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In the course of our daily reporting, we often uncover unusual projects, places, or connections that don't make the final cut. Instead of keeping it to ourselves, we're pleased to share our weekly Architrivia.
Alongside its neighbouring under-construction skyscrapers, the transformative Transbay Transit Center in San Francisco's South of Market (SoMa) neighbourhood is permanently altering the skies. But could it also be impacting the city's subterranean integrity? That's the assertion laid out to the Transbay Joint Powers Authority (TJPA), managers of the massive project, by real estate developer Millennium Partners. Why the accusation? Because the latter company's landmark Millennium Tower, the tallest residential building in San Francisco, is sinking and leaning.
The 58-storey luxury skyscraper has sunk 16 inches and tilted seven inches to the north since its completion in 2008. Though buildings are designed to settle over their lifetime, the Millennium Tower has already far exceeded the norm of about four to six inches. The unanticipated structural movement has sparked a series of governmental inquiries, lawsuits, and finger-pointing. The developer believes the pumping of water out of the neighbouring Transbay Transit Center site has led to a destabilization of the soil, causing the building to settle more than normal. The TJPA has refuted this, claiming most of the building's decline began before the government agency began underground work on the adjacent lot.
The cause of the unprecedented problem would then lie in the building's foundations. The megastructure's support pilings only descend 80 feet below the ground, instead of 200 feet, which would have secured the foundations into San Francisco's bedrock. With such a shallow anchoring, the building only reaches the dense mud and sand. Though structural engineers have declared the sinking building safe, that's not stopping a sharp drop in property values. On average, the 163 units within the skyscraper have seen their selling prices dwindle by over 40 percent.
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