Dispersive Soil Problem at Los Esteros Dam

Dispersive soil was discovered in the impervious borrow area at Los Esteros Dam and, through the use of sand filters and lime treatment of specific areas, the dispersive soil was used in the impervious core of the dam. Testing of the soil at the first laboratory was inconclusive, but testing at the second confirmed the soil to be dispersive. Tests were then conducted on the dispersive soil, sand filters, and lime-treated dispersive soil to determine whether sand filters and lime treatment could be used to control and alter the dispersive clay for use in the impervious core of the dam. Results of the program confirmed that a properly graded sand filter will control dispersive erosion through the impervious core and lime treatment alters the soil to a nondispersive material. A sand filter was constructed downstream of the impervious core and, where the base of the impervious core is founded on a fractured sandstone, a 5-ft (1.5-m) thick layer of the core was treated with lime.