The EPA Region 9 Regional Administrator Jared Blumenfeld signed the following proposed rule on November 2, 2012, and EPA is submitting it 

for publication in the Federal Register (FR). While we have taken steps to ensure the accuracy of this Internet version of the document, it is not 

the official version of the rule for purposes of public comment. Please refer to the official version in a forthcoming FR publication, which will 

appear on the Government Printing Office’s FDsys website (http://fdsys.gpo.gov/fdys/search/home.action) and on Regulations.gov 

(http://www.regulations.gov) in Docket No. EPA-R09-OAR-2012-0792. 

Billing Code: 6560-50-P 

ENVIRONMENTAL PROTECTION AGENCY 

40 CFR Parts 52 and 81 

[EPA-R09-OAR-2012-0792;_________] 

Approval and Promulgation of Implementation Plans and 

Designation of Areas for Air Quality Planning Purposes; State of 

Nevada; Redesignation of Clark County to Attainment for the 1997 

8-Hour Ozone Standard 

AGENCY: Environmental Protection Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: EPA is proposing to approve, as a revision of the 

Nevada state implementation plan, the State's plan for 

maintaining the 1997 8-hour ozone standard in Clark County for 

ten years beyond redesignation, and the related motor vehicle 

emissions budgets, because they meet the applicable requirements 

for such plans and budgets. EPA is also proposing to approve a 

request from the Nevada Division of Environmental Protection to 

redesignate the Clark County ozone nonattainment area to 

attainment of the 1997 8-hour ozone National Ambient Air Quality 

Standard because the request meets the statutory requirements 

for redesignation under the Clean Air Act. 

DATES: Comments must be received on or before [Federal Register: 

Insert date 30 days after the publication date]. 
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This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

ADDRESSES: Submit your comments, identified by Docket ID Number 

EPA-R09-OAR-2012-0792, by one of the following methods: 

1. http://www.regulations.gov: Follow the on-line 

instructions for submitting comments. 

2. Email: r9_airplanning@epa.gov. 

3. Fax: 415-947-3579. 

4. Mail or deliver: Ginger Vagenas (AIR-2), U.S. 

Environmental Protection Agency, Region IX, 75 Hawthorne Street, 

San Francisco, CA 94105-3901. Deliveries are only accepted 

during the Regional Office's normal hours of operation. 

Instructions: All comments will be included in the public 

docket without change and may be made available online at 

http://www.regulations.gov, including any personal information 

provided, unless the comment includes Confidential Business 

Information (CBI) or other information whose disclosure is 

restricted by statute. Information that you consider CBI or 

otherwise protected should be clearly identified as such and 

should not be submitted through http://www.regulations.gov or 

email. http://www.regulations.gov is an anonymous access system, 

and EPA will not know your identity or contact information 

unless you provide it in the body of your comment. If you send 

email directly to EPA, your email address will be automatically 

captured and included as part of the public comment. If EPA 

cannot read your comment due to technical difficulties and 
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This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

cannot contact you for clarification, EPA may not be able to 

consider your comment. 

Docket: Generally, documents in the docket for this action 

are available electronically at www.regulations.gov and in hard 

copy at EPA Region IX, 75 Hawthorne Street, San Francisco, 

California. While all documents in the docket are listed at 

www.regulations.gov, some information may be publicly available 

only at the hard copy location (e.g., copyrighted material, 

large maps), and some may not be publicly available in either 

location (e.g., CBI). To inspect the hard copy materials, please 

schedule an appointment during normal business hours with the 

contact listed in the FOR FURTHER INFORMATION CONTACT section. 

FOR FURTHER INFORMATION CONTACT: Ginger Vagenas, Air Planning 

Office (AIR-2), U.S. Environmental Protection Agency, Region IX, 

(415) 972-3964, vagenas.ginger@epa.gov. 

SUPPLEMENTARY INFORMATION: Throughout this document, whenever 

“we,” “us,” or “our” is used, we mean EPA. This supplementary 

information section is arranged as follows: 

Table of Contents 

I. Summary of Today's Proposed Action 

II. Background 

III. Procedural Requirements for Adoption and Submittal of SIP 

Revisions 

IV. Substantive Requirements for Redesignation 
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steps to ensure the accuracy of this version, but it is not the official version. 

V. Evaluation of the State's Redesignation Request for the 

Clark County 8-Hour Ozone Nonattainment Area 

A. Determination That the Area Has Attained the Applicable 

NAAQS. 

B. The Area Must Have a Fully Approved SIP Meeting 

Requirements Applicable for Purposes of Redesignation under 

Section 110 and Part D. 

1. Basic SIP Requirements under CAA Section 110 

2. Part D Requirements 

a. Introduction 

b. Emissions Inventory 

c. Permits for New and Modified Major Stationary Sources 

d. Compliance with Section 110(a)(2) 

e. Conformity Requirements 

C. The Area Must Show the Improvement in Air Quality is Due to 

Permanent and Enforceable Emissions Reductions. 

D. The Area Must Have a Fully Approved Maintenance Plan under 

CAA Section 175A. 

1. Attainment Inventory 

2. Maintenance Demonstration 

3. Monitoring Network 

4. Verification of Continued Attainment 

5. Contingency Provisions 

6. Subsequent Maintenance Plan Revisions 
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steps to ensure the accuracy of this version, but it is not the official version. 

7. Motor Vehicle Emissions Budgets 

VI. Proposed Action and Request for Public Comment 

VII. Statutory and Executive Order Reviews 

I. Summary of Today's Proposed Action 

EPA is proposing to take several related actions. First, 

under Clean Air Act (CAA or "Act") section 110(k)(3), EPA is 

proposing to approve a submittal from the Nevada Division of 

Environmental Protection (NDEP) dated April 11, 2011 of Clark 

County's Ozone Redesignation Request and Maintenance Plan (March 

2011) ("Clark County Ozone Maintenance Plan" or "Ozone 

Maintenance Plan") as a revision to the Nevada state 

implementation plan (SIP). 

In connection with the Clark County Ozone Maintenance Plan, 

EPA finds that the maintenance demonstration showing how the 

area will continue to attain the 1997 8-hour ozone national 

ambient air quality standard (NAAQS) for 10 years beyond 

redesignation (i.e., through 2022) 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. EPA is also proposing to approve 

the motor vehicle emissions budgets (MVEBs) in the Clark County 

Ozone Maintenance Plan because we find they meet the applicable 

transportation conformity requirements under 40 CFR 93.118(e). 
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This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

Second, under CAA section 107(d)(3)(D), EPA is proposing to 

approve NDEP's request that accompanied the submittal of the 

maintenance plan to redesignate the Clark County 8-hour ozone 

nonattainment area to attainment for the 1997 8-hour ozone 

NAAQS. We are doing so based on our conclusion that the area has 

met the five criteria for redesignation under CAA section 

107(d)(3)(E). Our conclusion in this regard is in turn based on 

our proposed determination that the area has attained the 1997 

8-hour ozone NAAQS, that relevant portions of the Nevada SIP are 

fully approved, that the improvement in air quality is due to 

permanent and enforceable reductions in emissions, that Nevada 

has met all requirements applicable to the Clark County 8-hour 

ozone nonattainment area with respect to section 110 and part D 

of the CAA, and based on our proposed approval as part of this 

action of the Clark County Ozone Maintenance Plan. 

II. Background 

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. 
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This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

In 1971, under section 109 of the Act, as amended in 1970, 

EPA promulgated the original NAAQS for several pervasive air 

pollutants, including photochemical oxidants. NAAQS represent 

concentration levels the attainment and maintenance of which, 

allowing for an adequate margin of safety, EPA has determined to 

be requisite to protect public health ("primary" NAAQS) and 

welfare ("secondary" NAAQS). 

In 1978, EPA designated the Las Vegas Valley (hydrographic 

area No. 212) as a nonattainment area for the photochemical 

oxidant NAAQS. See 43 FR 8962 (March 3, 1978). In 1979, EPA 

revised the NAAQS from an hourly average of 0.08 parts per 

million (ppm) oxidant to an hourly average of 0.12 ppm ozone. 

See 44 FR 8220 (February 8, 1979). The nonattainment designation 

for Las Vegas Valley for photochemical oxidant carried over to 

the 1-hour ozone NAAQS. 

During the 1980s, Clark County adopted a number of rules 

and prepared a number of nonattainment plans to address planning 

requirements under the CAA, as amended in 1977. NDEP submitted 

these rules and plans to EPA at various times, and EPA approved 

a number of them into the Nevada SIP. Among the rules approved 

by EPA as revisions to the Nevada SIP as part of the ozone 

control strategy in Las Vegas Valley are Clark County air 

pollution rules section 33, which relates to chlorine in 

chemical processes); sections 50, 51, and 52, which relate to 
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steps to ensure the accuracy of this version, but it is not the official version. 

storage and distribution of petroleum products; and section 60, 

which relates to evaporation and leakage. In 1986, in light of 

the approved control strategy and monitored levels below the 

NAAQS, EPA redesignated Las Vegas Valley to attainment for the 

1-hour ozone NAAQS. See 51 FR 41788 (November 19, 1986). 

In 1997, EPA revised the NAAQS for ozone, setting it at 

0.08 ppm averaged over an 8-hour time frame ("1997 8-hour ozone 

standard"). 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. EPA determined that the 1997 8-hour 

standard 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.1

In 2004, EPA designated areas of the country with respect 

to the 1997 8-hour ozone NAAQS. See 69 FR 23857 (April 30, 

2004). Under EPA's "Phase 1" implementation rule for the 1997 8-

hour ozone standard (69 FR 23951, April 30, 2004), an area was 

classified under subpart 2 based on its 8-hour ozone design 

 

1 On March 27, 2008 (73 FR 16436), EPA promulgated a revised 8-hour ozone 

standard of 0.075 ppm (the 2008 8-hour ozone standard), and on May 21, 2012, 

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. 
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steps to ensure the accuracy of this version, but it is not the official version. 

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 value2 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 values3 (69 FR 

23958). Clark County was designated as a "subpart 1" ozone 

nonattainment area by 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, EPA reduced the 

geographic extent of the ozone nonattainment area to encompass a 

portion of, but not all of, Clark County.4 See 69 FR 55956 

(September 17, 2004), 70 FR 71612 (November 29, 2005), and 40 

CFR 81.329. 

On December 22, 2006, the U.S. Court of Appeals for the 

District of Columbia Circuit (D.C. Circuit) vacated EPA's Phase 

1 implementation rule for the 1997 8-hour ozone standard (69 FR 

23591, April 30, 2004). South Coast Air Quality Management Dist. 

 

2 The 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 worst-case 

monitoring site in the area. 

3 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 worstcase monitoring site in the area.

