Manganese, arsenic and fluoride are widespread in Williams County wells.
3 widespread, 1 rare out of 4 health checks.
From 13 wells tested in Williams County since 2003; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: nitrate (6), uranium (7), 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 5,920 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 Williams County compares with North Dakota and the counties around it.
Each result puts Williams County next to the 7 counties that border it, on the chart's 0 to 50% scale.
These 3 are widespread in Williams County wells.
Manganese7 of 13 wells over
Too few tested to show: Burke, Divide, Sheridan, MT.
Arsenic3 of 12 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Burke, Divide, Sheridan, MT.
Fluoride2 of 13 wells over
Too few tested to show: Burke, Divide.
This one is rare in Williams County.
Lead0 of 13 wells over
Too few tested to show: Burke, Divide.
Too few Williams County wells were tested for these 3.
Nitrate6 wells tested
Uranium7 wells tested
Radon in water1 well tested
None of the 1 Williams 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 Williams County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 8 of 13 tested wells, and it isn't a health risk.
Iron stains8 of 13 wells had it
Too few tested to show: Burke, Divide.
Williams County has 13 tested wells, and the busiest decade for testing was the 2010s.
Only 1 of the 13 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Williams 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 Williams County.
- Bacteria
- Nitrate
- Manganese
- Arsenic
- Fluoride
What North Dakota offers well owners
- Free testingWe didn't find a free program for all of North Dakota. North Dakota's private well page
- Certified labsNorth Dakota's list of certified labs
- Well recordsNorth Dakota's well record search
Half the household wells here are shallower than 91 feet.
That comes from 229 household wells in North Dakota's drilling records. Most wells of every kind here are 68 to 160 feet deep. Wells as deep as Williams 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 20 of the 24 other North Dakota counties with enough drilling records.
Look up your own well's depth in North Dakota'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 Williams County.
Williams 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 Williams County test for PFAS. 1 found some PFAS, all below the new limits. No well in Williams 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 Williams County
Is well water in Williams County safe to drink?
7 of 13 wells tested in Williams County had manganese over the limit, about 5 in 10. Across North Dakota it's about 4 in 10. That's a bigger share than in 8 of the 9 other North Dakota 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.
Where can I get my well tested in Williams County?
Use a lab North Dakota has certified for drinking water. North Dakota's list is linked above, in the box about testing. Ask for bacteria, nitrate, manganese, arsenic and fluoride, the tests that matter most in Williams County.
How deep are wells in Williams County?
Half the household wells here are shallower than 91 feet. Typical household wells here are shallower than in 20 of the 24 other North Dakota counties with enough drilling records.
How does Williams County compare with the counties around it?
For manganese, the share of tested wells over the limit: Williams County, at 54%, had a higher share than all 4 neighboring counties with data. Groundwater doesn't stop at county lines, so Richland, MT's 44% is worth knowing about if you live near it.
How often should I test my well in Williams County?
None of the 1 wells tested for bacteria in Williams 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 Williams County numbers come from
- People on wells: 5,920 in Williams County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 110 well water samples from 13 wells in the Water Quality Portal, run by the USGS and EPA, 2003 to 2020.
- Well depths: 229 North Dakota drilling records for Williams County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 7 counties that share a border with Williams County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 3 town water systems in Williams County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Williams County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Department of Environmental Quality, checked November 1, 2026.