[Federal Register Volume 89, Number 190 (Tuesday, October 1, 2024)]
[Proposed Rules]
[Pages 79828-79850]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-22466]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R02-OAR-2024-0083; FRL-11767-01-R2]


Finding of Failure To Attain the Primary 2010 1-Hour Sulfur 
Dioxide Standard for the San Juan and Guayama-Salinas Nonattainment 
Areas; Approval and Conditional Approval of Air Quality State 
Implementation Plans; Puerto Rico; Attainment Plan for the 2010 1-Hour 
Sulfur Dioxide Standard for the San Juan and Guayama-Salinas 
Nonattainment Areas

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing two 
actions related to attainment of the 2010 primary 1-hour sulfur dioxide 
(SO<INF>2</INF>) National Ambient Air Quality Standard (NAAQS or 
``standard''). First, the EPA is proposing to determine that the San 
Juan and Guayama-Salinas SO<INF>2</INF> Nonattainment Areas (NAAs) 
failed to attain the 2010 primary 1-hour SO<INF>2</INF> NAAQS by the 
applicable attainment date of April 9, 2023, based upon a technical 
analysis of various evidence

[[Page 79829]]

available (i.e., weight-of-evidence analysis). If the EPA finalizes 
this determination as proposed, within one year, Puerto Rico will be 
required to submit revisions to the Puerto Rico State Implementation 
Plan (SIP) that, among other elements, provide for expeditious 
attainment of the 2010 SO<INF>2</INF> standard no later than five years 
from the publication date of the final rule. Second, the EPA is 
proposing to approve certain elements of Puerto Rico's November 22, 
2022, SIP revision (hereinafter referred to as the ``plan''), which was 
submitted to demonstrate attainment of the 2010 primary 1-hour 
SO<INF>2</INF> standard in the San Juan and Guayama-Salinas NAAs. 
Elements being proposed for approval include Puerto Rico's 
nonattainment new source review (NNSR) program and the base year 
emissions inventory. Finally, the EPA is proposing to approve in part, 
and conditionally approve in part, for SIP-strengthening purposes, 
other remaining elements of the plan, including amendments to Puerto 
Rico's Regulation for the Control of Atmospheric Pollution (or RCAP), 
which include control measures, emissions limitations, and reporting 
requirements for sources in the NAAs.

DATES: 
    Comments: Written comments must be received on or before December 
2, 2024.
    Public Information Sessions: The EPA will hold two public 
information sessions on this proposed rulemaking in Puerto Rico on 
dates and locations to be determined and announced at a later date.
    For more information on the public information sessions, see 
SUPPLEMENTARY INFORMATION.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R02-
OAR-2024-0083 at https://www.regulations.gov. Although listed in the 
index, some information is not publicly available, e.g., Controlled 
Unclassified Information (CUI) (formally referred to as Confidential 
Business Information (CBI)) or other information whose disclosure is 
restricted by statute. Certain other material, such as copyrighted 
material, is not placed on the internet and will be publicly available 
only in hard copy form. Publicly available docket materials are 
available electronically through https://www.regulations.gov. Follow 
the online instructions for submitting comments. Once submitted, 
comments cannot be edited or removed from Regulations.gov. The EPA may 
publish any comment received to its public docket. Do not submit 
electronically any information you consider to be CUI or other 
information whose disclosure is restricted by statute. Multimedia 
submissions (audio, video, etc.) must be accompanied by a written 
comment. The written comment is considered the official comment and 
should include discussion of all points you wish to make. The EPA will 
generally not consider comments or comment contents located outside of 
the primary submission (i.e., on the web, cloud, or other file sharing 
system). For additional submission methods, the full EPA public comment 
policy, information about CUI or multimedia submissions, and general 
guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    Docket: All documents in the electronic docket are listed in the 
www.regulations.gov index. Although listed in the index, some 
information is not publicly available, i.e., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, is not placed on the internet and will be 
publicly available only in hard copy form. The files will also be made 
available by appointment for public inspection between the hours of 
9:00 a.m. and 4:30 p.m. weekdays except for legal holidays. Contact the 
person(s) listed in the FOR FURTHER INFORMATION CONTACT paragraph below 
to make an appointment. If possible, please make the appointment at 
least two working days in advance of your visit. We may charge you a 
reasonable fee for copying parts of the docket.

FOR FURTHER INFORMATION CONTACT: Nicholas Ferreira, Environmental 
Protection Agency, Region 2, Air Programs Branch, 290 Broadway, New 
York, New York 10007-1866, at (212) 637-3127, or by email at 
<a href="/cdn-cgi/l/email-protection#d5b3b0a7a7b0bca7b4fbbbbcb6bdbab9b4a695b0a5b4fbb2baa3"><span class="__cf_email__" data-cfemail="82e4e7f0f0e7ebf0e3acecebe1eaedeee3f1c2e7f2e3ace5edf4">[email protected]</span></a>, and/or Andres Febres, Environmental 
Protection Agency, Region 2, Caribbean Environmental Protection 
Division Office, City View Plaza II, #48 RD. 165 km 1.2, Guaynabo, 
Puerto Rico, 00968-8069, at (787) 977-5801, or by email at <a href="/cdn-cgi/l/email-protection#7d1b181f0f180e50101c0f0914131807531c13190f180e3d180d1c531a120b"><span class="__cf_email__" data-cfemail="412724233324326c2c203335282f243b6f202f25332432012431206f262e37">[email protected]</span></a>.

SUPPLEMENTARY INFORMATION:

Public Information Session

    The EPA intends to provide two public information sessions 
concerning this proposed rule. The EPA will announce the date, time, 
and location for each session on its website. These public information 
sessions will provide informal opportunities for members of the public 
to learn about this proposed action. The EPA anticipates these sessions 
will allow the public to be better informed when submitting formal 
comments during the 60-day comment period for this proposed action.
    A translator will be present at the public engagement sessions to 
ensure participants are able to understand the information provided by 
the EPA. There will be no recording or transcript of these public 
information sessions since these sessions are not considered to be 
formal public hearings. Statements made and/or questions asked at these 
sessions will not be considered formal comments on the proposed rule 
and will not be included in the EPA's response to comments, unless 
submitted as a formal comment on the record.
    Members of the public who wish to formally comment should do so 
during the 60-day public comment period provided following the 
publication of this proposed rule.
    This notice is organized as follows:

Table of Contents

I. Background
    A. The 2010 SO<INF>2</INF> NAAQS
    B. Designations and Attainment Date Requirements for the 2010 
SO<INF>2</INF> NAAQS
    C. Finding of Failure To Submit and SIP Submittal
    D. Puerto Rico's Integrated Resource Plan
II. What is the EPA proposing?
III. Proposed Determination of Failure To Attain and the Associated 
Consequences
    A. Applicable Statutory and Regulatory Provisions
    B. San Juan and Guayama-Salinas SO<INF>2</INF> Monitoring 
Networks and Considerations
    C. SO<INF>2</INF> Data Considerations and the EPA's Proposed 
Determination
    1. SO<INF>2</INF> Monitor Data
    2. Modeling Data and Control Strategy Timeline
    3. Failure To Implement the Control Strategy
    4. SO<INF>2</INF> Emissions Data
    5. Weight-of-Evidence Analysis Conclusions and the EPA's 
Proposed Determination
    D. Consequences for SO<INF>2</INF> NAAs Failing To Attain 
Standards by Attainment Dates
IV. Requirements for SO<INF>2</INF> Nonattainment Area Plans
V. Review of Modeled Attainment Demonstration
    A. Modeling Approach
    B. Area of Analysis
    C. Receptor Grid
    D. Meteorological Data
    E. Source Characterization
    F. Emissions Data
    G. Retirements and Emission Limits
    H. Background Concentrations
    I. Summary of Results
VI. Review of Other Plan Requirements
    A. Emissions Inventory
    B. RACM and RACT and Enforceable Emission Limitations and 
Control Measures
    C. New Source Review
    D. Reasonable Further Progress

[[Page 79830]]

    E. Contingency Measures
    F. Conformity
VII. Puerto Rico's New Source Review Program
VIII. The EPA's Evaluation of Rule 425
IX. Environmental Justice Considerations
X. The EPA's Proposed Action
XI. Incorporation by Reference
XII. Statutory and Executive Order Reviews

I. Background

A. The 2010 SO2 NAAQS

    Under section 109 of the Clean Air Act (CAA), the EPA has 
established primary and secondary NAAQS for certain pervasive air 
pollutants (referred to as ``criteria pollutants'') and conducts 
periodic reviews of the NAAQS to determine whether they should be 
revised or whether new NAAQS should be established. The primary NAAQS 
represent ambient air quality standards the attainment and maintenance 
of which the EPA has determined, including a margin of safety, are 
requisite to protect the public health. The secondary NAAQS represent 
ambient air quality standards the attainment and maintenance of which 
the EPA has determined are requisite to protect the public welfare from 
any known or anticipated adverse effects associated with the presence 
of such air pollutant in the ambient air.
    Under the CAA, the EPA must establish NAAQS for criteria 
pollutants, including SO<INF>2</INF>. SO<INF>2</INF> is primarily 
released to the atmosphere through the burning of fossil fuels by power 
plants and other industrial facilities. Short-term exposure to 
SO<INF>2</INF> can damage the human respiratory system and increase 
breathing difficulties. Small children and people with respiratory 
conditions, such as asthma, are more sensitive to the effects of 
SO<INF>2</INF>. Sulfur oxides at high concentrations in ambient air can 
also react with compounds to form small particulates that can penetrate 
deeply into the lungs and cause health problems.
    The EPA first established primary SO<INF>2</INF> standards in 1971 
at 0.14 parts per million (ppm) over a 24-hour averaging period and 0.3 
ppm over an annual averaging period.\1\ On June 22, 2010, the EPA 
revised the primary NAAQS for SO<INF>2</INF> and published a new 1-hour 
primary SO<INF>2</INF> NAAQS of 75 parts per billion (ppb).\2\ The 
intent of this revision is to provide increased protection of public 
health, providing for revocation of the 1971 primary annual and 24-hour 
SO<INF>2</INF> standards for most areas of the country following area 
designations under the new NAAQS.
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    \1\ See 36 FR 8186 (April 30, 1971).
    \2\ See 75 FR 35520 (June 22, 2010), codified at 40 CFR 
50.17(a)-(b).
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    The 2010 standard is met at an ambient air quality monitoring site 
when the 3-year average of the annual 99th percentile of daily maximum 
1-hour average concentrations does not exceed 75 ppb, or 0.075 ppm, as 
determined in accordance with Appendix T of 40 CFR part 50.17. The EPA 
established the SO<INF>2</INF> NAAQS based on significant evidence and 
numerous studies demonstrating that serious health effects are 
associated with short-term exposures to SO<INF>2</INF> emissions 
ranging from five minutes to 24 hours, including an array of adverse 
respiratory effects such as narrowing of the airways, which can cause 
difficulty breathing (bronchoconstriction) and increased asthma 
symptoms. For more information regarding the health impacts of 
SO<INF>2,</INF> please refer to the June 22, 2010 final rulemaking. See 
75 FR 35520, codified at 40 CFR 50.17.

B. Designations and Attainment Date Requirements for the 2010 SO2 NAAQS

    Following promulgation of a new or revised NAAQS, the EPA is 
required by the CAA to designate areas throughout the United States as 
attaining or not attaining the NAAQS; this designation process is 
described in section 107(d)(1)-(2) of the CAA. For the 2010 
SO<INF>2</INF> NAAQS, the EPA defined a nonattainment area (NAA) as an 
area that the EPA determined violates the 2010 1-hour primary 
SO<INF>2</INF> NAAQS and/or contributes to a violation in a nearby 
area, based on the most recent 3 years of air quality monitoring data, 
appropriate dispersion modeling analysis, and any other relevant 
information.\3\
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    \3\ See 83 FR 1101 (Jan. 9, 2018).
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    On January 9, 2018, the EPA, as part of the third round \4\ of area 
designations for the 2010 1-hour primary SO<INF>2</INF> NAAQS, 
designated six areas of the country as nonattainment, including the San 
Juan and Guayama-Salinas NAAs.\5\ These area designations had an 
effective date of April 9, 2018.
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    \4\ 83 FR 1098 (Jan. 9, 2018), codified at 40 CFR part 81, 
subpart C.
    \5\ The EPA completed its first round of initial area 
designations for the 2010 1-hour primary SO<INF>2</INF> NAAQS 
effective October 4, 2013. See 78 FR 47191 (Aug. 5, 2013). A second 
round of designations was effective September 12, 2016, with a 
supplement effective January 17, 2017. See 81 FR 45039 (July 12, 
2016) and 81 FR 89870 (Dec. 13, 2016), respectively. A fourth round 
of designations was effective April 30, 2021. See 86 FR 16055 (Mar. 
26, 2021).
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    Areas designated nonattainment for the SO<INF>2</INF> NAAQS are 
subject to the general NAA planning requirements of CAA section 172 and 
to the SO<INF>2</INF>-specific planning requirements of subpart 5 of 
part D of Title I of the CAA (sections 191 and 192). All components of 
the SO<INF>2</INF> part D nonattainment area SIP, including the 
emissions inventory, attainment demonstration, reasonably available 
control measures (RACM) and reasonably available control technology 
(RACT), enforceable emissions limitations and control measures, 
Reasonable Further Progress (RFP) plan, nonattainment New Source Review 
(NNSR) program, and contingency measures, are due to the EPA within 18 
months of the effective date of designation of a nonattainment area 
under CAA section 191.
    Therefore, the nonattainment area SIPs for areas designated 
effective April 9, 2018, were due on October 9, 2019. These SIPs are 
required to demonstrate that their respective areas will attain the 
2010 1-hour primary SO<INF>2</INF> NAAQS as expeditiously as 
practicable, but no later than five years from the effective date of 
designation, or by April 9, 2023, for the San Juan and Guayama-Salinas 
NAAs.

C. Finding of Failure To Submit and SIP Submittal

    For a number of SO<INF>2</INF> NAAs, including the San Juan and 
Guayama-Salinas NAAs, the EPA published an action on November 3, 2020, 
effective December 3, 2020, finding that Puerto Rico and other 
pertinent states had failed to submit the required SO<INF>2</INF> 
nonattainment plan by the submittal deadline. See 85 FR 69504. This 
finding initiated a deadline under CAA section 179(a) for the potential 
imposition of two sanctions clocks related to new source review offsets 
(i.e., ``2-to-1 offsets'') and highway funding, within 18 and 24 months 
of the findings, respectively, unless the states and territories 
subject to the finding made the necessary complete SIP submittal. 
Additionally, this finding initiated a deadline under CAA section 
110(c) for the EPA to promulgate a Federal Implementation Plan (FIP) 
within two years of the finding unless, by that time, the EPA had 
approved the submittal as meeting applicable requirements.
    On June 3, 2022, the 2-to-1 offset sanctions took effect within the 
Puerto Rico NAAs. Before the highway funding sanctions could go into 
effect within the NAAs on December 3, 2022, the Puerto Rico Department 
of Natural and Environmental Resources (PRDNER) submitted a 
nonattainment plan for the San Juan and Guayama-Salinas NAAs (i.e., San 
Juan and Guayama-Salinas SO<INF>2</INF> plan) on November 22, 2022, and 
the EPA deemed the PRDNER's submittal administratively and technically 
complete on December 2, 2022. As a

[[Page 79831]]

result of the EPA's determination, the 2-to-1 offset sanctions clock 
was stopped and the highway sanctions never took effect, per the EPA's 
sanctions regulations at 40 CFR 52.31; however, this completeness 
determination did not terminate the EPA's FIP obligation that was 
triggered by the EPA's November 3, 2020, Finding of Failure to Submit.
    Within the San Juan and Guayama-Salinas SO<INF>2</INF> plan, 
amendments to Puerto Rico's RCAP were submitted for the EPA's approval. 
The RCAP amendments incorporate the SO<INF>2</INF> control measures and 
nonattainment provisions of the SO<INF>2</INF> plan and would become 
federally enforceable upon final approval by the EPA. The RCAP 
amendments consist of revisions to Rule 102, ``Definitions,'' as well 
as the adoption of Rule 210, ``Non-Attainment Provisions,'' and Rule 
425, ``Provisions for SO<INF>2</INF> Non-Attainment Areas.'' \6\ The 
PRDNER's permitting requirements to construct new sources or modify 
major sources of emissions of SO<INF>2</INF> and other pollutants in 
NAAs, including the San Juan and Guayama-Salinas NAAs, are set forth in 
the revisions to Rule 102, ``Definitions,'' and the recently adopted 
Rule 210, ``Nonattainment Provisions.'' Finally, the recently 
promulgated Rule 425 was adopted to include control measures, emission 
limits, test methods and procedures, reporting and recordkeeping 
requirements, and contingency measures for the San Juan and Guayama-
Salinas NAAs.
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    \6\ The RCAP amendments were approved by the Secretary of the 
PRDNER on November 21, 2022, and became effective on the same day.
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D. Puerto Rico's Integrated Resource Plan

