Eagan Water Hardness & Quality Report (2026)

Eagan, Minnesota, in Dakota County at the junction of I-35E and I-494 south of the Twin Cities — a major corporate and commercial hub (Delta Air Lines technology campus, Blue Cross Blue Shield of Minnesota) — draws its municipal water supply from deep bedrock groundwater wells via the City of Eagan Water Division, accessing the Jordan Sandstone (Upper Cambrian) and Prairie du Chien Group (Lower Ordovician — Oneota Dolomite, New Richmond Sandstone) aquifer system beneath Dakota County. Water hardness in Eagan measures 208 mg/L — classified as very hard.

Eagan's very hard supply reflects the Prairie du Chien Group dolomite aquifer's high carbonate dissolution — the same pattern observed in neighboring south and east Twin Cities Metro communities relying on deep bedrock wells. The Prairie du Chien Dolomite — the Oneota Dolomite (Lower Ordovician) and underlying New Richmond Sandstone — is one of the most calcareous and reactive dolomite aquifer sequences in the upper Midwest. Eagan's wells access the Prairie du Chien at approximately 400–600 feet depth in Dakota County, where extended groundwater residence time in the reactive dolomite matrix produces 200+ mg/L dissolved calcium and magnesium — characteristic of the southeast Metro deep bedrock supply zone (comparable to Woodbury: 220.5 mg/L).

At 208 mg/L, Eagan residents face significant hard water challenges. Scale deposits form rapidly on faucet aerators, showerheads, shower glass, and tile — monthly descaling with citric acid solution is essential maintenance. City of Eagan Water Division consistently delivers water meeting all Minnesota MDH and EPA Safe Drinking Water Act requirements.