# Partial Approval and Disapproval of Air Quality Implementation Plans; Arizona; Regional Haze State Implementation Plan for the Second Implementation Period and Prong 4 (Visibility) for the 2015 Ozone and 2012 Particulate Matter Standards > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2024-29508 ## Record - **Collection:** Federal Register - **Document type:** Rule - **Published:** December 18, 2024 - **Citation:** 89 FR 102744 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 52 [EPA-R09-OAR-2024-0005; FRL-11919-02-R9] Partial Approval and Disapproval of Air Quality Implementation Plans; Arizona; Regional Haze State Implementation Plan for the Second Implementation Period and Prong 4 (Visibility) for the 2015 Ozone and 2012 Particulate Matter Standards AGENCY: Environmental Protection Agency (EPA). ACTION: Final rule. SUMMARY: The Environmental Protection Agency (EPA) is partially approving and partially disapproving the regional haze state implementation plan (SIP) revision submitted by Arizona on August 15, 2022 (“2022 Arizona Regional Haze Plan”), under the Clean Air Act (CAA) and the EPA's Regional Haze Rule (RHR) for the program's second implementation period. Arizona's SIP submission was developed to address the requirement that states must periodically revise their long-term strategies for making reasonable progress towards the national goal of preventing any future, and remedying any existing, anthropogenic impairment of visibility, including regional haze, in mandatory Class I Federal areas. The SIP submission also addresses other applicable requirements for the second implementation period of the regional haze program. Within this action, the EPA is also disapproving the visibility transport prong of Arizona's infrastructure SIP submittals for the 2012 annual fine particulate matter (PM 2.5 ) and 2015 ozone National Ambient Air Quality Standards (NAAQS). The EPA is taking this action pursuant to CAA sections 110 and 169A. DATES: This rule is effective on January 17, 2025. ADDRESSES: The EPA has established a docket for this action under Docket ID No. EPA-R09-OAR-2024-0005. All documents in the docket are listed on the https://www.regulations.gov website. Although listed in the index, some information is not publicly available, e.g., Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form. Publicly available docket materials are available through https://www.regulations.gov, or please contact the person identified in the FOR FURTHER INFORMATION CONTACT section for additional availability information. If you need assistance in a language other than English or if you are a person with a disability who needs a reasonable accommodation at no cost to you, please contact the person identified in the FOR FURTHER INFORMATION CONTACT section. FOR FURTHER INFORMATION CONTACT: Michael Dorantes, Geographic Strategies & Modeling Section (AIR-2-2), Planning & Analysis Branch, Air and Radiation Division, EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105; phone: (415) 972-3934; email: dorantes.michael@epa.gov. SUPPLEMENTARY INFORMATION: Throughout this document, “we,” “us” and “our” refer to the EPA. Table of Contents I. Background A. Regional Haze Plan for the Second Implementation Period B. Prong 4 (Visibility) of the 2012 PM 2.5 NAAQS and 2015 Ozone NAAQS Infrastructure SIPs II. Public Comments and EPA Responses A. Comment Letter From Tri-State B. Comment Letter From ADEQ C. Comment Letter From the Chamber and AMC D. Comment Letter From TEP E. Comment Letter From SRP F. Community Sign-On Letter G. Comment Letter From NPCA et al. III. Final Action IV. Statutory and Executive Order Reviews I. Background A. Regional Haze Plan for the Second Implementation Period On August 15, 2022, 1 the Arizona Department of Environmental Quality (ADEQ) submitted the 2022 Arizona Regional Haze Plan. ADEQ supplemented its SIP revision on August 25, 2023, with nonpoint source rules (“2023 Arizona Regional Haze Rules Supplement”). 2 ADEQ made these SIP submissions to address requirements of the CAA's regional haze program pursuant to CAA sections 169A and 169B and 40 CFR 51.308. 1 Letter dated August 15, 2022, from Daniel Czecholinski, Director, Arizona Department of Environmental Quality Air Quality Division, to Martha Guzman, Regional Administrator, EPA Region IX (submitted electronically August 15, 2022). On August 16, 2022, the EPA determined that the SIP submittal met the completeness criteria outlined in 40 CFR part 51, Appendix V. Letter dated August 16, 2022, from Elizabeth Adams, Director, Air and Radiation Division, EPA Region IX, to Daniel Czecholinski, Director, Arizona Department of Environmental Quality Air Quality Division. 2 Letter dated August 21, 2023, from Daniel Czecholinski, Director, Arizona Department of Environmental Quality Air Quality Division, to Martha Guzman, Regional Administrator, EPA Region IX (submitted electronically August 25, 2023). On May 31, 2024, the EPA published a notice of proposed rulemaking proposing partial approval and partial disapproval of the 2022 Arizona Regional Haze Plan SIP submission as partially satisfying the regional haze requirements for the second implementation period contained in the CAA and 40 CFR 51.308. 3 We did not propose to act on the 2023 Arizona Regional Haze Rules Supplement. 3 89 FR 47398. The EPA is now approving the elements of the 2022 Arizona Regional Haze Plan related to requirements contained in 40 CFR 51.308(f)(1), (f)(4)-(6), and (g)(1)-(5). The EPA is disapproving the elements of the 2022 Arizona Regional Haze Plan related to requirements contained in 40 CFR 51.308(f)(2), (f)(3), and (i)(2)-(4). Our proposed action and our responses to comments in section II of this document contain more information on the basis for this rulemaking and on our evaluation of the submittal. B. Prong 4 (Visibility) of the 2012 PM 2.5 NAAQS and 2015 Ozone NAAQS Infrastructure SIPs Arizona submitted its infrastructure SIP submission for the 2012 PM 2.5 NAAQS on December 11, 2015 (“2015 PM 2.5 I-SIP submittal”). 4 Arizona also submitted its infrastructure SIP submission for the 2015 ozone NAAQS on September 24, 2018 (“2018 Ozone I-SIP submittal”). 5 4 Letter dated December 11, 2015, from Eric Massey, Director, Air Quality Division, ADEQ, to Jared Blumenfeld, Regional Administrator, EPA Region IX. 5 Letter dated September 24, 2018, from Timothy S. Franquist, Director, Air Quality Division, ADEQ, to Michael Stoker, Regional Administrator, EPA Region IX (submitted electronically September 24, 2018). Our May 31, 2024 proposed rulemaking action proposed to disapprove the prong 4 portions of Arizona's 2018 Ozone I-SIP submittal and 2015 PM 2.5 I-SIP submittal. The EPA is now disapproving the Prong 4 elements of Arizona's 2018 Ozone I-SIP submittal and 2015 PM 2.5 I-SIP submittal. Our proposed action contains more information on the basis for this rulemaking and on our evaluation of the submittals. II. Public Comments and EPA Responses The EPA's May 31, 2024 proposed rulemaking action provided a 30-day public comment period that would have ended on July 1, 2024. We received four comments requesting an extension of the comment period. On June 26, 2024, 6 the EPA extended the comment period for the proposed rulemaking action by 14 days in response to requests from commenters. This action extended the close of the comment period to July 15, 2024. 6 89 FR 53372. The EPA received an additional ten unique comments, including one anonymous comment, 7 two comments from private individuals, 8 and comment letters from Tri-State Generation and Transmission Association, Inc. (“Tri-State”), 9 ADEQ, 10 the Arizona Chamber of Commerce and Industry and the Arizona Manufacturers Council (“the Chamber and AMC”), 11 Tuscon Electric Power (TEP), 12 the Salt River Agricultural Improvement and Power District (SRP), 13 12 community organizations (“Community Sign-on Letter”), 14 and Earthjustice on behalf of the National Parks Conservation Association, Sierra Club, and the Coalition to Protect America's National Parks (“NPCA et al.”). 15 The anonymous comment and the comments from the private individuals were unrelated to our proposed rulemaking. These three comments do not require a response. We respond to the issues raised in the seven remaining comment letters received on our proposed rulemaking in this action. 7 Available at https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0014. 8 Available at https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0015 and https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0019. 9 Available at https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0016. 10 ADEQ submitted its comment letter twice. The letter is available at both https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0017 and https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0018. 11 Available at https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0020. 12 Available at https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0021. 13 Available at https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0023. 14 Available at https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0022. 15 The comment letter and all Exhibits except for Exhibits 24 and 60 are available at https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0024. Exhibits 24 and 60, including an emailed copy of the NPCA et al.'s comment letter, are available at https://www.regulations.gov/comment/EPA-R09-OAR-2024-0005-0025. A. Comment Letter From Tri-State Sections I (“Introduction”), II (“Background Information on Tri-State”), and III (“Tri-State Supports the Provisions of the Arizona Department of Environmental Quality's State Implementation Plan Submittal for which EPA has Proposed Approval”) of Tri-State's comment letter either provide background information or are supportive of the EPA's proposal and therefore do not require a response in our final action. We respond to sections IV (“The Partial Disapproval is Overly Vague and Should Be Reproposed with a Fulsome and Specific Explanation of What EPA Finds Inconsistent with the Clean Air Act and the Implementing Regulations”), V (“Additional Emission Reductions Are Inappropriate for Springerville Unit 3”), and VI (“EPA's Reliance on the July 8, 2021, Clarifications Memorandum Is Inappropriate Because It Was Issued Only Days Prior to the Regional Haze State Implementation Plans Being Due”) of Tri-State's comment letter below. Comment A.1. Tri-State comments that the proposed rule, specifically the partial disapproval, is overly vague and does not lend itself to the general public being able to adequately understand what the EPA finds objectionable regarding the SIP submission. Tri-State asserts that the EPA made broad statements about divergences from the Control Cost Manual and inadequacies in four-factor analyses and that “it [is] impossible to understand with certainty the sources to which these overly broad statements apply.” The commenter also notes that the proposed rulemaking action only gives limited examples of what the EPA is referring to and asserts that the EPA needs to clearly provide where it has issues with the SIP revision as it was submitted not just examples of what it is concerned about. Specifically, Tri-State states that the proposed rulemaking action makes general comments about ADEQ conducting analyses for well-controlled sources to further reduce emissions but makes no reference to which sources that the EPA finds to be lacking in this area. Tri-State also comments that the vagueness of the proposal is not consistent with the cooperative nature of the CAA in the EPA working with states. Response A.1. We do not agree that the proposal was overly vague or that the basis for our proposed partial disapproval was unclear. The proposal provided a detailed summary of the 2022 Arizona Regional Haze Plan and the EPA's evaluation of the Plan with regard to each of the applicable requirements of the CAA and the RHR. With respect to the EPA's partial disapproval specifically, the proposal laid out multiple reasons for the EPA's determination that the long-term strategy did not fully meet the requirements of 40 CFR 51.308(f)(2), related to source selection, four-factor analyses (specifically, controlled emissions rates and deviations from the Control Cost Manual), and control determinations (specifically, the application of cost thresholds, the use of visibility as a factor to avoid controls, and the mass-based emissions caps at Springerville Generating Station (SGS)). 16 In each instance, we provided at least one example of a unit to which this reason applied. 17 We also explained why the disapproval of the long-term strategy also necessitated disapproval of the RPG and FLM consultation elements. 18 16 89 FR 47398, 47428-47432. 17 Id. 18 Id. at 47432-47433 and 47435-47436. We disagree with the commenter's suggestion that it was necessary for the EPA to specify the extent to which each of the flaws identified by the EPA applied to each unit considered by ADEQ. The EPA's role in reviewing SIPs is to determine whether they meet all of the applicable CAA requirements. 19 In evaluating whether a SIP revision (or a portion thereof) meets all of the applicable requirements, the EPA is not required to separately evaluate and discuss each of the thousands of pieces of information, analyses and determinations comprising the SIP submission. Rather, the EPA may focus on those specific elements of the SIP revision that form the basis for our determination that certain applicable requirements are met and certain applicable requirements are not met. Therefore, in this instance, it was reasonable for the EPA to summarize our evaluation and cite to examples of where the State's documentation, analyses, and determinations did not meet CAA requirements, rather than separately evaluating and discussing every such instance throughout the SIP revision. 