The natural beauty of the Maroon Creek gorge and the form of the existing historic trestle bridge influenced the architectural design of Aspen’s Maroon Creek Bridge. It is a 670-ft-long, single-cell, cast-in-place balanced cantilever concrete bridge with three spans: 170 ft, 270 ft and 170 ft. (Photo by Terry Shapiro)
The Colorado Dept. of Transportation earned more national recognition for the State Highway 82 Maroon Creek Bridge replacement project, completed in 2008, with a 2009 American Segmental Bridge Institute Award of Excellence.
The Highway 82 Maroon Creek Bridge in Aspen is a 670-ft-long, single-cell, cast-in-place balanced cantilever concrete bridge with three spans: 170 ft, 270 ft and 170 ft. The bridge deck is 73 ft wide, accommodating two traffic lanes, two bus lanes and a 12-ft-wide pedestrian/bicycle path. The bridge deck is about 114 ft above the Maroon Creek.
The cast-in-place balanced cantilever design was chosen to minimize impact to the environmentally sensitive Maroon Creek Wetlands, which had been restored from previous construction by the city of Aspen.
The main span length of 270 ft was selected to keep bridge piers out of the wetland area. The unique shape of the piers and superstructure were chosen to mimic the adjacent 1890s vintage railroad trestle. The old railroad trestle had been converted for highway use by adding cross beams and outrigger bents resulting in the uneven hourglass shape.
“This Award of Excellence is a reflection on the strong relationships between CDOT, the local community, the innovative design process, and the construction teams that made the structure a reality,” said CDOT Program Engineer Joe Elsen. “The city of Aspen and Pitkin County were quite generous in their funding contributions, the design firm Parsons Transportation Group delivered a high-quality plan set, and contractor BTE/Atkinson, with construction engineering firm McNary-Bergeron, provided an extremely durable and good-looking structure.”
Parsons Transportation Group’s design of the replacement project included an aesthetic complement to an existing historic structure, a fast-track schedule in adherence to funding requirements, environmentally sensitive access to areas below the bridge and extensive public involvement. The 620-ft-long structure features a 270-ft main span supported by A-shaped piers 100 ft above the Maroon Creek basin.
“Parson’s design team did an amazing job of compressing a 12-month design process into less than five months,” Elsen said. “And with regards to the finished product, the structure fits harmoniously with the surrounding environment, especially the way that it pays homage to the adjacent, historic 1888 trestle.”
Features of the Maroon Creek Bridge design were noted by the ASBI nomination using the following award criteria:
• Innovation of Design and/or Construction: The concrete box girder was constructed from above, using procedures that would protect the environmentally sensitive area below, ease access and minimize construction impacts. The design also factored in the geology at each bridge abutment (where structure meets land) and the need to increase the stability of the slope while minimizing the load of the bridge.
• Rapid Construction: Awarded for construction in June 2005, the work was completed in early spring of 2008. The bridge opened to traffic in July of 2008 after completion of the roadway approaches in a subsequent project (the Aspen Bus Lanes). To accelerate the construction during the cold winter months, the project contractor, BTE/Atkinson JV, controlled temperature in the segments via a special insulation process.
• Aesthetics and/or Harmony with the Environment: The architectural design of the new Maroon Creek Bridge was influenced by the natural beauty of the Maroon Creek gorge and the form of the existing historic trestle bridge. Because of the historical significance of the original bridge, it will remain in place adjacent to the new bridge to honor its historic designation.
• Cost Competitiveness: Typically, for a segmental bridge to be cost-competitive, it has to be of a certain length. While the Maroon Creek Bridge was shorter than the common segmental structure, this design alternative was in fact economical over other strategies that could have been used, due to the bridge’s difficult access. The contractor’s bid price of $13.97 million was just below CDOT engineer’s estimate.
• Minimization of Construction Impact on the Traveling Public: By using cast-in-place segmental construction, crews greatly minimized impacts to the entrance into Aspen. Materials required for the segmental structure were easily transported to the site and lifted into position with a crane.
“While this bridge reconstruction was necessary for safety and capacity reasons, what set its design above the rest is that the resulting construction treaded so lightly on the Maroon Creek basin,” Elsen said. “The Maroon Creek Bridge project has provided CDOT and the local community with a structure that was cost competitive and that really works well for the setting.”