Well water in Monmouth, Maine
In Monmouth, 48% of 257 private wells tested had arsenic above the Maine guideline (10 ug/L), according to Maine CDC.
295 private wells tested in state summaries; 3 individual samples from 2 wells, 1967 to 2022. 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.
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.
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What this means
Among homeowners in Monmouth who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (48% of 257 wells), uranium (4% of 205 wells), and fluoride (4% of 270 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 Monmouth
- Volatile organic compounds (VOCs)5 leaking underground storage tank sites on record locally.
- PFAS1 unlined landfill on record locally.
- Metals panel2 hazardous waste sites on record locally.
- Arsenic48% of 257 local wells tested were above the Maine guideline.
- Uranium4% of 205 local wells tested were above the Maine guideline.
- Manganese4% of 235 local wells tested were above the Maine guideline.
- Fluoride4% of 270 local wells tested were above the Maine guideline.
- Nitrate<1% of 295 local wells tested were above the Maine guideline.
- Coliform bacteriaRecommended for every private well, every year.
- PFOAAbove the limit in 1 of 1 local samples; too few to quote a rate.
- PFOSAbove the limit in 1 of 1 local samples; too few to quote a rate.
Wells in Monmouth
548 domestic wells in Monmouth are on record with the state since 1971. 99% are drilled into bedrock, and the typical well is 284 feet deep (one in ten goes past 500 feet).
In a typical Monmouth well, bedrock starts about 25 feet down, the median yield is 6 gallons per minute, 22% 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 Monmouth
Maine DEP records 5 leaking underground storage tank sites, 1 unlined landfill, and 2 hazardous waste sites in Monmouth, among 12 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.
- 5
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 1
- unlined landfillOlder unlined landfills are a leading source of PFAS, VOCs and metals in nearby wells.
- 2
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 4
- other remediation projects
Treatment that fits the local profile
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Chloride
- Point-of-use reverse osmosis; Distillation
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Common questions
How deep are wells in Monmouth?
The typical domestic well in Monmouth is 284 feet deep, based on 548 wells reported to the state since 1971. One in ten is deeper than 500 feet. 99% are drilled into bedrock.
Is there arsenic in well water in Monmouth?
Arsenic was detected in 100% of 3 public well samples in Monmouth, and 100% 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 Monmouth?
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.
Sources
- USGS Water Quality Portal: 7 samples in Monmouth. 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 DEP PFAS investigation: 4 samples in Monmouth. PFAS results for private wells sampled by the Maine Department of Environmental Protection. Retrieved September 3, 2026.
- Maine Tracking Network private well summaries: summaries for 6 contaminants in Monmouth, up to 295 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: 572 well records in Monmouth, 548 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: 12 regulated sites located in Monmouth. 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.