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Draft Guidance on Progress Tracking Metrics,
Long-term Strategies, Reasonable Progress Goals
and Other Requirements for Regional Haze
State Implementation Plans for the
Second Implementation Period
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EPA-457/P-16-001
July 2016
Draft Guidance on Progress Tracking Metrics, Long-term Strategies, Reasonable Progress
Goals and Other Requirements for Regional Haze State Implementation Plans for the
Second Implementation Period
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Air Quality Policy Division
Research Triangle Park, North Carolina
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Table of Contents
Glossary of Terms Abbreviations and Acronyms vi
1. Introduction 1
1.1. Regional haze 1
1.2. Purpose of this guidance 1
1.3. Issues addressed in this guidance 2
1.4. How to use this guidance 3
1.5. Applicability to tribes and tribal lands 4
2. The statutory and regulatory provisions that address regional haze 5
2.1. Statutory provisions 5
2.2. EPA regulations and guidance 5
2.3. 2016 Revisions to the visibility protection program for Class I areas 8
3. The key steps in developing the regional haze SIP and the roadmap for this guidance
document 11
4. Overarching Issues 13
4.1. Screening sources prior to the four-factor analysis and deferring some sources to later
implementation periods 13
4.2. Considering visibility impacts and benefits when screening sources and conducting the
four-factor analysis 14
4.3. Focusing on the 20 percent most impaired days 16
4.4. Determining the measures "necessary to make reasonable progress" 17
4.5. The Relationship between the LTS and the RPGs 18
4.6. Comparing the RPGs to the URP 18
4.7. Documentation 19
4.8. Consultation 20
5. Ambient data analysis (Step 1) 26
5.1. What are the visibility progress tracking metrics and calculations required by the
Regional Haze Rule? 26
5.2. How was visibility progress tracked in the first implementation period of the Regional
Haze Rule? 26
5.3. How will visibility progress be tracked in the second and future implementation
periods? 28
5.4. What does it mean to choose the 20 percent most impaired days based on daily
anthropogenic impairment? 28
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5.5. How does the EPA recommend estimating daily natural and anthropogenic visibility
impacts and light extinction budgets? 31
5.6. How does the EPA recommend selecting the 20 percent most impaired days? 39
5.7. How do the 2016 Regional Haze Rule revisions require states to select the 20 percent
clearest days? 40
5.8. How are current visibility conditions determined? 41
5.9. How are baseline visibility conditions determined? 41
5.10. What natural visibility conditions estimates does the EPA recommend for use in the
impairment-based approach for selecting the 20 percent most impaired days? 42
5.11. What natural visibility conditions estimates does the EPA recommend for the 20
percent clearest days? 46
5.12. What are the associated values, equations and completeness criteria used in the
calculations of visibility impairment on the most impaired and clearest days? 46
5.13. Should each state perform these calculations for its Class I areas? 48
5.14. Can states use another strategy for choosing the 20 percent most impaired days? 48
5.15. Can states continue to use the first-implementation period approach for selecting the
haziest days as the most impaired days? 49
5.16. Calculation of actual progress and difference between current and natural visibility
conditions 49
5.17. How is the URP calculated and the URP line (or glidepath) drawn for each Class I area?
50
5.18. What are the results and implications of using the recommended methods to select the
most impaired days? 51
5.19. How can states account for international impacts in the URP framework? 53
5.20. How can impacts from prescribed fire be accounted for in the URP framework? 54
6. Screening of sources (Step 2) 57
6.1. How should a state determine which Class I areas need to be considered when screening
sources? 57
6.2. How should a state estimate visibility impacts for screening purposes? 58
6.3. How should a state select sources for four-factor analysis based on visibility impacts?71
6.4. What other factors may be considered when selecting sources for four-factor analysis?
77
6.5. Special considerations for particular types of sources 78
7. Source and emission control measure characterization (Step 3) 84
7.1. What emission control measures should states consider for sources selected for four-
factor analysis? 85
7.2. Statutory Factor #1 -The cost of compliance 89
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7.3. Statutory Factor #2 - Time necessary for compliance 92
7.4. Statutory Factor #3 - Energy and non-air environmental impacts 92
7.5. Statutory Factor #4 - Remaining useful life of the source 92
7.6. Reliance on previous analysis and previously approved approaches 93
7.7. Continued relevance of the BART Guidelines 94
7.8. Consideration of information provided through interagency consultation and public
comments 94
Decisions on the content of the LTS (Step 4) 95
8.1. How should a state that is not considering visibility benefits select measures for
inclusion in the LTS? 96
8.1.1. The meaning of "necessary to make reasonable progress" 96
8.1.2. Recommendation to rely on the cost/ton (cost-effectiveness) metric and comparisons
to past regulatory actions 97
8.1.3. The "worth" of emission reductions is not material 99
8.1.4. Separable sources and emission units 99
8.1.5. Multiple control alternatives, including combinations of controls 100
8.1.6. Viability of continued plant operations 101
8.2. How should a state that is considering visibility benefits along with the four factors
select measures for inclusion in the LTS? 101
8.2.1. The meaning of "necessary to make reasonable progress" 102
8.2.2. Consideration of past decisions regarding reasonable progress 103
8.2.3. Considering visibility benefits does not require "cost/benefit" analysis 104
8.2.4. Changes in the number of days above a visibility impact benchmark 104
8.2.5. Consideration of visibility benefits at multiple affected Class I areas 104
8.2.6. Considerations when weighing costs and visibility benefits 105
8.2.7. Separable sources and emissions units 106
8.2.8. Concerns with use of the cost/deciview metric 107
8.2.9. Visitation 107
8.2.10. Viability of continued plant operations 108
8.3. Time necessary for compliance 109
8.4. Energy impacts 109
8.5. Non-air quality environmental impacts 109
8.6. Remaining useful life 109
8.7. What special considerations apply in selecting additional controls for minor stationary
sources, area stationary sources and mobile sources? 110
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8.8. How should a state set emission limits, averaging periods and monitoring and record
keeping requirements? Ill
8.8.1. General CAA requirements and EPA guidance Ill
8.8.2. Current emissions rates versus enforceable limits Ill
8.8.3. EPA's Startup, Shutdown and Malfunction Policy 112
8.8.4. Averaging periods 112
8.8.5. Intermittent controls 113
8.8.6. Continued relevance of the BART Guidelines 114
8.9. How should a state set compliance deadlines? 114
9. Regional scale modeling of the LTS to set the RPGs for 2028 (Step 5) 116
9.1. Overview 117
9.2. EPA modeling guidance 117
9.3. Recognition of emission limits in the LTS and other emission reductions when
projecting the RPGs 117
9.4. Recommendations regarding adjustment of RPGs when the LTS in the SIP(s) is not the
same as assumed in an available photochemical modeling run 118
10. Progress, Degradation and Glidepath Checks (Step 6) 119
10.1. How should a state demonstrate that there will be improvement in visibility for the most
impaired days? 119
10.2. How should a state demonstrate that its 2028 RPG for the 20 percent clearest days
shows no degradation? 119
10.3. How should a state with an RPG that is not on the glidepath demonstrate that there are
no additional measures that are necessary to make reasonable progress? 119
10.4. Calculation of the number of years it would take to attain natural visibility conditions
121
11. What are the additional requirements for a regional haze SIP? 123
11.1. Additional requirements of Regional Haze Rule section 308(f)(2)(ii) for long-term
strategies 123
11.2. Other requirements in Regional Haze Rule section 308(f)(2)(iv) 124
11.3. Requirement for elements to make the SIP serve as a progress report on emission
reductions 125
11.4. Monitoring strategy elements 126
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APPENDIX A
APPENDIX B
APPENDIX C
APPENDIX D
APPENDIX E
APPENDIX F
APPENDIX G
Key Steps and Tasks in Developing a Regional Haze SIP
EPA Actions on Regional Haze SIPs and Progress Reports for the First
Implementation Period
Court Decisions on Regional Haze SIPs and FIPs for the First
Implementation Period
Identification of Provisions of the BART Guidelines that Are Applicable
as EPA Recommendations for Reasonable Progress Analysis and
Determinations in the Second Implementation Period
Identification of Provisions of the Previous Guidance Documents on
Natural Conditions and Progress Tracking that Are Applicable as EPA
Recommendations for Reasonable Progress Analysis and Determinations
in the Second Implementation Period
Identification of Answers in the September 27, 2006, Q&A Document that
Are Applicable as EPA Recommendations for Reasonable Progress
Analyses and Determinations in the Second Implementation Period
Relevant Provisions of the Regional Haze Rule (40 CFR Part 51) as
Revised in 2016
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Glossary of Terms Abbreviations and Acronyms
AERMOD - American Meteorological Society/Environmental Protection Agency Regulatory
Model.
AFUDC - Allowance for funds used during construction.
AirControlNet - A database tool for conducting pollutant emissions control strategy and costing
analysis, no longer supported by the EPA.
BART- Best Available Retrofit Technology.
Baseline period - The years of 2000 to 2004. The end of the baseline period is December 31,
2004.
bext - Light extinction coefficient.
Basic smoke management practices - Types of actions that the manager of a prescribed fire can
take to reduce the amount of smoke generated by a prescribed fire and/or to reduce public
exposure to the smoke that is generated.
CAA - Clean Air Act.
CAIR- Clean Air Interstate Rule, also referred to as the Transport Rule.
CALPUFF - A Lagrangian puff air quality modeling system.
CEM or CEMS - Continuous emissions monitoring system.
Class I area - In this document, this term is used for brevity and refers to a mandatory Federal
Class I area as defined in 40 CFR 51.301, unless the term "non-mandatory" appears before it.
This is a different usage than in 40 CFR part 51 subpart P, where this term encompasses both
mandatory and non-mandatory Class I areas.
Clearest days - The 20 percent of monitored days in a calendar year with the lowest actual
values of the deciview index.
CM - Coarse PM, equal to the difference between PMio and PM2.5.
CoST - Control Strategy Tool, part of the EPA's emissions modeling framework.
CSAPR- Cross State Air Pollution Rule.
Current visibility conditions - The average visibility impairment for the most impaired and
clearest days during the most recent rolling 5-year period for which IMPROVE data are available
as of a date 6 months preceding the required date of the progress report.
Deciview or dv - The unit of measurement on the deciview index scale for quantifying in a
standard manner human perceptions of visibility.
Deciview index - A value for a day that is derived from calculated light extinction, such that
uniform increments of the index correspond to uniform incremental changes in perception across
the entire range of conditions, from pristine to very obscured. The deciview index is calculated
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based on the following equation (for the purposes of calculating deciview, the atmospheric light
extinction coefficient must be calculated from aerosol measurements):
Deciview index = 10 In (bext/10 Mm"1).
bext= the atmospheric light extinction coefficient, expressed in inverse megameters
(Mm"1).
EGU- Electric generating unit.
End of the applicable implementation period - December 31 of the year in which the next
periodic implementation plan revision is due under 40 CFR 51.308(f).
Federal Class I area or Class I Federal area - Any federal land that is classified or reclassified
Class I.
Federal Land Manager - The Secretary of the department with authority over the Federal Class I
area (or the Secretary's designee) or, with respect to Roosevelt-Campobello International Park,
the Chairman of the Roosevelt-Campobello International Park Commission.
FIP - Federal implementation plan.
FLM - Federal land manager.
f(RH) - A function of relative humidity representing the growth in particle size/mass with
increasing ambient humidity.
Haziest days or worst visibility days - The 20 percent of monitored days in a calendar year with
the highest actual values of the deciview index.
Implementation plan - Any SIP, TIP or FIP.
IMPROVE - The Interagency Monitoring of Protected Visual Environments monitoring
program.
Indian tribe or tribe - Any Indian tribe, band, nation or other organized group or community,
including any Alaska Native village, which is federally recognized as eligible for the special
programs and services provided by the U.S. to Indians because of their status as Indians.
LAC - Light absorbing carbon, a species or component of PM.
Long-term strategy or LTS - The enforceable emissions limitations, compliance schedules and
other measures necessary to achieve the reasonable progress goals for Class I areas affected by
the state.
Mandatory Class I Federal Area, mandatory Federal Class I area - Any area identified in 40 CFR
part 81.
MEVEl - Mesa Verde National Park Class I area.
Mm - Millions of meters or megameters.
Mm"1 - Inverse megameters (used to indicate division by the number of megameters).
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NC-II natural visibility conditions - A set of estimates of natural conditions for each Class I,
widely used in the first implementation period. For each Class I area, the set included a value for
the 20 percent least impaired days ("plO"), a value for the 20 percent most impaired days
("p90") and an annual average value. As used in the first implementation period, the term "least
impaired days" corresponds to the term "clearest days" in this document, and the term "most
impaired days" corresponds to the term "haziest days."
O&M - Operation and maintenance.
MMBtu, mmBtu or mmbtu - Millions of British Thermal Units.
Most impaired days - The 20 percent of monitored days in a calendar year with the highest
amounts of visibility impairment.
Natural conditions - Naturally occurring phenomena that reduce visibility as measured in terms
of light extinction, visual range, contrast or coloration.
Natural visibility conditions - The visibility (contrast, coloration and texture) that would have
existed under natural conditions. Natural visibility conditions vary with time and location, and
are estimated or inferred rather than directly measured.
NOx- Nitrogen oxides.
OMC - Organic carbonaceous material, a component or species of PM.
plO - See NC-II natural visibility conditions.
p90 - See NC-II natural visibility conditions.
PM - Particulate matter.
PM species - A portion of PM of a certain chemical species or type, also referred to as a PM
component.
Prescribed fire - Any fire intentionally ignited by management actions in accordance with
applicable laws, policies and regulations to meet specific land or resource management
objectives.
Reasonably attributable - Attributable by visual observation or any other appropriate technique.
Reasonable progress goal or RPG - A visibility goal, in deciviews, for a Class I area that
provides for reasonable progress towards achieving natural visibility conditions. There are two
RPGs for each Class I area: one for the most impaired days and one for the clearest days.
Reasonably attributable visibility impairment or RAVI - Visibility impairment that is caused by
the emission of air pollutants from one, or a small number of sources.
Regional haze - Visibility impairment that is caused by the emission of air pollutants from
numerous sources located over a wide geographic area. Such sources include, but are not limited
to, major and minor stationary sources, mobile sources and area sources.
RH - Relative humidity.
RHR - Regional Haze Rule (used only in Appendix D).
RPO - Regional planning organization.
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SCICHEM - A Lagrangian photochemical puff air quality model.
SCR - Selective catalytic reduction.
SIP - State implementation plan.
Smoke management program - A framework to minimize the impact of smoke from prescribed
agricultural and/or wildland management burning operations that includes enforceable
restrictions on prescribed fire. In the context of the Regional Haze Rule, the EPA considers a
program to be a "smoke management program" if it has these six features: (i) authorization to
burn, (ii) minimizing air pollutant emissions, (iii) smoke management components of burn plans,
(iv) public education and awareness, (v) surveillance and enforcement and (vi) program
evaluation. "Authorization to burn" means that a government authority restricts where, when
and/or by whom a prescribed fire may be conducted.
SNCR - Selective non-catalytic reduction.
SCh - Sulfur dioxide.
Soil or fine soil - The portion, species or component of PM2.5 attributable to crustal material, as
estimated based on the quantity of certain chemical elements in the sample of PIVb.s.
State - One of the 50 states, the District of Columbia, or the Virgin Islands. Other U.S. territories
are not subject to the Regional Haze Rule.
Stationary source - The Regional Haze Rule defines this term as "any building, structure, facility
or installation which emits or may emit any air pollutant." In this document, the term is used less
precisely, and depending on context, it may also refer to a single emission release point, process
or unit at a facility. Statements in this document that include the word "source" are not
necessarily meant to interpret the provisions of the Regional Haze Rule.
TIP - Tribal implementation plan.
URP - Uniform rate of progress.
U.S.-TheUnited States.
Visibility - The degree of perceived clarity when viewing objects at a distance. Visibility
includes perceived changes in contrast, coloration and texture elements in a scene.
Visibility impairment - The Regional Haze Rule defines this term as "any humanly perceptible
difference between actual visibility conditions and natural visibility conditions. Because natural
visibility conditions can only be estimated or inferred, visibility impairment also is estimated or
inferred rather than directly measured." While the regulatory definition of visibility impairment
inherently means anthropogenic visibility impairment, this document sometimes adds the word
"anthropogenically" when it may be useful to the reader to emphasize this point or to draw a
distinction between reductions in visibility due to anthropogenic emissions and reductions in
visibility due to emissions from natural sources.
We, us or the EPA - The U.S. Environmental Protection Agency
Wildfire - Any fire started by an unplanned ignition caused by lightning; volcanoes; other acts of
nature; unauthorized activity; or accidental, human-caused actions, or a prescribed fire that has
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been declared to be a wildfire. A wildfire that predominantly occurs on wildland is a natural
event.
Wildland - An area in which human activity and development is essentially non-existent, except
for roads, railroads, power lines and similar transportation facilities. Structures, if any, are widely
scattered.
WEVIO - Wichita Mountains Class I area.
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1. Introduction
1.1. Regional haze
Regional haze, as defined in the Regional Haze Rule at 40 CFR 51.300, is "visibility impairment
that is caused by the emission of air pollutants from numerous sources located over a wide
geographic area. Such sources include, but are not limited to, major and minor stationary
sources, mobile sources, and area sources."1 This visibility impairment is a result of particles and
gases in the atmosphere that scatter and absorb light, thus acting to reduce overall visibility. The
primary cause of atmospheric haze is light extinction (scattering and absorption) by particulate
matter (PM).2 The Regional Haze Rule requires states to submit a series of state implementation
plans (SIPs) to protect visibility in certain national parks and wilderness areas, known as
mandatory Federal Class I areas. A state should also recognize that progress towards natural
visibility conditions will require the accumulation of reductions in air pollution and associated
light extinction that may not be individually perceptible.
1.2. Purpose of this guidance
The purpose of this guidance is to advise states on how to develop and submit regional haze SIPs
for the second implementation period (2018-2028), which are due by July 31, 2021. The required
content of these SIPs is specified in 40 CFR 51.308(f), which was revised in 2016.3 This
guidance contains current EPA interpretations of the requirements of the Clean Air Act (CAA)
and this section of the Regional Haze Rule.
None of the recommendations contained in this guidance are binding or enforceable against any
person, and no part of the guidance or the guidance as a whole constitutes final agency action
that could injure any person or represent the consummation of agency decision making. Because
this guidance is not binding or enforceable, states may choose not to follow the
recommendations in this guidance provided that they adhere to the relevant statutory and
regulatory requirements and provide rational explanations for their decision making. Only final
actions taken to approve or disapprove SIP submissions that implement any of the
recommendations in this guidance would be final actions for purposes of CAA section 307(b).
Therefore, this guidance is not judicially reviewable. This document is not a rule or regulation,
and the guidance it contains may not apply to a particular situation based upon the individual
1 While the Regional Haze Rule's definition of visibility impairment inherently means anthropogenic visibility
impairment, this document sometimes adds the word "anthropogenically" when it may be useful to the reader to
emphasize this point or to draw a distinction between reductions in visibility due to anthropogenic emissions and
reductions in visibility due to emissions from natural sources.
2 For purposes of the Regional Haze Rule, light extinction is estimated from measurements of PM and its chemical
components (sulfate, nitrate, organic carbonaceous material (OMC), light absorbing carbon (LAC), fine soil, sea salt
and coarse material (CM)), assumptions about relative humidity at the monitoring site and the use of a commonly
accepted algorithm. See section 5.12. These estimates of light extinction are logarithmically transformed to
deciviews. The PM measurements used in the regional haze program are collected by the IMPROVE (Interagency
Monitoring for PROtected Visual Environments) monitoring network.
3 Note to reviewers of this draft guidance document: For clarity for purposes of comment and for ease in
finalization, this draft version of this guidance document is written as if the revisions proposed in May 2016 have
been finalized as proposed. Later footnotes, addressed to reviewers like this one, provide most specific explanations
when needed for clarity. If the final revisions to the Regional Haze Rule differ from this assumption, corresponding
changes will be made in the final guidance document.
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facts and circumstances. This guidance does not change or substitute for any law, regulation or
other legally binding requirement and is not legally enforceable. The use of non-mandatory
language such as "guidance," "recommend," "may," "should" and "can" is intended to describe
the EPA's policies and recommendations. Mandatory terminology such as "must" and "required"
is intended to describe controlling legal requirements under the terms of the CAA and the EPA
regulations. Neither such language nor anything else in this document is intended to or does
establish legally binding requirements in and of itself.
This guidance may be replaced or supplemented for subsequent planning periods. It is not meant
to be the final road map for the regional haze program.
This guidance document frequently cites other, more detailed or specialized existing EPA
guidance already available to states. As needed, additional guidance will be prepared by the EPA
in a timely manner.
In any case in which a portion of this guidance conflicts with the revised 2016 Regional Haze
Rule, including any applicable interpretations by a court that may be issued, the rule or the court
interpretation supersedes that portion of this guidance.
The entirety of the following previous guidance document from the EPA is superseded by this
guidance document:
• Guidance for Setting Reasonable Progress Goals Under the Regional Haze Program,
June 1, 2007, revised.
1.3. Issues addressed in this guidance
In addition to providing states and tribes stepwise guidance to developing regional haze SIPs,
this guidance focuses on issues related to the determination of natural, baseline and current
visibility conditions and the uniform rate of progress (URP); the development of a long-term
strategy (LTS) consisting of emission reduction measures needed to make reasonable progress
towards the national goal of eliminating anthropogenic visibility impairment;4 and the projection
of visibility conditions as of the end of the second implementation period in order to set
reasonable progress goals (RPGs).
In particular, this guidance addresses a number of key concepts and issues that have sometimes
been a source of confusion or concern to states and stakeholders during the first implementation
period (2001-2018). It also addresses some issues that will be particularly important in the
second implementation period, as the focus of planning shifts from primarily the control of large
sources subject to best available retrofit technology (BART) requirements to other sources,
including non-BART sources and potentially more diverse sources that may need additional
controls in order to achieve reasonable progress toward the elimination of anthropogenic
impairment. These issues include the following:
4 Many emission reduction measures adopted to meet other requirements of the CAA, or to meet goals set by a state
for itself, will contribute to progress towards eliminating visibility impairment at Class I areas. In this document, the
term "long-term strategy" or "LTS" generally refers to the set of specific measures included in a periodic regional
haze SIP revision.
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• Whether and how visibility benefits should be considered along with the four statutory
factors a state must consider when developing its LTS to achieve reasonable progress.
• The relationship between the LTS and RPGs.
• The definition of the URP line and how the comparison of the RPG for the 20 percent
most impaired days affects the planning obligation of a state.
• How small stationary sources and area sources should be evaluated for additional
controls.
• The obligation of states to consider measures necessary to make reasonable progress at
Class I areas in other states.
• Improving the benefit of consultation among states and between states and federal land
managers (FLMs).
• The difficulty of discerning improvement in visibility due to control of anthropogenic
sources in areas where highly variable natural sources, especially large fires, can
dominate visibility on the haziest days.
• How impacts from sources outside the United States (U.S.) that are beyond the control of
states and the federal government can be accounted for in a reasonable way.
• How regional haze SIPs should address the expectation that climate change will make
wildfires on wildland more frequent.
1.4. How to use this guidance
This guidance contains the EPA's recommendations for how states should implement the
regional haze program. The preambles to previous rulemakings in which the EPA approved or
disapproved regional haze SIPs and court decisions reviewing those rulemaking should also be
consulted for a complete understanding of the relevant statutory and regulatory requirements and
permissible approaches. Appendices B and C list these rulemakings and court decisions. The
EPA believes that states have discretion to determine what emission reduction measures are
necessary to make reasonable progress.5 However, this discretion is not unbounded, and the
EPA's role in reviewing states' determinations is more than ministerial.6 In addition to reviewing
SIPs for completeness, the EPA conducts a substantive review to determine whether SIPs
comply with the requirements of the CAA and the Regional Haze Rule, and to assess whether
states have applied reasoned decision making and provided appropriate and sound technical
analyses to support their determinations. The EPA believes that reasoned decision making
includes substantial consideration of the recommendations in this guidance document. States that
choose not to follow one or more of the recommendations in this guidance document should
provide a detailed rationale for the departure, including an explanation why the chosen approach
is sufficient to meet the relevant statutory and regulatory requirements. We strongly encourage
states to discuss with their EPA regional office early in their SIP development the approach they
anticipate taking and how the recommendations in this guidance may affect their SIPs.
5 The preamble to the 1999 Regional Haze Rule stated: "The flexibility for State discretion is, of course, exactly
what the regional haze rule provides." 64 FR 35760.
6 See, e.g., North Dakota v. EPA, 730 F.3d 750, 760-61 (8th Cir. 2013) ("Although the CAA grants states the
primary role of determining the appropriate pollution controls within their borders, EPA is left with more than the
ministerial task of routinely approving SIP submissions.").
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1.5. Applicability to tribes and tribal lands
This guidance applies to plans to protect visibility in mandatory Class I areas, none of which are
located on tribal land.7 However, under the CAA and EPA regulations, a tribe may, but is not
required to, apply for "treatment in the same manner as a state" (TAS) status for purposes of
developing a tribal implementation plan (TIP), including a regional haze TIP. Many provisions
of the Regional Haze Rule would apply to a regional haze TIP in the same way they apply to a
SIP from a state that does not contain a mandatory Class I area. Thus, depending on context,
statements in this guidance referring to a "state" may apply to a tribe developing a regional haze
TIP. Also, the EPA may adopt a regional haze plan for a tribal area if the Administrator
determines such action is necessary or appropriate.8
7 While some tribes have voluntarily re-designated portions of their lands to Class I status, the Regional Haze Rule
does not apply to these non-mandatory Class I areas.
8 In the first implementation period, the EPA adopted federal implementation plan (FIP) requirements addressing
certain regional haze requirements for two sources on tribal lands, the Four Corners Power Plant and the Navajo
Generating Station.
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2. The statutory and regulatory provisions that address regional haze
For background, this section provides a summary of the decades-long evolution of the visibility
program established by the CAA. The program began in 1977, when Congress amended the
CAA to require EPA to issue regulations to protect and restore visibility in mandatory Class I
Federal areas. The most recent event in the evolution of the program was the EPA's 2016
revisions to the Regional Haze Rule that extended the submission deadline for SIPs covering the
second implementation period to July 31, 2021, and made several important substantive
clarifications and improvements to the program.9
2.1. Statutory provisions
In section 169A of the 1977 Amendments to the CAA, Congress created a program for
protecting and restoring visibility in the nation's national parks, wilderness areas, and other Class
I areas due to their "great scenic importance."10 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 which impairment results from manmade air pollution." This
section also required the EPA to issue regulations requiring states to adopt implementation plans
containing emission limits as may be necessary to make reasonable progress towards meeting
this goal, including BART limits for particular types of large industrial sources.
In 1990, Congress added section 169B to the CAA to focus on regional haze issues. Among
other things, this section included provisions for the EPA to conduct visibility research on
regional regulatory tools with the National Park Service and other federal agencies, and to
provide periodic reports to Congress on visibility improvements due to implementation of other
air pollution protection programs. Section 169B also allowed the Administrator to establish
visibility transport commissions and specifically required the Administrator to establish a
commission for the Grand Canyon area.
2.2. EPA regulations and guidance
1980 Reasonably Attributable Visibility Impairment (RAVI) Rule
In 1980, the EPA promulgated regulations to address visibility impairment in Class I areas,
including but not limited to impairment that is "reasonably attributable" to a single source or
small group of sources, i.e., "reasonably attributable visibility impairment" or "RAVI." 45 FR
80084 (December 2, 1980). These regulations, codified at 40 CFR 51.300 through 51.307 (since
revised), represented the first phase in addressing visibility impairment from existing sources.
They also addressed potential visibility and other air quality-related impacts from new and
modified major sources already subject to permitting requirements for purposes of protection of
the National Ambient Air Quality Standards (NAAQS) and preventing significant deterioration
of air quality. The EPA explicitly deferred action on regional haze (visibility-impairing pollution
9 For clarity for purposes of comment and for ease in finalization, this draft version of this guidance document is
written as if the revisions proposed in May 2016 have been finalized as proposed, except as specifically noted. If the
final revisions to the Regional Haze Rule differ from this assumption, corresponding changes will be made in the
final guidance document.
10 H.R. Rep. No. 294, 95th Cong. 1st Sess. at 205 (1977).
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that is caused by the emission of air pollutants from numerous sources located over a wide
geographic area) until some future date when improvement in monitoring techniques would
provide more data on source-specific levels of visibility impairment, regional scale models
would become refined and our scientific knowledge about the relationships between emitted air
pollutants and visibility impairment would improve. The regulations on RAVI originally
promulgated in 1980 were substantially revised in 2016.
11
1999 Regional Haze Rule
In 1999, the EPA promulgated new regulations to address regional haze. 64 FR 35714 (July 1,
1999). The Regional Haze Rule established a more comprehensive visibility protection program
for Class I areas. The requirements for regional haze are found at 40 CFR 51.308 and 51.309.
Applicability. All 50 states, the District of Columbia, and the Virgin Islands are subject to the
requirements of the Regional Haze Rule and must submit regional haze SIPs. (Other U.S.
territories do not contain mandatory Class I areas and are too distant from any Class I area to
affect it.)
Schedule for SIPs. States must submit the first implementation plans addressing regional haze
visibility impairment no later than December 17, 2007. 70 FR 39104. Further, under 40 CFR
51.308(f) states must submit periodic comprehensive revisions no later than July 31, 2018, and
every ten years thereafter.
Content of periodic SIPs. The periodic SIP revisions must address a number of elements,
including current visibility conditions and actual progress made toward natural conditions during
the previous implementation period, a reassessment of the effectiveness of the LTS at achieving
the RPGs over the prior implementation period and affirmation of or revision to the RPGs.
RPGs. States must set RPGs, calculated in deciviews, in every planning period for each Class I
area within the state that provide for reasonable progress towards achieving natural visibility
conditions. For each Class I area, states must set two RPGs, one for the most impaired days and
one for the least impaired days. The goal for the most impaired days must provide for an
improvement in visibility over the period of the implementation plan, and the goal for the least
impaired days must ensure no degradation of visibility over the period of the implementation
plan.
LTS. Each state must submit an LTS that addresses visibility impairment at Class I areas affected
by the state. The strategy includes enforceable emissions limitations and compliance schedules.
The contents of the LTS form the basis for the calculation of the visibility improvement expected
over the period of the implementation plan and the development of the RPGs.
Progress reports. 40 CFR 51.308(g) requires each state to submit progress reports, in the form of
SIP revisions, every 5 years following the submission of the initial SIP due on December 17,
2007. These progress reports must evaluate the progress made towards the RPGs for Class I
11 In summarizing the requirements of the 1999 Regional Haze Rule and the 2005 BART rule, the present tense is
used here even though some of these requirements were revised in 2016 and some of the requirements have already
been fully met by some or all states.
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areas located within the state as well as those Class I areas located outside the state that may be
affected by emissions from within the state.
Coordination with planning to address RAVI. The 1999 Regional Haze Rule sought to improve
efficiency and transparency by requiring states to coordinate their regional haze planning
obligations with their planning obligations under the 1980 RAVI rule.
URP framework. States must analyze and determine the consistent rate of progress over time
needed to attain natural visibility conditions on the 20 percent most impaired days by the year
2064. This glidepath is referred to in this document as the uniform rate of progress (URP) line.
The URP is the slope of this line. In establishing their RPGs, states must consider the URP and
the emission reduction measures needed to achieve this level of improvement in visibility for the
time period covered by the implementation plan. When the progress anticipated in the SIP for the
implementation period is less than the URP, a state must project when (after 2064) natural
visibility conditions would be reached if the SIP's rate of progress were to continue beyond the
end of the implementation period. Attaining natural visibility conditions by the end of 2064 is
not an enforceable requirement of the regional haze program.
BART. As a one-time requirement during the first implementation period, 40 CFR 51.308(e)
directs states to evaluate potential BART controls at certain larger, often uncontrolled, older
stationary sources in order to address visibility impacts from these sources. States must conduct
BART determinations for "BART-eligible" sources that are anticipated to cause or contribute to
any visibility impairment in a Class I area. As an alternative to requiring source-specific BART
controls, states have the flexibility to adopt an emissions trading program or other alternative
program as long as the alternative provided greater reasonable progress towards improving
visibility than BART and met certain other requirements set out in 40 CFR 51.308(e)(2).
2005 BART Guidelines
In 2005, the EPA 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 setting appropriate emission
limits for each applicable source. 70 FR 39104 (July 6, 2005). In this rulemaking, the EPA also
established that the Clean Air Interstate Rule (CAIR) would result in greater reasonable progress
than source-specific BART, and adopted regulations allowing states to rely on participation in
CAIR to meet the BART requirements with respect to SCh and NOx emissions from electric
generating units (EGUs) subject to CAIR.
States undertook the BART determination process during the first regional haze implementation
period; thus, this guidance document does not address the process for establishing BART
emission limitations. Although the BART process is not repeated in subsequent implementation
periods, BART-eligible sources may be re-assessed for more control in later implementation
periods as part of the requirement to provide for reasonable progress, which is addressed in this
guidance document.
While the BART Guidelines are not requirements that states must meet when addressing
reasonable progress, much of the material in the BART Guidelines is still informative and useful.
Appendix D contains a section-by-section explanation of what material in the BART Guidelines
is relevant to reasonable progress determinations.
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2006 Questions and Answers from the EPA
In 2006, the EPA informally distributed to the states a document titled "Additional Regional
Haze Questions, September 27, 2006 Revision." Most of these questions and answers related to
the BART requirements, but some were related to issues that still apply in the second
implementation period. Additionally, some of the information contained in the 2006 document is
superseded by this guidance document. Appendix F reproduces this earlier set of questions and
answers and indicates which answers are still relevant as EPA guidance for the second
implementation period.
2007 EPA Guidance on Reasonable Progress
In 2007, EPA issued a guidance document titled, "Guidance for Setting Reasonable Progress
Goals Under the Regional Haze Program," June 1, 2007, revised. As stated in section 1.1, this
2007 guidance document is hereby withdrawn and is no longer applicable.
2072 CSAPR Better-than-BARTrule
As mentioned above, the EPA's regulations allowed states to rely on participation in CAIR to
meet the BART requirements with respect to SCh and NOx emissions from EGUs subject to the
rule. Subsequently, CAIR was remanded by the D.C. Circuit, and the EPA promulgated the
Cross-State Air Pollution Rule (CSAPR) to replace CAIR. In 2012, the EPA finalized a rule that
allowed participation in the CSAPR trading programs to serve as an alternative to BART for
EGUs in participating states. In the 2012 rulemaking, the EPA also finalized limited disapprovals
of certain states' regional haze SIPs that previously relied on CAIR to improve visibility and
substituted federal implementation plans (FIP) that rely on CSAPR for some but not all of the
states affected by these disapprovals. 77 FR 33642.
2.3. 2016 Revisions to the visibility protection program for Class I areas
12
In 2016, the EPA issued a final rule revising certain requirements that states have to meet as they
implement programs for the protection of visibility in mandatory Class I areas.13 These revisions
supported continued environmental progress by clarifying or revising existing regulatory
provisions and removing older provisions that had been superseded by subsequent developments.
Many of the revisions addressed administrative aspects of the program in order to reduce
unnecessary burden. All of the revisions apply to periodic state implementation plans developed
for the second and subsequent implementation periods and for progress reports submitted
subsequent to those plans. These changes include:
12 Note to reviewers of this draft guidance document: For clarity for purposes of comment and for ease in
finalization, this draft version of this guidance document is written as if the revisions proposed in May 2016 have
been finalized as proposed. If the final revisions to the Regional Haze Rule differ from this assumption,
corresponding changes will be made in the final guidance document.
13 [Citation to final rule]
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Extension of 2018 due date for SIPs. The EPA extended the due date for the next round of
regional haze SIPs, from July 31, 2018, to July 31, 2021. This one-time change will benefit states
by allowing them to obtain and take into account information on the effects of a number of other
regulatory programs that may affect sources over the next several years, such as the Mercury and
Air Toxics Standards. The change will also allow states to develop SIP revisions for the second
implementation period that are more integrated with state planning for other upcoming planning
requirements, such as ozone and SCh attainment planning. This advantage was widely confirmed
in discussions with states and is anticipated to result in greater environmental progress than if
planning for these multiple programs were not as well integrated.
Relationship between the LTS andRPGs. The EPA clarified the relationship between LTS and
RPGs in state plans and the LTS obligation of all states. These clarifications reflect long-
standing EPA interpretation of the CAA and Regional Haze Rule and are intended to ensure
consistent understanding of these requirements as states prepare their plans for the second
implementation period.
Progress tracking. The EPA revised the way in which some days during each year are to be
selected for purposes of tracking progress towards natural visibility conditions in order to focus
attention on days when anthropogenic emissions impair visibility and away from days when
wildfires and natural dust storms are the greatest contributors to visibility impairment. These
changes will provide the public and state officials with more meaningful information on how
emission reduction measures contribute to reductions in anthropogenic visibility impairment by
greatly reducing the -distorting effect of wildfires and natural dust storms on estimates of
reasonable progress.
Possible adjustment of the URP for the impacts ofnon-U.S. anthropogenic sources and certain
wildland prescribed fire. The EPA added a provision that allows the Administrator to approve an
adjustment to the URP to reflect the impacts of these causes of visibility impairment, if the
adjustment has been developed through scientifically valid data and methods. The adjustment
would be done by adding to the value of natural visibility conditions the estimate of the impact
of one or both of these source types, only for the purposes of calculating the URP. The specific
type of wildland fires that could be included in this adjustments are fires that were conducted
with the objective to establish, restore and/or maintain sustainable and resilient wildland
ecosystems, to reduce the risk of catastrophic wildfires and/or to preserve endangered or
threatened species during which appropriate basic smoke management practices were applied.
Progress reports. The EPA revised the due dates for progress reports and removed the
requirement for progress reports to be SIP revisions.
RAVI. The EPA updated, simplified and extended to all states the provisions for RAVI. At the
same time, EPA revoked existing FIPs implementing the 1980 RAVI requirements.14
FLM consultation. The EPA made changes to FLM consultation requirements to help ensure that
the expertise and perspective of these officials are brought into the state plan development
14 Note to reviewers of this draft guidance document: This draft version of this guidance document does not further
address the RAVI provisions of the visibility protection regulations. See the discussion in Section IV. G of the May
4, 2016, proposed rulemaking for more information. 81 FR 26961.
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process early enough for them to meaningfully contribute during the state's technical analysis
and deliberations.
Monitoring strategy. The EPA removed the requirement for progress reports to re-address the
monitoring strategy for regional haze. The requirement for periodic SIP revisions to re-address
the monitoring strategy was retained.
Appendix G reproduces the sections of the 2016 Regional Haze Rule that are relevant to the
preparation of the SIPs due by July 31, 2021.
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3. The key steps in developing the regional haze SIP and the roadmap for this guidance
document
Key steps in developing the regional haze SIP
Table 3.1 lists the key steps in developing an LTS and RPGs for the second implementation
period that meet the requirements of the Regional Haze Rule. Each step corresponds to a section
of this guidance document. For each step, the governing provisions of the Regional Haze Rule
are listed. The complete relevant text from the Regional Haze Rule is in Appendix G. Specific
relevant rule provisions also appear at the start of many sections and subsections of this
document.
Table 3.1. Key steps in developing the regional haze SIP
Step 1
Ambient data analysis - Quantify baseline, current and natural
conditions of visibility and the uniform rate of progress that would
achieve natural conditions in 2064.
40CFR51.308(f)(l)
Section 5
Step 2
Screening of sources - Identify the pollutants and emission sources
for which a full reasonable progress analysis will be completed and
explain why it is appropriate to limit the full analysis to only these
sources.
40CFR51.308(f)(2)
Section 6
Step3
Source and emission control measure analysis - Identify potential
emission control measures for sources selected in the screening step
and develop data on the four statutory factors and visibility benefits if
they will be considered.
40CFR51.308(f)(2)
Section 7
Step 4
Decisions on the content of the LTS - Consider applicable factors and
decide on new emission controls for incorporation into the LTS.
40CFR51.308(f)(2)
Section 8
StepS
Regional scale modeling - Model the emission reductions that will
result from implementation of the LTS and other enforceable
measures that will reduce visibility impairment to set the RPGs for
2028.
40CFR51.308(f)(3)
Section 9
Step 6
Progress, degradation andglidepath checks - Demonstrate that there
will be an improvement on the 20 percent most impaired days.
Demonstrate that there is no degradation on the 20 percent clearest
days. Compare the 2028 RPG for the 20 percent most impaired days
to the 2028 point on the URP line (the glidepath) and, if required,
provide additional justification for the reasonableness of the RPG.
Section 10
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Revise the LTS if additional measures are identified as necessary to
make reasonable progress.
40CFR51.308(f)(3)
Step?
Additional requirements for SIPs - Provide additional information
necessary to ensure that other requirements of the Regional Haze
Rule are met.
Section 11
These steps can be broken down into a larger number of finer steps and tasks. Appendix A
contains a more detailed list of steps that may be helpful to states in planning their work. In
Appendix A, many of these finer steps and tasks are linked to the relevant sections of this
guidance document.
Roadmap
Section 4 of this document briefly covers a number of cross-cutting concepts that apply to one or
more of the seven steps listed in Table 3.1. An initial familiarity with these concepts will help the
reader's understanding of the remaining sections, which each address one of the steps in
developing the SIP, as indicated in Table 1.
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4. Overarching Issues
4.1. Screening sources prior to the four-factor analysis and deferring some sources to later
implementation periods
A state may use a screening analysis that considers visibility impacts, or surrogates for such
impacts,15 to select a subset of sources for full four-factor analysis and decision. However, the
state should conduct its screening analysis for each Class I area that may be affected by sources
within the state. In other words, if a source or group of sources has large visibility impacts at one
Class I areas but not at others, the state should bring forward the source for a full four-factor
analysis.
CAA section 169A(b)(2) does not provide any direction regarding which sources or source
categories a state should analyze when determining appropriate measures to ensure reasonable
progress. Similarly, CAA section 169A(g)(l) requires states to consider the four listed factors for
"any existing source subject to such requirements," but unlike the BART provisions that apply to
a specifically defined set of sources, this section does not identify which sources or source
categories should be subject to reasonable progress requirements. Given the statutory purpose of
the visibility program, we believe that allowing states to consider visibility impacts when
determining the scope of the reasonable progress analysis is a reasonable interpretation of the
statute.
The use of an appropriate screening analysis is also consistent with the Regional Haze Rule,
which anticipates that a state may not fully analyze all sources for the four factors in a given SIP
revision. Specifically, Section 51.308(f)(2)(i) requires states to document the criteria used to
determine which sources or groups of sources will be evaluated for potential controls. By
considering the visibility impacts of sources or groups of sources, states will have a rational way
to differentiate between potentially hundreds of sources that vary in distance from Class I areas,
emit different visibility impairing pollutants in varying amounts and are subject to diverse
meteorological conditions that affect the transport of visibility-impairing pollutants.
Accordingly, states may develop screening metrics and thresholds that identify those sources
with the greatest visibility impacts for further analysis in the second implementation period. A
state using a screening analysis would defer full consideration of sources with lower visibility
impacts to later implementation periods. A state should not justify its screening threshold based
on it being the limit of what is humanly perceptible. Progress towards natural visibility
conditions will require the accumulation of reductions in air pollution and associated light
extinction that may not be individually perceptible.
15 Surrogate here refers to a quantitative metric that is correlated to some degree with visibility impacts (or benefits)
as they would be estimated via air quality modeling. A simple surrogate is emissions in tons/year divided by
distance to an affected Class I area in miles or kilometers, also known as Q/d. A more complicated surrogate could,
for example, incorporate information from wind trajectories. See section 6.3.
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4.2. Considering visibility impacts and benefits when screening sources and conducting the
four-factor analysis
Consideration of visibility16 during the first implementation period
In the first implementation period, all of the regional planning organizations (RPOs) and states
gave at least some consideration to visibility in evaluating emission reductions measures to meet
the BART requirements and to ensure reasonable progress.
As a general matter, the RPOs and states considered visibility impacts when developing their
SIPs by considering source apportionment modeling results; the extinction budgets for
IMPROVE sites in Class I areas (which suggest which pollutants and thus source categories are
contributing to or causing current or projected impairment); and source emissions levels,
distances between sources and Class I areas and wind transport patterns (all of which are
indicators of the potential to contribute to or cause visibility impairment).
For individual subject-to-BART sources, the CAA and the Regional Haze Rule specify that the
expected visibility benefits of potential controls are a factor that states must consider when
determining BART for a particular source. Most states applied a visibility impact threshold to
determine if a source that was eligible for BART was also subject to BART. In most instances,
states individually modeled the expected visibility benefits of potential controls for their subject-
to-BART sources.17
States also modeled the visibility impact and/or benefits of control measures for some non-
BART sources and source categories (i.e., "reasonable progress sources") to decide whether to
require those measures (or to ask another state to require those measures).
In some FIP actions in the first implementation period, the EPA considered visibility impacts in a
screening step and/or the visibility benefits of controls along with the four statutory factors.
The EPA 's recommendation for considering visibility impacts and benefits in the second
implementation period
CAA section 169A(g)(l) lists four factors that a state must consider to decide what control
measures are necessary to make reasonable progress, none of which are the visibility
improvements that would result from implementation of the measure. Section 51.308(f)(2)(i) of
the Regional Haze Rule requires consideration of the same factors. Thus, baseline visibility
impacts and prospective visibility benefits are not a "fifth factor" that states must consider when
determining reasonable progress. However, given that the goal of the regional haze program is to
improve visibility, the EPA believes that states may consider visibility in addition to the four
16 Unless stated more specifically, in this document "consideration of visibility" refers to the consideration of recent,
or anticipated "future baseline," visibility impacts from sources or groups of sources and/or to consideration of
potential visibility benefits from additional emission reductions measures applied to such sources.
17 Source-specific visibility benefits were not required to be modeled or considered for BART-eligible EGUs
included in a CAIR-based or CSAPR-based better-than-BART alternative or for any source being subject to the
most stringent control technology.
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statutory factors when making their reasonable progress determinations, as long as they do so in
a reasonable fashion.18
For the second implementation period, we recommend that states first conduct a screening
analysis that considers baseline visibility impacts to identify the sources or source categories that
will be subject to a four-factor analysis. After the screening step, we recommend that states
consider only the four statutory factors to determine whether control measures are necessary to
achieve reasonable progress. For reasons explained below, we do not recommend that states
model visibility benefits and weigh those benefits against the four statutory factors to identify
appropriate control measures. Rather, for each source or source category that is selected for
further analysis during the screening process, states would require whatever control measures are
determined to be reasonable after considering the four statutory factors alone. Section 8.1
provides detailed recommendations for states that choose to follow the recommended approach.
In addition to the recommended approach, states may follow one of two alternative approaches.
Under the first alternative approach, states would simply consider the available control measures
for all sources. For each source or source category, states would adopt those measures that are
deemed reasonable after considering the four statutory factors. Visibility would not be used as
screening metric or as a consideration in the four-factor analysis. This approach is clearly
permissible under the plain language of CAA section 169A(g)(l), but may be very resource-
intensive for most air agencies.
Under the second alternative approach, states would consider visibility both during the screening
step and when considering the four statutory factors. When conducting their four-factor analyses,
states would weigh the visibility benefits of potential control measures along with the four
statutory factors and adopt those measure that are reasonable. It should be clear, however, that
under this approach, visibility is not an explicit fifth factor and does not have the same weight as
the four statutory factors. The EPA notes that regional haze is "visibility impairment that is
caused by the emission of air pollutants from numerous sources located over a wide geographic
area." 40 CFR 51.301. At any given Class I area, hundreds or even thousands of individual
sources may contribute to regional haze. Thus, it is not appropriate to reject a control measure for
a single emission unit, a single source, or even a group of sources on the basis of the associated
visibility benefits being imperceptible to the human eye. (Note, however, that we do expect that a
given Class I area will generally experience perceptible visibility improvements due to the
cumulative effect of LTSs in upwind states.) While this approach was used during the first
implementation period, experience has shown that it presents considerable technical challenges.
These technical challenges include modeling visibility improvement and interpreting the
modeled results, as well making comparisons among the results from different modeling
platforms that use different emission assumptions and chemistry.19 In addition, developing
information on visibility benefits can be very resource-intensive. Finally, the first
18 See our final action on the reasonable progress aspects of the Oklahoma and Texas regional haze SIPs. 81 FR 296
at 309, January 5, 2016. See also North Dakota v. EPA, 730 F.3d 750, 764-766 (8th Cir. 2013).
19 For example, a discussion Further discussion of these differences is between the modeling that was conducted for
BART determinations during the first implementation period and potential reasonable-progress modeling
approaches is provided in section 6.2.
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implementation period revealed that it can be very difficult for states to make logical and
consistent decisions regarding the appropriate weight to give visibility benefits when weighing
them against the four statutory factors. Consequently, we recommend that states considering this
second alternative approach seek input from EPA, FLMs and the public on a draft analytical
work plan and proposed decision-making criteria before committing to this approach. The EPA's
FIP for Texas20 during the first implementation period is an example of the analytical rigor that
we believe is required under this approach and the resources required to complete it.
4.3. Focusing on the 20 percent most impaired days
The EPA recommends that states focus on visibility impacts and benefits on the 20 percent most
impaired days when conducting their screening analyses and four-factor analyses.21
At the screening step, we recommend that states using a visibility-impact threshold consider both
(1) the maximum source impact within this set of days and (2) the average source impact across
this set of days multiplied by a constant value.22 If either metric exceeds the state's chosen
visibility-impact threshold, then the state should bring forward the source for a full four-factor
analysis. This will ensure that states analyze those sources that have relatively large impacts on
at least one of the 20 percent most impaired days, as well as those sources with more chronic
impacts during these this set of days. Section 6.2 and 6.3 discuss the use of thresholds in a
screening analysis in more detail.
The EPA also recommends that states following the second alternative approach (described in
section 4.2) consider both (1) the maximum visibility benefit on the 20 percent most impaired
days, as well as other values at the high end of this distribution, and (2) the average visibility
benefit across this set of days. Many people visit Class I areas only for one day, so it is important
to consider the days on which these visitors will receive the most benefit.
While the Regional Haze Rule does not require states to generate information on visibility
impacts or benefits on days other than the 20 percent most impaired days, states may nonetheless
choose to do so. Such information may also become available during the SIP development
process. In these cases, states should consider visibility impacts and benefits on days outside the
20 81FR 295 (Jan. 5, 2016).
21 This recommendations in this section presume that visibility impacts and benefits have been estimated for the
indicated types of days, or that a suitable surrogate for visibility impacts and benefits on particular days is available.
The day-specific source impacts and benefits should be included in the material provided for public comment and
submitted to the EPA with the SIP revision.
22 Note to reviewers of this draft guidance document: The text of this draft document refers to the use of one value
for the screening threshold, and of comparing both a source's or group of sources' maximum and average visibility
impacts to the one threshold, but only after multiplying the average impact by some constant value. Effectively, this
would be equivalent to having one threshold for the maximum impact and a second, lower threshold for the actual
value of the average impact. We specifically invite comment on the appropriateness of the final guidance
recommending a specific value for a constant multiplier, or a specific ratio of two separate thresholds, for this
purpose. We have observed that for the sources and Class I areas involved in the Texas FIP case, the maximum
visibility impact across the 20 percent haziest days was consistently about three times the average impact on these
days, and the same factor applied to visibility benefits. In a similar situation, using a multiple of about three would
likely not greatly affect what sources are brought forward, since sources with an average impact one-third of the
threshold would generally have a maximum impact greater than the threshold, while using a larger multiple might
bring forward additional sources.
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20 percent most impaired days if they are significant and would affect the state's decision
making.
4.4. Determining the measures "necessary to make reasonable progress"
The very definition of "regional haze" recognizes that progress towards natural visibility
conditions will require the accumulation of reductions in air pollution and associated light
extinction, achieved through emission control measures applied to many sources over a broad
geographic area. The visibility benefits of these measures may not be individually perceptible.
The EPA recognizes that determining whether a measure is necessary to make reasonable
progress is ultimately a fact-specific inquiry regarding a particular source or source category and
the affected Class I areas that takes place in the context of legal requirements and input from
stakeholders. In our actions on SIPs and FIPs in the first implementation period, we did not apply
any general formula or bright-line test to evaluate state decisions or reach our own decisions as
to what measures are necessary to make reasonable progress, and we are not recommending any
such formula in this guidance. This does not mean, however, that a state has unbounded
flexibility or discretion in its decision making. States must use reasoned decision making and
give due consideration to well-developed factual information and public comments. States
should develop their factual information according to the recommendations in sections 5, 6 and 7
of this guidance document. States may deviate from these recommendations, but must justify any
approach that contradicts a specific recommendation. States should avoid clear inconsistencies
when making control decisions for similarly situated sources and adequately explain relevant
distinguishing considerations. The EPA is likely to view unexplained inconsistencies as an
indication of arbitrary decision making.
The EPA believes that a state following the recommended approach to developing an LTS will
satisfy the Regional Haze Rule's LTS requirements as long as the state bases its decisions on
properly established facts; brings forward from screening sources that, in the aggregate, represent
the large majority of controllable emissions that are impairing visibility; reasonably considers the
four statutory factors for those sources; considers the recommendations in this guidance;
considers relevant FLM and public comments; and provides and documents a reasoned and
logical explanation for its decisions on the control measures necessary to make reasonable
progress. The EPA will review the substance of state SIPs for compliance with the applicable
requirements of the CAA and the Regional Haze Rule, consistency with this and other relevant
guidance and reasonableness. Except for the omission of any screening step, the same applies to
a state following the first alternative approach.
Similarly, the EPA believes that a state following the second alternative approach will satisfy the
Regional Haze Rule's LTS requirements as long as the state takes the steps explained above and
explains and documents how visibility benefits were taken into account in considering the four
statutory factors. In light of the challenges associated with the second alternative approach
mentioned above in section 4.3, we recommend that states considering this approach seek input
from EPA, FLMs and the public on their draft analytical work plans and proposed decision
making criteria before committing to this approach.
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4.5. The Relationship between the LTS and the RPGs
Under 40 CFR 51.308(f)(2)(i), states must consider the four statutory factors to decide what
emission control measures are necessary to make reasonable progress toward natural visibility
conditions at Class I areas. This obligation applies equally to states with Class I areas and states
with sources that contribute to impairment at Class I areas in other states.23 The four factors are:
• The costs of compliance.
• The time necessary for compliance.
• The energy and non-air quality environmental impacts of compliance.
• The remaining useful life of any potentially affected major or minor stationary source
or group of sources.
A state must incorporate all emission control measures necessary to make reasonable progress
into the LTS in enforceable form. Once a state has developed its LTS, the state must use a
regional photochemical air quality model to project the future visibility conditions at each of its
Class I areas on the 20 percent most impaired days and 20 percent clearest days.24 These
visibility conditions are the RPGs for each Class I area. Thus, the content of the LTS determines
the RPGs; the LTS is not a means to achieve RPGs set by some other process. The RPGs are
unenforceable analytical tools used to draw comparisons to the URP and to allow for
comparisons to actual visibility conditions in progress reports and future SIP revisions.25
4.6. Comparing the RPGs to the URP
Under 40 CFR 51.308(f)(3)(ii)(A), states with Class I areas must compare their RPGs for the 20
percent most impaired days to the URP in 2028 (as described in section 10 of this document).
The URP is the rate of progress necessary to reach natural visibility conditions at the Class I area
by the end of 2064. States are not required to set RPGs that meet or exceed the URP, nor does
meeting or exceeding the URP create a safe harbor that exempts states from the requirements of
the Regional Haze Rule. If the 2028 RPG is above the URP line, however, the state must
demonstrate that there are no additional emission reduction measures that would be reasonable to
include in the LTS. To satisfy this requirement, states may need to consider sources that screened
out of the four-factor analysis or take a second look at emission controls for sources that were
selected for the four-factor analysis. If the state determines that no additional emission control
measures are reasonable to bring the 2028 RPG at or below the URP line, the state must explain
23 Contributing states are those other states with sources that may be reasonably anticipated to contribute to visibility
impairment at the Class I area.
24 The future emissions scenario used to project the 2028 RPGs for a Class I area must be based on the content of the
LTS of the state with the Class I area, the LTS of any contributing states, and any other enforceable measures that
are in place or are otherwise scheduled to take effect by 2028. The 2028 RPGs also should reflect expected source
utilization in 2028, including for source categories treated as aggregated area sources.
25 The Regional Haze Rule requires states to include in their SIP submissions for the second implementation period,
due by July 31, 2021, a commitment to submit one progress report in each of the second and subsequent
implementation periods, the next of which will be due by January 31, 2025. The 2028 RPGs will serve as reference
points in the 2025 progress report for tracking whether actual progress is happening as anticipated. If not, states
should investigate the reasons for the lack of expected progress and determine whether additional reductions are
needed. The Regional Haze Rule requires every progress report to include a determination by the state as to whether
the SIP is adequate to achieve the RPGs. The Regional Haze Rule does not require the progress reports to be
submitted as SIP revisions.
18
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and document its reasoning. Under 40 CFR 51.308(f)(3)(ii)(B), upwind states that contribute to
impairment at a Class I area for which the 2028 RPG is above the URP line have the same
obligations, i.e., to take a second look at the LTS, determine whether additional control measures
are reasonable, and provide adequate documentation. Sections 4.5 and 11 of this guidance
document discuss this issue.
4.7. Documentation
Regional Haze Rule provisions
51.308(f)(2) Long-term strategy for regional haze and reasonably attributable visibility
impairment.
* * *
In establishing its long-term strategy for regional haze, the State must meet the following
requirements:
(i) The State must consider and analyze emission reduction measures based on 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 major or minor stationary source or group of sources. The State must document
the criteria used to determine which sources or groups of sources were evaluated, and
how these four factors were taken into consideration in selecting the measures for
inclusion in its long-term strategy.
A A A
(iii) The State must consult with those States which may reasonably be anticipated to
cause or contribute to visibility impairment in the mandatory Class I Federal area.
(A) Contributing States. Where the State has emissions that are reasonably anticipated to
contribute to visibility impairment in any mandatory Class I Federal area located in
another State or States, the State must consult with the other State(s) in order to develop
coordinated emission management strategies. The State must demonstrate that it has
included in its implementation plan all measures necessary to obtain its share of the
emission reductions needed to provide for reasonable progress towards natural visibility
conditions in the mandatory Class I Federal area located in the other State or States. If the
State has participated in a regional planning process, the State must also ensure that it has
included all measures needed to achieve its apportionment of emission reduction
obligations agreed upon through that process.
(B) States affected by contributing States. A State with a mandatory Class I Federal area
must consult with any other State having emissions that are reasonably anticipated to
contribute to visibility impairment in that area regarding the emission reductions needed
in each State to provide for reasonable progress towards natural visibility conditions in
that area. If the State has participated in a regional planning process, the State must
ensure it has included all measures needed to achieve its apportionment of emission
reduction obligations agreed upon through that process.
(C) In any situation in which a State cannot agree with another State or group of States on
the emission reductions needed for reasonable progress towards natural visibility
conditions in any mandatory Class I Federal area, each involved State must describe in its
19
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submittal the actions taken to resolve the disagreement. In reviewing the State's
implementation plan submittal, the Administrator will take this information into account
in determining whether the State's implementation plan provides for reasonable progress
towards natural visibility conditions at each mandatory Class I Federal area that is located
in the State or that may be affected by emissions from the State. All substantive interstate
consultations must be documented.
(iv) As part of the demonstration required by (f)(2)(i), the State must document the
technical basis, including information on the factors listed in (f)(2)(i) and modeling,
monitoring, and emissions information, on which the State is relying to determine the
emission reductions from anthropogenic sources in the State that are necessary for
achieving reasonable progress towards natural visibility conditions in each mandatory
Class I Federal area it affects. The State may meet this requirement by relying on
technical analyses developed by a regional planning process and approved by all State
participants. The State must identify the baseline emissions inventory on which its
strategies are based. The baseline emissions inventory year shall be the most recent year
for which the State has submitted emission inventory information to the Administrator in
compliance with the triennial reporting requirements of subpart A of this part unless the
State adequately justifies the use of another inventory year.
States should be attentive to the documentation requirements in the above provisions of the
Regional Haze Rule. The FLMs who reviewed all the SIP submissions in the first
implementation period have shared with the EPA their assessment that the SIPs from California,
Colorado, Florida, Minnesota, New Mexico and North Carolina provide good examples of how
to document the basis for a regional haze SIP submission. These submissions can be found in the
dockets for the EPA actions on them, listed in Appendix B.
4.8. Consultation
Consultation with other states
Regional Haze Rule provisions
51.308(f)(2) Long-term strategy for regional haze and reasonably attributable visibility
impairment.
* * *
(iii) The State must consult with those States which may reasonably be anticipated to
cause or contribute to visibility impairment in the mandatory Class I Federal area.
(A) Contributing States. Where the State has emissions that are reasonably anticipated to
contribute to visibility impairment in any mandatory Class I Federal area located in
another State or States, the State must consult with the other State(s) in order to develop
coordinated emission management strategies. The State must demonstrate that it has
included in its implementation plan all measures necessary to obtain its share of the
emission reductions needed to provide for reasonable progress towards natural visibility
conditions in the mandatory Class I Federal area located in the other State or States. If the
State has participated in a regional planning process, the State must also ensure that it has
included all measures needed to achieve its apportionment of emission reduction
obligations agreed upon through that process.
20
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(B) States affected by contributing States. A State with a mandatory Class I Federal area
must consult with any other State having emissions that are reasonably anticipated to
contribute to visibility impairment in that area regarding the emission reductions needed
in each State to provide for reasonable progress towards natural visibility conditions in
that area. If the State has participated in a regional planning process, the State must
ensure it has included all measures needed to achieve its apportionment of emission
reduction obligations agreed upon through that process.
(C) In any situation in which a State cannot agree with another State or group of States on
the emission reductions needed for reasonable progress towards natural visibility
conditions in any mandatory Class I Federal area, each involved State must describe in its
submittal the actions taken to resolve the disagreement. In reviewing the State's
implementation plan submittal, the Administrator will take this information into account
in determining whether the State's implementation plan provides for reasonable progress
towards natural visibility conditions at each mandatory Class I Federal area that is located
in the State or that may be affected by emissions from the State. All substantive interstate
consultations must be documented.
The Regional Haze Rule requires states to consult about interstate impacts on visibility in Class I
areas. See 40 CFR 51.308(f)(2)(iii). These consultation requirements apply to states with affected
Class I areas and states with sources that may reasonably be anticipated to contribute to visibility
impairment at out-of-state Class I areas. These requirements apply regardless of when states plan
to submit their SIP revisions.
The EPA offers the following recommendations to guide the interstate consultation process:
• If a source or sources in one state are reasonably anticipated to contribute to visibility
impairment at a Class I area in another state, the contributing state ("upwind state") must
consider the inclusion of control measures for its own sources in its LTS based on a
consideration of the four factors. If the upwind state is following the second alternative
approach, it would also consider visibility benefits along with the four factors.
• A state with a Class I area should consult with a contributing upwind state and, if
appropriate, request that the upwind state adopt additional emission controls on a source
or source category.
• In the interest of efficient use of resources, the states should consult early on a plan for
the development of factual information on the degree to which upwind sources
individually contribute to the visibility impact of downwind Class I areas, how those
sources can be controlled and the cost of those controls. Generally, the upwind state with
the source will be in the best position to obtain information on the source's physical
configuration, recent and current emissions, planned modifications and potential
additional emission controls. This may involve compilation of information already
available to the upwind state via routine reporting systems, special information
collection from source owners, air quality modeling, cost analysis and other efforts.
However, the downwind state with the Class I area cannot simply cite a lack of
information from the upwind state as justification for not considering a source in the
upwind state at all and thus not requesting additional control of it.
• The EPA recognizes that a state with a Class I area cannot actually require controls in a
contributing state. However, the EPA believes that every state has inherent authority to
21
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request such controls, because under the Regional Haze Rule such a request does not
itself create an obligation on the part of the contributing state.
• An upwind state should consider the information provided by the downwind state and
should take reasonable steps to obtain additional and more certain information relevant
to the visibility impacts from the source or source category in the upwind state and the
four factors. Generally, a state with authority over a source or source category will be
better able to obtain information on its baseline emissions and the potential for additional
emission control.
• An upwind state may recommend action by the downwind state with respect to the
downwind state's own sources but is not obligated to do so.
• If states disagree on the elements of the analysis or controls that are required for
reasonable progress, the respective EPA regional offices are available to assist the states
towards a mutually agreeable outcome that will be approvable under the Regional Haze
Rule. However, the EPA cannot direct either state as to the content of the SIP it submits.
Should two states ultimately submit SIP revisions that disagree on the controls in each
state that are needed for reasonable progress, the Regional Haze Rule provides for the
EPA to consider the technical information presented by both states when considering
whether to approve each state's SIP. This may entail reviewing and acting upon the two
state SIPs simultaneously. Even when there is agreement by the states on the controls
that are required (or not required) for reasonable progress, the EPA will independently
review their conclusions against Regional Haze Rule requirements.
Consultation between a state andFLMs
Regional Haze Rule provisions
51.307 New source review.
(a) For purposes of new source review of any new major stationary source or major
modification that would be constructed in an area that is designated attainment or
unclassified under section 107(d) of the CAA, the State plan must, in any review under
§51.166 with respect to visibility protection and analyses, provide for:
(1) Written notification of all affected Federal Land Managers of any proposed new
major stationary source or major modification that may affect visibility in any Federal
Class I area. Such notification must be made in writing and include a copy of all
information relevant to the permit application within 30 days of receipt of and at least 60
days prior to public hearing by the State on the application for permit to construct. Such
notification must include an analysis of the anticipated impacts on visibility in any
Federal Class I area,
(2) Where the State requires or receives advance notification (e.g. early consultation with
the source prior to submission of the application or notification of intent to monitor under
§51.166) of a permit application of a source that may affect visibility the State must
notify all affected Federal Land Managers within 30 days of such advance notification,
and
(3) Consideration of any analysis performed by the Federal Land Manager, provided
within 30 days of the notification and analysis required by paragraph (a)(l) of this
section, that such proposed new major stationary source or major modification may have
22
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an adverse impact on visibility in any Federal Class I area. Where the State finds that
such an analysis does not demonstrate to the satisfaction of the State that an adverse
impact will result in the Federal Class I area, the State must, in the notice of public
hearing, either explain its decision or give notice as to where the explanation can be
obtained.
(b) The plan shall also provide for the review of any new major stationary source or
major modification:
(1) That may have an impact on any integral vista of a mandatory Class I Federal area
listedin§51.304(b), or
(2) That proposes to locate in an area classified as nonattainment under section 107(d)(l)
of the Clean Air Act that may have an impact on visibility in any mandatory Class I
Federal area.
* * *
51.308(i) What are the requirements for State and Federal Land Manager coordination?
(1) By November 29, 1999, the State must identify in writing to the Federal Land
Managers the title of the official to which the Federal Land Manager of any mandatory
Class I Federal area can submit any recommendations on the implementation of this
subpart including, but not limited to:
(i) Identification of impairment of visibility in any mandatory Class I Federal area(s); and
(ii) Identification of elements for inclusion in the visibility monitoring strategy required
by §51.305 and this section.
(2) The State must provide the Federal Land Manager with an opportunity for
consultation, in person at a point early enough in the State's technical and policy analyses
of its long-term strategy emission reduction obligation and prior to development of
reasonable progress goals so that information and recommendations provided by the
Federal Land Manager can meaningfully inform the State's development of the long-term
strategy. The opportunity for consultation will be deemed to have been early enough if
the consultation has taken place at least 120 days prior to holding any public hearing or
other public comment opportunity on an implementation plan (or plan revision) or
progress report for regional haze required by this subpart. The opportunity for
consultation must be provided no less than 60 days prior to said public hearing or public
comment opportunity. This consultation must include the opportunity for the affected
Federal Land Managers to discuss their:
(i) Assessment of impairment of visibility in any mandatory Class I Federal area; and
(ii) Recommendations on the development of the reasonable progress goal and on the
development and implementation of strategies to address visibility impairment.
(3) In developing any implementation plan (or plan revision) or progress report, the State
must include a description of how it addressed any comments provided by the Federal
Land Managers.
(4) The plan (or plan revision) must provide procedures for continuing consultation
between the State and Federal Land Manager on the implementation of the visibility
protection program required by this subpart, including development and review of
23
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implementation plan revisions and progress reports, and on the implementation of other
programs having the potential to contribute to impairment of visibility in mandatory
Class I Federal areas.
Consultation between a state and FLMs should begin early and continue throughout development
of the SIP revision. This consultation should encompass the approach a state anticipates taking in
its SIP development, the state's photochemical and source apportionment modeling protocol
including any questions of the meaning or applicability of EPA's guidance for such modeling,
the assessment of the results of this modeling, and the decisions about the sources and source
categories to be carried from the screening analysis into the four factor analysis.
The 2016 Regional Haze Rule revisions added a requirement for consultation early enough to
allow full consideration of FLM input by the state. This is best accomplished by involving the
FLMs in the planning of information gathering and analytical work, including the specific topics
listed in the previous paragraph. FLM input on options is best sought before important decisions
are made by state decision makers as to what proposed LTS will be presented for public
comment. See section 51.308(i)(2). The Regional Haze Rule requires that consultation take place
no less than 60 days before the start of a public comment period or public hearing. While the rule
also provides that consultation will be considered to meet the requirement that it be "early
enough" if it takes place at least 120 days before the start of a public comment period or public
hearing, the EPA expects that most states will take significant steps in SIP development well
before the 120-day point, and that states will benefit from FLM input at those times.
Note that the Regional Haze Rule also requires the SIP to provide procedures for ongoing
consultation.
Section 40 CFR 51.307 on new source review was promulgated in 1980. This provision
implements certain requirements of the Prevention of Significant Deterioration Program under
section 165(d) of the Clean Air Act for the protection of visibility and extends them to sources
locating in areas designated as nonattainment under section 107 of the CAA. While it does not
establish any criteria for approval of regional haze SIPs, section 51.307 does provide criteria for
the new source review components of state SIPs to ensure the protection of visibility in Class I
areas. States should be aware of and comply with the notification and information sharing
requirements in this provision. State programs' rules should require written notification to the
FLMs of any proposed new major stationary source or major modification that may affect
visibility in a Class I area. Such notification must include a copy of all information relevant to
the permit application and an analysis of the anticipated visibility impacts of the source. The
FLMs consider relevant information to include the public notice (or draft public notice), draft
permit, associated staff analyses and the complete permit application.
