Well water in Columbia County, Wisconsin
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Testing recommended
private wells tested between 1988 and 2025 in Columbia County had nitrate above the Wisconsin enforcement standard (10 mg/L), according to the UWSP Well Water Quality Viewer.
2,862 private wells tested 1988 to 2025 in state summaries; 1,228 test results across 12 contaminants from at least 116 wells, 1944 to 2024; nitrate has the most at 281. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 21,589 people in Columbia County get their drinking water from a private well, per USGS 2015 county water use. That is about 38% of residents.
Separately, the USGS national arsenic model estimates that 5% of the 21,589 people on private wells in Columbia County draw water above 10 ug/L (the model's range is 4% to 6%), from geology and well depth rather than local tests.
What homeowner tests found
Wisconsin Well Water Quality Viewer samples: private wells tested and reported to the state, 1988 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 Columbia 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 | Above limit | Samples | Detected | Median | Highest | Limit |
|---|---|---|---|---|---|---|
| Nitrate 1961 to 2024 | 281 | 96% | 2.7 | 75 | 10 mg/L EPA limit | |
| Fluoride 1944 to 2024 | 178 | 92% | 0.1 | 0.5 | 4 mg/L EPA limit | |
| Copper 1976 to 2024 | 16 | 75% | 0.015 | 0.053 | 1.3 mg/L EPA limit | |
| Lead 1976 to 2024 | 15 | 67% | 0 | 0.185 | 15 ug/L EPA limit | |
| Arsenic 1976 to 2024 | 14 | 100% | 0.62 | 5.8 | 10 ug/L EPA limit | |
| Uranium 1980 to 2024 | 12 | 92% | 0.49 | 0.904 | 30 ug/L EPA limit | |
| Chloride 1944 to 2024 | no limit | 187 | 100% | 4.3 | 190 | 250 mg/L nuisance level |
| Manganese 1944 to 2024 | no limit | 183 | 68% | 20 | 460 | 300 ug/L health guideline |
| Iron 1944 to 2024 | no limit | 183 | 88% | 90 | 6,200 | 300 ug/L nuisance level |
| Sodium 1950 to 2024 | no limit | 148 | 100% | 3 | 120 | 20 mg/L health guideline |
Sampled fewer than 10 times, too few to summarize: Radium (226 + 228) (8), Radon (3).
Over time
Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.
| Contaminant | before 2000 | 2000s | 2010s | 2020s |
|---|---|---|---|---|
| Nitrate | 15%261 samples | 30%10 samples | n/a | n/a |
Closer than the county
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
Among homeowners in Columbia County who sent a sample to the state lab, the health-based limits most often exceeded were nitrate (18% of 2,862 wells), E. coli (12% of 34 wells), and total coliform (9% of 388 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 Columbia County
- 1Nitrate18% of 2,862 local wells tested were above the Wisconsin enforcement standard.
- 2E. coli12% of 34 local wells tested were above the Wisconsin limit (any detection).
- 3Total coliform9% of 388 local wells tested were above the Wisconsin limit (any detection).
- 4Copper2% of 277 local wells tested were above the Wisconsin enforcement standard.
- 5Lead2% of 277 local wells tested were above the Wisconsin enforcement standard.
- 6Arsenic2% of 446 local wells tested were above the Wisconsin enforcement standard.
- 7RadonMedian local reading is 310 pCi/L.
- 8Sodium10% of 239 local wells tested were above the EPA advisory level.
- 9Volatile organic compounds (VOCs)93 leaking underground storage tank sites on record locally.
Test your Columbia County well for nitrate, E. coli and total coliform
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
Where to get a well tested in Wisconsin: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Columbia County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under Columbia County
Cambrian-Ordovician aquifer system
Sandstone. Sandstone wells draw from pore space in the rock and tend to be dependable. Iron, manganese and hardness are common, and some sandstones carry arsenic or radium, so a first test should include both.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county centroid. A single well can sit in a different unit, especially near a boundary.
Official help in Wisconsin
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
- Wells, Wisconsin DNR
- Laboratory Certification, Wisconsin DNR
Contamination sources on record in Columbia County
Wisconsin DNR records 93 leaking underground storage tank sites in Columbia County, among 404 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.
- 93
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 45
- lined landfills and transfer facilities
- 266
- other remediation projects
Treatment that fits the local profile
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
E. coli
Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system
Total coliform
Inspect and repair the well cap and casing, then shock chlorinate and retest; UV disinfection whole-house; Chlorination system
Sodium
Point-of-use reverse osmosis; Distillation
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Manganese
Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
Systems we would look at first
Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For nitrate
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For nitrate
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
For E. coli
UV disinfection system
whole-house, at the point of entry, about $900
Fix the well cap and casing first; UV keeps bacteria from returning.
For E. coli
Aquasana Rhino Well Water with UV
whole-house, at the point of entry, about $2,871
Whole-house system built for wells: sediment pre-filter, KDF and carbon, and a UV lamp rated to kill 99.99% of bacteria and viruses. It does not remove arsenic, nitrate, uranium or radon.
For iron
Iron and manganese oxidizing filter
whole-house, at the point of entry, about $1,800
Air-injection or greensand media; fixes staining at the source.
Free, no obligation
Get on the list for a free in-home water test in Columbia County
No water treatment company serves Columbia County through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for Columbia County, and you get an email naming it first.
Common questions
Is there arsenic in well water in Columbia County?
Arsenic was detected in 100% of 14 public well samples in Columbia 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 often should I test a private well in Columbia 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 Columbia County
- Arlington46% nitrate
- Caledonia8% nitrate
- Columbus15% nitrate
- Courtland20% nitrate
- Dekorra12% nitrate
- Fort Winnebago7% nitrate
- Fountain Prairie10% nitrate
- Hampden39% nitrate
- Leeds62% nitrate
- Lewiston7% nitrate
- Lodi16% nitrate
- Lowville27% nitrate
- Marcellon30% nitrate
- Newport10% nitrate
- Otsego32% nitrate
- Pacific6% nitrate
- Randolph29% nitrate
- Scott41% nitrate
- Springvale30% nitrate
- West Point11% nitrate
- Wyocena8% nitrate
14 towns have fewer than 30 public samples and are included in the Columbia County totals above rather than shown separately: Arlington village, Cambria village, Columbus, Doylestown village, Fall River village, Friesland village, Lodi, Pardeeville village, Portage, Poynette village, Randolph village, Rio village, Wisconsin Dells, Wyocena village.
Counties near Columbia County
Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.
Want the numbers themselves? Download the Wisconsin dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 1,228 samples in Columbia 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 Columbia County, up to 2,862 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.
- USGS national arsenic model (Ayotte 2017): estimated share of 21,589 people on private wells in Columbia County above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
- Wisconsin DNR regulated sites: 404 regulated sites located in Columbia 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.