From the GMA Techline
Subject: Geotextile transport layer We need some information about the characteristics of the transport layer (special geotextile) used in association with leak-detection sensors and placed between a drainage geocomposite layer (geonet plus geotextile separator) and the HDPE geomembrane, corresponding to part of the impervious system projected for the base of a hazardous-waste landfill.
Reply: The typical geotextile used on a geonet (which eventually will interface with the HDPE geomembrane that you mentioned) is a needle-punched, nonwoven polypropylene fabric of about 180g/cc mass. The main reason is that this type of geotextile bonds nicely to the geonet during the manufacturing process. This process is accomplished by slightly heating the surface of the geonet and then laminating the geotextile to it. The bonding is very good.
Of course, any other mass of geotextile can also be used equally well. When it comes to bonding other types of geotextiles, the bonding is more difficult. Nonwoven heat-bonded, and even woven monofilament fabrics, have also been used, but rarely.
Don’t hesitate asking further questions.