Manganese is widespread in Washington County wells.
1 widespread, 1 worth checking, 3 rare out of 5 health checks.
From 215 wells tested in Washington County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: uranium (6), radon (1).
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 5 people 54,224 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 Washington County compares with Minnesota and the counties around it.
Each result puts Washington County next to the 7 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Washington County wells.
Manganese22 of 144 wells over
Too few tested to show: Chisago, Pierce, WI, Polk, WI, St. Croix, WI.
This one is worth checking in Washington County.
Nitrate12 of 205 wells over
Too few tested to show: Ramsey.
These 3 are rare in Washington County.
Arsenic1 of 139 wells over
Too few tested to show: Pierce, WI, Polk, WI, St. Croix, WI.
Lead0 of 139 wells over
Too few tested to show: Pierce, WI, Polk, WI, St. Croix, WI.
Too few Washington County wells were tested for these 2.
Uranium6 wells tested
Radon in water1 well tested
Coliform bacteria turned up in 48 of 64 tested Washington County wells, so test for it every year.
Coliform bacteria48 of 64 wells had it
Too few tested to show: Chisago, Pierce, WI, Polk, WI, Ramsey, St. Croix, WI.
E. coli39 of 51 wells had it
Too few tested to show: Chisago, Pierce, WI, Polk, WI, Ramsey, St. Croix, WI.
E. coli means human or animal waste is getting in, so if a test of your Washington County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 44 of 143 tested wells, and it isn't a health risk.
Iron stains44 of 143 wells had it
Too few tested to show: Pierce, WI, Polk, WI, St. Croix, WI.
Washington County has 215 tested wells, and the busiest decade for testing was the 2010s.
Only 38 of the 215 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Washington 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 Washington County.
- Bacteria
- Nitrate
- Manganese
- Arsenic
What Minnesota offers well owners
- Free testingWe didn't find a free program for all of Minnesota. Minnesota's private well page
- Certified labsMinnesota's list of certified labs
- Well recordsMinnesota's well record search
- New wellsThe well contractor must collect an initial water sample after construction to test for coliform bacteria, nitrate, and arsenic before the well is used.
Half the household wells here are shallower than 180 feet.
That comes from 13,247 household wells in Minnesota's drilling records. Most wells of every kind here are 118 to 245 feet deep. Wells as deep as Washington 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 65 of the 86 other Minnesota counties with enough drilling records.
Look up your own well's depth in Minnesota'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 Washington County.
Washington 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 12 town water systems in Washington County test for PFAS. 4 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 17 ng/L of PFOA. Only 97 wells in Washington 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 Washington County
Is well water in Washington County safe to drink?
22 of 144 wells tested in Washington County had manganese over the limit, about 2 in 10. Across Minnesota it's about 2 in 10. That's a smaller share than in 28 of the 44 other Minnesota counties with 10 or more tested wells, leaving out 1 county whose results are likely overstated. So test your own well for manganese before you count on it.
Where can I get my well tested in Washington County?
Use a lab Minnesota has certified for drinking water. Minnesota's list is linked above, in the box about testing. Ask for bacteria, nitrate, manganese and arsenic, the tests that matter most in Washington County.
How deep are wells in Washington County?
Half the household wells here are shallower than 180 feet. Typical household wells here go deeper than in 65 of the 86 other Minnesota counties with enough drilling records.
How does Washington County compare with the counties around it?
For manganese, the share of tested wells over the limit: 2 of the 3 neighboring counties with data had a higher share than Washington County, at 15%. Anoka had the most, at 43%. Groundwater doesn't stop at county lines, so Anoka's 43% is worth knowing about if you live near it.
How often should I test my well in Washington County?
In Washington County, 48 of 64 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 Washington County numbers come from
- People on wells: 54,224 in Washington County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 3,324 well water samples from 215 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2025.
- Well depths: 13,247 Minnesota drilling records for Washington County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 7 counties that share a border with Washington County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 12 town water systems in Washington County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Washington County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Minnesota Department of Health, checked November 1, 2026.