This action, pursuant to 5 U.S.C. 553, proposes to amend regulations issued to carry out a marketing order as defined in 7 CFR 900.2(j). This proposed rule is issued under Marketing Order No. 981, as amended (7 CFR part 981), regulating the handling of almonds grown in California. Part 981 (referred to as the “Order”) is effective under the Agricultural Marketing Agreement Act of 1937, as amended (7 U.S.C. 601-674), hereinafter referred to as the “Act.” The Board locally administers the Order and comprises growers and handlers of almonds operating within the production area.

The Department of Agriculture (USDA) is issuing this proposed rule in conformance with Executive Orders 12866 and 13563. Executive Orders 12866 and 13563 direct agencies to assess all costs and benefits of available regulatory alternatives and, if regulation is necessary, to select regulatory approaches that maximize net benefits (including potential economic, environmental, public health and safety effects, distributive impacts, and equity). Executive Order 13563 emphasizes the importance of quantifying both costs and benefits, reducing costs, harmonizing rules, and promoting flexibility. This action falls within a category of regulatory actions that the Office of Management and Budget (OMB) exempted from Executive Order 12866 review.

This proposed rule has been reviewed under Executive Order 13175—Consultation and Coordination with Indian Tribal Governments, which requires agencies to consider whether their rulemaking actions would have tribal implications. The Agricultural Marketing Service (AMS) has determined this proposed rule is unlikely to have substantial direct effects on one or more Indian tribes, on the relationship between the Federal Government and Indian tribes, or on the distribution of power and responsibilities between the Federal Government and Indian tribes.

This proposed rule has been reviewed under Executive Order 12988, Civil Justice Reform. This proposed rule is not intended to have retroactive effect.

The Act provides that administrative proceedings must be exhausted before parties may file suit in court. Under section 608c(15)(A) of the Act, any handler subject to an order may file with USDA a petition stating that the order, any provision of the order, or any obligation imposed in connection with the order is not in accordance with law and request a modification of the order or to be exempted therefrom. A handler is afforded the opportunity for a hearing on the petition. After the hearing, USDA would rule on the petition. The Act provides that the district court of the United States in any district in which the handler is an inhabitant, or has his or her principal place of business, has jurisdiction to review USDA's ruling on the petition, provided an action is filed not later than 20 days after the date of the entry of the ruling.

This proposed rule would amend administrative requirements in the Order regulating the roadside stand exemption, credit for market promotion activities, quality control, exempt dispositions, and interest and late charges provisions. In addition, the proposed rule would stay two sections of the administrative requirements that define almond butter and stipulate disposition in reserve outlets by handlers. These proposed changes modify the requirements to reflect updates in industry practices and are expected to help facilitate the orderly administration of the Order. The Board unanimously recommended these changes at meetings held on December 7, 2020, and June 17, 2021.

Multiple sections in the Order provide the authority for this proposed action. The authorities are cited with the descriptions of each of the proposed changes in the following narrative.

Section 981.13 of the Order defines the term “handler.” The definition includes an exemption for roadside stand sales. Section 981.413 of the Order's administrative requirements further expounds roadside stand sales by setting certain conditions that must be met for sales to be exempted from regulation under the Order. This proposed rule would add language to the requirements to clarify that sales of almonds through E-commerce (electronic commerce) are not exempt from regulation under the roadside stand exemption.

Section 981.41(c) of the Order provides the authority to establish provisions for crediting a handler's direct expenditures for marketing promotion against that handler's assessment obligation. Section 981.441 of the Order's administrative requirements delineates the provisions that handlers must meet to have a portion of their marketing promotion expenditures, including paid advertising, credited against their pro rata assessment obligation. This provision is otherwise known as Credit-Back. This proposed rule would allow the Board, with the approval of the Secretary, to annually establish a limit on the Credit-Back amount allowed for a handler's expenditures on E-commerce. Further, this rule would modify the receipt submission and reimbursement requirements for the Credit-Back program and update the provisions for appealing the Board's Credit-Back decisions.

Section 981.42 of the Order provides the authority to establish quality control regulations for both incoming and outgoing product. Section 981.442 of the Order's administrative requirements establishes quality control regulations under that authority. Section 981.442(a) establishes the quality requirements for incoming product received by handlers. Section 981.442(b) establishes the quality requirements for outgoing product prior to being shipped by handlers.

This proposal would modify provisions in § 981.442(a) to clarify ambiguous language, remove irrelevant dates, and more clearly define “accepted user” as it is referenced in the regulations. The proposed rule would also relax the requirements for handlers in meeting their disposition obligation under the regulations. The incoming quality requirements would be amended to allow inedible kernels, foreign material, and other defects sorted from off-site cleaning facilities to be credited to a handler's disposition obligation. In addition, almond meal would be allowed to meet the non-inedible portion of the disposition obligation, with the meal content to be determined in a manner acceptable to the Board.

In § 981.442(b), the proposed rule would amend the regulations to facilitate handlers utilizing off-site cleaning and treatment facilities in fulfillment of their quality control requirements. The proposal would allow the transfer of product for off-site cleaning without being considered a shipment, would designate off-site treatment facilities as “custom processors,” and would establish application and approval procedures for Board authorization of such custom processors. This action would also clarify the roles of the Technical Expert Review Panel (TERP) and the Board in administering the program as detailed in several provisions in § 981.442(b). Lastly, the proposed rule would refine the duties of a Direct Verifiable (DV) program auditor to disallow individuals who conduct process validations from being named as the DV auditor for that same equipment used in the treatment process.

Section 981.50 of the Order establishes handler reserve obligation requirements. Under those Order provisions, certain products are exempted from the reserve obligation, subject to the accountability of the Board. Section 981.450 establishes the provisions for exempt dispositions under the reserve obligation. This proposed rule would enhance the procedures currently in place for the Board to account for exempt dispositions. Under the proposed rule, outlets for exempted product would need to be pre-approved by the Board in accordance with the requirements contained in § 981.442(a)(7).

Section 981.66(b) of the Order establishes the conditions governing the disposition of reserve product. Within that paragraph, diversion of reserve almonds to be manufactured into almond butter is listed as an allowable outlet for such product. Section 981.466 further defines “almond butter” as used in § 981.66. The expanded definition of almond butter is no longer relevant in the administration of the program. The proposed rule would stay § 981.466 indefinitely.

Section 981.467 establishes the requirements regarding the disposition in reserve outlets by handlers. The section details the establishment of agents of the Board, delineates reserve credit in satisfaction of a reserve obligation, sets minimum prices, and establishes certain dates pertaining to the reserve disposition obligations. As the Order is not currently regulating volume, and a significant portion of the requirements is outdated, the provisions in § 981.467 are not currently relevant to the administration of the Order. As such, this proposed rule would stay the entire section indefinitely.

Lastly, § 981.481 stipulates the requirements for submission of handler assessment payments, which includes documentary requirements for proof of timely submission of assessment payments. Other than actual receipt of payment in the Board's office within 30 days of the invoice date on the handler's statement, the current provisions only identify the U.S. Postal Service postmark as proof of timely submission. This proposed rule would add “or by some other verifiable delivery tracking system” to allow handlers alternative delivery methods.

The Board believes that the changes recommended herein are necessary to update the Order's administrative requirements to adapt to changes in the industry and to reflect current industry practices. Many of the revisions may be considered conforming changes, but the proposed rule also makes changes to the Credit-Back provisions and quality control regulations that the Board views as essential to the continued efficient administration of the Order. The proposed changes contained herein are expected to facilitate the orderly marketing of California almonds and benefit growers and handlers in the industry.

Pursuant to requirements set forth in the Regulatory Flexibility Act (RFA) (5 U.S.C. 601-612), the Agricultural Marketing Service (AMS) has considered the economic impact of this action on small entities. Accordingly, AMS has prepared this initial regulatory flexibility analysis.

The purpose of the RFA is to fit regulatory actions to the scale of businesses subject to such actions in order that small businesses will not be unduly or disproportionately burdened. Marketing orders issued pursuant to the Act, are unique in that they are brought about through group action of essentially small entities acting on their own behalf.

There are approximately 7,600 almond growers in the production area and approximately 100 handlers subject to regulation under the Order. Small agricultural producers are defined by the Small Business Administration (SBA) as those having annual receipts of less than $1,000,000, and small agricultural service firms are defined as those having annual receipts of less than $30,000,000 (13 CFR 121.201).

The National Agricultural Statistics Service (NASS) reported in its 2017 Census of Agriculture (Census) that there were 7,611 almond farms in the production area, of which 6,683 had bearing acres. Additionally, the Census indicates that out of the 6,683 California farms with bearing acres of almonds, 4,425 (66 percent) have fewer than 100 bearing acres.

In another publication, NASS reported a 2019 crop year average yield of 2,160 pounds per acre and a season average grower price of $2.43 per pound. Therefore, a 100-acre farm with an average yield of 2,160 pounds per acre would produce about 216,000 pounds of almonds (2,160 pounds times 100 acres equals 216,000 pounds). At $2.43 per pound, that farm's production would be valued at $524,880 (216,000 pounds times $2.43 per pound equals $524,880). Since the Census indicated that 66 percent of California's almond farms are less than 100 acres, it could be concluded that the majority of California almond growers had annual receipts from the sale of almonds of less than $524,880 for the 2019-20 crop year, which is below the SBA threshold of $1,000,000 for small producers. Therefore, the majority of growers may be classified as small businesses.

To estimate the proportion of almond handlers that would be considered small businesses, it was assumed that the unit value per pound of almonds exported in a particular year could serve as a representative almond price at the handler level. A unit value for a commodity is the value of exports divided by the quantity exported. Data from the Global Agricultural Trade System (GATS) database of USDA's Foreign Agricultural Service showed that the value of almond exports from August 2019 to July 2020 (combining shelled and inshell) was $4.691 billion. The quantity of almond exports over that time-period was 1.78 billion pounds. Dividing the export value by the quantity yields a unit value of $2.64 per pound ($4.691 billion divided by 1.78 billion pounds equals $2.64).

NASS estimated that the California almond industry produced 2.55 billion pounds of almonds in 2019. Applying the $2.64 derived representative handler price per pound to total industry production results in an estimated total revenue at the handler level of $6.73 billion (2.55 billion pounds × $2.64 per pound). With an estimated 100 handlers in the California almond industry, average revenue per handler would be approximately $67.3 million ($6.73 billion divided by 100). Assuming a normal distribution of revenues, most almond handlers shipped almonds valued at more than $30,000,000 during the 2019-20 crop year. Therefore, the majority of handlers may be classified as large businesses.

This proposed rule would revise multiple provisions in the Order's administrative requirements. This proposal would amend regulations covering the Order's roadside stand exemption, credit for market promotion activities, quality control, exempt dispositions, and interest and late charges provisions. In addition, it would stay regulations contained in §§ 981.466 and 981.467. One of the sections defines almond butter and the other regulates almond disposition in reserve outlets by handlers. Both sections would be stayed indefinitely.

More specifically, the proposed rule would add language in § 981.413 to clarify that sales of almonds through E-commerce are not exempt from regulation under the roadside stand exemption.

In addition, the action would modify § 981.441 to allow the Board, with the approval of the Secretary, to annually establish a limit on the Credit-Back amount allowed for a handler's expenditures on E-commerce. Further, this rule would modify the receipt submission and reimbursement requirements for the Credit-Back program, as well as update the provisions for appealing the Board's Credit-Back decisions.

In § 981.442(a), the proposed rule would clarify ambiguous language, remove irrelevant dates, and more clearly define the term “accepted user” as it is referenced in the regulations. It would also relax the requirements for handlers in meeting their disposition obligation under the Order.

In § 981.442(b), the proposed rule would allow the transfer of product for off-site cleaning without being considered a shipment, designate off-site treatment facilities as “custom processors,” and establish the application and approval procedures for Board authorization of custom processors. This proposal would also clarify the roles of the TERP and the Board in administering the program in several subparagraphs in the section. Further, the proposed rule would refine the definition of a DV program auditor to disallow individuals who conduct process validations from being named as the DV auditor for that same equipment used in the treatment process.

Additionally, this proposed rule would amend § 981.450 to require outlets for exempted product be Board-approved, in accordance with § 981.442(a)(7).

Further, under the proposed action, § 981.466, which defines “almond butter” as it is used in § 981.66(b), is no longer relevant in the administration of the program and would be stayed indefinitely. In addition, as the Order is not currently regulating volume, § 981.467 is not necessary for the administration of the Order and would also be stayed indefinitely.

Lastly, this action would revise § 981.481 by adding “or by some other verifiable delivery tracking system” to the requirements to allow handlers alternative trackable delivery methods for demonstration of timely submission of assessment payments.

The authorities for the proposed changes above are contained in §§ 981.13, 981.41, 981.42, 981.50, 981.66, 981.67, and 981.81 of the Order.

The Board believes that the administrative requirement revisions recommended herein are necessary to reflect changes in the industry and to update the regulations to reflect current practices. Many of the modifications may be considered conforming changes, but this proposal also makes substantive changes to the Credit-Back provisions and quality control requirements that the Board views as essential to the efficient administration of the Order. The proposed changes contained herein are expected to facilitate the orderly marketing of California almonds and benefit growers and handlers in the industry. The Board unanimously recommended these changes at meetings held on December 7, 2020, and June 17, 2021.

AMS anticipates that this proposed rule would impose minimal, if any, additional costs on handlers or growers, regardless of size. The proposed changes to the administrative requirements are intended to clarify certain provisions, remove ambiguous and obsolete language, and adapt the requirements to facilitate the orderly marketing of almonds. The benefits derived from this proposed rule are not expected to be disproportionately more or less for small handlers or growers than for larger entities.

The Board considered alternatives to this action, including making no changes to the current requirements, only making changes to some of the requirements, and recommending the changes be considered as two separate rulemaking actions. Prior to the recommendation of the Board, the Board's Almond Quality, Food Safety and Services Committee reviewed the program, surveyed handlers, and unanimously recommended this action to the Board. After consideration of all the alternatives, and in consultation with USDA, the Board determined that making all the recommended changes, collectively in one rule, would be the best option to facilitate the Order's administration, contribute to the orderly marketing of almonds, and provide the greatest benefit to growers and handlers while maintaining the integrity of the Order.

Further, the Board's meetings were widely publicized throughout the California almond industry, and all interested persons were invited to attend the meetings and participate in Board deliberations. Like all Board and subcommittee meetings, the December 7, 2020, and June 17, 2021, meetings were public meetings, and all entities, both large and small, were able to express their views on this issue. Finally, interested persons are invited to submit comments on this proposed rule, including the regulatory and information collection impacts of this proposed action on small businesses.

In accordance with the Paperwork Reduction Act of 1995, (44 U.S.C. Chapter 35), the Order's information collection requirements have been previously approved by the Office of Management and Budget (OMB) and assigned OMB Nos. 0581-0178 (Vegetable and Specialty Crops) and 0581-0242 (Almond Salmonella). This proposed rule announces AMS's intent to request approval from OMB for amendments made to existing information collections under OMB Nos. 0581-0178 and 0581-0242, and for a new information collection under OMB No. 0581-NEW.

Upon finalization of the proposed rule, AMS will submit a Justification for Change to OMB for the Statement of Intent form contained in the ABC Credit-Back Guide (OMB No. 0581-0178). The form is necessary to administer the Credit-Back provisions as established in § 981.441 of the Order's requirements. This proposed rule would change the number of days that the applicant is afforded to submit all necessary paperwork for proper evaluation of their Credit-Back claim from 76 days to 60 days. The Credit-Back Statement of Intent form included in the Credit-Back Guide would be changed accordingly.

In addition, also upon finalization of the proposed rule, AMS will submit a Justification for Change to OMB for the ABC Form 52—Direct Verifiable (DV) Program for Further Processing of Untreated Almonds Application Form (OMB No. 0581-0242). The form is necessary to administer the DV Program established by § 981.442(b)(6)(i) in the Order's quality control requirements. The proposed rule would change the body that approves DV Program applications from the TERP to the Board. The instructions that accompany ABC Form 52 would need to be revised accordingly.

Lastly, this proposed rule would create a new form for California almond handlers, titled ABC Form 55—Custom Processor Application.

Title: Custom Processor Application (7 CFR part 981).

OMB Number: 0581-NEW.

Type of Request: New Collection.

Abstract: The information requirements in this request are essential to carry out the intent of the Act and to administer the Order. The Order is effective under the Act, and USDA is responsible for the oversight of the Order's administration.

The Order's quality control requirements for outgoing product require handlers to subject their almonds to a treatment process or processes prior to shipment to reduce potential Salmonella bacteria contamination. The Order's quality control requirements allow handlers to utilize off-site treatment facilities to fulfill that requirement. The Committee unanimously recommended that the Order's quality control requirements be amended to define off-site treatment facilities located within the production area as “custom processors” and to require such custom processors to annually apply to the Board for approval.

An individual desiring approval as a custom processor must demonstrate that their facility meets the Order's treatment process requirements and must submit an application to the Board. This form, numbered ABC Form 55 and titled “Custom Processor Application,” would be submitted directly to the Board once each year no later than July 31. The application would provide the Board with the name of the applicant, the location of each treatment facility covered by the application, applicant contact information, and certification that the applicant's technology and equipment provide a treatment process that has been validated by a Board-approved process authority.

The Order authorizes the Board to collect certain information necessary for the administration of the Order. The information collected would only be used by authorized representatives of the USDA, including the AMS Specialty Crops Program regional and headquarters staff, and authorized employees of the Board. All proprietary information would be kept confidential in accordance with the Act and the Order.

The proposed request for new information collection under the Order is as follows:

Estimate of Burden: Public reporting burden for this collection of information is estimated to be an average of 0.5 hours per response.

Respondents: Nut processors located within the Order's area of production.

Estimated Number of Respondents: 25.

Estimated Number of Responses per Respondent: 1.

Estimated Total Annual Responses: 25.

Estimated Total Annual Burden on Respondents: 12.5 hours.

Comments are invited on: (1) Whether the proposed collection of information is necessary for the proper performance of the functions of the Agency, including whether the information will have practical utility; (2) the accuracy of the Agency's estimate of the burden of the proposed collection of information, including the validity of the methodology and assumptions used; (3) ways to enhance the quality, utility, and clarity of the information to be collected; and (4) ways to minimize the burden of the collection of information on those who are to respond, including the use of appropriate automated, electronic, mechanical, or other technological collection techniques or other forms of information technology.

Comments should reference OMB No. 0581-NEW and the marketing order for almonds grown in California. Comments should be sent to the USDA in care of the Docket Clerk at the previously mentioned address or at https://www.regulations.gov.

All responses to this notice will be summarized and included in the request for OMB approval. All comments received will become a matter of public record and will be available for public inspection during regular business hours at the address of the Docket Clerk or at https://www.regulations.gov.

If this proposed rule is finalized, this information collection will be merged with the forms currently approved under OMB No. 0581-0242 (Almond Salmonella).

As with all Federal marketing order programs, reports and forms are periodically reviewed to reduce information requirements and duplication by industry and public sector agencies. USDA has not identified any relevant Federal rules that duplicate, overlap, or conflict with this proposed rule.

AMS is committed to complying with the E-Government Act, to promote the use of the internet and other information technologies to provide increased opportunities for citizen access to Government information and services, and for other purposes.

Further, the Board's meetings are widely publicized throughout the California almond industry, and all interested persons are invited to attend the meetings and participate in Board deliberations on all issues. Like all Board meetings, the December 7, 2020, and June 17, 2021, meetings were open to the public, and all entities, both large and small, were able to express their views on this issue. Also, the Board has several appointed committees to review certain issues and make recommendations to the Board. The Board's Almond Quality, Food Safety, and Services Committee met several times in 2019 and discussed this issue in detail. Those meetings were also public meetings, and both large and small entities were able to participate and express their views. Finally, interested persons are invited to submit comments on this proposed rule, including the regulatory and information collection impacts of this action on small businesses.

A small business guide on complying with fruit, vegetable, and specialty crop marketing agreements and orders may be viewed at: https://www.ams.usda.gov/rules-regulations/moa/small-businesses. Any questions about the compliance guide should be sent to Richard Lower at the previously mentioned address in the FOR FURTHER INFORMATION CONTACT section.

A 60-day comment period is provided to allow interested persons to respond to this proposal. All written comments timely received will be considered before a final determination is made on this matter.

For the reasons set forth in the preamble, the Agricultural Marketing Service proposes to amend 7 CFR part 981 as follows:

The revisions read as follows:

On May 21, 2018, the United States Coast Guard established a security zone to protect the President of the United States, members of the First Family, and/or other persons under the protection of the Secret Service when staying at the Mar-A-Lago Club in Palm Beach, FL. The security zone is described 33 CFR 165.785. With the inauguration of a new President of the United States on January 20, 2021, the Mar-A-Lago Club security zone is no longer needed.

The purpose of this rulemaking is to disestablish a security zone in certain waters of the Lake Worth Lagoon, Intercoastal Waterway (ICW), and Atlantic Ocean that are no longer need to protect official parties staying at the Mar-A-Lago Club. The Coast Guard is proposing this rulemaking under authority in 46 U.S.C. 70034 (previously 33 U.S.C. 1231).

The Coast Guard is proposing to disestablish the existing security zone published in 33 CFR 165.785. The regulation places unnecessary restrictions on vessel movement through the Lake Worth Lagoon, ICW, and Atlantic Ocean near the Mar-A-Lago Club and the Southern Boulevard Bridge in Palm Beach. The regulatory text we are proposing appears at the end of this document.

We developed this proposed rule after considering numerous statutes and Executive orders related to rulemaking. Below we summarize our analyses based on a number of these statutes and Executive orders, and we discuss First Amendment rights of protestors.

Executive Orders 12866 and 13563 direct agencies to assess the costs and benefits of available regulatory alternatives and, if regulation is necessary, to select regulatory approaches that maximize net benefits. This NPRM has not been designated a “significant regulatory action,” under Executive Order 12866. Accordingly, the NPRM has not been reviewed by the Office of Management and Budget (OMB).

This regulatory action determination is based on the removal of regulatory requirements for vessel navigation in the Lake Worth Lagoon, ICW, and Atlantic Ocean near the Mar-A-Lago Club and the Southern Boulevard Bridge in Palm Beach.

The Regulatory Flexibility Act of 1980, 5 U.S.C. 601-612, as amended, requires Federal agencies to consider the potential impact of regulations on small entities during rulemaking. The term “small entities” comprises small businesses, not-for-profit organizations that are independently owned and operated and are not dominant in their fields, and governmental jurisdictions with populations of less than 50,000. The Coast Guard certifies under 5 U.S.C. 605(b) that this proposed rule would not have a significant economic impact on a substantial number of small entities.

While some owners or operators of vessels intending to transit the Lake Worth Lagoon, ICW, and Atlantic Ocean, near the Mar-A-Lago Club and the Southern Boulevard Bridge in Palm Beach, may be small entities, for the reasons stated in section IV.A above, this proposed rule would not have a significant economic impact on any vessel owner or operator.

If you think that your business, organization, or governmental jurisdiction qualifies as a small entity and that this proposed rule would have a significant economic impact on it, please submit a comment (see ADDRESSES ) explaining why you think it qualifies and how and to what degree this rule would economically affect it.

Under section 213(a) of the Small Business Regulatory Enforcement Fairness Act of 1996 (Pub. L. 104-121), we want to assist small entities in understanding this proposed rule. If the proposed rule would affect your small business, organization, or governmental jurisdiction and you have questions concerning its provisions or options for compliance, please call or email the person listed in the FOR FURTHER INFORMATION CONTACT section. The Coast Guard will not retaliate against small entities that question or complain about this proposed rule or any policy or action of the Coast Guard.

This proposed rule would not call for a new collection of information under the Paperwork Reduction Act of 1995 (44 U.S.C. 3501-3520).

A rule has implications for federalism under Executive Order 13132 (Federalism), if it has a substantial direct effect 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. We have analyzed this proposed rule under that Order and have determined that it is consistent with the fundamental federalism principles and preemption requirements described in Executive Order 13132.

Also, this proposed rule does not have tribal implications under Executive Order 13175 (Consultation and Coordination with Indian Tribal Governments) because it would not have a substantial direct effect on one or more Indian tribes, on the relationship between the Federal Government and Indian tribes, or on the distribution of power and responsibilities between the Federal Government and Indian tribes. If you believe this proposed rule has implications for federalism or Indian tribes, please call or email the person listed in the FOR FURTHER INFORMATION CONTACT section.

The Unfunded Mandates Reform Act of 1995 (2 U.S.C. 1531-1538) requires Federal agencies to assess the effects of their discretionary regulatory actions. In particular, the Act addresses actions that may result in the expenditure by a State, local, or tribal government, in the aggregate, or by the private sector of $100,000,000 (adjusted for inflation) or more in any one year. Though this proposed rule would not result in such an expenditure, we do discuss the potential effects of this proposed rule elsewhere in this preamble.

We have analyzed this proposed rule under Department of Homeland Security Directive 023-01, Rev. 1, associated implementing instructions, and Environmental Planning COMDTINST 5090.1 (series), which guide the Coast Guard in complying with the National Environmental Policy Act of 1969 (42 U.S.C. 4321-4370f), and have made a preliminary determination that this action is one of a category of actions that do not individually or cumulatively have a significant effect on the human environment. This proposed rule involves disestablishing a security zone. Such actions are categorically excluded from further review under paragraph L60(b) of Appendix A, Table 1 of DHS Instruction Manual 023-01-001-01, Rev. 1. We seek any comments or information that may lead to the discovery of a significant environmental impact from this proposed rule.

The Coast Guard respects the First Amendment rights of protesters. Protesters are asked to call or email the person listed in the FOR FURTHER INFORMATION CONTACT section to coordinate protest activities so that your message can be received without jeopardizing the safety or security of people, places, or vessels.

We view public participation as essential to effective rulemaking, and will consider all comments and material received during the comment period. Your comment can help shape the outcome of this rulemaking. If you submit a comment, please include the docket number for this rulemaking, indicate the specific section of this document to which each comment applies, and provide a reason for each suggestion or recommendation.

Submitting comments. We encourage you to submit comments through the Federal Decision Making Portal at https://www.regulations.gov. To do so, go to https://www.regulations.gov, type USCG-2022-0054 in the search box and click “Search.” Next, look for this document in the Search Results column, and click on it. Then click on the Comment option. If you cannot submit your material by using https://www.regulations.gov, call or email the person in the FOR FURTHER INFORMATION CONTACT section of this proposed rule for alternate instructions.

Viewing material in docket. To view documents mentioned in this proposed rule as being available in the docket, find the docket as described in the previous paragraph, and then select “Supporting & Related Material” in the Document Type column. Public comments will also be placed in our online docket and can be viewed by following instructions on the https://www.regulations.gov Frequently Asked Questions web page. We review all comments received, but we will only post comments that address the topic of the proposed rule. We may choose not to post off-topic, inappropriate, or duplicate comments that we receive.

Personal information. We accept anonymous comments. Comments we post to https://www.regulations.gov will include any personal information you have provided. For more about privacy and submissions to the docket in response to this document, see DHS's eRulemaking System of Records notice (85 FR 14226, March 11, 2020).

For the reasons discussed in the preamble, the Coast Guard is proposing to amend 33 CFR part 165 as follows:

Public Participation: Submit your comments, identified by Docket ID No. EPA-R03-OAR-2021-0872, at https://www.regulations.gov (our preferred method), or the other method identified in the ADDRESSES section. Once submitted, comments cannot be edited or removed from the docket. The EPA may publish any comment received to its public docket. Do not submit to EPA's docket at https://www.regulations.gov 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).

There are two dockets supporting this action, EPA-R03-OAR-2021-0872 and EPA-HQ-OAR-2021-0663. Docket No. EPA-R03-OAR-2021-0872 contains information specific to Maryland, including the notice of proposed rulemaking. Docket No. EPA-HQ-OAR-2021-0663 contains additional modeling files, emissions inventory files, technical support documents, and other relevant supporting documentation regarding interstate transport of emissions for the 2015 8-hour ozone NAAQS which are being used to support this action. All comments regarding information in either of these dockets are to be made in Docket No. EPA-R03-OAR-2021-0872 only. For additional submission methods, please contact Mike Gordon, 215-814-2039, gordon.mike@epa.gov. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. Due to public health concerns related to COVID-19, the EPA Docket Center and Reading Room are open to the public by appointment only. Our Docket Center staff also continues to provide remote customer service via email, phone, and webform. For further information and updates on EPA Docket Center services, please visit us online at https://www.epa.gov/dockets.

The EPA continues to carefully and continuously monitor information from the Centers for Disease Control and Prevention (CDC), local area health departments, and our Federal partners so that we can respond rapidly as conditions change regarding COVID-19.

The index to the docket for this action, Docket No. EPA-R03-OAR-2021-0872, is available electronically at www.regulations.gov. While all documents in the docket are listed in the index, some information may not be publicly available via the online docket due to docket file size restrictions, such as certain modeling files, or content ( e.g., CBI). Please contact the EPA Docket Center Services for further information.

Throughout this document, “we,” “us,” and “our” means the EPA.

On October 1, 2015, the EPA promulgated a revision to the ozone NAAQS (2015 8-hour ozone NAAQS), lowering the level of both the primary and secondary standards to 0.070 parts per million (ppm). 1 Section 110(a)(1) of the CAA requires states to submit, within 3 years after promulgation of a new or revised NAAQS, SIP submissions meeting the applicable requirements of section 110(a)(2). 2 One of these applicable requirements is found in CAA section 110(a)(2)(D)(i)(I), otherwise known as the “interstate transport” or “good neighbor” provision, which generally requires SIPs to contain adequate provisions to prohibit in-state emissions activities from having certain adverse air quality effects on other states due to interstate transport of pollution. There are two so-called “prongs” within CAA section 110(a)(2)(D)(i)(I). A SIP for a new or revised NAAQS must contain adequate provisions prohibiting any source or other type of emissions activity within the state from emitting air pollutants in amounts that will significantly contribute to nonattainment of the NAAQS in another state (prong 1) or interfere with maintenance of the NAAQS in another state (prong 2). The EPA and states must give independent significance to prong 1 and prong 2 when evaluating downwind air quality problems under CAA section 110(a)(2)(D)(i)(I). 3

Throughout this document, “we,” “us” and “our” refer to the EPA.

Table 1 lists the rules addressed by this proposal with the dates that they were adopted by Clark County DES and submitted by the Nevada Division of Environmental Protection (NDEP).

On September 13, 2020, the submitted rules in Table 1 were deemed to be complete by operation of law to meet the completeness criteria in 40 CFR part 51 Appendix V, which must be met before formal EPA review.

