Underground storage tank system means an underground storage tank and the connected underground piping, underground ancillary equipment, and containment system, if any.
Underground storage tank or “UST” means any one or combination of tanks (including underground pipes connected thereto) that is used to contain an accumulation of regulated substances, and the volume of which (including the volume of underground pipes connected thereto) is 10 percent or more beneath the surface of the ground. This term does not include any:
Underground storage means storage of hazardous liquid in a subsurface stratum or formation of the earth.
Storage tank means an aboveground storage tank or underground storage tank as defined by this Regulation.
Aboveground storage tank or “AST” means any vessel that has a liquid capacity of 110 gallons or more, is intended for fixed installation, is not solely used for processing, and does not meet the definition of an underground storage tank.