This is a Presby septic system. It was installed in Farmington, NY. We used ASTM C-33 sand for the four inch bed under the pipe and to cover it up. The entire sand bed (30x60) had to be level within one inch. The effluent is supposed to be eaten up by the biomat that is formed within the Presby pipes. Proper venting is essential.
People never really see things that get buried in the ground. I like to think of our jobs as a work of art.
Steve Jobs said, "When you're a carpenter making a beautiful chest of drawers, you're not going to use a piece of plywood on the back, even though it faces the wall and nobody will ever see it. You'll know it's there, so you're going to use a beautiful piece of wood on the back."