Editing Cascade Tunnel (section)

===Original tunnel===
[[File:Great Northern Railway Oriental Limited Cascade Tunnel 1918.JPG|thumb|The [[Oriental Limited]] emerging from the old tunnel in 1918. The train was pulled by a [[Great Northern boxcab (3 phase)|Great Northern boxcab]] locomotive.]]

Construction began on the first tunnel on August 20, 1897, and was completed on December 20, 1900. The tunnel was {{convert|2.6|mi}} long. [[John Frank Stevens]] was the principal engineer on the interim switchback route (opened in 1893, with grades up to 4 percent) and the first Cascade Tunnel. [[Stevens Pass]], located above the tunnels, was named after him.

The tunnel had a fume problem from the coal-burning steam locomotives. It was built with a 1.7% (1:58.8) [[Grade (slope)#Railways|gradient]] eastbound, which was too close to the [[ruling gradient]] of 2.2%. Because of the steepness of the line, the locomotives had to pull hard to make the grade and thus burn more coal, which would lead to immense smoke in the bore. The tunnel was [[railway electrification system|electrified]], with the project completed on July 10, 1909, eliminating the problem. The unusual system used was [[Three-phase AC railway electrification|three-phase AC]], 6.6 kilovolts at 25&nbsp;Hz, from a {{cvt|5|MW|hp}} hydroelectric plant on the Wenatchee River just west of Leavenworth. The tunnel section only was electrified; {{convert|4.0|mi||adj=pre|route}} or {{convert|6.0|mi||adj=pre|track}} and 1.7 percent grade through the tunnel chamber.

The motive power for the section consisted of four [[Great Northern boxcab (3 phase)|GN boxcab]] locomotives supplied by the [[American Locomotive Company]]; they used electrical equipment from [[General Electric]] and were of {{convert|1500|hp}} and weighed {{convert|115|ST|tonne}} each.<ref>{{cite journal | title = Electric Locomotives for the Great Northern | journal = The Railroad Gazette | date=1909 | volume = 46 | issue = 1 | pages = 120–122 | url = https://archive.org/details/RailwayAge1909GreatNorthernElectricLocomotivesRailwayage46newy }}</ref>{{sfnp|Haut|1969|p=27}} Initially three locomotives were coupled together and hauled trains at a constant speed of {{convert|15.7|mph|abbr=on}},{{sfnp|American Railway Association, (Division V - Mechanical)|1922|p=901}} but when larger trains required four locomotives the motors were concatenated (cascade control), so that the speed was halved to {{convert|7.8|mph|abbr=on}} to avoid overloading the power supply. The consulting engineer, Cary T. Hutchinson, published a detailed description of the system in 1909.{{sfnp|Hutchinson|1909}}

{{main|Wellington, Washington avalanche}}
The tunnel was still plagued by snow slides in the area. On March 1, 1910, an avalanche at [[Wellington, Washington|Wellington]] (renamed Tye after the disaster) near the west portal of the original {{convert|2.6|mi}} Cascade Tunnel, killed 96–101{{sfn|Roe|1995|pp=79–91}}<ref>{{harvnb|Middleton|1974}}{{Page needed|date=July 2017}}</ref> people, the deadliest avalanche disaster in U.S. history.<ref>{{cite news |url=https://www.king5.com/article/news/history/deadliest-avalanche-us-history-stevens-pass-washington |title=Deadliest US avalanche was 111 years ago near Stevens Pass |date=March 1, 2021 |publisher=KING5}}</ref> This disaster prompted the construction of the current tunnel.

The old tunnel was abandoned in 1929, after the new longer and lower tunnel was opened. During the winter of 2007–2008, a section of the roof caved in and created a debris dam inside the tunnel, making it impassable to pedestrians due to standing water and ceiling debris. A warning was issued to stay clear of the western side of the old tunnel for a distance of {{cvt|0.5|mi}} for the indeterminate future.