Jefferson County, KY Environmental Rules: Stormwater Management (2026)

Louisville/Jefferson County Metropolitan Sewer District (MSD) holds the federal MS4 (Municipal Separate Storm Sewer System) permit under Clean Water Act §402 and manages all stormwater quality and floodplain functions county-wide. MSD Design Manual requires stormwater management plans for any project adding or replacing 2,500+ sq ft of impervious surface - detention, retention, bioretention (rain gardens), permeable pavement, or green roofs. Louisville's combined sewer system in older neighborhoods (Old Louisville, Portland, Butchertown) discharges mixed sewage-stormwater to the Ohio River and Beargrass Creek during storms. The 2005 EPA Consent Decree resulted in Project WIN (Waterway Improvement Now), a $1B+ program to reduce combined sewer overflows by 98%. MSD manages floodplain regulations under FEMA NFIP for Ohio River, Beargrass Creek, Floyds Fork, and Mill Creek corridors. Post-construction stormwater BMPs must be maintained by property owners with recorded maintenance agreements. Illicit discharges to storm drains are prohibited under LMCO Ch. 51 (Sewer and Stormwater).