Electrification
In 1909 the Great Northern Railway electrified the 2.5-mile (4.0 km) original Cascade Tunnel, which was near the summit of Stevens Pass in the Cascade Mountains. The electrified section was of 4.0-mile (6.4 km) route-miles or 6.0-mile (9.7 km) track-miles, with 1.7 percent grade through the tunnel. The system using 6600 volts 25 Hz was the only three-phase A.C. system ever used on North America railroads, see Three-phase AC railway electrification. Four 1500 hp locomotives of 115 tons each were supplied by the American Locomotive Co. Later GE-built electric boxcabs were used. They pulled trains through the tunnel with the steam locomotives still attached until they were retired from March 27, 1927. This was before the opening of the new tunnel, and the old tunnel and 8-mile (13 km) of the track to be abandoned was converted to the new single phase A.C. electrification system, using 11 Kv, 25 Hz supply and one instead of two overhead wires.
The new lower Cascade Tunnel of 7.8-mile (12.6 km) opened on January 12, 1929. Work had started in 1925 on the new route, and the electrification of a 73-mile (117 km) section of its main line route to Seattle, Washington, from Wenatchee to Skykomish. The new tunnel and electrification reduced the mainline by 9 miles (14 km), eliminated 502 feet (153 m) of elevation and 6 miles (9.7 km) of snow sheds. The new Baldwin-Westinghouse Z-1 electric locomotive consisted of a pair of semi-permanently coupled 1-D-1 box-cab units. The pair weighed over 371 tons, with an hourly rating of 4330 hp. They were used exclusively on this section, for both mainline freight and passenger trains. GN W-1 and GN Y-1 locomotives were also used.
The route was de-energized and dismantled in 1956, after the Cascade Tunnel was fitted with ventilation fans.
Read more about this topic: Great Northern Railway (U.S.)