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Blatnik scrutiny continues in July

Inspection work will cause some lane closures on the Blatnik Bridge in July. (2016 file / Duluth News Tribune)

Drivers traveling between Duluth and Superior may notice lane restrictions on the Blatnik Bridge next month, part of a three-week inspection project to assess the condition of the well-traveled span.

The News Tribune learned earlier this year that the Blatnik Bridge, which carriers travelers over St. Louis Bay, is being targeted for replacement by state traffic engineers as soon as 2028.

Until then, the 55-year-old bridge will continue to undergo routine inspection and scheduled maintenance and repair.

The latest inspection project will begin July 10 on the Superior-bound side before moving over to the Duluth-bound lanes, the Minnesota Department of Transportation said in a news release Tuesday.

Superior-bound lanes will be restricted to one lane from 9 a.m. to 3 p.m. through about July 18, followed by a one-lane Duluth-bound restriction from July 19 to about July 27. All traffic lanes will be open from 3 p.m. to 9 a.m. daily.

Previous inspections have revealed thinning, corroded spots in the gusset plates — the thick slabs of steel used to connect parts of the bridge to one another. Gusset plate reinforcement efforts were undertaken in 2008, 2012 and 2016.

“Recent experience has shown that additional deterioration somewhere in the bridge will be identified during the inspection process,” said Duane Hill, district engineer based in MnDOT’s Duluth office. “It is hard to say where this will be. Usually the inspection process initiates additional analysis.”

The bridge already is scheduled to undergo $9.1 million in maintenance, repainting and any necessary repairs in 2020 as part of the four-year State Transportation Improvement Program adopted last September.

Hill has previously explained to the News Tribune that a 1990 rehabilitation of the Blatnik Bridge widened its approaches, but added a heavier deck and concrete railings that increased the deck load on the bridge.

The Blatnik is a truss bridge like the Interstate 35 Mississippi River Bridge that collapsed in Minneapolis in 2007. The Blatnik, and others like it, have undergone increased scrutiny in the years since that tragedy.

Each subsequent annual inspection of Blatnik has revealed new deterioration and corrosion between gussets and the steel they’re riveted to — and the acknowledgement that added deck load has been coupled with lost capacity in gusset plates.

“We can’t ignore it,” Hill told the News Tribune in April, adding that, “Every time we do an inspection we have to go back and do calculations to determine, ‘Do we still have the capacity?’ “

Were the bridge integrity ever to be found substantially deficient, it’s conceivable the four lanes of traffic on the bridge would permanently be reduced to single lanes in either direction until a replacement bridge were in place, Hill has explained.

Such contingencies have left Hill and others in the district office to start planning for the replacement of the Blatnik Bridge. He told the News Tribune earlier this year that an upcoming 2018 update of the district’s 10-year infrastructure plan would include plans for a replacement of the bridge as soon as 2028.

Such a project would run into the hundreds of millions of dollars. President Donald Trump’s proposed $1 trillion investment in infrastructure could conceivably include funding for such a project. But until a budget is enacted, Hill has said, “it is just a discussion.”

As far as the upcoming inspection goes, motorists will be restricted to 45 mph in work zones and 10-foot widths. Vehicles that exceed the width limit will be forced to use the Bong Bridge farther south along I-35. Inspection timelines are subject to change depending on weather conditions.