Highway 50 Set to Reopen: But Slides in Pinole and Elsewhere Will Keep Crews Busy in a Drill They Know Well.

By Tony Bizjak and M.S. Enkoji, The Sacramento Bee, Calif.

May 10–Highway 50 in the Sierra is expected to fully reopen later today, officials said, three days after a rain-saturated hillside near Kyburz collapsed onto a 120-foot section of the roadway.

Meanwhile, at the scene of another landslide on Interstate 80 in Pinole, state officials say they will close most westbound freeway lanes at night for the next two weeks.

During that time, workers will lay the foundations of a retaining wall to protect drivers until the hillside above the freeway can be stabilized.

It’s work state road crews say they know well.

In California, where highways are cut through steep canyons and along rocky coastal cliffs, shoring up slumping embankments and restabilizing roads has for years been a never-ending Sisyphean task.

The wet spring has made this an especially treacherous year, and officials warn there could be more slides on the way.

Sunday’s midnight slide on Highway 50 is the second this year on that road, but it is not considered a significant ongoing risk.

“We think we are OK,” said Roy Bibbens, chief of geotechnical designs for the state Department of Transportation in the area.

“There is no evidence it is symptomatic of a bigger (problem) going on.”

Bibbens said Caltrans will probably shave the slope above the road a bit, and take some weight off the top of the hill.

Officials also will consider placing perforated plastic pipes in the hillside as drains, but even that may not be necessary if it is determined that the hillside is draining well enough on its own.

Caltrans road workers, nevertheless, are keeping a closer watch on the slopes above the highway.

This is the area where massive slides during rainy years in 1997 and 1983 closed the road for months.

The 1983 slide was so huge it temporarily blocked the American River.

Ironically, state officials say, highway deaths and injuries caused by landslides are so rare that the state’s system of collecting accident data has no category for such fatalities, said Mike Marando of the state Office of Traffic Safety.

But it does happen. In December 1992, a 16-year-old boy was killed while he was driving on Old Priest Grade, a narrow canyon road in Tuolumne County. Driving rain on a canyon slope left bare by a wildfire sent a wall of mud and debris spilling onto the roadway, washing the boy and his car over the edge.

State engineers say that while they have a lot of experience with landslides and know where high-risk areas are, they cannot predict a slide.

The section of Highway 50 near Kyburz “undoubtedly will have slides in the future,” said Caltrans’ Bibbens. “You (just) don’t know where.”

U.S. Geological Survey officials have one monitoring device in place along Highway 50 – at the site of the 1997 Mill Creek landslide – but that device is not used to predict a slide.

The monitor, which tracks earth movement, is not intended as an early-warning system, but serves as a tool to understand the causes and nature of landslides, said Mark Reid, a research hydrologist with the U.S. Geological Survey in Menlo Park.

“To be able to see precursors of that would be helpful,” Reid said.

Even when a hillside slumps, officials say they can’t be certain if the problem is minor or a sign that a major slide is about to happen.

In Pinole, state officials were making plans to repair a smaller slide that was pushing out a retaining wall when the bigger slide hit on April 30.

There were no reports of injuries, Caltrans spokeswoman Lauren Wonder said.

The nature of landslides defies any simple solution, said Richard Pike, a research geologist with the USGS in Menlo Park.

That’s why, despite control measures and improved engineering, landslides still occur, he said. Something as small as leaves and debris blocking a culvert can alter the dynamics of soil or topography.

“It becomes unpredictable what happens,” Pike said. “We should thank the engineers for getting as much done as they can.”

Often the greatest harm from a landslide is economic, officials said.

In El Dorado County, where a section of Mosquito Road above Placerville collapsed in December and won’t be repaired until May or June, residents of some small communities find themselves nearly isolated.

“We’re used to (slides closing roads), but it still causes us angst because we want to open these closures as quickly as we can so communities can get back to normal,” said Kris Payne, a supervising civil engineer for the county. “Residents have been vocal.”

Landslide repair costs can be substantial.

The project on Mosquito Road will cost $2 million, most of it federal and state emergency funds, Payne said.

Landslides annually in the United States cause about $3.5 billion in damage, according to the USGS.

In one case this year, repeated landslides have forced a dramatic solution. Caltrans will build two 3/4-mile tunnels to divert Highway 1 through a mountain away from the troublesome Devil’s Slide area south of Pacifica. The road has been plagued by slides, and rebuilt numerous times, since it opened in 1937.

“Essentially, the whole mountain is sliding into the ocean,” Caltrans spokesman John Cunliffe said.

The Devil’s Slide section of Highway 1 had to be closed again last month after more sliding caused the road to sink 3 feet, and may remain closed for several months.

The tunnels, scheduled for completion in 2011, represent another strategy for dealing with landslides, Cunliffe said. “Avoidance!”

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Copyright (c) 2006, The Sacramento Bee, Calif.

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