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Federal Register / Vol. 86, No. 183 / Friday, September 24, 2021 / Proposed Rules
only be those remaining after the NOX
budget has been met.257 The Plan also provides that the San Joaquin Valley MPOs shall clearly document the calculations used in the trading, along with any additional reductions of NOX
and PM2.5 emissions in the conformity analysis.
3. The EPAs Review of the States Submission The EPA generally first conducts a preliminary review of budgets submitted with an attainment or maintenance plan for PM2.5 for 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.
Based on our proposal to approve the States demonstration that emissions of ammonia, SO2, and VOCs do not contribute significantly to PM2.5 levels that exceed the 1997 24-hour PM2.5
NAAQS in the San Joaquin Valley, as discussed in section IV.B of this proposal, and the information about ammonia, SO2, and VOC emissions in the Plan, the EPA proposes to find that it is not necessary to establish motor vehicle emissions budgets for transportation-related emissions of ammonia, SO2, and VOC to attain the 1997 24-hour PM2.5 NAAQS in the San Joaquin Valley. Based on the information about re-entrained road dust in the Plan and in accordance with 40 CFR 93.102b3, the EPA proposes to find that it is not necessary to include re-entrained road dust emissions in the budgets for 1997 24-hour PM2.5 NAAQS
in the San Joaquin Valley.
For the reasons discussed in sections IV.D and IV.E of this proposed rule, the EPA is proposing to approve the attainment and RFP demonstrations, respectively, in the SJV PM2.5 Plan. The 2017 RFP and 2020 attainment year budgets, as shown in Table 8 of this preamble, are consistent with these demonstrations, are clearly identified and precisely quantified, and meet all other applicable statutory and regulatory requirements including the 257 2018

PM2.5 Plan, Appendix D, D126 and D

127.

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adequacy criteria in 40 CFR
93.118e4. For these reasons, the EPA
proposes to approve the 2017 and 2020
budgets listed in Table 8.258 We provide a more detailed discussion in section IV
of the EPAs 1997 24-hour PM2.5 TSD.
The budgets that the EPA is proposing to approve relate only to the 1997 24hour PM2.5 NAAQS, and our proposed approval does not affect the status of the budgets for the 1997 annual PM2.5
NAAQS or the previously-approved MVEBs for the 2006 PM2.5 NAAQS and related trading mechanism, which remain in effect for that PM2.5 NAAQS.
Although the post-attainment year quantitative milestone is a required element of the Serious area plan, it is not necessary to demonstrate transportation conformity for 2023 or to use the 2023 budgets in transportation conformity determinations until such time as the area fails to attain the 1997
24-hour PM2.5 NAAQS. As discussed in section V of this document, the EPA is proposing to find that the San Joaquin Valley area has attained the 1997 24hour PM2.5 NAAQS. The EPA does not believe that it is necessary to demonstrate conformity using postattainment year budgets in areas that attain by the attainment date. Therefore, if the EPA finalizes the determination that the San Joaquin Valley area attained by the December 31, 2020 attainment date, the requirement for postattainment year budgets will no longer apply in the area for the 1997 24-hour 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.
This trading mechanism would allow future decreases in NOX emissions from on-road mobile sources to offset any onroad increases in PM2.5, using a 2 to 1
NOX to PM2.5 ratio for the 1997 24-hour 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 emissions reductions available to supplement the PM2.5 budget would only be those remaining after the NOX budget has been met. The San Joaquin Valley 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 258 Although we are proposing to approve the 2017 budgets, we note that these budgets would not be used in any future transportation conformity determinations because the Plan contains budgets for 2020.

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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 to D127 in Appendix D of the 2018
PM2.5 Plan and finds it is appropriate for transportation conformity purposes in the San Joaquin Valley for the 1997 24hour 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 259 and the 2012
PM2.5 Plan for the 2006 24-hour PM2.5
NAAQS.260 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 emissions reductions, and to express the ratio of these modeled sensitivities as an inter-pollutant trading ratio.
In the updated analysis for the 2018
PM2.5 plan, the State completed separate sensitivity analyses for the annual and 24-hour NAAQS 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 San Joaquin Valley on ambient concentrations at the BakersfieldCalifornia 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 to PM2.5
ratios that range from a high of 2.3 at the Bakersfield-California Avenue monitor to a low of 1.6 at the Fresno-Hamilton & Winery monitor.261 In our July 22, 2020 action on the 2018 PM2.5 Plan for the 2006 PM2.5 NAAQS, we found that the States approach is a reasonable method to use to develop ratios for transportation conformity purposes and approved the 2 to 1 NOX to PM2.5
trading mechanism as an enforceable component of the transportation conformity program for the San Joaquin Valley for the 2006 PM2.5 NAAQS.262
Here, we similarly find that the States approach is reasonable and propose to 259 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.
260 81 FR 59876 August 31, 2016.
261 2018 PM
2.5 Plan, Appendix D, D126.
262 85 FR 44192.

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