4 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. 
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steps to ensure the accuracy of this version, but it is not the official version. 

v. EPA, 472 F.3d 882 (D.C. Cir. 2006). On June 8, 2007, in 

response to several petitions for rehearing, the D.C. Circuit 

Court (Court) clarified that the Phase 1 rule was vacated only 

for those parts of the rule that had been successfully 

challenged. The June 8, 2007, decision left intact the Court's 

rejection of 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 vacating of the 

provision of EPA’s Phase 1 implementation rule for the 1997 8-

hour ozone standard that placed certain nonattainment areas, 

including Clark County solely under subpart 1, EPA classified 

Clark County as a marginal ozone nonattainment area under 

subpart 2 of the CAA (77 FR 28424). 

On July 28, 2008, NDEP submitted the 8-hour Ozone Early 

Progress Plan for Clark County, Nevada (June 2008) ("Clark 

County Ozone EPP") to EPA as a revision to the Nevada SIP. The 

purpose of the Clark County Ozone EPP was to establish motor 

vehicle emissions budgets (MVEBs) consistent with progress 

towards attainment of the 1997 8-hour ozone standard in advance 

of completion and submittal of an attainment demonstration. The 

Clark County EPP established MVEBs of 64.2 and 76.1 tons per day 

(ozone season) for VOC and NOx, respectively, for 2008. On May 5, 

2009, EPA found the MVEBs in the Clark County EPP adequate for 
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steps to ensure the accuracy of this version, but it is not the official version. 

the purposes of transportation conformity. See 74 FR 22738 (May 

14, 2009). Since the effective date of EPA's adequacy finding 

(i.e., May 29, 2009), the applicable metropolitan planning 

organization (MPO), i.e., the Regional Transportation Commission 

of Southern Nevada (RTC), and the U.S. Department of 

Transportation have been required to use these budgets in 

transportation conformity analyses for regional transportation 

plans, programs and projects. 

On March 29, 2011, 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 

(76 FR 17343). As a result, the obligation for the State of 

Nevada to submit an attainment demonstration and associated 

reasonably available control measures (RACM), a reasonable 

further progress (RFP) plan, contingency measures and other 

planning requirements related to attainment of the 1997 8-hour 

ozone NAAQS was suspended until such time as: the area is 

redesignated to attainment, at which time the requirements no 

longer apply; or EPA determines that the area has violated the 

1997 8-hour ozone NAAQS. See 40 CFR 51.918. In this action, we 

are updating the determination of attainment to account for more 
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This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

recent ozone monitoring data consistent with the applicable 

criterion for redesignation under CAA section 107(d)(3)(E)(i). 

Lastly, on April 11, 2011, NDEP submitted the Clark County 

Ozone Maintenance Plan and requested that EPA redesignate the 

Clark County 8-hour ozone nonattainment area to attainment for 

the 1997 8-hour ozone standard. We are proposing action today on 

the NDEP's April 11, 2011 redesignation request and submittal of 

the Clark County Ozone Maintenance Plan. 

III. Procedural Requirements for Adoption and Submittal of SIP 

Revisions 

Section 110(l) of the Act requires States to provide 

reasonable notice and public hearing prior to adoption of SIP 

revisions. In this action, we are proposing action on NDEP's 

April 11, 2011 submittal of the Clark County Ozone Maintenance 

Plan as a revision to the Nevada SIP. 

Appendix C of the Clark County Ozone Maintenance Plan 

documents the public review process followed by Clark County in 

adopting the plan prior to transmittal to NDEP for subsequent 

submittal to EPA as a revision to the Nevada SIP. The 

documentation in appendix C 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 ozone maintenance plan was published on 
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This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

December 12, 2010 in a newspaper of general circulation within 

the Las Vegas area and on the County's webpage. No comments were 

submitted. 

On February 1, 2011, the Clark County Board of 

Commissioners set a public hearing for March 15, 2011 to 

consider and approve the Clark County Ozone Maintenance Plan. 

The announcement of the public hearing was subsequently 

published on the County's webpage. On March 15, 2011, the Clark 

County Board of Commissioners adopted the Clark County Ozone 

Maintenance Plan at the close of the public hearing. Following 

adoption, Clark County Department of Air Quality (DAQ) 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 EPA for approval on April 11, 2011. 

Based on the documentation contained in appendix C of the 

plan, we find that the submittal of the Clark County Ozone 

Maintenance Plan as a SIP revision satisfies the procedural 

requirements of section 110(l) of the Act for revising SIPs. 

IV. Substantive Requirements for Redesignation 

The CAA establishes the requirements for redesignation of a 

nonattainment area to attainment. Specifically, section 

107(d)(3)(E) allows for redesignation provided that the 

following criteria are met: (1) EPA determines that the area has 

attained the applicable NAAQS; (2) EPA has fully approved the 
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This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

applicable implementation plan for the area under section 

110(k); (3) EPA determines that the improvement in air quality 

is due to permanent and enforceable reductions in emissions 

resulting from implementation of the applicable SIP, applicable 

Federal air pollution control regulations, and other permanent 

and enforceable reductions; (4) EPA has fully approved a 

maintenance plan for the area as meeting the requirements of CAA 

section 175A; and (5) the State containing such area has met all 

requirements applicable to the area under section 110 and part D 

of the CAA. Section 110 identifies a comprehensive list of 

elements that SIPs must include, and part D establishes the SIP 

requirements for nonattainment areas. Part D is divided into six 

subparts. The generally-applicable nonattainment SIP 

requirements are found in part D, subpart 1, and the ozonespecific nonattainment SIP requirements are found in part D, 

subpart 2. 

EPA provided guidance on redesignations in a document 

entitled, “State Implementation Plans; General Preamble for the 

Implementation of Title I of the Clean Air Act Amendments of 

1990,” published in the Federal Register on April 16, 1992 (57 

FR 13498), and supplemented on April 28, 1992 (57 FR 18070) 

(referred to herein as the “General Preamble”). Another relevant 

EPA guidance document includes “Procedures for Processing 

Requests to Redesignate Areas to Attainment,” Memorandum from 
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This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

John Calcagni, Director, Air Quality Management Division, EPA 

Office of Air Quality Planning and Standards, September 4, 1992 

(referred to herein as the “Calcagni memo”). 

For the reasons set forth below in section V of this 

document, we propose to approve NDEP's request for redesignation 

of the Clark County 8-hour ozone nonattainment area to 

attainment for the 1997 8-hour ozone NAAQS based on our 

conclusion that all of the criteria under CAA section 

107(d)(3)(E) have been satisfied. 

V. Evaluation of the State's Redesignation Request for the Clark 

County 8-Hour Ozone Nonattainment Area 

A. Determination That the Area Has Attained the Applicable 

NAAQS. 

CAA section 107(d)(3)(E)(i) requires that we determine that 

the area has attained the NAAQS. EPA generally makes the 

determination of whether an area’s air quality meets the ozone 

NAAQS based upon the most recent three years of complete, 

quality-assured data gathered at established State and Local Air 

Monitoring Stations (SLAMS) in the nonattainment area and 

entered into the EPA Air Quality System (AQS) database. Data 

from air monitors operated by state/local agencies in compliance 

with EPA monitoring requirements must be submitted to AQS. Heads 

of monitoring agencies annually certify that these data are 

accurate to the best of their knowledge. Accordingly, EPA relies 
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primarily on data in AQS when determining the attainment status 

of areas. See 40 CFR 50.10; 40 CFR part 50, appendix I; 40 CFR 

part 53; 40 CFR part 58, appendices A, C, D and E. All data are 

reviewed to determine the area's air quality status in 

accordance with 40 CFR part 50, appendix I.

Under EPA regulations at 40 CFR part 50, the 1997 8-hour 

ozone standard is attained at a site when the 3-year average of 

the annual fourth-highest daily maximum 8-hour average ozone 

concentrations at an ozone monitor is less than or equal to 0.08 

ppm. See 40 CFR 50.10. This 3-year average is referred to as the 

design value. When the design value is less than or equal to 

0.084 ppm (based on the rounding convention in 40 CFR part 50, 

appendix I) at each monitoring site within the area, then the 

area is meeting the NAAQS. The data completeness requirement is 

met when the three-year average percent of days with valid 

ambient monitoring data is at least 90%, and no single year has 

less than 75% data completeness as determined in appendix I of 

40 CFR part 50. 

The Clark County Department of Air Quality (DAQ), 

(previously known as Clark County Department of Air Quality and 

Environmental Management, or DAQEM) is responsible for 

monitoring ambient air quality within Clark County. DAQ submits 

monitoring network plan reports to EPA on an annual basis. These 

reports discuss the status of the air monitoring network, as 
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steps to ensure the accuracy of this version, but it is not the official version. 

required under 40 CFR part 58. Beginning in 2007, EPA has 

reviewed these annual plans for compliance with the applicable 

reporting requirements in 40 CFR 58.10. With respect to ozone, 

we have found DAQ's annual network plans to meet the applicable 

requirements under 40 CFR part 58. See EPA letters to DAQ 

concerning DAQ's annual network plan reports for 2010 and 2011, 

included in the docket for this rulemaking. Furthermore, we 

concluded in our Technical System Audit Report (February 2010) 

that Clark County DAQ's ambient air monitoring network currently 

meets or exceeds the requirements for the minimum number of 

monitoring sites designated as SLAMS for all of the criteria 

pollutants. Also, DAQ annually certifies that the data it 

submits to AQS are complete and quality-assured. See, e.g., the 

letter dated February 28, 2012, from Lewis Wallenmeyer, 

Director, DAQ, to Jared Blumenfeld, EPA Region IX Regional 

Administrator. 

Clark County DAQ operated 13 ozone SLAMS monitoring sites 

during the 2009-2011 period5 within the Clark County ozone 

nonattainment area: Apex (Apex Valley), Boulder City (City of 

Boulder City), Craig Road (City of North Las Vegas), J.D. Smith 

 

5 As allowed by 40 CFR 58.14, Clark County DAQ has periodically modified its 

monitoring network and therefore not all monitors operated over the entire 

2009–2011 period. In 2010, the Craig Road, Lone Mountain, and Orr monitors 

were discontinued. EPA has approved the discontinuation of these sites (see 

letter dated October 23, 2012 from Matthew Lakin, Manager, Air Quality 

Analysis Office, EPA Region IX to Mike Sword, Engineering Manager, Clark 

County DAQ). Clark County’s monitoring network has exceeded the number of 

required monitors throughout the referenced time period. 
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School (City of North Las Vegas), Jean (City of Jean, south of 

Las Vegas), Jerome Mack (near North Las Vegas Airport), Joe Neal 

(northwest Las Vegas), Lone Mountain (northwest Las Vegas), Orr 

School (central-southeast Las Vegas), Paul Meyer Park (southwest 

Las Vegas), Palo Verde School (west Las Vegas), Walter Johnson 

(west Las Vegas), and Winterwood (southeast Las Vegas). All 13 

sites have monitored ozone concentrations on a continuous basis 

using ultraviolet absorption monitors.6 The spatial scale and 

monitoring objective of most of DAQ's ozone monitoring sites are 

“neighborhood” and “population exposure,” respectively. The 

exceptions are the Apex and Jean sites, whose spatial scale and 

monitoring objective is “regional” and “regional transport,” 

respectively, and the Joe Neal site, whose spatial scale is 

“neighborhood” and monitoring objective is “highest 

concentration.” See “Clark County Department of Air Quality and 

Environmental Management - Annual Network Plan Report (June 

2011).” 

