Arsenic, nitrate and manganese are widespread in Otter Tail County wells.
3 widespread, 2 rare out of 5 health checks.
From 247 wells tested in Otter Tail County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: uranium (2), 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
6 in 10 people 36,922 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Middle depth: some shelter from the surface, not complete.
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 Otter Tail County compares with Minnesota and the counties around it.
Each result puts Otter Tail County next to the 7 counties that border it, on the chart's 0 to 50% scale.
These 3 are widespread in Otter Tail County wells.
Arsenic53 of 192 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Grant, Wilkin.
Nitrate48 of 239 wells over
Too few tested to show: Grant, Wilkin.
Manganese37 of 192 wells over
Too few tested to show: Clay, Grant, Wilkin.
These 2 are rare in Otter Tail County.
Lead0 of 192 wells over
Too few tested to show: Grant, Wilkin.
Fluoride0 of 188 wells over
Too few tested to show: Grant, Wilkin.
Too few Otter Tail County wells were tested for these 2.
Uranium2 wells tested
Radon in water1 well tested
Coliform bacteria turned up in 4 of 5 tested Otter Tail County wells, so test for it every year.
Coliform bacteria4 of 5 wells had it
E. coli4 of 5 wells had it
E. coli means human or animal waste is getting in, so if a test of your Otter Tail County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 155 of 192 tested wells, and it isn't a health risk.
Iron stains155 of 192 wells had it
Too few tested to show: Grant, Wilkin.
About 8 in 10 of the 247 wells tested in Otter Tail County have a test from 2020 or later.
With 207 wells tested since 2020, age matters less here than who did the testing and why.
Most Otter Tail 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 Otter Tail County.
- Bacteria
- Nitrate
- Arsenic
- Manganese
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 89 feet.
That comes from 17,243 household wells in Minnesota's drilling records. Most wells of every kind here are 67 to 130 feet deep. Wells as deep as Otter Tail 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 71 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 Otter Tail County.
Otter Tail 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 2 town water systems in Otter Tail County test for PFAS. None found any. Only 3 wells in Otter Tail 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 Otter Tail County
Is well water in Otter Tail County safe to drink?
53 of 192 wells tested in Otter Tail County had arsenic over the limit, about 3 in 10. Across Minnesota it's about 1 in 7. That's a bigger share than in 36 of the 44 other Minnesota counties with 10 or more tested wells, leaving out 5 counties whose results are likely overstated. So test your own well for arsenic before you count on it.
Where can I get my well tested in Otter Tail 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, arsenic and manganese, the tests that matter most in Otter Tail County.
How deep are wells in Otter Tail County?
Half the household wells here are shallower than 89 feet. Typical household wells here are shallower than in 71 of the 86 other Minnesota counties with enough drilling records.
How does Otter Tail County compare with the counties around it?
For arsenic, the share of tested wells over the limit: 3 of the 5 neighboring counties with data had a higher share than Otter Tail County, at 28%. Clay had the most, at 50%. Groundwater doesn't stop at county lines, so Clay's 50% is worth knowing about if you live near it.
How often should I test my well in Otter Tail County?
In Otter Tail County, 4 of 5 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 Otter Tail County numbers come from
- People on wells: 36,922 in Otter Tail County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 1,992 well water samples from 247 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2025.
- Well depths: 17,243 Minnesota drilling records for Otter Tail County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 7 counties that share a border with Otter Tail County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 2 town water systems in Otter Tail County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Otter Tail County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Minnesota Department of Health, checked November 1, 2026.