Carbon Monoxide 

Redesignation Request and Maintenance 

Plan 

Las Vegas Valley Nonattainment Area 

Clark County, Nevada 

September 2008 

Clark County Department of Air Quality 

and Environmental Management
Carbon Monoxide Redesignation Request and Maintenance Plan

ACKNOWLEDGMENTS 

CLARK COUNTY BOARD OF COMMISSIONERS 

Rory Reid, Chair 

Chip Maxfield, Vice-Chair 

Susan Brager 

Tom Collins 

Chris Giunchigliani 

Lawrence Weekly 

Bruce Woodbury 

OFFICE OF THE COUNTY MANAGER 

Virginia Valentine, County Manager 

Darryl Martin, Assistant County Manager 

Phil Rosenquist, Assistant County Manager 

Jeff Wells, Assistant County Manager 

DEPARTMENT OF AIR QUALITY AND ENVIRONMENTAL MANAGEMENT 

Lewis Wallenmeyer, Director 

Tina Gingras, Assistant Director 

Dennis Ransel, Planning Manager 

John Koswan, Assistant Planning Manager 

Stephen Deyo, Assistant Planning Manager 

Robert Tekniepe, Principal Management Analyst 

Zheng Li, Sr. Air Quality Modeler 

Richard Ansson, Air Quality Specialist II 

Melissa Hamner, Technical Writer 

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Carbon Monoxide Redesignation Request and Maintenance Plan

EXECUTIVE SUMMARY 

This maintenance plan is a formal request by the Clark County Department of Air Quality and 

Environmental Management to the U.S. Environmental Protection Agency (EPA) to redesignate 

the Las Vegas Valley nonattainment area to attainment of the 8-hour carbon monoxide (CO) 

National Ambient Air Quality Standard (NAAQS). It summarizes the progress of the area in 

attaining the CO standard, demonstrates that all Clean Air Act requirements for attainment have 

been adopted, and presents a plan to assure continued attainment over the next ten years. 

This plan provides a revised CO attainment demonstration that incorporates proposed changes to 

existing control measures contained in the August 2000 CO state implementation plan (SIP) for 

Clark County and the October 2005 CO SIP revision, and makes use of the most recently 

adopted planning variables (e.g., updated vehicle miles traveled projections and population 

forecasts) approved by the designated Metropolitan Planning Organization for the Las Vegas 

urban area, the Regional Transportation Commission of Southern Nevada. The plan also 

provides, among other things, revised motor vehicle emission modeling, new emissions 

inventories, amended control measures, updated area-wide Urban Airshed Modeling, and 

microscale air quality modeling analyses (i.e., hotspot modeling (CAL3QHC) and airport 

modeling (EDMS)) using the updated inventories. 

In the mid-1980s, portions of the Las Vegas Valley began violating the CO NAAQS during the 

winter months. The number and severity of these violations caused EPA to designate the valley 

as a “moderate” nonattainment area upon enactment of the Clean Air Act Amendments in 

November 1990. When Clark County did not attain the CO standards after a one-year extension 

to the required attainment date, EPA reclassified the valley as a “serious” CO nonattainment 

area. The county developed a SIP to establish measures for attaining the standards, and in August 

2000 the Board of County Commissioners adopted the plan. EPA issued a final approval of the 

2000 CO SIP in September 2004, and in June 2005 EPA found that the Las Vegas Valley had 

attained the standards by the applicable date of December 31, 2000. In October 2005 the county 

submitted a revision to the 2000 CO SIP updating CO motor vehicle emissions budgets using 

MOBILE6. The 2005 CO SIP Revision was subsequently approved in August 2006. 

During the past several years, the valley has experienced substantial improvement in air quality: 

no violations of the 8-hour CO standard have been recorded since 1998. There has been a similar 

reduction in the intensity of CO concentrations. CO exceedances (not necessarily violations) 

often totaled 40 or more per year in the 1980s. During 1997 and 1998, the valley experienced 

only four unhealthful and three exceedance days. Exceedances and violations of the 8-hour CO 

NAAQS eased by 1999, and there have been no recorded exceedances since then. 

