Clean Air Plans; California; San Joaquin Valley Moderate Area Plan and Reclassification as Serious Nonattainment for the 2012 PM2.5

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The Environmental Protection Agency (EPA) proposes to take action on portions of four state implementation plan (SIP) revisions submitted by California to address Clean Air Act (CAA or “Act”) requirements for the 2012 fine particulate matter (PM_2.5) national ambient air quality standards (NAAQS or “standards”) and for the 2006 PM_2.5 NAAQS in the San Joaquin Valley (SJV) PM_2.5 nonattainment area. Specifically, the EPA proposes to approve all but the contingency measure element of the submitted Moderate area plan for the 2012 PM_2.5 NAAQS, as updated by the submitted Serious area plan and related Valley State SIP Strategy, as meeting all applicable Moderate area plan requirements for the 2012 PM_2.5 NAAQS and to approve 2022 motor vehicle emissions budgets for use in transportation conformity analyses for the 2012 PM_2.5 NAAQS. The EPA proposes to disapprove the contingency measure element with respect to the “Moderate” area requirements for the 2012 PM_2.5 NAAQS. The EPA also proposes to reclassify the SJV PM_2.5 nonattainment area, including reservation areas of Indian country and any other area of Indian country within it where the EPA or a tribe has demonstrated that the tribe has jurisdiction, as a “Serious” nonattainment area for the 2012 PM_2.5 NAAQS based on the EPA's determination that the area cannot practicably attain the standard by the applicable Moderate area attainment date of December 31, 2021. Upon final reclassification of the SJV as a Serious area for this NAAQS, California would be required to submit a Serious area plan for the area that includes a demonstration of attainment by the applicable Serious area attainment date, which is no later than December 31, 2025, or by the most expeditious alternative date practicable. However, we note that California has already submitted such Serious area plan that the EPA will address in a separate rulemaking. Lastly, the EPA is proposing to disapprove the contingency measure element in the Serious area plan for the 2006 PM_2.5 NAAQS.

DATES:

Any comments on this proposal must be received by October 1, 2021.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-R09-OAR-2021-0543 at https://www.regulations.gov,, or via email to mays.rory@epa.gov. For comments submitted at Regulations.gov, follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from Regulations.gov. For either manner of submission, the EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (e.g., audio or video) 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, please contact the person identified in the FOR FURTHER INFORMATION CONTACT section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. If you need assistance in a language other than English or if you are a person with disabilities who needs a reasonable accommodation at no cost to you, please contact the person identified in the FOR FURTHER INFORMATION CONTACT section.

FOR FURTHER INFORMATION CONTACT:

Rory Mays, Air Planning Office (AIR-2), EPA Region IX, by phone at (415) 972-3227 or email at mays.rory@epa.gov.

SUPPLEMENTARY INFORMATION:

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

Table of Contents

I. Background for Proposed Action

II. Summary of San Joaquin Valley 2016 and 2018 PM_2.5 Plans

A. 2016 PM_2.5 Plan Summary

B. 2018 PM_2.5 Plan Summary

C. Procedural Requirements for SIPs and SIP Revisions

III. Clean Air Act Requirements for Moderate PM_2.5 Nonattainment Area Plans

IV. Review of San Joaquin Valley Plans for Moderate Area Requirements

A. Emissions Inventory

B. PM_2.5 Precursors

C. Air Quality Modeling

D. Reasonably Available Control Measures and Control Strategy

E. Nonattainment New Source Review Requirements Under CAA Section 189(e)

F. Demonstration That Attainment by Moderate Area Attainment Date Is Impracticable

G. Reasonable Further Progress and Quantitative Milestones

H. Contingency Measures

I. Motor Vehicle Emissions Budgets

V. Reclassification as Serious Nonattainment and Serious Area SIP Requirements

A. Reclassification as Serious and Applicable Attainment Date

B. Clean Air Act Requirements for Serious Area Plans

C. Statutory Deadline for Submission of Serious Area Plan

VI. Reclassification of Areas of Indian Country

VII. Review of Contingency Measure Element for the 2006 PM_2.5 NAAQS

A. Requirements for Contingency Measures

B. Summary of State's Contingency Measure Element for 2006 PM_2.5 NAAQS

C. EPA Evaluation and Proposed Action

VIII. Summary of Proposed Actions and Request for Public Comment

IX. Statutory and Executive Order Reviews

I. Background for Proposed Action

On January 15, 2013, the EPA strengthened the primary annual NAAQS for particulate matter with a diameter of 2.5 microns or less (PM_2.5) by lowering the level from 15.0 micrograms per cubic meter (µg/m) to 12.0 µg/m (“2012 PM_2.5 NAAQS”). The EPA established these standards after considering substantial evidence from numerous health studies demonstrating that serious health effects are associated with exposures to PM_2.5 concentrations above these levels.

Epidemiological studies have shown statistically significant correlations between elevated PM_2.5 levels and premature mortality. Other important health effects associated with PM_2.5 exposure include aggravation of respiratory and cardiovascular disease (as indicated by increased hospital admissions, emergency room visits, absences from school or work, and restricted activity days), changes in lung function, and increased respiratory symptoms. Individuals particularly sensitive to PM_2.5 exposure include older adults, people with heart and lung disease, and children. PM_2.5 can be emitted directly into the atmosphere as a solid or liquid particle (“primary PM_2.5” or “direct PM_2.5”) or can be formed in the atmosphere (“secondary PM_2.5”) as a result of various chemical reactions among precursor pollutants such as nitrogen oxides (NO_X), sulfur oxides (SO_X), volatile organic compounds (VOC), and ammonia (NH₃).

Following promulgation of a new or revised NAAQS, the EPA is required by CAA section 107(d) to designate areas throughout the nation as attaining or not attaining the NAAQS. Under subpart 4 of part D of title I of the CAA and applicable implementing regulations, the EPA designates areas found to be violating the PM_2.5 NAAQS, and areas with emissions that contribute to such violations, as nonattainment and classifies them initially as Moderate. States with Moderate areas have to attain the NAAQS as expeditiously as practicable, but not later than the end of the sixth calendar year after the date of designation. The EPA reclassifies as Serious those Moderate areas that cannot practicably attain the NAAQS by the latest statutory attainment date and those areas that fail to attain the NAAQS by the applicable attainment date. States with Serious areas are subject to more stringent SIP revision requirements and must attain the NAAQS as expeditiously as practicable, but not later than the end of the tenth calendar year after designation.

On January 15, 2015, the EPA designated and classified the SJV as Moderate nonattainment for the 2012 PM_2.5 NAAQS. With respect to the 1997 PM_2.5 NAAQS and the 2006 PM_2.5 NAAQS, the SJV is designated nonattainment and is classified as Serious. The SJV PM_2.5 nonattainment area encompasses over 23,000 square miles and includes all or part of eight counties: San Joaquin, Stanislaus, Merced, Madera, Fresno, Tulare, Kings, and the valley portion of Kern. The area is home to four million people and is the nation's leading agricultural region. Stretching over 250 miles from north to south and averaging 80 miles wide, it is partially enclosed by the Coast Mountain range to the west, the Tehachapi Mountains to the south, and the Sierra Nevada range to the east. Under State law, the San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD or “District”) has primary responsibility for developing plans to provide for attainment of the NAAQS in this area. The District works cooperatively with the California Air Resources Board (CARB) in preparing these plans. Authority for regulating sources under state jurisdiction in the SJV is split between the District, which has responsibility for regulating stationary and most area sources, and CARB, which has responsibility for regulating most mobile sources and some categories of consumer products.

States with areas designated as nonattainment are required to submit SIP revisions that address various requirements, including the requirement to demonstrate attainment of the NAAQS as expeditiously as practicable but no later than the maximum attainment date established in the CAA or EPA's implementing regulations. However, states with Moderate PM_2.5 nonattainment areas may submit an impracticability demonstration, in lieu of a modeled attainment demonstration, if the state can establish that the area cannot practicably attain a particular PM_2.5 NAAQS by the outermost statutory Moderate area attainment date.

On May 10, 2019, CARB made two SIP submissions intended to address the attainment plan requirements for areas designated as nonattainment for the 2012 PM_2.5 NAAQS. First, the “2016 Moderate Area Plan for the 2012 PM_2.5 Standard” (“2016 PM_2.5 Plan”) addresses the Moderate area attainment plan requirements and includes a demonstration of impracticability of attaining the 2012 PM_2.5 NAAQS in the SJV by the latest permissible Moderate area attainment date of December 31, 2021. In this document, the EPA is proposing action on all portions of the 2016 PM_2.5 Plan. Second, the “2018 Plan for the 1997, 2006, and 2012 PM_2.5 Standards” (“2018 PM_2.5 Plan”) addresses the Serious area attainment plan requirements for the 2012 PM_2.5 NAAQS, in anticipation of the reclassification of SJV from Moderate to Serious for that PM_2.5 NAAQS. The 2018 PM_2.5 Plan incorporates by reference the “San Joaquin Valley Supplement to the 2016 State Strategy for the State Implementation Plan” (“Valley State SIP Strategy”), a related plan adopted by CARB on October 25, 2018, and submitted to the EPA with the 2018 PM_2.5 Plan on May 10, 2019. For the purposes of this action, the relevant portion of the Valley State SIP Strategy includes the control measure commitments associated with the quantitative milestones for 2019 and 2022.

The 2018 PM_2.5 Plan updates several elements in the 2016 PM_2.5 Plan, including the base year emissions inventory, plan precursor demonstration, controls analysis, reasonable further progress (RFP) and quantitative milestones, and motor vehicle emission budgets (MVEBs or “budgets”). In this document, the EPA is proposing action on those portions of the 2018 PM_2.5 Plan that apply to the Moderate area plan requirements for the 2012 PM_2.5 NAAQS. However, the EPA is not, at this time, proposing to act on those portions of the 2018 PM_2.5 Plan that are not relevant to our evaluation of compliance with Moderate area plan requirements for 2012 PM_2.5 NAAQS, such as the best available control measures (BACM) demonstration, control strategy commitments, attainment demonstration, RFP demonstration and quantitative milestones for later years, and MVEBs for later years.

The 2018 PM_2.5 Plan also addresses attainment plan requirements for areas classified as Serious for the 2006 PM_2.5 NAAQS. In 2020, we approved those portions of the 2018 PM_2.5 Plan that pertain to the 2006 PM_2.5 NAAQS, excluding the contingency measures element for the 2006 PM_2.5 NAAQS. In this document, we are proposing action on the portion of the 2018 PM_2.5 Plan that addresses the contingency measure requirement for the 2006 PM_2.5 NAAQS.

Lastly, the 2018 PM_2.5 Plan addresses the contingency measure requirement for the 2006 PM_2.5 NAAQS by reference to, among other things, a District contingency measure, and emissions estimates for the year following the attainment year for use in evaluating whether the emissions reductions from the contingency measure are sufficient. With respect to the District contingency measure, the 2018 PM_2.5 Plan calls for the District to amend District Rule 4901 (“Wood Burning Fireplaces and Wood Burning Heaters”) to include a requirement in the rule with a trigger that would activate the requirement should the EPA issue a final rulemaking that SJV failed to meet a regulatory requirement necessitating implementation of a contingency measure.

In response to the commitment made in the 2018 PM_2.5 Plan, in June 2019 the District adopted amendments to Rule 4901, including a new provision (codified as section 5.7.3 of the amended rule) that is a contingency measure. On July 19, 2019, CARB submitted the amended rule to the EPA for approval. We have already taken final action to approve the amended Rule 4901 (including the new section 5.7.3) into the California SIP, but in our approval we noted that we were not evaluating the contingency measure in section 5.7.3 of revised Rule 4901 for compliance with all requirements of the CAA and the EPA's implementing regulations that apply to such measures. Rather, we approved the new provision (section 5.7.3) into the SIP as part of our approval of the entire amended rule because the provision strengthens the rule by providing a possibility of additional curtailment days and thus potentially additional emissions reductions. We indicated that we would evaluate whether section 5.7.3, in conjunction with other submitted provisions, meets the statutory and regulatory requirements for contingency measures in a future action. In this document, we are evaluating District Rule 4901, and in particular section 5.7.3, in the context of our action on the contingency measure element in the 2016 PM_2.5 Plan for the 2012 PM_2.5 NAAQS and the contingency measure element in the 2018 PM_2.5 Plan for the 2006 PM_2.5 NAAQS.

II. Summary of San Joaquin Valley 2016 and 2018 PM_2.5 Plans

A. 2016 PM _2.5 Plan Summary

The SJVUAPCD Governing Board adopted the 2016 PM_2.5 Plan on September 15, 2016, and CARB adopted the plan on January 24, 2019. CARB submitted the plan to the EPA on May 10, 2019.

The 2016 PM_2.5 Plan is organized into three chapters, five appendices, and two attachments. Chapter 1 (“Introduction”) provides general background, including discussion of the federal PM_2.5 standards, PM_2.5 pollution and health effects in the SJV, challenges to attaining the standards, and the District's public process. Chapter 2 (“Impracticability Demonstration and Request for Reclassification”) presents CARB and the District's demonstration, based on air quality modeling, that attaining the 2012 PM_2.5 NAAQS by the latest permissible attainment date of December 31, 2021, is impracticable, and a request for reclassification to Serious. Chapter 3 (“Demonstration of Federal Clean Air Act Requirements”) describes how the 2016 PM_2.5 Plan addresses the federal requirements for Moderate PM_2.5 nonattainment areas, including a plan precursor demonstration, reasonably available control measures, RFP, quantitative milestones, contingency measures, stationary source permitting, and transportation conformity. The 2016 PM_2.5 Plan includes the following five technical appendices:

• Appendix A (“Air Quality Modeling”) provides the State's photochemical air quality modeling in support of the plan's impracticability demonstration and precursor demonstration;
• Appendix B (“Emissions Inventory”) presents the base year and future year emissions inventory for direct PM_2.5, NO_X, ammonia, SO_X, and VOC;
• Appendix C (“SIP Creditable Incentive-Based Emission Reductions”) provides a demonstration of NO_X emission reductions from heavy-duty off-road vehicle engine vehicle replacements under the 2011 Carl Moyer Guidelines in support of the plan's Moderate contingency measure element;
• Appendix D (“New Source Review and Emission Reduction Credits”) discusses the use of emission reduction credits (ERCs) in the context of the plan; and
• Appendix E (“Summary of Significant Comments and Responses”) summarizes significant comments received during the District's 2016 public review period and the District's responses thereto.

In addition, the 2016 PM_2.5 Plan includes Attachment 1 (“Stationary and Area Source Control Measure Analyses”) and Attachment 2 (“Mobile Source Control Measure Analyses”), which together resubmit the State's 2015 analyses that the District's stationary and area source control measures and CARB's mobile source control measures represent BACM and most stringent measures (MSM).

Lastly, on December 13, 2019, CARB submitted the following two additional documents that CARB had prepared for the 2016 PM_2.5 Plan and made available for public review along with the plan, but had inadvertently omitted them from the May 10, 2019 SIP submission to the EPA: (i) The “Staff Report, ARB Review of the San Joaquin Valley 2016 Moderate Area Plan for the 2012 PM_2.5 Standard,” released September 16, 2016 (“CARB 2016 Staff Report”), that provides CARB's staff review of the 2016 PM_2.5 Plan, including brief summaries for each of the Moderate area plan requirements; and (ii) the “Modeling Emission Inventory for the PM_2.5 State Implementation Plan in the San Joaquin Valley,” August 23, 2016 (“2016 Modeling Emissions Inventory”) that describes the development of the 2016 PM_2.5 Plan's modeling emissions inventory, estimation of the 2013 base year emissions inventory, the methodology used to develop the base year and baseline emissions inventory, and quality assurance of the modeling emissions inventory.

B. 2018 PM _2.5 Plan Summary

The SJVUAPCD Governing Board adopted the 2018 PM_2.5 Plan on November 15, 2018, and CARB adopted the plan on January 24, 2019. CARB submitted the 2018 PM_2.5 Plan to the EPA on May 10, 2019, concurrently with the 2016 PM_2.5 Plan.

The following portions of the 2018 PM_2.5 Plan and related support documents apply to the Moderate area attainment plan requirements for the 2012 PM_2.5 NAAQS in the SJV: (i) Chapter 4 (“Attainment Strategy for PM_2.5”); (ii) Chapter 7 (“Demonstration of Federal Requirements for the 2012 PM_2.5 Standard”); (iii) numerous appendices to the 2018 PM_2.5 Plan; (iv) CARB's “Staff Report, Review of the San Joaquin Valley 2018 Plan for the 1997, 2006, and 2012 PM_2.5 Standards,” release date December 21, 2018 (“CARB 2018 Staff Report”); and (v) the State's and District's board resolutions adopting the 2018 PM_2.5 Plan.

The appendices to the 2018 PM_2.5 Plan, in order of their evaluation in this proposal, include the following: (i) Appendix (“App.”) B (“Emissions Inventory”); (ii) a plan precursor demonstration and clarifications, including App. G (“Precursor Demonstration”) and Attachment A (“Clarifying information for the San Joaquin Valley 2018 Plan regarding model sensitivity related to ammonia and ammonia controls”) to the CARB 2018 Staff Report; (iii) control strategy appendices, including App. C (“Stationary Source Control Measure Analyses”) and App. D (“Mobile Source Control Measures Analyses”); and (iv) App. H (“RFP, Quantitative Milestones, and Contingency”). The 2018 PM_2.5 Plan addresses requirements for MVEBs in the “Transportation Conformity” section of App. D.

The 2018 PM_2.5 Plan also includes an Executive Summary, Introduction (Ch. 1), chapters on “Air Quality Challenges and Trends” (Ch. 2) and “Health Impacts and Health Risk Reduction Strategy” (Ch. 3), and appendices on “Public Education and Technology Advancement” (App. F), “Ambient PM_2.5 Data Analysis” (App. A), “New Source Review and Emission Reduction Credits” (App. I) and “Summary of Significant Comments and Responses” (App. M), as well other chapters and appendices that are primarily relevant to the Serious area plan requirements, including App. E (“Incentive-Based Strategy”), App. J (“Modeling Emission Inventory”), App. K (“Modeling Attainment Demonstration”), and App. L (“Modeling Protocol”).

Lastly, on February 11, 2020, CARB submitted, via the EPA State Planning Electronic Collaboration System, a revised version of App. H (“RFP, Quantitative Milestones, and Contingency”) that replaces the version submitted with the 2018 PM_2.5 Plan on May 10, 2019. All references to App. H of the 2018 PM_2.5 Plan in this proposed rule are to the revised version of Appendix H submitted February 11, 2020.

C. Procedural Requirements for SIPs and SIP Revisions

Sections 110(a)(1) and (2) and 110(l) of the CAA require each state to provide reasonable public notice and an opportunity for a public hearing prior to the adoption and submittal of a SIP or SIP revision to the EPA. To meet this requirement, every SIP submission should include evidence that adequate public notice was given and an opportunity for a public hearing was provided consistent with the EPA's implementing regulations in 40 CFR 51.102.

Both the District and CARB satisfied applicable statutory and regulatory requirements for reasonable public notice and hearing prior to adoption and submission of the 2016 PM_2.5 Plan and the 2018 PM_2.5 Plan. The District provided public notice and opportunity for public comment prior to its September 15, 2016 public hearing on and adoption of the 2016 PM_2.5 Plan. CARB also provided public notice and opportunity for public comment prior to its October 20, 2016 public hearing, where the 2016 PM_2.5 Plan was tabled.

Subsequently, the District provided public notice and opportunity for public comment prior to its November 15, 2018 public hearing on and adoption of the 2018 PM_2.5 Plan. CARB also provided public notice and opportunity for public comment prior to its January 24, 2019 public hearing, when CARB adopted the 2016 PM_2.5 Plan and the 2018 PM_2.5 Plan. The SIP submission includes proof of publication of notices for the respective public hearings. It also includes copies of the written and oral comments received during the State's and District's public review processes and the agencies' responses thereto. Therefore, we find that the 2016 PM_2.5 Plan and the 2018 PM_2.5 Plan meet the procedural requirements for public notice and hearing in CAA sections 110(a) and 110(l) and 40 CFR 51.102.

We present our evaluation of the 2016 PM_2.5 Plan (and 2018 PM_2.5 Plan as applicable to the Moderate area attainment plan requirements for the 2012 PM_2.5 NAAQS) in Section IV of this proposed rule. We present our evaluation of the 2018 PM_2.5 Plan as applicable to the contingency measure requirements for the 2006 PM_2.5 NAAQS in section VII of this proposed rule.

III. Clean Air Act Requirements for Moderate PM_2.5 Nonattainment Area Plans

With respect to the statutory requirements for particulate matter (PM) attainment plans, the general nonattainment area planning requirements of title I, part D of the CAA are found in subpart 1, and the attainment planning requirements specifically for PM are found in subpart 4.

The EPA has a longstanding general guidance document that interprets the 1990 amendments to the CAA, commonly referred to as the General Preamble for the Implementation of Title I of the Clean Air Act Amendments of 1990 (“General Preamble”). The General Preamble addresses the relationship between the subpart 1 and subpart 4 requirements and provides recommendations to states for meeting certain statutory requirements for PM attainment plans. As explained in the General Preamble, specific requirements applicable to Moderate area attainment plan SIP submissions for the PM NAAQS are set forth in subpart 4 of part D, title I of the Act, but such SIP submissions must also meet the general attainment planning provisions in subpart 1 of part D, title I of the Act, to the extent these provisions “are not otherwise subsumed by, or integrally related to,” the more specific subpart 4 requirements. The EPA provided further guidance to States on PM plan submissions in the Addendum to the General Preamble (“General Preamble Addendum”).

To implement the PM_2.5 NAAQS, the EPA has also promulgated the “Fine Particle Matter National Ambient Air Quality Standard: State Implementation Plan Requirements; Final Rule” (“PM_2.5 SIP Requirements Rule”). The PM_2.5 SIP Requirements Rule establishes regulatory requirements and provides additional guidance applicable to attainment plan submissions for the PM_2.5 NAAQS, including the 2012 annual PM_2.5 NAAQS and the 2006 24-hour PM_2.5 NAAQS, addressed in this section and section VII, respectively, of this proposed rule.

The general subpart 1 statutory requirements for attainment plans include the following: (i) The section 172(c)(1) requirement for reasonably available control measures (RACM)/reasonably available control technology (RACT) and attainment demonstrations; (ii) the section 172(c)(2) requirement to RFP; (iii) the section 172(c)(3) requirement for emissions inventories; (iv) the section 172(c)(5) requirement for a nonattainment new source review (NNSR) permitting program; and (v) the section 172(c)(9) requirement for contingency measures.

The more specific subpart 4 statutory requirements for Moderate PM_2.5 nonattainment areas include the following: (i) The section 189(a)(1)(A) and 189(e) NNSR permit program requirements; (ii) the section 189(a)(1)(B) requirement for attainment demonstrations; (iii) the section 189(a)(1)(C) requirement for RACM; and (iv) the section 189(c) requirements for RFP and quantitative milestones. Under subpart 4, states with Moderate PM_2.5 nonattainment areas must provide for attainment in the area as expeditiously as practicable but no later than the latest permissible attainment date under CAA section 188(c), i.e., December 31, 2021, for the 2012 PM_2.5 NAAQS in the SJV, unless the EPA determines, per section 188(b)(1), that the area cannot practicably attain the NAAQS by the Moderate area attainment date. In addition, under subpart 4, direct PM_2.5 and all precursors to the formation of PM_2.5 are subject to control unless the EPA approves a demonstration from the state establishing that a given precursor does not contribute significantly to PM_2.5 levels that exceed the PM_2.5 NAAQS in the area.

