# Approval and Promulgation of Implementation Plans; Arkansas; Regional Haze State Implementation Plan; Interstate Transport State Implementation Plan To Address Pollution Affecting Visibility and Regional Haze > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2011-26336 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** October 17, 2011 - **Citation:** 76 FR 64186 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 52 [EPA-R06-OAR-2008-0727; FRL-9478-2] Approval and Promulgation of Implementation Plans; Arkansas; Regional Haze State Implementation Plan; Interstate Transport State Implementation Plan To Address Pollution Affecting Visibility and Regional Haze AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule. SUMMARY: EPA is proposing to partially approve and partially disapprove a revision to the Arkansas State Implementation Plan (SIP) submitted by the State of Arkansas through the Arkansas Department of Environmental Quality (ADEQ) on September 23, 2008, August 3, 2010, and supplemented on September 27, 2011, that addresses regional haze (RH) for the first implementation period. These revisions were submitted to address the requirements of the Clean Air Act (CAA or Act) and our rules that require states to prevent any future and remedy any existing man-made impairment of visibility in mandatory Class I areas caused by emissions of air pollutants from numerous sources located over a wide geographic area (also referred to as the “regional haze program”). EPA is also proposing to partially approve and partially disapprove a portion of a SIP revision submitted by the State of Arkansas on April 2, 2008, and supplemented on September 27, 2011, to address the interstate transport requirements of the CAA that the Arkansas SIP contain adequate provisions to prohibit emissions from interfering with measures required in another state to protect visibility. This action is being taken under section 110 and part C of the CAA. DATES: Comments must be received on or before November 16, 2011. ADDRESSES: Submit your comments, identified by Docket No. EPA-R06-OAR-2008-0727, by one of the following methods: • Federal e-Rulemaking Portal: http://www.regulations.gov. Follow the online instructions for submitting comments. • E-mail: Mr. Guy Donaldson at donaldson.guy@epa.gov. Please also send a copy by e-mail to the person listed in the FOR FURTHER INFORMATION CONTACT section below. • Mail: Mr. Guy Donaldson, Chief, Air Planning Section (6PD-L), Environmental Protection Agency, 1445 Ross Avenue, Suite 1200, Dallas, Texas 75202-2733. • Hand or Courier Delivery: Mr. Guy Donaldson, Chief, Air Planning Section (6PD-L), Environmental Protection Agency, 1445 Ross Avenue, Suite 1200, Dallas, Texas 75202-2733. Such deliveries are accepted only between the hours of 8 a.m. and 4 p.m. weekdays, and not on legal holidays. Special arrangements should be made for deliveries of boxed information. • Fax: Mr. Guy Donaldson, Chief, Air Planning Section (6PD-L), at fax number 214-665-7263. Instructions: Direct your comments to Docket No. EPA-R06-OAR-2008-0727. Our policy is that all comments received will be included in the public docket without change and may be made available online at http://www.regulations.gov, including any personal information provided, unless the comment includes information claimed to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site is an “anonymous access” system, which means we will not know your identity or contact information unless you provide it in the body of your comment. If you send an e-mail comment directly to us without going through http://www.regulations.gov your e-mail address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, we recommend that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If we cannot read your comment due to technical difficulties and cannot contact you for clarification, we may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses. Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available either electronically in http://www.regulations.gov or in hard copy at the Air Planning Section (6PD-L), Environmental Protection Agency, 1445 Ross Avenue, Suite 700, Dallas, Texas 75202-2733. The file will be made available by appointment for public inspection in the Region 6 FOIA Review Room between the hours of 8:30 a.m. and 4:30 p.m. weekdays except for legal holidays. Contact the person listed in the FOR FURTHER INFORMATION CONTACT paragraph below or Mr. Bill Deese at 214-665-7253 to make an appointment. If possible, please make the appointment at least two working days in advance of your visit. There will be a 15 cent per page fee for making photocopies of documents. On the day of the visit, please check in at our Region 6 reception area at 1445 Ross Avenue, Suite 700, Dallas, Texas. The State submittal is also available for public inspection during official business hours, by appointment, at the Arkansas Department of Environmental Quality, 5301 Northshore Drive, North Little Rock, AR 72118-5317. FOR FURTHER INFORMATION CONTACT: Ms. Dayana Medina, Air Planning Section (6PD-L), Environmental Protection Agency, Region 6, 1445 Ross Avenue, Suite 700, Dallas, Texas 75202-2733, telephone 214-665-7241; fax number 214-665-7263; e-mail address medina.dayana@epa.gov. SUPPLEMENTARY INFORMATION: Throughout this document wherever “we,” “us,” or “our” is used, we mean the EPA. Table of Contents I. Overview of Proposed Actions A. Regional Haze B. Interstate Transport and Visibility II. What is the background for our proposed actions? A. Regional Haze B. Roles of Agencies in Addressing Regional Haze C. The 1997 NAAQS for Ozone and PM 2.5 and CAA 110(a)(2)(D)(i) III. What are the requirements for regional haze SIPs? A. The CAA and the Regional Haze Rule B. Determination of Baseline, Natural, and Current Visibility Conditions C. Determination of Reasonable Progress Goals D. Best Available Retrofit Technology E. Long-Term Strategy F. Coordinating Regional Haze and Reasonably Attributable Visibility Impairment G. Monitoring Strategy and Other SIP Requirements H. Consultation With States and Federal Land Managers IV. Our Analysis of Arkansas' Regional Haze SIP A. Affected Class I Areas B. Determination of Baseline, Natural and Current Visibility Conditions 1. Estimating Natural Visibility Conditions 2. Estimating Baseline Visibility Conditions 3. Natural Visibility Impairment 4. Uniform Rate of Progress C. Evaluation of Arkansas' Reasonable Progress Goals 1. Establishment of the Reasonable Progress Goals 2. ADEQ's Reasonable Progress “Four Factor” Analysis 3. Reasonable Progress Consultation D. Evaluation of Arkansas' BART Determinations 1. Identification of BART-Eligible Sources 2. Identification of Sources Subject to BART a. Modeling Methodology b. Contribution Threshold c. Sources Identified by ADEQ as Subject to BART 3. BART Determinations a. AECC Bailey Unit 1 and AECC McClellan Unit 1 BART Determinations b. AEP Flint Creek Boiler No. 1 BART Determination c. Entergy Lake Catherine Unit 4 BART Determination d. Entergy White Bluff Units 1, 2, and Auxiliary Boiler BART Determinations e. Domtar Power Boilers No. 1 and 2 BART Determinations f. ADEQ BART Results and Summary 4. Arkansas' Regional Haze Rule E. Long-Term Strategy 1. Emissions Inventories a. Arkansas' 2002 Emission Inventory b. Arkansas' 2018 Emission Inventory 2. Visibility Projection Modeling 3. Sources of Visibility Impairment a. Sources of Visibility Impairment in Caney Creek b. Sources of Visibility Impairment in Upper Buffalo c. Arkansas' Contribution to Visibility Impairment in Class I Areas Outside the State 4. Consultation and Emissions Reductions for Other States' Class I Areas 5. Mandatory Long-Term Strategy Factors a. Reductions Due to Ongoing Air Pollution Programs b. Measures To Mitigate the Impacts of Construction Activities c. Emissions Limitations and Schedules of Compliance d. Source Retirement and Replacement Schedules e. Agricultural and Forestry Smoke Management Techniques f. Enforceability of Emissions Limitations and Control Measures g. Anticipated Net Effect on Visibility Due to Projected Changes 6. Our Conclusion on Arkansas' Long-Term Strategy F. Coordination of RAVI and Regional Haze Requirements G. Monitoring Strategy and Other SIP Requirements H. Federal Land Manager Coordination I. Periodic SIP Revisions and Five-Year Progress Reports J. Determination of the Adequacy of Existing Implementation Plan V. Our Analysis of Arkansas' Interstate Visibility Transport SIP Provisions VI. Proposed Action A. Regional Haze B. Interstate Transport and Visibility VII. Statutory and Executive Order Reviews I. Overview of Proposed Actions A. Regional Haze We are proposing to partially approve and partially disapprove Arkansas' RH SIP revision submitted on September 23, 2008, August 3, 2010, and supplemented on September 27, 2011, as discussed in sections IV and VI of this proposed rulemaking. Specifically, we are proposing to approve the following: the State's identification of affected Class I areas; the establishment of baseline and natural visibility conditions; the Uniform Rate of Progress (URP); the State's reasonable progress goal (RPG) consultation and the long-term strategy (LTS) consultation; the regional haze monitoring strategy and other SIP requirements under section 51.308(d)(4); the State's commitment to submit periodic regional haze SIP revisions and periodic progress reports describing progress towards the RPGs; the State's commitment to make a determination of the adequacy of the existing SIP at the time a progress report is submitted; and the State's consultation and coordination with Federal land managers (FLMs). We are proposing to partially approve and partially disapprove those portions addressing the State's identification of BART-eligible sources and subject to BART sources; the requirements for best available retrofit technology (BART); the State's RH Rule; and the LTS. Specifically, we are proposing to approve the State's identification of BART-eligible sources, with the exception of the 6A Boiler at the Georgia-Pacific Crossett Mill, which we find to be BART-eligible. We are proposing to approve the State's identification of subject to BART sources, with the exception of the 6A and 9A Boilers at the Georgia-Pacific Crossett Mill, which we find to be subject to BART. We are also proposing to approve the following BART determinations made by ADEQ: The PM BART determination for the No. 1 Boiler of the American Electric Power (AEP) Flint Creek plant; the SO 2 and PM BART determinations for the natural gas firing scenario for Unit 4 of the Entergy Lake Catherine plant; the PM BART determinations for both the bituminous and sub-bituminous coal firing scenarios for Units 1 and 2 of the Entergy White Bluff plant; and the PM BART determination for the No. 1 Power Boiler of the Domtar Ashdown Mill. We are proposing to disapprove the following BART determinations made by ADEQ: The SO 2 , NO X , and PM BART determinations for both Unit 1 of the Arkansas Electric Cooperative Corporation (AECC) Bailey plant and Unit 1 of the AECC McClellan plant; the SO 2 and NO X BART determinations for the No. 1 Boiler of the AEP Flint Creek plant; the NO X BART determination for the natural gas firing scenario and the SO 2 , NO X , and PM BART determinations for the fuel oil firing scenario for Unit 4 of the Entergy Lake Catherine plant; the SO 2 and NO X BART determinations for both the bituminous and sub-bituminous coal firing scenarios for Units 1 and 2 of the Entergy White Bluff plant; the BART determination for the Auxiliary Boiler of the Entergy White Bluff Plant; the SO 2 and NO X BART determinations for the No. 1 Power Boiler of the Domtar Ashdown Mill; and the SO 2 , NO X and PM BART determinations for the No. 2 Power Boiler of the Domtar Ashdown Mill. We are proposing to disapprove these BART determinations because they do not comply with our regulations under 40 CFR 51.308(e). The Arkansas RH Rule, the Arkansas Pollution Control and Ecology Commission (APC&E Commission) Regulation 19, Chapter 15, was submitted by ADEQ on September 23, 2008, as part of the RH SIP. On August 3, 2010, we received a SIP submittal from ADEQ revising several chapters of APC&E Commission Regulation 19, including chapter 15. The revisions to Chapter 15 of APC&E Commission Regulation 19 that we received on August 3, 2010, are mostly non-substantive edits to the original rule we received on September 23, 2008. Therefore, in this proposed rulemaking we are proposing to take action on chapter 15 of APC&E Regulation 19 contained in the submittal we received on September 23, 2008, and as revised by the submittal we received on August 3, 2010. We are proposing to approve the portions of APC&E Commission Regulation 19, chapter 15, which we received on September 23, 2008, and as revised on August 3, 2010, that are consistent with the portions of the Arkansas RH SIP we are proposing to approve and we are proposing to disapprove the portions that are consistent with other portions of the Arkansas RH SIP we are proposing to disapprove. We are proposing to partially approve and partially disapprove the State's LTS because the LTS only partially satisfies the requirements under section 51.308(d)(3), and a portion of it relies on portions of the RH SIP we are proposing to disapprove. We are proposing to disapprove the reasonable progress goals (RPGs) under section 51.308(d)(1) because Arkansas did not consider the factors that states are required to consider in establishing RPGs under the CAA and section 51.308(d)(1)(A). Under the CAA, 1 we must, within 24 months following a final disapproval, either approve a SIP or promulgate a Federal Implementation Plan (FIP). At this time, we are not proposing a FIP for the portions of the Arkansas RH SIP we are proposing to disapprove because ADEQ has expressed its intent to revise the Arkansas RH SIP by correcting the deficiencies we have identified in this proposal. We are electing to not propose a FIP at this time in order to provide Arkansas time to correct these deficiencies. 