Touchdown! First bridge support set into seabed
Jay Patrick of the Gateway
New Tacoma Narrows span’s caisson installation goes smoothly Monday
Engineers stood in a tight group near jumbo air compressors on the deck of a barge saddled up to the Gig Harbor-side caisson of the new Tacoma Narrows Bridge.
A few visitors, in their distinguishing extra-bright orange vests, got a close-up of the historic moment of the caisson touching down on the Narrows’ floor from Pier Top City — the compact caisson construction headquarters squeezed onto the “distribution cap” atop the west caisson of the existing bridge.
Workers, decked out in heavy boots, grubby jumpsuits, stained orange lifejackets and weathered yellow hardhats, bounded lithely about the decks of the various barges and boats lashed together on either side of the caisson. Meanwhile, a company photographer bounced around documenting the historic scene late Monday afternoon.
Rushes of air louder than any jet engine occasionally blasted out as engineers released and pumped air and seawater into the 30,000-ton caisson — lifting and lowering it — as they attempted to settle the massive concrete box within a foot of an “X” theoretically marked on the sea bed 133 feet below.
“That is fabulous. Seeing it is incredible,” said David Pim, who along wife Donelda, braved frigid temperatures for over an hour to watch the tricky maneuver from the west tower of the existing span, about 180 feet above the water.
The Peninsula couple had rushed home from Bellevue and thrown on some warm clothes to witness the touchdown, which was scheduled to happen around 4:30 p.m. Monday. They figured the span would be packed with onlookers — much like when the caissons were towed to the Narrows this summer.
A handful showed up for this milestone, including Gig Harbor resident Larry Seaquist, who set foot on the bridge for the first time to see the touchdown.
One man showed up for about five minutes to record a home video of the scene.
Though the touchdown, which Tacoma Narrows Constructors engineers report went smoothly, was not an especially visual event, the Pims said they felt special being present.
“This is once in a lifetime,” said Donelda, who let out an exclamatory ‘Oh!’ when a diver plunged from a barge into the water to check the position of the caisson on the bottom.
“I’m glad we’re here.”
What they did
Crews began setting the 33,000-ton, 80-foot by 130-foot Gig Harbor caisson onto a pad of large rocks —riprap — at about 8:30 a.m. For the next eight hours, engineers lifted, dropped, and pulled the caisson into position using seawater and air pumped into the concrete box and anchor cables to steer it.
Through the day, crews sunk the caisson by pumping 12,000 tons of seawater into its 15 hollow cells.
Engineers used air to help balance the caisson and control the level of descent. Computer-monitored anchor cables guided the caisson.
They were helped by a slack tide that took the regular rip out of the Narrows current.
High-tech laser guidance and positioning systems set up on the caisson, the Tacoma-side shore, and the existing bridge monitored the caisson movements, instantly feeding data to engineers.
At 4:20 p.m., engineers successfully placed the 12-story tall caisson on their first try, said TNC engineers.
Crews subsequently pumped another 6,000 tons of water into the caisson, and released air inside the box, to keep it from lifting in the rising tide.
The caisson was sunk about one foot into the seabed shortly after touchdown.
On Tuesday crews placed more concrete in the caisson, continuing to build its walls, and adding weight to the structure, pinning it to the seabed.
What’s next
Over the next several months, crews will continue building the caisson’s walls and excavate soil out of each of its 15 cells with clamshell-bucket diggers.
The excavation will cause the caisson to sink under its own weight to about 57 feet below the seabed. The total height of the column then will be 190 feet — all underwater.
When completed, the caissons will be sealed with a 25-foot layer of concrete, a “distribution cap” that will serve as the base for the new bridge’s 510-foot tall towers.
The Tacoma caisson, which was towed to the site in July, about a month before the Gig Harbor caisson, is in deeper water — about 154 feet compared to 133 feet on the peninsula side.
Claudia Cornish, communications manager for the state on the bridge project, said the Tacoma caisson has served as the test caisson, leading to some time-consuming trial and error that resulted in a more refined and quicker process in building the Gig Harbor caisson.
“There’s been a bit of a learning curve with the Tacoma caisson,” Cornish said.
Several storms, many including high winds, have also slowed work on the Tacoma caisson, Cornish said. Tidal currents are also stronger on the Tacoma side of the Narrows, further complicating work there.
“There have been times the whitecaps have gotten so fierce we’ve had to pull employees off the caisson,” Cornish said.
The Tacoma-side caisson is expected to touchdown in mid-January. Work on both caisson installations should continue through most of next year.
The new bridge is on schedule to open in early 2007.
Reach reporter Jay Patrick at 253-853-9240 or by e-mail at jay.patrick@mail.tribnet.com.
