I have two retaining walls, one on either side of the driveway. They both need to be rebuilt, and one of them needs to be moved further back to widen the drive. I rebuilt parts of them last year, but after the winter snow melted I found that they had pushed back out. What are some things I can do so I do not have to worry about this happening next time? I want to plan and do it correctly; so any advice would be greatly appreciated.