We approved an earlier version of Rule 2 into the SIP on August 27, 1981 (46 FR 43141). The Clark County DES adopted revisions to the SIP-approved version on January 21, 2020, and NDEP submitted it to us on March 13, 2020.

We approved an earlier version of Rule 33 into the SIP on September 7, 2004 (69 FR 54006). The Clark County DES adopted a revision to the SIP-approved version on January 21, 2020, and NDEP submitted it to us on March 13, 2020.

We approved an earlier version of Rule 41 into the SIP on October 6, 2014 (79 FR 60078). The Clark County DES adopted a revision to the SIP-approved version on January 21, 2020, and NDEP submitted it to us on March 13, 2020.

We approved an earlier version of Rule 53 into the SIP on September 21, 2004 (69 FR 56351). The Clark County DES adopted a revision to the SIP-approved version on January 21, 2020, and NDEP submitted it to us on March 13, 2020.

We approved an earlier version of Rule 90 into the SIP on October 6, 2014 (79 FR 60078). The Clark County DES adodpted a revision to the SIP-approved version on January 21, 2020, and NDEP submitted it to us on March 13, 2020.

We approved an earlier version of Rule 93 into the SIP on October 6, 2014 (79 FR 60078). The Clark County DES adopted a revision to the SIP-approved version on January 21, 2020, and NDEP submitted it to us on March 13, 2020.

We approved an earlier version of Rule 94 into the SIP on October 30, 2006 (71 FR 63250). The Clark County DES adopted a revision to the SIP-approved vesion on January 21, 2020, and NDEP submitted it to us on March 13, 2020.

While we can act on only the most recently submitted version, we have reviewed materials provided with previous submittals.

The purpose of these submitted rule revisions is to delete “the department of air quality” everywhere it appears in the submitted rules and replacing it with “department” and to update formatting.

The EPA's technical support document (TSD) and submitted staff report have more information about these rules.

Rules in the SIP must be enforceable (see CAA section 110(a)(2)), must not interfere with applicable requirements concerning attainment and reasonable further progress or other CAA requirements (see CAA section 110(l)), and must not modify certain SIP control requirements in nonattainment areas without ensuring equivalent or greater emissions reductions (see CAA section 193).

Guidance and policy documents that we used to evaluate enforceability, revision/relaxation and rule stringency requirements for the applicable criteria pollutants include the following:

These rules are consistent with CAA requirements and relevant guidance regarding enforceability. The TSD has more information on our evaluation.

As authorized in section 110(k)(3) of the Act, the EPA proposes to fully approve the submitted rules because they fulfill all relevant requirements. We will accept comments from the public on this proposal until March 24, 2022. If we take final action to approve the submitted rules, our final action will incorporate these rules into the federally enforceable SIP.

In this proposed rule, the EPA is proposing to include in a final EPA rule regulatory text that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, the EPA is proposing to incorporate by reference the Clark County DES rules described in Table 1 of this preamble. The EPA has made, and will continue to make, these materials available through https://www.regulations.gov and at the EPA Region IX Office (please contact the person identified in the FOR FURTHER INFORMATION CONTACT section of this preamble for more information).

Under the Clean Air Act, the Administrator is required to approve a SIP submission that complies with the provisions of the Act and applicable federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, the EPA's role is to approve state choices, provided that they meet the criteria of the Clean Air Act. Accordingly, this proposed action merely proposes to approve state law as meeting federal requirements and does not impose additional requirements beyond those imposed by state law. For that reason, this proposed action:

• Is not a “significant regulatory action” subject to review by the Office of Management and Budget under Executive Orders 12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);

• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq. );

• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq. );

• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4);

• Does not have federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);

• Is not an economically significant regulatory action based on health or safety risks subject to Executive Order 13045 (62 FR 19885, April 23, 1997);

• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001);

• Is not subject to requirements of Section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the Clean Air Act; and

• Does not provide the EPA with the discretionary authority to address disproportionate human health or environmental effects with practical, appropriate, and legally permissible methods under Executive Order 12898 (59 FR 7629, February 16, 1994).

In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where the EPA or an Indian tribe has demonstrated that a tribe has jurisdiction. In those areas of Indian country, the proposed rule does not have tribal implications and will not impose substantial direct costs on tribal governments or preempt tribal law as specified by Executive Order 13175 (65 FR 67249, November 9, 2000).

Public participation: Submit your comments, identified by Docket ID No. EPA-R07-OAR-2021-0870, at https://www.regulations.gov (our preferred method), or the other methods identified in the ADDRESSES section. Once submitted, comments cannot be edited or removed from the docket. The EPA may publish any comment received to its public docket. Do not submit to EPA's docket at https://www.regulations.gov 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).

There are two dockets supporting this action, EPA-R07-OAR-2021-0870 and EPA-HQ-OAR-2021-0663. Docket No. EPA-R07-OAR-2021-0870 contains information specific to Iowa, including the notice of proposed rulemaking. Docket No. EPA-HQ-OAR-2021-0663 contains additional modeling files, emissions inventory files, technical support documents, and other relevant supporting documentation regarding interstate transport of emissions for the 2015 8-hour ozone NAAQS which are being used to support this action. All comments regarding information in either of these dockets are to be made in Docket No. EPA-R07-OAR-2021-0870. For additional submission methods, please contact William Stone, (913) 551-7714, stone.william@epa.gov. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. Due to public health concerns related to COVID-19, the EPA Docket Center and Reading Room are open to the public by appointment only. Our Docket Center staff also continues to provide remote customer service via email, phone, and webform. For further information and updates on EPA Docket Center services, please visit us online at https://www.epa.gov/dockets.

The EPA continues to carefully and continuously monitor information from the Centers for Disease Control and Prevention (CDC), local area health departments, and our Federal partners so that we can respond rapidly as conditions change regarding COVID-19. The index to the docket for this action, Docket No. EPA-R07-OAR-2021-0870, is available electronically at www.regulations.gov. While all documents in the docket are listed in the index, some information may not be publicly available due to docket file size restrictions or content ( e.g., CBI).

Throughout this document, “we,” “us,” and “our” means the EPA.

On October 1, 2015, the EPA promulgated a revision to the ozone NAAQS (2015 8-hour ozone NAAQS), lowering the level of both the primary and secondary standards to 0.070 parts per million (ppm). 1 Section 110(a)(1) of the CAA requires states to submit, within 3 years after promulgation of a new or revised standard, SIP submissions meeting the applicable requirements of section 110(a)(2). 2 One of these applicable requirements is found in CAA section 110(a)(2)(D)(i)(I), otherwise known as the “interstate transport” or “good neighbor” provision, which generally requires SIPs to contain adequate provisions to prohibit in-state emissions activities from having certain adverse air quality effects on other states due to interstate transport of pollution. There are two so-called “prongs” within CAA section 110(a)(2)(D)(i)(I). A SIP for a new or revised NAAQS must contain adequate provisions prohibiting any source or other type of emissions activity within the state from emitting air pollutants in amounts that will significantly contribute to nonattainment of the NAAQS in another state (prong 1) or interfere with maintenance of the NAAQS in another state (prong 2). The EPA and states must give independent significance to prong 1 and prong 2 when evaluating downwind air quality problems under CAA section 110(a)(2)(D)(i)(I). 3

The EPA is using the 4-step interstate transport framework (or 4-step framework) to evaluate the state's SIP submittals addressing the interstate transport provision for the 2015 8-hour ozone NAAQS. The EPA has addressed the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) with respect to prior ozone NAAQS in several regional regulatory actions, including the Cross-State Air Pollution Rule (CSAPR), which addressed interstate transport with respect to the 1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter standards, 4 and the Cross-State Air Pollution Rule Update (CSAPR Update)  5 and the Revised CSAPR Update, both of which addressed the 2008 ozone NAAQS. 6

Through the development and implementation of the CSAPR rulemakings and prior regional rulemakings pursuant to the interstate transport provision, 7 the EPA, working in partnership with states, developed the following 4-step interstate transport framework to evaluate a State's obligations to eliminate interstate transport emissions under the interstate transport provision for the ozone NAAQS: (1) Identify monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS ( i.e., nonattainment and/or maintenance receptors); (2) identify states that impact those air quality problems in other ( i.e., downwind) states sufficiently such that the states are considered “linked” and therefore warrant further review and analysis; (3) identify the emissions reductions necessary (if any), applying a multifactor analysis, to eliminate each linked upwind state's significant contribution to nonattainment or interference with maintenance of the NAAQS at the locations identified in step 1; and (4) adopt permanent and enforceable measures needed to achieve those emissions reductions.

In general, the EPA has performed nationwide air quality modeling to project ozone design values which are used in combination with measured data to identify nonattainment and maintenance receptors. To quantify the contribution of emissions from specific upwind states on 2023 ozone design values for the identified downwind nonattainment and maintenance receptors, the EPA performed nationwide, state-level ozone source apportionment modeling for 2023. The source apportionment modeling provided contributions to ozone at receptors from precursor emissions of anthropogenic nitrogen oxides (NO X ) and volatile organic compounds (VOCs) in individual upwind states.

The EPA has released several documents containing projected ozone design values, contributions, and information relevant to evaluating interstate transport with respect to the 2015 8-hour ozone NAAQS. First, on January 6, 2017, the EPA published a notice of data availability (NODA) in which we requested comment on preliminary interstate ozone transport data including projected ozone design values and interstate contributions for 2023 using a 2011 base year platform. 8 In the NODA, the EPA used the year 2023 as the analytic year for this preliminary modeling because that year aligns with the expected attainment year for Moderate ozone nonattainment areas for the 2015 8-hour ozone NAAQS. 9 On October 27, 2017, we released a memorandum (October 2017 memorandum) containing updated modeling data for 2023, which incorporated changes made in response to comments on the NODA, and noted that the modeling may be useful for states developing SIPs to address interstate transport obligations for the 2008 ozone NAAQS. 10 On March 27, 2018, we issued a memorandum (March 2018 memorandum) noting that the same 2023 modeling data released in the October 2017 memorandum could also be useful for identifying potential downwind air quality problems with respect to the 2015 8-hour ozone NAAQS at Step 1 of the 4-step interstate transport framework. 11 The March 2018 memorandum also included the then newly available contribution modeling data to assist states in evaluating their impact on potential downwind air quality problems for the 2015 8-hour ozone NAAQS under Step 2 of the 4-step interstate transport framework. 12 The EPA subsequently issued two more memoranda in August and October 2018, providing additional information to states developing interstate transport SIP submissions for the 2015 8-hour ozone NAAQS concerning, respectively, potential contribution thresholds that may be appropriate to apply in Step 2 of the 4-step interstate transport framework, and considerations for identifying downwind areas that may have problems maintaining the standard at Step 1 of the 4-step interstate transport framework. 13

Since the release of the modeling data shared in the March 2018 memorandum, the EPA performed updated modeling using a 2016-based emissions modeling platform ( i.e., 2016v1). This emissions platform was developed under the EPA/Multi-Jurisdictional Organization (MJO)/state collaborative project. 14 This collaborative project was a multi-year joint effort by the EPA, MJOs, and states to develop a new, more recent emissions platform for use by the EPA and states in regulatory modeling as an improvement over the dated 2011-based platform that the EPA had used to project ozone design values and contribution data provided in the 2017 and 2018 memoranda. The EPA used the 2016v1 emissions to project ozone design values and contributions for 2023. On October 30, 2020, in the Notice of Proposed Rulemaking for the Revised CSAPR Update, the EPA released and accepted public comment on 2023 modeling that used the 2016v1 emissions platform. 15 Although the Revised CSAPR Update addressed transport for the 2008 ozone NAAQS, the projected design values and contributions from the 2016v1 platform are also useful for identifying downwind ozone problems and linkages with respect to the 2015 ozone NAAQS. 16

Following the final Revised CSAPR Update, the EPA made further updates to the 2016 emissions platform to include mobile emissions from the EPA's Motor Vehicle Emission Simulator MOVES3 model  17 and updated emissions projections for electric generating units (EGUs) that reflect the emissions reductions from the Revised CSAPR Update, recent information on plant closures, and other sector trends. The construct of the updated emissions platform, 2016v2, is described in the emissions modeling technical support document (TSD) for this proposed rule. 18 The EPA performed air quality modeling of the 2016v2 emissions using the most recent public release version of the Comprehensive Air-quality Model with extensions (CAMx) photochemical modeling, version 7.10. 19 The EPA now proposes to primarily rely on modeling based on the updated and newly available 2016v2 emissions platform in evaluating these submissions with respect to Steps 1 and 2 of the 4-step interstate transport framework and generally referenced within this action as 2016v2 modeling for 2023. By using the updated modeling results, the EPA is using the most current and technically appropriate information for this proposed rulemaking. Section III of this document and the Air Quality Modeling TSD for 2015 Ozone NAAQS Transport SIP Proposed Actions, included in Docket ID No. EPA-HQ-OAR-2021-0663 for this proposal, contain additional detail on the EPA's 2016v2 modeling. In this document, the EPA is accepting public comment on this updated 2023 modeling, which uses a 2016v2 emissions platform. Comments on the EPA's air quality modeling should be submitted in the Regional docket for this action, docket ID No. EPA-R07-OAR-2021-0870. Comments are not being accepted in docket ID No. EPA-HQ-OAR-2021-0663.

The EPA proposes to apply a consistent set of policy judgments across all states for purposes of evaluating interstate transport obligations and the approvability of interstate transport SIP submittals for the 2015 8-hour ozone NAAQS. These policy judgments reflect consistency with relevant case law and past agency practice as reflected in the CSAPR and related rulemakings. Nationwide consistency in approach is particularly important in the context of interstate ozone transport, which is a regional-scale pollution problem involving many smaller contributors. Effective policy solutions to the problem of interstate ozone transport going back to the NO X SIP Call have necessitated the application of a uniform framework of policy judgments in order to ensure an “efficient and equitable” approach. See EME Homer City Generation, LP v. EPA, 572 U.S. 489, 519 (2014).

In the March, August, and October 2018 memoranda, the EPA recognized that states may be able to establish alternative approaches to addressing their interstate transport obligations for the 2015 8-hour ozone NAAQS that vary from a nationally uniform framework. The EPA emphasized in these memoranda, however, that such alternative approaches must be technically justified and appropriate in light of the facts and circumstances of each particular state's submittal. In general, the EPA continues to believe that deviation from a nationally consistent approach to ozone transport must be substantially justified and have a well-documented technical basis that is consistent with relevant case law. Where states submitted SIPs that rely on any such potential “flexibilities” as may have been identified or suggested in the past, the EPA will evaluate whether the state adequately justified the technical and legal basis for doing so.

The EPA notes that certain concepts included in an attachment to the March 2018 memorandum require unique consideration, and these ideas do not constitute agency guidance with respect to transport obligations for the 2015 ozone NAAQS. Attachment A to the March 2018 memorandum identified a “Preliminary List of Potential Flexibilities” that could potentially inform SIP development. 20 However, EPA made clear in that Attachment that the list of ideas were not suggestions endorsed by the Agency but rather “comments provided in various forums” on which EPA sought “feedback from interested stakeholders.”  21 Further, Attachment A stated, “EPA is not at this time making any determination that the ideas discussed below are consistent with the requirements of the CAA, nor are we specifically recommending that states use these approaches.”  22 Attachment A to the March 2018 memorandum, therefore, does not constitute agency guidance, but was intended to generate further discussion around potential approaches to addressing ozone transport among interested stakeholders. To the extent states sought to develop or rely on these ideas in support of their SIP submittals, EPA will thoroughly review the technical and legal justifications for doing so.

The remainder of this section describes the EPA's proposed framework with respect to analytic year, definition of nonattainment and maintenance receptors, selection of contribution threshold, and multifactor control strategy assessment.

In general, the states and the EPA must implement the interstate transport provision in a manner “consistent with the provisions of [title I of the CAA.]” CAA section 110(a)(2)(D)(i). This requires, among other things, that these obligations are addressed consistently with the timeframes for downwind areas to meet their CAA obligations. With respect to ozone NAAQS, under CAA section 181(a), this means obligations must be addressed “as expeditiously as practicable” and no later than the schedule of attainment dates provided in CAA section 181(a)(1). 23 Several D.C. Circuit court decisions address the issue of the relevant analytic year for the purposes of evaluating ozone transport air-quality problems. On September 13, 2019, the D.C. Circuit issued a decision in Wisconsin v. EPA, remanding the CSAPR Update to the extent that it failed to require upwind states to eliminate their significant contribution by the next applicable attainment date by which downwind states must come into compliance with the NAAQS, as established under CAA section 181(a). 938 F.3d at 313.

On May 19, 2020, the D.C. Circuit issued a decision in Maryland v. EPA that cited the Wisconsin decision in holding that the EPA must assess the impact of interstate transport on air quality at the next downwind attainment date, including Marginal area attainment dates, in evaluating the basis for the EPA's denial of a petition under CAA section 126(b). Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 2020). The court noted that “section 126(b) incorporates the Good Neighbor Provision,” and, therefore, “EPA must find a violation [of section 126] if an upwind source will significantly contribute to downwind nonattainment at the next downwind attainment deadline. Therefore, the agency must evaluate downwind air quality at that deadline, not at some later date.” Id. at 1204 (emphasis added). The EPA interprets the court's holding in Maryland as requiring the states and the Agency, under the good neighbor provision, to assess downwind air quality as expeditiously as practicable and no later than the next applicable attainment date, 24 which is now the Moderate area attainment date under CAA section 181 for ozone nonattainment. The Moderate area attainment date for the 2015 8-hour ozone NAAQS is August 3, 2024. 25 The EPA believes that 2023 is now the appropriate year for analysis of interstate transport obligations for the 2015 8-hour ozone NAAQS, because the 2023 ozone season is the last relevant ozone season during which achieved emissions reductions in linked upwind states could assist downwind states with meeting the August 3, 2024, Moderate area attainment date for the 2015 8-hour ozone NAAQS.

The EPA recognizes that the attainment date for nonattainment areas classified as Marginal for the 2015 8- hour ozone NAAQS was August 3, 2021. Under the Maryland holding, any necessary emissions reductions to satisfy interstate transport obligations should have been implemented by no later than this date. At the time of the statutory deadline to submit interstate transport SIPs (October 1, 2018), many states relied upon the EPA modeling of the year 2023, and no state provided an alternative analysis using a 2021 analytic year (or the prior 2020 ozone season). However, the EPA must act on SIP submittals using the information available at the time it takes such action. In this circumstance, the EPA does not believe it would be appropriate to evaluate states' obligations under CAA section 110(a)(2)(D)(i)(I) as of an attainment date that is wholly in the past, because the Agency interprets the interstate transport provision as forward looking. See 86 FR at 23074; see also Wisconsin, 938 F.3d at 322. Consequently, in this proposal the EPA will use the analytical year of 2023 to evaluate each state's CAA section 110(a)(2)(D)(i)(I) SIP submission with respect to the 2015 8-hour ozone NAAQS.

In Step 1, the EPA identifies monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS in the 2023 analytic year. Where the EPA's analysis shows that a site does not fall under the definition of a nonattainment or maintenance receptor, that site is excluded from further analysis under the EPA's 4-step interstate transport framework. For sites that are identified as a nonattainment or maintenance receptor in 2023, we proceed to the next step of our 4-step interstate transport framework by identifying the upwind state's contribution to those receptors.

The EPA's approach to identifying ozone nonattainment and maintenance receptors in this action is consistent with the approach used in previous transport rulemakings. The EPA's approach gives independent consideration to both the “contribute significantly to nonattainment” and the “interfere with maintenance” prongs of CAA section 110(a)(2)(D)(i)(I), consistent with the D.C. Circuit's direction in North Carolina v. EPA. 26

For the purpose of this proposal, the EPA identifies nonattainment receptors as those monitoring sites that are projected to have average design values that exceed the NAAQS and that are also measuring nonattainment based on the most recent monitored design values. This approach is consistent with prior transport rulemakings, such as the CSAPR Update, where the EPA defined nonattainment receptors as those areas that both currently measure nonattainment and that the EPA projects will be in nonattainment in the future analytic year ( i.e., 2023). 27

In addition, in this proposal, the EPA identifies a receptor to be a “maintenance” receptor for purposes of defining interference with maintenance, consistent with the method used in the CSAPR and upheld by the D.C. Circuit in EME Homer City Generation, L.P. v. EPA, 795 F.3d 118, 136 (D.C. Cir. 2015). 28 Specifically, the EPA identified maintenance receptors as those receptors that would have difficulty maintaining the relevant NAAQS in a scenario that takes into account historical variability in air quality at that receptor. The variability in air quality was determined by evaluating the “maximum” future design value at each receptor based on a projection of the maximum measured design value over the relevant period. EPA interprets the projected maximum future design value to be a potential future air quality outcome consistent with the meteorology that yielded maximum measured concentrations in the ambient data set analyzed for that receptor ( i.e., ozone conducive meteorology). EPA also recognizes that previously experienced meteorological conditions ( e.g., dominant wind direction, temperatures, air mass patterns) promoting ozone formation that led to maximum concentrations in the measured data may reoccur in the future. The maximum design value gives a reasonable projection of future air quality at the receptor under a scenario in which such conditions do, in fact, reoccur. The projected maximum design value is used to identify upwind emissions that, under those circumstances, could interfere with the downwind area's ability to maintain the NAAQS.

Recognizing that nonattainment receptors are also, by definition, maintenance receptors, the EPA often uses the term “maintenance-only” to refer to those receptors that are not nonattainment receptors. Consistent with the concepts for maintenance receptors, as described above, the EPA identifies “maintenance-only” receptors as those monitoring sites that have projected average design values above the level of the applicable NAAQS, but that are not currently measuring nonattainment based on the most recent official design values. In addition, those monitoring sites with projected average design values below the NAAQS, but with projected maximum design values above the NAAQS are also identified as “maintenance only” receptors, even if they are currently measuring nonattainment based on the most recent official design values.

In Step 2 the EPA quantifies the contribution of each upwind state to each receptor in the 2023 analytic year. The contribution metric used in Step 2 is defined as the average impact from each state to each receptor on the days with the highest ozone concentrations at the receptor based on the 2023 modeling. If a state's contribution value does not equal or exceed the threshold of 1 percent of the NAAQS ( i.e., 0.70 ppb for the 2015 8-hour ozone NAAQS), the upwind state is not “linked” to a downwind air quality problem, and the EPA, therefore, concludes that the state does not significantly contribute to nonattainment or interfere with maintenance of the NAAQS in the downwind states. However, if a state's contribution equals or exceeds the 1 percent threshold, the state's emissions are further evaluated in Step 3, considering both air quality and cost as part of a multi-factor analysis, to determine what, if any, emissions might be deemed “significant” and, thus, must be eliminated under CAA section 110(a)(2)(D)(i)(I). The EPA is proposing to rely in the first instance on the 1 percent threshold for the purpose of evaluating a state's contribution to nonattainment or maintenance of the 2015 8-hour ozone NAAQS ( i.e., 0.70 ppb) at downwind receptors. This is consistent with the Step 2 approach that the EPA applied in CSAPR for the 1997 ozone NAAQS, which has subsequently been applied in the CSAPR Update when evaluating interstate transport obligations for the 2008 ozone NAAQS. The EPA continues to find 1 percent to be an appropriate threshold. For ozone, as the EPA found in the Clean Air Interstate Rule (CAIR), CSAPR, and CSAPR Update, a portion of the nonattainment problems from anthropogenic sources in the U.S. results from the combined impact of relatively small contributions from many upwind states, along with contributions from in-state sources and, in some cases, substantially larger contributions from a subset of particular upwind states. The EPA's analysis shows that much of the ozone transport problem being analyzed in this proposed rule is still the result of the collective impacts of contributions from many upwind states. Therefore, application of a consistent contribution threshold is necessary to identify those upwind states that should have responsibility for addressing their contribution to the downwind nonattainment and maintenance problems to which they collectively contribute. Continuing to use 1 percent of the NAAQS as the screening metric to evaluate collective contribution from many upwind states also allows the EPA (and states) to apply a consistent framework to evaluate interstate emissions transport under the interstate transport provision from one NAAQS to the next. See 81 FR at 74518. See also 86 FR at 23085 (reviewing and explaining rationale from CSAPR, 76 FR at 48237-38, for selection of 1 percent threshold).

The EPA's August 2018 memorandum recognized that in certain circumstances, a state may be able to establish that an alternative contribution threshold of 1 ppb is justifiable. Where a state relies on this alternative threshold, and where that state determined that it was not linked at Step 2 using the alternative threshold, the EPA will evaluate whether the state provided a technically sound assessment of the appropriateness of using this alternative threshold based on the facts and circumstances underlying its application in the particular SIP submission.

Consistent with the EPA's longstanding approach to eliminating significant contribution or interference with maintenance, at Step 3, states linked at Steps 1 and 2 are generally expected to prepare a multifactor assessment of potential emissions controls. The EPA's analysis at Step 3 in prior Federal actions addressing interstate transport requirements has primarily focused on an evaluation of cost-effectiveness of potential emissions controls (on a marginal cost-per-ton basis), the total emissions reductions that may be achieved by requiring such controls (if applied across all linked upwind states), and an evaluation of the air quality impacts such emissions reductions would have on the downwind receptors to which a state is linked; other factors may potentially be relevant if adequately supported. In general, where the EPA's or alternative air quality and contribution modeling establishes that a state is linked at Steps 1 and 2, it will be insufficient at Step 3 for a state merely to point to its existing rules requiring control measures as a basis for approval. In general, the emissions-reducing effects of all existing emissions control requirements are already reflected in the air quality results of the modeling for steps 1 and 2. If the state is shown to still be linked to one or more downwind receptor(s), states must provide a well-documented evaluation determining whether their emissions constitute significant contribution or interference with maintenance by evaluating additional available control opportunities by preparing a multifactor assessment. While the EPA has not prescribed a particular method for this assessment, the EPA expects states at a minimum to present a sufficient technical evaluation. This would typically include information on emissions sources, applicable control technologies, emissions reductions, costs, cost effectiveness, and downwind air quality impacts of the estimated reductions, before concluding that no additional emissions controls should be required. 29

At Step 4, states (or the EPA) develop permanent and federally enforceable control strategies to achieve the emissions reductions determined to be necessary at Step 3 to eliminate significant contribution to nonattainment or interference with maintenance of the NAAQS. For a state linked at Steps 1 and 2 to rely on an emissions control measure at Step 3 to address its interstate transport obligations, that measure must be included in the state's SIP so that it is permanent and federally enforceable. See CAA section 110(a)(2)(D) (“Each such [SIP] shall . . . contain adequate provisions . . . .”). See also CAA 110(a)(2)(A); Committee for a Better Arvin v. U.S. E.P.A., 786 F.3d 1169, 1175-76 (9th Cir. 2015) (holding that measures relied on by state to meet CAA requirements must be included in the SIP).

On November 30, 2018, Iowa submitted a SIP revision addressing the CAA section 110(a)(2)(D)(i)(I) interstate transport requirements for the 2015 ozone NAAQS. Iowa chose to rely on the results of EPA's 2023 modeling, as presented in the March 2018 memorandum, to identify downwind nonattainment and maintenance receptors that may be impacted by emissions from sources in Iowa. Based on Iowa's review of the EPA's modeling assumptions and model performance evaluation, Iowa determined that EPA's future year projections were appropriate for purposes of evaluating Iowa's impact on attainment and maintenance of the 2015 ozone NAAQS in other states.

Iowa relied on EPA's 2023 modeling to conclude that the state does not contribute significantly to nonattainment or interfere with maintenance of the 2015 ozone NAAQS in any other state. Iowa referred to the analytic information in EPA's August 2018 memorandum as a basis to use a 1 ppb contribution threshold when evaluating the state's contribution to downwind receptors at Step 2 of EPA's four-step interstate transport framework. Using EPA's modeling, Iowa identified that it is projected to contribute below 1 percent of the 2015 ozone NAAQS ( i.e., less than 0.70 ppb) to all but two downwind receptors: The nonattainment receptor in Milwaukee County, Wisconsin (Milwaukee receptor), and the maintenance-only receptor in Allegan County, Michigan (Allegan receptor). Iowa's contribution to these two receptors was projected to be between 1 percent and 1 ppb. Iowa concluded that 1 ppb is an appropriate contribution threshold to apply with respect to the 2015 ozone NAAQS and that Iowa's emissions therefore do not contribute to nonattainment or maintenance problems at either receptor.

Iowa noted that its 2023 modeled contribution to the Milwaukee receptor is 0.79 ppb, and its 2023 modeled contribution to the Allegan receptor is 0.77 ppb. Iowa further noted that application of the 1 ppb threshold captures 83 percent of the upwind contribution captured at the 1 percent threshold at the Milwaukee receptor and 94 percent of the upwind contribution captured at the 1 percent threshold at the Allegan receptor. Based on these data, Iowa concluded that the 1 ppb threshold is therefore appropriate because it captures a “substantial portion” of the transported contribution from upwind states when compared to the 1 percent threshold at both receptors. Because the state's impact on both receptors was projected to be below the 1 ppb threshold, the state concluded that its emissions will not contribute significantly to nonattainment or interfere with maintenance of the 2015 ozone NAAQS in downwind states.

On March 2, 2020, EPA proposed to approve portions of the infrastructure SIP submission received from the State of Iowa on November 30, 2018, in accordance with section 110(a)(1) of the CAA. In the document, the EPA proposed to approve the portion of the SIP addressing section 110(a)(2)(D)(i)(I)—significant contribution to nonattainment (prong 1), and interference with maintenance of the NAAQS (prong 2). This proposal relied on results of EPA's 2023 modeling, as presented in the March 2018 memorandum explained above, as well as the State's argument for using the 1 ppb threshold in Step 2 rather than the 1 percent threshold. The action received two adverse comments. In this document, we are withdrawing our March 2, 2020, proposed approval. We are now reproposing approval based on new modeling and a new rationale for approval based on that new modeling, as discussed in section IV.

Iowa's SIP submission relies on analysis of the year 2023 (using a 2011 base year platform) to conclude that the State does not significantly contribute to nonattainment or interfere with maintenance of the 2015 ozone NAAQS in any other state. As explained in section I of this proposal, the EPA has conducted an updated analysis for the 2023 analytical year (using a 2016 base year platform) and proposes to rely primarily on this updated modeling to evaluate Iowa's transport SIP submission.

