Expanded clay and shale aggregates for leachate collection systems

In regions dominated by high-carbonate aggregates, landfill owners are faced with using alternative materials for leachate collection systems. Expanded clay and shale, known as lightweight aggregates, contain essentially no carbonates and may provide a suitable alternative. We performed an engineering evaluation of expanded clay and shale aggregates to assess their suitability for leachate collection systems. The hydraulic conductivities of the aggregates under 350 kPa normal stress exceeded the often-specified minimum regulatory value (0.01 cm/s) by one or two orders of magnitude. The aggregate showed no deterioration after being immersed in municipal solid waste leachate for more than 60 days. Interface friction angles between the dry aggregates and smooth high-density polyethylene geomembrane at 7 kPa normal stress ranged from 23 degrees to 27 degrees. Based on the results of our evaluation, it is our conclusion that expanded clay and expanded shale aggregates are viable and competent materials for use in leachate collection systems in municipal solid-waste landfills.