Casper, Wyo. (AP) — On a recent morning, the Nichols Ranch mine was quietly leaching uranium from rock formations buried hundreds of feet beneath the surface of the Powder River Basin.

A handful of employees slept in a trailer outside the plant after their 12-hour shifts as mine manager Bernard Bonifas pulled up at the main office to oversee operations. The haze from recent forest fires hid the dark ridge of the Big Horn Mountains on the western horizon.

On the surface, uranium mining at Nichols Ranch is surprisingly simple. Hundreds of little boxes pepper the hills about 70 miles north of Cas...