Kootenai County, Idaho: drinking water report. Kootenai County in northern Idaho has about 171,000 residents, with Coeur d'Alene as the county seat.
Kootenai County in northern Idaho has about 171,000 residents, with Coeur d'Alene as the county seat. The Rathdrum Prairie Aquifer – designated a sole-source aquifer by the EPA – provides drinking water for virtually the entire county. Lake Coeur d'Alene, one of the most scenic lakes in the Northwest, sits adjacent to the aquifer recharge zone but carries a hidden contamination burden from over a century of mining.
The Coeur d'Alene mining district upstream discharged millions of tons of mine tailings containing lead, zinc, arsenic, and cadmium into the South Fork Coeur d'Alene River, which feeds Lake Coeur d'Alene. According to the EPA's 2024 Bunker Hill Superfund site report, lake sediments contain elevated heavy metals, and the lake's bottom is essentially a toxic repository covered by cleaner water.
The Rathdrum Prairie Aquifer itself remains remarkably clean despite the lake contamination. According to Idaho DEQ's 2024 aquifer monitoring report, the aquifer's water quality meets all standards, with metal concentrations far below MCLs. The aquifer recharges primarily from the Spokane River and precipitation rather than directly from the contaminated lake. PFAS from Fairchild AFB in neighboring Spokane has been detected at 5 ppt at the Idaho-Washington border.
Kootenai County's aquifer produces excellent water despite the mining contamination in the adjacent lake. The main risk is development pressure over the recharge zone – as the county grows, protecting the aquifer from surface contamination becomes increasingly important.
Check your water for current data. For the clean aquifer water, a carbon filter addresses any treatment-related taste. For comprehensive protection, reverse osmosis handles the broadest range of contaminants. Our water filter guide covers both. Get your detailed report for local data, and visit our Idaho page for statewide patterns.