26910 Federal Register / Vol. 71, No. 89 / Tuesday, May 9, 2006 / Proposed Rules 

recordkeeping requirements, Volatile 

organic compounds. 

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

Dated: April 28, 2006. 

Alan J. Steinberg, 

Regional Administrator, Region 2. 

[FR Doc. 06–4287 Filed 5–8–06; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R09–OAR–2006–0322; FRL–8167–9] 

Approval and Promulgation of 

Implementation Plans; Las Vegas 

Valley Carbon Monoxide Attainment 

Plan 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: EPA proposes to approve a 

revised attainment plan for the Las 

Vegas Valley carbon monoxide 

nonattainment area on the condition 

that Clark County and the State of 

Nevada withdraw the 2030 motor 

vehicle emission budget, or, in the 

alternative, to disapprove the plan. This 

plan has been submitted to the Agency 

by the State of Nevada as a revision to 

the Nevada state implementation plan. 

The revised attainment plan includes 

revised base year and future year 

emissions inventories and a revised 

demonstration of continued attainment 

of the carbon monoxide national 

ambient air quality standard in Las 

Vegas Valley through 2030 based on the 

most recent emissions models and 

planning assumptions and establishes 

new motor vehicle emissions budgets. 

EPA is proposing this action under 

section 110(k) of the Clean Air Act, 

which obligates the Agency to take 

action on State submittals of revisions to 

state implementation plans. The 

intended effect of this proposed 

approval action is to update the carbon 

monoxide motor vehicle emissions 

budgets in the Las Vegas area and 

thereby make them available for the 

purposes of transportation conformity, 

and the intended effect of this proposed 

disapproval action is to retain the 

previously-approved budgets. 

DATES: Any comments on this proposal 

must arrive by June 8, 2006. Public 

comments on this action are requested 

and will be considered before taking 

final action. 

ADDRESSES: Submit comments, 

identified by docket number EPA–R09–

OAR–2006–0322, by one of the 

following methods: 

1. 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 

EPA–R09–OAR–2006–0322. 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 e-mail. The 

http://www.regulations.gov, Web site is 

an ‘‘anonymous access’’ system, which 

means EPA will not know your identity 

or contact information unless you 

provide it in the body of your comment. 

If you send an e-mail comment directly 

to EPA without going through http:// 

www.regulations.gov, your e-mail 

address will be 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 your 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 

electronic 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. Publicly 

available docket materials are available 

either electronically in http:// 

www.regulations.gov or in hard copy at 

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. 

FOR FURTHER INFORMATION CONTACT: 

Karina O’Connor, EPA Region IX, 

telephone number: (775) 833–1276; fax 

number: (775) 833–1276; e-mail address: 

oconnor.karina@epa.gov. 

SUPPLEMENTARY INFORMATION: 

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

and ‘‘our’’ refer to EPA. 

Table of Contents 

I. Summary of Action 

II. Introduction 

A. What Is the Purpose of this Proposed 

Rulemaking? 

B. What Did the State Submit To EPA? 

C. What Is a SIP and How Is it Revised 

From Time to Time? 

D. What Is the Background of Today’s 

Action? 

E. What Are MOBILE6 And MOBILE6.2? 

F. What Is the Current Status of CO Levels 

in Las Vegas Valley and how do the 

Levels Compare With the Federal 

Standards? 

III. Review of the Las Vegas Valley 2005 CO 

Plan Submittal 

A. What Is the Purpose and Content of 

Nevada’s Submittal? 

B. How Is EPA Evaluating This Submittal? 

C. How Have Emissions of Carbon 

Monoxide in Las Vegas Valley Changed? 

D. How Has the Attainment Demonstration 

Changed? 

E. Are Las Vegas Valley’s Motor Vehicle 

Emissions Budgets Approvable? 

F. How Does This Action Affect 

Transportation Conformity? 

IV. Proposed Action and Request for Public 

Comment 

V. Statutory and Executive Order Reviews 

I. Summary of Action 

Under section 110(k) of the Clean Air 

Act (CAA or Act), EPA proposes to 

approve a revised attainment plan for 

the Las Vegas Valley carbon monoxide 

(CO) nonattainment area on the 

condition that Clark County and the 

State of Nevada withdraw the 2030 

motor vehicle emission budget, or, in 

the alternative, to disapprove the plan. 

This plan has been submitted to EPA 

by the Nevada Division of 

Environmental Protection (NDEP) as a 

revision to the Nevada state 

implementation plan (SIP). The revised 

attainment plan includes revised base 

year and future year emissions 

inventories and a revised demonstration 

of continued attainment of the carbon 

monoxide national ambient air quality 

standard in Las Vegas Valley through 

2030 based on the most recent 

emissions models and planning 

assumptions and establishes new motor 

vehicle emissions budgets. The 

intended effect of this proposed 

approval action is to update the carbon 

monoxide motor vehicle emissions 

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Federal Register / Vol. 71, No. 89 / Tuesday, May 9, 2006 / Proposed Rules 26911 

1The 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. The 

2005 CO plan also allocates a small portion of the 

safety margins to certain point sources. 

2The boundaries of the Las Vegas Valley CO 

nonattainment area are defined by reference to State 

hydrographic area #212, which covers the central 

portion of Clark County. See 40 CFR 81.329. 

budgets in the Las Vegas area and 

thereby make them available for the 

purposes of transportation conformity, 

and the intended effect of this proposed 

disapproval action is to retain the 

previously-approved budgets. The 

currently approved attainment plan did 

not include 2030 budgets, therefore we 

do not need 2030 budgets to be able to 

approve the remaining budgets in the 

revised plan. 

II. Introduction 

A. What Is the Purpose of this Proposed 

Rulemaking? 

The purpose of this proposed 

rulemaking is to present our evaluation 

and conclusions with respect to a 

submittal of a revision to the Nevada 

SIP, identified below, that includes a 

revised attainment plan for the Las 

Vegas CO nonattainment area. The 

revised plan includes updated 

emissions inventories and dispersion 

modeling in support of new motor 

vehicle emissions budgets. 

B. What Did the State Submit to EPA? 

Under a letter dated February 14, 

2006, NDEP submitted the Carbon 

Monoxide State Implementation Plan 

Revision, Las Vegas Valley 

Nonattainment Area, Clark County, 

Nevada (October 2005) (‘‘2005 CO 

plan’’), to EPA as a revision to the 

Nevada SIP following the plan’s 

adoption by the Clark County Board of 

Commissioners on October 4, 2005. 

Prepared by the Clark County 

Department of Air Quality and 

Environmental Management (DAQEM), 

the 2005 CO plan includes a revised 

emissions inventory, a revised modeling 

demonstration of continued attainment, 

and revised motor vehicle emissions 

budgets. The inventories and modeling 

demonstration included in the 2005 CO 

plan relate to analysis years 1996, 2006, 

2010, 2015, 2020 and 2030. The plan 

allocates almost all of the estimated 

safety margins 1 in years 2006, 2010, 

2015, 2020, and 2030 to the on-road 

motor vehicle emissions category. 

