Utah Well Water Risk, County by County
If you're on a private well in Utah, the contaminants worth worrying about depend a lot on where you live — the granite country around Sanpete County has a different risk profile than the farmland of Cache Valley or the desert basins of the West Desert. Pick your county below to see what the public data says, then use it to decide what to actually test for instead of guessing.
Find Your County's Risk Factors
Select your county for a plain-language summary of radon potential and any documented regional nitrate or arsenic concerns.
Why county matters for well water risk
Nobody tests every private well in Utah — there's no statewide database of individual well results the way there is for public water systems. What does exist is regional geology and land-use data: the EPA's county-level radon potential map, and a handful of peer-reviewed and Utah Geological Survey (UGS) studies that sampled groundwater in specific valleys. That's what this tool is built from. It tells you what's plausible and worth testing for based on where you live — it is not a substitute for testing your own water.
This is a screening guide, not a lab result. The only way to know what's actually in your well is to test it. Use the numbers below to decide what to test for and how urgently — not as a stand-in for a real water test.
Radon potential by county
The EPA classifies every U.S. county into a radon zone based on indoor-air radon measurements and the uranium content of local geology. The same granite and metamorphic rock that drives high indoor radon can also put radon into groundwater — so counties in EPA Radon Zone 1 are the ones where it's most worth asking your test kit to include a radon-in-water panel, not just the standard bacteria/nitrate/hardness panel.
| EPA Radon Zone | Counties |
|---|---|
| Zone 1 — Highest potential | Carbon, Duchesne, Grand, Piute, Sanpete, Sevier, Uintah |
| Zone 2 — Moderate potential | Beaver, Box Elder, Cache, Daggett, Davis, Emery, Garfield, Iron, Juab, Kane, Millard, Morgan, Rich, Salt Lake, San Juan, Summit, Tooele, Utah, Wasatch, Washington, Wayne, Weber |
No Utah county falls in EPA Zone 3 (lowest potential). Source: EPA Map of Radon Zones.
Nitrate: the agricultural-valley risk
Nitrate gets into groundwater from fertilizer, manure, and septic systems, so it shows up most in valleys with a lot of farming, livestock, or dense septic use upstream of the water table. Two Utah studies give real, documented numbers:
Sanpete County: UGS groundwater-quality studies in Sanpete Valley have documented nitrate concentrations approaching and, in some sampled wells, exceeding the EPA's 10 mg/L drinking-water standard, tied to the valley's dense agricultural and livestock operations. If you're on a well in Sanpete County, nitrate should be on your test list every single year, not just once.
Goshen Valley (southwestern Utah County): A UGS hydrogeologic study of Goshen Valley (Special Study 171) measured nitrate as high as 256 mg/L in some sampled wells — more than 25 times the EPA standard — concentrated in the valley's irrigated agricultural zones. Not every well in the area tested that high, but it shows the ceiling is real, not theoretical.
Beyond these two documented cases, treat any well in an irrigated farming valley — parts of Cache, Box Elder, Millard, and Iron counties included — as a candidate for annual nitrate testing, especially if you're near feedlots, dairies, or a septic system upgradient of your well.
Arsenic: geology-driven, and harder to predict
Arsenic in Utah groundwater is usually geogenic — it leaches naturally out of volcanic and basin-fill sediment rather than coming from pollution — which makes it both harder to predict and impossible to rule out just because an area looks rural and undeveloped.
Goshen Valley (southwestern Utah County): the same UGS study cited above measured arsenic as high as 66.7 µg/L in sampled wells — more than 6 times the EPA standard of 10 µg/L — from naturally occurring geologic sources in the valley.
Separately, researchers from the Desert Research Institute and USGS studying the western Great Basin — the basin-and-range geology that extends across northern Nevada into western Utah — found geologic conditions favorable to elevated arsenic across alluvial (basin-fill) aquifers in that region. That study's published results were broken out by Nevada county, not Utah county, so we can't point to a specific western Utah county with a documented number the way we can for Goshen Valley. What it does tell you: if your well draws from a basin-fill aquifer in Utah's west desert — Tooele, Juab, Millard, Box Elder, or similar terrain — the regional geology is a real enough reason to include arsenic in your test panel, even with no local number to point to yet.
General baseline: what every Utah well owner should test for
Regardless of county, the EPA and CDC recommend every private well be tested at least once a year for the basics, and more often if anything changes nearby (new construction, flooding, a change in taste or smell):
- Total coliform bacteria and E. coli — the most common and fastest-changing risk, unrelated to geology
- Nitrate — annually, more often in agricultural valleys (see above)
- pH and hardness — affects plumbing, appliances, and how other results should be interpreted
- Arsenic — at least once, sooner if you're in a basin-fill or known-affected valley
- Radon — worth adding for Zone 1 counties (see table above)
For the full breakdown of test panels, costs, and when to retest, see our guide: What Should I Test My Well Water For?
Get a Test Kit That Covers Your County's Risk Factors
Look for a kit that includes bacteria, nitrate, arsenic, and — if you're in a Zone 1 county — a radon-in-water panel.
Varify 17-in-1 Water Test Kit — View on Amazon →As an Amazon Associate, we earn from qualifying purchases.
Frequently Asked Questions
Does this tool test my actual water?
No. It's a screening guide built from public county-level and regional data so you know what to prioritize. The only way to know what's in your specific well is a lab test.
My county isn't mentioned by name in the nitrate or arsenic sections — does that mean my water is safe?
No. It means no published study has sampled that area specifically, not that the risk is zero. Absence of data isn't the same as absence of risk — the general baseline testing recommendations above apply to every Utah well regardless of county.
How often should I retest?
At minimum, once a year for bacteria and nitrate. Retest sooner after flooding, nearby construction or land-use changes, a new baby or pregnancy in the household, or any change in taste, smell, or color.
Where do I get my well tested?
Your local health department can usually test for bacteria and nitrate at low cost. For a full panel including arsenic and radon, a certified private lab or an at-home kit that ships to a certified lab is usually faster.
Is radon in water the same as radon in air?
Related but not identical. Radon dissolved in well water can also be released into indoor air (especially during showers), so a high radon-in-water reading is a reason to also check indoor air, and vice versa.
Sources
- EPA, Map of Radon Zones — Utah
- Utah Geological Survey, Special Study 171 — Investigating Anthropogenic and Geogenic Sources of Groundwater Contamination in a Semi-Arid Alluvial Basin, Goshen Valley, UT
- Utah Geological Survey, Sanpete Valley groundwater-quality studies
- USGS, Quantifying Trends in Arsenic, Nitrate, and Dissolved Solids from Selected Wells in Utah
- Desert Research Institute / USGS, Predictions of Arsenic in Domestic Well Water Sourced from Alluvial Aquifers of the Western Great Basin, USA, Environmental Science & Technology
- EPA National Primary Drinking Water Regulations (MCLs for arsenic and nitrate)