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6560-50-P

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 51 and 52

[EPA-HQ-OAR-2015-0531; FRL-9935-27-OAR]

RIN 2060-AS55

Protection of Visibility: Amendments to Requirements for State Plans

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

SUMMARY: The Environmental Protection Agency (EPA) is proposing amendments to 

requirements under the Clean Air Act (CAA) for state plans for protection of visibility in 

mandatory Class I federal areas (Class I areas) in order to continue steady environmental 

progress while addressing administrative aspects of the program. The EPA amendments would 

clarify the relationship between long-term strategies and reasonable progress goals in state plans, 

and the long-term strategy obligation of all states. The amendments would also change the way 

in which some days during each year are to be selected for purposes of tracking progress towards 

natural visibility conditions to account for events such as wildfires; change aspects of the 

requirements for the content of progress reports; update, simplify and extend to all states the 

provisions for reasonably attributable visibility impairment and revoke existing federal 

implementation plans (FIPs) that require the EPA to assess and address any existing reasonably 

attributable visibility impairment situations in some states; and add a requirement for states to 

consult with Federal Land Managers (FLMs) earlier in the development of state plans. The EPA 

also proposes to address administrative aspects of the program by making a one-time adjustment 
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to the due date for the next state implementation plans (SIPs), revising the due dates for progress 

reports and removing the requirement for progress reports to be SIP revisions.

DATES: Comments. Written comments on this proposal must be received on or before 

[INSERT DATE 60 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL 

REGISTER]. Public hearing. The EPA is holding a public hearing concerning the proposed rule 

on [insert date], in Washington, D.C. The last day to pre-register to speak at the hearing is [insert 

date]. Please refer to SUPPLEMENTARY INFORMATION for additional information on 

submitting comments and the public hearing. Information collection request. Under the 

Paperwork Reduction Act (PRA), comments on the information collection provisions are best 

assured of having full effect if the Office of Management and Budget (OMB) receives a copy of 

your comments on or before [INSERT DATE 30 DAYS AFTER DATE OF PUBLICATION

IN THE FEDERAL REGISTER].

ADDRESSES: Comments: Submit your comments, identified by Docket ID No. EPA-HQOAR-2015-0531, at http://www.regulations.gov. Follow the online instructions for submitting 

comments. Once submitted, comments cannot be edited or removed from Regulations.gov. The 

EPA may publish any comment received to its public docket. Do not submit electronically any 

information you consider to be Confidential Business Information (CBI) or other information 

whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be 

accompanied by a written comment. The written comment is considered the official comment 

and should include discussion of all points you wish to make. The EPA will generally not 

consider comments or comment contents located outside of the primary submission (i.e., on the 

web, cloud, or other file sharing system). For additional submission methods, the full EPA public 

comment policy, information about CBI or multimedia submissions and general guidance on 
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making effective comments, please visit http://www2.epa.gov/dockets/comments.html. Public 

hearing: A public hearing will be held at [add location], in Washington, D.C. Identification is 

required. If your driver’s license is issued by American Samoa or Minnesota, you must present 

an additional form of identification to enter. Please refer to SUPPLEMENTARY 

INFORMATION for additional information on the public hearing and location requirements.

FOR FURTHER INFORMATION CONTACT: For general information on this proposed rule

and ICR, contact Mr. Christopher Werner, Office of Air Quality Planning and Standards, U.S. 

Environmental Protection Agency, by phone at (919) 541-5133 or by email at 

werner.christopher@epa.gov; or Ms. Rhea Jones, Office of Air Quality Planning and Standards, 

U.S. Environmental Protection Agency, by phone at (919) 541-2940 or by email at 

jones.rhea@epa.gov. For information on the public hearing or to register to speak at the hearing, 

contact Ms. Pamela Long, Office of Air Quality Planning and Standards, U.S. Environmental 

Protection Agency, by phone at (919) 541-0641 or by email at long.pam@epa.gov.

SUPPLEMENTARY INFORMATION: 

I. General Information

A. Preamble Glossary of Terms and Acronyms

The following are abbreviations of terms used in this document.

AQRV Air quality related value

BART Best available retrofit technology

bext Light extinction

CAA Clean Air Act

CFR Code of Federal Regulations

EGU Electric generating unit

EPA Environmental Protection Agency

FIP Federal implementation plan

FLM or FLMs Federal Land Manager or Managers

ICR Information collection request

IMPROVE Interagency monitoring of protected visual environments
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NAAQS National ambient air quality standards

NOx Nitrogen oxides

OMB Office of Management and Budget

PM Particulate matter

PM2.5 Particulate matter equal to or less than 2.5 microns in diameter (fine 

particulate matter)

PM10 Particulate matter equal to or less than 10 microns in diameter

PRA Paperwork Reduction Act

PSD Prevention of significant deterioration

RPO Regional planning organization

SIP State implementation plan

SO2 Sulfur dioxide

TAR Tribal Authority Rule

URP Uniform rate of progress

B. Does this action apply to me?

Entities potentially affected directly by this proposed rule include state, local and tribal1

governments, as well as FLMs responsible for protection of visibility in mandatory Class I areas. 

Entities potentially affected indirectly by this proposed rule include owners and operators of 

sources that emit particulate matter equal to or less than 10 microns in diameter (PM10),

particulate matter equal to or less than 2.5 microns in diameter (PM2.5 or fine PM), sulfur dioxide 

(SO2), oxides of nitrogen (NOx), volatile organic compounds and other pollutants that may cause 

or contribute to visibility impairment. Others potentially affected indirectly by this proposed rule 

include members of the general public who live, work or recreate in mandatory Class I areas 

affected by visibility impairment. Because emission sources that contribute to visibility 

 

1 The Regional Haze Rule may apply, as appropriate under the Tribal Authority Rule (TAR) in 

40 CFR part 49, to an Indian tribe that receives a determination of eligibility for treatment as a 

state for purposes of administering a tribal visibility protection program under section 169A of 

the CAA. No tribe has applied for such status, and so at present the EPA is responsible for 

implementation of the Regional Haze Rule in areas of tribal authority. The proposed rule 

changes may impact the development and approvability of tribal implementation plans that tribes 

may wish to develop in the future. We encourage states to provide outreach and engage in 

discussions with tribes about their regional haze SIPs as they are being developed.
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impairment in Class I areas also may contribute to air pollution in other areas, members of the 

general public may also be affected by this proposed rulemaking.

C. What should I consider as I prepare my comments for the EPA?

When submitting comments, remember to:

• Identify the rulemaking docket by docket number and other identifying 

information (subject heading, Federal Register date and page number).

• Follow directions. The proposed rule may ask you to respond to specific questions 

or organize comments by referencing a Code of Federal Regulations (CFR) part 

or section number.

• Explain why you agree or disagree, suggest alternatives and substitute language 

for your requested changes.

• Describe any assumptions and provide any technical information and/or data that 

you used to support your comment.

• If you estimate potential costs or burdens, explain how you arrived at your 

estimate in sufficient detail to allow for it to be reproduced.

• Provide specific examples to illustrate your concerns wherever possible, and 

suggest alternatives.

• Explain your views as clearly as possible, avoiding the use of profanity or 

personal threats.

• Make sure to submit your comments by the comment period deadline identified.

Please note that this is a narrow proposed rulemaking. Please focus your comments on 

only those sections of the CFR affected by our proposed changes.

D. What information should I know about the public hearing?
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The [insert date] public hearing will be held to accept oral comments on this proposed 

rulemaking. The hearing will be held at [insert location]. It will convene at [EPA to insert 

time] and continue until the earlier of [EPA to insert time] or 1 hour after the last registered 

speaker has spoken. We have scheduled a lunch break from [EPA to insert time]. People 

interested in presenting oral testimony should contact Ms. Pamela Long, Air Quality Planning 

Division, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, 

Research Triangle Park, NC 27711, telephone (919) 541-0641, fax number (919) 541-5509, 

email address long.pam@epa.gov, at least 2 days in advance of the public hearing (see DATES). 

Additionally, requests to speak will be taken the day of the hearing at the hearing registration 

desk, although preferences on speaking times may not be able to be fulfilled. Depending on the 

flow of the day, times may fluctuate. People interested in attending the public hearing should 

also call Ms. Long to verify the time, date and location of the hearing. While the EPA expects 

the hearing to go forward as set forth, we ask that you monitor our website at 

http://www.epa.gov/XXXXXX.html or contact Ms. Pamela Long to determine if there are any 

updates to the information on the hearing. 

Oral testimony will be limited to 5 minutes for each commenter. The EPA encourages 

commenters to provide the EPA with a copy of their oral testimony electronically (via email) 

before the hearing and in hard copy form at the hearing. 

The EPA may ask clarifying questions during the oral presentations, but will not respond 

to the presentations at that time. Written statements and supporting information submitted during 

the comment period will be considered with the same weight as oral comments and supporting 

information presented at the public hearing. Verbatim transcripts of the hearing and written 

statements will be included in the docket for the rulemaking. 
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Because this hearing is being held at United States (U.S.) government facilities, 

individuals planning to attend the hearing should be prepared to show valid picture identification 

to the security staff in order to gain access to the meeting room. Please note that the REAL ID 

Act, passed by Congress in 2005, established new requirements for entering federal facilities. If 

your driver’s license is issued by American Samoa or Minnesota, you must present an additional 

form of identification to enter the federal building. Acceptable alternative forms of identification 

include: federal employee badges, passports, enhanced driver’s licenses, and military 

identification cards. For additional information for the status of your state regarding REAL ID, 

go to http://www.dhs.gov/real-id-enforcement-brief. In addition, you will need to obtain a 

property pass for any personal belongings you bring with you. Upon leaving the building, you 

will be required to return this property pass to the security desk. No large signs will be allowed 

in the building, cameras may only be used outside of the building, and demonstrations will not be 

allowed on federal property for security reasons. 

Attendees may be asked to go through metal detectors. To help facilitate this process, 

please be advised that you will be asked to remove all items from all pockets and place them in 

provided bins for screening; remove laptops, phones, or other electronic devices from their 

carrying case and place in provided bins for screening; avoid shoes with metal shanks, toe 

guards, or supports as a part of their construction; remove any metal belts, metal belt buckles, 

large jewelry, watches, and follow the instructions of the guard if identified for secondary 

screening. Additionally, no weapons or drugs or drug paraphernalia will be allowed in the 

building. We recommend that you arrive 20 minutes in advance of your speaking time to allow 

time to go through security and to check in with the registration desk.

E. Where can I obtain a copy of this document and other related information?
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In addition to being available in the docket, an electronic copy of this Federal Register

document will be posted at http://www.epa.gov/XXXXXX.html.

F. How is this Federal Register document organized?

The information presented in this document is organized as follows:

I. General Information

A. Preamble Glossary of Terms and Acronyms

B. Does this action apply to me?

C. What should I consider as I prepare my comments for the EPA?

D. What information should I know about the public hearing?

E. Where can I obtain a copy of this document and other related information?

F. How is this Federal Register document organized?

II. What action is the EPA proposing to take?

III. What is the background for the EPA’s proposed action?

A. Reasonably Attributable Visibility Impairment

B. Regional Haze

1. Requirements of the 1990 CAA Amendments and the EPA’s Regional Haze 

Rule

2. Roles of Agencies in Addressing Regional Haze

3. Requirements for the Regional Haze SIPs

4. Requirements for the Regional Haze Progress Reports

5. Tribes and Regional Haze

C. Air Permitting

IV. Proposed Rule Changes

A. Clarifications to Reflect the EPA’s Long-Standing Interpretation of the Relationship 

Between Long-Term Strategies and Reasonable Progress Goals

B. Other Clarifications and Changes to Requirements for Periodic Comprehensive 

Revisions of Implementation Plans

C. Changes to Definitions and Terminology Related to How Days Are Selected for 

Tracking Progress

D. Impacts on Visibility from Anthropogenic Sources Outside the U.S.

E. Clarification of and Changes to the Required Content of Progress Reports

F. Changes to Reasonably Attributable Visibility Impairment Provisions

G. Consistency Revisions Related to Permitting of New and Modified Major Sources

H. Changes to FLM Consultation Requirements

I. Extension of Next Regional Haze SIP Deadline from 2018 to 2021

J. Changes to Scheduling of Regional Haze Progress Reports

K. Changes to the Requirement that Regional Haze Progress Reports be SIP Revisions

L. Changes to Requirements Related to the Grand Canyon Visibility Transport 

Commission

V. Environmental Justice Considerations

VI. Statutory and Executive Order Reviews
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A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: 

Improving Regulation and Regulatory Review

B. Paperwork Reduction Act (PRA)

C. Regulatory Flexibility Act (RFA)

D. Unfunded Mandates Reform Act (UMRA)

E. Executive Order 13132: Federalism

F. Executive Order 13175: Consultation and Coordination with Indian Tribal 

Governments

G. Executive Order 13045: Protection of Children from Environmental Health and Safety 

Risks

H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect 

Energy Supply, Distribution or Use

I. National Technology Transfer and Advancement Act

J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority 

Populations and Low-Income Populations

VII. Statutory Authority

II. What action is the EPA proposing to take?

The EPA is proposing changes to the requirements that states (and, if applicable, tribes) 

would have to meet as they implement programs for the protection of visibility in mandatory

Class I areas.

2 This proposal would support continued environmental progress by clarifying 

certain or revising existing regulatory provisions and removing older rule provisions that have 

been superseded by subsequent developments. The EPA is proposing to clarify the relationship 

between long-term strategies and reasonable progress goals in state plans and the long-term 

 

2 Areas designated as mandatory Class I areas consist of national parks exceeding 6,000 acres, 

wilderness areas and national memorial parks exceeding 5,000 acres, and all international parks 

that were in existence on August 7, 1977. 42 U.S.C. 7472(a). In accordance with section 169A of 

the CAA, the EPA, in consultation with the Department of Interior, promulgated a list of 156 

areas where visibility is identified as an important value. 44 FR 69122 (November 30, 1979). 

The extent of a mandatory Class I area includes subsequent changes in boundaries, such as park 

expansions. 42 U.S.C. 7472(a). Although states and tribes may designate as Class I additional 

areas that they consider to have visibility as an important value, the requirements of the visibility 

program set forth in section 169A of the CAA apply only to “mandatory Class I Federal areas.” 

Each mandatory Class I federal area is the responsibility of a “Federal Land Manager.” 42 

U.S.C. 7602(i). When we use the term “Class I area” in this action, we mean any one of the 156

“mandatory Class I Federal areas” where visibility has been identified as an important value.
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strategy obligation of all states. The EPA is also proposing to revise 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;

revise aspects of the requirements for the content of progress reports; update, simplify and 

extend to all states the provisions for reasonably attributable visibility impairment and revoke

existing FIPs that require the EPA to assess and address any existing reasonably attributable 

visibility impairment situations in some states; and add a requirement for states to consult with 

FLMs earlier in the development of state plans. Other changes address administrative aspects of 

the program in order to reduce unnecessary burden. Specifically, the EPA proposes to make a 

one-time adjustment to the due date for the next SIPs (from 2018 to 2021, which would help 

states to coordinate regional haze planning with that for other programs such as the Clean Power 

Plan), to revise the due dates for progress reports and to remove the requirement for progress 

reports to be SIP revisions. All of these changes would apply to periodic comprehensive state 

implementation plans developed for the second and subsequent implementation periods and for 

progress reports submitted subsequent to those plans. We do not intend the proposed changes to 

affect the development of state plans for the first implementation period or the first progress 

reports due under the existing Regional Haze Rule.

The EPA is proposing these changes for several reasons, as described more fully in the 

descriptions of each change detailed later in this proposed action. The proposed clarifications 

regarding the relationship between reasonable progress goals, long-term strategies and the longterm strategy obligation of all states reflect long-standing EPA interpretation of the Regional 

Haze Rule and are intended to ensure consistent (and appropriate) understanding of these 

requirements as states prepare their plans for the second implementation period. Changes to FLM
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consultation requirements would help ensure that the expertise and perspective of these officials 

are brought into the state plan development process earlier, so that they contribute meaningfully 

during the state’s technical analysis and deliberations. The proposals related to how days are 

selected for visibility progress tracking would provide the public and state officials more 

meaningful information on how existing and potential new emission reduction measures are 

contributing or could contribute to reasonable progress in reducing man-made visibility 

impairment, by greatly reducing the trend-distorting effect of wildfires and natural dust storms. 

Collectively, these changes would serve to strengthen the regional haze program based upon 

lessons learned during the decade and a half since the program’s inception.

With regard to the proposed extension of the current deadline of July 31, 2018, to July 

31, 2021, for states’ comprehensive SIP revisions for the second implementation period, the EPA 

believes this one-time change would benefit states by allowing them to obtain and take into 

account information on the effects of a number of other regulatory programs that will be 

affecting sources over the next several years. The change would also allow states to develop SIP 

revisions for the second implementation period that are more integrated with state planning for 

these other programs, an advantage that was widely confirmed in discussions with states and that 

is anticipated to result in greater environmental progress than if planning for these multiple 

programs were not as well integrated. Note that other than the proposed one-time change to the 

next due date for periodic comprehensive SIP revisions (i.e., for those currently due in 2018), no 

change is being proposed for due dates for future periodic comprehensive SIP revisions.

The proposed changes related to progress reports are intended to make the timing of 

progress reports more useful as mid-course reviews, to clarify the required content of progress 

reports for aspects on which there has been some ambiguity, and to allow states to conserve their 
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administrative resources and make progress reports more timely by removing the requirement 

that they be submitted as formal SIP revisions. We are proposing to retain a requirement that 

states consult with FLMs on their progress reports, and that states offer the public an opportunity 

to comment on progress reports before they are finalized, which are two of the steps that apply 

now to progress reports that are SIP revisions and which will help ensure ongoing accountability 

for progress reports.

Finally, the current provisions related to reasonably attributable visibility impairment

require a recurring process of assessment and planning by the states. Experience since the current 

provisions were promulgated suggests that situations involving reasonably attributable visibility 

impairment occur infrequently and therefore that an “as needed” approach for initiating a state 

planning obligation would be more efficient in the use of resources. The EPA is proposing to 

replace the recurring process of assessment with an as needed approach, and given our increased 

understanding of the interstate nature of visibility impairment to expand the applicability for 

reasonably attributable visibility impairment from only states with Class I areas to all states. This 

would improve visibility protection, if a situation exists or arises in which a source in a state 

without any Class I area causes reasonably attributable visibility impairment at a Class I area in 

another state.

The EPA intends to also provide states with updated guidance on the development of 

regional haze SIPs, in consultation with the states and FLMs, separately from this rulemaking.

The guidance will assist states as they refocus on reasonable progress analyses for the next

regional haze implementation period ending in 2028.

III. What is the background for the EPA’s proposed action?

A. Reasonably Attributable Visibility Impairment
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In section 169A of the 1977 Amendments to the CAA, Congress created a program for 

protecting visibility in the nation’s national parks, wilderness areas, national forests and other 

Class I areas due to their “great scenic importance.”

3 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.”

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.” 45 FR 80084

(December 2, 1980). These regulations, codified at 40 CFR 51.300 through 51.307, 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 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 provides more data on sourcespecific levels of visibility impairment, regional scale models become refined, and our scientific 

knowledge about the relationships between emitted air pollutants and visibility impairment 

improves. 

