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Two piers for the new Bay Bridge skyway stand on the Oakland, Calif. shoreline Thursday Feb. 17, 2011. Construction completion of the skyway awaits a rerouting of current traffic to allow partial demolition of the old span. (Karl Mondon/Staff)

OAKLAND -- Bay Bridge drivers will be diverted onto a new detour at the Oakland end of the bridge for two years, starting in May, so construction crews can finish the new east span of the bridge in late 2013, Caltrans announced Thursday.

The new detour on the bridge near the Oakland toll plaza will be straighter and gentler that the notorious S-curve that opened in the middle of the Bay Bridge in November 2009, and was followed by a surge in accidents. One trucker failed to negotiate the curve and plunged to his death.

As a safety precaution with the new detour, Caltrans wants to give motorists plenty of notice that the lanes along their familiar driving route across the region's busiest bridge will shift to the south slightly along 1,000 feet of Interstate 80.

(Caltrans)

"People need to know there's going to be a change from what they're used to," said Caltrans spokesman Bart Ney. "The bridge has been open for nearly 75 years."

In May, lanes for eastbound bridge traffic from San Francisco to Oakland will be moved to the south onto the new Oakland-side detour. Caltrans will need to close some bridge lanes during the changeover, but no full bridge closure will be necessary, Ney said.

In early 2012, Caltrans will open the detour for westbound motorists traveling from Oakland to San Francisco, also realigning lanes to the south. For this phase, it's possible Caltrans may need to close the entire bridge temporarily, Ney said.

"We can't say if there will be a full bridge closure," Ney said. "If there is a full closure, we will plan it to have the least impact. Right now, I couldn't say if it would be one day or two days."

Caltrans needs to build the detours to the south because part of the existing bridge is in the path of the new east span. Contractors have built much of the elevated skyway deck with eastbound lanes for the new span, but the workers can't build any farther east. As a result, the skyway deck stops in midair, with pieces of metal rebar hanging out the end.

"Part of the existing bridge is in the way of the new bridge," Ney explained Thursday during a news conference held in heavy rain and winds on a portion of the new bridge.

Building the detour will open up room for construction crews to finish the eastbound bridge deck in 2013, the same time as the westbound lanes on the new span, he added.

Until last year, Caltrans officials were worried that they would be forced to open the new eastern span in two phases, one in 2013 and another in 2014.

"The detour enables us to open the bridge in both directions in 2013," Ney said. "That puts motorists on a seismically stronger new bridge earlier."

Contact Denis Cuff at 925-943-8267. Read the Capricious Commuter at www.ibabuzz.com/transportation/. Follow him at Twitter.com/deniscuff.