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Federal Register / Vol. 86, No. 183 / Friday, September 24, 2021 / Proposed Rules Foundry AQS ID: 060192016, Manteca AQS ID: 060772010, and ClovisVilla AQS ID: 060195001
are sufficient nonetheless to produce a valid design value for the 1997 24-hour PM2.5 NAAQS pursuant to the rules governing design value validity in 40
CFR part 50, Appendix N, section 4.2.
We note that monitors with incomplete data in one or more quarters may still produce valid design values if the conditions for applying the EPAs data substitution test are met.281 The BakersfieldAirport Planz AQS ID:
060290016 and HanfordIrwin AQS
ID: 060311004 monitoring sites had incomplete data in the 4th quarter and 3rd quarter of 2018, respectively;
however, both sites had between 50 and 75 percent data completeness for these quarters and have valid design values after applying the maximum quarterly value data substitution test.
The Manteca monitoring site recorded data amounting to less than 75 percent completeness during the 1st, 2nd, and 3rd quarters of 2019 61 percent, 66
percent, and 67 percent, respectively due to ongoing instrument operational issues. Under Appendix N, section 4.2b data shall be considered valid, in spite of quarters with incomplete data, if the resulting annual 98th percentile value or resulting 24-hour NAAQS
design value exceeds the standard. Here, the incomplete annual 98th percentile value, 26.8 mg/m3, is well below the standard, and the resulting design value for the site, 59 mg/m3, is also below the standard. Therefore, this provision of section 4.2b does not validate the 2019
Manteca monitoring site data. Like BakersfieldAirport Planz and HanfordIrwin, the data for the Manteca site qualify for the maximum quarterly value data substitution test under 40
CFR part 50, Appendix N, section 4.2c.
However, upon applying the data substitution test to the Manteca monitoring site data, we find that the data do not pass the test i.e., after substituting the highest reported daily maximum PM2.5 value for a quarter for all missing daily data in the matching deficient quarter, the resulting test design value was above the 1997 24hour PM2.5 NAAQS. Because the data substitution test results in a test design value above the NAAQS, the Manteca monitoring site 2019 design value is considered invalid. The EPA then reviewed additional information about the monitoring network and air quality data, including historical 24-hour PM2.5
design value trends, to assess if the data collection deficiency, in the context of 281 See 40 CFR part 50, Appendix N, section 4.2b.

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data that otherwise show attainment, precludes the EPA from determining that the San Joaquin Valley area attained the 1997 24-hour PM2.5 NAAQS during the 20182020 period.
First, although the 2019 data were incomplete, the available data that were collected over a substantial amount of the year show zero exceedances of the NAAQS.
Second, the Manteca monitoring site has not historically been the 24-hour PM2.5 design value site for the San Joaquin Valley area. For example, the BakersfieldCalifornia AQS ID: 06
0290014 monitoring site was the design value site for the 24-hour PM2.5
NAAQS for 2011 to 2013, the BakersfieldAirport Planz monitoring site was the design value site in 2014, the CorcoranPatterson AQS ID: 06
0310004 monitoring site was the design value site from 2015 to 2019, and the Modesto14th Street AQS ID: 06
0990005 monitoring site was the design value site in 2020.
Third, an assessment of long-term trends at the Manteca monitoring site and nearby monitoring sites shows nearby sites have design values below the 24-hour PM2.5 NAAQS and the Manteca site typically has lower design values compared to nearby sites. For example, during the 2013 to 2020
period, the Manteca monitoring site had consistently lower design values for the 24-hour PM2.5 NAAQS than the StocktonHazelton AQS ID: 06077
1002 and Modesto14th Street monitoring sites, which are located approximately 11 miles and 18 miles, respectively, from the Manteca monitoring site. The StocktonHazelton and Modesto14th Street monitoring sites have complete annual 24-hour design values that are below the 1997
24-hour PM2.5 NAAQS after excluding monitored exceedances associated with the August 2024, 2020 wildfire exceptional event, as discussed below and provide an appropriate comparison and characterization of air quality for the areas surrounding the Manteca monitoring site. Thus, because the data that were collected provide a 98th percentile value below the standard, and the Manteca monitoring site has historically lower design value concentrations relative to the 24-hour PM2.5 NAAQS and design values at nearby locations, we find that the incomplete data should not preclude the EPA from determining that the San Joaquin Valley area has attained the 1997 24-hour PM2.5 NAAQS.
The remaining two sites, Fresno Foundry and ClovisVilla, recorded data amounting to less than 50 percent completeness during multiple quarters
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during the 20182020 period.
Specifically, the FresnoFoundry monitoring site recorded less than 50
percent data capture during all four quarters of 2018 and 2019 and the ClovisVilla monitoring site recorded less than 50 percent data capture during the 2nd and 4th quarters of 2019. Thus, the data in these quarters are not eligible for the maximum quarterly value data substitution test under the provisions in 40 CFR part 50 Appendix N, section 4.2ci, which state that if any quarter has less than 50 percent data capture, then the required test conditions are not met and the substitution test cannot be used. Additionally, the data collected at these sites did not result in an 98th percentile value or resulting 24-hour NAAQS design value that exceeds the standard under the provision of Appendix N section 4.2b. Therefore, the design values at these two sites are considered invalid. However, the EPA
reviewed historical 24-hour PM2.5
design value trends and the causes of the incomplete data in the context of data that otherwise show attainment, and found that the data collection deficiency should not preclude a determination that the San Joaquin Valley area attained the 1997 24-hour PM2.5 NAAQS during the 20182020
period.
The FresnoFoundry monitoring site began operation on January 1, 2020.
Although data completeness was 98
percent for year 2020, the data completeness requirements for the 20182020 period are not met since the site was not yet operational and thus data were not collected in 2018 and 2019. Because the incomplete data at the FresnoFoundry monitoring site is due to the site having only begun operation in 2020, the incomplete data should not preclude the EPA from determining whether the area has attained the NAAQS. Upon excluding monitored exceedances associated with the August 2024, 2020 wildfire exceptional event, as discussed below, the FresnoFoundry monitoring site has an incomplete 2020 design value of 64
mg/m3, which is below the level of the 1997 24-hour PM2.5 NAAQS.
The ClovisVilla monitoring site recorded less than 75 percent data capture during the 2nd, 3rd, and 4th quarters of 2019 48 percent, 66 percent, and 41 percent, respectively due to ongoing instrument operational issues.
Because the data substitution test under 40 CFR part 50, Appendix N, section 4.2c requires each quarter to have data completeness of at least 50 percent, the Clovis-Villa 2019 data do not qualify for the data substitution test. Like Manteca, the ClovisVilla site has not historically
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