 

3 H.R. Rep. No. 294, 95th Cong. 1st Sess. at 205 (1977).
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It is important to note that not all states were subject to the 1980 reasonably attributable 

visibility impairment requirements. Under the 1980 rules, the 35 states and one territory (Virgin 

Islands) containing Class I areas were required to submit SIPs addressing reasonably attributable 

visibility impairment. The 1980 rules required states to (1) develop, adopt, implement and 

evaluate long-term strategies for making reasonable progress toward remedying existing and 

preventing future impairment in the mandatory Class I areas through their SIP revisions; (2) 

adopt certain measures to assess potential visibility impacts due to new or modified major 

stationary sources, including measures to notify FLMs of proposed new source permit 

applications, and to consider visibility analyses conducted by FLMs in their new source 

permitting decisions; (3) conduct visibility monitoring in mandatory Class I areas, and (4) revise 

their SIPs at 3-year intervals to assure reasonable progress toward the national visibility goal. In 

addition, the 1980 regulations provided that an FLM may certify to a state at any time that 

visibility impairment at a Class I area is reasonably attributable to a single source or small group 

of sources. Following such a certification by an FLM, a state is required to address the 

requirements for best available retrofit technology (BART) for BART-eligible sources 

considered to be contributing to reasonably attributable visibility impairment. Also, the 

appropriate control of any source certified by an FLM, whether BART-eligible or not, would 

logically be specifically addressed in the long-term strategy for making reasonable progress

toward the national goal of natural visibility conditions as required by existing §51.302(c)(2)(i).

In practice, the 1980 rules resulted in few SIPs being submitted by states and approved by 

the EPA, requiring the EPA to develop and apply FIPs to those states that failed to submit an 

approvable reasonably attributable visibility impairment SIP. 52 FR 45132 (November 24, 

1987). Most of these FIPs contain planning requirements only, i.e., most of the FIPs merely 
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commit the EPA to assessing on a 3-year cycle whether reasonably attributable visibility 

impairment is occurring and to adopting an appropriate strategy of required emission controls if 

it is. 

We are proposing extensive changes to the existing provisions regarding reasonably 

attributable visibility impairment to improve coordination with the regional haze program 

requirements and enhance the potential for environmental protection, as described in the 

“Proposed Rule Changes” section of this document (section IV.G).

B. Regional Haze

Regional haze is visibility impairment that is produced by a multitude of sources and 

activities that are located across a broad geographic area and emit PM10, PM2.5 (e.g., sulfates,

nitrates, organic carbon, elemental carbon and soil dust) and their precursors (e.g., SO2, NOx

and, in some cases, ammonia and volatile organic compounds). Fine particle precursors react in 

the atmosphere to form PM2.5, which impairs visibility by scattering and absorbing light. This 

light scattering reduces the clarity, color and visible distance that one can see. Particulate matter

can also cause serious health effects in humans (including premature death, heart attacks, 

irregular heartbeat, aggravated asthma, decreased lung function and increased respiratory 

symptoms) and contribute to environmental effects such as acid deposition and eutrophication.

Data from the existing visibility monitoring network, the “Interagency Monitoring of 

Protected Visual Environments” (IMPROVE) monitoring network, show that at the time the 

Regional Haze Rule was finalized in 1999, visibility impairment caused by air pollution occurred
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virtually all the time at most national park and wilderness areas. The average visual range4in 

many Class I areas in the western U.S. was 62–93 miles, but in some Class I areas, these visual 

ranges may have been impacted by natural wildfire and dust episodes in addition to 

anthropogenic impacts. In most of the eastern Class I areas of the U.S., the average visual range 

was less than 19 miles. 64 FR 35715 (July 1, 1999).

Based on visibility data through 2014, considerable visibility improvements (4 to 7 

deciviews)

5

have been made in eastern Class I areas on the 20 percent haziest days. Some 

western Class I areas have also experienced visibility improvements on the 20 percent haziest 

days (1 to 4 deciviews). However, in some areas, such as Sawtooth Wilderness area in Idaho, 

improvements from reduced emissions from man-made sources have been overwhelmed by 

uncontrollable impacts from fire and/or dust events. There are also some western areas where 

visibility has changed only by a slight amount.

1. Requirements of the 1990 CAA Amendments and the EPA’s Regional Haze Rule

Congress added section 169B to the CAA in 1990 to address 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 

 

4 Visual range is the greatest distance, in kilometers or miles, at which a dark object can be 

discerned against the sky by a typical observer. Visual range is inversely proportional to light 

extinction (bext) by particles and gases and is calculated as: Visual Range = 3.91/bext (Bennett, 

M.G., The physical conditions controlling visibility through the atmosphere; Quarterly Journal of 

the Royal Meteorological Society, 1930, 56, 1-29). Light extinction has units of inverse distance 

(i.e., Mm-1or inverse Megameters [mega = 106]).

5 The deciview haze index (discussed in more detail in Section III.B.3) is logarithmically related 

to light extinction and is used by the regional haze program because it describes uniform 

differences in visibility across a range of visibility conditions.
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air pollution protection programs. Section 169B also generally allowed the Administrator to 

establish visibility transport commissions and specifically required the Administrator to establish 

a commission for the Grand Canyon area. The EPA promulgated a rule to address regional haze 

in 1999. 64 FR 35714 (July 1, 1999). The 1999 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.

The requirement to submit a regional haze SIP applies to all 50 states, the District of 

Columbia and the Virgin Islands.

6 Congress subsequently amended the deadlines for regional 

haze SIPs, and the EPA adopted regulations requiring states to submit the first implementation 

plans addressing regional haze visibility impairment no later than December 17, 2007. 70 FR 

39104. These initial SIPs were to address emissions from certain large stationary sources and 

other requirements, which we discuss in greater detail later. Few states submitted a regional haze 

SIP by the December 17, 2007, deadline, and on January 15, 2009, the EPA found that 37 states, 

the District of Columbia and the Virgin Islands had failed to submit SIPs addressing the regional 

haze requirements. 74 FR 2392. Because of these findings, CAA section 110(c)(1) requires the 

EPA to promulgate a FIP within 2 years unless the state submits a SIP and the agency approves it 

within the 2-year period. The EPA has fulfilled most but not all of these FIP obligations7. 

 

6 This requirement does not apply to other U.S. territories because they do not have mandatory 

Class I Federal areas, and they are too distant from any such areas to affect them.

7 Most states now have an approved SIP or FIP in place. [NOTE TO OMB: This footnote will be 

expanded to describe the up-to-date status of SIPs and FIPs at time of rule proposal publication, 

reflecting ongoing litigation that may affect SIP/FIP status at that time. The states that do not yet 

have a complete and approved SIP or complete FIP in place include AL, AR, LA, MT, ND, MS, 

MT, PA and TX. In addition, pending litigation might result in remands of portions of SIP 

actions and/or FIPs in other states including AZ and WY. ]
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Further, 40 CFR 51.308(f) currently requires states to submit periodic comprehensive

revisions of implementation plans (referred to in this document as periodic comprehensive SIP 

revisions) addressing regional haze visibility impairment no later than July 31, 2018, and every 

10 years thereafter. These periodic comprehensive 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 

long-term strategy for the achievement of reasonable progress goals over the prior 

implementation period, and affirmation of or revision to the reasonable progress goals. Further 

information on these periodic comprehensive SIP revisions can be found in section III.B.3 of this 

document. In addition, 40 CFR 51.308(g) requires each state to submit progress reports, in the 

form of SIP revisions, every 5 years counting from the submission of the initial SIP due on 

December 17, 2007. These progress reports are required to evaluate the progress made towards 

the reasonable progress goals for mandatory Class I areas located within the state as well as those 

mandatory Class I areas located outside the state that may be affected by emissions from within 

the state. Further information on these progress reports can be found in section III.B.4 of this 

document.

The 1999 Regional Haze Rule sought to improve efficiency and transparency by 

requiring states to coordinate their planning under the 1980 reasonably attributable visibility 

impairment provisions with their planning under the provisions added by the 1999 Regional 

Haze Rule. The states were directed to submit reasonably attributable visibility impairment SIPs 

every 10 years rather than the previously required every 3 years, and to do so as part of the newly 

required regional haze SIPs. Many but not all states submitted initial regional haze SIPs that
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committed to this coordinated planning process. Coordination of reasonably attributable 

visibility impairment and regional haze planning is described in more detail later.

2. Roles of Agencies in Addressing Regional Haze

Successful implementation of the regional haze program requires long-term regional 

coordination among states, tribal governments and various federal agencies. As noted earlier,

pollution affecting the air quality in Class I areas can be transported over long distances, even 

hundreds of miles. Therefore, to effectively address the problem of visibility impairment in Class 

I areas, states need to develop strategies in coordination with one another, taking into account the 

effect of emissions from one jurisdiction on the air quality in another.

Because the pollutants that lead to regional haze can originate from sources located 

across broad geographic areas, and because these sources may be numerous and emit amounts of 

pollutants that even though small contribute to the collective whole, the EPA has encouraged the 

states across the U.S. to address visibility impairment from a regional perspective. Five regional 

planning organizations (RPOs) were formed after the promulgation of the Regional Haze Rule in 

1999 to address regional haze and related issues. The RPOs first evaluated technical information 

to better understand how their states and tribes impact Class I areas across the country, and then 

supported the development (by states) of regional strategies to reduce emissions of pollutants 

that lead to regional haze.

3. Requirements for the Regional Haze SIPs

The following is a summary of the requirements for the periodic comprehensive SIP

revisions under the 1999 Regional Haze Rule. See 40 CFR 51.308 and 51.309 for further detail 

regarding the requirements of the rule.
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The implementation plans due in 2007, covering what we refer to as the first 

implementation period, were required to give specific attention to certain stationary sources that 

were in existence on August 7, 1977, but were not in operation before August 7, 1962, by 

requiring these sources, where appropriate, to install BART controls for the purpose of 

eliminating or reducing visibility impairment. The following paragraphs describe the one-time

BART requirement and the specific regional haze SIP requirements that continue to apply for the 

second and subsequent implementation periods.

BART Requirement. Section 169A of the CAA directs states to evaluate the use of retrofit

controls at certain larger, often uncontrolled, older stationary sources in order to address 

visibility impacts from these sources. Specifically, section 169A(b)(2)(A) of the CAA requires 

states to revise their SIPs to include such measures as may be necessary to make reasonable 

progress towards the natural visibility goal, including a requirement that certain categories of 

existing major stationary sources8procure, install, and operate BART as determined by the state.

Under the Regional Haze Rule, states are directed to conduct BART determinations for such

“BART-eligible9” sources that may be anticipated to cause or contribute to any visibility 

impairment in a Class I area. The EPA published the Guidelines for BART Determinations Under 

the Regional Haze Rule at appendix Y to 40 CFR part 51 (hereinafter referred to as the “BART 

Guidelines”) to assist states in determining which of their sources should be subject to the BART

requirements and in determining appropriate emission limits for each applicable source. 70 FR 

 

8 The set of “major stationary sources” potentially subject-to-BART is listed in CAA section 

169A(g)(7).

9 BART-eligible sources are those sources that have the potential to emit 250 tons or more of a 

visibility-impairing air pollutant, were not in operation prior to August 7, 1962, but were in 

existence on August 7, 1977, and whose operations fall within one or more of 26 specifically 

listed source categories. 40 CFR 51.301.
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39104 (July 6, 2005). The Regional Haze Rule also provides an alternative to requiring sourcespecific BART controls; under EPA’s regulations, states have the flexibility to adopt an 

emissions trading program or other alternative program as long as the alternative provides 

greater reasonable progress towards improving visibility than BART and meets certain other 

requirements set out in 40 CFR 51.308(e)(2).

States undertook the BART determination process during the first regional haze 

implementation period; thus the details of the process for establishing BART emission 

limitations are not material to the changes proposed in this document. Although the BART 

process is not repeated in subsequent implementation periods, BART-eligible sources may be reassessed for more control in later implementation periods as part of the requirement to provide 

for reasonable progress as described later. We are not proposing any changes to the BART 

provisions.

Visibility Metric. The Regional Haze Rule established a standard, conventional approach 

to quantifying visibility and tracking how it is changing over time. The Regional Haze Rule

established the 24-hour deciview haze index as the principal metric or unit for expressing 

visibility for any particular day. See 70 FR 39104, 39118. The deciview haze index is calculated 

from light extinction values, and this index expresses uniform changes in the degree of haze in 

terms of common increments across the entire range of visibility conditions, from pristine to 

extremely hazy conditions. Visibility expressed in deciviews is determined by using air quality

measurements to estimate light extinction, most recently using the revised IMPROVE algorithm,
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and then transforming the value of light extinction using a logarithmic function.10 The deciview 

is a more useful measure for comparing days and tracking progress in improving visibility than 

light extinction itself because each deciview change is an equal incremental change in visibility 

typically perceived by a human observer. Most people can detect a change in visibility at one 

deciview. The preamble to the 1999 Regional Haze Rule provides additional details about the 

deciview haze index. We are proposing minor editorial changes to definitions related to the 

deciview index in order for there to be more consistent terminology across sections of the 

Regional Haze Rule. 

Baseline, Current and Natural Conditions and Tracking Changes in Visibility. To track 

changes in visibility over time at each of the 156 Class I areas covered by the visibility program 

(40 CFR 81.401–437), and as part of the process for determining reasonable progress as 

described later, states must calculate the degree of existing visibility impairment at each Class I 

area for a 5-year period just preceding each periodic comprehensive SIP revision and, under the 

current version of the Regional Haze Rule, periodically review progress in reducing impairment 

every 5 years. To do this, the Regional Haze Rule requires states to determine the degree of 

impairment (in deciviews) for the average of the 20 percent least impaired and 20 percent most

impaired visibility days over a specified time period at each of their Class I areas.

States must also develop an estimate of natural visibility conditions for the purpose of 

estimating progress toward the national goal of preventing future and remedying existing 

visibility impairment from manmade air pollution. Natural visibility is determined by estimating 

 

10 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.
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the natural concentrations of pollutants that cause visibility impairment and then calculating total 

light extinction based on those estimates. The EPA has provided guidance to states regarding 

how to calculate baseline, natural and current visibility conditions.11 After the EPA issued this 

guidance, a number of interested parties developed an alternative set of natural conditions using 

a more refined approach (known as “NC-II”), which were used by most states in their first 

regional haze SIPs with EPA approval.12

Baseline visibility conditions represent the degree of visibility impairment for the 20 

percent least impaired days and 20 percent most impaired days for each calendar year from 2000 

to 2004. Using monitoring data for 2000 through 2004, states are required to calculate the 

average degree of visibility impairment for each Class I area, based on the average of annual 

values over the 5-year period. The comparison of initial baseline visibility conditions to natural 

visibility conditions indicates the amount of improvement that would be necessary to attain 

 

11 Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule, 

September 2003, EPA–454/B–03–005, available at 

http://www3.epa.gov/ttn/caaa/t1/memoranda/rh_envcurhr_gd.pdf; and Guidance for Tracking 

Progress Under the Regional Haze Rule, September 2003, EPA–454/B–03–004, available at 

http://www3.epa.gov/ttn/oarpg/t1/memoranda/rh_tpurhr_gd.pdf.

12 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_NaturalConditionsII_Description.pdf; Revised IMPROVE Algorithm for Estimating Light 

Extinction from Particle Speciation Data, available at 

http://vista.cira.colostate.edu/improve/Publications/GrayLit/019_RevisedIMPROVEeq/RevisedI

MPROVEAlgorithm3.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/index.html.
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natural visibility. Over time, the comparison of current conditions13 to the baseline conditions 

will indicate the amount of progress that has been made.

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. The rule text directed the tracking of visibility impairment on the 20 percent “most 

impaired days” and 20 percent “least impaired days” in order to determine progress towards 

natural visibility conditions. Section 51.308(d)(2)(i-iv). In light of the 1999 rule’s definition of 

“impairment,” the term “impaired” in the phrases “most impaired days” and “least impaired 

days” could be taken to connote anthropogenic impairment. However, the preamble to the 1999 

final rule stated that the least and most impaired days were to be selected as the monitored days 

with the lowest and highest actual deciview levels, respectively. In 2003, the EPA issued 

guidance describing in detail the steps necessary for selecting and calculating light extinction on 

the “worst” and “best” visibility days, and this guidance also indicated that the monitored days 

with the lowest and highest actual deciview levels were to be selected as the least and most 

impaired days.

14 This approach has worked well in many Class I areas but has not in other areas. 

Specifically, the “worst” visibility days in some Class I areas can be impacted by natural 

emissions (e.g., wildfires and dust storms). These natural contributions to haze vary in magnitude 

and timing. Anticipating this variability, in the 1999 Regional Haze Rule the EPA had decided to 

use 5-year averages of visibility data to minimize the impacts of the interannual variability in 

 

13 Given the required timing of the first regional haze SIPs that were due by December 17, 2007, 

“baseline visibility conditions” were also the “current” visibility conditions. For future SIPs, 

“current conditions” will be updated to the 5-year period just preceding the SIP revision.

14 Guidance for Tracking Progress Under the Regional Haze Rule, September 2003, 

http://www3.epa.gov/ttnamti1/files/ambient/visible/tracking.pdf.
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natural events. However, as the IMPROVE monitoring network has collected more years of data, 

it has become obvious that in many Class I areas 5-year averages are not sufficient for 

minimizing these impacts. As a result, visibility improvements resulting from decreases in 

anthropogenic emissions can be hidden in this uncontrollable natural variability. In addition, 

because of the logarithmic deciview scale, changes in PM concentrations and light extinction due 

to reductions in anthropogenic emissions have little effect on the deciview value on days with 

high PM concentrations and light extinction due to natural sources. The use of the days with the 

highest deciview index values, without consideration of the source of the visibility impacts, thus 

has created difficulties when attempting to track visibility improvements resulting from controls 

on anthropogenic sources. States have identified this difficulty and asked that the EPA explore 

options for focusing the visibility tracking metric on controllable anthropogenic emissions. To 

help states minimize the impacts of uncontrollable emissions on visibility tracking, the EPA is 

proposing to more explicitly (and consistently) address this issue for future implementation 

periods in the “Proposed Rule Changes” section of this document (sections IV.C. and IV.D).

Reasonable Progress Goals and Long-Term Strategy. To ensure continuing progress 

towards achieving the natural visibility goal, each SIP in the series of periodic comprehensive

regional haze SIPs must establish two distinct reasonable progress goals (one for the most 

impaired and one for the least impaired days) for every Class I area for the following

implementation period. See 40 CFR 51.308(d) and (f). The Regional Haze Rule does not 

mandate specific milestones or rates of progress, but instead calls for states to establish goals that 

provide for “reasonable progress” toward achieving natural visibility conditions. In setting 

reasonable progress goals, states must provide for an improvement in visibility for the most 

impaired days over the period of the SIP, and ensure no degradation in visibility for the least 
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impaired days over the same period. Id. Consistent with the requirement in section 169A(b) of 

the CAA that states include in their regional haze SIPs a 10- to 15-year strategy for making 

reasonable progress, §51.308(d)(3) of the Regional Haze Rule requires that states include their 

long-term strategy in their regional haze SIPs. The reasonable progress goals themselves, 

however, are not enforceable. 64 FR 35754.

