The U.S. Geological Survey, in cooperation with the U.S. Department of Energy, analyzed water-quality data collected from 67 aquifer wells and 7 surface-water sites at the Idaho National Laboratory (INL) from 1949 through 2009. The data analyzed included major cations, anions, nutrients, trace elements, and total organic carbon. The analyses were performed to examine water-quality trends that might inform future management decisions about the number of wells to sample at the INL and the type of constituents to monitor. Water-quality trends were determined using (1) the nonparametric Kendall's tau correlation coefficient, p-value, Theil-Sen slope estimator, and summary statistics for uncensored data; and (2) the Kaplan-Meier method for calculating summary statistics, Kendall's tau correlation coefficient, p-value, and Akritas-Theil-Sen slope estimator for robust linear regression for censored data.