11 ms·

Satellites Confirm Sinking of San Francisco's Millennium Tower

123 points by pmar 10y ago

laurencei 10y ago
"The Sentinel-1 satellites have shown that the Millennium Tower skyscraper in the centre of San Francisco is sinking by a few centimetres a year" I'm no engineer - but to me "a few cm a year" seems very significant, and would be easily detectable by current surveying technology? You would probably even visually be able to see it at the entrance to the building after 1-2 years? Why was a satellitie needed here to confirm it?
- eitally 10y ago
  It wasn't, but if you have a satellite, why not? :) http://www.nytimes.com/2016/11/04/us/san-francisco-files-lawsuit-against-sinking-millennium-tower.html?_r=0 http://www.nytimes.com/2016/11/04/us/san-francisco-files-law... http://sf.curbed.com/2016/9/16/12945600/why-millennium-tower-sinking http://sf.curbed.com/2016/9/16/12945600/why-millennium-tower... http://www.nbcbayarea.com/news/local/San-Francisco-Taxpayers-on-the-Hook-For-Millennium-Tower-Sinking-Documents-Suggest-400098591.html http://www.nbcbayarea.com/news/local/San-Francisco-Taxpayers...
- tajen 10y ago
  I've learnt from previous discussions on HN that it is indeed a major source of concern for everyone involved, especially since it's also tilting and since it's a seismic area. They build the sidewalks again a few times a year. The tower is quite new and the builders are probably liable. The use of the satellite is probably rather to highlight that the Millenium tower isn't the only one.
- Dylan16807 10y ago
  A cheap GPS device can give you millimeter-level measurements every few hours, so using an active satellite does seem like overkill.
  - clord 10y ago
    The article points out this can cover huge swaths and millions of buildings at once. It speaks of covering a continent with subsidence alerts. Afixing gps to each building might not be competitive.
    - Dylan16807 10y ago
      It can do that. And that's pretty cool. But that's not what they chose to focus the article on.
      - privong 10y ago
        > But that's not what they chose to focus the article on. The first few paragraphs are about the Millennium Tower, but that's just the hook. The rest of the article discusses the wide-area applications, including SF, elsewhere in the Bay Area, and Oslo, Norway.
  - surveyor 10y ago
    I don't know what your exact definitions is of "cheap", "millimeter-level", and "every few hours", but your comment does sound a bit misinformed. What you are possibly referring to is called dimensional control in geomatics and civil engineering, and there are various measurement techniques that can be applied, including GNSS-based. In a way, the hardest part of it is the planning phase, where you have to decide which technique is most appropriate to meet precision, accuracy, timeliness, and cost constraints. All those factors kind of fight against each other. Finding the sweet spot is non-trivial.
    - Dylan16807 10y ago
      Okay, tell me where I'm wrong: AFAIK you can buy a few hundred to few thousand dollar receiver that tracks the carrier phase, let it sit around for a few hours, and then with aggressive post-processing you should be able to figure out the right phase and know your location within a few mm. Edit: And worst-case, you should be able to do an exact survey once, and then you can remember that and know which phase to use in the future. (Barring sudden multi-cm shifts, but in that case you have bigger problems.) You still have atmospheric fluctuations to deal with, but that's why you're measuring all day.
- jdehls 10y ago
  You can certainly measure this with current surveying techniques. What the satellite InSAR technology allows is the measurement of millions of points at the same time, over thousands of square kilometres. And with the Sentinel-1 satellites providing free images every 6 or 12 days, the measurements can be updated frequently.
  - notahacker 10y ago
    Authoritative third party records that establish the period over which a building or land started to move is also potentially useful in resolving disputes over who and what might be responsible for the movement (nb: I'm currently working with startup that consults on satellite/legal issues)
  - Animats 10y ago
    You can certainly measure this with current surveying techniques. Not easily. And compared to what? The classic USGS survey markers don't have their height measured accurately enough, and they move with the land. The USGS does have precision "vertical control point" markers, and there are about ten of them along the northeastern coast of San Francisco. The highest precision vertical control point nearby is a GPS station on top of Building 1 at Fort Mason, and its height is valid only to 1.35cm accuracy at 95% confidence.[2] Absolute elevation is tough to measure at those scales. Relative elevation, relative to the average of all ground points for, say, a kilometer radius, is something a radar satellite can do well. [1] https://www.ngs.noaa.gov/NGSDataExplorer/ https://www.ngs.noaa.gov/NGSDataExplorer/ [2] http://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=AF8575 http://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=AF8575
joeblau 10y ago
I would be infuriated if I purchased a condo there. It seems like every month since last year, there are articles talking about the project. I haven't heard any solutions to the problem and I don't know anything about construction. Is this the type of problem that can be fixed, or will they have to destroy the building and rebuild it?
