As e2021 said, these are some kind of tailing dams to treat remaining water from mining. Google even has streetview photos from the nearby road, resolution is

As e2021 said, these are some kind of tailing dams to treat remaining water from mining. Google even has streetview photos from the nearby road, resolution is just enough to read "[something] wastewater evaporation ponds" on the fence sign: https://goo.gl/maps/WZKbdPxs5sS2 https://goo.gl/maps/WZKbdPxs5sS2 The mine itself looks cool, too: https://www.google.cz/search?q=Casa+Grande+Copper+Mine&safe=off&tbm=isch https://www.google.cz/search?q=Casa+Grande+Copper+Mine&safe=...