I designate my dirt into good clean fill material that I use for roads, building pads and of course, dam material.
The other category is bad dirt. Topsoil, sand and dirt with branches in it. That goes into a different area.
On my lake, I'm putting the bad dirt behind the dam and building up a large picnic area that will have a very gradual slope away from the dam. Something like a 2:12 slope that I'll plant grass on and make nice.
I did have to remove more trees from behind the dam for this, but in the end, I think it will be an attractive choice.
One thing to remember when piling dirt is to pack it down right away unless you are going to move it again fairly soon. Rain will erode it really quick and you end up with silt all over the place, not to mention weeds just take over faster than you'd belive. It's easier to spread it and create a nice shape to it when you first put it there than later on.
Sometimes a dirt pile will get all water loged too. If it sits and soaks up rain water, it can be near impossible to do anything with it.
I've had piles that got rained on and became totally useless for anything. You have to spread it out and wait for it to dry out enough to stop pumping water!!!
Good luck,
Eddie