By Karen Garcia
The Haines Borough Assembly last week voted to enter into an agreement with the state for replacement of the Klehini River bridge near 26 Mile Haines Highway.
The $8.3 million Department of Transportation project is slated for construction in the spring of 2016. It will replace the steel bridge with a “decked bulb-tee girder bridge,” similar to the structures crossing Big Boulder and Little Boulder creeks.
The project also will realign Porcupine Road from Haines Highway to the intersection of Chilkat Lake Road.
Matt Van Alstine, DOT’s engineering manager, said the existing bridge is displaying “noticeable and progressive deterioration every time we inspect it.” The bridge was designed to last 50 years, but has been in operation for more than 80, he said.
“To state the situation succinctly, load rating of the existing bridge will continue to decrease until it reaches a point where we need to close it. We cannot say how long the existing bridge will remain in service, but it is only a matter of time before the bridge will need to be closed permanently,” Van Alstine said.
Decked bulb-tee girder bridges have become the preferred standard in Alaska, Van Alstine said, because they use pre-fabricated concrete. “Pre-fabricating maximizes use of the short construction season in Alaska, because it is difficult and expensive to place concrete in sub-freezing weather. In addition, decked bulb-tee girder pre-fabrication results in a much stronger and more durable deck than using cast-in-place concrete,” he said.
According to the agreement, the borough will be responsible for maintenance of the new bridge.
Van Alstine said maintenance costs for the first 20 years of the bridge’s life aren’t expected to exceed $2,500 annually. The top two inches of asphalt pavement on the road and bridge must be replaced every 20 years, which amounts to between $165,000 and $330,000 in work every two decades, he said.
The borough via resolution assumed ownership of the bridge and Chilkat Lake Road in 2000 in exchange for the state funding improvements to the road. However, the state has still been responsible for maintenance of the bridge and road, including snow plowing.
The new alignment will bump the bridge slightly south of its current location, according to design documents.
The existing bridge will remain in service until the new bridge is completed, making the disruption to traffic minimal, Van Alstine said.
The bridge can’t be reused elsewhere because it is coated in lead-based paint, he said.
“Upon completion of the proposed bridge, the existing bridge would be dismantled and shipped to a steel smelting facility and recycled. This method of recycling eliminates the lead contaminant in a manner approved by the Environmental Protection Agency,” Van Alstine said.
Construction should be complete by fall of 2017.