Uranium Testing in Hunterdon, and What Local Wells Actually Show

If you are buying, selling, or renting out a well-served home in Hunterdon County, the results that come up most often are not the ones the county is best known for testing. NJDEP's records cover more than 13,700 Hunterdon wells tested at sales and rentals between September 2002 and December 2024. About 28% had a pH outside the optimum range, 23% had total coliform bacteria, 16% exceeded the arsenic limit, and 16% exceeded the iron standard. Uranium, the county-specific line item on Hunterdon's panel, exceeded its limit in 0.5% of wells. It is required, and worth understanding, but it is rarely where a Hunterdon report runs into trouble.

What Hunterdon well tests actually find

These are the share of tested Hunterdon wells that exceeded each standard, from NJDEP's Private Well Testing Act summary for the county. The water is tested untreated, and the wells are a very large sample, though not a random one, since they are the properties that were sold or rented.

pH outside the optimum range: 28.1% of 13,697 wells. Statewide, NJDEP's first PWTA report found that nearly all out-of-range wells were on the low, acidic side.
Total coliform bacteria: 23.1% of 13,686 wells. E. coli, the more serious finding, appeared in 3.3%.
Iron and manganese: 16.0% and 10.9%. Both are mainly staining and taste issues.
Arsenic: 15.7% of 13,700 wells above New Jersey's 5 µg/L limit, which is half the federal limit.
Gross alpha (a broad radioactivity screen): 5.8% of 12,490 wells.
PFAS: 4.4% of 1,905 wells tested since PFAS joined the panel in December 2021.
Nitrate and solvents (VOCs): 0.8% and 0.5%.
Uranium: 0.5% of 3,783 wells. Uranium testing was added for Hunterdon and eleven other northern counties in September 2018, so its record is shorter than the others.

Arsenic, acidity and bacteria are three different stories

Arsenic follows the rock. Research on the Newark Basin ties naturally occurring arsenic to its red mudstone and siltstone, and the county's results follow that map. In the Hunterdon towns that sit almost entirely on Newark Basin rock, about 22% of tested wells exceeded the arsenic limit, against about 0.5% in the towns on Highlands gneiss and granite. The extremes are striking: 43% in Kingwood Township, 42.5% in East Amwell Township, and 67% of the small number of wells tested in Frenchtown. Arsenic cannot be seen, smelled, or tasted, which is why testing is the only way to know.

Low pH follows the opposite pattern. The Highlands towns are where acidic water dominates, with about 58% of wells outside the optimum range, against about 17% in the Newark Basin towns. Acidic water is mostly a plumbing story: USGS research links acidic, low-alkalinity groundwater to lead and copper leaching from household pipes, so a low reading is often followed by a check at the tap.

Bacteria mostly do not follow the rock at all. Coliform depends on how a well is built, sealed, and maintained and how close it sits to a septic system or livestock. A positive result usually means disinfection and a retest, and it can change from one year to the next, which is why an annual coliform test is the most practical habit for any well owner.

Why Hunterdon requires uranium testing anyway

Uranium testing under the Private Well Testing Act is required in twelve of New Jersey's 21 counties: Hunterdon, Bergen, Essex, Hudson, Mercer, Middlesex, Morris, Passaic, Somerset, Sussex, Union, and Warren. The other nine counties, in central and southern New Jersey, require mercury testing instead, so every county has exactly one county-specific add-on. The statute lets NJDEP add parameters it deems significant in each county, and uranium was added for counties where the bedrock can carry it: most famously the granite and gneiss of the Highlands, but also the sedimentary rock of the Newark Basin, which underlies central and southern Hunterdon. USGS research on the Passaic Formation's red mudstone names uranium as its dominant alpha emitter.

In practice, uranium is a real but uncommon finding. Across Hunterdon it exceeded the limit in 0.5% of wells tested, with Clinton Township the highest municipality at 2.5% of 243 wells. Warren County, next door, is at 1.3%. The broader gross alpha screen, required statewide, turns up more: 5.8% countywide, and much higher in some Newark Basin towns, including West Amwell (16.6%), Kingwood (13%), Delaware (11.7%), and Raritan (11.2%). Long-term exposure to elevated uranium is linked to kidney effects, and the concern is cumulative exposure over years, not a single glass of water. That is the reason to test even when the odds are low: it cannot be detected without a lab.

Does this mean my well will have a problem?

Any single parameter passes in most Hunterdon wells, but several are flagged often enough that a clean sweep is not the default. Because pH alone is out of range in 28% of wells, at least 28% of tested wells had at least one flag, and the real figure is higher, since the bacteria, arsenic, and iron flags do not all fall in the same wells. None of this is pollution in the sense of a spill. It is geochemistry, and it is common enough that treatment for each of these issues is well established. The point is not to alarm anyone, but to show what the panel is most likely to turn up and why a neighbor's result is only a rough guide. Two wells a few miles apart can draw from very different ground.

What to do with this information

If you are buying, selling, or living on a well in Hunterdon County, plan for arsenic, pH, and bacteria first, and treat uranium as a required line that will most likely pass. Read the whole report: an elevated result on any line is a solvable problem with an established treatment path, not a reason to panic. Our town pages show the local numbers for each of Hunterdon's 26 municipalities, starting with Kingwood Township, Bethlehem Township and Raritan Township.

For what a specific number on your report actually means, see How to Read Your Test Report. For the county-by-county comparison of who requires what, see Hunterdon vs. Neighboring Counties. And if you are ready to schedule, our PWTA Testing page covers the full process from booking to results. If a result comes back elevated, our treatment referral page explains what usually follows.