The authors document a methodology for evaluating performance of a clay liner in terms of the possibility of meeting the U.S. Environmental Protection Agency's requirement on the hydraulic conductivity. Four major categories of factors affecting the performance of clay liners are identified through a review of literature. A survey of expert opinions was conducted to measure the extent of the contribution of each category to the performance of clay liners. In this proposed methodology, the clay liner is evaluated and rated using a linguistic assessment to reflect the uncertainty faced in the evaluation process. These grades are translated into fuzzy numbers and processed using fuzzy arithmetic. The final results of the analysis is a fuzzy number that represents the overall predicted performance of a clay liner. Example case studies are presented to demonstrate the methodology.