Demolition of the old Tanana River Bridge on March 1, 2011 as viewed from the deck of the new bridge. (Official DOT&PF photo)
Demolition of the old Tanana River Bridge on March 1, 2011 as viewed from the deck of the new bridge. (Official DOT&PF photo)
The old Tanana River Bridge on March 1, 2011, just before explosives were detonated. (Official DOT&PF photo by Audrey Scott)
FAIRBANKS — A piece of Alaska history was blown up Tuesday — on purpose.
It wasn’t necessarily a scene out of the classic World War II movie “Bridge Over the River Kwai,” but the demolition of the 946-foot-long Tanana River Bridge on the Alaska Highway east of Tok was dramatic nonetheless.
“It was impressive,” Department of Transportation engineer Jason Sakalaskas, one of about 30 people to witness the explosion, said. “It’s not everyday we get to do things like that.”
DOT and Alaska Interstate Construction, the company that built the bridge that replaced the old one, used explosives to demolish the bridge, at 1303 Mile of the Alaska Highway.
DOT videos of the explosion, as well as several videos posted on YouTube by witnesses, show four explosions on each of the two concrete piers supporting the bridge, followed by a loud boom resembling a lighting strike, at which point the bridge collapses in a huge cloud of snow and smoke.
“You felt some shock waves,” said Sakalaskas, who was standing on the river ice about 2,000 feet upstream of the explosion.
Onlookers reacted with “celebration and awe,” Sakalaskas said. Hooting and hollering can be heard following the explosion.
The old bridge, officially known as Tanana River Bridge No. 505, was one of five truss bridges built by the U.S. Army during construction of the Alaska Highway in 1943-44. The other four truss bridges are located at the Tok River (1309.4 Mile), the Robertson River (1345.3 Mile), the Johnson River (1380.4 Mile) and the Gerstle River (1392.7 Mile).
The old bridge was replaced with a 903-foot girder-style bridge, which is 225 feet downstream from the old bridge.
Traffic on the Alaska Highway was stopped for about 20 minutes for the detonation.
The new bridge is 12 feet wider than the old one, which will make for wider, safer lanes on the bridge, and has no overhead restrictions. It was built to withstand larger weight loads and is built to current earthquake standards.
Traffic was diverted to the new bridge last fall. DOT waited until March to demolish the old bridge to make cleanup easier.
UNIMAX, an extra gelatin nitroglycerin dynamite, was used to blow up the bridge. There were 10 detonation points set on each of the two concrete piers supporting the bridge, DOT spokeswoman Meadow Bailey said. About 1,250 pounds of explosive was used on each pier.
The explosion did not crack the river ice and none of the bridge pieces went through the ice, which was 5 to 6 feet thick, Sakalaskas said.
“That was the full intent,” he said. “The ice was built up thick enough that nothing punctured through to the existing river. Everything went as planned.”
Pieces of the old bridge will be removed from the ice using heavy equipment. Cleanup started immediately after the explosion and should be complete by the end of the month, Bailey said. The steel is being removed to the riverbank, cut into smaller sections and will be placed in containers for removal and recycling, she said.
Building the new bridge and blowing up the old one cost $31 million. It was a three-year project that will be completed in September when a boat ramp and interpretive wayside are built.
The DOT wants to remove the four other truss bridges on the Alaska Highway because of overhead, weight and load size restrictions, as well as safety concerns, Bailey said.
“We’re trying to phase them out,” she said. “We’ve had too many issues with loads hitting truss bridges.”
For Sakalaskas, who was the assistant project engineer during construction of the new bridge, demolition of the old bridge had special meaning. He was born and raised in Tok.
“I think I went under that bridge more fishing and boating then I did going over it in a car,” he said. “It meant a lot to me being a local growing up there. It was something more personal to me than a lot of folks.”
“It kind of takes down a piece of history, but that bridge has been in service for a long time,” he said. “It served its purpose and now it’s time to move on.”
Sakalaskas said he took the day off Tuesday to drive from Fairbanks to Tok to watch the demolition.
“I told my bosses that would be a day I’d be taking off work to go down and see it,” he said. “I knew it was going to be a pretty good sight to see. I’m glad I was there.”
No comments:
Post a Comment