ENVIRONMENTAL PROTECTION AGENCY 

40 CFR Parts 52 and 81 

[EPA-R09-OAR-2010-0585; FRL- ] 

Approval and Promulgation of Implementation Plans and 

Designation of Areas for Air Quality Planning Purposes; State of 

Nevada; Redesignation of Las Vegas Valley to Attainment for the 

Carbon Monoxide Standard 

AGENCY: Environmental Protection Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: EPA is proposing to approve the State of Nevada’s 

request to redesignate to attainment the Las Vegas Valley 

nonattainment area for the carbon monoxide national ambient air 

quality standard. EPA is also proposing to approve the carbon 

monoxide maintenance plan and motor vehicle emissions budgets 

for the area, as well as certain additional revisions to the 

Nevada state implementation plan. These revisions include the 

suspension of a local wintertime cleaner burning gasoline rule, 

and the relaxation of a State rule governing wintertime gasoline 

in Clark County. EPA’s proposed approval is contingent upon 

receipt of a supplemental submittal from the State of Nevada 

containing a commitment to reinstate the existing vapor pressure 

limit in the State wintertime gasoline rule, if necessary, and 

thereby to implement the related contingency measure in the 

maintenance plan. 
2 

DATE: Comments must be received on or before [INSERT DATE 30 

DAYS FROM DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 

ADDRESSES: Submit comments, identified by docket number EPAR09-OAR-2010-0585, by one of the following methods: 

 1. Federal eRulemaking Portal: http://www.regulations.gov. 

Follow the on-line instructions for submitting comments. 

 2. E-mail: oconnor.karina@epa.gov. 

 3. Mail or deliver: Karina O’Connor (AIR-2), U.S. 

Environmental Protection Agency Region IX, 75 Hawthorne Street, 

San Francisco, CA 94105-3901. 

Instructions: Direct your comments to Docket ID No. EPA-R09-

OAR-2010-0585. EPA’s policy is that all comments received 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 

information claimed to be Confidential Business Information 

(CBI) or other information whose disclosure is restricted by 

statute. Do not submit information that you consider to be CBI 

or otherwise protected through http://www.regulations.gov or email. The http://www.regulations.gov Web site is an “anonymous 

access” system, which means that EPA will not know your identity 

or contact information unless you provide it in the body of your 

comment. If you send e-mail directly to EPA, without going 

through http://www.regulations.gov, your e-mail address will be 
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automatically captured and included as part of the comment that 

is placed in the public docket and made available on the 

Internet. If you submit an electronic comment, EPA recommends 

that you include your name and other contact information in the 

body of the comment and with any disk or CD-ROM you submit. If 

EPA cannot read your comment due to technical difficulties and 

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

consider your comment. Electronic files should avoid the use of 

special characters, any form of encryption, and be free of any 

defects or viruses. 

Docket: All documents in the docket are listed in the 

http://www.regulations.gov index. Although listed in the index, 

some information is not publicly available, e.g., CBI or other 

information whose disclosure is restricted by statute. Certain 

other information, such as copyrighted material, will be 

publicly available only in hard copy form. Publicly available 

docket materials are available either electronically in 

http://www.regulations.gov or in hard copy at the Office of Air 

Planning, Environmental Protection Agency (EPA), Region IX, 75 

Hawthorne Street, San Francisco, California. 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. 
4 

FOR FURTHER INFORMATION CONTACT: Karina O’Connor, EPA Region 

IX, (775) 833-1276, oconnor.karina@epa.gov. 

SUPPLEMENTARY INFORMATION: Throughout this document, the terms 

“we,” “us,” and “our” refer to EPA. This supplementary 

information is organized 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 

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

Vegas Valley 

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. RFP and Attainment Demonstration 

c. Reasonable Available Control Measures/Control 

Technology 
5 

d. Emission Inventory 

e. Permits for New and Modified Major Stationary Sources 

f. Contingency Provisions 

g. Conformity Requirements 

h. VMT Forecasts and Annual Updates 

i. Vehicle Inspection and Maintenance Program 

j. TCMs to Offset VMT-Related Emissions Increases and to 

Provide for RFP 

k. Oxygenated Gasoline Program 

l. Clean Data Policy and CO Milestone Requirement 

3. Conclusion with respect to Section 110 and Part D 

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 

7. Motor Vehicle Emissions Budgets 

8. Conclusion 
6 

VI. Evaluation of Suspended or Relaxed Wintertime Gasoline 

Specifications 

VII. Proposed Action and Request for Comment 

VIII. Statutory and Executive Order Reviews 

I. Summary of Today's Proposed Action 

EPA is proposing to approve the Nevada Division of 

Environmental Protection’s (NDEP’s) request to redesignate to 

attainment the Las Vegas Valley1 carbon monoxide (CO) 

nonattainment area located within Clark County, Nevada, and 

related revisions to the Nevada state implementation plan (SIP). 

The specific SIP revision submittals that we are proposing to 

approve are listed in the following table: 

Plan or Rule Adoption date(s) State of Nevada 

submittal date(s) 

Carbon Monoxide 

Redesignation 

Request and 

Maintenance Plan, 

Las Vegas Valley 

Nonattainment Area, 

Clark County, Nevada 

(September 2008) 

Adopted by the 

Clark County Board 

of Commissioners 

on September 2, 

2008. 

Submitted by NDEP 

by letter dated 

September 18, 

2008. 

 

1

 Specifically, the Las Vegas Valley CO nonattainment area is defined by 

reference to State hydrographic area #212. See 40 CFR 81.329. The Las Vegas 

Valley encompasses roughly 1,500 square miles within Clark County and 

includes the cities of Las Vegas, North Las Vegas, and Henderson. Roughly two 

million people reside in Clark County, mostly within Las Vegas Valley. NDEP 

is the state agency under state law that is responsible for SIP matters for 

the State of Nevada. Within Clark County, the Clark County Board of 

Commissioners, acting through the Department of Air Quality and Environmental 

Management (DAQEM), is empowered under state law to develop air quality plans 

and to regulate stationary sources within the county with the exception of 

certain types of power plants, which lie exclusively within the jurisdiction 

of NDEP. 
7 

Clark County Air 

Quality Regulations, 

Section 54 (“Cleaner 

Burning Gasoline 

(CBG): Wintertime 

Program”)(Suspended) 

Adopted by the 

Clark County Board 

of Commissioners 

on September 15, 

2009, effective 

September 29, 

2010. 

Submitted by NDEP 

by letter dated 

March 26, 2010. 

Nevada 

Administrative Code 

(NAC) section 

590.065 (amended) 

Adopted by the 

Nevada Board of 

Agriculture on 

December 9, 2010, 

effective January 

28, 2010. 

Submitted by NDEP 

by letter dated 

March 26, 2010. 

Specifically, we are proposing to approve NDEP’s 

maintenance plan submittal dated September 18, 2008 titled 

Carbon Monoxide Redesignation Request and Maintenance Plan, Las 

Vegas Valley Nonattainment Area, Clark County, Nevada (September 

2008) (“Las Vegas Valley CO Maintenance Plan” or “Maintenance 

Plan”)2 as a revision to the Nevada SIP, and to approve NDEP’s 

request to redesignate Las Vegas Valley to attainment for the CO 

NAAQS. We are proposing to approve the Las Vegas Valley CO 

Maintenance Plan because we find that it meets all requirements 

for such plans in section 175A under the Clean Air Act (“Act” or 

CAA), and we are proposing to approve NDEP’s redesignation 

request for Las Vegas Valley from nonattainment to attainment 

because we believe that the area has met all of the criteria for 

redesignation under CAA section 107(d)(3)(E). The Las Vegas 

 

2

 The Las Vegas Valley CO Maintenance Plan consists of the main body of the 

plan and three appendices: Appendix A (“Wintertime Gasoline Fuel 

Specification Study”), Appendix B (Technical Support Document, Carbon 

Monoxide Modeling for the Clark County Maintenance Plan”), Appendix C 

(“Documentation of the Public Review Process”). 
8 

Valley CO Maintenance Plan includes CO motor vehicle emissions 

budgets (MVEBs) for years 2008, 2010, and 2020, and we are 

proposing to approve these budgets for the purposes of 

transportation conformity based on our conclusion that they meet 

the criteria for such budgets in 40 CFR 93.118(e). Final 

approval of the redesignation request and maintenance plan would 

change the legal description of the Las Vegas Valley CO 

nonattainment area in 40 CFR part 81 from nonattainment to 

attainment, and would make federally enforceable the commitments 

and contingency provisions contained in the maintenance plan. 

In connection with the CO Maintenance Plan, Clark County 

and the State of Nevada have decided to suspend or relax two 

gasoline-related regulations that formed part of the control 

strategy that has provided for attainment of the CO standard in 

Las Vegas Valley but that they believe are not needed for the 

purposes of maintaining the CO standard now that the CO standard 

has been attained. These are Clark County Air Quality 

Regulations (AQR) Section 54 (“Cleaner Burning Gasoline: 

Wintertime Program”)(herein, referred to as the “CBG Rule”), 

which establishes certain wintertime gasoline specifications 

related to sulfur and aromatic hydrocarbons (“aromatics”), and 

Nevada Administrative Code (NAC) section 590.065 (herein 

referred to as the “Low RVP Rule”), which establishes a low Reid 

vapor pressure (RVP) specification for gasoline sold during the 
9 

late fall and winter months in Clark County. We are proposing to 

approve the suspension of Clark County’s CBG Rule and the 

relaxation of the State’s Low RVP Rule because we conclude, in 

accordance with CAA section 110(l), that doing so would not 

interfere with attainment or maintenance of any of the NAAQS or 

any applicable requirement of the Clean Air Act.3 

The Las Vegas Valley CO Maintenance Plan includes 

reinstatement of the CBG Rule and the Low RVP Rule as 

contingency measures, as required under CAA section 175A(d). 

However, while Clark County, through adoption of the maintenance 

plan, has committed to reinstatement of the CBG Rule in 

accordance with the contingency provisions of the plan, the 

Nevada State Department of Agriculture, which is responsible for 

the Low RVP Rule, has not yet made a similar commitment with 

respect to the Low RVP Rule. Thus, our approval of the 

Maintenance Plan and redesignation request is contingent upon 

the submittal, and EPA approval, of such a commitment as a 

revision to the Nevada SIP.4

 

3

 We are not including subsection (7) of amended NAC 590.065 in our proposed 

approval because the limits in subsection (7) of the amended rule are 

unrelated to the vapor pressure requirement and associated CO emissions 

reductions, and are severable from the rest of the rule. 

4

 On July 12, 2010, the Nevada Department of Agriculture initiated a 30-day 

comment period to solicit comment (or request a public hearing) on the draft 

commitment regarding implementation of the contingency measure in the 

Maintenance Plan related to reinstatement of the Low RVP Rule. The 

Department’s notice of intent to solicit public comment, which includes the 

commitment language, has been placed in the docket for this rulemaking. We 

have reviewed the language of the Department’s draft commitment and expect to 
10 

II. Background 

Carbon monoxide (CO) is a colorless, odorless gas emitted 

in combustion processes. In most areas where elevated CO levels 

are found, CO comes primarily from tailpipe emissions of cars 

and trucks. Exposure to elevated CO levels is associated with 

impairment of visual perception, work capacity, manual dexterity 

and learning ability, and with illness and death for those who 

already suffer from cardiovascular disease, particularly angina 

or peripheral vascular disease. 

On April 30, 1971 (see 36 FR 8186), pursuant to section 109 

of the Act, as amended in 1970, EPA promulgated the original 

national ambient air quality standards (NAAQS) for several 

pervasive air pollutants, including CO. 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). The primary (i.e., health-based) 

NAAQS for CO is 9 parts per million (ppm) averaged over an 8-

hour period, and 35 ppm averaged over 1 hour, neither to be 

exceeded more than once per year. In our 1971 rulemaking, we 

established identical primary and secondary NAAQS for CO but 

later revoked the secondary (welfare) NAAQS for CO. See 50 FR 

 approve it if it is ultimately submitted to us without significant 

modification. 
11 

37484 (September 13, 1985). The (primary) CO NAAQS established 

by EPA in 1971, remain in effect today. See 40 CFR 50.8 

(“National primary ambient air quality standards for carbon 

monoxide”). 

 Under section 110 of the Act, each State is required to 

adopt and submit to EPA a plan that provides for the 

implementation, maintenance, and enforcement of the NAAQS within 

each State. These plans are referred to as “state implementation 

plans” or “SIPs.” Under the Clean Air Act, as amended in 1970, 

SIPs were required to provide for attainment of the NAAQS within 

3 years after EPA approval of the plan. However, many areas of 

the country did not attain the NAAQS within the statutory 

period. 

In response, Congress amended the Act in 1977 to establish 

a new approach, based on area designations, for attaining the 

NAAQS, and on March 3, 1978 (43 FR 8962), we promulgated 

attainment status designations for all areas within each of the 

States. In the 1978 rulemaking, we designated Las Vegas Valley 

as a “nonattainment” area for the CO NAAQS based on monitored 

violations of the 8-hour CO NAAQS.5 See 43 FR 8962, at 9013 

(March 3, 1978). 

 

5

 Thus, the CO plans previously approved by EPA for Las Vegas Valley assume 

that the 8-hour CO standard, rather than the 1-hour CO standard, is the 

controlling standard. That is, attainment of the former necessarily means 

attainment of the latter. The same holds true in the submitted Las Vegas 
12 

The Clean Air Act, as amended in 1977, required States to 

revise their SIPs by preparing, adopting and submitting 

attainment plans (for EPA approval) that set forth a strategy to 

achieve the NAAQS in designated nonattainment areas. The 

original statutory deadline for attainment under the 1977 

Amended Act was 1982, but extensions to 1987 were allowed if 

certain SIP requirements were met. In response, Clark County and 

the State of Nevada adopted and implemented various air quality 

plans and programs, including a vehicle inspection and 

maintenance (I/M) program, to reduce CO levels in Las Vegas 

Valley. EPA approved these plans and programs at various times 

as revisions to the Nevada state implementation plan (SIP). See 

46 FR 21758 (April 14, 1981); 47 FR 15790 (April 13, 1982); 49 

FR 44208 (November 5, 1984). Despite these programs, Las Vegas 

Valley did not attain the CO NAAQS by the then-applicable 1987 

attainment date. 

