Modeling the impact of risk-based corrective action on overall underground storage tank site management costs

The University of Tennessee Waste Management Research and Education Institute (WMREI) has been tracking remediation costs for Tennessee underground storage tanks (UST) site cleanup for the past five years, in order to study the cost-effectiveness of cleanup methodologies for different site characteristics. A major focus of the earlier research was to attempt to correlate site characteristics such as ground water plume size (aerial extent), volume of contaminated soil and soil permeability to the cleanup costs of petroleum UST sites. The results showed that it was very difficult to correlate individual site characteristics with costs; this may have been partly due to a limited data set size (76 sites) and the unique nature of each site which made comparison among sites difficult. It was concluded that the initial approach may have not entirely captured the complexity of predicting cleanup costs.

In order to encourage cost-effective cleanups, while safeguarding human health and the environment, Tennessee, like many other states, are implementing risk-based corrective action (RBCA) plans. Teimessee requires site owners to input geological parameters, exposure pathway parameters, and contaminant concentrations into a formula that assigns a numerical score to each site. For sites that score below 500, owners and operators are allowed to bypass cleanup and monitor the plume only.

A cost model was developed from collecting site information that predicts costs of site assessment, cleanup and monitoring. This cost model developed by the University of Tennessee may be used to determine the efficacy of Tennessee’s RBCA system in promoting cost-effectiveness in the management of these contaminated sites. Also, the current and potential future impact of RBCA on the composition (e.g. site characteristics, location) of sites undergoing cleanup was examined, as well as the cleanup methods being used. Finally, a statistical model was developed to test the validity of Tennessee’s scoring system to capture the risky sites, which pose a threat to human and environmental receptors.