Agreed! Grady does a great job of in depth explanations, and has even created some great demonstrations. I really like this classic on his channel: https://www.youtube.com/watch?v=SW-NoiM726U
He also has a video on the millennium tower collapse which I used in my research for this post!
> it’s not just the Millennium tower. Problems with settlement have long plagued projects built on reclaimed land...There are similar projects being built all over the world...Taking these costs into account, it may not make sense to build the building on that reclaimed land, opting instead for more steady ground in a less prime location...For these reasons, I think that we should adjust our priors and temper our expectations of land reclamation...I think that especially in the face of climate change and sea level rise, we ought to shift from the fanatic ideal of dense megastructures built on reclaimed areas...
Can you be more quantitative about these broad claims? My prior is that
(1) For every construction project on reclaimed land you hear about incurring large surprise costs due to poor handling of soil settlement, there are many similar projects that handle the issue safely and profitably, i.e., the big mistakes are outliers.
(2) As the number of such projects grows, the rate of costly errors will *fall* because builders learn and share best practices.
Are there any numbers that might pull me away from this prior?
These are more reasonable priors than I think the average person holds, so first off, good job!
A few things that I would add, not numbers, but a conceptual explanation:
In the case of the Millennium Tower, at least part of the problem (liability still being determined in court but this is what the developers claim) was due to a phenomenon known as subsidence (water leaving the soil voids) caused by adjacent city projects that were dewatering the soil for workability. In soils that were at some point reclaimed or filled, water makes up a much greater proportion of the fill as well as the underlying material (what was once the bottom of the river/lake/bay that has been filled). Therefore, even if a structure is soundly supported by reclaimed land at one point in time, the dynamic nature of local water tables can greatly impact the ability of those soils to support the structure properly. This means that as new projects are built on reclaimed land, the older adjacent projects are put at risk of being impacted by subsidence, so even if the new projects are better engineered, their disturbance of the local water table can turn "safe" projects into big mistake outliers. These effects are rather nebulous and although we know they happen, causality is extremely difficult to prove because of the slow nature of the phenomenon and the lack of active monitoring. This means that developers are largely willing to look the other way and ignore the potential of their projects to affect others, because they know the risk of being held responsible is low.
The only way in my eyes to guarantee that dense megastructures are properly supported regardless of the changing soil conditions is to model the soil at it's worst, which in places like SF is pretty bad because of the muddy conditions and seismic activity typical of the area. This often means that a foundation ends up being greatly overdesigned, (many more piles, driven far deeper, often hooking into bedrock, which can change seismic response properties of the building as well.) which balloons costs. This may not change whether or not we should build densely in these high demand areas, but an accurate cost analysis is key to determining what should be built where!
OK, thanks. This suggests to me that there would be benefits if municipalities better accounted for "dewatering externalities", but this doesn't sound like a reason to be bearish on land reclamation. I could definitely be misunderstanding, but if anything it sounds like a reason to think that the average cost will go *down* if the rate of reclamation increases: if old projects are harmed by new projects dewatering the soil, increasing the total cost of new projects, then there are probably gains to be had by reclaiming land en masse and doing a bunch of building all at once, so that fewer buildings are built under a false assumption that the soil conditions won't change.
I work in this area (in a planning sense) and I think you have hit the nail on the head. The total future redevelopment plan should somehow consider all of this and come up with a best for total area outcome.. which may or may not be individual buildings founding to bedrock etc etc.
However, planning considerations tend not to consider construction, rather the experienced nature of the built form, leaving construction issues to each building.. thus the lack of efficient consideration of the externalities...
Funnily enough, the main critics of more area wide construction considerations in planning tend to be the individual developers, who see this as interfering with their possible innovations.
It is a very important (in my view) but not often discussed 'tragedy of the commons'.
I would push it even further. The public interest shoukd be defined at different levels. In theblow lands, reclaimed land is increasingly re-swamped, to take into account climate crisis related water problems downstream. The interest of tyebdevelopper should be valanced with the interests of the long term occupants, neighboutlrhood, city, state.... yaking every risk into account, does it really make sense to develop further cities prone to water, drought and/or earthquakes? At least the question should be asked.
This is certainly an interesting topic and is worthy of consideration to developers contemplating these projects. The issues related to dewatering impacting nearby properties also seems like an an important consideration in the planning of such developments.
I am curious, did your research find any interesting lessons learned from Japan, other than the discussion of the problems at the Osaka Kansai Airport? Both Osaka and Tokyo have reclaimed hundreds of square kilometers of their waterfronts (see this article for some interesting graphics: https://storymaps.arcgis.com/stories/fdc02295fe7c4dce87a4b0926ecd6d95 ).
Tokyo definitely had plenty of examples of structural problems caused by soil liquification in the 2011 earthquake, but that was a huge earthquake, and most examples of structural failure that are easy to find are from smaller residential structures. Not large projects like the Millennium Tower.
I worked on an architectural team for a project built on reclaimed land in Osaka a few years back, but I didn't pay much attention to this sort of issue since that was the structural engineers responsibility. I kind of wish I had tried to learn more about it now.
Practical Engineering has done a few videos about these issues. I really recommend his YT channel to anyone interested in problems like this.
Great write-up!
