# Air Plan Approval; Ohio; Regional Haze Plan for the Second Implementation Period > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2024-19189 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** August 30, 2024 - **Citation:** 89 FR 71124 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 52 [EPA-R05-OAR-2021-0544; FRL-12175-01-R5] Air Plan Approval; Ohio; Regional Haze Plan for the Second Implementation Period AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule. SUMMARY: The Environmental Protection Agency (EPA) is proposing to approve the Ohio regional haze state implementation plan (SIP) revision submitted by the Ohio Environmental Protection Agency (Ohio or Ohio EPA) on July 30, 2021, which Ohio EPA supplemented on August 6, 2024, as satisfying applicable requirements under the Clean Air Act (CAA) and EPA's Regional Haze Rule for the program's second implementation period. EPA proposes to find that Ohio's SIP submission addresses 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, and also addresses other applicable requirements for the second implementation period of the regional haze program. EPA is taking this action pursuant to sections 110 and 169A of the CAA. DATES: Written comments must be received on or before September 30, 2024. ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R05-OAR-2021-0544 at https://www.regulations.gov or via email to langman.michael@epa.gov. For comments submitted at Regulations.gov , follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from the docket. EPA may publish any comment received to its public docket. Do not submit to EPA's docket at https://www.regulations.gov any information you consider to be confidential business information (CBI), Proprietary Business Information (PBI), or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. EPA will generally not consider comments or comment contents located outside of the primary submission ( i.e., on the web, cloud, or other file sharing system). For additional submission methods, please contact the person identified in the FOR FURTHER INFORMATION CONTACT section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. FOR FURTHER INFORMATION CONTACT: Alisa Liu, Air and Radiation Division (AR-18J), Environmental Protection Agency, Region 5, 77 West Jackson Boulevard, Chicago, Illinois 60604, (312) 353-3193, liu.alisa@epa.gov. The EPA Region 5 office is open from 8:30 a.m. to 4:30 p.m., Monday through Friday. SUPPLEMENTARY INFORMATION: Throughout this document whenever “we,” “us,” or “our” is used, we mean EPA. Table of Contents I. What action is EPA proposing? II. Background and Requirements for Regional Haze Plans A. Regional Haze Background B. Roles of Agencies in Addressing Regional Haze III. Requirements for Regional Haze Plans for the Second Implementation Period A. Identification of Class I Areas B. Calculations of Baseline, Current, and Natural Visibility Conditions; Progress to Date; and the Uniform Rate of Progress C. Long-Term Strategy for Regional Haze D. Reasonable Progress Goals E. Monitoring Strategy and Other State Implementation Plan Requirements F. Requirements for Periodic Reports Describing Progress Towards the Reasonable Progress Goals G. Requirements for State and Federal Land Manager Coordination IV. EPA's Evaluation of Ohio's Regional Haze Submission for the Second Implementation Period A. Background on Ohio's First Implementation Period SIP Submission B. Ohio's Second Implementation Period SIP Submission and EPA's Evaluation C. Identification of Class I Areas D. Calculations of Baseline, Current, and Natural Visibility Conditions; Progress to Date; and the Uniform Rate of Progress E. Long-Term Strategy for Regional Haze 1. Selection of Sources for Analysis 2. Emission Measures Necessary To Make Reasonable Progress 3. Ohio's Long-Term Strategy 4. EPA's Evaluation of Ohio's Compliance With 40 CFR 51.308(f)(2)(i) 5. Consultation With States 6. Five Additional Factors F. Reasonable Progress Goals G. Monitoring Strategy and Other Implementation Plan Requirements H. Requirements for Periodic Reports Describing Progress Towards the Reasonable Progress Goals I. Requirements for State and Federal Land Manager Coordination V. Proposed Action VI. Statutory and Executive Order Reviews I. What action is EPA proposing? On July 30, 2021, Ohio EPA submitted a revision to its SIP to address regional haze for the second implementation period and supplemented it on August 6, 2024. Ohio EPA made this SIP submission to satisfy the requirements of the CAA's regional haze program pursuant to CAA sections 169A and 169B and 40 CFR 51.308. EPA proposes to find that the Ohio regional haze SIP submission for the second implementation period meets the applicable statutory and regulatory requirements and thus proposes to approve Ohio's submission into its SIP. II. Background and Requirements for Regional Haze Plans A. Regional Haze Background In the 1977 CAA Amendments, Congress created a program for protecting visibility in the nation's mandatory Class I Federal areas, which include certain national parks and wilderness areas. 1 CAA 169A. The CAA establishes as a national goal the “prevention of any future, and the remedying of any existing, impairment of visibility in mandatory class I Federal areas which impairment results from manmade air pollution.” CAA 169A(a)(1). The CAA further directs EPA to promulgate regulations to assure reasonable progress toward meeting this national goal. CAA 169A(a)(4). On December 2, 1980, EPA promulgated regulations to address visibility impairment in mandatory Class I Federal areas (hereinafter referred to as “Class I areas”) that is “reasonably attributable” to a single source or small group of sources. (45 FR 80084, December 2, 1980). These regulations, codified at 40 CFR 51.300 through 51.307, represented the first phase of EPA's efforts to address visibility impairment. In 1990, Congress added section 169B to the CAA to further address visibility impairment, specifically, impairment from regional haze. CAA 169B. EPA promulgated the Regional Haze Rule (RHR), codified at 40 CFR 51.308, 2 on July 1, 1999. (64 FR 35714, July 1, 1999). These regional haze regulations are a central component of EPA's comprehensive visibility protection program for Class I areas. 1 Areas statutorily designated as mandatory Class I Federal areas consist of national parks exceeding 6,000 acres, wilderness areas and national memorial parks exceeding 5,000 acres, and all international parks that were in existence on August 7, 1977. CAA 162(a). There are 156 mandatory Class I areas. The list of areas to which the requirements of the visibility protection program apply is in 40 CFR part 81, subpart D. 2 In addition to the generally applicable regional haze provisions at 40 CFR 51.308, EPA also promulgated regulations specific to addressing regional haze visibility impairment in Class I areas on the Colorado Plateau at 40 CFR 51.309. The latter regulations are applicable only for specific jurisdictions' regional haze plans submitted no later than December 17, 2007, and thus are not relevant here. Regional haze is visibility impairment that is produced by a multitude of anthropogenic sources and activities which are located across a broad geographic area and that emit pollutants that impair visibility. Visibility impairing pollutants include fine and coarse particulate matter (PM) ( e.g., sulfates, nitrates, organic carbon, elemental carbon, and soil dust) and their precursors ( e.g., sulfur dioxide (SO 2 ), nitrogen oxides (NO X ), and, in some cases, volatile organic compounds (VOC) and ammonia (NH 3 )). Fine particle precursors react in the atmosphere to form fine particulate matter (PM 2.5 ), which impairs visibility by scattering and absorbing light. Visibility impairment reduces the perception of clarity and color, as well as visible distance. 3 3 There are several ways to measure the amount of visibility impairment, i.e., haze. One such measurement is the deciview, which is the principal metric used by the RHR. Under many circumstances, a change in one deciview will be perceived by the human eye to be the same on both clear and hazy days. The deciview is unitless. It is proportional to the logarithm of the atmospheric extinction of light, which is the perceived dimming of light due to its being scattered and absorbed as it passes through the atmosphere. Atmospheric light extinction (b ext ) is a metric used to for expressing visibility and is measured in inverse megameters (Mm-1). EPA's Guidance on Regional Haze State Implementation Plans for the Second Implementation Period (“2019 Guidance”) offers the flexibility for the use of light extinction in certain cases. Light extinction can be simpler to use in calculations than deciview, since it is not a logarithmic function. See, e.g., 2019 Guidance at 16, 19, https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period, EPA Office of Air Quality Planning and Standards, Research Triangle Park (August 20, 2019). The formula for the deciview is 10 ln (b ext )/10 Mm−1). 40 CFR 51.301. To address regional haze visibility impairment, the 1999 RHR established an iterative planning process that requires both States in which Class I areas are located and States “the emissions from which may reasonably be anticipated to cause or contribute to any impairment of visibility” in a Class I area to periodically submit SIP revisions to address such impairment. CAA 169A(b)(2); 4 see also 40 CFR 51.308(b), (f) (establishing submission dates for iterative regional haze SIP revisions); (64 FR 35714 at 35768, July 1, 1999). Under the CAA, each SIP submission must contain “a long-term (ten to fifteen years) strategy for making reasonable progress toward meeting the national goal,” CAA 169A(b)(2)(B); the initial round of SIP submissions also had to address the statutory requirement that certain older, larger sources of visibility impairing pollutants install and operate the best available retrofit technology (BART). CAA 169A(b)(2)(A); 40 CFR 51.308(d), (e). States' first regional haze SIPs were due by December 17, 2007, 40 CFR 51.308(b), with subsequent SIP submissions containing updated long-term strategies originally due July 31, 2018, and every ten years thereafter. (64 FR at 35768, July 1, 1999). EPA established in the 1999 RHR that all States either have Class I areas within their borders or “contain sources whose emissions are reasonably anticipated to contribute to regional haze in a Class I area”; therefore, all States must submit regional haze SIPs. 5 Id. at 35721. 4 The RHR expresses the statutory requirement for States to submit plans addressing out-of-state class I areas by providing that States must address visibility impairment “in each mandatory Class I Federal area located outside the State that may be affected by emissions from within the State.” 40 CFR 51.308(d) and (f). 5 In addition to each of the fifty States, EPA also concluded that the Virgin Islands and District of Columbia must also submit regional haze SIPs because they either contain a Class I area or contain sources whose emissions are reasonably anticipated to contribute regional haze in a Class I area. See 40 CFR 51.300(b) and (d)(3). Much of the focus in the first implementation period of the regional haze program, which ran from 2007 through 2018, was on satisfying States' BART obligations. First implementation period SIPs were additionally required to contain long-term strategies for making reasonable progress toward the national visibility goal, of which BART is one component. The core required elements for the first implementation period SIPs (other than BART) are laid out in 40 CFR 51.308(d). Those provisions required that States containing Class I areas establish reasonable progress goals (RPGs) that are measured in deciviews (dv) and reflect the anticipated visibility conditions at the end of the implementation period including from implementation of States' long-term strategies. The first planning period RPGs were required to provide for an improvement in visibility for the most impaired days over the period of the implementation plan and ensure no degradation in visibility for the least impaired days over the same period. In establishing the RPGs for any Class I area in a State, the State was required to consider four statutory factors: the costs of compliance, the time necessary for compliance, the energy and non-air quality environmental impacts of compliance, and the remaining useful life of any potentially affected sources. CAA 169A(g)(1); 40 CFR 51.308(d)(1). States were also required to calculate baseline (using the five year period of 2000-2004) and natural visibility conditions ( i.e., visibility conditions without anthropogenic visibility impairment) for each Class I area, and to calculate the linear rate of progress needed to attain natural visibility conditions, assuming a starting point of baseline visibility conditions in 2004 and ending with natural conditions in 2064. This linear interpolation is known as the uniform rate of progress (URP) and is used as a tracking metric to help States assess the amount of progress they are making towards the national visibility goal over time in each Class I area. 6 40 CFR 51.308(d)(1)(i)(B), (d)(2). The 1999 RHR also provided that States' long-term strategies must include the “enforceable emissions limitations, compliance, schedules, and other measures as necessary to achieve the reasonable progress goals.” 40 CFR 51.308(d)(3). In establishing their long-term strategies, States are required to consult with other States that also contribute to visibility impairment in a given Class I area and include all measures necessary to obtain their shares of the emission reductions needed to meet the RPGs. See 40 CFR 51.308(d)(3)(i), (ii). The provisions of 40 CFR 51.308(d) also contain seven additional factors States must consider in formulating their long-term strategies, 40 CFR 51.308(d)(3)(v), as well as provisions governing monitoring and other implementation plan requirements. 40 CFR 51.308(d)(4). Finally, the 1999 RHR required States to submit periodic progress reports—SIP revisions due every five years that contain information on States' implementation of their regional haze plans and an assessment of whether anything additional is needed to make reasonable progress, see 40 CFR 51.308(g),(h)—and to consult with the Federal Land Manager(s) 7 (FLMs) responsible for each Class I area according to the requirements in CAA 169A(d) and 40 CFR 51.308(i). 