Well water in Waldo County, Maine
In Waldo County, 9% of 1,434 private wells tested had arsenic above the Maine guideline (10 ug/L), according to Maine CDC.
1,664 private wells tested in state summaries; 401 individual samples from 401 wells, 1962 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, 20% of 401 PFOA results in Waldo County were above the EPA limit of 4 ng/L. In that targeted sampling, 6% of 401 PFOS results in Waldo 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 Waldo 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 2000 to 2011 | 14 | 93% | 79% | 34 | 290 | 10 ug/L EPA limit | |
| PFOA 2020 to 2026 | 401 | 50% | 20% | 0 | 5,830 | 4 ng/L EPA limit | |
| PFOS 2020 to 2026 | 401 | 33% | 6% | 0 | 668 | 4 ng/L EPA limit | |
| PFNA 2020 to 2026 | 401 | 13% | 3% | 0 | 1,580 | 10 ng/L EPA limit | |
| PFHxS 2020 to 2026 | 401 | 18% | <1% | 0 | 44 | 10 ng/L EPA limit | |
| Nitrate 1962 to 2011 | 14 | 57% | 0% | 0.076 | 8.4 | 10 mg/L EPA limit | |
| Chloride 1962 to 2011 | 10 | 100% | no limit | 5.2 | 18 | 250 mg/L nuisance level |
Sampled fewer than 10 times, too few to summarize: Uranium (8), Lead (3), Copper (2), E. coli (2), Radium (226 + 228) (2), Fluoride (1), Manganese (3), Sodium (1), Radon (1), Iron (1).
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What this means
Among homeowners in Waldo County who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (9% of 1,434 wells), uranium (6% of 1,191 wells), and fluoride (2% of 1,664 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 Waldo County
- Volatile organic compounds (VOCs)48 leaking underground storage tank sites on record locally.
- PFAS19 unlined landfills on record locally.
- Metals panel17 hazardous waste sites on record locally.
- PFOA20% of 401 local samples were above the limit.
- Uranium6% of 1,191 local wells tested were above the Maine guideline.
- PFOS6% of 401 local samples were above the limit.
- Manganese5% of 1,356 local wells tested were above the Maine guideline.
- PFNA3% of 401 local samples were above the limit.
- Fluoride2% of 1,664 local wells tested were above the Maine guideline.
- PFHxS<1% of 401 local samples were above the limit.
- Nitrate<1% of 1,654 local wells tested were above the Maine guideline.
Wells in Waldo County
3,853 domestic wells in Waldo County are on record with the state since 1970. 99% are drilled into bedrock, and the typical well is 205 feet deep (one in ten goes past 400 feet).
In a typical Waldo County well, bedrock starts about 18 feet down, the median yield is 8 gallons per minute, 17% 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 Waldo County
Maine DEP records 48 leaking underground storage tank sites, 19 unlined landfills, and 17 hazardous waste sites in Waldo County, among 181 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.
- 48
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 19
- unlined landfillsOlder unlined landfills are a leading source of PFAS, VOCs and metals in nearby wells.
- 17
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 97
- 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
- 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
- PFNA
- Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
- PFHxS
- Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
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Common questions
How deep are wells in Waldo County?
The typical domestic well in Waldo County is 205 feet deep, based on 3,853 wells reported to the state since 1970. One in ten is deeper than 400 feet. 99% are drilled into bedrock.
Is there arsenic in well water in Waldo County?
Arsenic was detected in 93% of 14 public well samples in Waldo County, and 79% 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 Waldo County?
The median radon level across 1 public samples in Waldo County was 3,480 pCi/L, with a high of 3,480 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Waldo 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 Waldo County
- Belfast20% arsenic
- Belmont6% arsenic
- Brooks2% uranium
- Burnham7% arsenic
- Frankfort14% uranium
- Freedom3% fluoride
- Jackson3% arsenic
- Knox0% nitrate
- Liberty2% uranium
- Lincolnville12% arsenic
- Monroe5% arsenic
- Montville5% arsenic
- Morrill4% arsenic
- Northport24% arsenic
- Palermo3% uranium
- Prospect51% uranium
- Searsmont11% arsenic
- Searsport14% uranium
- Stockton Springs13% uranium
- Swanville32% uranium
- Thorndike3% nitrate
- Troy3% nitrate
- Unity13% arsenic
- Waldo9% uranium
- Winterport2% arsenic
1 towns have fewer than 30 public samples and are included in the Waldo County totals above rather than shown separately: Islesboro.
Sources
- Maine DEP PFAS investigation: 1,604 samples in Waldo County. PFAS results for private wells sampled by the Maine Department of Environmental Protection. Retrieved September 3, 2026.
- USGS Water Quality Portal: 62 samples in Waldo 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 Waldo County, up to 1,664 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: 3,950 well records in Waldo County, 3,853 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: 181 regulated sites located in Waldo 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.