Cost-Effective Sampling of Groundwater Monitoring Wells: A Data Review and Well Frequency Evaluation

Cost-effective sampling (CES) is a methodology for reviewing and assessing ground water data. The CES program produces a data information sheet and a lowest-frequency sampling schedule for a given groundwater monitoring location that provides the needed information for regulatory and remedial decision-making. The determination of sampling frequency for a given location is based on trend, variability, and magnitude statistics describing the contaminants at that location. The underlying principle is that a location's schedule should be primarily determined by the rate of change in concentrations that have been observed there in the recent past. The higher the rate of change, whether upward or downward, the greater the need for frequent sampling. Conversely, where little change is observed, a more relaxed schedule can be followed. CES was implemented at LLNL in 1992 and approved by U.S. EPA - Region IX and the local regulators. Applying the CES methodology has produced a 40% reduction in the required annual number of routine ground water samples at LLNL. This reduction has saved LLNL $390,000 annually in sampling, data management, and analysis costs.