19 See CAA section 110(k)(3) (“the Administrator shall approve [a SIP] submittal as a whole if it meets all of the applicable requirements of [the CAA]. If a portion of the plan revision meets all the applicable requirements of [the CAA], the Administrator may approve the plan revision in part and disapprove the plan revision in part”). For example, regarding source selection, our proposal stated that: ADEQ did not provide an adequate justification for screening out certain sources and units from conducting a four-factor analysis on the basis that they are `effectively controlled' as part of its source selection process. Specifically, in some cases, ADEQ did not identify the controls for each pollutant at each unit or process, the associated limits, or where the controls/limits currently exist in the Arizona SIP. In other cases, ADEQ listed the controls, but did not clearly explain why it is reasonable to assume, without conducting a four-factor analysis, that no additional controls would be reasonable. We then provided examples of specific sources to which these concerns applied. In addition, table 3 of the proposal listed all of the units that ADEQ screened out as “effectively controlled” and includes the entirety of ADEQ's rationale for each unit. 20 This table clearly shows that for many of the units, ADEQ did not list controls for one or more of the three relevant pollutants (NO X , SO 2 , and PM). Moreover, even for those units where ADEQ did list this information, it did not explain why it is reasonable to assume, without conducting a four-factor analysis, that no additional controls would be reasonable. Furthermore, our proposed rulemaking action clearly stated that ADEQ did not adequately explain whether any of the existing controls for facilities evaluated within the SIP submittal were necessary for reasonable progress and therefore a part of the state's long-term strategy. Therefore, it was not necessary to specifically identify each source that was deficient in this respect because the deficiency applied to every source determined to be effectively controlled. 20 Consistent with their labeling in the Plan, Appendix C.1, Table 147, these rationales appear under the heading of “Comments.” Finally, regarding the cooperative nature of the CAA, we note that the EPA worked extensively with ADEQ during SIP development. EPA and ADEQ staff met on a monthly basis beginning in 2019 and continuing through 2021 to discuss the development of the Plan. The EPA also provided informal written feedback on various elements of the Plan between 2019 and 2022. In these communications, the EPA identified many of the flaws that are the basis for the partial disapproval, so ADEQ was aware of the EPA's concerns prior to the EPA's proposal. In conclusion, based on the findings discussed in our proposal and elsewhere in this document, we find that the long-term strategy in the 2022 Arizona Regional Haze Plan does not meet the requirements of 51.308(f)(2) and we are disapproving the Plan with respect to this requirement. Therefore, pursuant to CAA section 110(c), the EPA will be required to develop a new long-term strategy as part of a FIP, unless the EPA approves a subsequent SIP submission that fully meets these requirements. That long-term strategy would necessarily include updated source selection, four factor analyses, and control determinations that address the deficiencies we identified in the Plan. We are available to work with ADEQ following this final action to develop a SIP revision, including these elements. Comment A.2. Tri-State asserted that additional emissions reductions are “inappropriate” for Springerville Generating Station (SGS) Unit 3. Tri-State made a few arguments in support of this contention. First, Tri-State noted that ADEQ evaluated the currently installed NO X emissions controls against technically feasible emissions controls and concluded that the current NO X emissions controls constitutes best available control technology (BACT) for coal-fired electric generating units (EGUs). For SO 2 , Tri-State indicated that ADEQ's analysis for SGS Unit 3 clearly demonstrates that Unit 3's emissions ranged from 0.069 to 0.090 lb/MMBtu on an annual basis and has continuously complied with the Mercury and Air Toxics Standard (MATS) SO 2 emissions standard of 0.20 lb/MMBtu, and therefore does not warrant further emissions controls. Tri-State also noted language in the EPA's “Guidance on Regional Haze State Implementation Plans for the Second Implementation Period” (“2019 Guidance”) 21 that describes scenarios in which the EPA believes it may be reasonable for a state not to select a particular source for further analysis for EGUs that have add-on flue gas desulfurization (FGD) and that meets the applicable alternative SO 2 emissions limit of the MATS rule for power plants. 21 Guidance on Regional Haze State Implementation Plans for the Second Implementation Period. https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period. The EPA Office of Air Quality Planning and Standards, Research Triangle Park (August 20, 2019). Second, Tri-State noted the visibility improvement at the Mount Baldy Wilderness Area in the first planning period, and that Arizona will have four additional 10-year planning periods to achieve the 1.3 deciview improvement needed to achieve natural conditions. Finally, Tri-State stated that its intent is to retire SGS Unit 3 by September 15, 2031, and requested that the EPA include in the final rule a provision to allow sources to work with their state regulatory agencies to adopt an enforceable commitment to retire a unit, such as through a permit condition, to allow the source to forego any further emissions control or reduction requirements if a unit is retiring within ten years of the Regional Haze SIP approval. Response A.2. We partially agree with this comment. First, with respect to NO X emissions at SGS Unit 3, ADEQ noted in the Plan “[t]he current controls ([low-NO X burners (LNB), overfire air (OFA) with selective catalytic reduction (SCR)] represent the most effective NO X control technologies for coal fired EGUs and are estimated to achieve 85-95% removal efficiency.” 22 We agree that the existing LNB, OFA and SCR constitute effective controls for NO X at SGS Unit 3. As described in our proposal and in response B.1 of this document, existing effective controls are generally necessary to make reasonable progress and must be included in the SIP, unless the state provides a weight-of-evidence demonstration to justify that the existing effective controls are not necessary to make reasonable progress. Because the Arizona SIP does not include a NO X emissions limit corresponding to these controls for SGS Unit 3, the State should have provided such demonstration. Specifically, the State should have considered whether SGS Unit 3 is subject to an enforceable NO X emissions limit that ensures its NO X emissions rate will not increase. Without proper justification that emissions of visibility impairing pollutants will not increase, it is unclear how reasonable progress is being made within the State's long-term strategy for the second planning period. 23 22 2022 Arizona Regional Haze Plan, p. 219. 23 See CAA 169A(a)(1) “Congress hereby declares as a national goal the prevention of any future, and the remedying of any existing, impairment of visibility in [Class I areas.]” (emphasis added). Similarly, with respect to SO 2 emissions at SGS Unit 3, we agree that, as described in the 2019 Guidance, an add-on FGD meeting the appliable alternative SO 2 emissions standard under MATS may constitute an effective control for SO 2 . However, as noted in the previous paragraph, existing effective controls are generally necessary to make reasonable progress and must be included in the SIP, unless the state provides a weight-of-evidence demonstration to justify that the existing effective controls are not necessary to make reasonable progress. Because the Arizona SIP does not include a SO 2 emissions limit corresponding to the existing SO 2 controls at SGS Unit 3, the State should have provided such a demonstration, including consideration of whether SGS Unit 3 is subject to an enforceable SO 2 emissions limit that ensures its SO 2 emissions rate will not increase. Second, regarding the Mount Baldy Wilderness Area, although we commend the efforts in Arizona that contributed to the noted visibility improvement at the Mount Baldy Wilderness Area in the first planning period, previous and ongoing measures are not automatically sufficient to ensure ongoing reasonable progress. The regional haze requirements of CAA sections 169A and 169B and 40 CFR 51.308 need to be satisfied. 24 In particular, the increment of progress that is “reasonable progress” for a given implementation period is determined through the four statutory factors. 25 While progress made in the first implementation period, ongoing emissions trends, and anticipated changes in emissions may inform a state's regional haze planning process, these circumstances alone do not satisfy a state's obligation to determine and include in its SIP the measures that are necessary to make reasonable progress in the second planning period. We also note that, while Mount Baldy is the closest Class I area to SGS and therefore has the highest Q/d (emissions in tons per year divided by distance to an affected Class I area in kilometers) value (339) with respect to SGS, 26 this does not mean that Mount Baldy is the only Class I area affected by emissions from SGS. ADEQ did not specifically identify all the Class I areas that may be affected by emissions from each of the sources it evaluated. Nonetheless, given that SGS had a 2018 Q of 17,044 tons per year (tpy) 27 and is located within 300 km of 15 different Class I areas, 28 it is likely to contribute to visibility impairment at a number of Class I areas. 24 See 64 FR 35714 (July 1, 1999), 35721-35722 for additional explanation as to the EPA's determination that emissions from all States reasonably contribute to visibility impairment and thus are subject to the regional haze regulations. Additionally, in the 2017 RHR, the EPA “reiterat[ed] that the CAA requires States to consider the four statutory factors . . . in each implementation period to determine the rate of progress towards natural visibility conditions that is reasonable for each Class I area.” 82 FR 3078 (January 10, 2017), 3080. 25 40 CFR 51.308(f)(2)(i). 26 Plan Appendix C, p. 21, Table 1. Q is calculated as the total 2018 annual facility-wide NO X , SO 2 , and PM 10 emissions in tpy, excluding processes determined by ADEQ to be effectively controlled. 27 Id. 28 79 FR 9318, 9360, Table 50 (February 18, 2014). Finally, with respect to Tri-State's request regarding enforceable shutdowns, we note that the EPA's role in acting on SIP submittals is to evaluate whether they meet applicable CAA requirement, not to establish new requirements. Tri-State may choose to work with ADEQ to establish enforceable shutdowns as part of a subsequent SIP revision. However, we note that even if there were an enforceable shutdown in 2031, this would not automatically preclude the unit from consideration under a four-factor analysis. 29 29 See 2019 Guidance, pp. 20-21 (“It may be more challenging for a state to reasonably use a shorter remaining useful life as the basis for not selecting sources the further away the enforceable shutdown date gets from 2028”). Comment A.3. Tri-State comments that it was unreasonable for the EPA to use the July 8, 2021 “Clarifications Regarding Regional Haze State Implementation Plans for the Second Implementation Period” (“2021 Clarifications Memo”) as a basis for disapproval of the 2022 Arizona Regional Haze Plan. Tri-State indicated that although ADEQ submitted its plan over a year late on August 22, 2022, ADEQ was over three years into the process of developing the plan, working with the Western Regional Air Partnership, the EPA, other states, Federal Land Managers (FLMs) and members of the public, was nearly complete and ready to go through the Arizona rulemaking process when the EPA published the 2021 Clarifications Memo. Tri-State also noted that the rulemaking process can take over a year due to various tasks required. Response A.3. The EPA disagrees that it used the 2021 Clarifications Memo as a basis for disapproving portions of the 2022 Arizona Regional Haze Plan. Contrary to the commenter's suggestion, the EPA's guidance, including the 2021 Clarifications Memo, is not the basis for our disapproval. Rather, the partial disapproval is based on the Plan's failure to satisfy the requirements of the relevant portions of the RHR and CAA sections 169A and 169B. We did cite the guidance documents because these documents provide helpful context explaining the EPA's interpretations of the applicable statutory and regulatory requirements against which we are required to evaluate SIP submittals. Commenters are free to disagree and raise concerns with those interpretations as part of the notice and comment process on individual SIP actions. However, in this instance, the commenter does not appear to object to any of the interpretations in the 2021 Clarifications Memo, only to the fact that they were provided shortly before the due date for the plans. With regard to timing, we note that the 2021 Clarifications Memo was developed in response to issues that EPA regions and other stakeholders had raised regarding draft regional haze SIP revisions that were already under development by states. 30 The 2021 Clarifications Memo therefore necessarily came during the SIP development process and, in comparison to the SIP-specific feedback previously provided by the EPA prior to its issuance, was intended to “offer feedback more broadly to help support SIP development, submittal, review, and action for the second planning period.” 31 With regard to Arizona's Plan specifically, throughout the EPA's collaboration with ADEQ during early engagement, EPA staff advised ADEQ of many of the interpretations that would be expressed in the 2021 Clarifications Memo. Therefore, we do not agree that it was improper for the EPA to cite to the 2021 Clarifications Memo as further explanation for why portions of the 2022 Arizona Regional Haze Plan did not comply with the applicable statutory and regulatory requirements. 30 2021 Clarifications Memo, p. 1. 31 Id. B. Comment Letter From ADEQ Sections I (“Background”) and XI (“Conclusion”) of ADEQ's comment letter are informational and therefore do not require a response. We respond to sections II-X of ADEQ's comment letter below. Comment B.1. ADEQ asserts that the EPA's changing guidance increased the burden of ADEQ's planning efforts by introducing uncertainty and rework. ADEQ noted delays between final publication of the 2017 RHR and the 2019 Guidance, as well as later changes to the EPA's interpretation of the RHR that came close to the plan submittal deadline, including the 2021 Clarifications Memo. ADEQ asserts that the state did not have the resources to undertake the evaluation of existing control measures, as noted in the 2021 Clarifications Memo, a process that ADEQ states was unreasonably broad-reaching and duplicative. Response B.1. We disagree with ADEQ's assertions about the EPA's additional guidance increasing the burden of ADEQ's planning efforts by introducing uncertainty and rework. First and foremost, as stated previously and throughout this notice, the EPA did not rely on guidance as the basis for its partial disapprovals. Rather, the 2019 Guidance and the 2021 Clarifications Memo merely provide additional context to the EPA's interpretations of the statutory and regulatory requirements. Both the 2019 Guidance and the 2021 Clarifications Memo were drafted to be used as tools by States in the development of their second planning period regional haze plans. However, neither of these documents were necessary for States to develop and submit their SIP revisions. Regarding the contents of the guidance, we do not agree that the EPA significantly changed its interpretations in either the 2019 Guidance or the 2021 Clarifications Memo. The commenter has not provided any examples of interpretations that it believes were changed under the 2019 Guidance and provided only a single example from the 2021 Clarifications Memo, relating to the section entitled, “Determining When Existing Measures are Necessary for Reasonable Progress.” We do not agree that interpretations set forth in this section of the 2021 Clarifications Memo represented a significant change in interpretation. Rather, they were intended to clarify the following statement in the 2019 Guidance: If a state determines that an in-place emission control at a source is a measure that is necessary to make reasonable progress and there is not already an enforceable emission limit corresponding to that control in the SIP, the state is required to adopt emission limits based on those controls as part of its long-term strategy in the SIP via the regional haze second planning period plan submission. 