A Mound System is designed and located above the natural soil surface and constructed with suitable fill material. This type of system may be required if a restricive layer is too close to the surface or the ground does not perc well. The requirements for this type of system are a uniform distribution of effluent waste water, dosing and resting cycles, and the above ground construction. A minimum of twenty inches of soil must between the bottom of the disposal field and a restrictive layer, such as bedrock.