Wednesday, August 8, 2018

BNSF/Great Northern Cascade Tunnels

(1900 Bridge Hunter1929 Bridge HunterWest Portal Satellite, East Portal Satellite)

Also known as Stevens Pass Tunnel and GN Cascade #15. In 1900, a 2.6 mile tunnel was built by Great Northern to eliminate 8 switchbacks and avoid winter weather hazards caused by over 50' of snow during the winter including avalanches.  Unfortunately, this tunnel was still too high to avoid the winter weather. "On March 1, 1910, an avalanche at Wellington destroyed two Great Northern trains and killed 96 people. It was one of the worst railroad disasters in American history and closed the route for three weeks.  On January 22, 1916, an avalanche struck a passenger train near Corea, killing eight people and injuring several others. To keep trains on schedule and bolster public confidence, Great Northern added more snow sheds along the route, increasing the annual cost of maintenance and repair." [HistoryLink] To reduce the winter hazards, a new 7.8 mile tunnel was built 501' (or 500' or 502', depending on the source) below the first tunnel. This new tunnel was completed in 1929, and it remains the longest railroad tunnel in the United States.


New Cascade Tunnel booklet, p4 
Scott Ogle posted three photos with the comment: "Cascade Tunnel, BNSF mainline (formerly Great Northern). Stevens Pass, Washington, September 30, 2018"

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(new window) The guy taking the video never turns back so that we can't see how much the ears that were cut into the Cascade Tunnel (7.8 miles, the longest train tunnel in the US) clears the double stacks. The square top of the containers is the reason those "ears" were cut. Other tall cars such as autorack cars have curved upper edges so they don't need the "ears" in the tunnels.


"Due to the tunnel's length it has a rather problematic handicap, even today, of requiring ventilation of the shaft for up to 45 minutes. As a result Cascade is somewhat of a bottleneck on the BNSF system." The first ventilation system for the 1929 tunnel required an hour to clear the fumes produced by diesels working hard to scale the 1.7% grade from west to east. Today's fans can clear the tunnel in 20 minutes. "Train speeds today for BNSF freights and Amtrak passenger trains are held to 25 mph. One still has to wonder, however, why Burlington Northern did not exercise its ownership of nearby Snoqualmie Tunnel after the Milwaukee Road abandoned its main line through this region in 1980. Using that bore, which was the best engineered tunnel across the Cascade range, would have saved BN and BNSF millions in maintenance costs and liability." [American-Rails]

The grade is 1.6% and takes 30 minutes to clear the exhaust fumes according to Cascade Tunnel Ventilation. Another eastbound train must wait for the exhaust fumes to be blown out of the tunnel. But a westbound train does not have to wait because the exhaust of the previous eastbound train will stay in front of the westbound train. The exhaust plume of the westbound train leaves the tunnel with the train so neither the next eastbound nor westbound train is delayed.
In a discussion on the Trainorders forum, a former Chief Dispatcher for BN who was in charge of the line through the Cascade Tunnel said that the Tunnel Ventilation issue being a limiting factor on line capacity is a bunch of Horsefeathers. If it was a problem, then adding a mid-tunnel door like the Mount MacDonald Tunnel on CP has would solve the problem at a reasonable cost. The problem is the gradient through the tunnel and the distance between the sidings at either end. If the freight trains were the length of the Empire Builder and powered the same amount, you could operate a lot more trains per day through the tunnel. Where some problems with ventilating occur, they happen because the Dispatcher doesn't begin the ventilation promptly. This can happen because the Dispatcher is distracted by things happening elsewhere on his district, or if he (she) just isn't paying attention. And then there is the need for MOW to have track time, not just on the tunnel itself, but also anywhere between Skykomish and Wenatchee. [Trains, search for "2009 9:25"]

To build the 1929 tunnel, a work tunnel 8' high and 9' wide was first built and 21 connecting passages were dug to the main bore so that there was 42 working faces. 1,750 skilled workmen from around the country were hired to staff three shifts that worked seven days a week for 35 months. The blasting holes were 8' deep. After a blast the loose rock was cleared out using ore cars in the working tunnel. Each round took five hours. The tunnel was dug through granite, but they still used timber shoring. Even with the shoring, there were deaths due to rock slides. The concrete lining was constructed by placing reusable forms over the timbers and pouring concrete over them. Because of the length of the tunnel; cars filled with the correct ratio of cement, sand and gravel were hauled to a mixing plant at the face of the concrete work. "Some 923,000 cubic yards of rock and earth were removed from the bore, replaced by 264,000 cubic yards of concrete as lining for the tunnel." [HistoryLink]

HistoryLink has several photos of the 1929 construction.

The tunnel was electrified, but they had significant reliability issues with the electrification. One source indicated the system was not properly designed. As soon as the railroad finished converting to diesels in 1956, the electrification was replaced by a ventilation system at the east portal.

Claude Conrad posted
My time at the TUNNEL!! My son (Kevin Conrad) and I found are way to this view of the east portal. A consist of those beautiful GREEN SD40-2s heading west bound. A great day for us both!!
Dan Whitmasrh posted two photos with the comment:
A couple more from the archives. On a winter day sometime around 1982, my brother and a friend look on from a snowbank as an eastbound freight approaches the Cascade Tunnel, led by SD40-2 8127 and B30-7AB 4090. High on the mountain above the engines can be seen the snowshed guarding the eastern entrance of the Windy Point tunnel, part of the original Great Northern grade, abandoned in 1929 when the new tunnel bypassed the high country.
In the second picture, all but the caboose have entered the tunnel. The tunnel retains its perfect arch, lacking the notches carved into the top in later years to allow for double stacks to pass through.

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