Two bridges damaged in quake must be replaced

Posted: Tuesday, December 10, 2002

FAIRBANKS (AP) -- Two bridges damaged by last month's power Denali earthquake must be replaced and four others must be repaired, but state officials say the bridges are in good enough shape to make it through the winter.

Engineers with the state Department of Transportation inspected more than 100 bridges on the Parks, Richardson, Alaska, Tok Cutoff, Northway, Nabesna and Taylor highways following the magnitude 7.9 earthquake that struck the Interior Nov. 3.

The Slana Slough and Mabel Creek bridges, a pair of 41-foot spans located within a mile of each other on the Tok Cutoff, must be rebuilt after the bridges' abutment walls were moved almost a foot by the force of the quake. The movement put stress on the superstructure and leaves the bridges vulnerable to future earthquakes.

''These bridges still accommodate legal highway traffic, but they are seriously weakened,'' said Ralph Swarthout, the DOT's northern region director.

The bridges will remain open through the winter and DOT will replace them next spring and summer, DOT spokeswoman Shannon McCarthy said.

The 125-mile Tok Cutoff, which connects the Alaska and Richardson highways and sits atop of the Denali Fault on which the earthquake occurred, received the most damage of any Interior road during the earthquake.

The largest of the six bridges damaged by the quake was the 946-foot Tanana River bridge at Mile 1,303 of the Alaska Highway, about 11 miles south of Tok. A span of bridge weighing over 500 tons shifted off its concrete footing by 4 inches.

''That's pretty significant for something of that size,'' McCarthy said.

The bridge was built in 1944 during construction of the Alaska Highway.

The three other bridges that will need repair are the Slana River bridge on the Tok Cutoff, the Slana River bridge on the Nabesna Road, and the Little Tok River bridge on the Tok Cutoff.

Engineers are still trying to figure out how much it will cost to replace and repair the bridges. They expect to have an estimate by the end of the month, McCarthy said.

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