Deconstructing the East Span of the Oakland Bay Bridge

From Wired Magazine. 

History venerates the builders of great bridges, ... [b]ut rare are commemorative plaques for the un-builders—those charged with the equally heroic task of dismantling those grand structures, once they become dowdy, obsolete, or downright dangerous. Herewith, [a]case stud[y] in the art of mega-destruction ....the old, seismically shaky eastern span of the San Francisco–Oakland Bay Bridge. 

Demolition began: November 2013 | Duration of project: 3 years

The original eastern span of the San Francisco–Oakland Bay Bridge, photographed from the Oakland side on November 8, 2013. 

 Built during the Great Depression, the eastern span of the San Francisco-Oakland Bay Bridge was a marvel of utilitarian efficiency. (Some of the construction cranes were even incorporated as part of the structure.) But now that its graceful replacement is operational, the old span has to be taken down—without dropping anything into the water. Expected cost: $240 million. —Eric Smillie

To figure out the best sequence for removing the high-tension pieces, engineers will use a 3-D model, based on structural analysis and historical records, that shows how the forces are distributed. Bryan Christie Design

Control the Tension

The piers of the cantilever truss aren’t holding the bridge up. They’re holding it down. “This is like a highly strung bow,” says senior bridge engineer Brian Maroney. (A bow made of 50 million pounds of steel.) “You don’t want to just cut the bow because the thing will fly off in all directions.” So crews will first remove the pavement on the upper deck to lighten the bridge’s load and reduce the tension. Next they’ll isolate steel supports, jacking them out of tension until they can be cut without whipping apart. Then they’ll slowly release the jacks.

Cut the Truss Spans

Named for their length in feet, the 504 and 288 truss spans are not under as much tension as the cantilever, so there’s less chance they’ll explode in your face when you cut into them. Still, caution is called for: The 80-year-old steel is not like modern steel; crews must be prepared for differences in strength and hardness.

Cart the Pieces Away
The steel beams are coated with greenish-gray paint, under which is a coat of lead-based stuff. To avoid contaminating the bay, all that metal has to be trucked away and cleaned, after which it will be resold as scrap.

Build a Monument

The massive art-deco column of pier E1, near Yerba Buena Island, may be preserved as a monument to the bridge that served the Bay Area for 77 years. The E2 pier will also likely remain and be converted into an observation platform for the new span.

Blast Foundations

The foundations of piers E3 to E5 are like honeycomb inside. One idea for demolition: Drill into them, plant a series of computer-controlled explosives around the internal walls, set off the charges, and let the concrete collapse into the void.

Mind the Birds

The shallow-water foundations of piers E19 to E22 may be saved for a new pedestrian walkway and bird sanctuary. On the bridge itself, a long-armed snooper truck will be used to install spikes to deter nesting. Any avian holdouts will be removed by hand.