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Bonner bridges a “preview” of more I-90 work in years to come

Posted at 3:19 PM, Apr 18, 2019
and last updated 2019-04-18 18:51:42-04

MISSOULA – The administrator for the Montana Department of Transportation in Western Montana says the replacement of the Bonner bridges is a preview of the kind of work we’ll see much more of in the decades to come.

Missoula District Administrator Ed Toavs says it’s been nearly 45 years since I-90 was extended through this part of the state, and that means the dozens of bridges that cross the Clark Fork River and its tributaries are approaching the point where they’ll need to be replaced.

Bonner bridge construction to slow I-90 traffic
Bonner bridge project will impact Blackfoot River recreation

“As folks know that drive that, we have a lot of bridges. And a lot of them are long, 6, 8, 900 feet long. They’re very tall. And they’re all about the same age,” Toavs said.

“You know, they were built usually in the 70s, some in the 80s. Time gets away from you and pretty soon you reach that 60, 70, 80-year mark, where you need to start looking at, ‘is our superstructure on the bridge safe?’ And how much longer will this bridge function safely?” he added.

Toavs says the Bonner bridges, where demolition is starting on the second, upstream span over the Blackfoot River this week, are actually fairly “straightforward.”

He says the spans are only 200 feet long, not very high and straight. Even so, the cost of replacing the two bridges last summer and this year tops $15 million.

Toavs says that means the state will have some number crunching to do in the years to come, especially as federal dollars are harder to come by. But he says with safety at risk, the projects can’t wait.

“Bridges are generally the most critical. Because if a bridge fails, you have a road that’s out and you could have some pretty significant injuries and fatalities from that,” Toavs told MTN News.

The Bonner bridges will be demolished and replaced over the next few months. MDT is still looking at timing for plans to remove the old bridge piers, which have been a safety hazard in the river.

Reporting by Dennis Bragg for MTN News