ABSTRACT
A cap is an engineered impermeable barrier designed to cover the top of contaminated waste and prevent precipitation leaching from the waste and into the environment. In landfills, the cap also serves to control gas emissions from the waste. Materials used in a cap must not only survive aggressive installation conditions, but they must also be resilient to the deteriorating effects of long service life and environmental exposure. Bituminous geomembranes (BGMs) have been proposed by various authors as a material well suited to perform the barrier function of a cap in both exposed and unexposed conditions. In Australia, the application of BGMs for capping contaminated waste is growing rapidly. This paper describes three recent successful capping projects designed using a BGM barrier including one mining application and two landfill applications. For each project, the technical background of the site is explained and the important factors of the capping design and installation are described. The examples presented will give designers greater confidence in the use of a BGM as a cap in new and technically challenging applications.
