Cascade Tunnel
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The Cascade Tunnel is a 7.8 mile (12.5 km) long railroad tunnel at Stevens Pass through the Cascade Mountains approximately 65 miles to the east of Everett, Washington. It is the longest tunnel in the United States. It was built by the Great Northern Railway in 1929 at a lower elevation than the original, 2.6 mile (4.2 km) tunnel which had suffered problems with fumes, itself built to avoid problems caused by heavy winter snowfalls on the original line which had 8 Zig Zags (switchbacks). It is currently part of the BNSF Railway system on their mainline between Seattle and Spokane.
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History
The first tunnel had a fume problem because it was built too steep and too close to the ruling grade. The tunnel was electrified by 1909, which eliminated the fume problem.
The second Cascade Tunnel was constructed between 1925 and 1929 to replace a shorter, higher-elevation tunnel which was still plagued by snowslides in the area. The new alignment is a straight-line tunnel running between Berne and Scenic. The gradient in this tunnel is 1.7% ( 1 in 58) with the rise from west to east. The railroad line was electrified between Skykomish and Wenatchee. New electric locomotives were used in this portion which were again powered by overhead catenary.
In 1956 the electrification was removed. However the great length of the tunnel plus its steep gradient meant that the fume problem resurfaced. So a ventilation system was provided. As a train enters the east portal of the tunnel, doors close behind it and huge fans blow in cool air to help the diesel engines. After a train passes through the tunnel these fans operate for 20-30 minutes to clear the tunnel of exhaust before the next train passes through. Present-day train crews carry portable respirators for use in the event of a fan failure or a train stalling inside the tunnel.
Engineer
The principal engineer on the switchback route and the first Cascade tunnel was John Frank Stevens.
Accidents
On March 1, 1910 an avalanche at Wellington, the West portal of the original 2.6 mile-long Cascade Tunnel, killed 101 people, the deadliest avalanche disaster in U.S. history.
On April 4, 1996 an eastbound freight train broke through the doors at the east portal after they did not open properly. There were no injuries but the broken doors slowed operations for a couple days while replacement doors were brought up from the Seattle area.
References
- Legg, John F. UCRS-Reference (GN Stevens Pass). Retrieved on February 25, 2005.