2023-06578. Second 10-Year Maintenance Plan for the Coso Junction PM-10 Planning Area; California

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The Environmental Protection Agency (EPA) is proposing to approve the “Coso Junction PM₁₀ Planning Area Second 10-Year Maintenance Plan” (“Coso Junction Second Maintenance Plan” or “Plan”) as a revision to the state implementation plan (SIP) for the State of California. The Coso Junction Second Maintenance Plan includes, among other elements, a base year emissions inventory, a maintenance demonstration, and contingency provisions. The EPA is proposing this action because the SIP revision meets the applicable statutory and regulatory requirements for such plans. The EPA is also proposing to find the contribution of motor vehicles to the area's continued attainment of the 1987 PM₁₀ standard to be insignificant and is initiating the adequacy review process for this insignificance finding through this Notice of Proposed Rule Making (NPRM). If this insignificance finding is finalized, the area would not have to complete a regional emissions analysis for any transportation conformity determinations necessary for the Coso Junction Planning Area (CJPA).

DATES:

Comments must be received on or before May 1, 2023.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA–R09–OAR–2022–0972 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 (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission ( i.e., on the web, cloud, or other file sharing system). For additional submission methods, 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:

Lindsay Wickersham, EPA Region IX (ARD–2), 75 Hawthorne Street, San Francisco, CA 94105. By phone: [phone], or by email at [e-mail].

SUPPLEMENTARY INFORMATION:

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

Table of Contents

I. Background

A. The PM₁₀ National Ambient Air Quality Standards

B. The Coso Junction PM₁₀ Planning Area

C. Air Quality in the Coso Junction Planning Area

II. California's State Implementation Plan Submittal

III. Procedural Requirements for Adoption and Submittal of State Implementation Plan Revisions

IV. Requirements for Second 10-Year Maintenance Plans

V. Evaluation of the Coso Junction Second Maintenance Plan

A. Emissions Inventories Overview

B. Maintenance Demonstration

C. PM₁₀ Air Quality Monitoring Network

D. Verification of Continued Attainment

E. Contingency Provisions

F. Motor Vehicle Emissions Budgets for Transportation Conformity

VI. Environmental Justice Considerations

VII. Proposed Action and Request for Public Comment

VIII. Statutory and Executive Order Reviews

I. Background

A. The PM₁₀ National Ambient Air Quality Standards

Section 109 of the Clean Air Act (CAA or the “Act”) grants the EPA the authority to set national ambient air quality standards (NAAQS or “standards”) for certain ambient air pollutants in order to protect public health and welfare.^[1] Particulate matter (PM) refers to the mixture of solid particles and liquid droplets found in the air. PM is among the ambient air pollutants for which the EPA has established health-based standards. PM₁₀ is defined as inhalable particles with diameters that are 10 micrometers or less. PM₁₀ can cause adverse health effects by penetrating deep into the lungs and blood stream, leading to lung damage, increased respiratory disease, and premature death. Children, the elderly, and people with asthma and heart conditions are the most vulnerable.

On July 1, 1987, the EPA established primary and secondary NAAQS for PM₁₀ .^[2] At that time, the EPA established two PM₁₀ standards: an annual standard and a 24-hour standard.^[3] Effective December 18, 2006, the EPA revoked the annual PM₁₀ standard but retained the 24-hour PM₁₀ standard.^[4] An area attains the 24-hour standard of 150 micrograms per cubic meter (µg/m^[3] ) when the expected number of days per calendar year with a 24-hour concentration above the standard (referred to as an “exceedance”),^[5] averaged over three years, is equal to or less than one. The expected number of exceedances averaged over a three-year period at any regulatory monitor is known as the PM₁₀ design value. The PM₁₀ design value for the area is the highest design value within the nonattainment area.^[6]

Generally, the EPA determines whether an area's air quality is meeting the PM₁₀ NAAQS based on the most recent complete,^[7] quality-assured, and certified data measured at established state and local air monitoring stations (SLAMS) in the nonattainment area and entered into the EPA Air Quality System (AQS) database. Data from air monitoring sites operated by state, local, or tribal agencies in compliance with the EPA's monitoring requirements must be submitted to AQS. These monitoring agencies annually certify that these data are accurate to the best of their knowledge. Accordingly, the EPA relies primarily on data in AQS when determining the attainment status of an area.^[8] All valid data are reviewed to determine the area's air quality status in accordance with 40 CFR part 50, appendix K.

B. The Coso Junction PM₁₀ Planning Area

Through its enactment of the CAA Amendments of 1990, Congress designated certain areas of the country as nonattainment areas for the PM₁₀ NAAQS. The Searles Valley Planning Area was one of the areas designated as nonattainment. In 1991, the EPA classified the Searles Valley planning area as a “Moderate” PM₁₀ nonattainment area.^[9]

The Searles Valley Planning Area included three subregions (Coso Junction, Indian Wells Valley, and Trona) under the planning jurisdiction of different air pollution control agencies. On August 6, 2002, the EPA changed the boundaries of the Searles Valley PM₁₀ nonattainment area by dividing this area into three separate, newly-created PM₁₀ nonattainment areas, one of which is the CJPA.^[10] The CJPA is under the planning jurisdiction of the Great Basin Unified Air Pollution Control District (GBUAPCD or “District”).^[11] It covers approximately 792 square miles of sparsely populated, arid, high desert that receives less than five inches of rain per year. The CJPA is flanked by the Sierra Nevada Mountains to the west and the Coso Range to the east. A majority of the CJPA is covered by the China Lake Naval Air Weapons Station, which is generally restricted from public access.

Owens Lake, located in neighboring Inyo County and within the Owens Valley Planning Area, is also under the jurisdiction of GBUAPCD.^[12] Starting in 1913, the Los Angeles Department of Water and Power began diverting water from Owens Lake until the lake was almost completely dry. Winds blowing over the dry, alkaline bed of Owens Lake have produced among the highest measured concentrations of PM₁₀ ever recorded and can have impacts as far as 150 miles away.^[13] To mitigate impacts of Owens Lake dust, the GBUAPCD developed the controls and plans for the Owens Valley Planning Area with many participants including the California Air Resources Board (CARB), Los Angeles Department of Water and Power, the City of Los Angeles, tribal governments, federal land managers, the Navy, the State Lands Commission, and members of the public.

Since approval of the 1998 PM₁₀ Plan for the Owens Valley Planning Area,^[14] the GBUAPCD and City of Los Angeles have worked consistently to refine and optimize the complex set of control measures leading to substantial reductions of PM₁₀ from the dry Owens Lakebed and surrounding near-lake sources. Decades of work by the GBUAPCD and the City of Los Angeles culminated in the District's adoption and the EPA's approval of Rule 433, “Control of Particulate Emissions at Owens Lake,” into the SIP in 2016.^[15] Rule 433 requires the City of Los Angeles to implement dust control measures, including shallow flooding, managed vegetation, and application of gravel on designated areas of Owens Lake.^[16] The implementation of these dust control measures has led to more than a 90 percent decrease in emissions from Owens Lake ^[17] and significant improvement in the air quality in the CJPA.^[18]

On May 19, 2010, the EPA determined that the CJPA had attained the 24-hour PM₁₀ NAAQS.^[19] The determination was based on complete, quality-assured, and certified ambient air monitoring data that showed the area monitored attainment of the PM₁₀ NAAQS during 2006–2008.^[20] On September 3, 2010, the EPA finalized approval of the submitted “2010 PM₁₀ Maintenance Plan and Redesignation Request for the Coso Junction Planning Area” (“2010 Maintenance Plan”) and redesignated the CJPA to attainment, effective October 4, 2010.^[21] This redesignation was based on EPA's review of the 2010 Maintenance Plan, air quality monitoring data, and other relevant materials that satisfied all requirements for redesignation of the CJPA to attainment, pursuant to CAA sections 107(d)(3)(E) and 175A. Additionally, the maintenance plan was approved as it was consistent with applicable CAA provisions and EPA guidance.

GBUAPCD is a monitoring organization within the CARB Primary Quality Assurance Organization. GBUAPCD operates the PM₁₀ monitoring network in the CJPA. GBUAPCD submits annual monitoring network plans to the EPA that describe the monitoring network operated by GBUAPCD within the CJPA and discuss the status of the air monitoring network, as required under 40 CFR 58.10.^[22] The EPA regularly reviews these annual plans for compliance with the applicable reporting requirements in 40 CFR part 58. With respect to PM₁₀, the EPA has found that GBUAPCD's network plans meet the applicable reporting requirements for the area under 40 CFR part 58, appendix D.^[23] GBUAPCD annually certifies that the data it submits to AQS are complete and quality-assured.^[24]

The District operates one PM₁₀ monitoring station for the CJPA. The monitoring station is located near the State of California Coso Junction rest area in Rose Valley.^[25] The monitoring site is a designated SLAMS and collects hourly PM₁₀ data in accordance with 40 CFR parts 50, 53, and 58.

