They need to just haul a big trebuchet up there.Then they can just launch poop down the mountain in sealed containers with the poop trebuchet. Ideally you could have a few poop trebuchets in a line to launch em down one after another.
Have you ever heard about the guys who brought parachutes up Everest, and just glided back down?
Instead of a heavy trebuchet, you just redesign poop bags to have a little parachute attached to them. Then you release your poop to the winds... Who knows how far your poop might go?