2021-07574. Air Quality Designations for the 2010 Sulfur Dioxide (SO2

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Final rule.

SUMMARY:

The Environmental Protection Agency (EPA) is withdrawing the initial nonattainment designation for portions of the Outagamie County, Wisconsin, area for the 2010 sulfur dioxide (SO₂) primary National Ambient Air Quality Standard (NAAQS) and is finalizing a designation of attainment/unclassifiable for the area. The EPA Administrator signed an action on December 21, 2020, to designate certain areas in the United States (U.S.) for the 2010 SO₂ NAAQS, including the Outagamie County area. This action supplements the EPA's December 2020 designations, published in the Federal Register of March 26, 2021, which have not yet taken effect.

DATES:

This final rule is effective on April 30, 2021.

ADDRESSES:

The EPA has established a docket for this action at https://regulations.gov under Docket ID No. EPA-HQ-OAR-2020-0037. 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 and will be publicly available only in hard copy form.

Out of an abundance of caution for members of the public and our staff, the EPA Docket Center and Reading Room are currently closed to the public, with limited exceptions, to reduce the risk of transmitting COVID-19. The Docket Center staff will continue to provide remote customer service via email, phone, and webform. For further information on EPA Docket Center services and the current status, please visit us online at https://www.epa.gov/​dockets.

FOR FURTHER INFORMATION CONTACT:

For general questions concerning this action, please contact Andrew Leith, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Air Quality Policy Division, 109 T.W. Alexander Drive, Mail Code C539-04, Research Triangle Park, NC 27711, telephone [phone], email address: [e-mail]. For questions regarding the specific area in this action, please contact Alisa Liu, U.S. Environmental Protection Agency Region 5, Control Strategies Section, Air Programs Branch (AR-18J), 77 West Jackson Boulevard, Chicago, IL 60604; telephone: [phone]; email address: [e-mail].

Most EPA offices are closed to reduce the risk of transmitting COVID-19, but staff remain available via telephone and email. The EPA encourages the public to review information related to the Round 4 2010 SO₂ NAAQS designations online at https://www.epa.gov/​sulfur-dioxide-designations and also in the public docket at https://www.regulations.gov under Docket ID No. EPA-HQ-OAR-2020-0037.

SUPPLEMENTARY INFORMATION:

Table of Contents

The following is an outline of the Preamble.

I. Preamble Glossary of Terms and Acronyms

II. What is the purpose of this supplemental action?

III. Designation Decision Based on 2018-2020 Data

IV. Effective Date of This Action

V. Comments Received Regarding EPA's Round 4 Designations

VI. Environmental Justice Concerns

VII. Statutory and Executive Order Reviews

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 Government

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

H. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution or Use

I. National Technology Transfer and Advancement Act (NTTAA)

J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations

K. Congressional Review Act (CRA)

L. Judicial Review

I. Preamble Glossary of Terms and Acronyms

The following are abbreviations of terms used in the preamble.

APA Administrative Procedure Act

AQS Air Quality System

CAA Clean Air Act

CFR Code of Federal Regulations

DC District of Columbia

DRR Data Requirements Rule

E.O. Executive Order

EPA Environmental Protection Agency

FR Federal Register

NAAQS National Ambient Air Quality Standards

NTTAA National Technology Transfer and Advancement Act

OMB Office of Management and Budget

ppb Parts per billion

PRA Paperwork Reduction Act

RFA Regulatory Flexibility Act

SO₂ Sulfur Dioxide

TAR Tribal Authority Rule

UMRA Unfunded Mandate Reform Act of 1995

U.S. United States

II. What is the purpose of this supplemental action?

The EPA was under a December 31, 2020, court-ordered deadline to designate all remaining areas for the 2010 SO₂ NAAQS (“Round 4”). On December 21, 2020, the EPA Administrator signed a final action to designate 44 areas in accordance with section 107(d) of the Clean Air Act (CAA).^[1] Nine areas were designated as nonattainment; two areas were designated as unclassifiable; and 33 areas were designated as attainment/unclassifiable. The list of newly designated areas in each state, the boundaries of each area, and the designation of each area, appear in the tables at the end of that action.

