Eagle Water Hardness & Quality Report (2026)

Eagle, Idaho, in Ada County northwest of Boise in the rapidly growing Treasure Valley — one of the fastest-growing cities in the United States through the 2010s and 2020s, driven by Boise metro area expansion — receives its municipal water from the City of Eagle Water Division and United Water Idaho, drawing from the Boise River through Lucky Peak Reservoir in the Boise foothills and from local groundwater wells in the Boise River alluvial aquifer beneath the Treasure Valley. Eagle's water system reflects the characteristic mix of Boise River surface water and valley groundwater that supplies the Ada County metro area.

The moderately soft 61.5 mg/L hardness and low TDS of 117.7 mg/L reflect the Boise River's Idaho Batholith watershed origin. The Boise River and its South Fork tributaries originate in the Sawtooth Mountains and Western Idaho Batholith — a massive Cretaceous granite intrusion forming the core of central Idaho — draining ancient granodiorite, tonalite, and associated metamorphic rocks with virtually no carbonate content. Lucky Peak Reservoir stores this characteristically soft Sierra Nevada-like water from Idaho's crystalline mountain core. Local valley groundwater from the Boise River alluvium adds minimal mineral content.

At 61.5 mg/L, Eagle's water is moderately soft — excellent for appliances and comfortable for everyday use in this growing Treasure Valley community. Soap lathers well, appliances scale slowly over many months, and glassware from the dishwasher shows minimal spotting. Semi-annual descaling of kettles and coffee machines is typically sufficient. The outstanding feature of Eagle's water quality is the extraordinary PFAS level of just 1.6 ppt — the lowest in the entire Idaho dataset and among the very lowest in the USA survey — reflecting Eagle's position upstream of industrial PFAS sources and the clean character of the Idaho Batholith watershed.