The MacArthur Rail Bridge in downtown St. Louis is a critical link in the national freight and passenger rail transportation network. Owned by the Terminal Railroad Association of St. Louis (TRRA), it carries six Class I railroads, Amtrak and other shortline carriers. At 4.4 miles, the 100-year-old structure is the second-longest railroad bridge in the nation. It is also the fourth busiest bridge that crosses the Mississippi River. Although the bridge could certainly be classified as a workhorse, it was not without deficiencies that limited its utility. Due to a curve in the track next to a truss span the bridge could only accommodate a rail car width of 13 feet, 4 inches. This meant that dimensional loads – those wide cars carrying oversized loads such as wind turbines had to be rerouted over 300 miles.

The MacArthur Bridge West Approach Span Replacement project, located over Broadway Avenue, replaced the existing 125-foot open-deck-through-truss structure with a three-span, ballast deck, deck plate girder, and steel beam span bridge that will accommodate rail car width up to 15 feet. It features the innovative use of helical piles to support the bridge’s foundation, one of the first known applications of this solution on a bridge.

The project’s downtown location presented significant challenges during construction, as did the existing bridge’s unusual configuration. The team was only allowed 48 hours of accumulative time in which both tracks could be placed out of service as the existing span was removed and the new spans put into place. The task required extensive sequencing and logistics as every inch of limited space was needed to accommodate materials and equipment.

The Design-Build delivery method for the project proved to be advantageous given the site conditions, restrictions and challenges. Having the engineer on-site during construction was critical for keeping the project progressing ahead of schedule, as it allowed problems to be solved and challenges overcome much more quickly and efficiently. TRRA budgeted $14 million for this project. The team of Crawford, Murphy & Tilly and Goodwin Brothers Construction came in with a winning bid of $8.7 million, thanks to various cost-savings innovations and measures that opened opportunities to remove 2,600 linear feet of long-abandoned steel structural elements, enhancing aesthetics and safety for the neighborhood and traveling public. The team also proposed plans that reduced by half the time that both tracks needed to be out of service for the span change-out.