Practical Application of Statistics to Groundwater Monitoring Data, 2002 Environmental Conference Proceedings

M. Taylor, P. Dohney and S. McGee

Solid waste regulations in many states require statistical evaluation of groundwater monitoring data for landfill sites. Typically, a list of approved statistical methods is provided in the regulations with the option to propose an alternate statistical method. Frequently, permit holders are encouraged to use a simple statistical approach that is easily understood. Our experience suggests that the statistical approach should be tailored to the site and should be technically rigorous. In general, this means that the monitoring approach should be consistent with the geology of the site and that the statistical method should be valid. The owner should have confidence that groundwater-monitoring results will confirm the compliance of the facility. Misleading or invalid statistical data can be a liability if it comes under scrutiny. Common statistical methods will be reviewed, with an emphasis on the strengths and weaknesses of each method. The inherent pitfalls of nonparametric data will also be discussed. The application of statistics to data from three sites in Alabama will be used as examples. In each case, site geologic conditions and the nature of the groundwater data influenced the selection of the appropriate statistical method.