Consistent with the requirements contained in 40 CFR part 

50, EPA has reviewed the ozone ambient air monitoring data for 

the monitoring period from 2009 through 2011 collected at the 

monitoring sites discussed above, as recorded in AQS and 

 

6 DAQ operates Federal equivalent method (FEM) monitors for ozone. 

Specifically, API 400 Series ultraviolet absorption monitors. See the Clark 

County DAQ “Annual Network Plan Report”, page 12, June 2011. These monitoring 

devices have an EPA designation number EQOA-0992-087. See EPA “List of 

Designated Reference and Equivalent Methods”, page 28, June 6, 2012, 

available at: http://www.epa.gov/ttn/amtic/criteria.html. 
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summarized in table 1, and found that the data meet our 

completeness criteria, except at the discontinued or newlyoperating monitoring sites.7

Table 1 summarizes the site-specific annual fourth-high 

daily maximum 8-hour ozone concentrations and 3-year ozone 

design values for all monitoring sites within the Clark County 

8-hour ozone nonattainment area for the period of 2009-2011. As 

shown in table 1, the design value for the 2009-2011 period was 

less than 0.084 ppm at all of the monitors. Therefore, we are 

proposing to determine, based on the complete, quality-assured 

data for 2009-2011, that the Clark County 8-hour ozone 

nonattainment area has attained the 1997 8-hour ozone standard. 

There are ten ozone monitors currently operating in the 

nonattainment area. Preliminary SLAMS data for 2012 from these 

monitors, which are summarized in table 2, are also consistent 

with continued attainment. 

Table 1: Summary of Ambient Data Collected within Clark County 

8-Hour Ozone Nonattainment Area, 2009-2011 

Monitor 

Site 

Code 

2009 4th

highest 

2010 4th

highest 

2011 4th

highest 

2009 -

2011 

average 

 

7 Also, the data from the Boulder City ozone monitor did not meet EPA's 

completeness criteria during year 2010 because of a temporary shutdown (from 

November 2009 through March 2010)(i.e., the low ozone season) due to station 

repairs. This temporary shutdown was approved by EPA. See page 71 of the 

Clark County DAQ Annual Network Plan Report, June 2010. In addition, the data 

from the Apex ozone monitor likewise did not meet EPA completeness criteria 

during 2010 and 2011 but EPA has approved a shortened ozone monitoring season 

at the Apex site. See letter dated March 8, 2012 from Matthew Lakin, Manager, 

Air Quality Analysis Office, EPA Region IX to Mike Sword, Engineering 

Manager, Clark County DAQ. 
20 

This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

(ppm)

Craig Road 32-003-

0020 

0.072 * N/A N/A 

Apex 32-003-

0022 

0.070 0.068 0.070 0.069 

Paul Meyer 32-003-

0043 

0.071 0.070 0.078 0.073 

Walter 

Johnson 

32-003-

0071 

0.074 0.073 0.077 0.074 

Lone 

Mountain 

32-003-

0072 

0.072 * N/A N/A 

Palo Verde 32-003-

0073 

0.072 0.071 0.077 0.073 

Joel Neal 32-003-

0075 

0.074 0.074 0.077 0.075 

Winterwood 32-003-

0538 

0.070 0.068 0.073 0.070 

Jerome 

Mack** 

32-003-

9540 

N/A N/A 0.073 N/A 

Boulder City 32-003-

0601 

0.071 0.069 0.070 0.070 

Jean 32-003-

1019 

0.072 0.074 0.074 0.073 

Orr 32-003-

1021 

0.071 * N/A N/A 

J.D. Smith 32-003-

2002 

0.072 0.068 0.072 0.070 

* Monitor discontinued. N/A = not available. 

** 2011 was the first full year of operation of the Jerome Mack 

ozone monitor. 

Table 2: Preliminary 4th High Daily Maximum 

8-Hour Ozone Concentrations for 2012a

Monitor Site Code 

4

th highest 

value (ppm) 

Apex 32-003-0022 0.076 

Paul Meyer 32-003-0043 0.077 

Walter Johnson 32-003-0071 0.075 

Palo Verde 32-003-0073 0.078 

Joel Neal 32-003-0075 0.075 
21 

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steps to ensure the accuracy of this version, but it is not the official version. 

Winterwood 32-003-0538 0.074 

Jerome Mack 32-003-0540 0.073 

Boulder City 32-003-0601 0.077 

Jean 32-003-1019 0.077 

J.D. Smith 32-003-2002 0.076 

a The data in this table are from AQS Preliminary Design 

Value Report. Report Date: Oct. 11, 2012. See docket. 

 

B. The Area Must Have a Fully Approved SIP Meeting Requirements 

Applicable for Purposes of Redesignation under Section 110 and 

Part D. 

Section 107(d)(3)(E)(ii) and (v) require EPA to determine 

that the area has a fully approved applicable SIP under section 

110(k) that meets all applicable requirements under section 110 

and part D for the purposes of redesignation. 

1. Basic SIP Requirements under CAA Section 110 

Section 110(a)(2) sets forth the general elements that a 

SIP must contain in order to be fully approved. Although section 

110(a)(2) was amended in 1990, a number of the requirements did 

not change in substance, and therefore, EPA believes that the 

pre-amendment EPA-approved SIP met these requirements in Clark 

County with respect to ozone. As to those requirements that were 

amended, (see 57 FR 27936 and 27939, June 23, 1992), many are 

duplicative of other requirements of the Act. EPA has analyzed 

the Nevada SIP and determined that it is consistent with the 

requirements of amended section 110(a)(2). The Clark County 
22 

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steps to ensure the accuracy of this version, but it is not the official version. 

portion of the approved Nevada SIP contains enforceable emission 

limitations; requires monitoring, compiling and analyzing of 

ambient air quality data; requires preconstruction review of new 

or modified stationary sources; provides for adequate funding, 

staff, and associated resources necessary to implement its 

requirements; and provides the necessary assurances that the 

State maintains responsibility for ensuring that the CAA 

requirements are satisfied in the event that Clark County is 

unable to meet its CAA obligations.8 

 

8 The applicable SIP for NDEP and Clark County may be found at 

http://yosemite.epa.gov/r9/r9sips.nsf/allsips?readform&state=Nevada. We note 

that SIPs must be fully approved only with respect to applicable requirements 

for purposes of redesignation in accordance with section 107(d)(3)(E)(ii). 

Thus, for example, CAA section 110(a)(2)(D) requires that SIPs contain 

certain measures to prevent sources in a state from significantly 

contributing to air quality problems in another state. However, the section 

110(a)(2)(D) requirements for a state are not linked with a particular 

nonattainment area’s designation and classification in that state. EPA 

believes that the requirements linked with a particular nonattainment area’s 

designation and classification are the relevant measures to evaluate in 

reviewing a redesignation request. The transport SIP submittal requirements, 

where applicable, continue to apply to a state regardless of the designation 

of any one particular area in the state. 

Thus, we do not believe that these requirements should be construed to be 

applicable requirements for purposes of redesignation. In addition, EPA 

believes that the other section 110 elements not connected with nonattainment 

plan submissions and not linked with an area’s attainment status are not 

applicable requirements for purposes of redesignation. The State will still 

be subject to these requirements after the Clark County ozone planning area 

is redesignated. The section 110 and part D requirements, which are linked 

with a particular area’s designation and classification, are the relevant 

measures to evaluate in reviewing a redesignation request. This policy is 

consistent with EPA’s existing policy on applicability of conformity (i.e., 

for redesignations) and oxygenated fuels requirement. See Reading, 

Pennsylvania, proposed and final rulemakings 61 FR 53174-53176 (October 10, 

1996), 62 FR 24816 (May 7, 1997); Cleveland-Akron-Lorain, Ohio, final 

rulemaking 61 FR 20458 (May 7, 1996); and Tampa, Florida, final rulemaking 60 

FR 62748 (December 7, 1995). See also the discussion of this issue in the 

Cincinnati redesignation 65 FR 37890 (June 19, 2000), in the Pittsburgh 

redesignation 66 FR 50399 (October 19, 2001), and in the Los Angeles 

redesignation 72 FR 6986 (February 14, 2007) and 72 FR 26718 (May 11, 2007). 

EPA believes that section 110 elements not linked to the area’s nonattainment 

status are not applicable for purposes of redesignation.
23 

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steps to ensure the accuracy of this version, but it is not the official version. 

On numerous occasions over the past 38 years, NDEP has 

submitted and we have approved provisions addressing the basic 

CAA section 110 provisions. There are no outstanding or 

disapproved applicable SIP submittals with respect to the Clark 

County portion of the SIP that prevent redesignation of the 

Clark County 8-hour ozone nonattainment area for the 1997 8-hour 

ozone standard.9 Therefore, we propose to conclude that NDEP and 

Clark County have met all SIP requirements for Clark County 

applicable for purposes of redesignation under section 110 of 

the CAA (General SIP Requirements). 

2. Part D Requirements 

a. Introduction

The CAA contains two sets of provisions, subparts 1 and 2, 

that address planning and emission control requirements for 

ozone nonattainment areas. Both of these subparts are found in 

title I, part D of the CAA; sections 171-179 and sections 181-

185, respectively. Subpart 1 contains general, less prescriptive 

requirements for all nonattainment areas of any pollutant, 

 

9 Recently, EPA took final limited approval and limited disapproval on 

updated new source review (NSR) rules adopted by Clark County and submitted 

as a revision to the Nevada SIP (77 FR 64039, October 18, 2012) and issued a 

partial approval and partial disapproval of Nevada's "infrastructure" SIP for 

the 1997 8-hour ozone NAAQS (77 FR 64737, October 23, 2012). While these two 

final rules are not full approvals, they do not represent an obstacle to 

redesignation of the Clark County 8-hour ozone nonattainment area because 

EPA's rationale for finding that the State has met the requirements of CAA 

section 107(d)(3)(E)(ii) and (v) does not rely on a fully-approved 

nonattainment NSR program, and because the "infrastructure" SIP elements that 

EPA disapproved are not related to the nonattainment SIP requirements for the 

Clark County 8-hour ozone nonattainment area and thus are not relevant for 

the purposes of redesignation. 
24 

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steps to ensure the accuracy of this version, but it is not the official version. 

including ozone, governed by a NAAQS. Subpart 2 contains 

additional, more specific requirements for ozone nonattainment 

areas classified under subpart 2. 

