Diving the New York water tunnels

[Gilldiver]

The part you may have missed is

"The most immediate tasks are to fix a valve at the bottom of a 700-foot shaft in Dutchess County so pumps will eventually be able to drain the tunnel, and to ensure that the tunnel does not crack or collapse while it is empty."

The pipe may be only 13 feet across, but it is at almost 700 feet or so.

 

[dougchartier]

Gotcha. I saw that part, but wasn't certain how that was affecting the pressure in the tunnel. So if you have a 700-foot, waterfilled shaft leading down into the pipe, does that mean that the water pressure at any point along the entire length of the pipe is equivalent to being 700 feet down in a fresh water lake? Intuitively, that makes sense to me.

Thanks!

The part you may have missed is

"The most immediate tasks are to fix a valve at the bottom of a 700-foot shaft in Dutchess County so pumps will eventually be able to drain the tunnel, and to ensure that the tunnel does not crack or collapse while it is empty."

The pipe may be only 13 feet across, but it is at almost 700 feet or so.

 

[NudeDiver]

So if you have a 700-foot, waterfilled shaft leading down into the pipe, does that mean that the water pressure at any point along the entire length of the pipe is equivalent to being 700 feet down in a fresh water lake?

Pressure comes from the weight of the water. It doesn't matter if that water is contained by the ocean, a lake, a water tube, or a teaspoon. If you're at the bottom of it, you will experience pressure applied by the weight of the water around you.

 

[halocline]

Gotcha. I saw that part, but wasn't certain how that was affecting the pressure in the tunnel. So if you have a 700-foot, waterfilled shaft leading down into the pipe, does that mean that the water pressure at any point along the entire length of the pipe is equivalent to being 700 feet down in a fresh water lake? Intuitively, that makes sense to me.

Thanks!

The pressure is determined by the depth of the water, not the volume. If you have a vertical pipe leading down to a horizontal tunnel, and the pipe is filled with water, (and the top is open to the air) pressure in the pipe is determined by the depth the divers are at; 100 ft down the pipe they're at 100 ft, etc. If the tunnel is horizontal at 700 ft below the surface of the water, then, yes pressure in the tunnel is somewhere around 22 atm. (I think, approx 3 atm/100ft plus 1 atm.) At that depth a blend of somewhere around 6% O2 would approach a PO2 of 1.4, hence the high percentage of helium.

I read the article in the NYT. Interesting stuff. I hope they're getting paid well, it's dangerous, difficult work.

 

[GA Under Water]

Sorry for what might be a dumb question (I'm new to diving), but why do the divers have to breath a deep water mixture like that for a pipe that's only 13.5 feet wide? I presume that the divers must be subjected to high pressures, but from what?

Thanks.

Doug

From the EoRD:

Water Pressure. Underwater, youÃÓe subjected to water pressure (also called hydrostatic pressure). This is the weight of the water pressing down on you, just as the weight of the air causes atmospheric pressure.

 

[DaleC]

Well I'll try to get things back on track...


These NY water tunnels sound awesome! Have any cavers done them and, forget stage bottles, did you need stage scooters to do so?

 

[DaleC]

All I had to do is mention caving and it gets moved to the technical diving specialties forum. It's like voodoo...

 

[El Orans]

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[NudeDiver]

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A ScubaBoard Staff Message...

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Way to kill a thread!!

 

[EvenKeel]

As a way of reviving this thread, I doubt that anyone has done any diving in these tunnels. While it sounds like a fun excursion, it is the source for one half of New York City's potable water. Aside from possible security issues, if I lived in NYC, I wouldn't want your neoprened butt swimming around in my tap water.