Sinking and tilting of San Francisco’s Millennium Tower has led things to courts

In 2016, it became public that the 58–story skyscraper - the biggest residential building of San Francisco - was both sinking and tilting at non-acceptable rates. Blaming the building's inadequate foundation, the city of San Francisco and some of the homeowners have filed lawsuits against the scyscraper's developers, leading to one of the largest real estate litigations in the history of the U.S.

Built in 2009, Millennium Tower has already settled 16 inches, much more than the 4-6 inches that engineers had anticipated over the life of the project. The building also displays a two–inch northwest tilt at the base and an approximate six–inch tilt at the top. And it is continuing to sink at a rate of 2 inches per year, according to satellite imagery of the European Space Agency, which examined the building from orbit.

Millennium Tower is founded on a concrete slab built on 60–90 feet (18-27m) deep concrete friction piles driven into mudfill and sand; a quite poor ground type for supporting such structures. A number of other buildings in this part of San Francisco demanded the use of end-bearing piles, which load directly onto bedrock. If end-bearing piles were used for the Millennium Tower, they would have needed to be approximately 200 feet (60m) deep to bear onto bedrock, thus up to three times longer than the existing piling solution used. Transbay Joint Powers Authority (San Francisco's agency) blames the building's developers (Millennium Partners) for the problem, stating that the chosen foundation solution is inappropriate for such structures laying onto unstable mudfills.

On the other hand, Millennium Partners blames the sinking problem on the Transbay Joint Powers Authority (TJPA), stating that sinking was caused by pumping groundwater during the construction of the nearby Transbay Transit Center. However, the sinking problem had reportedly started before the initiation of the Transbay construction.

In a recent testimony last week, Jack Moehle, a professor of structural engineering at UC Berkeley, whom Millennium Partners had hired to conduct an independent peer review of the building design while it was being entitled, stated that he only reviewed the building's structural design; the foundation solution was not of his responsibility. However, no geotechnical engineer was ever hired by the developers of the building to do a geotechnical assessment.

A new city inspection at the beginning of 2017 has concluded that the building is still safe for occupancy, despite evidence that the skyscraper's uneven settlement has caused some strain on the building's foundation and electrical systems.