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Have Engineers Found a Solution to the Sinking Skyscraper in San Francisco?

Engineers may have hit on a way to prevent Millennium Tower, also known as the Leaning Tower of San Francisco, from sinking into the ground.

The sinking skyscraper was constructed over a landfill site in the city’s downtown area. The developer, together with the design team, consulting engineers, and contractors, drilled 900 piers to reinforce the original structure.

One of the factors that allegedly contributed to the lean is that the piers reached a level of 61 to 90 feet instead of solid bedrock 200 feet below the surface. When dewatering activities and construction of a transit centre took place nearby, the 58-storey building began to lean and sink at a faster speed.

DeSimone Consulting Engineers and the Lera firm are proposing that the parties responsible drill another 50 to 100 piers down to the bedrock to stabilise the sinking skyscraper from further movement. It remains to be seen whether this duty would fall to the City of San Francisco, the developers, or the Transbay Joint Powers Authority that is building the transit center.

Drilling the piers and levelling out the tower will cost an estimated $100 to $150 million, which is substantially less then earlier estimates of $1billion.

The city administrator’s office has confirmed that no one as of yet has filed for the permits needed to carry out the recommended repairs, and because of the legal issues surrounding the project, none of those immediately involved are making a statement.

 

Specialists in Construction Insurance

One problem could be a source of concern for those living in the upscale condominium project. The Arup Group has taken measurements that confirm that the tower has sunk another inch in the last seven months. There is also cracking in the basement that has been attributed to the pressure of the one-sided sinking.

According to some reports, residents can continue to live in the tower while repairs are carried out, assuming that they begin in a timely manner. As one might imagine, with all the accusations and threats of litigation flying around, no one is certain when the repairs will start. The progressive pace of the leaning and sinking will soon become a source of major concern for both building residents and developers, particularly since San Francisco is prone to earthquakes.

It remains to be seen whether the engineers and contractors can correct the sinking skyscraper and stabilise the movement. Residents are receiving a tax break, but it is not enough to make up for the loss of value that the defect has created.

 

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