Thermopolis Lagoon Wastewater Treatment Plant, Thermopolis, Wyoming

Thermopolis Lagoon is a municipal wastewater treatment facility serving the town of Thermopolis in Hot Springs County, Wyoming. The plant handles wastewater from a population of about 3,463 people, typical of a small agglomeration in the rural western United States. As a lagoon-based system, the plant likely provides secondary treatment through natural biological processes, which is common for small communities in this region. Under the U.S. Clean Water Act, such facilities are regulated through National Pollutant Discharge Elimination System (NPDES) permits issued by the Wyoming Department of Environmental Quality, ensuring compliance with water quality standards. The treated effluent discharges into a tributary of the Bighorn River, which flows northward through Wyoming and Montana before joining the Yellowstone River. The Bighorn River supports diverse aquatic life, including trout species, and is an important recreational and ecological corridor in the region.

The plant's discharge enters a tributary of the Bighorn River, which flows through the arid high plains of Wyoming. The Bighorn River eventually joins the Yellowstone River, a major tributary of the Missouri-Mississippi system. This watershed supports cold-water fisheries, including native cutthroat trout, and provides habitat for migratory birds. The region's semi-arid climate means that maintaining water quality in these rivers is critical for both ecological health and downstream agricultural uses.