Drivers headed south on Interstate 35 in Duluth may get a single lane of traffic reopened before the emergency repair of the roadway is complete -- but not yet.
The repairs, which began with Monday's closure of the interstate between Lake Avenue and 21st Avenue West, are expected to take three to four weeks, according to chief district engineer Duane Hill of the Minnesota Department of Transportation. Hill said the single-lane opening could occur "partway through."
"We don't have the details down, and we don't know when that might happen," he said.
The bridge is supported by piers, which use steel pilings driven into the bedrock. The pilings that support the pier being repaired are severely corroded, Hill said, and because they mostly are buried in soil, they are harder to see. That's why they weren't discovered during the recently completed I-35 "megaproject." All of the piers are inspected, he said, but what's underground is difficult to inspect.
The pilings are in such poor condition that extra precautions have to be taken for workers. A "strongback" system will be used this week on the bridge deck to take the load off the weakened pier while repairs are done.
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Hill said water helped cause the corrosion of the pilings.
"We're concerned they don't have enough load-carrying capacity to transfer the loads from the bridge down to the bedrock," Hill said of the pilings, so the plan is to add strength to them by way of concrete collars.
Deterioration has been found on other southbound-side piers, but not to the extent of the one that led to the emergency repairs. Northbound traffic isn't affected because the bridges for each side are separate, Hill said, and again, deterioration isn't as severe.
The initial cost estimate of the project is $250,000, but Hill said it could be more or less.
"It's expensive because it's so urgent we have to work 24/7," he said.
The extent to which the detour will affect emergency response times isn't known, Duluth Police Administrative Sgt. Ryan Morris said.
"We do have the ability to use our emergency lights anytime," he said.
The detour isn't ideal, said Daniel Fanning, spokesman for the Mayor Don Ness' office, but the police department is working closely with MnDOT and now is directing traffic in some spots. In the evening, officers are directing traffic where West Superior and Michigan streets intersect near the M&H gas station, and they were expected to be downtown doing the same on Superior Street this weekend.
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"It works pretty well," Fanning said. "Otherwise those poor people get stuck."
He said the biggest concern was getting through this weekend with the Christmas City of the North parade and the opening of Bentleyville at Bayfront Park. Traffic light timing along the detour route has been adjusted to make vehicles flow more smoothly.
"After the initial rush, flow has been pretty steady," Fanning said. "Slow, but steady."
Detour changes made this week were done with knowledge gained during the I-35 construction project, Hill said.
Putting interstate traffic onto city streets does lead to congestion, "but we don't have a choice," he said, considering what was found and the safety implications.
"It's a bummer for traffic," he said, "but the positive is we caught this early, and if it had failed, the repair would be greater and cost much more."
