Parametric Study of the Effect on Groundwater Quality of Leakage of Benzene and Toluene through Composite Liners

Composite liners with a geomembrane and either a compacted clay or a geosynthetic clay liner are widely used to minimize leakage from landfills and other containment systems such as leachate lagoons. While much work has been done to quantify the rates of leakage, few papers assess the impact of this leakage on groundwater quality. This is particularly important for organic contaminants because of the potential for diffusion through the intact parts of the geomembrane. Building on recent developments in modeling mass-transport through leaking geomembranes as a boundary condition to the diffusion-advection boundary value problem, we report the results of a 2D finite-element parametric study of the problem using the Soil Pollution Analysis System SPAS. We assess the effect of landfill cell size, groundwater Darcy velocity and groundwater horizontal mixing, on concentrations of Benzene and Toluene, underlying a landfill with a leaking GM. We make recommendations concerning the importance of leakage and the accuracy of 1D analytical tools, namely the Rowe Equation for leakage and the POLLUTEv7 program for the prediction of contaminant transport.