PROJECT SPOTLIGHT

made access a key challenge. As a first priority, the team has implemented an ex- haustive safety program to complete this dangerous work. Then a complete quality control plan has been put into place to en- sure the work is built to meet the project specific requirements. “All of the pieces on this project are

big,” Corn commented. “It’s not so much the number of pieces, but the size of the elements and the height that make it com- plicated. Access is the primary logistical issue.”

Unique Foundation System The Gerald Desmond Bridge Replace-

ment project broke ground in January of 2013 and, after some initial design hurdles, is currently in full construction mode with foundation work nearing the half-way mark. Innovation and efficiency were the key

drivers behind the selection of a cast-in- drilled-hole (CIDH) foundation system. The project is reportedly the first in the region to use such a foundation system, which differs substantially from the tra- ditional pile drilling approach by pressure grouting the tip of the pile, to ensure the pile meets its capacity. On this project,

With a total project

budget of about $1.3 billion, the new Gerald Desmond Bridge Replacement Project is already pumping plenty of money into the local economy. Some 3,000 jobs are expected to be generated as a result of the project.

this entails the placement of about 350 below-ground piles that support the above ground columns for the east and west ap- proach spans on the bridge.

How it Works The CIDH process begins with a large

metal temporary casing that is drilled into the ground. Sections of steel casing

are individually pushed down to the cor- rect depth, ranging from 102 to as much as 175 ft deep, as the soil is removed from inside the casing area. A rebar cage is then lowered into the hole which is next filled with concrete; at the same time, the steel casing is extracted. Throughout this entire procedure, crews must carefully moni- tor groundwater and mitigate any issues to ensure top quality results. A pile cap is used to connect each cluster of foundation piles, and each of the approximately 90 pile caps that are being installed will support the bridge columns. As outlined on the project’s official

website (www.newgdbridge.com), the size and quantity of materials required for the various components of the bridge construction are substantial. Some of the larger pile caps for the bridge’s approach columns will measure up to 48 ft wide and 14 ft tall and will require nearly 1,200 CY of concrete. The largest pile caps for the two main bridge towers require 3,150 CY of concrete – a total of about 300 truck- loads of concrete each. Implementing the CIDH system on this

project required an extensive, comprehen- sive review of the process up front, accord- ing to Corn, but the foundation work is

The new Gerald Desmond Replacement Bridge Project well under construction. Photo courtesy Shimmick Construction Company. www.AGC-CA.org Associated General Contractors of California 13