IV. Review of San Joaquin Valley Plans for Moderate Area Requirements

A. Emissions Inventory

1. Requirements for Emissions Inventories

Section 172(c)(3) of the CAA requires that each SIP include a comprehensive, accurate, current inventory of actual emissions from all sources of the relevant pollutant or pollutants in the nonattainment area. We refer to this inventory as the “base year inventory.” The EPA has established regulatory requirements for base year and other emissions inventories in the PM_2.5 SIP Requirements Rule and issued guidance concerning emissions inventories for PM_2.5 nonattainment areas.

The base year emissions inventory should provide a state's best estimate of actual emissions from all sources of the relevant pollutants in the area, i.e., all emissions that contribute to the formation of a particular NAAQS pollutant. For the PM_2.5 NAAQS, the base year emissions inventory must include direct PM_2.5 emissions, separately reported filterable and condensable PM_2.5 emissions, and emissions of all chemical precursors to the formation of secondary PM_2.5: NO_X, SO₂, VOC, and ammonia. In addition, the emissions inventory base year for a Moderate PM_2.5 nonattainment area must be one of the three years (i.e., 2011-2013) for which monitored data were used to designate the area as nonattainment, or another technically appropriate year justified by the state in its Moderate area attainment plan submission.

In its SIP submission, a state must include documentation explaining how it calculated emissions data. In estimating mobile source emissions, a state should use the latest emissions models and planning assumptions available at the time it develops the SIP submission. States are also required to use the EPA's “Compilation of Air Pollutant Emission Factors” (“AP-42”) road dust method for calculating re-entrained road dust emissions from paved roads. At the time the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan were developed, California was required to use EMFAC2014 to estimate tailpipe and brake and tire wear emissions of PM_2.5, NO_X, SO₂, and VOC from on-road mobile sources.

In addition to the base year inventory submitted to meet the requirements of CAA section 172(c)(3), a state must also submit future “baseline inventories” for the projected attainment year, each RFP milestone year, and any other year of significance for meeting applicable CAA requirements. By baseline inventories we mean projected emissions inventories for future years that account for, among other things, the ongoing effects of economic growth and adopted emission control requirements. The SIP submission should include documentation to explain how the state calculated the emissions projections.

2. Summary of State's Emissions Inventories

Within the 2016 PM_2.5 Plan, the annual average planning inventories for direct PM_2.5 and all PM_2.5 precursors (NO_X, ammonia, SO_X, and VOC) for the SJV PM_2.5 nonattainment area, together with documentation for the inventories, are found in Appendix B (“Emissions Inventory”). In addition, Appendix A (“Air Quality Modeling”) contains inventory documentation specific to the air quality modeling inventories. These portions of the 2016 PM_2.5 Plan contain annual average daily emission inventories for 2013 thru 2022 projected from the 2012 actual emissions inventory, including the 2013 base year, the 2019 RFP baseline year, the 2021 Moderate area attainment year, and the 2022 post-attainment RFP year. The winter average daily inventory is used to evaluate sources of emissions for attainment of the 2012 PM_2.5 NAAQS in the 2016 PM_2.5 Plan.

Similarly, within the 2018 PM_2.5 Plan, the annual average planning inventories for direct PM_2.5 and all PM_2.5 precursors, together with documentation for the inventories, are found in Appendix B (“Emissions Inventory”). In addition, Appendix J (“Modeling Emission Inventory”) contains inventory documentation specific to the air quality modeling inventories. These portions of the 2018 PM_2.5 Plan contain annual average daily emission inventories for 2013 thru 2028 projected from the 2012 actual emissions inventory, including the 2013 base year, the 2019 and 2022 RFP baseline years, the 2025 Serious area attainment year, and the 2028 post-attainment RFP year. Both the annual average and the winter average daily inventories are used to evaluate sources of emissions for attainment of the 2012 PM_2.5 NAAQS in the 2018 PM_2.5 Plan.

The base year inventories for stationary sources were developed using actual emissions reports made by facility operators. The State developed the base year emissions inventories for area sources using the most recent models and methodologies available at the time the State was developing the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan. Importantly, CARB and the District updated the emissions inventory in the 2018 PM_2.5 Plan using the latest available activity data and emission methodologies available at the time of plan development. The 2013 base year, annual average emissions inventories for most source categories did not change or only changed plus or minus 0.1 tons per day (tpd) between the two plans. However, the base year emissions inventory from several important source categories were smaller in the 2018 PM_2.5 Plan relative to the 2016 PM_2.5 Plan based on the latest information. These include a 1.2 tpd decrease in direct PM_2.5 emissions from residential fuel combustion based on a 2016 emissions inventory methodology update, a 0.4 tpd decrease in direct PM_2.5 emissions from farming operations based on updated estimates by the California Department of Conservation of harvested acreage in 2010-2020 rather than 2000-2009, and a 0.9 tpd decrease in NO_X emissions from trains based on updated locomotive data from 2016 on Class I and Class II railroads. Overall, for the 2013 base year, total emissions of both direct PM_2.5 and NO_X were 0.9 tpd smaller in the 2018 PM_2.5 Plan relative to the 2016 PM_2.5 Plan.

Furthermore, the 2016 PM_2.5 Plan's emissions inventory does not separately report filterable and condensable PM_2.5 emissions. However, the 2018 PM_2.5 Plan includes background, methodology, and inventories of condensable and filterable PM_2.5 emissions from stationary point and non-point combustion sources that are expected to generate condensable PM_2.5. It provides filterable and condensable emissions estimates, expressed as annual PM_2.5 emissions (tons per year), for all of the identified source categories for the years applicable to the Moderate area timeframe, including the 2013 base year, the 2019 RFP year, the 2021 Moderate area attainment year, and the 2022 post-attainment RFP year, as well as subsequent years.

CARB used EMFAC2014 to estimate on-road motor vehicle emissions based on transportation activity data from the 2014 Regional Transportation Plan adopted by the transportation planning agencies in the SJV. Re-entrained paved road dust emissions were calculated using a CARB methodology consistent with the EPA's AP-42 road dust methodology. CARB also provided emissions inventories for off-road equipment, including aircraft, trains, recreational boats, construction equipment, and farming equipment, among others. CARB uses a suite of category-specific models to estimate off-road emissions for many categories and, where a new model was not available, used the OFFROAD2007 model.

CARB developed the emissions forecasts by applying growth and control profiles to the base year inventory. CARB's mobile source emissions projections take into account predicted activity rates and vehicle fleet turnover by vehicle model year and adopted controls. In the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan, the District provides for use of pre-base year ERCs as offsets by accounting for such ERCs in the projected emissions inventory for the 2022 RFP year and the projected 2025 attainment year, respectively. The plans identify growth factors, control factors, and estimated offset use between 2013 and 2022, and between 2013 and 2025, for direct PM_2.5, NO_X, SO_X, and VOC emissions by source category and lists all pre-base year ERCs issued by the District for PM₁₀, NO_X, SO_X, and VOC emissions, by facility.

Table 1 provides a summary of the 2018 PM_2.5 Plan's winter (24-hour) average inventories in tpd of direct PM_2.5 and PM_2.5 precursor emissions for the 2013 base year. Table 2 provides a summary of 2018 PM_2.5 Plan's annual average inventories of direct PM_2.5 and PM_2.5 precursor emissions for the 2013 base year. For purposes of this proposal, these annual average inventories provide bases primarily for our evaluation of the precursor demonstration, control measure analysis, impracticability demonstration, RFP demonstration, and MVEBs in the 2018 PM_2.5 Plan with respect the Moderate area requirements.

3. EPA Evaluation and Proposed Action

Consistent with the requirement that inventories be based on the most current and accurate information available to the State and District at the time they were developing the plans and inventories, our evaluation for the SJV for the 2012 PM_2.5 NAAQS relies primarily on the emissions inventories in the 2018 PM_2.5 Plan. The inventories in the 2018 PM_2.5 Plan include the latest version of California's mobile source emissions model, EMFAC2014, that had been approved by the EPA at the time, and the EPA's most recent AP-42 methodology for paved road dust. The inventories comprehensively address all source categories in the SJV PM_2.5 nonattainment area and are consistent with the EPA's inventory guidance.

In accordance with 40 CFR 51.1008(a), the 2013 base year is one of the three years for which monitored data were used for designating the area, and it represents annual average emissions of all sources within the nonattainment area. Direct PM_2.5 and PM_2.5 precursors are included in the inventories, and filterable and condensable direct PM_2.5 emissions are identified separately.

With respect to future year baseline projections, we have reviewed the growth and control factors and find them acceptable and thus conclude that the future baseline emissions projections in the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan reflect appropriate calculation methods and the latest planning assumptions at the time the State and District were developing the plans and inventories. Also, as a general matter, the EPA will approve a SIP submission that takes emissions reduction credit for a control measure only where the EPA has approved the measure as part of the SIP. Thus, for example, to take credit for the emissions reductions from newly adopted or amended District rules for stationary and area sources, the related rules must be approved by the EPA into the SIP.

Given the State's impracticability demonstration for attaining the 2012 PM_2.5 NAAQS in the SJV by the outermost Moderate area attainment date, the 2016 PM_2.5 Plan describes the District rules achieving post-2013 emission reductions that contribute towards attaining the NAAQS. In our rulemaking on the State's attainment plan for the 2006 PM_2.5 NAAQS in the SJV, we reviewed the baseline measures identified as 2018 PM_2.5 Plan baseline controls to ensure that the measures that are relied upon in the plan have been submitted and approved as part of the California SIP. That set of 2018 PM_2.5 Plan baseline measures includes all those baseline measures identified in the 2016 PM_2.5 Plan's RFP demonstration as achieving emission reductions post-2013. Based on that review, we confirm that the stationary and area source baseline measures in the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan are approved into the SIP and support the emissions reductions for future years in the SJV. With respect to mobile sources, the EPA has acted in recent years to approve CARB mobile source regulations into the state-wide portion of the California SIP. We therefore find that the future year baseline projections in the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan are properly supported by SIP-approved stationary, area, and mobile source measures.

For these reasons, we are proposing to approve the 2013 base year emissions inventory in the 2018 PM_2.5 Plan as meeting the requirements of CAA section 172(c)(3) and 40 CFR 51.1008. We are also proposing to find that the future year baseline inventories in the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan satisfy the requirements of 40 CFR 51.1008(a)(2) and 51.1012(a)(2) and provide an adequate basis for the control measure, RFP, and impracticability demonstrations in the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan, respectively.

B. PM _2.5 Precursors

1. Requirements for Control of PM_2.5 Precursors

The provisions of subpart 4 of part D, title I of the CAA do not define the term “precursor” for purposes of PM_2.5, nor do they explicitly require the control of any specifically identified PM precursor. The statutory definition of “air pollutant” in CAA section 302(g), however, provides that the term “includes any precursors to the formation of any air pollutant, to the extent the Administrator has identified such precursor or precursors for the particular purpose for which the term `air pollutant' is used.” The EPA has identified NO_X, SO₂, VOC, and ammonia as precursors to the formation of PM_2.5. Accordingly, the attainment plan requirements of subpart 4 apply to emissions of all four precursor pollutants and direct PM_2.5 from all types of stationary, area, and mobile sources, except as otherwise provided in the Act (e.g., in CAA section 189(e)).

Section 189(e) of the Act requires that the control requirements for major stationary sources of direct PM₁₀ (which includes PM_2.5) also apply to major stationary sources of PM₁₀ precursors, except where the Administrator determines that such sources do not contribute significantly to PM₁₀ levels that exceed the standard in the area. Section 189(e) contains the only express exception to the control requirements under subpart 4 (e.g., requirements for RACM, RACT, BACM, best available control technology (BACT), MSM, and NNSR) for sources of direct PM_2.5 and PM_2.5 precursor emissions. Although section 189(e) explicitly addresses only major stationary sources, the EPA interprets the Act as authorizing it also to determine, under appropriate circumstances, that regulation of specific PM_2.5 precursors from other source categories in a given nonattainment area is not necessary. For example, under the EPA's longstanding interpretation of the control requirements that apply to stationary and mobile sources of PM₁₀ precursors in the nonattainment area under CAA section 172(c)(1) and subpart 4, a state may demonstrate in a SIP submission that control of a certain precursor pollutant is not necessary in light of its insignificant contribution to ambient PM₁₀ levels in the nonattainment area.

Under the PM_2.5 SIP Requirements Rule, a state may elect to submit to the EPA a “comprehensive precursor demonstration” for a specific nonattainment area to show that emissions of a particular precursor from all existing sources located in the nonattainment area do not contribute significantly to PM_2.5 levels that exceed the standard in the area. If the EPA determines that the contribution of the precursor to PM_2.5 levels in the area is not significant and approves the demonstration, the state is not required to control emissions of the relevant precursor from existing sources in the attainment plan.

We are evaluating the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan with respect to the Moderate area requirements in accordance with the presumption embodied within subpart 4 that all PM_2.5 precursors must be addressed in the State's evaluation of potential control measures, unless the State adequately demonstrates that emissions of a particular precursor or precursors do not contribute significantly to ambient PM_2.5 levels that exceed the PM_2.5 NAAQS in the nonattainment area. In reviewing any determination by the State to exclude a PM_2.5 precursor from the required evaluation of potential control measures, we consider both the magnitude of the precursor's contribution to ambient PM_2.5 concentrations in the nonattainment area and the sensitivity of ambient PM_2.5 concentrations in the area to reductions in emissions of that precursor.

2. Summary of State's Precursor Demonstrations

The State presents analyses of PM_2.5 precursors in both the 2016 PM_2.5 Plan and the 2018 PM_2.5 Plan and primarily relies on sensitivity-based contribution analyses to determine whether each PM_2.5 plan precursor contributes significantly to ambient PM_2.5 levels that exceed the 2012 PM_2.5 NAAQS. We summarize below key points from the State's analyses and conclusions for each pollutant, focusing on the three precursors (ammonia, SO_X, and VOC) that the State concludes do not contribute significantly to PM_2.5 levels that exceed the 2012 PM_2.5 NAAQS in the SJV.

In the 2016 PM_2.5 Plan, the State's precursor demonstration and conclusions are found in section 2.3 (“Summary of Modeling Results”), section 3.3 (“Precursor Demonstration”), and Appendix A (“Air Quality Modeling”). The State estimates that baseline anthropogenic emissions of NO_X, ammonia, SO_X, and VOC will decrease by 38 percent (%), 1%, 2%, and 8%, respectively, between 2013 and 2021. The State does not present a concentration-based analysis of the contribution of each precursor to ambient PM_2.5 concentrations, but does estimate PM_2.5 component concentrations in the 2013 base year across all SJV monitoring sites. The concentrations indicate that each precursor may have a significant impact on PM_2.5 levels. The State presents a sensitivity-based precursor analysis using the modeled response of ambient PM_2.5 concentrations to a 15% increase or decrease in the future baseline emissions of each precursor in 2025 (the latest permissible attainment year if the area is reclassified to Serious for the 2012 PM_2.5 NAAQS). For each precursor, the State then takes the difference between the PM_2.5 concentrations from the 15% increase and the 15% decrease to estimate the ambient PM_2.5 response to a 30% change in the precursor, and reviews the resulting change at each monitor to see whether any response exceeds a threshold of 0.2 µg/m.

The responses range from 0.5 µg/m to 1.5 µg/m for NO_X; from 0.1 µg/m to 0.2 µg/m for ammonia; from 0.1 µg/m to 0.2 µg/m for SO_X; and from -0.1 µg/m to 0.1 µg/m for VOC. The State concludes that emissions of NO_X (as well as direct PM_2.5) contribute significantly to ambient PM_2.5 levels that exceed the PM_2.5 NAAQS but ammonia, SO_X, and VOC do not contribute significantly to such exceedances. The 2016 PM_2.5 Plan, Appendix A, section 5.5 (“Discussion of Precursor Sensitivity”) includes additional discussion of ammonia's and VOC's role in the formation of ammonium nitrate and VOC's role in the formation of secondary organic aerosols.

In the 2018 PM_2.5 Plan, the State's precursor demonstration and conclusions are found in Chapter 7 (“Demonstration of Federal Requirements for 2012 PM_2.5 Standard”) and Appendix G (“Precursor Demonstration”). CARB also provides clarifying information on its precursor assessment, including an Attachment A to its letter transmitting the 2018 PM_2.5 Plan to the EPA and further clarifications in four email transmittals.

The State estimates that anthropogenic emissions of NO_X, ammonia, SO_X, and VOC will decrease by 64%, 1%, 6%, and 9%, respectively, between 2013 and 2025. The 2018 PM_2.5 Plan provides both concentration-based and sensitivity-based analyses of precursor contributions to ambient PM_2.5 concentrations in the SJV. Based on these analyses, the State concludes that emissions of NO_X (as well as direct PM_2.5) contribute significantly to ambient PM_2.5 levels that exceed the PM_2.5 NAAQS in the SJV but ammonia, SO_X, and VOC do not contribute significantly to such exceedances.

While these analyses are primarily designed to evaluate the role of precursors in attaining the 2006 24-hour PM_2.5 NAAQS by 2024 and the 2012 annual PM_2.5 NAAQS by 2025, they are important to the consideration of precursors for the State's Moderate area plan because they are based on updated data (e.g., updated emissions inventories, as discussed in section IV.A of this proposed rule), use an updated methodology to evaluate the sensitivity of ambient PM_2.5 to a range of precursor emission reductions, consistent with the EPA's guidance, and best reflect the State's understanding of the control strategies being implemented in the SJV.

We summarize the State's analyses and conclusions in the following paragraphs. For ammonia, SO_X, and VOC, CARB assesses the 2015 annual average concentration of each precursor in ambient PM_2.5 at Bakersfield, for which the necessary speciated PM_2.5 data is available and where the highest PM_2.5 design values have been recorded in most years, and compares those concentrations to the recommended annual average contribution threshold of 0.2 µg/m from the EPA's “Draft PM_2.5 Precursor Guidance” available at the time the State developed the SIP. The 2015 annual average contributions of ammonia, SO_X, and VOC are 5.2 µg/m³, 1.6 µg/m³ and 6.2 µg/m³, respectively.

Given that these levels are well above the EPA's recommended contribution threshold in the Draft PM_2.5 Precursor Guidance, the State models the sensitivity of ambient PM_2.5 in the SJV to reductions in each precursor pollutant. For direct PM_2.5 and NO_X, the State models the sensitivity of ambient PM_2.5 in the SJV to a 30% reduction in anthropogenic emissions of each pollutant in 2013, 2020, and 2024. The State concludes that direct PM_2.5 and NO_X emissions reductions will continue to have a significant impact on annual and 24-hour PM_2.5 design values in the SJV, with NO_X reductions being particularly important.

For ammonia, SO_X, and VOC, the State then models the sensitivity of ambient PM_2.5 to 30% and 70% reductions in anthropogenic emissions of each precursor pollutant in 2013 (the 2018 PM_2.5 Plan's base year), 2020 (the modeled attainment year for the 1997 PM_2.5 NAAQS), and 2024 (the modeled attainment year for the 2006 PM_2.5 NAAQS, and proxy for the modeled attainment year of 2025 for the 2012 PM_2.5 NAAQS). Depending on the analysis year and percentage precursor emission reduction, the sensitivity of ambient PM_2.5 to reductions in annual average precursor emissions ranges from 0.08 µg/m to 2.30 µg/m for ammonia; from −0.05 µg/m to 0.15 µg/m for SO_X; and from −0.50 µg/m to 0.40 µg/m for VOC.

For ammonia, the modeled sensitivity of ambient PM_2.5 levels to a 30% or 70% emission reduction exceed 0.2 µg/m in certain years at specific monitoring sites. We provide a detailed summary of these modeling results and our evaluations thereof in the “Technical Support Document, EPA Evaluation of Ammonia Precursor Demonstration, San Joaquin Valley Moderate Area PM_2.5 Plan for the 2012 PM_2.5 NAAQS,” August 2021 (“EPA's Ammonia Precursor TSD”). In contrast, for SO_X and VOC, the modeled sensitivity of ambient PM_2.5 levels to a 30% or 70% emission reduction in either precursor is below 0.2 µg/m, including a disbenefit at certain monitoring sites (i.e., ambient PM_2.5 level increase), in all scenarios except one. For 2013, the State's modeling shows an ambient PM_2.5 change greater than 0.2 µg/m in response to a 70% VOC emission reduction. According to the State, however, such sensitivity results do not reflect the atmospheric chemistry in the SJV given the projected emission reductions from 2013 to 2024 for all four PM_2.5 precursors, especially for VOC and NO_X.

The State supplements the sensitivity analysis, particularly for ammonia, with consideration of additional information, including factors identified in the Draft PM_2.5 Precursor Guidance, such as emission trends, the appropriateness of future year versus base year sensitivity, available emission controls, and the severity of nonattainment. The PM_2.5 Precursor Guidance confirms that these factors may be relevant to a sensitivity-based contribution analysis.

For ammonia, the State notes that a 53% reduction in (baseline) NO_X emissions is projected to occur between 2013 and 2024, so the conditions in the early years will not persist and the future year (2024) is more representative of the Valley's ambient conditions than earlier years. The 2018 PM_2.5 Plan's precursor demonstration also presents a review of District agricultural rules that control VOC emissions and also provide ammonia co-benefits. The State concludes that a 30% reduction is a reasonable upper bound on the ammonia reductions to model. Finally, the 2018 PM_2.5 Plan's precursor demonstration presents extensive support for the State's conclusion regarding an ambient excess of ammonia relative to NO_X, i.e., that particulate ammonium nitrate formation is NO_X-limited, beyond that presented in the 2016 PM_2.5 Plan's precursor demonstration.

3. EPA Evaluation and Proposed Action

The EPA has evaluated the State's precursor demonstrations in the 2016 PM_2.5 Plan, as supplemented and updated by the precursor demonstrations in the 2018 PM_2.5 Plan, as well as other relevant information available to the EPA, consistent with the PM_2.5 SIP Requirements Rule and the recommendations in the PM_2.5 Precursor Guidance. Based on this evaluation, the EPA agrees with the State's conclusion that NO_X emissions contribute significantly to ambient PM_2.5 levels that exceed the 2012 PM_2.5 NAAQS in the SJV and that NO_X emission sources, therefore, remain subject to control requirements under subparts 1 and 4 of part D, title I of the Act. Additionally, for the reasons provided in the following paragraphs, the EPA proposes to approve the State's comprehensive precursor demonstrations for ammonia, SO_X, and VOC based on a conclusion that emissions of these precursor pollutants do not contribute significantly to ambient PM_2.5 levels that exceed the 2012 PM_2.5 NAAQS in the SJV.

The State based its analyses on the latest available data and studies concerning ambient PM_2.5 formation in the SJV from precursor emissions. For the required concentration-based analysis, the State assessed the absolute annual average contribution of each precursor to ambient PM_2.5 (i.e., in 2015). Given the absolute concentrations in 2015 were above the EPA's recommended contribution thresholds for both the 24-hour and annual average PM_2.5 NAAQS, the State proceeded to a sensitivity-based analysis, consistent with the PM_2.5 SIP Requirements Rule.

For the sensitivity-based analysis, the State performed its analyses in a straightforward application of the EPA's recommended approach—i.e., for each modeled year and level of emissions reduction (in percentages), the State estimated the ambient PM_2.5 response using the procedure recommended in the PM_2.5 Precursor Guidance, and compared the result to the EPA's recommended contribution threshold. The EPA finds that the performance of the photochemical models were adequate for use in estimating the ambient PM_2.5 responses. In particular, for the 2018 PM_2.5 Plan precursor demonstration, the State considered the EPA's recommended range of emission reductions (30% to 70%) for the 2013 base year, 2020 (an interim year), and 2024 (as a proxy for the projected 2025 attainment year for the 2012 PM_2.5 NAAQS), and quantified the estimated response of ambient PM_2.5 concentrations to precursor emission changes in the SJV.