32 32 2019 Guidance, p. 423. Many states and other stakeholders raised questions about this statement. In response, as part of the 2021 Clarifications Memo, the EPA laid out in further detail our interpretation of the CAA and RHR regarding how to make such a determination. We also disagree, on multiple grounds, with the commenter's assertion that the “EPA's revised guidance requires an unreasonably broad-reaching review of all existing control measures that are not separately included in the regional haze plan to evaluate whether those same measures should be duplicated in the regional plan to support reasonable visibility progress.” First, the 2021 Clarifications Memo did not establish any new requirements. On the contrary, it clearly states that “[t]his memorandum does not change or substitute for provisions or requirements of the CAA or RHR, nor does it create any new requirements. Rather, this memorandum clarifies and provides further information on the existing statutory and regulatory requirements.” 33 One of the key requirements of the CAA and RHR is that all measures that are necessary to make reasonable progress must be included the SIP. 34 However, neither the CAA, the RHR, or the 2019 Guidance explain how to determine whether an existing measure that results from a four-factor analysis (or is used as the basis to avoid such an analysis) is necessary to make reasonable progress. Based on questions received on this subject during SIP development, it was clear that further guidance on this question would be helpful. Accordingly, the EPA provided this guidance in the 2021 Clarifications Memo. 35 33 2021 Clarifications Memo, p. 2. 34 CAA 169A(b)(2); 40 CFR 51.308(f)(2). 35 2021 Clarifications Memo, pp. 8-9. Regarding “existing measures,” the Memo explains: When the outcome of a four-factor analysis is that no new measures are reasonable for a source, the source's existing measures are generally needed to prevent future visibility impairment ( i.e., to prevent future emission increases) and thus necessary to make reasonable progress. Measures that are necessary to make reasonable progress must be included in the SIP. However, there may be circumstances in which a source's existing measures are not necessary to make reasonable progress. Specifically, if a state can demonstrate that a source will continue to implement its existing measures and will not increase its emission rate, it may not be necessary to require those measures under the regional haze program in order to prevent future emission increases. Similarly, with regard to existing “effective controls” used to screen out sources from a four-factor analysis: A decision to forgo a full four-factor analysis based on a source's existing effective controls is equivalent to a determination that no new measures are necessary to make reasonable progress. In this scenario, existing effective controls are, therefore, generally necessary to make reasonable progress and thus must be adopted into the regulatory portion of the SIP. However, the state may provide a weight-of-evidence demonstration as described in Section 4.1 to justify that the existing effective control is not necessary for reasonable progress. Thus, the 2021 Clarifications Memo clarifies that, under the CAA and the RHR, there is a general presumption that existing measures resulting from a four-factor analysis (or relied upon to avoid such an analysis) are necessary to prevent future visibility impairment and therefore necessary to make reasonable progress. Accordingly, states have the option to submit all such measures into the SIP (to the extent they are not already approved into the SIP) without further evaluation of whether the measures are necessary to make reasonable progress. Alternatively, states may choose to provide a weight-of-evidence demonstration that such measures are not necessary to make reasonable progress. Importantly, however, such a demonstration is needed only where an enforceable emissions limitation corresponding to an existing measure has not already been approved into the SIP and is not being submitted for SIP approval as part of the regional haze plan. Therefore, we do not agree that a review of “all existing control measures that are not separately included in the regional haze plan” is required. Third, to the extent that a state chooses to undertake such a demonstration that existing measures are not necessary to make reasonable progress, we do not agree that it would be duplicative. On the contrary, because such a demonstration is necessary only for measures for which emissions limitations are not submitted into the SIP, the state and the EPA need to evaluate relevant evidence concerning whether the source will continue to implement its existing measures and maintain its emissions rate in the absence of SIP-approved requirements to do so, to ensure that visibility impairment does not increase. In sum, we disagree with ADEQ's characterization of the contents of the 2021 Clarifications Memo and its role in our partial approval and partial disapproval of the Plan. Comment B.2. ADEQ comments that the EPA should not issue binding decisions based on guidance alone where the bases for disapproval are not in the rule or statute. ADEQ cites to statements in the 2019 Guidance and 2021 Clarifications Memo regarding screening out of effectively controlled sources and determinations of whether existing controls are necessary to make reasonable progress, as the examples of guidance. Specifically, ADEQ asserts that “[i]t was unreasonable for the EPA's clarification memo to issue these additional specific barriers to a determination that existing measures were effective at a given source late in the development of second round regional haze plans through guidance, and without additional notice and comment.” Response B.2. We disagree that we issued our proposed decision based on guidance. Rather, the proposal action clearly indicates that the partial disapproval was based on failing to satisfy the requirements of the relevant portions of the RHR and CAA sections 169A and 169B, with citations to our guidance as further explanation. See Response A.3 for more explanation. We also note that ADEQ's comment appears to conflate two separate questions: first, whether its justification for screening out a unit based on existing effective emissions controls was sufficient, and second, whether such existing effective control measures are necessary to make reasonable progress. In our proposal, we discussed each of these issues as two separate grounds for our proposed partial disapproval with respect to 40 CFR 51.308(f)(2). 36 While both questions apply to sources that are screened out from a four-factor analysis based on existing effective controls, they are distinct. The first issue is further addressed in Response B.3 of this document, while the second is addressed in Response B.1. Therefore, we do not agree that the 2021 Clarifications Memo created any additional barriers to a determination that existing measures were effective at a given source. 36 See 89 FR 47398, 47428 (“ADEQ did not provide an adequate justification for screening out certain sources and units from conducting a four-factor analysis on the basis that they are “effectively controlled” as part of its source selection process”) and 47431 (“ADEQ has not addressed whether any of the existing measures relied upon in its four-factor analyses or its `effective controls' determinations are necessary to make reasonable progress and thus should be a part of the State's long-term strategy for the second planning period.”). Comment B.3. ADEQ disagreed with the EPA's proposed determination that Arizona failed to provide adequate justification for deferring certain emissions units from consideration. ADEQ indicated that the state has the flexibility to reasonably select a set of sources for an analysis of control measures, and that it did not exclude entire facilities from consideration or exempt sources that had previously adopted BART or reasonable progress controls, but rather excluded just the emissions processes or units that recently installed highly effective controls from the calculation of the Q/d value for that facility. ADEQ also provided additional information regarding effective controls in Attachment A of its letter. Response B.3. We agree that states have flexibility to reasonably select a set of sources for analysis of controls measures. However, as described in our proposal, we find that ADEQ's approach to screening out units from conducting a four-factor analysis on the basis that they are “effectively controlled” was not adequately documented. 37 Specifically, in some cases, ADEQ did not identify the controls for each pollutant at each unit or process, the associated limits, or where the controls and/or limits currently exist in the Arizona SIP. In other cases, ADEQ listed the controls, but did not clearly explain why it is reasonable to assume, without conducting a four-factor analysis, that no additional controls would be reasonable. 38 Accordingly, ADEQ should have identified where the existing limits are found in the SIP or FIP and clearly explained why no additional controls would likely be reasonable under a four-factor reasonable progress analysis for the second planning period. Without this analysis and explanation, it is not clear what is a part of Arizona's long-term strategy for the second planning period. 37 89 FR 47398, 47428. 38 See 40 CFR 51.308(f)(2)(i) (“. . . The State must include in its implementation plan a description of the criteria is used to determine which sources or groups of sources it evaluated and how the four factors were taken into consideration in selecting the measures for inclusion in its long-term strategy”). See also 2021 Clarifications Memo, p. 5; 2019 Guidance, p. 23. As noted in its comment, ADEQ conducted its effective controls screening on a unit-specific basis. However, it did not do so on a pollutant-specific basis. Rather, ADEQ screened out entire units from further evaluation for NO X , SO 2 , or PM 10 if the units met ADEQ's screening criteria for any one of these pollutants. We find that this approach was unreasonable because it resulted in the screening out of entire units without consideration of whether the unit had effective controls for all three of the pollutants covered in ADEQ's long-term strategy. For example, ADEQ screened out AEPCO Apache Unit 3 and TEP Irvington Generating Station (IGS) Unit 4 from any further analysis because these units were converted from coal to natural gas under better-than-BART alternatives during the first planning period. 39 The EPA acknowledges that fuel combustion units that are required to combust pipeline-quality natural gas are generally considered to be effectively controlled for SO 2 and PM. 40 However, they are not necessarily effectively controlled for NO X , based on burning natural gas alone. Therefore, we find that ADEQ has not provided adequate justification for screening these units out from an analysis of NO X controls. 39 2022 Arizona Regional Haze Plan, Appendix C, Table 147. 40 See 2019 Guidance, p. 24. Additionally, we appreciate the documentation in Attachment A that ADEQ provided in its attachment letter. However, this information would need to be part of a SIP revision subject to review by the public and FLMs in order for the EPA to consider it as part of the long-term strategy. If ADEQ develops a new SIP revision intended to remedy the deficiencies discussed in our proposed and final actions on the Plan, it may be appropriate to include this information in that SIP revision. Comment B.4. ADEQ asserts that, despite indicating that flawed emissions rates were used for some of ADEQ's analyses, the proposed action identified one example of differing achievable emissions rates for selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) controls for SGS Units 1 and 2's four factor analyses. In this example, ADEQ used 0.060 lb/MMBtu and 0.15 lb/MMBtu as reasonable estimates of the achievable rates at TEP SGS Units 1 and 2 for SCR and SNCR, respectively. For SCR, ADEQ additionally states the study that the EPA cited for its justification that SCR has been demonstrated to achieve 0.05 lb/MMBtu (or up to 90 percent reduction) was published in 2005 and found that the 20 SCR systems examined in 2003 achieved NO X emissions rates between 0.04 and 0.07 lb/MMBtu. 41 In addition, ADEQ noted that EPA found 0.065 lb/MMBtu as a “reasonable estimate of average SCR performance” in its 2016 Regional Haze FIP action for the Salt River Project Coronado Generating Station Unit 1. 