San Francisco’s troubled Millennium Tower, which has continued to sink despite multimillion-dollar efforts to correct it, has yet developed another problem.
The luxury tower, popular among star athletes and retired Google employees before the tilting issues were widely publicized, has sunk 18in since construction was completed in 2009, and has a 26in tilt at the top. Now, the engineer overseeing the retrofit of the tower has said the movement caused the formation of a one-inch gap between the building and a smaller 12-storey adjacent structure.
“Given the present westward tilt of the building, about 24 inches as measured at the roof, the gap between the two buildings in the east-west direction has widened by about 1 inch[2.5cm],” the project engineer, Ron Hamburger, said in a statement to NBC Bay Area.
The Millennium Tower uses an underground parking garage housed within the smaller structure.
Despite the gap, engineers “determined that the building is not at risk due to this movement, or any movement likely to occur before construction completion”, Hamburger said, and the gap is not expected to get worse. He has previously warned that the tower’s elevators and plumbing may no longer work if sinking continues at its current rate.
Engineers are working on a retrofit of the building and plan to install 18 steel piles to bedrock, relieving pressure on the foundation, to stop further tilting and sinking as well as possibly reverse some of the movement.
“Once the voluntary upgrade is complete, further settlement of the building at the northwest corner will be arrested, some rebound will occur, and slight additional settlement of the rest of the main tower will act to reverse the tilting that has occurred and close the gap between the elevator thresholds in the adjacent podium building that connects the main tower and mid-rise together,” Hamburger told the San Francisco Chronicle.
Previous efforts to reinforce the foundation of the downtown tower came to a halt last summer, when engineers found the building had sunk an inch in the months since the attempted repairs started.