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I'd say it's less about piles going to bedrock and more about the ground itself.

Building on sand, trash, and whatever other gunk comprises San Francisco ground...

You could say whatever you like, but none of the other tall buildings in SF are sinking noticeably, which suggests your theory may itself lack a solid foundation.

Are the pilings for those other tall buildings in the bedrock?

Depends. Some are but but in recent years it's been more common to use steel structures which (being lighter) don't require that.

Noise might have something to do with too. The last building that I recall having bedrock-depth pilings involved loud shuddering bangs through the financial district for nearly a month. Like you could feel it through the ground 3 blocks away every time they dropped the hammer..

IIRC, a potential confounding factor was that this building is much heavier and has a smaller footprint than standard.

that's why you go down to the bedrock, because the earth in between is not strong/stable enough. also, while much of eastern SOMA is indeed landfill of the bay, this particular building is far enough inland and would be within the original SF coastline.

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