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Engineers scramble to save bridge south of Clinton

The bridge that spans the Clark Fork River five miles south of Clinton is in danger
Rock Creek Bridge
Posted at 6:25 PM, Feb 21, 2024

CLINTON — The bridge that spans the Clark Fork River five miles south of Clinton is in danger.

An inspector with the Montana Department of Transportation (MDT) deemed the Rock Creek Bridge to be ‘scour critical’ in October, meaning the creek bed under the bridge’s supports is being washed away.

This means that with spring runoff looming, any flood in the Clark Fork could destroy the bridge. Because of this, MDT, Missoula County, and the WGM group are rushing to come up with a plan to save the structure.

Erik Dickson, an engineer with the county said the danger is immediate enough that they are trying to expedite the permitting process.
“We’ve already asked the Army Corps of Engineers to fast-track the permitting, but they will move at their own schedule,” Dickson said. “We’re willing to begin work without the permit if necessary because a fine would likely be a lot cheaper than having the bridge fail.”

The partnership held an open house at the Clinton School for the community, sharing their findings with the public, and taking questions about the project.

Chris Evavold, who has lived in Rock Creek for four years, said he was very worried to hear about the danger.

rock creek bridge
An inspector with the Montana Department of Transportation deemed the Rock Creek Bridge to be ‘scour critical’ in October, meaning the creek bed under the bridge’s supports is being washed away.

“This bridge is one way in, one way out for all of us,” Evavold said. “If the bridge goes out, and it’s a many-month delay, who protects our property if we can't live there? Who's gonna fight a fire? Who’s going to deliver propane? Nobody is going to deliver mail.”

The bridge, which was built in 1972, was constructed using an older design of supports. The support pillars merely sit on the creek bed, while modern bridges drill the supports deep into the earth.

Representatives from the WGM group, the firm tasked with coming up with a solution, said they would like to place man-made boulders called riprap around each of the underwater supports.

These large blocks would absorb the energy impact of the flowing river, and prevent the soil under the supports from eroding further.

Officials estimate the repair process could take about a month to complete, and traffic impacts on the bridge are still unknown at this time.

If traffic was diverted, drivers would need to drive around to Philipsburg along a US Forest Service road. Along with emergency response delays, there are likely large economic damages to the community, as Rock Creek is a popular fishing destination.

rock creek4.jpg
Officials estimate the repair process for the Rock Creek Bridge could take about a month to complete, and traffic impacts on the bridge are still unknown at this time.

The announcement of the bridge’s danger follows the closure of several other bridges in Western Montana, including the Maclay Bridge in Missoula, the Boy Scout Bridge in Seeley Lake, and the Bridge Street Bridge in Bigfork.

Joel Boucher, a district pre-construction engineer with MDT, says the situation with Rock Creek is unique.

“There are more than 5,000 bridges and a lot of them are nearing their design life,” Boucher said. “This is not related to the other bridges around the district that have been closed. For a lot of them, it has to do with a load rating that has been reduced to zero. This bridge is different and unique as it is a scour critical issue that has to do with the hydraulics of the river.”

For now, the residents of Rock Creek will have to wait as the county springs into action. Evavold said he was nervous about the bridge’s future, but following the meeting, is relieved.

“There's a lot of good people here,” Evavold said. “I am actually leaving here with a more positive sense of what might happen.”