The "high bridge" between Duluth and Superior is officially on the clock for replacement.

The Blatnik Bridge was incorporated into a new 10-year plan by the Minnesota Department of Transportation, which is targeting replacement for 2028 at a cost share between $170 million and $230 million. The state of Wisconsin will be on the hook for the other half of the price tag, setting the current replacement cost at up to $460 million.

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"It's a big deal, and we've been thinking about it real hard," said MnDOT spokesman Kevin Gutknecht.

Opened in 1961 and known for its 120 feet of vertical clearance over the St. Louis River, the Blatnik Bridge appears as the last item on a long list of projects outlined in MnDOT's "District 1 10-year Capital Highway Investment Plan" published in February.

The News Tribune first reported the prospect of a Blatnik Bridge replacement in 2017, when it became apparent that each inspection was yielding new deterioration and corrosion between gusset plates and the steel they're riveted to.

"Ten years out is when we start identifying projects, and at four years we start applying money to it and scheduling it," Gutknecht said, describing MnDOT's planning process. "By appearing on our 10-year plan, what it's saying is, 'All right folks, this is coming up on the calendar.' "

Ironically, improvements to the Blatnik, including a 1990 rehabilitation that added a heavier deck and concrete railings, have hastened its deterioration by increasing the load on the bridge.

"We can't ignore it," district engineer Duane Hill said in 2017. "Every time we do an inspection we have to go back and do calculations to determine, 'Do we still have the capacity?' "

Hill oversees the District 1 office, based in Duluth, which encompasses oversight of state highways and bridges throughout Northeastern Minnesota. At the moment, he's limited in what he can say about Blatnik's future, because the state of Wisconsin will need to weigh in with approval before any planning or environmental study work can begin.

"That's the next step," Hill said. "We're waiting for Wisconsin Legislature approval."

The neighboring states share costs associated with the Blatnik and Bong bridges.

Functionally, MnDOT maintains the Blatnik and the Wisconsin Department of Transportation manages the Bong Bridge.

MnDOT's 10-year plan showed District 1 project costs from 2019 to 2027 fluctuating between $70 million and $180 million annually. The figure spikes in 2028 to $323 million with the inclusion of the Blatnik Bridge project.

At last check, it wasn't known if a new bridge would be built alongside the current Blatnik Bridge, or if it could be rebuilt incorporating structurally sound elements from the existing bridge. The pilings are among the things MnDOT will want to study going forward, Hill said.

"The proper way to do this will be to start with every possible idea and narrow it down," Hill said.

He half-jokingly referred to the idea that even a tunnel would be among the early replacement considerations - though one unlikely to be cost-effective, Hill admitted.

The Blatnik Bridge is a truss bridge, like the Interstate 35 Mississippi River Bridge that collapsed in Minneapolis in 2007, killing 13 people and injuring 145 more.

Increased scrutiny of bridges throughout the state followed that historic and tragic event.

MnDOT will proceed as scheduled with regular maintenance and inspections of the Blatnik Bridge. It will be the recipient of $9.1 million of maintenance, painting and repairs in 2020 - a follow-up to gusset plate reinforcement efforts from 2008, 2012 and 2016.

"It's going to be a fun project to work on," Hill said of replacing the 57-year-old bridge. "Hopefully, we can get started on having those discussions soon."