Carson, CA Environmental Rules: Stormwater Management (2026)

CMC § 5809 sets Carson's post-construction stormwater rule for "planning priority projects", generally one acre or more of disturbed area adding over 10,000 square feet of impervious surface, with lower thresholds (5,000 sq ft or 25 spaces) for gas stations, restaurants, and parking lots. Qualifying projects must prepare a low-impact-development (LID) plan that retains the site's Storm Water Quality Design Volume, the 85th-percentile 24-hour storm or a 0.75-inch rain event, whichever is greater, on site through infiltration, bioretention, or rainfall harvest, with biofiltration or treatment BMPs only when on-site retention is shown to be technically infeasible. No discretionary permit or certificate of occupancy may issue until compliance is confirmed.