Sinking 58 story luxury apartment building in San Francisco tilting about 3 inches per year

The 58-story Millennium Tower luxury apartment building in San Francisco continued to sink and tilts about three inches per year, continuing to tilt even as construction was underway for the prevent it from doing so.

Last week a NBC Bay Area Report found that there was an average interval of one to four days between the removal of the soil and the installation of the concrete grout, which experts believe may have contributed to the increase in the tilt rate during construction.

Ron Hamburger, the repair engineer overseeing the project, said during a hearing before the San Francisco Board of Supervisors last week that the move to a new plan to install 18 steel piles in the bedrock below the foundation of the building was preferable to the previous plan. of 52 piles.

“The pile installation procedures were basically the prerogative of the contractor,” Hamburger told city supervisors, according to NBC Bay Area. “We didn’t tell them how to install piles. We specified that we needed piles of a given diameter and strength. And he basically did them as a design to install the piles he determined. the methods by which he would install them. “

Of the approximately 26 inches that the building currently slopes to the northwest, 10 inches would have occurred while the building was undergoing work over the past year, according to NBC Bay Area.

Hamburger said that based on current rates, it would be beneficial to minimize the impact of construction on building sag and tilt rates, and that 18 steel piles would be the best way to prevent it. to sink in or to bow more.

He also said that within a few years, under the current rate, the building could reach its theoretical limit of 40 inches of tilt, which would likely be the point where elevators and plumbing would stop functioning properly.

A view of the Millennium Tower on August 11, 2016 in San Francisco, California. The engineer responsible for repairing the building reported last week that it has been sagging and tilting at a rate of about three inches per year since construction began fixing it.
Justin Sullivan / Getty Images

“The building continues to sag at a rate of about half an inch per year and tilt at a rate of about three inches per year,” he told supervisors last week. “It does, whether we’re doing work on site or not. “

The Millennium Tower opened with a bang in 2009, and all 419 apartments were quickly sold. High profile residents included former San Francisco 49er Joe Montana, late venture capitalist Tom Perkins and former San Francisco Giants outfielder Hunter Pence.

But by 2016, the building had sunk 40 centimeters (16 inches) into the soft soil and landfill of San Francisco’s dense financial district. It was also hunched over, creating a 2 inch (5 cm) tilt at the base and a 6 inch (15 cm) tilt at the top. The residents sued the developer and designers.

The Associated Press contributed to this report.

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