The CAA was significantly amended by Congress in 1990 to 

establish new attainment dates and planning and control 

requirements for areas, like Las Vegas Valley, that had failed 

to attain the NAAQS under the 1977 Amendments. Under the 1990 

Amended Act, Las Vegas Valley was initially classified as a 

“moderate” nonattainment area for CO (based on a design value of 

 Valley CO Maintenance Plan, which includes a maintenance demonstration for 

the 8-hour CO standard, not the 1-hour CO standard. 
13 

14.4 ppm) but was subsequently reclassified as a “serious” CO 

nonattainment area after having failed to attain the standard by 

the applicable attainment date (i.e., December 31, 1995) for 

moderate areas. See 62 FR 51604 (October 2, 1997). The Las Vegas 

Valley area was then subject to the applicable attainment 

deadline for “serious” CO nonattainment areas (i.e., December 

31, 2000). See CAA section 186(a)(1). 

In response to nonattainment classifications and related 

CAA requirements, Clark County and the State of Nevada adopted 

and implemented new air quality plans and programs, including a 

“serious” area attainment plan titled Carbon Monoxide State 

Implementation Plan, Las Vegas Valley Nonattainment Area, Clark 

County, Nevada (August 2000) (“2000 Las Vegas Valley CO Plan” or 

“2000 CO Plan”). We approved the 2000 Las Vegas Valley CO Plan 

in 2004. See 69 FR 56351 (September 21, 2004). 

In connection with the 2000 Las Vegas Valley CO Plan, we 

approved, among other plan elements, Clark County AQR Section 54 

(“Cleaner Burning Gasoline (CBG): Wintertime Program”)(i.e., the 

CBG Rule)(originally adopted by Clark County in 1999), the 

State’s alternate “low” enhanced vehicle I/M program for Las 

Vegas Valley and Boulder City, the State’s regulation 

establishing a low RVP wintertime gasoline specification for 

Clark County (i.e., the Low RVP Rule)(originally adopted by the 

State Board of Agriculture in 1995), the State’s alternative 
14 

fuels for government fleets program, the Regional Transportation 

Commission of Southern Nevada’s (RTC’s) Transportation Control 

Measures/ Transportation Demand Management (TCM/TDM) program, 

and an amended version of previously approved Clark County AQR 

Section 53 (“Oxygenated Gasoline Program”)(originally adopted by 

Clark County in 1991). The 2000 Las Vegas Valley CO Plan 

identifies the CBG Rule, I/M program, Low RVP Rule, and the 

oxygenated gasoline program, along with the Federal Motor 

Vehicle Control Program (FMVCP), as the primary control measures 

providing for attainment of the CO NAAQS in Las Vegas Valley by 

the applicable attainment date (2000). In 2004, we also approved 

the 2000 CO Plan’s motor vehicle emissions budgets (MVEBs) for 

years 2000, 2010 and 2020.6

In 2005, EPA determined that the Las Vegas Valley had 

attained the CO NAAQS by its applicable attainment deadline of 

December 31, 2000 [70 FR 31353 (June 1, 2005)], and had 

continued to attain through 2003 [70 FR 3174, at 3177 (January 

21, 2005)]. This attainment determination did not constitute 

redesignation to attainment, however, because it did not include 

consideration or approval of the additional requirements for 

 

6

 While important for the purposes of attaining the CO standard by the 

applicable attainment date (2000), the Maintenance Plan shows that the Low 

RVP Rule and the CBG Rule are no longer necessary for the purposes of 

maintaining the CO standard. The consistent, but more gradual, emissions 

reduction benefits of the FMVCP and natural vehicle turnover (i.e., 

replacement of older more polluting motor vehicles with newer cleaner 

vehicles) allow for the relaxation of these fuel rules consistent with 

continued maintenance of the CO standard. 
15 

redesignation set forth in CAA section 107(d)(3)(E), e.g., a 

maintenance plan satisfying CAA section 175A. 

In 2006, EPA approved a Las Vegas Valley CO plan titled 

Carbon Monoxide State Implementation Plan Revision, Las Vegas 

Valley Nonattainment Area, Clark County, Nevada (October 2005) 

(“2005 Las Vegas Valley CO Plan” or “2005 CO Plan”), which 

amended the emissions inventories, attainment demonstration, and 

related MVEBs from the 2000 Las Vegas Valley CO Plan in response 

to changes in the EPA-approved motor vehicle emission factor 

model and higher-than-forecast increases in population growth in 

Las Vegas Valley. See 71 FR 44587 (August 7, 2006). 

EPA today is proposing to approve the State’s request to 

redesignate the Las Vegas Valley to attainment for the CO NAAQS, 

and to approve the Las Vegas Valley CO Maintenance Plan. We are 

also proposing approval of the suspension or relaxation of two 

specific control measures that had previously been approved into 

the SIP, but that Clark County has shown are no longer needed to 

maintain the CO NAAQS in Las Vegas Valley: the County’s CBG 

Rule and the State’s Low RVP Rule. Our evaluation of the 

submittals and the redesignation request is provided in the 

following sections of this document. 

III. Procedural Requirements for Adoption and Submittal of SIP 

Revisions 
16 

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 the 

following SIP revisions: the Las Vegas Valley CO Maintenance 

Plan, submitted by NDEP on September 18, 2008; and the suspended 

or relaxed wintertime gasoline regulations, submitted by NDEP on 

March 26, 2010. 

Both of the SIP revision submittals cited above contain 

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 CO maintenance 

plan was published on several dates in a newspaper of general 

circulation within the Las Vegas area beginning on May 11, 2008. 

The Clark County Board of Commissioners adopted the Las Vegas 

Valley CO Maintenance Plan by resolution on September 2, 2008 at 

the close of the public hearing. Appendix C to the plan 

documents the public review process used by the county to adopt 

the plan. Following adoption, Clark County DAQEM 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. 

NDEP’s March 26, 2010 SIP submittal documents the public 

review process used by the Clark County Board of Commissioners 
17 

in suspending Section 54 (i.e., the CBG Rule) and by the State 

Board of Agriculture in relaxing the wintertime gasoline vapor 

pressure requirement. Specifically, NDEP’s March 26, 2010 

submittal documents the Clark County Board of Commissioners’ 

September 15, 2009 public hearing on, and subsequent adoption 

of, Ordinance No. 3809 suspending the CBG Rule, effective 

September 29, 2009. Notice of Clark County DAQEM’s workshop to 

discuss suspension of the CBG Rule was published on several 

dates in a newspaper of general circulation within the Las Vegas 

area beginning on May 17, 2009. 

The March 26, 2010 SIP revision submittal also documents 

the State Board of Agriculture’s December 9, 2009 public hearing 

on, and subsequent adoption of, amendments to NAC section 

590.065 (LCB File No. R111-08), effective January 28, 2010, 

including the relaxation of the RVP wintertime gasoline limit in 

Clark County from 9.0 to 13.5 pounds per square inch (psi). This 

action on the part of the Board of Agriculture was preceded by 

publication on September 16, 2009 by the Nevada Department of 

Agriculture of a notice of a workshop to be held on October 13, 

2009 to solicit comments on amendments to NAC section 590.065, 

and by publication on November 4, 2009 of a notice of intent to 

act upon a regulation. 

Based on the documentation submitted with the two SIP 

submittals and summarized above, we find that both SIP revisions 
18 

cited above satisfy 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 

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, including plan revisions 

meeting the requirements of part D (i.e., CAA section 171 

through section 193), and part D establishes the SIP 

requirements for nonattainment areas. Part D is divided into six 

subparts; the CO-specific nonattainment SIP requirements are 
19 

found in part D, subpart 3, which includes CAA sections 186 and 

187. 

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 

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 Las Vegas Valley nonattainment area to attainment for the 

CO NAAQS based on our conclusion that all of the criteria under 

CAA section 107(d)(3)(E) have been satisfied. For the reasons 

set forth in section V.D.5 of this document, our proposed 

approval is contingent upon NDEP’s submission of a commitment by 

the Nevada Department of Agriculture to reinstate the Low RVP 

Rule if necessary to address future violations of the CO NAAQS 

in Las Vegas Valley and thereby implement the related 

contingency measure in the Maintenance Plan. 
20 

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

Valley 

A. Determination that the Area has attained the Applicable 

NAAQS. 

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

the area has attained the NAAQS. EPA makes the determination as 

to whether an area's air quality is meeting the CO NAAQS based 

upon air quality data gathered at CO monitoring sites in the 

nonattainment area which have been entered into the Air Quality 

System (AQS) database. This data is reviewed to determine the 

area's air quality status in accordance with 40 CFR 50.8; EPA 

policy guidance as stated in a memorandum from William G. 

Laxton, Director Technical Support Division, entitled “Ozone and 

Carbon Monoxide Design Value Calculations,” dated June 18, 1990; 

and EPA's General Preamble at 57 FR 13535. 

The 8-hour and 1-hour CO design values are used to 

determine attainment of CO areas, and the design values are 

determined by reviewing 8 quarters of data, or a total of two 

complete calendar years of data for an area. The 8-hour design 

value is computed by first finding the maximum and second 

maximum (non-overlapping) 8-hour values at each monitoring site 

for each year of the two calendar years prior to and including 

the attainment date. Then the higher of the “second high” values 

is used as the design value for the monitoring site, and the 
21 

highest design value among the various CO monitoring sites 

represents the CO design value for the area. 

The CO NAAQS requires that not more than one 8-hour average 

per year equals or exceeds 9.5 ppm (values below 9.5 are rounded 

down to 9 and are not considered exceedances). If an area has a 

design value that is equal to or greater than 9.5 ppm, this 

means that there was a monitoring site where the second highest 

(non-overlapping) 8-hour average was measured to be equal to or 

greater than 9.5 ppm in at least one of the two years being 

reviewed to determine attainment for the area. This indicates 

that there were at least two values above the NAAQS during one 

year at that site and thus the NAAQS for CO was not met. 

Conversely, an 8-hour design value of less than 9.5 ppm 

indicates that the area has attained the CO NAAQS. The 1-hour CO 

design value is computed in the same manner. An area attains the 

one-hour CO NAAQS if the 1-hour design value is less than 35.5 

ppm.

On June 1, 2005 (70 FR 31353), we determined that the Las 

Vegas Valley “serious” CO nonattainment area had attained the CO 

NAAQS by the applicable attainment date (2000) based on complete 

quality-assured data showing a design value of the area (from 

Sunrise Acres station) for 1999-2000 of 8.2 ppm, eight-hour 

average, and 10.2 ppm, one-hour average. (The corresponding 

NAAQS are 9 ppm, eight-hour average, and 35 ppm, one-hour 
22 

average.) We also found that Las Vegas Valley had continued to 

attain the standard through year 2003. As part of that 

determination, we reviewed the ambient CO monitoring network 

operated by Clark County DAQEM and found that it met or exceeded 

our requirements. See 70 FR 3174 (January 21, 2005). 

In our proposed determination that the area had attained by 

its attainment deadline (2000)(70 FR 3174, January 21, 2005), we 

described Clark County’s CO monitoring network at that time as 

including 7 SLAMS sites, 4 NAMS sites, and 4 special purpose 

sites.7 Since our 2005 finding of attainment, Clark County has 

closed a number of CO monitoring sites. There are now five CO 

monitoring sites in Las Vegas Valley: Winterwood, East Sahara, 

Sunrise Acres, Orr School and J.D. Smith. All of the monitoring 

sites are SLAMS, and the J.D. Smith site is also a NAMS site. 

All sites have population exposure as their monitoring objective 

except Sunrise Acres, which has “highest concentration” as its 

monitoring objective. 

While the number of CO monitoring stations has been 

reduced, we conclude in our Technical Systems Audit Report 

(February 2010) that the network currently meets or exceeds the 

requirements for the minimum number of CO monitoring sites. 

 

7

 EPA has established ambient air quality monitoring requirements and 

standards for State and Local Air Monitoring Stations (SLAMS) and for 

National Air Monitoring Stations (NAMS). These requirements and standards 

provide for operating schedules, data quality assurance, and for the design 

and siting of CO samplers. 
23 

Moreover, we note that the Sunrise Acres monitoring station, 

which is the site at which the highest CO concentrations have 

historically been recorded, remains among those that continue to 

be operated by Clark County DAQEM. 

For the purposes of this proposed rule, we reviewed 

complete, quality-assured monitoring data that are uploaded to 

our Air Quality System (AQS) database. We found that no 

exceedances of the CO NAAQS were recorded in Las Vegas Valley 

during the entire period from 2004-2009. During this period, the 

highest 8-hour CO concentrations were 60% of the NAAQS or less 

at all of the monitoring stations. Table 1 summarizes the 2nd

highest 8-hour and 1-hour average CO concentrations at the 

various monitoring stations during the most recent two-year 

period. As shown in the table, the 8-hour design value for the 

area based on 2008-2009 data is 3.7 ppm, eight-hour average, and 

4.7 ppm, 1-hour average, both of which are well below the 

corresponding NAAQS of 9 and 35 ppm, respectively. Preliminary 

data available for 2010 show that there continue to be no 

exceedances of the CO NAAQS in the area. 

TABLE 1: SUMMARY OF LAS VEGAS VALLEY CO MONITORING DATA, 

 2008-2009 

Monitoring Site Name 

2nd

 Highest 8-hour 

Concentration (ppm) 

2nd Highest 1-hour 

Concentration (ppm) 

2008 2009 Design 

Value 2008 2009 Design 

Value 

Winterwood 2.9 2.8 2.9 3.8 3.7 3.8 
24 

East Sahara 3.7 3.1 3.7 4.7 4.2 4.7 

Sunrise Acres 3.5 2.8 3.5 4.2 4.7 4.7 

Orr School 2.6 2.6 2.6 3.2 3.2 3.2 

J.D. Smith 2.5 2.4 2.5 3.6 3.2 3.6 

Area Design Value 8-Hour CO Design 

Value = 3.7 ppm (East 

Sahara) 

1-Hour CO Design 

Value = 4.7 ppm 

(East Sahara and 

Sunrise Acres) 

CO NAAQS 9 ppm 35 ppm 

Based on the AQS data presented above and the positive 

assessment of the Clark County DAQEM ambient CO monitoring 

network that we made in February 2010, we propose to determine 

that Las Vegas Valley has attained the CO NAAQS, and thus meets 

the criterion for redesignation set forth in section 

107(d)(3)(E)(i). 