    The compliance strategy for Puerto Rico's SIP, and the accompanying 
RCAP amendments, were developed based on the most recent Integrated 
Resource Plan (IRP) approved by the Puerto Rico Energy Bureau 
(PREB),\7\ as well as additional updates provided by the PREB, which 
considered emission unit retirements within the San Juan and Guayama-
Salinas NAAs following the integration of renewable energy sources.
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    \7\ Final Resolution and Order on the Puerto Rico Electric Power 
Authority's Integrated Resource Plan, Review of the Puerto Rico 
Electric Power Authority Integrated Resource Plan, Case No. CEPR-AP-
2018-0001, August 24, 2020 (``Approved IRP''), available at https://energia.pr.gov/wp-content/uploads/sites/7/2020/08/AP20180001-IRP-Final-Resolution-and-Order.pdf.
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    The IRP is a plan that is required under Puerto Rico law, with the 
purpose of providing cost-effective electrical power to meet Puerto 
Rico's energy demand over a twenty-year planning period, while 
considering energy conservation, resiliency, reliability, efficiency, 
transparency, and the environment. Under Act 57-2014,\8\ a Puerto Rico 
law known as the Puerto Rico Energy Transformation and RELIEF Act, the 
Puerto Rico Electric Power Authority (PREPA), or the electric utility 
responsible for the operation of the electric power transmission and 
distribution system (currently LUMA Energy), is required to prepare an 
IRP for the PREB's approval, which considers reasonable resources to 
satisfy energy demand for up to a twenty-year period. Puerto Rico's 
electric utility is also responsible for updating the plan at least 
every three years to reflect changes in energy market conditions, 
regulations, fuel prices, and capital costs. Pursuant to Act 57-2014, 
the PREB is responsible for establishing and implementing regulations 
to ensure the capacity, reliability, safety, and efficiency of Puerto 
Rico's electrical system. This includes evaluating and approving the 
IRP, overseeing and ensuring compliance, and implementation.
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    \8\ See https://energia.pr.gov/wp-content/uploads/sites/7/2015/10/AN-ACT-57-20141.pdf.
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    On August 24, 2020, the PREB issued the IRP Final Order, based on 
the IRP submitted by PREPA. The Approved IRP included a Modified 
Preferred Resource Plan (Action Plan) considering specific power 
generation capacity additions and retirements. In the Approved IRP, the 
PREB established a schedule for minimum quantities of renewable 
resources, and battery energy storage resources to be procured through 
the Requests for Proposals processes, to be completed by June 2023. The 
Approved IRP also directed PREPA to submit a renewable resource and 
battery energy storage procurement plan. Specifically, the Approved IRP 
included a program for six tranches of procurement for renewable energy 
and battery storage resources that would add 3,750 MW of renewable 
sources to the energy grid. Based on the procurement of renewable 
resources to be integrated in the Puerto Rico Electric System, the 
Approved IRP authorized the retirement of PREPA's older, oil-fired 
steam resources, combined cycle turbines and peaking units for the 
period between 2021 and 2025.
    The PREB provided an updated schedule for emission unit retirements 
and the integration of new renewable energy and battery storage 
resources via letter to the PRDNER on October 18, 2022, which was 
updated on November 15, 2022.\9\ The IRP was scheduled to be revised 
and submitted to the PREB by June 28, 2024 by LUMA, the current 
operator of Puerto Rico's electrical power transmission and 
distribution system.\10\ However, on June 7, 2024, LUMA requested that 
the PREB suspend the June 28 deadline, due to modeling delays 
associated with its base case scenario.\11\ LUMA requested that the 
2024 IRP be filed on May 16, 2025, with an analysis of four 
supplemental scenarios proposed to be filed on June 19, 2025.\12\ On 
August 20, 2024, the PREB denied LUMA's request for an extension, until 
May 16, 2025, for a full IRP.
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    \9\ The October 18, 2022 and November 15, 2022 letters are 
available in the docket of this rulemaking.
    \10\ On June 22, 2020, LUMA entered into an operation and 
maintenance agreement under which it will operate the transmission 
and distribution system previously operated by PREPA. PREPA 
maintains ownership over the transmission and distribution system. 
See https://www.p3.pr.gov/wp-content/uploads/2020/06/executed-consolidated-om-agreement-td.pdf.
    \11\ See LUMA's Motion in Compliance with Resolution and Order 
of June 18, 2024, and Submitting Second Revised IRP Filing Schedule, 
dated June 28, 2024, at ] 18, available at https://energia.pr.gov/wp-content/uploads/sites/7/2024/07/20240628-AP20230004-Motion-in-Compliance-with-Resolution-and-Order-of-June-18-2024-and-Submitting-Second-Revised-IRP-Filing-Schedule.pdf.
    \12\ See id. at ] 27.
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    The PREB ordered LUMA to file the Preferred Resource Plan and 
``salient components'' of the base case and alternative case scenarios 
by no later than November 29, 2024, and ordered LUMA to file certain 
transmission and distribution related requirements by no later than 
February 28, 2025.\13\
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    \13\ See PREB Resolution and Order, dated August 20, 2024, 
available at https://energia.pr.gov/wp-content/uploads/sites/7/2024/08/20240820-AP20230004-Resolution-and-Order.pdf.
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II. What is the EPA proposing?

    The EPA is proposing several actions in this rulemaking. First, 
under CAA section 179(c), the EPA is proposing to determine that the 
San Juan and Guayama-Salinas SO<INF>2</INF> NAAs failed to attain the 
2010 1-hour primary SO<INF>2</INF> standard by the statutory attainment 
date of April 9, 2023. The EPA's proposed Finding of Failure to Attain 
(FFA) determination is based on a weight-of-evidence analysis that 
demonstrates that the San Juan and Guayama-Salinas areas failed to 
attain the standard by the mandatory attainment date. The EPA's 
reasoning for this decision is described in Section III of the 
preamble.
    Second, the EPA is proposing to approve certain elements of Puerto 
Rico's SO<INF>2</INF> plan, which was submitted to demonstrate how the 
San Juan and Guayama-Salinas areas would meet the 2010 1-hour 
SO<INF>2</INF> standard in the San Juan and Guayama-Salinas NAAs. The

[[Page 79832]]

EPA outlines the requirements for nonattainment plans under CAA section 
172(c), and reviews Puerto Rico's plan against these requirements in 
Sections IV, V and VI of this preamble.
    Although Puerto Rico submitted its plan to satisfy CAA section 
172(c) requirements, the EPA is proposing to approve only specific 
elements at this time for compliance with the CAA. The elements being 
proposed for approval include Puerto Rico's NNSR program and base year 
emissions inventory. The EPA is not proposing action on other elements 
of the plan, such as the attainment demonstration, RFP, RACM/RACT, 
emission limitation as necessary to provide for NAAQS attainment, and 
contingency measures. The EPA will address whether Puerto Rico is 
meeting its statutory obligations for those elements in a future 
rulemaking. Finally, amendments to the RCAP, which Puerto Rico 
submitted with the plan, are being proposed for approval, in part, and 
conditional approval, in part, based on providing SIP-strengthening.

III. Proposed Determination of Failure To Attain and the Associated 
Consequences

A. Applicable Statutory and Regulatory Provisions

    Section 179(c)(1) of the CAA requires the EPA to determine whether 
a NAA attained an applicable standard by the applicable attainment date 
based on the area's air quality as of the attainment date. In 
determining the attainment status of SO<INF>2</INF> NAAs, the EPA may 
consider ambient monitoring data, air quality dispersion modeling, and/
or a demonstration that the control strategy in the SIP has been fully 
implemented.\14\
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    \14\ EPA, Guidance for 1-Hour SO<INF>2</INF> Nonattainment Area 
SIP Submissions (April 2014) (``2014 SO<INF>2</INF> Guidance''), 49.
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    Under the EPA's regulations in 40 CFR 50.17, and in accordance with 
40 CFR part 50 Appendix T, the 2010 1-hour annual SO<INF>2</INF> 
standard is met when the design value is less than or equal to 75 ppb. 
Design values are calculated by computing the three-year average of the 
annual 99th percentile daily maximum 1-hour average concentrations.\15\ 
An SO<INF>2</INF> 1-hour primary standard design value is valid if it 
encompasses three consecutive calendar years of complete data. A year 
is considered complete when all four quarters are complete, and a 
quarter is complete when at least 75 percent of the sampling days are 
complete. A sampling day is considered complete if 75 percent of the 
hourly concentration values are reported; this includes data affected 
by exceptional events that have been approved for exclusion by the 
Administrator.\16\
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    \15\ As defined in 40 CFR part 50, Appendix T section 1(c), 
daily maximum 1-hour values refer to the maximum 1-hour 
SO<INF>2</INF> concentration values measured from midnight to 
midnight that are used in the NAAQS computations.
    \16\ See 40 CFR part 50, Appendix T sections 1(c), 3(b), 4(c), 
and 5(a).
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    A determination of whether an area's air quality meets applicable 
standards is generally based upon the most recent three calendar years 
of complete, quality-assured data gathered at established state and 
local air monitoring stations (SLAMS) in a nonattainment area and 
entered into the EPA's Air Quality System (AQS) database.\17\ Data from 
ambient air monitors operated by state and local agencies in compliance 
with the EPA monitoring requirements must be submitted to AQS.\18\ 
Monitoring agencies annually certify that these data are accurate to 
the best of their knowledge.\19\ All certified SO<INF>2</INF> air 
monitoring data are used to calculate design values that are used to 
determine the area's air quality status in accordance with 40 CFR part 
50, Appendix T.
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    \17\ AQS is the EPA's repository of ambient air quality data.
    \18\ 40 CFR 58.16.
    \19\ 40 CFR 58.15.
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    In addition to utilizing ambient monitoring data to make 
determinations of attainment by the attainment date, the EPA considers 
air quality dispersion modeling and/or a demonstration that the control 
strategy in the SIP has been fully implemented. With regard to the use 
of monitoring data for such determinations, EPA's 2014 Nonattainment 
SO<INF>2</INF> Guidance \20\ specifically notes that if the EPA 
determines the air quality monitors located in the affected area are 
located in the area of maximum concentration, the EPA may be able to 
use the data from these monitors to make the determination of 
attainment without the use of air quality modeling data.\21\ In this 
case, there are SO<INF>2</INF> monitors within the San Juan and 
Guayama-Salinas NAAs; however, there is no evidence indicating that the 
monitors are located within the areas of expected maximum 
concentration.
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    \20\ EPA, Guidance for 1-Hour SO<INF>2</INF> Nonattainment Area 
SIP Submissions (April 2014) (``2014 SO<INF>2</INF> Guidance''), 
p.49, available at https://www.epa.gov/sites/default/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf.
    \21\ Id., p.50.
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    Due to insufficient monitoring data collected for all three years 
in the 2020-2022 data period for the SO<INF>2</INF> monitors, the EPA 
is unable to determine valid monitor-based 2020-2022 design values. As 
a result, the EPA has considered available air modeling data submitted 
by the PRDNER with its November 22, 2022, SIP revision, as well as the 
designation modeling the EPA used to initially determine that the areas 
were in nonattainment, to assess whether the areas attained by the 
attainment date.
    According to the EPA's Modeling Technical Assistance Document 
(TAD),\22\ for the purpose of modeling to characterize air quality for 
use in designations, the recommended approach is to use the most recent 
3 years of actual emissions data and concurrent meteorological data. 
However, the TAD also indicates that it would be acceptable to use 
allowable emissions in the form of the most recently permitted 
(referred to as PTE or allowable) emissions rate that is federally 
enforceable and effective. When relying on a modeling demonstration 
based on allowable emissions for purposes of determining attainment by 
the attainment date, the EPA looks to whether the emission limit or 
limits were adopted and whether the relevant source or sources were 
complying with those modeled limits prior to the attainment date. That 
is, when determining attainment by the attainment date using air 
quality modeling of allowable emissions, the EPA looks to whether the 
state/commonwealth has demonstrated that the control strategy in the 
SIP has been fully implemented. This is necessary because a modeling 
demonstration based on allowable emissions is not itself sufficient 
since, without the supporting emissions information reflected in the 
control strategy, there would be no way to confirm that the actual 
emissions were below the modeled limits within the period under review.
---------------------------------------------------------------------------

    \22\ See https://www.epa.gov/so2-pollution/technical-assistance-documents-implementing-2010-sulfur-dioxide-standard.
---------------------------------------------------------------------------

    The EPA would like to clarify that a significant amount of 
information is required for the EPA to accurately conduct its own air 
quality dispersion modeling to determine attainment by the attainment 
date for these two NAAs. This information is not readily available, and 
the limited data currently accessible to the Agency raises concerns 
about the reliability of new modeling. Specifically, the EPA does not 
have access to fuel use data or concurrent meteorological data and 
continuous emissions monitoring systems (CEMS) data from the stacks at 
the PREPA facilities (the EPA also believes that CEMS provide 
acceptable historical

[[Page 79833]]

emissions information). As a result, it is the EPA's position that any 
air quality dispersion modeling the EPA would perform for the purpose 
of this determination would not be representative of air quality within 
the areas. Thus, the EPA is not performing air quality dispersion 
modeling to support its determination that the areas have failed to 
attain by their attainment dates. The EPA will instead consider the 
modeling conducted and provided by the PRDNER in its November 22, 2022, 
SIP submission, which shows that controls that PRDNER anticipates will 
lead to attainment were not in place prior to the areas' attainment 
dates.
    As noted earlier in this section, the EPA may also consider whether 
the state (or commonwealth) has demonstrated that the control strategy 
in the SIP has been fully implemented. That said, the PRDNER's control 
strategy has not been implemented, nor has it been approved by the EPA. 
As a result, the EPA cannot determine that the subject sources have 
achieved compliance with either the PRDNER's control strategy as 
submitted to the EPA, or a SIP-approved strategy. To address this, the 
EPA is proposing a determination that the areas did not attain by their 
attainment date which is based on a technical analysis of various 
evidence available (i.e., weight-of-evidence analysis): including the 
control strategy timeline Puerto Rico identified and adopted into its 
RCAP, which was determined in coordination with the air quality 
dispersion modeling submitted within its November 22, 2022 SIP revision 
as well as the EPA's designation modeling; Puerto Rico's failure to 
implement the control strategy in a timely manner thus far; and the 
EPA's review of annual facility-wide emissions data from January 2020 
through December 2022 for the PREPA San Juan, PREPA Palo Seco, and 
PREPA Aguirre facilities located within the NAAs--as described in 
Sections III.B and III.C of this notice. As noted, the determination of 
whether the monitors are located in the area of maximum concentration 
is not needed here, because a demonstration is not being made that the 
NAAs have attained the 2010 SO<INF>2</INF> NAAQS by the April 9, 2023 
attainment date.

B. San Juan and Guayama-Salinas SO2 Monitoring Networks and 
Considerations

    Section 110(a)(2)(B)(i) of the CAA requires states to establish and 
operate air monitoring networks to compile data on ambient air quality 
for all criteria pollutants. The EPA's monitoring requirements are 
specified by regulation in 40 CFR part 58. These requirements are 
applicable to state, and where delegated, local air monitoring agencies 
that operate criteria pollutant monitors. The regulations in 40 CFR 
part 58 establish specific requirements for operating air quality 
surveillance networks to measure ambient concentrations of 
SO<INF>2</INF>, including requirements for measurement methods, network 
design, quality assurance procedures, and the minimum number of 
monitoring sites designated as SLAMS.
    In sections 4.4 and 4.5 of Appendix D to 40 CFR part 58, the EPA 
specifies the minimum requirements for SO<INF>2</INF> monitoring sites 
to be classified as SLAMS. SLAMS produce data that are eligible for 
comparison with the NAAQS, and therefore, the monitor must be an 
approved federal reference method (FRM), federal equivalent method 
(FEM), or approved regional method (ARM) monitor, pursuant to section 2 
of Appendix C to 40 CFR part 58. Additionally, Appendix A to 40 CFR 
part 58 specifies quality assurance requirements for SLAMS monitors.
    During the 2020-2022 data period, the PRDNER operated three 
SO<INF>2</INF> SLAMS in the San Juan and Guayama-Salinas SO<INF>2</INF> 
NAAs. In the San Juan NAA, SLAMS monitors are in operation at 
Bayam[oacute]n (AQS Site ID 72-021-0010, Avenue Central Correcional) 
and at Cata[ntilde]o (AQS Site ID 72-033-0004, Northwest Street at the 
11 Final Street, Las Vegas). In the Guayama-Salinas NAA, a SLAMS 
monitor is located at Guayama (AQS Site ID 72-057-0011, Road #3 Cuartel 
Vehiculos Hurtados).

C. SO2 Data Considerations and the EPA's Proposed Determination

1. SO<INF>2</INF> Monitor Data
    As discussed in Section I.B of this preamble, the applicable 
attainment date for the San Juan and Guayama-Salinas areas was April 9, 
2023. In accordance with Appendix T to 40 CFR part 50, determinations 
of SO<INF>2</INF> NAAQS compliance are based on three consecutive 
calendar years of data. To determine the air quality as of the 
attainment date in the nonattainment area, the EPA reviewed the 
available data collected during the three calendar years immediately 
preceding the attainment date for the San Juan and Guayama-Salinas 
areas (i.e., January 1, 2020 through December 31, 2022), as well as 
SO<INF>2</INF> emissions data that resulted from the burning of fossil 
fuels for electricity generation at the PREPA San Juan, PREPA Palo 
Seco, and PREPA Aguirre facilities.
    The available annual 99th percentile daily maximum 1-hour average 
SO<INF>2</INF> data at each monitoring site within the San Juan and 
Guayama-Salinas areas for the 2020-2022 period are presented in Tables 
1 and 2 below. Moreover, the 1-hour SO<INF>2</INF> design values at the 
Bayam[oacute]n, Cata[ntilde]o, and Guayama SO<INF>2</INF> monitoring 
sites for the 2020-2022 period are shown in Tables 1 and 2 below.\23\
---------------------------------------------------------------------------

    \23\ A design value is a statistic that describes the air 
quality status of a given location relative to the level of the 
NAAQS. SO<INF>2</INF> design values at the Bayam[oacute]n, 
Cata[ntilde]o, and Guayama SO<INF>2</INF> monitoring sites for the 
2020-2022 period were obtained from the EPA's Air Quality Design 
Values web page. See https://www.epa.gov/air-trends/air-quality-design-values#report.
    \24\ Monitoring sites must meet the data completeness 
requirements listed in Appendix T to 40 CFR part 50 in order to have 
a valid design value. Annual 99th percentile daily maximum 1-hour 
averages with an asterisk (*) indicate that those values do not meet 
these completeness requirements.

