Tuesday, May 21, 2013

Bay Bridge Problems Literally Fixed With Duct Tape

Corrosion problems during construction of the $6.4 billion Bay Bridge discovered as early as November, 2004, were "fixed" by a bridge inspector using duct tape to cover leaking vents leading to ungrouted galvanized ducts containing already stressed post tension tendons designed to add strength to the bridge deck carrying traffic, according to CALTRANS inspection records uncovered recently. California Governor Jerry Brown announced yesterday that this, and other corrosion related problems arising during bridge construction, has initiated a review of bridge construction documents dating back to 2003 or earlier, and will likely delay the scheduled Labor Day opening of the iconic bridge.

"I take it very seriously, and that thing's not going to open unless it's ready," Brown said. Besides defective girder welds, fracturing seismic equipment bolts, and questions about the strength of the bridge's concrete foundations, inspection records released recently reflect that hundreds of steel tendon inserted into bridge deck segments and stretched, to add strength to the traffic carrying bridge deck, could have been seriously damaged by corrosion during early phases of the construction project. At one point, the situation brought one of the bridge's engineering managers to tears, as he observed workers pumping gallon after gallon of rusty water from ungrouted tendon ducts.

Post tension bridge construction involves using precast concrete panels for segments of the bridge decking. The panels are manufactured with galvanized ducts inside them. Once the precast panels are in place on the bridge, steel cables are inserted into the ducts, and stretched under tension to compress the precast panel, adding significantly to its load bearing strength. Commonly used engineering standards, included in the Bay Bridge contract, require the ducts to be filled with protective grout within ten days after the tendons are put under tension, to avoid corrosion and early failure of the steel cables. Failure to timely grout the ducts exposes the stressed cables to moist air and other elements that can corrode the steel.

During a November 2004 routine inspection of the under construction bridge deck, CALTRANS inspector Laura Rubalcaba found water inside ungrouted ducts containing cables which had been under tension for two months or more. That day, Rubalcaba wrote in her construction diary, "The top of the grout injection/vent hoses were not sealed against the rain. I ... found many instances where it was obvious that rain water was already in the ducts with the stressed tendons." Rather than stopping work on the deck section involved, Rubalcaba had a solution that should send chills up and down the spine of every bridge engineer around the world - "I duct taped over the tops of the tubes myself."

After Rubalcaba's report, and numerous other, similar observations of potentially destructive corrosion of post tensioned cables in wet ducts, CALTRANS undertook some inspection and testing efforts to evaluate the problem, finding it not a significant risk to the bridge. However, even after that report was issued, bridge builders left cables under stress within wet ducts for many months, and failed to use a special grout formula designed for wet ducts once the ducts were finally grouted, despite five to nine inches of rainfall during the six months it took to get around to grouting the wet cables.

The bridge is already billions over budget and years behind schedule. Any elected official who is in any part responsible for a premature decision to open this bridge to traffic, or releasing taxpayer dollars in final payment to the contractors involved in these failures, should be held fully accountable to the public for any future disasters which might befall this bridge.

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