Dive Brief:

• The developer of the Millennium Tower, a 58-story luxury residential high-rise in San Francisco, is being sued by a group of 20 homeowners following allegations that it knew the building was sinking faster than expected and failed to disclose the issue to buyers, according to SFGate.

• The claim lodged alleges that developer Millennium Partners knew in early 2009, before residents had moved in, that the tower had sunk 8.3 inches — compared to the 1 to 2 inches that project engineers estimated it would settle once the tower was complete.

• Millennium Tower unit owners also filed the lawsuit against the San Francisco Department of Building Inspection, the city attorney and the Transbay Joint Powers Authority. They claim the city agencies signed a confidentiality agreement with the developer to keep unit owners in the dark about the tower's structural problems. 

Dive Insight:

The move by homeowners to launch legal action against Millennium Partners and the city follows a decision by San Francisco City Attorney Dennis Herrera to file a civil suit against the developer in November amid claims that property managers failed to disclose known structural issues to buyers.

Officials have said the tower has already settled 16 inches and leans 2 inches at the base to the northeast compared to the projected 4 to 6 inches over its lifespan. It is estimated that the tower could eventually sink as much as 30 inches.

Developer Millennium Partners said in September that the tower's instability was caused by dewatering that occurred during construction of a $4.5 billion transit center next door. However, transit officials refuted that claim and said the issue was the result of foundation piles being 100 feet or more short of stabilizing bedrock.

In October, it was reported that Millennium Partners redesigned the foundation of another of their San Francisco high-rises under construction following the controversy. 

After the sinking situation became publicized, Mayor Ed Lee requested that San Francisco officials move to make building codes more strict in the city, implement an independent review process for buildings in the city and alter San Francisco's earthquake safety plans for the next 30 years to ensure that high-rises are safe.