Traditionally, the EPA has interpreted "may affect" to mean any major source or major
modification that is proposing to locate within 100 km of a Class I area, or any such source that
will be located further than 100 km from a Class I area and will have emissions that the FLM is
concerned may cause visibility (and other AQRV) impacts. In permitting guidance, the EPA has
recognized that sources locating beyond 100 km may cause adverse impact on Class I area under
some conditions. In light of the recognition that sources may affect visibility at Class I areas that
are several hundred or more kilometers from the source, a notion that is reflected in the regional
24
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haze program, states should not restrict this type of consultation to only permit activities
involving sources closer than 100 kilometers from the Class I area.26
Consultation with the EPA
Consultation with the EPA should also begin early and be continual. In these consultations, we
can help states understand the provisions of the Regional Haze Rule and this guidance document,
and advise the state on how they should be applied in the context of the state's SIP.
The EPA will, to the extent possible, support technical work by states through multi-state
organizations. The EPA's Office of Air Quality Planning and Standards routinely shares
technical products (modeling platform inputs and outputs for specific control scenarios and
projection years) that may be useful to individual states or multi-state organizations doing joint
technical work.
Consultation with tribes
Tribes have interests in the content of SIPs because SIPs affect air quality in and around tribal
land. The EPA recognizes the value in states and multi-state organizations maintaining an on-
going dialog with tribes through all stages of developing their regional haze SIPs. As noted
earlier, it may be that the tribe or the EPA has responsibility for regulating a source on tribal land
for purposes of regional haze, depending on the status of the tribe for purposes of implementing
CAA programs. If a state believes that additional control of a source on tribal land is needed for
reasonable progress at one of the state's Class I areas, the state may contact the EPA regional
office to discuss the situation and possible courses of action.
The EPA will consult with tribes under its tribal consultation policy as appropriate when acting
to approve or disapprove a regional haze SIP submitted by a state, when promulgating a FIP to
fill gaps in a state SIP and when developing a regional haze plan for a tribal area.
26 See the 1990 Draft NSR Workshop Manual at E. 16, http://www.epa.gov/nsr/nsr-workshop-manual-draft-october-
1990.
25
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5. Ambient data analysis (Step 1)
5.1. What are the visibility progress tracking metrics and calculations required by the
Regional Haze Rule?
Under 40 CFR 51.308(f)(l)(i)-(vi), states must calculate the following tracking metrics using
data collected by the IMPROVE monitoring program:
• Baseline, natural and current visibility conditions for the most impaired and clearest
days. These six conditions must be quantified in deciviews.
• Actual progress made on the most impaired and clearest days toward natural visibility
conditions (1) since the baseline period and (2) in the previous implementation
period. These four calculations must be quantified in deciviews.
• The difference between current and natural visibility conditions for the most impaired
and clearest days. These two calculations must be quantified in deciviews.
• The URP for the most impaired days between baseline visibility conditions and
natural visibility conditions. The URP must be quantified in deciviews per year.
More discussion of these calculations is provided throughout section 5 of this guidance
document, as shown in Table 5.1.
Table 5.1. Sections of this guidance that address ambient data analysis
20 Percent Most Impaired Days
20 Percent Clearest Days
Current Visibility Conditions
Baseline Visibility Conditions
Natural Visibility Conditions
Actual progress and difference
between current and natural
visibility conditions
Uniform Rate of Progress
Sections 5.2-5.6
Section 5.7
Section 5.8
Section 5.9
Section 5. 10 and 5. 11
Section 5.16
Section 5.17
5.2. How was visibility progress tracked in the first implementation period of the Regional
Haze Rule?
The rule text adopted in 1999 defined "visibility impairment" as a humanly perceptible change
(i.e., difference) in visibility from that which would have existed under natural conditions.27 The
1999 rule text directed states to track visibility impairment on the 20 percent "most impaired
days" and 20 percent "least impaired days" in order to determine progress towards natural
visibility conditions. 40 CFR 51.308(d)(2)(i)-(iv). The 1999 rule text did not define "most
impaired days" or "least impaired days" or clearly indicate whether they were the days with the
highest and lowest values for both natural and anthropogenic impairment or for anthropogenic
impairment only. However, the preamble to the 1999 final rule stated that the least and most
27 See 64 FR 35764. Section 51.301.
26
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impaired days were to be selected as the monitored days with the lowest and highest actual
deciview levels, respectively, which encompass both natural and anthropogenic contributions to
reduced visibility.28 In 2003, the EPA issued guidance describing in detail the steps for selecting
and calculating light extinction on the "worst" and "best" visibility days, which also indicated
that states should determine the least and most impaired days based on monitoring data rather
than determining and selecting the days with the highest and lowest anthropogenic impacts.29
The "worst" visibility days for some Class I areas are impacted by natural emissions (e.g.,
wildfires and dust storms). These natural contributions to haze vary in magnitude and timing.
Anticipating this variability, the 1999 Regional Haze Rule required states to use 5-year averages
of visibility data to minimize the impacts of inter-annual variability in natural events. However,
as the IMPROVE monitoring network has collected more years of data, it has become apparent
that 5-year averages do not sufficiently minimize these impacts for some Class I areas. Figure
5.1 shows an example of the extreme wildfire events that affected Sawtooth Wilderness Area,
especially in 2012.
Figure 5.1. Visibility conditions on the 20 percent worst visibility days at the
Sawtooth Wilderness Area (Idaho) from 2000 to 2013. Blue points are single-year
values; red points are 5-year averages.
25 -i
20 -
cu 10 H
Q
5 -
-Annual Avg.
-5-yr Avg.
OOOOOOOOO*-I<-I<-I
-------
revisions require a new approach to the tracking metrics; this new approach is described in the
remaining subsections of section 5.
5.3. How will visibility progress be tracked in the second and future implementation
periods?
The CAA established the national goal of remedying existing and preventing future visibility
impairment resulting from anthropogenic air pollution. The 2016 Regional Haze Rule revisions
require all states to use a new approach for tracking visibility on days with the most
anthropogenic impairment.30 Under the new approach, in the second and future implementation
periods states must select the "20 percent most impaired days" based on daily anthropogenic
impairment. The Regional Haze Rule does not specify how states should determine
anthropogenic impacts, but this guidance document contains the EPA's recommendations for
doing so for the second implementation period.31 States may deviate from these
recommendations if they demonstrate an adequate basis for taking another approach. The EPA
recommends that a justification for an alternative approach include a comparison of the state's
approach with the approach recommended here, including an explanation of why the state's
approach is more appropriate and how it affects the comparison of the RPG to the URP line.
Because the EPA or the IMPROVE program will provide user-ready data files reflecting the
approach recommended here, this comparison should not involve significant additional effort by
the state. The Regional Haze Rule continues to require the use of deciviews (dv) as the unit of
visibility and visibility impairment. The program has used and continues to use deciviews, rather
than light extinction (bext), because an increment on the deciview scale reflects increments in
human perception of visibility of a given scenic vista across a wide range of perceived visibility
conditions, while this is not true for the light extinction scale.
The Regional Haze Rule continues to require the use of the "20 percent least impaired days" for
setting the other RPG, but now refers to these days as the "20 percent clearest days" in an effort
to be as specific as possible.
The details of the steps involved in selecting days based on the amount of anthropogenic
impairment are provided in the following subsections of section 5. These subsections supersede
much of the previous 2003 guidance on progress tracking.32 The approaches presented in the
following subsections also apply to progress reports beginning with the reports due on January
31,2025.
5.4. What does it mean to choose the 20 percent most impaired days based on daily
anthropogenic impairment?
The 2016 Regional Haze Rule revisions define visibility impairment as "any humanly perceptible
difference between actual visibility conditions and natural visibility conditions. Because natural
30 Note to reviewers of this draft guidance document: The EPA has proposed in the alternative in the recent rule
revisions NPRM to either require states to use the new approach for choosing the 20 percent most impaired visibility
days or to allow each state to choose between the original (20 percent worst overall visibility days) and the new
approach. For simplicity, this draft has been written as if all states are required to use the new approach. When
finalized, the guidance will be written to be consistent with the final rule revisions.
31 As the scientific understanding of the sources of and contributors to haze are refined, the EPA may provide
additional guidance on determining anthropogenic impacts for the second and future implementation periods.
32 Appendix D identifies portions of this earlier guidance that are still informative and relevant going forward.
28
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visibility conditions can only be estimated or inferred, visibility impairment also is estimated or
inferred rather than directly measured." 40 CFR 51.301. In other words, the Regional Haze
Rule's definition of visibility impairment is synonymous with anthropogenic impairment. To
select the 20 percent most impaired days using anthropogenic impairment rather than total
impairment, a logical metric must be used that reflects both the magnitude of the light extinction
above natural levels (in Mm"1) as well as the logarithmic relationship between light extinction
and perceived visibility. This metric is the difference between the deciview value that actually
exists and the deciview value that would have existed if there were only natural sources causing
reduced visibility, i.e., the metric is the "delta deciviews" due to anthropogenic emissions. We
recommend that states use Equation 5.1, where dvtotai is the overall deciview value for a day, and
dvnaturai is the natural portion of the deciview value for a day, to calculate anthropogenic
impairment. We provide more details on the derivation of the impairment metric in the technical
support document (companion TSD) that accompanies this guidance document.33
"•^anthropogenic impairment ~ "-^total ~ "-^natural (^qn J.I)
Because of the logarithmic relationship between deciviews and light extinction, a high value of
light extinction due to anthropogenic impacts does not necessarily translate to a high value for
visibility impairment. For example, if large anthropogenic impacts occur on the same day that a
large natural impact occurs, then those anthropogenic impacts will not be as perceptible as if the
same anthropogenic impacts occurred on a day with smaller natural impacts. Conceptually,
choosing the 20 percent most impaired days based on days with the highest anthropogenic
impairment means that days dominated by anthropogenic impacts are selected and days
dominated by high natural impacts are not selected. Under this approach, the days with the
highest light extinction due to uncontrollable impacts from natural sources such as wildfires and
dust storms will no longer be selected, a result that particularly affects Class I areas in western
states. Days with moderate to high light extinction from anthropogenic sources and low light
extinction due to natural sources will instead be selected as the 20 percent most impaired days.
An illustration of the different approaches for selecting the most impaired days is shown in
Figure 5.2. In Figure 5.2, the vertical scale for the Current Approach is in light extinction (Mm"1)
and the vertical scale for the New Approach is in deciviews.
33 Draft Technical Support Document (TSD): Revised Recommendations for Visibility Progress Tracking Metrics
for the Regional Haze Program, USEPA Office of Air Quality Planning and Standards, Air Quality Assessment
Division, March 17, 2016.
29
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Figure 5.2. Illustration of the conceptual differences between choosing the 20
percent most impaired days based on total haze (top) versus anthropogenic
impairment (bottom).
First Implementation Period Approach: select days
with highest light extinction as most impaired days
tj
c
'
OJ
4_i 100
!§> ,
I
A B
hropogenic (Mm"1)
Natural (Mm"1)
New, Recommended Approach: select days with most
anthropogenic impairment as most impaired days
>
D
A C
In the approach used in the first implementation period (top of Figure 5.2), the days with the
highest overall light extinction (days similar to Day E) were selected into the 20 percent most
impaired days, even if the light extinction was primarily due to natural sources. In the new
approach, shown on the bottom, the days with the highest anthropogenic impairment, defined by
the "delta deciview" metric (days similar to Day B), are selected.
Table 5.2 translates the illustration shown in Figure 5.2 into numbers to further demonstrate the
results of using anthropogenic impairment and equation 5.1 to sort the IMPROVE data. For
example, Day C has higher light extinction due to anthropogenic sources (160.6 Mm"1) than Day
B (107 Mm"1), but Day C also has a higher natural contribution (32.2 Mm"1) than day B (16 Mm"
l). Therefore, anthropogenic impairment (calculated according to Eqn 5.1) on Day C (17.9
deciview) is lower than on Day B (20.4 deciview). We do not recommend selecting days based
only on the days with the largest anthropogenic contributions to light extinction (i.e., days like
Day C) because these may still occur on days with large natural contributions, where less of a
30
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difference in visibility would be noticeable due to a reduction in the anthropogenic
contribution.34
Table 5.2. Numerical illustration to accompany Figure 5.2. Column "Rank by
dviotai" corresponds to the top of Figure 5.2 (sorting by total haze). Column "Rank
by dvanthro impairment" corresponds to the bottom of Figure 5.2 (sorting by
anthropogenic impairment).
Day
A
B
C
D
E
Total
bext
(Mm"1)
75
123
193.8
300
342.8
Natural
bext
(Mm" )
42.8
16.0
32.2
231
214.2
Anthro
bext
(Mm" )
32.3
107
160.6
69.0
128.5
dVTotal
20.1
25.1
29.6
34.0
35.3
Rank
by
dVTotal
5
4
3
2
1
dVnatural
14.5
4.7
11.7
31.4
30.6
dVanthro
impairment
5.6
20.4
17.9
2.6
4.7
Rank by
dVanthro impairment
3
1
2
5
4
5.5. How does the EPA recommend estimating daily natural and anthropogenic visibility
impacts and light extinction budgets?
It currently is not possible to directly measure the natural or anthropogenic fractions of total light
extinction, so these fractions must be estimated. This guidance document presents our current
recommendation for estimating these fractions. The EPA may publish refinements to this method
or additional methods through additional guidance as such methods become available. The
34 We investigated selecting days based only on their rank in terms of anthropogenic light extinction contributions
(in Mm"1), rather than the difference in deciviews between actual/overall and natural visibility conditions as we are
recommending, but we decided that using anthropogenic impairment (in "delta deciviews") is more true to the
definition of visibility impairment within the Regional Haze Rule as "any humanly perceptible difference between
actual visibility conditions and natural visibility conditions". [Emphasis added.] This definition of visibility
impairment includes human perception of the differences in visibility with and without anthropogenic contributions.
Reduction of anthropogenic light extinction on days with high natural light extinction will not be as perceptible as
reductions of anthropogenic contributions on days with low natural contributions. This supports the recommendation
of using the difference in deciviews between actual and natural visibility conditions (rather than anthropogenic light
extinction) to select the most impaired days. For example, if a source or set of sources impacts a Class I area only on
days impacted by fire, then other sources that impact the area on non-fire days are more important to consider for
improving the perceptible differences invisibility. Additionally, we found that the recommended method (using the
difference, in deciviews, between actual and natural visibility conditions) it is less sensitive to the exact details of
the method selected for splitting the concentration data for each PM species into "natural" and "anthropogenic". We
found the two approaches often identified the same or nearly the same set of days at most eastern Class I areas,
while there are noticeable differences in the days selected as impaired in the West, especially during high fire years
(i.e., 2012). Our analysis shows that the "non-overlap" days (i.e., days not selected by anthropogenic impairment but
selected as having the highest anthropogenic light extinction) are more like Days D and E in Figure 5.2 than Day C,
which indicates that our recommended approach is not likely to miss inclusion of a day like Day C with high
anthropogenic light extinction. The resulting extinction budgets for the different sets of days may also differ. See
TSD for a more detailed explanation of the comparison between anthropogenic impairment and anthropogenic light
extinction.
-------
IMPROVE program and the EPA will work together to conduct these analyses and provide
datasets to states for their use. See section 5.13.
In general, the recommended approach to splitting daily light extinction into natural and
anthropogenic fractions is to estimate the natural contributions to light extinction, then attribute
the remaining light extinction to anthropogenic sources. The natural contributions can be of two
types - "episodic" and "routine." Episodic natural contributions are those that occur relatively
infrequently, may differ in number and size from year to year, and likely result from extreme
events. Routine natural contributions are those that occur on all or most days in a year or season
and are more consistent from year to year. Large wildfires and strong dust storms are examples
of episodic natural contributions, while biogenic secondary aerosol is an example of a routine
contribution.35 It is useful to make this distinction because the values used by most states in the
first implementation period to represent natural visibility conditions, the "NC-II" estimates,36 are
generally recognized as representing the influences of routine natural sources, but not episodic
natural sources.37 As explained below, the annual average NC-II estimates are used in the
recommended method described in this section, but in a manner that is consistent with the
premise that they represent only the influences of routine natural sources.
The recommended steps (A through E) to estimate natural and anthropogenic light extinction are
detailed below, using an example for Mesa Verde National Park (MEVE1). Note that the values
throughout this example are unique to MEVE1 and have been included for illustrative purposes
only. Each Class I area is treated individually, and these values do not apply to any site other
thanMEVEl.
35 The EPA recognizes that this dichotomy between "episodic" and "routine" natural contributions is a simplification
of actual emissions and atmospheric processes. For one thing, the distance between a natural emission source and
the Class I area may affect whether the source is effectively treated as episodic. The effective dichotomy is
operationally defined by the recommended calculation method as applied at each Class I area.
36 "NC-II" refers to a set of estimates of natural conditions for each Class I area contained in Regional Haze Rule
Natural Level Estimates Using the Revised IMPROVE Aerosol Reconstructed Light Extinction Algorithm, available
at
http://vista.cira.colostate.edu/improve/Publications/GrayLit/032_NaturalCondIIpaper/Copeland_etal_NaturalCond
itionsII_Description.pdf; Revised IMPROVE Algorithm for Estimating Light Extinction from Particle Speciation
Data, available at
http://vista, cira. colostate. edu/improve/Publications/GrayLit/019_RevisedIMPRO VEeq/RevisedlMPRO VEA Igorithm
3.doc; and Regional Haze Data Analysis Workshop, June 8, 2005, Denver, CO, agenda and documents available at
http://www.wrapair.org/forums/aamrf/meetings/050608den/mdex.html. These more recent estimates effectively
supplanted the values presented earlier in the EPA's 2003 guidance on estimating natural conditions. Both the values
in the EPA guidance and the NC-II estimates trace back to work by Trijonis. See Trijonis, J.C., Characterization of
Natural Background Aerosol Concentrations, Appendix A in Acidic Deposition: State of the Science and
Technology, Report 24, Visibility Existing and Historical Condition - Causes and Effects, National Acid
Precipitation Assessment Program, 1990.
37 Tombach, I. 2008. Natural Haze Levels Sensitivity, Assessment of Refinements of Estimates of Natural
Conditions. Prepared for the Western Governors Association. Available online at
http://www.wrapair.org/forums/aamrf/projects/NCS/Haze _Sensitivity_Report-Final.pdf.
32
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Step A: Establish light extinction thresholds to identify extreme events
For each Class I area, using data from the IMPROVE monitor associated with the area, identify
for each year the 95th percentile 24-hour carbon (organic + light-absorbing) light extinction.38
Choose the year between 2000 and 2014 with the lowest such value. This year represents the
"low wildfire" year of this period. Also, choose the year with the lowest 95th percentile 24-hour
dust (CM + fine soil) light extinction. This year represents the "low dust storm" year of this
period. It is possible that the same year will have the lowest 95th percentile values for both
carbon and dust. It is also possible that, at particular Class I areas, there will be little difference
among the 95th percentile values across the years. The 95th percentile carbon and dust values for
these years will serve as the threshold values used to identify impacts on carbon and dust light
extinction from extreme episodic events in those year and other years.
Using the 95th percentile value effectively defines what will be considered an extreme episodic
event. In the "low wildfire" or "low dust storm" years, there will typically be 5 or 6 monitored
days affected by an extreme episodic event because the IMPROVE program monitors every third
day. At Class I areas where episodic influences vary significantly from year to year, like some
western areas, it will not be unusual for more than five percent of the monitored days to be
affected by extreme episodic events in years other than the "low wildfire" and "low dust storm"
years. Thus, this approach allows a different number of high carbon days or high dust days in
different years to be identified as ones with an extreme episodic impact, but all the days that are
identified will have carbon or dust concentrations at least as high as the respective threshold.39
The EPA's recommendation that states use the 95th percentile dust and carbon values as
described above is a judgment call. Statisticians commonly use 95th percentiles to distinguish
between the part of a distribution that is "regularly behaved" and the part that reflects influences
from unusual or extreme processes, and we are using them here based on this reasoning.40 Our
investigations have indicated that the results would not be greatly different if another high
percentile were used for this purpose, and we provide more details in the companion TSD.
To find the 95th percentile value for carbon for one year, sort the carbon values from high to low.
Then, determine the number of complete values available for the year (n). For MEVEl in 2003,
there were 113 complete values for carbon. The 95th percentile value will be the 0.95*n
measured value. If 0.95*n is not an integer value, the 95th percentile value is the closest
monitored value higher than the 95th percentile. For MEVEl in 2003, 0.95*113 is 107.35, so the
95th percentile value would be the 108th highest value, out of 113. In 2003, the 108th highest
38 Total carbon is used here as an indicator of fire impact. See Jaffe et al. (2008) Interannual Variations in PM2 5 due
to Wildfires in the Western United States Environ. Sci. Technol. 42, 2812-2818 and Spracklen, D. V., J. A. Logan,
L. J. Mickley, R. J. Park, R. Yevich, A. L. Westerling; D. A. Jaffe (2007), Wildfires drive interannual variability of
organic carbon aerosol in the western U.S. in summer, Geophys. Res. Lett., 34, L16816,
doi: 10.1029/2007GL030037; Hand et al. Spatial and Seasonal Patterns and Temporal Variability of Haze and its
Constituents in the United States: Report V June 2011.
39 In contrast, if the 95th percentile point were used in each year separately, all years would be treated as having the
same number of days affected by what was called an extreme episodic event, but the severity of the impacts could be
very different from year to year.
40 This use of 95th percentile values is not related to the use of particular statistical forms for the National Ambient
Air Quality Standards. Such statistical forms are used in order to provide reasonable stability to the programs that
implement those standards.
33
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carbon value is 25.36 Mm"1. Repeat this process to get a 95th percentile value for each year for
carbon and dust. The results for each year of available data for MEVE1 are shown in Table 5.3.
Table 5.3. 95th percentile values for carbon and dust light extinction from
2000-2014 at MEVE1.
Year
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
Annual 95th percentile
carbon light extinction
(Mm'1)
12.68
7.00
16.14
25.36
5.94
9.64
7.81
11.72
7.54
10.55
7.11
5.29
10.66
5.40
5.05 (lowest)
Annual 95th
percentile dust light
extinction (Mm'1)
7.73
6.69
19.60
16.45
5.50
5.66
5.33 (lowest)
5.68
9.26
10.35
13.30
9.73
8.93
8.22
9.28
2014 and 2006 have the lowest carbon and dust 95th percentile values, respectively. The 95th
percentile value of carbon in 2014 was 5.05 Mm'1, and the 95th percentile value of dust in 2006
was 5.33 Mm"1. These 95th percentile values are the threshold values for identifying episodic
light extinction for MEVE1 for all years.
Step B: Assign the portions of carbon and dust light extinction that are in excess of these
thresholds to "natural (episodic) ".
Table 5.4. Total and speciated light extinction for an example day (May 12, 2003) in
MEVE1
PM Species
Sulfate
Nitrate
Total Light
Extinction
(Mm'1)
2.96
0.81
Threshold
(Mm'1)
NA
NA
Light
extinction
(Mm"1) on
May 12,
2003
associated
with natural
(episodic)
0
0
Light
extinction
(Mm'1)
on May
12, 2003
remaining
after
episodic
treatment
2.96
0.81
34
-------
CMC (2 1.78 Mm'1) +
LAC (3. 58 Mm'1)
Fine Soil (1.14 Mm'1) +
CM (1.56 Mm'1)
Sea salt
Rayleigh
TOTAL
25.36
2.70
0.00147
9
40.83
5.05
5.33
NA
NA
NA
20.31
0
0
0
20.31
5.05
2.70
0.00147
9
20.52
The IMPROVE light extinction data for one day (May 12, 2003) at MEVE1 are shown in Table
5.4. The light extinction from carbon (25.36 Mm"1) on this day is greater than the threshold of
5.05 Mm'1. Therefore, 25.36-5.05 or 20.31 Mm'1 is assigned to "natural (episodic)." Carbon light
extinction in the amount of 5.05 Mm"1 remains to be split between "natural (routine)" and
"anthropogenic." The dust-related light extinction of 2.70 Mm"1 is less than the threshold value
of 5.33 Mm"1, therefore no dust light extinction is assigned to "natural (episodic)." However, the
2.70 Mm"1 value for dust-related light extinction does need to be split between "natural
(routine)" and "anthropogenic" in Step D below, after the combined values of carbon and dust
are reallocated to OMC, LAC, Fine Soil and CM (Step C). A summary of the thresholds used
and the light extinction assigned to "natural (episodic)" is shown in Table 5.4.
Step C: Reallocate the combined carbon and dust light extinction remaining after assigning
values over the threshold values to "natural (episodic) " into OMC, LAC, FS and CM.
Separate the combined carbon and dust back into OMC, LAC, Fine Soil and CM based on the
original percentages of the individual PM species to the grouped light extinction. For example, at
MEVE1 on May 12, 2003, the total carbon light extinction was 25.36 Mm"1, with OMC light
extinction of 21.78 and LAC Mm'1 light extinction of 3.58 Mm'1. The total dust light extinction
was 2.70 Mm'1 with 1.14 Mm"1 from Fine Soil and 1.56 Mm"1 from CM. Therefore, on May 12,
2003, carbon light extinction was 85.9 percent from OMC and 14.1 percent from LAC; dust light
extinction was 42.2 percent from FS and 57.8 percent from CM. Separate the estimates of
"natural (episodic)" and the remaining light extinction back into OMC, LAC, FS and CM using
these percentages. Table 5.5 shows the results of these calculations for this example day at
MEVE1. For example, of the 20.31 Mm"1 of carbon assigned to natural ("episodic"), 17.45 Mm"1
(or 85.9 percent) is reallocated to OMC and 2.86 Mm"1 (14.1 percent) is reallocated to LAC.
Because there are no regulatory consequences to how carbon and dust are separated back into
OMC, LAC, Fine Soil and CM, states may use other approaches than the one recommended
here.
Table 5.5. Light extinction for an example day (May 12, 2003) in MEVE1 after
splitting into natural (episodic). Results of reallocating the carbon and dust into the
individual species are shown.
PM Species
OMC
Total Light
Extinction
(Mm"1)
21.78
Threshold
(Mm"1)
5.05
Light extinction (Mm"1) on
May 12, 2003 associated
with natural (episodic)
Grouped
20.31
Reallocated
17.45
Light extinction (Mm"1) on
May 12, 2003 remaining
after episodic treatment
Grouped
5.05
Reallocated
4.34
35
-------
(85.9% of
carbon)
LAC
(14.1% of
carbon)
FS
(42.2% of
dust)
CM
(57.8% of
dust)
3.58
1.14
1.56
5.33
0
2.86
0
0
2.70
0.712
1.14
1.56
Step D: Further split the remaining OMC, LAC, Fine Soil and CM light extinction into "natural
(routine) " and "anthropogenic" based in part on the NC-II estimates41.
Using the results from Step C for all days in a year, calculate the annual average light extinction
values for each PM species, excluding light extinction already attributed to episodic events. This
is the annual average corresponding to the right-most columns of Tables 5.4 and 5.5.
For all PM species except sea salt (which is treated as all "natural (routine)"), use the existing
NC-II annual average light extinction values to calculate a daily estimate of "natural (routine),"
along with the daily light extinction values and the annual averages for the site (both excluding
light extinction already attributed to episodic events).42 These values appear in Table 5.6 for the
MEVE1 example.
nhttp://vista. cira. colostate. edu/improve/Publications/GrayLit/gray_literature. htm;
http://vista.cira.colostate.edu/improve/Publications/GrayLit/032_NaturalCondIIpaper/Copeland_etal_NaturalCond
itionsII_Description.pdf
42 The EPA recognizes that use of the annual average NC-II estimates as a starting point for determining daily
estimates of "natural (routine) light extinction in the revised URP framework poses issues for at least some Class I
areas. One obvious issue, that observed average sea salt extinction at some Class I areas is higher than the NC-II
estimates of sea salt contributions to natural visibility conditions, has been addressed in our recommended approach
by treating all measured sea salt concentrations as natural. There also appear to be issues with the NC-II estimates of
naturally occurring OCM being too high at some eastern Class I areas. Because our approach to estimating natural
conditions on individual historical days makes use of the NC-II estimates (other than for sea salt) to help allocate
measured concentrations of PM species between natural and anthropogenic sources, these issues with the NC-II
estimates in some cases will affect the results of our recommended approach to calculating the single value of
"natural visibility conditions for the 20 percent most impaired days." However, we do not believe that these issues
rise to the level that would make our recommended approach inappropriate for use in SIP development. Also, a
state, or states and the EPA working together, may develop substitutes for the annual average values for particular
Class I areas (or all Class I areas) and re-execute the calculations.
36
-------
Table 5.6. The remaining light extinction at MEVE1 on May 12, 2003, after
applying thresholds to allocate some light extinction to natural ("episodic"). The
NC-II average light extinction estimates and the 2003 annual average light
extinction excluding the episodic light extinction are also shown.
PM Species
Sulfate
Nitrate
CMC
LAC
Soil
CM
Sea salt
Rayleigh
Light extinction on
May 12, 2003
remaining after
episodic treatment
(Mm'1)
2.96
0.81
4.34
0.712
1.14
1.56
0.00147
9
NC-II average
natural light
extinction
estimates (Mm'1)
0.57
0.58
1.83
0.2
0.50
1.73
NA
9
2003 Annual
average light
extinction
(excluding
episodic events)
(Mm'1)
4.12
1.60
3.19
0.86
0.88
2.35
0.028
9
The remainder of Step D depends on whether, for a given PM species, the annual average light
extinction value (excluding episodic events) for the particular year is greater than or less than the
NC-II estimate of annual average natural light extinction.
For sites and PM species with annual average light extinction values (excluding episodic events)
greater than the NC-II estimates, such as the example MEVE1 day illustrated here:
The daily estimates of "natural (routine)" light extinction are assumed to vary throughout the
year because there are natural seasonal variations in light extinction, but when averaged, the
daily contributions equal the NC-II annual average value. The daily contributions to "natural
(routine)" are calculated according to Equation 5.2:
natural (routine} =
daily extinction*NCII estimate
annual average excluding episodes
(Eqn 5.2)
An example for the carbon (LAC + OMC) light extinction on May 12, 2003 at MEVE1, using
extinction values shown in Table 5.6, is shown below.
, , . , 4.34*1.83 „,.,-.•,, i
natural(routine)carbon = —r~.— = 2.49 Mm'1
3.19
Repeat this calculation for dust, sulfate and nitrate light extinction (not shown here).
37
-------
For sites and PM species with annual average light extinction values (excluding episodic events)
less than the NC-II estimates:
Assign all of the daily light extinction associated with carbon or dust, after the threshold
treatment for extreme events, to "natural (routine)."43
Step E: Consider the remaining light extinction from sulfate, nitrate, carbon and dust
"anthropogenic."
Starting with the total light extinction measured on each day, subtract the "natural (episodic)"
and "natural (routine)" to find the natural and anthropogenic light extinction attributable to each
PM species and overall, i.e., the light extinction budgets.44 Results for each of the three budgets
and the total light extinction are shown in Table 5.7.
Table 5.7. The light extinction budgets at MEVE1 on May 12, 2003, after splitting
the light extinction into natural ("episodic"), natural ("routine") and anthropogenic.
PM
Species
Sulfate
Nitrate
CMC
LAC
Soil
CM
Sea salt
Rayleigh
TOTAL
Total
extinction on
May 12, 2003
atMEVEl
(Mm'1)
2.96
0.81
21.78
3.58
1.14
1.56
0.00147
9
40.83
Light extinction
on May 12, 2003
associated with
natural
(episodic)
(Mm'1)
NA
NA
17.45
2.86
0
0
0
NA
20.31
Light extinction
on May 12, 2003
associated with
natural (routine)
(Mm'1)
0.41
0.29
2.49
0.165
0.649
1.14
0.00147
9
14.15
Light extinction
on May 12,2003
associated with
anthropogenic
(Mm'1)
2.55
0.52
1.84
0.555
0.491
0.42
0
0
6.37
43 The EPA recognizes that situations in which all of the daily extinction associated with carbon or dust, after the
threshold treatment for extreme events, is assigned to "natural (routine)" may indicate that the NC-II estimate of
annual average light extinction due to natural sources is too high. We believe these overestimates, if present, are not
frequent or severe enough to make the recommended approach problematic for SIP development. Nevertheless, we
support the development of revised natural estimates that more accurately reflect natural contributions. As indicated
in section 5.10, states continue to maintain the flexibility to develop and apply other values for natural light
extinction.
44 The anthropogenic light extinction budget may be useful to states when determining screening approaches (see
section 6.3).
38
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5.6. How does the EPA recommend selecting the 20 percent most impaired days?
Regional Haze Rule provisions
51.301 Definitions:
Most impaired days means the twenty percent of monitored days in a calendar year with
the highest amounts of visibility impairment.
Visibility impairment means any humanly perceptible difference between actual visibility
conditions and natural visibility conditions. Because natural visibility conditions can only
be estimated or inferred, visibility impairment also is estimated or inferred rather than
directly measured.
The 20 percent most impaired days should be selected as follows:
Step F: Calculate anthropogenic impairment for each day using the daily estimates of natural
and anthropogenic light extinction, according to Eqn 5.1.
For each day at the Class I area of interest, calculate anthropogenic impairment according to Eqn
5.1. AtMEVEl, for May 12, 2003, the anthropogenic impairment is calculated as:
^-^anthropogenic impairment "-^total "-^natural
* „ , 40.83 . _ , 34.46 1 „_ ,
= 10*/n 10* In = 1.70dv
10 10
Step G: Sort the days by the anthropogenic impairment and choose the 20 percent most impaired
days based on this value.
Perform these calculations for each day at the Class I area of interest, then rank the days within
each year from high to low by anthropogenic impairment where a rank of 1 is the most impaired
day. At MEVE1, this day, May 12, 2003, with an anthropogenic impairment value of 1.70
deciview, is a relatively low impairment day and was ranked 99 out of 105 total days with
complete observations. Therefore, based on anthropogenic impairment, this day is not one of the
20 percent most impaired days for 2003.45 In contrast, if ranking this day based on either total
light extinction or overall visibility conditions (the ranking would be the same with these two
metrics), as the EPA's guidance for the first implementation period recommended, this day
would be ranked 14 out of 105 days with complete observations, and would be one of the 20
percent of days with the worst overall visibility conditions. These rankings are summarized in
Table 5.8.
45 See TSD for more details and equations governing the number of days to be included in quintiles when the
number of complete observations are not evenly divisible by 5. For example, if there are 111-115 days with
complete IMPROVE observations, 23 days are averaged to get the 20 percent most impaired (and 22 days are
averaged to get the 20 percent clearest).
39
-------
Table 5.8. Summary of the ranking of May 12, 2003 at MEVE1 using anthropogenic
impairment and total deciviews.
Day
May 12,
2003
QVanthropogenic
impairment
1.70 deciview
QVanthropogenic impairment
Rank, from high to low,
out of 105 days
99
dvtotal
14.1
deciview
dvtotal rank, from high
to low, out of 105
days
14
Average the deciviews of haze on the 20 percent most impaired days for each year to obtain a
single value for the visibility impairment for each year (for MEVE1 in 2003, which had 105
complete observations, 21 days will be in the 20 percent most impaired).
States may choose alternative approaches for estimating natural and anthropogenic contributions
to light extinction, as stated in Section 5.3, but the Regional Haze Rule requires states to choose
the 20 percent most impaired days based on anthropogenic impairment.46 In other words, while
Steps A through F described above are EPA recommendations and states are not precluded from
using other approaches to determine the anthropogenic impairment on each day, the Regional
Haze Rule requires states to follow Step G as described.
5.7. How do the 2016 Regional Haze Rule revisions require states to select the 20 percent
clearest days?
Regional Haze Rule provisions
51.301 Definitions:
Clearest days means the twenty percent of monitored days in a calendar year with the
lowest values of the deciview index.
The 2016 Regional Haze Rule revisions require states to select the 20 percent clearest days for
each year continue as the 20 percent of days with the lowest total light extinction. These will also
be the days with the lowest values of the deciview index. It is unnecessary to split the data into
"natural" and "anthropogenic" fractions. Sort the days of each year by total deciviews, and the
20 percent of days with the lowest deciviews are the 20 percent clearest days.47
We expect that the 20 percent clearest days (selection of which is based on visibility as affected
by all types of sources) will not include any days with notable effects from wildland wildfires.
Thus, we expect that wildland wildfires will not affect a state's ability to demonstrate that there
46 Actually, the EPA has proposed in the alternative in the recent rule revisions NPRM to either require states to use
a new approach for choosing the 20 percent most impaired visibility days or to allow each state to choose between
the original (20 percent "worst" visibility days) and the new approach. For simplicity, this draft has been written as
if all states are required to use the new approach. When finalized, the guidance will be written to be consistent with
the final rule revisions.
47 If instead the 20 percent of days with the lowest levels of anthropogenic impairment were selected, some days
with very poor visibility due to natural sources such as wildfires might be included because with very high light
extinction due to natural sources anthropogenic impairment calculated with Equation 5.1 will be low even if there is
substantial light extinction due to anthropogenic sources. The EPA believes it better serves the purpose of tracking
progress if the "20 percent best" set of days excludes such poor visibility days.
40
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will be no deterioration in visibility on the 20 percent clearest days, which is a requirement for
SIP approval.
5.8. How are current visibility conditions determined?
Regional Haze Rule provisions
51.308(f)(l) Calculations of baseline, current, and natural visibility conditions; progress
to date; and the uniform rate of progress. For each mandatory Class I Federal area located
within the State, the State must determine the following:
(iii) Current visibility conditions for the most impaired and clearest days. The period for
calculating current visibility conditions is the most recent 5-year period for which data
are available. Current visibility conditions must be calculated based on the annual
average level of visibility impairment for the most impaired and clearest days for each of
these 5 years. Current visibility conditions are the average of these annual values.
The revised Regional Haze Rule defines the period for calculating current visibility conditions as
the most recent 5-year period for which data are available.48 Due to the laboratory, data analysis,
and quality assurance procedures of the IMPROVE program, there is some delay between the
date of the filter collection and the date the data are ready for use in analyses. Current visibility
conditions must be calculated based on the annual average level of visibility impairment for the
most impaired (see more information on selecting the days in sections 5.5 and 5.6) and clearest
days (section 5.7). Current visibility conditions are the average of the five most recent annual
values available. Five years are averaged to account for variability in meteorology and
emissions. Current visibility conditions should be expressed in deciviews.
5.9. How are baseline visibility conditions determined?
Regional Haze Rule provisions
51.308(f)(l) Calculations of baseline, current, and natural visibility conditions; progress
to date; and the uniform rate of progress. For each mandatory Class I Federal area located
within the State, the State must determine the following:
(i) Baseline visibility conditions for the most impaired and clearest days. The period for
establishing baseline visibility conditions is 2000 to 2004. For purposes of calculating
and displaying the uniform rate of progress needed to attain natural visibility conditions
by the end of 2064, baseline visibility conditions must be associated with the last day of
this period. Baseline visibility conditions must be calculated, using available monitoring
data, by establishing the average deciview index for the most impaired and clearest days
for each calendar year from 2000 to 2004. The baseline visibility conditions are the
average of these annual values. For mandatory Class I Federal areas without onsite
monitoring data for 2000-2004, the State must establish baseline values using the most
48 The revised Regional Haze Rule does not specify the point in the development of a SIP at which this data
availability is to be determined. The EPA expects that the appropriate point may vary from state to state, depending
on the expected interval needed between retrieving the data for purposes of SIP development and submitting the
SIP, given a state's technical and administrative procedures.
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representative available monitoring data for 2000-2004, in consultation with the
Administrator or his or her designee. For mandatory Class I Federal areas with
incomplete data availability for 2000-2004, the State must establish baseline values using
the closest 5 complete years of monitoring data.
The period for establishing baseline visibility conditions remains 2000 to 2004 in the second and
future implementation periods.49 Visibility conditions in these 5 baseline years are the starting
point for calculating the URP and drawing the URP line for all implementation periods of the
Regional Haze Rule. The annual average visibility on the 20 percent most impaired days and 20
percent clearest days in each of the 5 years from 2000 to 2004 are averaged to obtain baseline
visibility conditions for the 20 percent most impaired days and 20 percent clearest days. The
EPA's recommendations for selecting the 20 percent most impaired days based on the days with
the highest anthropogenic impairment are given in sections 5.5 and 5.6. Guidance for selecting
the 20 percent clearest days is given in section 5.7. The EPA recommends using these
approaches for selecting the 20 percent most impaired and the 20 percent clearest days to
establish baseline visibility conditions.
Because of the 2016 revisions to the Regional Haze Rule, the term "most impaired days" has a
different meaning than EPA and states gave to that term in the first implementation period. The
"baseline visibility condition (in deciviews) for the 20 percent most impaired days" in a state's
SIP submission for the second implementation period will likely have a different value than the
baseline values used in SIPs for the first implementation period, even if there have been no
revisions to the IMPROVE data for the 2000-2004 period. The differences will be largest at
Class I areas impacted by fire and dust events in the baseline period.
5.10. What natural visibility conditions estimates does the EPA recommend for use in the
impairment-based approach for selecting the 20 percent most impaired days?
Regional Haze Rule provisions
51.308(f)(l) Calculations of baseline, current, and natural visibility conditions; progress
to date; and the uniform rate of progress. For each mandatory Class I Federal area located
within the State, the State must determine the following:
(ii) Natural visibility conditions for the most impaired and clearest days. Natural visibility
conditions must be calculated by estimating the deciview index existing under natural
conditions for the most impaired and clearest days, based on available monitoring
information and appropriate data analysis techniques;
49 IMPROVE data from the 2000-2004 period may be revised after initially reported because of more recently
revised methods for calculating ambient concentrations from measurements made on filters and because of revised
methods for filling in missing or invalidated data. Such revisions are "backcasted" in order to maintain consistency
in reported results across the years. Therefore, baseline visibility conditions should be recalculated for use in the
second and subsequent implementation periods.
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Overview of the recommended new approach to the natural visibility conditions estimate for the
most impaired days
The URP framework requires states to determine a value for "natural visibility conditions" for
the 20 percent most impaired days as the 2064 end point of the URP line (or glidepath) for each
Class I area. Given the inherent day-to-day variability of natural processes (e.g., windblown dust,
fire, volcanic activity, biogenic emissions, etc.), it follows that natural visibility conditions are
not constant and may vary day-to-day. Also, natural visibility conditions on days in the past were
not directly measured and therefore must be estimated. The steps for estimating natural and
anthropogenic fractions of light extinction recommended in this guidance result in estimates of
natural visibility conditions for each monitored day in the past, with a given past day having the
potential for both routine and episodic contributions to natural conditions. The selection of the
most appropriate single value to be used for "natural conditions on the 20 percent most impaired
days" as the 2064 end point of the URP line is a separate question from estimating natural
conditions for days in the past as part of determining which days are the 20 percent most
impaired, but related.
Under the Regional Haze Rule, the single value of natural visibility conditions for the 20 percent
most impaired days is to be used in several ways:
1. The value of natural visibility conditions is to be compared to "current conditions,"
i.e., the most recent 5-year average of actual visibility for the 20 percent most
impaired days.
2. The URP is calculated as the difference between 2000-2004 baseline visibility
conditions and natural conditions for the 20 percent most impaired days, divided by
60 years. In other words, the "glidepath" ends at natural conditions in 2064.
3. The 2028 RPG for the 20 percent most impaired days is compared to the 2028 point
on the URP line, which uses the value of natural visibility conditions as its endpoint.
This comparison determines an important aspect of the analysis required to support an
approvable SIP revision, as described in section 10.
The third of these uses of the value for natural visibility conditions has implications for the
analysis needed to support an approvable SIP revision. It is therefore important to maintain
consistency when selecting the 20 percent most impaired days for estimating the value of
"baseline conditions" for the 20 percent most impaired days (which is the starting point for the
URP line) and the value of "current conditions" for the 20 percent most impaired days, and the
approach for selecting the value of "natural visibility conditions" for the 20 percent most
impaired days.50 In particular, since the value for "current conditions" generally will not reflect
conditions on days with very high, episodic natural impairment (because such days generally will
not be among the days of highest anthropogenic impairment), the single value of "natural
visibility conditions" should also not include the influence of high natural emissions from
episodic events such as large wildfires and dust storms, even though these events may be natural.
In addition, there may be seasonal or other temporal patterns affecting the level of non-episodic
50 Current visibility conditions should be consistent because the 2028 RPGs will be forecasts that begin with the
value of current conditions for whatever recent period is used as the base year for air quality modeling of the RPGs.
This consistency is also important to avoid public misunderstanding of how close a SIP comes to providing progress
equal to the URP.
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natural conditions, and inconsistencies due to different samplings of these patterns would also be
problematic. Therefore, natural visibility conditions estimates should be developed for the set of
days that have levels of influence from natural sources that are consistent with the types of days
that are selected as the 20 percent most impaired days for purposes of estimating "current
conditions" (as selected using the impairment-based approach described in sections 5.5 and 5.6).
Because the "p90" NC-II Natural Haze estimate for a given Class I area was based on the 20
percent of days that have the worst overall visibility rather than the days with the worst
impairment, it is not suitable for direct use as the "natural visibility condition for the 20 percent
most impaired days" under the impairment-based approach. Instead, it is appropriate to use the
average of the new estimates of natural visibility conditions estimated for the particular days that
have been identified as the 20 percent most impaired days in past years.51
Specifics of the method used to develop the recommended values for the natural visibility
condition for the 20 percent most impaired days
The EPA has produced revised natural visibility conditions estimates for the 20 percent most
impaired days52 that are more consistent with using anthropogenic impairment to select the most
impaired days and that also consider all measured sea salt concentrations and extinction to be
natural.53 The method the EPA has used to do this takes advantage of the daily "natural
(episodic)" and "natural (routine)" estimates produced in steps A through C (section 5.5). For
each IMPROVE monitor, we averaged the daily natural (the sum of "episodic" and "routine")
light extinction estimates on the 20 percent most impaired days in each year from 2000 to 2014
to determine new estimates of natural visibility conditions. The light extinction values in
deciviews are used as the new natural visibility conditions estimates. These revised natural
visibility conditions are generally lower in magnitude than the "p90" NC-II haze estimates
(representing the average conditions for days between the 80th percentile and the 100th percentile)
and higher in magnitude than the annual average NC-II haze estimates. More details about the
methodology for producing these estimates and the estimates themselves can be found in the
companion TSD to this guidance document.
Relationship between the recommended approach and prior estimates and rationale for the
recommended approach
For the first implementation period SIPs, most states used the NC-II Natural Haze estimates
developed by the Natural Haze Levels II Committee in 2007 as their natural visibility conditions.
The NC-II estimates were improvements to the recommendations the EPA provided in the 2003
51 For some Class I areas, the natural visibility condition estimate for the 20 percent most impaired days may be less
than the baseline visibility condition value for the 20 percent clearest days. This is due to several factors, such as the
inclusion of anthropogenic impacts in the 20 percent clearest day value but not in the natural visibility value. As a
result, the 2064 URP line endpoint for the 20 most impaired days and the 20 percent clearest days are not directly
comparable. It should also be noted that even though the Regional Haze Rule only requires no degradation in
visibility for the 20 percent clearest days, we expect visibility to improve on these days as a result of the LTS
measures developed to address the 20 percent most impaired days.
52 These revised estimates are included in Appendix E of the TSD.
53 While some northern urban and suburban areas may experience relatively high ambient air salt concentrations
attributable to the salting of roads, this is not expected to be an issue in Class I areas.
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Natural Visibility Conditions Guidance,54 and the revised NC-II estimates attempted to account
for the variability in natural visibility conditions that existed in the baseline (2000-2004) period.
It is generally recognized that the "p90" NC-II estimates do not fully reflect the effects of
extreme episodic natural events at all Class I areas.55 This has been frequently cited as a problem
in the context of the URP framework based on the 20 percent of days with the worst overall
visibility that was used in the first implementation period, because it caused an inconsistency
between "current conditions" (which reflected any such extreme episodic natural influences) and
the 2064 endpoint of the URP line that was set equal to the "p90" NC-II value. However, as
explained above, with the new impairment-based URP framework, it is not intended or
appropriate for the 2064 "natural visibility conditions" value to include impacts from such
extreme episodic natural events. When selecting the 20 percent most impaired days based on
anthropogenic impairment, days with large impacts from extreme, episodic natural events such
as fires and dust storms are no longer selected. Therefore, these extreme impacts should also not
be included in estimates of natural visibility conditions that will be compared with the most
impaired days. This addresses past concerns that the NC-II estimates fail to include effects from
large episodic natural events because it will no longer be appropriate to include the days on
which these events occur among the most impaired days.
In addition to avoiding selecting historical days dominated by extreme natural events when
calculating the single value of natural visibility conditions that will be used in calculating the
URP (or, in other terms, used as the 2064 endpoint of the URP line or glidepath), it is important
to recognize that there are differences among the days that did not have extreme natural events.
The natural visibility conditions value that will be used in calculating the URP should be based
on the 20 percent most impaired historical days, rather than all the days without extreme events
or the 20 percent haziest days. Otherwise, an error could occur in the value of the URP. The
routine and episodic natural processes that form some PM species are expected to vary by
season, and the 20 percent most impaired days may be distributed across seasons of the year in a
particular way that differs from all non-extreme days and days with the worst haze.
Wildland wildfires and natural visibility conditions
Because wildland wildfires are natural events, emissions from wildland wildfires do not
contribute to "visibility impairment" given that this term refers only to reductions in visibility
attributable to anthropogenic sources. Under the new required approach of basing RPGs on the
20 percent most impaired days and our recommendations on how to estimate daily natural and
anthropogenic light extinction,56 we expect that days with large impacts from wildland wildfires
will not be included in the 20 percent most impaired days in each year, and we expect that
wildland wildfires will not significantly affect the estimate of "natural visibility conditions for
54 Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule. Available at:
https:'//www3. epa.gov/ttnamtil/files/ambient/visible/natural.pdf.
55 Tombach, I. 2008. Natural Haze Levels Sensitivity, Assessment of Refinements of Estimates of Natural
Conditions. Prepared for the Western Governors Association. Available online at
http://www.wrapair. org/forums/aamrf/projects/NCS/Haze_Sensitivity_Report-Final.pdf&nA see TSD, section 2.1.1.
56 Note to reviewers of this draft guidance document: For clarity for purposes of comment and for ease in
finalization, this draft version of this guidance document is written as if the revisions proposed in May 2016 have
been finalized as proposed. If the final revisions to the Regional Haze Rule differ from this assumption,
corresponding changes will be made in the final guidance document.
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the 20 percent most impaired days." Thus, we expect that wildland wildfires with notable effects
on visibility will not be a reason why a projected RPG for the 20 percent most impaired days
would be above the URP line, simply because the URP line will be about visibility on days that
have not been significantly affected by emissions from fires.
We also expect that wildland wildfires will not affect the value of "natural conditions on the 20
percent clearest days."
States may use alternative approaches with justification
States may use the revised natural visibility estimates contained in Appendix E of the TSD
accompanying this guidance, or may choose to use alternative estimates with justification
supporting that the alternative, refined approach is technically sound and provides regionally
representative estimates of natural visibility conditions for the most impaired days. More
guidance on developing alternatives is given in section 3 of the existing 2003 Natural Visibility
Conditions Guidance. Appendix E of this document explains what portions of the 2003
document continue to be applicable.
5.11. What natural visibility conditions estimates does the EPA recommend for the 20
percent clearest days?
Regional Haze Rule provisions
51.308(f)(l) Calculations of baseline, current, and natural visibility conditions; progress
to date; and the uniform rate of progress. For each mandatory Class I Federal area located
within the State, the State must determine the following:
(ii) Natural visibility conditions for the most impaired and clearest days. Natural visibility
conditions must be calculated by estimating the deciview index existing under natural
conditions for the most impaired and clearest days, based on available monitoring
information and appropriate data analysis techniques;
The Regional Haze Rule requires the establishment of RPGs which provide for an improvement
in visibility for the most impaired days over the period of the implementation plan and ensure no
degradation in visibility for the clearest days over the same period. Consequently, for the clearest
days, no URP line or glidepath is drawn, but the rule does require states to compare current
visibility conditions with natural visibility conditions for the clearest days. 40 CFR
51.308(f)(l)(i-vi). For this comparison, the EPA continues to recommend the use of the NC-II
("plO") estimates for the 20 percent clearest days. States may use alternative natural visibility
estimates for the clearest days if justified. This comparison is only for public information and
transparency purposes. There are no regulatory requirements or consequences that depend on the
values selected for natural visibility conditions on the 20 percent clearest days.
5.12. What are the associated values, equations and completeness criteria used in the
calculations of visibility impairment on the most impaired and clearest days?
For purposes of the Regional Haze Rule, light extinction is estimated from measurements of PM
and its chemical species, assumptions about relative humidity at the monitoring site, and the use
of a commonly accepted algorithm. This subsection contains details about the algorithm, relative
humidity (RH) values and data completeness criteria.
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The EPA recommends the use of the revised IMPROVE algorithm57 for estimating light
extinction from IMPROVE speciation measurements (shown below). Many states used this
algorithm in their SIPs covering the first implementation period. The revised IMPROVE
algorithm for calculating light extinction (bext) is:
bm = 2.2 x f^RH) x [Small Siiiftitc]
+ 4.8 x fi(RH) x {Large Sulfate}
+ 2.4 x fr(RH) x [Small Nitrtitc]
+ 5.1 x fi(RH) x [Large Nitrate]
+ 2.8 x \Sintitl Organic Mass]
+ 6.1 x [Large Organic Mass}
+ 10 x [Elemental Carbon] - I x [Fine Soil]
+ 1.7 x f«(RH) x [S«f Sdlf]
+ 0.6 x [awr«' Ata«]
+ Rayleigh Scattering (Site Specific)
+ 0.33 x [NO2 (ppb)]
This algorithm includes separate estimates of light extinction (in Mm"1) from small and large size
modes of sulfate, nitrate and organic mass to better represent light extinction at low and high
particulate matter concentrations. The fraction of particles estimated to be in the large size mode
is estimated to increase as the concentration of the PM species increases and plateaus at a
concentration of 20 jig/m3 at which point all particles are treated as large size particles.58 The
algorithm also uses size-fraction specific f(RH) values for sulfate and nitrate to account for the
dependence of light extinction on relative humidity for these species as detailed in Pitchford et
al. (2007). We recommend the continued usage of the monthly, site-specific f(RH) values for
subsequent implementation periods.59 However, states may update these values as appropriate
and with justification.
Data completeness recommendations as outlined in the 2003 tracking progress guidance60 remain
the recommended criteria:
In order for a year of data from a site to be used to track progress in improving visibility,
all four quarters of that year should be at least 50% complete, and overall, the year should
57 Pitchford, M; Malm, W.; Schichtel, B.; Kumar, N.; Lowenthal, D.; Hand, J. Revised algorithm for estimating
light extinction from IMPROVE particle speciation data; J. Air & Waste Manage. Assoc. 2007, 57, 1326-1336; doi:
3155/1047-3289.57.11.1326.
58 The algorithm estimates the fraction of large size particles by dividing the total concentration of a species (i.e.,
sulfate, nitrate, or organic carbon) by 20, then the remaining mass is in the small size fraction. For example, if a
sulfate concentration is 8 ug/m3, then 8/20, or 2/5, of the mass is in the large size fraction (3.2 ug/m3) and the
remainder (4.8 ug/m3) is in the small size fraction. If the total concentration of a species is higher than 20 ug/m3,
then all of the species is assumed to be in the large size fraction. More details are given in Pitchford et al. (2007) and
references therein.
59 These f(RH) values are included in past and current data summary files provided by IMPROVE data managers
(http://vista, cira. colostate. edu/datawareHouse/IMPRO VE/Data/SummaryData/RHR_2014/).
60 Guidance for Tracking Progress Under the Regional Haze Rule, September 2003,
http://www3.epa.gov/ttnamtil/files/ambient/visible/tracking.pdf.
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be 75% complete. That is, complete data (including that filled in by substitution of
averages), should be available for at least 50% of the sampling days in each quarter of the
year and for 75% of all scheduled sampling days for the year. In addition, there should be
no more than 10 missing sampling days in a row at any time during the calendar year.
Given the every third day of sampling, this requirement means that a site should not be
out of operation for any period of more than one consecutive month during the calendar
year.
Annual data sets meeting these completeness criteria should be used in subsequent steps
to calculate five-year average visibility results for tracking progress. Every attempt
should be made to get five years of complete data within each five-year period. However,
if maximum data recovery is not achieved, the EPA believes that a minimum of 3 years
of data meeting these completeness requirements is sufficient to calculate the five-year
averages within each five-year period.
If 3 years with complete data are not available, estimates for baseline or current conditions
should be prepared in coordination with the EPA and the IMPROVE program.
5.13. Should each state perform these calculations for its Class I areas?
The EPA will work with the IMPROVE program to offer datasets containing the 20 percent most
impaired days, selected based on anthropogenic impairment, and the 20 percent clearest days for
use by states. These data files will contain the 20 percent most impaired days and the estimates
of natural and anthropogenic contributions to light extinction by species. The 20 percent clearest
days will also be included in these data files. We also expect that these data files will include
natural and anthropogenic extinction budgets for each day, as shown in the example in Table 5.6
in section 5.5. These files are expected to be available at
http:'//vista, cira. colostate. edu/improve/Data/IMPRO VE/summary data, htm.
The companion TSD to this guidance document contains much of this same information for each
Class I area through 2014. Additionally, corresponding data files were included in the docket for
this draft guidance document and are still available.61
5.14. Can states use another strategy for choosing the 20 percent most impaired days?
While Steps A through F described above are the EPA recommendations for estimating the
anthropogenic impairment for each day before determining the 20 percent most impaired days,
states are not precluded from using other reasonable approaches.62 Whatever algorithm states use
to estimate daily anthropogenic impairment as a step in calculating the 20 percent most impaired
days, the same algorithm should be used consistently across the URP framework (i.e., states
61 See Technical Support Document (TSD) Revised Recommendations for Visibility Progress Tracking Metrics for
the Regional Haze Program, in Docket EPA-HQ-OAR-2016-0289 at www.regulations.gov.
62 Note to reviewers of this draft guidance document: For clarity for purposes of comment and for ease in
finalization, this draft version of this guidance document is written as if the revisions proposed in May 2016 have
been finalized as proposed. If the final revisions to the Regional Haze Rule differ from this assumption,
corresponding changes will be made in the final guidance document.
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should use the same approach to determine baseline visibility conditions and current visibility
conditions for the 20 percent most impaired days).
5.15. Can states continue to use the first-implementation period approach for selecting
the haziest days as the most impaired days?
States may choose to include the first-implementation period approach that uses the haziest days
as the most impaired days in addition to the new approach, but not instead of the new
approach.63 Consistent with the revised Regional Haze Rule, the EPA will evaluate a state's RPG
and URP determinations based on the anthropogenic impairment approach. If states choose to
also include the results of a "worst visibility days" approach for selecting the most impaired days
for informational purposes, then such states will also have the choice of whether or not to project
a second, supplemental RPG for the most impaired days based on the approach of using the 20
percent of days with the highest levels of overall haze. Such states will also have the choice of
whether and how to treat the additional RPG in the subsequent progress report. For example, a
state may choose to project the additional RPG for the 20 percent of days with the highest levels
of overall haze, but include it in the SIP only for informational purposes (i.e., it would not be
used in the 2025 progress report for purposes of determining whether the SIP is adequate to
achieve the RPGs in the SIP).
5.16. Calculation of actual progress and difference between current and natural visibility
conditions
Regional Haze Rule provisions
51.308(f)(l) Calculations of baseline, current, and natural visibility conditions; progress
to date; and the uniform rate of progress. For each mandatory Class I Federal area located
within the State, the State must determine the following:
(iv) Progress to date for the most impaired and clearest days. Actual progress made
towards natural conditions since the baseline period, and actual progress made during the
previous implementation period up to and including to the period for calculating current
visibility conditions, for the most impaired and clearest days, must be calculated, (v)
Difference between current visibility conditions and natural visibility conditions. The
number of deciviews by which current visibility conditions exceed natural visibility
conditions, for the most impaired and clearest days, must be calculated.
Actual progress made on the most impaired and clearest days toward natural visibility
conditions since the baseline period
For SIPs for the second implementation period, the actual progress made on the most impaired
days is calculated as the difference between the 5-year average of annual visibility conditions for
the 20 percent most impaired days in 2000-2004 and the 5-year average of annual visibility
conditions on these days for the most recent 5-year period of available data. The same applies for
63 Note to reviewers of this draft guidance document: The EPA has proposed in the alternative in the recent rule
revisions NPRM to either require states to use a new approach for choosing the 20 percent most impaired visibility
days or to allow each state to choose between the original (20 percent "worst" visibility days) and the new approach.
For simplicity, this draft has been written as if all states are required to use the new approach. When finalized, the
guidance will be written to be consistent with the final rule revisions.
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actual progress on the clearest days. See section 5.8 for discussion of the most recent period of
available data.
Actual progress made on the most impaired and clearest days toward natural visibility
conditions in the previous implementation period
For SIPs for the second implementation period, these parameters should be determined by taking
the difference between the referenced visibility conditions for 2000-2004 (the start of the
previous implementation period) and either (1) 2014-2018 (the end of the previous
implementation period) or (2) the most recent period of available data if this period does not
include 2018 as of the time the state prepares this part of its SIP.
5.17. How is the URP calculated and the URP line (or glidepath) drawn for each Class I
area?
Regional Haze Rule provisions
51.308(f)(l) Calculations of baseline, current, and natural visibility conditions; progress
to date; and the uniform rate of progress. For each mandatory Class I Federal area located
within the State, the State must determine the following:
(vi) Uniform rate of progress. (A) The uniform rate of progress needed to attain natural
visibility conditions by the end of 2064 for each mandatory Class I Federal area in the
State must be calculated. To calculate this uniform rate of progress, the State must
compare baseline visibility conditions to natural visibility conditions in the mandatory
Class I Federal area and determine the uniform rate of visibility improvement (measured
in deciviews of improvement per year) that would need to be maintained during each
implementation period in order to attain natural visibility conditions by the end of 2064.
States must analyze and determine the URP needed to attain natural visibility conditions by the
year 2064. The URP has units of deciviews per year or deciviews per decade. This rate of
progress is commonly called the URP line or glidepath between the baseline conditions and
2064. The URP line has a slope equal to the URP. It is part of the analytic framework for the
development of the LTS to achieve reasonable progress towards the goal of natural visibility
conditions. See section 4.6.
The URP is calculated and the URP line is drawn for the most impaired days only. While states
may estimate impairment for each day using an approach other than that recommended in this
guidance, the revised Regional Haze Rule requires states to then select the 20 percent most
impaired days. Additionally, the revised Regional Haze Rule clarified that the URP begins with
the baseline period of 2000-2004 for all implementation periods. More specifically, the URP line
is drawn starting from the value of 2000-2004 visibility conditions, with that value assumed to be
associated with the specific date of December 31, 2004, and extends downward to reach the
value of natural visibility conditions, with that value assumed to be associated with
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December 31, 2064. For purposes of comparison to the URP line, the RPG is assumed to be
associated with December 31 of the last year of an implementation period.64
It is possible that the IMPROVE program has revised some of its data from 2000-2004
subsequent to a state having submitted its first implementation period SIP; therefore, a state
should recalculate the value of the 2000-2004 baseline visibility condition (or use an updated
value provided by the EPA or the IMPROVE program) to ensure a consistent starting point for
development of the URP, even apart from the change from focusing on the 20 percent haziest
days to focusing on the 20 percent most impaired days. See section 5.9.
5.18. What are the results and implications of using the recommended methods to select
the most impaired days?
The EPA has executed the recommended methods for every Class I area using IMPROVE data
from 2000 to 2014 and has compared the results to the results using the approach nearly all states
followed in the first implementation period. The companion TSD to this guidance document
contains these detailed results for each Class I area, so results for only four example Class I areas
will be presented here, along with maps showing results nationwide. Figure 5.3 shows results
nationwide based on using the 20 percent worst visibility days; Figure 5.4 shows similar results
but using the 20 percent most impaired days. The maps are colored by the deciview difference
between the 2010-2014 5-year average and the URP in 2014; blue colors indicate Class I areas
below the URP (which is differently determined in the two approaches).
For the Mesa Verde National Park Class I area, for example, the high deciview values in 2003
shown in Figure 5.3 were likely the result of the influence of wildfire. We used the new
recommended approach to selecting the most impaired days shown in Figure 5.4. As a
comparison of Figures 5.3 and 5.4 demonstrates, the level of visibility impairment in 2003 (and
other years) on the 20 percent most impaired days is substantially less than for the twenty percent
worst visibility days. In both cases, however, the most recent 5-year average of visibility
conditions is below the URP line (by approximately 0.55 deciview when using the most impaired
days and by approximately 1.3 deciview when using the worst visibility days). The largest
percentage differences for other Class I areas (not displayed here but available in the TSD) occur
in the intermountain west and in many cases also are the result of the influence of wildfire. More
areas in the intermountain west are found to be "on or below the glidepath" as of 2010-2014 with
the new recommended approach than with the approach used in the first implementation period.
Differences for Class I areas in the eastern U.S., which is less subject to large wildfires, are
minor in comparison and do not change the fact that these areas are "below the glidepath."
64 The EPA's guidance for the first implementation period was not as explicit about associating the baseline
visibility conditions, natural visibility conditions and the RPG with any particular date. The specifics given in this
explanation were incorporated into the Regional Haze Rule as part of the 2016 revisions.
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Figure 5.3. National map of differences between 2010-2014 5-year averages and the
URP in 2014 based on the 20 percent worst visibility days (the approach used in the
first implementation period). Blue colors indicate sites with recent visibility data
below the URP.
Sawtooth
2COO 2002 200* 2005 2008 2010 2012 2014
Mesa Verde
deciview deviati.
••r
2,0 15
Guadafupe Mtns.
Shenandoah
2000 2002 2004 2006 2008 2010 2012 2014 2000 2002 2004 2006 2008 2010 2012 2014 20QO 2002 2004 2QQ.6 2QQ8 2010 2912 2014
Figure 5.4. National map of differences between 2010-2014 5-year averages and the
URP in 2014 based on the 20 percent most impaired days (the recommended
approach for the second implementation period). Blue colors indicate sites with
recent visibility data below the URP.
Sawtooth
Mesa Verde
Guadalupe Mtns.
Shenandoah
A A
2000 2002 2004 2006 2008 2010 2012 2014 2000 2002 2004 2006 2008 2010 2012 2014 2000 2002 2004 2006 2008 2010 2012 2014
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5.19. How can states account for international impacts in the URP framework?
Regional Haze Rule provisions
51.308(f)(l) Calculations of baseline, current, and natural visibility conditions; progress
to date; and the uniform rate of progress. For each mandatory Class I Federal area located
within the State, the State must determine the following:
(vi) Uniform rate of progress. (B) The State may submit a request to the Administrator
seeking an adjustment to the uniform rate of progress for a mandatory Class I Federal
area to account for impacts from (1) anthropogenic sources outside the United States
and/or (2) wildland prescribed fires that were conducted under a multi-year land or
resource management plan for a wildland area that has a stated objective to establish,
restore, or maintain sustainable and resilient wildland ecosystems or to preserve
endangered or threatened species through a program of prescribed fire and that provides
for the use of appropriate basic smoke management practices. To calculate the proposed
adjustment, the State must add the estimated impacts to natural visibility conditions and
compare the resulting value to baseline visibility conditions. If the Administrator
determines that the State has estimated the impacts from anthropogenic sources outside
the United States or wildland prescribed fires using scientifically valid data and methods,
the Administrator may approve the proposed adjustment to the uniform rate of progress
for use in the State's implementation plan.
The EPA is aware of states' concern that visibility at certain Class I areas is impacted not only by
natural and domestic anthropogenic emissions, but also by uncontrollable factors such as the
transport of international emissions. The EPA expects that the revised approach to selecting days
for purposes of defining RPGs and tracking progress, which focuses progress tracking on days
not affected by large episodic natural events such as dust storms and wildfires, will also largely
resolve issues stemming from the same types of natural emission sources in other countries.
However, the EPA does not believe it is appropriate to treat international anthropogenic impacts
as "natural; thus, estimates of visibility on the 20 percent most impaired days will include these
impacts. Given that it is appropriate for values for natural visibility conditions to not reflect
international anthropogenic impacts yet international anthropogenic impacts will be reflected in
"current conditions" and the 2028 RPGs, states have expressed concern that these international
anthropogenic impacts may affect their SIP development, and may result in an impression on the
part of some commenters that their SIPs do not show satisfactory progress towards natural
visibility conditions.
The Regional Haze Rule acknowledges that international impacts should not require states to
adopt more controls on their own sources in order to obtain EPA approval of their SIPs.65
Further, because even if international impacts were the "but for" cause of the 2028 RPG being
above the URP line and thus were to trigger the requirement for an additional demonstration (see
section 10.3), the existence of international impacts does not change the considerations for
65 The preamble to the 1999 Regional Haze Rule stated, "The EPA does not expect States to restrict emissions from
domestic sources to offset the impacts of international transport of pollution." 64 FR 35736, July 1, 1999.
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whether a particular additional measure for a particular source is reasonable and thus is necessary
to make reasonable progress.
International impacts may affect a state's SIP element by influencing the slope of the URP line
for a Class I area. The URP calculated according to the terms of the Regional Haze Rule, i.e., the
downward slope of the line from baseline to natural visibility conditions, may be larger in value
as a result of international impacts affecting the 2000-2004 starting point but not the 2064 end
point. Whatever impacts were occurring in 2000-2004 due to anthropogenic sources outside the
U.S. were included in the PM species concentrations measured by the IMPROVE program. In
contrast, the NC-II estimates of natural conditions, and estimates of natural conditions that will
be developed following the recommendations in this guidance document, will not reflect such
impacts. The more strongly downward sloping URP line may make it more difficult for the state
to develop an LTS that results in a 2028 RPG that is on or below the URP line. If international
impacts make a "but for" difference in whether the RPG is above the URP line, this would result
in an obligation for the state with the Class I area and any contributing state to conduct additional
analyses to show that no further domestic controls are reasonable.
To avoid this additional burden on states, the revised Regional Haze Rule includes a provision
that allows the Administrator to approve an adjustment to the URP to reflect the impacts of these
causes of visibility impairment, if the adjustment has been developed through scientifically valid
data and methods. The adjustment would be done by adding to the value of natural visibility
conditions the estimate of the impact of one or both of these source types, only for the purposes
of calculating the URP. The specific type of wildland fires that could be included in this
adjustments are fires that were conducted with the objective to establish, restore and/or maintain
sustainable and resilient wildland ecosystems, to reduce the risk of catastrophic wildfires and/or
to preserve endangered or threatened species during which appropriate basic smoke management
practices were applied. Only an RPG that is above the adjusted URP would then trigger the
requirement for the additional demonstration that there are no additional controls that would be
reasonable to include in the state's LTS. This adjusted framework should also be helpful to the
states when communicating with the public. See 40 CFR 51.308(f)(l)(vi)(B).
