MARK HARRISON / THE SEATTLE TIMES
With a push from the tugboat Terilyn, one of eight supplemental stability pontoons for the new Highway 520 floating bridge traveled from Tacoma through the Hiram M. Chittenden Locks into Lake Washington this week where they will be moored for later attachment. This pontoon passes under the Ballard Bridge on Thursday afternoon. These supplemental stability pontoons will add buoyancy to the huge lengthwise pontoons. This pontoon, 98 feet long, is one of the eight built in Tacoma. The pontoons will support the longest floating bridge in the world, at 1.4 miles.