Caltrans makes progress on fourth bore

August 27, 2010 8:45:48 PM PDT
In the East Bay, the Caldecott Tunnel fourth bore project has just entered a new phase -- the digging has now begun. It's been 20 years in the making and Caltrans will soon be drilling nearly all day and night.

At the east portal a massive drill studded with 60 tungsten steel points is digging its way west. It's called a road-header and it was built in Germany just for this job.

"Brand new, state of the art equipment, largest in the U.S. This is a world class job here," General Superintendent Bill Monahan said.

The road-header can be operated from the cab, or for a better view of the work, outside with a remote control.

It took a day and half to excavate the first five feet. After that, the portal walls and face had to be sprayed with concrete to stabilize the soil and rock. Now they're on to the next section.

This has been a training week for the four men who will run the road-header. Next week, they'll work continuously over two 10 hour shifts, Monday through Friday. The remaining four hours a day will be maintenance.

Every three hours, the sharp tips are inspected, and replaced if the carbide is chipped.

On Wednesday, a manager was injured when the road-header hit a steel dowel.

"The road-header hit a piece of steel that was supposed to be there, and it flew off and hit someone on the leg," Caltrans spokesperson Jeff Weiss said.

Next month, a smaller road-header starts digging at the west portal.

"They'll meet about two-thirds of the way through. This road-header goes ?two-thirds of the way, the other one-third and meet," Weiss said.

The injured manager was back on the job the next day. The two road-headers are expected to meet inside the tunnel after 260 days of simultaneous drilling.

The cost of the project is $420 million and that new fourth bore is expected to open in about three years.


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