40 C.F.R. § 257.5
Active life means the period of operation beginning with the initial receipt of solid waste and ending at the final receipt of solid waste.
Existing unit means any non-municipal non-hazardous waste disposal unit that is receiving VSQG hazardous waste as of January 1, 1998.
Facility means all contiguous land and structures, other appurtenances, and improvements on the land used for the disposal of non-municipal non-hazardous waste.
Lateral expansion means a horizontal expansion of the waste boundaries of an existing non-municipal non-hazardous waste disposal unit.
New unit means any non-municipal non-hazardous waste disposal unit that has not received VSQG hazardous waste prior to January 1, 1998.
State means any of the several States, the District of Columbia, the Commonwealth of Puerto Rico, the Virgin Islands, Guam, American Samoa, and the Commonwealth of the Northern Mariana Islands.
State Director means the chief administrative officer of the lead state agency responsible for implementing the state permit program for 40 CFR part 257, subpart B and 40 CFR part 258 regulated facilities.
Uppermost aquifer means the geologic formation nearest the natural ground surface that is an aquifer, as well as, lower aquifers that are hydraulically interconnected with this aquifer within the facility's property boundary.
Waste management unit boundary means a vertical surface located at the hydraulically downgradient limit of the unit. This vertical surface extends down into the uppermost aquifer.
40 C.F.R. §257.5