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Federal Register / Vol. 86, No. 183 / Friday, September 24, 2021 / Proposed Rules Third, the EPA must find that the emissions reductions that are relied on for attainment in the SIP submission are creditable. As discussed in section IV.C.2.a, the SJV PM2.5 Plan relies principally on rules that have already been adopted and approved by the EPA
to achieve the emissions reductions needed to attain the 1997 24-hour PM2.5
NAAQS in the San Joaquin Valley. We present our evaluation of the rules in section IV.C.2.a and in sections II and III
of the EPAs 1997 24-hour PM2.5 TSD.
We find that all but two of these rules are SIP-creditable and that the total emissions reductions attributed to the two measures that are not SIP-creditable have de minimis impacts on the attainment demonstration in the Plan.
The EPA has also reviewed ambient monitoring data recorded at air quality monitors throughout the San Joaquin Valley PM2.5 nonattainment area during the three years leading up to the projected December 31, 2020 attainment date i.e., 20182020. As discussed in section V of this proposal, based on these data, we are proposing to find that the San Joaquin Valley area attained the 1997 24-hour PM2.5 NAAQS by the December 31, 2020 attainment date.
Based on these evaluations, we propose to determine that the SJV PM2.5
Plan provides for attainment of the 1997
24-hour PM2.5 NAAQS by the most expeditious date practicable, consistent with the requirements of CAA section 189d. Furthermore, because the 2015
Serious area attainment date has passed, and the EPA found that the area failed to attain by the Serious area attainment date, we are evaluating the States compliance with the Serious area plan requirements in light of the attainment date required under CAA section 189d.189 Thus, we are also proposing to determine that the Plan meets the Serious area attainment plan requirement under CAA section 189b1A.
E. Reasonable Further Progress and Quantitative Milestones 1. Statutory and Regulatory Requirements CAA section 172c2 provides that all nonattainment area plans shall require RFP toward attainment. In addition, CAA section 189c requires that all PM2.5 nonattainment area SIPs include quantitative milestones to be achieved every three years until the area is redesignated to attainment and that demonstrate RFP. Section 171l of the Act defines RFP as such annual incremental reductions in emissions of
the relevant air pollutant as are required by Part D or may reasonably be required by the Administrator for the purpose of ensuring attainment of the applicable NAAQS by the applicable date. Neither subpart 1 nor subpart 4
of part D, title I of the Act requires that states achieve a set percentage of emissions reductions in any given year for purposes of satisfying the RFP
requirement. For purposes of the PM2.5
NAAQS, the EPA has interpreted the RFP requirement to require that the nonattainment area plans show annual incremental emissions reductions sufficient to maintain generally linear progress toward attainment by the applicable deadline.190
Attainment plans for PM2.5
nonattainment areas should include detailed schedules for compliance with emissions regulations in the area and provide corresponding annual emissions reductions to be achieved by each milestone in the schedule.191 In reviewing an attainment plan under subpart 4, the EPA considers whether the annual incremental emissions reductions to be achieved are reasonable in light of the statutory objective of timely attainment. Although early implementation of the most costeffective control measures is often appropriate, states should consider both cost-effectiveness and pollution reduction effectiveness when developing implementation schedules for control measures and may implement measures that are more effective at reducing PM2.5 earlier to provide greater public health benefits.192
The PM2.5 SIP Requirements Rule establishes specific regulatory requirements for purposes of satisfying the Acts RFP requirements and provides related guidance in the preamble to the rule. Specifically, under the PM2.5 SIP Requirements Rule, each PM2.5 attainment plan must contain an RFP analysis that includes, at minimum, the following four components: 1 An implementation schedule for control measures; 2 RFP projected emissions for direct PM2.5 and all PM2.5 plan precursors for each applicable milestone year, based on the anticipated control measure implementation schedule; 3 a demonstration that the control strategy and implementation schedule will achieve reasonable progress toward attainment between the base year and the attainment year; and 4 a demonstration that by the end of the calendar year for each milestone date for 190 General 191 Id.

189 See
CAA section 179d; 40 CFR 51.1004a3.

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the area, pollutant emissions will be at levels that reflect either generally linear progress or stepwise progress in reducing emissions on an annual basis between the base year and the attainment year.193 Additionally, states should estimate the RFP projected emissions for each quantitative milestone year by sector on a pollutantby-pollutant basis.194
Section 189c of the Act requires that PM2.5 attainment plans include quantitative milestones that demonstrate RFP. The purpose of the quantitative milestones is to allow periodic evaluation of the areas progress towards attainment of the NAAQS consistent with RFP
requirements. Because RFP is an annual emissions reduction requirement and the quantitative milestones are to be achieved every three years, when a state demonstrates compliance with the quantitative milestone requirement, it should also demonstrate that RFP has been achieved during each of the relevant three years. Quantitative milestones should provide an objective means to evaluate progress toward attainment meaningfully, e.g., through imposition of emissions controls in the attainment plan and the requirement to quantify those required emissions reductions. The CAA also requires states to submit milestone reports due 90
days after each milestone, and these reports should include calculations and any assumptions made by the state concerning how RFP has been met, e.g., through quantification of emissions reductions to date.195
The CAA does not specify the starting point for counting the three-year periods for quantitative milestones under CAA
section 189c. In the General Preamble and General Preamble Addendum, the EPA interpreted the CAA to require that the starting point for the first three-year period be the due date for the Moderate area plan submission.196 In keeping with this historical approach, the EPA
established December 31, 2014, the deadline that the EPA established for a states submission of any additional attainment-related SIP elements necessary to satisfy the subpart 4
Moderate area requirements for the 1997
PM2.5 NAAQS, as the starting point for the first three-year period under CAA
section 189c for the 1997 PM2.5
NAAQS in the San Joaquin Valley.197
193 40

CFR 51.1012a.
FR 58010, 58056.
195 General Preamble Addendum, 4201642017.
196 General Preamble, 13539, and General Preamble Addendum, 42016.
197 79 FR 31566 final rule establishing subpart 4
moderate area classifications and deadline for 194 81

192 Id.

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