In establishing reasonable progress goals, states are required to consider the following 

factors set out in the definition of “reasonable progress” in section 169A of the CAA and 

incorporated into the Regional Haze Rule at 40 CFR 51.308(d)(1)(i)(A): (1) the costs of 

compliance; (2) the time necessary for compliance; (3) the energy and non-air quality 

environmental impacts of compliance; and (4) the remaining useful life of any potentially 

affected sources. States must demonstrate in their SIPs how these factors have been considered 

when selecting the reasonable progress goals for the least impaired and most impaired days for 

each applicable Class I area. It is important to understand that a state’s long-term strategy is 

inextricably linked to the reasonable progress goals because the long-term strategy “must include 

enforceable emission limitations, compliance schedules, and other measures as necessary to 

achieve the reasonable progress goals established by states having mandatory Class I Federal 

areas.” 40 CFR 51.308(d)(3). As intended by the EPA and as understood by all states in the first 

implementation period, the four reasonable progress factors are considered by a state in setting 

the reasonable progress goal by virtue of the state having first considered them, and certain other 

factors listed in §51.308(d)(3) of the Regional Haze Rule, when deciding what controls are to be 

included in the long-term strategy. Then, the numerical levels of the reasonable progress goals 

are the predicted visibility outcome of implementing the long-term strategy in addition to 

ongoing pollution control programs stemming from other CAA requirements. To ensure 
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consistent understanding about the relationship between reasonable progress goals and the longterm strategy, we are proposing rule text changes to clarify this relationship in the “Proposed 

Rule Changes” section of this document (section IV.A). The proposed rule text is consistent with 

our long-held interpretation of the existing rule text as stated earlier.

15

In deciding on the long-term strategy and in setting the reasonable progress goals, states 

must also consider the rate of progress for the most impaired days that would be needed to reach 

natural visibility conditions by 2064 [referred to as the “uniform rate of progress” (URP)] and 

the emission reduction measures that would be needed to achieve that rate of progress over the 

approximately 10-year period of the SIP. Uniform progress towards achievement of natural

conditions by the year 2064 represents a rate of progress that states are to use for analytical 

comparison to the amount of progress they expect to achieve on average. The CAA has the goal 

of natural conditions, but does not have any date for achievement of that goal, requiring only that 

plans demonstrate reasonable progress towards it. The Regional Haze Rule reiterates the CAA 

goal, and provides for the use of an analytical framework that compares the rate of progress that 

will be achieved by a SIP (as represented by the reasonable progress goals for the end of the 

implementation period) to the rate of progress that if continued would result in natural conditions 

in 2064 (i.e., the URP). When a SIP contains a reasonable progress goal for the most impaired 

days that reflects progress that is equal to the URP, the reasonable progress goal is said to be “on 

the URP line” or “on the glidepath.” If a state’s reasonable progress goal for the most impaired 

days is not on the glidepath, §51.308(d)(1)(ii) requires the state to demonstrate that it would not 

 

15 The EPA’s interpretation of the proper relationship between a state’s reasonable progress goals 

and its long-term strategy is explained in detail in our proposed action on SIPs from Texas and 

Oklahoma. See section IV.C at 79 FR 74828. This interpretation was reaffirmed in our final 

action on these SIPs. See section II.B of 81 FR 296 (January 5, 2016).
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be reasonable to adopt a reasonable progress goal (and by implication a long-term strategy) that 

would be on the glidepath. The Regional Haze Rule does not establish an enforceable

requirement that natural conditions be reached in 2064. The EPA has approved a number of SIPs 

for the first implementation period that have projected that continued progress at the rate 

expected to be achieved during that first period would not result in natural conditions until a date 

after 2064.

In setting reasonable progress goals, each state with one or more Class I areas must also 

consult with potentially “contributing states,” i.e., other nearby states with emission sources that 

may be affecting visibility impairment in the state’s Class I areas. In such cases, the contributing 

state must demonstrate that it has included in its SIP all measures necessary to obtain its share of 

the emission reductions needed to meet the reasonable progress goals for the Class I area. 

Furthermore, section 169A(g)(1) of the CAA and §51.308(d)(1)(i)(A) of the Regional Haze Rule

require that states determine “reasonable progress” by considering the four statutory factors. 

Also, §51.308(d)(3) requires each state to consider its own Class I areas (if it has any) and 

downwind Class I areas (which may be affected by emissions from the state) when it develops its 

long-term strategy. In determining whether a state’s long-term strategy and reasonable progress 

goals provide for reasonable progress toward natural visibility conditions, the EPA is required to 

evaluate the demonstrations developed by the state. 40 CFR 51.308(d)(1). To ensure consistent 

understanding about the long-term strategy obligations of all states, we are proposing rule text 

changes to clarify these obligations in the “Proposed Rule Changes” section of this document 

(section IV.B). The proposed rule text is consistent with our long-held interpretation of the 

existing rule text as stated earlier.
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In accordance with the Regional Haze Rule, states should consider all types of

anthropogenic sources of visibility impairment in developing their long-term strategy, including 

major and minor stationary sources, mobile sources and area sources. At a minimum, states must 

describe how each of the following seven factors are taken into account in developing their longterm strategy: (1) Emission reductions due to ongoing air pollution control programs, including 

measures to address reasonably attributable visibility impairment; (2) measures to mitigate the 

impacts of construction activities; (3) emissions limitations and schedules for compliance to 

achieve the reasonable progress goal; (4) source retirement and replacement schedules; (5) 

smoke management techniques for agricultural and forestry management purposes including 

plans as currently exist within the state for these purposes; (6) enforceability of emissions 

limitations and control measures; and (7) 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. 40 CFR 51.308(d)(3)(v). We are not proposing any changes to the current requirements 

regarding these seven factors.

As discussed earlier, the current version of the Regional Haze Rule requires control 

strategies to cover an initial implementation period extending to the year 2018, with a

comprehensive reassessment and revision of those strategies, as appropriate, every 10 years 

thereafter. The reasonable progress goals are specific to the end date of a given implementation 

period. New reasonable progress goals for the end of the next period are established in the next 

periodic comprehensive SIP revision. We are proposing to extend, to July 31, 2021, the due date 

for the SIP revision that under the existing Regional Haze Rule is due July 31, 2018. This 

proposed change is discussed in the “Proposed Rule Changes” section of this document (section 

IV.J).
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Coordinating Regional Haze and Reasonably Attributable Visibility Impairment. The 

1999 Regional Haze Rule fulfilled the EPA’s responsibility to put in place a national regulatory 

program that addresses both reasonably attributable and regional haze visibility impairment. As 

part of the Regional Haze Rule, the EPA revised 40 CFR 51.306(c) regarding reasonably 

attributable visibility impairment assessment and planning to require that the reasonably 

attributable visibility impairment plan must continue to provide for a periodic review and SIP

revision not less frequently than every 3 years until the date of submission of the state’s first plan 

addressing regional haze visibility impairment, which was due December 17, 2007. On or before 

this date, the state must have revised its plan to provide for periodic review and revision of a 

coordinated long-term strategy for addressing reasonably attributable visibility impairment and 

regional haze, and the state must have submitted the first such coordinated long-term strategy

with its first regional haze SIP. Under the current version of the regulations, future coordinated 

long-term strategies, and periodic progress reports evaluating progress towards reasonable 

progress goals, must be submitted consistent with the schedule for SIP submission and periodic

progress reports set forth in 40 CFR 51.308(f) and 51.308(g), respectively. The periodic review 

of a state’s long-term strategy must report on both regional haze visibility impairment and

reasonably attributable visibility impairment and must be submitted to the EPA in the form of a 

periodic comprehensive SIP revision. Under our proposed changes to the reasonably attributable 

visibility impairment provisions, described in detail in section IV.G, this coordinated approach to 

a state’s long-term strategies for regional haze and reasonably attributable visibility impairment

would continue, but would apply only when the state is under an obligation to respond to a 

reasonably attributable visibility impairment certification.
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Monitoring Strategy and Other Implementation Plan Requirements. Section 51.308(d)(4) 

of the Regional Haze Rule includes the requirement for a monitoring strategy for measuring,

characterizing and reporting of regional haze visibility impairment that is representative of all 

mandatory Class I areas within the state. The strategy must be coordinated with the monitoring 

strategy required in the current version of §51.305 for reasonably attributable visibility 

impairment. Compliance with this requirement may be met through “participation” in the 

IMPROVE network.

16 A state’s participation in the IMPROVE network includes state support 

for the use of CAA state and tribal assistance grants funds to partially support the operation of 

the IMPROVE network as well as its review and use of monitoring data from the network. The

monitoring strategy was due with the first regional haze SIP, and under the current Regional 

Haze Rule it must be reviewed every 5 years as part of the progress reports. The monitoring 

strategy must also provide for additional monitoring sites if the IMPROVE network is not 

sufficient to determine whether reasonable progress goals will be met. To date, neither the EPA 

nor any state has concluded that the IMPROVE network is not sufficient in this way. The 

evolution of the IMPROVE network will be guided by a Steering Committee that has FLM, EPA 

and state participation, within the evolving context of available resources. It is the EPA’s 

objective that individual states will not be required to commit to providing monitoring sites 

beyond those planned to be operated by the IMPROVE program during the period covered by a 

SIP revision. The EPA also believes that if the IMPROVE program must discontinue a 

monitoring site, this would not be a basis for an approved regional haze SIP to be found

 

16 While compliance with §51.308(d)(4) for regional haze may be met through participation in 

the IMPROVE network, additional analysis or techniques beyond participation in IMPROVE 

may be required for compliance with §51.305 for reasonably attributable visibility impairment. 
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inadequate, but rather the state, the federal agencies and the IMPROVE Steering Committee 

should work together to address the Regional Haze Rule requirements when the next SIP 

revision is developed. As described in section IV.F, we are proposing that progress reports from 

individual states no longer be required to review and modify as necessary the state’s monitoring 

strategy. We believe the IMPROVE Steering Committee structure, the requirement to review the 

monitoring strategy as part of the periodic comprehensive SIP revision, and the requirement for a 

state to consider any recommendations from the EPA or a FLM for additional monitoring for 

purposes of reasonably attributable visibility impairment will be sufficient to achieve the 

objective of the current progress report requirement to review the monitoring strategy.

Consultation between States and FLMs. The Regional Haze Rule requires that states 

consult with FLMs before adopting and submitting their SIPs. 40 CFR 51.308(i). States must 

provide FLMs an opportunity for consultation, in person and at least 60 days prior to holding any

public hearing on the SIP. This consultation must include the opportunity for the FLMs to 

discuss their assessment of impairment of visibility in any Class I area and to offer

recommendations on the development of the reasonable progress goals and on the development

and implementation of strategies to address visibility impairment. Further, a state must include in 

its SIP a description of how it addressed any comments provided by the FLMs. Finally, a SIP 

must provide procedures for continuing consultation between the state and FLMs regarding the 

state’s visibility protection program, including development and review of SIP revisions, 

progress reports, and the implementation of other programs having the potential to contribute to

impairment of visibility in Class I areas. We are proposing to require that states also consult with 

FLMs earlier in the development of their SIPs, as described in section IV.I.

4. Requirements for the Regional Haze Progress Reports
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The current version of the Regional Haze Rule includes provisions for progress reports to 

be submitted at 5-year intervals, counting from the submission of the first required SIP revision 

by the particular state. The requirements for these reports are included for most states in 40 CFR 

51.308 (g) and (h). Three western states (New Mexico, Utah and Wyoming) exercised an option 

provided in the Regional Haze Rule to meet alternative requirements contained in 40 CFR 

51.309 for their SIPs. For these three states, the requirements for the content of the 5-year 

progress reports are identical to those for the other states, but for these states the requirements for 

the reports are codified in 40 CFR 51.309(d)(10). This section specifies fixed due dates in 2013 

and 2018 for these progress reports. Regardless, the current Regional Haze Rule provides that

these three states will revert to the progress report requirements in 40 CFR 51.308 after the 

report currently due in 2018.

An explanation of the 5-year progress reports is provided in the preamble to the 1999 

Regional Haze Rule. 64 FR 35747 (July 1, 1999). This 5-year review is intended to provide an 

interim report on the implementation of, and, if necessary, mid-course corrections to, the 

regional haze SIP, which, as noted earlier, is prepared in 10-year increments. The progress report 

provides an opportunity for public input on the state’s (and the EPA’s) assessment of whether the 

approved regional haze SIP is being implemented appropriately and whether reasonable visibility 

progress is being achieved consistent with the projected visibility improvement in the SIP.

Required elements of the progress report include: the status of implementation of all 

measures included in the regional haze SIP; a summary of the emissions reductions achieved 

throughout the state; an assessment of current visibility conditions and the change in visibility 

impairment over the past 5 years; an analysis tracking the change over the past 5 years in 

emissions of pollutants contributing to visibility impairment from all sources and activities 
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within the state; an assessment of any significant changes in anthropogenic emissions within or 

outside the state that have occurred over the past 5 years that have limited or impeded progress in 

reducing pollutant emissions and improving visibility; an assessment of whether the current SIP 

elements and strategies are sufficient to enable the state (or other states with mandatory Class I 

areas affected by emissions from the state) to meet all established reasonable progress goals; a

review of the state's visibility monitoring strategy and any modifications to the strategy as 

necessary; and a determination of the adequacy of the existing SIP (including taking one of four 

possible actions).

17 We are proposing a number of clarifications and changes to the requirements 

for the content of progress reports, as described in section IV.F.

In accordance with 40 CFR 51.308(g) and 51.309(d)(10), progress reports must currently 

take the form of SIP revisions, so states must follow formal administrative procedures (including 

public review and opportunity for a public hearing) before formally submitting the 5-year 

progress report to the EPA. See 40 CFR 51.102, 40 CFR 51.103, and Appendix V to Part 51 –

Criteria for Determining the Completeness of Plan Submissions. We are proposing to remove the 

requirement that progress reports be submitted as SIP revisions, as described in section IV.L.

In addition, as with SIPs, states are required to provide FLMs with an opportunity for inperson consultation at least 60 days prior to any public hearing on an implementation plan or 

plan revision, which must include an opportunity for FLMs to discuss their assessment of 

impairment of visibility in any mandatory Class I area, and discuss their recommendations on the 

 

17 40 CFR 51.308(g). See also 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, EPA–

454/B–03–005, available at http://www.4cleanair.org/Documents/haze_5year_4-10-13.pdf, 

(hereinafter referred to as “our 2013 Progress Report Guidance”).
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development of reasonable progress goals and the development of implementation strategies to 

address visibility impairment. See 40 CFR 51.308(i)(2) and (3). Procedures must also be 

provided for continuing consultation between the state and FLM regarding development and 

review of progress reports. See 40 CFR 51.308(i)(4). We are proposing to preserve the existing 

requirement for consultation with FLMs on progress reports.

The first progress reports are currently due 5 years from the initial SIP submittal (with the 

next progress reports for New Mexico, Utah, and Wyoming due in 2018). Most of these 

deadlines have already passed although some are due in 2016 and in 2017. We are proposing a 

set of common due dates for future progress reports from all states, as described in section IV.K.

5. Tribes and Regional Haze

Tribes have a distinct interest in regional haze due to the effects of visibility impairment 

on tribal lands as well as on other lands of high value to tribal members, such as landmarks 

considered sacred. Tribes, therefore, have a strong interest in emission control measures that

states and the EPA incorporate into SIPs and FIPs with regard to regional haze, and also have an 

interest in the state response to any reasonably attributable visibility impairment certification

made by an FLM.

The EPA takes seriously our Federal Indian trust responsibility and the government-togovernment relationship with tribes.18 The agency has a tribal consultation policy that covers any 

plan that the EPA would promulgate that may affect tribal interests. This consultation policy 

 

18 Like the EPA, the Department of the Interior and the U.S. Forest Service in the U.S. 

Department of Agriculture have strong tribal consultation policies. See:

http://www.epa.gov/tribal/consultation/index.htm; 

http://www.fs.fed.us/spf/tribalrelations/authorities.shtml, and 

https://www.doi.gov/tribes/Tribal-Consultation-Policy.
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applies to situations where a potentially affected source is located on tribal land, as well as 

situations where a SIP or FIP concerns a source that is located on state land and may affect tribal 

land or other lands that involve tribal interests. In addition, the EPA has and will continue to

consider any tribal comments on any proposed action on a SIP or FIP. 

In the first implementation period for regional haze SIPs, the partnerships within the 

RPOs included strong relationships between the states and the tribes, and the EPA encourages 

states to continue to invest in those relationships (including consulting with tribes), particularly 

with respect to tribes located near Class I areas. States should continue working directly with 

tribes on their SIPs and their response to any reasonably attributable visibility impairment

certification made by an FLM. The EPA believes that it is preferable for states to address tribal 

concerns during their planning process rather than the EPA addressing such concerns in its 

subsequent rulemaking process. During the development of this rulemaking, the EPA was asked 

by the National Tribal Air Association to adopt a requirement that states formally consult with 

tribes during the development of their regional haze SIPs. While we recognize the value of 

dialog between state and tribal representatives, we are not proposing to require it. We note that 

the CAA does not explicitly authorize the EPA to impose such a requirement on the states. 

C. Air Permitting

One part of the visibility protection program, 40 CFR §51.307, New Source Review , was 

created in 1980 with the rationale that while most new sources that may impair visibility were 

already subject to review under the Prevention of Significant Deterioration (PSD) provisions 

(Part C of Title I of the CAA), additional regulations would “ensure that certain sources exempt 

from the PSD regulations because of geographic criteria will be adequately reviewed for their 

potential impact on visibility in the mandatory Class I Federal area.” 45 FR 80084 (December 2, 
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1980). The EPA explained at proposal that this was necessary because the PSD regulations did 

not call for the review of major emitting facilities (or major modifications) located in 

nonattainment areas,

19 and that it was appropriate to “clarify certain procedural relationships 

between the FLM and the state in the review of new source impacts on visibility in Federal class 

I areas.” 45 FR 34765 (May 22, 1980). The EPA envisioned that state and FLM consultation 

would commence with the state notifying the FLM of a potential new source, and that 

consultation would continue throughout the permitting process. We are proposing to revise 

§51.307 only as needed to maintain consistency with revisions to other sections of 40 CFR part 

50 subpart P.

IV. Proposed Rule Changes

The changes being proposed by the EPA will continue steady environmental progress in 

the regional haze program while streamlining its administrative aspects that do not add to 

environmental protection. The EPA has gained a substantial amount of knowledge through the 

process of approving SIPs for the first regional haze implementation period and has learned what 

aspects of the program work well and what aspects should be modified going forward. Feedback 

received from co-regulators during this process has been invaluable in developing this proposal, 

 

19 In 1978, PSD rules were put in place that required permitting agencies to interact with FLMs 

and for air quality related values (AQRVs) to be taken into consideration in the PSD permitting 

process. 43 FR 26380 (June 19, 1978). Those PSD rules did not cover sources in nonattainment 

areas, and while there were EPA rules for nonattainment new source review in existence, they 

did not require consideration of Class I areas. In 1979, 40 CFR part 51, appendix S established 

rules for nonattainment permitting, but they did not (and still do not) require consideration of 

visibility or FLM notification. (The same is also true of a more recent addition, 40 CFR 51.165. 