C. Air Quality in the Coso Junction Planning Area

While the CJPA has had annual average PM₁₀ concentrations of less than 20 µg/m^[3] over the past 10 years, the PM₁₀ monitoring data within the CJPA includes 17 exceedances of the standard recorded during 2010–2020, as detailed in Table 1 of the Coso Junction Second Maintenance Plan.^[26] Since the submittal of the Plan, an additional three exceedances occurred in 2021; these exceedances occurred on September 19, September 27, and October 11.

On September 1, 2022, the District and CARB submitted a document titled, “Discussion of Coso Junction Federal PM₁₀ Exceedances Not Requested for Exclusion from the NAAQS, 2010 through 2021,” (“Exceedance Discussion”).^[27] The Exceedance Discussion documents the District's response to the exceedances that were not requested for exclusion as exceptional events between the years of 2010 and 2021. For exceedances that occurred before the adoption of the Coso Junction Second Maintenance Plan by the State on September 23, 2021, the District implemented its contingency plan as outlined in Section 5.1 of the 2010 Maintenance Plan. Exceedances that occurred after September 23, 2021, were subject to the contingency plan described in Section 7 of the Coso Junction Second Maintenance Plan, and in Section V.E of this document. Details of the subsequent investigations and District actions taken are outlined in Table 3 of the Exceedance Discussion and are consistent with the language of both the 2010 Maintenance Plan and the Coso Junction Second Maintenance Plan.^[28] Table 1 of this document lists the exceedances that occurred, the source of the exceedance, and the action taken by the District.

Table 1—Exceedances in Coso Junction From 2010 Through 2021

Exceedance date	Source of exceedance	District course of action
2/8/2011	North wind: regional event	2010 Maintenance Plan contingency provisions triggered. Phase 7a and Phase 8 dust controls ordered and implemented on Owens Lake.
11/30/2011	North wind: regional event	2010 Maintenance Plan contingency provisions triggered. Phase 7a and Phase 8 dust controls ordered and implemented on Owens Lake.
12/1/2011	North wind: regional event compounded by Owens Lake emissions, notably Phase 8 pre-gravel	2010 Maintenance Plan contingency provisions triggered. Phase 7a and Phase 8 dust controls ordered and implemented on Owens Lake.
3/6/2012	West wind: local sources	Not requested for exclusion as an Exceptional Event. No local sources identified as requiring control. No contingency provisions triggered.
8/7/2013	West wind: flash flood deposits	Requested for exclusion as Exceptional Event; the EPA deferred review.
9/25/2013	West wind: flash flood deposits	Requested for exclusion as Exceptional Event; the EPA deferred review.
2/16/2014	West wind: flash flood deposits	Requested for exclusion as Exceptional Event; the EPA deferred review.
4/25/2014	West wind: flash flood deposits	Requested for exclusion as Exceptional Event; The EPA deferred review.
12/31/2014	North wind: regional event, compounded by sources south of Owens Lake	No Owens Lake or other sources identified as requiring control. No contingency provisions triggered.
11/16/2016	West wind: local sources	Utilized existing District regulations, including District Rule 401, to ensure compliance with local sources.
3/31/2017	North wind: regional event	2010 Maintenance Plan contingency provisions triggered. District enforced timeline for ordered Owens Lake BACM construction and implementation. District continued to monitor, evaluate emissions from Owens Lake and surrounding areas.
7/29/2017	Local sources: paving operations a	District took enforcement action to bring the local emissive stationary source into compliance under District Rule 401. No additional actions or contingency provisions required.
12/20/2017	West wind: local sources	Utilize existing District regulations, including District Rule 401, to ensure compliance with local sources. No additional contingency provisions triggered.
2/11/2018	West wind: local sources	Utilize existing District regulations, including District Rule 401, to ensure compliance with local stationary sources. No additional contingency provisions triggered.
9/2/2019	Regional windblown dust: local sources	Not requested for exclusion as an Exceptional Event at this time due to mixed source contributions. Health advisories issued per District Rule 701 and the 2018 Coso Junction Exceptional Event Mitigation Plan.
9/7/2020	Creek Fire/SQF Complex wildfire smoke	Exceptional Event demonstration submitted and concurred on by the EPA.
9/8/2020	Creek Fire/SQF Complex wildfire smoke followed by regional windblown dust	Not requested for exclusion as an Exceptional Event at this time due to mixed source contributions. Health advisories issued per District Rule 701 and the 2018 Coso Junction Exceptional Event Mitigation Plan.
9/19/2021	Windy Fire/KNP Complex wildfire smoke	The District submitted request for exclusion from contingency measure trigger calculation; the EPA concurred.
9/27/2021	Windy Fire/KNP Complex wildfire smoke	The District submitted request for exclusion from contingency measure trigger calculation; the EPA concurred.
10/11/2021	West Wind: local sources	The District took enforcement action to bring the source into compliance under existing District rules and regulations including District Rule 401. No additional contingency provisions triggered.
a  AQS information qualifier code “J-construction.”
Source: Exceedance Discussion, Table 1 and Table 3.

1. Exceedances in the Coso Junction Planning Area

The District requested exclusion of 5 of the 17 exceedances due to exceptional events as defined in section 319(b) of the Act and its implementing regulations, referred to herein as the Exceptional Events Rule.^[29] The Exceptional Events Rule defines an exceptional event as an event and its resulting emissions that the EPA determines affects air quality in such a way that there is a clear causal relationship between the event and a monitored exceedance (or violation) that is not reasonably controllable or preventable. Such events can be natural (for example, high winds or wildfires) or can be caused by human activity that is unlikely to recur.^[30]

On May 3, 2016, the District submitted an initial notification of intent (INI) form to request exclusion under the Exceptional Events Rule for exceedances that occurred on four days: August 7, 2013, September 25, 2013, February 16, 2014, and April 25, 2014.^[31] The EPA deferred review of the data from these events because we did not anticipate the events will affect any future regulatory decision.^[32]

On August 24, 2021, CARB submitted a demonstration for a wildfire smoke PM₁₀ exceptional event for an exceedance recorded on September 7, 2020, at the CJPA monitoring station.^[33] The demonstration includes a narrative conceptual model of the event that describes the event-specific characteristics, evidence showing the exceedance was not reasonably controllable or preventable, and evidence of the clear causal relationship between the wildfire smoke event and the exceedance flagged as an exceptional event.

The EPA reviewed the documentation that CARB and the District developed to demonstrate that the exceedance on September 7, 2020, meets the criteria for an exceptional event under the Exceptional Events Rule. As conveyed in the EPA's concurrence letter, we concurred that, based on the weight of evidence, the September 7, 2020 exceedance was caused by exceptional events due to the Creek Fire in the Sierra National Forest and the SQF Complex wildfire in the Sequoia National Forest.^[34] Accordingly, the EPA determined that the monitored exceedances associated with this exceptional event should be excluded from use in determinations of exceedances and violations, including the evaluation of whether the Coso Junction PM₁₀ nonattainment area has maintained the standard.

Shortly before the State submitted the Coso Junction Second Maintenance Plan, three additional exceedances of the PM₁₀ NAAQS were recorded on September 19, 2021, September 27, 2021, and October 11, 2021. The District has submitted INI forms and additional supporting information for two of the three exceedances and the EPA has reviewed this information as discussed further in Section I.C.2 of this document.^[35]

2. Design Value in the Coso Junction Planning Area

Based on a review of air quality data during the three-year period covered by the Plan (2018–2020), excluding the exceedance flagged by CARB and GBUAPCD and concurred with by the EPA as an exceptional event, we find that the 2020 design value for the Coso Junction PM₁₀ nonattainment area is 1.0 and therefore is consistent with maintenance of the standard.

As discussed in Section I.C.1 of this document, in 2021 there were three additional exceedances of the PM₁₀ NAAQS in the area. These additional exceedances in 2021 caused the number of exceedances recorded at the air monitor averaged over three consecutive years ( i.e., 2019–2021) to be greater than 1.05. The District and CARB provided information to the EPA about the six exceedances that occurred in 2019–2021 that explained that three of the exceedances were not within the State's or the District's control.^[36] The information CARB and the District provided indicates that the September 7, 2020, September 19, 2021, and September 27, 2021 exceedances were all caused by wildfire smoke. The EPA has reviewed the information provided by the State regarding the 2019–2021 exceedances, and we agree that this information does not call into question the EPA's proposed action herein to approve the Coso Junction Second Maintenance Plan as providing for maintenance of the PM₁₀ NAAQS.^[37]

II. California's State Implementation Plan Submittal

In California, CARB is the state agency responsible for the adoption and submission to the EPA of California SIPs and SIP revisions, and it has broad authority to establish emissions standards and other requirements for mobile sources. Local and regional air pollution control districts in California are responsible for the regulation of stationary sources and are generally responsible for the development of air quality plans. In the portion of Inyo County that contains the CJPA, GBUAPCD develops and adopts air quality plans to address CAA planning requirements applicable to the CJPA. Such plans are then submitted to CARB for adoption and submittal to the EPA as revisions to the California SIP.

