The Mound System

The mound system is designed so that the bottom of the rock bed to the restrictive layer (water in the figure) is at least 36". The natural soil is scarified (scratched)  to break up the soil from weather's compaction. The sand under the rock bed has to meet a minimum standard for silt particles in it. The wastewater is sprayed across the rock bed using pipes that have orfices (holes) drilled in them, evenly spaced out. It functions like a underground irrigation system. The wastewater is then filtered through the clean sand and slowly leached into the natural soil, until it reaches the subsurface water (or restrictive layer).