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Posted Feb 3, 2009, 8:02 AM
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Join Date: Jun 2006
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Making up for lost time in building Bay Bridge
This:
Source: http://en.wikipedia.org/wiki/File:Ea...AKBrFromTI.jpg
is being replaced with this:
Source: http://www.mtc.ca.gov/images/ta0202/newspan_lg.jpg
Quote:
Making up for lost time in building Bay Bridge
Michael Cabanatuan, Chronicle Staff Writer
Monday, February 2, 2009
SAN FRANCISCO --
Months of delays caused by welding troubles at the Chinese company that is building the pieces of the new $6.3 billion Bay Bridge make this an even more critical year than anticipated for the construction of the single-tower suspension span.
This already was expected to be a hectic period in the seemingly endless effort to replace the eastern span of the Bay Area's busiest bridge to withstand a major earthquake. After years of controversy, politics, planning and preliminary work, this is the year that commuters and bridge watchers will begin to see the structure's soaring white suspension span rise from the waters of the bay.
They'll also face a three-day closure of the bridge and a shift of traffic onto a curving detour that will slow traffic for the next three to four years.
"This is the moment we have been waiting for," said Bart Ney, a Caltrans spokesman. "This is the start of the suspension bridge."
And it's the end of a six-year-long operation to demolish and rebuild the San Francisco approach to the bridge. On Monday, the Harrison Street off-ramp for westbound traffic will reopen at 5 a.m.
The barriers that slowed westbound traffic also will be removed. A week or two later, the eastbound barriers will be hauled off, and the project will be completed.
The rebuilt approach means "the entire Bay Bridge from Yerba Buena Island to the Fifth Street ramps is seismically safe," Ney said.
Dealing with delays
That, of course, leaves the east span. Despite a six-month delay to fix the welding problems, Caltrans officials say the $1.4 billion suspension span is on track to be completed in 2013 - thanks to some extra time built into the schedule for unanticipated problems.
But Caltrans can't afford any other delays. Officials are trying to make up for lost time by speeding fabrication of the bridge deck and tower pieces in Shanghai as well as the temporary trestle.
"We are very well aware that this project has been delayed many times by political delays," said Steve Heminger,executive director of the Metropolitan Transportation Commission and a member of the three-person committee overseeing construction of the eastern span. "This is really the first major construction delay. We've worked it out with the contractor, and we have picked up the pace."
Yerba Buena Island and the nearby waters of the bay are busy with crews building the double-deck bypass, towers for the temporary trestle and the massive concrete beam that will support the west end of the suspension span.
To the south of the existing bridge, the framework for the first 900 feet of the 1,200-foot- long bypass is in place, and workers are pouring the decks. The final section will be one of the most dramatic steps of the project.
An engineering feat
The entire bridge will be shut down for three days while crews slice through the steel of a 300-foot stretch of the existing span near Yerba Buena Island. That piece of bridge will be rolled to the north on a special set of rails. Then the connecting piece of the bypass will be lifted into the air, set atop rails and rolled into place.
The equipment, and the process, will be similar to what was used during the September 2007 bridge closure when a viaduct just east of the Yerba Buena tunnels was demolished and a replacement was rolled into place. The work is being done by C.C. Myers, the Sacramento-area contractor with a reputation for completing tough jobs with tight deadlines - such the MacArthur Maze replacement and the Yerba Buena viaduct work - ahead of schedule.
"The big difference," said Ney, "is that this time it will take place 150 feet in the air."
Caltrans and the contractor have yet to pick a date for the aerial act. Caltrans is eyeing Labor Day weekend, used for the 2006 and 2007 bridge closures because of historically light traffic, but is not sure if everything will be ready by then.
"We don't want to rush things," Ney said. "Because if something happens and we lose that section, we're not getting the Bay Bridge back for a long time."
At least three cable television networks - National Geographic Channel, HGTV and DIY Network - are working with Caltrans to record the event.
Once the drama is done, traffic will be switched onto the bypass, where a slight curve will cause a 10-15 mph reduction in the 50 mph speed limit. With the traffic shifted, the existing connection to the tunnels will be demolished and a link to the suspension span constructed. Caltrans plans to award a contract for that work in July.
Finishing touches
Across the island, to the north of the current bridge, a temporary steel trestle is rising from Yerba Buena Island and the bay. Towers, which will rise higher than the existing bridge, are being erected, and steel beams soon will reach between them, forming a structure that will support the suspension span's steel deck pieces until the 525-foot tower can be built and the bridge's supporting cable slung over the tower and under the deck.
The deck and tower pieces are expected to begin arriving from Shanghai beginning this spring or summer and continuing through the year. A huge floating crane also is expected to be delivered this spring. It will be used to lift the deck pieces and place them atop the temporary trestle, though cranes atop the temporary towers will be needed to lift the upper reaches of the 525-foot white steel tower. Once the tower and decks are in place, the cable will be slung over the tower and wrapped beneath the deck. Then the temporary trestle will be removed, and the suspension span will stand on its own.
"I think we're at the point now where everyone is excited about the suspension bridge," Ney said. "But we've got some really tough times ahead."
A temporary roadway (right) between Yerba Buena Island and the Bay Bridge will allow the old span (left) to be removed. (Lance Iversen / The Chronicle)
Workers prepare the new self-anchored suspension span tower of the Bay Bridge. (Lance Iversen / The Chronicle)
A construction worker walks on support beams that will later be covered with cement on the lower deck of the new Bay Bridge. (Lance Iversen / The Chronicle)
Terrance Otis, an employee of Tutor Saliva Construction, works on the cement finish of the new Bay Bridge off-ramp at Harrison Street. (Lance Iversen / The Chronicle)
E-mail Michael Cabanatuan at mcabanatuan@sfchronicle.com.
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