🚧 Keep up with all my projects here: practical.engineering/email-list 👷 My engineering failures playlist: ukposts.info/slow/PLTZM4MrZKfW_kLNg2HZxzCBEF-2AuR_vP

At least they didn't build it in an area prone to earthquakes and liquefaction.

Why didn't they just get the residents to put all their stuff at one side?

I did some geotechnical drilling in the Bay Area for a couple years and I hated that bay clay. We called it bay mud as it was super dense, very sticky, and stinky. Fun job though as it was very interesting to literally see the different layers of soil beneath you as you pull out sections of soil and rock. Bedrock coring was my favorite because we would drill and pull out a cylindrical tube of solid rock and we could see all the layering of millions of years of rock formations.

This video was made 7 mos. ago and Hamburger has made more mods to his proposed repair by reducing the number of piles from as I recall, 52 down to 18. This will produce less vibration during installation but pile loading will increase. The fact that they keep tweaking and tweaking the design suggests to me that ultimately this bldg will be torn down or at minimum some number of floors will be removed. All of these measures are stop gap to forestall the inevitable.

Speaking as a geotechnical engineer, this is the best project I’m glad I never worked on.

When The excavator was digging the basement for my new house we found bedrock just a few feet deeper than the original depth planned ... I paid extra to dig down to bedrock. The footings are drilled and pinned to that bedrock, and the ten foot ceilings in the basement make it a unique living space.

I was working on the new construction as a drywall, metal stud framer. The year was winter of 2008 . The windows weren’t installed on many floors and wind would come in and take out anything that wasn’t tied down. The fog would be so thick inside that you couldn’t see but 20’ and the cold temperatures coupled with wind was a challenge. I have some great memories of this project. I was 44 at the time, now 58 and retired from local 152 Martinez Ca. 36 years of framing in the city. The company was Anning Johnson Co. and the foreman’s name Jim Hayden (Retired) and Ted both long time employees of AJ. Thank you for sharing.

As an engineer (albeit in a rather different field) I can say that one of the most demoralizing things in my life have been situations where you discover “yet another problem” that threatens to unhinge the entire project. I have no idea whether and where the mistakes may have been made, but I empathize with what the various engineers in this story must have (and are likely still) gone/going through…

There's something uniquely unsettling about such a large building tilting.

I've probably said this before, but I'll say it again: I'm pleasantly surprised and gratified that such technical videos appear to be so popular. I'm sure that a lot of it has to do with how well they are assembled and presented, but I think it also says a lot about people's interest in technical subjects. People are smarter than they're often given credit for, and subjects can be highly technical as long as they are also clearly explained. Thanks for what you do and how well that you do it.

The UKposts channel "Building Integrity" had an interesting update on this a couple days ago where he predicted that the steel plates transferring the hydraulic load into the concrete are way too small. Now I'm the wrong kind of engineer to have an opinion on this but there might be a chance for an update video if this whole rescue plan fails spectacularly 😄

So my understand was that not only was it the piles not reaching through the old bay mud to the dense bedrock, but that the structural system was also changed. Originally the plan was for the building to be constructed with steel girders and columns and thus the engineers understood that the old bay mud should be enough for the structure as it was designed. The developer however in a bid to save cost on the structure proposed with the contractor to replace the structural system with a reinforced concrete design, not taking into account the design for the sub-structure that was going into the ground. This also contributed on top of the issues outlined in this video about why the building sunk faster, but the added weight of the concrete instead of steel was also not taken into account thus exacerbated the sinking.

“This structure is incomplete and already tilting” “No worries, just keep building”

“But the estimated cost for the repair was as much as $500 million, more than the original cost of the entire building. Turns out it’s a lot easier to drill foundation piles before the building’s built than afterwards.”. Great quote, you win this one

I can't believe I'm 2/3 the way through a video about clay consolidation and actually anxious to see the ending. This is thrilling.

Jeez, this channel is addicting. I love knowing how things work and am especially interested in infrastructure stuff you can't always see. It also helps that I'm in San Antonio so I see local stuff I've wondered about.

6:41 - a comprehensive settlement... (of the legal kind) 😆

Channels like this are literally all I wanted as a kid while watching shows like modern marvels. Its so fun and the content is informative.

I happened upon this video and am I glad a did. What a serendipitous find it was. Your explanation of what is going on at Millennium Tower is, perhaps, the best comprehensive overview I have ever heard...from the beginning of this ordeal back in 2016. The manner with which you explain the engineering situation even as you allow the listener to remain interested in the topic...is outstanding. I am not an engineer but you kept my interest for the entire video. You remind me of the professors I had as an undergrad who explained things so well, you actually didn't want the class to come to an end each day. Great job!

