This report presents qualitative and quantitative comparisons of water-quality data from the Idaho National Laboratory, Idaho, to determine if the change from purging three wellbore volumes to one wellbore volume has a discernible effect on the comparability of the data. Historical water-quality data for 30 wells were visually compared to water-quality data collected after purging only 1 wellbore volume from the same wells. Of the 322 qualitatively examined constituent plots, 97.5 percent met 1 or more of the criteria established for determining data comparability. A simple statistical equation to determine if water-quality data collected from 28 wells at the INL with long purge times (after pumping 1 and 3 wellbore volumes of water) were statistically the same at the 95-percent confidence level indicated that 97.9 percent of 379 constituent pairs were equivalent. Comparability of water-quality data determined from both the qualitative (97.5 percent comparable) and quantitative (97.9 percent comparable) evaluations after purging 1 and 3 wellbore volumes of water indicates that the change from purging 3 to 1 wellbore volumes had no discernible effect on comparability of water-quality data at the INL. However, the qualitative evaluation was limited because only October-November 2003 data were available for comparison to historical data. This report was prepared by the U.S. Geological Survey in cooperation with the U.S. Department of Energy.