The State's emissions projections in the 2016 PM_2.5 Plan and the 2018 PM_2.5 Plan show that baseline emissions of each of these precursors will decrease from the 2013 base year to 2021 and 2025, respectively (i.e., none of these pollutants is projected to increase). These decreases are included in the State's modeled projections of ambient PM_2.5 levels in the SJV for purposes of demonstrating attainment and RFP. The State's sensitivity analyses are consistent with these projections, in accordance with the EPA's recommendations in the PM_2.5 Precursor Guidance.

In the subsections that follow, we summarize below our evaluation of the State's precursor demonstrations for ammonia, SO_X, and VOC for purposes of the 2012 PM_2.5 NAAQS in the SJV.

a. Ammonia Precursor Demonstration

In the 2016 PM_2.5 Plan, CARB estimates the ambient PM_2.5 response to a 30% reduction in emissions in 2025 and, in the 2018 PM_2.5 Plan, CARB estimates the ambient PM_2.5 response to both a 30% and a 70% emission reduction in 2013, 2020, and 2024. We have evaluated CARB's sensitivity-based contribution analyses for 2013, 2020, and 2024 (in the 2018 PM_2.5 Plan) and for 2025 (in the 2016 PM_2.5 Plan), and CARB's determination that 2024, as a proxy for the projected attainment year of 2025, is more representative of conditions in the SJV for purposes of a sensitivity-based analysis, as discussed in the following paragraphs. We find it appropriate for the State to consider additional information as part of its evaluation of whether the ammonia contribution is significant and to rely on the responses to the 30% modeled ammonia emissions reduction in its precursor demonstration for ammonia. We provide a detailed evaluation of the State's precursor demonstration for ammonia emissions in the EPA's Ammonia Precursor TSD.

As part of its analysis in the 2016 PM_2.5 Plan, CARB estimates that the ambient PM_2.5 response to a 30% reduction in ammonia emissions would range from 0.1 µg/m³ to 0.2 µg/m³ in 2025 with 3 of 16 monitoring sites having a response of 0.2 µg/m³. However, the precursor demonstration in the 2018 PM_2.5 Plan indicates that the ambient response to a 30% ammonia emission reduction would exceed the EPA's recommended contribution threshold of 0.2 µg/m³ at a number of monitoring sites, primarily in the 2013 and 2020 analysis years. For example, the sensitivity results for a 30% reduction in ammonia emission reductions in 2020 (the closest analysis year to 2021), show that the ambient PM_2.5 response at 9 of 15 monitoring sites would exceed the 0.2 µg/m³ threshold. We consider two lines of reasoning provided by the State to support its conclusion that ammonia emissions do not contribute significantly to ambient PM_2.5 levels that exceed the 2012 PM_2.5 NAAQS in the SJV.

First, multiple researchers have suggested that ammonia emissions are underestimated in the SJV by a factor of two to five or more. This conclusion is based on comparing ambient and satellite measurements to model results that incorporate estimates of ammonia emissions and comparing monitoring or modeling results to what would be expected based on the size(s) of the ammonia and other precursor (e.g., NO_X) emission inventories. In a supplemental transmittal, CARB described the results of two analyses confirming the likely underestimation of ammonia emissions. CARB compared Community Multiscale Air Quality (CMAQ) model predictions of ammonia with the 2013 DISCOVER-AQ aircraft measurements and found that ammonia was underpredicted, and noted that this would result in the response to ammonia reductions being overpredicted. CARB also compared 2017 satellite measurements of ammonia with CMAQ model predictions and found that modeled ammonia concentrations were half of the magnitude of the satellite observations at some locations, and the modeled average in the SJV was about 25% less than observed. As a result of the likely ammonia emissions underestimation, the modeled response to ammonia precursor reductions in the 2018 PM_2.5 Plan's precursor demonstration may be unrealistically large.

If ammonia emissions were increased in the modeling to correct the likely underestimation, then modeled ammonia would be more abundant relative to nitrate; particulate nitrate formation would be more NO_X-limited, and less responsive to ammonia reductions; and the modeled response to ammonia reductions would be lower than is reported in the 2018 PM_2.5 Plan's precursor demonstration and likely below the EPA's recommended contribution threshold at most monitors in 2021.

In addition, an upward revision in the ammonia emission estimate would make the model response more consistent with the ambient measurement studies discussed in the submittal. The relevant studies suggest a very low ambient sensitivity to ammonia, based on measured excess ammonia relative to NO_X, the abundance of particulate nitrate relative to gaseous NO_X, and the large abundance of ammonia relative to nitric acid. The studies all conclude that there is a large amount of ammonia left over after reacting with NO_X, so that ammonia emission reductions would be expected mainly to reduce the amount of ammonia excess, rather than to reduce the particulate amonium nitrate.

Based on these evaluations, we find that a correction to the likely underestimation of the ammonia emission inventory would likely result in a modeled response to ammonia reductions below the 0.2 µg/m³ contribution threshold in 2021.

Second, the air quality benefit of ammonia emission reductions is projected to decline steeply over time and both the Moderate and Serious area plans for the 2012 PM_2.5 NAAQS for the SJV have been submitted to the EPA. While a concentration-based analysis is the initial step for a precursor demonstration under the PM_2.5 SIP Requirements Rule, a precursor demonstration may then proceed to a sensitivity-based contribution analysis to consider how sensitive ambient PM_2.5 levels would be to emissions reductions. Precursor concentration alone does not account for complications of meteorology and chemistry; ambient PM_2.5 may be relatively insensitive to emissions reductions and, in some circumstances, emissions reductions may even result in increased ambient PM_2.5, i.e., show a “disbenefit.”

In selecting the analysis year for a precursor demonstration, we find it appropriate to consider changes in atmospheric chemistry that may occur between the base or current year and the attainment year because the changes may ultimately affect the nonattainment area's progress toward expeditious attainment. Based on these considerations, we find it reasonable for the State to focus on the ambient PM_2.5 response to ammonia emission reductions in 2024, rather than an earlier year, as the modeled response in 2024 in the SJV better reflects the potential benefit of ammonia control measures for purposes of expeditious attainment of the 2012 PM_2.5 NAAQS. We consider the precursor demonstration in the 2018 PM_2.5 Plan as part of this evaluation, because the 2018 PM_2.5 Plan contains a Serious area attainment plan for the 2012 PM_2.5 NAAQS based on modeled emissions projections for 2024 and 2025 that are relevant to our evaluation of the ammonia precursor demonstration in the 2016 PM_2.5 Plan. The 2018 PM_2.5 Plan provides updated analyses with comprehensive modeling and additional information beyond that provided in the 2016 PM_2.5 Plan, and the 2024 model results in the 2018 PM_2.5 Plan corroborate the 2025 model results in the 2016 PM_2.5 Plan.

The State's precursor demonstrations in the 2016 PM_2.5 Plan and the 2018 PM_2.5 Plan show that ambient sensitivity to ammonia emission reductions in the SJV declines steeply over time. Between 2020 and 2024, the modeled response to a 30% ammonia emission reduction declines by 50% at the Bakersfield-Planz monitoring site, which has the highest projected PM_2.5 level, and by 37% averaged over all monitoring sites. In absolute terms, the ambient PM_2.5 response declines from 0.24 µg/m in 2020 to 0.12 µg/m in 2024 at Bakersfield-Planz, and from 0.23 µg/m to 0.14 µg/m as averaged over all monitoring sites, with the decline being generally larger for the sites with the highest projected PM_2.5 levels. Thus, between 2020 and 2024, the number of sites at which modeled sensitivity exceeds the 0.2 µg/m threshold declines from 9 of 15 to 1 or 2 of 15. As discussed above, ammonia sensitivity declines because of the shifting atmospheric chemistry caused by NO_X emissions decreases. NO_X emissions are projected to decrease 27% between 2020 and 2024 due to baseline measures (e.g., existing motor vehicle controls). The decreased NO_X emissions will make ammonia more abundant relative to NO_X, and even less of a limiting factor on PM_2.5 formation. In other words, the model response in the future attainment year 2024 gives a more realistic assessment of the potential effect of ammonia controls than past or current conditions.

Moreover, given the likely underestimate in ammonia emissions in the SJV, 2024 modeling results may be more representative even of current conditions than 2020 modeling results. For example, if 2013 ammonia emissions are underestimated by a factor of three, as suggested by the CalNex summary report, then the 2013 ratio of ammonia to NO_X emissions of 1.04 should be about 3.1, instead. The emissions ratio of ammonia to NO_X in 2024 is 2.2, which is closer to 3.1 than the emissions ratio of ammonia to NO_X in 2020, which is 1.6. Using 2024 modeling results partly compensates for the likely ammonia emissions underestimation.

Finally, the decision on whether to control ammonia does not affect the attainment year for the 2012 annual PM_2.5 NAAQS. From the 2020 sensitivity results, a 30% reduction in ammonia emissions would reduce the projected PM_2.5 level in 2021 by 0.24 µg/m³. The design value would decrease from a 2020 baseline value of 14.6 µg/m³ down to 14.3 µg/m³. The State uses a 30% ammonia emission reduction as an upper bound in the modeling but shows that even a 70% ammonia emission reduction would reduce the design value to only 13.8 µg/m³. The result of a 30% or even a 70% ammonia emission reduction, if those were possible, would still be well above the NAAQS level of 12.0 µg/m³. Attainment would remain impracticable in 2021. A decision to evaluate and possibly adopt additional ammonia controls in the 2016 PM_2.5 Plan would not remove the need for a Serious area plan identifying a later attainment year for the 2012 PM_2.5 NAAQS.

Such reductions would also have little effect in 2025. Based on the 2024 sensitivity results, if ammonia emissions were reduced by 30%, the area's 12.0 µg/m³ design value would be reduced by 0.12 µg/m³, which would not be considered significant (it is below the EPA's recommended threshold of 0.2 µg/m³). A 70% reduction might lower the design value by 0.36 µg/m³ to 11.7 µg/m³. Conceivably that could result in attainment of the 2012 PM_2.5 NAAQS in 2024 rather than 2025, but it is not clear whether reductions of that magnitude are feasible.

In sum, we find that the State quantified the sensitivity of ambient PM_2.5 levels to reductions in ammonia emissions using appropriate modeling techniques that performed well; there is likely an underestimation of ammonia emissions in the SJV and, if corrected, the modeled response to ammonia reductions would be lower than reported; and the State's choice of 2024 and 2025 as the reference points for purposes of evaluating the sensitivity of ambient PM_2.5 levels to ammonia emission reductions is well-supported. Based on all of these considerations, the EPA proposes to approve the State's demonstration that ammonia emissions do not contribute significantly to ambient PM_2.5 levels that exceed the 2012 PM_2.5 NAAQS in the SJV.

b. SO_X Precursor Demonstration0.05

As described in section IV.B.2 of this proposed rule, in the 2016 PM_2.5 Plan, CARB estimated the ambient PM_2.5 response to a 30% reduction in SO_X emissions in 2025 to range from 0.1 µg/m to 0.2 µg/m, with half the monitoring sites having a response of 0.2 µg/m. In the 2018 PM_2.5 Plan, CARB estimated the 2013 ambient PM_2.5 response to a 30% SO_X emission reduction to range from −0.01 µg/m to 0.07 µg/m and estimated the ambient PM_2.5 response to a 70% SO_X emission reduction to range from −0.05 µg/m to 0.15 µg/m. The State also provides an emissions trend chart that shows SO_X emissions to be steady at approximately 8 tpd from 2013 through 2024. Given that the relative levels of SO_X and ammonia emissions over that timeframe remain similar, the State concludes that the 2013 sensitivities are also representative of future years. The State also provides the ambient PM_2.5 responses in 2013, 2020, and 2024 to 30% and 70% reductions in SO_X emissions, all of which are below the 0.2 µg/m contribution threshold.

We note that the 2016 PM_2.5 Plan's sensitivity estimates for 2025 are at or below the EPA's recommended contribution threshold of 0.2 µg/m³, and that the 2018 PM_2.5 Plan's sensitivity estimates for 2013 are well below that threshold for both the 30% and 70% emission reduction scenarios and even negative for certain monitoring sites. Given that the latter precursor demonstration was based on updated data and an updated methodology, and the steady SO_X emission levels over 2013 to 2025 (as opposed to increases), the EPA agrees with the State's conclusion that the 2013 modeled sensitivities provide a sufficient basis for the SO_X precursor demonstration. The supplemental results provided by the State for 2020 and 2024 support this conclusion.

Therefore, on the basis of these modeled ambient PM_2.5 responses to SO_X emission reductions in the SJV, and the facts and circumstances of the area, the EPA proposes to approve the State's demonstration that SO_X emissions do not contribute significantly to ambient PM_2.5 levels that exceed the 2012 PM_2.5 NAAQS in the SJV.

c. VOC Precursor Demonstration

In the 2016 PM_2.5 Plan, CARB estimated the ambient PM_2.5 response to a 30% difference in VOC emissions in 2025 to range from −0.1 µg/m to 0.1 µg/m. In the 2018 PM_2.5 Plan, the State found that the ambient PM_2.5 response to VOC emission reductions were generally below the EPA's recommended contribution threshold of 0.2 µg/m, and often predicted an increase in ambient PM_2.5 levels in response to such reductions (i.e., a disbenefit), except for a 70% emission reduction for the 2013 base year, where the State predicted the ambient PM_2.5 response to be above both recommended thresholds at a majority of sites.

We note that the 2016 PM_2.5 Plan's sensitivity estimates for 2025 are at or below the EPA's recommended contribution threshold of 0.2 µg/m, and that the 2018 PM_2.5 Plan's sensitivity estimates for 2020 and 2024 are well below that threshold for both the 30% and 70% emission reduction scenarios, and even negative for certain monitoring sites. The State also provides an emissions trend chart that shows VOC emissions are projected to decrease by about 30 tpd, or 9% between 2013 and 2020 as well as between 2013 and 2024, and concludes that 2013 sensitivity results are not representative into the future and that the 2020 and 2024 results are representative. Finally, the State concludes that VOC emissions do not contribute significantly to PM_2.5 levels that exceed the 2012 PM_2.5 NAAQS.

The EPA has evaluated and agrees with the State's determination in the 2018 PM_2.5 Plan that the projected 2024 attainment year is more representative of conditions in the SJV for sensitivity-based analyses and that VOC reductions in 2024 would mostly result in a disbenefit to ambient PM_2.5 levels. The EPA agrees that the 9% VOC emissions decrease from 2013 to 2024 supports reliance on the 2024 modeling results. Furthermore, there is a large decrease in NO_X emissions over this period, as described in section IV.B.2 of this proposed rule, that affects the atmospheric chemistry with respect to ambient PM_2.5 formation from VOC emissions. The 9% VOC emission reductions and the vast majority of NO_X emissions reductions are expected to result from baseline measures already in effect. Therefore, we find it reasonable to rely on future year 2024 modeled responses to VOC reductions. The EPA also finds that the State provided a reasonable explanation for the VOC reduction disbenefit and evidence that it occurs in the SJV; as discussed in the EPA's “Technical Support Document, EPA Evaluation of PM_2.5 Precursor Demonstration, San Joaquin Valley PM_2.5 Plan for the 2006 PM_2.5 NAAQS,” February 2020 (“EPA's 2006 NAAQS Precursor TSD”), VOC reductions led to less peroxyacetyl nitrate formation, and greater availability of nitrate to form particulate ammonium nitrate.

For these reasons, we propose to approve the State's demonstration that VOC emissions do not contribute significantly to ambient PM_2.5 levels that exceed the 2012 PM_2.5 NAAQS in the SJV.

C. Air Quality Modeling

1. Requirements for Air Quality Modeling

Section 189(a)(1)(B) of the CAA requires each state in which a Moderate area is located to submit a plan that includes a demonstration (including air quality modeling) of either (i) attainment of the PM_2.5 NAAQS by the applicable attainment date, or (ii) attainment by that date is impracticable. The 2016 PM_2.5 Plan includes a demonstration that attainment by the Moderate attainment date is impracticable.

The EPA's PM_2.5 modeling guidance (“Modeling Guidance” and “Modeling Guidance Update”) recommends that a photochemical model, such as the Comprehensive Air Quality Model with Extensions or CMAQ, be used to simulate a base case, with meteorological and emissions inputs reflecting a base case year, to replicate concentrations monitored in that year. The model application to the base year undergoes a performance evaluation to ensure that it satisfactorily corroborates the concentrations monitored in that year. The model may then be used to simulate emissions occurring in other years required for a plan, namely the base year (which may differ from the base case year) and future year. The modeled response to the emission changes between those years is used to calculate relative response factors (RRFs) that are applied to the design value in the base year to estimate the projected design value in the future year for comparison against the NAAQS. Separate RRFs are estimated for each chemical species component of PM_2.5, and for each quarter of the year, to reflect their differing responses to seasonal meteorological conditions and emissions. Because each species is handled separately, before applying an RRF, the base year design value must be speciated using available chemical species measurements—that is, each day's measured PM_2.5 concentration must be split into its species components. The Modeling Guidance provides additional detail on the recommended approach.

The EPA has not issued modeling guidance specific to impracticability demonstrations but believes that a state seeking to make such a demonstration generally should provide air quality modeling similar to that required for an attainment demonstration. The main difference is that for an impracticability demonstration, the implementation of the SIP control strategy (including RACM) does not result in attainment of the standard by the Moderate area attainment date.

For an attainment demonstration, a thorough review of all modeling inputs and assumptions (including consistency with EPA guidance) is especially important because the modeling must ultimately support a conclusion that the plan (including its control strategy) will provide for timely attainment of the applicable NAAQS. In contrast, for an impracticability demonstration, the end point is a reclassification to Serious, which triggers the requirement for a new Serious area attainment plan with a new air quality modeling analysis, and a new control strategy. Thus, the Serious area planning process would provide an opportunity to refine the modeling analysis and/or correct any technical shortcomings in the impracticability demonstration. Therefore, the burden of proof will generally be lower for an impracticability demonstration compared to an attainment demonstration.

2. Summary of State's Air Quality Modeling

In the 2016 PM_2.5 Plan, the State discussed its air quality modeling in section 2.3 (“Summary of Modeling Results”) and Appendix A (“Air Quality Modeling”) and concludes that it is not practicable to attain the 2012 PM_2.5 NAAQS in the SJV by December 31, 2021. The State used CMAQ (version 5.02) to model three simulations: A 2013 base year to demonstrate that the model reasonably reproduced observed PM_2.5 concentrations, a 2013 reference base year simulation that excluded exceptional events such as wildfires, and a 2021 future year based on the reference year but using projected 2021 emissions. For the base year simulation, CARB conducted photochemical modeling with the CMAQ model using inputs developed from routinely available meteorological and air quality data, as well as more detailed and extensive data from the DISCOVER-AQ field study conducted in January to February 2013.

The State then generated site- and species-specific RRFs for the ammonium ion, nitrate ion, sulfate ion, organic carbon, elemental carbon, and a combined grouping of other primary PM_2.5 material for the 2021 future year simulation and calculated future year design values by multiplying the species- and site-specific RRFs by the corresponding quarterly mean component concentrations. The State summed the quarterly mean components to determine quarterly mean PM_2.5 concentrations, which it subsequently averaged to determine the annual design values. The future year design values reflect the weighted quarterly average concentration from the projections of five years of data. The State projected future year annual PM_2.5 design values for the 2021 Moderate area attainment year for the 2012 PM_2.5 NAAQS.

The 2021 baseline simulation used emission levels projected from the 2013 base year that reflect all control measures adopted by the time of the 2016 PM_2.5 Plan's development that would be implemented by December 31, 2021. This simulation indicates that the 2012 annual PM_2.5 standard will not be met in the SJV in 2021. The projected 2021 control scenario design value is 14.8 µg/m³ at Bakersfield-Planz, which is typically the monitoring site that records the highest PM_2.5 levels in the SJV.

The 2018 PM_2.5 Plan includes a modeled demonstration projecting that the SJV will attain the 2012 annual PM_2.5 NAAQS by December 31, 2025. It also includes a modeled demonstration projecting attainment of the 1997 annual PM_2.5 NAAQS by December 31, 2020, with a design value of 14.6 µg/m³ at Bakersfield-Planz. While the plan does not explicitly have a demonstration of impracticability of attaining the 2012 PM_2.5 NAAQS by 2021, the latter projections of annual PM_2.5 concentrations in 2020 provides additional information on which to judge the practicability of attaining by 2021 in that it is the closest analysis year available and represents modeling based on updated data. These projections lend support for the 2016 PM_2.5 Plan indication that the 2012 annual PM_2.5 standard will not be met in the SJV in 2021.

The Plan's primary discussion of the photochemical modeling appears in Appendix K (“Modeling Attainment Demonstration”) of the 2018 PM_2.5 Plan. The State briefly summarizes the area's air quality problem in Chapter 2.2 (“Air Quality Challenges and Trends”) and summarizes the modeling results in Chapter 6.4 (“Attainment Demonstration and Modeling”) of the 2018 PM_2.5 Plan. The State provides a conceptual model of PM_2.5 formation in the SJV as part of the modeling protocol in Appendix L (“Modeling Protocol”). Appendix J (“Modeling Emission Inventory”) describes emission input preparation procedures. The State presents additional relevant information in Appendix C (“Weight of Evidence Analysis”) of the CARB 2018 Staff Report, which includes ambient trends and other data in support of the demonstration of attainment by 2025.

3. EPA Evaluation and Conclusion

CARB's air quality modeling approach investigated the many interconnected facets of modeling ambient PM_2.5 in the SJV, including model input preparation, model performance evaluation, use of the model output for the numerical NAAQS attainment test, and modeling documentation. Specifically, this required the development and evaluation of a conceptual model, modeling protocol, episode (i.e., base year) selection, modeling domain, CMAQ model selection, initial and boundary condition procedures, meteorological model choice and performance, modeling emissions inventory preparation procedures, model performance, attainment test procedure, and adjustments to baseline air quality for modeling. These analyses are generally consistent with the EPA's recommendations in the Modeling Guidance.

The model performance evaluation in section 5.2 (“CMAQ Model Evaluation”) of both Appendix A of the 2016 PM_2.5 Plan and Appendix K of the 2018 PM_2.5 Plan included statistical and graphical measures of model performance.

The EPA previously evaluated and approved the modeling conducted for the 2006 24-hour PM_2.5 NAAQS as part of the 2018 PM_2.5 Plan; see the EPA's “Technical Support Document, EPA Evaluation of Air Quality Modeling, San Joaquin Valley PM_2.5 Plan for the 2006 PM_2.5 NAAQS,” February 2020 (“EPA's 2006 NAAQS Modeling TSD”) accompanying that action for details. The conclusions in the EPA's 2006 NAAQS Modeling TSD focused on the 24-hour PM_2.5 NAAQS; in this notice we extend the evaluation with information specific to the annual PM_2.5 NAAQS. Unless otherwise noted, the discussion applies to both the modeling in both the 2016 PM_2.5 Plan (Appendix A) and 2018 PM_2.5 Plan (Appendix K), since they followed the same model platform development procedures, and had identical meteorological inputs, very similar emissions inputs, and very similar model performance.

Most aspects of the 2018 PM_2.5 Plan modeling and the EPA's evaluation of it are the same for the 24-hour and the annual averaging times, and the EPA has found them adequate. These include the modeling protocol, choice of model, meteorological modeling, modeling emissions inventory, choice of model, modeling domain, and procedures for model performance evaluation. One aspect that differs between the 24-hour and annual averaging times is the specific calculation procedure for estimating a future design value. In the Modeling Guidance, for both averaging times, the model is used to calculate RRFs, the ratio of modeled future concentrations to base year concentrations, and the RRF is applied to monitored base year concentrations. This is done for each monitor, PM_2.5 species, and calendar quarter. But for the 24-hour averaging time, the procedure uses the highest individual concentration days in each quarter, whereas for the annual average, it uses the average of all days in each quarter. The EPA previously found that the procedures used in the 2018 PM_2.5 Plan for the 24-hour PM_2.5 NAAQS generally followed the EPA's recommendations and were adequate. For the current action, the EPA finds that State procedures for estimating future design values for the annual PM_2.5 NAAQS generally followed the EPA's recommendations and are adequate.