6 EPA established the URP framework in the 1999 RHR to provide “an equitable analytical approach” to assessing the rate of visibility improvement at Class I areas across the country. The start point for the URP analysis is 2004 and the endpoint was calculated based on the amount of visibility improvement that was anticipated to result from implementation of existing CAA programs over the period from the mid-1990s to approximately 2005. Assuming this rate of progress would continue into the future, EPA determined that natural visibility conditions would be reached in 60 years, or 2064 (60 years from the baseline starting point of 2004). However, EPA did not establish 2064 as the year by which the national goal must be reached. 64 FR at 35731-32. That is, the URP and the 2064 date are not enforceable targets but are rather tools that “allow for analytical comparisons between the rate of progress that would be achieved by the State's chosen set of control measures and the URP.” (82 FR 3078 at 3084, January 10, 2017). 7 EPA's regulations define “Federal Land Manager” as “the Secretary of the department with authority over the Federal Class I area (or the Secretary's designee) or, with respect to Roosevelt-Campobello International Park, the Chairman of the Roosevelt-Campobello International Park Commission.” 40 CFR 51.301. On January 10, 2017, EPA promulgated revisions to the RHR, (82 FR 3078, January 10, 2017), that apply for the second and subsequent implementation periods. The 2017 rulemaking made several changes to the requirements for regional haze SIPs to clarify States' obligations and streamline certain regional haze requirements. The revisions to the regional haze program for the second and subsequent implementation periods focused on the requirement that States' SIPs contain long-term strategies for making reasonable progress towards the national visibility goal. The reasonable progress requirements as revised in the 2017 rulemaking (referred to here as the 2017 RHR Revisions) are codified at 40 CFR 51.308(f). Among other changes, the 2017 RHR Revisions adjusted the deadline for States to submit their second implementation period SIPs from July 31, 2018, to July 31, 2021, clarified the order of analysis and the relationship between RPGs and the long-term strategy, and focused on making visibility improvements on the days with the most anthropogenic visibility impairment, as opposed to the days with the most visibility impairment overall. EPA also revised requirements of the visibility protection program related to periodic progress reports and FLM consultation. The specific requirements applicable to second implementation period regional haze SIP submissions are addressed in detail below. EPA provided guidance to the states for their second implementation period SIP submissions in the preamble to the 2017 RHR Revisions as well as in subsequent, stand-alone guidance documents. In August 2019, EPA issued “Guidance on Regional Haze State Implementation Plans for the Second Implementation Period” (“2019 Guidance”). 8 On July 8, 2021, EPA issued a memorandum containing “Clarifications Regarding Regional Haze State Implementation Plans for the Second Implementation Period” (“2021 Clarifications Memo”). 9 Additionally, EPA further clarified the recommended procedures for processing ambient visibility data and optionally adjusting the URP to account for international anthropogenic and prescribed fire impacts in two technical guidance documents: the December 2018 “Technical Guidance on Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program” (“2018 Visibility Tracking Guidance”), 10 and the June 2020 “Recommendation for the Use of Patched and Substituted Data and Clarification of Data Completeness for Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program” and associated Technical Addendum (“2020 Data Completeness Memo”). 11 8 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 EPA Office of Air Quality Planning and Standards, Research Triangle Park (August 20, 2019). 9 Clarifications Regarding Regional Haze State Implementation Plans for the Second Implementation Period. https://www.epa.gov/system/files/documents/2021-07/clarifications-regarding-regional-haze-state-implementation-plans-for-the-second-implementation-period.pdf. EPA Office of Air Quality Planning and Standards, Research Triangle Park (July 8, 2021). 10 Technical Guidance on Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program. https://www.epa.gov/sites/default/files/2021-03/documents/tracking.pdf EPA Office of Air Quality Planning and Standards, Research Triangle Park. (December 20, 2018). 11 Recommendation for the Use of Patched and Substituted Data and Clarification of Data Completeness for Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program. https://www.epa.gov/visibility/memo-and-technical-addendum-ambient-data-usage-and-completeness-regional-haze-program EPA Office of Air Quality Planning and Standards, Research Triangle Park (June 3, 2020). As explained in the 2021 Clarifications Memo, EPA intends the second implementation period of the regional haze program to secure meaningful reductions in visibility impairing pollutants that build on the significant progress States have achieved to date. The Agency also recognizes that analyses regarding reasonable progress are State-specific and that, based on States' and sources' individual circumstances, what constitutes reasonable reductions in visibility impairing pollutants will vary from State-to-State. While there exist many opportunities for States to leverage both ongoing and upcoming emission reductions under other CAA programs, the Agency expects States to undertake rigorous reasonable progress analyses that identify further opportunities to advance the national visibility goal consistent with the statutory and regulatory requirements. See generally 2021 Clarifications Memo. This is consistent with Congress's determination that a visibility protection program is needed in addition to the CAA's National Ambient Air Quality Standards (NAAQS) and Prevention of Significant Deterioration (PSD) programs, as further emission reductions may be necessary to adequately protect visibility in Class I areas throughout the country. 12 12 See, e.g., H.R. Rep No. 95-294 at 205 (“In determining how to best remedy the growing visibility problem in these areas of great scenic importance, the committee realizes that as a matter of equity, the national ambient air quality standards cannot be revised to adequately protect visibility in all areas of the country.”), (“the mandatory class I increments of [the PSD program] do not adequately protect visibility in class I areas”). B. Roles of Agencies in Addressing Regional Haze Because the air pollutants and pollution affecting visibility in Class I areas can be transported over long distances, successful implementation of the regional haze program requires long-term, regional coordination among multiple jurisdictions and agencies that have responsibility for Class I areas and the emissions that impact visibility in those areas. To address regional haze, States need to develop strategies in coordination with one another, considering the effect of emissions from one jurisdiction on the air quality in another. Five regional planning organizations (RPOs), 13 which include representation from State and Tribal governments, EPA, and FLMs, were developed in the lead-up to the first implementation period to address regional haze. RPOs evaluate technical information to better understand how emissions from State and Tribal land impact Class I areas across the country, pursue the development of regional strategies to reduce emissions of particulate matter and other pollutants leading to regional haze, and help States meet the consultation requirements of the RHR. 13 RPOs are sometimes also referred to as “multi-jurisdictional organizations,” or MJOs. For the purposes of this notice, the terms RPO and MJO are synonymous. The Lake Michigan Air Directors Consortium (LADCO) is an RPO that includes the States of Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin. LADCO's work is a collaborative effort of State governments, Tribal governments, and various Federal agencies established to initiate and coordinate activities associated with the management of regional haze, visibility, and other air quality issues in the Midwest. Along with the six LADCO States, participants in LADCO's Regional Haze Technical Workgroup include EPA, U.S. National Parks Service (NPS), U.S. Fish and Wildlife Service (FWS), and U.S. Forest Service (USFS). III. Requirements for Regional Haze Plans for the Second Implementation Period Under the CAA and EPA's regulations, all 50 States, the District of Columbia, and the U.S. Virgin Islands were required to submit regional haze SIPs satisfying the applicable requirements for the second implementation period of the regional haze program by July 31, 2021. Each State's SIP must contain a long-term strategy for making reasonable progress toward meeting the national goal of remedying any existing and preventing any future anthropogenic visibility impairment in Class I areas. CAA 169A(b)(2)(B). To this end, 40 CFR 51.308(f) lays out the process by which States determine what constitutes their long-term strategies, with the order of the requirements in 40 CFR 51.308(f)(1) through (3) generally mirroring the order of the steps in the reasonable progress analysis 14 and (f)(4) through (6) containing additional, related requirements. Broadly speaking, a State first must identify the Class I areas within the State and determine the Class I areas outside the State in which visibility may be affected by emissions from the State. These are the Class I areas that must be addressed in the State's long-term strategy. See 40 CFR 51.308(f), (f)(2). For each Class I area within its borders, a State must then calculate the baseline, current, and natural visibility conditions for that area, as well as the visibility improvement made to date and the URP. See 40 CFR 51.308(f)(1). Each State having a Class I area and/or emissions that may affect visibility in a Class I area must then develop a long-term strategy that includes the enforceable emission limitations, compliance schedules, and other measures that are necessary to make reasonable progress in such areas. A reasonable progress determination is based on applying the four factors in CAA section 169A(g)(1) to sources of visibility-impairing pollutants that the State has selected to assess for controls for the second implementation period. Additionally, as further explained below, the RHR at 40 CFR 51.308(f)(2)(iv) separately provides five “additional factors” 15 that States must consider in developing their long-term strategies. See 40 CFR 51.308(f)(2). A State evaluates potential emission reduction measures for those selected sources and determines which are necessary to make reasonable progress. Those measures are then incorporated into the State's long-term strategy. After a State has developed its long-term strategy, it then establishes RPGs for each Class I area within its borders by modeling the visibility impacts of all reasonable progress controls at the end of the second implementation period, i.e., in 2028, as well as the impacts of other requirements of the CAA. The RPGs include reasonable progress controls not only for sources in the State in which the Class I area is located, but also for sources in other States that contribute to visibility impairment in that area. The RPGs are then compared to the baseline visibility conditions and the URP to ensure that progress is being made towards the statutory goal of preventing any future and remedying any existing anthropogenic visibility impairment in Class I areas. 40 CFR 51.308(f)(2)and(3). 14 EPA explained in the 2017 RHR Revisions that we were adopting new regulatory language in 40 CFR 51.308(f) that, unlike the structure in 51.308(d), “tracked the actual planning sequence.” (82 FR 3091, January 10, 2017). 15 The five “additional factors” for consideration in section 51.308(f)(2)(iv) are distinct from the four factors listed in CAA section 169A(g)(1) and 40 CFR 51.308(f)(2)(i) that States must consider and apply to sources in determining reasonable progress. In addition to satisfying the requirements at 40 CFR 51.308(f) related to reasonable progress, the regional haze SIP revisions for the second implementation period must address the requirements in 40 CFR 51.308(g)(1) through (5) pertaining to periodic reports describing progress towards the RPGs, 40 CFR 51.308(f)(5), as well as requirements for FLM consultation that apply to all visibility protection SIPs and SIP revisions. 40 CFR 51.308(i). A State must submit its regional haze SIP and subsequent SIP revisions to EPA according to the requirements applicable to all SIP revisions under the CAA and EPA's regulations. See CAA 169A(b)(2); CAA 110(a). Upon EPA approval, a SIP is enforceable by the Agency and the public under the CAA. If EPA finds that a State fails to make a required SIP revision, or if EPA finds that a State's SIP is incomplete or disapproves the SIP, the Agency must promulgate a Federal implementation plan (FIP) that satisfies the applicable requirements. See CAA 110(c)(1). A. Identification of Class I Areas The first step in developing a regional haze SIP is for a State to determine which Class I areas, in addition to those within its borders, “may be affected” by emissions from within the State. In the 1999 RHR, EPA determined that all States contribute to visibility impairment in at least one Class I area and explained that the statute and regulations lay out an “extremely low triggering threshold” for determining “whether States should be required to engage in air quality planning and analysis as a prerequisite to determining the need for control of emissions from sources within their State.” 