Well water in Caribou County, Idaho
In Caribou County, none of 181 tested well samples exceeded the EPA limit for fluoride, based on public data from Idaho statewide ground water quality monitoring (IDWR EDMS) and USGS Water Quality Portal.
184 individual samples from 39 wells, 1974 to 2025. Data refreshed September 9, 2026.
What individual samples found
Each row summarizes every public sample for that contaminant inside Caribou 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 | |
|---|---|---|---|---|---|---|---|
| Fluoride 1990 to 2025 | 181 | 79% | 0% | 0.212 | 0.7 | 4 mg/L EPA limit | |
| Arsenic 1990 to 2025 | 175 | 61% | 0% | 0.9 | 7.8 | 10 ug/L EPA limit | |
| Nitrate 1990 to 2025 | 168 | 90% | 0% | 2.94 | 10 | 10 mg/L EPA limit | |
| Nitrite 1991 to 2011 | 110 | 7% | 0% | 0 | 0.033 | 1 mg/L EPA limit | |
| Copper 1990 to 2019 | 102 | 78% | 0% | 0.002 | 0.055 | 1.3 mg/L EPA limit | |
| E. coli 1990 to 2008 | 100 | 0% | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Lead 1990 to 2005 | 55 | 9% | 0% | 0 | 1.6 | 15 ug/L EPA limit | |
| Uranium 1974 to 2025 | 37 | 54% | 0% | 0.56 | 4.7 | 30 ug/L EPA limit | |
| Total coliform 2015 to 2016 | 13 | 0% | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Sodium 1990 to 2025 | 184 | 100% | no limit | 20 | 120 | 20 mg/L health guideline | |
| Chloride 1990 to 2025 | 183 | 100% | no limit | 15 | 191 | 250 mg/L nuisance level | |
| Manganese 1990 to 2025 | 160 | 42% | no limit | 0 | 1,600 | 300 ug/L health guideline | |
| Iron 1976 to 2025 | 157 | 49% | no limit | 0 | 3,300 | 300 ug/L nuisance level | |
| Radon 1992 to 1995 | 21 | 100% | no limit | 330 | 2,100 | 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
Among contaminants with a federal limit, no tested sample in Caribou County came back above it. That is reassuring, but sampling is uneven: wells that were never tested are not in this data.
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 Caribou County
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 330 pCi/L.
- ChlorideDetected in 100% of local samples.
- NitrateRecommended for every private well, especially near farms or septic systems.
- FluorideDetected in 79% of local samples.
- CopperDetected in 78% of local samples.
Treatment that fits the local profile
- 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 Caribou 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 Caribou County.
Common questions
Is there arsenic in well water in Caribou County?
Arsenic was detected in 61% of 175 public well samples in Caribou 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 Caribou County?
The median radon level across 21 public samples in Caribou County was 330 pCi/L, with a high of 2,100 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Caribou 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): 1,610 samples in Caribou 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: 40 samples in Caribou 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.