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Federal Register / Vol. 86, No. 25 / Tuesday, February 9, 2021 / Proposed Rules point sources include kraft mills, electrical generating units, and pharmaceutical factories. Nonpoint sources include emissions from equipment, operations, and activities that are numerous and in total have significant emissions. Examples include emissions from commercial and consumer products, portable fuel containers, home heating, repair and refinishing operations, and crematories.
The onroad emissions sector includes emissions from engines used primarily to propel equipment on highways and other roads, including passenger vehicles, motorcycles, and heavy-duty diesel trucks. The nonroad emissions sector includes emissions from engines that are not primarily used to propel transportation equipment, such as generators, forklifts, and marine pleasure craft. EPA reviewed the emissions inventory submitted by PADEP and proposes to conclude that the plans inventory is acceptable for the purposes of a subsequent maintenance plan under CAA section 175Ab.

B. Maintenance Demonstration In order to attain the 1997 ozone NAAQS, the three-year average of the fourth-highest daily average ozone concentration design value, or DV at each monitor within an area must not exceed 0.08 ppm. Based on the rounding convention described in 40
CFR part 50, appendix I, the standard is attained if the DV is 0.084 ppm or below. CAA section 175A requires a demonstration that the area will continue to maintain the NAAQS
throughout the duration of the requisite maintenance period. Consistent with the prior guidance documents discussed previously in this document as well as EPAs November 20, 2018 Resource Document for 1997 Ozone NAAQS
Areas: Supporting Information for States Developing Maintenance Plans 2018
Resource Document,11 EPA believes that if the most recent DV for the area is well below the NAAQS e.g., below 85%, or in this case below 0.071 ppm, the section 175A demonstration requirement has been met, provided that prevention of significant deterioration
requirements, any control measures already in the SIP, and any Federal measures remain in place through the end of the second 10-year maintenance period absent a showing consistent with section 110l that such measures are not necessary to assure maintenance.
For the purposes of demonstrating continued maintenance with the 1997
ozone NAAQS, PADEP provided 3-year DVs at monitors located in the Clearfield/Indiana Area from 2007 to 2018. This includes DVs at monitors for 20052007, 20062008, 20072009, 20082010, 20092011, 20102012, 20112013, 20122014, 20132015, 20142016, 20152017, and 20162018, which are shown in Table 2 of this document.12 In addition, EPA has reviewed the most recent ambient air quality monitoring data for ozone in the Clearfield/Indiana Area, as submitted by Pennsylvania and recorded in EPAs Air Quality System. The most recent DVs i.e., 20172019 at monitors located in the Clearfield/Indiana Area are also shown in Table 2.13

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TABLE 21997 OZONE NAAQS DESIGN VALUES IN PARTS PER MILLION FOR THE CLEARFIELD/INDIANA AREA
County
AQS site ID

Clearfield
Indiana

420334000
420630004

2005
2007

2006
2008

2007
2009

2008
2010

2009
2011

2010
2012

2011
2013

2012
2014

2013
2015

2014
2016

2015
2017

2016
2018

2017
2019

.076
.080

.073
.076

.071
.073

.073
.074

.072
.073

.074
.079

.071
.075

.066
.074

.065
.071

.064
.070

.066
.070

.064
.069

0.060
0.067

As can be seen in Table 2, DVs at all monitors located in the Clearfield/
Indiana Area have been below 85% of the 1997 ozone NAAQS i.e., 0.071
ppm since the 20142016 period. The highest DV for the 20172019 period at a monitor in the Clearfield/Indiana Area is 0.067 ppm, which is below 85% of the 1997 ozone NAAQS.
Additionally, states can support the demonstration of continued maintenance by showing stable or improving air quality trends. According to EPAs 2018 Resource Document, several kinds of analyses can be performed by states wishing to make such a showing. One approach is to take the most recent DV at a monitor located in the area and add the maximum design value increase over one or more consecutive years that has been observed in the area over the past
several years. For an area with multiple monitors, the highest of the most recent DVs should be used. A sum that does not exceed the level of the 1997 ozone NAAQS may be a good indicator of expected continued attainment. As shown in Table 2 of this document, the largest increase in DVs at a monitor located in the Clearfield/Indiana Area was 0.006 ppm, which occurred between the 20092011 0.073 ppm and 20102012 0.079 ppm DVs at monitoring site 420630004. Adding 0.006 ppm to the highest DV for the 20172019 period 0.067 ppm results in 0.073 ppm, a sum that is still below the 1997 ozone NAAQS.
The Clearfield/Indiana Area has maintained air quality levels well below the 1997 ozone NAAQS since the area first attained the NAAQS in 2006.14
Additional supporting information that
the area is expected to continue to maintain the standard can be found in projections of future year DVs that EPA
recently completed to assist states with the development of interstate transport SIPs for the 2015 8-hour ozone NAAQS.
Those projections, made for the year 2023, show that the highest DV at a monitor located in the Clearfield/
Indiana Area is expected to be 0.0654
ppm.15 Therefore, EPA proposes to determine that future violations of the 1997 ozone NAAQS in the Clearfield/
Indiana Area are unlikely.

11 This resource document is included in the docket for this rulemaking available online at https www.regulations.gov, Docket ID: EPAR03
OAR20200488 and is also available at https
www.epa.gov/sites/production/files/2018-11/
documents/ozone_1997_naaqs_lmp_resource_
document_nov_20_2018.pdf.
12 See also Table II2 of PADEPs February 27, 2020 submittal, included in the docket for this rulemaking available online at https

www.regulations.gov, Docket ID: EPAR03OAR
20200488.
13 This data is also included in the docket for this rulemaking available online at https
www.regulations.gov, Docket ID: EPAR03OAR
20200488 and is also available at https
www.epa.gov/air-trends/air-quality-designvaluesreport.
14 As explained in EPAs March 19, 2009
document proposing to redesignate the Clearfield/

Indiana Area as attainment for the 1997 ozone NAAQS 74 FR 11674, the 20042006 DV for the Clearfield/Indiana Area was 0.077 ppm.
15 See U.S. EPA, Air Quality Modeling Technical Support Document for the Updated 2023 Projected Ozone Design Values, Office of Air Quality Planning and Standards, dated June 2018, available at https www.epa.gov/airmarkets/air-qualitymodeling-technical-support-document-updated2023-projected-ozone-design.

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C. Continued Air Quality Monitoring and Verification of Continued Attainment Once an area has been redesignated to attainment, the state remains obligated to maintain an air quality network in accordance with 40 CFR part 58, in
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