Geosynthetic Clay Liners (GCLs) are factory-manufactured hydraulic barriers consisting of a layer of bentonite or other very low-permeability material supported by geotextiles and/or geomembranes, mechanically held together by needling, stitching, or chemical adhesives. Due to environmental laws, any seepage from landfills must be collected and properly disposed of, otherwise, contamination of the surrounding groundwater could cause major environmental and/or ecological problems. The lower the hydraulic conductivity the more effective the GCL will be at retaining seepage inside of the landfill.
Bentonite composed predominantly (>70%) of montmorillonite or other expansive clays, is preferred and most commonly used in GCLs. A general GCL construction would consist of two layers of geosynthetics stitched together enclosing a layer of natural or processed sodium bentonite. Typically, woven and/or non-woven textile geosynthetics are used, however, polyethylene or geomembrane layers or geogrid geotextiles materials have also
been incorporated into the design or in place of a textile layer to increase strength.