A $350 million skyscraper in San Francisco is tilting and sinking — here's why

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San Francisco seems to have its own leaning tower.

It's called the Millennium Tower, and according to the San Francisco Chronicle, it has sunk 16 inches into the ground and tilted two inches to the northwest since its completion in 2008.

The 58-story luxury skyscraper is home to many millionaires and billionaires, including famous quarterback Joe Montana and several leading Silicon Valley investors. 

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Though the tower houses some of the most expensive apartments in the city — condo prices range from $1.6 million to $10 million — it has a few critical design flaws. As The Chronicle notes, the skyscraper's frame uses huge slabs of concrete instead of steel, and the former is much heavier than the latter.

Its location is also not ideal — the $350 million tower is built on top of muddy land near the bay's shoreline. The construction crew filled mud holes on the site with gravel or cement, but the work hasn't held up.

The building's owners blame the neighboring bus and rail center that's set to be completed in 2017, however. They say that the 2010 excavation of the site — a half-mile tunnel that's 60 feet underground — caused the Millennium Tower to sink.

While the sinking and tilting doesn't pose any immediate safety risk for the residents, it may be a problem for future buyers and investors. Since San Francisco is susceptible to earthquakes, people likely won't want to pay to live in a building that's not upright. 

Civil engineers are working on a possible solution, however, which would involve pumping cement under the building to stabilize it. But the fix — like the price of the condos — won't be cheap.

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