Abstract

Despite interest in the no-purge method for groundwater sampling, little has been done or documented on carefully controlled field studies to compare the analytical test results from the traditional purge method with the no-purge method for various field conditions and over a wide range of concentrations of contaminants. To assist with regulatory decisions regarding to purge or not to purge, this paper introduces two statistical methods for analysis of purge and no-purge data. This paper also discusses the limitations of the statistical methods applied to the decision whether to purge or not to purge. The statistical methods used are the correlation coefficient and the analysis of variance. A case study is used to demonstrate the application of these two statistical methods to analyze groundwater data obtained from the purge and no-purge methods. In addition to statistical analysis results, site-specific evaluation is recommended. The factors of the site-specific evaluation may include the historical trend of monitoring data, concentration variations at the upgradient versus downgradient wells, concentration variation over time, and contaminant source removal situation. Reasonable and intelligent decisions will depend on all applicable factors for a site.