The Millennium Tower in San Francisco now stands 1 inch straighter after a $100 million fix.
Eighteen concrete piles meant to steady the sinking and tilting luxury condominium highrise have been driven into bedrock at 301 Mission Street in South of Market, the San Francisco Chronicle reported.
Project engineer Ronald Hamburger, known in the industry as “Mr. Fix-It,” said the engineering upgrade had “succeeded” after the piles were sunk 275 feet below the street.
What had been the city’s poshest tower, completed in 2009, was revealed five years later to have sunk 18 inches and tilted 24 inches toward Fremont Street and eight inches toward Mission Street.
The 58-story tower’s tilt may have partially been caused by “dewatering” during the construction of the Transbay transit terminal next door. But most engineers say the piles of the heavy concrete tower’s foundation should have been driven all the way to bedrock.
The new perimeter pile system has shifted 18 million pounds off of the tower’s original foundation, relieving stress on soils compressed beneath the building. Each pile was designed to support 1 million pounds.
Hamburger said an analysis of the foundation shows the building recovered nearly 1 inch of tilt after the repair.
He expects the building will “continue to experience significant recovery of the tilting that has occurred following the final load transfer.”
“We will be monitoring it continually for the next 10 years,” Hamburger told the Chronicle.
The work has been overseen by the Department of Building Inspection and an independent panel of experts hired by the city. The tower’s HOA has contracted with a surveyor to monitor the building’s performance.
Millennium Tower Condo Association President Howard Dickstein said he is confident the “engineering upgrade will restore our building’s reputation and the value of condominiums while putting to rest any lingering questions about the tower’s stability.”
This summer, construction workers will restore the Muni lines, pour new sidewalks and plant new red maples, water gums and Brisbane boxes along Fremont and Mission streets.
The $350 million Millennium Tower was built by Mission Street Development, an affiliate of Millennium Partners, based in San Francisco. It was designed by Handel Architects, engineered by DeSimone Consulting Engineers and constructed by Webcor Builders.
The tilting building led to a class-action lawsuit between its residents and Millennium Partners, which was settled in 2018.
— Dana Bartholomew
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