The purpose of this supplemental action is to withdraw the SO₂ designation for one area that the EPA designated as nonattainment in the December 2020 action and designate that area as attainment/unclassifiable. The EPA indicated in that action that if any state submitted complete, quality-assured, certified 2020 data to the appropriate EPA Regional office supporting a change of the designation status for any Round 4 area within that state, and the EPA agreed that a change of designation status was appropriate, the EPA would withdraw the December 21, 2020, designation for the area and issue another designation that reflects the analysis of such information.

The EPA received such 2020 air quality information from the state of Wisconsin on January 13, 2021, and this information is available in the docket for this action. Based on our evaluation of the 2020 monitoring data, in this supplemental action the EPA is changing its December 21, 2020, nonattainment designation for portions of Outagamie County, Wisconsin to attainment/unclassifiable. The portions of Outagamie County affected by this change cover Outagamie County except Oneida Township (which includes Oneida Reservation), Oneida Off-Reservation Trust Land, and noncontiguous portions of Seymour Township adjoining Oneida Nation Tribal Lands.^[2]

The December 21, 2020, action was based on application of the EPA's nationwide analytical approach and technical analysis, including evaluation of monitoring data and air quality modeling, to determine the appropriate designation and area boundary based on the weight of evidence for each area, which are hereby incorporated by reference into this supplement of that action. Modification to the December 21, 2020, designation for this area does not represent a “redesignation” because this change is a withdrawal of that initial designation prior to its effective date and is an issuance of a new initial designation. The EPA is making this change to reflect the most recent 3 years of complete, quality-assured, and certified data (i.e., 2018-2020) that have become available prior to the April 30, 2021, effective date of the December 21, 2020, action.

III. Designation Decision Based on 2018-2020 Data

In a May 1, 2020, letter, which the state later modified on July 17, 2020, the Wisconsin Department of Natural Resources (WDNR) recommended that the EPA designate Outagamie County, Wisconsin as nonattainment for the 2010 SO₂ NAAQS. On August 13, 2020, consistent with section 107(d)(1)(b)(ii) of the CAA, the EPA notified Wisconsin that it intended to designate portions of Outagamie County, Wisconsin as nonattainment based on the most recent 3 years (2017-2019), at that time, of complete, quality-assured, certified data from a monitor (Air Quality System (AQS) Site ID #55-087-0015) indicating a violation of the 2010 SO₂ NAAQS with a design value of 77 parts per billion (ppb).^[3] The EPA explained in its December 2020 Responses to Comments on the intended designations (see pp. 26-27) that if the Kaukauna SO₂ monitor produced a valid attaining design value for the 2018-2020 period, and Wisconsin submitted the certified data to the EPA prior to February 15, 2021, then the EPA would withdraw the nonattainment designation announced in the December 2020 action and change the initial designation of the Outagamie County area to attainment/unclassifiable.^[4]

On January 13, 2021, the WDNR submitted complete, quality-assured, and certified SO₂ air quality monitoring data from the Kaukauna monitor for calendar year 2020 to the EPA.^[5] Additionally, WDNR requested that the EPA use the most recently available data to change the designation of Outagamie County, Wisconsin from nonattainment to attainment/unclassifiable prior to the April 30, 2021 effective date of the December 2020 action.

The Kaukauna monitor is located 1.53 kilometers north northeast of the Ahlstrom-Munksjö NA Specialty Solutions, LLC—Kaukauna facility. The monitor was sited to characterize the maximum 1-hour SO₂ concentration in the area surrounding the facility. Based on the ambient monitoring data certified by WDNR in the EPA's AQS, the annual 99th percentiles for the daily maximum 1-hour SO₂ concentrations are 107.8 ppb for 2018, 32.3 ppb 2019, and 66.7 ppb for 2020. Data collected at this monitor show a valid, attaining 1-hour SO₂ design value of 69 ppb based on complete, certified 2018-2020 data. The design value was calculated according to the data handling procedures in 40 CFR part 50, Appendix T, and is valid for comparison to the NAAQS.

