Well water in Cass County, Minnesota
In Cass County, 4% of 3,976 private wells tested between 2008 and 2021 had arsenic above the EPA limit (10 ug/L), according to the Minnesota Department of Health.
3,976 private wells tested 2008 to 2021 in state summaries; 2,273 test results across 12 contaminants from at least 164 wells, 1965 to 2025; chloride has the most at 327. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 24,556 people in Cass County get their drinking water from a private well, per USGS 2015 county water use. That is about 86% of residents.
Separately, the USGS national arsenic model estimates that 6% of the 24,556 people on private wells in Cass 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 | 3,976 | 2 | 8.9 | 10 ug/L |
What individual samples found
Each row summarizes every public sample for that contaminant inside Cass 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 1987 to 2025 | 248 | 58% | 0.475 | 33.3 | 10 ug/L EPA limit | |
| Lead 1987 to 2025 | 248 | 16% | 0 | 7.65 | 15 ug/L EPA limit | |
| Fluoride 1965 to 2025 | 231 | 77% | 0.1 | 0.45 | 4 mg/L EPA limit | |
| Copper 1989 to 2025 | 151 | 17% | 0 | 0.02 | 1.3 mg/L EPA limit | |
| Nitrate 1965 to 2011 | 113 | 55% | 0.03 | 9.91 | 10 mg/L EPA limit | |
| PFOA 2022 to 2025 | 19 | 26% | 0 | 2.94 | 4 ng/L EPA limit | |
| Chloride 1965 to 2025 | no limit | 327 | 90% | 1.36 | 121 | 250 mg/L nuisance level |
| Sodium 1965 to 2025 | no limit | 315 | 100% | 4.01 | 119 | 20 mg/L health guideline |
| Iron 1965 to 2025 | no limit | 310 | 69% | 81.5 | 21,000 | 300 ug/L nuisance level |
| Manganese 1965 to 2025 | no limit | 302 | 74% | 93.2 | 4,800 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Uranium (7), PFOS (2).
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 |
|---|---|---|---|---|
| Arsenic | 6%36 samples | n/a | 6%169 samples | 0%37 samples |
| Lead | 0%36 samples | n/a | 0%169 samples | 0%37 samples |
| Fluoride | 0%90 samples | n/a | 0%99 samples | 0%36 samples |
| Copper | 0%28 samples | n/a | 0%80 samples | 0%37 samples |
| Nitrate | 0%97 samples | 0%14 samples | n/a | n/a |
Arsenic above the limit in Cass County fell from 6% of 169 samples in the 2010s to 0% of 37 in the 2020s.
Lead, fluoride, copper have held within a few points between the two most recent periods with enough samples.
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 Cass County who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (4% of 3,976 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 Cass County
- 1Arsenic5% of 248 local samples were above the limit.
- 2Coliform bacteriaRecommended for every private well, every year.
- 3NitrateRecommended for every private well, especially near farms or septic systems.
- 4ChlorideDetected in 90% of local samples.
- 5FluorideDetected in 77% of local samples.
- 6ManganeseDetected in 74% of local samples.
- 7IronDetected in 69% of local samples.
- 8Volatile organic compounds (VOCs)153 leaking underground storage tank sites on record locally.
- 9Metals panel3 hazardous waste sites on record locally.
Test your Cass County well for arsenic, coliform bacteria and nitrate
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 Cass County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Cass County
12,089 domestic wells in Cass County are on record with the state since 1962. <1% are drilled into bedrock, and the typical well is 69 feet deep (one in ten goes past 137 feet).
In a typical Cass County well, bedrock starts about 130 feet down.
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 Cass County
Not a principal aquifer
The USGS map places this area outside any principal aquifer, which usually means wells here draw from fractured bedrock or thin local deposits rather than a large regional aquifer. Bedrock wells of that kind are where arsenic, radon and uranium turn up, and yields vary from well to well.
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 Cass County
MPCA records 153 leaking underground storage tank sites and 3 hazardous waste sites in Cass County, among 444 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.
- 153
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 3
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 204
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 47
- lined landfills and transfer facilities
- 37
- other remediation projects
Treatment that fits the local profile
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Manganese
Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
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 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 Cass County
No water treatment company serves Cass 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 Cass County, and you get an email naming it first.
Common questions
How deep are wells in Cass County?
The typical domestic well in Cass County is 69 feet deep, based on 12,089 wells reported to the state since 1962. One in ten is deeper than 137 feet. <1% are drilled into bedrock.
Is there arsenic in well water in Cass County?
Arsenic was detected in 58% of 248 public well samples in Cass County, and 5% 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 Cass 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 Cass County
67 towns have fewer than 30 public samples and are included in the Cass County totals above rather than shown separately: Ansel township, Backus, Barclay township, Becker township, Bena, Beulah township, Birch Lake township, Blind Lake township, Boy Lake township, Boy River, Boy River township, Bull Moose township, Bungo township, Byron township, Cass Lake, Chickamaw Beach, Crooked Lake township, Deerfield township, East Cass UT, East Gull Lake, Fairview township, Federal Dam, Gould township, Hackensack, Hiram township, Home Brook township, Inguadona township, Kego township, Lake Shore, Leech Lake township, Longville, Loon Lake township, Maple township, May township, McKinley township, Meadow Brook township, Moose Lake township, Motley, North Central Cass UT, Otter Tail Peninsula township, Pillager, Pine Lake township, Pine River, Pine River township, Ponto Lake township, Poplar township, Powers township, Remer, Remer township, Rogers township, Salem township, Shingobee township, Slater township, Smoky Hollow township, Sylvan township, Thunder Lake township, Torrey township, Trelipe township, Turtle Lake township, Wabedo township, Wahnena UT, Walden township, Walker, Wilkinson township, Willow River UT, Wilson township, Woodrow township.
Counties near Cass 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: 2,273 samples in Cass 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 Cass County, up to 3,976 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 24,556 people on private wells in Cass 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: 12,917 well records in Cass County, 12,089 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: 444 regulated sites located in Cass 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.