Well water in Minidoka County, Idaho
In Minidoka County, 25% of 44 tested well samples exceeded the EPA limit for total coliform (0 MPN/100mL), based on public data from Idaho statewide ground water quality monitoring (IDWR EDMS) and USGS Water Quality Portal.
286 individual samples from 109 wells, 1956 to 2025. Data refreshed September 9, 2026.
What individual samples found
Each row summarizes every public sample for that contaminant inside Minidoka 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 | |
|---|---|---|---|---|---|---|---|
| Total coliform 2004 to 2019 | 44 | 25% | 25% | 0 | 2,420 | 0 MPN/100mL EPA limit | |
| Arsenic 1991 to 2025 | 134 | 94% | 21% | 4 | 43 | 10 ug/L EPA limit | |
| Nitrate 1970 to 2025 | 286 | 85% | 17% | 3.85 | 130 | 10 mg/L EPA limit | |
| Nitrite 1991 to 2019 | 114 | 15% | 2% | 0 | 27.5 | 1 mg/L EPA limit | |
| Uranium 1956 to 2025 | 155 | 98% | 0% | 2.7 | 9 | 30 ug/L EPA limit | |
| Fluoride 1991 to 2025 | 144 | 90% | 0% | 0.5 | 1.32 | 4 mg/L EPA limit | |
| E. coli 1991 to 2008 | 89 | 0% | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Copper 1991 to 2020 | 81 | 53% | 0% | 0.001 | 0.062 | 1.3 mg/L EPA limit | |
| Radium (226 + 228) 1989 to 1992 | 67 | 51% | 0% | 0.02 | 1 | 5 pCi/L EPA limit | |
| Lead 1989 to 2008 | 45 | 11% | 0% | 0 | 0.74 | 15 ug/L EPA limit | |
| Chloride 1973 to 2025 | 201 | 100% | no limit | 39 | 550 | 250 mg/L nuisance level | |
| Sodium 1991 to 2025 | 201 | 100% | no limit | 37 | 406 | 20 mg/L health guideline | |
| Manganese 1991 to 2025 | 191 | 51% | no limit | 0.3 | 480 | 300 ug/L health guideline | |
| Iron 1991 to 2025 | 186 | 45% | no limit | 0 | 5,940 | 300 ug/L nuisance level | |
| Radon 1989 to 1995 | 92 | 100% | no limit | 160 | 1,000 | 2,000 pCi/L health guideline |
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What this means
The contaminants most often above their limit here are total coliform (25% of 44 samples), arsenic (21% of 134 samples), and nitrate (17% of 286 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 and Manganese 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 Minidoka County
- Total coliform25% of 44 local samples were above the limit.
- Arsenic21% of 134 local samples were above the limit.
- Nitrate17% of 286 local samples were above the limit.
- Nitrite2% of 114 local samples were above the limit.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 160 pCi/L.
- ChlorideDetected in 100% of local samples.
Treatment that fits the local profile
- Total coliform
- Inspect and repair the well cap and casing, then shock chlorinate and retest; UV disinfection whole-house; Chlorination system
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Nitrate
- Point-of-use reverse osmosis; Anion exchange; Distillation
- Nitrite
- Point-of-use reverse osmosis; Anion exchange; Distillation
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
Get your Minidoka 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 Minidoka County.
Common questions
Is there arsenic in well water in Minidoka County?
Arsenic was detected in 94% of 134 public well samples in Minidoka County, and 21% 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 Minidoka County?
The median radon level across 92 public samples in Minidoka County was 160 pCi/L, with a high of 1,000 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Minidoka 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): 1,711 samples in Minidoka 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: 319 samples in Minidoka 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.