Also submitted by NDEP on February 

14, 2006 is a report entitled, 

‘‘Supplement to the Carbon Monoxide 

State Implementation Plan Revision,’’

which was prepared by DAQEM in 

response to comments raised by EPA 

subsequent to the Clark County Board of 

Commissioners’ adoption of the 2005 

CO plan. This supplemental report 

presents an air quality trends analysis in 

further support for the plan’s forecast of 

continued attainment through 2030 with 

the plan’s proposed motor vehicle 

emissions budgets. 

C. What is a SIP and How Is it Revised 

From Time to Time? 

The Clean Air Act requires States to 

attain and maintain ambient air quality 

equal to or better than standards that 

provide an adequate margin of safety for 

public health and welfare. These 

ambient air quality standards are 

established by EPA and are known as 

the National Ambient Air Quality 

Standards (NAAQS). Carbon monoxide 

(CO) is one of the pollutants for which 

EPA has established NAAQS. 

The State’s plan for attaining and 

maintaining the NAAQS are outlined in 

the SIP for that state. The SIP is a 

planning document that, when 

implemented, is designed to ensure the 

achievement of the NAAQS. Each State 

currently has a SIP in place, and the Act 

requires that States make SIP revisions 

periodically as necessary to provide 

continued compliance with the 

standards. The State of Nevada’s SIP is 

identified at title 40, part 52, subpart DD 

of the Code of Federal Regulations (40 

CFR part 52, subpart DD). 

SIPs may include, among other things, 

the following: (1) An inventory of 

emission sources; (2) statutes and 

regulations adopted by the State 

legislature and executive agencies; (3) 

air quality analyses that include 

demonstrations that adequate controls 

are in place to meet the NAAQS; and (4) 

contingency measures to be undertaken 

if an area fails to attain the standard or 

make reasonable progress toward 

attainment by the required date. The 

State must make the SIP available for 

public review and comment through a 

public hearing before it is adopted by 

the State and submitted to EPA by the 

Governor or his appointed designee. 

When EPA takes Federal action to 

approve the SIP submittal, the rules and 

regulations become federally 

enforceable. 

For an area designated as 

nonattainment for a given NAAQS, the 

State first submits a plan with emissions 

reduction measures to bring the area 

into attainment. Once the area has 

attained the standard based on 

monitored air quality, the State then 

submits a redesignation request to 

attainment and a maintenance plan 

demonstrating that the area will 

continue to maintain the standard for at 

least 10 years after the redesignation 

into attainment. 

D. What Is the Background of Today’s 

Action? 

Based on CO monitoring data from the 

mid-1970’s, EPA designated Las Vegas 

Valley 2 as a CO nonattainment area 

under the Clean Air Act, as amended in 

1977. See 43 FR 8962, 9012 (March 3, 

1978). 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, but the CO NAAQS was 

not attained by the then-applicable 1987 

attainment date. 

The Clean Air Act was significantly 

amended by Congress in 1990 to 

establish new attainment dates and 

planning and control requirements for 

areas that had failed to attain the 

NAAQS under the 1977 Amendments. 

Under the 1990 Amended Act, Las 

Vegas Valley was classified as a 

‘‘moderate’’ nonattainment area for CO 

with a new attainment date of December 

31, 1995 and subject to the specific 

requirements for such areas. EPA later 

extended the attainment date to 

December 31, 1996, but given 

monitoring data from that period 

showing continued CO NAAQS 

violations, EPA reclassified Las Vegas 

Valley in 1997 as a ‘‘serious’’ CO 

nonattainment area with an attainment 

date of December 31, 2000 and subject 

to the additional requirements 

applicable to such areas. See 62 FR 

51604 (October 2, 1997). 

In response to the ‘‘moderate’’, and 

then ‘‘serious,’’ nonattainment 

classification and related CAA 

requirements, Clark County and the 

State of Nevada adopted and 

implemented new air quality plans and 

programs, including wintertime gasoline 

specifications for oxygen content and 

Reid Vapor Pressure(RVP), 

enhancement to the vehicle I/M 

program and a ‘‘serious’’ area attainment 

plan, the Carbon Monoxide State 

Implementation Plan, Las Vegas Valley 

Nonattainment Area, Clark County, 

Nevada (August 2000) (‘‘2000 CO 

plan’’). The 2000 CO plan included a 

base year (1996) emission inventory, 

future-year emissions projections, an 

attainment demonstration, and 

additional control measures, including 

additional wintertime gasoline 

specifications for sulfur and aromatics 

(referred to as ‘‘cleaner burning 

gasoline’’), an alternative fuels program 

for government vehicles, and a 

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26912 Federal Register / Vol. 71, No. 89 / Tuesday, May 9, 2006 / Proposed Rules 

3Note that the contingency measure requirement 

was removed when EPA made a finding of 

attainment in June 2005 (See 70 FR 31353). 

transportation control measure program. 

The plan also established motor vehicle 

emissions budgets and provided 

modeling documentation showing that 

the CO standard would continue to be 

attained beyond the attainment deadline 

of 2000 through the 2020 analysis year. 

In 1998, we approved the wintertime 

gasoline specification for oxygen 

content (i.e. oxygenated fuel program) 

(64 FR 29573, June 2, 1999), and in 

2004, we approved the revised vehicle 

I/M program, the wintertime gasoline 

specification for RVP, and all of the 

elements of the 2000 CO plan (except 

for the contingency provisions 3, 

including the new control measures 

(e.g., cleaner burning gasoline rule), 

emissions inventories, attainment 

demonstration, and motor vehicle 

emissions budgets (69 FR 56351, 

September 21, 2004). 

The 2000 CO plan established motor 

vehicle emission budgets for years 2000, 

2010, and 2020. These budgets were 

developed using MOBILE5b, which was 

the latest EPA-approved motor vehicle 

emission factor model at that time. EPA 

officially released a new version of 

motor vehicle emissions model, 

MOBILE6, on January 29, 2002 (67 FR 

4254). All SIPs and SIP revisions that 

are developed after that date must use 

the new model to estimate motor 

vehicle emissions. The release of 

MOBILE6 also began a 24-month grace 

period for conformity. All conformity 

determinations that are initiated after 

January 29, 2004 must use MOBILE6. As 

discussed in the following section of 

this notice, MOBILE6 has now been 

revised with the release of MOBILE6.2. 

Besides the release of updated 

emissions models, another circumstance 

that has changed since adoption of the 

2000 CO plan is the change in the 

expected rate of population growth in 

Las Vegas Valley. The most recent 

forecasts show population growth 

outpacing the corresponding projections 

used for the 2000 CO plan. 

