A Quantitative Evaluation for Comparing Technologies for the Remediation of Leaking Underground Storage Tanks Open Access
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Petroleum releases from Underground Storage Tanks (USTs) and associated piping represent a major environmental threat to the nation's soil and groundwater. Leaking underground storage tanks (LUSTs) historically have been the nation's primary source of groundwater contamination. The U.S. Environmental Protection Agency's federal UST regulations require that contaminated underground storage tank sites be remediated by state environmental agencies to restore and protect groundwater resources and create a safe environment for those that live or work around these sites. Nationally, there is a need to address at least 80,000 groundwater petroleum releases on private property, public property (state and local government property), tribal lands, and federal facilities. Releases from tanks can cause well water contamination plus toxic vapors that affect human health. The releases also can result in fires and explosions.This research focused on the development of a quantitative evaluation for state program managers to use when managing LUSTs. The objective of this research was to develop a decision-aiding mechanism to assist State program managers in evaluating Air Sparging and Bioremediation remedial technologies in cleaning up contamination from LUST sites, and assist State program managers in forecasting what level of contamination will be removed when applying these two technologies. This research compared two in-situ groundwater remediation technologies: Air Sparging and Bioremediation. This quantitative evaluation examined data from 274 LUST sites from the state of South Carolina during the period 1997-2004. For the 274 LUST sites, 176 used Air Sparging while 98 used Bioremediation as a mitigation technology. Specifically, the quantitative evaluation allowed the computation of the cleanup levels for each of the two in-situ technologies at the respective LUST sites, and a comparison was made to determine which technology was more effective in removing contaminants from LUST sites.This research developed a decision-aiding mechanism to assist state program managers in determining which of the two technologies is best in removing contaminants from LUST sites. The results of this analysis for sample sizes with 30 or more observations, were as follows: (1) for LUST sites that utilized Air Sparging technology, it is estimated that on average approximately 82% of these sites will have between 11.2% and 99.9% of the contamination removed, and the decision maker can be 95% confident that the average percentage of contamination removed will fall between 67.8% and 76.5%; (2) for LUST sites that utilized Bioremediation technology, it is estimated that on average approximately 85% of these sites will have between 12.0% and 99.8% of the contamination removed, and the decision maker can be 95% confident that the average percentage of the contamination removed will fall between 64.4% and 75.1%; and (3) the null hypothesis should not be rejected, i.e., there is no statistically significant difference between the mean cleanup levels of Air Sparging and Bioremediation technologies in removing contaminants from LUST sites.