on cracked 520 pontoons
Washington’s Department of Transportation is set to start the final round of repairs on cracked and leaking pontoons for the 520 bridge.
The coffer cell is a large steel structure that measures 35 feet tall by 144 feet long. It was built in Tocoma and towed to Lake Washington on a barge. Once in place, the coffer cell will be used by SR 520 bridge construction crews to repair two concrete pontoons on the lake.
The beleaguered concrete pontoons for Seattle’s State Route 520 floating bridge are nearing their final fixes. A “coffer cell” — a 650-ton steel box on a floating dry dock — will be used for the repairs. “We needed to figure out a way to do the repairs out here and you have to do them in the dry so that’s why we have a coffer cell,” said Dave Becher, Washington State Department of Transportation’s floating bridge project director. Repairing the first four cracked pontoons is estimated to cost $49 million.