The applicable subpart 1 requirements are contained in 

sections 172(c)(1)-(9) and 176 of the CAA. Under subpart 1, with 

respect to the Clark County 8-hour ozone nonattainment area, the 

State of Nevada is required to submit SIP revisions that provide 

for: 

· Implementation of all reasonably available control measures 

(RACM), including, at a minimum, reasonably available 

control technology for existing sources and attainment of 

the standard (section 172(c)(1)); 

· Reasonable further progress (section 172(c)(2)); 

· A comprehensive, accurate, current inventory of actual 

emissions from all sources of the relevant pollutant or 

pollutants in the area (section 172(c)(3)); 

· Identification and quantification of the emissions, if any, 

of any such pollutants which will be allowed in accordance 

with section 173(a)(1)(B)(i.e., new or modified stationary 

sources located in established economic development zones) 

(section 172(c)(4)); 
25 

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steps to ensure the accuracy of this version, but it is not the official version. 

· Permits for the construction and operation of new and 

modified major stationary sources in the nonattainment area 

(section 172(c)(5)); 

· Enforceable emission limitations as may be necessary or 

appropriate to provide for attainment of such standard in 

such area by the applicable attainment date (section 

172(c)(6)); 

· Compliance with section 110(a)(2) of the Act (section 

172(c)(7)); 

· Use of equivalent modeling emission inventory, and planning 

procedures if approved by EPA (section 172(c)(8)); 

· Contingency measures (section 172(c)(9)); and 

· Interagency consultation and enforceability for the 

purposes of transportation conformity (section 176(c)(5) 

and 40 CFR 51.390). 

As noted above, EPA determined that the Clark County 8-hour 

ozone nonattainment area attained the 1997 8-hour ozone NAAQS 

based on 2007-2009 ozone data (76 FR 17343, March 29, 2011), and 

thereby suspended, under 40 CFR 51.918, the obligation on the 

State of Nevada to submit an attainment demonstration and 

associated reasonably available control measures (RACM), a 

reasonable further progress (RFP) plan, contingency measures and 

other planning requirements related to attainment of the 1997 8-
26 

This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

hour ozone NAAQS until such time as: the area is redesignated to 

attainment, at which time the requirements no longer apply; or 

EPA determines that the area has violated the 8-hour ozone 

NAAQS. As such, the State's compliance status with the 

attainment-related SIP requirements under subpart 1 is not 

relevant for the purposes of evaluating the State's 

redesignation request. In addition, we note that the State has 

not sought to exercise the options available under CAA sections 

172(c)(4) (identification and quantification of certain 

emissions increases) or 172(c)(8) (equivalent techniques). 

With respect to the requirements associated with subpart 2, 

we note that, as discussed in more detail above, the Clark 

County 8-hour ozone nonattainment area was initially designated 

nonattainment under subpart 1 of the CAA, but was subsequently 

classified as marginal nonattainment for the 1997 8-hour ozone 

standard under subpart 2 of part D of the CAA. See 77 FR 28424 

(May 14, 2012). The effective date of EPA's classification of 

the Clark County 8-hour ozone nonattainment area as marginal was 

June 13, 2012, and under the final May 14, 2012 subpart 2 

classifications rule, states have one year from the effective 

date of that final rule (i.e., June 13, 2013) to submit SIP 

revisions. 

NDEP has not submitted any SIP revisions for the Clark 

County 8-hour ozone nonattainment area in response to the area's 
27 

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steps to ensure the accuracy of this version, but it is not the official version. 

recent classification to marginal.10 However, EPA believes that 

this does not preclude this redesignation from being approved. 

This belief is based upon: (1) EPA’s longstanding policy of 

evaluating requirements in accordance with the requirements due 

at the time redesignation request is submitted; and (2) 

consideration of the inequity of applying retroactively any 

requirements that might in the future be applied. 

First, at the time the redesignation request was submitted 

(i.e., April 11, 2011), the Clark County 8-hour ozone 

nonattainment area was not classified under subpart 2, and thus, 

subpart 2 requirements were not yet due for this area. Under 

EPA’s longstanding interpretation of section 107(d)(3)(E) of the 

CAA, to qualify for redesignation, states requesting 

redesignation to attainment must meet only the relevant SIP 

requirements that came due prior to the submittal of a complete 

redesignation request. See the Calcagni memo and also the 

September 17, 1993, Michael Shapiro Memorandum ("State 

Implementation Plan (SIP) Requirements for Areas Submitting 

 

10 In any event, the State of Nevada would not be required to submit a SIP 

revision under section 182(a)(2)(A) to correct RACT rules for the Clark 

County 8-hour ozone nonattainment area because the area had not been 

identified by EPA under the pre-1990 CAA as an area that had RACT rule 

deficiencies. At that time, all of Clark County, including Las Vegas Valley, 

was designated as attainment for the then-current 1-hour ozone standard and 

had been so designated since 1986. See 51 FR 41788 (November 19, 1986). We 

also note that, for the purposes of meeting the SIP requirements for 

nonattainment areas for carbon monoxide, the State previously submitted, and 

EPA approved, SIP revisions that would meet the vehicle inspection and 

maintenance requirements under CAA section 182(a)(2)(B) for the Clark County 

8-hour ozone nonattainment area, if those requirements were applicable for 

the purposes of redesignation. See at 69 FR 56351 (September 21, 2004), 73 FR 

38124 (July 3, 2008), and 74 FR 3975 (January 22, 2009). 
28 

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steps to ensure the accuracy of this version, but it is not the official version. 

Requests for Redesignation to Attainment of the Ozone and Carbon 

Monoxide (CO) National Ambient Air Quality Standards (NAAQS) on 

or after November 15, 1992," Memorandum from Michael Shapiro, 

Acting Assistant Administrator for Air and Radiation), and 60 FR 

12459, 12465–66 (March 7, 1995) (Redesignation of Detroit-Ann 

Arbor, Michigan); Sierra Club v. EPA, 375 F.3d 537 (7th Cir. 

2004) (upholding this interpretation); 68 FR 25418, 25424, 25427 

(May 12, 2003) (redesignation of St. Louis, Missouri). 

Moreover, it would be inequitable to retroactively apply 

any new SIP requirements that were not applicable at the time 

the request was submitted. The DC Circuit Court has recognized 

the inequity in such retroactive rulemaking (see Sierra Club v. 

Whitman 285 F. 3d 63 (DC Cir. 2002)), in which the court upheld 

a district court’s ruling refusing to make retroactive an EPA 

determination of nonattainment that was past the statutory due 

date. Such a determination would have resulted in the imposition 

of additional requirements on the area. The court stated, 

"[a]lthough EPA failed to make the nonattainment determination 

within the statutory frame, Sierra Club’s proposed solution only 

makes the situation worse. Retroactive relief would likely 

impose large costs on the states, which would face fines and 

suits for not implementing air pollution prevention plans in 

1997, even though they were not on notice at the time." Id. at 

68. Similarly here, it would be unfair to penalize the Clark 
29 

This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

County 8-hour ozone nonattainment area by applying to it, for 

purposes of redesignation, additional SIP requirements under 

subpart 2 that were not in effect or yet due at the time it 

submitted its redesignation request, or the time that the Clark 

County 8-hour ozone nonattainment area attained the NAAQS. 

In the following paragraphs, we explain how the State has 

met the SIP revision requirements for those remaining 

requirements under part D that are not currently suspended or 

not otherwise applicable. 

b. Emissions Inventory 

EPA regulations at 40 CFR 51.915 extend the SIP 

requirements under CAA sections 172(c)(3) to areas designated as 

nonattainment for the 1997 8-hour ozone standard. CAA section 

172(c)(3) requires States to submit a comprehensive, accurate, 

current inventory of actual VOC and NOx emissions for the 

baseline year from all sources within the nonattainment area. 

The inventory is to address actual VOC and NOx emissions during 

the ozone season, and all stationary (generally referring to 

larger stationary source or “point” sources), area (generally 

referring to smaller stationary and fugitive (non-smokestack) 

sources), and mobile (on-road, nonroad, locomotive and aircraft) 

sources are to be included in the inventory. 

We interpret the Act such that the emission inventory 

requirements of section 172(a)(3) are satisfied by the inventory 
30 

This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

requirements of the maintenance plan. See 57 FR 13498, at 13564 

(April 16, 1992). Thus, our proposed approval of the Clark 

County Ozone Maintenance Plan and related VOC and NOx emission 

inventories and our proposed approval of NDEP's redesignation 

request would satisfy the requirements of sections 172(a)(3) for 

the purposes of redesignation of the Clark County 8-hour ozone 

nonattainment area to attainment for the 1997 8-hour ozone 

NAAQS. 

c. Permits for New and Modified Major Stationary Sources

To meet the requirements of CAA section 172(c)(5), states 

must submit SIP revisions that meet the requirements under 40 

CFR 51.165 ("Permit requirements"), and EPA regulations at 40 

CFR 51.914 extend the SIP requirements of 40 CFR 51.165 to areas 

designated as nonattainment for the 1997 8-hour ozone standard. 

Under 40 CFR 51.165, states are required to submit SIP 

revisions that establish certain requirements for new or 

modified stationary sources in nonattainment areas, including 

provisions to ensure that major new sources or major 

modifications of existing sources of nonattainment pollutants 

incorporate the highest level of control, referred to as the 

Lowest Achievable Emission Rate (LAER), and that increases in 

emissions from such stationary sources are offset so as to 

provide for reasonable further progress towards attainment in 

the nonattainment area. 
31 

This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

The process for reviewing permit applications and issuing 

permits for new or modified stationary sources of air pollution 

is referred to as “New Source Review” (NSR). With respect to 

nonattainment pollutants in nonattainment areas, this process is 

referred to as “nonattainment NSR.” With respect to pollutants 

for which an area is designated as attainment or unclassifiable, 

states are required to submit SIP revisions that ensure that 

major new stationary sources and major modifications of existing 

stationary sources meet the Federal requirements for Prevention 

of Significant Deterioration" (PSD), including application of 

"best available control technology," for each applicable 

pollutant emitted in significant amounts, among other 

requirements. 

