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Federal Register / Vol. 86, No. 24 / Monday, February 8, 2021 / Proposed Rules TABLE 12014 TYPICAL SUMMER DAY NOX AND VOC EMISSIONS FOR THE TIOGA COUNTY AREA
Tons/day NOX emissions
Source category Point
Nonpoint
Onroad
Nonroad

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 PTE 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 point sources include kraft mills, electrical generating units EGUs, 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 concentrations 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 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
VOC emissions
1.16
1.72
3.41
0.86

0.27
3.43
1.23
1.31

is well below the NAAQS i.e., below 85%, or in this case below 0.071 ppm, the section 175A demonstration requirement has been met, provided that Prevention of Significant Deterioration PSD 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 the monitor located in the Tioga County Area from 2007 to 2018. This includes DVs for 20052007, 2006
2008, 20072009, 20082010, 2009
2011, 20102012, 20112013, 2012
2014, 20132015, 20142016, 2015
2017, and 20162018, which are shown in Table 2.12 In addition, EPA has reviewed the most recent ambient air quality monitoring data for ozone in the Tioga County Area, as submitted by Pennsylvania and recorded in EPAs Air Quality System AQS. The most recent DVs i.e., 20172019 at monitors located in the Tioga County Area are also shown in Table 2.13

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TABLE 21997 OZONE NAAQS DESIGN VALUES PARTS PER MILLION PPM FOR THE TIOGA COUNTY AREA
County
AQS Site ID

Tioga

421174000

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

.075

.073

.070

.070

.069

.071

.069

.065

.063

.063

.064

.064

.060

The data in Table 2 show that the DVs for the Tioga County Area have been below 85% of the 1997 ozone NAAQS
i.e., less than or equal to 0.071 ppm since the 20072009 period. The DV for the 20172019 period at the monitor in the Tioga County Area is 0.060 ppm,
which is well below 85% of the 1997
ozone NAAQS.
States can also support the demonstration of continued maintenance by showing stable or improving air quality trends; several kinds of analyses can be performed by states wishing to make such a showing,
according to EPAs 2018 Resource Document. One approach is to take the most recent DV at a monitor located in the area and add the maximum DV
increase over one or more consecutive years that has been observed in the area over the past several years. A sum of these two values that does not exceed
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.

11 This resource document is included in the docket for this rulemaking available online at https www.regulations.gov, Docket ID: EPAR03
OAR20200316 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 March 10, 2020
submittal, included in the docket for this
rulemaking available online at https
www.regulations.gov, Docket ID: EPAR03OAR
20200316.
13 This data is also included in the docket for this rulemaking available online at https
www.regulations.gov, Docket ID: EPAR03OAR
20200316 and is also available at https
www.epa.gov/air-trends/air-quality-designvaluesreport.

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