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Alameda County, CA Environmental Rules: Stormwater Management (2026)

Heavy Restrictions

Verified 1 month ago|Source: Alameda Countywide Clean Water Program →

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Key Facts

Permit: MRP 3.0 (SF Bay Water Board)
C.3 threshold: 10,000 sf impervious
Single-family: 2,500 sf reduced threshold
Hydromodification: Over 1 acre
Local agency

City-specific rules exist: Fremont, Livermore, Berkeley, San Leandro, Hayward, and Oakland have their own stormwater management rules that differ from Alameda County's county-level regulations. If you live in one of those cities, check the city-specific page instead.

Summary

Alameda County complies with SF Bay Regional Water Board MRP 3.0. Projects disturbing 10,000 sf or more must incorporate Low Impact Development treatment per Provision C.3.

Full Breakdown

Stormwater management in Alameda County is governed by the Municipal Regional Permit (MRP 3.0) issued by the San Francisco Bay Regional Water Quality Control Board to the Alameda Countywide Clean Water Program and its 17 member agencies (14 cities, the county, Alameda County Flood Control District, and Zone 7 Water Agency). Projects creating or replacing 10,000 square feet or more of impervious surface must comply with Provision C.3 requiring Low Impact Development treatment such as bioretention, permeable pavement, green roofs, or tree-well filters. Single-family homes adding 2,500 square feet trigger a reduced C.3 threshold. Projects over 1 acre require full hydromodification management. Construction sites over 1 acre need coverage under the statewide Construction General Permit. Illicit discharges to storm drains including car wash runoff, paint, and landscape chemicals are prohibited and fineable.

Frequently Asked Questions

Do I need stormwater treatment for my home addition?

Only if the project creates or replaces 2,500 square feet or more of impervious surface on single-family lots. Most small additions fall below this threshold but still must avoid illicit discharges.

Can I wash my car in the driveway?

Soapy runoff to storm drains is an illicit discharge. Use commercial car washes that recycle water or wash on gravel or lawn where runoff soaks in rather than entering the street.

How does Alameda County compare?

See how Alameda County's stormwater management rules stack up against other locations.

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Alameda County, CA Environmental Rules: Stormwater Management (2026)

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