Scaled down from the original plan, the revised fix relies on 18 piles — instead of the initially proposed 52 — to anchor the 645-foot high-rise to bedrock on the two sides where it's leaned and tilted the most, helping both prevent future tilt and straighten the building.
San Francisco's own Leaning Tower of Pisa is currently leaning an astounding 29 inches at the top at the northwest corner. It's now sunk some 18 inches; it's rotated slightly; sidewalks that wrap the building continue to stress under its shifting weight and position. But in yet another effort to thwart the sinking and shift, San Francisco officials recently approved a plan that aims to stop the building's infamous tilt, all while helping it bend back to its original positioning.
As reported by NBC Bay Area, contracted engineers plan to install 18 piles to anchor the high-rise, which will both prevent more sinking and reverse the over two-foot tilt.
Initially, the plan included over 50 piles — but this was soon scrapped after the building was observed leaning even further, prompting a pause and rethink of the plan. Some engineers were skeptical and cautious of the plan's first iteration even before it began, citing that the complexity of the strategy would actually create opportunities for the building to shift further during the fix.
And that's exactly what happened.
However, this new 18-pile fix removes the complexity of the prior effort; it also will install the piles in a way that makes them act more like "adjustable cushions," rather than a rigid support structure. Nevertheless, geotechnical engineer Bob Pyke, who's been a longtime critic of the fix, notes that there are still risks involved.
Pyke fears that by excavating such a large portion of the ground, the fix will actually remove supportive bedrock where it’s needed most. “The last thing that you want to do to a tower — a building that is tilting in one direction — is digging 25 feet deep excavations along the sides of the building that are settling and tilting,” he told the news outlet.
The reduced number of piles — which, by proxy, allows more of the original bedrock to stay intact — will help mitigate this issue. Though, Pyke has argued it isn't necessarily a green light for the project to continue, arguing that city officials should still halt the project.
Nevertheless, engineers working on the scaled-down plan have said work at the corner of the tilting tower should be done by year’s end, which, if it proves successful, will afford a welcomed sigh of relief to residents who occupy Millennium Tower's 419 units.
Why? Because once the structure records 40 inches of tilt —an 11-inch increase from its current lean — the building’s elevator and life-safety systems would start to fail, creating a dangerous living environment for those who call the tower home.
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