Suanne Pelley, SR 520 Communications,
206-770-3578; 206-437-5717 (cell)
ABERDEEN – Another six State Route 520 bridge pontoons floated out of the Aberdeen casting basin today, marking completion of the third of six total pontoon cycles to be built in Grays Harbor.
“With the third cycle complete, we’re halfway done in Aberdeen,” said Julie Meredith, SR 520 program director for the Washington State Department of Transportation. “We’ve now finished 38 of 77 pontoons needed for a new SR 520 floating bridge that will serve the region for 75 years or more.”
The third pontoon construction cycle included four longitudinal pontoons and two supplemental stability pontoons. The 360-foot-long longitudinal pontoons will help form the backbone of the new bridge, while the supplemental pontoons provide additional stability and flotation.
Each longitudinal pontoon in this cycle includes transverse post-tensioning, a concrete strengthening technique endorsed earlier this year by a pontoon expert review panel. WSDOT managers, who conducted preliminary examinations in the casting basin, report the pontoons are performing as expected. The pontoons show no signs of the spalling that occurred in the first pontoons built last year, and end-wall cracking appears limited to predicted and acceptable levels.
Crews began lifting the 150-ton gate at 6 a.m. this morning to allow pontoons to leave the basin. The first pontoon – Pontoon O – exited the casting basin around 10 a.m., and the last pontoon will leave this afternoon.
The pontoons will be inspected at the Port of Grays Harbor and will then be moored until needed for construction on Lake Washington.
An additional cycle of pontoons is due this winter from Tacoma. Full pontoon tracking details are posted online.
More information about the SR 520 Bridge Replacement and HOV Program can be found at www.wsdot.wa.gov/projects/sr520bridge.