Well water in Barnstable County, Massachusetts
1in2
Testing strongly recommended
tested well samples in Barnstable County exceeded the EPA limit for PFOS (4 ng/L), based on public data from USGS Water Quality Portal.
83 private wells tested 2020 to 2023 in state summaries; 23,989 test results across 12 contaminants from at least 1,415 wells, 1948 to 2025; nitrate has the most at 10,914. Data refreshed September 16, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
MassDEP offered free PFAS tests to towns without public water and to wells near suspected sources such as landfills, fire stations and airports, so these shares describe the wells that took part rather than every well in town.
An estimated 12,247 people in Barnstable County get their drinking water from a private well, per USGS 2015 county water use. That is about 6% of residents.
Separately, the USGS national arsenic model estimates that 10% of the 12,247 people on private wells in Barnstable County draw water above 10 ug/L (the model's range is 7% to 16%), from geology and well depth rather than local tests.
What homeowner tests found
MassDEP Private Well PFAS Sampling Program: private wells tested and reported to the state, 2020 to 2023. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA. County and state figures combine the town summaries, weighted by wells tested; medians are not combined.
What individual samples found
Each row summarizes every public sample for that contaminant inside Barnstable 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 |
|---|---|---|---|---|---|---|
| PFOS 2020 to 2021 | 113 | 83% | 120 | 20,800 | 4 ng/L EPA limit | |
| PFOA 2020 to 2021 | 113 | 86% | 19 | 13,700 | 4 ng/L EPA limit | |
| Nitrate 1948 to 2025 | 10,914 | 88% | 1.47 | 330 | 10 mg/L EPA limit | |
| Lead 1976 to 2016 | 469 | 15% | 0 | 40 | 15 ug/L EPA limit | |
| Arsenic 1976 to 2016 | 122 | 70% | 0.8 | 19 | 10 ug/L EPA limit | |
| Fluoride 1948 to 2023 | 1,424 | 53% | 0 | 6.5 | 4 mg/L EPA limit | |
| Copper 1976 to 2016 | 484 | 20% | 0 | 0.12 | 1.3 mg/L EPA limit | |
| Uranium 1998 to 2016 | 25 | 4% | 0 | 0.02 | 30 ug/L EPA limit | |
| Chloride 1948 to 2023 | no limit | 3,760 | 100% | 19 | 20,000 | 250 mg/L nuisance level |
| Sodium 1962 to 2016 | no limit | 2,787 | 100% | 12 | 3,600 | 20 mg/L health guideline |
| Iron 1948 to 2016 | no limit | 1,974 | 64% | 10 | 35,000 | 300 ug/L nuisance level |
| Manganese 1956 to 2016 | no limit | 1,804 | 90% | 46.6 | 14,100 | 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 |
|---|---|---|---|---|
| Nitrate | 16%4,363 samples | 4%1,493 samples | 25%2,072 samples | 19%2,986 samples |
| Fluoride | <1%1,348 samples | 0%21 samples | 0%34 samples | 0%21 samples |
| Copper | 0%453 samples | 0%29 samples | n/a | n/a |
| Lead | 3%406 samples | 0%48 samples | 0%15 samples | n/a |
| Arsenic | 2%43 samples | 3%77 samples | n/a | n/a |
Nitrate above the limit in Barnstable County fell from 25% of 2072 samples in the 2010s to 19% of 2986 in the 2020s.
Fluoride, copper, lead, arsenic 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 Barnstable County who sent a sample to the state lab, the health-based limits most often exceeded were PFOA (11% of 83 wells), PFOS (7% of 83 wells), and PFHxS (1% of 83 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 Barnstable County
- 1PFOS81% of 113 local samples were above the limit.
- 2PFOA75% of 113 local samples were above the limit.
- 3Nitrate17% of 10,914 local samples were above the limit.
- 4Lead3% of 469 local samples were above the limit.
- 5Arsenic2% of 122 local samples were above the limit.
