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Federal Register / Vol. 86, No. 53 / Monday, March 22, 2021 / Rules and Regulations Docket ID No. EPAR06OAR2015
0189. Although listed in the index, some information is not publicly available, e.g., Confidential Business Information or other information whose disclosure is restricted by statute.
Certain other material, such as copyrighted material, is not placed on the internet. Publicly available docket materials are available electronically through https www.regulations.gov.
FOR FURTHER INFORMATION CONTACT:

James E. Grady, EPA Region 6 Office, Regional Haze and SO2 Section, 1201
Elm Street, Suite 500, Dallas TX 72570, 2146656745; grady.james@epa.gov.
Please call or email Mr. Grady or Mr.
Bill Deese at 2146657253 if you need alternative access to material indexed but not provided in the docket.
SUPPLEMENTARY INFORMATION:
Throughout this document we, us, and our mean the EPA.

Table of Contents I. Background A. Regional Haze Principles B. Requirements of the CAA and the EPAs Regional Haze Rule C. BART Requirements D. BART Alternative Requirements E. Long-Term Strategy and Reasonable Progress Requirements F. Previous Actions on Arkansas Regional Haze G. Arkansas Regional Haze Phase III SIP
Submittal H. Arkansas Visibility Transport II. Summary of Proposed Action and Our Final Decisions III. Public Comments and EPA Responses A. Demonstration That the BART
Alternative Is Better-Than-BART
B. Monitoring, Recordkeeping and Reporting Requirements C. Requirements for Emission Reductions To Occur During the First Implementation Period and for a Compliance Schedule D. The CAA Section 110l AntiBacksliding Provision E. Interstate Visibility Transport and Regional Haze Reasonable Progress Requirements F. Comments From Domtar IV. Final Action A. Arkansas Regional Haze Phase III SIP
Submittal B. Arkansas Visibility Transport C. CAA Section 110l V. Incorporation by Reference VI. Statutory and Executive Order Reviews
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I. Background A. Regional Haze Principles 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
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fine particulates PM2.5 1 into the air.
Fine particulates which cause haze are sulfates SO42-, nitrates NO3-, organic carbon OC, elemental carbon EC, and soil dust.2 PM2.5 precursors consist of SO2, NOX, volatile organic compounds VOCs, and in some cases, ammonia NH3. Airborne PM2.5 can scatter and absorb the incident light and, therefore, lead to atmospheric opacity and horizontal visibility degradation.
Regional haze limits visual distance and reduces color, clarity, and contrast of view. PM2.5 can cause serious adverse health effects and mortality in humans.
It also contributes to environmental effects such as acid deposition and eutrophication. Emissions that affect visibility include a wide variety of natural and man-made sources. Natural sources can include windblown dust and soot from wildfires. Man-made sources can include major and minor stationary sources, mobile sources, and area sources. Reducing PM2.5 and its precursor gases in the atmosphere is an effective method of improving visibility.
Data from the existing visibility monitoring network, Interagency Monitoring of Protected Visual Environments IMPROVE, shows that visibility impairment caused by air pollution occurs virtually all of the time at most national parks and wilderness areas. In 1999, the average visual range 3
in many mandatory Class I Federal areas 4 in the western United States was 1 Fine particles are less than or equal to 2.5
microns mm in diameter and usually form secondary in nature indirectly from other sources.
Particles less than or equal to 10 mm in diameter are referred to as PM10. Particles greater than PM2.5
but less than PM10 are referred to as coarse mass.
Coarse mass can contribute to light extinction as well and is made up of primary particles directly emitted into the air. Fine particles tend to be manmade, while coarse particles tend to have a natural origin. Coarse mass settles out from the air more rapidly than fine particles and usually will be found relatively close to emission sources. Fine particles can be transported long distances by wind and can be found in the air thousands of miles from where they were formed.
2 Organic carbon can be emitted directly as particles or formed through reactions involving gaseous emissions. Elemental carbon, in contrast to organic carbon, is exclusively of primary origin and emitted by the incomplete combustion of carbonbased fuels. Elemental carbon particles are especially prevalent in diesel exhaust and smoke from wild and prescribed fires.
3 Visual range is the greatest distance, in km or miles, at which a dark object can be viewed against the sky by a typical observer.
4 Mandatory Class I Federal areas consist of national parks exceeding 6,000 acres, wilderness areas and national memorial parks exceeding 5,000
acres, and all international parks that were in existence on August 7, 1977. The EPA, in consultation with the Department of Interior, promulgated a list of 156 areas where visibility was identified as an important value. The extent of a mandatory Class I area includes subsequent changes in boundaries, such as park expansions. Although states and tribes may designate additional areas as
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100150 kilometers km, or about onehalf to two-thirds of the visual range that would exist under estimated natural conditions.5 In most of the eastern Class I areas of the United States, the average visual range was less than 30 km, or about one-fifth of the visual range that would exist under estimated natural conditions. Since the promulgation of the original Regional Haze Rule in 1999, CAA programs have reduced emissions of haze-causing pollution, lessening visibility impairment and resulting in improved average visual ranges.6
B. Requirements of the CAA and the EPAs Regional Haze Rule In section 169A, enacted as part of the 1977 CAA Amendments, Congress created a program for protecting visibility in the nations national parks and wilderness areas. This section of the CAA establishes as a national goal the prevention of any future, and the remedying of any existing, visibility impairment in mandatory Class I
Federal areas where impairment results from manmade air pollution. Congress added section 169B to the CAA in 1990, which strengthened the visibility protection program of the Act, and the EPA promulgated final regulations addressing regional haze as part of the 1999 Regional Haze Rule, which was most recently updated in 2017.7 The Regional Haze Rule revised the existing 1980 visibility regulations and established a more comprehensive visibility protection program for Class I
areas. The requirements for regional haze, found at 40 CFR 51.308 and 51.309, are included in the EPAs broader visibility protection regulations at 40 CFR 51.300309. The regional haze regulations require states to demonstrate reasonable progress toward meeting the national goal of restoring natural visibility conditions for Class I
areas by 2064. The CAA requirement in section 169Ab2 to submit a regional haze SIP applies to all fifty states, the District of Columbia, and the Virgin Class I, the requirements of the visibility program set forth in the CAA applies only to mandatory Class I Federal areas. Each mandatory Class I
Federal area is the responsibility of a Federal Land Manager FLM. When the term Class I area is used in this action, it means mandatory Class I
Federal areas. See 44 FR 69122 November 30, 1979 and CAA Sections 162a, 169A, and 302i.
5 64 FR 35714, 35715 July 1, 1999.
6 An interactive story map depicting efforts and recent progress by the EPA and states to improve visibility at national parks and wilderness areas may be visited at: http arcg.is/29tAbS3.
7 See the July 1, 1999 Regional Haze Rule final action 64 FR 35714, as amended on July 6, 2005
70 FR 39156, October 13, 2006 71 FR 60631, June 7, 2012 77 FR 33656 and on January 10, 2017 82
FR 3079.

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