I asked for the opinion of the pool installer on what was the best for backfilling the void left when digging the extra 2' on the perimeter of the pool and they said to "just use the dirt". I don't know if I agree or like doing so considering it has a decent amount of gravel and clay. I also asked if I should use a foam barrier and their response was that it would just hold the moisture against the side and cause it to rust sooner. Any other opinions or preferences would be much appreciated! It is approximately 28-30" deep at the deepest part of the dig to pretty level ground. Thanks ahead of time, for your time!