JobSight: Target Field, Minneapolis
“By the time we got approval for how the panels were going to fit on the building, we had the stone for the panels here,” he says.
Vetter agrees that the process was tightly choreographed. He says that, because neither company had the space to store a large amount of material, it reached the point where Gage Brothers would know exactly what was on the truck scheduled to arrive at, say, 7 a.m. on a particular Monday.
“It was very specific stones they needed on a very specific schedule,” Vetter says. “It took a lot of coordinating and a lot of conversation. It was a matter of getting a good plan and then executing the plan well.”
The actual fabrication of the precast stone panels followed standard practice, Gage Brothers’ Kelley says. The stones were turned outside face down in the forms, and a 6-mil plastic sheet covered the backs to serve both as a bond-breaker, and allow the concrete and stone to expand/contract at their own rates.
Kelley adds that Vetter predrilled the backs of the panels to accept 3/16” stainless-steel hairpin anchors with one anchor approximately every 1-2 ft².
“There are about 50,000 of those anchors placed through the plastic into the back of the stone,” Kelley explains. “They would stick up 2”-3” and then the concrete was placed onto the back of the stone. We’d pour anywhere from 5 1/2” – 8” of concrete to maintain a constant 10” panel depending on the thickness of the stones.”
On the other end, timing became extremely critical. Because of the ballpark’s location between rail yards and an interstate-highway bridge, there was literally no place to store the completed panels onsite. The completed units shipped on an as-needed basis.
“The site is only about nine acres,” says Kelley. “If they needed a piece at 10 o’clock, it got there on a truck at ten minutes to 10.”
The small size of the site also made installation a real challenge, yielding another reason to utilize the panels.
“We literally could not get cranes around the outside of the building, so we could not effectively hand-set stone,” says Mortenson’s Mehls. “We needed to set the stone from inside, with a large crane that reached over the top of the building.”
Gage’s Kelley explains that the three large cranes located on the park’s infield performed different functions. One set the precast treads, risers and raker beams, which hold the seats; the second set the exterior; and the third set the structural steel for the scoreboard and overhanging roof.
“Our crane got a spot on the field; we had that spot for so many days, and then we had to move because someone else needed the crane in that location,” he says. “And, while all that was going on, they also built the infield, including the heating system underneath it, and installed all the grass.”