- jaclaz 10y ago
  The main issue here is understanding what is the actual cause of the sinking: 1) extensive dewatering of the soil under the building and around it 2) some mistake in the calculations of the project and/or some foundation work made in difformity from the project 3) a combination of the two IF it is only #1 (this is what the builders say) then stopping the water drainage or even (in certain case) re-watering appropriately the soil would stop the sinking (at a relatively low cost). IF it is #2 or #3 it is certainly possible to "better" the soil underneath or "add" some (underground) supporting structures (at a much, much higher cost). And of course someone will have to pay the bill. Techically, IF the cause is #1, it is called "subsidence": https://en.wikipedia.org/wiki/Subsidence https://en.wikipedia.org/wiki/Subsidence more specifically: https://en.wikipedia.org/wiki/Groundwater-related_subsidence https://en.wikipedia.org/wiki/Groundwater-related_subsidence Edit: P.S.: Seemingly the SF Millennium got just cited here also: https://en.wikipedia.org/wiki/List_of_leaning_towers https://en.wikipedia.org/wiki/List_of_leaning_towers (maybe exaggerating a little bit, look for Santos, Brazil, strangely not listed in the wikipedia page)
- cmurf 10y ago
  Too soon to tell. They need undisputable facts about the building shifting positions, and exactly what the risk is. High risk means the governing authority can condemn it, get people out, and sort out liability later. No doubt determining liability will involve a lot of insurance negotiations along with various court cases. Maybe there's a code violation, but plans showing an inevitable violation were approved? Who is liable for that? Etc. There are many possible sources, even distributed sources, for a mistake like this. But central is determining the scope of the damage.
cobbzilla 10y ago
it boggles my mind that the developers were not required to sink the foundation piles all the way into bedrock. how unusual is this for tall buildings in the city by the bay? there is so much wealth in SF, this is a luxury tower, it's all a bit strange.
- brogrammernot 10y ago
  I worked in business litigation for a few years and I obviously can't go into any specifics but you'd be shocked/surprised at the number of buildings that the plans say X but somehow Y happened....
  - brianwawok 10y ago
    Owned a condo. Code and plans said to install a drain clean out in the main sewer line. Cost to builder? Maybe $20. Done wrong and closed up, no one knew so he got away. Few years later, maybe 10k in damages and 5k to fix. All so the builder could save $20. Things like this x 100 are everywhere. This is why building codes are nice, although people complain about them.
    - arethuza 10y ago
      Even basics like "does the person/company building something own the land it is built on" can go horribly wrong. Edit: Here in Scotland if someone builds something on your land then it belongs to you and you are under no obligation to warn them of this fact!
      - brianwawok 10y ago
        Yah there is that. In the US, it is usually mandated that you get something called "title insurance". There are different levels depending who it protects (lender vs buyer). If down the line it turns out you don't own the land your house is on, the title insurance company does lawsuit magic or somehow pays to make the lender whole. End up costing ?? $1,000 or so per real estate transaction. 99.9999% of the time pays back zero. I suppose nice to have for the last .0001%.
physcab 10y ago
I'm no civil engineer but I talked to one about this story and the concerns seem to be overblown. First, the foundation as I am aware is created by drilling to the point of refusal. Obviously bedrock is ideal, but in a place like SF where some of the land is based off old landfill, refusal is acceptable. From there a concrete foundation is laid and the building rests upon it. Concrete slabs are secure and in the event of an earthquake it will be allowed to shift and "float" if the ground underneath liquifies. Secondly, the sinking and leaning can be corrected. Engineers account for some level of sinkage as the building settles, and if it tilts, they can apply ties to the sides to straighten it. In the most severe of cases they can shore up the foundation and build more supports. I'm sure the builders are examining their options currently so it'll be interesting to see what course of action they take.
- bluthru 10y ago
  >but in a place like SF where some of the land is based off old landfill, refusal is acceptable For a steel-frame building, yes. For a concrete high rise you're playing with fire. I'm surprised the building code allowed this.
- sgslo 10y ago
  Displacement like this seems like not such a big deal, especially when worded as it is in this article. You see "...several CM of displacement per year..." and you immediately are lead to believe that this displacement is equal over the entire footprint of the structure. That is usually not the case. Instead, you end up with differential displacement over the entire footprint of the building. Some areas will sink 1cm, while others will sink 3cm. This "imposed displacement" puts the foundation under constant force, causing some tremendous force to be placed on the structure itself, as the foundation is now behaving as a beam of sorts.
- tomarr 10y ago
