Well water in Madison, Maine
In Madison, 14% of 97 private wells tested had arsenic above the Maine guideline (10 ug/L), according to Maine CDC.
111 private wells tested in state summaries; 14 individual samples from 3 wells, 1984 to 2012. Data refreshed September 3, 2026.
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.
What individual samples found
Each row summarizes every public sample for that contaminant inside Madison. 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 | |
|---|---|---|---|---|---|---|---|
| Nitrate 1984 to 2011 | 14 | 50% | 0% | 0.105 | 2.94 | 10 mg/L EPA limit | |
| Copper 2000 to 2011 | 12 | 67% | 0% | 0.001 | 0.008 | 1.3 mg/L EPA limit | |
| Uranium 2000 to 2011 | 12 | 83% | 0% | 0.262 | 0.832 | 30 ug/L EPA limit | |
| Arsenic 2000 to 2011 | 12 | 83% | 0% | 0.305 | 0.51 | 10 ug/L EPA limit | |
| Chloride 1984 to 2011 | 13 | 100% | no limit | 11.4 | 89.3 | 250 mg/L nuisance level |
Sampled fewer than 10 times, too few to summarize: E. coli (4), Radium (226 + 228) (4), Lead (1), Radon (4), Sodium (2), Manganese (1).
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What this means
Among homeowners in Madison who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (14% of 97 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 Madison
- Volatile organic compounds (VOCs)2 leaking underground storage tank sites on record locally.
- PFAS2 unlined landfills on record locally.
- Arsenic14% of 97 local wells tested were above the Maine guideline.
- Manganese4% of 94 local wells tested were above the Maine guideline.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 1,895 pCi/L.
- ChlorideDetected in 100% of local samples.
- NitrateRecommended for every private well, especially near farms or septic systems.
- CopperDetected in 67% of local samples.
Wells in Madison
177 domestic wells in Madison are on record with the state since 1987. 99% are drilled into bedrock, and the typical well is 245 feet deep (one in ten goes past 400 feet).
In a typical Madison well, bedrock starts about 20 feet down, the median yield is 6 gallons per minute, 19% 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 Madison
Maine DEP records 2 leaking underground storage tank sites and 2 unlined landfills in Madison, among 8 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.
- 2
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 2
- unlined landfillsOlder unlined landfills are a leading source of PFAS, VOCs and metals in nearby wells.
- 4
- other remediation projects
Treatment that fits the local profile
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Copper
- Neutralizing filter to raise pH; Point-of-use reverse osmosis
- Chloride
- Point-of-use reverse osmosis; Distillation
- Manganese
- Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
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Common questions
How deep are wells in Madison?
The typical domestic well in Madison is 245 feet deep, based on 177 wells reported to the state since 1987. One in ten is deeper than 400 feet. 99% are drilled into bedrock.
Is there arsenic in well water in Madison?
Arsenic was detected in 83% of 12 public well samples in Madison, and 0% 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 Madison?
The median radon level across 4 public samples in Madison was 1,895 pCi/L, with a high of 3,400 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Madison?
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: 79 samples in Madison. 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 Madison, up to 111 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: 184 well records in Madison, 177 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: 8 regulated sites located in Madison. 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.