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Federal Register / Vol. 86, No. 25 / Tuesday, February 9, 2021 / Proposed Rules
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 Clearfield/
Indiana 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 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 27, 2020, PADEP submitted the Clearfield/
Indiana Area second maintenance plan, 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.
II. Summary of SIP Revision and EPA
Analysis PADEPs February 27, 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 nitrogen oxides NOX and volatile organic compounds VOC, the precursors to ozone formation. In the first maintenance plan for the Clearfield/Indiana Area, PADEP
used 2004 for the attainment year inventory, because 2004 was one of the years in the 20042006 three-year period when the area first attained the 1997 ozone NAAQS.8 The Clearfield/
Indiana Area continued to monitor attainment of the 1997 ozone NAAQS in 2014. Therefore, the emissions inventory from 2014 represents emissions levels conducive to continued attainment i.e., maintenance of the NAAQS. Thus, PADEP is using 2014 as representing attainment level emissions for its second maintenance plan.
Pennsylvania used 2014 summer day emissions from EPAs 2014 version 7.0
modeling platform as the basis for the 2014 inventory presented in Table 1.9

TABLE 12014 TYPICAL SUMMER DAY NOX AND VOC EMISSIONS FOR THE CLEARFIELD/INDIANA AREA IN TONS/DAY
Source category
Clearfield

Point
Nonpoint
Onroad
Nonroad
Point
Nonpoint
Onroad
Nonroad

Indiana

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NOX
emissions
County
0.14
18.44
2.43
1.30
0.73
43.89
1.70
0.80

VOC
emissions 13.16
1.52
8.42
0.67
105.90
2.00
3.47
0.94

The data shown in Table 1 is based on the 2014 National Emissions Inventory NEI version 2.10 The inventory addresses four anthropogenic emission source categories: Stationary point
sources, stationary nonpoint area sources, nonroad mobile, and onroad mobile sources. Point sources are stationary sources that have the potential to emit more than 100 tons per
year tpy of VOC, or more than 50 tpy of NOX, and which are required to obtain an operating permit. Data are collected for each source at a facility and reported to PADEP. Examples of
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 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.
8 For more information, see EPAs March 19, 2009
document proposing to redesignate the Clearfield/
Indiana Area to attainment for the 1997 ozone NAAQS 73 FR 43733.

9 For more information, visit https
www.epa.gov/sites/production/files/2018-11/ozone_
1997_naaqs_emiss_inv_data_nov_19_2018_0.xlsx.
10 The NEI is a comprehensive and detailed estimate of air emissions of criteria pollutants, criteria precursors, and hazardous air pollutants from air emissions sources. The NEI is released every three years based primarily upon data provided by State, Local, and Tribal air agencies for sources in their jurisdictions and supplemented by data developed by EPA.

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