Arsenic and uranium in private wells in Connecticut, 2013-15

Open-File Report 2017-1046
Prepared in cooperation with the Connecticut Department of Public Health
By:  and 



The occurrence of arsenic and uranium in groundwater at concentrations that exceed drinking-water standards is a concern because of the potential adverse effects on human health. Some early studies of arsenic occurrence in groundwater considered anthropogenic causes, but more recent studies have focused on sources of naturally occurring arsenic to groundwater, such as minerals within aquifer materials that are in contact with groundwater. Arsenic and uranium in groundwater in New England have been shown to have a strong association to the geologic setting and nearby streambed sediment concentrations. In New Hampshire and Massachusetts, arsenic and uranium concentrations greater than human-health benchmarks have shown distinct spatial patterns when related to the bedrock units mapped at the local scale.

The Connecticut Department of Public Health (DPH) reported that there are about 322,600 private wells in Connecticut serving approximately 823,000 people, or 23 percent of the State’s population. The State does not require that existing private wells be routinely tested for arsenic, uranium, or other contaminants; consequently, private wells are only sampled at the well owner’s discretion or when they are newly constructed. The U.S. Geological Survey (USGS), in cooperation with the DPH, completed an assessment in 2016 on the distribution of concentrations of arsenic and uranium in groundwater from bedrock in Connecticut. This report presents the major findings for arsenic and uranium concentrations from water samples collected from 2013 to 2015 from private wells.

Suggested Citation

Flanagan, S.M., and Brown, C.J., 2017, Arsenic and uranium in private wells in Connecticut, 2013–15: U.S. Geological Survey Open-File Report 2017–1046; 8 p.,

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Major Findings
  • Introduction
  • Sources of Data on Arsenic and Uranium Concentrations
  • Arsenic and Uranium Concentrations in the State
  • Arsenic and Uranium Occurrence in Relation to Bedrock Geology
  • Comparison of Arsenic and Uranium Exceedance Rates in Three Towns
  • Human Health Implications
  • Acknowledgments
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Arsenic and uranium in private wells in Connecticut, 2013-15
Series title Open-File Report
Series number 2017-1046
DOI 10.3133/ofr20171046
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) New England Water Science Center
Description Report: 8 p; Data Release
Country United States
State Connecticut
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details