88300 Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 

1 ‘‘Fact Sheet—2008 Final Revisions to the 

National Ambient Air Quality Standards for 

Ozone,’’ dated March 2008. 

(k) Appeals. Except as otherwise 

provided in this section, appeals shall 

be initiated and processed using the 

procedures in 38 CFR part 20 applicable 

to appeals under the modernized 

system. 

[FR Doc. 2023–28100 Filed 12–20–23; 8:45 am] 

BILLING CODE 8320–01–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R09–OAR–2022–0955; FRL–10549– 

01–R9] 

Approval of Implementation Plans for 

Air Quality Planning Purposes; State of 

Nevada; Clark County Second 10-Year 

Maintenance Plan for the 1997 8-Hour 

Ozone Standard 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to approve, 

as a revision of the Nevada state 

implementation plan (SIP), the State’s 

second 10-year plan for maintaining the 

1997 8-hour ozone standard in Clark 

County (‘‘Clark County Second 

Maintenance Plan’’ or ‘‘Plan’’). The 

Clark County Second Maintenance Plan 

includes, among other elements, a base 

year emissions inventory, a 

maintenance demonstration, 

contingency provisions, and motor 

vehicle emissions budgets for use in 

transportation conformity 

determinations to ensure the continued 

maintenance of the 1997 National 

Ambient Air Quality Standards for 

ozone (‘‘1997 ozone NAAQS’’ or ‘‘1997 

8-hour ozone standard’’). With this 

proposed rulemaking, the EPA is 

initiating the adequacy process for the 

2017, 2023, and 2033 motor vehicle 

emissions budgets. The EPA is 

proposing these actions because the SIP 

revision meets the applicable statutory 

and regulatory requirements for such 

plans and motor vehicle emissions 

budgets. 

DATES: Comments must be received on 

or before January 22, 2024. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R09– 

OAR–2022–0955, at https://

www.regulations.gov. For comments 

submitted at Regulations.gov, follow the 

online instructions for submitting 

comments. Once submitted, comments 

cannot be edited or removed from 

Regulations.gov. The EPA may publish 

any comment received to its public 

docket. Do not submit electronically any 

information you consider to be 

Confidential Business Information (CBI) 

or other information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

submission (i.e., on the web, cloud, or 

other file sharing system). For 

additional submission methods, please 

contact the person identified in the FOR

FURTHER INFORMATION CONTACT section. 

For the full EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

https://www.epa.gov/dockets/ 

commenting-epa-dockets. If you need 

assistance in a language other than 

English or if you are a person with a 

disability who needs a reasonable 

accommodation at no cost to you, please 

contact the person identified in the FOR

FURTHER INFORMATION CONTACT section. 

FOR FURTHER INFORMATION CONTACT: 

Andrew Ledezma, EPA Region IX, 75 

Hawthorne St., San Francisco, CA 

94105. By phone: (415) 972–3985 or by 

email at Ledezma.Andrew@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Throughout this document, ‘‘we,’’ ‘‘us,’’ 

and ‘‘our’’ refer to the EPA. 

Table of Contents 

I. Summary of Proposed Action 

II. Background 

III. Second 10-Year Maintenance Plan 

Submittal and Procedural Requirements 

IV. Requirements for Second 10-Year 

Maintenance Plans 

V. Evaluation of the Clark County Second 

Maintenance Plan 

A. Monitoring Network Requirements 

B. Attainment Inventory 

C. Maintenance Demonstration 

D. Verification of Continued Attainment 

E. Contingency Provisions 

F. Motor Vehicle Emissions Budgets for 

Transportation Conformity 

VI. Environmental Justice Considerations 

VII. Proposed Action and Request for Public 

Comment 

VIII. Statutory and Executive Order Reviews 

I. Summary of Proposed Action 

Under Clean Air Act (CAA or ‘‘the 

Act’’) section 110(k)(3), the EPA is 

proposing to approve two submittals 

from the Nevada Division of 

Environmental Protection (NDEP) as a 

revision to the Nevada SIP: the Clark 

County Second Maintenance Plan dated 

December 21, 2021, and a supplement to 

the Clark County Second Maintenance 

Plan (‘‘Contingency Measure Revision’’) 

dated August 16, 2023. In this action, 

we refer to the Clark County Second 

Maintenance Plan and the Contingency 

Measure Revision collectively as the 

‘‘Clark County Second Maintenance 

Plan submittal.’’ 

The EPA is proposing to find that the 

maintenance demonstration, showing 

how the area will continue to attain the 

1997 8-hour ozone NAAQS for 10 

additional years beyond the approval 

the State’s first 10-year plan for 

maintaining the 1997 8-hour ozone 

standard in Clark County (‘‘Clark 

County First Maintenance Plan’’ or 

‘‘first maintenance plan’’) (i.e., through 

2033), and the contingency provisions, 

describing the actions that Clark County 

will take in the event of a future 

monitored violation, meet all applicable 

requirements for maintenance plans and 

related contingency provisions in CAA 

section 175A. The EPA is also proposing 

to approve the motor vehicle emissions 

budgets (MVEBs or ‘‘budgets’’) in the 

Clark County Second Maintenance Plan 

because we find they meet the 

applicable transportation conformity 

requirements under 40 CFR 93.118(e). 

II. Background 

Sections 108 and 109 of the CAA 

govern the establishment, review, and 

revision, as appropriate, of the NAAQS 

to protect public health and welfare. 

The CAA requires the EPA to 

periodically review the air quality 

criteria, the science upon which the 

standards are based, and the standards 

themselves. Ground-level ozone is one 

of the criteria pollutants regulated under 

the NAAQS. 

Ground-level ozone is generally not 

emitted directly by sources. Rather, 

directly emitted oxides of nitrogen 

(NOX) and volatile organic compounds 

(VOC) react in the presence of sunlight 

to form ground-level ozone, as a 

secondary pollutant, along with other 

secondary compounds. NOX and VOC 

are ‘‘ozone precursors.’’ Reduction of 

peak ground-level ozone concentrations 

is typically achieved through 

controlling VOC and NOX emissions. 

Scientific evidence indicates that 

adverse public health effects occur 

following exposure to ozone, 

particularly in children and adults with 

lung disease. Breathing air containing 

ozone can reduce lung function and 

inflame airways, which can increase 

respiratory symptoms and aggravate 

asthma or other lung diseases.1


khammond on DSKJM1Z7X2PROD with PROPOSALS
Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 88301 

2 62 FR 38856 (July 18, 1997). 

3On March 27, 2008 (73 FR 16436), the EPA 

promulgated a revised 8-hour ozone standard of 

0.075 ppm (the 2008 8-hour ozone standard), and 

on May 21, 2012, the EPA designated the entire 

state of Nevada unclassifiable/attainment for the 

2008 8-hour ozone standard (77 FR 30088). This 

rulemaking relates only to the 1997 8-hour ozone 

standard and does not relate to the 2008 8-hour 

ozone standard. 

4 69 FR 23858 (April 30, 2004). 

5 69 FR 23951, (April 30, 2004). 

6The design value for the 1-hour ozone standard 

is the fourth-highest daily maximum 1-hour ozone 

concentration over a three-year period at the worstcase monitoring site in the area. 

7 69 FR 23951. The design value for the 8-hour 

standard is the three-year average of the annual 

fourth-highest daily maximum 8-hour ozone 

concentration at the worst-case monitoring site in 

the area. 

8 69 FR 55956 (September 17, 2004), 70 FR 71612 

(November 29, 2005), and 40 CFR 81.329. The 

boundaries of the Clark County ozone 

nonattainment area are defined in 40 CFR 81.329. 

Specifically, the area is defined as: ‘‘That portion 

of Clark County that lies in hydrographic areas 

164A, 164B, 165, 166, 167, 212, 213, 214, 216, 217, 

and 218 but excluding the Moapa River Indian 

Reservation and the Fort Mojave Indian 

Reservation.’’ The area includes a significant 

portion of the unincorporated portions of central 

and southern Clark County, as well as the cities of 

Las Vegas, Henderson, North Las Vegas, and 

Boulder City. 

