# Air Plan Approval; North Carolina; Second Period Regional Haze Plan > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2024-18495 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** August 20, 2024 - **Citation:** 89 FR 67341 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 52 [EPA-R04-OAR-2022-0786; FRL-10405-01-R4] Air Plan Approval; North Carolina; Second Period Regional Haze Plan AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule. SUMMARY: The Environmental Protection Agency (EPA) is proposing to approve in part and conditionally approve in part a regional haze State Implementation Plan (SIP) revision submitted by the North Carolina Department of Environmental Quality, Division of Air Quality (DAQ), dated April 4, 2022 (“Haze Plan” or “2022 Plan”) under the Clean Air Act (CAA or Act) and EPA's Regional Haze Rule (RHR) for the regional haze program's second planning period. North Carolina's 2022 SIP submission addresses the requirement that states must periodically revise their long-term strategies for making reasonable progress toward the national goal of preventing any future, and remedying any existing, anthropogenic impairment of visibility, including regional haze, in mandatory Class I Federal areas. The SIP submission also addresses other applicable requirements for the second planning period of the regional haze program. EPA is taking this action pursuant to sections 110 and 169A of the Act. DATES: Written comments must be received on or before September 19, 2024. ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R04-OAR-2022-0786, at http://www.regulations.gov. Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from Regulations.gov . EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) 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, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit http://www.epa.gov/dockets/commenting-epa-dockets. FOR FURTHER INFORMATION CONTACT: Michele Notarianni, Multi-Air Pollutant Coordination Section, Air Planning and Implementation Branch, Air and Radiation Division, U.S. Environmental Protection Agency, Region 4, 61 Forsyth Street SW, Atlanta, Georgia 30303-8960. Ms. Notarianni can be reached via telephone at (404) 562-9031 or electronic mail at notarianni.michele@epa.gov. SUPPLEMENTARY INFORMATION: 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 Planning 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 (URP) C. Long-Term Strategy (LTS) for Regional Haze D. Reasonable Progress Goals (RPGs) E. Monitoring Strategy and Other State Implementation Plan Requirements F. Requirements for Periodic Reports Describing Progress Toward the RPGs G. Requirements for State and Federal Land Manager (FLM) Coordination IV. EPA's Evaluation of North Carolina's Regional Haze Submission for the Second Planning Period A. Identification of Class I Areas B. Calculations of Baseline, Current, and Natural Visibility Conditions; Progress to Date; and the URP C. LTS for Regional Haze D. RPGs E. Monitoring Strategy and Other Implementation Plan Requirements F. Requirements for Periodic Reports Describing Progress Toward the RPGs G. Requirements for State and FLM Coordination H. Environmental Justice (EJ) Considerations V. Incorporation by Reference VI. Proposed Action VII. Statutory and Executive Order Reviews I. What action is EPA proposing? On April 4, 2022, the North Carolina DAQ submitted a revision to its SIP to address regional haze for the second planning period. DAQ 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. 1 EPA is proposing to approve in part and conditionally approve in part North Carolina's Haze Plan. For the reasons discussed in this document, EPA is proposing to approve the sections of the Haze Plan addressing the requirements of 40 CFR 51.308(f)(1), (f)(4) through(6), and (g)(1) through(5). EPA is proposing to conditionally approve the sections of the Haze Plan addressing the requirements of 40 CFR 51.308(f)(2), (f)(3), and (i)(2) through(4) due to concerns with the legal and practicable enforceability of certain permit conditions identified in the Haze Plan for incorporation into the SIP. 1 In a letter dated August 15, 2022, EPA found that North Carolina's Haze Plan meets the completeness criteria outlined in 40 CFR part 51, Appendix V. A completeness determination does not constitute a finding on the merits of the submission or whether it meets the relevant criteria for SIP approval. The August 15, 2022, letter is included in the docket for this proposed rulemaking. Consistent with CAA section 110(k)(3), EPA may approve in part portions of the SIP submittal if those portions meet the all the applicable requirements. Under CAA section 110(k)(4), EPA may conditionally approve a SIP revision based on a commitment from a state to adopt specific enforceable measures by a date certain, but not later than one year from the date of conditional approval of the plan revision. If the state fails to meet the commitment within one year of the final conditional approval, the conditional approval will be treated as a disapproval. North Carolina submitted a letter, dated July 30, 2024, (“Commitment Letter”), requesting partial conditional approval of its Haze Plan and committing to submit a SIP revision containing specific enforceable measures no later than one year from the effective date of a final conditional approval action, should EPA finalize this partial conditional approval as proposed. 2 EPA is proposing to conditionally approve the sections of the Haze Plan addressing the requirements of 40 CFR 51.308(f)(2), (f)(3), and (i)(2) through(4). These elements are fully separable from the elements proposed for partial approval. If North Carolina meets its commitment to submit the required SIP revision that adequately addresses the identified concerns related to the enforceability of certain permit conditions by the specified deadline and EPA approves the submission, then the conditional approval will be converted to a full approval. See Section IV.C.3.b of this document for a discussion of the enforceability concerns resulting in the proposed partial conditional approval and the commitments in North Carolina's Commitment Letter. 2 The Commitment Letter is in the docket for this proposed rulemaking. 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. 3 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. See 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 RHR, codified at 40 CFR 51.308, 4 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. 3 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. 4 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 )). Precursor pollutants react in the atmosphere to form fine particulate matter (particles less than or equal to 2.5 micrometers (µm) in diameter, 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. 5 5 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 defined and 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 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 deciviews 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 ). See 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); 6 see also 40 CFR 51.308(b), (f) (establishing submission dates for iterative regional haze SIP revisions); 64 FR at 35768. 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 (LTSs) originally due July 31, 2018, and every ten years thereafter. 64 FR at 35768. 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. 7 Id. at 35721. 6 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.” See 40 CFR 51.308(d), (f). 7 In addition to each of the 50 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), (d)(3). Much of the focus in the first planning period of the regional haze program, which ran from 2007 through 2018, was on satisfying states' BART obligations. First planning period SIPs were additionally required to contain LTSs for making reasonable progress toward the national visibility goal, of which BART is one component. The core required elements for the first planning period SIPs (other than BART) are laid out in 40 CFR 51.308(d). Those provisions require that states containing Class I areas establish “reasonable progress goals” (“RPGs”) that are measured in deciviews and reflect the anticipated visibility conditions at the end of the planning period including from implementation of states' LTSs. 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 (also referenced herein as “the four 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. See 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 toward the national visibility goal over time in each Class I area. 8 40 CFR 51.308(d)(1)(i)(B), and (d)(2). The 1999 RHR also provided that states' LTSs must include the “enforceable emissions limitations, compliance, schedules, and other measures as necessary to achieve the reasonable progress goals.” See 40 CFR 51.308(d)(3). In establishing their LTSs, 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) and (ii). Section 51.308(d) also contains seven additional factors states must consider in formulating their LTSs, 40 CFR 51.308(d)(3)(v), as well as provisions governing monitoring and other implementation plan requirements. See 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) and (h), and to consult with the Federal Land Manager(s) 9 (FLMs) responsible for each Class I area according to the requirements in CAA 169A(d) and 40 CFR 51.308(i). 