(1) The owner or operator of a new or modified facility or emitting unit for which a Montana air quality permit is required by this subchapter shall install on the new or modified facility or emitting unit the maximum air pollution control capability that is technically practicable and economically feasible, except that:

(a) BACT must be utilized.

(i) Existing emitting units and those emitting units constructed or installed after March 16, 1979, that were not previously subject to this subchapter become subject to this rule when any modification to the emitting unit requires a Montana air quality permit; however, only the specific emitting unit that is modified becomes subject to this rule.

(b) The lowest achievable emission rate must be met to the extent required by ARM Title 17, chapter 8, subchapters 9 and 10, for those emitting units subject to those subchapters.

(2) The owner or operator of a new or modified facility or emitting unit for which a permit is required by this subchapter shall operate all equipment to provide the maximum air pollution control for which it was designed.