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East Span 4x4!

Above photos: In the top photo, the last tower leg section begins to tilt up from the barge; in the bottom photo, the piece begins to rise above the SAS deck. Photos by Bill Hall, Caltrans

In this aerial view, the last tower leg section is seen below the SAS deck as it is rises up from the barge. Photo ©2011 Barrie Rokeach

Crews Lift Final Four Tower Leg Sections in Four Days

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Friday, March 4, 2011, 2 p.m.
The last leg of the last tier of Bay Bridge East Span tower legs touched down at 1:25 a.m. this morning, without a hitch and several hours ahead of schedule. The completion of the intense, four-day operation to place the fourth and final tier atop the four tower legs was marked with a quick round of handshakes on a platform at 400 feet or so above the Bay. Then it was back to work as the ironworkers labored for several more hours during the night from inside the hollow tower leg to securely bolt this section to the one below.

Starting before dawn on Monday, February 28, crews worked back-to-back shifts to first lift the massive, 500-ton, 105-foot tall steel tower legs one by one from a horizontal position on a barge at the water line to an upright position, and then slowly and carefully hoist them vertically more than 400 feet in the air by means of strand jacks mounted at the top of the framework surrounding the tower — a painstaking process that lasted 10 or more hours per leg section. As each piece reached the required height, it was shifted horizontally before being delicately lowered into place on top of the tier below.

American Bridge/Fluor (ABF), the joint venture constructing the self-anchored suspension span (SAS) portion of the new East Span, had built extra time into the schedule due to predictions of bad weather. But apart from a bout of heavy winds and rain that stalled work at one point, the skies were remarkably clear for most of the week, allowing crews to shave hours off the operation. “The weather was in our favor, “ said Brian Petersen, SAS project director for ABF.

Also in the project’s favor was the quality of the steel pieces, which were fabricated by Shanghai Zhen Hua Heavy Industry Co. Ltd. and arrived at Pier 7 in Oakland on February 14, 2011. “It has turned out to be a well-planned, well-fabricated mass of steel,” Petersen said.

Early Friday morning, it was apparent to observers at the tower seam line that precision manufacturing was indeed at work, with the bottom and sides of the massive tower section fitting precisely into the waiting sheath of splice plates below, with only millimeters of space to spare. The tower piece landed on the leg section below with the silence and gracefulness of a cat jumping on a table.

That quietude at the tower seam line belied the noise and human effort under way some185 feet above, in the sky-high shed housing the strand jacks. As the tower leg dangled underneath, a pair of ironworkers used their own legs and bodies to carefully control movements of the coils of cables feeding into the strand jacks, while the jacks hummed to life in wave after wave of incremental lifts.

The tower now reaches 480 feet above the water line, or 90 percent of the way toward its final 525-foot height. In the coming days, crews will install the remaining bolts securing the fourth tier of tower legs — as many as 10,000 bolts, according to Petersen. In a few weeks, ABF will crown the four legs with a cap that will tie them together into a single, tapering, elegant unit, and shortly after that, install the steel saddle that will cradle the main cable supporting the bridge.

On the scene continuously, the ABF team grabbed little sleep during this week’s 24/7 operation. But there’s no time to rest on their laurels or take time out for a proper celebration. “We just move from one challenge to the another,” Petersen said, with the next big challenge being the installation of the main cable that will loop over the top of the tower and anchor in the bridge’s deck itself.

“There’s never been one like this before,” Petersen said of the SAS’ unique design.

The East Span project is being overseen by Caltrans, MTC’s Bay Area Toll Authority and the California Transportation Commission, which together form the Toll Bridge Program Oversight Committee.
– Brenda Kahn

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