8 EPA established the URP framework in the 1999 RHR to provide “an equitable analytical approach” to assess 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. See 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.” See 82 FR 3078, 3084 (January 10, 2017). 9 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.” See 40 CFR 51.301. On January 10, 2017, EPA promulgated revisions to the RHR (82 FR 3078) that apply for the second and subsequent planning 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 planning periods focused on the requirement that states' SIPs contain LTSs for making reasonable progress toward 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 planning period SIPs from July 31, 2018, to July 31, 2021, clarified the order of analysis and the relationship between RPGs and the LTSs, 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 planning period regional haze SIP submissions are addressed in detail below. EPA provided guidance to the states for their second planning 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 its 2019 Guidance. 10 On July 8, 2021, EPA issued a memorandum containing “Clarifications Regarding Regional Haze State Implementation Plans for the Second Implementation Period” (“2021 Clarifications Memo”). 11 Additionally, EPA had 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”), 12 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”). 13 10 See footnote 5. 11 “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). 12 “Technical Guidance on Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program.” EPA Office of Air Quality Planning and Standards, Research Triangle Park (December 20, 2018). https://www.epa.gov/visibility/technical-guidance-tracking-visibility-progress-second-implementation-period-regional. 13 “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 previously explained in the 2021 Clarifications Memo, EPA intends the second planning 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. 14 14 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 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. In order 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), 15 which include representation from state and Tribal governments, EPA, and FLMs, were developed in the lead-up to the first planning 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 PM and other pollutants leading to regional haze, and help states meet the consultation requirements of the RHR. 15 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 Southeastern States Air Resource Managers, Inc. (SESARM), one of the five RPOs described above, is a collaborative effort of state and local agencies and Tribal governments established to initiate and coordinate activities associated with the management of regional haze, visibility, and other air quality issues in the Southeast. SESARM's coalition to conduct regional haze work is referred to as Visibility Improvement State and Tribal Association of the Southeast (VISTAS). 16 The member states, local air agencies, and Tribal governments of VISTAS are Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, and West Virginia; the local air agencies, represented by the President of Metro 4 or designee; 17 and the Tribes located within the VISTAS region, represented by the Eastern Band of the Cherokee Indians. The Federal partner members of VISTAS are EPA, U.S. National Park Service (NPS), U.S. Fish and Wildlife Service (FWS), and U.S. Forest Service (USFS). 18 16 The VISTAS technical work under SESARM is described at this website: https://www.metro4-sesarm.org/content/vistas-regional-haze-program. 17 Metro 4 is a Tennessee corporation which represents the local air pollution control agencies in EPA's Region 4 in the Southeast. See https://www.metro4-sesarm.org/content/metro-4-about-us. 18 The NPS, FWS, and USFS are collectively referred to as the “Federal Land Managers” or “FLMs” throughout this document. III. Requirements for Regional Haze Plans for the Second Planning Period Under the CAA and EPA's regulations, all 50 states, the District of Columbia, and the U.S. Virgin Islands are required to submit regional haze SIPs satisfying the applicable requirements for the second planning period of the regional haze program by July 31, 2021. Each state's SIP must contain a LTS 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 LTSs, with the order of the requirements in 40 CFR 51.308(f)(1) through (f)(3) generally mirroring the order of the steps in the reasonable progress analysis 19 and (f)(4) through (f)(6) containing additional related requirements. 19 EPA explained in the 2017 RHR Revisions that the Agency was 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). 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 LTS. 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 LTS 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 planning period. Additionally, as further explained below, the RHR at 40 CFR 51.3108(f)(2)(iv) separately provides five “additional factors” 20 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 LTS. After a state has developed its LTS, 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 planning 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 toward the statutory goal of preventing any future and remedying any existing anthropogenic visibility impairment in Class I areas. See 40 CFR 51.308(f)(2) and (3). 20 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 planning period must address the requirements in 40 CFR 51.308(g)(1) through (5) pertaining to periodic reports describing progress toward 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. See 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, 64 FR at 35720-22, 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.” Id. at 35721. 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, where appropriate, using the determinations previously made for the first planning period. 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 (URP) As part of assessing whether a SIP submission for the second planning period is providing for reasonable progress toward 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 subsection 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 21 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 at 3103-05. 21 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. EPA Office of Air Quality Planning and Standards, Research Triangle Park (September 2003). 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). 22 The RHR provides that the relevant sets of days for visibility tracking purposes are the 20 percent clearest days (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). 23 See 40 CFR 51.301. A state must calculate visibility conditions for both the 20 percent clearest days 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). See 40 CFR 51.308(f)(1)(i), (iii). States must also calculate natural visibility conditions for the clearest days and most impaired days 24 by estimating the conditions that would exist on those two sets of days absent anthropogenic visibility impairment. See 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 in order to reach natural visibility conditions. 22 The “deciview index” means a value for a day that is derived from calculated or measured light extinction, such that uniform increments of the index correspond to uniform incremental changes in perception across the entire range of conditions, from pristine to very obscured. The deciview index is calculated using Interagency Monitoring of Protected Visual Environments (IMPROVE) aerosol measurements. See 40 CFR 51.301. 23 This notice 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. 24 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 deciviews, that would need to be achieved during each planning period in order 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. 25 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 3107, footnote 116. 25 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 at 3093. 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 (LTS) for Regional Haze The core component of a regional haze SIP submission is a LTS 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 LTS “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).” See 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 (FFA). The outcome of that analysis is the emission reduction measures that a particular source or group of sources needs to implement in order to make reasonable progress toward 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 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” in a state's LTS in its SIP. See 40 CFR 51.308(f)(2). Section 51.308(f)(2)(i) provides the requirements for the FFA. 