Instead of dumping directly onto the ground, why not use a dumptruck with a regulating door to dump directly into the bucket of the front end loader? Sure the truck will have to be there on the spot while the loading process takes place but it eliminates the enviromental and wastage concerns.

The rear door in this video has a door with a slot in the middle. I know it's a small door but I've seen these type doors with bigger slots and also the entire rear door can be tied down to only open a certain amount to control the flow of material.
http://www.youtube.com/watch?v=umrFQkoxU_I

Soitenly.

Steve

Yes, this car is property of the Tennessee Valley Railroad.