For Impermeable lining, we mainly use Geomembrane sheet. A Geomembrane is a very low permeability synthetic membrane liner or barrier used with any geotechnical engineering related material so as to control fluid (or Gas) migration in a human-made project, structure, or system. Polymeric Geomembranes are not absolutely impermeable, but are relatively impermeable when compared to geotextiles or fine soils. Typical values of Geomembrane permeability is in the range of 1 x 10-12 to 1 x 10-15 m/s.