In this chapter, the following terms have the meanings indicated. Terms Defined. “Affected facility” means any one of the following electric generating stations: Brandon Shores; C. P. Crane; Chalk Point; Dickerson; H. A. Wagner; Morgantown; and R. P. Smith. “Ozone season” means the period beginning May 1 of any given year and ending September 30 of the same year. “System” means two or more electric generating units subject to this chapter that are owned, operated, or controlled by the same person. "12-month rolling average emission rate" means an average emission rate determined at the conclusion of each month by calculating: For each hour that the unit is operating, the arithmetic average of all hourly emission rates for each operating day of a given calendar month to obtain a monthly average; and The arithmetic monthly average, as determined in §B(4)(a) of this regulation, of the previous 12 calendar months.