Caltrans Planning to Scrape Away Malibu Hillside Before It Slides : Transportation: Officials OK $2-million venture to prevent further closures of Pacific Coast Highway.

Worried by mudslides that have closed Pacific Coast Highway six times in the last month, state transportation officials have approved a $2-million project to remove nearly 19,000 dump-truck loads of earth from one active slide and are studying ways to deal with a second.

The slide scheduled for excavation, just east of Tuna Canyon in Malibu, sent 100,000 cubic yards of mud and rock toward the highway Jan. 27. Geologists surveyed the slide over several days and have concluded that the hillside is enough of a threat to require the estimated 50-day excavation project, which is scheduled to begin next week.

A second slide, also in Malibu, slammed onto the highway Monday between Big Rock Drive and Las Flores Canyon, forcing temporary closure of the highway while Caltrans workers built a fence to catch boulders that continued to tumble toward the road Monday night.

“What happens is the hillsides get completely saturated and the rainwater gets to a point where it reaches a layer of clay,” said David Servaes, regional manager for Caltrans. “It greases the hillside up, and down it comes.”

While debris from both slides has been cleared, traffic has been restricted to one lane at the Tuna Canyon site and to two lanes at the slide between Las Flores Canyon and Big Rock Drive. The rerouting, which so far has not caused major traffic tie-ups, will continue until Caltrans workers finish working to stabilize the hillsides.

The work at the Tuna Canyon landslide, which runs along an earthquake fault, will involve removal of active portions of the slide amounting to 150,000 cubic yards of earth, or about 18,750 full dump trucks. Before starting work, Caltrans is seeking permission from owners of the property, which is undeveloped.

“We are going to remove earth back to where the mountainside is stable,” said Jim Hansen, Caltrans superintendent for the West Los Angeles and Malibu areas. Such projects are unusual for Caltrans, Hansen said, because they meet with resistance from homeowners or environmental groups.

After each of the six slides that have closed Pacific Coast Highway in the last 30 days, Caltrans has methodically scooped up, scraped away and dumped the debris. Caltrans officials say the agency felt that the time had come for more drastic action.

“We can’t just have (closure of Pacific Coast Highway) happening every other day,” said Russell Snyder, a Caltrans spokesman. “The nature of these slides is if you scoop and move them enough you destabilize them and more comes down. It’s sort of like trying to build a mountain out of sand.”

Caltrans has not yet decided how to shore up the slide between Las Flores Canyon Road and Big Rock Drive, across from Moonshadows restaurant. Among the solutions being considered is to install concrete rails or a retaining wall along Pacific Coast Highway at the base of the mountain.

A massive retaining wall was built along the highway just east of Big Rock Drive in the late 1980s. That wall has proved its worth several times, including one recent instance when it prevented a boulder from tumbling across the road into homes on the beachside of the highway.

Caltrans officials say they have not ruled out excavating portions of the slide. Unlike the situation at Tuna Canyon, the option would pose further problems because it would mean buying out homeowners in the Big Rock neighborhood above.

Whatever the solution, the officials said, it will be put the ultimate test. Hansen said: “It’s Mother Nature’s grand design to make those mountainsides come down.”