As described in section I, the EPA performed air quality modeling to project design values and contributions for 2023 using the 2016v2 emissions platform. The design values and contributions were examined to determine if Iowa contributes at or above the threshold of 1 percent of the 2015 ozone NAAQS (0.70 ppb) to any downwind nonattainment or maintenance receptor. The data  30 indicate that the highest contribution in 2023 from Iowa to a downwind nonattainment and maintenance receptors is 0.64 ppb and 0.58 ppb, respectively. 31

Based on the EPA's updated modeling, it is no longer necessary to evaluate Iowa's use of 1 ppb as a contribution threshold at Step 2. The state is projected to contribute less than a 1 percent threshold. While the EPA does not, in this action, approve of the state's application of the 1 ppb threshold, based on the state's contributions of less than 1 percent to projected downwind nonattainment or maintenance receptors, the state's use of this alternative threshold is inconsequential to our action on this SIP submittal. The EPA is proposing to approve Iowa's SIP submission on the basis of the use of a 1 percent contribution threshold at Step 2.

The EPA's evaluation of measured and monitored data and contribution values in 2023, as discussed in this section, is consistent with conclusions made by Iowa that emissions from sources in the State will not contribute to nonattainment or interfere with maintenance of the 2015 ozone NAAQS in any other state.

The EPA is proposing to approve a portion of Iowa's November 30, 2018, SIP submittal as meeting the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS. The EPA has addressed the remaining infrastructure elements included in Iowa's submittal in a separate action. Additionally, this proposal withdraws and replaces EPA's March 2, 2020, proposed rule as discussed in section III.

The Agency is soliciting public comments on its proposed approval of the CAA section 110(a)(2)(D)(i)(I) element of Iowa's infrastructure SIP submittal for the 2015 ozone NAAQS. Significant comments will be considered before taking final action. Interested parties may participate in the Federal rulemaking procedure by submitting written comments to this proposed rule by following the instructions listed in the ADDRESSES section of this Federal Register .

Under the Clean Air Act, the Administrator is required to approve a SIP submission that complies with the provisions of the Act and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to approve state choices, provided that they meet the criteria of the CAA. Accordingly, this proposed action merely approves state law as meeting Federal requirements and does not impose additional requirements beyond those imposed by state law. For that reason, this proposed action:

• Is not a significant regulatory action subject to review by the Office of Management and Budget under Executive Orders 12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);

• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq. );

• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq. );

• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4);

• Does not have federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);

• Is not an economically significant regulatory action based on health or safety risks subject to Executive Order 13045 (62 FR 19885, April 23, 1997);

• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001);

• Is not subject to requirements of section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the Clean Air Act; and

• Does not provide EPA with the discretionary authority to address, as appropriate, disproportionate human health or environmental effects, using practicable and legally permissible methods, under Executive Order 12898 (59 FR 7629, February 16, 1994).

In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where EPA or an Indian tribe has demonstrated that a tribe has jurisdiction. In those areas of Indian country, the rule does not have tribal implications and will not impose substantial direct costs on tribal governments or preempt tribal law as specified by Executive Order 13175 (65 FR 67249, November 9, 2000).

Part 52 of chapter I, title 40 of the Code of Federal Regulations is proposed to be amended as follows:

Public Participation: Submit your comments, identified by Docket ID No. EPA-R02-OAR-2021-0673 at https://www.regulations.gov. Once submitted, comments cannot be edited or removed from the docket. The EPA may publish any comment received to its public docket. Do not submit to the EPA's docket at https://www.regulations.gov 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).

There are two dockets supporting this action, EPA-R02-OAR-2021-0673 and EPA-HQ-OAR-2021-0663. Docket No. EPA-R02-OAR-2021-0673 contains information specific to New York and New Jersey, including the notice of proposed rulemaking. Docket No. EPA-HQ-OAR-2021-0663 contains additional modeling files, emissions inventory files, technical support documents, and other relevant supporting documentation regarding interstate transport of emissions for the 2015 8-hour ozone NAAQS which are being used to support this action. All comments regarding information in either of these dockets are to be made in Docket No. EPA-R02-OAR-2021-0673. For additional submission methods, please contact Kenneth Fradkin, Environmental Protection Agency, 290 Broadway, 25th Floor, New York, 10007-1866, (212) 637-3702, or by email at Fradkin.Kenneth@epa.gov. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. Due to public health concerns related to COVID-19, the EPA Docket Center and Reading Room are open to the public by appointment only. Our Docket Center staff also continues to provide remote customer service via email, phone, and webform. For further information and updates on the EPA Docket Center services, please visit us online at https://www.epa.gov/dockets.

The EPA continues to carefully and continuously monitor information from the Centers for Disease Control and Prevention (CDC), local area health departments, and our Federal partners so that we can respond rapidly as conditions change regarding COVID-19.

The index to the docket for this action, Docket No. EPA-R02-OAR-2021-0673, is available electronically at www.regulations.gov. While all documents in the docket are listed in the index, some information may not be publicly available due to docket file size restrictions or content ( e.g., CBI).

Throughout this document, “we,” “us,” and “our” means the EPA.

On October 1, 2015, the EPA promulgated a revision to the ozone NAAQS (2015 8-hour ozone NAAQS), lowering the level of both the primary and secondary standards to 0.070 parts per million (ppm). 1 Section 110(a)(1) of the CAA requires states to submit, within 3 years after promulgation of a new or revised standard, SIP submissions meeting the applicable requirements of section 110(a)(2). 2 One of these applicable requirements is found in CAA section 110(a)(2)(D)(i)(I), otherwise known as the “interstate transport” or “good neighbor” provision, which generally requires SIPs to contain adequate provisions to prohibit in-state emissions activities from having certain adverse air quality effects on other states due to interstate transport of pollution. There are two so-called “prongs” within CAA section 110(a)(2)(D)(i)(I). A SIP for a new or revised NAAQS must contain adequate provisions prohibiting any source or other type of emissions activity within the state from emitting air pollutants in amounts that will significantly contribute to nonattainment of the NAAQS in another state (prong 1) or interfere with maintenance of the NAAQS in another state (prong 2). The EPA and states must give independent significance to prong 1 and prong 2 when evaluating downwind air quality problems under CAA section 110(a)(2)(D)(i)(I). 3

The EPA is using the 4-step interstate transport framework (or 4-step framework) to evaluate the states' SIP submittals addressing the interstate transport provision for the 2015 8-hour ozone NAAQS. The EPA has addressed the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) with respect to prior ozone NAAQS in several regional regulatory actions, including the Cross-State Air Pollution Rule (CSAPR), which addressed interstate transport with respect to the 1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter standards, 4 and the Cross-State Air Pollution Rule Update (CSAPR Update)  5 and the Revised CSAPR Update, both of which addressed the 2008 ozone NAAQS. 6

Through the development and implementation of the CSAPR rulemakings and prior regional rulemakings pursuant to the interstate transport provision, 7 the EPA, working in partnership with states, developed the following 4-step interstate transport framework to evaluate a State's obligations to eliminate interstate transport emissions under the interstate transport provision for the ozone NAAQS: (1) Identify monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS ( i.e., nonattainment and/or maintenance receptors); (2) identify states that impact those air quality problems in other ( i.e., downwind) states sufficiently such that the states are considered “linked” and therefore warrant further review and analysis; (3) identify the emissions reductions necessary (if any), applying a multifactor analysis, to eliminate each linked upwind state's significant contribution to nonattainment or interference with maintenance of the NAAQS at the locations identified in Step 1; and (4) adopt permanent and enforceable measures needed to achieve those emissions reductions.

In general, the EPA has performed nationwide air quality modeling to project ozone design values which are used in combination with measured data to identify nonattainment and maintenance receptors. To quantify the contribution of emissions from specific upwind states on 2023 ozone design values for the identified downwind nonattainment and maintenance receptors, the EPA performed nationwide, state-level ozone source apportionment modeling for 2023. The source apportionment modeling provided contributions to ozone at receptors from precursor emissions of anthropogenic nitrogen oxides (NO X ) and volatile organic compounds (VOCs) in individual upwind states.

The EPA has released several documents containing projected ozone design values, contributions, and information relevant to evaluating interstate transport with respect to the 2015 8-hour ozone NAAQS. First, on January 6, 2017, the EPA published a notice of data availability (NODA) in which we requested comment on preliminary interstate ozone transport data including projected ozone design values and interstate contributions for 2023 using a 2011 base year platform. 8 In the NODA, the EPA used the year 2023 as the analytic year for this preliminary modeling because that year aligns with the expected attainment year for Moderate ozone nonattainment areas for the 2015 8-hour ozone NAAQS. 9 On October 27, 2017, we released a memorandum (October 2017 memorandum) containing updated modeling data for 2023, which incorporated changes made in response to comments on the NODA, and noted that the modeling may be useful for states developing SIPs to address interstate transport obligations for the 2008 ozone NAAQS. 10 On March 27, 2018, we issued a memorandum (March 2018 memorandum) noting that the same 2023 modeling data released in the October 2017 memorandum could also be useful for identifying potential downwind air quality problems with respect to the 2015 8-hour ozone NAAQS at Step 1 of the 4-step interstate transport framework. 11 The March 2018 memorandum also included the then newly available contribution modeling data for 2023 to assist states in evaluating their impact on potential downwind air quality problems for the 2015 8-hour ozone NAAQS under Step 2 of the 4-step interstate transport framework. 12 The EPA subsequently issued two more memoranda in August and October 2018, providing additional information to states developing interstate transport SIP submissions for the 2015 8-hour ozone NAAQS concerning, respectively, potential contribution thresholds that may be appropriate to apply in Step 2 of the 4-step interstate transport framework, and considerations for identifying downwind areas that may have problems maintaining the standard at Step 1 of the 4-step interstate transport framework. 13

Since the release of the modeling data shared in the March 2018 memorandum, the EPA performed updated modeling using a 2016-based emissions modeling platform ( i.e., 2016v1). This emissions platform was developed under the EPA/Multi-Jurisdictional Organization (MJO)/state collaborative project. 14 This collaborative project was a multi-year joint effort by the EPA, MJOs, and states to develop a new, more recent emissions platform for use by the EPA and states in regulatory modeling as an improvement over the dated 2011-based platform that the EPA had used to project ozone design values and contribution data provided in the 2017 and 2018 memoranda. The EPA used the 2016v1 emissions to project ozone Design values and contributions for 2023. On October 30, 2020, in the Notice of Proposed Rulemaking for the Revised CSAPR Update, the EPA released and accepted public comment on 2023 modeling that used the 2016v1 emissions platform. 15 Although the Revised CSPAR Update addressed transport for the 2008 ozone NAAQS, the projected design values and contributions from the 2016v1 platform are also useful for identifying downwind ozone problems and linkages with respect to the 2015 ozone NAAQS. 16

Following the final Revised CSAPR Update, the EPA made further updates to the 2016 emissions platform to include mobile emissions from the EPA's Motor Vehicle Emission Simulator MOVES3 model  17 and updated emissions projections for electric generating units (EGUs) that reflect the emissions reductions from the Revised CSAPR Update, recent information on plant closures, and other sector trends. The construct of the updated emissions platform, 2016v2, is described in the Emissions Modeling technical support document (TSD) for this proposed rule. The EPA performed air quality modeling of the 2016v2 emissions using the most recent public release version of the Comprehensive Air Quality Model with Extensions (CAMx) photochemical modeling, version 7.10. 18 The EPA now proposes to primarily rely on modeling based on the updated and newly available 2016v2 emissions platform in evaluating these submissions with respect to Steps 1 and 2 of the 4-step interstate transport framework. By using the updated modeling results, the EPA is using the most current and technically appropriate information for this proposed rulemaking. Section III of this notice and the Air Quality Modeling TSD for 2015 Ozone NAAQS Transport SIP Proposed Actions included in Docket ID No. EPA-HQ-OAR-2021-0663 for this proposal contains additional detail on the EPA's 2016v2 modeling. In this notice, the EPA is accepting public comment on this updated 2023 modeling, which uses a 2016v2 emissions platform. Comments on the EPA's air quality modeling should be submitted in the Regional docket for this action, Docket No. EPA-R02-OAR-2021-0673. Comments are not being accepted in Docket EPA-HQ-OAR-2021-0663.

In some cases, states may rely on the results of EPA modeling and/or alternative modeling performed by states or Multi-Jurisdictional Organizations (MJOs) to evaluate downwind air quality problems and contributions as part of their submissions. New York and New Jersey have done so, and so we have evaluated the use of that alternative modeling in Section III.

The EPA proposes to apply a consistent set of policy judgments across all states for purposes of evaluating interstate transport obligations and the approvability of interstate transport SIP submittals for the 2015 8-hour ozone NAAQS. These policy judgments reflect consistency with relevant case law and past agency practice as reflected in the CSAPR and related rulemakings. Nationwide consistency in approach is particularly important in the context of interstate ozone transport, which is a regional-scale pollution problem involving many smaller contributors. Effective policy solutions to the problem of interstate ozone transport going back to the NO X SIP Call have necessitated the application of a uniform framework of policy judgments in order to ensure an “efficient and equitable” approach. See EME Homer City Generation, LP v. EPA, 572 U.S. 489, 519 (2014).

In the March, August, and October 2018 memoranda, the EPA recognized that states may be able to establish alternative approaches to addressing their interstate transport obligations for the 2015 8-hour ozone NAAQS that vary from a nationally uniform framework. The EPA emphasized in these memoranda, however, that such alternative approaches must be technically justified and appropriate in light of the facts and circumstances of each particular state's submittal. In general, the EPA continues to believe that deviation from a nationally consistent approach to ozone transport must be substantially justified and have a well-documented technical basis that is consistent with relevant case law. Where states submitted SIPs that rely on any such potential “flexibilities” as may have been identified or suggested in the past, the EPA will evaluate whether the state adequately justified the technical and legal basis for doing so.

The EPA notes that certain concepts included in an attachment to the March 2018 memorandum require unique consideration, and these ideas do not constitute agency guidance with respect to transport obligations for the 2015 ozone NAAQS. Attachment A to the March 2018 memorandum identified a “Preliminary List of Potential Flexibilities” that could potentially inform SIP development. 19 However, the EPA made clear in that Attachment that the list of ideas were not suggestions endorsed by the Agency but rather “comments provided in various forums” on which the EPA sought “feedback from interested stakeholders.”  20 Further, Attachment A stated, “EPA is not at this time making any determination that the ideas discussed below are consistent with the requirements of the CAA, nor are we specifically recommending that states use these approaches.”  21 Attachment A to the March 2018 memorandum, therefore, does not constitute agency guidance, but was intended to generate further discussion around potential approaches to addressing ozone transport among interested stakeholders. To the extent states sought to develop or rely on these ideas in support of their SIP submittals, the EPA will thoroughly review the technical and legal justifications for doing so.

The remainder of this section describes the EPA's proposed framework with respect to analytic year, definition of nonattainment and maintenance receptors, selection of contribution threshold, and multifactor control strategy assessment.

In general, the states and the EPA must implement the interstate transport provision in a manner “consistent with the provisions of [title I of the CAA.]” CAA section 110(a)(2)(D)(i). This requires, among other things, that these obligations are addressed consistently with the timeframes for downwind areas to meet their CAA obligations. With respect to ozone NAAQS, under CAA section 181(a), this means obligations must be addressed “as expeditiously as practicable” and no later than the schedule of attainment dates provided in CAA section 181(a)(1). 22 Several D.C. Circuit court decisions address the issue of the relevant analytic year for the purposes of evaluating ozone transport air-quality problems. On September 13, 2019, the D.C. Circuit issued a decision in Wisconsin v. EPA, remanding the CSAPR Update to the extent that it failed to require upwind states to eliminate their significant contribution by the next applicable attainment date by which downwind states must come into compliance with the NAAQS, as established under CAA section 181(a). 938 F.3d at 313.

On May 19, 2020, the D.C. Circuit issued a decision in Maryland v. EPA that cited the Wisconsin decision in holding that the EPA must assess the impact of interstate transport on air quality at the next downwind attainment date, including Marginal area attainment dates, in evaluating the basis for the EPA's denial of a petition under CAA section 126(b). Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 2020). The court noted that “section 126(b) incorporates the Good Neighbor Provision,” and, therefore, “EPA must find a violation [of section 126] if an upwind source will significantly contribute to downwind nonattainment at the next downwind attainment deadline. Therefore, the agency must evaluate downwind air quality at that deadline, not at some later date.” Id. at 1204 (emphasis added). The EPA interprets the court's holding in Maryland as requiring the states and the Agency, under the good neighbor provision, to assess downwind air quality as expeditiously as practicable and no later than the next applicable attainment date, 23 which is now the Moderate area attainment date under CAA section 181 for ozone nonattainment. The Moderate area attainment date for the 2015 8-hour ozone NAAQS is August 3, 2024. 24 The EPA believes that 2023 is now the appropriate year for analysis of interstate transport obligations for the 2015 8-hour ozone NAAQS because the 2023 ozone season is the last relevant ozone season during which achieved emissions reductions in linked upwind states could assist downwind states with meeting the August 3, 2024 Moderate area attainment date for the 2015 8-hour ozone NAAQS.

The EPA recognizes that the attainment date for nonattainment areas classified as Marginal for the 2015 8-hour ozone NAAQS was August 3, 2021. Under the Maryland holding, any necessary emissions reductions to satisfy interstate transport obligations should have been implemented by no later than this date. At the time of the statutory deadline to submit interstate transport SIPs (October 1, 2018), many states relied upon the EPA modeling of the year 2023, and no state provided an alternative analysis using a 2021 analytic year (or the prior 2020 ozone season). However, the EPA must act on SIP submittals using the information available at the time it takes such action. In this circumstance, the EPA does not believe it would be appropriate to evaluate states' obligations under CAA section 110(a)(2)(D)(i)(I) as of an attainment date that is wholly in the past, because the Agency interprets the interstate transport provision as forward looking. See 86 FR at 23074; see also Wisconsin, 938 F.3d at 322. Consequently, in this proposal the EPA will use the analytical year of 2023 to evaluate each state's CAA section 110(a)(2)(D)(i)(I) SIP submission with respect to the 2015 8-hour ozone NAAQS.

In Step 1, the EPA identifies monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS in the 2023 analytic year. Where the EPA's analysis shows that a site does not fall under the definition of a nonattainment or maintenance receptor, that site is excluded from further analysis under the EPA's 4-step interstate transport framework. For sites that are identified as a nonattainment or maintenance receptor in 2023, we proceed to the next Step of our 4-step interstate transport framework by identifying the upwind state's contribution to those receptors.

The EPA's approach to identifying ozone nonattainment and maintenance receptors in this action is consistent with the approach used in previous transport rulemakings. The EPA's approach gives independent consideration to both the “contribute significantly to nonattainment” and the “interfere with maintenance” prongs of CAA section 110(a)(2)(D)(i)(I), consistent with the D.C. Circuit's direction in North Carolina v. EPA. 25

For the purpose of this proposal, the EPA identifies nonattainment receptors as those monitoring sites that are projected to have average design values that exceed the NAAQS and that are also measuring nonattainment based on the most recent monitored design values. This approach is consistent with prior transport rulemakings, such as the CSAPR Update, where the EPA defined nonattainment receptors as those areas that both currently measure nonattainment and that the EPA projects will be in nonattainment in the future analytic year ( i.e., 2023). 26

In addition, in this proposal, the EPA identifies a receptor to be a “maintenance” receptor for purposes of defining interference with maintenance, consistent with the method used in the CSAPR and upheld by the D.C. Circuit in EME Homer City Generation, L.P. v. EPA, 795 F.3d 118, 136 (D.C. Cir. 2015). 27 Specifically, the EPA identified maintenance receptors as those receptors that would have difficulty maintaining the relevant NAAQS in a scenario that takes into account historical variability in air quality at that receptor. The variability in air quality was determined by evaluating the “maximum” future design value at each receptor based on a projection of the maximum measured design value over the relevant period. The EPA interprets the projected maximum future design value to be a potential future air quality outcome consistent with the meteorology that yielded maximum measured concentrations in the ambient data set analyzed for that receptor ( i.e., ozone conducive meteorology). The EPA also recognizes that previously experienced meteorological conditions ( e.g., dominant wind direction, temperatures, air mass patterns) promoting ozone formation that led to maximum concentrations in the measured data may reoccur in the future. The maximum design value gives a reasonable projection of future air quality at the receptor under a scenario in which such conditions do, in fact, reoccur. The projected maximum design value is used to identify upwind emissions that, under those circumstances, could interfere with the downwind area's ability to maintain the NAAQS.

Recognizing that nonattainment receptors are also, by definition, maintenance receptors, the EPA often uses the term “maintenance-only” to refer to those receptors that are not nonattainment receptors. Consistent with the concepts for maintenance receptors, as described above, the EPA identifies “maintenance-only” receptors as those monitoring sites that have projected average design values above the level of the applicable NAAQS, but that are not currently measuring nonattainment based on the most recent official design values. In addition, those monitoring sites with projected average design values below the NAAQS, but with projected maximum design values above the NAAQS are also identified as “maintenance only” receptors, even if they are currently measuring nonattainment based on the most recent official design values.

In Step 2 the EPA quantifies the contribution of each upwind state to each receptor in the 2023 analytic year. The contribution metric used in Step 2 is defined as the average impact from each state to each receptor on the days with the highest ozone concentrations at the receptor based on the 2023 modeling. If a state's contribution value does not equal or exceed the threshold of 1 percent of the NAAQS ( i.e., 0.70 ppb for the 2015 8-hour ozone NAAQS), the upwind state is not “linked” to a downwind air quality problem, and the EPA, therefore, concludes that the state does not significantly contribute to nonattainment or interfere with maintenance of the NAAQS in the downwind states. However, if a state's contribution equals or exceeds the 1 percent threshold, the state's emissions are further evaluated in Step 3, considering both air quality and cost as part of a multi-factor analysis, to determine what, if any, emissions might be deemed “significant” and, thus, must be eliminated under CAA section 110(a)(2)(D)(i)(I). The EPA is proposing to rely in the first instance on the 1 percent threshold for the purpose of evaluating a state's contribution to nonattainment or maintenance of the 2015 8-hour ozone NAAQS ( i.e., 0.70 ppb) at downwind receptors. This is consistent with the Step 2 approach that the EPA applied in CSAPR for the 1997 ozone NAAQS, which has subsequently been applied in the CSAPR Update when evaluating interstate transport obligations for the 2008 ozone NAAQS. The EPA continues to find 1 percent to be an appropriate threshold. For ozone, as the EPA found in the Clean Air Interstate Rule (CAIR), CSAPR, and CSAPR Update, a portion of the nonattainment problems from anthropogenic sources in the U.S. results from the combined impact of relatively small contributions from many upwind states, along with contributions from in-state sources and, in some cases, substantially larger contributions from a subset of particular upwind states. The EPA's analysis shows that much of the ozone transport problem being analyzed in this proposed rule is still the result of the collective impacts of contributions from many upwind states. Therefore, application of a consistent contribution threshold is necessary to identify those upwind states that should have responsibility for addressing their contribution to the downwind nonattainment and maintenance problems to which they collectively contribute. Continuing to use 1 percent of the NAAQS as the screening metric to evaluate collective contribution from many upwind states also allows the EPA (and states) to apply a consistent framework to evaluate interstate emissions transport under the interstate transport provision from one NAAQS to the next. See 81 FR at 74518. See also 86 FR at 23085 (reviewing and explaining rationale from CSAPR, 76 FR at 48237-38, for selection of the 1 percent threshold).

The EPA's August 2018 memorandum recognized that in certain circumstances, a state may be able to establish that an alternative contribution threshold of 1 ppb is justifiable. Where a state relies on this alternative threshold, and where that state determined that it was not linked at Step 2 using the alternative threshold, the EPA will evaluate whether the state provided a technically sound assessment of the appropriateness of using this alternative threshold based on the facts and circumstances underlying its application in the particular SIP submission.

Consistent with the EPA's longstanding approach to eliminating significant contribution or interference with maintenance, at Step 3, states linked at Steps 1 and 2 are generally expected to prepare a multifactor assessment of potential emissions controls. The EPA's analysis at Step 3 in prior Federal actions addressing interstate transport requirements has primarily focused on an evaluation of cost-effectiveness of potential emissions controls (on a marginal cost-per-ton basis), the total emissions reductions that may be achieved by requiring such controls (if applied across all linked upwind states), and an evaluation of the air quality impacts such emissions reductions would have on the downwind receptors to which a state is linked; other factors may potentially be relevant if adequately supported. In general, where the EPA's or alternative air quality and contribution modeling establishes that a state is linked at Steps 1 and 2, it will be insufficient at Step 3 for a state merely to point to its existing rules requiring control measures as a basis for approval. In general, the emissions-reducing effects of all existing emissions control requirements are already reflected in the air quality results of the modeling for Steps 1 and 2. If the state is shown to still be linked to one or more downwind receptor(s), states must provide a well-documented evaluation determining whether their emissions constitute significant contribution or interference with maintenance by evaluating additional available control opportunities by preparing a multifactor assessment. While the EPA has not prescribed a particular method for this assessment, the EPA expects states at a minimum to present a sufficient technical evaluation. This would typically include information on emissions sources, applicable control technologies, emissions reductions, costs, cost effectiveness, and downwind air quality impacts of the estimated reductions, before concluding that no additional emissions controls should be required. 28

At Step 4, states (or the EPA) develop permanent and federally enforceable control strategies to achieve the emissions reductions determined to be necessary at Step 3 to eliminate significant contribution to nonattainment or interference with maintenance of the NAAQS. For a state linked at Steps 1 and 2 to rely on an emissions control measure at Step 3 to address its interstate transport obligations, that measure must be included in the state's SIP so that it is permanent and federally enforceable. See CAA section 110(a)(2)(D) (“Each such [SIP] shall . . . contain adequate provisions. . . .”). See also CAA 110(a)(2)(A); Committee for a Better Arvin v. U.S. E.P.A., 786 F.3d 1169, 1175-76 (9th Cir. 2015) (holding that measures relied on by state to meet CAA requirements must be included in the SIP).

On September 25, 2018, the New York State Department of Environmental Conservation (NYSDEC) submitted a revision to its SIP addressing the infrastructure SIP requirements for the 2015 ozone NAAQS, including the interstate transport obligations pursuant to the good neighbor provision. The EPA finalized approval of elements of New York's submittal, except for the portion of the SIP submittal addressing the good neighbor provision, on June 23, 2021. 29

In New York's SIP submittal, the State followed the 4-step framework for determining its good neighbor obligations. New York provided air quality modeling (Steps 1 and 2) and a list of already-enacted and “on-the-way” state air pollution control measures to conclude that New York satisfied its good neighbor obligations for the 2015 ozone NAAQS (under Step 3). The State did not reach Step 4 of the framework as it concluded that the State did not need additional emissions reductions at Step 3 to eliminate significant contribution.

At Step 1, New York identified nonattainment and maintenance receptors based on the EPA's 2023 projection modeling shared in the EPA March 2018 memorandum. New York identified nonattainment receptors at the Stratford (receptor ID 90013007) and Westport (receptor ID 90019003) monitoring sites in Fairfield County, in Connecticut, in 2023 and identified maintenance receptors at the Greenwich (receptor ID 900190017) and New Haven (receptor ID 90099002) monitoring sites in Fairfield and New Haven Counties, in Connecticut, respectively, in 2023.

New York submitted state-by-state contribution modeling for 2023 based on CAMx modeling performed by the Maryland Department of the Environment (MDE). New York coupled 2023 Community Multiscale Air Quality (CMAQ) projection modeling with MDE's CAMx contribution modeling to show that New York was linked to the Stratford, Westport, Greenwich, and New Haven monitoring sites in Connecticut using a 1 percent of the NAAQS threshold (0.70 ppb for the 2015 8-hour ozone NAAQS). Based on this information, New York conceded that it was linked to four Connecticut receptors at Step 2.

New York asserted that, despite its contributions, the State had met its good neighbor obligations through the implementation and enforcement of stringent NO X and VOC control measures that the State asserted go well beyond the EPA presumptive cost threshold in the CSAPR Update for highly cost-effective emissions reductions, and through the ongoing adoption and revision of additional control measures to further ensure the reduction of ozone in both New York State and downwind areas.

New York cited its Reasonably Available Control Technology (RACT) rules, which have been required on major sources of NO X throughout the State since 1995, and have been periodically updated (in 1999, 2004, and 2010) to keep up with advances in control technology. New York indicated that the State's RACT presumptive emissions limits and facility-specific emissions limits are based on inflation-adjusted control cost valued at $5,500 per ton of NO X reduced, which New York indicated was consistent with typical costs to install selective catalytic reduction (SCR) units, and above the EPA's $1,400 per ton control cost threshold used for the CSAPR Update that reflected the cost of turning on already-existing SCR controls at EGUs. New York also noted that the State's EGU NO X emissions rates are among the lowest in the country, as reflected in its CSAPR Update ozone season emissions budget, which is lower than all other states with the exception of New Jersey and Maryland. New York indicated that its $5,500 RACT control cost also applied to non-EGUs.

New York also stated in the September 2018 submittal that it was in various stages of the rulemaking process for additional measures to further control NO X and VOC emissions from EGU, non-EGU, area, and mobile sources.

Additional NO X reductions would be obtained, according to the State, through the following regulatory updates that were, at the time of the submittal, under development by the State: Establishing new NO X limits for simple cycle combustion turbines (or “peaking”  30 units), which New York noted would benefit the New York Metropolitan Area on hot summer days that are most conducive to ozone formation ( i.e., high electric demand days) (6 NYCRR Part 227); establishing NO X limits for distributed generation sources (6 NYCRR Part 222); applying NO X RACT requirements to municipal waste combustors (6 NYCRR Part 219); requiring new installation, recordkeeping and reporting requirements for aftermarket catalytic converters (Part 218); and the adoption of the CSAPR Update trading program (6 NYCRR Part 243).

New York's submittal also indicates that it will further control area-source VOC emissions through updates to State VOC RACT regulations for Oil and Gas (6 NYCRR Part 203); Architectural and Industrial Maintenance Coatings (6 NYCRR Part 205); Solvent Metal Cleaning Processes (Part 226); Motor Vehicle and Mobile Equipment Refinishing and Recoating Operations (6 NYCRR Part 228, Subpart 228-1); Gasoline Dispensing Sites and Transport Vehicles (6 NYCRR Part 230); and Consumer Products (6 NYCRR Part 235).

In its submittal to the EPA, New York commented that the State's mobile on-road sector alone (without considering other state emissions) “significantly impacted downwind monitors, with 2023 contributions as high as 4.64 ppb at the Greenwich, Connecticut monitor” (receptor ID 90010017), based on CAMx modeling conducted by the University of Maryland. 31

New York stated that the on-road sector is controlled through the inspection/maintenance and anti-idling standards in 6 NYCRR Part 217, “Motor Vehicle Emissions,” and the implementation of the California Low-Emission Vehicle Standards under 6 NYCRR Part 218, “Emission Standards for Motor Vehicles and Motor Vehicle Engines.”