                         Table 1--2020-2022 SO2 Monitor Data for the San Juan Area \24\
----------------------------------------------------------------------------------------------------------------
                                                  2020 Annual     2021 Annual     2022 Annual
                                                     99th            99th            99th
                                                  percentile      percentile      percentile      2020-2022 SO2
         SLAMS monitor            AQS site ID    daily maximum   daily maximum   daily maximum    design value
                                                1-hour average  1-hour average  1-hour average        (ppb)
                                                     (ppb)           (ppb)           (ppb)
----------------------------------------------------------------------------------------------------------------
Bayam[oacute]n................     72-021-0010          * 35.4             9.8            10.8  Not Valid (NV).
Cata[ntilde]o.................     72-033-0004          * 17.6          * 18.2           * 0.0  NV
----------------------------------------------------------------------------------------------------------------


[[Page 79834]]


                      Table 2--2020-2022 SO2 Monitor Data for the Guayama-Salinas Area \25\
----------------------------------------------------------------------------------------------------------------
                                                    2020 Annual     2021 Annual     2022 Annual
                                                       99th            99th            99th
                                                    percentile      percentile      percentile     2020-2022 SO2
          SLAMS monitor             AQS site ID    daily maximum   daily maximum   daily maximum   design value
                                                  1-hour average  1-hour average  1-hour average       (ppb)
                                                       (ppb)           (ppb)           (ppb)
----------------------------------------------------------------------------------------------------------------
Guayama.........................     72-057-0011              NV           * 3.4           * 3.4              NV
----------------------------------------------------------------------------------------------------------------

    The attainment date for the areas was April 9, 2023. In order for 
the EPA to determine that the areas attained by the April 9, 2023 
attainment date based solely on air quality monitoring data, the design 
value based upon complete, quality-assured monitored air quality data 
from three consecutive years (2020-2022) at each eligible monitoring 
site must be equal to or less than 75 ppb for the 1-hour standard, and 
air quality modeling would need to show that there was an air quality 
monitor located in the area of maximum concentration.
---------------------------------------------------------------------------

    \25\ Monitoring sites must meet the data completeness 
requirements listed in Appendix T to 40 CFR part 50 in order to have 
a valid design value. Annual 99th percentile daily maximum 1-hour 
averages with an asterisk (*) indicate that those values do not meet 
these completeness requirements.
---------------------------------------------------------------------------

    The EPA has not been provided with nor is the EPA aware of 
information indicating that these three monitors are located within the 
area of maximum concentration. Therefore, this information alone is 
insufficient to support a determination of whether the NAAs attained 
the 2010 SO<INF>2</INF> NAAQS by the attainment date.
2. Modeling Data and Control Strategy Timeline
    The EPA's Modeling TAD notes that for area designations under the 
2010 SO<INF>2</INF> NAAQS, the American Meteorological Society/
Environmental Protection Agency Regulatory Model (AERMOD) modeling 
system should be used, unless use of an alternative model can be 
justified. As previously stated, the EPA did not conduct its own air 
dispersion modeling demonstration with AERMOD and is instead relying on 
the air dispersion modeling conducted by the PRDNER, as provided within 
its attainment demonstration submitted to the EPA on November 22, 2022.
    The PRDNER's attainment demonstration utilized version 21112 of 
AERMOD, with default options. Version 21112 of AERMOD was the most 
recent version at the time the attainment demonstration modeling was 
conducted. Further information pertaining to the PRDNER's modeling, 
such as the area of analysis, source characterization, emissions, 
meteorology and surface characteristics, geography and terrain, and 
background concentrations, can be found in Section V, ``Review of 
Modeled Attainment Demonstration,'' of this proposed rulemaking. For 
purposes of the FFA, the EPA finds the PRDNER's modeling was conducted 
in a technically correct manner, consistent with the EPA's modeling 
guidance.
    The control strategy the PRDNER identified and modeled to provide 
for attainment of the standard relies primarily on the retirement of 
PREPA electricity generation units and is based on the integration of 
new renewable energy projects (as determined by PREB). However, this 
control strategy was not scheduled to start until February 2023, 
specifically involving the transition of several units to ultra-low 
sulfur diesel fuel. Specifically, the retirement of PREPA units was 
scheduled to occur in phases, from June 30, 2023, through December 31, 
2025, at PREPA San Juan and PREPA Palo Seco, and from December 31, 
2025, through December 31, 2029, at PREPA Aguirre.
    The projected attainment dates identified by the PRDNER, via its 
modeling of the control strategy were December 31, 2025, for the San 
Juan area and December 31, 2029, for the Guayama-Salinas Area. Although 
these attainment dates for the control strategy were identified as 
being as expeditious as practicable given the integration of renewable 
energy sources, they provide for attainment of the standard after the 
CAA mandatory attainment date of April 9, 2023. Thus, based on the 
PRDNER's own modeling of its control strategy, and unless that control 
strategy was implemented in a more expeditious manner than originally 
planned, the control strategy did not provide for attainment by the 
statutory deadline.
    Additionally, the EPA notes that the Round 3 designation modeling 
\26\ showed modeled concentrations well in exceedance of the standard 
within the San Juan and Guayama-Salinas areas, therefore requiring 
significant measures to be implemented to reduce such concentrations. 
Since it is the EPA's understanding that the emissions controls 
necessary to achieve attainment of the standard were not implemented 
(as further discussed in Section III.C.3 of this notice), the EPA 
proposes to find that attainment of the standard was not provided by 
the mandatory attainment date.
---------------------------------------------------------------------------

    \26\ The San Juan and Guayama-Salinas areas were designated 
nonattainment based on Puerto Rico's modeling, which indicated that 
the highest predicted 99th percentile daily maximum 1-hour 
concentration (i.e., modeled concentration) within the chosen 
modeling domain to be 422 [mu]g/m\3\ (equivalent to 161 ppb) for the 
San Juan area and 252 [mu]g/m\3\ (equivalent to 96 ppb) for the 
Guayama-Salinas area. These modeled concentrations, which are above 
the NAAQS level of 196.4 [mu]g/m\3\ (equivalent to the 2010 
SO<INF>2</INF> NAAQS of 75 ppb reflecting a 2.619 [mu]g/m\3\ 
conversion factor), were based on actual emissions from the 
facilities. The TSD for the Round 3 designations is found within the 
docket for this rulemaking.
---------------------------------------------------------------------------

3. Failure To Implement the Control Strategy
    As of the time of signature of this proposed rulemaking, the EPA 
has no evidence indicating that the control strategy identified by the 
PRDNER and adopted within the RCAP in support of its November 22, 2022 
SIP submission has in fact been implemented. Instead, available 
evidence indicates that the strategy has not yet been implemented, and 
that therefore, emissions reductions expected under the strategy have 
not yet been achieved. Although not federally SIP-approved, this 
absence of strategy implementation is considered as part of EPA's 
weight of evidence analysis.
    The control strategy under the PRDNER's SIP submission is based on 
the retirement of emission units and the implementation of emission 
limits based on the use of ULSD or LNG for units that will continue to 
operate and generate electricity at the PREPA San Juan, PREPA Aguirre, 
and PREPA Palo Seco facilities. As previously noted, the control 
strategy was to begin in February 2023, specifically involving the 
transition of several units to ULSD. The PREPA unit retirements were to 
occur in phases--from June 30, 2023, through December 31, 2025, at 
PREPA San Juan and PREPA Palo Seco, and from December 31, 2025, through 
December 31, 2029, at PREPA Aguirre.
    At PREPA Palo Seco and PREPA Palo San Juan, several boilers were 
required

[[Page 79835]]

to retire by June 30, 2023. Specifically, at PREPA Palo Seco, Boiler 1, 
Boiler 2, Power Block 2-2, Power Block 3-1, and Power Block 3-2 had a 
retirement compliance date of June 30, 2023. At PREPA San Juan, Boiler 
7, Boiler 8, and Boiler 10 were required to retire by June 30, 2023. 
Additional retirements are required at PREPA Palo Seco by December 31, 
2025 (i.e., Boiler 4), and PREPA San Juan by December 31, 2024 (i.e., 
Boiler 9). PREPA Aguirre units are scheduled to retire beginning 
December 31, 2025, through December 31, 2029.\27\
---------------------------------------------------------------------------

    \27\ Refer to Table 7. PREPA Aguirre SO<INF>2</INF> Emission 
Limits under Section V, ``Review of Modeled Attainment 
Demonstration'' of this rulemaking for more detailed information 
regarding the specific units scheduled to retire from December 31, 
2025, through December 31, 2029.
---------------------------------------------------------------------------

    A more detailed discussion of the retirement of emission units and 
the implementation of emission limits for units that will remain in 
operation at the PREPA San Juan, PREPA Aguirre, and PREPA Palo Seco 
facilities can be found under Section V, ``Review of Modeled Attainment 
Demonstration,'' subsection G, of this proposed rulemaking.
    As mentioned previously in Section I, ``Background,'' of this 
notice, the compliance strategy for Puerto Rico's SIP was developed 
based on the most recent IRP approved by the PREB in 2020, as well as 
additional updates provided by the PREB in 2022, which considered 
emission unit retirements within the San Juan and Guayama-Salinas NAAs 
following the integration of renewable energy sources and battery 
storage resources. It is the EPA's understanding that the integration 
of renewable energy sources has been delayed, including the deployment 
of solar projects under Tranche 1, due to renegotiations and legal 
challenges pertaining to the use of the land identified for 
development.\28\ Tranche 1 was expected to provide at least 1,000 MW 
solar PV (or energy-equivalent other renewables) and at least 500 MW 
(2,000 MWh or equivalent) battery energy storage; \29\ however, its 
delayed implementation has impacted the PREPA's ability to retire units 
in accordance with the submitted SIP control strategy since other means 
of providing electricity to citizens of the areas is not sufficient.
---------------------------------------------------------------------------

    \28\ See Section 6.2, ``Inputs and Assumptions'' of the ``Puerto 
Rico Grid Resilience and Transitions to 100% Renewable Energy Study 
(PR100)'' provided within the docket for this rulemaking.
    \29\ See ] 860 of the ``Final Resolution and Order on the 
PREPA's IRP'' included within the docket for this rulemaking.
---------------------------------------------------------------------------

    The transition to renewable energy, which will allow the retirement 
of units at PREPA San Juan, PREPA Aguirre, and PREPA Palo Seco, has an 
uncertain timeline. As indicated previously, the IRP was scheduled to 
be revised and submitted to the PREB in June 2024 by LUMA, but that 
process has been delayed to November 29, 2024. The EPA anticipates that 
a new IRP \30\ will provide an updated schedule for emission unit 
retirements and the integration of renewable energy. Moreover, under 
the current IRP,\31\ PREPA will retire units ``based on the 
installation schedule and location of new peaking generation, new solar 
PV, and energy storage resources to address overall and local resource 
adequacy.'' Accordingly, the retirement sequence of the existing PREPA 
units is contingent on the timing, amount, and location of replacement 
generation, which will further complicate Puerto Rico's ability to 
ensure that retirements of emission units occur as provided within its 
submitted control strategy timeline.
---------------------------------------------------------------------------

    \30\ Due to the complexity and coordination required between 
stakeholders such as the PREPA, the PREB, and LUMA, it is 
anticipated that a revised IRP will not be finalized until late 2026 
or 2027 at this point in time.
    \31\ See ] 870-873 of the ``Final Resolution and Order on the 
PREPA's IRP.''
---------------------------------------------------------------------------

    The delay in implementing the submitted control strategy and the 
extended timeline and uncertainty for transitioning to renewable energy 
projects serve as additional evidence that Puerto Rico has not met, and 
has fallen well behind, the statutorily required attainment date of 
April 9, 2023. Moreover, given that the modeling submitted by PRDNER 
did not anticipate the areas would attain the NAAQS until well beyond 
the statutory April 9, 2023 attainment date, the EPA proposes to find 
that attainment of the standard did not occur by the statutory 
attainment date of April 9, 2023.
4. SO<INF>2</INF> Emissions Data
    The EPA has compiled information from its Emission Inventory System 
(EIS) that details total SO<INF>2</INF> emissions from 2020-2022 across 
the three PREPA facilities.\32\ The Emissions Inventory System (EIS) 
Gateway was developed to provide registered EPA, state, local, and 
Tribal users with access to emissions inventory data.\33\ The EIS helps 
the EPA to build the National Emissions Inventory (NEI). Additionally, 
the EIS Gateway allows users to manage their profile information to 
add, view, and edit facility inventory information for their agency; 
extract data by running reports; and access reporting codes. Hourly and 
monthly data are not available in the EIS Gateway, so the EPA will 
utilize annual emissions from 2020-2022 at the three PREPA facilities 
within the discussion regarding annual emission trends in the NAAs 
since the designations. That information is as follows:
---------------------------------------------------------------------------

    \32\ 2021 and 2022 data are preliminary and will be finalized 
upon release of the 2023 NEI. The 2023 NEI inventory year is in 
progress and will not be published until March 2026. See https://www.epa.gov/air-emissions-inventories/2023-national-emissions-inventory-nei-documentation.
    \33\ For more information on EIS, refer to https://www.epa.gov/air-emissions-inventories/emissions-inventory-system-eis-gateway.

              Table 3--Facility-Wide SO2 Emissions of Point Sources in the NAAs From 2020-2022 \34\
----------------------------------------------------------------------------------------------------------------
                                                                     2020 SO2        2021 SO2        2022 SO2
                                                                     emissions       emissions       emissions
        Stationary point source            Nonattainment area        (tons per       (tons per       (tons per
                                                                       year)           year)           year)
----------------------------------------------------------------------------------------------------------------
PREPA San Juan........................  San Juan................           3,257           1,369           2,740
PREPA Palo Seco.......................  San Juan................           5,272           4,322           4,488
PREPA Aguirre.........................  Guayama-Salinas.........           8,829           8,164           5,434
----------------------------------------------------------------------------------------------------------------
\34\ 2021 and 2022 data are preliminary and will be finalized upon release of the 2023 NEI.

    The PREPA San Juan facility emitted 3,257 tons of SO<INF>2</INF> in 
2020, 1,369 tons of SO<INF>2</INF> in 2021, and 2,740 tons of 
SO<INF>2</INF> in 2022. The PREPA Palo Seco facility emitted 5,272 tons 
of SO<INF>2</INF> in 2020, 4,322 tons of SO<INF>2</INF> in 2021, and 
4,488 tons of SO<INF>2</INF> in 2022. Finally, the PREPA Aguirre 
facility emitted 8,829 tons of SO<INF>2</INF> in 2020, 8,164 tons of 
SO<INF>2</INF> in 2021, and 5,434 tons of SO<INF>2</INF> in 2022.

[[Page 79836]]



                Table 4--Facility-Wide SO2 Emissions of Point Sources in the NAAs From 2013-2015
----------------------------------------------------------------------------------------------------------------
                                                                     2013 SO2        2014 SO2        2015 SO2
                                                                     emissions       emissions       emissions
        Stationary point source            Nonattainment area        (tons per       (tons per       (tons per
                                                                       year)           year)           year)
----------------------------------------------------------------------------------------------------------------
PREPA San Juan........................  San Juan................           5,307           5,135           6,063
PREPA Palo Seco.......................  San Juan................           5,700           3,128           2,979
PREPA Aguirre.........................  Guayama-Salinas.........           9,640           9,261           9,585
----------------------------------------------------------------------------------------------------------------

    Notably, as provided within the Round 3 designations,\35\ Table 4 
indicates that SO<INF>2</INF> emissions were: (1) 5,307 tons in 2013, 
5,135 tons in 2014, and 6,063 tons in 2015 for PREPA San Juan; (2) 
5,700 tons in 2013, 3,128 tons in 2014, and 2,979 tons in 2015 for 
PREPA Palo Seco; and (3) 9,640 tons in 2013, 9,261 tons in 2014, and 
9,585 tons in 2015 for the PREPA Aguirre facility.
---------------------------------------------------------------------------

    \35\ Modeling of the 2013-2015 emissions data, which showed that 
the San Juan and Guayama-Salinas areas did not meet the 2010 
SO<INF>2</INF> NAAQS, was a basis for the nonattainment designation.
---------------------------------------------------------------------------

    While there has been a decrease in emissions at the PREPA San Juan 
and PREPA Aguirre facilities, it is important to note that the 
thousands of tons of SO<INF>2</INF> emitted by these facilities from 
2020 to 2022 are significant. Notably, although emissions at PREPA Palo 
Seco appear to have decreased from 2013 through 2015, emissions 
increased at the facility from 2015 to 2020. It is the EPA's 
understanding, based on the air quality dispersion modeling the PRDNER 
provided in its attainment modeling for its SO<INF>2</INF> plan, that 
SO<INF>2</INF> emissions from the three PREPA facilities would need to 
significantly decrease in order to provide for attainment of the 
SO<INF>2</INF> standard. The PRDNER projected that SO<INF>2</INF> 
emissions would be 43 tons per year (tpy) at PREPA San Juan and 12 tpy 
at PREPA Palo Seco by the PRDNER-projected attainment date of December 
31, 2025, as well as 4 tpy at PREPA Aguirre by the PRDNER-projected 
attainment date of December 31, 2029.\36\ In contrast, the 
SO<INF>2</INF> emissions listed in Table 3 are significantly higher 
than the emissions for which the PRDNER modeled to provide attainment. 
Thus, since the EPA was unable to conduct its own additional air 
quality dispersion modeling, the EPA has no evidence indicating that 
the SO<INF>2</INF> emissions at the facilities from 2020-2022 would 
provide for attainment of the 2010 1-hour primary SO<INF>2</INF> NAAQS 
by the statutory attainment date.
---------------------------------------------------------------------------

    \36\ The PRDNER's modeling results under the Attainment 
Demonstration provided in its November 22, 2022 SIP submission 
indicated that these emissions would result in a modeled 
concentration of 47.518 [mu]g/m\3\ for the San Juan NAA and 47.191 
[mu]g/m\3\ for the Guayama-Salinas NAA. These concentrations are 
below what would be required for the NAAs to attain the 2010 
SO<INF>2</INF> standard. For additional information on the projected 
emissions at the PREPA facilities, see Table 11, ``Projected 
Stationary Point Source SO<INF>2</INF> Emissions for 2019-2029'' 
under Section VI, subsection A, ``Emissions Inventory,'' within this 
proposed rulemaking.
---------------------------------------------------------------------------

    The EPA's emissions assessment focused specifically on the three 
PREPA sources: PREPA San Juan, PREPA Palo Seco, and PREPA Aguirre. 
These sources were significantly larger in terms of emissions compared 
to smaller and more distant sources like Bacardi, Edelcar, and Applied 
Energy System (AES). As a result, the smaller emissions from these 
distant sources were dwarfed by the impact of the explicitly modeled 
PREPA sources.\37\ For example, AES emitted 245 tons of SO<INF>2</INF> 
in 2014. The EPA's conclusion was based on this consideration, ensuring 
that the emissions assessment accurately reflected the most relevant 
contributors to air quality in the vicinity.
---------------------------------------------------------------------------

