SEWAGE DEPARTMENT TRAINING PROGRAM
How to Build an Elevated Sandmound Sewage Disposal System
To protect the absorption area from soil migrating into the aggregate, a soil barrier is installed. Geo-textile fabric is the preferred material as it will not degrade. A two inch layer of hay or straw may also be used.
If using hay or straw, be sure not skimp. Should the material degrades before grass roots can stabilize the cover soil, the soil will drop into the aggregate and clog the sand.
The soil barrier must cover the entire absorption area.