On May 13, 2019, New Jersey submitted a SIP revision that addressed infrastructure SIP requirements for the 2015 ozone NAAQS, 32 including its interstate transport obligations pursuant to the good neighbor provision. Except for the portion of the SIP submittal addressing the good neighbor provision for the 2015 8-hour ozone NAAQS, the EPA will act on the portion of the submittal addressing the remaining infrastructure SIP elements for the 2015 8-hour ozone NAAQS in a separate action at a later date.

In New Jersey's SIP submittal, the State followed the 4-step framework based on a 2023 analytic year for evaluating its significant contribution. New Jersey provided air quality modeling (Steps 1 and 2), and a list of its adopted and implemented air pollution control measures, to demonstrate that it satisfied its transport obligations for the 2015 8-hour ozone NAAQS (under Step 3). The State did not reach Step 4 of the framework as it concluded that the State did not need additional emissions reductions to eliminate significant contribution at Step 3.

At Step 1, New Jersey identified areas that the State potentially significantly contributed to in other states based on 2023 regional modeling  33 conducted under the coordination of the Ozone Transport Commission (OTC) modeling Committee. The OTC modeling used CAMx modeling, version 6.3, to project emissions to 2023 (using a 2011 base year). OTC used the Eastern Regional Technical Advisory Committee (ERTAC) EGU Projection Tool to estimate emissions from the EGU sector.

New Jersey identified four nonattainment and four maintenance receptors in the OTC/MANE-VU 12 kilometer (km) modeling domain utilized in the OTC modeling. 34 The nonattainment receptors were located at the Westport  35 (receptor ID 90019003) monitoring site in Fairfield County, in Connecticut; the Susan Wagner (receptor ID 360850067) and Babylon (receptor ID 36103002) monitoring sites in Richmond and Suffolk Counties, respectively, in New York; and the Edgewood (receptor ID 240251001) monitoring site in Harford County, Maryland. The maintenance receptors were located at the Greenwich (receptor ID 90010017), New Haven (receptor ID 90099002) and Stratford (receptor ID 90013007) monitoring sites in Fairfield, New Haven, and Fairfield Counties, in Connecticut, respectively; and the Queens College (receptor ID 360810124) in Queens County, in New York.

New Jersey relied on the OTC 2023 regional modeling using CAMx to determine the nonattainment and maintenance sites that it was linked to as a potential significant contributor based on its contribution above 1 percent of the NAAQS (0.70 ppb for the 2015 8-hour ozone NAAQS). The OTC modeling showed that New Jersey was linked above the 1 percent threshold to four receptors, including two nonattainment receptors at the Westport monitoring site in Connecticut and at the Susan Wagner and Babylon monitoring sites in New York. Additionally, the modeling demonstrated that New Jersey was linked to maintenance receptors located at the Greenwich, New Haven, and Stratford monitoring sites in Connecticut and the Babylon monitoring site in New York.

New Jersey asserted that considering air quality, emissions reductions from the State's adopted measures, and the cost effectiveness of those measures, no additional emissions reductions from New Jersey are necessary to address its good neighbor obligations to downwind nonattainment and maintenance areas.

New Jersey noted that from 1990 to 2017, annual NO X and VOC emissions in New Jersey have each decreased approximately 77 percent. From 2011 to 2017, annual NO X and VOC emissions decreased 31 percent and 17 percent, respectively. From 2002 to 2017, for point sources in the State, NO X was reduced by 81 percent and VOC emissions were reduced by 63 percent. New Jersey also noted that its point source emissions represent only about 8 percent of New Jersey's total NO X emissions, while mobile sources were approximately 43 percent.

New Jersey stated that there has been a significant decreasing trend in 8-hour ozone design values in New Jersey, approximately 40 percent from 1988 to 2017 and 13 percent from 2011 to 2017. According to the State, the significant decrease demonstrates the impact of New Jersey control measures.

New Jersey provided a list  36 of its post-2002 adopted NO X and VOC control measures, including estimated cost-effectiveness (dollar ($) per ton of NO X reduced or VOC reduced), and the EPA's approval date  37 for many of the measures. New Jersey notes that the State has met Reasonably Available Control Measures (RACM) and RACT requirements and has gone beyond RACM/RACT by adopting control measures more stringent than Federal rules and rules adopted by other states. Furthermore, New Jersey states that its rules are implemented statewide and not limited to the Northern New Jersey-New York-Connecticut ozone nonattainment area. New Jersey highlighted several of its control measures:

New Jersey also asserts that it has implemented its control measures before the attainment deadlines for downwind nonattainment areas. New Jersey provides the example of the New Jersey power generation and HEDD rules being effective in 2015 or earlier. New Jersey further asserts that, when determining New Jersey's significant contribution to interstate transport, the State should not be penalized for its early adoption of appropriate and effective rules in advance of and more stringent than other states.

In the State's evaluation of cost effectiveness, New Jersey claims that it has gone beyond the measures of other nearby and upwind states and previously established the EPA cost effectiveness thresholds. The State notes that the cost-effectiveness values associated with many of its adopted rules are several times greater than the threshold of $1,400 per ton NO X reduced set for upwind states in the CSAPR Update. For example, according to the State's list of existing NO X and VOC control measures  38 included in its SIP submittal, the control measures for turbines operating during HEDD had a cost effectiveness of $44,000 per ton NO X reduced; the control measures for oil-fired boilers operating during HEDD had a cost effectiveness up to $18,000 per ton NO X reduced; and, for natural gas compressor engines and turbines rules adopted in 2017, the rules have a cost effectiveness up to $26,020 per ton NO X reduced, with SCR costs up to $18,983 per ton NO X reduced.

The EPA is proposing to find that the New York SIP revision submitted on September 25, 2018, and the New Jersey SIP revision submitted on May 13, 2019, do not meet the States' obligations with respect to prohibiting emissions that contribute significantly to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in any other state based on the EPA's evaluation of the SIP submissions using the 4-step interstate transport framework. Both States conceded that they are linked to nonattainment and maintenance receptors in another state at Steps 1 and 2 of the 4-step interstate transport framework-which is confirmed by the EPA's most recent modeling. However, neither state conducted an adequate Step 3 analysis to conclude that either state's SIP contains adequate measures to prohibit significant contribution or interference with maintenance. Both states conclude that their existing (or certain “on-the-way”) control measures are already sufficient to meet good neighbor obligations. However, for this argument to provide support for their conclusions, an analysis as to why no additional control measures are justified is needed. Neither state provided such an analysis in their respective SIP submittals. Therefore, as discussed below, the EPA proposes to disapprove both New York's and New Jersey's good neighbor SIP submittals for the 2015 8-hour ozone NAAQS.

As described in section I, the EPA performed air quality modeling using the 2016v2 emissions platform to project design values and contributions for 2023. These data were examined to determine if New York contributes at or above the threshold of 1 percent of the 2015 8-hour ozone NAAQS (0.70 ppb) to any downwind nonattainment or maintenance receptor. As shown in Table 1, the data  39 indicate that in 2023, emissions from New York contribute greater than 1 percent of the standard to nonattainment or maintenance-only receptors in Stratford, Connecticut (receptor ID 90013007), Westport, Connecticut (receptor ID 90019003), Greenwich, Connecticut (receptor ID 90010017), New Haven, Connecticut (receptor ID 90099002), and Bucks County, Pennsylvania (receptor ID 480170012). 40

At Step 1 of the 4-step interstate transport framework, New York relied on EPA modeling released in the March 2018 memorandum to identify nonattainment and maintenance receptors in 2023. As described previously in this notice, the EPA has recently updated this modeling using the most current and technically appropriate information. The EPA proposes to primarily rely on the EPA's most recent modeling to identify nonattainment and maintenance receptors in 2023.

As described previously in this notice, the EPA has recently updated modeling to identify upwind state contributions to nonattainment and/or maintenance receptors in 2023. In this proposal, the EPA relies on the Agency's most recently available modeling to identify upwind contributions and “linkages” to downwind air quality problems in 2023 using a threshold of 1 percent of the NAAQS. As shown in Table 1, updated EPA modeling identifies New York's maximum contribution to a downwind nonattainment or maintenance receptor is greater than 1 percent of the standard ( i.e., 0.70 ppb).

Although New York relied on alternative modeling to the EPA's modeling at Step 2, New York acknowledged in its SIP submission that it is linked above 1 percent of the NAAQS to one or more downwind receptors in 2023. Because the alternative modeling relied on by the State also demonstrates that a linkage exists between the State and downwind receptors at Step 2, the EPA need not conduct a comparative assessment of the alternative modeling; the State concedes that it is linked. New York's analysis corroborates the conclusion in the EPA's most recent modeling. The EPA therefore will proceed to Step 3 of the 4-step interstate transport framework to assess arguments the State presented as to why, despite this linkage, the State should not be considered to significantly contribute to nonattainment or interfere with maintenance of the NAAQS in any other state such that additional emissions reductions are required.

At Step 3 of the 4-step interstate transport framework, a state's emissions are further evaluated, in light of multiple factors, including air quality and cost considerations, to determine what, if any, emissions significantly contribute to nonattainment or interfere with maintenance and, thus, must be eliminated under CAA section 110(a)(2)(D)(i)(I). To effectively evaluate which emissions in the state should be deemed “significant” and therefore prohibited, states generally should prepare an accounting of sources and other emissions activity and assess potential, additional emissions reduction opportunities and resulting downwind air quality improvements. The EPA has consistently applied this general approach ( i.e., Step 3 of the 4-step interstate transport framework) when identifying emissions contributions that the Agency has determined to be “significant” (or interfere with maintenance) in each of its prior Federal, regional ozone transport rulemakings, and this interpretation of the statute has been upheld by the Supreme Court. See EME Homer City, 572 U.S. 489, 519 (2014). While the EPA has not directed states that they must conduct a Step 3 analysis in precisely the manner the EPA has done in its prior regional transport rulemakings, state implementation plans addressing the obligations in CAA section 110(a)(2)(D)(i)(I) must prohibit “any source or other type of emissions activity within the State” from emitting air pollutants which will contribute significantly to downwind air quality problems. Thus, states must complete something similar to the EPA's analysis (or an alternative approach to defining “significance” that comports with the statute's objectives) to determine whether and to what degree emissions from a state should be “prohibited” to eliminate emissions that will “contribute significantly to nonattainment in, or interfere with maintenance of,” the NAAQS in any other state. New York did not conduct such an analysis in its SIP submission. Although in this action we are relying on the results of the EPA's most recent air quality modeling results for receptor identification and contributions, we will continue to evaluate the analysis provided by New York at Step 3 to assess whether the analysis provided adequately supports New York's conclusion, and whether the analysis could apply to the linkages identified by the EPA at Step 2.

As previously indicated in section II.A, New York asserted in its September 2018 submittal that, despite its contributions, the State had met its good neighbor obligations through the implementation and enforcement of stringent NO X and VOC control measures that go beyond the EPA's presumptive cost threshold in the CSAPR Update for highly cost-effective emissions reductions, and through the ongoing adoption and revision of additional control measures to further ensure the reduction of ozone in both New York and downwind areas.

The State's submittal, however, did not contain a demonstration at Step 3 that the State was adequately controlling its emissions for the purposes of the good neighbor provision, particularly because New York conceded in its submission that its emissions were linked to Connecticut receptors at Steps 1 and 2. The SIP submittal pointed to the State's existing NO X RACT measures with presumptive and facility-specific emission limits based on $5,500 per ton of NO X reduced, as well as ongoing state and local emission control efforts to conclude New York is already meeting its good neighbor obligations for the 2015 8-hour ozone NAAQS. However, the State's submittal does not include a sufficient examination or a technical justification that could support the conclusion that the State has no further good neighbor obligations for the 2015 8-hour ozone NAAQS. In particular, the State did not conduct in its submittal an analysis of potential additional emissions-reduction measures to further reduce its impact on the identified downwind receptors. For example, New York did not include in its submission an accounting of sources and other emissions activity in the State along with an analysis of potential NO X emissions control technologies, their associated costs, estimated emissions reductions, and downwind air quality improvements. Nor does the submittal include an analysis of whether such potential additional control technologies or measures could reduce the impact of New York's emissions on out of state receptors. Though there is not a prescribed method for a Step 3 analysis, EPA has consistently applied Step 3 of the good neighbor framework through a more rigorous evaluation of potential additional control technologies or measures than what was provided in the SIP submission. Identifying a range of various emissions control measures that have been or may be enacted at the state or local level, without analysis of the impact of those measures on the out of state receptors, is not analytically sufficient. In general, the air quality modeling that the EPA has conducted (as well the modeling relied on by New York in its submittal) already accounts for “on-the-books” emissions control measures. Both sets of modeling clearly establish continued linkage from New York to downwind receptors in 2023 at Steps 1 and 2, despite those emissions control efforts.

New York's September 2018 submittal referenced regulatory updates that New York asserted were in development and would provide for additional NO X and VOC reductions. The EPA notes that New York has since adopted many of these regulatory updates. 41 New York adopted 6 NYCRR Part 227, Subpart 227-3, “Ozone Season Oxides of Nitrogen (NO X ) Emission Limits for Simple Cycle and Regenerative Combustion Turbines,” with a State effective date of January 16, 2020, that lowered allowable NO X emissions from peaking units during the ozone season on high electric demand days, with compliance dates of May 1, 2023 (100 ppmvd  42 limit), and May 1, 2025 (25 ppmvd limit for gas and 42 ppmvd limit for oil). 43 New York adopted a regulation, 6 NYCRR Part 222, “Distributed Generation Sources,” with a State effective date of March 25, 2020, that established NO X emissions control requirements for distributed generation and price responsive generation sources  44 with compliance dates of May 1, 2021 and May 1, 2025. 45 New York adopted revisions, with a State effective date of March 13, 2020, to NYCRR Part 219, including adoption of a new Subpart 219-10, “Reasonably Available Control Technology (RACT) For Oxides of Nitrogen (NO X ) At Municipal and Private Solid Waste Incineration Units,” which established NO X limits for municipal waste combustors with a compliance date of March 14, 2021. 46 New York adopted revisions to NYCRR Part 218, subpart 218-7, “Aftermarket Parts,” with a State effective date of March 14, 2020, which required cleaner California certified aftermarket catalytic converters offered for sale or installed in New York State beginning January 1, 2023. 47 New York adopted revisions, with a State effective date of January 11, 2020, to 6 NYCRR Part 205, “Architectural and Industrial Maintenance Coatings,” with compliance effective January 1, 2021, 48 requiring more stringent VOC limits for coatings. 49 New York adopted revisions, with a State effective date of November 1, 2019, to 6 NYCRR Part 226, “Solvent Metal Cleaning Processes,” establishing VOC content limits for cleaning solvents used in operations not covered by other regulations, beginning November 1, 2020. 50 New York adopted revisions to 6 NYCRR Part 230, with a State effective date of February 11, 2021, “Gasoline Dispensing Sites and Transport Vehicles,” and 6 NYCRR Part 235, “Consumer Products.” Updates to NYCRR Part 230 include additional VOC control requirements for facilities during gasoline transfer operations beginning February 5, 2021. 51 Updates to Part 235, which require compliance by January 1, 2022, include revising and establishing VOC contents for consumer products. 52

Additionally, New York adopted a revised version of 6 NYCRR Part 243, “CSAPR NO X Ozone Season Group 2 Trading Program,” with a State effective date of January 2, 2019, in order to allow New York to allocate CSAPR allowances to regulated entities in New York under an abbreviated SIP. 53 However, the EPA notes that although New York's revised Part 243 replaced the EPA's default allocation procedures for the control periods in 2021 and beyond under the CSAPR Update FIP, the revised state rules did not create any enforceable emission limitations and did not replace the enforceable emission limitations set forth in the additional trading program provisions established under the CSAPR Update FIP. Moreover, the allowance allocations provisions adopted in Part 243 (as well as the additional trading program provisions established under the CSAPR Update) are no longer in effect for New York's sources because those provisions have been replaced as to the State's sources by the new trading program provisions established under the Revised CSAPR Update. 54

In any case, in both the CSAPR Update and the more recent Revised CSAPR Update, the EPA found, in spite of the nominal stringency of New York's control programs, additional emissions reductions were achievable from EGUs in the State. This was true even under the level of control stringency the EPA determined appropriate to eliminate significant contribution for the 2008 ozone NAAQS. Further, the EPA has not established a benchmark cost-effectiveness threshold for good neighbor obligations for the 2015 ozone NAAQS, and New York in its submittal has not conducted an analysis to establish one for EPA to evaluate. Additionally, while New York's existing control measures have undoubtedly reduced the amount of transported ozone pollution to other states and have contributed to the downward emissions trends and improving air quality in the State, in light of continuing contribution to out of state receptors from the State at Steps 1 and 2 despite these measures, New York's SIP submission failed to provide an adequate analysis at Step 3.

As of December 1, 2021, New York had not yet adopted revisions to 6 NYCRR Part 203, “Oil and Gas Sector,”  55 or NYCRR Part 228, Subpart 228-1, “Motor Vehicle and Mobile Equipment Refinishing and Recoating Operation.”

The EPA also notes that New York's 6 NYCRR Part 227, Subpart 227-3, which was approved into the SIP after EPA's receipt of this September 2018 submittal, and which implements NO X limits on combustion turbines that operate as peaking units, will not be fully phased in until 2025, which is past the August 3, 2024 Moderate area attainment date for the 2015 ozone NAAQS. Additionally, New York said that the State's mobile on-road sector alone significantly impacted downwind monitors and noted that it controls its mobile emissions through its inspection/maintenance (I/M) and anti-idling standards. However, New York did not explain the role its I/M and anti-idling standards play in eliminating its significant contribution.

The EPA acknowledges that New York's RACT presumptive emissions limits and facility-specific emissions limits are based on an inflation-adjusted control cost valued at $5,500 per ton of NO X reduced.

In general, however, the listing of existing or “on-the-way” control measures, whether approved into the State's SIP or not, does not substitute for a complete Step 3 analysis under the EPA's 4-step framework to define “significant contribution.” New York's submittal does not include an assessment of the overall effects of these measures, when the reductions would be achieved, and what the overall resulting air quality effects would be observed at identified out-of-state receptors. The State's submittal does not include an evaluation of additional potential emissions control opportunities, or their costs or impacts, or attempt to analyze whether, if applied more broadly across linked states, the emissions reductions would constitute the elimination of significant contribution on a regional scale. The State's submittal did not contain an explanation as to whether any faster or more stringent emissions reductions that may be available were prohibitively costly or infeasible. Although the EPA acknowledges states are not necessarily bound to follow its own analytical framework at Step 3, we note that the State did not attempt to determine or justify an appropriate uniform cost-effectiveness threshold for the more stringent 2015 ozone NAAQS, nor did the State offer an alternative to this analytical framework for determining “significant contribution” in its submittal. This would have been similar to the approach to defining significant contribution that the EPA has applied in prior rulemakings such as CSAPR and the CSAPR Update.

Further, the EPA's modeling already accounts for “on-the-books” control measures, and the State has not explained which of its measures were not already included in the EPA's modeling and thus deserve to be further credited as reducing the impact of the State's emissions beyond what the EPA's air quality modeling has already accounted for. In light of continuing contribution to out of state receptors from the State (at Steps 1 and 2) despite these measures, New York's SIP submission failed to evaluate the availability of any additional controls to improve downwind air quality at nonattainment and maintenance receptors at Step 3.

Finally, under the Wisconsin decision, states and the EPA may not delay implementation of measures necessary to address good neighbor requirements beyond the next applicable attainment date without a showing of impossibility or necessity. See 938 F.3d at 320. In those cases where the measures identified by the State had implementation timeframes beyond the next relevant attainment dates the submission did not offer a demonstration of impossibility of earlier implementation of those control measures. 56 Similarly, the State's submittal is insufficient to the extent the implementation timeframes for identified control measures were left unidentified, unexplained, or too uncertain to permit the EPA to form a judgment as to whether the timing requirements for good neighbor obligations have been met.

Step 4 of the 4-step interstate transport framework calls for development of permanent and federally enforceable control strategies to achieve the emissions reductions determined to be necessary at Step 3 to eliminate significant contribution to nonattainment or interference with maintenance of the NAAQS. New York identified a number of measures that were either in development or anticipated to occur in the future (See section III.4). 57 However, the State had not revised its SIP to include these emission reductions to ensure the reductions were permanent and enforceable. Although New York has subsequently adopted many of the measures identified in section III.4, several measures have not been approved into the SIP, either because the State failed to submit ( e.g., 6 NYCRR Part 218, Subpart 218-7, “Aftermarket Parts) or the EPA has not yet finalized approval into the SIP. Therefore, the emission reductions associated with those rules are not permanent and enforceable. As a result, EPA proposes to disapprove New York's submittal on the separate, additional basis that New York has not included permanent and enforceable emissions reductions in its SIP as necessary to meet the obligations of 110(a)(2)(d)(i)(I).

Based on the EPA's evaluation of New York's' SIP submission, the EPA is proposing to find that the portion of New York's September 25, 2018 SIP submission addressing CAA section 110(a)(2)(D)(i)(I) does not meet the State's interstate transport obligations for the 2015 8-hour ozone NAAQS, because it fails to contain the necessary provisions to eliminate emissions in amounts that will contribute significantly to nonattainment or interfere with maintenance of the NAAQS in any other state.

As described in section I, the EPA performed air quality modeling using the 2016v2 emissions platform to project design values and contributions for 2023. These data were examined to determine if New Jersey contributes at or above the threshold of 1 percent of the 2015 8-hour ozone NAAQS (0.70 ppb) to any downwind nonattainment or maintenance receptor. As shown in Table 2, the data  58 indicate that in 2023 emissions from New Jersey contribute greater than 1 percent of the standard to nonattainment or maintenance-only receptors in Stratford, Connecticut (receptor ID 90013007), Westport, Connecticut (receptor ID 90019003), Greenwich, Connecticut (receptor ID 90010017), Madison, Connecticut (receptor ID 90099002), and Bucks County, Pennsylvania (receptor ID 480170012). 59

As noted in section II.B., New Jersey submitted OTC modeling that identified nonattainment and maintenance receptors in 2023. Although the State used a different modeling approach (utilizing 2011 based modeling and the ERTAC EGU Projection tool), than the EPA's modeling, which used a 2016-based emissions platform developed under an EPA/MJO/state collaborative project, New Jersey's alternative modeling also identified a number of nonattainment and maintenance receptor sites in 2023. See page 9 of the May 30, 2019 SIP submission. New Jersey determined that there were nonattainment or maintenance problems at eight locations in Connecticut, New York, and Maryland, which exceeded the 5 locations in Connecticut and Pennsylvania that the EPA determined to have nonattainment or maintenance problems. Based on both the New Jersey and the EPA modeling, nonattainment and maintenance receptors are projected in 2023 at Step 1. Thus, even under the alternative modeling of 2023, New Jersey acknowledges in its submittal the existence of several nonattainment and maintenance receptors.

Although New Jersey relied on alternative modeling to the EPA's modeling at Step 2, New Jersey acknowledged in its SIP submission that it is linked above 1 percent of the NAAQS (0.70 ppb for the 2015 8-hour ozone NAAQS) to one or more downwind receptors in 2023. Because the alternative modeling relied on by the State also demonstrates that a linkage exists between the State and downwind receptors at Step 2, the EPA need not conduct a comparative assessment of the alternative modeling; the State concedes that it is linked. New Jersey's analysis corroborates the conclusion in the EPA's most recent modeling. The EPA therefore will proceed to Step 3 of the 4-step interstate transport framework to assess arguments the State presented as to why, despite this linkage, the State should not be considered to significantly contribute to nonattainment or interfere with maintenance of the NAAQS in any other state such that additional emissions reductions are required.

At Step 3 of the 4-step interstate transport framework, a state's emissions are further evaluated, in light of multiple factors, including air quality and cost considerations, to determine what, if any, emissions significantly contribute to nonattainment or interfere with maintenance and, thus, must be eliminated under CAA section 110(a)(2)(D)(i)(I).

To effectively evaluate which emissions in the state should be deemed “significant” and therefore prohibited, states generally should prepare an accounting of sources and other emissions activity and assess potential, additional emissions reduction opportunities and resulting downwind air quality improvements. The EPA has consistently applied this general approach ( i.e., Step 3 of the 4-step interstate transport framework) when identifying emissions contributions that the Agency has determined to be “significant” (or interfere with maintenance) in each of its prior Federal, regional ozone transport rulemakings, and this interpretation of the statute has been upheld by the Supreme Court. See EME Homer City, 572 U.S. 489, 519 (2014). While the EPA has not directed states that they must conduct a Step 3 analysis in precisely the manner the EPA has done in its prior regional transport rulemakings, state implementation plans addressing the obligations in CAA section 110(a)(2)(D)(i)(I) must prohibit “any source or other type of emissions activity within the State” from emitting air pollutants which will contribute significantly to downwind air quality problems. Thus, states must complete something similar to the EPA's analysis (or an alternative approach to defining “significance” that comports with the statute's objectives) to determine whether and to what degree emissions from a state should be “prohibited” to eliminate emissions that will “contribute significantly to nonattainment in, or interfere with maintenance of,” the NAAQS in any other state. New Jersey did not conduct such an analysis in its SIP submission.

As previously noted, New Jersey asserted in its May 2019 submittal that considering air quality, the emissions reductions from New Jersey's adopted measures, and the cost effectiveness of those measures, no additional emissions reductions from New Jersey are necessary to address its good neighbor obligations to downwind nonattainment and maintenance areas. New Jersey stated that control measures were adopted and implemented before attainment deadlines and go beyond previously established the EPA cost effectiveness thresholds. New Jersey also provided information documenting the emissions reductions that have been made throughout the State beginning in 2002 with corresponding improvements in air quality in New Jersey to demonstrate the impact of New Jersey's control measures.

New Jersey's submittal, however, did not contain a demonstration at Step 3 that the State was adequately controlling its emissions for purposes of the good neighbor provision, particularly because the State conceded in its submission that it was potentially significantly contributing to eight receptors in 2023 at Steps 1 and 2. The SIP submittal pointed to the State's existing NO X and VOC control measures that were adopted by the State to conclude New Jersey is already meeting its good neighbor obligations for the 2015 8-hour ozone NAAQS. However, the State's submittal does not include a sufficient examination or a technical justification that could support the conclusion that the State has no further good neighbor obligations for the 2015 8-hour ozone NAAQS. In particular, the State did not conduct in its submittal an analysis of potential additional emissions-reduction measures to further reduce its impact on the identified downwind receptors. For example, New Jersey did not include in its submission an accounting of individual emissions units at facilities in the State along with an analysis of potential NO X emissions control technologies, their associated costs, estimated emissions reductions, and downwind air quality improvements. Nor does the submittal include an analysis of whether such potential, additional control technologies or measures could reduce the impact of New Jersey's emissions on out of state receptors. Though there is not a prescribed method for a Step 3 analysis, the EPA has consistently applied Step 3 of the good neighbor framework through a more rigorous evaluation of potential additional control technologies or measures than what New Jersey provided in its submission. Identifying a range of various emissions control measures that have been or may be enacted at the state level, without analysis of the impact of those measures on the out of state receptors, is not analytically sufficient. In general, the air quality modeling that EPA has conducted (as well the modeling relied on by New Jersey in its submittal) already accounts for “on-the-books” emissions control measures. Both sets of modeling clearly establish continued linkage from New Jersey to downwind receptors in 2023 at Steps 1 and 2, despite those emissions control efforts.

The EPA acknowledges that the State's control measures listed in the State's SIP submittal may be nominally more stringent than the EPA cost-thresholds used for the CSAPR Update or Revised CSAPR Update. But those cost-thresholds were for the 2008 ozone NAAQS (a less stringent NAAQS than the 2015 ozone NAAQS). Further, in the Revised CSAPR Update, the EPA found that despite the nominal stringency of New Jersey's control programs, additional emissions reductions were achievable from EGUs in the State, even under the level of control stringency the EPA determined appropriate to eliminate significant contribution for the 2008 ozone NAAQS. In any case, the EPA has not established a benchmark cost-effectiveness threshold for good neighbor obligations for the 2015 ozone NAAQS, and New Jersey in its submittal has not conducted an analysis to establish one for the EPA to evaluate. Additionally, while New Jersey's existing control measures have undoubtedly reduced the amount of transported ozone pollution to other states and have contributed to the downward emissions trends and improving air quality in the State as shown in the State's SIP submittal, in light of continuing contribution to out of state receptors from the State at Steps 1 and 2 despite these measures, New Jersey's SIP submission failed to provide an adequate analysis at Step 3.

We therefore propose that New Jersey was required to analyze emissions from the sources and other emissions activity from within the state to determine whether its contributions were significant, and we propose to disapprove its submission because New Jersey failed to do so.

Step 4 of the 4-step interstate transport framework calls for development of permanent and federally enforceable control strategies to achieve the emissions reductions determined to be necessary at Step 3 to eliminate significant contribution to nonattainment or interference with maintenance of the NAAQS. As mentioned previously, New Jersey's SIP submission did not contain an evaluation of additional emission control opportunities (or establish that no additional controls are required), thus, no information was provided at Step 4. As a result, EPA proposes to disapprove New Jersey's submittal on the separate, additional basis that the State has not developed permanent and enforceable emissions reductions necessary to meet the obligations of CAA section 110(a)(2)(d)(i)(I).

Based on the EPA's evaluation of New Jersey's SIP submission, the EPA is proposing to find that the portion of New Jersey's May 13, 2019 SIP submission addressing CAA section 110(a)(2)(D)(i)(I) does not meet the State's interstate transport obligations for the 2015 8-hour ozone NAAQS, because it fails to contain the necessary provisions to eliminate emissions in amounts that will contribute significantly to nonattainment or interfere with maintenance of the NAAQS in any other state.

We are proposing to disapprove the portion of New York's and New Jersey's SIP submissions pertaining to interstate transport of air pollution which will significantly contribute to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in other states. Under CAA section 110(c)(1), disapproval, if finalized, would establish a 2-year deadline for the EPA to promulgate a FIP for New York and New Jersey to address interstate transport requirements for the 2015 8-hour ozone NAAQS, unless the EPA approves a SIP that meets these requirements. Disapproval does not start a mandatory sanctions clock for New York and New Jersey. The remaining elements of New York's September 25, 2018 submission, and New Jersey's May 13, 2019 submission are not addressed in this action and either have been or will be acted on in separate rulemakings.

This action is not a significant regulatory action and was therefore not submitted to the Office of Management and Budget for review.

This proposed action does not impose an information collection burden under the PRA because it does not contain any information collection activities

I certify that this action will not have a significant economic impact on a substantial number of small entities under the RFA. This action merely proposes to disapprove a SIP submission as not meeting the CAA.