    \37\ As discussed within Section V.B., ``Area of Analysis,'' 
within this notice, based on the magnitude of emissions and distance 
relative to the NAAs, the EPA concluded that the smaller and more 
distant sources were adequately represented in the monitored ambient 
background concentrations. The EPA concluded that these sources were 
not expected to have their maximum impacts in the vicinity of PREPA 
San Juan, PREPA Palo Seco, and PREPA Aguirre.
---------------------------------------------------------------------------

    Consequently, the EPA proposes to find that emissions from the 
PREPA San Juan, PREPA Palo Seco, and PREPA Aguirre facilities continue 
to be significant and provide additional evidence that the San Juan and 
Guayama-Salinas areas have not attained the 2010 1-hour primary 
SO<INF>2</INF> NAAQS by the statutory attainment date of April 9, 2023.
5. The Weight-of-Evidence Analysis Conclusions and the EPA's Proposed 
Determination
    The determination of failure to attain for the San Juan and 
Guayama-Salinas NAAs is based on a control strategy timeline that does 
not provide for attainment by the statutorily required attainment date, 
Puerto Rico's failure to implement its adopted control strategy in a 
timely manner, and the EPA's review of annual facility-wide emissions 
data from January 2020 through December 2022 for the PREPA San Juan, 
PREPA Palo Seco, and PREPA Aguirre facilities.
    As discussed in this notice, Puerto Rico's control strategy is 
deficient in providing for attainment by the mandatory attainment date. 
It provided for attainment after the statutory date and it failed to 
practicably account for the feasibility of retiring relevant emission 
units, resulting in its failure to be timely implemented. The EPA's 
assessment of the air quality dispersion modeling that the PRDNER 
provided in its November 22, 2022 SIP submittal provides further 
support for this determination. Moreover, due to its inability to 
obtain valid design values from SO<INF>2</INF> monitors in the San Juan 
and Guayama-Salinas areas, the EPA did not utilize monitoring data as 
the basis for this determination. The EPA obtained facility-wide 
SO<INF>2</INF> emissions from 2020-2022 at PREPA San Juan, PREPA Palo 
Seco, and PREPA Aguirre. This emissions data demonstrates that 
emissions from the three PREPA facilities continue to be significant 
and there is no evidence that they provide for attainment of the 
standard.
    The EPA proposes to find that this weight-of-evidence analysis is 
sufficient to demonstrate that the San Juan and Guayama-Salinas area 
failed to attain the standard by the mandatory attainment date. The EPA 
therefore proposes to find under CAA section 179(c)(1) that the San 
Juan and Guayama-Salinas NAAs failed to attain the 1-hour 
SO<INF>2</INF> NAAQS by the required attainment date of April 9, 2023.

D. Consequences for SO<INF>2</INF> NAAs Failing To Attain Standards by 
Attainment Date

    The consequences for SO<INF>2</INF> NAAs failing to attain the 
standards by the applicable attainment date are set forth in CAA 
section 179(d). Under section 179(d), a state must submit a SIP 
revision for the area meeting the requirements of CAA sections 110 and 
172, the latter of which requires, among other elements, a 
demonstration of attainment, an NNSR program, the base year emissions 
inventory, the requirements for meeting RFP, RACM/RACT, and contingency 
measures. In addition, under CAA section 179(d)(2), the SIP revision 
must include such additional measures as the EPA may reasonably 
prescribe, including all

[[Page 79837]]

measures that can be feasibly implemented in the area, in light of 
technological achievability, costs, and any non-air quality and other 
air quality-related health and environmental impacts.
    In this case, the primary sources of SO<INF>2</INF> emissions in 
the San Juan and Guayama-Salinas NAAs are the PREPA San Juan, PREPA 
Palo Seco, and PREPA Aguirre facilities. The EPA anticipates that the 
PRDNER will collect relevant information on the control measures 
necessary to achieve attainment by the required attainment date, as 
part of its development of the SIP revision triggered by a final FFA. 
The state (or commonwealth) is required to submit the SIP revision 
within one year after the EPA publishes a final action in the Federal 
Register determining that the NAA failed to attain the SO<INF>2</INF> 
NAAQS.
    With this proposed rulemaking, the EPA is also proposing to approve 
certain elements of the 2010 SO<INF>2</INF> attainment plans for the 
San Juan and Guayama-Salinas NAAs, as submitted on November 22, 2022, 
for compliance with the CAA and for SIP-strengthening purposes. 
Specifically, the EPA is proposing to approve Puerto Rico's NNSR 
program and the base year emissions inventory for compliance with the 
CAA; as well as proposing to approve, in part, and conditionally 
approve, in part, amendments to Puerto Rico's RCAP for SIP-
strengthening purposes. The EPA will not act on Puerto Rico's 
previously submitted demonstration of attainment, RACM/RACT, RFP, 
emission limitations as necessary to provide for attainment, and 
contingency measures, since these elements will be addressed in the 
subsequent submittal as a result of the FFA, should it become final.
    Under CAA sections 179(d)(3) and 172(a)(2), the new attainment date 
for each NAA is the date by which attainment can be achieved as 
expeditiously as practicable, but no later than five years after the 
EPA publishes a final action in the Federal Register determining that 
the NAA failed to attain the SO<INF>2</INF> NAAQS by the applicable 
attainment date.

IV. Requirements for SO2 Nonattainment Area Plans

    Nonattainment plans for SO<INF>2</INF> must meet the applicable 
requirements of the CAA, specifically CAA sections 110, 172, 191, and 
192. The EPA's regulations governing nonattainment SIP submissions are 
set forth in 40 CFR part 51, with specific procedural requirements and 
control strategy requirements codified at subparts F and G, 
respectively. Soon after Congress enacted the 1990 Amendments to the 
CAA, the EPA issued comprehensive guidance on SIP revisions in the 
``General Preamble for the Implementation of Title I of the Clean Air 
Act Amendments of 1990'' (``General Preamble'').\38\ Among other 
things, the General Preamble addressed SO<INF>2</INF> SIP submissions 
and fundamental principles for SIP control strategies.\39\ On April 23, 
2014, the EPA issued recommended guidance for meeting the statutory 
requirements in SO<INF>2</INF> SIP submissions in a document entitled, 
``Guidance for 1-Hour SO<INF>2</INF> Nonattainment Area SIP 
Submissions'' (``2014 SO<INF>2</INF> Guidance'').\40\
---------------------------------------------------------------------------

    \38\ 57 FR 13498 (April 16, 1992).
    \39\ Id. at 13548-13549, 13567-13568.
    \40\ See https://www.epa.gov/sites/default/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf.
---------------------------------------------------------------------------

    In the 2014 SO<INF>2</INF> Guidance, the EPA described the 
statutory requirements of CAA section 172(c) for a complete 
nonattainment plan, including: an accurate emissions inventory of 
current emissions for all sources of SO<INF>2</INF> within the NAA; an 
attainment demonstration; a demonstration of RFP; implementation of 
RACM (including RACT); new source review; enforceable emission 
limitations and control measures; and adequate contingency measures for 
the affected area.
    For the EPA to fully approve a SIP revision which meets the 
requirements of CAA sections 110, 172, 191, and 192, and the EPA's 
regulations at 40 CFR part 51, the plan for an affected area must 
demonstrate to the EPA's satisfaction that each of the aforementioned 
requirements has been met. Under CAA section 110(l), the EPA may not 
approve a plan that would interfere with any applicable requirement 
concerning NAAQS attainment and RFP, or any other applicable 
requirement. Under CAA section 193, no requirement in effect (or 
required to be adopted by an order, settlement, agreement, or plan in 
effect before November 15, 1990) within any area that is nonattainment 
for any of the NAAQS may be modified in any manner unless it ensures 
equivalent or greater emission reductions of such air pollutant.
    Sections 172(c)(1) and 172(c)(6) of the CAA direct states and 
territories with areas designated as nonattainment to demonstrate that 
the submitted plan, and the emissions limitations and control measures 
in it, provide for attainment of the NAAQS. 40 CFR part 51, subpart G 
further delineates the control strategy requirements that plans must 
meet, and the EPA has long required that all SIPs and control 
strategies reflect four fundamental principles of quantification, 
enforceability, replicability, and accountability.\41\ SO<INF>2</INF> 
nonattainment plans must consist of two components: (1) emission limits 
and other control measures that ensure implementation of permanent, 
enforceable, and necessary emission controls, and (2) a modeling 
analysis that meets the requirements of 40 CFR part 51, Appendix W and 
demonstrates that these emission limits and control measures provide 
for timely attainment of the primary SO<INF>2</INF> NAAQS as 
expeditiously as practicable, but no later than the attainment date for 
the affected area. In cases where the necessary emission limits have 
not previously been made a part of the state's SIP or have not 
otherwise become federally enforceable, the plan must include the 
necessary enforceable limits in an adopted form suitable for 
incorporation into the SIP in order for the plan to be approved by the 
EPA. In all cases, the emission limits and control measures must be 
accompanied by appropriate methods and conditions to determine 
compliance with the respective emission limits and control measures and 
must be quantifiable (i.e., a specific amount of emission reduction can 
be ascribed to the measures), fully enforceable (i.e., specifying 
clear, unambiguous, and measurable requirements for which compliance 
can be practicably determined), replicable (i.e., the procedures for 
determining compliance are sufficiently specific and objective so that 
two independent entities applying the procedures would obtain the same 
result), and accountable (i.e., source-specific limits must be 
permanent and must reflect the assumptions used in the SIP 
demonstrations).
---------------------------------------------------------------------------

    \41\ 57 FR at 13567-13568.
---------------------------------------------------------------------------

    The EPA's 2014 SO<INF>2</INF> Guidance recommends that emission 
limits be expressed as short-term average limits not to exceed the 
averaging time for the applicable NAAQS that the limit is intended to 
help maintain (e.g., addressing emissions averaged over one or three 
hours), but it also describes the option to utilize emission limits 
with longer averaging times of up to 30 days, so long as the state/
commonwealth meets various suggested criteria.\42\ The 2014 
SO<INF>2</INF> Guidance recommends that, should states/territories and 
sources utilize longer averaging times (such as 30 days), the longer-
term average limit should be set at an adjusted level that reflects a 
stringency comparable to the 1-hour average limit at the critical 
emission value shown to provide

[[Page 79838]]

attainment. Additional discussion of EPA's rationale for approving 
longer-term average limits in selected cases has been provided in 
several notices of proposed rulemaking. Examples include the Pekin, 
Illinois area,\43\ the Steubenville, Ohio-West Virginia area,\44\ and 
the Central New Hampshire area.\45\
---------------------------------------------------------------------------

    \42\ 2014 SO<INF>2</INF> Guidance, at 22-39.
    \43\ 82 FR 46434 (Oct. 5, 2017).
    \44\ 84 FR 29456 (June 24, 2019).
    \45\ 82 FR 45242 (Sept. 28, 2017).
---------------------------------------------------------------------------

    Preferred air quality models for use in regulatory applications are 
described in Appendix A of the EPA's ``Guideline on Air Quality 
Models'' (40 CFR part 51, Appendix W (``Appendix W'')).\46\ In general, 
nonattainment SIP submissions must demonstrate the adequacy of the 
selected control strategy using the applicable air quality model 
designated in Appendix W.\47\ However, where an air quality model 
specified in Appendix W is inappropriate for the particular 
application, the model may be modified or another model substituted, if 
the EPA approves of the modification or substitution.\48\ In 2005, the 
EPA promulgated the American Meteorological Society/Environmental 
Protection Agency Regulatory Model (AERMOD \49\) as the Agency's 
preferred near-field dispersion model for a wide range of regulatory 
applications addressing stationary sources (e.g., in estimating 
SO<INF>2</INF> concentrations) in all types of terrain based on an 
extensive developmental and performance evaluation. Supplemental 
guidance on modeling for purposes of demonstrating attainment of the 
SO<INF>2</INF> standard is provided in Appendix A of the 2014 
SO<INF>2</INF> Guidance.
---------------------------------------------------------------------------

    \46\ The EPA published revisions to Appendix W on January 17, 
2017, 82 FR 5182.
    \47\ 40 CFR 51.112(a)(1).
    \48\ 40 CFR 51.112(a)(2); Appendix W, section 3.2.
    \49\ See https://www.epa.gov/scram/air-quality-dispersion-modeling-preferred-and-recommended-models#aermod.
---------------------------------------------------------------------------

    Appendix A of the April 23, 2014, Guidance for 1-Hour 
SO<INF>2</INF> Nonattainment Area SIP Submissions provides extensive 
guidance on the modeling domain, the source inputs, assorted types of 
meteorological data, and background concentrations. Consistency with 
the recommendations in the 2014 SO<INF>2</INF> Guidance is generally 
necessary for the attainment demonstration to offer adequately reliable 
assurance that the plan provides for attainment.
    As stated previously, attainment demonstrations for the 2010 1-hour 
primary SO<INF>2</INF> NAAQS must demonstrate future attainment and 
maintenance of the NAAQS in the entire area designated as nonattainment 
(i.e., not just at the violating monitor) by using air quality 
dispersion modeling (see Appendix W) to show that the mix of sources 
and enforceable control measures and emission rates in an identified 
area will not lead to a violation of the SO<INF>2</INF> NAAQS. For the 
short-term (i.e., 1-hour) standard, the EPA believes that dispersion 
modeling, using allowable emissions and addressing stationary sources 
in the affected area (and in some cases those sources located outside 
the NAA that may affect attainment in the area) is technically 
appropriate. This approach is also efficient and effective in 
demonstrating attainment in NAAs because it takes into consideration 
combinations of meteorological and source operating conditions that may 
contribute to peak ground-level concentrations of SO<INF>2</INF>.
    The meteorological data used in the analysis should generally be 
processed with the most recent version of AERMET, which is the 
meteorological data preprocessor for AERMOD. Estimated concentrations 
should include ambient background concentrations, follow the form of 
the standard, and be calculated as described in the EPA's August 23, 
2010 clarification memorandum.\50\
---------------------------------------------------------------------------

    \50\ See ``Applicability of Appendix W Modeling Guidance for the 
1-hr SO<INF>2</INF> National Ambient Air Quality Standard'' (August 
23, 2010), available at https://www3.epa.gov/ttn/naaqs/aqmguide/collection/cp2/20100823_page_1-hr_so2_naaqs_psd_program.pdf.
---------------------------------------------------------------------------

V. Review of Modeled Attainment Demonstration

    The EPA is not at this time proposing action on the attainment 
demonstration submitted by the PRDNER that aims to provide for 
attainment of the 2010 SO<INF>2</INF> NAAQS. However, the following 
discussion addresses various features of the modeling that the PRDNER 
used in its submitted attainment demonstration for the San Juan and 
Guayama-Salinas NAAs. This discussion may be useful for the PRDNER as 
it continues its efforts. Additionally, the modeling was considered by 
the EPA in part of the weight-of-evidence analysis for the FFA. The EPA 
anticipates acting on an updated attainment demonstration in a future 
SIP submission.

A. Modeling Approach

    The PRDNER's submitted attainment demonstration utilized the EPA's 
preferred model, version 21112 of AERMOD, with default options. Version 
21112 of AERMOD was the most recent version at the time the attainment 
demonstration modeling was conducted; however, since then, version 
23132 of AERMOD has become the regulatory model version. There were no 
updates from version 21112 to version 23132 that would significantly 
affect the SO<INF>2</INF> concentrations predicted here. Therefore, for 
its own purposes, the EPA does not consider the model selection to have 
been inappropriate. However, in a future SIP submission, the EPA 
expects that the PRDNER would use the version of the model that is 
current at the time of the analysis.
    The PRDNER examined land use within three kilometers of the 
facilities in the two NAAs using the Auer technique, which is a 
technique in section 7.2.1.1 of Appendix W for establishing if an area 
should be modeled as either an urban or rural source. It was determined 
by PRDNER that San Juan should be modeled with urban dispersion 
characteristics and Guayama-Salinas should be modeled with rural 
dispersion characteristics. The EPA has reviewed the maps and images 
provided by the PRDNER and expects that it would be reasonable for the 
PRDNER to use these characteristics in future modeling.

