Blatnik Bridge future unfolds as agencies begin working toward major project in 2028

The project to determine the future of the 60-year-old Blatnik Bridge kicked off this week as state transportation departments in Minnesota and Wisconsin outlined the next several years during an online public meeting Tuesday.

It’s not clear yet whether the bridge that carries Interstate 535 between Duluth and Superior will be replaced in its entirety, rehabilitated or a combination of both. It could remain on its existing alignment or a new one.

Preliminary design of what Minnesota and Wisconsin choose to do won’t be completed until between 2024 and 2026.

Costs won’t be known anytime soon, either. The Minnesota Department of Transportation has budgeted $200 million as a placeholder, a figure that would double with a Wisconsin contribution since the states share costs equally on all of their border bridges.

“In order to know what something costs you have to know what you’re going to build,” said Pat Huston, major projects and assistant district engineer for the Duluth MnDOT office, describing two to three years of tasks ahead before coming up with what he called “scoping-level costs.”

Until then, teams will be assessing what’s needed for a bridge that's 12 stories off the water surface of the St. Louis River estuary. Later this year, divers will go underwater to assess the condition of four piers buried into the bed of the St. Louis River. The bridge features 14 piers on the Minnesota side and 33 on Wisconsin's side, with 49 approach spans and three bridge spans located under the arching truss.

The bridge, which receives 33,000 vehicles per day, has critical components under attack by rust due to chlorides in the ice repellant used on the bridge in the winter.

“Gusset plates are big steel plates that hold together members of the steel truss, and you can’t (just) replace them,” he said.

The deteriorating condition has forced the removal of oversize commercial loads from using the bridge, and caused more frequent inspection and maintenance, including structural maintenance later this year.

“I want to emphasize the bridge is certainly safe,” Huston said. “If it wasn’t safe, we’d close it.”

Since the future could come in many forms, the News Tribune answered key questions raised at the meeting:

Do Duluth and Superior still require two major bridges, including the Bong Bridge to the south?

Huston said predecessors thought it was important to have two bridges. He cited freight efficiency and emergency response actions. During the 2018 Husky refinery fire, “we contemplated turning all these bridges with traffic towards Duluth,” he said.

Lane closures and bridge maintenance also benefit from having two bridges, Huston said. Without redundancy, some commercial loads would be forced to go to Grantsburg, Wisconsin, before crossing state lines.

How will residents know if the project is necessary?

Jessica Felix, WisDOT's Northwest Region deputy director, said the agencies were employing asset management practices in order “to be good stewards for the taxpayer.” They’re developing purpose-and-need for questions like, “Why do we need two bridges?” she said. They’re weighing what type of project is necessary against factors such as perpetual maintenance and repair, and costs associated with user delays and frequent lane closures.

“What is the smallest project that is at the lower end of a cost assessment, and what is the biggest project needed in the project area of the Blatnik?” Felix said, posing the types of evaluations being considered.

Online viewers of the presentation wondered if MnDOT and WisDOT have considered adding bicycle and pedestrian lanes on a rebuilt Blatnik Bridge, which is currently a four-lane, 8,000-foot span featuring neither?

Huston said it will be a consideration throughout planning, but that certain alternatives might make it difficult. For instance, if the project turns out to replace the main span and truss arch, but only to rehabilitate the approach spans, “that would make it difficult to accommodate bikes and pedestrians,” Huston said, because the bridge wouldn’t be getting any wider.

Is a tunnel under the river still a possibility?

One of the resident’s questions asked at the meeting was if the agencies had considered an “immersed twin-tube tunnel.”

Huston said “probably not likely,” but Felix gave the idea credence.

“Internally, we have posed the question,” Felix said. “With a tunnel you have to get under the shipping channel, and also where do you exit on the other side?”

She said the possibility will continue to be looked at among the other options.

What is the timeline for the project in its entirety?

Preliminary design will take place from 2024 to 2026, followed by final design in 2026-28, with construction from 2028 to 2031.

But agencies are urging public commitment now. Projects such as this have a long lead time, with key decisions being made in the next 12-24 months, Huston said.

"It's super important folks speak up now," he said.

Input now means no surprises later when the project is rolled out. Visit MnDOT's Blatnik Bridge page for more information.

This story was updated at 9 a.m., Jan. 20, to reset the placeholder budget at $200 million each for MnDOT and WisDOT. It was originally posted at 2:48 p.m., Jan. 13.