Cost-effective sampling of ground water monitoring wells

Cost-Effective Sampling (CES) is a method for estimating the lowest-frequency (and, as a result, lowest-cost) sampling schedule for a given groundwater monitoring location which will still provide needed information for regulatory and remedial decision-making. Its initial development was motivated by the preponderance of sampling results showing little changes over time or failing below detection limits at Lawrence Livermore National Laboratory`s (LLNL`s) environmental restoration sites. The fact that many locations had never shown, or had ceased for some time to show, any detectable levels or changes in levels of contamination suggested that some of their 700+ groundwater monitoring wells were being sampled more often than necessary. Similar concerns were raised at the Savannah River Site (SRS), where some 10,000 samples are taken per year from 1500+ monitoring wells. The question facing both organizations has been how to reduce sampling costs while still satisfying both regulatory agencies and their own scientists and engineers that sufficient data will be collected for decision-making purposes. The first version of CES was implemented at LLNL`s Livermore site in 1992 and approved by regulators under CERCLA. It is designed to statistically evaluate the sampling results to be able to recommend sampling schedules of groundwater monitoring locations for a common suite of volatile organic compounds, with the goal of reducing frequencies. The table below presents the sampling status of monitoring wells at LLNL`s two restoration sites both before and after the application of CES.