The structural engineering team from Shuck-Britson provided final design services for the replacement of the Old Portland Road bridge over Interstate 80 in Dallas County, Iowa. The Iowa Department of Transportation project was part of broader corridor improvements and mainline widening along I-80 between De Soto and Van Meter, an area experiencing continued development and increased transportation demands.
With preliminary design already completed by another consultant, our team joined the project at the final design stage under an aggressive schedule. Maintaining the established letting date while coordinating the bridge replacement with roadway construction phasing was critical to keeping the larger corridor improvements moving forward.
Early Review Identifies Construction Conflict
As final design began, our team reviewed the proposed bridge geometry against the planned roadway construction phasing. That review identified a significant conflict: the proposed location of a middle bridge pier overlapped existing I-80 travel lanes that needed to remain in use during portions of construction.
Rather than carrying the preliminary configuration forward, the team evaluated alternative span arrangements and developed a revised bridge configuration that better accommodated the planned traffic staging. Clarifying the relationship between the bridge design and roadway phasing early in the process helped reduce potential construction conflicts before they could affect the project schedule.
Providing Flexibility for Bridge Construction
The team also identified an opportunity to give contractors additional flexibility when constructing one of the bridge piers. Final plans included two foundation alternatives — a steel pile option and a drilled shaft option — allowing the contractor to select the approach best suited to site access, shoring needs, construction sequencing, and cost.
Providing both options within the design created greater flexibility during construction while supporting the Iowa DOT’s goals of minimizing construction duration and achieving the lowest feasible project cost.
The bridge’s cross-section and optimized beam arrangement also required the development of new standard bridge drain details. These details were incorporated into the final plans to address drainage needs while maintaining the preferred structural configuration.
Keeping a Critical Corridor Project Moving
Despite the bridge configuration changes identified during final design, our team completed the plans on schedule and preserved the project’s critical letting date.
Through early design coordination, responsive problem-solving, and construction-minded design solutions, our team helped advance a bridge replacement that supports continued transportation improvements along one of central Iowa’s most important interstate corridors.
