San Francisco's Millennium Tower, completed in 2009 and famed for being the home to some high-profile locals like Joe Montana and Hunter Pence, has apparently sunk well over a foot sixteen inches into the earth in just eight years. And as the Chronicle's Matier and Ross report, the 58-story tower has also tilted two inches to the northwest according to an independent consultant.
The sinking and tilting do not, surprisingly, represent a significant safety concern for residents, however the consultant called in is Professor Greg Deierlein of Stanford's Earthquake Engineering Center.
While some ground settling is to be expected with large buildings, sixteen inches is more than what would be considered normal, according to Deierlein. He points to the 18-year-old Petronas Towers in Malaysia, saying they have sunk less than three inches, and tilted less than half an inch.
It seems likely that the excess settling was caused by the fact that the building's foundation, including 80-foot pilings, are in mud fill just off what was the original shoreline of the city, combined with the fact that the developer, Millennium Partners, opted for concrete construction rather than lighter weight steel.
Millennium Partners, however, may be seeking a big payday from the Transbay Joint Powers Authority, and in turn taxpayers, because they're shifting blame for tower's sinking and tilting to the large hole that was excavated next door for the Transbay Transit Center. Construction on that began in 2010 and included underground buttressing for Millennium Tower and the trouble with this theory is that Deierlein's initial report found that the tower had already sunk 10 inches by 2010.
Deierlein suggests that residents should be concerned for their investment, as tilting can cause elevators to malfunction, and the settling can cause cracks to appear inside the building. This is a bit ironic given the fanfare with which the tower went up, and the high price of its units it was even named to Worth magazine's list of the world's top ten residences in 2012.
No word on when this thing turns into our very own leaning tower and they can start charging admission.