Well water in Pierce County, Wisconsin

In Pierce County, 18% of 239 private wells tested between 1999 and 2025 had total coliform above the Wisconsin limit (any detection), according to the UWSP Well Water Quality Viewer.

1,818 private wells tested 1999 to 2025 in state summaries; 16 individual samples from 7 wells, 1965 to 2018. Data refreshed September 9, 2026.

What homeowner tests found

Wisconsin Well Water Quality Viewer samples: private wells tested and reported to the state, 1999 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.

Contaminant	Wells tested	Above state level	Highest	State level
Total coliform	239	18%
Nitrate	1,818	12%	37.8	10 mg/L
Iron	27	7%	940	300 ug/L
E. coli	42	5%
Sodium	27	4%	48.1	20 mg/L
Manganese	33	3%	350	300 ug/L
Lead	34	3%	171	15 ug/L
Chloride	557	0%	197	250 mg/L
Arsenic	142	0%	7	10 ug/L
Copper	33	0%	0.959	1.3 mg/L

What individual samples found

Each row summarizes every public sample for that contaminant inside Pierce 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
Uranium 1980 to 2018	16	69%	0%		0.482	3.59	30 ug/L EPA limit
Radium (226 + 228) 2007 to 2018	14	57%	0%		0.029	0.6	5 pCi/L EPA limit

Sampled fewer than 10 times, too few to summarize: Arsenic (2), Nitrate (2), Copper (2), Fluoride (1), Radon (7), Sodium (2), Manganese (1), Iron (1), Chloride (1).

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What this means

Among homeowners in Pierce County who sent a sample to the state lab, the health-based limits most often exceeded were total coliform (18% of 239 wells), nitrate (12% of 1,818 wells), and E. coli (5% of 42 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 Pierce County

Volatile organic compounds (VOCs)33 leaking underground storage tank sites on record locally.
Total coliform18% of 239 local wells tested were above the Wisconsin limit (any detection).
Nitrate12% of 1,818 local wells tested were above the Wisconsin enforcement standard.
Iron7% of 27 local wells tested were above the Wisconsin nuisance level.
E. coli5% of 42 local wells tested were above the Wisconsin limit (any detection).
Sodium4% of 27 local wells tested were above the EPA advisory level.
Manganese3% of 33 local wells tested were above the Wisconsin enforcement standard.
Lead3% of 34 local wells tested were above the Wisconsin enforcement standard.
RadonMedian local reading is 330 pCi/L.

Contamination sources on record in Pierce County

Wisconsin DNR records 33 leaking underground storage tank sites in Pierce County, among 158 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.

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

Treatment that fits the local profile

Total coliform: Inspect and repair the well cap and casing, then shock chlorinate and retest; UV disinfection whole-house; Chlorination system
Nitrate: Point-of-use reverse osmosis; Anion exchange; 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
Manganese: Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis

Get your Pierce County water tested at home

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Common questions

Is there arsenic in well water in Pierce County?

Arsenic was detected in 0% of 2 public well samples in Pierce 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 Pierce County?

The median radon level across 7 public samples in Pierce County was 330 pCi/L, with a high of 660 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

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

Clifton35% nitrate
Diamond Bluff3% nitrate
Ellsworth15% nitrate
El Paso13% nitrate
Gilman0% nitrate
Hartland15% nitrate
Isabelle13% nitrate
Maiden Rock4% nitrate
Martell8% nitrate
Oak Grove6% nitrate
River Falls9% nitrate
Rock Elm3% nitrate
Salem2% nitrate
Spring Lake2% nitrate
Trenton10% nitrate
Trimbelle11% nitrate
Union17% nitrate

8 towns have fewer than 30 public samples and are included in the Pierce County totals above rather than shown separately: Bay City village, Ellsworth village, Elmwood village, Maiden Rock village, Plum City village, Prescott, River Falls, Spring Valley village.

Sources

USGS Water Quality Portal: 49 samples in Pierce 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 Pierce County, up to 1,818 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: 158 regulated sites located in Pierce 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.