This paper presents the results of a numerical investigation of the transport of a volatile organic compound (VOC) through a composite liner system comprising a geomembrane (GM) overlying and in intimate contact with a geosynthetic clay liner (GCL), which is commonly used as an engineered barrier for containment of solid waste. The simulations were performed using the established CST2 model (i.e., Consolidation and Solute Transport 2). The results are presented in the form of VOC mass flux, cumulative VOC mass outflow, and distribution of VOC concentration within the GCL. Consolidation of the 10-mm-thick GCL is shown to result in a decrease in the thickness, void ratio, and effective diffusion coefficient of 41%, 49%, and 72%, respectively, such that the steady-state TCE mass flux and cumulative TCE mass outflow at the bottom of the GCL decreased by 47% and 43%, respectively, relative to results for traditional diffusive simulations that ignore the effect of consolidation. Thus, despite the thinness of the GCL, the effect of consolidation on the transport properties of the GCL can result in a significant decrease in VOC transport through a composite GM/GCL liner system.