Devil's Slide Tunnels - Caltrans 1st New Highway Tunnels in 50 years

In 1983, rock slope failures at a location called "Devil's Slide" caused Highway I (Pacific Coast Highway, south of San Francisco) to be closed for an extended period of time causing significant economic loss to the coastal communities. In mid-September, 2004, California Governor Arnold Schwarzenegger signed legislation directing Caltrans to transfer the land it was to use for a freeway bypass to the California Department of Parks and Recreation, clearing the Coastal Commission's final appeal of the Devil's Slide Tunnels. With further approval by the California Costal Commission (CCC), the construction began in early 2005. The bid for the first phase of construction projects (the South Rock Cut construction) was opened on 1/12/05. For the twin tunnels, each 9 m diameter tube will accommodate only one traffic lane. Each tunnel tube will accommodate a 3.6 m roadway, 0.6 m and 2.4 m inside and outside shoulders respectively, and 1.2 m walkways on each side. Cross passages will connect the bores at about 156 m intervals and jet fans will provide tunnel ventilation. The unique challenges of the project during planning, design and construction are as follows: 1. Environmental: Extensive public out reach program (monthly meetings for two years). 2. Design: NATM method, high seismic zone, leach water treatment system, longitudinal jet fan system, cross passage location/spacing consideration, fire protection, traffic monitoring/control and rock fall protection. 3. Construction package: First Caltrans tunnel project in 50 years, Geotechnical Baseline Report(GBR), bid item list (Caltrans format vs. tunnel industry format) and technical tunnel specification (Caltrans format vs. tunnel industry format). 4. Construction phase: South Rock Cut (1st phase construction), Twin Bridges (2nd phase construction) & Tunnels (3rd phase construction).