Well water in Hancock County, Maine
In Hancock County, 22% of 2,622 private wells tested had arsenic above the Maine guideline (10 ug/L), according to Maine CDC.
2,937 private wells tested in state summaries; 64 individual samples from 58 wells, 1967 to 2026. Data refreshed September 3, 2026.
Maine DEP samples private wells near fields where sludge or septage was spread and near other known PFAS sources, and resamples detections. PFAS shares describe wells that were tested for a reason, not every well in the area. In that targeted sampling, 12% of 58 PFOA results in Hancock County were above the EPA limit of 4 ng/L. In that targeted sampling, 5% of 58 PFOS results in Hancock County were above the EPA limit of 4 ng/L.
What homeowner tests found
Maine Tracking Network private well summaries: private wells tested and reported to the state. 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 Hancock 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 | Samples | Detected | Above limit | Median | Highest | Limit | |
|---|---|---|---|---|---|---|---|
| Arsenic 1981 to 2007 | 64 | 84% | 50% | 10.1 | 720 | 10 ug/L EPA limit | |
| Uranium 2003 to 2007 | 22 | 100% | 23% | 3.19 | 380 | 30 ug/L EPA limit | |
| PFOA 2021 to 2026 | 58 | 53% | 12% | 0.348 | 16.7 | 4 ng/L EPA limit | |
| PFOS 2021 to 2026 | 58 | 36% | 5% | 0 | 18 | 4 ng/L EPA limit | |
| PFHxS 2021 to 2026 | 58 | 14% | 0% | 0 | 1.04 | 10 ng/L EPA limit | |
| PFNA 2021 to 2026 | 58 | 10% | 0% | 0 | 2.4 | 10 ng/L EPA limit | |
| Nitrate 1967 to 2007 | 41 | 54% | 0% | 0.035 | 2.4 | 10 mg/L EPA limit | |
| Copper 1981 to 2006 | 17 | 65% | 0% | 0 | 0.02 | 1.3 mg/L EPA limit | |
| Chloride 1967 to 2008 | 41 | 100% | no limit | 4.43 | 227 | 250 mg/L nuisance level |
Sampled fewer than 10 times, too few to summarize: Lead (2), Fluoride (2), Sodium (5), Iron (3), Manganese (2).
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What this means
Among homeowners in Hancock County who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (22% of 2,622 wells), uranium (8% of 2,264 wells), and fluoride (6% of 2,937 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 Hancock County
- Volatile organic compounds (VOCs)68 leaking underground storage tank sites on record locally.
- PFAS29 unlined landfills on record locally.
- Metals panel25 hazardous waste sites on record locally.
- PFOA12% of 58 local samples were above the limit.
- Manganese6% of 2,494 local wells tested were above the Maine guideline.
- Fluoride6% of 2,937 local wells tested were above the Maine guideline.
- PFOS5% of 58 local samples were above the limit.
- Nitrate<1% of 2,898 local wells tested were above the Maine guideline.
- Coliform bacteriaRecommended for every private well, every year.
- ChlorideDetected in 100% of local samples.
Wells in Hancock County
8,970 domestic wells in Hancock County are on record with the state since 1970. 100% are drilled into bedrock, and the typical well is 220 feet deep (one in ten goes past 405 feet).
In a typical Hancock County well, bedrock starts about 13 feet down, the median yield is 5 gallons per minute, 24% of wells yield under 3 gallons per minute and usually need a storage tank.
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.
Contamination sources on record in Hancock County
Maine DEP records 68 leaking underground storage tank sites, 29 unlined landfills, and 25 hazardous waste sites in Hancock County, among 249 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.
- 68
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 29
- unlined landfillsOlder unlined landfills are a leading source of PFAS, VOCs and metals in nearby wells.
- 25
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 127
- other remediation projects
Treatment that fits the local profile
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Uranium
- Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Manganese
- Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
- 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
Book a free water test in Hancock County
A licensed local water treatment company tests your tap water in your home, walks you through the numbers, and quotes treatment only if something needs fixing. Free, about 30 minutes, no obligation.
Common questions
How deep are wells in Hancock County?
The typical domestic well in Hancock County is 220 feet deep, based on 8,970 wells reported to the state since 1970. One in ten is deeper than 405 feet. 100% are drilled into bedrock.
Is there arsenic in well water in Hancock County?
Arsenic was detected in 84% of 64 public well samples in Hancock County, and 50% 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 Hancock 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 Hancock County
- Bar Harbor7% arsenic
- Blue Hill41% arsenic
- Brooklin8% arsenic
- Brooksville17% arsenic
- Bucksport17% arsenic
- Dedham34% uranium
- Deer Isle8% arsenic
- Ellsworth26% arsenic
- Franklin17% arsenic
- Gouldsboro4% fluoride
- Hancock18% arsenic
- Lamoine8% arsenic
- Mariaville14% fluoride
- Mount Desert15% uranium
- Orland40% arsenic
- Otis49% arsenic
- Penobscot24% arsenic
- Sedgwick52% arsenic
- Southwest Harbor0% nitrate
- Stonington3% uranium
- Sullivan9% arsenic
- Surry46% arsenic
- Swans Island0% nitrate
- Tremont6% arsenic
- Trenton42% arsenic
- Verona Island11% arsenic
15 towns have fewer than 30 public samples and are included in the Hancock County totals above rather than shown separately: Amherst, Aurora, Castine, Central Hancock UT, Cranberry Isles, Eastbrook, East Hancock UT, Frenchboro, Great Pond, Marshall Island UT, Northwest Hancock UT, Osborn, Sorrento, Waltham, Winter Harbor.
Sources
- Maine DEP PFAS investigation: 232 samples in Hancock County. PFAS results for private wells sampled by the Maine Department of Environmental Protection. Retrieved September 3, 2026.
- USGS Water Quality Portal: 199 samples in Hancock 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.
- Maine Tracking Network private well summaries: summaries for 6 contaminants in Hancock County, up to 2,937 wells each. Town summaries of private well tests run by the Maine Health and Environmental Testing Laboratory, published by Maine CDC through the Maine Tracking Network. Shares are against Maine's guideline for each analyte (arsenic 10 ug/L, uranium 30 ug/L, fluoride 2 mg/L, manganese 0.3 mg/L, nitrate 10 mg/L, nitrite 1 mg/L). Towns with too few tests are suppressed (NR). Only the share above the guideline and wells tested are published; no medians. Retrieved September 3, 2026.
- Maine Geological Survey well database: 9,381 well records in Hancock County, 8,970 domestic. Well construction records reported to the Maine Geological Survey by licensed well drillers. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 3, 2026.
- Maine DEP regulated sites: 249 regulated sites located in Hancock County. Remediation sites, leaking underground storage tanks and closed municipal landfills from the Maine Department of Environmental Protection. Retrieved September 3, 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.