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A raft, guided by Montana Fish, Wildlife and Parks officials, floats in June 2013, near the Interstate 90 bridge piers in the middle of the Blackfoot River near its confluence with the Clark Fork River. Because of the danger to floaters, the bridges are being replaced to remove the piers. Construction on the eastbound bridge will begin in mid-April and the westbound bridge slated for 2018.

It’ll take $15 million and the next two construction seasons to replace both Interstate 90 bridges at the confluence with the Clark Fork River with ones that don’t need to be held up by pillars in the middle of the channel.

The process will entail river closures, Bob Vosen of the Montana Department of Transportation said Tuesday, but not during the heart of floating season.

“It looks like there’ll be three periods where we’ll be asking (Montana Fish, Wildlife and Parks) to keep people off the river this year, from mid-April to early May, from late August into September, and late September into October,” said Vosen, district construction engineer. 

FWP last week initiated a public comment process that’ll remain open through March 16. Upon approval by the state Fish and Wildlife Commission, the intermittent closures would limit floating, swimming, wading, boating and the like from the Weigh Station Fishing Access Site downstream to the Clark Fork.

That stretch, which passes behind the Bonner mill site, was opened for the first time two years ago.

In conjunction with the new bridges, a paved and lighted walking trail will line the west riverbank beneath them, one of the features of FWP's new Milltown State Park that's due to open this summer.

Frontier West and Morrison-Maierle, the same team that replaced the Madison Street Bridge in Missoula last year, won the construction bid for this one.

Their bid of $14.4 million was considerably less than the $22 million originally bandied about, though the higher cost included pre-bid costs to MDT.

“It’s a design-build project, so it’s an expedited process,” Vosen said. “Our normal process is design-bid-build, where MDT puts together the design, and then we solicit bids, then we go to construction. In this case we do the bidding part, we bring on a consultant firm who’s paired with the construction company. They’re going to put the design together and start construction before design is complete all the way.”

Donny Pfeifer, construction operations engineer for MDT’s Missoula District, said a request for bids was made last August and the construction team was selected over two other competitive bids on Nov. 1. The official award was made to Frontier West and Morrison-Maierle in mid-December, though the design was well along by then.

“They’ll hit the ground running on April 16,” Pfeifer said. “So to go from basically no design in December, then in two years it’s done, that’s pretty fast to complete two major structures.”

Because it’s an interstate bridge replacement, all funding comes from the Federal Highway Administration, with no matches required of the state.

The project has been talked about since the Milltown Dam was removed 10 years ago. The twin bridges were built in 1965 when Interstate 90 went through these parts, gobbling up a good chunk of Milltown. What was a reservoir then is a narrow river channel now, creating the potential of dangerous hydraulics between the huge piers and pillars and the steep banks on either side.

Pfeifer said the substructure of the new eastbound bridge will be installed first. Traffic will be slowed and diverted to the westbound bridge and a westbound lane for about a mile. Two piers on each side of the river are constructed and the bridge decking and pillar removed.

The large square pier that braces the pillar won’t be removed from the river until next year.

The I-90 Blackfoot bridge replacement is just one of a number of projects in the Missoula area slated to get underway when the snow melts.

Others include the long-awaited Russell Street remake across the Clark Fork River; the Van Buren Street interchange project that will include the installations of roundabouts on either side of the I-90 overpass; the major rebuild of the Frenchtown Frontage Road between Huson and U.S. 93 near the Wye, and the installation of bulb-outs and more than 350 disability-accessible ramps to replace curbs at some 100 intersections in central Missoula.

“It’s somewhere in the neighborhood of $95 million MDT is going to have in the greater Missoula area this summer,” Vosen said.

The department has enlisted the services of Big Sky Public Relations of Missoula and Kalispell to keep the community updated on road closures, delays and progress of most of the projects. Partners Creative and DOWL is handling communications for the I-90 Blackfoot bridge replacement.

The last paragraph of this story was updated to clarify the roles of Big Sky Public Relations and Partners Creative and DOWL.

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Mineral County, veterans issues

Outlying communities, transportation, history and general assignment reporter at the Missoulian