A’s ballpark construction: Why seating risers are produced 15 miles from stadium site

SLOAN — More than 1,000 custom-cast concrete risers for the Athletics’ Las Vegas ballpark are taking shape some 15 miles away from where the $2 billion stadium is being built on the Strip.

Western Pacific Precast is crafting the risers — known in the industry as stadia — that will be installed atop steel girders to hold the seating areas of the ballpark. Production began three months ago, and the first risers were installed behind home plate earlier this month, according to JR Elias, the company’s vice president and general manager.

“We have to start probably two to three months ahead so that the erect (adding the risers to the stadium) never catches the production,” Elias said.

Crews are starting with the main concourse of the upper balcony of the stadium and part of the outfield, with a goal of finishing this fall and not interfering with other work also underway on the project, according to Elias.

“Then we’ll come back on a second phase to allow them to start building out the bottom,” he said. “At that time, when we’re done with the first phase, production is still working to get the lower bowl completed with stadia so that we don’t catch them.”

Off-site production advantages

The A’s stadium project will use 1,166 pieces of precast stadia, custom sized for where they will be installed. Western Pacific Precast is storing the pieces at its Sloan plant until they are ready to be transported via flatbed truck to the stadium site.

“We stockpile it in a certain order, knowing that certain pieces are going to go first and they got to get stacked on a truck systematically,” Elias said.

Each truckload can fit anywhere from one piece to up to five pieces, depending on the shape of the risers and the size of the truck, Elias said. The pieces are delivered at the ballpark site in the evenings in order not to disrupt work occurring on site during the day.

The advantage of creating the risers off-site instead of at the construction site is the ability to work ahead and not have to take up space storing pieces where active construction work is occurring.

“If they were doing it on site (at the stadium), they’d have to wait until a particular area got into a certain position and then start doing casting,” Elias said. “That takes a lot of time over there to cast on site … and we take up a lot of acreage to store all these pieces. They have to be laid out because they can’t be stacked on top of each other.”

Overnight hours

During the summer heat, construction crews have been working mainly at night, with shifts usually running from 10 p.m. to 6 a.m., according to Elias. The hours will switch in the fall when temperatures cool down to a shift generally running between 7 a.m. and 3 p.m., Elias said.

There are around 60 people working at the Sloan production plant and about a dozen workers at the stadium site installing the risers on the structure, Elias said.

“A little less manpower to install it, but it doesn’t take away from the difficulties of putting it in place,” Elias said.

Almost no pieces the same

The majority of the more than 1,100 pieces are not the same, meaning crew members will have to make minor adjustments to most of the pieces in order for them to fit in place with each other.

Each riser form has a core of rebar with concrete poured separately on each portion of the riser to prevent bubbling. The risers are also prestressed to ensure they can endure the rigors of a raucous game day atmosphere.

“It’s got to take the pressure of all the people on there,” Elias said. “Then when they’re cheering on the A’s, doing wave and bouncing up and down, there’s a frequency that they’ve got to meet. So all that gets tested here. Not only the stressing of the tendons, but there’s a certain spec that we have to hit to make sure each one of them has the right stress on it.”

The installation of each piece can take anywhere from 20 minutes to an hour to complete.

“It just all depends on the shims, the alignment, the piece, the adjacent piece next to it, because of the tolerances,” Elias said. “So we have plus or minus, in some cases, quarter of an inch, some cases, three-eighths of an inch.”

Vast experience

Western Pacific has vast experience in building stadia for major sports and events facilities. Its portfolio includes Allegiant Stadium, Sphere, T-Mobile Arena and Lee’s Family Forum, as well as in California at the NBA’s Los Angeles Clippers’ new home the Intuit Dome in Inglewood, Pepperdine University’s new arena in Malibu and the Acrisure Arena in Palm Springs. Western Pacific also does precast work for parking garages, bridges and road projects.

Having the same construction manager on the A’s ballpark as was on the Allegiant Stadium build, the Mortenson-McCarthy joint venture, brings an added level of communication with that, Elias said.

“They know our work, we know how they work; so it makes that it makes the communication a lot better,” Elias said. “Knowing that we’ve been there before and not the pieces are all the same, but we’ve done this before, whether it’s underneath a deck or out in the open, the rigging and how you handle them and how you make them is pretty much all the same, just depending on the difference between Allegiant and A’s of what they want in the product for production.”

The main difference between creating the stadia for Allegiant Stadium and the A’s ballpark is the A’s plan to include air conditioning that comes up from beneath most seats in the ballpark to ensure fans are comfortable in the desert climate.

“This has a bunch of vents in there in the stadia so that it allows airflow at the seats,” Elias said. “That’s something that Allegiant didn’t have.”