Manganese, uranium and nitrate are widespread in San Juan County wells.
3 widespread, 2 worth checking, 1 rare out of 6 health checks.
From 60 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 (1).
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
1 in 7 people 18,341 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Shallow wells: watch for fertilizer and germs from above.
Well depths: US Groundwater Well Database
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 New Mexico and the counties around it.
Each result puts San Juan County next to the 8 counties that border it, on the chart's 0 to 50% scale.
These 3 are widespread in San Juan County wells.
Manganese26 of 56 wells over
Too few tested to show: Archuleta, CO.
Uranium4 of 14 wells over
Too few tested to show: Apache, AZ, Archuleta, CO, La Plata, CO.
Nitrate11 of 52 wells over
Too few tested to show: Archuleta, CO.
These 2 are worth checking in San Juan County.
Arsenic5 of 46 wells over
Too few tested to show: Archuleta, CO.
Fluoride6 of 60 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Archuleta, CO.
This one is rare in San Juan County.
Lead2 of 42 wells over
Too few tested to show: Archuleta, CO.
Too few San Juan County wells were tested for this one.
Radon in water1 well tested
None of the 1 San Juan County wells tested for bacteria had it, but every well needs a yearly test.
Coliform bacteria0 of 1 wells had it
E. coli0 of 1 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 23 of 43 tested wells, and it isn't a health risk.
Iron stains23 of 43 wells had it
Too few tested to show: Archuleta, CO.
About 4 in 10 of the 60 wells tested in San Juan County have a test from 2020 or later.
With 21 wells tested since 2020, age matters less here than who did the testing and why.
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 6 things to check in San Juan County.
- Bacteria
- Nitrate
- Manganese
- Uranium
- Arsenic
- Fluoride
What New Mexico offers well owners
- Free testingNMED offers free well water screening at water fairs and limited free nitrate, iron and fluoride screening at some field offices; these do not replace certified lab tests. See the program
- Certified labsNew Mexico's list of certified labs
- Well recordsNew Mexico's well record search
Half the household wells here are shallower than 49 feet.
That comes from 1,398 household wells in New Mexico's drilling records. Most wells of every kind here are 33 to 100 feet deep. Wells as shallow as San Juan County's pick up bacteria and nitrate from the surface more easily, so the yearly test matters even more here. That's the shallowest typical depth for household wells among the 32 New Mexico counties with enough drilling records.
Look up your own well's depth in New Mexico's well record search, or see how to find it.
Well depths: US Groundwater Well Database
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 8 town water systems in San Juan County test for PFAS. None found any. Only 6 wells in San Juan County have 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?
26 of 56 wells tested in San Juan County had manganese over the limit, about 5 in 10. Across New Mexico it's about 2 in 10. That's a bigger share than in 12 of the 13 other New Mexico 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.
Can I get my well tested for free in San Juan County?
NMED offers free well water screening at water fairs and limited free nitrate, iron and fluoride screening at some field offices; these do not replace certified lab tests. If not, use a lab New Mexico has certified for drinking water. Ask for bacteria, nitrate, manganese, uranium, arsenic and fluoride, the tests that matter most in San Juan County.
How deep are wells in San Juan County?
Half the household wells here are shallower than 49 feet. That's the shallowest typical depth for household wells among the 32 New Mexico counties with enough drilling records.
How does San Juan County compare with the counties around it?
For manganese, the share of tested wells over the limit: San Juan County, at 46%, had a higher share than all 7 neighboring counties with data. Groundwater doesn't stop at county lines, so San Juan, UT's 34% is worth knowing about if you live near it.
How often should I test my well in San Juan County?
None of the 1 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: 18,341 in San Juan County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 1,967 well water samples from 60 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2023.
- Well depths: 1,398 New Mexico drilling records for San Juan County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 8 counties that share a border with San Juan County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 8 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: Environment Department, checked November 1, 2026.