The County is required to regulate development and redevelopment projects so that associated activities do not result in the discharge of pollutants to the County storm drain system, natural surface waters, or watercourses. The County has created a resource to assist developers with implementing post-construction design measures to prevent stormwater pollution, the County’s Post-Construction Stormwater Design Manual.

In addition, to select and properly size low-impact development best management practices (LID BMPs) that meet California’s National Pollutant Discharge Elimination System (NPDES) Permit requirements for stormwater discharges from Phase II municipal separate storm sewer systems (MS4s), developers may consult the California Phase II LID Sizing Tool.