With all this talk of a stalled State Route 99 tunnel in Seattle—don’t worry, everything is still stalled and in a giant holding pattern as crews still try to figure out exactly how they will drill down and fix the damaged machine—the Washington State Dept. of Transportation most certainly enjoys the opportunity to tout some good news on another megaproject: the rebuild of the world’s longest floating bridge.
Construction of a new six-lane State Route 520 floating bridge across Lake Washington connecting Seattle to points east marked a milestone over the weekend as Pontoon A, a 240-ft-long, 10,000-ton structure, was permanently anchored in place on the bridge’s west side.
The pontoon comes complete with roadway-support columns mounted atop its deck. Pontoon W, on the opposite end of the lake, will bookend the floating bridge’s 21 longitudinal pontoons, each 360 ft long and serving as the bridge’s primary support.
“This pontoon placement essentially represents the start of bridge assembly,” says Julie Meredith, director of the SR 520 Bridge Replacement and HOV Program for WSDOT. “In coming months, the public will start to see a new floating bridge take shape as we align and connect other pontoons in between A and W.”
Pontoon A traveled from its moorage site near Medina to its permanent location about 50 ft north of the existing floating bridge’s west approach, near Madison Park. Steel cables will secure it to the lakebed this week. White buoys will mark the locations of the anchor lines during construction and serve as a sign for boats.
So far, 52 of the 77 pontoons have been constructed with 34 of those now floating on Lake Washington. The new—and quite visible—construction phase all gears toward opening the new bridge in spring 2016. At least there are no tunnels to bore on this project.
Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He also writes for Popular Mechanics, Sports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.