OLANCHA, Calif. — For more than 100 years, the Los Angeles Aqueduct has endured earthquakes, flash floods and dozens of bomb attacks as it wends and weaves through the canyons and deserts of the eastern Sierra Nevada.

But earlier this month, record storms accomplished the unthinkable when floodwaters undermined a 120-foot-long section of aqueduct in Owens Valley, causing its concrete walls to crumble.

“We’ve lost the aqueduct!” a Los Angeles Department of Water and Power inspector told his superiors by cellphone. As he spoke, chocolate-colored runoff and debris undercut the aqueduct just west of Highway 395 and the community of Olancha.

It was the first time in history that the 200-mile aqueduct had been breached by extreme weather, threatening water deliveries to 4 million ratepayers in Los Angeles.

It was also an indication of just how difficult it would be to defend the waterway against torrential runoff from a winter of near record snowpack. For weeks, DWP crews had been using heavy equipment and other means to control the anticipated spring runoff, but even longtime aqueduct workers were shocked by the suddenness of the break.

Among the first to arrive on the scene that March 10 morning was a team led by Ben Butler, senior aqueduct and reservoir keeper.

“Floodwater was coming down hard, creating a large, deep pool that pressed against the aqueduct’s walls,” he recalled. “We drove in as far as we could, then put on waders and headed for the breach.”

For the next five days, rescuing L.A.’s water lifeline became the DWP’s highest priority as all hell broke loose in Owens Valley.

Traditionally dry rocky arroyos and ditches were overrunning their banks; irrigation diversions and culverts were buried in mud the consistency of peanut butter. At Pleasant Valley Dam, about 8 miles north of the city of Bishop, stormwater laden with sediment was surging over its spillway and into the Owens River at a rate of 1,000 cubic feet per second.

“We were already in an all-hands-on-deck mode when we learned that the aqueduct was in serious trouble,” said Adam Perez, deputy manager of aqueduct operations. “By 3 p.m. that afternoon, we came up with a game plan to prevent further deterioration, patch the breach and maintain service.”

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