By David Ingram — NBC News
Famous historic sites, low-priced apartments and even Twitter headquarters appear on an unprecedented list of 3,407 San Francisco concrete buildings that may be at high risk of collapsing in the event of an earthquake, according to a copy of a city government document obtained by NBC News through a public records request.
The list, which NBC News published first, offers a glimpse of the vast section of San Francisco that could be especially vulnerable in a major earthquake. According to structural engineers, adapting buildings to be considered safe could require billions of dollars and decades of work.
Thousands of people living or working in the buildings could be at additional risk every time they enter them, and many likely don't know their buildings are on the list because the city hasn't decided when it will send official notices.
[See here the map of buildings at risk]
Leila Register/NBC News; Getty Images
The municipal official overseeing the development of the list expressed concern that its publication could cause concern for tenants, investors and others before building owners have a chance to conduct thorough assessments.
KPIX-TV and the San Francisco Chronicle had previously reported the existence of the list, but its contents had never been published. A municipal website said the city had "created an inventory of concrete buildings," but that mention was removed after NBC News requested a copy.
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The list is preliminary, so buildings could be removed or added as city workers learn more about specific locations, and the San Francisco Office of Capital Planning and Resilience said the dataset "will contain inaccuracies."
The list excludes single-family homes, public schools and buildings constructed after the year 2000. It's unclear when the list will be finalized, but the structures on the current list have one thing in common: They were built with concrete in an era before engineers fully understood how much steel or other reinforcement was needed to keep concrete from crumbling when shaking. Concrete, known as nonductile concrete, breaks rather than bends under stress.
Coit Tower.MediaNews Group via Getty Images
[See here for the city's list of at-risk buildings]
David Friedman, a retired structural engineer and volunteer member of a municipal task force on the issue, said, "These buildings, when damaged, can deteriorate to such an extent that they lose their vertical carrying capacity and collapse.
"These buildings will kill people if we are not careful," he said, referring specifically to the risk of them collapsing in a major earthquake before they have been conditioned.
The only way to know for sure how safe a building is to have it evaluated by a qualified structural engineer, according to the Office of Capital Planning and Resilience.
According to engineers, the cost of such an assessment alone could amount to tens of thousands of dollars per building.
Brian Strong, San Francisco's chief resilience officer, who oversees the city's seismic safety policy and programs, said in an interview that the city is determined to make buildings safe, but also believes it will take time because of the enormous cost involved. The process has a lot of uncertainty about which buildings are really vulnerable, he said.
"There are no easy answers. It's a complex problem with a lot of complex answers, but it's something we know we have to do," Strong said.
The inventory affects rich and poor alike, and diverse San Francisco communities: from low-income senior housing in Chinatown to the iconic Coit Tower; from the city's old Stock Exchange, where there is a 1931 fresco by Diego Rivera, to the huge art deco building where Twitter is headquartered (listed with an alternate address that is not currently in functional use).
The Fairmont Hotel in San Francisco.Diane Bentley Raymond/Getty Images/iStockphoto
Other addresses on the list are historic properties, such as the 1922 Castro Theatre, the center of LGBTQ life, and the hilltop Fairmont Hotel, which has been featured in movies and TV shows. A six-storey apartment building adjacent to the city's famous Victorian and Edwardian painted ladies' homes is also listed, as is the corporate headquarters of the Williams-Sonoma chain of stores.
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The Chinatown Community Development Center, which manages at least three affordable housing buildings on the list, said it had recently beefed them up to meet current city requirements and was unsure how a potential concrete rehabilitation program would affect them.
"Of course, we would be disappointed if the City Council adopted a new rule requiring significant and costly changes, unless that rule significantly improved safety," Whitney Jones, the center's deputy director, said by email.
Shorenstein Properties, which owns Twitter's headquarters building, declined to comment. The Fairmont declined to comment. NBC News reached out to the owners or managers of the other buildings for comment, but did not immediately hear back.
