Over the course of a week, DPR Construction completed the erection of two prefabricated steel structures atop the newest air traffic control tower in Mesa, Arizona. After the initial 206,000-lb. lower “bulge” pick, the structure was topped off with the 110,000-lb. cab. The two critical crane picks signaled the topping off of the largest single project in Phoenix-Mesa Gateway Airport Authority (PMGAA) history.

The frame for the lower-level bulge is supported by the precast concrete shaft of the tower. To successfully place the first structure, steel rods set in the concrete base had to line up with tightly fitted holes in the steel base plates of the bulge. “Aligning anchor bolts with 100 tons of steel on the crane hook required careful coordination and collaboration between trade partners,” said DPR project manager, Geoffrey Minor. “All the pieces had to align perfectly.”

The project team and trade partners developed a quality control plan to ensure the successful alignment of the anchor bolts. The DPR virtual design and construction (VDC) team used shared templates, surveying and laser scanning to verify all dimensions and identify any deviations prior to hoisting the bulge structure. Both steel structures were prefabricated onsite.

The team also was also challenged with a tight tolerance for the precast elevator shaft that extended through the bulge. The 30-foot-tall shaft had less than one inch of clearance on three sides. Onlookers compared it to threading a 200,000-lb needle.

Just six days later, the 110,000-lb.cab steel structure was hoisted onto the bulge and added another thirty feet to the tower’s height. Minor said precision was critical for the project.

“The attachment of the cab section required the splicing of all fourteen columns, meaning each bulge column had to align perfectly with each cab column,” said Minor. “Thorough planning and coordination across all trades resulted in zero injuries or incidents during the completion of both critical picks.”

At completion, the new tower will have space for eight controller stations and stand more than 190-feet-tall, more than 70 feet higher than the existing tower.