STATE OF MONTANA 

AIR QUALITY CONTROL 

IMPLEMENTATION PLAN 

AIR QUALITY 

17.8.740 DEFINITIONS For the purposes of this subchapter: 

(1) "Best available control technology (BACT)" means an emission !.imitation (including a visible emission 

standard), based on the maximum degree ofreduction for each pollutant subject to regulation under 42 U.S.c. 7410, 

ct seq. or 75-2-1 01, et seq., MCA, that would be emitted from allY proposed emitting unit or modification which the 

department, on a case-by-case basis, taking into account energy, environmental, and economic impacts and other 

costs, determines is achievable for such emitting unit or modification through application ofproduction processes or 

available methods, systems, and techniques, including fuel cleaning or treatment or innovative fuel combustion 

techniques for control of such contaminant. In no event may application of BACT result in emission of any 

regulated air pollutant that would exceed the emissions allowed by any applicable standard under ARM Title 17, 

chapter 8, subchapter 3, and this subchapter. Ifthe department detennines that technological or economic limitations 

on the application ofmeasurement methodology to a particular class ofemitting units would make the imposition of 

an emission standard infeasible, it may instead prescribe a design, equipment, work practice, or operational standard 

or combination thereof, to require the application ofBACT. Such standard must, to the degree possible, set forth the 

emission reduction achievable by implementation ofsuch design, equipment, work practice or operation and must 

provide for compliance by means that achieve equivalent results. 

(2) "Construct" or "construction" includes a reasonable period of time for startup and shakedown and 

means: 

(a) initiation of on-site fabrication, erection, or installation of an emitting unit or control equipment 

including, but not limited to: 

(i) installation of building supports or foundations; 

(ii) laying ofunderf,'Tound pipework; or 

(iii) construction of storage structures; or 

(h) tlle installation of any portable or temporary equipment or facilities. 

(3) "Day" means calendar day unless otherwise stated. 

(4) "Emitting unit" means: 

(a) allY equipment that emits or has the potmtial to emit any regulated air pollutant under the Clean Air Act 

of Montana through a stack(s) or vent(s); or 

(b) any equipment from which emissions consist solely of fugitive emissions of a regulated air pollutant 

under the Clean Air Act of Montana. 

ADMINISTRA TIVE RULES OF MONTANA 12131/02 17-427

Replaces Page: 

Page 9.2.2.7 (4) 
STATE OF MONTANA 

AIR QUALITY CONT 

lMPLEM PLAN 

17.8.740 ENVIRONMENTAL QUALITY 

(5) "Existing emitting unit" means an emitting unit that was in existence and operating or was capable of 

being operated on March 16, 1979, or for which the department had issued a permit by that date. 

(6) "Facility" means any real or personal property that is either stationary or portable and is located on one 

or more contiguous or adjacent properties under the control of the same owner or operator and that emits or has the 

potential to emit any air pollutant subject to regulation under the Clean Air Act ofMontana or the Federal Clean Air 

Act, including associated control equipment that affect') or would affect the nature, character, composition, amount, 

or environmental impacts of ail pollution and that has the same two-digit standard industrial classification code. A 

facility may consist of one or more emitting units. 

(7) "Install" or "installation" means to set into position and connect or adjust for use. 

(8) "Modify" does not include routine maintenance, repair, or replacement but means: 

(a) construction or changes in operation at a facility or emitting unit for which the department has issued a 

Montana air quality permit under this chapter, except when a permit is not required under ARM 17.8.745; 

(b) construction or changes in operation at a facility or emitting unit for which a Montana air quality permit 

has not been issued under this chapter but that subjects the facility or emitting unit to the requirement') of ARM 

17.8.743; 

(c) construction or changes in operation at a facility or emitting unit that would violate any condition in the 

facility's Montana air quality permit, any board or court order, any control plan within the Montana state 

implementation plan, or any rule in this chapter, except as provided in ARM 17.8.745; 

(d) construction or changes in operation at a facility or emitting wlit that would qualify as a major 

modification of a major stationary source under sub chapters 8, 9, or 10 of this chapter; 

(e) construction or changes in operation at a facility or emitting unit that would affect the plUllle rise or 

dispersion characteristics of emissions in a manner that would cause or contribute to a violation of an ambient air 

quality standard or an ambient air increment, as defined in ARM 17.8.804; or 

(f) any change in operation that affects emissions and that was not previously permitted, except that a 

change in operation that does not result in an increase in emissions because of the change is not a modification. 

