Rapid City Stormwater Runoff Design Requirements

Rapid City’s Code of Ordinances § 8.48.020 states that all new development, or any redevelopment, which causes an increase in the impervious percentage for that site, with a connected impervious area of greater than 15% shall be required to provide stormwater treatment of the runoff generated by the first 0.5 inch of rainfall. Stormwater treatment practices shall be designed to treat the first 0.5 inch of rainfall with an 80% total suspended solids (TSS) removal rate.