The Leaning Tower of San Francisco

San Francisco, the land of leftist leaning ideology and now a leaning skyscraper.  The Millennium Tower, sarcastically referred to locally as the "Leaning Tower of San Francisco" opened in 2009 but by November 2016 had settled up to 16 inches (based on publicly available reporting) and tilted 2 to 6 inches apparently to the northwest.  New settlement appears to continue, one reference indicating 1 to 2 inches per year.

The building was constructed (apparently) on skin friction piles through an old landfill and presumably into local native soils above bedrock (but not bearing deep to reach bedrock).  The geotechnical report by Treadwell and Rollo (firm acquired and is now a part of Langan Geotechnical) could not be obtained, but obviously there was a geotechnical modeling error that seriously overestimated skin friction capacity or underestimated any negative impacts from pile group settlement, or maybe the structural engineer underestimated dynamic structural loads (i.e. storm wind loading) given to the geotechnical engineer that would be maximum loads on the piles on one side of the building, i am only speculating.
Crack monitors are seen here on a lower level concrete wall.  Distress was also visible in the exterior sidewalks and their joints to the building.








You can research online all the litigation and municipal public policy issues that have arisen due to this fiasco, if you are curious to learn more about this situation.

If you are a Geotechnical Engineer working on a high rise project with recommended foundations supported on soil and not rock, you must, must, seek secondary review and commentary from another Geotechnical Engineer (or two), these projects are too expensive and too exposed publicly to permit any errors.  And in California where earthquakes occur, one has to wonder how this building will perform with piles embedded in saturated soils beyond a certain depth, soils susceptible to liquefaction.  Earthquake engineering is not a part of my purview of expertise so i defer to the California Geotechnical Engineers to figure this one out.