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Caldecott Tunnel Fourth Bore

WSP USA provided construction management support services to Caltrans, including sequential excavation method (SEM) tunneling engineering for the Caldecott Fourth Bore Tunnel.


Caldecott Tunnel

The addition of a fourth bore to the Caldecott Tunnel eases congestion on California’s busy State Route 24 between Alameda and Contra Costa counties. WSP provided construction management support services to the California Department of Transportation (Caltrans), including sequential excavation method (SEM) tunneling engineering, tunneling inspection, retaining wall inspection, electrical/mechanical inspection, scheduling, safety officer, cost control, risk management, claims and public information. The firm also prepared the final environmental impact statement/environmental impact report, which was released in 2007.

In August 2012, miners finished excavating the lower level or “bench” of the 1,032-meter (3,389-foot) horseshoe-shaped tunnel. Excavation of the top layer was completed in November 2011. When the fourth bore opened in late 2013, it eliminated the need for daily tunnel reversals and lane merges.

The project included construction of retaining walls and portals; temporary and permanent soundwalls on the west side; seven emergency cross-passages between the third and fourth bores; a two-story operations and maintenance center; operations, communications and emergency systems; and roadway improvements.

Situated in the Oakland/Berkeley Hills, the new tunnel is 1.4 kilometers (0.9 miles) from the active Hayward Fault, and will be used to transport emergency crews in the event of a major seismic event. Heat detectors, cameras, jet fans, and emergency cross-passages will assist commuters during an evacuation. Seventeen cameras will transmit vital information to emergency responders, and variable message signs will carry real-time updates.

The USD $420 million fourth bore project received USD $197.5 million from the American Recovery and Reinvestment Act of 2009 as well as substantial funds through Measure J, a local half-cent sales. The project also received funding through regional bridge tolls and state funds.