415 ILCS 5/3.285
"Municipal Solid Waste Landfill Unit" or "MSWLF unit" means a contiguous area of land or an excavation that receives household waste, and that is not a land application unit, surface impoundment, injection well, or any pile of noncontainerized accumulations of solid, nonflowing waste that is used for treatment or storage. A MSWLF unit may also receive other types of RCRA Subtitle D wastes, such as commercial solid waste, nonhazardous sludge, small quantity generator waste and industrial solid waste. Such a landfill may be publicly or privately owned. A MSWLF unit may be a new MSWLF unit, an existing MSWLF unit, or a lateral expansion. A sanitary landfill is subject to regulation as a MSWLF unit if it receives household waste.
"New MSWLF unit" means any municipal solid waste landfill unit that receives household waste on or after October 9, 1993, for the first time.
"Existing MSWLF unit" means any municipal solid waste landfill unit that has received solid waste before October 9, 1993.
415 ILCS 5/3.285