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Blue bridge falters again

The pedestrian lbridge across the Minnesota Slip was working again Monday morning after being out of commission again over the weekend, despite a recently completed $3 million overhaul that was supposed to make the structure more dependable. Bob King / rking@duluthnews.com

Despite undergoing a $3 million overhaul earlier this year, Duluth’s problem-plagued Minnesota Slip pedestrian lift bridge was again out of service last weekend, due to a failure in its wiring.

The structure, often referred to locally as “the blue bridge,” was disabled at about 9 a.m. Saturday and returned to service at about 10 a.m. Monday.

“We think we might have bad wire,” said Duncan Schwensohn, a senior engineer for the city of Duluth.

Plans now call for the complete replacement of a wiring harness that helps control the bridge’s brakes. The part has been ordered, and Schwensohn said he expects the work to take place over about a four-hour span Thursday night.

“It’s brand-new stuff. It’s not something that is supposed to break, but for some reason it is,” he said.

“It’s the wire that connects at a junction box on the tower with a counterweight, and it does move a bit, just because of the nature of the way that arm works. It should be well within the tolerance and the ability of the wire to move that much, but for some reason this is now the third wire we’ve had break in that harness. Fortunately, we have spares that are in there, and that’s what we did again this morning, is go to a spare,” Schwensohn said on Monday.

Schwensohn couldn’t say how long the temporary repair will last, however.

“This happened about two weeks ago, twice in one day. So we did that, and we were moving along OK. Now, it happened again on Saturday,”  he said, explaining the decision to replace the entire suspect wiring harness.

The total cost of the part is probably around $150, Schwensohn estimated, noting that it should be covered under warranty.

“But for this wiring harness, we’ve had zero other problems with the bridge for 3½ weeks now. Every problem we’ve had with the bridge we’ve now identified that, yup, it was caused by this wiring harness,” he said.

The bridge has been plagued with operational problems since it opened in 1991. In January, workers began to gut the bridge’s original winch-and-cable system and replace it with a more reliable rack-and-pinion mechanism at a total cost of about $3 million. Funding for the project will come from Duluth’s tourism tax collections in coming years.

The bridge spans the Minnesota Slip, providing pedestrians a direct connection between Canal Park and the Duluth Entertainment Convention Center. It lifts to provide access for marine traffic, including a fleet of charter fishing boats that dock in the slip.

Since the retrofitted bridge was returned to service shortly before Grandma’s Marathon, it has logged about 2,000 lifts, mostly without incident, Schwensohn said.

“There have been a number of iterations of troubleshooting and stuff on it, but I think we’re getting there,” he said.

As for how confident he felt that replacing the suspect wiring harness will put an end to the bridge’s performance issues, Schwensohn hedged a bit, however.

“I’ve learned not to make too many predictions by this point,” he said.

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