Based on complete, quality-assured and certified air quality monitoring data from 2020 submitted by WDNR, showing attainment of the 1-hour SO₂ primary NAAQS in the area, the EPA is changing the initial designation for this area. As noted in Section II of this notice, the EPA provided a process in the December 2020 action for considering 2020 air quality data if such data supported a change to the initial designation for an area. Pursuant to this process, the EPA is withdrawing the initial nonattainment designation for portions of Outagamie County, Wisconsin, and the EPA is changing the initial designation of these portions of Outagamie County to attainment/unclassifiable, thereby designating the entirety of Outagamie County as attainment/unclassifiable. Procedurally, this change in the initial designation is consistent with the EPA's early data certification and evaluation process, as described previously in this document and in the December 2020 action. The table at the end of this document (amendment to 40 CFR 81.350) lists the only area for which the EPA is changing the initial designation.

IV. Effective Date of This Action

The effective date of designation of the area addressed in this action is April 30, 2021, the same effective date as the December 21, 2020, final designations action. The EPA is making these changes without notice and comment in accordance with section 107(d)(2) of the CAA, which exempts the promulgation of these designations from the notice and comment provisions of the Administrative Procedure Act (APA). Section 553(d) of the APA generally provides that rulemakings shall not be effective less than 30 days after publication except where the agency finds good cause for an earlier date. 5 U.S.C. 553(d)(1) and (3). Were the EPA not to expedite the effective date of this action, and instead make the effective date 30 days after publication, there would be confusion regarding the appropriate designation for the affected area in Wisconsin, and the state and the EPA would likely have to expend unnecessary time and resources at a later time to resolve that confusion. The effective date for this action is, therefore, justified because the EPA finds that there is good cause to make the rule effective April 30, 2021, because it is in the public interest to avoid the potential delay and waste of resources associated with allowing the designations in the December 21, 2020, action to go into effect for this area, and the rule does not contain new requirements for which affected entities need time to prepare.

V. Comments Received Regarding the EPA's Round 4 Designations

During the 120-day notification period for the fourth round of designations, WDNR submitted comments, observing that SO₂ concentrations at the Kaukauna monitor have decreased since 2018. WDNR predicted that the 2018-2020 design value would be below the 2010 SO₂ NAAQS based on more recent data through September 2020 and suggested that this would potentially make finalization of a nonattainment designation unnecessary. If final quality assured data from the Kaukauna monitor at the end of 2020 showed a 2018-2020 design value that meets the 2010 1-hour SO₂ NAAQS, WDNR stated that it intended to early certify the 2020 data and request that the EPA change the initial designation for Outagamie County. The EPA did not receive any other comments regarding the Outagamie County, Wisconsin area during the 30-day public comment period.

VI. Environmental Justice Concerns

When the EPA establishes a new or revised NAAQS, the CAA requires the EPA to designate all areas of the U.S. as either nonattainment, attainment, or unclassifiable. Area designations address environmental justice concerns by ensuring that the public is properly informed about the air quality in an area. In locations where air quality does not meet the NAAQS, the CAA requires relevant state authorities to initiate appropriate air quality management actions to ensure that all those residing, working, attending school, or otherwise present in those areas are protected, regardless of minority and economic status.

VII. 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 exempt from review by the Office of Management and Budget because it responds to the CAA requirement to promulgate air quality designations after promulgation of a new or revised NAAQS.

B. Paperwork Reduction Act (PRA)

This action does not impose an information collection burden under the PRA. This action fulfills the non-discretionary duty for the EPA to promulgate air quality designations after promulgation of a new or revised NAAQS and does not contain any information collection activities.

C. Regulatory Flexibility Act (RFA)

This designation action under CAA section 107(d) is not subject to the RFA. The RFA applies only to rules subject to notice-and-comment rulemaking requirements under the APA, 5 U.S.C. 553, or any other statute. Section 107(d)(2)(B) of the CAA explicitly provides that designations are exempt from the notice-and-comment provisions of the APA. In addition, designations under CAA section 107(d) are not among the list of actions that are subject to the notice-and-comment rulemaking requirements of CAA section 307(d).

