We used to have a scalper. Basically a power grizzly. It sat close to the muck pile. You fed it with an excavator. It had a vibrating feeder. Oversized went off the top off the end. What you want, fell through and came off the front, and under sized went off the back. No belts just a lot of shaking. Full time job for a welder. We just sort it out with the excavator now. The excavator has to dig out from the face anyway.