Digital Journal reported in October that according to a consultant’s report submitted in 2011, two years after the Millennium Tower was completed in 2009, the building had already sunk 10 inches. And that was four more inches than the architects had predicted for the life of the building.
But recently released satellite images provided by the European Space Agency show the 58-story building is sinking twice as fast as previously thought, close to two inches a year instead of one, reports NBC News.
Since its completion in 2009, the tower has sunk 16 inches into the soft landfill in San Francisco’s Financial District and is now tilting two inches at the top and six inches at the bottom toward the northwest. Millennium Tower is now being called, quite appropriately, “the leaning tower of San Francisco.”
But NBC News is saying that the Transbay transit project next door has monitoring data taken from the basement of the leaning tower and their data shows the tower has only sunk about an inch since last year. This information is way off what the ESA’s Sentinel 1 satellite imagery is showing.
“The Sentinel-1 satellites have shown that the Millennium Tower skyscraper in the center of San Francisco is sinking by a few centimeters a year,” a statement by the ESA concludes. “Studying the city is helping scientists to improve the monitoring of urban ground movements, particularly for subsidence hot spots in Europe.”
ESA scientists used multiple radar scans from the Copernicus Sentinel-1 twin satellites of the same area in San Francisco to detect subtle surface changes, down to millimeters. This method works well with buildings because they better reflect radar beams. ESA also found that a number of other building in the area were also sinking.
ESA’s Copernicus Sentinel-1 twin satellites
The Sentinel 1 satellites are in orbit 400 miles above the Earth and are used to track urban ground movement and fault activity around the world using radar, particularly subsistence hotspots in Europe.
Because the Hayward fault line runs through the SanFrancisco Bay area, the ESA decided to track that fault line, too. This meant they could track the movement of the Millennium Tower very accurately.
Overall, the ESA estimates the tower is sinking at a consistent rate of 1.6-1.8-inches per year. That’s much faster than previous estimates on the ground of 1-inch per year. It’s also not slowing down, as Mission Street Developers have insisted. One thing is for sure, residents of the Millennium Tower now have twice as much to worry about.
