Project Overview
Designed to improve community connectivity between Interstate 10 and Arizona State Route 210 in Tucson, Ariz., the Downtown Links Phase III project features the construction of a new roadway alignment in the city’s downtown core. This transformative infrastructure effort, led by officials from the City of Tucson, includes three major bridge structures: the 6th Street Underpass at Union Pacific Railroad (UPRR), the 9th Avenue Deck Plaza, and the Maclovio Barraza Parkway Overpass at 6th Avenue. Each bridge was strategically designed to enhance multimodal transportation, including pedestrian, bicycle, and vehicular access, while also integrating public art and safety improvements. To bring their vision to reality, the City of Tucson partnered with project precast concrete manufacturer Stinger Bridge & Iron, HDR Engineering, and general contractor Downtown Links Constructors.
Speed, Precision, and Resilience
The decision to leverage precast, prestressed concrete girders for all three bridges on the Downtown Links Phase III project was driven by cost-efficiency considerations, accelerated construction timelines, and the need to meet complex geometric and structural requirements. For the 135-ft 6th Street Underpass, which supports four future rail lines on the UPRR Sunset Route, precast, prestressed, AASHTO Type V concrete girders were selected over the traditionally preferred steel superstructure. A preliminary analysis revealed that precast concrete offered a 15% cost savings while meeting the shallow-depth and skewed-geometry demands of the site. The use of 38 precast concrete girders, installed in just 6 days, minimized disruptions to active rail operations and capitalized on existing roadway closures.
The 9th Avenue Deck Plaza, a 100-ft pedestrian bridge with public amenities, was originally designed as a two-span, cast-in-place concrete slab bridge. To reduce costs and simplify construction, the design was revised to a single-span precast concrete Utah bulb-tee (UBT) girder bridge. This redesign leveraged updated Arizona Department of Transportation guidelines that allow higher concrete strengths—upward of 7.5 ksi initial and 9 ksi final compressive—enabling a shallower superstructure that met vertical-clearance requirements. The five UBT50 girders were installed in just 1.5 days, demonstrating precast concrete’s efficiency even under the stresses of a fast-tracked schedule and challenging geotechnical conditions.
The Maclovio Barraza Parkway Overpass at 6th Avenue also benefited from a redesign that replaced a cast-in-place, post-tensioned concrete box girder with precast concrete UBT42 girders. By using higher concrete strengths, the team achieved a shallower superstructure depth than the original design, eliminating the need for falsework over an active roadway. This not only reduced construction complexity but also allowed the 120-ft bridge to be built within an existing road-closure window, further streamlining the schedule. While the bridge as a whole took eight months to construct, the 11 girders were set in just two days.
Across all three bridges, precast concrete provided significant advantages: reduced construction time, lower costs, improved safety, and adaptability to site-specific constraints. Additionally, using precast concrete components eliminated the need for falsework, minimized site disturbance, and improved structural performance and durability for the entire Downtown Links Phase III project, resulting in enhanced infrastructure that the community and its stakeholders can rely on for decades to come.
Mason Nichols is a Grand Rapids, Mich.-based writer and editor who has covered the precast concrete industry since 2013.
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