Located in the northwest corner of Manning, this truss is one of the most distinctive railroad structures in the entire state of Iowa.
When the railroad relocated through town, a new bridge was going to be required to cross tracks of the Chicago & North Western, Chicago Great Western and the West Nishnabotna River.
The solution was to built a massive bridge to cross all three barriers at the same time. The resulting bridge is the structure visible today, consisting of a truss and girder spans, set on the distinctive concrete arch substructures.
On the west end, a 52-foot concrete arch abutment approached the bridge, with nine deck plate girders, four at 60 feet long, one at 75 feet long and the other four varying in length from 45 feet to 52 feet. These spans crossed the Chicago Great Western Railway, the West Nishnabotna River and some open land. The main span of the bridge is a massive 6-panel, riveted Pratt Through Truss, which runs at a considerable skew. That span is approached by two more concrete arch approaches, 56 feet in length.
The piers of the bridge were constructed of concrete arch shapes, typical for the Milwaukee Road at that time. The bridge also featured a ballasted deck, with 13 inch concrete panels set on top of the bridge. Furthermore, the bridge features skew on the truss spans, and three deck plate girder spans on the west end of the bridge. A slight curve is also found on the west end of the bridge.
Today, the bridge itself is virtually unchanged, and in excellent condition, especially compared to other structures along this route.
Bridge plans from Railway Review: Volume 54 (digitalized by Google)
The truss span is very heavily constructed, with a heavily constructed portal, built up members and riveted connections. The bridge also still features many of the original components, such as the ballasted deck, the pipe railings and the trainman walks.
Unfortunately, the concrete deck panels are beginning to spall and expose the rebar, which eventually may cause the superstructure of the bridge to corrode. The ballasted deck was added to this bridge to help with maintenance, as well as prevent deterioration of the steel components, which is typical to open deck spans.
The concrete arch abutments were common along the Milwaukee Road lines that were rebuilt. They were used to help with erosion and slope control on the ends of the bridge, and create a more natural slope.
The old bridge was built of several deck girder spans, on lightweight steel towers. Some piers of the old bridge were visible just north of Iowa Highway 141 until the 1960s.
Overall, the bridge appears to be in good to excellent condition, with no serious corrosion or spalling noted. Manning has decided to build a park along the southeast corner of the bridge, which grearly improves accessability to the structure.
The author has ranked the bridge as being regionally significant, due to the large size, unique design and iconic status of the bridge.
The photo above is an overview. As part of the documentation of this bridge, the author has numbered the piers and spans from east to west, such as in the original plans for this bridge.
