Here’s some good reference photos for those who don’t know the area.
West Portal.
Pioneer Tunnel Portal about 60’ south of the W. Portal.
I have somewhere a picture that shows the Mill Creek Shaft (the vertical shaft, Cascade Tunnel and Pioneer Tunnel. Here’s the best I could find online of the drawing that I was thinking about.
Slightly better, and official from GN promotional on the tunnel construction.
Another interesting tidbit about the Cascade Tunnel is that the fans are driven off a EMD powerplant. I’m not sure if it was the 12 or the 16 cylinder model that powered the fans…
Jake Smith said:
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.
I’m guessing the biggest expense, by far, would be the cost of routing all trains somewhere else, since they can’t simultaneously enlarge the tunnel while running trains through it.
I find this subject fascinating so I did a little digging. This engineer came up with a pretty good solution. Minus the Underground science stuff. I think he has a pretty good idea.