3 county-level rules, plus city-specific rules for 1 city in Sonoma County, California.
Verified from official government sources
Sonoma County operates under two separate Municipal Separate Storm Sewer System (MS4) NPDES permits - one issued by the North Coast Regional Water Quality Control Board for the Russian River basin and one by the San Francisco Bay Regional Water Quality Control Board for southern Sonoma County. Chapter 11 of the Sonoma County Code prohibits discharge of any pollutant (including muddy construction runoff) to the storm-drain system or waters of the state. Development and redevelopment projects must implement Low-Impact Development (LID) post-construction stormwater controls.
Sonoma County Code Chapters 11 and 11A require construction-grading permits and Erosion Prevention and Sediment Control plans for almost any ground-disturbing work. During the October 15 - May 15 wet season, no more than 1 acre or 20% of the permitted work area (whichever is greater) may have erodible soil exposed at any time, and best management practices (BMPs) must be functional whenever the National Weather Service forecasts a 30% or greater chance of rain within 24 hours - in any season. Sonoma's hillside and vineyard/orchard grading rules (Chapter 36 VESCO) add further restrictions on slopes over 10%.
Sonoma County Code Chapter 7B (Flood Damage Prevention) implements the National Flood Insurance Program inside the unincorporated county. New construction and substantial improvements within FEMA-mapped Special Flood Hazard Areas (the 100-year floodplain, including the F1 floodway and F2 floodplain zoning overlays) must elevate the lowest finished floor at least one foot above the Base Flood Elevation (BFE) and use flood-resistant materials below the BFE. The FEMA Russian River watershed maps were finalized July 31, 2024.
1 cities in Sonoma County have their own environmental rules rules. Each link goes to that city's dedicated page with code citations.
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