Well water in South Dakota
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Testing recommended
tested well samples in South Dakota exceeded the EPA limit for radium (226 + 228) (5 pCi/L), based on public data from USGS Water Quality Portal.
94,554 test results across 15 contaminants from at least 22,285 wells, 1893 to 2026; chloride has the most at 28,270. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 121,341 people in South Dakota get their drinking water from a private well, per USGS 2015 county water use.
Separately, the USGS national arsenic model estimates that <1% of the 121,341 people on private wells in South Dakota draw water above 10 ug/L (the model's range is <1% to 1%), from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside South Dakota. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Above limit | Samples | Detected | Median | Highest | Limit |
|---|---|---|---|---|---|---|
| Radium (226 + 228) 1978 to 2014 | 348 | 84% | 0.485 | 66 | 5 pCi/L EPA limit | |
| Nitrate 1923 to 2026 | 9,684 | 81% | 0.343 | 7,000 | 10 mg/L EPA limit | |
| Uranium 1954 to 2024 | 2,933 | 78% | 1.2 | 76,000 | 30 ug/L EPA limit | |
| Arsenic 1953 to 2024 | 4,157 | 47% | 0 | 2,700 | 10 ug/L EPA limit | |
| Fluoride 1923 to 2024 | 7,234 | 98% | 0.49 | 9,520 | 4 mg/L EPA limit | |
| E. coli 1995 to 2014 | 38 | 3% | 0 | 1 | 0 MPN/100mL EPA limit | |
| Lead 1953 to 2024 | 1,321 | 45% | 0 | 3,800 | 15 ug/L EPA limit | |
| Copper 1953 to 2024 | 3,449 | 37% | 0 | 6.7 | 1.3 mg/L EPA limit | |
| Chloride 1893 to 2024 | no limit | 28,270 | 96% | 40 | 122,000 | 250 mg/L nuisance level |
| Sodium 1895 to 2024 | no limit | 14,931 | 100% | 111 | 74,700 | 20 mg/L health guideline |
| Iron 1895 to 2024 | no limit | 12,596 | 83% | 160 | 90,000,000 | 300 ug/L nuisance level |
| Manganese 1936 to 2024 | no limit | 9,535 | 83% | 100 | 500,000 | 300 ug/L health guideline |
| Radon 1988 to 2014 | no limit | 54 | 81% | 280 | 6,600 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: PFOS (2), PFOA (2).
Over time
Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.
| Contaminant | before 2000 | 2000s | 2010s | 2020s |
|---|---|---|---|---|
| Nitrate | 7%9,164 samples | 16%314 samples | 5%139 samples | 9%67 samples |
| Fluoride | 3%7,102 samples | 0%62 samples | 0%40 samples | 0%30 samples |
| Arsenic | 4%3,890 samples | 22%120 samples | 37%115 samples | 22%32 samples |
| Copper | <1%3,332 samples | n/a | 0%76 samples | 0%32 samples |
| Uranium | 6%2,875 samples | n/a | 0%25 samples | 19%26 samples |
| Lead | 1%1,165 samples | 1%81 samples | 0%47 samples | 0%28 samples |
Arsenic above the limit in South Dakota fell from 37% of 115 samples in the 2010s to 22% of 32 in the 2020s.
Uranium above the limit in South Dakota rose from 0% of 25 samples in the 2010s to 19% of 26 in the 2020s.
Nitrate, fluoride, copper, lead have held within a few points between the two most recent periods with enough samples.
What this means
The contaminants most often above their limit here are radium (226 + 228) (9% of 348 samples), nitrate (7% of 9,684 samples), and uranium (6% of 2,933 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.
Chloride, Iron, and Manganese are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in South Dakota
- 1Radium (226 + 228)9% of 348 local samples were above the limit.
- 2Nitrate7% of 9,684 local samples were above the limit.
- 3Uranium6% of 2,933 local samples were above the limit.
- 4Arsenic6% of 4,157 local samples were above the limit.
- 5Fluoride3% of 7,234 local samples were above the limit.
- 6E. coli3% of 38 local samples were above the limit.
- 7Lead<1% of 1,321 local samples were above the limit.
- 8Volatile organic compounds (VOCs)16,166 reported spills and releases on record locally.
Test your South Dakota well for radium (226 + 228), nitrate and uranium
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
Where to get a well tested in South Dakota: certified labs, state programs and prices.
Already have results back? Get your lab report read against the South Dakota numbers, $29. Every line explained, ranked by what matters, with the fix for each.
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Send me the South Dakota report
The numbers above, which tests to order and where, and the treatment that fits the local profile, in one email.
Wells in South Dakota
37,991 domestic wells in South Dakota are on record with the state since 1970. the typical well is 235 feet deep (one in ten goes past 1,140 feet).
Find your own well's report
The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.
- Open DANR well completion reports and choose Water Well.
