Health problems are rare in tested Corson County wells.
All 6 health checks came back rare here.
From 11 wells tested in Corson County since 2015; your own well needs its own test. How to read this
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
8 in 10 people 3,011 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 Corson County compares with South Dakota and the counties around it.
Each result puts Corson County next to the 8 counties that border it, on the chart's 0 to 50% scale.
All 6 health checks are rare in Corson County.
Manganese0 of 11 wells over
Too few tested to show: Adams, ND, Campbell, Dewey, Emmons, ND, Perkins, Walworth, Ziebach.
Arsenic0 of 11 wells over
Too few tested to show: Adams, ND, Campbell, Dewey, Emmons, ND, Perkins, Walworth, Ziebach.
Uranium0 of 11 wells over
Nitrate0 of 11 wells over
Lead0 of 11 wells over
Too few tested to show: Adams, ND, Campbell, Dewey, Emmons, ND, Perkins, Walworth, Ziebach.
Fluoride0 of 11 wells over
Too few tested to show: Adams, ND, Campbell, Dewey, Emmons, ND, Perkins, Walworth, Ziebach.
Every well needs a bacteria test every year.
No bacteria tests from Corson County wells are in the public data. Test every year anyway.
Iron reached staining levels in 1 of 11 tested wells, and it isn't a health risk.
Iron stains1 of 11 wells had it
Too few tested to show: Adams, ND, Campbell, Dewey, Emmons, ND, Perkins, Walworth, Ziebach.
Corson County has 11 tested wells, and the busiest decade for testing was the 2010s.
None of the 11 wells has a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Corson 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 3 things to check in Corson County.
- Bacteria
- Nitrate
- Arsenic
What South Dakota offers well owners
- Free testingDANR points well owners to a free private well assessment, including water testing, offered by Midwest Assistance Program. See the program
- Certified labsSouth Dakota's list of certified labs
- Well recordsSouth Dakota's well record search
Half the household wells here are shallower than 170 feet.
That comes from 542 household wells in South Dakota's drilling records. Most wells of every kind here are 90 to 221 feet deep. Wells as deep as Corson 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 36 of the 65 other South Dakota counties with enough drilling records.
Look up your own well's depth in South Dakota'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 Corson County.
Corson 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
Radon zones: EPA Map of Radon Zones
Questions people ask about well water in Corson County
Is well water in Corson County safe to drink?
Most tested wells in Corson County came in under the limits. Of 6 health checks with enough tests, nitrate came closest, at 0 of 11 wells over. Every well is different, so test yours for bacteria, nitrate and arsenic.
Can I get my well tested for free in Corson County?
DANR points well owners to a free private well assessment, including water testing, offered by Midwest Assistance Program. If not, use a lab South Dakota has certified for drinking water. Ask for bacteria, nitrate and arsenic, the tests that matter most in Corson County.
How deep are wells in Corson County?
Half the household wells here are shallower than 170 feet. Typical household wells here are shallower than in 36 of the 65 other South Dakota counties with enough drilling records.
How does Corson County compare with the counties around it?
For manganese, the share of tested wells over the limit: Sioux, ND, the one neighbor with data, came in higher than Corson County, at 5% against 0%. Groundwater doesn't stop at county lines, so Sioux, ND's 5% is worth knowing about if you live near it.
How often should I test my well in Corson County?
Corson County has no public bacteria results for wells, so follow the CDC's advice: 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 Corson County numbers come from
- People on wells: 3,011 in Corson County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 84 well water samples from 11 wells in the Water Quality Portal, run by the USGS and EPA, 2015 to 2018.
- Well depths: 542 South Dakota drilling records for Corson County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 8 counties that share a border with Corson County, from the Census Bureau's county adjacency file.
- Radon: Corson County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Department of Agriculture and Natural Resources (DANR), checked November 1, 2026.