Ill. Admin. Code tit. 77 § 906.20
"Absorption Area" means the area of coarse aggregate in the absorption bed or trenches in a mound.
"Basal Area" means the area of natural soil under a mound which is effective in absorbing effluent.
"Depression" means an area that is sunk below its surroundings.
"Dosing" means the application of sewage under pressure to a sewage disposal system at constant intervals or in constant amounts per application.
"Drainageway" means a natural or artificial channel for the discharge of surface water through a given tract of land or region.
"Flood plain" means the land bordering a stream, built up of sediments from overflow of the stream and subject to inundation when the stream is at flood stage.
"Mound" means a soil absorption sewage treatment system that is elevated above the natural ground surface in a suitable fill material as defined in 906.40.
"Perched Water Table" means groundwater which is trapped above a normal water table by an impervious formation.
"Percolation Rate" means the downward movement of water through a saturated soil.
"Permeable Soil" means soil which has a percolation rate between 18 and 180 minutes. (See Appendix A, Illustration G of the Private Sewage Disposal Code for meaning of percolation rate and percolation test procedure.)
"Shallow Permeable Soil" means pervious soil over creviced or porous bed rock, 51/2 feet or less in thickness.
"Slowly Permeable Soil" means soil having a percolation rate of between 180 and 360 minutes.
Ill. Admin. Code tit. 77, § 906.20