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Federal Register / Vol. 86, No. 145 / Monday, August 2, 2021 / Proposed Rules
TABLE 2CURRENT AND HISTORICAL CO DESIGN VALUES DV FOR THE LAS VEGAS VALLEY AREAContinued Highest second maximum 8-hour CO value ppm Year J.D. Smith 320032002

Rancho &
Teddy 320031501

2.4
2.2
2 2
b 1.9

c 1.5
1.5
1.4
1.4

Jerome Mack 320030540
2014
2015
2016
2017
2018
2019
2020 a

2.7
2.7
2.3
2.35
2.5
2.3
2.1

Sunrise Acres 320030540
2.9
2.8
2.6
2.8
2.8
2.8
2.4

DV
ppm
2.9
2.8
2.6
2.8
2.8
2.8
2.4

Is DV less than 7.65
ppm?

Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.

Source: EPA, Air Quality System, Design Value Report, March 16, 2021.
a CO design values have no annual completeness requirement.
b The J.D. Smith station was permanently shut down with the EPAs approval on December 31, 2017, due to measurement challenges posed by siting obstructions.
c The Rancho & Teddy station opened in 2015 and began monitoring CO in January 2017.

3. Monitoring Network and Verification of Continued Attainment The EPA periodically reviews the CO
monitoring network operated and maintained by CCDES in accordance with 40 CFR part 58. This network is consistent with the Clark County ambient air monitoring network plan AMNP submitted annually to the EPA
after a public notification and comment process. The EPA has reviewed and approved the AMNP every year for the past three years from 20182020. The EPA is also required to conduct technical systems audits TSA every three years to ensure quality assurance of monitoring organizations.20 The most recent TSA for CCDES was in 2018, and the EPA found that CCDESs air monitoring program meets EPAs requirements.21
To verify the attainment status of the area over the maintenance period, the maintenance plan should contain provisions for continued operations of an EPA-approved monitoring network in accordance with 40 CFR part 58. The CCDESs network in the Las Vegas Valley area has been approved by the EPA in accordance with 40 CFR part 58.22 Furthermore, the CCDES has committed to continue to operate an air quality monitoring network in the Las Vegas Valley area in accordance with the EPA requirements to verify continued attainment of the CO
20 40

CFR 58 Appendix A, section 2.5.
dated August 23, 2018 from Elizabeth J.
Adams, Acting Director, Air Division Region IX, to Marci Henson, Director, Clark County Department of Air Quality with attached Technical Systems Audit of the Ambient Air Monitoring Program:
Clark County Department of Air Quality October 2325, 2017 and January 1618, 2018.
22 For further details, see CCDESs 2020 Annual Monitoring Network Plan AMNP, the EPAs approval letter for the 2020, 2019 and 2018 AMNP, as well as the EPAs Clark County 2018 TSA report, in the docket for this action.

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NAAQS.23 For the reasons stated in this section of the notice, we find Clark Countys monitoring network adequate to verify continued attainment of the CO
NAAQS in the Las Vegas Valley area.
4. Contingency Plan Section 175Ad of the CAA requires that a maintenance plan include contingency provisions. The purpose of these provisions is to prevent future violations of the NAAQS or promptly remediate any NAAQS violations that might occur during the maintenance period. These contingency provisions need not be fully adopted regulations at the time of the redesignation. However, the contingency plan is an enforceable part of the SIP and should ensure that contingency measures are adopted quickly once the contingency plan is triggered. The contingency plan should also identify the measures to be expeditiously adopted and provide a schedule and procedure for adoption and implementation. The state is also required to identify triggers that will be used to determine when contingency measures will need to be implemented.
In the 2019 LMP, the CCDES retains the reduced Reid vapor pressure RVP
gasoline program contingency measure from its first CO maintenance plan as a contingency measure. The RVP gasoline program relaxed the RVP from wintertime fuels sold in Clark County from 9.0 pounds per square inch psi to 13.5 psi, thereby increasing fuel volatility and therefore fuel-related emissions. The EPA approved this measure, finding that relaxation of RVP
would not interfere with maintenance of the CO standard in the area.24 The RVP
gasoline program contingency measure 23 See 2019 LMP, Section 3.3, Monitoring Network/Verification of Continued Attainment, 21.
24 75 FR 59090.

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would reinstate the prior, lower RVP
level. That is, if future CO levels trigger contingency measures, the CCDES will seek reinstatement and tightening of the RVP standard back to 9.0 psi. This contingency measure would be triggered by a verified second exceedance over 9
ppm during the winter season October 1 through March 31 within a consecutive two-year period.
The EPA proposes to find that the contingency provisions in the 2019 LMP
satisfy the contingency measure requirements of CAA section 175A for the second 10-year maintenance plan period.
IV. Transportation Conformity Transportation conformity is required by section 176c of the CAA.
Conformity to a SIP means that transportation activities will not produce new air quality violations, worsen existing violations, or delay timely attainment of the NAAQS. The EPAs conformity rule at 40 CFR part 93
requires that transportation plans, programs, and projects conform to SIPs and establishes the criteria and procedures for determining conformity.
The conformity rule generally requires a demonstration that emissions from the regional transportation plan RTP and the transportation improvement plan TIP are consistent with the motor vehicle emissions budget MVEB or budget contained in the control strategy SIP revision or maintenance plan.25 A budget is defined as the level of mobile source emissions of a pollutant relied upon in the attainment or maintenance demonstration to attain or maintain compliance with the 25 See
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40 CFR 93.101, 93.118, and 93.124.

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