Two local engineers warned in a report to San Francisco officials back in 2019 that a proposed foundation retrofit for the Millennium Tower would make the troubled building tilt even more.
It’s a prediction that has come painfully true for residents of the luxury high-rise, who have learned the tower is now leaning 22 inches toward Fremont Street, shifting five of those inches since work on the “perimeter pile upgrade” project began in May.
“It was doomed from the beginning, and writing this report was like shooting fish in a barrel, for people who know what they’re doing,” said Larry Karp, a six decade veteran geotechnical engineer based in Orinda. He co-prepared the analysis at the request of the Board of Supervisors in July of 2019.
“The drop is precipitous,” Karp said after analyzing recent monitoring data on the project. “Twenty-six percent occurred this year -- that’s the total tilt of the building -- and the building has been there for years and years and years.”
“I think this solution that is being built now is not working,” said Josh Kardon, a 45-year veteran structural engineer in Berkeley who co-authored the analysis with Karp.
The engineers who came up with the foundation proposal – which relies on the installation of 52 piles at the base of the building to stop it from sinking on two sides – have not talked about what might be causing the new settlement during construction.
But documents obtained by NBC Bay Area’s Investigative Unit under the Public Records Act summarize what they told the city’s engineering design review panel in late July.
They suspected the digging for the 36-inch diameter, 100 foot long shafts needed to install the new support piles, caused the soil to shift and settle.
The shaking from the work likely caused the soil under the existing foundation piles to become compacted, they said, triggering the foundation to sink. Another suspected culprit was the removal and displacement of soil underneath and around the foundation during the drilling effort.
Karp and Kardon’s report had in fact warned about the inevitable damage from drilling a total of 52 new piles clustered around the base of the building, especially the accompanying loss of groundwater that would otherwise have continued to support the sinking foundation.
“You take the water out, you lose your buoyancy,” Karp said. “It’s like a ship, you take out the water, the ship falls.”
The engineers predicted in their analysis that all the digging and water loss would inflict “more irreparable damage to the building's substructure” and would make the existing tilting problem “worse.”
But the engineers said this week they don’t even know if anyone in the city ever read their report. “We were never contacted by anybody with the city,” Kardon said.
“The city left the review up to the building department,” Karp said.
It was just a month after Karp and Kardon submitted their report that the engineering design panel declared “the building is expected to have performance consistent with the stated design objectives’’ after the project was completed. “We see no reason to withhold approval,” the panel concluded, without mentioning any of the concerns raised by Karp and Kardon.
The Department of Building Inspection said Thursday that the engineering design review panel had, in fact, seen the two engineers’ report. The panel discussed the findings with the engineers doing the retrofit, the agency said, and was satisfied with their response.
This July, after data showed the tower tilted three more inches since construction started, the city-appointed review panel chairman Greg Deierlein told city officials his panel had “full confidence” in the Millennium team’s “ability to address this challenge.’’
“They call it a fix, they call it a repair – it’s none of those things,” Karp said about the now beleaguered project. The only true “fix,’’ he said, is to sink new piles through the existing foundation to bedrock and then jack it up to level it.
This week, in a statement to residents, the Millennium Tower Association said the foundation retrofit work will be on hold for now as engineers explore ways to “mitigate” the problem.