Operations
The current Cascade Tunnel is in full operation and receives regular maintenance from BNSF Railway. The new alignment is a straight-line tunnel running between Berne and Scenic Hot Springs. It is currently part of the BNSF Scenic Subdivision between Seattle and Wenatchee, and Amtrak's Empire Builder runs through it. Because of safety and ventilation issues, this tunnel is a limiting factor on how many trains the railroad can operate over this route from Seattle to Spokane. The current limit is 28 trains per day. Speed through the tunnel is 25 miles per hour (40 km/h).
The gradient in this tunnel is 1.565% (1:64), with the rise from west to east. The gradient is 2.2% on the west side from the town of Skykomish. Most recently, telecommunications assets and track sections inside the tunnel were improved.
A ventilation system is used to reduce problems with fumes. As a train enters the west portal of the tunnel, doors close on the east portal and huge fans blow in cool air through a second portal to help the diesel engines. As long as the train is within the tunnel, the fans work with reduced power to avoid pressure problems. After the train has left the tunnel, the red-and-white-checked door immediately closes and the fans operate for 20 to 30 minutes with maximum power to clear the tunnel of exhaust before the next train passes through. In the opposite direction, the door opens when the train is about 0.6 mile (1 km) away from it. The fans are powered by two 800-horsepower electric motors, clearing the air through the seven miles of tunnel within 20 minutes. Present-day train crews carry portable respirators for use in the event of a fan failure or a train stalling inside the tunnel. In addition, there are emergency/safety stations spaced every 1500 and 2500 feet (460 and 760 m) apart, depending on the location within the tunnel, that provide additional air tanks and equipment to be used in the event of a ventilation/other failure.
Read more about this topic: Cascade Tunnel
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