Why didn't Amtrak rinse the salt out of the North River tunnels? Every time I ride through I can't believe there is caked salt on the walls so many years after Hurricane Sandy.
aegrotatio Why didn't Amtrak rinse the salt out of the North River tunnels?
Why didn't Amtrak rinse the salt out of the North River tunnels?
Start with the required time, cost, and access while the tunnels are heavily used. You need specialized pressure-washing equipment ideally with vacuum recovery, and a good source of hot water, all reasonably portable.
Why recovery? the tunnels slope down with considerable grade. salty wash water would just flow down and pool, and even if you were diligent about pumping it out (using miles of hose?) what was left would deposit salt when it dried...
..the chief problem with the salt not being that it causes corrosion in the tunnel lining or reinforcement, but it constitutes a conductive substance around the electrical return for the catenary and signal currents. Th thought of running a ballast cleaner in there is interesting ... but be prepared to have the bore in question out of service a LONG time to get that done.
I've assumed since long before Sandy that the best way to deal with fouls communication cables and the like is to restring them with modern sealed plastic cabling up close to the tunnel ceiling rather than on the 'step' walkways or adjacent walls
daveklepperAnd just where in the World would they get enough salt-free pure water to do the job, and how would they do it?
Of all the things not an issue in New York City, that is about the last one. Mr. Klepper, I thought you grew up in New York City. Free fresh water by the megaton is easily available via the aqueduct system, although you might have to plan up to days in advance to configure the valve and flow settings to get the mass flow delivered where you wanted it at a particular work time.
Now, once you get it: add a small amount of surfactant or 'water wetter' surface-tension reducer, make up your multiple-gun heads, and provide enough 'hydrostatic' pressure-washer pressure to get the water into the pores of the concrete (but not so much that you scale the surface off dramatically). Here pressure, not volume, is your friend, because you;re also going to want to use vacuum suction to pull the water back off the surface before it has much chance to run. Lay down plastic sheeting with some edge reinforcement at the flange ways so it keeps the ballast as (relatively) clean and dry as possible as you work, top to bottom cleaning, then do the track structure last.
Every study I've read wants to put more permanent track structure in the tunnels 'when the time comes'. To my knowledge the tunnels still 'breathe' up and down with the tidal load, and you'd want to take care of the weight distribution along the tube as you went. I'd go straight to the Class 9 slab track with top-down geometry that FRA tested successfully years ago, but with pads and fixation optimized for rapid adjustment of line and surface 'over the years' as that comes to be needed... but you basically need Gateway to be done before even one of the tubes gets that kind of attention, so effective remediation of the existing structure 'between trains' becomes the only real operational alternative.
I think what David meant was how do you effectively route the required amounts of fresh water into the tunnels themselves, especially when a "wash-down" was never even thought of when they were built.
Certainly except in times of severe drought NYC's never lacked for fresh water.
Anyway, washing out those tunnels is easier said than done, anyway you look at it.
Flintlock76I think what David meant was how do you effectively route the required amounts of fresh water into the tunnels themselves, especially when a "wash-down" was never even thought of when they were built.
Relatively easy. Pressure washers deliver much smaller volume (at higher pressure) so little more than a firehose-diameter supply main (probably at firehose typical pressure) can be provided between the rails with periodic 'manifold' fittings that have nonreturn valves, and hoses connected and disconnected as needed to these between trains.
Vacuum return is a bit more complicated as you'd need hardlines and there will be some suspended matter in the rebound, but a couple of concentric pipes going to some sort of well and trap toward the center would provide either full vacuum retrieval, or someplace that would be periodically evacuated via apparatus little more complicated than a sump pump, now under pressure so it could use a collapsible line also below railhead level with a nonreturn valve at the 'foot'.
This may turn out to be "difficult" meaning repeatedly expensive as Noo Yawk consultants try to 'get it right' on someone else's dime, but it isn't hard.
Overmod Flintlock76 I think what David meant was how do you effectively route the required amounts of fresh water into the tunnels themselves, especially when a "wash-down" was never even thought of when they were built. Relatively easy. Pressure washers deliver much smaller volume (at higher pressure) so little more than a firehose-diameter supply main (probably at firehose typical pressure) can be provided between the rails with periodic 'manifold' fittings that have nonreturn valves, and hoses connected and disconnected as needed to these between trains. Vacuum return is a bit more complicated as you'd need hardlines and there will be some suspended matter in the rebound, but a couple of concentric pipes going to some sort of well and trap toward the center would provide either full vacuum retrieval, or someplace that would be periodically evacuated via apparatus little more complicated than a sump pump, now under pressure so it could use a collapsible line also below railhead level with a nonreturn valve at the 'foot'. This may turn out to be "difficult" meaning repeatedly expensive as Noo Yawk consultants try to 'get it right' on someone else's dime, but it isn't hard.
Flintlock76 I think what David meant was how do you effectively route the required amounts of fresh water into the tunnels themselves, especially when a "wash-down" was never even thought of when they were built.
Are we sure the salt is from Sandy and not from 'normal' ground water drainage through the tunnel over time?
Never too old to have a happy childhood!
There was no salt precipitate on the walls until after Sandy from my observation. I travelled often enough to experience stoppages within the tunnels to be able to see pre- and post-Sandy conditions. There are some pre- and lots of post-Sandy photographs that also document the caked salt on the walls, the "knee" walls (I forget their name, they contain the conduits), track, signalling, and ballast.
aegrotatioAre we sure the salt is from Sandy and not from 'normal' ground water drainage through the tunnel over time? There was no salt precipitate on the walls until after Sandy from my observation. I travelled often enough to experience stoppages within the tunnels to be able to see pre- and post-Sandy conditions. There are some pre- and lots of post-Sandy photographs that also document the caked salt on the walls, the "knee" walls (I forget their name, they contain the conduits), track, signalling, and ballast.
Could the water from Sandy have washed away decades of accumulated grime and 'cleaned up' previous mineral deposits?
Vacuum? there is the atmospheric limit of about 34? feet rise and practical of about 20 feet? seems you would need a pump installed that will take a bore out of service for several ===== ?
blue streak 1Vacuum? there is the atmospheric limit of about 34? feet rise and practical of about 20 feet? seems you would need a pump installed that will take a bore out of service for several ===== ?
By 'vacuum' I mean negative pressure to pull the rebound out of the air and remaining water off the surfaces, as far as possible.
Water collecting in a sump or sumps along the track would be handled just as seepage is in mines -- see for example why Newcomen engines often had multiple rods for suction pumps. You perform multiple 'lifts' in sections of pipe along the bore, through nonreturn trash valves, with the pipes in hardline; then use suction for the last removal where putting some sort of pressure on the water is not as 'economical'. There are ways this can be induced via jet pumps (with no moving parts) similar to the design used in the Cunningham circulators for steam locomotives.
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