Pasquotank County, North Carolina: Private Well Water Quality
USGS models estimate the private-well arsenic exposure across Pasquotank County, and USGS laboratory samples from at least 17 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.
~77
people estimated to rely on private wells with modeled arsenic above the 10 µg/L EPA limit
53–111
90% confidence range for that estimate
20% of wells
sampled by USGS in the county measured > 300 µg/L for manganese (5 wells)
Find out what's actually in your well
Private wells are not regulated by the EPA — nobody tests wells in Pasquotank 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 Pasquotank County
Unlike the arsenic estimate above, these are real laboratory results: the USGS has published chemistry from at least 17 wells in Pasquotank County, sampled 1993–2015. 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)6 wells | 0 mg/L90th pct: 0 mg/L | 0%Low | > 10 mg/L (EPA MCL). Federal drinking-water limit. Nitrate from fertilizer, manure and septic systems; unsafe for infants and in pregnancy. |
| Manganese5 wells | 120 µg/L90th pct: 343 µg/L | 20%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. |
| Iron6 wells | 9,000 µg/L90th pct: 18,500 µg/L | 100%Elevated | > 300 µg/L (EPA secondary standard). Aesthetic standard — rust-colored staining, metallic taste, clogged fixtures. Not a health limit. |
| pH17 wells | 7.0 90th pct: 9.2 | 36%Some | 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): Nitrate was low in nearly all sampled wells (median 0 mg/L; 0% over the limit).
- Manganese: Manganese is widespread: 20% of sampled wells exceeded the 300 µg/L health advisory and 60% would stain fixtures (median 120 µg/L).
- Iron: Iron is a common nuisance: 100% of sampled wells exceeded 300 µg/L (median 9,000 µg/L) — expect rust staining without treatment.
- pH: pH is off-range in 36% of sampled wells (median 7.0; 12% acidic, 24% alkaline).
What to do about the biggest finding (manganese): Test for manganese; treat with an oxidizing (greensand / birm) filter or a softener for the whole house, plus reverse osmosis at the kitchen tap for drinking.
Source: USGS well samples aggregated to Pasquotank County, North Carolina — 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 Pasquotank 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.
Manganese: treat the whole house, then polish the tap
Manganese stains fixtures and laundry from every tap, so a whole-house oxidizing filter or softener is the primary fix. Add reverse osmosis at the kitchen sink for drinking water.
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