Homeowners on Jan. 6 added another lawsuit to the list pending against Millennium Partners, developer of the 645-ft-tall Millennium Tower, located in San Francisco’s South-of-Market district. The suit alleges that, as early as 2009, the developers knew the $350-million condo building was sinking faster than expected.

At the same time, Jerry Dodson, a Tower resident and attorney, took similar action against the city of San Francisco and the Transbay Joint Powers Authority, which the developer blames for disturbing the soil while dewatering and digging the foundation for the adjacent Transbay Transit Center. The suit follows one by the city against the developer in November, alleging nondisclosure.

A group of attorneys calling themselves Millennium Towers Litigation Group, in August filed class-action suits against the developer and TJPA stating that “as a result of the sinking and tilting, some cracking and buckling, as well as water intrusion, have appeared in both individual units and common area.”

The 60-story tower has settled 16 in. and tilted 2 in. to the northwest since completion in 2009. The suit claims that, “over time, the tower most likely will sink an additional 8 in. to 15 in. into the landfill,” for a total of 31 in.

Ronald Hamburger, a structural engineer at Simpson, Gumpertz and Heger, hired by Millennium Partners, says the settling “has not compromised the building’s ability to resist strong earthquakes.”

Designer Handel Architects, working with structural engineer DeSimone & Partners, predicted it would settle a total of 6 in. over the life of the building. Neither returned calls for comments.

Webcor Builders—also the general contractor on the Transbay Transit Center—built the tower using a braced soil-cement slurry-wall system with 80-ft-deep soldier piles, supporting a reinforced-concrete slab, rather than using piles drilled down to bedrock, as is planned for the Millennium Partners’ newest 47-story tower a few blocks away.

TJPA spokesman Scott Boule refutes any link between the sinking and Transbay, adding that “a major portion of the Tower’s tilt and two-thirds of the excessive settlement occurred before the TJPA started any underground work on the Transit Center.”