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5. CHAPTER

CONSTRUCTION AND MAINTENACE

5.1. CONSTRUTION

The first stage of the SR 520 floating bridge replacement project was the construction of

77 concrete pontoons in 2011 and 2012 by Kiewit-General-Manson at two purpose-built
facilities in Aberdeen and Tacoma. The pontoons were floated to the bridge on Lake

Washington via the Lake Washington Ship Canal. Pontoon assembly and fastening, to
form the floating bridge's deck, began in 2014 and concluded in July 2015.

In 2012, WSDOT identified cracks and other problems with the first batch of completed
pontoons, estimating that it would cost $400 million to repair cracks and other flaws that

would bring down the bridge's predicted lifespan below the desired 75 years. The problems

stemmed from shortcuts allegedly taken by contractors to complete pontoons to meet set
deadlines; the proposed solutions to fix the pontoons included adding high-tension steel

cables and post-tensioning of the concrete.A floating, 660-short-ton (600 t) cofferdam was
launched in November 2013 to assist in repairs of the pontoons, functioning as a

portable dry-dock that wrapped around parts of the pontoons. The repairs were made by
contractors from December 2013 to June 2014 and cost a total of approximately $208

million, using up the majority of the program's reserve funds. As a result of the pontoon

issues, the estimated opening of the bridge was pushed back from December 2014 into
2016.

Construction of the bridge deck, beginning with the eastern approach in Medina, began in
March 2012.

In March 2015, two construction accidents on the bridge slowed construction for
revaluation of safety measures: a contractor was killed after a high fall on the east high

rise and a crane-lifted load of steel pipes swung out of control into a King County
Metro bus and an overhead highway sign.

The bridge deck was lifted into place in August 2015, and the final concrete pour was
finished in October 2015, completing the bridge deck.

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