Ill. Admin. Code tit. 35 § 211.4730
"Plant" means, for purposes other than 35 Ill. Adm. Code 215, 218 and 219, all of the pollutant-emitting activities which belong to the same industrial grouping, are located on one or more contiguous or adjacent properties, and are under the control of the same person (or persons under common control), except the activities of any marine vessel. Pollutant-emitting activities shall be considered as part of the same industrial grouping if they belong to the same major group (i.e., which have the same two-digit code) as described in the "Standard Industrial Classification Manual," 1987 (incorporated by reference in 35 Ill. Adm. Code 218.112 and 219.112 ).
Ill. Admin. Code tit. 35, § 211.4730
Added at 17 Ill. Reg. 16504, effective September 27, 1993