Devil’s Slide Tunnel

The Devil’s Slide Tunnel project was located along the stretch of Highway 1 linking Half Moon Bay to Pacifica. Each year the roadway was closed as dangerous landslides impede motorists’ ability to traverse the famed Highway 1. To allow continual operations, the State of California determined that a tunnel was the preferred solution. The planned tunnels were two 30-foot diameter single-lane tunnels with shoulders and concrete barriers dividing the roadway from both a sidewalk and bike lanes. The distance between the bores ranged from 60 to 80 feet apart, one northbound and one southbound. Between the tunnels were cross-passages and emergency refuge rooms. Tunnel infrastructure systems included tunnel control, surveillance, traffic control, communications, emergency evacuation, environmental monitoring and tunnel maintenance systems.

CALTROP provided risk management and feasibility studies that identified an Owner Controlled Insurance Program (OCIP) to be a viable option for this complex project.

LOCATION: Half Moon Bay, CA
CLIENT: Caltrans District 4
PROJECT VALUE: $280 million


  • New Tunnel Construction to Maintain Highway Operations During Annual Landslide


  • Risk Management
  • Owner Controlled Insurance Program (OCIP)