1 CAA section 110(c)(1). B. Interstate Transport and Visibility We are proposing to partially approve and partially disapprove a portion of the SIP revision we received from the State of Arkansas on April 2, 2008, for the purpose of addressing the “good neighbor” provisions of the CAA section 110(a)(2)(D)(i) for the 1997 8-hour ozone NAAQS and the PM 2.5 NAAQS. Section 110(a)(2)(D)(i)(II) of the Act requires that states have a SIP, or submit a SIP revision, containing provisions “prohibiting any source or other type of emission activity within the state from emitting any air pollutant in amounts which will * * * interfere with measures required to be included in the applicable implementation plan for any other State under part C [of the CAA] to protect visibility.” Because of the impacts on visibility from the interstate transport of pollutants, we interpret the “good neighbor” provisions of section 110 of the Act described above as requiring states to include in their SIPs either measures to prohibit emissions that would interfere with the reasonable progress goals set to protect Class I areas in other states, or a demonstration that emissions from Arkansas sources and activities will not have the prohibited impacts on other states' existing SIPs. Arkansas stated in its April 2, 2008 submittal that it is relying on the Arkansas RH Rule, the APC&E Commission Regulation 19, Chapter 15, to satisfy the requirements of section 110(a)(2)(D)(i)(II) that emissions from Arkansas sources not interfere with measures required in the SIP of any other state under part C of the CAA to protect visibility. ADEQ also stated in its April 2, 2008 submittal that it is not possible to assess whether there is any interference with the measures in the applicable SIP for another state designed to protect visibility for the 8-hour ozone and PM 2.5 NAAQS until ADEQ submits and EPA approves Arkansas' RH SIP. In developing their Regional Haze SIP and RPGs, Arkansas and potentially impacted States collaborated through the Central Regional Air Planning (CENRAP) association. Each State developed its Regional Haze Plans and RPGs based on the CENRAP modeling. The CENRAP modeling was based in part on the emissions reductions each state intended to achieve by 2018. In the case of Arkansas, some of the emissions reductions included in the modeling, and thus relied upon by other States, were from BART controls on Arkansas subject to BART sources. In the State's September 27, 2011 supplemental submission, ADEQ clarified that the base year modeling inventory used by CENRAP in the 2002 base case modeling was prepared by the CENRAP Modeling Workgroup and its consultants, and was derived primarily from the 2002 National Emissions Inventory (NEI). ADEQ also clarified that it provided the CENRAP Modeling Workgroup with the controlled BART source emission limits contained in the State's RH Rule, the APC&E Commission Regulation 19, Chapter 15, for inclusion in the CENRAP's 2018 future case modeling. The State's RH Rule became effective October 15, 2007, and incorporates BART requirements for Arkansas' subject to BART sources. The current language of the regulation requires Arkansas' subject to BART sources to comply with BART requirements no later than five years after EPA approval of the RH SIP or 6 years after the effective date of the regulation, whichever is first. However, on March 26, 2010, the Arkansas Pollution Control and Ecology Commission, the environmental policy-making body for Arkansas, granted all Arkansas subject to BART sources a variance from the compliance deadline imposed by the State's RH Rule, such that these sources are now required to comply with BART requirements no later than 5 years after EPA approval of the RH SIP. Compliance with these BART requirements will ensure that Arkansas obtains its share of the emission reductions relied upon by other states to meet the RPGs for their Class I areas. Since compliance of Arkansas' subject to BART sources with BART requirements is dependent upon our approval of the RH SIP, and since we are proposing to disapprove the portion of the RH SIP which includes some of Arkansas' BART determinations, a portion of the emission reductions committed to by Arkansas and relied upon by other states will not be realized and, as a consequence, Arkansas' emissions will interfere with other states' SIPs to protect visibility. Therefore, we are proposing to partially approve and partially disapprove the portion of the Arkansas Interstate Transport SIP submittal that addresses the visibility requirement of section 110(a)(2)(D)(i)(II) that emissions from Arkansas sources not interfere with measures required in the SIP of any other state under part C of the CAA to protect visibility. II. What is the background for our proposed actions? A. Regional Haze RH is visibility impairment that is produced by a multitude of sources and activities which are located across a broad geographic area and emit fine particles (PM 2.5 ) ( e.g., sulfates, nitrates, organic carbon, elemental carbon, and soil dust) and their precursors ( e.g., SO 2, nitrogen oxides (NO X ), and in some cases, ammonia (NH 3 ) and volatile organic compounds (VOCs)). Fine particle precursors react in the atmosphere to form PM 2.5 ( e.g., sulfates, nitrates, organic carbon, elemental carbon, and soil dust), which also impair visibility by scattering and absorbing light. Visibility impairment reduces the clarity, color, and visible distance that one can see. PM 2.5 also can cause serious health effects and mortality in humans and contributes to environmental effects such as acid deposition and eutrophication. Data from the existing visibility monitoring network, the “Interagency Monitoring of Protected Visual Environments” (IMPROVE) monitoring network, show that visibility impairment caused by air pollution occurs virtually all the time at most national park and wilderness areas. The average visual range 2 in many Class I areas ( i.e., national parks and memorial parks, wilderness areas, and international parks meeting certain size criteria) in the western United States is 100-150 kilometers, or about one-half to two-thirds of the visual range that would exist without anthropogenic air pollution. 64 FR 35714, 35715 (July 1, 1999). In most of the eastern Class I areas of the United States, the average visual range is less than 30 kilometers, or about one-fifth of the visual range that would exist under estimated natural conditions. Id. 2 Visual range is the greatest distance, in kilometers or miles, at which a dark object can be viewed against the sky. In section 169A of the 1977 Amendments to the CAA, Congress created a program for protecting visibility in the nation's national parks and wilderness areas. This section of 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 3 which impairment results from man-made air pollution.” CAA § 169A(a)(1). The terms “impairment of visibility” and “visibility impairment” are defined in the Act to include a reduction in visual range and atmospheric discoloration. Id. section 169A(g)(6). In 1980, we promulgated regulations to address visibility impairment in Class I areas that is “reasonably attributable” to a single source or small group of sources, i.e., “reasonably attributable visibility impairment” (RAVI). 45 FR 80084 (December 2, 1980). These regulations represented the first phase in addressing visibility impairment. We deferred action on RH that emanates from a variety of sources until monitoring, modeling and scientific knowledge about the relationships between pollutants and visibility impairment improved. 3 Areas designated as mandatory Class I Federal areas consist of national parks exceeding 6000 acres, wilderness areas and national memorial parks exceeding 5000 acres, and all international parks that were in existence on August 7, 1977. See CAA section 162(a). In accordance with section 169A of the CAA, EPA, in consultation with the Department of Interior, promulgated a list of 156 areas where visibility is identified as an important value. See 44 FR 69122, November 30, 1979. The extent of a mandatory Class I area includes subsequent changes in boundaries, such as park expansions. CAA section 162(a). Although states and tribes may designate as Class I additional areas which they consider to have visibility as an important value, the requirements of the visibility program set forth in section 169A of the CAA apply only to “mandatory Class I Federal areas.” Each mandatory Class I Federal area is the responsibility of a “Federal Land Manager” (FLM). See CAA section 302(i). When we use the term “Class I area” in this action, we mean a “mandatory Class I Federal area.” Congress added section 169B to the CAA in 1990 to address RH issues, and we promulgated regulations addressing RH in 1999. 64 FR 35714 (July 1, 1999), codified at 40 CFR part 51, subpart P. The Regional Haze Rule (RHR) revised the existing visibility regulations to integrate into the regulations provisions addressing RH impairment and established a comprehensive visibility protection program for Class I areas. The requirements for RH, found at 40 CFR 51.308 and 51.309, are included in our visibility protection regulations at 40 CFR 51.300-309. Some of the main elements of the RH requirements are summarized in section III. The requirement to submit a RH SIP applies to all 50 states, the District of Columbia and the Virgin Islands. 4 States were required to submit the first implementation plan addressing RH visibility impairment no later than December 17, 2007. 40 CFR 51.308(b). We received the Arkansas RH SIP on September 23, 2008. 4 Albuquerque/Bernalillo County in New Mexico must also submit a regional haze SIP to completely satisfy the requirements of section 110(a)(2)(D) of the CAA for the entire State of New Mexico under the New Mexico Air Quality Control Act (section 74-2-4). B. Roles of Agencies in Addressing Regional Haze Successful implementation of the RH program will require long-term regional coordination among states, tribal governments and various federal agencies. As noted above, pollution affecting the air quality in Class I areas can be transported over long distances, even hundreds of kilometers. Therefore, to address effectively the problem of visibility impairment in Class I areas, states need to develop strategies in coordination with one another, taking into account the effect of emissions from one jurisdiction on the air quality in another. Because the pollutants that lead to RH can originate from sources located across broad geographic areas, we have encouraged the states and tribes across the United States to address visibility impairment from a regional perspective. Five regional planning organizations (RPOs) were developed to address RH and related issues. The RPOs first evaluated technical information to better understand how their states and tribes impact Class I areas across the country, and then pursued the development of regional strategies to reduce emissions of particulate matter (PM) and other pollutants leading to RH. The CENRAP is an organization of states, tribes, federal agencies and other interested parties that identifies RH and visibility issues and develops strategies to address them. CENRAP is one of the five RPOs across the U.S. and includes the states and tribal areas of Nebraska, Kansas, Oklahoma, Texas, Minnesota, Iowa, Missouri, Arkansas, and Louisiana. C. The 1997 NAAQS for Ozone and PM 2.5 and CAA 110(a)(2)(D)(i) On July 18, 1997, we promulgated new NAAQS for 8-hour ozone and for PM 2.5 . 62 FR 38652. Section 110(a)(1) of the CAA requires states to submit SIPs to address a new or revised NAAQS within 3 years after promulgation of such standards, or within such shorter period as we may prescribe. Section 110(a)(2) of the CAA lists the elements that such new SIPs must address, including section 110(a)(2)(D)(i), which pertains to the interstate transport of certain emissions. Thus, states were required to submit SIPs that satisfy the applicable requirements under sections 110(a)(1) and (2), including the requirements of section 110(a)(2)(D)(i), by July 2000. States, including Arkansas, did not meet the statutory July 2000 deadline for submission of these SIPs. Accordingly, on April 25, 2005, EPA made findings of failure to submit, notifying all states, including Arkansas, of their failure to make the required SIP submission to address interstate transport under section 110(a)(2)(D)(i). 70 FR 21147. This finding started a 24-month FIP clock under section 110(c). Pursuant to section 110(c), we are required to promulgate a FIP to address the applicable interstate transport requirements, unless the State makes the required submission and we fully approve such submission, within the 24-month period. On August 15, 2006, we issued our “Guidance for State Implementation Plan (SIP) Submissions to Meet Current Outstanding Obligations Under Section 110(a)(2)(D)(i) for the 8-Hour Ozone and PM 2.5 National Ambient Air Quality Standards” (2006 Guidance). We developed the 2006 Guidance to make recommendations to states for making submissions to meet the requirements of section 110(a)(2)(D)(i) for the 1997 8-hour ozone standards and the 1997 PM 2.5 standards. As identified in the 2006 Guidance, the “good neighbor” provisions in section 110(a)(2)(D)(i) of the CAA require each state to submit a SIP that prohibits emissions that adversely affect another state in the ways contemplated in the statute. Section 110(a)(2)(D)(i) contains four distinct requirements related to the impacts of interstate transport. The SIP must prevent sources in the state from emitting pollutants in amounts which will: (1) Contribute significantly to nonattainment of the NAAQS in other states; (2) interfere with maintenance of the NAAQS in other states; (3) interfere with provisions to prevent significant deterioration of air quality in other states; or (4) interfere with efforts to protect visibility in other states. In this action, we only address the fourth element regarding visibility. The 2006 Guidance stated that states may make a simple SIP submission confirming that it is not possible at that time to assess whether there is any interference with measures in the applicable SIP for another state designed to “protect visibility” for the 8-hour ozone and PM 2.5 NAAQS until RH SIPs are submitted and approved. RH SIPs were required to be submitted by December 17, 2007. See 74 FR 2392 (January 15, 2009). On April 2, 2008, we received a SIP revision from Arkansas to address the interstate transport provisions of CAA 110(a)(2)(D)(i) for the 1997 ozone and PM 2.5 NAAQS. For the reasons discussed in section V of this proposed rulemaking, a portion of the emission reductions committed to by Arkansas and relied upon by other states will not be realized and Arkansas' emissions will interfere with other states' SIPs to protect visibility. Therefore, we are proposing to partially approve and partially disapprove the portion of the Arkansas Interstate Transport SIP submittal that addresses the requirement that emissions from Arkansas sources not interfere with measures required in the SIP of any other state to protect visibility. See CAA section 110(a)(2)(D)(i)(II). We recognize that we have an outstanding obligation to promulgate a FIP for the portion of the Arkansas Interstate