CN Red Cedar River Bridge (Colfax)

Located west of Colfax, this unusual through truss bridge carries the former Soo Line mainline over the Red Cedar River. The first bridge at this location was likely a wooden truss bridge, constructed when the line was built. In 1896, the bridge was replaced with a pair of 120-foot, 5-panel, pin-connected Pratt through truss spans, set onto stone substructures. These spans used a standard WC design, with light members and a standard lattice portal bracing. An unknown contractor fabricated the superstructure, and an unknown contractor constructed the abutments. On June 7, 1905; the bridge collapsed due to flooding, sending a train plunging into the river. The bridge was temporarily rebuilt with a timber trestle bridge until a new bridge could be constructed. In the spring of 1906, work began on constructing the present bridge, which reused the stone abutments from the 1896 bridge. Due to the history of flooding, it was decided to construct the present bridge as a large single span bridge.

The bridge consists of a large 240-foot, 8-panel, riveted Pennsylvania through truss span, set onto stone abutments which have been repaired with concrete backings. The truss span is highly unusual, and has a number of unusual features. The endposts and top chord use a typical design, and are heavily constructed with V-lacing on the back side and solid plates on the remaining sides. The bottom chord and most members use a built-up design consisting of parallel channels, connected by square plates. Compression members use solid members, which appear to be constructed of rolled beams. Due to the length of the bridge, the truss span is very tall, and uses a lattice sway bracing and a crested lattice portal bracing overlaid with an A-frame bracing. The center two panels of the truss are horizontal, while the next two panels on each side are sloped at different angles. The end panels use a traditional angle, and the upper lateral bracing throughout the bridge uses an unusual lattice design. The floor of the bridge is traditionally composed, and consists of two stringers and floorbeams at the joints. A mid-level lateral bracing runs through the center four panels, giving the truss its Pennsylvania design. An unknown contractor fabricated the span, and it is likely that it was designed by WC engineers. The abutments are constructed of limestone quarried from an unknown location, and were constructed and repaired by unknown contractors.

Truss spans with a polygonal top chord were occasionally used by railroads, as the greater depth provided the required strength for a long span. Single intersection spans (also known as Parker spans) generally used either riveted or pinned connections, and were ideal for spans between 200 and 300 feet long. Double intersection spans (also known as Pennsylvania spans) were commonly used for spans in excess of 300 feet, and generally used pinned connections. This truss span is an oddity, as it combines features of both designs. The use of rigid connections on a double intersection span is relatively unusual, and few instances of this type of construction are known. In addition, the short length of this span is an oddity compared to other Pennsylvania through truss spans throughout the United States, which regularly exceed 400 feet. Overall, the bridge appears to be in fair to good condition, and appears well maintained. The author has ranked this bridge as being regionally significant, due to the unusual design and unknown history.