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.

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.

This action does not have tribal implications as specified in Executive Order 13175. This action does not apply on any Indian reservation land, any other area where the EPA or an Indian tribe has demonstrated that a tribe has jurisdiction, or non-reservation areas of Indian country. Thus, Executive Order 13175 does not apply to this action.

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 merely proposes to disapprove a SIP submission as not meeting the CAA.

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

This rulemaking does not involve technical standards.

The EPA believes the human health or environmental risk addressed by this action will not have potential disproportionately high and adverse human health or environmental effects on minority, low-income or indigenous populations. This action merely proposes to disapprove a SIP submission as not meeting the CAA.

Section 307(b)(1) of the CAA governs judicial review of final actions by the EPA. This section provides, in part, that petitions for review must be filed in the D.C. 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). 60

The EPA anticipates that this proposed rulemaking, if finalized, would be “nationally applicable” within the meaning of CAA section 307(b)(1) because it would take final action on SIP submittals for the 2015 ozone NAAQS for two states, which are located in two different Federal judicial circuits. It would apply uniform, nationwide analytical methods, policy judgments, and interpretation with respect to the same CAA obligations, i.e., implementation of good neighbor requirements under CAA section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS for states across the country, and final action would be based on this common core of determinations, described in further detail below.

If the EPA takes final action on this proposed rulemaking, in the alternative, the Administrator intends to exercise the complete discretion afforded to him under the CAA to make and publish a finding that the final action (to the extent a court finds the action to be locally or regionally applicable) is based on a determination of “nationwide scope or effect” within the meaning of CAA section 307(b)(1). Through this rulemaking action (in conjunction with a series of related actions on other SIP submissions for the same CAA obligations), the EPA interprets and applies section 110(a)(2)(d)(i)(I) of the CAA for the 2015 ozone NAAQS based on a common core of nationwide policy judgments and technical analysis concerning the interstate transport of pollutants throughout the continental U.S. In particular, the EPA is applying here (and in other proposed actions related to the same obligations) the same, nationally consistent 4-step framework for assessing good neighbor obligations for the 2015 ozone NAAQS. The EPA relies on a single set of updated, 2016-base year photochemical grid modeling results of the year 2023 as the primary basis for its assessment of air quality conditions and contributions at Steps 1 and 2 of that framework. Further, the EPA proposes to determine and apply a set of nationally consistent policy judgments to apply the 4-step framework. The EPA has selected a nationally uniform analytic year (2023) for this analysis and is applying a nationally uniform approach to nonattainment and maintenance receptors and a nationally uniform approach to contribution threshold analysis. 61 For these reasons, the Administrator intends, if this proposed action is finalized, to exercise the complete discretion afforded to him under the CAA to make and publish a finding that this action is based on one or more determinations of nationwide scope or effect for purposes of CAA section 307(b)(1). 62

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

Public Participation: Submit your comments, identified by Docket No. EPA-R04-OAR-2021-0841, at https://www.regulations.gov. Once submitted, comments cannot be edited or removed from the docket. EPA may publish any comment received to its public docket. Do not submit to EPA's docket at https://www.regulations.gov 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. 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).

There are two dockets supporting this action, EPA-R04-OAR-2021-0841 and EPA-HQ-OAR-2021-0663. Docket No. EPA-R04-OAR-2021-0841 contains information specific to Kentucky, including this notice of proposed rulemaking. Docket No. EPA-HQ-OAR-2021-0663 contains additional modeling files, emissions inventory files, technical support documents, and other relevant supporting documentation regarding interstate transport of emissions for the 2015 8-hour ozone NAAQS which are being used to support this action. All comments regarding information in either of these dockets are to be made in Docket No. EPA-R04-OAR-2021-0841. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. Due to public health concerns related to COVID-19, the EPA Docket Center and Reading Room are open to the public by appointment only. The Docket Center staff also continues to provide remote customer service via email, phone, and webform. For further information and updates on EPA Docket Center services, please visit EPA online at https://www.epa.gov/dockets.

EPA continues to carefully and continuously monitor information from the Centers for Disease Control and Prevention (CDC), local area health departments, and Federal partners so that EPA can respond rapidly as conditions change regarding COVID-19.

The indices to Docket No. EPA-R04-OAR-2021-0841 and Docket No. EPA-HQ-OAR-2021-0663 are available electronically at www.regulations.gov. While all documents in each docket are listed in their respective index, some information may not be publicly available due to docket file size restrictions or content ( e.g., CBI).

The following provides background for EPA's proposed action related to the interstate transport requirements for the 2015 8-hour ozone NAAQS for the Commonwealth of Kentucky.

On October 1, 2015, EPA promulgated a revision to the ozone NAAQS (2015 8-hour ozone NAAQS), lowering the level of both the primary and secondary standards to 0.070 parts per million (ppm). 1 Section 110(a)(1) of the CAA requires states to submit, within 3 years after promulgation of a new or revised standard, SIP submissions meeting the applicable requirements of section 110(a)(2). 2 One of these applicable requirements is found in CAA section 110(a)(2)(D)(i)(I), otherwise known as the “good neighbor” or “interstate transport” provision, which generally requires SIPs to contain adequate provisions to prohibit in-state emissions activities from having certain adverse air quality effects on other states due to interstate transport of pollution. There are two so-called “prongs” within CAA section 110(a)(2)(D)(i)(I). A SIP for a new or revised NAAQS must contain adequate provisions prohibiting any source or other type of emissions activity within the state from emitting air pollutants in amounts that will significantly contribute to nonattainment of the NAAQS in another state (prong 1) or interfere with maintenance of the NAAQS in another state (prong 2). EPA and states must give independent significance to prong 1 and prong 2 when evaluating downwind air quality problems under CAA section 110(a)(2)(D)(i)(I). 3

EPA is using the 4-step interstate transport framework (or 4-step framework) to evaluate the states' implementation plan submittals addressing the interstate transport provision for the 2015 8-hour ozone NAAQS. EPA has addressed the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) with respect to prior ozone NAAQS in several regional regulatory actions, including the Cross-State Air Pollution Rule (CSAPR), which addressed interstate transport with respect to the 1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter standards, 4 the Cross-State Air Pollution Rule Update (CSAPR Update)  5 and the Revised CSAPR Update, both of which addressed the 2008 ozone NAAQS. 6

Through the development and implementation of the CSAPR rulemakings and prior regional rulemakings pursuant to the interstate transport provision, 7 EPA, working in partnership with states, developed the following 4-step interstate transport framework to evaluate a state's obligations to eliminate interstate transport emissions under the interstate transport provision for the ozone NAAQS: (1) Identify monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS ( i.e., nonattainment and/or maintenance receptors); (2) identify states that impact those air quality problems in other ( i.e., downwind) states sufficiently such that the states are considered “linked” and therefore warrant further review and analysis; (3) identify the emissions reductions necessary (if any), applying a multifactor analysis, to eliminate each linked upwind state's significant contribution to nonattainment or interference with maintenance of the NAAQS at the locations identified in Step 1; and (4) adopt permanent and enforceable measures needed to achieve those emissions reductions.

In general, EPA has performed nationwide air quality modeling to project ozone design values which are used in combination with measured data to identify nonattainment and maintenance receptors. To quantify the contribution of emissions from specific upwind states on 2023 ozone design values for the identified downwind nonattainment and maintenance receptors, EPA performed nationwide, state-level ozone source apportionment modeling for 2023. The source apportionment modeling provided contributions to ozone at receptors from precursor emissions of anthropogenic nitrogen oxides (NO X ) and volatile organic compounds (VOCs) in individual upwind states.

EPA has released several documents containing projected design values, contributions, and information relevant to evaluating interstate transport with respect to the 2015 8-hour ozone NAAQS. First, on January 6, 2017, EPA published a notice of data availability (NODA) in which the Agency requested comment on preliminary interstate ozone transport data including projected ozone design values and interstate contributions for 2023 using a 2011 base year platform. 8 In the NODA, EPA used the year 2023 as the analytic year for this preliminary modeling because that year aligns with the expected attainment year for Moderate ozone nonattainment areas for the 2015 8-hour ozone NAAQS. 9 On October 27, 2017, EPA released a memorandum (October 2017 memorandum) containing updated modeling data for 2023, which incorporated changes made in response to comments on the NODA, and noted that the modeling may be useful for states developing SIPs to address interstate transport obligations for the 2008 ozone NAAQS. 10 On March 27, 2018, EPA issued a memorandum (March 2018 memorandum) noting that the same 2023 modeling data released in the October 2017 memorandum could also be useful for identifying potential downwind air quality problems with respect to the 2015 8-hour ozone NAAQS at Step 1 of the 4-step interstate transport framework. 11 The March 2018 memorandum also included the then newly available contribution modeling data for 2023 to assist states in evaluating their impact on potential downwind air quality problems for the 2015 8-hour ozone NAAQS under Step 2 of the 4-step interstate transport framework. 12 EPA subsequently issued two more memoranda in August and October 2018, providing additional information to states developing interstate transport SIP submissions for the 2015 8-hour ozone NAAQS concerning, respectively, potential contribution thresholds that may be appropriate to apply in Step 2 of the 4-step interstate transport framework, and considerations for identifying downwind areas that may have problems maintaining the standard at Step 1 of the 4-step interstate transport framework. 13

Since the release of the modeling data shared in the March 2018 memorandum, EPA performed updated modeling using a 2016-based emissions modeling platform ( i.e., 2016v1). This emissions platform was developed under the EPA/Multi-Jurisdictional Organization (MJO)/state collaborative project. 14 This collaborative project was a multi-year joint effort by EPA, MJOs, and states to develop a new, more recent emissions platform for use by EPA and states in regulatory modeling as an improvement over the dated 2011-based platform that EPA had used to project ozone design values and contribution data provided in the 2017 and 2018 memoranda. EPA used the 2016v1 emissions to project ozone design values and contributions for 2023. On October 30, 2020, in the Notice of Proposed Rulemaking for the Revised CSAPR Update, EPA released and accepted public comment on 2023 modeling that used the 2016v1 emissions platform. 15 Although the Revised CSAPR Update addressed transport for the 2008 ozone NAAQS, the projected design values and contributions from the 2016v1 platform are also useful for identifying downwind ozone problems and linkages with respect to the 2015 8-hour ozone NAAQS. 16

Following the Revised CSAPR Update final rule, EPA made further updates to the 2016 emissions platform to include mobile emissions from EPA's Motor Vehicle Emission Simulator (MOVES) model  17 and updated emissions projections for electric generating units (EGUs) that reflect the emissions reductions from the Revised CSAPR Update, recent information on plant closures, and other sector trends. The construct of the updated emissions platform, 2016v2, is described in the Preparation of Emissions Inventories for the 2016v2 North American Emissions Modeling Platform technical support document (TSD) for this proposed rule and is included in Docket No. EPA-HQ-OAR-2021-0663. EPA performed air quality modeling of the 2016v2 emissions using the most recent public release version of the Comprehensive Air Quality Modeling with Extensions (CAMx) photochemical modeling, version 7.10. 18 EPA proposes to primarily rely on modeling based on the updated and newly available 2016v2 emissions platform in evaluating these submissions with respect to Steps 1 and 2 of the 4-step interstate transport framework. By using the updated modeling results, EPA is using the most current and technically appropriate information for this proposed rulemaking. Section III of this notice and the Air Quality Modeling TSD included in Docket No. EPA-HQ-OAR-2021-0663 for this proposal contain additional detail on the modeling performed using the 2016v2 emissions modeling.

In this notice, EPA is accepting public comment on this updated 2023 modeling, which uses the 2016v2 emissions platform. Details on the air quality modeling and the methods for projecting design values and determining contributions in 2023 are described in the Air Quality Modeling TSD for 2015 8-hour Ozone NAAQS Transport SIP Proposed Actions. Comments on EPA's air quality modeling should be submitted in Docket No. EPA-R04-OAR-2021-0841. Comments are not being accepted in Docket No. EPA-HQ-OAR-2021-0663.

States may have chosen to rely on the results of EPA modeling and/or alternative modeling performed by states or Multi-Jurisdictional Organizations (MJOs) to evaluate downwind air quality problems and contributions as part of their submissions. In section III, EPA evaluates how Kentucky used air quality modeling information in its submission.

EPA proposes to apply a consistent set of policy judgments across all states for purposes of evaluating interstate transport obligations and the approvability of interstate transport SIP submittals for the 2015 8-hour ozone NAAQS. These policy judgments reflect consistency with relevant case law and past Agency practice as reflected in CSAPR and related rulemakings. Nationwide consistency in approach is particularly important in the context of interstate ozone transport, which is a regional-scale pollution problem involving many smaller contributors. Effective policy solutions to the problem of interstate ozone transport going back to the NO X SIP Call have necessitated the application of a uniform framework of policy judgments in order to ensure an “efficient and equitable” approach. See EME Homer City Generation, LP v. EPA, 572 U.S. 489, 519 (2014).

In the March, August, and October 2018 memoranda, EPA recognized that states may be able to establish alternative approaches to addressing their interstate transport obligations for the 2015 8-hour ozone NAAQS that vary from a nationally uniform framework. EPA emphasized in these memoranda, however, that such alternative approaches must be technically justified and appropriate in light of the facts and circumstances of each particular state's submittal. In general, EPA continues to believe that deviation from a nationally consistent approach to ozone transport must be substantially justified and have a well-documented technical basis that is consistent with relevant case law. Where states submitted SIPs that rely on any such potential concepts as may have been identified or suggested in the past, EPA will evaluate whether the state adequately justified the technical and legal basis for doing so.

EPA notes that certain potential concepts included in an attachment to the March 2018 memorandum require unique consideration, and these ideas do not constitute Agency guidance with respect to transport obligations for the 2015 8-hour ozone NAAQS. Attachment A to the March 2018 memorandum identified a “Preliminary List of Potential Flexibilities” that could potentially inform SIP development. 19 However, EPA made clear in that attachment that the list of ideas were not suggestions endorsed by the Agency but rather “comments provided in various forums” on which EPA sought “feedback from interested stakeholders.”  20 Further, Attachment A stated, “EPA is not at this time making any determination that the ideas discussed below are consistent with the requirements of the CAA, nor [is EPA] specifically recommending that states use these approaches.”  21 Attachment A to the March 2018 memorandum, therefore, does not constitute agency guidance, but was intended to generate further discussion around potential approaches to addressing ozone transport among interested stakeholders. To the extent states sought to develop or rely on these ideas in support of their SIP submittals, EPA will thoroughly review the technical and legal justifications for doing so.

The remainder of this section describes EPA's proposed framework with respect to analytic year, definition of nonattainment and maintenance receptors, selection of contribution threshold, and multifactor control strategy assessment.

In general, the states and EPA must implement the interstate transport provision in a manner “consistent with the provisions of [title I of the CAA].” See CAA section 110(a)(2)(D)(i). This requires, among other things, that these obligations are addressed consistently with the timeframes for downwind areas to meet their CAA obligations. With respect to ozone NAAQS, under CAA section 181(a), this means obligations must be addressed “as expeditiously as practicable” and no later than the schedule of attainment dates provided in CAA section 181(a)(1). 22 Several D.C. Circuit court decisions address the issue of the relevant analytic year for the purposes of evaluating ozone transport air-quality problems. On September 13, 2019, the D.C. Circuit issued a decision in Wisconsin v. EPA, remanding the CSAPR Update to the extent that it failed to require upwind states to eliminate their significant contribution by the next applicable attainment date by which downwind states must come into compliance with the NAAQS, as established under CAA section 181(a). See 938 F.3d 303, 313.

On May 19, 2020, the D.C. Circuit issued a decision in Maryland v. EPA that cited the Wisconsin decision in holding that EPA must assess the impact of interstate transport on air quality at the next downwind attainment date, including Marginal area attainment dates, in evaluating the basis for EPA's denial of a petition under CAA section 126(b). Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 2020). The court noted that “section 126(b) incorporates the Good Neighbor Provision,” and, therefore, “EPA must find a violation [of section 126] if an upwind source will significantly contribute to downwind nonattainment at the next downwind attainment deadline. Therefore, the agency must evaluate downwind air quality at that deadline, not at some later date.” Id. at 1204 (emphasis added). EPA interprets the court's holding in Maryland as requiring the states and the Agency, under the good neighbor provision, to assess downwind air quality as expeditiously as practicable and no later than the next applicable attainment date, 23 which is now the Moderate area attainment date under CAA section 181 for ozone nonattainment. The Moderate area attainment date for the 2015 8-hour ozone NAAQS is August 3, 2024. 24 EPA believes that 2023 is now the appropriate year for analysis of interstate transport obligations for the 2015 8-hour ozone NAAQS, because the 2023 ozone season is the last relevant ozone season during which achieved emissions reductions in linked upwind states could assist downwind states with meeting the August 3, 2024, Moderate area attainment date for the 2015 8-hour ozone NAAQS.

EPA recognizes that the attainment date for nonattainment areas classified as Marginal for the 2015 8-hour ozone NAAQS was August 3, 2021. Under the Maryland holding, any necessary emissions reductions to satisfy interstate transport obligations should have been implemented by no later than this date. At the time of the statutory deadline to submit interstate transport SIPs (October 1, 2018), many states relied upon EPA modeling of the year 2023, and no state provided an alternative analysis using a 2021 analytic year (or the prior 2020 ozone season). However, EPA must act on SIP submittals using the information available at the time it takes such action. In this circumstance, EPA does not believe it would be appropriate to evaluate states' obligations under CAA section 110(a)(2)(D)(i)(I) as of an attainment date that is wholly in the past, because the Agency interprets the interstate transport provision as forward looking. See 86 FR 23054, 23074; see also Wisconsin, 938 F.3d at 322. Consequently, in this proposal EPA will use the analytical year of 2023 to evaluate each state's CAA section 110(a)(2)(D)(i)(I) SIP submission with respect to the 2015 8-hour ozone NAAQS.

In Step 1, EPA identifies monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS in the 2023 analytic year. Where EPA's analysis shows that a site does not fall under the definition of a nonattainment or maintenance receptor, that site is excluded from further analysis under EPA's 4-step interstate transport framework. For sites that are identified as a nonattainment or maintenance receptor in 2023, EPA proceeds to the next step of the 4-step interstate transport framework by identifying the upwind state's contribution to those receptors.

EPA's approach to identifying ozone nonattainment and maintenance receptors in this action is consistent with the approach used in previous transport rulemakings. EPA's approach gives independent consideration to both the “contribute significantly to nonattainment” and the “interfere with maintenance” prongs of CAA section 110(a)(2)(D)(i)(I), consistent with the D.C. Circuit's direction in North Carolina v. EPA. 25

For the purpose of this proposal, EPA identifies nonattainment receptors as those monitoring sites that are projected to have average design values that exceed the NAAQS and that are also measuring nonattainment based on the most recent monitored design values. This approach is consistent with prior transport rulemakings, such as the CSAPR Update, where EPA defined nonattainment receptors as those areas that both currently measure nonattainment and that EPA projects will be in nonattainment in the future analytic year ( i.e., 2023). 26

In addition, in this proposal, EPA identifies a receptor to be a “maintenance” receptor for purposes of defining interference with maintenance, consistent with the method used in CSAPR and upheld by the D.C. Circuit in EME Homer City Generation, L.P. v. EPA, 795 F.3d 118, 136 (D.C. Cir. 2015). 27 Specifically, EPA identified maintenance receptors as those receptors that would have difficulty maintaining the relevant NAAQS in a scenario that takes into account historical variability in air quality at that receptor. The variability in air quality was determined by evaluating the “maximum” future design value at each receptor based on a projection of the maximum measured design value over the relevant period. EPA interprets the projected maximum future design value to be a potential future air quality outcome consistent with the meteorology that yielded maximum measured concentrations in the ambient data set analyzed for that receptor ( i.e., ozone conducive meteorology). EPA also recognizes that previously experienced meteorological conditions ( e.g., dominant wind direction, temperatures, air mass patterns) promoting ozone formation that led to maximum concentrations in the measured data may reoccur in the future. The maximum design value gives a reasonable projection of future air quality at the receptor under a scenario in which such conditions do, in fact, reoccur. The projected maximum design value is used to identify upwind emissions that, under those circumstances, could interfere with the downwind area's ability to maintain the NAAQS.

Recognizing that nonattainment receptors are also, by definition, maintenance receptors, EPA often uses the term “maintenance-only” to refer to those receptors that are not nonattainment receptors. Consistent with the concepts for maintenance receptors, as described above, EPA identifies “maintenance-only” receptors as those monitoring sites that have projected average design values above the level of the applicable NAAQS, but that are not currently measuring nonattainment based on the most recent official design values. In addition, those monitoring sites with projected average design values below the NAAQS, but with projected maximum design values above the NAAQS are also identified as “maintenance-only” receptors, even if they are currently measuring nonattainment based on the most recent official design values.

In Step 2, EPA quantifies the contribution of each upwind state to each receptor in the 2023 analytic year. The contribution metric used in Step 2 is defined as the average impact from each state to each receptor on the days with the highest ozone concentrations at the receptor based on the 2023 modeling. If a state's contribution value does not equal or exceed the threshold of 1 percent of the NAAQS ( i.e., 0.70 ppb for the 2015 8-hour ozone NAAQS), the upwind state is not “linked” to a downwind air quality problem, and EPA, therefore, concludes that the state does not significantly contribute to nonattainment or interfere with maintenance of the NAAQS in the downwind states. However, if a state's contribution equals or exceeds the 1 percent threshold, the state's emissions are further evaluated in Step 3, considering both air quality and cost as part of a multi-factor analysis, to determine what, if any, emissions might be deemed “significant” and, thus, must be eliminated under CAA section 110(a)(2)(D)(i)(I).

EPA is proposing to rely in the first instance on the 1 percent threshold for the purpose of evaluating a state's contribution to nonattainment or maintenance of the 2015 8-hour ozone NAAQS ( i.e., 0.70 ppb) at downwind receptors. This is consistent with the Step 2 approach that EPA applied in CSAPR for the 1997 ozone NAAQS, which has subsequently been applied in the CSAPR Update when evaluating interstate transport obligations for the 2008 ozone NAAQS. EPA continues to find 1 percent to be an appropriate threshold. For ozone, as EPA found in the CAIR, CSAPR, and the CSAPR Update, a portion of the nonattainment problems from anthropogenic sources in the U.S. result from the combined impact of relatively small contributions from many upwind states, along with contributions from in-state sources and, in some cases, substantially larger contributions from a subset of particular upwind states. EPA's analysis shows that much of the ozone transport problem being analyzed in this proposed rule is still the result of the collective impacts of contributions from many upwind states. Therefore, application of a consistent contribution threshold is necessary to identify those upwind states that should have responsibility for addressing their contribution to the downwind nonattainment and maintenance problems to which they collectively contribute. Continuing to use 1 percent of the NAAQS as the screening metric to evaluate collective contribution from many upwind states also allows EPA (and states) to apply a consistent framework to evaluate interstate emissions transport under the interstate transport provision from one NAAQS to the next. See 81 FR at 74518 (August 8, 2011); see also 86 FR at 23085 (April 30, 2021) (reviewing and explaining rationale from CSAPR, 76 FR at 48237-38 (August 8, 2011), for selection of 1 percent threshold).

EPA's August 2018 memorandum recognized that in certain circumstances, a state may be able to establish that an alternative contribution threshold of 1 ppb is justifiable. Where a state relies on this alternative threshold, and where that state determined that it was not linked at Step 2 using the alternative threshold, EPA will evaluate whether the state provided a technically sound assessment of the appropriateness of using this alternative threshold based on the facts and circumstances underlying its application in the particular SIP submission.

Consistent with EPA's longstanding approach to eliminating significant contribution or interference with maintenance, at Step 3, states linked at Steps 1 and 2 are generally expected to prepare a multifactor assessment of potential emissions controls. EPA's analysis at Step 3 in prior Federal actions addressing interstate transport requirements has primarily focused on an evaluation of cost-effectiveness of potential emissions controls (on a marginal cost-per-ton basis), the total emissions reductions that may be achieved by requiring such controls (if applied across all linked upwind states), and an evaluation of the air quality impacts such emissions reductions would have on the downwind receptors to which a state is linked; other factors may potentially be relevant if adequately supported. In general, where EPA's or alternative air quality and contribution modeling establishes that a state is linked at Steps 1 and 2, it will be insufficient at Step 3 for a state merely to point to its existing rules requiring control measures as a basis for approval. In general, the emissions-reducing effects of all existing emissions control requirements are already reflected in the air quality results of the modeling for Steps 1 and 2. If the state is shown to still be linked to one or more downwind receptor(s), states must provide a well-documented evaluation determining whether their emissions constitute significant contribution or interference with maintenance by evaluating additional available control opportunities by preparing a multifactor assessment. While EPA has not prescribed a particular method for this assessment, EPA expects states at a minimum to present a sufficient technical evaluation. This would typically include information on emissions sources, applicable control technologies, emissions reductions, costs, cost effectiveness, and downwind air quality impacts of the estimated reductions, before concluding that no additional emissions controls should be required. 28

At Step 4, states (or EPA) develop permanent and federally enforceable control strategies to achieve the emissions reductions determined to be necessary at Step 3 to eliminate significant contribution to nonattainment or interference with maintenance of the NAAQS. For a state linked at Steps 1 and 2 to rely on an emissions control measure at Step 3 to address its interstate transport obligations, that measure must be included in the state's implementation plan so that it is permanent and federally enforceable. See CAA section 110(a)(2)(D) (“Each such [SIP] shall . . . contain adequate provisions. . . .”). See also CAA section 110(a)(2)(A); Committee for a Better Arvin v. EPA, 786 F.3d 1169, 1175-76 (9th Cir. 2015) (holding that measures relied on by a state to meet CAA requirements must be included in the SIP).

On January 11, 2019, Kentucky submitted a SIP revision, a portion of which addressed the CAA section 110(a)(2)(D)(i)(I) interstate transport requirements for the 2015 8-hour ozone NAAQS. The Commonwealth's SIP submission provided Kentucky's analysis of its impact to downwind states and concluded that the Commonwealth had met the requirements of CAA section l10(a)(2)(D)(i)(I) ( i.e., prongs 1 and 2) because Kentucky's SIP contains adequate provisions to prevent sources and other types of emissions activities within the Commonwealth from significantly contributing to nonattainment, or interfering with the maintenance, of downwind states with respect to the 2015 8-hour ozone NAAQS.

The Commonwealth's submission relied on the results of EPA's modeling of the year 2023, contained in the March 2018 memorandum, to identify downwind nonattainment and maintenance receptors that may be “linked” to emissions from sources in Kentucky (which correlates to Step 1 of the 4-step framework). 29 The March 2018 modeling indicates that the Commonwealth was linked to four nonattainment receptors and one maintenance monitor above 1% of the NAAQS. The largest impact from Kentucky sources on any downwind nonattainment receptor in the East was projected to be 0.89 ppb at the Fairfield County, Connecticut (ID: 90013007) site. The other nonattainment receptors to which Kentucky was linked are: a second site in Fairfield County (ID: 90019003); Milwaukee, Wisconsin (ID: 550790085); and Sheboygan, Wisconsin (ID: 551170006). The impact from Kentucky sources on the one downwind maintenance-only receptor to which it was linked in that modeling was 1.52 ppb at the Harford County, Maryland monitor (ID: 240251001).

The Commonwealth reviewed EPA's August 2018 memorandum as it related to the use of a potential alternative contribution threshold of 1 ppb and agreed that use of a 1 ppb contribution threshold is comparable to the amount of collective contribution captured using a threshold equivalent to 1 percent of the NAAQS. Based on the March 2018 modeling and application of a 1 ppb alternative contribution threshold, the Commonwealth found that it would not be linked as a significant contributor to the four nonattainment receptors in Connecticut and Wisconsin (which correlates to EPA's Step 2), and therefore concluded that no further controls were required to address its contribution to those four receptors. Thus, the Commonwealth concluded that Kentucky's SIP contains adequate provisions to prevent sources and other types of emissions activities within the Commonwealth from contributing significantly to nonattainment in any other state ( i.e., “prong 1” of CAA section l10(a)(2)(D)(i)(I)) for the 2015 8-hour ozone NAAQS.

After application of the 1 ppb contribution threshold, Kentucky remained linked to the downwind maintenance-only receptor at Harford County, Maryland (ID: 240251001) because the Commonwealth's contribution of 1.52 ppb to this receptor was greater than the 1 ppb alternative threshold. Kentucky's SIP submission asserted that the amount of NO X emission reductions required for an upwind state should not be the same for a monitor that is already attaining the NAAQS as they are for a nonattainment monitor. The Commonwealth further asserted that local controls should be implemented before requiring upwind states to control their sources. Thus, Kentucky concluded that no further reductions other than on-the-books and on-the-way measures are required to address the Commonwealth's interstate transport obligation to eliminate its contribution to the Harford County, Maryland maintenance receptor.

In addition, Kentucky provided information intended to demonstrate that Kentucky's SIP contains adequate provisions to prevent sources and other types of emissions activities within the Commonwealth from significantly contributing to nonattainment, or interfering with the maintenance, of downwind states with respect to the 2015 8-hour ozone NAAQS, and thus, no additional emissions reductions from Kentucky are necessary. Specifically, Kentucky listed existing state, SIP-approved regulations and Federal programs for sources in the Commonwealth that it concluded address the requirements of CAA 110(a)(2)(D)(i)(I) for the 2015 8-hour ozone NAAQS. 30 Kentucky provided more detailed analyses related to several specific topics, which are summarized in sections below.

The Commonwealth also included documents attached as appendices to its submittal. The March 2018 memorandum and the August 2018 memorandum were attached at appendices A and B, respectively. 31 As Appendix C, the Commonwealth appended several documents developed and/or submitted by the Midwest Ozone Group (a consortium of upwind industries with emitting facilities). 32 This included a modeling analysis developed by Alpine Geophysics titled “Good Neighbor Modeling Technical Support Document for the 8-hour Ozone State Implementation Plans,” dated June 2018 (Alpine TSD). The Alpine TSD contains alternative modeling of 2023 performed by Alpine Geophysics sponsored by MOG, as well as additional policy suggestions that MOG suggested states could consider in developing good neighbor SIP submissions (see section 9 of the Alpine TSD). 33 The Alpine TSD also appended a separate set of MOG comments on EPA's March 2018 memorandum. 34 These comments and Alpine's modeling analysis were further summarized in a Microsoft PowerPoint Presentation titled “MOG's Preview of 2015 Ozone NAAQS Good Neighbor SIPs.” EPA also summarizes the materials developed by MOG that the Commonwealth included as Appendix C to its submittal, although it is unclear that Kentucky intended to rely on all aspects of these materials.