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 
25 

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

Vegas Valley with respect to CO. 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 Las 

Vegas Valley 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 
26 

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 Las 

Vegas Valley portion of the SIP. We propose to conclude that 

NDEP and Clark County have met all SIP requirements for Las 

Vegas Valley applicable for purposes of redesignation under 

section 110 of the CAA (General SIP Requirements). With the 

exception discussed below in Section V.B.2.l of this document, 

the SIP for Las Vegas Valley also has been approved as meeting 

applicable requirements under part D of Title I of the CAA. 

2. Part D Requirements 

a. Introduction

The requirements that apply under part D (of Title I) of 

the Act to “serious” CO nonattainment areas are set forth in 

sections 172, 176, 187, and 211. In the General Preamble, we 

have issued guidance describing how we will review SIPs and SIP 

 be subject to these requirements after Las Vegas Valley 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.
27 

revisions submitted under part D (of Title I) of the Act, 

including those containing “serious” CO nonattainment area SIP 

provisions. In the following paragraphs, we explain how the 

State has met the applicable SIP revision requirements under 

part D for the Las Vegas Valley CO nonattainment area or where, 

in the case of certain requirements, how the requirement does 

not apply because Las Vegas Valley has attained the CO standard.9 

b. RFP and Attainment Demonstration

Under CAA sections 172(c)(2) and 187(a)(7), with respect to 

a serious CO nonattainment area, States are required to a submit 

a SIP revision that provides, and a demonstration that the plan 

as revised will provide, for attainment of the CO NAAQS by the 

applicable attainment date and provisions for such specific 

annual emission reductions as are necessary to attain the 

standard by that date. In 2004, in approving the 2000 Las Vegas 

Valley CO Plan, we approved the area’s RFP demonstration under 

sections 172(c)(2) and 187(a)(7) and attainment demonstration 

under section 187(a)(7). See 69 FR 56351, at 56353 (September 

21, 2004). Thus, the area has met the SIP requirements under CAA 

sections 172(c)(2) and 187(a)(7). 

c. Reasonable Available Control Measures/Control Technology

 

9

 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) and 172(c)(8) (equivalent techniques). Thus, 

these provisions are not relevant to the request for redesignation for the 

Las Vegas Valley CO nonattainment area. 
28 

Section 172(c)(1) of the Act requires States to submit a 

SIP revision for nonattainment areas that provide for the 

implementation of all reasonably available control measures 

(RACM) as expeditiously as practicable (including such 

reductions in emissions from existing sources in the area as may 

be obtained through the adoption, at a minimum, of reasonably 

available control technology (RACT)) and shall provide for 

attainment of the NAAQS. RACM is a more general term that can 

refer to stationary, area or mobile sources while RACT is a term 

that refers to stationary sources. 

Attainment of the CO NAAQS in Las Vegas Valley relied upon 

the Federal Motor Vehicle Control Program and five State or 

local control measures: The State’s vehicle I/M program, the 

State’s Low RVP Rule, Clark County’s rules (AQR sections 53 

(i.e., wintertime oxygenated gasoline rule) and the CBG Rule) 

establishing wintertime gasoline requirements related to oxygen 

content, sulfur content, and aromatics, and to a lesser degree, 

the State’s Alternative Fuels for Government Fleets program, and 

RTC’s TCM/TDM program. We have previously approved all of these 

State and local control measures into the Nevada SIP. Based on 

our 2005 determination that Las Vegas Valley had attained the CO 

NAAQS by the applicable attainment date (2000), we believe that 

no additional measures need be submitted to fulfill the 
29 

RACM/RACT requirement of CAA section 172(c)(1) in the Las Vegas 

Valley CO nonattainment area. 

d. Emissions Inventory 

Sections 172(c)(3) and 187(a)(1) of the Act require States 

to submit a comprehensive, accurate, current inventory of actual 

CO emissions for year 1990 from all sources within the 

nonattainment area. The inventory is to address actual CO 

emissions during the peak CO season for the area, 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. Section 187(a)(5) requires States to 

submit periodic (every three years) updates to the inventories 

required under section 187(a)(1). 

We interpret the Act such that the emission inventory 

requirements of section 172(a)(3), 187(a)(1), and 187(a)(5) are 

satisfied by the inventory requirements of the maintenance plan. 

See 57 FR 13498, at 13564 (April 16, 1992). Thus, our proposed 

approval of the Las Vegas Valley CO Maintenance Plan and related 

CO emission inventories satisfies the requirements of sections 

172(a)(3), 187(a)(1), and 187(a)(5) for the purposes of 

redesignation of Las Vegas Valley to attainment for the CO 
30 

NAAQS. See section V.D herein for details concerning the CO 

emission inventories in the Maintenance Plan. 

e. Permits for New and Modified Major Stationary Sources

Under section 172(c)(5), the CAA requires States 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. 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.” 

In 2004 (69 FR 54006, September 7, 2004), we approved Clark 

County’s NSR rules as meeting the requirements of section 

172(c)(5). See our proposed rule at 69 FR 31056, at 31059 (June 

2, 2004) for details concerning how Clark County’s NSR rules 

comply with CAA requirements for CO nonattainment areas. We have 

also made a finding under section 187(c)(1) that stationary 

sources do not contribute significantly to ambient CO levels in 
31 

the Las Vegas Valley CO nonattainment area. See at 69 FR 56351, 

at 56353 (September 21, 2004). 

For certain types of power plants in Clark County, NDEP 

rather than Clark County has the authority to issue air 

pollution permits under State law. In 2004, we approved a State 

rule (NAC section 445B.22083) that prohibits new power plants or 

major modification to existing power plants under State 

jurisdiction within the Las Vegas Valley nonattainment area. See 

69 FR 31056, 31059 (June 2, 2004) and 69 FR 54006, at 54017 

(September 7, 2004). In 2008, we approved an amended version of 

NAC section 445B.22083. See 73 FR 20536 (April 16, 2008). 

Based on our previous approvals of Clark County’s NSR rules 

and NAC section 445B.22083, we find that the State has met the 

requirements of CAA section 172(c)(5). 

f. Contingency Provisions 

Sections 172(c)(9) and 187(a)(3) of the Act require a State 

to submit contingency measures that will be implemented if an 

area fails to make reasonable further progress (RFP), if VMT 

estimates in the attainment plan are exceeded, or if the area 

fails to attain by the applicable attainment date. In 2005, 

based on our determination that Las Vegas Valley had attained 

the CO NAAQS by the applicable attainment date, we found that 

the CAA’s requirement for the SIP to provide for CO contingency 
32 

provisions under CAA sections 172(c)(9) and 187(a)(3) no longer 

applies to Las Vegas Valley. See 70 FR 31353 (June 1, 2005). 

g. Conformity Requirements 

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

1990, States were 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 

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 
33 

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

(November 7, 2008). 

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. 

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 Las Vegas 

Valley 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. 

h. VMT Forecasts and Annual Updates 

 Under CAA section 187(a)(2)(A), States are required to 

submit a SIP revision for serious CO nonattainment areas that 

contains a forecast of VMT in the nonattainment area concerned 

for each year before the year in which the plan projects the CO 

standard will be attained, and must provide for annual updates 

of the VMT forecasts. In 2004, we approved VMT forecasts and the 
34 

responsible agencies’ commitments to revise and replace the VMT 

projections as needed and to monitor actual VMT levels in the 

future, under section 187(a)(2)(A) of the Act (see RTC’s 

Resolution No. 149, approved into the SIP in 2004). Thus, we 

find that the SIP requirement for VMT forecasts and annual 

updates for Las Vegas Valley under CAA section 187(a)(2)(A) has 

been met. 

i. Vehicle Inspection and Maintenance Program 

Under section 187(a)(6), the CAA requires States with 

serious CO nonattainment areas to submit a SIP revision that 

provides for a vehicle I/M program that meets applicable Federal 

I/M requirements, including the “enhanced” I/M performance 

standard. In 2004, we approved the “alternate low” enhanced 

vehicle I/M program for Las Vegas Valley and Boulder City as 

meeting the requirements of CAA section 187(a)(6) and EPA’s I/M 

Regulation (40 CFR part 52, subpart S (“Inspection/Maintenance 

Program Requirements”). See at 69 FR 56351, at 56353 (September 

21, 2004). Since then, we have approved an update to the 

statutory and regulatory elements of the vehicle I/M program. 

See 73 FR 38124, at 38127 (footnote 31), and 74 FR 3975 (January 

22, 2009). Thus, the vehicle I/M SIP requirement for Las Vegas 

Valley under CAA section 187(a)(6) has been met. 

j. TCMs to Offset VMT-Related Emissions Increases and to Provide 

for RFP
35 

 Section 187(b)(2) of the Clean Air Act applies the 

requirements of section 182(d)(1) to serious CO nonattainment 

areas with the purpose of reducing CO emissions rather than 

emissions of volatile organic compounds (VOC). Specifically, 

section 187(b)(2) requires States with a serious CO 

nonattainment area to submit a SIP revision that identifies and 

adopts specific enforceable transportation control strategies 

and transportation control measures (collectively, “TCMs”) to 

offset any growth in CO emissions from growth in VMT or numbers 

of vehicle trips in such area and to reduce motor vehicle CO 

emissions as necessary, in combination with other emission 

reductions requirements, to provide for RFP. As noted above, we 

approved the CO RFP demonstration for Las Vegas Valley as part 

of our approval of the Las Vegas Valley 2000 CO Plan. 

EPA has concluded that states are not required to submit 

such measures if the SIP includes a demonstration that, despite 

growth in projected VMT, CO emissions will decline each year 

through the attainment year. See, e.g., EPA proposed approval of 

California’s redesignation request for the South Coast Air Basin 

at 72 FR 6986 (February 14, 2007); finalized at 72 FR 26718 (May 

11, 2007). In the General Preamble, we state that: “If projected 

total motor vehicle emissions during the ozone season in one 

year are not higher than during the ozone season the year 

before, given the control measures in the SIP, the VMT offset 
36 

requirement is satisfied.” General Preamble at 57 FR 13522. For 

CO areas, the General Preamble principle quoted above applies to 

motor vehicle emissions of CO during the CO season. 

The Las Vegas Valley 2000 CO Plan includes CO emissions 

inventories for a base year (1996) and the attainment year 

(2000) that show a sharp decline in CO motor vehicle emissions 

during the 1996 through 2000 period. See page 6-3 of the Las 

Vegas Valley 2000 CO Plan. We approved the emissions inventories 

in 2004 (69 FR 56351, September 21, 2004). Thus, no TCMs for Las 

Vegas Valley were required to prevent an increase in emissions 

associated with a growth in VMT or vehicle trips, since 

emissions decline each year through the attainment year despite 

increases in VMT and vehicle trips. Nonetheless, the State did 

submit a TCM/TDM program (RTC’s CAT MATCH commuter incentive 

program) as part of the Las Vegas Valley 2000 CO Plan. See 2000 

CO Plan, appendix D, sections 2 and 9. In 2004, we approved the 

TCM/TDM program under section 187(b)(2) and our voluntary mobile 

source emissions reduction program policy. See 69 FR 56351, at 

56353 (September 21, 2004). 

Based on our 2004 approval of the emissions inventories and 

RFP demonstration from the Las Vegas Valley 2000 CO Plan that 

show that no additional TCMs are required to offset VMT-related 

emissions increases or to provide RFP, we find that the TCM-
37 

related requirements of CAA section 187(b)(2) for Las Vegas 

Valley have been met. 

k. Oxygenated Gasoline Program 

Under sections 187(b)(3) and 211(m), the CAA requires 

States with serious CO nonattainment areas to submit a SIP 

revision that provides for an oxygenated gasoline program. Such 

a program must require gasoline to be blended to contain not 

less than 2.7% oxygen by weight during the period of the year 

during which CO levels are elevated (i.e., the winter months). 

In 1999, we approved Clark County’s oxygenated gasoline rule, 

Section 53 (“Oxygenated Gasoline Program”) as meeting the 

requirements under sections 187(b)(3) and 211(m). See 64 FR 

29573 (June 2, 1999). Clark County AQR Section 53 requires 

gasoline sold in Las Vegas Valley, Eldorado Valley, Ivanpah 

Valley, and the Boulder City limits to be blended to contain 

3.5% oxygen by weight each year from October 1st through March 

31st. In 2004, we approved administrative changes to the rule. 

See 69 FR 56351, at 56353 (September 21, 2004). Thus, the 

oxygenated gasoline requirement under CAA sections 187(b)(3) and 

211(m) has been met. 

l. Clean Data Policy and CO Milestone Requirement

CAA section 187(d) (“CO Milestone”) applies to serious CO 

areas and requires: (1) The state to submit a demonstration 

that the area has achieved certain specific annual emission 
38 

reductions; (2) EPA to determine whether the demonstration is 

adequate; and (3) the state to submit a plan revision, if EPA 

notifies the state that the CO milestone demonstration is 

inadequate, that implements CAA section 182(g)(4) economic 

incentive and transportation control programs sufficient to 

achieve the specific annual emission reductions by the 

attainment date. EPA has not approved a CO Milestone 

demonstration for Las Vegas Valley, but, as explained below, the 

CO Milestone requirement is linked to the RFP requirement in 

section 187(a)(7), and because RFP has no meaning when the area 

has attained the standard, the CO Milestone requirement 

similarly is no longer meaningful and no corresponding SIP 

revision is required to be approved for purposes of 

redesignation. 

