Walk down Mission Street today and you’ll see it. It looks like every other sleek, glass-wrapped pillar of wealth in the South of Market district. But look closer. Or, better yet, bring a marble. If you placed that marble on the floor of a multi-million dollar penthouse near the top, it wouldn't stay put. It would roll. Fast.
The Millennium Tower is arguably the most famous engineering "oops" of the 21st century. It’s a 58-story luxury residential skyscraper that, shortly after completion, started doing something skyscrapers aren't supposed to do. It started sinking. And leaning. By the time the public caught wind of the scale of the disaster, the building wasn't just a few inches off; it was tilting like a vertical shipwreck in slow motion.
It's weird. You’d think a city built on a massive fault line would have the strictest skyscraper rules on the planet. They do. Yet, here we are, talking about a building that has sunk nearly 18 inches into the soft soil of the Bay Area.
The Problem With "Floating" on Mud
The Millennium Tower opened in 2009. It was the "it" building. Joe Montana lived there. It was the height of luxury. But while the glitterati were moving in, the ground underneath was quietly giving way. Most San Francisco skyscrapers are anchored. Engineers drill deep—we’re talking 200 feet or more—to hit the Franciscan bedrock. That’s the solid stuff.
The developers of the Millennium Tower, Millennium Partners, went a different route.
They used a "friction pile" design. Instead of hitting bedrock, they drove 950 reinforced concrete piles about 60 to 90 feet into the dense Colma sand. The idea was that the friction of the sand against the piles would hold the weight. It’s a common technique for shorter buildings. But the Millennium Tower is a 645-foot-tall concrete behemoth. Concrete is heavy. Way heavier than the steel frames used in nearby towers like the Salesforce Tower.
By 2016, the secret was out. The building wasn't just settling; it was sinking unevenly. Because the northwest corner was sinking faster than the rest, the whole structure began to tilt. It’s basically the Leaning Tower of Pisa, but with better WiFi and higher HOA fees.
Why Didn't Anyone See This Coming?
Engineering is usually a game of margins. You overbuild so that even the "worst-case scenario" is covered. In this case, the builders argued that the sinking was caused by nearby construction. Specifically, they pointed fingers at the Transbay Transit Center project next door. They claimed that dewatering—pumping groundwater out of the ground to build the transit hub—weakened the soil under the tower.
The Transbay Joint Powers Authority shot back. They said the tower was already sinking before they even broke ground. It turned into a massive legal mess. Dozens of lawsuits. Hundreds of millions of dollars at stake.
Honestly, it’s a miracle the building stayed occupied. Throughout the years of litigation, city inspectors maintained the building was safe to live in. It wouldn't fall over in an earthquake, they said. But "safe" is a relative term when you're paying $4 million for a condo that is technically crooked.
The $100 Million "Fix" That Made It Worse (At First)
You can't just push a skyscraper back up. The solution was something called "perimeter pile upgrade." Essentially, they decided to do what should have been done in the first place: anchor the building to bedrock.
The plan involved drilling 52 new steel-and-concrete piles 250 feet down into the rock. These piles would act like jacks. They would support the weight of the building on two sides to stop the tilt and maybe even pull it back toward center a little bit.
Construction started in 2020. Then, things got awkward.
In the summer of 2021, while they were installing the new piles, the building started sinking faster. In one month, it sank another inch. The drilling process was vibrating the soil so much that the tower was essentially vibrating itself deeper into the mud. They had to stop. They had to rethink the whole installation process. It was a PR nightmare on top of a structural nightmare.
Key Stats of the Lean
- Total Sinkage: Roughly 18 inches at the base.
- The Tilt: Measured at over 20 inches at the very top (toward the northwest).
- The Cost of Repair: Upwards of $100 million.
- Bedrock Depth: Approximately 200–250 feet below the surface.
Is It Actually Fixed Now?
As of 2024 and 2025, the "fix" is largely considered a success, or at least a stabilization. The new piles are in. They have been "pre-loaded," which means weight has been transferred from the old, failing foundation to the new piles anchored in the rock.
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Engineers like Ronald Hamburger, the lead on the repair project, have been vocal about the building's stability. The tilt has actually improved slightly. They managed to recover about 7 or 8 inches of the lean at the roof level. It’s not perfectly straight—and it likely never will be—but the "crashing into the street" scenario is effectively off the table.
But the stigma? That's harder to fix.
The Millennium Tower remains a cautionary tale for urban planners. It forced San Francisco to change its building codes. Now, if you're building a skyscraper of a certain height in specific soil zones, you must go to bedrock. No exceptions. No "friction pile" shortcuts.
What This Means for the Future of SF
The city is built on a mix of bedrock, sand, and "Man-made land." Large chunks of the Financial District and SoMa sit on what used to be the bay. It’s filled with old ships, trash, and dirt from the 1800s. When an earthquake hits, that ground can undergo "liquefaction." It basically turns into quicksand.
The Millennium Tower survived its lean, but it served as a wake-up call. The skyline is still growing. The Salesforce Tower, the 181 Fremont building—these are all anchored deep into the Franciscan rock. They aren't going anywhere.
If you're looking at the San Francisco skyline from a ferry in the bay, the Millennium Tower looks perfectly normal. You can't see the 20-inch tilt with the naked eye from a distance. But for the people who live there, and the engineers who spent years staring at sensors in the basement, it’s a reminder that even the most massive achievements of man are still at the mercy of the dirt beneath them.
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If you are following the status of the tower or considering property in San Francisco, you should check the San Francisco Department of Building Inspection (DBI) public records. They maintain the "Millennium Tower Monitoring" reports which are released periodically. These documents provide the most granular, data-driven updates on the building’s settlement and tilt.
Additionally, look into the USGS Liquefaction Maps for the Bay Area. Whether you are a renter or a buyer, knowing if a building sits on "Artificial Fill" or "Young Bay Mud" is the single most important factor in predicting how a structure will behave over the next fifty years. Most modern towers built after 2010 have corrected the mistakes of the Millennium, but older mid-rise buildings in the district often still rely on the same soil-friction principles that caused this mess.