Use of Organoclay as Secondary Containment for Gasoline Storage Tanks

Conventional clay liners, which are widely used as hydraulic barriers to water, have been shown to be adversely affected by organic fluids. However, the addition of quaternary amines into bentonite greatly enhances its compatibility with organic fluids and thus allows the clay barrier technology to be extended to the treatment of organic contaminants. In this study, an organically modified clay was studied for use as a secondary containment for gasoline underground storage tanks. Free swelling and hydraulic conductivity tests were performed on organoclay, pure bentonite, and natural soils. Results show that organoclay has a large swelling capacity in gasoline, whereas bentonite and natural soils shrink when immersed in gasoline. The hydraulic conductivities of bentonite and natural soils to gasoline are 2-5 orders of magnitude higher than that to water. In contrast, the hydraulic conductivity decreases by 2 orders of magnitude for organoclay and this low value can be maintained even under freeze-thaw and dry-wet cycles.