Transport SIP submittal we are proposing to disapprove. However, because we are not proposing a FIP for the portions of the Arkansas RH SIP we are proposing to disapprove at this time in order to provide Arkansas time to correct the deficiencies identified in this proposal, we are likewise not proposing a FIP at this time for the disapproved portion of the Arkansas Interstate Transport SIP. We believe it is appropriate to address the concerns with the Regional Haze SIP and the Interstate Transport SIP at the same time and it is appropriate, in this instance, to allow the state an opportunity to address the deficiencies we have identified in this proposed action before imposing a FIP. If we were to propose a FIP for the disapproved portion of the Arkansas Interstate Transport SIP without also proposing a FIP for the disapproved portions of the Arkansas RH SIP, this could potentially result in Arkansas' subject to BART sources being required to install two successive levels of control measures, the first in order to meet the requirements of section 110(a)(2)(D)(i), and the second in order to meet the requirements of the RH program. This would result in an inefficient use of resources by both the affected sources and us. III. What are the requirements for regional haze SIPs? The following is a summary and basic explanation of the regulations covered under the RHR. See 40 CFR 51.308 for a complete listing of the regulations under which this SIP was evaluated. A. The CAA and the Regional Haze Rule RH SIPs must assure reasonable progress towards the national goal of achieving natural visibility conditions in Class I areas. Section 169A of the CAA and our implementing regulations require states to establish long-term strategies for making reasonable progress toward meeting this goal. Implementation plans must also give specific attention to certain stationary sources that were in existence on August 7, 1977, but were not in operation before August 7, 1962, and require these sources, where appropriate, to install BART controls for the purpose of eliminating or reducing visibility impairment. The specific RH SIP requirements are discussed in further detail below. B. Determination of Baseline, Natural, and Current Visibility Conditions The RHR establishes the deciview (dv) as the principal metric for measuring visibility. See 70 FR 39104. This visibility metric expresses uniform changes in the degree of haze in terms of common increments across the entire range of visibility conditions, from pristine to extremely hazy conditions. Visibility is sometimes expressed in terms of the visual range, which is the greatest distance, in kilometers or miles, at which a dark object can just be distinguished against the sky. The deciview is a useful measure for tracking progress in improving visibility, because each deciview change is an equal incremental change in visibility perceived by the human eye. Most people can detect a change in visibility of one deciview. 5 5 The preamble to the RHR provides additional details about the deciview. 64 FR 35714, 35725 (July 1, 1999). The deciview is used in expressing Reasonable Progress Goals (RPGs) (which are interim visibility goals towards meeting the national visibility goal), defining baseline, current, and natural conditions, and tracking changes in visibility. The RH SIPs must contain measures that ensure “reasonable progress” toward the national goal of preventing and remedying visibility impairment in Class I areas caused by man-made air pollution by reducing anthropogenic emissions that cause RH. The national goal is a return to natural conditions, i.e., man-made sources of air pollution would no longer impair visibility in Class I areas. To track changes in visibility over time at each of the 156 Class I areas covered by the visibility program (40 CFR 81.401-437), and as part of the process for determining reasonable progress, states must calculate the degree of existing visibility impairment at each Class I area at the time of each RH SIP submittal and periodically review progress every five years midway through each 10-year implementation period. To do this, the RHR requires states to determine the degree of impairment (in deciviews) for the average of the 20 percent least impaired (“best”) and 20 percent most impaired (“worst”) visibility days over a specified time period at each of their Class I areas. In addition, states must also develop an estimate of natural visibility conditions for the purpose of comparing progress toward the national goal. Natural visibility is determined by estimating the natural concentrations of pollutants that cause visibility impairment and then calculating total light extinction based on those estimates. We have provided guidance to states regarding how to calculate baseline, natural and current visibility conditions. 6 6 Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule, September 2003, EPA-454/B-03-005, available at http://www.epa.gov/ttncaaa1/t1/memoranda/rh_envcurhr_gd.pdf, (hereinafter referred to as “our 2003 Natural Visibility Guidance”); and Guidance for Tracking Progress Under the Regional Haze Rule, (EPA-454/B-03-004, September 2003, available at http://www.epa.gov/ttncaaa1/t1/memoranda/rh_tpurhr_gd.pdf, (hereinafter referred to as our “2003 Tracking Progress Guidance”). For the first RH SIPs that were due by December 17, 2007, “baseline visibility conditions” were the starting points for assessing “current” visibility impairment. Baseline visibility conditions represent the degree of visibility impairment for the 20 percent least impaired days and 20 percent most impaired days for each calendar year from 2000 to 2004. Using monitoring data for 2000 through 2004, states are required to calculate the average degree of visibility impairment for each Class I area, based on the average of annual values over the five-year period. The comparison of initial baseline visibility conditions to natural visibility conditions indicates the amount of improvement necessary to attain natural visibility, while the future comparison of baseline conditions to the then current conditions will indicate the amount of progress made. In general, the 2000-2004 baseline period is considered the time from which improvement in visibility is measured. C. Determination of Reasonable Progress Goals The vehicle for ensuring continuing progress towards achieving the natural visibility goal is the submission of a series of RH SIPs from the states that establish two RPGs ( i.e., two distinct goals, one for the “best” and one for the “worst” days) for every Class I area for each (approximately) 10-year implementation period. See 70 FR 3915; see also 64 FR 35714. The RHR does not mandate specific milestones or rates of progress, but instead calls for states to establish goals that provide for “reasonable progress” toward achieving natural ( i.e., “background”) visibility conditions. In setting RPGs, states must provide for an improvement in visibility for the most impaired days over the (approximately) 10-year period of the SIP, and ensure no degradation in visibility for the least impaired days over the same period. Id. States have significant discretion in establishing RPGs, but are required to consider the following factors established in section 169A of the CAA and in our RHR at 40 CFR 51.308(d)(1)(i)(A): (1) The costs of compliance; (2) the time necessary for compliance; (3) the energy and non-air quality environmental impacts of compliance; and (4) the remaining useful life of any potentially affected sources. States must demonstrate in their SIPs how these factors are considered when selecting the RPGs for the best and worst days for each applicable Class I area. States have considerable flexibility in how they take these factors into consideration, as noted in our Reasonable Progress Guidance 7 . In setting the RPGs, states must also consider the rate of progress needed to reach natural visibility conditions by 2064 (referred to hereafter as the “Uniform Rate of Progress (URP)” and the emission reduction measures needed to achieve that rate of progress over the 10-year period of the SIP. Uniform progress towards achievement of natural conditions by the year 2064 represents a rate of progress, which states are to use for analytical comparison to the amount of progress they expect to achieve. In setting RPGs, each state with one or more Class I areas (“Class I State”) must also consult with potentially “contributing states,” i.e., other nearby states with emission sources that may be affecting visibility impairment at the Class I State's areas. 40 CFR 51.308(d)(1)(iv). 7 Guidance for Setting Reasonable Progress Goals under the Regional Haze Program, June 1, 2007, memorandum from William L. Wehrum, Acting Assistant Administrator for Air and Radiation, to EPA Regional Administrators, EPA Regions 1-10 (pp.4-2, 5-1). D. Best Available Retrofit Technology Section 169A of the CAA directs states to evaluate the use of retrofit controls at certain larger, often uncontrolled, older stationary sources with the potential to emit greater than 250 tons or more of any pollutant in order to address visibility impacts from these sources. Specifically, section 169A(b)(2)(A) of the Act requires states to revise their SIPs to contain such measures as may be necessary to make reasonable progress towards the natural visibility goal, including a requirement that certain categories of existing major stationary sources 8 built between 1962 and 1977 procure, install, and operate the “Best Available Retrofit Technology” (BART), as determined by the state or us in the case of a plan promulgated under section 110(c) of the CAA. Under the RHR, States are directed to conduct BART determinations for such “BART-eligible” sources that may be anticipated to cause or contribute to any visibility impairment in a Class I area. Rather than requiring source-specific BART controls, states also have the flexibility to adopt an emissions trading program or other alternative program as long as the alternative provides greater reasonable progress towards improving visibility than BART. 8 The set of “major stationary sources” potentially subject to BART are listed in CAA section 169A(g)(7). We promulgated regulations addressing RH in 1999, 64 FR 35714 (July 1, 1999), codified at 40 CFR part 51, subpart P. 9 These regulations require all states to submit implementation plans that, among other measures, contain either emission limits representing BART for certain sources constructed between 1962 and 1977, or alternative measures that provide for greater reasonable progress than BART. 40 CFR 51.308(e). 9 In American Corn Growers Ass'n v. EPA, 291 F.3d 1 (D.C. Cir. 2002), the U.S Court of Appeals for the District of Columbia Circuit issued a ruling vacating and remanding the BART provisions of the regional haze rule. In 2005, we issued BART guidelines to address the court's ruling in that case. See 70 FR 39104 (July 6, 2005). On July 6, 2005, we published the Guidelines for BART Determinations Under the Regional Haze Rule at Appendix Y to 40 CFR part 51 (“BART Guidelines”) to assist states in determining which of their sources should be subject to the BART requirements and in determining appropriate emission limits for each applicable source. 70 FR 39104. In making a BART determination for a fossil fuel-fired electric generating plant with a total generating capacity in excess of 750 megawatts (MW), a state must use the approach set forth in the BART Guidelines. A state is encouraged, but not required, to follow the BART Guidelines in making BART determinations for other types of sources. The process of establishing BART emission limitations can be logically broken down into three steps: first, states identify those sources which meet the definition of “BART-eligible source” set forth in 40 CFR 51.301 10 ; second, states determine whether such sources “emits any air pollutant which may reasonably be anticipated to cause or contribute to any impairment of visibility in any such area” (a source which fits this description is “subject to BART,”) and; third, for each source subject to BART, states then identify the appropriate type and the level of control for reducing emissions. 10 BART-eligible sources are those sources that have the potential to emit 250 tons or more of a visibility-impairing air pollutant, were put in place between August 7, 1962 and August 7, 1977, and whose operations fall within one or more of 26 specifically listed source categories. States must address all visibility-impairing pollutants emitted by a source in the BART determination process. The most significant visibility impairing pollutants are SO 2 , NO X , and PM. We have stated that states should use their best judgment in determining whether VOC or ammonia compounds impair visibility in Class I areas. Under the BART Guidelines, states may select an exemption threshold value for their BART modeling, below which a BART-eligible source would not be expected to cause or contribute to visibility impairment in any Class I area. The state must document this exemption threshold value in the SIP and must state the basis for its selection of that value. Any source with emissions that model above the threshold value would be subject to a BART determination review. The BART Guidelines acknowledge varying circumstances affecting different Class I areas. States should consider the number of emission sources affecting the Class I areas at issue and the magnitude of the individual sources' impacts. Any exemption threshold set by the state should not be higher than 0.5 dv. See also 40 CFR part 51, Appendix Y, section III.A.1. In their SIPs, states must identify potential BART sources, described as “BART-eligible sources” in the RHR, and document their BART control determination analyses. The term “BART-eligible source” used in the BART Guidelines means the collection of individual emission units at a facility that together comprises the BART-eligible source. In making BART determinations, section 169A(g)(2) of the CAA requires that states consider the following factors: (1) The costs of compliance; (2) the energy and non-air quality environmental impacts of compliance; (3) any existing pollution control technology in use at the source; (4) the remaining useful life of the source; and (5) the degree of improvement in visibility which may reasonably be anticipated to result from the use of such technology. States are free to determine the weight and significance to be assigned to each factor. See 40 CFR 51.308(e)(1)(ii). A RH SIP must include source-specific BART emission limits and compliance schedules for each source subject to BART. Once a state has made its BART determination, the BART controls must be installed and in operation as expeditiously as practicable, but no later than five years after the date of our approval of the RH SIP. CAA section 169(g)(4) and 40 CFR 51.308(e)(1)(iv). In addition to what is required by the RHR, general SIP requirements mandate that the SIP must also include all regulatory requirements related to monitoring, recordkeeping, and reporting for the BART controls on the source. See CAA section 110(a). As noted above, the RHR allows states to implement an alternative program in lieu of BART so long as the alternative program can be demonstrated to achieve greater reasonable progress toward the national visibility goal than would BART. E. Long-Term Strategy (LTS) Consistent with the requirement in section 169A(b) of the CAA that states include in their regional haze SIP a 10 to 15 year strategy for making reasonable progress, Section 51.308(d)(3) of the RHR requires that states include a LTS in their RH SIPs. The LTS is the compilation of all control measures a state will use during the implementation period of the specific SIP submittal to meet any applicable RPGs. The LTS must include “enforceable emissions limitations, compliance schedules, and other measures as necessary to achieve the reasonable progress goals” for all Class I areas within, or affected by emissions from, the state. 