Manganese is worth checking in Union County wells.

1 worth checking, 5 rare out of 6 health checks.

From 37 wells tested in Union County since 2001; your own well needs its own test. How to read this

Tested wells over the limit UnionArkansas

Manganese5%2 of 37 Lead3%1 of 37 Arsenic0%0 of 37 Nitrate0%0 of 17 Fluoride0%0 of 36 Uranium0%0 of 11

GermsTest every year, whatever the chart says

Coliform bacteria0%0 of 9 E. coli0%0 of 9

StainsNot a health risk

Iron stains22%8 of 37

Not charted, because fewer than 10 wells were tested: radon (9).

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

About 1 in 17 people 2,243 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

Less likely, but the EPA still says test your air.

Radon zones: EPA map

Here's how Union County compares with Arkansas and the counties around it.

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

This one is worth checking in Union County.

Manganese2 of 37 wells over

2 of 37 wells tested here from 2001 to 2019 were over the EPA health advisory of 0.3 mg/L, against about 3 in 10 across Arkansas. Half the results were under 0.0088 mg/L, and the top 1 in 10 were 0.068 mg/L or more. That's a smaller share than in 11 of the 16 other Arkansas counties with 10 or more tested wells, leaving out 2 counties whose results are likely overstated.

Union and its neighbors

Morehouse, LA30%

Union5%

Ouachita0%

Too few tested to show: Ashley, Bradley, Calhoun, Claiborne, LA, Columbia, Union, LA.

Manganese guide

These 5 are rare in Union County.

Lead1 of 37 wells over

1 of 37 wells tested here from 2001 to 2019 was over the EPA action level of 15 µg/L, against under 1 in 100 across Arkansas. At least half the results were too low for the lab to measure, and the top 1 in 10 were 1.5 µg/L or more. That's a bigger share than in 17 of the 18 other Arkansas counties with 10 or more tested wells.

Union and its neighbors

Union3%

Ouachita0%

Too few tested to show: Ashley, Bradley, Calhoun, Claiborne, LA, Columbia, Morehouse, LA, Union, LA.

Lead guide

Arsenic0 of 37 wells over

None of the 37 wells tested here from 2001 to 2019 were over the EPA limit of 10 µg/L, against about 1 in 45 across Arkansas. Union County had none, while 4 of the 18 other Arkansas counties with 10 or more tested wells had at least one.

Union and its neighbors

Ouachita0%

Union0%

Too few tested to show: Ashley, Bradley, Calhoun, Claiborne, LA, Columbia, Morehouse, LA, Union, LA.

Arsenic guide

Nitrate0 of 17 wells over

None of the 17 wells tested here from 2004 to 2019 were over the EPA limit of 10 mg/L, against under 1 in 100 across Arkansas. Union County had none, while 1 of the 4 other Arkansas counties with 10 or more tested wells had at least one.

Nitrate guide

Fluoride0 of 36 wells over

None of the 36 wells tested here from 2001 to 2019 were over the EPA limit of 4 mg/L, against under 1 in 100 across Arkansas. Half the results were under 0.17 mg/L, and the top 1 in 10 were 0.31 mg/L or more. Union County had none, and neither did any of the 17 other Arkansas counties with 10 or more tested wells.

Union and its neighbors

Morehouse, LA0%

Ouachita0%

Union0%

Too few tested to show: Ashley, Bradley, Calhoun, Claiborne, LA, Columbia, Union, LA.

Uranium0 of 11 wells over

None of the 11 wells tested here from 2012 to 2019 were over the EPA limit of 30 µg/L, against none across Arkansas. Union County had none, and neither did any of the 5 other Arkansas counties with 10 or more tested wells.

Uranium guide

Too few Union County wells were tested for this one.

Radon in water9 wells tested

Only 9 wells here were tested from 2012 to 2014, too few to say how common it is. Across Arkansas it's none.

