After Big Sur slide, mountain of issues ahead
The massive landslide that swallowed a stretch of Highway 1 on the Big Sur coast over the weekend was still spewing rock and dirt down a remote mountainside Thursday, and state officials say it will probably be next year before they get the wall of mud out of the way.
The continued movement of the quarter-milelong slide near the Monterey County community of Gorda has kept Caltrans engineers from taking stock of the situation and figuring out when — and if — the section of road that serves as the southern gateway to Big Sur can
be repaired and re-opened.
Independent experts say the solution may require constructing a sprawling bridge over the troublesome spot or a tunnel deep in the ground beneath it, a prospect that could take years and cost the state hundreds of millions of dollars.
“This one is quite a hurdle,” said Robb Moss, a professor of civil engineering at Cal Poly San Luis Obispo. “It exceeds a lot of the usual fixes.”
Saturday’s slide in the sparsely populated Mud Creek area is believed to have been caused by groundwater that has continued to percolate up and out of the mountains, months after the winter’s near-record rains. As the steep cliffs above the ocean became saturated, they collapsed under their own weight across the highway and into the ocean — where a peninsula of rock and mud has emerged.
Moss said the best-case scenario for getting the road open would be putting in a stretch of asphalt, at least temporarily, on top of the slide once the area dries out come summer. That option, though, is contingent on soil tests to determine whether the mountainside is secure.
“Hopefully, this season you can get in a couple of lanes,” he said. “But if it’s not remaining stable in the long term, you have to look at a more expensive fix.”
Stretches of Highway 1 have been washed out in the past, and a number of techniques have been used afterward. The simplest has been building a new road, which can be accomplished only when the ground, or at least the underlying rock, is strong enough to anchor new pavement. To guard against future landslides, nets, retaining walls or rock sheds, which offer overhead protection, have been installed.
Pricier fixes include viaducts that bypass the problem areas as well as tunneling into and below a landslide. Many have called for such big-ticket repairs at Mud Creek for decades and Moss and others say it may finally be time.
Some are likening the situation to Devil’s Slide in San Mateo County, where Caltrans went for years trying to clear the highway of wintertime debris before turning to two 4,200-feet long tunnels at a cost of more than $400 million.
“Long term, it may be the solution,” Moss said.
Caltrans officials won’t have a repair plan until they’re able to drill beneath the slide and evaluate the ground below. But they say they’re certain they’ll find a way — eventually — to reopen the area for travel.
“The Big Sur highway is a worldwide destination for people,” said Caltrans spokesman Jim Shivers. “We won’t walk away from Big Sur no more than we walk away from highways that run through Yosemite or Lake Tahoe or any area that could be impacted by weather.”
The transportation agency has racked up what may be a record backlog of roadwork because of storm damage across California.
Even before Saturday’s slide, an estimated $1 billion was needed for state highways fixes, Caltrans officials said, more than double the $383 million average annual repair bill from the previous five years. The high price is the result of an historically wet year that has left roads washed out from the Santa Cruz Mountains to the Sierra.
But nowhere has the damage been more severe than Big Sur. A condemned bridge over Pfeiffer Canyon, which has prompted a second closure of Highway 1 north of the recent slide, is expected to cost $26.5 million to replace. Several other landslides along the highway around Big Sur will cost millions more to clear.
At Mud Creek, the millionplus tons of debris that fell from the mountain is actually the result of four previous slides, each earning names from the locals over the years. Last weekend, they came together as one in an avalanche unlike any since the early ’80s.
Highway 1 in the area was closed at the time because of previous slides, and no one was injured.
“It’s some of the steepest, highest terrain closest to the ocean on the West Coast,” said Gary Griggs, a professor of earth sciences at UC Santa Cruz. “You can’t prevent these things from happening. The scale is too big. It’s just what we’ve got to live with here. It’s what Mother Nature gave us.”