On October 21, 2021, CARB submitted the “Coso Junction PM₁₀ Planning Area Second 10-Year Maintenance Plan (July 2019)” (“Coso Junction Second Maintenance Plan” or “the Plan”) for the 1987 24-hour PM₁₀ NAAQS.^[38] The Coso Junction Second Maintenance Plan includes a demonstration that the area is expected to remain in attainment for the PM₁₀ NAAQS through the last year of the second 10-year maintenance period, through 2030. If approval of this plan is finalized, the maintenance period for the CJPA will end on October 4, 2030, along with the conformity requirements for this area.

III. Procedural Requirements for Adoption and Submittal of State Implementation Plan Revisions

CAA sections 110(a)(1) and (2) and section 110(l) require states to provide reasonable notice and opportunity for public hearing prior to adoption and submission of a SIP or SIP revision. To meet these procedural requirements, 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.

CARB's October 21, 2021 SIP submittal package includes documentation of the public processes used by the District and CARB to adopt the Coso Junction Second Maintenance Plan.^[39] As documented in the submittal package, on May 28, 2021, the District published a notice in the Tahoe Daily Tribune, a newspaper in general circulation in South Lake Tahoe, that a public hearing to consider adoption of the Plan would be held on July 1, 2021.^[40] This same notice was re-published by the District on May 29, 2021, in The Sheet and in The Inyo Register, newspapers in general circulation in Mono and Inyo counties, respectively.^[41] As documented in GBUAPCD Resolution No. 2021–04 included in the SIP revision submittal package, the Governing Board of the GBUAPCD adopted the Coso Junction Second Maintenance Plan on July 1, 2021, following the public hearing.^[42] CARB published on its website a notice of public hearing to be held on September 23, 2021, to consider adoption of the Plan.^[43] As evidenced by CARB Resolution 21–19, CARB adopted the Coso Junction Second Maintenance Plan on September 23, 2021, following a public hearing.^[44] Based on documentation included in the October 21, 2021 SIP revision submittal package, both the District and CARB have satisfied the applicable statutory and regulatory requirements for reasonable public notice and hearing prior to adoption and submission of the Plan. Therefore, the submission of the Coso Junction Second Maintenance Plan meets the procedural requirements for public notice and hearing in CAA sections 110(a) and 110(l) and in 40 CFR 51.102.

IV. Requirements for Second 10-Year Maintenance Plans

Section 175A of the CAA provides the general framework for maintenance plans. The initial 10-year maintenance plan must provide for maintenance of the NAAQS for at least 10 years after redesignation, including any additional control measures necessary to ensure such maintenance. In addition, maintenance plans are to contain contingency provisions necessary to ensure the prompt correction of a violation of the NAAQS that occurs after redesignation. The contingency measures must include, at a minimum, a requirement that the state will implement all control measures contained in the nonattainment SIP prior to redesignation.

Section 175A(b) of the CAA requires states to submit a subsequent maintenance plan revision (“second 10-year maintenance plan”) eight years after redesignation. The Act requires only that this second 10-year maintenance plan maintain the applicable NAAQS for 10 years after the expiration of the first 10-year maintenance plan. Beyond these provisions, section 175A of the CAA does not define the content of a second 10-year maintenance plan.

The primary guidance on maintenance plans and redesignation requests is a 1992 memorandum from John Calcagni, titled “Procedures for Processing Requests to Redesignate Areas to Attainment” (“Calcagni Memo”).^[45] The Calcagni Memo outlines the key elements of a maintenance plan, which include an attainment emissions inventory, maintenance demonstration, monitoring and verification of continued attainment, and a contingency plan.

Maintenance plan submittals are SIP revisions, and therefore, the EPA is obligated under CAA section 110(k) to approve them or disapprove them depending upon whether they meet the applicable CAA requirements for such plans.

V. Evaluation of the Coso Junction Second Maintenance Plan

A. Emissions Inventories Overview

A maintenance plan for the PM₁₀ NAAQS should include an inventory of direct PM₁₀ emissions in the area.^[46] The inventory should be consistent with the EPA's most recent guidance on emissions inventories for nonattainment areas available at the time; must be comprehensive, including emissions from stationary point sources, area sources, and mobile sources; and must be based on actual emissions during the appropriate season, if applicable.^[47]

The specific PM₁₀ emissions inventory requirements are set forth in the Air Emissions Reporting Requirements rule,^[48] which requires that emissions inventories report filterable and condensable components, as applicable.^[49] The EPA has provided additional guidance for developing PM₁₀ emissions inventories in “PM₁₀ Emissions Inventory Requirements,” EPA–454/R–94–033 (September 1994) and “Emissions Inventory Guidance for Implementation of Ozone and Particulate Matter National Ambient Air Quality Standards (NAAQS) and Regional Haze Regulations” (May 2017).

The Coso Junction Second Maintenance Plan includes inventories for total primary PM₁₀ for the years 2008 (the base year of the first maintenance period), 2020 (the base year of the second maintenance period), and 2030 (the final year of the second maintenance period) as summarized in Table 2 of this document and further detailed in Appendix C of the Plan. ⁵⁰ The 2020 emissions inventory represents current emissions and was used to project emissions through 2030, as discussed further in Section I.B of this document. CARB and the District developed the PM₁₀ emissions inventories based on the methods and assumptions presented in detail in Appendix C of the Plan and summarized herein.

The District forecasts that the PM₁₀ precursors nitrogen oxides (NO_X), sulfur oxides (SO_X ), volatile organic compounds (VOCs),^[51] and ammonia will decline in Inyo County from 2008 to 2030; however, this small decline does not influence attainment.^[52] As discussed in Section 4 of the Plan, the emissions estimates from windblown dust from open areas constitute over 98 percent of the PM₁₀ emissions inventory for 2020 and 2030. Due to the nature of exceedances in the CJPA, the Coso Junction maintenance demonstration is based entirely on emissions of directly emitted PM₁₀ pollution. Thus, the EPA review focuses on direct PM₁₀ emissions estimates and does not include an in-depth analysis of the District's emissions estimates for PM₁₀ precursor emissions.

The emissions inventories in the Plan include PM₁₀ estimates from all source categories the District deems relevant i.e., stationary sources, entrained dust from vehicle travel, windblown dust from unpaved roads, windblown dust from open areas, and mobile sources.^[53] The District did not include windblown dust sources within the CJPA in the previous 2010 Maintenance Plan inventories because it considered the dust from Owens Lake to be a natural source, and the inventory was designed to include only emissions from anthropogenic sources. The District included this source in the inventories for the Coso Junction Second Maintenance plan due to the magnitude of the source of windblown dust contribution to current inventories.^[54]

1. Stationary Sources

As discussed in Section 4.1 and Appendix C of the Coso Junction Second Maintenance Plan, the District used information in District and federal Title V permit files as well as reporting from facilities to develop direct PM₁₀ emissions estimates for stationary point sources. The District calculated daily annual average values by dividing the total annual estimated PM₁₀ emissions from each site by 365 days.^[55] There are five stationary sources that emit an annual average of at least 50 pounds of PM₁₀ per day located within the CJPA: Coso Energy Developers, Twin Mountain Rock Venture, China Lake Naval Air Weapons Station, Southwest Pumice, LLC, and Bowman Asphalt, Inc.^[56]

The District does not expect a significant increase in stationary source emissions through 2030 because 97 percent of the land in the CJPA is federally controlled and little of the remaining land is undeveloped and/or zoned for commercial or industrial uses needed for substantial stationary source operation. Consequently, the District concludes new stationary sources are unlikely to be built in the CJPA. Additionally, the District observes that the construction of any major sources or major modifications to existing facilities will be subject to the District's new source review rules, although it notes it has no knowledge of any planned expansions in the existing stationary source facilities.^[57] Finally, the District notes that new minor sources or sources that wish to undergo minor modifications must obtain District Permits to Operate, which include provisions to ensure protection of and compliance with the NAAQS.

2. Re-Entrained Road Dust

Fugitive emissions from re-entrained dust from vehicle travel result when dust on roadways is disturbed by vehicle activity and re-entrained into the air. The District calculated dust emissions generated from paved and unpaved roads separately.^[58]

For paved roads, the District calculated emissions using CARB's California Emissions Projection Analysis Model (CEPAM) 2016v1.05 emissions inventory for paved road dust in Inyo County, as described in Section 4.2 and Appendix C of the Plan.^[59] Using the method described in Appendix C, the District used geographic information systems to determine that 6.5 percent of the total paved road length in Inyo County is located within the CJPA.^[60] This factor was applied to the Inyo County emissions data obtained from CEPAM to estimate the PM₁₀ dust emissions resulting from paved roads within the CJPA.

