"So what do you do?"

Environmental law enforcement. Training a new hire (first in years). They have to learn the capabilities of machinery.

"a Cat D9 big equipment"

Notice the 9 is just being used to clean up and feed the BWE. It is not considered big on a coal mining operation. These TX operations all use 10's and 11's to grade the dragline spoils.

I've seen the Komatsu Superdozer's work back in WV. They can move some spoil. Got some pictures somewhere.

Somewhere on the 'net are pictures of a dozer Peabody Coal built on its Kayenta, AZ operation. They hooked two big Komatsu's together with one huge blade between them. The controls were all linked and one guy operated it from one of the cabs. It was huge. I never saw it push dirt...I only watched it rust. I believe they scrapped it sometime in the early 90's.