The former Hoover Quarry is a 43-acre lake located next to the Nashville International Airport that holds stormwater runoff. By next summer, it will provide water for the airport’s cooling and irrigation systems with the use of geothermal plates, the largest project of its kind in North America, according to the Metropolitan Nashville Airport Authority.
The $10.4 million project is expected to save the airport close to $430,000 a year in cooling costs for the next 50 years. It replaces the current centralized system that relies on cooling Metro Nashville’s potable water in four cooling towers. Because water from the lake is naturally about 10 to 20 degrees cooler, at 50 degrees Fahrenheit, it will not require energy for chilling.
The geothermal system is expected to save the city 30 million gallons of potable water a year and cut 1.3 million kilowatt hours in electricity costs, according to Robert Ramsey, the airport authority’s chief engineer.
“It’s not only sustainable, it takes advantage of an unused asset existing here on the property,” said Tom Jurkovich, vice president of communications for the airport authority. “It’s a highly imaginative use of that asset that is a nationally noteworthy sustainability project.”
The project is funded through a $3.6 million federal grant, $1.3 million from the Tennessee Aeronautics Department and $5.5 million from the airport, financed through airport revenues and bonds. Planning for the cooling project began in 2008 and consultants Energy Systems Group conducted a study that explored uses for the quarry and examined methods of increasing efficiency.
Christine Vitt, who leads the airport’s strategic planning and sustainability, said the study assessed water quality, aquatic and plant life and water temperature and found no significant risks.
How it works:
Twelve yellow buoys mark the location where geothermal sets of plates will be submerged 50 feet deep in the lake in the coming weeks. The plates sit vertically, about 25 placed in a row, forming a box-like structure. About 1.6 miles of 20-inch black pipes will carry the lake’s water from the quarry to the airport and back, traveling under a runway and under Donelson Pike. As the water circulates through the airport system, it begins to absorb heat, which is transferred back to the lake plates when it returns to the quarry, allowing the water to cool again.
“The heat will be dispersed and the cool water will be brought back in,” Vitt said.
The cooling technique is used by other Tennessee lakes, including Lindsey Lake in Lawrenceburg and in Nashville’s Riverfront Park. Other airports use geothermal systems that are built from the ground, rather than through lake plate cooling.
The airport has used the 150-foot-deep quarry as a retention pond since 1988 and a third of the quarry was transformed into a runway. The new geothermal system could also serve the airport’s growth if an additional building or terminal is built on the east side of the quarry, Vitt said.
Blakley Construction Services in Nashville is the lead contractor and Energy Systems Group is among subcontractors. Scott Terry, project director for Blakley, estimates the project will employ 30 workers over the course of the project.
The geothermal plate installation is the latest among several initiatives focused on sustainability. The airport recycles concrete from runway projects, repurposes and recycles demolished materials and fallen trees. Most recently, the airport installed solar-powered charging stations for electric vehicles.
“We intend to be and have been a leader in the sustainability space,” Jurkovich said. “This quarry project is really going to be the crown jewel of our current efforts.”