Amtrak Gateway Tunnels

[EuroStar]

The Gateway Development Corporation has released a list of "mythbusters" on the new tunnels and the North Portal Bridge that you can read here http://www.gatewayprogram.org/content/d ... chment.pdf. A quote:

Building a single new tube is not practical because it would not comply with critical fire and life safety requirements.
• A single, one-track tube beneath the river would not provide safe exits for passengers in the case of an emergency.
• A two-track tunnel, as proposed for the new Hudson River Tunnel, provides cross passages every 750 feet for the length of the new tunnel, connecting the two separate tubes. With only one tube, there would be no other means to exit in an emergency.

[EuroStar]

For the mortal souls who cannot get a private tour of the existing tunnels, Gov. Cuomo presents the short movie "Tunnel Ninja" in which the governor kicks some rusty metal and crumbling concrete: http://gothamist.com/2018/10/18/cuomo_s ... hp#photo-1. Regardless of politics and your view of the governor, the movie gives a view of the state of the tunnels that is not available elsewhere. And while I am sure they picked the worst spots to showcase, what can be seen is just bad, bad, bad ...

[gokeefe]

Smartest thing he's ever done. With video like that out there the ball is now solidly in the feds' court.

Notice that the prospect of "Trump Tunnel" arises from the swamp yet again.

[bostontrainguy]

Looking at the curvature of the tunnel, I have to wonder what exactly is below the tracks. Is it possible to lower the tracks to allow higher bilevel cars? The tunnels have always been the limiting feature on the NEC but has this option ever been explored? Metal ties would help a bit too.

[gokeefe]

Well ... That kind of work would basically destroy the rubble pile that apparently exists right now. Even if the dimensions worked (they don't) the tunnel(s) wouldn't survive that level of modification.

[mtuandrew]

Looking at the curvature of the tunnel, I have to wonder what exactly is below the tracks. Is it possible to lower the tracks to allow higher bilevel cars? The tunnels have always been the limiting feature on the NEC but has this option ever been explored? Metal ties would help a bit too.

A) metal ties + 11kVAC isn’t a great idea, unless you want a really high power bill and lots of fried fish in the Hudson
B) No, there isn’t much room to lower tracks in the best of circumstances i.e. direct rail fixation on the bottom wall of the tunnel. Even that isn’t possible here due to the relatively fragile cast iron construction - first time you got a bad flat spot on a car, you’d run the risk of cracking the tunnel like an eggshell. Also, there’s a need to return current via the steel rails.

[Greg Moore]

Yeah, it's more accurate to describe these as metal tubes than actual tunnels. So there's no bedrock to cut down or remove. You have a tube of fixed diameter.

In the original construction, basically the outershell would be pushed ahead into the muck and then the muck removed (grossly simplifying of course).

[Backshophoss]

More like fried sludge with PCB dressing,VERY toxic! UGH!
NJT runs MLV I's and II's thru the North River tubes now,MARC's MLV II clones should fit,the LIRR C-3's and the MBTA K cars and Rotems DON"T fit.

[STrRedWolf]

Yeah, it's more accurate to describe these as metal tubes than actual tunnels. So there's no bedrock to cut down or remove. You have a tube of fixed diameter.

In the original construction, basically the outershell would be pushed ahead into the muck and then the muck removed (grossly simplifying of course).

For details, just check out PBS's American Experience episode on "The Rise and Fall of Penn Station." But I'll add a little bit of detail:

Original construction was, yes, a circular tube shell was push ahead into the muck and then the muck removed by shovel. Behind the shell, workers installed manufactured metal "shells" that were bolted into place, overlapping the joints as each one was bolted in. The same construction is in the East River tunnels. So there's some flex in it, but not much -- the tunnels are actually affected by the tides in the Hudson!

I forget if they were concreted over to solidify them. Maybe not.

That said, it's definitely a tube of fixed diameter. If they were re-bored, the cost would be... well, anyone want a trillion dollar railroad project after all is said and done?

[gokeefe]

More like fried sludge with PCB dressing,VERY toxic! UGH!

Actually ... PCBs didn't even exist at the time these tunnels we're built.

[mtuandrew]

It would be nice to design Gateway for Plate F - that fits Superliners and gallery cars. Granted, it isn’t necessary because Superliners won’t be on the Corridor, but still.

Mr. O’Keefe: maybe not, but they definitely existed in the GG-1

[east point]

More like fried sludge with PCB dressing,VERY toxic! UGH!

Actually ... PCBs didn't even exist at the time these tunnels we're built.

But now the sludge around the North river tunnel cast iron tubes containing PCBs is a major concern. That is the reason that the Gateway tunnel bores must go thru the bed rock underneath the sludge ?

[mtuandrew]

Precasting the tunnel segments, floating them into place, and dropping them into an excavated trench would undoubtedly be cheaper than boring the new tunnel through a combination of bedrock and muck (I don’t believe it is supposed to be entirely in rock even today.) Can’t dig that trench though, not without disturbing a couple hundred years of everything from PCBs to lead oxides to partly-decomposed animal remains.

[BandA]

Freeze the sediment, then you might be allowed to scoop it out.

[J.D. Lang]

I believe the plans call for freezing the muck on the approach to lower Manhattan, then run a TBM through it.

J.D. Lang