Air Quality State Implementation Plans; Approvals and Promulgations: California; 1997 Annual Fine Particulate Matter Serious and Clean Air Act Section 189(d) Nonattainment Area Requirements; San Joaquin Valley, CA

Federal RegisterJul 14, 2023

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2023-0263; FRL-10941-01-R9]

Air Quality State Implementation Plans; Approvals and Promulgations: California; 1997 Annual Fine Particulate Matter Serious and Clean Air Act Section 189(d) Nonattainment Area Requirements; San Joaquin Valley, CA

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The Environmental Protection Agency (EPA) is proposing to approve portions of state implementation plan (SIP) revisions submitted by the State of California to meet Clean Air Act (CAA or “Act”) requirements for the 1997 annual fine particulate matter (PM

2.5

) national ambient air quality standards (NAAQS or “standards”) in the San Joaquin Valley PM

2.5

nonattainment area. Specifically, the EPA is proposing to approve those portions of the submitted SIP revisions as they pertain to the Serious nonattainment area and CAA section 189(d) requirements for the 1997 annual PM

2.5

NAAQS, except for the requirement for contingency measures. In addition, the EPA is proposing to approve 2020 and 2023 motor vehicle emissions budgets and the trading mechanism for use in transportation conformity analyses for the 1997 annual PM

2.5

NAAQS. The EPA will accept comments on this proposed rule during a 30-day public comment period.

DATES:

Any comments on this proposal must be received by August 14, 2023.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-R09-OAR-2023-0263 at

https://www.regulations.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

. 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 a disability 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:

Ashley Graham, Geographic Strategies and Modeling Section (AIR-2-2), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105, (415) 972-3877, or by email at

graham.ashleyr@epa.gov.

SUPPLEMENTARY INFORMATION:

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

Table of Contents

I. Background for Proposed Action

A. PM

2.5

NAAQS

B. San Joaquin Valley PM

2.5

Designations, Classifications, and SIP Revisions

II. Summary and Completeness Review of the San Joaquin Valley PM

2.5

Plan

A. 2018 PM

2.5

Plan and 15 µg/m

SIP Revision

B. Procedural Requirements for SIPs and SIP Revisions

III. Clean Air Act Requirements for PM

2.5

Serious Area Plans and for Serious PM

2.5

Areas That Fail To Attain

A. Requirements for PM

2.5

Serious Area Plans

B. Requirements for Serious PM

2.5

Areas That Fail To Attain

IV. Review of the San Joaquin Valley PM

2.5

Plan for the 1997 Annual PM

2.5

NAAQS

A. Emissions Inventories

B. PM

2.5

Precursors

C. Attainment Plan Control Strategy

D. Attainment Demonstration and Modeling

E. Reasonable Further Progress and Quantitative Milestones

F. Motor Vehicle Emission Budgets

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

V. Environmental Justice Considerations

VI. CAA Section 110(a)(2)(E)(i) “Necessary Assurances” and Title VI of the Civil Rights Act of 1964

VII. Summary of Proposed Action and Request for Public Comment

VIII. Statutory and Executive Order Reviews

I. Background for Proposed Action

A. PM

2.5

NAAQS

Under section 109 of the CAA, the EPA has established NAAQS for certain pervasive air pollutants (referred to as “criteria pollutants”) and conducts periodic reviews of the NAAQS to determine whether the EPA should revise or establish new NAAQS to protect public health.

On July 18, 1997, the EPA revised the NAAQS for particulate matter by establishing new NAAQS for particles with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers (PM

2.5

The EPA established primary and secondary annual and 24-hour standards for PM

2.5

The EPA set the annual primary and secondary standards at 15.0 micrograms per cubic meter (μg/m

) based on a three-year average of annual mean PM

2.5

concentrations, and set the 24-hour primary and secondary standards at 65 μg/m

based on the three-year average of the 98th percentile of 24-hour PM

2.5

concentrations at each monitoring site within an area.

Collectively, we refer herein to the 1997 annual and 24-hour PM

2.5

NAAQS as the “1997 PM

2.5

NAAQS” or “1997 PM

2.5

standards.”

62 FR 38652.

For a given air pollutant, “primary” NAAQS are those determined by the EPA as requisite to protect the public health, allowing an adequate margin of safety, and “secondary” standards are those determined by the EPA as requisite to protect the public welfare from any known or anticipated adverse effects associated with the presence of such air pollutant in the ambient air. See CAA section 109(b).

40 CFR 50.7.

On October 17, 2006, the EPA revised the level of the 24-hour PM

2.5

NAAQS to 35 μg/m

and on January 15, 2013, the EPA revised the level of the primary annual PM

2.5

NAAQS to 12.0 μg/m

Even though the EPA lowered the 24-hour and annual PM

2.5

NAAQS, the 1997 24-hour PM

2.5

NAAQS remain in effect and the 1997 primary annual PM

2.5

NAAQS remains in effect in areas designated nonattainment for that NAAQS.

71 FR 61144.

78 FR 3086.

40 CFR 50.13(d).

The EPA established each of the PM

2.5

NAAQS 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 dates), changes in lung function and increased respiratory

symptoms, and new evidence for more subtle indicators of cardiovascular health. Individuals particularly sensitive to PM

2.5

exposure include older adults, people with heart and lung disease, and children.

EPA, Air Quality Criteria for Particulate Matter, No. EPA/600/P-99/002aF and EPA/600/P-99/002bF, October 2004.

2.5

can be particles emitted by sources directly into the atmosphere as a solid or liquid particle (“primary PM

2.5

” or “direct PM

2.5

”), or can be particles that form in the atmosphere as a result of various chemical reactions from PM

2.5

precursor emissions emitted by sources (“secondary PM

2.5

”). The EPA has identified the precursors of PM

2.5

to be oxides of nitrogen (“NO

”), sulfur oxides (“SO

”), volatile organic compounds (“VOC”), and ammonia.

For example, see 72 FR 20586, 20589 (April 25, 2007).

B. San Joaquin Valley PM

2.5

Designations, Classifications, and SIP Revisions

Following promulgation of a new or revised NAAQS, the EPA is required under CAA section 107(d) to designate areas throughout the nation as attainment, nonattainment, or unclassifiable for the NAAQS. Effective April 5, 2005, the EPA established the initial air quality designations for the 1997 annual and 24-hour PM

2.5

NAAQS, using air quality monitoring data for the three-year periods of 2001-2003 and 2002-2004.

The EPA designated the San Joaquin Valley as nonattainment for both the 1997 annual PM

2.5

NAAQS (15.0 µg/m

) and the 1997 24-hour PM

2.5

NAAQS (65 µg/m

70 FR 944 (January 5, 2005).

40 CFR 81.305.

The San Joaquin Valley 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 one of the nation's leading agricultural regions. 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 attainment plans. Authority for regulating sources under State jurisdiction in the San Joaquin Valley is split under State law between the District, which has responsibility for regulating stationary and most area sources, and CARB, which has responsibility for regulating most mobile sources.

For a precise description of the geographic boundaries of the San Joaquin Valley nonattainment area, see 40 CFR 81.305.

At the time of the initial designations for the 1997 PM

2.5

NAAQS, the EPA interpreted the CAA to require implementation of the NAAQS under the general nonattainment plan requirements of subpart 1.

Under subpart 1, states were required to submit nonattainment plan SIP submissions within three years of the effective date of designations, that, among other things, provided for implementation of reasonably available control measures (RACM), reasonable further progress (RFP), contingency measures, and a modeled attainment demonstration showing attainment of the NAAQS as expeditiously as practicable but no later than five years from the designation (in this instance, no later than April 5, 2010) unless the state justified an attainment date extension of up to five years.

72 FR 20586.

CAA sections 172(a)(2), 172(c)(1), 172(c)(2), and 172(c)(9).

Between 2007 and 2011, California submitted six nonattainment plan and supporting SIP revisions to address nonattainment area planning requirements for the 1997 PM

2.5

NAAQS in the San Joaquin Valley,

which we refer to collectively as the “2008 PM

2.5

Plan.” On November 9, 2011, the EPA approved the portions of the 2008 PM

2.5

Plan, as revised in 2009 and 2011, that addressed attainment of the 1997 PM

2.5

NAAQS in the San Joaquin Valley nonattainment area, except for the attainment contingency measures, which we disapproved.

We also granted the State's request to extend the attainment deadline for the 1997 PM

2.5

NAAQS in the San Joaquin Valley to April 5, 2015.

76 FR 69896, n. 2 (November 9, 2011).

Id. at 69924.

Id.

Following a January 4, 2013 decision of the U.S. Court of Appeals for the D.C. Circuit remanding the EPA's 2007 implementation rule for the 1997 PM

2.5

NAAQS,

the EPA published a final rule on June 2, 2014, classifying the San Joaquin Valley as a “Moderate” nonattainment area for the 1997 PM

2.5

NAAQS under subpart 4, part D of title I of the Act.

In that action, the EPA acknowledged that states must meet both subpart 1 and subpart 4 requirements in nonattainment plan SIP submissions for the 1997 24-hour and annual PM

2.5

NAAQS and provided states with additional time to supplement or withdraw and resubmit any pending nonattainment plan SIP submissions.

Natural Resources Defense Council

EPA,

706 F.3d. 428 (D.C. Cir. 2013) (“

NRDC”

). In

NRDC,

the court held that the EPA erred in implementing the 1997 PM

2.5

standards solely pursuant to the general implementation requirements of subpart 1, without also considering the requirements specific to nonattainment areas for particles less than or equal to 10 µm in diameter (PM

) in subpart 4, part D of title I of the CAA. The court reasoned that the plain meaning of the CAA requires implementation of the 1997 PM

2.5

standards under subpart 4 because PM

2.5

falls within the statutory definition of PM

and is thus subject to the same statutory requirements as PM

. The court remanded the rule, without vacatur, and instructed the EPA “to repromulgate these rules pursuant to Subpart 4 consistent with this opinion.”

79 FR 31566.

Effective May 7, 2015, the EPA reclassified the San Joaquin Valley as a “Serious” nonattainment area for the 1997 PM

2.5

NAAQS based on our determination that the State could not practicably attain these NAAQS in the San Joaquin Valley nonattainment area by the latest statutory Moderate area attainment date,

i.e.,

April 5, 2015.

Upon reclassification as a Serious area, the State became subject to the requirement of CAA section 188(c)(2) to attain the 1997 PM

2.5

NAAQS as expeditiously as practicable but no later than ten years after designation,

i.e.,

by no later than December 31, 2015. California submitted its Serious area plan for the 1997 PM

2.5

NAAQS for the San Joaquin Valley in two submissions dated June 25, 2015, and August 13, 2015, including a request under section 188(e) to extend the attainment date for the 1997 24-hour PM

2.5

NAAQS by three years (to December 31, 2018) and to extend the attainment date for the 1997 annual PM

2.5

NAAQS by five years (to December 31, 2020). On February 9, 2016, the EPA proposed to approve most of the Serious area plan and to grant the State's request for extensions of the December 31, 2015 attainment date.

However, on October 6, 2016, after considering public comments, the EPA denied California's request for these extensions of the attainment dates.

Consequently, on November 23, 2016, the EPA determined that the San Joaquin Valley had failed to attain the 1997 24-hour and annual PM

2.5

NAAQS

by the December 31, 2015 Serious area attainment date.

This determination triggered a requirement for California to submit a new SIP submission for the 1997 24-hour and annual PM

2.5

NAAQS for the San Joaquin Valley that satisfies the requirements of CAA section 189(d). The statutory deadline for this additional SIP submission was December 31, 2016. The EPA did not finalize the actions proposed on February 9, 2016, with respect to the submitted Serious area plan.

80 FR 18528 (April 7, 2015).

81 FR 6936. California's request for extension of the Serious Area attainment date for the San Joaquin Valley accompanied its Serious Area attainment plan for the 1997 PM

2.5

NAAQS and related motor vehicle emission budgets, submitted June 25, 2015 and August 13, 2015, respectively.

81 FR 69396.

81 FR 84481.

81 FR 69396, 69400.

On December 6, 2018, the EPA determined that California had failed to submit a complete section 189(d) attainment plan for the 1997 24-hour and annual PM

2.5

NAAQS, among other required SIP submissions for the San Joaquin Valley, by the statutory deadlines.

This finding, which became effective on January 7, 2019, triggered clocks under CAA section 179(a) for the application of emissions offset sanctions 18 months after the finding, and highway funding sanctions 6 months thereafter, unless the EPA affirmatively determined that the State made a complete SIP submission addressing the identified failure to submit deficiencies.

The finding also triggered the obligation under CAA section 110(c) for the EPA to promulgate a federal implementation plan no later than two years after the finding, unless the State has submitted, and the EPA has approved, the required SIP submission.

83 FR 62720.

Id. at 62723.

Id.

On May 10, 2019, CARB submitted the “2018 Plan for the 1997, 2006, and 2012 PM

2.5

Standards,” adopted by the SJVUAPCD on November 15, 2018, and by CARB on January 24, 2019 (“2018 PM

2.5

Plan”).

The 2018 PM

2.5

Plan addresses the Serious area nonattainment plan and CAA section 189(d) requirements for the 1997 24-hour and annual PM

2.5

NAAQS, among other requirements for the 2006 and 2012 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.

CARB clarified in its submittal letter that the 2018 PM

2.5

Plan superseded past submissions to the EPA that the agency had not yet acted on for the 1997 PM

2.5

NAAQS, including the 2015 Serious area attainment plan submissions.

On June 24, 2020, the EPA issued a letter finding these submissions complete and terminating the sanctions clocks under CAA section 179(a).

Letter dated May 9, 2019, from Richard Corey, Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9.

The EPA previously acted on those portions of the 2018 PM

2.5

Plan that pertain to the 2006 24-hour PM

2.5

NAAQS (except for contingency measures) (85 FR 44192, July 22, 2020), and Moderate area planning requirements for the 2012 annual PM

2.5

NAAQS and 2006 24-hour PM

2.5

NAAQS contingency measures (86 FR 67343, November 26, 2021). On December 29, 2021, the EPA proposed action on those portions of the plan that pertain to the Serious area requirements for the 2012 annual PM

2.5

NAAQS (86 FR 74310). On October 5, 2022, the EPA issued a supplemental proposal with respect to the Serious area requirements for the 2012 PM

2.5

NAAQS (87 FR 60494), and on October 27, 2022, California withdrew those portions of the plan that pertained to those requirements (letter dated October 27, 2022, from Steven S. Cliff, Executive Officer, CARB, to Martha Guzman, Regional Administrator, EPA Region IX).

Id.

The 2015 Serious area attainment plan submissions include the “2015 Plan for the 1997 Standard” (submitted by CARB on June 25, 2015) and motor vehicle emission budgets (submitted by CARB August 13, 2015)

Letter dated June 24, 2020, from Elizabeth J. Adams, Director, Air and Radiation Division, EPA Region IX, to Richard Corey, Executive Officer, CARB, Subject: “RE: Completeness Finding for State Implementation Plan (SIP) Submissions for San Joaquin Valley for the 1997, 2006, and 2012 Fine Particulate Matter (PM

2.5

) National Ambient Air Quality Standards (NAAQS) and Termination of Clean Air Act (CAA) Sanction Clocks.”

On January 28, 2022, the EPA approved those portions of the 2018 PM

2.5

Plan that pertain to the 1997 24-hour PM

2.5

NAAQS, except for the contingency measure element, which the EPA disapproved.

As part of that action, the EPA also finalized a determination that the San Joaquin Valley attained the 1997 24-hour PM

2.5

NAAQS by the applicable attainment date of December 31, 2020 and that therefore the requirement for contingency measures no longer applies in the San Joaquin Valley nonattainment area for the 1997 24-hour PM

2.5

NAAQS.

