Construction is underway on a new crossing of the Mendenhall River at Glacier Highway.
By the end of this year, the historic Brotherhood Bridge will be removed and disposed. It will eventually be replaced by a new, wider bridge that will be able to handle an expected 50 percent increase in traffic over the next 75-years.
Anyone who lives and works within blocks of the mouth of the Mendenhall River has heard the sound of a pile driver pounding two-foot diameter pieces of steel into the river bottom for a work trestle.
John Smithson, senior project manager for Orion Marine Contractors, said the trestle will cross the river and serve as a platform for the massive cranes and pile drivers used in constructing the replacement for the Brotherhood Bridge.
“They got the steel frame on it for the second section,” Smithson said. “Now, they’re getting ready to place more mats on that. Crane mats, they call them crane mats.”
Greg Lockwood is engineering manager for the state Department of Transportation. He said the half-century old Brotherhood Bridge does not meet current code. For example, the current bridge’s pilings only go down 45 feet into deposits, which are subject to liquefaction during a major earthquake.
“Because of the soils there, we had to go so deep with those piling to hit something solid,” Lockwood said.
I think that was the biggest challenge of the design. Glacier sediment depositing there and the glacial till.”
The new bridge’s 4-foot diameter pilings will go to the bedrock or down as far as 290 feet. That’s six times as deep as the current bridge’s pilings.
The new, wider bridge also will accommodate four lanes of traffic.
“When we design a bridge, we design them for 75-years,” Lockwood said. “So, we needed to make sure that bridge was capable of meeting our traffic demands 75-, 80 years from now.”
It’s not just the bridge that’s getting replaced. The $25.1 million project should improve vehicle and pedestrian traffic on Glacier Highway from Riverside Drive to Engineer’s Cutoff.
Lockwood said each direction of travel will have two lanes across the bridge and the roadway on both sides of the bridge will be expanded.
I think that everybody in Juneau is aware that that has always been a pinch point there where the two lanes – as you’re heading out the road — drop down to one.”
A sidewalk will run along the downriver side of Glacier Highway and a 10-foot wide multiuse path will be on the upriver side. Bridge underpasses on both riverbanks will allow pedestrians to safely cross the highway without having to dodge traffic.
Orion’s John Smithson said they’ll first build the upstream span of two lanes to allow traffic to cross the river before they remove the current bridge in November. When that’s done, they’ll build the downstream span.
Lockwood said no one was willing to buy the historic 319-foot bridge. Smithson said Orion will dispose of it.
“Actually, the contract requires that we have it melted down,” Smithson said. “So, it’ll be shipped south to a plant. We have to get certificate that it’s been melted down. That’s due to the lead paint that’s on the material on the bridge.”
Lockwood says bronze medallions that were installed when the original Brotherhood Bridge was dedicated in 1965 have been recovered and will be installed in the handrail of the new bridge.
Alaska Native leader and now-retired engineer Roy Peratrovich, Jr. designed the bridge to commemorate the 50th anniversary of the Alaska Native Brotherhood.
Completion date for the current project is planned for October 31, 2015. That’s within days of the 103rd anniversary of the creation of the ANB in Juneau.
Previous stories:
