But, at 58 stories, this was the tallest residential building to be built here, and with its concrete frame it is a rather heavy one. As we've heard before, many buildings in downtown that came before Millennium Tower had gotten away with drilling foundation piles into the layer of what's called Old Bay Clay, without their buildings settling too dramatically. So, maybe it's not hard to understand why, this many years later, we still haven't gotten a particularly great, layman's explanation for the whole thing.Įnter Practical Engineering, a YouTube channel with 2.4 million subscribers, which has now done an excellent 13-minute video explaining the history of Millennium Tower's troubles the mud, clay, and bedrock layers that lie underneath this part of downtown San Francisco and how, in some ways, it's not easy to cast blame on a single entity or engineer when it comes to why this residential tower can't stand up straight.įirst off, our narrator Grady Hillhouse diagrams the starting conditions when Millennium Tower was first being planned and constructed during the mid-aughts. The geotechnical conundrums of Millennium Tower's sinking and tilting problems are complicated even for engineers.

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