After what happened in Miami, you'd have to be crazy to trust a building with a history of problems like this.

I remember the master technician who came to install our new catheterization lab in our hospital. $2.2 million of new equipment. He was complaining that the new concrete ceiling was not quite parallel with the floor, so the suspended gantries for the equipment would tend to drift a bit. He asked me, the chief of the department, how this could be if the ceiling contractor had used laser levels as called for in the specs. I had not the courage to tell him that the guy had moved a stick around to measure the distance between the floor and ceiling.

I'd like to know a lot more about how the retrofit connects to the existing slab.

I’m a Structural Enginner and it is always a challenge when deciding how many would borings to do. Clients never want to pay for them all and we are forced to reduce them. I often think that since people build decks in their backyard or patch their sidewalk they think that they can be a civil or structural engineer. Backyard work is not 6 years of school for a masters degree, a PE and many years of working on projects as a design engineer.

Grady, I'd love a ~1 year update on this project as the saga continues!

I was an ironworker on this building from footings up. The amount of rebar in the foundation is nuts, but VERY early in the project it was well-known to be built to outdated foundation specs compared to the change orders tacked on going vertical. These issues were brought to the attention of the general contractor AND the developer. They could have been corrected early on, but the developer downplayed them to minimize costs and maximize profits. These issues were known BEFORE the structure reached street level. I’m not saying anything, I’m just saying… *cough* scumbags *cough*. Even before the iron stopped flying and the finish work began, the building was leaning. It was a fucking nightmare to work on if I was under someone that liked setting down (and subsequently losing) their tools and dropping them on me. It’s funny until you realize some sleever bars weigh 10lbs and have a tapered tip. This place is going ass over tea kettle during the next major earthquake. I hope the responsible parties have to sleep on the streets by the time the problems are corrected. They acted with zero regard and responsibility to the people dumb enough to move into this building… and what is the US if it isn’t coddling the stupidest, most entitled, and greediest among us?

I happen to be intimately familiar with this story and have to say, Grady did a fantastic job of explaining the high points and presenting accurate material. Extremely well done sir!

Very interesting! Always like to find out more about subjects outside my own line of business. I live close to the River Thames and saw apartment buildings being constructed directly on the southern banks, replacing wharves. They are only 10 storeys high, but when they started construction, the drills used for the foundations were as long as the buildings are now tall. On this side of the river we have the infamous London clay and building so close to the river must have been an additional challenge.

Thank you for that VERY interesting report !!! It is always fascinating to watch the videos you make on Civil Engineering - absolutely love them !!

I don't think that an engineering report stating that the building is already well out of spec, and that its condition continues to deteriorate, is quite the same thing as declaring it "perfectly safe". It's more like declaring it "not unsafe yet".

In my town here in the UK, every building, including homes, have to be bedrock piled. Our house is on 175' piles. The town is largely built on reclaimed beach and marshland. Watching piles being installed at the new build across the street was interesting, seeing the driver hammer away, adding pile after pile, then suddenly seeing the stack drop and freefall through some underground layer was quite astounding.

The 52 piles originally planned have apparently been reduced to 18 piles. These piles will be very slender. How on earth (no pun intended) can these piles be kept from buckling (see Euler) which reduces their load carrying capacity? If they are over drilling the holes so that "no part of the new piles can come into contact with the Old Bay Clay" and then the space filled with low strength material, what will prevent buckling of the columns under these very high loads of 800,000 pounds per pile? Have the engineers calculated what load (based on the length of the unsupported column) each pile can handle without beginning to buckle?

Another great video Grady. Let's hope this building remains safe and standing. Maybe sometimes it's just not worth building towers of such size and weight in certain areas.

This was a great explanation about something I see in the news often as a Bay Area resident. The media doesn't report the details, so putting the current pile upgrade into context was difficult. Seeing how the pile fix actually works, I can really see how incredibly challenging this fix is and why they're having some problems with it.

In a city known for earthquakes and unstable soil, it is unthinkable that ANY high rise was ever approved where there was a bedrock footing option. I heard it would only have cost $4 million more to do this. No doubt there are single units in this building that cost that much.

Everything above the bedrock just sounds like really thick porridge to me. I can understand the reasoning behind their initial design with the friction piles, but failing to account for the water getting squeezed out by the enormous pressure of the building is a pretty big failure.

First thing that came to mind was exactly what you said about the vibration is making it settle. Why not put pop out anchors similar to Wall anchors down that will open as it settles.