As noted above, under Nevada law, specific electric steamgenerating emission units (i.e., power plants) within Clark 

County are under NDEP jurisdiction. See Nevada Revised Statutes 

(NRS) section 445B.500. Thus, state regulations govern air 

pollution permits issued by NDEP to those units. Clark County 

DAQ is responsible for all other stationary sources emissions 

units, and Clark County regulations govern air pollutant permits 

issued to them. 

Under the Clean Air Act Amendments of 1977, States with 

designated nonattainment areas were required to amend their NSR 

rules to impose LAER and offset requirements on new major 
32 

This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

sources and major modifications of nonattainment pollutants in 

nonattainment areas. As noted previously, under the 1977 Act 

Amendments, we designated Las Vegas Valley as a nonattainment 

area for photochemical oxidant, later changed to ozone. To 

address the nonattainment NSR requirements flowing from the 1977 

Act Amendments, the State of Nevada amended its nonattainment 

NSR rules (Nevada Air Quality Regulations (NAQR) Article 13), 

and NDEP submitted them to EPA for approval as part of the 

Nevada SIP. We approved the amended NSR rules in 1981. See 46 FR 

21758 (April 14, 1981). Under these EPA-approved rules, LAER and 

offsets have been required for new "point sources" that cause 

emissions greater than 100 tons per year of ozone precursors in 

ozone nonattainment areas. In the 1980's EPA also approved Clark 

County NSR rules for Las Vegas Valley as meeting the related 

requirements under the 1977 Amended Act and EPA regulations. 

The 1990 Clean Air Act Amendments retained the core 

nonattainment NSR elements of LAER and offsets but added other 

requirements. To address the nonattainment designations of Las 

Vegas Valley for carbon monoxide and particulate matter for 

sources under NDEP jurisdiction and in lieu of amending the 

rules to meet the additional NSR requirements under the 1990 Act 

Amendments, the State of Nevada submitted a rule (Nevada 

Administrative Code (NAC) section 445B.22083) establishing a 

construction ban for new major sources and major modifications 
33 

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steps to ensure the accuracy of this version, but it is not the official version. 

within the nonattainment area. NAC 445B.22083, with a limited 

exception, prohibits new power plants or major modifications to 

existing power plants under State jurisdiction within four 

hydrographic areas in Clark County, including Las Vegas Valley 

(hydrographic area No. 212). See 69 FR 31056, 31059 (June 2, 

2004) and 69 FR 54006, at 54017 (September 7, 2004). We approved 

NAC 445B.22083 into the Nevada SIP most recently in 2008. See 73 

FR 20536 (April 16, 2008). However, the prohibition in NAC 

445B.22083 does not cover the entire Clark County 8-hour ozone 

nonattainment area, which includes the four hydrographic areas 

listed in NAC 445B.22083, but also includes all or portions of 

seven additional hydrographic areas in Clark County. See 40 CFR 

81.329. Thus, the State of Nevada does not have a nonattainment 

NSR program meeting the requirements of 40 CFR 51.165 for those 

sources under NDEP jurisdiction within the Clark County 8-hour 

ozone nonattainment area. 

With respect to Clark County regulations, EPA recently 

finalized a limited approval and limited disapproval of updated 

Clark County rules governing NSR, including nonattainment NSR, 

but also PSD. See 77 FR 64039 (October 18, 2012). Thus, Clark 

County does not have a nonattainment NSR program meeting the 

requirements of 40 CFR 51.165 for those sources under Clark 

County DAQ jurisdiction within the Clark County 8-hour ozone 

nonattainment area. 
34 

This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

We have determined, however, that, since PSD requirements11

will apply after redesignation, an area being redesignated to 

attainment need not comply with the requirement that a NSR 

program be approved prior to redesignation, provided that the 

state demonstrates maintenance of the NAAQS in the area without 

implementation of nonattainment NSR. A more detailed rationale 

for this view is described in a memorandum from Mary Nichols, 

Assistant Administrator for Air and Radiation, dated October 14, 

1994, titled “Part D New Source Review Requirements for Areas 

Requesting Redesignation to Attainment.” See redesignation 

rulemakings for Detroit, Michigan (60 FR 12467-12468, March 7, 

1995); Cleveland-Akron-Lorain, Ohio (61 FR 20458, 20469-20470, 

May 7, 1996); Louisville, Kentucky (66 FR 53665, October 23, 

2001); and, Grand Rapids, Michigan (61 FR 31834-31837, June 21, 

1996). 

Based on our review of the Clark County Ozone Maintenance 

Plan, we conclude the maintenance demonstration included therein 

does not rely on implementation of nonattainment NSR because the 

plan applies standard growth factors to stationary source 

emissions and does not rely on NSR offsets to reduce the rate of 

increase in emissions over time from point sources. The Ozone 

Maintenance Plan does include a line-item for emission reduction 

 

11 PSD requirements control the growth of new source emissions in areas 

designated as attainment for a NAAQS. 
35 

This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

credits for VOC and NOx but adds them to future projected 

emissions rather than assuming that they would be used to reduce 

emissions growth from stationary sources. Therefore, EPA 

concludes that the State need not have a fully approved 

nonattainment NSR program as an applicable requirement for 

approval of the State's ozone redesignation request for the 

Clark County ozone planning area. 

Because the State's PSD program has been disapproved with 

respect to sources under NDEP jurisdiction, the Federal PSD 

requirements under 40 CFR 52.21 will apply to new major sources 

or major modifications of ozone precursors under NDEP 

jurisdiction once the Clark County 8-hour ozone nonattainment 

area is redesignated to attainment. See 40 CFR 52.1485(b). NDEP 

implements and enforces the Federal PSD regulations under a 

delegation agreement with EPA Region IX. 

With respect to stationary sources under Clark County DAQ 

jurisdiction, the County’s PSD program will apply to ozone 

precursor emissions of new major sources or major modifications 

upon redesignation of the Clark County 8-hour ozone 

nonattainment area to attainment. We note that Clark County's 

PSD program is not fully approved, but the deficiencies that 

formed the basis for EPA's recent limited approval and limited 

disapproval action would not interfere with maintenance of the 

ozone standard for two reasons. First, the deficiencies that 
36 

This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

relate to ozone precursors are limited to a few definitions: 

"allowable emissions," "baseline actual emissions," "net 

emissions increase," and "major modification." See 77 FR 64039, 

at 64047 (October 18, 2012). Second, the limited disapproval 

triggered an obligation on EPA to promulgate a Federal 

implementation plan (FIP) to remedy the PSD deficiencies by 

November 19, 2014 unless NDEP submits, and EPA approves, amended 

Clark County rules that correct the deficiencies prior to that 

time. Thus, the overlap in time during which the Clark County 8-

hour area would be redesignated to attainment but would not be 

subject to a fully-approved PSD program would be less than two 

years. 

d. Compliance with Section 110(a)(2) 

Section 172(c)(7) requires the SIP to meet the applicable 

provisions of section 110(a)(2). As noted above, we conclude the 

Nevada SIP meets the requirements of section 110(a)(2) 

applicable for purposes of this redesignation. 

e. Conformity Requirements 

Under section 176(c) of the Clean Air Act Amendments of 

1990, States are required to establish criteria and procedures 

to ensure that Federally supported or funded projects conform to 

the air quality planning goals in the applicable SIP. Section 

176(c) further provided that State conformity provisions must be 

consistent with Federal conformity regulations that the CAA 
37 

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steps to ensure the accuracy of this version, but it is not the official version. 

required EPA to promulgate. EPA’s conformity regulations are 

codified at 40 CFR part 93, subparts A (referred to herein as 

“transportation conformity”) and B (referred to herein as 

“general conformity”). Transportation conformity applies to 

transportation plans, programs, and projects developed, funded, 

and approved under title 23 U.S.C. or the Federal Transit Act, 

and general conformity applies to all other Federally-supported 

or funded projects. SIP revisions intended to address the 

conformity requirements are referred to herein as “conformity 

SIPs.” 

In November 2008, EPA approved Clark County’s 

transportation conformity criteria and procedures as meeting the 

related SIP requirements under part 51, subpart T (“Conformity 

to State or Federal Implementation Plans of Transportation 

Plans, Programs, and Project Developed, Funded or Approved Under 

Title 23 U.S.C. or the Federal Transit Laws”). See 73 FR 66182 

(November 7, 2008). 

With respect to "general conformity," we note that, in 

August 2005, Congress passed the Safe, Accountable, Flexible, 

Efficient Transportation Equity Act: A Legacy for Users 

(SAFETEA-LU), which eliminated the requirement for States to 

adopt and submit conformity SIPs addressing general conformity 

requirements. See 75 FR 17254 (April 5, 2010) for conforming 

changes to EPA’s general conformity regulations. The State of 
38 

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Nevada is thus no longer required to submit a general conformity 

SIP for the Clark County 8-hour ozone planning area. 

Therefore, based on our approval of Clark County’s 

transportation conformity SIP and SAFETEA-LU’s elimination of 

the general conformity SIP requirement, we find that Clark 

County and the State have met the requirements for conformity 

SIPs in the Clark County 8-hour ozone nonattainment area under 

CAA section 176(c). In any event, EPA believes it is reasonable 

to interpret the conformity requirements as not applicable for 

purposes of evaluating a redesignation request under section 

107(d)(3)(E). See Wall v. EPA, 265 F.3d 426, 439 (6th Cir. 2001) 

upholding this interpretation. 

C. The Area Must Show the Improvement in Air Quality is Due to 

Permanent and Enforceable Emissions Reductions. 

Section 107(d)(3)(E)(iii) precludes redesignation of a 

nonattainment area to attainment unless EPA determines that the 

improvement in air quality is due to permanent and enforceable 

reductions in emissions resulting from implementation of the 

applicable SIP and applicable Federal air pollution control 

regulations and other permanent and enforceable regulations. 

Under this criterion, the state must be able to reasonably 

attribute the improvement in air quality to emissions reductions 

which are permanent and enforceable. Attainment resulting from 

temporary reductions in emissions rates (e.g., reduced 
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production or shutdown due to temporary adverse economic 

conditions) or unusually favorable meteorology would not qualify 

as an air quality improvement due to permanent and enforceable 

emission reductions. 

The Clark County Ozone Maintenance Plan credits the 

following control measures as providing the emissions reductions 

sufficient to attain the 1997 8-hour ozone NAAQS in the Clark 

County 8-hour ozone nonattainment area through year 2022: the 

Federal Tier 2 motor vehicle emissions standards; the Federal 

highway diesel rule; the Federal large nonroad diesel engines 

rule; the Federal nonroad spark-ignition engines and 

recreational engines standards; the Federal nonroad sparkignition engines and equipment standard; the State’s vehicle I/M 

program; and the County's NSR and stationary source prohibitory 

rules. As discussed above, the State's vehicle inspection and 

maintenance (I/M) program and the County's NSR rules and VOCrelated prohibitory rules (such as section 52 ("Handling of 

Gasoline at Service Stations, Airports and Storage Tanks")) have 

been approved into the SIP, and thus are federally enforceable. 