With respect to ozone precursors emitted from Kentucky sources, Kentucky focused its analysis on NO X emissions, as it found that ozone is far more sensitive to NO X emissions than VOC emissions in the Southeastern United States and that controlling NO X emissions is a more effective strategy in reducing ozone. Kentucky reviewed NO X emissions trends in the Commonwealth, comparing annual NO X emissions from 2008 to 2016, finding that NO X emissions in Kentucky have significantly decreased since 2008. The Commonwealth asserted that it has significantly lowered NO X emissions between 2008 and 2017  35 and contended that planned shutdowns and conversion to natural gas, along with the implementation of Federal and State programs, ensure Kentucky's emissions will continue to decrease. Based on the 2014 national emission inventory (NEI), Kentucky indicated that the major contributor of NO X emissions in the Commonwealth are point sources, mainly comprised of electric generating units (EGUs).

Kentucky asserted that NO X emissions from EGUs in the Commonwealth have decreased and would continue to decrease based, in part, on the implementation of CAIR, CSAPR, and the CSAPR Update, as well as retirements of several EGUs in the Commonwealth. The Commonwealth compared Kentucky's NO X ozone season allocations to actual EGU emissions in the Commonwealth, concluding that Kentucky's NO X ozone season budgets have decreased since the implementation of CSAPR and the CSAPR Update and actual ozone season NO X emissions are significantly lower than the trading program budgets. 36 The SIP submission summarized coal-fired unit retirements, shutdowns, and repowering from 2015 through 2017 as well as on-the-way reductions from natural gas conversions and retirements from 2017 through 2023. 37 Kentucky stated that it expected emissions will continue to decline in the future due to continued implementation of CSAPR, the CSAPR Update, and scheduled shutdowns, fuel switches, and retirements of facilities in the Commonwealth.

EPA's March 2018 modeling showed Kentucky linked to the two receptors located in Fairfield County, Connecticut, which is part of the New York-Northern New Jersey-Long Island, NY-NJ-CT (New York Metro Area) core based statistical area (CBSA). 38 Kentucky applied an alternative contribution threshold of 1 ppb, and thus determined that Kentucky was no longer linked to the Connecticut receptors. In addition, Kentucky provided information intended to demonstrate that emissions from local sources in the area surrounding the monitors contribute significantly to the continued nonattainment issues, and thus, that local controls should be implemented before requesting upwind states to control facilities.

In particular, Kentucky's SIP submission claims that the Westport Sherwood, Fairfield, Connecticut (ID: 90019003) and Stratford Point Lighthouse, Fairfield County (ID: 90013007) monitors are located less than three miles from the I-95 interstate highway corridor and over 500 miles from Kentucky. Kentucky asserted these monitors have a consistent pattern of violating the 2015 8-hour ozone NAAQS from 2007 to 2016. Kentucky also pointed out that it is not linked in the modeling to two other nonattainment receptors (the Greenwich Point Park and Criscuolo Park monitoring sites) that are in relatively close proximity to the Westport and Stratford monitors. Kentucky compared the distances between these sites with the distances of the sites to Kentucky's nearest border.

Kentucky's SIP submission also provided information related to the New York Metro Area, citing the 2014 NEI to state that the on-road source sector contributed the highest amount of NO X emissions and that the nonpoint source sector contributed the highest amount of VOC emissions in that area. The Commonwealth further provided information about high vehicle miles traveled (VMT) and commuting patterns in the New York Metro Area, as well as information regarding violating monitors along the I-95 corridor and outlying monitors that show attainment.

Additionally, Kentucky's SIP submission includes Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model back trajectory analysis to the two Connecticut receptors, 39 asserting that the HYSPLIT analysis indicates that the monitors are downwind of nonattainment areas in New York, New Jersey, Pennsylvania, and Maryland. The Commonwealth also asserted there is a consistent pattern of violating monitors located along the I-95 corridor. In addition, Kentucky asserted that pollutants are trapped in the marine boundary layer and then transported inland to coastal Connecticut receptors due to conditions on Long Island Sound.

The Commonwealth's SIP submission also discussed point sources in the New York Metro Area, providing information regarding the largest point sources in that area. In addition, Kentucky provided NO X and VOC emission information for 13 counties in the New York Metro Area that have NO X and VOC emission totals above 10,000 tpy, finding that three counties that surround Fairfield County (Suffolk, Queens, and Nassau Counties) had the highest NO X emissions.

Kentucky further evaluated high electric demand days in New York, discussing a New York Department of Environmental Conservation (NYDEC) determination that peaking units operating on peak electricity demand days are a major contributor of NO X (particularly units installed before 1987), and that such units can contribute 4.8 ppb of ozone on high ozone days. 40 Kentucky concluded NO X emission reductions from these EGUs point sources would have a significant impact on ozone levels in the New York Metro Area.

Kentucky acknowledged that EPA's March 27, 2018 modeling shows the potential for Kentucky emissions to significantly contribute to the Edgewood, Harford County, Maryland (ID: 240251001) maintenance-only monitor (Edgewood monitor) in 2023. However, Kentucky provided air quality data designed to demonstrate that emissions from local sources in the area surrounding the monitors contribute significantly to the continued air quality issues and concluded that there are local controls that should be implemented before requesting upwind states to control facilities.

Kentucky provided additional information with respect to the Edgewood Monitor, which is located 3 miles from the I-95 corridor and approximately 350 miles from Kentucky. Kentucky provided data to show that the Edgewood monitor consistently violated the 2015 8-hour ozone standard from 2007 to 2016. Kentucky also provided information related to other nonattainment monitors located in Baltimore County and Harford County.

The Commonwealth's SIP submission provided data related to the Baltimore- Columbia-Towson, MD CBSA (Baltimore Area), citing to the 2014 NEI to state that the on-road source sector contributed the highest amount of NO X emissions and that the nonpoint source sector contributed the highest amount of VOC emissions in that area. Kentucky further provided information about VMTs and commuting patterns in the Baltimore Area, as well as information regarding violating monitors along the I-95 corridor and outlying monitors that show attainment. The SIP submission asserted that local mobile emissions are a key contributor to the Edgewood monitor, which is also located in close proximity to the 1-95 corridor. Kentucky further cited to a presentation and remarks by Maryland officials, discussing programs to reduce emissions from local sources, specifically focusing on mobile source NO X reduction programs.

Kentucky cited a 2010 case study in the Chesapeake Bay that suggests the transport of pollution from nearby urban areas accumulates over the Bay and becomes stagnant, creating a bay breeze which is pushed by southerly winds northward towards the Edgewood monitor. Additionally, Kentucky's SIP submission also provided HYSPLIT model back trajectory analysis to the Edgewood receptor, 41 asserting that the HYSPLIT indicates that the monitors are downwind of nonattainment areas in Baltimore County, Baltimore City, Arlington County, and the District of Columbia. Kentucky also asserted that higher altitude particles from the northwest of Baltimore combine with lower-level particles from the south and southeast.

Kentucky's submission used information on local mobile emissions along the I-95 corridor and coastal air pollution formation and accumulation along the Maryland coast to support its conclusion that local air quality problems are the source of ozone violations at these monitors.

Additionally, Kentucky asserted that the implementation of local programs to reduce emissions should be sufficient for monitors in the Maryland area to attain the 2015 8-hour ozone NAAQS. Kentucky cited claims by MOG (appended to the submittal in Appendix C) that the modeling in EPA's March 2018 memorandum does not account for additional retirements, conversions, and modifications or emission control programs expected to be implemented before 2023. Kentucky concluded that because the Edgewood monitor is a maintenance receptor, the Commonwealth believes that no further reductions from Kentucky sources other than on-the-books controls should be required because maintenance receptors should be treated differently than nonattainment receptors in terms of upwind requirements. The Commonwealth also asserted that states linked to maintenance receptors should be held to less stringent standards of emissions reductions as compared to states linked to a nonattainment receptor.

The Commonwealth also asserted that local emission controls should be implemented before upwind states are required to control their facilities, which is based on Kentucky's concurrence with statements from MOG. The Commonwealth cited MOG's comments on local controls stating: “When an area is measuring nonattainment of a NAAQS, as is the case with the areas linked to Kentucky, the CAA requires that the effects and benefits of local controls on all source sectors be considered first, prior to pursuing controls of sources in upwind states.”  42 The Commonwealth concluded that the emissions reductions resulting from on-the-books and on-the-way measures are adequate to prohibit emissions within Kentucky from interfering with the maintenance of downwind states with respect to the 2015 8-hour ozone NAAQS.

In summary, based on Kentucky's reliance on the modeling results in EPA's March 2018 memorandum, the Commonwealth found that emissions from Kentucky sources were potentially linked to four nonattainment monitors in Connecticut and Wisconsin and one maintenance receptor in Harford County, Maryland. However, after utilizing a 1 ppb alternative contribution threshold, the Commonwealth concluded that it was no longer linked to the four nonattainment monitors, and thus, that the Kentucky SIP contains adequate provisions to prevent sources and other types of emissions activities within the State from contributing significantly to nonattainment in any other state ( i.e., “prong 1” of CAA section 110(a)(2)(D)(i)(I)) for the 2015 8-hour ozone NAAQS. Although modeling results indicated that Kentucky remained linked to the maintenance-only receptor in Harford County, Maryland, even after the application of the 1 ppb alternative threshold, Kentucky asserted that states should not be required to apply the same degree of reductions for maintenance receptors as nonattainment areas, and determined that additional NO X emission reductions other than those that are on-the-books or on-the-way are not required to address its downwind contribution to that receptor. Kentucky further provided an assessment of local sources in the vicinity of the Connecticut and Maryland monitors and concluded that local (particularly mobile) emissions, high VMTs and commuting patterns, and weather patterns are the primary cause of violating monitors in these areas. Therefore, Kentucky concluded that its SIP has adequate provisions to prohibit emissions from interfering with maintenance in another state ( i.e., “prong 2” of CAA section 110(a)(2)(D)(i)(I)) with respect to the 2015 8-hour ozone NAAQS.

Kentucky attached several materials developed by MOG to its submittal as Appendix C, which included a document titled “ `Good Neighbor' Modeling Technical Support Document for 8-Hour Ozone State Implementation Plans” prepared by Alpine Geophysics. 43 The Alpine Geophysics document also attached the following documents: 4 kilometer (km) modeling results for mid-Atlantic and Lake Michigan domains compared to EPA 12 km “No Water” Design Value Calculations from March 2018 memorandum (Appendix A); MOG comments on EPA's March 2018 memorandum (Appendix B); and a Microsoft PowerPoint presentation from MOG previewing 2015 8-hour ozone NAAQS good neighbor SIPs (Appendix C). EPA notes a number of modeling results and technical and policy arguments provided in the MOG attachments are not explicitly discussed in Kentucky's SIP submission narrative. Therefore, it is unclear whether Kentucky intended to rely on Alpine's modeling or MOG's policy argument to support the Commonwealth's overall transport SIP conclusions. To ensure review of all potentially relevant technical and policy issues identified in Kentucky's SIP package, this section summarizes key arguments presented in Appendix C. However, in EPA's evaluation of the SIP submittal in section III, EPA will differentiate between those positions clearly adopted by the Commonwealth and those where it is unclear and therefore a position espoused by MOG cannot be attributed to Kentucky.

Appendix C included modeling results performed by Alpine Geophysics as presented in the Alpine TSD. The Alpine modeling results identified the Harford, Maryland receptor as a nonattainment receptor, with Kentucky emissions contributing 2.07 ppb. In addition, the Alpine modeling results identified Kentucky linkages above 1 percent to the following maintenance-only receptors: Gloucester, New Jersey (ID: 340150002), with a Kentucky contribution of 1.69 ppb; Richmond, New York (ID: 360850067), with a Kentucky contribution of 0.93; and Philadelphia, Pennsylvania (ID: 421010024), with a Kentucky contribution of 1.53. (While MOG asserts in separate comments that emission reductions not accounted for in EPA's modeling suggests there will be no receptors by 2023, this is not consistent with Alpine's modeling.)

The Alpine TSD also evaluated additional approaches and flexibilities that states could apply in SIP revisions, based on the potential concepts provided in Appendix A of EPA's March 2018 memorandum. 44 These included reliance on alterative modeling data, evaluation of international contributions (both anthropogenic contribution and as an additional percentage of boundary conditions), alternate contribution thresholds, proportional control of upwind emissions by level of upwind state contribution, and addressing interference with maintenance obligations through use of 10-year projections.

MOG suggested states should be allowed to select multiple sources of modeling data rather than a single modeling simulation if such information is considered equally credible when making policy decisions related to the development of good neighbor SIPs.

With respect to international emissions, MOG cited to an attachment to EPA's 2018 memorandum and asserts that EPA's and Alpine's contribution modeling tracks and reports the relative impact contributions of anthropogenic emissions located within the 36 km modeling domain. Considering this information, MOG concluded that states seeking to avoid overcontrol may wish to consider removing that portion of the projected design value that is explicitly attributed to international anthropogenic contribution, which may be enough to demonstrate attainment with the 2008 or 2015 8-hour ozone NAAQS at multiple monitors in the U.S.

With respect to potential use of alternative contribution thresholds, MOG pointed to states raising concerns that the 1 percent threshold is more stringent than the 2016 EPA Significant Impact level (SIL) guidance of 1 ppb, which is designed as an individual source or group of sources' contribution limit (in the context of prevention of significant deterioration (PSD) permitting). 45 MOG suggested that states could submit SIP revisions citing the SIL of 1 ppb as an acceptable total state anthropogenic contribution threshold under Step 2 of the 4-step process, and request relief from the 1 percent threshold in lieu of using an alternate value.

MOG presented an alternative approach to how upwind-state emission reduction obligations could be allocated. Specifically, MOG proposed that upwind reductions could be allocated in proportion to the size of their contribution to downwind nonattainment. To illustrate this approach, MOG determined a proportional reduction requirement associated with the relative contribution from each upwind state to the Harford County, Maryland monitor. Under this analysis, MOG's approach indicated that Kentucky would be responsible for a 0.02 ppb reduction at the monitor and “would then need to craft a [good neighbor SIP] revision to generate reductions associated with this proportional amount.”

With respect to “interference with maintenance” obligations, MOG suggested that an upwind state could choose to indicate that no additional controls would be needed to address a maintenance monitor if the upwind state can show that either the monitor is likely to remain in attainment for a period of 10 years or that the upwind state's emissions will not increase for 10 years after the attainment date.

EPA is proposing to find that Kentucky's January 11, 2019, SIP submission does not meet the Commonwealth's obligations with respect to prohibiting emissions that contribute significantly to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in any other state based on EPA's evaluation of the SIP submission using the 4-step interstate transport framework, and therefore EPA is proposing to disapprove Kentucky's SIP submission.

As described in section I, EPA performed updated air quality modeling to project design values and contributions for 2023. These data were examined to determine if Kentucky contributes at or above the threshold of 1 percent of the 2015 8-hour ozone NAAQS (0.70 ppb) to any downwind nonattainment or maintenance receptor. As shown in Table 1, the data  46 indicate that in 2023, emissions from Kentucky contribute greater than 1 percent of the standard to nonattainment or maintenance-only receptors in Bucks County, Pennsylvania (ID: 420170012), New Haven County, Connecticut (ID: 90099002), and Fairfield County, Connecticut (ID: 90019003 and 90013007). 47

Public Participation: Submit your comments, identified by Docket ID No. EPA-R03-OAR-2021-0873, at https://www.regulations.gov (our preferred method), or the other methods identified in the ADDRESSES section. Once submitted, comments cannot be edited or removed from the docket. The EPA may publish any comment received to its public docket. Do not submit to EPA's docket at https://www.regulations.gov 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).

There are two dockets supporting this action, EPA-R03-OAR-2021-0873 and EPA-HQ-OAR-2021-0663. Docket No. EPA-R03-OAR-2021-0873 contains information specific to West Virginia, including the notice of proposed rulemaking. Docket No. EPA-HQ-OAR-2021-0663 contains additional modeling files, emissions inventory files, technical support documents, and other relevant supporting documentation regarding interstate transport of emissions for the 2015 8-hour ozone NAAQS which are being used to support this action. All comments regarding information in either of these dockets are to be made in Docket No. EPA-R03-OAR-2021-0873. For additional submission methods, please contact Michael Gordon, 215-814-2039, gordon.mike@epa.gov. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. Due to public health concerns related to COVID-19, the EPA Docket Center and Reading Room are open to the public by appointment only. Our Docket Center staff also continues to provide remote customer service via email, phone, and webform. For further information and updates on EPA Docket Center services, please visit us online at https://www.epa.gov/dockets.

The EPA continues to carefully and continuously monitor information from the Centers for Disease Control and Prevention (CDC), local area health departments, and our Federal partners so that we can respond rapidly as conditions change regarding COVID-19. The index to the docket for this action, Docket No. EPA-R03-OAR-2021-0873, is available electronically at www.regulations.gov. While all documents in the docket are listed in the index, some information may not be publicly available via the online docket, such as modeling data files, due to docket file size restrictions or content ( e.g., CBI). Please contact the EPA Docket Center Services for further information on how to obtain these files.

Throughout this document, “we,” “us,” and “our” means the EPA.

On October 1, 2015, the EPA promulgated a revision to the ozone NAAQS (2015 8-hour ozone NAAQS), lowering the level of both the primary and secondary standards to 0.070 parts per million (ppm). 1 Section 110(a)(1) of the CAA requires states to submit, within 3 years after promulgation of a new or revised standard, SIP submissions meeting the applicable requirements of section 110(a)(2). 2 One of these applicable requirements is found in CAA section 110(a)(2)(D)(i)(I), otherwise known as the “interstate transport” or “good neighbor” provision, which generally requires SIPs to contain adequate provisions to prohibit in-state emissions activities from having certain adverse air quality effects on other states due to interstate transport of pollution. There are two so-called “prongs” within CAA section 110(a)(2)(D)(i)(I). A SIP for a new or revised NAAQS must contain adequate provisions prohibiting any source or other type of emissions activity within the state from emitting air pollutants in amounts that will significantly contribute to nonattainment of the NAAQS in another state (prong 1) or interfere with maintenance of the NAAQS in another state (prong 2). The EPA and states must give independent significance to prong 1 and prong 2 when evaluating downwind air quality problems under CAA section 110(a)(2)(D)(i)(I). 3

The EPA is using the 4-step interstate transport framework (or 4-step framework) to evaluate the states' SIP submittals addressing the interstate transport provision for the 2015 8-hour ozone NAAQS. The EPA has addressed the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) with respect to prior ozone NAAQS in several regional regulatory actions, including the Cross-State Air Pollution Rule (CSAPR), which addressed interstate transport with respect to the 1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter standards, 4 and the Cross-State Air Pollution Rule Update (CSAPR Update)  5 and the Revised CSAPR Update, both of which addressed the 2008 ozone NAAQS. 6

Through the development and implementation of the CSAPR rulemakings and prior regional rulemakings pursuant to the interstate transport provision, 7 the EPA, working in partnership with states, developed the following 4-step interstate transport framework to evaluate a State's obligations to eliminate interstate transport emissions under the interstate transport provision for the ozone NAAQS: (1) Identify monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS ( i.e., nonattainment and/or maintenance receptors); (2) identify states that impact those air quality problems in other ( i.e., downwind) states sufficiently such that the states are considered “linked” and therefore warrant further review and analysis; (3) identify the emissions reductions necessary (if any), applying a multifactor analysis, to eliminate each linked upwind state's significant contribution to nonattainment or interference with maintenance of the NAAQS at the locations identified in Step 1; and (4) adopt permanent and enforceable measures needed to achieve those emissions reductions.

In general, the EPA has performed nationwide air quality modeling to project ozone design values which are used in combination with measured data to identify nonattainment and maintenance receptors. To quantify the contribution of emissions from specific upwind states on 2023 ozone design values for the identified downwind nonattainment and maintenance receptors, the EPA performed nationwide, state-level ozone source apportionment modeling for 2023. The source apportionment modeling provided contributions to ozone at receptors from precursor emissions of anthropogenic nitrogen oxides (NO X ) and volatile organic compounds (VOCs) in individual upwind states.

The EPA has released several documents containing projected ozone design values, contributions, and information relevant to evaluating interstate transport with respect to the 2015 8-hour ozone NAAQS. First, on January 6, 2017, the EPA published a notice of data availability (NODA) in which we requested comment on preliminary interstate ozone transport data including projected ozone design values (DVs) and interstate contributions for 2023 using a 2011 base year platform. 8 In the NODA, the EPA used the year 2023 as the analytic year for this preliminary modeling because that year aligns with the expected attainment year for Moderate ozone nonattainment areas for the 2015 8-hour ozone NAAQS. 9 On October 27, 2017, we released a memorandum (October 2017 memorandum) containing updated modeling data for 2023, which incorporated changes made in response to comments on the NODA, and noted that the modeling may be useful for states developing SIPs to address interstate transport obligations for the 2008 ozone NAAQS. 10 On March 27, 2018, we issued a memorandum (March 2018 memorandum) noting that the same 2023 modeling data released in the October 2017 memorandum could also be useful for identifying potential downwind air quality problems with respect to the 2015 8-hour ozone NAAQS at Step 1 of the 4-step interstate transport framework. 11 The March 2018 memorandum also included the then newly available contribution modeling data for 2023 to assist states in evaluating their impact on potential downwind air quality problems for the 2015 8-hour ozone NAAQS under Step 2 of the 4-step interstate transport framework. 12 The EPA subsequently issued two more memoranda in August and October 2018, providing additional information to states developing interstate transport SIP submissions for the 2015 8-hour ozone NAAQS concerning, respectively, potential contribution thresholds that may be appropriate to apply in Step 2 of the 4-step interstate transport framework, and considerations for identifying downwind areas that may have problems maintaining the standard at Step 1 of the 4-step interstate transport framework. 13

Since the release of the modeling data shared in the March 2018 memorandum, the EPA performed updated modeling using a 2016-based emissions modeling platform ( i.e., 2016v1). This emissions platform was developed under the EPA/Multi-Jurisdictional Organization (MJO)/state collaborative project. 14 This collaborative project was a multi-year joint effort by the EPA, MJOs, and states to develop a new, more recent emissions platform for use by the EPA and states in regulatory modeling as an improvement over the dated 2011-based platform that the EPA had used to project ozone design values and contribution data provided in the 2017 and 2018 memoranda. The EPA used the 2016v1 emissions to project ozone design values and contributions for 2023. On October 30, 2020, in the Notice of Proposed Rulemaking for the Revised CSAPR Update, the EPA released and accepted public comment on 2023 modeling that used the 2016v1 emissions platform. 15 Although the Revised CSPAR Update addressed transport for the 2008 ozone NAAQS, the projected design values and contributions from the 2016v1 platform are also useful for identifying downwind ozone problems and linkages with respect to the 2015 ozone NAAQS. 16

Following the final Revised CSAPR Update, the EPA made further updates to the 2016 emissions platform to include mobile emissions from the EPA's Motor Vehicle Emission Simulator MOVES3 model  17 and updated emissions projections for electric generating units (EGUs) that reflect the emissions reductions from the Revised CSAPR Update, recent information on plant closures, and other sector trends. The construct of the updated emissions platform, 2016v2 (2016v2 emissions platform), is described in the emissions modeling technical support document (TSD) for this proposed rulemaking. 18 The EPA performed air quality modeling of the 2016v2 emissions using the most recent public release version of the Comprehensive Air-quality Model with extensions (CAMx) photochemical modeling, version 7.10. 19 The EPA now proposes to primarily rely on modeling based on the updated and newly available 2016v2 emissions platform in evaluating these submissions with respect to Steps 1 and 2 of the 4-step interstate transport framework and generally referenced within this action as 2016v2 modeling for 2023. By using the updated modeling results, the EPA is using the most current and technically appropriate information for this proposed rulemaking. Section III of this document and the Air Quality Modeling TSD for 2015 8-hour Ozone NAAQS Transport SIP Proposed Actions, included in Docket ID No. EPA-HQ-OAR-2021-0663 for this proposal, contain additional detail on the EPA's 2016v2 modeling. In this document, the EPA is accepting public comment on this updated 2023 modeling, which uses a 2016v2 emissions platform. Comments on the EPA's air quality modeling should be submitted in the Regional docket for this action, Docket ID No. EPA-R03-OAR-2021-0873. No comments on any topic are being accepted in docket ID No. EPA-HQ-OAR-2021-0663.

States may have chosen to rely on the results of EPA modeling and/or alternative modeling performed by states or MJOs to evaluate downwind air quality problems and contributions as part of their submissions. EPA's evaluation of how West Virginia used air quality modeling information in their submission is in Section III of this document.

The EPA proposes to apply a consistent set of policy judgments across all states for purposes of evaluating interstate transport obligations and the approvability of interstate transport SIP submittals for the 2015 8-hour ozone NAAQS. These policy judgments reflect consistency with relevant case law and past agency practice as reflected in the CSAPR and related rulemakings. Nationwide consistency in approach is particularly important in the context of interstate ozone transport, which is a regional-scale pollution problem involving many smaller contributors. Effective policy solutions to the problem of interstate ozone transport going back to the NO X SIP Call have necessitated the application of a uniform framework of policy judgments in order to ensure an “efficient and equitable” approach. See EME Homer City Generation, LP v. EPA, 572 U.S. 489, 519 (2014).

In the March, August, and October 2018 memoranda, the EPA recognized that states may be able to establish alternative approaches to addressing their interstate transport obligations for the 2015 8-hour ozone NAAQS that vary from a nationally uniform framework. The EPA emphasized in these memoranda, however, that such alternative approaches must be technically justified and appropriate in light of the facts and circumstances of each particular state's submittal. In general, the EPA continues to believe that deviation from a nationally consistent approach to ozone transport must be substantially justified and have a well-documented technical basis that is consistent with relevant case law. Where states submitted SIPs that rely on any such potential “flexibilities” as may have been identified or suggested in the past, the EPA will evaluate whether the state adequately justified the technical and legal basis for doing so. The EPA's proposed framework with respect to analytic year, definition of nonattainment and maintenance receptors, selection of contribution threshold, and multifactor control strategy assessment is described in this section. The EPA notes that certain concepts included in an attachment to the March 2018 memorandum require unique consideration, and these ideas do not constitute agency guidance with respect to transport obligations for the 2015 ozone NAAQS. Attachment A to the March 2018 memorandum identified a “Preliminary List of Potential Flexibilities” that could potentially inform SIP development. 20 However, EPA made clear in that Attachment that the list of ideas were not suggestions endorsed by the Agency but rather “comments provided in various forums” on which EPA sought “feedback from interested stakeholders.”  21 Further, Attachment A stated, “EPA is not at this time making any determination that the ideas discussed below are consistent with the requirements of the CAA, nor is the EPA specifically recommending that states use these approaches.”  22 Attachment A to the March 2018 memorandum, therefore, does not constitute agency guidance, but was intended to generate further discussion around potential approaches to addressing ozone transport among interested stakeholders. To the extent states sought to develop or rely on these ideas in support of their SIP submittals, the EPA will thoroughly review the technical and legal justifications for doing so.

The remainder of this section describes the EPA's proposed framework with respect to analytic year, definition of nonattainment and maintenance receptors, selection of contribution threshold, and multifactor control strategy assessment.

In general, the states and the EPA must implement the interstate transport provision in a manner “consistent with the provisions of [title I of the CAA.]” CAA section 110(a)(2)(D)(i). This requires, among other things, that these obligations are addressed consistently with the timeframes for downwind areas to meet their CAA obligations. With respect to ozone NAAQS, under CAA section 181(a), this means obligations must be addressed “as expeditiously as practicable” and no later than the schedule of attainment dates provided in CAA section 181(a)(1). 23 Several D.C. Circuit court decisions address the issue of the relevant analytic year for the purposes of evaluating ozone transport air-quality problems. On September 13, 2019, the D.C. Circuit issued a decision in Wisconsin v. EPA, remanding the CSAPR Update to the extent that it failed to require upwind states to eliminate their significant contribution by the next applicable attainment date by which downwind states must come into compliance with the NAAQS, as established under CAA section 181(a). 938 F.3d 303 at 313.

On May 19, 2020, the D.C. Circuit issued a decision in Maryland v. EPA that cited the Wisconsin decision in holding that the EPA must assess the impact of interstate transport on air quality at the next downwind attainment date, including Marginal area attainment dates, in evaluating the basis for the EPA's denial of a petition under CAA section 126(b). Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 2020). The court noted that “section 126(b) incorporates the Good Neighbor Provision,” and, therefore, “EPA must find a violation [of section 126] if an upwind source will significantly contribute to downwind nonattainment at the next downwind attainment deadline. Therefore, the agency must evaluate downwind air quality at that deadline, not at some later date.” Id. at 1204 (emphasis added). The EPA interprets the court's holding in Maryland as requiring the Agency, under the good neighbor provision, to assess downwind air quality as expeditiously as practicable and no later than the next applicable attainment date, 24 which is now the Moderate area attainment date under CAA section 181 for ozone nonattainment. The Moderate area attainment date for the 2015 8-hour ozone NAAQS is August 3, 2024. 25 The EPA believes that 2023 is now the appropriate year for analysis of interstate transport obligations for the 2015 8-hour ozone NAAQS because the 2023 ozone season is the last relevant ozone season during which achieved emissions reductions in linked upwind states could assist downwind states with meeting the August 3, 2024 Moderate area attainment date for the 2015 8-hour ozone NAAQS.

The EPA recognizes that the attainment date for nonattainment areas classified as Marginal for the 2015 8-hour ozone NAAQS was August 3, 2021. Under the Maryland holding, any necessary emissions reductions to satisfy interstate transport obligations should have been implemented by no later than this date. At the time of the statutory deadline to submit interstate transport SIPs (October 1, 2018), many states relied upon the EPA modeling of the year 2023, and no state provided an alternative analysis using a 2021 analytic year (or the prior 2020 ozone season). However, the EPA must act on SIP submittals using the information available at the time it takes such action. In this circumstance, the EPA does not believe it would be appropriate to evaluate states' obligations under CAA section 110(a)(2)(D)(i)(I) as of an attainment date that is wholly in the past, because the Agency interprets the interstate transport provision as forward looking. See 86 FR at 23074(April 30, 2021); see also Wisconsin, 938 F.3d at 322. Consequently, in this proposal the EPA will use the analytical year of 2023 to evaluate each state's CAA section 110(a)(2)(D)(i)(I) SIP submission with respect to the 2015 8-hour ozone NAAQS.

