More bad news for San Francisco’s tilting tower
An underground wall could prove to be a serious obstacle to reversing the tilt of the Millennium Tower, a major goal of the US$100 million fix for the troubled 58-story San Francisco high rise.
Over the past six months, repair work has caused the building to tilt an additional 2.75 inches, with veteran Geotechnical Engineer Rob Pyke saying, “there is no question that the fixes made things worse.”
Mr. Pyke said that the tilting was predictable because part of the recent fix required digging to make room for an underground support wall that was discovered in 2021.
He went on to say that the digging would no doubt have displaced dirt that was acting as a buttress against the tower’s foundation, resisting the pressure as the tower leans to the west. Mr. Pyke also said that a similar thing happened in 2021, when crews dug deep underground to install support piles down to the bedrock. “That ground loss simply allowed the building to push outward, from the westward direction,” he said.
As a result of the recently discovered accelerated tilt, engineers working to fix the problem now say they are changing their strategy. Rather than try and sure up two sides of the foundation simultaneously, they are going to partially anchor just one quarter to the piles already installed.
With this year’s tilting, the tower is now tilting 29 inches at the northwest corner. Concerningly, engineers warn that the towers life safety systems, such as elevators and sewage lines, could stop working if the tilt reaches 40 inches. Here’s hoping the latest fixing solution stops the tilt!