40 CFR 51.308(d)(3). When a state's emissions are reasonably anticipated to cause or contribute to visibility impairment in a Class I area located in another state, the RHR requires the impacted state to coordinate with the contributing states in order to develop coordinated emissions management strategies. 40 CFR 51.308(d)(3)(i). Also, a state with a Class I area impacted by emissions from another state must consult with such contributing state, ( id. ) and must also demonstrate that it has included in its SIP all measures necessary to obtain its share of emission reductions needed to meet the reasonable progress goals for the Class I area. Id. at (d)(3)(ii). In such cases, the contributing state must demonstrate that it has included, in its SIP, all measures necessary to obtain its share of the emission reductions needed to meet the RPGs for the Class I area. The RPOs have provided forums for significant interstate consultation, but additional consultations between states may be required to sufficiently address interstate visibility issues. This is especially true where two states belong to different RPOs. States should consider all types of anthropogenic sources of visibility impairment in developing their LTS, including stationary, minor, mobile, and area sources. At a minimum, states must describe how each of the following seven factors listed below are taken into account in developing their LTS: (1) Emission reductions due to ongoing air pollution control programs, including measures to address RAVI; (2) measures to mitigate the impacts of construction activities; (3) emissions limitations and schedules for compliance to achieve the RPG; (4) source retirement and replacement schedules; (5) smoke management techniques for agricultural and forestry management purposes including plans as currently exist within the state for these purposes; (6) enforceability of emissions limitations and control measures; (7) the anticipated net effect on visibility due to projected changes in point, area, and mobile source emissions over the period addressed by the LTS. 40 CFR 51.308(d)(3)(v). F. Coordinating Regional Haze and Reasonably Attributable Visibility Impairment As part of the RHR, we revised 40 CFR 51.306(c) regarding the LTS for RAVI to require that the RAVI plan must provide for a periodic review and SIP revision not less frequently than every three years until the date of submission of the state's first plan addressing RH visibility impairment, which was due December 17, 2007, in accordance with 40 CFR 51.308(b) and (c). On or before this date, the state must revise its plan to provide for review and revision of a coordinated LTS for addressing RAVI and RH, and the state must submit the first such coordinated LTS with its first RH SIP. Future coordinated LTS and periodic progress reports evaluating progress towards RPGs, must be submitted consistent with the schedule for SIP submission and periodic progress reports set forth in 40 CFR 51.308(f) and 51.308(g), respectively. The periodic review of a state's LTS must report on both RH and RAVI impairment and must be submitted to us as a SIP revision. G. Monitoring Strategy and Other SIP Requirements Section 51.308(d)(4) of the RHR includes the requirement for a monitoring strategy for measuring, characterizing, and reporting of RH visibility impairment that is representative of all mandatory Class I Federal areas within the state. The strategy must be coordinated with the monitoring strategy required in section 51.305 for RAVI. Compliance with this requirement may be met through “participation” in the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, i.e., review and use of monitoring data from the network. The monitoring strategy is due with the first RH SIP, and it must be reviewed every five (5) years. The monitoring strategy must also provide for additional monitoring sites if the IMPROVE network is not sufficient to determine whether RPGs will be met. The SIP must also provide for the following: • Procedures for using monitoring data and other information in a state with mandatory Class I areas to determine the contribution of emissions from within the state to RH visibility impairment at Class I areas both within and outside the state; • Procedures for using monitoring data and other information in a state with no mandatory Class I areas to determine the contribution of emissions from within the state to RH visibility impairment at Class I areas in other states; • Reporting of all visibility monitoring data to the Administrator at least annually for each Class I area in the state, and where possible, in electronic format; • Developing 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 a baseline year, emissions for the most recent year for which data are available, and estimates of future projected emissions. A state must also make a commitment to update the inventory periodically; and • Other elements, including reporting, recordkeeping, and other measures necessary to assess and report on visibility. The RHR requires control strategies to cover an initial implementation period extending to the year 2018, with a comprehensive reassessment and revision of those strategies, as appropriate, every 10 years thereafter. Periodic SIP revisions must meet the core requirements of section 51.308(d) with the exception of BART. The requirement to evaluate sources for BART applies only to the first RH SIP. Facilities subject to BART must continue to comply with the BART provisions of section 51.308(e), as noted above. Periodic SIP revisions will assure that the statutory requirement of reasonable progress will continue to be met. H. Consultation With States and Federal Land Managers The RHR requires that states consult with Federal Land Managers (FLMs) before adopting and submitting their SIPs. 40 CFR 51.308(i). States must provide FLMs an opportunity for consultation, in person and at least 60 days prior to holding any public hearing on the SIP. This consultation must include the opportunity for the FLMs to discuss their assessment of impairment of visibility in any Class I area and to offer recommendations on the development of the RPGs and on the development and implementation of strategies to address visibility impairment. Further, a state must include in its SIP a description of how it addressed any comments provided by the FLMs. Finally, a SIP 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. IV. Our Analysis of Arkansas' Regional Haze SIP On September 23, 2008, we received a RH SIP revision from the State of Arkansas for approval into the Arkansas SIP. We received a supplemental submission to the RH SIP revision on September 27, 2011. In addition, we received a submittal revising several chapters of APC&E Commission Regulation 19, including Chapter 15 (Arkansas' RH Rule), on August 3, 2010. In this proposed rulemaking, the only portions of the August 3, 2010, submittal we are proposing to take action on are those addressing Chapter 15 of APC&E Commission Regulation 19. The following is a discussion of our evaluation of these submissions. The parts of the submittals that are interrelated are discussed together, in order to provide the reader with a more ready understanding of our evaluation. See the Technical Support Document (TSD) for this proposal for a step-wise evaluation of ADEQ's submissions in the order in which the regulations appear in 40 CFR 51.308, and a more comprehensive technical analysis. 11 11 The TSD can be found in the docket for this proposal at http://www.regulations.gov . The docket number is EPA-R06-OAR-2008-0727. A. Affected Class I Areas In accordance with 40 CFR 51.308(d), ADEQ has identified two Class I areas within its borders, the Caney Creek Wilderness Area (Caney Creek) in Ouachita National Forest and the Upper Buffalo Wilderness Area (Upper Buffalo) in the Ozark National Forest. ADEQ is responsible for developing RPGs for these two Class I areas. ADEQ has also determined that Arkansas emissions cause and contribute to visibility impairment at the two Class I areas in Missouri: Hercules Glades Wilderness Area (Hercules Glades) and Mingo National Wildlife Refuge (Mingo). The TSD for the CENRAP Emissions and Air Quality Modeling to Support Regional Haze State Implementation (TSD for CENRAP modeling) demonstrates Arkansas sources are responsible for a visibility extinction of approximately 7.1 inverse megameters 12 (Mm −1 ) at Hercules Glades and for a visibility extinction of approximately 4.95 Mm −1 at Mingo on the worst 20% days for 2002. 13 As discussed in section IV.C.3 of this proposed rulemaking, ADEQ consulted with the appropriate state air quality agency in Missouri to reach an agreement on whether it is necessary for Arkansas to commit to additional emission reductions that would help Missouri achieve its RPGs for Hercules Glades and Mingo. 12 An inverse megameter is the direct measurement unit for visibility impairment data. It is the amount of light scattered and absorbed as it travels over a distance of one million meters. Deciviews (dv) can be calculated from extinction data as follows: dv = 10 × ln (b ext (Mm −1 )/10), where dv stands for “deciviews;” ln stands for “natural logarithm;” and b ext stands for “extinction value.” 13 See Appendix E of the TSD for CENRAP Emissions and Air Quality Modeling to Support Regional Haze State Implementation, found in Appendix 8.1 of the Arkansas RH SIP. B. Determination of Baseline, Natural and Current Visibility Conditions As required by section 51.308(d)(2)(i) of the RHR and in accordance with EPA's 2003 Natural Visibility Guidance, 14 ADEQ calculated baseline/current 15 and natural visibility conditions for its two Class I areas, Caney Creek and Upper Buffalo, on the most impaired and least impaired days, as summarized below (and further described in the TSD). 14 Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule, EPA-454/B-03-005, September 2003. 15 Since this is the first RH SIP submittal, the calculated baseline visibility condition and the current visibility condition will be the same. It is expected that subsequent RH SIP submittals will reflect different calculated numbers for baseline and current visibility conditions due to the change in conditions. 1. Estimating Natural Visibility Conditions Natural background visibility, as defined in EPA's 2003 Natural Visibility Guidance, is estimated by calculating the expected light extinction using default estimates of natural concentrations of fine particle components adjusted by site-specific estimates of humidity. This calculation uses the IMPROVE equation, which is a formula for estimating light extinction from the estimated natural concentrations of fine particle components (or from components measured by the IMPROVE monitors). As documented in EPA's 2003 Natural Visibility Guidance, EPA allows states to use “refined” or alternative approaches to 2003 EPA guidance to estimate the values that characterize the natural visibility conditions of Class I areas. One alternative approach is to develop and justify the use of alternative estimates of natural concentrations of fine particle components. Another alternative is to use the “new IMPROVE equation” that was adopted for use by the IMPROVE Steering Committee in December 2005 16 . The purpose of this refinement to the “old IMPROVE equation” is to provide more accurate estimates of the various factors that affect the calculation of light extinction. 16 The IMPROVE program is a cooperative measurement effort governed by a steering committee composed of representatives from Federal agencies (including representatives from EPA and the FLMs) and RPOs. The IMPROVE monitoring program was established in 1985 to aid the creation of Federal and State implementation plans for the protection of visibility in Class I areas. One of the objectives of IMPROVE is to identify chemical species and emission sources responsible for existing anthropogenic visibility impairment. The IMPROVE program has also been a key participant in visibility-related research, including the advancement of monitoring instrumentation, analysis techniques, visibility modeling, policy formulation and source attribution field studies. ADEQ opted to use the new IMPROVE equation to calculate the “refined” natural visibility conditions. This is an acceptable approach under our 2003 Natural Visibility Guidance. For Caney Creek, ADEQ used the new IMPROVE equation to calculate the “refined” natural visibility value for the 20 percent worst days to be 11.58 deciviews and for the 20 percent best days to be 4.23 deciviews. For Upper Buffalo, ADEQ used the new IMPROVE equation to calculate the “refined” natural visibility value for the 20 percent worst days to be 11.57 deciviews and for the 20 percent best days to be 4.18 deciviews. We have reviewed ADEQ's estimates of the natural visibility conditions for Caney Creek and Upper Buffalo and are proposing to find these acceptable using the new IMPROVE equation. The new IMPROVE equation takes into account the most recent review of the science 17 and it accounts for the effect of particle size distribution on light extinction efficiency of sulfate (SO 4 ), nitrate (NO 3 ), and organic carbon. It also adjusts the mass multiplier for organic carbon (particulate organic matter) by increasing it from 1.4 to 1.8. New terms are added to the equation to account for light extinction by sea salt and light absorption by gaseous nitrogen dioxide. Site-specific values are used for Rayleigh scattering (scattering of light due to atmospheric gases) to account for the site-specific effects of elevation and temperature. Separate relative humidity enhancement factors are used for small and large size distributions of ammonium sulfate and ammonium nitrate and for sea salt. The terms for the remaining contributors, elemental carbon (light-absorbing carbon), fine soil, and coarse mass terms, do not change between the original and new IMPROVE equations. 