Geosynthetic clay liners (GCLs) are manufactured liners consisting of two needles punched geotextile layers encapsulating a layer of sodium bentonite for sealing applications. Can be manufactured with a PE (polyethylene) layer either laminated or coated to provide an additional barrier. Common uses are landfill secondary liners, landfill capping systems, tailings dams, groundwater protection, canals and watercourses.