ABSTRACT
Waste disposal facilities (landfills) need to be designed with two distinct and complementary barriers; polymeric and mineral low permeable materials i.e composite liners. In order to prevent contamination of subsoil and groundwater by the leachate provided by wastes, composite liners need to be installed with very strict regulations. Nonetheless, with the luck of natural sites meeting regulations and considering economic and technical concerns, designers used to search for an equivalent design solution on a landfill geographical site by considering alternative materials providing similar protection of the potential environmental impact of wastes on water resources and aquifers. This is where a thin low permeable material such as geosynthetic clay liners (GCLs) or treated soils as polymer-enhanced bentonite–sand mixture (PEBSM) could be added as reinforcement. In this study, analytical and numerical equivalency analyses have been performed on relative concentration evolution of inert contaminant through the geosynthetic reinforced barrier and soil liner in comparison with conventional low permeable soil in the same contamination configuration. Numerical modeling has been used to reproduce contaminant transfers into the entire barrier to the aquifer by SEEP/W and Ctran from Geostudio (2012). In this study, we found that the reinforcement of a non-regulatory passive barrier with a GCL or a PEBSM could provide similar protection level and in some cases enhance it by limiting the evolution of the contaminant migration into the groundwater and subsoil. In conclusion, equivalency is possible for passive barriers through different design solutions; however it is important to pay attention to provide minimum thicknesses of materials to avoid preferential flow paths. This study was inspired from the French guide line for equivalency of landfills passive barrier BRGM/RP-69449-FR (2019). As a result of this study, the proposed methodology for calculating contaminant transport through passive barriers was validated and could provide a reliable tool for other hydraulic applications.
