Stormwater Management: Castro Valley vs Fremont
How do stormwater management rules compare between Castro Valley, CA and Fremont, CA?
Fremont has fewer restrictions than Castro Valley.
Castro Valley, CA
Alameda County
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.
View full Castro Valley rules →Fremont, CA
Alameda County
Fremont enforces the Alameda Countywide Clean Water Program and C.3 post-construction requirements for new and redeveloped sites over 10,000 square feet.
View full Fremont rules →Key Facts Comparison
| Fact | Castro Valley | Fremont |
|---|---|---|
| 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 | Alameda Clean Water Program | - |
| C.3 Trigger | - | 10,000 sq ft impervious |
| Program | - | Alameda Clean Water |
| Illicit Discharge | - | Up to 10,000/day |
| Construction | - | SWPPP required |
| Contact | - | (510) 494-4700 |
Highlighted rows indicate differences between cities.
Castro Valley FAQ
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.
Fremont FAQ
Can I wash my car in the driveway?
Occasional home car washing is permitted, but commercial washing and any soapy discharge to storm drains is prohibited.
Do I need stormwater controls for a home addition?
Only if the project creates or replaces 10,000 sq ft or more of impervious area; smaller projects still need erosion control.
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