Composite GCL’s are constructed by either adding a thin membrane to a standard GCL or by adhering sodium bentonite directly onto a geomembrane. The thin membrane that is applied onto a standard GCL is designed to act as a vapor barrier or to protect the bentonite from harmful contaminants. When the bentonite is applied to a geomembrane, it acts as a composite lining system. The geomembrane backing can either be smooth or texted and can be welded together.