9 472 F.3d 882 (D.C. Cir. 2007). 

10 69 FR 23951. 

11 472 F.3d 882 (D.C. Cir. 2007). 

12 77 FR 28424. 

13 76 FR 17343. 

14 78 FR 1149. 

15 84 FR 33038 (July 11, 2019). 

16 84 FR 44699. 

17According to ‘‘Emissions Inventory Guidance 

for Implementation of Ozone and Particulate Matter 

National Ambient Air Quality Standards (NAAQS) 

and Regional Haze Regulations,’’ dated May 2017, 

terminology used has changed from ‘‘summer day’’ 

emissions to ‘‘ozone season’’ emissions. However, 

‘‘average summer day’’ emissions are used in this 

instance to stay consistent between motor vehicle 

emissions budgets of different ozone standards. 

18 86 FR 59643. 

In 1997, the EPA revised the NAAQS 

for ozone, setting it at 0.08 parts per 

million (ppm) averaged over an 8-hour 

time frame.2 The EPA set the 1997 8- 

hour ozone standard based on scientific 

evidence demonstrating that ozone 

causes adverse health effects at lower 

ozone concentrations and over longer 

periods of time, than was understood 

when the pre-existing 1-hour ozone 

standard was set. The EPA determined 

that the 1997 8-hour ozone NAAQS 

would be more protective of human 

health, especially for children and 

adults who are active outdoors, and 

individuals with a pre-existing 

respiratory disease, such as asthma.3

In 2004, the EPA designated areas of 

the country with respect to the 1997 8- 

hour ozone NAAQS.4 Under the EPA’s 

‘‘Phase 1’’ implementation rule for the 

1997 8-hour ozone standard 5 an area 

was classified under subpart 2 based on 

its 8-hour ozone design value (i.e., the 

3-year average annual fourth-highest 

daily maximum 8-hour average ozone 

concentration at the worst-case 

monitoring site in the area or in its 

immediate downwind environs), if it 

had a 1-hour ozone design value 6 at the 

time of designation at or above 0.121 

ppm. All other areas were covered 

under subpart 1 based on their 8-hour 

ozone design values.7 Clark County was 

designated as a subpart 1 ozone 

nonattainment area by the EPA on April 

30, 2004, based on air quality 

monitoring data from 2001–2003. The 

designation became effective on June 15, 

2004. On September 17, 2004, the EPA 

reduced the geographic extent of the 

ozone nonattainment area to encompass 

a portion, but not all, of Clark County.8

In South Coast Air Quality 

Management Dist. v. EPA 9 the U.S. 

Court of Appeals for the District of 

Columbia Circuit (D.C. Circuit, or 

‘‘Court’’) vacated the EPA’s Phase 1 

implementation rule for the 1997 8-hour 

ozone standard.10 In response to several 

petitions for rehearing, the D.C. Circuit 

clarified that the Phase 1 rule was 

vacated only for those parts of the rule 

that had been successfully challenged.11

The decision left intact the Court’s 

rejection of the EPA’s reasons for 

implementing the 8-hour ozone 

standard in certain nonattainment areas 

under subpart 1 in lieu of subpart 2 of 

the CAA. 

On May 14, 2012, in response to the 

Court’s vacatur of the provision of the 

Phase 1 rule for the 1997 8-hour ozone 

standard that placed certain 

nonattainment areas, including Clark 

County solely under subpart 1, the EPA 

classified Clark County as a marginal 

ozone nonattainment area under subpart 

2 of the CAA.12

On March 29, 2011, the EPA 

determined that the Clark County 8- 

hour ozone nonattainment area had 

attained the 1997 8-hour ozone NAAQS, 

based on complete, quality-assured, and 

certified ambient air monitoring data 

that showed the area monitored 

attainment of the 1997 8-hour ozone 

NAAQS for the 2007–2009 monitoring 

period.13

On April 11, 2011, NDEP submitted 

the Clark County First Maintenance 

Plan and requested that the EPA 

redesignate the Clark County 8-hour 

ozone nonattainment area to attainment 

for the 1997 8-hour ozone standard. On 

January 8, 2013, the EPA approved the 

Clark County First Maintenance Plan, 

and redesignated the area from 

nonattainment to attainment of the 1997 

8-hour ozone NAAQS.14

On October 31, 2018, NDEP submitted 

a Revision to Motor Vehicle Emissions 

Budgets in Ozone Redesignation 

Request and Maintenance Plan (‘‘2018 

Ozone Maintenance Plan Revision’’). 

The 2018 Ozone Maintenance Plan 

Revision updated elements of the Clark 

County First Maintenance Plan, 

including the attainment inventory, the 

maintenance demonstration, and the 

budgets. The 2018 Ozone Maintenance 

Plan Revision established ozone season 

budgets of 52.96 and 86.74 tons per day 

(tpd) for VOC and NOX, respectively, for 

2022 so that the area would have 

updated budgets available to use for 

transportation conformity 

determinations with respect to the 2015 

National Ambient Air Quality Standards 

for ozone (‘‘2015 ozone NAAQS’’).15 On 

August 27, 2019, the EPA conditionally 

approved the 2018 Ozone Maintenance 

Plan revisions, based on commitments 

to submit an additional SIP revision to 

reduce the safety margin allocations for 

the budgets within one year of the final 

conditional approval.16

On September 30, 2020, NDEP 

submitted an additional Revision to 

Motor Vehicle Emissions Budgets for the 

1997 ozone NAAQS, Clark County, 

Nevada (‘‘2020 Ozone Maintenance Plan 

Revision’’). The 2020 Ozone 

Maintenance Plan Revision was 

prepared in response to the EPA’s 

conditional approval of the 2018 Ozone 

Maintenance Plan Revision. The 2020 

Ozone Maintenance Plan Revision 

revised certain budgets from the 2018 

Ozone Maintenance Plan Revision to 

prevent interference with Reasonable 

Further Progress (RFP) or attainment of 

the 2008 and 2015 ozone NAAQS. The 

2020 Ozone Maintenance Plan Revision 

established budgets of 23.92 and 32.16 

tons per average summer day 17 for VOC 

and NOX, respectively, for 2022. On 

October 28, 2021, with the submittal of 

the 2020 Ozone Maintenance Plan 

Revision, the EPA approved the updates 

to the attainment inventory, the 

maintenance demonstration, and the 

budgets to the Clark County First 

Maintenance Plan.18

On January 24, 2022, NDEP submitted 

the Clark County Second Maintenance 

Plan showing how the area will 

continue to attain the 1997 8-hour ozone 

national ambient air quality standard 

(NAAQS) for 10 additional years beyond 

the approval the State’s first 10-year 

plan. 

Lastly, on August 16, 2023, NDEP 

submitted the Contingency Measure 

Revision, which revised the contingency 

measure section of the Clark County 

Second Maintenance Plan. In this 

action, we are proposing action on the 


khammond on DSKJM1Z7X2PROD with PROPOSALS
88302 Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 

19Memorandum dated September 4, 1992, from 

John Calcagni, Director, EPA Air Quality 

Management Division, to Regional Office Air 

Division Directors, Subject: Procedures for 

Processing Requests to Redesignate Areas to 

Attainment. 20Calcagni Memo, 8–13. 

NDEP’s Clark County Second 

Maintenance Plan submittal. 

III. Second 10-Year Maintenance Plan 

Submittal and Procedural 

Requirements 

CAA section 110(a)(1) and (2) and 

section 110(1) require states to provide 

reasonable notice and public hearing 

prior to adoption of SIP revisions. In 

this action, we are proposing action on 

NDEP’s January 24, 2022, submittal of 

the Clark County Ozone Second 

Maintenance Plan, and NDEP’s August 

16, 2023, submittal of the Contingency 

Measure Revision as a revision to the 

Nevada SIP, collectively referred to as 

the Clark County Second Maintenance 

Plan submittal. 

