Wyoming Stormwater Discharge Permits Under WYPDES

Authorized under Wyoming Statutes 35-11-301 and the federal Clean Water Act, WYPDES governs stormwater discharges from construction sites disturbing one or more acres, designated industrial activities, and small municipal separate storm sewer systems (MS4s). Operators must file Notices of Intent, prepare Stormwater Pollution Prevention Plans (SWPPPs), and implement best management practices for sediment, erosion, and pollutant control. Small Wyoming MS4 communities such as Cheyenne, Casper, and Laramie operate under general permits with mandatory public education, illicit discharge detection, and post-construction controls. Local stormwater ordinances must align with WYPDES minimums but may be stricter.

Violations carry civil penalties up to $10,000 per day per violation under W.S. 35-11-901, plus potential criminal liability for willful or negligent violations.