UPDATE: Thompson Bridge comes tumbling, tumbling down

• Thompson Bridge implosion

The old Thompson bridge collapses to the ice on the Red River as it implodes Friday morning. The new bridge is seen in the background. Photo by Eric Hylden/Grand Forks Herald

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RURAL THOMPSON, N.D. — The old Thompson Bridge was imploded this morning.

The Red River bridge, which connects Grand Forks County Road 7 with Polk County State Aid Highway 9, was replaced by a $7.2 million bridge in early October.

The bridge, located about 15 miles southeast of Grand Forks, carried about 1,100 vehicles a day.

Traffic over the new bridge was halted five minutes before the blast, with onlookers kept several hundred yards away.

At 9:18 a.m., 96 12-pound linear shape charges — the kind the military uses — were triggered. A black plume of smoke was followed by a gigantic blast that could be heard for miles around.

When the smoke cleared a couple of moments later, the old two-span truss bridge, which was about 400 feet long and estimated to weigh more than 300 tons, rested partly on riverbank piers and partially on or in the ice-covered river.

“Those are some pretty clean cuts,” Scott Gustafson told a couple of members of his crew, as they inspected the remains on the western span, which was mostly intact. “You could weld them right back together.”

Some beams on the eastern span were twisted like pretzels, a couple of them speared through the ice, lodging into the river.

Each beam contained one shape charge.

“Those military explosives are only good for cutting steel,” he said.

The new bridge has a deck elevation that is 13 feet higher than the old structure. The deck height is 3 feet above the level at which the Red River crested during the record 1997 flood.

It has a curb-to-curb width of 40 feet that provides for much safer conditions, especially for farm equipment and truck traffic, according to Richard Sanders, Polk County highway engineer.

The old bridge, which had only a 24-foot wide deck and just 16 feet of vertical clearance, had a rating of only 34.10 (on a scale to 100) when inspected in fall 2006.

The new 12-span steel and concrete beam structure is 1,209 feet long. Because of the instability of the Red River Valley soils, it has been constructed so it can be adjusted to accommodate soil movements that occur.

The sub-structure of the old bridge experienced major movement on the North Dakota side of the river during summer 2004.

After a resetting of the west truss then, the bridge moved back to within an inch of the 2004 position in just two years. The subsequent resetting was required in 2006.

The contractor, Robert L. Schroeder Construction Co., Glenwood, Minn., expects to have the debris removed from the river within a week and hauled away for recycling.

“In a couple of years,” Gustafson said, “it’ll probably come back as a Toyota.”

Reach Bonham at (701) 780-1110; (800) 477-6572, ext. 110; or send e-mail to kbonham@gfherald.com.

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