Carlsbad, NM isn't a big town. Head Southeast from there and it's quite a large stretch of land that's not used for much besides oil exploration, some cattle grazing, and the WIPP site. The population density is so low in that area that it seemed like a good place to test ways of storing nuclear waste long-term. This is one of the places where they're working on figuring out a way to warn future civilizations not to try and dig up what is buried there.

I'm not the least bit surprised it took aerial surveys to notice the situation.