Despite missing key pieces of rebar in three of the six pontoons built in Aberdeen by contractor Kiewit-General, the construction remains “structurally adequate,” according to a recently finished review by a third-party expert hired by the state Department of Transportation to look at problems dealing with the construction of the Highway 520 floating bridge in Seattle.
All six pontoons have shown signs of cracking or spalling, where the concrete breaks and pops off and the re-enforced steel and ductwork underneath can be seen. But, last month, the state Department of Transportation also said that rebar with 90-degree hooked ends was omitted during the first cycle of construction of three of the key pontoons needed to keep the bridge afloat. The hooked ends were key to “minimize potential cracking in areas where large bolts are used to join pontoons together,” according to a state DOT press release. Although the contractor didn’t use the required hooked ends, workers did add “extra shorter bars with 90-degree hooks at their ends” to two of the pontoons and part of the third pontoon, according to DOT. The third pontoon is still missing the critical hooked ends at its top portion, but the state DOT release says, “it still meets structural requirements because of the extensive steel rebar and added strength from the bolt beam in this location and because the rebar is sufficiently embedded in the concrete.”
The state hired engineering firm Parsons Brinckerhoff Inc. to ensure that the work would meet the qualifications in the contract. Based on the independent report, WSDOT Bridge and Structures Engineer Jugesh Kapur said, “There is no reduction in structural capacity.”
All of the problems that have come up in the first round of pontoon construction may very well delay the completion of the bridge until July of 2015. The agency had hoped to get the bridge done by December of 2014. Whether that means the Aberdeen bridge pontoon construction site will be in use longer than originally planned is unknown.
The state agency is still relying on an expert panel to review the floating bridge design and continue to make recommendations on how to repair the existing pontoons and change the construction methods of the next cycle of pontoons, already under way in Aberdeen. The agency just added a couple more members to its panel.
One of the members of the panel noted that although structural capacity doesn’t seem to be an issue, “we have additional work to address end wall cracking that occurred in cycle 1 and make modifications for future cycles.”