I recently hurt my hand shoveling dirt, and was looking for a way to dig a 3" trench, without strain, and came upon the idea of using a Shop Vac, now wait before you laugh, A shop vac can handle about 8 gallons of dirt, even if its wet dirt It has great suction, so it would suck up dirt, small rocks, etc -- and then you could use the same dirt you vacuumed to fill up the trench... Have a bigger job, dump the dirt into a larger pail, and keep working.
The way I did this job, was racked away the larger rocks from the area, I wanted to trench.
Then vacuumed up the dirt / rock / sand
Ran piping and some low voltage wiring
Used a small shovel to refill up the trench with the dirt I vacuumed
re-raked the rocks back over the filled holes.