Caltran Bridges at Devil's Slide

San Mateo County, California


Creating a safer passage at Devil’s Slide


•    Segmental bridges were the best solution to the environmentally sensitive location 
•    HNTB provided construction management for twin cantilever, cast-in-place segmental bridges

When it rains, the rocky hills and cliffs that hold Highway 1 above the Pacific Ocean in San Mateo County start to slide.  This project replaces the infamous coastal stretch of California’s State Highway 1, which hugged the coastline for much of the distance between the two towns and had a long history of extended closures, due to recurring rockslides. After years of studies, Caltrans decided to bypass the Devil’s Slide with two inland tunnels and a corresponding pair of cast-in-place, balanced cantilever concrete segmental bridges, providing a safe, dependable highway between the two towns.
 
The segmental bridges were the best solution to the environmentally sensitive location. Federally protected Peregrine falcons nested above the alignment and California’s endangered red-legged frogs were found living in the Shamrock Valley wetland area located directly beneath the twin bridges, making the terrain under the spans inaccessible. 

Designed in-house by Caltrans, these twin, balanced cantilever, cast-in-place segmental concrete bridges are the first bridges of their kind in California. HNTB provided both specialty bridge CM services for construction of the balanced cantilever, cast-in-place segmental bridges and tunneling expertise support during tunnel construction.