In some designated nonattainment areas, monitored data 

demonstrates that the NAAQS have already been achieved. Based on 

its interpretation of the Act, EPA has determined that certain 

SIP submission requirements of part D, subparts 1, 2, and 4 of 

the Act do not apply for purposes of evaluating redesignation 

requests and therefore we do not require certain submissions for 

an area that has attained the NAAQS. These include RFP 

requirements, attainment demonstrations and contingency 

measures, because these provisions have the purpose of helping 

achieve attainment of the NAAQS. 
39 

The Clean Data Policy is the subject of two EPA memoranda 

setting forth our interpretation of the provisions of the Act as 

they apply to areas that have attained the relevant NAAQS. EPA 

also finalized the statutory interpretation set forth in the 

policy in a final rule, 40 CFR 51.918, as part of its Final Rule 

to Implement the 8-hour Ozone National Ambient Air Quality 

Standard—Phase 2 (Phase 2 Final Rule). See discussion in the 

preamble to the rule at 70 FR 71645–71646 (November 29, 2005). 

We have also applied the same approach to the interpretation of 

the provisions of subparts 1 and 4 applicable to particulate 

matter with an aerodynamic diameter less than or equal to a 

nominal 10 micrometers (PM-10). For detailed discussions of this 

interpretation with respect to the CAA’s PM–10 requirements for 

RFP, attainment demonstrations, and contingency measures, see 71 

FR 6352, 6354 (February 8, 2006); 71 FR 13021, 13024 (March 14, 

2006); 71 FR 27440, 27443–27444 (May 11, 2006); and 71 FR 40952, 

40954 (July 19, 2006); and 71 FR 63642 (October 30, 2006). 

EPA believes that the legal bases set forth in detail in 

our Phase 2 Final rule, our May 10, 1995 memorandum from John S. 

Seitz, entitled “Reasonable Further Progress, Attainment 

Demonstration, and Related Requirements for Ozone Nonattainment 

Areas Meeting the Ozone National Ambient Air Quality Standard” 

(Seitz memo), and our December 14, 2004 memorandum from Stephen 

D. Page entitled “Clean Data Policy for the Fine Particle 
40 

National Ambient Air Quality Standards” (Page memo), are equally 

pertinent to the interpretation of provisions of subparts 1 and 

3 applicable to CO. EPA’s interpretation of how the provisions 

of the Act apply to areas with “clean data” is not logically 

limited to ozone, particulate matter with an aerodynamic 

diameter less than or equal to a nominal 2.5 micrometers (“fine 

particles” or PM-2.5), and PM–10, because the rationale is not 

dependent upon the type of pollutant. Our interpretation that an 

area that is attaining the standard is relieved of obligations 

to demonstrate RFP and to provide an attainment demonstration 

and contingency measures pursuant to part D of the CAA, pertains 

whether the standard is CO, 1-hour ozone, 8-hour ozone, PM–2.5, 

or PM–10. 

The reasons for relieving an area that has attained the 

relevant standard of certain part D, subpart 1 and 2 (sections 

171 and 172) obligations, applies equally as well to part D, 

subpart 3, which contains specific attainment demonstration and 

RFP provisions for CO nonattainment areas. As we have explained 

in the 8-hour ozone Phase 2 Final Rule, our ozone and PM–2.5 

clean data memoranda, and our approval of PM–10 SIPs, EPA 

believes it is reasonable to interpret provisions regarding RFP 

and attainment demonstrations, along with related requirements, 

so as not to require SIP submissions if an area subject to those 

requirements is already attaining the NAAQS (i.e., attainment of 
41 

the NAAQS is demonstrated with three consecutive years of 

complete, quality-assured air quality monitoring data for ozone 

and PM, and two consecutive years for CO). A number of U.S. 

Circuit Courts of Appeals have upheld EPA rulemakings applying 

its interpretation of subparts 1 and 2 with respect to ozone. 

Latino Issues Forum v. EPA, Nos. 06-75831 and 08-71239 (9th Cir. 

March 2, 2009)(memorandum opinion); Sierra Club v. EPA, 99 F.3d 

1551 (10th Cir. 1996); Sierra Club v. EPA, 375 F.3d 537 (7th 

Cir. 2004); Our Children’s Earth Foundation v. EPA, No. 04–73032 

(9th Cir. June 28, 2005) (memorandum opinion). It has been EPA’s 

longstanding interpretation that the general provisions of part 

D, subpart 1 of the Act (sections 171 and 172) do not require 

the submission of SIP revisions concerning RFP for areas already 

attaining the ozone NAAQS. In the General Preamble, we stated: 

[R]equirements for RFP will not apply in evaluating a 

request for redesignation to attainment, since, at a 

minimum, the air quality data for the area must show that 

the area has already attained. A showing that the State 

will make RFP towards attainment will, therefore, have no 

meaning at that point. 57 FR at 13564. 

See also page 6 of the Calcagni memo. EPA believes the same 

reasoning applies to the CO RFP provisions of part D, subpart 3. 

With respect to RFP, CAA section 171(1) states that, for 

purposes of part D of title I, RFP: 
42 

means such annual incremental reductions in emissions of 

the relevant air pollutant as are required by this part or 

may reasonably be required by the Administrator for the 

purpose of ensuring attainment of the applicable NAAQS by 

the applicable date. 

The stated purpose of RFP is to ensure attainment by the 

applicable attainment date, whether dealing with the general RFP 

requirement of section 172(c)(2), the ozone-specific RFP 

requirements of sections 182(b) and (c), the PM–10 specific RFP 

requirements of section 189(c)(1), or the CO-specific RFP 

requirements of section 187(a)(7). 

Section 187(a)(7) states that the SIP for moderate CO areas 

with a design value greater than 12.7 ppm must: 

provide a demonstration that the plan as revised will 

provide for attainment of the carbon monoxide NAAQS by the 

applicable attainment date and provisions for such specific 

annual emission reductions as are necessary to attain the 

standard by that date. 

This same requirement also applies to serious CO areas in 

accordance with CAA section 187(b)(1). 

It is clear that once the area has attained the standard, 

no further specific annual emission reductions are necessary or 

meaningful. With respect to CO areas, this interpretation is 

supported by language in section 187(d)(3), which mandates that 
43 

a state that fails to achieve the milestone must submit a plan 

that assures that the state achieves the “specific annual 

reductions in carbon monoxide emissions set forth in the plan by 

the attainment date.” Section 187(d)(3) assumes that the 

requirement to submit and achieve the milestone does not 

continue after attainment of the NAAQS. 

If an area has in fact attained the standard, the stated 

purpose of the RFP and specific annual emissions reductions 

requirements will have already been fulfilled.10 The specific 

annual emission reductions required are only those necessary to 

attain the standard by the attainment date. EPA took this 

position with respect to the general RFP requirement of section 

172(c)(2) in the April 16, 1992 General Preamble and also in the 

May 10, 1995 memorandum with respect to the requirements of 

sections 182(b) and (c). We are proposing to extend that 

interpretation to the specific provisions of part D, subpart 3. 

 

10 For PM-10 areas, we have concluded that it is a distinction without a 

difference that section 189(c)(1) speaks of the PM-10 nonattainment area RFP 

requirement as one to be achieved until an area is “redesignated as 

attainment”, as opposed to section 172(c)(2), which is silent on the period 

to which the requirement pertains, or the ozone and CO nonattainment area RFP 

requirements in sections 182(b)(1) or 182(c)(2) for ozone and 187(a)(7) for 

CO, which refer to the RFP requirements as applying until the “attainment 

date”, since, section 189(c)(1) defines RFP by reference to section 171(l) of 

the Act. Reference to section 171(l) clarifies that, as with the general RFP 

requirements in section 172(c)(2) and the ozone-specific requirements of 

section 182(b)(1) and 182(c)(2) and the CO-specific requirements of section 

187(a)(7), the PM-specific requirements may only be required for the purpose 

of ensuring attainment of the applicable national ambient air quality 

standard by the applicable date. 42 U.S.C. section 7501(1). As discussed in 

the text of this rulemaking, EPA interprets the RFP requirements, in light of 

the definition of RFP in section 171(l), to be a requirement that no longer 

applies once the standard has been attained.
44 

As noted above, CAA section 187(d), CO Milestone, applies 

to serious CO areas and requires the state to submit a 

demonstration that the area has achieved certain specific annual 

emission reductions. EPA interprets this provision consistent 

with its interpretation of section 182(g) in subpart 2. See May 

10, 1995 Seitz Memorandum at page 5. There, EPA included in its 

identification of SIP submission requirements linked with 

attainment and RFP requirements the “Section 182(g) requirements 

concerning milestones that are based on the section 182(b)(1) 

and 182(c)(2)(B) and (C) submissions.” In Subpart 3, similarly, 

milestone requirements are based on the section 187(a)(7) 

specific annual emission reduction requirements. 

Thus, while Las Vegas Valley does not have an approved SIP 

with respect to the CO Milestone demonstration, we believe that, 

for the reasons set forth here and established in our prior 

“clean data” memoranda and rulemakings, a CO nonattainment area 

that has “clean data” should be relieved of the part D, subpart 

3 obligation to provide the CAA section 187(d) CO milestone 

demonstration. Based on our 2005 determination that Las Vegas 

Valley attained the CO NAAQS by the applicable attainment date, 

and the above detailed rationale, we conclude that the 

requirement for a CO milestone demonstration under section 

187(d) no longer applies to Las Vegas Valley. 
45 

3. Conclusion with respect to Section 110 and Part D 

Requirements 

Based on our evaluation of the various SIP requirements and 

submittals discussed above, we propose to find that the State 

has a fully approved SIP for section 110 and part D requirements 

applicable for purposes of redesignation of Las Vegas Valley for 

the CO NAAQS, and that the criteria for redesignation in section 

107(d)(3)(E)(ii) and (v) are met. 

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. If 

EPA makes such a determination, then the criterion is satisfied. 

The 2000 and 2005 Las Vegas Valley CO plans credit the 

following control measures in demonstrating attainment of the CO 

NAAQS in Las Vegas Valley: the Federal Motor Vehicle Control 

Program; the State’s vehicle I/M program; the State’s Low RVP 

Rule (NAC section 590.065); Clark County’s wintertime gasoline 

requirements, including Clark County AQR Section 53 (“Oxygenated 

Gasoline Program”)and the CBG Rule; and to a lesser extent, the 
46 

State’s Alternative Fuels for Government Fleets Program and 

RTC’s voluntary TCM/TDM program. All of the state and local 

control measures listed above have been approved into the SIP 

and are thus federally enforceable. 

The Federal Motor Vehicle Control Program has 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 emissions reductions from the Federal 

Motor Vehicle Control Program 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. The state and local control 

measures further reduce CO emissions from on-road motor 

vehicles, the single largest source category in the CO emissions 

inventory for Las Vegas Valley. 

A rough sense of the effectiveness of the control measures 

to reduce CO emissions can be gained by a comparison between 

area-wide CO emissions in 1996 (a nonattainment year) with those 

in 2006 (an attainment year). In 1996, area-wide CO emissions in 

Las Vegas Valley were estimated to be approximately 662 tons per 

day (average winter weekday), and in 2006, despite an increase 

in population and VMT of approximately 90% and 70%, 
47 

respectively, area-wide CO emissions dropped approximately 10% 

(to 581 tons per day average winter weekday).11

With respect to permanence and enforceability, none of the 

state or local control measures relied upon for attainment have 

sunset clauses, and all would continue to be implemented under 

the Las Vegas Valley CO Maintenance Plan, with the exception of 

the State’s Low RVP Rule, and the County’s CBG Rule.12 For the 

reasons set forth in section VI of this document, we are 

proposing to approve the suspension or relaxation of these two 

control measures because, among other reasons, the maintenance 

demonstration in the Las Vegas Valley CO Maintenance Plan shows 

that they are not necessary to maintain the CO standard, at 

least through 2020. Moreover, as required under CAA section 

175A(d), Clark County has committed to reinstating the CBG Rule 

as a contingency measure if needed to address any violations of 

the CO standard that might occur after redesignation to 

attainment. The Nevada Department of Agriculture has not yet 

made the commitment to seek reinstatement of the Low RVP Rule, 

and thus our proposed approval of the relaxation of the Low RVP 

Rule is contingent upon submittal of the necessary commitment. 

 

11 See tables 3-2 and 3-12 from the 2005 CO Plan for estimates of population, 

VMT, and area-wide CO emissions. 

12 The CO Maintenance Plan also lists the State’s Alternative Fuels for 

Government Fleets Program and RTC’s TCM/TDM program as contingency measures, 

meaning that the plan takes no credit for the measures in its maintenance 

demonstration. However, the State has not requested rescission, suspension, 

or relaxation of these two control measures and thus they will remain 

federally enforceable control measures under the CAA until EPA approves such 

a request as a revision to the Nevada SIP. 
48 

The commitments to reinstatement of the wintertime gasoline 

requirements by Clark County and the Nevada Department of 

Agriculture, once approved, will become federally enforceable 

under the CAA. 

With respect to the connection between the emissions 

reductions and the improvement in air quality, the Las Vegas 

Valley CO Maintenance Plan provides a demonstration that the air 

quality improvement in Las Vegas Valley, that resulted in 

attainment of the CO NAAQS by 2000 and continued attainment 

since then, is due to emission reductions from implementation of 

the control measures discussed above and is not the result of a 

local economic downturn or unusual or extreme weather patterns. 

The demonstration shows that from 1990 to 2007, despite 

increases in population, employment growth, increases in vehicle 

miles traveled (VMT), and strong economic conditions, CO levels 

decreased. The demonstration also examined wintertime 

meteorological data for the years 1998 through 2007 to determine 

if favorable meteorology influenced CO levels. The data showed 

that only a few periods had favorable meteorology. See pages 5-1 

through 5-10 of the Las Vegas Valley CO Maintenance Plan. 

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

Vegas Valley is the result of permanent and enforceable 

emissions reductions from a combination of the Federal Motor 

Vehicle Control Program and EPA-approved State and local control 
49 

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 

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 Las Vegas Valley 
50 

CO Maintenance Plan because we believe that it meets the 

requirements of CAA section 175A. 