The requirement that states' proposed approaches be based on scientifically validated data and
methods may be more easily achieved for impacts from sources in Mexico and Canada near the
U.S. border than for more distant sources such as those across the Pacific Ocean. For sources in
Mexico and Canada, modeling approaches are well established and can be applied once robust
emission inventory information for anthropogenic sources is available. For more distant sources,
there are issues concerning the appropriate modeling approach and model validation.
The revised Regional Haze Rule does not specify the method for estimating international impacts
or the timeframe for which international impacts should be estimated. For the second
implementation period, states proposing to adjust their URPs should consult with the EPA on
how they will identify these particular impacts before they submit a request for approval of an
approach to adjust the URP.
5.20. How can impacts from prescribed fire be accounted for in the URP framework?
Regional Haze Rule provisions
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51.308(f)(l) Calculations of baseline, current, and natural visibility conditions; progress
to date; and the uniform rate of progress. For each mandatory Class I Federal area located
within the State, the State must determine the following:
(vi) Uniform rate of progress. (B) The State may submit a request to the Administrator
seeking an adjustment to the uniform rate of progress for a mandatory Class I Federal
area to account for impacts from (1) anthropogenic sources outside the United States
and/or (2) wildland prescribed fires that were conducted under a multi-year land or
resource management plan for a wildland area that has a stated objective to establish,
restore, or maintain sustainable and resilient wildland ecosystems or to preserve
endangered or threatened species through a program of prescribed fire and that provides
for the use of appropriate basic smoke management practices. To calculate the proposed
adjustment, the State must add the estimated impacts to natural visibility conditions and
compare the resulting value to baseline visibility conditions. If the Administrator
determines that the State has estimated the impacts from anthropogenic sources outside
the United States or wildland prescribed fires using scientifically valid data and methods,
the Administrator may approve the proposed adjustment to the uniform rate of progress
for use in the State's implementation plan.
Generally, we do not expect the total acreage subject to prescribed fires on wildlands to decrease
in the future because prescribed fire is needed for ecosystem health and to reduce the risk of
catastrophic wildfires.66 Thus, the occurrence of prescribed fire generally will not be projected to
decline towards zero by 2064, nor to decline over any one implementation period at the
proportional rate inherently assumed in the URP line. In fact, in many areas there may be reason
to adopt policies that facilitate, and accordingly to forecast for purposes of setting the RPG, more
use of prescribed fire and thus higher contributions to impairment on the 20 percent most
impaired days. At this time, we do not know whether or where such a projected trend may affect
whether the RPG for a Class I area will be above the URP line. However, we expect that if this is
an issue, western Class I areas would be the more likely to be affected.
Section 51.308(f)(l)(vi) of the Regional Haze Rule allows states with Class I areas significantly
impacted by emissions from wildland prescribed fires to make an adjustment to the URP with
specific approval by the Administrator. The adjustment would consist of adding to the value of
natural visibility conditions an estimate of wildland prescribed fire impacts, only for the purpose
of calculating the URP and only for prescribed fires that were conducted with the objective to
establish, restore and/or maintain sustainable and resilient wildland ecosystems, to reduce the
risk of catastrophic wildfires and/or to preserve endangered or threatened species during which
appropriate basic smoke management practices were applied. FLMs prepare multi-year land
and/or resource management plans for the areas they manage that document the objective of
prescribed fire for a land area. We would also consider a fire management plan for state, tribal or
private lands that has been reviewed and certified by the appropriate fire and/or resource
management professionals and agreed to and followed by the land owner/manager to be
sufficient to meet this restriction on the scope of the adjustment to the URP.67 Other evidence of
66 See the discussion of climate change effects on wildfire trends in the preamble to the proposed revisions of the
Exceptional Events Rule. 80 FR 72866-72871, November 20, 2015.
67 Examples of these plans include federal land or resource management plans, State Forest Action Plans, fire
management plans, prescribed fire on wildland management plans or landscape management plans.
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the objective of a prescribed fire would be considered on a case-by-case basis. This adjustment
will be permitted only if such prescribed fire impacts have been estimated with methods and data
that are scientifically valid.
The revised Regional Haze Rule does not specify the method for estimating prescribed fire
impacts or the timeframe for which impacts from the specified types of prescribed fire should be
estimated. For the second implementation period, states proposing to adjust their URPs should
consult with the EPA on how they will identify these particular impacts before they submit a
request for approval of an approach to adjust the URP.
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6. Screening of sources (Step 2)
Regional Haze Rule provisions
51.308(f)(2) Long-term strategy for regional haze and reasonably attributable visibility
impairment. Each State must submit a long-term strategy that addresses regional haze
visibility impairment, and if necessary any reasonably attributable visibility impairment
certified by the Federal Land Manager under §51.302(a), for each mandatory Class I
Federal area within the State and for each mandatory Class I Federal area located outside
the State that may be affected by emissions from the State. The long-term strategy must
include the enforceable emissions limitations, compliance schedules, and other measures
that are necessary to achieve reasonable progress, as determined pursuant to (f)(2)(i)
through (vi). In establishing its long-term strategy for regional haze, the State must meet
the following requirements:
(i) The State must consider and analyze emission reduction measures based on 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 major or minor stationary source or group of sources. The State must document
the criteria used to determine which sources or groups of sources were evaluated, and
how these four factors were taken into consideration in selecting the measures for
inclusion in its long-term strategy.
* * *
(v) The State must identify all anthropogenic sources of visibility impairment considered
by the State in developing its long-term strategy and the criteria used to select the sources
considered. The State should consider major and minor stationary sources, mobile
sources, and area sources.
Section 4.1 explains the function of a screening analysis and why the EPA believes that states
may use a screening step to select sources or groups of sources for a four-factor analysis. In the
recommended approach and the second alternative approach to considering visibility, a state
would use a screening step. In the first alternative approach, there would be no screening step
and all sources would be subject to a four-factor analysis.
6.1. How should a state determine which Class I areas need to be considered when
screening sources?
A state must develop an LTS that includes control measures necessary to make reasonable
progress at each of its own Class I areas and each Class I area outside the state that may be
affected by emissions from the state. In other words, a state's sources and its own Class I areas
are automatically linked. States must also link their sources with Class I areas in other states that
those sources may affect.
A variety of technical, quantitative approaches exist to assess which Class I areas are affected by
emissions from a given state. These approaches include, but are not limited to, emissions divided
by distance, emissions-weighted back trajectory analyses and the use of photochemical transport
models to track the contribution of specific sources or areas to specific Class I areas. Section 6.2
discusses these approaches in more detail. We also recommend that a state compare its linkages
for the purpose of developing its LTS for the second implementation period with the contribution
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linkages it acknowledged in its SIP for the first implementation period, and specifically explain
why any previous linkage has been dropped.
Once contributions by sources, groups of sources or geographic areas have been quantified in
some manner, the EPA recommends that states adopt a conservative (more protective approach
of visibility) approach to determining whether their sources may affect visibility at out-of-state
Class I areas. For example, states could consider all Class I areas for which the state contributes
at least one percent to anthropogenic light extinction from all U.S. sources on any day within the
20 percent most impaired days. States may choose a different threshold to determine which out-
of-state Class I areas may be affected by the States sources, but must provide an adequate
explanation of why the threshold is sufficiently protective of visibility.
6.2. How should a state estimate visibility impacts for screening purposes?
The role of estimates of visibility impact
This section assumes that a state will use an air quality model to develop estimates of the
visibility impacts of individual sources or groups of sources. With this assumption in mind, this
section offers recommendations on developing these visibility impact estimates, while section
6.3 offers recommendations on applying these estimates in a screening process that compares the
estimates to a threshold. However, the Regional Haze Rule does not require states to use an air
quality model to develop estimates of visibility impacts. Many, but not all, of the concepts and
recommendations in sections 6.2 and 6.3 can be applied to a screening analysis based on
surrogate metrics.
Applying these recommendations to estimate visibility benefits
Estimates of the visibility benefits of possible control measures for particular sources are not
relevant to the screening step. However, a state following the second alternative approach
described in section 4.2 will need to estimate the visibility benefits of possible control measures.
The visibility benefit of applying an emission control measure is the difference between the
source's visibility impact without that measure and the source's visibility impact with the
measure in place. While the recommendations in this section are primarily directed at estimating
source impacts on visibility using an air quality model, except where noted these
recommendations are also relevant to the estimation of visibility benefits from additional
emission control measures. Depending on the quality of a particular surrogate for visibility
impact, it may or may not be appropriate to treat the difference in the value of the surrogate
metric (without versus with an additional control) as a useful estimate of the visibility benefit of
the controls, for the purpose of weighing visibility benefits along with the four statutory factors
in the second alternative approach.
Should current or 2028 emission limits be used to estimate baseline emissions and visibility
impacts for screening purposes?
At the time of SIP development and submission, there may be enforceable emission limits that
have not yet affected source emissions, but that will affect source emissions before 2028. This
raises the question of whether baseline68 emissions used in screening should be based on the
68 "Baseline" here refers to the source conditions assumed to be the starting point for the analysis of additional
measures based on the four statutory factors and possibly visibility benefits.
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emission limits that apply at the time of SIP submission or the emission limits that will apply in
2028. The EPA generally recommends that if source-specific modeling of visibility impacts is
performed for screening purposes, it should be based on projected 2028 baseline emissions
assuming source compliance with emission limits that have been adopted and are enforceable.
The screening process may recognize current levels of emission control that are not enforceable
In projecting future baseline emissions, typical past actual emission rates may be assumed even
if lower than permitted emission rates, assuming there is no evident basis for assuming a change
in emission rates.69
Should the recent/current or a predicted 2028 level of source operation be used to estimate
visibility impacts for screening purposes?
Reasonable activity growth rates should be applied to area source categories, in which sources
are not individually represented in the emissions inventory. Available information on the future
levels of operation of individually inventoried sources should also be incorporated.
Generally, the assumed level of future operation for any type of source should not be less than a
recent period of actual operation that can reasonably be taken as representative of future
operation, unless there is strong reason to expect a reduction. Uncertain predictions of market-
driven changes in source operation or predictions of voluntary emission reductions should not
result in a source being excluded for full analysis if it would otherwise qualify for full analysis.
A state should explicitly identify any sources not selected in the screening step because of
enforceable future operating limitations, including enforceable shutdowns, and explain the
applicable future requirement and the enforcement mechanism for that requirement. As for
newly adopted emission limits, we recommend that operating restrictions (that are not
requirements for shutdown) that are being incorporated into the EPA-approved SIP for the first
time via the regional haze SIP revision should not be applied when estimating source impacts for
screening purposes unless those operating restrictions are effective by July 31, 2021.
States may but are not required to use the EPA projections of future emissions, e.g., IPM-based
projections of source-specific EGU emissions, from a national rulemaking analysis. An IPM-
based projection that an EGU will cease operation is not a sufficient basis for a state to assume
such shutdown when developing its LTS. The EPA projections for national rulemaking analysis
will also include projections for other major and minor stationary sources and area source types,
but these projections vary in the level of their sophistication and the actual data supporting them;
states may be able to make better projections for these source types. A state's use of estimates
previously used by or provided by the EPA does not ensure SIP approval in that regard, as any
contrary information in the record will bear on the EPA's decision.
69 However, if the source is retained through the screening step and the current (or a better) level of emission control
is determined to be necessary to make reasonable progress, which generally should be the case unless there is an
unusual reason to conclude that continued performance at that level cannot be reasonably required, an emission limit
should be set based on that level of emission control.
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Daily emissions
The temporal pattern of emissions during the year, not just annual total emissions, is important in
the consideration of modeling-based estimations of visibility impacts and benefits. When
available, states should use historical information on emissions patterns to inform the creation of
seasonal and diurnal emission patterns for purposes of air quality modeling. States should divide
annual emissions by 365 days per year and 24 hours per day only if no better information is
available. Unlike for BART analyses, states do not need to assume that maximum daily
emissions recur every day.
Models and methods for estimating visibility impacts
The Regional Haze Rule does not require states to use air quality modeling with source
apportionment to identify which sources or source categories should be subject to a four-factor
analysis, but modeling can be very useful to identify which geographic areas, individual sources
or source sectors, and pollutants are most responsible for impairment at a given Class I area. The
EPA recommends that states or multi-state organizations planning to conduct source contribution
modeling make their study plan for the modeling available (before beginning the modeling) for
review by the EPA.
Air quality models can be used to estimate source's contributions to primary and secondary
PM2.5 using source apportionment and source sensitivity approaches.70 These techniques allow
for source differentiation by country, state or county boundaries,71 broad source sectors,72 and
even specific facilities.73 Regional photochemical grid models can also be used to estimate the
contribution of lateral boundary chemical inflow of speciated PM2.5 using both reactive and
unreactive tracers.74 Source-based apportionment approaches implemented in air quality models
can be limited by deficiencies in model inputs (e.g., emissions or meteorology) and formulation
70 Cohan, D.S., Napelenok, S.L., 2011. Air quality response modeling for decision support. Atmosphere 2,
407-425.
71 U.S. Environmental Protection Agency, 2005. Technical Support Document for the Final Clean Air Interstate
Rule Air Quality Modeling, http://archive.epa.gov/airmarkets/programs/cair/web/pdf/fmaltech02.pdf, Research
Triangle Park, North Carolina; U.S. Environmental Protection Agency, 2011; Air Quality Modeling Final Rule
Technical Support Document. http://www3.epa.gov/airtransport/CSAPR/pdfs/AQModeling.pdf, Research Triangle
Park, North Carolina.
72 Farm, N., Fulcher, C.M., Baker, K., 2013. The Recent and Future Health Burden of Air Pollution
Apportioned Across US Sectors. Environmental Science & Technology 47, 3580-3589.
73 Baker, K.R., Kelly, J.T., 2014. Single source impacts estimated with photochemical model source sensitivity and
apportionment approaches. Atmospheric Environment 96, 266-274; Bergin, M.S., Russell, A.G., Odman, M.T.,
Cohan, D.S., Chameldes, W.L., 2008. Single-Source Impact Analysis Using Three-Dimensional Air Quality
Models. Journal of the Air & Waste Management Association 58, 1351-1359; Zhou, W., Cohan, D.S., Finder, R.W.,
Neuman, J.A., Holloway, J.S., Peischl, I, Ryerson, T.B., Nowak, J.B., Flocke, F., Zheng, W.G., 2012. Observation
and modeling of the evolution of Texas power plant plumes. Atmospheric Chemistry and Physics 12, 455-468.
74 Baker, K.R., Emery, C., Dolwick, P., Yarwood, G., 2015. Photochemical grid model estimates of lateral boundary
contributions to ozone and paniculate matter across the continental United States. Atmospheric Environment 123,
49-62; Dolwick, P., Akhtar, F., Baker, K.R., Possiel, N., Simon, H., Tonnesen, G., 2015. Comparison of background
ozone estimates over the western United States based on two separate methodologies. Atmospheric Environment
109, 282-296.
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(e.g., chemistry and deposition) approaches.75 In some situations where primary PM is most
important, other types of air quality models, such as Gaussian dispersion (e.g., AERMOD)
models may provide useful information. And where demonstrated appropriate, other types of
chemical transport models that treat gas and aerosol chemistry (e.g., SCICHEM) may be an
option for screening analysis.
Chemical transformations can play an important role in defining the concentrations and
properties of certain air pollutants such as PM and haze. Where this is a factor, it is thus
important that models used for screening and to assess visibility benefits take into account
chemical reactions and physical processes of various pollutants (including precursors) in
determining the current state of air quality, as well as predicting and projecting the future
evolution of these pollutants. It is important that a modeling system provide a realistic
representation of chemical and physical processes leading to secondary pollutant formation and
removal from the atmosphere. Chemical transport models treat atmospheric chemical and
physical processes such as deposition and motion. There are two types of chemical transport
models, Eulerian (grid based) and Lagrangian. These types of models differ in their frame of
reference. Eulerian models are based on a fixed frame of reference, and Lagrangian models use a
frame of reference that moves with parcels of air between the source and receptor point.76
Some Lagrangian models treat in-plume gas and particulate chemistry. These models require
time and space varying oxidant concentrations, and in the case of PM2.5 also neutralizing agents
such as ammonia, as important secondary impacts happen when plume edges start to interact
with the surrounding chemical environment.77 These oxidant and neutralizing agents are not
routinely measured, but can be generated with a three dimensional photochemical grid model.
Photochemical grid models are three-dimensional Eulerian grid-based models that treat chemical
and physical processes in each grid cell and use diffusion and transport processes to move
75 Kwok, R., Baker, K., Napelenok, S., Tonnesen, G., 2015. Photochemical grid model implementation of
VOC, NO x, and O 3 source apportionment. Geoscientific Model Development 8, 99-114; Kelly, J.T., Baker, K.R.,
Napelenok, S.L., Roselle, S.J., 2015. Examining single-source secondary impacts estimated from brute-force,
decoupled direct method, and advanced plume treatment approaches. Atmospheric Environment 111, 10-19.
76 McMurry, P.H., Shepherd, M.F., Vickery, J.S., 2004. Particulate matter science for policy makers: A NARSTO
assessment. Cambridge University Press.
77 Baker, K.R., Kelly, J.T., 2014. Single source impacts estimated with photochemical model source sensitivity and
apportionment approaches. Atmospheric Environment, 96: 266-274; ENVIRON, 2012. Evaluation of Chemical
Dispersion Models using Atmospheric Plume Measurements from Field Experiments. ENVIRON International,
Corp., Novato, CA. Prepared under contract No. EP-D-07-102 for U.S. Environmental Protection Agency, Research
Triangle Park, NC. https://www3.epa.gov/ttn/scram/reports/Plume_Eval_Final_Sep_2012v5.pdf.
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chemical species between grid cells.78 These types of models are appropriate for assessment of
near-field and regional scale reactive pollutant impacts from specific sources79 or all sources.80
Even though single source emissions are injected into a grid volume, photochemical grid models
have been shown to adequately capture single source impacts when compared with downwind
in-plume measurements.81 Where set up appropriately for the purposes of assessing the
contribution of single sources or groups of sources to primary and secondarily formed pollutants,
photochemical grid models could be used with a variety of approaches to estimate these impacts.
These approaches generally fall into the category of source sensitivity (how air quality changes
due to changes in emissions) and source apportionment (what air quality impacts are related to
certain emissions). Source apportionment has been used to differentiate the contribution from
single sources on model predicted ozone and PM2.5.82 The direct decoupled method has also been
used to estimate Cb and PIVb.s impacts from specific sources as well as the simpler brute-force
sensitivity approach.83 Limited comparison of single source impacts between models and
approaches to differentiate single source impacts84 show generally similar downwind spatial
gradients and impacts.
78 McMurry, P.H., Shepherd, M.F., Vickery, J.S., 2004. Paniculate matter science for policy makers: A NARSTO
assessment. Cambridge University Press. Available at http://narsto.org/pm_science_assessment.
79 Baker, K.R., Foley, K.M., 2011. A nonlinear regression model estimating single source concentrations of primary
and secondarily formed PM2.5. Atmospheric Environment, 45: 3758-3767; Baker, K.R., Kelly, J.T., 2014. Single
source impacts estimated with photochemical model source sensitivity and apportionment approaches. Atmospheric
Environment, 96: 266-274; Bergin, M.S., Russell, A.G., Odman, M.T., Cohan, D.S., Chameldes, W.L., 2008.
Single-Source Impact Analysis Using Three-Dimensional Air Quality Models. Journal of the Air & Waste
Management Association, 58: 1351-1359; Zhou, W., Cohan, D.S., Finder, R.W., Neuman, J.A., Holloway, J.S.,
Peischl, I, Ryerson, T.B., Nowak, J.B., Flocke, F., Zheng, W.G., 2012. Observation and modeling of the evolution
of Texas power plant plumes. Atmospheric Chemistry and Physics, 12: 455-468.
80 Chen, I, Lu, I, Avise, J.C., DaMassa, J.A., Kleeman, M.J., Kaduwela, A.P., 2014. Seasonal modeling of PM 2.5
in California's San Joaquin Valley. Atmospheric Environment, 92: 182-190; Russell, A.G., 2008. EPA Supersites
program-related emissions-based paniculate matter modeling: initial applications and advances. Journal of the Air &
Waste Management Association, 58: 289-302; Tesche, T., Morris, R., Tonnesen, G., McNally, D., Boylan, J.,
Brewer, P., 2006. CMAQ/CAMx annual 2002 performance evaluation over the eastern US. Atmospheric
Environment, 40: 4906-4919.
81 Baker, K.R., Kelly, J.T., 2014. Single source impacts estimated with photochemical model source sensitivity and
apportionment approaches. Atmospheric Environment, 96: 266-274; Zhou, W., Cohan, D.S., Finder, R.W., Neuman,
J.A., Holloway, J.S., Peischl, J., Ryerson, T.B., Nowak, J.B., Flocke, F., Zheng, W.G., 2012. Observation and
modeling of the evolution of Texas power plant plumes. Atmospheric Chemistry and Physics, 12: 455-468.
82 Baker, K.R., Kelly, J.T., 2014. Single source impacts estimated with photochemical model source sensitivity and
apportionment approaches. Atmospheric Environment, 96: 266-274; Baker, K.R., Foley, K.M., 2011. A nonlinear
regression model estimating single source concentrations of primary and secondarily formed PM 2.5. Atmospheric
Environment, 45: 3758-3767.
83 Baker, K.R., Kelly, J.T., 2014. Single source impacts estimated with photochemical model source sensitivity and
apportionment approaches. Atmospheric Environment, 96: 266-274; Bergin, M.S., Russell, A.G., Odman, M.T.,
Cohan, D.S., Chameldes, W.L., 2008. Single-Source Impact Analysis Using Three-Dimensional Air Quality
Models. Journal of the Air & Waste Management Association, 58: 1351-1359; Zhou, W., Cohan, D.S., Finder,
R.W., Neuman, J.A., Holloway, J.S., Peischl, J., Ryerson, T.B., Nowak, J.B., Flocke, F., Zheng, W.G., 2012.
Observation and modeling of the evolution of Texas power plant plumes. Atmospheric Chemistry and Physics, 12:
455-468.
84 Baker, K.R., Kelly, J.T., 2014. Single source impacts estimated with photochemical model source sensitivity and
apportionment approaches. Atmospheric Environment, 96: 266-274; Baker, K.R., Kelly, J.T., Fox, T., 2013.
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The Regional Haze Rule does not prescribe or recommend any particular air quality model or
modeling approach for estimating visibility impacts or benefits for purposes of determining what
measures are necessary to make reasonable progress. In 2015, the EPA proposed revisions to 40
CFR Part 51 Appendix W, Guideline on Air Quality Models.85 As part of this proposal, the EPA
has proposed that photochemical grid models should be the generally preferred approach for
estimating source impacts on secondary PM concentrations. Photochemical grid models include
all emissions sources and have realistic representations of formation, transport, and removal
processes of the PM that causes visibility degradation. We recommend states consult with their
EPA regional office to determine the appropriate use of an air quality model for the purpose of
evaluating source-specific or source group-specific visibility impacts, consistent with existing
EPA technical guidance.
Development of the requisite meteorological and emissions databases that are necessary to use
photochemical grid models to estimate visibility impacts should conform to recommendations on
those specific topics in the 2015 proposed revisions to the Guideline on Air Quality Modeling
(40 CFR part 51 appendix W) and the recommendations outlined in the EPA's Modeling
Guidance for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional
Haze ("Modeling Guidance").86
The Modeling Guidance also outlines a procedure where model estimates at Class I areas
projected for the future year scenario, defined by the meteorological and emissions inputs, are
used to develop Class I area-specific relative response factors. The estimated relative response
factor for each PM species is multiplied by the corresponding historical concentration metric for
that species to project future year PM conditions and thus visibility. This relative response factor
approach has been part of the EPA's guidance for many years and is familiar to state air quality
modelers. The new development is in the selection and grouping of days prior to the calculation
of the relative response factors. In the first implementation period, the 20 percent haziest days
and the 20 percent clearest days (using those terms as meant in this document) were grouped and
averaged. In the second implementation period, the relative response factors will be averaged
over the 20 percent most impaired days and 20 percent clearest days to generate relative response
factors for these sets of days, consistent with the 2016 revision of the Regional Haze Rule and
the recommendations in section 5.87
Estimating second pollutant impacts from single sources (control #27). http://aqmodels.awma.org/conference-
proceedings.
85 80 FR 45340, July 29, 2015.
86 The most recent finalized version of this "SIP Modeling Guidance" was issued in 2007. See
https://www3.epa.gov/ttn/scram/guidance/guide/fmal-03-pm-rh-guidance.pdf. A draft of a revised version of the SIP
Modeling Guidance was made available for public comment in 2014. The 2014 revisions concerned section of the
document relevant to ozone and PM2.5 SIPs. See https://www3.epa.gov/ttn/scram/guidance/guide/Draft_O3-PM-
RH_Modeling_Guidance-2014.pdf. The SIP Modeling Guidance will be issued as a new final version shortly. On
the specific topics of meteorology and emissions inputs, we expect that new version to be stable for an extended
period. After this new guidance on the Regional Haze SIPs is finalized, the EPA expects to seek public comment on
a further revision of the SIP Modeling Guidance, to make it consistent with this guidance.
87 The EPA expects to seek public comment on a further revision of the SIP Modeling Guidance with respect to
other aspects of a complete modeling analysis, including this selection of days aspect, to make it fully consistent
with this guidance document on Regional Haze SIPs.
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States can demonstrate the adequacy of air quality modeling fields through appropriate
diagnostic and statistical performance evaluations consistent with recommendations provided in
the Modeling Guidance. If there are doubts about whether an element of the Modeling Guidance
is applicable to the development of a regional haze SIP in the second implementation period, a
state should consult with its EPA regional office.
Though the Modeling Guidance focuses on the process for calculating RPGs based on the
aggregate effect of emission controls for diverse sources, the same relative reduction approach
can be used to determine the improvement in visibility as a result of emission controls at a
specific source or for a source sector. This information would not be relevant at the screening
step, but could be used subsequently by a state following the second alternative approach. One
approach to estimating such visibility benefits would be to run two emission scenarios through
the complete modeling process, and take the difference. Another approach would be to make a
single source apportionment modeling run. The latter would involve several post-processing
steps. First, the modeled contribution estimates to each PM species in the IMPROVE light
extinction equation for the particular source or source sector of interest should be subtracted
from the total contribution estimated from all sources in the future year baseline to create an
"alternative scenario" that is simply the projected future year visibility without the source(s) of
interest. Second, relative response factors should be estimated for each PM species that
comprises the constituents in the IMPROVE light extinction equation using the "alternative
scenario" as the numerator and future year scenario with all sources as the denominator
consistent with procedures detailed in the Modeling Guidance for purposes of calculating RPGs.
Third, these relative response factors should be applied to estimate the portion of projected future
year visibility contributed by the source(s) tracked for source attribution. The difference between
the scenario with all emissions sources and the "alternative scenario" represent the contribution
from the source(s) of interest. This difference in visibility attributed to the source(s) of interest
should then be compared to natural background estimates.
Selecting days for estimating and considering visibility impacts
Variations in the operation of sources, transport/dispersion influences (e.g., wind direction and
atmospheric stability), and photochemistry typically combine to change the visibility impact
from a source (and the benefit of an emission control measure) on different days of the year, in
some cases with a strong seasonal pattern.88 As explained in section 5, the URP framework
focuses on baseline, current, natural and projected future visibility conditions on the 20 percent
most impaired days in each year. Therefore, the EPA recommends that states focus on estimating
and considering source impacts on the 20 percent most impaired days when conducting their
screening analyses. Sections 4.3 and 6.2 discuss this topic in more detail.89
88 Variations in emission control performance from day-to-day or across a year may also be a factor contributing to
variability in the benefit of an emission control.
89 The following information is provided as background, to avoid possible confusion about how this
recommendation relates to analysis of visibility impacts (and benefits) in the first implementation period. In the first
implementation period, analysis of whether a BART-eligible source was subject to BART was based on assessing
the 98th percentile daily visibility impact assuming maximum historical daily emissions from the source, which may
or may not have occurred on one of the 20 percent haziest days. This approach was also used in some cases to
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Considering source impacts on the 20 percent most impaired days will focus attention on
improving visibility on the days that currently are furthest from having natural visibility
conditions. The EPA also recommends that a state following the second alternative approach
consider the whole of the distribution of the individual visibility benefits on the 20 percent most
impaired days, specifically including both the maximum benefit and other values at the high end
of this distribution, in addition to the average benefit across each of this set of days. People may
visit a Class I area only for one day, and the highest daily impacts and benefits will affect some
visitors. Measures adopted because they are judged necessary to make reasonable progress and
prevention of degradation on these days will have benefits on other days of the year also.
While the Regional Haze Rule does not require states to generate information on visibility
impacts or benefits on days other than the 20 percent most impaired days, states may nonetheless
choose to do so. Such information may also become available during the SIP development
process. In these cases, states should consider visibility impacts and benefits on days outside the
20 percent most impaired days if they are significant and would affect the state's decision
making.
A state or multi-state organization may also present in its SIP the median light extinction impact
from a source or group of sources, or the impact on an annual average basis. This information
may help identify sources or groups of sources with unusual contribution patterns and help
public understanding of how contributions by sources and groups of sectors to visibility
impairment vary with meteorological and other conditions.
Use of a "clean" background when assessing source-specific visibility impacts
Importantly, states must consider source impacts (and, for states following the second alternative
approach, the potential visibility benefits of additional measures) on the 20 percent most
impaired days relative to a light extinction level that represents a clean/natural background,
rather than the visibility conditions existing at the time a SIP revision is developed.90
consider the expected visibility impact and potential benefits of individual reasonable progress sources, as well as to
evaluate whether an alternative to BART provided "greater reasonable progress" towards natural visibility
conditions than would implementation of source-specific BART. The CALPUFF model was used for this purpose.
In other cases, a comparison of benefits on the 20 percent haziest and 20 percent clearest days was the basis for
determining whether an alternative to BART provided greater reasonable progress, under section 51.308(e)(3).A
photochemical grid model was used for this purpose. While CALPUFF was considered adequate for predicting a
source's largest potential impacts in a Class I area during a year, it was not recognized as being able to predict
concentration impacts on particular days. Therefore, the EPA and state could not have drawn conclusions from
CALPUFF modeling about impacts on days within the set of the 20 percent most impaired days.
90 This approach to the treatment of background air quality when quantifying source impacts (and potential benefits
from additional measures) is different than the approach to background air quality when projecting how all emission
reductions measures combined will affect visibility conditions at the end of the implementation period for purposes
of setting the RPGs. In the first implementation period, some stakeholders argued that is appropriate to consider only
the amount by which a potential measure or combination of measures would change the projected overall deciview
index value as of the end of the implementation period, i.e., the degree by which the RPGs would differ with and
without the controls being included in the LTS. We do not agree. The RPGs are values that will be compared in a
progress report to actual visibility conditions, and of course accordingly must represent the expected actual overall
visibility conditions. In contrast, estimates of source impacts and measure benefits have a different purpose, which is
to help guide decisions on the control of individual sources.
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The logic of considering visibility impacts and benefits relative to clean/natural conditions was
articulated, in the context of BART, in the preamble to the final rule that established the BART
Guidelines:
Using existing conditions as the baseline for single source visibility impact
determinations would create the following paradox: the dirtier the existing air, the
less likely it would be that any control is required. This is true because of the
nonlinear nature of visibility impairment. In other words, as a Class I area becomes
more polluted, any individual source's contribution to changes in impairment
becomes geometrically less. Therefore the more polluted the Class I area would
become, the less control would seem to be needed from an individual source. ...
Such a reading would render the visibility provisions meaningless, as EPA and the
States would be prevented from assuring "reasonable progress" and fulfilling the
statutorily-defmed goals of the visibility program. Conversely, measuring
improvement against clean conditions would ensure reasonable progress toward
those clean conditions. 70 FR 39124, July 6, 2005.
The same logic applies to the evaluation of visibility impacts and benefits of non-BART sources.
Accordingly, the EPA has used clean background conditions in evaluating the benefits of
controls on individual reasonable progress sources and has disapproved reasonable progress
decisions by states that relied on modeling employing dirty background conditions.91 This
approach has been upheld by the Eighth Circuit.92
Because of the logarithmic deciview scale, the use of natural background conditions will result in
higher values for "delta deciview" impacts on visibility from sources than otherwise. This result
is illustrated in Figure 6.1. The figure shows that an increment in light extinction of 10 Mm"1
causes a deciview scale increment of only 1.26 when the light extinction increment is assumed to
be "on top of an extinction level of 75 Mm"1 from other sources. However, if the same light
extinction increment is assumed to be "on top of the natural light extinction value for this
example Class I area, the deciview scale increment or "delta deciview" is 3.86.
91 The EPA has followed this logic in the North Dakota (77 FR 20894, April 6, 2012), Montana (77 FR 57864,
September 18, 2012), Arizona (79 FR 52420, September 3, 2014), and Texas (81 FR 296, January 5, 2016) FIPs and
partial disapprovals of North Dakota (77 FR 20894, April 6, 2012) and Texas (81 FR 296, January 5, 2016) SIPs.
92 North Dakota v. EPA, 730 F.3d 750, 764-766 (8th Cir. 2013). ("Although the State was free to employ its own
visibility model and to consider visibility improvement in its reasonable progress determinations, it was not free to
do so in a manner that was inconsistent with the CAA. Because the goal of § 169A is to attain natural visibility
conditions in mandatory Class I Federal areas, see 42 U.S.C. § 7491(a)(l), and EPA has demonstrated that the
visibility model used by the State would serve instead to maintain current degraded conditions, we cannot say that
EPA acted in a manner that was arbitrary, capricious, or an abuse of discretion by disapproving the State's
reasonable progress determination based upon its cumulative source visibility modeling.")
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Figure 6.1. Illustration of the different "delta deciview" values, depending on
whether projected conditions or natural background conditions are used as the
starting point. ("WIMO" means the Wichita Mountains Class I area. "Mm" means
megameters.)
Deciview vs. Total extinction
20
o
Q
t-
3.86 dv
10
30
40 50 60 70
Total Extinction (I/Mm)
10
SO
90
100
dv = 10*ln(Bext/10)
Natural visibility conditions vary from day to day, and the condition on a particular day or group
of days can be estimated in the manner recommended in section 5 or in some other way justified
by a state. If PM species impacts by a source have been estimated to allow each estimate of daily
impacts to be associated with a particular day of IMPROVE data, this allows the option of using
a day-specific estimate of natural PM species concentrations to develop the corresponding value
of natural visibility condition to use as the background value for calculating the visibility impact
in deciviews. In other cases, it may only be possible to use the estimate of natural visibility
conditions across the 20 percent most impaired days as the background for impacts on those
days. It is also acceptable to use the estimate of annual average natural visibility conditions as
the background for estimating all daily values of source impact. As a simple and conservative
approach, the EPA recommends that the background PM species concentrations should be
assumed to be equal to the value of annual average natural visibility conditions.
The visibility benefit of a potential additional emission control measure is the difference between
the baseline visibility impact in deciviews and the reduced visibility impact assuming that the
additional measure is in place. This means that estimates of visibility benefits will also be
influenced by this approach to using natural background conditions.
If a state also quantifies and presents visibility impacts and benefits in deciview units based on
an assumption of current conditions as background, the state should clearly state that this
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information is presented only for context and that it is not the basis for its decisions on what
measures are necessary to make reasonable progress.93
Aggregation of sources during the screening step
A state may aggregate sources and show that even the aggregate visibility impact (or benefit) is
below an appropriate screening threshold, such that none of the sources needs to be selected for
full analysis. This is a logical application of conservative screening.
Continued relevance of the BART Guidelines
Many of the statements in the BART Guidelines continue to be relevant as recommendations for
how a state should assess facts related to visibility impacts and visibility benefits. Appendix D
indicates which parts of the BART Guidelines continue to be relevant in this way.
Contrasting the above recommendations to typical visibility analysis for the purpose of BART
The following paragraphs provide more detail on how states typically conducted BART and
individual reasonable progress source assessments during the first planning period, and on how
the details of those assessments differ from an approach using a chemical transport model and
the recommendations in this guidance. This information is presented to provide clarity for air
agencies so that they do not approach the development of regional haze SIPs based on
impressions and expectations formed in the first implementation period that will not carry over to
the second implementation period.
Single-source air quality modeling for BART assessments during the first implementation period
was typically done using the CALPUFF modeling system, using maximum emission rates (24-hr
maximum mass emission rates during the baseline period) and consideration of the maximum or
near-maximum modeled visibility impact from the source. 94
Effect of the air quality model: The 2005 BART Guidelines established the appropriateness of
CALPUFF for the purposes of BART analysis.95 (States and the EPA also used CALPUFF for
93 The EPA presented this type of information in the TSD for the reasonable progress FIP for Texas, but only for
transparency in how we had derived the estimates of visibility benefits relative to the natural conditions background.
Our decisions on what measures are necessary to make reasonable progress were not based on an assumption of
current conditions as background.
94 The BART Guidelines allowed the use of the 98th percentile modeled impact rather than the highest modeled
impact in light of uncertainty regarding the accuracy of the very highest modeled impacts in a year. Thus, the
highest modeled impacts were not typically compared directly to visibility thresholds, recognizing some uncertainty
exists in the modeling system and abnormal meteorology may result in an unusually high source contribution.70 FR
39121 and 39124. Note, however, that in some cases in which a state's modeling did not adhere to the BART
Guideline with respect to the meteorology inputs for CALPUFF modeling, we approved the use of the maximum
modeled impact instead of the 98th percentile impact as a compensating adjustment.
95 In the BART Guidelines, the EPA addressed the question of how states could best predict a single source's
contribution to visibility impairment. At the time, the EPA recognized that CALPUFF had not yet been fully
evaluated for secondary pollutant formation, but the EPA still considered CALPUFF to be the best application for
assessing a single source's impact on visibility in a Class I area for purposes of the regional haze program. The EPA
took note of the limitations of CALPUFF for this purpose but concluded that CALPUFF was the best modeling
application for use in evaluating BART, especially given how the modeling results would be used. Based on this
assessment, the EPA recommended that the states use CALPUFF. The EPA also made clear, however, that states
could use other alternative approaches, including photochemical grid models, if done in consultation with the
appropriate EPA regional office. See 70 FR 39104, 39122-23 (July 6, 2005).
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evaluating visibility impacts and potential control benefits for individual reasonable progress
sources during the first implementation period.) In 2015, the EPA proposed revisions to 40 CFR
Part 51 Appendix W, Guideline on Air Quality Models. As part of this proposal, the EPA
proposed that photochemical grid models should be the generally preferred approach for
estimating source impacts on secondary PM concentrations. Photochemical grid models include
all emissions sources and include representations of formation, transport, and removal processes
of the PM that causes visibility degradation. Therefore, if a state chooses to conduct single
source modeling for the purpose of evaluating source-specific or source group-specific visibility
impacts or benefits from emissions controls for reasonable progress and LTS development, the
state should utilize photochemical grid models (with appropriate post-processing to apply natural
visibility conditions as the background for assessing deciview impacts, to estimate potential
future year visibility benefits from controls).
Single source impacts estimated for reasonable progress assessments using photochemical grid
modeling and single source impacts estimated for prior BART and reasonable progress
assessments using CALPUFF will be different due to fundamental differences between
photochemical grid models and puff dispersion models such as CALPUFF. Photochemical grid
models include all emissions sources and provide a dynamic chemical and physical environment
to estimate source emission impacts. The CALPUFF model uses fixed uniform concentrations of
important oxidants such as ozone and neutralizing agents such as ammonia and does not perform
key thermodynamic transformations that can strongly influence atmospheric residence time and
thus transport.96 CALPUFF's representation of these important chemical species and PM2.5
chemistry will result in different estimated source impacts than a photochemical grid model even
if the exact same source emissions and release characteristics are used in both modeling systems.
Additionally, Lagrangian puff models such as CALPUFF allow the project source full access to
oxidants (e.g., ozone) and neutralizing agents (e.g., ammonia) while the same source in a
photochemical model competes for oxidants and neutralizing agents, which may result in
different and possibly lower modeled impacts.
Because of these differences in modeling approach, states should expect that many of the
estimates of daily visibility impacts within the set of the 20 percent most impaired days using the
photochemical modeling approach will be smaller than the single value of visibility impact from
a CALPUFF modeling assessment.
Effect of differences in the approach to emissions inputs: To whatever extent realistic estimates
of daily emissions are used to estimate visibility impacts for a screening analysis (see Daily
Emissions, above), some of the estimates of daily visibility impacts will be lower than the
estimates derived in a BART analysis, all other factors being the same. The degree of difference
will depend on each source's temporal pattern of emissions. However, it is also possible that the
estimate of the maximum 24-hour impact derived from a reasonable progress analysis done
according to the recommendations in this document will be close to the estimate that would be
derived with a BART-like approach.
96 Karamchandani, P., Chen, S.-Y., Seigneur, C., 2008. CALPUFF Chemistry Upgrade. Prepared for American
Petroleum Institute, 1220 L Street NW, Washington, DC 20005. Document CP277-07-01; Karamchandani, P.,
Lohman, K., Seigneur, C., 2009. Using a sub-grid modeling approach to simulate the transport and fate of toxic air
pollutants. Environmental Fluid Mechanics, 9: 59-71.
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Effect of the selection of day or days: BART determinations are intended to provide information
about the high end of the distribution of impacts and potential benefits for a single facility at
Class I areas, to supplement other relevant emissions control information. In a BART analysis,
states typically evaluated the 98th percentile visibility impact (which will be the 8th highest
modeled estimate when 365 days are modeled) at Class I areas from each year modeled to
provide a single-value estimate of source impacts.97 This estimate of source impact was often
used to determine whether a BART-eligible source was also subject to BART. The difference
between 98th percentile impacts with and without a potential additional control was typically
used as the metric for consideration of visibility benefits, which was a statutory factor for BART.
A similar approach was also used in some cases to evaluate visibility impacts of individual
reasonable progress sources during the first implementation period.
In the second implementation period, we recommend in this guidance document that the highest
daily visibility impact among the 20 percent most impaired days, as well as the average source
impact across this set of days multiplied by a constant value, be used for purposes of screening
sources and groups of sources to select those that will be subject to four-factor analysis.98 For a
state following the second alternative approach, we recommend that in the four-factor analysis,
the whole of the distribution of the individual visibility benefits on the 20 percent most impaired
days, specifically including the maximum benefit among these days be weighed along with the
four statutory factors.
In summary, a BART determination or a single source reasonable progress determination using
CALPUFF is based on a "high end" single-source impact scenario, while a reasonable progress
assessment using a photochemical grid model is intended to provide projections of the whole of
the distribution of future visibility impacts during two sets of days, or an entire year. The
differences in the types of models, the inputs to the models and the focus on particular days mean
that the single visibility impact (or benefit) result from a BART determination (or any similar
modeling using CALPUFF) will differ from, and should not be directly compared to, the
maximum visibility impact or any other particular point on the distribution (or the average) of
estimated visibility impacts (or benefits) on the 20 percent most impaired days from a reasonable
progress analysis that uses a photochemical grid model and follows the recommendations in this
guidance document. Reasonable progress analysis results that have been based on the
recommendations in this guidance will likely be lower in magnitude than visibility impact results
from BART determinations in the first planning period. These different visibility impact results,
which result from a combination of different inputs, models and visibility metrics, do not conflict
with BART determinations from the first planning period.
97 As previously noted, however, in some cases in which a state's modeling did not adhere to the BART Guideline
with respect to the meteorology inputs for CALPUFF modeling, we approved the use of the maximum modeled
impact instead of the 98th percentile impact as a compensating adjustment.
98 Note to reviewers of this draft guidance document: See a footnote in section 4.3 inviting comment on the subject
of using the average impact across the 20 percent most impaired days multiplied by a constant value.
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6.3. How should a state select sources for four-factor analysis based on visibility impacts?
Screening based on PM species contributions to anthropogenic light extinction
It is possible using the methods recommended in section 5 of this guidance to develop an
extinction budget specifically for anthropogenic impairment at a Class I area for each day based
on IMPROVE data, and to then calculate an average anthropogenic "extinction budget" for the
20 percent most impaired days." Typically, the state with a Class I area should take the lead on
developing the extinction budget for the Class I area (if a multistate organization or a federal
agency has not already provided this information), but the implications of the budget apply to all
states with sources that contribute to impairment at the area. If a PM species makes only a small
absolute and relative contribution to overall anthropogenic light extinction at a Class I area on
each of the 20 percent most impaired days, and if there is no reason for concern about
degradation on the 20 percent most impaired or 20 percent clearest days due to future increases
in that PM species, in general each contributing state may justify screening out sources of that
PM species and its precursors for purposes of reasonable progress at that Class I area for the
second implementation period. However, a contributing state should retain such a PM species in
its screening step if a there are only a small number of sources responsible for the PM species
and some of those sources are in-state, because each of those sources could be making a
contribution to impairment that is comparable to the contributions of the more numerous sources
of other PM species. The EPA recommends that states not exclude PM species representing more
than 10 percent of current anthropogenic light extinction at the Class I area on the 20 percent
most impaired days, and that excluded PM species should not total more than 20 percent of
current anthropogenic light extinction.
As noted, the state should make its screening decision based on the absolute light extinction and
the percentage contribution to anthropogenic light extinction on these days, rather than on the
contribution to overall light extinction. For example, while OMC accounts for a high fraction of
light extinction at many western Class I areas on the days with the worst overall haze, it may not
account for a high fraction of light extinction on the most impaired days.
The size of the light extinction contribution from an ambient PM species should be compared to
estimated natural visibility conditions (in light extinction units of Mm"1) as well as to overall
current anthropogenic light extinction. For example, if current anthropogenic light extinction is
dominated by sulfate with a relatively small percentage due to nitrate, but current anthropogenic
nitrate concentrations are nevertheless sizable compared to natural conditions, this indicates that
natural conditions cannot be reached or approached without nitrate reductions.
IMPROVE data can be used directly to develop an extinction budget only for historical period.
When IMPROVE data and photochemical models are combined, it may be possible to construct
light extinction budgets that have a 2028 perspective, and apply these same concepts using those
rather than the extinction budgets based on past IMPROVE data.
99 The EPA recognizes that for some Class I areas there is considerable uncertainty regarding the portion of some
PM species that is due to anthropogenic sources. Accordingly, it may be appropriate to consider the weight of
evidence bearing on this issue, rather than only the estimate of the anthropogenic portion of the PM species that
results from the calculation steps described in section 5 of this guidance.
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The remainder of this section applies to sources of PM species that have not been eliminated
from further consideration.
Selecting a screening threshold level for air quality impacts
A state may define a visibility impact level to serve as a threshold below which no further
analysis of additional control measures will be undertaken in its first analysis of sources and
measures required for reasonable progress.100 At the screening step, we recommend that states
using a visibility-impact threshold compare the selected threshold to both (1) the maximum
source impact within the 20 percent most impaired days and (2) the average source impact across
this set of days multiplied by a constant value.101 If either metric exceeds the state's chosen
visibility-impact threshold, then the state should bring forward the source for a full four-factor
analysis. This will ensure that states analyze those sources that have relatively large impacts on
at least one of the 20 percent most impaired days, as well as those sources with more chronic
impacts on such days.
Regardless of how it has selected its screening threshold for visibility impacts, the state should
demonstrate that its threshold, in combination with other aspects of its screening approach,
results in the screening process selecting for full analysis and decision a combination of major
stationary sources, minor stationary sources and minor/area stationary source categories that
collectively account for a reasonably large fraction of all the in-state major, minor and area
stationary source emissions contributing to any PM species that is a significant portion of the
anthropogenic extinction budget. To show that this coverage has been achieved, a state could
first determine the aggregate light extinction impact of all in-state stationary sources averaged
over the 20 percent most impaired days,102 for example through source apportionment modeling,
and then compare the sum of the impacts from the sources being brought forward from the
screening process to this aggregate impact. Alternatively, a state could assess the individual
impact of each source or group of sources in the state, and compare the sum of the impacts of the
sources being brought forward from screening to the sum of the impacts from the sources not
being brought forward. This demonstration process should be repeated from the perspective of
each Class I area to which sources in the state are linked. The EPA considers 80 percent to be a
reasonably large fraction for this purpose in the second planning period. If an approach does not
reach this 80 percent inclusion level, the threshold for major stationary sources, minor stationary
sources and/or categories of area stationary sources should be reassessed for reasonableness.103 A
more refined approach to demonstrating that a state's screening threshold has brought forward a
100 A second analysis of sources and measures will be required if the initially determined RPG for the most impaired
days is above the URP line. See section 10.
101 Note to reviewers of this draft guidance document: See a footnote in section 4.3 inviting comment on the subject
of using the average impact across the 20 percent most impaired days multiplied by a constant value.
102 This aggregate impact of in-state sources will be a portion of the overall extinction budget at the given Class I
area.
103 This recommendation based on 80 percent of the aggregate light extinction impacts may not be fully applicable
when Q/d is used as a surrogate for visibility impacts. Mechanically, it is possible to compare the sum of the
individual Q/d values for the "above threshold sources" to the sum of the Q/d values for all in-state sources, but this
may not give a good indicator of what fraction of in-state light extinction impacts are attributable to the first set of
sources. A state planning on relying on Q/d, or another surrogate, for screening purposes should consult with its
EPA regional office about the specifics of its planned screening approach.
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reasonably inclusive set of sources is to count in the "capture" assessment only sources that in
2028 will not already have the most effective control technology under other enforceable
requirements. In this refined approach, there would be a sharper focus on the sources with
potential for visibility benefits.
We recommend that the threshold for visibility impact from a source or group of sources be
quantified in units of deciviews (based on a background of natural visibility conditions as
described in section 6.2). However, a state may instead use units of light extinction. A state may
also use a threshold based on a percentage of current aggregate anthropogenic light extinction
from all sources or all in-state sources, or a percentage of the aggregate deciview impacts from
all sources or all in-state sources, rather than an absolute light extinction or deciview threshold.
The EPA recommends, with one exception, that major stationary sources be compared to a
threshold individually, but that minor sources of a similar type be grouped.104 The exception is
that for sources that are clustered geographically near a Class I area, all sources including major
sources should be grouped and aggregated. In discussing with their Regional office which
sources to group and aggregate, states should consider factors such as relative proximity of the
sources, distance to the nearest Class I areas and whether emissions from such sources are likely
to comingle before impacting the nearest Class I area. The EPA recommends that sources that
have been aggregated under the general recommendation or the exception should be screened by
comparing their combined visibility impact to the threshold developed for individual major
sources of the same type, or a lower threshold if needed to reach a sufficient degree of
inclusiveness. For example, combustion engines that drive pumps and compressors that are
minor sources should be aggregated and their impact compared to a threshold no higher than the
one that a state uses for larger individual sources in the same industrial category. Where there is
a basis for separating categories of minor or area sources into geographic subgroups with clearly
different visibility impacts, a state may do so. This may be the case in states with large
dimensions such that sources differ markedly in their distance to relevant Class I areas, or states
with complex transport patterns.
The EPA recommends that a state treat units at one facility in the aggregate.105 Because there
may be numerous small sources that are aggregated with the primary emission units when a state
follows this recommendation, we believe it would be reasonable for a state to choose to not bring
forward from the screening process every unit or piece of emitting equipment at a facility whose
total visibility impact is above the selected screening threshold, provided that the units that are
104 If a threshold for visibility impacts, or for a surrogate for visibility impacts, is applied to individual minor
sources, the threshold selected should be low enough to be consistent with the principle that the overall screening
approach should select for full analysis and decision sources and/or source categories that can reasonably be
concluded to collectively account for a reasonably large fraction of all the in-state emissions contributing to
visibility impairment. Thus, any threshold value needs to be chosen with consideration of how many individual
sources will be tested against it. If there are many sources with small impacts that add up to a "significant" impact,
the threshold should not be so high that each small source is screened out.
105 If instead of following this recommendation a state "breaks up" facilities into their separate units for screening
purposes, the individual units may "screen out" while some of the facilities treated as a whole would not. If this
causes the number of sources that are brought forth for four-factor analysis to be less than necessary to account for a
reasonably large fraction of all the in-state stationary source emissions contributing to any PM species that is a
significant portion of the anthropogenic extinction budget, the screening threshold should be reduced and the
process repeated.
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brought forward account for 80 percent of the visibility impairment from the facility as a whole,
with respect to each affected Class I area.
If a state is following the recommended approach and will not be estimating and considering
visibility benefits along with the four factors, it should demonstrate in its SIP that its screening
threshold has brought forward a reasonably large and prioritized set of sources for four-factor
analysis, in the context of the series of five remaining required periodic SIP revisions. The state
should not select screening thresholds that would exclude sources from four-factor analysis on
the basis that the visibility benefits are outweighed by the cost of compliance.
If the state intends to follow the second alternative approach described in section 4.2, a screening
threshold that "captures" an even higher percentage of aggregate source impacts is appropriate.
The four-factor analysis will consider whether an additional measures for a source that has
relatively small baseline impacts also has a relatively low compliance cost. Sources that have
low baseline impacts because they are physically small or have low (but steady) throughput are
likely to have relatively low costs of compliance in dollar terms. Therefore, a state taking the
second alternative approach should retain sources with relatively small baseline impacts in order
to consider whether additional measures for these sources are necessary to make reasonable
progress, when their possibly small visibility impact is considered along with their possibly small
cost of compliance.
Any threshold justified by comparison to thresholds used by states or the EPA in the past, or by
comparison to visibility benefits from emission control measures that were or were not
incorporated into other SIPs or FIPs, needs to take into consideration differences in the modeling
approaches and metrics used to quantify baseline visibility impacts or visibility benefits
(Lagrangian versus photochemical grid modeling, for example, and differences in the selection
of days). Also, a state should consider that in the second and successive planning periods,
achieving reasonable progress logically should involve examination of sources making smaller
individual impacts than in the first implementation period.
A state should not carry into the second implementation period pre-conceptions formed in the
first implementation period regarding what level of estimated visibility impact is cause for
concern and action. The BART guidelines allowed states to use a deciview value of 0.5 for
visibility impacts (specifically, the 98th percentile impacts predicted by the CALPUFF air quality
model) as the upper limit for a state-selected threshold for subject-to-BART, and most states
used this value. However, there is no similar provision the Regional Haze Rule with respect to
reasonable progress requirements, and this value should not be used as a screening threshold for
reasonable progress purposes. The EPA expects that visibility impacts and available benefits
from many individual sources estimated with the methods and metrics recommended in this
guidance will be notably lower than 0.5 deciview, yet additional control of some of those will be
necessary to make reasonable progress.106 See "Contrast to visibility analysis for the purpose of
ice por exampie the EPA analysis for the Texas FIP used photochemical modeling to estimate visibility benefits
from the scrubber upgrades and retrofits on the 20 percent worst visibility days when compared to average natural
visibility conditions, averaged across these days. At the most impacted Class I areas, the individual scrubber
upgrades were estimated to improve visibility by 0.135 to 0.312 dv. The finalized scrubber retrofits were estimated
to improve visibility, when compared to average natural visibility conditions, at the most impacted Class I areas by
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BART" in section 6.2 for a detailed explanation of the differences between the approach to air
quality modeling and decision making in the context of a BART assessment and the approach to
the same steps in a reasonable progress assessment.
A state should not justify its screening threshold based on it being the limit of what is humanly
perceptible. Progress towards natural visibility conditions will require the accumulation of
reductions in air pollution and associated light extinction that may not be individually
perceptible.
Visibility impacts at multiple affected Class I areas
Air quality modeling will typically produce estimates of a source's impacts at each affected
Class I area. Using this information, a state should repeat the screening step from the perspective
of each source-linked Class I area. That is, the impacts from sources at one Class I area should be
compared to the screening threshold for that area to select the sources that will be subject to four-
factor analysis, and this process repeated for other Class I areas. A source identified for four-
factor analysis based on the screening from the perspective of any of the Class I areas should be
brought forth from the screening step.
If impacts at different areas are estimated using different approaches or if different thresholds are
used for different Class I areas, this should be clearly explained in the presentation of the results,
including the state's rationale for using different approaches or thresholds.
A state may also consider the suite of visibility impacts from one source across affected Class I
areas as a supplement to considering the individual Class I area-specific impacts in this repetitive
way. This may lead a state to bring forward a source that causes relatively small impacts on
multiple Class I areas. The suite of visibility impacts may be summarized and considered by
summing the individual impacts. However, (1) it is not necessarily appropriate to compare such a
sum to the same threshold used in the area-by-area screening process, and (2) the state should
explain to readers of the SIP that the sum of the deciview impacts across multiple Class I areas
cannot be properly compared to any benchmark for whether a visibility effect is perceptible to
people.107
0.087-0.438 dv. See the right-most columns of Tables A.6-2 a-c of the technical support document for this action
(docket item EPA-R06-OAR-2014-0754-0007 at http://www.regulations.gov). Note that this guidance document
recommends consideration of the both the average benefit across the 20 percent most impaired days and the
maximum benefit among these days, which are both different from the specific metric that Is the basis for the values
quoted here. The quoted values are the average visibility benefits across the 20 percent haziest days. The maximum
benefits among these days were about three times higher.
107 In the preamble to the 1997 proposal for the Regional Haze Rule, the EPA stated: "Due to the broad variety of
scenic, atmospheric, and lighting conditions at the mandatory Class I Federal areas across the country, at any
specific time a given area may contain vistas for which slightly more or less than one deciview above background
conditions represents a perceptible impact for the components of the scene. For example, a view of a snow-capped
mountain may be more sensitive to changes in air quality than a view of a forest with the result that less than a 1.0
deciview change is perceptible for that portion of the scene. Conversely, in another scene a deciview change slightly
greater than 1.0 may not be perceptible." 62 FR 41148. The preamble to the 2005 BART Guidelines final rule
included a more extensive discussion of the perceptibility of deciview increments, and that final rule established 0.5
deciview as the upper limit on any threshold a state may establish for purposes of determining that a BART-eligible
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BART-eligible sources should be considered for selection
States should treat BART-eligible sources the same as other reasonable progress sources going
forward. States undertook the BART determination process during the first implementation
period. The BART requirement was a one-time requirement. Although the BART process is not
repeated in subsequent implementation periods, states must include BART-eligible sources in the
screening process and subsequent steps, as part of the requirement to provide for reasonable
progress as described later. The potential re-assessment of BART-eligible sources under
reasonable progress has always been a requirement of the Regional Haze Rule.108 As a practical
matter, the BART process sometimes resulted in minor or no controls on sources, and while this
does not necessarily mean that BART-eligible sources will need to install additional controls for
purposes of reasonable progress, it makes sense to re-assess these sources.
Screening based on an emissions-divided-by-distance (Q/d) threshold
A state may use annual emissions in tons divided by distance in kilometers between a source and
the nearest Class I area, or Q/d, as a surrogate for baseline visibility impact, with appropriate
recognition that this metric is only a rough indicator of actual visibility impact because it does
not consider transport direction/pathway and dispersion and photochemical processes. Before
relying on Q/d as a surrogate for screening purposes, a state should investigate how well Q/d
relates to visibility impacts for the 20 percent most impaired and 20 percent clearest days, in
terms of both the central tendency of the relationship (e.g., the regression line) and the variability
of the relationship (e.g., the error of the regression). This understanding should be developed
through relevant modeling of some actual cases or model plant scenarios, or another appropriate
approach. This understanding is important because if Q/d is a poor surrogate for a particular set
of sources and a Class I area, the results of the screening step may appear to, but not actually,
bring forward for four-factor analysis a set of sources that actually accounts for a large majority
of the in-state impairment at the Class I area. Even if widely accepted for its original purposes,
any Q/d threshold that was used in the past for purposes of screening of sources in the first
implementation period or for possible impacts on air quality related values should not be used in
the screening step without more justification.
Thresholds may be defined on the basis of the sum or weighted sum of emissions of multiple
pollutants if that approach is justified based on the contributions of those pollutants to current
impairment and on how emissions of each pollutant differently translate to ambient impacts.
Thresholds may also be pollutant-specific, with any pollutant able to cause a source to be
selected for four-factor analysis.
When applying a screening step to a group of minor or area sources spread over a large
geographic area, the state may consider the fact that a given quantity of emissions may have a
sources is not subject to BART. 70 FR 39120. The important point for states to make clear in their SIPs, if they in
any refer to a perceptibility benchmark, is that such benchmarks apply to perceptions of a single scenic vista. A
deciview value that is the sum of deciview changes at multiple areas should not be compared to this range or to any
single value within the range.
108 40 CFR 51.308(e)(5), promulgated in 1999 and not revised since then states that "After a State has met the
requirements for BART or implemented emissions trading program or other alternative measure that achieves more
reasonable progress than the installation and operation of BART, BART-eligible sources will be subject to the
requirements of paragraph (d) of this section in the same manner as other sources."
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smaller impact on a particular Class I area when distributed among such sources than when
emitted by a hypothetical single point source located at the centroid of the group. On the other
hand, the group of widely distributed sources may affect more Class I areas.
Screening analysis based on emissions combined with wind patterns
In the first implementation period, some states, through their RPOs, selected sources for four-
factor analysis using an approach that gave each point source a score that took into account the
source's emissions of a PM species or precursor, the daily values of PM species concentrations at
a Class I area as measured by the IMPROVE monitoring site, the distance between the source
and a Class I area and the relative frequency with which each source was linked to the
IMPROVE monitoring site by a wind trajectory.109 Large sources of pollutants contributing more
to light extinction that are near the Class I area and frequently upwind of the Class I area got
higher scores. The score was not in units of light extinction or deciviews. Even so, the EPA
believes that this surrogate approach can be more informative than the Q/d approach. As
recommended above for the Q/d metric, selection of a threshold for use with this sort of scoring
system should be based on knowledge of how the scoring metric relates to visibility impacts for
the 20 percent most impaired days, for example through relevant modeling of some actual cases
or model plant scenarios.
6.4. What other factors may be considered when selecting sources for four-factor analysis?
Screening based on an existing requirement to use the most effective control technology
A source subject to a federally enforceable emission limit that effectively requires it to apply the
most effective control technology for a given PM species or precursor may be screened out of
further analysis for that pollutant. For such a source, a four-factor analysis is unnecessary
because no additional measures are available for inclusion in the LTS. This concept is essentially
the same as the abbreviated BART analysis option that was available for BART-eligible sources
in the first implementation period. See section IV.D, Step 1, paragraph 9 of the BART
Guidelines, which is reprinted in Appendix D.
The EPA also believes that in certain limited situations, in the second implementation period, it
may be reasonable for a state to screen a source out of further consideration without determining
that the emission control technology employed by a source is the most effective available. If an
EGU has been modified (or newly constructed) with highly effective control technology within
the 5 years prior to submission of the SIP, such as year-round operation of flue gas
desulfurization (FGD) with an effectiveness of at least 90 percent or year-round operation of
selective catalytic reduction with an effectiveness of at least 90 percent (in both cases calculating
the effectiveness as the total for the system, including any bypassed flue gas), the state may
choose to not bring the source forward from the screening step. Before doing so, however, the
state should obtain and reference solid information documenting the current level of
effectiveness of the existing emission control system, rather than relying only on its type or
unsupported claims about its effectiveness. The SIP should explicitly list any sources that have
109 VISTAS narrowed its focus to sulfate impacts prior to this step of its analysis, and consequently considered only
the pattern of sulfate concentrations along with SCh emissions.
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been removed from further consideration on this basis and document the technology employed
and the regulatory requirement for that technology.110
Screening based on the four factors
Remaining useful life - If a source is certain to close by 2028 under an enforceable requirement,
a state may consider that to be sufficient reason to remove the source from further analysis and
reasonable progress consideration. This is a recommendation that applies to the second planning
period, in light of the shorter-than-normal interval between the 2021 and 2028 SIP submission
deadlines. As stated in section 8.10, it is acceptable for a state to "start the clock" on the
reasonable time for compliance at the date of EPA approval of the SIP. When this delay, the
reasonable time required to come into compliance and the 7.5-year interval from the SIP due date
of July 31, 2021 to the end of the second implementation period on December 31, 2028, are
considered, the time period in which additional controls could provide a visibility benefit prior to
shutdown of the source would be limited compared to other implementation periods.
Cost of compliance - At the screening step, states are unlikely to have sufficient cost data (and
visibility benefit information) for additional emission reduction measures to be able to conclude
that there is no measure for the source that would be reasonable based on the four statutory
factors alone (and reasonable based on weighing visibility benefits along with the four statutory
factors, for a state following the second alternative approach). Therefore, we recommend that
cost of compliance not be used as a factor in the screening step.
Time necessary for compliance - The time necessary for compliance should not be used for
screening.
Energy impacts - States should generally monetize energy impacts and consider them as part of
the cost factor during the four-factor analysis, so energy impacts should not be used as a separate
screening factor.
Non-air impacts - Non-air impacts, if present, are likely to be complex and should be considered
in the context of the other statutory factors and (if applicable) visibility benefits. States therefore
should not use any threshold for non-air impacts in the screening step.
6.5. Special considerations for particular types of sources
Sources presenting special implementation challenges
A state may have a source category consisting of many small sources, such that inspections and
enforcement on an ongoing basis may appear to be impracticable for technical reasons or would
reasonably be expected to be beyond agency resources during the second implementation period.
We note, however, that many states have successfully addressed some types of small sources,
including wood-burning appliances and construction sites. A state should not screen out a source
type that another state has demonstrated can be practicably regulated.
110 Note to reviewers of this draft guidance document: The EPA requests comment on whether to include this
additional screening mechanism and if so, then what criteria may be appropriate for its inclusion.
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Sources not within state authority
A state does not need to perform a reasonable progress analysis for sources/controls over which
the state does not have regulatory authority. For example, with respect to emission limits on new
mobile sources prior to introduction into commerce, a state may not go beyond adopting
California emission standards and may do that only under certain conditions specified in the
CAA. If a state has sovereign authority to regulate a type of source, the SIP submission may not
simply rely on the fact that no particular state agency has regulatory authority as its justification
for not performing a four-factor analysis for a source.
A state agency submitting a SIP revision on behalf of a state may also not rely on the fact that its
authorizing legislation prohibits it from adopting controls more stringent than required by federal
law or regulation, as a reason for not considering whether additional measures for some sources
are necessary to make reasonable progress.111
Under section 118 of the CAA, federal agencies must comply with all federal, state and interstate
requirements related to the control and abatement of air pollution in the same manner and to the
same extent, as any nongovernmental entity. Thus, federal agencies must follow state-imposed
requirements related to the control and abatement of air pollution, including requirements related
to visibility impairment within Class I areas, "in the same manner, and to the same extent as any
nongovernmental entity." The following discussion of wildland fires, and sections 7.1 and 8.8,
provide specific information about state obligations to consider programs and practices to
address emissions from wildland fires that occur on federally managed (and other) lands.
Wildland fire
For ease of understanding for the reader, this section provides a comprehensive discussion of
how the provisions of the Regional Haze Rule, and other considerations, shape the way a state
should address fires in wildland in its SIP submission for the second implementation period,
going beyond the single topic of screening and addressing both wildland wildfire and wildland
prescribed fire. Later sections of this guidance document on topics other than screening refer to
this discussion.
Fires on wildlands within the U.S. can significantly impact visibility in some Class I areas on
some days and have lesser impacts on a greater number of days. Fires on wildland play an
important ecological role across the globe, benefiting those plant and animal species that depend
upon natural fires for propagation, habitat restoration and reproduction. Wildland can include
forestland, shrubland, grassland and wetlands. Fires on wildland can be of two types: wildfire
(unplanned) and prescribed fire (intentionally ignited for management purposes including
ecosystem health and to reduce the risk of catastrophic wildfires). The EPA anticipates that
wildfires will become more frequent on wildlands in the future due to the natural accumulation
of fuels in the absence of fire, and due to climate change that is leading to increased incidence of
111 The CAA requires states to adopt a LTS that includes emission limitation and such other measures as are
necessary to achieve the national goal of remedying all anthropogenic visibility impairment although a state has
discretion in deciding what controls are necessary for that purpose.
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wildfire, which may necessitate land managers employing prescribed fire more frequently to
manage fuel loads and achieve other benefits as described below.112
Wildfire emissions account for a large portion of direct PM2.5 emissions nationally and can
contribute to periodic high levels of PM2.5 and PMio levels that reduce visibility. Wildfires also
emit volatile organic compounds and NOx, which are precursors to PM2.5 and PMio. Besides
their effect on air quality, wildfires pose a direct threat to public safety. Changes in wildfire risk
and occurrence are closely associated with the lack of periodic fire in fire-dependent ecosystems,
demographic changes and associated infrastructure investment at the margins of wildland and, as
already noted, climate change and climate variability. The threat from wildfires can be mitigated
through management of wildland vegetation. Attempts to suppress wildfires have resulted in
unintended consequences, especially the buildup of fuel loads, which can create a lingering fire
liability that will eventually find resolution, unplanned or planned. Unplanned fires in areas with
high fuel loads present high risks to both humans and ecosystems.
Because wildland wildfires are considered natural events, emissions from wildfires are natural
emissions that contribute to natural reductions in visibility. Thus, the Regional Haze Rule does
not obligate states to select wildland wildfires for four-factor analysis and to then consider
whether measures to reduce emissions from such wildfires are necessary to make reasonable
progress towards natural visibility conditions. Because a state is not required to consider
measures to reduce the visibility impact of wildland wildfires, this document does not include
any recommendations for how the four statutory factors could be applied when considering the
use of prescribed fire to reduce impacts from wildfires. However, the EPA encourages states to
consider that use of prescribed fire may reduce the incidence and severity of wildfires, and
thereby improve the experience of Class I area visitors who visit during a day or a period in
which visibility would otherwise be very adversely affected by a wildfire. In thinking about how
prescribed fire can reduce emissions from wildfires, states may also consider how the use of
prescribed fire can benefit ecosystem health, protect public health from the air quality impacts of
catastrophic wildfires and protect against other risks from catastrophic wildfires. The Regional
Haze Rule gives states the flexibility to provide and plan for the use of prescribed fire, with basic
smoke management practices113 applied, to an extent and in a manner that states believe
appropriate. The EPA is committed to working with states, tribes, FLMs, other federal agencies
and other stakeholders concerning the use of prescribed fire, as appropriate, to reduce the impact
of wildland fire emissions on visibility.
