Well water in Marshall County, Minnesota
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Testing recommended
private wells tested between 2008 and 2021 in Marshall County had arsenic above the EPA limit (10 ug/L), according to the Minnesota Department of Health.
226 private wells tested 2008 to 2021 in state summaries; 460 test results across 9 contaminants from at least 76 wells, 1953 to 2025; chloride has the most at 86. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 4,133 people in Marshall County get their drinking water from a private well, per USGS 2015 county water use. That is about 44% of residents.
Separately, the USGS national arsenic model estimates that 5% of the 4,133 people on private wells in Marshall County draw water above 10 ug/L (the model's range is 4% to 7%), 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 | 226 | 2 | 16.1 | 10 ug/L |
What individual samples found
Each row summarizes every public sample for that contaminant inside Marshall 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 |
|---|---|---|---|---|---|---|
| Arsenic 1991 to 1995 | 10 | 50% | 0.13 | 30 | 10 ug/L EPA limit | |
| Nitrate 1953 to 1995 | 65 | 85% | 1.1 | 432 | 10 mg/L EPA limit | |
| Lead 1991 to 1995 | 27 | 15% | 0 | 50.2 | 15 ug/L EPA limit | |
| Fluoride 1953 to 1995 | 68 | 100% | 0.4 | 1.1 | 4 mg/L EPA limit | |
| Copper 1991 to 1995 | 27 | 7% | 0 | 0.11 | 1.3 mg/L EPA limit | |
| Chloride 1953 to 2025 | no limit | 86 | 100% | 17 | 4,670 | 250 mg/L nuisance level |
| Sodium 1954 to 1995 | no limit | 73 | 100% | 77 | 2,680 | 20 mg/L health guideline |
| Iron 1953 to 1995 | no limit | 67 | 100% | 1,500 | 8,900 | 300 ug/L nuisance level |
| Manganese 1953 to 1995 | no limit | 37 | 100% | 45 | 320 | 300 ug/L health guideline |
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 Marshall County who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (14% of 226 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 Marshall County
- 1Arsenic40% of 10 local samples were above the limit.
- 2Nitrate18% of 65 local samples were above the limit.
- 3Lead7% of 27 local samples were above the limit.
- 4Coliform bacteriaRecommended for every private well, every year.
- 5FluorideDetected in 100% of local samples.
- 6ChlorideDetected in 100% of local samples.
- 7IronDetected in 100% of local samples.
- 8Volatile organic compounds (VOCs)61 leaking underground storage tank sites on record locally.
Test your Marshall County well for arsenic, nitrate and lead
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 Minnesota: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Marshall County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Marshall County
1,142 domestic wells in Marshall County are on record with the state since 1901. 0% are drilled into bedrock, and the typical well is 150 feet deep (one in ten goes past 291 feet).
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 Marshall County
Lower Cretaceous aquifers
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 Marshall County
MPCA records 61 leaking underground storage tank sites in Marshall County, among 143 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.
- 61
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 59
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 6
- lined landfills and transfer facilities
- 17
- other remediation projects
Treatment that fits the local profile
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
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
Chloride
Point-of-use reverse osmosis; Distillation
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 arsenic
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For arsenic
Whole-house arsenic and uranium filter
whole-house, at the point of entry, about $2,500
Adsorptive iron-based media; sized to your well yield.
For arsenic
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.
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Common questions
How deep are wells in Marshall County?
The typical domestic well in Marshall County is 150 feet deep, based on 1,142 wells reported to the state since 1901. One in ten is deeper than 291 feet. 0% are drilled into bedrock.
Is there arsenic in well water in Marshall County?
Arsenic was detected in 50% of 10 public well samples in Marshall County, and 40% 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 Marshall 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 Marshall County
60 towns have fewer than 30 public samples and are included in the Marshall County totals above rather than shown separately: Agder township, Alma township, Alvarado, Argyle, Augsburg township, Big Woods township, Bloomer township, Boxville township, Cedar township, Como township, Comstock township, Donnelly township, Eagle Point township, East Park township, East Valley township, Eckvoll township, Espelie township, Excel township, Foldahl township, Fork township, Grand Plain township, Grygla, Holt, Holt township, Huntly township, Lincoln township, Linsell township, Marsh Grove township, McCrea township, Middle River, Middle River township, Moose River township, Moylan township, Mud Lake UT, Nelson Park township, Newfolden, New Folden township, New Maine township, New Solum township, Oak Park township, Oslo, Parker township, Rollis township, Sinnott township, Spruce Valley township, Stephen, Strandquist, Tamarac township, Thief Lake township, Valley township, Vega township, Veldt township, Viking, Viking township, Wanger township, Warren, Warrenton township, West Valley township, Whiteford township, Wright township.
Counties near Marshall 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: 460 samples in Marshall 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 Marshall County, up to 226 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 4,133 people on private wells in Marshall 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: 2,023 well records in Marshall County, 1,142 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: 143 regulated sites located in Marshall 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.