Lee County, Illinois: Private Well Water Quality
USGS models estimate the private-well arsenic exposure across Lee County, and USGS laboratory samples from at least 21 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.
Quick answer: Arsenic is the headline concern for Lee County well water: USGS modeling estimates about 479 residents on private wells with arsenic above the EPA limit of 10 µg/L. Of the 12 Lee County wells the USGS actually tested for arsenic, 0% were over the limit (median 3 µg/L). The most common measured contaminant in local wells is pH: 19% of 21 sampled wells were outside 6.5–8.5. These figures describe wells across the Illinois county — not your tap — so the only way to know your own water is a certified lab test.
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.
~479
people estimated to rely on private wells with modeled arsenic above the 10 µg/L EPA limit
388–592
90% confidence range for that estimate
19% of wells
sampled by USGS in the county measured outside 6.5–8.5 for pH (21 wells)
Find out what's actually in your well
USGS models flag arsenic in Lee County, but two wells on the same road can test very differently. 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.
Basic screening only. Confirm arsenic, nitrate and bacteria with a certified lab.
Find a certified drinking-water labAmazon links are affiliate links — we may earn a commission at no extra cost to you.
Measured well tests in Lee County
Unlike the arsenic estimate above, these are real laboratory results: the USGS has published chemistry from at least 21 wells in Lee County, sampled 1991–2014. 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 Lee County (fewer than 5) — see the state page. | ||
| Manganese | Not enough USGS well samples in Lee County (fewer than 5) — see the state page. | ||
| Iron | Not enough USGS well samples in Lee County (fewer than 5) — see the state page. | ||
| pH21 wells | 6.8 90th pct: 7.5 | 19%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): Not enough USGS well samples in Lee County — see the state page.
- Manganese: Not enough USGS well samples in Lee County — see the state page.
- Iron: Not enough USGS well samples in Lee County — see the state page.
- pH: pH is off-range in 19% of sampled wells (median 6.8; 19% acidic, 0% alkaline).
- Arsenic (measured, 12 wells): Measured arsenic was low in most sampled wells (median 3 µg/L; 0% over the limit).
What to do about the biggest finding (pH): Test pH and first-draw lead and copper; a calcite or soda-ash neutralizer corrects acidic water and protects your plumbing. Read more: Lead from corroded plumbing.
Source: USGS well samples aggregated to Lee County, Illinois — 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.
Arsenic in Lee County drinking water: what the 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 Lee 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.
Because arsenic is tasteless and invisible, a certified lab test is the only way to detect it — and unlike bacteria, boiling does not remove arsenic (it slightly concentrates it as water evaporates). A lab reports total arsenic; if yours is elevated, reverse osmosis or an adsorptive arsenic filter reduces it, while carbon pitchers and water softeners do not.
What to do
- Test your well for arsenic, nitrate — 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.
- Re-test annually; well chemistry changes over time.
Lee County well water: frequently asked questions
Is there arsenic in Lee County drinking water?
Arsenic occurs naturally in the bedrock under Lee County, Illinois, and dissolves into some private wells with no color, taste or smell. USGS modeling estimates about 479 residents (range 388–592) on private wells with arsenic above the EPA limit of 10 µg/L. USGS also sampled 12 wells in the county for arsenic directly: the median was 3 µg/L and 0% were over the limit. These are area and other-well figures, not a test of your own well — the only way to know your arsenic level is a certified lab test of your tap.
Lee County, IL water contamination: what have well tests found?
USGS laboratory samples from at least 21 wells in Lee County (1991–2014) measured: arsenic 0% of 12 wells > 10 µg/L; pH 19% of 21 wells outside 6.5–8.5. The biggest measured issue is pH. These are tests of other wells in the county, not a public water system report — private wells are unregulated, so your own well needs its own lab test for arsenic, nitrate, manganese and iron.
Are domestic wells in Lee County, IL acidic — do I need an acid neutralizer?
Acidic water turns up regularly in Lee County domestic wells: 19% of the 21 wells the USGS sampled (1991–2014) had pH below 6.5, with a median pH of 6.8. Acidic water corrodes copper plumbing (blue-green stains, pinhole leaks) and can dissolve lead and copper into your tap water. You only need a neutralizer if your own well tests below about 6.5: a calcite (or calcite/Corosex) tank handles mildly acidic water (roughly pH 6–6.5), while very acidic water usually needs soda-ash injection. Test pH together with first-draw lead and copper.
How do I remove arsenic from Lee County well water?
Test first so you know your level and form of arsenic. If arsenic is present, a point-of-use reverse-osmosis system under the kitchen sink removes 90%+ of it; carbon pitchers and standard "filter" jugs do not remove arsenic or nitrate. Whole-house treatment (adsorptive arsenic media) is used when the level is high. Re-test after installing and then annually.
Acidic water: neutralize before it corrodes your plumbing
Low-pH well water leaches lead and copper from pipes. A whole-house acid neutralizer is the fix; reverse osmosis at the tap removes any metals already picked up.
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