64 FR 35714 at 35720-22, July 1, 1999. A State must determine which Class I areas must be addressed by its SIP by evaluating the total emissions of visibility impairing pollutants from all sources within the State. While the RHR does not require this evaluation to be conducted in any particular manner, EPA's 2019 Guidance provides recommendations for how such an assessment might be accomplished, including by, where appropriate, using the determinations previously made for the first implementation period. See 2019 Guidance at 8-9. In addition, the determination of which Class I areas may be affected by a State's emissions is subject to the requirement in 40 CFR 51.308(f)(2)(iii) 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.” B. Calculations of Baseline, Current, and Natural Visibility Conditions; Progress to Date; and the Uniform Rate of Progress As part of assessing whether a SIP submission for the second implementation period is providing for reasonable progress towards the national visibility goal, the RHR contains requirements in 40 CFR 51.308(f)(1) related to tracking visibility improvement over time. The requirements of this section apply only to States having Class I areas within their borders; the required calculations must be made for each such Class I area. EPA's 2018 Visibility Tracking Guidance 16 provides recommendations to assist States in satisfying their obligations under 40 CFR 51.308(f)(1); specifically, in developing information on baseline, current, and natural visibility conditions, and in making optional adjustments to the URP to account for the impacts of international anthropogenic emissions and prescribed fires. See 82 FR 3078 at 3103-05, January 10, 2017. 16 The 2018 Visibility Tracking Guidance references and relies on parts of the 2003 Tracking Guidance: “Guidance for Tracking Progress Under the Regional Haze Rule,” which can be found at https://www.epa.gov/sites/default/files/2021-03/documents/tracking.pdf. The RHR requires tracking of visibility conditions on two sets of days: the clearest and the most impaired days. Visibility conditions for both sets of days are expressed as the average deciview index for the relevant five-year period (the period representing baseline or current visibility conditions). The RHR provides that the relevant sets of days for visibility tracking purposes are the 20 percent clearest (the 20 percent of monitored days in a calendar year with the lowest values of the deciview index) and 20 percent most impaired days (the 20 percent of monitored days in a calendar year with the highest amounts of anthropogenic visibility impairment). 17 40 CFR 51.301. A State must calculate visibility conditions for both the 20 percent clearest and 20 percent most impaired days for the baseline period of 2000-2004 and the most recent five-year period for which visibility monitoring data are available (representing current visibility conditions). 40 CFR 51.308(f)(1)(i) and (iii). States must also calculate natural visibility conditions for the clearest and most impaired days, 18 by estimating the conditions that would exist on those two sets of days absent anthropogenic visibility impairment. 40 CFR 51.308(f)(1)(ii). Using all these data, States must then calculate, for each Class I area, the amount of progress made since the baseline period (2000-2004) and how much improvement is left to achieve to reach natural visibility conditions. 17 This action also refers to the 20 percent clearest and 20 percent most anthropogenically impaired days as the “clearest” and “most impaired” or “most anthropogenically impaired” days, respectively. 18 The RHR at 40 CFR 51.308(f)(1)(ii) contains an error related to the requirement for calculating two sets of natural conditions values. The rule says, “most impaired days or the clearest days” where it should say “most impaired days and clearest days.” This is an error that was intended to be corrected in the 2017 RHR Revisions but did not get corrected in the final rule language. This is supported by the preamble text at 82 FR 3098: “In the final version of 40 CFR 51.308(f)(1)(ii), an occurrence of “or” has been corrected to “and” to indicate that natural visibility conditions for both the most impaired days and the clearest days must be based on available monitoring information.” Using the data for the set of most impaired days only, States must plot a line between visibility conditions in the baseline period and natural visibility conditions for each Class I area to determine the URP—the amount of visibility improvement, measured in dv, that would need to be achieved during each implementation period to achieve natural visibility conditions by the end of 2064. The URP is used in later steps of the reasonable progress analysis for informational purposes and to provide a non-enforceable benchmark against which to assess a Class I area's rate of visibility improvement. 19 Additionally, in the 2017 RHR Revisions, EPA provided States the option of proposing to adjust the endpoint of the URP to account for impacts of anthropogenic sources outside the United States and/or impacts of certain types of wildland prescribed fires. These adjustments, which must be approved by EPA, are intended to avoid any perception that States should compensate for impacts from international anthropogenic sources and to give States the flexibility to determine that limiting the use of wildland-prescribed fire is not necessary for reasonable progress. See 82 FR 3078 at 3107, January 10, 2017, footnote 116. 19 Being on or below the URP is not a “safe harbor”; i.e., achieving the URP does not mean that a Class I area is making “reasonable progress” and does not relieve a State from using the four statutory factors to determine what level of control is needed to achieve such progress. See, e.g., 82 FR 3078 at 3093, January 10, 2017. EPA's 2018 Visibility Tracking Guidance can be used to help satisfy the 40 CFR 51.308(f)(1) requirements, including in developing information on baseline, current, and natural visibility conditions, and in making optional adjustments to the URP. In addition, the 2020 Data Completeness Memo provides recommendations on the data completeness language referenced in 40 CFR 51.308(f)(1)(i) and provides updated natural conditions estimates for each Class I area. C. Long-Term Strategy for Regional Haze The core component of a regional haze SIP submission is a long-term strategy that addresses regional haze in each Class I area within a State's borders and each Class I area that may be affected by emissions from the State. 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)(2). 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 emission reduction measures that a particular source or group of sources needs to implement to make reasonable progress towards the national visibility goal. See 40 CFR 51.308(f)(2)(i). Emission reduction measures that are necessary to make reasonable progress may be either new, additional control measures for a source, or they may be the existing emission reduction measures that a source is already implementing. See 2019 Guidance at 43; 2021 Clarifications Memo at 8-10. 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. 40 CFR 51.308(f)(2). The construct of 40 CFR 51.308(f)(2)(i) provides the requirements for the four-factor analysis. The first step of this analysis entails selecting the sources to be evaluated for emission reduction measures; to this end, the RHR requires States to consider “major and minor stationary sources or groups of sources, mobile sources, and area sources” of visibility impairing pollutants for potential four-factor control analysis. 40 CFR 51.308(f)(2)(i). A threshold question at this step is which visibility impairing pollutants will be analyzed. As EPA previously explained, consistent with the first implementation period, EPA generally expects that each State will analyze at least SO 2 and NO X in selecting sources and determining control measures. See 2019 Guidance at 12, 2021, Clarifications Memo at 4. A State that chooses not to consider at least these two pollutants should demonstrate why such consideration would be unreasonable. 2021 Clarifications Memo at 4. While States have the option to analyze all sources, the 2019 Guidance explains that “an analysis of control measures is not required for every source in each implementation period,” and that “[s]electing a set of sources for analysis of control measures in each implementation period is . . . consistent with the Regional Haze Rule, which sets up an iterative planning process and anticipates that a state may not need to analyze control measures for all its sources in a given SIP revision.” 2019 Guidance at 9. However, given that source selection is the basis of all subsequent control determinations, a reasonable source selection process “should be designed and conducted to ensure that source selection results in a set of pollutants and sources the evaluation of which has the potential to meaningfully reduce their contributions to visibility impairment.” 2021 Clarifications Memo at 3. EPA explained in the 2021 Clarifications Memo that each State has an obligation to submit a long-term strategy that addresses the regional haze visibility impairment that results from emissions from within that State. Thus, source selection should focus on the in-state contribution to visibility impairment and be designed to capture a meaningful portion of the State's total contribution to visibility impairment in Class I areas. A State should not decline to select its largest in-state sources on the basis that there are even larger out-of-state contributors. 2021 Clarifications Memo at 4. 20 20 Similarly, in responding to comments on the 2017 RHR Revisions, EPA explained that “[a] state should not fail to address its many relatively low-impact sources merely because it only has such sources and another state has even more low-impact sources and/or some high impact sources.” Responses to Comments on Protection of Visibility: Amendments to Requirements for State Plans; Proposed Rule (81 FR 26942 at 26987-88, May 4, 2016). Thus, while States have discretion to choose any source selection methodology that is reasonable, whatever choices they make should be reasonably explained. To this end, 40 CFR 51.308(f)(2)(i) requires that a State's SIP submission include “a description of the criteria it used to determine which sources or groups of sources it evaluated.” The technical basis for source selection, which may include methods for quantifying potential visibility impacts such as emissions divided by distance metrics, trajectory analyses, residence time analyses, and/or photochemical modeling, must also be appropriately documented, as required by 40 CFR 51.308(f)(2)(iii). Once a State has selected the set of sources, the next step is to determine the emissions reduction measures for those sources that are necessary to make reasonable progress for the second implementation period. 21 This is accomplished by considering the four factors—“the costs of compliance, the time necessary for compliance, and the energy and non-air quality environmental impacts of compliance, and the remaining useful life of any existing source subject to such requirements.” CAA 169A(g)(1). EPA has explained that the four-factor analysis is an assessment of potential emission reduction measures ( i.e., control options) for sources; “use of the terms `compliance' and `subject to such requirements' in section 169A(g)(1) strongly indicates that Congress intended the relevant determination to be the requirements with which sources would have to comply to satisfy the CAA's reasonable progress mandate.” 82 FR 3078 at 3091, January 10, 2017. Thus, for each source it has selected for four-factor analysis, 22 a State must consider a “meaningful set” of technically feasible control options for reducing emissions of visibility impairing pollutants. Id. at 3088. The 2019 Guidance provides that “[a] state must reasonably pick and justify the measures that it will consider, recognizing that there is no statutory or regulatory requirement to consider all technically feasible measures or any particular measures. A range of technically feasible measures available to reduce emissions would be one way to justify a reasonable set.” 2019 Guidance at 29. 21 The CAA provides that, “[i]n determining reasonable progress there shall be taken into consideration” the four statutory factors. CAA 169A(g)(1). However, in addition to four-factor analyses for selected sources, groups of sources, or source categories, a State may also consider additional emission reduction measures for inclusion in its long-term strategy, e.g., from other newly adopted, on-the-books, or on-the-way rules and measures for sources not selected for four-factor analysis for the second planning period. 22 “Each source” or “particular source” is used here as shorthand. While a source-specific analysis is one way of applying the four factors, neither the statute nor the RHR requires States to evaluate individual sources. Rather, States have “the flexibility to conduct four-factor analyses for specific sources, groups of sources or even entire source categories, depending on state policy preferences and the specific circumstances of each state.” 82 FR 3078 at 3088, January 10, 2017. However, not all approaches to grouping sources for four-factor analysis are necessarily reasonable; the reasonableness of grouping sources in any particular instance will depend on the circumstances and the manner in which grouping is conducted. If it is feasible to establish and enforce different requirements for sources or subgroups of sources, and if relevant factors can be quantified for those sources or subgroups, then States should make a separate reasonable progress determination for each source or subgroup. 2021 Clarifications Memo at 7-8. EPA's 2021 Clarifications Memo provides further guidance on what constitutes a reasonable set of control options for consideration: “A reasonable four-factor analysis will consider the full range of potentially reasonable options for reducing emissions.” 2021 Clarifications Memo at 7. In addition to add-on controls and other retrofits ( i.e., new emissions reduction measures for sources), EPA explained that States should generally analyze efficiency improvements for sources' existing measures as control options in their four-factor analyses, as in many cases such improvements are reasonable given that they typically involve only additional operation and maintenance costs. Additionally, the 2021 Clarifications Memo provides that States that have assumed a higher emissions rate than a source has achieved or could potentially achieve using its existing measures should also consider lower emissions rates as potential control options. That is, a State should consider a source's recent actual and projected emission rates to determine if it could reasonably attain lower emission rates with its existing measures. If so, the State should analyze the lower emission rate as a control option for reducing emissions. 