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 control analysis ( i.e., FFA). See 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 planning 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 and 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.” See 2021 Clarifications Memo at 3. EPA explained in the 2021 Clarifications Memo that each state has an obligation to submit a LTS 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. See 2021 Clarifications Memo at 4. 26 26 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, May 4, 2016) (December 2016), Docket Number EPA-HQ-OAR-2015-0531, U.S. Environmental Protection Agency at 87-88, available at www.regulations.gov. 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 planning period. 27 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.” See CAA 169A(g)(1). EPA has explained that the FFA 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 in order to satisfy the CAA's reasonable progress mandate.” See 82 FR at 3091. Thus, for each source a state has selected for a FFA, 28 it 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.” See 2019 Guidance at 29. 27 The CAA provides that “[i]n determining reasonable progress there shall be taken into consideration” the four statutory factors. See 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. 28 “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 at 3088. 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. See 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.” See 2021 Clarifications Memo at 7. In addition to add-on controls and other retrofits ( i.e., new emission reduction measures for sources), EPA explained that states should generally analyze efficiency improvements for sources' existing measures as control options in their FFAs, 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 emission rate than a source has achieved or could potentially achieve using its existing measures should also consider lower emission 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. See 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 FFA and those that have forgone a FFA 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. 29 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 FFA. See 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. See 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.” 29 See, e.g., Responses to Comments on Protection of Visibility: Amendments to Requirements for State Plans; Proposed Rule (81 FR 26942, May 4, 2016) (December 2016), Docket Number EPA-HQ-OAR-2015-0531, U.S. Environmental Protection Agency at 186, available at www.regulations.gov; 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 toward the national visibility goal must be included in a state's LTS and in its SIP. 30 If the outcome of a FFA is a new, additional emission reduction measure for a source, that new measure is necessary to make reasonable progress toward remedying existing anthropogenic visibility impairment and must be included in the SIP. If the outcome of a FFA 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 toward 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 FFA 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 emission rate, it may not be necessary to have those measures in the LTS in order to prevent future emission 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 LTS or its SIP. 30 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 at 3108-09 (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. 31 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. 31 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 LTS for making reasonable progress. Additionally, the RHR at 40 CFR 51.3108(f)(2)(iv) separately provides five “additional factors” 32 that states must consider in developing their LTSs: (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 LTS. The 2019 Guidance provides that a state may satisfy this requirement by considering these additional factors in the process of selecting sources for a FFA, 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 FFAs. See 2021 Clarifications Memo at 13. 32 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. See 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. See 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. See 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. See 40 CFR 51.308(f)(2)(ii)(C). D. Reasonable Progress Goals (RPGs) RPGs “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.” See 82 FR at 3091. Their primary purpose is to assist the public and EPA in assessing the reasonableness of states' LTSs for making reasonable progress toward 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—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, measured in deciviews, are intended to reflect the projected impacts, on each set of days, of the emission reduction measures the state with the Class I area and other contributing states have included in their LTSs for the second planning period. 33 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' LTSs (as well as other measures required under the CAA), they cannot be determined before states have conducted their FFAs and determined the control measures that are necessary to make reasonable progress. 34 See 2021 Clarifications Memo at 6. 33 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. See 2019 Guidance at 47-48. 34 The 2019 Guidance allows for the possibility of post-modeling adjustments to the RPGs to account for the fact that final LTS decisions for the state or for other states may not be known until late in the process, or even after SIPs are submitted. See 2019 Guidance at 46-48. See also, 82 FR 3078, 3080 (January 10, 2017). For the second planning period, the RPGs are set for 2028. RPGs 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.” See 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 LTSs 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 at 3097-98. So that RPGs may also serve as a metric for assessing the amount of progress a state is making toward 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 FFA required under 40 CFR 51.308(f)(2)(i), that no additional emission reduction measures would be reasonable to include in its LTS. 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 FFA is conducted) is not a “safe harbor” from the CAA's and RHR's requirement that all states must conduct a FFA to determine what emission reduction measures constitute reasonable progress. 35 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 planning period is “reasonable progress.” See 82 FR at 3093, 3099-3100; 2019 Guidance at 22; 2021 Clarifications Memo at 15-16. 35 In lieu of conducting a FFA, states may elect to show the source has existing effective controls for the particular pollutants under evaluation or that the source is shutting down by the end of the planning period (or close to it). E. Monitoring Strategy and Other State Implementation Plan Requirements Section 51.308(f)(6) requires states to have certain strategies and elements in place for assessing and reporting on visibility. Individual requirements under this subsection 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 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. See 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' implementation plans 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). Section 51.308(f)(6)(v) further requires that all states' implementation plans 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. 36 All states' implementation plans must also provide for any other elements, including reporting, recordkeeping, and other measures, that are necessary for states to assess and report on visibility. See 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. 37 36 See “Step 8: Additional requirements for regional haze SIPs” in 2019 Guidance at 55. 37 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.” 38 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 (RAVI), the state must include in its SIP revision for the second planning period an appropriate strategy for evaluating such impairment. 