News

Both shafts, the Main Shaft and the Ancillary Shaft have been constructed, and the Concourse Cross Adits North and South have been excavated. At 45ft width, these are the largest tunnels excavated in soft ground in the United States to date using the Sequential Excavation Method (SEM). To minimize the risk of ground loss in the extremely complex geology, the dual side wall drift excavation method was used. In addition, the ground was improvement by dewatering and jet grouting and special pre-support measures such as pipe umbrellas, spiling and grouting are implemented.

Services Provided by URS/DSC

The URS / Dr. G. Sauer Corporation JV was awarded the Caltrans on-call contract for providing Construction Inspection Services for the Devil’s Slide Tunnel project in Pacifica, California.  The URS/DSC JV will provide SEM/NATM engineers and field inspectors, engineering geologists, civil, mechanical and electrical inspection personnel and other technical support services as needed. URS/DSC will be working as an integrated Team with the Caltrans Construction Management Team in their field office, which is located in Pacifica, just South of San Francisco.  

Traffic Planners in urban areas have three options for establishing new arteries or expanding existing lines: to locate them at grade, to elevate them or to put them underground.  Unfortunately, capital costs are usually the governing factor used for deciding which option to use.  As environmental, social and real estate issues are increasingly getting into the equation as do maintenance and operational costs, planners may look underground for the solution.