I find everything about this building hilarious in a dark, horrifying engineering and bureaucratic sense.
Part of what started this: a NYC architect and NYC construction contractor came to SF for the first time in their corporate and professional experiences and decided to build a building, cutting corners on standard local construction standards, regulations and laws because they found loopholes in all three and they thought it would save a lot of money.
So they did NOT do any of the standard "ground work" (sic) to prepare the foundation as every other skyscraper in SF and California normally does.
The normal process is to drive piles down to bedrock. They didn't do this. They put piles into sand. SF is primarily all sand sitting atop of deeper rocks but some of that rock is very deep below the surface. In that particular area, the rock is quite deep (all the hills you see like Nob Hill, Coit Tower, etc. are the rocky high spots surrounded by deep valleys covered with sand from ancient water inlets).
Local construction companies know all about this geophysical reality. Apparently these NYC companies did not and had zero engineering/professional intuition about the nature of earthquakes and construction in California.
Because of this the building started to both sink and tilt. And honestly, ANYTHING short of tearing the building down and starting again is at best a bandaid fix that may or may not work for long. This is a legendary FU.
And you are seeing these New Yorkers trying to lawyer their way out of the liability they will inevitably face by doing things on-the-cheap and half-assed. Here they got caught doing just that!
My late father was a big name in construction in the SF Bay Area. He was involved with most skyscrapers built in SF from 1970-1985 which includes the WF tower, Hyatt-Regency, Embarcadero Center building complex, etc. At that time I was a kid and he'd "take me to work" at these sites while under construction and I got to talk to construction workers, structural engineers, etc. about how it was done. It fascinated me enough to go into engineering professionally though the later PC and semiconductor revolution of the 1970s drove me to an EE degree instead of ME/CivE.
It's unlikely to come out in court, but my father worked on the investigation and it became clear both the engineer and architect had e-mail corresponding showing they planned to blame various 3rd parties for several secondary effects of the tower's sinking, including cracking caused by the tower pushing on the exterior wall of the underground garage causing water intrusion.
There was so much corruption here, and my personal belief is the city was paid off to facilitate the settlement.
> The normal process is to drive piles down to bedrock.
Citation needed. Friction piles are quite normal too. I've lived in buildings in SoMa that used friction piles and none of them were tilting as much as this building. There's something more going on here (design or construction flaws), but it isn't as simple as "friction piles bad".
The piles they used for the Millennium Tower were the same length—80 feet[0]—as those they'd use for a 22-story highrise on, say, 6th St. Millennium Tower is 58 stories and right on the water.
You can imagine why they floated that idea but the site is surrounded by other buildings which survived intact, including a 100-year-old unreinforced brick building.
In other parts of the world, far taller buildings are constructed using friction piles[1].
Again, friction piles are not unusual at all. Drilling into bedrock happens in parts of Manhattan[2] , but that's because the bedrock is generally close to the surface.
Whatever's going on with Millennium Tower, it's not "friction piles bad".
I am just a layman when it comes to this kind of thing, but I notice that many articles online claim that variable bedrock depth explains why Manhattan's skyscrapers come in two distinct clumps. If this is true, then it seems strange to me that NYC professionals would ignore bedrock depth in SF out of pure ignorance.
I just found a blog where the author explains that its actually a myth and mostly coincidental. The reason the skyscrapers are in midtown and downtown was due to historical and economic reasons. Those were the dense wealthy business areas where people wanted and needed to build taller buildings and it turned out they also had the shallowest bedrock.
They also said the shallow bedrock didn't force them to stay there. It isn't much of a problem to drill deeper and a number of early skyscrapers were built elsewhere... It's just that people wanted their skyscrapers to be in midtown and downtown.
Aren’t piles that don’t extend to bedrock common in many cities? They are ubiquitous in Dubai, and are even used in the Burj Khalifa. There’s a way to do it right. One confounding factor with this SF tower is the later construction of the Transbay Center nearby, which I read may have destabilized soils nearby through dewatering. Apparently their process reduced the water table by 20 feet (https://sf.curbed.com/2016/9/20/12991602/millennium-tower-si...), which would change the bearing capacity of soils and affect friction piles.
One oddity is that the city’s inspectors and departments approved all of this - their surveys, geological analyses, foundation design, building design, and so on. That work spanned many contractors. SF is a city with many controls to prevent this kind of situations, so it is unclear as yet where all the faults lies.
Part of what started this: a NYC architect and NYC construction contractor came to SF for the first time in their corporate and professional experiences and decided to build a building, cutting corners on standard local construction standards, regulations and laws because they found loopholes in all three and they thought it would save a lot of money.
So they did NOT do any of the standard "ground work" (sic) to prepare the foundation as every other skyscraper in SF and California normally does.
The normal process is to drive piles down to bedrock. They didn't do this. They put piles into sand. SF is primarily all sand sitting atop of deeper rocks but some of that rock is very deep below the surface. In that particular area, the rock is quite deep (all the hills you see like Nob Hill, Coit Tower, etc. are the rocky high spots surrounded by deep valleys covered with sand from ancient water inlets).
Local construction companies know all about this geophysical reality. Apparently these NYC companies did not and had zero engineering/professional intuition about the nature of earthquakes and construction in California.
Because of this the building started to both sink and tilt. And honestly, ANYTHING short of tearing the building down and starting again is at best a bandaid fix that may or may not work for long. This is a legendary FU.
And you are seeing these New Yorkers trying to lawyer their way out of the liability they will inevitably face by doing things on-the-cheap and half-assed. Here they got caught doing just that!
My late father was a big name in construction in the SF Bay Area. He was involved with most skyscrapers built in SF from 1970-1985 which includes the WF tower, Hyatt-Regency, Embarcadero Center building complex, etc. At that time I was a kid and he'd "take me to work" at these sites while under construction and I got to talk to construction workers, structural engineers, etc. about how it was done. It fascinated me enough to go into engineering professionally though the later PC and semiconductor revolution of the 1970s drove me to an EE degree instead of ME/CivE.