NewsMissoula County


Second half of Bonner bridge demolition underway

Posted at 6:22 PM, Apr 17, 2019
and last updated 2019-04-17 20:22:51-04

MISSOULA – Contractors are starting to rip apart the second of bridges over the Blackfoot River on Interstate 90, part of a two-year effort to replace the structures that carry thousands of cars per day.

It’s not only a significant upgrade for the interstate, but a key part of the ongoing restoration at the confluence of the Blackfoot and the Clark Fork rivers.

With traffic condensed down to single lanes, using the bridges that were replaced last year, crews are wasting no time demolishing the bridges on the upriver side of the Blackfoot crossing. Diamond Drilling and Sawing Company is slicing through the old bridge deck, and the “jersey” barriers on either side, with Frontier West crews responsible for removing all the debris, and then building the new spans.

Although visually this is probably the most impressive part of the Bonner bridge project, the Montana Department of Transportation says it won’t take very long. Demolition should be wrapped up in a couple of weeks.

“This contract is roughly $15 million, and there was more work put into that before the contract was executed,” said MDT Missoula District Manager Ed Toavs. “So you kind of get the idea of how much this is to replace interstate-era bridges. And keep in mind these are about 2-hundred and 20-feet long each. They’re straight bridges. They’re not very complicated. Relatively easy compared to a lot of our other interstate bridges.”

In fact, Toavs says the Bonner project is a preview of the work we’ll see all through Western Montana in the coming years, with the dozens of I-90 bridges now more than 40-years old.

“Bonner demonstrates on a smaller scale a long-term look ahead, as far as bridge needs,” Toavs said. “When those bridges start to come due, because they’ll all start to come due at the same time.”

But this project is about more than just replacing the bridges. It’s also the latest major project that’s part of the re-engineering of the Blackfoot confluence that started with removal of the Milltown Dam just over a decade ago.

“You know, most folks will appreciate the new bridges on the interstate. But I think it’s what’s under the bridges is what we get the questions on. You know, ‘when are those piers coming out?’ So we have a more comfortable area of the Blackfoot to float on,” Toavs said. “Also another point is the park just opened up down there. And of course there’s a lot of interest in connecting the path over towards the Bonner side of the interstate. And so, this project will include work to make that connection possible to the north side of the interstate.”

While the work is underway, this stretch of the Blackfoot will remain closed both on the river and on land. MDT had planned to remove the piers this summer, but Toavs says the department is evaluating new hydrological data on new currents in the river, and will adjust plans to remove the piers based on that review.