Because the EPA found that the State has satisfied its planning obligations for the San Joaquin Valley with respect to the 1997 24-hour PM

2.5

NAAQS, this proposed action addresses only the requirements for the 1997 annual PM

2.5

NAAQS.

87 FR 4503 (January 28, 2022).

Id at 4506.

On July 22, 2021, the EPA proposed to partially approve and partially disapprove portions of the 2018 PM

2.5

Plan that address attainment of the 1997 annual PM

2.5

NAAQS in the San Joaquin Valley nonattainment area.

The EPA proposed to approve the 2013 base year emissions inventories and disapprove the attainment demonstration and related elements, including the comprehensive precursor demonstration, five percent annual emissions reductions demonstration, best available control measures (BACM) demonstration, RFP demonstration, quantitative milestones, and motor vehicle emission budgets established for 2017, 2020, and 2023. We proposed to disapprove the attainment demonstration and related elements because certified air quality data were available that established that the San Joaquin Valley area did not attain the 1997 annual PM

2.5

NAAQS by December 31, 2020, as projected in the 2018 PM

2.5

Plan. The EPA also proposed to disapprove the contingency measures element because of several identified deficiencies, including that the measure did not address the potential for failures to meet RFP, to meet a quantitative milestone, or to submit a quantitative milestone report.

On November 26, 2021, the EPA finalized the partial approval and partial disapproval of the 2018 PM

2.5

Plan for the 1997 annual PM

2.5

NAAQS as proposed.

86 FR 38652.

Id. at 38669.

86 FR 67329.

As a result of the November 26, 2021 disapprovals, California was required to develop and submit a revised attainment plan for the San Joaquin Valley area that addresses the applicable CAA requirements, including the Serious area plan requirements and the requirements of CAA section 189(d), for the 1997 annual PM

2.5

NAAQS. In accordance with sections 179(d)(3) and 172(a)(2) of the CAA, the revised plan must demonstrate attainment of these NAAQS as expeditiously as practicable and no later than 5 years from the date of the EPA's prior determination that the area failed to attain (

i.e.,

by November 23, 2021), except that the EPA may extend the attainment date to a date no later than 10 years from the date of this determination (

i.e.,

to November 23, 2026), “considering the severity of nonattainment and the availability and feasibility of pollution control measures.”

81 FR 84481, 84482 (final EPA action determining that the San Joaquin Valley had failed to attain the 1997 PM

2.5

NAAQS by the December 31, 2015, Serious area attainment date).

On November 8, 2021, CARB submitted the “Attainment Plan Revision for the 1997 Annual PM

2.5

Standard” (“15 µg/m

SIP Revision”), adopted by the SJVUAPCD on August 19, 2021, and adopted by CARB on September 23, 2021.

In the letter

accompanying the submission, CARB clarifies that the 15 µg/m

SIP Revision amends the 2018 PM

2.5

Plan and addresses all CAA requirements for the 1997 annual PM

2.5

NAAQS except for contingency measures, which CARB stated it will address at a later date.

Letter dated November 8, 2021, from Richard W. Corey, Executive Officer, CARB, to Deborah Jordan, Acting Regional Administrator, EPA Region

9. The 15 µg/m

SIP Revision was developed jointly by CARB and the District.

Id. at 1.

II. Summary and Completeness Review of the San Joaquin Valley PM

2.5

Plan

We are proposing action on those portions of the 15 µg/m

SIP Revision, 2018 PM

2.5

Plan, and Valley State SIP Strategy that pertain to the 1997 annual PM

2.5

NAAQS. Herein, we refer to these three submissions collectively as the “SJV PM

2.5

Plan” or “Plan.” The SJV PM

2.5

Plan addresses Serious area nonattainment plan and CAA section 189(d) requirements for the 1997 annual PM

2.5

NAAQS in the San Joaquin Valley, including the State's demonstration that the area will attain the 1997 annual PM

2.5

NAAQS by December 31, 2023.

A. 2018 PM

2.5

Plan and 15 µg/m

SIP Revision

CARB and the District describe the 15 µg/m

SIP Revision as an “administrative revision” to the 2018 PM

2.5

Plan that “has been prepared as a streamlined document that utilizes the existing emissions inventory, air quality analysis and modeling from the

2018 PM

2.5

Plan.

”

In its submission of the 15 µg/m

SIP Revision to the EPA, the State included a redline strikeout version highlighting the updates that were made relative to the 2018 PM

2.5

Plan submitted on May 10, 2019, as well as final versions of those sections that were revised relative to the 2018 PM

2.5

Plan.

15 µg/m

SIP Revision, p. 5.

The State updated the following portions of the 2018 PM

2.5

Plan and resubmitted them to the EPA as the 15 µg/m

SIP Revision to address both the Serious area requirements in CAA section 189(b) and the CAA section 189(d) requirements for the 1997 annual PM

2.5

NAAQS in the San Joaquin Valley: (i) Chapter 4 (“Attainment Strategy for PM

2.5

”); (ii) Chapter 5 (“Demonstration of Federal Requirements for 1997 PM

2.5

Standards”); (iii) Appendix D (“Mobile Source Control Measure Analyses”); (iv) Appendix H (“RFP, Quantitative Milestones, and Contingency”); and (v) Appendix K (“Modeling Attainment Demonstration”). The November 8, 2021 submittal package also included CARB's “Staff Report, Proposed SIP Revision for the 15 ug/m3 Annual PM

2.5

Standard for the San Joaquin Valley,” release date August 13, 2021 (“August 2021 Staff Report”),

and the State's and District's board resolutions adopting the 15 µg/m

SIP Revision (CARB Resolution 21-21 and SJVUAPCD Governing Board Resolution 21-08-13).

CARB's August 2021 Staff Report includes CARB's review of, among other things, the control strategy in the 15 µg/m

SIP Revision and assessment of the differences between the emissions inventories in the Plan and updated inventories more recently developed by CARB.

CARB Resolution 21-21, “San Joaquin Valley State Implementation Plan Revision for the 15 μg/m

Annual PM

2.5

Standard,” September 23, 2021, and SJVUAPCD Governing Board Resolution 21-08-13, “Adopting the San Joaquin Valley Unified Air Pollution Control District

Proposed Attainment Plan Revision For the 1997 Annual PM

2.5

Standard,”

August 19, 2021.

The portions of the Plan that address the requirements for the 1997 annual PM

2.5

NAAQS and that the State did not revise relative to the 2018 PM

2.5

Plan include: (i) Appendix A (“Ambient PM

2.5

Data Analysis”); (ii) Appendix B (“Emissions Inventory”); (iii) Appendix C (“Stationary Source Control Measure Analyses”); (iv) Appendix G (“Precursor Demonstration”); (v) Appendix I (“New Source Review and Emission Reduction Credits”); (vi) Appendix J (“Modeling Emission Inventory”); and (vii) Appendix L (“Modeling Protocol”). The May 10, 2019 submittal package also included 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 (“December 2018 Staff Report”);

and the State's and District's board resolutions adopting the 2018 PM

2.5

Plan (CARB Resolution 19-1 and SJVUAPCD Governing Board Resolution 18-11-16).

Letter dated December 11, 2019, from Richard Corey, Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9, transmitting the December 2018 Staff Report. The December 2018 Staff Report includes CARB's review of, among other things, the 2018 PM

2.5

Plan's control strategy and attainment demonstration.

CARB Resolution 19-1, “2018 PM

2.5

State Implementation Plan for the San Joaquin Valley,” January 24, 2019, and SJVUAPCD Governing Board Resolution 18-11-16, “Adopting the [SJVUAPCD] 2018 Plan for the 1997, 2006, and 2012 PM

2.5

Standards,” November 15, 2018.

As noted above, the 2018 PM

2.5

Plan incorporates by reference the Valley State SIP Strategy. For the purposes of this action, the relevant portions of the Valley State SIP Strategy are the mobile source control measure commitments associated with the quantitative milestones for the 1997 annual PM

2.5

NAAQS.

B. Procedural Requirements for SIPs and SIP Revisions

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

Both the District and CARB satisfied the applicable statutory and regulatory requirements for reasonable public notice and hearing prior to adoption and submission of the 2018 PM

2.5

Plan and 15 µg/m

SIP Revision. 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 on and adoption of the 2018 PM

2.5

Plan.

Subsequently, the District provided public notice and opportunity for public comment prior to its August 19, 2021 public hearing on and adoption of the 15 µg/m

SIP Revision.

CARB also provided public notice and opportunity for public comment prior to its September 23, 2021 public hearing on and adoption of the 15 µg/m

SIP Revision.

The SIP submissions include proof of publication of notices for the respective public hearings. They also include copies of the written and oral comments received during the State's and District's public review processes and the agencies' responses thereto.

49 50

Therefore, we find that the

2018 PM

2.5

Plan and 15 µg/m

SIP Revision meet the procedural requirements for public notice and hearing in CAA sections 110(a) and 110(l) and 40 CFR 51.102.

SJVUAPCD, “Notice of Public Hearing for Adoption of Proposed 2018 PM

2.5

Plan for the 1997, 2006, and 2012 Standards,” October 16, 2018, and SJVUAPCD Governing Board Resolution 18-11-16.

CARB, “Notice of Public Meeting to Consider the 2018 PM

2.5

State Implementation Plan for the San Joaquin Valley,” December 21, 2018, and CARB Resolution 19-1.

SJVUAPCD, “Notice of Public Hearing: Adopt Attainment Plan Revision for the 1997 Annual PM

2.5

Standard,” July 20, 2021, and SJVUAPCD Governing Board Resolution 21-08-13.

CARB, “Notice of Public Meeting to Hear an Update on the 2018 PM

2.5

State Implementation Plan for the San Joaquin Valley and Consider a State Implementation Plan Revision for the 15 µg/m

Annual PM

2.5

Standard,” September 23, 2021, and CARB Resolution 21-21.

CARB, “Board Meeting Comments Log,” March 29, 2019; J&K Court Reporting, LLC, “Meeting, State of California Air Resources Board,” January 24, 2019 (transcript of CARB's public hearing), and 2018 PM

2.5

Plan, Appendix M (“Summary of Significant Comments and Responses”).

CARB, “Board Meeting Comments Log,” September 23, 2021; J&K Court Reporting, LLC,

“Videoconference Meeting, State of California Air Resources Board,” September 23, 2021 (transcript of CARB's public hearing).

CAA section 110(k)(1)(B) requires the EPA to determine whether a SIP submission is complete within 60 days of receipt. This section also provides that any plan that the EPA has not affirmatively determined to be complete or incomplete will become complete by operation of law six months after the date of submission. The EPA's SIP completeness criteria are found in 40 CFR part 51, Appendix V.

We have reviewed the 15 µg/m

SIP Revision for completeness and find that it meets the completeness criteria in 40 CFR part 51 Appendix V. On May 8, 2022, the 15 µg/m

SIP Revision was deemed complete by operation of law under CAA section 110(k)(1)(B). The 2018 PM

2.5

Plan and Valley State SIP Strategy became complete by operation of law on November 10, 2019, and the EPA subsequently issued a letter making an affirmative completeness finding and terminating the sanctions clocks under CAA section 179(a) on June 24, 2020.

2.5

) National Ambient Air Quality Standards (NAAQS) and Termination of Clean Air Act (CAA) Sanction Clocks.”

III. Clean Air Act Requirements for PM

2.5

Serious Area Plans and for Serious PM

2.5

Areas That Fail To Attain

A. Requirements for PM

2.5

Serious Area Plans

Upon reclassification of a Moderate nonattainment area as a Serious nonattainment area under subpart 4 of part D, title I of the CAA, the Act requires the state to make a SIP submission that addresses the following Serious nonattainment area requirements:

40 CFR 51.1003(b)(1); 81 FR 58010, 58074-58075 (August 24, 2016).

1. 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));

2. Provisions to assure that BACM, including best available control technology (BACT), 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)), unless the state elects to make an optional precursor demonstration that the EPA approves authorizing the state not to regulate one or more of these pollutants;

3. A demonstration (including air quality modeling) that the plan provides for attainment as expeditiously as practicable but no later than the end of the tenth calendar year after designation as a nonattainment area (

i.e.,

December 31, 2015, for the San Joaquin Valley for the 1997 PM

2.5

NAAQS);

4. Plan provisions that require RFP (CAA section 172(c)(2));

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

6. 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));

7. Contingency measures to be implemented if the area fails to meet RFP or to attain by the applicable attainment date (CAA section 172(c)(9)); and

8. A revision to the nonattainment new source review (NSR) program to lower the applicable “major stationary source”

thresholds from 100 tons per year (tpy) to 70 tpy (CAA section 189(b)(3)).

For any Serious area, the terms “major source” and “major stationary source” include any stationary source that emits or has the potential to emit at least 70 tons per year of PM

2.5

. CAA section 189(b)(3) and 40 CFR 51.165(a)(1)(iv)(A)(

)(

vii

) and (

viii

) (defining “major stationary source” in Serious PM

2.5

nonattainment areas).

A state's Serious area plan must also satisfy the requirements for Moderate area plans in CAA section 189(a), to the extent the state has not already met those requirements in the Moderate area plan submitted for the area. In addition, the Serious area plan must meet the general requirements applicable to all SIP submissions under section 110 of the CAA, including the requirement to provide necessary assurances that the implementing agencies have adequate personnel, funding, and authority under section 110(a)(2)(E); and the requirements concerning enforcement provisions in section 110(a)(2)(C).

B. Requirements for Serious PM

2.5

Areas That Fail To Attain

In the event that a Serious area fails to attain the PM

2.5

NAAQS by the applicable attainment date, CAA section 189(d) requires that “the State in which such area is located shall, after notice and opportunity for public comment, submit within 12 months after the applicable attainment date, plan revisions which provide for attainment of the . . . standard . . .” An attainment plan under section 189(d) must, among other things, demonstrate expeditious attainment of the NAAQS within the time period provided under CAA section 179(d)(3) and provide for annual reductions in emissions of direct PM

2.5

or a PM

2.5

plan precursor pollutant within the area of not less than five percent per year from the most recent emissions inventory for the area until attainment.

CAA section 189(d), 40 CFR 51.1004(a)(3), 40 CFR 51.1010(c).

In addition to the requirement to submit control measures providing for a five percent reduction in emissions of certain pollutants on an annual basis, the EPA interprets CAA section 189(d) as requiring a state to submit an attainment plan that includes the same basic statutory plan elements that are required for other attainment plans.

Specifically, a state must submit to the EPA its plan to meet the requirements of CAA section 189(d) in the form of a complete attainment plan submission that includes the following elements:

81 FR 58010, 58098.

40 CFR 51.1003(c)(1).

1. A comprehensive, accurate, current inventory of actual emissions from all sources of PM

2.5

and PM

2.5

precursors in the area;

2. A Serious area plan control strategy that ensures that BACM, including BACT, for the control of direct PM

2.5

and PM

2.5

precursors are implemented in the area, unless the state elects to make an optional precursor demonstration that the EPA approves authorizing the state not to regulate one or more of these pollutants;

3. Additional measures (beyond those already adopted in previous nonattainment plan SIP submissions for the area as RACM/RACT, BACM/BACT, and most stringent measures (MSM) (if applicable)

) that provide for attainment of the NAAQS as expeditiously as practicable and, from the date of such submission until attainment, demonstrate that the plan will, at a minimum, achieve an annual five percent reduction in emissions of direct PM

2.5

or any PM

2.5

plan precursor;

MSM is applicable if the EPA has previously granted an extension of the attainment date under CAA section 188(e) for the nonattainment area and NAAQS at issue.

4. A demonstration (including air quality modeling) that the plan provides

for attainment of the NAAQS at issue as expeditiously as practicable;

5. Plan provisions that require RFP;

6. Quantitative milestones that the state is to meet every three years until the area is redesignated attainment and that demonstrate RFP toward attainment by the applicable date;

7. Contingency measures to be implemented if the state fails to meet any requirement concerning RFP or quantitative milestones or to attain the NAAQS at issue by the applicable attainment date; and

8. 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 NAAQS at issue in the area.