41 Ravi K. Srivastava, Robert E. Hall, Sikander Khan, Kevin Culligan & Bruce W. Lani (2005) Nitrogen Oxides Emission Control Options for Coal-Fired Electric Utility Boilers, Journal of the Air & Waste Management Association, 55:9, 1367-1388, DOI: 10.1080/10473289.2005.10464736. Available at: https://doi.org/10.1080/10473289.2005.10464736. For SNCR, ADEQ additionally states that the EPA did not provide a technical citation for disagreeing with ADEQ's use of 0.15 lb/MMBtu for SNCR. ADEQ noted that the proposed rule indicated that ADEQ did not demonstrate why source specific conditions would cause SNCR on these units to achieve as little as a 15 percent reduction. ADEQ noted that Srivastava et al. found that while smaller boilers ( e.g., 76-78 MW units) were able to achieve greater than 60 percent NO X reductions, larger boilers ( e.g., 500 MW units) “may be capable of achieving reductions of only ~30%.” ADEQ indicates that SGS Units 1 and 2 units have nameplate ratings of 425 MW and would be expected to achieve less reductions than smaller units. ADEQ also points to the inlet concentration as another consideration for achievable emissions rates with post combustion emissions control. Citing Srivastava et al., ADEQ notes that the study found that “in the absence of reliable SCR inlet NO X data, the SCR efficiencies are estimated using an inlet NO X level of 0.5 lb/10 6 Btu.” However, in the case of SGS Units 1 and 2, the NO X concentration in the exhaust from these units is less than 100 parts per million by volume (ppmv) with an assumed rate of 0.174 lb/MMBtu and 0.178 lb/MMBtu being used in ADEQ's four factor analysis cost calculations for Unit 1 and Unit 2, respectively. Given the already low NO X inlet concentration, an achievable emissions rate of 0.15 lb/MMBtu was determined to be reasonable. ADEQ further noted that additional information related to achievable emissions rates for SNCR for SGS Unit 1 and Unit 2 can be found in Appendix K, Section II(J), Comment 10 of the 2022 Arizona Regional Haze Plan. Response B.4. We acknowledge that we only highlighted a single example of flawed emissions rates in our proposal—for NO X at SGS Units 1 and 2. However, as explained in response A.1, in evaluating whether a SIP revision (or a portion thereof) meets each of these CAA requirements, the EPA is not required to separately evaluate and discuss each of the thousands of pieces of information, analyses and determinations comprising the SIP submission. Rather, the EPA may focus on those specific elements of the SIP revision that form the basis for our determination that certain applicable requirements are met and certain applicable requirements are not met. In this instance, we focused on these units because they are expected to have the highest NO X emissions of any units in the State (2,099 and 2,283 tpy respectively) by 2028, so it is important to carefully examine whether additional NO X reductions from these units are necessary to make reasonable progress. Given this context, and for the reasons outlined below, we do not agree with ADEQ that it has adequately documented the emissions rates assumed in this analysis, which are a critical component of a four-factor analysis. The emissions rate achievable by a unit equipped with SCR is determined by several parameters and technological limitations. There are periods of operation in which the SCR is not able to operate, particularly during periods of startup and shutdown. 42 The SCR emissions rate (lb/MMBtu) achievable by a particular unit represents the combination of two primary elements: (1) the controlled NO X emissions rate during periods of normal unit operation when the SCR is able to operate, and (2) the uncontrolled NO X emissions rate during periods of startup and shutdown when the SCR system cannot operate, and result in unit emissions higher than the SCR controlled emissions rate that increase the unit's overall emissions rate. 42 Control Cost Manual, Section 4, Chapter 2 Selective Catalytic Reduction (June 2019), section, 2.2.1 Reduction Chemistry, Reagents, and Catalyst, available at https://www.epa.gov/sites/default/files/2017-12/documents/scrcostmanualchapter7thedition_2016revisions2017.pdf. With regard to the first element, the 2005 study is not the sole basis for our finding that an overall emissions rate of 0.050 lb/MMBtu is achievable with SCR on an annual average basis. There are multiple instances of coal-fired units installing SCR on a retrofit basis and achieving 0.050 lb/MMBtu in practice on an annual average basis. 43 These units are typically able to achieve this overall level of control by being able to operate at NO X annual emissions rates at or below 0.050 lb/MMBtu based upon periods of normal operation. Even several of the units identified by ADEQ operating in the annual average emissions rate range of 0.055 to 0.065 lb/MMBtu are still achieving emissions rates of 0.050 lb/MMBtu and lower based upon periods of normal operation. 44 We consider this information sufficient to establish that an 0.050 lb/MMBtu emissions rate warrants consideration as technically feasible for coal fired units generally during periods of normal operation, absent source specific factors affecting feasibility. We are not aware of assertions by either ADEQ or TEP that the Springerville units specifically cannot achieve 0.050 lb/MMBtu when operating with SCR during periods of normal operation. 45 Therefore, we find that ADEQ should have considered a controlled NO X emissions rate of 0.050 lb/MMBtu for SGS Units 1 and 2 when operating with SCR during periods of normal operation. 43 See Docket Item F-16 “SCR Tangentially fired Coal.xlsx.” 44 Id. 45 TEP has indicated that vendors have been unwilling to provide manufacturer guarantees of 0.050 lb/MMBtu over the lifetime of the SCR system. Because manufacturer guarantees include contractual and financial considerations beyond technical performance of the SCR system, we do not consider an inability to secure a manufacturer guarantee to constitute a determination that an emission rate of 0.050 lb/MMBtu is not technically feasible, particularly with regard to periods of normal operation. The majority of analysis performed by ADEQ is relevant to the second element and is intended to support a position that, when the annual emissions rate achievable during normal operations is combined with emissions from the number of startup/shutdown cycles exhibited by SGS Units 1 and 2, an annual average emissions rate of 0.06 lb/MMBtu is what is reasonably achievable for these units. We consider it appropriate to account for the effect of startup/shutdown emissions on the emissions rate achievable by the unit, but disagree that the analysis provided by ADEQ supports an annual average emissions rate of 0.060 lb/MMBtu. TEP's four factor analysis and ADEQ's SIP submittal did not include startup/shutdown history to support the assertion that Springerville has more startup/shutdown events than comparable tangentially-fired coal fired boilers. A review of Clean Air Markets Program Data (CAMPD) emissions and operating data over a 2021-2023 timeframe indicate that SGS Units 1 and 2 each experienced approximately 9 to 14 startup events per year. While we acknowledge that some portion of SGS baseline emissions consist of startup/shutdown emissions that cannot be controlled by an SCR system, the substantial majority of baseline emissions are attributable to emissions during normal operation. We estimate that approximately 97-98% of baseline emissions are attributable to normal operations that could be controlled by SCR. 46 Given that the majority of unit emissions can be controlled by SCR to 0.050 lb/MMBtu or lower and that the remaining 2-3 percent of operations are characterized by low inlet SCR emissions rates, we do not consider the historical startup/shutdown operating profile to support deviating to an 0.06 lb/MMBtu emissions rate on an annual average basis. 46 See Docket Item F-17 [SGS CAMPD 2021-23.xlsx]. To illustrate SCR control potential during periods of normal operation, this spreadsheet is based on the key assumption that emissions from any day a unit did not operate a full 24 hours would be attributable to startup/shutdown periods. An hourly analysis would provide a more refined and precise assessment, though we consider this assumption to overestimate the emissions attributable to startup/shutdown by including all emissions from partial operating days towards startup/shutdown. ADEQ cites a limit of 0.065 lb/MMBtu established for SRP Coronado Unit 1 in a 2016 Regional Haze FIP action as support for the use of an annual average emissions rate of 0.060 lb/MMBtu. We wish to clarify that the 0.065 lb/MMBtu value was not the annual average emissions rate used in cost calculations, but was the emissions limit established on a rolling 30-boiler operating day (BOD) average, for Coronado Unit 1. We relied upon an 0.050 lb/MMBtu annual average emissions rate in developing cost calculations for SCR, 47 which is consistent with our action here. In establishing a rolling 30-BOD limit for Coronado Unit 1 in that action, we acknowledged that upward revisions to the SCR design rate achievable on an annual average basis would be appropriate in order to accommodate the effect that multiple startup/shutdown events would have to overall unit emissions rates on an averaging period that could be as short as 30 days. Based upon startup/shutdown frequency and projected controlled emissions rate information provided by SRP, we finalized 0.065 lb/MMBtu as an appropriate emissions limit and reasonable estimate of SCR performance over a short-term period. 48 Given that the 0.065 lb/MMBtu limit reference here corresponds to a different, shorter averaging period, and was itself based on an 0.05 lb/MMBtu annual average emissions rate, we do not consider it supportive of an 0.060 lb/MMBtu annual average emissions rate. 47 See Docket Item EPA-R09-OAR-2012-0021-0204 for cost calculation details. More information related to establishing a 30 BOD limit relative to an annual emissions rate can be found in our March 31, 2015 (80 FR 17010) proposed reconsideration, including Docket Items EPA-R09-OAR-2015-0165-0029 through -0033 for further details. We note that SRP identified an SCR design target during periods of normal operation as low as 0.03 lb/MMBtu for Coronado Unit 1, though we acknowledge there are source specific differences with the SGS units. 48 It is unclear to what extent a comparable 30-BOD limit may be appropriate for the SGS units, but we note that the SGS units appear to have historically had at least as many startup/shutdown events as Coronado Unit 1. For SNCR, we appreciate the additional analysis provided in the comment and citation to Appendix K summarizing ADEQ's responses to public comments. We acknowledge that low inlet NO X concentrations are a general consideration in evaluating NO X controls that can negatively impact control efficiencies and achievable controlled emissions rates. Therefore, in order to further evaluate whether a rate lower than 0.15 lb/MMBtu may be achievable with SNCR at SGS Units 1 and 2 on an annual basis, we examined CAMPD emissions data over a 2019-2023 time period for SNCR-equipped units comparable to SGS Units 1 and 2, specifically filtering for tangentially-fired coal units operating with SNCR on a retrofit basis. 49 We identified four currently operating SNCR-equipped units achieving NO X emissions rates below 0.15 lb/MMBtu, ranging between 0.10 to 0.12 lb/MMBtu. 50 These values represent the highest performing SNCR-equipped units, with the next best performing units operating at emissions rates of 0.15 lb/MMBtu and higher. At least one of the four units we identified has the capability to use natural gas, which could have the effect of lowering emissions rates relative to units that do not have this capability, such as SGS Units 1 and 2. 51 Based on the three remaining units, each unit had relatively low pre-SNCR emissions rates that are comparable to SGS Unit 1 and 2, and each unit is able to achieve SNCR emissions rates below 0.15 lb/MMBtu and control efficiencies better than 15 percent. Neither ADEQ or TEP has provided documentation to support a claim that SGS Units 1 and 2 specifically cannot achieve an annual emissions rate lower than 0.15 lb/MMBtu with SNCR. Therefore, we find that ADEQ should have considered a NO X emissions rate of lower than 0.15 lb/MMBtu for SNCR at SGS Units 1 and 2. 49 See Docket Item F-21, “SNCR Tangential Coal Units.xlsx.” 50 See Docket Item F-21. These units include Boswell Energy Center (MN) Unit 4, Will County (IL) Unit 4, and Jeffrey Energy Center (KS) Units 2 and 3. 51 Based on reported natural gas fuel usage, the Boswell Energy Center appears to use natural gas primarily as a startup fuel, but does periodically use quantities of natural gas that suggest co-firing with coal for electricity generation purposes. We also note that this was one of multiple flaws that formed the basis of our determination that the State's long-term strategy did not satisfy the requirements of 40 CFR 51.308(f)(2), including reasons related to source selection and control determinations, as detailed in our proposal and elsewhere in this document. Therefore, even assuming that a control efficiency of 15 percent for SNCR at SGS Units 1 and 2 was reasonable, it would not have changed our determination that the 2022 Arizona Regional Haze Plan did not satisfy the requirements of 40 CFR 51.308(f)(2). Comment B.5. ADEQ disagrees with the EPA's determination that Arizona deviated from the Control Cost Manual without documentation as part of its four factor analyses with regards to remaining useful life calculations for the El Paso Natural Gas (EPNG) Williams facility and the use of source specific interest rates without providing adequate documentation in the control measure analyses for the EPNG Williams and Willcox facilities. ADEQ indicates that the EPA Control Cost Manual Section 4, Chapter 2, states that “. . . a representative value of the equipment life for SCR at power plants can be considered as 30 years . . . [f]or other sources, the equipment life can be between 20 and 30 years.” ADEQ noted that while it erroneously omitted this citation from the EPNG Williams Turbine analysis, the Control Cost Manual citation and justification for use of 25 years is the midpoint between the 20-30 year range for non-EGU SCR systems and was included in the EPNG Willcox SCR analysis for Turbines 1 and 2. 52 ADEQ also noted that it received cost calculation spreadsheets utilizing a 25-year useful life for SCR for the EPNG Williams Turbine 1 from the US Forest Service. 53 52 2022 Arizona Regional Haze Plan, Appendix C, Section C3.8.5.2, Page 146. 53 2022 Arizona Regional Haze Plan, Appendix L, Section 4.2.4, Comment 14. ADEQ also explains that in its analysis of remaining useful life for compressor engines at the EPNG Williams facility, ADEQ documented the assumptions and basis for using 20 years to amortize NO X controls in Appendix C, Section C3.7.6.5, which includes citations to the Control Cost Manual and the EPA's 2016 technical support document for the Cross State Air Pollution Rule for the 2008 Ozone NAAQS. Response B.5. We appreciate the clarification regarding ADEQ's reasoning for use of a 25-year remaining useful life for the EPNG Williams turbines and 20 years for the EPNG Williams engines. While there are instances of combustion turbines with operating lifetimes beyond 25 years (with or without retrofit controls), we acknowledge that EPA guidance such as the Control Cost Manual has not recommended a value beyond the 20-30 year range. ADEQ's use of a 25-year useful life represents the midpoint of Control Cost Manual recommendations, and therefore we agree that it is consistent with the Control Cost Manual. However, we note that the lack of documentation of remaining useful life for the units at Williams Compressor Station was one of the many flaws that we identified in the state's long-term strategy including reasons related to source selection and control determinations, as detailed in our proposal and elsewhere in this document. Therefore, this clarification does not change our determination that the 2022 Arizona Regional Haze Plan did not satisfy the requirements of 40 CFR 51.308(f)(2). Comment B.6. ADEQ disagrees with the EPA's determination that ADEQ did not reasonably weigh the statutory factors in reaching its control determinations with regards to application of cost thresholds. ADEQ disagrees that Arizona's consideration of incremental cost effectiveness in its four factor analyses were done in an unreasonable manner. ADEQ cites to its explanation that the incremental cost of requiring low-emission combustion 2 (LEC 2) as opposed to Air-Fuel ratio adjustments is $5,034/ton, which ADEQ considered reasonable, and therefore ADEQ found that LEC 2 is a more appropriate control for Williams Reciprocating Engine 1 (RECIP-1). 