region 9 is the permitting authority for Indian lands in California. The vast majority of construction sites and industrial facilities within EPA Region 9 (and nationally) which discharge stormwater are permitted under general NPDES permits.

The California State Water Resources Control Board (SWRCB) is responsible for administering the state’s stormwater management program.  The SWRCB oversees 9 Regional Water Resources Control Boards that develop stormwater requirements for their particular regions.  Municipalities and counties must comply with the requirements established by their regional boards.  Many of California’s large municipalities have stormwater programs of their own with additional treatment requirements.  To date, the majority of California’s stormwater programs require that stormwater be treated to the maximum extent practicable.  Numeric treatment requirements have not been established at the state or regional level. California’s regulatory structure is fairly complex.  At the state level, all construction sites disturbing more than one acre, many industrial sites, and all designated Municipal Separate Storm Sewer Systems (MS4s) are required to obtain and meet the requirements of NPDES permit coverage.