Manganese is widespread in El Dorado County wells.
1 widespread, 1 likely overstated, 1 worth checking, 4 rare out of 7 health checks.
From 115 wells tested in El Dorado County since 2000; your own well needs its own test. How to read this
*Radon: All of these tests come from the US Geological Survey between 2007 and 2008 in one small part of the county, so this likely overstates it.
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 53,523 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 El Dorado County compares with California and the counties around it.
Each result puts El Dorado County next to the 5 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in El Dorado County wells.
Manganese13 of 68 wells over
Too few tested to show: Alpine.
This one has turned up often here, mostly in older study samples.
Radon in water6 of 18 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Alpine, Amador, Douglas, NV.
All of these tests come from the US Geological Survey between 2007 and 2008 in one small part of the county, so this likely overstates it.
This one is worth checking in El Dorado County.
Arsenic5 of 68 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Alpine.
These 4 are rare in El Dorado County.
Uranium2 of 68 wells over
Too few tested to show: Alpine.
Nitrate2 of 115 wells over
Too few tested to show: Alpine.
Fluoride0 of 69 wells over
Too few tested to show: Alpine.
Lead0 of 45 wells over
Too few tested to show: Alpine.
Coliform bacteria turned up in 10 of 31 tested El Dorado County wells, so test for it every year.
Coliform bacteria10 of 31 wells had it
Too few tested to show: Alpine, Douglas, NV.
E. coli2 of 31 wells had it
Too few tested to show: Alpine, Douglas, NV.
E. coli means human or animal waste is getting in, so if a test of your El Dorado County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 19 of 68 tested wells, and it isn't a health risk.
Iron stains19 of 68 wells had it
Too few tested to show: Alpine.
Most of the 115 wells tested in El Dorado County were last tested before 2010.
An old result shows the water as it was then, so treat these 115 wells as a starting point and test your own.
Most El Dorado 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 El Dorado County.
- Bacteria
- Nitrate
- Radon in water
- 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 250 feet.
That comes from 14,790 household wells in California's drilling records. Most wells of every kind here are 150 to 400 feet deep. Wells as deep as El Dorado 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 40 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 El Dorado County.
El Dorado 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 6 town water systems in El Dorado County test for PFAS. 2 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 6.1 ng/L of PFOA. Only 8 wells in El Dorado 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 El Dorado County
Is well water in El Dorado County safe to drink?
6 of 18 wells tested in El Dorado County had radon in water over the limit, about 1 in 3. Across California it's about 1 in 30. We don't rank this against other California counties, because most of these tests are old study samples. All of these tests come from the US Geological Survey between 2007 and 2008 in one small part of the county, so this likely overstates it. So test your own well for radon in water before you count on it.
Can I get my well tested for free in El Dorado 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, radon in water, manganese and arsenic, the tests that matter most in El Dorado County.
How deep are wells in El Dorado County?
Half the household wells here are shallower than 250 feet. Typical household wells here go deeper than in 40 of the 56 other California counties with enough drilling records.
How does El Dorado County compare with the counties around it?
For radon in water, the share of tested wells over the limit: El Dorado County, at 33%, had a higher share than all 2 neighboring counties with data. Groundwater doesn't stop at county lines, so Placer's 0% is worth knowing about if you live near it.
How often should I test my well in El Dorado County?
In El Dorado County, 10 of 31 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 El Dorado County numbers come from
- People on wells: 53,523 in El Dorado County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 1,846 well water samples from 115 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2022.
- Well depths: 14,790 California drilling records for El Dorado County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 5 counties that share a border with El Dorado County, from the Census Bureau's county adjacency file.
- Results marked likely overstated: our own check of who tested the wells, when and where.
- PFAS: EPA tests of 6 town water systems in El Dorado County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: El Dorado County is zone 2 on the EPA Map of Radon Zones.
- State programs and links: State Water Resources Control Board, checked November 1, 2026.