ORINDA, Calif. (KCBS) – Crews will begin drilling into the mountainside near Orinda on Monday as they start work on excavating the fourth bore of the Caldecott Tunnel.
The 130-ton, 50-foot-long tunnel boring machine, known as a “road header”, will make its first cut into the retaining wall on the east side of the tunnel during a tunneling commencement event Monday morning, project spokesman Jeff Weiss said.
Crews plan to begin by grinding through the rock on the Contra Costa County side, but will eventually drill from both sides to complete the tunnel, which will be about two-thirds of a mile long.
Because the rock is relatively soft, crews will have to stop about every three feet to build support, Weiss said. They expect to be able to drill only about 10 feet a day.
The four-year, $420 million project will alleviate traffic congestion on state Highway 24 between Oakland and Contra Costa County and create more than 5,000 construction jobs. The project is expected to be completed in late 2013 or early 2014.
Nearly half the project, $197.5 million of it, is being funded by money from the American Recovery and Reinvestment Act of 2009.