An outside expert is now advising the City of San Francisco and the Millennium Tower Owners Association on how to proceed with the proposed tests on the problematic solution of the sinking and tilting building.
While the proposal is on hold at the moment, Millennium officials hope to begin installing on a test stack as early as next week. The tests are designed to help determine what caused the additional sudden sinking and tilting since work began in May on the fix.
However, patch designer Ron Hamburger predicted that the drilling required for the test pile could worsen the building’s tilt.
Patrick Hannan, a spokesperson for the Building Inspection Department, said drilling expert Dan Brown was hired last week to assess the test plan. “He provided comments and information on the planned proposal going forward,” Hannan said.
“The good news is that this is on hold until we have a third pair of eyes,” City Supervisor Aaron Peskin said in an interview after meeting with the patch designer, representatives of the. building and the technical review committee appointed by the city on the status of the 100 million dollar project.
It was Peskin who called for an external review shortly after NBC’s Bay Area Investigation Unit announced in August that the building had experienced an accelerated sinking and tipping since work began on repair in May.
By the time work began to install piles to support the bedrock structure on two sides, the tower was leaning 17 inches west toward Fremont Street. But after crews dug 33 holes to install support piles, the tower tilted an additional 5.5 inches. This prompted all work to stop in August.
At this point, the building was tilted 22.5 inches west toward Fremont Street. Last month, the building sank again when crews drilled new test holes in the corner where the structure slopes the most. That test work alone, the data shows, led to another quarter of an inch lean to the west.
Fix designer Ron Hamburger now proposes to pour the new test pile into bedrock on the Fremont side of the building. But in a letter to city officials last week, he admitted the new battery could trigger up to three-quarters of an inch of extra lean westward.
Hamburger also specified 29 inches as the outer limit of the building’s tilt to keep the tower “safe and stable” during a major earthquake, leaving about six inches of additional tilt on the west side of the structure.
One inch of settlement at the base, according to the data, translates to four to five inches of additional tilt at the top of the 58-story tower.
“The ultimate question here is whether the cure is worse than the disease,” Supervisor Peskin said. “Not to use a cliché term, but if you want to bomb the village to save it, that might turn out to be a very bad idea.”