That’s interesting. Is the financial district built on top of fill, by any chance?
Not by chance-—they planned it that way. The area used to be a small boat harbor that gradually degenerated into a landfill. The buildings there are on pilings. In the case of this tower the claim is they just got tired of sinking piles and finally convinced themselves they had enough “friction” in the mud. They are nowhere near bedrock. Investment hint: don’t buy into this one.
It’s kind of a layer cake. Top layer is fill, then a layer of something called “old bay clay” and then a layer of the “Colma formation”. Finally get down to a bedrock formation. The fix, currently under construction is steel micropiles driven to bedrock.
The original design, which is the same for all of the tall buildings in the area was friction piles driven into the Colma formation.
No but the bay tides do cause erosion under neath some of the buildings
Much of that area is built on fill. When I worked in the area and watched construction of skyscrapers, they often had to stop work when old ships were found in the fill. What was left of the ships was carted off to museums. In the 1800's, creeks and streams went far inland and the bay shore also extended inland. During and after the gold rush days, this watery land was filled with debris from abandoned ships. Up until the 1960's, bay marshland was filled in with garbage and debris until environmental laws put a stop to it. Much of the financial district is built on reclaimed bayshore marshland. There were very few towers south of Mission Street in the 1960's; now there are many dozens of hi-rise towers up to 50 stories.
What's interesting is that the Salesforce Tower across the street doesn't seem to be experiencing this problem.
-PJ
“Is the financial district built on top of fill, by any chance?”
It was built in the general proximity of a major fault line. One should not do this.
wy69
I think it’s on fill and that’s the problem. yes.