17 The science behind the revised IMPROVE equation is summarized in Appendix 5.1 of the Arkansas RH SIP and in numerous published papers. See for example: Hand, J.L., and Malm, W.C., 2006, Review of the IMPROVE Equation for Estimating Ambient Light Extinction Coefficients—Final Report. March 2006. Prepared for Interagency Monitoring of Protected Visual Environments (IMPROVE), Colorado State University, Cooperative Institute for Research in the Atmosphere, Fort Collins, Colorado, available at http://vista.cira.colostate.edu/improve/publications/GrayLit/016_IMPROVEeqReview/IMPROVEeqReview.htm and Pitchford, Marc., 2006, Natural Haze Levels II: Application of the New IMPROVE Algorithm to Natural Species Concentrations Estimates. Final Report of the Natural Haze Levels II Committee to the RPO Monitoring/Data Analysis Workgroup. September 2006, available at http://vista.cira.colostate.edu/improve/Publications/GrayLit/029_NaturalCondII/naturalhazelevelsIIreport.ppt. 2. Estimating Baseline Visibility Conditions As required by section 51.308(d)(2)(i) of the RHR and in accordance with EPA's 2003 Natural Visibility Guidance 18 , ADEQ calculated baseline visibility conditions for Caney Creek and Upper Buffalo. The baseline condition calculation begins with the calculation of light extinction, using the IMPROVE equation. The IMPROVE equation sums the light extinction 19 resulting from individual pollutants, such as sulfates and nitrates. As with the natural visibility conditions calculation, ADEQ chose to use the new IMPROVE equation. 18 Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule, EPA-454/B-03-005, September 2003. 19 The amount of light lost as it travels over one million meters. The haze index, in units of deciviews (dv), is calculated directly from the total light extinction, b ext expressed in inverse megameters (Mm −1 ), as follows: HI = 10 ln(b ext /10). The period for establishing baseline visibility conditions is 2000-2004, and baseline conditions must be calculated using available monitoring data. 40 CFR 51.308(d)(2). The IMPROVE monitor at Caney Creek was installed between 2000 and 2002, and therefore ADEQ used visibility data for 2002-2004. The resulting baseline conditions represent an average for 2002-2004. ADEQ calculated the baseline conditions at Caney Creek as 26.36 deciviews on the 20 percent worst days, and 11.24 deciviews on the 20 percent best days. In calculating the baseline conditions at Upper Buffalo, ADEQ used visibility data for 2000-2004. ADEQ calculated the baseline conditions at Upper Buffalo as 26.27 deciviews on the 20 percent worst days, and 11.71 deciviews on the 20 percent best days. We have reviewed ADEQ's estimation of baseline visibility conditions at Caney Creek and Upper Buffalo and are proposing to find these estimates acceptable. 3. Natural Visibility Impairment To address 40 CFR 51.308(d)(2)(iv)(A), ADEQ also calculated the number of deciviews by which baseline conditions exceed natural visibility conditions for the best and worst days at Caney Creek and Upper Buffalo. At Caney Creek for the 20 percent worst days, ADEQ calculated the number of deciviews by which baseline conditions exceed natural visibility conditions to be 14.78 dv (baseline of 26.36 dv−natural conditions of 11.58 dv). For the 20 percent best days at Caney Creek, the baseline conditions exceed natural visibility conditions by 7.01 dv (baseline of 11.24 dv−natural conditions of 4.23 dv). At Upper Buffalo for the 20% worst days, ADEQ calculated the number of deciviews by which baseline conditions exceed natural visibility conditions to be 14.7 dv (baseline of 26.27 dv−natural conditions of 11.57 dv). For the 20 percent best days at Upper Buffalo, the baseline conditions exceed natural visibility conditions by 7.53 dv (baseline of 11.71 dv−natural conditions of 4.18 dv). We have reviewed ADEQ's estimates of the natural visibility impairment at Caney Creek and Upper Buffalo and are proposing to find these estimates acceptable. 4. Uniform Rate of Progress In setting the RPGs, ADEQ analyzed and determined the Uniform Rate of Progress (URP) needed to reach natural visibility conditions by the year 2064. In so doing, ADEQ compared the baseline visibility conditions to the natural visibility conditions in Caney Creek and compared the baseline visibility conditions to the natural visibility conditions in Upper Buffalo (as described above), and determined the uniform rate of progress needed in order to attain natural visibility conditions by 2064. ADEQ constructed the URP consistent with the requirements of the RHR and our 2003 Tracking Progress Guidance by plotting a straight graphical line from the baseline level of visibility impairment for 2000-2004 to the level of visibility conditions representing no anthropogenic impairment in 2064 for Caney Creek and for Upper Buffalo. Using a baseline visibility value of 26.36 dv and a “refined” natural visibility value of 11.58 dv for the 20 percent worst days for Caney Creek, ADEQ calculated the URP to be approximately 0.246 dv per year. This results in a total reduction of 14.78 dv that are necessary to reach the natural visibility condition of 11.58 dv in 2064 for Caney Creek. The URP results in a visibility improvement of 3.45 dv for Caney Creek for the period covered by this SIP revision submittal (up to and including 2018). Using a baseline visibility value of 26.27 dv and a “refined” natural visibility value of 11.57 dv for the 20 percent worst days for Upper Buffalo, ADEQ calculated the URP to be approximately 0.245 dv per year. This results in a total reduction of 14.70 dv that are necessary to reach the natural visibility condition of 11.57 dv in 2064 for Upper Buffalo. The URP results in a visibility improvement of 3.43 dv for Upper Buffalo for the period covered by this SIP revision submittal (up to and including 2018). Table 1—Summary of Uniform Rate of Progress Visibility metric Caney Creek Upper Buffalo Baseline Conditions 26.36 dv 26.27 dv. Natural Visibility 11.58 dv 11.57 dv. Total Improvement by 2064 14.78 dv 14.70 dv. Improvement for this SIP by 2018 3.45 dv 3.43 dv. Uniform Rate of Progress 0.246 dv/year 0.245 dv/year. We are proposing to find that ADEQ has appropriately calculated the URP and has satisfied the requirement in section 51.308(d)(1)(i)(B). C. Evaluation of Arkansas' Reasonable Progress Goals We are proposing to disapprove Arkansas's Reasonable Progress Goals because the State did not establish the RPGs for Caney Creek and Upper Buffalo in accordance with the requirements of the RHR. As a result, ADEQ's RH SIP fails to ensure adequate reasonable progress toward meeting the national visibility goal. Section 169A(g)(1) of the CAA and section 51.308(d)(1)(i)(A) of the RHR require states to take into account certain factors in establishing its reasonable progress goals and to demonstrate how those factors were taken into consideration in selecting the goals. ADEQ did not do so. We do note that ADEQ did consult with other states regarding the development of RPGs in accordance with the RHR, but this is not enough for us to approve the RPGs. 1. Establishment of the Reasonable Progress Goal ADEQ adopted the CENRAP modeled 2018 visibility conditions as the RPGs for Caney Creek and Upper Buffalo Class I areas. ADEQ established a RPG of 22.48 dv for Caney Creek for 2018 for the 20% worst days. This represents a 3.88 dv improvement over a baseline of 26.36 dv. For Upper Buffalo, ADEQ established a RPG of 22.52 dv for 2018 for the 20% worst days, which represents a 3.75 dv improvement over a baseline of 26.27 dv. ADEQ calculated that under its RPGs, it would attain natural visibility conditions in 2062 for Caney Creek and 2063 for Upper Buffalo. The CENRAP's projections for 2018 for the 20% best days for Caney Creek and Upper Buffalo, which represent ADEQ's RPGs for the 20% best days, are shown in Figures 10.4 and 10.6 of the RH SIP and in Appendix D to the TSD for CENRAP Emissions and Air Quality Modeling to Support RH State Implementation. 20 A comparison of ADEQ's RPGs to baseline conditions on the least impaired days shows that control of Arkansas sources will result in no degradation in visibility conditions in the first planning period. The CENRAP modeling shows that for the 20% best days, there would be a 0.89 dv and a 0.91 dv improvement in visibility from the baseline for Caney Creek and Upper Buffalo, respectively. 20 The TSD for CENRAP Emissions and Air Quality Modeling to Support RH State Implementation is found in Appendix 8.1 of the Arkansas RH SIP. ADEQ established RPGs that ensure no degradation in visibility for the least impaired days. See 40 CFR 51.308(d)(1). However, in setting its RPGs for its Class I areas for the 20% worst days, the State relied on the fact that the emission reductions from BART and from the implementation of other requirements of the CAA would result in RPGs that provided for a slightly greater rate of improvement in visibility than would be needed to attain the URP. Based on this fact, ADEQ did not undertake any further analysis. As discussed below, we do not believe this provides sufficient analysis under section 169A of the CAA and our RHR, and discuss it further in the next section. 2. ADEQ's Reasonable Progress “Four Factor” Analysis In establishing a RPG for a Class I Federal area located within a state, the State is required by CAA § 169A(g)(1) and 40 CFR 51.308(d)(1)(i)(A) to “[c]onsider 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, and include a demonstration showing how these factors were taken into consideration in selecting the goal.” In addition to this explicit statutory requirement, the RHR also establishes an analytical requirement to ensure that each State considers carefully the suite of emission reduction measures necessary to attain the URP. The RHR provides that EPA will consider both the State's consideration of the four factors in section 51.308(d)(1)(i)(A) and its analysis of the URP “[i]n determining whether the State's goal for visibility improvement provides for reasonable progress.” 40 CFR 51.308(d)(1)(iii). As explained in the preamble to the RHR, the URP analysis was adopted to ensure that States use a common analytical framework and to ensure an informed and equitable decision making process to ensure a transparent process that would, among other things, ensure that the public would be provided with the information necessary to understand the emission reductions needed, the costs of such measures, and other factors associated with improvements in visibility. 64 FR at 35733. The preamble to the Rule (64 FR 35732) also makes clear that the URP does not establish a “safe harbor” for the State in setting its progress goals: If the State determines that the amount of progress identified through the [URP] analysis is reasonable based upon the statutory factors, the State should identify this amount of progress as its reasonable progress goal for the first long-term strategy, unless it determines that additional progress beyond this amount is also reasonable. If the State determines that additional progress is reasonable based on the statutory factors, the State should adopt that amount of progress as its goal for the first long-term strategy. In establishing its RPGs for 2018 for the 20% worst days, ADEQ relied on the improvements in visibility that are anticipated to result from federal, State, and local control programs that are either currently in effect or with mandated future-year emission reduction schedules that predate 2018, including BART emission limitations established by ADEQ. Based on the emissions reductions from these measures, CENRAP modeled the projected visibility conditions anticipated at each Class I area in 2018 and ADEQ used these results to establish RPGs. ADEQ argued that because this rate of progress, if sustained, will result in a return to natural visibility prior to 2064, no additional analysis was required and would be an unnecessary exercise. We consistently informed States, including Arkansas, throughout the regional haze development process that the above interpretation of the statute and our regulations is incorrect. ADEQ cannot rely solely on meeting the URP to justify the conclusion that its goals provide for reasonable progress. We provided comments to ADEQ on the draft Arkansas RH SIP to that effect. 21 21 See Appendix 2.1 of the Arkansas RH SIP States do have discretion in setting RPGs, but are required to go beyond the URP analysis in establishing RPGs. ADEQ made no attempt to determine whether additional progress would be reasonable based on the statutory factors. It does not appear that such an analysis would have been an unnecessary exercise, as claimed by ADEQ. As discussed in section IV.D.2 of this proposed rulemaking, there are at least two point sources in Arkansas not subject to the BART requirements that contribute to visibility impairment at Arkansas' Class I areas. This conclusion is based on the information in the RH SIP indicating that these sources have predicted impacts exceeding the 0.5 dv threshold ADEQ used to determine whether BART sources contribute to visibility impairment. Given their contribution to visibility impairment, these two sources are potential candidates for emissions controls under reasonable progress, as may be other Arkansas point sources whose visibility impact was not evaluated by ADEQ. Also, as discussed in section IV.E.3 of this proposed notice, Arkansas sources are projected to remain significant contributors to visibility impairment in 2018 and thus providing further support that additional analysis should have been performed according to the statutory factors. Given that ADEQ did not provide an analysis that considered the four statutory factors under 40 CFR 51.308(d)(1)(i)(A) to evaluate the potential of controlling certain sources or source categories for addressing visibility impacts from man-made sources, it is not possible to assess whether any additional control measures for improving visibility are reasonable. Section 51.308(d)(1)(iii) requires that in determining whether the State's goal for visibility improvement provides for reasonable progress towards natural visibility conditions, the Administrator will evaluate the demonstrations developed by the State pursuant to paragraphs (d)(1)(i) and (d)(1)(ii) of this section. Consequently, for the reasons outlined above, we are proposing to find that Arkansas has not satisfied the requirements to establish reasonable progress goals under section 51.308(d)(1)(i)(A). 