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. The action imposes no enforceable duty on any state, local, or tribal governments, or the private sector.

E. Executive Order 13132: Federalism

This action does not have federalism implications. It will not have substantial direct effects on the state, on the relationship between the national government and the state, or on the distribution of power and responsibilities among the various levels of government. The division of responsibility between the federal government and the state for purposes of implementing the NAAQS is established under the CAA.

F. Executive Order 13175: Consultation and Coordination With Indian Tribal Government

This action does not have tribal implications, as specified in Executive Order 13175. This action concerns the designation of certain areas in the U.S. for the 2010 SO₂ NAAQS. The CAA provides for states, territories, and eligible tribes to develop plans to regulate emissions of air pollutants within their areas, as necessary, based on the designations. The Tribal Authority Rule (TAR) provides tribes the opportunity to apply for eligibility to develop and implement CAA programs, such as programs to attain and maintain the SO₂ NAAQS, but it leaves to the discretion of the tribe the decision of whether to apply to develop these programs and which programs, or appropriate elements of a program, the tribe will seek to adopt. This rule does not have a substantial direct effect on one or more Indian tribes. It would not create any additional requirements beyond those of the SO₂ NAAQS. This rule establishes the designations for certain areas of the country for the 2010 SO₂ NAAQS, but no areas of Indian country are being designated as nonattainment by this action. Furthermore, this rule does 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 developing plans to attain the NAAQS, and this rule does nothing to modify that relationship. Thus, Executive Order 13175 does not apply.

Although Executive Order 13175 does not apply to this rule, after the EPA promulgated the 2010 primary SO₂ NAAQS, the EPA communicated with tribal leaders and environmental staff regarding the designations process. In 2011, the EPA also sent individualized letters to all federally recognized tribes to explain the designation process for the 2010 SO₂ NAAQS, to provide the EPA designations guidance, and to offer consultation with the EPA. The EPA provided further information to tribes through presentations at the National Tribal Forum and through participation in National Tribal Air Association conference calls. The EPA also sent individualized letters to all federally recognized tribes that submitted recommendations to the EPA about the EPA's intended Round 1 designations for the SO₂ standard and offered tribal leaders the opportunity for consultation.^[6] These communications provided opportunities for tribes to voice concerns to the EPA about the general designations process for the 2010 SO₂ NAAQS, as well as concerns specific to a tribe, and informed the EPA about key tribal concerns regarding designations as the designations process was under development and through its implementation up to that point. For the second, third, and fourth rounds of SO₂ designations, the EPA sent additional letters to tribes that could potentially be affected and offered additional opportunities for participation in the designations process.

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

The EPA interprets Executive Order 13045 as applying 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 establish an environmental standard intended to mitigate health or safety risks.

H. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution or Use

This action is not subject to Executive Order 13211 because it is not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act (NTTAA)

This rulemaking does not involve technical standards.

J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations

This action does not have disproportionately high and adverse human health or environmental effects on minority populations, low-income populations and/or indigenous peoples, as specified in Executive Order 12898 (59 FR 7629, February 16, 1994). The documentation for this determination is contained in Section VI of this action, “Environmental Justice Concerns.”

K. Congressional Review Act (CRA)

This action is subject to the CRA, and the EPA will submit a rule report to each House of the Congress and to the Comptroller General of the U.S. This action is not a “major rule” as defined by 5 U.S.C. 804(2).

L. Judicial Review

Section 307(b)(1) of the CAA indicates which Federal Courts of Appeal have venue for petitions of review of final actions by the EPA. This section provides, in part, that petitions for review must be filed in the Court of Appeals for the District of Columbia Circuit: (i) When the agency action consists of “nationally applicable regulations promulgated, or final actions taken, by the Administrator,” or (ii) when such action is locally or regionally applicable, if “such action is based on a determination of nationwide scope or effect and if in taking such action the Administrator finds and publishes that such action is based on such a determination.” For locally or regionally applicable final actions, the CAA reserves to the EPA complete discretion whether to invoke the exception in (ii).

