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Federal Register / Vol. 86, No. 25 / Tuesday, February 9, 2021 / Proposed Rules
TABLE 2RECENT 1997 OZONE NAAQS DESIGN VALUES ppm AT MONITORING SITES IN THE YORK-ADAMS AREA
County
AQS Site ID

Adams
Adams
Adams
York
York

420010001
420010002
420019991
421330008
421330011

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

0.078
0.083

0.077
0.080

0.073
0.077

b 0.071
0.074
d 0.073

0.071
0.072

0.073
0.076

0.072
0.074

c 0.067
0.069
0.070

0.065
0.066
0.068

0.067
0.066
0.070

a 0.066
0.066
0.066
0.070

0.067
0.066
0.065
0.067

0.064
0.062
0.063
0.061

a Monitor
420010001 began operation on November 1, 2014, with 2017 being the first valid DV.
420010002 was discontinued on July 31, 2011, with 2010 being the last valid DV.
c Monitor 420019991 began operation in January 2011, with 2014 being the first valid DV.
d Monitor 421330011 began operation on April 22, 2008, with 2010 being the first valid DV.
b Monitor
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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 for 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 that does not exceed the level of the 1997 ozone NAAQS may be a good indicator of expected continue attainment. As shown in Table 2 in this document, the largest increases in DVs from 2007 to 2019 was 0.04 ppm, which occurred between the 20112013 0.074 ppm and 20122014 0.070 ppm DVs at the monitor located in York County AQS
ID 421330011. Adding 0.004 ppm to the highest DV for the 20172019 period 0.064 ppm results in 0.068 ppm, a sum that is still below the 1997 ozone NAAQS.
The York-Adams Area has maintained the 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 average DV for the York-Adams Area is projected to be 0.058 ppm.15 Therefore, EPA proposes to determine that future violations of the 14 As explained in EPAs October 24, 2007 notice proposing to redesignate the York-Adams Area as attainment for the 1997 ozone NAAQS 72 FR
60296, the 20042006 average DV for the YorkAdams Area was 0.081 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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1997 ozone NAAQS in the York-Adams Area are unlikely.
C. Continues Air Quality Monitoring and Verification of Continue 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 order to verify the areas attainment status. In the March 10, 2020 submittal, PADEP commits to continue to operate their air monitoring network in accordance with 40 CFR part 58. PADEP
also commits to track the attainment status of the York-Adams Area for the 1997 ozone NAAQS through the review of air quality and emissions data during the second maintenance period. This includes an annual evaluation of vehicles miles traveled VMT and stationary source emissions data compared to the assumptions included in the LMP. PADEP also states that it will also evaluate the periodic i.e., every three years emissions inventory prepared under EPAs Air Emission Reporting Requirements 40 CFR part 51, subpart A. Based on these evaluations, PADEP will consider whether any further emission control measures should be implemented for the York-Adams Area. EPA has analyzed the commitments in PADEPs submittal and is proposing to determine that they meet the requirements for continued air quality monitoring and verification of continued attainment.
D. Contingency Plan The contingency plan provisions are designed to promptly correct or prevent a violation of the NAAQS that might occur after redesignation of an area to attainment. Section 175A of the CAA
requires that a maintenance plan include such contingency measures as EPA deems necessary to assure that the state will promptly correct a violation of the NAAQS that occurs after redesignation. The maintenance plan should identify the contingency measures to be adopted, a schedule and procedure for adoption and implementation of the contingency
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measures, and a time limit for action by the state. The state should also identify specific indicators to be used to determine when the contingency measures need to be adopted and implemented. The maintenance plan must require that the state will implement all pollution control measures that were contained in the SIP
before redesignation of the area to attainment. See section 175Ad of the CAA.
PADEPs March 10, 2020 submittal includes a contingency plan for the York-Adams Area. In the event that the fourth highest 8-hour ozone concentrations at a monitor in the YorkAdams Area exceeds 84 ppb equivalent to 0.084 ppm for two consecutive years, but prior to an actual violation of the NAAQS, PADEP will evaluate whether additional local emission control measures should be implemented that may prevent a violation of the NAAQS.16 After analyzing the conditions causing the excessive ozone levels, evaluating the effectiveness of potential corrective measures, and considering the potential effects of Federal, state, and local measures that have been adopted but not yet implemented, PADEP will begin the process of implementing selected measures so that they can be implemented as expeditiously as practicable following a violation of the NAAQS. In the event of a violation, PADEP commits to adopting additional emission reduction measures as expeditiously as practicable in accordance with the schedule included in the contingency plan as well as the CAA and applicable Pennsylvania statutory requirements.
PADEP will use the following criteria when considering additional emission reduction measures to adopt to address a violation of the 1997 ozone NAAQS in the York-Adams Area: 1 Air quality analysis indicating the nature of the violation, including the cause, location, and source; 2 emission reduction 16 A violation of the NAAQS occurs when an areas 3-year design value exceeds the NAAQS.

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