Estimated PM₁₀ emissions from re-entrained road dust from unpaved roads is based on an adjusted emissions factor calculated by the methodology in the EPA's Compilation of Air Pollution Emission Factors, AP–42, Section 13.2.2 and is described in detail in Section 4.2 and Appendix C of the Plan.^[61] The District applied the adjusted emissions factor of 0.76 pounds per vehicle miles traveled to estimated vehicle traffic on unpaved roads to calculate emissions.^[62]

3. Windblown Dust

Windblown dust is generated when wind moves across open areas and unpaved roads and can contribute to ambient PM₁₀ . Potential windblown dust emissions from all unpaved roads and open areas across the CJPA were estimated to determine its contribution to ambient PM₁₀, consistent with other planning areas in Inyo County.

The District applied an emission factor to the estimated area of unpaved roads within the CJPA to estimate emissions from windblown dust from unpaved roads.^[63] The methodology is described in the District's 2010 technical memorandum and is consistent with other SIPs in Inyo County, such as the 2016 Owens Valley Planning Area PM₁₀ State Implementation Plan, (“2016 Owens Valley SIP”).^[64]

Windblown dust emissions from open areas vary with the category of land use, with some surfaces more emissive than others. The land use types with the potential to emit PM₁₀ in the CJPA are developed or urban areas, shrublands, forests, and barren land. The District estimated the area of each of these land use types using the 2011 National Land Cover Database and adjusted the total to remove acreage related to unpaved roads, as these are emissions that are already accounted for.^[65] Emission factors for each land use type were multiplied by the acreages of the corresponding land use type.^[66] This methodology is described in detail in Appendix C of the Plan, and is consistent with other SIPs in Inyo County, such as the 2016 Owens Valley SIP.^[67]

4. Mobile Sources

The District calculated emissions from on-road mobile sources, which include tailpipe emissions, tire wear, and brake wear using CARB's EMFAC2017 model for Inyo County.^[68] The District further estimated emissions generated within the CJPA by adjusting the total Inyo County emissions by the same factor used to calculate re-entrained road dust from paved roads (6.5 percent).^[69]

The category of off-road mobile sources includes planes, trains, and farm and construction equipment and was estimated for the entirety of Inyo County at 0.017 tons per day using CEPAM.^[70] Approximately half of these county level emissions were identified as resulting from commercial aircraft. The CJPA has no commercial airports or identified agricultural acreage. Therefore, off-road mobile sources for the CJPA were excluded as negligible from this inventory, and not included in the analysis for maintenance.

5. Emissions Summary

Based on the emission estimates for the year 2020 as shown in Table 2 of this document, the District finds that windblown dust from open areas accounts for over 98 percent of total PM₁₀ emissions in CJPA.^[71] The second highest source of emissions comes from stationary sources, which contribute 1.3 percent of the total PM₁₀ emissions in the CJPA. Windblown dust from unpaved roads, entrained dust from vehicle travel, and mobile source emission, together contribute less than 0.5 percent of the total PM₁₀ emissions.^[72]

Table 2—Coso Junction PM ₁₀ Emission Inventory, 2008, 2020, 2030

[Annual average, tpd]

Emissions source	2008	2020	2030
Stationary Sources	0.64	0.49	0.49
Entrained Dust from Vehicle Travel	0.09	0.06	0.06
Mobile Sources	0.01	0.01	0.01
Total	0.74	0.56	0.56
Windblown dust—unpaved roads		0.11	0.11
Windblown dust—Open Areas		36.34	36.34
Total including windblown dust		37.01	37.01
Source: Coso Junction Second Maintenance Plan, Table 4 and Appendix C.
Totals may not add up due to rounding.
The 2010 Maintenance plan did not include windblown dust in the Plan's emissions inventory. The missing values are represented here with a hyphen.

Due to the sparse population of the CJPA, and the fact that over 97 percent of land in this maintenance area is federally controlled and operated, the District concludes that future projected growth of emissions and population in the CJPA is unlikely and would be limited in scope.^[73] The majority of unpaved roads and open areas within the CJPA are located on federally controlled lands, where access and development are limited to the public.^[74] In addition, any substantive development on federal lands is subject to general conformity requirements under District Regulation XIII.^[75] Due to these reasons, the District has determined that emissions in the CJPA will remain relatively constant over the 2020–2030 maintenance period.

The EPA believes the selection of the 2020 base year inventory is appropriate given that it is the most recent emissions inventory associated with the triennial reporting schedule required under the Air Emissions Reporting Requirements rule. Moreover, preparation of an annual average daily inventory, as opposed to a seasonal or episodic inventory, is appropriate given that elevated PM₁₀ concentrations in CJPA do not exhibit a clear seasonal or episodic pattern. Based on our review of the documentation provided with the plan, we are proposing to find that the 2020 emissions inventory for direct PM₁₀ is based on reasonable assumptions and methodologies, and that the inventory is comprehensive, current, accurate, and consistent with applicable CAA provisions and the Calcagni Memo, and are therefore proposing that the 2020 inventory is acceptable for use in demonstrating maintenance of the PM₁₀ NAAQS.

B. Maintenance Demonstration

Section 175A(a) of the CAA requires that the maintenance plan “provide for the maintenance of the national primary ambient air quality standard for such air pollutant in the area concerned for at least 10 years after the redesignation.” A state may generally demonstrate maintenance of the NAAQS by either showing that future emissions of a pollutant or its precursors will not exceed the level of the attainment inventory, or by conducting modeling that shows that the future mix of sources and emissions rates will not cause a violation of the NAAQS.^[76] Projected emissions inventories for future years must account for, among other things, the ongoing effects of economic growth and adopted emissions control requirements, and the inventories are expected to be the best available representation of future emissions. The plan submission should include documentation explaining how the state calculated the emissions data for the base year and projected inventories.

In the Coso Junction Second Maintenance Plan, the District demonstrates continued maintenance of the PM₁₀ NAAQS by projecting the direct PM₁₀ emissions in the area through 2030 and showing that future emissions of PM₁₀ will not exceed the level of the attainment inventory. As discussed in Section V.A of this document, the Plan includes emissions inventories representing actual emissions in 2020 (the Plan's base year) and projected emissions through 2030 (the final year of the second maintenance period) for sources in the CJPA.^[77]

The District derived projected inventories by applying expected growth trends for each source category based on data that reflect historical trends, current conditions, and recent economic and demographic forecasts with expected emissions reductions resulting from adopted control measures to the base year inventory. For the Coso Junction Second Maintenance Plan, emission methodologies used in the 2010 Maintenance Plan were reviewed by the District and updated as appropriate to generate emissions for this Plan. Appendix C of the Plan documents the methods and assumptions used to develop the emissions projections upon which the maintenance demonstration relies and presents the detailed source category-specific estimates for each of the analysis years.

As discussed in Section I.B of this document, the emissions reductions from Owens Lake were the primary factor leading to attainment for the CJPA, and Owens Lake is the paramount source of emissions that must be addressed to ensure maintenance for the area.^[78] District Rule 433, “Control of Particulate Emissions at Owens Lake,” ^[79] provides a federally enforceable regulatory mechanism to ensure continued success of the established dust control strategy on Owens Lake, and ensures that emissions from Owens Lake do not cause or contribute to exceedances in the CJPA.^[80]

For these reasons, and due to the unique nature of the CJPA, the EPA believes that the District's determination that the total daily emissions of PM₁₀ from sources within the CJPA will remain constant at 37.01 tons per day from 2020 through 2030 is reasonable. We agree that the projected emissions inventories for direct PM₁₀ for years 2020 through 2030 are based on reasonable methods, growth factors, and assumptions, and are based on the most current and accurate information available to CARB and GBUAPCD at the time the Plan and its inventories were being developed. We also agree that the Coso Junction Second Maintenance Plan provides an adequate basis to demonstrate maintenance of the PM₁₀ NAAQS within the CJPA through 2030. Consequently, we are proposing to approve the Plan because it demonstrates maintenance of the PM₁₀ NAAQS for more than 10 years after the expiration of the first 10-year maintenance plan, in accordance with section 175A(b) of the CAA.

C. PM₁₀ Air Quality Monitoring Network

After an area has been redesignated, the state should continue to operate an appropriate air quality monitoring network, in accordance with 40 CFR part 58, to verify the attainment status of the area.^[81]

As discussed in Section I.B of this document, GBUAPCD monitors ambient concentrations of PM₁₀ in the CJPA near the State of California Coso Junction Rest Area in the Rose Valley.^[82] In Section 10 of the Coso Junction Second Maintenance Plan, the District commits to continue to operate and maintain a PM₁₀ ambient air quality monitor in the CJPA in accordance with 40 CFR parts 50, 53, and 58 to verify the attainment status of the area. The monitoring will also allow the District to notify the public during air pollution episodes as provided for in District Rule 701, “Air Pollution Episode Plan” and in the District's 2018 Exceptional Events Mitigation Plan for the CJPA.^[83] Data collected by the monitoring network are also needed to implement the contingency provisions of the maintenance plan. We are proposing that the Coso Junction Second Maintenance Plan contains adequate provisions for continued ambient PM₁₀ monitoring to verify continued attainment through the full maintenance period, ending on October 4, 2030.

