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Northern Pacific Railway Bridge 5.46 (Weyerhaeuser Snoqualmie Mill Spur)

Bridge 5.46 was erected over the Snoqualmie River in 1916.  The steel span portion of the structure dated from 1896 and was 180 feet long.  It was first used in Wisconsin on the Superior Division of the Northern Pacific Railway where it supported heavy iron ore freights for nearly 20 years.  Rising tonnage and larger locomotives required a stronger bridge but in keeping with Northern Pacific practice, and that common on many railroads, the span was dismantled and moved in pieces to Snoqualmie where it was reassembled and used to replace a wooden truss.  It saw heavy use supporting trains of logs and finished lumber until shortly after the Northern Pacific Railway merged with other roads to form the Burlington Northern Railroad.  From 1975 until 1989, the bridge connected the Northwest Railway Museum with the general system of railroads but in 1990 a portion of the structure - a short plate girder section - was damaged by floodwaters.  In 1994 the structure was sold to King County for reuse as a trail.  Other priorities intervened and in May and June 2005 it was demolished and scrapped by the Army Corp of Engineers.

The span was a through-pin-connected Pratt truss, the predominant style of railway bridge construction in the era from 1890 until 1920 and was designed and built by the A & P Roberts Company (merged into American Bridge Company in 1900).  It was nearly identical to the Northwest Railway Museum's Northern Pacific Railway Bridge 35, rehabilitated in 2003/2004.  This bridge design revolutionized the railroad allowing greater tonnage and a significant increase in locomotive size over earlier designs.  Its modular design also sped fabrication and construction, particularly in remote wilderness areas.  The design was itself superseded by even stronger bridge construction to support the continuing increases in train tonnage and locomotive size.  For the Northern Pacific Railway, that was the arrival of the Z class and other large motive power pushing total engine and tender weights to 500,000 pounds and beyond.

1Alone and without rail, this classic Pratt truss awaits the scrapper's torch in May 2005

Large steel pins connected individual modules together.  Each module was small enough to ship on a railway flatcar.  The modules were assembled in a Chicago factory.

Latticework chords at left and box girders at right were significant structural features.

Rail has been removed from the deck.  The elegance of the design remains for a few more days.  The timber deck absorbed vibrations (shock) from a train helping protect the steel structure.Rail has been removed from the deck. The elegance of the design remains for a few more days. The timber deck absorbed vibrations (shock) from a train helping protect the steel structure.

Bridge 546One of the striking qualities of any bridge is the environment in which it is located. Few locations can rival the Snoqualmie Valley but this beauty had a cost: railway builders faced many expensive river and valley crossings.

Bridge 5

Intricate components complete the first and last chord of a pin-connected truss. 

20

A seldom seen sight on this bridge was the bracing in the plate girder sections, below the timber deck.

         

Evidence of earlier trestle construction, perhaps from the false work used to erect the truss in 1916, remained in 2005 and appears on the left. On the right, the bridge foundation, a series of square piles driven to refusal, remained sound to the end.  Creosote-treated old growth fir can perform well over a very long period, even in a river channel.

Special Update

ALL TRAIN PASSENGERS AND CREW MUST WEAR MASKS

Why do we still require masks? Transportation Security Adminsitration ("TSA") regulations currently require all railways, airlines and buses to have persons masked through January 2022. Though social distancing regulations are loosening in much of the region, the Snoqualmie Valley Railroad falls under the jurisdiction of the Federal Railway Administration and TSA. We ask that all visitors over the age of 2 and require for those over the age of 5 to wear a mask that covers both nose and mouth while visiting. By order of King County, proof of vaccination will be required beginning October 25 for all visitors aged 12 and older. The vaccine requirement is a legal mandate imposed by King County. The Museum is required to enforce the law as a condition of remaining open to the public. The Museum has already lost $1.4 million from closures and capacity reductions, further closures would be absolutely disasterous to the Museum. For more information about our social distancing restrictions please visit our Social Distancing Updates page.

Museum Hours

Snoqualmie Depot Hours: 10am - 5pm, 7 days a week. No admission charge to visit the depot and grounds

Closed Thanksgiving, Christmas Day and New Year's Day. There is limited access during Day Out With Thomas and Santa Train events.

Railway History Campus Hours: 11am to 4pm, Wednesdays-Mondays through November 22. Click here for the holiday schedule. Closed Thanksgiving, December 18, 2021 -January 14, 2022.

Price: No admission charge to visit the Snoqualmie Depot and grounds. Admission $10 per adult (age 13+), $5 per child (2-12) to visit the Train Shed Exhibit Hall

Riding the Train: Saturdays, January-March; Saturdays and Sundays, April-December