ABERDEEN, Wash. (AP) Construction crews at the Highway 520 pontoon project in Aberdeen closed off the mouth of the massive casting basin Nov. 3, using a 300-ton (272 t) crane to lower two 50-ton (45 t) sections of gate into place and setting the stage for crews to finish a channel running from the basin to the Harbor.
Where an empty Weyerhaeuser log yard once stood, hundreds of workers now toil amid towering concrete walls and metal reinforcements. Dozens poured concrete panels or set rebar Nov. 3 while others constructed wooden forms or ran excavators.
Spokesman Joe Irwin with the state Department of Transportation looked out over the bustling construction site shortly after the huge, white sections of gate had been lowered into place.
“It looks a little different [now],” he said with a laugh. “They’ve been pretty busy.”
Crews broke ground earlier this year at the waterfront site to build a large graving dock for constructing the concrete pontoons needed to support the Highway 520 floating bridge in Seattle. Transportation officials plan to have dozens of pontoons, some measuring 360 ft. (110 m) long, finished by 2014 when the floating bridge is rebuilt.
Irwin said the local effort continues to ramp up with new workers added each week as the basin project gets closer to completion. He said the project now employs nearly 300 people at the site with 124 of those workers residing in Grays Harbor County.
“We’re still building up,” he said.
Many workers focused Nov. 3 on installing the first two of three sections of gate to close off the mouth of the basin, which is about three stories deep. Each gate section measures 110 ft. (33.5 m) long and 10 ft. (3 m) high. The third section was scheduled to arrive Nov. 7.
While crews will construct the pontoons in the dry basin, the gate and a system of pumps will allow them to flood the basin when the pontoons are finished and float them out into the Harbor.
Irwin said a crane can lift the gates straight up and out to open or close the entrance to the basin. When crews want to flood the basin they can open water mains on the side of the gate.
A filtering system keeps out fish and debris.
As the water level equalizes between the Harbor and the basin, each gate can be pulled out until the Harbor runs into the basin. Irwin said crews will have to time the flooding and draining with appropriate tide cycles.
“The tide plays a huge role,” he said, adding, “The whole process takes several hours to complete. ... Seeing is believing. It’s impressive.”
When the basin is flooded, crews will use tugboats to tow the pontoons out into the Harbor where they will be stored in a group on the south side of the Harbor channel near Johns River. Tugboats will then tow the approximately 32 pontoons up to Seattle as needed for the bridge project.
While some crews fit the gates into place, several workers poured concrete into wooden and rebar panels to be used as forms for the pontoons. Nick Taylor, an oversight inspector on the project, said building the pontoons requires hundreds of form panels. Carpenters were busy building the wooden frames for the panels.
“Look at all those wood forms,” he said. “We’ve got an army of carpenters.”
An excavation barge also floated nearby as it dug away at the shoreline. Irwin said approximately 80,000 cu. yds. (61,164 cu m) of dirt will be removed to create the channel from the Harbor to the mouth of the casting basin.
Irwin said crews have already removed 280,000 cu. yds. (214,075 cu m) of dirt to create the casting basin.
“That’s just an astounding amount of material,” he said.
Irwin, who worked with the Hood Canal bridge project, said the local pontoon effort has benefited from the lessons of previous projects. He said the latest project utilizes the most advanced concrete techniques, but the scale is also much larger than any previously attempted in Washington state. As he walked among the soaring cranes and enormous forms, he marveled a bit.
“I haven’t been in any this big,” he said.
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