Two mile-long tunnels constructed with cutting-edge engineering technology are set to open early this year south of San Francisco after transportation officials complete final safety tests on the tunnels.
The tunnels, known as the Tom Lantos Tunnels after the late Democratic lawmaker from California, are designed to divert traffic away from a dangerous 1.2-mile stretch of the Pacific Coast Highway approximately 15 miles south of San Francisco. That stretch of roadway has been dubbed Devil’s Slide because it has tended to erode, disintegrate and collapse for decades. The new tunnels are expected to improve highway safety and reduce the number of deadly crashes in the area.
Digging the Tunnels
The Tom Lantos Tunnels, located between the municipalities of Montara and Pacifica, will carry motorists through smooth and mountainous terrain instead of along the treacherous coast. Transportation construction workers bored the two tunnels through San Pedro Mountain with the assistance of two road-headers weighing 120 tons each. A road-header is a type of excavating equipment designed to bore holes into rock face.
The Tom Lantos Tunnels, which are the first tunnels built in California in more than five decades, are each 4,200 feet long and 30 feet wide. Two bridges carry motorists toward the tunnels. Each bridge is 125 feet high and approximately 1,000 feet long.
The tunnel project has taken more time and more money than originally projected. The project has lasted seven years and cost $439 million. Transportation officials originally envisioned the plan as a five-year project that would have cost $240 million. Federal emergency relief dollars completely paid for the project. The California Department of Transportation, which initially began exploring the idea of the bypass in 1958, oversaw the entire project.
Features of the Tunnels
The side-by-side cylindrical Tom Lantos Tunnels will have many innovative technological features. Huge exhaust fans will keep air flowing through the tunnels. Workers have installed carbon monoxide sensors throughout the tunnels to help ensure the safety of drivers and tunnel employees. The two tunnels are connected by 10 fireproof shelters that motorists can use in the event of an emergency. The tunnels also include safety cameras that are monitored 24 hours a day by a staff of 15 employees.
Engineers relied in part on technology developed in Austria in designing the tunnels, which feature elegant rounded ceilings, pristine walls and gleaming pipes.
The new route through the tunnels is expected to improve highway safety as well. The old coastal roadway, which was narrow and filled with twists and hairpin turns, frequently was the site of deadly crashes.