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Part of Palos Verdes Drive South damaged by landslide will close temporarily for repairs

RANCHO PALOS VERDES, CALIF. - MAR. 3, 2023. Sewage pipes run above ground along Palos Verdes Drive South at Portuguese Bend, where a stretch of roadway is uneven and erratic because of land movement on the coastline. (Luis Sinco / Los Angeles Times)
Land movement could temporarily close a stretch of Palos Verdes Drive South in Rancho Palos Verdes, officials said. (Luis Sinco / Los Angeles Times)

For the record:
8:48 p.m. March 22, 2024: An earlier version of this story incorrectly characterized a grant from the Federal Emergency Management Agency. The grant amount is $23.3 million, not $33 million, and a portion of that money will not be used to pay for emergency hydraugers.

Rancho Palos Verdes officials are preparing to close a section of Palos Verdes Drive South for repairs after the two-lane roadway suffered damage from an accelerating landslide complex that continues to wreak havoc on the coastal city.

Palos Verdes Drive South is a major two-lane road that spans a roughly 5-mile stretch of the California coast along which 15,000 vehicles pass every day, officials said. At the moment, visible cracks in the asphalt can be seen where the road has fallen into disrepair due to shifting sediment.

"We're doing short-term repairs right now," said City Manager Ara Mihranian. But an "imminent road closure" will take place over the next month to address a "severe drop" in the roadway that locals call "the ski jump," he said.

Officials are recommending that this section of roadway be flatted out to some extent, Mihranian said. The section runs between Narcissa and Peppertree drives. Details of the planned road closure and its repairs will be presented to the City Council on April 2.

The Portuguese Bend Landslide Complex that underlies much of the city has been slowly shifting for decades, but over the last few months, the movement has increased alarmingly. Heavy rains over the last two winters have contributed to the problem.

The land in some areas is descending toward the Pacific Ocean at a rate of about half an inch a day, according to Michael Phipps, a geologist working for the city. The landslide has already damaged some homes and recently forced the closure of the historic Wayfarers Chapel, a popular wedding site perched on a hillside overlooking the ocean.

In a recent report presented to the City Council, Phipps found that the current pace is three or four times the rate recorded in 2023.

A particular type of soil makes the Portuguese Bend especially vulnerable to landslides, Phipps said. Millions of years ago a volcanic eruption deposited ash that became bentonite clay. "When [bentonite] gets wet, it becomes even weaker," said Phipps. "So we've really got the worst of all situations."

The city is using underground pumps called dewatering wells to drain the water table to help stabilize the land, officials said. The city has also halted development in certain affected areas. So far, Mihranian said, only two damaged homes have been marked as uninhabitable.

The Federal Emergency Management Agency has selected Rancho Palos Verdes for a $23.3- million grant to help with remediation efforts.

"There's other discussions about trying to intercept the water that's coming down to natural canyons up into the head of the landslide," Phipps said. But all the city's measures will at best only slow the landslide to imperceptible movement, not completely stop it, he said.

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This story originally appeared in Los Angeles Times.