Large Scale Central

Question about the Cascade Tunnel

Prototypes
#1

Ok, this is probably for Craig Townsend, our resident BNSF locomotive engineer, but anyone can jump on it…

I read somewhere, don’t remember where, that the Great Northern (now BNSF) Cascade Tunnel can only handle 27 trains per day, because of the necessity of having to exhaust the diseasal fumes before the next train can go through. That’s only slightly more than 1 per hour!

If that is true, and I have no way of verifying it, why did the GN abandon electrification in favor of diesels? It seems to me that the electrics would be able to haul more than 27 trains per day through the tunnel.

#2

Quick reply, yes, capacity is limited to about 24-27 trains per day because of tunnel flushes.

Bigger question? Why did GN abandon electrification? Who knows. But if the tunnel was electrified now, it wouldn’t have double stack capacity. So the tunnel would have needed major undercutting to a point that I think it would have made electrification useless in terms of saving money.

The MILW held out a bit longer on the electrics, but they too abandoned it in the final years.

#3

I suppose that makes sense, but there is always the third rail technology…

#4

Steve,

Here’s how the tunnel works and why it has a limited capacity. A EB train takes 20minutes to travel through the tunnel at track speed (20mph). If for any reason the EB train can’t do 20 mph (tonnage, lack of hpt, overheating motors, etc) it takes anywhere from 30-40 minutes. If the lineup is working correct and a WB is heading up the hill, the dispatcher will hold the WB at Berne or Merritt for the EB. Then after the EB has cleared the E. portal, the door is closed and the two fans are turned on for 10-15 minutes depending on how many trains are waiting at Scenic… The WB then pulls through the tunnel downgrade, pushing the dirty air from the EB out ahead (the WB train acts like a plunger, one fan on). The trick on an WB train is not to go 20 mph through the tunnel as you’ll run out of clean air and catch up to the dirty air. The fans blow the air WB at 16-18mph. When the tail end of the WB train is inside the tunnel, the door is closed, and both fans are turned back on, thus pushing the dirty/clean air from the EB train (and the WB train) out the W. portal.

So the EB takes 20-25 minutes to get through the tunnel. Once the EB clears the W portal, both fans remain on for 20 minutes to continue the flush. Many dispatchers will “cheat” by turning on the fan signal after only 10 minutes… Crews know better and wait the full 20 minutes. So now the second EB train is waiting at Scenic by now, and after 20 minutes after the WB clears Scenic, the second EB train starts pulling. At this time, the dispatcher will turn off one fan, and keep the other fan on, with the door closed. As the train approaches the E. Portal, about 2000’-2500’ from the portal the door automatically opens (your ears pop normally) and the EB train exits, pushing a small amount of dirty air E, but a majority of the air is still traveling W.

Rinse, wash, and repeat! A lot of the times the WB or EB trains will be stacked up one after another and this cycle is messed up even more. When two EB trains go through the tunnel with no WB following it takes a good 30-40 minutes to flush the tunnel. Not once did I go through the tunnel and felt that I was breathing ‘clean air’. It was full of fumes even after the flushes. The few times I deadheaded on Amtrak, I could smell the soot, etc inside the Amtrak cars…

(As a side note the company provides SCBA’s for employees to “use” in the tunnel if they want. Problem is this, the average SCBA tank only lasts for 15-20 minutes, transit time in the tunnel is at least 20… Secondly spare tanks are located every 1500’-2000’ (one tank!) So if you where to use your air in a non-emergency you would most likely run out of air before you made it out of the tunnel. Then if something happened (loco shut down, needed to be restarted, heaven forbid the trainline dumped and you had to walk in the tunnel) you wouldn’t have enough air to make it to the closest spare tank… The Cascade Tunnel (and I’m guessing the Flathead Tunnel) is the only place where it’s okay to “cut and run” if something happens. In other words get out of the tunnel as fast as possible.)

#5

Steve Featherkile said:

I suppose that makes sense, but there is always the third rail technology…

True, but where are you going to power swap? Seattle to Wenatchee? Or Sky to Leavenworth like in the old days? Swapping power takes time (and thus money). So the solution is to run stacks through Cascade, and empty coal/grain, and light manifest over Stampede. Any heavy trains get run through the Gorge.

#6

Not to put too fine a point on it, it was Sky to Wenatchee, in the old days. The Chumstick Cutoff bypassed Leavenworth and the Tumwater.

Why not Seattle to Wenatchee?

How long would it take to do a power swap, compared to increased utility of the Cascade Tunnel?

Just thinkin’…

#7

Steve Featherkile said:

Not to put too fine a point on it, it was Sky to Wenatchee, in the old days. The Chumstick Cutoff bypassed Leavenworth and the Tumwater.

Why not Seattle to Wenatchee?

How long would it take to do a power swap, compared to increased utility of the Cascade Tunnel?

