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.
What indication do you have that the construction time for tunnel 3 is due to corruption or even that it's taking longer than necessary? It seems like a very large engineering project; sometimes those take time.
Yeah, I have no idea how long a tunnel of this size is supposed to take, and I’m surprised if many people here do.
It’s a big project, and it is tricky to patch it after release. The thing is supposed to last 300 years, and usually we use infrastructure well past it’s intended lifespan…
Why do people say NYC is more corrupt? I don't know of evidence or reports. To me, it doesn't seem more or less corrupt than other major cities in the US. It's hard to compare to other countries, where city government may have different roles.
Certainly NY's government and budget are larger than other US cities, for obvious reasons.
If empirical observation is 'technical', then keen eyes can spot the grifters before they can be elected or corrupt the already-elected. Then we just need the will to permanently deter them.
Kind of - the art of fortune telling plays a big part in things
It's not needed now, but we think that it will be needed in the future
It's needed now, but we don't know if we will use it in the future
How MUCH will it be needed in the future
Will there be a future technology that makes this investment unnecessary, or even obselete before the project ever completes
For the latter, a big argument of "No need to invest in commuter trains" argument was "self driving cars are 'just around the corner' and they will make mass transit a quaint thing of the past" was used to deny investment in trains.
> For the latter, a big argument of "No need to invest in commuter trains" argument was "self driving cars are 'just around the corner' and they will make mass transit a quaint thing of the past" was used to deny investment in trains.
People don’t want to invest in trains because Americans don’t like trains. We have only one real city, and that city’s population consistently has net domestic outmigration. The city’s population is kept stable by a steady supply of international migrants: https://www.cityandstateny.com/media/ckeditor-uploads/2025/0....
Most Americans don’t want to commute sitting next to strangers. It’s not complicated.
They use them heavily when they're available. The NYC subway is very popular and successful, and many see it as a selling point of the city.
> Most Americans don’t want to commute sitting next to strangers.
I never hear city residents talk about 'strangers'. Interacting with others is a pleasure of cities, in fact - it's energizing, it builds social trust. We're social animals. I've never gotten on public transit, or walked down a busy sidewalk, and thought about 'strangers'. Most of those people are pretty sociable.
> They use them heavily when they're available. The NYC subway is very popular and successful, and many see it as a selling point of the city.
NYC has only 2.5% of the U.S. population and even then it has net domestic outmigration (meaning more people move out every year than move in). The city would be shrinking if it wasn’t for international immigrants, who don’t come to the city for the public transit, but rather the welfare system and ethnic social networks.
You have to deal with directly affecting real estate owners, potentially 100s of thousands of different ones in NYC. Not to mention 100s of years of underground infra and all the different companies that own that stuff without cutting service to anyone. It's insanely difficult and I'm not sure I understand why you think it wouldn't be.
You're missing what I'm saying. I'm poking fun at devs that think AGI will magically solve all our problems - they have no idea just how insanely complicated physical infrastructure is.
They need to do a post-apocalyptic movie with a scene set in Fresno with unfinished CA HSR viaducts hulking in the background against a polluted orange sky.
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.
Yeah, that's certainly possible for Brooklyn and Queens. Manhattan and The Bronx have very shallow bedrock, but Brooklyn and Queens have lots of clay, sand, and silt.
> Also, what is the general mathematical relationship between depth, rock pressure / weight, and energy required to drill?
There isn't any. It completely depends on the local geology.
Liquids are easy because there are no lateral load transfers, and the structures have to bear the weight of the entire water column above them. But with soil you get lateral load transfer, so the pressure on the tunnel is not easily relatable to its depth.
That's also why you can have mines that are kilometers deep, yet with tunnels held by wooden beams.
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.
The one that made me think of this is Metropolitan Area Outer Underground Discharge Channel in Kasukabe, but I’m sure there are others. If you find a list of civil engineering tours available, please share!
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.
Yeah that makes sense but if growth dictates another tunnel... And it takes another 60 years, your capital expense starts to look a lot like an operating expense. Not to mention one of the big stated purposes of this tunnel is actually to facilitate maintenance of the other tunnels. There is probably more operation cost hidden here than seems obvious.
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.
> Desalination will be a West Coast thing. The East Coast has abundant fresh water.
