This industry idea, to give proper credit, was found ages ago in an OLD mrr magazine article (maybe late '40s or early '50s).
Small Sand & Gravel Company on Switchback: Will present this industry as how yours truly plans to locate it on my HO pike. Other modelers could tweak, reverse, relocate it to fit on their layout. Foreground main runs left-right. Spur branches off in rear, w/ right-facing points and travels downhill to left, to 1- 2 hopper-capacity, mid-grade switchback tail track.( NOTE: Here's where a hill-holder, made with the small tuft of bristles from an artist's paintbrush, inserted between rails, could be put to good use, safely holding tail track hoppers by an axle center, until daily switching turn arrives to service facility). Line then drops to grade at right; dead-ends at bumper, substantial enough to stop any runaways from tail track. Small office shack is situated in any convenient out-of-the-way place nearby. HUGE pile of sand and another of gravel, sits on left and right, a short distance from lower track. Portable, diesel-powered conveyer and/or bucket loader handles all loading chores. Piles are replished by Euclid dump, trundling from rear. In my case, t'will be emerging from a rear track underpass, located against module backdrop. A sand/ gravel pit is PRESUMED to exist behind rear, elevated rails. Handy diesel fuel truck is kept parked near office to service units. Electric power/ phone lines could be strung to office shack from off-layout and some little people present, would give a nice touch, along with heavy rear foliage, trees, bushes and access road, going off to side or rear and a few employees vehicles parked here and there, should about complete the scene
....papasmurf
Added Info: Back in the era before the tightened Federal regulations, when one could get away with this kind of move: With MTs spotted on tail track, lower track empty and S&G loading crew out of work and idle, company crew sometimes released brakes, let cars roll to lower track, so they could continue loading w/o having to wait a day for switcher's return. .....papasmurf