3. Reasonable Progress Consultation ADEQ worked with the Missouri Department of Natural Resources (MDNR) and CENRAP to jointly develop the consultation strategy. Consultations were held jointly by Arkansas and Missouri. ADEQ used CENRAP as the main vehicle for facilitating collaboration with FLMs and other states in developing its RH SIP. ADEQ was able to use CENRAP generated products, such as regional photochemical modeling results and visibility projections, and source apportionment modeling to assist in identifying neighboring states' contributions to the visibility impairment at Caney Creek and Upper Buffalo. ADEQ determined that in addition to Arkansas, the following states have a significant contribution to decreased visibility in one or both of Arkansas' Class I areas: Illinois, Indiana, Kentucky, Missouri, Ohio, Oklahoma, Tennessee, and Texas. ADEQ sent a letter dated February 26, 2007, to these states, requesting that they participate in the consultation process for the Arkansas RH SIP. These states complied with ADEQ's request and participated in the consultation process for the Arkansas RH SIP. ADEQ and MDNR jointly conducted three consultations in the form of conference calls on April 3, May 11, and June 7, 2007. Participants in the consultation process included states and tribes, CENRAP and other Regional Planning Organizations (RPOs), EPA, and FLMs. At the three consultations held by ADEQ and MDNR, a URP was developed for each Class I area in Arkansas and Missouri (Caney Creek and Upper Buffalo in Arkansas, and Hercules Glades and Mingo in Missouri). The participating states also determined that regional modeling and other findings based on existing and proposed controls arising from local, state, and federal requirements indicated that the two Class I areas in Arkansas and the two Class I areas in Missouri are on the glidepath and are expected to meet the rate of progress goals for the first implementation period ending in 2018. ADEQ determined that additional emissions reductions from other States are not necessary to address visibility impairment at Caney Creek and the Upper Buffalo for the first implementation period ending in 2018, and all states participating in its consultations agreed with this. Therefore, we are proposing to find that Arkansas has satisfied the requirement under section 308(d)(1)(iv) to consult with other States which may reasonably be anticipated to cause or contribute to visibility impairment at Arkansas' two Class I areas. D. Evaluation of Arkansas' BART Determinations Arkansas' RH Rule, APC&E Commission Regulation 19, chapter 15, was included in the Arkansas RH SIP submittal, and became effective on October 15, 2007. On August 3, 2010, we received a SIP revision from ADEQ containing amendments to several chapters of APC&E Commission Regulation 19, including Chapter 15. The revisions to Chapter 15 of APC&E Commission Regulation 19, contained in the August 3, 2010 submittal, are mostly non-substantive amendments to the rule we received on September 23, 2008. Chapter 15 of Regulation 19 incorporates by reference the definitions contained in section 40 CFR 51.301 of the Act, as in effect on June 22, 2007. Chapter 15 also identifies the Arkansas BART-eligible sources, the subject to BART sources and their BART requirements, and the BART compliance provisions. The rules further provide that the source's air quality permit be revised to incorporate the resulting source-specific requirements. The State's RH Rule and our proposed action on it are discussed in section IV.D.4 of this proposed rulemaking. BART is an element of Arkansas' LTS for the first implementation period. As discussed in more detail in section III.D. of this preamble, the BART evaluation process consists of three components: (1) An identification of all the BART-eligible sources, (2) an assessment of whether those BART-eligible sources are in fact subject to BART and (3) a determination of any BART controls. ADEQ addressed these steps as follows: 1. Identification of BART-Eligible Sources The first step of a BART evaluation is to identify all the BART-eligible sources within the state's boundaries. ADEQ identified the BART-eligible sources in Arkansas by utilizing the three eligibility criteria in the BART Guidelines (70 FR 39158) and our regulations (40 CFR 51.301): (1) One or more emission units at the facility fit within one of the 26 categories listed in the BART Guidelines; (2) the emission unit(s) began operation on or after August 6, 1962, and was in existence on August 6, 1977; and (3) potential emissions of any visibility-impairing pollutant from subject units are 250 tons or more per year. ADEQ initially screened its emissions inventory and permitting database to identify major facilities with emission units in one or more of the 26 BART source categories. Following this, ADEQ used its databases and records to identify facilities in these source categories with potential emissions of 250 tons per year (tpy) or more of the following visibility impairing pollutants: sulfur dioxide (SO 2 ), nitrogen dioxide (NO X ), particulate matter equal to or smaller than ten microns (PM 10 ), volatile organic compounds (VOC) or ammonia (NH 3 ). Using its databases and records, ADEQ then determined which of these facilities had units that were in existence on August 7, 1977 and began operation after August 7, 1962. ADEQ contacted the sources, when necessary, to obtain or confirm this information. From this, ADEQ determined there are 18 facilities with BART-eligible units. Table 2 lists Arkansas' BART-eligible sources, as identified by Arkansas in Table 9.1 of the RH SIP: Table 2—Facilities With BART-Eligible Units in Arkansas BART source category Facility name County Unit description Fossil fuel-fired steam electric plants of more than 250 MMBTU/hr heat input AEP Flint Creek Power Plant Benton Boiler AECC Carl E. Bailey Generating Woodruff Boiler AECC John L. McClellan Generating Ouachita Boiler Entergy Lake Catherine Plant Hot Spring Unit 4 Boiler Entergy Robert E. Ritchie Plant Phillips Unit 2 Entergy White Bluff Plant Jefferson Unit 1 Unit 2 Auxiliary Boiler Kraft pulp mills Domtar Ashdown Mill Little River No. 1 Power No. 2 Power Delta Natural Kraft Jefferson Recovery Boiler Evergreen Packaging/International Jefferson No. 4 Recovery Georgia-Pacific Crossett Mill Ashley 9A Boiler Green Bay Packaging Conway Recovery Boiler Potlatch Forest Products/Clearwater Desha Power Boiler Petroleum Lion Oil Company Union No. 7 Catalyst Sulfur recovery Albermarle Corporation South Plant Columbia Tail Gas Sintering plants Big River Industries—Arkalite Crittenden Kiln A Chemical process plants Albermarle Corporation South Plant Columbia No. 1 Boiler No. 2 Boiler Future Fuels/Eastman Chemical Independence 3 Coal Boilers El Dorado Chemical Company Union West Nitric Acid East Nitric Acid Nitric Acid We note that in chapter 15 of APC&E Regulation 19, contained in the RH SIP submittal we received on September 23, 2008, and as revised by the submittal we received on August 3, 2010, ADEQ identified one more unit (not listed in Table 2), the 6A Boiler at the Georgia-Pacific Crossett Mill, as being BART-eligible. ADEQ did not identify the 6A Boiler as BART-eligible in the RH SIP narrative. Appendix 9.1A states the 6A Boiler began operation prior to August 7, 1962, and that it falls out of the BART eligibility criteria because of its start of operations date. On September 27, 2011, ADEQ submitted supplemental information clarifying that the Georgia-Pacific Crossett Mill provided ADEQ a copy of a boiler inspection report for the 6A Boiler, which states that the inspection of the new boiler took place on August 6, 1962, to determine if the boiler complied with the State and American Society of Mechanical Engineers (ASME) codes. 22 However, ADEQ stated it cannot say with certainty whether the 6A boiler was in operation as of August 6, 1962, or at a later date. 23 Since there is not sufficient information to determine the date of start of operations of the 6A Boiler, we cannot make the determination that the boiler is not BART-eligible. Therefore, we are proposing to find that the 6A Boiler at the Georgia-Pacific Crossett Mill is BART-eligible. 22 A copy of the boiler inspection report for the 6A Boiler at the Georgia-Pacific Crossett Mill can be found in the docket for this proposed rulemaking. 23 The BART Guidelines define “in operation” as “engaged in activity related to the primary design function of the source.” In the RH SIP, ADEQ identified one unit (the No. 4 recovery boiler) at International Paper/Evergreen Packaging as BART-eligible (shown in Table 2). ADEQ included two other units (the No. 1 and 2 Power Boilers) at International Paper/Evergreen Packaging in its evaluation to determine what sources are subject to BART. The International Paper/Evergreen Packaging No. 1 and No. 2 Power Boilers are not BART-eligible because they were constructed and were in operation prior to August 7, 1962. 24 We agree that the No. 1 and 2 Power Boilers at International Paper/Evergreen Packaging are not BART-eligible. 24 On May 27, 1958, the Arkansas Department of Labor performed an annual inspection of the International Paper No. 1 and 2 Boilers. On June 26, 1958, the Arkansas Department of Labor issued an inspection certificate to the International Paper Company for the No. 1 and 2 Boilers. Since the No. 1 and 2 Boilers were in operation prior to August 7, 1962, they fall out of the startup date criteria for BART eligibility. The inspection certificate for the can be viewed in the docket for this proposed rulemaking. In the RH SIP, ADEQ did not identify Boilers SN-301A and SN-302A at the Great Lakes Chemical Plant as BART-eligible, but since these units were at one point believed to be BART-eligible, ADEQ included these units in its evaluation to determine what sources are subject to BART. EPA reviewed the federally enforceable operating permit for the Great Lakes Chemical Plant and determined that Boilers SN-301A and SN-302A are not BART-eligible because they are boilers with a heat input rating less than 250 MMBtu/hr and are not integral to the process, as the permit states they are used to supply heat to the process. 25 The BART Guidelines provide that an individual fossil fuel boiler smaller than 250 MMBtu/hr that does not fall into source Category 1 ( i.e., Fossil-fuel fired steam electric plants of more than 250 MMBtu/hr heat input), falls into one of the other source categories for BART eligibility only if it is an integral part of a process description at a plant. If the boiler is integral to the process description at a plant, it falls into the source category of the process which it serves. In general, if the boiler serves the process in any way beyond contributing heat, it is integral to the process. Based on information in the current operating air permit for the Great Lakes Chemical Plant, we agree that Boilers SN-301A and SN-302A are not BART-eligible. 25 ADEQ Operating Air Permit for the Great Lakes Chemical Corporation—Central Plant (Permit No. 1077-AOP-R1). This permit can be viewed at http://www.adeq.state.ar.us/ftproot/pub/WebDatabases/PermitsOnline/Air/1077-AOP-R1.pdf. As discussed above, there is a discrepancy between the BART-eligible sources identified in the RH SIP narrative, and those identified in the State's RH Rule. Because ADEQ submitted supplemental information on September 27, 2011, clarifying that it did not know with certainty the startup date of operations of the 6A Boiler at the Georgia-Pacific Crossett Mill, we are proposing to find that the 6A Boiler is BART-eligible. We are proposing to approve ADEQ's identification of the remaining BART-eligible sources. 2. Identification of Sources Subject to BART The second step of the BART evaluation is to identify those BART-eligible sources that may reasonably be anticipated to cause or contribute to visibility impairment at any Class I area, i.e. those sources that are subject to BART. The BART Guidelines allow states to consider exempting some BART-eligible sources from further BART review because they may not reasonably be anticipated to cause or contribute to any visibility impairment in a Class I area. Consistent with the BART Guidelines, ADEQ required each of its BART-eligible sources to develop and submit dispersion modeling to assess the extent of their contribution to visibility impairment at surrounding Class I areas. The BART Guidelines direct states to address SO 2 , NO X and direct PM (including both PM 10 and PM 2.5 ) emissions as visibility-impairing pollutants, and States must exercise their “best judgment to determine whether VOC or ammonia emissions from a source are likely to have an impact on visibility in an area.” See 70 FR 39162. CENRAP modeling demonstrated that VOCs from anthropogenic sources are not significant visibility-impairing pollutants at Caney Creek and Upper Buffalo. Ammonia emissions in Arkansas are primarily due to area sources, such as livestock and fertilizer application. Because these are not point sources, they are not subject to BART. The emissions inventory prepared for the CENRAP modeling demonstrates that ammonia from point sources are not significant visibility-impairing pollutants in Arkansas. ADEQ further argued that only specific VOCs form secondary organic aerosols that affect visibility and that these compounds are a fraction of the total VOCs reported in Arkansas' emissions inventory. ADEQ does not have the breakdown of VOC emissions necessary to model only those that impair visibility. Because CALPUFF, EPA's prescribed screening model, cannot simulate formation of particles from anthropogenic VOCs, nor their visibility impacts, ADEQ did not evaluate emissions of VOCs in making BART determinations. We have reviewed this information and propose to agree with ADEQ's decision to address only SO 2, NO X , and PM as visibility impairing pollutants because VOC emissions from anthropogenic sources are not significant visibility-impairing pollutants at Caney Creek and Upper Buffalo and ammonia emissions in Arkansas are primarily due to area sources. a. Modeling Methodology The BART Guidelines provide that states may choose to use the CALPUFF 26 modeling system or another appropriate model to predict the visibility impacts from a single source on a Class I area and to therefore, determine whether an individual source is anticipated to cause or contribute to impairment of visibility in Class I areas, i.e., “is subject to BART”. The Guidelines state that we believe CALPUFF is the best regulatory modeling application currently available for predicting a single source's contribution to visibility impairment (70 FR 39162). ADEQ used the CALPUFF modeling system to determine whether individual sources in Arkansas were subject to or exempt from BART. 26 Note that our reference to CALPUFF encompasses the entire CALPUFF modeling system, which includes the CALMET, CALPUFF, and CALPOST models and other pre and post processors. The different versions of CALPUFF have corresponding versions of CALMET, CALPOST, etc. which may not be compatible with previous versions ( e.g., the output from a newer version of CALMET may not be compatible with an older version of CALPUFF). The different versions of the CALPUFF modeling system are available from the model developer at http://www.src.com/verio/download/download.htm. The BART Guidelines also recommend that states develop a modeling protocol for making individual source attributions, and suggest that states may want to consult with us and their RPO to address any issues prior to modeling. The CENRAP states, including Arkansas, developed the “CENRAP BART Modeling Guidelines”. 