Following a 30-day public comment 

period, the Clark County Second 

Maintenance Plan was adopted by the 

Clark County Board of Commissioners, 

submitted to NDEP, and submitted to 

the EPA. Appendix B of the Clark 

County Second Maintenance Plan 

documents the public review process 

followed by Clark County in adopting 

the plan prior to transmittal to NDEP for 

subsequent submittal to the EPA as a 

revision to the Nevada SIP. The 

documentation in appendix B provides 

evidence that reasonable notice of a 

public hearing was provided to the 

public and that a public hearing was 

conducted prior to adoption. 

Specifically, notice of the availability of, 

and opening of a 30-day comment 

period on, the draft Clark County 

Second Maintenance Plan was 

published on October 14, 2021, on the 

Clark County Department of 

Environment and Sustainability (DES) 

website, the DES official Facebook page, 

and the DES official Twitter. No 

comments were submitted. 

On December 7, 2021, the Clark 

County Board of Commissioners set a 

public hearing for December 21, 2021, to 

consider and approve the Clark County 

Second Maintenance Plan. The 

announcement of the public hearing 

was subsequently published on the 

County’s web page. On December 21, 

2021, the Clark County Board of 

Commissioners adopted the Clark 

County Second Maintenance Plan at the 

close of the public hearing. Following 

adoption, Clark County DES forwarded 

the plan to NDEP, the Governor of 

Nevada’s designee for SIP matters, and 

NDEP then submitted the plan as a 

revision to the Nevada SIP to the EPA 

for approval on January 24, 2022. 

Appendix A of the Contingency 

Measure Revision documents the board 

approval process followed by Clark 

County in adopting the plan prior to 

transmittal to NDEP for subsequent 

submittal to the EPA as a revision to the 

Nevada SIP. On July 18, 2023, the Clark 

County Board of Commissioners put the 

Contingency Measure Revision up for 

public notice and adopted the 

Contingency Measure Revision at the 

close of the public hearing. Following 

adoption, Clark County DES forwarded 

the plan to NDEP and NDEP then 

submitted the plan, as a revision to the 

Nevada SIP, to the EPA for approval on 

August 16, 2023. 

Based on the documentation 

contained in appendix B of the Plan and 

appendix A of the Contingency Measure 

Revision, we find that the Clark County 

Second Maintenance Plan submittal 

satisfies the procedural requirements of 

section 110(l) of the Act. 

IV. Requirements for Second 10-Year 

Maintenance Plans 

Section 175A of the CAA provides the 

general framework for a maintenance 

plan. The initial 10-year maintenance 

plan must provide for maintenance of 

the NAAQS for at least 10 years after 

redesignation, including any additional 

control measures necessary to ensure 

such maintenance. In addition, 

maintenance plans are to contain 

contingency provisions necessary to 

ensure the prompt correction of a 

violation of the NAAQS that occurs after 

redesignation. The contingency 

measures must include, at a minimum, 

a requirement that the state will 

implement all control measures 

contained in the nonattainment SIP 

prior to redesignation. Beyond these 

provisions, section 175A of the CAA 

does not define the content of a second 

10-year maintenance plan. 

The primary guidance on 

maintenance plans and redesignation 

requests is a September 4, 1992, 

memorandum from John Calcagni, titled 

‘‘Procedures for Processing Requests to 

Redesignate Areas to Attainment’’ 

(Calcagni Memo).19 The Calcagni Memo 

outlines the key elements of a 

maintenance plan, which include 

verification of continued attainment, 

monitoring network requirements, 

attainment emissions inventory, 

maintenance demonstration, and a 

contingency plan. We evaluate the 

Second 10-Year Maintenance Plan based 

on the satisfactory fulfillment of these 

and all relevant procedural 

requirements of the CAA. 

CAA section 175A(b) requires states 

to submit an additional SIP revision 

(Second 10-Year Maintenance Plan) to 

maintain the NAAQS for an additional 

10 years after the expiration of the 10- 

year period covered by the initial 

maintenance plan approved in 

connection with the redesignation of the 

area from nonattainment to attainment. 

The revision is submitted eight years 

after the original redesignation request 

and maintenance plan have been 

approved. The deadline to submit Clark 

County’s Second Maintenance Plan was 

January 8, 2021. On January 24, 2022, 

NDEP submitted the Clark County 

Second Maintenance Plan, to meet the 

requirement for the subsequent 

maintenance plan under CAA section 

175A(b). The Clark County Second 

Maintenance Plan is intended to 

provide for continued maintenance of 

the 1997 ozone NAAQS for the 10-year 

period following the end of the first 10- 

year period, i.e., from 2024 through 

2033. 

V. Evaluation of the Clark County 

Second Maintenance Plan 

Section 175A of the CAA sets forth 

the elements of a maintenance plan. We 

interpret this section of the Act to 

require, in general, the following core 

elements: attainment inventory, 

maintenance demonstration, monitoring 

network, verification of continued 

attainment, and contingency plan.20

Under CAA section 175A, a 

maintenance plan must demonstrate 

continued attainment of the applicable 

NAAQS for at least ten years after the 

EPA approves a redesignation to 

attainment. Eight years after 

redesignation, the State must submit a 

revised maintenance plan that 

demonstrates continued attainment for 

the subsequent ten-year period 

following the initial ten-year 

maintenance period. To address the 

possibility of future NAAQS violations, 

the maintenance plan must contain such 

contingency provisions that the EPA 

deems necessary to promptly correct 

any violation of the NAAQS that occurs 

after redesignation of the area. Based on 

our review and evaluation of the plan, 

as detailed below, we are proposing to 

approve the Clark County Second 

Maintenance Plan submittal because we 

believe that it meets the requirements of 

CAA section 175A. 

A. Monitoring Network Requirements 

Continued ambient monitoring of an 

area is generally required over the 

maintenance period. Clark County DES 

currently operates ozone monitors at 

thirteen sites within the Clark County 8- 

hour ozone maintenance area. 


khammond on DSKJM1Z7X2PROD with PROPOSALS
Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 88303 

21Clark County Second Maintenance Plan, 20–23. 22Although the Clark County Second 

Maintenance Plan is not explicit in this regard, we 

presume that Clark County DES’s intention to 

continue operation of a monitoring network means 

that the agency intends to do so consistent with the 

EPA’s monitoring requirements in 40 CFR part 58 

(‘‘Ambient Air Quality Surveillance’’). 23The EPA’s requirements for annual review of 

monitoring networks are no longer codified at 40 

CFR 58.20(d) but are now found at 40 CFR 58.10. 24 76 FR 17343 (Apr. 29, 2011). 25The emissions inventories reflect county-wide 

emissions which include both the nonattainment 

area portion of the county and the portion of the 

county designated as ‘‘unclassifiable/attainment’’ 

for the 1997 8-hour ozone NAAQS. County-wide 

emissions are acceptable to characterize emissions 

within the Clark County ozone nonattainment area 

because over 95% of the population of the county 

resides in the nonattainment area. 

26The 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 the EPA. 

27The Clark County Second Maintenance Plan 

uses the term, ‘‘point sources,’’ to refer to those 

stationary source facilities that are required to 

report their emissions to Clark County DES or 

NDEP. 

28The Clark County Second Maintenance Plan 

uses the term, ‘‘nonpoint sources,’’ to refer to those 

stationary and area sources that fall below point 

source reporting levels and that are too numerous 

or small to identify individually. 

29The Clark County Second Maintenance Plan 

uses the term, ‘‘ERCs’’ to refer to allowances earned 

through voluntary pollutant emission reductions 

such as equipment shutdowns or voluntarily 

installed controls. 

