Cromwell Field won't look any different when it reopens in March 2005 for the Trojan Invitational Track Meet, but what lies beneath the green carpet of newly planted grass will be brand new – and cool.

USC alumna Aimee Lopez was Turner Construction project manager for the 3 million-gallon water storage tank built 40 feet below the field. The new thermal energy storage (TES) system, which brought Lopez back to USC five years after her graduation, has given the Trojan an opportunity to "thank USC" for her undergraduate education and very successful career.

"This is my mark on the world," said Lopez, who earned a bachelor's degree in civil engineering in 1999.

"This is the culmination of all my education and training in engineering – something that will last forever and reflects the latest techniques in civil engineering. It's a landmark, and I'm very happy I was able to work on the project."

Unbeknownst to spectators in the 3,000-seat stadium, or to the athletes racing across its eight, 42-inch Rekortan surfaced lanes, the unseen storage tank will be doing its thing: circulating chilled water to all of the air conditioning systems on campus, said Richard Snouffer, director of Energy Services in USC's Facilities Management Office.

TES is expected to save USC about 4,500 megawatt-hours of electricity a year and roughly $400,000 annually in electricity costs.

"Once this tank is buried, we never want to see it again," Snouffer said.

"This tank is designed to last forever," Lopez added.

Measuring 123 feet in diameter and extending 40 feet underground, TES incorporates the latest construction materials and state-of-the-art design for water storage tanks. It was built with 2,310 cubic yards of pre-stressed concrete and 484,000 pounds of steel reinforcements to safeguard it from cracks or damage that could be incurred during an earthquake.

"The cold water will be circulated day and night to air conditioning systems all over campus and used in some of the new buildings, such as Tutor Hall and the new Molecular Biology building," Snouffer said. "The project actually expands the capacity of the campus' existing chilled-water system and reduces our utility costs in the long run."

TES consists of two components, according to Lopez: the chilled water storage tank under Cromwell Field and a new pump house in the basement of Grace Ford Salvatori Hall. Construction workers had to tunnel 17 feet underground to connect two 24-inch-diameter pipelines from the water tank to the pump house.

"The warmer water coming back through these pipes will have a chance to chill overnight before it is recirculated," Snouffer said. "That allows us to shift a lot of our kilowatt-hour usage to off-peak hours – at night – when electricity is less expensive. That's the beauty of the system."

Sensors suspended in the tank will monitor water temperature and height. A computer energy control management system will alert facilities personnel if anything goes awry.

Lopez has been overseeing the project from a trailer next to Grace Ford Salvatori Hall since the start of the preconstruction phase during the spring. Before the excavation could begin, construction crews had to build a bridge over the track for dump trucks, cranes and other heavy equipment moving on and off the field.

"It would cost more than a million dollars to replace that track," Snouffer said. "The bridge, which is about 4 feet above the track, turned out to be the most viable way of protecting it."