2021 Clarifications Memo at 7. EPA's recommendations to analyze potential efficiency improvements and achievable lower emission rates apply to both sources that have been selected for four-factor analysis and those that have forgone a four-factor analysis on the basis of existing “effective controls.” See 2021 Clarifications Memo at 5, 10. After identifying a reasonable set of potential control options for the sources it has selected, a State then collects information on the four factors with regard to each option identified. EPA has also explained that, in addition to the four statutory factors, States have flexibility under the CAA and RHR to reasonably consider visibility benefits as an additional factor alongside the four statutory factors. 23 The 2019 Guidance provides recommendations for the types of information that can be used to characterize the four factors (with or without visibility), as well as ways in which States might reasonably consider and balance that information to determine which of the potential control options is necessary to make reasonable progress. See 2019 Guidance at 30-36. The 2021 Clarifications Memo contains further guidance on how States can reasonably consider modeled visibility impacts or benefits in the context of a four-factor analysis. 2021 Clarifications Memo at 12-13, 14-15. Specifically, EPA explained that while visibility can reasonably be used when comparing and choosing between multiple reasonable control options, it should not be used to summarily reject controls that are reasonable given the four statutory factors. 2021 Clarifications Memo at 13. Ultimately, while States have discretion to reasonably weigh the factors and to determine what level of control is needed, 40 CFR 51.308(f)(2)(i) provides that a State “must include in its implementation plan a description of . . . how the four factors were taken into consideration in selecting the measure for inclusion in its long-term strategy.” 23 See, e.g., Responses to Comments on Protection of Visibility: Amendments to Requirements for State Plans; Proposed Rule (81 FR 26942, May 4, 2016), Docket Number EPA-HQ-OAR-2015-0531, U.S. Environmental Protection Agency at 186; 2019 Guidance at 36-37. As explained above, 40 CFR 51.308(f)(2)(i) requires States to determine the emission reduction measures for sources that are necessary to make reasonable progress by considering the four factors. Pursuant to 40 CFR 51.308(f)(2), measures that are necessary to make reasonable progress towards the national visibility goal must be included in a State's long-term strategy and in its SIP. 24 If the outcome of a four-factor analysis is a new, additional emission reduction measure for a source, that new measure is necessary to make reasonable progress towards remedying existing anthropogenic visibility impairment and must be included in the SIP. If the outcome of a four-factor analysis is that no new measures are reasonable for a source, continued implementation of the source's existing measures is generally necessary to prevent future emission increases and thus to make reasonable progress towards the second part of the national visibility goal: preventing future anthropogenic visibility impairment. See CAA 169A(a)(1). That is, when the result of a four-factor analysis is that no new measures are necessary to make reasonable progress, the source's existing measures are generally necessary to make reasonable progress and must be included in the SIP. However, there may be circumstances in which a State can demonstrate that 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 emissions rate, it may not be necessary to have those measures in the long-term strategy to prevent future emissions increases and future visibility impairment. EPA's 2021 Clarifications Memo provides further explanation and guidance on how States may demonstrate that a source's existing measures are not necessary to make reasonable progress. See 2021 Clarifications Memo at 8-10. If the State can make such a demonstration, it need not include a source's existing measures in the long-term strategy or its SIP. 24 States may choose to, but are not required to, include measures in their long-term strategies beyond just the emission reduction measures that are necessary for reasonable progress. See 2021 Clarifications Memo at 16. For example, States with smoke management programs may choose to submit their smoke management plans to EPA for inclusion in their SIPs but are not required to do so. See, e.g., 82 FR 3078 at 3108-09, January 10, 2017, (requirement to consider smoke management practices and smoke management programs under 40 CFR 51.308(f)(2)(iv) does not require States to adopt such practices or programs into their SIPs, although they may elect to do so). As with source selection, the characterization of information on each of the factors is also subject to the documentation requirement in 40 CFR 51.308(f)(2)(iii). The reasonable progress analysis, including source selection, information gathering, characterization of the four statutory factors (and potentially visibility), balancing of the four factors, and selection of the emission reduction measures that represent reasonable progress, is a technically complex exercise, but also a flexible one that provides States with bounded discretion to design and implement approaches appropriate to their circumstances. Given this flexibility, 40 CFR 51.308(f)(2)(iii) plays an important function in requiring a State to document the technical basis for its decision making so that the public and EPA can comprehend and evaluate the information and analysis the State relied upon to determine what emission reduction measures must be in place to make reasonable progress. 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. This documentation requirement can be met through the provision of and reliance on technical analyses developed through a regional planning process, so long as that process and its output has been approved by all State participants. In addition to the explicit regulatory requirement to document the technical basis of their reasonable progress determinations, States are also subject to the general principle that those determinations must be reasonably moored to the statute. 25 That is, a State's decisions about the emission reduction measures that are necessary to make reasonable progress must be consistent with the statutory goal of remedying existing and preventing future visibility impairment. 25 See Arizona ex rel. Darwin v. U.S. EPA, 815 F.3d 519, 531 (9th Cir. 2016); Nebraska v. U.S. EPA, 812 F.3d 662, 668 (8th Cir. 2016); North Dakota v. EPA, 730 F.3d 750, 761 (8th Cir. 2013); Oklahoma v. EPA, 723 F.3d 1201, 1206, 1208-10 (10th Cir. 2013); cf. also Nat'l Parks Conservation Ass'n v. EPA, 803 F.3d 151, 165 (3d Cir. 2015); Alaska Dep't of Envtl. Conservation v. EPA, 540 U.S. 461, 485, 490 (2004). The four statutory factors (and potentially visibility) are used to determine what emission reduction measures for selected sources must be included in a State's long-term strategy for making reasonable progress. Additionally, the RHR at 40 CFR 51.308(f)(2)(iv) separately provides five “additional factors” 26 that States must consider in developing their long-term strategies: (1) Emission reductions due to ongoing air pollution control programs, including measures to address reasonably attributable visibility impairment; (2) measures to reduce the impacts of construction activities; (3) source retirement and replacement schedules; (4) basic smoke management practices for prescribed fire used for agricultural and wildland vegetation management purposes and smoke management programs; and (5) the anticipated net effect on visibility due to projected changes in point, area, and mobile source emissions over the period addressed by the long-term strategy. The 2019 Guidance provides that a State may satisfy this requirement by considering these additional factors in the process of selecting sources for four-factor analysis, when performing that analysis, or both, and that not every one of the additional factors needs to be considered at the same stage of the process. See 2019 Guidance at 21. EPA provided further guidance on the five additional factors in the 2021 Clarifications Memo, explaining that a State should generally not reject cost-effective and otherwise reasonable controls merely because there have been emission reductions since the first planning period owing to other ongoing air pollution control programs or merely because visibility is otherwise projected to improve at Class I areas. Additionally, States generally should not rely on these additional factors to summarily assert that the State has already made sufficient progress and, therefore, no sources need to be selected or no new controls are needed regardless of the outcome of four-factor analyses. 2021 Clarifications Memo at 13. 26 The five “additional factors” for consideration in section 51.308(f)(2)(iv) are distinct from the four factors listed in CAA section 169A(g)(1) and 40 CFR 51.308(f)(2)(i) that States must consider and apply to sources in determining reasonable progress. Because the air pollution that causes regional haze crosses State boundaries, 40 CFR 51.308(f)(2)(ii) requires a State to consult with other States that also have emissions that are reasonably anticipated to contribute to visibility impairment in a given Class I area. Consultation allows for each State that impacts visibility in an area to share whatever technical information, analyses, and control determinations may be necessary to develop coordinated emission management strategies. This coordination may be managed through inter- and intra-RPO consultation and the development of regional emissions strategies; additional consultations between States outside of RPO processes may also occur. If a State, pursuant to consultation, agrees that certain measures ( e.g., a certain emission limitation) are necessary to make reasonable progress at a Class I area, it must include those measures in its SIP. 40 CFR 51.308(f)(2)(ii)(A). Additionally, the RHR requires that States that contribute to visibility impairment at the same Class I area consider the emission reduction measures the other contributing States have identified as being necessary to make reasonable progress for their own sources. 40 CFR 51.308(f)(2)(ii)(B). If a State has been asked to consider or adopt certain emission reduction measures, but ultimately determines those measures are not necessary to make reasonable progress, that State must document in its SIP the actions taken to resolve the disagreement. 40 CFR 51.308(f)(2)(ii)(C). EPA will consider the technical information and explanations presented by the submitting State and the State with which it disagrees when considering whether to approve the State's SIP. See Id.; 2019 Guidance at 53. Under all circumstances, a State must document in its SIP submission all substantive consultations with other contributing States. 40 CFR 51.308(f)(2)(ii)(C). D. Reasonable Progress Goals Reasonable progress goals “measure the progress that is projected to be achieved by the control measures States have determined are necessary to make reasonable progress based on a four-factor analysis.” 82 FR 3078 at 3091, January 10, 2017. Their primary purpose is to assist the public and EPA in assessing the reasonableness of States' long-term strategies for making reasonable progress towards the national visibility goal. See 40 CFR 51.308(f)(3)(iii)and(iv). States in which Class I areas are located must establish two RPGs, both in dv—one representing visibility conditions on the clearest days and one representing visibility on the most anthropogenically impaired days—for each area within their borders. 40 CFR 51.308(f)(3)(i). The two RPGs are intended to reflect the projected impacts, on the two sets of days, of the emission reduction measures the State with the Class I area, as well as all other contributing States, have included in their long-term strategies for the second implementation period. 27 The RPGs also account for the projected impacts of implementing other CAA requirements, including non-SIP based requirements. Because RPGs are the modeled result of the measures in States' long-term strategies (as well as other measures required under the CAA), they cannot be determined before States have conducted their four-factor analyses and determined the control measures that are necessary to make reasonable progress. See 2021 Clarifications Memo at 6. 27 RPGs are intended to reflect the projected impacts of the measures all contributing States include in their long-term strategies. However, due to the timing of analyses, control determinations by other States, and other on-going emissions changes, a particular State's RPGs may not reflect all control measures and emissions reductions that are expected to occur by the end of the implementation period. The 2019 Guidance provides recommendations for addressing the timing of RPG calculations when States are developing their long-term strategies on disparate schedules, as well as for adjusting RPGs using a post-modeling approach. 2019 Guidance at 47-48. For the second implementation period, the RPGs are set for 2028. Reasonable progress goals are not enforceable targets, 40 CFR 51.308(f)(3)(iii); rather, they “provide a way for the states to check the projected outcome of the [long-term strategy] against the goals for visibility improvement.” 2019 Guidance at 46. While States are not legally obligated to achieve the visibility conditions described in their RPGs, 40 CFR 51.308(f)(3)(i) requires that “[t]he long-term strategy and the reasonable progress goals must provide for an improvement in visibility for the most impaired days since the baseline period and ensure no degradation in visibility for the clearest days since the baseline period.” Thus, States are required to have emission reduction measures in their long-term strategies that are projected to achieve visibility conditions on the most impaired days that are better than the baseline period and shows no degradation on the clearest days compared to the clearest days from the baseline period. The baseline period for the purpose of this comparison is the baseline visibility condition—the annual average visibility condition for the period 2000-2004. See 40 CFR 51.308(f)(1)(i), 82 FR 3078 at 3097-98, January 10, 2017. So that RPGs may also serve as a metric for assessing the amount of progress a State is making towards the national visibility goal, the RHR requires States with Class I areas to compare the 2028 RPG for the most impaired days to the corresponding point on the URP line (representing visibility conditions in 2028 if visibility were to improve at a linear rate from conditions in the baseline period of 2000-2004 to natural visibility conditions in 2064). If the most impaired days RPG in 2028 is above the URP ( i.e., if visibility conditions are improving more slowly than the rate described by the URP), each State that contributes to visibility impairment in the Class I area must demonstrate, based on the four-factor analysis required under 40 CFR 51.308(f)(2)(i), that no additional emission reduction measures would be reasonable to include in its long-term strategy. 