Radon guide

None of the 9 Union County wells tested for bacteria had it, but every well needs a yearly test.

Coliform bacteria0 of 9 wells had it

None of the 9 wells tested here from 2012 to 2014 had coliform bacteria, against about 2 in 10 across Arkansas.

Bacteria guide

E. coli0 of 9 wells had it

None of the 9 wells tested here from 2012 to 2014 had E. coli, against about 1 in 15 across Arkansas.

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

Bacteria guide

Iron reached staining levels in 8 of 37 tested wells, and it isn't a health risk.

Iron stains8 of 37 wells had it

About 2 in 10 wells tested here from 2001 to 2019 had enough iron to stain (0.3 mg/L), against about 4 in 10 across Arkansas.

Union and its neighbors

Ouachita53%

Morehouse, LA50%

Union22%

Too few tested to show: Ashley, Bradley, Calhoun, Claiborne, LA, Columbia, Union, LA.

Iron guide

Most of the 37 wells tested in Union County were last tested before 2010.

27 wells had a test in the 2000s and 18 in the 2010s.

An old result shows the water as it was then, so treat these 37 wells as a starting point and test your own.

Most Union 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 Union County.

Bacteria
Nitrate
Manganese
Arsenic

What Arkansas offers well owners

Free testingThe state Public Health Laboratory tests private well samples for total coliform and E. coli for $17 per sample, with kits from local health units. See the program
Certified labsWe didn't find an online list.
Well recordsArkansas's well record search

Half the household wells here are shallower than 248 feet.

That comes from 132 household wells in Arkansas's drilling records. Most wells of every kind here are 60 to 320 feet deep. Wells as deep as Union 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 43 of the 60 other Arkansas counties with enough drilling records.

Look up your own well's depth in Arkansas'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 Union County.

Union County is in the EPA's lowest radon zone, so radon from well water is unlikely to be a problem. Radon guide

Between 2023 and 2025 the EPA had 2 town water systems in Union County test for PFAS. None found any. No well in Union 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

Other counties in Arkansas

Fulton Sharp Faulkner Boone

All of Arkansas

Questions people ask about well water in Union County

Is well water in Union County safe to drink?

2 of 37 wells tested in Union County had manganese over the limit, about 1 in 18. Across Arkansas it's about 3 in 10. That's a smaller share than in 11 of the 16 other Arkansas counties with 10 or more tested wells, leaving out 2 counties 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 Union County?

The state Public Health Laboratory tests private well samples for total coliform and E. coli for $17 per sample, with kits from local health units. If not, use a lab Arkansas has certified for drinking water. Ask for bacteria, nitrate, manganese and arsenic, the tests that matter most in Union County.

How deep are wells in Union County?

Half the household wells here are shallower than 248 feet. Typical household wells here go deeper than in 43 of the 60 other Arkansas counties with enough drilling records.

How does Union County compare with the counties around it?

For manganese, the share of tested wells over the limit: 1 of the 2 neighboring counties with data had a higher share than Union County, at 5%. Morehouse, LA had the most, at 30%. Groundwater doesn't stop at county lines, so Morehouse, LA's 30% is worth knowing about if you live near it.

How often should I test my well in Union County?

None of the 9 wells tested for bacteria in Union 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 HealthUpdated November 8, 2026

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Where the Union County numbers come from

People on wells: 2,243 in Union County, from EPA estimates built on the 2020 Census (Murray et al.).
Lab tests: 519 well water samples from 37 wells in the Water Quality Portal, run by the USGS and EPA, 2001 to 2019.
Well depths: 132 Arkansas drilling records for Union County, gathered in the US Groundwater Well Database (Lin and others, 2024).
Neighboring counties: the 8 counties that share a border with Union County, from the Census Bureau's county adjacency file.
PFAS: EPA tests of 2 town water systems in Union County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
Radon: Union County is zone 3 on the EPA Map of Radon Zones.
State programs and links: Department of Health, checked November 1, 2026.

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