54 54 2022 Arizona Regional Haze Plan, Appendix C, Section C3.7.6.2, page 129. ADEQ also asserts that it also analyzed other determinations from the regional haze first implementation period besides the incremental cost effectiveness value for the Nelson Lime Plant action, and ADEQ provides this information in Table 1 of its comment letter. Response B.6. We appreciate ADEQ's explanation about LEC 2 on RECIP-1, but we note that ADEQ also rejected LEC 3 on Williams RECIP-1, on the grounds that the incremental costs of these controls, relative to less stringent controls, were excessive. In addition, ADEQ did not provide or consider incremental cost effectiveness values for the same controls for the other units at the same source (RECIP-2 or RECIP-5). Although states may choose to consider incremental costs in a reasonable manner, 55 we find it was unreasonable for ADEQ to do so only for specific units and controls, rather than in a consistent manner across all units and controls. Such inconsistent treatment of sources without explanation is the “the hallmark of arbitrary action.” 56 55 See, e.g., 2019 Guidance, p. 40. 56 Nat'l Parks Conservation Ass'n v. EPA, 788 F.3d 1134, 1145 (9th Cir. 2015). We also appreciate the addition of Table 1 identifying other first implementation period incremental cost effectiveness decisions. However, this information was not included in the Plan and therefore not subject to review by the public or FLMs. Accordingly, it cannot be relied upon to meet the requirement of 40 CFR 51.308(f)(2)(iii) for States to document the technical basis for their long-term strategy. Moreover, even if the information had been included in the Plan, it would not have justified ADEQ's inconsistent consideration of incremental cost effectiveness, for the reasons described in our proposal and the preceding paragraph. Comment B.7. ADEQ states that, contrary to the EPA's contention, ADEQ did not rely upon visibility benefits for its control determinations, but rather visibility impacts were reported for some sources to give reference to the reader as to the relative impact of these sources or controls on visibility. ADEQ also asserts that nothing in the CAA, RHR, or 2019 Guidance prevents the department from considering visibility benefits as part of its analysis and stated that “the ADEQ's labeling of the visibility benefits associated with specific control scenarios as `small' comports with similar language used by the EPA in their regional haze actions.” 57 57 Citing e.g., “relatively small visibility benefits” in 79 FR 52419, 52439 (September 3, 2014). Response B.7. We agree with ADEQ that in its Response to Comments, ADEQ stated that “[v]isibility impacts were reported for some sources to give reference to the reader as to the relative impact of these sources or controls considered on visibility. However, this information was not considered in the Department's emissions control measure determinations.” 58 However, this assertion is contradicted by the language of some of the control determinations in the Plan. For example, in the NO X four-factor analysis for SGS, ADEQ stated that: 58 Id., Appendix K, p. 9. ADEQ does find visibility impacts a useful consideration given the goal of the regional haze program is to improve visibility in Class I areas. As such, ADEQ reports modeled visibility impacts in this documentation. The small modeled visibility benefits associated with the modeled hypothetical NO X emission reduction supports the determination that no additional NO X controls are necessary to make reasonable progress towards natural visibility at Class I areas during this implementation period. 59 59 Plan, Appendix C, p. 221 (emphases added). Similar language appears following the SO 2 four factor analysis for SGS 60 and in the summary of ADEQ's NO X reasonable progress determination for IGS Unit 3. 61 This language indicates that ADEQ did consider visibility for these units, and specifically, that it weighed the “small modeled benefits” of controls in determining that no additional NO X controls were warranted at SGS Units 1 and 2 and IGS Unit 3, and no more stringent SO 2 controls were warranted at SGS Units 1 and 2. 60 Id. at 234 (“The small visibility benefits associated with the modeled SO 2 controls supports the determination that CDS and wet FGD control options are not necessary to make reasonable progress towards natural visibility at Class I areas during this implementation period.”). 61 Id. at 197 (“The small modeled visibility benefits associated with additional controls support the determination that no additional controls are necessary to make reasonable progress towards natural visibility at Class I areas during this implementation period.”). While states have the option to consider visibility benefits, along with the four statutory factors, in making control determinations, if they choose to do so, they must do so “in a reasonable way that does not undermine or nullify the role of the four statutory factors in determining what controls are necessary to make reasonable progress.” 62 In this case, we find it was not reasonable for ADEQ to consider visibility benefits only for specific sources and without any explanation of what would constitute a significant visibility benefit. 62 2021 Clarifications Memo, p. 12 (quoting Response to Comments on Protection of Visibility: Amendments to Requirements for State Plans; Proposed Rule at 186). In the action cited by ADEQ where the EPA considered “relatively small visibility benefits,” 63 we were comparing the relatively small benefits of a control at one source to the relatively larger visibility benefits expected to result from controls at other sources. 64 In contrast, in the 2022 Arizona Regional Haze Plan, ADEQ did not find any visibility benefits at any source to be anything other than small. Thus, as explained in our proposal regarding SGS Units 1 and 2, “[i]n the absence of any opportunities for larger emissions reductions and corresponding visibility benefits, we find that ADEQ's reliance on `small' visibility benefits as an additional justification for not adopting more stringent controls at these units is not persuasive.” 65 63 79 FR 52420, 52439. 64 See, e.g., id. at 52442 (referring to “large visibility benefits) and 52458 (“we consider this visibility benefit sufficient to support installation of controls.”). 65 89 FR 47398, 47430. Finally, we note that, even assuming that ADEQ did not consider visibility benefits as part of its control determinations for SGS Units 1 and 2, we would still conclude that the determinations were flawed for other reasons. In particular, for NO X , ADEQ did not adequately justify the control efficiency used for SCR and SNCR, as discussed in the proposal and response B.4. 66 For SO 2 , ADEQ unreasonably rejected wet FGD on the basis of incremental cost, and set mass-based caps that will not ensure implementation of the emissions reduction measures that are necessary to make reasonable progress at these units, as discussed in the proposal and response B.8. Furthermore, the lack of clarity in the Plan regarding whether or not ADEQ considered visibility benefits in making its control determinations for SGS Units 3 and 4 and IGS Unit 3, indicates a lack of reasoned decision making that also supports our disapproval of the Plan's long-term strategy. 66 89 FR 47398, 47428 (May 31, 2024). Comment B.8. ADEQ disagrees with the EPA's determination that ADEQ did not reasonably weigh the statutory factors in reaching its control determinations with regards to three issues noted in the proposed rule concerning the mass-based emissions caps at SGS and IGS. First, ADEQ asserts that the EPA's rationale is arbitrary and capricious in regard to the rejection of wet FGD for SGS Units 1 and 2. ADEQ states that the use of emissions limits in lieu of codifying specific control technologies is a flexibility that the EPA itself used in its reasonable progress determination for Phoenix Cement Clarkdale (PCC). 67 ADEQ asserts that the EPA established an emissions limit for PCC that did not require the installation of a particular control technology but rather compliance through other means of meeting the limit. 67 79 FR 52420, 52460. Second, regarding the EPA's contention that spray dry absorber (SDA) upgrades may still be cost effective after the establishment of the mass-based emissions caps, ADEQ comments that this manner of analysis is not contemplated in the four-factor analysis as outlined in the RHR or the 2019 Guidance. ADEQ asserts that the EPA has never applied this standard whereby after the establishment of an emissions limit based on the reductions achievable from a considered control technology that a State must revisit and update the baseline emissions of its four-factor analysis to reflect the new emissions limit. ADEQ claims that for its analysis of SGS, ADEQ did not select a control scenario in its four-factor analysis that included the imposition of both emissions limits and the installation of SDA upgrades, and therefore, the EPA should not substitute its judgment for ADEQ's selection of SDA upgrades as the evaluated control measure for SGS Units 1 and 2 or reject ADEQ's determination based on an arbitrary and circular four factor analysis standard. Third, ADEQ further disagrees with the EPA's assertion that the mass-based emissions caps at SGS and IGS would not meaningfully constrain the emissions from one unit during periods when the other unit is not operating and argues that the rationale is arbitrary and capricious. ADEQ notes that the EPA referenced TEP's 2023 Integrated Resources Plan (IRP) and highlighted TEP's plans to retire SGS Unit 1 in 2027, but states that as the operating scenarios outlined in the IRP are not federally enforceable conditions, ADEQ has no basis for the consideration of these future scenarios as part of its control measure analysis and the establishment of the mass-based emissions limits. ADEQ states that the EPA should not rely upon unenforceable and hypothetical operating scenarios to reject ADEQ's reasonable progress determinations. Lastly, ADEQ disagrees with the EPA's rationale that IGS Unit 3's mass- based emissions limits are not yet enforceable and therefore are not an appropriate basis for modifying the baseline control scenario for a four-factor analysis. ADEQ cites that for the EPA's BART determination for Arizona Public Service (APS) Cholla generating station, the EPA accepted a source specific permit revision for APS Cholla Unit 2 that included a trigger that was conditional on the EPA's approval of the SIP revision that altered the remaining useful life of the unit in ADEQ's four factor analysis. 68 Therefore, ADEQ concludes that the EPA should approve ADEQ's reasonable progress determination for IGS Unit 3. 68 81 FR 46852, 46860 (July 19, 2016). Response B.8. We disagree with ADEQ's comments arguing that the EPA's justification for disapproving the reasonable progress determinations for SGS and IGS as it relates to the mass-based emissions caps at SGS and IGS was improper. First, we wish to clarify that we do not object to the use of numeric emissions limitations as a means to implement control determinations. Indeed, CAA section 169A(b)(2) specifically requires the long-term strategy to include “enforceable emissions limitations, compliance schedules, and other measures that are necessary to make reasonable progress.” As explained in our proposal: The amount of progress that is “reasonable progress” is based on applying the four statutory factors in CAA section 169A(g)(1) in an evaluation of potential control options for sources of visibility impairing pollutants, which is referred to as a “four-factor” analysis. The outcome of that analysis is the emissions reduction measures that a particular source or group of sources needs to implement to make reasonable progress towards the national visibility goal. . . . Such measures must be represented by “enforceable emissions limitations, compliance schedules, and other measures” ( i.e., any additional compliance tools) in a state's long-term strategy in its SIP. 69 69 89 FR 47398, 47402-47403. We find that the mass-based emissions caps set for SGS do not represent the emissions reduction measures that were the outcome of the state's four-factor analysis for the reasons described in our proposal 70 and herein. Therefore, these caps do not meet the requirements of 169A(b)(2) and (g)(1), or the corresponding provisions of the RHR. 70 89 FR 47398, 47430. Regarding PCC, we agree that in the EPA's reasonable progress determination for PCC in the first implementation period, the EPA established a mass-based emissions limitation for NO X . However, the circumstances between PCC and SGS Units 1 and 2 differ in important ways. The limit for PCC was set pursuant to 40 CFR 51.308(d)(3), which required the long-term strategy for the first implementation period to “include enforceable emissions limitations, compliance schedules, and other measures as necessary to achieve the reasonable progress goals established by States having mandatory Class I Federal areas.” 71 In this instance, the Class I areas primarily affected by emissions from PCC were in Arizona, 72 and the emissions reductions from PCC were reflected in the applicable RPGs for these areas by scaling of visibility extinction components in proportion to changes in total annual emissions. 73 Under these circumstances, an annual mass-based emissions limit corresponding to the level of annual emissions reductions assumed in the RPG calculations was sufficient to meet the applicable requirement for an emissions limit “as necessary to achieve” the relevant RPGs. 71 40 CFR 51.308(d)(3) (emphasis added). 72 See 79 FR 9318, 9354 Table 41 (showing impacts on Arizona I class I areas). 