Cottage Grove Water Hardness & Quality Report (2026)

The City of Cottage Grove, Minnesota operates a municipal water utility serving approximately 34,232 residents in Washington County. All drinking water is sourced entirely from groundwater, extracted via 12 wells ranging from 284 to 475 feet deep, all drawing exclusively from the Jordan Aquifer. The city operates its own treatment and distribution infrastructure from the main facility at 12800 Ravine Parkway South, providing safe, reliable water that meets all federal and state quality requirements and is managed by the municipality.

Cottage Grove's supply originates in the Jordan Aquifer, a Cambrian-age sandstone formation underlying the Twin Cities region. As groundwater percolates through layers of limestone, dolomite, and carbonate-rich rock formations deposited during ancient marine periods, it dissolves significant quantities of calcium and magnesium minerals. This geological setting—typical of Minnesota's glaciated landscape—naturally produces a very hard water supply with elevated mineral content, reflecting the aquifer's interaction with surrounding bedrock.

At the very hard classification, Cottage Grove's water causes noticeable mineral scale buildup in pipes, water heaters, and appliances over time. Dishwashers, washing machines, and hot water heaters are particularly vulnerable to efficiency loss and shortened lifespan. Residents commonly experience stiff laundry, soap scum on fixtures, and reduced lather. A water softener is strongly recommended to reduce scale accumulation and extend appliance life. The supply maintains a pH of 7.6 and alkalinity of 236 mg/L, with monitoring confirming no contamination above federal drinking water standards.