Asbestos-Tainted Runoff May Be Let Into Aqueduct

To avoid flooding in the San Joaquin Valley south of Huron, the State Water Resources Department announced Wednesday that it may have to allow some storm runoff containing naturally occurring asbestos to flow into the California Aqueduct.

Department spokesman Jeff Cohen said the runoff had been carried from the Arroyo Pasajero, a watercourse that drains lower mountain ranges on the west side of the valley, into a collection basin next to the aqueduct near Huron in western Fresno County. With recent heavy rains, he said, the basin has filled, threatening to flood surrounding farmland.

Cohen said department engineers would maintain an all-night vigil at the basin and, if it appeared close to a spillover, they would open emergency gates allowing it to empty into the aqueduct. The water would then be pumped over the Tehachapi Mountains into the west branch of the aqueduct for eventual delivery to Castaic Lake.

He said little is known about the effects of asbestos in water, but officials believe most of the sediment would settle before the water was taken for use by the Metropolitan Water District, a water wholesaler that supplies much of Southern California.

“Despite the (known harm) of airborne asbestos, it is not yet known whether asbestos in water constitutes a health hazard, and no standard has been set for acceptable exposure levels to water-borne asbestos,” a department position paper said.

MWD spokesman Bob Muir said district water quality experts were certain that by the time the water leaves treatment plants “well over 99% of the traces of asbestos will have been removed.”