With respect to wildland prescribed fire, as explained below the Regional Haze Rule does not
specifically require regional haze SIPs to include measures to limit emissions from prescribed
fire. By describing the paths that may result in a state not including such measures in its SIP, it is
not our intention to in any way discourage federal, state, local or tribal agencies or private land
owners from taking situation-appropriate steps to minimize emissions from prescribed fires on
wildland, or other types of land. The EPA joins the FLMs in encouraging all land owners and
managers to apply appropriate basic smoke management practices to reduce emissions from
112 An extensive discussion of the background on wildland fire concepts, including actions that the manager of a
prescribed fire can take to reduce the amount of smoke generated by a prescribed fire and/or to reduce public
exposure to the smoke that is generated (i.e., smoke management practices), was presented in the proposed revisions
to the Exceptional Events rule (80 FR 72840, November 20, 2015).
113 Basic smoke management practices are described in Section 7.1.
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prescribed fires. The EPA understands that the FLMs apply these measures routinely and will be
available to consult with other agencies and private parties interested in doing the same. It is
recommended that states consult with DOT, the USDA Forest Service, the USDA Natural
Resources Conservation Service and state forestry agencies when considering requirements for
specific basic smoke management practices. These agencies and other stakeholders can assist in
addressing applicability of the measures in specific ecosystems and situations.
With respect to prescribed fire, section 51.308(f)(2)(iv)(E) of the Regional Haze Rule requires all
states to consider basic smoke management practices. Also, if there is an existing smoke
management program in the state the same section requires the state to consider smoke
management programs, whether or not the rules for the smoke management program have been
incorporated into the EPA-approved SIP.114 The options for a state to meet one or both of these
requirements related to prescribed fire depend on whether prescribed fires have a significant
visibility impact in and downwind of the state.
If in-state prescribed fires do not contribute significantly to visibility impairment on the 20
percent most impaired and 20 percent clearest days at every Class I area to which the state's
sources contribute (some or all of which may be in another state), the state may meet one or both
requirements, as applicable, simply by making this observation. The state should describe in its
SIP narrative the facts and analysis on which it has reached this conclusion. This can be done, for
example, by observing that there is very little in-state prescribed fire activity and/or observing
that light extinction at the Class I area(s) in question due to elemental and organic carbon has had
a level and pattern in recent years that is not consistent with a significant impact from biomass
burning generally or from prescribed fire specifically. In this situation, there would be no need to
subject prescribed fire to any further screening step or to consider measures to reduce emissions
from prescribed fire considering the four statutory factors. While a state in this situation could
nevertheless continue to consider or adopt measures to reduce emissions from in-state prescribed
fires this may not be an efficient use of air agency resources.
If in-state prescribed fires do contribute significantly to visibility impairment at one or more
Class I areas that are linked to the sources in a state, the state may select prescribed fire as a
category for four-factor analysis, but even in this situation it is not required to do so because
there is an alternate path to meeting the requirement to consider basic smoke management
practices and (if applicable) smoke management programs. The EPA is not offering a
recommendation on this point, as the situations among the states and Class I areas are too varied
for a general recommendation. A state may consult with the EPA regional office about its
particular situation and its choice between the two paths described below.
First path. If such a state with a level of prescribed fire that contributes significantly to visibility
impairment at one or more Class I areas does not select prescribed fire as a category for four-
factor analysis, the state must nevertheless show it has considered basic smoke management
114 We do not consider the term smoke management program for the purposes of §51.308(f)(2)(v)(E) to mean
programs that include only seasonal restrictions on burning because of fire safety concerns, voluntary educational
programs designed to raise air quality awareness of potential prescribed fire users, voluntary programs in which land
managers agree to coordinate their prescribed fire activities but are free to withdraw from the program at any time or
some combination of the above. The EPA does support these latter types of programs. We note that the determining
factor is the existence of a smoke management program or programs, not whether the program or programs have
been incorporated into the SIP as enforceable measures or described in the narrative portion of the SIP.
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practices in some reasonable way. The EPA recommends that states with prescribed fire levels
that cause significant visibility impacts due to promote or require appropriate basic smoke
management practices to be applied during prescribed fires on wildland (and other types of land
also). If a state does so, it can show that it has considered basic smoke management practices by
explaining that basic smoke management practices are promoted by state actions or required by
state law. The state can also show that it has considered basic smoke management practices by
explaining why it does not promote or require basic smoke management practices. For example,
the state might document that the large majority of prescribed fire managers already employ
these practices.
In addition, if such a state does not select prescribed fire as a category for four-factor analysis but
there is an existing smoke management program (in the SIP or not) the state must consider
smoke management programs in some reasonable way. The state can do this by explaining why
it is or is not revising the existing smoke management program. A state may but is not required
to include its smoke management program in the EPA-approved SIP. The EPA is not offering a
general recommendation on whether states following this path should consider a smoke
management program as a control measure for prescribed fire. It is recommended that states
consult with DOI, the USDA Forest Service, the USDA Natural Resources Conservation
Service, state forestry agencies and other wildland managers/owners when considering
requirements for new or revised smoke management programs.
Second path. If a state with a level of prescribed fire that contributes significantly to visibility
impairment at one or more Class I areas does select prescribed fire as a category for four-factor
analysis, the state must conduct a four-factor analysis and a decision must be reached regarding
what if any measures to limit emissions from prescribed fire are needed for reasonable progress.
The requirement that a state consider basic smoke management practices as control measures for
prescribed fire applies to such a state (as it does to all states) and in this situation this
consideration logically should be given through the four-factor analysis, by deciding whether and
which basic smoke management practices are needed for reasonable progress. If there is an
existing smoke management program (in the SIP or not) then the state must also consider smoke
management programs. Again, in this situation the required consideration of smoke management
programs logically should be given through the four-factor analysis.
If a state conducts a four-factor analysis of basic smoke management practices and/or smoke
management programs as measures to reduce the visibility impacts of prescribed fire, the EPA
recommends that the state consider the remaining useful life factor by saying that this factor is
not relevant to prescribed fire. The EPA recommends that the state consider the cost of
compliance factor by considering the cost of implementing basic smoke management practices or
a smoke management program. This consideration may be qualitative, especially if the state is
concluding that basic smoke management practices or a smoke management program is needed
for reasonable progress. The EPA recommends that the time required for compliance be
considered by providing regulated parties a reasonable phase-in of any new requirement to apply
basic smoke management practices or to comply with a smoke management program. The EPA
recommends that the non-air quality environmental impacts factor for basic smoke management
practices be considered by considering positive and negative (if any) non-air quality
environmental impacts of applying basic smoke management practices during prescribed fire.
EPA recommends that the non-air quality environmental impacts factor for smoke management
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programs be considered by considering the higher (or lower) risk of ecosystem resource losses
from wildfires that would result from more (or less) restriction on the use of prescribed fire.
If a state selects wildland prescribed fire as a source for four-factor analysis, the state must
conclude this analysis by determining whether any additional measures to reduce emissions from
wildland prescribed fire, such as use of certain basic smoke management practices or compliance
with a smoke management program of a particular design, are necessary to make reasonable
progress. Any such measures must be included in the LTS.
Because some of the basic smoke management practices are difficult to describe with the
specificity needed to make them practically enforceable, it may not be appropriate to conclude
that a SIP requirement for the use of each practice is necessary to make reasonable progress. For
example, one basic smoke management practice is to monitor the effects on air quality due to the
smoke plume from a prescribed fire. "Monitoring" could include ground-based visual
observations, aircraft observations, meteorology-based modeling, fixed or portable air quality
monitoring stations, hand-held monitors, etc. Because the most appropriate monitoring approach
is often situation- and resource-specific, mandating a specific approach is inadvisable. Therefore,
a SIP commitment for a state or local agency to include the use of basic smoke management
practices could be more desirable than a SIP requirement for land managers to use each basic
smoke management practice.
Other natural sources
A state has no obligation to consider controls on natural sources, and such sources do not need to
be selected for four-factor analysis and decision. However, a state is expected to consider
controls on human-influenced sources that are also affected by natural events, for example,
windblown dust from soils that have been disturbed by human activity.
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7. Source and emission control measure characterization (Step 3)
This section addresses how a state should research and document the facts about sources and
emission control measures. Section 8 addresses how these facts should be taken into
consideration in the development of the LTS.
Regional Haze Rule provisions
51.308(f)(2) Long-term strategy for regional haze and reasonably attributable visibility
impairment. Each State must submit a long-term strategy that addresses regional haze
visibility impairment, and if necessary any reasonably attributable visibility impairment
certified by the Federal Land Manager under §51.302(a), for each mandatory Class I
Federal area within the State and for each mandatory Class I Federal area located outside
the State that may be affected by emissions from the State. The long-term strategy must
include the enforceable emissions limitations, compliance schedules, and other measures
that are necessary to achieve reasonable progress, as determined pursuant to (f)(2)(i)
through (vi). In establishing its long-term strategy for regional haze, the State must meet
the following requirements:
(i) The State must consider and analyze emission reduction measures based on 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 major or minor stationary source or group of sources. The State must document
the criteria used to determine which sources or groups of sources were evaluated, and
how these four factors were taken into consideration in selecting the measures for
inclusion in its long-term strategy.
(ii) The State must consider the uniform rate of improvement in visibility, the emission
reduction measures identified in (f)(2)(i), and additional measures being adopted by other
contributing states in (f)(2)(iii) as needed to make reasonable progress towards natural
visibility conditions for the period covered by the implementation plan.
(iii) The State must consult with those States which may reasonably be anticipated to
cause or contribute to visibility impairment in the mandatory Class I Federal area.
(A) Contributing States. Where the State has emissions that are reasonably anticipated to
contribute to visibility impairment in any mandatory Class I Federal area located in
another State or States, the State must consult with the other State(s) in order to develop
coordinated emission management strategies. The State must demonstrate that it has
included in its implementation plan all measures necessary to obtain its share of the
emission reductions needed to provide for reasonable progress towards natural visibility
conditions in the mandatory Class I Federal area located in the other State or States. If the
State has participated in a regional planning process, the State must also ensure that it has
included all measures needed to achieve its apportionment of emission reduction
obligations agreed upon through that process.
(B) States affected by contributing States. A State with a mandatory Class I Federal area
must consult with any other State having emissions that are reasonably anticipated to
contribute to visibility impairment in that area regarding the emission reductions needed
in each State to provide for reasonable progress towards natural visibility conditions in
that area. If the State has participated in a regional planning process, the State must
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ensure it has included all measures needed to achieve its apportionment of emission
reduction obligations agreed upon through that process.
(iv) The State must consider, at a minimum, the following factors in developing its long-
term strategy:
(A) Emission reductions due to ongoing air pollution control programs, including
measures to address reasonably attributable visibility impairment;
(B) Measures to mitigate the impacts of construction activities;
(C) Emissions limitations and schedules for compliance to achieve the reasonable
progress goal;
(D) Source retirement and replacement schedules;
(E) Basic smoke management practices for prescribed fire used for agricultural and
wildland vegetation management purposes and smoke management programs as currently
exist within the State for these purposes;
(F) Enforceability of emissions limitations and control measures; and
(G) The anticipated net effect on visibility due to projected changes in point, area, and
mobile source emissions over the period addressed by the long-term strategy.
7.1. What emission control measures should states consider for sources selected for four-
factor analysis?
In general
For sources brought forward from the screening step, a state should identify and consider all
available control measures that are technically feasible for the source or source type in question.
Continued relevance of the BART Guidelines for stationary sources
Many of the statements in the BART Guidelines continue to be relevant as recommendations for
how a state should evaluate and select emission control measures for stationary sources.
Appendix D indicates which parts of the BART Guidelines continue to be relevant in this way.
However, the BART Guidelines were not developed with any intention that they would address
mobile sources or non-industrial sources, such as wildland prescribed fires.
Measures for a group of sources
For groups of sources, the potential control measures may vary for different sources within the
group because of differences in source design or method of operation, existing controls or other
factors. If a state does not identify potential control measures and establish facts relevant to the
four factors on a source-specific basis within the group, it should nevertheless give appropriate
consideration to the range of circumstances at the individual sources. Subdividing the larger
group and analyzing a representative source from each subgroup, or using a model plant
approach, may be useful.
Work practices
In considering what emission control measures may be necessary to make reasonable progress,
states should not overlook the potential for emission reductions through improved work
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practices. States should give emission limits first preference for achieving better emission control
performance. However, a state should consider mandatory work practices if there is evidence
that current source operations can be revised for better emission control that cannot be achieved
via numerical limits on emissions or emissions-related operating parameters. Work practices can
also supplement numerical limits on emissions.115
Replacement and retrofit
A state should consider early replacement of emissions-generating equipment with newer,
cleaner versions of that equipment, as well as the option of applying retrofit emission controls to
such old equipment. In addition, a state should consider requiring the replacement of emission
controls that have exceeded the original expectation for their useful life with more effective
controls. This is particularly the case with older internal combustion engines, including older
combustion turbines, for which emission standards have recently been made more stringent.
Fuels
For sources that are capable of using multiple fuels, reasoned decision making requires states to
consider increasing or mandating the fuel with inherently lower SCh, NOx and/or PM emissions.
The EPA recognizes that there can be a variety of valid reasons why mandating the use of one
fuel may be unreasonable, such as possible fuel supply emergencies, but a state should consider
more restrictions or conditions on the use of fuels with higher emissions. The EPA strongly
recommends that states consider tighter restrictions on the sulfur content of primary and back-up
fuels.
Year-round operation of controls
For any NOx source brought forward from screening, a state should consider requiring year-
round operation of any installed SCR and SNCR units (e.g., those that currently operate only
during the ozone season). A state following the recommended or the second alternative approach
to consideration of visibility will have considered whether nitrate significantly contributes to
visibility impairment; see section 6.3. A state following the second alternative approach will also
weigh visibility benefits from continuous operation of the SCR or SNCR units with the four
statutory factors, see section 8.2.
Operating restrictions, including shutdowns
The Regional Haze Rule permits but does not require states to consider operating restrictions
(e.g., limits on the hours of operation, fuel input or product or service output) as potential control
measures that are necessary to make reasonable progress. Although the EPA and states have
generally not imposed restrictions on source operation in regional haze implementation plans, we
recognize that some plans included such restrictions. This generally occurred when a source
owner/operator elected to curtail or eliminate the source's operation rather than comply with a
technology-based measure. If a state chooses, it may adopt a similar approach this
implementation period by including an enforceable limit on source operations in the SIP rather
115 The FIP for Arizona included work practices for several affected sources, in addition to emission limits. 79 FR
52420, September 3, 2014.
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than an enforceable emission limit that would require the installation and use of a control
technology.
Energy efficiency and renewable energy measures
Energy efficiency and renewable energy programs can reduce emissions that contribute to
visibility impairment at Class I areas by reducing the need for energy generated by sources that
emit visibility-impairing pollutants. We encourage states to consider adopting or strengthening
such programs, to make use of available EPA guidance when doing so and to consult with their
EPA regional offices on this subject. The Regional Haze Rule does not require a state to
incorporate its energy efficiency or renewable energy program into the SIP in enforceable form.
Section 9.3 discusses whether the effects of such programs should be incorporated into the RPGs
for 2028.
Redefinition of the source
A state may conclude that it would be unreasonable to require changes in the design or operation
of an existing source that are so fundamental to source design and operation that, in the context
of pre-construction permitting, the changes would constitute "redefining the source." For
example, the Regional Haze Rule does not require states to consider retrofitting an existing coal-
fired boiler so that it can combust natural gas or replacing an existing coal-fired boiler with a
stationary combustion turbine.
Separable control measures
A state should not reject a bundle of control measures that have the potential to be implemented
independently. For example, if there is a fuel switching option and an after-treatment option, a
state should assess each option individually, as well as the combination of the two, to determine
whether they are necessary to make reasonable progress.
Control efficiency and emission limits
In order to define a control measure with sufficient specificity to assess its cost and potential for
emission reductions, the state should specify and consider the range of control efficiencies that
the measure is capable of achieving. For example, when evaluating a flue gas desulfurization
system to reduce SCh emissions, the state should consider both a system capable of achieving a
90 percent reduction in SCh emissions as well as a more advanced system capable of achieving a
97 or 98 percent reduction. The state should not limit its analysis to either an unrealistically high
and prohibitively expensive control efficiency or to a control efficiency that is substantially
lower than has been achieved at other sources. In addition to considering a range of control
efficiencies, the state may need to evaluate an emission limit or averaging period to have
sufficient information to conclude whether or not the control measure is necessary to make
reasonable progress. In such a case, the parameters of the emission limit that inform the four-
factor analysis and control selection should be the same as those that are ultimately adopted into
the LTS.
Prescribed fire as a measure to moderate the impact of wildland wildfires
See the discussion of wildland fire in Section 6.5.
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Basic smoke management practices for wildland prescribed fires
See the discussion of wildland fire in Section 6.5.
Basic smoke management practices are types of actions that the manager of a prescribed fire can
take to reduce the amount of smoke generated by a prescribed fire and/or to reduce public
exposure to the smoke that is generated. These practices are described in more detail in a
publication issued by federal agencies that use prescribed fire as part of their land management
programs.116 Table 7-1 provides a summary of six common basic smoke management practices.
Table 7.1. Summary of Basic Smoke Management Practices, benefit achieved with
the practice and when it is applied"
Basic Smoke
Management Practice
Evaluate Smoke Dispersion
Conditions.
Monitor Effects on Air
Quality.
Record-Keeping/Maintain
a Burn/Smoke Journal.
Communication - Public
Notification.
Consider Emission
Reduction Techniques.
Share the Airshed -
Coordination of Area
Burning.
Benefit Achieved with the
Basic Smoke Management
Practice
Minimize smoke impacts.
Be aware of where the smoke is
going and degree it impacts air
quality.
Retain information about the
weather, burn and smoke. If air
quality problems occur,
documentation helps analyze and
address air regulatory issues.
Notify neighbors and those
potentially impacted by smoke,
especially sensitive receptors.
Reduce emissions through
mechanisms such as reducing
fuel loading can reduce
downwind impacts.
Coordinate multiple burns in the
area to manage exposure of the
public to smoke.
When the Basic Smoke
Management Practice is
Applied -
Before/During/After the
Burn
Before, During, After.
Before, During, After.
Before, During, After.
Before, During.
Before, During, After.
Before, During, After.
a Elements of these basic smoke management practices could also be beneficial to apply to wildfires for areas likely
to experience recurring wildfires.
Smoke management programs for wildland prescribed fire
See the discussion of wildland fire in Section 6.5.
116 USDA Forest Service and Natural Resources Conservation Service, Basic Smoke Management Practices Tech
Note, October 2011, http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdbl046311.pdf.
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One of the distinguishing elements of a smoke management program is a provision for periodic
program evaluation. We recommend that every smoke management program include a plan for
this periodic assessment by the responsible authorities that provides for input from federal, state
and private land managers, affected communities and other stakeholders. This evaluation should
include an assessment of whether the program is meeting its goals regarding improving
ecosystem health and reducing the damaging effects of catastrophic wildfires. Section 51.308(g)
of the Regional Haze Rule requires the periodic progress report on a state's regional haze
program to include a summary of the most recent periodic assessment of any smoke management
program that is part of the LTS including conclusions that were reached in the assessment as to
whether the program is meeting its goals regarding improving ecosystem health and reducing the
damaging effects of catastrophic wildfires.
7.2. Statutory Factor #1 - The cost of compliance
Annualizing compliance costs
The first step in any cost analysis is to estimate the capital and annual operating and maintenance
(O&M) costs of the control measure in light of the design parameters of the source. States should
combine and annualize these costs over the expected life of the source or the control equipment,
whichever is shorter.
States should calculate O&M costs for new emission controls on an incremental basis, i.e., by
comparing them to current O&M costs. This will matter, for example, if the installation of a new
control will involve the discontinuation of a current operating cost or an increase in the operating
cost of existing equipment at the source.
In some instances, the installation of a new control may require the removal or discontinuation of
existing emission controls for engineering reasons or business reasons. Such situations present
special issues regarding the annualization of capital costs. States should consult with their EPA
regional offices for advice.
Air Pollution Control Cost Manual accounting principles
The BART Guidelines require states to make cost estimates for large coal-fired EGUs based on
the EPA Air Pollution Control Cost Manual (Control Cost Manual) where possible.117 For
purposes of the second implementation period, the EPA strongly recommends that states adhere
to the accounting principles and generic factors from the Control Cost Manual, in particular
those presented below. These principles and generic factors are explained in more detail in the
chapter 2 of section 1 of the Control Cost Manual. We also recommend the Control Cost Manual
as a source of generic cost estimates and algorithms. As of the date of this guidance, the EPA is
engaged in a 3-year process to update the Control Cost Manual.118
117 EPA Air Pollution Control Cost Manual, Sixth Edition, EPA/452/B-02-001, January 2002. The EPA is in the
process of updating portions of the Control Cost Manual. As draft or final updated chapters are available, states
should follow the recommendations in those rather than in the 6th Edition. See
http://www3. epa.gov/ttn/ecas/costmodels. html.
118 http://www3.epa.gov/ttn/ecas/models/TimelineU-18-2014.pdf 'describes the scope and schedule for this update
effort.
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• Use of the OMB-approved discount rate to annualize costs, rather than a market interest
rate or "real" interest rate. The discount (or interest) rate in this case can act as a proxy of
the opportunity cost of capital, though this rate is adjusted for inflation to be consistent
with the Control Cost Manual methodology as mentioned below in this section.
• Inclusion/exclusion of certain types of costs as capital and annual costs. See chapter 2 of
section 1 of the Control Cost Manual for a complete list.
• Exclusion of income tax effects from the costs of control.
• Exclusion of owners' costs from the costs of control.
• Exclusion of allowance for funds used during construction (AFUDC), i.e., the borrowing
or opportunity cost of the funds being invested, from the costs of control. AFUDC is not
allowed under the methodology for estimating costs found in the Control Cost Manual
because the Control Cost Manual methodology requires estimates of costs expressed in
constant dollars for the base year of estimation. This methodology is called an
"overnight" methodology because capital costs estimated in such an approach do not
include escalation of costs during construction nor interest costs from financing. Thus,
financing costs during construction such as AFUDC are not part of the cost of control.
• Values for the useful life of particular types of emission control equipment unless source-
specific circumstances clearly indicate that a different value is more appropriate.
• Use of real (or inflation adjusted) cost values. Including inflation in control cost estimates
is not consistent with the methodology for estimating costs in the Control Cost Manual.
Costs should be estimated indexed to the base year of estimation, which should be a year
close to when the analysis takes if at all possible. Discussion and the rationale behind this
issue can be found in chapter 2 of section 1 of the Control Cost Manual (either current or
newly revised version).
The EPA strongly recommends that states adhere to these aspects of the Control Cost Manual to
ensure that apples-to-apples comparisons of different controls options for the same source, and
similar control options across different sources, can be made. This type of consistency is
necessary to support informed public comment and reasoned decision making. Also, state-level
review of source-prepared cost estimates and EPA review of SIPs will be more efficient if states
use these familiar principles and generic factors. States that wish to deviate from these principles
and factors must explain their reasons for doing so and adequately justify any alternative
approaches.
Use of generic cost estimates for particular types of control equipment
States may reduce the time and effort required to quantify control costs, with some loss of
precision, by using generic cost estimates or estimation algorithms for particular types of control
equipment.
The Control Strategy Tool, or CoST, is a software tool that states can use as a source of cost
estimates primarily for non-EGUs. CoST replaces AirControlNet, which the EPA previously
used to estimate the costs of some national rules affecting non-EGUs, including the 1999
Regional Haze Rule. CoST is best applied for estimates of average or typical control costs rather
than costs for a particular source. Even so, the cost estimates for individual control measures,
which are found in the control measure documentation for CoST, may be useful as range-finding
or preliminary estimates. The cost equations and control measure database documentation reports
for CoST at http://www3.epa.gov/ttn/ecas/cost.htm are useful references.
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Use of source-specific cost estimates, such as vendor quotes
Source-specific estimates prepared by knowledgeable engineering professionals provide more
reliable information than generic cost estimates, As a result, states should exercise caution before
rejecting controls based on generic cost estimates. In addition, when considering source-specific
estimates, states should place greater weight on vendor quotes that represent an offer to enter a
contract at that price than estimates without an offer to enter a contract. States should limit their
consideration of vendor- or expert-supplied cost estimates (those that are not quotes) to those
endorsed by a licensed professional engineer. However, significant care should be used when
using a vendor-supplied cost estimate to ensure that its treatment of costs related to planning,
outages, installation and additional operation and maintenance activities is consistent with the
principles in the Control Cost Manual; adjustments or exclusions may be needed to achieve this
consistency. If a quote or opinion prepared for one source is adopted or adapted to another
source, the source for which the original cost estimate was made must be representative/relevant
to the source in question. States may be able to require sources to provide confidential
information that will allow better source-specific cost analyses, similar to the EPA's CAA
section 114 authority.
When using source-specific cost estimates not prepared in accordance with the Control Cost
Manual, states should review and adjust the estimates as necessary to achieve as much
consistency as possible with the accounting principles and generic factors identified above.
Examples of such adjustments can be found in the EPA's cost analyses for a number of FIP
actions during the first implementation period.119
Every source-specific cost estimate used to support a four-factor analysis must be well
documented for purposes of public comment and EPA review.
Calculating emission reduction for use in calculating cost/ton
The emission reduction used as the denominator for the cost/ton metric should be the annual tons
of reduction from implementation of the additional measure.
The recommendations in section 6.2 regarding emission values to be used in estimating visibility
impacts and visibility benefits apply as well to the emissions values to be used in calculating the
cost/ton metric.
Differences within a group of sources
The cost of compliance expressed in dollars per ton may vary for different sources within a
group of relatively small but well-characterized sources in the same market or industry sector
due to age or design differences. For example, within a group of stationary source internal
combustion engines, replacing 5-year old engines with cleaner models may have a relatively high
cost/ton value compared to replacing 20-year old engines because the owners of the older
engines face replacement costs fairly soon in any case. In other situations, factors other than
119 See the EPA's Wyoming regional haze action, 79 FR 5032, January 30, 2014, NOX BART and RP analyses,
Tables 2 through 17, pp. 5039-5044, docket number EPA-R08-OAR-2012-0026, Cost of NOX Controls on Wyoming
EGUs, document number EPA-R08-OAR-2012-0026-0241.
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remaining useful life could create cost/ton differences that states should consider in a reasonable
manner.
7.3. Statutory Factor #2 - Time necessary for compliance
For stationary sources, the provisions of the BART Guidelines regarding this factor are relevant
to reasonable progress analyses. Prior experiences with the planning and installation of new
emission controls is the best guide to how much time a particular source will reasonably need for
compliance. However, source-specific factors should also be considered. Sections 8.land 8.2
discuss how a state should give consideration to the time necessary for compliance, once that
time is determined.
7.4. Statutory Factor #3 - Energy and non-air environmental impacts
Energy impacts
For stationary sources, the provisions of the BART Guidelines regarding this factor are relevant
to reasonable progress analyses. The energy impacts of an emission control measure are a matter
of engineering, so prior experience at similar sources will be informative. The Control Cost
Manual provides advice on estimating energy requirements or savings for some situations. States
may consider energy impacts in terms of kilowatt-hours or mass of fuels used. States should
focus their analysis on direct energy consumption at the source rather than indirect energy inputs
needed to produce raw materials for the construction of control equipment.
Non-air environmental impacts
For stationary sources, the provisions of the BART Guidelines regarding this factor are relevant
to reasonable progress analyses. When there are significant potential non-air environmental
impacts, characterizing those impacts will usually be very source-specific, so no general
guidance is offered in this document. Other guidance intended for use in assessments under the
National Environmental Policy Act may be relevant.
The EPA considers GHG emissions to be an air impact. Therefore, a state is not required to
consider GHG emission impacts, or climate change effects, in the development of its LTS.
However, we encourage states to consider GHG impacts. Some measures that would reduce
emissions that contribute to visibility impairment will also reduce GHG emissions, such as
measures that reduce the use of energy produced from combusting fossil fuels with relatively
high GHG emissions. Where a measure necessary to make reasonable progress towards natural
visibility conditions would increase GHG emissions, we encourage states to work to harmonize
visibility and climate change objectives, such as by identifying GHG emission offsets that can be
implemented as well.
7.5. Statutory Factor #4 - Remaining useful life of the source
Stationary sources
For stationary sources, the provisions of the BART Guidelines regarding this factor are relevant
to reasonable progress analyses. Generally, the remaining useful life of the source itself will be
longer than the useful life of the emission control measure under consideration unless there is an
enforceable requirement for the source to cease operation sooner. Thus, states should normally
use the useful life of the control measure to calculate emission reductions, amortized costs and
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cost per ton. However, if there is an enforceable requirement for the source to cease operation by
a date before the end of what would otherwise be the useful life of the control measure under
consideration, then states should use the enforceable shutdown date to calculate remaining useful
life.
The Control Cost Manual provides guidance on typical values for the useful life of various
emission control systems used at stationary sources. The EPA recommends that states use these
values rather than relying on the values used in the first implementation period. The EPA is
reviewing these values as part of the update to the Control Cost Manual.
Engines
Some types of mobile and stationary internal combustion engines are typically replaced at
specific intervals that depend on their type and application. For these sources, states may rely on
a reasonable estimate of when the engine will be replaced in the normal course of business (or
personal use) instead of an enforceable requirement to cease operation. The shorter the remaining
useful life of an engine, the higher the cost per ton of a control measure will be. However, some
types of engines typically are rebuilt or reconditioned rather than being completely replaced. For
such engines, states should take care when calculating the useful life of control measures. For
some measures, such as exhaust after treatment systems that are not closely integrated with the
engine, the useful life of the measure may extend beyond the next engine rebuild or
reconditioning.
7.6. Reliance on previous analysis and previously approved approaches
It may be appropriate for a state to rely on the results of a previous analysis of a factor, for
example information developed in the first planning period on the availability, cost and
effectiveness of controls for categories of sources, if the previous analysis was sound and no
significant new information is available. If doing so, the state should explain why it concludes
that no important facts have changed in a way that would require an update. The state should also
consider whether newly available or newly recommended analytical approaches would affect the
characterization of the factual situation. In other words, not all conclusions on factual matters
and approaches to determining factual matters used in the first implementation period can be
presumed to be appropriate for the development of SIPs in the second implementation period. A
state relying on previously developed information must adequately address any adverse
comments on the state's previous factual information that were made during the state's public
comment process for the SIP for the first implementation period, during the public comment
process on the EPA's proposed action on that SIP, during the public review of a subsequent
progress report or during the public comment process on the EPA action on the subsequent
progress report.
A state should apply a still-valid result of a previous analysis of a factor consistently with the
requirements of the 2016 Regional Haze Rule and the recommendations in this guidance
document, which may be different than the way the state or another state applied that result in the
first implementation period. For example, some states noted that the EPA chose a benchmark
cost/ton value of $500/ton for the purpose of setting state-wide emission allowances for EGUs
under a FIP to address the CAA requirement regarding interstate transport affecting NAAQS
attainment and maintenance. In the second implementation period, under the recommendations
provided in Section 8.1 and 8.2 of this document, a state could use this value to establish that a
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measure for EGUs with the same cost/ton was within the range of reasonableness for the cost of
compliance and thus cannot be eliminated as a measure needed for reasonable progress based on
the cost of compliance. A state should not rely on this value to conclude that a measure for EGUs
with a higher cost/ton value should be rejected as not needed for reasonable progress.
7.7. Continued relevance of the BART Guidelines
Many of the statements in the BART Guidelines continue to be relevant as recommendations for
how a state should assess facts related to the four statutory factors. Appendix D indicates which
parts of the BART Guidelines continue to be relevant in this way.
7.8. Consideration of information provided through interagency consultation and public
comments
Prior to the opening of a public comment period on the draft SIP revision, states should
document that they have considered EPA and FLM comments on the factual information they
developed and previously shared with the EPA and the FLM(s). This will assure the public that
the state has received and considered this input and help establish a record showing that a state
has used reasoned decision making. Also, states should consider public comments containing
relevant factual data and recommendations regarding available control measures. Public
comments may present data developed in ways that depart from the guidance in this document.
States should not dismiss such publicly provided data simply because they were not developed
according to this guidance document. Rather, states should consider what aspects of the data are
relevant and valid, following the concepts presented in this guidance document.
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8. Decisions on the content of the LTS (Step 4)
Regional Haze Rule provisions
51.308(f)(2) Long-term strategy for regional haze and reasonably attributable visibility
impairment. Each State must submit a long-term strategy that addresses regional haze
visibility impairment, and if necessary any reasonably attributable visibility impairment
certified by the Federal Land Manager under §51.302(a), for each mandatory Class I
Federal area within the State and for each mandatory Class I Federal area located outside
the State that may be affected by emissions from the State. The long-term strategy must
include the enforceable emissions limitations, compliance schedules, and other measures
that are necessary to achieve reasonable progress, as determined pursuant to (f)(2)(i)
through (vi). In establishing its long-term strategy for regional haze, the State must meet
the following requirements:
(i) The State must consider and analyze emission reduction measures based on 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 major or minor stationary source or group of sources. The State must document
the criteria used to determine which sources or groups of sources were evaluated, and
how these four factors were taken into consideration in selecting the measures for
inclusion in its long-term strategy.
(ii) The State must consider the uniform rate of improvement in visibility, the emission
reduction measures identified in (f)(2)(i), and additional measures being adopted by other
contributing states in (f)(2)(iii) as needed to make reasonable progress towards natural
visibility conditions for the period covered by the implementation plan.
* * *
(vi) The State must consider, at a minimum, the following factors in developing its long-
term strategy:
(A) Emission reductions due to ongoing air pollution control programs, including
measures to address reasonably attributable visibility impairment;
(B) Measures to mitigate the impacts of construction activities;
(C) Emissions limitations and schedules for compliance to achieve the reasonable
progress goal;
(D) Source retirement and replacement schedules;
(E) Basic smoke management practices for prescribed fire used for agricultural and
wildland vegetation management purposes and smoke management programs as currently
exist within the State for these purposes;
(F) Enforceability of emissions limitations and control measures; and
(G) The anticipated net effect on visibility due to projected changes in point, area, and
mobile source emissions over the period addressed by the long-term strategy.
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8.1. How should a state that is not considering visibility benefits select measures for
inclusion in the LTS?
Note on applicability of this subsection
Section 8.1 applies to states that are following either the recommended approach or the first
alternative approach to developing a LTS described in section 4.2. Under both approaches, states
do not weigh the visibility benefits of potential emission control measures along with the four
statutory factors. While some of the guidance in this section is identical to the guidance in
section 8.2, which applies to states that are following the second alternative approach, other
issues discussed in this section differ from the second alternative approach in important ways.
See section 4.2 for the EPA's recommendations regarding the consideration of visibility in
developing the LTS.
8.1.1. The meaning of "necessary to make reasonable progress"
CAA section 169A(b)(2) requires states to develop a SIP that includes "emission limits,
compliance schedules and other measures as may be necessary to make reasonable progress
toward meeting the national goal." As stated in section 4.4, the EPA recognizes that determining
whether a measure is necessary to make reasonable progress is ultimately a fact-specific inquiry
regarding a particular source or source category and the affected Class I areas that takes place in
the context of legal requirements, input from stakeholders, and reasoned judgment. In our actions
on SIPs and FIPs in the first implementation period, we did not apply any general formula or
bright-line test to evaluate state decisions or reach our own decisions as to what measures are
necessary to make reasonable progress, and we are not recommending any such formula in this
guidance. This does not mean, however, that a state has unbounded flexibility or discretion in its
decision making. States must use reasoned decision making and give due consideration to well-
developed factual information and public comments.
We recommend that for each source, group of sources or source category that has been selected
for four-factor analysis, a state following the recommended approach or the first alternative
approach include in its LTS the most effective measures that are reasonable to require in light of
the four factors alone. This recommendation has two important features. First, we recommend
that a state following the recommended approach reject a control measure only when one of the
four statutory factors, or some combination of the four factors, makes it unreasonable to require
the control. The state should not use the information regarding a source's visibility impacts
developed at the screening state in evaluating the four factors. Second, we recommend that the
state select the most effective emission reduction measure for each source that is within a range
of reasonableness.
We expect that the outcome of this decision-making process will most often depend on the costs
of compliance. States should consider the remaining useful life of a source by annualizing the
costs of compliance over the useful life of the control or the remaining useful life of the source,
whichever is shorter. States should consider the time necessary for compliance by setting a
compliance deadline that provides a reasonable amount of time for the source to implement the
measure. States should consider energy and non-air quality impacts primarily as components of
the costs of compliance. Only in unusual situations will energy or non-air environmental impacts
be such significant considerations that they influence the decision for or against the control
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measure under consideration. As a result, the discussion in this section focuses on providing
guidance regarding when the state should consider the costs of compliance to be within a range
of reasonableness. The other three statutory factors are explicitly discussed in sections 8.3 (time
necessary for compliance), 8.4 (energy impacts), 8.5 (non-air environmental impacts) and 8.6
(remaining useful life). These discussions apply to all states regardless of the approach taken to
considering visibility.
To determine whether a control measure is reasonable, we recommend that states compare the
costs of compliance with the measure (using the cost/ton metric) to the costs that other similar
sources have had to bear (using the same metric) in other regulatory actions. Consistent with the
guidance in this section, states may determine in the second implementation period that the costs
of compliance associated with a given control measure are unreasonable and not include the
measure in the LTS without contradicting the national goal. In future implementation periods,
newer technology may reduce the costs of compliance for certain sources or sources that are
expensive to control may retire.
8.1.2. Recommendation to rely on the cost/ton (cost-effectiveness) metric and comparisons
to past regulatory actions
We recommend that a state consider the costs of compliance by comparing the cost/ton metric
for a control measure to the same metric from other regulatory actions, in the manner explained
in this section. If the cost/ton of a measure under consideration is about the same as for a
measure that has been previously required for a similar source, then the state should conclude
that measure under consideration has a reasonable cost of compliance and should not eliminate
the measure as being needed for reasonable progress based on the cost of compliance.120 If the
measure under consideration has a cost/ton higher than any measure that has been previously
required, the state should do a deeper and more source-specific assessment of whether the cost of
compliance is nevertheless within the reasonable range. The fact that a previous regulatory action
rejected a measure with a similar cost/ton should not by itself be taken as sufficient support for a
conclusion that the cost of compliance for the measure is outside the reasonable range; the
rejection by the regulatory authority may have considered factors other than the cost of
compliance and/or there may be other past actions that would support a conclusion that the cost
of compliance is reasonable. If a state chooses to use another approach to assessing the
reasonableness of the costs of compliance, it should explain and document why its chosen
method is more appropriate than relying on the cost/ton metric and comparisons to other
regulatory actions in this way.
The absolute capital and annual operating and maintenance costs of compliance of available
emission control measures vary with a source's operating scale. Therefore, it is more meaningful
to compare the cost-effectiveness (cost/ton) of a potential control measure to the cost/ton of
measures required in the past for other sources than to compare absolute costs of compliance
across sources because the cost/ton metric helps to normalize for differences in operating scale.
The EPA believes that comparisons with regulatory actions on other sources on the basis of the
cost/ton metric is an appropriate and reasonable way to evaluate potential new control measures.
120 In comparing the cost/ton of a measure under consideration to past regulatory actions affecting a group of
sources, a state should consider the cost/ton of the past action for individual sources, not the average cost/ton across
the group. There typically will have been some affected sources with a higher cost/ton than the average.
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Specifically, if the cost/ton of a potential control measure is less than or comparable to the
cost/ton values from previous regulatory actions, states should consider the costs of compliance
to be reasonable. This concept is further discussed in section 8.1.3.
However, the cost/ton metric may not always be sufficient to put the costs of compliance into
perspective relative to the operating scale of a source. For example, when a source is already
operating emission controls with an intermediate or high degree of effectiveness, the potential
emission reduction from applying better control technology may be relatively small. In these
cases, the cost/ton may be relatively high, even if the absolute cost of the control is not
unreasonable in light of the operating scale of the source. Therefore, in situations where the
cost/ton is outside the range of previous regulatory actions, states should also consider the
absolute cost of control compared to the operating scale of the source to determine whether the
costs of compliance are actually unreasonable.
Another situation that may result in a high cost/ton value is where an uncontrolled or lightly
controlled source operates relatively few hours per year or with a relatively low hourly
throughput compared to its capacity. In such a situation, the cost/ton value inherently accounts
for the actual operating scale of the source and can be relied upon to reach a conclusion
regarding reasonableness, unless other considerations prevent such reliance.
Most retrofit controls that states will consider in the second implementation period will reduce a
single pollutant that affects visibility. For example, switching to a lower sulfur coal or fuel oil
will predominantly reduce emissions of SCh. In these cases, the cost/ton metric for the measure
only needs to reflect the emission reductions of the predominantly affected pollutant. However,
other control measures may significantly reduce multiple pollutants that affect visibility.
Examples include operating restrictions, source closures, engine replacement or switching from
coal to natural gas. When a control measure reduces multiple pollutants that affect visibility,
states must allocate the costs of control between pollutants or sum dissimilar pollutants to
calculate the scalar cost/ton metric. In these situations, states should clearly describe the
approach to allocation or summing in the SIP and at a minimum provide a qualitative analysis of
how other allocation approaches would change the analysis.
Once a state has estimated the cost/ton of a measure under consideration, it should consider past
conclusions that the state itself, other states and the EPA have made regarding whether the costs
of compliance would be unreasonable. If the state determines that that the costs of compliance
would be unreasonable despite a cost/ton value that falls within the general range of previous
regulatory decisions by the same state, other states and the EPA for sources with sufficiently
similar features (other than differences in size), then the state must explain how important
distinguishing factors influenced its determination.
For states following the recommended approach or the first alternative approach, the
environmental objective of the control measure is not relevant to whether the costs of control can
reasonably be borne by the source. Therefore, states should not limit their consideration to
previous state and EPA actions within the regional haze program. States should also consider
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past state and EPA decisions about the reasonableness of certain cost/ton levels in other CAA
programs.121
The EPA may separately provide states with information on the costs of compliance of control
measures previously required by states and the EPA in the regional haze program to assist states
in making comparisons. Meanwhile, Appendix B of this document provides citations to EPA
actions on SIPs in the first implementation period and can be used to research specific past
examples of how states and the EPA have treated the costs of compliance factor. In addition, the
EPA's RACT/BACT/LAER Clearinghouse contains information on the cost/ton associated with
many past regulatory actions that imposed a cost of compliance.
In comparing cost/ton values associated with past regulatory actions and cost/ton values
developed more recently for measures under consideration for the second implementation period,
a state should consider whether each value reflects the principles in the Control Cost Manual and
how changes in capital and operating and maintenance costs in the period between the dates on
which the two values were developed affects the comparison.
In summary, when the cost/ton of a measure would be in the range of cost/ton values that have
been incurred multiple times by sources in generally similar situations, states should presume
that the costs of compliance are not an obstacle to the measure being considered necessary to
make reasonable progress. Where a comparison to the cost/ton metric for other regulatory actions
does not clearly indicate that the costs of compliance with a measure is within the range of
reasonableness, however, states should not automatically assume that the costs are unreasonable.
Rather, states may need to conduct further investigation before a conclusion can be reached as to
whether unreasonable impacts would result from requiring the particular measure at the
particular source.
8.1.3. The "worth" of emission reductions is not material
A state that has chosen not to consider visibility benefits after the screening analysis should
avoid effectively treating emission reductions as a surrogate for visibility benefits by arguing that
a certain cost is unreasonable because the cost is not "worth" the quantity of emission reductions
that the measure will achieve. For states following the recommended approach described in
section 4.2, comparisons to the cost/ton value of controls imposed on other sources allow states
to determine whether there would be unreasonably negative impacts to the source, not whether
the emission reductions achieved are "worth" the cost. States that wish to weigh visibility
improvements with the four statutory factors should do so explicitly by following the second
alternative approach. Section 8.2 provides recommendations for states following the second
alternative approach.
8.1.4. Separable sources and emission units
It can be efficient for a state to consider a group of similar sources when determining what
measures are necessary to make reasonable progress. Assuming that it is feasible to distinguish
121 The issue being addressed in the development of an LTS for a regional haze SIP is the reasonableness of the cost
impacts of complying with a certain measure. The environmental objective of a control measure required under
another CAA provision in a previous example is not relevant to whether the cost impacts of a similar measure that
might be adopted for regional haze purposes are unreasonable, assuming a state is following the recommended
approach or the first alternative approach.
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among sources to select and enforce different requirements, the entire group of sources should
not be excused from additional control because the costs of control for some of the sources
would be unreasonable. If such a distinction is not possible, however, the decision on what
common control to require for all sources in the group should be based on consideration of the
costs of compliance and emission reductions in the aggregate.
For source sectors in which sources are smaller and more numerous or for which specific
information on the design and operation of each source is not available, it may not be possible to
give separate consideration to the specifics of each source. The only practical choice may be to
subject all the sources to a common requirement or to exclude them as a group. Similarly, for a
source sector where there is only one practical method of enforcement, it may be necessary to
treat all sources in the sector in a common way in terms of costs incurred and emissions reduced.
For example, a fuel-oil sulfur-content requirement may be practically enforceable only at the
distributor level such that all customers will be affected the same way. In such situations, states
should conduct an aggregate assessment of the four statutory factors.
At a single source, the same concept applies at the unit or process level for facilities that include
multiple units or processes that emit separately and could be controlled separately, i.e., states
should assess units that can be controlled with separate equipment separately. States should not
combine two potential emission control systems that have significantly different cost/ton values
as if there were only the option of requiring both together. The combination of the two systems
might have a cost/ton value that casts doubt as to its reasonableness, while one of the systems
alone may be very reasonable based on a cost/ton comparison to other actions and consideration
of the other three statutory factors.
8.1.5. Multiple control alternatives, including combinations of controls
When multiple control options are available for one source (e.g., low-NOx burners can be
applied separately or combined with either SNCR or SCR), states following the preferred
approach or the first alternative approach should select the most effective control (or
combination of controls) that can be considered reasonable in light of the costs of compliance
and include that control in the LTS. States should not consider the incremental differences in cost
between the alternatives. As explained above, the cost/ton metric helps to put absolute costs into
perspective with the operating scale of the source. The incremental cost/ton of one possible
control option versus another, on the other hand, does not bear any close relation to the operating
scale of a source. Finally, the EPA notes that sources must bear the full compliance costs of a
control measure regardless of what other alternatives might exist. In other words, the incremental
cost/ton between the most effective control measure and the next most effective alternative is not
relevant to determining whether the costs of compliance for the most effective measure would
have unreasonable impacts at the source.
In light of the above, the EPA recommends that states following the recommended approach or
the first alternative approach use a top-down sequence to analyzing multiple control options.
Under this method, states (1) identify available control measures; (2) eliminate those that are
technically infeasible; (3) rank the remaining measures in terms of their effectiveness; (4)
analyze the most effective measure using the four statutory factors to determine whether it is
necessary to make reasonable progress; and (5) establish an enforceable emission limit and other
requirements for the selected measure. In step 4, states should consider the next most effective
control measure only if the first measure is rejected based on consideration of the four factors.
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This approach is efficient because states can avoid gathering facts and analyzing the four factors
for control measures less stringent than the one selected for the LTS. For example, a state that
determines SCR would not have any unreasonable impacts based on the four statutory factors
would not need to estimate the costs, energy, or non-air quality impacts of an SNCR system.
8.1.6. Viability of continued plant operations
Even when the cost/ton of a control measure is within the range of previous regulatory actions, in
unusual cases the costs of compliance may raise issues regarding the viability of continued plant
operations. The BART Guidelines address this possibility (see section IV.E.3.2 of the BART
Guidelines, which are reproduced in Appendix D), and we recommend that states follow the
same approach in the context of reasonable progress.
In determining whether the cost of compliance raises issues regarding the viability of continued
plant operations, a state may take into consideration the conditions of the plant and economic
effects, such as the effect on product prices and the market share and profitability of the source.
Where these effects are judged to have a severe impact on plant operations, a state may consider
them when determining whether the measure will have unreasonable impacts overall, but the
state should provide an economic analysis that demonstrates, in sufficient detail for public
review, the specific economic effects, parameters and reasoning. We recognize that this review
process must preserve the confidentiality of any sensitive business information. The analysis
may also consider whether other competing plants in the same industry have been required to
install similar-cost controls if this information is available.
At the same time, in a robust competitive market for a product or service with many producers, it
is often the case that one or more producers may be only marginally competitive, with a small
margin of operating profit. Therefore, it is not unsurprising that the additional cost of complying
with a newly required emission control measure may make marginal producers uncompetitive.
We believe that in requiring states to have an LTS that contains measures necessary to make
reasonable progress, Congress did not intend to indefinitely protect the market position of
marginal producers by shielding them from the costs of additional emission controls that have
already been put in place on similar sources in other locations or markets. Accordingly, states
should not consider a control measure to be unreasonable on the sole basis that one or a small
number of marginal producers would be at risk of leaving the market.
In future implementation periods, if the facts surrounding the economic effects change in the
case of a source for which a measure was excluded from consideration during the second
implementation period because of issues regarding the viability of continued plant operations,
then that measure should be reconsidered.
8.2. How should a state that is considering visibility benefits along with the four factors
select measures for inclusion in the LTS?
Note on applicability of this subsection
Section 8.2 applies to states that are following the second alternative approach to developing a
LTS described in section 4.2. Under this approach, states consider the visibility benefits of
emission controls measures for individual sources or groups of sources along with the four
statutory factors. While some of the guidance in this section is identical to the guidance in
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section 8.1, which applies to states that are following the preferred and first alternative
approaches, other issues discussed in this section differ in important ways.
See section 4.2 for the EPA's recommendations regarding the consideration of visibility in
developing the LTS. Developing the type of robust information on visibility benefits that we
believe is necessary for reasoned decision making can be very resource intensive. In addition,
given the complexity of assessing the import of visibility modeling, it can be very difficult for
states to make logical and consistent decisions regarding the appropriate weight to give visibility
benefits when weighing them against the four statutory factors. Consequently, we recommend
that states considering the second alternative approach seek input from the EPA, FLMs and
public on a draft analytical work plan and proposed decision-making criteria before committing
to this approach.
8.2.1.
approach.
The meaning of "necessary to make reasonable progress'
section 169A(b)(2) requires states to develop a SIP that includ
CAA section 169A(b)(2) requires states to develop a SIP that includes "emission limits,
compliance schedules and other measures as may be necessary to make reasonable progress
toward meeting the national goal." As stated in section 4.4, the EPA recognizes that determining
whether a measure is necessary to make reasonable progress is ultimately a fact-specific inquiry
regarding a particular source or source category and the affected Class I areas that takes place in
the context of legal requirements and input from stakeholders. In our actions on SIPs and FIPs in
the first implementation period, we did not apply any general formula or bright-line test to
evaluate state decisions or reach our own decisions as to what measures are necessary to make
reasonable progress, and we are not recommending any such formula in this guidance. This does
not mean, however, that a state has unbounded flexibility or discretion in its decision making.
States must use reasoned decision making and give due consideration to well-developed factual
information and public comments.
We recommend that for each source, group of sources or source category that has been selected
for four-factor analysis, a state following the second alternative approach include in its LTS the
most effective measures that are (part 1 of the reasonableness assessment) reasonable to require
in light of the four factors alone122 and (part 2 of the reasonableness assessment) reasonable to
require when weighing visibility benefits along with the four factors.
We expect that the outcome of this decision-making process will most often depend on the
outcome of weighing the costs of compliance and visibility benefits. States should consider the
remaining useful life of a source by annualizing the costs of compliance over the useful life of
the control or the remaining useful life of the source, whichever is shorter. States should consider
the time necessary for compliance by setting a compliance deadline that provides a reasonable
amount of time for the source to implement the measure. States should consider energy and non-
air quality impacts primarily as components of the costs of compliance. Only in unusual
situations will energy or non-air environmental impacts be such significant considerations that
they influence the decision for or against the control measure under consideration. As a result,
the discussion in this section focuses on providing guidance regarding on weighing the costs of
compliance and visibility benefits. The other three statutory factors are explicitly discussed in
122 States following this approach should refer to the guidance in Section 8.1 regarding when a measure should be
considered reasonable or unreasonable based on the four statutory factors alone.
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sections 8.3 (time necessary for compliance), 8.4 (energy impacts), 8.5 (non-air environmental
impacts) and 8.6 (remaining useful life). These discussions apply to all states regardless of the
approach taken to considering visibility.
To determine whether a control measure is reasonable, we recommend that states following the
second alternative approach consider the whole distribution of visibility benefits on the 20
percent most impaired days, including the maximum visibility benefit and other values at the
high end of the distribution, as well as the average benefit across the distribution. Consistent with
the guidance in this section, states may determine in the second implementation period that the
costs of compliance associated with a given control measure outweigh the visibility benefits of
that measure and not include the measure in the LTS without contradicting the national goal. In
future implementation periods, newer technology may reduce the costs of compliance for certain
sources or sources that are expensive to control may retire. However, states should also consider
how control determinations they make in the second and subsequent implementation periods will
affect their progress in relation to the URP. Ultimately, we expect that states will find in later
implementation periods that additional controls are necessary to make reasonable progress. A
state should also recognize that progress towards natural visibility conditions will require the
accumulation of reductions in air pollution and associated light extinction that may not be
individually perceptible.
8.2.2. Consideration of past decisions regarding reasonable progress
A state should consider how it, other states and the EPA made BART and reasonable progress
decisions during the first implementation period. Consultation between states on the
development of their SIPs will also allow states to understand how other states are contemplating
making decisions on how to weigh costs and visibility benefits in the second implementation
period. States should consider the decisions made by other states (or being made by other states)
and the EPA because Class I areas are national treasures visited by people from all states; they
are valued even by people who have not yet visited them or who do not plan to visit them.
Moreover, the costs of controlling sources that affect visibility in a given Class I area may
ultimately be borne by residents of many states due to the interwoven nature of the national
economy, including the broadly distributed ownership of many of the corporations owning the
sources. Thus, states should not view the weighing of costs and visibility benefits as an in-state
issue, and the preferences of the state's own decision makers should not be the only determinant
of how decisions are made on what additional measures are necessary to make reasonable
progress at a Class I area. Any state decisions that fall outside the general range of previous
decisions by the same state, other states and the EPA should be based on important
distinguishing factors. However, a state should not conclude that a measure is sufficient for
reasonable progress only on the basis that the measure is in the range of previous decisions,
without also considering whether a reasonable weighing of visibility benefits would indicate that
a measure that is even more protective of visibility also is in that range.
When comparing situations, states should consider how different analytical methods may have
influenced the facts on which past decisions were based. For example, states should consider
whether visibility benefits in a past case were estimated using an air quality modeling approach
that is similar to or different than the one the state is using to develop its SIP for the second
implementation period. States conducted BART determinations by considering 98th percentile
visibility impacts modeled using CALPUFF and maximum actual daily emissions. Therefore,
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states should not compare past BART determinations to average or maximum visibility benefits
on the 20 percent most impaired days, which are estimated using actual daily emissions and a
different air quality modeling approach.
Additionally, past regulatory decisions aimed at improvements in other environmental endpoints
such as NAAQS attainment, PSD increment protection or reduction in the exposure to hazardous
air pollutants are not directly relevant. However, states may find such past decisions to be useful
benchmarks for the value given to avoiding air pollution and its effects in a very broad sense.
8.2.3. Considering visibility benefits does not require "cost/benefit" analysis
States following the second alternative approach should not base their decisions on a
"cost/benefit analysis" that monetizes the value of visibility benefits and other co-benefits and
then compares that value to the costs of compliance. Monetizing the value of visibility benefits
would be extremely difficult. More importantly, conducting a cost/benefit analysis would be
inconsistent with the recommendations in this guidance regarding visitation and the importance
of less heavily visited Class I areas, like wilderness areas. If a state chooses to conduct a
cost/benefit analysis for public information purposes rather than decision purposes, as the EPA
does for many national rules, the state should follow the relevant guidance of the U.S. Office of
Management and Budget.
8.2.4. Changes in the number of days above a visibility impact benchmark
The BART Guidelines allow states to consider the number of days on which a source's modeled
visibility impacts at a Class I area remain above 0.5 or 1.0 deciviews when considering visibility
benefits. For reasonable progress determinations in the second implementation period, the EPA
recommends that states give little weight to this type of metric. Whereas the BART requirements
targeted the impacts of single sources that cause or contribute to visibility impairment, the
reasonable progress requirements are intended to remedy visibility impairment from all sources
on all days, with a focus on the 20 percent most impaired days. While the number of days on
which a single source has impacts above a certain threshold says something about the magnitude
of that source's impacts, the metric does not capture the magnitude of the visibility benefit of
controls. Even a small visibility benefit could change the number of days a source has impacts
below a threshold if the source's baseline impacts were already close to that threshold.
8.2.5. Consideration of visibility benefits at multiple affected Class I areas
In many cases, the control measures considered by a state for its LTS will have visibility benefits
at multiple Class I areas. When a state following the second alternate approach considers
whether an emission control measure is necessary to make reasonable progress, it must give
appropriate weight to the visibility benefits at all Class I areas affected by the source. During the
first implementation period, most states followed this approach, and the EPA disapproved the
SIPs of states that considered benefits only at the most impacted Class I area. Considering
visibility benefits at only the most impacted area is inconsistent with the CAA's goal of
"remedying . . . impairment of visibility in mandatory class I Federals areas"'' 42 USC
7491(a)(l) (emphasis added).
States should consider the individual visibility benefits at multiple Class I areas and present to
the public for comment a set of the individual values for each area. For each Class I area, states
should consider the whole distribution of visibility benefits on the 20 percent most impaired
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days, including the maximum visibility benefit and other values at the high end of the
distribution, as well as the average benefit (in delta deciviews) for that area. States should
consider all of this information when weighing costs and visibility benefits to decide whether an
emission control measure is necessary to make reasonable progress. If a state estimates visibility
benefits at different Class I areas using different approaches, the state should clearly explain the
differences in its SIP.
We recommend that states also sum the visibility benefits across affected Class I areas, present
this information in their SIPs as a supplement to the information for individual Class I areas and
consider this sum as well as the several individual values of visibility benefit. This practice is be
a useful way to help characterize the number of affected areas and the magnitude of the
cumulative visibility benefits. However, states should explain that this cumulative sum does not
represent the perceptible effect of the benefits at any one Class I area.123
8.2.6. Considerations when weighing costs and visibility benefits
States following the recommended approach or the first alternative approach can rely on a
comparison of the cost/ton metric for an emission control measure to the same metric from
previous regulatory actions to show that the costs of compliance with the measure are
reasonable, as explained in Section 8.1.2. States following the second alternative approach
should not rely on such a comparison and should provide a reasoned and logical explanation for
how it considered costs, assessed visibility benefits, and weighed costs and visibility benefits in
deciding what measures are necessary to make reasonable progress.
To begin, states following the second alternative approach need not adopt a measure for which
the costs of compliance considered alone or in combination with the other statutory factors are
unreasonable. Thus, states following the second alternative approach should perform the same
"part 1" reasonableness assessment mentioned in section 8.2.1 as being part of the recommended
approach, before proceeding to weigh visibility benefits.
With regard to the "part 2" assessment mentioned in section 8.2.1, in which visibility benefits are
weighed along with the cost of compliance, the EPA notes that regional haze is "visibility
impairment that is caused by the emission of air pollutants from numerous sources located over a
wide geographic area." 40 CFR 51.301. At any given Class I area, hundreds or even thousands of
individual sources may contribute to regional haze. Thus, it is not appropriate to reject a control
123 In the preamble to the 1997 proposal, the EPA stated: "Due to the broad variety of scenic, atmospheric, and
lighting conditions at the mandatory Class I Federal areas across the country, at any specific time a given area may
contain vistas for which slightly more or less than one deciview above background conditions represents a
perceptible impact for the components of the scene. For example, a view of a snow-capped mountain may be more
sensitive to changes in air quality than a view of a forest with the result that less than a 1.0 deciview change is
perceptible for that portion of the scene. Conversely, in another scene a deciview change slightly greater than 1.0
may not be perceptible." 62 FR 41148. The preamble to the 2005 BART Guidelines final rule included a more
extensive discussion of the perceptibility of deciview increments, and that final rule established 0.5 deciview as the
upper limit on any threshold a state may establish for purposes of determining that a B ART-eligible sources is not
subject to BART. 70 FR 39120. The important point for states to make clear in their SIPs, for good public
understanding, is that the cited deciview values of 0.5 and 1.0 apply to perceptions of a single scenic vista. A
deciview value that is the sum of deciview changes at multiple areas should not be compared to this range or to any
single value within the range.
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measure for a single emission unit, a single source, or even a group of sources on the basis of the
associated visibility benefits being imperceptible to the human eye. (Note, however, that we do
expect that a given Class I area will generally experience perceptible visibility improvements due
to the cumulative effect of LTS' in upwind states.)
With this overarching principle in mind, the EPA offers the following recommendations as to
how states should weigh costs and visibility benefits. As a general matter, the larger the visibility
benefit, the larger the costs of compliance that will be justified. However, for extremely cost-
effective controls, states should strongly consider requiring controls if an appropriate analytical
approach indicates a visibility benefit.
For more expensive controls, states may find it useful to develop thresholds or some other metric
to organize and guide their initial decision making. As the Ninth Circuit explained in NPCA v.
EPA, 788 F.3d 1134, 1142 (9th Cir. 2015),124 the Regional Haze Rule does not prevent states
from implementing "bright line" rules, such as thresholds, when weighing costs and visibility
benefits. For example, a state could require all control measures that cost less than $X/ton and
that result in either (1) a visibility benefit greater than Y deciview at the most impacted Class I
area or (2) cumulative visibility benefits across multiple affected Class I areas greater than Z
deciview. In establishing such thresholds, however, states should determine whether the
thresholds selected will result in a LTS that provides sufficient emission reductions to achieve
the URP. If not, states should be mindful that they will be required to demonstrate that there are
no additional measures that would be reasonable to include in the LTS. See section 10.3. States
will need to consider the progress needed at each affected Class I area and the sources
contributing to visibility impairment to determine appropriate thresholds.
States must also ensure that their control decisions are consistent among sources. A state should
not reject a control measure for a source if that measure would result in similar costs and benefits
to measures required at other sources unless there are distinguishing factors. States should also
consider the decisions that are being made by other states following the second alternative
approach, for the reasons given above. Absent a thorough explanation, inconsistent control
determinations are "the hallmark of arbitrary action." NPCA, 788 F.3d at 1145 (citation omitted).
Finally, in its consideration of visibility under the second alternative approach, states should take
into account the deciview metric, as well as the reduction in total light extinction and the
reduction in a source's percent contribution to light extinction before making a final control
determination. See 79 FR 74882 (The EPA's proposed FIP for Texas). If a source is one of the
largest contributors to anthropogenic light extinction at a Class I area, then the state should
strongly consider including cost-effective measures for the source in its LTS in order to help
meet Congress' national visibility goal.
8.2.7. Separable sources and emissions units
It can be efficient for a state to consider a group of similar sources when determining what
measures are necessary to make reasonable progress. Assuming that it is feasible to distinguish
among sources to select and enforce different requirements, the entire group of sources should
not be excused from additional control because the costs of control for some of the sources
124 See Appendix C for a list of all relevant circuit court decisions on regional haze in the first implementation
period.
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would be unreasonable. If such a distinction is not possible, however, the decision on what
common control to require for all sources in the group should be based on consideration of the
costs of compliance and emission reductions in the aggregate.
Similarly, sources within a sector will typically have different visibility impacts depending on
their geographic proximity to affected Class I areas. Where it is feasible to discern among the
sources to select and enforce different requirements, the entire group of sources should not be
excused from additional control because the visibility benefits for some of the sources are
deemed insufficient in comparison to the costs of control. If such distinction is not possible,
however, the decision on what common control to require for all sources in the group should be
based on consideration of the costs of compliance, emission reductions, and visibility benefits in
the aggregate.
For source sectors in which sources are smaller and more numerous or for which specific
information on the design and operation of each source is not available, it may not be possible to
give separate consideration to the specifics of each source. The only practical choice may be to
subject all the sources to a common requirement or to exclude them as a group. Similarly, for a
source sector where there is only one practical method of enforcement, it may be necessary to
treat all sources in the sector in a common way in terms of costs incurred, emissions reduced,
and visibility benefits achieved. For example, a fuel-oil sulfur-content requirement may be
practically enforceable only at the distributor level such that all customers will be affected the
same way. In such situations, states should conduct an aggregate assessment of the four statutory
factors and visibility benefits.
At a single source, the same concept applies at the unit or process level for facilities that include
multiple units or processes that emit separately and could be controlled separately, i.e., states
should assess units that can be controlled with separate equipment separately. States should not
combine two potential emission control systems that have significantly different cost/ton values
as if there were only the option of requiring both together. The combination of the two systems
might have a cost/ton value that casts doubt as to its reasonableness, while one of the systems
alone may be very reasonable based on a cost/ton comparison to other actions and consideration
of the other three statutory factors and visibility benefits.
8.2.8. Concerns with use of the cost/deciview metric
The cost/deciview metric directly compares the costs of compliance with the visibility benefits of
compliance. The EPA recommends that states not use the cost/deciview metric in their SIPs
because it has the potential for being misunderstood by the public and state decision makers who
are more familiar with the cost/ton metric. Moreover, the cost/deciview metric does not allow for
apples-to-apples comparisons between sources because it does not adequately capture the
magnitude of visibility benefits at multiple Class I areas or the fact that different sources impact
different numbers of Class I areas.
8.2.9. Visitation
States should give equal consideration to visibility benefits at every Class I area and for every
visitor. It is not appropriate to give less weight to protecting visibility in Class I areas with lower
visitation. Some Class I areas, such as national parks, are intended by their authorizing
legislation to be visited by many people and are managed towards that purpose, while others,
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such as wilderness areas, are intended to be protected from most types of human disturbances
and correspondingly do not host nearly as many visitors per year. The EPA does not believe that
Congress intended there to be disparities in protection of visibility across these types of areas, as
might result if states put more value on visibility protection in highly visited Class I areas or put
less value on visibility protection in less visited areas. In addition, we do not believe that a state
should give less weight to protecting visibility in a given Class I area during times of the year
with lower visitation because we believe Congress intended the goal of eliminating visibility
impairment to benefit all visitors.125
8.2.10. Viability of continued plant operations
Even when the cost/ton of a control measure is within the range of previous regulatory actions, in
unusual cases the costs of compliance may raise issues regarding the viability of continued plant
operations. The BART Guidelines address this possibility (see section IV.E.3.2 of the BART
Guidelines, which are reproduced in Appendix D), and we recommend that states follow the
same approach in the context of reasonable progress.
In unusual circumstances, states may investigate and take into consideration the conditions of the
plant and the economic effects of requiring the use of a given control measure. These effects
could include effects on product prices and the market share and profitability of the source.
Where such unusual circumstances are judged to affect plant operations, a state may take into
consideration the conditions of the plant and the economic effects of requiring the use of a
control technology. Where these effects are judged to have a severe impact on plant operations, a
state may consider them when determining whether the measure will have unreasonable impacts
overall, but the state should provide an economic analysis that demonstrates, in sufficient detail
for public review, the specific economic effects, parameters and reasoning. We recognize that
this review process must preserve the confidentiality of any sensitive business information. The
analysis may also consider whether other competing plants in the same industry have been
required to install similar-cost controls if this information is available.
At the same time, in a robust competitive market for a product or service with many producers, it
is often the case that one or more producers may be only marginally competitive, with a small
margin of operating profit. Therefore, it is not unsurprising that the additional cost of complying
with a newly required emission control measure may make marginal producers uncompetitive.
We believe that in requiring states to have an LTS that contains measures necessary to make
reasonable progress, Congress did not intend to indefinitely protect the market position of
marginal producers by shielding them from the costs of additional emission controls that have
already been put in place on similar sources in other locations or markets. Accordingly, states
should not consider a control measure to be unreasonable on the sole basis that one or a small
number of marginal producers would be at risk of leaving the market.
125 The 2005 BART rule preamble stated, "Other ways that visibility improvement may be assessed to inform the
control decisions would be to examine distributions of the daily impacts, determine if the time of year is important
(e.g. high impacts are occurring during tourist season), consideration of the cost-effectiveness of visibility
improvements (i.e. the cost per change in deciview), using the measures of deciview improvement identified by the
State, or simply compare the worst case days for the pre- and post-control runs." This is no longer our position on
the subject of considering visitation.
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8.3. Time necessary for compliance
While the CAA and the Regional Haze Rule require states to consider the four statutory factors
when selecting emission control measures for the LTS, we believe that the time necessary for
compliance factor should enter the decision-making process in a different way than the other
three factors. Whereas high compliance costs, adverse energy or non-air quality impacts or a
short remaining useful life may weigh in the direction of not including a particular control
measure in the LTS, the time necessary for compliance does not present the same type of barrier
because the long time perspective of the regional haze program extends well beyond the time
required to install and "shake down" any emission control system. Therefore, the EPA believes
that states should consider the time necessary for compliance by setting reasonable compliance
deadlines for selected control measures rather than when deciding whether to adopt the control
measures in the first instance. In other words, the other three factors determine how much
progress is reasonable, while the time necessary for compliance factor determines when that
progress is reasonable.
8.4. Energy impacts
The EPA recommends that states consider energy impacts by accounting for any increase or
decrease in energy use at the source as part of the costs of compliance. Upstream energy impacts,
like the energy used to produce construction materials, are already be reflected in the price of
those materials and should not be double counted.
8.5. Non-air quality environmental impacts
The EPA recommends that states consider ordinary non-air quality environmental impacts, such
as water usage or waste disposal of spent catalyst or reagent, by accounting for them as part of
the costs of compliance. In rare location-specific cases, the installation of a control measure may
lead to adverse non-air quality environmental impacts that are extreme or unusual for a particular
type of source. In these cases, states may consider such impacts separately from the costs of
compliance when determining whether the measure is necessary to make reasonable progress.
States should also consider any beneficial non-air quality environmental impacts, which could
result in the adoption of an emission control measure that otherwise would seem less attractive or
reasonable.
Air deposition effects on water, soils and vegetation are air impacts. The CAA does not require
states to consider air impacts when determining reasonable progress. Therefore, states may but
are not required to consider such impacts. Generally, when visibility-impairing emissions are
reduced, reductions in the deposition of substances that have adverse effects on the environment
will also occur. Greenhouse gas emissions and climate change impacts are also air impacts, so
states may but are not required to consider such impacts.
8.6. Remaining useful life
Section 7.5 discusses how states should determine the remaining useful life of a source and the
useful life of new emission control systems. States should consider remaining useful life to
calculate emission reductions, amortized costs and cost/ton values.
If a source is certain to close by 2028 under an enforceable requirement, states may consider that
to be a sufficient reason not to require any additional controls at the source in the LTS. This is a
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recommendation that applies only to this implementation period in light of the shorter-than-
normal interval between the 2021 and 2028 SIP submission deadlines. See the discussion in
section 6.4 of this situation in the context of the screening step.
8.7. What special considerations apply in selecting additional controls for minor stationary
sources, area stationary sources and mobile sources?