B. Area of Analysis

    The PRDNER accounted for SO<INF>2</INF> impacts in the modeling 
domain through the inclusion of measured background levels and 
explicitly modeled emission sources. In the San Juan NAA, the PRDNER 
included the largest SO<INF>2</INF> sources in the modeling-PREPA San 
Juan and PREPA Palo Seco. The impact from other sources of 
SO<INF>2</INF> in the San Juan NAA (contributions from Bacardi U.S.A., 
Inc. (200 PR-165 Cata[ntilde]o, 00962), Edelcar Inc. (CVMQ+FGQ, Calle 
B, Guaynabo, 00965), and other minor and distant sources), are included 
in the background monitored concentrations, which are added to the 
concentrations from the explicitly modeled sources. In the Guayama-
Salinas NAA, the PRDNER included the largest SO<INF>2</INF> source in 
the modeling-PREPA Aguirre (State Road No. 3, Int. 705, Salinas, 
00751). The impact from the other sources of SO<INF>2</INF> in the 
Guayama-Salinas NAA (i.e., Applied Energy System (AES) Puerto Rico, LP 
(PR-3 Km. 142.0, Jobos Ward, Guayama, 00784) and other minor and 
distant sources) are included in the background monitored 
concentrations, which are also added to the concentration from the 
explicitly modeled sources.
    The PRDNER modeled sources in the NAAs (i.e., PREPA San Juan, PREPA 
Palo Seco, and PREPA Aguirre) that could cause or contribute to a NAAQS 
violation. The impacts of emissions of SO<INF>2</INF> from smaller and 
distant sources are represented by background monitored concentrations 
(such as

[[Page 79839]]

Bacardi, Edelcar, and AES). These emissions were dwarfed by emissions 
from the three much larger PREPA sources and would not be expected to 
have their maximum impacts in the vicinity of the sources of 
interest.\51\ However, they may have a smaller impact, which is 
measured at the ambient monitor and added to the modeled concentration. 
For instance, AES, which is situated in Jobos and within close 
proximity to PREPA Aguirre (i.e., less than 5 kilometers away), is a 
relatively small source of SO<INF>2</INF> emissions when compared to 
the PREPA facility. In 2014,\52\ AES emitted 245 tons of 
SO<INF>2</INF>, whereas PREPA Aguirre released a significantly larger 
amount of 9,261 tons of SO<INF>2</INF> during the same period. Further, 
AES is approximately 8.5 kilometers east of PREPA Aguirre and less than 
5 kilometers upwind of the Guayama background monitor. Thus, the AES 
concentration in the area of PREPA Aguirre is captured by the measured 
ambient background monitored concentration and added to PREPA Aguirre's 
maximum modeled concentration for a total air quality SO<INF>2</INF> 
concentration in the area.\53\
---------------------------------------------------------------------------

    \51\ When considering other sources to include in the modeling 
(other than those that are driving the nonattainment), Appendix W in 
section 8.3.3.b states that all sources expected to cause a 
significant concentration gradient in the vicinity of the source of 
interest should be explicitly modeled and that the number of such 
sources is expected to be small except in unusual cases.
    \52\ Data from 2014 was representative of the emissions data 
that was used for the designations of the SO<INF>2</INF> NAAs in 
Puerto Rico. Furthermore, the PRDNER used 2014 as the base year for 
emissions inventory preparation. The base year inventory establishes 
a baseline that is used to evaluate emission reductions achieved by 
the control strategy.
    \53\ See the Technical Support Document, Chapter 36, Final Round 
3 Area designations for the 2010 1-Hour SO<INF>2</INF> Primary 
National Ambient Air Quality Standard for Puerto Rico, available at 
https://www.epa.gov/sites/default/files/2017-12/documents/36-pr-so2-rd3-final.pdf.
---------------------------------------------------------------------------

    Based on the magnitude of emissions and distance relative to the 
NAAs, the EPA expects that the smaller and more distant sources would 
not have their maximum impacts in the vicinity of PREPA San Juan, PREPA 
Palo Seco, and PREPA Aguirre. Accordingly, the EPA expects that in 
future modeling, those sources could be adequately represented in the 
monitored ambient background concentrations, and that the PRDNER's 
future attainment demonstration could account for them in this way. 
Additionally, the EPA believes that the background levels could 
reasonably account for other sources influencing air quality within the 
NAAs because data used to develop background levels include hours 
during which those sources may have impacted the monitors. However, the 
EPA acknowledges that conditions pertaining to ambient background level 
concentrations of these smaller and distant sources could be different 
in the future.

C. Receptor Grid

    Within AERMOD, air quality concentration results are calculated at 
discrete locations identified by the user; these locations are called 
receptors. The PRDNER used a coarse grid to determine the maximum 1-
hour SO<INF>2</INF> concentrations and the extent of the significant 
impact area. A denser refined grid was placed around the areas of 
maximum 1-hour concentration and discrete receptors were placed around 
the facility fence lines.
    For the San Juan NAA, a coarse receptor grid with 250-meter spacing 
covers areas with violating receptors and the extent of the significant 
impact area. Two refined 50-meter spacing receptor grids cover the two 
areas with maximum 1-hour SO<INF>2</INF> concentrations around PREPA 
San Juan and PREPA Palo Seco.
    For the Guayama-Salinas NAA, a coarse grid with 1000-meter spacing 
extending out to 50 kilometers from the source is used to determine the 
significant impact area. Two refined 50-meter spacing receptor grids 
cover the area with the maximum 1-hour SO<INF>2</INF> concentration and 
another area approximately five miles northwest of the facility. Beyond 
the 50-meter refined grid around the facility, a 250-meter spacing grid 
is also placed around the facility area to ensure that any significant 
concentrations are identified.
    The EPA expects that the receptor network could be sufficient to 
identify maximum impacts from all the facilities in consideration for 
characterizing the NAAs in the PRDNER's future submission.

D. Meteorological Data

    The PRDNER utilized onsite meteorological data from both the PREPA 
San Juan and PREPA Aguirre meteorological stations, which was collected 
and provided by PREPA. The PRDNER utilized concurrent Upper Air data 
measured at the San Juan National Weather Service located at the San 
Juan Airport. The PRDNER provided confirmation that PREPA collected the 
meteorological data and conducted quality assurance/quality control 
(QA/QC) procedures on the data in accordance with EPA's meteorological 
guidance.\54\ The PRDNER further reviewed the data for relevance and 
quality assurance, as per the EPA's guidelines, prior to processing it 
for use within AERMOD. Since there was one year that satisfied the 
EPA's data completeness requirements, the PRDNER utilized only one year 
of meteorological data from 2013 for the San Juan NAA. In the Guayama-
Salinas NAA, the PRDNER used three years of meteorological data from 
2014-2016, since multiple years of data were available.
---------------------------------------------------------------------------

    \54\ See ``Meteorological Monitoring Guidance for Regulatory 
Modeling Applications'' (Feb. 2000), available at https://www.epa.gov/sites/default/files/2020-10/documents/mmgrma_0.pdf.
---------------------------------------------------------------------------

    The EPA observed that the temperature data at both stations was 
measured at three meters above the rooftop and could be possibly 
influenced by other radiation sources. The concurrent San Juan National 
Weather Service data was used as a substitute only for the temperature 
data. Additionally, since the wind sensor was switched during the data 
collection period, the EPA requested that the PRDNER perform additional 
analysis on the data collected at PREPA Aguirre. The new sensor has a 
higher wind threshold compared to the older sensor. The EPA recommended 
that the PRDNER perform two separate AERMET runs, one with the older 
sensor threshold and another with the new sensor threshold, and then 
combine the files for use in AERMOD. The PRDNER followed this 
recommendation to process the data and used it for the AERMOD runs for 
the Guayama-Salinas NAA.
    The PRDNER used AERMOD's meteorological data preprocessor AERMET 
(version 21112) with the ADJ_U* option (with no turbulence data 
included), and Upper Air meteorological data from the San Juan National 
Weather Service site, to process the data in AERMOD. The PRDNER used 
AERSURFACE (version 20060) using land cover data from the National Land 
Cover Database 200 (NLCD 2001) to estimate the surface characteristics 
(albedo, Bowen ratio, and surface roughness length).

E. Source Characterization

    The EPA also reviewed the PRDNER's source characterization in its 
modeling assessment, including source types, use of accurate stack 
parameters, and inclusion of building dimensions for building downwash. 
The EPA expects that the PRDNER would use these in its future 
submission.

[[Page 79840]]

F. Emissions Data

    The PRDNER used maximum allowable 1-hour emissions from PREPA San 
Juan and PREPA Palo Seco for the San Juan NAA, and from PREPA Aguirre 
for the Guayama-Salinas NAA. The modeling included the certified 
SO<INF>2</INF> emission rates as provided by PREPA. The modeling 
demonstration considers unit retirements at the PREPA facilities as 
discussed in Section V, subsection G below. The PRDNER did not include 
start-up and shut-down emissions in the modeling due to their 
infrequent occurrence of up to 2-3 times a year.

G. Retirements and Emission Limits

    The PRDNER's attainment modeling in both the San Juan and Guayama-
Salinas NAAs is based on the retirement of emission units and the 
implementation of emission limits for units that will remain in 
operation for electricity generation at the PREPA San Juan, PREPA 
Aguirre, and PREPA Palo Seco facilities through requiring fuel 
switching to ULSD (Ultra Low Sulfur Diesel) fuel and LNG (Liquified 
Natural Gas). The PRDNER noted in its SIP narrative and Rule 425 of the 
RCAP that the retirement dates for the plan were provided by the PREB 
based on the projected integration of renewable energy to the 
generation grid.\55\ The PRDNER noted that this compliance strategy is 
consistent with the existing approved IRP, as it considers the addition 
of power generation and emission unit retirements within the PREPA 
fleet.
---------------------------------------------------------------------------

    \55\ The PREB provided a projected schedule for emission unit 
retirements and the integration of new renewable energy and battery 
storage resources via letter to the PRDNER on October 18, 2022, 
which was updated on November 15, 2022. These letters are available 
in the docket of this rulemaking.
---------------------------------------------------------------------------

    Table 5 summarizes the SO<INF>2</INF> emission limits (lb/hr) and/
or other requirements, including fuel to be fired (0.0015% by weight 
(15 ppm) ULSD) and retirements, for emission units at the PREPA Palo 
Seco facility.

              Table 5--PREPA Palo Seco SO2 Emission Limits
------------------------------------------------------------------------
                                  SO2 emission limit
          Emission unit              and/or other       Compliance date
                                     requirements
------------------------------------------------------------------------
Boiler 1........................  Retire............  June 30, 2023
Boiler 2 \56\...................  Retire............  June 30, 2023
Boiler 3........................  Retire............  December 31, 2024
Boiler 4........................  Retire............  December 31, 2025
Power Block 1-1, 1-2............  0.5 lb/hr, ULSD...  February 1, 2023
Power Block 2-1.................  0.5 lb/hr, ULSD...  February 1, 2023
Power Block 2-2 \61\............  Retire............  June 30, 2023
Power Block 3-1.................  Retire............  June 30, 2023
Power Block 3-2 \61\............  Retire............  June 30, 2023
FT8 MobilePac 1.................  0.4 lb/hr, ULSD...  February 1, 2023
FT8 MobilePac 2.................  0.4 lb/hr, ULSD...  February 1, 2023
FT8 MobilePac 3.................  0.4 lb/hr, ULSD...  February 1, 2023
------------------------------------------------------------------------

    Table 6 summarizes the SO<INF>2</INF> emission limits (lb/hr) and/
or other requirements, including fuel to be fired (0.0015% by weight 
(15 ppm) ULSD and 1 gram/100 dscf LNG) and retirements, for emission 
units at the PREPA San Juan facility.
---------------------------------------------------------------------------

    \56\ Palo Seco Boiler 2, Power Block 2-2, and Power Block 3-2 
were permanently shut down and out of service on November 9, 2022 
(to generate netting credits for three MobilePac units in Palo 
Seco).
    \57\ The Gas Turbines SJ 5&6 have been operating as dual-fuel 
units since late 2019. The PRDNER required the units to switch to 
ULSD by February 1, 2023. As of February 1, 2023, the SJ 5&6 
emission units have been subject to a maximum sulfur content of 
0.0015% by weight (15 ppm) (which is equivalent to an SO<INF>2</INF> 
emission rate of 5.1 lb/hr under ULSD firing), as well as a separate 
SO<INF>2</INF> limit of 9.8 lb/hr under LNG firing. As listed in 
Table 2 above, the PRDNER utilized the more conservative rate under 
LNG firing load for the attainment demonstration. More information 
pertaining to this can be reviewed on page 59 of the Modeling 
Protocol included in the docket for this rulemaking.

               Table 6--PREPA San Juan SO2 Emission Limits
------------------------------------------------------------------------
                                  SO2 emission limit
          Emission unit              and/or other       Compliance date
                                     requirements
------------------------------------------------------------------------
Gas Turbines SJ 5 & 6 \57\......  9.8 lb/hr, ULSD/    February 1, 2023
                                   LNG.
Boiler 7........................  Retire............  June 30, 2023
Boiler 8........................  Retire............  June 30, 2023
Boiler 9........................  Retire............  December 31, 2024
Boiler 10.......................  Retire............  June 30, 2023
------------------------------------------------------------------------

    Table 7 summarizes the SO<INF>2</INF> emission limits (lb/hr) and/
or other requirements, including fuel to be fired (0.0015% by weight 
(15 ppm) ULSD) and retirements, for emission units at the PREPA Aguirre 
facility.

               Table 7--PREPA Aguirre SO2 Emission Limits
------------------------------------------------------------------------
                                  SO2 emission limit
          Emission unit              and/or other       Compliance date
                                     requirements
------------------------------------------------------------------------
AG1.............................  Retire............  December 31, 2025
AG2.............................  Retire............  December 31, 2026
Gas Turbine CC1-1HRSG...........  Retire............  December 31, 2028
Gas Turbine CC1-2HRSG...........  Retire............  December 31, 2028
Gas Turbine CC1-3HRSG...........  Retire............  December 31, 2028
Gas Turbine CC1-4HRSG...........  Retire............  December 31, 2029
Gas Turbine CC2-1HRSG...........  Retire............  December 31, 2029
Gas Turbine CC2-3HRSG...........  Retire............  December 31, 2029
------------------------------------------------------------------------

    As indicated earlier in this section, the PRDNER's control strategy 
is based on the retirement of emission units and the implementation of 
emission limits for units that will remain in operation at the PREPA 
San Juan, PREPA Aguirre, and PREPA Palo Seco facilities through 
requiring fuel switching to ULSD and LNG. There is no intention and/or 
indication of an intention to implement longer-term averaging limits 
within the PRDNER's submission, and therefore, no

[[Page 79841]]

discussion regarding longer-term averaging limits is warranted.
    Rule 425 of the RCAP provides requirements for the SO<INF>2</INF> 
plan, including providing emission reductions through an interim 
remedy. Under the ``Interim Plan,'' as detailed within Sections II, 
``Emission Limitations for PREPA San Juan and PREPA Palo Seco'' and 
III, ``Emission Limitations for PREPA Aguirre'' of Rule 425, certain 
emission units located at the PREPA facilities in Palo Seco, San Juan, 
and Aguirre are prohibited from burning any fuel oil above a maximum 
sulfur content of 0.0015 percent by weight (15ppm) after February 1, 
2023. To clarify, while the interim plan requiring ULSD provides for 
significant SO<INF>2</INF> emission reductions, there is no indication 
that the reductions are enough to provide for attainment of the NAAQS.
    The PRDNER has provided a schedule of retirements for the PREPA 
steam generating units based on the integration of renewable energy 
into the system. According to Section II(B) and Section III(B) of Rule 
425, the emission units from the PREPA San Juan, PREPA Palo Seco, and 
PREPA Aguirre facilities shall be retired as early as the dates 
provided in tables 5-7 above, unless an alternative date is authorized 
by the PREB. This alternative date shall be no later than December 31, 
2025, for PREPA San Juan and Palo Seco, and no later than December 31, 
2029, for PREPA Aguirre.\58\ If an alternative date is requested, PREPA 
would be required to submit to the PRDNER a revision to the 
construction and operation emission source permits, a copy of the 
PREB's alternative retirement date authorization, and an explanation 
for the necessity of the alternative date.
---------------------------------------------------------------------------

    \58\ Apart from Palo Seco Boiler 2, Power Block 2-2, and Power 
Block 3-2, the EPA is not aware of any other retirements that have 
been made according to the proposed schedule in the tables herein.
---------------------------------------------------------------------------

    The EPA is not acting on Section II(B) and Section III(B) of Rule 
425 since the EPA anticipates these provisions will be revised 
following the EPA's final action on the FFA, which will require the 
PRDNER to submit a subsequent SIP revision. The EPA further evaluates 
the approvability of Rule 425 within Section VI of the preamble for 
this notice of proposed rulemaking, entitled, ``The EPA's Evaluation of 
Rule 425.''

H. Background Concentrations

    The PRDNER developed background concentrations for the NAAs using 
hourly SO<INF>2</INF> measurements from 2007-2009 at the Guayama 
SO<INF>2</INF> monitor, Air Quality System (AQS) number 72-057-
0009.\59\ Other SO<INF>2</INF> monitors, such as the Cata[ntilde]o (AQS 
ID 72-033-0004) or Bayam[oacute]n (AQS ID 72-021-0010) monitors, are 
likely to be impacted by the PREPA facilities discussed here. This 
would result in double-counting of the impacts from those emissions, 
since the impacts from PREPA are modeled and the measured ambient data 
are added to the modeled impacts for a total concentration, which is 
compared to the NAAQS. The Guayama monitor is representative of the 
regional background and includes impacts from natural and man-made 
sources not explicitly included as sources in the modeling. The PRDNER 
used a design value from 2007-2009, since the more recent monitored 
data was incomplete and did not satisfy the EPA's data completeness 
requirements. The EPA also recommended that for 2007, the PRDNER use 
the maximum daily value of 36 ppb, instead of the 99th percentile 
concentration of 6 ppb, since there were some missing values in the 
second quarter of 2007.
---------------------------------------------------------------------------

    \59\ This SO<INF>2</INF> monitor site closed on January 1, 2023.
---------------------------------------------------------------------------

I. Summary of Results

    Because a new attainment date will be established upon the EPA's 
final determination that the NAAs failed to attain the standard by the 
mandatory attainment date of April 9, 2023, the EPA is not proposing 
action on the attainment demonstration portion of the PRDNER's November 
2022 SIP submission within this rulemaking. Instead, the EPA will 
address the PRDNER's revised attainment demonstration following the SIP 
revision the PRDNER will be required to submit within 12 months of the 
EPA finalizing its determination that the areas failed to attain the 
standard.

