However, unexpected conditions were encountered when crews tried to install the rock-socket portion of the Tower 2 foundations. The bedrock was found to be "incompetent." Caltrans has authorized the joint venture of Flatiron, Cleveland Bridge, FCI North and Interbeton to order an under-reaming attachment for the drill. It is expected to arrive at the job site in early February.

Looking north across the Carquinez Strait, you can see the old trestle bridge on the right. In the foreground, two legs of Pier 1 are under construction. In the center is a barge at Tower 3, and beyond that, a crane at the far end of the temporary trestle that is being erected at Tower 2.

This specialty equipment will allow crews to drill a rock socket larger in diameter than the driven pipe piling. They will then fill the 11-foot-diameter hole with concrete. After the 9-foot-diameter rock socket is drilled through the concrete, an approximately 12-inch concrete shell will be left to stabilize the sides of the hole. This operation will be done 30 vertical feet at a time to make a total of 160 feet of rock socket.

Although rock socket installation has been suspended at Tower 2 until the drill attachment arrives, pile driving has resumed at Tower 3. The bedrock in that area was considered to be competent. Crews are using piles that have been extended approximately 1 to 4 meters longer than shown in the original plans.

To read more about this project, visit our Carquinez Project page.