Private Well Water Testing in Idaho
County-by-county USGS area-risk estimates for private wells across Idaho — arsenic exceedance probability and private-well population — plus how to test your own well at a Idaho-certified laboratory.
Idaho private-well risk summary
Counties covered
44
Idaho counties with modeled risk data.
People on private wells
area estimate314,557
estimated across covered Idaho counties.
Average arsenic risk
area estimate10%
average modeled chance a well exceeds 10 µg/L arsenic across covered counties.
Idaho counties
- Canyon County36% arsenic exceedance (area estimate)34,703 people on private wells
- Ada County14% arsenic exceedance (area estimate)30,355 people on private wells
- Bingham County7% arsenic exceedance (area estimate)20,628 people on private wells
- Twin Falls County33% arsenic exceedance (area estimate)19,337 people on private wells
- Bonner County8% arsenic exceedance (area estimate)16,268 people on private wells
- Bonneville County4% arsenic exceedance (area estimate)12,340 people on private wells
- Jefferson County13% arsenic exceedance (area estimate)12,230 people on private wells
- Kootenai County10% arsenic exceedance (area estimate)11,939 people on private wells
- Madison County7% arsenic exceedance (area estimate)10,026 people on private wells
- Minidoka County5% arsenic exceedance (area estimate)9,930 people on private wells
- Cassia County9% arsenic exceedance (area estimate)9,765 people on private wells
- Jerome County7% arsenic exceedance (area estimate)9,024 people on private wells
- Payette County35% arsenic exceedance (area estimate)8,215 people on private wells
- Elmore County13% arsenic exceedance (area estimate)8,117 people on private wells
- Bannock County8% arsenic exceedance (area estimate)7,911 people on private wells
- Gem County17% arsenic exceedance (area estimate)7,499 people on private wells
- Latah County7% arsenic exceedance (area estimate)7,351 people on private wells
- Gooding County20% arsenic exceedance (area estimate)6,466 people on private wells
- Idaho County5% arsenic exceedance (area estimate)6,021 people on private wells
- Fremont County5% arsenic exceedance (area estimate)5,843 people on private wells
- Owyhee County28% arsenic exceedance (area estimate)5,543 people on private wells
- Blaine County6% arsenic exceedance (area estimate)5,514 people on private wells
- Valley County6% arsenic exceedance (area estimate)5,350 people on private wells
- Teton County5% arsenic exceedance (area estimate)5,265 people on private wells
- Lemhi County6% arsenic exceedance (area estimate)4,381 people on private wells
- Washington County10% arsenic exceedance (area estimate)3,360 people on private wells
- Nez Perce County6% arsenic exceedance (area estimate)3,331 people on private wells
- Boise County5% arsenic exceedance (area estimate)2,745 people on private wells
- Power County7% arsenic exceedance (area estimate)2,455 people on private wells
- Benewah County9% arsenic exceedance (area estimate)2,363 people on private wells
- Boundary County8% arsenic exceedance (area estimate)2,113 people on private wells
- Clearwater County5% arsenic exceedance (area estimate)2,072 people on private wells
- Lincoln County6% arsenic exceedance (area estimate)2,055 people on private wells
- Custer County4% arsenic exceedance (area estimate)1,927 people on private wells
- Oneida County5% arsenic exceedance (area estimate)1,833 people on private wells
- Adams County5% arsenic exceedance (area estimate)1,830 people on private wells
- Franklin County12% arsenic exceedance (area estimate)1,666 people on private wells
- Caribou County6% arsenic exceedance (area estimate)1,464 people on private wells
- Butte County10% arsenic exceedance (area estimate)1,357 people on private wells
- Shoshone County7% arsenic exceedance (area estimate)1,220 people on private wells
- Bear Lake County6% arsenic exceedance (area estimate)1,154 people on private wells
- Lewis County5% arsenic exceedance (area estimate)663 people on private wells
- Camas County9% arsenic exceedance (area estimate)637 people on private wells
- Clark County7% arsenic exceedance (area estimate)291 people on private wells
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Upload my well testThese figures are USGS area estimates: statistical groundwater models describing how likely elevated contaminant levels are across a county. They are not designed to predict the concentration in any single well. Only testing your own well reveals its water quality.
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