No one paid much attention to the 400-foot-deep pit at the edge of the Nashville International Airport complex.
Not until the 2010 flood, says Christine Vitt, the airport's head of strategic planning and sustainability. That's when the abandoned limestone quarry overflowed for the first time ever.
"And we had the energy consultant there, who said, 'Well hey, maybe there's a win-win here,'" Vitt recalled.
Five years later, that thought has led to a plan airport officials hope will save as much as $400,000 a year.