Where applicable to nonattainment areas, this rule does not require Class I reviews. While 40 

CFR 51.165(b) requires that sources located in attainment areas cannot cause or contribute to a 

NAAQS violation anywhere, this does not cover AQRVs in Class I areas.) As a result, in 1980, 

the EPA added requirements to 40 CFR 51.307 for notification of FLMs of pending permits for 

new sources in nonattainment areas.
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which seeks to reduce administrative burdens of the regional haze program without sacrificing 

environmental protection. Indeed, the EPA believes that reducing administrative burdens will 

result in a more effective program in terms of achieving the goal of improved visibility.

A. Clarifications to Reflect the EPA’s Long-Standing Interpretation of the Relationship Between 

Long-Term Strategies and Reasonable Progress Goals.

The EPA is proposing to amend §51.308(f) of the Regional Haze Rule, which contains 

the requirements for comprehensive periodic revisions to regional haze SIPs, by adding new 

provisions that will govern the development of long-term strategies and reasonable progress 

goals in future implementation periods. The proposed provisions are consistent with the EPA’s 

long-standing interpretation20 of the existing regulations at §51.308(d), but are organized in a 

more logical fashion. While the new provisions track the language of the existing regulations at 

§51.308(d) in many respects, the EPA also has proposed changes in certain places to eliminate 

ambiguities created by the existing language and to conform with substantive changes being 

proposed elsewhere in this rulemaking. In this section, we discuss only those changes that are 

intended to provide clarity regarding the relationship between long-term strategies and 

reasonable progress goals. Unlike some of the provisions discussed in subsequent sections of this 

preamble, the changes discussed in this section do not create new requirements for states.

 

20 The EPA’s interpretation of the proper relationship between a state’s reasonable progress goals 

and its long-term strategy in explained in detail in our proposed action on SIPs from Texas and 

Oklahoma. See section IV.C at 79 FR 74828. This interpretation was reaffirmed in our final 

action on these SIPs. See section II.B of [add citation to the final rule for federal implementation 

plans for Texas and Oklahoma, once published. This FR notice currently can be viewed at 

http://www.epa.gov/sites/production/files/2015-12/documents/tx-ok-rh-sip-final-disapprovaland-fip_disclaimer_signed_.pdf.]
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Section 51.308(d) of the existing Regional Haze Rule is organized into four subsections: 

(d)(1), concerning the calculation of reasonable progress goals; (d)(2), concerning the calculation 

of baseline and natural visibility conditions; (d)(3), concerning the development of long-term 

strategies; and (d)(4), concerning the development of monitoring strategies. This organizational 

structure does not reflect the actual sequence of steps in the regional haze planning process. For 

example, §51.308(d) lists the requirements for reasonable progress goals before the requirements 

for long-term strategies. In practice, states must evaluate the four statutory factors to select 

emission control measures for their long-term strategies before they can calculate their 

reasonable progress goals by modeling the visibility improvement that will result from the 

implementation of those controls. 

To address this issue and provide clarity to states and other stakeholders, the EPA is 

proposing to organize the requirements in §51.308(f) in a more logical fashion. First, proposed 

subsection (f)(1) provides the requirements governing the calculation of baseline and natural 

visibility conditions, which are necessary to calculate the URP. A state should calculate current 

visibility conditions, the URP and the URP line first. In doing so, the contributions of PM 

species to current anthropogenic light extinction (referred to as the anthropogenic light extinction 

budget) will become evident, which will inform the state’s thinking as to which sources or source 

categories should be evaluated for potential reasonable progress control measures. Second, 

proposed subsection (f)(2) provides the requirements governing the development of long-term 

strategies. In this step, states must, among other things, evaluate sources that impact visibility at 

one or more Class I areas for potential control measures by considering the four statutory factors. 

Third, proposed subsection (f)(3) provides the requirements governing the calculation of 

reasonable progress goals. Once a state has established emission limitations and other control 
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measures as part of its long-term strategy, the state will have the information necessary to model 

the visibility improvement that will result at each Class I area on the 20 percent most impaired 

days and 20 percent clearest days after the long-term strategy has been implemented. The 

projected visibility conditions at the end of the applicable implementation period constitute the 

reasonable progress goals. States must then compare the goals for the Class I area to the URP. If 

the goal for the 20 percent most impaired days is above the URP line the state must demonstrate 

that there are no additional control measures for sources reasonably anticipated to contribute to 

visibility impairment in the Class I area that are reasonable to include in the long-term strategy. 

(Note this language is intended to be more helpful than the language in the comparable provision 

in §51.308(d)(1)(ii).) Finally, proposed subsection (f)(4) provides the requirements governing 

monitoring strategies, which must be sufficient to allow states to assess the adequacy of their 

long-term strategies going forward.

In addition to these organizational changes, the EPA is proposing new language in 

§51.308(f)(2) that differs from the existing language in §51.308(d)(3), but is intended to achieve 

the same result. First, the EPA is proposing language in §51.308(f)(2)(i) and (iv) to clarify that 

all states, not just those with Class I areas, must consider the four statutory factors and properly 

document all cost, visibility and other technical analyses when developing their long-term 

strategies. Second, the EPA is proposing language in §51.308(f)(2)(ii) to require that states must 

consider the URP and the measures that contributing states are including in their long-term 

strategies when determining whether the state’s own long-term strategy is sufficient to ensure 
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reasonable progress.21 Finally, the EPA is proposing language in §51.308(f)(2)(iii) to clarify the 

respective obligations of “contributing states” and “states affected by contributing states,” during

interstate consultation. As is the case under the existing rule text, the EPA will evaluate the 

sufficiency of the record developed by each state, the state’s conclusions, and any disagreements 

among states to determine whether the state has used reasoned decisionmaking in choosing a set 

of a control measures that will achieve reasonable progress at the Class I areas impacted by the 

state’s sources. 

B. Other Clarifications and Changes to Requirements for Periodic Comprehensive Revisions of 

Implementation Plans

The following clarifications and changes are also proposed to be included in the revised 

§51.308(f).

The URP line starts at 2000-2004, for every implementation period. The current text of 

§51.308(d)(1)(i)(B) contains a discussion of how states must analyze and determine “the rate of 

progress needed to attain natural visibility conditions by the year 2064.” While not actually used 

within the current rule text, the term that has been commonly used to describe this rate is the

“uniform rate of progress” or URP. The current text of §51.308(f) indicates that states must 

evaluate and reassess all elements required by §51.308(d), and hence the URP, in the second and 

subsequent implementation periods. Section 51.308(d) is not perfectly clear about whether “the 

rate of progress needed to attain natural visibility conditions by the year 2064” is meant to refer 

to needed progress measured from visibility conditions in the baseline period of 2000-2004, or 

 

21 The EPA views this as a clarification of the requirement that states with sources affecting a 

given Class I area consult on the content of their long-term strategies. Such consultation would 

be pointless if each state were not meant to consider the other states’ planned emission control 

measures.
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further needed progress measured from “current” visibility conditions (i.e., the visibility 

conditions during a 5-year period ending shortly before SIP submission). In other words, the 

section is not perfectly clear as to whether the glidepath or URP line that applies to the SIP for 

the second or a later implementation period always starts in the baseline period of 2000-2004, or 

in the most recent 5-year period. It is clear that the glidepath or URP line then reaches natural 

visibility conditions in “2064,” but no exact date in 2064 is specified.

To ensure consistent understanding, the EPA is proposing rule revisions to state explicitly 

that in every implementation period, the glidepath or URP line for each Class I area is drawn 

starting on December 31, 2004, at the value of the 2000-2004 baseline visibility conditions for 

the 20 percent most impaired days, and ending at the value of natural visibility conditions on 

December 31, 2064. In this way, it is clear that for a Class I area that has achieved more than the 

URP in the first implementation period, the state can take that into account in its URP analysis 

for the second implementation period. Specifying that the 5-year average baseline visibility 

conditions are associated with the date of December 31, 2004 and that natural visibility 

conditions are associated with the date of December 31, 2064 also clarifies that the period of 

time between the baseline period and natural visibility conditions, which is needed for 

determining the URP (deciviews/year) is 60 years.

Note that because of updates to the IMPROVE program, some data values from 2000-

2004 may be revised over time.22 Therefore, the value of the starting point for the URP (i.e., 

baseline visibility conditions) should be re-calculated for purposes of accuracy of analysis in any 

 

22 IMPROVE data from the 2000-2005 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 made in order to maintain consistency in reported results across the years.
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given periodic comprehensive SIP revision. In addition, the value of the baseline visibility 

conditions must be recalculated to be consistent with the approach used for the selection of the 

most impaired days in the SIP revision under preparation (see section IV.C of this document).

As part of this clarification and to maintain consistency in the reasonable progress goal

framework, the proposed language in §51.308(f)(3)(i) (and an accompanying definition of “end 

of the applicable implementation period” added to §51.301) would make clear that reasonable 

progress goals are to address the period extending to the end of the year of the due date of the 

next periodic comprehensive SIP revision. Also, proposed §51.308(f)(1)(iv) specifies the end day 

of 2064 as the ending point of the glidepath or URP line.

Analytical Obligation When the Reasonable Progress Goal for the 20 Percent Most 

Impaired Days Is Not On or Below the URP Line. The EPA is proposing to clarify how the

comparison of the reasonable progress goal for the 20 percent most impaired days to the rate of 

visibility improvement needed to attain natural conditions by 2064 (i.e., the glidepath or URP

line) determines the content of the demonstration the state must submit to show that its long-term 

strategy provides for reasonable progress. This clarification appears in the proposed

§51.308(f)(3)(ii).

The current text of §51.308(d)(1)(ii) discusses required actions of the state containing the 

Class I area should it set a reasonable progress goal that provides for a slower rate of visibility 

improvement than that needed to attain natural conditions by 2064 (i.e., a reasonable progress 

goal for the 20 percent most impaired days that is above the URP line). This section provides that 

in this situation, the state must demonstrate, based on the four reasonable progress factors, that 

the rate of progress for the implementation plan to attain natural conditions by 2064 is not 

reasonable, and that the progress goal adopted by the state is reasonable. To clarify how a state 
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must show that being on the URP line is not reasonable in its SIP for the second and subsequent 

regional haze implementation periods, the EPA is proposing that if the reasonable progress goal

is above the URP line, the state must demonstrate, based on the four reasonable progress factors, 

that there are no additional emission reduction measures for any source or group of sources that 

are reasonably anticipated to contribute to visibility impairment that would be reasonable to 

include in the long-term strategy.

In existing sections 51.308(d)(2)(iv) and 51.308(d)(3)(i) and (ii), sentences addressing 

obligations of the state with the Class I area and obligations of the contributing state(s) are 

juxtaposed in such a way that it can be confusing for a reader to understand which of the two 

states is being referred each time the word “state” appears. The proposed §51.308(f)(2)(iii) more 

clearly spells out the respective consultation responsibilities of states containing Class I areas as 

well as states with sources that may reasonably be anticipated to cause or contribute to visibility 

impairment in those areas.

To clarify and solidify the obligations of what we are referring to as contributing states, 

§51.308(f)(3)(ii)(B) is proposed to specify that in situations where reasonable progress goals are 

set above the glidepath, a contributing state must make the same demonstration with respect to 

its own long-term strategy that is required of the state containing the Class I area, namely that 

there are no other measures needed to provide for reasonable progress. This provision will ensure 

that states perform rigorous analyses, and adopt measures necessary for reasonable progress, 

with respect to Class I areas that their sources contribute to, regardless of whether such areas are 

physically located within their borders.

Emission inventories. The proposed language of §51.308(f)(2)(iv) regarding the baseline 

emissions inventory to use in developing the technical basis for the state’s long-term strategy
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would reconcile this section with changes that have occurred to 40 CFR part 51, subpart A, Air 

Emissions Reporting Requirements, since the Regional Haze Rule was originally promulgated in 

1999. The proposed changes also would provide flexibility in the base inventory year the state 

chooses to use, as the EPA has always intended if there is good reason to use another inventory 

year.

EPA action on reasonable progress goals. Proposed language in §51.308(f)(3)(iv) would 

make clear that in approving a state’s reasonable progress goals, the EPA will consider the 

controls and technical demonstration provided by a contributing state with respect to its longterm strategy, in addition to those developed by the state containing the Class I area with respect 

to its long-term strategy. This section is a clarification of §51.308(d)(1)(iii), which only 

explicitly mentions the demonstration provided by the state containing the Class I area.

Progress reports. Finally, proposed language in §51.308(f)(5) complements proposed 

changes regarding progress reports and the proposal to eliminate separate progress reports being 

due simultaneously with periodic comprehensive SIP revisions. This language would require the 

periodic comprehensive SIP revision to include certain items of information that would have 

been addressed in the progress report, thereby expanding its scope somewhat. While the state 

would no longer need to prepare and submit two separate documents at the same time (the 

periodic comprehensive SIP revision and a progress report), the same information would still be 

covered. Combining requirements in this way will avoid the overlap in content that would occur 

with two separate documents.

C. Changes to Definitions and Terminology Related to How Days Are Selected for Tracking 

Progress
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Section 51.308(d) of the existing Regional Haze Rule requires states to determine the 

visibility conditions (in deciviews) for the average of the 20 percent least impaired and 20 

percent most impaired visibility days over a specified time period at each of their Class I areas. 

Section 51.301 of the Regional Haze Rule defines visibility impairment as the humanly 

perceptible change in visibility from that which would have existed under natural conditions.

This definition of visibility impairment suggests that only visibility impacts from anthropogenic 

sources should be included when considering the degree of visibility impairment. However, the 

preamble to the 1999 final rule stated that the least and most impaired days were to be selected as

the monitored days with the lowest and highest actual deciview levels, respectively. 64 FR 35728 

(July 1, 1999). The interpretation in the preamble was subsequently reflected in the EPA 

guidance on setting reasonable progress goals and tracking progress. In practice, in their SIPs for 

the first implementation period states followed the approach described in the 1999 preamble and 

the subsequent guidance, and the EPA approved the SIPs with respect to that aspect. However, as 

described later, experience now indicates that for the most impaired days an approach focusing 

on anthropogenic impairment in particular is more appropriate going forward. We are not 

proposing to change the approach of using the 20 percent of days with the best visibility to 

represent good visibility conditions for reasonable progress goal and tracking purposes, but we 

are proposing text changes to accurately describe how those days are to be selected. These days 

would be referred to as the 20 percent clearest days.

Natural contributions to the total actual deciview levels vary from year to year. In order 

to minimize interannual variability, the Regional Haze Rule uses 5-year averages for determining 

the baseline and current visibility conditions. Also, under the EPA’s modeling guidance for 

regional haze SIPs, reasonable progress goals are projected starting from the average of visibility 
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conditions in a 5-year period that is centered around (or at least includes) the year of the base 

emission inventory used in the air quality modeling process. Now that many visibility monitoring 

sites have at least 15 years of data, it is clear that in some locations 5-year averages are not long 

enough to dampen the visibility impacts of occasional extreme fire years. In their SIPs and SIP 

revisions for the first implementation period, some states explained that the 20 percent most 

impaired days in certain Class I areas can be dominated by uncontrollable visibility impacts. 

Many states, particularly western states, have urged the EPA to make rule changes that would 

allow them to track visibility progress in Class I areas using a method that is more closely linked 

with visibility impacts from controllable emissions.

To help states minimize the impacts of uncontrollable emissions on visibility tracking, 

the EPA proposes to more explicitly (and consistently) address this issue for future 

implementation periods. In general, the proposed changes related to the selection of days for 

visibility tracking are intended to accomplish the following for future implementation periods: 

(1) clarify that “visibility impairment” means the deviation from natural visibility and therefore 

is due to anthropogenic impacts, (2) revise definitions in §51.301 to make clear that the 20

percent most impaired days should be selected based on anthropogenic visibility impairment 

rather than based on the days with highest deciview values due to impacts from all types of 

sources, and (3) continue to use the 20 percent of days with the lowest total deciviews (i.e., 

“clearest days”) rather than the 20 percent least impaired days for purposes of tracking any 

adverse trend in visibility on clear days.

The definitions in §51.301 for several terms and phrases related to the selection of days 

for visibility tracking have been clarified in the proposed revisions of the rule text. Definitions 
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that are proposed to be changed slightly to provide more clear explanations of their meanings 

include the following: deciview, most impaired days, and visibility impairment.

Additionally, we propose definitions for the following previously undefined terms be 

included in §51.301: clearest days, the deciview index (the term was deciview haze index in the 

1999 Regional Haze Rule), natural visibility conditions and visibility. We propose the addition of 

the term clearest days to unambiguously describe the days with the lowest actual deciview 

values, for which there is to be no degradation in visibility. We propose changing the deciview 

haze index to the deciview index to remove the word haze, since the deciview index can be used 

for visibility impairment as well as for the total effect of all sources.

23 Visibility was previously 

undefined although used in the definitions of several other important terms, and so we have 

added a proposed definition to describe that visibility is the change in optical clarity when 

viewing objects at a distance. We also propose adding a definition for natural visibility 

conditions to clarify that natural visibility conditions cannot be measured and must be inferred or 

estimated, and to distinguish the visibility conditions that occur due to natural conditions from 

natural conditions themselves such as humidity, emissions from natural sources, etc.

Given the current Regional Haze Rule’s definitions of most impaired days and visibility 

impairment, the regulations could be read to direct states and the EPA to use the days with the 

most perceptible anthropogenic impairment as the 20 percent most impaired days. The proposed 

changes to these definitions in §51.301 do not change this direction. The EPA solicits comments 

on a first proposal, fully reflected in the proposed rule text, which would require that states select 

 

23 We note that the very definition of “regional haze” refers to “impairment,” making it 

confusing to use “haze” to refer to the actual level or degree of visibility considering the effects 

of both natural and anthropogenic sources. Our proposed edits are aimed at avoiding any 

inconsistent use of the term “haze.”
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the 20 percent most impaired days based on anthropogenic impairment, rather than based on the 

highest deciview values due to all sources affecting visibility. If this approach is finalized, states 

would still have the option to also present the visibility data using the current approach based on 

the days with the highest overall deciview index values. Including this information in the SIP 

may help communicate to the public the magnitude of impacts from natural sources including 

wildfires and dust storms, and thus the utility of the change in approach. Under this first 

proposal, the reasonable progress goals and URP line that are calculated using anthropogenic 

impairment to select the most impaired days will be the glidepath that is used to trigger the 

requirement for a state to show that it is not reasonable for the SIP to provide for the rate of 

progress that would be needed to reach natural visibility conditions in 2064 (see section IV.B of 

this document).

The EPA seeks comment also on a second, alternative proposal under which the final rule

would allow each state with a Class I area to choose between using the revised approach 

described earlier (using the 20 percent most anthropogenically impaired days) and using the 20

percent haziest days (whether dominated by natural or anthropogenic impacts) to track visibility

as all states with Class I areas did in the first regional haze SIPs. (This alternative approach is not 

laid out in proposed rule text revisions, but only minor edits would be required to implement it in 

the final rule.) If the final rule takes this approach, states would still have the option to also 

present the visibility data using the other approach. The EPA will consider comments received 

on these two options or additional options offered by commenters.