Another modeling aspect that can differ between 24-hour and annual average is the focus of the model performance evaluation on the respective averaging times. For the 24-hour average, it is especially important that modeled concentrations on the highest days are comparable to those on the highest monitored days, since calculation of the design value for the 24-hour PM_2.5 NAAQS uses the 98th percentile concentrations, i.e., the top 2%. For the annual average, peak concentrations continue to be important, but lower concentration days are also important since all days are included in the average. Under- and over-predictions on non-peak days may average out and have little overall effect on the modeled annual concentration, but systematic underprediction on non-peak days could lead to model underprediction of the annual average concentration. This problem of model bias is mitigated by the use of the model in a relative sense as recommended in the Modeling Guidance. In the RRF, model bias “cancels out” to a degree since it would be present in both its numerator (future year) and its denominator (base year); and applying the RRF to monitored base year concentration anchors the final model prediction to unbiased real-world concentrations. Further, RRFs are calculated on a quarterly basis, so the bias correction can better account for emissions sources and atmospheric chemistry that differ between the seasons.

The 2018 PM_2.5 Plan did not have a separate model performance evaluation for the 24-hour and annual PM_2.5 averaging times; it used statistical and graphical analyses applicable to both. For the most part, the EPA's 2006 NAAQS Modeling TSD did not distinguish between the two averaging times either but drew conclusions for the 24-hour averaging time rather than the annual averaging time. It did note a large negative bias (underprediction) in the ammonium and nitrate performance statistics for the 2nd quarters for monitoring sites in Bakersfield, Fresno, and Visalia; and we add here that the 3rd quarter has similar negative bias. The negative model bias in the 2016 PM_2.5 Plan was slightly better than in the 2018 PM_2.5 Plan, i.e., the underprediction was slightly less. Underprediction of total PM_2.5 in the 2nd and 3rd quarters is also evident in time series plots for most monitoring sites, though by only a small amount for several monitoring sites. The EPA's 2006 NAAQS Modeling TSD noted that since those quarters have concentrations that are less than half of those in the 1st and 4th, this may not be much of a concern for the annual average. (It is of less concern for the 24-hour average, since peak 24-hour concentrations occur in winter, i.e., in the 1st and 4th quarters.) As noted above, the RRF procedure removes much of this bias, so the underprediction in the model performance evaluation does not directly translate into an underpredicted 2020 design value. In addition, the 2018 PM_2.5 Plan shows that annual model performance for each PM_2.5 species is quite good relative to that seen in other modeling studies, for multiple performance statistics.

The high days are generally captured by the model, even though some are underpredicted in December at certain monitoring sites such as Fresno. Overall, the modeled site maxima are comparable to the measurements; also, the frequency of high and low days generally matches observations so the annual as well as the daily model performance is acceptable.

The EPA evaluated the State's choice of model for the impracticability demonstration and the extensive discussion in the 2016 PM_2.5 Plan about modeling procedures, tests, and performance analyses, as well as the State's modeling choices, procedures, test, and performance analyses in the 2018 PM_2.5 Plan. We find the State's analyses consistent with the EPA's guidance on modeling for PM_2.5 attainment planning purposes. Based on these reviews, we find that the modeling in the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan is adequate for the purposes of supporting the RFP demonstration and the demonstration of impracticability in the 2016 PM_2.5 Plan.

D. Reasonably Available Control Measures and Control Strategy

1. Requirements for RACM/RACT and Control Strategies

The general subpart 1 attainment plan requirement for RACM/RACT is described in CAA section 172(c)(1), which requires that attainment plan submissions “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 provide for attainment of the NAAQS.

The attainment planning requirements specific to PM_2.5 under subpart 4 likewise impose an obligation upon states with nonattainment areas classified as Moderate to develop attainment plans that require RACM/RACT on sources of direct PM_2.5 and all PM_2.5 plan precursors. CAA section 189(a)(1)(C) requires that Moderate area PM_2.5 SIPs contain provisions to assure that RACM/RACT are implemented no later than four years after designation of the area. The EPA reads CAA section 172(c)(1) and 189(a)(1)(C) together to require that attainment plans for Moderate nonattainment areas provide for the implementation of RACM/RACT for existing sources of PM_2.5 and those PM_2.5 precursors subject to control in the nonattainment area as expeditiously as practicable but no later than four years after designation.

The PM_2.5 SIP Requirements Rule defines RACM as “any technologically and economically feasible measure that can be implemented in whole or in part within 4 years after the effective date of designation of a PM_2.5 nonattainment area and that achieves permanent and enforceable reductions in direct PM_2.5 emissions and/or PM_2.5 plan precursor emissions from sources in the area. RACM includes reasonably available control technology (RACT).” The EPA has historically defined RACT as the lowest emission limitation that a particular stationary source is capable of meeting by the application of control technology that is reasonably available considering technological and economic feasibility.

Under the PM_2.5 SIP Requirements Rule, those control measures that otherwise meet the definition of RACM but “can only be implemented in whole or in part during the period beginning 4 years after the effective date of designation of a nonattainment area and no later than the end of the sixth calendar year following the effective date of designation of the area” must be adopted and implemented as “additional reasonable measures.”

States must provide written justification in a SIP submission for eliminating potential control options from further review on the basis of technological or economic infeasibility. An evaluation of technological feasibility may include consideration of factors such as a source's process and operating conditions, raw materials, physical plant layout, and non-air quality and energy impacts (e.g., increased water pollution, waste disposal, and energy requirements). An evaluation of economic feasibility may include consideration of factors such as cost per ton of pollution reduced (cost-effectiveness), capital costs, and operating and maintenance costs. Absent other indications, the EPA presumes that it is reasonable for similar sources to bear similar costs of emission reductions. Economic feasibility of RACM/RACT is thus largely informed by evidence that other sources in a source category have in fact applied the control technology, process change, or measure in question in similar circumstances.

Consistent with these requirements, CARB and SJVUAPCD must implement RACM, including RACT, for sources of direct PM_2.5 and PM_2.5 plan precursors no later than April 15, 2019, and must implement additional reasonable measures for these sources no later than December 31, 2021.

2. Summary of State's Control Strategy

The RACM/RACT evaluation for sources of direct PM_2.5 and NO_X emissions in the SJV area is presented in Chapter 3 of the 2016 PM_2.5 Plan and in Attachment 1 and Attachment 2 to the 2016 PM_2.5 Plan. Attachment 1 to the 2016 PM_2.5 Plan contains (1) a copy of the BACM/BACT and MSM control strategy evaluation for stationary and area sources that the District adopted on April 16, 2015, as part of its “2015 Plan for the 1997 PM_2.5 Standard” (“2015 PM_2.5 Plan”), and (2) a copy of the RACM/RACT control strategy evaluation for stationary and area sources that the District adopted on June 16, 2016, as part of its “2016 Plan for the 2008 8-Hour Ozone Standard” (“2016 Ozone Plan”). Attachment 2 to the 2016 PM_2.5 Plan contains (1) a copy of the BACM/BACT and MSM control strategy evaluation for mobile sources that CARB adopted on May 21, 2015, as part of the 2015 PM_2.5 Plan, and (2) a copy of the RACM/RACT control strategy evaluation for mobile sources that CARB adopted on July 21, 2016, as part of the 2016 Ozone Plan.

The 2015 PM_2.5 Plan and 2016 Ozone Plan contain comprehensive analyses to identify potential emission reduction opportunities for sources of direct PM_2.5 and NO_X emissions and to determine whether additional measures would be technologically and economically feasible for implementation in the SJV. The District states in the 2016 PM_2.5 Plan that it has not identified any new emission control technologies that could further reduce emissions in the SJV area, that the cost of technologies recently found not to be cost-effective has not changed, and that potential additional measures remain economically infeasible, consistent with the analyses and conclusions in the 2015 PM_2.5 Plan and the 2016 Ozone Plan. Based on these analyses, the District concludes that the 2016 PM_2.5 Plan satisfies the RACM/RACT requirement for stationary and area sources of direct PM_2.5 and NO_X emissions. The 2018 PM_2.5 Plan, submitted May 10, 2019, supplements these analyses by providing updated evaluations of potential control measures for sources of direct PM_2.5 and NO_X emissions and the District's rationale for finding that additional control measures are not technologically and economically feasible for implementation in the SJV.

With respect to mobile sources, the 2016 PM_2.5 Plan states that CARB has implemented the most stringent mobile source emissions control program in the nation, including emission standards for new vehicles, in-use programs for exiting vehicles and fleets, cleaner fuels, and incentive programs to accelerate penetration of cleanest vehicles. CARB states that its analyses of these mobile source control measures are presented in the 2015 PM_2.5 Plan and the 2016 Ozone Plan (included as Attachment 2 to the 2016 PM_2.5 Plan) and states that there are no additional reasonably available control measures that would advance attainment of the PM_2.5 NAAQS in the SJV. Based on these analyses, CARB concludes that the 2016 PM_2.5 Plan satisfies the RACM/RACT requirement for mobile sources of direct PM_2.5 and NO_X emissions. The 2018 PM_2.5 Plan, submitted May 10, 2019, supplements these analyses by providing updated evaluations of CARB's mobile source control measures and its rationale for finding that additional control measures are not technologically and economically feasible for implementation in the SJV at this time.

Finally, with respect to transportation control measures (TCMs), the 2016 PM_2.5 Plan states that the eight county metropolitan planning organizations (MPOs) of the SJV (“SJV MPOs”) identified and evaluated all TCMs during development of the plan. The plan states that the SJV MPOs implement TCMs in CAA section 108(f) consistent with the Congestion Mitigation and Air Quality cost effectiveness policy when developing each MPO's Regional Transportation Plan. In 2016 the Valley MPOs revisited the minimum cost effectiveness standard for TCMs during the development of the MPOs' 2017 Federal Transportation Improvement Program. The District concludes that the Valley MPOs are implementing all reasonable TCMs under the MPOs' jurisdictions and that adoption of additional TCMs would not expedite attainment of the 2012 PM_2.5 NAAQS in the SJV. The 2018 PM_2.5 Plan, submitted May 10, 2019, supplements these analyses by providing an updated discussion of the transportation control measures being implemented in the SJV.

3. EPA's Evaluation and Proposed Action

We have reviewed the State and District's demonstrations in the 2016 PM_2.5 Plan concerning RACM/RACT and additional reasonable measures for mobile, stationary, and area sources of direct PM_2.5 and one PM_2.5 plan precursor (i.e., NO_X) in the SJV. Our evaluation relies primarily on our previous evaluations of the State and District rules in connection with our February 12, 2019 approval of the SJV RACM demonstration for the 2008 ozone NAAQS (for NO_X emission sources) and in connection with our July 22, 2020 approval of the State and District's demonstrations to meet the BACM (including BACT) and MSM requirements for the 2006 PM_2.5 NAAQS. We provide a detailed discussion of these evaluations in the technical support document for this proposed rule. Based on these reviews, we propose to find that the District's rules provide for the implementation of RACM and additional reasonable measures for stationary and area sources of direct PM_2.5 and NO_X and that CARB's current program implements RACM and additional reasonable measures for mobile sources of direct PM_2.5 and NO_X emissions for purposes of the 2012 PM_2.5 NAAQS in the SJV.

With respect to transportation controls, we find that the SJV MPOs have well-established TCM development programs in which TCMs are continuously identified, reviewed, and evaluated throughout the transportation planning process. Overall, we believe that the programs developed and administered by CARB and the SJV MPOs provide for the implementation of RACM and additional reasonable measures for sources of direct PM_2.5 and NO_X in the SJV.

For these reasons, we propose to find that the 2016 PM_2.5 Plan provides for the implementation of RACM and additional reasonable measures for all sources of direct PM_2.5 and NO_X as expeditiously as practicable, for purposes of implementing the 2012 PM_2.5 NAAQS in the SJV in accordance with the requirements of CAA section 189(a)(1)(C) and 40 CFR 51.1009.

E. Nonattainment New Source Review Requirements Under CAA Section 189(e)

Section 189(e) of the CAA specifically requires that the control requirements applicable to major stationary sources of direct PM_2.5 also apply to major stationary sources of PM_2.5 precursors, except where the Administrator determines that such sources do not contribute significantly to PM_2.5 levels that exceed the standards in the area. The control requirements applicable to major stationary sources of direct PM_2.5 in a Moderate PM_2.5 nonattainment area include, at a minimum, the requirements of an NNSR permit program meeting the requirements of CAA sections 172(c)(5) and 189(a)(1)(A). In the PM_2.5 SIP Requirements Rule, we established a deadline for states to submit NNSR plan revisions to implement the PM_2.5 NAAQS 18 months after an area is initially designated and classified as a Moderate nonattainment area.

California submitted NNSR SIP revisions for the SJV to address the subpart 4 requirements for Moderate PM_2.5 nonattainment areas on May 19, 2011. The EPA fully approved these SIP revisions on September 17, 2014. California also submitted NNSR SIP revisions for the SJV to address the subpart 4 requirements for Moderate and Serious PM_2.5 nonattainment areas on November 20, 2019. The EPA is evaluating this SIP submission and will act on it in a separate rulemaking. Accordingly, in this action, the EPA is not addressing the NNSR control requirements that apply to major stationary sources of direct PM_2.5 and PM_2.5 precursors in the SJV under CAA section 189(e).

F. Demonstration That Attainment by Moderate Area Attainment Date Is Impracticable

1. Requirements for Attainment/Impracticability of Attainment Demonstrations

Section 189(a)(1)(B) of the CAA requires that each Moderate area attainment plan include a demonstration that the plan provides for attainment by the applicable Moderate area attainment date or, alternatively, that attainment by such date is impracticable. This provision explicitly requires that a demonstration of attainment be based on air quality modeling but does not require such modeling for an impracticability demonstration. Although the EPA expects that most impracticability demonstrations will also be supported by air quality modeling, it may be possible in some cases to support an impracticability demonstration with ambient PM_2.5 data and other relevant non-modeling information.

Section 188(c) of the CAA states, in relevant part, that the Moderate area attainment date “shall be as expeditiously as practicable but no later than the end of the sixth calendar year after the area's designation as nonattainment . . . .” For the SJV, which was initially designated as nonattainment for the 2012 PM_2.5 standard effective April 15, 2015, the applicable Moderate area attainment date under section 188(c) for this standard is as expeditiously as practicable but no later than December 31, 2021.

In SIP submissions that demonstrate impracticability, the state should document how its required control strategy in the attainment plan represents the application of RACM/RACT and additional reasonable measures, at minimum, to existing sources. The EPA believes it is appropriate to require adoption of all available control measures that are reasonable, i.e., technologically and economically feasible, in areas that do not demonstrate timely attainment, even where those measures cannot be implemented within the 4-year timeframe for implementation of RACM/RACT under CAA section 189(a)(1)(C). The impracticability demonstration will then be based on a showing that the area cannot attain by the applicable attainment date, notwithstanding implementation of the required controls.

2. Summary of State's Impracticability Demonstration

The 2016 PM_2.5 Plan includes a demonstration, based on air quality modeling, that even with the implementation of RACM/RACT and additional reasonable measures for all appropriate sources, attainment by December 31, 2021, is not practicable. The impracticability demonstration is included in Appendix A of the 2016 PM_2.5 Plan. As described in section IV.C.2 of this proposed rule, the projected 2021 control scenario design value is 14.8 µg/m³ at Bakersfield-Planz, which is typically the monitoring site that records the highest PM_2.5 levels in the SJV.

As further described in section IV.C.2 of this proposed rule, the 2018 PM_2.5 Plan includes a modeled demonstration that projects annual PM_2.5 concentrations in 2020 that provides additional information on which to judge the practicability of attaining by 2021 in that it is the closest analysis year available and represents modeling based on updated data. These projections lend support for the 2016 PM_2.5 Plan conclusion that the 2012 annual PM_2.5 standard will not be met in the SJV in 2021.

Table 3 shows the projected annual PM_2.5 concentrations at the four PM_2.5 monitoring sites in the SJV that are equipped with comprehensive particulate matter species characterization, as well as Bakersfield-Planz, given that it is the site with the highest annual PM_2.5 concentrations in the base year and projected future year. From the 2016 PM_2.5 Plan, the projections are for 2021 (latest permissible Moderate area attainment year); from the 2018 PM_2.5 Plan, the projections are for 2020 (the analysis year closest to 2021).

3. EPA Evaluation and Proposed Action

The impracticability demonstration in the 2016 PM_2.5 Plan is based on air quality modeling that is generally consistent with applicable EPA guidance. We find the modeling adequate to support the impracticability demonstration in the plan, as discussed in section IV.C.3 of this notice. Similarly, the attainment modeling demonstration in the 2018 PM_2.5 Plan is generally consistent with applicable EPA guidance and provides additional support that it is impracticable to attain the 2012 PM_2.5 NAAQS by 2021.

We have also evaluated the State's control measure demonstration, which relies on its BACM/MSM demonstration, as updated by the 2018 PM_2.5 Plan, and find that it provides for the expeditious implementation of all RACM/RACT and additional reasonable measures that may feasibly be implemented at this time, consistent with the requirements of CAA sections 172(c)(1) and 189(a)(1)(C) for the 2012 PM_2.5 NAAQS in the SJV, as discussed in section IV.D of this notice.

Finally, we have reviewed available monitored data to assess the practicability of attaining by 2021. Specifically, the certified 2018-2020 annual average design value for SJV is 17.6 µg/m (at Bakersfield-Planz), with exceedances of the 12.0 µg/m standard throughout the area. We note that the SJV may have experienced higher than normal PM_2.5 concentrations in 2018 and 2020 due to wildfires in the surrounding areas during the summer and fall months. This monitored data similarly supports the State's demonstration that it is impracticable to attain the 2012 PM_2.5 NAAQS by the end of 2021.

Based on this evaluation, we propose to approve the State's demonstration in the 2016 PM_2.5 Plan that attainment of the 2012 PM_2.5 NAAQS in the SJV by the Moderate area attainment date of December 31, 2021, is impracticable, consistent with the requirements of CAA section 189(a)(1)(B)(ii). On this basis, we also propose to reclassify the SJV as a Serious nonattainment area, which would trigger requirements for the State to submit a Serious area attainment plan consistent with the requirements of subparts 1 and 4 of part D, title I of the Act (as described in section V of this notice).

G. Reasonable Further Progress and Quantitative Milestones

1. Requirements for Reasonable Further Progress and Quantitative Milestones

Section 172(c)(2) of the CAA states that all nonattainment area plans shall require RFP. In addition, CAA section 189(c) requires that all PM_2.5 nonattainment area plans include quantitative milestones that the state must achieve every three years until the area is redesignated to attainment and that demonstrate RFP. Section 171(1) defines RFP as “such annual incremental reductions in emissions of the relevant air pollutant as are required by [Part D] or may reasonably be required by the Administrator for the purpose of ensuring attainment of the applicable [NAAQS] by the applicable date.” Neither subpart 1 nor subpart 4 of part D, title I of the Act requires a set percentage of emission reductions that states must achieve in any given year for purposes of satisfying the RFP requirement.

For purposes of the PM_2.5 NAAQS, the EPA has interpreted the RFP requirement to require that nonattainment area plans show annual incremental emission reductions sufficient to maintain generally linear progress toward attainment by the applicable deadline. As discussed in the EPA's guidance in the General Preamble Addendum, requiring linear progress in reductions of direct PM_2.5 and any individual precursor in a PM_2.5 plan may be appropriate in the following situations:

• The pollutant is emitted by a large number and range of sources,
• the relationship between any individual source or source category and overall air quality is not well known,
• a chemical transformation is involved (e.g., secondary particulate contributes significantly to PM_2.5 levels over the standard), and/or
• the emission reductions necessary to attain the PM_2.5 standard are inventory-wide.

The General Preamble Addendum indicates that requiring linear progress may be less appropriate in other situations, such as in situations where:

• there are a limited number of sources of direct PM_2.5 or a precursor,
• the relationships between individual sources and air quality are relatively well defined, and/or
• the emission control systems utilized (e.g., at major point sources) will result in a swift and dramatic emission reductions.

In nonattainment areas characterized by any of these latter conditions, RFP may be better represented as stepwise progress as controls are implemented and achieve significant reductions soon thereafter. For example, if an area's nonattainment problem can be attributed to a few major sources, the EPA's guidance indicates that “RFP should be met by `adherence to an ambitious compliance schedule' which is likely to periodically yield significant emission reductions of direct PM_2.5 or a PM_2.5 precursor.”

Attainment plans for the PM_2.5 NAAQS must include detailed schedules for compliance with emission regulations in the nonattainment area and provide corresponding emissions projections for each applicable milestone year that represent generally linear or stepwise progress in reducing emissions on an annual basis. In reviewing an attainment plan under subpart 4, the EPA considers whether the annual incremental emission reductions to be achieved are reasonable in light of the statutory objective of timely attainment. Although early implementation of the most cost-effective control measures is often appropriate, states should consider both cost-effectiveness and pollution reduction effectiveness when developing implementation schedules for control measures and may implement measures that are more effective at reducing PM_2.5 earlier to provide greater public health benefits.

The PM_2.5 SIP Requirements Rule establishes specific regulatory requirements for purposes of satisfying the Act's RFP requirements and provides related guidance in the preamble to the rule. Specifically, under the PM_2.5 SIP Requirements Rule, each PM_2.5 attainment plan must contain an RFP analysis that includes, at a minimum, the following four components: (1) An implementation schedule for control measures; (2) RFP projected emissions for direct PM_2.5 and all PM_2.5 plan precursors for each applicable milestone year, based on the anticipated control measure implementation schedule; (3) a demonstration that the control strategy and implementation schedule will achieve reasonable progress toward attainment between the base year and the attainment year; and (4) a demonstration that by the end of the calendar year for each milestone date for the area, pollutant emissions will be at levels that reflect either generally linear progress or stepwise progress in reducing emissions on an annual basis between the base year and the attainment year. States should estimate the RFP projected emissions for each quantitative milestone year by sector on a pollutant-by-pollutant basis. In an area that cannot practicably attain the PM_2.5 standard by the applicable Moderate area attainment date, full implementation of a control strategy that satisfies the Moderate area control requirements represents RFP towards attainment.

Section 189(c) requires that attainment plans include quantitative milestones that demonstrate RFP. The purpose of the quantitative milestones is to allow for periodic evaluation of the area's progress towards attainment of the NAAQS consistent with RFP requirements. Because RFP is an annual emission reduction requirement and the quantitative milestones are to be achieved every three years, when a state demonstrates compliance with the quantitative milestone requirement, it will demonstrate that RFP has been achieved during each of the relevant three years. Quantitative milestones should provide an objective means to evaluate progress toward attainment meaningfully, e.g., through imposition of emission controls in the attainment plan and the requirement to quantify those required emission reductions. The CAA also requires states to submit milestone reports (due 90 days after each milestone), and these reports should include calculations and any assumptions made by the state concerning how RFP has been met, e.g., through quantification of emission reductions to date. The Act requires states to include RFP and quantitative milestones even for areas that cannot practicably attain.

