This 58-Story Skyscraper Sank 16 Inches. The $100 Million Fix Made It Lean Faster

In 2009, the first residents moved into a 58-story glass tower in downtown San Francisco. By then, the building was already going down. Engineers had expected it to settle 4 to 6 inches over its whole life. Seven years later it had sunk 16, and one corner was dropping faster than the rest. This is the story of Millennium Tower at 301 Mission Street. Nobody skimped on the concrete, and the foundation followed a design used across downtown. The trouble was deeper: 950 piles that stop in sand, a layer of ancient clay full of water underneath, and a city block where everyone kept pumping that water out. Then came the repair. In 2021, crews began drilling new piles down to bedrock, and within months the tower was leaning faster than ever. In this video: • what Millennium Tower actually stands on, and why it never reaches rock • how wet clay shrinks under weight and never springs back • what pumping groundwater on the same block did to the tower • why a $100 million fix sped up the tilt before it stopped the sinking • where the building stands today, and what engineers still disagree about Chapters: 0:00 The tower that was already sinking 0:59 Not a cheap building 1:30 What it stands on 2:39 The clay under the sand 3:47 Someone starts pumping 4:35 2016: the story goes public 5:02 The $100 million fix 5:25 2021: leaning faster 6:05 From 52 piles to 18 6:48 Held, but not straight 7:35 How long does it have? 8:52 What really sank the tower Tilt and recovery figures are as reported in early 2024 and may have changed since. #MillenniumTower #Engineering #SanFrancisco Sources: ENR — After 15 Years, Settlement Arrested at San Francisco's Millennium Tower https://www.enr.com/articles/56665-after-1... Practical Engineering — What Really Happened at the Millennium Tower? https://practical.engineering/blog/2021/11... NBC News — Leaning San Francisco skyscraper is tilting 3 inches per year as engineers rush to implement fix https://www.nbcnews.com/news/us-news/leani... SFGate — New problem at SF's sinking Millennium Tower https://www.sfgate.com/local/article/new-p... Archinect — San Francisco's Millennium Tower is sinking again despite foundational corrections https://archinect.com/news/article/1504176... NBC Bay Area — SF's Millennium Tower now may be sinking in the center https://www.nbcbayarea.com/investigations/... NBC Bay Area — Millennium Tower residents billed $6.8 million for fix overruns https://www.nbcbayarea.com/news/local/mill... SFist — Millennium Tower Residents Stuck With Unanticipated $6.8 Million Tab For Repair Cost Overruns https://sfist.com/2023/09/29/millennium-to... KQED — Tentative Settlement Reached Over Sinking, Tilting Millennium Tower https://www.kqed.org/news/11770616/tentati... KTVU — SF luxury Millennium Tower penthouse sells for $9M, millions less than original asking price https://www.ktvu.com/news/sf-luxury-millen... millennium tower, millennium tower san francisco, sinking skyscraper, leaning tower of san francisco, 301 mission street, sinking tower, leaning skyscraper, engineering failure, engineering disaster, foundation failure, old bay clay, friction piles, bedrock piles, transbay transit center, san francisco skyscraper, structural engineering, geotechnical engineering, why is it sinking, engineering documentary, megaprojects, construction failure, skyscraper foundation