The Federal on-road and nonroad vehicle and engine 

standards cited above have contributed to improved air quality 

through the gradual, continued turnover and replacement of older 

vehicle models with newer models manufactured to meet 

increasingly stringent Federal tailpipe emissions standards. The 
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steps to ensure the accuracy of this version, but it is not the official version. 

new Federal fuel standards cited above have resulted in more 

immediate emissions reductions of ozone precursors and provide 

for the use of advanced pollution control technology that would 

not otherwise be possible. The emissions reductions from the 

Federal vehicle and fuel standards are reflected in the 

emissions inventories and maintenance demonstration discussed 

later in this document through the use of EPA’s MOBILE emission 

factor model for on-road motor vehicles and NONROAD emission 

factor model for nonroad vehicles. 

We note that some of the control measures cited in the 

Clark County Ozone Maintenance Plan provided emissions 

reductions since 2002, and thus, the improvement in air quality 

since 2002 may reasonably be attributed to them. For instance, 

the new Federal gasoline and diesel fuel standards have greatly 

lowered the allowable sulfur content of these fuels and have 

resulted in lower emissions from cars and trucks, particularly 

of sulfur dioxide, particulate matter, and NOx. The Clark County 

Ozone Maintenance Plan (see Figure 4-1 from the plan) 

illustrates the ambient ozone trend in the nonattainment area 

from 2003-to 2009 and layers the sequence of Federal engine and 

fuel standards phase-in over that period to support the 

inference that the standards have contributed to the declining 

trend in ambient ozone concentrations. 
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A rough sense of the effectiveness of the control measures 

to reduce VOC and NOx emissions can be gained by a comparison 

between area-wide emissions in 2002 (a nonattainment year) with 

those in 2008 (an attainment year). In 2002, area-wide VOC and 

NOx emissions in the Clark County 8-hour ozone nonattainment area 

were estimated to be approximately 318 and 279 tons per day 

(summer average day), respectively, and in 2008, despite an 

increase in population and vehicle-miles-traveled (VMT) of 

approximately 27% and 48%, respectively, area-wide emissions 

dropped significantly (to 302 tons per day of VOC and 164 tons 

per day of NOx).12

With respect to the connection between the emissions 

reductions and the improvement in air quality, we also conclude 

that the air quality improvement in the Clark County 8-hour 

ozone nonattainment area since 2002 is not the result of a local 

economic downturn or unusual or extreme weather patterns. To 

draw this conclusion, we reviewed temperature and precipitation 

data for Las Vegas13 and did not observe any anomaly over the 

period from 2002 relative to long-term averages. We do recognize 

that a significant economic slowdown occurred nationally 

starting in 2008, and that the Las Vegas metropolitan area was 

 

12 See table 4-1, and appendix A, table 3-1, from Clark County DAQ's 8-Hour 

Ozone Early Progress Plan for Clark County, Nevada (June 2008) and tables 4-

1, 6-1, 6-2, and 6-3 from the Clark County Ozone Maintenance Plan. 

13 Our reference for climate data is "Climate of Las Vegas, Nevada," by 

Andrew Gorelow and Chris Stachelski, updated October 2012, as well as the 

climate data discussed on pages 4-2 and 4-3 of the Ozone Maintenance Plan. 
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more significantly affected than most other areas, but we note 

that the downward ozone trend had already been established 

before that time (see Figure 4-1 on page 4-8 of the Ozone 

Maintenance Plan). 

Thus, we find that the improvement in air quality in the 

Clark County 8-hour ozone nonattainment area is the result of 

permanent and enforceable emissions reductions from a 

combination of the Federal vehicle and fuel measures and EPAapproved State and local control measures. As such, we propose 

to find that the criterion for redesignation set forth at CAA 

section 107(d)(3)(E)(iii) is satisfied. 

D. The Area Must Have a Fully Approved Maintenance Plan under 

CAA Section 175A. 

Section 175A of the CAA sets forth the elements of a 

maintenance plan for areas seeking redesignation from 

nonattainment to attainment. 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. See Calcagni memo, pages 8 through 13. 

Under CAA section 175A, a maintenance plan must demonstrate 

continued attainment of the applicable NAAQS for at least ten 

years after EPA approves a redesignation to attainment. Eight 

years after redesignation, the State must submit a revised 
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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 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 

Ozone Maintenance Plan because we believe that it meets the 

requirements of CAA section 175A. 

1. Attainment Inventory 

A maintenance plan for the 1997 8-hour ozone standard must 

include an inventory of emissions of ozone precursors (VOC and 

NOx) in the area to identify a level of emissions that are 

sufficient to attain the 1997 8-hour ozone NAAQS. This inventory 

must be consistent with EPA’s most recent guidance on emissions 

inventories for nonattainment areas available at the time and 

should represent emissions during the time period associated 

with the monitoring data showing attainment. The inventory must 

also be comprehensive, including emissions from stationary point 

sources, area sources, nonroad mobile sources, and on-road 

mobile sources, and must be based on actual “ozone season data” 

(i.e., summertime) emissions. 
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Clark County DAQ selected year 2008 as the year for the 

attainment inventory in the Clark County Ozone Maintenance Plan. 

Year 2008 is one of the years of the three-year period (2007-

2009) on which EPA made an attainment determination for the 

Clark County 8-hour ozone nonattainment area in 2011. See 76 FR 

17343 (March 29, 2011). The attainment inventory will generally 

be the actual inventory during the time period the area attained 

the standard. Thus, Clark County DAQ's selection of 2008 for the 

attainment inventory is acceptable. 

Based on our review of the Clark County Ozone Maintenance 

Plan, we find that the emissions inventories in the plan are 

comprehensive in that they include estimates of VOC and NOx

emissions from all of the relevant source categories, which the 

plan divides among point sources,14 nonpoint sources,15 commercial 

aviation, Federal aviation (i.e., Nellis Air Force Base), onroad mobile, nonroad mobile, and biogenic16 sources. See table 6-

2 and pages 6-2 through 6-5 in the Ozone Maintenance Plan. 

Appendix A to the Ozone Maintenance Plan contains sourcespecific descriptions of emission calculation procedures and 

sources of input data. 

 

14 The Ozone Maintenance Plan uses the term, "point sources," to refer to 

those stationary source facilities that are required to report their 

emissions to Clark County DAQ or NDEP. 

15 The Ozone 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. 

16 For the Ozone Maintenance Plan, "biogenic sources" include agricultural 

crops; lawn grass; forests that produce isoprene, monoterpene, alpha-pinene, 

and other VOC emissions; and soils that generate trace amounts of NOx. 
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steps to ensure the accuracy of this version, but it is not the official version. 

For point sources, Clark County DAQ based the inventory 

estimates on source-reported actual 2008 emissions data but 

adjusted the reported values to reflect a typical summer day at 

each emissions unit within the source facilities based on 

information provided by the facilities. For nonpoint sources, 

Clark County DAQ 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. The 

documentation supplied in the emissions inventory submittal 

(i.e., appendix A to the Ozone Maintenance Plan) shows how the 

specific emissions were calculated for each area source 

category. 

With respect to most nonroad mobile sources, Clark County 

DAQ used EPA's nonroad emissions model NONROAD2008a, the current 

version of the model at the time the plan was created. The model 

includes both emissions factors and default county level 

population and activity data. The model estimates both emissions 

factors and emissions. This includes more than 80 basic and 260 

specific types of non-road equipment, and further stratifies 

equipment by horsepower rating and fuel type. The model has 

default estimates, variables and factors used in the 
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steps to ensure the accuracy of this version, but it is not the official version. 

calculations. No local data sets were available for Clark 

County, therefore only model defaults were used. 

With respect to commercial and Federal aviation sources, 

Clark County DAQ relied on airport-specific emissions inventory 

information provided by the Clark County Aviation Department for 

the five commercial airports located within the nonattainment 

area (McCarran International Airport, North Las Vegas Airport, 

Henderson Executive Airport, Jean Airport, and Perkins Field 

Airport) and information provided by the U.S. Air Force for 

Nellis Air Force Base. Airport support equipment and airportrelated stationary source emissions were included in the 

airport-specific inventories rather than in the general source 

categories such as point sources or nonroad mobile. Locomotive 

emissions were estimated by Clark County DAQ based on fuel 

consumption within the nonattainment area by the Union Pacific 

Railroad and included in the aggregate emissions estimates for 

"nonroad mobile." To estimate biogenic emissions, Clark County 

DAQ used the Model of Emissions of Gasses and Aerosols from 

Nature (MEGAN) estimates, measured emission factors, and species 

information from completed surveys. 

The on-road mobile source emissions estimates in the Ozone 

Maintenance Plan were prepared by Clark County DAQ using the 
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CONCEPT MV emissions model,17 EPA's MOBILE6.2 emissions factors, 

the Regional Transportation Commission of Southern Nevada's 

(RTC's) transportation demand modeling results,18 and Highway 

Performance Monitoring System (HPMS) data from the Nevada 

Department of Transportation. 

MOBILE6.2 estimates emissions by vehicle class, and 

provides emissions factors for exhaust emissions; evaporative 

emissions; and brake and tire wear emissions. There are a total 

of 28 vehicle classes used in MOBILE6.2. For the Ozone 

Maintenance Plan, Clark County DAQ aggregated the emissions 

factors calculated from MOBILE6.2 into eight vehicle classes, 

which are the same as used in MOBILE5. The VMT was adjusted by 

comparisons to observed vehicle counts by facility types, by 

using HPMS adjustment factors and to account for additional 

transit vehicles. The CONCEPT MV model processes detailed inputs 

(e.g., VMT mix varying by hour of day, day of week, and month of 

year) and adjusts speeds to account for congestion based on 

transportation demand modeling outputs. For areas outside of the 

Las Vegas Valley, county level VMT estimates based on HPMS data 

was used and no reductions associated with the State's motor 

vehicle inspection and maintenance (I/M) program were included 

 

17 "CONCEPT" refers to the CONsolidated Community Emissions Processor Tool 

(CONCEPT,) and "MV" refers to the motor vehicle module of the CONCEPT model. 

18 One of the principal sources of transportation data used to develop the 

emissions inventories in the Ozone Maintenance Plan is the Regional 

Transportation Plan 2009-2030, approved by the RTC in November 2008. See 

page 6-1 of the maintenance plan. 
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since vehicles in the rural portions of the county are not 

required to participate in the program. 

