Well water in Oglala Lakota County, South Dakota
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Testing recommended
tested well samples in Oglala Lakota County exceeded the EPA limit for arsenic (10 ug/L), based on public data from USGS Water Quality Portal.
738 test results across 12 contaminants from at least 87 wells, 1962 to 1997; sodium has the most at 93. Data refreshed September 3, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 7,370 people in Oglala Lakota County get their drinking water from a private well, per USGS 2015 county water use. That is about 51% of residents.
What individual samples found
Each row summarizes every public sample for that contaminant inside Oglala Lakota County. 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 |
|---|---|---|---|---|---|---|
| Arsenic 1979 to 1997 | 59 | 100% | 6 | 77 | 10 ug/L EPA limit | |
| Uranium 1979 to 1997 | 39 | 97% | 13 | 92 | 30 ug/L EPA limit | |
| Nitrate 1962 to 1997 | 75 | 97% | 1.01 | 57 | 10 mg/L EPA limit | |
| Fluoride 1962 to 1997 | 81 | 100% | 0.4 | 9.1 | 4 mg/L EPA limit | |
| Copper 1979 to 1997 | 59 | 34% | 0 | 0.03 | 1.3 mg/L EPA limit | |
| Lead 1987 to 1997 | 39 | 13% | 0 | 10 | 15 ug/L EPA limit | |
| E. coli 1995 to 1997 | 26 | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Sodium 1962 to 1997 | no limit | 93 | 100% | 63 | 795 | 20 mg/L health guideline |
| Chloride 1962 to 1997 | no limit | 92 | 99% | 5.8 | 147 | 250 mg/L nuisance level |
| Iron 1962 to 1997 | no limit | 87 | 64% | 10 | 4,900 | 300 ug/L nuisance level |
| Manganese 1962 to 1997 | no limit | 86 | 44% | 0 | 1,400 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Radium (226 + 228) (2).
Closer than the county
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
The contaminants most often above their limit here are arsenic (15% of 59 samples), uranium (10% of 39 samples), and nitrate (3% of 75 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 and Iron 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 Oglala Lakota County
- 1Arsenic15% of 59 local samples were above the limit.
- 2Uranium10% of 39 local samples were above the limit.
- 3Nitrate3% of 75 local samples were above the limit.
- 4Fluoride1% of 81 local samples were above the limit.
- 5Coliform bacteriaRecommended for every private well, every year.
- 6ChlorideDetected in 99% of local samples.
- 7IronDetected in 64% of local samples.
- 8Volatile organic compounds (VOCs)75 reported spills and releases on record locally.
Test your Oglala Lakota County well for arsenic, uranium and nitrate
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 Oglala Lakota County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Oglala Lakota County
460 domestic wells in Oglala Lakota County are on record with the state since 1972. the typical well is 140 feet deep (one in ten goes past 360 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 Oglala Lakota County
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 county 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 Oglala Lakota County
South Dakota DANR tank facilities and spills records 75 reported spills and releases in Oglala Lakota County, among 107 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.
- 75
- reported spills and releasesMost spills are fuel; a few are solvents or chemicals that reach the water table.
- 25
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 7
- other solid waste facilities
Treatment that fits the local profile
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Uranium
Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
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 arsenic
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For arsenic
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 arsenic
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 iron
Iron and manganese oxidizing filter
whole-house, at the point of entry, about $1,800
Air-injection or greensand media; fixes staining at the source.
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Common questions
How deep are wells in Oglala Lakota County?
The typical domestic well in Oglala Lakota County is 140 feet deep, based on 460 wells reported to the state since 1972. One in ten is deeper than 360 feet.
Is there arsenic in well water in Oglala Lakota County?
Arsenic was detected in 100% of 59 public well samples in Oglala Lakota County, and 15% 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 often should I test a private well in Oglala Lakota County?
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 near Oglala Lakota County
Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.
Want the numbers themselves? Download the South Dakota dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 738 samples in Oglala Lakota County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- South Dakota DANR well completion reports: 815 well records in Oglala Lakota County, 460 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: 107 regulated sites located in Oglala Lakota County. 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.