Radon and manganese are widespread in Sweetwater County wells.

2 widespread, 4 worth checking, 1 rare out of 7 health checks.

From 40 wells tested in Sweetwater County since 2001; your own well needs its own test. How to read this

Tested wells over the limit SweetwaterWyoming

Radon16%5 of 31 Manganese16%6 of 38 Uranium13%5 of 38 Arsenic13%5 of 38 Nitrate8%3 of 40 Fluoride5%2 of 38 Lead0%0 of 38

GermsTest every year, whatever the chart says

Coliform bacteria0%0 of 6 E. coli0%0 of 6

StainsNot a health risk

Iron stains26%10 of 38

Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+

Lab results: Water Quality Portal (USGS and EPA)

Show bacteria and iron

Who drinks from a well here

1 in 2 people 20,111 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)

LowMiddleHigh

Likely here. Test your home's air first.

Radon zones: EPA map

Here's how Sweetwater County compares with Wyoming and the counties around it.

Each result puts Sweetwater County next to the 8 counties that border it, on the chart's 0 to 50% scale.

These 2 are widespread in Sweetwater County wells.

Radon in water5 of 31 wells over

About 2 in 10 wells tested here from 2002 to 2017 were over 4,000 pCi/L, a level the EPA proposed, against about 1 in 18 across Wyoming. Half the results were under 670 pCi/L, and the top 1 in 10 were 4,320 pCi/L or more. That's the highest share among the 5 Wyoming counties with 10 or more tested wells.

Sweetwater and its neighbors

Sweetwater16%

Carbon2%

Too few tested to show: Daggett, UT, Fremont, Lincoln, Moffat, CO, Sublette, Summit, UT, Uinta.

Radon guide

Manganese6 of 38 wells over

About 2 in 10 wells tested here from 2002 to 2017 were over the EPA health advisory of 0.3 mg/L, against about 1 in 10 across Wyoming. Half the results were under 0.032 mg/L, and the top 1 in 10 were 0.57 mg/L or more. That's a bigger share than in 10 of the 13 other Wyoming counties with 10 or more tested wells, leaving out 2 counties whose results are likely overstated.

Sweetwater and its neighbors

Fremont55%

Sweetwater16%

Carbon12%

Summit, UT5%

Sublette0%

* Likely overstated, so we don't rank it.

Too few tested to show: Daggett, UT, Lincoln, Moffat, CO, Uinta.

Manganese guide

These 4 are worth checking in Sweetwater County.

Uranium5 of 38 wells over

About 1 in 8 wells tested here from 2002 to 2017 were over the EPA limit of 30 µg/L, against about 1 in 10 across Wyoming. Half the results were under 0.67 µg/L, and the top 1 in 10 were 40 µg/L or more. That's a bigger share than in 9 of the 13 other Wyoming counties with 10 or more tested wells, leaving out 1 county whose results are likely overstated.

Sweetwater and its neighbors

Fremont18%

Sweetwater13%

Carbon8%

Sublette0%

* Likely overstated, so we don't rank it.

Too few tested to show: Daggett, UT, Lincoln, Moffat, CO, Summit, UT, Uinta.

Uranium guide

Arsenic5 of 38 wells over

About 1 in 8 wells tested here from 2002 to 2017 were over the EPA limit of 10 µg/L, against about 1 in 18 across Wyoming. At least half the results were too low for the lab to measure, and the top 1 in 10 were 17 µg/L or more. That's a bigger share than in 13 of the 15 other Wyoming counties with 10 or more tested wells.

Sweetwater and its neighbors

Sweetwater13%

Carbon8%

Fremont0%

Sublette0%

Summit, UT0%

Too few tested to show: Daggett, UT, Lincoln, Moffat, CO, Uinta.

Arsenic guide

Nitrate3 of 40 wells over

3 of 40 wells tested here from 2001 to 2019 were over the EPA limit of 10 mg/L, against about 1 in 15 across Wyoming. At least half the results were too low for the lab to measure, and the top 1 in 10 were 40 mg/L or more. That's a bigger share than in 15 of the 19 other Wyoming counties with 10 or more tested wells, leaving out 1 county whose results are likely overstated.

Sweetwater and its neighbors

Sweetwater8%

Uinta7%

Carbon5%

Fremont0%

Sublette0%

Summit, UT0%

Too few tested to show: Daggett, UT, Lincoln, Moffat, CO.

Nitrate guide

Fluoride2 of 38 wells over

2 of 38 wells tested here from 2002 to 2017 were over the EPA limit of 4 mg/L, against about 1 in 44 across Wyoming. Half the results were under 0.47 mg/L, and the top 1 in 10 were 3.1 mg/L or more. That's a bigger share than in 13 of the 15 other Wyoming counties with 10 or more tested wells.

