Well water in Cottage Grove, Minnesota
1in5
Testing strongly recommended
private wells tested between 2014 and 2019 in Cottage Grove had nitrate above the EPA limit (10 mg/L), according to the Minnesota Department of Agriculture.
248 private wells tested 2014 to 2019 in state summaries; 1,679 test results across 11 contaminants from at least 184 wells, 1961 to 2025; PFOA has the most at 234. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
What homeowner tests found
MDA Township Testing Program nitrate: private wells tested and reported to the state, 2014 to 2019. 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 |
|---|---|---|---|---|---|---|
| Nitrate | 248 | 10 mg/L |
What individual samples found
Each row summarizes every public sample for that contaminant inside Cottage Grove. 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 |
|---|---|---|---|---|---|---|
| PFOA 2007 to 2025 | 234 | 6% | 0 | 1,200 | 4 ng/L EPA limit | |
| PFOS 2007 to 2023 | 228 | 0% | 0 | 0 | 4 ng/L EPA limit | |
| Lead 1996 to 2025 | 157 | 3% | 0 | 4.12 | 15 ug/L EPA limit | |
| Copper 1996 to 2025 | 149 | 14% | 0 | 0.084 | 1.3 mg/L EPA limit | |
| Arsenic 1996 to 2025 | 87 | 7% | 0 | 0.849 | 10 ug/L EPA limit | |
| Fluoride 1961 to 2025 | 85 | 75% | 0.13 | 0.2 | 4 mg/L EPA limit | |
| Nitrate 1961 to 2007 | 17 | 94% | 4 | 9 | 10 mg/L EPA limit | |
| Chloride 1961 to 2025 | no limit | 201 | 99% | 18.2 | 351 | 250 mg/L nuisance level |
| Iron 1961 to 2025 | no limit | 180 | 48% | 0 | 3,200 | 300 ug/L nuisance level |
| Sodium 1961 to 2025 | no limit | 173 | 100% | 6.04 | 105 | 20 mg/L health guideline |
| Manganese 1968 to 2025 | no limit | 168 | 35% | 0 | 206 | 300 ug/L health guideline |
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 |
|---|---|---|---|---|
| Lead | 0%76 samples | n/a | 0%59 samples | 0%22 samples |
| Copper | 0%76 samples | n/a | 0%51 samples | 0%22 samples |
| Fluoride | 0%56 samples | n/a | 0%11 samples | 0%18 samples |
| Arsenic | n/a | n/a | 0%59 samples | 0%22 samples |
Lead, copper, arsenic have held within a few points between the two most recent periods with enough samples.
Closer than the town
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 Cottage Grove who sent a sample to the state lab, the health-based limits most often exceeded were nitrate (20% of 248 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 Cottage Grove
- 1Nitrate20% of 248 local wells tested were above the EPA limit.
- 2PFOA6% of 234 local samples were above the limit.
- 3Coliform bacteriaRecommended for every private well, every year.
- 4ChlorideDetected in 99% of local samples.
- 5FluorideDetected in 75% of local samples.
- 6Volatile organic compounds (VOCs)20 leaking underground storage tank sites on record locally.
- 7Metals panel3 hazardous waste sites on record locally.
Test your Cottage Grove well for nitrate, PFOA 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 $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 Cottage Grove numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Cottage Grove
544 domestic wells in Cottage Grove are on record with the state since 1963. 97% are drilled into bedrock, and the typical well is 270 feet deep (one in ten goes past 360 feet).
In a typical Cottage Grove well, bedrock starts about 42 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.
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 Cottage Grove
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 town 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 Cottage Grove
MPCA records 20 leaking underground storage tank sites and 3 hazardous waste sites in Cottage Grove, among 77 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.
- 20
- 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.
- 36
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 2
- lined landfills and transfer facilities
- 16
- other remediation projects
Treatment that fits the local profile
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
PFOA
Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
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 PFOA
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 PFOA
Whole-house PFAS carbon system
whole-house, at the point of entry, about $3,000
Granular activated carbon certified to NSF/ANSI 53 for PFOA and PFOS; replace media on schedule.
For PFOA
Aquasana HealthShield whole-house filter
whole-house, at the point of entry, about $2,099
Whole-house carbon system the maker certifies to reduce PFAS (PFOA and PFOS) and VOCs at every tap; a UV option adds bacteria protection.
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 Cottage Grove
No water treatment company serves Cottage Grove 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 Cottage Grove, and you get an email naming it first.
Common questions
How deep are wells in Cottage Grove?
The typical domestic well in Cottage Grove is 270 feet deep, based on 544 wells reported to the state since 1963. One in ten is deeper than 360 feet. 97% are drilled into bedrock.
Is there arsenic in well water in Cottage Grove?
Arsenic was detected in 7% of 87 public well samples in Cottage Grove, 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 Cottage Grove?
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 near Cottage Grove
Closest first. Groundwater does not stop at a line on a map, so the next town 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: 1,679 samples in Cottage Grove. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- MDA Township Testing Program nitrate: summaries for 1 contaminants in Cottage Grove, up to 248 wells each. Nitrate results from the Minnesota Department of Agriculture Township Testing Program, 2013 to 2019, which offered a free test to every well in 344 townships with vulnerable groundwater. Townships were selected for vulnerable geology and row-crop land use, so their shares run above the state as a whole; county and state figures are not derived from them. Share is the final (follow-up) result above 10 mg/L as N. Retrieved September 15, 2026.
- Minnesota Well Index: 915 well records in Cottage Grove, 544 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: 77 regulated sites located in Cottage Grove. 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.