40 CFR 51.308(f)(3)(ii). To this end, 40 CFR 51.308(f)(3)(ii) requires that each State contributing to visibility impairment in a Class I area that is projected to improve more slowly than the URP provide “a robust demonstration, including documenting the criteria used to determine which sources or groups [of] 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.” The 2019 Guidance provides suggestions about how such a “robust demonstration” might be conducted. See 2019 Guidance at 50-51. The 2017 RHR, 2019 Guidance, and 2021 Clarifications Memo also explain that projecting an RPG that is on or below the URP based on only on-the-books and/or on-the-way control measures ( i.e., control measures already required or anticipated before the four-factor analysis is conducted) is not a “safe harbor” from the CAA's and RHR's requirement that all States must conduct a four-factor analysis to determine what emission reduction measures constitute reasonable progress. 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.” See 82 FR at 3093, 3099-3100; 2019 Guidance at 22; 2021 Clarifications Memo at 15-16. E. Monitoring Strategy and Other State Implementation Plan Requirements The provisions of 40 CFR 51.308(f)(6) require States to have certain strategies and elements in place for assessing and reporting on visibility. Individual requirements under this section apply either to States with Class I areas within their borders, States with no Class I areas but that are reasonably anticipated to cause or contribute to visibility impairment in any Class I area, or both. A State with Class I areas within its borders must submit with its SIP revision a monitoring strategy for measuring, characterizing, and reporting regional haze visibility impairment that is representative of all Class I areas within the State. SIP revisions for such States must also provide for the establishment of any additional monitoring sites or equipment needed to assess visibility conditions in Class I areas, as well as reporting of all visibility monitoring data to EPA at least annually. Compliance with the monitoring strategy requirement may be met through a State's participation in the Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring network, which is used to measure visibility impairment caused by air pollution at the 156 Class I areas covered by the visibility program. 40 CFR 51.308(f)(6), (f)(6)(i), (f)(6)(iv). The IMPROVE monitoring data is used to determine the 20 percent most anthropogenically impaired and 20 percent clearest sets of days every year at each Class I area and tracks visibility impairment over time. All States' SIPs must provide for procedures by which monitoring data and other information are used to determine the contribution of emissions from within the State to regional haze visibility impairment in affected Class I areas. 40 CFR 51.308(f)(6)(ii), (iii). The provisions of 40 CFR 51.308(f)(6)(v) further require that all States' SIPs provide for a statewide inventory of emissions of pollutants that are reasonably anticipated to cause or contribute to visibility impairment in any Class I area; the inventory must include emissions for the most recent year for which data are available and estimates of future projected emissions. States must also include commitments to update their inventories periodically. The inventories themselves do not need to be included as elements in the SIP and are not subject to EPA review as part of the Agency's evaluation of a SIP revision. 28 All States' SIPs must also provide for any other elements, including reporting, recordkeeping, and other measures, that are necessary for States to assess and report on visibility. 40 CFR 51.308(f)(6)(vi). Per the 2019 Guidance, a State may note in its regional haze SIP that its compliance with the Air Emissions Reporting Rule (AERR) in 40 CFR part 51, subpart A satisfies the requirement to provide for an emissions inventory for the most recent year for which data are available. To satisfy the requirement to provide estimates of future projected emissions, a State may explain in its SIP how projected emissions were developed for use in establishing RPGs for its own and nearby Class I areas. 29 28 See “Step 8: Additional requirements for regional haze SIPs” in 2019 Guidance at 55. 29 Id. Separate from the requirements related to monitoring for regional haze purposes under 40 CFR 51.308(f)(6), the RHR also contains a requirement at 40 CFR 51.308(f)(4) related to any additional monitoring that may be needed to address visibility impairment in Class I areas from a single source or a small group of sources. This is called “reasonably attributable visibility impairment.” 30 Under this provision, if EPA or the FLM of an affected Class I area has advised a State that additional monitoring is needed to assess reasonably attributable visibility impairment, the State must include in its SIP revision for the second implementation period an appropriate strategy for evaluating such impairment. 30 EPA's visibility protection regulations define “reasonably attributable visibility impairment” as “visibility impairment that is caused by the emission of air pollutants from one, or a small number of sources.” 40 CFR 51.301. F. Requirements for Periodic Reports Describing Progress Towards the Reasonable Progress Goals The provisions of 40 CFR 51.308(f)(5) require a State's regional haze SIP revision to address the requirements of paragraphs 40 CFR 51.308(g)(1) through (5) so that the plan revision due in 2021 will serve also as a progress report addressing the period since submission of the progress report for the first implementation period. The regional haze progress report requirement is designed to inform the public and EPA about a State's implementation of its existing long-term strategy and whether such implementation is in fact resulting in the expected visibility improvement. See 81 FR 26942, 26950, May 4, 2016, (82 FR 3078 at 3119, January 10, 2017). To this end, every State's SIP revision for the second implementation period is required to describe the status of implementation of all measures included in the State's long-term strategy, including BART and reasonable progress emission reduction measures from the first implementation period, and the resulting emissions reductions. 40 CFR 51.308(g)(1) and (2). A core component of the progress report requirements is an assessment of changes in visibility conditions on the clearest and most impaired days. For second implementation period progress reports, 40 CFR 51.308(g)(3) requires States with Class I areas within their borders to first determine current visibility conditions for each area on the most impaired and clearest days, 40 CFR 51.308(g)(3)(i), and then to calculate the difference between those current conditions and baseline (2000-2004) visibility conditions to assess progress made to date. See 40 CFR 51.308(g)(3)(ii). States must also assess the changes in visibility impairment for the most impaired and clearest days since they submitted their first implementation period progress reports. See 40 CFR 51.308(g)(3)(iii), (f)(5). Since different States submitted their first implementation period progress reports at different times, the starting point for this assessment will vary State by State. Similarly, States must provide analyses tracking the change in emissions of pollutants contributing to visibility impairment from all sources and activities within the State over the period since they submitted their first implementation period progress reports. See 40 CFR 51.308(g)(4), (f)(5). Changes in emissions should be identified by the type of source or activity. The provisions of 40 CFR 51.308(g)(5) also address changes in emissions since the period addressed by the previous progress report and requires States' SIP revisions to include an assessment of any significant changes in anthropogenic emissions within or outside the State. This assessment must explain whether these changes in emissions were anticipated and whether they have limited or impeded progress in reducing emissions and improving visibility relative to what the State projected based on its long-term strategy for the first implementation period. G. Requirements for State and Federal Land Manager Coordination CAA section 169A(d) requires that before a State holds a public hearing on a proposed regional haze SIP revision, it must consult with the appropriate FLM or FLMs; pursuant to that consultation, the State must include a summary of the FLMs' conclusions and recommendations in the notice to the public. Consistent with this statutory requirement, the RHR also requires that States “provide the [FLM] with an opportunity for consultation, in person and at a point early enough in the State's policy analyses of its long-term strategy emission reduction obligation so that information and recommendations provided by the [FLM] can meaningfully inform the State's decisions on the long-term strategy.” 40 CFR 51.308(i)(2). Consultation that occurs 120 days prior to any public hearing or public comment opportunity will be deemed “early enough,” but the RHR provides that in any event the opportunity for consultation must be provided at least 60 days before a public hearing or comment opportunity. This consultation must include the opportunity for the FLMs to discuss their assessment of visibility impairment in any Class I area and their recommendations on the development and implementation of strategies to address such impairment. 40 CFR 51.308(i)(2). For EPA to evaluate whether FLM consultation meeting the requirements of the RHR has occurred, the SIP submission should include documentation of the timing and content of such consultation. The SIP revision submitted to EPA must also describe how the State addressed any comments provided by the FLMs. 40 CFR 51.308(i)(3). Finally, a SIP revision must provide procedures for continuing consultation between the State and FLMs regarding the State's visibility protection program, including development and review of SIP revisions, five-year progress reports, and the implementation of other programs having the potential to contribute to impairment of visibility in Class I areas. 40 CFR 51.308(i)(4). IV. EPA's Evaluation of Ohio's Regional Haze Submission for the Second Implementation Period A. Background on Ohio's First Implementation Period SIP Submission Ohio submitted its regional haze SIP for the first implementation period for 2007-2018 to EPA on December 31, 2008. Based on the failure to submit a complete SIP addressing all elements of 40 CFR 51.308, EPA issued a finding of failure to submit on January 9, 2009. 74 FR 2392, January 15, 2009. On March 11, 2011, Ohio submitted an updated first implementation period regional haze SIP, and EPA finalized a limited approval on May 29, 2012. 77 FR 39177, July 2, 2012. In a separate action, EPA finalized a limited disapproval of Ohio's March 11, 2011, regional haze SIP because of deficiencies arising from the remand of the Clean Air Interstate Rule (CAIR). EPA promulgated a Federal Implementation Plan (FIP) to replace Ohio's reliance on CAIR with the Cross-State Air Pollution Rule (CSAPR). 77 FR 33642, June 7, 2012. On April 14, 2014, Ohio submitted a revision to its March 11, 2011, regional haze SIP and supplemented it on July 27, 2015, to extend the compliance date for the non-EGU BART emission limits for SO 2 , which EPA approved on February 22, 2016. 81 FR 11445, March 4, 2016. On November 30, 2016, Ohio EPA submitted a second revision to change reliance on CAIR to reliance on the CSAPR, which EPA approved on April 30, 2018, converting EPA's limited approval/limited disapproval of Ohio's March 11, 2011, regional haze SIP to a full approval, and withdrawing the FIP provisions that addressed the limited disapproval. See 83 FR 21719, May 10, 2018. The requirements for regional haze SIPs for the first implementation period are contained in 40 CFR 51.308(d) and (e). 