VI. Review of Other Plan Requirements

A. Emissions Inventory

    The emissions inventory and source emission rate data for an area 
serve as the foundation for air quality modeling and other analyses 
that enable states/territories to: (1) estimate the degree to which 
different sources within a NAA contribute to violations within the 
affected area, and (2) assess the expected improvement in air quality 
within the NAA as a result of the adoption and implementation of 
control measures. The state/commonwealth must develop and submit to the 
EPA a comprehensive, accurate, and current inventory of actual 
emissions from all sources of SO<INF>2</INF> in each NAA, as well as 
any sources located outside the NAA that may affect attainment in the 
area.\60\
---------------------------------------------------------------------------

    \60\ CAA section 172(c)(3), 42 U.S.C. 7502(c)(3).
---------------------------------------------------------------------------

    The base year inventory establishes a baseline that is used to 
evaluate emission reductions achieved by the control strategy and to 
assess RFP requirements. In its submittal, the PRDNER used 2014 as the 
base year for emissions inventory preparation. 2014 data was used as 
the base year because SO<INF>2</INF> emissions data from this year was 
the most recently completed emissions data available for all sectors in 
the inventory. Data from 2014 was also representative of the emissions 
data that was used for the designations of the two SO<INF>2</INF> NAAs 
in Puerto Rico, which were based on emissions data between 2013 and 
2015.
    The PRDNER considered using 2017 as an emissions base year; 
however, it was determined that 2017 was not a representative year for 
fuel consumption due to the impacts from Hurricanes Irma and Maria. 
These hurricanes caused PREPA power plants, which generate electricity 
via the burning of fossil fuels and are the principal sources 
contributing to nonattainment in the San Juan and Guayama-Salinas 
areas, to be inoperative, or operate at reduced capacity, for several 
months. As a result, the PRDNER estimated that electrical generation 
was below fifty percent of the normal average in the last quarter of 
2017.
    The PRDNER utilized SO<INF>2</INF> actual emissions reported for 
the principal stationary point sources in the San Juan and Guayama-
Salinas NAAs (i.e., PREPA San Juan, PREPA Palo Seco, and PREPA Aguirre 
facilities), which were submitted under the SIP-approved RCAP Rule 410 
(Maximum Sulfur Content in Fuels), and as a permit condition, which 
requires submission of certified annual reports to the PRDNER by PREPA. 
The PRDNER included the emissions calculations used to determine the 
actual SO<INF>2</INF> emissions using reported fuel usage data in its 
SIP submittal.\61\ The 2014 National Emissions Inventory (2014 NEI) was 
used for the other emission inventory sectors.
---------------------------------------------------------------------------

    \61\ Included in the appendix of the Baseline Emission Inventory 
2014.
---------------------------------------------------------------------------

    Table 8 summarizes the 2014 SO<INF>2</INF> base year emission 
inventory by sector for the San Juan NAA.

[[Page 79842]]



                                           Table 8--Base Year SO2 Emissions Inventory for the San Juan SO2 NAA
                                                                     [Tons per year]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        Stationary
                       Year                            Stationary        nonpoint        Stationary    Fuel combustion   Onroad mobile    Nonroad mobile
                                                     point sources       sources      nonpoint events                       sources          sources
--------------------------------------------------------------------------------------------------------------------------------------------------------
2014..............................................           8,262               37               <1               39               33              437
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Table 9 summarizes the 2014 SO<INF>2</INF> base year emission 
inventory by sector for the Guayama-Salinas NAA.

                                       Table 9--Base Year SO2 Emissions Inventory for the Guayama-Salinas SO2 NAA
                                                                     [Tons per year]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        Stationary
                       Year                            Stationary        nonpoint        Stationary    Fuel combustion   Onroad mobile    Nonroad mobile
                                                     point sources       sources      nonpoint events                       sources          sources
--------------------------------------------------------------------------------------------------------------------------------------------------------
2014..............................................           9,261                4                7               <1                3               <1
--------------------------------------------------------------------------------------------------------------------------------------------------------

    As shown in Tables 8 and 9, the majority of SO<INF>2</INF> 
emissions in the 2014 base year inventory can be attributed to the 
stationary point source category. Emissions for this category are 
provided in further detail in Table 10.

   Table 10--Base Year Stationary Point Source SO2 Emissions Inventory
------------------------------------------------------------------------
                                                        Emissions (tons
     Stationary point source      Nonattainment area       per year)
------------------------------------------------------------------------
PREPA Palo Seco.................            San Juan               3,128
PREPA San Juan..................            San Juan               5,135
PREPA Aguirre...................     Guayama-Salinas               9,261
------------------------------------------------------------------------

    A projected attainment year emissions inventory should also be 
included in the SIP submission, according to the 2014 SO<INF>2</INF> 
Guidance. This emissions inventory should include, in a manner 
consistent with the attainment demonstration, estimated emissions for 
all SO<INF>2</INF> sources that were determined to have an impact on 
the affected NAA for the projected attainment year.
    In addition to the 2014 base year inventory of actual emissions, 
the PRDNER's submission included a projected emission inventory for the 
PREPA San Juan, PREPA Palo Seco, and PREPA Aguirre facilities that 
includes allowable emissions from 2019 through 2029. The emissions 
projections represent current permit allowable emissions (2019-2022), 
emissions based on an interim remedy relying on the mandatory use of 
ULSD for certain units starting in February 2023, and emissions that 
provided for attainment of the 1-hour SO<INF>2</INF> NAAQS based on 
their final remedy (i.e., emission unit retirements and fuel switching 
to ULSD or LNG from 2022-2029). Based on the schedule for enforceable 
retirements, the final projected emissions occur through December 31, 
2025, for PREPA Palo Seco and PREPA San Juan, and December 31, 2029, 
for PREPA Aguirre, which extends beyond the April 9, 2023 attainment 
date. The PRDNER did not include an emission inventory for the actual 
2023 attainment deadline year.
    Table 11 summarizes the PRDNER's projected emissions for the PREPA 
San Juan, PREPA Palo Seco, and PREPA Aguirre facilities for 2019-2029.

                     Table 11--Projected Stationary Point Source SO2 Emissions for 2019-2029
                                                 [Tons per year]
----------------------------------------------------------------------------------------------------------------
                                                  Base potential    Interim PTE                    Change (base
             Stationary point source               to emit (PTE)      (2023)         Final PTE       to final)
----------------------------------------------------------------------------------------------------------------
PREPA Palo Seco.................................          17,157          11,013              12         -17,145
PREPA San Juan..................................          10,215           9,496              43         -10,172
PREPA Aguirre...................................          31,246          19,199               4         -31,242
----------------------------------------------------------------------------------------------------------------

    The EPA has evaluated the PRDNER's 2014 base year inventory and the 
2019-2029 projection year inventory. The EPA proposes to find the base 
year inventory and the methodologies used for its development 
consistent with the EPA's guidance. As a result, the EPA is proposing 
to determine that the San Juan and Guayama-Salinas SO<INF>2</INF> 
nonattainment plan meets the requirements of CAA section 172(c)(3) for 
the San Juan and Guayama-Salinas SO<INF>2</INF> NAAs for its 2014 base 
year inventory.
    As previously stated, the projected emissions inventory includes 
estimated emissions for SO<INF>2</INF> emission sources for a projected 
attainment year that extends beyond the CAA mandatory attainment date 
of April 9, 2023. That said, since a new attainment date will be

[[Page 79843]]

established following the EPA's final determination that the areas 
failed to attain the standard, the PRDNER will be expected to update 
the projection year emissions inventory in its subsequent SIP revision. 
The subsequent SIP revision will be required to be submitted within 12 
months of a final determination on the EPA's proposed determination, in 
accordance with CAA section 179(d). Consequently, the EPA is not 
proposing action on the projection year emissions inventory in this 
rulemaking.

B. RACM and RACT and Enforceable Emission Limitations and Control 
Measures

    CAA section 172(c)(1) states that nonattainment plans should 
``provide for the implementation of all reasonably available control 
measures as expeditiously as practicable (including such reductions in 
emissions from existing sources in the area as may be obtained through 
the adoption, at a minimum, of reasonably available control technology) 
and shall provide for attainment of the national primary ambient air 
quality standards.'' CAA section 172(c)(6) requires plans to ``include 
enforceable emissions limitations, and such other control measures [. . 
.] as may be necessary or appropriate to provide for attainment of [the 
NAAQS].''
    The necessary emissions limitations or other control measures in 
the PRDNER's 2022 submitted plan for attaining the 1-hour 
SO<INF>2</INF> NAAQS in the San Juan and Guayama-Salinas NAAs are based 
on emission unit retirements and fuel switching to ULSD. As previously 
mentioned, the enforceable control measures established in RCAP Rule 
425 were to be implemented from June 30, 2023, through December 31, 
2025, in the San Juan NAA, and December 31, 2025, through December 31, 
2029, in the Guayama-Salinas NAA.
    Rule 425 provides exemptions allowing for alternative retirement 
dates, provided they are approved by PRDNER and the PREB, but no later 
than December 31, 2025 for the San Juan NAA, and December 31, 2029 for 
the Guayama-Salinas NAA. As a result of these exemptions, the EPA 
believes the retirement dates listed under Rule 425 would not provide 
permanently enforceable measures for major sources of SO<INF>2</INF>. 
The EPA anticipates that the PRDNER will remove these exemptions within 
the subsequent SIP revision that Puerto Rico will be required to submit 
within one year of the final determination of the EPA's proposed 
finding that the areas failed to attain the standard by the statutory 
attainment date.
    Because the San Juan and Guayama-Salinas NAAs will be subject to a 
new attainment date, which will be five years following the EPA's final 
determination that the areas failed to attain the standard, the EPA is 
not proposing action on the PRDNER's RACM/RACT and emissions 
limitations or control measures that were submitted in accordance with 
CAA sections 172(c)(1) and (6). As a result of this new attainment 
date, the EPA expects these elements will be revised within the 
subsequent SIP revision that the PRDNER will be required to submit 
within one year of the EPA's final finding that the areas failed to 
attain the standard. The EPA will act on these elements upon receipt of 
the PRDNER's subsequent SIP revision.

C. New Source Review

    Part D of title I of the CAA prescribes the procedures and 
conditions under which a new major stationary source or major 
modification may obtain a preconstruction permit in an area designated 
nonattainment for any criteria pollutant. The nonattainment new source 
review (NNSR) permitting requirements in section 172(c)(5) and 173 of 
the CAA are among ``the requirements of this part'' to be submitted to 
the EPA as part of a revised SIP for a nonattainment area within 18 
months of the effective date of a designation or redesignation to 
nonattainment. The NNSR permitting requirements provide for the 
permitting of any proposed major stationary source of SO<INF>2</INF> 
located in a NAA under the 2010 SO<INF>2</INF> NAAQS.
    The PRDNER submitted its NNSR program's rules for SO<INF>2</INF> 
and other future potential nonattainment pollutants in its SIP 
submission to the EPA on November 22, 2022. Specifically, the PRDNER 
submitted \62\ for SIP approval, Rule 102, ``Definitions,'' as amended, 
which includes definitions relevant to nonattainment; and Rule 210, 
``Nonattainment Provisions,'' which establishes the requirements 
necessary to construct or modify major emission sources of 
SO<INF>2</INF> and other pollutants in areas designated as NAAs.
---------------------------------------------------------------------------

    \62\ Rule 425, ``Provisions for SO<INF>2</INF> Nonattainment 
Areas,'' which contains the emission limits and other control 
measures for the PREPA San Juan, PREPA Palo Seco, PREPA Aguirre 
facilities, as well as for the San Juan and Guayama-Salinas NAAs, is 
evaluated in Section VI.B of this notice.
---------------------------------------------------------------------------

    The PRDNER's NNSR program rules are evaluated in Section VII, 
``Puerto Rico's New Source Review Program'' of the preamble within this 
notice of proposed rulemaking. These rules provide appropriate new 
source review for SO<INF>2</INF> sources undergoing construction or 
major modification in the San Juan and Guayama-Salinas NAAs, including 
meeting the applicable statutory requirements, which include but are 
not limited to the installation of Lowest Achievable Emissions Rate 
(LAER) control technology and the acquisition of emissions reductions 
to offset new emissions of nonattainment pollutant(s). Based on the 
EPA's evaluation in Section VII, the EPA is proposing, upon final 
approval of the RCAP's Rules 102 and 210, that the new source 
requirements have been met for the San Juan and Guayama-Salinas NAAs.

D. Reasonable Further Progress

    The EPA's policy that Reasonable Further Progress (RFP) for 
SO<INF>2</INF> may be satisfied by ``adherence to an ambitious 
compliance schedule'' is based on the fact that ``for SO<INF>2</INF> 
there is usually a single `step' between pre-control nonattainment and 
post-control attainment.'' \63\ Because a new attainment date will be 
promulgated upon the EPA's final determination that the NAAs failed to 
attain the standard by the statutory attainment date, and the EPA 
expects this element will be revised by the PRDNER with the subsequent 
SIP revision required following the EPA's final determination, the EPA 
is not proposing action on the requirements listed under CAA section 
172(c)(2), to provide for RFP toward attainment in the San Juan and 
Guayama-Salinas SO<INF>2</INF> NAAs.
---------------------------------------------------------------------------

    \63\ 2014 SO<INF>2</INF> Guidance, at 40.
---------------------------------------------------------------------------

E. Contingency Measures

    As discussed in the EPA's SO<INF>2</INF> guidance, section 
172(c)(9) of the CAA defines contingency measures as measures in a SIP 
that are to be implemented in the event an area fails to make RFP, or 
fails to attain the NAAQS, by the applicable attainment date. 
Contingency measures are to become effective without further action by 
the state/commonwealth or the EPA, where the area has failed to (1) 
achieve RFP or (2) attain the NAAQS by the statutory attainment date 
for the affected area. These control measures are to consist of other 
available control measures that are not included in the control 
strategy for the NAA SIP. The EPA's guidance describes special features 
of SO<INF>2</INF> planning that influence the suitability of 
alternative means of addressing the requirement in section 172(c)(9) 
for contingency measures for SO<INF>2</INF>. Because SO<INF>2</INF> 
control measures are by definition based on what are directly and 
quantifiably necessary emissions

[[Page 79844]]

controls, any violations of the NAAQS are likely related to source 
violations of a source's permit terms. Therefore, an appropriate means 
of satisfying this requirement for SO<INF>2</INF> is for a state to 
have a comprehensive enforcement program that identifies sources of 
violations of the SO<INF>2</INF> NAAQS and to undertake an aggressive 
follow-up for compliance and enforcement.
    For its contingency measures program, the PRDNER indicated it will 
continue to operate a comprehensive program to identify sources 
violating the SO<INF>2</INF> NAAQS, and that it will undertake 
compliance inspections and necessary enforcement actions.
    In its submission to the EPA, the PRDNER clarified that it has 
authority under Article 9(a)(7) of the Puerto Rico Energy Public Policy 
Act (PREPPA) to order persons causing or contributing to a condition 
which harms the environment and natural resources, or which poses an 
imminent danger for the public health and safety, to immediately 
diminish or discontinue their actions. Furthermore, the PRNDER 
indicated that Article 9(a)(8) of PREPPA provides the PRDNER with the 
authority to issue orders to take the preventative or control measures 
necessary.
    Accordingly, the PRDNER also included a provision that, upon 
notification by the PRDNER that a nearby monitor has four validated 
SO<INF>2</INF> concentrations in excess of the standard or has a 
monitored SO<INF>2</INF> violation based on the design value, PREPA 
would be required to undertake a system audit of emissions units. 
Consequently, an audit report would be required for submission by PREPA 
to the PRDNER within 90 days of the notification. An audit report would 
detail the operating parameters of all emissions units for four 10-day 
periods up to and including the date upon which the reference monitor 
registered each exceedance, together with recommended SO<INF>2</INF> 
emission control strategies, and evidence that the strategies have been 
deployed, as appropriate. Upon receipt of the report, the PRDNER would 
begin a 60-day evaluation period to diagnose the exceedance, to be 
followed by a 60-day consultation period with PREPA to develop and 
implement necessary operational changes. The PRDNER indicated that such 
changes may include fuel switching, physical or operational reductions, 
or other changes that the PRDNER determined to be appropriate. 
Additionally, if any new emission limits were deemed necessary, the 
PRDNER indicated they would be submitted to the EPA as a SIP revision.
    The PRDNER has also provided details on the corrective actions to 
occur if emission sources do not comply with required emission limits 
and other requirements in Section VI of Rule 425. Specifically, this 
includes expedited procedures for establishing enforceable consent 
agreements when the adoption of revised SIPs is pending, and subjecting 
any source that is found to be in violation of an approved compliance 
plan or requirement within such plan to repercussions listed under Rule 
115. Additionally, under Rule 425, the PRDNER indicated that if a new 
measure or control was determined to be sufficient to address 
violations of the SO<INF>2</INF> NAAQS and was promulgated or scheduled 
to be implemented at the federal or state level, additional local 
measures might be unnecessary following the PRDNER's submission of an 
analysis to the EPA demonstrating that such proposed measures were 
adequate to return an area to attainment. Under Rule 425, the PRDNER 
will also have the authority to require any owner or operator of an 
SO<INF>2</INF> emissions source contributing to air pollution to 
install, operate, and maintain monitoring devices; as well as maintain 
records and file periodic reports to the PRDNER. The PRDNER will also 
have the ability under Rule 425 to require the submission of an 
``Ambient Air Quality Monitoring Plan'' that complies with the EPA's 
guidelines and includes an air quality and meteorological measurement 
network which collects accurate SO<INF>2</INF> air quality and 
meteorology data within the zone impacted by SO<INF>2</INF> emissions 
from a source. Finally, the PRDNER will have authority under Rule 425 
to issue additional orders which require that a previously submitted 
plan be clarified, updated, corrected, supplemented, or otherwise 
amended.
    The PRDNER also provided information regarding a proposed 
``Attainment Ambient Monitoring Network'' (or AAMN). The PRDNER 
proposed that the AAMN would establish 12 SO<INF>2</INF> monitoring 
stations, with six in each of the two nonattainment areas. The location 
of these proposed stations would be determined based on an analysis 
that predicts the maximum concentrations using the EPA-approved AERMOD 
model. Additionally, the PRDNER indicated that the proposed 
SO<INF>2</INF> monitoring will be subject to 40 CFR part 58 
requirements to be used for comparison to the NAAQS. The EPA did not 
approve any new SO<INF>2</INF> sites as part of PRDNER's 2023 AMNP.\64\ 
Based on the preliminary information provided, the EPA does not believe 
there is sufficient information to evaluate the appropriateness of the 
AAMN as part of the contingency measures for the plan.
---------------------------------------------------------------------------

    \64\ See letter dated January 10, 2023, from Richard Ruvo, 
Director, EPA Region II, Air and Radiation Division to Ana[iacute]s 
Rodr[iacute]guez Vega, Secretary, Puerto Rico Department of Natural 
and Environmental Resources.
---------------------------------------------------------------------------

    Although Puerto Rico has taken significant steps to develop a 
comprehensive program to satisfy the contingency measures requirement 
for SO<INF>2</INF>, the EPA's policy is premised on full compliance 
with the approvable controls and limits required in the approvable plan 
to ensure attainment. However, as previously discussed, the EPA is not 
proposing action on related CAA section 172(c) elements of the 
attainment plan, including the attainment demonstration, the RFP, and 
the RACM/RACT and enforceable emission limitation elements of the SIP, 
because Puerto Rico will be required to submit a revised SIP which the 
EPA anticipates will contain an updated control strategy based on the 
new attainment date that will be established with the EPA's final 
determination that the areas failed to attain the standard. Thus, the 
EPA is not proposing action on the contingency measures the PRDNER 
provided in its submission to satisfy section 172(c)(9), because the 
approvability of the contingency measures element depends upon the 
approvability of the attainment demonstration.

