Edit: add this update --
Interestingly this link: http://www.freerepublic.com/focus/f-news/843626/posts claims that the ET3 bid was 1.2B$ which is $12.5M/mile which is a lot more credible (still low though since the surrounding infrastructure to keep the tube evacuated, the mag lev stuff, etc all add cost over regular fused rail electrified service (which California is considering for its fast rail) and that is looking closer to $25M/mile in the current state of the art)
Part of it is that some folks really hate rail, so much so that they will continually sue anyone who is working to build it. They will argue wildlife endangerment, habitat destruction, cancer risk, suicide risk, traffic risk, earthquake/disaster risk, global epidemic risk, job preservation/creation/destruction risk, you name it. Anything to get back in court and have a judge temporarily suspend work. Because you hire someone to work on a project, and they can't because of some court order, you still have to pay them. So what happens is these projects have 'burn rates' (which is the cost of renting equipment (or depreciating it if you own it) and labor and materials (some of which degrade over time if not used)) and then you have 'able to work' days. Actual work days might be 90 for a mile of track, but time actually passed is like a year. So the other 275 days people sat on their hands while expensive lawyers argued to get work restarted.
Its one of the things I bring up at town hall meetings with politicians. The tax payer, and the 'NIMBY' [1] folks, fight a very asymmetric kind of warfare. No court challenges until funds are committed, and then six. You need look no further than the maneuvering around the California High Speed Rail project to see it play out in all of its ugliness.
[1] NIMBY -acronym Not In My Back Yard for people who are opposed to any new infrastructure near where they live.
I'm not saying an undersea rail system is practical or smart. I'm just asking the relevance of your comparisons to US urban construction costs to begin with.
As a suggestion, a different tone might make your post seem more useful and less trollish. For example "An undersea tunnel will require serious construction breakthroughs to be practical. As a comparison, today's costs...". That would be a lot more constructive than attacking the people behind the article.
>San Jose was celebrating their first 4 miles of light rail (in just 10 years from the start of the project!)
> Actual work days might be 90 for a mile of track, but time actually passed is like a year
So currently, San Jose can build 0.25 mi/year. Optimistically, with no lawsuits, their actual work days could increase to say, 225 days/year, which is 2.5x faster. So we're up to say, 0.66 mi/year, which still sounds way too low. What are the other bottlenecks?
Modern trains also are heavier and accelerate and decelerate faster than the trains you see in westerns. Both mean that they exert greater forces on the rails.
Finally, safety standards are way higher. That means that material must be of higher quality and tested better, both at the factory and after installation.
[1] http://tacnet.missouri.org/history/railroads/rrcosts.html
Don't forget every 10m adds 1atm water pressure. Building a glass enclosed under sea walkway 30m down is not that much harder than building one 20m down and these projects are going to be using glass.
It's 50% harder.
What pressure are the passengers exposed to?
I ask because 1 hour @ 4 atmospheres of 80% N2/20% O2 is risking decompression illness. (Yes, 4 - you've got 1 atmosphere at sea level.) You can reduce that risk by increasing the O2 percentage but if you do that too much, you're risking O2 toxicity.
Firstly: As I see it, an evacuated tunnel at 20m is a very different proposition to a non-evacuated tunnel at 30m, even if the pressure difference is the same. Why? Well, your big problem is always going to be leaks. In an air-filled tunnel you can get away with microscopic cracks, no problem; you've got a small direct interface between water and air, and the surface tension of the water is enough to keep the water in place. It's very hard to force water through a really tiny crack. In a vacuum, however, surface tension goes away -- liquid water at an interface with vacuum will boil, and all of a sudden you've got water vapour filling your nice evacuated tube through every microscopic crack in its five thousand mile length. Nasty. Clearly the joined-concrete construction used for the Transbay Tube isn't going to be sufficient.
Secondly: unfortunately the Atlantic Ocean isn't 20m deep, or 30m deep, or even 40m deep like the deepest point of the Transbay Tube. It's several kilometers deep.
The ocean depth point is interesting. The article says "engineers would tether the tunnel at a fixed depth." I take this to mean tethering to the bottom and relying on buoyancy to keep the tunnel floating at the right depth, which presumably could be 30m or so.
