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Federal Register / Vol. 86, No. 114 / Wednesday, June 16, 2021 / Rules and Regulations
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ADEQ considered the types of emission sources in each of the nonattainment areas where it has minor source permitting jurisdiction that contribute to nonattainment. For example, the Hayden and Miami SO2 nonattainment areas are attributable to the copper smelters operating in each area, and the Nogales nonattainment area for particular matter with an aerodynamic diameter less than or equal to 10
microns PM10 is attributable to paved road dust, construction, and residential wood burning. As we summarized in the TSD for our December 23, 2020 proposed action, this discussion shows that minor sources are not currently significant contributors to the nonattainment issues in these areas. 28
In consideration of the information summarized in this response, we disagree with the commenters that the ADEQs approach to revising its minor source permitting thresholds for PM2.5
and in designated nonattainment areas where it has minor source permitting jurisdiction was arbitrary and unsupported. We find that the ADEQ
has provided sufficient evidence that its NSR program will apply to the vast majority of emissions where the ADEQ
has permitting jurisdiction, including in Arizonas nonattainment areas, and including PM2.5 emissions in attainment areas.29 As a result, we conclude that those emissions exempted from the ADEQs NSR program under its minor NSR permitting exemption thresholds will be inconsequential to attainment and maintenance of the NAAQS.
While we agree with the commenters general proposition that the NSR
program focuses on the review of new sources and modifications to existing sources, we disagree that this means that the rationale and analysis provided by the ADEQ to support its permitting exemption thresholds is inadequate.
The commenters have not suggested or provided an alternative analysis that they believe would be appropriate to demonstrate the insufficiency of the minor NSR thresholds at issue, other than a generic reference to modeling.
We find the ADEQs rationale persuasive and find that the ADEQ has demonstrated that the permitting thresholds it has established by 28 Technical Support Document for EPAs Notice of Proposed Rulemaking: Air Plan Approval;
Arizona; Stationary Sources; New Source Review Updates, November 2020 EPAs 2020 TSD at 15.
29 The ADEQs program requires permitting or registration for new and existing sources. While a NAAQS review is generally only triggered for new sources or modifications, the ADEQs permitting of existing sources provides additional protection that such sources are also complying with all other applicable CAA requirements.

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considering local conditions will capture the types and sizes of sources that are necessary for review to ensure such sources will not interfere with attainment and maintenance of the NAAQS in the areas where the ADEQ
has minor NSR permitting jurisdiction.30 Thus, the additional analysis and information provided by the ADEQ in the 2020 Minor NSR
submittal is sufficient for demonstrating that the permitting thresholds for minor sources in nonattainment areas and minor sources of PM2.5 in attainment areas meet the requirements of CAA
section 110l and Appendix V to 40
CFR part 51 31 and will not interfere with attainment and maintenance of the NAAQS.
Comment: The commenters assert that the 2020 Minor NSR submittal fails to demonstrate under 40 CFR 51.160e that review of agricultural equipment used in normal farm operations under the ADEQs minor NSR program is not needed for the ADEQs program to meet federal NSR requirements for attainment and maintenance of the NAAQS or review for compliance with the control strategy. The commenters take issue with several aspects of the ADEQs rationale, that we discuss in detail below, and further conclude that this exemption violates CAA section 110l and sections 2.2d and e of Appendix V to 40 CFR part 51.
Response: As discussed below, we respectfully disagree with the commenters that the 2020 Minor NSR
submittal does not demonstrate that the States exemption for agricultural equipment used in normal farm operations in its NSR program is approvable under 40 CFR 51.160e. The ADEQs submittal demonstrates that regulation of these exempt sources under its minor NSR program is not needed for ADEQs program to meet federal NSR requirements for attainment and maintenance of the NAAQS or review for compliance with the control strategy. As the ADEQ has explained in 30 The NSR program is only one aspect of the CAA requirements that must be implemented to ensure attainment and maintenance of the NAAQS.
The NSR program is generally intended to allow for increases in emissions if it can be demonstrated that the increases will not interfere with attainment.
Among other CAA programs, the comprehensive set of requirements found in CAA title I, part D are designed to ensure that State and local authorities with jurisdiction over nonattainment areas require the necessary reductions to reach attainment.
31 As explained above, the commenters do not accurately characterize the SIP submittal completeness criteria in Section 2.2e of Appendix V to 40 CFR part 51 as it relates to modeling. We find that section 2.2e is not applicable to the 2020
Minor NSR submittal because it did not contain modeling to support the SIP revision, nor is modeling required in this instance.

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detail, this exemption could potentially apply only to a very narrow group of minor sources that would not otherwise be exempt from minor NSR review under exemptions already approved by the EPA in our 2015 NSR action.
Further, the ADEQ retains authority to require a permit even for the sources that will fit within this exemption if it determines that doing so is necessary to protect the NAAQS or enforcement of the control strategy. For these reasons, we also disagree that the exemption violates CAA section 110l and section 2.2d of Appendix V to 40 CFR part 51.32
The State of Arizona exempts agricultural equipment used in normal farm operations from the general requirement to obtain an air permit.33
The ADEQs permitting regulations implement this exemption by exempting agricultural equipment used in normal farm operations from the requirement to obtain a registration or permit at R18
2302C. R182302C makes clear that this exemption does not apply if the source is a major source or if operation without a permit would result in a violation of the Clean Air Act. R182302C2 also clarifies that agricultural equipment used in normal farm operations does not include equipment classified as a source that requires a permit under title V of the Act or that is subject to a standard under 40 CFR parts 60, 61, or 63.
We identified this exemption as one of the bases for our limited disapproval of the ADEQs 2012 NSR SIP submittal in our 2015 NSR action because the submittal did not adequately justify the exemption as required by 40 CFR
51.160e,34 and it was unclear how the 32 As noted previously, the commenters do not accurately characterize section 2.2e of Appendix V, which requires that SIP submittals include certain information that supports modeling when modeling is otherwise required to be conducted for a SIP revision. The CAA does not require all SIP
submittals to contain modeling, and modeling was not included in or required to support the 2020
Minor NSR submittal. Therefore, we continue to find that section 2.2e of Appendix V is not applicable to the 2020 Minor NSR submittal in general, nor does it apply specifically to the ADEQs demonstration supporting the exemption of agricultural equipment used in normal farm operations.
33 See ARS 49426B, which states, in part, in reference to the State law requirements for obtaining air permits: The provisions of this section shall not apply to motor vehicles, to agricultural vehicles or agricultural equipment used in normal farm operations, or to fuel burning equipment which, at a location or property other than a one or two family residence, is rated at less than one million British thermal units per hour.
emphasis added 34 See 40 CFR 51.160e: The procedures must identify types and sizes of facilities, buildings, structures, or installations which will be subject to
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