

[Federal Register: May 9, 2006 (Volume 71, Number 89)]
[Proposed Rules]               
[Page 26910-26918]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr09my06-27]                         

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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.

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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

[[Page 26911]]

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.
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    \1\ 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. The 2005 CO plan also allocates a 
small portion of the safety margins to certain point sources.
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    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.
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    \2\ The 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.
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    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

[[Page 26912]]

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).
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    \3\ Note that the contingency measure requirement was removed 
when EPA made a finding of attainment in June 2005 (See 70 FR 
31353).
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    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 on-road 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

[[Page 26913]]

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 on-road 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 on-road 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\
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    \4\ That is, except for on-road motor vehicles, which reflect 
average daily conditions during the month of December.
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    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

[[Page 26914]]

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 ``test-only'' 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).
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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.
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    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 
``test-only'' 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.
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    \6\ NONROAD 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.
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    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

[[Page 26915]]


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 micro-scale 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
------------------------------------------------------------------------
                                                         Concentrations
                         Year                                (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.

[[Page 26916]]



                       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
------------------------------------------------------------------------
                                                         Concentrations
                         Year                                (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, on-road 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\
---------------------------------------------------------------------------

    \7\ Note 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 6.--Base and Scaled On-Road Emissions For the Final Sensitivity Analysis
                                           [Tons per December weekday]
----------------------------------------------------------------------------------------------------------------
                                                              Base                            Scaled
                     Year                      -----------------------------------------------------------------
                                                  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

[[Page 26917]]


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 on-road 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

[[Page 26918]]

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]
------------------------------------------------------------------------
                                                                Tons per
                             Year                                 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]

BILLING CODE 6560-50-P