The CAA does not specify the starting point for counting the three-year periods for quantitative milestones under CAA section 189(c). In the General Preamble and General Preamble Addendum, the EPA interpreted the CAA to require that the starting point for the first three-year period be the due date for the Moderate area plan submission. Consistent with this longstanding interpretation of the Act, the PM_2.5 SIP Requirements Rule requires that each plan for a Moderate PM_2.5 nonattainment area contain quantitative milestones to be achieved no later than milestone dates 4.5 years and 7.5 years from the date of designation of the area. Because the EPA designated the SJV nonattainment for the 2012 PM_2.5 NAAQS effective April 15, 2015, the applicable quantitative milestone dates for purposes of this NAAQS in the SJV are October 15, 2019, and October 15, 2022. Following reclassification of the SJV as Serious for the 2012 PM_2.5 standard, later milestones would be addressed by the Serious area plan.

2. Summary of State's Reasonable Further Progress Demonstrations and Quantitative Milestones

a. 2016 PM_2.5 Plan RFP and Quantitative Milestones

The RFP demonstration and quantitative milestones are discussed in section 3.5 of the 2016 PM_2.5 Plan. The plan estimates that emissions of direct PM_2.5 and NO_X will generally decline from the 2013 base year and states that emissions of each of these pollutants will remain at or below the levels needed to show “generally linear progress” through 2022, the Moderate area post-attainment milestone year for the 2012 PM_2.5 NAAQS. The Plan's emissions inventory shows that direct PM_2.5 and NO_X are emitted by a large number and range of sources in the SJV and that the emission reductions needed for these pollutants are inventory-wide. The Plan states that all RACM and RACT for stationary, area, and mobile sources have been identified and adopted, and identifies the District rules achieving emission reductions post-2013 in Table 3-2 and CARB regulations contributing to attainment in Table 3-3.

Table 3-6 of the 2016 PM_2.5 Plan presents target RFP emission levels, based on linear emission reductions from 2013 through 2022, and the RFP projected emissions, based on the plan's baseline emissions inventory and control strategy (i.e., RACM/RACT and additional reasonable measures) for each quantitative milestone year (2019 and 2022). We reproduce Table 3-6, in part, along with the plan's 2013 base year inventory from Table 3-5, in Table 4. Based on these analyses, the District and CARB conclude that their adopted control strategy will achieve sufficient reductions in emissions of direct PM_2.5 and NO_X to result in emission levels at or below the RFP and quantitative milestone target emission levels for 2019 and 2022.

The 2016 PM_2.5 Plan documents the State's conclusion that all RACM/RACT and additional reasonable measures for these pollutants are being implemented as expeditiously as practicable and identifies projected levels of direct PM_2.5 and NO_X emissions that reflect full implementation of the State, District, and SJV MPOs' RACM/RACT and additional reasonable measure control strategy for these pollutants. The control strategy that provides the basis for these emission projections is described in attachments 1 and 2 of the 2016 PM_2.5 Plan.

For quantitative milestones, the 2016 PM_2.5 Plan identifies 2019 and 2022 as the applicable milestone years and includes milestones to track the State's and District's implementation of control measures and to document updated emissions data. For 2019, the milestone includes a “list of measures in the SIP control strategy and key implementation requirements,” including compliance milestones in CARB's Truck and Bus Regulation and in the District's Rule 4901 on residential wood burning. For 2022, the milestone includes a “list of measures in the SIP control strategy and key implementation requirements,” including compliance milestones in CARB's Truck and Bus Regulation.

b. 2018 PM_2.5 Plan RFP and Quantitative Milestones

Appendix H of the 2018 PM_2.5 Plan provides the State's updated RFP demonstration and quantitative milestones, based on updated data (e.g., updated emissions inventories, as discussed in section IV.A of this proposed rule) for the 2019 and 2022 milestone years. Following the identification of a transcription error in the RFP tables of Appendix H, the State submitted a revised version of Appendix H that corrects the transcription error and provides additional information on the RFP demonstration. Given the State's conclusions that ammonia, SO_X, and VOC emissions do not contribute significantly to PM_2.5 levels that exceed the 2012 PM_2.5 NAAQS in the SJV, as discussed in section IV.B of this proposed rule, the RFP demonstration provided by the State addresses emissions of direct PM_2.5 and NO_X. Similarly, the State developed quantitative milestones based upon the 2018 PM_2.5 Plan's strategy for reducing emissions of direct PM_2.5 and NO_X.

Like the 2016 PM_2.5 Plan, the 2018 PM_2.5 Plan estimates that emissions of direct PM_2.5 and NO_X will generally decline from the 2013 base year to the 2022 RFP milestone year and beyond, and that direct PM_2.5 and NO_X are emitted by a large number and range of sources in the SJV. The 2018 PM_2.5 Plan relies on the same set of identified control measures as the 2016 PM_2.5 Plan to demonstrate RFP through 2022, i.e., the baseline measures reflected in each plan's emissions inventory.

In addition to these baseline measures, the 2018 PM_2.5 Plan's control strategy includes specific control measure commitments for purposes of attaining the 2012 PM_2.5 NAAQS by 2025, including commitments by the State and District to develop and propose to their respective boards specific regulatory and incentive-based measures identified in the plan by specific years leading up to 2025, including 2019 and 2022. Although the attainment demonstration does not rely on these control measure commitments for emission reductions until 2024, the RFP and quantitative milestone elements of the 2018 PM_2.5 Plan rely on these control measure commitments to demonstrate that the plan requires RFP toward attainment.

Specifically, for the 2019 milestone year, Appendix H of the 2018 PM_2.5 Plan describes the District's quantitative milestone as a report on “[t]he status of SIP measures adopted between 2017 and 2019 as per the schedule included in the adopted Plan, including Residential Wood Burning Strategy and Commercial Under-Fired Charbroiler incentive-based strategy.” The schedule for development of new or revised SIP measures is in Chapter 4 of the 2018 PM_2.5 Plan and identifies an “action date” between 2017 and 2019 for one District measure: “Rule 4901, Wood Burning Fireplaces and Wood Burning Heaters (Hot-spot Strategy).”

Appendix H describes CARB's quantitative milestones as a report on three measure-specific milestones: (1) Actions taken between 2017 and 2019 to implement the Truck and Bus Regulation that required particulate filters and cleaner engine standards on existing heavy-duty diesel trucks and buses in California; (2) implementation of the “In-Use Off-Road Diesel-Fueled Fleets Regulation” (the “Off-Road Regulation”) that began in 2014 for large fleets and in 2017 for medium fleets and limited emissions from existing off-road diesel vehicles operated in California; and (3) the “status of SIP measures adopted between 2017 and 2019, including the California Low-NO _X Engine Standard for new on-road heavy-duty engines used in medium- and heavy-duty trucks purchased in California.” The schedule for development of new or revised CARB measures is in Chapter 4 of the 2018 PM_2.5 Plan and identifies “action” dates between 2017 and 2019 for eight CARB measures: “Lower Opacity Limits for Heavy-Duty Vehicles,” “Amended Warranty Requirements for Heavy-Duty Vehicles,” the “Low-NO_X Engine Standard,” “Innovative Clean Transit,” “Advanced Clean Local Trucks (Last Mile Delivery),” “Zero-Emission Airport Shuttle Buses,” “Zero-Emission Airport Ground Support Equipment,” and “Transport Refrigeration Units Used for Cold Storage.”

For the 2022 milestone year, Appendix H of the 2018 PM_2.5 Plan describes the District's quantitative milestone as a report on “[t]he status of SIP measures adopted between 2019 and 2022 as per the schedule included in the adopted Plan, including Residential Wood Burning Strategy and Commercial Under-Fired Charbroiler incentive-based strategy.” The schedule for development of new or revised SIP measures in the 2018 PM_2.5 Plan identifies “action dates” between 2019 and 2022 for 12 District measures listed in tables 4-4 and 4-5 of Chapter 4, including, for example, “Rule 4311, Flares,” “Rule 4702, Internal Combustion Engines,” and “Rule 4354, Glass Melting Furnaces.” Appendix H describes CARB's quantitative milestone as a report on two measure-specific milestones: (1) Actions taken between 2019 and 2022 to implement the Truck and Bus Regulation that required particulate filters and cleaner engine standards on existing heavy-duty diesel trucks and buses in California, and (2) the “status of SIP measures adopted between 2019 and 2022, including Advanced Clean Cars 2 and the Heavy-Duty Vehicle Inspection and Maintenance Program.” The schedule for development of new or revised CARB measures in the 2018 PM_2.5 Plan identifies “action” dates between 2019 and 2022 for 13 CARB measures listed in Table 4-8 of Chapter 4, including, for example, the “Heavy-Duty Vehicle Inspection and Maintenance Program,” “Small Off-Road Engines,” and the “Low-Emission Diesel Fuel Requirement.”

Appendix H of the 2018 PM_2.5 Plan identifies October 15, 2019, and October 15, 2022, as applicable milestone dates for the 2012 PM_2.5 NAAQS. Table H-11 in Appendix H presents the RFP projected emissions levels for 2019 and 2022, based on the plan's emissions inventory and baseline measures. We reproduce Table H-11, in part, along with the 2018 PM_2.5 Plan's base year inventory for 2013 from Appendix B, in Table 5.

The majority of the NO_X and PM_2.5 reductions from 2013 to 2019 and 2022 result from CARB's current mobile source control program, which provides significant ongoing reductions in emissions of direct PM_2.5 and NO_X from on-road and non-road mobile sources, such as light duty vehicles, heavy-duty trucks and buses, non-road equipment, and fuels. The District has also adopted numerous stationary and area source rules for direct PM_2.5 and NO_X emission sources that are projected to contribute to RFP towards attainment of the PM_2.5 standards. These include control measures for stationary internal combustion engines, residential fireplaces and woodstoves, glass manufacturing facilities, agricultural burning sources, and various sizes of boilers, steam generators, and process heaters used in industrial operations. CARB's mobile source BACM and MSM analysis in Appendix D of the 2018 PM_2.5 Plan and the District's stationary and area source BACM and MSM analysis in Appendix C of the 2018 PM_2.5 Plan provide a more comprehensive overview of each of these programs and regulations, among many others.

3. EPA Evaluation and Proposed Action

a. Reasonable Further Progress

The EPA has evaluated the RFP demonstrations in the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan (Appendix H) and proposes to find that they satisfy the statutory and regulatory requirements for RFP. Because the RFP demonstration in Appendix H of the 2018 PM_2.5 Plan is based on updated emissions data and updated information about the control strategies being implemented in the SJV, we focus our evaluation on Appendix H of the 2018 PM_2.5 Plan.

First, the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan document the State's, District's, and MPOs' conclusions that they are implementing all RACM/RACT and additional reasonable measures for direct PM_2.5 and NO_X emissions in the SJV as expeditiously as practicable. The 2018 PM_2.5 Plan also identifies the State's and District's schedules for developing and proposing certain new or revised control measures listed in their respective control measure commitments. These schedules are found in tables 4-4, 4-5, and 4-8 of the 2018 PM_2.5 Plan and in Table H-2 of Appendix H.

Second, the RFP demonstration contains projected emission levels for direct PM_2.5 and NO_X for each applicable milestone year. These projections are based on continued implementation of the existing control measures in the area (i.e., baseline measures) and reflect full implementation of the State, District, and MPOs' RACM/RACT and additional reasonable measures control strategy for these pollutants.

As shown in tables 4 and 5 of this proposed rule, the projected RFP emission levels in each plan for 2019 and 2022 are equal to the target RFP emission levels in 2019 and 2022, respectively. We note that the 2013 base year emissions in the 2018 PM_2.5 Plan's emissions inventory are 0.9 tpd lower for both direct PM_2.5 and NO_X compared to the base year emissions in the 2016 PM_2.5 Plan's emissions inventory, and that the 2018 PM_2.5 Plan's projected RFP emission levels for the 2019 and 2022 milestone years represent emission reductions that exceed those of the 2016 PM_2.5 Plan's projected RFP levels by 0.1 tpd direct PM_2.5 and 4.0 tpd NO_X in 2019, and by 0.2 tpd direct PM_2.5 and 4.5 tpd NO_X in 2022. In other words, the 2018 PM_2.5 Plan's RFP demonstration indicates a slightly faster pace of emission reductions relative to those in the 2016 PM_2.5 Plan's RFP demonstration, and thus represents a slightly more stringent RFP demonstration than that in the 2016 PM_2.5 Plan. These projected emissions levels demonstrate that the RACM/RACT and additional reasonable measures control strategy in the 2016 PM_2.5 Plan will achieve RFP toward attainment.

Finally, the RFP demonstration shows that overall pollutant emissions in each milestone year will be at levels that reflect generally linear progress toward attainment. The RFP target emissions levels for 2019 and 2022 identified in both the 2016 PM_2.5 Plan and the 2018 PM_2.5 Plan reflect consistent progress in emission reductions from the 2013 base year to the 2022 post-attainment milestone year for the 2012 PM_2.5 NAAQS, based on the implementation of the RACT/RACT and additional reasonable measures control strategy.

For these reasons, we propose to determine that the 2016 PM_2.5 Plan, as revised and supplemented by Appendix H of the 2018 PM_2.5 Plan, satisfies the requirements for RFP in CAA section 172(c)(2) and 40 CFR 51.1012 for the 2012 PM_2.5 NAAQS in the SJV.

b. Quantitative Milestones

The 2016 PM_2.5 Plan identifies the appropriate years (2019 and 2022) for quantitative milestones and Appendix H of the 2018 PM_2.5 Plan identifies specific quantitative milestone dates (i.e., October 15, 2019, and October 15, 2022) that are consistent with the requirements of 40 CFR 51.1013(a)(4). Both plans also identify the target emission levels for direct PM_2.5 and NO_X to be achieved by these milestone dates through implementation of the control strategy. Finally, Appendix H of the 2018 PM_2.5 Plan identifies commitments by the State and the District to develop and propose new or revised control measures on a fixed timeframe, for purposes of attaining the 2012 PM_2.5 NAAQS as expeditiously as practicable. These target emission levels and associated control requirements, together with the State's and District's commitments to develop and propose new or revised control measures on a fixed timeframe, provide for objective evaluation of the area's progress towards attainment of the 2012 PM_2.5 NAAQS.

The State's quantitative milestones in Appendix H are to implement specific baseline measures identified in the plan (i.e., the Truck and Bus Regulation and the Off-Road Regulation) and to develop and propose several new or revised measures listed in the State's control measure commitments that apply to heavy-duty trucks and buses and non-road equipment sources. These commitments to develop and propose additional direct PM_2.5 and NO_X control measures for mobile sources are part of CARB's strategy for attaining the 2012 PM_2.5 NAAQS in the SJV. Similarly, the District's quantitative milestones in Appendix H are to develop and propose several new or revised measures listed in the District's control measure commitments that apply to sources such as residential wood burning, conservation management practices, glass melting furnaces, and internal combustion engines. These commitments to develop and propose additional direct PM_2.5 and NO_X control measures for stationary and area sources are part of the District's strategy for attaining the 2012 PM_2.5 NAAQS in the SJV. Thus, the State's and District's obligations to implement the identified baseline control measures and to fulfil their respective commitments to develop and propose new or revised control measures for purposes of attaining the 2012 PM_2.5 NAAQS provide objective means for evaluating the SJV's progress toward timely attainment.

For these reasons, we propose to determine that the 2016 PM_2.5 Plan, as revised and supplemented by Appendix H of the 2018 PM_2.5 Plan, satisfies the requirements for quantitative milestones in CAA section 189(c) and 40 CFR 51.1013 for the 2012 PM_2.5 NAAQS in the SJV.

We note that on January 13, 2020, CARB submitted the SJV “2019 Quantitative Milestone Report for the 2012 PM_2.5 NAAQS” (“2019 QM Report”) to the EPA. The EPA is currently reviewing the SJV 2019 QM Report and will determine, as part of its action on the submitted report, whether the State and District have met their identified quantitative milestones for 2019.

H. Contingency Measures

We are presenting our review of the SIP submittals for compliance with contingency measure requirements in two different sections of this document. In this section, we present our review of the submittals with respect to the contingency measure requirements for the SJV as a Moderate area for the 2012 PM_2.5 NAAQS for which the state has submitted an impracticability demonstration. In section VII of this document, we present our review of the submittals with respect to the contingency measure requirements for the SJV for the 2006 PM_2.5 NAAQS.

1. Requirements for Contingency Measures

Under CAA section 172(c)(9), states required to make an attainment plan SIP submission must include contingency measures that they will implement if the area fails to meet RFP (“RFP contingency measures”) or fails to attain the NAAQS by the applicable attainment date (“attainment contingency measures”). Under the PM_2.5 SIP Requirements Rule, states must include contingency measures that will be implemented following a determination by the EPA that the state has failed: (1) To meet any RFP requirement in the approved SIP; (2) to meet any quantitative milestone in the approved SIP; (3) to submit a required quantitative milestone report; or (4) to attain the applicable PM_2.5 NAAQS by the applicable attainment date. Contingency measures must be fully adopted rules or control measures that are ready to be implemented quickly upon failure to meet RFP or failure of the area to meet the relevant NAAQS by the applicable attainment date.

The EPA does not interpret the requirement for contingency measures for failing to attain the NAAQS by the applicable attainment date to apply to a Moderate area that a state adequately demonstrates cannot practicably attain the NAAQS by the statutory attainment date. Rather, the EPA believes it is appropriate for the state to identify and adopt these contingency measures in a timely way as part of the Serious area attainment plan that it will develop once the EPA reclassifies such an area. However, if a state with a Moderate area that the EPA has found cannot practicably attain the NAAQS by the attainment date fails to meet RFP, when reviewed as part of the quantitative milestone either 4.5 or 7.5 years after designation, then the requirement to implement contingency measures would be triggered as required by CAA section 172(c)(9).

The purpose of contingency measures is to continue progress in reducing emissions while a state revises its SIP to meet the missed RFP requirement or to correct ongoing nonattainment. Neither the CAA nor the EPA's implementing regulations establish a specific level of emission reductions that implementation of contingency measures must achieve, but the EPA recommends that contingency measures should provide for emission reductions equivalent to approximately one year of reductions needed for RFP in the nonattainment area, calculated as the overall level of reductions needed to demonstrate attainment divided by the number of years from the base year to the attainment year. In general, we expect all actions needed to effect full implementation of the measures to occur within 60 days after the EPA notifies the state of a failure to meet RFP or to attain.

To satisfy the requirements of 40 CFR 51.1014, the contingency measures adopted as part of a PM_2.5 attainment plan must consist of control measures for the area that are not otherwise required to meet other attainment plan requirements (e.g., to meet RACM/RACT requirements) and must specify the timeframe within which their requirements become effective following any of the EPA determinations specified in 40 CFR 51.1014(a). In a 2016 decision called Bahr v. EPA (“Bahr”), the Ninth Circuit Court of Appeals rejected the EPA's interpretation of CAA section 172(c)(9) to allow approval of already-implemented control measures as contingency measures. In Bahr, the Ninth Circuit concluded that contingency measures must be measures that are triggered and implemented only after the EPA determines that an area fails to meet RFP requirements or to attain by the applicable attainment date, and the state must not have begun to implement such measures before this determination is made. Thus, already implemented measures cannot serve as contingency measures under CAA section 172(c)(9). To comply with section 172(c)(9), as interpreted in the Bahr decision, a state must develop, adopt, and submit one or more contingency measures to be triggered upon a failure to meet any RFP requirement, failure to meet a quantitative milestone requirement, or failure to attain the NAAQS by the applicable attainment date regardless of the extent to which already-implemented measures would achieve surplus emission reductions beyond those necessary to meet RFP or quantitative milestone requirements and beyond those predicted to achieve attainment of the NAAQS.

2. Summary of State's Contingency Measures

a. 2016 PM_2.5 Plan Contingency Measures

The 2016 PM_2.5 Plan includes a contingency measure element that is intended to address a potential failure to meet RFP but, consistent with the plan's demonstration that it is impracticable to attain the 2012 PM_2.5 NAAQS by December 31, 2021, that does not address a potential failure to attain the NAAQS by the applicable attainment date. Rather, the State and District conclude that they intend to identify and adopt contingency measures for failure to attain as part of the Serious area attainment plan (and, in fact, have done so in the 2018 PM_2.5 Plan). The State and District use the plan's RFP analysis through 2022 to calculate the amount of direct PM_2.5 and NO_X emission reductions that represents one year's worth of RFP. Specifically, the State and District divided the difference in emissions in 2022 and 2013 by nine to estimate one year's worth of RFP. The 2016 PM_2.5 Plan estimates that one year's worth of RFP is 0.4 tpd of direct PM_2.5 and 14.8 tpd of NO_X. The contingency measure element does not address ammonia, SO_X, and VOC in light of the State and District's conclusion that each of these three pollutants does not contribute significantly to exceedances of the 2012 PM_2.5 NAAQS in the SJV. In addition, the contingency measure element in the 2016 PM_2.5 Plan only addresses the potential failure to meet the 2019 RFP milestone, not the potential failure to meet the 2022 RFP milestone.

CARB and the District prepared the 2016 PM_2.5 Plan prior to the Bahr decision, and thus did not include any contingency measures that would only be triggered conditionally and prospectively, upon a future failure to meet RFP or other relevant event. Instead, CARB and the District relied only on emissions reductions from already-implemented measures to satisfy the contingency measure requirement. To demonstrate sufficient reductions for contingency purposes, the 2016 PM_2.5 Plan relies on three types of emission reductions: (1) 0.6 tpd direct PM_2.5 and 9.7 tpd NO_X emission reductions that are surplus to those needed by 2019 to meet that year's linear RFP target emissions, (2) 0.3 tpd NO_X emission reductions from the January 2015 amendment to Rule 4905 (“Natural Gas-Fired, Fan-Type Central Furnaces”) as being surplus to those captured in the 2016 PM_2.5 Plan's emissions inventory, and (3) 3.0 tpd NO_X of incentive-based emission reductions in conjunction with Rule 9610 (“State Implementation Plan Credit for Emission Reductions Generated Through Incentive Programs”).

CARB and the District then established a ratio of 1:8.8 to trade direct PM_2.5 emissions for NO_X emissions based on the 2016 PM_2.5 Plan's precursor sensitivity analysis for the traditional high design value sites in Bakersfield. After accounting for the 0.4 tpd direct PM_2.5 emission reductions that would meet the 2019 RFP target emission reductions, per the 2019 RFP target emission reductions, the contingency measure element relies on this trading ratio to convert 0.2 tpd of additional direct PM_2.5 emission reductions in 2019 into 1.8 tpd of NO_X emission reductions equivalent (after rounding to the tenths place). Then, after accounting for NO_X emission reductions that would meet the 2019 RFP target emissions reductions, the contingency measure element sums 9.7 tpd of surplus NO_X emission reductions with 0.3 tpd from the 2015 amendment to Rule 4905, 1.8 tpd from the surplus direct PM_2.5 conversion, and 3.0 tpd from the incentive-based emission reductions. The sum of these four types of reductions equals 14.8 tpd NO_X, which matches the State's estimate of one year's worth of RFP.

Therefore, the 2016 PM_2.5 Plan concludes that these emission reductions (equivalent to one year's worth of progress, i.e., 0.4 tpd direct PM_2.5 and 14.8 tpd NO_X) are sufficient to satisfy the contingency measure requirements for the 2012 PM_2.5 NAAQS in the SJV.

b. 2018 PM_2.5 Plan Contingency Measures

The 2018 PM_2.5 Plan addresses the contingency measure requirement for the 2012 PM_2.5 NAAQS by reference to the contingency measure portion of a December 2018 SIP submission that involved enhanced enforcement of CARB regulations in the SJV, a commitment to amend the District's residential wood burning rule (District Rule 4901) to include contingent provisions, and emissions estimates for the year following the attainment year for use in evaluating whether the emissions reductions from the contingency measures are sufficient. Recently, CARB withdrew the enhanced enforcement contingency measure of the December 2018 SIP submission as it pertained to the 2012 PM_2.5 NAAQS in the SJV. In addition, the 2018 PM_2.5 Plan does not include updated emissions estimates for the years following the 2019 and 2022 RFP milestone years with which to evaluate the sufficiency of contingency measure intended to address the applicable Moderate area requirements for the 2012 PM_2.5 NAAQS. Rather, with respect to the 2012 PM_2.5 NAAQS, the contingency measure element of the 2018 PM_2.5 Plan only includes estimates for the year (2026) following the Serious area attainment year (2025), and thus, these estimates are not relevant for evaluating the sufficiency of contingency measures submitted to comply with the Moderate area requirements for the 2012 PM_2.5 NAAQS.

