Manganese is worth checking in Butte County wells.
1 worth checking, 6 rare out of 7 health checks.
From 48 wells tested in Butte County since 2006; 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
1 in 4 people 47,277 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)
Less likely, but the EPA still says test your air.
Radon zones: EPA map
Here's how Butte County compares with California and the counties around it.
Each result puts Butte County next to the 6 counties that border it, on the chart's 0 to 50% scale.
This one is worth checking in Butte County.
Manganese5 of 45 wells over
Too few tested to show: Colusa, Plumas.
These 6 are rare in Butte County.
Arsenic1 of 46 wells over
Too few tested to show: Colusa, Plumas.
Nitrate0 of 48 wells over
Too few tested to show: Colusa, Plumas.
Uranium0 of 46 wells over
Too few tested to show: Colusa, Plumas.
Radon in water0 of 13 wells over
Fluoride0 of 48 wells over
Too few tested to show: Colusa, Plumas.
Lead0 of 39 wells over
Too few tested to show: Colusa, Plumas, Yuba.
Coliform bacteria turned up in 6 of 36 tested Butte County wells, so test for it every year.
Coliform bacteria6 of 36 wells had it
Too few tested to show: Colusa, Glenn, Plumas.
E. coli0 of 36 wells had it
Too few tested to show: Colusa, Glenn, Plumas.
E. coli means human or animal waste is getting in, so if a test of your Butte County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 5 of 47 tested wells, and it isn't a health risk.
Iron stains5 of 47 wells had it
Too few tested to show: Colusa, Plumas.
About 6 in 10 of the 48 wells tested in Butte County have a test from 2020 or later.
With 29 wells tested since 2020, age matters less here than who did the testing and why.
Most Butte 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 Butte County.
- Bacteria
- Nitrate
- Manganese
- Arsenic
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 150 feet.
That comes from 13,432 household wells in California's drilling records. Most wells of every kind here are 108 to 290 feet deep. Wells as deep as Butte 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 45 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 Butte County.
Butte 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 7 town water systems in Butte County test for PFAS. 3 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 22 ng/L of PFOS. Only 29 wells in Butte 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 Butte County
Is well water in Butte County safe to drink?
5 of 45 wells tested in Butte County had manganese over the limit, about 1 in 9. Across California it's about 1 in 12. That's a bigger share than in 25 of the 45 other California counties with 10 or more tested wells. So test your own well for manganese before you count on it.
Can I get my well tested for free in Butte 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, manganese and arsenic, the tests that matter most in Butte County.
How deep are wells in Butte County?
Half the household wells here are shallower than 150 feet. Typical household wells here are shallower than in 45 of the 56 other California counties with enough drilling records.
How does Butte County compare with the counties around it?
For manganese, the share of tested wells over the limit: 1 of the 4 neighboring counties with data had a higher share than Butte County, at 11%. Sutter had the most, at 32%. Groundwater doesn't stop at county lines, so Sutter's 32% is worth knowing about if you live near it.
How often should I test my well in Butte County?
In Butte County, 6 of 36 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 Butte County numbers come from
- People on wells: 47,277 in Butte County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 512 well water samples from 48 wells in the Water Quality Portal, run by the USGS and EPA, 2006 to 2021.
- Well depths: 13,432 California drilling records for Butte County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 6 counties that share a border with Butte County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 7 town water systems in Butte County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Butte County is zone 3 on the EPA Map of Radon Zones.
- State programs and links: State Water Resources Control Board, checked November 1, 2026.