Flow of Gasoline through Composite Liners

A composite liner composed of a soil/clay liner and a flexible membrane is widely used for waste containment facilities. In this research, an organically modified clay (organoclay BB-40) liner and a high-density polyethylene (HDPE) membrane were studied for preventing the leakage and migration of gasoline from underground storage tanks into the surrounding environment. The equivalent hydraulic conductivity of intact HDPE to gasoline was determined using a specially built system, and the conventional hydraulic conductivity testing method was employed to determine the hydraulic conductivity of compacted organoclays and the permeation rate of gasoline through composite liners. The equivalent hydraulic conductivity of intact HDPE to gasoline was about 10–13 cm/s, and the hydraulic conductivity of the organoclay liner was approximately 6.0×10-9cm/s, which is nearly 4 orders of magnitude lower than that obtained for unmodified clay. These results show that both organoclay and HDPE are effective in reducing the release of gasoline by advective flow, especially the intact HDPE. The flow of gasoline through the composite liners under the worst condition, was of the same magnitude as that through a single organoclay liner, independent of the flow shape. It can be anticipated that under good contact conditions, the defective HDPE would still be beneficial in reducing the permeation of gasoline due to the decrease of the wetted area of the underlying layer exposed to gasoline leakage.