Santa Clara County, CA Environmental Rules: Stormwater Management (2026)

Santa Clara County unincorporated area implements stormwater rules through Division B11 of the County Code and the SCVURPPP program, operating under the Municipal Regional Permit Order R2-2022-0018, known as MRP 3.0, issued by the San Francisco Bay Regional Water Quality Control Board. Provision C.3 of that permit requires projects that create or replace 10000 square feet or more of impervious surface to provide hydromodification and water quality treatment using Low Impact Development such as bioretention, biotreatment soil media, permeable pavement, or flow-through planters. Single-family projects over 2500 square feet of new impervious in designated priority areas also trigger C.3 requirements. Illicit discharges of anything other than rain water to storm drains are prohibited under Division B11 and federal 40 CFR 122.26, with typical violations including car washing soap, paint rinse, pool water with chlorine, and construction sediment. Construction sites over 1 acre must enroll in the state Construction General Permit under Water Code 13260 and implement Best Management Practices. Santa Clara Valley Water District operates the flood protection and creek stewardship side. Reports of illicit discharge can go to Valley Water or the County through the regional 1 866 HEY BAUA hotline. Violations can carry administrative penalties up to 10000 dollars per day plus cleanup costs.