Well Water Nerd

Well water in Brown County, Wisconsin

In Brown County, 3% of 532 private wells tested between 1993 and 2025 had arsenic above the Wisconsin enforcement standard (10 ug/L), according to the UWSP Well Water Quality Viewer.

1,748 private wells tested 2002 to 2025 in state summaries; 8 individual samples from 7 wells, 1946 to 2015. Data refreshed September 9, 2026.

What homeowner tests found

Wisconsin Well Water Quality Viewer samples: private wells tested and reported to the state, 2002 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.

ContaminantWells testedAbove state levelMedian95th pctHighestState level
Sodium7010%16720 mg/L
Iron709%11,460300 ug/L
Arsenic5323%61510 ug/L
Nitrate1,7483%26.510 mg/L
Lead763%5515 ug/L
Total coliform1262%
Chloride1262%317250 mg/L
Manganese761%317300 ug/L
Copper760%1.051.3 mg/L
E. coli20%

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What this means

Among homeowners in Brown County who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (3% of 532 wells), nitrate (3% of 1,748 wells), and lead (3% of 76 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.

Sodium exceeds the state's advisory level in a sizable share of wells; this is mostly a taste, staining or diet issue rather than a toxicity one.

What to test for in Brown County

  • Volatile organic compounds (VOCs)429 leaking underground storage tank sites on record locally.
  • Sodium10% of 70 local wells tested were above the EPA advisory level.
  • Iron9% of 70 local wells tested were above the Wisconsin nuisance level.
  • Arsenic3% of 532 local wells tested were above the Wisconsin enforcement standard.
  • Nitrate3% of 1,748 local wells tested were above the Wisconsin enforcement standard.
  • Lead3% of 76 local wells tested were above the Wisconsin enforcement standard.
  • Total coliform2% of 126 local wells tested were above the Wisconsin limit (any detection).
  • Chloride2% of 126 local wells tested were above the Wisconsin nuisance level.
  • Manganese1% of 76 local wells tested were above the Wisconsin enforcement standard.

Contamination sources on record in Brown County

Wisconsin DNR records 429 leaking underground storage tank sites in Brown County, among 1,168 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.

429
leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
58
lined landfills and transfer facilities
681
other remediation projects

Treatment that fits the local profile

Sodium
Point-of-use reverse osmosis; Distillation
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Copper
Neutralizing filter to raise pH; Point-of-use reverse osmosis
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
Chloride
Point-of-use reverse osmosis; Distillation

Get your Brown County water tested at home

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Common questions

Is there arsenic in well water in Brown County?

Arsenic was detected in 100% of 3 public well samples in Brown County, and 0% 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 high is radon in well water in Brown County?

The median radon level across 6 public samples in Brown County was 325 pCi/L, with a high of 980 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Brown 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 Brown County

8 towns have fewer than 30 public samples and are included in the Brown County totals above rather than shown separately: Allouez village, Ashwaubenon village, Denmark village, De Pere, Green Bay, Howard village, Pulaski village, Wrightstown village.

Sources

  • USGS Water Quality Portal: 42 samples in Brown 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 Brown County, up to 1,748 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: 1,168 regulated sites located in Brown 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.