A state's section 189(d) plan submission must demonstrate attainment as expeditiously as practicable, and no later than 5 years from the date of the EPA's determination that the area failed to attain, except that the Administrator may extend the attainment date to no later than 10 years from the failure to attain determination, consistent with sections 179(d)(3) and 172(a)(2) of the CAA.

81 FR 84481, 84482.

A state with a Serious PM

2.5

nonattainment area that fails to attain the NAAQS by the applicable Serious area attainment date must also address any statutory requirements applicable to Moderate and Serious nonattainment area plans under CAA sections 172 and 189 of the CAA to the extent that those requirements have not already been met.

Because the EPA has not previously approved a SIP submission for the San Joaquin Valley as meeting the subpart 4 RACM Moderate area planning requirements under CAA section 189 for the 1997 annual PM

2.5

NAAQS, the EPA is evaluating relevant portions of the SJV PM

2.5

Plan for compliance with this requirement. In addition, as discussed above, the EPA has not previously approved a SIP submission for the San Joaquin Valley as meeting the Serious area planning requirements under CAA section 189(b)(1) for the 1997 annual PM

2.5

NAAQS. Some Serious area planning requirements operate on a timeline that is based on the outermost statutory Serious area attainment date of the end of the tenth calendar year following the area's designation to nonattainment. Because section 189(d) requires a state to address any applicable Serious area requirements that the state has not already met in the area, and the section 189(d) obligations do not come into effect until an area has failed to attain the NAAQS by the Serious area attainment date, the EPA is evaluating any previously unmet Serious area planning obligations based on the current, applicable attainment date appropriate under section 189(d), and not the original Serious area attainment date.

81 FR 58010, 58098.

See,

e.g.,

86 FR 53150 (September 24, 2021) and 87 FR 4503 (January 28, 2022) (proposed and final actions evaluating a previously unmet Serious area planning obligation based on the applicable attainment date under section 189(d), not the original Serious area attainment date).

The EPA provided its preliminary views on the CAA's requirements for particulate matter plans under part D, title I of the Act in the following guidance documents: (1) “State Implementation Plans; General Preamble for the Implementation of Title I of the Clean Air Act Amendments of 1990” (“General Preamble”);

(2) “State Implementation Plans; General Preamble for the Implementation of Title I of the Clean Air Act Amendments of 1990; Supplemental”;

and (3) “State Implementation Plans for Serious PM-10 Nonattainment Areas, and Attainment Date Waivers for PM-10 Nonattainment Areas Generally; Addendum to the General Preamble for the Implementation of Title I of the Clean Air Act Amendments of 1990” (“General Preamble Addendum”).

More recently, in an August 24, 2016 final rule entitled, “Fine Particulate Matter National Ambient Air Quality Standards: State Implementation Plan Requirements” (“PM

2.5

SIP Requirements Rule”), the EPA established regulatory requirements and provided further interpretive guidance on the statutory SIP requirements that apply to areas designated nonattainment for the PM

2.5

NAAQS.

We discuss these regulatory requirements and interpretations of the Act as appropriate in our evaluation of the SJV PM

2.5

Plan that follows.

57 FR 13498 (April 16, 1992).

57 FR 18070 (April 28, 1992).

59 FR 41998 (August 16, 1994).

81 FR 58010.

IV. Review of the San Joaquin Valley PM

2.5

Plan for the 1997 Annual PM

2.5

NAAQS

The EPA is evaluating the SJV PM

2.5

Plan against the Serious area requirements for the 1997 annual PM

2.5

NAAQS and the section 189(d) requirements for the 1997 annual PM

2.5

NAAQS, as laid out in Section III of this document. Many requirements for both a Serious area plan and a section 189(d) plan are structured around the relevant statutory attainment date. The latest statutory Serious area attainment date for the San Joaquin Valley area was December 31, 2015.

On November 23, 2016, the EPA determined that the area failed to attain by the Serious area attainment date.

As discussed in Section I.B of this proposal, California submitted its Serious area plan for the 1997 annual PM

2.5

NAAQS in two submissions dated June 25, 2015 and August 13, 2015, including a request under section 188(e) to extend the attainment date for the 1997 annual PM

2.5

NAAQS by five years (to December 31, 2020). On October 6, 2016, the EPA denied the request for an extension, but did not finalize action on the Serious area plan submissions. Accordingly, the Serious area attainment date remained unchanged: as expeditiously as practicable but no later than December 31, 2015.

For the purposes of the section 189(d) requirements, the attainment date is the date by which a state can attain the NAAQS as expeditiously as practicable, but no later than 5 years from the publication date of the final determination of failure to attain, except that the EPA may extend the attainment date to a date no later than 10 years from the date of the determination (

i.e.,

to November 23, 2026), “considering the severity of nonattainment and the availability and feasibility of pollution control measures.”

The SJV PM

2.5

Plan projects that attainment will be achieved by December 31, 2023, approximately seven years after the determination of failure to attain. The EPA is proposing to approve the SJV PM

2.5

Plan's attainment date in this action.

CAA section 172(a)(2) and 179(d)(3); 81 FR 84481, 84482. The determination of failure to attain published on November 23, 2016.

When the State submitted the 2018 PM

2.5

Plan in 2019, the State withdrew its previous Serious area plan that it had developed to meet the December 31, 2015 Serious area attainment date. Because the State submitted the 2018 PM

2.5

Plan and subsequent 15 µg/m

SIP Revision after the EPA's finding that the area had failed to attain by the applicable Serious area attainment date, the State could not demonstrate that the area would attain by the Serious area attainment date, nor could it address other requirements based on this attainment date, such as RFP and quantitative milestones, because many of the relevant dates had already passed. As described in Section III of this document, in a section 189(d) plan, a state must address any statutory requirements applicable to Moderate and Serious nonattainment area plans to the extent that it has not already met those requirements, but the EPA

believes that it should base this evaluation on the current applicable attainment date under section 189(d). For example, it would be illogical to require a state to submit a Serious area modeled attainment demonstration that provided for attainment by December 31, 2015, after the EPA has already determined based on monitoring data that the state failed to attain by such date.

For the purposes of our evaluation of the Serious area plan requirements, although the State is required to submit a Serious area plan and it must structure such a plan based on the Serious area attainment date, it would serve no purpose to evaluate the SJV PM

2.5

Plan against the now-passed Serious area attainment date by which the area has already failed to attain. For example, RFP and quantitative milestones normally are dependent upon the attainment date. Accordingly, because the State must still meet all Serious area plan requirements, even if doing so later in conjunction with the section 189(d) plan and its later attainment date, we will evaluate the State's compliance with the Serious area plan requirements in light of the later section 189(d) attainment date, as appropriate. Where the State in the SJV PM

2.5

Plan applies the section 189(d) attainment date to a Serious area requirement, we will note the statutory Serious area timeline and accept the submission in fulfillment of the State's Serious area plan obligation but evaluate the submission in light of the section 189(d) attainment date.

A. Emissions Inventories

1. Statutory and Regulatory Requirements

CAA section 172(c)(3) 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. The EPA discussed the emissions inventory requirements that apply to PM

2.5

nonattainment areas in the PM

2.5

SIP Requirements Rule and codified these requirements in 40 CFR 51.1008.

The EPA has also issued guidance concerning emissions inventories for PM

2.5

nonattainment areas.

81 FR 58010, 58098-58099.

“Emissions Inventory Guidance for Implementation of Ozone and Particulate Matter National Ambient Air Quality Standards (NAAQS) and Regional Haze Regulations,” U.S. EPA, May 2017 (“Emissions Inventory Guidance”), available at

https://www.epa.gov/air-emissions-inventories/air-emissions-inventory-guidance-implementation-ozone-and-particulate.

The base year emissions inventory for a Serious area attainment plan or a CAA section 189(d) plan must 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 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

i.e.,

nitrogen oxides (NO

), sulfur dioxide (SO

), volatile organic compounds (VOC), and ammonia.

The Emissions Inventory Guidance identifies the types of sources for which the EPA expects states to provide condensable PM emissions inventories. Emissions Inventory Guidance, Section 4.2.1 (“Condensable PM Emissions”), pp. 63-65.

40 CFR 51.1008(b)(1) and (c)(1).

The emissions inventory base year for a Serious area attainment plan must be one of the three years for which monitoring data were used to reclassify the area to Serious, or another technically appropriate year justified by the state in its Serious area SIP submission.

The emissions inventory base year for a Serious PM

2.5

nonattainment area subject to CAA section 189(d) must be one of the three years for which the EPA used monitored data to determine that the area failed to attain the PM

2.5

NAAQS by the applicable Serious area attainment date, or another technically appropriate year justified by the state in its Serious area SIP submission.

40 CFR 51.1008(b)(1).

40 CFR 51.1008(c)(1).

A state's SIP submission must include documentation explaining how it calculated emissions data for the inventory. In estimating mobile source emissions, a state should use the latest emissions models and planning assumptions available at the time the SIP is developed.

In addition to the base year inventory submitted to meet the requirements of CAA section 172(c)(3), the state must also submit a projected attainment year inventory and emissions projections for each RFP milestone year.

These future emissions projections are necessary components of the attainment demonstrations required under CAA sections 189(b)(1) and 189(d) and the demonstration of RFP required under section 172(c)(2).

Emissions projections for future years (referred to in the Plan as “forecasted inventories”) should account for, among other things, the ongoing effects of economic growth and adopted emissions control requirements. The state's SIP submission should include documentation to explain how the state calculated the emissions projections. Where a state chooses to allow new major stationary sources or major modifications to use emissions reduction credits (ERCs) that were generated through shutdown or curtailed emissions units occuring before the base year of an attainment plan, the projected emissions inventory used to develop the attainment demonstration must explicitly include the emissions from such previously shutdown or curtailed emissions units.

40 CFR 51.1008 and 51.1012. See also Emissions Inventory Guidance, Section 3 (“SIP Inventory Requirements and Recommendations”).

40 CFR 51.1004, 51.1008, 51.1011, and 51.1012.

40 CFR 51.165(a)(3)(ii)(C)(1).

2. Summary of the State's Submission

The State included summaries of the planning emissions inventories for direct PM

2.5

and PM

2.5

precursors (NO

, SO

VOC,

and ammonia) and the documentation for the inventories for the San Joaquin Valley PM

2.5

nonattainment area in Appendix B (“Emissions Inventory”) and Appendix I (“New Source Review and Emission Reduction Credits”) of the 2018 PM

2.5

Plan. In addition, Appendix J (“Modeling Emission Inventory”) of the 2018 PM

2.5

Plan contains inventory documentation specific to the air quality modeling inventories.

The SJV PM

2.5

Plan generally uses “sulfur oxides” or “SO

” in reference to SO

as a precursor to the formation of PM

2.5

. We use SO

and SO

interchangeably throughout this document.

The SJV PM

2.5

Plan generally uses “reactive organic gasses” or “ROG” in reference to VOC as a precursor to the formation of PM

2.5

. We use ROG and VOC interchangeably throughout this document.

CARB and District staff worked together to develop the emissions inventories for the San Joaquin Valley PM

2.5

nonattainment area. The District worked with operators of the stationary facilities in the nonattainment area to develop the stationary source emissions estimates. The responsibility for developing emissions estimates for area sources such as agricultural burning and paved road dust was shared by the District and CARB. CARB staff developed the emissions inventories for both on-road and non-road mobile sources.

The EPA regulations refer to “non-road” vehicles and engines whereas CARB regulations refer to “Other Mobile Sources” or “off-road” vehicles and engines. These terms refer to the same types of vehicles and engines. We refer herein to such vehicles and engines as “non-road” sources.

The SJV PM

2.5

Plan includes winter (24-hour) average and annual average daily emissions inventories for the 2013 base year, which CARB derived from the 2012 emissions inventory, and

estimated emissions for forecasted years from 2017 through 2028, as developed as part of the 2018 PM

2.5

Plan for the attainment and RFP demonstrations for the 1997, 2006, and 2012 PM

2.5

NAAQS.

In this proposal, we are evaluating those winter average and annual average emissions inventories necessary to support the Serious area and CAA section 189(d) nonattainment plans for the 1997 annual PM

2.5

NAAQS,

i.e.,

the 2013 base year inventory, forecasted inventories for the RFP milestone years of 2017, 2020, 2023 (attainment year), and 2026 (post-attainment milestone year), and additional forecasted emissions inventories for 2018, 2019, 2021, and 2022 to support the five percent annual emissions reduction demonstration as required by CAA section 189(d). Each inventory includes emissions from stationary, area, on-road, and non-road sources.

2018 PM

2.5

Plan, Appendix B, pp. B-18 to B-19. The winter average daily planning inventory corresponds to the months of November through April, when daily ambient PM

2.5

concentrations are typically highest. The base year inventory is from the California Emissions Inventory Development and Reporting System and future year inventories were estimated using the California Emission Projection Analysis Model (CEPAM), 2016 SIP Baseline Emission Projections, version 1.05.

The State selected 2013 for the base year emissions inventory, building on the 2012 actual emissions inventory and considering available air quality data, trends, and field studies.

Specifically, the State worked with local air districts and selected 2012 for the actual emissions inventory as it aligned with the 2012 data collection year of the Multiple Air Toxics Exposure Study IV (MATES IV)

of the South Coast Air Quality Management District (SCAQMD) and to maintain consistency across various California air quality plans.

The State then projected the 2013 base year emissions inventory (also referred to as the planning emissions inventory), presented in Appendix B of the 2018 PM

2.5

Plan, from that 2012 actual emissions inventory. The State developed the modeling emissions inventory from the base year emissions inventory, and conducted its base case modeling using 2013 for several reasons: Analysis of air quality trends, adjusted for meteorology, that indicated 2013 as a year conducive to ozone and PM

2.5

formation; availability of research-grade measurements of two significant pollution episodes in the DISCOVER-AQ field study of January to February 2013; and the relatively high design values for 2013, making it a conservative choice for attainment modeling.

2018 PM

2.5

Plan, Appendix L, pp. 11-12.

Additional information on the MATES IV study performed in 2012 is available at:

https://www.aqmd.gov/home/air-quality/air-quality-studies/health-studies/mates-iv.

SCAQMD performed the subsequent MATES V study in 2018 and issued the MATES V final report in August 2021. See

https://www.aqmd.gov/home/air-quality/air-quality-studies/health-studies/mates-v,

and “MATES V, Multiple Air Toxics Exposure Study in the South Coast AQMD, Final Report,” SCAQMD, August 2021.

2018 PM

2.5

Plan, Appendix B, p. B-18

2018 PM

2.5

Plan, Appendix L, p. 12. The State presents further information in the “APPENDIX: San Joaquin Valley PM

2.5

SIP (2018)” of Appendix L and highlights that 2013 was one of the worst years in the decade preceding 2018 for PM

2.5

pollution in the San Joaquin Valley, underscoring its use as a conservative base year for attainment modeling.

CARB developed the base year inventories for stationary sources using actual emissions reports from facility operators. The State developed the base year emissions inventory for area sources using the most recent models and methodologies available at the time the State was developing the 2018 PM

2.5

Plan.

The Plan also 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

2018 PM

2.5

Plan, Appendix B, Section B.2 (“Emissions Inventory Summary and Methodology”).

Id. at B-42 to B-44.

CARB used EMFAC2014 to estimate on-road motor vehicle emissions based on transportation activity data from the 2017 Transportation Improvement Plan (2017 TIP) adopted by the transportation planning agencies in the San Joaquin Valley.

EMFAC2014 was the latest EPA-approved version of California's mobile source emission factor model for estimating tailpipe, brake, and tire wear emissions from on-road mobile sources that was available during the State's and District's development of the emissions inventories in the 2018 PM

2.5

Plan.