40 CFR 51.308(b). Pursuant to 40 CFR 51.308(g), Ohio was also responsible for submitting a five-year progress report as a SIP revision for the first implementation period, which it did on March 11, 2016. EPA approved this five-year progress report as a revision to the Ohio SIP at 40 CFR 52.1870(e) on December 8, 2017 (82 FR 60543, December 21, 2017). B. Ohio's Second Implementation Period SIP Submission and EPA's Evaluation In accordance with CAA sections 169A and the RHR at 40 CFR 51.308(f), Ohio EPA submitted a revision to the Ohio SIP on July 30, 2021, to address its regional haze obligations for the second implementation period, which runs through 2028. Ohio EPA supplemented its SIP submittal on August 6, 2024. Ohio initiated an FLM consultation process and provided three public comment periods on the regional haze SIP for the second implementation period. The first public comment period on the initial SIP revision ran from May 10, 2021 through June 28, 2021, and a public hearing was held on June 14, 2021. The second public comment period, limited to proposed emission limitations for three sources, ran from January 16, 2024 through March 18, 2024, and a public hearing was held on March 18, 2024. The third public comment period, regarding draft administrative orders effectuating the proposed emission limitations for the three sources, ran from June 6, 2024 through July 8, 2024, and a public hearing was held on July 9, 2024. Ohio received and responded to comments from FLMs and the public. Ohio included the comments and responses in Appendices K1-K4, L1-L4, M1-M3, N1-N2, O, and P9-P12 of its July 30, 2021, submission and in Appendices C3, C4, C7, C8, E2, E3, F2, F3, F4, F5, and G of its August 6, 2024, supplement. The following sections describe Ohio's SIP submission, including Ohio's assessment of progress made since the first implementation period in reducing emissions of visibility impairing pollutants, and the visibility improvement progress at nearby Class I areas. Also described is Ohio's August 6, 2024 supplement, which provides administrative orders effectuating emission limitations for three sources to be incorporated into the regulatory portion of Ohio's SIP at 40 CFR 52.1870(d). This action also contains EPA's evaluation of Ohio's submission against the requirements of the CAA and the RHR for the second implementation period of the regional haze program. C. Identification of Class I Areas The provisions of section 169A(b)(2) of the CAA require each State in which any Class I area is located or “the emissions from which may reasonably be anticipated to cause or contribute to any impairment of visibility” in a Class I area to have a plan for making reasonable progress toward the national visibility goal. The RHR implements this statutory requirement at 40 CFR 51.308(f), which provides that each State's plan “must address regional haze in each mandatory Class I Federal area located within the State and in each mandatory Class I Federal area located outside the State that may be affected by emissions from within the State,” and (f)(2), which requires each State's plan to include a long-term strategy that addresses regional haze in such Class I areas. Ohio has no Class I areas within its borders that are among the 156 mandatory Class I Federal areas where EPA deemed visibility to be an important value. See 40 CFR part 81, subpart D. Thus, Ohio EPA only considered out-of-state mandatory Class I Federal areas covered under the RHR. Ohio is a member of LADCO and participated in its regional approach for developing a strategy for making reasonable progress towards the national visibility in the northern Midwest Class I areas. Ohio EPA reviewed technical analyses conducted by LADCO to determine what Class I areas outside the State are affected by Ohio emission sources. For the second regional haze implementation period, LADCO used the Comprehensive Air Quality Model with extensions Particulate Matter Source Apportionment Tool (PSAT). LADCO tagged States and regions as well as individual point sources and inventory source groups to apportion emissions to States and regions. LADCO assessed relative visibility impacts in 2028 by projecting representative emissions inventories and known emission controls from 2016. 31 A group of RPOs, States, and EPA established 2016 as the base year for a national air quality modeling platform for future ozone, PM 2.5 , and regional haze SIP development because of fairly typical ozone conditions and wildfire conditions. 32 LADCO relied upon EPA's inventory estimates for 2016 and 2028 for most emission sectors as described in EPA's September 19, 2019, “Availability of Modeling Data and Associated Technical Support Document for the EPA's Updated 2028 Visibility Air Quality Modeling,” (EPA's Updated 2028 Visibility Air Quality Modeling). 33 For Electric Generating Units (EGUs), LADCO used forecasts from the Eastern Regional Technical Advisory Committee (ERTAC) based on continuous emissions monitoring data from 2016 instead of the Integrated Planning Model used in EPA's 2016 modeling platform. LADCO also incorporated State-reported changes to EGUs received through September 2020 to estimate 2028 EGU emissions. 31 See appendix A of Ohio EPA's SIP submittal. Details of the analysis and source-apportioned visibility contributions at Class I areas within the LADCO region for regional haze second planning period are documented in LADCO's modeling technical support document (TSD), dated June 17, 2021. 32 See “Base Year Selection Workgroup Final Report,” produced by the Inventory Collaborative Base Year Selection Workgroup, April 5, 2017. https://www.wrapair2.org/pdf/2017-12-12_Base_Year_Selection_Report_V1.1.pdf. 33 EPA, Office of Air Quality Planning and Standards, “Availability of Modeling Data and Associate Technical Support Document for EPA's Updated 2028 Visibility Air Quality Modeling,” September 19, 2019. https://www.epa.gov/sites/default/files/2019-10/documents/updated_2028_regional_haze_modeling-tsd-2019_0.pdf Ohio identified affected Class I areas where progress toward natural visibility conditions may be impacted by emissions from sources in Ohio. Ohio reviewed technical analyses conducted by LADCO and other RPOs to determine which Class I areas outside the State are affected by Ohio emission sources. For the second implementation period, Ohio used LADCO's modeled emissions projections for 2028 as a framework to assess the potential for changes in visibility-impairing emissions. Like the metrics used in the first implementation period, 34 Ohio EPA retained the 2 percent light extinction threshold for determining Ohio's contribution to visibility at Class I areas. LADCO's modeling results showed that a 2 percent light extinction threshold, when applied to all six LADCO States and seven other States, would account for 92 percent or more of the total light extinction at the Class I areas located in the LADCO States on the most impaired days. When applying the 2 percent total light extinction threshold, Ohio identified 17 Class I areas affected by Ohio emission sources for the second implementation period. These Class I areas, along with Ohio's 2028 projected contributions to visibility impairment, are: Sipsey Wilderness Area in Alabama (2.3 percent); Cohutta Wilderness Area in Georgia (2.1 percent); Mammoth Cave National Park in Kentucky (5.9 percent); Seney Wilderness Area in Michigan (2.0 percent); Great Gulf Wilderness Area (2.5 percent) and Presidential Range—Dry River Wilderness in New Hampshire (2.5 percent); Brigantine Wilderness Area in New Jersey (4.3 percent); Linville Gorge (3.8 percent) and Shining Rock Wilderness Areas (2.8 percent) and Swanquarter National Wildlife Refuge in North Carolina (3.6 percent); Great Smoky Mountains National Park (2.3 percent) and Joyce-Kilmer-Slickrock Wilderness Area in Tennessee (2.3 percent); Lye Brook Wilderness Area in Vermont (3.3 percent); James River Face Wilderness Area (6.5 percent) and Shenandoah National Park in Virginia (10.5 percent); and Dolly Sods (13.1 percent) and Otter Creek Wilderness Areas (13.1 percent) in West Virginia. 35 Based on the adjusted URP glidepaths for each of these Class I areas provided in EPA's Updated 2028 Visibility Air Quality Modeling, visibility conditions, as depicted in Table 1 of Ohio's SIP submission, are projected to be below their respective glidepaths in 2028. Visibility conditions at Dolly Sods and Otter Creek Wilderness Areas, the Class I areas impacted most significantly by Ohio, are projected to be approximately 5 dv below their respective glidepaths in 2028. 34 See Section III.2. and Appendix A of Ohio's SIP submission for LADCO's technical support document and supporting materials. 35 The list of Class I areas impacted by Ohio, including the 2028 projections for visibility on the 20 percent most impaired days and Ohio's contribution, is found in Table 1 of Ohio's SIP submission. D. Calculations of Baseline, Current, and Natural Visibility Conditions; Progress to Date; and the Uniform Rate of Progress The provisions of 40 CFR 51.308(f)(1) require States to determine the following for “each mandatory Class I Federal area located within the State”: baseline visibility conditions for the most impaired and clearest days, natural visibility conditions for the most impaired and clearest days, progress to date for the most impaired and clearest days, the differences between current visibility conditions and natural visibility conditions, and the URP. This section also provides the option for States to propose adjustments to the URP line for a Class I area to account for visibility impacts from anthropogenic sources outside the United States and/or the impacts from wildland prescribed fires that were conducted for certain, specified objectives. 40 CFR 51.308(f)(1)(vi)(B). Ohio has no mandatory Class I areas within its borders to which the requirements of the visibility protection program apply in 40 CFR part 81, subpart D, and therefore, 40 CFR 51.308(f)(1) and its requirements do not apply. E. Long-Term Strategy for Regional Haze Each State having a Class I area within its borders or emissions that may affect visibility in a Class I area must develop a long-term strategy for making reasonable progress towards the national visibility goal. CAA 169A(b)(2)(B). As explained in the Background section of this notice, reasonable progress is achieved when all States contributing to visibility impairment in a Class I area are implementing the measures determined through application of the four statutory factors to sources of visibility impairing pollutants to be necessary to make reasonable progress. 40 CFR 51.308(f)(2)(i). Each State's long-term strategy must include the enforceable emission limitations, compliance schedules, and other measures that are necessary to make reasonable progress. 40 CFR 51.308(f)(2). All new ( i.e., additional) measures that are the outcome of four-factor analyses are necessary to make reasonable progress and must be in the long-term strategy. If the outcome of a four-factor analysis and other measures necessary to make reasonable progress is that no new measures are reasonable for a source, that source's existing measures are necessary to make reasonable progress, unless the State can demonstrate that the source will continue to implement those measures and will not increase its emission rate. Existing measures that are necessary to make reasonable progress must also be in the long-term strategy. In developing its long-term strategies, a State must also consider the five additional factors in 40 CFR 51.308(f)(2)(iv). As part of its reasonable progress determinations, the State must describe the criteria used to determine which sources or group of sources were evaluated ( i.e., subjected to four-factor analysis) for the second implementation period and how the four factors were taken into consideration in selecting the emission reduction measures for inclusion in the long-term strategy. 40 CFR 51.308(f)(2)(iii). 1. Selection of Sources for Analysis This section summarizes how Ohio EPA's SIP submission addressed the requirements of 40 CFR 51.308(f)(2)(i) of the Regional Haze Rule. Specifically, it describes the criteria Ohio EPA used to determine the selection of sources or groups of sources it evaluated for an analysis of potential emission control measures. States may rely on technical information developed by the RPOs of which they are members to select sources for four-factor analysis and to conduct that analysis, as well as to satisfy the documentation requirements under 40 CFR 51.308(f). In selecting sources to determine possible additional control measures during the second planning period, Ohio EPA considered NO X , SO 2 , PM 2.5 , and NH 3 , which are direct or precursor pollutants than can impair visibility. Based on EPA's Updated 2028 Visibility Air Quality Modeling showing that the EGU and non-EGU point source sectors contribute 37 to 76 percent of the visibility impact at Class I areas impacted by Ohio sources, Ohio found it reasonable to focus on point sources for the second implementation period. To assist States with their source selection, LADCO generated source lists based on total process-level emissions (Q) divided by distance (d) to the nearest Class I area, where Q/d was used as a surrogate quantitative metric of visibility impact. Total emissions of Q refer to the sum of NO X , SO 2 , PM 2.5 , and NH 3 . The National Emissions Inventory Collaborative 2016 alpha inventory was selected by participants in the LADCO Regional Haze Technical Workgroup for the Q/d analysis in 2018 as the best available inventory at that time. LADCO identified unit level sources above Q/d thresholds of 1, 4, and 10, providing key information the States could use to select potential sources to be subject to the four-factor analysis. For details on the data and methods used in the Q/d analysis, see LADCO's October 14, 2020, technical memorandum “Description of the Sources and Methods Used to Support Q/d Analysis for the 2nd Regional Haze Planning Period” and section 5 of LADCO's June 17, 2021, Technical Support Document “Modeling and Analysis for Demonstrating Reasonable Progress for the Regional Haze Rule 2018-2028 Planning Period,” (LADCO's 2021 TSD) contained in appendix A and B of Ohio's SIP submission. In addition to LADCO's Q/d analysis, Ohio EPA compared point source inventories from the 2017 National Emissions Inventory (NEI) and the 2018 Ohio Emissions Inventory System (EIS) 36 with the emissions used in LADCO's analysis. For sources where Q was greater than 500 tons per year for the sum of NO X , SO 2 , PM 2.5 , and NH 3 in either the emissions data from the 2016 alpha inventory, 2017 NEI, or 2018 Ohio EIS, Ohio calculated updated Q/d values to determine if any additional sources would be identified beyond those in LADCO's list. However, the process did not result in the identification of any additional sources. As such, Ohio EPA relied upon the Q/d information developed by LADCO to select emission units for further analysis. 36 Ohio EPA's Emission Inventory System (EIS) is a compilation of data describing emissions from different sources of air pollution. Ohio EPA's EIS data and reports are available at https://epa.ohio.gov/divisions-and-offices/air-pollution-control/reports-and-data/emision-inventory-system. Ohio EPA began by using a unit Q/d greater than 5 as a threshold for selecting sources for further evaluation. Then on May 12, 2020, and October 2, 2020, Ohio received lists of sources recommended for four-factor analyses that were prepared by NPS and USFS, respectively, and are included in Appendices K2, K3, and K4 in Ohio's SIP submission. The list from NPS identified facilities with emissions comprising 80 percent of Ohio's total Q based on only SO 2 and NO X that covered a mix of years from 2014 to 2017, whereas the list from USFS identified facilities with a Q/d greater than 8 as calculated by LADCO with the addition of VOC to represent 80 percent of Ohio's total Q at the closest Class I area to Ohio managed by USFS, the Dolly Sods Wilderness Area. While Ohio EPA's primary approach was to consider Q/d on an individual unit basis, the FLM's consideration of Q/d on a facility-wide basis prompted Ohio to include facility-wide contribution as an additional consideration. As such, Ohio EPA added a secondary selection criterion for facility-wide Q/d and developed a two-tiered approach to capture significant point source emissions in Ohio for further analysis. Ohio EPA's first tier identified individual units with a Q/d greater than 5 for a potential four-factor analysis. For facilities with Q/d greater than 10, Ohio EPA's second tier selected individual units with Q/d greater than 4 for a potential four-factor analysis. This secondary selection criteria resulted in the addition of two units to Ohio EPA's initial list for a total of 38 units at 16 facilities, accounting for 73 percent of the total Q for all sources in Ohio with Q greater than 0.1 tons per year, including 80 percent of SO 2 , 57 percent of NO X , 47 percent of PM 2.5 , and 23 percent of NH 3 . Using this two-tiered approach, Ohio EPA identified the following facilities and units: Avon Lake Power Plant Unit B012; Cardinal Power Plant Units B001, B002, B009; Carmeuse Lime, Inc.