1. Attainment Inventory 

The plan must contain an attainment year emissions 

inventory to identify a level of emissions in the area that is 

sufficient to attain the CO NAAQS. This inventory is to 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 

should also be based on actual “CO season data” (i.e., 

wintertime) emissions for an attainment year. 

In this case, we have already approved an “attainment year” 

emissions inventory in that we approved the 2006 emissions 

inventory contained in the 2005 CO plan. The emissions 

inventories in the Las Vegas Valley CO Maintenance Plan 

represent updates to the previously approved emissions 

inventories in the 2005 CO Plan. As with the previous plan, the 

emission inventories in the Las Vegas Valley CO Maintenance are 

comprehensive, including emissions from stationary point 

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

mobile sources, and represent CO season data (weekday in 

December). As was the case with the inventories in the 2000 and 

2005 CO attainment plans for Las Vegas Valley, the CO 
51 

inventories in the Maintenance Plan are not used directly to 

demonstrate maintenance of the CO standard, but they reflect the 

same methods, factors, and assumptions used to develop the CO 

emission rates used for the dispersion modeling analysis which 

provides the basis for the maintenance demonstration. 

As noted in our proposed approval of the 2005 CO Plan, the 

2005 CO Plan provided a comprehensive revision to the base year 

(1996) emissions inventory and future year emissions projections 

reflecting updated underlying data, such as population and VMT 

forecasts, and updated methods, such as MOBILE6.2 and 

NONROAD2004. The 2005 CO Plan presented an emissions inventory 

for years 2006, 2010, 2015, 2020, and 2030. The Las Vegas Valley 

CO Maintenance Plan presents emissions inventories for 2008, 

2010, and 2020 that were developed using similar emissions 

calculations procedures, models, and assumptions as were used 

for the 2005 CO Plan (and described in detail in our proposed 

approval of the 2005 CO Plan at 71 FR 26910, at 26913-26915, May 

9, 2006), but that were revised to reflect use of: 

• Updated population and vehicle activity projections 

developed by the Regional Transportation Commission (RTC) 

(from RTC’s FY2006-2030 Regional Transportation Plan, 

approved by RTC in October 2006); 

• Updated TransCAD travel demand model output from RTC; 
52 

• Revised wintertime gasoline properties that assume 

relaxation of the RVP limit from 9.0 psi to 13.5 psi, and 

suspension of the County’s CBG Rule (i.e., suspension of 

the local sulfur content and aromatic hydrocarbon limits);13

• An updated emissions factor model (NONROAD2005, Core Model 

Version 2005a, February 2006) to estimate emissions for the 

nonroad source category; and 

• Updated emissions information for Nellis Air Force Base. 

In addition, the emissions projections in the Las Vegas Valley 

CO Maintenance Plan take no credit for the RTC’s TCM program or 

the State’s alternative fuels for government vehicles program. 

More detailed descriptions of the 1996 base year inventory, the 

2008 projected inventory, and the 2010 and 2020 projected 

inventory are documented in the Las Vegas Valley CO Maintenance 

Plan on pages 7-2 through 7-8, and in the plan’s Technical 

Support Document (attached to the plan as appendix B). 

We have summarized the emissions projections in table 2, 

below. As shown in table 2, on-road mobile sources would 

continue to dominate CO emissions within the nonattainment area 

through the initial maintenance period (i.e., 10 years beyond 

redesignation). The 2005 CO Plan estimated on-road CO emissions 

at approximately 441 tons per day (see table 3-12 of the 2005 

 

13 The revised wintertime gasoline specifications were used in developing the 

emissions inventories in the Maintenance Plan to calculate CO emissions from 

both on-road and nonroad gasoline-powered vehicles. 
53 

plan) for year 2006, and the increase in CO emissions from onroad mobile sources for 2008, 2010, and 2020 as shown in table 2 

(relative to 2006) reflects the change in wintertime gasoline 

specifications, as described above. The change in wintertime 

gasoline specifications has not yet occurred, and will not occur 

until EPA approves the suspension/relaxation of the State and 

local gasoline rules, as proposed herein, thus, the emissions 

projections shown in table 2 below overestimate emissions that 

actually occurred in year 2008. Aggregate emissions of CO are 

expected to hold steady, or to increase slightly, over the 

course of the initial maintenance period. 

TABLE 2: SUMMARY OF CO EMISSIONS IN TONS PER DAY 

 (FOR A WEEKDAY IN DECEMBER) 

---------------------------------------------------------------- 

2008 2010 2020 

---------------------------------------------------------------- 

Point sources 15.8 15.8 15.8 

Area sources 13.9 14.7 18.6 

Aviation 39.7 42.2 53.5 

Railway 0.3 0.3 0.4 

Non-road mobile sources 57.7 60.8 71.2 

On-road mobile sources 579.3 579.7 574.4 

--------------------------------------------------------------- 

Total 706.7 713.5 733.9 

---------------------------------------------------------------- 

SOURCE: See Las Vegas Valley CO Maintenance Plan, Table 7-3. 

Based on our review and prior approval of the emissions 

inventories (and related documentation) from the 2005 CO plan, 

and our review of the changes to the earlier-approved 

inventories, we find that the 2006 emission inventory from the 

2005 CO Plan suffices as an attainment inventory for Las Vegas 
54 

Valley, and that the emissions inventories in the Maintenance 

Plan reflect the latest planning assumptions and emissions 

models and provide a comprehensive and reasonably accurate 

forecast of CO emissions in Las Vegas Valley for years 2010 and 

2020. As described in the next section in this document, 

dispersion modeling results derived from the same emissions 

methods, factors and assumptions used to develop the inventories 

provide the basis for the demonstration of maintenance of the CO 

NAAQS through 2020. 

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 

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

state may demonstrate maintenance of the CO 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. Because the attainment demonstration for Las Vegas Valley in 

the 2000 CO Plan, and revised in the 2005 CO Plan, relied upon 

modeling techniques, the CO Maintenance Plan also relies on 
55 

modeling techniques to demonstrate maintenance of the standard 

through the initial maintenance period. 

The Las Vegas Valley CO Maintenance Plan builds upon, and 

updates, previous modeling efforts conducted, most recently, in 

support of attainment demonstration in the 2005 CO Plan. Like 

the previous approved plan, the maintenance plan includes both 

area-wide modeling analysis and micro-scale modeling analyses at 

heavily-traveled intersections and local airports. As before, 

area-wide analysis, was conducted using the Urban Airshed Model 

(UAM), and the micro-scale analyses were conducted using CAL3QHC 

for local intersections, and the Emissions Dispersion Modeling 

System (EDMS) for the local airports. Generally, the micro-scale 

analyses combine the results of UAM modeling with those using 

either CAL3QHC (for intersections) or EDMS (for airports) to 

generate worst-case maximum CO concentrations in the various 

analysis years. The maintenance demonstration is discussed on 

pages 7-6 through 7-14 of the Maintenance Plan, and at more 

length in appendix B to the plan. 

The Maintenance Plan provides an area-wide UAM-based 

modeling demonstration of maintenance from year 2008 through 

year 2020 using December 8-9, 1996 episode conditions (which is 

the same episode used in the 2000 and 2005 CO plans) to 

determine peak CO concentrations. The UAM modeling for the 

Maintenance Plan uses updated emission inventories (see table 2, 
56 

above) that reflect continued implementation of those control 

measures that are being retained for CO maintenance purposes, 

including the State’s vehicle I/M program and the county’s 

wintertime oxygenated gasoline program. The concentration 

estimates are shown in table 3, below. The estimates in table 3 

do not include any CO emissions reductions from those measures 

in the maintenance plan that are identified as contingency 

measures, such as the State’s Low RVP Rule and the County’s CBG 

Rule. 

In the area-wide modeling demonstration, spatial patterns 

of predicted 8-hour CO are similar to those predicted by 

previous modeling in the 2005 CO plan. While the CO 

concentrations estimated for the Maintenance Plan are higher 

than those estimated in previous modeling completed for the 2005 

CO Plan (due to the suspended/relaxed gasoline requirements 

assumed for the maintenance plan), they are below the 8-hour CO 

standard of 9 ppm and decrease over time. Also, as in previous 

modeling, the area-wide impact of McCarran Airport increases 

over time with peak values increasing around the airport due to 

growth in airport activities. 

TABLE 3: LAS VEGAS VALLEY CO MAINTENANCE PLAN 

AREA-WIDE MODELING RESULTS 

[PEAK 8-HOUR UAM CONCENTRATIONS] 

-------------------------------------------------------- 

 Year Concentration (ppm) 

------------------------------------------------------- 
57 

2008 .............. 8.8 

2010 .............. 8.5 

2020 .............. 7.7 

------------------------------------------------------- 

Source: Table 7-4 of the Las Vegas Valley CO Maintenance 

Plan. 

As noted above, in addition to the area-wide modeling effort, 

two micro-scale models, CAL3QHC and EDMS, were used to predict 

maximum CO concentrations at potential hot spot receptors at 

heavily traveled intersections and at local area airports. 

CAL3QHC is used to predict the micro-scale impacts of vehicles 

operating at congested intersections. Vehicles operating under 

congested conditions spend more time in idle mode that can 

contribute to high levels of CO near the roadways. As in the 

2005 CO plan, micro-scale modeling was completed for three 

intersections (1) Eastern Avenue/Charleston Blvd., (2) Eastern 

Avenue/Fremont Street, and (3) Fremont Street/Charleston Blvd. 

These three intersections comprise the “5 points” area, which is 

near the Sunrise Acres CO monitoring station. Traffic data from 

the 2005 CO Plan were scaled based on updated TransCAD 

transportation modeling outputs and combined with emission 

factors from MOBILE6.2 and worst-case meteorological data to 

predict local hotspot concentrations. These hourly results from 

the micro-scale model were then combined with hourly 

concentrations from the background UAM grid cell to compute 
58 

maximum running 8-hour concentrations. The combined results from 

CAL3QHC and UAM are shown in table 4, below. 

TABLE 4: LAS VEGAS VALLEY CO MAINTENANCE PLAN 

MAXIMUM PREDICTED COMBINED MODELING RESULTS AT SELECTED 

INTERSECTIONS 

[PEAK 8-HOUR CO CONCENTRATIONS] 

-------------------------------------------------------- 

Year 

Intersection 2008 2010 2020 

------------------------------------------------------- 

Eastern Ave./Charleston Blvd. 8.1 7.7 6.9 

Eastern Ave./Fremont St. 7.7 7.4 6.7 

Fremont St./Charleston Blvd. 7.0 6.7 6.0 

------------------------------------------------------- 

Source: Table 3-2 in appendix B to the Las Vegas Valley CO 

Maintenance Plan. 

To model the impact of airport sources, EDMS was used again 

as in the 2005 CO Plan. This model was developed for evaluating 

the specific emission sources typically located at airports. The 

hotspot results from EDMS were combined with the results of the 

UAM analysis to predict the concentrations at receptors around 

the airports. The Maintenance Plan presents the results of the 

combined UAM and EDMS models for the all future years in table 

3–3 of appendix B. No values were modeled above the 9.0 ppm CO 

standard at any publicly accessible receptor location. The peak 

combined concentration at McCarran International Airport for 

future years is 8.9 ppm for 2020. 
59 

Lastly, UAM was used to identify a safety margin14 to be 

included in the on-road motor vehicle emissions budgets to 

facilitate future transportation conformity determinations for 

CO during the initial maintenance period. See section V.D.7 of 

this document for EPA’s review and proposed approval of the 

budgets in the Las Vegas Valley CO Maintenance Plan. 

To identify a safety margin consistent with maintenance of 

the CO standard through the initial maintenance period, the 

maintenance plan scaled up the on-road motor vehicle emissions 

initially estimated and used for concentration modeling purposes 

(see table 2 above) over the entire modeling domain to the point 

at which the peak 8-hour CO concentration reached 8.9 ppm in 

2008, 2010, and 2020. The on-road motor vehicle emissions 

outside the central urban sub-domain were then increased by an 

additional 60% in each year to reach a maximum peak 8-hour CO 

concentration of just under 9.0 ppm in the peak UAM grid cell, 

at peak UAM plus CAL3QHC receptor, or at the peak UAM plus EDMS 

receptor. See pages 3-11 through 3-16 of appendix B to the 

Maintenance Plan. 

The target CO concentration was reached at the point where 

on-road motor vehicle emissions were increased to 658 tpd (13% 

higher than baseline 2008 on-road emissions), 686 tpd (18% 

 

14 The term “safety margin” refers to the amount by which the total projected 

emissions from all sources of a given pollutant are less than the total 

emissions that would satisfy the applicable requirement for reasonable 

further progress, attainment or maintenance. See 40 CFR 93.101. 
60 

higher), and 704 tpd (23% higher), in 2008, 2010, and 2020, 

respectively. See table 3-5 of appendix B to the Maintenance 

Plan. The corresponding peak 8-hour modeled concentrations 

(assuming this higher level of on-road motor vehicle emissions) 

ranged from 8.87 ppm in 2008 to 8.98 ppm in 2020. The 2020 value 

reflects microscale analysis (combining UAM plus EDMS) for a 

receptor at McCarron Airport. We find this procedure to be a 

reasonable means to identify an acceptable safety margin for CO 

emissions in Las Vegas Valley. 

Based on our review of the documentation provided in the CO 

maintenance plan as summarized above, we find that the revised 

modeling results are consistent with the underlying emission 

estimates and reflect reasonable methods and assumptions. 

Further, we find that the revised modeling results demonstrate 

continued maintenance of the CO NAAQS in Las Vegas Valley 

through 2020. 

