Well water in Washtenaw County, Michigan
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Testing strongly recommended
tested well samples in Washtenaw County exceeded the EPA limit for arsenic (10 ug/L), based on public data from USGS Water Quality Portal.
1,080 test results across 13 contaminants from at least 193 wells, 1884 to 2026; nitrate has the most at 256. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 66,798 people in Washtenaw 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 8% of the 66,798 people on private wells in Washtenaw County draw water above 10 ug/L (the model's range is 6% to 11%), from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside Washtenaw 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 1971 to 2016 | 45 | 87% | 1.2 | 72 | 10 ug/L EPA limit | |
| Nitrate 1941 to 2026 | 256 | 79% | 0 | 33.7 | 10 mg/L EPA limit | |
| Fluoride 1944 to 2016 | 68 | 97% | 0.3 | 2.4 | 4 mg/L EPA limit | |
| Lead 1971 to 2016 | 31 | 45% | 0 | 0.1 | 15 ug/L EPA limit | |
| Copper 1971 to 2016 | 30 | 60% | 0 | 0.06 | 1.3 mg/L EPA limit | |
| Uranium 1976 to 2016 | 27 | 85% | 0.714 | 7.8 | 30 ug/L EPA limit | |
| Radium (226 + 228) 2007 to 2016 | 22 | 91% | 0.59 | 1.4 | 5 pCi/L EPA limit | |
| E. coli 1999 to 2016 | 15 | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Chloride 1884 to 2016 | no limit | 225 | 100% | 10.8 | 26,200 | 250 mg/L nuisance level |
| Iron 1897 to 2016 | no limit | 213 | 97% | 1,800 | 10,000 | 300 ug/L nuisance level |
| Sodium 1884 to 2016 | no limit | 73 | 100% | 23 | 14,600 | 20 mg/L health guideline |
| Manganese 1944 to 2016 | no limit | 64 | 95% | 38.2 | 170 | 300 ug/L health guideline |
| Radon 1996 to 1998 | no limit | 11 | 100% | 200 | 530 | 2,000 pCi/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 |
|---|---|---|---|---|
| Nitrate | <1%208 samples | 15%26 samples | 22%18 samples | n/a |
| Fluoride | 0%45 samples | 0%14 samples | n/a | n/a |
| Arsenic | 40%25 samples | 0%11 samples | n/a | n/a |
| Lead | 0%11 samples | 0%11 samples | n/a | n/a |
| Copper | 0%10 samples | 0%11 samples | n/a | n/a |
Nitrate above the limit in Washtenaw County rose from <1% of 208 samples before 2000 to 15% of 26 in the 2000s.
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
The contaminants most often above their limit here are arsenic (22% of 45 samples) and nitrate (4% of 256 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.
Chloride, Iron, and Manganese are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Washtenaw County
- 1Arsenic22% of 45 local samples were above the limit.
- 2Nitrate4% of 256 local samples were above the limit.
- 3Coliform bacteriaRecommended for every private well, every year.
- 4RadonMedian local reading is 200 pCi/L.
- 5ChlorideDetected in 100% of local samples.
- 6IronDetected in 97% of local samples.
- 7FluorideDetected in 97% of local samples.
- 8Volatile organic compounds (VOCs)114 leaking underground storage tank sites on record locally.
- 9Metals panel467 hazardous waste sites on record locally.
Test your Washtenaw County well for arsenic, nitrate 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 Michigan: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Washtenaw County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Washtenaw County
30,428 domestic wells in Washtenaw County are on record with the state since 1922. 11% are drilled into bedrock, and the typical well is 92 feet deep (one in ten goes past 171 feet).
In a typical Washtenaw County well, bedrock starts about 109 feet down, the median yield is 15 gallons per minute, <1% of wells yield under 3 gallons per minute and usually need a storage tank.
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 Wellogic (EGLE) and choose Water Well.
- The record lists depth, casing, static water level, the pump test and the geologic log.
Michigan has required well records since 1966, so most drilled wells are on file.
The rock under Washtenaw 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 Michigan
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.
- Private Residential Water Well Testing, Michigan EGLE
- Laboratory certification program, Michigan EGLE
Contamination sources on record in Washtenaw County
Michigan EGLE records 114 leaking underground storage tank sites and 467 hazardous waste sites in Washtenaw County, among 1,282 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.
- 114
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 467
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 700
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 1
- lined landfill or transfer facility
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
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Manganese
Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
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 Washtenaw County
No water treatment company serves Washtenaw 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 Washtenaw County, and you get an email naming it first.
Common questions
How deep are wells in Washtenaw County?
The typical domestic well in Washtenaw County is 92 feet deep, based on 30,428 wells reported to the state since 1922. One in ten is deeper than 171 feet. 11% are drilled into bedrock.
Is there arsenic in well water in Washtenaw County?
Arsenic was detected in 87% of 45 public well samples in Washtenaw County, and 22% 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 high is radon in well water in Washtenaw County?
The median radon level across 11 public samples in Washtenaw County was 200 pCi/L, with a high of 530 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Washtenaw 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 Washtenaw County
25 towns have fewer than 30 public samples and are included in the Washtenaw County totals above rather than shown separately: Ann Arbor, Ann Arbor charter township, Augusta charter township, Bridgewater township, Chelsea, Dexter, Dexter township, Freedom township, Lima township, Lyndon township, Manchester township, Milan, Northfield township, Pittsfield charter township, Salem township, Saline, Saline township, Scio township, Sharon township, Superior charter township, Sylvan township, Webster township, York charter township, Ypsilanti, Ypsilanti charter township.
Counties near Washtenaw 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 Michigan dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 1,080 samples in Washtenaw 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.
- USGS national arsenic model (Ayotte 2017): estimated share of 66,798 people on private wells in Washtenaw 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.
- Michigan Wellogic well records: 30,428 well records in Washtenaw County, 30,428 domestic. Water well records from Wellogic, the Michigan Department of Environment, Great Lakes, and Energy statewide well database. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 16, 2026.
- Michigan EGLE regulated sites: 1,282 regulated sites located in Washtenaw County. Part 201 environmental contamination sites, underground storage tank facilities and Part 115 landfills from the Michigan Department of Environment, Great Lakes, and Energy. Retrieved September 16, 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.