It's amusing to me watching devs talk about the breakneck pace of AI and LLMS, AGI all that sorts of stuff, what that wild future will give us - when there are far, far more difficult problems that lie directly in front of us, mainly getting public infrastructure projects done in normal spans of time, or hell, getting them done at all.
My immediate thought is at what point does desalination tech + clean energy reach the crossover where building a 60 mile tunnel over 60 years not make sense?
It feels like very soon, and coastal cities can stop relying on hinterland reservoirs for water.
Probably never. The tunnels cost a lot to build but, once built run almost for free - they're powered by gravity and will keep running for close to a century before major maintained is needed.
Capital vs operating is a big factor here. The tunnels operations & maintenance cost is probably far lower than a desalinization plant that could produce an equivalent volume of potable water.
So many questions ... which probably have been asked on prior HN threads ...
I wonder why 800 feet underground: Is that necessary to pass beneath all other infrastructure (to prevent flooding it?)? Remain beneath waterline to create negative pressure and reduce leaking? ?
Also, what is the general mathematical relationship between depth, rock pressure / weight, and energy required to drill? That is, what is the proportion of energy required to drill beneath 800 feet of material compared to drilling beneath 400 feet?
I don't know about New York in particular, but Chicago water engineering seems a related topic.
Here you do deep tunnels to avoid the surface, in ways another poster said; everything is easier when nothing is in the way.
For the mathematical difference, 400 feet below sea level and 800 feet below are almost exactly the same: difficulties are water getting in to your pit, but the machines that work on rock, work on rock at the same speed regardless of depth, so the difference between 400 feet and 800 feet is best described as 400 feet difference. A big issue here is that they do not drill; they hammer. Pounding base pylons into bedrock causes dramatic rhythms in the surrounding 500m, but that's to deal with the bedrock, not depth.
Rivers (e.g. Mississipi) work with much smaller gradient of just 0.01% [1], while with your assumption it would be 0.25%, so 25x.
Maybe instead it needs to pass under the rivers [2: cross-section] surrounding New-York, which may be much deeper, especially when it comes closer to the bay passing Queens and Brooklyn [2: map]
This piqued my interest, so I checked: Tunnel #3 passes under the Harlem River and then the East River, but the Harlem River is less than 30 feet deep for the most part and the East River is around 40 feet deep at the most.
(The Army Corps of Engineers has great detailed depth surveys for most of NY's waterways[1].)
Edit: There's also a higher-resolution render of the tunnel layout here[2].
> I'd guess the reason for the 800 ft is because the reservoir it'll draw from is near sea level.
I believe Tunnel #3 connects to the Catskill Aqueduct[1], which draws from the Schoharie and Ashokan reservoirs. Both are at least a few hundred feet above sea level (the Ashokan is about 600 feet above, since it was formed by flooding a valley in the Catskills).
But I have no idea why they dug it so deep, given that! Maybe to give themselves an (extremely) ample buffer for any future infrastructure in Manhattan.
One diagram I saw indicated 2 different layers of bedrock. I didn't find anything real clear, but it can be that the lower layer is a more suitable material for the tunnel.
Still a bit more to go. Hopefully they offer some tours of the final phase before it’s flooded and no longer accessible for decades.
> The Bronx and Manhattan already receive water from it, and the final phase — extending service to Brooklyn and Queens — is expected to be completed by 2032.
It's amusing to me watching devs talk about the breakneck pace of AI and LLMS, AGI all that sorts of stuff, what that wild future will give us - when there are far, far more difficult problems that lie directly in front of us, mainly getting public infrastructure projects done in normal spans of time, or hell, getting them done at all.
Wild to think this is the same project featured in the third Die Hard, which turned 30 this year.
Should they ever reboot Die Hard; it'll need a sequence involving CA HSR infrastructure.
Die Hard: The most expensive mile
The project started in 1954. A 70 year old project.
My immediate thought is at what point does desalination tech + clean energy reach the crossover where building a 60 mile tunnel over 60 years not make sense?
