Well water in Bonner County, Idaho
In Bonner County, 10% of 340 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.
364 individual samples from 73 wells, 1990 to 2025. Data refreshed September 9, 2026.
What individual samples found
Each row summarizes every public sample for that contaminant inside Bonner 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 | 340 | 58% | 10% | 0.6 | 23.9 | 10 ug/L EPA limit | |
| Nitrate 1990 to 2025 | 350 | 63% | 0% | 0.085 | 7.1 | 10 mg/L EPA limit | |
| Fluoride 1990 to 2025 | 331 | 44% | 0% | 0 | 0.8 | 4 mg/L EPA limit | |
| Nitrite 1991 to 2011 | 250 | 3% | 0% | 0 | 0.01 | 1 mg/L EPA limit | |
| Copper 1990 to 2020 | 226 | 49% | 0% | 0 | 0.089 | 1.3 mg/L EPA limit | |
| E. coli 1990 to 2008 | 224 | 0% | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Lead 1990 to 2005 | 127 | 13% | 0% | 0 | 9.3 | 15 ug/L EPA limit | |
| Uranium 1999 to 2025 | 66 | 45% | 0% | 0 | 6.9 | 30 ug/L EPA limit | |
| Radium (226 + 228) 1999 | 12 | 100% | 0% | 0 | 1 | 5 pCi/L EPA limit | |
| Sodium 1990 to 2025 | 364 | 100% | no limit | 4.11 | 150 | 20 mg/L health guideline | |
| Chloride 1990 to 2025 | 359 | 91% | no limit | 0.8 | 694 | 250 mg/L nuisance level | |
| Manganese 1990 to 2025 | 349 | 66% | no limit | 3.9 | 4,200 | 300 ug/L health guideline | |
| Iron 1990 to 2025 | 337 | 61% | no limit | 10 | 6,720 | 300 ug/L nuisance level | |
| Radon 1991 to 1999 | 55 | 100% | no limit | 650 | 3,930 | 2,000 pCi/L health guideline |
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What this means
The contaminants most often above their limit here are arsenic (10% of 340 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 Bonner County
- Arsenic10% of 340 local samples were above the limit.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 650 pCi/L.
- NitrateRecommended for every private well, especially near farms or septic systems.
- ChlorideDetected in 91% of local samples.
- ManganeseDetected in 66% of local samples.
- IronDetected in 61% of local samples.
Treatment that fits the local profile
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Chloride
- Point-of-use reverse osmosis; Distillation
- Manganese
- Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
- Iron
- Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Get your Bonner 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 Bonner County.
Common questions
Is there arsenic in well water in Bonner County?
Arsenic was detected in 58% of 340 public well samples in Bonner County, and 10% 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 Bonner County?
The median radon level across 55 public samples in Bonner County was 650 pCi/L, with a high of 3,930 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Bonner 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): 3,301 samples in Bonner 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: 89 samples in Bonner 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.