Source: www.TurfMagazine.com
University of Phoenix stadium installs first tray field in the U.S.
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The University of Phoenix Stadium, home to the Arizona Cardinals, sits in Glendale, in the middle of the Arizona desert, about 15 minutes from downtown Phoenix. The $455 million stadium opened in 2006 and is a shining steel structure whose exterior design replicates a barrel cactus, native to the desert. The steel panels reflect the changing desert light, providing visitors views of the desert backdrop, contrasting with the green grass and trees surrounding the stadium.
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While the stadium design itself is exciting, the 2-acre playing field maintained by the Cardinals is an architectural wonder. Despite its high-tech design, the tray field is maintained in much the same fashion as any high-end playing field. The field tray weighs about 18.9 million pounds and rolls in and out of the stadium. The tray rests on 13 rail tracks and 42 rows of wheel assemblies that move the tray. The time to roll the tray in or out of the stadium is about 75 minutes each way. The stadium design with the movable tray field is the only one of its kind in the United States.
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John Drum, Cardinals stadium operations manager said, “The movable tray playing field improves the usefulness of the stadium. It allows access to the concrete floor, and we can host concerts, trade shows and various other shows and expositions.”
The stadium’s translucent Bird-Air fabric roof has two retractable panels covering the entire playing field and providing shade for fans. It can remain closed during hot summer months. The stadium can seat up to 73,000 and hosts the Tostitos Fiesta Bowl.
The stadium is owned by the Arizona Sports & Tourism Authority with the surrounding land owned by the Cardinals. The Cardinals contribute an estimated $150 million annually to the Arizona economy. Global Spectrum is responsible for stadium management.
Growing turf
Tim Peterson, Cardinals turf manager, said, “The tray resides outside the stadium until about 48 hours before game time, so we don’t have many of the problems often associated with humidity in indoor stadium turf.” Peterson is also responsible for the Cardinals training facility turf in nearby Tempe.
Spring 2008 meant installing a new field following Super Bowl XLII, which was played at the stadium. The NFL purchases its own sod for Super Bowl games. The Super Bowl sod was placed on top of the field tray turf. “When the Super Bowl sod was removed after six weeks, the previous field was dead. We installed a new field at the end of March,” Peterson said.
About 1 inch of soil was excavated before the new 419 bermuda sod was laid. Extra heavy topdressing and precise rolling have been done to assure that all areas are level.
“We want to get it as flat as we can,” said Andy Levy, tray turf manager. Barkshire Laser Leveling, Inc., Mesa, Ariz., provided laser leveling to help assure that absolutely flat playing surface.
The 419 Tifway bermuda field installed this spring will be overseeded with ryegrass in October for November and December play. Both grasses are grown by Evergreen Turf in nearby Maricopa.
A slow-release fertilizer applied to the field throughout the summer months is combined with foliar feeding as the preseason approaches. Aeration is done throughout the year with a Toro Pro Core 648. “It’s our most cherished piece of machinery,” Levy said. He noted that the size of the Pro Core 648 allows it to be used to address spot problems in high-traffic areas as they occur. Aeration is done just prior to ryegrass overseeding and anytime that spot reseeding is needed throughout the year.
Deep-tine aeration is done about twice a year with a Wiedenmann deep-tine aerator. Levy noted that while deep-tine aeration may be only 6 or 7 inches deep due to the tray construction, it is enough to help avoid compaction that could occur without proper soil movement.
The field is mowed at .75 inch with Toro 5510, five-gang reel mowers. In May, the field is transitioned from ryegrass to the all-bermuda turf. “We get very aggressive with lower mowing heights,” Levy said. The lowered mowing heights result in the ryegrass dying off and the bermuda taking over. Dethatching is done primarily during the summer when the 419 bermuda is growing well.
The Arizona desert sun provides an excellent growing environment for grass, and when in its outdoor position, the field lies along a northwest to southeast axis for maximum sun exposure. Irrigation water is provided by public water supply from the city of Glendale.
A variable speed Flowtronex pump station was installed by Horizon Equipment of Phoenix. Water is pumped through a 4-inch flexible pipe, then into the tray. The stadium’s concrete base is covered by two 1-inch layers of AirField to help drainage. A few inches of water remain in the tray during play to keep the grass moist. Hunter opposing nozzle I-40 heads are on the field with regular nozzle I-40 heads on the perimeter. Rain Bird pop-up heads are on the lawn. A Toro Irrigation monitoring system is being considered for the field.
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The movement of the tray into the stadium creates at least one challenging aspect to turf management. Peterson said, “The 62-degree, air-conditioned temperature makes the turf think it’s November and time to go dormant.” Coordinated efforts with stadium management have resulted in the tray being inside the stadium only two days, instead four as was done initially.
“It’s mostly a matter of patience waiting for the grass to recover in about three days,” Levy said.
Greenspace surrounds stadium
Approximately 1,200 trees highlight the 25 acres that surround the stadium. A wide range of varieties were selected for shade, color and blossoming times. Varieties include Arizona cypress, live oak, tipu and Chinese Pistache, which reflects the cardinal red color associated with the Cardinals team. Sportsman’s Park, a landscaped 8-acre park Youth Sports Complex and Youth Sports Fields owned by the city of Glendale, are adjacent to the stadium grounds.
Super Bowl turf
Following Super Bowl XLII, the NFL turf was removed. The turf was grown in Alabama and transported in climate-controlled trucks to the Arizona stadium for the Super Bowl. The NFL and Cardinals cooperated to bring about transfer of the turf to local Moon Valley High School where it now provides a top-notch playing surface. The NFL plan called for the turf to be donated to a school in need of an upgrade.
When Susan Hertneky, Moon Valley assistant principal and athletic director, learned that the turf would be donated, she wrote a request convincing the NFL that her school should receive the turf. Moon Valley players formerly played on a 40-year-old, poor-quality field, and the school’s limited budget did not allow upgrading.
Evergreen Turf installed the field, but preparation was handled by Cardinals volunteers, along with students and parents. Ongoing maintenance was a requirement considered when a recipient was selected for the Super Bowl sod.
Hertneky noted, “We promised we would do our best to take care of the field.” In addition to high school football, the field is used for soccer, band practice and youth football leagues.
Nancy Riggs is a freelance writer and frequent contributor to Turf. She resides in Mt. Zion, Ill.