Manganese and uranium have turned up often in Fremont County wells, mostly from one small area.
2 likely overstated, 3 rare out of 5 health checks.
From 18 wells tested in Fremont County since 2001; your own well needs its own test. How to read this
*Manganese: All of these tests come from the US Geological Survey in one small part of the county, so this likely overstates it.
*Uranium: All of these tests come from the US Geological Survey 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: radon (9), lead (9).
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 2 people 15,974 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Middle depth: some shelter from the surface, not complete.
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 Fremont County compares with Wyoming and the counties around it.
Each result puts Fremont County next to the 8 counties that border it, on the chart's 0 to 50% scale.
These 2 have turned up often here, mostly from one small area.
Manganese6 of 11 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Hot Springs, Natrona.
All of these tests come from the US Geological Survey in one small part of the county, so this likely overstates it.
Uranium2 of 11 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Hot Springs, Natrona, Park.
All of these tests come from the US Geological Survey in one small part of the county, so it may not match the rest of the county.
These 3 are rare in Fremont County.
Nitrate0 of 18 wells over
* Likely overstated, so we don't rank it.
Arsenic0 of 11 wells over
Too few tested to show: Hot Springs, Natrona.
Fluoride0 of 11 wells over
Too few tested to show: Hot Springs, Natrona.
Too few Fremont County wells were tested for these 2.
Radon in water9 wells tested
Lead9 wells tested
Coliform bacteria turned up in 1 of 9 tested Fremont County wells, so test for it every year.
Coliform bacteria1 of 9 wells had it
E. coli0 of 9 wells had it
E. coli means human or animal waste is getting in, so if a test of your Fremont County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 3 of 11 tested wells, and it isn't a health risk.
Iron stains3 of 11 wells had it
Too few tested to show: Hot Springs, Natrona.
Most of the 18 wells tested in Fremont County were last tested before 2010.
An old result shows the water as it was then, so treat these 18 wells as a starting point and test your own.
Most Fremont 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 Fremont County.
- Bacteria
- Nitrate
- Manganese
- Uranium
- Arsenic
What Wyoming offers well owners
- Free testingWe didn't find a free program for all of Wyoming. Wyoming's private well page
- Certified labsWyoming's list of certified labs
- Well recordsWyoming's well record search
Half the household wells here are shallower than 100 feet.
That comes from 4,167 household wells in Wyoming's drilling records. Most wells of every kind here are 52 to 325 feet deep. Wells as deep as Fremont 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 are shallower than in 13 of the 22 other Wyoming counties with enough drilling records.
Look up your own well's depth in Wyoming'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 Fremont County.
Fremont 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 3 town water systems in Fremont County test for PFAS. 1 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 7.0 ng/L of PFOS. No well in Fremont 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 Fremont County
Is well water in Fremont County safe to drink?
6 of 11 wells tested in Fremont County had manganese over the limit, about 5 in 10. Across Wyoming it's about 1 in 10. We don't rank this against other Wyoming counties, because most of these tests come from one small area. All of these tests come from the US Geological Survey in one small part of the county, so this likely overstates it. So test your own well for manganese before you count on it.
Where can I get my well tested in Fremont County?
Use a lab Wyoming has certified for drinking water. Wyoming's list is linked above, in the box about testing. Ask for bacteria, nitrate, manganese, uranium and arsenic, the tests that matter most in Fremont County.
How deep are wells in Fremont County?
Half the household wells here are shallower than 100 feet. Typical household wells here are shallower than in 13 of the 22 other Wyoming counties with enough drilling records.
How does Fremont County compare with the counties around it?
For manganese, the share of tested wells over the limit: Fremont County, at 55%, had a higher share than all 6 neighboring counties with data. Groundwater doesn't stop at county lines, so Teton's 54% is worth knowing about if you live near it.
How often should I test my well in Fremont County?
In Fremont County, 1 of 9 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 Fremont County numbers come from
- People on wells: 15,974 in Fremont County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 112 well water samples from 18 wells in the Water Quality Portal, run by the USGS and EPA, 2001 to 2020.
- Well depths: 4,167 Wyoming drilling records for Fremont County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 8 counties that share a border with Fremont 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 3 town water systems in Fremont County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Fremont County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Department of Environmental Quality (DEQ), Know Your Well program, checked November 1, 2026.