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Federal Register / Vol. 86, No. 167 / Wednesday, September 1, 2021 / Proposed Rules
khammond on DSKJM1Z7X2PROD with PROPOSALS2

adequacy, prior to taking action on the plan itself, and did so with respect to the PM2.5 budgets in the 2018 PM2.5
Plan. On June 18, 2019, the EPA
announced the availability of the 2018
PM2.5 Plan with MVEBs and a 30-day public comment period. This announcement was posted on the EPAs adequacy website at: https
www.epa.gov/state-and-localtransportation/state-implementationplans-sip-submissions-currently-underepa. The comment period for this notification ended on July 18, 2019. We did not receive any comments during this comment period.
The 2018 PM2.5 Plan establishes budgets for the 2022 RFP milestone year for direct PM2.5 and NOX, but not for the other PM2.5 precursor emissions i.e., VOC, SO2, and ammonia. We propose to find that it is not necessary to establish motor vehicle emissions budgets for transportation-related emissions of VOC, SO2, and ammonia to attain the 2012 annual PM2.5 NAAQS in the SJV based on our proposal to approve the States demonstration that emissions of VOC, SO2, and ammonia do not contribute significantly to PM2.5
levels that exceed the 2012 PM2.5
NAAQS in the SJV, as discussed in section IV.B of this proposed rule. Our finding in this regard is also supported by information about VOC, SO2, and ammonia in the 2018 PM2.5 Plan documenting the small contribution by motor vehicles to regional precursor inventories and to PM2.5 design values within the SJV.233 In addition, based on similar documentation about reentrained road dust and constructionrelated fugitive dust in the 2018 PM2.5
Plan and in accordance with 40 CFR
93.102b3 and 93.122f, the EPA
proposes to find that it is not necessary to include re-entrained road dust emissions or road construction dust in the direct PM2.5 budgets for 2012 PM2.5
NAAQS in the SJV.234
For the reasons discussed in sections IV.G of this proposed rule, the EPA
proposes to approve the RFP
demonstration in the 2018 PM2.5 Plan.
233 2018 PM
2.5 Plan, App. D. pages D121, D122
and D123. Motor vehicle emissions of VOC
represent approximately 10% of the total VOC
emissions in the SJV, but VOC controls are generally ineffective at reducing ambient PM2.5
levels. Motor vehicle emissions of SO2 are less than one tpd, and motor vehicle emissions of ammonia represent approximately 1% of total ammonia emissions in the SJV.
234 Id. Paved and unpaved road dust emissions represent less than 17% of the total PM2.5 emissions in the SJV but contribute only approximately 4%
to the design values. Construction dust emissions are less than 5% of the total PM2.5 emissions in the SJV. In addition, the 2018 PM2.5 Plan does not include additional control measures for these sources.

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The 2022 RFP budgets, as shown in Table 6 of this proposed rule, are consistent with this demonstration, are clearly identified and precisely quantified, and meet all other applicable statutory and regulatory requirements including the adequacy criteria in 40
CFR 93.118e4 and 5. For these reasons, the EPA proposes to approve the budgets listed in Table 6. We provide a more detailed discussion in the EPAs memo to file regarding MVEB.235 We are not proposing to approve the 2018 PM2.5 Plans budgets that pertain solely to the Serious area time frame i.e., 2025 attainment year budget or the post-attainment year 2028
budget for the 2012 PM2.5 NAAQS at this time. The budgets that the EPA is proposing to approve relate to the 2012
annual PM2.5 NAAQS only, and our proposed approval does not affect the status of the previously-approved MVEBs for the 1997 annual and 24-hour PM2.5 NAAQS and 2006 24-hour PM2.5
NAAQS and related trading mechanisms that remain in effect for that PM2.5 NAAQS.
As noted above, the State included a trading mechanism to be used in transportation conformity analyses that would be used in conjunction with the budgets in the 2018 PM2.5 Plan, as allowed for under 40 CFR 93.124b.
Furthermore, the trading ratio in the 2018 PM2.5 Plan is based on updated air quality modeling and analysis relative to the analysis that the 2016 PM2.5 Plan relies on i.e., analysis and trading ratio in the 2008 PM2.5 Plan for the 1997
PM2.5 NAAQS. The trading mechanism in the 2018 PM2.5 Plan would allow future decreases in annual NOX
emissions from on-road mobile sources to offset any on-road increases in annual direct PM2.5 emissions using a 6.5:1
NOX:PM2.5 ratio for conformity for the 2012 annual PM2.5 NAAQS. To ensure that the trading mechanism does not affect the ability to meet the NOX
budget, the plan provides that the NOX
emission reductions available to supplement the PM2.5 budget would only be those remaining after the NOX
budget has been met. The SJV MPOs will have to document clearly the calculations used in the trading when demonstrating conformity, along with any additional reductions of NOX and PM2.5 emissions in the conformity analysis. The trading calculations must be performed prior to the final rounding
to demonstrate conformity with the budgets.
The EPA has reviewed the trading mechanism as described on pages D
125 through D127 in Appendix D of the 2018 PM2.5 Plan and finds it is appropriate for transportation conformity purposes in the SJV for the 2012 annual PM2.5 NAAQS. The methodology for estimating the trading ratio for conformity purposes is essentially an update based on newer modeling of the approach that the EPA
previously approved for the 2008 PM2.5
Plan for the 1997 PM2.5 NAAQS 236 and the 2012 PM2.5 Plan for the 2006 24hour PM2.5 NAAQS.237 The States approach in the previous plans was to model the ambient PM2.5 effect of areawide NOX emissions reductions and of areawide direct PM2.5 reductions, and to express the ratio of these modeled sensitivities as an interpollutant trading ratio.
In the updated analysis for the 2018
PM2.5 Plan, the State completed separate sensitivity analyses for the annual and 24-hour standards and modeled only transportation-related sources in the nonattainment area. The ratio the State is proposing to use for transportation conformity purposes is derived from air quality modeling that evaluated the effect of reductions in transportationrelated NOX and PM2.5 emissions in the SJV on ambient concentrations at the Bakersfield-California Avenue, Bakersfield-Planz, Fresno-Garland, and Fresno-Hamilton & Winery monitoring sites. The modeling that the State performed to evaluate the effectiveness of NOX and PM2.5 reductions on ambient 24-hour concentrations showed NOX:PM2.5 ratios that range from a high of 7.1 at the Bakersfield-California Avenue monitor to a low of 6.0 at the two Fresno monitors.238 We find that the States approach is a reasonable method to use to develop ratios for transportation conformity purposes. We therefore propose to approve the 6.5:1
NOX for PM2.5 trading mechanism as enforceable components of the transportation conformity program for the SJV for the 2012 annual PM2.5
NAAQS.
Under the transportation conformity rule, once budgets are approved, they cannot be superseded by revised budgets submitted for the same CAA
purpose and the same years addressed by the previously approved SIP until the EPA approves the revised budgets as a
235 Memorandum of July 30, 2021, from Rory Mays and Karina OConnor, Air Planning Office, Air and Radiation Division, Region IX, EPA, EPA
Review of 2018 PM2.5 Plan Transportation Conformity Emission Budgets for the 2012 Annual PM2.5 NAAQS Moderate Area Requirements.

236 80 FR 1816, 1841 January 13, 2015 noting the EPAs prior approval of MVEBs for the 1997
annual and 24-hour PM2.5 standards in the 2008
PM2.5 Plan at 76 FR 69896.
237 81 FR 59876 August 31, 2016.
238 2018 PM
2.5 Plan, App. D, D126.

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