Well you'll need to find the dump first. If there are any hillsides or creeks on the property, start looking there. If you don't find one there then things get harder. Sometimes you can find dumps where they piled rocks up along the sides of the field. If you've got a metal detector you can try looking for hidden dumps with that.
If your looking for a visable surface dump just head straight back to edge of property line if you know where that is? if not just head straight back to where you think it is & if not there look straight to your left & right. if not there look for a Ravine or hillside. 2 great spots for a surface dump. Good luck. LEON.
I agree with sunrunner. That foundation still looks surprisingly new. If it's not brick or, better still, stone, then it's seldom terribly old. Plain, flat-faced concrete blocks are also a bad sign in most cases. Especially if the holes in them are square, not round.