AWWA JAW20480

Flood inflows from Arroyo Pasajero and Cantua and Salt creeks have introduced sediment into the California Aqueduct that contains high concentrations of crysotile asbestos fibers of up to 2.6 percent by weight. The California Department of Water Resources used commercially available equipment to dredge the asbestos-laden sediment from a 10-mile (16 km) portion of the aqueduct to determine whether removal of sediment is a feasible means of controlling concentrations of asbestos in water. It was found that thorough dredging essentially eliminated the resuspension of asbestos fibers in water flowing through the dredged reach of the aqueduct, and that asbestos concentrations in the dredged reach were not statistically different from the upstream background levels. Dredging to control asbestos makes a significant difference in water quality for the small domestic water systems that are supplied by the aqueduct. Includes 9 references, tables, figures.