Manganese and arsenic are widespread in San Juan County wells.
2 widespread, 2 worth checking, 2 rare out of 6 health checks.
From 73 wells tested in San Juan County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: radon (4).
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
6 in 10 people 8,229 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
Radon risk (a gas from rock)
Possible here. A home air test is inexpensive.
Radon zones: EPA map
Here's how San Juan County compares with Utah and the counties around it.
Each result puts San Juan County next to the 14 counties that border it, on the chart's 0 to 50% scale.
These 2 are widespread in San Juan County wells.
Manganese24 of 70 wells over
Too few tested to show: Dolores, CO, Garfield, Mesa, CO, San Miguel, CO.
Arsenic11 of 69 wells over
Too few tested to show: Dolores, CO, Garfield, Mesa, CO, San Miguel, CO.
These 2 are worth checking in San Juan County.
Uranium3 of 29 wells over
Too few tested to show: Apache, AZ, Dolores, CO, Emery, Garfield, Mesa, CO, San Miguel, CO, Wayne.
Nitrate6 of 71 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Dolores, CO, Garfield, San Miguel, CO.
These 2 are rare in San Juan County.
Lead2 of 61 wells over
Too few tested to show: Dolores, CO, Garfield, Kane, Mesa, CO, San Miguel, CO, Wayne.
Fluoride1 of 50 wells over
Too few tested to show: Dolores, CO, Emery, Garfield, Mesa, CO, San Miguel, CO, Wayne.
Too few San Juan County wells were tested for this one.
Radon in water4 wells tested
None of the 4 San Juan County wells tested for bacteria had it, but every well needs a yearly test.
Coliform bacteria0 of 4 wells had it
E. coli0 of 4 wells had it
E. coli means human or animal waste is getting in, so if a test of your San Juan County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 28 of 72 tested wells, and it isn't a health risk.
Iron stains28 of 72 wells had it
Too few tested to show: Dolores, CO, Mesa, CO, San Miguel, CO.
Most of the 73 wells tested in San Juan County were last tested before 2010.
An old result shows the water as it was then, so treat these 73 wells as a starting point and test your own.
Most San Juan County wells in these records were tested for research or because someone suspected a problem, which can push the shares above what a typical home well would show (how we read the numbers).
One mail-in lab test covers the 5 things to check in San Juan County.
- Bacteria
- Nitrate
- Manganese
- Arsenic
- Uranium
What Utah offers well owners
- Free testingWe didn't find a free program for all of Utah. Utah's private well page
- Certified labsUtah's list of certified labs
- Well recordsUtah's well record search
Here's what we know about radon and PFAS in San Juan County.
San Juan County is in the EPA's middle radon zone. An indoor air test is cheap and tells you whether to look at your water. Radon guide
Between 2023 and 2025 the EPA had 1 town water system in San Juan County test for PFAS. None found any. No well in San Juan County has public PFAS results, so the town systems are the best clue to what's in the groundwater nearby. PFAS guide
Radon zones: EPA Map of Radon Zones. PFAS: EPA tests of town water systems, 2023 to 2025
Questions people ask about well water in San Juan County
Is well water in San Juan County safe to drink?
24 of 70 wells tested in San Juan County had manganese over the limit, about 1 in 3. Across Utah it's about 1 in 9. That's a bigger share than in 20 of the 21 other Utah counties with 10 or more tested wells, leaving out 1 county whose results are likely overstated. So test your own well for manganese before you count on it.
Where can I get my well tested in San Juan County?
Use a lab Utah has certified for drinking water. Utah's list is linked above, in the box about testing. Ask for bacteria, nitrate, manganese, arsenic and uranium, the tests that matter most in San Juan County.
How does San Juan County compare with the counties around it?
For manganese, the share of tested wells over the limit: 2 of the 10 neighboring counties with data had a higher share than San Juan County, at 34%. Montrose, CO had the most, at 46%. Groundwater doesn't stop at county lines, so Montrose, CO's 46% is worth knowing about if you live near it.
How often should I test my well in San Juan County?
None of the 4 wells tested for bacteria in San Juan County had it, but the CDC still says to test for bacteria and nitrate every year, and right away after a flood, a repair, or any change in taste or smell.
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Where the San Juan County numbers come from
- People on wells: 8,229 in San Juan County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 1,095 well water samples from 73 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2023.
- Neighboring counties: the 14 counties that share a border with San Juan County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 1 town water systems in San Juan County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: San Juan County is zone 2 on the EPA Map of Radon Zones.
- State programs and links: Department of Health and Human Services (Utah Public Health Laboratory) and local health departments, checked November 1, 2026.