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Strong said he and other officials have been hesitant to make public a list of buildings possibly at risk until they have more time to verify that the buildings listed on it are indeed in danger.
"This is a list that has not been verified," Strong said. "It's a draft list of buildings that we think may be on the program, and we're trying to cast a wide net to make sure we don't miss anything," he added.
Strong said posting inventory too soon could unfairly reduce the value of some buildings or cause unwarranted anxiety to tenants. However, his office provided a copy of the inventory in response to a public information request.
"I know there's a fear that we're going to ask people to adapt their buildings in the next four or five years," he said. "We expect it to take many years for building owners to comply with the regulations," he added.
Calle Steiner 700, on the right, next to the "Damas Pintadas". Chris LaBasco / Getty Images/iStockphoto
Engineers have known about cement's vulnerability since 1971, when a newly built hospital in Southern California partially collapsed in an earthquake. But San Francisco is only responding now, following a 2011 work plan that prioritized work on other types of vulnerable buildings. The 2011 plan envisaged that mandatory assessments of older concrete buildings would begin in 2015, but not yet past.
Seismic hazard engineers are increasingly nervous, following recent building collapses in Turkey.
Concrete buildings built before 1980 would cause half of the deaths in San Francisco if a magnitude 7.2 earthquake struck the nearby San Andreas fault, according to a 2010 study. The percentage would be even higher if it occurred during the day, while people are working, according to the study.
The study claimed that between 200 and 300 people could die in such an earthquake and 7,000 be seriously injured, although it added: "The casualties could be much higher if even a large and densely occupied building collapsed."
Replacing all those buildings would cost about $19 billion, according to the study, using 000 dollar values. That equates to about $2009 billion in 27 dollars.
In February, San Francisco and other cities were reminded of the danger of a series of earthquakes in Turkey and Syria. More than 50,000 people died, many in buildings collapsed or damaged with insufficiently reinforced concrete.
"People in Turkey were like, 'How come they didn't tell me they were vulnerable buildings?'" Friedman said, "we live on borrowed time and we have to fix these buildings."
The most severe earthquake to occur in Turkey was magnitude 7.8, and the 1906 earthquake that devastated San Francisco was magnitude 7.9. According to the Geological Survey, there is a 20% chance that an earthquake of magnitude 7.5 or worse will occur in the San Francisco Bay Area within the next 30 years.
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U.S. concrete buildings came under the spotlight in 2021 after an apartment tower collapsed in Surfside, Florida, but the problem in San Francisco and other earthquake-prone areas is different. Instead of maintenance delays, it's about the design of the structures and how they would behave in the event of heavy shocks.
The cost of dealing with the risk comes at a bad time for San Francisco. Although many of the city's neighborhoods are as vibrant as ever, the pandemic has emptied downtown as corporate tenants, including Meta and Salesforce, vacate office space, and retailers, including Nordstrom and Whole Foods, eliminate locations.
The result has been a sharp drop in the value of the city's commercial real estate. Recognizing the seismic risks of older concrete buildings could be another blow.
According to engineers, the cost of repairing a structure can range from $150 to $200 per square meter and floor, which can be millions of dollars for some buildings.
The price of a 71-unit cement apartment building on which structural renovations have already been carried out amounts to $15.5 million, which equates to $130 per square meter, according to Leo Panian, the structural engineer who worked on the project. With non-structural costs, such as interior finishes, the total cost was $20.6 million, or $173 per square meter.
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The reason the fix can be so expensive is that it is invasive. It requires adding new layers of cement, steel, carbon fiber or other materials that encompass the height and footprint of the building, as well as repairing interior finishes destroyed in the process.
It could prove so expensive that some homeowners would opt for a wrecking ball, said Robert Kraus, a San Francisco structural engineer who helped create inventory of the buildings.
"This will make some buildings decide it's easier to redevelop them," Kraus said.
