Well water in Winona County, Minnesota

In Winona County, none of 327 private wells tested between 2008 and 2021 had arsenic above the EPA limit (10 ug/L), according to the Minnesota Department of Health.

The strongest signal is nitrate: 13% of 24 local samples were above the limit, too few samples to carry the headline but first on the test list below.

327 private wells tested 2008 to 2021 in state summaries; 883 test results across 14 contaminants from at least 110 wells, 1963 to 2025; chloride has the most at 134. Data refreshed September 15, 2026.

Compiled by Nick at Well Water Nerd from public records. How these pages are built

An estimated 10,535 people in Winona County get their drinking water from a private well, per USGS 2015 county water use. That is about 21% of residents.

Separately, the USGS national arsenic model estimates that 2% of the 10,535 people on private wells in Winona County draw water above 10 ug/L (the model's range is 2% to 3%), from geology and well depth rather than local tests.

What homeowner tests found

MDH new private well arsenic tests: private wells tested and reported to the state, 2008 to 2021. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA.

Contaminant	Above state level	Wells tested	Median	95th pct	Highest	State level
Arsenic	0%	327	2	3.5		10 ug/L

What individual samples found

Each row summarizes every public sample for that contaminant inside Winona 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 1963 to 2013	13%	24	71%	0.165	28	10 mg/L EPA limit
Lead 1980 to 2024	<1%	109	48%	0	23.9	15 ug/L EPA limit
Fluoride 1963 to 2024	0%	117	97%	0.12	1.27	4 mg/L EPA limit
Arsenic 1980 to 2024	0%	107	39%	0	1.62	10 ug/L EPA limit
Copper 1980 to 2024	0%	17	35%	0	0.168	1.3 mg/L EPA limit
Chloride 1963 to 2024	no limit	134	72%	1.1	144	250 mg/L nuisance level
Sodium 1963 to 2024	no limit	128	99%	2.29	175	20 mg/L health guideline
Iron 1963 to 2024	no limit	127	65%	237	2,800	300 ug/L nuisance level
Manganese 1963 to 2024	no limit	110	77%	14.7	4,650	300 ug/L health guideline

Sampled fewer than 10 times, too few to summarize: Uranium (4), Radium (226 + 228) (2), PFOA (2), E. coli (1), Radon (1).

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
Fluoride	0%17 samples	n/a	0%97 samples	n/a
Lead	9%11 samples	n/a	0%95 samples	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 address

What this means

Among homeowners in Winona County who sent a sample to the state lab, no health-based limit was exceeded often enough to publish a share. That is good news, but a single well can still be the exception.

What to test for in Winona County

1
Nitrate
13% of 24 local samples were above the limit.
2
Lead
<1% of 109 local samples were above the limit.
3
Coliform bacteria
Recommended for every private well, every year.
4
Radon
Median local reading is 211 pCi/L.
5
Fluoride
Detected in 97% of local samples.
6
Manganese
Detected in 77% of local samples.
7
Chloride
Detected in 72% of local samples.
8
Volatile organic compounds (VOCs)
222 leaking underground storage tank sites on record locally.
9
Metals panel
6 hazardous waste sites on record locally.

Test your Winona County well for nitrate, lead and coliform bacteria

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 $209 Already 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 Minnesota: certified labs, state programs and prices.

Already have results back? Get your lab report read against the Winona County numbers, $29. Every line explained, ranked by what matters, with the fix for each.

Wells in Winona County

1,812 domestic wells in Winona County are on record with the state since 1904. 91% are drilled into bedrock, and the typical well is 215 feet deep (one in ten goes past 595 feet).

In a typical Winona County well, bedrock starts about 25 feet down.

Bedrock wells are where arsenic, uranium and radon come from: the water sits in fractures in granite and metamorphic rock and picks up whatever the rock carries. That is why testing for those three matters more here than in a dug or gravel well.

1930s

1940s

1950s

1960s

220

1970s

175

1980s

633

1990s

585

2000s

2010s

Find your own well's report

The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.

Open Minnesota Well Index and choose Water Well.
The record shows depth, casing, depth to bedrock, aquifer, static water level and the driller; new wells since 2008 also show the arsenic test result.

Wells drilled since 1974 have records; older wells appear only if a later owner reported them.

The rock under Winona 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 Minnesota

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 and Borings, Minnesota Department of Health
Accredited Laboratories as Well Partners, Minnesota Department of Health

Contamination sources on record in Winona County

MPCA records 222 leaking underground storage tank sites and 6 hazardous waste sites in Winona County, among 555 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.

222: leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
6: hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
232: registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
64: lined landfills and transfer facilities
31: other remediation projects

Treatment that fits the local profile

Nitrate

Point-of-use reverse osmosis; Anion exchange; Distillation

Lead

Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching

Iron

Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration

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 lead

Aquasana Claryum 3-Stage under-sink filter

under-sink or countertop, about $175

Certified to NSF/ANSI 53 to reduce 99% of lead and 99.7% of PFOA and PFOS at the tap. Not a fix for arsenic, nitrate or bacteria.

For lead

Acid neutralizing filter

whole-house, at the point of entry, about $1,200

Raises pH so plumbing stops leaching lead and copper.

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 Winona County

No water treatment company serves Winona 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 Winona County, and you get an email naming it first.

Common questions

How deep are wells in Winona County?

The typical domestic well in Winona County is 215 feet deep, based on 1,812 wells reported to the state since 1904. One in ten is deeper than 595 feet. 91% are drilled into bedrock.

Is there arsenic in well water in Winona County?

Arsenic was detected in 39% of 107 public well samples in Winona 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 Winona 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 Winona County

21 towns have fewer than 30 public samples and are included in the Winona County totals above rather than shown separately: Altura, Dakota, Dresbach township, Elba, Fremont township, Goodview, Homer township, La Crescent, Lewiston, Minneiska, Minnesota City, Mount Vernon township, New Hartford township, Richmond township, Rollingstone, Rollingstone township, St. Charles, Stockton, Utica, Whitewater township, Winona.

Counties near Winona 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 Minnesota dataset as CSV, every county and town, with the sources named.

Sources

USGS Water Quality Portal: 883 samples in Winona 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.
MDH new private well arsenic tests: summaries for 1 contaminants in Winona County, up to 327 wells each. Arsenic results for every new private well drilled and tested August 2008 to December 2021, reported to the Minnesota Department of Health by well contractors and published by county. Mandatory test on new wells only, so older wells are not represented; 64,793 wells statewide. Shares are against 10 ug/L, which MDH applies as its advice level. Median and 95th percentile published per county. Retrieved September 15, 2026.
USGS national arsenic model (Ayotte 2017): estimated share of 10,535 people on private wells in Winona 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.
Minnesota Well Index: 2,367 well records in Winona County, 1,812 domestic. Well construction records from the Minnesota Well Index (Minnesota Department of Health), non-public-supply wells. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 15, 2026.
MPCA regulated sites: 555 regulated sites located in Winona County. Tank, leak, remediation, Superfund and landfill sites from the Minnesota Pollution Control Agency What's In My Neighborhood database. Retrieved September 15, 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.