How much dirt would be in a hole 6 feet deep and 6 feet wide that has been dug with a square edged shovel?
None.
No matter how big a hole is, it's still a hole: the absence of dirt.
And those of you who said 36 cubic feet are wrong for another reason, too.
You would have needed the length measurement too.
So you don't even know how much air is in the hole.
