A newly built high-rise residential tower in San Francisco that's home to famed 49ers' quarterback Joe Montana and Giants' outfielder Hunter Pence is slowly sinking and shifting, and may ignite a court battle between residents and the city.

The 58-story Millennium Tower, located at 301 Mission Street just south of the city's financial district, was completed in 2008 and has sunk 16 inches and shifted 2 inches to the northwest since opening, according to a report issued by an independent consultant obtained by KTVU-TV.

The owners of the $350 million building told KTVU the construction next door of the Transbay Transit Center, a $4.5 billion project to serve as a hub of mass transit, has caused the ground movements.

P.J. Johnston, spokesman for Millennium Partners, which built the tower, told KTVU in a written statement that the transit center has been a negative impact on the luxury high-rise.

"All buildings settle over time," the statement said. "However, 301 Mission exists in a location where major underground construction work was subsequently performed by others, who were obligated to monitor and protect existing structures, and to mitigate any impacts of their work. 301 Mission has settled more than originally anticipated because it was affected by such subsequent construction by others."

The Millennium Tower Association, the building's home owners association, told the television station it has hired its own group of consultants to try and figure out what's going on.

"The Association has retained a number of engineering consultants to investigate the causes and long-term impact of these settlement conditions," the group said in a written statement. "Importantly, the Association has been assured that there are currently no short or long-term concerns with regard to building integrity or safety."

The HOA added that it is exploring its legal option and could pursue damages from several parties, including the developer, the original design professionals, the original contractors and the Transbay Joint Powers Authority.

In a response, the Transbay Joint Powers Authority said Monday that residents' claims against the TJPA are "misplaced; as demonstrated by data collected over more than seven years," adding that "full responsibility for the tilting and excessive settlement of the building lies with Millennium Partners, the developer of the Tower."

The transit authority also said the high-rise is made of concrete rather than steel, "resulting in a very heavy building. This heavy structure rests on layers of soft, compressible soil. The foundation of the Tower, however, consists only of a concrete slab supported by short piles that fail to reach the bedrock below. That foundation is inadequate to prevent settlement of a building with the weight of the Tower."

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