In response to these changes, 

DAQEM, in consultation with the 

Regional Transportation Commission of 

Southern Nevada (RTC), undertook a 

comprehensive air quality planning 

effort to review and update the 2000 CO 

plan and the associated motor vehicle 

emission budgets to maintain 

consistency for future conformity 

findings. The planning efforts included 

detailed technical analyses, such as 

preparation of new base and future year 

emissions inventories and regional and 

hotspot dispersion modeling, and 

culminated in the preparation, adoption 

and submittal of the 2005 CO plan, 

which is the subject of today’s proposed 

action. 

E. What Are MOBILE6 and MOBILE6.2? 

MOBILE is an EPA emissions factor 

model for estimating pollution from onroad motor vehicles in states except for 

California. MOBILE calculates 

emissions of volatile organic 

compounds (VOCs), nitrogen oxides 

(NOX) and carbon monoxide (CO) from 

passenger cars, motorcycles, buses, and 

light-duty and heavy-duty trucks. The 

model accounts for the emission 

impacts of factors such as changes in 

vehicle emission standards, changes in 

vehicle populations and activity, and 

variation in local conditions such as 

temperature, humidity, fuel quality, and 

air quality programs. 

MOBILE is used to calculate current 

and future inventories of motor vehicle 

emissions at the national and local 

level. These inventories are used to 

make decisions about air pollution 

policies and programs at the federal, 

state and local level. Inventories based 

on MOBILE are also used to meet the 

Federal Clean Air Act’s SIP and 

transportation conformity requirements. 

The MOBILE model was first 

developed in 1978. It has been updated 

many times to reflect changes in the 

vehicle fleet and fuels, to incorporate 

EPA’s growing understanding of vehicle 

emissions, and to cover new emissions 

regulations and modeling needs. 

Although some minor updates were 

made in 1996 with the release of 

MOBILE5b, MOBILE6 was the first 

major revision to MOBILE since 

MOBILE5a was released in 1993. 

Released in 2002 (67 FR 4254, January 

29, 2002), MOBILE6 incorporates new 

and improved vehicle and emissions 

data and a new understanding of vehicle 

emissions processes. 

In 2004 (69 FR 28830), MOBILE6 was 

updated with the release of MOBILE6.2, 

which adds the capability to generate 

direct particulate matter emission 

factors and emission factors for 

particulate precursors. MOBILE6.2 also 

corrects some minor coding errors in 

MOBILE6 and incorporates some 

revisions to CO emission factors for cars 

and light-duty trucks that meet national 

low emission vehicle (NLEV), low 

emission vehicle (LEV), and Tier 2 

vehicle standards. MOBILE6.2 is now 

the latest emission model released by 

EPA and should be used by all areas for 

SIP and conformity analyses. Further 

details on MOBILE models can be found 

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

mobile6.htm. 

F. What Is the Current Status of CO 

Levels in Las Vegas Valley and How Do 

the Levels Compare With the Federal 

Standards? 

The national 8-hour CO ambient 

standard is attained when the highest 8- 

hour CO concentration of 9 parts per 

million (ppm) is exceeded no more than 

one time in a calendar year. Since the 

initial operation of CO monitors in Las 

Vegas Valley in the 1970’s, exceedances 

of the CO standard occurred relatively 

frequently during the winter months, 

but, with the implementation of various 

State and local CO control measures 

(e.g., fuel specifications and vehicle I/M 

program) and also the implementation 

of the Federal motor vehicle control 

program (e.g., exhaust emission 

standards for new light-duty vehicles, 

light-duty trucks, and heavy-duty 

trucks), CO levels trended downward in 

Las Vegas Valley despite large increases 

in population and VMT through the 

1980’s and 1990’s. 

By the late-1990’s, ambient CO 

conditions had improved to such an 

extent that exceedances were no longer 

recorded at any of the CO monitoring 

stations. The last exceedances of the 8- 

hour CO standard in Las Vegas Valley 

were recorded in 1998, and based on the 

record of clean data during the 1999–

2000 period, we determined that Las 

Vegas Valley attained the CO NAAQS 

by the applicable ‘‘serious’’ area 

attainment date of December 31, 2000. 

See 70 FR 31353 (June 1, 2005). Since 

2000, and through year 2005, the 

highest 8-hour CO concentration 

measured by the CO monitoring 

network in Las Vegas Valley was 7 ppm 

(measured at the Sunrise Acres 

monitoring site), which is well below 

the CO standard of 9 ppm. Thus, after 

attaining the CO standard in 2000, Las 

Vegas Valley has continued to attain the 

standard up to the present time. 

III. Review of Las Vegas Valley 2005 

CO Plan Submittal 

A. What Is the Purpose and Content of 

Nevada’s Submittal? 

DAQEM’s purpose in preparing the 

2005 CO plan is to update the CO motor 

vehicle emissions budgets from the 2000 

CO plan for use in transportation 

conformity determinations. 

The 2005 CO plan generally follows 

the outline of the 2000 CO plan and 

provides expanded discussion of the 

plan elements for which new 

information is available or for which 

circumstances have changed since 

adoption of the previous plan. First, the 

2005 CO plan discusses the changes to 

the CO monitoring network and ambient 

CO level trends since 2000, as well as 

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Federal Register / Vol. 71, No. 89 / Tuesday, May 9, 2006 / Proposed Rules 26913 

4That is, except for on-road motor vehicles, 

which reflect average daily conditions during the 

month of December. 

the results of the CO saturation study, 

which was completed in January 2002. 

See chapter 2 and appendix B of the 

2005 CO plan. The 2005 CO plan then 

provides 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 

also updated methods, such as 

MOBILE6.2 and NONROAD2004 for onroad and nonroad sources, respectively. 

The 2005 CO plan summarizes the 

control measures that have contributed 

to attainment of the CO NAAQS in Las 

Vegas Valley and that are being counted 

on for continued attainment of the 

standard but neither repeals nor 

modifies any such measure. The 

remainder of the 2005 CO plan provides 

updated dispersion modeling results 

reflecting the updated emissions 

estimates and extends the showing of 

continued attainment from 2020 (as 

provided for in the 2000 CO plan) to 

2030, and supporting the establishment 

of new motor vehicle emissions budgets. 

Included with the 2005 CO plan are 

technical appendices which include a 

technical support document for the 

emission inventory and dispersion 

modeling, the carbon monoxide 

monitoring saturation study, a study on 

the effectiveness of the area’s vehicle 

I/M program, airport modeling studies, 

a support letter from the area’s 

Metropolitan Planning Organization 

(i.e., the RTC) and documentation of the 

public review process for the plan. 

