The U.S. Geological Survey (USGS) has collected water-quality data at six Resource Conservation and Recovery Act (RCRA) wells at the Letterkenny Army Depot since the 1990s. Electronic data (field and analytical) for this project were put into the USGS National Water Information System (NWIS) database beginning in 2017. Analytical data include total forms of selected metals and volatile organic compounds (VOCs). The data from 2017 through 2023 are provided in this data release. The data includes routine and quality control samples.