Underwood Lagoon Wastewater Treatment Plant, Underwood, North Dakota

Underwood Lagoon is a municipal wastewater treatment facility located in Underwood, North Dakota, serving a small community of around 778 people. The plant is situated in McLean County, within the state's central region, and operates as a lagoon-based system providing secondary treatment. The plant has a designed capacity of 340.69 units and a current discharge volume of 264.98 units. As a secondary treatment facility, it meets the standard requirements under the US Clean Water Act for small communities. The National Pollutant Discharge Elimination System (NPDES) permit program, administered by the North Dakota Department of Environmental Quality, governs its discharge. The treated effluent is discharged into local waterways that ultimately drain into the Missouri River basin. The plant's location more than 10 km from the coast reduces direct marine impact, but its proximity to the Missouri River watershed means it plays a role in protecting downstream aquatic ecosystems.

Underwood Lagoon discharges into the Missouri River watershed, which flows through the Great Plains and eventually joins the Mississippi River. The receiving waters support diverse aquatic life, including fish species such as walleye and catfish. The plant's secondary treatment helps reduce organic pollutants and protect water quality in this agriculturally influenced region.