The Millenium Tower in downtown SF is sinking. Before it’s completing, the concrete skyscraper had already sunk 16 inches—building code allows for 6 inches of sinkage.
It’s construction is supported using 950 friction piles to evenly distribute the weight. This is a common technique, but the skyscraper far heavier than previously built.
Below the friction piles is an ice-age-old layer of mud known as Old Bay Clay. Possibly due to other construction in the area, Old Bay Clay is settling faster than anticipated which is causing the Millenium Tower to sink and lean to one side.
Read about What Really Happened at the Millenium Tower?