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Federal Register / Vol. 86, No. 120 / Friday, June 25, 2021 / Rules and Regulations
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reductions as to VOC reductions on a percentage basis.
In addition, the 2007 Ozone Plan for San Joaquin Valley included isopleth diagrams for every monitoring site, including those in Kern County, just upwind of Eastern Kern.47 The State used photochemical modeling to assess the effect of NOX and VOC emissions reductions for projected years 2020 and 2023 at every site. For every location for both years, NOX emissions reductions were more effective than VOC at reducing ozone. For example, the projected 2020 8-hour ozone design value at the Bakersfield-California Avenue site was modeled to decrease from 87 to 86 ppb when VOC is reduced by 20 percent, and from 87 to 83 ppb when NOX is reduced by 20 percent.
The corresponding values for 2023 are a decrease from 88 to 87 ppb for VOC, and a decrease from 88 to 84 ppb for NOX.48 This is additional evidence that NOX reductions are more effective than VOC reductions in Eastern Kern.
Air quality in the Eastern Kern nonattainment area is also strongly affected by ozone transport from the SCAB through the Soledad Canyon located between Santa Clarita in the SCAB and Palmdale, south of Eastern Kern.49 Santa Clarita is approximately 65 miles from the Mojave monitor and approximately 50 miles from the southern boundary of the nonattainment area. In the South Coast Air Quality Management Districts SCAQMDs Final 2016 Air Quality Management Plan South Coast 2016 AQMP, SCAQMD included an isopleth for the Santa Clarita monitoring site.50 The isopleths for the Santa Clarita site clearly show that NOX reductions in the area upwind of Eastern Kern are more effective than VOC reductions at reducing ozone.
The documentation associated with the Clovis and Santa Clarita monitors, representative locations in the SJV and SCAB upwind of the mountain passes through which ozone is transported to downwind Eastern Kern, demonstrates that NOX reductions are more effective than VOC reductions in the Eastern Kern nonattainment area. This further supports the conclusion that NOX
substitution results in a reduction in 47 San Joaquin Valley Unified Air Pollution Control District, 2007 Ozone Plan, April 30, 2007.
The EPA approved the 2007 Ozone Plan at 77 FR
12652 March 1, 2012.
48 Id. in Appendix F. Photochemical Modeling Support Documents, F15F58.
49 Eastern Kern 2017 Ozone Plan, Appendix F, F
15.
50 South Coast 2016 AQMP, Appendix V, Attachment 4 2031 8-Hour Ozone Isopleths, 21;
and Attachment 5 2023 8-Hour Ozone Isopleths, 21.

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ozone concentrations at least equivalent to that which would result from the amount of VOC emission reductions otherwise required for RFP. Even though the States submittal lacks an isopleth diagram specifically for the Mojave site in Eastern Kern, the supporting documentation i.e., Figure 14; the comparison of Eastern Kern emissions with emissions from western Kern County and Los Angeles County;
VOC emissions from biogenic sources;
and isopleths from upwind sites in the SJV and SCAB demonstrates that the resulting NOX reductions here will be at least equivalent to that which would result from VOC reductions alone, as required in section 182c2C.
Based on the above, we disagree with the commenters assertion that CAA
section 182c2C requires the District to provide additional photochemical grid modeling to demonstrate that the substituted NOX reductions are at least as effective as the VOC reductions that would otherwise be required under section 182c2B.
Further, we believe that the commenters comparison to the EPAs recommendations with respect to interpollutant trading for nonattainment NSR permitting purposes and eligibility for an exemption from NOX
requirements under CAA 182f are not relevant for NOX substitution under CAA section 182c2C. The guidance documents cited by the commenter for these examples are non-binding and do not constrain the EPAs discretion to adopt a different approach where appropriate.51 The documents recommend photochemical grid modeling in some scenarios but do not require this approach or any other specific demonstration. This reflects the EPAs acknowledgement that the level of analysis required for any particular demonstration related to NOX and VOC
reductions will differ based on context and local conditions, such as those noted by the commenter regarding the relative effectiveness of controlling each. In the context of CAA 182c2C
and based on the EPAs responses 51 See EPA, Guideline for Determining the Applicability of Nitrogen Oxide Requirements under Section 182f December 16, 1993, 1;
Memorandum dated January 14, 2005, from Stephen D. Page, Director, Office of Air Quality Planning and Standards, U.S. EPA, to EPA Regional Air Directors, Regions IX, Subject: Guidance on Limiting Nitrogen Oxides NOX Requirements Related to 8-Hour Ozone Implementation, 3; EPA
454/R18004, Technical Guidance for Demonstration of Inter-Precursor Trading IPT for Ozone in the Nonattainment New Source Review Program, Office of Air Quality Planning and Standards May 2018 IPT Guidance, 2. The IPT
Guidance specifically excludes applicability to RFP
demonstrations. IPT Guidance at 2, n.1.

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herein, no additional modeling or demonstration is required.
Comment 3: The commenter also contends that an equivalence demonstration under CAA section 182c2C must show equivalence throughout the nonattainment area, must be quantitative, and must be as technically rigorous as an attainment demonstration.
First, the commenter states that because CAA section 182c2C uses the plural ozone concentrations, the equivalency demonstration must show equivalence throughout the nonattainment area, and not just at a single monitoring site. Otherwise, there could be ozone increases in NOXsaturated areas within the nonattainment area that might interfere with attainment of the more stringent 2015 ozone NAAQS, and that might result in adverse public health effects even for locations meeting the ozone NAAQS because there is no safe level of ozone.
Second, the commenter criticizes the technical information in the Eastern Kern 2017 Ozone Plan as insufficient to show that NOX substitution will result in equivalent reductions in ozone concentrations throughout the nonattainment area. The commenter states that the Eastern Kern 2017 Ozone Plan submittal documents the ozone decrease from weekend NOX reductions at a single Mojave monitor during 2000
2015 to conclude the area is NOXlimited, and that it makes general observations about the magnitude and distance of emissions. The commenter states that the technical information in the Eastern Kern 2017 Ozone Plan is merely qualitative, whereas the word equivalent in CAA section 182c2C means that the demonstration should be quantitative.
The commenter also states that the 2017
Eastern Kern Ozone SIP should consider post-2015 data, because of post-2015
emissions changes like the replacement of NOX combustion sources with wind and solar electricity generation, and because of the changing geographic distribution of emissions.
Lastly, the commenter states that an equivalence demonstration should be as rigorous as an attainment demonstration, which is based on photochemical modeling or another equally rigorous technique. The commenter suggests that the state could compare modeled relative response factors RRFs for each RFP milestone year for the 3 percent per year VOC
reductions to corresponding factors from the control strategy. Alternatively, for the demonstration, the commenter suggests that the state could use ozone
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