Fluoride has turned up often in La Plata County wells, mostly from one small area.
1 likely overstated, 4 rare out of 5 health checks.
From 56 wells tested in La Plata County since 2017; your own well needs its own test. How to read this
*Fluoride: Almost all of these tests come from a single agency in one small part of the county, so it may not match the rest of the county.
Not charted, because fewer than 10 wells were tested: uranium (2), radon (2).
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 3 people 22,036 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Deep wells: fewer surface germs, more minerals from the rock.
Well depths: US Groundwater Well Database
Radon risk (a gas from rock)
Likely here. Test your home's air first.
Radon zones: EPA map
Here's how La Plata County compares with Colorado and the counties around it.
Each result puts La Plata County next to the 6 counties that border it, on the chart's 0 to 50% scale.
This one has turned up often here, mostly from one small area.
Fluoride9 of 55 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Archuleta, Dolores, Hinsdale, San Juan.
Almost all of these tests come from a single agency in one small part of the county, so it may not match the rest of the county.
These 4 are rare in La Plata County.
Manganese0 of 13 wells over
Too few tested to show: Archuleta, Dolores, Hinsdale, San Juan.
Arsenic0 of 55 wells over
Too few tested to show: Archuleta, Dolores, Hinsdale, San Juan.
Nitrate0 of 18 wells over
Too few tested to show: Archuleta, Dolores, Hinsdale, San Juan.
Lead0 of 56 wells over
Too few tested to show: Archuleta, Dolores, Hinsdale, San Juan.
Too few La Plata County wells were tested for these 2.
Uranium2 wells tested
Radon in water2 wells tested
Coliform bacteria turned up in 2 of 5 tested La Plata County wells, so test for it every year.
Coliform bacteria2 of 5 wells had it
E. coli0 of 5 wells had it
E. coli means human or animal waste is getting in, so if a test of your La Plata County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 4 of 55 tested wells, and it isn't a health risk.
Iron stains4 of 55 wells had it
Too few tested to show: Archuleta, Dolores, Hinsdale, San Juan.
About 5 in 10 of the 56 wells tested in La Plata County have a test from 2020 or later.
With 27 wells tested since 2020, age matters less here than who did the testing and why.
Most La Plata 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 4 things to check in La Plata County.
- Bacteria
- Nitrate
- Fluoride
- Arsenic
What Colorado offers well owners
- Free testingCDPHE offers free PFAS testing for private wells through its PFAS Testing and Assistance Program. See the program
- Certified labsColorado's list of certified labs
- Well recordsColorado's well record search
Half the household wells here are shallower than 160 feet.
That comes from 9,885 household wells in Colorado's drilling records. Most wells of every kind here are 95 to 240 feet deep. Wells as deep as La Plata County's are usually better protected from fertilizer and bacteria at the surface, but they can pick up more of what's in the rock, like arsenic and uranium. Typical household wells here go deeper than in 32 of the 63 other Colorado counties with enough drilling records.
Look up your own well's depth in Colorado'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 La Plata County.
La Plata County is in the EPA's highest radon zone. Radon from well water adds to the radon in your indoor air, so test your air first, and your water too if the air is high. Radon guide
Between 2023 and 2025 the EPA had 1 town water system in La Plata County test for PFAS. None found any. No well in La Plata 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 La Plata County
Is well water in La Plata County safe to drink?
9 of 55 wells tested in La Plata County had fluoride over the limit, about 2 in 10. Across Colorado it's about 1 in 26. We don't rank this against other Colorado counties, because most of these tests come from one small area. Almost all of these tests come from a single agency in one small part of the county, so it may not match the rest of the county. So test your own well for fluoride before you count on it.
Can I get my well tested for free in La Plata County?
CDPHE offers free PFAS testing for private wells through its PFAS Testing and Assistance Program. If not, use a lab Colorado has certified for drinking water. Ask for bacteria, nitrate, fluoride and arsenic, the tests that matter most in La Plata County.
How deep are wells in La Plata County?
Half the household wells here are shallower than 160 feet. Typical household wells here go deeper than in 32 of the 63 other Colorado counties with enough drilling records.
How does La Plata County compare with the counties around it?
For fluoride, the share of tested wells over the limit: 1 of the 2 neighboring counties with data had a higher share than La Plata County, at 16%. Montezuma had the most, at 30%. Groundwater doesn't stop at county lines, so Montezuma's 30% is worth knowing about if you live near it.
How often should I test my well in La Plata County?
In La Plata County, 2 of 5 tested wells had coliform bacteria, so the CDC's advice matters here: 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 La Plata County numbers come from
- People on wells: 22,036 in La Plata County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 298 well water samples from 56 wells in the Water Quality Portal, run by the USGS and EPA, 2017 to 2026.
- Well depths: 9,885 Colorado drilling records for La Plata County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 6 counties that share a border with La Plata County, from the Census Bureau's county adjacency file.
- Results marked likely overstated: our own check of who tested the wells, when and where.
- PFAS: EPA tests of 1 town water systems in La Plata County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: La Plata County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Department of Public Health and Environment, checked November 1, 2026.