7/30/2014

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Problem Solvers

WSDOT admits mistakes on 520 Bridge pontoons

WSDOT admits mistakes on 520 Bridge pontoons
SEATTLE -- Repairs and design modifications are coming to the pontoons that will support the new State Route 520 floating bridge, the state Department of Transportation announced Tuesday.

The changes come on the heels of several KOMO Problem Solver investigative reports that uncovered on-going issues with cracks and leaks in the massive concrete pontoons.

State Transportation Secretary Paula Hammond says the upcoming changes are the result of an expert panel's findings.

"The panel agrees the pontoons are structurally sufficient, and we take our responsibility for public safety seriously. These changes will ensure the SR 520 bridge is built to the highest standards," said Hammond.

WSDOT also admitted it made mistakes in approving the designs.

"The results of our internal review show that we did not follow standards of good practice to validate the pontoon design elements, and as an engineer, that is particularly frustrating," Hammond said. "We also did not strictly follow some of our protocols for oversight and administration of the contract on the construction site."

Hammond said disciplinary action will be taken against state bridge division staff who signed off on the design without running models that might have foreseen the cracking.

An October Problem Solvers investigation revealed all six of the first pontoons were leaking. Some of WSDOT's own engineers questioned the construction quality of the pontoons and, in some cases, would not structurally approve pontoons that were missing some key steel re-bar pieces. A former inspector told KOMO News the quality of the first pontoons built in Aberdeen was so shoddy that it's a "disaster waiting to happen."

Underwater inspections revealed the pontoons' worst cracks grew over the winter. The most serious cracks begin in the end walls, and wrap around the upper and lower edges to continue along the top and bottoms.

An untreated underwater crack can let in water at rates of 1 cubic foot per hour, according to a technical report on the bridge.

But WSDOT remains confident in the pontoons' structure.

"The structural capacity of the SR 520 pontoons is sound, and more than adequate for all anticipated loads," said John Reilly, chair of the expert review panel. "Achieving the 75-year service life can be accomplished with normal maintenance."

WSDOT says they will retrofit the first pontoons and that changes made to the second set of pontoons under construction has limited cracking.

"The overall level of cracking is lower than the first cycle at this same stage," the agency said in a news release. "The second cycle of pontoons is anticipated to float out of the Aberdeen casting basin this spring."

A total of 77 pontoons will make the world's longest floating bridge. Completion of the $4.1 billion bridge is already delayed by about six months; it's now not scheduled to open until mid-2015.

The Associated Press contributed to this report.
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