A 58-story skyscraper in San Francisco is sinking - now the city is suing its developers

Jeff Chiu/AP

City Attorney Dennis Herrera gestures while speaking about a lawsuit filed against developers of the Millennium Tower at a news conference in San Francisco on Nov. 3rd.

The San Francisco City Attorney's office put Millennium Tower in its crosshairs on November 3rd when it announced it's suing the sinking skyscraper's developers.

Millennium Tower, a residential skyscraper, rises 58 stories above San Francisco's Financial District. Since the luxury condo building opened doors in 2009, the building has sunk 16 inches and tilted two inches.

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The city attorney's office alleges the group behind the tower, Millennium Partners, failed to disclose that it was sinking to buyers as early as 2009, NBC Bay Area's Jax Van Derbeken and Jodi Hernandez reported. Millennium Tower contains some 400 multimillion-dollar condos.

The lawsuit is just the latest in a string of attempts to figure out what led to the development and sinking of the $350 million residential high-rise. The city attorney's office issued subpoenas to Millennium Partners in September in a hunt for answers.

While the building is not currently at risk of keeling over, residents are angry that their property values are plummeting. All told, the building could sink over 30 inches, according to CBS.

AP/Eric Risberg

Jerry Dodson and his wife Pat stand inside their home on the 42nd floor of the Millennium Tower in San Francisco.

According to NBC Bay Area, "Under California law, owners, or developers are obligated to notify buyers of any problems or building defects and can be prosecuted under civil law for withholding the information," The outlet talked to multiple tenants who said they received no notice.

City Attorney Dennis Herrera called the situation "every homeowner's worse nightmare."

The issue first came to light in 2010, when the developers of a neighboring construction project hired a consultant to find out how excavation could affect Millennium Tower. The Transbay Joint Powers Authority broke ground on a new transportation hub, the Transbay Transit Center, in 2010. Its development includes a 60-foot hole for a train tunnel and an underground buttress between Millennium Tower and the transit site.

Millennium Partners argues that construction on the Transbay Transit Center is to blame for any sinking or tilting, while the Transbay Joint Powers Authority maintains it is not at fault.

Google Earth; Melia Robinson/Business Insider

In September, San Francisco Supervisor Aaron Peskin raised suspicion that Millennium Partners and city officials knew the building might sink before anyone moved in.

Peskin, who served on the Board of Supervisors from 2005 to 2009 and was reelected last year, uncovered documents from 2009 allegedly showing the city's building inspection department expressed concerns about the tower's unusual settling to its developers, just before the tower was supposed to open its doors. Six months later, tenants were approved for move-in.

Millennium Tower was built on packed sand instead of being anchored to bedrock. The design, however, is not that unusual among some of the city's best known skyscrapers.