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, CO is currently monitored by Clark County 

DAQEM at five stations within Las Vegas Valley. In the Las Vegas 

Valley CO Maintenance Plan (see page 7-15 of the plan), Clark 

County DAQEM indicates its intention to continue operation of an 

air quality monitoring network consistent with EPA’s monitoring 
61 

requirements in 40 CFR part 58 (“Ambient Air Quality 

Surveillance”) to verify continued attainment of the CO NAAQS 

within Las Vegas Valley. The Las Vegas Valley CO Maintenance 

Plan also states that, in addition, Clark County DAQEM’s CO 

monitoring network will be reviewed annually pursuant to 40 CFR 

58.10 to determine whether the system continues to meet the 

monitoring objectives in 40 CFR part 58, appendix D. We find the 

County’s commitment for continued ambient CO monitoring as set 

forth in the Las Vegas Valley CO Maintenance Plan to be 

acceptable. 

4. Verification of Continued Attainment 

NDEP, the State Board of Agriculture, and the Clark County 

Board of County Commissioners have the legal authority to 

implement and enforce the requirements of the Las Vegas Valley 

CO Maintenance Plan. This includes the authority to adopt, 

implement and enforce any emission control contingency measures 

determined to be necessary to correct CO NAAQS violations. To 

verify continued attainment, Clark County DAQEM commits in the 

Maintenance Plan to the continued operation of a CO monitoring 

network that meets EPA monitoring requirements, and also to 

conduct studies to determine whether additional or re-sited CO 

monitors are necessary in response to measured changes in mobile 

source parameters (e.g., VMT, fleet mix). See page 7-15 of the 

Las Vegas Valley CO Maintenance Plan. This is acceptable. 
62 

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 

triggers, which will be used to determine when the contingency 

measures need to be implemented. 

The Las Vegas Valley CO Maintenance Plan identifies four 

specific contingency measures: RTC’s TDM/TCM program, the 

State’s Alternative Fuels for Government Fleets Program, Clark 
63 

County’s CBG Rule, and the State’s Low RVP Rule. All of these 

measures have been approved by EPA into the SIP and are 

currently in effect. The first two measures would remain in 

effect but are identified as “contingency measures” in the 

Maintenance Plan because the maintenance demonstration takes no 

emissions credit for these programs. EPA has concluded that 

contingency measures need not be new measures that would be 

triggered by a violation, but may consist of early 

implementation of measures that provide surplus reductions 

beyond those needed for attainment or maintenance. See “Early 

Implementation of Contingency Measures for Ozone and Carbon 

Monoxide (CO) Nonattainment Areas,” memorandum from G.T. Helms 

to EPA Air Branch Chiefs, August 13, 1993. Identification of 

RTC’s TDM/TCM program and the State’s Alternative Fuels for 

Government Fleets Program as contingency measures in the Las 

Vegas Valley CO Maintenance Plan is acceptable because, based on 

the rationale presented above, we believe that the Maintenance 

Plan adequately demonstrates maintenance of the CO NAAQS without 

taking any credit for these two measures. 

With respect to the Clark County’s CBG Rule and the State 

Board of Agriculture’s Low RVP Rule, we are proposing to approve 

the suspension of the former, and the relaxation of the latter, 

in this document. As noted above, contingency provisions must 

include a requirement that the State will implement all measures 
64 

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. In this instance, Clark County’s 

CBG Rule and the State’s Low RVP Rule are two measures that were 

contained in the SIP prior to redesignation and thus must be 

included as contingency measures in the maintenance plan. The 

Maintenance Plan does in fact list both measures as contingency 

measures (see page 5-8 of the Maintenance Plan), and we believe 

that, by adopting the Las Vegas Valley CO Maintenance Plan, 

Clark County has adequately committed to reinstate the suspended 

fuels program, if necessary in light of a monitored violation of 

the CO NAAQS, and thereby implement the related contingency 

measure. The State Department of Agriculture has yet to 

specifically commit to seek reinstatement by the Board of 

Agriculture of the Low RVP Rule if needed to remedy future CO 

NAAQS violations in Las Vegas Valley. Based on our discussions 

with Clark County, NDEP and the Department of Agriculture, 

however, we expect that such a commitment from the Department of 

Agriculture will be forthcoming in the near future, and we will 

not finalize our proposed approval of the Maintenance Plan and 

redesignation request unless and until we receive and approve 

the State’s submittal of this commitment as a revision to the 

Nevada SIP. 
65 

The contingency provisions of the Las Vegas Valley CO 

Maintenance Plan (see pages 7-15 and 7-16 of the plan) are 

triggered upon the occurrence of an exceedance of the 8-hour CO 

standard (i.e., a monitored level of 9.5 ppm or greater) at any 

of the monitoring stations in the area. Upon such an occurrence, 

Clark County DAQEM will review and verify the monitoring data 

within three months, and recommend contingency measures within 

six months. The types of contingency measures envisioned under 

these circumstances would be local, voluntary measures. 

However, if a second exceedance occurs at the same 

monitoring site within a consecutive two-year period, DAQEM will 

make a recommendation to the Clark County Board of County 

Commissioners (within six months of the second exceedance) from 

among those contingency measures specifically listed in the 

Maintenance Plan, as described above, including reinstatement of 

Clark County’s CBG Rule and reinstatement of the State’s Low RVP 

Rule. The Maintenance Plan would not require implementation of 

these contingency measures unless the area experiences a 

violation of the 8-hour CO NAAQS (i.e. a second exceedance at 

the same site during the same calendar year). The Maintenance 

Plan states that the contingency measures will be implemented 

six to 12 months after approval by the Clark County Board of 

Commissioners, depending on the time needed to put the measures 

in place. See page 7-16 of the Maintenance Plan. 
66 

Upon our review of the plan, as summarized above, we find 

that the contingency provisions of the Maintenance Plan 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, with the exception 

of the absence of a commitment by the State Department of 

Agriculture to seek reinstatement by the Board of Agriculture of 

the Low RVP Rule, the contingency provisions of the Las Vegas 

Valley CO Maintenance Plan are adequate to ensure prompt 

correction of a violation and therefore comply with section 

175A(d) of the Act. We will not take final action to approve the 

Maintenance Plan until we receive the commitment by the State 

Department of Agriculture to seek reinstatement of the Low RVP 

Rule if needed to remedy a future CO NAAQS violation in Las 

Vegas Valley. 15

6. Subsequent Maintenance Plan Revisions 

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

revision 8 years after redesignation providing for maintaining 

 

15 On July 12, 2010, the Nevada Department of Agriculture initiated a 30-day 

comment period to solicit comment (or request a public hearing) on the draft 

commitment regarding implementation of the contingency measure in the 

Maintenance Plan related to reinstatement of the Low RVP Rule. The 

Department’s notice of intent to solicit public comment, which includes the 

commitment language, has been placed in the docket for this rulemaking. We 

have reviewed the language of the Department’s draft commitment and expect to 

approve it if it is ultimately submitted to us without significant 

modification. 
67 

the NAAQS for an additional 10 years. The Las Vegas Valley CO 

Maintenance Plan provides that Clark County DAQEM will prepare a 

revised maintenance plan eight years after redesignation to 

attainment. See page 7-17 of the 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 

violations, or delay timely attainment of the national ambient 

air quality standards. 

Maintenance plan submittals must specify the maximum 

emissions of transportation-related CO emissions allowed in the 

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

emissions budget (MVEB). 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 
68 

applicable policies on MVEBs, please visit our transportation 

conformity Web site at: 

http://www.epa.gov/otaq/stateresources/transconf/index.htm. 

The Las Vegas Valley CO Maintenance Plan includes the CO 

MVEBs shown in table 5 below. The budgets are based on table 7-9 

of the Maintenance Plan and other documentation in section 7.5 

of the plan. See also the discussion of projected emissions in 

section V.D.2 (“Maintenance Demonstration”) of this document. 

TABLE 5: LAS VEGAS VALLEY CO MAINTENANCE PLAN, 

 MOTOR VEHICLE EMISSIONS BUDGETS 

 (Winter weekday emissions in tons per day) 

Year MVEB

2008 658 

2010 686 

2020 704 

In setting MVEBs, States generally use the on-road motor 

vehicle portion of the emission inventories in the associated 

plan. Clark County, however, did not cap MVEBs at projected 

motor vehicle emissions levels. Because overall projected levels 

of emissions from all sources are expected to be significantly 

less than the levels necessary to maintain the CO NAAQS, Clark 

County scaled up emissions in the maintenance demonstration to 

set MVEBs at a higher level. As long as emissions from all 

sources are lower than needed to provide for continued 

maintenance of the standard, the State may allocate additional 
69 

emissions to future mobile source growth by assigning a portion 

of the safety margin to the MVEBs (see 40 CFR 93.124). 

The criteria by which we determine whether a SIP's MVEBs 

are adequate and approvable for conformity purposes are outlined 

in 40 CFR 93.118(e)(4) and (5). The following paragraphs provide 

our review of the budgets in the Las Vegas Valley CO Maintenance 

Plan against our adequacy criteria and provide the basis for our 

proposed approval of the MVEBs. 

Under 40 CFR 93.118(e)(4)(i), we review a submitted plan to 

determine whether the plan was endorsed by the Governor (or 

designee) and was subject to a public hearing. The Las Vegas 

Valley CO Maintenance Plan was submitted to EPA on September 18, 

2008 by NDEP’s Administrator, the Governor of Nevada’s designee 

for all SIP revision submittals. This SIP submittal documents 

that the Clark County Board of Commissioners held a public 

hearing on the plan on September 2, 2008, and adopted the plan 

on that same date. Therefore, we conclude that the plan and 

related budgets meet the criterion under 40 CFR 93.118(e)(4)(i). 

Under 40 CFR 93.118(e)(4)(ii), we review a submitted plan 

to determine whether the plan was developed through consultation 

with Federal, State and local agencies, whether full 

implementation plan documentation was provided to EPA, and 

whether EPA's stated concerns, if any, were addressed. 

Consultation for development of this plan largely consisted of 
70 

public meetings (see appendix C to the Maintenance Plan); 

discussions with Federal, State, and local transportation 

planning agencies; and a public hearing, preceded by notices 

that were published in a newspaper of general circulation. 

Documentation was provided to EPA, and EPA's stated concerns 

were addressed. We conclude that adequate consultation occurred 

prior to submittal of the Maintenance Plan to EPA, and that 

EPA’s concerns were adequately addressed for the purposes of 40 

CFR 93.118(e)(4)(ii). 

Under 40 CFR 93.118(e)(4)(iii), we review a submitted plan 

to determine whether the MVEBs are clearly identified and 

precisely quantified. The Maintenance Plan clearly identifies 

and precisely quantifies the CO MVEBs for the years 2008, 2010 

and 2020 on page 7-15 of the plan (and table 5, above). We 

conclude therefore that the plan and related budgets meet the 

adequacy criterion under 40 CFR 93.118(e)(4)(iii). 

Under 40 CFR 93.118(e)(4)(iv), we review a submitted plan 

to determine whether the MVEBs, when considered together with 

all other emissions sources, are consistent with applicable 

requirements for reasonable further progress, attainment, or 

maintenance (whichever is relevant to a given SIP submission). 

The Maintenance Plan shows how the MVEBs and related safety 

margins are consistent with maintenance of the CO NAAQS through 

2020 (see pages 7-6 through 7-15 of the Maintenance Plan). In 
71 

particular, Tables 7-6, 7-7, 7-8, and 7-9 of the Maintenance 

Plan show the extent to which maximum future year emissions 

(including the budget safety margins) fall below ambient 

concentration levels for the 8-hour CO NAAQS. Consequently, we 

find that the plan and related budgets meet this criterion for 

adequacy. 

Under 40 CFR 93.118(e)(4)(v), we review a plan to determine 

whether the MVEBs are consistent with and clearly related to the 

emissions inventory and the control measures in the submitted 

control strategy plan or maintenance plan. The MVEBs in the 

Maintenance Plan appropriately reflect the measures relied upon 

for continued maintenance of the CO standard in Las Vegas 

Valley, including the wintertime oxygenated gasoline program and 

the State’s vehicle I/M program, as well as the decision by 

State and Clark County to suspend or relax certain other 

wintertime gasoline requirements (i.e., suspend the CBG Rule and 

relax the Low RVP Rule) and to take no CO credit for certain 

other measures (i.e., the Alternative Fuels for Government 

Fleets program and RTC’s TDM/TCM program). Thus, we find that 

the MVEBs are consistent with and clearly related to the 

emissions inventory and the control measures in the submitted 

maintenance plan and thereby meet the criterion for adequacy 

under 40 CFR 93.118(e)(4)(v). 
72 

Under 40 CFR 93.118(e)(4)(vi), we review a submitted plan 

to determine whether revisions to previously submitted plans 

explain and document any changes to previously submitted budgets 

and control measures; impacts on point and area source 

emissions; any changes to established safety margins; and 

reasons for the changes (including the basis for any changes 

related to emissions factors or estimates of vehicle miles 

traveled and changes in control measures). There are no 

previously submitted CO maintenance plans for the Las Vegas 

Valley. Changes in the MVEBs relative to the previously approved 

MVEBs from the attainment plans (i.e., the Las Vegas Valley 2000 

CO Plan and then later from the Las Vegas Valley 2005 CO Plan) 

reflect updates to EPA’s MOBILE model, RTC’s planning 

assumptions regarding employment and population, and RTC’s 

travel activity and fleet mix projections; the decision to 

establish safety margins for motor vehicle emissions; and the 

decision to take no CO emission reduction credit for certain 

control measures (e.g., CBG Rule and Low RVP Rule). Thus, we 

find that the Maintenance Plan meets the criterion for adequacy 

under 40 CFR 93.118(e)(4)(vi). 

Under 40 CFR 93.118(e)(5), we review the State's 

compilation of public comments and response to comments that are 

required to be submitted with any SIP revision. Appendix C of 

the Maintenance Plan submittal documents the notice for public 
73 

comments on the draft Maintenance Plan and documents the 

proceedings at the public hearing. The only comments on the 

draft Maintenance Plan were submitted by EPA, and appendix C (to 

the Maintenance Plan) documents how the draft Maintenance Plan 

was amended in response to those comments. We find Clark County 

DAQEM’s responses to our comments on the draft plan to be 

acceptable, and thus, we find that the Maintenance Plan meets 

the criterion for adequacy under 40 CFR 93.118(e)(5). 

