Jul 22, · The thickness of HDPE geomembrane is 0.2 mm – 3 mm. The HDPE geomemebrane liner with thickness more than 2mm is also called HDPE polythene sheet. The HDPE geomembrane liner is the most st effective and adaptable liners available. It is ideal for ponds of all sizes with steel or gentle slope sides, tight rners, ntours and shelving.