The on-road emissions estimates for the Ozone Maintenance 

Plan assumed the implementation of the Federal heavy-duty diesel 

rule, limits to Reid Vapor Pressure (RVP) of 9 pounds per square 

inch (psi) with a 1.0 psi waiver for ethanol-blended fuels19 and 

the phase-in of tier 2 motor vehicle emission standards, and the 

operation of an enhanced vehicle I/M program in the urban areas 

of Clark County. 

Table 3 presents the VOC and NOx emissions estimates 

contained in the Ozone Maintenance Plan for 2008 and also 

presents the plan's projected emissions inventories of ozone 

precursors in an interim year (2015) and the maintenance plan's 

horizon year (2022).20 Based on the estimates in Table 3, on-road 

emissions sources accounted for approximately 22% of the VOC and 

42% of the NOx emissions generated within the 8-hour ozone 

nonattainment area in 2008. Nonroad sources (including nonroad 

equipment, airports, and locomotives) accounted for 

approximately 15% and 34% of the VOC and NOx inventory, 

respectively. Point and area source emissions accounted for 

 

19 The market share of ethanol blend in summertime is assumed to be 

approximately 63% for 2008 and 100% for 2015 and 2022. 

20 The 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. 
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approximately 19% and 21% of the VOC and NOx inventory, 

respectively, while biogenic emissions contributed 44% of the 

VOC inventory but little (3%) to the overall NOx inventory. 

Table 3: 2008 and Projected 2015 and 2022 VOC and NOx Emissions 

Total Daily Emissions (tons per day, average summer weekday)a

Emission

Source

Category 2008 2015 2022

VOC NOX VOC NOX VOC NOX

Point 

Clark 

County 

Point 

1 12 1 12 1 12

Projected 

Power 

Plant 

0 0 < 0.5 3 < 0.5 3

Clark 

County 

NDEP Point

< 0.5 17 < 0.5 17 < 0.5 17

Airports Clark 

County DOA 

3 11 3 15 3 17

Ivanpah 

Airport 

0 0 < 0.5 < 

0.5

1 11

Nellis 

AFB 

Nellis AFB 1 1 1 2 1 2

Nonpoint 

Sources 

Nonpoint 

Sources 

57 5 66 6 76 6

Locomoti

ve 

Locomotive < 0.5 2 < 0.5 2 < 0.5 2

On-road 

Mobile 

On-road 

Mobile 

65 68 45 35 37 23

Nonroad 

Mobile 

Nonroad 

Mobile 

43 41 32 28 30 18

Biogenic Biogenic 132 5 132 5 132 5

Banked 

Emission 

Reductio

n 

Credits 

DAQ ERC 

Bank 

0 0 < 0.5 1 < 0.5 1

ERCs from 

Mohave 

Generating 

0 0 < 0.5 20 < 0.5 20
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(ERCs ERCs from 

ReidGardner 

0 0 0 2 0 2

Total 302 164 282 146 282 139 

a Derived from table 1-1 of appendix A to the Ozone Maintenance 

Plan. For the purposes of this table, the estimates contained in 

the maintenance plan have been rounded to the nearest whole 

number (except for values greater than zero but less than 0.5, 

which are shown as "< 0.5"). The sum of the values in each 

column may not equal the total shown due to rounding. DOA = 

Clark County Department of Aviation; AFB = Air Force Base; and 

ERCs = emission reduction credits. 

Based on our review of the emissions inventories (and 

related documentation) from the Ozone Maintenance Plan, we find 

that the inventories for 2008 are comprehensive, that the 

methods and assumptions used by Clark County DAQ to develop the 

2008 emission inventory are reasonable, and that the inventories 

reasonably estimate actual ozone season emissions in an 

attainment year. Moreover, we find that the 2008 emissions 

inventories in the Ozone Maintenance Plan reflect the latest 

planning assumptions and emissions models available at the time 

the plan was developed, and provide a comprehensive and 

reasonably accurate basis upon which to forecast ozone precursor 

emissions for years 2015 and 2022. 

2. 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 
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for at least 10 years after the redesignation.” Generally, a 

state may demonstrate maintenance of the ozone NAAQS by either 

showing that future emissions 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. For areas that are required under the Act to submit 

modeled attainment demonstrations, the maintenance demonstration 

should use the same type of modeling. Calcagni memorandum, page 

9. The Clark County 8-hour ozone nonattainment area was not 

required to submit a modeled attainment demonstration, and thus, 

the Clark County Ozone Maintenance Plan may demonstrate 

maintenance based on a comparison of existing and future 

emissions of ozone precursors.21

Clark County DAQ used projected emissions22 for point and 

non-point sources from calendar years 2008 and 2018 to back 

calculate the growth factors for all ozone precursor emissions 

for both inventory years. The derived growth factors were then 

mathematically extrapolated to account for a 14-year (2008 

through 2022) spread. These 2022 growth factors were then 

multiplied by the 2008 actual emissions to produce the 2022 

projected point source emissions. An interim year (2015) 

 

21 A maintenance demonstration need not be based on ozone modeling. See Wall 

v. EPA, 375 F.3d 537 (7th Cir. 2004). See also 66 FR 53094, 53099-53100 

(October 19, 2001), and 68 FR 25413, 25430-25432 (May 12, 2003). 

22 The projected emissions were obtained from the 2005 Clark County 

Consolidated Emission Inventory Report (Environ, May 31, 2007, Appendix A). 
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projected emissions inventory is also included. The 2015 

emissions were calculated using half of the growth value of the 

2022 projections. Corrections for rule effectiveness were not 

applied to these projected emissions. On-road emissions were 

estimated for the 2008 base year and for projection years 2015 

and 2022 and reflect a 26% increase in VMT from 2008 to 2015 and 

a 63% increase in VMT from 2008 to 2022 based on RTC 

projections. See table 6-1 in the Ozone Maintenance Plan. 

In addition to accounting for area-wide growth trends, 

Clark County DAQ added emissions from specific projects that are 

expected to become operational during the maintenance period, 

including the Nellis Air Force Base F-35 beddown project, a new 

power plant, a new airport (Ivanpah), and new heliport (Sloan), 

in the future- year emissions inventories, and also added in 

emissions reduction credits (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 DAQ used to project emissions to 

2015 and 2022 for the various source categories and find them to 

be reasonable. 

Table 3 compares the VOC and NOx emissions estimated for the 

Clark County 8-hour ozone nonattainment area for 2008 with those 
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for 2015 and 2022 by source category. The projected VOC and NOx

emissions show that VOC and NOx emissions would remain well below 

the attainment levels throughout the 10-year maintenance period 

and thereby adequately demonstrating maintenance through that 

period. 

3. Monitoring Network 

Continued ambient monitoring of an area is generally 

required over the maintenance period. As discussed in section 

V.A of this document, ozone is currently monitored by Clark 

County DAQ at ten sites within the Clark County 8-hour ozone 

nonattainment area. In the Ozone Maintenance Plan (see page 6-11 

of the plan), Clark County DAQ indicates its intention to 

continue operation of an air quality monitoring network to 

verify continued attainment of the 1997 8-hour ozone NAAQS.23 The 

Clark County Ozone Maintenance Plan also notes that Clark County 

DAQ’s SLAMS air quality monitoring system (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.24 We find the County’s 

 

23 Although the Ozone Maintenance Plan is not explicit in this regard, we 

presume that Clark County DAQ's intention to continue operation of a 

monitoring network means that the agency intends to do so consistent with 

EPA’s monitoring requirements in 40 CFR part 58 (“Ambient Air Quality 

Surveillance”). 

24 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. 
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commitment for continued ambient ozone monitoring as set forth 

in the Ozone Maintenance Plan to be acceptable. 

4. 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 Ozone Maintenance Plan. This includes the 

authority to adopt, implement and enforce any emission control 

contingency measures determined to be necessary to correct ozone 

NAAQS violations. To verify continued attainment, Clark County 

DAQ commits in the Ozone Maintenance Plan to the continued 

operation of an ozone monitoring network that meets EPA ambient 

air quality surveillance requirements. 

Second, the transportation conformity process, which would 

require a comparison of on-road motor vehicle emissions that 

would occur under new or amended regional transportation plans 

and programs with the MVEBs in the Ozone Maintenance Plan, 

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. See page 

6-13 of the Ozone Maintenance Plan. Lastly, while not cited in 

the plan, NDEP and Clark County DAQ must inventory emissions 

sources and report to EPA on a periodic basis under 40 CFR part 

51, subpart A ("Air Emissions Reporting Requirements"). These 
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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. 

5. Contingency Provisions 

Section 175A(d) of the Act requires that maintenance plans 

include contingency provisions, as 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 considered to 

be 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 
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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 DAQ 

has adopted a contingency plan to address possible future ozone 

air quality problems. See section 6.8 of the maintenance plan. 

Clark County DAQ commits to examining ambient air quality data 

within 30 days of collection to determine if the ozone NAAQS has 

been exceeded. The contingency plan will be triggered 60 days 

after Clark County DAQ confirms a violation of the 1997 8-hour 

ozone NAAQS (i.e., a design value equal to or greater than 0.085 

ppm). Within 45 days of the trigger date, Clark County will 

notify EPA that it is evaluating potential contingency measures. 

Within 90 days of that notification, Clark County will send a 

report to EPA and then will initiate a public process to 

consider the recommended contingency measures, including 

soliciting stakeholder involvement and holding public hearings. 

The necessary emission control measures will be adopted and 

implemented no later than 18 months after the information report 

is submitted to EPA. 

Contingency measures contained in the maintenance plan are 

those emission controls or other measures that Clark County, the 

Nevada State Board of Agriculture, and/or the Nevada State 

Environmental Commission choose to adopt and implement in 

response to the contingency trigger. The contingency plan in the 
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Ozone Maintenance Plan 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 cutpoints for VOCs and NOx applicable to pre1996 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, as summarized above, we find 

that the contingency provisions of the Ozone Maintenance Plan 
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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 Clark County Ozone Maintenance Plan are 

adequate to ensure prompt correction of a violation and 

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

6. Subsequent Maintenance Plan Revisions 

CAA section 175A(b) provides that States shall submit a SIP 

revision 8 years after redesignation providing for maintaining 

the NAAQS for an additional 10 years. The Clark County Ozone 

Maintenance Plan provides that Clark County commits to prepare 

and submit a revised maintenance plan eight years after 

redesignation to attainment. See page 6-13 of the Ozone 

Maintenance Plan. 

7. Motor Vehicle Emissions Budgets 

Transportation conformity is required by section 176(c) of 

the CAA. Our transportation conformity rule (codified in 40 CFR 

part 93, subpart A) requires that transportation plans, 

programs, and projects conform to SIPs and establishes the 

criteria and procedures for determining whether or not they do 

so. Conformity to the SIP means that transportation activities 

will not produce new air quality violations, worsen existing 
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steps to ensure the accuracy of this version, but it is not the official version. 

violations, or delay timely attainment of the national ambient 

air quality standards. 