Enclosed with the 2005 CO plan, 

NDEP also submitted a report entitled, 

‘‘Supplement to the Carbon Monoxide 

State Implementation Plan Revision,’’

which was prepared by DAQEM in 

response to comments raised by EPA 

after adoption of the 2005 CO plan on 

October 4, 2005. The supplemental 

report presents an air quality trends 

analysis in further support for the plan’s 

forecast of continued attainment 

through 2030 with the plan’s proposed 

motor vehicle emissions budgets. 

B. How Is EPA Evaluating This 

Submittal? 

Section 110(l) of the Clean Air Act 

requires SIP revisions to be subject to 

reasonable notice and public hearing 

prior to adoption by the applicable State 

or local agency and submittal to EPA. In 

this instance, the Clark County Board of 

Commissioners adopted the 2005 CO 

plan on October 4, 2005, following a 30- 

day comment period and a public 

hearing, properly noticed in a 

newspaper of general circulation in Las 

Vegas Valley. NDEP, the Governor’s 

designee for SIP submittals in Nevada, 

then submitted the 2005 CO plan to EPA 

as a revision to the Nevada SIP on 

February 14, 2006. Thus, we find that 

the procedural requirements for SIP 

submittals under CAA section 110(l) 

have been satisfied. 

Section 110(l) also prohibits EPA from 

approving any SIP revision that would 

interfere with any applicable 

requirement concerning attainment and 

reasonable further progress or any other 

applicable requirement of the Act. In 

this instance, the SIP revision involves 

an update to emissions inventories, 

dispersion modeling, and motor vehicle 

emissions budgets previously approved 

by EPA. 

We review emissions inventories to 

ensure they are comprehensive and 

accurate and are based on the latest 

planning assumptions and emissions 

models. We review modeling 

demonstrations to ensure they are 

consistent with the underlying 

emissions estimates and reflect 

reasonable methods and assumptions. 

We review motor vehicle emissions 

budgets to ensure that the budgets are 

clearly related to the emissions 

inventory and the control measures in 

the applicable plan and that the 

budgets, when considered together with 

all other emissions sources, are 

consistent with applicable requirements 

for reasonable further progress, 

attainment, or maintenance. 

As described in the following sections 

of this notice, we conclude that, for the 

base year (1996) through 2020, the 

models and methods used to revise the 

emissions inventories and dispersion 

modeling are acceptable and that the 

motor vehicle emissions budgets are 

clearly related to the revised inventories 

and EPA-approved CO control measures 

for Las Vegas Valley and that the 

budgets are consistent with continued 

attainment of the CO NAAQS in Las 

Vegas Valley through 2030 and thus 

approvable under CAA section 110(l). 

However, the 2005 CO plan fails to 

demonstrate continued attainment in 

the horizon year of 2030 because the 

micro-scale modeling for Clark County 

airports extends only through 2020. 

Based on these conclusions, we are 

proposing to approve the Las Vegas 

Valley 2005 CO plan and related motor 

vehicle emissions budgets as a revision 

to the Nevada SIP on the condition that 

Clark County and the State of Nevada 

withdraw the 2030 motor vehicle 

emissions budgets, or to disapprove the 

plan in the alternative if no such 

withdrawal is made. 

C. How Have Emissions of Carbon 

Monoxide in Las Vegas Valley Changed? 

The emissions inventory is a list, by 

source, of the air contaminants directly 

emitted into the air within a given area. 

The data in the emissions inventory are 

based on calculations and are developed 

using emission factors, which convert 

source activity levels into an estimate of 

emissions contributions for those 

sources. For the 2000 CO plan, the Clark 

County Department of Air Quality, 

which performed the air quality 

planning functions now performed by 

DAQEM, developed a base case 

emissions inventory for the base year 

1996 and then projected inventories for 

years 2000, 2010 and 2020. The general 

categories of CO sources included onroad motor vehicles, nonroad mobile 

sources, and stationary area and point 

sources, and the emissions estimates 

corresponded to an average day during 

the peak CO (i.e., winter) season.4

For the 2005 CO plan, DAQEM 

developed updated estimates for the 

1996 base year and for years 2010 and 

2020 but also developed new estimates 

of emissions for certain interim years, 

2006 and 2015, not previously 

quantified, and developed an emissions 

inventory for a new horizon year, 2030. 

The 2005 CO plan inventories cover the 

same basic source categories but adjust 

the emissions estimates to correspond to 

the second Sunday and second Monday 

in December consistent with the 

December 8–9, 1996 episode used for 

dispersion modeling purposes in the 

plan. The most significant changes in 

the emission inventories for the 2005 

CO plan are in the on-road motor 

vehicle and nonroad mobile source 

categories. 

The 2005 CO plan is based on the 

latest available forecasts of population. 

These updated forecasts reflect a higher 

rate of growth in population in Las 

Vegas Valley than had been assumed for 

the 2000 CO plan. For example, for 

years 2010 and 2020, the population 

forecasts used in the 2005 CO plan are 

25 to 30% higher than the 

corresponding forecasts used in the 

2000 CO plan. 

The RTC used the updated population 

forecasts to provide updated travel 

demand forecasts for the purposes of 

emissions inventory preparation and 

dispersion modeling for the 2005 CO 

plan. To develop the travel demand 

forecasts for future years, RTC used the 

TransCAD travel demand model, a 

model that has replaced TRANPLAN, 

the older model that had been used for 

the 2000 CO plan. For the base year, the 

original TRANPLAN-derived data was 

used, but TransCAD-derived data was 

used for all future years. TransCAD 

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5 Vehicles are tested annually in a decentralized 

network that employs stations licensed as either 

test-only or test-and-repair. 6NONROAD is EPA’s model for estimating 

emissions from nonroad vehicles such as 

construction equipment, lawn and garden 

equipment and recreational equipment. For the 

2005 CO plan, DAQEM used the latest version of 

NONROAD (NONROAD2004) available at the time 

of plan preparation. NONROAD2004 has since been 

superseded by NONROAD2005, which is the final 

version of NONROAD. The previous versions, 

including NONROAD2004, were draft versions, but 

nonetheless represented the best method for 

calculating emissions from nonroad mobile sources, 

excluding commercial marine, locomotive, and 

aircraft, at the time of their release. 

incorporates a number of refinements as 

compared to TRANPLAN including 

more accurate temporal and spatial 

allocation of vehicle miles traveled 

(VMT). Further details regarding VMT 

processing are provided in chapter 2 of 

DAQEM’s Technical Support Document, 

which is included as appendix A of the 

2005 CO plan. 

RTC’s updated travel demand 

forecasts provided the basis for updated 

motor vehicle emissions estimates 

through application of MOBILE6.2 

emissions factors. As noted above, 

MOBILE6.2 represents a significant 

revision of the previous model, 

MOBILE5b, which was used for the 

2000 CO plan, is the latest EPA 

emissions factor model for estimating 

pollution from on-road motor vehicles, 

and incorporates the effects of national 

vehicle control programs and, with the 

appropriate input controls, the effects of 

local control programs such as the 

State’s alternate ‘‘low’’ enhanced 

vehicle I/M program and the wintertime 

gasoline specifications for RVP, sulfur 

and oxygen. 