30For the Clark County Second Maintenance 

Plan, ‘‘biogenic sources’’ include agricultural crops; 

lawn grass; forests that produce isoprene, 

monoterpene, and other VOC emissions; and soils 

that generate trace amounts of NOX. 

In the Clark County Second 

Maintenance Plan,21 Clark County DES 

indicates its intention to continue 

operation of an air quality monitoring 

network to verify continued attainment 

of the 1997 8-hour ozone NAAQS.22 The 

Clark County Second Maintenance Plan 

also notes that Clark County DES’s State 

and Local Air Monitoring Stations 

(SLAMS) air quality monitoring network 

(which includes ambient ozone 

monitoring) will be reviewed annually 

pursuant to 40 CFR 58.20(d) to 

determine whether the system continues 

to meet the applicable monitoring 

objectives.23 We approved Clark 

County’s SLAMS air quality network in 

their Annual Monitoring Network Plan 

for year 2020 on October 28, 2020, prior 

to Clark County’s submittal of the Clark 

County Second Maintenance Plan. We 

find the County’s commitment for 

continued ambient ozone monitoring as 

set forth in the Clark County Second 

Maintenance Plan to be acceptable. 

B. Attainment 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 the EPA’s most recent 

guidance. For ozone, the inventory 

should be based on typical ozone season 

day emissions of NOX and VOC. 

In the Clark County First Maintenance 

Plan, Clark County DES used 2008 for 

the attainment year inventory, because 

2008 was one of the years in the 2007– 

2009 three-year period when the area 

first attained the 1997 ozone NAAQS.24

Clark County DES continued to monitor 

attainment of the 1997 ozone NAAQS in 

2017. Therefore, the emissions 

inventory from 2017 represents 

emissions levels consistent with 

continued attainment (i.e., maintenance) 

of the NAAQS. Thus, Clark County DES 

selected 2017 as the year for the 

attainment inventory in the Clark 

County Second Maintenance Plan. We 

consider the selection of the 2017 base 

year inventory to be appropriate given 

that it was the most recent emissions 

inventory associated with the reporting 

schedule required under the Air 

Emissions Reporting Requirements rule 

at the time of Plan drafting. 

Table 1 presents the VOC and NOX

emissions estimates contained in the 

Clark County Second Maintenance Plan 

for 2017 and presents the Plan’s 

projected emissions inventories of 

ozone precursors in an interim year 

(2023) and the maintenance plan’s 

horizon year (2033).25

TABLE 1—CLARK COUNTY 2017 AND PROJECTED 2023 AND 2033 VOC AND NOX EMISSIONS TOTAL DAILY EMISSIONS

[Tpd, average summer ozone season weekday] 

Emissions source 

2017 2023 2033 

VOC NOX VOC NOX VOC NOX

Point Source ............................................ 2.95 12.34 2.62 11.41 2.63 11.33 

Nonpoint Source ...................................... 64.69 4.69 67.83 5.03 71.31 4.78 

Mobile—On-road ...................................... 26.27 42.20 17.85 22.22 11.50 11.13 

Mobile—Nonroad ..................................... 28.86 37.45 27.24 23.27 27.82 15.37 

Airports ..................................................... 1.96 11.90 2.64 15.53 3.05 19.77 

Locomotives ............................................. 0.07 1.42 0.05 1.21 0.04 0.96 

Emission Reduction Bank ........................ 0.00 0.00 0.43 22.23 0.43 22.23 

Biogenic ................................................... 362.61 2.43 362.61 2.43 362.61 2.43 

Total .................................................. 487.41 112.43 481.27 103.33 479.39 88.00 

Source: Clark County Second Maintenance Plan, 17, Tables 2–4 and 2–5. aEmissions associated with the proposed Department of Air Force (DAF) Training Project is included in Airport emissions projections for the 

2023 and 2033 emissions projections for general conformity purposes. Emissions associated with the proposed Southern Nevada Supplemental 

Airport and proposed Sloan Regional Heliport are included for the 2033 emissions projection for general conformity purposes. 

The data shown in Table 1 in this 

document is based on the 2017 National 

Emissions Inventory (NEI).26 The 

inventory addresses point sources,27

nonpoint sources,28 on-road mobile, 

non-road mobile, airports, locomotives, 

Emission Reduction Credits (ERCs),29

and biogenic 30 sources. Appendix A to 

the Clark County Second Maintenance 

Plan contains source-specific 

descriptions of emissions calculation 

procedures and sources of input data. 

Point sources are stationary sources 

that have a potential to emit (PTE) 

greater than 100 tons per year of NOX

or VOC. Clark County DES adopted a 

lower threshold by including all title V 

stationary sources and minor sources 

with a PTE greater than 10 tons of VOC 

or 25 tons of NOX per year. Clark 

County DES based the inventory 

estimates on source reported actual 

2017 emissions data but adjusted the 

reported values to reflect a typical ozone 


khammond on DSKJM1Z7X2PROD with PROPOSALS
88304 Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 

31Clark County DES completed a vehicle 

classification study in June 2018. The study used 

2014–2016 traffic count data collected by the 

Nevada Department of Transportation (NDOT). 

Clark County DES incorporated VMT mix profiles 

and temporal profiles, which DES incorporated into 

the 2017 MOVES3 input database. 

32 79 FR 62350 (October 17, 2014). 

33See ‘‘DAQEM ERC Bank’’ for a list of sources 

contributing to the DAQEM ERC Bank in Clark 

County. 

34NDEP banked Reid Gardner ERCs after the NV 

Energy—Reid Gardner Station Power Plant, Unit #4 

Steam Boiler was controlled with a low-NOX burner 

in January 2010. 

35NDEP banked Mohave ERCs after the 

permanent shut down and dismantling of the 

Southern California Edison Mohave Generating 

Station in November 2009. 

36Calcagni Memo, 9–11. 

37 Id. 

38A maintenance demonstration need not be 

based on ozone modeling. See Wall v. EPA, 265 

F.3d. 426 (6th Cir. 2001); Sierra Club v. EPA, 375 

F.3d 537 (7th Cir. 2004). See also 66 FR 53094 

(October 19, 2001), and 68 FR 25418 (May 12, 

2003). 

39Clark County Second Maintenance Plan, 

Appendix A, 23. 

40Clark County Second Maintenance Plan, 

Appendix A, 24. 

41Clark County Second Maintenance Plan, 

Appendix A, 29. 

42Clark County Second Maintenance Plan, 

Appendix A, 31. 

43Clark County Second Maintenance Plan, 27, 

Table 6–1. 

season day at each emissions unit 

within the source facilities based on 

information provided by the facilities. 

Nonpoint sources include emissions 

from equipment, operations and 

activities that are numerous and in total 

have significant emissions. Clark 

County DES included emissions from 

minor sources, residential combustion, 

agricultural burning, industrial solvents 

and graphic arts, and degreasing 

operations. Clark County DES used 

several methods to estimate area source 

activity levels and emissions, including 

applying local activity levels, 

apportioning national or statewide 

activity levels to the local level, 

applying per capita emission factors 

considering county-specific populations 

and using specific method abstracts 

detailed within the submittal. 

Non-road emissions sources include 

equipment that either move under their 

own power or can be moved from site 

to site. 

The on-road 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. Clark County DES used 

MOVES3, EPA’s MOVES3 emissions 

factors, fleet data from Department of 

Motor Vehicles (DMV) registration data, 

Coordinated Research council (CRC) 

vehicle speed data, the Regional 

Transportation Commission (RTC) of 

Southern Nevada’s transportation 

demand modeling results, vehicle 

classification data from the June 2018 

Clark County Vehicle Classification 

Study,31 and 2017 Highway 

Performance Monitoring System 

(HPMS) data from the Nevada 

Department of Transportation (NDOT). 

