The U.S. Bank Center is seen in this file photo. Credit: Mike De Sisti

Land and Space Journal Sentinel business reporter Tom Daykin talks about commercial real estate and development. SHARE

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Downtown's U.S. Bank Center, Milwaukee's tallest office tower, has temporarily closed its parking structure after a slight movement was caused by a neighboring construction project.

U.S. Bank, which owns the building, 777 E. Wisconsin Ave., sent an email late Monday night to its tenants and employees announcing the closure. The parking structure is south of the office tower, between E. Michigan and E. Clybourn streets, east of N. Van Buren St.

That notice didn't explain why the structure was suddenly closed, other than saying U.S. Bank "received a differing engineering opinion regarding the Parking Structure which has required this step to be taken."

The closing was the result of excavation work at the neighboring site of the 17-story 833 East office tower, which is being built by Irgens Development Partners LLC. That project started this summer in the 800 block of E. Michigan St.

A slight movement — no more than 2 inches — was detected at one of the parking structure's north walls on Sept. 16, said Mark Irgens, the firm's president. The firm's general contractor was monitoring possible effects from the excavation work on adjacent structures, a routine part of any major construction project, he said.

After that movement was detected, the firm contacted U.S. Bank, which had engineers inspect the parking structure, Irgens said Tuesday. That inspection concluded "it was okay to occupy the deck," but some of the parking spaces near the north wall were closed as a precautionary move, he said.

Also, an earth berm was created adjacent to the north wall to brace it as a temporary measure, Irgens said.

On Friday night, an engineering firm involved in the parking deck's construction reversed its opinion, and said it was concerned about the structural integrity, Irgens said.

U.S. Bank immediately closed the parking deck. However, that engineering firm indicated if an additional bracing system was added, the parking deck could reopen, Irgens said.

That system was installed Saturday and Sunday, and the parking structure was again cleared for use except for a limited area at the north wall, Irgens said. That area covers about 100 spaces on five levels, he said.

The parking structure was open on Monday.

But, at around 6 p.m., U.S. Bank received a letter from a contractor involved in the parking structure's original construction, saying it was concerned about the structure until a further investigation could be conducted, Irgens said.

So, the parking structure was again closed until that inspection is completed, he said.

Since a week ago, no additional movement has been detected at the parking structure, Irgens said. He said excavation work for the office tower was suspended Tuesday, but is to resume Wednesday on a portion of the construction site that isn't near the parking structure.

U.S. Bank, in a statement, said it is “working closely with the developer and contractor of the adjacent building and engineers to assure the soundness of our parking structure to allow it to re-open as soon as possible.”

The city Department of Neighborhood Services, which oversees building inspections, learned about the situation on Sept. 18, and ordered an engineering analysis and solution to restore the integrity of the parking structure's wall, said Todd Weiler, department spokesman.

U.S. Bank made the decision on its own to close the parking structure until the safety concerns are resolved, Weiler said.

Tenants and employees from the 42-story U.S. Bank Center are being provided free alternate parking at a Maier Festival Park parking lot, 651 E. Polk St. The bank is providing a shuttle service between the lot and the office tower.

The six-level parking structure, with around 1,000 spaces, was built in 2009 and 2010 to replace an older structure that was demolished.