Agreed! Grady does a great job of in depth explanations, and has even created some great demonstrations. I really like this classic on his channel: https://www.youtube.com/watch?v=SW-NoiM726U
He also has a video on the millennium tower collapse which I used in my research for this post!
> it’s not just the Millennium tower. Problems with settlement have long plagued projects built on reclaimed land...There are similar projects being built all over the world...Taking these costs into account, it may not make sense to build the building on that reclaimed land, opting instead for more steady ground in a less prime location...For these reasons, I think that we should adjust our priors and temper our expectations of land reclamation...I think that especially in the face of climate change and sea level rise, we ought to shift from the fanatic ideal of dense megastructures built on reclaimed areas...
Can you be more quantitative about these broad claims? My prior is that
(1) For every construction project on reclaimed land you hear about incurring large surprise costs due to poor handling of soil settlement, there are many similar projects that handle the issue safely and profitably, i.e., the big mistakes are outliers.
(2) As the number of such projects grows, the rate of costly errors will *fall* because builders learn and share best practices.
Are there any numbers that might pull me away from this prior?
These are more reasonable priors than I think the average person holds, so first off, good job!
A few things that I would add, not numbers, but a conceptual explanation:
In the case of the Millennium Tower, at least part of the problem (liability still being determined in court but this is what the developers claim) was due to a phenomenon known as subsidence (water leaving the soil voids) caused by adjacent city projects that were dewatering the soil for workability. In soils that were at some point reclaimed or filled, water makes up a much greater proportion of the fill as well as the underlying material (what was once the bottom of the river/lake/bay that has been filled). Therefore, even if a structure is soundly supported by reclaimed land at one point in time, the dynamic nature of local water tables can greatly impact the ability of those soils to support the structure properly. This means that as new projects are built on reclaimed land, the older adjacent projects are put at risk of being impacted by subsidence, so even if the new projects are better engineered, their disturbance of the local water table can turn "safe" projects into big mistake outliers. These effects are rather nebulous and although we know they happen, causality is extremely difficult to prove because of the slow nature of the phenomenon and the lack of active monitoring. This means that developers are largely willing to look the other way and ignore the potential of their projects to affect others, because they know the risk of being held responsible is low.
The only way in my eyes to guarantee that dense megastructures are properly supported regardless of the changing soil conditions is to model the soil at it's worst, which in places like SF is pretty bad because of the muddy conditions and seismic activity typical of the area. This often means that a foundation ends up being greatly overdesigned, (many more piles, driven far deeper, often hooking into bedrock, which can change seismic response properties of the building as well.) which balloons costs. This may not change whether or not we should build densely in these high demand areas, but an accurate cost analysis is key to determining what should be built where!
OK, thanks. This suggests to me that there would be benefits if municipalities better accounted for "dewatering externalities", but this doesn't sound like a reason to be bearish on land reclamation. I could definitely be misunderstanding, but if anything it sounds like a reason to think that the average cost will go *down* if the rate of reclamation increases: if old projects are harmed by new projects dewatering the soil, increasing the total cost of new projects, then there are probably gains to be had by reclaiming land en masse and doing a bunch of building all at once, so that fewer buildings are built under a false assumption that the soil conditions won't change.
I work in this area (in a planning sense) and I think you have hit the nail on the head. The total future redevelopment plan should somehow consider all of this and come up with a best for total area outcome.. which may or may not be individual buildings founding to bedrock etc etc.
However, planning considerations tend not to consider construction, rather the experienced nature of the built form, leaving construction issues to each building.. thus the lack of efficient consideration of the externalities...
Funnily enough, the main critics of more area wide construction considerations in planning tend to be the individual developers, who see this as interfering with their possible innovations.
It is a very important (in my view) but not often discussed 'tragedy of the commons'.
I would push it even further. The public interest shoukd be defined at different levels. In theblow lands, reclaimed land is increasingly re-swamped, to take into account climate crisis related water problems downstream. The interest of tyebdevelopper should be valanced with the interests of the long term occupants, neighboutlrhood, city, state.... yaking every risk into account, does it really make sense to develop further cities prone to water, drought and/or earthquakes? At least the question should be asked.
This is certainly an interesting topic and is worthy of consideration to developers contemplating these projects. The issues related to dewatering impacting nearby properties also seems like an an important consideration in the planning of such developments.
I am curious, did your research find any interesting lessons learned from Japan, other than the discussion of the problems at the Osaka Kansai Airport? Both Osaka and Tokyo have reclaimed hundreds of square kilometers of their waterfronts (see this article for some interesting graphics: https://storymaps.arcgis.com/stories/fdc02295fe7c4dce87a4b0926ecd6d95 ).
Tokyo definitely had plenty of examples of structural problems caused by soil liquification in the 2011 earthquake, but that was a huge earthquake, and most examples of structural failure that are easy to find are from smaller residential structures. Not large projects like the Millennium Tower.
I worked on an architectural team for a project built on reclaimed land in Osaka a few years back, but I didn't pay much attention to this sort of issue since that was the structural engineers responsibility. I kind of wish I had tried to learn more about it now.
Very interesting! Gives the folks in Colorado some peace of mind, yes?
Very interesting! Gives the folks in Colorado some peace of mind, yes?