Bentonite Sealing Methods Compared in the Field

Two field studies were designed to test methods of sealing with bentonite. Twelve small reservoirs were constructed at each site. Utah bentonite was installed as the following types of seals: (1) waterborne-harrowed, (2) waterborne-over-a-gravel surface, (3) surface blanket, (4) buried blanket, and (5) buried membrane. The waterborne-harrowed seals were short lived. The waterborne seals on reservoirs with graveled surfaces were effective only slightly longer, becoming ineffective after the third season. The 4-in. surface blanket seals were more durable, their effectiveness lasting about five seasons. The buried blanket and buried membrane seals proved to be the best, retaining 60% effectiveness 6 yrs. after installation. Seal costs varied from $0.20 to $1.30 per sq yd of soil surface. These costs are comparable with other methods of sealing, such as plastics.