Erosion Control: San Mateo vs South San Francisco
How do erosion control rules compare between San Mateo, CA and South San Francisco, CA?
San Mateo and South San Francisco have similar restriction levels.
San Mateo, CA
San Mateo County
San Mateo requires Erosion and Sediment Control Plans for all projects requiring a demolition, grading, or building permit that involve site disturbance. Projects disturbing one acre or more require a state Construction General Permit with SWPPP. The city's hillside areas require particular attention to erosion prevention.
View full San Mateo rules →South San Francisco, CA
San Mateo County
San Mateo County Planning & Building Department requires submittal of an Erosion and Sediment Control Plan prior to issuance of any demolition, grading, or building permit that involves site disturbance. Standard BMPs include silt fencing, straw wattles, erosion control blankets, stabilized construction entrances, and covered stockpiles. Wet-season work (October 1 - April 30) triggers additional inspection requirements and may be restricted on steep slopes. SWPPP required for sites 1+ acre.
View full South San Francisco rules →Key Facts Comparison
| Fact | San Mateo | South San Francisco |
|---|---|---|
| Required | All construction with site disturbance | - |
| SWPPP Threshold | 1+ acres of disturbance | - |
| Rainy Season | October through April — high risk | - |
| Hillside Areas | Elevated erosion concern | - |
| Public Works | 650-522-7300 | - |
| ESCP Required | - | All ground-disturbing work |
| Wet Season | - | Oct 1 to Apr 30 |
| SWPPP | - | Sites 1+ acre |
| Stabilization | - | Within 14 days |
| Final Cover | - | 70% vegetation |
Highlighted rows indicate differences between cities.
San Mateo FAQ
Do I need an erosion control plan in San Mateo?
Yes. All projects with site disturbance requiring a demolition, grading, or building permit must submit an Erosion and Sediment Control Plan.
When is erosion risk highest in San Mateo?
The rainy season from October through April presents the highest erosion risk, especially on the western hillside areas.
What happens if sediment enters the storm drain?
Sediment discharge to storm drains is a violation of the city's NPDES permit and the federal Clean Water Act. State fines can reach $10,000 per day.
South San Francisco FAQ
Do I need erosion controls for a small addition?
Any project that disturbs soil — even a small addition or trench for utilities — requires basic BMPs like silt fence at the downslope edge and inlet protection on nearby storm drains. The County ESC Manual shows simplified standards for residential-scale projects. Your building plans must include an ESC sheet.
What happens if a storm washes sediment off my site into a creek?
You face enforcement from both the County (stop-work, fines) and the SF Bay RWQCB, which can assess up to $25,000/day under the Porter-Cologne Act. You'll also be responsible for cleanup costs and potential CDFW notification if fish habitat is affected. Maintain BMPs before every rain event.
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