Last week the Caltrans crew working on the tunnel project in the notorious Devil's Slide area on Highway 1 between Montara and Pacifica broke through after three years of construction (see QUEST's story on the breakthrough.) Photo courtesy of terraplanner.
The combination of steep terrain and the geology of the area have made this area prone to landslides since Highway 1 was constructed in the mid 1930s. For example, a slide in 1995 closed the road for more than 150 days and cost $3 million to repair.
The Caltrans' Devil's Slide Tunnels Project aims to remedy this chronic geoengineering issue:
"The project calls for construction of two tunnels beneath San Pedro Mountain, each 30-feet wide and 4,200-feet long. At the northern end, a 1,000-feet bridge will span the valley at Shamrock Ranch. A re-alignment of Route 1 at the southern end will provide safe transition into and out of the tunnel."
The map below shows major faults in the region (Devil's Slide area is #8 on the map).