  I'm in a similar line of work and don't fully agree with this. Yes everything he's said is true, but to an extent, and having these rates of settlement per year is very troubling for a structure designed to live 60-100+ years. If the issue is not groundwater related (which seems unlikely with surrounding structures largely OK) then expensive remedial work (underpinning / grouting / similar) is going to be required in the immediate future before this causes serious issues. Admittedly I don't work in an seismically active region but I design for max settlements of ~50mm over a building's lifetime, and the Millennium Tower is experiencing that every year.
sulam 10y ago
It's not discussed in the article but I'm very curious about the brightest spot in the SF Bay Area in the survey image. It's not Millenium Tower (which I work next to so that's pretty interesting too). It's actually the land just west of Oakland airport, the part of Alameda built up in the 80s called Bay Farm. As I understand it the area was marsh up until then -- that and a garbage dump that has since been covered. Does anyone know if the land there really is sinking so fast? It's not on a fault so I'm fairly sure it's not moving much laterally.
- dspig 10y ago
  Maybe a garbage dump that has been covered would be expected to sink?
  - sulam 10y ago
    Sure, but it's the entire development.
woliveirajr 10y ago
I find it amazing how civil satellite can be kept in orbit, be it geostationary or not, and monitor "millions of points" spread to some great km and be able to detect (or provide image with enough resolution) so that a move of few cm can be detected.
- dogma1138 10y ago
  Most countries launch EOS's that are either civilian grade or considerably lesser than that. Only the US has really the ability to fund the crazy bus sized EOS platforms.
  - adrianN 10y ago
    Himawari is a Japanese weather satellite that is 8m long and weighs 3.5 tons.
    - dogma1138 10y ago
      Block III and newer K-11 platforms are 20 meters in length and weight 20,000 KG. Also the dry mass of Himawari is 1300 kg, it's based on the MELCO DS-2000 bus which is meant for communication satellites, it doesn't have an 8M telescope assembly.
      - adrianN 10y ago
        Okay, that's really big. Thanks for the info!
deegles 10y ago
Somewhat unrelated, but for me this is another argument in favor of renting vs. buying. Sure, most people won't buy a super expensive condo in a super expensive city that happens to be sinking into the ground, but if you taken that $1.5m (they go for much more[0]) and put it into index funds instead, you could pay ~$5k/mo in rent forever and just leave when problems arise. http://sf.curbed.com/2016/8/5/12390756/on-sale-millennium-tower http://sf.curbed.com/2016/8/5/12390756/on-sale-millennium-to...
- aristus 10y ago
  4% return above inflation and taxes is a bit optimistic long-term, but otherwise this is correct. However where you stand depends on where you sit. Many other factor have to be "priced in" and the prices are dependent on what's important to you. Eg, factor in equity (after 15-30 years of mortgage you own a condo), valuation (in 15-30 years that condo will be worth more than 1.5M), risk (...unless that condo sinks into the mud!), finance (you can borrow 1.5M to buy a condo but you can't borrow 1.5M to invest and rent), and flexibility (you can move out of a rental more easily then selling a condo).
  - xapata 10y ago
    Many financial planners assume 4% or even 5% annual returns above inflation. Heck, I forget which state it was, but I remember reading about some boneheaded assumption of 8% annually written into the laws for its pension fund. I agree that 4% is optimistic.
    - shostack 10y ago
      Why is that do you think? If you pay them a fee and they aren't pushing investment products you'd think they'd be more realistic...
      - xapata 10y ago
        Historically, 4 or 5% appears to be a reasonable expectation over a 30-year timeframe after 1940 if you consider each year as an independent random variable and expect that the future will look mostly like the past.
packetized 10y ago
Interesting that the lead photo[0] also shows Salesforce East (formerly Salesforce Plaza, 350 Mission) also sinking at a similar rate. I'm wondering what all of this will end up meaning for Salesforce Tower (the large hole in the ground to the left of the Millennium Tower), since it's close to topping out and will be one of the two tallest buildings west of the Mississippi River. [0]: http://www.esa.int/spaceinimages/Images/2016/11/Millennium_Tower_sinking http://www.esa.int/spaceinimages/Images/2016/11/Millennium_T...
- packetized 10y ago
  Also of note: you can actually see the buckling of the sidewalk and curbing immediately adjacent to the Millennium Tower. I'll see if I can get a photo to share today. There's certainly quite a bit of heavy construction equipment traveling on Fremont/Mission, but I can't see how it would cause buckling sidewalks.
debt 10y ago
could there possibly be an enormous sinkhole beneath or nearby the pilons?
mannykannot 10y ago
This is from memory, and I have not been able to confirm it with a cursory search, but FWIW: In most of central London, the bedrock is far below (which allows for deep Tube tunnels), so high-rises do not rest on bedrock, and are at least partially supported by the buoyancy of large rigid basements. Of course, London does not have the seismic risk of San Francisco. I would guess that buoyancy might be an asset with regard to support, but possibly a liability with regard to stability, in the face of liquefaction.