—Maple Grove Operations Units P003, P004; Conesville Power Plant Units B004, B007, B008; City of Orrville Department of Public Utilities Units B001, B004; Dover Municipal Light & Power Plant Unit B004; DP&L, J.M. Stuart Generating Station Units B001, B002, B003, B004; DP&L, Killen Generating Station Unit B001; FirstEnergy Generation LLC—Bay Shore Plant Unit B006; General James M. Gavin Power Plant Units B003, B004; Haverhill Coke Company LLC Unit P902; Miami Fort Power Station Units B015, B016; Ohio Valley Electric Corp.—Kyger Creek Station Units B001, B002, B003, B004, B005; P.H. Glatfelter Company—Chillicothe Facility Units B002, B003; W.H. Sammis Plant Units B007, B008, B009, B010, B011, B012, B013; and Zimmer Power Station Unit B006. Ohio then refined the list above by considering whether units had permanently shut down, accepted a commitment to permanently shut down by 2028, converted to natural gas only, converted to limited use, accepted new emission limits, or had existing effective controls such that, in all these cases, a full four-factor analysis would likely result in a conclusion that no further controls are necessary. For units accepting a commitment to permanently shut down by 2028 or to comply with new emission limits by 2025, Ohio issued Director's Final Findings and Orders (DFFO) and requested they be incorporated into its SIP to ensure that the measures become permanent and federally enforceable. For units that had already permanently shut down or had converted to natural gas or limited use, Ohio ensured measures were permanent and federally enforceable through Ohio's permitting process under its SIP approved Permit to Install (PTI) program and its title V program. Ohio has PTI rules under Ohio Administrative Code (OAC) Chapter 3745-31 that have been approved into Ohio's SIP at 40 CFR 52.1870 as well as a federally approved title V operating permit program set forth at 40 CFR part 70. When an owner or operator certifies a permanent shutdown and notifies Ohio EPA, the unit cannot resume operation without being considered a new source subject to the Federal New Source Review (NSR) requirements. Ohio's rules at OAC 3745-31 prevent installation or modification and subsequent operation of a new source without a new permit. Of the emission units that had already permanently shut down during the second implementation period, 12 met Ohio's two-tier Q/d source selection criteria. For Conesville Power Plant, coal-fired boiler B007 permanently shut down on May 31, 2019, and coal-fired boilers B004 and B008 permanently shut down on May 31, 2020. DP&L—J.M. Stuart Generating Station permanently shut down its coal-fired boiler B001 on September 30, 2017, and boilers B002, B003, and B004 on June 1, 2018. DP&L—Killen Generating Station also shut down its coal-fired boiler B001 on June 1, 2018. W.H. Sammis Plant permanently shut down its coal-fired boilers B007, B008, B009, and B010 on May 31, 2020. 37 37 Each of these units have been certified by the source owner or operator as retired under the provisions for Retired Unit Exemptions in the Acid Rain Program and/or CSAPR NO X and SO 2 Trading Programs. The Retired Unit Exemption prohibits these units from emitting SO 2 , NO X , or both starting on the day the exemption takes effect. See 40 CFR 72.8, 40 CFR 97.405, 40 CFR 97.505, 40 CFR 97.605, CFR 97.705, 40 CFR 97.805. Copies of the Retired Unit Exemption forms for each of these units are included in the docket. Also included in the docket is a copy of the list of retired generators from the Pennsylvania-New Jersey-Maryland Interconnection (PJM) Regional Transmission Organization (RTO), which includes each of these units as well. Of the units that met Ohio's Q/d source selection criteria but had not yet permanently shut down by Ohio's SIP submittal date in 2021, 3 units accepted enforceable commitments to permanently shut down by 2028: Miami Fort Power Station's coal-fired boilers B015 and B016 and Zimmer Power Station's coal-fired boiler B006. On September 29, 2020, the owner of Miami Fort and Zimmer Power Stations announced plans to permanently shut down these units. In lieu of a four-factor analysis, Ohio determined that these permanent shutdowns were necessary for reasonable progress. As such, on July 9, 2021, Ohio EPA issued DFFOs which established enforceable commitments for the shutdown of these three units by January 1, 2028, and requested that the DFFOs be approved into Ohio's SIP at 40 CFR 52.1870(d) for EPA approved State source-specific requirements. 38 38 Appendix C of Ohio's July 30, 2021, SIP revision contains the DFFOs issued for the Miami Fort and Zimmer Power Stations. Units that met Ohio's Q/d source selection criteria but have since converted from coal to natural gas or limited use include the non-EGUs at P.H. Glatfelter Company—Chillicothe Facility Units B002 and B003 as well as the EGUs at the City of Orrville Department of Public Utilities Units B001 and B004. P.H. Glatfelter Company, now Pixelle Specialty Solutions LLC, converted units B002 and B003 to natural gas on May 31, 2016, and September 6, 2016, respectively. The conversions were part of a strategy to address BART requirements under the first implementation planning period as well as Boiler Maximum Achievable Control Technology (Boiler MACT) under permit PTI P0118906. Following the conversions, SO 2 emissions from P.H. Glatfelter Company units B002 and B003 decreased from 2,873 tons per year (tpy) and 5,708 tpy in 2016 to 1 tpy and 1 tpy in 2018, respectively, and NO X emissions decreased from 412 tpy and 691 tpy in 2016 to 134 tpy and 195 tpy in 2018, respectively. Similarly, the City of Orrville Department of Public Utilities converted B004 to natural gas on December 20, 2016, and converted B001 to a limited use boiler beginning January 31, 2017, to comply with requirements of Boiler MACT and the Data Requirements Rule (DRR) for the SO 2 NAAQS designation process under permit PTI P0124959 and title V Permit No. P0125633. Following the conversions, SO 2 emissions from B001 and B004 decreased from 3,846 tpy and 3,030 tpy in 2016 to 275 tpy and 0 tpy in 2018, respectively, and NO X emissions decreased from 647 tpy and 510 tpy in 2016 to 57 tpy and 20 tpy in 2018, respectively. For both facilities, reversing the conversion back to coal or fulltime use would require approval for a modification of its federally enforceable permit. Beyond the 15 units shutting down and 4 units converting to natural gas or limited use as described above, Ohio EPA also evaluated 13 units at 5 facilities for existing effective controls. As explained in EPA's July 8, 2021, Clarifications Memo (section 4.1), a “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, 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 its long-term strategy or SIP in order to prevent future emission increases. The units that Ohio identified with existing effective controls are FirstEnergy Generation LLC—Bay Shore Plant Unit B006; Haverhill Coke Company LLC Unit P902; and W.H. Sammis Plant Units B011, B012, B013. Ohio provided a weight-of-evidence demonstration as each unit has consistently implemented their existing measures and have achieved, using those measures, a reasonably consistent emission rate. With historical data from 2016 through 2019 showing reasonably consistent emission rates and 2028 projections from LADCO showing rates consistent with 2016, Ohio demonstrated that NO X and SO 2 emission rates for these units are not expected to increase in the future. As such, except where expressly noted below for Cardinal Power Plant, Ohio Valley Electric Corp.—Kyger Creek Station, and General James M. Gavin Power Plant, Ohio determined the existing measures are not necessary to make reasonable progress or prevent future emission increases and, thus, do not need to be included in the regulatory portion of the SIP. FirstEnergy Generation LLC—Bay Shore Plant Unit B006 is a fluidized bed boiler with limestone injection and a baghouse. The operational nature of this process, whereby calcium sulfate is formed in the boiler and is captured in the baghouse, results in approximately 94 percent removal of SO 2 and a SO 2 emission rate of 0.34 pounds per million British thermal units (lbs/MMBtu) or less. Unit B006 operates with low combustion temperatures along with very low nitrogen content petroleum coke fuel, which have resulted in NO X emission rates of 0.08 lbs/MMBtu and less from 2016 to 2019. The facility's title V permit contains both SO 2 and NO X emission limits as well as a requirement for 90 percent SO 2 reduction. Given the reasonably consistent emission rates, the permitted emission limitations, and the operational nature of the process in which SO 2 is inherently controlled and NO X has a low formation potential, Ohio determined that B006 is effectively controlled and that a full four-factor analysis would likely result in the conclusion that no further controls are necessary for reasonable progress. Haverhill Coke Company LLC Unit P902 is a coke battery with SO 2 controls installed in 2007 with design control efficiency of 92 percent. Under the terms of a Federal consent decree entered in 2014 and amended in 2018, 39 portions of which were incorporated into the facility's title V permit, Heat Recovery Steam Generators were installed on P902. This resulted in further SO 2 emission reductions from 1,183 tpy in 2016 to 777 tpy in 2019. With SO 2 controls demonstrating greater than 90 percent effectiveness, title V permit limits, and consent decree requirements resulting in decreasing emissions, Ohio EPA determined that P902 is effectively controlled. 39 United States of America, the State of Illinois and the State of Ohio v. Gateway Energy & Coke Company, LLC, Haverhill Coke Company, LLC and Suncoke Energy, Inc. (S.D. Illinois Case No. 3:13-cv-00616-DH-SCW), entered on November 10, 2014, as amended on June 5, 2015, and July 10, 2018. While W.H. Sammis Plant permanently shut down coal-fired Units B007, B008, B009, and B010 in 2020 as noted above, there are three remaining coal-fired Units B011, B012, B013 operating with an SO 2 emission limit of 0.130 lbs/MMBtu under the terms of a Federal consent decree, 40 which was incorporated into the facility's title V permit. For NO X control, a selective non-catalytic reduction (SNCR) system was installed on B011 in 2006, and selective catalytic reduction (SCR) systems with at least 90 percent control efficiency were installed on B012 and B013 in 2010, all of which must be operated continuously under the Federal consent decree. Flue Gas Desulfurization (FGD) systems with 95 percent SO 2 control efficiency were installed on each unit in 2010. With SO 2 and NO X controls achieving greater than 90 percent control efficiency, title V SO 2 permit limits below the 0.2 lbs/MMBtu limit in the Mercury and Air Toxics Standards for coal-fired EGUs, and reasonably consistent emission rates showing no increasing future trends, Ohio EPA determined that B012 and B013 are effectively controlled as described in the 2019 Guidance. For B011 with a Q/d of 5, Ohio determined that although the existing SNCR does not meet the examples of in the 2019 Guidance, its year-round operation and an emission rate consistently between 0.13 and of 0.15 lbs/MMBtu with no future projected increase indicate that a full four-factor analysis would likely result in the conclusion that no further controls are necessary. 40 United States of America, et al. v. Ohio Edison Company, et al., U.S. District Court for the Southern District of Ohio, Eastern Division, Civil Action No. C2-99-1181, entered on March 18, 2005. Ohio EPA provided a link to the Consent Decree, a copy of which is provided in the docket. Of the 13 units that Ohio initially identified with existing effective controls, there were 8 units for which Ohio later provided, in its August 6, 2024, supplement, new enforceable measures necessary for reasonable progress as described below: Cardinal Power Units B001, B002, B009; and Ohio Valley Electric Corp.—Kyger Creek Station Units B001, B002, B003, B004, B005. Cardinal Power Plant operates three coal-fired boilers: B001, B002, and B009. For NO X control, SCRs with approximately 90 percent control efficiency were installed on all three boilers in 2003. The SCRs must be continuously operated under the terms of their PTI permits and a Federal consent decree. 41 From 2016-2019, the SCRs have consistently achieved NO X emission rates of 0.09 lbs/MMBtu and lower. For SO 2 control, FGD systems with approximately 95 percent control efficiency were installed on B001 in 2008, on B002 in 2007, and on B009 in 2011. The FGD systems must be operated continuously under the terms of the same Federal consent decree that were incorporated into their PTI permits. The permitted SO 2 emission limits were set at 1.056 lbs/MMBtu for B001 and B002 as well as 0.66 lbs/MMBtu for B009. From 2016-2019, the FGDs have consistently achieved SO 2 emission rates at or below 0.24 lbs/MMBtu for B001, 0.27 lbs/MMBtu for B002, and 0.15 for B009. With FGD systems achieving at least 90 percent effectiveness that were installed since 2007 and emission rates that were reasonably consistent from 2016 to 2019 with no projected increase, Ohio determined that the units were effectively controlled as described in the 2019 Guidance. 