To the extent a court finds this action locally or regionally applicable, the Administrator is exercising the complete discretion afforded to him under the CAA to make and publish a finding that this action is based on a determination of “nationwide scope or effect” within the meaning of CAA section 307(b)(1).^[7] As explained in this document, this final action withdrawing the designation and promulgating a new initial designation of one area for the 2010 SO₂ primary NAAQS supplements the nationally applicable December 2020 final action taken by the EPA to issue a fourth round of designations for areas across the U.S., located in 21 states, nine EPA regions, and 10 federal judicial circuits, for the 2010 SO₂ primary NAAQS.^[8] The December 21, 2020, signed action and this supplemental action, replacing the initial designation of one area in the December 21, 2020, signed action prior to the effective date of that action, are promulgated pursuant to a common, nationwide analytical method and interpretation of CAA section 107(d). In other words, this supplemental action applies the same uniform, nationwide analytical method and interpretation of CAA section 107(d) applied across the country in the December 2020 final action, including the EPA's nationwide analytical approach to and technical analysis of evaluating monitoring data and air quality modeling within the EPA's interpretation of statutory terms in the CAA such as the definitions of nonattainment, attainment, and unclassifiable under section 107(d)(1) of the CAA. Both the supplemental action and the December 21, 2020, action are based on this same common core of determinations regarding the nationwide analytical method and interpretation of CAA section 107(d), and the Administrator previously made and published a finding in the December 2020 final action that such action is based on a determination of “nationwide scope or effect” within the meaning of CAA section 307(b)(1).^[9] More specifically, this final action is based on a determination by the EPA to evaluate areas nationwide under a common five factor analysis in determining whether areas are in violation of the 2010 SO₂ NAAQS, as follows: 1. Air quality characterization via ambient monitoring and/or dispersion modeling results; 2. emissions-related data; 3. meteorology; 4. geography and topography; and 5. jurisdictional boundaries.^[10]

For these reasons, the Administrator is exercising the complete discretion afforded to him by the CAA and hereby finds that this final action is based on a determination of nationwide scope or effect for purposes of CAA section 307(b)(1) and is hereby publishing that finding in the Federal Register.

Under section 307(b)(1) of the CAA, petitions for judicial review of this action must be filed in the United States Court of Appeals for the District of Columbia Circuit within 60 days from the date this final action is published in the Federal Register. Filing a petition for reconsideration by the Administrator of this final action does not affect the finality of the action for the purposes of judicial review, nor does it extend the time within which a petition for judicial review must be filed, and shall not postpone the effectiveness of such rule or action.

List of Subjects in 40 CFR Part 81

• Environmental protection
• Air pollution control
• National parks
• Wilderness areas

Michael S. Regan,

Administrator.

For the reasons set forth in the preamble, the EPA amends 40 CFR part 81 as follows:

PART 81—DESIGNATIONS OF AREAS FOR AIR QUALITY PLANNING PURPOSES

1. The authority citation for part 81 continues to read as follows:

Authority: 42 U.S.C. 7401, et seq.

Subpart C—Section 107 Attainment Status Designations

2. In § 81.350, the table titled “Wisconsin—2010 Sulfur Dioxide NAAQS [Primary]” is amended by removing the entry for “Outagamie County (part)”, and removing the entry for “Outagamie County (remainder)” and adding an entry for “Outagamie County” in its place.

The addition reads as follows:

§ 81.350

Wisconsin.

