The Bay Bridge's original east span was so state-of-the-art 80 years ago that dismantling it will be as difficult as constructing the replacement, officials said.
“Demolishing is 12 guys, me and my boys, beating a structure down,” said Brian Maroney, Caltrans' chief bridge design engineer. “But this is a world-class structure and we need to take it down in a world-class way.”
Using modern-day technology to map every intricacy of the old span in 3-D, a team of engineers determined the bridge would have to be taken apart in the reverse of the way it was put together, meaning starting from the middle of the cantilever and working outward.
The span is akin to an archery bow — highly strained and full of tension — and could break if not pulled apart with care. Much like the original construction, demolition workers will have to install temporary jacks to relieve the stress when they obstruct the middle of the cantilever.
“If we just cut it, it would spring back and send a shock all the way back and we would not be able to stand on it,” said Caltrans bridge engineer Mike Whiteside. “It's very, very dangerous, and we have to break it down in a very precise manner.”
Complete demolition, which is expected to total $239 million, will be divided into three parts: the cantilever section and S-curve, smaller trusses and then the foundation.
Bay Bridge officials awarded the cantilever section to California Engineering Contractors and Silverado Contractors in a joint venture, for their reasonable bid and relatively speedy timeline of about three years.
They will start once the new bridge opens and they can access the old span, according to Bay Bridge spokesman Andrew Gordon. Bids for the remaining work will be awarded soon after the cantilever work begins.
The eight decades since construction started in the early 1930s have brought along new factors that must be accounted for.
Environmental and safety standards have become more stringent. Lead paint, used on the original span for its protective qualities, is now frowned upon as toxic.
The steel, the kind used during World War I, is cracked and rusted and requires special handling.
Figuring out a way to dismantle the original span has been even more exciting than constructing the new one, Maroney admitted. Standing on the old span Thursday, he pointed out the complex connections, some containing six or eight beams, and the triangular, prismatic rivet patterns.
“I love this structure; it's going to be an honor taking it down,” Maroney said with a smile. “I have respect for my elders and this bridge is my elder.”