Biogenic emissions are from 

vegetation and soil, and include crops, 

lawn grass, and forests. Clark County 

DES used the Biogenic Emissions 

Inventory System version 3.61 

(BEIS3.61) embedded in the SMOKE 4.7 

model for the month of July to generate 

average ozone season day emissions for 

Clark County. 

The airport sector includes emissions 

from aircraft from commercial and 

federal aviation sources. Clark County 

DES relied on airport-specific emissions 

inventory information provided by the 

Clark County Department of Aviation 

(CCDOA) for the five commercial 

airports located within the 

nonattainment area. 

Locomotives include emissions from 

railroad and high-speed passenger train 

emissions. Locomotive emissions were 

estimated by Clark County DES based 

on local activity data collected for the 

Clark County First Maintenance Plan 

and predicted emissions from highspeed passenger train service. 

ERCs refer to allowances earned 

through voluntary pollutant emissions 

reductions such as equipment 

shutdowns or voluntarily installed 

controls. Clark County adopted New 

Source Review (NSR) rule, Section 

12.7.5—Emission Reduction credits into 

the SIP,32 allowing Clark County to 

adopt ERCs. In the Clark County First 

Maintenance Plan, Clark County banked 

NOX and VOC credits from the Clark 

County Department of Air Quality and 

Environmental Management (DAQEM) 

ERC Bank,33 Reid Gardner ERCs,34 and 

Mohave ERCs.35 In the Clark County 

Second Maintenance Plan, Clark County 

noted that ERCs have not changed from 

the Clark County First Maintenance 

Plan. 

The EPA has reviewed the emissions 

inventory submitted by Clark County 

and proposes to conclude that the plan’s 

inventory is based on reasonable 

assumptions and methodologies, and 

that the inventory is comprehensive, 

current, accurate, and consistent with 

applicable CAA provisions and the 

Calcagni Memo. Therefore, we are 

proposing that the inventory is 

acceptable for use in demonstrating 

maintenance of the 1997 ozone NAAQS. 

C. Maintenance Demonstration 

CAA section 175A(a) requires that the 

maintenance plan ‘‘provide for the 

maintenance of the national primary 

ambient air quality standard for such air 

pollutant in the area concerned for at 

least 10 years after the redesignation.’’ 

Generally, a state may demonstrate 

maintenance of the ozone NAAQS by 

either showing that future emissions of 

a pollutant or its precursors will not 

exceed the level of the attainment 

inventory or by modeling to show that 

the future mix of sources and emissions 

rates will not cause a violation of the 

NAAQS.36 For areas that are required 

under the Act to submit modeled 

attainment demonstrations, the 

maintenance demonstration should use 

the same level of modeling.37 The Clark 

County 8-hour ozone nonattainment 

area was not required to submit a 

modeled attainment demonstration, and 

thus, the Clark County Second 

Maintenance Plan may demonstrate 

maintenance based on a comparison of 

existing and future emissions of ozone 

precursors.38

Clark County used the 2017 national 

emissions inventory (NEI) data as the 

baseline to develop growth factors for 

point, nonpoint, and locomotive 

sources. Clark County DES used the 

EPA 2016 v.1 modeling platform 

emissions data to develop per-year 

growth adjustment factors for point, 

nonpoint, federal aviation, and 

locomotives. Clark County DES used 

local activity data to develop 

commercial airport growth factors and 

conducted MOVES3 modeling to project 

on-road and non-road emissions. The 

derived growth adjustment factors were 

used to extrapolate emissions to account 

for a 16-year (2017 through 2033) 

spread. The 2033 growth factors were 

multiplied by the 2017 actual emissions 

to produce the 2033 projected point 

source and various other stationary 

source emissions; including Residential 

Wood Combustion,39 non-point VOC,40

airport,41 and locomotive emissions.42

An interim year (2023) projected 

emissions inventory is also included. 

On-road emissions were estimated for 

the 2017 base year and for projection 

years 2023 and 2033 and reflect a 32 

percent decrease in VMT from 2017 to 

2023 and a 56 percent decrease in VMT 

from 2017 to 2033 based on Regional 

Transit Commission (RTC) 

projections.43

In addition to accounting for areawide 

growth trends, Clark County DES added 

emissions from specific projects that are 

expected to become operational during 

the second maintenance period, 


khammond on DSKJM1Z7X2PROD with PROPOSALS
Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 88305 

44Clark County Second Maintenance Plan, 12, 

Figure 2–1. 

45Clark County Second Maintenance Plan, Page 

15. 

46Contingency Measure Revision, Section 2, 

‘‘Contingency Measures Plan.’’ 

including the proposed Southern 

Nevada Supplemental Airport, the 

proposed Sloan Regional Heliport, and 

DAF training program in the future-year 

emissions inventories, and also added 

in ERCs from certain stationary sources 

in the event that the ERCs are used for 

the purposes of issuing permits for new 

or modified stationary sources in the air 

quality planning area. We have 

reviewed the methods and assumptions, 

as described in connection with the 

attainment inventory, that Clark County 

DES used to project emissions to 2023 

and 2033 for the various source 

categories and find them to be 

reasonable. 

Table 1 compares the VOC and NOX

emissions estimated for the Clark 

County 8-hour ozone maintenance area 

for 2017 with those for 2023 and 2033 

by source category. The projected VOC 

and NOX emissions show that VOC and 

NOX emissions would remain well 

below the attainment levels throughout 

the second 10-year maintenance period 

and thereby adequately demonstrate 

maintenance through that period. 

In addition, historical monitoring data 

presented in the plan shows a gradual 

downward trend in ozone design values 

during 2008–2020. The 1997 NAAQS 

level of 80 ppb was achieved in 2009, 

and the 2020 value of 74 ppb is well 

below the NAAQS.44 This supports the 

maintenance demonstration, and the 

EPA expects this downward trend will 

continue given the projected emissions 

decreases. 

D. Verification of Continued Attainment 

NDEP and the Clark County Board of 

County Commissioners have the legal 

authority to implement and enforce the 

requirements of the Clark County 

Second Maintenance Plan. This 

includes the authority to adopt, 

implement and enforce any emissions 

control contingency measures 

determined to be necessary to correct 

ozone NAAQS violations. To verify 

continued attainment, Clark County 

DES commits in the Clark County 

Second Maintenance Plan to the 

continued operation of an ozone 

monitoring network that meets the EPA 

ambient air quality surveillance 

requirements. 

Secondly, the transportation 

conformity process represents another 

means by which to verify continued 

attainment of the 1997 8-hour ozone 

NAAQS in the Clark County 8-hour 

ozone area given the relative importance 

of motor vehicle emissions to the overall 

emissions inventories of ozone 

precursors.45

Lastly, while not cited in the plan, 

NDEP and Clark County DES must 

inventory emissions sources and report 

to the EPA on a periodic basis under 40 

CFR part 51, subpart A (‘‘Air Emissions 

Reporting Requirements’’). These 

emissions inventory updates will 

provide a third means with which to 

track emissions in the area relative to 

those projected in the maintenance plan 

and thereby verify continued attainment 

of the NAAQS. These methods are 

sufficient for the purpose of verifying 

continued attainment. 

E. Contingency Provisions 

Section 175A(d) of the Act requires 

that maintenance plans include 

contingency provisions, as the EPA 

deems necessary, to promptly correct 

any violations of the NAAQS that occur 

after redesignation of the area. Such 

provisions must include a requirement 

that the State will implement all 

measures with respect to the control of 

the air pollutant concerned which were 

contained in the SIP for the area before 

redesignation of the area as an 

attainment area. 

Under section 175A(d), contingency 

measures identified in the contingency 

plan do not have to be fully adopted at 

the time of redesignation. However, the 

contingency plan is an enforceable part 

of the SIP and should ensure that the 

contingency measures are adopted 

expeditiously once they are triggered by 

a specified event. The maintenance plan 

should clearly identify the measures to 

be adopted, a schedule and procedure 

for adoption and implementation, and a 

specific timeline for action by the State. 