123 points by pmar 10y ago

"The Sentinel-1 satellites have shown that the Millennium Tower skyscraper in the centre of San Francisco is sinking by a few centimetres a year" I'm no engineer - but to me "a few cm a year" seems very significant, and would be easily detectable by current surveying technology? You would probably even visually be able to see it at the entrance to the building after 1-2 years? Why was a satellitie needed here to confirm it?

eitally 10y ago
It wasn't, but if you have a satellite, why not? :) http://www.nytimes.com/2016/11/04/us/san-francisco-files-lawsuit-against-sinking-millennium-tower.html?_r=0 http://www.nytimes.com/2016/11/04/us/san-francisco-files-law... http://sf.curbed.com/2016/9/16/12945600/why-millennium-tower-sinking http://sf.curbed.com/2016/9/16/12945600/why-millennium-tower... http://www.nbcbayarea.com/news/local/San-Francisco-Taxpayers-on-the-Hook-For-Millennium-Tower-Sinking-Documents-Suggest-400098591.html http://www.nbcbayarea.com/news/local/San-Francisco-Taxpayers...
tajen 10y ago
I've learnt from previous discussions on HN that it is indeed a major source of concern for everyone involved, especially since it's also tilting and since it's a seismic area. They build the sidewalks again a few times a year. The tower is quite new and the builders are probably liable. The use of the satellite is probably rather to highlight that the Millenium tower isn't the only one.
Dylan16807 10y ago
A cheap GPS device can give you millimeter-level measurements every few hours, so using an active satellite does seem like overkill.
- clord 10y ago
  The article points out this can cover huge swaths and millions of buildings at once. It speaks of covering a continent with subsidence alerts. Afixing gps to each building might not be competitive.
  - Dylan16807 10y ago
    It can do that. And that's pretty cool. But that's not what they chose to focus the article on.
    - privong 10y ago
      > But that's not what they chose to focus the article on. The first few paragraphs are about the Millennium Tower, but that's just the hook. The rest of the article discusses the wide-area applications, including SF, elsewhere in the Bay Area, and Oslo, Norway.
- surveyor 10y ago
  I don't know what your exact definitions is of "cheap", "millimeter-level", and "every few hours", but your comment does sound a bit misinformed. What you are possibly referring to is called dimensional control in geomatics and civil engineering, and there are various measurement techniques that can be applied, including GNSS-based. In a way, the hardest part of it is the planning phase, where you have to decide which technique is most appropriate to meet precision, accuracy, timeliness, and cost constraints. All those factors kind of fight against each other. Finding the sweet spot is non-trivial.
  - Dylan16807 10y ago
    Okay, tell me where I'm wrong: AFAIK you can buy a few hundred to few thousand dollar receiver that tracks the carrier phase, let it sit around for a few hours, and then with aggressive post-processing you should be able to figure out the right phase and know your location within a few mm. Edit: And worst-case, you should be able to do an exact survey once, and then you can remember that and know which phase to use in the future. (Barring sudden multi-cm shifts, but in that case you have bigger problems.) You still have atmospheric fluctuations to deal with, but that's why you're measuring all day.
jdehls 10y ago
You can certainly measure this with current surveying techniques. What the satellite InSAR technology allows is the measurement of millions of points at the same time, over thousands of square kilometres. And with the Sentinel-1 satellites providing free images every 6 or 12 days, the measurements can be updated frequently.
