Rivers are usually too shallow and of course there is the movement of water which tends to bring unwanted things back.
Now, the ocean, that is a great place to dump stuff, preferably a very deep place,
this for example.
Once you have decided on a good place I am definatly there to back you up bro. I'll even carry the sack for you (will give me some workout too)

Oh, btw, I agree with ya.