Dalton Bridge project out for bid

Six and a half years ago Dalton Mountain Road bridge was closed due to failing piles. Although it re-opened a few weeks later as a one lane bridge, the lingering question has been: when will it be replaced?

This year finally seems to be the year, as the Montana Department of Transportation opened bids Feb. 1 for the bridge's replacement.

At the. Feb. 2 Lincoln Government Day meeting, Lewis and Clark County Public Works Director Jenny Chambers said the Montana Department of Transportation engineering estimate for the project was approximately $4.5 million. She said Sletten Construction came in with a bid a little over $3.9 million, while Frontier West LSD came in at $4.6 million.

"The good news is they've got some bids. They got a reasonable bid that looks like within the range of what they thought was the funded cost," Chambers said.

MDT is handling the Dalton Mountain bridge replacement under their off-system bridge program. They accepted it into that program in July 2019. Lewis and Clark County approached MDT about including it in the program shortly after the Montana Legislature approved $$558,806 in funding through the Treasure State Endowment Program. Since then, MDT requirements and budgeting issues have pushed the bridge replacement back several times.

During a Nov. 18, 2021 public meeting on the bridge replacement, MDT project manager Ryan Boysen unveiled the proposed design for the new bridge: a single span, pony-truss bridge without any piles or piers in the river. At the time he said MDT had to work through a series of environmental concerns such as county flood plain requirements and issues with threatened and endangered species. From a construction standpoint, bull trout concerns will limit in-stream work to window between July 15 and Sept. 15.

Roger Dey

A display shows the preferA detour sign at the intersection of Dalton Mountain and Herrin Lakes Roads warns traffic away from the Dalton Mountain Road Bridge shortly after it was closed for failing piles Aug. 4, 2017. Herrin Lakes Road will once again be the detour route when work to replace the bridge begins later this year.red design for the replacement bridge, a single span, pony truss bridge that doesn't require piles or piers in the river. The display was part of an MDT open house Nov. 18, 2021.

Initial work on the project should get underway once the contract is awarded, but on-the-ground work probably won't start until May or June, when staging for the project is likely to get underway. The project is expected to last between 130-160 days.

"The road will probably be closed when they start formal construction; probably mid June-ish," Chambers said.

While construction is underway, there will not be a detour at the bridge site. Instead, traffic to the Dalton Mountain and Willow Creek areas will be routed down Stemple Pass Road and around Herrin Lake Road. County commission chairman Andy Hunthausen noted the Herrin Lake detour has always been part of the plan, since there isn't space to build a detour bridge across the Blackfoot River at the construction site.

Chambers said the contractor will likely build a temporary bridge for their use while they tear down the old bridge, but the construction corridor will be closed to traffic. "It's going to be a definite impact to the community."

"We're hoping to get plans from MDT on traffic safety and overall how their contractors are going to be working on the detour of the area," Chambers said.

She added they've asked that MDT to include in the contract that the contractor has to maintain traffic around the detour and address the impact to the county road and count assets. "That will include, hopefully, some (magnesium chloride dust control), it will include some signage; will include some additional gravel and material if it has to be graded...during the time of the project and based upon those impacts."

Those plans likely won't be established until after the contractor is hired.

"That's why I want them to come up here in the spring to give the community an update and really do a robust public outreach on what those alternatives are going to be; How they're gong to manage the traffic," Chambers said.

She is planning to talk to MDT and ask the county commission to invite them to Lincoln in March or April to provide an update on the bridge construction as well as on other projects that are planned in the area this summer, including a chip seal project on Highway 279 over Flesher Pass.