Since the Millennium Tower was built in San Francisco in 2009, there have been concerns that it is sinking and tilting. And now those fears have been confirmed by satellite imagery.
The 58-story building is 197 meters (645 feet) tall from its base to the top of its spire. But owing to the area being earthquake-prone, it was built on some notoriously soft ground. What’s more, its foundations – known as piles – are only 24 meters (80 feet) deep and not built on the bedrock, which is 61 meters (200 feet) down.
As a result, earlier this year an examination found the building – located in San Francisco’s Financial District – had sunk by 41 centimeters (16 inches) since its construction, and had tilted 5 centimeters (2 inches) to the northwest at its base and 15 centimeters (6 inches) at its top. And now, ESA’s Sentinel-1 satellites have confirmed it is indeed sinking, at a rate of up to 5 centimeters a year.
Scientists used multiple radar scans from the satellites to detect subtle changes down to just millimeters. The New York Times reported in September that concerns about sinking were first raised seven years ago when the building was built, but were not acted upon.
Ground deplacement in San Francisco. Green indicates no movement, while yellow, orange, and red denote areas where buildings are sinking. Copernicus Sentinel data (2015-16) / ESA SEOM INSARAP study / PPO.labs / Norut / NGU
It’s not entirely clear what sort of danger the building is in at the moment, but it’s certainly not good news. NBC Bay Area said that the San Francisco Attorney’s office has sued the building’s developers, Millennium Partners, for not disclosing that the building was sinking back in 2009.
“California law mandates owners or developers to notify buyers of any problems or building defects and can be prosecuted under civil law for withholding the information,” NBC reported.
The data from ESA has also pinpointed “hot spots” of deplacement in this and other regions. For example, a 4-year drought that ended in 2015 also seems to have created an uplift of land around the nearby city of Pleasanton.
As for the Millennium Tower, well, things aren’t looking great. The building has been given the unwanted nickname of the “leaning tower of San Francisco,” and it probably won’t be losing that moniker anytime soon.