In Step 1, the EPA identifies monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS in the 2023 analytic year. Where the EPA's analysis shows that a site does not fall under the definition of a nonattainment or maintenance receptor, that site is excluded from further analysis under the EPA's 4-step interstate transport framework. For sites that are identified as a nonattainment or maintenance receptor in 2023, we proceed to the next step of our 4-step interstate transport framework by identifying the upwind state's contribution to those receptors.

The EPA's approach to identifying ozone nonattainment and maintenance receptors in this action is consistent with the approach used in previous transport rulemakings. The EPA's approach gives independent consideration to both the “contribute significantly to nonattainment” and the “interfere with maintenance” prongs of CAA section 110(a)(2)(D)(i)(I), consistent with the D.C. Circuit's direction in North Carolina v. EPA. 26

For the purpose of this proposal, the EPA identifies nonattainment receptors as those monitoring sites that are projected to have average design values that exceed the NAAQS and that are also measuring nonattainment based on the most recent monitored design values. This approach is consistent with prior transport rulemakings, such as the CSAPR Update, where the EPA defined nonattainment receptors as those areas that both currently measure nonattainment and that the EPA projects will be in nonattainment in the future analytic year ( i.e., 2023). 27

In addition, in this proposal, the EPA identifies a receptor to be a “maintenance” receptor for purposes of defining interference with maintenance, consistent with the method used in the CSAPR and upheld by the D.C. Circuit in EME Homer City Generation, L.P. v. EPA, 795 F.3d 118, 136 (D.C. Cir. 2015). 28 Specifically, the EPA identified maintenance receptors as those receptors that would have difficulty maintaining the relevant NAAQS in a scenario that takes into account historical variability in air quality at that receptor. The variability in air quality was determined by evaluating the “maximum” future design value at each receptor based on a projection of the maximum measured design value over the relevant period. The EPA interprets the projected maximum future design value to be a potential future air quality outcome consistent with the meteorology that yielded maximum measured concentrations in the ambient data set analyzed for that receptor ( i.e., ozone conducive meteorology). The EPA also recognizes that previously experienced meteorological conditions ( e.g., dominant wind direction, temperatures, air mass patterns) promoting ozone formation that led to maximum concentrations in the measured data may reoccur in the future. The maximum design value gives a reasonable projection of future air quality at the receptor under a scenario in which such conditions do, in fact, reoccur. The projected maximum design value is used to identify upwind emissions that, under those circumstances, could interfere with the downwind area's ability to maintain the NAAQS.

Recognizing that nonattainment receptors are also, by definition, maintenance receptors, the EPA often uses the term “maintenance-only” to refer to those receptors that are not nonattainment receptors. Consistent with the concepts for maintenance receptors, as described above, the EPA identifies “maintenance-only” receptors as those monitoring sites that have projected average design values above the level of the applicable NAAQS, but that are not currently measuring nonattainment based on the most recent official design values. In addition, those monitoring sites with projected average design values below the NAAQS, but with projected maximum design values above the NAAQS are also identified as “maintenance only” receptors, even if they are currently measuring nonattainment based on the most recent official design values.

In Step 2, the EPA quantifies the contribution of each upwind state to each receptor in the 2023 analytic year. The contribution metric used in Step 2 is defined as the average impact from each state to each receptor on the days with the highest ozone concentrations at the receptor based on the 2023 modeling. If a state's contribution value does not equal or exceed the threshold of 1 percent of the NAAQS ( i.e., 0.70 parts per billion (ppb) for the 2015 8-hour ozone NAAQS), the upwind state is not “linked” to a downwind air quality problem, and the EPA, therefore, concludes that the state does not significantly contribute to nonattainment or interfere with maintenance of the NAAQS in the downwind states. However, if a state's contribution equals or exceeds the 1 percent threshold, the state's emissions are further evaluated in Step 3, considering both air quality and cost as part of a multi-factor analysis, to determine what, if any, emissions might be deemed “significant” and, thus, must be eliminated under CAA section 110(a)(2)(D)(i)(I). The EPA is proposing to rely in the first instance on the 1 percent threshold ( i.e., 0.70 ppb) for the purpose of evaluating a state's contribution to nonattainment or maintenance of the 2015 8-hour ozone NAAQS at downwind receptors. This is consistent with the Step 2 approach that EPA applied in CSAPR for the 1997 ozone NAAQS, which has subsequently been applied in the CSAPR Update when evaluating interstate transport obligations for the 2008 ozone NAAQS. The EPA continues to find 1 percent to be an appropriate threshold. For ozone, as the EPA found in the Clean Air Interstate Rule (CAIR), CSAPR, and CSAPR Update, a portion of the nonattainment problems from anthropogenic sources in the U.S. result from the combined impact of relatively small contributions from many upwind states, along with contributions from in-state sources and, in some cases, substantially larger contributions from a subset of particular upwind states. The EPA's analysis shows that much of the ozone transport problem being analyzed in this proposed rulemaking is still the result of the collective impacts of contributions from many upwind states. Therefore, application of a consistent contribution threshold is necessary to identify those upwind states that should have responsibility for addressing their contribution to the downwind nonattainment and maintenance problems to which they collectively contribute. Continuing to use 1 percent of the NAAQS as the screening metric to evaluate collective contribution from many upwind states also allows the EPA (and states) to apply a consistent framework to evaluate interstate emissions transport under the interstate transport provision from one NAAQS to the next. See 81 FR at 74518 (October 26, 2016). See also 86 FR at 23085 (April 30, 2021) (reviewing and explaining rationale from CSAPR, 76 FR at 48237-38 (August 8, 2011), for selection of 1 percent threshold).

The EPA's August 2018 memorandum recognized that in certain circumstances, a state may be able to establish that an alternative contribution threshold of 1 ppb is justifiable. Where a state relies on this alternative threshold, and where that state determined that it was not linked at Step 2 using the alternative threshold, the EPA will evaluate whether the state provided a technically sound assessment of the appropriateness of using this alternative threshold based on the facts and circumstances underlying its application in the particular SIP submission.

Consistent with the EPA's longstanding approach to eliminating significant contribution or interference with maintenance, at Step 3, states linked at Steps 1 and 2 are generally expected to prepare a multifactor assessment of potential emissions controls. The EPA's analysis at Step 3 in prior Federal actions addressing interstate transport requirements has primarily focused on an evaluation of cost-effectiveness of potential emissions controls (on a marginal cost-per-ton basis), the total emissions reductions that may be achieved by requiring such controls (if applied across all linked upwind states), and an evaluation of the air quality impacts such emissions reductions would have on the downwind receptors to which a state is linked; other factors may potentially be relevant if adequately supported. In general, where the EPA's or alternative air quality and contribution modeling establishes that a state is linked at Steps 1 and 2, it will be insufficient at Step 3 for a state merely to point to its existing rules requiring control measures as a basis for approval. In general, the emissions-reducing effects of all existing emissions control requirements are already reflected in the air quality results of the modeling for Steps 1 and 2. If the state is shown to still be linked to one or more downwind receptor(s), states must provide a well- documented evaluation determining whether their emissions constitute significant contribution or interference with maintenance by evaluating additional available control opportunities by preparing a multifactor assessment. While the EPA has not prescribed a particular method for this assessment, the EPA expects states at a minimum to present a sufficient technical evaluation. This would typically include information on emissions sources, applicable control technologies, emissions reductions and costs, cost effectiveness, and downwind air quality impacts of the estimated reductions, before concluding that no additional emissions controls should be required. 29

At Step 4, states (or the EPA) develop permanent and federally enforceable control strategies to achieve the emissions reductions determined to be necessary at Step 3 to eliminate significant contribution to nonattainment or interference with maintenance of the NAAQS. For a state linked at Steps 1 and 2 to rely on an emissions control measure at Step 3 to address its interstate transport obligations, that measure must be included in the state's SIP so that it is permanent and federally enforceable. See CAA section 110(a)(2)(D) (“Each such [SIP] shall . . . contain adequate provisions . . .”). See also CAA section 110(a)(2)(A); Committee for a Better Arvin v. U.S. E.P.A., 786 F.3d 1169, 1175-76 (9th Cir. 2015) (holding that measures relied on by state to meet CAA requirements must be included in the SIP).

On September 14, 2018, the West Virginia Department of Environmental Protection (WVDEP), on behalf of the State of West Virginia, made a SIP submission to address most of the 2015 8-hour ozone NAAQS i-SIP requirements under CAA section 110(a)(2), except for the CAA section 110(a)(2)(D)(i)(I) (the “Good Neighbor” or “interstate transport”) requirements, which West Virginia proposed to address in a separate SIP submittal. The EPA published a final approval of this SIP submission on March 17, 2020. 85 FR 15071. On February 4, 2019, WVDEP submitted a separate, supplemental SIP revision addressing only the CAA Section 110(a)(2)(D)(i)(I) interstate transport requirements for the 2015 8-hour ozone NAAQS (the 2019 SIP). 30 West Virginia's 2019 SIP submittal evaluated different modeling options, provided an analysis of ozone monitoring data and emission trends, and argued that the State has already implemented adequate measures to address pollutant transport that may significantly contribute to downwind states' ozone maintenance and nonattainment problems, before concluding that West Virginia has satisfied its section 110(a)(2)(D)(i)(I) Good Neighbor obligations for the 2015 8-hour ozone NAAQS.

WVDEP requested that the EPA “conditionally” approve the 2019 SIP submittal, because at the time of submission, WVDEP had a proposed rulemaking pending before the West Virginia Legislature for approval during the 2019 legislative session. The proposed rulemaking, entitled “45CSR43—Cross-State Air Pollution Rule to Control Annual Nitrogen Oxide Emissions, Annual Sulfur Dioxide Emissions and Ozone Season Nitrogen Oxide Emissions,” would incorporate by reference into the West Virginia regulations the following emissions trading programs set forth in the CSAPR and CSAPR Update regulations: 40 CFR part 97, subpart AAAAA (CSAPR NO X Annual Trading Program), subpart CCCCC (CSAPR SO 2 Group 1 Trading Program), and subpart EEEEE (CSAPR NO X Ozone Season Group 2 Trading Program). Following the submission of this 2019 SIP revision, the West Virginia Legislature approved the state regulation incorporating by reference these subparts, and WVDEP submitted a SIP revision requesting that the EPA approve this regulation into the West Virginia SIP on June 5, 2019. The EPA proposed approval of this SIP revision on August 16, 2019. 84 FR 41944. 31 WVDEP claimed that following the EPA final approval of the SIP revision incorporating these programs, the West Virginia SIP would contain all the measures necessary to ensure that it met the good neighbor obligations of the CAA section 110(a)(2)(D)(i)(I) for the 2015 8-hour ozone NAAQS. The EPA has not taken final action on that SIP revision. 32

WVDEP's submittal to address interstate transport for the 2015 8-hour ozone NAAQS roughly followed the 4-step interstate transport framework, as briefly described here. At Step 1, WVDEP discussed and compared the EPA's transport modeling provided in the March 2018 memorandum against transport modeling provided by Alpine and LADCO and decided that the Alpine modeling was the “most appropriate, robust modeling available to identify the nonattainment and maintenance receptors to which West Virginia significantly contributes.” Alpine released air quality modeling in June 2018, which used a 12-km grid (supplemented with two 4-km nested grids) based on the EPA's 2023en modeling platform and preliminary source contribution assessment. In addition to air quality modeling, the Alpine TSD  33 included a discussion of “Selected SIP Revision Approaches” based on information on the “flexibilities” listed in an appendix to the EPA's March 2018 Memorandum. Alpine's air quality modeling incorporated meteorological data from the WRF model along with emissions data developed using SMOKE, MOVES2014, and BEIS version 3.61. Alpine used CAMx, and the OSAT/APCA tool to project ozone concentrations at downwind receptors. The modeling used 2023 as the projection year based on the EPA's guidance in the 2017 Memorandum stating that 2023 was the appropriate year to use. As shown in Table 1 of this document, Alpine modeling projected that in the Mid-Atlantic region, one receptor would have nonattainment issues and nine receptors would have maintenance problems in 2023 with respect to the 2015 ozone NAAQS.

Public participation: Submit your comments, identified by Docket ID No. EPA-R07-OAR-2021-0851, at https://www.regulations.gov (our preferred method), or the other methods identified in the ADDRESSES section. Once submitted, comments cannot be edited or removed from the docket. The EPA may publish any comment received to its public docket. Do not submit to EPA's docket at https://www.regulations.gov 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).

There are two dockets supporting this action, EPA-R07-OAR-2021-0851 and EPA-HQ-OAR-2021-0663. Docket No. EPA-R07-OAR-2021-0851 contains information specific to Missouri, including the notice of proposed rulemaking. Docket No. EPA-HQ-OAR-2021-0663 contains additional modeling files, emissions inventory files, technical support documents, and other relevant supporting documentation regarding interstate transport of emissions for the 2015 8-hour ozone NAAQS which are being used to support this action. All comments regarding information in either of these dockets are to be made in Docket No. EPA-R07-OAR-2021-0851. For additional submission methods, please contact William Stone, (913) 551-7714, stone.william@epa.gov. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. Due to public health concerns related to COVID-19, the EPA Docket Center and Reading Room are open to the public by appointment only. Our Docket Center staff also continues to provide remote customer service via email, phone, and webform. For further information and updates on EPA Docket Center services, please visit us online at https://www.epa.gov/dockets.

The EPA continues to carefully and continuously monitor information from the Centers for Disease Control and Prevention (CDC), local area health departments, and our Federal partners so that we can respond rapidly as conditions change regarding COVID-19.

The index to the docket for this action, Docket No. EPA-R07-OAR-2021-0851, is available electronically at www.regulations.gov. While all documents in the docket are listed in the index, some information may not be publicly available due to docket file size restrictions or content ( e.g., CBI).

Throughout this document, “we,” “us,” and “our” means the EPA.

On October 1, 2015, the EPA promulgated a revision to the ozone NAAQS (2015 8-hour ozone NAAQS), lowering the level of both the primary and secondary standards to 0.070 parts per million (ppm). 1 Section 110(a)(1) of the CAA requires states to submit, within 3 years after promulgation of a new or revised standard, SIP submissions meeting the applicable requirements of section 110(a)(2). 2 One of these applicable requirements is found in CAA section 110(a)(2)(D)(i)(I), otherwise known as the “interstate transport” or “good neighbor” provision, which generally requires SIPs to contain adequate provisions to prohibit in-state emissions activities from having certain adverse air quality effects on other states due to interstate transport of pollution. There are two so-called “prongs” within CAA section 110(a)(2)(D)(i)(I). A SIP for a new or revised NAAQS must contain adequate provisions prohibiting any source or other type of emissions activity within the state from emitting air pollutants in amounts that will significantly contribute to nonattainment of the NAAQS in another state (prong 1) or interfere with maintenance of the NAAQS in another state (prong 2). The EPA and states must give independent significance to prong 1 and prong 2 when evaluating downwind air quality problems under CAA section 110(a)(2)(D)(i)(I). 3

The EPA is using the 4-step interstate transport framework (or 4-step framework) to evaluate the state's SIP submittals addressing the interstate transport provision for the 2015 8-hour ozone NAAQS. The EPA has addressed the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) with respect to prior ozone NAAQS in several regional regulatory actions, including the Cross-State Air Pollution Rule (CSAPR), which addressed interstate transport with respect to the 1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter standards, 4 and the Cross-State Air Pollution Rule Update (CSAPR Update)  5 and the Revised CSAPR Update, both of which addressed the 2008 ozone NAAQS. 6

Public Participation: Submit your comments, identified by Docket No. EPA-R04-OAR-2021-0841, at https://www.regulations.gov. Once submitted, comments cannot be edited or removed from the docket. EPA may publish any comment received to its public docket. Do not submit to EPA's docket at https://www.regulations.gov 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. 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).

There are two dockets supporting this action, EPA-R04-OAR-2021-0841 and EPA-HQ-OAR-2021-0663. Docket No. EPA-R04-OAR-2021-0841 contains information specific to Alabama, Mississippi, and Tennessee, including this notice of proposed rulemaking. Docket No. EPA-HQ-OAR-2021-0663 contains additional modeling files, emissions inventory files, technical support documents, and other relevant supporting documentation regarding interstate transport of emissions for the 2015 8-hour ozone NAAQS which are being used to support this action. All comments regarding information in either of these dockets are to be made in Docket No. EPA-R04-OAR-2021-0841. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. Due to public health concerns related to COVID-19, the EPA Docket Center and Reading Room are open to the public by appointment only. The Docket Center staff also continues to provide remote customer service via email, phone, and webform. For further information and updates on EPA Docket Center services, please visit EPA online at https://www.epa.gov/dockets.

EPA continues to carefully and continuously monitor information from the Centers for Disease Control and Prevention (CDC), local area health departments, and Federal partners so that EPA can respond rapidly as conditions change regarding COVID-19.

The indices to Docket No. EPA-R04-OAR-2021-0841 and Docket No. EPA-R04-OAR-2021-0841 are available electronically at www.regulations.gov. While all documents in each docket are listed in their respective index, some information may not be publicly available due to docket file size restrictions or content ( e.g., CBI).

The following provides background for EPA's proposed actions related to the interstate transport requirements for the 2015 8-hour ozone NAAQS for the states of Alabama, Mississippi, and Tennessee.

On October 1, 2015, EPA promulgated a revision to the ozone NAAQS (2015 8-hour ozone NAAQS), lowering the level of both the primary and secondary standards to 0.070 parts per million (ppm). 1 Section 110(a)(1) of the CAA requires states to submit, within 3 years after promulgation of a new or revised standard, SIP submissions meeting the applicable requirements of section 110(a)(2). 2 One of these applicable requirements is found in CAA section 110(a)(2)(D)(i)(I), otherwise known as the “good neighbor” or “interstate transport” provision, which generally requires SIPs to contain adequate provisions to prohibit in-state emissions activities from having certain adverse air quality effects on other states due to interstate transport of pollution. There are two so-called “prongs” within CAA section 110(a)(2)(D)(i)(I). A SIP for a new or revised NAAQS must contain adequate provisions prohibiting any source or other type of emissions activity within the state from emitting air pollutants in amounts that will significantly contribute to nonattainment of the NAAQS in another state (prong 1) or interfere with maintenance of the NAAQS in another state (prong 2). EPA and states must give independent significance to prong 1 and prong 2 when evaluating downwind air quality problems under CAA section 110(a)(2)(D)(i)(I). 3

EPA is using the 4-step interstate transport framework (or 4-step framework) to evaluate the states' implementation plan submittals addressing the interstate transport provision for the 2015 8-hour ozone NAAQS. EPA has addressed the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) with respect to prior ozone NAAQS in several regional regulatory actions, including the Cross-State Air Pollution Rule (CSAPR), which addressed interstate transport with respect to the 1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter standards, 4 the Cross-State Air Pollution Rule Update (CSAPR Update)  5 and the Revised CSAPR Update, both of which addressed the 2008 ozone NAAQS. 6

Through the development and implementation of the CSAPR rulemakings and prior regional rulemakings pursuant to the interstate transport provision, 7 EPA, working in partnership with states, developed the following 4-step interstate transport framework to evaluate a state's obligations to eliminate interstate transport emissions under the interstate transport provision for the ozone NAAQS: (1) Identify monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS ( i.e., nonattainment and/or maintenance receptors); (2) identify states that impact those air quality problems in other ( i.e., downwind) states sufficiently such that the states are considered “linked” and therefore warrant further review and analysis; (3) identify the emissions reductions necessary (if any), applying a multifactor analysis, to eliminate each linked upwind state's significant contribution to nonattainment or interference with maintenance of the NAAQS at the locations identified in Step 1; and (4) adopt permanent and enforceable measures needed to achieve those emissions reductions.

In general, EPA has performed nationwide air quality modeling to project ozone design values which are used in combination with measured data to identify nonattainment and maintenance receptors. To quantify the contribution of emissions from specific upwind states on 2023 ozone design values for the identified downwind nonattainment and maintenance receptors, EPA performed nationwide, state-level ozone source apportionment modeling for 2023. The source apportionment modeling provided contributions to ozone at receptors from precursor emissions of anthropogenic nitrogen oxides (NO X ) and volatile organic compounds (VOCs) in individual upwind states.

EPA has released several documents containing projected design values, contributions, and information relevant to evaluating interstate transport with respect to the 2015 8-hour ozone NAAQS. First, on January 6, 2017, EPA published a notice of data availability (NODA) in which the Agency requested comment on preliminary interstate ozone transport data including projected ozone design values and interstate contributions for 2023 using a 2011 base year platform. 8 In the NODA, EPA used the year 2023 as the analytic year for this preliminary modeling because that year aligns with the expected attainment year for Moderate ozone nonattainment areas for the 2015 8-hour ozone NAAQS. 9 On October 27, 2017, EPA released a memorandum (October 2017 memorandum) containing updated modeling data for 2023, which incorporated changes made in response to comments on the NODA, and noted that the modeling may be useful for states developing SIPs to address interstate transport obligations for the 2008 ozone NAAQS. 10 On March 27, 2018, EPA issued a memorandum (March 2018 memorandum) noting that the same 2023 modeling data released in the October 2017 memorandum could also be useful for identifying potential downwind air quality problems with respect to the 2015 8-hour ozone NAAQS at Step 1 of the 4-step interstate transport framework. 11 The March 2018 memorandum also included the then newly available contribution modeling data for 2023 to assist states in evaluating their impact on potential downwind air quality problems for the 2015 8-hour ozone NAAQS under Step 2 of the 4-step interstate transport framework. 12 EPA subsequently issued two more memoranda in August and October 2018, providing additional information to states developing interstate transport SIP submissions for the 2015 8-hour ozone NAAQS concerning, respectively, potential contribution thresholds that may be appropriate to apply in Step 2 of the 4-step interstate transport framework, and considerations for identifying downwind areas that may have problems maintaining the standard at Step 1 of the 4-step interstate transport framework. 13

Since the release of the modeling data shared in the March 2018 memorandum, EPA performed updated modeling using a 2016-based emissions modeling platform ( i.e., 2016v1). This emissions platform was developed under the EPA/Multi-Jurisdictional Organization (MJO)/state collaborative project. 14 This collaborative project was a multi-year joint effort by EPA, MJOs, and states to develop a new, more recent emissions platform for use by EPA and states in regulatory modeling as an improvement over the dated 2011-based platform that EPA had used to project ozone design values and contribution data provided in the 2017 and 2018 memoranda. EPA used the 2016v1 emissions to project ozone design values and contributions for 2023. On October 30, 2020, in the Notice of Proposed Rulemaking for the Revised CSAPR Update, EPA released and accepted public comment on 2023 modeling that used the 2016v1 emissions platform. 15 Although the Revised CSAPR Update addressed transport for the 2008 ozone NAAQS, the projected design values and contributions from the 2016v1 platform are also useful for identifying downwind ozone problems and linkages with respect to the 2015 8-hour ozone NAAQS. 16

Following the Revised CSAPR Update final rule, EPA made further updates to the 2016 emissions platform to include mobile emissions from EPA's Motor Vehicle Emission Simulator (MOVES) model  17 and updated emissions projections for electric generating units (EGUs) that reflect the emissions reductions from the Revised CSAPR Update, recent information on plant closures, and other sector trends. The construct of the updated emissions platform, 2016v2, is described in the Preparation of Emissions Inventories for the 2016v2 North American Emissions Modeling Platform technical support document (TSD) for this proposed rule and is included in Docket No. EPA-HQ-OAR-2021-0663. EPA performed air quality modeling of the 2016v2 emissions using the most recent public release version of the Comprehensive Air Quality Modeling with Extensions (CAMx) photochemical modeling, version 7.10. 18 EPA proposes to primarily rely on modeling based on the updated and newly available 2016v2 emissions platform in evaluating these submissions with respect to Steps 1 and 2 of the 4-step interstate transport framework. By using the updated modeling results, EPA is using the most current and technically appropriate information for this proposed rulemaking. Section II of this notice and the Air Quality Modeling TSD included in Docket No. EPA-HQ-OAR-2021-0663 for this proposal contain additional detail on the modeling performed using the 2016v2 emissions modeling.

In this notice, EPA is accepting public comment on this updated 2023 modeling, which uses the 2016v2 emissions platform. Details on the air quality modeling and the methods for projecting design values and determining contributions in 2023 are described in the Air Quality Modeling TSD for 2015 8-hour ozone NAAQS Transport SIP Proposed Actions. Comments on EPA's air quality modeling should be submitted in Docket No. EPA-R04-OAR-2021-0841. Comments are not being accepted in Docket No. EPA-HQ-OAR-2021-0663.

States may have chosen to rely on the results of EPA modeling and/or alternative modeling performed by states or Multi-Jurisdictional Organizations (MJOs) to evaluate downwind air quality problems and contributions as part of their submissions. In Section II, EPA evaluates how Alabama, Mississippi, and Tennessee used air quality modeling information in their submissions.

EPA proposes to apply a consistent set of policy judgments across all states for purposes of evaluating interstate transport obligations and the approvability of interstate transport SIP submittals for the 2015 8-hour ozone NAAQS. These policy judgments reflect consistency with relevant case law and past agency practice as reflected in CSAPR and related rulemakings. Nationwide consistency in approach is particularly important in the context of interstate ozone transport, which is a regional-scale pollution problem involving many smaller contributors. Effective policy solutions to the problem of interstate ozone transport going back to the NO x SIP Call have necessitated the application of a uniform framework of policy judgments in order to ensure an “efficient and equitable” approach. See EME Homer City Generation, LP v. EPA, 572 U.S. 489, 519 (2014).

In the March, August, and October 2018 memoranda, EPA recognized that states may be able to establish alternative approaches to addressing their interstate transport obligations for the 2015 8-hour ozone NAAQS that vary from a nationally uniform framework. EPA emphasized in these memoranda, however, that such alternative approaches must be technically justified and appropriate in light of the facts and circumstances of each particular state's submittal. In general, EPA continues to believe that deviation from a nationally consistent approach to ozone transport must be substantially justified and have a well-documented technical basis that is consistent with relevant case law. Where states submitted SIPs that rely on any such potential concepts as may have been identified or suggested in the past, EPA will evaluate whether the state adequately justified the technical and legal basis for doing so.

EPA notes that certain potential concepts included in an attachment to the March 2018 memorandum require unique consideration, and these ideas do not constitute agency guidance with respect to transport obligations for the 2015 8-hour ozone NAAQS. Attachment A to the March 2018 memorandum identified a “Preliminary List of Potential Flexibilities” that could potentially inform SIP development. 19 However, EPA made clear in that attachment that the list of ideas were not suggestions endorsed by the Agency but rather “comments provided in various forums” on which EPA sought “feedback from interested stakeholders.”  20 Further, Attachment A stated, “EPA is not at this time making any determination that the ideas discussed below are consistent with the requirements of the CAA, nor is EPA specifically recommending that states use these approaches.”  21 Attachment A to the March 2018 memorandum, therefore, does not constitute agency guidance, but was intended to generate further discussion around potential approaches to addressing ozone transport among interested stakeholders. To the extent states sought to develop or rely on these ideas in support of their SIP submittals, EPA will thoroughly review the technical and legal justifications for doing so.

The remainder of this section describes the EPA's proposed framework with respect to analytic year, definition of nonattainment and maintenance receptors, selection of contribution threshold, and multifactor control strategy assessment.

In general, the states and EPA must implement the interstate transport provision in a manner “consistent with the provisions of [title I of the CAA.]” See CAA section 110(a)(2)(D)(i). This requires, among other things, that these obligations are addressed consistently with the timeframes for downwind areas to meet their CAA obligations. With respect to ozone NAAQS, under CAA section 181(a), this means obligations must be addressed “as expeditiously as practicable” and no later than the schedule of attainment dates provided in CAA section 181(a)(1). 22 Several D.C. Circuit court decisions address the issue of the relevant analytic year for the purposes of evaluating ozone transport air-quality problems. On September 13, 2019, the D.C. Circuit issued a decision in Wisconsin v. EPA, remanding the CSAPR Update to the extent that it failed to require upwind states to eliminate their significant contribution by the next applicable attainment date by which downwind states must come into compliance with the NAAQS, as established under CAA section 181(a). See 938 F.3d 303, 313.

On May 19, 2020, the D.C. Circuit issued a decision in Maryland v. EPA that cited the Wisconsin decision in holding that EPA must assess the impact of interstate transport on air quality at the next downwind attainment date, including Marginal area attainment dates, in evaluating the basis for EPA's denial of a petition under CAA section 126(b). Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 2020). The court noted that “section 126(b) incorporates the Good Neighbor Provision,” and, therefore, “EPA must find a violation [of section 126] if an upwind source will significantly contribute to downwind nonattainment at the next downwind attainment deadline. Therefore, the agency must evaluate downwind air quality at that deadline, not at some later date.” Id. at 1204 (emphasis added). EPA interprets the court's holding in Maryland as requiring the states and the Agency, under the good neighbor provision, to assess downwind air quality as expeditiously as practicable and no later than the next applicable attainment date, 23 which is now the Moderate area attainment date under CAA section 181 for ozone nonattainment. The Moderate area attainment date for the 2015 8-hour ozone NAAQS is August 3, 2024. 24 EPA believes that 2023 is now the appropriate year for analysis of interstate transport obligations for the 2015 8-hour ozone NAAQS, because the 2023 ozone season is the last relevant ozone season during which achieved emissions reductions in linked upwind states could assist downwind states with meeting the August 3, 2024, Moderate area attainment date for the 2015 8-hour ozone NAAQS.

EPA recognizes that the attainment date for nonattainment areas classified as Marginal for the 2015 8-hour ozone NAAQS was August 3, 2021. Under the Maryland holding, any necessary emissions reductions to satisfy interstate transport obligations should have been implemented by no later than this date. At the time of the statutory deadline to submit interstate transport SIPs (October 1, 2018), many states relied upon EPA modeling of the year 2023, and no state provided an alternative analysis using a 2021 analytic year (or the prior 2020 ozone season). However, EPA must act on SIP submittals using the information available at the time it takes such action. In this circumstance, EPA does not believe it would be appropriate to evaluate states' obligations under CAA section 110(a)(2)(D)(i)(I) as of an attainment date that is wholly in the past, because the Agency interprets the interstate transport provision as forward looking. See 86 FR 23054, 23074; see also Wisconsin, 938 F.3d at 322. Consequently, in this proposal EPA will use the analytical year of 2023 to evaluate each state's CAA section 110(a)(2)(D)(i)(I) SIP submission with respect to the 2015 8-hour ozone NAAQS.

In Step 1, EPA identifies monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS in the 2023 analytic year. Where EPA's analysis shows that a site does not fall under the definition of a nonattainment or maintenance receptor, that site is excluded from further analysis under EPA's 4-step interstate transport framework. For sites that are identified as a nonattainment or maintenance receptor in 2023, EPA proceeds to the next step of the 4-step interstate transport framework by identifying the upwind state's contribution to those receptors.