Great report! Nicely done! As a Structural Engineer for 4 decades, a few notes for your consideration: 1. Residential foundations are designed for a maximum 1500 PSF per the building code. The typical footing pressure is around 1000-1200 PSF, not 100PSF. 2. Friction piles rely on their skin contact with the soil. In most large scale projects, this is tested first with a test pile. It's not clear if they did this here, but should have to verify the pile solution was practical. In design process, engineers will use friction values from a "table" but should always field verify this is realistic by using test piles. 3. Dewatering is a definite cause of distress because loss of water will accelerate settlement, as you pointed out. The engineers should have considered this fact in their design. Fluctuating ground water table is also a cause of concern and in SF area is a contributing cause to settlement of structures. The original design engineers are De Simone based out of Chicago, IL, and it's unclear whether they have this local expertise. 4. The retrofit design was not from De Simone [developer's engineer] but instead from Simpson-Gumpertz, a SF based engineer. They did not predict accurately the potential settlement during construction and have resulted in recent work stoppages. 5. The seismic resistance of this building is highly questionable, in my opinion, because of all the errors made thus far and I would not advise anyone to buy a unit let alone live here. Thanks! Dilip Khatri, PhD, SE

This reminds me of the new hospital in Muskegon. MI. They never accounted for all the sand it is built on top of. The new ER has I believe, 62 rooms. Half could not be used at first because the doors were stuck to the floor. I had a CT scan there a few years after it was built, and they had that door held open with weighted bags. A nurse told us that upstairs, they can't leave patient carts in the hallway as they roll away.

Thank you soo much ! I love learning from your presentations !!

"The developer's engineers and the City have shown that the building is perfectly safe through detailed modelling and investigation." Literally the ENTIRE story of this building, including the novel fix you mentioned before this point, can be summed up as "This thing isn't behaving like we expected it to." I get that media can be sensationalist and click-baity, but given what's happened with this building would YOU trust it? I wouldn't. Confidence can come when the engineers don't have to go back to the drawing board every month.

I have designed a few 42-floor buildings with friction bored pile foundations that went down to 45m. It shocks me to learn that simple reinforced concrete-driven piles were used for the Millennium Tower and it was only driven to 24m !! The correct choice of foundation should have been large diameter cast in situ concrete bored piles installed to a depth slightly beyond the Old Bay Clay layer. Large diameter bored piles also overcome the slenderness problem of conventional driven piles which have limited load-bearing capacity.

"Soils don't care about property lines." Succinctly put and true of Nature in general. And I think this channel Rocks!

I really enjoy your explanations sir, very entertaining indeed! 👍🏻👍🏻

In Germany there is a 16th century fortress that has broke apart due to nearby surface mining if brown coal. They also stabilized it and half the buildings inside (a school) stand on giant dampeners

Growing up we were always taught that all skyscrapers had foundations that reached down to bedrock. Thanks to this illuminating video presentation, I now see that that isn’t always true! Thank you for this great educational program.

10:50 "The story of the Millennium Tower is a fascinating case study in geo-technical engineering". None of the news stories I read had that as a headline. Maybe they should have.

It's a real pleasure to get an informed and indepth look into a troublesome project like this, beyond the clickbait headlines

in Santos Beach city in Brazil we had exactly the same problem, but for smaller and older buildings. A plenty of them have tilted over the years

I remember mounting TVs and other Audio Video equipment in that building years ago before they announced the lean. It was hilarious having to call my colleagues into the rooms to assist me in leveling the equipment. All of our bubble levels were so off that we had to measure from the floor & ceiling to get things plumb. 😂

"Turns out, it's easier to build the foundations before you build the building." I think these are words to live by

Are there more videos about the millennial tower with more detail about how they actually build the structure to support how they did all the retro? Love this video also thanks very much.

Well presented! I was drawn here from the articles and came to seek out more information!

I would like to know why this tower had this issue while larger towers nearby didn't suffer the same fate. You discussed that the dewatering for other projects affected this one. His did those same Fircrest affect the others or what did they design differently?

If anyone is curious, the SF region in general has much if not most of its buildings sitting on this clay. Every year, buildings flex a bit when the ground dries and rehydrates. The Gently Rolling Hills of the Bay Area are thousands-feet-high clay on rock. And we have multiple fault lines running through, just to make things interesting. I get nervous about a big quake anytime it's been raining for a few weeks: hill leveling.

