Popular Trail Link Disrupted when Bridge Demolished by Ice Dam
The 3.75-mile-long Trestle-to-Trestle Trail connects the Inter-Urban Trail in Des Moines to the Johnston trail system on the north side of Interstate 35/80. In the spring of 2019, the Trestle-to-Trestle Trail Bridge over Beaver Creek was severely damaged by an ice dam and collapsed. The loss of this critical piece of infrastructure meant a major detour for trail users. Through a multi-agency effort that included Polk County Conservation, the Des Moines Metropolitan Planning Organization, the State of Iowa, and city leaders from Johnston and Des Moines, the Snyder & Associates team, along with our structural subsidiary, Shuck-Britson, were able to create a replacement bridge that far surpassed the structural stability of its damaged predecessor.
Rail Bridge Replaced with a Modern Structure
The former trail bridge was originally a 316’-long timber and steel railroad bridge that had been repurposed for trail use. When the ice dam caused its collapse, designers knew they needed to create a replacement that could withstand more significant threats from flooding and debris. The final design for the new bridge is a much more solid structure that incorporates modern aesthetics with practical design applications. At the same time, it honors the history of the former rail bridge with decorative Corten Steel design features integrated into the safety railing to resemble wooden trestles. This feature also mimics the styling used on several other area trail bridges, creating a cohesiveness to the mid-Iowa trail network.
The nearly 320’-long replacement structure utilizes pretensioned, prestressed concrete beams instead of the trestle-style construction. This allowed for two large concrete and steel piers better suited to withstand the flooding forces and ice flow issues experienced along Beaver Creek. An observation “bump-out” near the middle of the span provides a place for trail users to stop and admire the surrounding creek and natural environment.
On both ends of the bridge are stone pillars built to resemble the welcome signs in nearby Johnston. These predominantly limestone structures have a nameplate on one side with “Beaver Creek Crossing” displayed. A structural steel “archway” at the bridge entrance provides a whimsical decorative feature.
Distinctive Aesthetic & Customized Lighting System Sets this Bridge Apart
The customized LED lighting system incorporated into the design is unique to a structure of this type. It illuminates the bridge deck and approaching trail path and the bridge’s underside. The lighting system can be programmed to change colors in a near-unlimited pattern, sequence, or timeframe, creating a one-of-kind visual attraction for trail users and vehicle traffic on nearby Interstate 80.
With this new trail bridge open and serving residents again, trail users no longer need to take an extensive detour to reach their destination. The solid construction and long-lasting materials ensure this structure will withstand whatever mother nature throws at it in the future. And thanks to its unique design and eye-catching lighting system, this bridge attracts people’s attention in the area and will for many years to come.