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 non-road equipment, including aircraft, trains, recreational boats, construction equipment, and farming equipment, among others. CARB uses a suite of category-specific models to estimate non-road emissions for many categories and, where a new model was not available, used the OFFROAD2007 model.

2018 PM

2.5

Plan, Appendix D, p. D-123.

80 FR 77337 (December 14, 2015). EMFAC is short for

ission

FAC

tor. The EPA announced the availability of the EMFAC2014 model, effective on the date of publication in the

Federal Register,

for use in state implementation plan development and transportation conformity in California. Upon that action, EMFAC2014 was required to be used for all new regional emissions analyses and CO, PM

, and PM

2.5

hot-spot analyses that were started on or after December 14, 2017, which was the end of the grace period for using the prior mobile source emissions model, EMFAC2011. On August 15, 2019, the EPA approved EMFAC2017, a revision to the mobile source emissions model (84 FR 41717). The grace period for new regional emissions analyses began on August 15, 2019, and ended on August 16, 2021, while the grace period for hot-spot analyses began on August 15, 2019, and ended on August 17, 2020. Id. at 41720. On November 15, 2022, the EPA approved EMFAC2021, a subsequent revision to the mobile source emissions model (87 FR 68483). The grace period for new regional emissions analyses began on November 15, 2022, and ends on November 15, 2024, while the grace period for hot-spot analyses began on November 15, 2022, and ends on November 15, 2023. Id. at 68487-68488.

2018 PM

2.5

Plan, Appendix B, p. B-28. AP-42 has been published since 1972 as the primary source of the EPA's emission factor information and is available at

https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors.

It contains emission factors and process information for more than 200 air pollution source categories. A source category is a specific industry sector or group of similar emitting sources. The emission factors have been developed and compiled from source test data, material balance studies, and engineering estimates. The EPA released an update to AP-42 in January 2011 that revised the equation for estimating paved road dust emissions based on an updated data regression that included new emissions tests results. 76 FR 6328 (February 4, 2011). CARB used the revised 2011 AP-42 methodology in developing on-road mobile source emissions; see

https://www.arb.ca.gov/ei/areasrc/fullpdf/full7-9_2016.pdf.

2018 PM

2.5

Plan, Appendix B, pp. B-38 through B-40. The EPA regulations refer to “non-road” vehicles and engines whereas CARB regulations refer to “Other Mobile Sources” or “off-road” vehicles and engines. These terms refer to the same types of vehicles and engines. We refer herein to such vehicles and engines as “non-road” sources.

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 addition, the Plan states that the District is providing for use of pre-base year ERCs as offsets by accounting for such ERCs in the projected 2025 emissions inventory.

The 2018 PM

2.5

Plan identifies growth factors, control factors, and estimated offset use between 2013 and 2025 for direct PM

2.5

, NO

, SO

, and VOC emissions by source category and lists all pre-base year ERCs issued by the District for PM

, NO

, SO

, and VOC emissions, by facility.

Id. at B-18 and B-19.

2018 PM

2.5

Plan, Appendix I, pp. I-1 to I-5.

Id. at tables I-1 to I-5.

Table 1 provides a summary of the winter (24-hour) average inventories in tons per day (tpd) of direct PM

2.5

and PM

2.5

precursors for the 2013 base year. Table 2 provides a summary of annual

average inventories of direct PM

2.5

and PM

2.5

precursors for the 2013 base year. For the purposes of this proposal, these annual average inventories provide the bases for our evaluation of the precursor demonstration, control measure analysis, attainment demonstration, RFP demonstration, and the motor vehicle emission budgets (“budgets”) in the SJV PM

2.5

Plan with respect to the Serious area and CAA section 189(d) requirements for the 1997 annual PM

2.5

NAAQS.

Table 1—San Joaquin Valley Winter Average Emissions Inventory for Direct PM

2.5

and PM

2.5

Precursors for the 2013 Base Year

[tpd]

Category

Direct PM

2.5

VOC

Ammonia

Stationary Sources

8.8

38.6

7.2

87.1

13.9

Area Sources

41.5

8.1

0.3

153.4

310.9

On-Road Mobile Sources

6.4

183.1

0.6

49.8

4.4

Non-Road Mobile Sources

5.8

87.4

0.3

33.8

0.0

Totals

62.5

317.2

8.5

324.1

329.2

Source: 2018 PM

2.5

Plan, Appendix B, tables B-1 to B-5.

Totals reflect disaggregated emissions and may not add exactly as shown here due to rounding.

CARB explains in its August 2021 Staff Report that although it has updated the emissions inventories since development of the 2018 PM

2.5

Plan, the 15 µg/m

SIP Revision “uses the same inventory as the one in the 2018 PM

2.5

Plan, which it amends, for consistency.” To support this approach, CARB included in its August 2021 Staff Report comparisons between the estimated annual NO

and PM

2.5

emissions in the 2013 base year inventory developed using EMFAC2014 with those developed using the more recent EPA-approved version of EMFAC, EMFAC2017. CARB subsequently provided similar comparisons for the 2020 RFP and 2023 attainment years, as well as comparisons with emissions derived using EMFAC2021.

Table 3 shows the comparisons between on-road mobile source emissions derived using EMFAC2014, EMFAC2017, and EMFAC2021 for NO

and PM

2.5

in 2013, 2020, and 2023.

Email dated March 29, 2022, from Nesamani Kalandiyur, CARB, to Karina O'Connor et al., EPA Region IX, Subject: “RE: EMFAC Discussion,” (“March 2022 EMFAC Clarification”). The email also includes model results for the 2026 post-attainment milestone year. CARB initially released EMFAC2021 v1.0.0 on January 15, 2021. CARB released an updated version, EMFAC2021 v1.0.1, on April 30, 2021, and the EPA approved the use of EMFAC2021 for use in SIP development on November 15, 2022 (87 FR 68483).

Table 3—On-Road Mobile Source NO

and Direct PM

2.5

Emissions Derived Using EMFAC2014, EMFAC2017, and EMFAC2021

[tpd]

2013

2020

2023

Direct PM

2.5

2013

2020

2023

EMFAC2014

183.1

96.9

57.9

6.5

3.4

3.2

EMFAC2017

170.0

89.3

61.2

6.8

4.0

3.3

EMFAC2021

193.5

84.4

54.9

6.1

2.3

1.8

EMFAC2017/EMFAC2014

93%

92%

106%

116%

105%

EMFAC2021/EMFAC2014

106%

87%

95%

66%

56%

Source: CARB's March 2022 EMFAC Clarification.

CARB determined that PM

2.5

emissions estimates for 2013 derived using EMFAC2017 are approximately six percent higher than estimates derived using EMFAC2014, and that NO

emissions estimates for 2013

derived using EMFAC2017 are seven percent lower than the emissions estimates derived using EMFAC2014. On-road PM

2.5

and NO

estimates derived using EMFAC2021 are five percent lower and six percent higher, respectively, in 2013 as compared with estimates from EMFAC2014. In the 2023 attainment year, on-road PM

2.5

and NO

emissions estimates derived using EMFAC2017 are approximately 5 percent and 6 percent higher, respectively, than estimates derived using EMFAC2014, whereas on-road PM

2.5

and NO

emissions estimates derived using EMFAC2021 are approximately 44 percent and 5 percent lower, respectively, than in EMFAC2014.

Based on these model results, CARB concludes that the differences in emissions derived using the different EMFAC model versions are not significant enough to affect the modeled attainment demonstration in the 15 µg/m

SIP Revision.

3. The EPA's Review of the State's Submission

As part of our July 22, 2021 proposed and November 26, 2021 final rules,

we reviewed the emissions inventories in the 2018 PM

2.5

Plan that pertain to the 1997 annual PM

2.5

NAAQS and the emissions inventory estimation methodologies used by California for consistency with CAA requirements and the EPA's guidance. We found that the inventories were based on the most current and accurate information available to the State and District at the time they were developing the 2018 PM

2.5

Plan and inventories, including the latest version of California's mobile source emissions model that had been approved by the EPA at the time, EMFAC2014. We also found that the inventories comprehensively address all source categories in the San Joaquin Valley PM

2.5

nonattainment area and are consistent with the EPA's inventory guidance. In our November 26, 2021 final action, we approved the 2013 base year emissions inventories in the 2018 PM

2.5

Plan as meeting the requirements of CAA section 172(c)(3) and 40 CFR 51.1008 for purposes of both the Serious area and the CAA section 189(d) attainment plans for the 1997 annual PM

2.5

NAAQS.

86 FR 38652 and 86 FR 67329.

86 FR 67329, 67341.

For purposes of evaluating the 15 µg/m

SIP Revision, we have reviewed the additional information comparing the emissions derived using EMFAC2014, EMFAC2017, and EMFAC2021 that was provided by CARB in its August 2021 Staff Report and subsequent email transmittal. The State modeled reductions of direct PM

2.5

and NO

on-road mobile emissions and calculated the sensitivity of the PM

2.5

design value per tpd of emissions.

The EPA used those sensitivity results with the EMFAC emissions estimates to assess the effects of the various EMFAC model version results on the attainment demonstration in the Plan. We are proposing to find that although NO

and PM

2.5

emissions estimates in the 2023 attainment year are slightly higher in EMFAC2017 than in EMFAC2014, the effect on PM

2.5

concentrations is small enough that the attainment demonstration in the 15 µg/m

SIP Revision remains valid.

Furthermore, more up-to-date emissions information from EMFAC2021 indicates lower emissions of NO

and PM

2.5

in the attainment year, indicating that the attainment modeling results derived using EMFAC2014 are conservative and that the 2023 attainment year design values are expected to be lower than those modeled in the Plan.

15 µg/m

SIP Revision, Appendix D, p. D-125. Transportation Conformity Budgets, Emissions Trading Mechanism, Table 21. These sensitivity simulations used the same modeling base case as the attainment demonstration for the 15 µg/m

SIP Revision.

Spreadsheet “EMFAC update effect on annual 1997 PM

2.5

NAAQS attainment demonstration,” EPA Region IX, May 1, 2023.

With respect to future year emissions projections in the 15 µg/m

SIP Revision, we have reviewed the growth and control factors and are proposing to find them acceptable and thus conclude that the future baseline emissions projections in the SJV PM

2.5

Plan, which reflect ongoing emissions reductions from existing (

i.e.,

“baseline”) control measures as discussed in Section IV.C.2.a, reflect appropriate calculation methods and the latest planning assumptions. 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 sources, the related rules must be approved by the EPA into the SIP. Table 2 of the EPA's “Technical Support Document, San Joaquin Valley PM

2.5

Plan Revision for the 1997 Annual PM

2.5

NAAQS,” April 2023 (“EPA's 1997 Annual PM

2.5

TSD”) shows District rules with post-2013 compliance dates that are reflected in the future year baseline inventories, along with information on the EPA's approval of these rules, and shows that stationary source emissions reductions assumed by the SJV PM

2.5

Plan for future years are supported by rules approved as part of the California SIP for the San Joaquin Valley. With respect to mobile sources, the EPA has taken action 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 SJV PM

2.5

Plan are properly supported by SIP-approved stationary and mobile source measures.

For these reasons, we are proposing to find that the 2013 base year emissions inventories in the SJV PM

2.5

Plan for the 1997 annual PM

2.5

NAAQS continue to satisfy the requirements of CAA section 172(c)(3) and 40 CFR 51.1008 for purposes of both the Serious area and the CAA section 189(d) attainment plans. We are also proposing to find that the forecasted inventories in the Plan for the years 2017, 2018, 2019, 2020, 2023, and 2026 provide an adequate basis for the BACM, RFP, and the modeled attainment demonstration analyses in the SJV PM

2.5

Plan.

B. PM

2.5

Precursors

1. Statutory and Regulatory Requirements

Under subpart 4 of part D, title I of the CAA and the PM

2.5

SIP Requirements Rule, each state containing a PM

2.5

nonattainment area must evaluate all PM

2.5

precursors for regulation unless, for any given PM

2.5

precursor, the state demonstrates to the Administrator's satisfaction that such precursor does not contribute significantly to PM

2.5

levels that exceed the NAAQS in the nonattainment area.

The provisions of subpart 4 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

, SO

, VOC, and ammonia as precursors to the formation of PM

2.5

100

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)).

81 FR 58010, 58017-58020.

CAA section 302(g).

100

81 FR 58010, 58015.

Section 189(e) of the Act requires that the control requirements for major stationary sources of direct PM

(which includes PM

2.5

) also apply to major stationary sources of PM

precursors, except where the Administrator determines that such sources do not contribute significantly to PM

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, BACT, MSM, and nonattainment new source review (NSR)). 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.

101

For example, under the EPA's longstanding interpretation of the control requirements that apply to stationary and mobile sources of PM

precursors in nonattainment areas under CAA section 172(c)(1) and subpart 4,

102

a state may demonstrate in a SIP submission that control of a certain precursor pollutant is not necessary because it does not contribute significantly to ambient PM

levels in the nonattainment area and is not needed for attainment.

103

101

Id. at 58018-58019.

102

General Preamble, 13539-13542.

103

Courts have upheld this approach to the requirements of subpart 4 for PM

. See,

e.g., Assoc. of Irritated Residents

EPA, et al.,

423 F.3d 989 (9th Cir. 2005).

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.

104

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.

105

104

40 CFR 51.1006(a)(1).

105

Id. A state may also perform a separate, “NNSR precursor demonstration” to evaluate the sensitivity of PM

2.5

levels in the nonattainment area to an increase in emissions of a particular precursor and determine if new major stationary sources and major modifications of a precursor would contribute significantly to PM

2.5

levels that exceed the standard in the nonattainment area. 40 CFR 51.1006(a)(3).

In addition, in May 2019, the EPA issued the “PM

2.5

Precursor Demonstration Guidance” (“PM

2.5

Precursor Guidance”),

106

which provides recommendations to states for analyzing nonattainment area PM

2.5

emissions and developing such optional precursor demonstrations, consistent with the PM

2.5

SIP Requirements Rule. The EPA developed recommended contribution thresholds to help assess whether a precursor significantly contributes to PM

2.5

levels above the NAAQS. The thresholds are based on the size of PM

2.5

concentration increases that are statistically indistinguishable from the inherent variability in the measured atmospheric concentrations.

107

If the chemical component of PM

2.5

ambient concentrations corresponding to emissions of a precursor (

e.g.,

the concentration of sulfate, which corresponds to SO

emissions) is below the threshold, that is evidence that the precursor does not significantly contribute. If the precursor is above the threshold in this concentration-based test, the State can use a sensitivity-based test, in which the modeled sensitivity or response of ambient PM

2.5

concentrations to changes in emissions of the precursor is estimated and then compared to the threshold. The EPA's recommended annual average contribution threshold for purposes of the 2012 annual PM

2.5

NAAQS is 0.2 µg/m

108

The PM

2.5

Precursor Guidance explains that this threshold represents a percentage of the 2012 annual NAAQS and that “[d]ifferent thresholds may be applicable to other levels and/or forms of the NAAQS (either past or future).”

109

In addition to comparing the concentration or modeled response to the threshold, the State can consider other information in assessing whether the precursor significantly contributes.

106

“PM

2.5

Precursor Demonstration Guidance,” EPA-454/R-19-004, May 2019, including memorandum dated May 30, 2019, from Scott Mathias, Acting Director, Air Quality Policy Division and Richard Wayland, Director, Air Quality Assessment Division, Office of Air Quality Planning and Standards (OAQPS), EPA to Regional Air Division Directors, Regions 1-10, EPA. The PM

2.5

Precursor Guidance builds upon the draft version of the guidance, released on November 17, 2016 (“Draft PM

2.5

Precursor Guidance”), which CARB referenced in developing its precursor demonstration in the SJV PM

2.5

Plan. “PM

2.5

Precursor Demonstration Guidance, Draft for Public Review and Comments,” EPA-454/P-16-001, November 17, 2016, including memorandum dated November 17, 2016, from Stephen D. Page, Director, OAQPS, EPA to Regional Air Division Directors, Regions 1-10, EPA.