D. Verification of Continued Attainment

The EPA recommends that the state verify continued attainment through methods in addition to the ambient air monitoring program, e.g., through periodic review of the factors used in development of the attainment inventory to show no significant change.^[84] GBUAPCD commits to review the emissions inventory inputs on an annual basis and, if the District finds that these inputs have changed significantly, to request that CARB update the existing inventory and to compare the revised inventory with the inventories in the Coso Junction Second Maintenance Plan.^[85] Additionally, the District commits to updating its calculated three-year design value for the CJPA annually. This design value will also be included in the annual network monitoring plan submitted to the EPA to confirm the area continues to meet the PM₁₀ NAAQS. We are proposing to find that the District's commitments are acceptable to verify continued attainment of the PM₁₀ NAAQS.

E. Contingency Provisions

Section 175A(d) of the CAA requires that maintenance plans include contingency provisions, as the EPA deems necessary, to promptly correct any violations of the NAAQS that occur after redesignation of the area. Such provisions must include a requirement that the state will implement all measures with respect to the control of the relevant air pollutants that were contained in the SIP for the area before redesignation of the area as an attainment area. These contingency provisions are distinguished from contingency measures required for nonattainment areas under CAA section 172(c)(9) in that they are not required to be fully adopted measures that will take effect without further action by the state for the maintenance plan to be approved. However, the contingency provisions of a maintenance plan are an enforceable part of the SIP and should ensure that contingency measures are adopted expeditiously once they are triggered. The maintenance plan should clearly identify the measures to be adopted, include a schedule and procedure for adoption and implementation of the measures, and contain a specific timeline for action by the state. In addition, the state should identify the specific indicators or triggers that will be used to determine when the contingency measures need to be implemented.

The District has adopted a contingency plan to address possible future PM₁₀ air quality problems in the CJPA. The contingency plan is detailed in Section 7 of the Plan. As noted by the District in the Plan, contingency provisions are typically implemented when air quality deteriorates beyond a specified level, such as a certain number of exceedances of the standard or a violation of the standard. In this case, the contingency provisions will be triggered if an exceedance of the federal PM₁₀ standard is monitored within the CJPA.^[86]

The contingency plan also includes a screening process that allows the District and CARB, subject to the EPA's review, to exclude exceedances from the trigger calculation if the agencies collectively determine that information developed by the District is sufficient to support exclusion. The purpose of the screening process is to differentiate between exceedances that are not within the District or State control ( i.e., exceedances that occur despite the implementation of reasonable measures), and exceedances that are within the District's or State's control and should be included in the trigger calculation. It is important to note that, should the District or State exclude an exceedance from the contingency trigger calculation using this process, it would not constitute the EPA's concurrence that the exceedance was caused by an exceptional event. The exceedance will therefore continue to be included in design value calculations for the CJPA unless CARB, following opportunity for public comment, submits a request for the EPA to concur on the exceedance as an exceptional event pursuant to 40 CFR 50.14, and the EPA reviews the submittal and formally concurs.

If an exceedance occurs, the District will start the screening process to investigate the cause of the exceedance within 60 days following the end of the calendar quarter during which the event occurred. An exceedance determined by the District to be caused by or significantly contributed to by emissions from the Owens Lake area would trigger contingency measures, as outlined in Section 7.1, “Owens Valley Planning Area Contingency Measures,” of the Coso Junction Second Maintenance Plan. In brief, the District will investigate the exceedance within 60 days of the end of the calendar quarter in which it occurred to determine whether the required control measures on Owens Lake were properly implemented in accordance with District Rule 433 or if the emissions are from a new source on Owens Lake.^[87] For exceedances found to be caused by dust from existing dust control areas, the District will order corrective actions no more than 18 months after the 60 day period of investigation. Exceedances found to be caused by dust from a new source on Owens Lake will be subject to the contingency provisions under section C of District Rule 433. Mitigation of emissions from uncontrolled areas of Owens Lake will be addressed as expeditiously as possible by the District under the legal constraints of the 2014 Stipulated Judgement, the 2016 Owens Valley SIP, and District Rule 433.^[88] Additionally, at least once per year, the District will make an additional best available control measure contingency determination to evaluate if uncontrolled areas on the Owens Lakebed or implemented controls are not sufficient to mitigate emissions to attain the NAAQS in the Owens Valley Planning Area.

An exceedance determined to be caused by emissions from sources located within the CJPA would trigger the contingency provisions outlined in Section 7.2, “Additional Contingency Measures,” of the Coso Junction Second Maintenance Plan. Following the end of the calendar quarter in which the exceedance occurs, the District will investigate the cause of the exceedance within 60 days. Exceedances found to be caused by emissions from local sources already subject to District regulations will be promptly addressed no more than 18 months after the 60-day period of investigation.^[89] If the exceedance cannot be addressed through existing District rules and regulations and is not covered by the EPA Exceptional Events Policy, the District will adopt and implement additional control measures necessary to meet and maintain the NAAQS within 18 months after the 60 day period of investigation. Control measures could include expanding existing rules or utilizing measures from outside existing rules and regulations to achieve the necessary emissions reductions within 18 months.

Within 60 days of the end of each calendar quarter, the District will provide a list of exceedances that occurred during that previous quarter to CARB, identify those exceedances that the District believes to be exceedances that are not within the District's or State's control, and flag the relevant data and provide an initial description in AQS.

If the District seeks to exclude an exceedance from the contingency measures trigger calculation, the District will notify CARB and the EPA by submitting an INI. The EPA, CARB, and the District will confer to determine whether additional information should be submitted along with the INI. The District will submit the INI and any additional requested information to CARB and the EPA for review. After review, CARB and the EPA will notify the District if the Agencies agree that the exceedance appears to be an uncontrollable event and therefore will not be counted towards the contingency measure trigger calculation, or if the Agencies determine that the exceedance was likely caused by an exceptional event and that the District must include the event in the contingency measure trigger calculation. If the District still considers the event in question to be exceptional, the District may then opt to submit a full Exceptional Events Demonstration.

Based on our review of the Coso Junction Second Maintenance Plan, as summarized herein, we propose to find that the contingency provisions of the Plan clearly identify specific contingency measures, contain a triggering mechanism to determine when contingency measures are needed, contain a description of the process of recommending and implementing contingency measures, and contain specific and appropriate timelines for action. We also propose to find that the contingency trigger screening process, including the associated EPA review, is reasonably designed to distinguish between exceedances that are not within the District or State control, and exceedances that are within the District's or State's control and for which new or tightened control measures might be effective. Thus, we propose to conclude that the contingency plan in the Coso Junction Second Maintenance Plan is adequate to ensure correction of any violation of the PM₁₀ NAAQS that occurs after redesignation, as required by section 175A(d) of the CAA.

F. Motor Vehicle Emissions Budgets for Transportation Conformity

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

Transportation actions involving Federal Highway Administration (FHWA) or Federal Transit Administration (FTA) funding or approval are subject to the EPA's transportation conformity rule, codified at 40 CFR part 93, subpart A. Under this rule, metropolitan planning organizations (MPOs) in nonattainment and maintenance areas coordinate with state and local air quality and transportation agencies, the EPA, FHWA, and FTA to demonstrate that an area's regional transportation plans and transportation improvement programs conform to the applicable SIP. This demonstration is typically done by showing that estimated emissions from existing and planned highway and transit systems are less than or equal to the motor vehicle emissions budgets (“budgets”) contained in submitted or approved control strategy SIPs and maintenance plans.^[90]

However, an isolated rural area does not have an MPO and is not required to prepare transportation plans or transportation improvement programs. Therefore, in isolated rural areas such as the CJPA, conformity is determined only when a nonexempt FHWA or FTA project needs approval or funding.^[91]

Control strategy SIPs and maintenance plans typically set budgets for criteria pollutants and/or their precursors to address pollution from cars and trucks. Budgets are generally established for specific years and specific pollutants or precursors. PM₁₀ maintenance plan submittals should identify budgets for transportation-related PM₁₀ emissions in the last year of the maintenance period.^[92]

Section 93.109(f) of EPA's transportation conformity regulation (40 CFR part 93) states that an area is not required to satisfy a regional emissions analysis for a pollutant if the EPA finds that motor vehicle emissions of that pollutant are an insignificant contributor to the area's air quality problem. To make this demonstration, the submitted SIP would have to show that it would be unreasonable to expect that the area would experience enough motor vehicle emissions growth in that pollutant/precursor for a NAAQS violation to occur. Factors to consider in such a demonstration include the percentage of motor vehicle emissions in the context of the total attainment plan inventory; the current state of air quality as determined by monitoring data for that NAAQS; the absence of SIP motor vehicle control measures; and historical trends and future projections of the growth of motor vehicle emissions.