The MOBILE6.2-derived emissions 

factors for the 2005 CO plan reflect an 

assumed vehicle I/M effectiveness of 

100% instead of 50% as assumed for the 

2000 CO plan. To provide support for 

this change, DAQEM commissioned a 

study of the effectiveness of the 

decentralized (i.e., privately owned and 

operated as opposed to state-run or 

‘‘centralized’’) network of I/M testing 

stations in Las Vegas Valley that 

concluded that the ‘‘test-and-repair’’

stations are equally as effective as ‘‘testonly’’ stations at reducing emissions. 

We note that Nevada I/M regulations 

allow ‘‘test-only 5’’ stations to perform 

certain types of automotive services 

(e.g., change of oil; and replacement of 

oil, air, or fuel filters) that ‘‘test-only’’

stations as defined in EPA’s I/M 

regulations are not allowed to perform. 

See 40 CFR 51.353(a). 

However, we also note that, based on 

information contained in the DAQEM 

study cited above, only 25% of the 

‘‘test-only’’ stations in Las Vegas Valley 

actually offer these limited services and 

75% only perform emissions testing. 

Thus, the presumptive equivalency (to 

centralized test-only stations), i.e., 

assumption of 100% I/M effectiveness, 

allowed under 40 CFR 51.353(a) is not 

unreasonable with respect to the ‘‘testonly’’ stations in Las Vegas Valley. 

Furthermore, given the results of the 

DAQEM study cited above that the 

‘‘test-and-repair’’ stations are equally as 

effective as the ‘‘test-only’’ stations, the 

assumption of 100% effectiveness for 

the overall I/M program in Las Vegas 

Valley is also not unreasonable. DAQEM 

included a copy of the study of I/M 

effectiveness as appendix C of the 2005 

CO plan. 

With respect to nonroad mobile 

sources, the 2005 CO plan incorporates 

updated information concerning airport 

and railroad operations and activities, 

and reflects use of an emissions model 

(NONROAD) 6 for the other types of 

nonroad sources. NONROAD was not 

available at the time when the 2000 CO 

plan was being prepared and represents 

a significant refinement in the method 

for estimating emissions from nonroad 

sources as compared to the 1991 EPA 

study that was used for the 2000 CO 

plan. Clark County land use/land cover 

data were used as inputs to the 

NONROAD model to estimate revised 

emissions for these categories in both 

the base and future year inventories. 

For the 2005 CO plan, stationary area 

and point sources are largely consistent 

with the corresponding emissions 

estimates for these source categories in 

the 2000 CO plan except for seven 

specific point sources for which the 

future-year projections in the 2005 CO 

plan incorporate potentials to emit 

(rather than projected actual emissions) 

plus a 70 tons per year additional buffer. 

Tables 1 and 2 summarize the 

emissions estimates contained in the 

2005 CO plan. Table 1 represents the 

second Sunday in December and table 2 

represents the second Monday in 

December. The inventories were 

prepared for these particular conditions 

because the dispersion modeling 

demonstration of continued attainment 

is predicated on the December 8–9, 1996 

episode. 

As shown in these two tables, on-road 

motor vehicles continue to represent the 

most significant source category for CO 

emissions in Las Vegas Valley, but the 

contribution from on-road sources is 

expected to decrease from roughly 70 to 

75% of the total CO inventory under 

existing conditions to 65 to 70% by 

2030. Nonroad mobile source account 

for 20 to 25% of the total inventory 

under existing conditions but the 

relative contribution from this source 

category is expected to increase to 25 to 

30% by 2030. The 2005 CO plan 

estimates that stationary area and point 

sources account for 5 to 10% of the CO 

inventory both now and in the future. 

TABLE 1.—LAS VEGAS VALLEY CO NONATTAINMENT AREA EMISSIONS, DECEMBER SUNDAY (TONS) BY SOURCE

CATEGORY

Source category 1996 2006 2010 2015 2020 2030 

On-road motor vehicle ............................................................................. 329 275 287 276 273 296 

Nonroad mobile ........................................................................................ 102 89 99 109 121 143 

Stationary area ......................................................................................... 9 13 14 16 18 22 

Point ......................................................................................................... 3 16 16 16 16 16 

Total .................................................................................................. 445 392 415 418 428 477 

TABLE 2.—LAS VEGAS VALLEY CO NONATTAINMENT AREA EMISSIONS, DECEMBER MONDAY (TONS) BY SOURCE

CATEGORY

Source category 1996 2006 2010 2015 2020 2030 

On-road motor vehicle ............................................................................. 511 441 464 451 447 486 

Nonroad mobile ........................................................................................ 138 111 123 136 150 178 

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TABLE 2.—LAS VEGAS VALLEY CO NONATTAINMENT AREA EMISSIONS, DECEMBER MONDAY (TONS) BY SOURCE

CATEGORY—Continued 

Source category 1996 2006 2010 2015 2020 2030 

Stationary area ......................................................................................... 10 13 15 17 19 23 

Point ......................................................................................................... 3 16 16 16 16 16 

Total .................................................................................................. 662 581 617 619 631 702 

Source: Derived from 2005 CO plan, Table 3–12. 

Based on our review of the 

documentation provided in the 2005 CO 

plan as summarized above, we find that 

the revised base year and future year CO 

emissions inventories reflect the latest 

planning assumptions and emissions 

models and provide a comprehensive 

and accurate assessment of CO 

emissions in Las Vegas Valley for the 

various impact analysis years. 

Furthermore, we find that the revised 

inventories provide a reasonable basis 

upon which to update the dispersion 

modeling analysis, as discussed in the 

following section of this notice. 

D. How Has the Attainment 

Demonstration Changed? 

The 2000 CO plan’s attainment 

demonstration included both an 

areawide and a hot-spot modeling 

analysis at heavily-traveled 

intersections, and the revised 

demonstration in the 2005 CO plan also 

includes both the regional and microscale modeling analyses. As in the 

previous attainment demonstration, 

areawide analysis was conducted using 

the Urban Airshed Model (UAM), 

according to our ‘‘Guidance for 

Application of Urban Areawide Models 

for CO Attainment Demonstrations’’

(1992). 

The 2000 CO plan provided a 

modeling demonstration of attainment 

from the nonattainment conditions in 

1996 for the applicable attainment date 

of 2000 through implementation of new 

control measures. The 2000 CO plan 

also demonstrated continued attainment 

beyond 2000 by developing CO level 

estimates for impact analysis years 2010 

and 2020. Since Las Vegas Valley has 

already attained the CO NAAQS, the 

2005 CO plan does not need to 

demonstrate attainment per se but must 

demonstrate continued attainment of 

the standard, and it does so for the 

following impact analysis years: 2006, 

2010, 2015, 2020 and 2030. 

