California is building a $400 million shield to protect Highway 140, Yosemite’s most dangerous highway.
Over the summer, the agency began building a 675-foot rock shed over the highway, meant to restore the vulnerable segment so it can open in five years. When finished, the vaulted concrete arch will offer vehicles safe passage through a crumbling mountainside. Its big, sturdy piers will feel at once man-made and strangely organic, a medieval fortress that evokes the granite bulk of El Capitan.
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“There’s not anything like this in the world,” said Corey Casey, Caltrans’ project manager for the shed. He described the new $400 million infrastructure as a colossal “tunnel with windows,” comprising 6,000 ton segments of concrete and rebar that crews have to skillfully fit around a curve in the road. Designed to last a hundred years, the structure could tolerate just about any catastrophic shift in earth and weather, including being completely entombed “to a depth of 40 feet by a rock avalanche in seconds,” he said.
“Anything larger than this,” he added, “will simply go over the shed and into the river.”
Yosemite park employees and residents of the surrounding towns have watched with fascination as Caltrans workers haul materials to the site, batching their own cement at the side of the road. Many share Casey’s enthusiasm. Beneath it some also feel a twinge of anxiety. At its inception, the highway was viewed as a human conquest of the rugged landscape. Now with climate change and intensifying winter storms, the canyon seems to be reasserting its domain. In the coming years, the slopes might only become more treacherous. Caltrans will spend nearly half a billion dollars shielding traffic from the Ferguson Slide. But what about the rest of the highway?
“We have an El Niño coming,” said Tom DeVries, whose house in Mariposa is due south of the Ferguson Slide, with a lot of rough terrain in between. DeVries considers this section of 140 to be Yosemite’s version of Devil’s Slide, the deadly coastal bluff that cursed Highway 1 for decades. Even after Caltrans constructed the Tom Lantos Tunnels in 2013, people driving in that area were prone to crashes. The Merced Canyon, DeVries said, is every bit as humbling.
“I’m sure by any modern environmental sensibility (Highway 140) is an aggressive interference into a beautiful canyon” carved out by tectonic forces and water flow, DeVries said. “And probably if we were going to build it now, we would build somewhere else.”
Still, he offered, “this is California. We’re always going to build things where they shouldn’t be built. Our whole existence is a wishful dream that the worst won’t happen, or that we’ve engineered our way out of it.”
When Highway 140 opened to the public a hundred years ago, local politicians, park service workers and state highway commissioners held a dedication ceremony at the Clark Ranch, just outside Yosemite Valley. They commemorated prisoners from San Quentin and Folsom correctional facilities who had built much of what was then called the “Yosemite All-Year Road,” by hollowing out rock from canyon walls between Briceberg and El Portal. Prison wardens and members of automobile clubs also attended the festivities, which culminated with a motorcade over the new highway, according to a July 1926 issue of the California Highways bulletin.
Motorists who drove in the procession promptly suffered more than 300 flat tires, as documented in a Historic American Engineering Record for the National Park Service. Closer inspection revealed that the road’s gravel pavement had been poached from an old mine dump with railroad spikes and metal debris.
Despite these early bumps, the highway transformed access to a national park, carrying millions of visitors each year toward the waterfalls and towering sequoia groves. Towns that grew up along 140 became tourist destinations in their own right. Gold Rush storefronts in Mariposa house art galleries, souvenir shops and Mexican restaurants. There are taprooms where any backpacker can mingle with mountain dwellers who know how to weld or fix a car engine. In El Portal, travelers can “glamp” in tent cabins or bed-and-breakfasts. The number of hotel rooms and short-term vacation rentals dwarfs the permanent housing stock.
“Everywhere along the highway are these amazing scenes and historical markers,” said Kim Lawson, director of communications and content for the Yosemite Mariposa County Tourism Bureau. “Even before you get to downtown Mariposa, you can stop at the fruit barn or the winery in Merced. It really becomes a road trip experience.” She noted that tourism is now the No. 1 industry in Mariposa County, funding many of the public services.
For people who live along this corridor, 140 is as much a workhorse road as it is a scenic approach. It’s the most logical way to get to the park from Mariposa, Midpines or El Portal, but it’s always at the mercy of the elements. Right now people routinely have to wait 5-10 minutes at the light before crossing the temporary bridges, an inconvenience that many will be glad to give up when Caltrans completes the project.
Yet some worry that even if Caltrans girds that isolated section of 140, slides will continue to threaten vehicles on other parts of the highway. And residents are particularly preoccupied with what will happen this winter, when a strong El Niño is expected to bring pounding rain that could cause the mountain to give way. Drivers who cross the quarter-mile of bypass road and bridges may return to the main highway only to find rocks in their path.
It happened a couple years ago, said Art Baggett, a former Mariposa County supervisor who lives in El Portal. He recalled a boulder “the size of a truck” tumbling down and blocking the road near Cedar Lodge.
“They had to blast the rock in half to get it off,” Baggett said. “Took about three days.”
Last year workers had to contend with another hulking mass that fell about 1,500 feet from the job site, Casey said.
“Similar to Big Sur on Highway 1, we just have lots of splitting rock and slides in this area,” he explained. But whereas most slides can be cleared and managed within a few days, Ferguson demanded a far more ambitious fix. Immense and thousands of years old, it’s one of the few places where a mountainside could cascade onto a highway.
“When you see it,” Baggett said, “you’ll appreciate it.”
If you are headed to Yosemite by car or bus from Merced County, the slide serves as a point of drama in an already breathtaking drive. Up steep hillsides tangled with valley oak trees, past driveways that lead up to red barns or horse pastures, a giant cross with the words “Jesus Saves,” a cluster of dilapidated trailers and the occasional roadside diner. Through mid-town Mariposa, where all the buildings are decked in bunting and a weathered mining wagon sits outside the museum. And from there, the road winds through patches of chaparral and scabbed rock. Orange signs warning of “slide areas” precede sheer cliffs covered in netting.
“I really only get nervous when it’s raining,” said Nicole Rocha, a bus driver for the Yosemite Area Regional Transit System. Darkness had fully engulfed the highway when she pulled up to the bypass at 8 p.m. on a recent Saturday night and sat for 10 minutes in a line of cars. The October air was warm and crisp, with a small chance of rain in the forecast the next day. Yosemite weather would become more unpredictable in the coming weeks, a thought that made Rocha suck in breath.
“An inch of rain can put rocks on that road,” she said.
Baggett has glimpsed signs of progress on his regular commute down 140, including on a turnout past Cedar Lodge that Caltrans has turned into a “mini concrete plant,” with six trucks “permanently living” in the canyon.
“They appear to restock at 5 or 6 in the mornings so they can take sand and gravel up,” he said. “So they’ll probably have the first footings before winter.”
The excitement caught on when Casey appeared last month at a celebration for the centennial of Highway 140, which began with a parade of vintage cars through downtown Mariposa. Regional leaders planted a redbud tree outside the town’s museum to help propagate a native plant that explodes in magenta blossoms each spring. Casey provided an update on the rock-shed project and displayed renderings of the protective shelter that would be constructed by 2031.
Attendees were rapt, said Lawson of the tourism bureau. The shed heralded a new era for 140, promising that engineers could once again keep the canyon’s rockfalls at bay. Nature would test that optimism the very first winter.