As a necessary part of the plan, the State 

should also identify specific indicators 

or triggers, which will be used to 

determine when the contingency 

measures need to be implemented. 

As required by section 175A of the 

CAA, Clark County DES has adopted a 

contingency plan to address possible 

future ozone air quality problems.46

Clark County DES identifies the trigger 

date as 60 days after a determination of 

a confirmed violation of the 1997 8-hour 

ozone NAAQS. Within 45 days of the 

trigger date, Clark County will notify the 

EPA that it is evaluating potential 

contingency measures. Within 90 days 

of the trigger date, Clark County will 

send a report to the EPA and then will 

initiate a public process to consider the 

recommended contingency measures, 

including soliciting stakeholder 

involvement and holding public 

hearings. The necessary emissions 

control measures will be adopted and 

implemented no later than 18 months 

after the trigger date. 

Potential contingency measures listed 

in the maintenance plan are those 

emissions controls or other measures 

that Clark County, the Nevada State 

Board of Agriculture, and/or the Nevada 

State Environmental Commission may 

choose to adopt and implement in 

response to the contingency trigger. The 

contingency measures plan in the 

Contingency Measure Revision lists the 

following potential contingency 

measures that will be considered for 

adoption and implementation by the 

applicable State or County agency, but 

the Plan indicates that the list is not to 

be considered exclusive: 

• Reid vapor pressure reduction (i.e., 

in gasoline sold during the summer 

ozone season; would need to be adopted 

and implemented by the Nevada State 

Board of Agriculture); 

• Inspection/maintenance program 

changes and additions (e.g., lowering 

the cut points for VOCs and NOX

applicable to pre-1996 vehicles; would 

need to be adopted and implemented by 

the State Environmental Commission 

and/or the State Department of Motor 

Vehicles); 

• Consumer and commercial products 

(Clark County would be responsible for 

adoption and implementation); 

• Architectural surface coatings 

(Clark County would be responsible for 

adoption and implementation); 

• Lawn and garden equipment use 

(Clark County would be responsible for 

adoption and implementation); and 

• Establish/enhance trip reduction 

programs (Clark County and the RTC 

would be responsible for adoption and 

implementation). 

Upon our review of the plan, we find 

that the contingency provisions of the 

Contingency Measure Revision clearly 

identify specific contingency measures, 

contain tracking and triggering 

mechanisms to determine when 

contingency measures are needed, 

contain a description of the process of 

recommending and implementing 

contingency measures, and contain 

specific timelines for action. Thus, we 

conclude that the contingency 

provisions of the Contingency Measure 

Revision are adequate to ensure prompt 

correction of a violation and therefore 

comply with section 175A(d) of the Act. 

F. Motor Vehicle Emissions Budgets for 

Transportation Conformity 

Section 176(c) of the CAA requires 

federal actions in nonattainment and 


khammond on DSKJM1Z7X2PROD with PROPOSALS
88306 Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 

47Control strategy SIPs refer to RFP and 

attainment demonstration SIPs. 40 CFR 93.101. 

48 40 CFR 93.118(e)(4) and (5). For more 

information on the transportation conformity 

requirement and applicable policies on MVEBs, 

please visit our transportation conformity website 

at: http://www.epa.gov/otaq/stateresources/ 

transconf/index.htm. 

49 40 CFR 93.118(f)(2). 

50See the EPA Memorandum dated August 22, 

2023 titled: Adequacy Documentation for Motor 

Vehicle Emissions Budgets in Clark County Second 

Maintenance Plan.’’ 

maintenance areas to conform to the 

SIP’s goals of eliminating or reducing 

the severity and number of violations of 

the NAAQS and achieving expeditious 

attainment of the standards. Conformity 

to the SIP’s goals means that such 

actions will not: (1) cause or contribute 

to violations of a NAAQS, (2) worsen 

the severity of an existing violation, or 

(3) delay timely attainment of any 

NAAQS or any interim milestone. 

Actions involving Federal Highway 

Administration (FHWA) or Federal 

Transit Administration (FTA) funding 

or approval are subject to the EPA’s 

transportation conformity rule, codified 

at 40 CFR part 93, subpart A. Under this 

rule, RTCs in nonattainment and 

maintenance areas coordinate with state 

and local air quality and transportation 

agencies, the EPA, FHWA, and FTA to 

demonstrate that an area’s regional 

transportation plans and transportation 

improvement programs conform to the 

applicable SIP. This demonstration is 

typically done by showing that 

estimated emissions from existing and 

planned highway and transit systems 

are less than or equal to the motor 

vehicle emissions budgets (‘‘budgets’’) 

contained in submitted or approved 

control strategy SIPs and maintenance 

plans.47

These control strategy SIPs and 

maintenance plans typically set budgets 

for criteria pollutants and/or their 

precursors to address pollution from 

cars and trucks. Budgets are generally 

established for specific years and 

specific pollutants or precursors. 

Maintenance plan submittals should 

identify budgets for transportationrelated VOC and NOX emissions in the 

last year of the maintenance period. 

For budgets in a maintenance plan to 

be approvable, they must meet, at a 

minimum, the EPA’s adequacy 

criteria.48 To meet these requirements, 

the budgets must be consistent, when 

considered with emissions from all 

other sources, with maintenance of the 

NAAQS and reflect all the motor vehicle 

control measures relied upon for the 

maintenance demonstration. The EPA’s 

process for determining adequacy of a 

budget consists of three basic steps: (1) 

providing public notification of a SIP 

submission; (2) providing the public the 

opportunity to comment on the MVEB 

during a public comment period; and (3) 

making a finding of adequacy. The 

process for determining the adequacy of 

a submitted budget is codified at 40 CFR 

93.118(f). The EPA can notify the public 

by either posting an announcement that 

the EPA has received SIP budgets on the 

EPA’s adequacy website, or via a 

Federal Register notice of proposed 

rulemaking when the EPA reviews the 

adequacy of a maintenance plan budget 

simultaneously with its review and 

action on the SIP submittal itself.49

Clark County’s Second Maintenance 

Plan contains VOC and NOX budgets for 

2017, 2023 and 2033. Any and all 

comments on the approvability of the 

budgets should be submitted during the 

comment period stated in the DATES

section of this document. 

The EPA proposes to approve 2017, 

2023, and 2033 budgets in the Clark 

County Second Maintenance Plan for 

transportation conformity purposes in 

the final rulemaking on Clark County’s 

ozone redesignation request. If the EPA 

approves the budgets in the final 

rulemaking action, the new budgets 

must be used in future transportation 

conformity determinations for Clark 

County for the 2015 ozone standard. 

The new budgets, if approved in the 

final rulemaking, will be effective on the 

date of the EPA’s final rulemaking in the 

Federal Register. The applicable VOC 

and NOX MVEBs for the Clark County 

ozone nonattainment area are defined in 

table 2. 

TABLE 2—PROPOSED MOTOR VEHICLE EMISSIONS BUDGETS (MVEBS) FOR CLARK COUNTY

Budget year VOC 

(tpd, average summer weekday) 

NOX

(tpd, average summer weekday) 

2017 ......................................................................................................... 26.27 42.2 

2023 ......................................................................................................... 20.92 26.77 

2033 ......................................................................................................... 15.51 23.35 

From Table 6–3 and 6–4 of the Clark County Second Maintenance Plan. 

The MVEBs are the on-road mobile 

source VOC and NOX emissions for 

Clark County for 2017, 2023 and 2033. 

The budgets are compatible with the 

2017, 2023, and 2033 on-road mobile 

source VOC and NOX emissions 

included in Clark County’s 2017, 2023, 

and 2033 VOC and NOX emission 

inventories, as summarized in Table 2. 

The derivation of the budgets is 

thoroughly discussed in Appendix A, 

Chapter 2 of Clark County’s Second 

Maintenance Plan. While the Plan 

includes budgets for 2017, we are not 

evaluating the 2017 budgets because 

that year would not be used in any 

future conformity determination 

because the plan contains budgets for 

2023 and because 2017 budgets are not 

required for the submitted second 

maintenance plan. 

