Crews are preparing to float the last three pontoons of the total of 77 needed for the new bridge being built by Kiewit/General/Mansonin the US state of Washington.
Washington State Department of Transportation’s contractors built pontoons in both Aberdeen and Tacoma. Of the 33 constructed in Aberdeen, 21 - including the final three - were the massive longitudinal pontoons, 110m long, three storeys high and 11,000t. The casting facility in Aberdeen also produced two cross pontoons that bookend the floating portion of the new bridge, and 10 supplemental stability pontoons, which are about the size of a basketball court.
Pontoon construction in Aberdeen began in winter 2011. Crews also built 44 supplemental stability pontoons in Tacoma.
The final three will be floated out of the casting basin today. The float-out process involves raising three 50t gate sections to let tidal waters into the casting basin, then navigating the pontoons into the Chehalis River. Once the float-out process is complete, the pontoons will be held in the river until they are inspected. When weather conditions permit, they will be towed by tugboat to Lake Washington for assembly as part of the new bridge.
