Costa Mesa, CA Environmental Rules: Stormwater Management (2026)

Costa Mesa enforces stormwater management under Title 14 of the Municipal Code (Water Quality chapter) and as a co-permittee under the Orange County NPDES Municipal Separate Storm Sewer System (MS4) Permit. The city participates in the Orange County Stormwater Program with 25 other cities and the County. All new development and significant redevelopment projects must prepare a Water Quality Management Plan (WQMP) incorporating site design, source control, and structural treatment control BMPs. Projects disturbing one acre or more require a Construction General Permit from the State Water Resources Control Board and must file a Stormwater Pollution Prevention Plan (SWPPP). Low Impact Development (LID) strategies such as bioretention, permeable pavement, and infiltration are required where feasible. It is unlawful to discharge or cause to be discharged any non-stormwater substance into the municipal storm drain system. Common prohibited discharges include wash water, pool drainage, paint, oil, pesticides, fertilizer runoff, and sediment. Construction sites must implement erosion and sediment controls, track-out prevention, and proper material storage.