Millennium Tower now partially rests on Bedrock

San Francisco’s troubled high-rise Millennium Tower is now partially supported on one side by piles sunk into rock, which should ensure the $100 million project is completed without further lowering and tilting the building, a lead troubleshooting engineer tells residents.

The high-rise is currently leaning more than 29 inches in the northwest corner, with about a third of that leaning occurring since construction work began in 2021 to stabilize the building.

In an email to the building’s residents Saturday, lead renovation engineer Ron Hamburger said the building’s three million pounds of weight along the Mission Street side are supported by six piles that reach the cliff on the north side. That’s about half the load the Mission Street piles will eventually carry, he says.

The goal for now, he said, is to stabilize the north side of the tower so crews can dig much more to expand the foundation along the west side of the structure along Fremont Street. The building will eventually be tied to 18 piles already embedded in the rock, six on Mission and the rest on Fremont Street.

“The purpose of this first phase of loading,” Hamburger explained in an email to residents, “is to stabilize the building during the remainder of construction, including excavation along Fremont Street to tie the 12 piles already installed last year to the rock. ”

Hamburger told residents that he expects that simply removing the weight from the building along the Mission will “substantially slow, if not stop” further settlement, adding that preliminary data shows the early phase “has been successful and exceeded the engineering team’s forecasts.”

Once the foundation expansion work along Fremont is complete, crews will transfer 15 million pounds of weight to a dozen piles along the tower’s west side, Hamburger said.

Computer models designed to predict behavior suggest that if all goes according to plan, the job will compensate for about 4.5 inches of slope in the northwest corner.

But Harry Poulos, a world-renowned high-rise expert, points out that even if the renovation works as planned, it will make up for less than half of the 10-inch slope caused by the renovation.

“I don’t think there’s any reason to be optimistic here,” Poulos said, adding: “Because it’s like a medical procedure where you think you’re treating a patient and you’re actually doing something wrong and you’re actually making it worse for him.”

But Hamburger emphasizes that the main goal of the project has always been the final stabilization of the structure. Compensating for tilt, he said, was a secondary goal.

The project is currently expected to be completed by September of this year, says Hamburger.