Manganese is widespread in Middlesex County wells.
1 widespread, 1 worth checking, 4 rare out of 6 health checks.
From 27 wells tested in Middlesex County since 2001; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: radon (3).
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 18 people 92,311 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 Middlesex County compares with Massachusetts and the counties around it.
Each result puts Middlesex County next to the 5 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Middlesex County wells.
Manganese4 of 12 wells over
Too few tested to show: Essex, Norfolk, Suffolk.
This one is worth checking in Middlesex County.
Arsenic1 of 12 wells over
Too few tested to show: Essex, Norfolk, Suffolk.
These 4 are rare in Middlesex County.
Nitrate0 of 27 wells over
Too few tested to show: Essex, Norfolk, Suffolk, Worcester.
Uranium0 of 12 wells over
Too few tested to show: Essex, Norfolk, Suffolk.
Lead0 of 27 wells over
Too few tested to show: Essex, Norfolk, Suffolk.
Fluoride0 of 12 wells over
Too few tested to show: Essex, Norfolk, Suffolk.
Too few Middlesex County wells were tested for this one.
Radon in water3 wells tested
None of the 4 Middlesex County wells tested for bacteria had it, but every well needs a yearly test.
Coliform bacteria0 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 Middlesex County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 3 of 12 tested wells, and it isn't a health risk.
Iron stains3 of 12 wells had it
Too few tested to show: Essex, Norfolk, Suffolk.
Most of the 27 wells tested in Middlesex County were last tested before 2010.
An old result shows the water as it was then, so treat these 27 wells as a starting point and test your own.
Most Middlesex 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 Middlesex County.
- Bacteria
- Nitrate
- Manganese
- Arsenic
What Massachusetts offers well owners
- Free testingWe didn't find a free program for all of Massachusetts. Massachusetts's private well page
- Certified labsMassachusetts's list of certified labs
- Well recordsMassachusetts's well record search
Half the household wells here are shallower than 320 feet.
That comes from 17,703 household wells in Massachusetts's drilling records. Most wells of every kind here are 220 to 500 feet deep. Wells as deep as Middlesex 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 10 of the 13 other Massachusetts counties with enough drilling records.
Look up your own well's depth in Massachusetts'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 Middlesex County.
Middlesex 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 54 town water systems in Middlesex County test for PFAS. 24 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 37 ng/L of PFOS. Only 9 wells in Middlesex 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 Middlesex County
Is well water in Middlesex County safe to drink?
4 of 12 wells tested in Middlesex County had manganese over the limit, about 1 in 3. Across Massachusetts it's about 2 in 10. That's the highest share among the 5 Massachusetts counties with 10 or more tested wells. So test your own well for manganese before you count on it.
Where can I get my well tested in Middlesex County?
Use a lab Massachusetts has certified for drinking water. Massachusetts's list is linked above, in the box about testing. Ask for bacteria, nitrate, manganese and arsenic, the tests that matter most in Middlesex County.
How deep are wells in Middlesex County?
Half the household wells here are shallower than 320 feet. Typical household wells here go deeper than in 10 of the 13 other Massachusetts counties with enough drilling records.
How does Middlesex County compare with the counties around it?
For manganese, the share of tested wells over the limit: Middlesex County, at 33%, had a higher share than all 2 neighboring counties with data. Groundwater doesn't stop at county lines, so Worcester's 9% is worth knowing about if you live near it.
How often should I test my well in Middlesex County?
None of the 4 wells tested for bacteria in Middlesex County had it, but the CDC still says to 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 Middlesex County numbers come from
- People on wells: 92,311 in Middlesex County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 333 well water samples from 27 wells in the Water Quality Portal, run by the USGS and EPA, 2001 to 2019.
- Well depths: 17,703 Massachusetts drilling records for Middlesex County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 5 counties that share a border with Middlesex County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 54 town water systems in Middlesex County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Middlesex County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Massachusetts Department of Environmental Protection (MassDEP), checked November 1, 2026.