F. Conformity

    Generally, as set forth in section 176(c) of the CAA, conformity 
requires that actions by federal agencies do not cause new air quality 
violations, worsen existing violations, or delay timely attainment of 
the relevant NAAQS. General conformity applies to federal actions, 
other than certain highway and transportation projects, if the action 
takes place in a NAA or maintenance area (i.e., an area which submitted 
a maintenance plan that meets the requirements of section 175A of the 
CAA and has been redesignated to attainment) for ozone, particulate 
matter, nitrogen dioxide, carbon monoxide, lead, or SO<INF>2</INF>. The 
EPA's General Conformity Rule establishes the criteria and procedures 
for determining if a federal action conforms to the SIP.\65\
---------------------------------------------------------------------------

    \65\ 40 CFR 93.150 to 93.165.
---------------------------------------------------------------------------

    With respect to the 2010 SO<INF>2</INF> NAAQS, federal agencies are 
expected to continue to estimate emissions for conformity analyses in 
the same manner as they estimated emissions for conformity analyses 
under the previous NAAQS for SO<INF>2</INF>. The EPA's General

[[Page 79845]]

Conformity Rule includes the basic requirement that a federal agency's 
general conformity analysis be based on the latest and most accurate 
emission estimation techniques available.\66\ When updated and improved 
emission estimation techniques become available, the EPA expects 
federal agencies will continue to use these techniques to ensure 
projects conform to the SIP.
---------------------------------------------------------------------------

    \66\ 40 CFR 93.159(b).
---------------------------------------------------------------------------

    The EPA concluded in its 1993 transportation conformity rule that 
highway and transit vehicles are not significant sources of 
SO<INF>2</INF>. As a result, transportation conformity determinations 
are not required in SO<INF>2</INF> nonattainment and maintenance areas. 
Therefore, transportation plans, transportation improvement programs, 
and projects are presumed to conform to applicable implementation plans 
for SO<INF>2</INF>.

VII. Puerto Rico's New Source Review Program

    The PRDNER's permitting requirements for the preconstruction review 
of new major sources in NAAs are set forth in the revisions to Rule 
102, ``Definitions,'' and the newly adopted Rule 210, ``Nonattainment 
Provisions.'' The PRDNER's NNSR program applies to the construction and 
modification of any major stationary source of air pollution in a NAA, 
as required by part D of title I of the CAA. To receive approval to 
construct, a source that is subject to these regulations must show that 
it will not cause a net increase in pollution with more than a 1:1 
offset ratio, will not create a delay in meeting the NAAQS, and will 
install and use control technology that achieves the LAER. The 
revisions to Rule 102 and the newly created Rule 210 within the RCAP, 
which the EPA is proposing to approve into the SIP, incorporate 
provisions that are consistent with the current federal requirements 
for an approvable nonattainment NSR program in 40 CFR 51.165. Among 
these provisions is the prohibition of construction, unless an 
effective permit is issued that meets the requirements of Rule 210, and 
a certification from the applicant that all existing major stationary 
sources owned and operated by the applicant in Puerto Rico are 
complying with all applicable emissions standards of the CAA or that 
such stationary sources are in compliance with an expeditious schedule 
which is federally enforceable or contained in a court decree.
    As part of its review of the PRDNER's NNSR submittal, the EPA has 
determined that the revisions are consistent with the program 
requirements for the preparation, adoption, and submittal of 
implementation plans for NNSR, set forth at 40 CFR 51.165.

VIII. The EPA's Evaluation of Rule 425

    On November 21, 2022, the PRDNER promulgated the new Rule 425, 
``Provisions for SO<INF>2</INF> Non-Attainment Areas.'' The new Rule 
425 was included within the November 22, 2022 SIP revision submitted by 
the PRDNER.
    The EPA is proposing to approve, for SIP-strengthening purposes and 
to make federally enforceable, the following sections of Rule 425: 
Section I, ``Applicability;'' Section IV, ``Emission Limitations for 
San Juan and Guayama-Salinas Non-Attainment Areas,'' Section V, 
``Measurement methods and procedures,'' Subsections (A), (B), and (E); 
and Section VI, ``Contingency Measures.'' Additionally, the EPA is 
proposing to conditionally approve Section II, ``Emission Limitations 
for PREPA San Juan and PREPA Palo Seco,'' Subsection (A), Section III, 
``Emission Limitations for PREPA Aguirre,'' Subsection (A), Section V, 
``Measurement methods and procedures,'' Subsections (C), (D), and (F).
    Rule 425 is applicable to the current and future owners or 
operators of the PREPA San Juan, PREPA Palo Seco, and PREPA Aguirre 
facilities, as indicated under Section I, ``Applicability'' of Rule 
425. Additionally, under Section I of Rule 425, any other major sources 
in or nearby the NAAs that have not undergone a major modification or 
construction of a new emission unit subject to Rule 210 are also 
subject to the provisions of Rule 425. The EPA proposes to approve the 
applicability provisions listed under Section I of Rule 425 for SIP-
strengthening purposes.
    Under Section II, ``Emissions Limitations for PREPA San Juan and 
PREPA Palo Seco'' and Section III, ``Emission Limitations for PREPA 
Aguirre'' of Rule 425, details are provided regarding compliance start 
dates for fuel switching to ULSD of certain emission units, retirement 
schedules for emission units not being converted to ULSD, and emission 
limits for units using ULSD or LNG at the PREPA San Juan, PREPA Palo 
Seco, and PREPA Aguirre facilities. The EPA is proposing to 
conditionally approve the ULSD emission limits for units listed under 
Section II(A) and Section III(A) of Rule 425, which prevent the burning 
of any fuel oil above a maximum sulfur content of 15 ppm at the three 
aforementioned PREPA facilities, since fuel switching of emission units 
to ULSD is expected to result in a significant decrease of sulfur 
emissions, providing for improved air quality. Details regarding the 
conditional approval and revisions the PRDNER has committed to make to 
Rule 425 as discussed in its September 2, 2024 commitment letter \67\ 
are provided in the following paragraphs of this section. In accordance 
with section 110(k)(4) of the CAA, this proposed conditional approval 
is based on the PRDNER's commitment to make specific revisions to 
Section V of Rule 425, which will address concerns the EPA has 
regarding the enforceability of emission limits for the specific units 
listed under Section II(A) and Section III(A), and to submit such 
revisions to the EPA by January 1, 2026 for approval into the SIP for 
Puerto Rico.
---------------------------------------------------------------------------

    \67\ Details regarding the EPA's conditional approval and the 
revisions which the PRDNER has committed to make to RCAP Rule 425 by 
January 1, 2026, can be found within the commitment letter the 
PRDNER submitted to the EPA on September 2, 2024, and which the EPA 
has included within the docket for this action.
---------------------------------------------------------------------------

    The EPA is not proposing to approve and is taking no action on 
Section II(B) and Section III(B) of Rule 425, which list the retirement 
schedules for emission units and detail emission limits for units at 
the three PREPA facilities, since the EPA anticipates these schedules 
will be revised by Puerto Rico to conform with the updated control 
strategy submitted by the PRDNER in the subsequent SIP submission 
required under the CAA following the EPA's final determination that the 
areas failed to attain. Additionally, the retirement provisions within 
Section II(B) and Section III(B) of Rule 425 allow the PRDNER to 
request an alternate date, which provides exemptions to a control 
strategy and are therefore not a permanently enforceable control 
strategy.
    In addition, under Section IV, ``Emission Limitations for San Juan 
and Guayama-Salinas Non-Attainment Areas'' of Rule 425, any emission 
source (or any nearby sources having a significant impact) within the 
boundaries of the San Juan and Guayama-Salinas NAAs, except for PREPA 
emission units, shall comply \68\ with all the provisions within 
subsection IV(A). Thus, no owner or operator of any combustion units 
within the boundaries of the NAAs, or nearby sources having a 
significant air quality impact on SO<INF>2</INF>, shall cause or permit 
the burning of any fuel oil above a maximum sulfur content of 0.0015

[[Page 79846]]

percent by weight (15 ppm) by no later than April 9, 2023 (Sections 
IV(A)(l)-(2) of Rule 425). Under Section IV(B), owners or operators of 
stationary sources subject to the limitations of Section IV(A) are 
required to certify in writing to the PRDNER that such source complies 
with Rule 425. Finally, under Section IV(C), any owner or operator of a 
stationary source subject to the limitations of Section IV(A) that 
cannot comply with the emission limits established by the date required 
under Rule 425 shall create a compliance plan which implements RACT in 
accordance with Rule 205 and in compliance with Rule 425. Upon the 
PRDNER's approval, a compliance plan must then be implemented and 
certified by a responsible official for accuracy. The EPA is proposing 
to approve Section IV of Rule 425 for SIP-strengthening purposes, as it 
provides for the reduction of SO<INF>2</INF> emissions within the NAAs 
and provides air quality benefits.
---------------------------------------------------------------------------

    \68\ Emission sources are also required to comply with 
provisions provided under Rules 401 through 421 of the RCAP.
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    Regarding the test methods to be utilized when determining 
compliance with the allowable emission limits listed under Rule 425, 
the PRDNER requires the use of test methods provided in 40 CFR part 60. 
Further detail regarding the test methods and procedures for PREPA to 
determine compliance with the allowable emission limit for any fuel 
other than coal at the PREPA facilities in San Juan, Palo Seco, and 
Aguirre is provided under Section V, ``Measurement methods and 
procedures'' of Rule 425. The EPA acknowledges the PRDNER's recommended 
on-site fuel sampling of ULSD (and LNG for PREPA San Juan) in 
accordance with USEPA Method 19, ASTM D2622, D4294, D5453, D7039, or 
other appropriate EPA or ASTM method. The EPA also acknowledges the 
requirement for the PREPA facilities to have monitors recording the 
amount of each fuel type burned at each emission unit on an hourly 
basis and the requirement for PREPA to sample each batch of fuel prior 
to use for sulfur content (percent by weight), heat value, and density. 
Additional provisions under Rule 425 concern sample submission for 
laboratory analysis and maintenance of laboratory analysis records for 
a period of at least five years. Under this rule, PREPA will also be 
required to maintain monthly records listing (a) the fuel used (hourly 
usage and total fuel used for the month), (b) sulfur content of the 
fuel, fuel density, fuel heating value, and the basis for the sulfur 
content used (fuel analysis showing the date the sample was collected, 
type of fuel, sulfur content, and fuel heating value), and (c) 
SO<INF>2</INF> emission rates (lb/hr) with the assumption that 100% of 
the sulfur in the fuel is converted to SO<INF>2</INF>. Accordingly, the 
EPA proposes to approve Subsections (A), (B), and (E) of Section V 
under Rule 425 for SIP-strengthening.
    Furthermore, under the current Section V of Rule 425, the PREPA San 
Juan, PREPA Palo Seco, and PREPA Aguirre facilities (and any owner or 
operator of an SO<INF>2</INF> emission source subject to Rule 425) will 
be required to retain all data, calculations, and reports from any 
performance test or fuel sample developed for the purpose of 
demonstrating compliance with the applicable emission limits, emission 
tracking requirements, or emission rate limits, for a minimum of five 
years. Additionally, Section V will require that these records be made 
available for inspection to the PRDNER upon its request. Under Rule 
425, the PRDNER will also have the authority to issue orders to require 
performance testing, fuel sampling, or require record-keeping and 
reporting of emission information.
    The EPA is proposing to conditionally approve the reporting 
provisions under Rule 425, Section V, Subsections (C), (D), and (F), 
which only require an owner or operator of an SO<INF>2</INF> emission 
source in the NAAs to make records available for inspection purposes 
and following the PRDNER's request. Section V of Rule 425 includes 
provisions imposing monitoring and recordkeeping obligations on the 
relevant sources, such as performance and fuel testing, and retention 
of records needed to demonstrate compliance with the relevant emission 
limitations; however, the EPA is concerned that the absence of periodic 
reporting obligations under Subsections (C), (D), and (F) may interfere 
with enforcement of the rule. On September 2, 2024, the PRDNER 
submitted a letter committing to revise the reporting provisions under 
Subsections (C), (D), and (F) by January 1, 2026, which will require 
facilities subject to Rule 425 to submit reports semi-annually (i.e., 
every six months). In accordance with section 110(k)(4) of the CAA, the 
EPA may conditionally approve a plan based on a commitment from a 
State/commonwealth to adopt specific enforceable measures and submit 
the necessary SIP revisions to the EPA by a date certain.
    If this conditional approval is finalized as proposed, the 
conditionally approved provisions of Rule 425 will become part of the 
SIP and will be federally enforceable as of the effective date of the 
final conditional approval. If the PRDNER submits the revisions to Rule 
425 by January 1, 2026, as committed to in its September 2, 2024 
commitment letter, the conditionally approved provisions will remain a 
part of the SIP unless the EPA disapproves the revisions to Rule 425 
through notice-and-comment rulemaking. If the EPA takes final action 
approving the revisions to Rule 425 into the SIP, in the same final 
action, the EPA will also convert the conditional approval of Rule 425, 
Section V, Subsections (C), (D), and (F), to an approval by making 
appropriate revisions to the SIP in the Code of Federal Regulations. If 
the EPA disapproves the revisions to Rule 425 intended to satisfy the 
PRDNER's commitment, the conditional approval will convert to a 
disapproval, and the conditionally approved provisions of Rule 425 will 
no longer be a part of the approved SIP for Puerto Rico.
    If the PRDNER fails to meet its commitment to submit the necessary 
SIP revisions to the EPA by January 1, 2026, or if the PRDNER submits 
timely SIP revisions, but the EPA finds the SIP submittal to be 
incomplete, this conditional approval will be converted to a 
disapproval. In either case, the EPA would notify the PRDNER by letter 
that the conditional approval has converted to a disapproval and the 
EPA would subsequently publish a document in the Federal Register 
announcing that the conditional approval converted to a disapproval.
    As previously stated, the EPA is proposing to conditionally approve 
the ULSD emission limits described in Section II(A) and Section III(A) 
of Rule 425, since the emission limits provide for a significant 
decrease in sulfur emissions. The EPA is also proposing to 
conditionally approve the reporting provisions which apply to these 
limits described in Section V, Subsections (C), (D), and (F). The EPA, 
however, is not conditionally approving these sections for compliance 
with CAA section 172(c) requirements.
    Finally, as previously discussed under Section VI.E, ``Contingency 
Measures,'' of this preamble, Section VI, ``Contingency Measures'' of 
Rule 425 specifies corrective actions \69\ to be taken if emission 
sources do not achieve compliance with emission limits

[[Page 79847]]

established in Rule 425 by the dates specified.
---------------------------------------------------------------------------

    \69\ These provisions, which are more fully discussed by EPA in 
Section VI, subsection E of this proposed rulemaking, include 
expedited procedures for establishing enforceable consent 
agreements; repercussions for violations; assessing new measures; 
monitoring, reporting, and recordkeeping requirements; assessment of 
additional local measures; and the PRDNER's ability to require 
previously submitted plans to be clarified, updated, corrected, 
supplemented, or otherwise amended.
---------------------------------------------------------------------------

    Moreover, in Section VI. E of this notice of proposed rulemaking, 
the EPA has indicated that the Agency is not proposing action on the 
contingency measures within the PRDNER's plan. That is because the 
EPA's policy is premised on full compliance with approvable controls 
and limits required in the approvable plan to ensure attainment. 
However, the EPA recognizes that the corrective actions outlined in 
Section VI of Rule 425 will have an overall positive impact on air 
quality in the San Juan and Guayama-Salinas NAAs. Therefore, the EPA is 
proposing to approve Section VI of Rule 425 for SIP strengthening and 
not to satisfy the contingency measure requirements of CAA 172(c)(9).

