SHELBY WWTP - Wastewater Treatment Plant in Shelby, Montana

SHELBY WWTP is a municipal wastewater treatment facility located in Shelby, Toole County, Montana. It serves a population of around 3,400 people, making it a small to medium-sized plant typical of rural communities in the northern Great Plains. The plant is situated near Marias Park Road, within the Marias River watershed. As a U.S. facility, SHELBY WWTP operates under the Clean Water Act and is subject to National Pollutant Discharge Elimination System (NPDES) permitting, administered by the Montana Department of Environmental Quality. For a plant serving approximately 3,400 people, secondary treatment is the standard requirement, with additional nutrient controls possible depending on the receiving water body's sensitivity. The plant's treated effluent ultimately drains into the Marias River, a tributary of the Missouri River, which flows into the Mississippi River and then the Gulf of Mexico. This connection to the larger Mississippi Basin means the plant's discharge contributes to downstream water quality, including nutrient loading concerns in the Gulf of Mexico hypoxic zone.

SHELBY WWTP discharges into the Marias River watershed, which flows into the Missouri River and eventually the Mississippi River to the Gulf of Mexico. The region is semi-arid with cold winters, and the river supports diverse aquatic life including native fish species. Downstream water quality is important for irrigation and recreation, and nutrient management is a key concern due to the cumulative impact on the Gulf of Mexico hypoxic zone.