Oklahoma County, OK Environmental Rules: Stormwater Management (2026)

Oklahoma County participates in the regional MS4 (Municipal Separate Storm Sewer System) permit program administered by the Oklahoma Department of Environmental Quality (ODEQ) under 27A O.S. §2-6-301. Oklahoma City holds permit OKS000201 and regulates stormwater under Chapter 40 of the Municipal Code. Development projects disturbing 1 acre or more require a Stormwater Pollution Prevention Plan (SWPPP) and ODEQ OKR10 construction general permit. Post-construction stormwater BMPs (Best Management Practices) must treat runoff from the water quality volume (1.5 inches over impervious area). Detention basins must handle 100-year, 24-hour storm events — critical given OKC's tornado-season flash flooding. OKC §40-206 requires detention/retention for any project adding over 10,000 sq ft of impervious surface. Low-impact development features including bioswales, rain gardens, and permeable pavers qualify for reduced detention requirements. The North Canadian River watershed and Deep Fork watershed drain most of the county. Property owners responsible for ongoing maintenance of private stormwater facilities. Illicit discharge to storm drains is prohibited under OKC §40-251 with fines up to $10,000 per day. Edmond administers its own MS4 permit with similar requirements under Edmond Code Chapter 24.