A follow up on this would be great. From what I saw in December 2023 significant issues were still ongoing

i was working on a bridge above a soft soil, which are 60 meters thick, and me and my team wouldn't even hesitate to used 60m bored pile down to the bed rock, as when engineers faced with this kind of problem, we don't messing around, we go to the basic, it might be expensive design, but it would be the one that make us the engineers sleep well at night.

Funnily enough there's a "Millennium Tower" in Glasgow in Scotland that also had major problems. (tallest structure capable of rotating 360 degrees)

I think we need an update. I read recently that the "mat" in the lowest basement is also unevenly sinking, suggesting even more issues. Thanks for the great videos. To compensate you, I have added my like, above.

Thank you for sharing this wonderful analysis

I honestly don’t know why people would ever move into a place like that. What a nightmare.

Thanks for this! One fun detail for the folks at home is that the tilting is starting to affect the drainage of the sewer. Having dealt with an expensive sewer replacement caused by poor drainage, at some point the residents are going to get a large bill.

Apparently another because of the problem is that initially the building was supposed to be a lighter all steel structure but after the foundation was completed, they decided to make it a concrete structure or a mix of concrete and steel, the new construction method being much heavier than initially planned. Rather than verifying this foundation could handle the extra weight, they just did it and got burned.

This is such a fascinating story, especially because I grew up in Central California (near the SF Bay).

Well done. I do not find this video boring at all...but would love more pictures. Thanks!

I think we've all had a bad case of friction piles.

I am just a truck driver from Oregon but everything about this video was super fascinating. I have taken days off in San Francisco a few times, and I have walked by this building wondering what they planned on doing with it, and this video gave me all the answers I was looking for. FYI I STILL WOULD NEVER TRUST THAT BUILDING!!!

Excellent explanation! Thank you!

Great video. Much info.

"Safe" it may be, but settling that far has misaligned the utilities with the ground, and horizontal plumbing lines inside the building no longer have enough slope to drain properly.

“How do engineers predict how soil will behave under extreme loading conditions?” Often poorly, it seems

When you build up on the sand...this is why you drill to bedrock! Always always always! And instead of hammering the piles down to bedrock they should drill down to bedrock that would reduce the vibration to the surrounding buildings because you have an auger like mechanism bringing the soils you are displacing up to the surface versus just pounding them down

Excellent presentation thank you!

I love your content you have educated me so much on general engineering thank you so much keep doing what you're doing your efforts are bountifully appreciated

Excellent vid! I was wondering what happened with this structure a few weeks ago, glad you cleared it up. "a comprehensive settlement, the legal kind." lol. Nice.

Extremely well-done, thanks. Regards from Baltimore.

Clear and interesting! Thank you. 👏

As a sf resident I have been witnessing this mess first hand. There was a firm who tried telling the city/developers the building would sink way more than expect. They were ignored. It’s relevant because now the same firm is desperately trying to get city halls attention because they think the fix will only temporarily be effective then make things worse.

"Let me know what you think" What I think is that with my studies in engineering school (majoring in soil mechanics and structures, but got engineering jobs after graduation in 1974 in different areas of engineering), I recall designs solving the problem of erection of commercial buildings over compressible clay layers by driving piles (creosoted wood, steel cross sections, or reinforced concrete depending on the building, the clay layer etc.) down to bedrock or a at least a less-compressible stratum. I can't say for certain, but it seems to me to expect a clay layer to support a skyscraper is really sketchy in both of the aspects of consolidation of the clay and the expected friction of the clay against the piles. The design engineers were probably told to come up with the cheapest design they could think of. lol The owners also may have told the general contractor to skip some of the soil exploration and testing and use test data from adjacent buildings in order to save money. Projects have failed due to that error. At least back in 1974 and earlier.

This was fantastic, keep it up!

I can’t believe they EVER let a skyscraper get built on anything BUT bedrock, a LOT of bedrock. It’s a miracle ANY of those Mud Towers are still standing at all.

As someone who works in a field very distant engineering or architecture, this articulation was so helpful! Really made it easy to track and understand. Thank you 🙏🏾

I live in the tower, and your analysis completely neglected the most important concern. My pool table is regularly out of level. It’s a damn nightmare

Thanks for the explanation.

Fantastic video!!! Great job

Beat me to it! Wish I wasn't so busy. Good job Grady.

In another decade, we will be hearing: The new plan is to put flying buttresses on the tower providing it with a tasteful Notre Dame look while reducing tilting.

Great presentation. If the new piles are eventually driven, I can picture another issue - problems tying in the the slab extensions to the existing slab. That’s a lot of doweling.

excellent summary, thanks!

