Contra Costa County, CA Environmental Rules: Stormwater Management (2026)

Ordinance Code Chapter 1014-6 prohibits the discharge of any material other than rainwater or permitted non-stormwater flows into the County's municipal separate storm sewer system (MS4). Prohibited discharges include motor oil, antifreeze, paint, solvents, pesticides, fertilizers, soapy water, pool/spa water with chlorine, pet waste, construction debris, concrete washout, food waste, sanitary wastewater, and sediment from construction or landscaping. The Municipal Regional Stormwater NPDES Permit (MRP) requires the County to maintain an effective Illicit Discharge Detection and Elimination (IDDE) program, including public reporting hotlines, investigation protocols, and enforcement response. Discharges from car washing, power washing, and pool draining are permitted only when properly managed (e.g., pool water must be dechlorinated, temperature-balanced, and pH-neutral before discharge, or routed to the sanitary sewer). Commercial and industrial facilities are subject to additional inspection. Residents who observe suspicious discharges (oily sheens in creeks, discolored water, unusual odors, dumping into storm inlets) should call the Contra Costa Clean Water Program hotline. First-time minor violations may be addressed with education; repeat or egregious violations can result in daily fines, costs of cleanup, and referral for civil or criminal prosecution under the California Water Code.