WorldWide Drilling Resource

29 JUNE 2022 WorldWide Drilling Resource® An Update on the Leaning Tower of San Francisco Compiled by Amy White, Associate Editor, WorldWide Drilling Resource®® Constructed in 2009, the Millenium Tower is supported by 950 reinforced concrete piles placed 60-90 feet deep in clay and mud, never reaching bedrock. Previous buildings in downtown San Francisco were constructed the same way without issues, but with 58 stories and a concrete frame, the Millenium Tower is substantially heavier than earlier designs. Known as “The Leaning Tower of San Francisco,” the troubled structure was first covered by WWDR in 2017. At the time, the luxury apartment building had sunk 16 inches and tilted around 2 inches northwest at its base, creating a staggering 15-inch tilt at the top of the building. In an effort to find a solution for the tower’s unstable foundation, a series of exploratory drilling tests were performed to assess soil conditions. The proposed solution was to drill down to bedrock on two sides of the building, and install concrete piles to function as hydraulic jacks to level out the tilt. When the foundation work finally began in 2021, the tower had sunk even more to a total of 18 inches, and the top of the building was tilting 22 inches. Dirt was removed to make way for piles to be installed. Unfortunately, removing this soil from below the building only made it tilt worse even faster, and the work was halted as a result. At this point, the tower is slanting 26 inches. At the current sinking and tilting rate, it would no longer be safe a few years from now. Once leaning reaches the 40-inch mark, elevators and plumbing could cease to function. In an update hearing with the San Francisco Board of Supervisors, Ronald Hamburger, structural engineer on the repair project, said the building is safe at the moment. His new plan of action involves anchoring 18 steel pi les down to bedrock to support the structure. The 18-beam support plan has been approved by the San Francisco Department of Building Inspection. The beams will be inspected by the department upon installation for added safety. As early as 2018, residents reportedly heard unsettling cracking sounds. Many have chosen to sell their units in spite of assurance from city officials that the building is safe. The leaning tower is set for a $100 million foundation upgrade designed to gradually recover its tilt. Construction is planned to resume once the building’s current settlement has been recorded. C&G August Issue Deadlines Editorial: June 15th Space Reservation: June 25th Display & Classified Ad Copy: July 1st