Sargent County, North Dakota: Private Well Water Quality
USGS models estimate the private-well arsenic exposure across Sargent County, and USGS laboratory samples from at least 289 wells in the county show measured nitrate, manganese, iron and pH. The arsenic figure is an area estimate; the measurements are of other wells — neither is a test of your own well.
This is a modeled probability for the area, not a measurement of your well. USGS statistical models estimate how many private wells in this area are likely to exceed the federal limit — they cannot tell you what is in your water. Two neighbors can have very different results. The only way to know your well is to test it.
~13
people estimated to rely on private wells with modeled arsenic above the 10 µg/L EPA limit
10–20
90% confidence range for that estimate
77% of wells
sampled by USGS in the county measured > 10 µg/L for arsenic (30 wells)
Find out what's actually in your well
Private wells are not regulated by the EPA — nobody tests wells in Sargent County for you. Arsenic, nitrate and coliform bacteria are the three most common private-well problems, and none of them has a taste or smell. A certified lab test checks all of them at once; the CDC and EPA recommend testing every well at least once a year.
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Measured well tests in Sargent County
Unlike the arsenic estimate above, these are real laboratory results: the USGS has published chemistry from at least 289 wells in Sargent County, sampled 1989–2016. They describe other wells in the county — domestic, public-supply and monitoring wells — not your well.
| Parameter | Median | Wells over threshold | What the threshold means |
|---|---|---|---|
| Nitrate (as N) | Not enough USGS well samples in Sargent County (fewer than 5) — see the state page. | ||
| Manganese289 wells | 618 µg/L90th pct: 1,302 µg/L | 83%Elevated | > 300 µg/L (EPA health advisory). Lifetime health advisory; above 50 µg/L it already stains fixtures and tastes metallic. Neurological concern for infants. |
| Iron33 wells | 510 µg/L90th pct: 1,280 µg/L | 67%Elevated | > 300 µg/L (EPA secondary standard). Aesthetic standard — rust-colored staining, metallic taste, clogged fixtures. Not a health limit. |
| pH289 wells | 7.8 90th pct: 8.2 | 3%Low | outside 6.5–8.5 (EPA secondary range). Low pH is corrosive and leaches lead and copper from plumbing; high pH causes scale and bitter taste. |
What the samples show
- Nitrate (as N): Not enough USGS well samples in Sargent County — see the state page.
- Manganese: Manganese is widespread: 83% of sampled wells exceeded the 300 µg/L health advisory and 97% would stain fixtures (median 618 µg/L).
- Iron: Iron is a common nuisance: 67% of sampled wells exceeded 300 µg/L (median 510 µg/L) — expect rust staining without treatment.
- pH: pH is in the normal range for most sampled wells (median 7.8).
- Arsenic (measured, 30 wells): Measured arsenic confirms the model: 77% of sampled wells exceeded the 10 µg/L limit (median 22 µg/L).
What to do about the biggest finding (arsenic): Test for arsenic; reverse osmosis or an arsenic-specific adsorption filter removes it — carbon pitchers do not. Read more: Arsenic in well water.
Source: USGS well samples aggregated to Sargent County, North Dakota — manganese, pH and arsenic from USGS ScienceBase 5f36baa782cee144fb3873e8 (site medians, 1988–2019); nitrate and iron from McMahon et al. (2019), Environ. Sci. Technol. 53:29–38 (NWIS wells). County assignment by Census 2020 boundaries. Statistics shown only where ≥ 5 wells were sampled. USGS well samples; not a test of your well.
What the arsenic estimate means
Arsenic occurs naturally in bedrock and can dissolve into groundwater, so it shows up in private wells with no color, taste or smell. The USGS estimate above combines a statistical model of arsenic probability with the number of people on domestic wells in Sargent County. A higher number means more of your neighbors are likely drinking water over the federal limit — but your own well could be higher or lower. Long-term arsenic exposure is linked to skin, bladder and lung cancers, so the EPA sets the limit at 10 µg/L.
What to do
- Test your well for arsenic, nitrate, manganese and iron — it's the only way to know your actual level.
- If arsenic or nitrate is present, install a reverse-osmosis system — carbon pitchers do not remove either.
- For manganese or iron staining, a whole-house oxidizing filter or softener is the fix; RO for the drinking tap.
- Re-test annually; well chemistry changes over time.
Match the filter to your test result
Carbon pitchers and faucet filters do not remove arsenic or nitrate. Reverse osmosis is the point-of-use fix; a whole-house system handles the rest of the home.
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Check price on Amazon →Affiliate links — we may earn a commission at no extra cost to you. Re-test after installing to confirm the system is working.