Well water in Chittenden County, Vermont
In Chittenden County, 4% of 4,475 private wells tested had arsenic above the Vermont limit (10 ug/L), according to the Vermont Department of Health.
5,062 private wells tested in state summaries; 11 individual samples from 11 wells, 1980 to 2003. Data refreshed September 3, 2026.
What homeowner tests found
Vermont Tracking 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 Chittenden 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 | |
|---|---|---|---|---|---|---|---|
| Lead 2003 | 10 | 0% | 0% | 0 | 0 | 15 ug/L EPA limit | |
| Copper 2003 | 10 | 60% | 0% | 0 | 0 | 1.3 mg/L EPA limit | |
| Arsenic 2003 | 10 | 40% | 0% | 0 | 2.8 | 10 ug/L EPA limit | |
| Uranium 2003 | 10 | 80% | 0% | 0.1 | 0.6 | 30 ug/L EPA limit | |
| Sodium 1980 to 2003 | 11 | 73% | no limit | 1.9 | 47 | 20 mg/L health guideline | |
| Manganese 1980 to 2003 | 11 | 100% | no limit | 90 | 1,000 | 300 ug/L health guideline | |
| Iron 1980 to 2003 | 11 | 45% | no limit | 0 | 27,000 | 300 ug/L nuisance level |
Sampled fewer than 10 times, too few to summarize: Fluoride (1), Nitrate (1), Chloride (1).
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What this means
Among homeowners in Chittenden County who sent a sample to the state lab, the health-based limits most often exceeded were arsenic (4% of 4,475 wells), uranium (2% of 4,228 wells), and nitrate (<1% of 4,814 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.
Radon was above the Vermont advisory level of 4,000 pCi/L in 3% of 438 wells. Radon in water matters because it moves into indoor air during showers and laundry.
What to test for in Chittenden County
- Volatile organic compounds (VOCs)610 leaking underground storage tank sites on record locally.
- PFAS11 unlined landfills on record locally.
- Metals panel239 hazardous waste sites on record locally.
- Gross alpha9% of 2,624 local wells tested were above the Vermont limit.
- Arsenic4% of 4,475 local wells tested were above the Vermont limit.
- Radon3% of 438 local wells tested were above the Vermont advisory level.
- Uranium2% of 4,228 local wells tested were above the Vermont limit.
- Nitrate<1% of 4,814 local wells tested were above the Vermont limit.
- Fluoride<1% of 5,062 local wells tested were above the Vermont limit.
- Coliform bacteriaRecommended for every private well, every year.
- ManganeseDetected in 100% of local samples.
Wells in Chittenden County
4,721 domestic wells in Chittenden County are on record with the state since 1971. 96% are drilled into bedrock, and the typical well is 400 feet deep (one in ten goes past 675 feet).
In a typical Chittenden County well, bedrock starts about 27 feet down, the median yield is 6 gallons per minute, 29% 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 Chittenden County
Vermont ANR records 610 leaking underground storage tank sites, 11 unlined landfills, 239 hazardous waste sites, and 19 reported spills and releases in Chittenden County, among 1,264 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.
- 610
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 11
- unlined landfillsOlder unlined landfills are a leading source of PFAS, VOCs and metals in nearby wells.
- 239
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 19
- reported spills and releasesMost spills are fuel; a few are solvents or chemicals that reach the water table.
- 385
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
Treatment that fits the local profile
- Gross alpha
- Point-of-use reverse osmosis; Water softener (cation exchange) for radium; Anion exchange for uranium
- Copper
- Neutralizing filter to raise pH; Point-of-use reverse osmosis
- 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
- Chloride
- Point-of-use reverse osmosis; Distillation
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Common questions
How deep are wells in Chittenden County?
The typical domestic well in Chittenden County is 400 feet deep, based on 4,721 wells reported to the state since 1971. One in ten is deeper than 675 feet. 96% are drilled into bedrock.
Is there arsenic in well water in Chittenden County?
Arsenic was detected in 40% of 10 public well samples in Chittenden County, 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 often should I test a private well in Chittenden 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 Chittenden County
- Bolton3% nitrate
- Burlington0% arsenic
- Charlotte2% arsenic
- Colchester1% uranium
- Essex7% arsenic
- Hinesburg9% arsenic
- Huntington2% arsenic
- Jericho<1% arsenic
- Milton3% arsenic
- Richmond3% arsenic
- Shelburne1% uranium
- South Burlington0% arsenic
- St. George10% uranium
- Underhill2% nitrate
- Westford12% arsenic
- Williston13% arsenic
3 towns have fewer than 30 public samples and are included in the Chittenden County totals above rather than shown separately: Buels gore, Essex Junction, Winooski.
Sources
- USGS Water Quality Portal: 76 samples in Chittenden 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.
- Vermont Tracking private well summaries: summaries for 6 contaminants in Chittenden County, up to 5,062 wells each. Town summaries of private well tests reported to the Vermont Department of Health, published through Vermont Environmental Public Health Tracking. Shares are against the limit Vermont applies to each analyte: arsenic 10 ug/L, uranium 20 ug/L (stricter than EPA), fluoride 4 mg/L, nitrate 10 mg/L, gross alpha 15 pCi/L, radon 4,000 pCi/L advisory. Only towns with 20 or more results are published; statistics below the reporting limit show as *. Retrieved September 3, 2026.
- Vermont ANR well completion reports: 4,989 well records in Chittenden County, 4,721 domestic. Well completion reports filed with the Vermont Agency of Natural Resources since 1966. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 3, 2026.
- Vermont ANR regulated sites: 1,264 regulated sites located in Chittenden County. Hazardous waste sites, landfills and underground storage tanks from the Vermont Agency of Natural Resources. 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.