The sinking and tilting Millennium Tower would safely survive a major earthquake at the moment but should be re-evaluated in the future, a city-appointed panel concluded in a report issued Monday.
“To an extent consistent with the scope of our review, our professional opinion is that the foundation settlement experienced by the tower has not appreciatively affected the safety of the building at this time,” the three-member expert panel wrote in the report released by San Francisco officials.
“However, because the structure is still settling, continued monitoring and further study of the cause of the settlements is recommended to allow a better understanding of maximum future settlements.”
The panel's findings were not received well by some tower residents.
“Consequently, it’s not worth very much at all,” said engineer and lawyer Jerry Dodson. “It’s a snapshot in time and has no assurances about the future performance of the building.”
The report notes that as of July, the tower has settled 17 inches at its northwest corner and is leaning 14 inches toward Fremont Street and the Salesforce building and more than 6 inches toward Mission Street.
“This settlement has not occurred uniformly, causing a distortion and tilting of the mat foundation, along with a lean (out-of-plumbness) of the building,” the panel wrote in its report, noting that the building is now leaning twice as much as engineers consider acceptable for high rises.
The panel, headed by Stanford professor Greg Deierlein, was charged with reviewing the work of Ronald Hamburger, a Millennium-hired engineer who wrote several reports declaring the building safe.
Deierlein’s panel backed Hamburger’s conclusion that the foundation problems have “not compromised the building’s ability to resist strong earthquakes and have not had a significant effect on the building’s safety.”
Dodson says that he's not assured because the Deierlein report is merely analysis of Hamburger’s findings and did not involve independent modeling or analysis. Also, he said, Deierlein’s panel accepted Hamburger’s refusal to analyze the future impact of settlement on the structure’s safety.
“They shouldn’t have accepted that. They should have pushed back and said, we want to know what the future of this building is, and they didn’t,” Dodson said.
Deierlein’s panel delved into problems found during NBC Bay Area’s investigation into the building, including that a Millennium consulting engineer’s concerns about “outriggers,” giant steel reinforced concrete structures that tie the tower’s core to its outer walls.
Hamburger acknowledged that advanced computer modeling confirmed that outriggers would fail in a major quake. But, he said, the building would still handle a quake without collapse, as required by code.
However, two independent experts have told NBC Bay Area, that the failure of the outriggers could mean that the building would be red-tagged as unsafe.
Deierlein’s panel also mentioned a problem identified by NBC Bay Area stemming from unexplained odors plaguing several condo units. Outside engineers say the odors are getting in via previously unidentified gaps around the holes drilled in concrete for ducts, pipes and electrical lines.
The unsealed holes, fire experts told NBC Bay Area, could allow fires to spread more quickly. At least one resident, Paula Pretlow, has since filed a complaint about the apparent fire safety risk to city building inspectors.
Without elaborating, Deierlein’s report acknowledged “a few issues that either have been or are in the process of being addressed."