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Pontoon Update: WSDOT Confident Pontoon Repairs Will Ensure 75-Year Design Life of New Bridge

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Today, WSDOT provided media a firsthand look at the beginning stages of superstructure construction on Pontoon W and the interior of Pontoon V. Nine pontoons are on Lake Washington, including five built in Aberdeen and four in Tacoma. Three pontoons remain in Tacoma for additional outfitting. Photos of construction on Lake Washington are available on the WSDOT Flickr site.

During the summer, crews made repairs and modifications to the first construction cycle in Aberdeen. At the same time, WSDOT convened a panel of experts to review those repairs, identify causes of end-wall cracking and spalling, and make recommendations for future cycles of construction. The panel’s report and WSDOT’s response are available online. Washington Transportation Secretary Paula Hammond reconvened the panel in October to review remaining repair procedures and to evaluate the structural sufficiency of the pontoons in Cycle 1.

John Reilly, chair and representative of the expert review panel, noted, “The condition of the pontoons now on Lake Washington is better than the panel originally observed in Aberdeen now that many cracks have been repaired with either epoxy grout or crystalline sealant.”

In a recent pontoon site visit on Lake Washington, Reilly and the panel saw no significant water coming through the end walls, and no evidence that cracks were weeping, or continuing to weep, in critical locations that they observed within Pontoon U. Previously one of the panel members had visited Pontoon V and reported the same observation. Another panel member is going to visit Pontoon V and W this coming Friday. The panel would expect the above observation to be consistent for all Cycle 1 pontoons.

WSDOT and floating bridge project contractor Kiewit/General/Manson, A Joint Venture (KGM), are developing options for final repairs to pontoons on Lake Washington. KGM recently hired marine construction experts from Ben C. Gerwick Inc. to develop repair options for KGM and WSDOT to assess.

In addition, WSDOT is further analyzing potential effects of the omission of one specific shape of rebar from the longitudinal pontoons built in the first construction cycle. (There will 21 total 360-foot-long longitudinal pontoons that will form the backbone of the bridge.) The end walls were designed to have rebar bent in a 90-degree shape as a design measure to minimize potential cracking in the bolt beam area. However, this bend was not made in the rebar installed at those locations. WSDOT engineers are currently evaluating the effects of this omission and what, if any, repairs may be needed.

The next steps include continuing construction on east- and west-end bridge piers, setting anchors for the new pontoons, and beginning outfitting the pontoons for future precast deck panels that will form the roadway of the new SR 520 floating bridge.

Construction on the $367 million SR 520 Pontoon Construction Project broke ground in February 2011 in Aberdeen. Construction on the $586.6 million SR 520 Floating Bridge and Landings Project began in spring 2012. The floating bridge contract requires the new six-lane SR 520 floating bridge to open to traffic by July 2015.

The latest jobs report counted 832 jobs directly connected to the pontoon and floating bridge project sites in Aberdeen, Tacoma, Kenmore, Bellevue and Lake Washington.

Project information is available at www.wsdot.wa.gov/Projects/SR520bridge.

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