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Federal Register / Vol. 86, No. 131 / Tuesday, July 13, 2021 / Proposed Rules
175Ab.3 However, in South Coast Air Quality Management District v. EPA 4
South Coast II, the United States Court of Appeals for the District of Columbia D.C. Circuit vacated EPAs interpretation that, because of the revocation of the 1997 ozone standard, second maintenance plans were not required for orphan maintenance areas, i.e., areas like the Greene County Area that had been redesignated to attainment for the 1997
ozone NAAQS and were designated attainment for the 2008 ozone NAAQS.
Thus, states with these orphan maintenance areas under the 1997
ozone NAAQS must submit maintenance plans for the second maintenance period.
As previously discussed, CAA section 175A sets forth the criteria for adequate maintenance plans. In addition, EPA
has published longstanding guidance that provides further insight on the content of an approvable maintenance plan, explaining that a maintenance plan should address five elements: 1
An attainment emissions inventory; 2
a maintenance demonstration; 3 a commitment for continued air quality monitoring; 4 a process for verification of continued attainment; and 5 a contingency plan. The 1992 Calcagni Memo 5 provides that states may generally demonstrate maintenance by either performing air quality modeling to show that the future mix of sources and emission rates will not cause a violation of the NAAQS or by showing that future emissions of a pollutant and its precursors will not exceed the level of emissions during a year when the area was attaining the NAAQS i.e., attainment year inventory. See 1992
Calcagni Memo at p. 9. EPA further clarified in three subsequent guidance memos describing limited maintenance plans LMPs 6 that the requirements of CAA section 175A could be met by demonstrating that the areas design value 7 was well below the NAAQS and 3 See
80 FR 12315 March 6, 2015.
F.3d 1138 D.C. Cir. 2018.
5 Procedures for Processing Requests to Redesignate Areas to Attainment, Memorandum from John Calcagni, Director, Air Quality Management Division, September 4, 1992 1992
Calcagni Memo.
6 See Limited Maintenance Plan Option for Nonclassifiable Ozone Nonattainment Areas from Sally L. Shaver, Office of Air Quality Planning and Standards OAQPS, dated November 16, 1994;
Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment Areas from Joseph Paisie, OAQPS, dated October 6, 1995; and Limited Maintenance Plan Option for Moderate PM10 Nonattainment Areas from Lydia Wegman, OAQPS, dated August 9, 2001.
7 The ozone design value for a monitoring site is the 3-year average of the annual fourth-highest daily maximum
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that the historical stability of the areas air quality levels showed that the area was unlikely to violate the NAAQS in the future. Specifically, EPA believes that if the most recent air quality design value for the area is at a level that is below 85% of the standard, or in this case below 0.071 ppm, then EPA
considers the state to have met the section 175A requirement for a demonstration that the area will maintain the NAAQS for the requisite period. Accordingly, on February 25, 2020, PADEP submitted an LMP for the Greene County Area, following EPAs LMP guidance and demonstrating that the area will maintain the 1997 ozone NAAQS through April 20, 2029, i.e., through the entire 20-year maintenance period.
After PADEPs submittal of this LMP, it was determined that the most current certified design value period 2017
2019 was invalid due to incomplete data. PADEP operates and maintains one ozone monitor at the Holbrook ambient air monitoring station AQS ID
420590002 in Greene County, PA.
During the 2018 and 2019 ozone monitoring seasons, the Holbrook ambient air monitoring station had missing ozone data for 35 and 39 days, respectively. The Holbrook ozone data was missing for a total of 74 days in the two-year span because of several reasons, including power outages and quality assurance criteria not being met.
As a result of the frequency of missing data, the total valid ozone data capture at the Holbrook monitoring site was 86% in 2018 and 84% in 2019. With an ozone data capture of 93% in 2017, the three-year 20172019 average was 88%. According to 40 CFR part 50
appendix P, section 2.3b, three consecutive years of ambient air ozone data with data availability of at least 90% of the days within the ozone monitoring season, on average, are required, with a minimum data completeness in any one year of at least 75% within the ozone monitoring season. Since the 2019 ozone design value average data completeness was 88%, it did not meet the 90% criteria outlined in 40 CFR part 50 appendix P, section 2.3b.
PADEP submitted a data completeness substitution analysis for the Holbrook monitor on March 3, 2021, which included data substitutions for 41
of the missing days. The data substitution methodology relied on meteorological data, historical records for the Holbrook ozone monitoring site 8-hour average ozone concentrations. The design value for an ozone nonattainment area is the highest design value of any monitoring site in the area.

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and surrounding monitoring sites, and daily maximum regional ozone monitoring values for the 20152019
period. PADEP used a conservative approach of replacing the missing data at Holbrook in 2018 and 2019 with the regional maximum 8-hour ozone concentration and calculated updated design values for the 20172019 period.
EPA analyzed PADEPs submittal and found it acceptable and provided PADEP with Regional Administrator review and approval as required by Appendix I on March 24, 2021. PADEPs data substitution brings the data capture rate to 90% for 2018, 91% for 2019, and 91% for the 20172019 design value, which meets the requirements of 40 CFR
part 50 appendix P, section 2.3b. For more information on PADEPs data substitution analysis, including PADEPs methodology, raw data, and design value calculations, as well as EPAs review and approval, please see the rulemaking docket.8
II. Summary of SIP Revision and EPA
Analysis PADEPs February 25, 2020 SIP
submittal outlines a plan for continued maintenance of the 1997 ozone NAAQS
which addresses the criteria set forth in the 1992 Calcagni Memo as follows.
A. Attainment Emissions Inventory For maintenance plans, a state should develop a comprehensive and accurate inventory of actual emissions for an attainment year which identifies the level of emissions in the area which is sufficient to maintain the NAAQS. The inventory should be developed consistent with EPAs most recent guidance. For ozone, the inventory should be based on typical summer days emissions of oxides of nitrogen NOX and volatile organic compounds VOC, the precursors to ozone formation. In the first maintenance plan for the Greene County Area, PADEP
used 2004 for the attainment year inventory because 2004 was one of the years in the 20032005 three-year period when the area first attained the 1997 ozone NAAQS.9 The Greene County Area continued to monitor attainment of the 1997 ozone NAAQS in 2014. Therefore, the emissions inventory from 2014 represents 8 Specifically, the documents labeled PADEP
Transmittal Letter Greene County SIP, EPA RA
Approval Letter for PADEP Holbrook Missing Ozone Data Analysis, EPA Holbrook 20172019
Design Value Report, and EPA Holbrook 2018
2019 Raw Data Qualifier Report in Docket ID
EPAR03OAR20210358.
9 For more information, see EPAs July 16, 2008
notice proposing to redesignate the Greene County Area to attainment for the 1997 ozone NAAQS 73
FR 40813.

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