Maintenance plan submittals must specify the maximum 

emissions of transportation-related VOC and NOx emissions allowed 

in the last year of the maintenance period, i.e., the motor 

vehicle emissions budgets (MVEBs). (MVEBs may also be specified 

for additional years during the maintenance period.) The MVEBs 

serve as a ceiling on emissions that would result from an area's 

planned transportation system. The MVEB concept is further 

explained in the preamble to the November 24, 1993, 

transportation conformity rule (58 FR 62188). The preamble 

describes how to establish MVEBs in the SIP and how to revise 

the MVEBs if needed. 

The submittal must also demonstrate that these emissions 

levels, when considered with emissions from all other sources, 

are consistent with maintenance of the NAAQS. In order for us to 

find these emissions levels or “budgets” adequate and 

approvable, the submittal must meet the conformity adequacy 

provisions of 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 

Web site at: 

http://www.epa.gov/otaq/stateresources/transconf/index.htm. 
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steps to ensure the accuracy of this version, but it is not the official version. 

EPA's process for determining adequacy of a MVEB 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 MVEB is codified at 40 CFR 93.118. 

The Clark County Ozone Maintenance Plan submitted by NDEP 

for Clark County, contains new VOC and NOx MVEBs for Clark County 

for 2008, 2015, and 2022. The availability of the SIP submission 

with MVEBs was announced for public comment on EPA's Adequacy 

Web site on June 14, 2011, at: 

http://www.epa.gov/otaq/stateresources/tansconf/currsips.htm, 

which provided a 30-day public comment period. The comment 

period for this notification ended on July 14, 2011, and EPA 

received no comments from the public. Note, however, that a 

second mechanism is also provided for EPA review and public 

comment on MVEBs, as described in 40 CFR 93.118(f)(2). This 

mechanism provides for EPA's review of the adequacy of an 

implementation plan MVEB simultaneously with its review and 

approval and disapproval of the implementation plan itself. In 

this action, EPA used the web notification discussed above to 

solicit public comments on the adequacy of Clark County’s MVEBs, 

but is taking comment on the approvability of the submitted 

MVEBs through this proposed rule. 
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Clark County’s ozone maintenance plan contains VOC and NOx

MVEBs for 2008, 2015 and 2022. Any and all comments on the 

approvability of the MVEBs should be submitted during the 

comment period stated in the DATES section of this document. 

EPA proposes to approve 2008, 2015, and 2022 MVEBs in the 

Clark County Ozone Maintenance Plan for transportation 

conformity purposes in the final rulemaking on Clark County’s 

ozone redesignation request. If EPA approves the MVEBs in the 

final rulemaking action, the new MVEBs must be used in future 

transportation conformity determinations for Clark County. The 

new MVEBs, if approved in the final rulemaking, will be 

effective on the date of EPA's final rulemaking in the Federal

Register. The existing 2008 VOC and NOx MVEBs from the Clark 

County EPP, which EPA found adequate in 2009, will be replaced 

by these budgets. The applicable VOC and NOx MVEBs for the Clark 

County ozone nonattainment area are defined in table 4. 

Table 4: Motor Vehicle Emissions Budgets in the Clark County 

Ozone Maintenance Plana

Budget 

Year 

VOC (tpd, average 

summer weekday) 

NOx (tpd, average 

summer weekday) 

2008 65.08 68.46 

2015 45.32 34.69 

2022 36.71 23.15 

a From Table 7-1 (page 7-1) of the Ozone Maintenance 

Plan. 
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steps to ensure the accuracy of this version, but it is not the official version. 

The MVEBs are the on-road mobile source VOC and NOx

emissions for Clark County for 2008, 2015 and 2022. The MVEBs 

are compatible with the 2008, 2015, and 2022 on-road mobile 

source VOC and NOx emissions included in Clark County’s 2008, 

2015, and 2022 VOC and NOx emission inventories, as summarized 

above in table 3. The derivation of the MVEBs is thoroughly 

discussed in appendix A, chapter 7 of Clark County’s Ozone 

Maintenance Plan. Updated vehicle miles traveled (VMT) data from 

the Regional Transportation Commission’s TRANSCAD transportation 

demand model was adjusted with Highway Performance Monitoring 

System (HPMS) data and then combined with emission factors from 

MOBILE6 to estimate ozone precursor emissions. 

We note that the MVEBs in the Ozone Maintenance Plan for 

2008 differ from those contained for that same year in the Clark 

County Ozone EPP, but Clark County DAQ has explained the 

differences stem not from a different approach but from changes 

with regard to the fuel parameters and updated vehicle activity 

data for 2008. Specifically, the MOBILE input files used for the 

Ozone Maintenance Plan were updated to show the use of ethanol 

in summertime with a 1.0 psi waiver, resulting in higher VOC 

emissions, and the VMT estimates for 2008 were adjusted 

downwards to reflect the latest transportation data from RTC. 

The net effect of these changes resulted in higher VOC emissions 
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This document is a prepublication version, signed by Region 9 Regional Administrator Jared Blumenfeld on November 2, 2012. We have taken 

steps to ensure the accuracy of this version, but it is not the official version. 

but lower NOx emissions for 2008 relative to the corresponding 

estimates in the Clark County Ozone EPP. 

EPA is proposing to approve the MVEBs for 2008, 2015 and 

2022 as part of our approval of Clark County's Ozone Maintenance 

Plan. EPA has determined that the MVEB emission targets are 

consistent with emission control measures in the SIP and that 

Clark County can maintain attainment of the 1997 8-hour ozone 

NAAQS. The details of EPA's evaluation of the MVEBs for 

compliance with the budget adequacy criteria of 40 CFR 93.118(e) 

are provided in a separate memorandum25 included in the docket of 

this rulemaking. 

VI. Proposed Action and Request for Public Comment 

Under CAA section 110(k)(3), and for the reasons set forth 

above, EPA is proposing to approve NDEP's submittal dated April 

11, 2011 of Clark County's Ozone Redesignation Request and 

Maintenance Plan (March 2011) ("Clark County Ozone Maintenance 

Plan") as a revision to the Nevada state implementation plan 

(SIP). In connection with the Clark County Ozone Maintenance 

Plan, EPA finds that the maintenance demonstration showing how 

the area will continue to attain the 1997 8-hour ozone NAAQS for 

10 years beyond redesignation (i.e., through 2022) and the 

contingency provisions describing the actions that Clark County 

 

25 See EPA memorandum dated October 15, 2012 titled, "Adequacy Documentation 

for Motor Vehicle Emission Budgets in April 2011 Clark County Ozone 

Maintenance State Implementation Plan." 
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steps to ensure the accuracy of this version, but it is not the official version. 

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. EPA is also 

proposing to approve the motor vehicle emissions budgets (MVEBs) 

in the Clark County Ozone Maintenance Plan (shown in table 4 of 

this document) because we find they meet the applicable 

transportation conformity requirements under 40 CFR 93.118(e). 

Second, under CAA section 107(d)(3)(D), we are proposing to 

approve NDEP's request, which accompanied the submitted of the 

maintenance plan, to redesignate the Clark County 8-hour ozone 

nonattainment area to attainment for the 1997 8-hour ozone 

NAAQS. We are doing so based on our conclusion that the area has 

met the five criteria for redesignation under CAA section 

107(d)(3)(E). Our conclusion in this regard is in turn based on 

our proposed determination that the area has attained the 1997 

8-hour ozone NAAQS, that relevant portions of the Nevada SIP are 

fully approved, that the improvement in air quality is due to 

permanent and enforceable reductions in emissions, that Nevada 

has met all requirements applicable to the Clark County 8-hour 

ozone nonattainment area with respect to section 110 and part D 

of the CAA, and based on our proposed approval as part of this 

action of the Clark County Ozone Maintenance Plan. 

EPA is soliciting public comments on the issues discussed 

in this document or on other relevant matters. We will accept 
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steps to ensure the accuracy of this version, but it is not the official version. 

comments from the public on this proposal for the next 30 days. 

We will consider these comments before taking final action. 

VII. Statutory and Executive Order Reviews 

Under the CAA, redesignation of an area to attainment and 

the accompanying approval of a maintenance plan under section 

107(d)(3)(E) are actions that affect the status of a 

geographical area and do not impose any additional regulatory 

requirements on sources beyond those imposed by State law. 

Redesignation to attainment does not in and of itself create any 

new requirements, but rather results in the applicability of 

requirements contained in the CAA for areas that have been 

redesignated to attainment. Moreover, 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, EPA's role is to approve State choices, provided 

that they meet the criteria of the Clean Air Act. Accordingly, 

these actions merely propose to approve a State plan and 

redesignation request as meeting Federal requirements and do not 

impose additional requirements beyond those by State law. For 

these reasons, these proposed actions: 

· Are not a "significant regulatory action” subject to review 

by the Office of Management and Budget under Executive 

Order 12866 (58 FR 51735, October 4, 1993); 
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steps to ensure the accuracy of this version, but it is not the official version. 

· Do not impose an information collection burden under the 

provisions of the Paperwork Reduction Act (44 U.S.C. 3501 

et seq.); 

· Are 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.); 

· Do 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); 

· Do not have Federalism implications as specified in 

Executive Order 13132 (64 FR 43255, August 10, 1999); 

· Are not an economically significant regulatory action based 

on health or safety risks subject to Executive Order 13045 

(62 FR 19885, April 23, 1997); 

· Are not a significant regulatory action subject to 

Executive Order 13211 (66 FR 28355, May 22, 2001); 

· Are 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 CAA; and 

· Do not provide EPA with the discretionary authority to 

address disproportionate human health or environmental 

effects with practical, appropriate, and legally 
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permissible methods under Executive Order 12898 (59 FR 

7629, February 16, 1994). 

In addition, this proposed rule does not have Tribal 

implications as specified by Executive Order 13175 (65 FR 67249, 

November 9, 2000), because the SIP is not approved to apply in 

Indian country located in the State, and EPA notes that it will 

not impose substantial direct costs on Tribal governments or 

preempt Tribal law. Nonetheless, EPA has discussed the proposed 

action with the one Tribe, the Las Vegas Paiute Tribe, located 

within the Clark County 8-hour ozone nonattainment area. 

List of Subjects 

40 CFR Part 52 

Environmental protection, Air pollution control, 

Intergovernmental relations, Nitrogen dioxide, Ozone, Reporting 

and recordkeeping requirements, Volatile organic compounds. 

40 CFR Part 81 

Environmental protection, Air pollution control, National 

parks, Wilderness areas. 

November 2, 2012______ ___________/s/_____________ 

Dated: Jared Blumenfeld 

 Regional Administrator, 

Region IX.