73 79 FR 52420, 52468-52469; FIP_RPG_estimates.xlsx. In contrast, for the second planning period, the EPA clarified in 40 CFR 51.308(f)(2) that “the long-term strategy must include the enforceable emissions limitations, compliance schedules, and other measures that are necessary to make reasonable progress, as determined pursuant to (f)(2)(i) through (iv).” 40 CFR 51.308(f)(i) in turn requires the state to “evaluate and determine the emission reduction measures that are necessary to make reasonable progress by considering” the four statutory factors. Thus, the revised rule clarifies that the long-term strategy must include emissions limitations, compliance schedules, and other measures representing the emissions reduction measures that the state determined to be necessary to make reasonable progress, considering the four statutory factors. The EPA provided recommendations on the appropriate form of such emissions limitations and other measures in the 2019 Guidance and the Clarifications Memo. Specifically, the 2019 Guidance recommends the use of throughput-based limits, rather than mass-based limits ( i.e., “caps”) for emissions limitations to implement measures necessary for reasonable progress in most instances. 74 The Guidance notes that mass-based limits are allowed under the RHR, but explains that, “[i]f the state has determined, independent of the forecasted operating level, that operation of the emission control equipment . . . is necessary to make reasonable progress, a mass-based emission limit may not be appropriate.” 75 The Clarifications Memo also reaffirms that “whether for new or existing measures . . . an emission limit . . . should be in the form of the emission rate achieved when implementing those measures ( e.g., pounds per million British thermal units or lbs/MMBtu, pounds per hour or lbs/hr, or pounds per ton or lbs/ton of produced material).” 76 74 2019 Guidance p. 44. 75 Id. pp. 44-45. 76 2021 Clarifications Memo, p. 11. With regard to SGS 1 and 2, ADEQ concluded, based on a four-factor analysis that, “it is reasonable to require TEP to upgrade the current SDA systems” 77 and did not indicate that this determination was conditioned on a particular level of operation. Therefore, ADEQ should have set limits in the form of the emissions rates achieved when implementing SDA upgrades, e.g., lb/MMBtu limits, or should have provided a rationale for why the mass-based limits, which could be met without any control upgrades, nonetheless represent SDA upgrades. 77 Plan Appendix C, p. 232. We also note that the mass-based limit at PCC was for a single unit, meaning that it necessarily constrained the emissions from that unit on an annual basis. In contrast, the mass-based limit at SGS Units 1 and 2 were set across two units. Accordingly, if one unit ceases to operate, the limits would not meaningfully constrain emissions from the other unit. In addition, ADEQ rejected more stringent controls at SGS Units 1 and 2 based on its “determination that another viable reasonable control exists to reduce SO 2 emissions from Units 1 & 2 (upgraded SDA).” In contrast, the EPA did not reject any more stringent controls for PCC based on incremental cost effectiveness. Furthermore, the cap at PCC was intended, in part, to address concerns raised during consultation with the facility's owner, the Salt River Pima Maricopa Indian Community (SRPMIC). 78 No similar considerations exist with respect to SGS Units 1 and 2. Therefore, we find that the circumstances concerning the PCC mass-based cap are distinguishable from those concerning SGS Units 1 and 2. 78 79 FR 9318, 9366 (“An annual cap would allow SRPMIC to delay installation of controls until the Plant's production returns to pre-recession levels and would thus help to address the Community's concerns about the budgetary impacts of control requirements.”) Second, regarding our finding that SDA upgrades would be cost effective after the establishment of the mass-based emissions caps, we disagree that we substituted our judgment for ADEQ's by arbitrarily rejecting ADEQ's determination based on a circular four-factor analysis standard. Contrary to ADEQ's suggestion, we did not state that ADEQ was required to revisit and update the baseline emissions of its four-factor analysis to reflect the new emissions limitation. However, we note that ADEQ did use this approach for IGS Unit 3 and determined that with the emissions reductions associated with the new Unit 3 emissions caps, no additional controls are necessary to make reasonable progress. ADEQ did not provide any rationale for why it used this approach for IGS Unit 3, but not for SGS Units 1 and 2. Furthermore, the fact that the SDA upgrades would still be cost effective following implementation of the mass-based caps at SGS Units 1 and 2 is relevant to whether the use of caps (in lieu of throughput-based limits) is reasonable and appropriate in this particular case. The fact that throughput-based ( e.g., lb/MMBtu) limits equivalent to SDA would still be cost-effective following implementation of the caps ( i.e., if TEP complies with the caps by lowering its operating level) indicates that throughput limits based on the emissions rates achievable with SDA upgrades may be necessary to make reasonable progress, regardless of the future operating level. As previously noted, the 2019 Guidance explains that, under such circumstances, mass-based caps are generally not appropriate. Therefore, we believe this consideration is relevant to the evaluation of whether mass-based caps were reasonable and consistent with the requirements of the RHR in this case. Third, we agree with ADEQ's statement that the operating scenarios outlined in the IRP are not federally enforceable conditions. However, ADEQ's statement in its comment letter that it has “no basis for the consideration of these future scenarios as part of its control measure analysis and the establishment of the mass-based emission limits” is inconsistent with its stated rationale in the Plan for establishing caps instead of mass-based limits. Specifically, ADEQ stated that: As discussed in TEP's 2020 IRP, Units 1 will transition to seasonal operation in 2023 and Unit 2 in 2024. TEP is planning to retire Unit 1 in 2027 and Unit 2 in 2032. TEP will be very likely to manage its operating level strategically instead of completing the upgrades to the SDA systems for meeting the RP requirements. Therefore, ADEQ determines that a mass-based emission limit is reasonable. 79 79 2022 Arizona Regional Haze Plan, Appendix C, p. 236. In other words, ADEQ elected to establish caps specifically because it anticipated that TEP could comply with these caps by reducing its operating level consistent with its then-current IRP. Therefore, we do not agree that it was inappropriate for the EPA to consider information contained in TEP's most recent (2023) IRP in evaluating whether the mass-based caps were reasonable and consistent with the RHR. Lastly, we agree that for APS Cholla Unit 2, the EPA accepted a source-specific permit revision that included a trigger that was conditional on the EPA's approval of the SIP revision that altered the remaining useful life of the unit in ADEQ's four factor analysis. However, the APS Cholla scenario was distinguishable because, as explained in the proposed rule, 80 the SIP revision for APS Cholla replaced the FIP that was applicable to these units. 81 Therefore, it would not have been reasonable to subject them to two inconsistent requirements, one State and one Federal, under the RHR at the same time. Thus, under these circumstances it was appropriate for ADEQ to make the effectiveness of the permit conditions contingent on EPA SIP approval. In the current case, there is no existing FIP in place applicable to IGS Unit 3, so no similar rationale exists for making the cap contingent upon approval by the EPA. 80 89 FR 47398, 47407, Table 1. 81 77 FR 72511 (December 5, 2012). Comment B.9. ADEQ asserts that the EPA should approve ADEQ's reasonable progress goal (RPG) for the Sycamore Canyon Wilderness Area. The state indicates that it provided the required “robust demonstration” by including a detailed analysis of visibility data at the Sycamore site to demonstrate that its slower rate of progress results from significant increases in light extinction from coarse mass. Response B.9. As ADEQ notes in its comment, its analysis regarding Sycamore Canyon focused on the substantial increase in coarse mass and soil impairment at the Sycamore Canyon site. However, as explained in our proposal, the rule requires a state with a Class I area whose RPG is above the glidepath to demonstrate, based on the source selection and four factor analyses required under 40 CFR 51.308(f)(2)(i), that there are no additional emissions reduction measures for sources that may reasonably be anticipated to contribute to visibility impairment in the Class I area that would be reasonable to include in the long-term strategy. 82 Although ADEQ provided a detailed analysis of monitoring data concerning Sycamore Canyon, it did not provide “a robust demonstration, including documenting the criteria used to determine which sources or groups or sources were evaluated and how the four factors required by paragraph (f)(2)(i) were taken into consideration in selecting the measures for inclusion in its long-term strategy.” 83 Instead, it relied solely on monitoring data and the source selection and four-factor analyses contained elsewhere in the Plan. 84 For the reasons described in our proposal and elsewhere in this document, we find that these analyses were inadequate to meet the requirements of 40 CFR 51.308(f)(2). Therefore, the Plan also did not meet the requirements of 40 CFR 51.308(f)(3)(ii)(A) with respect to Sycamore Canyon. 82 89 FR 47398, 47433. 83 40 CFR 51.308(f)(ii)(A). 84 See Plan p. 106, footnote 112 (citing Plan Section 8 and Appendix C). Comment B.10. ADEQ indicates that the State intends to coordinate with EPNG to provide supporting documentation for the interest rate. ADEQ indicates that it intends to provide the interest rate documentation as confidential business information (CBI) to the EPA for review prior to publication of the final rule and requests that the EPA approve the cost calculation for EPNG Willcox and Williams based on the site-specific interest rate and supporting documentation. Response B.10. Although ADEQ referenced the existence of documentation and the possibility of sharing it with the EPA in its response to comments in the Plan, 85 no supporting documentation for the interest rate was submitted as part of the Plan or prior to the close the public comment period on the EPA's proposed partial approval and partial disapproval. Therefore, the EPA is unable consider the interest rate information as part of this action. 85 2022 Arizona Regional Haze Plan, Appendix K. Additionally, we note that the lack of documentation of EPNG's firm-specific interest rate was one of several flaws that we identified in the state's long-term strategy. Therefore, even if the appropriate documentation had been submitted and within the proper time frame, that alone would not have changed our determination that the 2022 Arizona Regional Haze Plan did not satisfy the long-term strategy requirements of 40 CFR 51.308(f)(2). Comment B.11. ADEQ voiced procedural concerns with the lack of specificity in the EPA's proposed disapproval of the 2022 Arizona Regional Haze Plan. ADEQ cites CAA 307(d)(3) as requiring a detailed notice of rulemaking and cites Small Ref. Lead Phase-Down Task Force v. EPA, 705 F.2d 506, 518-19 (D.C. Cir. 1983), for the proposition that the notice provided in the proposal may be too general to be adequate and that “[a]gency notice must describe the range of alternatives being considered with reasonable specificity.” The commenter asserts that the EPA's proposed rule does not provide “detailed notice” of certain specific issues that form the basis for disapproval of entire sections of the 2022 Arizona Regional Haze Plan, denying ADEQ the opportunity to specifically address those bases for disapproval during the comment period. Response B.11. We disagree that the EPA's proposal provided inadequate notice. The EPA's action on the 2022 Arizona Regional Haze Plan is not subject to the requirements of CAA section 307(d). Those requirements apply only to specific enumerated types of actions under the CAA and to “such other actions as the Administrator may determine.” 86 Actions on SIPs are not one of the enumerated actions, and the Administrator had not determined that this action is subject to 307(d) pursuant to Section 307(d)(1)(V). Therefore, this action is subject to the procedural requirements of the Administrative Procedure Act (APA). 86 CAA Section 307(d)(1). Accordingly, pursuant to 5 U.S.C. 553(b)(2) and (3), the EPA's notice of proposed rulemaking regarding the Plan was required to include “reference to the legal authority under which the rule is proposed” and “either the terms or substance of the proposed rule or a description of the subjects and issues involved.” The proposal clearly met these requirements, as it stated the applicable legal authorities and provided the EPA's review of the Plan in relation to those requirements. The comment provides no basis to conclude that the proposal failed to meet these requirements. Indeed, the opinion cited by the commenter contrasts these more general APA requirements to the more exacting requirements of CAA section 307(d) concerning the contents of proposed rulemaking. 87 While we agree with the commenter that “[a]gency notice must describe the range of alternatives being considered with reasonable specificity,” 88 we find that our proposal met this requirement, as it plainly stated that the EPA was considering partially approving and partially disapproving the 2022 Arizona Regional Haze Plan and detailed the reason for this proposed action. Please also see Responses A.1. 87 Small Ref. Lead Phase-Down Task Force v. EPA, 705 F.2d 506, 518-19 (D.C. Cir. 1983), 88 Id. at 549. Comment B.12. ADEQ acknowledges that further FLM consultation is required for a plan revision that will correct the deficiencies identified in the proposed rulemaking action, but contends that the inclusion of the nonpoint source selection analysis and selected controls for nonpoint sources in the FLM review draft of the plan provided FLMs adequate notice and review of Arizona's nonpoint source rules that were codified after plan submission and submitted in the 2023 Arizona Regional Haze Rules Supplement. 