Regional Haze Rule provision
(2) Long-term strategy for regional haze and reasonably attributable visibility
impairment.
* * *
(v) The State must identify all anthropogenic sources of visibility impairment considered
by the State in developing its long-term strategy and the criteria used to select the sources
considered. The State should consider major and minor stationary sources, mobile
sources, and area sources.
Minor stationary sources and area stationary sources may be important contributors to
anthropogenic visibility impairment, and present significant opportunity for visibility
improvements in the second implementation period for some Class I areas. The Regional Haze
Rule recommends that states consider minor stationary sources, area sources and mobile sources
in addition to major stationary sources, and that the state identify which of these source types it
has considered. Some of the statements in this guidance about decision making logically apply to
these sources or may be logically adapted and extended to them. Other sections of this document
contain information or recommendations specific to minor stationary sources, area stationary
sources and/or mobile sources. The EPA regional offices are available to discuss how
information and advice from EPA may bear on particular situations.
One recommendation for screening is that sources in these categories be aggregated for purposes
of any screening step based on visibility impacts or surrogates for visibility impacts, so that the
individual sources in a group or category with substantial aggregate impacts will be selected
four-factor analysis. However, the EPA recommends that differences among the sources in a
group of small sources with respect to the four CAA-specified factors should be taken into
account in the four-factor analysis the four-factor analysis when determining whether and what
additional emission controls are needed for reasonable progress, to the extent practicable. For
example, in a group of internal combustion engines there may be considerable variation in their
vintage, existing emission controls and remaining useful life that would affect some of the four
factors.
Generally, the EPA does not recommend that states use their analytical and decision making
resources to consider new emissions standards for highway vehicles, locomotives, non-road
vehicles, hand-held and self-propelled equipment, or turbine-powered aircraft, given that new
vehicles and engines in these categories are subject to stringent EPA or California emission
standards.126
126 Federal and California emissions standards have generally become more closely aligned in the past decade or so,
and California versions are often sold in other states.
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Some engines used at major or minor stationary sources are regulated as mobile sources by
virtue of being moved at least once per year. As mobile sources, emissions from these engines
are not counted in determining whether a source is subject to major source new source review,
and even if a source is subject to such review due to emissions that are considered to be
stationary source emissions, these mobile engines are not subject to BACT, LAER, or emission
offsets. Depending on age, an engine of this type at the time of first sale or installation may have
been subject to new engine emission standards that were lenient compared to emission standards
applying to engines sold more recently. Aggregate emissions of such mobile source engines in
some areas may be considerable, particularly when they provide mechanical or electrical power
in the absence of service from an electric grid. Replacement of such engines with newer engines,
or retrofit with engine modifications or after treatment systems, may provide emission reductions
that would contribute to reasonable progress towards natural visibility conditions. States where
this type of situation occurs should not remove these engines at the screening step, and should
evaluate potential emission reductions measures with respect to the four factors.
8.8. How should a state set emission limits, averaging periods and monitoring and record
keeping requirements?
Regional Haze Rule provisions
51.308(f)(2) Long-term strategy for regional haze and reasonably attributable visibility
impairment.
* * *
(vi) The State must consider, at a minimum, the following factors in developing its long-
term strategy:
* * *
(C) Emissions limitations and schedules for compliance to achieve the reasonable
progress goal;
8.8.1. General CAA requirements and EPA guidance
The Regional Haze Rule requires SIPs to include enforceable emission limits including
averaging times, monitoring and record keeping and reporting requirements for each measure
included in the LTS. This requirement is in common with many other parts of the air program,
and there is a considerable body of applicable EPA rules, EPA guidance and EPA and state
practice on these topics.
Generally, limits should initially be determined in terms of pounds per input or output (or per
hour of operation), so that they can be clearly related to the technology or other emission control
measure that has been determined to be needed for reasonable progress. Then, these limits may
be replaced with time-based limits (e.g., a cap on 30-day or annual emissions) that would allow
operating changes to be used for compliance.
8.8.2. Current emissions rates versus enforceable limits
In the BART process, a state was generally required to establish emission limits reflecting the
capability of currently installed control technology if that technology was determined to be
BART for a source. For reasonable progress purposes, the same requirement applies. That is, if a
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state determines that the in-place emission controls at a source are necessary to make reasonable
progress, the state is required to adopt an LTS that includes those controls if those controls are
not already federally enforceable. The LTS can be said to include those controls only if it
includes emission limits (with associated averaging periods and other compliance program
elements) that effectively require the use of the controls, or a more effective control. If the
currently enforceable emission limits are not stringent enough to ensure the continued use of that
technology (and good operating practices), then they must be revised in order for the LTS to
meet this requirement.127
8.8.3. EPA's Startup, Shutdown and Malfunction Policy
The EPA's June 12, 2015, restatement of its SSM Policy for SIPs applies to regional haze
SIPs.128 SSM exemptions, director's discretion (unless narrowly constrained), SIP provisions that
impinge on federal enforceability and affirmative defenses for federal enforcement are not
allowed. As discussed in section 8.9.4, alternative emissions limitations may be appropriate
during startup, shutdown and other periods of normal operation during which compliance with
the emission limit applicable during most source operation is not feasible or is unreasonable to
require.
8.8.4. Averaging periods
To avoid possible confusion, we address here a difference in how averaging periods should be
considered in the context of reasonable progress in a regional haze SIP and in the context of
programs oriented towards protecting the NAAQS.129 The NAAQS and PSD increments are
"hard limits" on ambient air quality that are not to be violated, and if violations occur they are to
be corrected. For these requirements, it is appropriate to consider the possibility that a source (or
group of nearby sources) subject to an emission limit with an averaging period longer than the
averaging period of the NAAQS (or PSD increment) might have a period of emissions high
enough to cause an exceedance of the NAAQS, and the issues that would exist if those emissions
could not be treated as a violation of the source's emission limit. Such high emissions might
occur due to a malfunction, a startup or shutdown period, a period of improper source operation
or a period of normal source operation but a high level of source activity. EPA rules and policies
aim to avoid this situation in order to protect the NAAQS and PSD increments. Towards this
end, the EPA's SSM Policy for SIPs, consistent with a fundamental CAA requirement, requires
any emission limitation in a SIP to apply continuously including periods of startup, shutdown
and malfunction. However, the specific numerical limit that applies during startup or shutdown
may be different than during other periods of operation, in which case the limit is referred to as
127 This situation is not the same as a situation in which via a screening process a state has decided not to advance a
source to a full reasonable progress analysis. In such a situation, the state is not determining that the existing
controls on the source are necessary and sufficient for reasonable progress and is not including those controls in its
LTS revision. Rather, it is deferring a decision on that source until a later implementation period. Thus, it is not true
that a state must revise every sources' emission limits to reflect the capability of the control technology in use at the
source.
128 State Implementation Plans: Response to Petition for Rulemaking; Restatement and Update of EPA's SSM
Policy Applicable to SIPs; Findings of Substantial Inadequacy; and SIP Calls To Amend Provisions Applying to
Excess Emissions During Periods of Startup, Shutdown and Malfunction; Final Rule, 80 FR 33840, June 12, 2015.
129 This discussion also has relevance to protection of PSD increments.
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an alternative emission limit. Also, in certain situations, the emission limitation during startup or
shutdown may take the form of a work practice instead of a numerical limit.
In contrast, the reasonable progress component of the regional haze program is not based on any
"hard limits" for actual visibility conditions. Rather, it is based on requiring the implementation
of emission reduction measures necessary to make reasonable progress by establishing
enforceable emission limits on sources, and by implication also requiring the proper operation of
those controls on a continuous basis. The visibility conditions that would be achieved by such
implementation (in addition to other measures required under other CAA provisions), whatever
those conditions are, is by definition the goal of the program at a particular point in time.
In this context, it is still important to the goal of the regional haze program that there be
appropriate emission limits during startup and shutdown, as required by the CAA and the EPA's
SSM policy for SIPs. It is also still important that malfunctions and improper source operation
constitute violations that can be subject to enforcement; this can be achieved if emission limits
and averaging periods are coordinated so that the combination of the two does not have so much
"slack" that malfunctions and improper source operation do not constitute violations.130 It is not
always necessary to have a short averaging period to achieve this effect.
While it is important that the combination of emission limit and averaging period not have so
much "slack" that malfunctions and improper source operation do not constitute violations, there
is not the same concern about a source (or group of sources) subject to a long averaging period
operating at a high level of throughput or output for a period of one or a few days and as a result
having a relatively high impact on visibility at a Class I area during that period. Rather, the need
is for sources with high and variable operating levels to have effective emission controls in
operation at all times. While our recommendations in section 6 regarding screening could have
the effect that a source that contributes substantially to impairment on as few as one of the 20
percent most impaired days would be brought forward from screening to assess what emission
control is necessary to make reasonable progress, this does not mean that such a source should be
expected to reduce its operations. We do not interpret the Regional Haze Rule as requiring states
to consider restricting the level or timing of source operation. Therefore, a state may adopt an
averaging period longer than 24 hours without demonstrating that the combination of emission
limit and averaging period will prevent a source from having a particularly high visibility impact
on one day due to a high level of activity. We note that under requirements flowing from other
CAA provisions and EPA rules, sources may be subject to emission limits for pollutants that
contribute to visibility that have averaging periods as short as 1 hour.
8.8.5. Intermittent controls
If it can be reasonably anticipated that a source will only operate during certain times of the year,
for example wood-burning home heating units, measures may be explicitly limited to those times
of the year. Otherwise, any state considering adoption of a measure that would set an emission
limitation that only applies during specified portions of a year or during specified conditions
should consult with its EPA regional office, as the requirements of the CAA on the subject of
130 As previously noted, if the pattern of future source operation is too variable to set a single emission limit for a
single averaging period, more complicated approaches are available to ensure that malfunctions and improper source
operation will trigger enforcement.
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intermittent controls require situation-specific interpretation. We note that even if the 20 percent
most impaired day together fall only in some of the four seasons, the CAA goal of achieving
natural visibility conditions is not restricted to those days.
8.8.6. Continued relevance of the BART Guidelines
Many of the statements in the BART Guidelines continue to be relevant as recommendations for
how a state should address emission limits, averaging periods and monitoring and record keeping
requirements. Appendix D indicates which parts of the BART Guidelines continue to be relevant
in this way.
8.9. How should a state set compliance deadlines?
The state should set a compliance deadline that provides reasonable time for the source to come
into compliance in an efficient manner, without unusual amounts of overtime, above-market
wages and prices, or premium charges for expedited delivery of control equipment. The CAA
and Regional Haze Rule provide that compliance deadlines for BART requirements be as
expeditiously as practicable but in no case later than 5 years from EPA approval of the SIP
containing a new BART requirement. There is no similar provision for controls adopted for
purposes of reasonable progress. While a state may be able to demonstrate that in some cases a
reasonable compliance deadline is later than a deadline that is "as expeditiously as practicable,"
we expect such cases to be very unusual. The EPA believes that only in an unusual situation
would a reasonable compliance deadline be more than 5 years after EPA approval of the SIP.
It is reasonable for a state to tie the compliance deadline for a new requirement to EPA approval
of the specific SIP provision containing that new requirement, as otherwise a source might have
to make investments that would be at risk if the EPA disapproves the SIP provision. However,
the language a state uses to establish this link should not make the compliance date dependent on
full EPA approval of the SIP revision. It should be sufficient if the EPA approves the particular
emission limit as adequate for purposes of the LTS for that particular source, even if the LTS is
not fully approved overall.
The RPGs for the second implementation period are to be based only on the combined effect of
the controls with compliance dates on or before December 31, 2028 (the end of the second
implementation period). Given the July 31, 2021, SIP revision submission deadline and the CAA
deadline of 1 year for EPA action on a submitted and complete SIP revision, we expect that all
measures included in the SIP for the second implementation period to be implementable by
December 31, 2028, even if the compliance date is tied to EPA approval. Thus, the RPGs
generally should reflect all measures in the LTS.
The time necessary for compliance generally should be considered to be a source-by-source
question, with each source required to comply by the soonest date that can be considered
reasonable. The EPA does not expect that in the second implementation period there will be a
situation in which the time necessary for compliance at one source is increased because available
design, construction, general project management or financing resources are oversubscribed due
to an unusually large number of similar projects needing to move forward about the same time.
However, a state may set a compliance schedule that appropriately takes into account the risks of
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taking multiple electrical generating units serving the same market offline at the same time if
these risks have been well researched and documented.131
131 In the first implementation period, the EPA considered and invited public comment on the question in Wyoming
of whether requiring multiple EGUs to install SCR units (as BART) close in time would be overly risky to power
system reliability, or would cause unreasonable additional cost to purchase replacement power, given that each unit
would have to be taken off line during construction.
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9. Regional scale modeling of the LTS to set the RPGs for 2028 (Step 5)
Regional Haze Rule provisions
51.308(f)(2) Long-term strategy for regional haze and reasonably attributable visibility
impairment. Each State must submit a long-term strategy that addresses regional haze
visibility impairment, and if necessary any reasonably attributable visibility impairment
certified by the Federal Land Manager under §51.302(a), for each mandatory Class I
Federal area within the State and for each mandatory Class I Federal area located outside
the State that may be affected by emissions from the State. The long-term strategy must
include the enforceable emissions limitations, compliance schedules, and other measures
that are necessary to achieve reasonable progress, as determined pursuant to (f)(2)(i)
through (vi). In establishing its long-term strategy for regional haze, the State must meet
the following requirements:
(i) The State must consider and analyze emission reduction measures based on 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 major or minor stationary source or group of sources. The State must document
the criteria used to determine which sources or groups of sources were evaluated, and
how these four factors were taken into consideration in selecting the measures for
inclusion in its long-term strategy.
(ii) The State must consider the uniform rate of improvement in visibility, the emission
reduction measures identified in (f)(2)(i), and additional measures being adopted by other
contributing states in (f)(2)(iii) as needed to make reasonable progress towards natural
visibility conditions for the period covered by the implementation plan.
* * *
(3) Reasonable progress goals, (i) A state in which a mandatory Class I Federal area is
located must establish reasonable progress goals (expressed in deciviews) that reflect the
visibility conditions that are projected to be achieved by the end of the applicable
implementation period as a result of all enforceable emissions limitations, compliance
schedules, and other measures required under paragraph (f)(2) and the implementation of
other requirements of the CAA. The long-term strategy and the reasonable progress goals
must provide for an improvement in visibility for the most impaired days and ensure no
degradation in visibility for the clearest days since the baseline period.
* * *
(iii) The reasonable progress goals established by the State are not directly enforceable
but will be considered by the Administrator in evaluating the adequacy of the measures in
the implementation plan in providing for reasonable progress towards achieving natural
visibility conditions at that area.
(iv) In determining whether the State's goal for visibility improvement provides for
reasonable progress towards natural visibility conditions, the Administrator will also
evaluate the demonstrations developed by the State pursuant to paragraphs (f)(2) and
(f)(3)(ii)(A) of this section and the demonstrations provided by other States pursuant to
paragraphs (f)(2) and (f)(3)(ii)(B) of this section.
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9.1. Overview
After a state has used reasoned decision making to determine an emissions control scenario that
reflects reasonable progress at Class I areas affected by sources in the state (step 4, section 8),
the state must use this control scenario and the measures adopted by any contributing states into
their LTSs, along with recent visibility conditions (i.e., the conditions in the year chosen as the
base year for the air quality modeling), to project visibility conditions on the 20 percent most
impaired and 20 percent clearest days at Class I areas within the state as of the end of the
implementation period.132 These visibility projections (in deciviews) are the RPGs and are the
visibility outcomes projected to occur at the end of the implementation period. If some
contributing states have not yet determined the measures that will be included in their LTSs, then
the state with the Class I area is to set RPGs based on confirmed measures.
The state's goals must provide for an improvement in visibility for the most impaired days and
ensure no degradation in visibility for the clearest days over the implementation period. After a
state projects an RPG for the most impaired days based on the components of the LTS, the state
must compare the RPG for the end of the implementation period with the same year on the URP
line (for the second implementation period this year is 2028), and if the RPG provides for a
slower rate of progress (i.e., the RPG is above the line), the state has additional obligations to
provide justification for the reasonableness of the RPG. This analysis is described more in
section 10 (step 6).
9.2. EPA modeling guidance
Many of the details associated with the modeling process for projecting RPGs are carefully
explained in the EPA's Modeling Guidance, section 4.8 of which directs states through the steps
required to apply base period and future year air quality model simulation results to ambient
data, resulting in calculations of RPGs.
9.3. Recognition of emission limits in the LTS and other emission reductions when
projecting the RPGs
A state's RPGs for the end of each implementation period should only reflect the benefits of
controls in the LTS that will be enforceable as of the last day of the implementation period. (For
example, for the second implementation period, RPGs should reflect only the controls in the LTS
that will be enforceable as of December 31, 2028. If some measures are to take effect during
2028, we recommend that daily emission values for days in 2028 used in air quality modeling
reflect the emission limits that are effective as of each day.) Other enforceable emission limits
should be recognized in the emissions projections as well.
The recognition of factors that may be limiting emissions but are not enforceable measures, such
as voluntary and incentive-based programs (include energy efficiency and renewable energy
programs) and market price conditions that might change in the future, is a complex topic. States
should consult with their EPA regional offices on this topic if they do not find clear guidance in
available EPA guidance on this topic.
132 States with no Class I areas do not set RPGs, but must consult with states affected by their emissions.
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9.4. Recommendations regarding adjustment of RPGs when the LTS in the SIP(s) is not the
same as assumed in an available photochemical modeling run
While in concept every contributing state's LTS should be determined and then air quality
modeling should translate those strategies into the projected RPGs, the EPA realizes that in
practice this sequence may not hold entirely. At the time the air quality modeling is performed, it
may be necessary to assume the outcome of final decisions by some states on the content of their
LTS. Also, subsequent SIP revisions or FIPs may alter the content of the LTS in one or more
states contributing to visibility impairment at a Class I area. Because the air quality modeling to
calculate RPGs is resource intensive and time consuming, we do not expect it to be repeated after
each change in the content of an LTS. Nevertheless, the revised Regional Haze Rule requires the
RPGs and the LTS to be consistent. An RPG may be adjusted to reflect a difference between the
final LTS and the assumptions used in the initial projection of the RPGs without re-running the
air quality modeling if time and resources to do so are not reasonably available. States in this
situation should consult with the EPA about an appropriate method for doing so, which may
depend on the specifics of the case and information that is available. Any such adjustment should
be clearly documented in the SIP submission.
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10. Progress, Degradation and Glidepath Checks (Step 6)
10.1. How should a state demonstrate that there will be improvement in visibility for the
most impaired days?
Regional Haze Rule provisions
51.308(f)(3) Reasonable progress goals, (i) ... The long-term strategy and the reasonable
progress goals must provide for an improvement in visibility for the most impaired days
The 2028 RPG for the 20 percent most impaired days is to be compared to the 2000-2004
"baseline conditions" for the same days. The "baseline conditions" are determined from
IMPROVE data, using the approach recommended in section 5 of this document or another
method justified by the state.
10.2. How should a state demonstrate that its 2028 RPG for the 20 percent clearest days
shows no degradation?
Regional Haze Rule provisions
51.308(f)(3) Reasonable progress goals, (i) ... The long-term strategy and the reasonable
progress goals must... ensure no degradation in visibility for the clearest days since the
baseline period.
The 2028 RPG for the 20 percent clearest days is to be compared to the 2000-2004 "baseline
conditions" for the same days. The "baseline conditions" are determined from IMPROVE data,
using the approach recommended in section 5 of this document or another method justified by
the state.
We expect that the RPG for the end of the second implementation period will be predicted by air
quality modeling that is based on meteorology from a year in the range of 2011 to 2017
depending on SIP submittal date and the timing of SIP development (and a base emissions
inventory from a year within the same range and close to the year of the meteorology). It is
conceivable for there to be differences between the meteorology in the 2000-2004 period and the
meteorology for the base year for the air quality modeling that would introduce some positive or
negative increment into this comparison, unrelated to emission changes between 2000-2004 and
2028, particularly because only a single year of meteorology will be used in the air quality
modeling. A state may develop a technically valid adjustment for such a difference, but should
consult with EPA and the FLMs before incorporating that adjustment into its SIP.
10.3. How should a state with an RPG that is not on the glidepath demonstrate that there
are no additional measures that are necessary to make reasonable progress?
Regional Haze Rule provisions
51.308(f)(3) Reasonable progress goals.
* * *
(ii)(A) If a State in which a mandatory Class I Federal area is located establishes a
reasonable progress goal for the most impaired days that provides for a slower rate of
improvement in visibility than the uniform rate of progress calculated under paragraph
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(f)(l)(vi) of this section, the State must demonstrate, based on the analysis required by
paragraph (f)(2)(i) of this section, that there are no additional emission reduction
measures for anthropogenic sources or groups of sources in the State that may reasonably
be anticipated to contribute to visibility impairment in the Class I area that would be
reasonable to include in the long-term strategy. The State must provide a robust
demonstration, including documenting the criteria used to determine which sources or
groups or sources were evaluated and how the four factors required by paragraph (f)(2)(i)
were taken into consideration in selecting the measures for inclusion in its long-term
strategy...
(B) If a State contains sources which are reasonably anticipated to contribute to visibility
impairment in a mandatory Class I Federal area in another State for which a
demonstration by the other State is required under (f)(3)(ii)(A), the State must
demonstrate that there are no additional emission reduction measures for anthropogenic
sources or groups of sources in the State that may reasonably be anticipated to contribute
to visibility impairment in the Class I area that would be reasonable to include in its own
long-term strategy. The State must provide a robust demonstration, including
documenting the criteria used to determine which sources or groups or sources were
evaluated and how the four factors required by paragraph (f)(2)(i) were taken into
consideration in selecting the measures for inclusion in its long-term strategy.
The Regional Haze Rule includes a requirement that the state with a Class I area compare its
2028 RPG for the 20 percent most impaired days to the 2028 point on the URP line. This
comparison determines whether the state, and any contributing upwind states, must submit an
additional demonstration that its LTS provides for reasonable progress.
Thus, if a state in which a mandatory Class I Federal area is located establishes an RPG for the
most impaired days that provides for a slower rate of improvement in visibility than the uniform
rate of progress calculated under paragraph (f)(l)(vi) of this section, that state and any
contributing states must demonstrate, based on the factors in paragraph (f)(2)(i) of this section,
that there are no additional emission reduction measures for any of its own anthropogenic
sources or source categories that may reasonably be anticipated to contribute to visibility
impairment in the Class I area that would be reasonable to include in the LTS.
A state's response in this situation should include, but not necessarily be limited to, the following
steps:
• For any sources for which additional technically feasible controls were rejected because
the cost/ton for the measure was higher than for a prior regulatory requirement at a
similar source, consider whether there are distinguishing features of the specific source
that would make the cost of compliance with the measure reasonable for that source.
• Compare the visibility impact threshold (or threshold for a surrogate for visibility
impacts) it has used in screening to the thresholds used by other states that contribute to
visibility impairment at the same Class I area. If the state's threshold is significantly
higher than used by other states, the screening should be repeated with a more similar
threshold.
• Bring forward for four-factor analysis sources in any sector that has recently experienced,
or may reasonably be expected to experience, emissions growth that is higher than the
overall economic growth rate in the state.
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• If the Class I area is one which is currently relatively close to natural visibility conditions
compared to more impaired Class I areas affected by sources in the state, repeat the
screening step using a percentage of impairment threshold rather than an absolute
visibility impact threshold. The percentage used as the threshold can be set equal to or
similar to the percentage that corresponds to the absolute impact threshold at the more
impaired Class I area.
• Review the sources and source categories that still are not brought forward from the
revised screening step and assess whether any of them are of a type and size for which
more effective emission control measures are in place, or will be required by the LTS as
it has been formulated so far, at similar sources in the same or other states.133
10.4. Calculation of the number of years it would take to attain natural visibility
conditions
Regional Haze Rule provisions
51.308(f)(3) Reasonable progress goals.
* * *
(ii)(A) If a State in which a mandatory Class I Federal area is located establishes a
reasonable progress goal for the most impaired days that provides for a slower rate of
improvement in visibility than the uniform rate of progress calculated under paragraph
(f)(l)(vi) of this section, the State ... must provide to the public for review as part of its
implementation plan an assessment of the number of years it would take to attain natural
visibility conditions if visibility improvement were to continue at the rate of progress
selected by the State as reasonable for the implementation period.
If the RPG for the 20 percent most impaired days for a Class I area is above the URP line, the
state with the Class I area must provide to the public for review as part of its implementation
plan an assessment of the number of years it would take to attain natural visibility conditions for
the 20 percent most impaired days if visibility improvement continues at the rate of progress
selected by the State as reasonable.134
133 The EPA's approach in developing a FIP for reasonable progress for sources in Texas is an example of
estimating visibility impacts at each Class I area, in both absolute terms (relative to a natural/clean background) and
as a percentage of overall impairment at the Class I area. We removed from four-factor analysis some sources that
were responsible for only very small fractions of overall impairment. We then estimated visibility benefit from
potential controls at the remaining sources and weighed these benefits against the four factors.
134 Note to reviewers of this draft guidance document: The recommendation here in essence makes a projection of
the number of years needed to reach natural visibility conditions based on the rate of progress achieved since the
baseline period of 2000-2004 as of 2028. An alternative approach would make this projection by starting with
"current visibility conditions," typically representing a period shortly before SIP submission. From this point, the
number of years needed to reach natural visibility conditions would be calculated based on the rate of progress
between the current visibility condition period and the 2028 RPG in the SIP revision. Comment is invited on which
approach would be most useful to public understanding, as such public understanding is the goal of this requirement
of the Regional Haze Rule. We note that no consequences to a state or to approval of the SIP would be based on this
projection of the number of years that would be required to reach natural visibility conditions.
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The number of years (N) should be calculated as follows.
(Baseline visibility conditions — Natural visibility conditions)
N =
[(Baseline visibility conditions — /?PG2028)/24]
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11. What are the additional requirements for a regional haze SIP?
11.1. Additional requirements of Regional Haze Rule section 308(f)(2)(ii) for long-term
strategies
Regional Haze Rule provisions
51.308(f)(2) Long-term strategy for regional haze and reasonably attributable visibility
impairment. Each State must submit a long-term strategy that addresses regional haze
visibility impairment, and if necessary any reasonably attributable visibility impairment
certified by the Federal Land Manager under §51.302(a), for each mandatory Class I
Federal area within the State and for each mandatory Class I Federal area located outside
the State that may be affected by emissions from the State. The long-term strategy must
include the enforceable emissions limitations, compliance schedules, and other measures
that are necessary to achieve reasonable progress, as determined pursuant to (f)(2)(i)
through (vi). In establishing its long-term strategy for regional haze, the State must meet
the following requirements:
(i) The State must consider and analyze emission reduction measures based on 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 major or minor stationary source or group of sources. The State must document
the criteria used to determine which sources or groups of sources were evaluated, and
how these four factors were taken into consideration in selecting the measures for
inclusion in its long-term strategy.
(ii) The State must consider the uniform rate of improvement in visibility, the emission
reduction measures identified in (f)(2)(i), and additional measures being adopted by other
contributing states in (f)(2)(iii) as needed to make reasonable progress towards natural
visibility conditions for the period covered by the implementation plan.
The state must consider the uniform rate of improvement in visibility.
A state with a Class I area gives adequate consideration to this factor by determining the uniform
rate of visibility improvement per the requirement of section 308(f)(l) and comparing its RPG
for the 20 percent most impaired days to the URP line and, if applicable, providing the additional
demonstration per the requirement of section 308(f)(3)(ii)(A).
A state with sources that may be reasonably anticipated to contribute to impairment at a Class I
area in another state gives sufficient consideration to the first of these items by being aware of
the outcome of the comparison of the RPG for the 20 percent most impaired days to the URP line
and providing the additional demonstration per the requirement of section 308(f)(3)(ii)(B).
The state must consider the emission reduction measures identified in (f)(2)(i).
This requirement applies in the same way to all states affecting a given Class I area. Section
(f)(2)(i) contains two references to "measures." The first sentence refers to measures that a state
considers and analyzes. The second sentence refers to measures that the state has selected for
inclusion in its LTS. Section (f)(2)(ii) refers to the first sentence, i.e., all the measures that the
state has chosen for four-factor analysis, because it would not be logical to say that in selecting
measures for the LTS a state should consider the measures it has already selected for such
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inclusion. A state gives adequate consideration to the emission reduction measures it is analyzing
by comparing them to measures being considered (or already adopted) by other contributing
states and by meeting the other requirements of the Regional Haze Rule.
The state must consider the additional measures being adopted by other contributing states in
(f)(2)(iii) as needed to make reasonable progress towards natural visibility conditions for the
period covered by the implementation plan.
This requirement applies in the same way to all states affecting a given Class I area. A state gives
adequate consideration to this factor by consulting with other contributing states to learn what
additional measures they are considering or plan to adopt and how they are taking the CAA-
specified factors, and visibility benefits if applicable, into consideration when determining what
additional measures are necessary to make reasonable progress. A state should not fail to adopt a
measure for a source within its own boundaries solely on the rationale that sufficient progress is
being provided by measures adopted by another state, regardless of the known or anticipated
position of the RPG relative to the URP line. If a state is applying an explicit decision rule with
respect to one of the CAA-specified factors, or to visibility benefits that is less protective of
visibility than other contributing states, the state should explain in its SIP why it is reasonable to
take that approach for its own sources.
11.2. Other requirements in Regional Haze Rule section 308(f)(2)(iv)
Section 308(f)(2)(iv) of the revised Regional Haze Rule requires that when developing its LTS, a
state must consider seven listed factors. A state necessarily gives consideration to some of these
factors as it meets other requirements of the Regional Haze Rule. Some of the listed factors are
associated with requirements that apply to all SIPs but are not explicitly repeated in the text of
the Regional Haze Rule. Particular EPA guidance on each of these factors is provided below. In
general, the EPA believes that these factors can be adequately considered without consuming
substantial state resources in terms of research, deliberation or documentation in the SIP revision
submittal.
308(f)(2)(iv)(A) - Emission reductions due to ongoing air pollution control programs, including
measures to address reasonably attributable visibility impairment.
This factor is considered by taking into account the existing and to-be-installed emission controls
at each source that is subject to a screening analysis or considered for a new requirement for
additional controls. It is also considered when the RPGs are determined via air quality modeling
that uses baseline and projected emission inventories that reflect these ongoing programs, and
then the RPGs are compared to the URP line to determine whether additional analysis of
measures for possible inclusion in the LTS is needed.
308(f)(2)(iv)(B) -Measures to mitigate the impacts of construction activities.
The SIP submission for the second planning period should refer to the section of the regional
haze SIP submission for the first implementation period that showed that the state had considered
this issue, indicate that the EPA has approved that portion of the previous SIP submission, and
qualitatively describe any significant changes including any large positive or negative change in
construction activity and significant measure to mitigate impacts of construction activity adopted
since the previous SIP revision. The state is not required to incorporate such measures into the
SIP.
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308(f)(2)(iv)(C) - Emissions limitations and schedules for compliance to achieve the RPG.
It is a general requirement that SIPs include emissions limitations and schedules for compliance
with required measures, so a state will adequately consider these by meeting that requirement for
additional measures included in the LTS as necessary to make reasonable progress.
308(f)(2)(iv)(D) - Source retirement and replacement schedules.
The state will adequately consider this factor as part of adequately considering the remaining
useful life of sources subject to full reasonable progress analysis.
308(f)(2)(iv)(E) -Basic smoke management practices for prescribedfire used for agricultural
and forestry management purposes and smoke management programs as currently exist within
the state for these purposes.
The recommendations in sections 6.5 and 7.1 address this requirement.
308(f)(2)(iv)(F) - Enforceability of emissions limitations and control measures.
It is a general requirement that measures incorporated into a SIP be enforceable.
308(f)(2)(iv)(G) - The anticipated net effect on visibility due to projected changes in point, area,
and mobile source emissions over the period addressed by the LTS.
The state gives adequate consideration to this factor when it determines the RPGs that reflect
measures in its own and contributing states' LTS.
11.3. Requirement for elements to make the SIP serve as a progress report on emission
reductions
Regional Haze Rule provisions
40 CFR 51.308(f)(5) So that the plan revision will serve also as a progress report, the
State must address in the plan revision the requirements of paragraphs (g)(l), (g)(2),
(g)(4), and (g)(5) of this section. However, the period to be addressed for these elements
shall be the period since the past progress report.
40 CFR 51.308(g) .. .Periodic progress reports must contain at a minimum the following
elements:
(1) A description of the status of implementation of all measures included in the
implementation plan for achieving reasonable progress goals for mandatory Class I
Federal areas both within and outside the State.
(2) A summary of the emissions reductions achieved throughout the State through
implementation of the measures described in paragraph (g)(l) of this section.
(4) An analysis tracking the change over the period since the period addressed in the most
recent plan required under paragraph (f) of this section in emissions of pollutants
contributing to visibility impairment from all sources and activities within the State.
Emissions changes should be identified by type of source or activity. With respect to all
sources and activities, the analysis must extend at least through the most recent year for
which the state has submitted emission inventory information to the Administrator in
compliance with the triennial reporting requirements of subpart A of this part. With
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respect to sources that report directly to a centralized emissions data system operated by
the Administrator, the analysis must extend through the most recent year for which the
Administrator has provided a State-level summary of such reported data or an internet-
based tool by which the State may obtain such a summary. The State is not required to
backcast previously reported emissions to be consistent with more recent emissions
estimation procedures, and may draw attention to actual or possible inconsistencies
created by changes in estimation procedures.
(5) An assessment of any significant changes in anthropogenic emissions within or
outside the State that have occurred since the period addressed in the most recent plan
required under paragraph (f) of this section including whether or not these changes in
anthropogenic emissions were anticipated in that most recent plan and whether they have
limited or impeded progress in reducing pollutant emissions and improving visibility.
For a SIP for the second implementation period, the "period since the past progress report" will
be the period since submission of the first progress report for the first implementation period,
since the 2016 revisions to the Regional Haze rule eliminated the requirement for any other
progress report that would otherwise have been due before 2025. Many of these first progress
reports were submitted late, and may not have described implementation activities during the few
years prior to their actual submission. Consequently, the interval between when this first
progress report was submitted and when the SIP for the second implementation period is
submitted may not include some historical years that would still be of public interest. To avoid a
gap in the reporting of past implementation activities, we recommend that the SIP for the second
implementation period cover the period starting with the first year that was not actually covered
by the first progress report through a year that is as close as possible to the point of submission
of the SIP.
The EPA issued general principles for the first progress reports in 2013.135 Except where these
guidelines for progress reports are not consistent with the current provisions of the Regional
Haze Rule as revised in 2016,136 these guidelines may be applied to the "progress report" aspect
of the SIP due in 2021.
11.4. Monitoring strategy elements
Regional Haze Rule provisions
40CFR51.308(f)
* * *
(4) If the Administrator, Regional Administrator, or the affected Federal Land Manager
has advised a State of a need for additional monitoring to assess reasonably attributable
visibility impairment at a mandatory Class I Federal area in addition to the monitoring
currently being conducted, the State must include in the plan revision an appropriate
135 General Principles for the 5-Year Regional Haze Progress Reports for the Initial Regional Haze State
Implementation Plans (Intended to Assist States and EPA Regional Offices in Development and Review of the
Progress Reports), April 2013. https://www. epa.gov/sites/production/files/2016-03/documents/haze_5year_4-10-
13.pdf.
136 The 2016 revisions to the Regional Haze Rule provided more specificity as to the most recent year for which
emissions must be reported than was stated in the General Principles.
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strategy for evaluating reasonably attributable visibility impairment in the mandatory
Class I Federal area by visual observation or other appropriate monitoring techniques.
* * *
(6) Monitoring strategy and other implementation plan requirements. The State must
submit with the implementation plan a monitoring strategy for measuring, characterizing,
and reporting of regional haze visibility impairment that is representative of all
mandatory Class I Federal areas within the State. Compliance with this requirement may
be met through participation in the Interagency Monitoring of Protected Visual
Environments network. The implementation plan must also provide for the following:
(i) The establishment of any additional monitoring sites or equipment needed to assess
whether reasonable progress goals to address regional haze for all mandatory Class I
Federal areas within the State are being achieved.
(ii) Procedures by which monitoring data and other information are used in determining
the contribution of emissions from within the State to regional haze visibility impairment
at mandatory Class I Federal areas both within and outside the State.
(iii) For a State with no mandatory Class I Federal areas, procedures by which monitoring
data and other information are used in determining the contribution of emissions from
within the State to regional haze visibility impairment at mandatory Class I Federal areas
in other States.
(iv) The implementation plan must provide for the reporting of all visibility monitoring
data to the Administrator at least annually for each mandatory Class I Federal area in the
State. To the extent possible, the State should report visibility monitoring data
electronically.
(v) A statewide inventory of emissions of pollutants that are reasonably anticipated to
cause or contribute to visibility impairment in any mandatory Class I Federal 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. The State must
also include a commitment to update the inventory periodically.
(vi) Other elements, including reporting, recordkeeping, and other measures, necessary to
assess and report on visibility.
At the time this document was prepared, the EPA is not expecting that any state will need to
address these requirements in a manner differently than in its SIP for the first implementation
period. States with questions or concerns, or that receive public comments that raise issues
related to these requirements, should consult with their EPA regional office and with the FLMs
for affected Class I areas.
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APPENDIX A
Key Steps and Tasks in Developing a Regional Haze SIP
Reference
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Step or Task
Take inventory of information resources available for SIP development.
Determine Class I areas in other states that may be reasonably anticipated to be
affected by emission sources in the state.
Determine which other states have sources that may be reasonably anticipated to
affect in-state Class I areas.
Consult with these states on an ongoing basis, through multi-state organizations
and directly.
Consult with FLMs for these in-state and out-of-state Class I areas on an ongoing
basis.
Determine baseline, current and natural visibility conditions for the 20 percent
most impaired days and the 20 percent clearest days, for each in-state and out-of-
state Class I area.
Develop current extinction budgets for each Class I area.
Identify significant future trends in emissions.
(Optional) Conduct source apportionment modeling and/or review available results
from such modeling by other parties.
(Optional) Estimate visibility impacts for screening purposes.
Select sources for four-factor analysis.
Identify emission control measures to be considered for these sources.
Quantify the four factors for these sources and measures.
(Optional) Quantify visibility benefits for these sources and measures.
Select measures for inclusion in the LTS
Set emission limits, averaging periods and monitoring and record keeping
requirements.
Set compliance deadlines.
Project the 2028 RPGs for the 20 percent most impaired and 20 percent clearest
days.
Compare 2028 RPG for the 20 percent most impaired days to the 2028 point on the
URP line and if above the line demonstrate that there are no additional measures
that are necessary to make reasonable progress.
Relevant Regional
Haze Rule Provisions
Not explicitly addressed.
51.308(f)(2)
51.308(f)(2)
51.308(f)(2)
51.308(1)
51.308(f)(l)
Not explicitly addressed.
51.308(f)(4)
Not explicitly addressed.
Not explicitly addressed.
51.308(f)(2)
51.308(f)(2)
51.308(f)(2)(i)
Not explicitly addressed.
51.308(f)(2)
51.308(f)(2)(vi)(C)
51.308(f)(2)(i)
51.308(f)(3)
51.308(f)(3)(ii)
Relevant Document
Section
Not explicitly addressed.
6.1
Not explicitly addressed.
4.8
4.8
5.9,5.8,5.11
See the TSD.
Not explicitly addressed.
6.2
6.2
6.3
7.1
7.2-7.5
6.2
8
7.1
7.3
9
10
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Reference
Number
20
21
22
23
24
25
26
27
28
29
30
31
32
Step or Task
Compare 2028 RPG for the 20 percent clearest days to the 2000-2004 conditions
for the same days, and strengthen the LTS if there is degradation. Also, compare
the 2028 RPG for the 20 percent most impaired days to the 2000-2004 conditions
for the same days, and strengthen the LTS if the RPG does not show an
improvement.
Identify all anthropogenic sources of visibility impairment considered by the State
in developing its LTS and the criteria used to select the sources considered.
Document the criteria used to determine which sources or groups of sources were
evaluated, and how these four factors were taken into consideration in selecting the
measures for inclusion in its LTS.
Document the technical basis, including information on the four factors and
modeling, monitoring and emissions information, on which the State is relying to
determine the emission reductions from anthropogenic sources in the State that are
necessary for achieving reasonable progress towards natural visibility conditions in
each mandatory Class I Federal area it affects.
Identify the baseline emissions inventory on which its strategies are based.
Calculate the number of years it would take to reach natural conditions at the rate
of progress provided by the SIP for the implementation period.
Consider:
The uniform rate of improvement in visibility.
The emission reduction measures considered with respect to the four factors.
Additional measures being adopted by other contributing states in (f)(2)(iii) as
needed to make reasonable progress towards natural visibility conditions for the
period covered by the implementation plan.
Consider, emission reductions due to ongoing air pollution control programs,
including measures to address RAVI.
Consider measures to mitigate the impacts of construction activities.
Consider emissions limitations and schedules for compliance to achieve the RPG.
Consider source retirement and replacement schedules.
Consider smoke management techniques for agricultural and forestry management
purposes including plans as currently exist within the State for these purposes.
Consider enforceability of emissions limitations and control measures.
Relevant Regional
Haze Rule Provisions
51.308(f)(3)(i)
51.308(f)(2)(v)
51.308(f)(2)(iv)
51.308(f)(2)(iv)
51.308(f)(2)(iv)
51.308(f)(3)(ii)(A)
51.308(f)(2)(ii)
51.308(f)(2)(vi)(A)
51.308(f)(2)(vi)(B)
51.308(f)(2)(vi)(C)
51.308(f)(2)(vi)(D)
51.308(f)(2)(vi)(E)
51.308(f)(2)(vi)(F)
Relevant Document
Section
10
4.7
4.7
4.7
6.2
10.4
10.1
10.1
10.1
10.1
10.1
10.1
10.1
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Reference
Number
33
34
35
36
37
38
39
40
41
42
Step or Task
Consider the anticipated net effect on visibility due to projected changes in point,
area and mobile source emissions over the period addressed by the LTS.
Demonstrate that the state has included in its implementation plan all measures
necessary to obtain its share of the emission reductions needed to provide for
reasonable progress towards natural visibility conditions in the mandatory Class I
Federal area located in the other state or states. If the state has participated in a
regional planning process, the state must also ensure that it has included all
measures needed to achieve its apportionment of emission reduction obligations
agreed upon through that process.
Submit a monitoring strategy for measuring, characterizing and reporting of
regional haze visibility impairment that is representative of all mandatory Class I
Federal areas within the State.
Provide for the establishment of any additional monitoring sites or equipment
needed to assess whether reasonable progress goals to address regional haze for all
mandatory Class I Federal areas within the State are being achieved.
Provide for procedures by which monitoring data and other information are used in
determining the contribution of emissions from within the State to regional haze
visibility impairment at mandatory Class I Federal areas both within and outside
the State.
For a State with no mandatory Class I Federal areas, provide for procedures by
which monitoring data and other information are used in determining the
contribution of emissions from within the State to regional haze visibility
impairment at mandatory Class I Federal areas in other States.
Provide for reporting of all visibility monitoring data to the Administrator at least
annually for each mandatory Class I Federal area in the State. To the extent
possible, the State should report visibility monitoring data electronically.
Provide for a statewide inventory of emissions of pollutants that are reasonably
anticipated to cause or contribute to visibility impairment in any mandatory Class I
Federal 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. The State must also include a commitment to update the
inventory periodically.
Provide other elements, including reporting, recordkeeping and other measures,
necessary to assess and report on visibility.
Commit to submit the January 31, 2025, progress report.
Relevant Regional
Haze Rule Provisions
51.308(f)(2)(vi)(G)
51.308(f)(2)(iii)(A)
51.308(f)(6)
51.308(f)(6)(i)
51.308(f)(6)(ii)
51.308(f)(6)(iii)
51.308(f)(6)(iv)
51.308(f)(6)(v)
51.308(f)(6)(vi)
51.308(f) opening text
Relevant Document
Section
10.1
Not explicitly addressed.
11.4
11.4
11.4
11.4
11.4
11.4
11.4
Not explicitly addressed.
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APPENDIX B
EPA Actions on Regional Haze SIPs
for the First Implementation Period
State /Territory
Required SIP
Elements
Addressed
Alabama, Georgia,
Indiana, Iowa,
Louisiana, Michigan,
Mississippi, Missouri,
North Carolina, Ohio,
Pennsylvania, South
Carolina, Virginia and
Texas
EGU BART and LTS
forNOxandSCh
Georgia, Indiana, Iowa,
Kentucky, Michigan,
Missouri, Ohio,
Pennsylvania, South
Carolina, Tennessee,
Virginia and West
Virginia
Most Recent
EPA Action
Final Limited
Disapprovals of SIPs
Final Partial FIPs
Additional
Explanation
Limited disapproval of
these states SIPs due
to their reliance on
CAIR to satisfy the
BART and LTS
requirements. In the
same action (see next
entry), the EPA
finalized partial FIPs
relying on CSAPR to
remedy this deficiency
for certain of these
states.
FIPs rely on CSAPR
to address the
deficiencies in the
SIPs of the listed
states. (See above
entry).
Hyperlinks to Federal Register Notices137
Proposed Rule - Regional Haze: Revisions to Provisions Governing Alternatives to Source-
Specific Best Available Retrofit Technology (BART) Determinations, Limited SIP Disapprovals,
and Federal Implementation Plans, 76 FR 82219 ("Dec. 30, 2011).
Notice Of Extension Of Public Comment Period - Regional Haze: Revisions to Provisions
Governing Alternatives to Source-Specific Best Available Retrofit Technology (BART)
Determinations, Limited SIP Approvals, and Federal Implementation Plans, 77 FR 4735 (Jan. 31,
2012).
Final Rule - Regional Haze: Revisions to Provisions Governing Alternatives to Source-Specific
Best Available Retrofit Technology (BART) Determinations, Limited SIP Disapprovals, and
Federal Implementation Plans, 77 FR 33642 (June 7, 2012).
Proposed Rule - Regional Haze: Revisions to Provisions Governing Alternatives to Source-
Specific Best Available Retrofit Technology (BART) Determinations, Limited SIP Disapprovals,
and Federal Implementation Plans, 76 FR 82219 (Dec. 30, 2011).
Notice Of Extension Of Public Comment Period - Regional Haze: Revisions to Provisions
Governing Alternatives to Source-Specific Best Available Retrofit Technology (BART)
Determinations, Limited SIP Approvals, and Federal Implementation Plans, 77 FR 4735 (Jan. 31,
2012).
137 Some of the listed Federal Register notices also contain EPA actions on SIP elements that address the CAA section 110 "infrastructure SIP" requirement
regarding interstate visibility transport, but this table does not capture all such actions.
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State /Territory
Required SIP
Elements
Addressed
EGU BART and LTS
for NOx and SO2
Alabama
Remaining elements
Alaska
All BART elements
Alaska
All remaining elements
Albuquerque/Bernalillo
County
All elements
Arizona
BART for Cholla,
Apache, and Coronado
EGUs
Most Recent
EPA Action
Final Limited
Approval
Final Approval
Final Approval
Final Approval
Final Partial
Approval/Partial
Disapproval and
Partial FIP
Additional
Explanation
Limited approval of
remaining elements of
regional haze SIP.
Disapproval of NOx
BART and FIP
requiring NOx
controls at these
EGUs.
Hyperlinks to Federal Register Notices137
Final Rule - Regional Haze: Revisions to Provisions Governing Alternatives to Source-Specific
Best Available Retrofit Technology (BART) Determinations, Limited SIP Disapprovals, and
Federal Implementation Plans, 77 FR 33642 ( June 7, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of
Alabama; Regional Haze State Implementation Plan, 77 FR 1 1937 (Feb. 28, 2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of Alabama; Regional
Haze State Implementation Plan, 77 FR 38515 (June 28, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Alaska; Regional
Haze State Implementation Plan, 77 FR 1 1022 (Feb. 24, 2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of Alaska; Regional
Haze State Implementation Plan, 78 FR 10546 (Feb. 14, 2013).
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Alaska; Regional
Haze State Implementation Plan, 77 FR 1 1022 (Feb. 24, 2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of Alaska; Regional
Haze State Implementation Plan, 78 FR 10546 (Feb. 14, 2013).
Proposed Rule - Approval and Promulgation of State Implementation Plans; City of
Albuquerque-Bernalillo County, NM; Interstate Transport Affecting Visibility and Regional Haze
Rule Requirements for Mandatory Class I Areas, 77 FR 24767 (Apr. 25, 2012).
Final Rule - Approval and Promulgation of State Implementation Plans; City of Albuquerque-
Bernalillo County, New Mexico; Interstate Transport Affecting Visibility and Regional Haze
Rule Requirements for Mandatory Class I Areas, 77 FR 71 1 1 9 (Nov. 29, 2012).
Proposed Rule - Approval, Disapproval and Promulgation of Air Quality Implementation Plans;
Arizona; Regional Haze State and Federal Implementation Plans, 77 FR 42833 (July 20, 2012).
Proposed Rule; Notice Of Additional Public Hearings And Extension Of Comment Period -
Approval, Disapproval and Promulgation of Air Quality Implementation Plans; Arizona;
Regional Haze State and Federal Implementation Plans, 77 FR 45326 (July 31, 2012).
132
-------
State /Territory
Required SIP
Elements
Addressed
Arizona
All remaining BART
and regional haze SIP
elements
Arizona
Section 309 SO2
Program
Arizona
Hay den and Miami
copper smelters
SundtUnit4and
Chemical Lime (two
kilns).
Most Recent
EPA Action
Final Partial
Approval/Partial
Disapproval
Final Partial
Disapproval
Final Partial FIP
Additional
Explanation
Disapproval of
remaining elements.
Disapproval of prior
SIP submittal because
it does not satisfy
requirements of 40
CFR51.309(d)(4).
FIP requiring controls
to address the BART
requirements at these
sources.
Hyperlinks to Federal Register Notices137
Final Rule - Approval Disapproval and Promulgation of Air Quality Implementation Plans:
Arizona; Regional Haze State and Federal Implementation Plans, 77 FR 7251 1 (Dec. 5, 2012).
Proposed Rule - Partial Approval and Disapproval of Air Oualitv Implementation Plans; Arizona;
Regional Haze and Visibility Impacts of Transport, Ozone and Fine Particulates, 77 FR 75703
(Dec. 21,2012).
Notice; Extension of Comment Period - Partial Approval and Disapproval of Air Oualitv
Implementation Plans; Arizona; Regional Haze and Visibility Transport; Extension of Comment
Period, 78 FR 7702 (Feb. 4, 2013).
Proposed Rule - Partial Approval and Partial Disapproval of Air Oualitv State Implementation
Plans; Arizona; Regional Haze Requirements, 78 FR 29292 (May 20, 2013).
Final Rule - Approval and Disapproval of Air Oualitv State Implementation Plans; Arizona;
Regional Haze and Interstate Transport Requirements, 78 FR 46141 (July 30, 2013).
Final Rule; Correction - Approval and Disapproval of Air Oualitv State Implementation Plans;
Arizona; Regional Haze and Interstate Transport Requirements, 78 FR 49684 (Aug. 15, 2013).
Proposed Rule - Partial Disapproval of State Implementation Plan; Arizona; Regional Haze
Requirements, 78 FR 8083 (Feb. 5, 2013).
Final Rule - Partial Disapproval of State Implementation Plan; Arizona; Regional Haze
Requirements, 78 FR 48326 (Aug. 8, 2013).
Proposed Rule - Promulgation of Air Oualitv Implementation Plans; Arizona; Regional Haze and
Interstate Visibility Transport Federal Implementation Plan, 79 FR 9317 (Feb. 18, 2014).
Final Rule - Promulgation of Air Oualitv Implementation Plans; Arizona; Regional Haze and
Interstate Visibility Transport Federal Implementation Plan, 79 FR 524 1 9 (Sept. 3, 20 14).
133
-------
State /Territory
Required SIP
Elements
Addressed
Arizona
Revisions to FIP for
some sources
Apache Generating
Station
Nelson Lime Plant (two
kilns)
Coronado Generating
Station
Arkansas
All elements
Most Recent
EPA Action
Several revisions of
previously adopted
FIP requirements for
specific sources
Final Partial
Approval/Partial
Disapproval
Additional
Explanation
Revision of FIP for
these sources on the
request of the owners
of the sources.
Disapproval of BART
determinations for
some EGUs and
industrial boilers and
reasonable progress
analysis/LTS.
Hyperlinks to Federal Register Notices137
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Arizona;
Regional Haze State and Federal Implementation Plans; Reconsideration, 79 FR 56322 (Sept. 19,
2014) [Steam Units 1-3 at Arizona Electric Power Cooperative's (AEPCO) Apache Generating
Station ( Apache)].
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Arizona; Regional
Haze State and Federal Implementation Plans; Reconsideration, 80 FR 19220 ("Apr. 10, 2015)
[Steam Units 1-3 at Arizona Electric Power Cooperative's (AEPCO) Apache Generating Station
( Apache)].
Proposed Rule - Promulgation of Air Quality Implementation Plans; Arizona; Regional Haze
Federal Implementation Plan; Reconsideration, 80 FR 1 608 (Jan. 13,2015) [Kilns 1 -2 at Nelson
Lime Plant].
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Arizona; Regional
Haze Federal Implementation Plan; Reconsideration, 80 FR 21 176 (Apr. 17, 2015) [Kilns 1-2 at
Nelson Lime Plant] .
Proposed Rule: Promulgation of Air Quality Implementation Plans; Arizona; Regional
Haze Federal Implementation Plan; Reconsideration, 80 FR 17010 (March 31, 2015).
(Coronado Generating Station)
Final Rule: Promulgation of Air Quality Implementation Plans; Arizona; Regional Haze Federal
Implementation Plan; Reconsideration 81 FR 21735 (April 13, 2016). (Coronado Generating
Station)
Proposed Rule - 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, 76 FR 64185 (Oct. 17, 2011).
Proposed Rule; Extension of Comment Period - Extension of Public Comment Period for
Proposed Action on Arkansas Regional Haze State Implementation Plan and Interstate Transport
State Implementation Plan To Address Pollution Affecting Visibility and Regional Haze, 76 FR
70952 (Nov. 16,2011).
134
-------
State /Territory
Required SIP
Elements
Addressed
Arkansas
Proposed FIP to address
previously disapproved
elements
California
All elements
Colorado
All elements
Connecticut
All elements
Most Recent
EPA Action
Proposed partial FIP
Final Approval
Final Approval (Re-
issued to more
adequately respond to
public comments)
Final Approval
Additional
Explanation
Hyperlinks to Federal Register Notices137
Final Rule - 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, 77 FR 14603 (Mar. 12, 2012).
Proposed Rule - Promulgation of Air Quality Implementation Plans; State of Arkansas; Regional
Haze and Interstate Visibility Transport Federal Implementation Plan, 80 FR 18943 (Apr. 8,
2015).
Proposed Rule; Extension Of Comment Period; Availability Of Supplemental Information -
Approval and Promulgation of Implementation Plans; Arkansas; Regional Haze and Interstate
Visibility Transport Federal Implementation Plan; Extension of Comment Period and Notice of
Availability, 80 FR 24872 (May 1, 2015).
Proposed Rule; Reopening of Comment Period - Approval and Promulgation of Implementation
Plans; Arkansas; Regional Haze and Interstate Visibility Transport Federal Implementation Plan;
Reopening of Comment Period, 80 FR 43661 (July 23, 2015).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of
California; Regional Haze State Implementation Plan and Interstate Transport Plan; Interference
With Visibility Requirement, 76 FR 13944 (Mar. 15, 201 1).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; State of California;
Interstate Transport, 76 FR 34608 (June 14, 201 1).
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Colorado;
Regional Haze State Implementation Plan, 77 FR 18051 (Mar. 26, 2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of Colorado; Regional
Haze State Implementation Plan, 77 FR 76871 (Dec. 31, 2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of Colorado; Regional
Haze State Implementation Plan, 80 FR 29953 (May 26, 2015).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Connecticut;
Regional Haze, 77 FR 17367 (Mar. 26, 2012).
Supplemental Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans;
Connecticut; Regional Haze, 78 FR 5158 (Jan. 24, 2013).
135
-------
State /Territory
Required SIP
Elements
Addressed
Delaware
All elements
District of Columbia
All elements
Florida
BART for Big Bend 1,
2, 3; Purdom Unit 7;
Port Everglades 3, 4;
and Cemex, White
Spring SR/SC Complex
Florida
Remaining elements
Florida
Subsequent SIP
revision
Most Recent
EPA Action
Final Approval
Final Approval
Final Partial
Approval
Final Approval
Final Approval
Additional
Explanation
Approval of a SIP
revision addressing the
NOX BART
requirements. This
revision sets a new
emission limit to better
reflect the capability of
Hyperlinks to Federal Register Notices137
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Connecticut
Regional Haze, 79 FR 39322 (July 10, 2014).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of
Delaware; Regional Haze State Implementation Plan, 76 FR 27973 (May 13, 201 1).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Delaware;
Regional Haze State Implementation Plan, 76 FR 42557 ( July 19, 201 1).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; District of
Columbia; Regional Haze State Implementation Plan, 76 FR 70929 (Nov. 16, 2011).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; District of
Columbia; Regional Haze State Implementation Plan, 77 FR 5191 ("Feb. 2, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of
Florida; Regional Haze State Implementation Plan, 77 FR 31240 (May 25, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; State of Florida;
Regional Haze State Implementation Plan, 77 FR 71 1 1 1 (Nov. 29, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of
Florida; Regional Haze State Implementation Plan, 77 FR 73369 (Dec. 10, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; State of Florida;
Regional Haze State Implementation Plan, 78 FR 53250 (Aug. 29, 2013).
Proposed Rule - Approval and Promulgation of Implementation Plans; Florida; Regional Haze
Plan Amendment-Lakeland Electric C.D. Mclntosh, 80 FR 50591 (Aug. 20, 2015).
Final Rule - Approval and Promulgation of Implementation Plans; Florida; Regional Haze Plan
Amendment-Lakeland Electric C.D. Mclntosh, 80 FR 64344 (Oct. 23, 2015).
136
-------
State /Territory
Required SIP
Elements
Addressed
Unit 1 at the Lakeland
Electric-C.D. Mclntosh
Power Plant
Georgia
Remaining elements
Hawaii
All elements
Idaho
All BART elements
Idaho
All remaining elements
Idaho
Subsequent SIP
revision for BART
alternative for TASCO
Amalgamated Sugar
Most Recent
EPA Action
Final Limited
Approval/ Limited
Disapproval
Final FIP
Final Partial
Approval
Final Approval
Final approval of
revised BART for
PM and alternative
control for SCh
BART
Additional
Explanation
the BART approach
previously approved.
Limited disapproval
due to reliance on
CAIR.
The state chose not to
submit a SIP.
Hyperlinks to Federal Register Notices137
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of
Georgia; Regional Haze State Implementation Plan, 77 FR 1 1452 (Feb. 27, 2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of Georgia; Regional
Haze State Implementation Plan, 77 FR 38501 (June 28, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Hawaii; Regional
Haze Federal Implementation Plan, 77 FR 31691 (May 29, 2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of Hawaii; Regional
Haze Federal Implementation Plan, 77 FR 61477 (Oct. 9, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Idaho; Regional
Haze State Implementation Plan and Interstate Transport Plan, 76 FR 1 579 (Jan. 1 1 , 201 1 ).
Final Rule - Approval and Promulgation of Implementation Plans; State of Idaho; Regional Haze
State Implementation Plan and Interstate Transport Plan, 76 FR 36329 (June 22, 201 1).
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Idaho; Regional
Haze State Implementation Plan, 77 FR 30248 (May 22, 2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of Idaho; Regional Haze
State Implementation Plan, 77 FR 66929 (Nov. 8, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Idaho
Amalgamated Sugar Company Nampa BART Alternative, 78 FR 38872 (June 28, 2013).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Idaho
Amalgamated Sugar Company Nampa BART Alternative, 79 FR 23273 (Apr. 28, 2014).
137
-------
State /Territory
Required SIP
Elements
Addressed
Illinois
All elements
Illinois
Subsequent SIP
revision for Ameren
Multi-Pollutant
Standard Group
Illinois
Subsequent SIP
revision for Midwest
Generation, LLC
facilities)
Indiana
Remaining elements
Iowa
Remaining elements
Most Recent
EPA Action
Final Approval
Proposed Approval
Final Approval
Final Limited
Approval
Final Limited
Approval
Additional
Explanation
Proposed approval of
Illinois SIP variances
for certain EGUs.
Final approval of
Illinois SIP variances
for certain EGUs.
Remaining elements
were approved.
Remaining elements
were approved.
Hyperlinks to Federal Register Notices137
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Illinois;
Regional Haze, 77 FR 3966 ( Jan. 26, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Illinois; Regional
Haze, 77 FR 39943 (July 6, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Illinois;
Illinois Power Holdings and AmerenEnergy Medina Valley Cogen Variance, 80 FR 21681 (Apr.
20,2015).
Final Rule - Air Quality Implementation Plan Approval; Illinois; Illinois Power Holdings and
AmerenEnergy Medina Valley Cogen Variance, 80 FR 79261 (Dec. 21, 2015).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Illinois;
Midwest Generation Variances, 80 FR 22662 (Apr. 23, 2015).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Illinois; Midwest
Generation Variances, 80 FR 42726 (July 20, 2015).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Indiana;
Regional Haze, 77 FR 3975 (Jan. 26, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Indiana; Regional
Haze, 77 FR 34218 (June 11, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Iowa Regional
Haze State Implementation Plan, 77 FR 11974 (Feb. 28,2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of Iowa: Regional Haze,
77 FR 38006 (June 26, 2012).
138
-------
State /Territory
Required SIP
Elements
Addressed
Kansas
All elements
Kentucky
All elements
Louisiana
Remaining elements
Maine
All elements
Maryland
All elements
Massachusetts
Most Recent
EPA Action
Final Approval
Final Limited
Approval/ Limited
Disapproval
Final Partial
Approval/Partial
Disapproval
Final Approval
Final Approval
Final Approval
Additional
Explanation
Limited disapproval
due to reliance on
CAIR.
Partial disapproval of
BART determination
for four non-EGU
sources.
Hyperlinks to Federal Register Notices137
Proposed Rule - Approval and Promulgation of Implementation Plans: State of Kansas Regional
Haze State Implementation Plan, 76 FR 52604 (Aug. 23, 201 1).
Final Rule - Approval and Promulgation of Implementation Plans; State of Kansas: Regional
Haze, 76 FR 80754 (Dec. 27, 2011).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans:
Commonwealth of Kentucky: Regional Haze State Implementation Plan, 76 FR 78194 (Dec. 16,
2011).
Final Rule - Approval and Promulgation of Implementation Plans: Commonwealth of Kentucky:
Regional Haze State Implementation Plan, 77 FR 19098 (Mar. 30, 2012).
Final Rule: Correcting Amendment - Approval and Promulgation of Implementation Plans:
Commonwealth of Kentucky: Regional Haze State Implementation Plan: Correction, 77 FR
27626 (May 11, 20 12).
Proposed Rule - Approval and Promulgation of Implementation Plans: Louisiana: Regional Haze
State Implementation Plan, 77 FR 1 1839 (Feb. 28, 2012).
Final Rule - Approval and Promulgation of Implementation Pans: Louisiana: Regional Haze State
Implementation Plan, 77 FR 39425 (July 3, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans: Maine:
Regional Haze, 76 FR 73955 (Nov. 29, 2011).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans: Maine: Regional
Haze, 77 FR 24385 (Apr. 24, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans: State of
Maryland: Regional Haze State Implementation Plan, 77 FR 1 1827 (Feb. 28, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans: Maryland:
Regional Haze State Implementation Plan, 77 FR 39938 (July 6, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans:
Massachusetts: Regional Haze, 77 FR 30932 (May 24, 2012).
139
-------
State /Territory
Required SIP
Elements
Addressed
All elements
Michigan
All remaining elements
except BART for
taconite plants
Michigan
Taconite BART FIP
Michigan
Taconite BART SIP
Michigan
Taconite BART FIP
Minnesota
All SIP elements except
BART for 6 taconite
facilities
Most Recent
EPA Action
Final Limited
Approval/ Limited
Disapproval and
Partial FIP
Final Partial FIP
Final Partial
Disapproval
Reconsideration of
taconite BART FIP
Final Partial
Approval
Additional
Explanation
Final limited approval
of SIP and partial
disapproval of NOx
and SO2 BART
determinations. Partial
FIP.
Disapproval of BART
determination for
taconite plants
Hyperlinks to Federal Register Notices137
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Massachusetts;
Regional Haze, 78 FR 57487 (Sept. 19, 2013).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Michigan;
Regional Haze State Implementation Plan; Federal Implementation Plan for Regional Haze, 77
FR 46911 (Aug. 6,2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Michigan;
Regional Haze State Implementation Plan; Federal Implementation Plan for Regional Haze, 77
FR 71533 (Dec. 3,2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; States of Minnesota and
Michigan; Regional Haze Federal Implementation Plan, 77 FR 49307 (Aug. 15, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; States of
Minnesota and Michigan; Regional Haze State Implementation Plan; Federal Implementation
Plan for Regional Haze, 78 FR 8705 (Feb. 6, 2013).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; States of
Michigan and Minnesota; Regional Haze, 78 FR 8478 (Feb. 6, 2013).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; States of Michigan
and Minnesota; Regional Haze, 78 FR 59825 (Sept. 30, 2013),
Proposed rule: Air Plan Approval; Minnesota and Michigan; Revision to Taconite Federal
Implementation Plan, 80 FR 64159 (October 22, 2015)
Final Rule - Air Plan Approval; Minnesota and Michigan; Revision to 20 1 3 Taconite Federal
Implementation Plan Establishing BART for Taconite Plants. 81 FR 21671 (April 12, 2016)
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Minnesota;
Regional Haze, 77 FR 3681 (Jan. 25, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Minnesota;
Regional Haze, 77 FR 34801 (June 12, 2012).
140
-------
State /Territory
Required SIP
Elements
Addressed
Minnesota
Taconite BART FIP
Minnesota
Taconite BART SIP
Minnesota
Taconite BART FIP
Minnesota
Mississippi
Remaining elements
Missouri
Most Recent
EPA Action
Final FIP
Final Partial
Disapproval
Reconsideration of
taconite BART FIP
Final FIP
Final Limited
Approval
Final Limited
Approval
Additional
Explanation
FIP obligation arose
from the failure of the
state to submit a SIP
on time. The later EPA
action on the SIP is
listed in the next entry.
Disapproval of BART
for taconite plants
FIP implements a
settlement agreement
related to a FLM
RAVI certification for
the Northern States
Power Company's
(NSP's) Sherburne
County Generating
Station (Sherco)
Remaining elements
were approved.
Remaining elements
were approved.
Hyperlinks to Federal Register Notices137
Proposed Rule - Approval and Promulgation of Implementation Plans: States of Minnesota and
Michigan; Regional Haze Federal Implementation Plan, 77 FR 49307 (Aug. 15, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; States of
Minnesota and Michigan; Regional Haze State Implementation Plan; Federal Implementation
Plan for Regional Haze, 78 FR 8705 (Feb. 6, 2013).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; States of
Michigan and Minnesota; Regional Haze, 78 FR 8478 (Feb. 6, 2013).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; States of Michigan
and Minnesota; Regional Haze 78 FR 59825 (Sept. 30, 2013).
Proposed rule: Air Plan Approval; Minnesota and Michigan; Revision to Taconite Federal
Implementation Plan, 80 FR 64159 (October 22, 2015)
Final Rule - Air Plan Approval; Minnesota and Michigan; Revision to 20 1 3 Taconite Federal
Implementation Plan Establishing BART for Taconite Plants. 81 FR 21671 (April 12, 2016)
Proposed Rule - Air Plan Approval; Minnesota; Revision to Visibility Federal Implementation
Plan, October 27, 2015 (80 FR 65675)
Final rule - Air Plan Approval; Minnesota; Revision to Visibility Federal Implementation Plan,
March 7, 2016 (81 FR 11668)
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of
Mississippi; Regional Haze State Implementation Plan, 77 FR 1 1879 (Feb. 28, 2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of Mississippi; Regional
Haze State Implementation Plan, 77 FR 38191 (June 27, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of
Missouri; Regional Haze State Implementation Plan, 77 FR 1 1958 (Feb. 28, 2012).
141
-------
State /Territory
Required SIP
Elements
Addressed
Remaining elements
Montana
All elements
Nebraska
All elements
Nevada
All elements except for
Reid Gardner BART
Most Recent
EPA Action
Final FIP
Final Limited
Approval/ Limited
Disapproval and FIP
Final Partial
Approval
Additional
Explanation
Montana did not
submit a SIP.
The EPA approved the
state's SIP, except for
the portion regarding
S02 EGU BART at
Gerald Gentleman
Station. This
deficiency is addressed
through a FIP relying
on CSAPR.
Hyperlinks to Federal Register Notices137
Final Rule - Approval and Promulgation of Implementation Plans; State of Missouri: Regional
Haze, 77 FR 38007 ( June 26, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Montana; State
Implementation Plan and Regional Haze Federal Implementation Plan, 77 FR 23987 (Apr. 20,
2012).
Proposed Rule; Corrections - Approval and Promulgation of Implementation Plans; State of
Montana; State Implementation Plan and Regional Haze Federal Implementation Plan, 77 FR
29270 (May 17, 20 12).
Final Rule - Approval and Promulgation of Implementation Plans; State of Montana; State
Implementation Plan and Regional Haze Federal Implementation Plan, 77 FR 57863 (Sept. 18,
2012).
Proposed Rule - Approval, Disapproval and Promulgation of Implementation Plans; Nebraska;
Regional Haze State Implementation Plan; Federal Implementation Plan for Best Available
Retrofit Technology Determination, 77 FR 12770 (Mar. 2, 2012).
Proposed Rule; Extension of Public Comment Period and Opportunity for Public Hearing -
Approval, Disapproval and Promulgation of Implementation Plans; Nebraska; Regional Haze
State Implementation Plan; Federal Implementation Plan for Best Available Retrofit Technology
Determination; Extension of Public Comment Period, 77 FR 20333 (Apr. 4, 2012).
Final Rule - Approval, Disapproval and Promulgation of Implementation Plans; State of
Nebraska; Regional Haze State Implementation Plan; Federal Implementation Plan for Best
Available Retrofit Technology Determination, 77 FR 40149 (July 6, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of
Nevada; Regional Haze State Implementation Plan, 76 FR 36450 (June 22, 201 1).
