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 system s. Expanded clay and shale, known as lightweight aggregates, contain e ssentially no carbonates and may provide a suitable alternative. We pe rformed an engineering evaluation of expanded clay and shale aggregate s to assess their suitability for leachate collection systems. The hyd raulic conductivities of the aggregates under 350 kPa normal stress ex ceeded the often-specified minimum regulatory value (0.01 cm/s) by one or two orders of magnitude. The aggregate showed no deterioration aft er being immersed in municipal solid waste leachate for more than 60 d ays. Interface friction angles between the dry aggregates and smooth h igh-density polyethylene geomembrane at 7 kPa normal stress ranged fro m 23 degrees to 27 degrees. Based on the results of our evaluation, it is our conclusion that expanded clay and expanded shale aggregates ar e viable and competent materials for use in leachate collection system s in municipal solid-waste landfills.