Well water in Dodge County, Wisconsin

In Dodge County, 12% of 286 private wells tested between 1995 and 2025 had total coliform above the Wisconsin limit (any detection), according to the UWSP Well Water Quality Viewer.

2,244 private wells tested 2000 to 2025 in state summaries; 6 individual samples from 6 wells, 1946 to 2014. Data refreshed September 9, 2026.

What homeowner tests found

Wisconsin Well Water Quality Viewer samples: private wells tested and reported to the state, 2000 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
Sodium	123	24%	183	20 mg/L
Iron	112	21%	9,326	300 ug/L
Total coliform	286	12%
E. coli	34	9%
Arsenic	425	8%	118	10 ug/L
Nitrate	2,244	6%	67.9	10 mg/L
Lead	177	2%	34	15 ug/L
Chloride	540	<1%	332	250 mg/L
Copper	178	<1%	1.38	1.3 mg/L
Manganese	177	0%	275	300 ug/L

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What this means

Among homeowners in Dodge County who sent a sample to the state lab, the health-based limits most often exceeded were total coliform (12% of 286 wells), E. coli (9% of 34 wells), and arsenic (8% of 425 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 and iron exceed the state's advisory level in a sizable share of wells; these are mostly a taste, staining or diet issue rather than a toxicity one.

What to test for in Dodge County

Volatile organic compounds (VOCs)103 leaking underground storage tank sites on record locally.
Sodium24% of 123 local wells tested were above the EPA advisory level.
Iron21% of 112 local wells tested were above the Wisconsin nuisance level.
Total coliform12% of 286 local wells tested were above the Wisconsin limit (any detection).
E. coli9% of 34 local wells tested were above the Wisconsin limit (any detection).
Arsenic8% of 425 local wells tested were above the Wisconsin enforcement standard.
Nitrate6% of 2,244 local wells tested were above the Wisconsin enforcement standard.
Lead2% of 177 local wells tested were above the Wisconsin enforcement standard.
Chloride<1% of 540 local wells tested were above the Wisconsin nuisance level.

Contamination sources on record in Dodge County

Wisconsin DNR records 103 leaking underground storage tank sites in Dodge County, among 474 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.

103: leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
46: lined landfills and transfer facilities
325: 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
E. coli: Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system
Arsenic: Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Nitrate: Point-of-use reverse osmosis; Anion exchange; Distillation
Sodium: Point-of-use reverse osmosis; Distillation
Fluoride: Point-of-use reverse osmosis; Activated alumina; Distillation

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Common questions

Is there arsenic in well water in Dodge County?

Arsenic was detected in 100% of 1 public well samples in Dodge 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 Dodge County?

The median radon level across 1 public samples in Dodge County was 251 pCi/L, with a high of 251 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

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

Ashippun6% nitrate
Beaver Dam23% total coliform
Beaver Dam9% nitrate
Burnett22% nitrate
Calamus1% nitrate
Chester0% nitrate
Clyman1% nitrate
Elba0% nitrate
Emmet30% arsenic
Fox Lake11% nitrate
Herman6% nitrate
Hubbard0% nitrate
Hustisford2% nitrate
Juneau5% nitrate
Lebanon2% nitrate
Leroy18% nitrate
Lomira16% nitrate
Lowell2% nitrate
Oak Grove5% nitrate
Portland12% nitrate
Rubicon3% nitrate
Shields4% nitrate
Theresa8% nitrate
Trenton13% nitrate
Westford1% nitrate

19 towns have fewer than 30 public samples and are included in the Dodge County totals above rather than shown separately: Brownsville village, Clyman village, Columbus, Fox Lake, Hartford, Horicon, Hustisford village, Iron Ridge village, Kekoskee village, Lomira village, Lowell village, Mayville, Neosho village, Randolph village, Reeseville village, Theresa village, Watertown, Waupun, Williamstown.

Sources

USGS Water Quality Portal: 22 samples in Dodge 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 Dodge County, up to 2,244 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: 474 regulated sites located in Dodge 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.