41 United States, et al. v. American Electric Power Service Corp., et al., S.D. Ohio Civil Action Nos. C2-99-1250, C2-99-1182, C2-05-360, and C2-04-1098 entered on December 10, 2007, and substantively modified on July 17, 2019 (AEP Consent Decree). Ohio provided a link to the AEP Consent Decree and modification, which are included in the docket. Subsequently, on August 6, 2024, Ohio EPA submitted a supplement to its July 30, 2021, Regional Haze SIP after going through FLM consultation and two public notice and comment periods. Units B001, B002, and B009 combined are subject to a SO 2 emission limit of 4,858.75 lbs/hour as a rolling, thirty-day average that was derived as a part of the attainment demonstration for the Steubenville, OH-WV 2010 1-hour SO 2 nonattainment area. The SO 2 limit became effective on July 5, 2019 and was approved into Ohio`s SIP, effective November 21, 2019. 42 84 FR 56385, October 22, 2019. Ohio EPA submitted its August 6, 2024, supplement to incorporate the SO 2 limit through a DFFO into the SIP for Regional Haze purposes and to ensure reasonable progress by maintaining the existing measures. 42 For the technical justification and development methodology behind the SO 2 limit, Ohio EPA provided a link to its June 2019 Redesignation Request and Maintenance Plan for the Ohio Portion of the Steubenville, OH-WV 1-hour SO 2 Nonattainment Area, a copy of which is provided in the docket. Ohio Valley Electric Corp.—Kyger Creek Station operates five coal-fired boilers: B001, B002, B003, B004, and B005. For SO 2 control, FGD systems operating year-round with 97 percent control efficiency were installed on B001 and B002 in 2012 and on B003, B004, and B005 in 2011. Under its title V permit, the facility demonstrates compliance with the Mercury and Air Toxics Standard through the SO 2 emission limit of 0.2 lbs/MMBtu. For NO X control, SCRs with 70-90 percent efficiency were installed on B001 and B002 in 2002 and on B003, B004, and B005 in 2003. Together with overfire air systems, the SCRs achieve an average 87 percent NO X control efficiency. Ohio EPA recognized that the SCRs do not meet the 90 percent control efficiency examples of effectively controlled units in the 2019 Guidance and that NO X emission control is limited by ammonia slip and mercury oxidation that jeopardize compliance with the Mercury and Air Toxics Standards. Since Ohio submitted its SIP in 2021, Kyger Creek enhanced its preventative maintenance and made process improvements to increase the reliability of the urea injection system. This is expected to increase both seasonal and year-round NO X removal efficiency. To ensure that these recent improvements are sustained going forward, Ohio EPA adopted NO X emission limits of 0.4 lbs/MMBtu on a 720-operating rolling hourly average for each stack: Common Stack 12 for combined emissions from B001 and B002 and Common Stack 35 for combined emissions from B003, B004, and B005. Both stacks are equipped with continuous emissions monitoring systems. The limits were developed by analysis of NO X emission rates from 2018 to 2023, prior to and following system improvements, and represent a reduction from the previous permitted limit of 0.84 lbs/MMBtu. As such, in the supplement that Ohio EPA submitted on August 6, 2024, Ohio requested to incorporate the new NO X emission limit of 0.4 lbs/MMBtu for both Common Stacks 12 and 35 into Ohio's SIP at 40 CFR 52.1870(d) through a DFFO for Regional Haze purposes to ensure reasonable progress by maintaining the recent improvements. After refining the list of 38 units identified by Ohio's Q/d source selection threshold and addressing 32 of those as described above, Ohio EPA provided four-factor analyses for the remaining 6 units at the following 4 facilities: Avon Lake Power Plant Unit B012; Carmeuse Lime, Inc.—Maple Grove Operations Units P003 and P004; Dover Municipal Light & Power Plant Unit B004; and General James M. Gavin Power Plant Units B003 and B004. The emission units that Ohio selected for a four-factor analysis are described below. Consistent with the first regional haze implementation period, Ohio EPA focused on NO X and SO 2 emissions in considering potential additional control measures at these four facilities. As demonstrated by the analysis in LADCO's Technical Support Document of the IMPROVE monitoring data, the NO X and SO 2 emissions lead to the formation of the particulate species of nitrate and sulfate that currently contribute more to visibility impairment in the LADCO Class I Areas than PM 2.5 , NH 3 , and VOC. The LADCO Class I Areas consist of Boundary Waters Canoe Area Wilderness and Voyageurs National Park in Minnesota, as well as Isle Royale National Park and Seney Wilderness Area in Michigan. Additionally, in Table 20 of its submittal, Ohio EPA provided 2017 NEI data for Ohio point sources, showing smaller VOC, PM, and NH 3 emissions relative to NO X and SO 2 emissions. For this reason, Ohio EPA chose to focus on reducing emissions of NO X and SO 2 , which the 2019 Guidance recommended would be a reasonable approach for the second implementation period. See 2019 Guidance at page 12. Nevertheless, Ohio considered emissions from each of the regional haze precursors NO X , SO 2 , PM 2.5 , NH 3 and VOC in the source selection process. As shown in Table 4 of its submittal, the sources meeting Ohio's primary and secondary Q/d selection criteria account for 38 units at 16 facilities, representing 80 percent of SO 2 emissions, 57 percent of NO X emissions, 47 percent of PM 2.5 emissions, and 23 percent of NH 3 emissions for all sources with a sum of SO 2 , NO X , PM 2.5 , and NH 3 emissions from 2016 greater than 0.1 tpy. The background on each of the 6 units selected for a four-factor analysis is described below. Avon Lake Power Plant Avon Lake Power Plant is an EGU, and Unit B012 is a 6,040 MMBtu/Hour pulverized coal-fired boiler that was installed in 1970. For NO X control, B012 is equipped with low-NO X cell burners and overfire air. For SO 2 control, Avon Lake Power Plant accepted a federally enforceable SO 2 emissions limit of 9,600 lbs/hr on a 1-hour average basis for all SO 2 -emitting sources at the facility (B010, B012, B013, B015, and B016) to satisfy requirements under the DRR for the 2010 SO 2 NAAQS designation process. 43 See 83 FR 40723, August 16, 2018. The facility's title V permit P0085253, effective April 18, 2017, contains a SO 2 permit limit for B012, which was reduced from the previous limit of 4.65 lbs/MMBtu to a new combined SO 2 permit limit on B010 and B012 of 1.59 lbs/MMBtu as a rolling, 30-day average. To comply with the new SO 2 emissions limits, the facility switched to a blend of Western Bituminous and Powder River Basin coal in 2016, which contributed to reductions in annual SO 2 emissions for B012 from 8,862 tpy in 2016 to 1,597 tpy in 2019, lowered the SO 2 emission rate from 1.60 lbs/MMBtu in 2016 to 0.70 lbs/MMBtu in 2019, and reduced Q/d from 32 in 2016 to 7 in 2019. 43 Ohio's January 13, 2017, submittals for the 2010 SO 2 NAAQS DRR describing the AERMOD Modeling Results for Avon Lake Power Plant with the derivation of the limits of 1.59 lbs/MMBtu and 9,600 lbs/hour as the resulting critical emissions value is available at https://www.epa.gov/so2-pollution/so2-data-requirements-rule-january-13-2017-state-submittals-ohio. Carmeuse Lime, Inc.—Maple Grove Operations Carmeuse Lime, Inc.—Maple Grove Operations is a lime manufacturing plant. Unit P003 and Unit P004 both consist of a rotary kiln and cooler as well as a shared stack for emissions. P003 and P004 burn coal, petroleum coke, and/or natural gas. For PM control, both units have baghouses, however, there are no add-on controls for SO 2 or NO X . Although both units were subject to a best available control technology analysis under the Federal PSD program in 2002-2003 when lime manufacturing operations were restarted, no add-on control technologies for NO X or SO 2 were found to be cost-effective. However, SO 2 at both units is inherently controlled when calcium-rich lime kiln dust chemically absorbs the SO 2 in the flue gas, which is then removed in the baghouse. NO X emissions at both units are controlled by good combustion practices. Limits on SO 2 and NO X are included in the facility's title V Permit P0125171. The permit includes a maximum sulfur content limit for fuel of 5.50 percent for coal and 6.50 percent for coke by weight. P003 and P004 are subject to SO 2 limits of 1,102 lbs/hour and 4,826.80 tons per rolling, 12-month period. P003 and P004 are also subject to NO X limits of 1,234.90 lbs/hour and 5,408.90 tons per rolling 12-month period. Dover Municipal Light & Power Plant Dover Municipal Light & Power Plant is a coal-fired electrical generating plant. Unit B004 is a 247 MMBtu/hour coal-fired stoker boiler that was installed in 1962 that uses natural gas as a backup fuel. Under title V Permit P0090810, B004 is subject to SO 2 emissions limit of 4.60 lbs/MMBtu. General James M. Gavin Power Plant General James M. Gavin Power Plant is a coal-fired electrical generating plant. Unit B003 and Unit B004 are both 11,936 MMBtu/hr pulverized coal-fired, dry-bottom boilers installed in 1974. For SO 2 , wet FGD systems with 95 percent control efficiency were installed on B003 in 1994 and on B004 in 1995. NO X emissions for B003 and B004 are controlled through the use of low NO X burners and SCR, achieving 91 percent control efficiency. The FGDs and SCRs are operated continuously under the terms of the facility's title V Permit P0089258 and the Federal AEP Consent Decree. A federally enforceable SO 2 emission limit of 7.41 lbs/MMBtu applies to both B003 and B004 under the title V permit. From 2016 to 2019, SO 2 emission rates have ranged from 0.27 to 0.37 lbs/MMBtu for B003 and 0.29 to 0.39 lbs/MMBtu for B004, while NO X emission rates have remained between 0.10 and 0.11 for both units during the same time period. 2. Emission Measures Necessary To Make Reasonable Progress The provisions of 40 CFR 51.308(f)(2)(i) require States to evaluate and determine the emission reduction measures that are necessary to make reasonable progress by applying the four statutory factors to sources in a control analysis. The emission reduction measures that are necessary to make reasonable progress must be included in the long-term strategy. 40 CFR 51.308(f)(2). Ohio EPA's four-factor analyses are described below for each of the 6 units identified through its Q/d source selection process. This includes units that had not already permanently shut down, accepted an enforceable commitment to permanently shut down or comply with new limits, converted to natural gas or limited use, or had existing effective controls. Avon Lake Power Plant Avon Lake Power Plant Unit B012 was selected for a four-factor analysis based on 2016 emissions resulting in a Q/d of 32. Avon Lake evaluated B012 for both NO X and SO 2 controls. Avon Lake evaluated wet FGD and a spray dryer absorber (SDA) for SO 2 control. Capital costs were estimated at $417,000,000 for SDA and $483,000,000 for wet FGD. Annual operating costs were estimated at $44,500,000 for SDA and $51,600,000$ for wet FGD. Based on a remaining useful life of either 20 or 30 years and retrofit factors of 1.2 and 1, the cost effectiveness was estimated at $19,500/ton and $22,600/ton for wet FGD for 2,284 tpy in potential emission reductions from either control option. For NO X control, Avon Lake evaluated SNCR and SCR with capital costs ranging from $13,000,000 for SNCR to $191,000,000 for SCR, while annual operating costs were estimated at $1,679,100 for SNCR and $25,600,000 for SCR. Cost effectiveness was estimated at $10,200/ton for SNCR for 164 tpy in potential emission reductions and $26,700/ton for SCR for 959 tpy in reductions. Installation time was estimated at 5 years for SO 2 controls and 2 to 5 years for SNCR and SCR, respectively. Impacts from energy requirements, solid waste, and ammonia usage were also evaluated. Carmeuse Lime, Inc.—Maple Grove Operations Carmeuse Lime, Inc.—Maple Grove Operations Units P003 and P004 were selected for a four-factor analysis. The evaluation of SO 2 controls at Units P003 and P004 included conditioning tower slurry injection, DSI, and wet scrubbers. Capital costs for each unit were estimated at $14,437,783 for conditioning tower slurry injection, $16,960,653 for DSI, and $23,784,927 for wet scrubbers. Annual costs were estimated at $3,982,597 for conditioning tower slurry injection, $9,140,819 for DSI, and $6,305,184 for wet scrubber. The cost effectiveness values at Units P003 and P004, respectively, were estimated for conditioning tower slurry injection at $3,266 and $3,274/ton, DSI at $5,857 and $5,862/ton, and wet scrubbing at $4,506 and 4,043/ton SO 2 . Potential SO 2 emission reductions for each unit P003 and P004, respectively, were 1,221 and 1,216 tpy for conditioning tower slurry injection, 1,566 and 1,559 tpy for DSI, and 1,559 and 1,559 tpy for wet scrubbing. Switching fuel to solely natural gas was also evaluated and found to be technically infeasible due to the insufficient supply of natural gas in the region as well as the impact on the production process that would result from altering the product chemistry and capacity. The switch to natural gas would fundamentally change the production process since the flame temperature would be lower, altering product chemistry and quality, changing the thermal profile of the kiln, and reducing production capacity. For NO X , several control options were evaluated, including preheater installation, low-NO X burners, SCR, and SNCR. However, no options were determined to be technically feasible beyond current operation under good combustion practices. Despite the concerns about technical feasibility, Carmeuse Lime, Inc.—Maple Grove Operations performed a four-factor analysis on the addition of tail-end SCR, which would have required the installation of an SO 2 wet scrubber upstream and stack gas reheat downstream. Estimated capital costs for Units P003 and P004 were $16,878,012 and $16,722,674, respectively, while estimated annual costs were $11,596,001 and $11,431,638, resulting in cost effectiveness values of $10,419 and $11,484/ton NO X . Both SO 2 and NO X analyses considered a remaining useful life of 20 or 25 years, a 4 to 5 year installation time, and energy and non-air quality environmental impacts. In addition to the consideration of candidate control options, Carmeuse Lime, Inc.,—Maple Grove Operations considered visibility impact and noted that an analysis done during the first implementation period shows that the facility is located outside the area of influence for the closest Class I area, the Dolly Sods Wilderness Area, and that it was not one of the four sources in Ohio identified by VISTAS in their June 22, 2020, request as a source that strongly contributes to regional haze. Dover Mu [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%3A2024-19189. Public record. Not legal advice.