Impact of dichloromethane on groundwater below landfills with geomembrane composite liners

This paper examines dichloromethane (DCM) transport through geomembrane (GMB) composite liners with holed wrinkles. Consideration is given to the specified GMB composite liner designs from different jurisdictions on an attenuation layer (AL) with a GMB overlying a geosynthetic clay liner (GCL) and/or a compacted clay liner (CCL): (1) the GMB+CCL+AL liner, (2) the GMB+GCL+AL liner, and (3) the GMB+GCL+CCL+AL liner. The peak DCM impact on groundwater quality and the leakage rate from different GMB composite liner designs are compared using a two-dimensional numerical model. Sensitivity analysis indicates that the key factors affecting the GMB composite liner performance are the utilization of a GCL and/or a CCL, the CCL hydraulic conductivity when used, the AL thickness, and the aquifer potentiometric head. Most results show poor performance of examined GMB+CCL+AL liners to limit the peak DCM impact at the landfill cell downgradient edge within the jurisdictional allowable limits for DCM in drinking water. GMB+GCL+CCL+AL liners outperform GMB+GCL+AL liners because the additional layer of protection provided by the CCL (with the hydraulic conductivity of 1 × 10⁻⁹ m/s or lower) in the case of GCLs experienced typical cation exchange or permeated with aggressive inorganic solutions under holed wrinkles.