When the $550 million construction for the Millennium Tower in San Francisco was announced, there were no shortage of buyers ready to spend millions of dollars to purchase living space. However, less than a decade later, those buyers have lost significant value in their investment due to various unforeseen issues to the tower.
Various structural engineering companies, as well as geotechnical companies, are evaluating the building daily to analyze the cracks, sinking and leaning that are clearly present. While the problems with the Millennium Tower are evident, there are still plenty of questions surrounding the safety of it, who is responsible for these issues and what structural engineering experts are going to do about it.
How Safe Is The Building Today?
The good news is the last time a structural engineer evaluated the building, it was deemed to be safe to live in, even if an earthquake occurred. However, the fact that the sinking of the building doesn’t appear to be slowing down anytime soon can’t be ignored. Structural engineering experts estimate the building will continue sinking between 1.5” to 2” every year, which simply means action needs to be taken now to prevent a potential disaster in the ensuing years.
Where The Blame Lies
Initial inspections indicate the main problem being in the foundation of the Millennium Tower. The soil it’s built on consists of sand, clay and mud, and the foundation does not even extend far enough down to reach solid bedrock. There’s some controversy surrounding the City of San Francisco and why they allowed the construction and design team to not anchor the foundation low enough to reach the bedrock.
Another area of blame has to do with the construction of the transit center that was newly built adjacent to the tower. The construction company responsible for building the Millennium Tower is suggesting the company that constructed the transit center pumped too much groundwater during their project, which caused the sand under the Millennium Tower to compress, and has resulted in the sinking.
Possible Solutions To Fix The Millennium Tower
As structural engineering experts continue to discover the reasons why the Millennium Tower is experiencing these problems, they are also developing short-term and long-term solutions. One of the possible solutions includes removing some of the top floors in order to reduce the weight of the tower. The most discussed solution for the long-term is to bore micro piles on the side of the building that’s sinking in order to eventually anchor it to the bedrock underneath. Once this occurs, the high side of the building must sink to the level of the low side before the anchoring can occur. This proposed solution could take up to five years and cost several hundred million dollars, but it is the most viable solution for the long-term, as analyzed by structural engineering experts.
At BE Structural, we always monitor these types of stories and are actually involved in many of them. We are a structural engineering company with experts coming from many different backgrounds and having various levels of experience. If you have any specific questions about the problems the Millennium Tower in San Francisco is facing, or have a need for a structural engineer, contact us today.