What is the Biomat Formation Pattern in Soil?
The biomat forms first along the trench bottom near the perforations [in the drainfield piping which delivered the effluent along the trench] where the effluent is discharged, and then up along the trench walls. [As the bottom becomes clogged effluent rises in the trench and seeps into the soil along the trench sides.] The biomat-coated soil is less permeable than fresh soil, so incoming effluent will move across the biomat and trickle along the trench bottom to an area where there is little or no biomat growth.