Proposed Rule; Extension of Public Comment Period - Regional Haze State Implementation Plan;
State of Nevada; Extension of Comment Period, 76 FR 43963 (July 22, 201 1).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; State of Nevada;
Regional Haze State Implementation Plan, 77 FR 17334 (Mar. 26, 2012).
142
-------
State /Territory
Required SIP
Elements
Addressed
Nevada
Reid Gardner BART
New Hampshire
All elements
New Jersey
All elements
New Mexico
NOx and SO2 BART
for San Juan Generating
Station
Most Recent
EPA Action
Final Partial
approval/Partial
disapproval and
Partial FIP
Final Approval
Final Approval
Final FIP
Additional
Explanation
Disapproval of two
aspects of the SIP in
regards to NOx BART
for Reid Gardner
Generating Station.
FIP obligation arose
from the disapproval
of the state's
infrastructure SIP for
visibility transport.
Hyperlinks to Federal Register Notices137
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of
Nevada; Regional Haze State and Federal Implementation Plans; BART Determination for Reid
Gardner Generating Station, 77 FR 21896 (Apr. 12, 2012).
Announcement Of Second Public Hearing And Extension Of Public Comment Period - State of
Nevada; Regional Haze State and Federal Implementation Plans; BART Determination for Reid
Gardner Generating Station, 77 FR 25660 (May 1, 2012).
Final Rule - Approval and Promulgation of Air Ouality Implementation Plans; Nevada; Regional
Haze State and Federal Implementation Plans; BART Determination for Reid Gardner Generating
Station, 77 FR 50936 (Aug. 23, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; New
Hampshire; Regional Haze, 77 FR 11809 (Feb. 28, 2012).
Proposed Rule; Reopening Of Comment Period - Approval and Promulgation of Air Quality
Implementation Plans; New Hampshire; Regional Haze; Reopening of Comment Period, 77 FR
22550 (Apr. 16,2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; New Hampshire;
Regional Haze, 77 FR 50602 (Aug. 22, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of New
Jersey; Regional Haze State Implementation Plan, 76 FR 4971 1 (Aug. 1 1, 201 1).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; State of New
Jersey; Regional Haze State Implementation Plan, 77 FR 19 (Jan. 3, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; New Mexico; Federal
Implementation Plan for Interstate Transport of Pollution Affecting Visibility and Best Available
Retrofit Technology Determination, 76 FR 491 (Jan. 5, 201 1).
Notice of Public Hearing - Approval and Promulgation of Implementation Plans; New Mexico;
Federal Implementation Plan for Interstate Transport of Pollution Affecting Visibility and Best
Available Retrofit Technology Determination, 76 FR 1578 (Jan. 1 1, 201 1).
143
-------
State /Territory
Required SIP
Elements
Addressed
New Mexico
All remaining SIP
elements
New Mexico
Subsequent SIP
revision to replace the
FIP for San Juan
Generating Station
Most Recent
EPA Action
Final Partial
Approval
Final Approval
Additional
Explanation
The EPA withdrew its
FIP and approved a
SIP with alternative
requirements preferred
by the source owners.
Hyperlinks to Federal Register Notices137
Proposed Rule: Extension of Comment Period - Extension of Public Comment Period for
Proposed Action on Interstate Transport of Pollution Affecting Visibility and Best Available
Retrofit Technology Determination for New Mexico, 76 FR 12305 (Mar. 7, 2011).
Final Rule - Approval and Promulgation of Implementation Plans; New Mexico; Federal
Implementation Plan for Interstate Transport of Pollution Affecting Visibility and Best Available
Retrofit Technology Determination, 76 FR 52387 (Aug. 22, 201 1).
Final Rule - Stay of the Effectiveness of Requirements; Approval and Promulgation of
Implementation Plans; New Mexico; Federal Implementation Plan for Interstate Transport of
Pollution Affecting Visibility and Best Available Retrofit Technology Determination, 77 FR
41697 (July 16, 2012).
Final Rule - Extension of Administrative Stay; Approval and Promulgation of Implementation
Plans; New Mexico; Federal Implementation Plan for Interstate Transport of Pollution Affecting
Visibility and Best Available Retrofit Technology Determination, 77 FR 64908 (Oct. 24, 2012).
Proposed Rule - Approval and Promulgation of State Implementation Plans; New Mexico;
Regional Haze Rule Requirements for Mandatory Class I Areas, 77 FR 36043 (June 15, 2012).
Final Rule - Approval and Promulgation of State Implementation Plans; State of New Mexico;
Regional Haze Rule Requirements for Mandatory Class I Areas, 77 FR 70693 (Nov. 27, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; New Mexico; Regional
Haze and Interstate Transport Affecting Visibility State Implementation Plan Revisions;
Withdrawal of Federal Implementation Plan for the San Juan Generating Station, 79 FR 26909
(May 12, 2014).
Final Rule - Approval and Promulgation of Implementation Plans; New Mexico; Regional Haze
and Interstate Transport Affecting Visibility State Implementation Plan Revisions; Withdrawal of
Federal Implementation Plan for the San Juan Generating Station, 79 FR 60978 (Oct. 9, 2014).
Final Rule - Approval and Promulgation of Implementation Plans; New Mexico; Regional Haze
and Interstate Transport Affecting Visibility State Implementation Plan Revisions, 79 FR 60985
(Oct. 9,2014).
144
-------
State /Territory
Required SIP
Elements
Addressed
New York
All elements
North Carolina
Remaining elements
North Carolina
EGU BART
North Dakota
All elements
Most Recent
EPA Action
Final Partial
Approval/Partial
Disapproval and
Partial FIP
Final Limited
Approval
Final Full Approval
Final Partial
Approval/Partial
Disapproval and
Partial FIP
Additional
Explanation
The EPA found the
SIP's BART
provisions for two
power plants were not
approvable.
Remaining elements
were approved.
EGU BART
requirements for NOx
and SO2 are met by an
alternative program
Partial disapproval for
EGU BART at Coal
Creek Station and
Antelope Valley
Station.
Hyperlinks to Federal Register Notices137
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of New
York; Regional Haze State Implementation Plan and Federal Implementation Plan, 77 FR 24793
(Apr. 25,2012).
Notice of Data Availability (Noda) - Notice of Data Availability Supporting Approval and
Promulgation of Air Quality Implementation Plans; State of New York; Regional Haze State
Implementation Plan and Federal Implementation Plan, 77 FR 27162 (May 9, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; State of New
York; Regional Haze State Implementation Plan and Federal Implementation Plan, 77 FR 51915
(Aug. 28,2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of North
Carolina; Regional Haze State Implementation Plan, 77 FR 11858 (Feb. 28,2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of North Carolina;
Regional Haze State Implementation Plan, 77 FR 38185 (June 27, 2012).
Proposed Rule - Air Plan Approval; North Carolina; Regional Haze, 8 1 FR 1 95 1 9 (April 5,
2016).
Final Rule - Air Plan Approval; North Carolina; Regional Haze, 81 FR 32652 (May 24, 2016).
Proposed Rule - Approval and Promulgation of Implementation Plans; North Dakota; Regional
Haze State Implementation Plan; Federal Implementation Plan for Interstate Transport of
Pollution Affecting Visibility and Regional Haze, 76 FR 58569 (Sept. 21, 201 1).
Proposed Rule; Correction of Public Hearing - Approval and Promulgation of Implementation
Plans; North Dakota; Regional Haze State Implementation Plan; Federal Implementation Plan for
Interstate Transport of Pollution Affecting Proposed Rule; Correction of Public Hearing -
Visibility and Regional Haze; Correction of Public Hearing, 76 FR 60777 (Sept. 30, 201 1).
Final Rule - Approval and Promulgation of Implementation Plans; North Dakota; Regional Haze
State Implementation Plan; Federal Implementation Plan for Interstate Transport of Pollution
Affecting Visibility and Regional Haze, 77 FR 20893 (Apr. 6, 2012).
145
-------
State /Territory
Required SIP
Elements
Addressed
North Dakota
EPA reconsideration of
approval of BART SIP
for Milton R. Young
Station and Leland Olds
Station
Ohio
Remaining elements
Oklahoma
BART for several
EGUs
Oklahoma
Most Recent
EPA Action
Re-affirmation of
prior partial approval
Final Limited
Approval
Final Partial
Approval/Partial
Disapproval and
Partial FIP
Final Partial
Approval/Partial
Disapproval
Additional
Explanation
The EPA analyzed a
petition to reconsider
the prior approval of
the SIP in regard to
BART for Milton R.
Young Station and
Leland Olds Station,
and decided that no
change in the prior
action is necessary.
Remaining elements
were approved.
Partial disapproval of
the SIP in regards to
BART SO2 for several
units.
The EPA disapproved
Oklahoma' sRPGs for
the Wichita Mountains
Class I area and
Hyperlinks to Federal Register Notices137
Proposed Rule - Approval and Promulgation of Implementation Plans: North Dakota; Regional
Haze State Implementation Plan; Federal Implementation Plan for Interstate Transport of
Pollution Affecting Visibility and Regional Haze; Reconsideration, 78 FR 16452 (Mar. 15, 2013).
Notice of Public Hearings; Extension of Comment Period - Approval and Promulgation of
Implementation Plans; North Dakota; Regional Haze State Implementation Plan; Federal
Implementation Plan for Interstate Transport of Pollution Affecting Visibility and Regional Haze;
Reconsideration; Announcement of Public Hearings, 78 FR 24700 (Apr. 26, 2013).
Notice of Final Action on Reconsideration - Approval and Promulgation of Implementation
Plans; North Dakota; Regional Haze State Implementation Plan; Federal Implementation Plan for
Interstate Transport of Pollution Affecting Visibility and Regional Haze; Reconsideration, 80 FR
8550 (Feb. 18,2015).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Ohio;
Regional Haze, 77 FR 3712 (Jan. 25, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Ohio; Regional
Haze, 77 FR 39177 (July 2, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; Oklahoma; Regional Haze
State Implementation Plan; Federal Implementation Plan for Interstate Transport of Pollution
Affecting Visibility and Best Available Retrofit Technology Determinations, 76 FR 16167 (Mar.
22,2011).
Announcement of Public Hearing - Approval and Promulgation of Implementation Plans;
Oklahoma; Regional Haze State Implementation Plan; Federal Implementation Plan for Interstate
Transport of Pollution Affecting Visibility and Best Available Retrofit Technology
Determinations, 76 FR 17584 (Mar. 30, 201 1).
Final Rule - Approval and Promulgation of Implementation Plans; Oklahoma; Federal
Implementation Plan for Interstate Transport of Pollution Affecting Visibility and Best Available
Retrofit Technology Determinations, 76 FR 81727 (Dec. 28, 201 1).
Proposed Rule - Approval and Promulgation of Implementation Plans; Texas and Oklahoma;
Regional Haze State Implementation Plans; Interstate Transport State Implementation Plan To
Address Pollution Affecting Visibility and Regional Haze; Federal Implementation Plan for
146
-------
State /Territory
Required SIP
Elements
Addressed
Remaining elements
Oklahoma
Subsequent SIP
revision to replace part
of the FIP for two units
at one power plant, with
alternative requirements
preferred by the source
owners.
Oregon
Most Recent
EPA Action
Final action to
withdraw of BART
FIP and approval of
revised BART SIP
for two EGUs
Final Partial
Approval
Additional
Explanation
adopted a partial FIP
setting new goals.
Hyperlinks to Federal Register Notices137
Regional Haze and Interstate Transport of Pollution Affecting Visibility, 79 Fed. Reg 74817
(Dec. 16,2014).
Proposed Rule; Extension of Comment Period - Approval and Promulgation of Implementation
Plans; Texas and Oklahoma; Regional Haze State Implementation Plans; Interstate Transport
State Implementation Plan To Address Pollution Affecting Visibility and Regional Haze; Federal
Implementation Plan for Regional Haze and Interstate Transport of Pollution Affecting Visibility;
Extension of Comment Period, 80 FR 3536 (Jan. 23, 2015).
Final Rule - Approval and Promulgation of Implementation Plans; Texas and Oklahoma;
Regional Haze State Implementation Plans; Interstate Visibility Transport State Implementation
Plan to Address Pollution Affecting Visibility and Regional Haze; Federal Implementation Plan
for Regional Haze, 81 FR 296 (Jan. 5, 2016).
Proposed rule: Approval and Promulgation of Implementation Plans; Oklahoma; Regional Haze
and Interstate Transport Affecting Visibility State Implementation Plan Revisions; Withdrawal of
Federal Implementation Plan for American Electric Power/Public Service Company of
Oklahoma, 78 FR 51686 (August 21, 2013)
Final withdrawal of FIP: Approval and Promulgation of Air Quality Implementation Plans;
Oklahoma; Regional Haze and Interstate Transport Affecting Visibility State Implementation
Plan Revisions; Withdrawal of Federal Implementation Plan for American Electric Power/Public
Service Company of Oklahoma, 79 FR 12954 (March 7, 2014)
Final approval of SIP to replace FIP: Approval and Promulgation of Air Quality Implementation
Plans; Oklahoma; Regional Haze and Interstate Transport Affecting Visibility; State
Implementation Plan Revisions; Revised BART Determination for American Electric
Power/Public Service Company of Oklahoma Northeastern Power Station Units 3 and 4, 79 FR
12944 (March 7, 2014)
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Oregon; Regional
Haze State Implementation Plan, 76 FR 12651 (Mar. 8, 201 1).
147
-------
State /Territory
Required SIP
Elements
Addressed
All BART elements
Oregon
All remaining regional
haze SIP elements
Pennsylvania
Remaining elements
Pennsylvania
Pennsylvania
Subsequent SIP
revision correcting PM
BART requirements for
one EGU
Most Recent
EPA Action
Final Approval
Final Limited
Approval
Final Limited
Approval
Final Approval
Additional
Explanation
Remaining elements
were approved.
2012 final action re-
issued with additional
responses to comments
Hyperlinks to Federal Register Notices137
Final Rule - Approval and Promulgation of Implementation Plans; State of Oregon; Regional
Haze State Implementation Plan and Interstate Transport Plan, 76 FR 38997 (July 5, 201 1).
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Oregon; Regional
Haze State Implementation Plan, 77 FR 30454 (May 23, 2012).
Final Rule - Approval and Promulgation of Implementation Plans; State of Oregon; Regional
Haze State Implementation Plan, 77 FR 5061 1 (Aug. 22, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans;
Commonwealth of Pennsylvania; Regional Haze State Implementation Plan, 77 FR 3984 (Jan. 26,
2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Pennsylvania;
Regional Haze State Implementation Plan, 77 FR 41279 (July 13, 2012).
Final Rule; Correction- Approval and Promulgation of Air Ouality Implementation Plans;
Pennsylvania; Regional Haze State Implementation Plan; Correction, 77 Fed Reg. 48061 (Aug.
13,2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Pennsylvania;
Regional Haze State Implementation Plan, 79 FR 24340 (Apr. 30, 2014).
Proposed Rule - Approval and Promulgation of Implementation Plans; Pennsylvania;
Pennsylvania Regional Haze State Implementation Plan Revision-Particulate Matter Best
Available Retrofit Technology Limit for the Cheswick Power Plant in Allegheny County, 79 FR
64539 (Oct. 30, 2014).
Final Rule - Approval and Promulgation of Implementation Plans; Pennsylvania; Pennsylvania
Regional Haze State Implementation Plan Revision-Particulate Matter Best Available Retrofit
Technology Limit for the Cheswick Power Plant in Allegheny County, 80 FR 2834 (Jan. 21,
2015).
148
-------
State /Territory
Required SIP
Elements
Addressed
Pennsylvania
Subsequent SIP
revision removing
unintended source-
specific SO2 and NOx
BART requirements for
one EGU because those
BART requirements are
addressed by the FIP
relying on CSAPR
Rhode Island
All elements
South Carolina
Remaining elements
South Dakota
All elements
Tennessee
Most Recent
EPA Action
Limited
Appro val/Disapprova
1
Final Approval
Final Limited
Approval
Final Approval
Final Limited
Approval/ Limited
Disapproval
Additional
Explanation
Limited disapproval
due to reliance on
CAIR.
Remaining elements
were approved.
Limited disapproval
due to reliance on
CAIR.
Hyperlinks to Federal Register Notices137
Proposed Rule - Approval and Promulgation of Implementation Plans: Pennsylvania;
Pennsylvania Regional Haze State Implementation Plan Revision: Sulfur Dioxide and Nitrogen
Oxide Best Available Retrofit Technology Limits for the Cheswick Power Plant, 80 FR 2841
dan. 21,20151.
Final Rule - Approval and Promulgation of Implementation Plans; Pennsylvania; Pennsylvania
Regional Haze State Implementation Plan Revision: Sulfur Dioxide and Nitrogen Oxide Best
Available Retrofit Technology Limits for the Cheswick Power Plant 80 FR 16286 (Mar. 27,
2015).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Rhode Island;
Regional Haze, 77 FR 1 1798 (Feb. 28, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Rhode Island;
Regional Haze, 77 FR 30214 (May 22, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; South
Carolina; Regional Haze State Implementation Plan, 77 FR 11894 (Feb. 28,2012).
Final Rule - Approval and Promulgation of Implementation Plans; South Carolina; Regional Haze
State Implementation Plan, 77 FR 38509 (June 28, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; South Dakota; Regional
Haze State Implementation Plan, 76 FR 76646 (Dec. 8, 201 1).
Final Rule - Approval and Promulgation of Implementation Plans; South Dakota; Regional Haze
State Implementation Plan, 77 FR 24845 (Apr. 26, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; State of
Tennessee; Regional Haze State Implementation Plan, 76 FR 33662 (June 9, 201 1).
Proposed Rule; Limited Reopening of Comment Period - Approval and Promulgation of Air
Quality Implementation Plans; Tennessee; Regional Haze State Implementation Plan; Limited
Reopening of the Comment Period, 76 FR 44534 (July 26, 201 1).
149
-------
State /Territory
Required SIP
Elements
Addressed
All elements except
Eastman Chemical
BART
Tennessee
Eastman Chemical
BART
Texas
Remaining elements
except for EGU BART
Tribal
Four Corners Power
Plant
Most Recent
EPA Action
Final Approval
Final Partial
Approval/Partial
Disapproval and FIP
for Reasonable
Progress
Final FIP
Additional
Explanation
Final partial
disapproval of the SIP
as not adequately
addressing
requirements of the
regional haze program
related to reasonable
progress, the LTS, and
the calculation of
natural visibility
conditions.
No tribal plan was
required or submitted.
The EPA promulgated
a source-specific FIP
for the Four Comers
Power Plant to achieve
reductions in NOx.
The FIP provided an
Hyperlinks to Federal Register Notices137
Final Rule - Approval and Promulgation of Implementation Plans; Tennessee; Regional Haze
State Implementation Plan, 77 FR 24392 (Apr. 24, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; Tennessee; Regional Haze
State Implementation Plan; Best Available Retrofit Technology for Eastman Chemical Company,
77 FR 51739 (Aug. 27, 2012).
Final Rule - Approval and Promulgation of Implementation Plans; Tennessee; Regional Haze
State Implementation Plan; Best Available Retrofit Technology Requirements for Eastman
Chemical Company, 77 FR 70689 (Nov. 27, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; Texas and Oklahoma;
Regional Haze State Implementation Plans; Interstate Transport State Implementation Plan To
Address Pollution Affecting Visibility and Regional Haze; Federal Implementation Plan for
Regional Haze and Interstate Transport of Pollution Affecting Visibility, 79 Fed. Reg 74817
(Dec. 16,2014).
Proposed Rule; Extension of Comment Period - Approval and Promulgation of Implementation
Plans; Texas and Oklahoma; Regional Haze State Implementation Plans; Interstate Transport
State Implementation Plan To Address Pollution Affecting Visibility and Regional Haze; Federal
Implementation Plan for Regional Haze and Interstate Transport of Pollution Affecting Visibility;
Extension of Comment Period, 80 FR 3536 (Jan. 23, 2015).
Final Rule - Approval and Promulgation of Implementation Plans; Texas and Oklahoma;
Regional Haze State Implementation Plans; Interstate Visibility Transport State Implementation
Plan to Address Pollution Affecting Visibility and Regional Haze; Federal Implementation Plan
for Regional Haze, 81 FR 295 (Jan. 5, 2016).
Proposed Rule - Source Specific Federal Implementation Plan for Implementing Best Available
Retrofit Technology for Four Comers Power Plant: Navaio Nation, 75 FR 64221 (Oct. 19, 2010).
Supplemental Proposed Rule - Supplemental Proposed Rule of Source Specific Federal
Implementation Plan for Implementing Best Available Retrofit Technology for Four Corners
Power Plant: Navaio Nation, 76 FR 10530 (Feb. 25, 201 1).
150
-------
State /Territory
Required SIP
Elements
Addressed
Tribal
Navajo Generating
Station
Utah
All elements
Most Recent
EPA Action
Final FIP
Final Partial
Approval/Partial
Disapproval
Additional
Explanation
alternative compliance
option, under which
three of the five units
were voluntarily
shutdown in 2013.
No tribal plan was
required or submitted.
The EPA promulgated
a source-specific FIP
for the Navajo
Generating Station to
achieve reductions in
NOX. The FIP provides
for alternative
compliance
approaches.
Disapproval of NOx
and PM BART
provisions for four
PacifiCorp EGUs.
Hyperlinks to Federal Register Notices137
Final Rule - Source Specific Federal Implementation Plan for Implementing Best Available
Retrofit Technology for Four Comers Power Plant: Navaio Nation, 77 FR 51619 (Aug. 24, 2012).
Proposed Rule - Approval of Air Quality Implementation Plans; Navaio Nation; Regional Haze
Requirements for Navaio Generating Station, 78 FR 8273 (Feb. 5, 2013).
Proposed Rule; Extension of Comment Period - Approval of Air Quality Implementation Plans;
Navaio Nation; Regional Haze Requirements for Navaio Generating Station; Extension of
Comment Period, 78 FR 16825 (Mar. 19, 2013).
Notice of Intent to Hold Public Hearings - Approval of Air Quality Implementation Plans; Navaio
Nation; Regional Haze Requirements for Navaio Generating Station; Notice of Intent To Hold
Public Hearings, 78 FR 36716 (June 19, 2013).
Proposed Rule; Notice of Extended Comment Period - Approval of Air Quality Implementation
Plans; Navaio Nation; Regional Haze Requirements for Navaio Generating Station; Extension of
Public Comment Period, 78 FR 41012 (July 9, 2013).
Proposed Rule; Notice of Extended Comment Period - Approval of Air Quality Implementation
Plans; Navaio Nation; Regional Haze Requirements for Navaio Generating Station; Extension of
Public Comment Period, 78 FR 58987 (Sept. 25, 2013).
Supplemental Proposed Rule And Notice Of Public Hearings - Approval of Air Quality
Implementation Plans; Navaio Nation; Regional Haze Requirements for Navaio Generating
Station; Supplemental Proposal, 78 FR 62509 (Oct. 22, 2013).
Final Rule - Approval of Air Quality Implementation Plans; Navaio Nation; Regional Haze
Requirements for Navaio Generating Station, 79 FR 46513 (Aug. 8, 2014).
Proposed Rule - Approval, Disapproval and Promulgation of State Implementation Plans; State of
Utah; Regional Haze Rule Requirements for Mandatory Class I Areas, 77 FR 28825 (May 16,
2012).
151
-------
State /Territory
Required SIP
Elements
Addressed
Utah
EGU BART -Revised
SIP
Vermont
All elements
Virgin Islands
All elements
Virginia
Remaining elements
Most Recent
EPA Action
Proposal in the
alternative to approve
the revised SIP or to
disapprove it and
promulgate a FIP to
fill the gap
Final Approval
Final FIP
Final Limited
Approval
Additional
Explanation
The EPA requested
comment on whether
the alternative
program in the SIP is
better-than-BART
The territory did not
submit a SIP.
Remaining elements
were approved.
Hyperlinks to Federal Register Notices137
Final Rule - Approval Disapproval and Promulgation of State Implementation Plans; State of
Utah; Regional Haze Rule Requirements for Mandatory Class I Areas Under 40 CFR 51.309, 77
FR 74355 (Dec. 14,2012).
Final Rule; Correction - Approval, Disapproval and Promulgation of State Implementation Plans;
State of Utah; Regional Haze Rule Requirements for Mandatory Class I Areas Under 40 CFR
51.309; Correction, 78 FR 4341 (Jan. 22, 2013).
Proposed Rule - Approval, Disapproval and Promulgation of Air Quality Implementation Plans;
Partial Approval and Partial Disapproval of Air Quality Implementation Plans and Federal
Implementation Plan; Utah; Revisions to Regional Haze State Implementation Plan; Federal
Implementation Plan for Regional Haze, 81 FR 2003 (Jan. 14, 2016).
The final action on this proposed rule was signed on June 1, 2016.
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Vermont;
Regional Haze, 77 FR 1 1914 (Feb. 28, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Vermont;
Regional Haze, 77 FR 30212 (May 22, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; United States
Virgin Islands; Regional Haze Federal Implementation Plan, 77 FR 37842 (Dec. 25, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; United States
Virgin Islands; Regional Haze Federal Implementation Plan, 77 FR 64414 (Oct. 22, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans;
Commonwealth of Virginia; Regional Haze State Implementation Plan, 77 FR 3691 (Jan. 25,
2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Virginia; Regional
Haze State Implementation Plan, 77 FR 35287 (June 13, 2012).
152
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State /Territory
Required SIP
Elements
Addressed
Washington
Transalta BART
Washington
Non-BART EGU and
all remaining regional
haze SIP elements
West Virginia
All elements
Wisconsin
All elements
Most Recent
EPA Action
Final Partial
Approval
Final Partial
Approval/Partial
Disapproval and
Partial FIP
Final Limited
Approval/ Limited
Disapproval
Final Approval
Additional
Explanation
The EPA disapproved
the SIP for BART at a
refinery and two
aluminum plants.
Limited disapproval
due to reliance on
CAIR.
Hyperlinks to Federal Register Notices137
Proposed Rule - Approval and Promulgation of Implementation Plans: State of Washington;
Regional Haze State Implementation Plan, 77 FR 30467 (May 23, 2012).
Final Rule - Approval and Promulgation of State Implementation Plans: State of Washington;
Regional Haze State Implementation Plan, 77 FR 72742 (Dec. 6, 2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Washington;
Regional Haze State Implementation Plan; Federal Implementation Plan for Best Available
Retrofit Technology for Alcoa Intalco Operations and Tesoro Refining and Marketing, 77 FR
76 173 (Dec. 26,2012).
Proposed Rule - Approval and Promulgation of Implementation Plans; State of Washington;
Regional Haze State Implementation Plan; Federal Implementation Plan for Best Available
Retrofit Technology for Alcoa Wenatchee, 78 FR 79344 (Dec. 30, 201 3).
Final Rule - Approval and Promulgation of Implementation Plans; State of Washington; Regional
Haze State Implementation Plan; Federal Implementation Plan for Best Available Retrofit
Technology for Alcoa Intalco Operations, Tesoro Refining and Marketing, and Alcoa Wenatchee,
79 FR 33438 (June 1 1, 2014).
Direct Final Rule - Approval and Promulgation of Implementation Plans; State of Washington;
Regional Haze State Implementation Plan; Federal Implementation Plan for Best Available
Retrofit Technology for Alcoa Intalco Operations, Tesoro Refining and Marketing, and Alcoa
Wenatchee, 79 FR 69767 (Nov. 24, 2014).
Proposed Rule - Approval and Promulgation of Air Ouality Implementation Plans; West Virginia;
Regional Haze State Implementation Plan, 76 FR 41 158 (July 13, 201 1).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; West Virginia;
Regional Haze State Implementation Plan, 77 FR 16937 (Mar. 23, 2012).
Proposed Rule - Approval and Promulgation of Air Quality Implementation Plans; Wisconsin;
Regional Haze, 77 FR 1 1928 (Feb. 28, 2012).
Final Rule - Approval and Promulgation of Air Quality Implementation Plans; Wisconsin;
Regional Haze, 77 FR 46952 (Aug. 7, 2012).
153
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State /Territory
Required SIP
Elements
Addressed
Wyoming
All elements other than
section 309 SO2
Program
Wyoming
Section 309 SO2
Program
Most Recent
EPA Action
Final Partial
Approval/Partial
Disapproval and
Partial FIP
Final Approval
Additional
Explanation
The EPA disapproved
the state' sNOx
determinations for
certain EGUs, RPGs,
monitoring and
reporting
requirements, and part
of the LTS and RAVI
program. EPA adopted
a partial FIP to fill the
resulting gaps.
Hyperlinks to Federal Register Notices137
Proposed Rule- Approval, Disapproval and Promulgation of Implementation Plans; State of
Wyoming; Regional Haze State Implementation Plan; Federal Implementation Plan for Regional
Haze, 77 FR 33021 ( June 4, 2012).
Proposed Rule - Approval, Disapproval and Promulgation of Implementation Plans; State of
Wyoming; Regional Haze State Implementation Plan; Federal Implementation Plan for Regional
Haze, 78 FR 34737 ( June 10, 2013).
Notice of Public Hearings; Extension of Comment Period - Approval, Disapproval and
Promulgation of Implementation Plans; State of Wyoming; Regional Haze State Implementation
Plan; Federal Implementation Plan for Regional Haze; Notice of Public Hearings, 78 FR 40654
(July 8, 2013).
Final Rule - Approval, Disapproval and Promulgation of Implementation Plans; State of
Wyoming; Regional Haze State Implementation Plan; Federal Implementation Plan for Regional
Haze, 79 FR 5031 (Jan. 30, 2014).
Proposed Rule - Approval and Promulgation of State Implementation Plans; State of Wyoming;
Regional Haze Rule Requirements for Mandatory Class I Areas, 77 FR 30953 (May 24, 2012).
Final Rule - Approval and Promulgation of State Implementation Plans; State of Wyoming;
Regional Haze Rule Requirements for Mandatory Class I Areas Under 40 CFR 51 .309, 77 FR
73926 (Dec. 12,2012).
154
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APPENDIX C
Court Decisions on Regional Haze SIPs and FIPs for the First Implementation Period
Case Name
Oklahoma v. EPA, 723 F.3d 1201 (10th
Cir. 2013)
North Dakota v. EPA, 730 F.3d 750 (8th
Cir. 2013)
Utah v. EPA, 750 F.3d 1 182 (10th Cir.
2014)
Nat'l Parks Conservation Ass'n v. EPA,
759 F.3d 969 (8th Cir. 2014)
WildEarth Guardians v. EPA, 759 F.3d
1196 (10th Cir. 2014)
WildEarth Guardians v. EPA, 759 F.3d
1064 (9th Cir. 2014)
Utah v. EPA, 765 F.3d 1257 (10th Cir.
2014) (rehearing en bane)
WildEarth Guardians v. EPA, 770 F.3d
919 (10th Cir. 2014)
St. Marys Cement Inc. v. EPA, 782 F.3d
280 (6th Cir. 2015)
Nat'l Parks Conservation Ass'n v. EPA,
788 F.3d 11 34 (9th Cir. 2015)
Nat'l Parks Conservation Ass'n v. EPA,
803 F.3d 151 (3rd Cir. 2015)
Nat'l Parks Conservation Ass'n v.
McCarthy, 2016 U.S. App. LEXIS 977
(8th Cir. Jan. 21,2016)
Nat'l Parks Conservation Ass'n v.
McCarthy, 2016 Mar. 14, 2016,
Nebraska v. EPA, 2016 U.S. App. LEXIS
1773 (8th Cir. Feb. 3,2016)
Arizona ex rel. Darwin v. EPA, 2016 U.S.
App. LEXIS 3196 (9th Cir. Feb. 24, 2016)
State(s)/Tribe
Involved
OK
NO
UT
MN
Navajo Nation
NV
UT
NM, UT, WY
MI
MT
PA
MN
MN
NE
AZ
Decision
Petitions for review denied.
Petitions granted in part and denied in part.
Petitions for review denied.
Judgment reversed.
Petitions for review denied.
Petitions for review was dismissed in part and denied in part.
Panel rehearing denied.
Petitions for review denied.
Petition denied.
Petitions for review granted in part and denied in part.
Petitions for review granted in part and denied in part.
Opinion and judgement vacated following petition for reconsideration.
Petitions for review denied (revised opinion).
Petitions for review denied.
Petitions denied.
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APPENDIX D
Identification of Provisions of the BART Guidelines138 that Are Applicable as EPA Recommendations for
Reasonable Progress Analysis and Determinations in the Second Implementation Period
BART Guideline Provisions
EPA Recommendation Regarding
Applicability to Reasonable
Progress Determinations in the
Second Implementation Period
Appendix Y to Part 51—Guidelines for BART Determinations Under the Regional Haze Rule
Table of Contents
L Introduction and Overview
A. What is the purpose of the guidelines?
B. What does the CAA require generally for improving visibility?
C. What is the BART requirement in the CAA?
D. What types of visibility problems does EPA address in its regulations?
E. What are the BART requirements in EPA's regional haze regulations?
F. What is included in the guidelines?
G. Who is the target audience for the guidelines?
H. Do EPA regulations require the use of these guidelines?
IL How to Identify BART-eligible Sources
A. What are the steps in identifying BART-eligible sources?
1. Step 1: Identify emission units in the BART categories
2. Step 2: Identify the start-up dates of the emission units
3. Step 3: Compare the potential emissions to the 250 ton/yr cutoff
4. Final step: Identify the emission units and pollutants that constitute the BART-eligible source.
m. How to Identify Sources "Subject to BART"
IV. The BART Determination: Analysis of BART Options
A. What factors must I address in the BART Analysis?
B. What is the scope of the BART review?
C. How does a BART review relate to maximum achievable control technology (MACT) standards under CAA section 112?
D. What are the five basic steps of a case-by-case BART analysis?
1. Step 1: How do I identify all available retrofit emission control techniques?
2. Step 2: How do I determine whether the options identified in Step 1 are technically feasible?
3. Step 3: How do I evaluate technically feasible alternatives?
4. Step 4: For a BART review, what impacts am I expected to calculate and report? What methods does EPA recommend for the impacts analyses?
! 40 CFR part 51 appendix Y.
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a. Impact analysis part 1: how do I estimate the costs of control?
b. What do we mean by cost effectiveness?
c. How do I calculate average cost effectiveness?
d. How do I calculate baseline emissions?
e. How do I calculate incremental cost effectiveness?
f What other information should I provide in the cost impacts analysis?
g. What other things are important to consider in the cost impacts analysis?
h. Impact analysis part 2: How should I analyze and report energy impacts?
i. Impact analysis part 3: How do I analyze "non-air quality environmental impacts?"
j. Impact analysis part 4: What are examples of non-air quality environmental impacts?
k. How do I take into account a project's "remaining useful life" in calculating control costs?
5. Step 5: How should I determine visibility impacts in the BART determination?
E. How do I select the "best" alternative, using the results of Steps 1 through 5?
1. Summary of the impacts analysis
2. Selecting a "best" alternative
3. In selecting a "best" alternative, should I consider the affordability of controls?
4. SO2 limits for utility boilers
5. NOx limits for utility boilers
V. Enforceable Limits/Compliance Date
Explanation of Entries in this Column:
No comment necessary - The statement in the
BART Guidelines speaks for itself and needs no
further interpretation.
Applies only to BART - The statement in the
BART Guidelines has no relevance to the
development of an LTS for reasonable progress,
except to the extent that BART for a BART-
eligible source must be determined and thus
becomes part of the LTS.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. - This
guidance document does not provide any
additional recommendation on this topic that
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would need to be considered along with the
statement in the BART Guidelines.
Applies only to BART. This guidance document
provides new guidance on this topic in the
context of the development of the LTS in the
second implementation period, -which is not
consistent with this answer. - The statement in
the BART Guidelines applies only to BART
determinations. The general sense of that
statement should not be applied to the
development of the LTS for reasonable progress.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. This
guidance document provides new guidance on
this, which is consistent with this answer. -
While the statement in the BART Guidelines
applies only to BART determinations, the
general sense of that statement should also be
applied to the development of the LTS for
reasonable progress but taking into consideration
related statements in this document. While there
are no points of disagreement between the BART
Guidelines and this guidance document, there is
additional relevant material in this guidance
document, so the BART Guidelines should not
be used alone.
L Introduction and Overview
A. What is the purpose of the guidelines?
The Clean Air Act (CAA), in sections 169A and 169B, contains requirements for the protection of visibility in 156 scenic areas
across the United States. To meet the CAA's requirements, we published regulations to protect against a particular type of
visibility impairment known as "regional haze." The regional haze rule is found in this part at 40 CFR 51.300 through 51.309.
These regulations require, in 40 CFR 51.308(e), that certain types of existing stationary sources of air pollutants install best
No comment necessary.
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available retrofit technology (BART). The guidelines are designed to help States and others (1) identify those sources that must
comply with the BART requirement, and (2) determine the level of control technology that represents BART for each source.
B. What does the CAA require generally for improving visibility?
Section 169A of the CAA, added to the CAA by the 1977 amendments, requires States to protect and improve visibility in
certain scenic areas of national importance. The scenic areas protected by section 169A are "the mandatory Class I Federal
Areas * * * where visibility is an important value." In these guidelines, we refer to these as "Class I areas." There are 156 Class
I areas, including 47 national parks (under the jurisdiction of the Department of Interior—National Park Service), 108
wilderness areas (under the jurisdiction of the Department of the Interior—Fish and Wildlife Service or the Department of
Agriculture—U.S. Forest Service), and one International Park (under the jurisdiction of the Roosevelt-Campobello
International Commission). The Federal Agency with jurisdiction over a particular Class I area is referred to in the CAA as the
Federal Land Manager. A complete list of the Class I areas is contained in 40 CFR 81.401 through 81.437, and you can find a
map of the Class I areas at the following Internet site:
http://www.epa.gov/ttn/oarpg/tl/frjiotices/classimp.gif.
The CAA establishes a national goal of eliminating man-made visibility impairment from all Class I areas. As part of the plan
for achieving this goal, the visibility protection provisions in the CAA mandate that EPA issue regulations requiring that States
adopt measures in their State implementation plans (SIPs), including long-term strategies, to provide for reasonable progress
towards this national goal. The CAA also requires States to coordinate with the Federal Land Managers as they develop their
strategies for addressing visibility.
No comment necessary.
C. What is the BART requirement in the CAA?
1. Under section 169A(b)(2)(A) of the CAA, States must require certain existing stationary sources to install BART. The
BART provision applies to "major stationary sources" from 26 identified source categories which have the potential to emit 250
tons per year or more of any air pollutant. The CAA requires only sources which were put in place during a specific 15-year
time interval to be subject to BART. The BART provision applies to sources that existed as of the date of the 1977 CAA
amendments (that is, August 7,1977) but which had not been in operation for more than 15 years (that is, not in operation as of
August 7, 1962).
2. The CAA requires BART review when any source meeting the above description "emits any air pollutant which may
reasonably be anticipated to cause or contribute to any impairment of visibility" in any Class I area. In identifying a level of
control as BART, States are required by section 169A(g) of the CAA to consider:
(a) The costs of compliance,
(b) The energy and non-air quality environmental impacts of compliance,
(c) Any existing pollution control technology in use at the source,
(d) The remaining useful life of the source, and
Applies only to BART.
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(e) The degree of visibility improvement which may reasonably be anticipated from the use of BART.
3. The CAA further requires States to make BART emission limitations part of their SIPs. As with any SIP revision, States
must provide an opportunity for public comment on the BART determinations, and EPA's action on any SIP revision will be
subject to judicial review.
D. What types of visibility problems does EPA address in its regulations?
1. We addressed the problem of visibility in two phases. In 1980, we published regulations addressing what we termed
"reasonably attributable" visibility impairment. Reasonably attributable visibility impairment is the result of emissions from
one or a few sources that are generally located in close proximity to a specific Class I area. The regulations addressing
reasonably attributable visibility impairment are published in 40 CFR 51.300 through 51.307.
2. On July 1, 1999, we amended these regulations to address the second, more common, type of visibility impairment known as
"regional haze." Regional haze is the result of the collective contribution of many sources over a broad region. The regional
haze rule slightly modified 40 CFR 51.300 through 51.307, including the addition of a few definitions in §51.301, and added
new §§51.308 and 51.309.
No comment necessary.
E. What are the BART requirements in EPA's regional haze regulations?
1. In the July 1, 1999 rulemaking, we added a BART requirement for regional haze. We amended the BART requirements in
2005. You will find the BART requirements in 40 CFR 51.308(e). Definitions of terms used in 40 CFR 51.308(e)(l) are found
in 40 CFR 51.301.
2. As we discuss in detail in these guidelines, the regional haze rule codifies and clarifies the BART provisions in the CAA.
The rule requires that States identify and list "BART-eligible sources," that is, that States identify and list those sources that fall
within the 26 source categories, were put in place during the 15-year window of time from 1962 to 1977, and have potential
emissions greater than 250 tons per year. Once the State has identified the BART-eligible sources, the next step is to identify
those BART-eligible sources that may "emit any air pollutant which may reasonably be anticipated to cause or contribute to
any impairment of visibility." Under the rule, a source which fits this description is "subject to BART." For each source subject
to BART, 40 CFR 51.308(e)(l)(ii)(A) requires that States identify the level of control representing BART after considering the
factors set out in CAA section 169A(g), as follows:
—States must identify the best system of continuous emission control technology for each source subject to BART taking into
account the technology available, the costs of compliance, the energy and non-air 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 visibility
improvement that may be expected from available control technology.
Applies only to BART.
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3. After a State has identified the level of control representing BART (if any), it must establish an emission limit representing
BART and must ensure compliance with that requirement no later than 5 years after EPA approves the SIP. States may
establish design, equipment, work practice or other operational standards when limitations on measurement technologies make
emission standards infeasible.
F. What is included in the guidelines?
1. The guidelines provide a process for making BART determinations that States can use in implementing the regional haze
BART requirements on a source-by-source basis, as provided in 40 CFR 51.308(e)( 1). States must follow the guidelines in
making BART determinations on a source-by-source basis for 750 megawatt (MW) power plants but are not required to use the
process in the guidelines when making BART determinations for other types of sources.
2. The BART analysis process, and the contents of these guidelines, are as follows:
(a) Identification of all BART-eligible sources. Section II of these guidelines outlines a step-by-step process for identifying
BART-eligible sources.
(b) Identification of sources subject to BART. As noted above, sources "subject to BART" are those BART-eligible sources
which "emit a pollutant which may reasonably be anticipated to cause or contribute to any impairment of visibility in any Class
I area." We discuss considerations for identifying sources subject to BART in section III of the guidance.
(c) The BART determination process. For each source subject to BART, the next step is to conduct an analysis of emissions
control alternatives. This step includes the identification of available, technically feasible retrofit technologies, and for each
technology identified, an analysis of the cost of compliance, the energy and non-air quality environmental impacts, and the
degree of visibility improvement in affected Class I areas resulting from the use of the control technology. As part of the BART
analysis, the State should also take into account the remaining useful life of the source and any existing control technology
present at the source. For each source, the State will determine a "best system of continuous emission reduction" based upon its
evaluation of these factors. Procedures for the BART determination step are described in section IV of these guidelines.
(d) Emissions limits. States must establish emission limits, including a deadline for compliance, consistent with the BART
determination process for each source subject to BART. Considerations related to these limits are discussed in section V of
these guidelines.
Applies only to BART.
G. Who is the target audience for the guidelines?
1. The guidelines are written primarily for the benefit of State, local and Tribal agencies, and describe a process for making the
BART determinations and establishing the emission limitations that must be included in their SIPs or Tribal implementation
plans (TIPs). Throughout the guidelines, which are written in a question and answer format, we ask questions "How do I * *
No comment necessary.
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*?" and answer with phrases "you should * * *, you must * * *" The "you" means a State, local or Tribal agency conducting
the analysis. We have used this format to make the guidelines simpler to understand, but we recognize that States have the
authority to require source owners to assume part of the analytical burden, and that there will be differences in how the
supporting information is collected and documented. We also recognize that data collection, analysis, and rule development
may be performed by Regional Planning Organizations, for adoption within each SIP or TIP.
2. The preamble to the 1999 regional haze rule discussed at length the issue of Tribal implementation of the requirements to
submit a plan to address visibility. As explained there, requirements related to visibility are among the programs for which
Tribes may be determined eligible and receive authorization to implement under the "Tribal Authority Rule" ("TAR") (40 CFR
49.1 through 49.11). Tribes are not subject to the deadlines for submitting visibility implementation plans and may use a
modular approach to CAA implementation. We believe there are very few BART-eligible sources located on Tribal lands.
Where such sources exist, the affected Tribe may apply for delegation of implementation authority for this rule, following the
process set forth in the TAR.
H. Do EPA regulations require the use of these guidelines?
Section 169A(b) requires us to issue guidelines for States to follow in establishing BART emission limitations for fossil-fuel
fired power plants having a capacity in excess of 750 megawatts. This document fulfills that requirement, which is codified in
40 CFR 51.308(e)( 1 )(ii)(B). The guidelines establish an approach to implementing the requirements of the BART provisions of
the regional haze rule; we believe that these procedures and the discussion of the requirements of the regional haze rule and the
CAA should be useful to the States. For sources other than 750 MW power plants, however, States retain the discretion to adopt
approaches that differ from the guidelines.
Applies only to BART.
IL How To Identify BART-Eligible Sources
This section provides guidelines on how to identify BART-eligible sources. A BART-eligible source is an existing stationary
source in any of 26 listed categories which meets criteria for startup dates and potential emissions.
Applies only to BART.
A. What are the steps in identifying BART-eligible sources?
Figure 1 shows the steps for identifying whether the source is a "BART-eligible source:"
Step 1: Identify the emission units in the BART categories,
Step 2: Identify the start-up dates of those emission units, and
Step 3: Compare the potential emissions to the 250 ton/yr cutoff.
Figure 1. How to determine whether a source is BART-eligible:
Applies only to BART.
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Step 1: Identify emission units in the BART categories
Does the plant contain emissions units in one or more of the 26 source categories?
-> No -> Stop
-> Yes -> Proceed to Step 2
Applies only to BART.
Step 2: Identify the start-up dates of these emission units
Do any of these emissions units meet the following two tests?
In existence on August 7, 1977
AND
Began operation after August 7, 1962
-> No -> Stop
—» Yes —» Proceed to Step 3
Applies only to BART.
Step 3: Compare the potential emissions from these emission units to the 250 ton/yr cutoff
Identify the "stationary source" that includes the emission units you identified in Step 2.
Add the current potential emissions from all the emission units identified in Steps 1 and 2 that are included within the
"stationary source" boundary.
Are the potential emissions from these units 250 tons per year or more for any visibility-impairing pollutant?
-> No -> Stop
—> Yes —> These emissions units comprise the "BART-eligible source."
Applies only to BART.
1. Step 1: Identify Emission Units in the BART Categories
1. The BART requirement only applies to sources in specific categories listed in the CAA. The BART requirement does not
apply to sources in other source categories, regardless of their emissions. The listed categories are:
(1) Fossil-fuel fired steam electric plants of more than 250 million British thermal units (BTU) per hour heat input,
(2) Coal cleaning plants (thermal dryers),
(3) Kraft pulp mills,
(4) Portland cement plants,
(5) Primary zinc smelters,
(6) Iron and steel mill plants,
(7) Primary aluminum ore reduction plants,
(8) Primary copper smelters,
(9) Municipal incinerators capable of charging more than 250 tons of refuse per day,
(10) Hydrofluoric, sulfuric, and nitric acid plants,
(11) Petroleum refineries,
(12) Lime plants,
(13) Phosphate rock processing plants,
Applies only to BART.
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(14) Coke oven batteries,
(15) Sulfur recovery plants,
(16) Carbon black plants (furnace process),
(17) Primary lead smelters,
(18) Fuel conversion plants,
(19) Sintering plants,
(20) Secondary metal production facilities,
(21) Chemical process plants,
(22) Fossil-fuel boilers of more than 250 million BTUs per hour heat input,
(23) Petroleum storage and transfer facilities with a capacity exceeding 300,000 barrels,
(24) Taconite ore processing facilities,
(25) Glass fiber processing plants, and
(26) Charcoal production facilities.
2. Some plants may have emission units from more than one category, and some emitting equipment may fit into more than one
category. Examples of this situation are sulfur recovery plants at petroleum refineries, coke oven batteries and sintering plants
at steel mills, and chemical process plants at refineries. For Step 1, you identify all of the emissions units at the plant that fit
into one or more of the listed categories. You do not identify emission units in other categories.
Example: A mine is collocated with an electric steam generating plant and a coal cleaning plant. You would identify emission
units associated with the electric steam generating plant and the coal cleaning plant, because they are listed categories, but not
the mine, because coal mining is not a listed category.
Applies only to BART.
3. The category titles are generally clear in describing the types of equipment to be listed. Most of the category titles are very
broad descriptions that encompass all emission units associated with a plant site (for example, "petroleum refining" and "kraft
pulp mills"). This same list of categories appears in the PSD regulations. States and source owners need not revisit any
interpretations of the list made previously for purposes of the PSD program. We provide the following clarifications for a few
of the category titles:
(1) "Steam electric plants of more than 250 million BTU/hr heat input." Because the category refers to "plants," we interpret
this category title to mean that boiler capacities should be aggregated to determine whether the 250 million BTU/hr threshold is
reached. This definition includes only those plants that generate electricity for sale. Plants that cogenerate steam and electricity
also fall within the definition of "steam electric plants". Similarly, combined cycle turbines are also considered "steam electric
plants" because such facilities incorporate heat recovery steam generators. Simple cycle turbines, in contrast, are not "steam
electric plants" because these turbines typically do not generate steam.
Example: A stationary source includes a steam electric plant with three 100 million BTU/hr boilers. Because the aggregate
capacity exceeds 250 million BTU/hr for the "plant," these boilers would be identified in Step 2.
Applies only to BART.
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(2) "Fossil-fuel boilers of more than 250 million BTU/hr heat input." We interpret this category title to cover only those boilers
that are individually greater than 250 million BTU/hr. However, an individual boiler smaller than 250 million BTU/hr should
be subject to BART if it is an integral part of a process description at a plant that is in a different BART category—for example,
a boiler at a Kraft pulp mill that, in addition to providing steam or mechanical power, uses the waste liquor from the process as
a fuel. In general, if the process uses any by-product of the boiler and the boiler's function is to serve the process, then the boiler
is integral to the process and should be considered to be part of the process description.
Also, you should consider a multi-fuel boiler to be a "fossil-fuel boiler" if it bums any amount of fossil fuel. You may take
federally and State enforceable operational limits into account in determining whether a multi-fuel boiler's fossil fuel capacity
exceeds 250 million Btu/hr.
(3) "Petroleum storage and transfer facilities with a capacity exceeding 300,000 barrels." The 300,000 barrel cutoff refers to
total facility-wide tank capacity for tanks that were put in place within the 1962-1977 time period, and includes gasoline and
other petroleum-derived liquids.
(4) "Phosphate rock processing plants." This category descriptor is broad, and includes all types of phosphate rock processing
facilities, including elemental phosphorous plants as well as fertilizer production plants.
(5) "Charcoal production facilities." We interpret this category to include charcoal briquet manufacturing and activated carbon
production.
(6) "Chemical process plants." and pharmaceutical manufacturing. Consistent with past policy, we interpret the category
"chemical process plants" to include those facilities within the 2-digit Standard Industrial Classification (SIC) code 28.
Accordingly, we interpret the term "chemical process plants" to include pharmaceutical manufacturing facilities.
(7) "Secondary metal production." We interpret this category to include nonferrous metal facilities included within SIC code
3341, and secondary ferrous metal facilities that we also consider to be included within the category "iron and steel mill
plants."
(8) "Primary aluminum ore reduction." We interpret this category to include those facilities covered by 40 CFR 60.190, the new
source performance standard (NSPS) for primary aluminum ore reduction plants. This definition is also consistent with the
definition at 40 CFR 63.840.
2. Step 2: Identify the Start-Up Dates of the Emission Units
1. Emissions units listed under Step 1 are BART-eligible only if they were "in existence" on August 7, 1977 but were not "in
operation" before August 7,1962.
Applies only to BART.
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What does "in existence on August 7, 1977" mean?
1. The regional haze rule defines "in existence" to mean that:
"the owner or operator has obtained all necessary preconstruction approvals or permits required by Federal, State, or local air
pollution emissions and air quality laws or regulations and either has (1) begun, or caused to begin, a continuous program of
physical on-site construction of the facility or (2) entered into binding agreements or contractual obligations, which cannot be
canceled or modified without substantial loss to the owner or operator, to undertake a program of construction of the facility to
be completed in a reasonable time. "40 CFR 51.301.
As this definition is essentially identical to the definition of "commence construction" as that term is used in the PSD
regulations, the two terms mean the same thing. See 40 CFR 51.165(a)(l)(xvi) and 40 CFR 52.21(b)(9). Under this definition,
an emissions unit could be "in existence" even if it did not begin operating until several years after 1977.
Example: The owner of a source obtained all necessary permits in early 1977 and entered into binding construction agreements
in June 1977. Actual on-site construction began in late 1978, and construction was completed in mid-1979. The source began
operating in September 1979. The emissions unit was "in existence" as of August 7, 1977.
Major stationary sources which commenced construction AFTER August 7, 1977 (i.e., major stationary sources which were not
"in existence" on August 7,1977) were subject to new source review (NSR) under the PSD program. Thus, the August 7, 1977
"in existence" test is essentially the same thing as the identification of emissions units that were grandfathered from the NSR
review requirements of the 1977 CAA amendments.
Applies only to BART.
3. Sources are not BART-eligible if the only change at the plant during the relevant time period was the addition of pollution
controls. For example, if the only change at a copper smelter during the 1962 through 1977 time period was the addition of acid
plants for the reduction of SCh emissions, these emission controls would not by themselves trigger a BART review.
Applies only to BART.
What does "in operation before August 7, 1962" mean?
An emissions unit that meets the August 7, 1977 "in existence" test is not BART-eligible if it was in operation before August 7,
1962. "In operation" is defined as "engaged in activity related to the primary design function of the source." This means that a
source must have begun actual operations by August 7, 1962 to satisfy this test.
Example: The owner or operator entered into binding agreements in 1960. Actual on-site construction began in 1961, and
construction was complete in mid-1962. The source began operating in September 1962. The emissions unit was not "in
operation" before August 7,1962 and is therefore subject to BART.
Applies only to BART.
What is a "reconstructed source? "
1. Under a number of CAA programs, an existing source which is completely or substantially rebuilt is treated as a new source.
Such "reconstructed" sources are treated as new sources as of the time of the reconstruction. Consistent with this overall
approach to reconstructions, the definition of BART-eligible facility (reflected in detail in the definition of "existing stationary
Applies only to BART.
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facility") includes consideration of sources that were in operation before August 7, 1962, but were reconstructed during the
August 7, 1962 to August 7, 1977 time period.
2. Under the regional haze regulations at 40 CFR 51.301, a reconstruction has taken place if "the fixed capital cost of the new
component exceeds 50 percent of the fixed capital cost of a comparable entirely new source." The rule also states that "[a]ny
final decision as to whether reconstruction has occurred must be made in accordance with the provisions of §§60.15 (f)(l)
through (3) of this title." "[T]he provisions of §§60.15(f)(l) through (3)" refers to the general provisions for New Source
Performance Standards (NSPS). Thus, the same policies and procedures for identifying reconstructed "affected facilities" under
the NSPS program must also be used to identify reconstructed "stationary sources" for purposes of the BART requirement.
3. You should identify reconstructions on an emissions unit basis, rather than on a plantwide basis. That is, you need to identify
only the reconstructed emission units meeting the 50 percent cost criterion. You should include reconstructed emission units in
the list of emission units you identified in Step 1. You need consider as possible reconstructions only those emissions units with
the potential to emit more than 250 tons per year of any visibility-impairing pollutant.
4. The "in operation" and "in existence" tests apply to reconstructed sources. If an emissions unit was reconstructed and began
actual operation before August 7,1962, it is not BART-eligible. Similarly, any emissions unit for which a reconstruction
"commenced" after August 7, 1977, is not BART-eligible.
How are modifications treated under the BART provision?
1. The NSPS program and the major source NSR program both contain the concept of modifications. In general, the term
"modification" refers to any physical change or change in the method of operation of an emissions unit that results in an
increase in emissions.
2. The BART provision in the regional haze rule contains no explicit treatment of modifications or how modified emissions
units, previously subject to the requirement to install best available control technology (BACT), lowest achievable emission
rate (LAER) controls, and/or NSPS are treated under the rule. As the BART requirements in the CAA do not appear to provide
any exemption for sources which have been modified since 1977, the best interpretation of the CAA visibility provisions is that
a subsequent modification does not change a unit's construction date for the purpose of BART applicability. Accordingly, if an
emissions unit began operation before 1962, it is not BART-eligible if it was modified between 1962 and 1977, so long as the
modification is not also a "reconstruction." On the other hand, an emissions unit which began operation within the 1962-1977
time window, but was modified after August 7, 1977, is BART-eligible. We note, however, that if such a modification was a
major modification that resulted in the installation of controls, the State will take this into account during the review process
and may find that the level of controls already in place are consistent with BART
Applies only to BART.
3. Step 3: Compare the Potential Emissions to the 250 Ton/Yr Cutoff
The result of Steps 1 and 2 will be a list of emissions units at a given plant site, including reconstructed emissions units, that are
within one or more of the BART categories and that were placed into operation within the 1962-1977 time window. The third
Applies only to BART.
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step is to determine whether the total emissions represent a current potential to emit that is greater than 250 tons per year of any
single visibility impairing pollutant. Fugitive emissions, to the extent quantifiable, must be counted. In most cases, you will add
the potential emissions from all emission units on the list resulting from Steps 1 and 2. In a few cases, you may need to
determine whether the plant contains more than one "stationary source" as the regional haze rule defines that term, and as we
explain further below.
What pollutants should I address?
Visibility-impairing pollutants include the following:
(1) Sulfur dioxide (SO2),
(2) Nitrogen oxides (NOx), and
(3) Particulate matter.
You may use PMio as an indicator for particulate matter in this initial step. [Note that we do not recommend use of total
suspended particulates (TSP) as in indicator for particulate matter.] As emissions of PMio include the components of PM2.5 as a
subset, there is no need to have separate 250 ton thresholds for PMio and PM2.5; 250 tons of PMio represents at most 250 tons of
PM2.5, and at most 250 tons of any individual particulate species such as elemental carbon, crustal material, etc.
However, if you determine that a source of particulate matter is BART-eligible, it will be important to distinguish between the
fine and coarse particle components of direct particulate emissions in the remainder of the BART analysis, including for the
purpose of modeling the source's impact on visibility. This is because although both fine and coarse particulate matter
contribute to visibility impairment, the long-range transport of fine particles is of particular concern in the formation of regional
haze. Thus, for example, air quality modeling results used in the BART determination will provide a more accurate prediction
of a source's impact on visibility if the inputs into the model account for the relative particle size of any directly emitted
particulate matter (i.e. PMio vs. PM2.5).
You should exercise judgment in deciding whether the following pollutants impair visibility in an area:
(4) Volatile organic compounds (VOC), and
(5) Ammonia and ammonia compounds.
You should use your best judgment in deciding whether VOC or ammonia emissions from a source are likely to have an impact
on visibility in an area. Certain types of VOC emissions, for example, are more likely to form secondary organic aerosols than
others. 139 Similarly, controlling ammonia emissions in some areas may not have a significant impact on visibility. You need
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
139 Fine particles: Overview of Atmospheric Chemistry, Sources of Emissions, and Ambient Monitoring Data, Memorandum to Docket OAR 2002-006, April 1,
2005.
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not provide a formal showing of an individual decision that a source of VOC or ammonia emissions is not subject to BART
review. Because air quality modeling may not be feasible for individual sources of VOC or ammonia, you should also exercise
your judgement in assessing the degree of visibility impacts due to emissions of VOC and emissions of ammonia or ammonia
compounds. You should fully document the basis for judging that a VOC or ammonia source merits BART review, including
your assessment of the source's contribution to visibility impairment.
What does the term "potential" emissions mean?
The regional haze rule defines potential to emit as follows:
"Potential to emit" means the maximum capacity of a stationary source to emit a pollutant under its physical and operational
design. Any physical or operational limitation on the capacity of the source to emit a pollutant including air pollution control
equipment and restrictions on hours of operation or on the type or amount of material combusted, stored, or processed, shall be
treated as part of its design if the limitation or the effect it would have on emissions is federally enforceable. Secondary
emissions do not count in determining the potential to emit of a stationary source.
The definition of "potential to emit" means that a source which actually emits less than 250 tons per year of a visibility-
impairing pollutant is BART-eligible if its emissions would exceed 250 tons per year when operating at its maximum capacity
given its physical and operational design (and considering all federally enforceable and State enforceable permit limits.)
Example: A source, while operating at one-fourth of its capacity, emits 75 tons per year of SO2. If it were operating at 100
percent of its maximum capacity, the source would emit 300 tons per year. Because under the above definition such a source
would have "potential" emissions that exceed 250 tons per year, the source (if in a listed category and built during the 1962-
1977 time window) would be BART-eligible.
Applies only to BART.
How do I identify whether a plant has more than one "stationary source? "
1. The regional haze rule, in 40 CFR 51.301, defines a stationary source as a "building, structure, facility or installation which
emits or may emit any air pollutant."140 The rule further defines "building, structure or facility" as: all of the pollutant-emitting
activities which belong to the same industrial grouping, are located on one or more contiguous or adjacent properties, and are
under the control of the same person (or persons under common control). Pollutant-emitting activities must be considered as
part of the same industrial grouping if they belong to the same Major Group (i.e., which have the same two-digit code) as
Applies only to BART.
The term "source" has particular meaning in the
context of BART that should not be presumed to
carry over to development of the LTS in the
second implementation period where non-BART
sources are concerned.
140 Note: Most of these terms and definitions are the same for regional haze and the 1980 visibility regulations. For the regional haze rule we use the term
"BART-eligible source" rather than "existing stationary facility" to clarify that only a limited subset of existing stationary sources are subject to BART.
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described in the Standard Industrial Classification Manual, 1972 as amended by the 1977 Supplement (U.S. Government
Printing Office stock numbers 4101-0066 and 003-005-00176-0, respectively).
2. In applying this definition, it is necessary to determine which facilities are located on "contiguous or adjacent properties."
Within this contiguous and adjacent area, it is also necessary to group those emission units that are under "common control."
We note that these plant boundary issues and "common control" issues are very similar to those already addressed in
implementation of the title V operating permits program and in NSR.
3. For emission units within the "contiguous or adjacent" boundary and under common control, you must group emission units
that are within the same industrial grouping (that is, associated with the same 2-digit SIC code) in order to define the stationary
source. 141 For most plants on the BART source category list, there will only be one 2-digit SIC that applies to the entire plant.
For example, all emission units associated with kraft pulp mills are within SIC code 26, and chemical process plants will
generally include emission units that are all within SIC code 28. The "2-digit SIC test" applies in the same way as the test is
applied in the major source NSR programs. 142
4. For purposes of the regional haze rule, you must group emissions from all emission units put in place within the 1962-1977
time period that are within the 2-digit SIC code, even if those emission units are in different categories on the BART category
list.
Examples: A chemical plant which started operations within the 1962 to 1977 time period manufactures hydrochloric acid
(within the category title "Hydrochloric, sulfuric, and nitric acid plants") and various organic chemicals (within the category
title "chemical process plants"). All of the emission units are within SIC code 28 and, therefore, all the emission units are
considered in determining BART eligibility of the plant. You sum the emissions over all of these emission units to see whether
there are more than 250 tons per year of potential emissions.
141 We recognize that we are in a transition period from the use of the SIC system to a new system called the North American Industry Classification System
(NAICS). For purposes of identifying BART-eligible sources, you may use either 2-digit SICS or the equivalent in the NAICS system.
142 Note: The concept of support facility used for the NSR program applies here as well. Support facilities, that is facilities that convey, store or otherwise assist
in the production of the principal product, must be grouped with primary facilities even when the facilities fall within separate SIC codes. For purposes of BART
reviews, however, such support facilities (a) must be within one of the 26 listed source categories and (b) must have been in existence as of August 7, 1977, and
(c) must not have been in operation as of August 7, 1962.
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A steel mill which started operations within the 1962 to 1977 time period includes a sintering plant, a coke oven battery, and
various other emission units. All of the emission units are within SIC code 33. You sum the emissions over all of these
emission units to see whether there are more than 250 tons per year of potential emissions.
4. Final Step: Identify the Emissions Units and Pollutants That Constitute the BART-Eligible Source
If the emissions from the list of emissions units at a stationary source exceed a potential to emit of 250 tons per year for any
visibility-impairing pollutant, then that collection of emissions units is a BART-eligible source.
Example: A stationary source comprises the following two emissions units, with the following potential emissions:
Emissions unit A
200 tons/yr SO2
150tons/yrNOx
25 tons/yr PM
Emissions unit B
100 tons/yr SO2
75 tons/yr NOx
lOtons/yrPM
For this example, potential emissions of SO2are 300 tons/yr, which exceeds the 250 tons/yr threshold. Accordingly, the entire
"stationary source", that is, emissions units A and B, may be subject to a BART review for SO2, NOx, and PM, even though the
potential emissions of PM and NOx at each emissions unit are less than 250 tons/yr each.
Example: The total potential emissions, obtained by adding the potential emissions of all emission units in a listed category at a
plant site, are as follows:
200 tons/yr SO2
150 tons/yr NOx
25 tons/yr PM
Even though total emissions exceed 250 tons/yr, no individual regulated pollutant exceeds 250 tons/yr and this source is not
BART-eligible.
Applies only to BART.
Can States establish de minimis levels of emissions for pollutants at BART-eligible sources?
In order to simplify BART determinations, 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 SO2 and NOx and 15 tons/yr for PMio. These de minimis levels may
only be applied on a plant-wide basis.
Applies only to BART. This guidance document
provides new guidance on this topic in the
context of the development of the LTS in the
second implementation period, which is not
consistent with this answer.
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m. How To Identify Sources "Subject to BART"
Once you have compiled your list of BART-eligible sources, you need to determine whether (1) to make BART determinations
for all of them or (2) to consider exempting some of them from BART because they may not reasonably be anticipated to cause
or contribute to any visibility impairment in a Class I area. If you decide to make BART determinations for all the BART-
eligible sources on your list, you should work with your regional planning organization (RPO) to show that, collectively, they
cause or contribute to visibility impairment in at least one Class I area. You should then make individual BART determinations
by applying the five statutory factors discussed in Section IV below.
On the other hand, you also may choose to perform an initial examination to determine whether a particular BART-eligible
source or group of sources causes or contributes to visibility impairment in nearby Class I areas. If your analysis, or information
submitted by the source, shows that an individual source or group of sources (or certain pollutants from those sources) is not
reasonably anticipated to cause or contribute to any visibility impairment in a Class I area, then you do not need to make BART
determinations for that source or group of sources (or for certain pollutants from those sources). In such a case, the source is not
"subject to BART" and you do not need to apply the five statutory factors to make a BART determination. This section of the
Guideline discusses several approaches that you can use to exempt sources from the BART determination process.
Applies only to BART.
A. What Steps Do I Follow To Determine Whether a Source or Group of Sources Cause or Contribute to Visibility Impairment
for Purposes of BART?
1. How Do I Establish a Threshold?
One of the first steps in determining whether sources cause or contribute to visibility impairment for purposes of BART is to
establish a threshold (measured in deciviews) against which to measure the visibility impact of one or more sources. A single
source that is responsible for a 1.0 deciview change or more should be considered to "cause" visibility impairment; a source
that causes less than a 1.0 deciview change may still contribute to visibility impairment and thus be subject to BART.
Because of varying circumstances affecting different Class I areas, the appropriate threshold for determining whether a source
"contributes to any visibility impairment" for the purposes of BART may reasonably differ across States. As 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.
This answer applies only to BART. This
guidance document provides new guidance on
this topic in the context of the development of
the LTS in the second implementation period,
which supersedes this answer.
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In setting a threshold for "contribution," you should consider the number of emissions sources affecting the Class I areas at
issue and the magnitude of the individual sources' impacts.143 In general, a larger number of sources causing impacts in a Class
I area may warrant a lower contribution threshold. States remain free to use a threshold lower than 0.5 deciviews if they
conclude that the location of a large number of BART-eligible sources within the State and in proximity to a Class I area justify
this approach.144
2. What Pollutants Do I Need To Consider?
You must look at SCh, NOx, and direct particulate matter (PM) emissions in determining whether sources cause or contribute to
visibility impairment, including both PMio and PM2.5. Consistent with the approach for identifying your BART-eligible
sources, you do not need to consider less than de minimis emissions of these pollutants from a source.
As explained in section II, you must use your best judgement to determine whether VOC or ammonia emissions are likely to
have an impact on visibility in an area. In addition, although as explained in Section II, you may use PMio an indicator for
particulate matter in determining whether a source is BART-eligible, in determining whether a source contributes to visibility
impairment, you should distinguish between the fine and coarse particle components of direct particulate emissions. Although
both fine and coarse particulate matter contribute to visibility impairment, the long-range transport of fine particles is of
particular concern in the formation of regional haze. Air quality modeling results used in the BART determination will provide
a more accurate prediction of a source's impact on visibility if the inputs into the model account for the relative particle size of
any directly emitted particulate matter (i.e., PMio vs. PM2.5).
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. This
guidance document provides new guidance on
this, which is consistent with this answer
3. What Kind of Modeling Should I Use To Determine Which Sources and Pollutants Need Not Be Subject to BART?
This section presents several options for determining that certain sources need not be subject to BART. These options rely on
different modeling and/or emissions analysis approaches. They are provided for your guidance. You may also use other
reasonable approaches for analyzing the visibility impacts of an individual source or group of sources.
See entries on the sub-topics that follow.
Option 1: Individual Source Attribution Approach (Dispersion Modeling)
Applies only to BART. This guidance document
provides new guidance on this topic in the
143 We expect that regional planning organizations will have modeling information that identifies sources affecting visibility in individual class I areas.
144 Note that the contribution threshold should be used to determine whether an individual source is reasonably anticipated to contribute to visibility impairment.
You should not aggregate the visibility effects of multiple sources and compare their collective effects against your contribution threshold because this would
inappropriately create a "contribute to contribution" test.
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You can use dispersion modeling to determine that an individual source cannot reasonably be anticipated to cause or contribute
to visibility impairment in a Class I area and thus is not subject to BART. Under this option, you can analyze an individual
source's impact on visibility as a result of its emissions of SCh, NOx and direct PM emissions. Dispersion modeling cannot
currently be used to estimate the predicted impacts on visibility from an individual source's emissions of VOC or ammonia.
You may use a more qualitative assessment to determine on a case-by-case basis which sources of VOC or ammonia emissions
may be likely to impair visibility and should therefore be subject to BART review, as explained in section II.A.3. above.
