Main breaks double over last year

The number of major water main breaks in Los Angeles has more than doubled this month compared with the same period last year, Department of Water and Power officials said Monday.

Since Sept. 1, the agency has recorded 43 breaks requiring significant repairs, officials said. There were 21 such breaks in September 2008, 17 in September 2007 and 13 in September 2006.

Despite recent dramatic images of major water main breaks, including a 10-foot geyser of water and mud in Studio City and a sinkhole that swallowed half a fire engine in Valley Village, leaks and ruptures are a routine occurrence in the city’s aging network of pipes, officials said. They said the number of breaks and leaks large and small -- 151 so far this month -- is within the normal range.

The most recent rupture occurred about 6 a.m. Monday at San Vicente Boulevard and Fairfax Avenue, interrupting service to dozens of customers and causing flooding on the streets. Service was cut for 40 to 50 DWP customers, mainly commercial businesses, as repairs were underway, said DWP spokeswoman Maychelle Yee.

The rupture came on the heels of other water main breaks of varying sizes reported over the weekend in Encino, Sylmar and the Hollywood Hills.

Officials said the department averages about four leaks a day in the city’s 7,200 miles of water mains.

The DWP typically sees about 1,400 leaks and breaks per year, about 200 of which are categorized as requiring “significant repairs,” causing street closures or requiring repairs in excess of 100 square feet, officials say.

September’s incidents, on average, affected 25 customers for about six hours or less, officials said.

Water loss has been minimal.

DWP has replaced 30 miles of mainline pipes in the last two years and plans to replace an additional 20 miles in the coming year.

Some experts have postulated that the city’s recent decision to allow sprinklers to be used only on Mondays and Thursdays may be increasing stress on the pipes because of sudden changes in pressure when customers turn water on and off at the same time.

But DWP officials said they would not speculate as to the cause of the severe water main breaks until their ongoing investigation was concluded. The department has asked experts from USC, NASA’s Jet Propulsion Laboratory and Cornell University to look into the cause.

“We do realize this is a little bit higher than normal,” Yee said of the breaks. “We’re just looking at everything to see how that might be affecting it.”

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victoria.kim@latimes.com