For the 2005 CO plan, the UAM 

analysis uses the same December 8–9, 

1996 episode as in the previous 

demonstration, but with the revised 

emission inventory information 

described in the previous section of this 

notice. Overall, the spatial pattern of 

predicted 8-hour maximum CO agrees 

with the previous modeling in the 2000 

CO plan and with the distribution of 

observed CO for this period. Unlike the 

modeling documented in the 2000 CO 

plan, no external scaling was needed for 

the UAM results in the new modeling 

runs. The maximum CO concentration 

predicted for the base case 1996 episode 

was 11.4 ppm which is close to the 11.2 

ppm predicted in the 2000 CO plan, 

along Las Vegas Boulevard near the 

intersection with Spring Mountain 

Road. Model performance for the base 

year UAM simulation is within our 

acceptable range of accuracy: +19 

percent for the unpaired peak 

prediction, -15% percent for the paired 

peak prediction, and 1 hour for the 

timing error. See the 2005 CO plan, page 

5–2. Once the model performance was 

verified, the 1996 base case emission 

inventory was projected into the future 

and then these projected emission 

inventories were used with the 1996 

meteorological conditions to simulate 

the impact of emission changes in the 

future. 

The simulations showed that 

emissions in future years with controls 

would continue to support peak 

concentrations well below the 9 ppm 8- 

hour CO standard. Concentrations for 

the 8-hour average are shown for the 

maximum concentration predicted over 

the modeling domain. The predicted 

regional maximum 8-hour average CO 

concentration is 8.0 ppm in the year 

2030, assuming continued 

implementation of all previously 

adopted control measures (e.g., the 

vehicle I/M program and the wintertime 

gasoline specifications). Results for all 

future years modeled are shown in table 

3. 

TABLE 3.—UAM RESULTS FOR

FUTURE YEAR SCENARIOS

Year Concentrations 

(ppm) 

2006 ................................ 7.37 

2010 ................................ 7.17 

2015 ................................ 6.47 

2020 ................................ 6.74 

2030 ................................ 7.96 

Source: 2005 CO plan, Table 6–3. 

The UAM analysis thus shows 

attainment with a margin of safety based 

on continued implementation of fully 

adopted control measures. However, an 

additional model, CAL3QHC must be 

used to determine the maximum CO 

levels in the area. CAL3QHC is needed 

to predict the micro-scale impacts of 

vehicles operating at congested 

intersections. Vehicles operating within 

congested conditions spend more time 

in idle modes that can contribute to 

high levels of CO near the roadways. As 

in the 2000 CO plan, micro-scale 

modeling was completed for three 

intersections (1) Charleston Blvd./ 

Eastern Avenue, (2) Charleston Blvd./ 

Fremont Street and (3) Eastern Avenue/ 

Fremont Street. These three 

intersections comprise the ‘‘5 points’’

area, which is near the Sunrise Acres 

CO monitoring station. For years 2006, 

2010, 2015, 2020 and 2030, traffic data 

from the roadways were combined with 

emission factors from MOBILE6.2 and 

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 maximum 

running 8-hour concentrations. The 

combined results of the CAL3QHC and 

UAM results are shown in Table 4 

below. 

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7Note that DAQEM has not submitted, and EPA 

is not acting on, sub-area motor vehicle emission 

budgets for the Las Vegas area. The modeling 

domain was split into urban and outer areas so that 

DAQEM could examine the sensitivity of the model 

to increases in emissions in the outer areas. For 

transportation conformity purposes, we are only 

acting on the total motor vehicle emissions budgets 

from both areas combined together. 

TABLE 4.—INTERSECTION MAXIMUM PREDICTED COMBINED 8-HOUR CO LEVELS

[ppm] 

Intersection 2006 2010 2015 2020 2030 

Charleston/Eastern ...................................................................................................... 6.14 5.61 4.97 4.67 4.83 

Charleston/Fremont ..................................................................................................... 5.09 4.81 4.31 4.07 4.20 

Eastern/Fremont .......................................................................................................... 5.66 5.32 4.76 4.48 4.58 

Source: 2005 CO plan, Table 6–5. 

As in the 2000 CO plan, in addition 

to roadway intersections modeling, the 

2005 CO plan includes an analysis of 

CO levels at airports in Las Vegas 

Valley. To model the impact of airport 

sources, the Emissions and Dispersion 

Modeling System (EDMS) model was 

again used. This model was developed 

for evaluating the specific emission 

sources typically located at airports. The 

hotspot results from EDMS must be 

combined with the results of the UAM 

analysis to predict the concentrations at 

receptors around the airports. The 2005 

CO plan presents the results of the 

combined UAM and EDMS models for 

the all future years in table 4–5 of 

appendix A. 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 8.45 ppm for 2020. We 

note however that the micro-scale 

analysis for the airports’ environs does 

not extend beyond year 2020, and thus 

that analysis demonstrates continued 

attainment through 2020, but not in year 

2030. 

Based on our review of the 

documentation provided in the 2005 CO 

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 attainment of 

the CO NAAQS in Las Vegas Valley 

through 2020 but that the plan fails to 

demonstrate continued attainment in 

2030 because of the lack of micro-scale 

analysis in the environs of the Clark 

County airports in that year. 

E. Are Las Vegas Valley’s Motor Vehicle 

Emissions Budgets Approvable? 

The CO motor vehicle emissions 

budgets from the EPA-approved 2000 

CO plan are 310.2, 329.5, and 457.4 tons 

of CO per average (December) day for 

years 2000, 2010, and 2020, 

respectively. Conformity determinations 

must be made using the latest planning 

assumptions and emissions models. In 

light of updated population forecasts for 

Las Vegas Valley that show higher levels 

of growth than expected in the 2000 CO 

plan as well as the significant 

differences between the MOBILE6.2 and 

MOBILE5b emissions model, DAQEM, 

in consultation with the RTC, developed 

the 2005 CO plan to replace the budgets 

from the 2000 CO plan, which are based 

on outdated population forecasts and 

MOBILE5b, with new budgets reflecting 

the latest planning assumptions and 

MOBILE6.2 and thereby provide for 

consistency between the CO attainment 

planning in Las Vegas Valley and future 

conformity determinations. 

During the course of preparing the 

2005 CO plan, DAQEM recognized, from 

the revised dispersion modeling 

analysis discussed above, the possibility 

that the reduction in CO emissions 

factors over time due to the 

implementation of new Federal motor 

vehicle standards, the area’s I/M 

program and wintertime gasoline 

specifications, would offset the higher 

level of expected population growth and 

keep the area in attainment of the CO 

NAAQS with some margin of safety. 

