In a preview to a changed downtown Stillwater, the city's Lift Bridge will close to vehicle traffic Monday for a three-month rehabilitation project.

The shutdown will divert Wisconsin commuter traffic that became a principal argument favoring construction of a new St. Croix River bridge. When the four-lane bridge opens in Oak Park Heights in 2016 or 2017, the Lift Bridge will close permanently to traffic and become part of a new loop trail.

"We all love it when the bridge is closed," said Meg Brownson, who owns a downtown business, Alfresco Casual Living. "More residents will come down because they know they don't have to deal with the hassle of traffic. They know they won't get stuck in it. People also get curious to see what it's like."

Monday's shutdown, a project the Minnesota Department of Transportation (MnDOT) planned far in advance, didn't result from any danger to motorists, said Eric Rustad, the project construction engineer.

The $3.5 million rehabilitation will include repairing steel connections, replacing and repairing mechanical and electrical components, repairing concrete surfaces, repairing floor beams, painting portions of the bridge and replacing guardrails, curbs and gutters.

Repairs to the Lift Bridge began July 9, but most of it wasn't evident to motorists because the initial work was done beneath the bridge. The lift span now will be open on Sundays only from Oct. 15 through Nov. 5.

It will open again about Dec. 9, when the project is scheduled to end, MnDOT said.

Rustad said the new work will include repairing concrete on the pedestrian concourse to the west end of the bridge -- matching the historical appearance -- and replacing several weathered gusset plates. To do the latter, workers will place steel straps over beams to support the bridge's weight.

"That's one of the reasons we have to shut down the bridge," he said.

Another upgrade involves electrical and mechanical work on the lift house, where an operator raises and lowers the span that allows boats to pass beneath the bridge.

Work will be done by Edward Kraemer and Sons of Burnsville. The contractor will earn an incentive of $10,000 a day, up to $50,000, for work completed in advance of the scheduled completion date, Rustad said.

The 1931 state highway bridge, which connects Stillwater with St. Joseph Township, Wis., has closed dozens of times in the past five years for repairs and maintenance, for durations ranging from a few hours to several days.

The bridge was closed five times for major structural repairs, as many as 10 times for electrical repairs, more than 15 times for cable greasing and haul-rope adjustments, up to 10 times for minor structural repairs and 10 times for annual bridge inspections. Historically, the bridge often closes for a few days each spring when the St. Croix River reaches flood stage.

In 2005, the bridge closed for three months for a $5 million repair job. Traffic detoured to the Interstate 94 bridge, 5.6 miles to the south, and to the Hwy. 243 bridge at Osceola, Wis., 22 miles to the north.

Rustad said the Lift Bridge isn't in any danger of collapse, and the current work continues improvements made in 2005.

"This will definitely handle the traffic until the new bridge is built," he said.

Brownson said that while she regrets losing some of her Wisconsin customers while the bridge is closed, people will get a clear look at how Stillwater's fabled downtown will look once the new bridge opens.

The downtown has a new pedestrian plaza, a new rooftop restaurant and a second one coming, several new shops and restaurants, and now will see a major reduction in commuters jostling to cross the bridge, she said.

"It really is wonderful without all the traffic," Brownson said.

Kevin Giles • 651-925-5037 Twitter: @stribgiles