- 6PFHxS1% of 83 local wells tested were above the EPA limit.
- 7Fluoride<1% of 1,424 local samples were above the limit.
- 8Coliform bacteriaRecommended for every private well, every year.
- 9PFAS20 unlined landfills on record locally.
- 10Volatile organic compounds (VOCs)20 unlined landfills on record locally.
- 11Metals panel31 hazardous waste sites on record locally.
Test your Barnstable County well for PFOS, PFOA 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 Massachusetts: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Barnstable County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Barnstable County
7,320 domestic wells in Barnstable County are on record with the state since 1914. <1% are drilled into bedrock, and the typical well is 54 feet deep (one in ten goes past 92 feet).
In a typical Barnstable County well, bedrock starts about 14 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 MassDEP Well Location Viewer and choose Water Well.
- The completion report lists total depth, depth to bedrock, static water level, yield and the driller.
Drillers have filed completion reports with the state since 1984; the viewer's public copy is refreshed a few times a year.
The rock under Barnstable 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 Massachusetts
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 Wells, MassDEP
- Certified Laboratories, MassDEP
Contamination sources on record in Barnstable County
MassDEP records 20 unlined landfills and 31 hazardous waste sites in Barnstable County, among 275 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
- unlined landfillsOlder unlined landfills are a leading source of PFAS, VOCs and metals in nearby wells.
- 31
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 199
- 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
- 23
- 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
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
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
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 lead
Acid neutralizing filter
whole-house, at the point of entry, about $1,200
Raises pH so plumbing stops leaching lead and copper.
Free, no obligation
Get on the list for a free in-home water test in Barnstable County
No water treatment company serves Barnstable 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 Barnstable County, and you get an email naming it first.
Common questions
How deep are wells in Barnstable County?
The typical domestic well in Barnstable County is 54 feet deep, based on 7,320 wells reported to the state since 1914. One in ten is deeper than 92 feet. <1% are drilled into bedrock.
Is there arsenic in well water in Barnstable County?
Arsenic was detected in 70% of 122 public well samples in Barnstable County, and 2% 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 Barnstable 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 Barnstable County
- Barnstable Town17% nitrate
- Bourne<1% nitrate
- Brewster0% nitrate
- Chatham0% nitrate
- Dennis0% nitrate
- Eastham35% nitrate
- Falmouth14% nitrate
- Harwich0% nitrate
- Mashpee0% nitrate
- Orleans52% nitrate
- Sandwich15% nitrate
- Truro6% pfoa
- Wellfleet15% pfoa
- Yarmouth0% nitrate
1 towns have fewer than 30 public samples and are included in the Barnstable County totals above rather than shown separately: Provincetown.
Counties near Barnstable 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 Massachusetts dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 23,989 samples in Barnstable 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.
- MassDEP Private Well PFAS Sampling Program: summaries for 4 contaminants in Barnstable County, up to 83 wells each. Private well PFAS results from the Massachusetts Department of Environmental Protection free sampling program, 2020 to 2023, one anonymized row per well. Shares are against the EPA limit for each compound (4 ng/L for PFOA and PFOS, 10 ng/L for PFHxS and PFNA). Massachusetts applies its own PFAS6 standard of 20 ng/L to the sum of six compounds; that sum is not a contaminant page here. Zero means not detected. Retrieved September 16, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 12,247 people on private wells in Barnstable 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.
- MassDEP well completion reports: 10,976 well records in Barnstable County, 7,320 domestic. Well completion reports filed with the Massachusetts Department of Environmental Protection, as published in the Well Location Viewer (April 2023 vintage). Only aggregates are shown; owner names and addresses are never stored. Retrieved September 16, 2026.
- MassDEP regulated sites: 275 regulated sites located in Barnstable County. Chapter 21E release sites, solid waste landfills and underground storage tank facilities from the Massachusetts Department of Environmental Protection, through MassGIS. 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.