A Systematic Approach for Evaluating the Quality of Ground Water Monitoring Data

The recognition and assurance of the quality of ground water monitoring data are crucial to the correct assessment of the magnitude and extent of a ground water contamination problem. This article addresses an approach being developed to systematically evaluate the quality of a given set of ground water monitoring data collected during site investigation/ remedial action efforts. The system consists of a checklist of criteria, grouped into four major categories, which can be applied to laboratory or field measurements.
The first category, basis of measurement, considers whether the appropriate sampling, boring and/or analytical methods were chosen to obtain the measurement and the limitations of each method. Secondly, application of the method is assessed. This includes examination of the extent to which procedures were correctly performed, the use of quality control measures and calibration, and possible sources of error in the measurements. Third, evaluation of applied statistical methods is made, with consideration given to which statistics are meaningful in a given context and whether measurements are reproducible. The final category, corroborative information, considers whether independent data or other information are available that add credibility to the values measured.
In this approach, a "high quality" data value is defined as one in which accuracy is supported by meeting the preceding criteria. When accompanied by precision information, high quality data allow for defensible assessments and actions. This evaluation system is useful in developing monitoring programs and in guiding documentation of field and laboratory methods during data collection. It relies heavily on experienced judgment and can be catalyst for the beneficial exchange of knowledge and ideas among ground water professionals.