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.
The County's erosion control requirements implement NPDES MRP Provision C.6 (Construction Site Controls) and state Construction General Permit (SWRCB Order 2022-0057-DWQ) for sites 1+ acre. An Erosion and Sediment Control Plan (ESCP) must be submitted with building permit applications for any project involving ground disturbance. Required BMPs per the County ESC Manual: silt fence along downslope property perimeter, straw wattles on contour for sheet flow control, stabilized construction entrance (rock pad) to prevent tracking onto roads, gravel bag checks in swales, erosion control blankets on disturbed slopes, inlet protection at storm drain catch basins, stockpile covers. Wet-season work (Oct 1 - Apr 30) requires enhanced inspections and stabilization before each storm event; active grading on slopes steeper than 3:1 may be restricted. Disturbed areas must be stabilized (via vegetation, hydroseed, or mulch) within 14 days of disturbance cessation. Final stabilization with 70% vegetation cover or paved/landscaped finish is required before project closeout. Steep-slope projects may also trigger Geotechnical Review. Pre-site inspections for erosion control and tree protection are now required on specific site types.
Missing/inadequate ESC: stop-work order and fines $250-$2,500 per County Code. Sediment discharge to waterway: RWQCB enforcement $1,000-$25,000 per day plus cleanup cost. Failure to stabilize within 14 days: daily fines until corrected. Violating Construction General Permit: SWRCB penalties up to $10,000/day plus $10/gallon.
San Mateo County, CA
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