MISSOULA — With several bridges out of service due to structural issues, Missoula County on Tuesday approved an agreement with a local engineering firm to draft a grant application in hopes of landing funding to complete repairs.
The county also amended a contract to conduct a subsurface analysis at Boy Scout Bridge in Seeley Lake. The county closed the bridge in November after an inspection by the Montana Department of Transportation determined that the structure could no longer carry traffic “safely or reliably.”
The amended contract is with HDR.
“When we hired HDR to do the preliminary engineering report, we didn't include the subsurface investigation to try and keep our costs as low as possible,” said Shane Stack, the county's director of public works.
Stack added that assessing risk was one of the project's top challenges.
“One of the bigger risks with Boy Scout Bridge, as far as the unknowns and the potential of a large cost increase during construction, is driving the piles and how deep those piles need to go before they reach a point where we know the foundations will be supported,” he said.
The state inspection found deterioration in the timber piling foundation that supports the bridge and could affect the bridge's load capacity. The bridge was built in 1937 and serves as a vital link around Seeley Lake.
Stack said some risk could be reduced with known soil information. HDR secured a geotechnical engineering firm that can complete the soil tests sooner rather than later. The amended contract adds $15,000 to cover the analysis.
“They'll drill down, figure out what those soils look like, and give us an analysis back on how deep those piles really have to go,” he said. “We'll have a better handle on what our cost is going to be for the pilings.”
With bridges in mind, the county also approved an agreement with DJ&A to complete a Bridge Investment Program (BIP) grant application in hopes of securing funding to help replace or repair three bridges, including Sunset Hill over the Blackfoot River, Glacier Creek Road Bridge, and Boy Scout Bridge.
Stack said the county will simultaneously apply for a federal RAISE grant in hopes of landing one of the two grants, or both. It also has set aside roughly $1 million to serve as a local match if one of the grants is awarded.
“We apply for RAISE and if we don't get that, we'll also have applied for the BID program. It's kind of backup plan, if you will. I would hope we find out by July or August,” said Stack.
Commissioners said they plan to visit the bridges in person this month to gather more details on the extent of the pending projects.
The Glacier Creek Bridge, located near Condon, was partially closed in December after an upstream timber piling was damaged, most likely by debris during runoff.
Also in November, state engineers placed the bridge on Rock Creek Road in “scour critical” condition, largely due to channel erosion. The county must create a plan of action, including a detour route to Interstate 90, in the event the bridge were to fail or close for repairs.
The county also must pursue a mitigation plan for the Rock Creek structure in order to remain illegible for federal or state assistance to address repairs. Late last year, the county approved a $32,000 contract with the WGM Group to design a scour mitigation plan.
