With a ceremonial scratch of the surface, Caltrans declared the tunneling of the fourth bore of the Caldecott officially underway.
"Today, we dig. Every day after today will take us one day of digging closer to the completion of the fourth bore project," Bijan Sartipi from Caltrans said.
The giant road header will do the bulk of the work. It is an 18-month process of cutting through 3,400 feet of clay, dirt and stone.
About two-thirds of the tunneling will be done from the east side near Orinda and the remaining 700 feet will be done from the Oakland side.
Total cost of the project is $420 million.
"We are going to improve safety in the future, reduce congestion, but most importantly this is a project that's actually partially funded by the Recovery Act," Victor Mendez from the U.S. Department of Transportation said.
In all, nearly 6.5 million cubic feet of material will be excavated from the site. The initial work won't be done by the road header, but by blow torches.
"They're going to cut a big arch, the outline of the tunnel and once that arch has been removed, they're going to use the tunnel-boring machine to dig away the hillside," Jeff Weiss from Caltrans said.
Next week, the huge road header will take over. The $5 million drill was designed just for the Caldecott, shipped in pieces from Germany and it will bore six to eight feet per day.
In late September, separate machinery will begin drilling from the Oakland side, where temporary sound walls have been constructed to minimize the noise disturbance to nearby homes.
The long-awaited fourth bore is set for completion in late 2013.