38 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 Toward the RPGs Section 51.308(f)(5) requires 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 planning period. The regional haze progress report requirement is designed to inform the public and EPA about a state's implementation of its existing LTS and whether such implementation is in fact resulting in the expected visibility improvement. See 81 FR 26942, 26950 (May 4, 2016), 82 FR 3119 (January 10, 2017). To this end, every state's implementation plan revision for the second planning period is required to describe the status of implementation of all measures included in the state's LTS, including BART and reasonable progress emission reduction measures from the first planning period, and the resulting emissions reductions. See 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 planning 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 in order 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 planning period progress reports. See 40 CFR 51.308 (f)(5) and (g)(3)(iii). Since different states submitted their first planning 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 planning period progress reports. See 40 CFR 51.308 (f)(5) and (g)(4). Changes in emissions should be identified by the type of source or activity. Section 51.308(g)(5) also addresses changes in emissions since the period addressed by the previous progress report and requires states' implementation plan revisions to include an assessment of any significant changes in anthropogenic emissions within or outside the state. This assessment must include an explanation of 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 LTS for the first planning period. G. Requirements for State and Federal Land Manager (FLM) 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.” See 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). In order 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. See 40 CFR 51.308(i)(4). IV. EPA's Evaluation of North Carolina's Regional Haze Submission for the Second Planning Period On April 4, 2022, DAQ submitted a revision to the North Carolina SIP to address the State's regional haze obligations for the second planning period, which runs through 2028, in accordance with CAA sections 169A and the RHR at 40 CFR 51.308(f). 39 The following sections contain EPA's evaluation of North Carolina's Haze Plan with respect to the requirements of the CAA and RHR for the second planning period of the regional haze program. 39 On June 27, 2012, EPA finalized a limited approval of North Carolina's first planning period regional haze plan submitted to EPA on December 17, 2007 (77 FR 38185). On June 7, 2012 (77 FR 33642), EPA finalized a limited disapproval of the December 17, 2007, submission. On May 24, 2016, EPA approved North Carolina's October 31, 2014, BART alternative demonstration, which was a revision to its regional haze plan and converted the limited approval of the December 17, 2007, submission to a full approval (81 FR 32652). On August 25, 2016, EPA approved North Carolina's May 31, 2013, progress report for the first planning period (81 FR 58400). North Carolina has five Class I areas, two of which are shared with Tennessee: Linville Gorge National Wilderness Area (“Linville Gorge”); Shining Rock National Wilderness Area (“Shining Rock”); Swanquarter National Wilderness Area (“Swanquarter”); Great Smoky Mountains National Park (“Great Smoky Mountains”) (NC/TN); and Joyce Kilmer-Slickrock National Wilderness Area (“Joyce Kilmer”) (NC/TN). The following sections describe North Carolina's Haze Plan, including analyses conducted by VISTAS and North Carolina's determinations based on those analyses, North Carolina's assessment of progress made since the first planning period in reducing emissions of visibility impairing pollutants, and the visibility improvement progress at its Class I areas and nearby Class I areas. This document also contains EPA's evaluation of North Carolina's Haze Plan against the requirements of the CAA and RHR for the second planning period of the regional haze program. A. Identification of Class I Areas 1. RHR Requirement: Section 169A(b)(2) of the CAA requires 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 40 CFR 51.308(f)(2), which requires each state's plan to include a LTS that addresses regional haze in such Class I areas. To develop a state's LTS, a state must first determine which Class I areas may be affected by its own emissions. For out-of-state Class I areas, states must assess their visibility impacts on a statewide basis which is discussed in Section IVA.2, below, and on a source specific basis which is discussed in Section IV.C.2, below. 2. State Assessment: To address 40 CFR 51.308(f), North Carolina identified Class I areas affected by North Carolina's statewide emissions of visibility impairing pollutants and then consulted with states with Class I areas affected by North Carolina's statewide emissions. DAQ presented the results of Particulate Matter Source Apportionment Technology (PSAT) 40 modeling which VISTAS conducted to estimate the projected impact of statewide SO 2 and NO X emissions across all emissions sectors in 2028 on total light extinction for the 20 percent most impaired days in all Class I areas in the VISTAS modeling domain. 41 In Table 7-14 of the 2022 Plan, DAQ lists the total sulfate plus nitrate contribution from all source sectors in North Carolina to total visibility impairment for the 20 percent most impaired days at Class I areas in the VISTAS modeling domain in inverse megameters (Mm − 1 ). North Carolina's top three highest sulfate plus nitrate impairment impacts to out-of-state Class I areas are: Wolf Island National Wilderness Area (Wolf Island) (0.78 Mm − 1 ) and Okefenokee National Wilderness Area (Okefenokee) (0.67 Mm − 1 ) in Georgia and James River Face National Wilderness Area (James River Face) (0.45 Mm − 1 ) in Virginia. 42 40 PSAT is Particulate Matter Source Apportionment Technology, which is an option in the photochemical visibility impact modeling performed by VISTAS that is a methodology to track the fate of both primary and secondary PM. PSAT allows emissions to be tracked (“tagged”) for individual facilities as well as various combinations of sectors and geographic areas ( e.g., by state). The PSAT results provide the modeled contribution of each of the tagged sources or groups of sources to the total visibility impacts. 41 DAQ did not include primary PM (directly emitted) data in this analysis because the PSAT analyses performed by VISTAS tagged statewide emissions of SO 2 and NO X and did not tag primary total PM emissions in the analysis after concluding that emissions of the PM precursors SO 2 and NO X , particularly from point sources, are projected to have the largest impact on visibility impairment in 2028 and that SO 2 and NO X are the most significant visibility impairing pollutants from controllable anthropogenic sources. 42 In contrast, North Carolina's sulfate plus nitrate impairment impacts to the State's Class I areas are: 0.95 Mm − 1 , 1.13 Mm − 1 , 1.83 Mm − 1 , 0.89 Mm − 1 , 0.43 Mm − 1 for Linville Gorge, Shining Rock, Swanquarter, Great Smoky Mountains, and Joyce Kilmer, respectively. Based on these results for the out-of-state Class I areas, North Carolina consulted with the VISTAS states (see Section 10.1 and Appendix F-1 of the 2022 Plan) and the Mid-Atlantic/Northeast Visibility Union (MANE-VU) 43 states (see Section 10.3 and Appendix F-4 of the 2022 Plan) which contain Class I areas located nearest to North Carolina and to which North Carolina's emissions had the highest sulfate plus nitrate contribution to total sulfate plus nitrate visibility impairment. The purpose of this consultation was to identify whether North Carolina's statewide impacts to the VISTAS and MANE-VU states are significant enough to develop coordinated emission management strategies containing the emission reductions necessary to make reasonable progress. 44 With respect to MANE-VU, none of the states in this RPO contacted North Carolina for consultation with the exception of New Hampshire and New Jersey. North Carolina's consultation with MANE-VU, New Hampshire, and New Jersey is further discussed in Section IV.C.2.e of this document and Section I.E of EPA's Technical Support Document (TSD) for this proposed rulemaking. 43 MANE-VU was established in 2001 to assist the Mid-Atlantic and Northeast states in planning and developing their regional haze SIP revisions. The MANE-VU states are Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont. 44 North Carolina did not consult with states with Class I areas in the Central States Air Resource Agencies (CENSARA), Lake Michigan Air Directors' Consortium (LADCO), and Western Regional Air Partnership (WRAP) RPO regions because North Carolina's statewide sulfate plus nitrate contribution to total sulfate plus nitrate impairment in the Class I areas in these regions was relatively low ( i.e., ranging from zero percent to 0.12 percent of total sulfate plus nitrate impairment). Additionally, no states in CENSARA, LADCO, and WRAP requested consultation with North Carolina regarding its statewide emissions. 