Well water in Denville township, New Jersey
In Denville township, 19% of 116 private wells tested between 2002 and 2024 had total coliform above the New Jersey limit (any detection), according to NJDEP.
116 private wells tested 2002 to 2024 in state summaries; 3 individual samples from 3 wells, 1985. 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.
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What this means
Among homeowners in Denville township who sent a sample to the state lab, the health-based limits most often exceeded were PFOA (20% of 15 wells), total coliform (19% of 116 wells), and nitrate (3% of 116 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.
Manganese and iron 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 Denville township
- Volatile organic compounds (VOCs)1 hazardous waste site on record locally.
- Metals panel1 hazardous waste site on record locally.
- Manganese21% of 116 local wells tested were above the New Jersey nuisance level.
- PFOA20% of 15 local wells tested were above the New Jersey limit.
- Total coliform19% of 116 local wells tested were above the New Jersey limit (any detection).
- Iron16% of 116 local wells tested were above the New Jersey nuisance level.
- Nitrate3% of 116 local wells tested were above the New Jersey limit.
- E. coli<1% of 115 local wells tested were above the New Jersey limit (any detection).
Contamination sources on record in Denville township
NJDEP records 1 hazardous waste site in Denville township, among 102 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.
- 1
- hazardous waste siteSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 79
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 22
- other remediation projects
Treatment that fits the local profile
- PFOA
- Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
- Total coliform
- Inspect and repair the well cap and casing, then shock chlorinate and retest; UV disinfection whole-house; Chlorination system
- Manganese
- Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
- Iron
- Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
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Common questions
Is there arsenic in well water in Denville township?
Arsenic was detected in 33% of 3 public well samples in Denville township, 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 Denville township?
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: 3 samples in Denville township. 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 Denville township, up to 116 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: 102 regulated sites located in Denville township. 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.