Well water in Washington County, Minnesota
In Washington County, 3% of 1,247 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 PFOA: 22% of 701 local samples were above the limit, too few samples to carry the headline but first on the test list below.
1,247 private wells tested 2008 to 2021 in state summaries; 8,031 test results across 15 contaminants from at least 436 wells, 1957 to 2025; chloride has the most at 1,203. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 47,417 people in Washington County get their drinking water from a private well, per USGS 2015 county water use. That is about 19% of residents.
Separately, the USGS national arsenic model estimates that 3% of the 47,417 people on private wells in Washington County draw water above 10 ug/L (the model's range is 3% to 4%), 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 | 1,247 | 2 | 7.9 | 10 ug/L |
What individual samples found
Each row summarizes every public sample for that contaminant inside Washington 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 |
|---|---|---|---|---|---|---|
| PFOA 2005 to 2025 | 701 | 26% | 0 | 1,200 | 4 ng/L EPA limit | |
| PFOS 2005 to 2023 | 648 | 21% | 0 | 500 | 4 ng/L EPA limit | |
| Nitrate 1961 to 2018 | 472 | 83% | 0.8 | 32.4 | 10 mg/L EPA limit | |
| Arsenic 1979 to 2025 | 615 | 18% | 0 | 15.5 | 10 ug/L EPA limit | |
| Lead 1972 to 2025 | 721 | 5% | 0 | 29.2 | 15 ug/L EPA limit | |
| Copper 1972 to 2025 | 631 | 24% | 0 | 0.224 | 1.3 mg/L EPA limit | |
| Fluoride 1957 to 2025 | 399 | 59% | 0.1 | 0.34 | 4 mg/L EPA limit | |
| Radium (226 + 228) 2007 to 2018 | 26 | 42% | 0 | 1 | 5 pCi/L EPA limit | |
| Uranium 1979 to 2018 | 24 | 75% | 0.488 | 2.7 | 30 ug/L EPA limit | |
| E. coli 2007 to 2018 | 11 | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Chloride 1957 to 2025 | no limit | 1,203 | 99% | 25 | 4,400 | 250 mg/L nuisance level |
| Iron 1957 to 2025 | no limit | 944 | 47% | 0 | 52,200 | 300 ug/L nuisance level |
| Sodium 1961 to 2025 | no limit | 824 | 100% | 7 | 340 | 20 mg/L health guideline |
| Manganese 1957 to 2025 | no limit | 803 | 34% | 0 | 4,330 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Radon (9).
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 | <1%135 samples | n/a | 0%401 samples | 0%177 samples |
| PFOA | n/a | 20%637 samples | n/a | 40%63 samples |
| PFOS | n/a | 21%637 samples | n/a | 20%10 samples |
| Copper | 0%135 samples | n/a | 0%311 samples | 0%177 samples |
| Arsenic | 7%29 samples | n/a | <1%401 samples | 0%177 samples |
| Nitrate | 6%90 samples | 2%368 samples | 14%14 samples | n/a |
PFOA above the limit in Washington County rose from 20% of 637 samples in the 2000s to 40% of 63 in the 2020s.
Lead, copper, arsenic, nitrate 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 Washington County who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (3% of 1,247 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 Washington County
- 1PFOA22% of 701 local samples were above the limit.
- 2PFOS21% of 648 local samples were above the limit.
- 3Arsenic3% of 1,247 local wells tested were above the EPA limit.
- 4Nitrate3% of 472 local samples were above the limit.
- 5Lead<1% of 721 local samples were above the limit.
- 6Coliform bacteriaRecommended for every private well, every year.
- 7RadonMedian local reading is 370 pCi/L.
- 8Volatile organic compounds (VOCs)445 leaking underground storage tank sites on record locally.
- 9Metals panel20 hazardous waste sites on record locally.
Test your Washington County well for PFOA, PFOS and arsenic
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 Washington County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Washington County
12,707 domestic wells in Washington County are on record with the state since 1914. 75% are drilled into bedrock, and the typical well is 180 feet deep (one in ten goes past 300 feet).
In a typical Washington County well, bedrock starts about 82 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 Washington 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 Washington County
MPCA records 445 leaking underground storage tank sites and 20 hazardous waste sites in Washington County, among 1,028 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.
- 445
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 20
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 383
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 49
- lined landfills and transfer facilities
- 131
- other remediation projects
Treatment that fits the local profile
PFOA
Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
PFOS
Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
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
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 PFOA
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
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 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 PFOS
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 PFOS
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 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.
Free, no obligation
Get on the list for a free in-home water test in Washington County
No water treatment company serves Washington 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 Washington County, and you get an email naming it first.
Common questions
How deep are wells in Washington County?
The typical domestic well in Washington County is 180 feet deep, based on 12,707 wells reported to the state since 1914. One in ten is deeper than 300 feet. 75% are drilled into bedrock.
Is there arsenic in well water in Washington County?
Arsenic was detected in 18% of 615 public well samples in Washington County, and <1% 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 Washington 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 Washington County
- Baytown township0% lead
- Cottage Grove20% nitrate
- Denmark township8% nitrate
- Grant0% copper
- Hugo4% nitrate
- Lake Elmo1% nitrate
- May township30 samples
- Scandia45 samples
- West Lakeland township3% nitrate
- Woodbury1% nitrate
23 towns have fewer than 30 public samples and are included in the Washington County totals above rather than shown separately: Afton, Bayport, Birchwood Village, Dellwood, Forest Lake, Grey Cloud Island township, Hastings, Lakeland, Lakeland Shores, Lake St. Croix Beach, Landfall, Mahtomedi, Marine on St. Croix, Newport, Oakdale, Oak Park Heights, Pine Springs, Stillwater, Stillwater township, St. Marys Point, St. Paul Park, White Bear Lake, Willernie.
Counties near Washington 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: 8,031 samples in Washington 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 Washington County, up to 1,247 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 47,417 people on private wells in Washington 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: 15,030 well records in Washington County, 12,707 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: 1,028 regulated sites located in Washington 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.