A $100 million construction effort to address the sinking and tilting issues at the Millennium Tower, an infamous leaning luxury condo building in San Francisco’s SoMa District, has been substantially completed, according to the building’s homeowners association.
The association said that an intensive engineering project to drive 18 concrete piles into bedrock deep under the property at 301 Mission St. and shift a portion of the building’s load onto the new structures was finished earlier this month.
The completion is a major milestone in a yearslong saga involving multiple lawsuits, millions of dollars and an embarrassing error in the construction of one of the city’s top luxury high-rise developments.
“No one had ever done this for a 60-story structure and 18 million pounds of load,” said Ron Hamburger, a senior principal with Simpson Gumpertz & Heger, the firm charged with stabilizing the leaning tower.
Hamburger said his firm utilized a relatively common engineering technique called underpinning—though the sheer scale of the effort made the project unusual. The upgrade relieves stress on the soil underneath the building on its north and west sides, which had compressed under the structure’s weight and led to the sinking and tilting issues.
The fix underpins the more seriously impacted corner of the building, with the rest of the building expected to continue to settle and stabilize over time. The completion of maintenance access systems and the restoration of transit lines, sidewalks and landscaping on Fremont and Mission streets impacted by the construction effort will be wrapped up by August.
“We look forward to completing the remaining non-structural elements of the Perimeter Pile Upgrade in the coming months and are confident that the engineering upgrade will restore our building’s reputation and the value of condominiums while putting to rest to any lingering questions about the Tower’s stability,” Millennium Tower Homeowners Association President Howard Dickstein said in a statement.
Litigation brought by the homeowners association against the developer over the sinking and tilting issues was settled in 2020, which paved the way for the retrofit to move forward.
The solution is a scaled-down version of a fix originally proposed by Hamburger, which involved the use of 52 piles. When those piles began to be installed, however, it led to additional sinking of the building.
Work was paused for months in 2021 as the construction and engineering teams devised a pared-down version of the solution that was eventually implemented.
“It’s a great relief,” Hamburger said. “It’s been a challenging project both technically and also because it was so much in the public eye and every incident was widely reported coast to coast.”
The property was opened to residents in 2009 and is the tallest residential high-rise building in San Francisco. The 419 residential units were sold over the next four years, generating some $750 million in total sales revenue for developer Millennium Partners. Among the previous inhabitants of the tower were Kevin Durant, Joe Montana and late billionaire venture capitalist Thomas Perkins.
Hamburger said that outside of addressing the sinking and tilting issues, the project also made the structure more earthquake-resistant. As part of the building permit process imposed by San Francisco, the tower is subject to a 10-year monitoring plan with surveying and measurements periodically recorded and sent to city officials.