107

2.5

Precursor Guidance, p. 15.

108

Id. at 17.

109

Id. at fn. 20.

As explained in the PM

2.5

Precursor Guidance, and consistent with the PM

2.5

SIP Requirements Rule (40 CFR 51.1010(a)(2)(ii), 51.1006(a)(1)(ii)), the EPA may require an air agency to identify and evaluate potential control measures for a precursor to determine the potential emissions reductions achievable, in support of a precursor demonstration that relies on a sensitivity analysis.

110

The guidance states that such evaluation is particularly important for an area in which the PM

2.5

response to a 30 percent reduction in precursor emissions is close to the contribution threshold. In the case of a nonattainment area classified as Serious, this analysis would include identification and evaluation of measures that would constitute BACM/BACT level control for such pollutant.

111

Consistent with these regulations, the EPA requested that the State identify and evaluate potential control measures for ammonia to determine the potential emissions reductions achievable for purposes of the 1997 annual PM

2.5

NAAQS.

110

Id. at 31.

111

Id.

We are evaluating the SJV PM

2.5

Plan in accordance with the presumption embodied within subpart 4, that states must address all PM

2.5

precursors in the 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 a 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, where the state has conducted sensitivity-based analyses, the sensitivity of ambient PM

2.5

concentrations in the area to reductions in emissions of that precursor in accordance with the PM

2.5

Precursor Guidance.

2. Summary of the State's Submission

The State presents some results and conclusions from its PM

2.5

precursor sensitivity analysis in Chapter 5 (“Demonstration of Federal Requirements for 1997 PM

2.5

Standards”), Section 5.3.1 (“Summary of Modeling Results”) of the 15 µg/m

SIP Revision, and presents the full

precursor demonstration in Appendix G (“Precursor Demonstration”) of the 2018 PM

2.5

Plan.

112

CARB presents additional modeling results in Appendix K (“Modeling Attainment Demonstration”) of the 15 µg/m

SIP Revision. CARB also provided clarifying information on its precursor assessment, including an Attachment A to its letter transmitting the 2018 PM

2.5

Plan to the EPA

113

and further clarifications in five email transmittals.

114

CARB's December 2018 Staff Report and August 2021 Staff Report contain additional discussion of the role of ammonia in the formation of ammonium nitrate and the role of VOC in the formation of ammonium nitrate and secondary organic aerosol.

115

Lastly, on March 30, 2023, CARB transmitted to the EPA a technical supplement titled “Ammonia: Supplemental Information for EPA in Support of 15 µg/m

Annual PM

2.5

Standard, March 2023” (“March 2023 Ammonia Supplement”) in which CARB and the District “clarify CARB's assessment of ammonia as a precursor to fine particulate matter (PM

2.5

) for the 15 µg/m

annual standard by summarizing information previously submitted to EPA and providing new detailed control measure analysis”

116

to assess potential ammonia emissions reductions achievable in the San Joaquin Valley through the implementation of best available controls.

112

Appendix G was not changed relative to the 2018 PM

2.5

Plan for the 15 µg/m

SIP Revision.

113

Letter dated May 9, 2019, from Richard Corey, Executive Officer, CARB, to Michael Stoker, Regional Administrator, EPA Region 9, Attachment A (“Clarifying information for the San Joaquin Valley 2018 Plan regarding model sensitivity related to ammonia and ammonia controls”).

114

Email dated June 20, 2019, from Jeremy Avise, CARB, to Scott Bohning, EPA Region IX, Subject: “RE: SJV model disbenefit from SO

reduction,” with attachment (“CARB's June 2019 Precursor Clarification”); email dated September 19, 2019, from Jeremy Avise, CARB, to Scott Bohning, EPA Region IX, Subject: “FW: SJV species responses,” with attachments (“CARB's September 2019 Precursor Clarification”); email dated October 18, 2019, from Laura Carr, CARB, to Scott Bohning, Jeanhee Hong, and Rory Mays, EPA Region IX, Subject: “Clarifying information on ammonia,” with attachment “Clarifying Information on Ammonia” (“CARB's October 2019 Precursor Clarification”); email dated April 19, 2021, from Laura Carr, CARB, to Rory Mays, EPA Region IX, Subject: “Ammonia update,” with attachment “Update on Ammonia in the San Joaquin Valley” (“CARB's April 19, 2021 Precursor Clarification”); and email dated April 26, 2021, from Laura Carr, CARB, to Scott Bohning, EPA Region IX, Subject: “RE: Ammonia update,” with attachment “Ammonia in San Joaquin Valley” (“CARB's April 26, 2021 Precursor Clarification”).

115

December 2018 Staff Report, Appendix C, pp. 9-16, and August 2021 Staff Report, pp. 8-9 and Attachment 1. Attachment 1 is identical to the attachment to CARB's April 19, 2021 Precursor Clarification.

116

Letter dated March 29, 2023, from Steven S. Cliff, Executive Officer, CARB, to Martha Guzman, Regional Administrator, EPA Region 9, with enclosures.

The SJV PM

2.5

Plan provides both concentration-based and sensitivity-based analyses of precursor contributions to ambient PM

2.5

concentrations in the San Joaquin Valley. For the concentration-based analysis, CARB assessed the 2015 annual average concentration of each precursor in ambient PM

2.5

at Bakersfield, for which the necessary speciated PM

2.5

data are available and where the highest PM

2.5

design values have been recorded in most years. CARB concludes that the 2015 annual average contributions of ammonia, SO

, and VOC are 5.2 µg/m

, 1.6 µg/m

, and 6.2 µg/m

, respectively. Given that these levels are above the EPA's recommended contribution threshold, the State proceeded with a sensitivity-based analysis.

CARB's sensitivity-based analysis used the same Community Multiscale Air Quality (CMAQ) modeling platform as that used for the Plan's attainment demonstration, described in Section IV.D. of this proposal. The State modeled the sensitivity of ambient PM

2.5

concentration in the San Joaquin Valley to 30 percent and 70 percent reductions in anthropogenic emissions of each precursor pollutant for modeled years 2013, 2020, and 2024. The year 2013 is the 2018 PM

2.5

Plan's base year; 2020 is the modeled attainment year for the 1997 24-hour PM

2.5

NAAQS and former modeled attainment year for the 1997 annual PM

2.5

NAAQS; and 2024 is the modeled attainment year for the 2006 24-hour PM

2.5

NAAQS. For the 1997 annual PM

2.5

NAAQS, the revised modeled attainment year is 2023, but the State did not conduct precursor sensitivity modeling for that additional year. Instead, the State assumed that 2023 and 2024 would have very similar results;

117

and results for 2024 were used as a proxy for those in 2023.

117

15 µg/m

SIP Revision, Chapter 5, p. 5-8, and March 2023 Ammonia Supplement, fn. 35.

In Appendix G of the 2018 PM

2.5

Plan, the State compared its sensitivity modeling results to the recommended annual average contribution threshold of 0.2 µg/m

in the PM

2.5

Precursor Guidance. As discussed in Section IV.B.1, the 0.2 µg/m

contribution threshold was derived based on the level of the 2012 annual PM

2.5

NAAQS (

i.e.,

12.0 µg/m

). In the March 2023 Ammonia Supplement, the State explains that adjusting the contribution threshold to the level of the 1997 annual PM

2.5

NAAQS (

i.e.,

15.0 µg/m

) results in a contribution threshold of 0.25 µg/m

and presents an updated evaluation of the modeled concentration-based and sensitivity-based analyses for ammonia using the 0.25 µg/m

threshold.

118

The State did not provide an updated analysis using the 0.25 µg/m

threshold for SO

or VOC.

In collaboration with the District, the State supplemented the sensitivity analysis, particularly for ammonia, with consideration of additional information such as emissions trends, the appropriateness of future year versus base year sensitivity, the severity of nonattainment, and a detailed controls analysis.

119

These factors were identified in the then-available Draft PM

2.5

Precursor Guidance, as well as in the final PM

2.5

Precursor Guidance, as factors that may be relevant to a sensitivity-based contribution analysis.

120

119

2018 PM

2.5

Plan, Appendix G, pp. 8-10, and March 2023 Ammonia Supplement, pp. 13-96.

120

2.5

Precursor Guidance, pp. 18-19 (consideration of additional information), p. 31 (available emission controls), and pp. 35-36 (appropriateness of future year versus base year sensitivity).

Taken together, these analyses led CARB to conclude that NO

remains a plan precursor but that ammonia, SO

, and VOC do not contribute significantly to ambient PM

2.5

levels that exceed the PM

2.5

NAAQS in the San Joaquin Valley. We summarize the State's analysis and conclusions below. For a more detailed summary of the precursor demonstration in the Plan, please refer to 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 February 2020 Precursor TSD”).

a. Ammonia

For the ammonia analysis presented in Appendix G of the 2018 PM

2.5

Plan, the State compared the annual precursor contributions to 0.2 µg/m

, the contribution threshold recommended for the 2012 annual PM

2.5

NAAQS in the PM

2.5

Precursor Guidance. The State supplemented this analysis in the March 2023 Ammonia Supplement by comparing the annual ammonia contributions to the 0.25 µg/m

threshold it derived for the 1997 annual PM

2.5

NAAQS. For a modeled 30 percent ammonia emissions reduction, the ambient PM

2.5

responses in 2013 ranged from 0.20 to 0.72 µg/m

across 15 monitoring sites, with all of the sites at or above the 0.2 µg/m

contribution threshold and all but two of the sites above the 0.25 µg/m

contribution threshold. PM

2.5

responses in 2020 ranged from 0.12 to 0.42 µg/m

, with nine sites above the 0.2 µg/m

contribution threshold and four sites

above the 0.25 µg/m

contribution threshold. Responses in 2024 ranged from 0.08 to 0.26 µg/m

, with two sites above the 0.2 µg/m

contribution threshold and one site above the 0.25 µg/m

contribution threshold. For a modeled 70 percent ammonia emissions reduction, the ambient PM

2.5

responses were above both thresholds at all 15 sites for all three modeled years.

The State based its ammonia precursor determination on the sensitivity analysis for the future years, using a 30 percent ammonia emissions reduction. This was supported by its assessment of research studies and the Plan's projected emissions reductions, and its assessment of available emissions controls. As explained in the PM

2.5

Precursor Guidance, precursor responses may be above the recommended contribution threshold and yet not contribute significantly to levels that exceed the standard in the area.

121

Therefore, the State considered additional information to examine whether the identified PM

2.5

responses constituted a significant contribution to ambient PM

2.5

in the San Joaquin Valley. The additional information included emissions trends, support for the State's reliance on modeling results for a 30 percent ammonia emissions reduction, as well as conclusions from research studies.

121

2.5

Precursor Guidance, p. 18.

The State estimates that NO

emissions in the San Joaquin Valley are projected to decrease by 53 percent from 2013 to 2024, while ammonia emissions are projected to remain relatively flat, thereby increasing the relative abundance of ammonia.

122

Based on the Plan's emission reduction projections combined with the research study conclusions, the State relies on the modeled responses for the 2024 future year, rather than the 2013 base year, stating that the future year NO

emissions are more representative of San Joaquin Valley emissions conditions.

123

The State references the Draft PM

2.5

Precursor Guidance, which notes that it may be appropriate to model future conditions that are more representative of current atmospheric conditions and those conditions expected closer to the attainment date.

124

The State concludes that this in fact applies to the San Joaquin Valley.

125

122

March 2023 Ammonia Supplement, pp. 14-15.

123

Id. at 15 and 17.

124

Id. at 13 (referencing Draft PM

2.5

Precursor Guidance, p. 33). See also PM

2.5

Precursor Guidance, p. 35.

125

Id. at 15.

The State also describes previous research studies that support its conclusion that ammonium nitrate PM

2.5

formation in the San Joaquin Valley is NO

-limited rather than ammonia-limited.

126

For example, based on aircraft-borne measurements during the 2013 DISCOVER-AQ campaign,

127

the State concluded that ammonium nitrate formation is NO

-limited based on the large amount of “excess ammonia,” which is defined as the amount of measured ammonia left over if all the nitrate and sulfate present were to combine with available ammonia to form particulate.

128

CARB's December 2018 Staff Report describes these conclusions in more detail and lists results from multiple other recent studies with similar conclusions.

129

The studies suggest a very low ambient sensitivity to ammonia, based on measured excess ammonia relative to NO

, the abundance of particulate nitrate relative to gaseous NO

, 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

, so that ammonia emission reductions would be expected mainly to reduce the amount of ammonia excess, rather than to reduce the particulate amonium nitrate.

126

2018 PM

2.5

Plan, Appendix G, pp. 9-10; December 2018 Staff Report, Appendix C, pp. 12-15; and Attachment A to CARB's May 9, 2019, submittal letter.

127

Deriving Information on Surface conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality,”

https://www.nasa.gov/mission_pages/discover-aq/index.html.

128

2018 PM

2.5

Plan, Appendix G, Figure 2.

129

December 2018 Staff Report, Appendix C, p. 12; and Attachment A to CARB's May 9, 2019 submittal letter. These studies are also discussed in the EPA's February 2020 Precursor TSD.

CARB also describes the results of two studies indicating that ammonia concentrations may be underestimated in modeling of the DISCOVER-AQ early 2013 study period, which would result in the response to ammonia reductions being overpredicted.

130

CARB conducted its own analysis comparing 2017 satellite observations with CMAQ model predictions and found that modeled ammonia concentrations were half of the magnitude of the satellite observations at some locations and that the modeled valley-wide average was approximately 25 percent less than observed. Taken together, CARB concludes that these studies provide evidence that PM

2.5

would respond only weakly to ammonia emissions reductions.

130

CARB's April 19, 2021 Precursor Clarification; CARB's April 26, 2021 Precursor Clarification. The modeling used for the attainment demonstration has enough excess ammonia to correctly predict ammonium nitrate and ammonium sulfate PM

2.5

concentrations, but likely less of an excess than indicated from ambient measurements of ammonia itself.

Finally, the State and District provided additional information, both in the SJV PM

2.5

Plan and in the March 2023 Ammonia Supplement, to support its conclusion that 30 percent is a reasonable upper bound on the ammonia reductions that are practically available, and as a basis for its reliance on the modeling results for a 30 percent ammonia emissions reduction. This information includes a review of ammonia emission reductions achieved nationwide from 2011 to 2017 as summarized in the EPA's PM

2.5

Precursor Guidance,

131

an evaluation of the main ammonia source categories in the San Joaquin Valley,

132

a summary of existing control measures in the San Joaquin Valley that affect ammonia from these sources,

133

a review of existing control measures implemented by other air districts,

134

and an evaluation of additional mitigation options for ammonia sources in the Valley.

135

We briefly summarize the State's analyses and conclusions for relying on a 30 percent upper bound in the following paragraphs. For a more detailed summary of the State's ammonia control measure analysis, please refer to the EPA's 1997 annual PM

2.5

TSD.

136

131

March 2023 Ammonia Supplement, p. 11. See also PM

2.5

Precursor Guidance, Section 4.1.1.

132

March 2023 Ammonia Supplement, pp. 20-25.

133

Id. at 25, and 2018 PM

2.5

Plan, Appendix C, Section C-25.

134

March 2023 Ammonia Supplement, pp. 26-27, and 2018 PM

2.5

Plan, Appendix C, Section C-25.

135

March 2023 Ammonia Supplement, pp. 28-96.

136

EPA, Technical Support Document, “San Joaquin Valley PM

2.5

Plan Revision for the 1997 annual PM

2.5

NAAQS,” April 2023.

