Millennium Tower Sinks More, Halting Repairs – By Bob Cronin (Newser) / Aug 26 2021
Construction stops on $100M project in San Francisco
(NEWSER) – The $100 million project to stop the Millennium Tower from sinking into the San Francisco earth was going fine—until the building sank another inch. Now the construction work has been stopped, SFGate reports, and luxury condo residents who have worried about this since 2016 will continue to stress. Since the work began in May, the building has added to its lean; it’s now tilting 5 inches toward Fremont Street, 25% more than before, per NBC Bay Area. The work was halted on Aug. 2, shortly after the project’s lead designer offered reassurance in late July that a half-inch settlement was nothing to worry about. The steps involved in the fix were:
- Drill holes 3 feet across along Mission Street.
- Line the holes with tubular, steel shafts.
- Sink smaller piles inside the steel shafts to bedrock, 250 feet deep.
- Connect the new foundation, under the sidewalk, to the original one.
The problem might be the steel shafts. Ronald Hamburger endorsed stopping the drilling for the shafts to see if that was compressing the soil; the 1-inch drop happened once 39 of the 52 piles had been installed. The foundation is built on sand instead of bedrock, but that’s true for other San Francisco towers that aren’t sinking. Hamburger said the work will stop for two to four weeks.
One structural engineer said it’s clear this fix isn’t going to work. “The way to solve the problem, as I see it, is not to continue going on the route that is showing you the wrong route, but to recoup, reconfigure the solution and do something that has a better chance of working,” Joshua Kardon said. Hamburger stands by the plan, saying that once the piles are in place and the weight shifted to them, the tower will “begin to recover some of the tilting,” he said. “There has been no material harm to the building and it remains fully safe.” (Read more Millennium Tower stories.)
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