Well water in Caribou, Maine
In Caribou, 8% of 64 private wells tested had nitrate above the Maine guideline (10 mg/L), according to Maine CDC.
65 private wells tested in state summaries; 7 individual samples from 4 wells, 1956 to 1986. 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.
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What this means
Among homeowners in Caribou who sent a sample to the state lab, the health-based limits most often exceeded were nitrate (8% of 64 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 Caribou
- Volatile organic compounds (VOCs)13 leaking underground storage tank sites on record locally.
- PFAS1 unlined landfill on record locally.
- Nitrate8% of 64 local wells tested were above the Maine guideline.
- Manganese2% of 58 local wells tested were above the Maine guideline.
- Coliform bacteriaRecommended for every private well, every year.
- ChlorideDetected in 86% of local samples.
Wells in Caribou
110 domestic wells in Caribou are on record with the state since 1979. 83% are drilled into bedrock, and the typical well is 112 feet deep (one in ten goes past 280 feet).
In a typical Caribou well, bedrock starts about 10 feet down, the median yield is 10 gallons per minute, 5% 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 Caribou
Maine DEP records 13 leaking underground storage tank sites and 1 unlined landfill in Caribou, among 35 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.
- 13
- 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.
- 21
- other remediation projects
Treatment that fits the local profile
- Nitrate
- Point-of-use reverse osmosis; Anion exchange; Distillation
- Chloride
- Point-of-use reverse osmosis; Distillation
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Common questions
How deep are wells in Caribou?
The typical domestic well in Caribou is 112 feet deep, based on 110 wells reported to the state since 1979. One in ten is deeper than 280 feet. 83% are drilled into bedrock.
How often should I test a private well in Caribou?
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: 15 samples in Caribou. 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 Caribou, up to 65 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: 156 well records in Caribou, 110 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: 35 regulated sites located in Caribou. 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.