17-428 12C, },'02 ADMINTSTRA TfVE RULES OF MONT ANA 

Replaces Page: 

Page 9.2.2.7 (5) 
STATE OF MONTANA 

AIR QUALITY CONT 

IMPLEME PLAN 

AIR QUALITY 17.8.740 

(9) "Montana air quality pennit" means a preconstruction pennit issued under this 

subchapter that may include requirements for the construction and subsequent operation of an 

emitting unites) or facility. 

(10) "Negligible risk to the public health, safety, and welfare and to the environment" 

means an increase in excess lifetime cancer risk of less than 1.0 x 10-6

, for any individual 

pollutant, and 1.0 x 10-5

, for the aggregate of all pollutants, and an increase in the sum of the 

non-cancer hazard quotients for all pollutants with similar toxic effects of less than 1.0, as 

detennined by a human health risk assessment conducted according to ARM 17.8.767. The 

department shall also consider environmental impacts identified in any environmental analysis 

conducted pursuant to the Montana Environmental Policy Act, Title 75, chapter 1, parts 1 

through 3, MCA, in detennining compliance with all applicable rules or other requirements 

requiring protection of public health, safety, and welfare and the environment. 

(11) "New or modified emitting unit" meads an emitting unit that was not constructed or 

upon which construction was not commenced prior to March 16, 1979. 

(12) "Owner or operator" means the owner ofa facility or other person designated by the 

owner as responsible for overall operation of the facility. 

(13) "Potential to emit" means the maximum capacity of a facility or emitting unit, 

within physical and operational design, to emit a pollutant. Any physical or operational 

limitation on the capacity of the facility or emitting unit to emit a pollutant, including air 

pollution control equipment and restrictions on hours of operation or on the type or amount of 

material combusted, stored, or processed, is treated as part of its design only ifthe limitation or 

the effect it would have on emissions is federally enforceable. Secondary emissions are not 

considered in detennining potential to emit. 

(14) "Routine maintenance, repair, or replacement" means any action taken upon an 

emitting unit by the owner or operator that is necessary on a periodic basis to assure proper 

operation ofthe emitting unit. The tenn routine does not include activities that: 

(a) have associated fixed capital costs in excess of 50% of the fixed capital cost 

necessary to construct a comparable, entirely new emitting unit; 

ADMINISTRATIVE RUl.ES OF MONT ANA . . 12/31/02 17-429 

Page9.2.2.7 (6) 
STATE OF MONTANA 

AIR QUALITY CONT 

~LE PLAN 

ENVIRONMENTAL QUALITY 

(b) design of the emitting unit, including associated control c 

(c) incrcase the p tial to emit of the emitting unit. 

(15) "Secondary emissl " means emissions that would oce s a result of the construction or 

operation ofa facility or emitting unit, 0 not corne from th cllity or emitting unit itself. Secondary 

emissions must be specific, well defined, qua impact the same general area as the facility or 

emitting unit which causes the secondary emi~. _ ondary emissions may include, but are not limitcd 

to: ~ 

(a) emissions from trains ng to or from the facility 0 ' itting unit; 

(b) emissions fro y off-site support facility that otherwIse ould not be constructed or 

increase its emission ' a result of the construction or opcration ofthe facility 0 itting unit. (History: 

75-2-111,75-1 4, MeA; lMP, 75-2-211, MeA; NEW, 2002 MAR p. 3567, Eff. _ 77/02) 

Rules 17.8.741 and 17.8.742 reserved 

17.8.743 MONTANA AIR QUALITY PERMn:S--WHEN REQUIRED 

(1) Except as provided in ARM 17.8.744 and 17.8 .745, a person may nolconstruct, install, 

modify, or operate any of the following without first obtaining a Montana air quality pcrmit issued by the 

department: 

(a) a new facility or emitting unit with the potential to emit airborne lead in an amount greater 

than five tons per year or a modification to an existing facility or emitting unit that results in an increase in 

the facility or emitting unit's potential to emit airborne lead by an amount greater than 0.6 tons per year; 

(b) a~~flBlt e6fterete piMa, fflifwra! effi~ftef8, B:ne mineral screens that have the potential to emit 

more than 15 tons per year of any airborne pollutant, other than lead, that is regulated under this chapter; 

(c) any incinerator, as defined in 75-2-103(11), MeA, and that is subject to the requirements of 

75-2-215, MeA; 

(d) any facility or emitting unit upon which construction commenced, or that was installed, before 

November 23 , 1968, when that facility or emitting unit is modified after that date and the modification 

increases the potential to emit by more than 25 tons per year of any airborne pollutant, other than lead, that 

is regu lated under this chapter; or 

17-430 -12/31/02 ADMfNTSTRATIVE RULES OF MONTANA 

Dated: 

December 6, 2002 Page: 7 of 30