It feels like very soon, and coastal cities can stop relying on hinterland reservoirs for water.
Probably never. The tunnels cost a lot to build but, once built run almost for free - they're powered by gravity and will keep running for close to a century before major maintained is needed.
It’s probably more likely AI will become sentient and kill us than it is desalination and clean energy are cheaper than this.
This was only a 60 year project because of politics.
Desalination will be a West Coast thing. The East Coast has abundant fresh water.
Capital vs operating is a big factor here. The tunnels operations & maintenance cost is probably far lower than a desalinization plant that could produce an equivalent volume of potable water.
So many questions ... which probably have been asked on prior HN threads ...
I wonder why 800 feet underground: Is that necessary to pass beneath all other infrastructure (to prevent flooding it?)? Remain beneath waterline to create negative pressure and reduce leaking? ?
Also, what is the general mathematical relationship between depth, rock pressure / weight, and energy required to drill? That is, what is the proportion of energy required to drill beneath 800 feet of material compared to drilling beneath 400 feet?
...
I don't know about New York in particular, but Chicago water engineering seems a related topic.
Here you do deep tunnels to avoid the surface, in ways another poster said; everything is easier when nothing is in the way.
For the mathematical difference, 400 feet below sea level and 800 feet below are almost exactly the same: difficulties are water getting in to your pit, but the machines that work on rock, work on rock at the same speed regardless of depth, so the difference between 400 feet and 800 feet is best described as 400 feet difference. A big issue here is that they do not drill; they hammer. Pounding base pylons into bedrock causes dramatic rhythms in the surrounding 500m, but that's to deal with the bedrock, not depth.
The depth allows it to be drilled through bedrock, which avoids a bunch of complications on an already complicated project.
This thing will probably be operating hundreds of years from now. What a project.
It's a 60 mile long tunnel and in order for water to flow through it, you need either pumps or a downhill gradient.
I'd guess the reason for the 800 ft is because the reservoir it'll draw from is near sea level.
Rivers (e.g. Mississipi) work with much smaller gradient of just 0.01% [1], while with your assumption it would be 0.25%, so 25x.
Maybe instead it needs to pass under the rivers [2: cross-section] surrounding New-York, which may be much deeper, especially when it comes closer to the bay passing Queens and Brooklyn [2: map]
1. https://en.wikipedia.org/wiki/Mississippi_River
2. https://gordonsurbanmorphology.wordpress.com/2014/10/26/wate...
This piqued my interest, so I checked: Tunnel #3 passes under the Harlem River and then the East River, but the Harlem River is less than 30 feet deep for the most part and the East River is around 40 feet deep at the most.
(The Army Corps of Engineers has great detailed depth surveys for most of NY's waterways[1].)
Edit: There's also a higher-resolution render of the tunnel layout here[2].
[1]: https://www.nan.usace.army.mil/Missions/Navigation/Controlli...
[2]: https://extapps.dec.ny.gov/docs/water_pdf/nycsystem.pdf
> I'd guess the reason for the 800 ft is because the reservoir it'll draw from is near sea level.
I believe Tunnel #3 connects to the Catskill Aqueduct[1], which draws from the Schoharie and Ashokan reservoirs. Both are at least a few hundred feet above sea level (the Ashokan is about 600 feet above, since it was formed by flooding a valley in the Catskills).
But I have no idea why they dug it so deep, given that! Maybe to give themselves an (extremely) ample buffer for any future infrastructure in Manhattan.
The average depth is more like 400 feet.
One diagram I saw indicated 2 different layers of bedrock. I didn't find anything real clear, but it can be that the lower layer is a more suitable material for the tunnel.
Those are… actually some very good questions.
They finally got Water Tunnel #3 close to completion? Work was stopped a decade or so ago, but apparently it was restarted.
Still a bit more to go. Hopefully they offer some tours of the final phase before it’s flooded and no longer accessible for decades.
> The Bronx and Manhattan already receive water from it, and the final phase — extending service to Brooklyn and Queens — is expected to be completed by 2032.