In our rulemaking approving the 2010 Maintenance Plan for the CJPA, the EPA found the contribution of motor vehicles to be an insignificant source of PM₁₀ to the CJPA.^[93] As part of the Coso Junction Second Maintenance Plan, GBUAPCD requested that the EPA find that on-road emissions of PM₁₀ are insignificant for conformity purposes, and therefore the District did not submit any motor vehicle emissions budgets. The EPA is proposing to approve GBUAPCD's insignificance demonstration for the on-road motor vehicle contribution of PM₁₀ emissions to the overall PM₁₀ emissions in the Coso Junction Second Maintenance Plan. Additionally, in this notice, the EPA is initiating the adequacy review process for this insignificance finding. The EPA invites the public to comment on the adequacy of this insignificance finding as well as other actions the EPA is proposing in this notice.

This insignificance finding is based on the following consideration of the factors identified in the EPA's transportation conformity regulations, as discussed in sections 4 and 8 of the Coso Junction Second Maintenance Plan, and on the unique circumstances of the CJPA.

1. The Percentage of Motor Vehicle Emissions in the Context of the Total SIP Inventory

The District calculated the percentage of on-road motor vehicle emissions by adding together direct emissions from on-mobile source emissions,^[94] entrained dust from vehicle travel on paved roads, and entrained dust from vehicle travel on unpaved roads, and dividing the sum by the total PM₁₀ emissions including windblown dust. These values can be found in Table 2 of this notice. On-road mobile emissions constitutes less than 0.2 percent of the PM₁₀ emissions inventory in the CJPA.^[95] The District attributes this to the low population of the CJPA.

2. The Coso Junction Planning Area Is Attaining the PM₁₀ NAAQS

As discussed in Section 3 of the Coso Junction Second Maintenance Plan and in Section I.C.2 of this document, the 2018–2020 PM₁₀ monitoring data show that the CJPA is in attainment of the PM₁₀ NAAQS. The District observes that this current state of air quality coincides with the improvements in the Owens Valley area as emissions from Owens Lake have been mitigated over time, and notes that these continual improvements in air quality have resulted in annual average PM₁₀ concentrations of less than 20 µg/m³ over the past ten years.

3. Motor Vehicle Control Measures Were Not Adopted for the Purpose of Bringing the Area Into Attainment

As discussed in Section V.A of this document, the control measures relied upon in the Coso Junction Second Maintenance Plan are primarily related to windblown dust, which accounts for over 98 percent of the PM₁₀ emissions in the CJPA. As discussed in Section 4 of the Coso Junction Second Maintenance Plan and in Section V.A of this notice, on-road mobile emissions in the CJPA, including exhaust, tire wear, brake wear, and re-entrained road dust from paved and unpaved roads, make up less than 0.2 percent of the daily PM₁₀ emissions in the CJPA.^[96] There are currently no GBUAPCD adopted motor vehicle control measures specific to the CJPA. Any national and statewide motor vehicle emission control measures that may apply would contribute to reductions in motor vehicle related PM₁₀ emissions in the CJPA, which as noted previously, amount to less than 0.2 percent of the total PM₁₀ emissions inventory.

4. Historical Trends and Future Projections Indicate Motor Vehicle PM₁₀ Emissions Are Consistent Over Time

Historical on-road mobile emissions have constituted a tiny fraction of the overall PM₁₀ emissions inventory in the CJPA.^[97] The District attributes this to the low population of the CJPA. Despite some population growth in the area, the population of the CJPA occupies only 1.3 percent of the land area of Inyo County, and substantial population growth is limited by the high percentage of federally controlled land where access, development, or both are restricted.^[98] For these reasons, the District states that on-road mobile emissions can reasonably be expected to remain relatively small and unchanging over the 2020–2030 maintenance period.^[99]

Given these factors, we are proposing to find that motor vehicle-related PM₁₀ emissions are insignificant contributors to PM₁₀ in the CJPA and that it would be unreasonable to expect that PM₁₀ emissions from motor vehicles would grow enough within the CJPA to cause a violation of the PM₁₀ standard. If this insignificance finding is finalized as proposed, a regional emissions analysis would not be required for PM₁₀ in any future conformity determination for the 1987 PM₁₀ NAAQS in the CJPA.^[100] The EPA's insignificance finding should, however, be noted in any transportation conformity documentation that is prepared for this area. Areas with insignificant regional motor vehicle emissions for a pollutant or precursor are still required to make a conformity determination that satisfies other relevant conformity requirements such as fiscal constraint, timely implementation of transportation control measures, interagency consultation, and hot-spot analyses for projects, if required.

VI. Environmental Justice Considerations

The EPA performed and reviewed a screening-level analysis using the EPA's environmental justice (EJ) screening and mapping tool (“EJSCREEN”). Our screening-level analysis included multiple environmental and demographic indicators, including the EJSCREEN “Demographic Index,” which is the average of an area's percentage of minority and low-income populations. The Demographic Index for the southwest portion of Inyo County, which contains the CJPA, is at the 52nd percentile, compared to the United States as a whole.^[101] The results of this analysis are being provided for informational purposes. The results of the demographic analysis indicate that, for populations within the CJPA, the percentage of people of color (persons who reported their race as a category other than White alone (not Hispanic or Latino)) is similar to the national average, both at 40 percent. The percent of people living below the poverty level in the CJPA is 21 percent, which is lower than the national average of 30 percent.

This proposed action addresses a plan for continued maintenance of the 1987 PM₁₀ NAAQS for the CJPA. Approval of this plan does not impose any additional regulatory requirements on sources beyond those imposed by state law. As discussed in this document, California has demonstrated that the CJPA is attaining the 1987 PM₁₀ NAAQS and the Coso Junction Second Maintenance Plan provides for the maintenance of the NAAQS for the reminder of the maintenance period. At a minimum, this action would not worsen any existing air quality and is expected to ensure the area is meeting requirements to maintain air quality standards. Further, there is no information in the record indicating that this action is expected to have disproportionately high or adverse human health or environmental effects on a particular group of people.

VII. Proposed Action and Request for Public Comment

Under CAA section 110(k)(3), and for the reasons set forth in this document, the EPA is proposing to approve the Coso Junction Second Maintenance Plan submitted electronically on October 21, 2021, by CARB, as a revision to the California SIP. We are proposing to approve the maintenance demonstration and contingency provisions as meeting all the applicable requirements for maintenance plans and related contingency provisions in CAA section 175A, and we are proposing an insignificance finding for motor vehicle emissions in the CJPA. Additionally, the EPA is also initiating the adequacy process for this insignificance finding included in this SIP submission.

We are soliciting comments on these proposed actions and on the adequacy of the maintenance plan's demonstration that motor vehicle emissions are insignificant. We will accept comments from the public for 30 days following publication of this proposal in the Federal Register and will consider any relevant comments before taking final action or making an adequacy determination.

VIII. Statutory and Executive Order Reviews

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

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

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

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

• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104–4);
• Does not have federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);
• Is not an economically significant regulatory action based on health or safety risks subject to Executive Order 13045 (62 FR 19885, April 23, 1997);
• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001);
• Is not subject to requirements of section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the Clean Air Act; and

In addition, there are no areas of Indian country within the CJPA, and the state plan for which the EPA is proposing approval does not apply on any Indian reservation land or in any other area where the EPA or an Indian tribe has demonstrated that a tribe has jurisdiction. Therefore, this proposed action does not have tribal implications and would not, if approved, impose substantial direct costs on tribal governments or preempt tribal law as specified by Executive Order 13175 (65 FR 67249, November 9, 2000).

Executive Order 12898 (Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations, 59 FR 7629, Feb. 16, 1994) directs Federal agencies to identify and address “disproportionately high and adverse human health or environmental effects” of their actions on minority populations and low-income populations to the greatest extent practicable and permitted by law. EPA defines environmental justice (EJ) as “the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies.” EPA further defines the term fair treatment to mean that “no group of people should bear a disproportionate burden of environmental harms and risks, including those resulting from the negative environmental consequences of industrial, governmental, and commercial operations or programs and policies.”

The air agency did not evaluate environmental justice considerations as part of its SIP submittal; the CAA and applicable implementing regulations neither prohibit nor require an evaluation. EPA performed an environmental justice analysis, as is described above in the section titled, “Environmental Justice Considerations.” The analysis was done for the purpose of providing additional context and information about this rulemaking to the public, not as a basis of the action. Due to the nature of the action being taken here, this action is expected to have a neutral to positive impact on the air quality of the affected area. In addition, there is no information in the record upon which this decision is based that is inconsistent with the stated goal of E.O. 12898 of achieving environmental justice for people of color, low-income populations, and Indigenous peoples.

List of Subjects in 40 CFR Part 52

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

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

Dated: March 24, 2023.

Kerry Drake,

Acting Regional Administrator, Region IX.