For all of your real estate needs, contact RE/MAX Executives professional REALTOR Teresa Rebo @ 253-732-5439 or via email at teresa@teresarebo.com
MAKE YOUR NEXT MOVE YOUR BEST MOVE....START BY CALLING TERESA! 253-732-5439
New Tacoma Narrows span’s caisson installation goes smoothly Monday
Engineers stood in a tight group near jumbo air compressors on the deck of a barge saddled up to the Gig Harbor-side caisson of the new Tacoma Narrows Bridge.
A few visitors, in their distinguishing extra-bright orange vests, got a close-up of the historic moment of the caisson touching down on the Narrows’ floor from Pier Top City — the compact caisson construction headquarters squeezed onto the “distribution cap” atop the west caisson of the existing bridge.
Workers, decked out in heavy boots, grubby jumpsuits, stained orange lifejackets and weathered yellow hardhats, bounded lithely about the decks of the various barges and boats lashed together on either side of the caisson. Meanwhile, a company photographer bounced around documenting the historic scene late Monday afternoon.
Rushes of air louder than any jet engine occasionally blasted out as engineers released and pumped air and seawater into the 30,000-ton caisson — lifting and lowering it — as they attempted to settle the massive concrete box within a foot of an “X” theoretically marked on the sea bed 133 feet below.
“That is fabulous. Seeing it is incredible,” said David Pim, who along wife Donelda, braved frigid temperatures for over an hour to watch the tricky maneuver from the west tower of the existing span, about 180 feet above the water.
The Peninsula couple had rushed home from Bellevue and thrown on some warm clothes to witness the touchdown, which was scheduled to happen around 4:30 p.m. Monday. They figured the span would be packed with onlookers — much like when the caissons were towed to the Narrows this summer.
A handful showed up for this milestone, including Gig Harbor resident Larry Seaquist, who set foot on the bridge for the first time to see the touchdown.
One man showed up for about five minutes to record a home video of the scene.
Though the touchdown, which Tacoma Narrows Constructors engineers report went smoothly, was not an especially visual event, the Pims said they felt special being present.
“This is once in a lifetime,” said Donelda, who let out an exclamatory ‘Oh!’ when a diver plunged from a barge into the water to check the position of the caisson on the bottom.
“I’m glad we’re here.”
What they did
Crews began setting the 33,000-ton, 80-foot by 130-foot Gig Harbor caisson onto a pad of large rocks —riprap — at about 8:30 a.m. For the next eight hours, engineers lifted, dropped, and pulled the caisson into position using seawater and air pumped into the concrete box and anchor cables to steer it.
Through the day, crews sunk the caisson by pumping 12,000 tons of seawater into its 15 hollow cells.
Engineers used air to help balance the caisson and control the level of descent. Computer-monitored anchor cables guided the caisson.
They were helped by a slack tide that took the regular rip out of the Narrows current.
High-tech laser guidance and positioning systems set up on the caisson, the Tacoma-side shore, and the existing bridge monitored the caisson movements, instantly feeding data to engineers.
At 4:20 p.m., engineers successfully placed the 12-story tall caisson on their first try, said TNC engineers.
Crews subsequently pumped another 6,000 tons of water into the caisson, and released air inside the box, to keep it from lifting in the rising tide.
The caisson was sunk about one foot into the seabed shortly after touchdown.
On Tuesday crews placed more concrete in the caisson, continuing to build its walls, and adding weight to the structure, pinning it to the seabed.
What’s next
Over the next several months, crews will continue building the caisson’s walls and excavate soil out of each of its 15 cells with clamshell-bucket diggers.
The excavation will cause the caisson to sink under its own weight to about 57 feet below the seabed. The total height of the column then will be 190 feet — all underwater.
When completed, the caissons will be sealed with a 25-foot layer of concrete, a “distribution cap” that will serve as the base for the new bridge’s 510-foot tall towers.
The Tacoma caisson, which was towed to the site in July, about a month before the Gig Harbor caisson, is in deeper water — about 154 feet compared to 133 feet on the peninsula side.
Claudia Cornish, communications manager for the state on the bridge project, said the Tacoma caisson has served as the test caisson, leading to some time-consuming trial and error that resulted in a more refined and quicker process in building the Gig Harbor caisson.
“There’s been a bit of a learning curve with the Tacoma caisson,” Cornish said.
Several storms, many including high winds, have also slowed work on the Tacoma caisson, Cornish said. Tidal currents are also stronger on the Tacoma side of the Narrows, further complicating work there.
“There have been times the whitecaps have gotten so fierce we’ve had to pull employees off the caisson,” Cornish said.
The Tacoma-side caisson is expected to touchdown in mid-January. Work on both caisson installations should continue through most of next year.
The new bridge is on schedule to open in early 2007.
Reach reporter Jay Patrick at 253-853-9240 or by e-mail at jay.patrick@mail.tribnet.com.
For all of your real estate needs, contact RE/MAX Executives professional REALTOR Teresa Rebo @ 253-732-5439 or via email at teresa@teresarebo.com
MAKE YOUR NEXT MOVE YOUR BEST MOVE....START BY CALLING TERESA! 253-732-5439
