Well water in Hunterdon County, New Jersey
In Hunterdon County, 23% of 13,686 private wells tested between 2002 and 2024 had total coliform above the New Jersey limit (any detection), according to NJDEP.
13,703 private wells tested 2002 to 2024 in state summaries; 196 individual samples from 115 wells, 1969 to 2026. Data refreshed September 9, 2026.
What homeowner tests found
NJDEP Private Well Testing Act summaries: private wells tested and reported to the state, 2002 to 2024. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA.
| Contaminant | Wells tested | Above state level | Median | 95th pct | Highest | State level | |
|---|---|---|---|---|---|---|---|
| Total coliform | 13,686 | 23% | |||||
| Iron | 13,701 | 16% | 300 ug/L | ||||
| Arsenic | 13,700 | 16% | 5 ug/L | ||||
| Manganese | 13,703 | 11% | 50 ug/L | ||||
| Gross alpha | 12,490 | 6% | 15 pCi/L | ||||
| E. coli Fecal coliform or | 13,655 | 3% | |||||
| PFOA | 1,905 | 3% | 14 ng/L | ||||
| PFOS | 1,905 | 3% | 13 ng/L | ||||
| Nitrate | 13,702 | <1% | 10 mg/L | ||||
| Uranium | 3,783 | <1% | 30 ug/L | ||||
| PFNA | 1,905 | <1% | 13 ng/L |
What individual samples found
Each row summarizes every public sample for that contaminant inside Hunterdon 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 | |
|---|---|---|---|---|---|---|---|
| PFOA 2021 to 2026 | 16 | 44% | 25% | 0 | 7.9 | 4 ng/L EPA limit | |
| PFOS 2021 to 2026 | 16 | 31% | 13% | 0 | 29 | 4 ng/L EPA limit | |
| Arsenic 1983 to 2026 | 196 | 74% | 11% | 2 | 57 | 10 ug/L EPA limit | |
| Radium (226 + 228) 1985 to 2011 | 82 | 65% | 6% | 0 | 51 | 5 pCi/L EPA limit | |
| Uranium 1985 to 2012 | 79 | 95% | 1% | 2.8 | 48.2 | 30 ug/L EPA limit | |
| Radon 1986 to 2011 | 61 | 100% | no limit | 2,560 | 38,300 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: Copper (8), Fluoride (5), Nitrate (4), Lead (3), Manganese (4), Sodium (3), Iron (3), Chloride (2).
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What this means
Among homeowners in Hunterdon County who sent a sample to the state lab, the health-based limits most often exceeded were total coliform (23% of 13,686 wells), arsenic (16% of 13,700 wells), and E. coli (3% of 13,655 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.
Iron and manganese exceed the state's advisory level in a sizable share of wells; these are mostly a taste, staining or diet issue rather than a toxicity one.
What to test for in Hunterdon County
- Volatile organic compounds (VOCs)3 hazardous waste sites on record locally.
- Metals panel3 hazardous waste sites on record locally.
- Total coliform23% of 13,686 local wells tested were above the New Jersey limit (any detection).
- Iron16% of 13,701 local wells tested were above the New Jersey nuisance level.
- Manganese11% of 13,703 local wells tested were above the New Jersey nuisance level.
- Radium (226 + 228)6% of 82 local samples were above the limit.
- Gross alpha6% of 12,490 local wells tested were above the New Jersey limit.
- E. coli3% of 13,655 local wells tested were above the New Jersey limit (any detection).
- Nitrate<1% of 13,702 local wells tested were above the New Jersey limit.
- PFNA<1% of 1,905 local wells tested were above the New Jersey limit.
Contamination sources on record in Hunterdon County
NJDEP records 3 hazardous waste sites in Hunterdon County, among 859 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.
- 3
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 693
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 5
- lined landfills and transfer facilities
- 158
- other remediation projects
Treatment that fits the local profile
- Total coliform
- Inspect and repair the well cap and casing, then shock chlorinate and retest; UV disinfection whole-house; Chlorination system
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Gross alpha
- Point-of-use reverse osmosis; Water softener (cation exchange) for radium; Anion exchange for uranium
- Iron
- Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
- Manganese
- Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
- PFOA
- Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
Get your Hunterdon County water tested at home
A licensed local water treatment company tests your tap water in your home, walks you through the numbers, and quotes treatment only if something needs fixing. Free, about 30 minutes, no obligation. Tell us what you need and we match you with a company that serves Hunterdon County.
Common questions
Is there arsenic in well water in Hunterdon County?
Arsenic was detected in 74% of 196 public well samples in Hunterdon County, and 11% 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 Hunterdon County?
The median radon level across 61 public samples in Hunterdon County was 2,560 pCi/L, with a high of 38,300 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Hunterdon 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 Hunterdon County
- Alexandria township24% arsenic
- Bethlehem township19% total coliform
- Califon borough41% total coliform
- Clinton township23% total coliform
- Delaware township22% total coliform
- East Amwell township43% arsenic
- Franklin township35% total coliform
- Frenchtown borough67% arsenic
- Glen Gardner borough20% total coliform
- High Bridge borough23% total coliform
- Holland township27% total coliform
- Kingwood township43% arsenic
- Lambertville34% total coliform
- Lebanon township23% total coliform
- Raritan township22% arsenic
- Readington township25% total coliform
- Tewksbury township18% total coliform
- Union township25% total coliform
- West Amwell township23% total coliform
7 towns have fewer than 30 public samples and are included in the Hunterdon County totals above rather than shown separately: Bloomsbury borough, Clinton, Flemington borough, Hampton borough, Lebanon borough, Milford borough, Stockton borough.
Sources
- USGS Water Quality Portal: 482 samples in Hunterdon 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.
- NJDEP Private Well Testing Act summaries: summaries for 11 contaminants in Hunterdon County, up to 13,703 wells each. Share of private wells exceeding each standard in tests required at sale or lease under the New Jersey Private Well Testing Act, September 2002 to December 2024, published by NJDEP. Tests are untreated water at the time of sale or lease, so every well is counted once per transaction. Municipalities with fewer than ten wells are suppressed. Standards are New Jersey's: arsenic 5 ug/L, PFOA 14 ng/L, PFOS 13 ng/L, PFNA 13 ng/L, manganese and iron secondary standards. Uranium and PFAS were added to the required panel in 2021 and 2020, so their well counts are smaller. Retrieved September 9, 2026.
- NJDEP regulated sites: 859 regulated sites located in Hunterdon County. Known Contaminated Sites, regulated underground storage tank facilities and solid waste landfills from the New Jersey Department of Environmental Protection (NJ-GeoWeb). Retrieved September 9, 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.