89 89 ADEQ SIP Revision: Nonpoint Rules to Supplement Arizona's 2022 Regional Haze SIP, “2023 Arizona Regional Haze Rule Supplement,” August 22, 2023. Response B.12. The EPA disagrees with ADEQ's contention that it provided the FLMs with adequate notice and review of Arizona's nonpoint source rules. The information about FLM consultation regarding the rules specifically is not detailed in either the 2023 Arizona Regional Haze Rules Supplement, or the 2022 Arizona Regional Haze Plan. The 2023 Arizona Regional Haze Rules Supplement indicated that further information on how this SIP revision complied with 40 CFR 51.308(i) requirements for federal land manager consultation is section 2.4 of the 2022 Arizona Regional Haze Plan. 90 However, section 2.4 of the plan only describes the FLM review of the 2022 Arizona Regional Haze Plan, and does not specify if ADEQ provided a draft of the three nonpoint source rules to the FLMs for review. The rules were not included in the 2022 Arizona Regional Haze Plan. Should Arizona choose to submit a SIP revision, clarification of the FLM review process of the nonpoint source rules that are listed in Table 1-1 of the 2023 Arizona Regional Haze Rules Supplement would be helpful for EPA review. 90 Id, at Chapter 4. C. Comment Letter From the Chamber and AMC Parts I (“The Chamber and AMC are supportive of the goals of the Regional Haze Rule”) and III (“Conclusion”) of the Chamber and AMC's comment letter are informational and therefore do not require a response. We respond to part II, sections A-E of the Chamber and AMC's comment letter below. Comment C.1. The Chamber and AMC note that the EPA's delayed action and partial disapproval of Arizona's Regional Haze Plan is an example of erosion of cooperative federalism. The commenter contends that the timeline of events leading up to the EPA's partial disapproval of Arizona's Regional Haze Plan is problematic and that the EPA seems to routinely miss statutory deadlines, only to get sued by third-party entities for failure to act, resulting in agreements to deadline extensions that delay action for years. In the meantime, the resources and analysis invested by states depreciate in value, often requiring states to reinvest in efforts to update an analysis with new information. The commenter also asserted that “[r]egularly, an even worse scenario plays out in which EPA denies a SIP because the information submitted in good faith by a state has since become dated and stale.” Response C.1. We do not agree that either the timing or substance of the EPA's partial disapproval of Arizona's Regional Haze Plan is an example of the erosion of cooperative federalism. We acknowledge that the EPA did not act on the 2022 Arizona Regional Haze Plan within the statutory deadline under CAA section 110(k)(3), and that we were subsequently sued for failing to meet that deadline. This resulted in a court-ordered deadline for the EPA to take action on the Plan by March 30, 2025. 91 However, we do not agree that this resulted in a “deadline extension” of any sort, or an erosion of cooperative federalism. On the contrary, in issuing a partial approval and partial disapproval of the Plan, the EPA is fulfilling our statutorily-mandated role to review SIPs for compliance with the requirements of the CAA and the RHR, as further described in Response D.3. 91 Sierra Club v. EPA (D.D.C. Case No. 1:23-cv-01744-JDB), Consent Decree entered July 12, 2024. We also disagree with the suggestion that the EPA is disapproving the 2022 Arizona Regional Haze Plan, partially or entirely because information became “dated or stale.” The comment did not provide examples of information becoming dated, resulting in disapproval; thus, we cannot comment on any specific concerns the commenter has with the information within the 2022 Arizona Regional Haze Plan. Further, as explained in Responses A.1 EPA staff also discussed with ADEQ many of the concerns that became bases for our disapproval during the SIP development process. Comment C.2. The Chamber and AMC state that guidance should not be cited as grounds to disapprove the 2022 Arizona Regional Haze Plan. The commenter asserts that guidance should be viewed only as a reference and not a legal requirement to be used to approve or disapprove a state's plan. The Chamber and AMC also claim that the EPA published final guidance for Regional Haze Plans three weeks before the plans were due, making compliance with the guidance practically impossible before the deadline. The commenter concludes that relying on the guidance to partially disapprove the Plan was therefore arbitrary and capricious, and the EPA should withdraw all of the proposed disapprovals based upon the 2021 Clarifications Memo. Response C.2. The EPA disagrees that it relied on guidance, including the 2021 Clarifications Memo, as the basis for our partial disapproval. See responses A.5, B.1, and B.2. Comment C.3. The Chamber and AMC assert that Arizona's source selection methodology was reasonable and that the EPA should give deference to the State on this matter. The commenter indicates that sources that applied controls in the first round of Regional Haze had recently made significant investments in the design, engineering, procurement, construction and operation of those air pollution control devices. They note that forcing facilities to consider improvement or replacement of these air pollution control devices long before they have depreciated is an unnecessary economic burden for the source and the State. The Chamber and AMC note that ADEQ chose not to force additional analysis from these sources and reasonably relied upon reductions from other emissions sources for visibility improvement, a method that resulted in all but one of Arizona's Class I areas either meeting or exceeding the uniform rate of progress (URP) toward natural conditions. Response C.3. We disagree that it was reasonable for Arizona to screen out sources solely because they applied controls during the first planning period, for the reasons described in section IV.E.2.a. of our proposal and in response B.3 of this document. We also disagree that our disapproval will automatically force sources to consider improving or replacing any recently installed air pollution devices. Rather, ADEQ has the option to provide additional documentation and justification for its effective control determinations in a responsive SIP revision. We anticipate that for many units that recently installed controls, ADEQ will be able to provide an adequate demonstration of effective controls on a unit-specific and pollutant-specific basis, if it chooses to do so, which would preclude the need for a four-factor analysis for those units and pollutants. Any affected units and pollutants for which ADEQ is unable to make such demonstration would be subject to the four-factor analysis requirement as required by 40 CFR 51.308(f)(2). Finally, we note that all states are subject to the requirements at 40 CFR 51.308(f)(2) and (3) regardless of whether the 2028 RPGs for Class I Areas they affect are above or below URP. Comment C.4. The Chamber and AMC assert that the EPA should give deference to Arizona's deviation from the EPA Control Cost Manual in developing cost estimates. The commenter notes that the Cost Control Manual is not accurate for all sources and cites examples such as variable interest and emissions rates. They conclude that the use of different interest rates and different control efficiencies for different projects should be viewed as reasonable. Response C.4. We do not agree that we should have deferred to Arizona's deviation from the EPA Control Cost Manual in the absence of adequate justification. As discussed in Response D.3, Congress charged the EPA with independently evaluating and reviewing SIP submissions for compliance with the applicable requirements under the CAA. 40 CFR 51.308(f)(2)(iii) requires states to “document the technical basis, including modeling, monitoring, cost, engineering, and emissions information, on which the State is relying to determine the emission reduction measures that are necessary to make reasonable progress in each mandatory Class I Federal area it affects.” The technical documentation must include the modeling, monitoring, cost, engineering, and emissions information on which the state relied to determine the measures necessary to make reasonable progress. For the reasons noted in section IV.E.2.b.ii (“Deviations from Cost Control Manual”) of our proposed rule, we found that Arizona failed to adequately document the technical basis that it relied upon to determine emissions reduction measures, as required by 40 CFR 51.308(f)(2)(iii). Specifically, as explained in our proposal, it is important to use consistent methods in order to allow for reasoned comparisons between different sources within a state, and cost analyses in other states. 92 Therefore, while our regulations allow for flexibility among various methodologies, where a state deviates from these methods, it should explain how its alternative approach is reasonable, appropriate, and consistent with the regulations and the statutory requirement to make reasonable progress towards the national goal. Arizona did not do so. We therefore disagree that the EPA should give deference to Arizona's approach in the Plan. 92 89 FR 47398, 47428-47429. Comment C.5. The Chamber and AMC indicate that Arizona's plan should be viewed in the context that it results in all but one monitor having an RPG that provides for a greater rate of visibility improvement than the adjusted URP. The commenter asserts that Arizona has created a plan that meets or exceeds the URP at all monitors except for Sycamore Canyon, which was moved to an intersection of two dirt roads in 2014. The commenter concludes that the fact that visibility at Arizona's Class I areas is improving at a pace to reach natural conditions prior to the RHR goal of 2064 is important context in evaluating the source selection methodology and other decisions made by Arizona. Response C.5. We do not agree with the commenter's characterization of the role of the URP. As explained in our proposal: The URP is a planning metric used to gauge the amount of progress made thus far and the amount left before reaching natural visibility conditions. However, the URP is not based on consideration of the four statutory factors and therefore cannot answer the question of whether the amount of progress being made in any particular implementation period is “reasonable progress.” 93 93 89 FR 47398, 47406. Moreover, being on or below the URP does not exempt a state from any of the requirements of the CAA or the Regional Haze Rule. 94 94 See 82 FR 3078,3093 and 3099-3100. It should also be noted that the URP represents the amount of visibility improvement that would need to be achieved during each implementation period to achieve natural visibility conditions by the end of 2064. However, the 2064 date is used solely to calculate the URP as a tracking metric. The CAA and RHR do not contain any end dates for the regional haze program and do not have a “goal” or requirement to achieve natural conditions by 2064 specifically. Please also see Response B.9 for more information on the robust demonstration required for Sycamore Canyon under 40 CFR 51.308(f)(3)(ii), which is missing from Arizona's submission. D. Comment Letter From TEP The “Background” section of TEP's comment letter is informational and therefore does not require a response. We respond to the “Comments of Proposed Disapproval” section of TEP's comment letter below. Comment D.1. TEP claims that ADEQ's source selection methodology was reasonable and the EPA should approve the determination. First, TEP cites to the 2019 Guidance and 2021 Clarifications Memo as providing states discretion for source selection and notes that ADEQ applied a Q/d screening threshold of 10 for each process at a source. TEP further describes ADEQ's screening out processes where the facility recently adopted “effective controls,” which the Agency defined as controls installed to meet the requirements of the PSD program (BACT), the first regional haze planning period (BART), or other NAAQS requirements. Second, TEP further suggests that the EPA is proposing to approve “many aspects of ADEQ's source selection process,” including ADEQ's choice of screening threshold and focus on NO X, SO 2 , and PM 10 in evaluating visibility impacts, but simultaneously proposing to find that the State did not adequately justify its determination of effective emissions reduction measures. Response D.1. First, we disagree with the commenter that ADEQ applied a Q/d screening threshold of 10 for each process at a source. As noted in the 2022 Arizona Regional Haze Plan, the Q value was calculated from facility-wide PM 10, NO X , and SO 2 annual emissions, not process-specific emissions. 95 95 2022 Arizona Regional Haze Plan, Appendix C2.2, p. 26. Second, we clarify that the EPA did not propose to approve “many aspects of ADEQ's source selection process.” We found that ADEQ reasonably and adequately explained and documented many aspects of its source selection process, such as its focus on sulfate, nitrate, and coarse mass and its use of a Q/d value of 10 for point sources. However, we are not separately approving or disapproving specific elements of ADEQ's long-term strategy, including any elements of the source-selection process. Rather, we are disapproving the long-term strategy as a whole under 40 CFR 51.308(f)(2), for the reasons described in our proposal and in this document. Comment D.2. TEP asserts that ADEQ reasonably evaluated existing controls at IGS Unit 4 and SGS Units 3 and 4. First, the commenter states that ADEQ did not determine that sources were effectively controlled based on BART controls alone, but also evaluated additional emissions reduction measures at several units that were controlled during the first regional haze planning period, citing Table 8-2 in the 2022 Arizona Regional Haze Plan. For IGS Unit 4 specifically, the commenter states that ADEQ evaluated existing emissions reduction measures at IGS Unit 4 from a source-specific perspective, and determined that further analysis would be futile. TEP cites to statements regarding post-combustion controls in the 2019 Guidance and states that, in a recent FIP action for Arizona, the EPA determined that eliminating coal combustion at Unit 4 would control emissions beyond the best available NO X and SO 2 controls. 96 TEP concludes that these emissions reduction measures remain the best available controls at this unit in the second planning period. TEP further notes that ADEQ's determination that IGS Unit 4 is well-controlled is also consistent with recent decreasing emissions trends across BART-eligible EGUs, including IGS Unit 4, and between 2014 and 2019. TEP points to the recent proposed rule for Georgia's Regional Haze SIP, 97 and comments that the EPA cited to similar visibility-impairing emissions trends as support for Georgia's source-selection methodology. Citing to the 2021 Clarifications Memo, 98 TEP also indicates that ADEQ was not required to consider emissions trends and that the State has discretion to emphasize other considerations, such as the EPA's prior FIP evaluation. 96 79 FR 52420, 52422. 97 89 FR 47481 (June 3, 2024). 