A Sustainable Design for More Reliable Train Movement

The Elkhorn River Bridge along Union Pacific’s Blair Subdivision between Missouri Valley, Iowa, and Fremont, Nebraska, is one of many critical links in Union Pacific’s freight rail network. When river migration and scour posed a risk to the century-old railroad bridge, Union Pacific brought HDR on board to design and manage the construction of a new bridge and track alignment that would provide reliable service for decades to come.

Our team helped Union Pacific progress a preferred alignment that flattened curvature to improve track speed along the segment, while avoiding the highest risk stream migration patterns and natural behavior of the Elkhorn River. The project involved the offline construction of a new 450-foot-long main river bridge, two auxiliary structures, and about 1.4 miles of embankment and railroad track.

We conducted a detailed study of river morphology to provide Union Pacific the best solution to challenges created by a gradually shifting river. The study reviewed multiple alignments and found the most reliable option involved relocating the track and bridge a quarter mile upstream. The selected alignment enhances track speed while mitigating the risks posed by the Elkhorn River.

A debris risk assessment performed by our team noted the high potential for debris-related issues along this stretch of the river — particularly during flooding events. The result was essential to the design of the main river bridge, which was sized to provide passage of large tree and ice debris while continuing to meet hydraulic demands.

The main spans of the bridge are comprised of welded plate girders with a cast-in-place, composite concrete bridge deck, which improves constructability, saving the project over a million dollars. This decision proved to be a cost-saving measure that reduced overall bridge depth and the amount of required embankment fill. The pier wall foundations that support the main river spans are designed to provide a high level of redundancy and withstand scour from extreme flooding, similar to events experienced in 2011 and 2019.

HDR led quality audits for Union Pacific throughout fabrication and final assembly of the bridge. Our team made regular visits to the production facility to monitor manufacturing stages and final assembly of each span. While providing onsite construction observation, inspectors and construction professionals worked to verify that quality standards and scheduled milestones were met throughout construction.

The replacement bridge opened to train traffic in November 2022, thanks to the success of a collaborative design and broad understanding of the site and challenges presented by the Elkhorn River. By working alongside Union Pacific, our team shaped and delivered a quality design that eliminated existing vulnerability and improved network resiliency in the region.