IX. Environmental Justice Considerations

    The PRDNER did not provide any information within its November 22, 
2022, SIP submittal to the EPA regarding environmental justice (EJ) 
considerations within the two NAAs. For informational purposes only, 
the EPA evaluated EJ considerations during its review of the PRDNER's 
SO<INF>2</INF> SIP submittal. The EPA did not rely on this information 
to reach any decisions described in this action. Notably, the CAA and 
applicable implementing regulations neither prohibit nor require such 
evaluation of EJ. The following information and discussion is provided 
for informational purposes only. An informational application of the 
White House's Climate and Economic Justice Screening Tool (CEJST) \70\ 
produced information that indicates that nearly all census tracts (or 
95% of the population) within Puerto Rico are considered 
disadvantaged.\71\
---------------------------------------------------------------------------

    \70\ See https://screeningtool.geoplatform.gov/en/#3/33.47/-97.5.
    \71\ A census tract is considered disadvantaged if it meets the 
thresholds for at least one of the tool's categories of burden or it 
is on the lands of a federally recognized Tribe. Additional 
information on the categories of burden can be found at https://screeningtool.geoplatform.gov/en/methodology.
---------------------------------------------------------------------------

    The evaluation here of environmental burdens and susceptible 
populations is based on screening-level analyses utilizing version 2.2 
of the EPA's Environmental Justice Screening and Mapping Tool 
(EJScreen).\72\ EJScreen is the EPA's EJ screening and mapping tool 
that provides EPA with a nationally consistent dataset and approach for 
combining environmental and demographic socioeconomic indicators. 
EJScreen is not a detailed risk analysis of EJ issues/concerns; rather, 
it is a screening tool that examines some of the relevant issues 
related to EJ, and there is uncertainty in the data included.
---------------------------------------------------------------------------

    \72\ See https://www.epa.gov/ejscreen.
---------------------------------------------------------------------------

    Through its use of EJScreen, the EPA determined that there may be 
potential EJ concerns within both SO<INF>2</INF> NAAs and the areas 
within a 1-mile radius of the three PREPA facilities. The EJScreen 
Community Reports are provided in the docket for this action. The 
results of these analyses are being provided for informational and 
transparency purposes only.
    In using EJScreen, if any of the EJ indices for the areas under 
consideration are at or above the 80th percentile nationally, then 
further review may be appropriate.\73\ Thus, the EPA's discussion of 
EJScreen results will focus on bringing attention to indices at or 
above the 80th percentile. As discussed in the EPA's EJ technical 
guidance,\74\ people of color and low-income populations often 
experience greater exposure and disease burdens than the general 
population, which can increase their susceptibility to adverse health 
effects from environmental stressors. Underserved communities can also 
experience reduced access to health care, nutritional, and fitness 
resources, further increasing their susceptibility.
---------------------------------------------------------------------------

    \73\ For early applications of EJScreen, the EPA identified the 
80th percentile filter as the initial starting point for the purpose 
of identifying geographic areas that may warrant further 
consideration. In other words, an area with any of the 13 EJ Indices 
at or above the 80th percentile nationally should be considered as a 
potential candidate for further review. See https://www.epa.gov/ejscreen/how-interpret-ejscreen-data.
    \74\ See https://www.epa.gov/system/files/documents/2023-06/ejscreen-tech-doc-version-2-2.pdf.
---------------------------------------------------------------------------

    Furthermore, the EJScreen tool provides information on 13 EJ 
Indices and 13 Supplemental Indices. Out of these, 11 indices have 
available data to derive in parts of Puerto Rico. Each index combines 
one environmental measure with demographic data \75\ to characterize 
potential areas of EJ concern that may warrant further consideration, 
analysis, or outreach. The EJ indices help screen for potential EJ 
concerns and combine data on low-income and people of color populations 
with a single environmental indicator. The supplemental indices offer a 
perspective on community-level vulnerability and combine data on 
percent low-income, percent linguistically isolated, percent with less 
than a high school education, percent unemployed, and low life 
expectancy with a single environmental indicator. It is also possible 
to compare indices for a given area to other locations within the 
nation and a State (or commonwealth). Specific background and source 
information on these indices and environmental indicators can be found 
in the EPA's ``EJScreen Technical Documentation for Version 2.2.'' \76\
---------------------------------------------------------------------------

    \75\ Demographic and socioeconomic data utilized within EJS is 
obtained from the U.S. Census Bureau's American Community Survey 
(ACS) 2017-2021 5-Year Estimates.
    \76\ See https://www.epa.gov/system/files/documents/2023-06/ejscreen-tech-doc-version-2-2.pdf.
---------------------------------------------------------------------------

    The population living within the San Juan NAA has high (for the 
purpose of this discussion, at or above the 80th percentile) EJ and/or 
Supplemental Index values at the national and/or State (or 
commonwealth) level for 9 of the 11 indices available in EJScreen. 
These include Diesel Particulate Matter, Toxic Releases to Air, Traffic 
Proximity, Lead Paint, Superfund Proximity, RMP Facility Proximity, 
Hazardous Waste Proximity, Underground Storage Tanks, and Wastewater 
Discharge. While none of these indices have direct implications to 
SO<INF>2</INF> emissions, and are not at issue in the SIP submission, 
they highlight that there may be some potential EJ concerns within the 
area.
    The population living within the Guayama-Salinas NAA also has high 
(for the purpose of this discussion, at or above the 80th percentile) 
EJ and/or Supplemental Index values at the national and/or State (or 
commonwealth) level for 6 of the 11 indices available in EJScreen. 
These include Air Toxics Cancer Risk, Toxic Releases to Air, Traffic 
Proximity, Lead Paint, Superfund Proximity, and Wastewater Discharge. 
While none of these indices have direct implications to SO<INF>2</INF> 
emissions, and are not at issue in the SIP submission, they highlight 
that there may be some potential EJ concerns within the area.
    The EPA elected to conduct further analysis of the areas within a 
1-mile radius of the three PREPA facilities (and within the NAAs) to 
ensure that the areas of maximum impact from emissions at the PREPA 
facilities were being considered.
    The results in EJScreen for the areas within a 1-mile radius of 
both the PREPA San Juan and PREPA Palo Seco facilities indicated that 
the populations were in the 96th percentile for People of Color 
nationally (99 percent of the population in both of the areas within a 
1-mile radius are considered People of Color). The area within a 1-mile 
radius of the PREPA San Juan facility is in the 97th percentile 
nationally for low income (81 percent of the population within a 1-mile 
radius of the PREPA San Juan facility is considered to be low-income), 
and the area within a 1-mile radius of the PREPA Palo Seco facility

[[Page 79848]]

is in the 76th percentile (46 percent of the population within a 1-mile 
radius of the PREPA Palo Seco facility is considered to be low-income). 
The population living within a 1-mile radius of the PREPA San Juan 
facility is at or above the 90th percentile for EJ and/or Supplemental 
Index values at the national and/or State (or commonwealth) level for 
all 11 available indices in EJScreen. The population living within a 1-
mile radius of the PREPA Palo Seco facility is at or above the 80th 
percentile for EJ and/or Supplemental Index values at the national/and 
or State (or commonwealth) level for 7 of the 10 available indices. In 
addition, the population within the Guayama-Salinas NAA, and within a 
1-mile radius of the PREPA Aguirre facility, are both in the 98th 
percentile nationally for People of Color (with 100 percent of the 
population considered People of Color), and in the 96th percentile 
nationally for low-income (with 78 percent of the population considered 
low-income).
    Based on all the screening-level demographic and socioeconomic data 
previously detailed, the populations within both NAAs and within a 1-
mile radius of the three PREPA facilities are predominately made up of 
people of color and/or low-income individuals. As a result, conditions 
that exist prior to this action have the potential to result in 
disproportionate and adverse effects on communities with EJ concerns.
    The reliability of Puerto Rico's energy infrastructure has been 
impacted by a combination of factors, including its vulnerability to 
severe storms and an aging fossil fuel-reliant generation fleet. After 
Hurricane Maria in 2017, Puerto Rican households experienced the 
largest and longest blackout in U.S. history, and the second-longest 
blackout in the world, with 80 percent of the island's power lines 
leveled.\77\ Moreover, Puerto Rico's fleet of fossil fuel generators is 
the oldest in the United States, with an average age of 44 years as 
compared with the national average of 18 years.\78\ Notably, although 
the poverty rate in Puerto Rico is more than three times the national 
average, Puerto Ricans pay an average of almost twice as much for 
electricity as U.S. mainland customers.\79\ The average price of 
electricity in 2022 across all sectors (residential, commercial, and 
industrial) in Puerto Rico averaged 29.63 cents/kWh, which is higher 
than every U.S. State except Hawaii (and excluding other U.S. 
Territories).\80\
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    \77\ See https://www.fema.gov/disaster/4339.
    \78\ See Jones, G., The Future of Energy in Puerto Rico: Current 
Challenges and Opportunities for a Resilient Power Grid. On Behalf 
of the U.S. Environmental Protection Agency, Region 2 Brownfields 
Program (2021/12/15), https://www.bu.edu/rccp/files/2022/01/Energy-Resilience-in-Puerto-Rico.pdf.
    \79\ See U.S. Energy Information Administration, ``Puerto Rico, 
Territory Profile and Energy Estimates,'' available at https://
www.eia.gov/state/
?sid=RQ#:~:text=Puerto%20Rico%27s%20reliance%20on%20petroleum, 
fired%20power%20plant and https://www.eia.gov/electricity/annual/html/epa_02_10.html.
    \80\ See U.S. Energy Information Administration, ``State Energy 
Profiles, Puerto Rico,'' available at https://www.eia.gov/beta/states/states/RQ/data.
---------------------------------------------------------------------------

    The EPA anticipates that its proposed conditional approval of the 
use of ULSD at the three PREPA facilities will not negatively impact 
energy reliability for citizens within the NAAs. The lower sulfur 
content in ULSD (15 ppm) has the potential to reduce harmful emissions 
from nonroad diesel sources by more than 90%.\81\ Thus, the anticipated 
significant reduction in sulfur content, compared to the sulfur content 
of diesel fuel previously used at the three PREPA facilities, is 
expected to result in approximately 15,000 tons of projected 
SO<INF>2</INF> reductions annually that will bring the NAAs closer to 
attainment of the NAAQS.\82\ At a minimum, this action is not expected 
to worsen any existing air quality, and the EPA believes that this 
proposed action will provide benefits to communities living within the 
NAAs, as it will provide for emission reductions along with ensuring 
the continued operation of existing electric generating units at the 
PREPA facilities.
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    \81\ See https://www.epa.gov/diesel-fuel-standards/diesel-fuel-standards-and-rulemakings.
    \82\ See docket for projected SO<INF>2</INF> emission 
reductions.
---------------------------------------------------------------------------

    Public participation and community involvement are crucial for 
ensuring that decisions affecting human health and the environment 
advance environmental justice considerations. Communities affected by 
environmental justice issues often face many challenges and barriers 
associated with meaningful involvement and adequate representation in 
the development, implementation, and enforcement of environmental laws, 
regulations, and policies. Consequently, to provide ample time for 
meaningful involvement, the EPA will extend its comment period for this 
notice of proposed rulemaking (NPRM) from the customary 30 days to 60 
days.
    Additionally, as previously detailed within this NPRM, to provide 
effective and meaningful involvement from community members during the 
comment period for this NPRM, the EPA will hold public information 
sessions concerning this proposed rulemaking. Given the high percentage 
of households whose primary language is Spanish, the EPA intends to 
provide all public distributions and supporting and related materials 
for this rulemaking that are legally permitted to be translated, in 
both Spanish and English, to the best of its ability. A Spanish 
translator will also be present at these public information sessions to 
ensure participants are able to understand the information provided by 
the EPA. The EPA will announce the date, time, and location for each 
session on its website. These sessions will allow citizens an 
opportunity to learn more about this proposed action, which will 
enhance their ability to provide more informed official comments during 
the public comment period. See the Supplementary Information section 
for additional information regarding the Public Information Sessions.
    As previously stated, this analysis of EJ considerations was done 
solely for the purpose of providing additional context and information 
about this proposed rulemaking to the public and is not a basis for the 
action. The EPA is taking action under the CAA and on bases independent 
of EJ.

X. The EPA's Proposed Action

    First, the EPA proposes, under CAA section 179(c)(1), to determine 
that the San Juan and Guayama-Salinas areas failed to attain the 2010 
1-hour SO<INF>2</INF> standard by the statutory attainment date of 
April 9, 2023. This determination is based upon a weight-of-evidence 
analysis, including (1) the control strategy timeline Puerto Rico 
identified and adopted into its RCAP and submitted in support of its 
air quality dispersion modeling of its November 22, 2022 SIP revision, 
which did not provide for attainment by the statutory attainment date; 
(2) Puerto Rico's inability to effectively implement the control 
strategy it identified and adopted within a timely manner thus far; and 
(3) the EPA's review of annual facility-wide emissions data from 
January 2020 through December 2022 for the PREPA San Juan, PREPA Palo 
Seco, and PREPA Aguirre facilities located within the NAAs.
    If the EPA's determination is finalized as proposed, the 
Commonwealth of Puerto Rico will be required under CAA section 179(d) 
to submit revisions to the SIP for the San Juan and Guayama-Salinas 
SO<INF>2</INF> NAAs. The required SIP revision for each area must, 
among other elements, demonstrate expeditious attainment of the 
standards within the time period prescribed by CAA section 179(d). If 
the EPA's determination is finalized as proposed, the SIP revisions 
required under CAA section 179(d) will be due for submittal to the EPA 
no later

[[Page 79849]]

than one year after the publication date of the final action notice.
    Second, the EPA proposes to approve certain but not all elements of 
Puerto Rico's SIP submission, submitted to the EPA by the PRDNER on 
November 22, 2022. Specifically, the EPA is proposing to approve the 
following elements for compliance with the requirements of section 
172(c) of the CAA: Puerto Rico's NNSR program, the base year emissions 
inventory, and to affirm that the NNSR requirements for the NAAs have 
been met. If finalized, this action would incorporate RCAP amendments 
under Rules 102 and 210 into Puerto Rico's approved and federally 
enforceable SIP.
    The EPA is not proposing action on other remaining elements within 
Puerto Rico's November 22, 2022 submission, as a result of the 
anticipated revisions to the SIP, which Puerto Rico would be required 
to submit within one year of the publication date of the final action 
pursuant to CAA section 179(d), should the EPA finalize its 
determination that the areas failed to meet the attainment date of 
April 9, 2023. The EPA is therefore not proposing action on the 
PRDNER's attainment demonstration, contingency measures, RACM/RACT and 
emission limitations necessary for attainment, as well as the 
requirements for meeting RFP toward attainment of the NAAQS.
    Additionally, the EPA proposes to approve, in part, and 
conditionally approve, in part, and not for compliance with the CAA 
section 172(c) requirements, specific amendments to Rule 425 of Puerto 
Rico's RCAP, which include control measures, emission limitations, and 
reporting requirements for sources in the NAAs. Specifically, the EPA 
is proposing to approve for SIP-strengthening, the following sections 
of Rule 425: Section I, ``Applicability;'' Section IV, ``Emission 
Limitations for San Juan and Guayama-Salinas Non-Attainment Areas;'' 
Section V, ``Measurement methods and procedures,'' Subsections (A), 
(B), and (E); and Section VI, ``Contingency Measures.'' Moreover, the 
EPA is proposing to conditionally approve Section II, ``Emission 
Limitations for PREPA San Juan and PREPA Palo Seco,'' Subsection (A), 
Section III, ``Emission Limitations for PREPA Aguirre,'' Subsection 
(A), Section V, ``Measurement methods and procedures,'' Subsections 
(C), (D), and (F).
    The EPA is soliciting public comments on this proposed action. The 
EPA will accept comments from the public on this proposal for the next 
60 days and will consider these comments before taking final action.

XI. Incorporation by Reference

    In this 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 Puerto Rico's RCAP, Rule 102, ``Definitions,'' and Rule 210, 
``Non-Attainment Provisions,'' as well as portions of Rule 425, 
``Provisions for SO<INF>2</INF> Non-Attainment Areas,'' with a State/
commonwealth effective date of November 21, 2022, and as described in 
Sections VI through VIII of this preamble.
    Specifically, the EPA is proposing to incorporate by reference the 
following sections of Rule 425: Section I, ``Applicability''; Section 
II, ``Emission Limitations for PREPA San Juan and PREPA Palo Seco,'' 
Subsection (A); Section III, ``Emission Limitations for PREPA 
Aguirre,'' Subsection (A); Section IV, ``Emission Limitations for San 
Juan and Guayama-Salinas Non-Attainment Areas;'' Section V, 
``Measurement methods and procedures;'' and Section VI, ``Contingency 
Measures.'' These documents are available in the docket of this 
rulemaking through www.regulations.gov.

XII. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders 
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review, and Executive 
Order 14094: Modernizing Regulatory Review

    This action is not a significant regulatory action as defined in 
Executive Order 12866, as amended by Executive Order 14094, and was 
therefore not submitted to the Office of Management and Budget (OMB) 
for review.

B. Paperwork Reduction Act (PRA)

    This action does not impose an information collection burden under 
the PRA because this action does not impose additional requirements 
beyond those imposed by State law.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action will not impose any requirements on small entities beyond those 
imposed by State/commonwealth law.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C.1531-1538, and does not significantly or uniquely affect 
small governments. This action does not impose additional requirements 
beyond those imposed by State/commonwealth law. Accordingly, no 
additional costs to State, local, or Tribal governments, or to the 
private sector, will result from this action.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the States, on the relationship between 
the National Government and the Sates, or on the distribution of power 
and responsibilities among the various levels of government.

F. Executive Order 13175: Coordination With Indian Tribal Governments

    This action does not have Tribal implications, as specified in 
Executive Order 13175, because 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 and will not 
impose substantial direct costs on Tribal governments or preempt Tribal 
law. Thus, Executive Order 13175 does not apply in this action.

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

    The EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that the EPA has reason to believe may disproportionately affect 
children, per the definition of ``covered regulatory action'' in 
section 2-202 of the Executive order. This action is not subject to 
Executive Order 13045 because it does not impose additional 
requirements beyond those imposed by State/commonwealth law.

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

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

I. National Technology Transfer and Advancement Act (NTTAA)

    Section 12(d) of the NTTAA directs the EPA to use voluntary 
consensus standards in its regulatory activities

[[Page 79850]]

unless to do so would be inconsistent with applicable law or otherwise 
impractical. The EPA believes that this action is not subject to the 
requirements of section 12(d) of the NTTAA because application of those 
requirements would be inconsistent with the CAA.

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

    Executive Order 12898 (Federal Actions to Address Environmental 
Justice in Minority Populations and Low-Income Populations, 59 FR 7629, 
February 16, 1994) directs federal agencies to identify and address 
``disproportionately high and adverse human health or environmental 
effects'' of their actions on minority populations and low-income 
populations to the greatest extent practicable and permitted by law. 
The EPA defines EJ as ``the fair treatment and meaningful involvement 
of all people regardless of race, color, national origin, or income 
with respect to the development, implementation, and enforcement of 
environmental laws, regulations, and policies.'' The EPA further 
defines the term ``fair treatment'' to mean that ``no group of people 
should bear a disproportionate burden of environmental harms and risks, 
including those resulting from the negative environmental consequences 
of industrial, governmental, and commercial operations or programs and 
policies.''
    The PRDNER did not evaluate environmental justice considerations as 
part of its SIP submittal; the CAA and applicable implementing 
regulations neither prohibit nor require such an evaluation. Consistent 
with the EPA's discretion under the CAA, the EPA evaluated the 
environmental justice considerations of this action, as is described 
above in the section titled, ``Environmental Justice Considerations.'' 
The analysis was done for the purpose of providing additional context 
and information about this rulemaking to the public, and not as a basis 
of the action. Due to the nature of the action being taken here, this 
action is expected to have a neutral to positive impact on the air 
quality of the affected area. In addition, there is no information in 
the record inconsistent with the stated goal of E.O. 12898 of achieving 
environmental justice for communities with environmental justice 
concerns.

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Sulfur dioxide, Reporting and 
recordkeeping requirements.

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

Lisa Garcia,
Regional Administrator, Region 2.
[FR Doc. 2024-22466 Filed 9-30-24; 8:45 am]
BILLING CODE 6560-50-P


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