An analytical solution to contaminant advection and dispersion through a GCL/AL liner system

Abstract

An one-dimensional model for contaminant advection and dispersion through a GCL/AL liner system was developed to analyze the equivalence between a GCL (geosynthetic clay liner) and a CCL (compacted clay liner). The continuity of contaminant concentration and flux at the interface between the GCL and the underlying attenuation liner (AL) are obeyed in the model, and background concentrations in the soil liner are also considered. Based on the assumption that contaminant transport through a GCL was a steady state process, an analytical solution was obtained. Increasing the leachate head from 0.3 m to 10 m results in a reduction of the breakthrough time of benzene by a factor of 2.7. The breakthrough time of benzene increases by a factor of 7.0 when the hydraulic conductivity of GCL decreases by one order of magnitude. The breakthrough curves are more sensitive to the hydraulic conductivities of the GCL and AL (attenuation layer) than to the thickness of the AL. The standard 75 cm CCL can be replaced by a combination of a GCL and a 1.0–4.0 m thickness of AL. The proposed method can be used for preliminary design of GCL composite liners, assessing the equivalence between GCL and CCL, preliminary design of a remediation method for contaminated soils, and evaluating experimental results.