BNSF West Branch Big Rock Creek Bridge

Located along US Route 30 west of Big Rock, this through plate girder bridge carries the former Chicago, Burlington & Quincy Railroad over the West Branch of Big Rock Creek. The first bridge at this location was likely a timber pile trestle or truss. In 1891, the bridge would be replaced by a steel structure. This bridge consisted of a 50-foot through plate girder span, approached by a 25-foot deck plate girder span on either end, set onto stone abutments and steel caisson piers. The superstructure of the bridge was fabricated by New Jersey Steel & Iron Company, and the caissons were fabricated by the CB&Q shops at Aurora. As traffic on this line increased and became heavier, the bridge would require reinforcement. The bridge was strengthened in both 1927 and 1935. By the 1950s, the bridge was in poor condition. The caissons of the bridge were split and had to be banded, the steel was in poor condition and the bridge was too light for modern diesel locomotives. In response, the bridge would be replaced by the current structure in 1960. Currently, the bridge consists of a 100-foot through plate girder span, approached by a 47-foot deck plate girder span on either end. The bridge is set onto concrete pile substructures, which are capped with concrete. All spans of the bridge were reused from other locations, and have lengthy histories.

CB&Q bridge records indicate the main span was originally constructed at Bridge #139.29 across Beaver Creek, north of Hazard, Nebraska. There is possibly some discrepancy on the history of this span. Railroad records show a faded fabrication date, which may be 1931, 1937 or 1951. A 1918 record indicates that Bridge #139.29 consisted of a 50-foot and two 35-foot through plate girders, which would not have included this span. Aerial imagery indicates that a 35-foot through plate girder and pile trestle bridge was in place in 1948, and a track chart indicates the bridge retained that configuration in 1967. A likely theory is that the girder was used at that location for a short period of time, and removed upon construction of the trestle spans. However, it is unclear why a steel span on a mainline would be replaced with timber spans. A missing plaque on the span indicates a builder of either McClintic-Marshall Construction Company or Bethlehem Steel Company. The approach were originally used as part of an approach viaduct for Bridge #262.58 over Quincy Bay in Quincy, Illinois. The spans consist of 47-foot deck plate girder spans, which were cut from larger spans. These spans were fabricated in 1898 by Union Bridge Company, and removed from the CB&Q constructed a new bridge across the Mississippi River on a new alignment.

The through girder span utilizes a standard CB&Q design, with deep tapered ends and a ballast deck constructed on parallel floorbeams. This girder design was the standard for the CB&Q from the early 1900s through the 1950s. Both the through girder and the deck girders appear to have been heavily reconstructed upon relocation. New bracings have been added, and high strength bolts added where the pieces of each span were reassembled. The bridge utilizes a ballast deck, constructed with timber. Ballast decks were standard for CB&Q bridges, as they reduced maintenance costs. Concrete piles became popular for substructure use in the early 20th Century, as they could be mass produced offsite and shipped to individual job sites. These piles could be installed by railroad crews, saving the cost of using contract labor. Railroads often reused steel bridge spans, as this method provided a cost effective way to repair and replace bridges without requiring new material. The CB&Q heavily reused bridge spans up until the BN merger. It is somewhat unusual to have installed secondhand material on a mainline, although the spans were clearly strengthened upon relocation. Overall, the bridge appears to be well maintained and in good condition. The author has ranked this bridge as being locally significant, due to the common design.