Vulnerability of drinking water supply wells to VOCs

As part of a US Geological Survey study of national water quality, untreated water samples from ~ 1,100 public supply and 2,400 domestic wells were analyzed for 55 volatile organic compounds (VOCs). Findings indicated that drinking water from public supply wells is more vulnerable than domestic well water to VOC contamination. Analyses showed that the solvents perchloroethene and trichloroethene in public well samples were associated with point sources and pumping rates, potentially resulting from contaminant plumes that are drawn into wells with large capture zones. In contrast, detections of the trihalomethanes chloroform and bromodichloromethane and detections of methyl tertiary butyl ether were not associated with pumping rates. Chloroform detections were inversely correlated with the percentage of undeveloped land, indicating a nonpoint source signal. Widespread VOC detections in public well samples confirmed that wellhead protection efforts are warranted and that prudent managerial decisions regarding well planning, construction, and operation can result in reduced risks of VOC contamination to drinking water supplies.