Welcome to Caltrans District 4

Devil's Slide Project | Re-alignment


Re-aligning Route 1 at the south portal ensures sufficient line of sight for vehicles traveling at 45 mph to exit and enter the tunnels safely. Removing approximately 85,000 cubic yards of rock from the west facing rock slope allows the road to have the required curve radius. A 12-inch thick concrete retaining wall is anchored to the cut rock face by 1200 'soil nails'. Soil nails are actually steel rods, 30 feet long and 1.2-inch diameter grouted into holes drilled in the rock. The retaining wall is surfaced with a layer of steel reinforced shotcrete**, 2 to 6 inches thick. The shotcrete is hand sculptured to resemble the texture of natural rock and then colored to complete the simulated rock effect.

South Development PDF