If the 20 percent most anthropogenically impaired days are used to estimate natural 

visibility conditions, current visibility conditions and the uniform rate of progress, they must also 

be used in setting reasonable progress goals and in progress reports. Conforming edits are being 
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proposed to the provisions related to each of these, for that purpose. If the final rule requires the 

revised approach described earlier in the first proposal, it would apply starting with the second 

and subsequent periodic comprehensive SIP revisions and then to progress reports submitted 

after the second SIP revision. There would be no change with respect to the EPA action on SIP 

revisions for the first implementation period.

In order to select the 20 percent most impaired days based on the days with the most 

anthropogenic impairment, natural contributions to daily deciview values must be estimated by 

some method. This in turn requires measured concentration values for PM components to be 

allocated to natural versus anthropogenic sources. The EPA is not proposing that any particular

method for determining natural contributions to daily haze and thus the degree of visibility 

impairment for each monitored day be codified in the rule text. The EPA plans to issue guidance 

describing a recommended approach along with a process for routinely providing relevant 

datasets for use by states when they develop their SIPs and progress reports. Because no 

particular method would be prescribed by rule, states could develop, justify and use another 

method in their SIPs, if the final rule requires (or allows) the 20 percent most impaired days 

based on anthropogenic impairment to be used.

D. Impacts on Visibility from Anthropogenic Sources Outside the U.S.

The EPA acknowledges that emissions (natural and anthropogenic) from other countries 

(and from marine vessel activity in non-U.S. waters) may impact Class I areas, especially those 

areas near borders and coastlines. We have had requests from states with such Class I areas that 

given these emissions are beyond states’ control, the states should be allowed to account for 

international impacts when preparing SIPs and progress reports. For example, states have 

requested that they be allowed to consider impacts from international emissions when comparing 
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their reasonable progress goals to the URP line. This comparison matters because (as described 

in section IV.C) it may trigger an additional analytical requirement by the state. Impacts from 

international emissions can also affect whether a progress report will conclude that actual 

visibility conditions are approaching the reasonable progress goals for the end of the 

implementation period. It has been suggested to the EPA that estimated impacts from 

international emissions might be added to the 2064 end point of the URP line. It has also been 

suggested that estimated impacts from international emissions be subtracted from baseline and 

current visibility conditions.

On this issue, we first wish to clarify that it has never been the intention of the EPA that 

states be obligated to in any way compensate for haze impacts from international emissions by 

adopting more stringent emission controls on their own sources. We also wish to note that 

impacts from natural sources in other countries should be considered part of natural visibility 

conditions. States have the flexibility under the Regional Haze Rule to justify and use values for 

natural visibility conditions that include such effects. We believe the proposed changes regarding 

which days in a year are used for tracking progress (see section IV.D), when supplemented by 

our planned guidance on this topic, will adequately address international impacts related to 

significant wildfires in Canada and Mexico and dust storms in Mexico (and perhaps also dust 

storms in northern Africa). 

The EPA has further considered possible approaches regarding the impacts from 

anthropogenic sources in other countries. It is the role of the federal government, much more 

than of the states, to work with other countries to make such reasonable progress. The EPA is, in 

fact, actively engaged with other countries to help them reduce their anthropogenic emissions, 
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particularly emissions in Mexico from sources near the U.S.-Mexico border. See

http://www2.epa.gov/border2020.

We believe that it may be appropriate to allow states to adjust the reasonable progress 

goal framework, including their progress reports, to explicitly take into account international 

impacts from anthropogenic sources, but only when and if these impacts can be estimated with 

sufficient accuracy. We do not believe that explicit consideration of impacts from anthropogenic 

sources outside the U.S. would actually affect the conclusions that states should make about what 

emission controls for their own sources are needed for reasonable progress. Even so, explicit 

quantification of international impacts, if accrurate, could improve public understanding and 

effective participation in the development of regional haze SIPs. Also, taking international 

impacts into account in some cases may affect whether a state (and contributing states) are 

subject to the requirement of proposed §51.308(f)(3)(ii) regarding a demonstration that there are 

not additional emission reduction measures needed for reasonable progress. However, we are not 

convinced that such impacts can be estimated with sufficient accuracy at this time, in part due to 

great uncertainty about past, present and future emissions from sources in most other countries. 

However, it may be that by the time some future periodic comprehensive SIP revisions are to be 

prepared, for some states possibly as early as when they are preparing their second SIP, methods 

and data for estimating international impacts will be substantially more robust.

Therefore, the EPA is requesting comment on whether the final rule should contain a 

provision that would allow states with Class I areas (and those states with sources contributing to 

Class I areas) significantly impacted by international emissions to incorporate this information 
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into the reasonable progress goal framework for their regional haze SIPs.24 We believe that this 

should be permitted only if the international impacts have been estimated with methods and data 

approved by the Administrator as sufficiently reliable for that purpose and if the exact manner in 

which the information is incorporated into the reasonable progress goal framework is logical and 

consistent with the purposes of the CAA and the Regional Haze Rule. We are not proposing 

specific rule text for this purpose. We welcome suggestions for specific rule text as well as 

comments in general support or opposition to this concept.

E. Clarification of and Changes to the Required Content of Progress Reports

The EPA believes that additional amendments to §51.308(g) are appropriate at this time 

in order to clarify the substance of the regional haze progress reports. In its current form, there is 

ambiguity in this section with respect to the period to be used for calculating current visibility 

conditions, as well as ambiguity with respect to whether forward-looking, quantitative modeling 

is required in the progress reports to assess whether reasonable progress goals will be met. The 

EPA wishes to clarify both of these and other issues, and so proposes to amend §51.308(g) in the 

following ways. The EPA seeks comment on these proposed amendments as well as alternative 

approaches.

Section 51.308(g)(3)(ii) is proposed to be amended by adding a number of explanatory 

sentences to better indicate what “current visibility conditions” are and how to calculate them. 

 

24 This information in concept might be incorporated into the reasonable progress goal

framework in two ways, and possibly other ways also, if valid methods for doing so were 

available. IMPROVE monitoring data could be adjusted to remove the influence of non-U.S. 

anthropogenic emissions and projected goals could also exclude such influence. Or, the 2064 end 

point of the URP line could be increased by the estimated amount of this influence. At this time, 

the EPA is not proposing a specific approach to incorporation of this information, but rather is 

seeking comment on including in the final rule a provision that would allow the Administrator to 

approve a state’s proposed approach to such incorporation on a case-by-case basis.
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Under the current version of the rule, it is not clear what “current visibility conditions” are, in 

part because the term is not defined in §51.301. Although §51.308(g)(3) makes reference to 5-

year averages of annual values for most impaired and least impaired days, and §51.308(g)(3)(i) 

requires states to assess current visibility conditions for the most impaired and least impaired 

days, there is no clear indication as to which 5-year average the state should and can practicably 

use in a progress report for the current visibility conditions calculation. For example, the “current 

conditions” terminology does not explicitly allow for the time delay needed for the IMPROVE 

network manager to get quality assured data into its database so they are accessible to the states 

preparing progress reports.Practicality requires that “current conditions” should mean 

“conditions for the most recent period of available data.”25 There is also an issue of whether this 

availability is to be determined based on the start of work on the progress report, the due date for 

the progress report, or the actual submission date of the progress report. The proposed text makes 

clear that the period for calculating current visibility conditions is 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. Because we are also proposing that progress reports no longer be 

submitted as SIP revisions, meaning that there would be a much simpler and expeditious state 

administrative process to submit a progress report once technical work on it is completed, we 

 

25 In our guidance on the preparation of progress reports, the EPA has indicated that for “current 

visibility conditions,” the reports should include the 5-year average that includes the most recent 

quality assured public data available at the time the state submits its 5-year progress report for 

public review. See section II.C of General Principles for the 5-Year Regional Haze Progress 

Reports for the Initial Regional Haze State Implementation Plans, April 2013.
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believe that this 6-month period would be sufficient for states to incorporate the most recent 

available data into their progress reports.26

Section 51.308(g)(3)(iii), as currently written, requires a progress report to contain the 

value of the change in visibility impairment for the most and least impaired days over the past 5 

years. This text fails to make clear what the “past 5 years” are for assessing the change in 

visibility impairment. Because of data reporting delays, the period covered by available 

monitoring data will not line up with the periods defined by the submission dates for progress 

reports. Moreover, it is important to ensure that each year of visibility information is included 

either in a periodic comprehensive SIP revision or the progress report that follows it. Therefore, 

the “past 5 years” text is proposed to be deleted and replaced with text indicating the change in 

visibility impairment is to be assessed over the period since the period addressed in the most 

recent periodic comprehensive SIP revision. 

The same change to existing “past 5 years” text is proposed to be made to the first 

sentence of §51.308(g)(4) for the purposes of reporting changes in emissions of pollutants 

contributing to visibility impairment, for similar reasons. Like monitoring trend summaries, 

available emissions trend summaries will not line up with the periods defined by the submission 

dates of progress reports. Therefore, the proposed language removes the “past 5 years” text and 

replaces it with text indicating the change in emissions of pollutants contributing to visibility 

impairment is to be assessed over the period since the period addressed in the most recent 

periodic comprehensive SIP revision. 

 

26 Note that we are not proposing this specification of 6 months for the progress report aspects of 

a periodic comprehensive SIP revision (see section IV.C), in light of the longer time needed for 

administrative steps between completion of technical work and submission to the EPA.
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The final sentence of §51.308(g)(4) is proposed to be modified to revise and clarify the 

obligation of states regarding emissions inventories. The current rule text directs the analysis be 

based on the “most recent updated emissions inventory,” with emissions estimates “projected 

forward as necessary and appropriate to account for emissions changes during the applicable 5-

year period.” States are otherwise required by 40 CFR part 51, subpart A (Air Emissions 

Reporting Requirements) to prepare complete emission inventories only for every third calendar 

year (2011, 2014, etc.) and to submit these inventories to the EPA’s National Emissions 

Inventory (NEI). (After aggregating and quality assuring these submissions, the EPA then 

publicly provides summaries of the inventories that have been submitted.) The current text of 

§51.308(g)(4) seemingly requires a state to “project” the most recent of these inventories to the 

end of the “applicable 5-year period” whenever that end is not the year of a triennial inventory 

required by subpart A. Emissions projection is not a simple or low-resource task even if limited 

to a projection date that is in the recent past, as would be the case here. We do not think the 

informational value of such projections is in balance with the effort and time that would be 

required. At the same time, we believe that progress reports should present for each significant 

source sector the most recently available information, which may be newer for some sectors than 

for others. For most sectors, this will be the information for the triennial year of the most recent 

NEI submission. However, the EPA operates a data system that provides information on 

emissions from electric generating units (EGUs), which account for a significant percentage of 

visibility impairing pollution in many states, with only a few months lag time. This information 

comes from reports submitted by the EGU operators based on continuous emissions monitoring 

systems. Therefore, we are proposing text changes that explain clearly the most recent year 

through which the emissions analysis must be extended, by sector. States would be required to 
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include in their progress reports emissions with respect to all sources and activities up to the 

triennial year for which information has already been submitted to the NEI. With regard to 

EGUs, states would need to include data up to the most recent year for which the EPA has 

provided a state-level summary of such EGU-reported data. Finally, the last sentence of the 

proposed text for this section makes clear that if emission estimation methods have changed from 

one reporting year to the next, states need not backcast, i.e., use the newest methods to repeat the 

estimation of emissions in earlier years, in order to create a consistent trend line over the whole 

period. The EPA has never expected states to backcast in this context, but some states have 

expressed concern that other parties may interpret the current Regional Haze Rule as requiring 

such backcasting. This final change would remove any uncertainty about the sufficiency of a 

state’s progress report.

Section 51.308(g)(5) involves assessments of any significant changes in anthropogenic 

emissions that have occurred, and is proposed to be changed in a similar fashion to other 

sections, deleting the reference to the “past 5 years” and instead directing that the period to be 

assessed involves that since the last periodic comprehensive SIP revision. Text is also proposed 

to be added that would require states to report whether these changes were anticipated in the 

most recent SIP. Having this explanation within the progress report should not be a significant 

burden on the state and will assist the FLMs, the public and the EPA in understanding the 

significance of any change in emissions for the adequacy of the SIP to achieve established 

visibility improvement goals. The EPA was encouraged in pre-proposal consultations with FLMs 

to add this requirement.

Proposed changes to §51.308(g)(6) regarding assessment of progress toward meeting 

reasonable progress goals would clarify that the reasonable progress goals to be assessed are 
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those established for the period covered by the most recent periodic comprehensive SIP revision. 

This does not change the intended meaning of this section, and only clarifies that in a progress 

report, a state is not required to look forward to visibility conditions beyond the end of the 

current implementation period.

A final proposed change to §51.308(g) is to remove §51.308(g)(7) entirely, relieving the 

state of the need to review its visibility monitoring strategy within the context of the progress 

report. This change was requested by many states during our pre-proposal consultations, and is 

appropriate in our view. Because all states currently rely on their participation in the IMPROVE 

monitoring program and expect to continue to do so, continuing the requirement for every state 

to submit a distinct monitoring strategy element in each progress report would consume state and 

EPA resources with little or no practical value for visibility protection. As needed, the EPA will 

work with involved states and the IMPROVE Steering Committee to address any needed 

changes in the visibility monitoring program.

It should be noted that minor changes are proposed to §51.308(h) regarding actions the 

state is required to take based on the progress report. These changes merely remove the 

implication that all progress reports are to be submitted at 5-year intervals. Minor changes are 

also proposed to §51.308(i) in order to create a stand-alone requirement that states must consult 

with FLMs regarding progress reports. This stand-alone requirement is needed if progress reports 

are not SIP revisions, because at present the FLM consultation requirements are applicable only 

to SIP revisions.

F. Changes to Reasonably Attributable Visibility Impairment Provisions

The EPA is proposing extensive changes to 40 CFR 51.300 through 51.308 in regard to 

reasonably attributable visibility impairment. As discussed in section III of this document, the 
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reasonably attributable visibility impairment provisions were originally promulgated in 1980, 

when technology for evaluating visibility impairment and its causes was in its infancy and visual 

observation of “plume blight” was the main method of determining whether a source was 

affecting a mandatory Class I area. Since that time, there have been many advances in ambient 

monitoring, emissions quantification, emission control technology and meteorological and air 

quality modeling. These advances have been built into the regional haze program, such that state 

compliance with the Regional Haze Rule’s requirements will largely ensure that progress is 

made towards the goal of natural visibility conditions. Therefore, it is likely that some aspects of 

the reasonably attributable visibility impairment provisions of the visibility regulations have less 

potential benefit than they did when they originally took effect over 3 decades ago. In addition, 

the reasonably attributable visibility impairment provisions have received few amendments over 

the years, including during amendments made by the Regional Haze Rule in 1999 where the 

changes to integrate the reasonably attributable visibility impairment assessment and mitigation 

provisions with the new regional haze program requirements were limited to putting the two 

separately designed programs on the same recurring schedule. This has left a substantial amount 

of confusing and outdated language within the current visibility regulations including seemingly 

overlapping and redundant requirements, particularly between §§51.302 and 51.306. Also, as 

noted in section III.A, in actual practice the portion of the reasonably attributable visibility 

impairment provisions mandating periodic assessment of reasonably attributable visibility 

impairment by states (or by the EPA in the case of states that do not have an approved 

reasonably attributable visibility impairment SIP) has not resulted in any additional emission 

control requirements being placed on emission sources. While there have been very few 

certifications of existing reasonably attributable visibility impairment by an FLM, in several 
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situations a certification by an FLM has ultimately resulted in new controls or changes in source 

operation.

The EPA therefore believes it is time to bring clarity to the reasonably attributable 

visibility impairment provisions of the rule and enhance the potential for environmental 

protection. The proposed changes would (1) eliminate recurring requirements on states that we 

believe have no significant benefit for visibility protection,27 (2) clarify and strengthen the 

existing provisions under which states must address reasonably attributable visibility impairment

when an FLM certifies that reasonably attributable visibility impairment is occurring in a 

particular Class I area due to a single source or a small number of sources, (3) remove existing 

FIP provisions which require the EPA to periodically assess whether reasonably attributable 

visibility impairment is occurring and to respond to FLM certifications of reasonably attributable 

visibility impairment, and (4) edit various portions of §§51.300-308 to make them clearer and 

more compatible with each other. The substantive and clarifying changes are described here in 

order of section number. The EPA seeks comment on each of the following proposed changes, as 

well as any alternative approaches to modernizing the reasonably attributable visibility 

impairment provisions.

Proposed changes to §51.300, Purpose and applicability, would include a proposed 

change to section (b) to delete the reference to reasonably attributable visibility impairment only 

being applicable to the 36 states and territories with mandatory Class I areas. Instead, under the 

proposed amendments, the amended reasonably attributable visibility impairment requirements 

 

27 These changes, when finalized, would mean that those states with SIPs that commit them to 

periodically assess whether reasonably attributable visibility impairment is occurring at their 

Class I areas could remove that commitment from their SIPs.
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would apply to all states and territories with the exceptions of Guam, Puerto Rico, American 

Samoa, and the Northern Mariana Islands, since those territories have no mandatory Class I areas

and are sufficiently far from other Class I areas to have no anticipated impact on visibility in 

these areas. The geographical coverage of the reasonably attributable visibility impairment

provisions and the regional haze provisions would then be the same. The EPA believes these 

changes are appropriate and would strengthen the visibility program, given the evolved 

understanding that pollutants emitted from one or a small number of sources can affect Class I 

areas many miles away, so that emissions occurring in states without Class I areas can affect 

downwind states with Class I areas. The proposed changes, therefore, would provide these areas 

with additional protection from reasonably attributable visibility impairment.

Proposed changes to §51.301, Definitions, would involve changes to the definition of 

reasonably attributable. The current definition of reasonably attributable, “attributable by visual 

observation or any other technique the State deems appropriate,” is proposed to be changed to 

“attributable by visual observation or any other appropriate technique.” This change would 

remove the current implication that only the state can determine what technique is appropriate, 

even if the FLM is certifying reasonably attributable visibility impairment. The proposed change 

would make it clear that a state does not have complete discretion to determine what techniques 

are appropriate for attributing visibility impairment to specific sources. It is appropriate that the 

EPA be able to review the technique(s) that an FLM has relied upon to determine that reasonably 

attributable visibility impairment is occurring, in light of the views and supporting information 

provided by both the FLM and the state.

Due to the confusing and in large part outdated content of §51.302, the entire text of this 

section is proposed to be deleted and completely new language inserted. The new text would 
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clearly describe a state’s responsibilities upon FLM certification of reasonably attributable 

visibility impairment. The proposed changes also include a change to the current section title, 

“Implementation control strategies for reasonably attributable visibility impairment,” such that it 

reads “Reasonably attributable visibility impairment.” 

The proposed §51.302(a) involves FLM certification of reasonably attributable visibility 

impairment and reads much like the existing §51.302(c), with the added language that FLMs 

would identify in the certification which single source or small number of sources is responsible 

for the reasonably attributable visibility impairment being certified.28 Further, the original 

reasonably attributable visibility impairment formulation did not anticipate a situation where one 

or a small number of sources in one state could create impairment of visibility in other state(s). 

Therefore, proposed language is included to explain that the FLMs would provide the 

certification to the state in which the source or small number of sources is located, which may 

not necessarily be the state where the visibility impairment occurs. The proposed language also 

addresses the possible situation that a “small number of sources” may be partially in one state 

and partially in another, such that a certification might be addressed to multiple states.

