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Federal Register / Vol. 86, No. 114 / Wednesday, June 16, 2021 / Rules and Regulations for each category of equipment was determined by estimating the worst-case potential emissions for the category and ensuring that such emissions would be below the ADEQs permitting exemption thresholds.51 With this clarification, we approved of the categorically exempt activities in the 2015 NSR action.52 To illustrate this concept, the 2020 Minor NSR submittal also contains a sample calculation for a boiler burning No. 6
fuel oil with a heat input rating of 10
MMBtu/hr. The sample calculation shows that potential emissions of NOX
from such equipment would be 16.1
tons per year and below the ADEQs 20
tpy minor NSR permitting exemption threshold for NOX. Accordingly, the smaller fuel-burning equipment, rated less than 1 MMBtu/hr, that is exempt under ARS section 49426B would have emissions well below the ADEQs approved permitting exemption thresholds, and therefore would not otherwise require a permit or registration under the ADEQs program.
The ADEQ explains that the purpose of the exemption for categorically exempt activities is to allow such low-emitting small fuel-burning installations, which would not in any case require a permit, to avoid having to perform unnecessary emissions calculations.53
Given the rationale provided by the ADEQ, and our prior review and approval under 40 CFR 51.160e of the ADEQs exemption of categorically exempt activities under its minor NSR
program, we disagree with the commenters that the ADEQ has not adequately justified the state law exemption.54 The ADEQ has demonstrated that fuel burning equipment rated less than 1 MMBtu/hr is equipment that falls within the existing SIP-approved category of categorically exempt activities, and also that it is equipment that would otherwise not require a permit or registration compared to the ADEQs approved 55 permitting thresholds. In sum, the state law exemption for small fueling burning equipment has previously been determined by the EPA

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51 See
Appendix A to the 2012 NSR SIP submittal at 1570 and 1571.
52 EPAs 2015 TSD at 25.
53 Section 4.3 of 2020 Minor NSR submittal at 13
14.
54 The commenters specifically identified modeling as an example of the type of evidence to support this exemption. Modeling was not required to make this demonstration.
55 In our 2015 NSR action, we approved of the ADEQs permitting exemption thresholds for each regulated pollutant, except PM2.5, and our approval of the thresholds was limited to their application in attainment areas. With todays action, we are now also approving the thresholds as they apply to PM2.5 and nonattainment areas.

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to be inconsequential to attainment and maintenance of the NAAQS, and the commenters have not provided information demonstrating why they believe this exemption is not protective of the NAAQS, or otherwise provided information that calls into question our previous approval of the ADEQs exemption for categorically exempt activities under 40 CFR 51.160e.
Comment: The ADEQ states that its NSR program applies to the areas of the State where the ADEQ has permitting jurisdiction all counties in Arizona other than Maricopa, Pima, and Pinal, except where the ADEQ asserts jurisdiction. The commenters state that the ADEQ should explain whether the minor NSR programs in Maricopa, Pima, and Pinal counties are SIP-approved and meet all CAA requirements. To the extent they do not, the ADEQ should fix any deficiencies with the 2020 Minor NSR submittal.
Response: As the commenters note, the 2020 Minor NSR submittal, and the requirements therein relating to the ADEQs minor NSR permitting program, are applicable only to those portions of the Arizona SIP where the ADEQ has minor NSR permitting jurisdiction. The EPA reviewed the ADEQs submitted SIP revision and determined that it complies with all relevant CAA
requirements for approval into the Arizona SIP. In addition, this revision will correct several outstanding deficiencies in the ADEQs minor NSR
program that were previously identified by the EPA. The commenters questions about the sufficiency of the minor NSR
permitting programs for other areas and sources within Arizona that are within the jurisdiction of Maricopa, Pima, and Pinal counties, and which are not covered by ADEQs minor NSR program, are not germane to the EPAs current SIP
action on the 2020 Minor NSR
submittal. The CAA does not require that the ADEQ or the EPA address all components of the minor NSR program implemented by all permitting authorities in Arizona in any particular SIP action.
III. EPA Action No comments changed our assessment of our proposed action. Therefore, as authorized in section 110k3 of the Act, the EPA is approving the ADEQs 201920 NSR submittals, specifically including the 2020 Minor NSR
submittal and the Ammonia PM2.5 NSR
submittal. We find that the ADEQ has corrected all remaining deficiencies identified as the bases for our final limited disapproval of the ADEQs NSR
program in our 2015 NSR action and the basis for our conditional approval of the
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ADEQs NNSR program in our 2018
Major NSR action. Thus, the issues that formed the basis for our final limited disapproval in 2015 of the ADEQs minor NSR, PSD, and NNSR programs and our conditional approval in 2018 of the ADEQs NNSR program are now fully resolved. Our final action updates the ADEQs SIP-approved NSR program, corrects previously identified deficiencies, and recognizes that the ADEQs NSR program also satisfies the CAA visibility requirements in 40 CFR
51.307. Additionally, the sanctions and sanctions clocks triggered by our 2016
PM2.5 precursor action for the West Pinal and Nogales PM2.5 nonattainment areas will be permanently terminated on the effective date of this final approval action.
This action approves the rules listed in Table 1 of this notice into the ADEQ
portion of the Arizona SIP and removes or supersedes the rules listed in Table 2 of this notice from the ADEQ portion of the Arizona SIP. We are also revising 40 CFR 52.119 to remove the conditional approval of the States plan related to ammonia as a PM2.5 precursor, as we are now fully approving this component of the States plan. Finally, in conjunction with the EPAs SIP
approval of the ADEQs visibility program for sources subject to the ADEQs PSD and NNSR programs, we are revising 40 CFR 52.145b to remove the visibility FIP at 40 CFR 52.27, as well as the visibility FIP at 40 CFR 52.28
for those stationary sources subject to the ADEQs permitting jurisdiction, as these FIPs are no longer applicable.
IV. Incorporation by Reference In this rule, the EPA is finalizing regulatory text that includes incorporation by reference. In accordance with requirements of 1 CFR
51.5, the EPA is finalizing the incorporation by reference of the ADEQ
rules described in the amendments to 40
CFR part 52 set forth below. Therefore, these materials have been approved by the EPA for inclusion in the SIP, have been incorporated by reference by the EPA into that plan, are fully federally enforceable under sections 110 and 113
of the CAA as of the effective date of the final rulemaking of the EPAs approval, and will be incorporated by reference in the next update to the SIP
compilation.56 The EPA has made, and will continue to make, these documents available through https
www.regulations.gov and at the EPA
Region IX Office please contact the person identified in the FOR FURTHER
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