MILLTOWN — A wet blanket has been thrown over the plan to excise two large bridge piers from the middle of the Blackfoot River here.
The Montana Department of Transportation told state and federal agency partners in Helena on Tuesday it’s not going to happen, at least not as part of ongoing reconstruction of two Interstate 90 bridges that the concrete structures used to hold up.
Dwane Kailey, MDT’s highways and engineering administrator, said Montana Rail Link modeling found that removal would increase the river flow enough to require new riverside piers for the railroad bridge just upstream. The piers have been in place since the bridge was opened in 1908.
The cost of replacing them, some $17 million, outstrips the scope and budget of the $15 million Bonner Bridges project. Roughly $12.5 million are available each year for all interstate projects in the Missoula district.
“We found out in working with Montana Rail Link that the cost of mitigation to that structure was well beyond what MDT could reasonably and feasibly participate in,” Kailey said, adding, “It’s not something I'm happy with at all.”
MDT and MRL have been working together for nearly a year to analyze impacts on the railroad bridge once the midstream piers are removed and to “allow Montana Rail Link time to figure out what mitigations were necessary,” Kailey said.
He said MDT learned of the findings less than a month ago.
The transportation department's agency partners include the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, and the Federal Highway Administration, as well as the state’s Natural Resource Damage Program, Department of Environmental Quality and Montana Fish, Wildlife and Parks.
“This was a shocker to them, and rightfully so,” Kailey said.
“We’re still trying to get our heads wrapped around it,” said Pat Saffel, regional fisheries manager for Montana FWP. “Obviously it’s a setback. It was kind of the last piece of the Milltown cleanup and restoration at the site that we thought needed to be done for the river, and for the fish and for river users. We’re looking at what the options are now.”
When he was Missoula County’s environmental health supervisor, Peter Nielsen participated in most of the planning and design of Milltown Dam’s removal and river restoration. He said at the time participants recognized the railroad bridge was the oldest and most solidly constructed span across the Blackfoot. It also didn’t have piers in the river channel, unlike the other three bridges.
Since then, the county’s Black Bridge pedestrian crossing and the state’s Highway 200 bridge have been rebuilt with single-span designs that don’t require piers in the river. But the Army Corps of Engineers rebuilt Interstate 90’s span with a new set of piers that both impeded river passage for floaters and fish and was prone to scour damage from the newly free-flowing Blackfoot.
“Those bridge piers and the way they did that was the one major disappointment many of us had with the whole Milltown project,” Nielsen said Tuesday. “Now we’re on the verge of getting rid of that one disappointment and we can’t get it done?”
Kailey said he doesn’t blame Montana Rail Link, a short-line partner of rail giant Burlington Northern Santa Fe.
“I wouldn’t say they’re playing hardball. I think they’re looking at it kind of like we did from the get-go,” he said. “They weren’t the ones who wanted the dam removed, they aren’t the ones fixing our structures. They’re innocent bystanders, in a way.”
MRL representatives were at Tuesday’s meeting. Spokesman Ross Lane said Tuesday evening he hadn’t had a chance to talk with “folks internally” and was withholding comment until he did.
When the issue of not removing the I-90 piers was first announced in late April, Lane said the railroad didn’t anticipate “any impact to our structure or to our operations. But if impacts were to come up or if we do anticipate impacts, we’ll continue to work with (MDT).”
From MDT’s perspective, the primary reason for replacing the Bonner I-90 bridges was to stabilize them.
“We had concerns of their long-term suitability and survivability” after the river piers were enlarged and fortified by the Army Corps of Engineers, Kailey said.
Failure of the bridge embankments and the highway they supported would “be a catastrophic event,” an MDT press release said.
“It was clear that a major river event could create a dangerous situation for the traveling public,” Kailey said. “We didn’t know when a river event would de-stabilize the bridges, but we did know that we needed to start working on a solution before river conditions forced us to be reactive instead of proactive.”
The Bonner Bridges project started last year with the replacement of the eastbound bridge. The westbound span has been removed this spring and will be completed this construction season. Kailey said removal of the top of the existing piers in the river bed to the 100-year flood level was built into the project. It was completed last weekend by a private contractor to help in construction of the new bridge.
Lane said in April the railroad bridge, while more than 110 years old, is subject to twice-a-year inspections by the Federal Railroad Administration. The piers are out of the river except in high water. Kailey said MDT was aware of mitigation efforts to stabilize the bridge due to the removal of Milltown Dam, but that mitigation was reduced when the larger interstate piers were put in place.
“We’re going to try to huddle with the agencies hopefully in the next month or so to see if we can come up with a solution and definitely at a lesser cost than what we’re looking at right now,” Kailey said. “I still have hope we’ll be able to achieve the ultimate goal. I just don’t have the options right now.”
"In the meantime, the piers are dangerous," Saffel said. "I don't think they're the best for fish passage and it’s not best for the river either. That’s the frustration.
"This was the icing on the cake, the cherry on top. We're just not getting it done as soon as we wanted to."
Reporter Rob Chaney contributed to this story.