It took four and a half hours, but all six of the mammoth, concrete pontoons that will eventually support the Highway 520 Bridge across Lake Washington were floated out into Grays Harbor Monday night and will be inspected over the next few days before they continue on their next leg of the journey — around the Olympic Peninsula and down Puget Sound to Lake Washington.
The first cycle of pontoons built at the giant casting basin in Aberdeen went off without a hitch. There were a few cracks found early on, which delayed the float-out by a couple of months, but the cracks were fixed and work is under way to see what kinds of design changes can be done to ensure the cracks don’t form in the future, according to state Transportation Secretary Paula Hammond.
Hammond credits a special peer review panel of experts and professors that have come up with some solid ideas to help the problem in the future. There were no celebratory bottles of champagne or streamers. Just a bunch of hard hats and big grins — although state Rep. Brian Blake, D-Aberdeen, lit up a celebratory cigar.
“This is a time for great celebration,” Blake said.
The pontoon construction project, at its height a few months ago, had about 400 jobs. Roughly half of them are considered local by the state Department of Transportation standards. Many of those jobs will stick around as 27 more pontoons are built at the location through the end of 2014.
Aberdeen Mayor Bill Simpson watched the first few pontoons come out into the Harbor and gave a pat on the back to the dozens of workers, who stood and watched. “They truly care about the job they did and it shows,” he said.
State DOT officials and general contractor Kiewit-General couldn’t have asked for a better day on Monday. The sun was shining with no rain clouds in sight. Wind wasn’t a problem and waves in the Harbor were at a minimum.
At about 10 a.m., the contractor filled the casting basin with roughly 10 feet of water — not enough to get the pontoons to float, but enough to make sure everything would go fine. They took a small boat around to inspect the pontoons to ensure everything was going as planned.
By about 5 p.m., they opened the sluice gate to let in another five feet of water. Within a couple hours, the casting basin had a total of 15 feet of water and the pontoons began to float.
Each pontoon was built with “cells” inside of them that created air pockets that allow the pontoons to float.
“A long time ago, people doubted we could ever get concrete to float,” Hammond said. “We continue to prove them wrong.”
The first pontoon left the casting basin at about 7 p.m. and within the hour, the second pontoon was already under way. By about 11:30 at night, all of the pontoons had exited the casting basin.There’s a time lapse video showing all of the work at http://youtu.be/GW_rp4KrQkY.
Five tug boats were used, including several from local firm Brusco Tug & Barge.
Two tug boats would enter the casting basin and one would be out front of the giant gate helping maneuver the pontoons as they were pushed and prodded along. Special wooden blocks were attached to the sides of each pontoon specifically for the tug boats to use. Several workers from Kiewit-General stayed on top of the pontoons as they were being maneuvered into the Harbor. A small motor boat followed the pontoons out.
Once out into the Harbor two other tug boats would be used to manipulate the giant pontoons while fighting against the current.
The four largest pontoons were taken to the Port of Grays Harbor’s Terminal 4 in Aberdeen.
The two smallest pontoons were taken to Terminal 3 in Hoquiam at Bowerman Basin. And “smallest” is relative, given that even these supplemental stability pontoons are still huge at 98 feet by 60 feet by 28 feet. The biggest pontoons are 360 feet by 75 feet by 29 feet and 240 feet by 75 feet by 33 feet.
To accommodate for any fish that tried to get into the casting basin, the contractor had to build a giant mesh screen to place over the giant gate and a special box to hold fish. When the casting basin is drained, Hammond said a crew will spend extra time ensuring the safety of the fish. Some of the water was drained out this morning, although there was still some water present this morning.
Hammond said that a special diving crew will look over the pontoons and make sure there are no leaks. They have 14 days to do the inspection, although Hammond suspected everything may be done sooner than that. After that, the pontoons will make their way around the Olympic Peninsula to Seattle. The biggest challenge will be to maneuver the pontoons through the Ballard Locks, connecting Puget Sound to Lake Washington.
A total of 33 pontoons are being built in Aberdeen. Another 44 pontoons are being built in Tacoma.