A Composite Liner is an engineered containment system used in mining to prevent the seepage or leakage of potentially harmful liquids — such as leachate from heap leach pads, tailings slurry, or acid mine drainage — into underlying soils and groundwater. In bauxite, gold, iron ore, and diamond mining, composite liners are deployed in critical containment structures including tailings storage facilities, heap leach pads, solution ponds, evaporation ponds, and waste rock facility drainage collection systems. A composite liner typically consists of two primary components working in combination: a low-permeability geomembrane — commonly a High-Density Polyethylene (HDPE) or Linear Low-Density Polyethylene (LLDPE) sheet — placed in direct and intimate contact with a compacted soil layer, such as compacted clay or a Geosynthetic Clay Liner (GCL). The combination of these two materials provides a barrier that is far more effective at preventing liquid migration than either component alone, as the geomembrane resists bulk flow while the fine-grained soil layer limits seepage through any pinholes or imperfections in the membrane. Design specifications for composite liners — including material thickness, permeability coefficients, and quality assurance testing requirements — are governed by engineering standards, regulatory requirements, and international guidelines such as those published by the Mining Association of Canada and the Global Tailings Review.
