Only 2 health checks had enough tested wells in Boone County, and both came back rare.
Both health checks came back rare here.
From 14 wells tested in Boone County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: nitrate (6), arsenic (2), uranium (2), radon (2), lead (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 4 people 14,978 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 Boone County compares with Illinois and the counties around it.
Each result puts Boone County next to the 6 counties that border it, on the chart's 0 to 50% scale.
Both health checks are rare in Boone County.
Manganese0 of 11 wells over
Too few tested to show: DeKalb, Ogle, Rock, WI, Walworth, WI, Winnebago.
Fluoride0 of 11 wells over
Too few tested to show: DeKalb, Ogle, Rock, WI, Walworth, WI, Winnebago.
Too few Boone County wells were tested for these 5.
Nitrate6 wells tested
Arsenic2 wells tested
Uranium2 wells tested
Radon in water2 wells tested
Lead2 wells tested
Coliform bacteria turned up in 1 of 1 tested Boone County wells, so test for it every year.
Coliform bacteria1 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 Boone County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 6 of 11 tested wells, and it isn't a health risk.
Iron stains6 of 11 wells had it
Too few tested to show: DeKalb, Ogle, Rock, WI, Walworth, WI, Winnebago.
Most of the 14 wells tested in Boone County were last tested before 2010.
An old result shows the water as it was then, so treat these 14 wells as a starting point and test your own.
Most Boone 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 3 things to check in Boone County.
- Bacteria
- Nitrate
- Arsenic
What Illinois offers well owners
- Free testingWe didn't find a free program for all of Illinois. Illinois's private well page
- Certified labsIllinois's list of certified labs
- Well recordsIllinois's well record search
Half the household wells here are shallower than 167 feet.
That comes from 4,022 household wells in Illinois's drilling records. Most wells of every kind here are 105 to 225 feet deep. Wells as deep as Boone 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 68 of the 101 other Illinois counties with enough drilling records.
Look up your own well's depth in Illinois'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 Boone County.
Boone 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 Boone County test for PFAS. 1 found some PFAS, all below the new limits. No well in Boone 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 Boone County
Is well water in Boone County safe to drink?
Most tested wells in Boone County came in under the limits. Of 2 health checks with enough tests, manganese came closest, at 0 of 11 wells over. Every well is different, so test yours for bacteria, nitrate and arsenic.
Where can I get my well tested in Boone County?
Use a lab Illinois has certified for drinking water. Illinois's list is linked above, in the box about testing. Ask for bacteria, nitrate and arsenic, the tests that matter most in Boone County.
How deep are wells in Boone County?
Half the household wells here are shallower than 167 feet. Typical household wells here go deeper than in 68 of the 101 other Illinois counties with enough drilling records.
How does Boone County compare with the counties around it?
For manganese, the share of tested wells over the limit: McHenry, the one neighbor with data, came in higher than Boone County, at 6% against 0%. Groundwater doesn't stop at county lines, so McHenry's 6% is worth knowing about if you live near it.
How often should I test my well in Boone County?
In Boone County, 1 of 1 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 Boone County numbers come from
- People on wells: 14,978 in Boone County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 67 well water samples from 14 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2017.
- Well depths: 4,022 Illinois drilling records for Boone County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 6 counties that share a border with Boone County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 3 town water systems in Boone County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Boone County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Illinois Department of Public Health, checked November 1, 2026.