First, CARB and the District reason that trends in ammonia emissions provided in the PM

2.5

Precursor Guidance, which show a national increase of 0.8 percent in ammonia emissions between 2011-2017, are indicative of a lack of controls on ammonia sources nationwide.

137

The March 2023 Ammonia Supplement includes a comparison of the guidance trends in ammonia with trends in NO

and SO

over the same period, which decreased by 63.6 percent and 31.8 percent, respectively, which CARB and the District attribute to control measures to reduce emissions of these pollutants. The State acknowledges that new controls for ammonia are being researched but states that the recent emissions trends suggest that a 30 percent reduction in ammonia is a conservative upper bound on what is achievable. To further support that statement, the District and State

collaborated on an evaluation of potential control measures to reduce ammonia emissions in the San Joaquin Valley for the March 2023 Ammonia Supplement.

137

March 2023 Ammonia Supplement, p. 11.

The first step in the control measure evaluation was to characterize the key sources of ammonia in the Valley. The three main sources of ammonia emissions identified in the Plan are: (1) confined animal facilities (CAFs); (2) agricultural fertilizers; and (3) composting operations, which together account for 94 percent of the Valley's ammonia emissions.

138

CAFs are subject to District Rule 4570 (“Confined Animal Facilities”), and composting operations are subject to District Rule 4565 (“Biosolids, Animal Manure, and Poultry Litter Operations”) and District Rule 4566 (“Organic Material Composting Operations”). Although these District rules explicitly apply only to VOC emissions from these sources, the State concludes that these rules have also resulted in significant reductions in ammonia emissions.

139

Appendix C of the 2018 PM

2.5

Plan cites a number of scientific studies that address the correlation between VOC and ammonia emissions from these emission sources.

140

Given that CAFs and agricultural fertilizers account for 92 percent of the ammonia emissions inventory in the San Joaquin Valley,

141

and that ammonia emissions from composting operations account for only 2 percent of the ammonia emissions inventory and have already been reduced through District Rules 4565 and 4566, the ammonia control measure evaluation focused primarily on potential controls for CAFs and agricultural fertilizers.

138

Id. at 20.

139

Id. at 26 and 96.

140

2018 PM

2.5

Plan, Appendix C, Section C-25.

141

March 2023 Ammonia Supplement, Figure 4.

For CAFs, the District provides an inventory of the types of facilities operating in the Valley subject to Rule 4570 and the corresponding ammonia emissions from each facility type.

142

For dairy cattle, which accounts for an estimated 67.2 percent of ammonia emissions from CAFs, the District assessed how the different CAF operations contribute to the overall ammonia inventory. For example, the District estimates that 56.6 percent of dairy cattle ammonia emissions are from housing dairy cattle in corrals/pens, 11.1 percent of emissions are from lagoons and storage ponds, and 12.0 percent of emissions occur during land application of liquid manure.

143

142

Id. at Figure 5 and Table 7.

143

Id. at Figure 7.

Next, the District discusses ammonia mitigation measures that are already being implemented in the Valley. The District discusses in detail in Appendix C of the 2018 PM

2.5

Plan how Rule 4570 is structured (

e.g.,

to address varying types of CAFs); the five main CAF operations/emission sources: feeding, housing (including distinctions for housing configurations), solid waste, liquid waste, and land application of manure; the control menu requirements for each of those five operations; and research papers that estimate ammonia emission reductions from some of the measures.

144

The District explains that some of the measures in Rule 4570 are required to be implemented but that the rule also requires additional measures to be selected from a menu of options.

145

The menu-based approach is intended to allow facilities flexibility to select measures that are the most practical and effective for their design and operation given the District's findings of variability within the industry.

146

144

2018 PM

2.5

Plan, Appendix C, pp. C-312 to C-323.

145

Id. and March 2023 Ammonia Supplement, pp. 25-26.

146

Id.

As a first step in assessing whether there are additional feasible control measures for CAFs that are not yet being implemented in the Valley, the District evaluated other district CAF rules with requirements comparable to those in Rule 4570.

147

The District reviewed CAF rules implemented by the South Coast Air Quality Management District (AQMD), Bay Area AQMD, Ventura County Air Pollution Control District (APCD), Sacramento Metropolitan AQMD, Imperial County APCD, and the State of Idaho.

148

The District also points to comparisons between Rule 4570 and two additional sets of requirements imposed by Butte County APCD and Yakima Regional Clean Air Agency, as conducted for the “2016 Plan for the 2008 8-hour Ozone Standard.”

149

Based on comparisons between specific requirements, the State concludes that Rule 4570 is more stringent than other district rules and no additional requirements are currently being implemented in other areas.

150

147

March 2023 Ammonia Supplement, pp. 26-27.

148

2018 PM

2.5

Plan, Appendix C, Section C-25.

149

March 2023 Ammonia Supplement, p. 27.

150

Id.

The second step in the control measure analysis was to review scientific research studies on mitigating ammonia emissions from CAFs. In Appendix A of the March 2023 Ammonia Supplement, the District provides a list of research studies and potential ammonia control measures it considered. For each of the 46 mitigation measures identified in the literature, the State provides a narrative detailing its evaluation of the feasibility of implementation of the measure in the San Joaquin Valley.

151

The State's analysis covers a broad range of CAF activities, including animal feeding and housing, and the storage, handling, and land application of manure. The analysis also addresses a number of other mitigation options, such as pasture and range land management, land use changes, and planting a tree shelter belt near CAFs.

152

Based on these evaluations, the State identified three measures that could provide further reductions in ammonia emissions in the San Joaquin Valley. These measures include 1) reducing the crude protein content in feed for beef finishing cattle, 2) incorporating solid manure into the soil within 24-hours, and 3) adding acidifying amendments to poultry litter and manure.

153

Based on control efficiencies cited in the literature, the District estimates that the total emissions reductions achievable from these measures is 6.6 tons per day (tpd), which is approximately two percent of the 2023 inventory. For those measures it found to be infeasible in the San Joaquin Valley, the District includes a narrative explaining its conclusion.

151

Id. at 28-85.

152

Id. at 86-88.

153

Id. at 88-89.

Regarding fertilizer application, the State provides an estimate of 111.2 tpd of ammonia emissions in 2023.

154

In the 2018 PM

2.5

Plan, the District describes key research assessing nitrogen in California, as well as regulations adopted by the California Water Resources Control Board, including orders adopted by the Central Valley Regional Water Quality Control Board (

e.g.,

a Nutrient Management Plan), the Irrigated Lands Regulatory Program (

e.g.,

a Nitrogen Management Plan), and other individual orders on agricultural operations not subject to those programs.

155

These orders subject agricultural operators, including dairies, bovine feedlots, poultry operations, and crop farmers to “waste discharge requirements that protect both surface water and groundwater.”

156

154

Id. at 89.

155

2018 PM

2.5

Plan, Appendix C, pp. C-339 to C-343.

156

Id. at C-341.

In the March 2023 Ammonia Supplement, the State supplemented its prior analysis by explaining how various state agencies are engaged in fertilizer use and application and discussing its efforts to identify any

existing rules or regulations in the nation controlling ammonia emissions from this source category.

157

CARB states that it has not identified any measures that are being implemented to reduce ammonia and thus, again turns to scientific research studies on ammonia mitigation measures to assess the potential emissions reductions that could be achieved from fertilizer application. The measures identified in the literature for reducing ammonia emissions from fertilizer application include optimizing fertilizer use, adding a urease inhibitor, mixing and injecting fertilizer into the soil quickly, and applying fertilizer during optimal weather conditions. Based on its review, the State finds that several of the strategies identified in the literature are consistent with strategies recommended by the California Department of Food and Agriculture Fertilizer Research and Education Program as part of its Irrigation and Nitrogen Management training program, which includes overviews of the “4 R's” of nitrogen management: “Right source” of nitrogen at the “right rate,” “right time,” and “right place.”

158

However, the State concludes that more research is needed to explore the feasibility and effectiveness of requiring some of the identified strategies in California, due in part to the warmer and dryer climate conditions in the San Joaquin Valley compared to, for example, the European climate in which many of the research studies were conducted, and due to the need to explore any potential adverse consequences. Thus, the State concludes that additional reductions in ammonia from fertilizer application are not feasible at this time.

159

157

March 2023 Ammonia Supplement, pp. 89-92.

158

Id. at 92.

159

Id. at 96.

For composting operations and other ammonia sources, the District notes that it currently regulates ammonia emissions from composting though Rules 4565 and 4566 and states that these rules have reduced ammonia emissions by 44 percent. Given that composting amounts to only two percent of the total ammonia emissions, the District did not provide any further evaluation for this source category. For the remaining ammonia sources in the Valley covered under “other” source category, which amounts to 6 percent of the total inventory, the District notes that ammonia emissions are primarily from mobile sources and fuel combustion, which it asserts are also already controlled. The District concludes that no additional reductions are available from composting operations or other ammonia sources.

160

Id.

Taken together, the State estimates that ammonia emissions could be reduced by 6.6 tpd in the San Joaquin Valley through three additional mitigation measures for CAFs, which would amount to a total ammonia reduction of 2 percent. Based on this analysis, the State concludes that ammonia control measures achieving even the low end of the modeled range (

i.e.,

30 percent) are not feasible for implementation in the San Joaquin Valley, and that it is therefore reasonable to treat a 30 percent ammonia reduction as a conservative upper bound on the reductions that are achievable, and to base the analysis in the precursor demonstration on the model response to a 30 percent reduction.

In summary, the State's sensitivity analysis presents a range of PM

2.5

responses to ammonia emissions reductions in multiple modeled years. The State describes in the Plan its bases for finding that the 2024 future year sensitivity results better represent conditions in the San Joaquin Valley than the 2013 base year, and for finding a 30 percent ammonia reduction to be a reasonable upper bound on the ammonia emissions reductions available for assessing the ammonia contribution. Based on these analyses of the modeled response to ammonia reductions below the threshold, additional ambient evidence, and the amount of reductions available from controls, the State concludes that ammonia does not contribute significantly to ambient PM

2.5

levels above the 1997 annual PM

2.5

NAAQS in the San Joaquin Valley.

b. SO

For SO

, the State compares the annual precursor contributions to the contribution threshold of 0.2 µg/m

recommended for the 2012 annual PM

2.5

NAAQS in the PM

2.5

Precursor Guidance. For modeled SO

emissions reductions of 30 percent and 70 percent, the ambient PM

2.5

responses in 2013 ranged from -0.05 µg/m

to 0.15 µg/m

across 15 monitoring sites, which all fall below the 0.20 µg/m

contribution threshold.

161

The response was below zero in select cases, indicating an increase, rather than a decrease, in ambient PM

2.5

in response to SO

emissions reductions (

i.e.,

a disbenefit). For 2020, the responses to 30 percent and 70 percent emissions reductions ranged from −0.01 µg/m

to 0.16 µg/m

while for 2024, the responses ranged from 0.01 µg/m

to 0.08 µg/m

; these are also all below the 0.2 µg/m

contribution threshold.

162

161

2018 PM

2.5

Plan, Appendix G, tables 8 and 9.

162

CARB's September 2019 Precursor Clarification, 2020 analysis tables 7 and 8, and 2024 analysis tables 7 and 8.

To explain the SO

emissions reduction disbenefit that is observed in some cases, CARB refers to the non-linearity of inorganic aerosol thermodynamics, as described in a study by West et al.

163

The paper discusses how, under certain conditions, reducing SO

could free ammonia to combine with nitrate, increasing overall PM

2.5

mass. To investigate this issue further, CARB conducted simulations with the ISORROPIA inorganic aerosol thermodynamic equilibrium model used within the CMAQ model and provided clarifications to the EPA.

164

In essence, CARB states that for some conditions typical of San Joaquin Valley, ISORROPIA switches to a different chemical regime in which the disbenefit occurs. CARB states that it is not known how well this model behavior reflects the actual atmosphere, but CARB accepts the results because it is a well-known and widely used chemical model.

163

15 µg/m

SIP Revision, Appendix K, Section 5.7 (“PM

2.5

Precursor Sensitivity Analysis”); and West, J.J., Ansari, A.S., Pandis, S.N., 1999, Marginal PM

2.5

: Nonlinear aerosol mass response to sulfate reductions in the eastern United States,

Journal of the Air & Waste Management Association,

49, 1415-1424.

https://doi.org/10.1080/10473289.1999.10463973.

164

CARB's June 2019 Precursor Clarification.

The State also provides an emissions trend chart that shows that SO

emissions are approximately constant at 8 tpd from 2013 through 2024. Given that the relative levels of estimated SO

and ammonia emissions over the timeframe remain similar, the State concludes that 2013 sensitivities are also representative of future years.

165

2018 PM

2.5

Plan, Appendix G, p. 15. The State includes modeling of 30 percent and 70 percent reductions of SO

for 2013 only, finding that the sensitivity of ambient PM

2.5

to such changes were below the EPA's recommended threshold, and that the 2020 and 2024 results would differ little from 2013 due to the similarity of emissions conditions over time. Appendix G, p. 17. CARB's September 2019 Precursor Clarification provides the 2020 and 2024 sensitivity results, which are indeed very close to those for 2013.

Based on the small modeled response of ambient PM

2.5

to SO

emissions reductions, the constant SO

emissions over time, and its scientific understanding of sulfate interactions with other molecules in the air, the State concludes that SO

does not contribute significantly to ambient PM

2.5

levels that exceed the 1997 annual

2.5

NAAQS in the San Joaquin Valley.

c. VOC

For VOC, CARB compared the annual precursor contributions to the EPA's recommended contribution threshold for the 2012 PM

2.5

NAAQS of 0.2 µg/m

. For a modeled 30 percent VOC emissions reduction, the ambient PM

2.5

responses in 2013 ranged from 0.01 µg/m

to 0.16 µg/m

across 15 monitoring sites, with all sites below the 0.2 µg/m

contribution threshold.

166

The 2020 and 2024 responses ranged from -0.07 µg/m

to 0.06 µg/m

, with all monitoring sites below the 0.2 µg/m

contribution threshold for both years. For a modeled 70 percent VOC emissions reduction, the PM

2.5

responses in 2013 ranged from 0.05 µg/m

to 0.40 µg/m

, including responses at or above the 0.2 µg/m

contribution threshold at 8 of the 15 sites. However, for 2020 and 2024 all responses were below the 0.2 µg/m

contribution threshold; 2020 responses ranged from -0.10 µg/m

to 0.16 µg/m

and the 2024 responses ranged from -0.18 µg/m

to 0.08 µg/m

. The negative responses to VOC reductions represent an increase in PM

2.5

levels,

i.e.,

a disbenefit. The 2024 results show a disbenefit at 11 of the 15 sites for both the 30 percent and the 70 percent VOC emissions reductions scenarios.

166

2018 PM

2.5

Plan, Appendix G, Table 10.

CARB then considered additional information to assess whether these PM

2.5

responses constituted a significant contribution to ambient PM

2.5

in the San Joaquin Valley, including emissions trends and an assessment of the modeled disbenefit of VOC emissions reductions. VOC emissions are projected to decrease approximately 30 tpd (or 9 percent) from 2013 to 2024, with approximately 28 out of the 30 tpd reduction taking place by 2020.

167

The State concludes that the formation of ambient PM

2.5

from VOC may therefore differ in base and future years and that the sensitivity analysis for 2013, which showed some contributions above 0.2 µg/m

, is not representative of current or future conditions.

167

Id. at p. 19 and Figure 5.

CARB explained the modeled disbenefit of VOC reductions as follows: emissions of VOC and NO

react in the atmosphere to form organic nitrate species, such as peroxyacetyl nitrate, meaning that some portion of the NO

emissions is not available to react with ammonia to form ammonium nitrate particulate matter. In other words, VOC emissions can be a “sink” for NO

emissions. Reducing VOC emissions therefore reduces the formation of organic nitrates, so the sink is smaller and nitrate molecules are freed to react with ammonia to form particulate ammonium nitrate.

