Owner
California Department of Transportation - Caltrans
Client
California Department of Transportation - Caltrans
Cost
$273 million USD
Timeframe
January 2007
— March 2011
Services performed
Construction inspection and scheduling for initial and final liner and waterproofing; analysing monitoring data and project's progress; daily site inspection and ground conditions reports.
Description
Devil's Slide is located south of the City of Pacifica in California along the coastal road of Highway 1. Landslides and grade subsidence in the Devil's Slide area along Route 1 led to the road being closed for extended periods causing significant economic loss to the surrounding communities. The solution: Construct a tunnel through the mountain to bypass the dangers and reoccurring problems. Construction of 1250m twin tunnels, 9m wide, 6.8m high using Sequential Excavation Method (SEM). Additionally, drill and blast and roadheader excavation through weathered rock were utilised.
Geology
The geological setting comprised quartz diorite, marine sandstone, conglomerate and clay-siltstone. Four main fault zones were encountered.
Location
Pacifica, CA, USA
Highlights
- California's first new highway tunnel since 1964
- Use of canopy pipe umbrellas
- Outstanding Environmental & Engineering Project Award 2010
Drill jumbo drilling blast holes in top heading advance face
Finished southbound tunnel with textured cast-in-situ concrete
Tunnel Portals
Aerial view of completed portals