Change in leachate chemistry and porosity as leachate permeates through tire shreds and gravel

Rubber tire shreds are an attractive potential alternative to conventional gravel in the drainage layer of leach- ate collection systems at the base of landfills, yet the clogging and thus the long-term performance of tire shreds in this application is not known. This paper presents the results of an experimental investigation into the clogging poten- tial of rubber tire shreds used as part of a leachate collection system at the base of a landfill when permeated with leachate. Experimental columns filled with two different rubber tire shreds and a conventional gravel drainage material were used to study the spatial and temporal variation of leachate characteristics and porosity changes within the drain- age materials. It is shown that there are significant differences in the pore structures of the drainage materials and that these differences affect clog development and the length of time it takes for the hydraulic conductivity to drop below a threshold of 10 -5 m/s. The gravel is found to have a service life at least three times greater than that of an equivalent