168

The State further explored the VOC disbenefit based on a 2016 CARB modeling assessment provided in Appendix A (“Air Quality Modeling”) of the “2016 Moderate Area Plan for the 2012 PM

2.5

Standard” for the San Joaquin Valley (“2016 PM

2.5

Plan”), which CARB submitted to the EPA as a SIP revision on May 10, 2019.

169

168

15 µg/m

SIP Revision, Appendix K, pp. 81-82 (citing Meng, Z., D. Dabdub, D., Seinfeld, J.H., Chemical Coupling Between Atmospheric Ozone and Particulate Matter,

Science

277, 116 (1997). DOI: 10.1126/science.277.5322.116).

169

2016 PM

2.5

Plan, Appendix A, p. A-57. See also 15 µg/m

SIP Revision, Appendix K, Section 5.7 (“PM

2.5

Precursor Sensitivity Analysis”).

Based on its sensitivity-based analysis of VOC emissions reductions, VOC emissions trends, and the scientific understanding of VOC chemistry in the San Joaquin Valley, CARB concludes that VOC emissions do not contribute significantly to PM

2.5

levels that exceed the 1997 annual PM

2.5

NAAQS in the San Joaquin Valley.

3. The EPA's Review of the State's Submission

The EPA has evaluated the State's precursor demonstration in the SJV PM

2.5

Plan, consistent with the PM

2.5

SIP Requirements Rule and the recommendations in the PM

2.5

Precursor Guidance. The State did not present a precursor demonstration for NO

, and indeed stated that controlling it is essential for the attainment strategy;

170

emission sources, therefore, remain subject to control requirements under subparts 1 and 4 of part D, title I of the Act. For the reasons provided in the following paragraphs, the EPA proposes to approve the State's comprehensive demonstrations for ammonia, SO

, 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 1997 annual PM

2.5

NAAQS in the San Joaquin Valley. For further discussion of the EPA's evaluation of the precursor demonstration, please see the EPA's February 2020 Precursor TSD, which provides the EPA's summary of the State's precursor analyses for all four PM

2.5

precursors.

171

170

2018 Plan Appendix G, p. 2.

171

Much of the analysis in the EPA's February 2020 Precursor TSD is applicable to SJV PM

2.5

Plan for the 1997 annual PM

2.5

NAAQS. For example, the State's precursor demonstration used 2015 annual average concentration data for its concentration-based analysis, examined annual average sensitivities of ambient PM

2.5

concentrations to reductions in each precursor in 2013, 2020, and 2024, and presented information on research studies and emission trends that are relevant for assessing the sensitivity of annual average ambient PM

2.5

concentrations to emission reductions of each PM

2.5

precursor. Our evaluation of such factors is similarly applicable for the 1997 annual PM

2.5

NAAQS and we expand on such evaluation for purposes of those NAAQS specifically herein.

The State based its analyses on the latest available data and studies concerning ambient PM

2.5

formation in the San Joaquin Valley 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

in 2015. Given that the absolute concentrations in 2015 were above the EPA's recommended contribution thresholds for both the 2006 24-hour and 2012 annual average NAAQS, the State proceeded with a sensitivity-based analysis, consistent with the recommendations in the PM

2.5

SIP Requirements Rule.

For the sensitivity-based analysis, the State performed its analyses based on the EPA's recommended approach—

i.e.,

for each modeled year and level of precursor emissions reduction (in percentages), the State estimated the ambient PM

2.5

response using the procedure recommended in the PM

2.5

Precursor Guidance. In particular, the State considered the EPA's recommended range of emissions reductions (30 percent to 70 percent) for the 2013 base year, 2020 interim year, and 2024 future year, and quantified the estimated response of ambient PM

2.5

concentrations to precursor emission changes in the San Joaquin Valley.

The State's emissions projections in the 2018 PM

2.5

Plan show that baseline emissions of each of these precursors will decrease from the 2013 base year to the 2023 attainment year. These decreases are included in the State's modeled projections of ambient PM

2.5

levels in the San Joaquin Valley 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.

172

2.5

Precursor Guidance, p. 35.

The EPA is proposing to find that such quantification and CARB's consideration of additional information provide an informed basis on which to make a determination as to whether ammonia, SO

, and VOC contribute significantly to ambient PM

2.5

levels that exceed the 1997 annual PM

2.5

NAAQS in the San Joaquin Valley.

173

If we

finalize this proposal to approve the State's precursor demonstrations, the State will not be required to implement BACM/BACT level controls for sources of ammonia, SO

, and VOC for purposes of the SJV PM

2.5

Plan for 1997 annual PM

2.5

NAAQS that is the subject of this proposed action. Under 40 CFR 51.1006(b), such precursor demonstration approval would apply only to this attainment plan. For any new PM

2.5

attainment plan that the State is required to submit in accordance with 40 CFR 51.1003 for purposes of any PM

2.5

NAAQS, the State will be required to submit an updated precursor demonstration if it seeks to exempt sources of a particular precursor from control requirements in that attainment plan. In the subsections that follow, we summarize our evaluation of the State's precursor demonstrations for each of these three precursor pollutants.

173

The State did not evaluate the 2015 Serious area attainment year. Because the year has passed and the area failed to attain by the Serious area attainment date, we will evaluate the precursor

analysis for the Serious area plan based on the current section 189(d) projected attainment date of December 31, 2023.

a. Ammonia

We have evaluated CARB's sensitivity-based contribution analyses for 2013, 2020, and 2024 in the 2018 PM

2.5

Plan and supplemental materials provided by the State, as well as CARB's determination that the 2024 results are representative of conditions in the San Joaquin Valley for purposes of a sensitivity-based analysis for the 1997 annual PM

2.5

NAAQS. The EPA's PM

2.5

Precursor Guidance explicitly provides for consideration of a future year, and we are proposing to find that the State provided sufficient justification for relying on modeling results for 2024.

174

2.5

Precursor Guidance, p. 35.

We also consider it appropriate for the State to take into account additional information as part of its evaluation of whether the ammonia contribution is significant and to rely on the responses to the 30 percent modeled ammonia emissions reduction in its precursor demonstration for ammonia. The modeled PM

2.5

response to the 30 percent reduction is only marginally above the contribution threshold at a single monitoring site in 2024, and the EPA has evidence from the State and elsewhere that the response was overestimated, as discussed below. Together these suggest that ammonia does not contribute significantly to ambient PM

2.5

levels. However, because the response is so close to the threshold at a 30 percent reduction, such a conclusion strongly depends on the emission reduction benefit of potential controls being 30 percent or less; larger reductions could give responses above the threshold. Therefore, per 40 CFR 51.1010(a)(2)(ii), the EPA required an analysis of potential controls to aid the EPA in its evaluation of the precursor demonstration, which the State provided in the March 2023 Ammonia Supplement. The response of ambient PM

2.5

to an actual assessment of the benefit from potential controls could then be used by the State to determine whether controlling ammonia would significantly affect PM

2.5

levels.

The State relied on the 2024 modeled ambient PM

2.5

responses to a 30 percent reduction in ammonia after concluding that 30 percent was a reasonable upper bound on potential ammonia reductions, based on past research on ammonia emissions and its evaluation of potential control options. Based on the EPA's review of the State's rationale, including its ammonia control measure analysis, the EPA agrees that the reductions that the State could achieve through additional available BACM/BACT level controls on ammonia sources would be below 30 percent, and thus that the PM

2.5

response to the ammonia emission reductions available would be below the contribution threshold at all sites for purposes of this plan, as discussed in the following paragraphs.

175

Note that the task for the State is not to show whether controls could reduce ammonia by 30 percent, though that is the focus of the State's March 2023 Ammonia Supplement. The SIP requirements rule and the PM

2.5

Precursor Guidance do not establish potential reductions of 30 percent as a “bright line” test for determining precursor significance. Rather, information from the control evaluation is to be used in conjunction with other information to determine whether ammonia reductions are effective in reducing PM

2.5

levels, and so whether ammonia contributes significantly to PM

2.5

The State compared the ammonia modeled sensitivity results in Appendix G of the 2018 PM

2.5

Plan to the 0.2 µg/m

contribution threshold recommended by the EPA for the 2012 annual PM

2.5

NAAQS in the PM

2.5

Precursor Guidance. However, in the March 2023 Ammonia Supplement, the State also compared the model results against the 0.25 µg/m

contribution threshold it calculated based on the level of the 1997 annual PM

2.5

NAAQS. We find that the State's use of a 0.25 µg/m

threshold is consistent with the recommendations in the PM

2.5

Precursor Guidance,

176

and is appropriate for purposes of evaluating the modeling results for the 1997 annual PM

2.5

NAAQS, given the EPA's method of calculating the threshold and the level of the 1997 annual PM

2.5

NAAQS (15.0 µg/m

176

2.5

Precursor Guidance, fn. 20.

The precursor demonstration in the SJV PM

2.5

Plan indicates that the ambient response to a 30 percent ammonia emission reduction would exceed the 0.25 µg/m

contribution threshold for 13 out of 15 monitoring sites in the 2013 analysis year, and at 4 out of 15 for the 2020 analysis year. For the 2024 analysis year, 1 of the 15 sites (Hanford) would exceed the contribution threshold. 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, the highest concentration site. The Hanford responses decline from 0.42 µg/m

in 2020 to 0.26 µg/m

in 2024. The average response over all monitoring sites declines from 0.23 µg/m

to 0.14 µg/m

, with the decline being generally larger for the sites with the highest projected PM

2.5

levels.

While the 2024 Hanford modeled response to a 30 percent ammonia reduction is above the contribution threshold, additional information about this location leads the EPA to give the response lower weight in the overall assessment of whether ammonia contributes significantly to PM

2.5

levels. An independent study using aircraft and surface data from the winter 2013 DISCOVER-AQ

177

campaign, a key period in the SJV PM

2.5

Plan's 2013 model base case, found that the CMAQ model underestimated ammonia at Hanford by roughly a factor of five; Hanford is just outside a region with high ammonia emissions in the model (western Tulare County).

178

If the modeled ammonia concentrations were higher to better match observations, there would be relatively more ammonia per NO

and the model response to ammonia reductions would be lower. This is consistent with CARB's conclusions regarding ammonia as described earlier.

177

NASA, “Deriving Information on Surface conditions from Column and VERtically Resolved Observations Relevant to Air Quality,” described at

https://www.nasa.gov/mission_pages/discover-aq/index.html.

178

Kelly, J.T.

et al.

2018, “Modeling NH

over the San Joaquin Valley during the 2013 DISCOVER-AQ campaign,” Journal of Geophysical Research: Atmospheres, 123, pp. 4727-4745,

https://doi.org/10.1029/2018JD028290

at 4733. The paper notes that, despite the ammonia underestimation, model performance was good for particulate ammonium nitrate and the ammonium nitrate was not sensitive to the ammonia underestimate since its formation was NO

-limited.

In choosing which year's modeled response to ammonia to rely on, the EPA considered the State's point that the PM

2.5

benefit of ammonia emission reductions is projected to decline steeply over time. We believe it is 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. The PM

2.5

Precursor Guidance explicitly states that a future year may be used, and that there are a multitude of considerations in choosing the analysis year.

179

The “anticipated growth or loss of sources . . . or trends in ambient speciation data and precursor emissions”

180

are among the “facts and circumstances of the area”

181

to consider in determining the significance of a precursor. The Guidance states that a future year could be more appropriate if it better represents the period that sources will operate in. As discussed in more detail below, the 2024 model results better represent the period that ammonia sources will operate in than 2013 and 2020 because of the steep decline in NO

emissions projected to occur by 2023 and 2024. We consider it reasonable for the State to focus on the ambient PM

2.5

response to ammonia emission reductions in 2024, rather than 2013 or 2020, as the modeled response in 2024 in the San Joaquin Valley better reflects the potential benefit of ammonia control measures for purposes of expeditious attainment of the 1997 annual PM

2.5

NAAQS.

179

2.5

Precursor Guidance, p. 35.

180

Id. at 18.

181

2.5

SIP Requirements Rule, 40 CFR 51.1006(a)(1)(ii).

The State's precursor demonstration in the SJV PM

2.5

Plan shows that ambient sensitivity to ammonia emissions reductions in the San Joaquin Valley declines steeply over time. Between 2020 and 2024, the modeled response to a 30 percent ammonia emissions reduction declines by 50 percent at the Bakersfield-Planz monitoring site, which has the highest projected PM

2.5

level, and by 37 percent averaged over all monitoring sites. As noted above, 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 0.25 µg/m

threshold for the 1997 annual PM

2.5

NAAQS declines from 4 out of 15 down to 1 out of 15.

182

As discussed earlier, ammonia sensitivity declines because of the shifting atmospheric chemistry caused by NO

emissions decreases. NO

emissions are projected to decrease by 27 percent between 2020 and 2024 due to baseline measures (

e.g.,

existing motor vehicle controls), with 91 percent of those emissions reductions occurring between 2020 and 2023.

183

That is, NO

emissions in 2023 are 24 percent lower than NO

emissions in 2020 and 3 percent higher than NO

emissions in 2024. Thus, conditions in 2024 are anticipated to be much more similar to those in 2023 compared to 2020. The decreased NO

emissions will make ammonia more abundant relative to NO

, and even less of a limiting factor on PM

2.5

formation. In other words, the model response in the future year 2024 gives a more realistic assessment of the potential effect of ammonia controls than past conditions.

184

182

2018 PM

2.5

Plan, Appendix G, tables 4 and 5.

183

emissions in 2020, 2023, and 2024 are 203.3 tpd, 153.6 tpd, and 148.9 tpd, respectively.

184

Since precursor sensitivity modeling results were not available for the specific year of 2023, the EPA estimated the 2023 PM

2.5

response to a 30 percent ammonia reduction using the modeling results for 2020 and 2024. As for the 2024 modeled sensitivities, we found that Hanford was the only site that would be above the 0.25 µg/m

contribution threshold for 2023, with a response of 0.27 µg/m

. Thus, the results of this exercise do not change our conclusions. Spreadsheet “Estimated 2023 annual PM

2.5

sensitivity to ammonia reductions.xlsx,” EPA Region IX, June 26, 2023.

Additionally, the ambient studies described by the State and in independent research studies provide strong evidence that PM

2.5

would respond only weakly to ammonia emissions reductions. As described above, those include a large measured excess of ammonia relative to the amount of nitrate available to interact with it to form PM

2.5

, and satellite and aircraft measurements indicating a larger amount of ammonia than is derived in model predictions. This evidence reflects actual measurements of the atmosphere, independent of uncertainties in the modeling and independent of estimates of ammonia and other emissions that are input to the model.

Finally, the EPA has reviewed the additional information provided by the State to support its assertion that 30 percent is a reasonable upper bound on the ammonia reductions that could be achieved in the San Joaquin Valley and the State's reliance on the 30 percent sensitivity modeling results for the precursor demonstration for the 1997 annual PM

2.5

NAAQS. The EPA proposes to find that the additional information adequately supports the conclusion that potential ammonia controls would yield less than a 30 percent reduction, such that the resulting decrease in ambient PM

2.5

concentration would be below the contribution threshold. As discussed in Section IV.B.1 of this document, the PM

2.5

Precursor Guidance indicates that the EPA may require air agencies to identify and evaluate potential emissions controls in support of a precursor demonstration that relies on a sensitivity analysis, particularly for an area in which the PM

2.5

response to a 30 percent reduction in precursor emissions is close to the contribution threshold. For the San Joaquin Valley, the modeled response to a single site, Hanford, is just above the 0.25 µg/m

threshold for the 1997 annual PM

2.5

NAAQS at 0.26 µg/m

. Furthermore, several analyses show ambient ammonia concentrations are underestimated at Hanford and so we believe that the 2024 modeled response of 0.26 µg/m

is likely overestimated. Supporting that conclusion is the evidence of the large ambient excess of ammonia relative to nitrate, which suggests that the actual PM

2.5

response to reductions in ammonia emissions would be very small, and less than the response seen in the modeling. Thus, we conclude that in the San Joaquin Valley, the PM

2.5

response to a 30 percent reduction in ammonia emissions is close to the contribution threshold and that the State's approach to evaluate additional information in support of the precursor demonstration sensitivity analysis, including additional potential ammonia control measures, is consistent with the EPA's recommendations in the PM

2.5

Precursor Guidance and responsive to the EPA's request for such additional information and analysis.

