Well water in Blaine County, Idaho
In Blaine County, 5% of 139 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.
144 individual samples from 67 wells, 1956 to 2025. Data refreshed September 9, 2026.
What individual samples found
Each row summarizes every public sample for that contaminant inside Blaine 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 1991 to 2025 | 139 | 60% | 5% | 0.5 | 45 | 10 ug/L EPA limit | |
| E. coli 1991 to 2012 | 137 | 3% | 3% | 0 | 55 | 0 MPN/100mL EPA limit | |
| Fluoride 1986 to 2025 | 142 | 88% | 0% | 0.25 | 1.7 | 4 mg/L EPA limit | |
| Nitrate 1991 to 2025 | 141 | 99% | 0% | 0.65 | 5.1 | 10 mg/L EPA limit | |
| Nitrite 1991 to 2011 | 96 | 3% | 0% | 0 | 0.01 | 1 mg/L EPA limit | |
| Copper 1991 to 2019 | 88 | 70% | 0% | 0.002 | 0.035 | 1.3 mg/L EPA limit | |
| Lead 1991 to 2006 | 52 | 19% | 0% | 0 | 2 | 15 ug/L EPA limit | |
| Uranium 1956 to 2025 | 31 | 94% | 0% | 1.9 | 6.1 | 30 ug/L EPA limit | |
| Chloride 1991 to 2025 | 144 | 100% | no limit | 3.31 | 23 | 250 mg/L nuisance level | |
| Sodium 1991 to 2025 | 142 | 100% | no limit | 5.2 | 47 | 20 mg/L health guideline | |
| Manganese 1991 to 2025 | 138 | 14% | no limit | 0 | 5.1 | 300 ug/L health guideline | |
| Iron 1991 to 2025 | 130 | 12% | no limit | 0 | 88 | 300 ug/L nuisance level | |
| Radon 1989 to 1995 | 34 | 100% | no limit | 875 | 2,610 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: Radium (226 + 228) (4).
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What this means
The contaminants most often above their limit here are arsenic (5% of 139 samples) and e. coli (3% of 137 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 is widespread in local groundwater. It is mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Blaine County
- Arsenic5% of 139 local samples were above the limit.
- E. coli3% of 137 local samples were above the limit.
- RadonMedian local reading is 875 pCi/L.
- ChlorideDetected in 100% of local samples.
- NitrateRecommended for every private well, especially near farms or septic systems.
- FluorideDetected in 88% of local samples.
- CopperDetected in 70% of local samples.
Treatment that fits the local profile
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- E. coli
- Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system
- 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 Blaine 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 Blaine County.
Common questions
Is there arsenic in well water in Blaine County?
Arsenic was detected in 60% of 139 public well samples in Blaine County, and 5% 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 Blaine County?
The median radon level across 34 public samples in Blaine County was 875 pCi/L, with a high of 2,610 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Blaine 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): 1,308 samples in Blaine 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: 110 samples in Blaine 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.