The proposed §51.302(b) describes the required state action in response to any FLM 

reasonably attributable visibility impairment certification, i.e., regardless of the type of source, 

namely that a state shall revise its regional haze implementation plan to include a determination, 

 

28 The existing rule text at §51.302(c)(1) does not explicitly require the FLM to identify a 

particular source or small number of sources as responsible for the reasonably attributable 

impairment, but the EPA and the FLMs understand that such identification should be part of a 

certification. See 45 FR 80086, “The Federal Land Manager may provide the State with a list of 

sources suspected of causing or contributing to visibility impairment in the mandatory Class I 

Federal area.” Under the proposed new language of §51.302(b), if the FLM does not identify the 

source or small number of sources causing the impairment, the certification would not create any 

obligation on the state to respond with a SIP revision.
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based on the four reasonable progress factors set forth in §51.308(d)(1)(i)(A), of any controls 

necessary on the certified source(s) to make reasonable progress toward natural visibility 

conditions in the affected Class I area. This preserves the current state obligation with much the 

same wording as in the current section. The proposed section further maintains the current 

requirement that the state include emissions limitations and schedules for compliance, and adds 

the requirement that SIPs include monitoring, recordkeeping and reporting requirements in order 

to enforce those emissions limitations.

The proposed §51.302(c) addresses those situations where an FLM certifies as a 

reasonably attributable visibility impairment source a BART-eligible source where there is at 

that time no SIP or FIP in place setting BART emission limits for that source or addressing 

BART requirements via a better-than-BART alternative program.29 In such an instance, the 

proposed rule requires the state to revise its regional haze SIP to meet the requirements of 

§51.308(e), BART requirements for regional haze visibility impairment, and notes that this 

requirement exists in addition to the requirements of §51.302(b) regarding imposition of controls 

for reasonable progress. The new version of §51.302(c) clarifies two aspects of the current rule 

to match the EPA’s past and current interpretations. First, a reasonably attributable visibility 

impairment certification for a BART-eligible source prior to the EPA’s approval of a state’s 

BART SIP for that source does not impose any substantive obligation on a state that is over and 

above the BART obligation imposed by §51.308. However, the state’s response to the reasonably 

attributable visibility impairment certification of a BART-eligible source must take into account 

 

29 Although most of the BART requirements have been addressed in most states, there remain a 

handful of states with BART obligations. In addition, there is litigation over the BART element 

in some approved SIPs and promulgated FIPs. We expect that this situation may exist in one or 

more states at some time after the effective date of the final rule.
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current information. This may require a state to update an analysis prepared earlier in support of 

a BART SIP that has not been approved. Second, a reasonably attributable visibility impairment

certification of a BART-eligible source after the state’s BART SIP for that source has been 

approved by the EPA does not trigger a requirement for a new BART determination based on the 

five statutory factors for BART. Rather, the state’s obligation with respect to that source is the 

same as for a non-BART eligible source, as stated in the paragraph immediately earlier. This is 

true regardless of how the state’s SIP has addressed the BART requirement for the source, 

whether through source-specific emission limits, an alternative better-than-BART analysis, or the 

special provisions of §51.309, which may have not resulted in any new emission limit for the 

source.

Regarding the time schedule for state response to an FLM certification of reasonably 

attributable visibility impairment, the proposed §51.302(d) provides for different deadlines for 

the state response to the certification depending on when in the cycle of periodic comprehensive 

SIP revisions the reasonably attributable visibility impairment certification is made. Table 1 

provides specific examples of how application of the proposed approach would determine due 

dates for the state response to a certification.

 If the certification is made more than 2 years prior to the due date for any periodic 

comprehensive regional haze SIP revision required under §51.308(f) (but, with respect to 

the SIP due for the just-prior period, not so early as to be within the 6-month window 

described next), then a state must respond to the certification in that upcoming SIP 

revision. Failure to respond adequately would prevent full approval of that SIP revision. 
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If the certification is made more than 2 years before the SIP due date, the state would 

have more than 2 years to respond, except as provided in the next bullet.30

 If the certification is made less than 2 years prior to the due date for any periodic 

comprehensive SIP revision (but no more than 6 months subsequent to the submission 

date of that periodic comprehensive regional haze SIP revision or a SIP revision that 

amends a previous submission in a way that affects the emission limits applicable to the 

reasonably attributable visibility impairment-certified source 31), then the state must 

submit a revision to its regional haze SIP within 2 years from the date of certification. 

The EPA believes that in this second timing situation, when the state’s analytical 

infrastructure has been recently used to prepare a SIP revision and thus would not be in 

need of much if any refreshment, it is appropriate to require a responding SIP revision 

without waiting longer than 2 years for the next periodic comprehensive SIP revision. In 

this timing situation, the EPA would act on the state’s standard regional haze SIP without 

regard to the not-yet-due obligation for a reasonably attributable visibility impairmentresponse SIP revision.

Table 1: Example FLM Reasonably Attributable Visibility Impairment Certification Dates 

and Corresponding Due Dates for State Response. All assume submission of a SIP revision 

by July 31, 2021, unless otherwise noted.

Date of FLM certification Proposed due date for state response

July 30, 2019 July 31, 2021

August 1, 2019 August 1, 2021

January 30, 2022 January 30, 2024

 

30 For a certification made between the 2021 and 2028 SIP due dates, the state might have up to 

6.5 years to respond, assuming the next bullet does not apply. For a certification made between 

the 2028 and 2038 due dates, the state might have up to 9.5 years to respond.

31 If a certification is made not too long after a SIP due date, this parenthetical provision would 

operate to require the SIP revision needed to respond to the reasonably attributable visibility 

impairment certification to be due sooner than the 6.5 or 9.5 year extreme noted in the previous 

footnote.
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February 1, 2022 July 31, 2028

April 1, 2022, after late submission of a SIP 

on March 1, 2022

April 1, 2024

August 31, 2022, after revised SIP 

submission on July 31, 2021, affecting the 

source identified in the reasonably 

attributable visibility impairment

certification

August 31, 2024

The EPA considers these timing provisions the best compromise between possibly requiring

more than one major planning activity during each (approximately) 10-year SIP cycle and 

obtaining the benefit of additional emission controls via a response to an FLM certification of 

reasonably attributable visibility impairment within a reasonable time period. These proposed 

provisions also reflect the fact that an FLM may, in rare cases, wish to certify a reasonably 

attributable visibility impairment source after reviewing (and having disagreements with) a SIP 

that a state has recently submitted to the EPA. The EPA invites comment on this timing approach 

as well as other approaches that may provide an even better compromise between the often 

competing analysis and planning obligations and workloads of states, the EPA and FLMs, and 

the need to respond in a timely way to a reasonably attributable visibility impairment

certification by an FLM.

It is important to note that as proposed, if the periodic comprehensive regional haze SIP 

for a state with a Class I area (and thus required to have reasonable progress goals in its SIP for 

that area) is approved prior to the approval of its own or a contributing state’s separate 

reasonably attributable visibility impairment-response SIP, the state would not be required to 

revisit and revise its reasonable progress goals to take into account any additional emission 

reductions from the certified source until the next due date for a periodic comprehensive SIP 

revision. 
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Proposed changes to §51.303, Exemptions from control, are minor edits to paragraph (a) 

designed to correctly refer to the new §51.302(c) as well as to the BART provisions in 

§51.308(e). These proposed changes do not alter which existing facilities may apply to the 

Administrator for an exemption from BART. Rather, the proposed changes simply make the 

language more clear and direct the reader to the appropriate sections for reference information.

Proposed changes to §51.304, Identification of integral vistas, are more extensive. An 

integral vista is defined in §51.301 as a view perceived from within the Class I area of a specific 

landmark or panorama located outside the boundary of the Class I area. The current version of 

§51.304 was written at a time when FLMs were still in the process of identifying integral vistas. 

We are proposing to remove antiquated language in §51.304 in light of the fact that FLMs were 

required to identify any such integral vistas on or before December 31, 1985. The proposed 

language would explain this fact as well as list those few integral vistas that were properly 

identified during the applicable time period. States would continue to be subject to the 

requirement that these integral vistas be listed in their SIPs. The EPA notes that the current 

version of 40 CFR part 51, subpart P is not perfectly clear on how the existence of an identified 

integral vista affects obligations on states and sources, but we are not proposing any clarification 

as part of this rulemaking.32 We invite comment on whether all references to integral vistas 

should be removed from subpart P, and we may do so in the final rule.

 

32 Section 51.301 states that “visibility in any mandatory Class I Federal area includes any 

integral vista associated with that area” but also that “adverse impact on visibility” does not 

include effects on integral vistas. Section 307(b) requires that SIPs provide for the review of any 

new major stationary source or major modification that may have an impact on any integral vista 

of a mandatory Class I Federal area. Other references to “integral vista” are merely definitional 

or relate to the procedure for identifying integral vistas.
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Proposed changes to §51.305, Monitoring for reasonably attributable visibility 

impairment, involve adding language stating that the requirement for a state to include in a 

periodic comprehensive SIP revision a monitoring strategy specifically for evaluating reasonably 

attributable visibility impairment in Class I area(s) only applies in situations where the 

Administrator, Regional Administrator or FLM has advised the state of a need for it. In concept, 

special monitoring for reasonably attributable visibility impairment purposes might be 

appropriate for a Class I area without an IMPROVE monitoring station or when the impairment 

is from a relatively narrow plume such that the existing IMPROVE monitoring site is not 

affected. The nature of the special monitoring might be situation-specific, and might be the same 

as or different than the IMPROVE monitoring protocols. These proposed changes would reduce 

the paperwork that states are required to submit to the EPA on a recurring schedule, since under 

the proposed language a state containing one or more Class I areas and participating in the 

IMPROVE monitoring program would be relieved of the need to include information in its SIP 

regarding monitoring to specifically assess reasonably attributable visibility impairment absent 

being advised to do so. A strategy for monitoring for regional haze visibility impairment under 

§51.308(d)(4) is still required and any monitoring for reasonably attributable visibility 

impairment under §51.305 would be in addition to that requirement.

Section 51.306, on long-term strategy requirements for reasonably attributable visibility 

impairment, is proposed to be completely removed and reserved. Like the current version of 

§51.302, the language of this section is out-dated. In this case, the EPA believes it makes sense 

to delete the entire text of this section and instead refer to long-term strategy requirements for 

reasonably attributable visibility impairment within the text of §51.308, specifically in 

§51.308(f)(2). In this way, long-term strategy requirements for reasonably attributable visibility 
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impairment would be retained in clearer form, and the visibility program would be more 

understandable to states and the public by listing the long-term strategy requirements for both 

regional haze and reasonably attributable visibility impairment in one place. Such a change 

would also reduce the planning burden on states by making clear in §51.308(f)(2) that a longterm strategy for reasonably attributable visibility impairment is not required without an FLM 

having made a reasonably attributable visibility impairment certification under §51.302(a).

Several proposed changes in §51.308 were discussed in sections IV.A, B, C, D, E and F

of this document. We are also proposing changes in §51.308 related to reasonably attributable 

visibility impairment. The proposed addition of §51.308(c) (currently a reserved section) 

explains the relationship between regional haze and reasonably attributable visibility impairment

and the state requirements for each, including that a state would not be required to address 

reasonably attributable visibility impairment unless triggered to do so by an FLM certification 

under §51.302(a), and that a state would not be required to re-address its monitoring strategy for 

reasonably attributable visibility impairment unless advised to perform monitoring as described 

in the proposed §51.305. 

The EPA is also proposing changes to the language of §51.308(f)(2) to describe when 

reasonably attributable visibility impairment must be addressed in the long-term strategy

required for regional haze. Finally, proposed changes to §51.308(f)(6) regarding the monitoring 

strategy requirements for SIPs would remove references to §51.305 that exist in the 

corresponding subsection in §51.308(d), namely, subsection (4) (again, regarding monitoring for 

reasonably attributable visibility impairment).

Proposed changes to §51.308(e), BART, relate to a state’s option to enact an emissions 

trading program or other alternative measure in lieu of source-specific BART. Under the 
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proposed approach, if a source is already covered for BART by an approved emissions trading 

program or other alternative measure (or the program codified in §51.309), certification of that 

source by an FLM would not trigger a new BART determination. However, certification would 

still trigger the requirement for a reasonable progress analysis. Proposed changes to 

§51.308(e)(4) are similar in nature and motivated by the same concerns.

Consistent with our proposal to remove the requirement for states to periodically assess 

reasonably attributable visibility impairment, we are also proposing to amend many sections of 

40 CFR part 52, to remove provisions that establish FIPs that require the EPA to periodically 

assess whether reasonably attributable visibility impairment exists at Class I areas in certain 

states and to address it if it does, and to respond to any reasonably attributable visibility 

impairment certification that may be directed to a state that does not have an approved 

reasonably attributable visibility impairment SIP. These changes include the removal of §§52.26 

and 52.29, which now contain the statement of the EPA’s obligations, and specific provisions for 

30 states to establish that §§52.26 and 52.29 are applicable to those states.

G. Consistency Revisions Related to Permitting of New and Modified Major Sources

Proposed changes to §51.307, New Source Review, involve a few proposed changes to 

maintain consistency with other sections of the Regional Haze Rule and with the CAA. The first 

change involves §51.307(b)(1) concerning integral vistas, for which we are proposing deletion of 

obsolete language regarding the now-expired identification period for integral vistas. Instead, the 

newly proposed addition of a listing of integral vistas in §51.304(b) will be referenced. In section 

§51.307(b)(2), the deletion of a reference to specific sections of the CAA is proposed in order to 

remove unnecessary language, as the EPA believes a reference simply to section “107(d)(1)” is 

sufficient.
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H. Changes to FLM Consultation Requirements

The EPA believes that state consultation with FLMs is a critical part of the creation of 

quality SIPs. As mentioned earlier, the EPA is proposing to extend the FLM consultation 

requirements of §51.308(i)(2) to progress reports that are not SIP revisions. In addition, the EPA 

believes further edits to §51.308(i)(2) are necessary because the current requirement for 

consultation at least 60 days prior to a public hearing may not occur sufficiently early in the 

state’s planning process to meaningfully inform the state’s development of the long-term 

strategy. This proposed rule change would add a requirement that such consultation occur early 

enough to allow the state time for full consideration of FLM input.

I. Extension of Next Regional Haze SIP Deadline from 2018 to 2021

The EPA is proposing to amend the requirements in 40 CFR 51.308(f) regarding state 

submission of periodic comprehensive SIP revisions beginning no later than July 31, 2018, and 

every 10 years thereafter. We are proposing to amend this section to instead allow states until 

July 31, 2021, to submit the periodic comprehensive SIP revisions originally due by July 31, 

2018. A state would have the option of submitting its SIP revision before July 31, 2021, with the 

SIP being evaluated under the same criteria as a SIP submitted on the due date. The end of the 

implementation period for these SIP revisions would remain 2028, regardless of when the SIP 

revision is submitted. We propose this as a one-time schedule adjustment. Beginning with the 

next periodic comprehensive SIP revision due date of July 31, 2028, the 10-year cycle of 

submission deadlines would resume, with periodic comprehensive SIP revisions due every 10 

years following. 

The extension of the due date to 2021 for states to submit the periodic comprehensive SIP 

revisions now due in 2018 would allow states to coordinate regional haze planning with other 
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regulatory programs, including but not limited to the Mercury and Air Toxics Standards,33 the 

2010 1-hour SO2 NAAQS,34 the 2012 annual PM2.5 NAAQS35 and the Clean Power Plan.36

States would be able to gather more information on the effects of these programs and develop 

periodic comprehensive SIP revisions (for the second implementation period) that are more 

integrated with state planning for these other programs, an advantage that was widely confirmed 

in discussions with states. A required element of the Regional Haze Rule is that states address 

the impacts of other regulatory programs when developing regional haze plans. The EPA 

believes that as the number of programs taking effect in this timeframe is unusually high, this 

presents an excellent opportunity for state coordination of strategies to address significant 

sources of emissions. The EPA expects this coordination to lead to better overall policies and 

therefore enhanced environmental protection.

J. Changes to Scheduling of Regional Haze Progress Reports

The EPA is proposing to amend the requirements in 40 CFR 51.308(g) and (h) regarding 

the timing of submission of reports evaluating progress towards the natural visibility goal. Under 

the current rule, regional haze progress reports are required to be submitted 5 years after 

submission of periodic comprehensive SIP revisions. Because states submitted these first SIP 

revisions on dates spread across about a 3-year period, many of the due dates for progress reports 

currently do not fall mid-way between the due dates for periodic comprehensive SIP revisions, as 

the EPA initially envisioned that they would. Looking forward, the current Regional Haze Rule

would in many cases require a progress report shortly before or shortly after a periodic 

 

33 77 FR 9304, February 16, 2012.

34 75 FR 35520, June 22, 2010.

35 78 FR 3086, January 15, 2013. 

36 80 FR 64662, October 23, 2015.
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comprehensive SIP revision, at which time it could not be expected to have much utility as a 

mid-course review of environmental progress or much incremental informational value for the 

public compared to the data contained in that SIP revision.

Complementing the proposed amendments to 40 CFR 51.308(f) regarding the deadlines 

for submittal of periodic comprehensive revisions, we propose to amend 40 CFR 51.308 (g) and 

(h) such that second and subsequent progress reports would be due by January 31, 2025, July 31, 

2033, and every 10 years thereafter, placing one progress report mid-way between the due dates 

for periodic comprehensive SIP revisions. The EPA believes that this timing provides a good 

balance between allowing the implementation of the most recent SIP revision to have proceeded 

far enough since its adoption for a review to be possible and worthwhile and having enough time 

remaining before the next comprehensive SIP revision for state action to make changes in its 

rules or implementation efforts, if necessary, separately from the actions in that next SIP.

Regarding the concept of a progress report also being useful at or near the time of 

submission of a periodic comprehensive SIP revision, as the EPA envisioned in the 1999 

Regional Haze Rule, we note that although they are expressed with somewhat different 

terminology, in practical terms a progress report would provide little additional information 

beyond that required to be addressed in a periodic comprehensive SIP revision. The only 

significant additional information required in a progress report but not explicitly required in a 

periodic comprehensive SIP revision is the requirement to report on the trend in visibility over 

the whole period since the baseline period of 2000-2004. While the EPA believes that a state 

should be aware of, and share with the public, information on the trend in visibility over the 

whole period since the baseline period of 2000-2004, we believe it would be inefficient to 

require the preparation of a separate progress report for this purpose. Therefore, we are 
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proposing to limit the requirement for separate progress reports to the one due mid-way between 

periodic comprehensive SIP revisions, and to add to the requirement for periodic comprehensive 

SIP revisions a requirement to include this trend information. The EPA believes this approach 

would substantially reduce administrative burdens and make progress reports of more 

informational use to the public, with no attendant reduction in environmental protection. The 

EPA solicits comment on this and any alternative approaches to progress report scheduling.

K. Changes to the Requirement that Regional Haze Progress Reports be SIP Revisions

The EPA is proposing to amend 40 CFR 51.308(g) regarding the requirements for the 

form of progress reports. Under the current regulations, progress reports must take the form of 

SIP revisions that comply with the procedural requirements of 40 CFR 51.102, 40 CFR 51.103 

and Appendix V to Part 51 – Criteria for Determining the Completeness of Plan Submissions. 

