Editing Cascade Tunnel (section)

===Current tunnel===
{{more citations needed section|date=July 2015}}
[[File:Cascade Tunnel Great Northern Railway illustration.JPG|thumb|left|Postcard illustration of the old and new tunnels from the Great Northern Railway]]
[[File:Great Northern officials at Cascade Tunnel 1926.jpg|thumb|Railroad officials at the Mill Creek shaft, allowing excavation to proceed outwards from within the mountains]] 
[[File:Great Northern Railway and A. Guthrie Co. officials at the entrance to the Cascade Tunnel, the longest tunnel in America (7.8 miles).jpg|thumb|Opening of the new tunnel, January 12, 1929]]

The new Cascade Tunnel was opened on January 12, 1929.<ref name=gtoprdy/><ref name=wonbore/> The new line had {{cvt|72.9|mi||adj=pre|route}} or {{convert|93.2|mi||adj=pre|route}} electrified, between [[Skykomish, Washington|Skykomish]] and [[Wenatchee, Washington|Wenatchee]]. The ruling grade was still 2.2 percent, although {{convert|21|mi}} of 2 percent or worse grade was eliminated. The line length was reduced by {{convert|8.7|mi|0}}, and maximum elevation was lowered by {{convert|502|ft}} from {{convert|3382|ft}} to {{convert|2881|ft}}.

The new tunnel was started in December 1925, and was built in just over three years by A. Guthrie of [[St. Paul, Minnesota]]; the aim was to finish by the winter of 1928–1929 so that further maintenance on deteriorating snow sheds could be avoided. Project manager and engineer [[Frederick Mears]] was assigned to make sure the project was completed.{{sfnp|Cascade Tunnel (Part 1)|1929}}<ref name="Echo">{{cite web|last1=Jordan|first1=Lee|title=Railroad Created Alaska's Largest City|url=https://www.echoak.com/2017/04/alaska-railroad/|website=Echo News|accessdate=3 July 2017}}</ref>

While the new tunnel was being constructed, the Great Northern received delivery of [[Great Northern Z-1|five new electric locomotives]]. The new locomotives had a [[motor-generator]] supplying DC traction motors, and the single-phase AC supply required only one instead of two overhead conductors. Hence, the Great Northern re-electrified {{convert|21|mi}} of the original route at single-phase (11 kV, 25&nbsp;Hz) AC, including {{convert|8|mi}} that were subsequently abandoned upon completion of the new tunnel, and used steam locomotives on the short remaining stretches of the old line.

On March 5, 1927, the three-phase electrification was abandoned, and the new locomotives were placed in service between Skykomish and the east portal of the old tunnel; the time was reduced from 4 hours for a {{cvt|2500|ST|t}} eastbound train to 1 hour 45 minutes for a {{cvt|3500|ST|t}} train. Furthermore, for the first time regenerated power could be used by another train or fed back to the utility company (power from regenerative braking was previously dissipated in a [[Liquid rheostat|water rheostat]] at the power station).<ref name=":0">{{harvnb|Middleton|1974|pp=163-169}}</ref>

Two years later, the new tunnel opened.<ref name=":0" /> It was the longest railroad tunnel in the Americas until 1989, when the [[Mount Macdonald Tunnel]] in [[British Columbia]] was completed, moving the Cascade into second place.

Electrification was removed in 1956, after a ventilation system was installed to eliminate diesel fumes.<ref>{{Harvnb|Hidy|Hidy|Scott|Hofsummer|2004|pp=267–268}}</ref>

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 of days while replacement doors were brought up from the Seattle area.{{citation needed|date=December 2016}}

[[File:Railway and locomotive engineering - a practical journal of railway motive power and rolling stock (1928) (14574492017).jpg|thumb|The [[Great Northern Z-1]], one of the locomotives used on the new Cascade Tunnel]]
[[File:Great Northern electric locomotive Y-1 1927.JPG|thumb|The [[Great Northern Y-1]], the other locomotive used on the current tunnel]]