Well water in Marinette County, Wisconsin
In Marinette County, 12% of 430 private wells tested between 1992 and 2025 had arsenic above the Wisconsin enforcement standard (10 ug/L), according to the UWSP Well Water Quality Viewer.
1,869 private wells tested 1992 to 2025 in state summaries; 12 individual samples from 6 wells, 1950 to 2024. Data refreshed September 9, 2026.
What homeowner tests found
Wisconsin Well Water Quality Viewer samples: private wells tested and reported to the state, 1992 to 2025. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA. County and state figures combine the town summaries, weighted by wells tested; medians are not combined.
What individual samples found
Each row summarizes every public sample for that contaminant inside Marinette 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 | Samples | Detected | Above limit | Median | Highest | Limit | |
|---|---|---|---|---|---|---|---|
| Radium (226 + 228) 2003 to 2015 | 12 | 92% | 0% | 0.375 | 3.6 | 5 pCi/L EPA limit | |
| Uranium 2002 to 2024 | 10 | 100% | 0% | 0.29 | 3.56 | 30 ug/L EPA limit |
Sampled fewer than 10 times, too few to summarize: Copper (3), Radon (5), Iron (2).
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What this means
Among homeowners in Marinette County who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (12% of 430 wells), total coliform (4% of 109 wells), and nitrate (2% of 1,869 wells). These are ordinary wells tested by their owners, so the shares are the best available picture of a typical well here, with one caveat: people test more often when they suspect a problem.
What to test for in Marinette County
- Volatile organic compounds (VOCs)108 leaking underground storage tank sites on record locally.
- Arsenic12% of 430 local wells tested were above the Wisconsin enforcement standard.
- Iron10% of 41 local wells tested were above the Wisconsin nuisance level.
- Total coliform4% of 109 local wells tested were above the Wisconsin limit (any detection).
- Sodium2% of 41 local wells tested were above the EPA advisory level.
- Nitrate2% of 1,869 local wells tested were above the Wisconsin enforcement standard.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 620 pCi/L.
- CopperDetected in 67% of local samples.
Contamination sources on record in Marinette County
Wisconsin DNR records 108 leaking underground storage tank sites in Marinette County, among 348 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.
- 108
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 54
- lined landfills and transfer facilities
- 186
- other remediation projects
Treatment that fits the local profile
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Iron
- Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
- Copper
- Neutralizing filter to raise pH; Point-of-use reverse osmosis
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Common questions
How high is radon in well water in Marinette County?
The median radon level across 5 public samples in Marinette County was 620 pCi/L, with a high of 770 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Marinette 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.
Towns in Marinette County
- Amberg0% nitrate
- Athelstane<1% nitrate
- Beaver11% nitrate
- Beecher0% nitrate
- Dunbar0% nitrate
- Goodman0% nitrate
- Grover2% nitrate
- Lake6% nitrate
- Marinette0% nitrate
- Middle Inlet6% nitrate
- Niagara36% arsenic
- Pembine0% nitrate
- Peshtigo0% nitrate
- Porterfield0% nitrate
- Pound14% nitrate
- Silver Cliff3% nitrate
- Stephenson4% nitrate
- Wausaukee2% nitrate
7 towns have fewer than 30 public samples and are included in the Marinette County totals above rather than shown separately: Coleman village, Crivitz village, Niagara, Peshtigo, Pound village, Wagner, Wausaukee village.
Sources
- USGS Water Quality Portal: 32 samples in Marinette 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.
- Wisconsin Well Water Quality Viewer samples: summaries for 10 contaminants in Marinette County, up to 1,869 wells each. Private well samples compiled by the UWSP Center for Watershed Science and Education from the DNR Groundwater Retrieval Network, DATCP surveys, the UWSP Water and Environmental Analysis Lab and county health programs, published in the Wisconsin Well Water Quality Viewer with Wisconsin DHS. Samples are located to the town, village or city they fall in; one result per well and parameter (the latest) so repeat samples do not double count; wells without a state well number are keyed by location. Shares are against Wisconsin NR 140 enforcement standards (arsenic 10 ug/L, nitrate 10 mg/L as N, manganese 300 ug/L, lead 15 ug/L, copper 1.3 mg/L) and the iron and chloride secondary levels. Many samples were submitted by homeowners with a reason to test, so shares can run above a random survey. Retrieved September 9, 2026.
- Wisconsin DNR regulated sites: 348 regulated sites located in Marinette County. Open and closed remediation activities (BRRTS, including leaking underground storage tanks and spills) and landfill and waste sites from the Wisconsin Department of Natural Resources. Retrieved September 9, 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.