Changes Being Made to Aberdeen Pontoon Construction

Changes are being made to the SR 520 floating bridge pontoons built in Aberdeen following recommendations by a review panel.

Washington Transportation Secretary Paula Hammond announced repairs and design modifications for the pontoons in order to ensure a 75-year life of the new floating bridge.

Last year, WSDOT convened an expert panel to review the causes of cracking and spalling on the first cycle of pontoons built in Aberdeen. The panel’s recommendations to reduce cracking have been incorporated in the second cycle of pontoons, already under way. The panel was reconvened in fall 2012 to look over progress.

Hammond said “We are implementing the expert review panel’s findings to make repairs to the pontoons on Lake Washington and design modifications to the pontoons still to be built in Aberdeen”.

She added “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.”

There has been limited cracking in the second cycle of construction to date, and the overall level of cracking is lower than the first cycle at this same stage. The second cycle of pontoons is anticipated to float out of Aberdeen this spring.

“Based on the panel’s findings, we will add post-tensioning across the pontoons on Lake Washington, in addition to the length-wise post-tensioning that is already in place,” said WSDOT construction engineer Jeff Carpenter.

Crews will add “transverse post-tensioning” to each of the 21 longitudinal pontoons constructed for the new SR 520 floating bridge. In the first cycle, these pontoons were post-tensioned lengthwise only. For Cycles 2-6, each longitudinal pontoon will be post-tensioned fully within the Aberdeen casting basin.

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, but includes incentives for an earlier opening in December 2014.

The latest jobs report counted 801 jobs directly connected to the pontoon and floating bridge project sites in Aberdeen, Tacoma, Kenmore and Bellevue and on Lake Washington.