You can use CALPUFF145 or other appropriate model to predict the visibility impacts from a single source at a Class I area.
CALPUFF is the best regulatory modeling application currently available for predicting a single source's contribution to
visibility impairment and is currently the only EPA-approved model for use in estimating single source pollutant concentrations
resulting from the long range transport of primary pollutants.146 It can also be used for some other purposes, such as the
visibility assessments addressed in today's rule, to account for the chemical transformation of SCh and NOx.
context of the development of the LTS in the
second implementation period, which is not
consistent with this answer. Specifically, EPA
has recently proposed to remove CALPUFF as a
preferred model for long-range transport
assessments and to recommend its use as a
screening technique along with other Lagrangian
models for addressing PSD increment beyond 50
km from a new or modifying source.
There are several steps for making an individual source attribution using a dispersion model:
1. Develop a modeling protocol. Some critical items to include in the protocol are the meteorological and terrain data that will
be used, as well as the source-specific information (stack height, temperature, exit velocity, elevation, and emission rates of
applicable pollutants) and receptor data from appropriate Class I areas. We recommend following EPA's Interagency
Workgroup on Air Quality Modeling (IWAQM) Phase 2 Summary Report and Recommendations for Modeling Long Range
Transport Impactsl47 for parameter settings and meteorological data inputs. You may use other settings from those in
IWAQM, but you should identify these settings and explain your selection of these settings.
One important element of the protocol is in establishing the receptors that will be used in the model. The receptors that you use
should be located in the nearest Class I area with sufficient density to identify the likely visibility effects of the source. For
other Class I areas in relatively close proximity to a BART-eligible source, you may model a few strategic receptors to
determine whether effects at those areas may be greater than at the nearest Class I area. For example, you might chose to locate
receptors at these areas at the closest point to the source, at the highest and lowest elevation in the Class I area, at the
IMPROVE monitor, and at the approximate expected plume release height. If the highest modeled effects are observed at the
nearest Class I area, you may choose not to analyze the other Class I areas any further as additional analyses might be
unwarranted.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. See above
entry regarding the status of the CALPUFF
model.
145 The model code and its documentation are available at no cost for download from http://www.epa.gov/scram001/tt22.htmttcalpuff.
146 The Guideline on Air Quality Models, 40 CFR part 51, appendix W, addresses the regulatory application of air quality models for assessing criteria pollutants
under the CAA, and describes further the procedures for using the CALPUFF model, as well as for obtaining approval for the use of other, nonguideline models
147 Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 2 Summary Report and Recommendations for Modeling Long Range Transport Impacts,
U.S. Environmental Protection Agency, EPA-454/R-98-019, December 1998.
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You should bear in mind that some receptors within the relevant Class I area may be less than 50 km from the source while
other receptors within that same Class I area may be greater than 50 km from the same source. As indicated by the Guideline on
Air Quality Models, 40 CFR part 51, appendix W, this situation may call for the use of two different modeling approaches for
the same Class I area and source, depending upon the State's chosen method for modeling sources less than 50 km. In situations
where you are assessing visibility impacts for source-receptor distances less than 50 km, you should use expert modeling
judgment in determining visibility impacts, giving consideration to both CALPUFF and other appropriate methods.
In developing your modeling protocol, you may want to consult with EPA and your regional planning organization (RPO). Up-
front consultation will ensure that key technical issues are addressed before you conduct your modeling.
2. With the accepted protocol and compare the predicted visibility impacts with your threshold for "contribution." You should
calculate daily visibility values for each receptor as the change in deciviews compared against natural visibility conditions. You
can use EPA's "Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule," EPA-454/B-03-005
(September 2003) in making this calculation. To determine whether a source may reasonably be anticipated to cause or
contribute to visibility impairment at Class I area, you then compare the impacts predicted by the model against the threshold
that you have selected.
The emissions estimates used in the models are intended to reflect steady-state operating conditions during periods of high
capacity utilization. We do not generally recommend that emissions reflecting periods of start-up, shutdown, and malfunction
be used, as such emission rates could produce higher than normal effects than would be typical of most facilities. We
recommend that States use the 24 hour average actual emission rate from the highest emitting day of the meteorological period
modeled, unless this rate reflects periods start-up, shutdown, or malfunction. In addition, the monthly average relative humidity
is used, rather than the daily average humidity—an approach that effectively lowers the peak values in daily model averages.
For these reasons, if you use the modeling approach we recommend, you should compare your "contribution" threshold against
the 98th percentile of values. If the 98th percentile value from your modeling is less than your contribution threshold, then you
may conclude that the source does not contribute to visibility impairment and is not subject to BART.
Applies only to BART.
Option 2: Use of Model Plants To Exempt Individual Sources With Common Characteristics
Under this option, analyses of model plants could be used to exempt certain BART-eligible sources that share specific
characteristics. It may be most useful to use this type of analysis to identify the types of small sources that do not cause or
contribute to visibility impairment for purposes of BART, and thus should not be subject to a BART review. Different Class I
areas may have different characteristics, however, so you should use care to ensure that the criteria you develop are appropriate
for the applicable cases.
In carrying out this approach, you could use modeling analyses of representative plants to reflect groupings of specific sources
with important common characteristics. Based on these analyses, you may find that certain types of sources are clearly
Applies only to BART.
In carrying out this approach, you could use modeling analyses ol representative plants to reflect groupings ot specitic si
with important common characteristics. Based on these analyses, you may find that certain types of sources are clearly
anticipated to cause or contribute to visibility impairment. You could then choose to categorically require those types of
sources
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to undergo a BART determination. Conversely, you may find based on representative plant analyses that certain types of
sources are not reasonably anticipated to cause or contribute to visibility impairment. To do this, you may conduct your own
modeling to establish emission levels and distances from Class I areas on which you can rely to exempt sources with those
characteristics. For example, based on your modeling you might choose to exempt all NOx-only sources that emit less than a
certain amount per year and are located a certain distance from a Class I area. You could then choose to categorically exempt
such sources from the BART determination process.
Our analyses of visibility impacts from model plants provide a useful example of the type of analyses that can be used to
exempt categories of sources from BART. 148 In our analyses, we developed model plants (EGUs and non-EGUs), with
representative plume and stack characteristics, for use in considering the visibility impact from emission sources of different
sizes and compositions at distances of 50, 100 and 200 kilometers from two hypothetical Class I areas (one in the East and one
in the West). As the plume and stack characteristics of these model plants were developed considering the broad range of
sources within the EGU and non-EGU categories, they do not necessarily represent any specific plant. However, the results of
these analyses are instructive in the development of an exemption process for any Class I area.
In preparing our analyses, we have made a number of assumptions and exercised certain modeling choices; some of these have
a tendency to lend conservatism to the results, overstating the likely effects, while others may understate the likely effects. On
balance, when all of these factors are considered, we believe that our examples reflect realistic treatments of the situations
being modeled. Based on our analyses, we believe that a State that has established 0.5 deciviews as a contribution threshold
could reasonably exempt from the BART review process sources that emit less than 500 tons per year of NOx or SO2 (or
combined NOx and SO2), as long as these sources are located more than 50 kilometers from any Class I area; and sources that
emit less than 1000 tons per year of NOx or SO2 (or combined NOx and SO2) that are located more than 100 kilometers from
any Class I area. You do, however, have the option of showing other thresholds might also be appropriate given your specific
circumstances.
Option 3: Cumulative Modeling To Show That No Sources in a State Are Subject to BART
You may also submit to EPA a demonstration based on an analysis of overall visibility impacts that emissions from BART-
eligible sources in your State, considered together, are not reasonably anticipated to cause or contribute to any visibility
impairment in a Class I area, and thus no source should be subject to BART. You may do this on a pollutant by pollutant basis
or for all visibility-impairing pollutants to determine if emissions from these sources contribute to visibility impairment.
For example, emissions of SO2from your BART-eligible sources may clearly cause or contribute to visibility impairment while
direct emissions of PlVb.sfrom these sources may not contribute to impairment. If you can make such a demonstration, then you
Applies only to BART.
148 CALPUFF Analysis in Support of the June 2005 Changes to the Regional Haze Rule, U.S. Environmental Protection Agency, June 15, 2005, Docket No.
EPA-HQ-OAR-2002-0076.
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may reasonably conclude that none of your BART-eligible sources are subject to BART for a particular pollutant or pollutants.
As noted above, your demonstration should take into account the interactions among pollutants and their resulting impacts on
visibility before making any pollutant-specific determinations.
Analyses may be conducted using several alternative modeling approaches. First, you may use the CALPLTFF or other
appropriate model as described in Option 1 to evaluate the impacts of individual sources on downwind Class I areas,
aggregating those impacts to determine the collective contribution of all BART-eligible sources to visibility impairment. You
may also use a photochemical grid model. As a general matter, the larger the number of sources being modeled, the more
appropriate it may be to use a photochemical grid model. However, because such models are significantly less sensitive than
dispersion models to the contributions of one or a few sources, as well as to the interactions among sources that are widely
distributed geographically, if you wish to use a grid model, you should consult with the appropriate EPA Regional Office to
develop an appropriate modeling protocol.
IV. The BART Determination: Analysis of BART Options
This section describes the process for the analysis of control options for sources subject to BART
A. What factors must I address in the BART review?
The visibility regulations define BART as follows:
Best Available Retrofit Technology (BART) means an emission limitation based on the degree of reduction achievable through
the application of the best system of continuous emission reduction for each pollutant which is emitted by ... [a BART-eligible
source] . The emission limitation must be established, on a case-by-case basis, taking into consideration the technology
available, the costs of compliance, the energy and non-air quality environmental impacts of compliance, any pollution control
equipment in use or in existence 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.
The BART analysis identifies the best system of continuous emission reduction taking into account:
(1) The available retrofit control options,
(2) Any pollution control equipment in use at the source (which affects the availability of options and their impacts),
(3) The costs of compliance with control options,
(4) The remaining useful life of the facility,
(5) The energy and non-air quality environmental impacts of control options
(6) The visibility impacts analysis.
B. What is the scope of the BART review?
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See entries on the sub-topics that follow.
Applies only to BART.
Applies only to BART.
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Once you determine that a source is subject to BART for a particular pollutant, then for each affected emission unit, you must
establish BART for that pollutant. The BART determination must address air pollution control measures for each emissions
unit or pollutant emitting activity subject to review.
Example: Plantwide emissions from emission units within the listed categories that began operation within the "time window"
for BART149 are 300 tons/yr of NOx, 200 tons/yr of SCh, and 150 tons/yr of primary particulate. Emissions unit A emits 200
tons/yr of NOx, 100 tons/yr of SO2, and 100 tons/yr of primary particulate. Other emission units, units B through H, which
began operating in 1966, contribute lesser amounts of each pollutant. For this example, a BART review is required for NOx,
SO2, and primary particulate, and control options must be analyzed for units B through H as well as unit A.
C. How does a BART review relate to Maximum Achievable Control Technology (MACT) Standards under CAA section 112,
or to other emission limitations required under the CAA?
For VOC and PM sources subject to MACT standards, States may streamline the analysis by including a discussion of the
MACT controls and whether any major new technologies have been developed subsequent to the MACT standards. We believe
that there are many VOC and PM sources that are well controlled because they are regulated by the MACT standards, which
EPA developed under CAA section 112. For a few MACT standards, this may also be true for SO2. Any source subject to
MACT standards must meet a level that is as stringent as the best-controlled 12 percent of sources in the industry. Examples of
these hazardous air pollutant sources which effectively control VOC and PM emissions include (among others) secondary lead
facilities, organic chemical plants subject to the hazardous organic NESHAP (HON), pharmaceutical production facilities, and
equipment leaks and wastewater operations at petroleum refineries. We believe that, in many cases, it will be unlikely that
States will identify emission controls more stringent than the MACT standards without identifying control options that would
cost many thousands of dollars per ton. Unless there are new technologies subsequent to the MACT standards which would
lead to cost-effective increases in the level of control, you may rely on the MACT standards for purposes of BART.
We believe that the same rationale also holds true for emissions standards developed for municipal waste incinerators under
CAA section 11 l(d), and for many NSR/PSD determinations and NSR/PSD settlement agreements. However, we do not
believe that technology determinations from the 1970s or early 1980s, including new source performance standards (NSPS),
should be considered to represent best control for existing sources, as best control levels for recent plant retrofits are more
stringent than these older levels.
Where you are relying on these standards to represent a BART level of control, you should provide the public with a discussion
of whether any new technologies have subsequently become available.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. However,
the reference to technology determinations in the
1970s or early 1980s should be interpreted as
now applying to technology determinations in
the 1990s and early 2000s as well.
149
That is, emission units that were in existence on August 7, 1977, and which began actual operation on or after August 7, 1962.
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D. What Are the Five Basic Steps of a Case-by-Case BART Analysis?
The five steps are:
STEP 1—Identify A11150 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.
This answer applies only to BART.
1. STEP 1: How do I identify all available retrofit emission control techniques?
1. Available retrofit control options are those air pollution control technologies with a practical potential for application to the
emissions unit and the regulated pollutant under evaluation. Air pollution control technologies can include a wide variety of
available methods, systems, and techniques for control of the affected pollutant. Technologies required as BACT or LAER are
available for BART purposes and must be included as control alternatives. The control alternatives can include not only
existing controls for the source category in question but also take into account technology transfer of controls that have been
applied to similar source categories and gas streams. Technologies which have not yet been applied to (or permitted for) full
scale operations need not be considered as available; we do not expect the source owner to purchase or construct a process or
control device that has not already been demonstrated in practice.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. This
guidance document provides new guidance on
this topic, which is consistent with this answer.
2. Where a NSPS exists for a source category (which is the case for most of the categories affected by BART), you should
include a level of control equivalent to the NSPS as one of the control options. 151 The NSPS standards are codified in 40 CFR
part 60. We note that there are situations where NSPS standards do not require the most stringent level of available control for
all sources within a category. For example, post-combustion NOx controls (the most stringent controls for stationary gas
turbines) are not required under subpart GG of the NSPS for Stationary Gas Turbines. However, such controls must still be
considered available technologies for the BART selection process.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. This
guidance document provides new guidance on
this topic, which is consistent with this answer.
150 In identifying "all" options, you must identify the most stringent option and a reasonable set of options for analysis that reflects a comprehensive list of
available technologies. It is not necessary to list all permutations of available control levels that exist for a given technology—the list is complete if it includes
the maximum level of control each technology is capable of achieving.
151 In EPA's 1980 BART guidelines for reasonably attributable visibility impairment, we concluded that NSPS standards generally, at that time, represented the
best level sources could install as BART. In the 20 year period since this guidance was developed, there have been advances in SCh control technologies as well
as technologies for the control of other pollutants, confirmed by a number of recent retrofits at Western power plants. Accordingly, the EPA no longer concludes
that the NSPS level of controls automatically represents "the best these sources can install." Analysis of the BART factors could result in the selection of a NSPS
level of control, but you should reach this conclusion only after considering the full range of control options.
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3. Potentially applicable retrofit control alternatives can be categorized in three ways.
• Pollution prevention: use of inherently lower-emitting processes/practices, including the use of control techniques (e.g., low-
NOx burners) and work practices that prevent emissions and result in lower "production-specific" emissions (note that it is not
our intent to direct States to switch fuel forms, e.g., from coal to gas),
• Use of (and where already in place, improvement in the performance of) add-on controls, such as scrubbers, fabric filters,
thermal oxidizers and other devices that control and reduce emissions after they are produced, and
• Combinations of inherently lower-emitting processes and add-on controls.
4. In the course of the BART review, one or more of the available control options may be eliminated from consideration
because they are demonstrated to be technically infeasible or to have unacceptable energy, cost, or non-air quality
environmental impacts on a case-by-case (or site-specific) basis. However, at the outset, you should initially identify all control
options with potential application to the emissions unit under review.
5. We do not consider BART as a requirement to redesign the source when considering available control alternatives. For
example, where the source subject to BART is a coal-fired electric generator, we do not require the BART analysis to consider
building a natural gas-fired electric turbine although the turbine may be inherently less polluting on a per unit basis.
6. For emission units subject to a BART review, there will often be control measures or devices already in place. For such
emission units, it is important to include control options that involve improvements to existing controls and not to limit the
control options only to those measures that involve a complete replacement of control devices.
Example: For a power plant with an existing wet scrubber, the current control efficiency is 66 percent. Part of the reason for the
relatively low control efficiency is that 22 percent of the gas stream bypasses the scrubber. A BART review identifies options
for improving the performance of the wet scrubber by redesigning the internal components of the scrubber and by eliminating
or reducing the percentage of the gas stream that bypasses the scrubber. Four control options are identified: (1)78 percent
control based upon improved scrubber performance while maintaining the 22 percent bypass, (2) 83 percent control based upon
improved scrubber performance while reducing the bypass to 15 percent, (3) 93 percent control based upon improving the
scrubber performance while eliminating the bypass entirely, (this option results in a "wet stack" operation in which the gas
leaving the stack is saturated with water) and (4) 93 percent as in option 3, with the addition of an indirect reheat system to
reheat the stack gas above the saturation temperature. You must consider each of these four options in a BART analysis for this
source.
7. You are expected to identify potentially applicable retrofit control technologies that represent the full range of demonstrated
alternatives. Examples of general information sources to consider include:
• The EPA's Clean Air Technology Center, which includes the RACT/BACT/LAER Clearinghouse (RBLC);
EPA Recommendation Regarding
Applicability to Reasonable
Progress Determinations in the
Second Implementation Period
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
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• State and Local Best Available Control Technology Guidelines—many agencies have online information—for example South
Coast Air Quality Management District, Bay Area Air Quality Management District, and Texas Natural Resources
Conservation Commission;
• Control technology vendors;
• Federal/State/Local NSR permits and associated inspection/performance test reports;
• Environmental consultants;
• Technical journals, reports and newsletters, air pollution control seminars; and
• The EPA's NSR bulletin board—http://www.epa.gov/ttn/nsr;
• Department of Energy's Clean Coal Program—technical reports;
• The NOx Control Technology "Cost Tool"—Clean Air Markets Division Web page—
http://www.epa.gov/airmarkets/arp/nox/controltech.html;
• Performance of selective catalytic reduction on coal-fired steam generating units—final report. OAR/ARD, June 1997 (also
available at http://www.epa.gov/airmarkets/arp/nox/controltech.html);
• Cost estimates for selected applications of NOx control technologies on stationary combustion boilers. OAR/ARD June 1997.
(Docket for NOx SIP Call, A-96-56, item II-A-03);
• Investigation of performance and cost of NOx controls as applied to group 2 boilers. OAR/ARD, August 1996. (Docket for
Phase II NOx rule, A-95-28, item IV-A-4);
• Controlling SO2 Emissions: A Review of Technologies. EPA-600/R-00-093, USEPA/ORD/NRMRL, October 2000; and
• The OAQPS Control Cost Manual.
You are expected to compile appropriate information from these information sources.
8. There may be situations where a specific set of units within a fenceline constitutes the logical set to which controls would
apply and that set of units may or may not all be BART-eligible. (For example, some units in that set may not have been
constructed between 1962 and 1977.)
Applies only to BART.
9. If you find that a BART source has controls already in place which are the most stringent controls available (note that this
means that all possible improvements to any control devices have been made), then it is not necessary to comprehensively
complete each following step of the BART analysis in this section. As long these most stringent controls available are made
federally enforceable for the purpose of implementing BART for that source, you may skip the remaining analyses in this
section, including the visibility analy sis in step 5. Likewise, if a source commits to a BART determination that consists of the
most stringent controls available, then there is no need to complete the remaining analyses in this section.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. This
guidance document provides new guidance on
this topic, which is consistent with this answer.
2. STEP 2: How do I determine whether the options identified in Step 1 are technically feasible?
In Step 2, you evaluate the technical feasibility of the control options you identified in Step 1. You should document a
demonstration of technical infeasibility and should explain, based on physical, chemical, or engineering principles, why
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
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technical difficulties would preclude the successful use of the control option on the emissions unit under review. You may then
eliminate such technically infeasible control options from further consideration in the BART analysis.
In general, what do we mean by technical feasibility?
Control technologies are technically feasible if either (1) they have been installed and operated successfully for the type of
source under review under similar conditions, or (2) the technology could be applied to the source under review. Two key
concepts are important in determining whether a technology could be applied: "availability" and "applicability." As explained
in more detail below, a technology is considered "available" if the source owner may obtain it through commercial channels, or
it is otherwise available within the common sense meaning of the term. An available technology is "applicable" if it can
reasonably be installed and operated on the source type under consideration. A technology that is available and applicable is
technically feasible.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
What do we mean by "available " technology?
1. The typical stages for bringing a control technology concept to reality as a commercial product are:
• Concept stage;
• Research and patenting;
• Bench scale or laboratory testing;
• Pilot scale testing;
• Licensing and commercial demonstration; and
• Commercial sales.
2. A control technique is considered available, within the context presented above, if it has reached the stage of licensing and
commercial availability. Similarly, we do not expect a source owner to conduct extended trials to learn how to apply a
technology on a totally new and dissimilar source type. Consequently, you would not consider technologies in the pilot scale
testing stages of development as "available" for purposes of BART review.
3. Commercial availability by itself, however, is not necessarily a sufficient basis for concluding a technology to be applicable
and therefore technically feasible. Technical feasibility, as determined in Step 2, also means a control option may reasonably be
deployed on or "applicable" to the source type under consideration.
Because a new technology may become available at various points in time during the BART analysis process, we believe that
guidelines are needed on when a technology must be considered. For example, a technology may become available during the
public comment period on the State's rule development process. Likewise, it is possible that new technologies may become
available after the close of the State's public comment period and before submittal of the SIP to EPA, or during EPA's review
process on the SIP submittal. In order to provide certainty in the process, all technologies should be considered if available
before the close of the State's public comment period. You need not consider technologies that become available after this date.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
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As part of your analysis, you should consider any technologies brought to your attention in public comments. If you disagree
with public comments asserting that the technology is available, you should provide an explanation for the public record as to
the basis for your conclusion.
What do we mean by "applicable " technology?
You need to exercise technical judgment in determining whether a control alternative is applicable to the source type under
consideration. In general, a commercially available control option will be presumed applicable if it has been used on the same
or a similar source type. Absent a showing of this type, you evaluate technical feasibility by examining the physical and
chemical characteristics of the pollutant-bearing gas stream, and comparing them to the gas stream characteristics of the source
types to which the technology had been applied previously. Deployment of the control technology on a new or existing source
with similar gas stream characteristics is generally a sufficient basis for concluding the technology is technically feasible
barring a demonstration to the contrary as described below.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
What type of demonstration is required if I conclude that an option is not technically feasible?
1. Where you conclude that a control option identified in Step 1 is technically infeasible, you should demonstrate that the option
is either commercially unavailable, or that specific circumstances preclude its application to a particular emission unit.
Generally, such a demonstration involves an evaluation of the characteristics of the pollutant-bearing gas stream and the
capabilities of the technology. Alternatively, a demonstration of technical infeasibility may involve a showing that there are
unresolvable technical difficulties with applying the control to the source (e.g., size of the unit, location of the proposed site,
operating problems related to specific circumstances of the source, space constraints, reliability, and adverse side effects on the
rest of the facility). Where the resolution of technical difficulties is merely a matter of increased cost, you should consider the
technology to be technically feasible. The cost of a control alternative is considered later in the process.
2. The determination of technical feasibility is sometimes influenced by recent air quality permits. In some cases, an air quality
permit may require a certain level of control, but the level of control in a permit is not expected to be achieved in practice (e.g.,
a source has received a permit but the project was canceled, or every operating source at that permitted level has been
physically unable to achieve compliance with the limit). Where this is the case, you should provide supporting documentation
showing why such limits are not technically feasible, and, therefore, why the level of control (but not necessarily the
technology) may be eliminated from further consideration. However, if there is a permit requiring the application of a certain
technology or emission limit to be achieved for such technology, this usually is sufficient justification for you to assume the
technical feasibility of that technology or emission limit.
3. Physical modifications needed to resolve technical obstacles do not, in and of themselves, provide a justification for
eliminating the control technique on the basis of technical infeasibility. However, you may consider the cost of such
modifications in estimating costs. This, in turn, may form the basis for eliminating a control technology (see later discussion).
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
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4. Vendor guarantees may provide an indication of commercial availability and the technical feasibility of a control technique
and could contribute to a determination of technical feasibility or technical infeasibility, depending on circumstances. However,
we do not consider a vendor guarantee alone to be sufficient justification that a control option will work. Conversely, lack of a
vendor guarantee by itself does not present sufficient justification that a control option or an emissions limit is technically
infeasible. Generally, you should make decisions about technical feasibility based on chemical, and engineering analyses (as
discussed above), in conjunction with information about vendor guarantees.
5. A possible outcome of the BART procedures discussed in these guidelines is the evaluation of multiple control technology
alternatives which result in essentially equivalent emissions. It is not our intent to encourage evaluation of unnecessarily large
numbers of control alternatives for every emissions unit. Consequently, you should use judgment in deciding on those
alternatives for which you will conduct the detailed impacts analysis (Step 4 below). For example, if two or more control
techniques result in control levels that are essentially identical, considering the uncertainties of emissions factors and other
parameters pertinent to estimating performance, you may evaluate only the less costly of these options. You should narrow the
scope of the BART analysis in this way only if there is a negligible difference in emissions and energy and non-air quality
environmental impacts between control alternatives.
3. STEP 3: How do I evaluate technically feasible alternatives?
Step 3 involves evaluating the control effectiveness of all the technically feasible control alternatives identified in Step 2 for the
pollutant and emissions unit under review.
Two key issues in this process include:
(1) Making sure that you express the degree of control using a metric that ensures an "apples to apples" comparison of
emissions performance levels among options, and
(2) Giving appropriate treatment and consideration of control techniques that can operate over a wide range of emission
performance levels.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
What are the appropriate metrics for comparison?
This issue is especially important when you compare inherently lower-polluting processes to one another or to add-on controls.
In such cases, it is generally most effective to express emissions performance as an average steady state emissions level per unit
of product produced or processed.
Examples of common metrics:
• Pounds of SO2 emissions per million Btu heat input, and
• Pounds of NOx emissions per ton of cement produced.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period.
How do I evaluate control techniques with a wide range of emission performance levels?
The general sense of this answer applies as a
recommendation for the development of the LTS
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1. Many control techniques, including both add-on controls and inherently lower polluting processes, can perform at a wide
range of levels. Scrubbers and high and low efficiency electrostatic precipitators (ESPs) are two of the many examples of such
control techniques that can perform at a wide range of levels. It is not our intent to require analysis of each possible level of
efficiency for a control technique as such an analysis would result in a large number of options. It is important, however, that in
analyzing the technology you take into account the most stringent emission control level that the technology is capable of
achieving. You should consider recent regulatory decisions and performance data (e.g., manufacturer's data, engineering
estimates and the experience of other sources) when identifying an emissions performance level or levels to evaluate.
2. In assessing the capability of the control alternative, latitude exists to consider special circumstances pertinent to the specific
source under review, or regarding the prior application of the control alternative. However, you should explain the basis for
choosing the alternate level (or range) of control in the BART analysis. Without a showing of differences between the source
and other sources that have achieved more stringent emissions limits, you should conclude that the level being achieved by
those other sources is representative of the achievable level for the source being analyzed.
3. You may encounter cases where you may wish to evaluate other levels of control in addition to the most stringent level for a
given device. While you must consider the most stringent level as one of the control options, you may consider less stringent
levels of control as additional options. This would be useful, particularly in cases where the selection of additional options
would have widely varying costs and other impacts.
4. Finally, we note that for retrofitting existing sources in addressing BART, you should consider ways to improve the
performance of existing control devices, particularly when a control device is not achieving the level of control that other
similar sources are achieving in practice with the same device. For example, you should consider requiring those sources with
electrostatic precipitators (ESPs) performing below currently achievable levels to improve their performance.
in the second implementation period. This
guidance document provides new guidance on
this topic, which is consistent with this answer.
4. STEP 4: For a BART review, what impacts am I expected to calculate and report? What methods does EPA recommend for
the impacts analysis?
After you identify the available and technically feasible control technology options, you are expected to conduct the following
analyses when you make a BART determination:
Impact analysis part 1: Costs of compliance,
Impact analysis part 2: Energy impacts, and
Impact analysis part 3: Non-air quality environmental impacts.
Impact analysis part 4: Remaining useful life.
In this section, we describe how to conduct each of these three analyses. You are responsible for presenting an evaluation of
each impact along with appropriate supporting information. You should discuss and, where possible, quantify both beneficial
and adverse impacts. In general, the analysis should focus on the direct impact of the control alternative.
This answer applies only to BART. The statutory
factors for reasonable progress are different.
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a. Impact analysis part 1: how do I estimate the costs of control?
1. To conduct a cost analysis, you:
(1) Identify the emissions units being controlled,
(2) Identify design parameters for emission controls, and
(3) Develop cost estimates based upon those design parameters.
2. It is important to identify clearly the emission units being controlled, that is, to specify a well-defined area or process
segment within the plant. In some cases, multiple emission units can be controlled jointly. However, in other cases, it may be
appropriate in the cost analysis to consider whether multiple units will be required to install separate and/or different control
devices. The analysis should provide a clear summary list of equipment and the associated control costs. Inadequate
documentation of the equipment whose emissions are being controlled is a potential cause for confusion in comparison of costs
of the same controls applied to similar sources.
3. You then specify the control system design parameters. Potential sources of these design parameters include equipment
vendors, background information documents used to support NSPS development, control technique guidelines documents, cost
manuals developed by EPA, control data in trade publications, and engineering and performance test data. The following are a
few examples of design parameters for two example control measures:
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. This
guidance document provides new guidance on
this topic, which is consistent with this answer.
Control device
Wet Scrubbers
Selective Catalytic Reduction
Examples of design
parameters
Type of sorbent used (lime, limestone, etc.).
Gas pressure drop.
Liquid/gas ratio.
Ammonia to NOx molar ratio.
Pressure drop.
Catalyst life.
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4. The value selected for the design parameter should ensure that the control option will achieve the level of emission control
being evaluated. You should include in your analysis documentation of your assumptions regarding design parameters.
Examples of supporting references would include the EPA OAQPS Control Cost Manual (see below) and background
information documents used for NSPS and hazardous pollutant emission standards. If the design parameters you specified
differ from typical designs, you should document the difference by supplying performance test data for the control technology
in question applied to the same source or a similar source.
5. Once the control technology alternatives and achievable emissions performance levels have been identified, you then develop
estimates of capital and annual costs. The basis for equipment cost estimates also should be documented, either with data
supplied by an equipment vendor (i.e., budget estimates or bids) or by a referenced source (such as the OAQPS Control Cost
Manual, Fifth Edition, February 1996, EPA 453/B-96-001).152 In order to maintain and improve consistency, cost estimates
should be based on the OAQPS Control Cost Manual, where possible.153 The Control Cost Manual addresses most control
technologies in sufficient detail for a BART analysis. The cost analysis should also take into account any site-specific design or
other conditions identified above that affect the cost of a particular BART technology option.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. This
guidance document provides new guidance on
this topic, which is consistent with this answer.
152 The OAQPS Control Cost Manual is updated periodically. While this citation refers to the latest version at the time this guidance was written, you should use
the version that is current as of when you conduct your impact analysis. This document is available at the following website:
http://www.epa.gov/ttn/catc/dirl/cslch2.pdf.
153 You should include documentation for any additional information you used for the cost calculations, including any information supplied by vendors that
affects your assumptions regarding purchased equipment costs, equipment life, replacement of major components, and any other element of the calculation that
differs from the Control Cost Manual.
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b. What do we mean by cost effectiveness?
Cost effectiveness, in general, is a criterion used to assess the potential for achieving an objective in the most economical way.
For purposes of air pollutant analysis, "effectiveness" is measured in terms of tons of pollutant emissions removed, and "cost"
is measured in terms of annualized control costs. We recommend two types of cost-effectiveness calculations—average cost
effectiveness, and incremental cost effectiveness.
Applies only to BART. This guidance document
provides new guidance on this topic in the
context of the development of the LTS in the
second implementation period.
c. How do I calculate average cost effectiveness?
Average cost effectiveness means the total annualized costs of control divided by annual emissions reductions (the difference
between baseline annual emissions and the estimate of emissions after controls), using the following formula:
Average cost effectiveness (dollars per ton removed) =Control option annualized cost154
Baseline annual emissions—Annual emissions with Control option
Because you calculate costs in (annualized) dollars per year ($/yr) and because you calculate emissions rates in tons per year
(tons/yr), the result is an average cost-effectiveness number in (annualized) dollars per ton ($/ton) of pollutant removed.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. This
guidance document provides new guidance on
this topic, which is consistent with this answer
d. How do I calculate baseline emissions?
1. The baseline emissions rate should represent a realistic depiction of anticipated annual emissions for the source. In general,
for the existing sources subject to BART, you will estimate the anticipated annual emissions based upon actual emissions from
a baseline period.
2. When you project that future operating parameters (e.g., limited hours of operation or capacity utilization, type of fuel, raw
materials or product mix or type) will differ from past practice, and if this projection has a deciding effect in the BART
determination, then you must make these parameters or assumptions into enforceable limitations. In the absence of enforceable
limitations, you calculate baseline emissions based upon continuation of past practice.
3. For example, the baseline emissions calculation for an emergency standby generator may consider the fact that the source
owner would not operate more than past practice of 2 weeks a year. On the other hand, baseline emissions associated with a
base-loaded turbine should be based on its past practice which would indicate a large number of hours of operation. This
produces a significantly higher level of baseline emissions than in the case of the emergency/standby unit and results in more
cost-effective controls. As a consequence of the dissimilar baseline emissions, BART for the two cases could be very different.
The general sense of this answer applies as a
recommendation for the development of the LTS
in the second implementation period. This
guidance document provides new guidance on
this topic, which is consistent with this answer.
While this document recommends a focus on the
baseline situation anticipated to exist in 2028 for
screening purposes, consideration of costs and
emission reductions in a four-factor analysis
should not necessarily be limited to that single
year.
154 Whenever you calculate or report annual costs, you should indicate the year for which the costs are estimated. For example, if you use the year 2000 as the
basis for cost comparisons, you would report that an annualized cost of $20 million would be: $20 million (year 2000 dollars).
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e. How do I calculate incremental cost effectiveness?
1. In addition to the average cost effectiveness of a control option, you should also calculate incremental cost effectiveness.
You should consider the incremental cost effectiveness in combination with the average cost effectiveness when considering
whether to eliminate a control option. The incremental cost effectiveness calculation compares the costs and performance level
of a control option to those of the next most stringent option, as shown in the following formula (with respect to cost per
emissions reduction):
Incremental Cost Effectiveness (dollars per incremental ton removed) = (Total annualized costs of control option) - (Total
annualized costs of next control option) -=- (Control option annual emissions) - (Next control option annual emissions)
Example 1: Assume that Option F on Figure 2 has total annualized costs of $1 million to reduce 2000 tons of a pollutant, and
that Option D on Figure 2 has total annualized costs of $500,000 to reduce 1000 tons of the same pollutant. The incremental
cost effectiveness of Option F relative to Option D is ($ 1 million - $500,000) divided by (2000 tons - 1000 tons), or $500,000
divided by 1000 tons, which is $500/ton.
Example 2: Assume that two control options exist: Option 1 and Option 2. Option 1 achieves a 1,000 ton/yr reduction at an
annualized cost of $1,900,000. This represents an average cost of ($1,900,000/1,000 tons) = $l,900/ton. Option 2 achieves a
980 tons/yr reduction at an annualized cost of $1,500,000. This represents an average cost of ($1,500,000/980 tons) =
$1,53 I/ton. The incremental cost effectiveness of Option 1 relative to Option 2 is ($1,900,000 - $1,500,000) divided by (1,000
tons - 980 tons). The adoption of Option 1 instead of Option 2 results in an incremental emission reduction of 20 tons per year
at an additional cost of $400,000 per year. The incremental cost of Option 1, then, is $20,000 per ton - 11 times the average
cost of $ 1,900 per ton. While $ 1,900 per ton may still be deemed reasonable, it is useful to consider both the average and
incremental cost in making an overall cost-effectiveness finding. Of course, there may be other differences between these
options, such as, energy or water use, or non-air environmental effects, which also should be considered in selecting a BART
technology.
2. You should exercise care in deriving incremental costs of candidate control options. Incremental cost-effectiveness
comparisons should focus on annualized cost and emission reduction differences between "dominant" alternatives. To identify
dominant alternatives, you generate a graphical plot of total annualized costs for total emissions reductions for all control
alternatives identified in the BART analysis, and by identifying a "least-cost envelope" as shown in Figure 2. (A "least-cost
envelope" represents the set of options that should be dominant in the choice of a specific option.)
The information on how to calculate incremental
cost-effectiveness is applicable. This guidance
document provides new guidance discouraging
the consideration of incremental cost-
effectiveness when determining whether the cost
of compliance is reasonable.
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I
H
Dominant controls (B, D, F, G, H)
lie on envelope
Inferior controls
(A, C, E)
delta" Costs
"delta"
Emissions
i > i_
INCREASING EMtSSJONS REDUCTION
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Example: Eight technically feasible control options for analysis are listed. These are represented as A through H in Figure 2. The
dominant set of control options, B, D, F, G, and H, represent the least-cost envelope, as we depict by the cost curve connecting
them. Points A, C and E are inferior options, and you should not use them in calculating incremental cost effectiveness. Points A,
C and E represent inferior controls because B will buy more emissions reductions for less money than A; and similarly, D and F
will buy more reductions for less money than C and E, respectively.
3. In calculating incremental costs, you:
(1) Array the control options in ascending order of annualized total costs,
(2) Develop a graph of the most reasonable smooth curve of the control options, as shown in Figure 2. This is to show the "least-
cost envelope" discussed above; and
(3) Calculate the incremental cost effectiveness for each dominant option, which is the difference in total annual costs between
that option and the next most stringent option, divided by the difference in emissions, after controls have been applied, between
those two control options. For example, using Figure 2, you would calculate incremental cost effectiveness for the difference
between options B and D, options D and F, options F and G, and options G and H.
4. A comparison of incremental costs can also be useful in evaluating the viability of a specific control option over a range of
efficiencies. For example, depending on the capital and operational cost of a control device, total and incremental cost may vary
significantly (either increasing or decreasing) over the operational range of a control device. Also, the greater the number of
possible control options that exist, the more weight should be given to the incremental costs vs. average costs. It should be noted
that average and incremental cost effectiveness are identical when only one candidate control option is known to exist.
5. You should exercise caution not to misuse these techniques. For example, you may be faced with a choice between two
available control devices at a source, control A and control B, where control B achieves slightly greater emission reductions. The
average cost (total annual cost/total annual emission reductions) for each may be deemed to be reasonable. However, the
incremental cost (total annual costA - B/total annual emission reductionsA - B) of the additional emission reductions to be achieved
by control B may be very great. In such an instance, it may be inappropriate to choose control B, based on its high incremental
costs, even though its average cost may be considered reasonable.
6. In addition, when you evaluate the average or incremental cost effectiveness of a control alternative, you should make
reasonable and supportable assumptions regarding control efficiencies. An unrealistically low assessment of the emission
reduction potential of a certain technology could result in inflated cost-effectiveness figures.
The information on how to calculate
incremental cost-effectiveness is applicable.
This guidance document provides new
guidance discouraging the consideration of
incremental cost-effectiveness when
determining whether the cost of compliance is
reasonable.
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f. What other information should I provide in the cost impacts analysis?
You should provide documentation of any unusual circumstances that exist for the source that would lead to cost-effectiveness
estimates that would exceed that for recent retrofits. This is especially important in cases where recent retrofits have cost-
effectiveness values that are within what has been considered a reasonable range, but your analysis concludes that costs for the
source being analyzed are not considered reasonable. (A reasonable range would be a range that is consistent with the range of
cost effectiveness values used in other similar permit decisions over a period of time.)
Example: In an arid region, large amounts of water are needed for a scrubbing system. Acquiring water from a distant location
could greatly increase the cost per ton of emissions reduced of wet scrubbing as a control option.
The general sense of this answer applies as a
recommendation for the development of the
LTS in the second implementation period.
g. What other things are important to consider in the cost impacts analysis?
In the cost analysis, you should take care not to focus on incomplete results or partial calculations. For example, large capital
costs for a control option alone would not preclude selection of a control measure if large emissions reductions are projected. In
such a case, low or reasonable cost effectiveness numbers may validate the option as an appropriate BART alternative
irrespective of the large capital costs. Similarly, projects with relatively low capital costs may not be cost effective if there are
few emissions reduced.
The general sense of this answer applies as a
recommendation for the development of the
LTS in the second implementation period.
This guidance document provides new
guidance on this topic, which is consistent
with this answer.
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h. Impact analysis part 2: How should I analyze and report energy impacts?
1. You should examine the energy requirements of the control technology and determine whether the use of that technology
results in energy penalties or benefits. A source owner may, for example, benefit from the combustion of a concentrated gas
stream rich in volatile organic compounds; on the other hand, more often extra fuel or electricity is required to power a control
device or incinerate a dilute gas stream. If such benefits or penalties exist, they should be quantified to the extent practicable.
Because energy penalties or benefits can usually be quantified in terms of additional cost or income to the source, the energy
impacts analysis can, in most cases, simply be factored into the cost impacts analysis. The fact of energy use in and of itself does
not disqualify a technology.
2. Your energy impact analysis should consider only direct energy consumption and not indirect energy impacts. For example,
you could estimate the direct energy impacts of the control alternative in units of energy consumption at the source (e.g., BTU,
kWh, barrels of oil, tons of coal). The energy requirements of the control options should be shown in terms of total (and in
certain cases, also incremental) energy costs per ton of pollutant removed. You can then convert these units into dollar costs and,
where appropriate, factor these costs into the control cost analysis.
3. You generally do not consider indirect energy impacts (such as energy to produce raw materials for construction of control
equipment). However, if you determine, either independently or based on a showing by the source owner, that the indirect
energy impact is unusual or significant and that the impact can be well quantified, you may consider the indirect impact.
4. The energy impact analysis may also address concerns over the use of locally scarce fuels. The designation of a scarce fuel
may vary from region to region. However, in general, a scarce fuel is one which is in short supply locally and can be better used
for alternative purposes, or one which may not be reasonably available to the source either at the present time or in the near
future.
5. Finally, the energy impacts analysis may consider whether there are relative differences between alternatives regarding the use
of locally or regionally available coal, and whether a given alternative would result in significant economic disruption or
unemployment. For example, where two options are equally cost effective and achieve equivalent or similar emissions
reductions, one option may be preferred if the other alternative results in significant disruption or unemployment.
The general sense of this answer applies as a
recommendation for the development of the
LTS in the second implementation period.
This guidance document provides new
guidance on this topic, which is consistent
with this answer.
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i. Impact analysis part 3: How do I analyze "non-air quality environmental impacts?"
1. In the non-air quality related environmental impacts portion of the BART analysis, you address environmental impacts other
than air quality due to emissions of the pollutant in question. Such environmental impacts include solid or hazardous waste
generation and discharges of polluted water from a control device.
2. You should identify any significant or unusual environmental impacts associated with a control alternative that have the
potential to affect the selection or elimination of a control alternative. Some control technologies may have potentially
significant secondary environmental impacts. Scrubber effluent, for example, may affect water quality and land use.
Alternatively, water availability may affect the feasibility and costs of wet scrubbers. Other examples of secondary
environmental impacts could include hazardous waste discharges, such as spent catalysts or contaminated carbon. Generally,
these types of environmental concerns become important when sensitive site-specific receptors exist or when the incremental
emissions reductions potential of the more stringent control is only marginally greater than the next most-effective option.
However, the fact that a control device creates liquid and solid waste that must be disposed of does not necessarily argue against
selection of that technology as BART, particularly if the control device has been applied to similar facilities elsewhere and the
solid or liquid waste is similar to those other applications. On the other hand, where you or the source owner can show that
unusual circumstances at the proposed facility create greater problems than experienced elsewhere, this may provide a basis for
the elimination of that control alternative as BART.
3. The procedure for conducting an analysis of non-air quality environmental impacts should be made based on a consideration
of site-specific circumstances. If you propose to adopt the most stringent alternative, then it is not necessary to perform this
analysis of environmental impacts for the entire list of technologies you ranked in Step 3. In general, the analysis need only
address those control alternatives with any significant or unusual environmental impacts that have the potential to affect the
selection of a control alternative, or elimination of a more stringent control alternative. Thus, any important relative
environmental impacts (both positive and negative) of alternatives can be compared with each other.
4. In general, the analysis of impacts starts with the identification and quantification of the solid, liquid, and gaseous discharges
from the control device or devices under review. Initially, you should perform a qualitative or semi-quantitative screening to
narrow the analysis to discharges with potential for causing adverse environmental effects. Next, you should assess the mass and
composition of any such discharges and quantify them to the extent possible, based on readily available information. You should
also assemble pertinent information about the public or environmental consequences of releasing these materials.
The general sense of this answer applies as a
recommendation for the development of the
LTS in the second implementation period.
This guidance document provides new
guidance on this topic, which is consistent
with this answer.
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j. Impact analysis part 4: What are examples of non-air quality environmental impacts?
The following are examples of how to conduct non-air quality environmental impacts:
(1) Water Impact
You should identify the relative quantities of water used and water pollutants produced and discharged as a result of the use of
each alternative emission control system. Where possible, you should assess the effect on ground water and such local surface
water quality parameters as pH, turbidity, dissolved oxygen, salinity, toxic chemical levels, temperature, and any other important
considerations. The analysis could consider whether applicable water quality standards will be met and the availability and
effectiveness of various techniques to reduce potential adverse effects.
(2) Solid Waste Disposal Impact
You could also compare the quality and quantity of solid waste (e.g., sludges, solids) that must be stored and disposed of or
recycled as a result of the application of each alternative emission control system. You should consider the composition and
various other characteristics of the solid waste (such as permeability, water retention, rewatering of dried material, compression
strength, leachability of dissolved ions, bulk density, ability to support vegetation growth and hazardous characteristics) which
are significant with regard to potential surface water pollution or transport into and contamination of subsurface waters or
aquifers.
(3) Irreversible or Irretrievable Commitment of Resources
You may consider the extent to which the alternative emission control systems may involve a trade-off between short-term
environmental gains at the expense of long-term environmental losses and the extent to which the alternative systems may result
in irreversible or irretrievable commitment of resources (for example, use of scarce water resources).
(4) Other Adverse Environmental Impacts
You may consider significant differences in noise levels, radiant heat, or dissipated static electrical energy of pollution control
alternatives. Other examples of non-air quality environmental impacts would include hazardous waste discharges such as spent
catalysts or contaminated carbon.
The general sense of this answer applies as a
recommendation for the development of the
LTS in the second implementation period.
This guidance document provides new
guidance on this topic, which is consistent
with this answer.
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k. How do I take into account a project's "remaining useful life" in calculating control costs?
1. You may decide to treat the requirement to consider the source's "remaining useful life" of the source for BART
determinations as one element of the overall cost analysis. The "remaining useful life" of a source, if it represents a relatively
short time period, may affect the annualized costs of retrofit controls. For example, the methods for calculating annualized costs
in EPA's OAQPS Control Cost Manual require the use of a specified time period for amortization that varies based upon the type
of control. If the remaining useful life will clearly exceed this time period, the remaining useful life has essentially no effect on
control costs and on the BART determination process. Where the remaining useful life is less than the time period for amortizing
costs, you should use this shorter time period in your cost calculations.
2. For purposes of these guidelines, the remaining useful life is the difference between:
(1) The date that controls will be put in place (capital and other construction costs incurred before controls are put in place can
be rolled into the first year, as suggested in EPA's OAQPS Control Cost Manual); you are conducting the BART analysis; and
(2) The date the facility permanently stops operations. Where this affects the BART determination, this date should be assured
by a federally- or State-enforceable restriction preventing further operation.
3. We recognize that there may be situations where a source operator intends to shut down a source by a given date, but wishes
to retain the flexibility to continue operating beyond that date in the event, for example, that market conditions change. Where
this is the case, your BART analysis may account for this, but it must maintain consistency with the statutory requirement to
install BART within 5 years. Where the source chooses not to accept a federally enforceable condition requiring the source to
shut down by a given date, it is necessary to determine whether a reduced time period for the remaining useful life changes the
level of controls that would have been required as BART.
If the reduced time period does change the level of BART controls, you may identify, and include as part of the BART emission
limitation, the more stringent level of control that would be required as BART if there were no assumption that reduced the
remaining useful life. You may incorporate into the BART emission limit this more stringent level, which would serve as a
contingency should the source continue operating more than 5 years after the date EPA approves the relevant SIP. The source
would not be allowed to operate after the 5-year mark without such controls. If a source does operate after the 5-year mark
without BART in place, the source is considered to be in violation of the BART emissions limit for each day of operation.
The general sense of this answer applies as a
recommendation for the development of the
LTS in the second implementation period.
This guidance document provides new
guidance on this topic, which is consistent
with this answer.
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5. Step 5: How should I determine visibility impacts in the BART determination?
The following is an approach you may use to determine visibility impacts (the degree of visibility improvement for each source
subject to BART) for the BART determination. Once you have determined that your source or sources are subject to BART, you
must conduct a visibility improvement determination for the source(s) as part of the BART determination. When making this
determination, we believe you have flexibility in setting absolute thresholds, target levels of improvement, or de minimis levels
since the deciview improvement must be weighed among the five factors, and you are free to determine the weight and
significance to be assigned to each factor. For example, a 0.3 deciview improvement may merit a stronger weighting in one case
versus another, so one "bright line" may not be appropriate. [Note that if sources have elected to apply the most stringent
controls available, consistent with the discussion in section E. step 1. below, you need not conduct, or require the source to
conduct, an air quality modeling analysis for the purpose of determining its visibility impacts.]
Use CALPUFF,155 or other appropriate dispersion model to determine the visibility improvement expected at a Class I area from
the potential BART control technology applied to the source. Modeling should be conducted for SCh, NOx, and direct PM
emissions (PM2.5 and/or PMio). If the source is making the visibility determination, you should review and approve or disapprove
of the source's analysis before making the expected improvement determination. There are several steps for determining the
visibility impacts from an individual source using a dispersion model:
• Develop a modeling protocol.
Some critical items to include in a modeling protocol are meteorological and terrain data, as well as source-specific information
(stack height, temperature, exit velocity, elevation, and allowable and actual emission rates of applicable pollutants), and
receptor data from appropriate Class I areas. We recommend following EPA's Interagency Workgroup on Air Quality Modeling
(IWAQM) Phase 2 Summary Report and Recommendations for Modeling Long Range Transport Impacts156 for parameter
settings and meteorological data inputs; the use of other settings from those in IWAQM should be identified and explained in the
protocol.
One important element of the protocol is in establishing the receptors that will be used in the model. The receptors that you use
should be located in the nearest Class I area with sufficient density to identify the likely visibility effects of the source. For other
Class I areas in relatively close proximity to a BART-eligible source, you may model a few strategic receptors to determine
whether effects at those areas may be greater than at the nearest Class I area. For example, you might chose to locate receptors at
these areas at the closest point to the source, at the highest and lowest elevation in the Class I area, at the IMPROVE monitor,
and at the approximate expected plume release height. If the highest modeled effects are observed at the nearest Class I area, you
may choose not to analyze the other Class I areas any further as additional analyses might be unwarranted.
You should bear in mind that some receptors within the relevant Class I area may be less than 50 km from the source while other
receptors within that same Class I area may be greater than 50 km from the same source. As indicated by the Guideline on Air
Quality Models, this situation may call for the use of two different modeling approaches for the same Class I area and source,
depending upon the State's chosen method for modeling sources less than 50 km. In situations where you are assessing visibility
impacts for source-receptor distances less than 50 km, you should use expert modeling judgment in determining visibility
impacts, giving consideration to both CALPUFF and other EPA-approved methods.
In developing your modeling protocol, you may want to consult with EPA and your regional planning organization (RPO). Up-
front consultation will ensure that key technical issues are addressed before you conduct your modeling.
• For each source, run the model, at pre-control and post-control emission rates according to the accepted methodology in the
protocol.
Applies only to BART.
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Use the 24-hour average actual emission rate from the highest emitting day of the meteorological period modeled (for the pre-
control scenario). Calculate the model results for each receptor as the change in deciviews compared against natural visibility
conditions. Post-control emission rates are calculated as a percentage of pre-control emission rates. For example, if the 24-hr pre-
control emission rate is 100 Ib/hr of SCh, then the post control rate is 5 Ib/hr if the control efficiency being evaluated is 95
percent.
• Make the net visibility improvement determination.
Assess the visibility improvement based on the modeled change in visibility impacts for the pre-control and post-control
emission scenarios. You have flexibility to assess visibility improvements due to BART controls by one or more methods. You
may consider the frequency, magnitude, and duration components of impairment. Suggestions for making the determination are:
• Use of a comparison threshold, as is done for determining if BART-eligible sources should be subject to a BART
determination. Comparison thresholds can be used in a number of ways in evaluating visibility improvement (e.g., the number of
days or hours that the threshold was exceeded, a single threshold for determining whether a change in impacts is significant, or a
threshold representing an x percent change in improvement).
• Compare the 98th percent days for the pre- and post-control runs.
Note that each of the modeling options may be supplemented with source apportionment data or source apportionment modeling.
155 The model code and its documentation are available at no cost for download from http://www.epa.gov/scram001/tt22.htmncalpuff.
156 Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 2 Summary Report and Recommendations for Modeling Long Range Transport Impacts,
U.S. Environmental Protection Agency, EPA-454/R-98-019, December 1998.
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E. How do I select the "best" alternative, using the results of Steps 1 through 5?
1. Summary of the Impacts Analysis
From the alternatives you evaluated in Step 3, we recommend you develop a chart (or charts) displaying for each of the
alternatives:
(1) Expected emission rate (tons per year, pounds per hour);
(2) Emissions performance level (e.g., percent pollutant removed, emissions per unit product, Ib/MMBtu, ppm);
(3) Expected emissions reductions (tons per year);
(4) Costs of compliance—total annualized costs ($), cost effectiveness ($/ton), and incremental cost effectiveness ($/ton), and/or
any other cost-effectiveness measures (such as $/deciview);
(5) Energy impacts;
(6) Non-air quality environmental impacts; and
(7) Modeled visibility impacts.
The general sense of this answer applies as a
recommendation for the development of the
LTS in the second implementation period. The
factors to be displayed in such a chart would
be the four statutory factors for reasonable
progress, and also visibility benefits for a state
following the second alternative approach to
considering visibility benefits.
2. Selecting a "best" alternative
1. You have discretion to determine the order in which you should evaluate control options for BART. Whatever the order in
which you choose to evaluate options, you should always (1) display the options evaluated; (2) identify the average and
incremental costs of each option; (3) consider the energy and non-air quality environmental impacts of each option; (4) consider
the remaining useful life; and (5) consider the modeled visibility impacts. You should provide a justification for adopting the
technology that you select as the "best" level of control, including an explanation of the CAA factors that led you to choose that
option over other control levels.
2. In the case where you are conducting a BART determination for two regulated pollutants on the same source, if the result is
two different BART technologies that do not work well together, you could then substitute a different technology or combination
of technologies.
Applies only to BART. This guidance
document provides new guidance on this topic
in the context of the development of the LTS
in the second implementation period, which is
not consistent with this answer.
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3. In selecting a "best" alternative, should I consider the affordability of controls?
1. Even if the control technology is cost effective, there may be cases where the installation of controls would affect the viability
of continued plant operations.
2. There may be unusual circumstances that justify taking into consideration the conditions of the plant and the economic effects
of requiring the use of a given control technology. These effects would include effects on product prices, the market share, and
profitability of the source. Where there are such unusual circumstances that are judged to affect plant operations, you may take
into consideration the conditions of the plant and the economic effects of requiring the use of a control technology. Where these
effects are judged to have a severe impact on plant operations you may consider them in the selection process, but you may wish
to provide an economic analysis that demonstrates, in sufficient detail for public review, the specific economic effects,
parameters, and reasoning. (We recognize that this review process must preserve the confidentiality of sensitive business
information). Any analysis may also consider whether other competing plants in the same industry have been required to install
BART controls if this information is available.
Applies only to BART. This guidance
document provides new guidance on this topic
in the context of the development of the LTS
in the second implementation period, which is
consistent with this answer.
4. Sulfur dioxide limits for utility boilers
You must require 750 MW power plants to meet specific control levels for SCh of either 95 percent control or 0.15 Ibs/MMBtu,
for each EGU greater than 200 MW that is currently uncontrolled unless you determine that an alternative control level is
justified based on a careful consideration of the statutory factors. Thus, for example, if the source demonstrates circumstances
affecting its ability to cost-effectively reduce its emissions, you should take that into account in determining whether the
presumptive levels of control are appropriate for that facility. For a currently uncontrolled EGU greater than 200 MW in size, but
located at a power plant smaller than 750 MW in size, such controls are generally cost-effective and could be used in your
BART determination considering the five factors specified in CAA section 169A(g)(2). While these levels may represent current
control capabilities, we expect that scrubber technology will continue to improve and control costs continue to decline. You
should be sure to consider the level of control that is currently best achievable at the time that you are conducting your BART
analysis.
Applies only to BART.
For coal-fired EGUs with existing post-combustion SChcontrols achieving less than 50 percent removal efficiencies, we
recommend that you evaluate constructing a new FGD system to meet the same emission limits as above (95 percent removal or
0.15 Ib/mmBtu), in addition to the evaluation of scrubber upgrades discussed below. For oil-fired units, regardless of size, you
should evaluate limiting the sulfur content of the fuel oil burned to 1 percent or less by weight.
For those BART-eligible EGUs with pre-existing post-combustion SChcontrols achieving removal efficiencies of at least 50
percent, your BART determination should consider cost effective scrubber upgrades designed to improve the system's overall
SChremoval efficiency. There are numerous scrubber enhancements available to upgrade the average removal efficiencies of all
types of existing scrubber systems. We recommend that as you evaluate the definition of "upgrade," you evaluate options that
Applies only to BART. The general sense of
this answer applies as a recommendation for
the development of the LTS in the second
implementation period.
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not only improve the design removal efficiency of the scrubber vessel itself, but also consider upgrades that can improve the
overall SCh removal efficiency of the scrubber system. Increasing a scrubber system's reliability, and conversely decreasing its
downtime, by way of optimizing operation procedures, improving maintenance practices, adjusting scrubber chemistry, and
increasing auxiliary equipment redundancy, are all ways to improve average SCh removal efficiencies.
We recommend that as you evaluate the performance of existing wet scrubber systems, you consider some of the following
upgrades, in no particular order, as potential scrubber upgrades that have been proven in the industry as cost effective means to
increase overall SCh removal of wet systems:
(a) Elimination of Bypass Reheat;
(b) Installation of Liquid Distribution Rings;
(c) Installation of Perforated Trays;
(d) Use of Organic Acid Additives;
(e) Improve or Upgrade Scrubber Auxiliary System Equipment;
(f) Redesign Spray Header or Nozzle Configuration.
We recommend that as you evaluate upgrade options for dry scrubber systems, you should consider the following cost effective
upgrades, in no particular order:
(a) Use of Performance Additives;
(b) Use of more Reactive Sorbent;
(c) Increase the Pulverization Level of Sorbent;
(d) Engineering redesign of atomizer or slurry injection system.
You should evaluate scrubber upgrade options based on the 5 step BART analysis process.
5. Nitrogen oxide limits for utility boilers
You should establish specific numerical limits for NOx control for each BART determination. For power plants with a
generating capacity in excess of 750 MW currently using selective catalytic reduction (SCR) or selective non-catalytic reduction
(SNCR) for part of the year, you should presume that use of those same controls year-round is BART. For other sources
currently using SCR or SNCR to reduce NOx emissions during part of the year, you should carefully consider requiring the use
of these controls year-round as the additional costs of operating the equipment throughout the year would be relatively modest.
Applies only to BART. The general sense of
this answer applies as a recommendation for
the development of the LTS in the second
implementation period.
For coal-fired EGUs greater than 200 MW located at greater than 750 MW power plants and operating without post-combustion
controls (i.e. SCR or SNCR), we have provided presumptive NOx limits, differentiated by boiler design and type of coal burned.
You may determine that an alternative control level is appropriate based on a careful consideration of the statutory factors. For
Applies only to BART.
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coal-fired EGUs greater than 200 MW located at power plants 750 MW or less in size and operating without post-combustion
controls, you should likewise presume that these same levels are cost-effective. You should require such utility boilers to meet
the following NOx emission limits, unless you determine that an alternative control level is justified based on consideration of
the statutory factors. The following NOx emission rates were determined based on a number of assumptions, including that the
EGU boiler has enough volume to allow for installation and effective operation of separated overfire air ports. For boilers where
these assumptions are incorrect, these emission limits may not be cost-effective.
Table 1 (below)
EPA Recommendation
Regarding Applicability to
Reasonable Progress
Determinations in the Second
Implementation Period
Applies only to BART.
Table 1—Presumptive NOx Emission Limits for BART-Eligible Coal-Fired Units.1
Unit type
Dry-bottom wall-fired
Tangential-fired
Cell Burners
Dry-turbo-fired
Wet-bottom tangential-fired
Coal type
Bituminous
Sub-bituminous
Lignite
Bituminous
Sub-bituminous
Lignite
Bituminous
Sub-bituminous
Bituminous
Sub-bituminous
Bituminous
STOx presumptive limit
(lb/mmbtu)20
0.39
0.23
0.29
0.28
0.15
0.17
0.40
0.45
0.32
0.23
0.62
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19No Cell burners, dry-turbo-fired units, nor wet-bottom tangential-fired units burning lignite were identified as BART-eligible, thus no presumptive limit was determined.
Similarly, no wet-bottom tangential-fired units burning sub-bituminous were identified as BART-eligible.
20These limits reflect the design and technological assumptions discussed in the technical support document for NOx limits for these guidelines. See Technical Support Document
for BART NOx Limits for Electric Generating Units and Technical Support Document for BART NOx Limits for Electric Generating Units Excel Spreadsheet, Memorandum to
Docket OAR 2002-0076, April 15, 2005.
BART Guideline Provisions
EPA Recommendation
Regarding Applicability to
Reasonable Progress
Determinations in the Second
Implementation Period
Most EGUs can meet these presumptive NOx limits through the use of current combustion control technology, i.e. the careful
control of combustion air and low-NOx burners. For units that cannot meet these limits using such technologies, you should
consider whether advanced combustion control technologies such as rotating opposed fire air should be used to meet these limits.
Because of the relatively high emission rates of cyclone units, SCR is more cost-effective than the use of current combustion
control technology for these units. The use of SCRs at cyclone units burning bituminous coal, sub-bituminous coal, and lignite
should enable the units to cost-effectively meet NOx rates of 0.10 Ibs/mmbtu. Asa result, we are establishing a presumptive
NOx limit of 0.10 Ibs/mmbtu based on the use of SCR for coal-fired cyclone units greater than 200 MW located at 750 MW
power plants. As with the other presumptive limits established in this guideline, you may determine that an alternative level of
control is appropriate based on your consideration of the relevant statutory factors. For other cyclone units, you should review
the use of SCR and consider whether these post-combustion controls should be required as BART.
Applies only to BART.
For oil-fired and gas-fired EGUs larger than 200MW, we believe that installation of current combustion control technology to
control NOx is generally highly cost-effective and should be considered in your determination of BART for these sources. Many
such units can make significant reductions in NOx emissions which are highly cost-effective through the application of current
combustion control technology.157
The general sense of this answer applies
as a recommendation for the development
of the LTS in the second implementation
period.
157 See Technical Support Document for BART NOx Limits for Electric Generating Units and Technical Support Document for BART NOx Limits for Electric
Generating Units Excel Spreadsheet, Memorandum to Docket EPA-HQ-OAR 2002-0076, April 15, 2005.
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BART Guideline Provisions
EPA Recommendation
Regarding Applicability to
Reasonable Progress
Determinations in the Second
Implementation Period
V. Enforceable Limits/Compliance Date
To complete the BART process, you must establish enforceable emission limits that reflect the BART requirements and require
compliance within a given period of time. In particular, you must establish an enforceable emission limit for each subject
emission unit at the source and for each pollutant subject to review that is emitted from the source. In addition, you must require
compliance with the BART emission limitations no later than 5 years after EPA approves your regional haze SIP. If
technological or economic limitations in the application of a measurement methodology to a particular emission unit make a
conventional emissions limit infeasible, you may instead prescribe a design, equipment, work practice, operation standard, or
combination of these types of standards. You should consider allowing sources to "average" emissions across any set of BART -
eligible emission units within a fenceline, so long as the emission reductions from each pollutant being controlled for BART
would be equal to those reductions that would be obtained by simply controlling each of the BART-eligible units that constitute
BART-eligible source.
You should ensure that any BART requirements are written in a way that clearly specifies the individual emission unit(s) subject
to BART regulation. Because the BART requirements themselves are "applicable" requirements of the CAA, they must be
included as title V permit conditions according to the procedures established in 40 CFR part 70 or 40 CFR part 71.
Section 302(k) of the CAA requires emissions limits such as BART to be met on a continuous basis. Although this provision
does not necessarily require the use of continuous emissions monitoring (CEMs), it is important that sources employ techniques
that ensure compliance on a continuous basis. Monitoring requirements generally applicable to sources, including those that are
subject to BART, are governed by other regulations. See, e.g., 40 CFR part 64 (compliance assurance monitoring); 40 CFR
70.6(a)(3) (periodic monitoring); 40 CFR 70.6(c)(l) (sufficiency monitoring). Note also that while we do not believe that CEMs
would necessarily be required for all BART sources, the vast majority of electric generating units potentially subject to BART
already employ CEM technology for other programs, such as the acid rain program. In addition, emissions limits must be
enforceable as a practical matter (contain appropriate averaging times, compliance verification procedures and recordkeeping
requirements). In light of the above, the permit must:
• Be sufficient to show compliance or noncompliance (i.e., through monitoring times of operation, fuel input, or other indices of
operating conditions and practices); and
• Specify a reasonable averaging time consistent with established reference methods, contain reference methods for determining
compliance, and provide for adequate reporting and recordkeeping so that air quality agency personnel can determine the
compliance status of the source; and
• ForEGUs, specify an averaging time of a 30-day rolling average, and contain a definition of "boiler operating day" that is
consistent with the definition in the proposed revisions to the NSPS for utility boilers in 40 CFR Part 60, subpart Da.22 You
should consider a boiler operating day to be any 24-hour period between 12:00 midnight and the following midnight during
which any fuel is combusted at any time at the steam generating unit. This would allow 30-day rolling average emission rates to
be calculated consistently across sources.
Applies only to BART. This guidance
document provides new guidance on this
topic in the context of the development of
the LTS in the second implementation
period.
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APPENDIX E
Identification of Provisions of the Previous Guidance Documents on Natural
Conditions and Progress Tracking that Are Applicable as EPA
Recommendations for Reasonable Progress Analysis and Determinations in
the Second Implementation Period
Guidance for Tracking Progress Under the Regional Haze Rule (September 2003),
available at: httDs://www3.eDa.gov/ttnamtil/files/ambient/visible/tracking.Ddf
Section
1.1, 1.4
1.6
1.10
1.13
2.2
2.3
4.5,4.6
4.7
Topic
Background on regional haze and the statutory and regulatory basis for the
program
Explanation of the haze index and deciview scale
Acceptability of progress goals that provide for visibility degradation
History of the IMPROVE visibility monitoring program
Assessing data completeness and data substitution for missing values (Steps 1-7
remain applicable) (Though IMPROVE program data managers typically
conduct this work, the steps outlined here remain the approach the data
managers use).
Guidance for the inclusion of incomplete data years (provided the user
substitutes most impaired days for worst days)
Recommendations for states if changes to the IMPROVE monitoring site and
location occur
Advantages of analyzing trends in individual extinction species
Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule,
(September 2003), available at:
httDs://www3.eDa.gov/ttn/caaa/tl/memoranda/rh envcurhr gd.pdf
Section
1.1, 1.5
1.6
1.10
3.1
3.4
Topic
Background on regional haze and the statutory and regulatory basis for the
program
Explanation of the haze index and deciview scale
Natural visibility conditions should reflect current development patterns and
levels without human impacts (This 2016 guidance document implements this
principle to the best of our current scientific understanding).
Why might states choose to use a refined approach to estimating natural
visibility conditions?
If states choose to use an alternative approach to estimating natural visibility
conditions, what supporting information and justification should be included?
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APPENDIX F
Identification of Answers in the September 27, 2006, Q&A Document that Are Applicable as EPA
Recommendations for Reasonable Progress Analysis and Determinations in the Second Implementation
Period
Q&A
BART
1. Should a State promulgate a BART rule? Should a State's BART rule declare that VOC (and possibly
ammonia) is/are not visibility impairing pollutant(s), or can this declaration be part of the SIP narrative?
Relevance to the Second Implementation
Period
Explanation of Entries in this Column:
Applies only to BART - The statement in the Q&A has no
relevance to the development of an LTS for reasonable
progress, except to the extent that BART for a BART-eligible
source must be determined and thus becomes part of the LTS.
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
period. - This guidance document does not provide any
additional recommendation on this topic that would need to be
considered along with the statement in the Q&A.
Applies only to BART. This guidance document provides new
guidance on this topic in the context of the development of the
LTS in the second implementation period, -which is not
consistent -with this answer. - The statement in the Q&A applies
only to BART determinations. The general sense of that
statement should not be applied to the development of the LTS
for reasonable progress.
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
period. This guidance document provides new guidance on this,
•which is consistent -with this answer. - While the statement in
the Q&A applies only to BART determinations, the general
sense of that statement should also be applied to the
development of the LTS for reasonable progress but taking into
consideration related statements in this document.
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
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Q&A
Relevance to the Second Implementation
Period
The regional haze rule (RHR) does not require that States promulgate BART rules. States are, however,
required under 40 CFR 51.230 to show they have the legal authority to carry out the SIP. To the extent a
BART rule can aid in this requirement, then it should be considered. A State's regional haze (RH) SIP
submittal must include source- specific BART emission limits and compliance schedules for each source
subject to BART. See 40 CFR 51.308(e). All regulatory requirements must be approved into the SIP.
A State's BART rule should not declare that VOCs or ammonia are not visibility- impairing pollutants unless
the State has evidence that VOCs (or ammonia) from its BART-eligible sources are not significant
contributors to particle formation. Such a declaration must be substantiated in the SIP documentation. This
declaration may be placed in the SIP narrative, which will be approved into the non-regulatory portion of the
SIP following an opportunity for public review and comment on the State's conclusion. Furthermore, we
recommend that prior to SIP submittal that collaboration between and among States and RPOs and Federal
Land Managers (FLMs) occur such that the application of exemptions or other principles used by a State/RPO
is done with full knowledge among the affected States/RPOs/FLMs
period. While there are no points of disagreement between the
Q&A and this guidance document, there is additional relevant
material in this guidance document, so the Q&A should not be
used alone.
