Sentinel Butte Lagoon Wastewater Treatment Plant, Golden Valley County, North Dakota

Sentinel Butte Lagoon is a wastewater treatment facility located in Beach Township, Golden Valley County, North Dakota, serving a small population of 56 residents. The plant provides secondary treatment, which is the standard level required under the U.S. Clean Water Act for municipal wastewater before discharge into surface waters. The plant has a designed capacity of 75.71 megaliters and reports an annual discharge volume of 37.85 megaliters, indicating it operates well below its capacity. As a small facility in a rural area, it is subject to the National Pollutant Discharge Elimination System (NPDES) permitting program, which sets effluent limits to protect water quality. The treated effluent is discharged into local waterways that eventually drain into the Missouri River basin. The plant's location in the Great Plains region means the receiving waters support agricultural and ecological uses, and the secondary treatment helps reduce nutrient and pathogen loads to maintain downstream water quality.

The plant discharges into tributaries of the Little Missouri River, which flows into the Missouri River and ultimately the Gulf of Mexico. The surrounding watershed is part of the Northern Great Plains, characterized by semi-arid conditions and agricultural land use. The plant's secondary treatment helps protect downstream aquatic habitats and supports the ecological health of the Missouri River system.