Are you drawing plenty of points around the measurement area?
Is it on a flat surface?
The area of the pile is roughly 3300 yd² or so. I am seeing heights of 25 ft to 50 ft above the ground. (8.3 yards to 16.6 yards)
Is the average height of the pile 2.1 yards (2.1 yards x 3300 yd² = 7100 cubic yards) or is it more like 4 yards (4 yards * 3300 yd² = 13,000)?