Caltrans to drill in PCH landslide zone next week; lane closure ahead Play

Landslides that threaten to fall onto PCH near Sunset Boulevard are going to get some heavy-duty Caltrans attention next week — and it means a lane closure.

Caltrans will set up drilling rigs along Pacific Coast Highway near the Getty Villa Museum on Monday. They will be doing geotechnical work at two landslides that threaten the road. The landslides — called the Tramonto and Castellamare incidents — are between Sunset Boulevard and the Getty Museum entrance.

A state engineer told KBUU last spring it will cost well above $1 billion just for the engineering studies about how to stabilize the complicated landslides. It may take billions to protect the road from Malibu to Santa Monica just at this one spot.

State Transportation Commission members were told as many as nine new concrete and steel retaining walls will have to be installed up the cliff and bluff from collapsing onto PCH.

If there is a collapse, it would be an unthinkable disaster. PCH could be closed for months.

In 1959, a similar landslide caused PCH to be relocated out towards the ocean, on top of a new oceanfront roadbed out in the ocean southeast of Temescal Canyon. Malibu's water and gas supply pipeline runs under PCH.

The road was built in 1922. The land started sliding in 1932.

Caltrans blames landowners up the hill, including the City of Los Angeles. Caltrans says it has been unable to repair PCH because the city of L.A. has failed to stabilize the hillside above it. Caltrans owns the highway, but the City of Los Angeles and private parties own the lots up the steep hill.

Earth movement accelerated last year after the Palisades Fire plowed though and then heavy winter rains hit the area. The wreckage of a half dozen or so collapsed houses, collapsed over the years, continues to creep towards the highway and ocean.

Caltrans crews are working at the bottom of the landslide this summer, trying to replace small concrete retaining walls that gave out after the fire. But that work is a mere bandaid compared to what is ahead.

The geophysical work — the exploratory drilling — will start Monday along westbound PCH. Caltrans is warning that one lane heading towards Malibu will be closed just past Sunset, at least during daytime hours, possibly at night as well. All week, next week.

More than 47,000 cars per day use PCH to and from Malibu below the landslide. One of the five lanes on PCH has been closed for five years now and has been covered with slowly moving dirt and mud.

The new project includes drilling rock bores. Into those holes, engineers will lower geotechnical monitoring instruments to give engineers and geologists a way to study the movement of the earth and groundwater. Monitoring will be conducted at regular intervals for the next year, and the instruments will be removed by December 2027. Then the boreholes will be backfilled with cement grout.

The engineers need baseline data to identify possible ways to strengthen the slope and guide future safety improvements to protect PCH. But the state has been doing surveys of the landslide since 2010.

The permanent solution may mean building major retaining walls on private property to prevent that land from falling onto the only major road out of Malibu.

The cost? One Caltrans engineer told KBUU last spring it will take $1 billion just to do the engineering studies at the landslides. Building walls to lock down the 95-year-old landslides — uncalculated billions.

And don't forget: just one quarter of a mile to the west, PCH is built on top of a sand ridge that is washing away.