WSDOT: SR-520 pontoon repairs top $70M

The Washington State Department of Transportation (WSDOT) and its contractors have reached agreements on the cost of repairing four pontoons from the first construction cycle and modifying another four pontoons from the second cycle for the new State Route 520 floating bridge.

In February, WSDOT acknowledged a design error that led to cracks in the initial cycle of concrete pontoons, which also required modifications to the second construction cycle to meet the new bridge’s 75-year design life. At that time, WSDOT estimated repairs would cost tens of millions of dollars.

Repairs were recommended by an engineering firm specializing in the repair of concrete structures, and then endorsed by an expert review panel.

“These repairs are important to ensure we are building a safe bridge that meets the needs of the traveling public and supports the regional transportation system for many years,” said WSDOT Secretary Lynn Peterson. “We are committed to following the recommendations of the expert review panel and moving forward.”

For the first change order, WSDOT will pay $48.8 million to floating bridge contractor Kiewit/General/Manson, A Joint Venture, to complete Cycle 1 pontoon crack repairs. These repairs for Cycle 1 have been underway since June to help keep overall bridge construction moving.

The repair procedure will address cracks that developed in the keel slabs and end walls on four of the first six pontoons built in Aberdeen. The repairs include leasing and towing pontoons to drydock facilities in Portland and Seattle; building a coffer cell in Tacoma and towing it to Seattle for repairs on the other two pontoons; and implementing repair procedures on all four pontoons: epoxy injections, transverse post-tensioning, and the application of carbon-fiber wrap.

For the second change order, WSDOT will pay $22.4 million to pontoon construction contractor Kiewit-General to add transverse post-tensioning to four pontoons while they were in the casting basin in Aberdeen. The work was completed prior to float-out in April. Both costs will be paid from the SR 520 risk reserve developed to address unforeseen project issues as part of the $2.7 billion SR 520 program budget. With these charges paid, the current risk reserve is now $100 million.

With the two change orders complete, the new floating bridge is now estimated to open to traffic in late 2015 or early 2016. The final date will be determined as part of the schedule negotiated with contractors.

Additional change orders to be finalized later this year include adding transverse post-tensioning to the pontoons built in cycles three through six (these cycles will be built using the revised design); and scheduling effects to the pontoon construction project and the floating bridge and landings project with their respective contractors.

The current bridge, which will be 50 years old in August, is vulnerable to earthquakes and windstorms and must be replaced, according to WSDOT officials. Construction on the replacement began in April 2012, and pontoon construction is underway at two casting basins, one in Aberdeen and one in Tacoma. Eight pontoons recently floated out of the Tacoma casting basin. With the recent Tacoma float-out, 32 of the 77 pontoons needed to replace the bridge are complete.

More information about the SR 520 Bridge Replacement and HOV Program is available at

Six more stability pontoons for the State Route 520 bridge floated out of Tacoma July 27. A WSDOT engineer looks on as the T-pontoon squeezes between pontoons in the casting basin. The T-pontoon, specially built for these pontoons, removes the supplemental stability pontoons from the casting basin in pairs. (PHOTO COURTESY WSDOT)