NASHVILLE (AP) - The Nashville International Airport has begun using an abandoned quarry to halve its cooling costs by taking advantage of the reservoir's year-round 50-degree temperature.

Christine Vitt is the airport authority's vice president of strategic planning and sustainability. She says the geothermal lake cooling system is expected to save the facility about $430,000 per year.

The system pumps hot water from the terminal's cooling plant to stainless steel heat exchangers submerged in the reservoir. The heat exchangers are about the size of an SUV and work similarly to a car radiator. Water enters at about 79 degrees, is cooled by the surrounding reservoir water, and returns to the plant at about 63 degrees.

Vitt says the system is the largest of its kind in North America.