Sweetwater and its neighbors

Sublette15%

Sweetwater5%

Carbon2%

Fremont0%

Summit, UT0%

Too few tested to show: Daggett, UT, Lincoln, Moffat, CO, Uinta.

This one is rare in Sweetwater County.

Lead0 of 38 wells over

None of the 38 wells tested here from 2002 to 2017 were over the EPA action level of 15 µg/L, against under 1 in 100 across Wyoming. Sweetwater County had none, while 1 of the 14 other Wyoming counties with 10 or more tested wells had at least one.

Sweetwater and its neighbors

Carbon0%

Sublette0%

Summit, UT0%

Sweetwater0%

Too few tested to show: Daggett, UT, Fremont, Lincoln, Moffat, CO, Uinta.

Lead guide

None of the 6 Sweetwater County wells tested for bacteria had it, but every well needs a yearly test.

Coliform bacteria0 of 6 wells had it

None of the 6 wells tested here from 2014 to 2017 had coliform bacteria, against about 5 in 10 across Wyoming.

Bacteria guide

E. coli0 of 6 wells had it

None of the 6 wells tested here from 2014 to 2017 had E. coli, against under 1 in 50 across Wyoming.

E. coli means human or animal waste is getting in, so if a test of your Sweetwater County well finds it, boil drinking water until the well is fixed.

Bacteria guide

Iron reached staining levels in 10 of 38 tested wells, and it isn't a health risk.

Iron stains10 of 38 wells had it

About 1 in 4 wells tested here from 2002 to 2017 had enough iron to stain (0.3 mg/L), against about 2 in 10 across Wyoming.

Sweetwater and its neighbors

Carbon28%

Fremont27%

Sweetwater26%

Sublette7%

Summit, UT5%

Too few tested to show: Daggett, UT, Lincoln, Moffat, CO, Uinta.

Iron guide

Most of the 40 wells tested in Sweetwater County were last tested before 2010.

33 wells had a test in the 2000s and 9 in the 2010s.

An old result shows the water as it was then, so treat these 40 wells as a starting point and test your own.

Most Sweetwater 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 Sweetwater County.

Bacteria
Nitrate
Radon in water
Manganese
Arsenic
Uranium

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 185 feet.

That comes from 637 household wells in Wyoming's drilling records. Most wells of every kind here are 102 to 636 feet deep. Wells as deep as Sweetwater 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 16 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 Sweetwater County.

Sweetwater 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 2 town water systems in Sweetwater County test for PFAS. None found any. No well in Sweetwater 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

Next door to Sweetwater County

Fremont Summit, UT

Elsewhere in Wyoming

Laramie Park Campbell

All of Wyoming

Questions people ask about well water in Sweetwater County

Is well water in Sweetwater County safe to drink?

5 of 31 wells tested in Sweetwater County had radon in water over the limit, about 2 in 10. Across Wyoming it's about 1 in 18. That's the highest share among the 5 Wyoming counties with 10 or more tested wells. So test your own well for radon in water before you count on it.

Where can I get my well tested in Sweetwater 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, radon in water, manganese, arsenic and uranium, the tests that matter most in Sweetwater County.

How deep are wells in Sweetwater County?

Half the household wells here are shallower than 185 feet. Typical household wells here go deeper than in 16 of the 22 other Wyoming counties with enough drilling records.

How does Sweetwater County compare with the counties around it?

For radon in water, the share of tested wells over the limit: Carbon, the one neighbor with data, came in lower than Sweetwater County, at 2% against 16%. Groundwater doesn't stop at county lines, so Carbon's 2% is worth knowing about if you live near it.

How often should I test my well in Sweetwater County?

None of the 6 wells tested for bacteria in Sweetwater 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.

By the Tested Water teamData from the USGS, EPA and Department of Environmental Quality (DEQ), Know Your Well programUpdated November 8, 2026

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Where the Sweetwater County numbers come from

People on wells: 20,111 in Sweetwater County, from EPA estimates built on the 2020 Census (Murray et al.).
Lab tests: 323 well water samples from 40 wells in the Water Quality Portal, run by the USGS and EPA, 2001 to 2019.
Well depths: 637 Wyoming drilling records for Sweetwater County, gathered in the US Groundwater Well Database (Lin and others, 2024).
Neighboring counties: the 8 counties that share a border with Sweetwater County, from the Census Bureau's county adjacency file.
PFAS: EPA tests of 2 town water systems in Sweetwater County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
Radon: Sweetwater 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.

Download this county's data (CSV)How we read these numbers Report an error