A lawyers wet dream....

San Francisco's Millennium Tower fix halted after further sinking observed

Andrew Chamings

The major construction fix to stop San Francisco's beleaguered Millennium Tower from sinking further into the earth has been halted after the building suddenly sank another inch within a few weeks, as first reported by NBC Bay Area. 

The $100 million “perimeter pile upgrade” project began in November, and was seen as a final resolution to the lopsided building's woes after an inspection in 2018 revealed the northwest corner had descended at least 18 inches into the bay fill at Mission and Fremont streets.

The fix has been likened to putting a bumper jack next to a flat tire, and involves the installation of piles 250 feet deep along the north and west sides of the tower, to be tied beneath the sidewalk to the original foundation.

That plan has now been put on pause after the unexpected sinking observed in recent weeks.

NBC's report says that after 39 of the 52 piles had been installed, something went "seriously wrong." That alleged sudden drop of an inch on the Fremont Street side occurred after crews had reportedly drilled halfway down to bedrock to install new piles, and translates to 5 inches of lean on the 58th floor. 

Principal engineer on the project Ronald Hamburger of Simpson Gumpertz Heger told SFGATE on Tuesday that "monitoring has indicated an increased rate of settlement associated with pile installation. Out of an abundance of caution, we have placed a two- to four-week moratorium on pile installation while we try to understand better the mechanisms associated with the increased settlement rate and available means of mitigating this."

The news marks the latest problem in five years of upheaval and worry for residents of the luxury building. 

The blue-gray glassy modernist tower, completed in 2009 at 301 Mission Street, is the tallest residential building in the city and won numerous engineering awards upon its construction. 

In May 2016, residents in the 58-story high-rise were informed that the main tower that housed their luxury condos was sinking. The foundation at 301 Mission was built into deep, dense sand but not bedrock, unlike other downtown towers. (Though many other large downtown buildings are also constructed in the same way, including the Embarcadero Center, SFMOMA, the Marriott and 101 California.)

The blame game and many, many lawsuits began.

The building's homeowners association sued the main contractor Webcor and the developer Millennium Partners. The city of San Francisco also filed suit against the tower's developers. The developer blamed the problem on the Transbay Joint Powers Authority, which was responsible for construction of the neighboring Transbay Transit Center. All suits were later consolidated into a global agreement. The current fix on the tower is partly paid for as a portion of the settlement. 

In 2018, when the sinking had increased to 18 inches with a lean of 14 inches, residents reported hearing various "creaking sounds," and then a "popping sound" at about 2:30 a.m. on the morning of Sept. 8, 2018.

The following day, a resident living in a corner unit on the 36th floor found a crack across a glass window that was rated to withstand hurricane-force winds. Concerns that the creaking, popping and cracking were another symptom of the structural failure grew. A report conducted on behalf of the tower’s managers blamed the crack on an “exterior impact,” but gave no indication as to what might have struck the window.

Later that year, a solution to the blighted building's tilt from Hamburger at Simpson Gumpertz Heger was finally proposed and approved. 

"There has been no material harm to the building and it remains fully safe," Hamburger told SFGATE. "Once pile installation is complete and load is transferred to the new piles, the building will experience substantial improvement and begin to recover some of the tilting that has occurred over the years."

NBC reports that since the newly observed 1-inch sink, the tower's homeowners association told residents this week that further pile installation was being put on hold in light of  “an increased rate of settlement’’ and out of an “abundance of caution” as engineers try to better understand the cause.