Editing Cascade Tunnel (section)

== Operations ==
[[Image:Cascade Tunnel.jpg|thumb|<!--The-->East Portal doors<!-- of the Cascade Tunnel--> opening<!--so a train can pass through-->]]
[[File:CascadeTunnelWestPortal.jpg|thumb|West Portal<!--of the Cascade Tunnel--> in 2011]]

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, Washington|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.<ref>{{Cite web |url=http://www.wsdot.wa.gov/NR/rdonlyres/34925D95-4F59-44B6-90DD-6BE102B33C15/0/StateFreightRailPlan.pdf |title=Washington State, 2010–2030 Freight Rail Plan, pg 81 |access-date=2011-02-12 |archive-url=https://web.archive.org/web/20121224140702/http://www.wsdot.wa.gov/NR/rdonlyres/34925D95-4F59-44B6-90DD-6BE102B33C15/0/StateFreightRailPlan.pdf |archive-date=2012-12-24 |url-status=dead }}</ref> Speed through the tunnel is {{convert|30|mph}} for passenger trains, {{convert|25|mph}} for freight trains.

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.{{When|date=February 2011}}

===Ventilation operations===
Because of the length of the tunnel, an unusual system is used to ensure that the air inside remains breathable and reduce problems with excess [[Exhaust gas|fumes]]. As a train enters the west portal of the tunnel, a red-and-white-checkered door closes on the east portal and high-power 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. When the train is {{convert|0.5|mi|0}} to the tunnel exit, the door begins to open.{{citation needed|date=August 2020}}

Once the train has cleared the tunnel, the door closes again 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 within {{convert|0.6|mi|0}}. The fans are powered by two {{convert|800|hp}} electric motors, clearing the air through the {{convert|7|mi|0|spell=in}} 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 {{convert|1500|–|2500|ft|-1}} 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.

The tunnel door is protected by an [[railway signal|absolute signal]] near the east portal; on the west side, another signal with dual-flashing [[Glossary of rail transport terms#Lunar|lunar]] aspects indicates to eastbound trains that the tunnel fans are operating.