Willow Creek Sewer District Wastewater Treatment Plant, Willow Creek, Montana

Willow Creek Sewer District is a municipal wastewater treatment facility located in Willow Creek, Montana, a small community in Gallatin County. The plant serves a population of 192, classifying it as a very small agglomeration under US regulatory frameworks. The plant provides secondary treatment, which is the standard level required by the US Clean Water Act for most municipal facilities. It has a designed capacity of 113.56 volume units and a current discharge volume of 83.28, indicating it operates below its capacity. As a US facility, it is subject to National Pollutant Discharge Elimination System (NPDES) permits issued by the Montana Department of Environmental Quality, which set effluent limits to protect water quality. The treated effluent is discharged into local streams that drain into the Missouri River watershed, ultimately reaching the Mississippi River and the Gulf of Mexico. The plant's operation helps protect the water quality of these downstream water bodies, supporting aquatic life and recreational uses in the region.

The plant discharges into tributaries of the Missouri River, which flows into the Mississippi River and then the Gulf of Mexico. The local watershed supports diverse aquatic life, including native fish species, and the plant's secondary treatment helps reduce nutrient and pollutant loads that could contribute to downstream eutrophication and hypoxia in the Gulf.