CN Boyer River Bridge #4

Located near the small town of Deloit, this through and deck plate girder bridge is the fourth bridge carrying a former Illinois Central Railroad mainline over the Boyer River. When the railroad originally was constructed, the first bridge at this location consisted of a 75-foot and two 30-foot deck plate girder spans, set onto concrete substructures. The Boyer River had long experienced severe floods, and by the early to mid-20th Century it was decided to channelize the river. In 1961, the bridge was extensively reconstructed by raising the bridge, installing a new main span, new south approach span and shortening and reusing the original north approach span. Currently, the bridge consists of a 76-foot through plate girder span, approached by a 24-foot deck plate girder span on the north end and a 48-foot steel stringer span on the south end. The entire bridge is set onto concrete substructures. An unknown contractor fabricated the main span and south approach, while American Bridge Works fabricated the north approach span. George B. Swift Company constructed the original piers, while Illinois Central Railroad company forces rebuilt the piers and constructed new abutments.

The center span follows a standard design for the era, with two heavy plate girders, square girder ends and a standard floor. While welded and bolted construction was becoming more common by the early 1960s, this span still is heavily riveted and uses a largely traditional design for the early 20th Century. The north approach span also uses a standard design for the era, with two light plate girders and an open deck. It is believed that this span was cut down from an original length of 30 feet. The south span follows a standard design for the era, with four shallow beams and mainly welded connections. Originally, the piers consisted of rectangular structures founded on timber piles. During the 1961 reconstruction, the north pier was rebuilt with concrete additions on either side and a steel riser to fit the deck plate girder girder span. The south pier was rebuilt with additions on either side and a large concrete riser in the middle. Both abutments use a standard U-shaped design with no wing walls, typical of some bridges along this line. Through plate girder spans were popular for railroad use, as they were durable and easy to construct. Since the 1961 reconstruction, the bridge has seen no significant alterations, and remains in regular use. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The author has ranked the bridge as being locally significant, due to the common design.