- notahacker 10y ago
  Authoritative third party records that establish the period over which a building or land started to move is also potentially useful in resolving disputes over who and what might be responsible for the movement (nb: I'm currently working with startup that consults on satellite/legal issues)
- Animats 10y ago
  You can certainly measure this with current surveying techniques. Not easily. And compared to what? The classic USGS survey markers don't have their height measured accurately enough, and they move with the land. The USGS does have precision "vertical control point" markers, and there are about ten of them along the northeastern coast of San Francisco. The highest precision vertical control point nearby is a GPS station on top of Building 1 at Fort Mason, and its height is valid only to 1.35cm accuracy at 95% confidence.[2] Absolute elevation is tough to measure at those scales. Relative elevation, relative to the average of all ground points for, say, a kilometer radius, is something a radar satellite can do well. [1] https://www.ngs.noaa.gov/NGSDataExplorer/ https://www.ngs.noaa.gov/NGSDataExplorer/ [2] http://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=AF8575 http://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=AF8575

joeblau 10y ago

I would be infuriated if I purchased a condo there. It seems like every month since last year, there are articles talking about the project. I haven't heard any solutions to the problem and I don't know anything about construction. Is this the type of problem that can be fixed, or will they have to destroy the building and rebuild it?

jaclaz 10y ago
The main issue here is understanding what is the actual cause of the sinking: 1) extensive dewatering of the soil under the building and around it 2) some mistake in the calculations of the project and/or some foundation work made in difformity from the project 3) a combination of the two IF it is only #1 (this is what the builders say) then stopping the water drainage or even (in certain case) re-watering appropriately the soil would stop the sinking (at a relatively low cost). IF it is #2 or #3 it is certainly possible to "better" the soil underneath or "add" some (underground) supporting structures (at a much, much higher cost). And of course someone will have to pay the bill. Techically, IF the cause is #1, it is called "subsidence": https://en.wikipedia.org/wiki/Subsidence https://en.wikipedia.org/wiki/Subsidence more specifically: https://en.wikipedia.org/wiki/Groundwater-related_subsidence https://en.wikipedia.org/wiki/Groundwater-related_subsidence Edit: P.S.: Seemingly the SF Millennium got just cited here also: https://en.wikipedia.org/wiki/List_of_leaning_towers https://en.wikipedia.org/wiki/List_of_leaning_towers (maybe exaggerating a little bit, look for Santos, Brazil, strangely not listed in the wikipedia page)
cmurf 10y ago
Too soon to tell. They need undisputable facts about the building shifting positions, and exactly what the risk is. High risk means the governing authority can condemn it, get people out, and sort out liability later. No doubt determining liability will involve a lot of insurance negotiations along with various court cases. Maybe there's a code violation, but plans showing an inevitable violation were approved? Who is liable for that? Etc. There are many possible sources, even distributed sources, for a mistake like this. But central is determining the scope of the damage.