Accordingly, we have evaluated the relevant portions of the 2018 PM_2.5 Plan and District Rule 4901 (specifically, section 5.7.3 of Rule 4901), and the contingency measure element in the 2016 PM_2.5 Plan as discussed above, for compliance with the applicable requirements for Moderate areas for the 2012 PM_2.5 NAAQS. However, while the 2018 PM_2.5 Plan does not provide updated emissions estimates for the years following the 2019 and 2022 RFP milestone years, the updated emission estimates in the 2018 PM_2.5 Plan do provide the basis for an updated estimate of one year's worth of RFP for the purposes of evaluating the sufficiency of contingency measures to meet the applicable Moderate area requirements for the 2012 PM_2.5 NAAQS. The updated estimates of emissions one year's worth of RFP based on the updated emissions estimates in the 2018 PM_2.5 Plan are 0.5 tpd direct PM_2.5 and 15.3 tpd NO_X. This is slightly more reductions than the 0.4 tpd direct PM_2.5 and 14.8 tpd NO_X emission reductions estimated as one year's RFP within the 2016 PM_2.5 Plan, consistent with the slightly faster pace of emission reductions reflected in the 2018 PM_2.5 Plan and discussed in section IV.G.3 of this proposed rule.

With respect to the District contingency measure, the 2018 PM_2.5 Plan calls for the District to amend District Rule 4901 (Wood Burning Fireplaces and Wood Burning Heaters) to include a requirement in the rule with a trigger that would be activated should the EPA issue a final rulemaking that the SJV failed to meet a regulatory requirement necessitating implementation of a contingency measure. In response to the commitment made in the 2018 PM_2.5 Plan, in June 2019, the District adopted amendments to Rule 4901 including a contingency measure (in section 5.7.3 of the amended rule), and, as an attachment to a letter dated July 19, 2019, CARB submitted the amended rule to the EPA for approval. The EPA has taken final action to approve amended Rule 4901, but in that approval, we noted that we were not evaluating the contingency measure in section 5.7.3 of revised Rule 4901 for compliance with all requirements of the CAA and the EPA's implementing regulations that apply to such measures. Rather, we approved the measure into the SIP because it strengthened the rule by providing a possibility of additional curtailment days, and thus potentially additional emissions reductions. We indicated that we would evaluate whether this provision, in conjunction with other submitted provisions, meets the statutory and regulatory requirements for contingency measures in future actions. In this proposal, we are now evaluating District Rule 4901, specifically, section 5.7.3, for compliance with the requirements for contingency measures for Moderate areas that cannot practicably attain the 2012 PM_2.5 NAAQS by the applicable Moderate area attainment date.

District Rule 4901 is designed to limit emissions generated by the use of wood burning fireplaces, wood burning heaters, and outdoor wood burning devices. The rule establishes requirements for the sale/transfer, operation, and installation of wood burning devices and for advertising the sale of seasoned wood consistent with a moisture content limit within the SJV.

The rule includes a two-tiered, episodic wood burning curtailment requirement that applies during four winter months, November through February. During a level one episodic wood burning curtailment, section 5.7.1 prohibits any person from operating a wood burning fireplace or unregistered wood burning heater but permits the use of a properly operated wood burning heater that meets certification requirements and has a current registration with the District. Sections 5.9 through 5.11 impose specific registration requirements on any person operating a wood burning fireplace or wood burning heater and section 5.12 imposes specific certification requirements on wood burning heater professionals. During a level two episodic wood burning curtailment, operation of any wood burning device is prohibited by section 5.7.2.

Prior to the 2019-2020 wood burning season, the District imposed a level one curtailment when the PM_2.5 concentration was forecasted to be between 20-65 µg/m³ and imposed a level two curtailment when the PM_2.5 concentration was forecasted to be above 65 µg/m³ or the PM₁₀ concentration was forecasted to be above 135 µg/m³. In 2019 the District adopted revisions to Rule 4901 to lower the wood burning curtailment thresholds in the “hot spot” counties of Madera, Fresno, and Kern. The District lowered the level one PM_2.5 threshold for these three counties from 20 µg/m³ to 12 µg/m³, and the level two PM_2.5 threshold from 65 µg/m³ to 35 µg/m³. The District did not modify the curtailment thresholds for other counties (i.e., Kings, Merced, San Joaquin, Stanislaus, and Tulare counties) in the SJV, and those levels remained at 20 µg/m³ for level one and 65 µg/m³ for level two.

The District's 2019 revision to Rule 4901 also included the addition of a contingency measure in section 5.7.3 of the rule, requiring that 60 days following the effective date of an EPA final rulemaking that the SJV has failed to attain the 1997, 2006, or 2012 PM_2.5 NAAQS by the applicable attainment date, the PM_2.5 curtailment levels for any county that has failed to attain the applicable standard will be lowered to the curtailment levels in place for hot spot counties.

3. EPA Evaluation and Proposed Action

We have evaluated the contingency measure element in the 2016 PM_2.5 Plan, as amended in the 2018 PM_2.5 Plan, and we find that the fact that the element focuses only on direct PM_2.5 and NO_X (and not ammonia, SO₂, and VOC) is acceptable in light of our proposed approval of the precursor demonstration in section IV.B of this document.

PM_2.5 attainment plan SIP submission for Moderate areas that cannot practicably attain by the Moderate area attainment date must include contingency measures for potential failures to meet RFP, submit a quantitative milestone report or meet the quantitative milestones associated with the period 4.5 and 7.5 years after designation (in this case, the 2019 and 2022 RFP milestone years). With respect to both RFP milestone years, we find that the contingency measure element is inadequate to meet the Moderate area contingency measure requirements for several reasons.

First, the emission reductions relied upon in the contingency measure element to show compliance with the contingency measure requirement (i.e., those surplus to RFP, reductions from the 2015 amendments to Rule 4905, and incentive-based emission reductions from projects in 2011-2016 in conjunction with District Rule 9610) come from measures that are not prospective (i.e., to-be-triggered) but rather come from measures that have already been implemented, and thus would not constitute contingency measures under CAA section 172(c)(9) consistent with the Bahr decision.

We recognize that the District has taken action to fulfill the commitment in the 2018 PM_2.5 Plan to revise District Rule 4901 to include specific to-be-triggered contingency provisions. However, the contingency measure provision (section 5.7.3) added to the rule is only triggered by a finding of failure to attain the PM_2.5 NAAQS by the applicable attainment date and not by failures to meet a quantitative milestone, submit a quantitative milestone report, or failure to meet an RFP requirement. Thus, the rule does not include contingency provisions to address the types of failures that are the triggering events for contingency measures for Moderate areas that cannot practicably attain the PM_2.5 NAAQS by the applicable attainment date. Therefore, section 5.7.3 of District Rule 4901 does not meet the contingency measure requirements of CAA section 172(c)(9) and 40 CFR 51.1014 for the SJV with respect to Moderate area requirements for the 2012 PM_2.5 NAAQS.

Second, as a general matter, we find that surplus emissions reductions in the years following RFP milestone years can be taken into account in determining whether a contingency measure or contingency measures are adequate for a given area for a given pollutant notwithstanding the fact that the contingency measure or contingency measures would not achieve reductions equivalent to one year's worth of RFP. However, the contingency measure element in the 2016 PM_2.5 Plan provides no emissions estimates for the year following the 2022 RFP milestone year for such an evaluation. The contingency measure element of the nonattainment area plan only provides estimates of surplus emissions reductions in 2019.

Furthermore, with respect to the emissions analysis for 2019, neither Rule 9610 (“State Implementation Plan Credit for Emission Reductions Generated Through Incentive Programs”) nor the list of Carl Moyer incentive projects in Appendix C of the 2016 PM_2.5 Plan may be relied upon as a source for surplus emissions reductions because Rule 9610 is not an emission reduction measure and because the Carl Moyer incentive projects listed in Appendix C of the 2016 PM_2.5 Plan do not satisfy CAA requirements for SIP emission reduction credit, as interpreted in the EPA's guidance. In addition, the emission reductions that might otherwise be considered surplus due to the 2015 adoption of tighter emissions limits in District Rule 4905 would not be considered surplus without additional documentation because of the option in Rule 4905 to pay mitigation fees in lieu of compliance with emissions limits.

Third, as a general matter, we agree that the use of trading ratios established through modeling techniques to convert surplus reductions of direct PM_2.5 emissions to equivalent PM_2.5 precursor emissions may be appropriate as part of the explanation for why a given contingency measure or measures are sufficient in an area with respect to a specific NAAQS. In this instance, however, we note that reliance on trading surplus direct PM_2.5 reductions for NO_X reductions at a ratio of 1:8.8 may overestimate the amount of equivalent NO_X reductions based on the information in the 2018 PM_2.5 Plan. For the 2018 PM_2.5 Plan, the State conducted further analysis of the sensitivity of ambient PM_2.5 to emission reductions in PM_2.5 precursors, as discussed in section IV.I.2 of this proposal. Based on this updated analysis for Bakersfield and Fresno sites, the State proposes to use a 1:6.5 trading ratio between direct PM_2.5 and NO_X for purposes of the 2018 PM_2.5 Plan's MVEBs. This suggests that, while for a different CAA purpose (i.e., MVEB rather than contingency measures), any excess direct PM_2.5 used for evaluation of contingency measures would be equivalent to fewer NO_X emissions reductions than assumed for the 2016 PM_2.5 Plan.

Therefore, in light of the deficiencies described in the preceding paragraphs, we are proposing to disapprove the contingency measure element of the 2016 PM_2.5 Plan, as amended in the 2018 PM_2.5 Plan, for failure to meet the requirements for contingency measures under CAA section 172(c)(9) and 40 CFR 51.1014(a) in the SJV with respect to Moderate area requirements for the 2012 PM_2.5 NAAQS. More specifically, we are proposing to disapprove the contingency measure element for failure to provide for the implementation of specific measures to be undertaken if the area fails, with respect to the 2019 and 2022 RFP milestone years, to meet RFP, to submit a quantitative milestone report (2022 RFP milestone year only), or to meet the quantitative milestones and that, once triggered, provide sufficient emissions reductions to meet the purposes of contingency measures under the CAA and EPA's implementing regulations.

I. Motor Vehicle Emissions Budgets

1. Requirements for Motor Vehicle Emissions Budgets

Section 176(c) of the CAA requires federal actions in nonattainment and maintenance areas to conform to the SIP's goals of eliminating or reducing the severity and number of violations of the NAAQS and achieving timely attainment of the standards. Conformity to the SIP's goals means that such actions will not: (1) Cause or contribute to violations of a NAAQS, (2) worsen the severity of an existing violation, or (3) delay timely attainment of any NAAQS or any interim milestone.

Actions involving Federal Highway Administration (FHWA) or Federal Transit Administration (FTA) funding or approval are subject to the EPA's transportation conformity rule, codified at 40 CFR part 93, subpart A. Under this rule, MPOs in nonattainment and maintenance areas coordinate with state and local air quality and transportation agencies, the EPA, the FHWA, and the FTA to demonstrate that an area's regional transportation plans and transportation improvement programs conform to the applicable SIP. This demonstration is typically done by showing that estimated emissions from existing and planned highway and transit systems are less than or equal to the MVEBs contained in all control strategy SIPs. An attainment, maintenance, or RFP SIP should include budgets for the attainment year, each required RFP milestone year, and the last year of the maintenance plan, as appropriate. Budgets are generally established for specific years and specific pollutants or precursors and must reflect all of the motor vehicle control measures contained in the attainment and RFP demonstrations.

Under the PM_2.5 SIP Requirements Rule, each attainment plan submittal for a Moderate PM_2.5 nonattainment area must contain quantitative milestones to be achieved no later than 4.5 years and 7.5 years after the date the area was designated nonattainment. The second of these milestone dates, October 15, 2022, falls after the latest permissible Moderate area attainment date for the SJV, which is December 31, 2021. As the EPA explained in the preamble to the PM_2.5 SIP Requirements Rule, it is important to include a post-attainment year quantitative milestone to ensure that, if the area fails to attain by the attainment date, the EPA can continue to monitor the area's progress toward attainment while the state develops a new attainment plan. Moderate area plans demonstrating that attainment by the Moderate area attainment date is impracticable must, therefore, include budgets for both of the milestone dates. States that submit impracticability demonstrations for Moderate areas under CAA section 189(a)(1)(B)(ii), however, are not required to submit budgets for the attainment year because the submitted SIP does not demonstrate attainment.

PM_2.5 plans should identify budgets for direct PM_2.5, NO_X, and all other PM_2.5 precursors for which on-road emissions are determined to contribute significantly to PM_2.5 levels in the area for each RFP milestone year and the attainment year, if the plan demonstrates attainment. All direct PM_2.5 SIP budgets should include direct PM_2.5 motor vehicle emissions from tailpipes, brake wear, and tire wear. With respect to PM_2.5 from re-entrained road dust and emissions of VOC, SO₂, and/or ammonia, the transportation conformity provisions of 40 CFR part 93, subpart A, apply only if the EPA Regional Administrator or the director of the state air agency has made a finding that transportation-related emissions of these pollutants within the area are a significant contributor to the PM_2.5 nonattainment problem and has so notified the MPO and Department of Transportation (DOT), or if the applicable implementation plan (or implementation plan submission) includes any of these pollutants in the approved (or adequate) budget as part of the RFP, attainment, or maintenance strategy. Additionally, as the EPA explained in its May 6, 2005 transportation conformity rule amendments for the PM_2.5 NAAQS, it is not necessary for a SIP to explicitly state that VOC, SO₂, and/or ammonia are insignificant precursors. Instead, states should consider the on-road contribution of all four precursors to the PM_2.5 problem as they develop their SIPs and establish emissions budgets for those precursors for which on-road emissions need to be addressed in order to attain the PM_2.5 standard as expeditiously as practicable. Conformity determinations must address all precursors for which the SIP establishes a budget and need not address those precursors for which the state has not established a budget because the emissions of that precursor are insignificant.

By contrast, transportation conformity requirements apply with respect to emissions of NO_X unless both the EPA Regional Administrator and the director of the state air agency have made a finding that transportation-related emissions of NO_X within the nonattainment area are not a significant contributor to the PM_2.5 nonattainment problem and have so notified the MPO and DOT, or the applicable implementation plan (or implementation plan submission) does not establish an approved (or adequate) budget for such emissions as part of the RFP, attainment, or maintenance strategy.

The criteria for insignificance determinations are provided in 40 CFR 93.109(f). In order for a pollutant or precursor to be considered an insignificant contributor, the control strategy SIP must demonstrate that it would be unreasonable to expect that such an area would experience enough motor vehicle emissions growth in that pollutant/precursor for a NAAQS violation to occur. Insignificance determinations are based on factors such as air quality, SIP motor vehicle control measures, trends and projections of motor vehicle emissions, and the percentage of the total SIP inventory that is comprised of motor vehicle emissions. The EPA's rationale for providing for insignificance determinations is described in the July 1, 2004, revision to the transportation conformity rule.

The EPA's process for determining the adequacy of a budget consists of three basic steps: (1) Notifying the public of a SIP submittal; (2) providing the public the opportunity to comment on the budget during a public comment period; and (3) making a finding of adequacy or inadequacy. The EPA can notify the public by either posting an announcement that the EPA has received SIP budgets on the EPA's adequacy website (40 CFR 93.118(f)(1)), or through a Federal Register notice of proposed rulemaking when the EPA reviews the adequacy of an implementation plan budget simultaneously with its review and action on the SIP itself (40 CFR 93.118(f)(2)).

For budgets to be approvable, they must meet, at a minimum, the EPA's adequacy criteria (40 CFR 93.118(e)(4)). To meet these requirements, the budgets must be consistent with the attainment and RFP requirements and reflect all of the motor vehicle control measures contained in the attainment and RFP demonstrations.

2. Summary of State's Motor Vehicle Emissions Budgets

The 2016 PM_2.5 Plan includes budgets for direct PM_2.5 and NO_X for 2019 (RFP milestone year) and 2022 (post-attainment RFP milestone year) and no other year given the plan's demonstration of the impracticability of attaining the 2012 PM_2.5 NAAQS by 2021. Similarly, for the Moderate area timeframe, the 2018 PM_2.5 Plan includes budgets for direct PM_2.5 and NO_X for 2019 and 2022 RFP milestone years. We consider the 2019 and 2022 RFP milestone budgets from the 2018 PM_2.5 Plan as superseding the corresponding budgets from the 2016 PM_2.5 Plan.

The budgets in both the 2016 PM_2.5 Plan and the 2018 PM_2.5 Plan were calculated using EMFAC2014 and the latest modeled vehicle activity data (vehicle miles traveled and speed distributions) available at the time of plan development. In the case of the 2016 PM_2.5 Plan, vehicle activity data are derived from the draft 2017 Federal-Statewide Transportation Improvement Program (2017 FSTIP) from each of the SJV's eight MPOs. The 2018 PM_2.5 Plan budgets are based on updated motor vehicle activity data from the most recently amended 2017 FSTIP (as of January 2018) from each of the SJV's eight MPOs. The budgets reflect annual average emissions consistent with the annual averaging period of the 2012 PM_2.5 NAAQS and the 2018 PM_2.5 Plan's RFP demonstration.

As with the 2016 PM_2.5 Plan, the 2018 PM_2.5 Plan includes direct PM_2.5 budgets for tailpipe, brake wear, and tire wear emissions, but does not include paved road dust, unpaved road dust, and road construction dust emissions. The 2018 PM_2.5 Plan also includes budgets for NO_X, as a regulated precursor under the plan, but does not include budgets for VOC, SO₂, or ammonia. The budgets included in the 2018 PM_2.5 Plan with respect to the Moderate area timeframe are shown in Table 6.

The 2018 PM_2.5 Plan also includes a proposed trading mechanism for transportation conformity analyses that would allow future decreases in NO_X emissions from on-road mobile sources to offset any on-road increases in direct PM_2.5 emissions. For the 2012 PM_2.5 NAAQS, the State is proposing to use the 6.5:1 NO_X:PM_2.5 ratio. The ratio is based on a sensitivity analysis based on a 30% reduction of NO_X or PM_2.5 emissions and the corresponding impact on design values at sites in Bakersfield and Fresno (i.e., updated analysis relative to the 2008 PM_2.5 Plan for the 1997 PM_2.5 NAAQS). For the sake of comparison, in approving the budgets for the SJV 2008 PM_2.5 Plan for the 1997 PM_2.5 NAAQS, the EPA approved a trading mechanism for transportation conformity analyses that allowed for such one-way trades (i.e., only excess NO_X can be used to offset PM_2.5, not vice versa) at a 9:1 NO_X:PM_2.5 ratio.

To ensure that the trading mechanism does not affect the ability of the SJV to meet the NO_X budget, the NO_X emission reductions available to supplement the PM_2.5 budget would only be those remaining after the NO_X budget has been met. The Plan also provides that the SJV MPOs shall clearly document the calculations used in the trading, along with any additional reductions of NO_X and PM_2.5 emissions in the conformity analysis.

In the submittal letter for the 2018 PM_2.5 Plan, CARB requested that we limit the duration of our approval of the budgets to the period before the effective date of the EPA's adequacy finding for any subsequently submitted budgets.

3. EPA Evaluation and Proposed Action

For the reasons discussed in section IV.F of this proposed rule, we are proposing to approve the State's demonstration that it is impracticable to attain the 2012 PM_2.5 standard in the SJV by the applicable Moderate area attainment date of December 31, 2021, and are proposing to reclassify the area as Serious. Accordingly, we are proposing action on the Moderate post-attainment year budgets for 2022 for the 2012 PM_2.5 NAAQS in the SJV. The EPA is not reviewing the submitted motor vehicle emissions budgets for 2019 because that year will not be an applicable conformity analysis year in the next conformity analysis for the SJV MPOs. Also, as noted above, we consider the 2022 RFP milestone budgets from the 2018 PM_2.5 Plan as superseding the corresponding budgets from the 2016 PM_2.5 Plan and thus are proposing action only on the former.

The EPA generally first conducts a preliminary review of budgets submitted with an attainment or maintenance plan for PM_2.5 for adequacy, prior to taking action on the plan itself, and did so with respect to the PM_2.5 budgets in the 2018 PM_2.5 Plan. On June 18, 2019, the EPA announced the availability of the 2018 PM_2.5 Plan with MVEBs and a 30-day public comment period. This announcement was posted on the EPA's adequacy website at: https://www.epa.gov/state-and-local-transportation/state-implementation-plans-sip-submissions-currently-under-epa. The comment period for this notification ended on July 18, 2019. We did not receive any comments during this comment period.

The 2018 PM_2.5 Plan establishes budgets for the 2022 RFP milestone year for direct PM_2.5 and NO_X, but not for the other PM_2.5 precursor emissions (i.e., VOC, SO₂, and ammonia). We propose to find that it is not necessary to establish motor vehicle emissions budgets for transportation-related emissions of VOC, SO₂, and ammonia to attain the 2012 annual PM_2.5 NAAQS in the SJV based on our proposal to approve the State's demonstration that emissions of VOC, SO₂, and ammonia do not contribute significantly to PM_2.5 levels that exceed the 2012 PM_2.5 NAAQS in the SJV, as discussed in section IV.B of this proposed rule. Our finding in this regard is also supported by information about VOC, SO₂, and ammonia in the 2018 PM_2.5 Plan documenting the small contribution by motor vehicles to regional precursor inventories and to PM_2.5 design values within the SJV. In addition, based on similar documentation about re-entrained road dust and construction-related fugitive dust in the 2018 PM_2.5 Plan and in accordance with 40 CFR 93.102(b)(3) and 93.122(f), the EPA proposes to find that it is not necessary to include re-entrained road dust emissions or road construction dust in the direct PM_2.5 budgets for 2012 PM_2.5 NAAQS in the SJV.

For the reasons discussed in sections IV.G of this proposed rule, the EPA proposes to approve the RFP demonstration in the 2018 PM_2.5 Plan. The 2022 RFP budgets, as shown in Table 6 of this proposed rule, are consistent with this demonstration, are clearly identified and precisely quantified, and meet all other applicable statutory and regulatory requirements including the adequacy criteria in 40 CFR 93.118(e)(4) and (5). For these reasons, the EPA proposes to approve the budgets listed in Table 6. We provide a more detailed discussion in the EPA's memo to file regarding MVEB. We are not proposing to approve the 2018 PM_2.5 Plan's budgets that pertain solely to the Serious area time frame (i.e., 2025 attainment year budget or the post-attainment year 2028 budget for the 2012 PM_2.5 NAAQS) at this time. The budgets that the EPA is proposing to approve relate to the 2012 annual PM_2.5 NAAQS only, and our proposed approval does not affect the status of the previously-approved MVEBs for the 1997 annual and 24-hour PM_2.5 NAAQS and 2006 24-hour PM_2.5 NAAQS and related trading mechanisms that remain in effect for that PM_2.5 NAAQS.

