Caldecott Tunnel 4th Bore

The Caldecott Fourth Bore Project was a partnership between the California Department of Transportation (Caltrans), the Contra Costa Transportation Authority (CCTA) and the Alameda County Congestion Management Agency (ACCMA) to build a two-lane tunnel bore north of the existing three Caldecott tunnels. The project is located on State Route 24 between Oakland and Orinda. The $420 million project also included two smaller projects that will enhance traffic flow. With State Route 24 carrying about 160,000 vehicles per day traveling through the three tunnels, the new fourth bore was designed to relieve congestion in the off-peak direction and eliminate the need to switch the direction of traffic flow in the middle bore to accommodate shifting traffic demands.