Amtrak Gateway Tunnels

From a diagram posted on here, I was under the impression the original tunnels were in Bedrock, part least part of the way ?.

David Benton wrote:From a diagram posted on here, I was under the impression the original tunnels were in Bedrock, part least part of the way ?.

Under Manhattan and on the NJ side but under the river it's pretty much sediment left over from the glaciers and since then.

(In fact I believe someone has reported that there's risk of the tides and currents scouring the to of the current tubes. Which could be bad.)

The recent Penn station documentary said that the current tubes rise and fall with the tides in the Hudson as the weight of the water compresses and releases the sediments through which the tunnels pass. (An unexpected discovery during construction)

Thanks to both of you, I must have misinterpreted the diagrams.

If they can dredge a slot in a river in Netherlands were its either mud, clay or sand and most in rivers much faster than Hudson, they should be able to do it here.
They have build tunnels like this in Oude Maas, Nieuwe Waterweg, Rijn, etc the Danish have used it to make a bridge tunnel at Oresund Bridge Between Sweden & Denmark.
yet here we can't get across a little stream called the Hudson ??

Can someone explain about the tides and currents with the Hudson Rivers. Is it normal for the tunnels to move or something ? I've seen this in another fourm concerning building new tunnels. Is it a bad that the tunnels move with the tide ?

sammy2009 wrote:.. Is it a bad that the tunnels move with the tide ?

When it was first discovered during construction that the tunnels were moving it was very scary to some of the Pennsylvania officers and engineers, notably the project engineer, Samuel Rea, later PRR president. This is from the transcript of the PBS TV documentary mentioned, The Rise and Fall of Penn Station Link:

By the spring of 1906...General Charles W. Raymond overseeing the tunnel project first reported the deeply troubling problem of “The Behavior of the Subaqueous Tunnels.” According to Raymond, the Chairman of the [PRR's] Board of Engineers, the tunnels under the Hudson River were shifting...The riverbed underneath the Hudson River consisted of soft, muddy silt, and Raymond’s data showed the tunnels regularly rising and falling as much as two feet within the silt.

Eventually the engineers discovered the tunnel, buried in the soft silt, clay and mud of the riverbed, sank as the tide came in. When the tide went out the tunnel rose. Pennsylvania considered but rejected using screw piles to anchor the tunnel to bed rock. It was feared making the tunnel resistant to the tidal action might eventually cause a stress failure.

On page 89 of the book Crossing the Hudson (Link} by Daniel Wolf, it is explained,

The magnitude of those variations diminished over time, and it was decided to ignore them.

So far it's worked!

Greg Moore wrote:Not sure the Hudson is deep enough there for that, which means dredging and with the currents that might be tricky.

How deep is the Hudson around 30th Street and 12th Avenue in Manhattan?

25Hz wrote:Block 780.

Tunnel box.

Deep level.



- Andy

Anything can happen regarding the Block 780 Station...

Below is a piece of a nautical chart for the Hudson River, extending roughly from about W. 28th Street to W. 45th Street. As you can see, off W. 30th Street the depth varies from about four feet right along the shoreline to twenty-one feet outside the pier line to forty-five to fifty feet deep in mid-channel.




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Tommy Meehan wrote:Below is a piece of a nautical chart for the Hudson River, extending roughly from about W. 28th Street to W. 45th Street. As you can see, off W. 30th Street the depth varies from about four feet right along the shoreline to twenty-one feet outside the pier line to forty-five to fifty feet deep in mid-channel.




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That's a great find.

I suppose that Amtrak will not confront major difficulties when it comes to extending the Tunnel Box below the Hudson River--as the descending depth should enable enough room to get below the water as the tunnels continue west.

However:

1. When is it likely for the Tunnel Box Extension to begin construction?

2. How likely is it for many years to go by between extending the Tunnel Box and the actual beginning of the overall Gateway Project?

Thomas wrote:

That's a great find.

I suppose that Amtrak will not confront major difficulties when it comes to extending the Tunnel Box below the Hudson River--as the descending depth should enable enough room to get below the water as the tunnels continue west.

However:

1. When is it likely for the Tunnel Box Extension to begin construction?

2. How likely is it for many years to go by between extending the Tunnel Box and the actual beginning of the overall Gateway Project?

The Concrete Casing Project (the "Tunnel Box") will not extend below the Hudson River. It will stop at a shaft located at the southeast corner of 12th Avenue and 30th Street.

DutchRailnut wrote:If they can dredge a slot in a river in Netherlands were its either mud, clay or sand and most in rivers much faster than Hudson, they should be able to do it here.
They have build tunnels like this in Oude Maas, Nieuwe Waterweg, Rijn, etc the Danish have used it to make a bridge tunnel at Oresund Bridge Between Sweden & Denmark.
yet here we can't get across a little stream called the Hudson ??

I'm sure it's technically possible. However, aren't the sediments in the North River contaminated w. PCB's and other nastiness? Not sure the EPA/Army Corps/whomever would bless a dredging project of this magnitude if it involved stirring up contamination from the riverbed muck.

Don31 wrote: The Concrete Casing Project (the "Tunnel Box") will not extend below the Hudson River. It will stop at a shaft located at the southeast corner of 12th Avenue and 30th Street.

Thanks for the update.

But, do you know if the extension of the Concrete Casing Project (the "Tunnel Box") will force 30th street near 12th Avenue to be closed--or can the Extension "underpin" the street (which means 30th street would not have to be closed between 11th and 12th Avenue)?

Also, is the Concrete Casing Project being designed so that when it gets to 12th Avenue, rocks will be excavated to enable deep-bore tunnels to go to the Lower Level of a future Penn Station South?

Thomas wrote:I suppose that Amtrak will not confront major difficulties when it comes to extending the Tunnel Box below the Hudson River--as the descending depth should enable enough room to get below the water as the tunnels continue west.

Don31 wrote:The Concrete Casing Project (the "Tunnel Box") will not extend below the Hudson River. It will stop at a shaft located at the southeast corner of 12th Avenue and 30th Street.

I think what Thomas is getting at is, if and when Amtrak decides to bore under the Hudson, from the Manhattan shore the river bottom descends somewhat gradually -- and only to a depth of about fifty-five feet at mid-channel -- so there will be no big challenge in doing it. I'm sure that's right. The technology is there, it's the required amount of money, will and political support that are in question.

The Pennsylvania tunnels were said to be built about ninety feet under mean low water, or about thirty-five feet under the river bottom. The excerpt below is from an article (LINK) written by H.G. Prout, the editor of the Railroad Gazette (and also a railway engineer), for the New York Times in 1902, based on information supplied by the PRR.

That link says eighty feet (instead of 90 feet).

But, regarding the Gateway Tunnels, isn't there supposed to be a split or Stub Tunnel near 12th Avenue to enable a connection to go to a Lower Level of Penn Station South?