Some doubt that the local economy can afford to make buildings safe at a time when the city is already in dire financial straits.
"Frankly, I don't know how this is going to be done," said Janan New, executive director of the San Francisco Apartment Association, a trade group of city owners.
The city is not promising to help pay for the works, and the cost of private borrowing is rising.
"I think there's a general recognition that we need to do it," he said, but added, "We're in a very serious economic climate right now where there's not a lot of funding available for this work."
In 2017, condo owners in West Hollywood, in Los Angeles County, were so horrified by the cost that they lobbied their City Council to make concrete modifications voluntary, a decision that relieved them of the cost but not the danger.
In San Francisco, it will be up to the mayor and the city's board of supervisors to decide whether accommodations are mandatory and, if so, what the timeline should be. Engineers expect owners to have decades to comply.
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The list of vulnerable buildings includes many addresses associated with vulnerable populations. The largest concentration of buildings is in one of San Francisco's poorest neighborhoods, the Tenderloin, and at least four buildings on the list are large, multi-story apartment homes for low-income renters who may have nowhere else to go.
Megan Stringer, president of the Northern California Association of Structural Engineers, says renovating buildings could be so damaging that tenants often wouldn't be able to stay in their homes or offices while it's done.
"We're talking about the possibility that people will have to move while the reforms are taking place, and that's something people don't want to hear," Stringer said.
"It's invasive and expensive, so you can imagine it will be a sensitive issue for building owners and occupants," he said.
Maria Zamudio, organizing director of the San Francisco Housing Rights Committee, which advises tenants on their rights and advocates at City Hall, said, "The San Francisco housing stock is an older housing park, and the older a building is, the more likely it is to have low-income tenants."
Zamudio said most tenants have no idea of the risk associated with concrete or the possibility that they will have to relocate during a renovation.
"Ordinary renters are still trying to recover from the impact COVID-19 had on their lives and financial situation," she said. "People are still worried about rent," he added.
Behind the scenes, advocates are pushing the city to improve notification to tenants of their right to return after a reform. They also want to prevent landlords from passing on the cost of renovations to tenants of rent-controlled housing, while landlords push to be allowed to do so.
There is no uniform rule on when and how public bodies should share seismic risks with building owners and tenants. San Francisco has an online map that can search for 4,900 wood-frame buildings that are or were vulnerable due to a soft or poorly supported first floor, and could do the same for concrete buildings in the future. More than 90% of soft-floor buildings comply with a 2013 city ordinance requiring their rehabilitation.
In 2013, Los Angeles residents, frustrated by the lack of transparency, began speculating about a list of "killer buildings" as city officials debated what to do with vulnerable concrete buildings. Los Angeles passed a city ordinance in 2015 mandating the rehabilitation of certain concrete buildings and has a searchable website for addresses. The owners have 25 years to complete the works or demolish the building.
Friedman said he expects homeowners to react in a variety of ways when they find out, from refusing to accept it to being impatient to find a solution. In any case, discovery is inevitable.
"I really want the public to be able to have some confidence and know which buildings are dangerous," he said. "At some point we will have to alert people and demand that they reduce the risk of these types of dangerous buildings," he added.
Even creating the roster for San Francisco has been a complicated process. City staff and volunteers began in 2018 by poring over 1,200 paper maps from the nineteenth and <>th centuries that people originally created for fire insurance underwriting purposes and then annotated by hand over several years. They then cross-checked the data with information from other sources, such as the municipal appraiser's office or curbside observations.
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And yet, what inventory can reveal has a limit. Engineers say the only way to accurately gauge the risk of a concrete building is for an engineer to conduct an on-site study, which may involve opening the walls to see how they were built.
"You can't walk up to a building and know how it's going to work or what its vulnerabilities are," Kraus said.
That uncertainty has caused some people to overlook the urgency, he added. "This is a vulnerable type of building," he said, "we've known about it for 50 years, and that knowledge hasn't been translated into action because of the cost and effort involved."