Hi, My house is a one floor, raised foundation, no basement home. The square hole that you jump into in the ground is too small in front of the Access opening to the crawl space under the house. I want to make the hole bigger and deeper. My questions are How deep can I go next to the house footing? Should I slop the bottom ground so rain water will run away from house? Then put some gravel on top? Then put my three retaining walls on top of the gravel?