3. EPA Evaluation: EPA proposes to conclude that North Carolina adequately addressed 40 CFR 51.308(f) regarding identification of its statewide visibility impacts to Class I areas outside of the State and consulting with states with Class I areas which may reasonably be anticipated to cause or contribute to any impairment of visibility due to North Carolina's emissions. EPA proposes to agree with the State's approach of focusing on SO 2 and NO X impacts from North Carolina on the basis that for current visibility conditions evaluated for the 2014-2018 period, ammonium sulfate is the dominant visibility impairing pollutant at most of the VISTAS Class I areas followed by organic carbon and ammonium nitrate (depending on the area). 45 VISTAS focused on controllable emissions from point sources, and thus, initially considered impacts from sulfates and nitrates on regional haze at Class I areas affected by VISTAS states. EPA agrees that North Carolina adequately identified Class I areas outside of North Carolina that may be affected by emissions from within the State and consulted with affected states. The information submitted by North Carolina supports this finding, because it shows that the state analyzed its statewide sulfate and nitrate contributions to total visibility impairment at out-of-state Class I areas in Table 7-14 of the 2022 Plan; none of the Class I areas in MANE-VU and VISTAS have 2028 RPGs on the 20 percent most impaired days above the URP; 46 with the exception of Joyce Kilmer, the visibility impairment due to emissions from North Carolina at in-state Class I areas is greater than the impairment due to emission from North Carolina at out-of-state Class I areas; and the State completed consultation with VISTAS and MANE-VU states via the RPO processes and, in some cases, on a state-to-state basis and documented those consultations. 47 45 See Figures 2-17 and 2-18 of the 2022 Plan for the VISTAS Class I areas. See also section IV.C.2.a of this notice. 46 See Memorandum from Richard A. Wayland, OAQPS, to Regional Air Division Directors re: Availability of Modeling Data and Associated Technical Support Document for the EPA's Updated 2028 Visibility Air Quality Modeling (September 19, 2019), available at: https://www.epa.gov/sites/default/files/2019-10/documents/updated_2028_regional_haze_modeling-tsd-2019_0.pdf. 47 See Section IV.C.2.e of this notice and Section I.E of EPA's TSD for additional detail regarding consultation. B. Calculations of Baseline, Current, and Natural Visibility Conditions; Progress to Date; and the URP 1. RHR Requirement: Section 51.308(f)(1) requires states to determine the following for “each mandatory Class I Federal area located within the State”: baseline visibility conditions for the clearest days and most impaired days, natural visibility conditions for clearest days and most impaired days, progress to date for the clearest days and most impaired 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. See 40 CFR 51.308(f)(1)(vi)(B). 2. State Assessment: In the 2022 Plan, North Carolina calculated baseline visibility conditions (2000-2004) in Table 2-3; current visibility conditions (2014-2018) in Table 2-5; 48 and natural visibility conditions in Table 2-2 for the 20 percent most impaired and 20 percent clearest days for the State's Class I areas in deciviews as shown in Table 1, below. North Carolina also calculated for its Class I areas the actual progress made toward natural visibility conditions to date since the baseline period (current minus baseline), and the additional progress needed to reach natural visibility conditions from current conditions (natural minus current), in deciviews, in Table 2-6 (for the 20 percent most impaired days) and Table 2-7 (for the 20 percent clearest days) as shown in Table 2, below. 48 The period 2014-2018 represents current visibility conditions for North Carolina because it is the most recent five-year period for which visibility monitoring data were available at the time of SIP development. Table 1—Baseline, Current, and Natural Visibility Conditions in North Carolina's Class I Areas in Deciviews ( dv ) Class I area Baseline 20% clearest days Baseline 20% most impaired days Current 20% clearest days Current 20% most impaired days Natural 20% clearest days Natural 20% most impaired days Great Smoky Mountains 13.58 29.11 8.35 17.21 4.62 10.05 Joyce Kilmer 13.58 29.11 8.35 17.21 4.62 10.05 Linville Gorge 11.11 28.05 7.61 16.42 4.07 9.70 Shining Rock 7.70 28.13 4.40 15.49 2.49 * 10.25 Swanquarter 12.34 23.79 10.61 16.30 5.71 * 10.01 * The 2022 Plan indicates in Table Ex-1-3 and Table 8-1 that natural conditions are 10.01 and 9.79 deciviews for Shining Rock and Swanquarter, respectively. Tables Ex-1-1, Table 2-2, and Tables 2-6 reflect the correct values shown here which are derived from EPA's June 3, 2020, Technical Addendum available at: https://www.epa.gov/sites/default/files/2020-06/documents/memo_data_for_regional_haze_technical_addendum.pdf. Table 2—Actual Progress for Visibility Conditions in North Carolina's Class I Areas in Deciviews ( dv ) Class I area Current minus baseline for 20% clearest days Current minus baseline for 20% most impaired days Natural minus current for 20% clearest days Natural minus current for 20% most impaired days Great Smoky Mountains −5.23 −11.90 −3.73 −7.16 Joyce Kilmer −5.23 −11.90 −3.73 −7.16 Linville Gorge −3.50 −11.63 −3.54 −6.72 Shining Rock −3.30 −12.64 −1.91 −5.24 Swanquarter −1.73 −7.49 −4.90 −6.29 Additionally, Figures 3-1, 3-2, 3-3, and 3-4 of the 2022 Plan provide the URP figures for the 20 percent most impaired days for Great Smoky Mountains (which also represents the URP for Joyce Kilmer), Linville Gorge, Shining Rock, and Swanquarter, respectively. The URPs were developed using EPA guidance 49 and used data collected from the 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. All North Carolina Class I areas are projected to be below the 2028 URP values for the second planning period based on VISTAS' modeling. 49 “Technical Guidance on Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program.” EPA Office of Air Quality Planning and Standards, Research Triangle Park (December 20, 2018). https://www.epa.gov/sites/default/files/2018-12/documents/technical_guidance_tracking_visibility_progress.pdf and https://www.epa.gov/sites/default/files/2020-06/documents/memo_data_for_regional_haze_technical_addendum.pdf. 3. EPA Evaluation: EPA finds that North Carolina's Haze Plan meets the requirements of 40 CFR 51.308(f)(1) because the State provided for its five Class I areas: baseline, current, and natural visibility conditions for the 20 percent clearest days and most impaired days; progress to date for the 20 percent clearest days and most impaired days; differences between the current visibility conditions and natural visibility conditions; and the URP for each Class I area in North Carolina. Therefore, EPA is proposing to approve the portions of the North Carolina SIP submission related to 40 CFR 51.308(f)(1). C. LTS for Regional Haze 1. RHR Requirement: Each state having a Class I area within its borders or emissions that may affect visibility in a Class I area must develop a LTS for making reasonable progress toward the national visibility goal. CAA 169A(b)(2)(B). As explained in Section II of this document, 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 LTS 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 FFAs are necessary to make reasonable progress and must be in the LTS. If the conclusion of a FFA and other measures necessary to make reasonable progress for a particular source is that no new measures are reasonable, 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 LTS. In developing its LTS, 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 FFA) for the second planning period and how the four factors were taken into consideration in selecting the emission reduction measures for inclusion in the LTS. 40 CFR 51.308(f)(2)(iii). States may rely on technical information developed by the RPOs of which they are members to select sources for FFA and to satisfy the documentation requirements under 40 CFR 51.308(f). Where an RPO has performed source selection and/or FFAs (or considered the five additional factors in 40 CFR 51.308(f)(2)(iv)) for its member states, those states may rely on the RPO's analyses for the purpose of satisfying the requirements of 40 CFR 51.308(f)(2)(i) so long as the states have a reasonable basis to do so and all state participants in the RPO process have approved the technical analyses. 