There is an old apple tree in our backyard. About 8 feet from this tree is a hole that we cannot seem to fill. Two years ago we put a cement block in the hole and filled it with earth. Last summer we put more earth a levelled it but this summer we had to add more earth. We put in 3 bags of earth and planted grass seed but 3 months later it was sinking again. The hole is about 15 inches across and has sunk about 6 inches down.
Answer:
You might want to dig down a few feet to determine where all this fill is going. It could be something as simple as water run-off washing things away. What you'll have to determine is where it is washing it to and that can only be done by digging.
