1. "Actual emissions" means the actual rate of emissions of an air pollutant from an emissions unit, as determined in accordance with Subsections R307-401-2(1) through R307-401-2(3).

   1. (1) In general, actual emissions as of a particular date shall equal the average rate, in tons per year, at which the unit actually emitted the air pollutant during a consecutive 24-month period which precedes the particular date and which is representative of normal source operation. The director shall allow the use of a different time period upon a determination that it is more representative of normal source operation. Actual emissions shall be calculated using the unit's actual operating hours, production rates, and types of materials processed, stored, or combusted during the selected time period.
   2. (2) The director may presume that source-specific allowable emissions for the unit are equivalent to the actual emissions of the unit.
   3. (3) For any emissions unit that has not begun normal operations on the particular date, actual emissions shall equal the potential to emit of the unit on that date.

2. "Best available control technology" means an emissions limitation, including a visible emissions standard, based on the maximum degree of reduction for each air pollutant which would be emitted from any proposed stationary source or modification which the director, on a case-by-case basis, taking into account energy, environmental, and economic impacts and other costs, determines is achievable for such source or modification through application of production processes or available methods, systems, and techniques, including fuel cleaning or treatment or innovative fuel combustion techniques for control of such pollutant. In no event shall application of best available control technology result in emissions of any pollutant which would exceed the emissions allowed by any applicable standard under 40 CFR parts 60 and 61. If the director determines that technological or economic limitations on the application of measurement methodology to a particular emissions unit would make the imposition of an emissions standard infeasible, a design, equipment, work practice, operational standard or combination thereof, may be prescribed instead to satisfy the requirement for the application of best available control technology. Such standard shall, to the degree possible, set forth the emissions reduction achievable by implementation of such design, equipment, work practice or operation, and shall provide for compliance by means which achieve equivalent results.

   "Air Strippers" are systems designed to pump groundwater to the surface for treatment, usually by aeration.

3. "Building, structure, facility, or installation" means 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 vessel. Pollutant-emitting activities shall be considered as part of the same industrial grouping if they belong to the same Major Group which have the same two-digit code as described in the Standard Industrial Classification Manual, 1972, as amended by the 1977 Supplement, U.S. Government Printing Office stock numbers 4101-0066 and 003-005-00176-0, respectively.
4. "Construction" means any physical change or change in the method of operation including fabrication, erection, installation, demolition, or modification of an emissions unit that would result in a change in emissions.
5. "Emissions unit" means any part of a stationary source that emits or would have the potential to emit any air pollutant.
6. "Fugitive emissions" means those emissions which could not reasonably pass through a stack, chimney, vent, or other functionally equivalent opening.
7. "Indirect source" means a building, structure, facility, or installation which attracts or may attract mobile source activity that results in emissions of a pollutant for which there is a national standard.
8. "Potential to emit" means the maximum capacity of a stationary source to emit an air pollutant under its physical and operational design. Any physical or operational limitation on the capacity of the source 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, shall be treated as part of its design if the limitation or the effect it would have on emissions is enforceable. Secondary emissions do not count in determining the potential to emit of a stationary source.

9. "Secondary emissions" means emissions which occur as a result of the construction or operation of a major stationary source or major modification, but do not come from the major stationary source or major modification itself. Secondary emissions include emissions from any offsite support facility which would not be constructed or increase its emissions except as a result of the construction or operation of the major stationary source or major modification. Secondary emissions do not include any emissions which come directly from a mobile source, such as emissions from the tailpipe of a motor vehicle, from a train, or from a vessel.

   "Soil Aeration" is an ex-situ treatment process where excavated soil from a remediation project is spread in a thin layer to encourage biodegradation of soil contamination. Biodegradation may be stimulated through aeration or the addition of minerals, nutrients, or moisture.

   "Soil Vapor Extraction", or SVE, is a system designed to extract vapor phase contaminants from the subsurface. SVE systems are often combined with other technologies, such as air sparging or vacuum-enhanced recovery systems.

10. "Stationary source" means any building, structure, facility, or installation which emits or may emit an air pollutant.

KEY: air pollution, permits, approval orders, greenhouse gases

Date of Last Change: December 19, 2025

Notice of Continuation: May 4, 2022

Authorizing, and Implemented or Interpreted Law: 19-2-104(3)(b)(iii); 19-2-108