40 CFR 51.308(f)(3)(iii). States may also satisfy the requirement of 40 CFR 51.308(f)(2)(ii) to engage in interstate consultation with other states that have emissions that are reasonably anticipated to contribute to visibility impairment in a given Class I area under the auspices of intra- and inter-RPO engagement. The consultation requirements of 40 CFR 51.308(f)(2)(ii) provide that states must consult with other states that are reasonably anticipated to contribute to visibility impairment in a Class I area to develop coordinated emission management strategies containing the emission reductions measures that are necessary to make reasonable progress. Section 51.308(f)(2)(ii)(A) and (B) require states to consider the emission reduction measures identified by other states as necessary for reasonable progress and to include agreed upon measures in their SIPs, respectively. Section 51.308(f)(2)(ii)(C) speaks to what happens if states cannot agree on what measures are necessary to make reasonable progress. The documentation requirement of 40 CFR 51.308(f)(2)(iii) provides that states may meet their obligations to document the technical bases on which they are relying to determine the emission reductions measures that are necessary to make reasonable progress through an RPO, as long as the process has been “approved by all State participants.” Section 51.308(f)(2)(iii) also requires that the emissions information considered to determine the measures that are necessary to make reasonable progress include information on emissions for the most recent year for which the state has submitted triennial emissions data to the EPA (or a more recent year), with a 12-month exemption period for newly submitted data. 2. State Assessment: To develop North Carolina's LTS, DAQ set criteria to identify sources to evaluate for potential controls using the four factors outlined in Section II.B, selected sources based on those criteria, considered the four factors for the selected sources, provided emissions limits and supporting conditions for adoption into the regulatory portion of the SIP, and evaluated the five additional factors at 40 CFR 51.308(f)(2)(iv). a. Source Selection Criteria: With respect to 40 CFR 51.308(f)(2)(i), North Carolina, through VISTAS, used a two-step source selection process: (1) Area of Influence (AoI) analysis, and (2) PSAT 50 modeling for sources exceeding an AoI threshold. 51 North Carolina considered the four factors for sources that exceeded both the AoI and PSAT thresholds. Both sulfates and nitrates were considered in the source selection process. To identify sources having the most impact on visibility at Class I areas for PSAT modeling, DAQ used an AoI threshold of greater than or equal to three percent for sulfate and nitrate combined at any North Carolina Class I area for all sources within and outside of the State. Sources which exceeded North Carolina's AoI threshold are listed in Tables 7-20 through 7-24 of the Haze Plan. Of these sources, five sources in North Carolina exceeded the AoI threshold for any Class I area in the State: Blue Ridge Paper Products—Canton Mill (BRPP); Domtar Paper LLC (Domtar); 52 Duke Energy Carolinas LLC (DEC)—Marshall Steam Station (DEC-Marshall); PCS Phosphate Inc.—Aurora (PCS); and SGL Carbon LLC. 53 50 PSAT modeling is a type of photochemical modeling which quantifies individual facility visibility impacts to an area. See footnote 40. DAQ applied its PSAT threshold by facility whereas in the first period, DAQ applied the threshold by emissions unit at selected facilities. 51 The AoI represents the geographical area around a Class I area in which emissions sources located in the AoI have the potential to contribute to visibility impairment at that Class I area. Emissions data from sources in the AoI is then evaluated to determine which of those sources are most likely contributing to visibility impairment at that Class I area. VISTAS used AoI analysis for all point source facilities in the VISTAS modeling domain to determine the relative visibility impairment impacts at each Class I area associated with sulfate and nitrate. The results of the facility-level AoI analyses were then used to rank and prioritize facilities for further evaluation via PSAT. 52 On December 1, 2023, DAQ issued Air Quality Permit No. 04291T51 authorizing modifications to the Domtar facility, which is available at: https://edocs.deq.nc.gov/AirQuality/DocView.aspx?id=457541&dbid=0&repo=AirQuality&searchid=c271acf8-6535-4306-8cfb-9a0caa2b3d97. Because these authorized permit modifications are subsequent to the North Carolina SIP submission, North Carolina did not consider the modification to determine reasonable progress in the second planning period. 53 See Table 7-29 on p. 227 of the 2022 Plan. North Carolina, in coordination with the other VISTAS states, set a PSAT threshold of greater than or equal to one percent for sulfate or nitrate. Sources identified based on the State's PSAT threshold are listed in Tables 7-36, 7-37, and 7-38 of the 2022 Plan. Of the 19 sources that exceeded the sulfate PSAT threshold, 16 sources are located in 10 other states and three are located in North Carolina. North Carolina selected the three in-state sources (BRPP, Domtar, and PCS) for an emissions control analysis. 54 The projected 2028 SO 2 emissions (in tons per year (tpy)) from BRPP, Domtar, and PCS are 483, 1,120, and 3,045, respectively. 55 No sources modeled for PSAT exceeded the PSAT threshold for nitrates. Because no sources exceeded the State's PSAT threshold for nitrates and because ammonium sulfate continues to be the dominant visibility impairing pollutant at the North Carolina Class I areas (as discussed in the following paragraphs), DAQ focused solely on evaluating potential SO 2 controls from BRPP, Domtar, and PCS to address regional haze in potentially affected Class I areas. Section I.A of the TSD provides additional detail regarding the State's source selection process. 54 BRPP and Domtar are pulp and paper mills. PCS is a fertilizer plant with sulfuric acid plants on site. 55 See Tables 7-48, 7-55, and 7-60 on pp. 271, 275, and 279, respectively, of the 2022 Plan. The 2022 Plan shows the VISTAS model projections demonstrating that ammonium sulfate is expected to remain the dominant visibility impairing pollutant through 2028, by a factor of four or greater, over ammonium nitrate at Class I areas in North Carolina. 56 In Section 7.4 of the 2022 Plan, DAQ explains the VISTAS analyses relied upon to support the State's focus on SO 2 control evaluations. Additionally, Section 10.4.1 of the Haze Plan provides the State's responses to FLM comments on the exclusion of NO X control evaluations from the FFAs. 56 See Figures 2-7 through 2-18 and Figure 10-10 of the 2022 Plan. Figures 2-7 through 2-10 provide 2009-2013 speciated PM data for North Carolina's Class I areas showing that ammonium sulfate is the dominant visibility impairing pollutant. Figures 2-11 and 2-12 provide speciated PM data for 2009-2013 for the VISTAS Class I areas and neighboring areas on the 20 percent most impaired days and 20 percent clearest days, respectively. Figures 2-13 to 2-18 show the speciated PM data for North Carolina's Class I areas for the period 2014-2018 showing that ammonium sulfate is the dominant visibility impairing pollutant. Figures 2-17 and 2-18 provide speciated PM data for 2014-2018 for the VISTAS Class I areas and neighboring areas on the 20 percent most impaired days and 20 percent clearest days, respectively. Although ammonium nitrate contributions to light extinction have increased in recent years (2016-2018), sulfate is still the highest contributor to visibility impairment in North Carolina's Class I areas. DAQ provided light extinction data on the 20 percent most impaired and 20 percent clearest days for the North Carolina Class I areas for the 2009-2013 modeling base period and the 2014-2018 current conditions period which show that ammonium sulfate continues to be the dominant visibility impairing pollutant on the 20 percent most impaired visibility days during the 2009-2013 period and 2014-2018 period. 57 57 See Section 2.5.2 (particularly Figures 2-7 through 2-11 for the 2009-2013 period and Figures 2-13 through 2-18 for the 2014-2018 period), and Section 10.4.1 of the 2022 Plan related to ammonium nitrate. In Section 10.4.1, DAQ reviewed more recent visibility monitoring data for the period 2015-2019 from the IMPROVE monitoring network for Great Smoky Mountains, Linville Gorge, and Shining Rock. 58 Table 3, below, summarizes the percent contribution on the 20 percent most impaired days at Great Smoky Mountains (also Joyce Kilmer), Linville Gorge, and Shining Rock for certain PM species ( i.e., ammonium sulfate, ammonium nitrate, and organic carbon) in 2009-2013 versus 2015-2019. 59 58 DAQ did not include 2015-2019 IMPROVE monitoring data for Swanquarter in Section 10.4.1 because NPS and USFS did not request that DAQ consider more recent visibility monitoring data for Swanquarter. 