To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2005.12.018 Byline: Jianbing Li (a), Gordon H. Huang (b)(c), Guangming Zeng (c), Imran Maqsood (d), Yuefei Huang (e) Keywords: Contaminated site; Fuzzy set; Risk assessment; Simulation; Stochastic modeling; Uncertainty Abstract: An integrated fuzzy-stochastic risk assessment (IFSRA) approach was developed in this study to systematically quantify both probabilistic and fuzzy uncertainties associated with site conditions, environmental guidelines, and health impact criteria. The contaminant concentrations in groundwater predicted from a numerical model were associated with probabilistic uncertainties due to the randomness in modeling input parameters, while the consequences of contaminant concentrations violating relevant environmental quality guidelines and health evaluation criteria were linked with fuzzy uncertainties. The contaminant of interest in this study was xylene. The environmental quality guideline was divided into three different strictness categories: 'loose', 'medium' and 'strict'. The environmental-guideline-based risk (ER) and health risk (HR) due to xylene ingestion were systematically examined to obtain the general risk levels through a fuzzy rule base. The ER and HR risk levels were divided into five categories of 'low', 'low-to-medium', 'medium', 'medium-to-high' and 'high', respectively. The general risk levels included six categories ranging from 'low' to 'very high'. The fuzzy membership functions of the related fuzzy events and the fuzzy rule base were established based on a questionnaire survey. Thus the IFSRA integrated fuzzy logic, expert involvement, and stochastic simulation within a general framework. The robustness of the modeling processes was enhanced through the effective reflection of the two types of uncertainties as compared with the conventional risk assessment approaches. The developed IFSRA was applied to a petroleum-contaminated groundwater system in western Canada. Three scenarios with different environmental quality guidelines were analyzed, and reasonable results were obtained. The risk assessment approach developed in this study offers a unique tool for systematically quantifying various uncertainties in contaminated site management, and it also provides more realistic support for remediation-related decisions. Author Affiliation: (a) Environmental Engineering Program, University of Northern British Columbia, Prince George, British Columbia, Canada V2N 4Z9 (b) Faculty of Engineering, University of Regina, Regina, Saskatchewan, Canada S4S 0A2 (c) China-Canada Center of Energy and Environment Research, Hunan University, Changsha, 410082, China (d) Saskatchewan Environment, Regina, Saskatchewan, Canada S4S 0B1 (e) Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China Article History: Received 13 April 2005; Revised 14 December 2005; Accepted 14 December 2005