Rosemount Water Hardness & Quality Report (2026)

Rosemount, Minnesota, in Dakota County in the south Twin Cities metro — a growing suburb east of Burnsville home to the Pine Bend Refinery (one of the largest petroleum refineries in the upper Midwest) and rapidly expanding residential development — receives its municipal water from the City of Rosemount Public Works, drawing from the Mississippi River or local Dakota County groundwater wells tapping the Prairie du Chien Dolomite aquifer. Rosemount's southern Dakota County position places it on the Mississippi River corridor's highly mineralized reach.

The very hard 282.5 mg/L hardness and high TDS of 751.4 mg/L reflect the Mississippi River's extreme carbonate loading in the south Twin Cities corridor. The Mississippi in Dakota County flows through the Twin Cities carbonate basin — the same Ordovician and Silurian carbonate platform geology responsible for very hard water throughout southern and central Minnesota. The Prairie du Chien Dolomite and Jordan Sandstone form the major aquifer formations in Dakota County, with the Mississippi River receiving substantial carbonate groundwater baseflow from these formations. Agricultural drainage from Dakota County's corn and soybean belt further concentrates dissolved minerals in both surface runoff and groundwater recharge.

At 282.5 mg/L, Rosemount residents face very hard water requiring consistent household management. Scale forms within days on all heated water surfaces, dishwashers produce scaled glassware without water softener treatment, and the TDS of 751 mg/L imparts a noticeable mineral character to tap water. Descaling appliances every four to six weeks is the necessary schedule. A whole-house water softener is standard equipment for Dakota County homes at this hardness level. The PFAS level of 7.6 ppt warrants a certified drinking water filter — the Pine Bend Refinery and Dakota County's industrial corridor contribute to the regional PFAS profile in the south Twin Cities water supply.