- It lists depth, aquifer, static water level and the driller.
South Dakota has required reports since 1986.
The rock under South Dakota
Not a principal aquifer
The USGS map places this area outside any principal aquifer, which usually means wells here draw from fractured bedrock or thin local deposits rather than a large regional aquifer. Bedrock wells of that kind are where arsenic, radon and uranium turn up, and yields vary from well to well.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the state centroid. A single well can sit in a different unit, especially near a boundary.
Official help in South Dakota
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
- Test a Private Well, South Dakota Department of Health
- Drinking Water Program - Laboratory Certification, South Dakota DANR
Contamination sources on record in South Dakota
South Dakota DANR tank facilities and spills records 16,166 reported spills and releases in South Dakota, among 21,051 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.
- 16,166
- reported spills and releasesMost spills are fuel; a few are solvents or chemicals that reach the water table.
- 3,228
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 1,657
- other solid waste facilities
Treatment that fits the local profile
Radium (226 + 228)
Water softener (cation exchange); Point-of-use reverse osmosis
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Uranium
Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
Systems we would look at first
Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For radium (226 + 228)
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For nitrate
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
For uranium
Whole-house arsenic and uranium filter
whole-house, at the point of entry, about $2,500
Adsorptive iron-based media; sized to your well yield.
For E. coli
UV disinfection system
whole-house, at the point of entry, about $900
Fix the well cap and casing first; UV keeps bacteria from returning.
For E. coli
Aquasana Rhino Well Water with UV
whole-house, at the point of entry, about $2,871
Whole-house system built for wells: sediment pre-filter, KDF and carbon, and a UV lamp rated to kill 99.99% of bacteria and viruses. It does not remove arsenic, nitrate, uranium or radon.
Common questions
How deep are wells in South Dakota?
The typical domestic well in South Dakota is 235 feet deep, based on 37,991 wells reported to the state since 1970. One in ten is deeper than 1,140 feet.
Is there arsenic in well water in South Dakota?
Arsenic was detected in 47% of 4,157 public well samples in South Dakota, and 6% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How high is radon in well water in South Dakota?
The median radon level across 54 public samples in South Dakota was 280 pCi/L, with a high of 6,600 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in South Dakota?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Counties in South Dakota
- Aurora0% fluoride
- Beadle9% nitrate
- Bennett1% nitrate
- Bon Homme13% nitrate
- Brookings12% uranium
- Brown9% fluoride
- Brule0% fluoride
- Buffalo81 samples
- Butte14% uranium
- Campbell22% nitrate
- Charles Mix4% nitrate
- Clark8% fluoride
- Clay4% nitrate
- Codington11% uranium
- Corson8% nitrate
- Custer13% arsenic
- Davison1% nitrate
- Day12% fluoride
- Deuel10% nitrate
- Dewey9% fluoride
- Douglas3% nitrate
- Edmunds3% nitrate
- Fall River10% uranium
- Faulk4% nitrate
- Grant6% fluoride
- Gregory40% nitrate
- Haakon19% fluoride
- Hamlin11% nitrate
- Hand9% nitrate
- Hanson12% nitrate
- Harding7% uranium
- Hughes7% nitrate
- Hutchinson10% arsenic
- Hyde5% nitrate
- Jerauld0% fluoride
- Jones3% fluoride
- Kingsbury23% fluoride
- Lake3% uranium
- Lawrence3% arsenic
- Lincoln9% nitrate
- Lyman2% nitrate
- Marshall31% fluoride
- McCook3% nitrate
- McPherson9% nitrate
- Meade10% uranium
- Mellette10% nitrate
- Miner3% fluoride
- Minnehaha17% nitrate
- Moody14% nitrate
- Oglala Lakota15% arsenic
- Pennington14% arsenic
- Perkins2% nitrate
- Potter0% fluoride
- Roberts15% arsenic
- Sanborn0% fluoride
- Spink3% fluoride
- Stanley0% fluoride
- Sully7% nitrate
- Todd37% arsenic
- Tripp7% nitrate
- Turner3% nitrate
- Union7% uranium
- Walworth3% nitrate
- Yankton18% arsenic
- Ziebach5% nitrate
1 counties have fewer than 30 public samples and are included in the South Dakota totals above rather than shown separately: Jackson.
Want the numbers themselves? Download the South Dakota dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 94,554 samples in South Dakota. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 121,341 people on private wells in South Dakota above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
- South Dakota DANR well completion reports: 78,321 well records in South Dakota, 37,991 domestic. Well completion reports filed with the South Dakota Department of Agriculture and Natural Resources. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 18, 2026.
- South Dakota DANR tank facilities and spills: 21,051 regulated sites located in South Dakota. Regulated tank facilities and spill reports from the South Dakota Department of Agriculture and Natural Resources. Retrieved September 18, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.