59 The data in Table 1 is derived from Figures 10-1, 10-2, and 10-3 of the 2022 Plan. Swanquarter speciation data is shown in Figures 2-10 through 2-12 and 2-16 through 2-18 of the 2022 Plan. 60 DAQ provided IMPROVE monitoring data in Figures 10-1, 10-2, and 10-3 regarding Great Smoky Mountains (also for Joyce Kilmer), Linville Gorge, and Shining Rock. For Swanquarter, 2015-2019 IMPROVE data for the 20 percent most impaired days are: 50 percent, 17 percent, and 17 percent for ammonium sulfate, ammonium nitrate, and organic carbon, respectively. See https://vista.cira.colostate.edu/Improve/rhr-summary-data/. Table 3—Five-Year Average (2009-2013 vs. 2015-2019) Percent (%) Particle Contributions to Light Extinction for 20% Most Impaired Days at Great Smoky Mountains,* Linville Gorge, and Shining Rock 60 PM species Great smoky mountains 2009-2013 (%) 2015-2019 (%) Linville gorge 2009-2013 (%) 2015-2019 (%) Shining rock 2009-2013 (%) 2015-2019 (%) Ammonium Sulfate 76.3 54.4 77.2 56.9 74.5 58.1 Ammonium Nitrate 5.2 16.6 2.5 8.0 5.5 10.3 Organic Carbon 11.1 17.4 12.5 22.4 12.5 19.4 * Monitoring data for Great Smoky Mountains serves as the IMPROVE data for Joyce Kilmer. Figures 7-27 (Swanquarter), 7-28 (Shining Rock), 7-29 (Linville Gorge), 7-30 (Joyce Kilmer), and 7-31 (Great Smoky Mountains) in the 2022 Plan show that the majority of 2028 predicted nitrate light extinction on the 20 percent most impaired days at North Carolina's Class I areas is not caused by NO X emissions from EGU and non-EGU point sources. 61 At Shining Rock, Linville Gorge, Joyce Kilmer, and the Great Smoky Mountains, projected 2028 total sulfate extinction is greater than 17 Mm −1 and total projected 2028 total nitrate extinction is less than 3.5 Mm −1 . At Swanquarter, the projected 2028 sulfate extinction is 16.6 Mm −1 and the projected 2028 nitrate extinction is 4.5 Mm −1 . DAQ states that North Carolina sources contribute a small percentage to total nitrate impairment in all cases (ranging from less than one percent of all nitrate visibility impairment at the Great Smoky Mountains to 13 percent at Swanquarter). 61 Figure 7-26 provides the 2028 visibility impairment from nitrate on the 20 percent most impaired days for all 18 Class I Areas in VISTAS. The figure shows the EGU and non-EGU contributions to total nitrate derived light extinction in 2028. DAQ states that it is unclear why ammonium nitrate has started to increase at some but not all VISTAS Class I areas while point and mobile source NO X emissions have been declining. VISTAS modeling for 2028 suggests that sources outside of North Carolina may be the likely contributor. DAQ indicates that further research is needed to identify the emission sources and geographic locations of those sources contributing to the ammonium nitrate fraction of PM 2.5 contributing to regional haze. DAQ notes that at some locations, one ton of SO 2 reduction can have anywhere from twice to more than 100 times the impact on visibility impairment as one ton of NO X reduction. 62 62 See pp. 333-335 and Table 10-8 of the 2022 Plan. In Section 7.7.3.2 of the 2022 Plan, DAQ reviewed North Carolina facilities that were not selected for PSAT modeling and which had an AoI contribution between one and three percent for one or more Class I areas in North Carolina and which were not selected for FFA evaluation. This review included the eight Duke Energy power plants with coal units in North Carolina which, with the exception of DEC-Marshall, did not meet North Carolina's AoI threshold (see Table 7-43 of the 2022 Plan). DAQ reviewed existing SO 2 and NO X controls for the Duke Energy facilities with coal units and non-EGUs with an AOI contribution between one and three percent sulfate plus nitrate and based on this review, DAQ did not identify any uncontrolled or lightly controlled facilities that were large contributors to anthropogenic light extinction at any of North Carolina's Class I areas that were missed by North Carolina's source selection process. b. Consideration of the Four Factors: North Carolina considered each of the four CAA factors for BRPP and Domtar and described how the four factors were taken into consideration in selecting the SO 2 measures for inclusion in the State's LTS. For PCS, DAQ considered the four CAA factors for its existing measures for the affected units and determined that there are no technically feasible control measures beyond the existing measures to further reduce SO 2 emissions, and thus, no new measures were evaluated using the four factors. The following subsections summarize the State's evaluation of these facilities. Additional detail is provided in Section I.B. of the TSD. i. BRPP: During 2017 to 2019, BRPP implemented SO 2 controls on existing processes and replaced two coal-fired boilers with new natural gas-fired boilers to comply with a Special Order by Consent (SOC) between the North Carolina Environmental Management Commission and BRPP. 63 As a result of the SOC, BRPP reduced actual annual SO 2 emissions by 93 percent (5,470 tons per year) from 2017-level emissions. 63 See Section 7.8.1.1 of the 2022 Plan. North Carolina and BRPP entered into the SOC on October 9, 2017, to implement facility process modifications, upgrade existing control equipment, as well as to install new control equipment to comply with the Boiler Maximum Achievable Control Technology (MACT) standard by May 20, 2019, that cumulatively resulted in the control and reduction of facility-wide SO 2 emissions. The SOC is available in Docket ID No. EPA-R04-OAR-2020-0001 on www.regulations.gov. The FFA focused on the No. 4 Power Boiler, Riley Bark Boiler, and the Riley Coal Boiler because these three boilers comprise 90.2 percent of the BRPP's total 2019 actual emissions and 91.8 percent of the BRRP's total 2028 projected SO 2 emissions. 64 These units are equipped with wet flue gas desulfurization (WFGD). 65 66 To complete the cost of compliance analysis, BRPP evaluated replacing coal with ultra-low sulfur diesel (ULSD) (all three boilers) and adding dry sorbent injection (DSI) (for the Riley Coal Boiler and No. 4 Power Boiler). Table 7-54 of the 2022 Plan shows that of the new control measures considered, the lowest cost effectiveness was $13,477 per ton of SO 2 removed using a 3.25 percent interest rate and a 30-year equipment life in the cost calculations. The State notes that based on the FFA, BRPP identified no cost-effective control measures to further reduce SO 2 emissions for the three boilers evaluated. 64 See Table 7-48 on p. 271 of the 2022 Plan. 65 The SO 2 removal efficiency from the existing control measures at the Riley Coal Boiler, Riley Bark Boiler, and the No. 4 Power Boiler is approximately 90 percent. See Section 7.8.1.1 of the 2022 Plan. 66 WFGD, also referred to as wet scrubbers, are a type of control technology which removes SO 2 and other pollutants from gaseous exhaust streams. WFGD is considered the most efficient way to remove SO 2 from gaseous waste streams if the removal efficiency is optimized. Regarding the other statutory factors, the State identifies the remaining useful life of the source is estimated at more than 25 years, and the equipment life of the control options evaluated is 30 years for both the DSI and ULSD options. The State identifies that the time necessary to comply for both the DSI and ULSD options is at least three years to accommodate time for corporate funding approval, permitting, re-engineering, and planned outage scheduling. Regarding energy and non-air quality environmental impacts of compliance, DAQ explains that adding DSI would increase energy usage as well as PM emissions from materials handling and landfill operations and it would also decrease the useful life of the mill landfill and increase truck traffic on local streets. Regarding ULSD, no significant energy and non-air quality environmental impacts were identified. Given the 93 percent decrease in SO 2 emissions due to the SOC and the State's determination that there are no cost-effective control SO 2 measures available based on a review of the four factors, DAQ concluded that only existing SO 2 measures are necessary for reasonable progress for the second planning period at BRPP's Riley Coal Boiler, Riley Bark Boiler, and the No. 4 Power Boiler. No source-specific changes were proposed to the North Carolina SIP for BRPP because these existing SO 2 measures are already incorporated into the SIP. 67 67 See 85 FR 74884 (November 24, 2020); 40 CFR 52.1770(d). The SIP contains specific SO 2 permit limits and associated operating restrictions; monitoring, recordkeeping, and reporting; and testing compliance parameters from BRPP's title V permit (No. 08961T29) reflecting the requirements of the SOC. ii. Domtar: The FFA for Domtar focused on Hog Fuel Boiler 2 (“HFB2”) because this unit is projected to emit approximately 90 percent of the facility's total projected SO 2 emissions in 2028 (1,010 tpy out of 1,120 tpy). 