SAN FRANCISCO — The developers of the luxurious Millennium Tower laid out the risks and potential defects of the 58-story building in minute detail when its apartments went on sale seven years ago.
The color and texture of the marble and granite hallways “may not be completely uniform,” said a disclosure statement given to potential buyers. The streets below the tower could be “congested and noisy,” and the landscaping in the common areas could change, subject to availability of certain species of plants.
But the 21-page disclosure document left out what owners of units in the buildings now say was a crucial detail: that the building had already sunk more than eight inches into the soft soil by the time it was completed in 2009, much more than engineers had anticipated.
“If they had disclosed the defect, I would have never bought here,” said Jerry Dodson, the owner of a two-bedroom apartment on the 42nd floor that he bought with his wife for $2.1 million. “Never was there a hint that the building was sinking beyond design.”
The Millennium Tower, which its developers say is the largest reinforced concrete building in the western United States, has now sunk about 16 inches and is leaning six inches toward a neighboring skyscraper. The building’s tilt has become a public scandal, a dispute that has produced a wide-eyed examination of whether or not San Francisco’s frenetic skyscraper-building spree was properly monitored by city authorities. In a city bracketed by two major earthquake fault lines, the possibility of engineering flaws generates particular unease.
“This is the first sentinel telling us maybe we should be a little more careful,” said Nicholas Sitar, a professor of civil engineering at the University of California, Berkeley, who specializes in how buildings respond to earthquakes. “Any time you have a tall structure leaning, you have to start looking very carefully.”
As the scandal has unfolded in recent weeks, Senator Dianne Feinstein, a former mayor of San Francisco, wrote to the current mayor, Edwin M. Lee, expressing concern about the number of buildings like Millennium Tower that are not anchored in bedrock.
Mr. Lee responded that he had instructed city officials to amend the city’s earthquake safety plan to require a review of soil conditions and mandatory earthquake evaluations during property sales. At a hearing on Thursday convened by a Board of Supervisors committee, city officials said the Millennium Tower situation had caused them to reassess the way buildings are vetted.
The building spree in San Francisco has taken place for the most part in an area that used to be part of San Francisco Bay, land created using dredged soil as well as piles of detritus from the 1906 earthquake.
Professor Sitar calls the soil conditions “very challenging” for engineers, especially when compared to the Manhattan schist that anchors New York’s skyscrapers.
“For a long time you didn’t see very tall structures in San Francisco,” Professor Sitar said. With advances in engineering and by studying responses of buildings in earthquake zones, he said, engineers have grown more confident. “Is that confidence warranted? To some extent it is. At that the same time, there has to be an abundance of caution.”
Outside the living room of Mr. Dodson’s apartment is a panorama of this new San Francisco, the collection of skyscrapers that are partly a byproduct of the technology boom and the foreign money pouring into luxury condominium buildings. The Millennium Tower sits across from the Salesforce Tower, which when completed will be the tallest structure in San Francisco.
Mr. Dodson is helping to organize a number of the owners of the more than 400 units to demand compensation from the developers, Millennium Partners.
“City officials have said it’s at a critical point right now,” Mr. Dodson said of the building. He said the sewage connections to the building may no longer function properly if it continues to sink. And engineers fear that the building’s high-speed elevators may fail if the building tilts farther, he said. He fears that if it continues to tilt, it may become unlivable.
A government agency, the Transbay Joint Powers Authority, that is building a transportation hub next to the Millennium Tower said the sinking and tilt of the building are due “exclusively to the deficient foundation system” of Millennium Tower.
Millennium Partners, after a long period of silence, told reporters this week that while their own removal of groundwater had been responsible for the initial sinking of the building, the subsequent sinking was caused by the digging next door at the transportation hub.
Chris Jeffries, a founding partner of Millennium Partners, blamed the “reckless behavior” of the Transbay Joint Powers Authority.
At the hearings on Thursday, city officials were asked why correspondence with the engineers of the Millennium Tower project had disappeared from files. A city official replied that they were not required to keep them.
Hanson Tom, the city’s principal engineer, said that at the time Millennium Tower was being constructed the developers had not agreed to a review by outside experts on the soil conditions or the foundations of the building and that the city had no laws to compel them to conduct these reviews.
The city was not prepared to assess the structural integrity of the Millennium Tower because it was one of the first skyscrapers erected in the business district, officials said.
“We didn’t have anything in place from a regulatory perspective on how to deal with buildings of this nature,” said Ronald Tom, the deputy director of the city’s department of building inspection.
The city now relies on outside experts to verify the structural integrity of proposed skyscrapers because they do not have the technology to verify the computer models used by developers.
But the hearing on Thursday did not clarify why city officials had declared the building safe for occupancy despite the problems with the foundation. Aaron Peskin, the San Francisco supervisor who called Thursday’s hearing, said the inquiry would continue in the coming weeks.
The tilting tower has produced introspection among engineers in part because when the building was completed the developers received at least nine awards for “excellence in structural engineering,” among other citations.
Mr. Dodson’s wife, Pat, said one of the possible solutions proposed by an engineer who homeowners have consulted is to lessen the weight of the building by lopping off the top 20 floors.
Today, the only beneficiaries of the Millennium Tower appear to be the armies of lawyers mobilizing for what is expected to be years of litigation.
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