Uranium is widespread in Cumberland County wells.
1 widespread, 1 likely overstated, 2 worth checking, 2 rare out of 6 health checks.
From 55 wells tested in Cumberland County since 2000; your own well needs its own test. How to read this
*Arsenic: All of these tests come from the US Geological Survey, mostly before 2013, so this likely overstates it.
Not charted, because fewer than 10 wells were tested: radon (4).
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 3 people 88,596 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 Cumberland County compares with Maine and the counties around it.
Each result puts Cumberland County next to the 4 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Cumberland County wells.
Uranium5 of 22 wells over
Too few tested to show: Oxford, Sagadahoc.
This one has turned up often here, mostly in older study samples.
Arsenic18 of 44 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Oxford, Sagadahoc.
All of these tests come from the US Geological Survey, mostly before 2013, so this likely overstates it. Household tests at Maine's state lab from 2005 to 2009 found about 2 in 10 Cumberland County wells over the limit.
These 2 are worth checking in Cumberland County.
Manganese3 of 25 wells over
Too few tested to show: Oxford, Sagadahoc.
Nitrate5 of 52 wells over
Too few tested to show: Oxford, Sagadahoc.
These 2 are rare in Cumberland County.
Lead0 of 21 wells over
Too few tested to show: Oxford, Sagadahoc.
Fluoride0 of 49 wells over
Too few tested to show: Oxford, Sagadahoc.
Too few Cumberland County wells were tested for this one.
Radon in water4 wells tested
Coliform bacteria turned up in 1 of 4 tested Cumberland County wells, so test for it every year.
Coliform bacteria1 of 4 wells had it
E. coli0 of 4 wells had it
E. coli means human or animal waste is getting in, so if a test of your Cumberland County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 2 of 25 tested wells, and it isn't a health risk.
Iron stains2 of 25 wells had it
Too few tested to show: Oxford, Sagadahoc.
Cumberland County has 55 tested wells, and the busiest decade for testing was the 2000s.
None of the 55 wells has a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Cumberland 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 Cumberland County.
- Bacteria
- Nitrate
- Arsenic
- Uranium
- Manganese
What Maine offers well owners
- Free testingWe didn't find a free program for all of Maine. Maine's private well page
- Certified labsMaine's list of certified labs
- Well recordsMaine's well record search
Half the household wells here are shallower than 264 feet.
That comes from 10,672 household wells in Maine's drilling records. Most wells of every kind here are 160 to 400 feet deep. Wells as deep as Cumberland 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 12 of the 15 other Maine counties with enough drilling records.
Look up your own well's depth in Maine'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 Cumberland County.
Cumberland 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 Cumberland County test for PFAS. 1 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 9.2 ng/L of PFOA. Only 1 well in Cumberland 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 Cumberland County
Is well water in Cumberland County safe to drink?
18 of 44 wells tested in Cumberland County had arsenic over the limit, about 4 in 10. Across Maine it's about 1 in 10. We don't rank this against other Maine counties, because most of these tests are old study samples. All of these tests come from the US Geological Survey, mostly before 2013, so this likely overstates it. Household tests at Maine's state lab from 2005 to 2009 found about 2 in 10 Cumberland County wells over the limit. So test your own well for arsenic before you count on it.
Where can I get my well tested in Cumberland County?
Use a lab Maine has certified for drinking water. Maine's list is linked above, in the box about testing. Ask for bacteria, nitrate, arsenic, uranium and manganese, the tests that matter most in Cumberland County.
How deep are wells in Cumberland County?
Half the household wells here are shallower than 264 feet. Typical household wells here go deeper than in 12 of the 15 other Maine counties with enough drilling records.
How does Cumberland County compare with the counties around it?
For arsenic, the share of tested wells over the limit: 2 of the 2 neighboring counties with data had a higher share than Cumberland County, at 41%. York had the most, at 62%. Groundwater doesn't stop at county lines, so York's 62% is worth knowing about if you live near it.
How often should I test my well in Cumberland County?
In Cumberland County, 1 of 4 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 Cumberland County numbers come from
- People on wells: 88,596 in Cumberland County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 678 well water samples from 55 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2019.
- Well depths: 10,672 Maine drilling records for Cumberland County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 4 counties that share a border with Cumberland County, from the Census Bureau's county adjacency file.
- Arsenic for comparison: Loiselle and others (2001), cited in USGS SIR 2010-5199.
- Results marked likely overstated: our own check of who tested the wells, when and where.
- PFAS: EPA tests of 3 town water systems in Cumberland County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Cumberland County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Maine CDC (Department of Health and Human Services), Drinking Water Program, checked November 1, 2026.