68 A hog fuel boiler at a paper mill typically burns wood waste known as “hog fuel” to generate electricity for the mill. In addition, Domtar currently routes the majority of its noncondensible waste gases through HFB2. The sulfur compounds from the waste gases accounts for the vast majority of the SO 2 emissions. HFB2 uses low sulfur fuels and inherent bark scrubbing to control SO 2 emissions. To complete the cost of compliance analysis, Domtar evaluated HFB2 for WFGD and DSI. 69 Table 7-58 of the 2022 Plan provides summary cost data showing that the cost effectiveness of the addition of a WFGD would be $3,660/ton and the addition of DSI would cost $22,092/ton of SO 2 removed using a 3.25 percent interest rate, a 30-year equipment life, and assuming a 95 percent SO 2 control efficiency for the scrubber and a 50 percent control efficiency for DSI. 70 68 With respect to Domtar's Hog Fuel Boiler 1 (“HFB1”), this unit is projected to emit 12 tpy SO 2 in 2028. HFB1 was not included in the FFA because it is currently equipped to burn only natural gas and biomass with No. 2 fuel oil as a backup fuel. Also, based on updated 2028 emissions projections data, the unit will only contribute two percent of the facility's total SO 2 emissions. In the docket to this proposed rule is a legible copy of the May 12, 2020, letter from Domtar to DAQ provided in Appendix G-2a of the Haze Plan. 69 In addition to the FFA, DAQ provided, as supplemental information, that the use of a WFGD on HFB2 would improve visibility by 0.03 deciview and improve visual range by approximately 0.16 mile at Swanquarter and that the WFGD would reduce Domtar's contribution to total visibility impairment at Swanquarter by 0.33 percent (0.152 Mm −1 ). DAQ did not rely upon this supplemental information for the Domtar FFA analysis and conclusions. 70 In Appendix I of the Haze Plan, DAQ notes that HFB2 is used as a control device for several process gas streams at Domtar. DAQ checked EPA's RACT/BACT/LAER Clearinghouse available at https://www.epa.gov/catc/ractbactlaer-clearinghouse-rblc-basic-information and was unable to find documentation of similar emissions units to HFB2 to compare costs of WFGD at this type of unit. Regarding the other statutory factors, the remaining useful life of HFB2 is 20 years or more, and the equipment life assumed in the cost calculations is 30 years for both the WFGD and DSI control options. The time necessary to comply for both the WFGD and DSI options is at least three years due to corporate funding approval, permitting, re-engineering, and planned outage scheduling. Regarding energy and non-air quality environmental impacts of compliance, additional electricity would be needed to operate a DSI system, and a DSI system would create additional solid waste. Regarding the WFGD, additional electricity and water would be needed to run the system and additional fan power would be required overcome the additional pressure drop through the WFGD. Other environmental and energy impacts associated with operating a WFGD include generation and disposal of wastewater. DAQ concluded that there are no cost-effective control SO 2 measures available based on a review of the four factors and that only existing SO 2 measures at HFB2 are necessary for reasonable progress during the second planning period. North Carolina identified permit conditions reflecting these existing measures in Section 7.8.3.1 of the 2022 Plan for incorporation into the North Carolina SIP. In its Commitment Letter, DAQ committed to revise certain permit conditions and submit, no later than one year from the effective date of a final conditional approval action (should EPA finalize the proposed partial conditional approval), a SIP revision requesting incorporation of the revised permit conditions and additional existing specific permit conditions into the SIP. DAQ's commitments are discussed in Section IV.C.3.b.ii of this document. iii. PCS: The FFA for PCS focused on evaluating Sulfuric Acid Plants (SAPs) 5, 6, and 7 for additional SO 2 controls because these three SAPs accounted for over 97 percent of total facility SO 2 emissions in 2016 and are estimated to account for 94 percent of the total facility SO 2 emissions in 2028. During 2017-2019, PCS implemented upgrades to enhance the SO 2 conversions in the catalytic systems on SAPs 5, 6, and 7 pursuant to a consent decree with EPA entered on February 26, 2015. 71 Table 7-61 of the 2022 Plan summarizes the SO 2 emissions reductions from the upgrades involving a dual absorption process with cesium catalyst. 72 PCS' title V permit includes the SO 2 emissions limits required under the consent decree and prohibits relaxation of these emissions limits after the consent decree has been terminated. 71 The consent decree entered by the Court on February 26, 2015, is located in the docket for this proposed rulemaking. This consent decree terminated on April 3, 2023. 72 See Appendix G-3 of the 2022 Plan for additional information regarding the dual absorption process with cesium catalyst. For PCS, the State evaluated whether there are any technically feasible control technologies available for SAPs 5, 6, and 7 at the facility beyond the current SO 2 emissions control technology in place (dual absorption process with cesium catalyst) to further reduce SO 2 emissions at these units and concluded that there are none. Given this conclusion and the SO 2 reductions at PCS due to the upgrades, DAQ concluded that only the existing measures for SAPs 5, 6, and 7 are necessary for reasonable progress during the second planning period. North Carolina identified permit conditions reflecting these existing measures in Section 7.8.3.2 of the 2022 Plan for incorporation into the North Carolina SIP. 73 In its Commitment Letter, DAQ committed to submit, no later than one year from the effective date of a final conditional approval action (should EPA finalize the proposed partial conditional approval), a SIP revision requesting incorporation of additional existing specific permit conditions into the SIP. DAQ's commitments are discussed in Section IV.C.3.b.iii of this document. 73 In an email dated March 28, 2024, DAQ clarified that the text of Condition 2.5 A.1.p of PCS' title V permit, proposed for adoption into the SIP on page 289 of the Haze Plan, was inadvertently excluded from the excerpts of permit conditions provided in Section 7.8.3.2 of the Haze Plan under “ Section 2.5 A.1.k through p—Emissions Monitoring Requirements. ” c. Documentation of Technical Basis: With respect to emissions information documentation pursuant to 40 CFR 51.308(f)(2)(iii), Section 4 of the 2022 Plan explains the State's use of emissions inventories to develop the plan with additional documentation provided in Appendix B. North Carolina, through VISTAS, developed a 2011 statewide base year emissions inventory which was used to project emissions out to 2028, the end of the second planning period. DAQ also evaluated emissions data from 2017, the year of the most recent triennial emissions data available at the time of the development of the 2022 Plan. 74 DAQ also provided annual, statewide anthropogenic SO 2, NO X , and PM 2.5 emissions data from 2011 through 2019 for North Carolina in Tables 13-9, 13-10, and 13-11, respectively, of the 2022 Plan. 74 2017 emissions data is included in the following tables and figures in the 2022 Plan: Table 7-41 (SO 2 ) and 7-42 (NO X ) for certain non-EGU sources in North Carolina; Tables 13-9 (SO 2 ), 13-10 (NO X ), 13-11 (PM 2.5 ), 13-12 (PM 10 ), 13-13 (VOC) for anthropogenic statewide emissions of these pollutants; Table 13-14 (SO 2 , NO X for all RPOs); Figures 13-9 (SO 2 ), 13-10 (NO X ), 13-11 (PM 2.5 ), 13-12 (PM 10 ), 13-13 (VOC)) for anthropogenic statewide emissions of these pollutants; and Figures 13-14 and 13-15 (SO 2 , NO X for all RPOs). With respect to modeling information documentation pursuant to 40 CFR 51.308(f)(2)(iii), Sections 5 and 6 of the 2022 Plan describe the modeling methods used to develop the plan with additional documentation provided in Appendix E and results of the RPG modeling in Section 8 of the plan. Appendix D contains AoI analyses documentation. With respect to cost and engineering information documentation pursuant to 40 CFR 51.308(f)(2)(iii), Section 7.8 of the 2022 Plan details the State's analysis of proposed FFAs for BRPP and Domtar located in Appendix G which evaluated the four factors, including the cost of compliance factor, and provided detailed cost calculations for potential new control measures assessed as part of the engineering analyses. With respect to monitoring information documentation pursuant to 40 CFR 51.308(f)(2)(iii), the State assessed baseline (2000-2004), current (2014-2018), and natural visibility conditions for North Carolina's Class I areas in Section 2 of the 2022 Plan with supporting information located in Appendix C. Section I.D of the TSD provides a more detailed summary of the State's assessment of the documentation of the technical basis for the 2022 Plan under 40 CFR 51.308(f)(2)(iii) and 40 CFR 51.308(f)(6)(v). d. Assessment of the Five Additional Factors in 40 CFR 51.308(f)(2)(iv): With respect to 40 CFR 51.308(f)(2)(iv), North Ca [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%3A2024-18495. Public record. Not legal advice.