98 Specifically, TEP quotes page 3 of the 2021 Clarifications Memo (“[t]he [Regional Haze Rule] does not explicitly list factors that states must or may not consider when selecting sources for analysis,”) and cites page 5 of the 2021 Clarifications Memo as supporting its assertion that “EPA has recommended that states consider projected and actual emissions in evaluating existing emission reduction measures.” Second, TEP states that the EPA's proposed disapproval fails to engage with ADEQ's analysis for SGS Unit 3 and 4. TEP notes that ADEQ considered potential additional control measures that could be used to achieve emissions reductions at SGS Units 3 and 4 based on an initial control analysis submitted by TEP. 99 In this analysis, TEP provided information on technically feasible control measures, as well as the actual and projected emissions rates at each unit. 99 TEP, Identification and Evaluation of Emission Control Measures for Units 3 and 4 at the Springerville Generating Station for Purposes of the Regional Haze Second Planning Period Under 40 CFR 51.308(f)(2) (Mar. 2020), available at https://static.azdeq.gov/aqd/haze/tep_spr_4fa_u34.pdf. Response D.2. We disagree that ADEQ's evaluations regarding effective controls at IGS Unit 4 and SGS Units 3 and 4 were reasonable and justified. Contrary to TEP's claim, ADEQ did not evaluate additional emissions reduction measures at several units that were controlled during the first regional haze planning period. Table 8-2 cited by TEP to support its claim that ADEQ evaluated additional emissions reduction measures at units that were controlled during the first regional haze planning period only depicts annual, source-level total emissions of NO X, SO 2 and PM 10 and does not include any information regarding unit-specific or pollutant specific emissions rates or controls. The commenter also provides no citation for its assertion that ADEQ evaluated existing emissions reduction measures at IGS Unit 4 from a source-specific perspective. Therefore, based on the contents of the 2022 Arizona Regional Haze Plan, it was reasonable for the EPA to determine that ADEQ did not evaluate additional emissions reduction measures at units that were controlled during the first regional haze planning period. Similarly, the commenter's citation to the discussion of post-combustion controls in the 2019 Guidance is misleading because no such controls were installed at IGS Unit 4. Rather, the unit was converted from coal to gas as part of a “better-than-BART” determination pursuant to 40 CFR 51.308(e)(2). 100 Therefore, the actual relevant effective controls discussion in the 2019 Guidance is the discussion of fuel combustion units that are required to burn pipeline quality natural gas. Such units are generally considered to be effectively controlled for SO 2 and PM. 101 However, they are not necessarily effectively controlled for NO X . Therefore, we disagree with the commenter that, given TEP's recent conversion of IGS Unit 4 from coal to natural gas, ADEQ's conclusion that further analysis was not required was reasonable. As stated in the proposed rule, 102 ADEQ should have explained why it is reasonable to assume, without conducting a four-factor analysis, that no additional NO X controls would be reasonable. 103 100 See 40 CFR 52.145(j)(4). 101 See 2019 Guidance, p. 24. 102 89 FR 47398, 47428. 103 See 40 CFR 51.308(f)(2)(i) (“. . .The State must include in its implementation plan a description of the criteria is used to determine which sources or groups of sources it evaluated and how the four factors were taken into consideration in selecting the measures for inclusion in its long-term strategy.”). See also 2021 Clarifications Memo, p. 5; 2019 Guidance, p. 23. The commenter's discussion of emissions trends is also misleading on several grounds. First, the commenter mischaracterizes the EPA's review of Georgia's regional haze source selection methodology. In the section of the Georgia proposal cited by TEP, the EPA considered trends in total measured visibility impairment at three Class I areas affected by Georgia's sources as supporting the reasonableness of the state's overall source selection methodology. 104 The EPA did not, however, consider trends in emissions from specific sources and did not indicate that such trends would be relevant either to the reasonableness of a state's overall source selection methodology or especially to the question of a whether a particular source may be screened out on the grounds that it is “effectively controlled.” Furthermore, the trends cited by the commenter were for multiple BART-eligible EGUs, not just IGS. Therefore, we do not agree that decreasing SO 2 and NO X emissions at BART-eligible EGUs in Arizona between 2014 and 2019 are relevant to whether IGS Unit 4 is effectively controlled. 104 89 FR 47481, 47497-47498. Second, the commenter mischaracterizes the contents of the 2021 Clarifications Memo as it relates to how to determine whether a source is effectively controlled. The first section cited by the commenter, regarding “Factors to Consider for Source Selection” 105 relates to a State's overall source selection methodology, which is generally considered to be the first step of determining what measures are necessary for reasonable progress. 106 Whether and how to screen out particular sources on the grounds that they are effectively controlled is a subsequent step. As previously noted, we found that many aspects of ADEQ's source selection process were reasonable and adequately explained and documented, 107 consistent with the statement in the Clarifications Memo that, “whatever choices states make should be reasonably explained and produce a reasonable outcome.” 108 However, once the sources were initially selected for evaluation of additional control measures, we found that ADEQ did not provide an adequate justification for subsequently screening out certain sources and units from ultimately conducting a four-factor analysis on the basis that they are effectively controlled. 105 2021 Clarifications Memo, p. 3. 106 Id. (“Source selection is a critical step in states' analytical processes. All subsequent determinations of what constitutes reasonable progress flow from states' initial decisions regarding the universe of pollutants and sources they will consider for the second planning period.”) 107 89 FR 47428. 108 2021 Clarifications Memo, p. 3. The second section of the 2021 Clarifications Memo mischaracterized by the commenter, “Sources that are Not Selected Based on Existing Effective Controls,” does address the screening out of particular sources on the grounds that they are effectively controlled. In particular, this section recommends that, “States should first assess whether the source in question already operates an `effective control' as described in the August 2019 Guidance. They should further consider information specific to the source, including recent actual and projected emission rates, to determine if the source could reasonably attain a lower rate.” 109 For the reasons detailed in our proposal and elsewhere in this document, we find that ADEQ did not reasonably explain and support its determination at the first step that IGS Unit 4 already operates effective controls, particularly for NO X . Moreover, even if IGS Unit 4 does have effective controls, ADEQ should have considered recent actual and projected emissions rates for this particular unit, not for all BART-eligible units as a group, in order to determine whether these controls are necessary to make reasonable progress. 109 Id., p. 5 (emphasis added). Finally, we disagree that our proposed disapproval fails to engage with ADEQ's analysis for SGS Unit 3 and 4. Contrary to the commenter's suggestion, ADEQ did not screen out SGS Units 3 and 4 at the source selection stage, 110 but instead conducted four-factor analyses for these units. 111 We summarized these analyses on pages 47422-47423 of our proposal. We did not note any particular flaws in these analyses or the resulting determinations that no additional controls were necessary to make reasonable progress in our proposal. However, we found that ADEQ had not addressed whether any of the existing measures relied upon in these four-factor analyses were necessary to make reasonable progress and thus should be a part of the State's long-term strategy for the second planning period. 112 We also noted that, as part of its analysis of whether these existing measures are necessary to make reasonable progress, the State should have considered whether the relevant sources are subject to enforceable emissions limits that ensure their emissions rates will not increase. Without this information, it is not clear what measures are in the State's long-term strategy for the second planning period and how controls on these units result in each of the affected Class I areas making reasonable progress towards the national goal. 110 2022 Arizona Regional Haze Plan, Appendix C, Exhibit CI. 111 Id., Chapter C3.13. 112 89 FR 47431. Comment D.3. TEP asserts that ADEQ reasonably evaluated additional control measures using a four-factor analysis for SGS Units 1 and 2. Citing Oklahoma v. EPA, 723 F.3d 1201, 1209 (10th Cir. 2013), the commenter asserts that while the statute identifies the factors that must be considered, Congress left to states the determination as to how these factors should be weighed. Response D.3. While we agree that states have significant discretion in how they consider and apply the four statutory factors as part of a Regional Haze SIP, they do not have unlimited discretion. On the contrary, the EPA has a crucial role in reviewing such SIP submissions for compliance with the requirements of the CAA and the RHR. Pursuant to CAA section 110, states must submit SIP revisions to the EPA for review and the EPA must evaluate whether each SIP submission meets all of the applicable requirements of the Act. 113 The EPA must disapprove any SIP revision that “would interfere with any applicable requirement” of the Act. 114 CAA section 110(a)(2)(J) specifically requires that SIPs “meet the applicable requirements” of Part C of Title I of the CAA including the requirements for visibility protection set forth in sections 169A and 169B. 115 Pursuant to section 169A(b), the EPA is required to promulgate visibility protection regulations that apply to “each applicable implementation plan” ( i.e., each SIP or FIP) 116 for each State containing one or more Class I areas and each State “emissions from which may reasonably be anticipated to cause or contribute to any impairment of visibility in any [Class I area].” The CAA specifies that these regulations (including the RHR) must require each such SIP or FIP to “contain such emission limits, schedules of compliance and other measures as may be necessary to make reasonable progress toward meeting the national goal.” 117 Thus, the statute provides the EPA a key oversight role in reviewing SIPs, including regional haze SIPs, and the “EPA has substantive authority to assure that a state's proposals comply with the Act, not simply the ministerial authority to assure that the state has made some determination.” 118 113 CAA section 110(a)(1), (k)(3), 42 U.S.C. 7410(a)(1) and (k)(3). 114 CAA section 110(l), 42 U.S.C. 7410(l). 115 CAA sections 110(a)(2)(J), 169A and 169B 42 U.S.C. 7410(a)(2)(J), 7491 and 7492. 116 Under the CAA, “applicable implementation plan” is defined as “the portion (or portions) of the implementation plan, or most recent revision thereof, which has been approved under [CAA section 110], or promulgated under [CAA section 110](c) . . . and which implements the relevant requirements of [the CAA].” CAA section 302(q), 42 U.S.C. 7602(q). In other words, an “applicable implementation plan” is an EPA-approved SIP or Tribal Implementation Plan, or an EPA-promulgated FIP. 117 42 U.S.C. 7491(b)(2). 118 Arizona ex. rel. Darwin v. EPA, 815 F.3d 519, 531 (9th Cir. 2016). Nothing in the Oklahoma case cited by the commenter undermines this authority. On the contrary, the Oklahoma court upheld the EPA's disapproval of BART determinations that were part of a regional haze SIP, noting BART “does not differ from other parts of the CAA—states have the ability to create SIPs, but they are subject to EPA review.” 119 Likewise, all regional haze SIPs are subject to EPA review, as described in the preceding paragraph. 119 Oklahoma v. EPA, 723 F.3d 1201, 1209 (10th Cir. 2013). In our action on the Plan, we are exercising our substantive authority to review the state's submittal for compliance with the applicable requirements of the CAA and RHR. Based on our review of the Plan, we find, among other things, that ADEQ had not reasonably evaluated and weighed the four statutory factors for SGS Units 1 and 2 for the reasons noted in section IV.E.2 of our proposal and responses B.4., B.6, B.7 and B.8 of this document. Comment D.4. TEP states that ADEQ's choice of cost-effectiveness threshold was reasonable, and that the EPA's proposed rule did not afford appropriate deference to ADEQ's assessment of reasonable cost-effectiveness values. TEP also cites a previous EPA action stating that “Congress did not provide any direction as to how states should consider `the costs of compliance' when determining reasonable progress.” 120 TEP also provides the following reasons for why it believes ADEQ's choice of cost-effectiveness threshold was reasonable. 120 81 FR 296, 310 (January 5, 2016). First, TEP states that ADEQ selected a threshold based on the State's evaluation of the highest cost controls during the first planning period. TEP notes that this threshold is nearly $1,000/ton higher than the 98th percentile value for EGU boilers during the first planning period and $1,500/ton higher than costs rejected by Georgia in evaluating additional emissions reduction measures in its SIP submission. 121 121 89 FR 47494. Second, TEP claims that ADEQ's bright-line approach to analyzing available controls above its cost-effectiveness threshold was also reasonable. TEP disagrees with the EPA's concern about the average cost of installing SNCR at SGS Unit 2 being $269/ton above ADEQ's $6,500/ton threshold. 122 TEP states that the 2019 Guidance emphasized that the RHR does not prevent states from implementing “bright line” cost-effectiveness thresholds when considering additional control measures, consistent with the Ninth Circuit's decision in NPCA v. EPA. 123 TEP asserts that this threshold sets an amount above which a state would reject control options as too expensive, and that for controls falling below this threshold, it is reasonable for ADEQ to evaluate additional factors, such as incremental costs, visibility impacts, and the other statutory factors, in determining whether these controls are necessary for reasonable progr [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2024-29508. Public record. Not legal advice.