ASU Sun Devil Stadium

Sun Devil Stadium, located on Arizona State University's (ASU) campus in Tempe, has long been regarded as one of the nation's outstanding sports facilities. It is the largest on-campus stadium in the Pac-10 Conference, complete with 74,000 seats housed within six stories that rise 111 feet. The stadium's state-of-the-art features include a dot matrix scoreboard system with computer animation capability, a color video instant replay board, and a lighting and sound system worth $1.4 million.

And the sports field? A superior combination of computer-controlled irrigation, subsurface drainage, high-tech heating and sand-based soil create optimum growing conditions for the lush green playing surface. There are few other sports fields like it in the nation.

Sun Devil is home to the ASU Sun Devils and the NFL Arizona Cardinals, which moved to Phoenix from St. Louis in 1988. The stadium has been host to the Fiesta Bowl for two decades and was the 1996 site for the NCAA national championship game and the NFL's Super Bowl XXX.

Irrigation and Drainage System: A Real Throwback

Since its inception in 1957, Sun Devil stadium has been a work in progress. Yet, during most of the major renovations made to the facility over the years, the playing surface remained relatively the same: Santa Ana hybrid Bermuda turf, planted in clay soil, overseeded with perennial rye during the winter.

The irrigation system, consisting of a hodgepodge of heads from a variety of manufacturers, was barely adequate. And the field had no built-in drainage, with the exception of a crown in the middle of the field for surface runoff.

Consequently, "if it rained just a little bit, we had puddles of water everywhere," said Don Follett, the stadium's head grounds keeper.

As if the rain wasn't enough, the two teams trodding down the soil made the field as hard as concrete by mid season. "The grass would die down the middle of the field and we would have to paint the dirt green just to make it look good for television," said Follett.

A Rebuilding Year for the Sports Field

In 1992, after two seasons of complaints from the players, a complete $2 million renovation of the stadium began. The goals were to create a more durable playing surface, provide better sight lines for spectators, and expand the sideline area for players and media.

Stadium officials turned to CMX Group in Phoenix to design, engineer and construct the field. Considering that two teams used the field and that its turf turned dormant during the winter, CMX concluded that a sand-based field and underground drainage system, combined with a heating and automatic sprinkler system, would be the necessary tools to optimize the difficult growing conditions.

The construction crews scraped out the old field, lowered the field four and a half feet, and widened and lengthened it. After the excavation, a subgrade of sand was leveled and trenches for the drainpipes were dug. A polyethylene liner was laid over the subgrade of sand while French tiles were placed every 10 feet and connected to storm drains on either side of the field. Next, approximately 10,500 tons of pure, washed mortar sand was brought in, measuring about 18 inches deep once it was laid on top of the liner and drainage system. No soil amendments were added to the sand.

To channel the warm water for the heating system, high-temperature polyethylene tubing was installed in the root zone at 12-inch spacings from end zone to end zone in a looped system with a manifold. Temperature sensors were installed in the field to automatically control the on/off operation of the heating system, much like a thermostat. A heat exchanger in the university's central steam plant heats the water, which is then mixed with cold water-to about 73 to 74° F-and sent out into the root zone.

"This process gives me an optimum soil temperature for growing Bermuda grass," said Follett.

Finally, the sod was installed. Tifway hybrid Bermuda (T-419), grown especially for the stadium by West Coast Turf in Palm Springs, California. Tifway is a dark-green turfgrass with a medium-fine texture and a vigorous growth habit.

Rain Bird System Offers Balanced Attack

CMX hired Pentacore Engineering, based in Las Vegas, to design the field's irrigation system. The goal was to offer a flexible system that could water the field during the optimum times of the day and allow multiple watering cycles needed for the porous, sand-based soil. A complete Rain Bird irrigation system was installed with the large area rotors installed down the middle of the field and small rotors in the corners.

"The Rain Bird sprinklers have a great, even spray pattern from the head all the way out to the end of the spray," said Sun Devil's Follett. "I get uniform distribution of water in close to the head and out at the end of the spray."

The field is designed with one rotor on each valve zone. The valves are wired to the Rain Bird ISC-24B+, 24-station field satellites and can be operated from the university's MAXICOM® central control system. "With the Rain Bird system I can water just one head at a time or up to six heads at a time in any combination." The system is operated at a maximum of 150 gpm and 90 psi, and it takes about an hour and a half to two hours to water the entire field.

The Rain Bird system has also helped save water-not a thing to take lightly in the desert. "Before, we were just pouring water down the drain, rather than getting it to the plants so they could use it," said Follett.

"The new field compared to the old one is like night and day, and the Arizona Cardinals were really pleased with the improvements," he said. In a poll taken in 1995, NFL players ranked Sun Devil the third best playing surface in the league.