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Millennium Tower: San Francisco’s Sinking Skyscraper

In 2009, the Millennium Tower opened in San Francisco to fanfare from the public and awards from engineering associations. At the time of its completion, it was the tallest residential building west of the Mississippi. The skyscraper was filled with residents by the end of the year, its tenants including a local football hero, a pioneer of venture capitalism, and the National Basketball Association’s Most Valuable Player. Demand was so high for the building’s condos that new buyers were reselling their lofts for two or three times the price that they paid.

But that all changed in 2016 when the building’s developers informed the public that it was sinking at an alarming rate, resulting in a disturbing northwest tilt. Following this revelation, everyone from the residents to the developers to the city government to the local transport authority found someone else to blame the mistake on. In the process, the lawyers and reporters uncovered a story much juicier than they imagined.

Let’s discuss the Leaning Tower of San Francisco: Millennium Tower.

Planning and Construction

millennium tower is under constructions
A construction worker hosing down the Millennium Tower (301 Mission Street) construction site.By Hydrogen Iodide, is licensed under CC-BY-SA

The San Francisco Bay Area is home to some of the world’s most valuable real estate. As the urban capital of the expanded Silicon Valley, actually living in San Francisco is not an option for most of the area’s residents. High rents often made apartment buildings ridiculously profitable ventures, so, in 2002, the real estate development firm Millennium Partners set out to build the city’s largest residential building. The massive concrete skyscraper would stand in the South Market, or SoMa, district of downtown San Francisco, the first building of its size to be built downtown in more than twenty years. In 2003 the city planning commission approved the high-rise, and construction began in 2005. 

Construction was completed in 2009, with the total cost of the project reaching $350 million. The final product was a 197-meter (645 feet) late-modernist style skyscraper, with the concrete frame supporting a blue-grey glass facade. While the top floor is listed as the 60th, it’s actually the 58th, as the 13th and 44th floors were removed to appease superstitious potential buyers from western and east Asian backgrounds. The tower is slender, with each floor containing 1,300 square meters (14,000 square feet) of floor space.

Upon its completion, the building received a slew of awards for its outstanding architecture and engineering achievements, including the “Structural Engineering Project of the Year” and the American Concrete Institute Award for construction. It turns out these awards should really be given in hindsight, as, somewhere in California, a smug engineer is sitting with a trophy on his desk for a building that is now literally sinking.

Opening and Discovering the Tilt

Once opened in 2009, most of the building’s condos sold out in the first five weeks. The lower half of the building comprises “lower-cost”, loft-style apartments, and the upper half includes spacious luxury condos. The condos ranged in price from 1.6-10 million dollars, with the majority selling between 1.6 and 4 million dollars. Within a few years, though, prices skyrocketed. The Millennium became one of the most in-demand locations in the entire city, and, suddenly, the cheapest apartments were reselling for 4 million dollars.

Joe Montana
Joe Montana.By Phil Hull, is licensed under CC-BY-SA

Millennium Partners and their associates were ecstatic. They called their building the hottest new property and declared that it would “set a whole new economic standard for luxury units downtown.” They pointed to the building’s community and amenities, like the Olympic-sized swimming pool and weekly movie nights at their onsite theater, as significant draws for potential residents. They touted famous tenants like local football legend Joe Montana and a few professional baseball players. 

But they also mentioned a nearby construction project that might have played a factor in the building’s value— the 2 billion dollar Transbay Terminal transit center, which was in progress just across the street. The state-of-the-art terminal was going to shrink the city and make it more accessible to anyone living nearby. Of course, I have to wonder whether anyone that can afford a 4 million dollar apartment actually rides public transit, but that’s beside the point. 

Then, in 2016, the news broke. The holding company informed the tower’s residents that the building had sunk by 16 inches and was now tilting several inches to the northwest. Word quickly spread throughout the town, and news reporters descended on the tower to seek the residents’ and developers’ opinions. The developers blamed the city, while the city and residents blamed the developers. Then, in typical American fashion, they all sued each other. The lawsuits would go on for several years, and, in the process, they revealed the deeper layers to the story that had remained hidden.

Doomed From the Start

Following this revelation, the development company rejected any claims of negligence on their part, instead placing the blame on the city transit officials, the Transbay Joint Powers Authority (TJPA). Remember that 2 billion dollar Transbay Terminal across the street that the realtors loved so much? In preparation for that project, the TJPA dewatered the foundation’s soil to improve workers’ safety and prevent soil erosion. According to Millennium Partners, the sapping of all moisture from the ground caused the sand beneath Millennium Tower to compress, resulting in the sunken skyscraper.