We evaluated the budgets against our 

adequacy criteria in 40 CFR 93.118(e)(4) 

and (5) as part of our review of the 

budget’s approvability and expect to 

complete the adequacy review of the 

budgets concurrent with our final action 

on the Clark County’s Second 

Maintenance Plan. The EPA is not 

required under its transportation 

conformity rule to find budgets 

adequate prior to proposing approval of 

them. In this notice, the EPA is 

announcing that the adequacy process 

for these budgets begins, and the public 

has 30 days to comment on their 

adequacy, per the transportation 

conformity rule at 40 CFR 93.118(f)(2)(i) 

and (ii). 

Clark County DES developed the 

budgets for 2023 and 2033 using onroad motor vehicle emission estimates 

made using the EPA’s MOVES3 model, 

fleet data from DMV registration data, 

CRC vehicle speed data, NDOT HPMS 

data, travel demand modeling from the 

Regional Transportation Commission 

and vehicle classification data from the 

June 2018 Clark County On-road 

Vehicle Classification Study. 

As documented in the separate 

memorandum 50 included in the docket 

for this rulemaking, we preliminarily 

conclude that the budgets in the Second 

Maintenance Plan meet each adequacy 

criterion. While adequacy and approval 


khammond on DSKJM1Z7X2PROD with PROPOSALS
Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 88307 

51Clark County Ozone NAA EJSCREEN Report 

dated February 10, 2023. 

52Clark County Second Maintenance Plan 

(submitted electronically January 24, 2022). 

are two separate actions, reviewing the 

budgets in terms of the adequacy criteria 

informs the EPA’s decision to propose 

to approve the budgets. We have 

completed our detailed review and are 

proposing to approve the demonstration 

of maintenance for the 1997 ozone 

maintenance area through the year 2033. 

We have also reviewed the budgets in 

Clark County’s Second Maintenance 

Plan and found that they are consistent 

with the maintenance demonstration for 

which we are proposing approval, are 

clearly identified and precisely 

quantified, are based on control 

measures that have already been 

adopted and implemented, and meet all 

other applicable statutory and 

regulatory requirements including the 

adequacy criteria in 40 CFR 93.118(e)(4) 

and (5). The EPA is proposing to 

approve the budgets for 2023 and 2033 

as part of our approval of Clark County’s 

Second Maintenance Plan. At the point 

when we either finalize the adequacy 

process or approve the budgets as 

proposed (whichever occurs first; note 

that they could also occur concurrently 

per 40 CFR 93.118(f)(2)(iii)), the budgets 

must be used by the Regional 

Transportation Commission (i.e., the 

Metropolitan Planning Organization 

(MPO) for this area) for transportation 

conformity determinations for the Clark 

County 2015 ozone nonattainment area. 

VI. Environmental Justice 

Considerations 

The EPA performed a screening-level 

analysis using the EPA’s environmental 

justice (EJ) screening and mapping tool 

(‘‘EJSCREEN’’). Our screening-level 

analysis included multiple 

environmental and demographic 

indicators, including the EJSCREEN 

‘‘Demographic Index,’’ which is the 

average of an area’s percentage of 

minority and low-income populations. 

The Demographic Index of Clark County 

is at the 68th percentile, compared to 

the United States as a whole.51 The 

results of this analysis are being 

provided for informational and 

transparency purposes. 

This action addresses a plan for 

continued maintenance of the 1997 

ozone NAAQS for Clark County. 

Approval of this plan does not impose 

any additional regulatory requirements 

on sources beyond those imposed by 

state law. As discussed in this 

document, Nevada has demonstrated 

that the Clark County is attaining the 

1997 ozone NAAQS and the Clark 

County Second Maintenance Plan 

provides for the maintenance of the 

NAAQS for the reminder of the 

maintenance period. We expect that this 

action will generally be neutral or 

contribute to reduced environmental 

and health impacts on all populations in 

Clark County, including people of color 

and low-income populations. At a 

minimum, this action would not worsen 

any existing air quality and is expected 

to ensure the area is meeting 

requirements to maintain air quality 

standards. Further, there is no 

information in the record indicating that 

this action is expected to have 

disproportionately high or adverse 

human health or environmental effects 

on a particular group of people. 

VII. Proposed Action and Request for 

Public Comment 

Under CAA section 110(k)(3), and for 

the reasons set forth in this document, 

the EPA is proposing to approve the 

Clark County Second Maintenance Plan 

submitted by NDEP on January 24, 2022, 

as a revision to the Nevada SIP.52 We 

are proposing to approve the 

maintenance demonstration and 

contingency provisions as meeting all 

applicable requirements for 

maintenance plans and related 

contingency provisions in CAA section 

175A, and the budgets for 2023 and 

2033 (shown in Table 2) for 

transportation conformity purposes as 

we find they meet all applicable criteria 

for such budgets including the adequacy 

criteria under 40 CFR 93.118(e). 

We are soliciting comments on these 

proposed actions. We will accept 

comments from the public for 30 days 

following publication of this proposal in 

the Federal Register and will consider 

any relevant comments before taking 

final action. 

VIII. Statutory and Executive Order 

Reviews 

Under the Clean Air Act, the 

Administrator is required to approve a 

SIP submission that complies with the 

provisions of the Act and applicable 

federal regulations. 42 U.S.C. 7410(k); 

40 CFR 52.02(a). Thus, in reviewing SIP 

submissions, the EPA’s role is to 

approve state choices, provided that 

they meet the criteria of the Clean Air 

Act. Accordingly, this proposed action 

merely proposes to approve state law as 

meeting federal requirements and does 

not impose additional requirements 

beyond those imposed by state law. For 

that reason, this proposed action: 

• Is not a ‘‘significant regulatory 

action’’ subject to review by the Office 

of Management and Budget under 

Executive Orders 12866 (58 FR 51735, 

October 4, 1993) and 13563 (76 FR 3821, 

January 21, 2011); 

• Does not impose an information 

collection burden under the provisions 

of the Paperwork Reduction Act (44 

U.S.C. 3501 et seq.); 

• Is certified as not having a 

significant economic impact on a 

substantial number of small entities 

under the Regulatory Flexibility Act (5 

U.S.C. 601 et seq.); 

• Does not contain any unfunded 

mandate or significantly or uniquely 

affect small governments, as described 

in the Unfunded Mandates Reform Act 

of 1995 (Pub. L. 104–4); 

• Does not have federalism 

implications as specified in Executive 

Order 13132 (64 FR 43255, August 10, 

1999); 

• Is not an economically significant 

regulatory action based on health or 

safety risks subject to Executive Order 

13045 (62 FR 19885, April 23, 1997); 

• Is not a significant regulatory action 

subject to Executive Order 13211 (66 FR 

28355, May 22, 2001); 

• Is not subject to requirements of 

section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (15 U.S.C. 272 note) because 

application of those requirements would 

be inconsistent with the Clean Air Act; 

and 

• Will not have disproportionately 

high and adverse human health or 

environmental effects on minority 

populations, low-income populations 

and/or indigenous peoples, as specified 

in Executive Order 12898 (59 FR 7629, 

February 16, 1994), as discussed in 

section VI of this proposal. 

In addition, there are no areas of 

Indian country within the planning 

area, and the state plan for which the 

EPA is proposing approval does not 

apply on any Indian reservation land or 

in any other area where the EPA or an 

Indian tribe has demonstrated that a 

tribe has jurisdiction. In those areas of 

Indian country, the Clark County 

Second Maintenance Plan does not 

apply, and therefore, this proposed 

action does not have tribal implications 

and would not, if approved, impose 

substantial direct costs on tribal 

governments or preempt tribal law as 

specified by Executive Order 13175 (65 

FR 67249, November 9, 2000). 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Nitrogen dioxide, Particulate 

matter, Sulfur dioxide, Reporting and 

recordkeeping requirements, Volatile 

organic compounds. 