It's not entirely accurate to say that the West Coast doesn't have enough fresh water. Oregon and Washington have a lot of rain, and many groundwater resources.
California kneecaps itself with perpetual deeded water rights and mismanagement/closure/lack of improvement to reservoirs and related infrastructure. There's a long history of this kind of stuff in the state (see the watering LA desert, the Salton Sea experiment, and many others).
The corruption and graft run so deep you would have to literally murder a lot of people to get that to happen.
It’s a big project, and it is tricky to patch it after release. The thing is supposed to last 300 years, and usually we use infrastructure well past it’s intended lifespan…
That one is ~2600 years old
(The classic form of griping over NYC corruption is the MTA which is notable for not being administrated by the city.)
[1]: https://www.vitalcitynyc.org/articles/how-corrupt-is-new-yor...
Certainly NY's government and budget are larger than other US cities, for obvious reasons.
There typically are no technical solutions to rhose.
It's not needed now, but we think that it will be needed in the future
It's needed now, but we don't know if we will use it in the future
How MUCH will it be needed in the future
Will there be a future technology that makes this investment unnecessary, or even obselete before the project ever completes
For the latter, a big argument of "No need to invest in commuter trains" argument was "self driving cars are 'just around the corner' and they will make mass transit a quaint thing of the past" was used to deny investment in trains.
People don’t want to invest in trains because Americans don’t like trains. We have only one real city, and that city’s population consistently has net domestic outmigration. The city’s population is kept stable by a steady supply of international migrants: https://www.cityandstateny.com/media/ckeditor-uploads/2025/0....
Most Americans don’t want to commute sitting next to strangers. It’s not complicated.
They use them heavily when they're available. The NYC subway is very popular and successful, and many see it as a selling point of the city.
> Most Americans don’t want to commute sitting next to strangers.
I never hear city residents talk about 'strangers'. Interacting with others is a pleasure of cities, in fact - it's energizing, it builds social trust. We're social animals. I've never gotten on public transit, or walked down a busy sidewalk, and thought about 'strangers'. Most of those people are pretty sociable.
NYC has only 2.5% of the U.S. population and even then it has net domestic outmigration (meaning more people move out every year than move in). The city would be shrinking if it wasn’t for international immigrants, who don’t come to the city for the public transit, but rather the welfare system and ethnic social networks.
https://www.nyc.gov/assets/dep/downloads/pdf/water/drinking-...
https://old.reddit.com/r/nyc/comments/in5lm7/cross_section_s...
Potentially related:
Discussing Waterworks, Stanley Greenberg's Photos of NY's Hidden Water System [video] - https://news.ycombinator.com/item?id=46416871 - December 2025
(Tunnel 3 will deliver 1B gallons/day and has a 200-300 year expected service life)
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?
...
This thing will probably be operating hundreds of years from now. What a project.
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.
I'd guess the reason for the 800 ft is because the reservoir it'll draw from is near sea level.
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...
(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 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.
There isn't any. It completely depends on the local geology.
Liquids are easy because there are no lateral load transfers, and the structures have to bear the weight of the entire water column above them. But with soil you get lateral load transfer, so the pressure on the tunnel is not easily relatable to its depth.
That's also why you can have mines that are kilometers deep, yet with tunnels held by wooden beams.
> 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.
Tokyo Metropolitan Area Outer Underground Discharge Channe - https://news.ycombinator.com/item?id=43816183 - April 2025 (6 comments)
Tokyo's Underground Discharge Channel - https://news.ycombinator.com/item?id=19785044 - May 2019 (40 comments)
Tokyo Is Preparing for Floods ‘Beyond Anything We’ve Seen’ - https://news.ycombinator.com/item?id=15436943 - October 2017 (210 comments)
It feels like very soon, and coastal cities can stop relying on hinterland reservoirs for water.
There are Roman aqueducts in continuous operation for two millenia.
This was only a 60 year project because of politics.
It's not entirely accurate to say that the West Coast doesn't have enough fresh water. Oregon and Washington have a lot of rain, and many groundwater resources.
California kneecaps itself with perpetual deeded water rights and mismanagement/closure/lack of improvement to reservoirs and related infrastructure. There's a long history of this kind of stuff in the state (see the watering LA desert, the Salton Sea experiment, and many others).