Caltrans last week finished excavating the new Devil’s Slide Tunnel in coastal San Mateo County. Construction crews from general contractor Kiewit removed the last of the soil from the northbound tunnel, while the last of the excavation for the southbound tunnel was completed a week earlier.
“Tunneling is never easy,” says Bijan Sartipi, Caltrans District 4 director. “It requires intelligent planning, brilliant engineering and a lot of old-fashioned hard work. Reaching this milestone required plenty of all three.”
The digging began when Caltrans broke ground at the south portal on Sept. 17, 2007. Since then, roughly 314,000 cu yds of soil, clay, and rock have been removed from the mountain. In fact, construction crews have literally “built a mountain” on the project site out of the excavated soil, clay and rock.
For the past several decades, the adjacent segment of State Highway 1 has been subjected to numerous slipouts and rockslides. Many of them necessitated short and long term closures of the highway. Those closures had a devastating effect on the local economy. The new tunnel is designed to bypass that section of Highway 1.
Crews are now working on the final insulation and lining of the walls, and the installation of electrical and other systems. Financed entirely with federal funding, the $300-million dollar tunnels, each just over 4,000 ft feet long and 30 ft wide, are expected to be completed in early 2012.
Once the tunnels are open to traffic, Caltrans will relinquish the property to San Mateo County. Future plans for the property include a new park with bicycle and pedestrian pathways.
The coast between Pacifica and Montara is unsurpassed in scenic beauty. Carved out of the steep cliff sides, Route 1 hugs the coastline for much of the distance between these two towns. One of the longest Devil’s Slide road closures happened in 1995. It lasted 158 days, and cost almost $3 million to repair.