Authority: 42 U.S.C. 7401 et seq. 


khammond on DSKJM1Z7X2PROD with PROPOSALS
88308 Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules 

1See 75 FR 35520 and https://www.gpo.gov/ 

fdsys/pkg/FR-2010-06-22/pdf/2010-13947.pdf. 2See also NAAQS Table at https://www.epa.gov/ 

criteria-air-pollutants/naaqs-table. 

3On February 25, 2019, EPA finalized a second 

review of the SO2 standard, retaining the existing 

primary 1-hour SO2 NAAQS based on a review of 

the full body of currently available scientific 

evidence and exposure/risk information at the time. 

See 84 FR 9866 and https://www.epa.gov/so2- 

pollution/primary-national-ambient-air-qualitystandard-naaqs-sulfur-dioxide. 

4EPA promulgated the 1971 primary and 

secondary NAAQS for SO2 on April 30, 1971. See 

36 FR 8186. The 1971 primary SO2 standards of 365 

mg/m3 (0.14 ppm), averaged over a period of 24 

hours and not to be exceeded more than once per 

year, and 80 mg/m3 (0.03 ppm), as an annual 

arithmetic mean. 

5EPA did not revise the secondary 3-hour SO2

NAAQS set at 0.5 ppm in the 2010 or 2019 NAAQS 

review. 

6EPA arrived at the same conclusion in the 2019 

review of the SO2 standard when the agency 

retained the 1-hour SO2 standard of 75 ppb stating 

(respecting the rationale to revoke the previous SO2

standard) ‘‘the evidence in this review [2019] is not 

substantively changed from that in the last review 

[2010].’’ See 84 FR 9866 (March 18, 2019). 

7The owner or operator of a new or modified 

source will still be required to demonstrate 

compliance with the annual and 24-hour SO2

increments, even when their counterpart NAAQS 

are revoked. The annual and 24-hour increments 

are established in the CAA and will need to remain 

in the prevention of significant deterioration 

regulations because EPA does not interpret the CAA 

to authorize EPA to remove them. See 75 FR at 

35578. 

Dated: December 14, 2023. 

Martha Guzman Aceves, 

Regional Administrator, Region IX. 

[FR Doc. 2023–27874 Filed 12–20–23; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R04–OAR–2023–0232; FRL–11600– 

01–R4] 

Air Plan Approval; GA; Miscellaneous 

Rule Revision 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to approve a 

State Implementation Plan (SIP) 

revision submitted by the State of 

Georgia, through the Georgia 

Environmental Protection Division 

(EPD) via a letter dated October 20, 

2022. The revision seeks to change 

Georgia’s Rules for Air Quality Control 

in the SIP by removing the 1971 annual 

and 24-hour ambient air quality primary 

standard for sulfur dioxide (SO2), which 

no longer applied in Georgia as of April 

30, 2022. EPA is proposing to approve 

this SIP revision because the State has 

demonstrated that this change is 

consistent with the Clean Air Act (CAA 

or Act). 

DATES: Comments must be received on 

or before January 22, 2024. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. at EPA– 

R04–OAR–2023–0232 at https://

www.regulations.gov. Follow the online 

instructions for submitting comments. 

Once submitted, comments cannot be 

edited or removed from Regulations.gov. 

EPA may publish any comment received 

to its public docket. Do not submit 

electronically any information you 

consider to be Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Multimedia submissions (audio, video, 

etc.) must be accompanied by a written 

comment. The written comment is 

considered the official comment and 

should include discussion of all points 

you wish to make. EPA will generally 

not consider comments or comment 

contents located outside of the primary 

submission (i.e., on the web, cloud, or 

other file sharing system). For 

additional submission methods, the full 

EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

https://www.epa.gov/dockets/ 

commenting-epa-dockets. 

FOR FURTHER INFORMATION CONTACT: 

Josue Ortiz Borrero, Air Regulatory 

Management Section, Air Planning and 

Implementation Branch, Air and 

Radiation Division, U.S. Environmental 

Protection Agency, Region 4, 61 Forsyth 

Street SW, Atlanta, Georgia 30303–8960. 

The telephone number is (404) 562– 

8085. Mr. Ortiz Borrero can also be 

reached via electronic mail at 

ortizborrero.josue@epa.gov. 

SUPPLEMENTARY INFORMATION: 

I. Background 

On June 2, 2010, EPA revised the 

primary SO2 national ambient air 

quality standards (NAAQS or standards) 

to provide requisite protection of public 

health with an adequate margin of 

safety. See 75 FR 35520 (June 22, 2010). 

Specifically, EPA established a new 1- 

hour SO2 standard at a level of 75 parts 

per billion (ppb), codified at 40 CFR 

50.17.1 2 The 1-hour standard is met at 

an ambient air quality monitoring site 

when the 3-year average of the annual 

99th percentile of daily maximum 1- 

hour average concentrations is less than 

or equal to 75 ppb, as determined in 

accordance with Appendix T of 40 CFR 

part 50 and 40 CFR 50.17(a) and (b).3

EPA set this new 1-hour short-term 

standard to replace the 1971 primary 24- 

hour standard of 0.14 parts per million 

(ppm) and the annual SO2 standard set 

of 0.03 ppm.4 5 In the 2010 SO2 NAAQS 

final rulemaking, the Administrator 

concluded it was appropriate to revoke 

the 24-hour and annual primary 

standards,6 stating ‘‘a 1-hour standard at 

[a] level of 75 ppb would have the effect 

of maintaining 24-hour and annual SO2

concentrations generally well below the 

levels of the current 24-hour and annual 

NAAQS.’’ See 75 FR at 35550. The final 

rule also states, based on health 

evidence and risk-based information, 

that the 1971 SO2 standards ‘‘ ‘are not 

adequate to protect public health, 

especially in relation to short-term 

exposures to SO2 (5–10 minutes) by 

exercising asthmatics’ ’’ and that the 

new 1-hour standard would provide 

requisite protection of public health 

with an adequate margin of safety. See 

75 FR at 35530, 35550. 

Anti-Backsliding 

When EPA revised the SO2 NAAQS in 

2010, replacing the annual and 24-hour 

standards with a short term 1-hour 

standard, EPA also addressed the 

section 172(e) anti-backsliding 

provision of the CAA and determined 

what provisions are appropriate to 

provide for transition to the new 

standard. Section 172(e) of the CAA 

specifies that if EPA relaxes a NAAQS, 

control obligations no less stringent 

than those that apply in nonattainment 

area SIPs may not be relaxed, and 

adopting those controls that have not 

yet been adopted as needed may not be 

avoided. Even though the 2010 1-hour 

standard is more protective than the 

previous SO2 NAAQS, anti-backsliding 

provisions were necessary to insure that 

the health protection provided by the 

prior NAAQS continues to be achieved 

as well as maintained as states 

transition to the new standard.7

Specifically, EPA established at 40 CFR 

50.4(e) when the 1971 SO2 NAAQS 

would be revoked in areas, and when it 

was necessary to retain the older SO2

standards, setting conditions needed for 

the eventual transition to the new 1- 

hour SO2 NAAQS. Specifically, 40 CFR 

50.4(e) provides that the 1971 SO2

NAAQS will no longer apply to an area 

one year after the effective date of the 

designation of that area for the 2010 SO2

NAAQS set forth in § 50.17; except that 

the 1971 SO2 NAAQS remains in effect 

for areas that are nonattainment for that 

NAAQS as of the effective date of the 

2010 SO2 NAAQS, and areas not 

meeting the requirements of a SIP call 

with respect to requirements for the 

1971 SO2 NAAQS until that area 

submits, and EPA approves, an 


khammond on DSKJM1Z7X2PROD with PROPOSALS