As noted above, the State included a trading mechanism to be used in transportation conformity analyses that would be used in conjunction with the budgets in the 2018 PM_2.5 Plan, as allowed for under 40 CFR 93.124(b). Furthermore, the trading ratio in the 2018 PM_2.5 Plan is based on updated air quality modeling and analysis relative to the analysis that the 2016 PM_2.5 Plan relies on (i.e., analysis and trading ratio in the 2008 PM_2.5 Plan for the 1997 PM_2.5 NAAQS). The trading mechanism in the 2018 PM_2.5 Plan would allow future decreases in annual NO_X emissions from on-road mobile sources to offset any on-road increases in annual direct PM_2.5 emissions using a 6.5:1 NO_X:PM_2.5 ratio for conformity for the 2012 annual PM_2.5 NAAQS. To ensure that the trading mechanism does not affect the ability to meet the NO_X budget, the plan provides that the NO_X emission reductions available to supplement the PM_2.5 budget would only be those remaining after the NO_X budget has been met. The SJV MPOs will have to document clearly the calculations used in the trading when demonstrating conformity, along with any additional reductions of NO_X and PM_2.5 emissions in the conformity analysis. The trading calculations must be performed prior to the final rounding to demonstrate conformity with the budgets.

The EPA has reviewed the trading mechanism as described on pages D-125 through D-127 in Appendix D of the 2018 PM_2.5 Plan and finds it is appropriate for transportation conformity purposes in the SJV for the 2012 annual PM_2.5 NAAQS. The methodology for estimating the trading ratio for conformity purposes is essentially an update (based on newer modeling) of the approach that the EPA previously approved for the 2008 PM_2.5 Plan for the 1997 PM_2.5 NAAQS and the 2012 PM_2.5 Plan for the 2006 24-hour PM_2.5 NAAQS. The State's approach in the previous plans was to model the ambient PM_2.5 effect of areawide NO_X emissions reductions and of areawide direct PM_2.5 reductions, and to express the ratio of these modeled sensitivities as an interpollutant trading ratio.

In the updated analysis for the 2018 PM_2.5 Plan, the State completed separate sensitivity analyses for the annual and 24-hour standards and modeled only transportation-related sources in the nonattainment area. The ratio the State is proposing to use for transportation conformity purposes is derived from air quality modeling that evaluated the effect of reductions in transportation-related NO_X and PM_2.5 emissions in the SJV on ambient concentrations at the Bakersfield-California Avenue, Bakersfield-Planz, Fresno-Garland, and Fresno-Hamilton & Winery monitoring sites. The modeling that the State performed to evaluate the effectiveness of NO_X and PM_2.5 reductions on ambient 24-hour concentrations showed NO_X:PM_2.5 ratios that range from a high of 7.1 at the Bakersfield-California Avenue monitor to a low of 6.0 at the two Fresno monitors. We find that the State's approach is a reasonable method to use to develop ratios for transportation conformity purposes. We therefore propose to approve the 6.5:1 NO_X for PM_2.5 trading mechanism as enforceable components of the transportation conformity program for the SJV for the 2012 annual PM_2.5 NAAQS.

Under the transportation conformity rule, once budgets are approved, they cannot be superseded by revised budgets submitted for the same CAA purpose and the same year(s) addressed by the previously approved SIP until the EPA approves the revised budgets as a SIP revision. As a general matter, such approved budgets cannot be superseded by revised budgets found adequate, but rather only through approval of the revised budgets, unless the EPA specifies otherwise in its approval of a SIP by limiting the duration of the approval to last only until subsequently submitted budgets are found adequate.

In the submittal letter for the 2018 PM_2.5 Plan, CARB requested that we limit the duration of our approval of the budgets to the period before the effective date of the EPA's adequacy finding for any subsequently submitted budgets. The transportation conformity rule allows us to limit the approval of budgets. However, we will consider a state's request to limit an approval of its MVEBs only if the request includes the following elements: (1) An acknowledgement and explanation as to why the budgets under consideration have become outdated or deficient; (2) a commitment to update the budgets as part of a comprehensive SIP update; and (3) a request that the EPA limit the duration of its approval to the period before new budgets have been found to be adequate for transportation conformity purposes.

CARB's request includes an explanation for why the budgets have become, or will become, outdated or deficient. In short, CARB has requested that we limit the duration of the approval of the budgets in light of the EPA's approval of EMFAC2017, an updated version of the EMFAC2014 used for the budgets in the 2018 PM_2.5 Plan. EMFAC2017 updates vehicle mix and emissions data of the previously approved version of the EMFAC2014.

In light of the EPA's approval of EMFAC2017, CARB explains that the budgets in the 2018 PM_2.5 Plan, which we are proposing to approve in this action, will become outdated and will need to be revised using EMFAC2017. In addition, CARB states that, without the ability to replace the budgets using the budget adequacy process, the benefits of using the updated data may not be realized for a year or more after the updated SIP (with the EMFAC2017-derived budgets) is submitted, due to the length of the SIP approval process. We find that CARB's explanation for limiting the duration of the approval of the budgets is appropriate and provides us with a reasonable basis for limiting the duration of the approval of the budgets.

We note that CARB has not committed to update the budgets as part of a comprehensive SIP update, but as a practical matter, CARB must submit a SIP revision that includes updated demonstrations as well as the updated budgets to meet the adequacy criteria in 40 CFR 93.118(e)(4). Therefore, we do not need a specific commitment for such a plan at this time. For the reasons provided above, and in light of CARB's explanation for why the budgets will become outdated and should be replaced upon an adequacy finding for updated budgets, we propose to limit the duration of our approval of the budgets in the 2018 PM_2.5 Plan to the period before we find revised budgets based on EMFAC2017 to be adequate.

Lastly, in section IV.H of this proposed rule, the EPA is proposing to disapprove the contingency measure element of the 2016 PM_2.5 Plan, as amended in the 2018 PM_2.5 Plan, with respect to Moderate area requirements for the 2012 PM_2.5 NAAQS. If the EPA were to finalize the proposed disapproval of the 2012 PM_2.5 NAAQS Moderate area contingency measure element, the area would be eligible for a protective finding under the transportation conformity rule because the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan reflect adopted control measures that fully satisfy the emissions reductions requirements for RFP for years 2019 and 2022.

V. Reclassification as Serious Nonattainment and Serious Area SIP Requirements

A. Reclassification as Serious and Applicable Attainment Date

Section 188 of the Act outlines the process for classification of PM_2.5 nonattainment areas and establishes the applicable attainment dates. Under section 188(b)(1) of the Act, the EPA has general authority to reclassify at any time before the applicable attainment date any area that the EPA determines cannot practicably attain the standard by such date. Accordingly, section 188(b)(1) of the Act is a general expression of delegated rulemaking authority. In addition, subparagraphs (A) and (B) of section 188(b)(1) mandate that the EPA reclassify “appropriate” PM₁₀ nonattainment areas at specified time frames (i.e., by December 31, 1991, for the initial PM₁₀ nonattainment areas, and within 18 months after the SIP submittal due date for subsequent nonattainment areas). These subparagraphs do not restrict the EPA's general authority but simply specify that, at a minimum, it must be exercised at certain times.

We have reviewed the air quality modeling and impracticability demonstration in the 2016 PM_2.5 Plan, as well as the air quality modeling in the 2018 PM_2.5 Plan. Based on our review, we agree with the District's conclusion that implementation of the State/District's SIP control strategy, including RACM/RACT and additional reasonable measures, is insufficient to bring the SJV into attainment of the 2012 PM_2.5 NAAQS by the December 31, 2021 Moderate area attainment deadline. See sections IV.C and IV.F of this proposed rule. In addition, we have reviewed recent PM_2.5 monitoring data for SJV available in the EPA's Air Quality System (AQS) database. These data show that annual PM_2.5 levels in the SJV continue to be above 12.0 µg/m, the numerical level of the 2012 PM_2.5 standard, and the recent trends in the SJV annual PM_2.5 levels indicate that the SJV will not attain by the end of 2021.

In accordance with section 188(b)(1) of the Act, the EPA is proposing to reclassify the SJV from Moderate to Serious nonattainment for the 2012 annual PM_2.5 standard of 12.0 µg/m³, based on the EPA's determination that the SJV cannot practicably attain the standard by the applicable attainment date of December 31, 2021.

Under section 188(c)(2) of the Act, the attainment date for a Serious area “shall be as expeditiously as practicable but no later than the end of the tenth calendar year beginning after the area's designation as nonattainment . . .” The EPA designated the SJV as nonattainment for the 2012 PM_2.5 NAAQS effective April 15, 2015. Therefore, upon final reclassification of the SJV as a Serious nonattainment area, the latest permissible attainment date under section 188(c)(2) of the Act, for purposes of the 2012 PM_2.5 NAAQS in this area, will be December 31, 2025.

Under section 188(e) of the Act, a state may apply to the EPA for a single extension of the Serious area attainment date of up to five additional years, which the EPA may grant if the state satisfies certain statutory conditions. Before the EPA may extend the attainment date for a Serious area under section 188(e), the state must: (1) Apply for an extension of the attainment date beyond the statutory attainment date; (2) demonstrate that attainment by the statutory attainment date is impracticable; (3) demonstrate that it has complied with all requirements and commitments pertaining to the area in the implementation plan; (4) demonstrate to the satisfaction of the Administrator that the plan for the area includes the most stringent measures that are included in the implementation plan of any state or are achieved in practice in any state, and can feasibly be implemented in the area; and (5) submit a demonstration of attainment by the most expeditious alternative date practicable.

B. Clean Air Act Requirements for Serious Area Plans

Upon reclassification as a Serious nonattainment area for the 2012 PM_2.5 NAAQS, California will be required to submit additional SIP revisions to satisfy the statutory requirements that apply to Serious PM_2.5 nonattainment areas, including the requirements of subpart 4 of part D, title I of the Act.

The Serious area SIP elements that California will be required to submit are as follows:

1. Provisions to assure that BACM, including BACT for stationary sources, for the control of direct PM_2.5 and PM_2.5 precursors shall be implemented no later than four years after the area is reclassified (CAA section 189(b)(1)(B));

2. a demonstration (including air quality modeling) that the plan provides for attainment as expeditiously as practicable but not later than December 31, 2025, or where the state is seeking an extension of the attainment date under section 188(e), a demonstration that attainment by December 31, 2025, is impracticable and that the plan provides for attainment by the most expeditious alternative date practicable and not later than December 31, 2030 (CAA sections 189(b)(1)(A), 188(c)(2), and 188(e));

3. plan provisions that require RFP (CAA section 172(c)(2));

4. quantitative milestones that are to be achieved every three years until the area is redesignated to attainment and that demonstrate RFP toward attainment by the applicable date (CAA section 189(c));

5. provisions to assure that control requirements applicable to major stationary sources of PM_2.5 also apply to major stationary sources of PM_2.5 precursors, except where the state demonstrates to the EPA's satisfaction that such sources do not contribute significantly to PM_2.5 levels that exceed the standard in the area (CAA section 189(e));

6. a comprehensive, accurate, current inventory of actual emissions from all sources of PM_2.5 and PM_2.5 precursors in the area (CAA section 172(c)(3));

7. contingency measures to be implemented if the area fails to meet RFP (including quantitative milestones and related reports) or to attain by the applicable attainment date (CAA section 172(c)(9)); and

8. a revision to the NNSR program to lower the applicable “major stationary source” thresholds from 100 tpy to 70 tpy (CAA section 189(b)(3)) and to satisfy the subpart 4 control requirements for major stationary sources of PM_2.5 precursors (CAA section 189(e)).

As discussed in section IV.E of this proposed rule, California submitted NNSR SIP revisions for the SJV to address the subpart 4 NNSR requirements for Serious PM_2.5 nonattainment areas on November 20, 2019. The EPA is evaluating this SIP submission and will act on it in a separate rulemaking.

Finally, reclassification of the SJV as Serious nonattainment for the 2012 annual PM_2.5 NAAQS would lower the de minimis threshold under the CAA's general conformity requirements (40 CFR part 93, subpart B) from 100 tpy to 70 tpy for PM_2.5 and PM_2.5 precursors. In this case, however, reclassification would have no impact on the applicable general conformity de minimis thresholds, because the SJV is already subject to the 70 tpy de minimis threshold for PM_2.5 and all PM_2.5 precursors as a result of the EPA's previous actions reclassifying the area as Serious nonattainment for the 1997 annual and 24-hour PM_2.5 NAAQS and the 2006 24-hour PM_2.5 NAAQS.

C. Statutory Deadline for Submission of Serious Area Plan

When the EPA reclassifies a nonattainment area to a higher classification, the CAA sets the parameters for establishing deadlines for attainment plan SIP submissions for that higher classification. The State has already made submissions intended to address the Serious area attainment plan requirements for the 2012 PM_2.5 NAAQS for the SJV, yet the EPA reclassification rulemaking must still establish the submission deadlines, as discussed in the following paragraphs. Among other things, such deadlines make clear the time frame for any future SIP submission should the State find the need to withdraw any particular element of the Serious area plan requirements (i.e., without the submittal of a replacement element meeting the completeness criteria).

For an area reclassified as a Serious nonattainment area before the applicable attainment date under CAA section 188(b)(1), section 189(b)(2) requires the state to submit the required BACM provisions “no later than 18 months after reclassification of the area as a Serious Area” and to submit the required attainment demonstration “no later than 4 years after reclassification of the area to Serious.” Section 189(b)(2) establishes outer bounds on the SIP submission deadlines as necessary or appropriate to assure consistency among the required submissions and to implement the statutory requirements.

The Act provides the state with up to 18 months after final reclassification of an area to Serious to submit the required BACM provisions. Because an up-to-date emissions inventory serves as the foundation for a state's BACM/BACT determination, the PM_2.5 SIP Requirements Rule requires the state to submit the emissions inventory required under CAA section 172(c)(3) within 18 months after the effective date of final reclassification. Similarly, because an effective evaluation of BACM/BACT measures requires evaluation of the precursor pollutants that must be controlled to provide for expeditious attainment in the area, if the state chooses to submit an optional precursor insignificance demonstration to support a determination to exclude a PM_2.5 precursor from the required control measure evaluations for the area, the EPA requires that the state submit any such demonstration by this same date. An 18-month time frame for submission of these plan elements is consistent with both the time frame for submission of BACM/BACT provisions under CAA section 189(b)(2) and the time frame for submission of subpart 1 plan elements under section 172(b) of the Act.

The PM_2.5 SIP Requirements Rule also establishes a specific deadline for submission of the attainment demonstration and attainment-related plan elements following discretionary reclassification, which is the earlier of four years from the date of reclassification, or the end of the eighth calendar year after designation. In this case, the earlier of these two dates will be the end of the eighth calendar year after designation—i.e., December 31, 2023. The attainment-related plan elements required within the same timeframe as the attainment demonstration are as follows: (1) The RFP demonstration required under section 172(c)(2); (2) the quantitative milestones required under section 189(c); (3) any additional control measures necessary to meet the requirements of section 172(c)(6); and (4) the contingency measures required under section 172(c)(9). Although section 189(b)(2) generally provides for up to four years after a discretionary reclassification for the state to submit the required attainment demonstration, given the timing of this reclassification action less than two years before the Moderate area attainment date, it is appropriate in this case for the EPA to establish an earlier SIP submission deadline to assure timely implementation of the statutory requirements.

Finally, the PM_2.5 SIP Requirements Rule establishes a regulatory requirement that the state submit revised NNSR program requirements no later than 18 months after final reclassification. The Act does not specify a deadline for the state's submission of SIP revisions to meet NNSR program requirements to lower the “major stationary source” threshold from 100 tpy to 70 tpy (CAA section 189(b)(3)) and to address the control requirements for major stationary sources of PM_2.5 precursors (CAA section 189(e)) following reclassification of a Moderate PM_2.5 nonattainment area as Serious nonattainment under subpart 4. Pursuant to the EPA's gap-filling authority in CAA section 301(a) and to effectuate the statutory control requirements in section 189 of the Act, the PM_2.5 SIP Requirements Rule requires the state to submit these NNSR SIP revisions, as well as any necessary analysis of and additional control requirements for major stationary sources of PM_2.5 precursors, no later than 18 months after the effective date of final reclassification of the SJV as Serious nonattainment for the 2012 PM_2.5 standard. This due date will ensure that necessary control requirements for major sources are established in advance of the required attainment demonstration. An 18-month timeframe for submission of the NNSR SIP revisions also aligns with the statutory deadline for submission of BACM and BACT provisions and the broader analysis of PM_2.5 precursors for potential controls on existing sources in the area.

Accordingly, if we finalize our proposal to reclassify the SJV as a Serious nonattainment area for the 2012 PM_2.5 NAAQS, California would be required to submit the emissions inventory required under CAA section 172(c)(3), the BACM/BACT provisions required under CAA section 189(b)(1)(B), and any NNSR SIP revisions required to satisfy the requirements of CAA sections 189(b)(3) and 189(e) for the 2012 PM_2.5 NAAQS no later than 18 months after the effective date of a final reclassification action. Additionally, California would be required to submit the Serious area attainment demonstration and all attainment-related plan elements no later than the end of the eighth calendar year after designation—i.e., by December 31, 2023.

We note that the 2018 PM_2.5 Plan submitted on May 10, 2019, includes a Serious area plan containing an attainment demonstration, emissions inventory, attainment-related plan elements, and BACM/BACT provisions. Also, the State submitted a SIP revision for the Serious area NNSR requirements on November 20, 2019. The EPA intends to evaluate and act on the Serious area plan and NNSR SIP submissions for the 2012 PM_2.5 NAAQS in the SJV through separate rulemakings, as appropriate.

VI. Reclassification of Areas of Indian Country

Eight Indian tribes are located within the boundaries of the SJV nonattainment area for the 2012 PM_2.5 NAAQS. These tribes include Big Sandy Rancheria of Western Mono Indians of California, Cold Springs Rancheria of Mono Indians of California, Northfork Rancheria of Mono Indians of California, Picayune Rancheria of Chukchansi Indians of California, Santa Rosa Indian Community of the Santa Rosa Rancheria, California, Table Mountain Rancheria, Tejon Indian Tribe, and Tule River Indian Tribe of the Tule River Reservation, California.

We have considered the relevance of our proposal to reclassify the SJV as Serious nonattainment for the 2012 PM_2.5 standard for each tribe located therein. We believe that the same facts and circumstances that support the proposal for the non-Indian country lands also support the proposal for reservation areas of Indian country and any other areas of Indian country where the EPA or a tribe has demonstrated that the tribe has jurisdiction located within the SJV nonattainment area. The EPA is therefore proposing to exercise our authority under CAA section 188(b)(1) to reclassify areas of Indian country geographically located in the SJV nonattainment area. Section 188(b)(1) broadly authorizes the EPA to reclassify a nonattainment area—including any Indian country located within such an area—that the EPA determines cannot practicably attain the relevant standard by the applicable attainment date.

Directly-emitted PM_2.5 and its precursor pollutants (i.e., NO_X, SO₂, VOC, and ammonia) are emitted throughout a nonattainment area and can be transported throughout that nonattainment area. Therefore, boundaries for nonattainment areas are drawn to encompass both areas with direct sources of the pollutant problem as well as nearby areas in the same airshed. Initial classifications apply to the entire nonattainment area, i.e., they exactly match the nonattainment area boundaries. The EPA believes this approach best ensures public health protection from the adverse effects of PM_2.5 pollution. Therefore, it is generally counterproductive from an air quality and planning perspective to have a disparate classification for a land area located within the boundaries of a nonattainment area, such as the reservation areas of Indian country contained within the SJV PM_2.5 nonattainment area. Violations of the 2012 PM_2.5 standard, which are measured and modeled throughout the nonattainment area, as well as shared meteorological conditions, would dictate the same conclusion. Furthermore, emission increases in portions of a PM_2.5 nonattainment area that are left classified as Moderate could counteract the effects of efforts to attain the standard within the overall area because less stringent requirements would apply in those Moderate portions relative to those that would apply in the portions of the area reclassified to Serious.

Uniformity of classification throughout a nonattainment area is thus a guiding principle and premise when an area is being reclassified. In this particular case, we are proposing to determine, based on the State's demonstration and current ambient air quality trends, that the entire SJV nonattainment area, including all reservations areas of Indian country and any other area located within the SJV where a tribe has jurisdiction, cannot practicably attain the 2012 PM_2.5 standard by the applicable Moderate area attainment date of December 31, 2021.

In light of the considerations outlined above that support retention of a uniformly-classified PM_2.5 nonattainment area, and our proposal to find that it is impracticable for the area to attain by the applicable attainment date, we propose to reclassify the entire SJV nonattainment area, including reservation areas of Indian country and any other area of Indian country located within it where the EPA or a tribe has demonstrated that the tribe has jurisdiction, as Serious nonattainment for the 2012 PM_2.5 standard.

Generally, the effect of reclassification is to lower the applicable “major source” threshold for purposes of the NNSR program and the Title V operating permit program from 100 tpy to 70 tpy, thus subjecting additional new or modified stationary sources to these requirements. Reclassification also lowers the de minimis threshold under the CAA's general conformity requirements from 100 tpy to 70 tpy. In this case, however, reclassification would not change the “major source” thresholds because, as a result of the EPA's January 2016 reclassification of the SJV as a Serious nonattainment area for the 2006 PM_2.5 NAAQS, the area is already subject to the 70 tpy major source threshold for Serious PM_2.5 nonattainment areas in CAA section 189(b)(3). Likewise, reclassification would have no impact on the applicable general conformity de minimis thresholds, because the SJV is already subject to the 70 tpy de minimis threshold for PM_2.5 and all PM_2.5 precursors as a result of the EPA's previous reclassification of the area as Serious for the 2006 PM_2.5 NAAQS.

The EPA has contacted tribal officials to invite government-to-government consultation on this rulemaking effort. The EPA specifically solicits additional comment on this proposed rule from tribal officials. We note that although eligible tribes may seek EPA approval of relevant tribal programs under the CAA, none of the affected tribes will be required to submit an implementation plan as a result of this reclassification.

VII. Review of Contingency Measure Element for the 2006 PM_2.5 NAAQS

A. Requirements for Contingency Measures

With one exception, the SIP requirements for contingency measures that apply to areas classified as Serious for the 2006 PM_2.5 NAAQS are the same as those described in section IV.H.1 of this document for areas that are classified as Moderate for the 2012 PM_2.5 NAAQS and cannot practicably attain the NAAQS by the statutory attainment date, and thus, are not repeated here. However, in addition to the contingency measures requirements that apply to Moderate areas with adequate impracticability demonstrations, states with areas classified as Serious must identify and adopt contingency measures to address the potential for the area to fail to attain the NAAQS by the applicable attainment date.

B. Summary of State's Contingency Measure Element for 2006 PM _2.5 NAAQS

The EPA deferred action on the contingency measure element of the 2018 PM_2.5 Plan for the 2006 PM_2.5 NAAQS when we took final action on the other elements in the 2018 PM_2.5 Plan for that NAAQS. In this section of this document, we are proposing action on the contingency measure element of the 2018 PM_2.5 Plan for the 2006 PM_2.5 NAAQS.

The 2018 PM_2.5 Plan addresses the contingency measure requirement for the 2006 24-hour PM_2.5 NAAQS by reference to the contingency measure portion of a December 2018 SIP submission that involved enhanced enforcement of CARB regulations in the SJV, a commitment to amend the District's residential wood burning rule (i.e., District Rule 4901) to include contingent provisions, and updated emissions estimates for the year following the attainment year for use in evaluating whether the emissions reductions from the contingency measures are sufficient. Recently, CARB withdrew the enhanced enforcement portion of the December 2018 SIP submission as it pertained to the 2006 PM_2.5 NAAQS in the SJV.

Accordingly, we have evaluated the relevant portions of the 2018 PM_2.5 Plan and District Rule 4901 (specifically, section 5.7.3 of Rule 4901) for compliance with the applicable requirements for Serious areas for the 2006 PM_2.5 NAAQS.

