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

Stormwater discharge from unincorporated Riverside County is regulated under federal Clean Water Act NPDES permits issued by the Santa Ana, Colorado River (Whitewater), and San Diego Regional Water Quality Control Boards. The County, cities, and the Riverside County Flood Control and Water Conservation District are co-permittees. Property owners must comply with several key rules: (1) no non-stormwater discharges to the MS4 (pool water, car wash runoff, landscape over-irrigation, paint, oil, pet waste, etc.); (2) construction sites disturbing 1+ acre must obtain coverage under the statewide General Construction Permit and file a Storm Water Pollution Prevention Plan (SWPPP) electronically through SMARTS; (3) priority development projects (creating/replacing 10,000+ sq ft of impervious area in Santa Ana region, 1+ acre in Whitewater region) must implement Low Impact Development (LID) features per the county WQMP - bioretention, permeable paving, infiltration, and treatment trains. The County Flood Control District enforces via the Stormwater/Cleanwater Protection Program and issues Notices of Violation and administrative penalties up to $10,000/day under Water Code §13385. Common residential violations include draining pools to the gutter, hosing driveway debris into the storm drain, and washing concrete trucks on-site.