Well water in Kootenai County, Idaho
In Kootenai County, 6% of 171 tested well samples exceeded the EPA limit for arsenic (10 ug/L), based on public data from Idaho statewide ground water quality monitoring (IDWR EDMS) and USGS Water Quality Portal.
241 individual samples from 49 wells, 1977 to 2025. Data refreshed September 9, 2026.
What individual samples found
Each row summarizes every public sample for that contaminant inside Kootenai County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Samples | Detected | Above limit | Median | Highest | Limit | |
|---|---|---|---|---|---|---|---|
| Arsenic 1990 to 2025 | 171 | 42% | 6% | 0 | 73 | 10 ug/L EPA limit | |
| Nitrate 1990 to 2025 | 178 | 73% | 1% | 0.15 | 14 | 10 mg/L EPA limit | |
| Fluoride 1990 to 2025 | 190 | 58% | 0% | 0.16 | 1.76 | 4 mg/L EPA limit | |
| Copper 1990 to 2020 | 125 | 58% | 0% | 0.001 | 0.029 | 1.3 mg/L EPA limit | |
| Nitrite 1991 to 2011 | 110 | 12% | 0% | 0 | 0.04 | 1 mg/L EPA limit | |
| E. coli 1990 to 2008 | 99 | 0% | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Lead 1978 to 2006 | 70 | 26% | 0% | 0 | 2 | 15 ug/L EPA limit | |
| Uranium 1999 to 2025 | 64 | 25% | 0% | 0 | 6.6 | 30 ug/L EPA limit | |
| Total coliform 2006 to 2009 | 48 | 0% | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Radium (226 + 228) 1999 | 20 | 100% | 0% | 0 | 0 | 5 pCi/L EPA limit | |
| Chloride 1990 to 2025 | 241 | 99% | no limit | 1.86 | 24 | 250 mg/L nuisance level | |
| Sodium 1990 to 2025 | 198 | 100% | no limit | 6.58 | 136 | 20 mg/L health guideline | |
| Manganese 1990 to 2025 | 186 | 63% | no limit | 1.6 | 620 | 300 ug/L health guideline | |
| Iron 1977 to 2025 | 179 | 59% | no limit | 9.3 | 16,000 | 300 ug/L nuisance level | |
| Radon 1991 to 1999 | 30 | 100% | no limit | 759 | 2,940 | 2,000 pCi/L health guideline |
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What this means
The contaminants most often above their limit here are arsenic (6% of 171 samples) and nitrate (1% of 178 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.
Chloride, Manganese, and Iron are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Kootenai County
- Arsenic6% of 171 local samples were above the limit.
- Nitrate1% of 178 local samples were above the limit.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 759 pCi/L.
- ChlorideDetected in 99% of local samples.
- ManganeseDetected in 63% of local samples.
- IronDetected in 59% of local samples.
Treatment that fits the local profile
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Nitrate
- Point-of-use reverse osmosis; Anion exchange; Distillation
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Copper
- Neutralizing filter to raise pH; Point-of-use reverse osmosis
- Chloride
- Point-of-use reverse osmosis; Distillation
Get your Kootenai County water tested at home
A licensed local water treatment company tests your tap water in your home, walks you through the numbers, and quotes treatment only if something needs fixing. Free, about 30 minutes, no obligation. Tell us what you need and we match you with a company that serves Kootenai County.
Common questions
Is there arsenic in well water in Kootenai County?
Arsenic was detected in 42% of 171 public well samples in Kootenai County, and 6% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How high is radon in well water in Kootenai County?
The median radon level across 30 public samples in Kootenai County was 759 pCi/L, with a high of 2,940 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Kootenai County?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Sources
- Idaho statewide ground water quality monitoring (IDWR EDMS): 1,821 samples in Kootenai County. Ground water quality results from the Idaho Department of Water Resources statewide monitoring program and partner agencies (ISDA, IDEQ, INL), EDMS bulk download. Retrieved September 9, 2026.
- USGS Water Quality Portal: 88 samples in Kootenai County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.