Minnehaha County, SD Environmental Rules: Stormwater Management (2026)

Minnehaha County exercises planning and zoning authority over unincorporated areas under SDCL Chapter 11-2 (county zoning enabling act) and SDCL Chapter 11-3 (county subdivision regulation). Subdivision plats reviewed by the Minnehaha County Planning Commission must demonstrate adequate drainage and stormwater conveyance; major developments are subject to the regional Big Sioux River Drainage Basin standards co-administered with the City of Sioux Falls. Under the federal NPDES program (Clean Water Act § 402, 33 USC 1342) and South Dakota's delegated Surface Water Discharge System, any construction project disturbing one acre or more (or part of a larger common plan of development) must file a Notice of Intent for coverage under SD's General Permit for Stormwater Discharges Associated with Construction Activity, administered by SD DANR under SDCL Chapter 34A-2 (water pollution control). A Stormwater Pollution Prevention Plan (SWPPP) is required, including BMPs such as silt fence, inlet protection, stabilized construction entrances, and post-construction stabilization. Sioux Falls (a Phase II MS4 community under 40 CFR 122.32) operates a separate municipal stormwater program; the county's unincorporated areas do not currently hold MS4 designation but coordinate with Sioux Falls on the Big Sioux watershed. Agricultural stormwater discharges from normal farming operations are statutorily exempt under 33 USC 1362(14) and SDCL 34A-2-36 (silvicultural and irrigated agriculture exemption).