For the reasons set forth above, we find that the MVEBs in 

the Las Vegas Valley CO Maintenance Plan meet the requirements 

under 40 CFR 93.118(e)(4) and (5), and that the maintenance plan 

as a whole will ensure maintenance of the CO NAAQS through the 

last year of the maintenance plan. Thus, we propose to approve 

the motor vehicle emissions budgets for transportation 

conformity purposes. If we finalize our action as proposed, RTC 

(which is the area’s Metropolitan Planning Organization) and the 

U.S. Department of Transportation will be required to use the CO 

MVEBs from the Maintenance Plan for future transportation 

conformity determinations.16

 

16 The current approved CO motor vehicle emissions budgets from the 2005 CO 

(Attainment) Plan are: 690, 768, and 817 tons per winter weekday for 2010, 

2015, and 2015, respectively. See 71 FR 44587 (August 7, 2006). The 

Maintenance Plan does not explicitly indicate that the budgets set forth 

therein are intended to replace the budgets from the 2005 CO Plan. Thus, if 

EPA takes final action to approve the Maintenance Plan budgets as proposed, 

then both sets of budgets (i.e., those from the 2005 CO Plan, and those from 

the Maintenance Plan) would apply because they relate to different CAA 

requirements for the same years. As a practical matter, however, the 
74 

EPA generally first reviews budgets submitted with an 

attainment, RFP, or maintenance plan for adequacy, prior to 

taking action on the plan itself. The availability of the Las 

Vegas CO Maintenance Plan with the 2008, 2010, and 2020 budgets 

was announced for public comment on EPA's adequacy Web page on 

September 30, 3008, at: 

http://www.epa.gov/otaq/transp/conform/adequacy.htm. The public 

comment period on the adequacy of the budgets closed on October 

30, 2008. EPA did not receive any comments on the budgets, but 

did not complete the process and make an adequacy determination 

on the budgets. Instead, we are now proposing to approve the 

budgets. 

8. Conclusion 

For the reasons set forth above, we find that the Las Vegas 

Valley CO Maintenance Plan satisfies the applicable CAA 

requirements, including CAA section 175A, and thus, we propose 

to approve it as a revision to the Nevada SIP under section 

110(k)(3), contingent upon receipt of a commitment from the 

State Department of Agriculture to seek reinstatement by the 

State Board of Agriculture of the Low RVP Rule if needed to 

remedy a future violation of the CO NAAQS in Las Vegas Valley. 

 Maintenance Plan budgets, being lower than the 2005 CO Plan budgets, would be 

the constraining budgets for determining conformity. 
75 

VI. Evaluation of Suspended or Relaxed Wintertime Gasoline 

Specifications 

 As noted previously, NDEP’s March 26, 2010 SIP revision 

includes an amended State fuels rule that relaxes the existing 

wintertime gasoline requirement for RVP (referred to herein as 

the “Low RVP Rule”), and includes the suspension by Clark County 

of their local Cleaner Burning Gasoline (CBG) rule (referred to 

herein as the “CBG Rule”). The CBG Rule established sulfur and 

aromatics limits for gasoline sold in Clark County during the 

period from November 1 to March 31. 

On December 9, 2009, the State Board of Agriculture amended 

NAC section 590.065 (i.e., the Low RVP Rule) to incorporate 

updated ASTM standard specifications and to relax the vapor 

pressure limit for wintertime gasoline sold in Clark from 9.0 

psi to 13.5 psi.17 EPA first approved the Low RVP Rule as a 

revision to the Nevada SIP in 2004 when EPA approved the rule as 

a CO control measure of the 2000 CO Plan. See 69 FR 56351 

(September 21, 2004). EPA’s proposed approval of the Low RVP 

Rule (68 FR 4141, January 28, 2003) describes how lower vapor 

pressure in gasoline reduces CO emissions and the relative 

magnitude in the corresponding reduction in vehicular CO 

 

17 The State’s wintertime vapor pressure limit (raised from 9.0 psi to 13.5 

psi) would continue to apply to gasoline sold within Clark County from 

October 1st through March 31st. Another revision to the rule would extend the 

wintertime vapor pressure limit in Clark County to “any blend of gasoline and 

ethanol.” 
76 

emissions. Please see EPA’s January 28, 2003 proposed rule for 

additional information on this topic at 68 FR 4141, 4150-4151. 

In our 2003 proposed approval of the Low RVP Rule, we 

considered whether the RVP specification is preempted under the 

Act. Section 211(c)(4)(A) preempts certain state fuel 

regulations by prohibiting a state from prescribing or 

attempting to enforce “any control or prohibition respecting any 

characteristic or component of a fuel or fuel additive” for the 

purposes of motor vehicle emission control, if EPA has 

prescribed under section 211(c)(1), “a control or prohibition 

applicable to such characteristic or component of the fuel or 

fuel additive,” unless the state control or prohibition is 

identical to the control or prohibition prescribed by EPA. In 

our 2003 proposed rule, we concluded that, because the Federal 

controls on RVP, promulgated under section 211(h) and section 

211(c)(1), apply only in the summer months, there would be no 

Federal preemption of the State’s Low RVP Rule. What was true in 

2003 remains true today. There is still no Federal RVP control 

applicable to gasoline in the wintertime, and thus, no Federal 

preemption of the relaxed vapor pressure limit (13.5 psi) 

established in amended NAC section 590.065. 

Further, in 2004, EPA approved CBG into the Nevada SIP. See 

69 FR 56351 (September 21, 2004). The CBG Rule is described in 

detail in EPA’s proposed approval of the rule and the related 
77 

2000 CO Plan on January 28, 2003 (68 FR at 4151-4152). At the 

time, we also considered whether the sulfur content and 

aromatics limits for CBG were preempted under CAA section 

211(c)(4)(C).18 As earlier explained, CAA section 211(c)(4)(A) 

preempts certain state fuel regulations by prohibiting a state 

from prescribing or attempting to enforce “any control or 

prohibition respecting any characteristic or component of a fuel 

or fuel additive” for the purposes of motor vehicle emission 

control, if EPA has prescribed under section 211(c)(1), “a 

control or prohibition applicable to such characteristic or 

component of the fuel or fuel additive,” unless the state 

control or prohibition is identical to the control or 

prohibition prescribed by EPA. Further, under CAA section 

211(c)(4)(C), a State may prescribe and enforce an otherwise 

preempted fuel control if EPA approves the control into the 

State’s SIP. In order to approve a preempted control into a SIP, 

EPA must find that the State control is necessary to achieve a 

NAAQS either because no other measures that would bring about 

timely attainment exist or that such measures exist but are 

either unreasonable or impracticable. CAA section 211(c)(4)(C) 

 

18 The CBG Rule establishes a maximum sulfur content limit of 80 ppm (by 

weight). With respect to sulfur content, producers and importers must also 

meet a 40 ppm flat limit or an average limit of 30 ppm subject to the 80 ppm 

cap. The standards for aromatic hydrocarbons include a 30% cap (by volume), 

with producers and importers required to meet a 25% flat limit or an average 

limit of 22% (subject to the 30% cap). The applicable geographic area is 

Clark County, and the applicable period for use of CBG is November 1st through 

March 31st. 
78 

is intended to ensure that a state resorts to a fuel measure 

only if there are no available practicable and reasonable nonfuel measures, and in our 2004 approval of the CBG Rule, we 

found that Clark County’s requirements for sulfur and aromatics 

limits were “necessary” to achieve the CO NAAQS. 

In addition, the Energy Policy Act of 2005 (EPAct) amended 

section 211(c)(4)(C) by including a number of provisions 

addressing state “boutique” fuel programs.19 The EPAct required 

EPA, in consultation with the Department of Energy, to determine 

the total number of fuels approved into all SIPs under section 

211(c)(4)(C) as of September 1, 2004, and to publish a list that 

identifies these fuels, the States and Petroleum Administration 

for Defense Districts (PADD) in which they are used. CAA section 

211(c)(4)(C)(v)(II). 

On December 28, 2006, EPA published a notice containing the 

final interpretation, which was by fuel type, of the EPAct 

provisions in the Federal Register. See 71 FR 78192. We also 

determined and published a list of a total of eight (8) fuel 

types approved into SIPs, under section 211(c)(4)(C) as of 

September 1, 2004, the States and the PADD in which they are 

used. Clark County CBG, which as earlier explained has sulfur 

 

19 While the phrase “boutique” fuels programs can mean different things, it 

generally refers to state fuels programs that establish different 

requirements than the federal fuels program required in a given area, 

typically for the purpose of addressing specific local air quality issues. 
79 

and aromatics content limits for gasoline in use during the 

period from November 1 to March 31, is on the list. 

The EPAct also placed the following three additional 

restrictions on EPA’s authority to waive preemption by approving 

a State fuel program into SIPs under section 211(c)(4)(C): 

• First, EPA may not approve a State fuel program into the SIP 

if it would cause an increase in the total number of fuel 

types approved into SIPs as of September 1, 2004. 

• Second, in cases where EPA approval of a fuel would increase 

the total number of fuel types on the list but not above the 

number approved as of September 1, 2004, because the total 

number of fuel types in SIPs is below the number of fuel 

types as of September 1, 2004, we are required to make a 

finding after consultation with DOE, that the new fuel will 

not cause supply or distribution interruptions or have a 

significant adverse impact on fuel producibility in the 

affected or contiguous areas. 

• Third, with the exception of 7.0 psi RVP, EPA may not 

approve a state fuel into a SIP unless that fuel type is 

already approved in at least one SIP in the applicable PADD. 

CAA Section 211(c)(4)(C)(v)(I), (IV) and (V). 

Therefore, EPAct also amended section 211(c)(4)(C) to make 

any new EPA approvals of State fuels under section 211(c)(4)(C) 

significantly more difficult by, for example, limiting the total 

number of approved “boutique” fuel types to the number of fuel 

types approved into SIPs as of September 1, 2004. If there is no 
80 

room on the list, for example, then EPA cannot approve any more 

boutique fuels regardless of the needs of a given area to 

address air pollution problems. 

Lastly, CAA section 211(c)(4)(C)(v)(III) requires EPA to 

remove a fuel from the boutique fuels list described above if a 

fuel either ceases to be included in a SIP or if a fuel in a SIP 

is identical to a Federal fuel formulation implemented by EPA. 

CBG will not cease to be included in the SIP because, as earlier 

discussed, CBG is currently in the SIP and will continue in the 

SIP as a specific contingency measure in the Las Vegas Valley CO 

Maintenance Plan, and because we intend to synchronize our final 

actions on the Maintenance Plan and the (suspended) CBG Rule 

(and thereby avoid a gap in time when the CBG Rule would not be 

either an active or contingency measure in the SIP). Thus, in 

today’s action, we are not proposing to remove CBG from the 

boutique fuels list. In addition, since we are not approving any 

new fuel into the SIP under section 211(c)(4)(C), no issues are 

raised concerning the three restrictions on such an approval 

described above. 

As a general matter, under CAA section 110(l), EPA may 

approve relaxations or suspensions of control measures so long 

as doing so would not interfere with attainment or maintenance 

of any of the NAAQS or would otherwise conflict with applicable 

CAA requirements. In this instance, the relaxation of the Low 
81 

RVP Rule and the suspension of the CBG Rule (and related sulfur 

and aromatics content limits) would not conflict with any 

applicable CAA requirement. However, the changes to the two 

fuels rules would affect the properties of the gasoline sold in 

Clark County during the winter and would thereby change 

vehicular emissions relative to those that would occur without 

these changes with concomitant effects on ambient pollutant 

concentrations (and potentially interfering with attainment or 

maintenance of the NAAQS). 

To specify the changes in the properties of wintertime 

gasoline due to the changes in the fuels rules, Clark County 

DAQEM commissioned a study by ENVIRON and Sierra Research. The 

study was submitted as appendix A to the Las Vegas Valley CO 

Maintenance Plan. As far as changes to sulfur content are 

concerned, the study authors predict essentially no increase in 

gasoline sulfur content due to the applicability of federal tier 

2 gasoline sulfur limits [which are very similar (30 ppm 

average, with an 80 ppm cap) to the corresponding limits under 

the CBG rule]. We agree that any increase would be minimal due 

to the similarities between the federal sulfur limits and those 

in the CBG Rule, and would expect the federal gasoline sulfur 

content limits to essentially backstop the emissions reductions 

associated with the low sulfur content limit in the CBG Rule. 
82 

As far as aromatics are concerned, the study predicts an 

increase in aromatic content from the current (2006) wintertime 

average of approximately 20% (by volume) to approximately 23%, 

based on the average aromatics content in gasoline nationwide. 

See page 12 of appendix A to the Maintenance Plan. Moreover, 

wintertime gasoline RVP could increase from the current (2006) 

average of 8.8 psi to as high as 13.5 psi in response to the 

relaxation of the Low RVP Rule. The relative increases in 

aromatics and RVP would lead to higher emissions of CO and VOC, 

and potentially of particulate matter as well. We review these 

increases or potential increases, in the context of attainment 

and maintenance of the CO, ozone, and particulate matter NAAQS 

in the paragraphs that follow. 

With respect to CO, we conclude that the changes in 

wintertime gasoline specifications due to the rules changes 

would not interfere with the NAAQS based on the modeling results 

documented in the Las Vegas Valley CO Maintenance Plan and our 

proposed approval of the Maintenance Plan herein. The modeling 

conducted for the Maintenance Plan relies on emissions factors 

that take no credit for either the CBG Rule or the Low RVP Rule 

and still demonstrates maintenance of the CO NAAQS in Las Vegas 

Valley through 2020. 

