The use of geosynthetics in landfill lining systems is now common. HDPE, Geosynthetic Clay Liners (GCL’s) and geotextiles are commonly used. The purpose of the liner is to separate the leachate produced by the stored waste from the underlying water table. A typical arrangement consists of a GCL in contact with the subgrade of the landfill overlaid by a 1.5mm HDPE followed by a heavy geotextile to give mechanical protection to the HDPE. A drainage layer of gravel or sand is then placed. A lighter geotextile is often provided above the drainage layer to act as a filter between the drainage layer and the stored waste.
Following completion of the landfill the top surface may be sealed with a system of geosynthetics which may include; an LLDPE (Linear Low Density Polyethylene), a geocomposite (Drainage mesh + two layers of geotextile) and a cover soil. The landfill will often produce biogas which needs to be vented or flared. A system of polyethylene pipes may be installed through the waste layers to capture and vent the gas.
The leachate which is drained from the landfill is taken either to holding ponds or a treatment plant. The holding pond is often lined with HDPE and is on some occasions provided with a floating cover in order to prevent the entry and dilution by rainfall.