Well water in Butte County, Idaho
In Butte County, 5% of 38 tested well samples exceeded the EPA limit for E. coli (0 MPN/100mL), based on public data from USGS Water Quality Portal and Idaho statewide ground water quality monitoring (IDWR EDMS).
458 individual samples from 101 wells, 1949 to 2026. Data refreshed September 9, 2026.
What individual samples found
Each row summarizes every public sample for that contaminant inside Butte 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 | |
|---|---|---|---|---|---|---|---|
| E. coli 1991 to 2011 | 38 | 5% | 5% | 0 | 190 | 0 MPN/100mL EPA limit | |
| Nitrate 1952 to 2023 | 109 | 99% | 5% | 1.4 | 13.3 | 10 mg/L EPA limit | |
| Radium (226 + 228) 1989 to 1992 | 163 | 44% | 1% | 0 | 21 | 5 pCi/L EPA limit | |
| Uranium 1957 to 2026 | 458 | 99% | <1% | 1.78 | 81,600 | 30 ug/L EPA limit | |
| Arsenic 1990 to 2023 | 65 | 71% | 0% | 1 | 6.8 | 10 ug/L EPA limit | |
| Fluoride 1960 to 2023 | 64 | 75% | 0% | 0.2 | 0.5 | 4 mg/L EPA limit | |
| Copper 1968 to 2022 | 62 | 55% | 0% | 0 | 0.12 | 1.3 mg/L EPA limit | |
| Lead 1972 to 2023 | 50 | 24% | 0% | 0 | 11 | 15 ug/L EPA limit | |
| Nitrite 1991 to 2010 | 40 | 8% | 0% | 0 | 0.01 | 1 mg/L EPA limit | |
| Chloride 1957 to 2023 | 96 | 100% | no limit | 15 | 290 | 250 mg/L nuisance level | |
| Sodium 1954 to 2023 | 90 | 100% | no limit | 12 | 75 | 20 mg/L health guideline | |
| Iron 1949 to 2023 | 70 | 41% | no limit | 0 | 15,100 | 300 ug/L nuisance level | |
| Radon 1989 to 1995 | 59 | 100% | no limit | 170 | 1,200 | 2,000 pCi/L health guideline | |
| Manganese 1977 to 2023 | 58 | 22% | no limit | 0 | 10.3 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Total coliform (1).
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What this means
The contaminants most often above their limit here are e. coli (5% of 38 samples), nitrate (5% of 109 samples), and radium (226 + 228) (1% of 163 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 Butte County
- E. coli5% of 38 local samples were above the limit.
- Nitrate5% of 109 local samples were above the limit.
- Radium (226 + 228)1% of 163 local samples were above the limit.
- Uranium<1% of 458 local samples were above the limit.
- RadonMedian local reading is 170 pCi/L.
- ChlorideDetected in 100% of local samples.
- FluorideDetected in 75% of local samples.
Treatment that fits the local profile
- E. coli
- Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system
- Nitrate
- Point-of-use reverse osmosis; Anion exchange; Distillation
- Radium (226 + 228)
- Water softener (cation exchange); Point-of-use reverse osmosis
- Uranium
- Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
Get your Butte 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 Butte County.
Common questions
Is there arsenic in well water in Butte County?
Arsenic was detected in 71% of 65 public well samples in Butte County, and 0% 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 Butte County?
The median radon level across 59 public samples in Butte County was 170 pCi/L, with a high of 1,200 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Butte 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
- USGS Water Quality Portal: 916 samples in Butte 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.
- Idaho statewide ground water quality monitoring (IDWR EDMS): 507 samples in Butte 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.
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.