Officials Rush to Guard Against New Pipe Breaks

Saying this growing city could be vulnerable to another catastrophic water-main blowout like the one that flooded streets this weekend, Calleguas Municipal Water District officials said Monday they will consider toughening the pipeline system at their own cost.

Steady growth in Simi Valley has put an extra strain on Calleguas’ water system there, so much so that “there appear to be some scenarios where we’re vulnerable,” said Donald Kendall, the district’s general manager.

“It was a miracle that no one was injured,” Kendall said of Saturday’s water-main rupture, which flung chunks of asphalt into the air, opened a gaping sinkhole in Madera Road and flooded surrounding streets.

While rush-hour traffic crept past the massive sinkhole and engineers laid plans for the two-week job to repair the pipe, water officials began weighing the cost of preventing another break.

“My job is to make sure it doesn’t happen again,” Kendall said. “We’re probably going to have to design additional facilities and put in surge tanks to be able to absorb large pressure surges.”

Such tanks, designed to withstand sudden surges of water, could cost a dollar per gallon of storage capacity. But the district might also consider building an extra pipeline or cheaper blowout valves that could vent future surges into the Arroyo Simi, Kendall said.

A Calleguas contractor is hurriedly building a 20-foot section of pipe to replace the ruptured 5 1/2-foot-diameter water main, which could take a week or two to complete, Kendall said.

Calleguas’ insurance adjuster is already consulting with one couple who said the flooding damaged their apartment, and with a man whose corn crop will have to be replanted, Kendall said.

Meanwhile, interagency finger pointing has begun, with Calleguas partly blaming an electrical power failure for the pipe rupture, and Southern California Edison officials declaring they had nothing to do with it.

Calleguas staff concluded that a drop in power supplied by Edison, coupled with a closed water-main valve at Madera Road, caused the break.

Kendall said Edison employees told his engineers Saturday that the power was cut off between 4:06 and 4:11 p.m. so that Edison could trim a tree that was brushing a power line.

And pump monitoring machinery showed a sudden loss of pressure around that time--usually a clear sign of power failure, he said.

But Edison spokesman Rudy Gonzales said Monday that the limited blackout was postponed from its scheduled 4 p.m. start time because Edison workers had gone to their Thousand Oaks equipment yard to retrieve a tree-trimming tool. They could not get back into the Simi Valley neighborhood because the streets were already flooded, he said.

It was 5:39 p.m. by the time the Edison workers cut the power to trim the tree, Gonzales said. Edison switched the power on again at 6:11 p.m., he said.

In any case, Kendall said, power failure stopped four water pumps that ordinarily suck water into branch lines feeding neighborhoods along the main line and uphill from it. The pump stoppage allowed all the water to flow suddenly down out of the branch lines and back into the main at the rate of 20,000 gallons per minute, creating a pipeline surge that engineers call a “water hammer.”

This massive wave barreled westward toward a valve that had been shut off to allow repairs farther down the line in Wood Ranch, where a contractor had cracked the main.

When the tons of water ran into the closed valve, they smashed through the steel-jacketed, 4-inch-thick concrete pipe and burst into the street, he said.