GCLS to mitigate natural contamination from excavated rocks

The adverse effects of acid rock drainage (ARD) on the environment are due to its low pH and subsequent release of metal, and could be intensified by climate change. Using a lining system in rock containment facilities is considered a cost-effective measure to prevent this problem from spreading. Factors that impact hydraulic conductivity and metal transport due to ARD permeation are discussed in this paper based on the authors' previous data. Moreover, authors' previous data was compared with results obtained by other researchers. The parameters that affect the hydraulic performance of GCLs can be classified into: type of bentonite, pH, and presence of metal type and concentration. Two relationships that predict the hydraulic conductivity were presented, one for granular and another for powdered bentonite. The retention of metals through GCLs is governed by pH, metals present in solution, as well as buffering capacity of the bentonite. Secondary sorption on ferrihydrite or gypsum of metalloids such as As, which cannot be sorbed by bentonite directly, also play an important role in the immobilization of contaminants.