I have a customer who wants a stone retaining wall 43' in length. The problem is it's at the end of his driveway that drops off at a 30 degree slope. I know there's going to be a lot of work with a shovel, but my question is how to keep it from sinking into the ground. One idea that I have is to put down 2" of crushed lime stone, but am open for other ideas. Also need to know what most would charge for something like this? Some of the other factors are: 1) it will make (1) 90 degree bend to the left and (1) one 180 degree bend. 2) average is 4' in width 3) graduated wall- 1' in height at shallow point and 5' high at tallest point. Any ideas?