Footnotes

1.  CAA section 109(b). For a given air pollutant, “primary” standards are those determined by the EPA as requisite to protect the public health. “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.

2.  52 FR 24634.

3.  The primary and secondary standards were set at the same level for both the 24-hour and the annual PM₁₀ standards.

4.  71 FR 61144 (October 17, 2006).

5.  An exceedance is defined as a daily value that is above the level of the 24-hour standard ( i.e., 150 µg/m3. ) after rounding to the nearest 10 µg/m3. ( i.e., values ending in five or greater are to be rounded up). Thus, a recorded value of 154 µg/m3. would not be an exceedance because it would be rounded to 150 µg/m3. . A recorded value of 155 µg/m3. would be an exceedance because it would be rounded to 160 µg/m3. . 40 CFR part 50, appendix K, section 1.0.

6.  40 CFR 50.6 and 40 CFR part 50, appendix K. The comparison with the allowable expected exceedance rate of one per year averaged over three years is made in terms of a number rounded to the nearest tenth (fractional values equal to or greater than 0.05 are to be rounded up; e.g., an exceedance rate of 1.05 would be rounded to 1.1, which is the minimum design value for nonattainment). 40 CFR part 50, appendix K, section 2.1(b).

7.  For PM₁₀, a complete year of air quality data includes all four calendar quarters with each quarter having valid data on a minimum of 75 percent of the scheduled PM₁₀ sampling days. 40 CFR part 50, appendix K, section 2.3(a).

8.  40 CFR 50.6; 40 CFR part 50, appendix J; 40 CFR part 53; and 40 CFR part 58, appendices A, C, D, and E.

9.  52 FR 29383 (August 7, 1987).

10.  67 FR 50805 (August 6, 2002).

11.  For a description of the geographic boundaries of the CJPA, see 40 CFR 81.305.

12.  For the history of Owens Lake and its impact on the CJPA, see 75 FR 36023 (June 24, 2010).

13.  64 FR 34173 (June 25, 1999).

14.  82 FR 13390 (March 13, 2017).

15.  81 FR 95473 (December 28, 2016).

16.  GPUAPCD Rule 433, “Control of Particulate Emissions at Owens lake,” adopted April 13, 2016.

17.  75 FR 36023.

18.  The number of monitored and expected exceedances at the Rose Valley monitoring station in the CJPA has dropped from a high of 12 exceedances per year to the value of 1 per year, excluding exceptional events, in 2020. See Table 2 in the Coso Junction Second Maintenance Plan for a summary of exceedances from 1985 through 2020.

19.  75 FR 27944.

20.  Id.

21.  75 FR 54031.

22.  The most recent annual network plan was submitted via email dated April 26, 2022, from Chris Howard, GBUAPCD, to Gwen Yoshimura, EPA Region IX, Subject: “Great Basin Unified APCD Ambient Air Monitoring Data Certification for 2021,” with attachment.

23.  For example, see letter dated December 19, 2022, from Gwen Yoshimura, Manager, Air Quality Analysis Office, EPA Region IX, to Phillip Kiddoo, Air Pollution Control Officer, GBUAPCD.

24.  See email dated April 26, 2022, from Chris Howard, GBUAPCD, to Gwen Yoshimura, EPA Region IX, Subject: “Great Basin Unified APCD Ambient Air Monitoring Data Certification for 2021,” with attachment.

25.  See Figure 3 in the Coso Junction Second Maintenance Plan.

26.  Coso Junction Second Maintenance Plan, Appendix A includes the daily average PM₁₀ monitor readings from the CJPA and surrounding monitor stations for every day from January 1, 2010, to December 31, 2020.

27.  Submitted via email on September 1, 2022 from Sylvia Vanderspek, CARB, to Gwen Yoshimura, EPA Region IX, Subject: “FW: Coso Junction Initial Notification Forms for 2nd PM₁₀ MP Contingency.” with attachments.

28.  Id., attachment titled “Discussion of PM₁₀ Exceedances at Coso Junction 2010 through 2021.pdf.”

29.  72 FR 13560 (March 22, 2007); revised 81 FR 68216 (October 3, 2016).

30.  40 CFR 50.1.

31.  Email dated May 3, 2016, from Chris Lanane, Air Monitoring Specialist, GBUAPCD, to Randall Chang, EPA Region IX, Subject: “Fwd: Exceptional Event Documentation for Coso Junction,” with attachment.

32.  Email dated June 1, 2016, from Meredith Kurpius, EPA Region IX, to Chris Lanane, GBUAPCD, and Theresa Najita, CARB, Subject: “Coso Junction PM₁₀ High Wind Exceptional Events.”

33.  Email dated August 24, 2021, from Clawson Candance, CARB, to Michael Benjamin, CARB, Subject: “CARB letter to EPA GBUAPCD PM₁₀ NEE_signed, EPA Cvr Ltr—2021 2nd Maint. Plan-EE Submittal-2021073_signed and GBUAPCD Exceptional Event Demonstration September 7 2020 FINAL,” with three attachments. While submitted by CARB, the demonstrations and addendums were developed through a joint effort by CARB and the GBUAPCD.

34.  Email dated July 12, 2022, from Anna Mebust, EPA Region IX, to Sylvia Vanderspek, CARB, Subject: “EPA Concurrence on 2020 PM₁₀ Wildfire Exceptional Event,” with attachments, “DD_Concurrence_Letter.pdf;” “CosoJunctionWildfirePM₁₀ _ConcurrenceTSD.pdf.”

35.  Submitted via email on September 1, 2022, from Sylvia Vanderspek, CARB to Gwen Yoshimura, EPA Region IX, Subject: “FW: Coso Junction Initial Notification Forms for 2nd PM₁₀ MP Contingency,” with attachments, “INI 2010–2020 Coso Junction PM₁₀ .pdf,” “Discussion of PM₁₀ Exceedances at Coso Junction 2010 through 2021.pdf,” “INI 2021 Coso Junction PM₁₀ .pdf,” and “Coso Junction 2021 Wildfire Smoke Exceedances.pdf.” For INI forms, see attachment “INI 2021 Coso Junction PM₁₀.pdf” and for additional information documenting the District's claim, see “Coso Junction 2021 Wildfire Smoke Exceedances.pdf.”

36.  Id.

37.  Letter dated November 14, 2022, from Gwen Yoshimura, Manager, Air Quality Analysis Office, EPA Region IX, to Sylvia Vanderspek, Branch Chief, CARB, titled, “Re: EPA Response to Coso Junction initial Notification Forms for 2nd PM₁₀ MP Contingency, September 1, 2022.”

38.  Letter dated October 20, 2021, from Richard W. Corey, Executive Officer, CARB, to Deborah Jordan, Acting Regional Administrator, EPA Region IX (submitted electronically October 21, 2021).

39.  In this package, CARB submitted an unsigned version of its “Notice of Public Meeting to Consider Coso Junction PM₁₀ Maintenance Plan SIP Submittal.” On December 28, 2022, the EPA received a signed and dated copy of this document from the District. Both documents are included in the docket for this action.

40.  “Notice of Public Hearing Adoption and Approval of 2021 Coso Junction PM₁₀ Planning Area Second 10-Year Maintenance Plan,” Phillip L. Kiddoo, Air Pollution Control Officer, GBUAPCD.

41.  Id.

42.  GBUAPCD, “B/O #210701–05,” dated July 1, 2021, attested by Tori DeHaven, Clerk of the Board.

43.  “Notice of Public Meeting to Consider Coso Junction PM₁₀ Maintenance Plan SIP Submittal,” Richard W. Corey, Executive Officer, CARB. Available at: https://ww2.arb.ca.gov/​sites/​default/​files/​2021-09/​cosojunctionpm10sipnotice.pdf.

44.  Proposed agenda dated September 23, 2021, “Coso Junction PM₁₀ Planning Area Second 10-Year Maintenance Plan, Resolution 21–19,” CARB.

45.  Memorandum dated September 4, 1992, from John Calcagni, Director, Air Quality Management Division, EPA, to EPA Regional Office Air Division Directors, Subject: “Procedures for Processing Requests to Redesignate Areas to Attainment.”

46.  PM₁₀ precursor emissions should also be included depending upon the contribution of secondary particulate matter to high ambient PM₁₀ concentrations in the area. In this instance, an inventory of PM₁₀ precursor emissions is not required because PM₁₀ precursor controls were not relied upon to achieve attainment of the PM₁₀ NAAQS in the CJPA nor are they relied upon to demonstrate maintenance of the NAAQS (see Coso Junction Second Maintenance Plan, sections 2 and 4, and 75 FR 36023, 36027). While not required, the CARB Staff Report submitted with the Coso Junction Second Maintenance Plan includes inventories of NO_X, SO_X, ROG, and ammonia in Inyo County for 2008, the base year of the first maintenance plan, and for 2030, the horizon year for the Coso Junction Second Maintenance Plan (“Table 1. Inyo County Annual Average Day PM₁₀ and Precursor Emissions (ton/day)”).