* * * * *

Wisconsin-2010 Sulfur Dioxide NAAQS

[Primary]

Designated area 1	Designation
	Date 2	Type
*    *    *    *    *
Outagamie County	4/30/2021	Attainment/Unclassifiable.
*    *    *    *    *
1 Includes any Indian country in each county or area, unless otherwise specified. EPA is not determining the boundaries of any Indian country in this table, including any area of Indian country located in the larger designation area. The inclusion of any Indian country in the designation area is not a determination that the state has regulatory authority under the Clean Air Act for such Indian country.
2 This date is April 9, 2018, unless otherwise noted.
3 Includes Indian country of the tribe listed in this table located in Forest County, Wisconsin. Information pertaining to areas of Indian country in this table is intended for Clean Air Act planning purposes only and is not an EPA determination of Indian country status or any Indian country boundary. EPA lacks the authority to establish Indian country land status, and is making no determination of Indian country boundaries, in this table.

* * * * *

Footnotes

1.  The Round 4 2010 SO₂ NAAQS designations action was signed by the EPA Administrator, Andrew Wheeler, on December 21, 2020, pursuant to a court-ordered deadline of December 31, 2020. That document with the original signature and date is maintained by the EPA. For administrative purposes only, and in compliance with requirements of the Office of the Federal Register, Acting Administrator Jane Nishida re-signed the same action on March 10, 2021, for publication (86 FR 16055, March 26, 2021). The administrative process in no way alters the legal effect of the action upon publication in the Federal Register.

2.  In the December 2020 action, the EPA designated Oneida Township (which includes the Oneida Reservation), Oneida Off-Reservation Trust Land, and the noncontiguous portions of Seymour Township adjoining Oneida Nation Tribal Lands as attainment/unclassifiable. See the EPA's intended designations technical support document for Wisconsin at https://www.epa.gov/​sites/​production/​files/​2020-08/​documents/​11-wi-rd4_​intended_​so2_​designations_​tsd.pdf.

3.  The 2010 1-hour SO₂ NAAQS is 75 ppb, based on the 3-year average of the 99th percentile of the annual distribution of daily maximum 1-hour average concentrations. See 40 CFR 50.17.

4.  Response to Comments on EPA's Intended Designations for the 2010 Sulfur Dioxide Primary National Ambient Air Quality Standard (NAAQS)—Round 4, December 2020. Available at https://www.epa.gov/​sites/​production/​files/​2020-12/​documents/​rd4_​so2_​designations_​responses_​to_​comments_​final_​v2.pdf.

5.  The docket for this action includes WDNR's AMP600 and AMP450NC Data Certification Reports dated January 7, 2021, and Letter dated January 13, 2021, and the EPA's Concurrence dated January 19, 2021.

6.  These communication letters to the tribes are provided in the dockets for Round 1 (Docket ID No. EPA-HQ-OAR-2012-0233), Round 2 (Docket ID NO. EPA-HQ-OAR-2014-0464), and Round 3 (Docket ID NO. EPA-HQ-OAR-2017-0003).

7.  In deciding whether to invoke the exception by making and publishing a finding that this final action is based on a determination of nationwide scope or effect, the Administrator has also taken into account a number of policy considerations, including his judgment balancing the benefit of obtaining the D.C. Circuit's authoritative centralized review versus allowing development of the issue in other contexts and the best use of agency resources.

8.  The rulemaking docket, EPA-HQ-OAR-2020-0037, is the same docket for both the December 21, 2020, signed action and for this supplemental action, with the relevant difference being that in addition to the materials it contained regarding this Wisconsin area generated through December 21, 2020—the date that action was signed by the Administrator—it now also contains the supplemental information submitted by Wisconsin related to this area.

9.  In the report on the 1977 Amendments that revised section 307(b)(1) of the CAA, Congress noted that the Administrator's determination that the “nationwide scope or effect” exception applies would be appropriate for any action that has a scope or effect beyond a single judicial circuit. See H.R. Rep. No. 95-294 at 323, 324, reprinted in 1977 U.S.C.C.A.N. 1402-03.

10.  See “Area Designations for the 2010 Primary Sulfur Dioxide National Ambient Air Quality Standard—Round 4,” memorandum to Regional Air Division Directors, Regions 1-10, from Peter Tsirigotis, dated September 5, 2019, available at https://www.epa.gov/​sites/​production/​files/​2019-09/​documents/​round_​4_​so2_​designations_​memo_​09-05-2019_​final.pdf.