Photo Courtesy USACE/William Gilmour
One of the major challenges at Olmsted was transporting 5,000-ton dam components.


When Bruce Bennett became executive project director for the joint venture of URS Corp., San Francisco, and Alberici Constructors, St. Louis, his task was to build the dam section of Olmsted Locks and Dam. He was bound by certain contract constraints—namely, no cofferdams.

The contract required construction "in the wet," which meant that Bennett had to figure out a way to lift, move, lower and secure the 5,000-ton concrete shells that form the dam, which stretches 2,596 feet across the Ohio River.

"This manner of dam building has never been done to such a scale," says William Gilmour, resident engineer at the Olmsted Locks and Dam site for the owner, the U.S. Army Corp of Engineers. Gilmour has worked with Bennett throughout the project. Bennett and his team "do what it takes to get the technical challenges solved," says Gilmour.

All of Bennett's skills come into play at the riverine jobsite, which is characterized by murky, 60-ft-deep moving waters through which enormous objects must be lowered and placed in the blind to final tolerances within 0.5 inches.

"We knew we were going to have to figure out a way to set these shells to these kind of tolerances, but we didn't know how," says Bennett.

To meet the challenge, Bennett and his team had to improvise. They invented a pile-driving template that could accept variable shapes and sizes of pile; a screed that could work at a 70-ft depth through water; and software to lower and place fragile, 10-million-lb objects by coordinating GPS, total stations and ten 1,000-ton strand jacks atop the world's biggest catamaran gantry crane. As the project moves into 2012, Bennett will continue innovating to try and meet a newly adjusted budget and schedule.