Considerable attention has recently been focused on the potential incompatibility between various liquids found in landfill leachate and geosynthetic clay liners (GCLs). Many investigators have reported that the hydraulic conductivity of GCLs used in covers and liners can increase by several orders of magnitude when permeated with liquids containing polyvalent cations. One limitation of these results is that the impacts of the increase in hydraulic conductivity of the GCL on the overall performance of the waste containment system are presently unknown. In this investigation, the effects of adverse chemical interactions between cover percolation and landfill leachate with GCLs on the performance of a municipal solid waste landfill are evaluated. Based on results from this study, it appears that the overall performance of composite landfill covers and liners may not be degraded as much as may be inferred from hydraulic conductivity tests on GCLs. For instance, for composite liners having a GCL, assuming typical design constraints, an increase in hydraulic conductivity of the geosynthetic clay liner from 1x10~(-11) m/s to 3x10~(-10) m/s, results in an increase in the leakage rate by a factor of approximately 1.6. Furthermore, it is demonstrated that the performance of individual components of cover and liner systems should be considered with respect to the overall performance of the integrated system to reach rational conclusions regarding the performance of individual components of the system.
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