A design-build Arizona freeway brings to life Frank Lloyd Wright’s early designs.
By Sara Geer
When drivers travel the newly constructed Loop 202 South Mountain Freeway in Arizona, they will witness history as Frank Lloyd Wright’s early experiments in desert architecture are featured throughout the design-build project.
The 22-mile corridor provided a unique opportunity for the Arizona Department of Transportation and developer Connect 202 Partners to work with the Frank Lloyd Wright Foundation to apply new aesthetic design concepts appropriate to the area.
Bringing history to life
Joseph Salazar, ADOT’s project landscape and architecture coordinator, explained that in the late 1920s, Wright built a winter encampment, named Ocatillo, near the new freeway location at the foothills of South Mountain, part of the East Valley region of Phoenix. A common feature of Wright’s structures was his frequent use of horizontal lines, which is boldly expressed in the wooden walls of the camp that echo the flat desert floor and long horizons.
To enhance the designs seen specifically on the 40 overpass bridges, uniquely designed precast concrete MSE walls were manufactured and installed. As an homage, horizontal lines serve to influence the design, which features the lines along all the MSE walls. This contrasts with the vertical lines of other Phoenix-area freeways.
“With this in mind, ADOT consulted with the Frank Lloyd Wright Foundation to provide context-sensitive design aesthetic features for the freeway bridges, landscape and other freeway elements,” Salazar said. “The freeway aesthetics will attempt to tell a story by showing difference in land uses, land forms and history as you progress throughout the freeway’s different segments.”
No small task
Approximately 700,000 square feet of MSE wall panels will be installed for the project, which is more surface area than the retractable roof at State Farm Stadium, home of the Arizona Cardinals.
Oldcastle Infrastructure’s plant in Chandler, Ariz., manufactured the wall panels, while Reinforced Earth Company provided the formliners, forms and panel accessories. Production officially started in 2017, and the last wall panel was poured April 2019.
Justin Folts, Oldcastle Infrastructure fulfillment manager, said nearly every MSE wall panel had a custom dimension and design element. Different formliners were used while casting the wall panels, which made it challenging to plan which forms could be poured that day and for which panel. Some panels also included exceptionally tight tolerances depending on where they were being installed on the job site.
“Some were corner panels or below grade or we may have even had to build different headers for different cut panels,” Folts said. “The whole project required a lot of quality control to ensure each piece was correct. As an architectural piece, everyone was paying attention to the details.”
A mix design that had already been approved by ADOT was used to cast the panels. The mix design had a higher strength than required, but it allowed production staff to strip product earlier and move it around the yard without causing damage. Prefabricated mesh increased production efficiency and eliminated manual wire tying.
Since the production crew was more accustomed to working on underground precast concrete products, there was a learning curve involved at first. Folts said communicating regularly with the production team and stressing the need to maintain tight tolerances helped make the project a smooth experience for all.
Another solution that improved efficiency was the plant did not ship product to the job site until an entire wall was cast. In addition, if the project at any given time had to move faster, construction could continue without waiting for product deliveries.
“Overall it was a cool project to work on since once we produce most products and send them out, we never see them again because they are buried underground,” Folts said. “So, it’s nice to see our work displayed since a lot of the freeway is still under construction. We have a few people that drive on it and come back to the plant talking about it.”
According to Salazar, the freeway is divided into five distinct aesthetic areas. Once the panels were installed on the job site, they were sandblasted and painted. An earth tone base paint used throughout the project complements the color of South Mountain, the desert terrain and the area’s vegetation. Several accent colors enhance the designs seen in each of the five segments. For example, the Ahwatukee Foothills/Cholla Ocotillo segment features desert plants and simple shapes, while aesthetics and landscaping in the Laveen village/River Bank segment feature the area’s agricultural heritage.
Other precast concrete products manufactured and installed on the South Mountain Freeway included bridge deck panels and more than 1,000 girders.
Historic and history-making
Dustin Krugel, ADOT’s public information officer, said the South Mountain Freeway is the largest single highway project in Arizona’s history. The freeway provides a direct link for commuters traveling between the East Valley and West Valley, a much-needed alternative to taking Interstate 10 through downtown Phoenix.
The project is also the state’s first public-private partnership on a highway, and the first time right-of-way acquisition and utility relocation have been included in the design-build portion of the project. Public private partnerships make it possible to deliver much-needed transportation projects on an accelerated schedule and reduce the overall cost of the project, which can be passed onto taxpayers or savings for other transportation projects.
“Had the project been delivered under traditional project-delivery methods, the project would have been split into several small projects, which would not be efficient since work would be split by several contractors and take more time to complete,” Krugel said. “By keeping one development team, the South Mountain Freeway can be accelerated and taxpayers, ADOT and the developer will reap the cost savings by not having to tie up resources, personnel and equipment to the project.”
Sara Geer is NPCA’s communication manager and is managing editor of Precast Inc.