if ya goto some local nursery were they sell dirt, sand, rock, but the truck load. take a look at there setups, most places around me, all have cut back into a hill side, and then built 3 walls, 1 wall acting liking a retaining wall, that is up against the cut out hillside, then 2 other walls that are sides.
this gives you something to run your FEL along on the sides, and then you can take run tractor right into the rear, (not slamming into the rear wall) but up to it, and curl the bucket to get the sand.
that 40 to 45 HP tractor you have, will more than likely tear anything else up in a heart beat. or less ya bomb sheltered the walls.....
you can normally pickup some cheap "ties" kinda rough timbers and may look like rail road ties, but are not black. if i bid my time, i can normally get seconds for 1/2 off price or more. granted the seconds look like crud. but after a few winters hitting rear wall and scrapping along the sides with tractor, ya not going to have a perfect good looking wall.
4x6 or 6x6 ties. get yourself a couple auger drill bits for a drill (if ya get one drill bit, it is bound to bust off in a hole). and then "spikes" *duh* forget size, about a foot long 1/2" in diameter. a chain saw works nicely in cutting things down, trying to get ends perfectly square, *shrugs* you won't be able to notice ya got things square after a couple years. a small little sledge hammer say 2 to 5lbs, with a short handle. tends to work better for me to drive the spikes after pre-drilling....
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getting that rear wall so you can slide your FEL bucket into the area for a bucket full of sand, and/or bust the chunks up, can make life easier.
if ya do not want to fight with the tarps. just put a cheap plastic corrogated roof over the area. (3 walls, 1 roof) and leave the one side open, so you can make sure you can get in there with tractor.
make sure ya get good drainage of water out of the area. both gutters, and just sloping the ground around the area down and away from this sand pile area.
a concrete slab is going to make things cleaner, vs ending up with chunks of dirt and sand.