Adia Sisson

CCSF Architecture: Problems with the Millennium Tower

In my City College of San Francisco Architecture 100 class, we were assigned a research essay investigating The Leaning Tower of San Francisco, aka The Millennium Tower, why it’s tilting, how it can be fixed, and who is at fault.


Adia Sisson

Paul Nowicki

ARCH 100

27 June 2018

The Millennium Tower

“The Leaning Tower of San Francisco” is how the Millennium Tower is now commonly known. Designed by Handel Architects and constructed by Webcor Builders, the story of the tower is one of corruption and incompetence, a messy game of ‘who’s to blame’. As of 2016, the 58 story, $350 million skyscraper has sunk 16 inches and tilted 2 inches northwest (6). The questions everyone is asking are: Why is the building sinking? How do they plan to fix it? Who’s responsible for the problem?

The Problem

A striking difference between the Millennium Tower and other buildings of its type is that most modern skyscrapers are built with steel foundations, often averaging approximately 2000-3000 lbs./sq. ft. of pressure (6). This tower, however, is made almost entirely of reinforced concrete, averaging a pressure of 14,000 lbs./sq. ft., according to CSRI (4).

The Millennium Tower is secured to the soil by 950 friction piles, a tried-and-true method using weight-distribution and the friction between the piles and the soil to slow sinkage and hold a building in place. Some have theorized that the friction piles may have achieved vertical equilibrium but failed to account for natural torque, causing the building to begin to tilt first, thereby beginning the sinking process (4). Because the land on which the tower is built is composed mainly of mud-fill and sand, heavy buildings are predisposed to sinkage, making end- bearing piles a trustier method to secure the tower. However, end-bearing piles must be drilled directly into the bedrock, requiring significantly more work and funds to install. The decision to use friction piles was theoretically sound but argued against by many geotechnical engineers due to the nature of the soil in the location (6).

How It Can Be Fixed

Depending on the specific cause of the tower’s issues, there are different possible solutions which vary in likelihood due to construction restraints. One possibility would be to reinforce the soil with concrete, increasing the force required for the tower to sink (4). Another would be to secure half of the foundation to the bedrock using end-bearing piles. This method would allow the unsecured half to continue to sink until the foundation levels itself, at which point construction would restart to secure the entire foundation (3). More radical proposals are to install and connect an adjacent, heavier building to balance the weight, or to simply do nothing (3, 4). As Millennium Partners have continually insisted, the building may not worsen to the point of danger, allowing those inside to live their lives safely and construction-free. Every solution comes with pros and cons and the possibility of failure. Because of this uncertainty, fingers continue to be pointed about who’s at fault for this mess.

Who's Responsible

The Millennium Partners, the developers of the tower, place the blame on the Transbay Joint Powers Authority, claiming that their construction nearby ruined the soil, possibly shifting it below the surface (5). TJPA countered this, saying this claim was untrue and that the tower had been sinking before construction even began (1).

Another group places the blame of the Millennium Partners themselves, with a resident of the tower stating, “The Millennium Partners did not build to bedrock, and that’s the cause of the problem” (5). Throughout the design and construction process, the developers repeatedly had issues brought to their attention but ignored the red flags. An investigation lead by NBC also placed the blame on the developers, claiming that the issues “may have been avoided had the city building officials heeded experts’ warnings” (6).

Overall, the whole debacle has resulted in a pattern of the Millennium Partners being accused of omitting crucial information to current and potential residents. The City of San Francisco even filed a suit against them for withholding information about the building’s sinkage from possible buyers (6). Visual cues such as cracks and splintering were said to have been “marbled over by the developer”, intentionally trying to hide the possibly dangerous state of the building (5).


Bibliography

  1. “San Francisco Millennium Tower Sinking, Tilting.” YouTube, uploaded by KPIX CBS SF Bay Area, 1 Aug 2016, www.youtube.com/watch?v=WMutQBXj5X4.
  2. “More Bad News for San Francisco's Troubled Millennium Tower.” YouTube, uploaded by Newshd1, 14 Mar 2017, www.youtube.com/watch?v=wfmHw91tuWI.
  3. Brinklow, Adam. The $500 million plan to fix Millennium Tower. Curbed, 16 Apr. 2018, sf.curbed.com/2018/4/16/17242450/millennium-tower-sinking-repair-tilting-building-san-francisco.
  4. Brinklow, Adam. An engineer’s short, simple explanation of Millennium Tower problem. Curbed, 16 Sep. 2018, sf.curbed.com/2016/9/16/12945600/why-millennium-tower-sinking.
  5. Smiley, Lauren and Joe Eskenazi. The Big Sink. San Francisco Magazine, 21 Oct. 2016, modernluxury.com/san-francisco/story/the-big-sink.
  6. The Millennium Tower – Importance of Geotechnical Engineering, 21 Oct. 2016, www.spargrp.com/millennium-tower-geotechnical-engineering-importance.