San Francisco’s Millennium Tower repair halted after additional sinking noticed
The major construction work to prevent the beleaguered Millennium Tower of San Francisco from sinking further into the earth was stopped after the building suddenly sank another centimeters within a few weeks, as was first reported by NBC Bay Area.
The $ 100 million post upgrade project began in November and was seen as the definitive solution to the leaning building problems after a 2018 inspection found the northwest corner at least 18 inches into the bay fill in the streets Mission and Fremont had sunk.
The repair has been likened to putting a bumper jack next to a flat tire and involves installing 250 foot stakes along the north and west sides of the tower that will be tied to the original foundation under the sidewalk.
This plan has now been put on hold after the unexpected decline in recent weeks.
After 39 of the 52 stakes, something “went seriously wrong,” the NBC report said. This alleged one inch sudden drop on the Fremont Street side came after crews reportedly drilled halfway to bedrock to install new piles and meant 5 inches of lean on the 58th floor.
Simpson Gumpertz Heger’s project lead engineer, Ronald Hamburger, told SFGATE on Tuesday that “surveillance has revealed an increased rate of subsidence associated with the pile installation as we seek to understand the mechanisms associated with the increased rate of settlement and the means available to mitigate it to understand better.”
The news marks the newest problem in five years of upheaval and concern for the residents of the luxury building.
The blue-gray, glass modernist tower, which was completed in 2009 at 301 Mission Street, is the tallest residential building in the city and has received numerous engineering awards for its construction.
In May 2016, residents of the 58-story skyscraper were informed that the main tower that housed their luxury apartments was sinking. The foundation of the 301 Mission, unlike other towers in the city center, was built in deep, dense sand, but not in bedrock. (Although many other large downtown buildings were also built the same way, including the Embarcadero Center, SFMOMA, the Marriott, and 101 California.)
The blame game and many, many lawsuits began.
The building’s community of owners sued prime contractor Webcor and property developer Millennium Partners. The city of San Francisco also filed a lawsuit against the tower’s developers. The developer blamed the problem on the Transbay Joint Powers Authority, which was responsible for building the neighboring Transbay Transit Center. All of the lawsuits were later combined into a global agreement. The current fix on the tower is paid in part as part of the settlement.
In 2018, when the sink had increased to 18 inches by a 14-inch slope, local residents reported hearing various “creaking noises” and then a “creaking” sound around 2:30 am on the morning of September 8, 2018.
The next day, a resident of a corner apartment found the 36th. Concern that the creaking, popping, and popping were another symptom of structural failure grew. A report commissioned by the tower’s managers blamed an “outside impact” for the crack, but gave no indication of what might have hit the window.
Finally, later that year, a solution to the slope of the damaged building was proposed and approved by Hamburger at Simpson Gumpertz Heger.
“The building has not suffered any material damage and it remains completely safe,” Hamburger told SFGATE. “As soon as the pile installation is complete and the load has been transferred to the new piles, the building will see a significant improvement and will absorb some of the tilts that have occurred over the years.”
NBC reports that since the newly observed 1-inch dip, the tower’s homeowners’ association told residents this week that further stake installation has been put on hold in the face of “an increased settlement rate” and an “overuse of caution” engineers are trying to better address the cause to understand.