The EPA included the requirements for progress reports in the Regional Haze Rule primarily 

with an emphasis toward ensuring that the states remain on track during the 10 years between 

periodic comprehensive SIP revisions. By requiring progress reports to be in the form of SIP 

revisions, the 1999 Regional Haze Rule ensured an opportunity for public input on the progress 

reports, while specifically pointing out that the EPA “intends for progress reports to involve 

significantly less effort than a comprehensive SIP revision.” 64 FR 35747 (July 1, 1999). For all 

SIP revisions, however, the state must provide public notice and a public hearing if requested, 

and it must conform to certain administrative procedural requirements and provide various 

administrative material. Also, the submission must be made by an official who is authorized by 

state law to submit a SIP revision. As a required SIP revision, a finding by the EPA that a state 

has not submitted a complete progress report by the deadline would start a “clock” for the EPA 
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to prepare, take public comment on, and issue a progress report like the state was required to 

submit. 

We are proposing that progress reports need not be in the form of SIP revisions, but that 

states must consult with FLMs and obtain public comment on their progress reports before 

submission to the EPA. We are also proposing that the SIP revision that would be due in 2021 

must include a commitment to prepare and submit these progress reports to the EPA according to 

the proposed revised schedule (see previous section). These progress reports would be 

acknowledged and assessed by the EPA, but our review of these reports would not result in a 

formal approval or disapproval of them.

The EPA is proposing these changes because it believes these reports are not the kind of 

state submissions for which the formality of a SIP revision, and the accompanying requirement 

for the EPA to have to prepare the report within 2 years of finding that a state has failed to do so, 

are warranted. It is important to note that as part of the EPA’s review of the report, we will 

follow up with the state on any appropriate next steps. There are also additional remedies, such 

as undertaking a less formal assessment of the results of the implementation of the previously 

submitted SIP, that are available to the EPA in the event a state fails to properly submit a 

progress report. These changes have been widely supported by state air agencies in our preproposal consultations because they would allow more efficient use of state resources. This 

option would relieve states of the obligation to follow the procedural requirements of 40 CFR 

51.102 and 51.103. States have expressed concern that these procedural requirements are 

resource-intensive, and increase the burden on states by requiring formal procedures be followed 

when submitting progress reports. By avoiding the specific formal steps required for a SIP 

revision, including requirements imposed by state law that may involve time-consuming steps 
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beyond those required by the EPA, this proposal may also reduce the time between the 

completion of the technical analysis in the progress report and when the final report becomes 

available to the EPA and the public. Thus, progress reports could contain fresher information on 

the environmental progress being made by a state. Removing the requirement that progress 

reports be submitted as SIP revisions is consistent with regulatory requirements for similar 

reports from states for progress reporting or planning purposes where control requirements are 

not imposed, such as annual reports required under the Clean Power Plan for states that choose a 

state measures plan,37 or annual monitoring plans required for planning and maintenance of state 

monitoring networks.38

The EPA wishes to make clear that after considering comments, the EPA may or may not 

finalize this proposed change. Also, the EPA may elect to make changes to the progress report 

scheduling as described in the previous section without making any change to the requirement 

that progress reports take the form of SIP revisions, and vice versa. The EPA solicits comments 

on these alternative approaches.

It is important to note that under this option, states would still be required to include the

required progress report elements listed in 40 CFR 51.308(g)(1) through (g)(6). Also, §51.308(h) 

would continue to require that at the same time the state is required to submit a progress report, it 

must also take one of four listed actions concerning whether the SIP is adequate to achieve 

established goals for visibility improvement. Where a state determines that its own SIP is or may 

be inadequate to ensure reasonable progress due to emissions from sources within the state, the 

 

37 See 40 CFR 60.57805870(c).

38 See 40 CFR 58.10(a)(1) and (a)(2).
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state will continue to have an obligation to revise its SIP to address the plan’s deficiencies within 

1 year.

Upon receipt of such progress reports, the EPA would review the reports. Although the 

EPA would not formally approve or disapprove a progress report, the EPA would still have 

discretion to assess the adequacy of the SIP, relying in part on the information in the progress 

report. Under the CAA, a discretionary determination that the SIP is inadequate would create a 

non-discretionary duty for the EPA to issue a SIP call requiring the state to correct the 

inadequacy. A failure by the state to submit a progress report could be determined by the EPA to 

constitute failure to implement the regional haze SIP, given that we are proposing that every 

regional haze SIP include a commitment to submit the required progress reports (see next 

paragraph).

We are proposing that the next periodic comprehensive SIP revisions (currently due in 

2018 but proposed to be due in 2021) would need to include a commitment for states to provide 

progress reports. The 1999 Regional Haze Rule does not require such a commitment because the 

current requirement for progress reports to be submitted in the form of SIP revisions makes such 

a commitment superfluous. The EPA solicits comment on this or alternative approaches to 

ensuring that states continue to provide progress reports.

L. Changes to Requirements Related to the Grand Canyon Visibility Transport Commission

Section 51.309 has limited applicability going forward because its provisions apply only 

to 16 Class I areas covered by the Grand Canyon Visibility Transport Commission Report, and 

only to the first regional haze implementation period (i.e., through 2018). Nevertheless, certain 

conforming amendments at this time are appropriate to avoid confusion going forward. Section 

51.309(d)(4)(v) is proposed to be amended to correctly refer to the new §51.302(b) (in lieu of 
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(e), which no longer exists in the proposed section §51.302) and to delete the reference to BART

since it does not appear in §51.302(b). The title of §51.309(c)(10), Periodic implementation plan 

revisions, is proposed to be amended to include “and progress reports” at the end. This insertion

would complement the proposed amendments that will no longer require progress reports be 

considered SIP revisions by making clear from the title of the section that it applies to both SIP 

revisions and progress reports. Within §51.309(c)(10), amendments are proposed that would 

preserve the existing requirement that the progress reports due in 2013 were to take the form of 

SIP revisions, but direct the reader to the provisions of §51.308(g) for subsequent progress 

reports. In similar fashion, §51.309(c)(10)(i) and (ii) would be amended to specifically refer to 

the 2013 progress reports, while §51.309(c)(10)(iii) would point to §51.308(g) for subsequent 

progress reports. Section 51.309(c)(10)(iv) is proposed to be added to indicate that subsequent 

progress reports are subject to the requirements of §51.308(h) regarding determinations of 

adequacy of existing SIPs.

A final change in section 51.309 appears in §51.309(g)(2)(iii). This change is purely to 

correct a typographical error and the EPA will therefore not consider comments on this 

subsection.

V. Environmental Justice Considerations

The EPA believes this action would not have disproportionately high and adverse human 

health, well-being or environmental effects on minority, low-income or indigenous populations 

because it would not negatively affect the level of protection provided to human health, wellbeing or the environment under the CAA’s visibility protection program. When promulgated, 

these proposed regulations will revise procedural and timing aspects of the SIP requirements for 

visibility protection but will not substantively change the requirement that SIPs provide for 
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reasonable progress towards the goal of natural visibility conditions. These SIP requirements are 

designed to protect all segments of the general population.

The EPA acknowledges that the proposed delay in submitting SIP revisions from 2018 to 

2021 might cause delays in when sources must comply with any new requirements. However,

because neither the CAA nor the existing Regional Haze Rule set specific deadlines for when 

sources must comply with any new requirements in a state’s next periodic comprehensive SIP 

revision, states have substantial discretion in establishing reasonable compliance deadlines for 

measures in their SIPs. Given this, we expect to see a range of compliance deadlines in the next 

round of regional haze SIPs from early in the second implementation period to 2028, depending 

on the types of measures adopted, whether or not these proposed rule changes are finalized. 

Thus, the EPA believes the delay in the periodic comprehensive SIP revision submission 

deadline from 2018 to 2021 will not meaningfully reduce the overall progress towards better 

visibility made by the end of 2028 and will not meaningfully adversely affect environmental 

protection for all general segments of the population.

VI. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: 

Improving Regulation and Regulatory Review

This action is a significant regulatory action that was submitted to the OMB for review 

because it raises novel policy issues. Any changes made in response to OMB recommendations 

have been documented in the docket. 

B. Paperwork Reduction Act (PRA)

The information collection activities in this proposed rule have been submitted for 

approval to the OMB under the PRA. The Information Collection Request (ICR) document that 
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the EPA prepared has been assigned the EPA ICR number 1813.10, OMB Control No. 2060-

0421. You can find a copy of the ICR in the docket for this rule, and it is briefly summarized 

here.

The EPA is proposing these amendments to requirements for state regional haze planning

to change the requirements that must be met by states in developing regional haze SIPs, periodic 

comprehensive SIP revisions, and progress reports for regional haze. The main intended effects

of this rulemaking are to provide states with additional time to submit regional haze plans for the 

second implementation period and to provide states with an improved schedule and process for 

progress report submission. Further reductions in burden on states include this proposal’s 

removal of the requirement for progress reports to be SIP revisions, clarifying that states are not 

required to project emissions inventories as part of preparing a progress report, and relieving the 

state of the need to review its visibility monitoring strategy within the context of the progress 

report. All states are required to submit regional haze SIPs and progress reports under this rule.

Respondents/affected entities: All state air agencies.

Respondent’s obligation to respond: Mandatory, in accordance with the provisions of the 1999 

Regional Haze Rule.

Estimated number of respondents: 52: 50 states, District of Columbia and U.S. Virgin Islands.

Frequency of response: Approximately every 10 years (SIP) and approximately every 10 years 

(progress report).

Total estimated burden: 5,840 hours (per year). Burden is defined at 5 CFR 1320.3(b).

Total estimated cost: $289,238 (per year), includes $0 annualized capital or operation & 

maintenance costs. 
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An agency may not conduct or sponsor, and a person is not required to respond to, a 

collection of information unless it displays a currently valid OMB control number. The OMB 

control numbers for the EPA's regulations in 40 CFR are listed in 40 CFR part 9. 

Submit your comments on the agency’s need for this information, the accuracy of the 

provided burden estimates and any suggested methods for minimizing respondent burden to the 

EPA using the docket identified at the beginning of this rule. You may also send your ICRrelated comments to OMB’s Office of Information and Regulatory Affairs via email to 

oria_submissions@omb.eop.gov, Attention: Desk Officer for the EPA. Since OMB is required to 

make a decision concerning the ICR between 30 and 60 days after receipt, OMB must receive 

comments no later than [INSERT DATE 30 DAYS AFTER PUBLICATION IN THE 

FEDERAL REGISTER]. The EPA will respond to any ICR-related comments in the final rule.

C. Regulatory Flexibility Act (RFA)

I certify that this action will not have a significant economic impact on a substantial 

number of small entities under the RFA. This action will not impose any requirements on small 

entities. Entities potentially affected directly by this proposal include state governments, and for 

the purposes of the RFA, state governments are not considered small government. Tribes may 

choose to follow the provisions of the Regional Haze Rule but are not required to do so. Other 

types of small entities are not directly subject to the requirements of this rule. The EPA continues 

to be interested in the potential impacts of the proposed rule on small entities and welcomes 

comments on issues related to such impacts.

D. Unfunded Mandates Reform Act (UMRA)

This action does not contain any unfunded mandate as described in UMRA, 2 U.S.C. 

1531-1538, and does not significantly or uniquely affect small governments. This action imposes 
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no enforceable duty on any state, local or tribal governments or the private sector. The CAA 

imposes the obligation for states to submit regional haze SIPs. In this rule, the EPA is proposing 

to revise those requirements in a manner that would not increase the obligation of any state, local 

or tribal governments or the private sector. In this rule, the EPA is also proposing to extend the 

reasonably attributable visibility impairment certification provisions to some additional states, 

but these states are not small governments and any mandate on the private sector would be 

indirect since this rule does not mandate how an affected state should address such a 

certification. Therefore, this action is not subject to the requirements of sections 202, 203 and 

205 of the UMRA.

E. Executive Order 13132: Federalism

This action does not have federalism implications. It will not have substantial direct 

effects on the states, on the relationship between the national government and the states, or on 

the distribution of power and responsibilities among the various levels of government. The 

requirement to submit regional haze SIPs is mandated by the CAA. Thus, Executive Order 13132 

does not apply to these proposed regulations.

In the spirit of Executive Order 13132 and consistent with the EPA policy to promote 

communications between the EPA and state and local governments, the EPA has already 

consulted extensively with state air agency officials prior to this proposal. The EPA specifically 

solicits comments on this proposed action from state and local officials. In addition, the EPA 

intends to meet with organizations representing state and local officials during the comment 

period for this action.

F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments
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This proposed action does not have tribal implications as specified in Executive Order 

13175. It would not have a substantial direct effect on one or more Indian tribes. Furthermore, 

these proposed regulation revisions do not affect the relationship or distribution of power and 

responsibilities between the federal government and Indian tribes. The CAA and the TAR

establish the relationship of the federal government and tribes in characterizing air quality and 

developing plans to protect visibility in Class I areas. Thus, Executive Order 13175 does not 

apply to this action. 

Although Executive Order 13175 does not apply to this action, the EPA solicits comment 

on this proposed action from tribal officials. The EPA also intends to offer to consult with any 

tribal government to discuss this proposal. See also section III.B.5 for further discussion 

regarding the role of tribes in visibility protection. 

G. Executive Order 13045: Protection of Children from Environmental Health and Safety Risks

The EPA interprets Executive Order 13045 as applying only to those regulatory actions 

that concern environmental health or safety risks that the EPA has reason to believe may 

disproportionately affect children, per the definition of “covered regulatory action” in section 2-

202 of the Executive Order. This action is not subject to Executive Order 13045 because it does 

not concern an environmental health risk or safety risk.

H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy 

Supply, Distribution or Use

This action is not a “significant energy action” because it is not likely to have a 

significant adverse effect on the supply, distribution or use of energy.

I. National Technology Transfer and Advancement Act

This rulemaking does not involve technical standards. 
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J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority 

Populations and Low-Income Populations

The EPA believes the human health or environmental risk addressed by this action will 

not have disproportionately high and adverse human health or environmental effects on minority,

low-income or indigenous populations. The results of our evaluation are contained in section V

of this document.

VII. Statutory Authority

The statutory authority for this action is provided by 42 U.S.C. 7403, 7407, 7410 and 

7601.

Page 85 of 120 - Protection of Visibility: Amendments to Requirements for State Plans

List of Subjects 

40 CFR Part 51

Environmental protection, Administrative practice and procedure, Air pollution control, Nitrogen 

dioxide, Particulate matter, Sulfur oxides, Transportation, Volatile organic compounds.

40 CFR Part 52
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Environmental protection, Administrative practice and procedure, Air pollution control, 

Incorporation by reference, Nitrogen dioxide, Particulate matter, Sulfur oxides, Transportation, 

Volatile organic compounds.

__________________________________

Dated:

__________________________________

Gina McCarthy,

Administrator.
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For the reasons stated in the preamble, Title 40, Chapter I of the Code of Federal Regulations is 

proposed to be amended as follows:

PART 51–-REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL 

OF IMPLEMENTATION PLANS

1. The authority citation for part 51 continues to read as follows:

Authority: 23 U.S.C. 101; 42 U.S.C. 7401-7671q.

2. In §51.300, revise paragraph (b) to read as follows:

§51.300 Purpose and applicability.

* * * * *

(b) Applicability—The provisions of this subpart are applicable to all States as defined in section 

302(d) of the Clean Air Act (CAA) except Guam, Puerto Rico, American Samoa, and the 

Northern Mariana Islands.

* * * * *

3. In §51.301:

a. Add definitions for “Clearest days,” “Deciview index,” “End of the applicable implementation 

period,” “Natural visibility conditions,” and “Visibility.” 

b. Revise the definitions for “Deciview,” “Federal Class I area,” “Least impaired days,” 

“Mandatory Class I Federal Area,” “Most impaired days,” “Reasonably attributable,” and 

“Visibility impairment.” 
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The revisions and additions read as follows:

§51.301 Definitions.

* * * * *

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 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, the atmospheric light 

extinction coefficient must be calculated from aerosol measurements):

Deciview index=10 lne (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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Least impaired days means the twenty percent of monitored days in a calendar year with the 

lowest amounts of visibility impairment.

* * * * *

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 visibility conditions means visibility (light extinction, visual range, contrast, coloration) 

that would have existed under natural conditions. Natural visibility conditions vary with time and 

location, and are estimated or inferred rather than directly measured.

* * * * *

Reasonably attributable means attributable by visual observation or any other appropriate 

technique. 

* * * * *

Visibility means the degree of perceived clarity when viewing objects at a distance. Visibility 

depends on light extinction, visual range, contrast, or coloration.

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.
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* * * * *

4. In §51.302:

a. Revise the section heading.

b. Revise paragraphs (a), (b), and (c).

c. Add paragraph (d).

The revisions and addition read as follows:

§51.302 Reasonably attributable visibility impairment.

(a) The affected Federal Land Manager may certify, at any time, that there exists reasonably 

attributable impairment of visibility in any mandatory Class I Federal area and identify which 

single source or small number of sources is responsible for such impairment. The affected 

Federal Land Manager will provide the certification to the State in which the impairment occurs 

and the State(s) in which the source(s) is located.

(b) The State(s) shall revise its regional haze implementation plan, in accordance with the 

schedules set forth in paragraphs (d)(1) and (d)(2) of this section, to include for each source or 

small number of sources that the Federal Land Manager has identified in whole or in part for 

reasonably attributable visibility impairment as part of a certification under paragraph (a) of this 

section:

(1) A determination, based on the factors set forth in §51.308(d)(1)(i)(A), of the control 

measures, if any, that are necessary with respect to the source or sources in order for the plan to 

make reasonable progress toward natural visibility conditions in the affected Class I Federal 

area;
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(2) Emission limitations that reflect the degree of emission reduction achievable by such control 

measures and schedules for compliance as expeditiously as practicable; and

(3) Monitoring, recordkeeping, and reporting requirements sufficient to ensure the enforceability 

of the emission limitations.

(c) If a source that the Federal Land Manager has identified as responsible in whole or in part for 

reasonably attributable visibility impairment as part of a certification under paragraph (a) of this 

section is a BART-eligible source, and if there is not in effect as of the date of the certification a 

fully or conditionally approved implementation plan addressing the BART requirement for that 

source (which existing plan may incorporate either source-specific emission limitations 

reflecting the emission control performance of BART, an alternative program to address the 

BART requirement under §51.308(e)(2), (3), and (4), or for sources of SO2 a program approved 

under paragraph §51.309(d)(4)), then the State shall revise its regional haze implementation plan 

to meet the requirements of §51.308(e) with respect to that source, taking into account current 

conditions related to the factors listed in §51.308(e)(1)(ii)(A). This requirement is in addition to 

the requirement of paragraph (b) of this section. 

(d)(1) For any existing reasonably attributable visibility impairment the Federal Land Manager 

certifies to the State(s) under paragraph (a) of this section more than 2 years prior to the due date 

for a regional haze implementation plan revision required under §51.308(f), the State(s) shall 

include the elements described in paragraphs (b) and (c) in such revision and such elements shall 

be considered a required part of such revision.

