DWP Starts Repair of Historic Spillway

Workers have begun repairs on a historic concrete spillway that collapsed over the weekend, Department of Water and Power officials said Tuesday.

Parts of the base of the 150-foot-wide Cascades spillway, christened in 1913 by former chief city engineer William Mulholland, apparently collapsed under a heavy water flow Friday evening, DWP spokesman Mitchell M. Kodama said. The spillway links the first Los Angeles aqueduct to the city’s water system.

Kodama said the structural failure was discovered Saturday afternoon when water fouled by the accident triggered an alarm at the San Fernando Reservoir. The walls of the spillway did not break, and no spill was reported, Kodama said. However, the spillway will be closed for up to two weeks, he said.

The damaged spillway is at the end of one of two aqueducts that normally supply 80% of the city’s water, Kodama said. The spillways are at the southern edge of the Tehachapi Mountains near the Golden State Freeway.

Laurent McReynolds, an assistant chief engineer with the DWP, said the collapse of the spillway will not cause water shortages. If necessary, the DWP will draw additional water from reservoirs maintained by the Metropolitan Water District, McReynolds said.

McReynolds said the concrete lining of the spillway began breaking apart when water flowing at a rate of 180,000 gallons a minute was released Friday afternoon after a routine weeklong shutdown of the aqueduct. McReynolds said the second aqueduct had been closed as the first was reopened, causing an uncharacteristically heavy flow of water.

Kodama said the earth beneath the spillway apparently had been eroding since the 1971 Sylmar earthquake. Many cracks in the spillway were repaired shortly after the earthquake, he said.

The second aqueduct is operating smoothly, carrying a standard flow of 150,000 gallons a minute, McReynolds said.