Date of Conferral
Hazardous waste site remediation cost estimation requires a good estimate of the contaminated soil volume. The United States Environmental Protection Agency (U.S. EPA) currently uses deterministic point values to estimate soil volumes but the literature suggests that probability bounds analysis (PBA) is the more accurate method to make estimates under uncertainty. The underlying statistical theory is that they are more accurate than deterministic estimates because probabilistic estimates account for data uncertainties. However, the literature does not address the problem of selecting an optimal decision point from the interval-valued PBA estimates. The purpose of this study was to identify the optimal PBA decision point estimator and use it to demonstrate that because the PBA method also accounts for data uncertainties, PBA estimates of remedial soil volumes are more accurate than the U.S. EPA deterministic estimates. The research questions focused on determining whether the mean or the 95th percentile decision point is the optimal PBA estimator. A convenience sample of seven sites was selected from the U.S. EPA Superfund Database. The PBA method was used to estimate the remedial soil volumes for the sites. Correlation analyses were performed between the mean and 95th percentile PBA estimates and the actual excavated soil volumes. The study results suggest that the lower bound 95th percentile PBA estimate, which had the best R2-value of 89%, is the optimal estimator. The R2-value for a similar correlation analysis using the U.S. EPA deterministic estimates was only 59%. This confirms that PBA is the better estimator. The PBA estimates are less contestable than the current U.S. EPA deterministic point estimates. Thus, the PBA method will reduce litigation and speed up cleanup activities to the benefit of the U.S. EPA, corporations, the health and safety of nearby residents, and society in general.