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Federal Register / Vol. 86, No. 183 / Friday, September 24, 2021 / Proposed Rules approve the 2 to 1 NOX to PM2.5 trading ratio.
If approved, this trading ratio will replace the 9 to 1 NOX to PM2.5 trading ratio approved for the San Joaquin Valley for analysis years after 2014 for the 1997 24-hour PM2.5 NAAQS.263
Under the transportation conformity rule, once budgets are approved, they cannot be superseded by revised budgets submitted for the same CAA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 SIP revision. In other words, as a general matter, such approved budgets cannot be superseded by revised budgets found adequate, but rather only through approval of the revised budgets, unless the EPA specifies otherwise in its approval of a SIP by limiting the duration of the approval to last only until subsequently submitted budgets are found adequate.264
In the submittal letter for the 2018
PM2.5 Plan, CARB requested that we limit the duration of our approval of the budgets to the period before the effective date of the EPAs adequacy finding for any subsequently submitted budgets.265 The transportation conformity rule allows us to limit the approval of budgets.266 However, we will consider a states request to limit an approval of its budgets only if the request includes the following elements: 267
1 An acknowledgement and explanation as to why the budgets under consideration have become outdated or deficient;
2 A commitment to update the budgets as part of a comprehensive SIP
update; and 3 A request that the EPA limit the duration of its approval to the period before new budgets have been found to be adequate for transportation conformity purposes.
CARBs request includes an explanation for why the budgets have become, or will become, outdated or deficient. In short, CARB has requested that we limit the duration of the approval of the budgets in light of the EPAs approval of EMFAC2017, an updated version of the model EMFAC2014 used for the budgets in the SJV PM2.5 Plan.268 EMFAC2017
263 76

FR 69896.
CFR 93.118e1.
265 Letter dated May 9, 2019, from Richard W.
Corey, Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9, 3.
266 40 CFR 93.118e1.
267 67 FR 69139 November 15, 2002, limiting our prior approval of MVEBs in certain California SIPs.
268 On August 15, 2019, the EPA approved and announced the availability of EMFAC2017, the 264 40

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updates vehicle mix and emissions data of the previously approved version of the model, EMFAC2014.
In light of the EPAs approval of EMFAC2017, CARB explains that the budgets in the SJV PM2.5 Plan, which we are proposing to approve in todays action, will become outdated and will need to be revised using EMFAC2017.
In addition, CARB states that, without the ability to replace the budgets using the budget adequacy process, the benefits of using the updated data may not be realized for a year or more after the updated SIP with the EMFAC2017derived budgets is submitted, due to the length of the SIP approval process.
We find that CARBs explanation for limiting the duration of the approval of the budgets is appropriate and provides us with a reasonable basis for limiting the duration of the approval of the budgets.
We note that CARB has not committed to update the budgets as part of a comprehensive SIP update, but as a practical matter, CARB must submit a SIP revision that includes updated demonstrations as well as the updated budgets to meet the adequacy criteria in 40 CFR 93.118e4.269 Therefore, we do not need a specific commitment for such a plan at this time. For the reasons provided above, and in light of CARBs explanation for why the budgets will become outdated and should be replaced upon an adequacy finding for updated budgets, we propose to limit the duration of our approval of the budgets addressed in this action to the period before we find revised budgets based on EMFAC2017 to be adequate.
H. Nonattainment New Source Review Requirements Under CAA Section 189e CAA section 189e specifically requires that the control requirements applicable to major stationary sources of direct PM2.5 also apply to major stationary sources of PM2.5 precursors, except where the Administrator determines that such sources do not contribute significantly to PM2.5 levels that exceed the NAAQS in the area.270
The control requirements applicable to major stationary sources of direct PM2.5
in a Serious PM2.5 nonattainment area include, at minimum, the requirements latest update to the EMFAC model for use by the State and local governments to meet CAA
requirements. 84 FR 41717.
269 Under 40 CFR 93.118e4, the EPA will not find a budget in a submitted SIP to be adequate unless, among other criteria, the budgets, when considered together with all other emissions sources, are consistent with applicable requirements for RFP and attainment. 40 CFR
93.118e4iv.
270 General Preamble, 13539 and 1354113542.

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of a nonattainment NSR permit program meeting the requirements of CAA
sections 172c5 and 189b3. As part of our April 7, 2015 final action to reclassify the San Joaquin Valley area as Serious nonattainment for the 1997
PM2.5 standards, we established a May 7, 2016 deadline for the State to submit nonattainment NSR SIP revisions addressing the requirements of CAA
sections 189b3 and 189e of the Act for the 1997 PM2.5 NAAQS.271
California submitted nonattainment NSR SIP revisions to address the subpart 4 requirements for the San Joaquin Valley Serious PM2.5
nonattainment area on November 20, 2019.272 We are not proposing any action on this submission at this time.
We will act on this submission through a separate rulemaking, as appropriate.
V. Determination of Attainment by the Attainment Date A. Requirements for Attainment Determinations Sections 179c1 and 188b2 of the CAA require the EPA to determine whether a state with a PM2.5
nonattainment area attained the applicable PM2.5 NAAQS by the applicable attainment date, based on the areas air quality as of the attainment date. A determination of whether an areas air quality currently meets the PM2.5 NAAQS is generally based upon the most recent three years of complete, quality-assured data gathered at established State and Local Air Monitoring Stations SLAMS in a nonattainment area and entered into the EPAs Air Quality System AQS
database. Data from ambient air monitors operated by state/local agencies in compliance with the EPA
monitoring requirements must be submitted to AQS. 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 areas.273 The EPA
reviews all data to determine the areas air quality status in accordance with 40
CFR part 50, Appendix N.
Under EPA regulations in 40 CFR 50.7
and in accordance with Appendix N, the 1997 24-hour PM2.5 NAAQS are met when the design value is less than or equal to 65 mg/m3 based on the rounding convention in 40 CFR part 50, 271 80

FR 18528, 18533.
dated November 15, 2019, from Richard W. Corey, Executive Officer, CARB, to Michael Stoker, Regional Administrator, EPA Region IX.
273 See 40 CFR 50.7; 40 CFR part 50, Appendix L; 40 CFR part 53; 40 CFR part 58, and 40 CFR part 58, appendices A, C, D, and E.
272 Letter
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