MONTARA -- Call it an exorcism.
Seventy-six years after building an extension of Highway 1 at Devils Slide, Caltrans is ready to shut down the landslide-prone coastal road forever and open a pair of state-of-the-art tunnels through a mountainside behind the precarious cliffs.
The ceremonial opening Monday morning of the Tom Lantos Tunnels will put an end to decades of peril and frustration for motorists, and it closes the book on a fierce political battle to protect the rural character of the central and southern San Mateo County coast.
Caltrans will hold an invitation-only celebration with politicians and supporters at the south portal of the $439 million tunnels, the first in California since the 1964 completion of the third bore of the Caldecott Tunnel in the East Bay. The 4,200-foot tunnels will open to regular traffic that night or Tuesday morning.
That Caltrans is christening a tunnel, and not a 4.5-mile freeway bypass to the east, is the result of a remarkable grass-roots coalition of environmentalists and Coastside residents who rose up to oppose the agency's plans for an inland route. The four-lane bypass would have cut McNee Ranch State Park in half and, activists feared, opened the coast to more aggressive development.
"It feels like an extraordinary victory," said Moss Beach resident Zoe Kersteen-Tucker, a leader of the residents group. "So many people have worked for so many years to see this project come to completion."
The tunnels promise real improvement in the lives of people who reside and work on the coast. The landslides that plagued the road since it opened, including closures for several months in 1995 and 2006, turned their commutes into nightmares and threatened their livelihoods.
"This project will finally end the lengthy closures of Highway 1 that isolated communities, worsened commutes and hurt tourism along the coast," said Sen. Barbara Boxer, who along with Rep. Tom Lantos obtained key financing for the federally funded project. "And it permanently solves the problem in a way that protects the environment and the beauty of the San Mateo coast."
Devils Slide -- less than a quarter-mile of steep, crumbling rock between Pacifica and Montara -- has tormented travelers since the late 19th century.
The promontory forms the western flank of San Pedro Mountain, rising abruptly from the Pacific Ocean to a height of about 1,000 feet. Its presence sealed off the coast from the sort of development that occurred in Pacifica and Daly City during the mid-20th century.
In 1937, Caltrans carved a 5.9-mile extension of Highway 1 into the cliffs, just down the slope from a more primitive road built in 1879. It suffered its first major closure the following year. Fatal accidents, with cars plunging into the rocks at surf's edge, became a regular occurrence.
By the 1960s, state and county officials were eyeing a bypass of four to six lanes that would run east of San Pedro Mountain. The road was tied to a bold idea for development on the sparsely populated coast.
"They saw another couple hundred thousand people living out there," said Mitch Postel of the San Mateo County Historical Association. "Maybe more."
But the plan collided with the burgeoning environmental movement. The Sierra Club and others sued to block the project in 1972, sparking an epic legal and political fight that reached a climax in 1996 when county voters overwhelmingly approved a ballot measure in favor of a tunnel.
That victory remains a crowning achievement for the Committee for Green Foothills, said the environmental group's legislative advocate, Lennie Roberts, adding it proves "the power of people working together for a vision."
As the project moved toward groundbreaking in 2005, and the cost for the tunnels more than tripled, land that was once tagged for subdivisions became protected open space. The abandoned section of Highway 1 will become a public trail in 2014.
Annette Lantos, 81, recalled her late husband's deep commitment to fixing Devils Slide. One of his first major accomplishments after joining Congress in 1981 was securing about $50 million to repair the slipping road.
"I am very, very pleased that they named the tunnels after him," she said. "It will be a nice memorial."
Contact Aaron Kinney at 650-348-4357. Follow him at Twitter.com/kinneytimes.
The twin tunnels are each 30 feet wide and 4,200 feet long, making them the second-longest in California behind the Wawona Tunnel in Yosemite National Park.
The excavation involved removing about 11.4 million cubic feet of rock from inside San Pedro Mountain.
Each tunnel is equipped with sensors that monitor heat as well as nitrous oxide and carbon monoxide levels.
The tunnels are monitored by cameras 24 hours a day. Tunnel operators can override motorists' car stereos to communicate during emergencies.
There are 16 powerful jet fans affixed to the ceiling of each tunnel to provide ventilation in the event of a fire or other incident.
The southern entrances to the tunnels are covered in a fake rock surface, created by a man who worked on Disneyland's Indiana Jones ride, that is designed to blend into surroundings.