California’s stormwater permits fall under the National Pollutant Discharge Elimination System (NPDES) program, managed by the State Water Resources Control Board (State Water Board) and the Regional Water Quality Control Boards (RWQCBs).

There are three primary categories of stormwater permits in California:

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Industrial Stormwater Permit

Who?: Industrial Facility Operators
Covers: Industrial facilities under EPA-regulated sectors

From the California Water Boards:
“The Industrial General Permit regulates industrial stormwater discharges and authorized non-stormwater discharges from industrial facilities in California. The Industrial General Permit is called a general permit because many industrial facilities are covered by the same permit, but comply with its requirements at their individual industrial facilities. The State Water Resources Control Board (State Water Board) and Regional Water Quality Control Boards (collectively, the Water Boards) implement and enforce the Industrial General Permit.”

Construction Stormwater General Permit

Who?: Developers, Contractors
Covers: Construction activities disturbing 1+ acre or part of a common plan

From the California Water Boards:
“The California State Water Resources Control Board (State Water Board) regulates stormwater discharges from construction sites because of its potential to mobilize pollutants and discharge into waterbodies or watersheds. By regulating these discharges, the State Water Board is preserving, enhancing, and restoring California's waterbodies and its resources.

Construction activity subject to this permit includes clearing, grading and disturbances to the ground such as stockpiling, or excavation, but does not include regular maintenance activities performed to restore the original line, grade, or capacity of the facility. Dischargers whose projects disturb one (1) or more acres of soil or whose projects disturb less than one acre but are part of a larger common plan of development that in total disturbs one or more acres, are required to obtain coverage under the National Pollutant Discharge Elimination System (NPDES) General Permit for Stormwater Discharges Associated with Construction and Land Disturbance Activities.” ‍

‍Municipal MS4 Permit

Who?: Municipalities, School Districts, Caltrans
Covers: Cities, counties, and public agencies with storm sewer systems

From the California Water Boards:
"The Municipal Storm Water Program regulates storm water discharges from municipal separate storm sewer systems (MS4s) throughout California. U.S. EPA defines an MS4 as a conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains) owned or operated by a State (40 CFR 122.26(b)(8)).

Pursuant to the Federal Water Pollution Control Act (Clean Water Act) section 402(p), storm water permits are required for discharges from an MS4 serving a population of 100,000 or more. The Municipal Storm Water Program manages the Phase I Permit Program (serving municipalities over 100,000 people), the Phase II Permit Program (for municipalities less than 100,000), and the Statewide Storm Water Permit for the State of California Department of Transportation. The State Water Resources Control Board (State Water Board) and Regional Water Quality Control Boards (collectively, the Water Boards) implement and enforce the Municipal Storm Water Program."

Regional Permits & TMDLs

Some RWQCBs (e.g., LA, San Francisco Bay, San Diego) have more stringent regional permits, and certain areas require compliance with Total Maximum Daily Load (TMDL) limitations for pollutants like copper, zinc, or bacteria.

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For help navigating applicable permits, reach out to our team.

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