Arsenic is widespread in Kern County wells.
1 widespread, 3 worth checking, 3 rare out of 7 health checks.
From 208 wells tested in Kern County since 2001; your own well needs its own test. How to read this
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
About 1 in 17 people 53,705 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)
Possible here. A home air test is inexpensive.
Radon zones: EPA map
Here's how Kern County compares with California and the counties around it.
Each result puts Kern County next to the 8 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Kern County wells.
Arsenic52 of 207 wells over
These 3 are worth checking in Kern County.
Uranium21 of 179 wells over
Manganese19 of 199 wells over
Nitrate13 of 185 wells over
These 3 are rare in Kern County.
Radon in water1 of 42 wells over
Too few tested to show: Inyo, Kings, Ventura.
Fluoride0 of 195 wells over
Lead0 of 171 wells over
Coliform bacteria turned up in 5 of 47 tested Kern County wells, so test for it every year.
Coliform bacteria5 of 47 wells had it
Too few tested to show: Inyo, San Luis Obispo, Ventura.
E. coli1 of 47 wells had it
Too few tested to show: Inyo, San Luis Obispo, Ventura.
E. coli means human or animal waste is getting in, so if a test of your Kern County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 20 of 195 tested wells, and it isn't a health risk.
Iron stains20 of 195 wells had it
About 4 in 10 of the 208 wells tested in Kern County have a test from 2020 or later.
With 83 wells tested since 2020, age matters less here than who did the testing and why.
Most Kern 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 Kern County.
- Bacteria
- Nitrate
- Arsenic
- Uranium
- Manganese
What California offers well owners
- Free testingThe State and Regional Water Boards fund or regulate 11 domestic well programs that offer free well testing in their service areas. See the program
- Certified labsCalifornia's list of certified labs
- Well recordsCalifornia's well record search
Half the household wells here are shallower than 303 feet.
That comes from 8,147 household wells in California's drilling records. Most wells of every kind here are 250 to 602 feet deep. Wells as deep as Kern 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 50 of the 56 other California counties with enough drilling records.
Look up your own well's depth in California'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 Kern County.
Kern County is in the EPA's middle radon zone. An indoor air test is cheap and tells you whether to look at your water. Radon guide
Between 2023 and 2025 the EPA had 28 town water systems in Kern County test for PFAS. 5 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 19 ng/L of PFOA. Only 48 wells in Kern County have 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 Kern County
Is well water in Kern County safe to drink?
52 of 207 wells tested in Kern County had arsenic over the limit, about 1 in 4. Across California it's about 1 in 7. That's a bigger share than in 41 of the 46 other California counties with 10 or more tested wells. So test your own well for arsenic before you count on it.
Can I get my well tested for free in Kern County?
The State and Regional Water Boards fund or regulate 11 domestic well programs that offer free well testing in their service areas. If not, use a lab California has certified for drinking water. Ask for bacteria, nitrate, arsenic, uranium and manganese, the tests that matter most in Kern County.
How deep are wells in Kern County?
Half the household wells here are shallower than 303 feet. Typical household wells here go deeper than in 50 of the 56 other California counties with enough drilling records.
How does Kern County compare with the counties around it?
For arsenic, the share of tested wells over the limit: 1 of the 8 neighboring counties with data had a higher share than Kern County, at 25%. Kings had the most, at 45%. Groundwater doesn't stop at county lines, so Kings's 45% is worth knowing about if you live near it.
How often should I test my well in Kern County?
In Kern County, 5 of 47 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 Kern County numbers come from
- People on wells: 53,705 in Kern County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 2,244 well water samples from 208 wells in the Water Quality Portal, run by the USGS and EPA, 2001 to 2023.
- Well depths: 8,147 California drilling records for Kern County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 8 counties that share a border with Kern County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 28 town water systems in Kern County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Kern County is zone 2 on the EPA Map of Radon Zones.
- State programs and links: State Water Resources Control Board, checked November 1, 2026.