Therefore, as part of this SIP revision, 

DAQEM explored scaling up emissions 

to determine how much more the area’s 

emissions estimate could grow while 

still keeping the area in attainment. 

DAQEM conducted several sensitivity 

analyses to determine the impacts of 

scaling up emissions in the modeling 

domain. In the first test runs, the 

modeling domain was split into a 

central urban core and an outer domain. 

Total emissions for all sources were 

doubled in the outer domain. The 

resulting UAM predicted concentrations 

for all future years modeled are shown 

in table 5. A comparison of the results 

in table 5 with the results in table 3 

shows that CO concentrations only 

increase slightly with the doubling of 

outer domain CO emissions. 

TABLE 5.—UAM RESULTS FOR FUTURE YEAR SCENARIOS WITH DOUBLED OUTER DOMAIN EMISSIONS

Year Concentrations 

(ppm) 

2006 ................................ 7.41 

2010 ................................ 7.24 

2015 ................................ 6.54 

2020 ................................ 6.80 

2030 ................................ 8.03 

Source: 2005 CO plan, Table 6–3. 

In the next sensitivity analysis, onroad motor vehicle emissions were 

scaled up from the base case over the 

entire modeling domain until the 

modeled UAM concentrations reached 

8.9 ppm. Then, motor vehicle emissions 

in the outer domain were increased an 

additional 70%. The final revised 

emissions for this sensitivity analysis 

are shown in table 6.7

TABLE 6.—BASE AND SCALED ON-ROAD EMISSIONS FOR THE FINAL SENSITIVITY ANALYSIS

[Tons per December weekday] 

Year 

Base Scaled 

Urban Outer Total Urban Outer Total 

2006 ......................................................................................................... 345 96 441 427 196 623 

2010 ......................................................................................................... 347 117 464 438 252 690 

2015 ......................................................................................................... 320 131 451 453 315 768 

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TABLE 6.—BASE AND SCALED ON-ROAD EMISSIONS FOR THE FINAL SENSITIVITY ANALYSIS—Continued 

[Tons per December weekday] 

Year 

Base Scaled 

Urban Outer Total Urban Outer Total 

2020 ......................................................................................................... 309 138 447 463 354 817 

2030 ......................................................................................................... 318 167 485 464 417 881 

Source: Derived from 2005 CO plan, Table 6–4. 

The final scaled revised emissions 

were then input into UAM to determine 

the resulting peak UAM concentrations. 

Then, to assess the micro-scale impacts 

of increased numbers of vehicles 

operating at congested intersections, the 

UAM results in the appropriate grid 

cells were combined with additional 

CAL3QHC modeling of increased traffic. 

Those combined results, and the 

maximum modeled UAM CO 

concentrations are presented in table 7. 

Increased UAM concentrations in grid 

cells around the airports were also 

examined with the combined EDMS 

modeling. Again, no values were 

modeled above the 9.0 ppm standard in 

any publicly accessible receptor 

locations. The peak combined 

concentration at McCarran International 

Airport for future years is 8.98 ppm for 

2020. However, as noted in the previous 

section of this notice, the micro-scale 

analysis for the airports’ environs does 

not extend beyond 2020. 

TABLE 7.—UAM AND CAL3QHC MAXIMUM PREDICTED 8-HOUR CO LEVELS

[ppm] 

Modeled cell or intersection 2006 2010 2015 2020 2030 

Peak UAM Grid Cell (Domain-wide): ........................................................................... 8.96 8.98 8.98 8.97 8.97 

Peak Combined UAM (for applicable grid cell) & CAL3QHC: 

Charleston/Eastern ...................................................................................................... 7.45 6.97 6.85 6.78 6.84 

Charleston/Fremont ..................................................................................................... 6.17 5.99 5.93 5.88 5.91 

Eastern/Fremont .......................................................................................................... 6.85 6.61 6.54 6.48 6.45 

Source: 2005 CO plan, Appendix A: Tables 5–5 and Table 5–6. 

Since the maximum modeled 

concentrations for this final sensitivity 

test resulted in concentrations close to 

the standard, to account for modeling 

uncertainty, DAQEM also completed an 

air quality trend analysis for the ten year 

period from 1996 to 2005 to provide 

additional support for the modeling 

demonstration. DAQEM prepared this 

additional analysis in response to EPA 

comments after adoption of the 2005 CO 

plan by the Clark County Board of 

Commissioners, and NDEP enclosed this 

analysis, entitled ‘‘Supplement to the 

Carbon Monoxide State Implementation 

Plan Revision,’’ with the February 14, 

2006 SIP revision containing the 2005 

CO plan. 

DAQEM conducted the trend analysis 

based on meteorological and monitoring 

data collected at the Sunrise monitoring 

station for each day from November 1st 

though January 31st (CO season), 

because the 8-hour maximum CO 

concentrations are typically recorded at 

this site. After normalization, linear 

regression analysis and a multivariate 

linear regression analysis was 

performed to predict trends at the site. 

The results of the analysis show a 

continued downward trend of 

maximum CO concentrations for future 

years, independent of meteorology, and 

suggest that event if CO emissions were 

increased by 80%, that future emissions 

would still be below 9.0 ppm, i.e., in 

attainment with the CO NAAQS. 

The 2005 CO plan establishes the 

emissions shown in the final scaled onroad motor vehicle emissions table (see 

the far-right column in table 6, above) as 

the new motor vehicle emissions 

budgets for Las Vegas Valley. The 

budgets are also summarized below in 

table 8. These budgets reflect allocations 

of the safety margin to the motor vehicle 

source category varying from 

approximately 180 tons per year in 2006 

to nearly 400 tons per day in 2030. 

Based on the scaled modeling results in 

the 2005 CO plan and the supplemental 

trend analysis prepared by DAQEM, we 

find that, with the exception of the 2030 

budget, replacement of the current 

budgets with the motor vehicle 

emissions budgets in the 2005 CO plan 

would not interfere with continued 

attainment of the CO NAAQS in Las 

Vegas Valley and are therefore 

approvable. However, we cannot find 

that establishment of the 2030 budget 

would not interfere with continued 

attainment because the micro-scale 

analysis in the environs of the County 

airports does not extend to that year. 

TABLE 8.—ON-ROAD MOTOR VEHICLE

EMISSIONS BUDGETS

[Tons per December weekday] 

Year Budget 

2006 .............................................. 623 

2010 .............................................. 690 

2015 .............................................. 768 

2020 .............................................. 817 

2030 .............................................. 881 

Source: 2005 CO plan, Table 7–1. 

F. How Does This Action Affect 

Transportation Conformity? 

