Ok I have a patio I am bidding on. It is on a slope, I will have a wall on the lower part of the hill about 2 feet in the center and maybe a foot to 6 inches into the hill about 23 feet long curved. Question is when I excavate for the patio should I put some dirt behind the wall or use only base material and clear? There will be a 2 foot planting area between the wall and the patio. I have done quite a few patios and walls but none on a hill and had to use a wall to make the grade level. Thanks for any suggestions.