EPA's approach to identifying ozone nonattainment and maintenance receptors in this action is consistent with the approach used in previous transport rulemakings. EPA's approach gives independent consideration to both the “contribute significantly to nonattainment” and the “interfere with maintenance” prongs of CAA section 110(a)(2)(D)(i)(I), consistent with the D.C. Circuit's direction in North Carolina v. EPA. 25

For the purpose of this proposal, EPA identifies nonattainment receptors as those monitoring sites that are projected to have average design values that exceed the NAAQS and that are also measuring nonattainment based on the most recent monitored design values. This approach is consistent with prior transport rulemakings, such as the CSAPR Update, where EPA defined nonattainment receptors as those areas that both currently measure nonattainment and that EPA projects will be in nonattainment in the future analytic year ( i.e., 2023). 26

In addition, in this proposal, EPA identifies a receptor to be a “maintenance” receptor for purposes of defining interference with maintenance, consistent with the method used in CSAPR and upheld by the D.C. Circuit in EME Homer City Generation, L.P. v. EPA, 795 F.3d 118, 136 (D.C. Cir. 2015). 27 Specifically, EPA identified maintenance receptors as those receptors that would have difficulty maintaining the relevant NAAQS in a scenario that takes into account historical variability in air quality at that receptor. The variability in air quality was determined by evaluating the “maximum” future design value at each receptor based on a projection of the maximum measured design value over the relevant period. EPA interprets the projected maximum future design value to be a potential future air quality outcome consistent with the meteorology that yielded maximum measured concentrations in the ambient data set analyzed for that receptor ( i.e., ozone conducive meteorology). EPA also recognizes that previously experienced meteorological conditions ( e.g., dominant wind direction, temperatures, air mass patterns) promoting ozone formation that led to maximum concentrations in the measured data may reoccur in the future. The maximum design value gives a reasonable projection of future air quality at the receptor under a scenario in which such conditions do, in fact, reoccur. The projected maximum design value is used to identify upwind emissions that, under those circumstances, could interfere with the downwind area's ability to maintain the NAAQS.

Recognizing that nonattainment receptors are also, by definition, maintenance receptors, the EPA often uses the term “maintenance-only” to refer to those receptors that are not nonattainment receptors. Consistent with the concepts for maintenance receptors, as described above, the EPA identifies “maintenance-only” receptors as those monitoring sites that have projected average design values above the level of the applicable NAAQS, but that are not currently measuring nonattainment based on the most recent official design values. In addition, those monitoring sites with projected average design values below the NAAQS, but with projected maximum design values above the NAAQS are also identified as “maintenance-only” receptors, even if they are currently measuring nonattainment based on the most recent official design values.

In Step 2, EPA quantifies the contribution of each upwind state to each receptor in the 2023 analytic year. The contribution metric used in Step 2 is defined as the average impact from each state to each receptor on the days with the highest ozone concentrations at the receptor based on the 2023 modeling. If a state's contribution value does not equal or exceed the threshold of 1 percent of the NAAQS ( i.e., 0.70 ppb for the 2015 8-hour ozone NAAQS), the upwind state is not “linked” to a downwind air quality problem, and EPA, therefore, concludes that the state does not significantly contribute to nonattainment or interfere with maintenance of the NAAQS in the downwind states. However, if a state's contribution equals or exceeds the 1 percent threshold, the state's emissions are further evaluated in Step 3, considering both air quality and cost as part of a multi-factor analysis, to determine what, if any, emissions might be deemed “significant” and, thus, must be eliminated under CAA section 110(a)(2)(D)(i)(I).

EPA is proposing to rely in the first instance on the 1 percent threshold for the purpose of evaluating a state's contribution to nonattainment or maintenance of the 2015 8-hour ozone NAAQS ( i.e., 0.70 ppb) at downwind receptors. This is consistent with the Step 2 approach that EPA applied in CSAPR for the 1997 ozone NAAQS, which has subsequently been applied in the CSAPR Update when evaluating interstate transport obligations for the 2008 ozone NAAQS. EPA continues to find 1 percent to be an appropriate threshold. For ozone, as EPA found in the CAIR, CSAPR, and CSAPR Update, a portion of the nonattainment problems from anthropogenic sources in the U.S. result from the combined impact of relatively small contributions from many upwind states, along with contributions from in-state sources and, in some cases, substantially larger contributions from a subset of particular upwind states. EPA's analysis shows that much of the ozone transport problem being analyzed in this proposed rule is still the result of the collective impacts of contributions from many upwind states. Therefore, application of a consistent contribution threshold is necessary to identify those upwind states that should have responsibility for addressing their contribution to the downwind nonattainment and maintenance problems to which they collectively contribute. Continuing to use 1 percent of the NAAQS as the screening metric to evaluate collective contribution from many upwind states also allows EPA (and states) to apply a consistent framework to evaluate interstate emissions transport under the interstate transport provision from one NAAQS to the next. See 81 FR at 74518; see also 86 FR at 23085 (reviewing and explaining rationale from CSAPR, 76 FR at 48237-38, for selection of 1 percent threshold).

EPA's August 2018 memorandum recognized that in certain circumstances, a state may be able to establish that an alternative contribution threshold of 1 ppb is justifiable. Where a state relies on this alternative threshold, and where that state determined that it was not linked at Step 2 using the alternative threshold, EPA will evaluate whether the state provided a technically sound assessment of the appropriateness of using this alternative threshold based on the facts and circumstances underlying its application in the particular SIP submission.

EPA here shares further evaluation of its experience since the issuance of the August 2018 memorandum regarding use of alternative thresholds at Step 2. This experience leads the Agency to now believe it may not be appropriate to continue to attempt to recognize alternative contribution thresholds at Step 2. The August 2018 memorandum stated that “it may be reasonable and appropriate” for states to rely on an alternative threshold of 1 ppb threshold at Step 2. 28 (The memorandum also indicated that any higher alternative threshold, such as 2 ppb, would likely not be appropriate.) However, EPA also provided that “air agencies should consider whether the recommendations in this guidance are appropriate for each situation.” Following receipt and review of 49 good neighbor SIP submittals for the 2015 8-hour ozone NAAQS, EPA's experience has been that nearly every state that attempted to rely on a 1 ppb threshold did not provide sufficient information and analysis to support a determination that an alternative threshold was reasonable or appropriate for that state.

For instance, in nearly all submittals, the states did not provide EPA with analysis specific to their state or the receptors to which its emissions are potentially linked. In one case, the proposed approval of Iowa's SIP submittal, EPA expended its own resources to attempt to supplement the information submitted by the state, in order to more thoroughly evaluate the state-specific circumstances that could support approval. 29 It was at EPA's sole discretion to perform this analysis in support of the state's submittal, and the Agency is not obligated to conduct supplemental analysis to fill the gaps whenever it believes a state's analysis is insufficient. The Agency no longer intends to undertake supplemental analysis of SIP submittals with respect to alternative thresholds at Step 2 for purposes of the 2015 8-hour ozone NAAQS.

Furthermore, EPA's experience since 2018 is that allowing for alternative Step 2 thresholds may be impractical or otherwise inadvisable for a number of additional policy reasons. For a regional air pollutant such as ozone, consistency in requirements and expectations across all states is essential. Based on its review of submittals to-date and after further consideration of the policy implications of attempting to recognize an alternative Step 2 threshold for certain states, the Agency now believes the attempted use of different thresholds at Step 2 with respect to the 2015 8-hour ozone NAAQS raises substantial policy consistency and practical implementation concerns. 30 The availability of different thresholds at Step 2 has the potential to result in inconsistent application of good neighbor obligations based solely on the strength of a state's implementation plan submittal at Step 2 of the 4-step interstate transport framework. From the perspective of ensuring effective regional implementation of good neighbor obligations, the more important analysis is the evaluation of the emissions reductions needed, if any, to address a state's significant contribution after consideration of a multifactor analysis at Step 3, including a detailed evaluation that considers air quality factors and cost. Where alternative thresholds for purposes of Step 2 may be “similar” in terms of capturing the relative amount of upwind contribution (as described in the August 2018 memorandum), nonetheless, use of an alternative threshold would allow certain states to avoid further evaluation of potential emission controls while other states must proceed to a Step 3 analysis. This can create significant equity and consistency problems among states.

Further, it is not clear that national ozone transport policy is best served by allowing for less stringent thresholds at Step 2. EPA recognized in the August 2018 memorandum that there was some similarity in the amount of total upwind contribution captured (on a nationwide basis) between 1 percent and 1 ppb. However, EPA notes that while this may be true in some sense, that is hardly a compelling basis to move to a 1 ppb threshold. Indeed, the 1 ppb threshold has the disadvantage of losing a certain amount of total upwind contribution for further evaluation at Step 3 ( e.g., roughly 7 percent of total upwind state contribution was lost according to the modeling underlying the August 2018 memorandum;  31 in EPA's updated modeling, the amount lost is 5 percent). Considering the core statutory objective of ensuring elimination of all significant contribution to nonattainment or interference of the NAAQS in other states and the broad, regional nature of the collective contribution problem with respect to ozone, there does not appear to be a compelling policy imperative in allowing some states to use a 1 ppb threshold while others rely on a 1 percent of the NAAQS threshold.

Consistency with past interstate transport actions such as CSAPR, and the CSAPR Update and Revised CSAPR Update rulemakings (which used a Step 2 threshold of 1 percent of the NAAQS for two less stringent ozone NAAQS), is also important. Continuing to use a 1 percent of NAAQS approach ensures that as the NAAQS are revised and made more stringent, an appropriate increase in stringency at Step 2 occurs, so as to ensure an appropriately larger amount of total upwind-state contribution is captured for purposes of fully addressing interstate transport. See 76 FR 48208, 48237-38 (August 8, 2011).

Therefore, notwithstanding the August 2018 memorandum's recognition of the potential viability of alternative Step 2 thresholds, and in particular, a potentially applicable 1 ppb threshold, EPA's experience since the issuance of that memorandum has revealed substantial programmatic and policy difficulties in attempting to implement this approach. Nonetheless, EPA is not at this time rescinding the August 2018 memorandum. As discussed further below, the basis for disapproval of Alabama, Mississippi, and Tennessee's SIP submissions with respect to the Step 2 analysis is, in the Agency's view, warranted even under the terms of the August 2018 memorandum. EPA invites comment on this broader discussion of issues associated with alternative thresholds at Step 2. Depending on comment and further evaluation of this issue, EPA may determine to rescind the August 2018 memorandum in the future.

Consistent with EPA's longstanding approach to eliminating significant contribution or interference with maintenance, at Step 3, states linked at Steps 1 and 2 are generally expected to prepare a multifactor assessment of potential emissions controls. EPA's analysis at Step 3 in prior Federal actions addressing interstate transport requirements has primarily focused on an evaluation of cost-effectiveness of potential emissions controls (on a marginal cost-per-ton basis), the total emissions reductions that may be achieved by requiring such controls (if applied across all linked upwind states), and an evaluation of the air quality impacts such emissions reductions would have on the downwind receptors to which a state is linked; other factors may potentially be relevant if adequately supported. In general, where EPA's or alternative air quality and contribution modeling establishes that a state is linked at Steps 1 and 2, it will be insufficient at Step 3 for a state merely to point to its existing rules requiring control measures as a basis for approval. In general, the emissions-reducing effects of all existing emissions control requirements are already reflected in the air quality results of the modeling for Steps 1 and 2. If the state is shown to still be linked to one or more downwind receptor(s), states must provide a well-documented evaluation determining whether their emissions constitute significant contribution or interference with maintenance by evaluating additional available control opportunities by preparing a multifactor assessment. While EPA has not prescribed a particular method for this assessment, EPA expects states at a minimum to present a sufficient technical evaluation. This would typically include information on emissions sources, applicable control technologies, emissions reductions, costs, cost effectiveness, and downwind air quality impacts of the estimated reductions, before concluding that no additional emissions controls should be required. 32

At Step 4, states (or EPA) develop permanent and federally enforceable control strategies to achieve the emissions reductions determined to be necessary at Step 3 to eliminate significant contribution to nonattainment or interference with maintenance of the NAAQS. For a state linked at Steps 1 and 2 to rely on an emissions control measure at Step 3 to address its interstate transport obligations, that measure must be included in the state's implementation plan so that it is permanent and federally enforceable. See CAA section 110(a)(2)(D) (“Each such [SIP] shall . . . contain adequate provisions . . . .”). See also CAA section 110(a)(2)(A); Committee for a Better Arvin v. EPA, 786 F.3d 1169, 1175-76 (9th Cir. 2015) (holding that measures relied on by a state to meet CAA requirements must be included in the SIP).

The following section provides information related to Alabama's SIP submission addressing interstate transport requirements for the 2015 8-hour ozone NAAQS, and EPA's analysis of Alabama's submission.

On August 20, 2018, 33 Alabama submitted a SIP revision addressing the CAA section 110(a)(2)(D)(i)(I) good neighbor interstate transport requirements for the 2015 8-hour ozone NAAQS. 34 The SIP submission provided Alabama's analysis of its impact to downwind states and concluded that emissions from the State will not significantly contribute to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in other states, based on modeling results included in EPA's March 2018 memorandum. Alabama's submission relied on the results of EPA's modeling of 2023 using a 2011 base year, as contained in the March 2018 memorandum (which the State attached to its submittal), to identify downwind nonattainment and maintenance receptors that may be impacted by emissions from sources in the State at Step 1 of the 4-step framework. 35

Alabama Department of Environmental Management (ADEM) reviewed this modeling, concurred with the results, and determined that the future year projections were appropriate for the purposes of evaluating Alabama's impact on nonattainment and maintenance receptors in other states at Step 1. Alabama used this information to find that emissions from Alabama would not contribute above 1 percent of the NAAQS at any projected nonattainment or maintenance receptors at Step 2 of the 4-step framework (using EPA's approach to defining such receptors).

Alabama's August 20, 2018, submittal also identified existing SIP-approved regulations and Federal programs  36 that ADEM noted regulate ozone-precursor emissions from sources in the State, including CSAPR trading programs. 37 Alabama's submission acknowledges that CSAPR does not address interstate transport for the 2015 ozone standard but does provide residual NO X emissions reductions and notes the adoption of CSAPR NO X ozone season trading programs into the Alabama SIP on August 31, 2016, and October 6, 2017. 38 Alabama notes that the implementation of the existing SIP-approved regulations and Federal programs provide for a decline in ozone precursors emissions in the State. Alabama also stated that ozone-precursor emissions would continue to decline in the State.

Based on the information from Alabama's transport SIP, ADEM concluded that emissions from Alabama sources will not significantly contribute to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in any other state.

Previously, EPA proposed approval of Alabama's interstate transport provisions for the 2015 8-hour ozone NAAQS as addressed in Alabama's August 20, 2018 SIP submission and based on the contribution modeling provided in the March 2018 memorandum. See 84 FR 71854 (December 30, 2019). When EPA completed updated modeling of 2023 in 2020 using a 2016-based emissions modeling platform (2016v1), it became evident that Alabama was projected to be linked to downwind nonattainment and maintenance receptors (see footnote 40 below). As a result, EPA deferred acting on Alabama's SIP submittal when it published a supplemental proposal in 2021 to approve four other southeastern states' good neighbor SIP submissions using the updated 2023 modeling. See 86 FR 37942, 37943 (July 19, 2021). The updated 2023 modeling using an updated 2016-based emissions modeling platform (2016v2) confirms the prior 2016-based modeling of 2023 in that it continues to show Alabama is linked to at least one downwind nonattainment or maintenance receptor. Based on this updated modeling using the 2016-based emissions modeling platform, discussed in section I.C above, EPA is now withdrawing its 2019 proposed approval on Alabama's September 13, 2018, interstate transport SIP as published on December 30, 2019, at 84 FR 71854.

EPA is proposing to find that Alabama's August 20, 2018, SIP submission does not meet Alabama's obligations with respect to prohibiting emissions that contribute significantly to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in any other state based on EPA's evaluation of the SIP submission using the 4-step interstate transport framework, and EPA is therefore proposing to disapprove Alabama's SIP submission.

As described in section I, EPA performed updated air quality modeling to project design values and contributions for 2023. These data were examined to determine if Alabama contributes at or above the threshold of 1 percent of the 2015 8-hour ozone NAAQS (0.70 ppb) to any downwind nonattainment or maintenance receptor. As shown in Table 1, the data  39 indicate that in 2023, emissions from Alabama contribute greater than 1 percent of the standard to a nonattainment receptor in Harris County, Texas (ID#: 482010055) and a maintenance-only receptor in Denton County, Texas (ID#: 481210034). 40

At Step 1 of the 4-step interstate transport framework, Alabama relied on EPA modeling included in the March 2018 memorandum to identify nonattainment and maintenance receptors in 2023. As described in section II.A.3.a, EPA has recently updated this modeling using the most current and technically appropriate information. EPA proposes to rely on EPA's most recent modeling to identify nonattainment and maintenance receptors in 2023. That information establishes that there are two receptors to which Alabama is projected to be linked in 2023.

At Step 2 of the 4-step interstate transport framework, Alabama relied on EPA modeling released in the March 2018 memorandum to identify upwind state linkages to nonattainment and maintenance receptors in 2023. As described in section I.C of this notice, EPA has recently updated modeling to identify upwind state contributions to nonattainment and maintenance receptors in 2023. In this action, EPA proposes to rely on the Agency's most recently available modeling to identify upwind contributions and “linkages” to downwind air quality problems in 2023 using a threshold of 1 percent of the NAAQS. See section I.D for a general explanation of the use of 1 percent of the NAAQS.

As shown in Table 1, updated EPA modeling identifies Alabama's maximum contribution to downwind nonattainment and maintenance receptors as greater than 1 percent of the standard ( i.e., 0.70 ppb). Therefore, the State is linked to a downwind air quality problem at Steps 1 and 2. Because the entire technical basis for Alabama's interstate transport SIP submission is that Alabama is not linked at Step 2, and thus Alabama's SIP contains the necessary provisions to eliminate emissions that will contribute significantly to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in any other state, EPA proposes to disapprove Alabama's SIP submission based on EPA's finding that such a linkage does exist. 41

Although Alabama did not rely on the 1 ppb threshold in its SIP submittal, EPA recognizes that the most recently available EPA modeling at the time Alabama submitted its SIP submittal indicated that Alabama did not contribute above 1 percent of the NAAQS to a projected downwind nonattainment or maintenance receptor. Therefore, Alabama may not have considered analyzing the reasonableness and appropriateness of a 1 ppb threshold at Step 2 of the 4-step interstate transport framework per the August 2018 memorandum. However, EPA's August 2018 memorandum provided that whether use of a 1 ppb threshold is appropriate must be based on an evaluation of state-specific circumstances, and no such evaluation was included in the submittal. EPA's experience with the alternative Step 2 thresholds is further discussed in section I.D.3.a. As discussed there, EPA is considering withdrawing the August 2018 memorandum.

At Step 3 of the 4-step interstate transport framework, a state's emissions are further evaluated, in light of multiple factors, including air quality and cost considerations, to determine what, if any, emissions significantly contribute to nonattainment or interfere with maintenance and, thus, must be eliminated under CAA section 110(a)(2)(D)(i)(I).

To effectively evaluate which emissions in the state should be deemed “significant” and therefore prohibited, states generally should prepare an accounting of sources and other emissions activity for relevant pollutants and assess potential, additional emissions reduction opportunities and resulting downwind air quality improvements. EPA has consistently applied this general approach ( i.e., Step 3 of the 4-step interstate transport framework) when identifying emissions contributions that the Agency has determined to be “significant” (or interfere with maintenance) in each of its prior Federal, regional ozone transport rulemakings, and this interpretation of the statute has been upheld by the Supreme Court. See EME Homer City, 572 U.S. 489, 519 (2014). While EPA has not directed states that they must conduct a Step 3 analysis in precisely the manner EPA has done in its prior regional transport rulemakings, state implementation plans addressing the obligations in CAA section 110(a)(2)(D)(i)(I) must prohibit “any source or other type of emissions activity within the State” from emitting air pollutants which will contribute significantly to downwind air quality problems. Thus, states must complete something similar to EPA's analysis (or an alternative approach to defining “significance” that comports with the statute's objectives) to determine whether and to what degree emissions from a state should be “prohibited” to eliminate emissions that will “contribute significantly to nonattainment in or interfere with maintenance of” the NAAQS in any other state. Alabama did not conduct such an analysis in its SIP submission.

Based on Alabama's finding that emissions from Alabama do not contribute above 1 percent of the NAAQS at any monitors that are projected to be in nonattainment or maintenance, the SIP submission identified SIP-approved provisions and Federal programs in the context that no further emissions reductions were necessary, and determined that the SIP contained adequate provisions to prohibit emissions that will significantly contribute to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in any other state. However, the State did not analyze total ozone precursors that continue to be emitted from sources and other emissions activity within the State, evaluate the emissions reduction potential of any additional controls using cost or other metrics, nor evaluate any resulting downwind air quality improvements that could result from such controls.

Among the Federal programs referenced in Alabama's submission was the NO X ozone season trading program of CSAPR for the 2008 ozone standard, which ADEM adopted into the Alabama SIP. 42 This reference suggests that Alabama may have intended to rely on its electric generating units (EGUs) being subject to CSAPR Update (which reflected a stringency at the nominal marginal cost threshold of $1,400/ton (in 2011 dollars) for the 2008 8-hour ozone NAAQS) to argue that it has already implemented all cost-effective emissions reductions at EGUs.

EPA does not support the concept that reliance on CSAPR Update is appropriate to conclude that no further emissions reductions are necessary under Step 3 for the 2015 8-hour ozone NAAQS. First, CSAPR Update did not regulate non-electric generating units (non-EGUs), and thus this analysis, even for the 2008 ozone NAAQS, was incomplete, and EPA acknowledged at the time that CSAPR Update was not a full remedy for interstate transport under that NAAQS. See Wisconsin, 938 F.3d at 318-20. Second, relying on CSAPR Update's (or any other CAA program's) determination of cost-effectiveness without further Step 3 analysis is not approvable. Cost-effectiveness must be assessed in the context of the specific CAA program; assessing cost-effectiveness in the context of ozone transport should reflect a more comprehensive evaluation of the nature of the interstate transport problem, the total emissions reductions available at several cost thresholds, and the air quality impacts of the reductions at downwind receptors. While EPA has not established a benchmark cost-effectiveness value for 2015 8-hour ozone NAAQS interstate transport obligations, it is reasonable to expect control measures or strategies to address interstate transport under this NAAQS to reflect higher marginal control costs because the 2015 8-hour ozone NAAQS is a more stringent and more protective air quality standard. As such, the marginal cost threshold of $1,400/ton for the CSAPR Update (which addresses the 2008 ozone 8-hour NAAQS and is in 2011 dollars) is not an appropriate cost threshold and cannot be approved as a benchmark to use for interstate transport SIP submissions for the 2015 8-hour ozone NAAQS. In addition, the updated EPA modeling captures all existing CSAPR trading programs in the baseline, and that modeling confirms that these control programs were not sufficient to eliminate the Alabama's linkage at Steps 1 and 2 under the 2015 8-hour ozone NAAQS even if the CSAPR Update provisions had been adopted into Alabama's SIP. The State was therefore obligated at Step 3 to assess additional control measures using a multifactor analysis.

As mentioned above, EPA has newly available information that indicates sources in Alabama are linked to downwind air quality problems for the 2015 ozone standard. Therefore, EPA proposes to disapprove Alabama's August 20, 2018, interstate transport SIP submission on the separate, additional basis that the SIP submittal did not assess additional emissions control opportunities.

Step 4 of the 4-step interstate transport framework calls for development of permanent and federally enforceable control strategies to achieve the emissions reductions determined to be necessary at Step 3 to eliminate significant contribution to nonattainment or interference with maintenance of the NAAQS. As mentioned in section II.A.3.d, Alabama's SIP submission did not contain an evaluation of additional emissions control opportunities (or establish that no additional controls are required), thus, no information was provided at Step 4. As a result, EPA proposes to disapprove Alabama's August 20, 2018, submittal on the separate, additional basis that the State has not developed permanent and enforceable emissions reductions necessary to meet the obligations of CAA section 110(a)(2)(d)(i)(I).

Based on EPA's evaluation of Alabama's SIP submission and after consideration of updated EPA modeling using the 2016-based emissions modeling platform, EPA is proposing to find that the 2015 8-hour ozone NAAQS good neighbor interstate transport portion of Alabama's August 20, 2018, SIP submission addressing CAA section 110(a)(2)(D)(i)(I) does not meet the State's interstate transport obligations because it fails to contain the necessary provisions to eliminate emissions that will contribute significantly to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in any other state.

The following section provides information related to Mississippi's SIP submission addressing interstate transport requirements for the 2015 8-hour ozone NAAQS, and EPA's analysis of Mississippi's submission.

On September 3, 2019, the Mississippi Department of Environmental Quality (MDEQ) submitted a SIP revision addressing the CAA section 110(a)(2)(D)(i)(I) interstate transport requirements for the 2015 8-hour ozone NAAQS. 43 The SIP submission provided Mississippi's analysis of its impact to downwind states and concluded that emissions from the State will not significantly contribute to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in other states.

MDEQ's submission relied on the results of EPA's modeling for the 2015 8-hour ozone NAAQS, contained in the March 2018 memorandum, to identify projected downwind nonattainment and maintenance receptors and contribution linkages in 2023 that may be impacted by emissions from sources in Mississippi at Steps 1 and 2 of the 4-step interstate transport framework, 44 respectively. MDEQ reviewed EPA's March 2018 modeling and found that the modeled contributions for Mississippi were below 1 percent of the NAAQS for all nonattainment and maintenance receptors, except the Deer Park nonattainment receptor in Harris County, Texas (Monitor ID: 482011039). The SIP submission identified Mississippi as linked to the Deer Park receptor with an upwind contribution of 0.79 ppb.

In its submittal, MDEQ discussed EPA's August 2018 memorandum, explaining that 0.79 ppb is 1.12 percent of the 2015 8-hour ozone NAAQS, which is greater than the 1 percent contribution threshold of 0.70 ppb but less than a 1 ppb alternative contribution threshold. The SIP submission also states that the Deer Park receptor design value was projected to be greater than the 2015 ozone standard in 2023, but that the actual 2015-2017 design value was below the NAAQS at 68 ppb. Based on the modeling in the March 2018 memo, along with application of a 1 ppb alternative contribution threshold and information regarding 2015-2017 monitored values at the Deer Park receptor, MDEQ concluded that sources in Mississippi were not linked to downwind nonattainment or maintenance receptors at Step 2, and therefore, the State does not significantly contribute to nonattainment in another state for the 2015 ozone standard. Further, MDEQ stated that the SIP contains adequate provisions to prohibit sources and other types of emissions activities within the State from contributing to nonattainment in another state with respect to the 2015 8-hour ozone NAAQS.

In its submission, MDEQ treated the Deer Park receptor as a maintenance receptor because the most recent measured design value at the time of its submission ( i.e., the 2017 design value of 68 ppb) was below the level of the NAAQS at this monitor. Based on MDEQ's interpretation of EPA's October 19, 2018, memorandum, the State eliminated the Deer Park monitor site in Harris County, Texas, as a maintenance receptor in 2023 (although EPA's modeling of 2023 released with the October 2017 memorandum had identified this monitoring site as a nonattainment receptor).

To support eliminating the Deer Park monitor as a receptor, MDEQ's demonstration included: (1) Evaluating ozone season temperatures in the period 2014-2017 in Harris County to determine if conditions were conducive for ozone formation; (2) assessing monitored ozone design values from 2011-2017 at the Deer Park monitor; and (3) reviewing ozone precursor emission trends in the Houston Area, Texas (statewide), and Mississippi (statewide). In its demonstration, MDEQ stated that temperatures in 2015 and 2016 were above average, and in 2014 and 2017 temperatures were near normal. Based on this information, MDEQ concluded that conditions were conducive to ozone formation during this three-year time period ( i.e., 2015 to 2017). MDEQ's submission also states that design values from 2011 to 2017 at the Deer Park receptor showed a downward trend and that design values have been meeting the 2015 8-hour ozone NAAQS since 2015. Further, according to the submittal, ozone precursor emissions in Texas and Mississippi both showed a downward trend based on data from 2008, 2011, and 2014. Based on the downward trend in emissions and the fact that the Deer Park monitor was measuring attainment in 2015, 2016, and 2017, MDEQ determined that the Deer Park receptor should be eliminated as a maintenance receptor. Thus, based on the elimination of the Deer Park receptor, along with application of a 1 ppb threshold, Mississippi concluded that the State did not significantly interfere with maintenance (prong 2) in another state for the 2015 ozone standard.

In summary, MDEQ concluded that sources in the State do not significantly contribute to nonattainment or interfere with maintenance in another state, that no further emission reductions were necessary, and that Mississippi's SIP contains adequate provisions to prevent sources and other types of emissions activities within the State from contributing significantly to nonattainment or interfering with maintenance in another state with respect to the 2015 8-hour ozone NAAQS.

EPA is proposing to find that Mississippi's September 3, 2019, SIP submission does not meet Mississippi's obligations with respect to prohibiting emissions that contribute significantly to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in any other state based on EPA's evaluation of the SIP submission using the 4-step interstate transport framework, and EPA is therefore proposing to disapprove Mississippi's submission.

At Step 1 of the 4-step interstate transport framework, MDEQ relied on EPA modeling released in the March 2018 memorandum to identify nonattainment and maintenance receptors in 2023.

In its submittal, MDEQ attempted to utilize the October 2018 memorandum along with 2014 to 2017 ozone design values (the most recent data available at the time of submittal) to eliminate the Deer Park receptor in Harris County, Texas (Monitor ID: 482011039) as a maintenance receptor. Table 2 of the submittal correctly indicates that this monitoring site was a projected nonattainment receptor, not a maintenance-only receptor, in 2023 based on the EPA's modeling data included in the March 2018 memorandum. However, in its submittal, the State relied on the 2014 to 2017 design values at the Deer Park receptor ( i.e., 69 ppb, 67 ppb, and 68 ppb, respectively) as the basis for stating that this receptor met EPA's definition of a maintenance receptor. Based on this information, the State applied an alternative definition of a maintenance receptor utilizing the potential concepts included in the October 2018 memorandum. This memorandum included a description of the approach that EPA has historically used to identify maintenance-only receptors  45 and identified potential alternate ways to define maintenance receptors based on certain criteria suggested in the memorandum including an evaluation of meteorology conductive to ozone formation, review of ozone monitored concentrations, and precursor emissions trends.