It seemed that Millennium Partners had dealt a fatal blow to the TJPA’s case. After all, their argument was rooted in well-known engineering principles. However, the TJPA was prepared with its own rebuttal. Construction on the Transbay Terminal began in 2012, but the TJPA had conducted a series of studies in 2010 to ensure that their excavation would not affect the tower. They discovered that it had already sunk ten inches within one year of the building’s completion. For some context, all skyscrapers sink a bit as they settle into the earth, but engineers had predicted that Millennium Tower would only decline four inches throughout its life.

Given their alarming discovery, the TJPA informed Millennium Partners, who kept the information safely guarded from potential buyers as they sold off the rest of their vacant condos. That formed the basis for the city’s suit against Millennium Partners, as they knowingly concealed information to potential purchasers. But, as the lawsuit progressed, it turned out that, perhaps, they had known of this sinking risk long before TJPA uncovered it in 2010.

Back in 2003, when the Millennium Tower was in the early planning stages, there was a proposal for a similar concrete skyscraper in the same district. It was called the 80 Natoma skyscraper, and it underwent a strict peer-review process before it went before the Department of Building Inspections. The proposal was rejected, though, as the peer-review revealed that the building had a high risk of sinking due to the weak soil conditions in that neighborhood and the concrete structure’s immense weight.

The Millennium Tower, planned for construction in that same neighborhood and even larger than 80 Natoma, never underwent a peer-review. The developers determined that a peer-review was unnecessary because it could have delayed construction of the tower by several years. And they were right, if, by several years, they meant forever. But this lack of peer-review suggested that perhaps they understood the potential for structural issues with their skyscraper.

Of course, if they did understand that potential, they did almost nothing to combat it. The building rests on a concrete slab built around more than 1,000 concrete friction piles, which descend 18 to 27 meters (60 to 90 feet) into the ground, meaning that the piles are surrounded exclusively by sand. This method had been effective with buildings throughout the area, but never with such a big, heavy structure. In fact, consulting engineers had advised the planners to drill piles into the foundation’s bedrock, more than 60 meters (200 feet) into the ground. In an attempt to cut costs, they ignored this advice and determined to build their skyscraper on a foundation of wet sand.

Blowback, Concerns, and Solutions

The Millennium Tower.By Victorgrigas is licensed under CC-BY-SA

Once the sinking foundation was made public in 2016, property values at Millennium Tower plummeted. Residents who bought during the previous years’ boom now discovered that their property was worth a fraction of what they paid for it—those poor millionaires. 

But, then again, why would anyone want to buy property in a sinking building? Well, inspections financed by Millennium Partners have claimed that the building is still entirely safe to live in despite the weak foundation. Some would call those inspections optimistic, and others downright dangerous. While the foundation is certainly strong enough to keep the building from collapsing on its own, the worst-case scenario could be catastrophic. 

Keep in mind, this building is in downtown San Francisco, the site of some of America’s most famous earthquakes. The last substantial and destructive quake to hit the city came in 1989, but experts warn that the region is overdue. They place the short-term likelihood of a magnitude 7.0 quake at 51 percent and a 6.7 at 72 percent. 

This disaster’s potential consequences are unknown, but the city and its residents aren’t waiting to find out. Despite the seemingly clear evidence that Millennium Partners built the high-rise with full awareness of the risk, the cost of repairs would far exceed their liability insurance. This would leave San Francisco taxpayers responsible for financing the restoration of the already-profitable building that houses some of the city’s wealthiest citizens.

Thankfully, that wasn’t the case. Instead, the lawsuits are being consolidated, and responsibility will be shared. The 100 million dollar project will involve installing 52 piles reaching 76 meters (250 feet) into the bedrock that lies beneath San Francisco, which is precisely what the developers were advised to do in the first place. The majority of the costs will be split between the building’s various stakeholders, though taxpayers will provide an additional 30 million dollars.

As of this video’s publishing, the tower has sunk almost two feet and leans about 15 inches to the northwest. The repairs are expected to finish within a few years, at which point the building will undergo a ten-year re-shifting process. In the end, the building will still have a slight tilt, likely around 7 inches, but it should refrain from any further sinking.

It seems that many of the tower’s residents remain entirely unfazed by the situation, as the skyscraper’s penthouse recently sold for a record 13 million dollars. Nowadays, the high-rise is a popular destination on tour bus stops, as visitors hope to catch a glimpse of the Leaning Tower of San Francisco.

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