Temporary support structures are beginning to rise out of the water at Yerba Buena Island as construction moves ahead on the self-anchored suspension span on the eastern portion of the San Francisco-Oakland Bay Bridge, California Department of Transportation spokesman Bart Ney said Tuesday.
Ney told reporters at a briefing that the new eastern span of the Bay Bridge, which is aimed at making the bridge more seismically safe in the wake of the Oct. 17, 1989, Loma Prieta earthquake, is being built in “the absolute opposite” manner in which the Golden Gate Bridge and other suspension spans were built.
Ney said when other suspension spans were built, their towers, main cables and suspension cables went up first and their roadways were put in last.
But with the new eastern span, the roadway will be constructed first, so a temporary structure has to be built in the early phase of the construction process in order to support work on the permanent span.
“It's a bridge to build a bridge,” Ney said.
He said the self-anchored suspension span will only have three support foundations, but the temporary structure will have seven.
The first temporary support on Yerba Buena Island has already been built and the second support is under construction, according to Ney.
Ney said drivers on the existing eastern span will see the temporary structures, but he said they look nothing like the final bridge,
which he said will have a more aesthetically-pleasing design.
“Aesthetics are the big reason why this design (the self-anchored suspension span) was chosen,” Ney said.
He said the suspension span will be 2,047 feet long, which will make it the world's largest self-anchored suspension bridge, with the suspension.
Ney said the span's tower will be 525 feet tall, which is as tall as the largest towers on the western span of the Bay Bridge, so there will be architectural continuity on the bridge, which is 8.25 miles long.
As workers build the temporary supports, crews will begin building the permanent roadway and the tower for the suspension span.
A barge equipped with a 300-foot-long boom that will be visible to drivers on the Bay Bridge will assist the construction process, according to Ney.
In addition to temporary foundations and the permanent roadway, crews will build a footbridge that will travel the path of the suspension cable so ironworkers can work on the cable as it is laid in place.
Once the permanent suspension span is in place, the temporary supports will be removed, shifting the weight off the temporary foundations and onto the cables, Ney said.
He said 67,000 tons of steel will be needed for the tower and roadway sections.
Ney said work on the new eastern span of the Bay Bridge is on schedule.
He said the new span is expected to open for westbound traffic in 2012 and open for eastbound traffic in 2013.
After westbound traffic begins flowing, it will take a year to demolish the existing eastern span, Ney said.
He said people who want to monitor the work on the new span can go to www.baybridgeinfo.org.
Ney said the Web site has been upgraded and includes a “Bay Bridge 360” section which contains photographs, animations and construction footage.