Graceville Lagoon Wastewater Treatment Plant, Big Stone County, Minnesota

Graceville Lagoon is a wastewater treatment facility located in Big Stone County, Minnesota, United States. The plant serves a small population of 571 residents and is situated in a rural agricultural region. As a lagoon-based system, it provides secondary treatment to municipal wastewater before discharge. The plant has a designed capacity of 476.96 and an annual discharge volume of 465.61, indicating near-capacity operation. Under the US Clean Water Act, facilities of this scale are typically permitted through the National Pollutant Discharge Elimination System (NPDES), which sets effluent limits to protect water quality. Secondary treatment is the standard requirement for municipal plants, ensuring removal of organic matter and suspended solids. The treated effluent is discharged into local waterways that drain into the Minnesota River basin, ultimately reaching the Mississippi River and the Gulf of Mexico. The plant plays a role in protecting downstream aquatic ecosystems, including the Mississippi River's diverse fish and wildlife habitats. Its location in an agricultural area means careful nutrient management is important to prevent impacts on receiving waters.

Graceville Lagoon discharges into local streams that flow into the Minnesota River, a tributary of the Mississippi River. The Mississippi River system supports a wide range of aquatic life and is a critical migratory corridor for birds and fish. The plant's secondary treatment helps reduce organic pollutants, but nutrient removal may be limited, which is a consideration for downstream water quality in the Gulf of Mexico hypoxic zone.