Cross Plains STP - Secondary Wastewater Treatment in Village of Cross Plains, Wisconsin

Cross Plains STP is a municipal wastewater treatment facility located in the Village of Cross Plains, Dane County, Wisconsin. The plant serves a population of approximately 3,341 people and operates under the regulatory framework of the U.S. Clean Water Act, which governs wastewater discharges through National Pollutant Discharge Elimination System (NPDES) permits issued by the Wisconsin Department of Natural Resources. The plant provides secondary treatment, a standard level required for most municipal facilities in the United States. With a designed capacity of 1,703.43 million gallons per day and an average discharge volume of 764.65 million gallons per day, the plant operates well within its capacity. The treatment process typically involves biological treatment followed by sedimentation to remove organic matter and suspended solids. The treated effluent is discharged to a receiving water body that ultimately drains into the Lake Michigan basin. The plant plays a key role in protecting downstream water quality, including the Yahara River chain and the broader Great Lakes ecosystem. Its location in an inland agricultural and suburban setting means the plant helps manage nutrient loads that could otherwise contribute to algal blooms in downstream waters.

The plant discharges into local streams that flow into the Yahara River system, which drains into the Rock River and eventually reaches the Mississippi River basin. This watershed supports diverse aquatic life and is important for regional water quality. The plant's secondary treatment helps reduce organic pollutants and nutrients, protecting downstream habitats from eutrophication and maintaining ecological balance in the Yahara chain of lakes.