Comparison of four composite landfill liner systems considering leakage rate and mass flux

Performance of four different municipal solid waste landfill liner systems, i.e., Subtitle D composite liner system, composite liner system with a geosynthetic clay liner (GCL) instead of low permeability compacted soil, Wisconsin NR500 liner system, and proposed four-component composite liner system that is a combination of the GCL composite liner system and the Subtitle D liner (with a 61 cm (2 feet) or 91.5 cm (3 feet) thick compacted clay liner), were evaluated in terms of leakage rate and mass flux. The leakage rate through circular and non-circular geomembrane (GM) defects was analyzed using both analytical and numerical methods. For the mass flux evaluation, solute transport analyses using GM defects and diffusion of volatile organic compounds through intact liners were conducted using one- and three-dimensional numerical models. Cadmium and toluene were used as typical inorganic and organic substances, respectively, in the analyses. The comparison shows that the proposed four-component composite liner system outperforms the other liner systems based on leakage rate and mass flux and is a viable choice for a liner system.