27 Stakeholders, including EPA, FLMs, industrial sources, trade groups, and other interested parties, actively participated in the development and review of the CENRAP protocol. CENRAP provided readily available modeling data bases for use by states to conduct their analyses. We note that the original meteorological databases generated by CENRAP did not include observations as EPA guidance recommends, therefore sources were evaluated using the 1st High values instead of the 8th High values. The use of the 1st High modeling values was agreed to by EPA, representatives of the Federal Land Managers, and CENRAP stakeholders. We are proposing to find the chosen model and the general modeling methodology for screening modeling acceptable. 27 CENRAP BART Modeling Guidelines, T. W. Tesche, D. E. McNally, and G. J. Schewe (Alpine Geophysics LLC), December 15, 2005, available at http://www.deq.state.ok.us/aqdnew/RulesAndPlanning/Regional_Haze/SIP/Appendices/index.htm. b. Contribution Threshold For states using modeling to determine the applicability of BART to single sources, the BART Guidelines note that the first step is to set a contribution threshold to assess whether the impact of a single source is sufficient to cause or contribute to visibility impairment at a Class I area. The BART Guidelines state that, “[a] single source that is responsible for a 1.0 deciview change or more should be considered to `cause' visibility impairment.” 70 FR 39104, 39161. The BART Guidelines also state that “the appropriate threshold for determining whether a source contributes to visibility impairment may reasonably differ across states,” but, “[a]s a general matter, any threshold that you use for determining whether a source ‘contributes’ to visibility impairment should not be higher than 0.5 deciviews.” Id. Further, in setting a contribution threshold, states should “consider the number of emissions sources affecting the Class I areas at issue and the magnitude of the individual sources' impacts. The Guidelines affirm that states are free to use a lower threshold if they conclude that the location of a large number of BART-eligible sources in proximity of a Class I area justifies this approach. Considering the number of sources affecting Arkansas' Class I areas and the magnitude of each source's impact, ADEQ used a contribution threshold of 0.5 dv for determining which sources are subject to BART. We agree with the State's selection of this threshold value. c. Sources Identified by ADEQ as Subject to BART Following the elimination of those sources that were found to have visibility impacts well below the 0.5 dv threshold, ADEQ identified the sources contained in Table 3 as being subject to BART. Table 3—Sources in Arkansas Subject to BART Facility name BART emission units Source category Pollutants evaluated AECC Carl E. Bailey Generating Station Unit 1 fossil fuel-fired steam electric plants SO 2 NO X PM 10 AECC John L. McClellan Generating Station Unit 1 fossil fuel-fired steam electric plants SO 2 NO X PM 10 AEP Flint Creek Power Plant Boiler No. 1 fossil fuel-fired steam electric plants SO 2 NO X PM 10 Entergy Lake Catherine Plant Unit 4 fossil fuel-fired steam electric plants SO 2 NO X PM 10 Entergy White Bluff Plant Units 1, 2, and Auxiliary Boiler fossil fuel-fired steam electric plants SO 2 NO X PM 10 Domtar Ashdown Mill Power Boilers No. 1 and 2 kraft pulp mill SO 2 NO X PM 10 In Appendix 9.2B of the RH SIP, ADEQ provided screening modeling results for all sources identified in the RH SIP as BART-eligible sources, as well as for the SN-301A and SN-302A Boilers at the Great Lakes Chemical plant, the No. 1 and No. 2 Power Boilers at International Paper/Evergreen Packaging, and the 6A and 9A Boilers at the Georgia-Pacific Crossett Mill (as discussed above). Our evaluation of these results showed that four facilities that ADEQ did not identify as subject to BART had modeled visibility impacts that exceed the 0.5 dv contribution threshold used by ADEQ to determine what sources are subject to BART. Our evaluation to determine whether these sources are subject to BART or not is discussed below: • As discussed in section V.D.1., ADEQ included the No. 1 and No. 2 Power Boilers at International Paper/Evergreen Packaging and the SN-301A and SN-302A Boilers at the Great Lakes Chemical plant in its modeling evaluation to determine what sources are subject to BART. As already discussed elsewhere in this proposed notice, we are proposing to approve ADEQ's identification of these two sources as not BART-eligible and not subject to BART. • As discussed in section IV.D.2.a. of this proposed rulemaking, the original meteorological databases generated by CENRAP did not include observations as EPA guidance recommends. Therefore, in their evaluation to determine if a source exceeds the 0.5 dv contribution threshold at nearby Class I areas, states used the 1st high values ( i.e. , maximum value) of modeled visibility impacts instead of the 8th high values ( i.e. , 98th percentile value). The use of the 1st high modeled values was agreed to by EPA, representatives of the Federal Land Managers, and CENRAP stakeholders. ADEQ's modeling shows that Future Fuels/Eastman Chemical has a modeled visibility impact of 0.711 dv at Hercules-Glade. Further examination of the modeling results reveals that only one day of the three years modeled exceeds the 0.5 dv contribution threshold value at any Class I area. Since only one day is projected above the threshold, we believe it is very unlikely that a refined modeling approach using updated meteorological data, which would allow for the use of the 98th percentile modeled visibility impact rather than the maximum impact, would show modeled impacts above the threshold. Therefore, we are proposing that this facility is not subject to BART. • The visibility modeling provided in Appendix 9.2B of the Arkansas RH SIP shows that the 9A Boiler of the Georgia-Pacific Crossett Mill has visibility impacts exceeding the 0.5 dv contribution threshold, with a visibility impact above 1 dv at Caney Creek and Hercules-Glade. EPA also reviewed ADEQ's revised modeling for this source, which looked at the visibility impacts of both the 6A and 9A Boilers at the Georgia-Pacific Crossett Mill. Using updated emission rates, ADEQ's revised modeling showed projected visibility impacts of the two boilers combined below the 0.5 dv threshold. The revised emission rates were based on stack test results and assumptions based on worst case monthly fuel usage, from the perspective of total emissions. However, from the data provided, it is unclear if the modeled emissions are representative of the actual maximum 24 hour emissions from the highest emitting day over the modeled period. There is no supporting technical analysis discussing the assumptions made in the revised emission estimates and explaining how stack test data was used to estimate maximum emissions nor is fuel usage information provided for the modeled period. We are proposing to disapprove ADEQ's determination that the Georgia-Pacific Crossett Mill's 6A and 9A Boilers are not subject to BART because ADEQ has not modeled the visibility impact of the 6A and 9A Boilers using acceptable estimates of maximum 24 hour emissions, and as a result we do not know if the boilers have a combined visibility impact below the 0.5 dv contribution threshold or not. Based on the permit allowables and available information, the two boilers are subject to BART and require a full BART analysis. We are proposing to approve ADEQ's identification of subject to BART sources, except for ADEQ's determination that the Georgia-Pacific Crossett Mill 6A and 9A Boilers are not subject to BART. 3. BART Determinations The third step of a BART evaluation is to perform the BART analysis. BART is a source-specific control determination, based on consideration of several factors set out in section 169A(g)(2) of the CAA. These factors include the costs of compliance and the degree of improvement in visibility associated with the use of possible control technologies. EPA issued BART Guidelines (Appendix Y to Part 51) in 2005 to clarify the BART provisions based on the statutory and regulatory BART requirements (70 FR 39164). The BART Guidelines describe the BART analysis as consisting of the following five basic steps: • Step 1: Identify All Available Retrofit Control Technologies, • Step 2: Eliminate Technically Infeasible Options, • Step 3: Evaluate Control Effectiveness of Remaining Control Technologies, • Step 4: Evaluate Impacts and Document the Results, and • Step 5: Evaluate Visibility Impacts. We note the BART Guidelines (Appendix Y to part 51) provide that states must follow the guidelines in making BART determinations on a source-by-source basis for 750 MW power plants but are not required to use the process in the guidelines when making BART determinations for other types of sources. States with subject to BART units with a generating capacity less than 750 MW are strongly encouraged to follow the BART Guidelines in making BART determinations, but they are not required to do so. However, the requirement to perform a BART analysis that considers “the technology available, the costs of compliance, the energy and nonair quality environmental impacts of compliance, any pollution control equipment in use at the source, the remaining useful life of the source, and the degree of improvement in visibility which may reasonably be anticipated to result from the use of such technology,” is found in section 51.308(e)(1)(ii)(A) and the RHR, and applies to all subject to BART sources. All of the sources that are subject to BART presented in Table 3 are fossil fuel fired electricity generating units, with the exception of the Domtar Ashdown Mill, which is a kraft pulp mill. ADEQ performed BART determinations for these sources for NOx, SO 2 , and PM. We have found several problems in these BART determinations, which lead us to propose disapproval of some of ADEQ's BART determinations. We discuss these problems in detail in the individual BART determination sections, and we summarize some general issues in the paragraphs that follow. For some sources, ADEQ did not adequately consider whether retrofit controls should be required based on a flawed analysis of the source's potential visibility impacts. ADEQ assumed that if pre-control modeling 28 conducted on the basis of a single pollutant showed that the source's emissions of the pollutant in question did not “contribute” to visibility impairment, then further BART analysis for that pollutant was unnecessary. This approach is unacceptable. Due to the nonlinear nature and complexity of atmospheric chemistry and chemical transformation among pollutants, ideally all relevant pollutants should be modeled together to predict the total visibility impact at each Class I area receptor. 29 At a minimum, NO X and SO 2 emissions should be modeled together to determine the visibility impacts attributable to these pollutants when evaluating controls and combinations of controls in determining BART for a source. Predicting the impacts of PM on visibility is relatively straight-forward, unlike predicting the impacts of SO 2 and NO X . Using CALPUFF on a pollutant specific basis to model only the impact of PM emissions on visibility is an acceptable approach to determine whether a source should be subject to review for PM controls, or alternatively, that the source is not subject to BART for PM. ADEQ applied a threshold of 0.5 dv for determining whether a source “contributes” to visibility impairment on a per-pollutant basis. As discussed above, the State selected a threshold of 0.5 dv for the initial screening modeling that included all pollutants. Clearly, a lower threshold value is needed in evaluating pollutant-specific modeling for sources that emit more than one visibility impairing pollutant. Furthermore, this approach is only acceptable for PM-specific modeling. We note that a State may establish de minimis levels of emissions (applicable on a plant-wide basis) of visibility impairing pollutants to exclude some sources from further evaluation when the emissions are so minimal that they are unlikely to contribute to regional haze. 30 28 Throughout this document, any reference to “ADEQ modeling” refers to modeling performed or reviewed by ADEQ. 29 Memo from Joseph Paisie (Geographic Strategies Group, OAQPS) to Kay Prince (Branch Chief EPA Region 4) on Regional Haze Regulations and Guidelines for Best Available Retrofit Technology (BART) Determinations, July 19, 2006. 30 “States may choose to identify de minimis levels of pollutants at BART-eligible sources (but are not required to do so). De minimis values should be identified with the purpose of excluding only those emissions so minimal that they are unlikely to contribute to regional haze. Any de minimis values that you adopt must not be higher than the PSD applicability levels: 40 tons/yr for SO 2 and NO X and 15 tons/yr for PM 10 . These de minimis levels may only be applied on a plant-wide basis.” 