UP Eau Claire River Bridge

Located on the east side of Eau Claire, this large deck truss bridge carries the former Chicago, St. Paul, Minneapolis & Omaha Railway mainline over the Eau Claire River. The first bridge at this location was likely a timber deck truss bridge, constructed when the line was first built. It is unknown if this first bridge was located on the present alignment, or possibly further upstream. In the late 1870s and early 1880s, the Omaha Road replaced most wooden truss bridges with new iron spans. In 1881, Leighton Bridge & Iron Works was contracted to fabricate a new iron deck truss bridge, and James McClure was contracted to construct new stone substructures for the iron bridge. The iron bridge was completed in late 1881 or early 1882, and was located on the present alignment. By the late 1890s, the Omaha Road was investing significant capital into replacing light iron bridges along this line with heavier steel structures. In 1898, the previous iron bridge was replaced by the present steel bridge, reusing the stone substructures. It is believed that concrete repairs were made to the substructures in the early 20th Century, giving the bridge its present configuration.

Currently, the bridge consists of two 157-foot, 11-panel, riveted double intersection Warren deck truss spans, approached by an 80-foot deck plate girder span on either side. The bridge is set onto stone substructures, which have been encased and repaired with concrete. While almost all of the Wyeville to St. Paul line was double tracked, this bridge was operated as a gauntlet bridge until 1962. A gauntlet bridge operates by using two sets of rails, slightly offset from each other to allow two tracks to use the space of one. The truss spans use standard features for the design, including a combination of solid and built-up members, deep truss webs and a traditionally composed floor. The top chord and lower lateral bracing consist of typical V-laced members, while the bottom chord and some diagonals use a built-up design including two steel channels connected by steel plates. The deck plate girder spans use a typical design, with heavy girders and an open deck. The deck girder spans are supported by steel bents, placed on the outside piers of the bridge. At the abutments, the deck girder spans are supported by tall stone blocks, which were installed to make up for the height difference between the previous deck truss and the girder spans. The bridge also runs at a slight skew, due to the angle of the river. Lassig Bridge & Iron Works fabricated the superstructure, and an unknown contractor completed the concrete repairs to the substructure.

While lattice truss spans were relatively uncommon through the United States, the Chicago & North Western Railway (C&NW) and Omaha Road used the design extensively. Other railroads in the Midwest also occasionally used the design, although not as frequently. Engineers for the C&NW and Omaha Road favored the design, due to its resilience and greater strength without sacrificing economy. Metal lattice truss designs were initially developed for railroad use in the 1870s, often using deep spans with numerous intersections. Through the mid-1880s, short to medium length spans were simplified into double intersection spans, as seen on this bridge. Most lattice spans through the 1880s and 1890s were constructed by the Lassig Bridge & Iron Works, which produced a vast majority of iron and steel bridges for the C&NW and Omaha Road during this era. While the Omaha Road stopped using lattice trusses in the early 20th Century, the C&NW continued to use lattice truss designs nearly exclusively into the 1920s. This shift represents one of the few known instances where C&NW and Omaha Road engineers had differing opinions on bridge design. Today, the bridge remains in daily use. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The author has ranked this bridge as being moderately significant, due to the truss design.