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Federal Register / Vol. 86, No. 120 / Friday, June 25, 2021 / Rules and Regulations
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satisfy the general RFP requirements of section 172c2 for the time period discussed.16
We agree with CBD that the EPA has adapted the RFP requirements under the CAA to implement the three 8-houraverage ozone NAAQS that have been promulgated since the 1990 CAA
Amendments. In the Phase 2 SIP
Requirements Rule 17 for the 1997
Ozone NAAQS Phase 2 rule, the Agency adapted the RFP requirements of CAA sections 172c2 and 182a1
so as to require plans to provide for the minimum required percent reductions and, for certain Moderate areas, to provide for the reductions as necessary for attainment. See, e.g., 40 CFR
51.910a1iiA and b2iiC.
In 2015, the EPA replaced the regulations promulgated through the Phase 2 rule with the regulations promulgated through the 2008 Ozone SIP Requirements Rule SRR.18 In the 2008 Ozone SRR, the EPA established RFP requirements for the 2008 ozone NAAQS that are similar, in most respects, to those in the Phase 2 rule for the 1997 ozone NAAQS but that do not carry forward the aspect of the RFP
requirement for the 1997 ozone NAAQS
that defined RFP for certain years for certain Moderate areas in terms of the reductions needed for attainment.19
More explicitly, in the 2008 Ozone SRR, the EPA defined RFP as meaning both the emissions reductions required under CAA section 172c2 which the EPA interprets to be an average 3
percent per year emissions reductions of either VOC or NOX and CAA sections 182c2B and c2C and the 15
percent reductions over the first six years of the plan and the following three percent per year average under 40 CFR
51.1110. 20 emphasis added. Thus, under the 2008 Ozone SRR, the RFP
emissions reductions required for Serious and above ozone nonattainment areas under CAA section 172c2 are based on a set annual percentage found in the CAA, not on the specific attainment needs for the area. In this regard, we have been even more explicit in our SRR for the 2015 ozone NAAQS: 21 Reasonable further progress 16 57 FR 13498, at 13510 Moderate areas and at 13518 Serious areas April 16, 1992.
17 70 FR 71612 November 29, 2005.
18 80 FR 12264 March 6, 2015. Under 40 CFR
51.919 and 51.1119, the regulations promulgated through the 2008 Ozone SRR replaced the regulations promulgated through the Phase 2 rule, with certain exceptions not relevant here.
19 Compare the RFP requirements for the 1997
ozone NAAQS at 40 CFR 51.910a1iiA and b2iiC with the analogous provisions for the 2008 ozone NAAQS at 40 CFR 51.1110a2iB.
20 40 CFR 51.1100t.
21 83 FR 62998 December 6, 2018.

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RFP means the emissions reductions required under CAA sections 172c2, 182c2B, 182c2C, and 51.1310.
The EPA interprets RFP under CAA
section 172c2 to be an average 3
percent per year emissions reduction of either VOC or NOX. 22
In the 2008 Ozone SRR, which is the set of regulations that governs the EPAs action here, RFP is defined in terms of percent reduction requirements, not in terms of the reductions necessary for attainment. In other words, for the 2008
ozone NAAQS, the RFP targets represent the minimum progress that is required under the CAA and our regulations, not necessarily all of the reductions necessary to achieve attainment of the ozone NAAQS, which could vary largely from one nonattainment area to another.
Eastern Kern is a Serious nonattainment area for the 2008 ozone NAAQS, and the RFP demonstration in the 2017 Eastern Kern Ozone SIP was developed to meet the applicable requirements of the CAA and our 2008
Ozone SRR, not the Phase 2 rule for the 1997 ozone NAAQS. Specifically, we reviewed the RFP demonstration in the 2017 Eastern Kern Ozone SIP for compliance with the requirements under 40 CFR 51.1110a2i, which adapts the requirements under CAA
sections 172c2 and 182b1 for Moderate areas, and 40 CFR
51.1110a2ii, which adapts the requirements of CAA section 182c2B for Serious areas.23 The requirements under 40 CFR
51.1110a2i and 40 CFR
51.1110a2ii are cumulative and, together, they require a 15 percent emission reduction from the baseline year within 6 years after the baseline year and an average emissions reduction of 3 percent per year for all remaining 3-year periods after the first 6-year period until the year of the areas attainment date. As explained further in our proposed rule, based on our evaluation, we found that the 2017
Eastern Kern Ozone SIP provided for the percent reductions required under the 2008 Ozone SRR.24
Importantly, under the 2008 Ozone SRR, the RFP demonstration for the 2008 ozone NAAQS does not need to provide for the reductions needed for attainment. Thus, contrary to CBDs assertion, the RFP demonstration for Eastern Kern can be severed from the attainment demonstration and control 22 40

CFR 51.1300l.
23 40 CFR 51.1110a2 applies to Eastern Kern because Eastern Kern is an area with an approved 1-hour ozone NAAQS 15 percent VOC Rate of Progress ROP plan.
24 85 FR 68268, at 6827468276.

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strategy and can be independently approved, and we do so in this final rule by taking final action to approve the RFP demonstration in the 2017 Eastern Kern Ozone SIP while deferring action on the attainment demonstration.
Comment 2: CBD comments that the submittal fails to show that the substitute NOX emissions reductions will result in a reduction in ozone concentrations at least equivalent to the required three percent per annum VOC emissions reductions, and as a result, the EPAs proposed approval of the RFP demonstration is arbitrary and capricious.
The commenter describes the relative roles of VOC and NOX in ozone formation, including the existence of an optimum VOC to NOX ratio for a given level of VOC i.e., a NOX
concentration at which the maximum amount of ozone is produced. As explained by the commenter, in a NOX
saturated situation where NOX levels exceed this optimum ratio, a reduction in NOX emissions can lead to increases in ozone levels, whereas in a NOX
limited situation with NOX levels below the optimum ratio, a reduction in NOX emissions decreases ozone levels.
The commenter quotes the EPAs report to Congress as including, ozone response to precursor control can vary greatly with each area and the relative effectiveness of controls of volatile organic compounds VOCs and oxides of nitrogen NOX in ozone abatement varies widely. 25 The commenter argues that language in the CAA, including CAA sections 185B, 182f, and 182c2C, indicates that Congress was aware of the issue of the relative roles of NOX and VOC in ozone formation, including that in some scenarios NOX reductions may actually increase ozone concentrations or at least not help to reduce ozone concentrations.
The commenter then points to the EPAs consideration of the relative effectiveness of NOX and VOC controls for interpollutant offset trading under the new source review NSR permitting program and in applying requirements for major stationary sources of VOC to NOX sources under CAA section 182f, noting that in these situations EPA
guidance indicates that photochemical grid modeling of multiple scenarios should be conducted to support demonstrations related to the relative 25 Excerpt from CBD comments see page 10
citing The Role of Ozone Precursors in Tropospheric Ozone Formation and Control: A
Report to Congress, EPA454/R93024, at 22
July 1993, EPA Office of Air Quality Planning and Standards report to Congress mandated by section 185B, 42 U.S.C. 7511f.

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