(2) For any existing reasonably attributable visibility impairment the Federal Land Manager 

certifies to the State(s) under paragraph (a) of this section less than 2 years prior to the due date 
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for a regional haze implementation plan revision required under §51.308(f), but no more than 6 

months subsequent to that due date, the State(s) shall submit a revision to its regional haze 

implementation plan that includes the elements described in paragraph (b) and (c) no later than 2 

years after the date of the certification. The State(s) is not required at that time to also revise its 

reasonable progress goals to reflect the additional emission reductions required from the source 

or sources. 

5. In §51.304:

a. Revise paragraphs (a), (b), and (c).

b. Remove and reserve paragraph (d).

The revisions read as follows:

§51.304 Identification of integral vistas.

(a) Federal Land Managers were required to identify any integral vistas on or before December 

31, 1985, according to criteria the Federal Land Managers developed. These criteria must have 

included, but were not limited to, whether the integral vista was important to the visitor's visual 

experience of the mandatory Class I Federal area. 

(b) The following integral vistas were identified by Federal Land Managers: at Roosevelt 

Campobello International Park, from the observation point of Roosevelt cottage and beach area, 

the viewing angle from 244 to 256 degrees; and at Roosevelt Campobello International Park, 

from the observation point of Friar’s Head, the viewing angle from 154 to 194 degrees. 

(c) The State must list in its implementation plan any integral vista listed in paragraph (b) of this 

section.
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(d) [Reserved]

6. Section 51.305 is revised to read as follows:

§51.305 Monitoring for reasonably attributable visibility impairment.

For the purposes of addressing reasonably attributable visibility impairment, if the 

Administrator, Regional Administrator, or the affected Federal Land Manager has advised a 

State containing a mandatory Class I Federal area of a need for monitoring to assess reasonably 

attributable visibility impairment at a mandatory Class I Federal area in addition to the 

monitoring currently being conducted to meet the requirements of §51.308(d)(4), the State must 

include in the next implementation plan revision to meet the requirement of §51.308(f) an 

appropriate strategy for evaluating reasonably attributable visibility impairment in the mandatory 

Class I Federal area by visual observation or other appropriate monitoring techniques. Such 

strategy must take into account current and anticipated visibility monitoring research, the 

availability of appropriate monitoring techniques, and such guidance as is provided by the 

Agency.

7. Section 51.306 is removed and reserved.

§51.306 [Removed and Reserved]

8. In §51.307, revise paragraphs (a) introductory text and (b) to read as follows:

§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 
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107(d) of the CAA, the State plan must, in any review under §51.166 with respect to visibility 

protection and analyses, provide for:

* * * * * 

(b) * * *

(1) That may have an impact on any integral vista of a mandatory Class I Federal area listed in 

§51.304(b), or

(2) That proposes to locate in an area classified as nonattainment under section 107(d)(1) of the 

Clean Air Act that may have an impact on visibility in any mandatory Class I Federal area.

* * * * * 

9. In §51.308:

a. Add paragraphs (c), (f)(4), (f)(5), (f)(6), (g)(3)(i)(A), (g)(3)(i)(B), (g)(3)(ii)(A), (g)(3)(ii)(B), 

(g)(3)(iii)(A), and (g)(3)(iii)(B).

b. Revise paragraphs (b), (d)(2)(iv), (d)(3), (e)(2)(v), (e)(4), (e)(5), (f), (g) introductory text, 

(g)(3), (g)(4), (g)(5), (g)(6), (h) introductory text, (h)(1), (i)(2), (i)(3), and (i)(4).

c. Remove paragraphs (d)(2)(iv)(A), (d)(2)(iv)(B), and (g)(7).

The revisions and additions read as follows:

§51.308 Regional haze program requirements.

* * * * *

(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 
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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 

a State under §51.305 of a need for additional monitoring to assess reasonably attributable 

visibility impairment at a mandatory Class I Federal area. 

(d) * * *

(2) * * *

(iv) For the first implementation plan addressing the requirements of paragraphs (d) and (e) of 

this section, the number of deciviews by which baseline conditions exceed natural visibility 

conditions for the most impaired and least impaired days.

(3) Long-term strategy for regional haze. Each State listed in §51.300(b) must submit a longterm strategy that addresses regional haze visibility impairment 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 

enforceable emissions limitations, compliance schedules, and other measures as necessary to 

achieve the reasonable progress goals established by States having mandatory Class I Federal 

areas. In establishing its long-term strategy for regional haze, the State must meet the following 

requirements:
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* * * * *

(e) * * *

(2) * * *

(v) At the State's option, a provision that the emissions trading program or other alternative 

measure may include a geographic enhancement to the program to address the requirement under 

§51.302(b) related to reasonably attributable impairment from the pollutants covered under the 

emissions trading program or other alternative measure.

* * * * *

(4) A State subject to a trading program established in accordance with §52.38 or §52.39 under a 

Transport Rule Federal Implementation Plan need not require BART-eligible fossil fuel-fired 

steam electric plants in the State to install, operate, and maintain BART for the pollutant covered 

by such trading program in the State. A State that chooses to meet the emission reduction 

requirements of the Transport Rule by submitting a SIP revision that establishes a trading 

program and is approved as meeting the requirements of §52.38 or §52.39 also need not require 

BART-eligible fossil fuel-fired steam electric plants in the State to install, operate, and maintain 

BART for the pollutant covered by such trading program in the State. A State may adopt 

provisions, consistent with the requirements applicable to the State for a trading program 

established in accordance with §52.38 or §52.39 under the Transport Rule Federal 

Implementation Plan or established under a SIP revision that is approved as meeting the 

requirements of §52.38 or §52.39, for a geographic enhancement to the program to address any 

requirement under §51.302(b) related to reasonably attributable impairment from the pollutant 

covered by such trading program in that State.
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(5) 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 paragraphs (d) 

and (f) of this section, as applicable, in the same manner as other sources.

* * * * *

(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 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 
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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. 

(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. 

(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.
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(vi) Uniform rate of progress. 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.

(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.
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(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 ensure it has included all measures 

needed to achieve its apportionment of emission reduction obligations agreed upon through that 

process.
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(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.

(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. 
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(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) Smoke management techniques for agricultural and forestry management purposes including 

plans 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.

(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 
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visibility than the uniform rate of progress calculated under paragraph (f)(1)(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 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 make the same demonstration with 

respect to its own 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 

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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(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)(1), (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.
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(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.

(g) Requirements for periodic reports describing progress towards the reasonable progress 

goals. Each State identified in §51.300(b) must periodically submit a report to the Administrator 

evaluating progress towards the reasonable progress goal for 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. The first progress report is due 5 years 

from submittal of the initial implementation plan addressing paragraphs (d) and (e) of this 

section. The first progress reports must be in the form of implementation plan revisions that 

comply with the procedural requirements of §51.102 and §51.103. Subsequent progress reports 

are due by January 31, 2025, July 31, 2033, and every 10 years thereafter. Subsequent progress 
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reports must be made available for public inspection and comment for at least 60 days prior to 

submission to EPA and all comments received from the public must be submitted to EPA along 

with the subsequent progress report, along with an explanation of any changes to the progress 

report made in response to these comments. Periodic progress reports must contain at a minimum 

the following elements:

* * * * *

(3) For each mandatory Class I Federal area within the State, the State must assess the following 

visibility conditions and changes, with values for most impaired, least impaired and/or clearest 

days as applicable expressed in terms of 5-year averages of these annual values. The period for 

calculating current visibility conditions is the most recent 5-year period preceding the required 

date of the progress report for which data are available as of a date 6 months preceding the 

required date of the progress report. 

(i)(A) Progress reports due before January 31, 2025. The current visibility conditions for the 

most impaired and least impaired days.

(B) Progress reports due on and after January 31, 2025. The current visibility conditions for the 

most impaired and clearest days;

(ii) (A) Progress reports due before January 31, 2025. The difference between current visibility 

conditions for the most impaired and least impaired days and baseline visibility conditions. 

(B) Progress reports due on and after January 31, 2025. The difference between current visibility 

conditions for the most impaired and clearest days and baseline visibility conditions. 
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(iii) (A) Progress reports due before January 31, 2025. The change in visibility impairment for 

the most impaired and least impaired days over the period since the period addressed in the most 

recent plan required under paragraph (f) of this section.

(B) Progress reports due on and after January 31, 2025. The change in visibility impairment for 

the most impaired and clearest days over the period since the period addressed in the most recent 

plan required under paragraph (f) 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 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 
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were anticipated in that most recent plan and whether they have limited or impeded progress in 

reducing pollutant emissions and improving visibility.

(6) An assessment of whether the current implementation plan elements and strategies are 

sufficient to enable the State, or other States with mandatory Class I Federal areas affected by 

emissions from the State, to meet all established reasonable progress goals for the period covered 

by the most recent plan required under paragraph (f) of this section.

(h) Determination of the adequacy of existing implementation plan. At the same time the State is 

required to submit any progress report to EPA in accordance with paragraph (g) of this section, 

the State must also take one of the following actions based upon the information presented in the 

progress report:

(1) If the State determines that the existing implementation plan requires no further substantive 

revision at this time in order to achieve established goals for visibility improvement and 

emissions reductions, the State must provide to the Administrator a negative declaration that 

revision of the existing implementation plan is not needed at this time.

* * * * *

(i) * * *

(2) The State must provide the Federal Land Manager with an opportunity for consultation, in 

person at a point early enough in planning the development of its long-term strategy so that 

information and recommendations provided by the Federal Land Manager can meaningfully 

inform the State’s development of the long-term strategy and at least 60 days prior to holding 

any public hearing or other public comment opportunity on an implementation plan (or plan 
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revision) or progress report for regional haze required by this subpart. This consultation must 

include the opportunity for the affected Federal Land Managers to discuss their:

* * * * *

(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.

10. In §51.309:

a. Revise paragraphs (d)(4)(v), (d)(10), (d)(10)(i) introductory text, (d)(10)(ii) introductory text, 

and (g)(2)(iii). 

b. Add new paragraphs (d)(10)(iii) and (d)(10)(iv).

The revisions and additions read as follows:

§51.309 Requirements related to the Grand Canyon Visibility Transport Commission.

* * * * *

(d) * * *

(4) * * *

(v) Market Trading Program. The implementation plan must include requirements for a market 

trading program to be implemented in the event that a milestone is not achieved. The plan shall 
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require that the market trading program be activated beginning no later than 15 months after the 

end of the first year in which the milestone is not achieved. The plan shall also require that 

sources comply, as soon as practicable, with the requirement to hold allowances covering their 

emissions. Such market trading program must be sufficient to achieve the milestones in 

paragraph (d)(4)(i) of this section, and must be consistent with the elements for such programs 

outlined in §51.308(e)(2)(vi). Such a program may include a geographic enhancement to the 

program to address the requirement under §51.302(b) related to reasonably attributable 

impairment from the pollutants covered under the program.

* * * * *

(10) Periodic implementation plan revisions and progress reports. Each Transport Region State 

must submit to the Administrator periodic reports in the years 2013 and as specified for 

subsequent progress reports in §51.308(g). The progress report due in 2013 must be in the form 

of an implementation plan revision that complies with the procedural requirements of §§51.102 

and 51.103.

(i) The report due in 2013 will assess the area for reasonable progress as provided in this section 

for mandatory Class I Federal area(s) located within the State and for mandatory Class I Federal 

area(s) located outside the State that may be affected by emissions from within the State. This 

demonstration may be based on assessments conducted by the States and/or a regional planning 

body. The progress report due in 2013 must contain at a minimum the following elements:

* * * * *
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(ii) At the same time the State is required to submit the 5-year progress report due in 2013 to 

EPA in accordance with paragraph (d)(10)(i) of this section, the State must also take one of the 

following actions based upon the information presented in the progress report:

* * * * *

(iii) The requirements of §51.308(g) regarding requirements for periodic reports describing 

progress towards the reasonable progress goals apply to States submitting plans under this 

section, with respect to subsequent progress reports due after 2013.

(iv) The requirements of §51.308(h) regarding determinations of the adequacy of existing 

implementation plans apply to States submitting plans under this section, with respect to 

subsequent progress reports due after 2013.

* * * * *

(g) * * *

(2) * * *

(iii) The Transport Region State may consider whether any strategies necessary to achieve the 

reasonable progress goals required by paragraph (g)(2) of this section are incompatible with the 

strategies implemented under paragraph (d) of this section to the extent the State adequately 

demonstrates that the incompatibility is related to the costs of the compliance, the time necessary 

for compliance, the energy and non air quality environmental impacts of compliance, or the 

remaining useful life of any existing source subject to such requirements.

PART 52 – APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

1. The authority citation for part 52 continues to read as follows:
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Authority: 42 U.S.C. 7401 et seq.

2. In §52.26:

a. Remove and reserve the entire section.

The removal reads as follows:

§52.26 [Reserved] 

* * * * *

3. In §52.29:

a. Remove and reserve the entire section.

The removal reads as follows:

§52.29 [Reserved] 

* * * * *

4. In §52.29:

a. Remove and reserve paragraph (b).

The removal reads as follows:

§52.61 Visibility protection. 

* * * * *

(b) [Reserved]

* * * * *
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5. In §52.145:

a. Revise paragraph (b).

b. Remove and reserve paragraph (c).

The revisions and removal read as follows:

§52.145 Visibility protection.

* * * * *

(b) Regulations for visibility monitoring and new source review. The provisions of §§52.27 and 

52.28 are hereby incorporated and made part of the applicable plan for the State of Arizona.

(c) [Reserved]

* * * * *

6. In §52.281:

a. Remove and reserve paragraphs (b) and (e).

The removals read as follows:

§52.281 Visibility protection.

* * * * *

(b) [Reserved]

* * * * *

(e) [Reserved] 

* * * * *

7. In §52.344:

a. Revise paragraph (b).
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The revision reads as follows:

§52.344 Visibility protection.

* * * * *

(b) The Visibility NSR regulations are approved for industrial source categories regulated by the 

NSR and PSD regulations which have previously been approved by EPA. However, Colorado's 

NSR and PSD regulations have been disapproved for certain sources as listed in 40 CFR 

52.343(a)(1). The provisions of 40 CFR 52.28 are hereby incorporated and made a part of the 

applicable plan for the State of Colorado for these sources.

* * * * *

8. In §52.633:

a. Revise paragraph (b).

b. Remove and reserve paragraph (c).

The revisions and removal read as follows:

§52.633 Visibility protection.

* * * * *

(b) Regulations for visibility monitoring and new source review. The provisions of §§52.27 and 

52.28 are hereby incorporated and made part of the applicable plan for the State of Hawaii.

(c) [Reserved]

* * * * *

9. In §52.690:

a. Remove and reserve paragraphs (b) and (c).
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The removals read as follows:

§52.690 Visibility protection.

* * * * *

(b) [Reserved]

(c) [Reserved]

* * * * *

10. In §52.1033:

a. Remove and reserve paragraphs (a) and (c).

The removals read as follows:

§52.1033 Visibility protection.

(a) [Reserved]

* * * * *

(c) [Reserved]

* * * * *

11. In §52.1183:

a. Revise paragraph (b).

b. Remove and reserve paragraphs (a) and (c).

The revision and removals read as follows:

§52.1183 Visibility protection.

(a) [Reserved]
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(b) Regulation for visibility monitoring and new source review. The provisions of §52.28 are 

hereby incorporated and made a part of the applicable plan for the State of Michigan.

(c) [Reserved]

* * * * *

12. In §52.1236:

a. Revise paragraph (b).

b. Remove and reserve paragraph (c).

The revisions and removal read as follows:

§52.1236 Visibility protection.

* * * * *

(b) Regulation for visibility monitoring and new source review. The provisions of §52.28 are 

hereby incorporated and made a part of the applicable plan for the State of Minnesota.

(c) [Reserved]

* * * * *

13. In §52.1339:

a. Remove and reserve paragraph (b).

The removal reads as follows:

§52.1339 Visibility protection.

* * * * *

(b) [Reserved]

* * * * *
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14. In §52.1387:

a. Remove and reserve paragraph (b).

The removal reads as follows:

§52.1387 Visibility protection.

* * * * *

(b) [Reserved]

* * * * *

15. In §52.1488:

a. Revise paragraph (b).

b. Remove and reserve paragraph (c).

The revisions and removal read as follows:

§52.1488 Visibility protection.

* * * * *

(b) Regulation for visibility monitoring and new source review. The provisions of §52.28 are 

hereby incorporated and made a part of the applicable plan for the State of Nevada except for 

that portion applicable to the Clark County Department of Air Quality and Environmental 

Management.

* * * * *

16. In §52.1531:

a. Revise paragraph (b).

b. Remove and reserve paragraph (c).
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The revisions and removal read as follows:

52.1531 Visibility protection.

* * * * *

(b) Regulation for visibility monitoring and new source review. The provisions of §52.28 are 

hereby incorporated and made a part of the applicable plan for the State of New Hampshire.

(c) [Reserved]

* * * * *

17. In §52.2132:

a. Remove and reserve paragraphs (b) and (c).

The removals read as follows:

§52.2132 Visibility protection.

* * * * *

(b) [Reserved]

(c) [Reserved]

* * * * *

18. In §52.2179:

a. Revise paragraph (b).

b. Remove and reserve paragraph (c).

The revisions and removal read as follows:

§52.2179 Visibility protection.

* * * * *
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(b) Regulation for visibility monitoring and new source review. The provisions of §52.28 are 

hereby incorporated and made a part of the applicable plan for the State of South Dakota.

(c) [Reserved]

* * * * *

19. In §52.2304:

a. Remove and reserve paragraph (b).

The removal reads as follows:

§52.2304 Visibility protection.

* * * * *

(b) [Reserved]

* * * * *

20. In §52.2383:

a. Revise paragraph (b).

The revisions read as follows:

§52.2383 Visibility protection.

* * * * *

(b) Regulations for visibility monitoring and new source review. The provisions of §52.27 are 

hereby incorporated and made part of the applicable plan for the State of Vermont.

* * * * *

21. In §52.2452:
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a. Revise paragraph (a).

b. Remove and reserve paragraphs (b) and (c).

The revisions and removals read as follows:

§52.2452 Visibility protection.

(a) Reasonably Attributable Visibility Impairment. The requirements of section 169A of the 

Clean Air Act are not met because the plan does not include approvable measures for meeting 

the requirements of 40 CFR 51.305 for protection of visibility in mandatory Class I Federal 

areas.

(b) [Reserved]

(c) [Reserved]

* * * * *

22. In §52.2533:

a. Revise paragraphs (a) and (b).

b. Remove and reserve paragraph (c).

The revisions and removal read as follows:

§52.2533 Visibility protection.

(a) Reasonably Attributable Visibility Impairment. The requirements of section 169A of the 

Clean Air Act are not met because the plan does not include approvable measures for meeting 

the requirements of 40 CFR 51.305 and 51.307 for protection of visibility in mandatory Class I 

Federal areas.
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(b) Regulation for visibility monitoring and new source review. The provisions of §52.28 are 

hereby incorporated and made a part of the applicable plan for the State of West Virginia.

(c) [Reserved]

* * * * *

23. In §52.2781:

a. Remove and reserve paragraphs (b) and (c).

The removals read as follows:

§52.2781 Visibility protection.

* * * * *

(b) [Reserved]

(c) [Reserved]