BRIDGE CONSTRUCTION: Repaired pontoon headed for S.R. 520

Crews sealed cracks with epoxy, post-tensioning and a carbon-fiber wrap

Bridge Construction News WSDOT August 26, 2013
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Construction crews have completed repairs to a S.R. 520 pontoon in a Portland, Ore., dry dock facility.


Pontoon T was floated out of the Vigor-owned dry dock Thursday, Aug. 22. It is being towed to Lake Washington. Pontoon watchers can expect to see the massive concrete pontoon travel through the Hiram M. Chittenden Locks and the Lake Washington Ship Canal this week.


The repairs, completed by Washington State Department of Transportation’s (WSDOT) contractor Kiewit/General/Manson, A Joint Venture, addressed cracks that developed in the keel slabs and end walls on four of the first six pontoons built in Aberdeen as part of Cycle 1 construction.


Crews sealed cracks in Pontoon T by injecting epoxy, adding post-tensioning across the ends of the pontoon and applying a carbon-fiber wrap to portions of the keel slab. Post-tensioning is a common construction process in which steel cables are placed through the concrete and tightened to increase strength. The repairs, endorsed by an expert review panel, will help ensure that the new floating bridge meets its 75-year design life.


“The repairs were completed on schedule, and we look forward to welcoming Pontoon T back to Lake Washington,” said Dave Becher, WSDOT construction manager for the Floating Bridge and Landings Project. “We’ll moor the pontoon on Lake Washington until it’s ready to be joined with other pontoons, forming the backbone of the new floating bridge.”


Repairs on a second pontoon, Pontoon W, are moving ahead at a Seattle dry dock and are on track for completion in several weeks.


The existing bridge, which will be 50 years old this month, is vulnerable to earthquakes and windstorms and must be replaced. Construction on the replacement bridge began in April 2012, and pontoon construction is under way at two casting basins: one in Aberdeen and one in Tacoma. Thirty-two of the 77 pontoons needed to replace the bridge are complete.

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