California Statewide Rule

California Stormwater NPDES Permits Govern All Cities

Heavy RestrictionsApplies statewide across California (2026)

Key Facts

Permit authority: Water Code 13383
Maximum daily fine: $10,000 per violation
Per-gallon penalty: $10 per gallon
Construction threshold: 1 acre disturbed
Enforcement agency: Regional Water Boards

Last verified: September 5, 2026Source: California Water Code 13260

Summary

California Water Code sections 13260 and 13383 implement the federal Clean Water Act through statewide MS4 NPDES permits issued by the State and Regional Water Boards, binding all municipal stormwater dischargers uniformly.

Notwithstanding any other provision of this division, the state board or the regional boards shall, as required or authorized by the Federal Water Pollution Control Act, as amended, issue waste discharge requirements and dredged or fill material permits which apply and ensure compliance with all applicable provisions of the act and acts amendatory thereof or supplementary, thereto, together with any more stringent effluent standards or limitations necessary to implement water quality control plans, or for the protection of beneficial uses, or to prevent nuisance.

Source: California Water Code 13260View official code

Full Breakdown

Water Code 13260 requires anyone discharging waste into state waters to file a Report of Waste Discharge. Section 13383 authorizes the State Water Resources Control Board to issue NPDES permits enforcing federal Clean Water Act requirements. Statewide MS4 Phase I and Phase II General Permits regulate municipal separate storm sewer systems, requiring construction site BMPs, post-construction stormwater retention, and illicit discharge controls. Local agencies must adopt ordinances at least as stringent as their NPDES permits; they cannot weaken the standards. The Construction General Permit (Order 2022-0057-DWQ) covers projects disturbing one acre or more.

Violations & Penalties

Water Code 13385 authorizes administrative civil liability up to $10,000 per day per violation plus $10 per gallon of unauthorized discharge. Willful violations are misdemeanors. EPA and Regional Water Board enforcement actions are common.

Frequently Asked Questions

Do California stormwater rules apply uniformly?

Yes. Statewide NPDES MS4 and Construction General Permits set minimum standards that all permittees must meet. Local agencies may add stricter rules but cannot weaken state and federal requirements.

Who enforces stormwater violations?

The nine Regional Water Quality Control Boards lead enforcement under Water Code 13385, with EPA backup. Penalties can reach $10,000 per day plus $10 per gallon of illegal discharge.

Sources

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