For the ozone NAAQS, we recognize that a portion of Clark 

County is designated nonattainment for the 8-hour ozone NAAQS, 
83 

and thus, absent modeling results or other convincing evidence 

showing non-interference, we would not normally approve a SIP 

revision that would result in an increase in ozone precursors 

within the nonattainment area. However, in the Las Vegas Valley 

CO Maintenance Plan, Clark County DAQEM contends that there 

would be no interference with the ozone NAAQS in this instance 

because the effect of the gasoline fuel changes is limited to 

the winter months whereas ozone exceedances occur during the 

summertime. See pages 6-2 and 6-3 of the Maintenance Plan. At 

the outset, we generally find this line of reasoning for a noninterference finding to be acceptable, but to gain a more 

detailed understanding of the seasonal nature of ozone 

exceedances in Las Vegas Valley, we reviewed ozone data by month 

to determine when exceedances of the 0.075 ppm, eight-hour 

average, ozone NAAQS occurred. The data indicates that, over the 

past 6 years (2004-2009), all exceedances of the 0.075 ppm 

standard occurred during and between the months of April and 

September. Conversely, no ozone NAAQS exceedances were recorded 

from October through March, which is the period of time affected 

by the suspension of the CBG Rule and relaxation of the RVP 

specification. Thus, we find that the changes in Clark County 

wintertime gasoline specifications would not interfere with 

attainment or maintenance of the ozone NAAQS. 
84 

With respect to the 1987 (24-hour average) PM-10, Las Vegas 

Valley is classified as a “serious” nonattainment area. See 40 

CFR 81.329. In 2004, EPA approved the “serious” area PM-10 plan 

for Las Vegas Valley and approved the request to extend the 

applicable attainment date to the end of 2006. See 69 FR 32273 

(June 9, 2004). In our 2004 final rule approving the PM-10 plan, 

we approved a number of fugitive dust rules, including Clark 

County Air Quality Regulations (AQR) Sections 90 through 94, 

that limit emissions from such sources as open areas and vacant 

lots; unpaved roads, unpaved alleys and unpaved easement roads; 

unpaved parking lots; construction sites; and paved roads and 

street sweeping equipment. In approving the Las Vegas Valley 

“serious” area PM-10 plan, we also indicated that we agreed with 

Clark County DAQEM’s conclusion that nonroad and on-road vehicle 

exhaust are not significant source categories in Las Vegas 

Valley for the purpose of implementing Best Available Control 

Measures (BACM). See our proposed approval of the PM-10 plan at 

68 FR 2954, at 2959 (January 22, 2003). 

In the Las Vegas Valley CO Maintenance Plan, Clark County 

DAQEM contends that the changes in wintertime gasoline 

specifications would not interfere with the PM-10 NAAQS based on 

the determination in the approved serious area PM-10 plan that 

vehicular exhaust is not a significant source of PM-10 in Las 
85 

Vegas Valley.20 See pages 6-3 and 6-4 of the Maintenance Plan. 

Clark County DAQEM also contends that removing fuels controls 

has no impact on PM-10 emissions from vehicular exhaust. Lastly, 

Clark County DAQEM points to the most recent PM-10 emissions 

inventory that shows vehicular exhaust to account for less than 

one percent of the total PM-10 emissions in Las Vegas Valley in 

year 2006. 

First of all, Clark County DAQEM is correct in pointing out 

that vehicular exhaust was determined not to be a significant 

source of PM-10 emissions in Las Vegas Valley for the purposes 

of implementing the BACM requirement. We also believe that Clark 

County DAQEM’s most recent inventory presents reasonable 

estimates of existing sources of PM-10 in Las Vegas Valley. As a 

general matter, we do not agree that removal of fuels controls 

has no affect on vehicular exhaust emissions of PM-10, but we 

recognize that the extent to which the higher aromatics content 

(from 20% to 23%, by volume) and higher RVP (from 8.8 to 13.5 

psi) would affect PM-10 from vehicle exhaust, and whether that 

effect would be positive or negative, is difficult to predict 

because EPA’s MOBILE emissions factor model, which was used in 

 

20 The significant source categories identified in the serious area PM-10 

plan for Las Vegas Valley are fugitive types of sources, including disturbed 

vacant land/unpaved parking lots, construction (including highway 

construction), and vehicular travel on paved and unpaved roads. See 68 FR 

2954, at 2959 (January 22, 2003). 
86 

the development of the Maintenance Plan, does not have the 

capability to quantify the resulting emissions changes. 

However, even assuming the effect would be an increase in 

PM-10 from vehicle exhaust, we can still find that the changes 

in wintertime gasoline specifications due to the fuels changes 

would not interfere with attainment of the PM-10 NAAQS, because, 

in addition to the minimal impact of vehicular emissions on PM10 concentrations in Las Vegas Valley (based on PM-10 

inventories), the area appears to have attained the standard due 

to the implementation and enforcement of fugitive dust controls. 

To determine whether Las Vegas Valley is attaining the PM-10 

standard, we reviewed 2007-2009 PM-10 monitoring data from the 

various monitoring stations for which Clark County DAQEM reports 

data into EPA’s Air Quality Database (AQS). The review of the 

data reveals two exceedances (i.e., 24-hour-average 

concentrations equal to or greater than 155 μg/m3) over the 2007-

2009 period, both of which were recorded during year 2008 at the 

Craig Road PM-10 monitoring site in North Las Vegas. The PM-10 

monitor at the Craig Road site is a continuous monitor, and thus 

the expected number of days per year, averaged over the 2007-

2009 period, is less than 1.0,21 which means that the PM-10 NAAQS 

 

21 The PM-10 NAAQS is 150 micrograms per cubic meter (μg/m3

), 24-hour average 

concentration. The standard is attained when the expected number of days per 

calendar year with a 24-hour average concentration above 150 μg/m3

, as 

determined in accordance with appendix K to 40 CFR part 50, is equal to or 

less than one. See 40 CFR 50.6. 
87 

has been met at the Craig Road monitor, and since the Craig Road 

monitor is the only site recording any exceedances, it follows 

that the entire valley has attained the standard.22 

We do not believe that a hypothetical, incremental increase 

in PM-10 emissions, from a source category (vehicular exhaust) 

estimated to contribute less than 1% to the overall emissions 

inventory, would have a discernible effect on ambient PM-10 

concentrations. This lack of discernible effect, coupled with an 

attainment finding, provides us with a sufficient rationale for 

concluding that the changes in wintertime gasoline properties, 

expected to occur with the relaxation of the Low RVP Rule and 

the suspension of the CBG Rule, would not interfere with 

attainment or maintenance of the PM-10 NAAQS in Las Vegas 

Valley. 

With respect to the 1997 (annual) and 2006 (24-hour) PM-2.5 

NAAQS, Las Vegas Valley and the various other hydrographic areas 

that comprise Clark County, are designated as 

“unclassifiable/attainment” areas. See 40 CFR 81.329. A review 

of AQS data from the various PM-2.5 monitoring sites in Clark 

County reveals that PM-2.5 concentrations are well below the PM2.5 NAAQS. Over the past three years, the highest 98th percentile 

value (for the 24-hour average), recorded at the Sunrise Avenue 

 

22 An attainment finding is not the same as redesignation of an area to 

attainment. The latter type of action can only be approved by EPA if all of 

the criteria under CAA section 107(d)(3)(E) are met, including submittal of, 

and EPA approval of, a maintenance plan. 
88 

site, is 23 μg/m3, well below the corresponding 24-hour NAAQS of 

35 μg/m3. The highest annual concentration, also recorded as the 

Sunrise Avenue site, is 10.3 μg/m3, well below the corresponding 

annual NAAQS of 15.0 μg/m3. 

As discussed above for PM-10, the changes to wintertime 

gasoline properties due to the relaxed Low RVP Rule and 

suspended County CBG Rule could result in increases in PM-10 

emissions from vehicular exhaust. All of the PM-10 from 

vehicular exhaust can be assumed also to be fine particulate 

matter (i.e., PM-2.5), and thus the changes to the wintertime 

gasoline properties could also result in increased PM-2.5 

emissions from vehicular exhaust. However, we have no reason to 

believe that this hypothetical increase would be large enough to 

cause an exceedance of the 24-hour or annual PM-2.5 NAAQS. 

Therefore, we conclude that the changes in wintertime gasoline 

properties, expected to occur with the relaxation of the Low RVP 

Rule and the suspension of the CBG Rule, would not interfere 

with attainment or maintenance of the PM-2.5 NAAQS in Clark 

County. 

Based on our previous approvals of NAC section 590.065 

(i.e., the Low RVP Rule) and the CBG Rule, and the nature of the 

regulatory changes submitted to us (e.g., relaxing a vapor 

pressure limit (not subject to preemption), updating 

specifications and test methods in the State rule, suspension of 
89 

the county CBG rule) as well as the above evaluation of the 

impact of the changes in wintertime gasoline properties in Clark 

County on ambient CO, ozone, PM-10, and PM-2.5 concentrations, 

we find that the changes would not interfere with attainment or 

maintenance of any of the NAAQS, nor would they interfere with 

any applicable requirement of the Act, and thus are approvable 

under CAA section 110(l). As such, we propose to approve the 

amendments to NAC section 590.065, and suspension of the CBG 

Rule, as submitted by NDEP on March 26, 2010, as revisions to 

the Nevada SIP.23

VII. Proposed Action and Request for Comment 

Under section 110(k)(3) of the Act, EPA is proposing to 

approve NDEP’s submittal dated September 18, 2008 of the Las 

Vegas Valley CO Maintenance Plan as a revision to the Nevada SIP 

because we find that it satisfies the requirements of section 

175A of the CAA to include a reasonably accurate and 

comprehensive attainment inventory, an adequate maintenance 

demonstration, contingency provisions, and commitments to 

continue operation of an acceptable ambient monitoring network 

to verify continued attainment. Final approval of the Las Vegas 

 

23 In addition to gasoline vapor pressure requirements, NAC section 590.065 

also includes maximum content limits in gasoline for lead, phosphorus, 

manganese, ethanol, and sulfur. See NAC section 590.065(7). Because none of 

these content limits relate to gasoline vapor pressure requirements in Las 

Vegas Valley nor the CO emissions reductions achieved therefrom, and because 

the subsection in NAC section 590.065 containing these limits (i.e., 

subsection (7)) is severable from the rest of the rule, we are not including 

NAC section 590.065(7) in our proposed approval of amendments to NAC section 

590.065. 
90 

Valley CO Maintenance Plan would make federally enforceable the 

commitments, such as the commitment to continue operation of an 

adequate CO monitoring network, and the contingency provisions, 

contained therein. In addition, we are proposing to approve for 

transportation conformity purposes the motor vehicle emissions 

budgets in the Las Vegas Valley CO Maintenance Plan for years 

2008, 2010, and 2020 because we find they meet the criteria 

found in 40 CFR 93.118(e). The budgets for 2008, 2010 and 2020 

are 658 tons per day, 686 tons per day, and 704 tons per day, 

respectively (based on typical weekday during the winter). 

Based in part on our proposed approval of the Las Vegas 

Valley CO Maintenance Plan, we are also proposing to approve 

NDEP’s September 18, 2008 request to redesignate Las Vegas 

Valley to attainment for the CO NAAQS. In doing so, we find that 

the area has met all of the criteria for redesignation under CAA 

section 107(d)(3)(E), i.e., the area has attained the CO 

standard; EPA has fully approved the Las Vegas Valley SIP for 

all requirements under section 110 and part D of the CAA that 

are applicable for purposes of redesignation; the improvement in 

CO conditions in Las Vegas Valley is due to permanent and 

enforceable reductions; and as described above, the State has 

submitted a maintenance plan for the area that meets the 

requirements of section 175A. 
91 

Contingency provisions in maintenance plans must include 

the measures contained in the SIP prior to redesignation, and 

for one such contingency measure included in the Las Vegas 

Valley CO Maintenance Plans, the State’s Low RVP Rule, the 

responsible State agency (State Department of Agriculture) has 

not yet made the necessary commitment. Thus, our proposed 

approval of the Maintenance Plan and redesignation request is 

contingent upon submittal (and approval by EPA) of such a 

commitment as a revision to the Nevada SIP.24

We are also proposing to approve, under section 110(k)(3) 

of the CAA, NDEP’s March 26, 2010 submittal of the suspension of 

Clark County’s Air Quality Regulations (AQR) Section 54 

(“Cleaner Burning Gasoline: Wintertime Program”)(“CBG 

Regulation”), and the amendments to the NAC section 590.065, 

including the relaxation in the State’s wintertime gasoline RVP 

requirement for Clark County from 9.0 to 13.5 psi, because we 

find that doing so would not interfere with attainment or 

maintenance of any of the NAAQS or any applicable requirement of 

the Clean Air Act for the purposes of CAA section 110(l). We are 

not including subsection (7) of amended NAC section 590.065 in 

 

24 On July 12, 2010, the Nevada Department of Agriculture initiated a 30-day 

comment period to solicit comment (or request a public hearing) on the draft 

commitment regarding implementation of the contingency measure in the 

Maintenance Plan related to reinstatement of the Low RVP Rule. The 

Department’s notice of intent to solicit public comment, which includes the 

commitment language, has been placed in the docket for this rulemaking. We 

have reviewed the language of the Department’s draft commitment and expect to 

approve it if it is ultimately submitted to us without significant 

modification. 
92 

our proposed approval because the limits in subsection (7) of 

the amended rule are unrelated to the vapor pressure requirement 

and associated CO emissions reductions, and are severable from 

the rest of the rule. 

We will accept comments from the public on this proposal 

for the next 30 days.

VIII. 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. A 

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 
93 

impose additional requirements beyond those imposed by State 

law. For these reasons, these actions: 

• are not “significant regulatory actions” subject to review 

by the Office of Management and Budget under Executive 

Order 12866 (58 FR 51735, October 4, 1993); 

• 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 (Public Law 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 
94 

(15 U.S.C. 272 note) because application of those 

requirements would be inconsistent with the Clean Air Act; 

and 

• do not provide EPA with the discretionary authority to 

address, as appropriate, disproportionate human health or 

environmental effects, using practicable and legally 

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 Las Vegas Valley. 
List of Subjects 

40 CFR Part 52 

Environmental protection, Air pollution control, Carbon 

monoxide, Intergovernmental relations, ~eporting and 

recordkeeping requirements. 

40 CFR Part 81 

Environmental protection, Air pollution control, Carbon 

monoxide, National parks, Wilderness areas. 

+,LC) 

Da ed: