MONTARA — Caltrans engineer Dave Pang stands amongst great piles of deeply rutted dirt, heaps of rock and hauling trucks in the belly of the Devil's Slide tunnel construction site next to Highway 1. As machines deposit rubble scraped away from the hillside, followed by a dirt compactor and a water-spraying truck, Pang describes phase one of the project that has been more than 40 years in the offing.

"It's like making mud pies," he says.

It doesn't look like much now, but this horseshoe-shaped gully will eventually hold all the debris from two tunnels that will be cut through Montara Mountain, bypassing a treacherous, landslide-prone portion of highway known as Devil's Slide.

Phase one — the mud-pie phase — began in late April and is due to be completed by next spring. Workers will remove part of the mountain to widen the road into an intersection where cars can safely pass into and out of the tunnel.

They have already constructed anaccess road next to Highway 1 to minimize truck traffic; eventually, the access road will become part of the highway's new alignment.

The project, which starts north of Gray Whale Cove and ends just south of Shamrock Ranch in Pacifica, will be built in three phases. The south rock cut will be completed by spring. Then Caltrans will begin building a 1,000-foot bridge over a valley on the other side of the mountain, to reconnect tunnel traffic to the existing highway road.


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In the third phase, workers will blast two 4,000-foot-long, 30-foot-wide single-lane tunnels through the mountain, trucking all the debris to the south cut site. If all goes well, the tunnels will be completed by 2010.

Precarious roadway

The stretch of highway between Pacifica and Half Moon Bay is one of the most famously scenic — and precarious — coastside drives in the state. Every day, 9,000 cars pick their way along the hairpin turns of the two-lane road, parts of which offer no protection from a cliffside tumble into the ocean below.

Devil's Slide, a stretch of the road no more than 600 feet long, is plagued by landslides. Over the years, water-drainage problems have caused the road to sink as the earth underneath crumbles away — fully 47 feet from when it was first built.

It has been closed for repair seven times between 1937 and 1995. In the latter year, the road sank 8 feet and cut commuters off for six months.

The closures prompted Coastsiders to call for a solution, but it took them 45 years to agree on one. Caltrans' solution — a concrete highway bypass that would cut through the natural landscape and climb the steep ridge next to Montara Mountain — did not sit well with environmentalists. From 1960 to 1995, Caltrans backed several versions of the bypass plan, and environmental groups did everything they could to stop them. Worried that a large highway would destroy wetland habitat and spur development along the Coast, they brought lawsuits against Caltrans in 1972 and 1983 that effectively shut down the project.

Tunnel solution

The Committee for Green Foothills was one local group that fought the bypass.

One of its leaders, Lennie Roberts, said that she had feared the area would be transformed into another Daly City.

"If you build it, they will come. That always happens with roads," she said. Roberts' group favored an alternative scheme to fix the existing road by pushing it back into the hillside and dumping the excess fill into the ocean, called the Marine Disposal Alternative. But in 1995, they started pushing the idea of a tunnel instead.

"We thought it was the most elegant solution," Roberts said. "It would be safe, and it would preserve the whole area."

Caltrans, however, continued to back the bypass, infuriating the green groups.

Caltrans spokesman Jeff Weiss remembers attending a community meeting about Devil's Slide in 1995.

"You could feel the heat coming off the audience. It was a tough time for [us—," Weiss said. "Caltrans got portrayed as the agency that wanted to build the bypass, but we just wanted to build the project that had guaranteed funding," he said.

Funding for the tunnel project finally became available when county voters approved Measure T in 1996, favoring a tunnel over any other alternative. 

"Caltrans was an enthusiastic supporter of the tunnel after that," Roberts said. At a party following the Devil's Slide groundbreaking ceremony in May 2005, environmentalists and Caltrans engineers stood in a circle and sang "Kumbaya."

Wetland concerns

But the project's delays didn't end with the groundbreaking. No sooner had construction workers reached the south rock cut site in April when they found peregrine falcons, a threatened species, nesting in the cliffside. They had to shut off their machines and wait for the eggs to hatch and the birds to abandon their nests.

Then workers discovered endangered red-legged frog tadpoles swimming around a wetland adjacent to the south cut site.

"We weren't anticipating the frogs. When they started showing up, that delayed our operations," said Pang.

There are red-legged frogs, and frog habitat, throughout the Devil's Slide project area. Dirt-laden trucks rumble past a protected habitat right in the middle of the south cut site. A colony of frogs lives along the edges of a man-made pond at Shamrock Ranch, directly below the future location of the north portal bridge.

These sites, and several others, have been fenced off to protect the frogs from construction debris. Before approving the tunnel project, the California Coastal Commission, the Department of Fish and Game and other agencies required Caltrans to build or restore a number of wetlands around the perimeter of the construction area that will act as future homes for the frogs. The discovery of a single frog can halt construction for days, during which a designated handler comes to transfer it to a permanent wetland.

Back to nature

The tunnel design has another advantage: as soon as it is built, the old Devil's Slide road will become part of the Golden Gate National Recreation Area, and will be transformed into a private trail for hikers and mountain bikers.

Beyond that, its future is uncertain.

"The road will always have the same problem," said Weiss. "It may have to be closed eventually, because there won't be any roadbed left."

Roberts acknowledged that the highway pass would eventually erode. She said that an additional coastal trail will be constructed inland from the existing road, for bikers to travel over the mountain at their own pace. It will connect to the trail system that crisscrosses the San Mateo coastside.

Bikers and pedestrians are also welcome to use the tunnels, which are designed to accommodate them. A powerful ventilation system will ensure that there is clean air to breathe.

"They could keep the (highway road) open if it only slumps a foot or two at a time, but it won't be there forever," said Roberts. "It's a fact of nature. That's why we built something to replace it."

Staff writer Julia Scott covers the North County and the Coast. She can be reached at 348-4340 or by e-mail at jscott@sanmateocountytimes.com.