Caltrans maintenance superintendent Victor Althaus said he has learned a thing or two about landslides in his 29 years of clearing California highways.
But one sliding bluff in Big Rock Mesa has him stumped. "This slide is entirely different from any I've ever worked on," he said, gazing at the craggy, 200-foot cliff that geologists say could fail at any moment. "This one worries me."
The bluff was weakened by the massive landslide that hit Big Rock Mesa in Malibu in September, 1983. And now, he said, "the cracks on top have been opening up all week" and there have been no small, pressure-relieving slides from the face of the bluff. "That means it could go all at once," Althaus said.
He and his state Department of Transportation crew have set up a command post across Pacific Coast Highway from the bluff. They wait 24 hours a day, trucks and snowplows ready in case a slide occurs. They could be waiting for days or months.
Their vigil started after a small slide Feb. 17 prompted geologists to examine the bluff. They found dramatic widening of previously mapped cracks about 150 feet above the highway and warned that the bluff could fail in the near future, but they could not say exactly when or how.
In the worst case, they said, as much as 60,000 cubic yards of rock weighing 90,000 tons (as much as two battleships) could fall at once, closing the highway for at least two weeks and endangering motorists and residents of 16 oceanfront town houses across the highway.
Or the bluff could come down in bits and pieces, sending boulders crashing onto the highway or into the houses.
When asked to predict when the bluff would fail, geologist Dennis Evans, a consultant for the County of Los Angeles, responded, "Soon--days or weeks."
Geologist Eugene Don Michael, who works with Evans, said dry weather this week might delay the movement, while heavy rainfall could produce a major slide. He said a series of minor failures may be more likely than a "catastrophic" slide.
Too Big to Predict
But the consequences of a major slide make presuming that one will occur the accepted course of action for the county. "We have a pretty good idea there will be continuous failure along the bluff over the next year," county geologist Arthur G. Keene said. It is just that "the magnitude of the problem is too great to be able to predict."
Warnings of an imminent slide prompted officials to monitor the bluff. A sheriff's helicopter started to patrol the area to check the system of cracks. California Highway Patrol officers have been leading columns of motorists gingerly past the slide area.
At emergency meetings, officials discussed closing the highway before another slide. "We had three meetings on it," Althaus said. "It's been decided not to close it. Nothing is happening off the face of the slide where it would be a danger to the traveling public."
The county last week ordered 30 town-house residents to evacuate, but most of them planned to appeal the order.
A few decided to leave, including Ron Rainey, who packed his belongings into a van Saturday while his neighbors calmly went about their business: A man washed his Cadillac in his driveway; two girls played in front of their house.
'Can't Afford' to Move
Resident Carrie Calderone said the worst that could happen would be a boulder crashing through her living room. "We're not going anywhere. They'd have to airlift me out of here. We can't afford to move out."
The residents have been meeting to try to determine what to do. Many said they are angry and feel that government agencies are not doing enough to help them. So far, they have failed to get Caltrans to build a concrete barrier along the highway median and to install sensors in the cliff and a siren to warn them if a slide occurs.
The absence of a warning system finally persuaded Rainey, a resident for seven years, to leave. He slept through the Feb. 17 slide and was concerned that he might sleep through a bluff failure. He said that he has been worried about the situation since the 1983 slide. "Today is the first step of getting it off my mind--by leaving. But I can't say I won't come back. I like the way of life."
In the Feb. 17 slide, about 500 cubic yards of rock fell onto the highway, closing it for 12 hours. The next day, Michael and another geologist, Richard Lownes, climbed to the top of the bluff and noticed that the cracks, which ran for more than 100 feet, had widened since they had mapped them several months ago.
'More and Bigger' Coming
Geologist Evans then wrote to county officials, who had hired his firm to work in the Big Rock area after the 1983 slide. "We said you've got more coming and what will be coming will be bigger," he said. "The (landslide) that happened (Feb. 17) is a small part of a larger failure due in the very near future."
The warnings prompted the county to post evacuation notices on town-house doors.