Membrane Behavior of Exhumed Geosynthetic Clay Liners

Geosynthetic clay liners (GCLs) containing sodium bentonite (NaB) exhibit semipermeable membrane behavior. However, experimental studies to date have evaluated the existence and significance of membrane behavior only of virgin GCLs, and there is no evidence of the persistence of the phenomenon in the field. In this study, membrane behavior was measured for GCL specimens exhumed from a landfill site. The specimens were obtained from a bottom liner system that was left exposed without placement of overlying waste for over a decade. Multistage membrane behavior tests were performed with potassium chloride (KCl) solutions ranging in concentration from 5 to 50 mM to allow for comparison with the literature on membrane behavior of virgin GCLs and NaB. The results showed that membrane behavior persisted in the exhumed GCLs. However, membrane efficiency coefficients (ω) for the exhumed GCLs were