cobbzilla 10y ago

it boggles my mind that the developers were not required to sink the foundation piles all the way into bedrock. how unusual is this for tall buildings in the city by the bay? there is so much wealth in SF, this is a luxury tower, it's all a bit strange.

brogrammernot 10y ago
I worked in business litigation for a few years and I obviously can't go into any specifics but you'd be shocked/surprised at the number of buildings that the plans say X but somehow Y happened....
- brianwawok 10y ago
  Owned a condo. Code and plans said to install a drain clean out in the main sewer line. Cost to builder? Maybe $20. Done wrong and closed up, no one knew so he got away. Few years later, maybe 10k in damages and 5k to fix. All so the builder could save $20. Things like this x 100 are everywhere. This is why building codes are nice, although people complain about them.
  - arethuza 10y ago
    Even basics like "does the person/company building something own the land it is built on" can go horribly wrong. Edit: Here in Scotland if someone builds something on your land then it belongs to you and you are under no obligation to warn them of this fact!
    - brianwawok 10y ago
      Yah there is that. In the US, it is usually mandated that you get something called "title insurance". There are different levels depending who it protects (lender vs buyer). If down the line it turns out you don't own the land your house is on, the title insurance company does lawsuit magic or somehow pays to make the lender whole. End up costing ?? $1,000 or so per real estate transaction. 99.9999% of the time pays back zero. I suppose nice to have for the last .0001%.

physcab 10y ago

I'm no civil engineer but I talked to one about this story and the concerns seem to be overblown. First, the foundation as I am aware is created by drilling to the point of refusal. Obviously bedrock is ideal, but in a place like SF where some of the land is based off old landfill, refusal is acceptable. From there a concrete foundation is laid and the building rests upon it. Concrete slabs are secure and in the event of an earthquake it will be allowed to shift and "float" if the ground underneath liquifies. Secondly, the sinking and leaning can be corrected. Engineers account for some level of sinkage as the building settles, and if it tilts, they can apply ties to the sides to straighten it. In the most severe of cases they can shore up the foundation and build more supports. I'm sure the builders are examining their options currently so it'll be interesting to see what course of action they take.

bluthru 10y ago
>but in a place like SF where some of the land is based off old landfill, refusal is acceptable For a steel-frame building, yes. For a concrete high rise you're playing with fire. I'm surprised the building code allowed this.
sgslo 10y ago
Displacement like this seems like not such a big deal, especially when worded as it is in this article. You see "...several CM of displacement per year..." and you immediately are lead to believe that this displacement is equal over the entire footprint of the structure. That is usually not the case. Instead, you end up with differential displacement over the entire footprint of the building. Some areas will sink 1cm, while others will sink 3cm. This "imposed displacement" puts the foundation under constant force, causing some tremendous force to be placed on the structure itself, as the foundation is now behaving as a beam of sorts.
tomarr 10y ago
I'm in a similar line of work and don't fully agree with this. Yes everything he's said is true, but to an extent, and having these rates of settlement per year is very troubling for a structure designed to live 60-100+ years. If the issue is not groundwater related (which seems unlikely with surrounding structures largely OK) then expensive remedial work (underpinning / grouting / similar) is going to be required in the immediate future before this causes serious issues. Admittedly I don't work in an seismically active region but I design for max settlements of ~50mm over a building's lifetime, and the Millennium Tower is experiencing that every year.

sulam 10y ago

It's not discussed in the article but I'm very curious about the brightest spot in the SF Bay Area in the survey image. It's not Millenium Tower (which I work next to so that's pretty interesting too). It's actually the land just west of Oakland airport, the part of Alameda built up in the 80s called Bay Farm. As I understand it the area was marsh up until then -- that and a garbage dump that has since been covered. Does anyone know if the land there really is sinking so fast? It's not on a fault so I'm fairly sure it's not moving much laterally.

