Weston has one of the most striking arsenic records in Connecticut's public well data. In a USGS report on 2013 to 2015 samples, 47.3% of 110 Weston well samples were above the EPA arsenic limit of 10 µg/L, against 3.6% of the statewide dataset (USGS Open-File Report 2017-1046). CT DPH recommends testing every private well for arsenic, uranium and radon at least once (CT DPH).
● Key Takeaways
47.3% of 110 Weston samples (2013 to 2015) exceeded the 10 µg/L arsenic limit, versus 3.6% of the statewide dataset. About 76% of Weston is mapped on Ordovician(?) granitic gneiss: statewide, 14.2% of its samples exceeded the arsenic limit and 25.6% the 30 µg/L uranium limit. The Weston samples had no uranium results. Test for arsenic, uranium and radon at least once.
What Rock Is Under Weston?
Weston sits mostly on one rock unit. About three quarters of the town is mapped as Ordovician(?) granitic gneiss, and no Connecticut town has a larger area of it.
| Rock unit | Share of town (CT DEEP map) | USGS samples above 10 µg/L arsenic | USGS samples above 30 µg/L uranium |
|---|---|---|---|
| Ordovician(?) granitic gneiss | About 76% | 14.2% of 106 | 25.6% of 86 |
| Ratlum Mountain Schist (queried on the map) | About 10% | 8.3% of 12 | 0% of 6 |
| Trap Falls Formation and Ordovician(?) granitic gneiss, undivided | About 8% | 0% of 5 | 9.1% of 11 |
| Harrison Gneiss | About 4% | 14.3% of 7 | 46.7% of 15 |
| Ratlum Mountain Schist | About 2% | 0% of 114 | 9.6% of 104 |
The share of town is the area of each unit inside Weston's boundary on the CT DEEP bedrock map (CT DEEP); units under 1% are left out. The percentages are from USGS Table 4 and describe wells in that rock unit statewide, not wells in Weston (USGS Open-File Report 2020-1111). Units with only a handful of samples tell you very little.
That unit stands out statewide. Of the rock units with at least 10 USGS samples for each element, it is the only one where 10% or more of samples exceeded both the arsenic and the uranium limits. Our regional guide lists the other high-rate units and where they are.
What Has Testing Found in Weston?
USGS's 2017 report looked at every available result from three towns with unusually many samples: Stamford, Weston and Wilton. In Weston, 47.3% of 110 samples had arsenic above 10 µg/L. The report has no uranium results for Weston. Next door in Wilton, only 2.5% of 81 samples exceeded the arsenic limit, and USGS attributed the contrast to geology: Weston's dominant unit is the Ordovician(?) granitic gneiss, which had high arsenic in 14.3% of its 56 samples in the 2017 statewide dataset (USGS Open-File Report 2017-1046).
Those results are about a decade old and describe the wells that were sampled, not every home in town. They are a strong reason to test, and a reason to include uranium, which those Weston samples did not measure.
What Should Weston Well Owners Test, and How Often?
CT DPH's schedule applies to every private well in Connecticut, whatever the town (CT DPH, updated May 2026):
- Basic indicators every year (bacteria, nitrate, nitrite, sodium, chloride, iron, manganese, hardness, pH and others), and after any well, pump or pipe repair or a flooded wellhead.
- Arsenic, uranium and radon at least once, ideally every 5 years. Levels can fluctuate.
- Lead and volatile organic compounds at least once, and lead again when planning a pregnancy or with a child under 6.
- Fluoride every 5 years when a child under 12 lives in the home.
Since October 1, 2022, new wells have been tested for arsenic and uranium when drilled (CT DPH arsenic; CT DPH uranium). If your well is older and has no arsenic or uranium result on file, that is the gap to close first. CT DPH also recommends a radon in water test for every home on a well, even if indoor air tested low (CT DPH, revised February 2025).
Use a laboratory certified by CT DPH for the tests you need, and compare results with CT DPH Action Levels and EPA limits: 10 µg/L for arsenic, 30 µg/L for uranium, and CT DPH's recommended 5,000 pCi/L action level for radon in water. If a result is high, CT DPH says to retest, stop drinking the water until it is resolved, and contact your local health department (find yours) or the CT DPH Private Well Program at (860) 509-8401. The full schedule, lab tips and how to read a report are in our Connecticut private well testing guide.
What This Page Does Not Tell You
It does not tell you what is in your well. USGS cautions that rock-unit exceedance rates "may not represent the actual hazard for existing and future wells," and the study's lead author said bedrock geology "is not always predictive" (USGS Open-File Report 2020-1111; USGS, April 2021). Even neighboring towns can differ sharply, as Weston and Wilton do in USGS's 2013 to 2015 data. Only a certified lab test of your water answers the question.
Test your Weston well
A water specialist can arrange certified lab testing for your well, starting with arsenic, uranium, radon and a basic indicators panel.
CheckYourTap is an independent water-quality service, not your town or utility. We connect you with a vetted local partner. Your online report is free. Testing and treatment are paid services, and there's no cost to talk.
Keep Reading
- Private well testing in Connecticut: the complete guide
- Arsenic and uranium in Connecticut wells, by region
- Radon in Connecticut well water
- Wilton well water testing
- Redding well water testing
How we built this page: rock unit shares come from overlaying the CT DEEP bedrock geology map (Rodgers, 1985, digitized at 1:50,000) on the CTDOT municipal boundary for Weston. Exceedance percentages and sample counts are copied from USGS Open-File Report 2020-1111, Table 4. Weston's town-level results are from USGS Open-File Report 2017-1046, Table 4. This page describes geology and published sampling. It is not a measurement or rating of any home's well.
Sources: Gross and Brown, USGS Open-File Report 2020-1111; Flanagan and Brown, USGS Open-File Report 2017-1046; USGS news release (April 2021); CT DEEP, Bedrock Geology of Connecticut; CTDOT Municipalities; CT DPH, Educational materials: testing recommendations for private wells (updated May 2026); CT DPH, Arsenic in private well water; CT DPH, Uranium in Private Well Water (April 2024); CT DPH, Radon in Your Well Water (revised February 2025).
About this guide: CheckYourTap is an independent water-quality service funded by Valiant Energy Solutions, a Connecticut water quality and energy services company established in 1930. Valiant offers paid well testing and treatment, which is what the request button on this page connects you with. You can also contact any CT DPH-certified laboratory directly. The facts on this page come from the public sources cited above.
