Menifee, CA Environmental Rules: Stormwater Management (2026)

Menifee participates in the Riverside County Flood Control & Water Conservation District (RCFC&WCD) MS4 program. Most of Menifee drains north through Salt Creek into the Santa Ana watershed (Region 8 NPDES Order R8-2010-0033, MS4 Permit CAS618033), while southern portions drain to the Santa Margarita system (Region 9 Order R9-2013-0001 / R9-2015-0100 amended permit). Both permits require new development and redevelopment over 10,000 sq ft (or single-family hillside, ESA-adjacent, parking lots ≥5,000 sq ft, restaurants, gas stations, auto repair) to prepare a project-specific WQMP that retains/treats the 85th-percentile 24-hour storm via Low Impact Development (LID) BMPs such as bioretention, infiltration, biofiltration, or harvest-and-use. Construction sites ≥1 acre must obtain coverage under the State Construction General Permit (Order 2009-0009-DWQ, as amended) by filing a Notice of Intent on SMARTS and preparing a Stormwater Pollution Prevention Plan (SWPPP) signed by a Qualified SWPPP Developer (QSD). Sites under 1 acre still must implement an Erosion and Sediment Control Plan reviewed by city Engineering. Illicit discharge is prohibited; only uncontaminated dewatering, fire hydrant flushing, and de-chlorinated pool water (after pH neutralization and visible-chlorine elimination) are conditional exempt discharges under the MS4 permit.