Standing 645 ft tall and boasting 58 stories, the luxury residential skyscraper known as Millennium Tower in San Francisco has engineers scrambling for a solution. The building has been leaning 3 inches each year and slowly sinking to the ground. Now at 26 inches off center, stability is the main goal from the structural engineer tackling the building’s foundation.

Located in the heart of San Francisco’s financial district, Millennium Tower started to settle and tilt more than anticipated in 2016. Earlier efforts were made to halt sinking and tilting, but matters seemed to get worse and all work was called off in 2021 while a better plan was formulated. Ronald O. Hamburger is the engineer pitching his proposal to solve the building’s north west leaning and foundation sinking problem.

The first attempt caused more foundation settling

November 2020 saw $100 million go toward the perimeter pile upgrade repair project. 52 pilings would be sunk to the bedrock and tied into the existing foundation to put a break on the sinking. A year later, monitoring of the foundation showed Millennium Tower had dropped an additional inch with 39 of the planned 52 piles in place. In September of 2021, Millennium Tower management was told to cease any repair work by the city until an updated approach was approved.

Pile proposal illustration. Source: SGH

Hamburger’s proposal will keep 18 of the original 52 piles; less soil being removed for the piles means less vibration and stress on the building. The plan will be solidified at the end of February before moving forward. Currently, the building has 419 luxury condos and is home to International Smoke, a renowned woodfire restaurant. Ronald O. Hamburger is a senior engineer with Simpson Gumpertz & Heger.