40 CFR Appendix Y to part 51. For some BART determinations, ADEQ did not properly determine BART, but instead concluded that the presumptive limits in the BART Guidelines could be adopted in place of a careful source-specific analysis of the appropriate level of controls. As noted above, EPA issued BART Guidelines in 2005 that address the BART determination process by laying out a step by step process for taking into consideration the factors relevant to a BART determination. In that rulemaking, EPA also established presumptive BART limits for certain electric generating units (EGUs) located at power plants 750 MW or greater in size based variously on the size of the unit, the type of unit, the type of fuel used, and the presence or absence of controls. 31 Having identified controls that the Agency considered to be generally cost-effective across all affected units, the EPA took into account the substantial degree of visibility improvement anticipated to result from the use of such controls on these EGUs and concluded that such BART-eligible sources should at least meet the presumptive limits. The presumptive limits accordingly are the starting point in a BART determination for these units—unless the State determines that the general assumptions underlying EPA's analysis are not applicable in a particular case. EPA did not provide that States could avoid a source-specific BART determination by adopting the presumptive limits. In fact, nothing on the record would support the conclusion that the presumptive limits represent the “best available retrofit controls” for all EGUs at these large power plants. EPA did not address the question of whether in specific cases more stringent controls would be called for but rather simply concluded that it could not reach a generalized conclusion as to the appropriateness of more stringent controls for categories of EGUs. As a result, the BART Rule does not establishing a “safe harbor” from more stringent regulation under the BART provisions. We have consistently informed ADEQ in comments to its draft SIP and in conversations that foregoing a BART analysis is not acceptable. 31 70 FR at 39131-39136. For the BART determinations for which ADEQ did perform a full BART analysis that considered the statutory factors under section 51.308(e)(1)(ii)(A), we are proposing to find that ADEQ did not adequately consider one or more of the factors it is required to consider in determining whether retrofit controls should be required. For more details, please see our evaluation of the BART determination for each subject to BART unit, below, and the TSD. a. AECC Bailey Unit 1 and AECC McClellan Unit 1 BART Determinations The AECC Bailey Unit 1 and the AECC McClellan Unit 1 are BART-eligible sources. The AECC Bailey Unit 1 is a boiler with a gross output of 122 MW and a maximum heat input rate of 1350 MMBtu/hr, and is currently permitted to burn both natural gas and fuel oil. The fuel oil burned at the plant is subject to an operating air permit sulfur content limit of 2.3% by weight. The AECC McClellan Unit 1 is a boiler with a gross output of 134 MW and a maximum heat input rate of 1436 MMBtu/hr, and is currently permitted to burn both natural gas and fuel oil. The fuel oil burned at the plant is subject to an operating air permit sulfur content limit of 2.8% by weight. Regarding BART for NO X and PM, ADEQ conducted pollutant specific pre-control CALPUFF 32 modeling for the AECC Bailey Unit 1 and the AECC McClellan Unit 1. AECC stated that the results of the NO X modeling show that NO X does not cause or contribute to visibility impacts. 33 Based on this, AECC determined and ADEQ agreed it was not necessary to make a BART determination for NO X for either the AECC Bailey Unit 1 or AECC McClellan Unit 1. However, the ADEQ's modeling results presented indicate that the predicted visibility impacts from NO X are as high as 0.347 dv at Mingo due to emissions from the AECC Bailey Unit 1, and 0.421 dv at Caney Creek due to emissions from the AECC McClellan Unit 1. As stated above, NO X and SO 2 emissions should be modeled together due to the nonlinear nature and complexity of atmospheric chemistry and chemical transformation among pollutants. Evaluation of the screening modeling results for these units reveals that on some of the most impacted days, NO X is a significant contributor to the visibility impairment due to these units. Post-control modeling performed by ADEQ, applying the use of 1% sulfur fuel, show that these units would continue to cause or contribute to visibility impairment at a number of Class I areas, with NO X emissions responsible for over 50% of the impairment on some days under this control scenario. In light of the relatively high impacts due to NO X , a combination of NO X and SO 2 controls may prove to be cost-effective and provide for substantial visibility improvement and should therefore be evaluated. 32 The CALPUFF modeling system consists of a meteorological data pre-processor (CALMET), an air dispersion model (CALPUFF), and post-processor programs (POSTUTIL, CALSUM, CALPOST). The CALPUFF modeling system is the recommended model for conducting BART visibility analysis. 33 Arkansas Electric Cooperative Corporation Best Available Retrofit Technology Engineering Analysis prepared by Stephen Cain, October 20, 2006. For PM BART, AECC decided and ADEQ agreed that PM does not cause visibility impacts because the PM emissions are less than those of NO X at these units. This conclusion is not supported in the record by PM visibility modeling results, additional technical analysis, or reference to a permit limit for PM that restricts emissions below a level that will impact visibility. Neither the State nor AECC have completed a BART analysis that considers the statutory factors under section 51.308(e)(1)(ii)(A) that states are required to consider in determining what type and level of control is BART for a source for NO X and PM, or fully demonstrated that these units have sufficient pollution controls in place for these pollutants such that additional controls would likely achieve very low emissions reductions, have minimal visibility benefit, and not be cost-effective. Therefore, we are proposing to disapprove the NO X and PM BART determinations for these two units. Regarding BART for SO 2 for the two sources, AECC performed a BART analysis to determine what retrofit controls are BART for AECC Bailey Unit 1 and AECC McClellan Unit 1. In Step 1 of this BART analysis, AECC identified use of fuel oil with 1% sulfur content and installation of a scrubber as the only two control options available. This is a problem because 1% sulfur fuel oil is not the maximum level of control available when it comes to the use of low sulfur fuel as a control strategy for SO 2 emissions. After completing the remaining steps of the BART analysis, AECC determined and ADEQ agreed that BART for the AECC Bailey Unit 1 and the AECC McClellan Unit 1 is use of fuel oil with 1% sulfur content. Our evaluation of AECC's BART analysis beyond Step 1 can be found in the TSD. We are not discussing in this proposed notice our evaluation of AECC's BART analysis for the AECC Bailey Unit 1 and the AECC McClellan Unit 1 beyond Step 1, as we are proposing that AECC did not properly complete the first step of the BART analysis and thus we find that AECC and ADEQ did not properly follow the requirements of section 51.308(e)(1)(ii)(A) in determining BART. Specifically, we are proposing that AECC and ADEQ did not properly “take into consideration the technology available” by failing to consider the maximum level of control each control option is capable of achieving. The BART Guidelines (Appendix Y to Part 41) provide that in identifying all options, you must identify the most stringent option ( i.e., maximum level of control each technology is capable of achieving) as well a reasonable set of options for analysis. The requirement to consider the most stringent level of control when making BART determinations is also found in the RHR (64 FR 35740), which provides that in establishing source specific BART emission limits, the State should identify and consider in the BART analysis the maximum level of emission reduction that has been achieved in other recent retrofits at existing sources in the source category. The visibility regulations define BART as “an emission limitation based on the degree of reduction achievable through the application of the best system of continuous emission reduction.” Since recent retrofits at existing sources provide a good indication of the current “best system” for controlling emissions, these controls must be considered in the BART analysis. In considering use of fuel oil with low sulfur content as a control option in the BART analysis, AECC did not identify and consider the maximum level of control achievable from the use of low sulfur fuel oil, and thus the BART analysis is flawed. Sulfur content in fuel oil currently can be found in industry to be 0.5% by weight or less. AECC should have considered the use of fuel oil with 0.5% sulfur content or less in the BART analysis for the two units in question. We are aware of several fossil-fuel fired steam electric plants throughout the country that are currently limited by permit to burn fuel oil with a sulfur content of 0.5% or less by weight. Connecticut limits the sulfur content of fuel oil to a maximum 0.3% 34 and New York requires facilities to comply with the use of fuel oil with varying sulfur content limits, with facilities in New York City being required to use fuel oil with a maximum 0.3% sulfur content. 35 Lowering the sulfur content in fuel oil is also a part of the long-term strategy recommended by the Mid-Atlantic/Northeast Visibility Union (MANE-VU) states to reduce and prevent regional haze. 36 The MANE-VU states in the inner zone (New Jersey, New York, Delaware, and Pennsylvania) plan to reduce the sulfur content of No. 6 residual fuel oil to 0.3-0.5% sulfur by weight by no later than 2012. 37 Therefore, the use of fuel oil with a 0.5% sulfur content or lower is technically feasible and either AECC or ADEQ should have evaluated its cost effectiveness for the AECC Bailey Unit 1 and the AECC McClellan Unit 1. In addition, an operating air permit restriction to use only natural gas as the fuel source for the two units would have also been acceptable. As part of the BART analysis, ADEQ and/or AECC must perform a cost analysis in which all cost estimates are properly documented and must evaluate the visibility impacts of all technically feasible control options considered before making a BART determination. 34 Connecticut Department of Environmental Protection (DEP). “22a-174-19a: Control of Sulfur Dioxide Emissions from Power Plants and Other Large Stationary Sources of Air Pollution,” Regulations of Connecticut State Agencies, Title 22a: Abatement of Air Pollution, December 28, 2000. http://www.dep.state.ct.us/air2/regs/mainregs/sec19a.pdf. 35 New York State Department of Environmental Conservation (DEC). “Subpart 225-1: Fuel Composition and Use-Sulfur Limitations,” Environmental Conservation Rules and Regulations, May 8, 2005. http://www.dec.state.ny.us/website/regs/subpart225_1.html. 36 MANE-VU is an RPO that includes the following states: Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania, Maryland, Delaware, and also the District of Columbia. 37 See 76 FR 27973. Therefore, for the reasons expressed above, we are proposing to disapprove the SO 2 , NO X , and PM BART determinations for the AECC Bailey Unit 1 and the AECC McClellan Unit 1. b. AEP Flint Creek No. 1 Boiler BART Determination The AEP Flint Creek No. 1 Boiler is a BART-eligible source. The unit has a gross output of 558 MW and a maximum heat input rate of 6324 MMBtu/hr, and burns primarily low sulfur western coal, but can also combust fuel oil and tire derived fuels (TDF). Fuel oil firing is only allowed during startup and shutdown of the boiler, startup and shutdown of the pulverizer mills, for flame stabilization when the coal is frozen, for fuel oil tank maintenance, to prevent boiler tube failure in extreme cold weather, and when the unit is offline for maintenance. Regarding BART for PM, ADEQ conducted pre-control CALPUFF modeling for the AEP Flint Creek No. 1 Boiler showing that PM 10 and PM 2.5 emissions from the source have minimal visibility impacts at each Class I area within 300 km. Based on this, AEP decided and ADEQ agreed that the existing PM emission limit in the operating air permit, which is achievable through the use of the existing electrostatic precipitator (ESP), is BART for PM for AEP Flint Creek No. 1 Boiler. We reviewed the CALPUFF visibility modeling submitted by ADEQ for AEP Flint Creek No. 1 Boiler, and agree that PM 10 and PM 2.5 emissions from the source have minimal visibility impacts at each Class I area within 300 km. As explained in section IV.D.3 of this proposed rulemaking, using CALPUFF on a pollutant specific basis to model only the impact of PM emissions on visibility is an acceptable approach to determine whether a source should be subject to review for PM controls. In the case of the AEP Flint Creek No. 1 Boiler, we have found that the visibility impact due to PM emissions alone is so minimal such that the installation of any additional PM controls on the unit would likely achieve very low emissions reductions, have minimal visibility benefit, and not be cost-effective. Therefore, we are proposing to approve ADEQ's determination that PM BART for AEP Flint Creek No. 1 Boiler is the existing PM emission limit. The federally enforceable operating air permit for the source sets the PM emission limit for the unit at 0.1 lb/MMBtu. 38 38 ADEQ Operating Air Permit for AEP-Flint Creek Power Plan (Permit No. 0276-AOP-R5). This permit can be viewed at http://www.adeq.state.ar.us/ftproot/pub/WebDatabases/PermitsOnline/Air/0276-AOP-R5.pdf. Regarding BART for SO 2 and NO X , neither AEP nor ADEQ performed a BART analysis that considered the statutory factors states are required to consider in determining what retrofit controls are BART for the AEP Flint Creek No. 1 Boiler. Instead, AEP determined and ADEQ agreed that BART for SO 2 is the presumptive limit of 0.15 lb/MMBtu and that BART for NO X is the presumptive limit of 0.23 lb/MMBtu for AEP Flint Creek No. 1 Boiler. 39 We are aware that the AEP Flint Creek Power Plant has a 558 MW generating capacity, and is therefore not required to follow the BART Guidelines in making BART determinations for the No. 1 Boiler. However, this facility and/or the State must still conduct a BART analysis as specified in 40 CFR 51.308(e)(1)(ii)(A), which provides that: 39 The “presumptive limits” are the rebuttable specific limits established in the BART Rule for SO 2 and NO X for certain EGUs based on fuel type, unit size, cost effectiveness, and the presence [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%3A2011-26336. Public record. Not legal advice.