Just thinkin’…

Originally the helper district was from Sky to Leavenworth (old Cascade Tunnel), than after the new tunnel was built the district went to Wenatchee… So when I said Sky to Leavenworth I was talking about the original tunnel, not the new tunnel.

A power swap wouldn’t take much more than 30-40mins. But you’d have the cost of re electrifying the whole subdivision, acquiring new locomotives, etc. Overall you might save “time” but the “cost” would be much higher… And how are you going to get electricity to run the motors? Buy from BPA?

The much more practical thing in my mind would be to undercut the Stampede Tunnel for double stacks. Any train originating or terminating out of the Port of Tacoma could go through Stampede instead of Scenic. But then enlarging the Stampede Tunnel opens up a whole new can of worms that goes back to the MILW folding, and UP trackage rights… As Stampede has room to double track from Lester to Easton… All the bridges are double track width (not sure if they could hold the new modern weights of heavier trains with two on the bridge at once).

#8

The tunnel is interesting. When a non-responsive BN engineer ran through the doors several years ago…well, they found the “spare” set, Morrison’s company did the electrical work for backups and a new second door.
Original (still in use) goes up and down. New door, outside of old one, goes side to side. They alternate.
Never be on the bridge with fans on “full” and have the door open…you may get wet as it blows you into the creek.

There is (or used to be) and “air lock” to the left of the tunnel door as looking from outside.

On excursions, we used to enter the tunnel, fans on full, doors closed…amazing…in the old days.

#9

Can you imagine going thru that back in the days of steam power?

#10

Toc,

I think BN only uses the new door now. The old door is in ‘backup’ mode. The airlock that your talking about still exists, as an emergency exit. Along with instructions in the rulebook about how to open both doors manually.

#11

Here’s a nice picture of the cloud of smoke that comes out the E. Portal…

I found a link with a nice diagram that explains with pictures what I was discussing.

http://dslweb.nwnexus.com/tawhite/CASCADE%20TUNNEL.html

#12

Craig Townsend said:

Toc,

I think BN only uses the new door now. The old door is in ‘backup’ mode. The airlock that your talking about still exists, as an emergency exit. Along with instructions in the rulebook about how to open both doors manually.

Last time I was up there, I observed sequential operation of the doors. Explained to me it keeps them moving…bearings, guides, motors.
Leave it to BunSniff to kill that functionality…and next time a Santa Fe engineer runs through the door, it will take 3 weeks to get the backup doors functional again, eh?

#13

Curmudgeon mcneely said:

Leave it to BunSniff to kill that functionality…and next time a Santa Fe engineer runs through the door, it will take 3 weeks to get the backup doors functional again, eh?

There’s a reason being the “F” in Santa Fe… Almost as good as flatlander RFE’s that come up on the hill and think they know everything.

#14

Maybe this is a dumb question, but why don’t they drill some holes down into the tunnel to provide ventilation?

#15

How GN solved the problem in the early 1900’s.

#16

John Bouck said:

Can you imagine going thru that back in the days of steam power?

They didn’t. That’s why they electrified the tunnel. They had problems with crews getting near asphyxiated in the old tunnel at the top of the hill.

@ Craig, I didn’t realize that you had jumped that far back in history. Since the old Leavenworth yard is now occupied by the town of Leavenworth and US 2, it didn’t occur to me that you would consider that to be a viable option. :slight_smile:

#17

Ray Dunakin said:

Maybe this is a dumb question, but why don’t they drill some holes down into the tunnel to provide ventilation?

Its a long drill, Ray. They’d probably hit oil, first. :slight_smile:

#18

John Bouck said:

How GN solved the problem in the early 1900’s.

I’d forgotten about those, JB. Any idea on how well they worked? It looks like the exhaust would back draft right into the cab.

#19

From a strictly engineer’s (not choo choo, calculator guy) point of view. It is very expensive to enlarge a tunnel. It is possible and has been done, but it has to outweigh the alternative. At this time it must be too dang expensive.

To answer Ray’s question. A simple and probably cheaper solution would be to drive a second smaller ventilation tunnel parallel to the Cascade. Then install connecting drifts between the Cascade and new vent tunnel. Install ventilation fans in these new drifts to pull the air away from the train and into the ventilation tunnel and then push the bad air out. With this solution you would be able to have almost continuous movement of traffic because you would not have to mess with pressuring the tunnel and pushing air.

#20

Steve Featherkile said:

Ray Dunakin said:

Maybe this is a dumb question, but why don’t they drill some holes down into the tunnel to provide ventilation?

Its a long drill, Ray. They’d probably hit oil, first. :slight_smile:

Actually the old vertical shaft is still in place, but it has been capped off in both the tunnel, and at the surface. I’ve been told that the reason it was capped off was because of ventilation. I’m not exactly sure how but if it was open it would change the physics of the air moving through the tunnel. The other access tunnel that still exists (and is in the same shape) is the Pioneer Tunnel that runs just to the S. of the main tunnel. Same problems with air dynamics. The pioneer tunnel only has a portal on the W. end as well.