2. At sources that require BART but that have PTEs of less than 250 TPY for VOCs and ammonia, must the
BART proposal analyze controls for VOCs and ammonia?
States must use their judgment to determine whether VOC or ammonia emissions from individual sources in
their State are likely to have an impact on visibility in an area. For a source such as the one you have
described, the State must consider whether its VOC or ammonia emissions are likely to have an impact on
visibility at a Class I area. If so, the BART proposal must analyze controls for such VOCs and/or ammonia.
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
period.
3. Should a State declare the exemption threshold value is 0.5 dv (or some other value) in their rule? EPA has
simply set an upper bound.
The exemption threshold value selected by the State in determining whether a BART- eligible source can
reasonably be anticipated to cause or contribute to visibility impairment must be specified in the SIP
documentation, as must the basis for the States' selection of this threshold. The appropriateness of the
threshold used by the State will be subject to public review and comment, and States should consult with the
affected States/RPOs/FLMs in establishing this value.
This answer applies only to BART. This guidance document
provides new guidance on the topic of screening thresholds in
the context of the development of the LTS in the second
implementation period.
4. How should a State document in the SIP that BART controls will be installed and in operation as
expeditiously as practicable, but no later than 5 years after approval of the SIP? Must BART controls be
housed in a Title V permit modification?
As specified in 40 CFR 51.308(e)(l)(v), States are required to ensure each source subject to BART install and
operate BART as expeditiously as practicable, but in no event later than 5 years after approval of the
implementation plan revision. States should ensure that BART requirements in a SIP are written in a way that
clearly specifies the individual emission unit(s) subject to BART regulation and the time by which the
emission unit(s) must begin to comply with the BART limit. Because the BART requirements are
"applicable" requirements of the CAA, they must be included as title V permit conditions according to the
procedures established in 40 CFR part 70 or 40 CFR part 71. Under 70.7(f)(l )(i) Title V permits must be
This answer applies only to BART. This guidance document
provides new guidance on this topic in the context of the
development of the LTS in the second implementation period.
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Period
reopened and revised to include new applicable requirements if the permit has three or more years of life. The
reopening must be completed within 18 months after promulgation of the new applicable requirement and the
reopening must follow the same procedures (public comment, etc) as apply to initial permit issuance. This
may require that States provide commitments in the SIPs to ensure that all applicable construction permits
under Title 1, and the operating permits under Title V are revised in time.
The following elements, at a minimum, must be addressed to ensure the BART controls are adopted into the
State's SIP. These elements are discussed in detail with other circumstances in 40 CFR Part 51, Appendix Y -
Section V.
Name of source facility and the specific emission units and pollutants being controlled. (40 CFR
• Specifics of the controls, control efficiency (ies), emissions reductions expected
Enforceable emission limitations representing BART (40 CFR 51 .308(d)(3);(e))
Schedules for compliance with BART (40 CFR 51.308(d)(3);(e))
A requirement that each source subject to BART maintains the control equipment and establish
procedures to ensure such equipment is properly operated and maintained. (40 CFR 5 1 .308(e)(v))
Reporting, monitoring, and recordkeeping requirements adequate to determine the source's
compliance (40 CFR Part 5 1 , Appendix Y - V).
Averaging times and reference methods to determine compliance (40 CFR Part 5 1 , Appendix Y -
VI
5. In the BART guidelines under step 4 of a BART determination is a discussion of average cost effectiveness,
yet we don't see anything being averaged. If one were to average all the individual annual cost effectiveness
over the remaining life of a plant, then we could see that we were averaging something. Can you explain this?
The term "average cost effectiveness" is a term that the Agency has long used to describe one method of
looking at the costs of control when considering economic impacts. See e.g,. New Source Review Draft
Manual (Oct. 1990) at B. 36 describing the process for making best available control technology
determinations (BACT). The Appendix at the end of this document contains equations that can be used for
determining average cost effectiveness and should help you to understand how to estimate the "average cost
effectiveness" of various control measures.
The explanation of the term "average cost effectiveness"
continues to apply.
6. Is there a guideline on how to "annualize" costs (capital recovery factors and levelizing inflation adjusted
operation & maintenance costs)?
Yes. The EPA Control Cost Manual, referenced in the final BART rule (see 70 FR 39104, 39163-39167 (July
6, 2005). As noted in the Guidelines, the Control Cost Manual is updated periodically. This document is
available at the following Web site: http://www.epa.Kov/ttn/catc/products.html.
The current version of the EPA Control Cost Manual applies.
7. In the BART guidelines under step 4 of a BART determination, "how do I calculate baseline emissions?" it
would help if a method were suggested to depict anticipated annual emissions from the source. Otherwise,
sources will do this in many different ways. Should States suggest facilities use a method similar to PSD - the
highest 12 consecutive months in the past 120 months (or whatever it is for PSD)? If so, should it be different
for EGUs as it is for PSD? Or, should a facility take the highest 24-hour actual rate and multiply it times their
This answer applies only to BART. This guidance document
provides new guidance on this topic in the context of the
development of the LTS in the second implementation period.
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Period
average utilization rate for the highest 2 of the past 5 years? In either case, if these cost effectiveness numbers
are compared to the BACTYRACTYLAER clearinghouse, it will make a difference.
The BART Guidelines state that the baseline emissions used for estimating the average cost effectiveness of a
control technology should represent a realistic depiction of anticipated annual emissions for the source. The
approach for making BACT determinations in the PSD program is similar. The methodology of looking at the
annual average of the highest 24 consecutive months in the past 120 months is one approach that has been
used in PSD when determining if there has been an emissions increase as a result of a modification. In some
cases, this approach could a reasonable method of estimating anticipated annual emissions for a source.
8. How do you address an issue in which the installation of a BART control causes an increase in another
pollutant?
In some cases, the installation of controls to reduce emissions of a pollutant can result in collateral increases
in another pollutant. For example, the use of low NOx burners can result in an increase in CO emissions. If
the increase in emissions of a collateral pollutant would trigger other requirements under the Clean Air Act,
such as New Source Review, the State may include the costs, if any, of controlling emissions of a collateral
pollutant to meet these other requirements in considering the economic impacts of a technology under
consideration for BART.
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
period.
9. How will EPA address the cost effectiveness of control options? If an option reduces more than one
pollutant, how is that addressed?
If an option reduces more than one visibility-impairing pollutant, it could be justified in terms of the greater
overall emission reduction. The State will need to evaluate the cost- effectiveness of controlling both
pollutants in light of its evaluation of the other BART factors. In general, the greater the overall emissions
from multiple pollutants, the more closely the State should consider controls on multiple pollutants.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period.
10. It is unclear in the responses to the BART Q and A the meaning of some terms. Some appear to be
interchangeable. It would be helpful to have definitions for source, site, unit, and plant-wide (as they pertain
to BART).
General terms not defined in the BART Guidelines should be given the same plain language meaning that
they have under other Clean Air Act programs. Terms which are defined in this and other CAA regulations,
and in the statute, should retain those definitions; note however that the "BART-eligible source" refers only to
stationary sources built within the BART time period (1962-77) comprised of the emissions units meeting all
three BART-eligibility criteria. See 40 CFR 51.301 for definitions of "stationary source" and "BART-eligible
source." "Plantwide" means across the entire geographic entity, or across all "BART-eligible" sources at the
geographic entity (depending on the context).
The term "source" has particular meaning in the context of
BART that should not be presumed to carry over to
development of the LTS in the second implementation period
where non-BART sources are concerned.
11. In the BART rule, are we to assume that de minimis levels for pollutants are only based on BART-eligible
sources, even when the term "plant-wide" is used?
Generally yes. The approach used by EPA in the BART Guidelines for identifying a BART-eligible source
begins with the identification of those emissions units at a plant that fall within one or more BART categories
and that were put into operation within the 1962-1977 timeframe. In 2004, after proposing that States be
This answer applies only to BART.
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Period
allowed to establish de minimis levels for pollutants at BART-eligible sources, EPA received comments
suggesting that de minimis levels be applied on a unit by unit basis. EPA rejected this suggestion in the final
rule; the regulations allow States to establish de minimis levels that apply to a BART-eligible source. In light
of the comments received requesting that the de minimis exemption be applied on a unit by unit basis and its
decision to reject this approach, EPA made the statement in the BART Guidelines that "[these de minimis
levels may only be applied on a plant-wide basis." This statement was intended to clarify that the State should
consider the cumulative emissions from the units at a plant that comprise the BART-eligible source in
determining whether the BART-eligible source meets the de minimis exemption requirements.
Note, however, that for category one (fossil fuel fired steam electric plants >250 million Btu/hour), our
interpretation of the source category title is that the State should add all EGU emissions at a plant together
when determining plant capacity, in order to see if the plant falls within category one. Once you have
determined that the plant does fall within the category, the State would only consider those EGUs built within
the 1962-77 timeframe to actually be BART-eligible.
12. If a State determines that a recent BACT determination on an emission unit is BART, then is a BART
emission limit created that is the same as the BACT limit, and is the Title V permit changed so that BART is
also listed as a basis for that emission limit?
Yes, if a State makes such a determination and includes it in its SIP, then a BART emission limit is created
that is the same as the BACT limit. The Title V permit must be amended to "specify and reference the origin
of and authority for" the emission limit. 40 CFR 70.6(a)(l)(ii).
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
period.
13. Is EPA presuming a level of control for BART eligible sources in guidance to consider CAIR plus BART
plus other "reasonable" measures?
Guidance on the level of BART controls is not being developed. BART can only be determined on a case-by-
case-basis and source-by-source-basis using the modeling and statutory factors listed in 40 CFR
51.308(e)(l)(ii)(A). Sources have expressed concern that reasonable progress guidance might be interpreted to
override BART guidance. The BART assessment is a separate requirement from the reasonable progress test.
It may be that to meet reasonable progress, more controls are needed from certain sources which may or may
not include those sources previously controlled under BART. There is no way for EPA or the States to
determine the final strategy to comply with the reasonable progress demonstration until the BART assessment
is completed and the suite of controls that are needed for RH is determined. There could also be additional
controls that may be identified as needed to demonstrate compliance for the 8-hour ozone and PM2.5
NAAQS. This may or may not affect the control identified under BART or CAIR. The States have flexibility
in determining the type, pollutants and mix of sources that could be used in developing a strategy for attaining
a NAAQS per the modeling guidance and implementation policy.
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
period.
The Cross State Air Pollution Rule has replaced the Clean Air
Interstate Rule.
14. Can a source avoid BART by taking synthetic minor limits on the PTE of visibility- impairing pollutants?
If so, by when do those limits need to be in place? What kind of mechanism must be in place to ensure those
limits are met? For how long?
This answer applies only to BART.
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Yes, a source can opt to revise its Title I permit to provide for synthetic minor limits so that it falls under the
BART eligibility threshold. The limitations of a source's potential to emit should be in place prior to the start
of the State's public comment period on its proposed Regional Haze SIP to EPA and a description of the
State's action should be included in the SIP narrative. To prevent circumvention of the BART requirements, it
may be necessary to include a permit term or SIP provision that provides that changes at the BART-eligible
source or in its permit that allow for increases in emissions would subject the source to BART review.
15. If the unit is already controlled (e.g., under MACT or BACT) and it is the best, the latest control
technology, does the source still need to conduct a full blown BART analysis and control technology
evaluation including the installed control device? Or, can the source just describe the control device on their
BART-eligible source unit and make the case that it qualifies as BART, without having to evaluate other
technologies?
If the unit has "best, latest...", then the source can just describe the control device on their BART-eligible
source unit and make the case that it qualifies as BART, without having to evaluate other technologies. The
streamlining of BART analyses in this situation is addressed in Section IV.C of the BART Guidelines, "How
does a BART review relate to [MACT] Standards under CAA section 112, or to other emission limitations
required under the CAA?"
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
period.
16. A source is built prior to 1962. Between 1962 and 1977, it builds a new emission unit that otherwise meets
BART eligible requirements. Is the new unit subject to BART?
If a State is following the approach for identifying BART-eligible units described in the BART Guidelines,
the unit built between 1962 and 1977 is considered to be BART- eligible.
This answer applies only to BART.
17. Although the rule in the Federal Register (FR), July 6, 2005 page 39107 and elsewhere indicates that the
max 24 hour emissions should be used, would EPA approve using double the actuals instead for CALPUFF
BART modeling?
As noted in the final BART rule, emissions from a source can vary widely on a day to day basis and the "24-
hour actual emission rate could be more than double the daily average. See 70 FR at 39129. We recommend
that States use the highest 24-hour average actual emission rate for the most recent three or five year period of
meteorological data in the CALPUFF model. As EPA explained, "[t]he emission estimates used in the models
are intended to reflect steady-state operating conditions during periods of high capacity utilization." Id. Given
the potential variability in actual emissions, use of actual emissions (even double actual emissions) does not
necessarily represent this.
This answer applies only to BART.
18. If a State participates fully in CAIR, and satisfies its BART obligation for EGUs for NOx and SO2, must
the PM BART eligibility analysis consider whether all visibility impairing pollutants, summed across a
facility, exceed 250 tpy, or must only the PM emissions be considered?
If at the final step of identifying the emission units that constitute a BART-eligible source, the State finds that
a potential BART-eligible source has the potential to emit 250 tpy of any visibility-impairing pollutant, then
the source is considered BART-eligible.
This answer applies only to BART. The Cross State Air
Pollution Rule has replaced the Clean Air Interstate Rule.
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For example, if a potential BART-eligible source has emissions of more than 250 tpy of SO2 and meets the
other applicable requirements, then it may be subject to BART review for its emissions of PM. However, if
the source's emissions of PM10 are less than 15 typ (assuming the State has established a de minimis level of
15 tpy), then the source's PM10 emissions need not be addressed in a BART determination.
19. An EGU has three boilers: a) coal boiler (5500 mmbtu/hr); and b) two auxilliary boilers (181.6 mmBtu/hr
each). The State has determined the coal boiler to meet the first test for BART-eligibility. Since the two
auxilliary [sic] boilers do not appear to fall under any of the 26 BART categories, would they pass the first
test for BART-eligibility because they contribute to the "steam electric plant"?
As a general matter, all the emission units, including any auxiliary boilers, at a fossil-fuel fired steam electric
plant of more than 250 million BTU/hour heat input would be considered part of the same stationary source.
Under the RH regulations, BART applies to certain existing stationary sources; stationary sources, in turn, are
defined to include "all of the pollutant-emitting activities which belong to the same industrial grouping, are
located on one or more contiguous or adjacent properties, and are under the control of the same person (or
persons under common control)." 50 CFR 51.301. The regulations further provide that "[pjollutant-emitting
activities must be considered part of the same industrial grouping if they belong to the same Major Group (i.e.
which have the same two-digit [SIC] code)." For most plants on the BART list, there will be only one 2-digit
SIC code that applies to the entire plant. As you have described the source in your question, the auxilliary
boilers would fall within the same 2-digit SIC code as the coal boiler; these units accordingly are part of the
same stationary source as the coal boiler.
Note, however, that if the auxiliary boilers are only used during startup, then since we do not model startup
conditions, those boilers would not contribute any emissions to the modeled visibility impact from the source;
therefore those particular boilers may be exempted.
This answer applies only to BART.
Reasonable Progress
1. Is there a metric for determining if controls required for PM2.5, O3, CAIR, or BART are "reasonable"
without defining benefit of controls?
Unlike the technical demonstration for CAIR or BART, the reasonable progress demonstration involves a test
of a strategy. The strategy includes a suite of controls that has been identified through the identification of
pollutants and source categories of pollutants for visibility impairment - the possible controls for these
pollutants (and their precursors) and source categories - the application of four statutory factors and how much
progress is made with a potential strategy with respect to the glide path. Modeling occurs with a strategy and
is not a source-specific demonstration like the BART assessment.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which supersedes this answer.
The EPA does not consider a reasonable progress demonstration
to only involve "a test of a strategy," i.e., a collection of
measures affecting multiple sources. Rather, each source
selected for four-factor analysis, or each group of sources,
should be subject to a separate analysis of what additional
measures for that source or group of sources are necessary to
make reasonable progress towards natural visibility conditions.
Sections 6.3, 7.1, 7.2, 8.1.5 and 8.2.7 address screening and the
four-factor analysis of a group of sources.
As stated in this Q&A, air quality modeling does occur "with a
strategy" for purposes of setting the RPG that corresponds to
the LTS, but not necessarily only at that point in SIP
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development. Air quality modeling of the visibility impact from
the source or group of sources may also be done at the
screening step as part of determining whether to bring the
source or group of sources forward for four-factor analysis and
(for a state following the second alternative approach) to
estimate visibility benefits of specific measures.
The Cross State Air Pollution Rule has replaced the Clean Air
Interstate Rule.
2. How can States demonstrate benefits of controls from a single source for RH without doing single source
impact modeling, e.g. CALPUFF?
Reasonable progress is not required to be demonstrated on a source-by-source basis. It is demonstrated based
on a control strategy developed from a suite of controls that has been assessed with the four statutory factors
and the uniform rate of progress.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period that supersedes this answer.
The EPA does not consider a reasonable progress demonstration
to only involve a test of a strategy affecting multiple sources.
Rather, each source selected for four-factor analysis, or each
group of sources, should be subject to a separate analysis of
what additional measures for that source are necessary to make
reasonable progress towards natural visibility conditions. In
addition, the 2028 RPG for the 20 percent most impaired days
corresponding to the LTS is to be compared to the 2028 point
on the URP line as described in this document.
As discussed in Sections 4.2, 6.2 and 8.1, single-source impact
modeling is not specifically required.
3. What if a State is on the glidepath, but can still install cost effective controls? Is it obligated to install those
controls?
From the preamble to the Regional Haze Rule (64 FR 35732), EPA explained:
"If the State determines that the amount of progress identified through the 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."
The statutory factors must be applied before determining whether given emission reduction measures are
reasonable. For example, even if emissions reductions from one source category are projected to be enough to
achieve the uniform rate of progress towards natural background in 60 years, States should not forego an
analysis of what degradation is being caused by pollutants from other source categories, or what
improvements could be made by controlling them.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which is consistent with this answer.
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4. A. What type of demonstration is acceptable to justify a reasonable progress goal (RPG) that is less than the
glidepath?
B. What if controls needed for other programs (e.g., PM2.5, ozone, CAIR) are installed?
A. If after applying the four statutory reasonable progress factors, the rate of visibility improvement is still
less than the uniform glide path, States may adopt the calculated RPGs, provided that they explain in the SIP
how achieving the uniform glide path is not reasonable based on the application of the factors. States must
demonstrate why the slower rate is reasonable, and state the projected date for achieving natural background
under this alternative rate of progress.
B. Existing controls that are installed as a result of other existing CAA programs can contribute to a State's
ability to satisfy its RPG. However, the statutory factors must be applied before determining whether given
emission reduction measures are reasonable. In particular, the State should adopt a rate of progress greater
than the glidepath if this is found to be reasonable according to the statutory factors. See in particular the
directive in the preamble to the RHR at 64 FR 35732
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which is supersedes this answer in part.
The sentence, "Existing controls that are installed as a result of
other existing CAA programs can contribute to a State's ability
to satisfy its RPG." presumes that RPGs are set first and the
LTS must be designed to meet them. The 2016 revisions to the
Regional Haze Rule clarified that the LTS is developed first,
and the RPGs are predictions of the overall benefit from the
LTS along with other enforceable measures.
The Cross State Air Pollution Rule has replaced the Clean Air
Interstate Rule.
5. Can a source commit to extra control of one visibility-impairing pollutant in exchange for doing less to
control a less significant pollutant (inter-pollutant trading)?
The regulations require the States to adopt measures that will make reasonable progress toward the national
goal. States have the flexibility in developing these measures to focus on those pollutants that have the most
significant impact on visibility. A State could conclude that after application of the four statutory reasonable
progress factors, it is "reasonable" to control one pollutant to a higher level than another pollutant.
In the context of BART, the RHR does not provide for inter-pollutant trading where the source is installing
controls based on the State's BART determination. The regulations, however, do allow States to adopt
alternative measures in lieu of BART, so long as the alternative measures provides for greater reasonable
progress than would BART. Inter- pollutant trading is not allowed in a trading program alternative to BART, -
-see 64 FR at 35743.
In addition, States may allow sources to "average" emissions across any set of BART- eligible emission units
within a fenceline, so long as the emission reductions from each pollutant being controlled for BART would
be equal to those reductions that would be obtained by simply controlling each of the BART-eligible units that
constitute BART- eligible source (70 FR 39172).
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
period.
Coordination with RPOs, States, and FLMs
1. What are EPA's expectations and the basis for consultation requirements regarding formal consultative
procedures? What constitutes effective FLM communication? Can it be assumed that if the FLM attends the
RPO meetings and calls and doesn't raise any concerns it has no problems with a State's SIP?
40 CFR 51.308(i) requires that States consult with FLMs before adopting and submitting their RH SIPs.
These requirements are summarized as follows:
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
period. In addition, changes were made to the FLM consultation
requirements as part of the 2016 revisions to the Regional Haze
Rule. See Section 4.8 of this document.
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States must provide the FLM an opportunity for consultation, in person and at least 60 days prior to holding
any public hearing on the SIP. The State must also provide the opportunity for the FLMs to discuss their: (i)
assessment of impairment of visibility in any Class I area; and, (ii) recommendations on the development of
the RPG and on the development and implementation of strategies to address visibility impairment. Further,
the State must include in the SIP a description of how it addressed any comments provided by the FLMs.
Lastly, the SIP must provide procedures for continuing consultation between the State and FLMs on the
implementation of 51.308, including development and review of SIP revisions and 5-year progress reports,
and on the implementation of other programs having the potential to contribute to impairment of visibility in
Class I areas.
This is a formal consultative process. The basis for requiring written consultation procedures is 40 CFR
51.308(i)(4). To satisfy this requirement, States should contact the FLMs to ensure their input to the RH SIP
process is solicited and documented. While effective FLM consultation relies on both parties (States and
FLMs) communicating early and often, the State is only required to meet the provisions of 40 CFR 51.308(i)
and is not responsible if a FLM chooses not to participate in the either the RPO activities or the SIP
development and review process. In such cases, the State should document its outreach efforts to the FLM.
2. Is there a protocol for resolving disputes between States and RPOs regarding technical differences between
upwind and downwind States on El, modeling, natural background, apportionment, controls, etc.? How will
EPA address States/RPOs adopting different IMPROVE algorithms (old vs. new) to look at the same Class I
area?
EPA is developing a State and Federal Protocol which will describe the goals and objectives, consultation
requirements, principles of collaboration, and process for collaboration for the RH process. While conceptual
in nature, this document will be designed to form the basis for a common understanding, approach, process
and expectations for consultation and consistency in developing the 308 Regional Haze SIPs. EPA is
encouraging the early identification of any potential disputes. This will allow all parties ample opportunity to
address and document any disagreements
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period. The EPA has not issued a protocol as
described in the answer.
3. We understand that EPA is requiring each State with a Class I area to submit a SIP that addresses its
obligations relative to that Class I area including establishment of a uniform rate of progress, imposition of
requirements to install controls on sources in that State that are considered reasonable, documentation of its
collaborative efforts with other States impacting that Class I area, and also documentation of interactions with
surrounding States regarding that State's contributions to Class I areas in other States. The question is, "When
is a State no longer obligated to consult with another State?"
States are required under 40 CFR 51.308(d)(3), to collaborate and develop coordinated emission management
strategies to address RH visibility impairment not only for Class I areas within their own borders, but also for
each Class I areas located outside their borders which may be affected by their emissions. The obligation for
States to consult with each other ultimately remains in place for the period of time covered by 40 CFR
51.308. In practice, States will satisfy this obligation mainly during the preparation of the RH SIPs for the first
planning period (2018), due by 12/17/07, and in the preparation of the ten-year periodic revisions, and the
five-year periodic reports described in 40 CFR 51.308(f) and (g), respectively.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which is consistent with this answer.
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4. A. Does a State have obligations under the RHR for reasonable progress to initiate discussions with another
State whose sources impact one of its Class I areas if the projected interim visibility improvement in 2018
falls directly on the uniform rate of progress line for that area? Or can the State focus on defining reasonable
progress for its sources without engaging other States with contributing sources in discussions?
B. Conversely, do States have obligations under the RHR to evaluate whether their sources are contributing to
Class I areas in surrounding States even though the Class I areas surrounding it are achieving the uniform rate
of progress?
A. Yes, a State must consult with States having sources reasonably anticipated to cause or contribute to
visibility impairment in a Class I area to develop their RPGs pursuant to 40 CFR 51.308(d)(l)(iv) regardless
of the uniform rate of progress for an area.
B. Yes, States must evaluate whether their sources are contributing to Class I areas in surrounding States even
though the Class I areas surrounding it are achieving the uniform rate of progress as noted in answer 4.A.
Note also that 40 CFR 51.308(d)(3)(i) specifically requires that States with emissions that are reasonably
anticipated to contribute to visibility impairment in another State's Class I area consult with that State to
develop coordinated emission management strategies.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which is consistent with this answer.
5. For Class I areas that span two or more States, is there a requirement for establishing a "lead" State?
There is no requirement in the RH regulations nor in guidance documents to identify a "lead" State for shared
Class I areas. However, states may choose to establish a "lead" state if it facilitates their collaboration and
consultation. The RH rule relies on States collaborating and using the consultation process (RPOs) to address
shared Class I areas. Also, we assume the technical work that is used as the basis would be the same for all
SIPs. One may also want to take a look at where the IMPROVE monitor is located that "represents" the Class
I area in question, as that location may also help define the "lead" State. Another option is the State with the
largest portion of the Class I area in their State to be the "lead" State. These are ideas that could be used, but it
is up to the States to work this out as part of the collaboration and consultation process. We view shared Class
I areas similar to interstate NAAQS nonattainment areas. The States involved would collaborate to set one
RPG for the area, and work together to define a consistent, coordinated approach to develop the long-term
strategy for the area. As with interstate NAAQS nonattainment areas, each State has lead responsibility for
developing, adopting and submitting its own SIP revisions affecting their portion of the Class I area.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which supersedes this answer in part.
The sentence, "The States involved would collaborate to set one
RPG for the area, and work together to define a consistent,
coordinated approach to develop the LTS for the area."
presumes that RPGs are set first and the LTS must be designed
to meet them. The 2016 revisions to the Regional Haze Rule
clarified that the LTS is developed first, and the RPGs are
predictions of the overall benefit from the LTS along with other
enforceable measures. In a case of multiple states impacting the
same Class I area, the state with the Class I area sets an RPG
reflecting the combined effect of all the relevant LTSs. If some
contributing states have not yet determined the measures they
will include in their LTSs, then the state with the Class I area is
to set RPGs based on confirmed measures.
6. What if one State with the Class I area sets an RP goal that requires an upwind State to make reductions
that it won't make?
If a State with a Class I area determines that a contributing State is not doing what is reasonable to meet the
RPG set for the area, and has attempted to resolve this issue, the State with the Class I area should notify EPA
and document this issue in its initial RH SIP. For all revisions to the initial RH SIP revision, 40 CFR
51.308(h)(2) requires that the State with the Class I area provide notification to EPA and to the other States
which participated in the regional planning process. This subsection further requires the State with the Class I
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which supersedes this answer. The 2016
revisions to the Regional Haze Rule clarified that the LTS is
developed first, and the RPGs are predictions of the overall
benefit from the LTS along with other enforceable measures. In
a case of multiple states impacting the same Class I area, the
state with the Class I area sets an RPG reflecting the combined
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area to collaborate with those States in the regional planning process to develop additional strategies. It is
EPA's expectation that issues of communication/collaboration problems such as this be brought to our
attention as early in the process as possible.
effect of all the relevant LTSs. If some contributing states have
not yet determined the measures they will include in their LTSs,
then the state with the Class I area is to set RPGs based on
confirmed measures.
7. If State A is at or below the glide path for an area, and a neighboring State (State B) impacting State A's
Class I area does not do all it can to meet that area's RPGs, what happens? Is State A responsible to file a 126
petition or other action? Could State A's Regional Haze SIP be disapproved because of State B? Are the
answers to these questions any different if State A's RPG is above the glide path? In summary, if consultation
does not work what happens and who is responsible?
State A is responsible for establishing RPGs for its Class I areas based on its consideration of the factors set
forth in the statute and implementing regulations, in consultation with State B and other States that may be
contributing to impairment in the area. See 40 CFR 51.308(d)(l). Each State, including State B, is required to
submit a SIP with a long-term strategy that includes measures as necessary to achieve the RPGs established
for the Class I areas. Where States have participated in a regional planning process, the State must ensure that
its SIP includes all measures needed to achieve its share of emissions reductions agreed upon through that
process. If there is a disagreement among States as to what constitutes reasonable progress, the question of
whether State A's or State B's RH SIP could be disapproved will depend on the specific of the situation. Each
State is also responsible for documenting its good faith attempt to consult with State B, as outlined in 40 CFR
51.308(d)(l)(iv). EPA will take this information into account in determining whether the State's goal for
visibility improvement provides for reasonable progress towards natural visibility conditions.
States are under no obligation to file petitions under Section 126 of the CAA to satisfy the reasonable progress
requirement under the RH program.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which supersedes this answer. The 2016
revisions to the Regional Haze Rule clarified that the LTS is
developed first, and the RPGs are predictions of the overall
benefit from the LTS along with other enforceable measures. In
a case of multiple states impacting the same Class I area, the
state with the Class I area sets an RPG reflecting the combined
effect of all the relevant LTSs. If some contributing states have
not yet determined the measures they will include in their LTSs,
then the state with the Class I area is to set RPGs based on
confirmed measures.
8. What is necessary in a SIP/template to demonstrate "continuing consultation" under 51.308(i)(4)?
Most States are currently consulting with other States and with the FLMs by participating in an RPO. EPA
anticipates that most States will address their future FLM consultation requirements by continuing to
participate in an RPO that is engaged in an ongoing assessment of visibility issues. If a State demonstrates that
it has met current consultation requirements through participation in an RPO that is engaging in the necessary
consultations, and if the State intends to satisfy future consultation requirements (for periodic comprehensive
SIP revisions or for other issues that arise) by continued participation in their RPO, then such a State need
only commit to such participation.
For a State that has not fully engaged in the RPO process, the State must provide a description of the process
by which it intends to consult with the FLMs in preparing future submittals and addressing issues that arise.
Similarly, if a State has participated in an RPO but intends to discontinue this participation, the State must
provide extensive description of the alternative means by which the State will engage in the required
consultations.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which is consistent with this answer.
9. To what extent does EPA expect RPOs to motivate States to communicate directly with and engage the
FLMs, particularly for Class I areas where those FLMs have not been participating in the RPO's work?
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period.
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EPA expects that the RPOs will serve as the coordinating entities to facilitate State-to- State and State-FLM
consultation. To that end, EPA recommends that RPOs individually set up a formal process to encourage
State-to-State and State-FLM consultation to take place, perhaps in the form of a coordinating workgroup.
Through managing this process, RPO's can help identify areas where more FLM participation may be needed.
However, RPO's are not responsible if a FLM opts not to participate in these consultation opportunities.
Ultimately, it is the State's responsibility to ensure the FLM consultation requirements housed in 40 CFR
51.308(i) are satisfied
10. What are EPA's expectations of an RPO for written consultation procedures with the other RPOs/States
outside its jurisdiction? Given limited funds and much technical and policy work needed, it is suggested this
be made as simple and straightforward as possible.
EPA expects that RPOs will serve as the facilitating entities for State-to-State resolution of issues relating to
State apportionment of visibility impairment at Class I areas. RPOs should also assist States in the resolution
of disputes over the levels of control required by upwind States that contribute to visibility impairment of
downwind States' Class I areas. This process should begin by each RPO identifying Class I areas for which
their member States individually cause or contribute to visibility impairment. Following this, the RPOs should
meet to broker consensus between the States on the technical approaches to these issues.
There is no requirement for an RPO to establish written consultation procedures with the other RPOs/States
outside its jurisdiction. EPA expects RPOs to facilitate and/or establish procedures in any format (informal or
formal) as needed that works best for the parties involved
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which is supersedes this answer in part.
The sentences, "EPA expects that RPOs will serve as the
facilitating entities for State-to-state resolution of issues
relating to State apportionment of visibility impairment at Class
I areas. RPOs should also assist States in the resolution of
disputes over the levels of control required by upwind States
that contribute to visibility impairment of downwind States'
Class I areas." could be read as being based on the premise that
RPGs are set first and the LTS must be designed to meet them,
such that there may be disagreements among states on how
much each state should contribute to the necessary emission
reductions. The 2016 revisions to the Regional Haze Rule
clarified that the LTS is developed first, and the RPGs are
predictions of the overall benefit from the LTS along with other
enforceable measures.
11. Does section 169A(c)(3) of the CAA require a State to obtain FLM concurrence with a State's proposal to
exempt sources from being subject to BART in its Regional Haze SIP submitted to EPA?
No. The CAA requires States to make BART determinations for BART-eligible sources that may reasonably
be anticipated to cause or contribute to any impairment of visibility in a Class I area. In the BART Guidelines,
we provides States with an approach for exempting potential BART sources from BART by demonstrating
that a source does not meet this threshold. In contrast, under section 169A(c)(l) of the CAA, the
Administrator has the authority to exempt most sources from BART if he determines that the source is not
reasonably anticipated to cause or contribute to significant impairment of visibility.
Section 169A(c)(2) contains a similar provision for certain powerplants. The exemptions under section
169A(c), however, are effective only on concurrence by the FLM. In sum, while States must consult with
FLMs as part of the SIP process, they are not required to obtain FLM concurrence with their determination
that a BART-eligible source does not cause or contribute to any impairment.
This answer applies only to BART.
Miscellaneous
1. On December 20, 2005, the IMPROVE Steering Committee approved a new algorithm for calculating
current and natural background visibility. If states use the new equation in BART and reasonable progress
analyses, will EPA accept it?
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period. The approaches recommended in
Section 5 are based on the revised IMPROVE algorithm.
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Yes, either the new IMPROVE extinction equation as recommended in 2005 by the IMPROVE Steering
Committee or the original equation recommended by EPA in the "Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Rule" (September 2003, EOA-454/B-03-005) may be used to develop
Regional Haze SIPs.
Regardless of which algorithm is used for a Class I area, that methodology should be applied in a consistent
manner. Consistency should be maintained across Regional Haze applications (i.e., BART and Reasonable
Progress), across time (e.g., baseline and future calculation for natural conditions), and among the
stakeholders involved who need to be consulted on the development of a LTS for a Class I Area (i.e., FLMs,
states, industry). Specifically, we recommend that the same version of the IMPROVE equation be used by
States/sources which are impacting the same Class I area to calculate visibility conditions for that area.
2. Instead of a single value, can the RPG be satisfied using a natural conditions range that captures the
variability in year-year emissions of natural events?
The 1999 RHR states that in comparing "current conditions" against "natural conditions," natural conditions
means "[t]he level of visibility (in deciviews) for the 20 percent most- impaired days, and for the 20 percent
least-impaired days, that would exist if there were no manmade impairment." 64 FR at 35730. EPA issued a
guidance document concerning this entitled, "Guidance for Estimating Natural Visibility Conditions Under
the Regional Haze Rule." Under this guidance, a single value for natural visibility for each class I area is
calculated for each of the 20 percent most-impaired days and the 20 percent least- impaired days. This
guidance document describes "default" and "refined" approaches for estimating natural conditions. The EPA
methodology that allows for the 20% best days and 20% worst days to calculate natural and background levels
is designed to avoid a single value (i.e., the single best day or the single worst day). The single value that
represents the 20% best days is considered representative of the range. Consequently, it would be redundant
and unnecessary to further consider ranges of visibility values in determining natural and background levels.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which supersedes this answer.
3. What obligation does a downwind State have if it conducts modeling based on an upwind State's emission
inventory, and the upwind States subsequently changes its inventory? What is EPA's expectation here?
EPA expects that States will continue to work together in addressing the problem of RH, both inside and
outside the RPO context and that States will share pertinent aspects of their SIP planning with other States, as
appropriate. Upwind States should use their best efforts to provide potentially relevant information, such as
changes in emissions inventories, to downwind States in timely fashion. We are relying on the RPOs, in large
part, to ensure this coordination takes place.
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
period. Section 9.4 addresses this specific issue.
4. How does the CAIR substitute for BART?
States subject to and participating in the CAIR cap and trade program for SO2 and NOx may treat the CAIR
requirements for EGUs as a substitute for the application of BART controls for these pollutants. States do not
need to require BART-eligible EGUs subject to the CAIR to install, maintain, and operate BART per 40 CFR
51.308(e)(4).
In addition, a State which is only subject to CAIR for NOx, but which also chooses to participate in the CAIR
trading program for both SO2 and NOx, may consider BART to be satisfied for both SO2 and NOx from
EGUs. Because EPA modeled these States as controlling for both SO2 and NOx in the CAIR NFR, the better
This answer applies only to BART. The Cross State Air
Pollution Rule has replaced the Clean Air Interstate Rule.
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than BART demonstration presented in that action would be valid in that scenario. Conversely, if such States
choose to participate only in the ozone season NOx trading program, the updated projections presented in the
BART rule (70 FR 39104) demonstrate that BART would be satisfied for NOx, but such States would still
need to address BART for SO2 emissions from EGUs (70 FR 39143).
Also, EPA's assessment that the CAIR cap and trade programs can substitute for BART controls does not
extend to cases where a State has identified source-specific BART requirements as a result of a reasonable
attribution determination. In such cases, the source-specific BART requirements must be met at the source.
Finally, the CAIR does not address other potential visibility impairing pollutants such as PM, VOCs, and
ammonia. Also, the determination that the CAIR makes greater reasonable progress than BART for EGUs is
not a determination that the CAIR satisfies all reasonable progress requirements in CAIR affected States.
5. If a CAIR facility is found to be exempt from BART for SO2 and NOx, and the State does exemption
modeling on PM10 and concludes there is no impact on a Class I area, can the State totally exempt the utility
from BART?
States subject to and participating in the CAIR cap and trade program for SO2 and NOx are allowed to treat
the CAIR requirements for EGUs as a substitute for the application of BART controls per 40 CFR
51.308(e)(4). This does not mean EGUs are exempt for SO2 and NOx, only that CAIR satisfies the BART
requirement for those pollutants.
The remaining visibility pollutants to consider for determining BART-eligible sources are PM, and, using
judgment, VOCs, and ammonia. For PM, the July 6, 2005, final BART rule at 70 FR 39160 notes PM10 may
be used an indicator for PM in this step of the determination and thus, PM10 can be used for the exemption
modeling.
This answer applies only to BART. The Cross State Air
Pollution Rule has replaced the Clean Air Interstate Rule.
6. What is the relationship of CAIR to reasonable progress? Does CAIR satisfy reasonable progress
requirements for EGUs for NOx and SO2?
As discussed in the answer to the previous question, participation in the CAIR can substitute for a State's
BART obligation in certain narrowly defined areas. However, for the purpose of satisfying the RPG, CAIR
has no more applicability than does BART - it is a control that can be part of a State's RPG. The preamble to
the 2005 BART Rule states that EPA's determination that participation in the CAIR trading program would
provide for greater reasonable progress from EGUs than would BART "is not a determination that CAIR
satisfies all reasonable progress requirements in CAIR affected States." (70 FR 39143). In other words,
although EPA has determined that the CAIR trading program would provide greater reasonable progress than
source specific BART controls for affected EGUs for SO2 and NOx, a State's reasonable progress analyses
may indicate that additional controls beyond CAIR may be necessary to meet the RPGs set for one or more
the Class I areas.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which is consistent with this answer.
The Cross State Air Pollution Rule has replaced the Clean Air
Interstate Rule.
7. What is the relationship of RH BART to RAVI BART?
RAVI BART (Part I of the visibility program) is a separate regulatory requirement from RH BART (Part II of
the visibility program). RAVI BART treats visibility impacts from one source or a small group of sources, as
The RAVI provisions were revised and explained as part of the
2016 rulemaking to revise the Regional Haze Rule. States
should rely on statements in those proposed and final actions
instead of this answer.
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opposed to RH BART, which treats visibility impacts over a wide geographic area. EPA promulgated
regulations addressing "reasonably attributable visibility impairment" or RAVI in 1980. Under these
regulations, the requirement for a BART analysis is triggered where the FLM certifies there exists reasonable
attributable impairment of visibility. You may find this document a useful guide to understanding the RAVI
process: http://www.wrapair.org/forums/mtf/documents/ravi_bart/Final_RA_BART_Report.pdf
Once a State has met the requirements in the RH regulations for BART or implemented an alternative
measure, then the BART requirements of the Act have been met and BART sources will be subject to
regulation under the RH program in the same manner as other sources. 40 CFR 51.308(e)(3). Therefore, even
though a State may satisfy BART via a 308 SIP, an FLM may still certify RAVI, thus triggering a RAVI
BART attribution determination.
8. What happens if RH SIPs are late?
Section 110(m) of the CAA provides discretionary authority for EPA to impose sanctions for failure to submit
a required plan.
This answer still applies.
9. What is EPA's position on the need to treat VOCs and ammonia as visibility-impairing pollutants? If a State
wishes to address VOCs and/or ammonia as visibility impairing pollutants, what tools are available to do this?
The BART Guidelines direct that States should look at SO2, NOx, and direct PM emissions in determining
whether sources cause or contribute to visibility impairment, including both PM10 and PM2.5. As stated in
the BART Guidelines (70 FR 39160), "States should exercise their judgment in deciding whether [VOCs or
ammonia] impair visibility in an area ... and in deciding whether VOCs or ammonia emissions from a source
are likely to have an impact on visibility in an area." A formal showing of an individual decision that a source
of VOC or ammonia emissions is not subject to BART review is not necessary.
The general sense of this answer applies as a recommendation
for the development of the LTS in the second implementation
period.
10. 51.308(d)(3)(v)(B) requires that the State, in developing its LTS, consider measures to mitigate the
impacts of construction activities. What should this include?
States should include construction activities in their emission inventories that are used for long-term strategy
development. When EPA promulgated the RHR in 1999, emissions from construction activities, such as
emissions from non-road diesel equipment, and large scale wind-blown dust from rapidly growing areas like
Las Vegas and Phoenix, were a major concern. Subsequently, EPA has promulgated rules for on-road and
non-road heavy duty diesel engines. States should include the emission reductions from those rules in their
SIP planning. If States have areas where wind blown dust from human activities contributes to a reduction in
visibility at Class I areas, they should consider measures to mitigate this source of visibility-impairment. The
Western Regional Air Partnership (WRAP) has a number of products related to dust that can be downloaded
from their site at: http://www.wrapair.org.
This guidance document provides new guidance on this topic in
the context of the development of the LTS in the second
implementation period, which is consistent with this answer.
11. What is EPA's expectation for filling missing data in the IMPROVE record? How many years are required
to determine the baseline visibility if data is missing in the 2000-2004 record? Are 3 years sufficient
(IMPROVE expectation)? Need to create 5 years?
The "Guidance for Tracking Progress Under the Regional haze Rule" addresses this question in several areas.
Five (5) years of data from the 2000-2004 period should be used. However, because of the deployment of
This guidance document provides new guidance on this topic
for the second implementation period, which supersedes this
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monitors this length of data may not be available for all Class I areas. The Tracking guidance recognizes this
and recommends that a minimum of three years of data should be used if more years do not exist (see pages 1-
4, and 2-8).
All five years should be used if available and suitable per guidance recommendations. If not, then a minimum
of three years is recommended. You should not recreate data for years that the monitor was not operational
because of the further uncertainty that this data adds. If less than three years of complete data are not
available, consultation with EPA is recommended. The Tracking guidance suggests that a case-by-case
proposal on how this data should be processed should be developed in consultation with EPA OAQPS (and
the Regional Office).
12. How are international emissions and natural events addressed in the RH SIPs?
EPA addressed the treatment of international emissions in the 1999 RHR in a discussion of the long-term
strategy for making reasonable progress in section III.G of the preamble to the final regional haze rule as
follows:
"The EPA agrees that the projected emissions from international sources will in some cases affect the ability
of States to meet reasonable progress goals. The EPA does not expect States to restrict emissions from
domestic sources to offset the impacts of international transport of pollution. We believe that States should
evaluate the impacts of current and projected emissions from international sources in their regional haze
programs, particularly in cases where it has already been well documented that such sources are important. At
the same time, EPA will work with the governments of Canada and Mexico to seek cooperative solutions on
transboundary pollution problems." 64 FR 35714, 35736 (July 1, 1999).
EPA provided additional clarification in the preamble to the 1999 RHR on how States should properly
evaluate international emissions, when we discussed the States' obligation to submit five-year reports
evaluating progress toward the RPG for each Class I area:
"If the State finds that international emissions sources are responsible for a substantial increase in emissions
affecting visibility conditions in any Class I area or causing a deficiency in plan implementation, the State
must submit a technical demonstration to EPA in support of its finding. If EPA agrees with the State's finding,
EPA will take appropriate action to address the international emissions through available mechanisms.
Appropriate mechanisms for addressing visibility-impairing emissions from international sources are further
discussed in unit III.G on the long-term strategy." 64 FR at 35747.
Both in explaining RPGs and in assessing whether current implementation plan strategies are achieving them,
States can take into account the nature of international emissions. For instance, after having applied the four
statutory factors and calculated their RPGs, states can at their discretion, quantify the effects of international
emissions on their ability to reach RPGs. However, States should not directly consider the effects of
international emissions when calculating their uniform rates of progress by either adding the effects of
international emissions to their estimates of natural conditions, or by subtracting international emissions from
current conditions. Either of these approaches conflicts with the basic definitions of "current conditions"
This guidance document provides new guidance on these topics
for the second implementation period, which supersedes this
answer.
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(baseline conditions for the first SIP) and "natural conditions," as described in the 1999 RHR. 64 FR 35728,
(My 1,1999).
Those natural events most commonly linked to RH are wind blown dust and emissions from biomass burning.
EPA has long recognized the natural role of fire in the ecosystem. Consequently, in determining natural
background for a Class I area, EPA believes States should be permitted to consider some amount of fire in the
calculation. If a State finds during the five year period review that an unusual natural event such as a large
wildfire is affecting progress, this can be taken into account in its assessment of whether the current SIP are
sufficient to meet the RPGs. The State should submit a technical demonstration showing its estimate of the
wildfires' contribution to visibility impairment to support its conclusion.
September 27, 2006, Revision:
Q: Can a State determine that a BART-eligible source is not subject to BART if the source's potential to emit
is limited such that the source meets the applicable model plant criteria? Can a State make the same
determination if a BART-eligible source's potential to emit is limited such that based on air quality modeling,
the source's predicted impacts on any Class I area are less than 0.5 dv above natural background? If the
answer to these questions is yes, can a State limit a source's emissions through the following methods:
(a) Requiring installation of a control device. A change in the maximum actual emissions may occur as
a result of additional controls or from changes in work practice (e.g., operational hours) that limit the total
annual emissions. Where emissions controls are installed and operational by December 2007, reductions will
be achieved earlier than the BART control deadline of 2013 and reductions will be certain.
(b) Changing permitted potential emissions. A permit change without a change in maximum actual
emissions would mean that a BART-eligible source is willing to take a federally enforceable permit limit that
restricts them from emitting above a certain amount. This type of change would only be made in cases where
the existing potential emissions are clearly not reflective of actual maximum emissions and the state
permitting authority is assured that the new, lower permit limit is achievable and enforceable.
A: Yes, a State can determine that a BART-eligible source is not subject to BART if the source's
potential to emit is limited such that the source meets the applicable model plant criteria as described below.
For example, a State that has selected 0.5 dv as its contribution threshold, (see 70 FR 39163, July 6, 2005) and
is using EPA's model plant analyses, could exempt a BART-eligible source from BART if the source's
potential to emit is less than 500 tons per year of SO2 and/or NOx, and the plant is located at a distance from a
Class I area of at least 50 km. If a change in emissions is required to meet the model plant criteria, either of
the methods described in Q(a) and Q(b) to limit a source's potential to emit would be appropriate. The
limitations of a source's potential to emit should be in place prior to the start of the State's public comment
period on its proposed Regional Haze SIP to EPA and a description of the State's action should be included in
the SIP narrative. To prevent circumvention of the BART requirements, it may be necessary to include a
permit term or SIP provision that provides that changes at the BART-eligible source or in its permit that allow
for increases in emissions would subject the source to BART review.
This answer applies only to BART. This guidance document
provides new guidance on this topic in the context of the
development of the LTS in the second implementation period.
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Similar to the approach described in the preceding paragraph, a State may allow a BART-eligible source to
reduce its emissions such that individual source dispersion modeling shows the source's impact falls below
the contribution threshold established by the State. As discussed in the BART Guidelines, when modeling a
source's predicted impacts on visibility, States should use emissions estimates that reflect steady-state
operating conditions during periods of high capacity utilization. As a result, EPA recommends that States use
the 24-hour average actual emission rate from the highest emitting day of the meteorological period modeled.
In cases where the State has limited information on the source's potential to emit, the State will need to
develop a reliable and technically supportable estimate of the source's highest future 24-hour actual emission
rate based on its allowable emission rate, or use the new potential to emit limit for the modeling. As with the
case above, the mechanism containing these enforceable limits would need to be in place prior to the date that
the Regional Haze SIP is submitted to EPA, and other measures may be necessary to avoid circumvention of
the BART requirement.
Please remember that States must provide an explanation for selection of the contribution threshold, whether it
is 0.5 dv or some other threshold. As described in the BART Guidelines contained in 40 CFR Part 51,
Appendix Y, consideration for establishing the threshold should include the number of emission sources
affecting the Class I areas at issue, the magnitude of the sources' impacts, and the location of the sources. (See
70 FR 39161-39162, July 6, 2005.)
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APPENDIX G
Relevant Provisions of the Regional Haze Rule (40 CFR Part 51)
as Revised in 2016
51.301 Definitions.
For purposes of this subpart:
Adverse impact on visibility means, for purposes of section 307, visibility impairment which
interferes with the management, protection, preservation, or enjoyment of the visitor's visual
experience of the Federal Class I area. This determination must be made on a case-by-case basis
taking into account the geographic extent, intensity, duration, frequency and time of visibility
impairments, and how these factors correlate with (1) times of visitor use of the Federal Class I
area, and (2) the frequency and timing of natural conditions that reduce visibility. This term does
not include effects on integral vistas.
* * *
Building, structure, or facility means all of the pollutant-emitting activities which belong to the
same industrial grouping, are located on one or more contiguous or adjacent properties, and are
under the control of the same person (or persons under common control). Pollutant-emitting
activities must be considered as part of the same industrial grouping if they belong to the same
Major Group (i.e., which have the same two-digit code) as described in the Standard Industrial
Classification Manual, 1972 as amended by the 1977 Supplement (U.S. Government Printing
Office stock numbers 4101-0066 and 003-005-00176-0 respectively).
Clearest days means the twenty percent of monitored days in a calendar year with the lowest
values of the deciview index.
Deciview is the unit of measurement on the deciview index scale for quantifying in a standard
manner human perceptions of visibility.
Deciview index means a value for a day that is derived from calculated or measured light
extinction, such that uniform increments of the index correspond to uniform incremental changes
in perception across the entire range of conditions, from pristine to very obscured. The deciview
index is calculated based on the following equation (for the purposes of calculating deciview
using IMPROVE data, the atmospheric light extinction coefficient must be calculated from
aerosol measurements and an estimate of Rayleigh scattering):
Deciview index = 10 In (bext/10 Mm"1).
bext= the atmospheric light extinction coefficient, expressed in inverse megameters
(Mm-1).
End of the applicable implementation period means December 31 of the year in which the next
periodic comprehensive implementation plan revision is due under §51.308(f).
* * *
Federal Class I area or Class I Federal area means any Federal land that is classified or
reclassified Class I. Mandatory Federal Class I areas are identified in part 81, subpart D. Other
Federal Class I areas are identified in part 52 of this title.
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Federal Land Manager means the Secretary of the department with authority over the Federal
Class I area (or the Secretary's designee) or, with respect to Roosevelt-Campobello International
Park, the Chairman of the Roosevelt-Campobello International Park Commission.
Federally enforceable means all limitations and conditions which are enforceable by the
Administrator under the Clean Air Act including those requirements developed pursuant to parts
60 and 61 of this title, requirements within any applicable State Implementation Plan, and any
permit requirements established pursuant to §52.21 of this chapter or under regulations approved
pursuant to part 51, 52, or 60 of this title.
Fixed capital cost means the capital needed to provide all of the depreciable components.
* * *
Implementation plan means, for the purposes of this part, any State Implementation Plan, Federal
Implementation Plan, or Tribal Implementation Plan.
Indian tribe or tribe means any Indian tribe, band, nation, or other organized group or
community, including any Alaska Native village, which is federally recognized as eligible for the
special programs and services provided by the United States to Indians because of their status as
Indians.
* * *
Installation means an identifiable piece of process equipment.
* * *
Least impaired days means the twenty percent of monitored days in a calendar year with the
lowest amounts of visibility impairment.
Major stationary source and major modification mean major stationary source and major
modification, respectively, as defined in §51.166.
Mandatory Class I Federal Area or Mandatory Federal Class I Area means any area identified
in part 81, subpart D of this title.
Most impaired days means the twenty percent of monitored days in a calendar year with the
highest amounts of visibility impairment.
Natural conditions includes naturally occurring phenomena that reduce visibility as measured in
terms of light extinction, visual range, contrast, or coloration.
Natural visibility conditions means visibility (contrast, coloration, and texture) that would have
existed under natural conditions. Natural visibility conditions vary with time and location, and
are estimated or inferred rather than directly measured.
* * *
Prescribed fire means any fire intentionally ignited by management actions in accordance with
applicable laws, policies, and regulations to meet specific land or resource management
objectives.
Reasonably attributable means attributable by visual observation or any other appropriate
technique.
Reasonably attributable visibility impairment means visibility impairment that is caused by the
emission of air pollutants from one, or a small number of sources.
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* * *
Regional haze means visibility impairment that is caused by the emission of air pollutants from
numerous sources located over a wide geographic area. Such sources include, but are not limited
to, major and minor stationary sources, mobile sources, and area sources.
Secondary emissions means emissions which occur as a result of the construction or operation of
an existing stationary facility but do not come from the existing stationary facility. Secondary
emissions may include, but are not limited to, emissions from ships or trains coming to or from
the existing stationary facility.
* * *
State means "State" as defined in section 302(d) of the CAA.
Stationary Source means any building, structure, facility, or installation which emits or may emit
any air pollutant.
Visibility means the degree of perceived clarity when viewing objects at a distance. Visibility
includes perceived changes in contrast, coloration, and texture elements in a scene.
Visibility impairment means any humanly perceptible difference between actual visibility
conditions and natural visibility conditions. Because natural visibility conditions can only be
estimated or inferred, visibility impairment also is estimated or inferred rather than directly
measured.
Visibility in any mandatory Class I Federal area includes any integral vista associated with that
area.
Wildfire means any fire started by an unplanned ignition caused by lightning; volcanoes; other
acts of nature; unauthorized activity; or accidental, human-caused actions, or a prescribed fire
that has been declared to be a wildfire. A wildfire that predominantly occurs on wildland is a
natural event.
Wildland means an area in which human activity and development is essentially non-existent,
except for roads, railroads, power lines, and similar transportation facilities. Structures, if any,
are widely scattered.
* * *
51.308 Regional haze program requirements
(a) What is the purpose of this section? This section establishes requirements for implementation
plans, plan revisions, and periodic progress reviews to address regional haze.
(b) When are the first implementation plans due under the regional haze program? Except as
provided in §51.309(c), each State identified in §51.300(b) must submit, for the entire State, an
implementation plan for regional haze meeting the requirements of paragraphs (d) and (e) of this
section no later than December 17, 2007.
(c) What is the relationship between requirements for regional haze and requirements for
reasonably attributable visibility impairment? A State must address any reasonably attributable
visibility impairment certified by a Federal Land Manager under §51.302(a) in its regional haze
implementation plan, as required by §51.302(b)-(d). A State must also meet the requirements of
§51.305 if the Administrator, Regional Administrator, or the Federal Land Manager has advised
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a State under §51.305 of a need for additional monitoring to assess reasonably attributable
visibility impairment at a mandatory Class I Federal area.
* * *
(f) Requirements for periodic comprehensive revisions of implementation plans for regional
haze. Each State identified in §51.300(b) must revise and submit its regional haze
implementation plan revision to EPA by July 31, 2021, July 31, 2028, and every 10 years
thereafter. The plan revision due on or before July 31, 2021 must include a commitment by the
State to meet the requirements of paragraph (g). In each plan revision, the State must address
regional haze in each mandatory Class I Federal area located within the State and in each
mandatory Class I Federal area located outside the State that may be affected by emissions from
within the State. To meet the core requirements for regional haze for these areas, the State must
submit an implementation plan containing the following plan elements and supporting
documentation for all required analyses:
(1) Calculations of baseline, current, and natural visibility conditions; progress to date; and the
uniform rate of progress. For each mandatory Class I Federal area located within the State, the
State must determine the following:
(i) Baseline visibility conditions for the most impaired and clearest days. The period for
establishing baseline visibility conditions is 2000 to 2004. For purposes of calculating and
displaying the uniform rate of progress, baseline visibility conditions must be associated with the
last day of this period. Baseline visibility conditions must be calculated, using available
monitoring data, by establishing the average deciview index for the most impaired and clearest
days for each calendar year from 2000 to 2004. The baseline visibility conditions are the average
of these annual values. For mandatory Class I Federal areas without onsite monitoring data for
2000-2004, the State must establish baseline values using the most representative available
monitoring data for 2000-2004, in consultation with the Administrator or his or her designee. For
mandatory Class I Federal areas with incomplete data availability for 2000-2004, the State must
establish baseline values using the closest 5 complete years of monitoring data.
(ii) Natural visibility conditions for the most impaired and clearest days. Natural visibility
conditions must be calculated by estimating the deciview index existing under natural conditions
for the most impaired and clearest days, based on available monitoring information and
appropriate data analysis techniques; and
(iii) Current visibility conditions for the most impaired and clearest days. The period for
calculating current visibility conditions is the most recent 5-year period for which data are
available. Current visibility conditions must be calculated based on the annual average level of
visibility impairment for the most impaired and clearest days for each of these 5 years. Current
visibility conditions are the average of these annual values.
(iv) Progress to date for the most impaired and clearest days. Actual progress made towards
natural conditions since the baseline period, and actual progress made during the previous
implementation period up to and including to the period for calculating current visibility
conditions, for the most impaired and clearest days, must be calculated.
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(v) Difference between current visibility conditions and natural visibility conditions. The number
of deciviews by which current visibility conditions exceed natural visibility conditions, for the
most impaired and clearest days, must be calculated.
(vi) Uniform rate of progress. (A) The uniform rate of progress for each mandatory Class I
Federal area in the State must be calculated. To calculate this uniform rate of progress, the State
must compare baseline visibility conditions to natural visibility conditions in the mandatory
Class I Federal area and determine the uniform rate of visibility improvement (measured in
deciviews of improvement per year) that would need to be maintained during each
implementation period in order to attain natural visibility conditions by the end of 2064.
(B) The State may submit a request to the Administrator seeking an adjustment to the uniform
rate of progress for a mandatory Class I Federal area to account for impacts from (1)
anthropogenic sources outside the United States and/or (2) wildland prescribed fires that were
conducted with the objective to establish, restore, and/or maintain sustainable and resilient
wildland ecosystems, to reduce the risk of catastrophic wildfires, and/or to preserve endangered
or threatened species during which appropriate basic smoke management practices were applied.
To calculate the proposed adjustment, the State must add the estimated impacts to natural
visibility conditions and compare the resulting value to baseline visibility conditions. If the
Administrator determines that the State has estimated the impacts from anthropogenic sources
outside the United States or wildland prescribed fires using scientifically valid data and methods,
the Administrator may approve the proposed adjustment to the uniform rate of progress for use
in the State's implementation plan.
(2) Long-term strategy for regional haze and reasonably attributable visibility impairment. Each
State must submit a long-term strategy that addresses regional haze visibility impairment, and if
necessary any reasonably attributable visibility impairment certified by the Federal Land
Manager under §51.302(a), for each mandatory Class I Federal area within the State and for each
mandatory Class I Federal area located outside the State that may be affected by emissions from
the State. The long-term strategy must include the enforceable emissions limitations, compliance
schedules, and other measures that are necessary to achieve reasonable progress, as determined
pursuant to (f)(2)(i) through (vi). In establishing its long-term strategy for regional haze, the
State must meet the following requirements:
(i) The State must consider and analyze emission reduction measures based on 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 major or minor
stationary source or group of sources. The State must document the criteria used to determine
which sources or groups of sources were evaluated, and how these four factors were taken into
consideration in selecting the measures for inclusion in its long-term strategy.
(ii) The State must consider the uniform rate of improvement in visibility, the emission reduction
measures identified in (f)(2)(i), and additional measures being adopted by other contributing
states in (f)(2)(iii) as needed to make reasonable progress towards natural visibility conditions
for the period covered by the implementation plan.
(iii) The State must consult with those States which may reasonably be anticipated to cause or
contribute to visibility impairment in the mandatory Class I Federal area.
(A) Contributing States. Where the State has emissions that are reasonably anticipated to
contribute to visibility impairment in any mandatory Class I Federal area located in another State
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or States, the State must consult with the other State(s) in order to develop coordinated emission
management strategies. The State must demonstrate that it has included in its implementation
plan all measures necessary to obtain its share of the emission reductions needed to provide for
reasonable progress towards natural visibility conditions in the mandatory Class I Federal area
located in the other State or States. If the State has participated in a regional planning process,
the State must also ensure that it has included all measures needed to achieve its apportionment
of emission reduction obligations agreed upon through that process.
(B) States affected by contributing States. A State with a mandatory Class I Federal area must
consult with any other State having emissions that are reasonably anticipated to contribute to
visibility impairment in that area regarding the emission reductions needed in each State to
provide for reasonable progress towards natural visibility conditions in that area. If the State has
participated in a regional planning process, the State must ensure it has included all measures
needed to achieve its apportionment of emission reduction obligations agreed upon through that
process.
(C) In any situation in which a State cannot agree with another State or group of States on the
emission reductions needed for reasonable progress towards natural visibility conditions in any
mandatory Class I Federal area, each involved State must describe in its submittal the actions
taken to resolve the disagreement. In reviewing the State's implementation plan submittal, the
Administrator will take this information into account in determining whether the State's
implementation plan provides for reasonable progress towards natural visibility conditions at
each mandatory Class I Federal area that is located in the State or that may be affected by
emissions from the State. All substantive interstate consultations must be documented.
(iv) As part of the demonstration required by (f)(2)(i), the State must document the technical
basis, including information on the factors listed in (f)(2)(i) and modeling, monitoring, and
emissions information, on which the State is relying to determine the emission reductions from
anthropogenic sources in the State that are necessary for achieving reasonable progress towards
natural visibility conditions in each mandatory Class I Federal area it affects. The State may meet
this requirement by relying on technical analyses developed by a regional planning process and
approved by all State participants. The State must identify the baseline emissions inventory on
which its strategies are based. The baseline emissions inventory year shall be the most recent
year for which the State has submitted emission inventory information to the Administrator in
compliance with the triennial reporting requirements of subpart A of this part unless the State
adequately justifies the use of another inventory year.
(v) The State must identify all anthropogenic sources of visibility impairment considered by the
State in developing its long-term strategy and the criteria used to select the sources considered.
The State should consider major and minor stationary sources, mobile sources, and area sources.
(vi) The State must consider, at a minimum, the following factors in developing its long-term
strategy:
(A) Emission reductions due to ongoing air pollution control programs, including measures to
address reasonably attributable visibility impairment;
(B) Measures to mitigate the impacts of construction activities;
(C) Emissions limitations and schedules for compliance to achieve the reasonable progress goal;
(D) Source retirement and replacement schedules;
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(E) Basic smoke management practices for prescribed fire used for agricultural and wildland
vegetation management purposes and smoke management programs as currently exist within the
State for these purposes;
(F) Enforceability of emissions limitations and control measures; and
(G) The anticipated net effect on visibility due to projected changes in point, area, and mobile
source emissions over the period addressed by the long-term strategy.
(3) Reasonable progress goals, (i) A state in which a mandatory Class I Federal area is located
must establish reasonable progress goals (expressed in deciviews) that reflect the visibility
conditions that are projected to be achieved by the end of the applicable implementation period
as a result of all enforceable emissions limitations, compliance schedules, and other measures
required under paragraph (f)(2) and the implementation of other requirements of the CAA. The
long-term strategy and the reasonable progress goals must provide for an improvement in
visibility for the most impaired days and ensure no degradation in visibility for the clearest days
since the baseline period.
(ii)(A) If a State in which a mandatory Class I Federal area is located establishes a reasonable
progress goal for the most impaired days that provides for a slower rate of improvement in
visibility than the uniform rate of progress calculated under paragraph (f)(l)(vi) of this section,
the State must demonstrate, based on the analysis required by paragraph (f)(2)(i) of this section,
that there are no additional emission reduction measures for anthropogenic sources or groups of
sources in the State that may reasonably be anticipated to contribute to visibility impairment in
the Class I area that would be reasonable to include in the long-term strategy. The State must
provide a robust demonstration, including documenting the criteria used to determine which
sources or groups or sources were evaluated and how the four factors required by paragraph
(f)(2)(i) were taken into consideration in selecting the measures for inclusion in its long-term
strategy. The State must provide to the public for review as part of its implementation plan an
assessment of the number of years it would take to attain natural visibility conditions if visibility
improvement were to continue at the rate of progress selected by the State as reasonable for the
implementation period.
(B) If a State contains sources which are reasonably anticipated to contribute to visibility
impairment in a mandatory Class I Federal area in another State for which a demonstration by
the other State is required under (f)(3)(ii)(A), the State must demonstrate that there are no
additional emission reduction measures for anthropogenic sources or groups of sources in the
State that may reasonably be anticipated to contribute to visibility impairment in the Class I area
that would be reasonable to include in its own long-term strategy. The State must provide a
robust demonstration, including documenting the criteria used to determine which sources or
groups or sources were evaluated and how the four factors required by paragraph (f)(2)(i) were
taken into consideration in selecting the measures for inclusion in its long-term strategy.
(iii) The reasonable progress goals established by the State are not directly enforceable but will
be considered by the Administrator in evaluating the adequacy of the measures in the
implementation plan in providing for reasonable progress towards achieving natural visibility
conditions at that area.
(iv) In determining whether the State's goal for visibility improvement provides for reasonable
progress towards natural visibility conditions, the Administrator will also evaluate the
demonstrations developed by the State pursuant to paragraphs (f)(2) and (f)(3)(ii)(A) of this
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section and the demonstrations provided by other States pursuant to paragraphs (f)(2) and
(f)(3)(ii)(B) of this section.
(4) If the Administrator, Regional Administrator, or the affected Federal Land Manager has
advised a State of a need for additional monitoring to assess reasonably attributable visibility
impairment at a mandatory Class I Federal area in addition to the monitoring currently being
conducted, the State must include in the plan revision an appropriate strategy for evaluating
reasonably attributable visibility impairment in the mandatory Class I Federal area by visual
observation or other appropriate monitoring techniques.
(5) So that the plan revision will serve also as a progress report, the State must address in the
plan revision the requirements of paragraphs (g)(l), (g)(2), (g)(4), and (g)(5) of this section.
However, the period to be addressed for these elements shall be the period since the past
progress report.
(6) Monitoring strategy and other implementation plan requirements. The State must submit
with the implementation plan a monitoring strategy for measuring, characterizing, and reporting
of regional haze visibility impairment that is representative of all mandatory Class I Federal
areas within the State. Compliance with this requirement may be met through participation in the
Interagency Monitoring of Protected Visual Environments network. The implementation plan
must also provide for the following:
(i) The establishment of any additional monitoring sites or equipment needed to assess whether
reasonable progress goals to address regional haze for all mandatory Class I Federal areas within
the State are being achieved.
(ii) Procedures by which monitoring data and other information are used in determining the
contribution of emissions from within the State to regional haze visibility impairment at
mandatory Class I Federal areas both within and outside the State.
(iii) For a State with no mandatory Class I Federal areas, procedures by which monitoring data
and other information are used in determining the contribution of emissions from within the State
to regional haze visibility impairment at mandatory Class I Federal areas in other States.
(iv) The implementation plan must provide for the reporting of all visibility monitoring data to
the Administrator at least annually for each mandatory Class I Federal area in the State. To the
extent possible, the State should report visibility monitoring data electronically.
(v) A statewide inventory of emissions of pollutants that are reasonably anticipated to cause or
contribute to visibility impairment in any mandatory Class I Federal 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. The State must also include a commitment
to update the inventory periodically.
(vi) Other elements, including reporting, recordkeeping, and other measures, necessary to assess
and report on visibility.
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(i) What are the requirements for State and Federal Land Manager coordination? (1) By
November 29, 1999, the State must identify in writing to the Federal Land Managers the title of
the official to which the Federal Land Manager of any mandatory Class I Federal area can submit
any recommendations on the implementation of this subpart including, but not limited to:
(i) Identification of impairment of visibility in any mandatory Class I Federal area(s); and
(ii) Identification of elements for inclusion in the visibility monitoring strategy required by
§51.305 and this section.
(2) The State must provide the Federal Land Manager with an opportunity for consultation, in
person at a point early enough in the State's technical and policy analyses of its long-term
strategy emission reduction obligation and prior to development of reasonable progress goals so
that information and recommendations provided by the Federal Land Manager can meaningfully
inform the State's development of the long-term strategy. The opportunity for consultation will
be deemed to have been early enough if the consultation has taken place at least 120 days prior to
holding any public hearing or other public comment opportunity on an implementation plan (or
plan revision) or progress report for regional haze required by this subpart. The opportunity for
consultation must be provided no less than 60 days prior to said public hearing or public
comment opportunity. This consultation must include the opportunity for the affected Federal
Land Managers to discuss their:
(i) Assessment of impairment of visibility in any mandatory Class I Federal area; and
(ii) Recommendations on the development of the reasonable progress goal and on the
development and implementation of strategies to address visibility impairment.
(3) In developing any implementation plan (or plan revision) or progress report, the State must
include a description of how it addressed any comments provided by the Federal Land Managers.
(4) The plan (or plan revision) must provide procedures for continuing consultation between the
State and Federal Land Manager on the implementation of the visibility protection program
required by this subpart, including development and review of implementation plan revisions and
progress reports, and on the implementation of other programs having the potential to contribute
to impairment of visibility in mandatory Class I Federal areas.
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United States Office of Air Quality Planning and Standards Publication No. EPA-457/P-16-001
Environmental Protection [Name of Division] July 2016
Agency Research Triangle Park, NC
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