Use of organophilic clay in sand-bentonite as a barrier to diesel fuel

A laboratory research program was conducted to evaluate the long-term hydraulic performance of sand–bentonite liners augmented with organophilic clay and permeated with diesel fuel. This program was also designed to establish guidelines for the incorporation of organophilic clay in sand–bentonite liners. The study involved three areas of testing. The first was to characterize the materials. The second was to evaluate various combinations of materials and preparation techniques through hydraulic conductivity tests. The third area involved unconfined infiltration tests. The primary hydraulic conductivity testing was broken into three phases. These investigated the hydraulic conductivity of organophilic sand–bentonite liners using various percentages of organophilic clay and evaluated the hydraulic performance of these specimens when permeated with distilled water and diesel fuel. Hydraulic conductivity was measured in specially designed low gradient, low effective stress stainless-steel triaxial permeameters. The results of this test program indicated that small percentages (3%) of organophilic clay in a sand–bentonite liner material could effectively be used to avoid desiccation cracking in a liner permeated with petroleum products. High percentages (7.5%) of organophilic clay in a sand–bentonite mixture resulted in a liner permeable to water, but reduced permeability to diesel fuel.