The Caldecott Tunnel
Oakland & Contra Costa County, California - Transportation
The tunnel, on State route 24, connects Oakland and central Contra Costa County. The fourth bore is 3,771 feet long, with a clearance of 14.58 feet. Channel Lumber began working with General Contractor Tutor-Saliba in 2010 with a budget of $402 million. The project finished in 2013.
Once the tunnel was excavated, three layers of lining were applied. The first layer was shotcrete, sealing the tunnel and providing a rough form. Second, a waterproof polymer based material was applied on to the shotcrete, sealing the tunnel. Finally, rebar, and Channel Lumber concrete forms were built and the final layer of concrete was poured through holes in the form, establishing the finish layer.
Prior to the new tunnel, State route 24 carried about 160,000 vehicles per day through three lanes. The direction of traffic in the third lane switched depending on commute flow. There was significant congestion on this route, and the fourth bore has elevated off-peak traffic, and allowed for two dedicated lanes in each direction.