47.  CAA section 172(c)(3).

48.  40 CFR part 51, subpart A.

49.  40 CFR 51.15(a)(1)(vii). The primary emissions source in the CJPA is windblown dust. Therefore, reporting condensible components of PM₁₀ was not applicable in this plan.

50.  Coso Junction Second Maintenance Plan, Appendix C consists of an email memorandum dated June 9, 2021, from Emily Weissinger and Julia Lester, Ramboll US Consulting, Inc., to Ann Logan, GBUAPCD, Subject: “24-Hour PM₁₀ Emissions Inventory for the 2nd Maintenance Plan for the Coso Junction Planning Area, Inyo County, California.” Appendix C provides emission analyses for the years 2020–2030.

51.  Some California air quality plans use the term reactive organic gases (ROG) instead of VOC. The terms cover essentially the same compounds, and herein we use the term VOC.

52.  See CARB Staff Report Table 1, “Inyo County Annual Average Day PM₁₀ and Precursor Emissions (tons/day).”

53.  Coso Junction Second Maintenance Plan, Section 4, “Emissions Inventory.”

54.  See CARB Staff Report, “Attainment Year Emission Inventory.” Windblown dust accounts for 98.2 percent of the current emissions inventories.

55.  Unpaved road and haul road emissions for permitted sources are included in the daily emissions for each facility.

56.  These sources are listed in descending order of annual averages of PM₁₀ emissions in pounds per day and are the following: 289 pounds per day, 235 pounds per day, 191 pounds per day, 185 pounds per day, and 86 pounds per day of PM₁₀, respectively.

57.  GBUAPCD Rule 209–A, “Standards for Authorities to Construct” (adopted May 12, 1993) and Rule 216, “New Source Review Requirements for Determining Impact on Air Quality” (adopted March 10, 1976).

58.  For detailed explanations of the calculations for paved roads and unpaved roads, see Coso Junction Second Maintenance Plan, Section 4.2 and Appendix C.

59.  CEPAM2016v1.05 was the most recent version of the CEPAM model available during SIP development and when the SIP was submitted in 2021. It has since been updated to CEPAM 2019 v1.03.

60.  Coso Junction Second Maintenance Plan, Appendix C, Figure 1 and Figure 2.

61.  EPA, “AP–42, Fifth Edition Compilation of Air Pollutant Emissions Factors, Volume 1: Stationary Point and Area Sources, Section 13.2.2 Unpaved Roads,” November 2006.

62.  Vehicle traffic on unpaved roads was calculated assuming an average of 2 trips per day along 50 miles of regularly traveled unpaved public roads in the CJPA, consistent with the 2010 Maintenance Plan. This assumption is reasonable considering the sparse population of the CJPA and that most of the unpaved roads are located on federally controlled land where access and development are restricted. Coso Junction Second Maintenance Plan, p. 17.

63.  Coso Junction Second Maintenance Plan, Appendix C. An emission factor of 0.0241 tons/acre/year for “barren” land uses was applied to the unpaved roadway area of the estimated 675 miles of unpaved roads in the CJPA, with an assumed roadway width of 20 feet.

64.  See 81 FR 89407, 89411 (December 12, 2016) and GBUAPCD technical memorandum dated May 3, 2010, “Unpaved Road Dust Inyo County (Revised).”

65.  Available at https://data.nal.usda.gov/​dataset/​national-land-cover-database-2011-nlcd-2011#:~:text=​National%20Land%20Cover%20Database%202011%20%28NLCD%202011%29%20is,across%20the%20United%20States%20from%202001%20to%202011. Since the submission of this plan, newer landcover products became available, however no significant differences were observed within the CJPA when comparing the newer landcover data to the 2011 landcover data.

66.  Emission factors for urban areas, shrublands, forest, and barren land are 0.0001, 0.0272, 0.0034, and 0.0241 respectively.

67.  See 81 FR 89407, 89411.

68.  EMFAC is short for EMission FACtor. The EPA approved EMFAC2017 for SIP development and transportation conformity purposes in California on August 15, 2019. 84 FR 41717. EMFAC2017 was the most recently approved version of the EMFAC model that was available at the time of preparation of the Coso Junction Second Maintenance Plan.

69.  Coso Junction Second Maintenance Plan, Appendix C, Table 6.

70.  CEPAM2016v1.05 was the most recent version of the CEPAM model available during SIP development and when the SIP was submitted in 2021. It has since been updated to CEPAM 2019 v1.03.

71.  Coso Junction Second Maintenance Plan, Table 4, “Emissions Inventory Summary for the Coso Junction PM₁₀ Planning Area.”

72.  Windblown dust from unpaved road contributes 0.29 percent (0.11 tons/day), entrained dust from vehicle travel contributes 0.16 percent (0.06 tons/day), and mobile sources contribute 0.02 percent (0.01 ton/day) of the total PM₁₀ emissions in the CJPA.

73.  The 2020 US census showed a population of 241 people living in the CJPA, approximately 1.3 percent of the 17,900 people living in Inyo County. While this number did grow from the 2010 US Census of 64 people, the population remains a small portion of Inyo County. Further population growth is also limited by the lack of land available for development.

74.  Coso Junction Second Maintenance Plan, Appendix C, Figure 2.

75.  GBUAPCD, Regulation XIII, “General Conformity,” adopted October 5, 1994.

76.  Calcagni Memo, pp. 9–11.

77.  Coso Junction Second Maintenance Plan, Section 4 and Appendix C.

78.  75 FR 36023, 36030.

79.  Rule 433 was adopted by GBUAPCD on April 13, 2016, and approved by EPA on December 28, 2016 (81 FR 95473).

80.  Coso Junction Second Maintenance Plan, Section 6.1 and Appendix D.

81.  Calcagni Memo, p. 11.

82.  AQS Site No. 06–027–1001.

83.  GBUAPCD, Rule 701, “Air Pollution Episode Plan,” adopted March 3, 2014.

84.  Calcagni Memo, p. 11.

85.  Coso Junction Second Maintenance Plan, Section 11.

86.  An exceedance of the PM₁₀ NAAQS is determined when the number of exceedances at the monitor, averaged over three years, is greater than 1.05.

87.  District Rule 433, “Control of Particulate Emissions at Owens Lake,” contains contingency measures for the Owens Valley Planning Area and provides the following: clearly identified control measures, a schedule and procedure for adoption and implementation of the measures, a time limit in which to take action, and an established threshold that triggers the contingency measures. See Coso Junction Second Maintenance Plan, Appendix D.

88.  The EPA approved District Rule 433 into the California SIP on December 27, 2016 (81 FR 95473).

89.  Table 5 in the Coso Junction Second Maintenance Plan lists existing District rules and regulations to control sources of PM_10.

90.  Control strategy SIPs refer plans that contain specific strategies for controlling the emissions of and reducing ambient levels of pollutants in order to satisfy CAA requirements for demonstrations of reasonable further progress and attainment. 40 CFR 93.101.

91.  40 CFR 93.109(g)

92.  Transportation-related emissions of VOC and NO_X must also be specified in PM₁₀ maintenance plans if the EPA or the state find that transportation-related emissions of one or both of these precursors within the nonattainment area are a significant contributor to the PM₁₀ nonattainment problem and has so notified the MPO and the U.S. Department of Transportation (DOT), or the applicable SIP (or SIP revision submission) establishes an approved (or adequate) budget for such emissions as part of the reasonable further progress, attainment, or maintenance strategy. 40 CFR 93.102(b)(2)(iii). Neither of these conditions apply to the Coso Junction PM₁₀ maintenance area.

93.  75 FR 54031.

94.  Direct emissions from vehicle exhaust tire wear and brake wear comprised this source category and accounted for 0.010 tpd of the CJPA PM₁₀ emissions inventory

95.  Coso Junction Second Maintenance Plan, p. 25.

96.  Table 6 in the Coso Junction Second Maintenance Plan provides specific breakdowns of each category.

97.  In the 2010 Maintenance Plan, on-road mobile emissions constituted less than 1 percent of the daily PM₁₀ emissions (12 of 1478 pounds of PM₁₀ per day), excluding windblown dust.

98.  According to the 2000 U.S. Census, 102 people lived in Pearsonville and Homewood Canyon, which are located at the southern end of the CJPA. The 2010 U.S. Census reported a decrease to 61 people, and the 2020 U.S. Census reports 241 people. Despite the population growth, the population still represents less than 2 percent of Inyo County's population and is not expected to have a significant effect on on-road mobile emissions.

99.  See Coso Junction Second Maintenance Plan, Section 8.4.

100.  Upon the completion of the adequacy finding, conformity can be determined without a regional emissions analysis regardless of the finalization of the rest of the items proposed in this notice.

101.  Coso Junction PM₁₀ NAA EJSCREEN Report, dated January 18, 2023.