The Caldecott Tunnel Fourth Bore Project involves the construction of a two-lane tunnel north of three existing tunnels. The project is located on busy State Route 24 between Oakland and Orinda. The $420 million project will take approximately 4 years to build and will include two smaller projects that will enhance traffic flow in the vicinity of the tunnels, and enable a future project to landscape the area once the tunnel project is completed.
Alta Vista provided materials engineering and inspection services during excavation and construction of the fourth bore project. More than 1,500 data points were collected using the Impact-Echo testing method on the final lining surface along with impulse response testing for selected area. Eleven cores were extracted for Impact-Echo calibration and ten cores were used for compressive strength testing and partial petrographic examination. Timely completion of plant inspection activities played a vital role in the successful construction of retaining wall structures.
Alta Vista’s team worked closely with the California Department of Transportation’s construction staff and has received recognition for its efforts, abilities and positive attitude in facing the project’s challenges head-on.