Always scared every time I drive by it, especially when I'm on the Bay Bridge. I'm always thinking "Not today please"

I object to the "perfectly safe" bit. It's perfectly safe *now*, but the exact same reports warn about the risk of it becoming unsafe as the settlement continues. People don't buy expensive condos to leave after a year, they typically want to keep them for a long time. They definitely don't want to lose access to their home because it becomes unsafe. It's not the safety *now* that matters, it's the safety outlook for the next 30 years.

Excellent explanation. Thanks.

Great video and explanation. Thank you

The same issue occurred with the old cantilever section of the Bay Bridge. Cheaper to not go all the way to bedrock, so thousands of fir pilings driven into the mud supported the concrete pillars. The 1989 earthquake exposed what a problem this was. It is funny that the developer doesn't have the money to do it right the first time, but they have the money to try and repair it later.

Yeah... I remember the fist time I heard about the Millennium Tower in our local news... they were showing residents setting down a ball on their floor and watching it roll (with some speed) towards the corner of their condo. At first I wasn't sure what I was seeing, little did I know it would turn out to be a huge problem like it did. The building also had broken windows high up, they said "wasn't caused by the settling" but if not, then that's odd, and you mentioned the trans-bay terminal, I think it had problems from settlement too, they had to close the road under the crossing, rerouting the buses and vehicle traffic, making a real headache... I think the steel support beams were cracking so for that they put jacks while they retrofitted the supports... that whole area is just a hot-mess of construction issues plaguing both of these projects. I'm glad I don't live in S.F. but the whole SF Bay Area is an earthquake disaster area waiting to happen.

really intereesting!!! thank you!

Hi, Grady. Would you do a video on the Orroville Dam Spillway?

Every video you ever make is so absolutely interesting and insightful! As an engineer myself I still constantly find myself learning bits and pieces from your videos. Keep up the great work!

Scary! Funny, we (Toronto) have the total opposite problem. Our entire substrata is solid rock, that is rising, or rebounding, up to 1-3 cm per year, why? During the last Ice Age, where Toronto currently sits, was 2km of ice, it’s immense weight pushing the ground down. Since the last glacier retreated, the ground has continued to rebound to this very day. It’s great for stable foundations, hence the explosion of skyscraper construction over the last 15 years (we now have the most skyscrapers in North America, second only to NYC)….but despite all those heavy towers, the solid rock beneath our feet continues to rise, creating numerous issues that we’ve now learned to overcome. After the initial foundations are dug, and it’s walls securely in place, they install countless rods into those walls, and wait approximately 3 months. If the rods begin falling out, they must wait until the foundation has sufficiently equalized before pouring the base slab. To do so too soon, could result in the same problem the tower in this video has, but for totally different reasons. However, with hundreds of skyscrapers recently built, under construction, or awaiting approval, it seems they’ve conquered this problem…if only they’d use quality materials. Dozens of condo towers, most by the waterfront, owned by a Chinese consortium, were built with the cheapest materials possible, resulting in brand new buildings falling apart. They’ve had to replace all the windows and glass panels after a series of disasters, with huge glass slabs falling off from 40+ stories up, crashing to the ground, I’ll never understand how they received final approval before allowing tenants to move in, when these building were falling apart! Someone is getting rich from bribe money! My co-worker was unlucky enough to have bought one of these units, a 650 sq ft 1BR unit on the 45th floor. The day she moved in, none of the doors would close fully, her balcony door was frozen in place, due to installing all doors and windows, before the concrete had cured sufficiently, causing all doors and windows to be immobile. She had no water in her kitchen, the drains weren’t even connected, forcing her to use her bathroom sink for everything. Then, as winter approached, all her windows and balcony glass panels fell out, nearly killing several people on the street below! She paid $1.1 million for it, yet it was like living in a slum! All the residents hired a lawyer and sued the developer, but surprise surprise, they were in China, refused to do anything about it, and hid from our officials, after making billions off this disaster. So, all owners were on the hook to pay for all repairs! Luckily, city council knew they screwed up, as that building, along with over a dozen others, all built by the same crooked, criminal consortium from China, should NEVER have been given final inspection approval. Knowing the people would sue the city as they were unable to sue the developer, the city quietly paid for all repairs, costing we, the fax payers, well over $300 000 000!!! (The feds paid most of it). The moral of the story? BUYER BEWARE!!! ESPECIALLY IN TORONTO AND VANCOUVER ( Same Chinese developers did the same in Vancouver over 20 years ago). This is why I prefer to rent, owning is now a game of Russian roulette…if I do finally buy when I retire in a few years, it will be in a well established, older building, that was built properly.

Thank you for telling!