Soil absorption septic treatment systems are the oldest form. People have been putting sewage underground since the Roman empire. These system types are successful today if the soil is
Free of limiting conditions Have the correct percentage porosity/amount of void space between soil particles Adequate treatment depth Free of compaction and other site disturbancesIn the US, different states have different regulations governing which systems are allowed to be installed. Even some states have differing regulations between the individual counties in the state. Most all regulators of onsite wastewater treatment require a soil test or sometimes called a perc test, short for percolation.
The soil test is usually conducted by a registered soil professional or sometimes by a local county regulator. Typically the regulator is the local public health department
One of the goals of the soil test is to determine the depth of any limiting conditions in the soil. Also, loading rates can be determined for the soil depths which have no found limiting condition.