Under section 176(c) of the Act, 

transportation plans, programs, and 

projects in nonattainment or 

maintenance areas that are funded or 

approved under 23 U.S.C or Federal 

Transit Laws, must conform to the 

applicable SIPs. In short, a 

transportation plan is deemed to 

conform to the applicable SIP if the 

emissions resulting from 

implementation of that transportation 

plan are less than or equal to the motor 

vehicle emissions budget established in 

the SIP for the attainment year and other 

analysis years. If the condition is met on 

our proposed approval (i.e., Clark 

County and the State of Nevada 

withdraw the 2030 budget) and our 

action is otherwise finalized as 

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26918 Federal Register / Vol. 71, No. 89 / Tuesday, May 9, 2006 / Proposed Rules 

proposed here today, the CO motor 

vehicle emissions budgets shown in 

table 8 above (minus the 2030 budget) 

must be used by U.S. Department of 

Transportation and the Regional 

Transportation Commission of Southern 

Nevada for transportation conformity 

determinations made after the effective 

date of our final rule. 

IV. Proposed Action and Request for 

Public Comment 

Pursuant to section 110(k) of the Act, 

we propose to approve the Carbon 

Monoxide State Implementation Plan 

Revision, Las Vegas Valley 

Nonattainment Area, Clark County, 

Nevada (October 2005), which was 

adopted by the Clark County Board of 

Commissioners on October 4, 2005 and 

submitted to EPA by NDEP on February 

14, 2006, as a revision to the Nevada SIP 

on the condition that Clark County and 

the State of Nevada withdraw the 2030 

motor vehicle emission budget, or, in 

the alternative, we propose to 

disapprove the plan. The plan 

disapproval will not trigger any Clean 

Air Act 179(b) sanctions. 

Our proposed approval is based on 

our evaluation of the plan submittal and 

determination that the plan’s revised 

base year and projected emission 

inventories and modeling 

demonstration of continued attainment 

of the CO standard through 2020 reflect 

acceptable methods and the most recent 

models and planning assumptions. Our 

proposed disapproval is based on our 

finding that the plan does not 

demonstrate continued attainment in 

year 2030 because it lacks micro-scale 

modeling analysis for the environs of 

the County’s airports in that year. 

Furthermore, we find that, with the 

exception of the 2030 budget, the new 

motor vehicle emissions budgets 

established in the plan and reflecting 

scaled inventories are also consistent 

with continued attainment of the CO 

NAAQS in Las Vegas Valley. Thus, we 

propose to approve the following motor 

vehicle emissions budgets from the 2005 

CO plan as meeting the purposes of 

section 176(c)(1) and the transportation 

conformity rule at 40 CFR part 93, 

subpart A contingent upon the 

withdrawal of the 2030 budget by Clark 

County and the State of Nevada, and to 

disapprove the submitted budgets in the 

2005 CO plan, in the alternative, if no 

such withdrawal is made: 

CO MOTOR VEHICLE EMISSIONS

BUDGET

[December weekday] 

Year Tons per 

day 

2006 .............................................. 623 

2010 .............................................. 690 

2015 .............................................. 768 

2020 .............................................. 817 

Our action in approving the submitted 

plan revision and related motor vehicle 

emissions budgets, if the county and 

state withdraw the 2030 budget and if 

this action is otherwise finalized as 

proposed, would have the effect of 

replacing the existing CO motor vehicle 

emissions budgets from the Las Vegas 

Valley 2000 CO plan for the purposes of 

transportation conformity. EPA is 

soliciting public comment on the issues 

discussed in this document. These 

comments will be considered before 

taking final action. 

V. Statutory and Executive Order 

Reviews 

Under Executive Order 12866 (58 FR 

51735, October 4, 1993), this proposed 

action is not a ‘‘significant regulatory 

action’’ and therefore is not subject to 

review by the Office of Management and 

Budget. For this reason, this proposed 

action is also not subject to Executive 

Order 13211, ‘‘Actions Concerning 

Regulations That Significantly Affect 

Energy Supply, Distribution, or Use’’ (66 

FR 28355, May 22, 2001). This proposed 

action merely approves an air quality 

plan as meeting Federal requirements or 

disapproves the plan in the alternative 

and imposes no additional requirements 

beyond those imposed by state law. 

Accordingly, the Administrator certifies 

that this proposed rule will not have a 

significant economic impact on a 

substantial number of small entities 

under the Regulatory Flexibility Act (5 

U.S.C. 601 et seq.). Because this 

proposed rule approves or disapproves 

in the alternative pre-existing 

requirements under state law and does 

not impose any additional enforceable 

duty beyond that required by state law, 

it does not contain any unfunded 

mandate or significantly or uniquely 

affect small governments, as described 

in the Unfunded Mandates Reform Act 

of 1995 (Pub. L. 104–4). 

This proposed rule also does not have 

tribal implications because it will not 

have a substantial direct effect on one or 

more Indian tribes, on the relationship 

between the Federal Government and 

Indian tribes, or on the distribution of 

power and responsibilities between the 

Federal Government and Indian tribes, 

as specified by Executive Order 13175 

(65 FR 67249, November 9, 2000). This 

proposed action also does not have 

Federalism implications because it does 

not have substantial direct effects on the 

States, on the relationship between the 

national government and the States, or 

on the distribution of power and 

responsibilities among the various 

levels of government, as specified in 

Executive Order 13132 (64 FR 43255, 

August 10, 1999). This proposed action 

merely approves a state plan 

implementing a Federal standard or 

disapproves the plan in the alternative, 

and does not alter the relationship or 

the distribution of power and 

responsibilities established in the Clean 

Air Act. This proposed rule also is not 

subject to Executive Order 13045, 

‘‘Protection of Children from 

Environmental Health Risks and Safety 

Risks’’ (62 FR 19885, April 23, 1997), 

because it is not economically 

significant. 

In reviewing SIP submissions, EPA’s 

role is to approve state choices, 

provided that they meet the criteria of 

the Clean Air Act. In this context, in the 

absence of a prior existing requirement 

for the State to use voluntary consensus 

standards (VCS), EPA has no authority 

to disapprove a SIP submission for 

failure to use VCS. It would thus be 

inconsistent with applicable law for 

EPA, when it reviews a SIP submission, 

to use VCS in place of a SIP submission 

that otherwise satisfies the provisions of 

the Clean Air Act. Thus, the 

requirements of section 12(d) of the 

National Technology Transfer and 

Advancement Act of 1995 (15 U.S.C. 

272 note) do not apply. This proposed 

rule does not impose an information 

collection burden under the provisions 

of the Paperwork Reduction Act of 1995 

(44 U.S.C. 3501 et seq.). 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Carbon monoxide, 

Intergovernmental relations, Reporting 

and recordkeeping requirements. 

Dated: May 1, 2006. 

Wayne Nastri, 

Regional Administrator, Region IX. 

[FR Doc. E6–7032 Filed 5–8–06; 8:45 am] 

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