The service life of polyethylene geomembrane barriers

Abstract

The long-term service life of HDPE geomembrane liners depends upon the rate of generation of holes in the liner and the acceptability of leachate or gas leakage at a particular site. The development of holes with time until the landfilled waste no longer poses an environmental hazard is important in assessing the long-term performance of landfills. A thorough review of physical damage, material degradation processes and the development of holes by stress cracking has been undertaken. This paper summarises the findings of the research project, which forms the basis on which guidance and assumptions on medium to long-term landfill liner performance can be formulated in the UK. A conceptual model of hole generation in six stages throughout the service life of an HDPE liner is presented. Electrical leak location surveys are seen to be effective means of identifying holes caused by physical damage during liner installation and waste disposal, and permitting their repair. Degradation of the HDPE liner is controlled by the liner exposure conditions, the activation energy of the antioxidant depletion process and the oxidative resistance of the material. Where the liner is subjected to long-term stresses, stress cracking will lead to the development to holes, and the rate of cracking will increase once oxidation of the liner commences. Methods to minimise and retard the development of holes are discussed.