Description of the units in the interpreted stratigraphic column for an installation.  

Every installation should have an official, master stratigraphic column designated/interpreted by a geologist.  There may be more than one record of a particular lithology (at different depths) depending upon whether the lithologic sampling is performed continuously, every five feet, or when the lithology type changes.  Usually, when lithology is described continuously, or every five feet, the potential to have more than one record of the same lithology is possible. Not every layer (or stratigraphic unit) will be found at every location, so it is important that lithologic information from sampling locations (as found in the Lithology Description table) be in agreement with the master column.