In areas with shallow soils, high water tables, rock or other restrictive soils, sand mounds provide another tool to provide effective treatment and dispersal of waste water.
They have been subjected to extensive long-term research and testing, and often provide a way to service properties that would otherwise be difficult or impossible to deal with in a cost-effective manner.
These types of systems are sometimes described as an above grade pressurized field. They are custom designed utilizing information about the soils on the site, their ability to accept water long-term(percolation or permeameter tests), and the planned usage of the residence or commercial building.
The system it’s self is composed of some components familiar to most people; septic tanks and pump chambers. Where they differ from most other systems is in the field area.
As the name suggests, these are a “mound” of carefully produced custom clean treatment sand. On this bed of sand is laid a layer of rock or infiltrator chambers. Within the rock or chambers are a custom-built series of perforated piping designed to apply small doses of effluent. The entire system is then typically covered with a sandy loam like material that can be seeded with grass.
While these systems provide effective treatment of wastewater, they can be expensive to build and maintain. They also protrude above the surrounding grade, and can therefore be less than ideal from an aesthetic perspective. That aside, they do allow development of difficult sites, and that is often the only real determining factor when it comes to selection of these systems.