Joy Carpine-Cazzanti, SR 520 Communications, 206-491-6974 (cell)
ABERDEEN – Progress continues for the new State Route 520 floating bridge, as the second cycle of new pontoons left the Aberdeen casting basin in the pre-dawn hours Monday morning, to coincide with the favorable high tide needed for float-out.
“We have now constructed 24 out of the 77 bridge pontoons we need for the new floating bridge,” said Julie Meredith, SR 520 program director. “We’re making steady progress to build a new structure that will serve the region for 75 years or more.”
In the second cycle, crews built three longitudinal pontoons, two supplemental stability pontoons and one cross pontoon. The 360-foot-long longitudinal pontoons are the backbone of the new bridge, the supplemental pontoons provide stability and flotation, and the cross pontoons cap the bridge on the east and west ends. Crews will build a total of six cycles of new pontoons in Aberdeen.
The longitudinal and cross pontoons include transverse post-tensioning, a concrete strengthening method recommended by the pontoon expert review panel. The additional post-tensioning performed as expected and addressed the spalling and cracking issues found in the previous cycle of pontoons last year.
The float-out process began Sunday afternoon, when crews opened small gates on the basin walls so water could begin entering the basin. Around 8 p.m., crews lifted the three sections of the 150-ton gate. By 11:50 p.m., water in the basin was level with the Chehalis River, and the first pontoon was towed from the basin. Crews expect to tow the sixth and final second-cycle pontoon from the basin early Monday, April 29.
The pontoons will remain at the Port of Grays Harbor for inspections and will then be moored until needed for construction on Lake Washington.
Kiewit-General crews built the casting basin and will build 33 total bridge pontoons in Aberdeen as part of a $367.3 million design-build contract. An additional 44 pontoons will be built in Tacoma under a separate contract. The floating bridge contract requires the new, six-lane SR 520 floating bridge to open to traffic by July 2015. WSDOT is in negotiations with its contractors for pontoon issues encountered in spring 2012 and has not made an official determination on any potential schedule effects.
Project information is available at www.wsdot.wa.gov/Projects/SR520/Pontoons.htm.