A Fuzzy-Set Approach for Addressing Uncertainties in Risk Assessment of Hydrocarbon-Contaminated Site

This study presented an integrated approach for evaluating environmental risks associated with hydrocarbon-contaminated sites through incorporation of a multiphase multi-component modeling system within a general risk assessment framework. The uncertainties associated with risk evaluation criteria were emphasized and effectively addressed through the development of a fuzzy-set approach. This development was based on (a) simulation of the fate of the contaminant in the subsurface to calculate contaminant concentrations in groundwater; (b) examination of the excess lifetime cancer risk (ELCR) distributions; (c) quantification of uncertainties in ELCR evaluation criteria using fuzzy membership functions; (d) categorization of the related risk levels into low, low-to-medium, medium, medium-to-high, and high, and (e) assessment of risk levels based on ELCR distribution and fuzzy evaluation criteria. The developed fuzzy risk assessment approach (FRA) was applied to a hydrocarbon-contaminated site in western Canada. Three remediation scenarios with different efficiencies (0, 60, and 90%) and planning periods (10, 20, 40, and 60 years later) were considered, and the spatial and temporal variations of risk values were examined. The temporal variation of membership values for different risk levels at locations of interest was also identified. The FRA is useful for the decision maker to gain insight into the environmental risks by considering uncertainties and to make more realistic remediation decisions.