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Federal Register / Vol. 86, No. 114 / Wednesday, June 16, 2021 / Rules and Regulations
exemption in state law applied in the context of the ADEQs NSR program.35
In response to this limited disapproval, the ADEQ provided a detailed discussion of the exemption in the 2020
Minor NSR submittal. As summarized below, the ADEQs 2020 Minor NSR
submittal demonstrates that the exemption is only available to a limited set of minor sources not otherwise exempt under exemptions we have already approved into the Arizona SIP
as part of the ADEQs NSR program, and the programs potential exemption of such sources would be inconsequential to attainment and maintenance of the NAAQS.
First, the 2020 Minor NSR submittal clarified that the exemption at R182
302C represents the ADEQs interpretation of the agricultural exemption in Arizona Revised Statutes ARS section 49426B:
This rule represents ADEQs official implementation and interpretation of the statutory exemption under its rulemaking authority in ARS 49425 and 49426B.
The rule has been recognized as valid by the Arizona Attorney General in its opinion supporting the states Title V program in 1993.36 In approving Arizonas Title V
program in 1996, EPA deferred to this opinion but stated that it would revisit this issue if a successful legal challenge to the regulatory exemption occurs. 37 In the subsequent 23 years, there has been no such challenge.

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Section 4.2.1 of the 2020 Minor NSR
submittal at 10.
Second, the ADEQ confirmed that the ADEQ interprets its permitting requirements such that its permitting determinations including for the registration program component of its minor NSR program are made on a source-wide basis. As a result, if agricultural equipment used in normal farm operations is located at the same stationary source as equipment that requires a permit, then the ADEQs permit requirements, and potentially NSR, extend to the entire source and all of its pollutant-generating activities, including any equipment that might otherwise meet the definition of agricultural equipment used in normal farm operations. These two clarifications mean that the agricultural equipment exemption is potentially available only to a subset of minor sources. See section 4.2.2 of the 2020
Minor NSR submittal at 1011.
review under this section. The plan must discuss the basis for determining which facilities will be subject to review.
35 See section 5.2.2.3 of the EPAs 2015 TSD at 2627 and 80 FR 67319, 67323.
36 Attorney Generals Opinion, 2 Nov. 15, 1993, Appendix D of the 2020 Minor NSR submittal.
37 61 FR 55910, 55915 Oct. 30, 1996.

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While the term normal farm operations is not specifically defined by statute or rule, the ADEQ stated that the State of Arizonas Agricultural Best Management Practices Ag BMP
program for commercial farming operations in PM10 nonattainment areas provides guidance on the States interpretation of the types of activities that constitute normal farm operations.
This includes activities such as tillage, planting, and harvesting; areas of a commercial farm that are not normally in crop production i.e., fallow; areas of a commercial farm that are normally in crop production; significant agricultural earthmoving activities; traffic over unpaved access connections or unpaved roads or feed lanes; animal waste handling and transporting; arenas, corrals, and pens; and canals. The ADEQ stated that it interprets the normal farm operations exemption as applicable to the types of equipment used for these activities and to crop and feed processing equipment that produces only fugitive emissions. In the ADEQs experience, farm emissions tend to consist almost exclusively of fugitive dust generated by the disturbance of soils. It is important to note that the ADEQs current SIPapproved NSR program already exempts fugitive emissions,38 at R182302F, in determining whether a stationary source is subject to minor NSR
permitting requirements. See sections 4.2.3 and 4.2.4 of the 2020 Minor NSR
submittal at 1112.39 As a result, most of the sources that would meet the definition of agricultural equipment used in normal farm operations would be sources of fugitive emissions that are already exempt from minor NSR under the ADEQs SIP-approved minor NSR
program.
The ADEQ also recognized that it is possible for equipment used in normal farm operations to be a part of a stationary source that produces stack i.e., non-fugitive emissions greater than the ADEQs permitting exemption thresholds, and it may also be possible for normal farm operations themselves to be configured in such a way as to produce stack emissions. However, the ADEQ believes that, in most cases, such a stationary source would not qualify for the permitting exemption because equipment used in normal farm operations does not include equipment classified as a source that requires a 38 Fugitive emissions are defined in the ADEQs SIP-approved regulations at R18210159 as those emissions which could not reasonably pass through a stack, chimney, vent, or other functionally equivalent opening. See section 4.2 of the 2020 Minor NSR submittal at 9, n.14.
39 See also 80 FR 67319, 67320, Table 1.

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permit under Title V of the Act, or that is subject to a standard under 40 CFR
60, 61, or 63. Because the ADEQ
determines permit applicability on a source-wide basis, if a stationary source that engaged in normal farm operations qualified as a CAA title V source or included equipment subject to a New Source Performance Standard NSPS or National Emission Standard for Hazardous Air Pollutants NESHAP in 40 CFR parts 60, 61, or 63, then the entire source would require a permit, and potentially be subject to minor NSR
if its emissions were above the ADEQs minor NSR permitting exemption thresholds. In the ADEQs experience, most permitted sources include one or more pieces of equipment subject to an NSPS, such as a boiler, stationary engine, or fuel storage tank. The ADEQ
concluded that it is likely that if equipment used in normal farm operations were collocated with equipment with stack emissions exceeding the permitting exemption thresholds, at least some of that equipment would be subject to an NSPS, and therefore the normal farm operations exemption would not apply.
See section 4.2.5 of the 2020 Minor NSR
submittal at 1213.
Finally, the ADEQ explained that under R182302C, equipment used in normal farm operations is not exempt if operation of the equipment without a permit would result in a violation of the Act, which provides a final safeguard for its NSR program. In a situation where agricultural equipment used in normal farm operations with stack emissions above the permitting exemption thresholds used the exemption to avoid permitting, the ADEQ would invoke this provision as necessary to ensure that any such source does not endanger attainment or maintenance of the NAAQS or enforcement of the control strategy. The ADEQ explained that whenever it becomes aware of such a source through citizen complaint, inspection of the facility under the Ag BMP program, inspection of a nearby or related facility, notice from a building permit agency, or other means, the ADEQ will evaluate the facility using the methodology in R182302.01C to determine whether it should be subject to permitting and minor NSR. See section 4.2.5 of the 2020 Minor NSR submittal at 13.
In our proposed action, we found that the ADEQ had demonstrated that its exemption for agricultural equipment used in normal farm operations is extremely limited in scope, and the potential sources exempted from permitting would be inconsequential to attainment and maintenance of the
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