dspig 10y ago
Maybe a garbage dump that has been covered would be expected to sink?
- sulam 10y ago
  Sure, but it's the entire development.

woliveirajr 10y ago

I find it amazing how civil satellite can be kept in orbit, be it geostationary or not, and monitor "millions of points" spread to some great km and be able to detect (or provide image with enough resolution) so that a move of few cm can be detected.

dogma1138 10y ago
Most countries launch EOS's that are either civilian grade or considerably lesser than that. Only the US has really the ability to fund the crazy bus sized EOS platforms.
- adrianN 10y ago
  Himawari is a Japanese weather satellite that is 8m long and weighs 3.5 tons.
  - dogma1138 10y ago
    Block III and newer K-11 platforms are 20 meters in length and weight 20,000 KG. Also the dry mass of Himawari is 1300 kg, it's based on the MELCO DS-2000 bus which is meant for communication satellites, it doesn't have an 8M telescope assembly.
    - adrianN 10y ago
      Okay, that's really big. Thanks for the info!

deegles 10y ago

Somewhat unrelated, but for me this is another argument in favor of renting vs. buying. Sure, most people won't buy a super expensive condo in a super expensive city that happens to be sinking into the ground, but if you taken that $1.5m (they go for much more[0]) and put it into index funds instead, you could pay ~$5k/mo in rent forever and just leave when problems arise. http://sf.curbed.com/2016/8/5/12390756/on-sale-millennium-tower http://sf.curbed.com/2016/8/5/12390756/on-sale-millennium-to...

aristus 10y ago
4% return above inflation and taxes is a bit optimistic long-term, but otherwise this is correct. However where you stand depends on where you sit. Many other factor have to be "priced in" and the prices are dependent on what's important to you. Eg, factor in equity (after 15-30 years of mortgage you own a condo), valuation (in 15-30 years that condo will be worth more than 1.5M), risk (...unless that condo sinks into the mud!), finance (you can borrow 1.5M to buy a condo but you can't borrow 1.5M to invest and rent), and flexibility (you can move out of a rental more easily then selling a condo).
- xapata 10y ago
  Many financial planners assume 4% or even 5% annual returns above inflation. Heck, I forget which state it was, but I remember reading about some boneheaded assumption of 8% annually written into the laws for its pension fund. I agree that 4% is optimistic.
  - shostack 10y ago
    Why is that do you think? If you pay them a fee and they aren't pushing investment products you'd think they'd be more realistic...
    - xapata 10y ago
      Historically, 4 or 5% appears to be a reasonable expectation over a 30-year timeframe after 1940 if you consider each year as an independent random variable and expect that the future will look mostly like the past.

packetized 10y ago

Interesting that the lead photo[0] also shows Salesforce East (formerly Salesforce Plaza, 350 Mission) also sinking at a similar rate. I'm wondering what all of this will end up meaning for Salesforce Tower (the large hole in the ground to the left of the Millennium Tower), since it's close to topping out and will be one of the two tallest buildings west of the Mississippi River. [0]: http://www.esa.int/spaceinimages/Images/2016/11/Millennium_Tower_sinking http://www.esa.int/spaceinimages/Images/2016/11/Millennium_T...

packetized 10y ago
Also of note: you can actually see the buckling of the sidewalk and curbing immediately adjacent to the Millennium Tower. I'll see if I can get a photo to share today. There's certainly quite a bit of heavy construction equipment traveling on Fremont/Mission, but I can't see how it would cause buckling sidewalks.

debt 10y ago

could there possibly be an enormous sinkhole beneath or nearby the pilons?

mannykannot 10y ago

This is from memory, and I have not been able to confirm it with a cursory search, but FWIW: In most of central London, the bedrock is far below (which allows for deep Tube tunnels), so high-rises do not rest on bedrock, and are at least partially supported by the buoyancy of large rigid basements. Of course, London does not have the seismic risk of San Francisco. I would guess that buoyancy might be an asset with regard to support, but possibly a liability with regard to stability, in the face of liquefaction.