In my imagination, the bulldozer that was gouging the earth to get “fill” to build the highway that runs nearby still sits at the bottom of this turquoise pool. I like to think that when the ‘dozer struck the spring that provides the limestone-rich water that fills the hole it dug, the bulldozer operator had time only to scramble off the iron monster and get to safety before the water sealed its grave. That’s probably not exactly how it happened, although the basics of that story are true: A quarry created to provide fill for widening Louisiana Highway 165 became…