He noted that engineers now propose relying on 42 piles, instead of the original 52, and could reduce that number further, based on the outcome of a key planned test of sinking a pile to bedrock in coming weeks.The Millennium Tower has sunk and tilted 18 inches toward the north-west since it was built in 2008. Hamburger stressed it’s not likely the building would tilt that much, given that the completed fix will arrest the settlement and even reverse some of the tilting. I would like to have a third set of eyes on that.” “That a building can tilt six and a half feet in the muck in an earthquake prone part of Northern California and not be a seismic or life safety hazard. “That sounds just ludicrous to me,” Peskin said at the hearing. Hamburger also said that 40-inch level was about maximum amount of the building could be expected to experience based on soil conditions, had no fix work ever been done.Īs to the 6.5-foot tilt level Hamburger now says the building could survive in a quake, San Francisco Supervisor Aaron Peskin - who convened the hearing after NBC Bay Area first reported about the fix problems - was dubious. “We’ve concluded that the building is still able to safely resist this maximum considered earthquake shaking with that amount of tilting,” he said, but indicated the “practical maximum” for tilting to maintain operations for the building’s elevators and plumbing systems is on the order of 40 inches, about half as much.Įven the lower limit, he said, provides a margin of nearly a foot more of additional tilting before the “practical maximum” is reached. He pointed to a new analysis showing the building could tilt just over six and half feet to the west and nearly three feet to the north - and still safely survive a massive quake. That’s roughly the same weekly rate that triggered a halt to the fix project back in August, before any measures were taken to limit ground loss or vibration.ĭuring his testimony, Hamburger downplayed the potential that current rates of tilting pose any issue – restating his belief that the fix was not even needed to preserve the building’s safety. “We have successfully mitigated the vibration,” Hamburger said, adding that crews also limited the amount of soil taken away from around the foundation in the revised digging process.īut data released this week – as work resumed with new installation of 100-foot long steel casings on Mission Street – show the high rise settled one tenth of an inch, triggering a quarter-inch of more tilt to the west. Hamburger said the building experienced negligible amount of settlement during a recent test conducted of new installation methods designed to limit two suspected factors – soil lost during digging and vibration during construction. While acknowledging he had concerns about the accelerated sinking and tilting soon after installation work began, Hamburger said engineers have since learned important lessons on ways to anchor the project with piles sunk to bedrock on two sides without adding to tilting and sinking. ![]() Sign up for NBC Bay Area’s Housing Deconstructed newsletter. Get a weekly recap of the latest San Francisco Bay Area housing news.
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