Cause of Coon Rapids Land Bridge Failure Unclear, County Engineer Says

The land bridge on County State-Aid Highway 14, just east of Coon Creek Boulevard. Photo: Courtesy Coon Rapids Public TV
The land bridge on County State-Aid Highway 14, just east of Coon Creek Boulevard.

February 13, 2018 04:45 PM

It was an Anoka County employee who had a hunch a land bridge on Main Street in Coon Rapids didn’t sound right when passing over it a couple weeks ago. 

That hunch has led to a six- to eight-week closure of the 17-year-old bridge over bogland on a stretch of a busy north metro thoroughfare, and a headache for some area residents.

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The employee quickly brought his concern to an assistant county engineer, who couldn’t make a determination without getting underneath the bridge, which was packed thick with frozen dirt. 

A bridge engineer consulting with the county suggested the altered sound of the “thump” of a vehicle passing over one of the bridge’s 34 spans was concerning enough to warrant further investigation.

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By that time, in late January, Doug Fischer, the county engineer, was concerned about the structural integrity of the bridge, located just east of Coon Creek Boulevard. He immediately ordered the bridge closed for inspection, which involved using a backhoe to rip up the frost-laden dirt underneath that covers deep bog and peat, soil unsuitable for the average roadway.

They saw the source of the altered sound: a platform bench that sits atop a piling on the north side of the bridge had fractured. It is that bench, among others, that a portion of the bridge deck relies on for support.

“The deck did not have all the support it was meant to have,” Fischer said. “And certainly not to continue to carry traffic with a road like that.” 

The cause of the failure is unclear, Fischer said, and would be near impossible to pinpoint.

“Land bridges are different creatures with different stresses,” he said. “Could be the weather. Obviously they contract in cold weather. Did that shrinkage cause this? Did water freeze where it shouldn’t?

"Was it an overweight truck in combination with frigid temperatures in combination with construction?”

Either way, Fischer said he understands that rerouting a main drag is a pain for some. 

“It affects lots of traffic. We know it’s going to be disruptive, so we take our closures very seriously.” 

Fischer set in motion plans for an emergency fix and detour, which went into place immediately.

The westbound lanes of the bridge will be closed for six to eight weeks – likely until early April – while the repairs are made, Fischer said. The bridge is part of County State-Aid Highway 14, also known as Main Street, a four-lane thoroughfare that runs between Highway 10 in Anoka to the west and the Coon Rapids-Blaine border to the east.

It carries between 12,000 to 19,000 vehicles per day, Fischer said.

The westbound lanes are closed between Shenandoah Boulevard and Coon Creek Boulevard; the official detour runs north on Hanson Boulevard into Andover, west on Bunker Lake Boulevard, and south on Coon Creek. 

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There are no businesses and just a few residential homes along the closure. A number of businesses to the west said they learned about the detour first-hand, rather than from the county, though they said they weren't concerned the closure would hurt business.

Andover mayor Julie Trude says the county clued her engineering team in on the detour almost immediately.

“We’ve had no negative feedback on phone calls, so I think people figured it out pretty quickly,” Trude said.

The land bridge was built by the state, which then owned the roadway as Highway 242, in 2001. Fischer said a new bridge at that time could expect to have a lifespan of 50-75 years. 

Fischer said the emergency fix will be labor intensive, and should cost between $75,000 and $100,000. That money will come from county state-aid funds, which includes the gas tax, motor vehicle tax and highway user tax. 

Becky Heitman, who lives off Shenandoah, said the detour has more than tripled the time it takes to pick up her kids each day. But beyond that, she says, “I’m not blaming anyone. (The bridge) needs to be fixed, so I’m glad.”

Comments were mixed under the City of Coon Rapids Jan. 29 Facebook post announcing the closure, though most were pleased to be notified by the city. And city manager Matt Stemwedel said he hasn’t heard any negative feedback. 

“People understand the need and that it’s unfortunate, but that there wasn’t really another solution at this stage given what has happened to the bridge,” he said. “I think people are comfortable getting it open as soon as possible.”

Fischer said the emergency closure is the first such that he’s ordered in 16 years as county engineer. He said the rare wintertime fix is short-term, and that the county could pursue permanent repairs to the bridge – complete with the regular bid process – at some point in the future. 

He said the county would hope to insert that permanent fix into the five-year capital improvement program for funding. 

In the meantime, Fischer said, his team will look at other bridges built on bog and peat for similar deficiencies. 

“This was unexpected, not anticipated,” he said. “From our standpoint right now, we’re just dealing with what happened. It happened, we have to deal with it, and we’re going to deal with it as quickly and effectively as we possibly can.”
 

Credits

Michael Oakes

Copyright 2018 - KSTP-TV, LLC A Hubbard Broadcasting Company

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