As discussed in Section IV.B.2.a of this document, the State began its analysis to identify and evaluate potential emissions controls for ammonia by characterizing key ammonia source categories in the Valley (

i.e.,

CAFs, agricultural fertilizers, and composting operations), and identifying existing rules that have resulted in ammonia emission reductions from these sources. Specifically, the State discusses the ammonia control effectiveness of a number of existing rules designed to reduce VOC emissions from these sources.

185

While there are no ammonia-specific controls in place for these source categories, the EPA agrees with the District's information indicating that some of the management practices in the District's rules to reduce VOC emissions also reduce ammonia

emissions by limiting ammonia formation and volatilization.

186

185

2018 PM

2.5

Plan, Appendix C, pp. C-311 to C-358.

186

For example, see 2018 PM

2.5

Plan, Appendix C, p. C-313 (for CAFs).

Regarding the analysis for CAFs, we find that the District provided a thorough evaluation of potential ammonia mitigation measures by CAF type and activity through its comparison of the applicability and requirements of Rule 4570 with comparable rules that are being implemented in other air districts and its review of scientific research studies. In considering the technical feasibility of each identified measure, the District assessed factors such as how the measure compares with requirements already being implemented under District Rule 4570, the compatibility of the measure with the types of CAFs operating in the Valley (considering, for example, CAF size and common practices employed), compatibility of the measure with the climate conditions in the Valley, and any cobenefits and/or undesirable consequences of implementing the measure.

Based on its evaluation, the District determined that several measures identified in the literature are already required in the San Joaquin Valley by Rule 4570 (

e.g.,

washing floors and other soiled areas in livestock facilities), or by other State regulations (

e.g.,

requirements to carefully time manure application as required by the California Regional Water Quality Control Board).

187 188

For measures that the District identified as feasible for implementation in the San Joaquin Valley, the District provided information detailing how it estimated the potential ammonia emission reductions that could be achieved based on control efficiencies cited in the literature. For measures that the State determined to be infeasible in the San Joaquin Valley, the District provided a narrative justification for its conclusion.

187

March 2023 Ammonia Supplement, pp. 47-49.

188

Id. at 77.

Reasons for concluding that a particular measure is infeasible included that the measure is not conducive to the type, size, or standard practices of CAFs operating in the Valley; the measure is not compatible with the hot, dry, drought climate conditions in the Valley; the measure is not economically feasible; or that the measure would have undesirable consequences (

e.g.,

adverse effects on water quality, reduced dairy cattle milk production). The District also concluded that more research is needed to examine the technical and/or economic feasibility of implementing some of the measures in the Valley specifically. For those measures that the District found to be economically infeasible (

e.g.,

biofilters and wet scrubbers, oxygenation of liquid manure lagoons), it provided detailed cost analyses to support its assertion.

189

Based on our review of the District's controls analysis for CAFs, we find that the District provided a robust analysis of its Rule 4570 and a thorough review of 46 possible mitigation measures for reducing ammonia emissions from CAFs in the San Joaquin Valley.

189

Id. at 59-60 and Appendix B.

For fertilizer application, the State emphasizes that it has not identified any SIP-approved requirements that are being implemented in other areas. Thus, it describes regulations adopted by other California State agencies to control fertilizer application, such as regulations adopted by the California Water Resources Board, and otherwise focuses its review on several research studies on reducing ammonia emissions from synthetic fertilizer application. Based on its review of mitigation options in the literature, the State concludes that some of the mitigation strategies are already required by current State regulations, and that further research is needed to explore the feasibility and effectiveness of those measures that are not currently in practice.

Regarding State regulations that are currently in place to control fertilizer application, we generally agree with the State that those regulations are likely to enhance the retention of nitrogen from manure and nitrogen-based chemical fertilizers in the San Joaquin Valley and to limit the loss of nitrogen as pollution to water and air, thereby potentially reducing ammonia emissions. Additionally, as discussed earlier, District Rules 4570 and 4565 have provisions that reduce ammonia emissions by addressing the land application of manure from CAFs and of biosolids, animal manure, and poultry litter from composting operations. The EPA believes that the State's review of both existing ammonia mitigation measures and the research literature is an appropriate and thorough method for identifying potential measures. We also believe it reasonable that the State concludes that several of the specific mitigation strategies identified in the literature, such as optimizing fertilizer use, are already being implemented in the San Joaquin Valley due to these current State regulations and co-benefits such as reduced cost to farmers, and that more research is needed to assess the feasibility of other additional measures identified. Based on our review, and the fact that the State did not identify any ammonia mitigation measures for fertilizer application being implemented in other areas, we conclude that the State's overall conclusions are reasonable.

For composting and other sources, the District notes that significant ammonia reductions are already being achieved by existing rules, including a 44 percent reduction from composting operations from Rules 4565 and 4566, and reductions from mobile source and fuel combustion measures. As discussed earlier, the EPA agrees that Rules 4565 and 4566 have reduced ammonia emissions in the Valley. We also agree that the State's stringent controls for on-road mobile sources have resulted in ammonia reductions from those sources. While the State continues to work to reduce emissions from mobile sources to reduce NO

and other pollutants in the Valley, since on-road mobile sources account for approximately one percent of the ammonia emissions inventory,

190

any ammonia reductions achievable through additional on-road mobile source controls would be small. The District states that it did not identify any additional potential mitigation measures for these source categories.

190

2018 PM

2.5

Plan, Appendix B, Table B-5.

While we generally find that the State provided a robust review of existing regulations and potential additional mitigation measures in the research literature, we note that a limitation of the District's analysis is that there remains some uncertainty as to how much reduction is currently being achieved by State and District rules and thus if some incremental additional reduction may be available. For fertilizer application specifically, the District does not attempt to quantify or otherwise substantiate the scale of ammonia emission reductions from existing regulations, nor their enforceability, which confounds the prospects for quantifying how much additional reductions may be available. Furthermore, while the District provides a detailed controls analysis for CAFs, with regard to Rule 4570, as the EPA has previously noted,

191

the State has not sufficiently substantiated its calculation of the 100 tpd of ammonia emission reductions attributed to Rule 4570. In the 2018 PM

2.5

Plan, the State references an analysis from 2006 that relied on a different baseline emissions inventory, but has not supplemented this analysis, or reconciled it with more recent

emissions inventory data.

192

While the EPA agrees that meaningful ammonia reductions have been achieved from Rule 4570, there remains some uncertainty as to the precise magnitude of those reductions. Notwithstanding this uncertainty, as discussed in more detail below, given the scarcity of additional feasible measures identified by the State, and the scale of potential additional emissions reductions available in the context of the sensitivity of PM

2.5

to ammonia reductions in the nonattainment area for the 1997 annual PM

2.5

NAAQS, we find that the controls analysis provided by the State is sufficient to support its conclusion that that ammonia emissions do not contribute significantly to ambient PM

2.5

levels that exceed the 1997 annual PM

2.5

NAAQS in the San Joaquin Valley.

191

81 FR 69396, 69397-69398 (October 6, 2016) and 87 FR 60494, 60503-60504 (October 5, 2022).

192

2018 PM

2.5

Plan, Appendix C, pp. C-311 to C-339 and SJVUAPCD, “Final Draft Staff Report, Proposed Re-Adoption of Rule 4570 (Confined Animal Facilities),” June 18, 2009, at Appendix F, “Ammonia Reductions Analysis for Proposed Rule 4570 (Confined Animal Facilities),” June 15, 2006 (discussing various assumptions underlying the District's calculation of ammonia emission factors without identifying relevant emissions inventories).

Based on its analysis, the State concludes that significant ammonia reductions have already been achieved in the San Joaquin Valley through existing State regulations and standard practices, and that the potential additional ammonia emissions reductions achievable through the implementation of additional best available controls is two percent of the total ammonia emissions in the San Joaquin Valley. This value is well below the lower end (

i.e.,

30 percent) of the ammonia reductions that the State modeled for analytical purposes for its sensitivity-based analysis. While there remains some uncertainty as to the ammonia reductions that are currently being achieved by existing rules and standard practices, and thus the additional reductions that could be achieved by those rules and practices, we believe the State has provided sufficient evidence to support its assertion that the additional available reductions are less than 30 percent.

Specifically, the District has made a convincing case that significant ammonia reductions have already been achieved through District Rule 4570 and that few additional mitigation measures could provide only modest further reductions from CAFs, which account for 58 percent of the total ammonia inventory. Similarly, the State has provided support for its assertion that additional reductions are not feasible from the fertilizer, composting, and other smaller source categories through its analysis of potential fertilizer controls, in particular, in addition to information regarding controls that are already in place for these source categories.

193

Based on our review of the analysis, we conclude that the potential reduction from available controls would be well below 30 percent. Given that the State's modeled sensitivities of PM

2.5

concentrations to a 30 percent ammonia reduction are approximately at or below the threshold used for identifying an impact that is significant for the 1997 annual PM

2.5

NAAQS, and that potential reductions would be below 30 percent, the EPA agrees that the response of PM

2.5

to an ammonia reduction of a percentage smaller than 30 percent would be below the contribution threshold, indicating that ammonia does not contribute significantly to ambient PM

2.5

concentrations for purposes of the SJV PM

2.5

Plan for the 1997 annual PM

2.5

NAAQS.

193

The State has not provided an estimate of the reductions that are currently being achieved for the fertilizer category, which accounts for 34 percent of the total ammonia emissions inventory. Nevertheless, even if ammonia emissions from fertilizers could be reduced by a very high percentage (

e.g.,

70 percent), that would correspond to a smaller percentage reduction of the total ammonia emissions. Such conservatively high reductions from fertilizers added to the potential ammonia reductions from CAFs identified by the State would still amount to less than a 30 percent reduction of the total ammonia emissions.

In summary, we conclude that the State quantified the sensitivity of ambient PM

2.5

levels to reductions in ammonia emissions using appropriate modeling techniques, the modeled response to ammonia reductions is likely lower than reported, and the State's choice of 2024 as the reference point for purposes of evaluating the sensitivity of ambient PM

2.5

levels to ammonia emissions reductions is well-supported. The State also provided strong evidence to support its conclusion that additional controls on ammonia sources would achieve ammonia emissions reductions well below 30 percent, including its estimate, following review of the measures the State and District consider feasible, that the reductions available are approximately 2 percent. Since the modeled ambient PM

2.5

response to a 30 percent ammonia reduction is only marginally above the contribution threshold at a single monitoring site, that response may be overestimated, and potential reductions are below 30 percent, the PM

2.5

response to additional ammonia controls would be below the contribution threshold. Based on 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 1997 annual PM

2.5

NAAQS in the San Joaquin Valley.

We note that this proposed determination is specific to the facts and circumstances of this particular plan—including but not limited to the specific level of the 1997 annual PM

2.5

NAAQS and the proportional modeling response needed to be considered significant, the State's modeling indicating that ammonia levels the San Joaquin Valley are at or below the contribution threshold for the 1997 annual PM

2.5

NAAQS, the unique atmospheric conditions in the Valley in which the PM

2.5

response to reductions in ammonia emissions would be relatively small

the demonstration that the potential reductions from additional control measures that are not currently being implemented would be below 30 percent, and the current limited research in key areas of ammonia controls—and that it does not pre-determine the outcome of significance determinations of precursors in the future.

b. SO

For SO

, the 2018 PM

2.5

Plan's sensitivity estimates for 2013 are well below the EPA's recommended threshold for both the 30 percent and 70 percent emission reduction scenarios and are even negative for some monitoring sites. Given those results and the steady SO

emission levels over 2013 to 2023 (as opposed to increases), the EPA agrees with the State's conclusion that the 2013 modeled sensitivities provide a sufficient basis for the SO

precursor demonstration. The supplemental results provided by the State for 2020 and 2024 support this conclusion.

Therefore, based on these modeled ambient PM

2.5

responses to SO

emissions reductions in the San Joaquin Valley, and on the facts and circumstances of the area, the EPA proposes to approve the State's demonstration that SO

emissions do not contribute significantly to ambient PM

2.5

levels that exceed the 1997 annual PM

2.5

NAAQS in the San Joaquin Valley. We note that this proposed determination is specific to the facts and circumstances of this particular plan and that it does not pre-determine the outcome of significance determinations of precursors in the future.

c. VOC

For VOC, the State found that the ambient PM

2.5

response to VOC emissions reductions were generally

below the EPA's recommended contribution threshold of 0.2 μg/m

, and predicted an increase in ambient PM

2.5

levels in response to VOC reductions (

i.e.,

a disbenefit) at 2 out of 15 monitoring sites in 2020, and at 11 out 15 sites in 2024. Only for a 70 percent emissions reduction for the 2013 base year did the State predict the ambient PM

2.5

response to be above the threshold at a majority of sites.

194

2018 PM

2.5

Plan, Appendix G, tables 10 and 11.

The EPA has evaluated and agrees with the State's determination in the 2018 PM

2.5

Plan that the modeling for future years is more representative of conditions in the San Joaquin Valley than the 2013 modeling for sensitivity-based analyses and the State's resulting conclusion that the contribution from VOC emissions is not significant. The EPA agrees that the 8.6 percent decrease in VOC emissions from 2013 to 2020 and the 9.2 percent projected decrease from 2013 to 2024 favors reliance on the future year modeling results. Furthermore, there is a large decrease in NO

emissions over this period, as discussed 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 9.2 percent VOC emissions reductions and the vast majority of NO

emissions reductions are expected to result from baseline measures already in effect. Therefore, we conclude that it is reasonable to rely on future year 2020 or 2024 modeled responses to VOC emissions reductions. The EPA also concludes that the State provided a reasonable explanation for the VOC emissions reduction disbenefit and evidence that it occurs in the San Joaquin Valley.

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 1997 annual PM

2.5

C. Attainment Plan Control Strategy

1. Statutory and Regulatory Requirements

Section 189(b)(1)(B) of the Act requires for any Serious PM

2.5

nonattainment area that the state submit provisions to assure that best available control measures (BACM), including controls that reflect best available control technology (BACT), for the control of PM

2.5

and PM

2.5

precursors shall be implemented no later than four years after the date the area is reclassified as a Serious area. The EPA has defined BACM in the PM

2.5

SIP Requirements Rule to mean “any technologically and economically feasible control measure that can be implemented in whole or in part within four years after the date of reclassification of a Moderate PM

2.5

nonattainment area to Serious and that generally can achieve greater permanent and enforceable emissions reductions in direct PM

2.5

emissions and/or emissions of PM

2.5

plan precursors from sources in the area than can be achieved through the implementation of RACM on the same source(s). BACM includes best available control technology (BACT).”

195

40 CFR 51.1000 (definitions). In longstanding guidance, the EPA has similarly defined BACM to mean, “among other things, the maximum degree of emissions reduction achievable for a source or source category, which is determined on a case-by-case basis considering energy, environmental, and economic impacts.” General Preamble Addendum, 42010, 42013.

Because the 2015 Serious area attainment date has passed, and the EPA found that the area failed to attain by the Serious area attainment date, we are evaluating the submission for compliance with the BACM/BACT requirements now, in conjunction with the State's SIP submission intended to meet both the Serious area and section 189(d) plan requirements.

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