Wabash Trace Nature Trail - West Nishabotna River Bridge

Located east of Malvern at the former station of White Cloud, this unique Whipple through truss bridge carries a former Wabash Railroad branch line over the West Nishnabotna River. The first bridge at this location consisted of a wooden Howe through truss span, set onto timber pile piers and approached by timber pile trestle spans on either end. The bridge was rebuilt in 1902, using a similar wooden truss span. In 1910, the bridge was significantly rebuilt, and a secondhand truss span was installed. Further alterations to the bridge were made in 1951, when a steel stringer span was added east of the truss. The most recent alterations came in the 1960s, when the timber approaches were rebuilt, giving the structure its present configuration. Currently, the bridge consists of a 114-foot, 8-panel, pin-connected Whipple through truss span, approached by a 46-foot steel stringer span to the east. Seven timber pile trestle spans approach the steel spans to the east, and eight timber pile trestle spans approach the bridge to the west. The truss span was originally fabricated in 1884 as a deck truss span for use at Bridge #110 across the Sangamon River at Decatur, Illinois. When that bridge was replaced by the present concrete arch bridge in 1907, the three spans were released for reuse at other locations. One span was reused here, and it is unclear where the other spans may have been reused. Detroit Bridge & Iron Works fabricated the main span, while American Bridge Company reconfigured the span from a deck truss to a through truss. An unknown contractor fabricated the steel stringer span, and an additional unknown contractor constructed the concrete piers. It is believed that the timber components were constructed by railroad company forces.

The truss span follows a highly unusual design, with built-up members, a unique floor and heavy modifications. During the 1910 modifications, the original floor system was removed from the top of the truss, and a new floor system installed at the bottom of the truss. It is unclear if the present floor system reused material from the original floor system, although it appears the stringers may be original to the bridge. Further alterations included adding new portal bracing, new sway bracing, new upper and lower lateral bracing and a general strengthening of the original material. Due to the extensive modifications, a number of empty holes, splice plates and other unusual features are present throughout the span. It is also unclear how much of the new material was reused from other bridges. In addition, it is believed that much of the original truss span was built using wrought iron, while the alterations were likely done using steel. Both the top chord and endposts are composed of built-up beams, which consist of two channels connected by solid plates on the top and X-lacing on the bottom. The bottom chord is constructed of eyebars, with the outer panels using three eyebars and the inner panels using six, arranged into three sets of two. The vertical members consist of built-up beams, formed from two channels connected by V-lacing on both sides. The diagonal members are mainly composed of iron bars, with eyebars at the ends. The floor system is highly unusual, consisting of six light stringers arranged into two sets of three. These stringers are supported by hangers on the floorbeams and riser blocks at the ends of the span. The floorbeams are formed out of plate girders, with additional "prongs" at each end that are connected to the vertical members with splice plates. Both the upper and lower lateral bracing is formed out of heavy L-shaped bars. The portal bracing is constructed using a solid beam above the top chord with triangular plates forming heel bracing. The sway bracing is formed out of thin V-laced bars, which are connected to the vertical members with diagonal L-bar brackets. The steel stringer span follows a standard design, with four equally spaced shallow I-beams. This design is unusual for mid-20th Century Wabash spans, and it is unclear if this span is original to this location or if it was also moved here. The piers consist of two different designs, with the east pier using a rounded design and the west pier using a diamond shaped design. It is unclear when these piers were built, and the different designs possibly indicate they were built at different times. The east approach is supported by a timber pile bent pier, while the remaining substructures use standard timber pile bents. To help stabilize the creek banks, scrap boxcars were added to the banks in the mid-20th Century. Although badly deteriorated, these scrap cars remain intact today.

Whipple trusses are relatively uncommon for railroad use, as they were complex and costly. This design was mainly used for larger spans crossing major waterways. By the 1880s, the design had largely fallen out of favor, and was superseded by other pin-connected designs such as the Baltimore and Pennsylvania patterns. Because of the generally light nature of these spans, a majority of the Whipple trusses constructed in the United States were scrapped prior to 1950. In Iowa, only a handful of Whipple trusses were ever built for railroad use, and only three are known to remain intact today. Railroads often reused steel and iron spans, as it provided a cost effective way to upgrade bridges without requiring large amounts of new material. Many of the steel bridges on this line were constructed using secondhand material. Steel stringer spans were also popular for railroad use, as they were durable and easy to construct. The Wabash used steel stringer spans extensively, especially in place of traditional timber stringers supported by timber piles. Typical of most bridges along this line, a majority of the substructures are made from timber components, which provided a cost effective material. Since the initial construction, the bridge has seen no significant alterations. A timber deck and railings were added to the bridge, and it now carries the Wabash Trace Nature Trail. Overall, the bridge appears to be in fair condition, with some deterioration noted to the timber components. However, the truss span appears to be in good condition. Should the bridge eventually require significant maintenance, any rehabilitation should seek to preserve the superstructure. One possible solution could include replacing deteriorated timber approaches with new steel pile and beam spans, while retaining the original superstructure. In addition, sheet piling should be added around the base of the west concrete pier to prevent further scouring. The author has ranked this bridge as being highly significant, due to the age, design and history.