Data used to evaluate arsenic and uranium occurrence in Connecticut groundwater through spatially weighted and bedrock geology assessments

This data release contains two spatial datasets and a data table in support of an evaluation of arsenic and uranium occurrence in Connecticut groundwater through spatially weighted and bedrock geology assessments.

Spatial datasets include 1) a shapefile of 130 equal-area grid cells with associated arsenic attribute data, and 2) a shapefile of 110 equal-area grid cells with associated uranium attribute data. The State of Connecticut was divided based on a set of randomized equal-area grid cells based on the method of Scott (1990); one grid was created for arsenic, with 130 grid cells, and one was created for uranium, with 110 grid cells. Arsenic and uranium attribute data associated with the equal-area grid cells include the number of wells in each grid cell, the number of wells with constituent concentrations above three selected thresholds, the fraction of wells with constituent concentrations above three selected thresholds, and the percentage of wells with constituent concentrations above three selected thresholds. The three selected thresholds for arsenic include 3, 5, and 10 micrograms per liter (ug/L), with 10 ug/L representing the maximum contaminant level (MCL) established by the U.S. Environmental Protection Agency (EPA) for human health for arsenic. The three selected thresholds for uranium include 1, 10, and 30 ug/L, with 30 ug/L representing the EPA MCL for human health for uranium.

The bedrock geology data table is table 4 from Gross and others (2020) formatted so that it can easily be joined with Connecticut's bedrock geology dataset (Connecticut Department of Environmental Protection, 2000) using the geologic unit abbreviation (UNIT attribute) in order to recreate figure 3 from Gross and others (2020). The data table includes counts and percentages of arsenic and uranium concentrations that exceed maximum contaminant levels from private wells in Connecticut, by geologic unit and major bedrock category, 2013-18.