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California's first highway tunnels in 50 years open today

March 25, 2013|By Lee Romney

SAN FRANCISCO -- A ribbon-cutting ceremony Monday morning will celebrate completion of the state's first highway tunnels in nearly 50 years -- and commuters should be gliding through the engineering wonder on the San Mateo County coast early Tuesday.

The $439-million dual tunnels at Devil's Slide between Pacifica and Montara were funded entirely by the federal government and came after decades of community debate.

A citizens movement successfully defeated an earlier Caltrans proposal to build a four-lane freeway bypass that crtitics said would have opened the coast to new development. Instead, constuction of the two 4,200 foot-long tunnels was approved as a solution to the landslides that have intermittently closed the scenic stretch of Highway 1 since its construction in 1937.

One closure, in 1995, lasted 158 days and cost almost $3 million to repair, according to Caltrans. The closures forced commuters to detour along Highway 92 in order to reach the coast and strangled local business.

The tunnels, each 30-feet wide, pass beneath San Pedro Mountain, where Highway 1 previously gave motorists the jitters with its plummeting drops.

Excavation techniques relied on inherent rock strength for support, an approach known as the New Austrian Tunneling Method. Open to bicyclists, the tunnels feature state of the art ventilation, fire detection and supression systems. 

Two 1,000-foot bridges complete the project.


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