BNSF Grand River Bridge (Talmage)

Located west of Thayer near the former station of Talmage Junction, this deck truss bridge carried a former Chicago, Burlington & Quincy Railroad mainline over the Grand River. Originally, the CB&Q ran on a different alignment, crossing the Grand River about 1,700 feet southwest. It is believed the first bridge at that location consisted of a wooden truss bridge, constructed when the line was first built. It is likely that the bridge was upgraded in the late 1870s or early 1880s with a new iron truss bridge of an unknown design. It is not clear if the bridge was again upgraded in the late 1880s or early 1890s. Between 1900 and 1901, the CB&Q constructed a new alignment and double tracked the line between Murray and Creston. As part of the project, a new double track bridge was constructed on a more northerly alignment. The bridge originally featured a secondhand deck truss span, approached by a single large deck plate girder span and timber pile trestle on either end. In 1914, new approach spans were added at either end, giving the bridge its final configuration. The bridge consisted of a 150-foot, 6-panel, pin-connected Pratt deck truss span, approached by a 105-foot and a 44-foot deck plate girder span on either end. The entire bridge was set onto concrete substructures, with timber helper bents added under the 105-foot spans in the late 20th Century. The truss span was reportedly fabricated in 1890 for use at an unknown location, before being moved here with minimal alterations. An unknown contractor fabricated the truss span (span #3) and the approach spans (spans #1 and #5), while American Bridge Company fabricated the 105-foot spans (spans #2 and #4) at their Lassig Plant in Chicago. It is believed that the main piers (piers #2 and #3) were constructed by railroad company forces, and it is unclear if the remainder of the substructures were constructed by railroad company forces or by an unknown contractor.

The truss span followed a standard CB&Q design, with light built-up members, a standard floor system and pinned connections of various sizes. The top chords and endposts both consisted of built-up square beams, with V-lacing on the bottom and solid plates on top. The bottom chord used eyebars at the center two panels and built-up beams with V-lacing on both sides at the outer two panels. The three center vertical members were composed of built-up beams which used V-lacing on both sides, while the outer vertical members consisted of extremely light rods. These vertical members connected to the bottom chord with small diameter pins, while the remainder of the connections used standard sized pins. The diagonal members were exclusively composed of steel bars, which were formed into eyebars at either end. At each end of the truss, a bent was present which was formed from built-up V-laced beams. The truss was braced by an internal lateral bracing composed of solid beams, which likely replaced the original bracing in approximately 1940. In addition, the endposts were braced by a series of V-laced beams. The floor system included floorbeams placed above the top chord, which consisted of plate girders. Two plate girder stringers supported each track, and also appear to have been added in the mid-20th Century. Both the upper and lower lateral bracing were composed of L-shaped steel bars. The 105-foot deck plate girders used a standard design, with two massive girders per track and a standard open deck design. The approach spans were similar, but used shallow girders. The abutments used a standard U-shaped design, while the piers consisted of both a standard rounded design and a standard rectangular design. The substructures were most likely founded on timber piles.

Due to the flat terrain, deck truss spans are relatively uncommon in Iowa. Deck trusses were most often used for tall bridges, which minimized substructure costs. The Pratt truss pattern was arguably the most common truss design for railroad use during the second half of the 20th Century, due to the simplicity of the design. By the turn of the 20th Century, the design was largely superseded by riveted Warren trusses, which gave greater loading and rigidity while not significantly increasing costs. The 105-foot spans were unusually large for the era, with most plate girders limited to approximately 90 feet. Deck plate girder spans were popular for railroad use, due to the durability and ease of construction. After 125 years of use, the bridge was replaced by a modern bridge during the summer of 2026. At the time of documentation, the bridge appeared to be in fair condition, but was likely too light for modern railroad traffic. The author has ranked the bridge as being regionally significant, due to the truss design, age and unknown history.