With respect to the District contingency measure, the 2018 PM_2.5 Plan calls for the District to amend District Rule 4901 to include a requirement in the rule with a trigger that that would be activated should the EPA issue a final rulemaking that the SJV failed to meet a regulatory requirement necessitating implementation of a contingency measure. In response to the commitment made in the 2018 PM_2.5 Plan, in June 2019, the District adopted amendments to Rule 4901 including a contingency measure (in section 5.7.3 of the amended rule), and CARB submitted the amended rule to the EPA for approval as an attachment to a letter dated July 19, 2019. The EPA has taken final action to approve amended Rule 4901, but in that approval, we noted that we were not evaluating the contingency measure in section 5.7.3 of revised Rule 4901 for compliance with all requirements of the CAA and the EPA's implementing regulations that apply to such measures. Rather, we approved the measure into the SIP because it strengthened the rule by providing a possibility of additional curtailment days, and thus potentially additional emissions reductions. We indicated that we would evaluate whether this provision, in conjunction with other submitted provisions, meets the statutory and regulatory requirements for contingency measures in future actions. In this proposal, we are now evaluating District Rule 4901, specifically, section 5.7.3, for compliance with the requirements for contingency measures for purposes of the 2006 PM_2.5 NAAQS.

District Rule 4901 is designed to limit emissions generated by the use of wood burning fireplaces, wood burning heaters, and outdoor wood burning devices. The rule establishes requirements for the sale/transfer, operation, and installation of wood burning devices and for advertising the sale of seasoned wood consistent with a moisture content limit within the SJV.

The rule includes a two-tiered, episodic wood burning curtailment requirement that applies during four winter months, November through February. During a level one episodic wood burning curtailment, section 5.7.1 prohibits any person from operating a wood burning fireplace or unregistered wood burning heater but permits the use of a properly operated wood burning heater that meets certification requirements and has a current registration with the District. Sections 5.9 through 5.11 impose specific registration requirements on any person operating a wood burning fireplace or wood burning heater and section 5.12 imposes specific certification requirements on wood burning heater professionals. During a level two episodic wood burning curtailment, operation of any wood burning device is prohibited by section 5.7.2.

Prior to the 2019-2020 wood burning season, the District imposed a level one curtailment when the PM_2.5 concentration was forecasted to be between 20-65 µg/m³ and imposed a level two curtailment when the PM_2.5 concentration was forecasted to be above 65 µg/m³ or the PM₁₀ concentration was forecasted to be above 135 µg/m³. In 2019, the District adopted revisions to Rule 4901 to lower the wood burning curtailment thresholds in the “hot spot” counties of Madera, Fresno, and Kern. The District lowered the level one PM_2.5 threshold for these three counties from 20 µg/m³ to 12 µg/m³, and the level two PM_2.5 threshold from 65 µg/m³ to 35 µg/m³. The District did not modify the curtailment thresholds for other counties in the SJV, and those levels remained at 20 µg/m³ for level one and 65 µg/m³ for level two.

The District's 2019 revision to Rule 4901 also included the addition of a contingency measure in section 5.7.3 of the rule, requiring that 60 days following the effective date of an EPA final rulemaking that the SJV has failed to attain the 1997, 2006, or 2012 PM_2.5 NAAQS by the applicable attainment date, the PM_2.5 curtailment levels for any county that has failed to attain the applicable standard will be lowered to the curtailment levels in place for hot spot counties. The District estimates that the potential emissions reduction in direct PM_2.5 would be in the range of 0.014 tpd (if the contingency is triggered in Kings County but not the other non-hot-spot counties) to 0.387 tpd (if the contingency is triggered in all five of the non-hot-spot counties), but there would be no emissions reduction if, at the time of the determination of failure to attain the 2006 PM_2.5 NAAQS by the attainment date, violations of the 2006 PM_2.5 NAAQS were only observed at monitors in the hot-spot counties. Corresponding potential emissions reduction in NO_X would be in the range of 0.002 tpd to 0.060 tpd, respectively, but as noted in the preceding paragraphs there may be no emissions reduction if the violations are monitored in the hot-spot counties only.

The 2018 PM_2.5 Plan also provides estimates of regional emissions in the year following the attainment year with which to evaluate the sufficiency of the emissions reductions from the contingency measure (i.e., section 5.7.3 of Rule 4901). For the 2006 PM_2.5 NAAQS, the attainment year is 2024 and the year after the attainment year is therefore 2025. Based on Table H-5 in the 2018 PM_2.5 Plan, the annual average emission reductions from 2024 to 2025 due to baseline measures and CARB and the District's aggregate tonnage commitment are estimated to be 0 tpd direct PM_2.5 and 5.2 tpd NO_X. For comparison purposes, one year's worth of RFP (based on emissions estimates in the 2018 PM_2.5 Plan) is approximately 0.6 tpd direct PM_2.5 and 18.4 tpd NO_X.

C. EPA Evaluation and Proposed Action

For the 2006 PM_2.5 NAAQS, we have similarly evaluated the contingency measure demonstration in the 2018 PM_2.5 Plan and associated contingency provision of the 2019 amendment to Rule 4901. Specifically, we have evaluated the contingency provision in District Rule 4901 (i.e., section 5.7.3 of the rule) against the requirements of CAA section 172(c)(9) and 40 CFR 51.1014 for both attainment and RFP contingency measures, the latter of which also includes submittal of quantitation milestone reports and compliance with quantitative milestones.

As noted in our summary of the State's submission, the contingency provision in District Rule 4901 is structured to provide for implementation if the area fails to attain the 2006 PM_2.5 NAAQS, not before, and is therefore consistent with CAA section 172(c)(9). However, as structured by the District, the contingency provision of Rule 4901 (i.e., section 5.7.3) would provide for emissions reductions only in Kings, Merced, San Joaquin, Stanislaus, and/or Tulare counties, not the “hot spot” counties of Fresno, Kern, and Madera, and only if a violating monitoring site (i.e., a site where the collected data represent a violation of the NAAQS) is located in said county. In other words, if the EPA's determination of failure to attain the NAAQS by the applicable attainment date indicates violations at monitoring location sites in Fresno and Kern (“hot spot” counties) and Tulare (non-hot-spot county) counties, the contingency provision would provide for emissions reductions by lowering the wood burning curtailment thresholds in only Tulare County. The “hot spot” counties are already subject to the lower wood burning curtailment thresholds in the rule and thus would not be affected by the finding of failure to attain determination and the other non-“hot spot” counties (i.e., other than Tulare County in this example) would not be subject to the lower wood burning curtailment thresholds.

In accordance with 40 CFR 51.1014, the contingency provision in District Rule 4901 identifies a specific triggering mechanism. In this case, the triggering mechanism in the rule is the EPA's final determination that the SJV has failed to attain the 2006 PM_2.5 NAAQS by the applicable attainment date. The rule also specifies a timeframe within which its requirements become effective after a failure-to-attain determination (i.e., on and after 60 days from the effective date of the EPA's final determination), and would take effect with minimal further action by the state or the EPA. However, the contingency provision in District Rule 4901 does not address the potential for State failures to meet a quantitative milestone, submit a quantitative milestone report, or failure to meet an RFP requirement.

In addition, the contingency measure provision of Rule 4901 is not structured to achieve any additional emissions reductions if the EPA finds that the monitoring locations in the “hot spot” counties (i.e., Fresno, Kern, or Madera Counties) are the only ones in the SJV that are violating the 2006 PM_2.5 NAAQS as of the attainment date. To qualify as a contingency measure, a measure must be structured to achieve emissions reductions, if triggered, and the contingency provision of District Rule 4901 provides for such reductions only under certain circumstances and should be revised to provide for additional emissions reductions in the SJV (if triggered) regardless of which monitoring site(s) is determined to be violating the 2006 PM_2.5 NAAQS as of the attainment date.

Next, we considered the adequacy of the section 5.7.3 of District Rule 4901 from the standpoint of the magnitude of emissions reductions the measures would provide (if triggered). Neither the CAA nor the EPA's implementing regulations for the PM_2.5 NAAQS establish a specific amount of emissions reductions that implementation of contingency measures must achieve, but we generally expect that contingency measures should provide for emissions reductions approximately equivalent to one year's worth of RFP, which amounts to reductions of approximately 0.6 tpd of direct PM_2.5 and 18.4 tpd of NO_X for the 2006 PM_2.5 NAAQS in the SJV. As noted in our summary of the State's submission, the emissions reductions from the contingency provisions in District Rule 4901 would amount to approximately 0.00 tpd to 0.387 tpd of direct PM_2.5, which equates to approximately 0% to 67% of one year's worth of RFP for direct PM_2.5. With respect to NO_X emissions reductions, the contingency provisions in District Rule 4901 would amount to approximately 0.00 tpd to 0.06 tpd, which equates to approximately 0% to 0.3% of one year's worth of RFP for NO_X.

The State's contingency measure element in the 2018 PM_2.5 Plan provides the larger SIP planning context in which to judge the adequacy of the amount of emission reductions resulting from the contingency measure by calculating the surplus emissions reductions estimated to be achieved in the year after the attainment year. More specifically, the 2018 PM_2.5 Plan identifies additional NO_X reductions in the year following the attainment year of 2024. For the SJV, the estimates of additional reductions in the post-attainment year (2025) are 0 tpd direct PM_2.5 and 5.2 tpd NO_X. Generally, we will consider such surplus emissions reductions in evaluating the sufficiency of the emissions reductions from contingency measures identified by the state, however, in this case, because the identified contingency measure may result in no emissions reductions, the larger planning context is not relevant to our review of the sufficiency of the contingency measure.

For these reasons, we propose to disapprove the contingency measure element of the 2018 PM_2.5 Plan under CAA section 179(c)(9) and 40 CFR 51.1014 with respect to the State's Serious area attainment plan for the 2006 PM_2.5 NAAQS in the SJV. While the contingency measure provision of the 2019 amendment to Rule 4901 has an adequate triggering mechanism for failure to attain, we propose to disapprove it because it may result in no emissions reductions if the area fails to attain the NAAQS by the applicable attainment date. Furthermore, as the contingency measure element and the contingency provision of Rule 4901 lack any to-be-triggered measure for failure to meet a quantitative milestone, submit a quantitative milestone report, or failure to meet an RFP requirement, we propose that the submission is also inadequate for RFP contingency measures.

Lastly, if the EPA finalizes the proposed disapproval of the contingency measure element for the 2006 PM_2.5 NAAQS, the area would be eligible for a protective finding under the transportation conformity rule because the 2018 PM_2.5 Plan reflects adopted control measures and contains enforceable commitments that fully satisfy the emissions reductions requirements for RFP and attainment for the 2006 PM_2.5 NAAQS.

VIII. Summary of Proposed Actions and Request for Public Comment

Under CAA section 110(k)(3), the EPA is proposing to approve the following elements of the 2016 PM_2.5 Plan and 2018 PM_2.5 Plan submitted by California to address the CAA's Moderate area planning requirements for the 2012 PM_2.5 NAAQS in the SJV nonattainment area:

1. The 2013 base year emissions inventories in the 2016 PM_2.5 Plan, as revised in the 2018 PM_2.5 Plan, as meeting the requirements of CAA section 172(c)(3) and 40 CFR 51.1008(a);

2. The reasonably available control measures/reasonably available control technology demonstration in the 2016 PM_2.5 Plan, as supplemented in the 2018 PM_2.5 Plan, as meeting the requirements of CAA sections 172(c)(1) and 189(a)(1)(C);

3. The demonstration in the 2016 PM_2.5 Plan that attainment by the Moderate area attainment date of December 31, 2021, is impracticable as meeting the requirements of CAA section 189(a)(1)(B)(ii) and 40 CFR 51.1011(a);

4. The reasonable further progress demonstration in the 2016 PM_2.5 Plan, as revised in 2018 PM_2.5 Plan, as meeting the requirements of CAA section 172(c)(2) and 40 CFR 51.1012(a);

5. The quantitative milestones in the 2016 PM_2.5 Plan, as revised in the 2018 PM_2.5 Plan and the Valley State SIP Strategy, as meeting the requirements of CAA section 189(c) and 40 CFR 51.1013(a)(1); and

6. The motor vehicle emissions budgets for 2022 in the 2018 PM_2.5 Plan as shown in Table 6 of this proposed rule because they are derived from an approvable RFP demonstration and meet the requirements of CAA section 176(c) and 40 CFR part 93, subpart A. With respect to the budgets, we are proposing to limit the duration of the approval of the budgets to last only until the effective date of the EPA's adequacy finding for any subsequently submitted budgets. We are proposing to do so at CARB's request and in light of the benefits of using EMFAC2017-derived budgets prior to our taking final action on the future SIP revision that includes the updated budgets.

Pursuant to CAA section 110(k)(3), the EPA proposes to disapprove the contingency measure element of the 2016 PM_2.5 Plan for the 2012 PM_2.5 NAAQS, as revised in the 2018 PM_2.5 Plan and supplemented by section 5.7.3 of District Rule 4901, and the contingency measure element of the 2018 PM_2.5 Plan for the 2006 PM_2.5 NAAQS, as supplemented by section 5.7.3 of District Rule 4901, because, among other reasons, the elements include no specific measures to be undertaken if the state fails to submit a quantitative milestone report for the area, or if the area fails to meet RFP or a quantitative milestone. In addition, with respect to the contingency measure element in the 2018 PM_2.5 Plan for the 2006 PM_2.5 NAAQS (as supplemented by section 5.7.3 of District Rule 4901), the element includes a specific measure that may not result in any emissions reductions following a failure to attain the 2006 PM_2.5 NAAQS by the applicable attainment date under certain circumstances.

If we finalize the disapproval of the contingency measure elements as proposed, the offset sanction in CAA section 179(b)(2) would apply in the SJV 18 months after the effective date of a final disapproval, and the highway funding sanctions in CAA section 179(b)(1) would apply in the area six months after the offset sanction is imposed. Neither sanction will be imposed under the CAA if the State submits and we approve, prior to the implementation of the sanctions, a SIP revision that corrects the deficiencies that we identify in our final action. The EPA intends to work with CARB and the SJVUAPCD to correct the deficiencies in a timely manner.

In addition to the sanctions, CAA section 110(c)(1) provides that the EPA must promulgate a federal implementation plan (FIP) addressing any disapproved elements of the plan two years after the effective date of disapproval unless the State submits, and the EPA approves, the required SIP submittal. As a result of the EPA's December 6, 2018 determination that California had failed to submit the required contingency measures for the 2006 PM_2.5 NAAQS and the 2012 PM_2.5 NAAQS, among other required SIP submissions for the SJV, the EPA is already subject to a statutory deadline to promulgate a FIP for this purpose no later than two years after the effective date of that determination.

Also, because we previously approved the Serious area plan RFP and attainment demonstrations and the motor vehicle emissions budgets for the 2006 PM_2.5 NAAQS, and because in this proposed rule we are proposing to approve the Moderate area plan RACM, additional reasonable measures, and RFP demonstrations, and motor vehicle emission budgets for the 2012 PM_2.5 NAAQS, we are proposing to issue a protective finding under 40 CFR 93.120(a)(3) to the disapproval of the contingency measures elements. Without a protective finding, the final disapprovals would result in a conformity freeze, under which only projects in the first four years of the most recent conforming Regional Transportation Plan (RTP) and Transportation Improvement Programs (TIP) can proceed. Generally, during a freeze, no new RTPs, TIPs, or RTP/TIP amendments can be found to conform until another control strategy implementation plan revision fulfilling the same CAA requirements is submitted, the EPA finds its motor vehicle emissions budget(s) adequate pursuant to § 93.118 or approves the submission, and conformity to the implementation plan revision is determined. Under a protective finding, the final disapproval of the contingency measures elements would not result in a transportation conformity freeze in the SJV PM_2.5 nonattainment area and the MPOs may continue to make transportation conformity determinations.

Finally, pursuant to CAA section 188(b)(1), the EPA is proposing to reclassify the SJV PM_2.5 nonattainment area, including reservation areas of Indian country and any other area where the EPA or a tribe has demonstrated that a tribe has jurisdiction within the SJV, as Serious nonattainment for the 2012 PM_2.5 standard based on the agency's determination that the SJV cannot practicably attain the standard by the Moderate area attainment date of December 31, 2021. Upon final reclassification as a Serious area, California will be required to submit, within 18 months after the effective date of the reclassification, an emissions inventory, provisions to assure that BACM shall be implemented no later than four years after the date of reclassification, and any NNSR SIP revisions required to satisfy the requirements of CAA sections 189(b)(3) and 189(e). California will also be required to submit, by December 31, 2023, a Serious area plan that satisfies the requirements of part D of title I of the Act. This plan must include a demonstration that the SJV will attain the 2012 PM_2.5 standard as expeditiously as practicable but no later than December 31, 2025, or by the most expeditious alternative date practicable and no later than December 31, 2030, in accordance with the requirements of CAA sections 189(b) and 188(e).

We note that the 2018 PM_2.5 Plan, submitted concurrently with the 2016 PM_2.5 Plan on May 10, 2019, includes a Serious area attainment demonstration, emissions inventory, attainment-related plan elements, and BACM/BACT provisions. The State also submitted a SIP submission for the Serious area NNSR requirements on November 20, 2019. The EPA intends to evaluate and act on the Serious area plan and NNSR SIP submissions for the 2012 PM_2.5 NAAQS in the SJV through separate rulemakings, as appropriate.

In addition, because the EPA is proposing to similarly reclassify reservation areas of Indian country and any other area of Indian country where the EPA or a tribe has demonstrated that the tribe has jurisdiction within the SJV PM_2.5 nonattainment area as Serious nonattainment for the 2012 PM_2.5 standard, consistent with our proposed reclassification of the surrounding non-Indian country lands, the EPA has invited consultation with interested tribes concerning this issue. Although eligible tribes may seek the EPA's approval of relevant tribal programs under the CAA, none of the affected tribes will be required to submit an implementation plan as a result of this reclassification.

We will accept comments from the public on these proposals for the next 30 days. The deadline and instructions for submission of comments are provided in the DATES and ADDRESSES sections at the beginning of this proposed rule.

IX. Statutory and Executive Order Reviews

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

A. Executive Order 12866: Regulatory Planning and Review, and Executive Order 13563: Improving Regulation and Regulatory Review

The proposed actions are not a significant regulatory action and were therefore not submitted to the Office of Management and Budget (OMB) for review.

B. Paperwork Reduction Act (PRA)

The proposed actions do not impose an information collection burden under the PRA because they do not contain any information collection activities.

C. Regulatory Flexibility Act (RFA)

I certify that the proposed actions will not have a significant economic impact on a substantial number of small entities under the RFA. The proposed actions will not impose any requirements on small entities. This proposed rule would approve or disapprove State plans as meeting federal requirements and would not impose additional requirements beyond those imposed by State law. Additionally, the proposed rule would reclassify the SJV nonattainment area as Serious nonattainment for the 2012 PM_2.5 NAAQS and would not itself regulate small entities.

D. Unfunded Mandates Reform Act (UMRA)

The proposed actions do not contain an unfunded mandate of $100 million or more as described in UMRA, and does not significantly or uniquely affect small governments. This proposed rule would approve or disapprove State plans as meeting federal requirements and would not impose additional requirements beyond those imposed by State law. Additionally, the proposed rule would reclassify the SJV nonattainment area as Serious nonattainment for the 2012 PM_2.5 NAAQS and would not itself impose any federal intergovernmental mandate. The proposed actions would not require any tribe to submit implementation plans.

E. Executive Order 13132: Federalism

The proposed actions do not have federalism implications. They will not have substantial direct effects on the states, on the relationship between the national government and the states, or on the distribution of power and responsibilities among the various levels of government.

F. Executive Order 13175: Coordination With Indian Tribal Governments

Executive Order 13175, entitled “Consultation and Coordination with Indian Tribal Governments” (65 FR 67249, November 9, 2000), requires the EPA to develop an accountable process to ensure “meaningful and timely input by tribal officials in the development of regulatory policies that have tribal implications.” “Policies that have Tribal implications” is defined in the Executive Order to include regulations that have “substantial direct effects on one or more Indian tribes, on the relationship between the Federal government and the Indian tribes, or on the distribution of power and responsibilities between the Federal government and Indian Tribes.”

Eight Indian tribes are located within the boundaries of the SJV nonattainment area for the 2012 PM_2.5 NAAQS: The Big Sandy Rancheria of Western Mono Indians of California, the Cold Springs Rancheria of Mono Indians of California, the Northfork Rancheria of Mono Indians of California, the Picayune Rancheria of Chukchansi Indians of California, the Santa Rosa Indian Community of the Santa Rosa Rancheria, California, the Table Mountain Rancheria, the Tejon Indian Tribe, and the Tule River Indian Tribe of the Tule River Reservation, California.

The EPA's proposed actions on the SIP elements submitted by California to address the Moderate area requirements for the 2012 PM_2.5 NAAQS and the contingency measure requirement for the 2006 PM_2.5 NAAQS would not have tribal implications 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. In those areas of Indian country, the proposed actions on the SIP submittals do not have tribal implications and will not impose substantial direct costs on tribal governments or preempt tribal law as specified by Executive Order 13175.

The EPA has concluded that the proposed reclassification might have tribal implications for the purposes of Executive Order 13175, but would not impose substantial direct costs upon the tribes, nor would it preempt tribal law. The proposed reclassification from Moderate to Serious for a PM_2.5 NAAQS would typically affect the EPA's implementation of the new source review program because of the lower “major source” threshold triggered by reclassification (70 tons per year for direct PM_2.5 and precursors to PM_2.5). However, because the SJV nonattainment area is already classified as Serious for the 1997 and 2006 PM_2.5 NAAQS, the lower thresholds already apply within the nonattainment area, and the proposed reclassification from Moderate to Serious for the 2012 PM_2.5 NAAQS would have no additional effect. The same is true for any tribal projects that require federal permits, approvals, or funding. Such projects are subject to the requirements of the EPA's general conformity rule, and federal permits, approvals, or funding for the projects would typically become more difficult to obtain because of the lower de minimis thresholds triggered by reclassification but, in this case, the lower de minimis thresholds already apply within the SJV.

Given the potential implications, the EPA contacted tribal officials during the process of developing this proposed rule to provide an opportunity to have meaningful and timely input into its development. On March 3, 2021, we sent letters to leaders of the eight tribes with areas of Indian country in the SJV nonattainment area inviting government-to-government consultation on the rulemaking effort. We requested that the tribal leaders, or their designated consultation representatives, notify us of their interest in government-to-government consultation by April 5, 2021. We intend to continue communicating with all eight tribes located within the boundaries of the SJV nonattainment area for the 2012 PM_2.5 NAAQS as we move forward in developing a final rule. The EPA specifically solicits additional comment on this proposed rule from tribal officials.

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. The proposed rule is not subject to Executive Order 13045 because it would approve or disapprove a State plan implementing a federal standard, and reclassify the SJV nonattainment area as Serious nonattainment for the 2012 PM_2.5 NAAQS, triggering Serious area planning requirements under the CAA. This proposed action does not establish an environmental standard intended to mitigate health or safety risks.

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

This proposed rule 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

This rulemaking does not involve technical standards.

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

The EPA has determined that the proposed actions will not have potential disproportionately high and adverse human health or environmental effects on minority or low-income populations because they do not affect the level of protection provided to human health or the environment. The proposed actions would only approve or disapprove State plans implementing a federal standard, and reclassify the SJV nonattainment area as Serious nonattainment for the 2012 PM_2.5 NAAQS, triggering additional Serious area planning requirements under the CAA.

List of Subjects

40 CFR Part 52

• Environmental protection
• Air pollution control
• Ammonia
• Incorporation by reference
• Intergovernmental relations
• Nitrogen dioxide
• Particulate matter
• Reporting and recordkeeping requirements
• Sulfur dioxide
• Volatile organic compounds

40 CFR Part 81

• Environmental protection
• Air pollution control
• Particulate matter

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