New USGS Report Shows High Levels of Arsenic and Uranium in Some Wells

his research builds on a USGS report published in 2017, with the new study including additional groundwater samples and focusing on previously underrepresented areas.


The research, undertaken in cooperation with the Connecticut Department of Public Health, projects that approximately 3.9% of private wells across Connecticut contain water with arsenic at concentrations higher than the U.S. Environmental Protection Agency’s maximum contaminant level for public drinking-water supplies. This research also projects that 4.7% of private wells in the state have uranium concentrations higher than the EPA’s standards.

CT DPH officials urge all private well owners to have their water tested for possible arsenic and uranium.

Arsenic and uranium are naturally occurring metals in bedrock around the world. Sometimes wells drilled into bedrock aquifers can produce water containing arsenic or uranium. Unless wells are tested, there’s no way to confirm the presence or absence of these contaminants.

Read more at: US Geological Survey

The colors on this map identify the estimated percentage of private wells in Connecticut with water containing arsenic concentrations greater than 10 micrograms per liter, the U.S. Environmental Protection Agency's maximum contaminant level for arsenic in drinking water supplies. These percentages were determined based on an analysis of water samples from more than 2,000 private wells in the state as well as underlying geology, with bedrock types indicative of arsenic concentrations in groundwater. The black symbols identify arsenic concentrations in water from sampled wells. White areas on the map, representing 1.9% of the state, indicate geologic units from which no arsenic samples are available. Well locations are approximate. (Photo Credit: USGS)

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