After EPA approval, the maintenance plan will become a federally enforceable plan that 

identifies how Clark County will maintain the CO NAAQS for the Las Vegas Valley through 

2020. Once approved, the motor vehicle emission budgets contained in the plan will become the 

projected budgets that the Regional Transportation Commission will use for conformity 

determinations in future regional transportation plans. 

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Carbon Monoxide Redesignation Request and Maintenance Plan

TABLE OF CONTENTS 

1.0 INTRODUCTION................................................................................................................ 1-1

1.1 Characteristics and Health Effects of Carbon Monoxide .......................................... 1-1 

1.2 National Ambient Air Quality Standards for Carbon Monoxide............................... 1-1 

1.3 History of the LasVegas Valley Nonattainment Area ............................................... 1-1 

1.4 Required Components of a Redesignation Request................................................... 1-3 

1.5 Use of MOBILE6.2 Emissions Factor Model............................................................ 1-3 

2.0 PRELIMINARY ANALYSIS OF PROPOSED MODIFICATIONS TO EXISTING 

CONTROL MEASURES IN THE NONATTAINMENT AREA ................................... 2-1

2.1 Introduction................................................................................................................ 2-1 

2.2 Cleaner Burning Gasoline: Wintertime Program....................................................... 2-1 

2.3 Vapor Pressure Limitations........................................................................................ 2-2 

2.4 Transportation Control Measures/Transportation Demand Management ................. 2-3 

2.5 Alternative Fuels for Government Fleets Program.................................................... 2-4 

2.6 Summary of Preliminary Control Measure Analysis................................................. 2-4 

3.0 ATTAINMENT OF CARBON MONOXIDE STANDARD............................................ 3-1

3.1 Introduction................................................................................................................ 3-1 

3.2 Historical Perspective ................................................................................................ 3-1 

3.3 Monitoring Network .................................................................................................. 3-2 

3.4 Monitoring Results and Attainment Demonstration.................................................. 3-6 

3.5 Quality Assurance Program ....................................................................................... 3-6 

4.0 STATE IMPLEMENTATION PLAN APPROVAL ........................................................ 4-1

4.1 Introduction................................................................................................................ 4-1 

4.2 Summary of Previous State Implementation Plan Approvals.................................... 4-1 

5.0 PERMANENT AND ENFORCEABLE IMPROVEMENT IN AIR QUALITY........... 5-1

5.1 Introduction................................................................................................................ 5-1 

5.2 Economic Conditions................................................................................................. 5-1 

5.2.1 Population Trends .......................................................................................... 5-1 

5.2.2 Total Full-Time Employment Growth........................................................... 5-2 

5.2.3 Vehicle Miles Traveled.................................................................................. 5-2 

5.3 Meteorological Conditions......................................................................................... 5-2 

5.4 Attainment and Maintenance Control Measures........................................................ 5-5 

5.4.1 Permanent and Enforceable Emissions Reduction Control Measures........... 5-5 

5.4.2 Other Carbon Monoxide Control Programs................................................... 5-7 

5.4.2.1 Contingency Measure Programs.................................................. 5-7 

5.4.2.2 State Mandated and Voluntary Emission Reduction Programs... 5-9 

5.4.3 Stationary Point and Area Source Programs................................................ 5-10 

6.0 SECTION 110 AND PART D REQUIREMENTS ........................................................... 6-1

6.1 Introduction................................................................................................................ 6-1 

6.2 Section 110 Requirements ......................................................................................... 6-1 

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Carbon Monoxide Redesignation Request and Maintenance Plan

6.2.1 Section 110(a)(2) Analysis ............................................................................ 6-1 

6.2.2 Section 110(l) Analysis.................................................................................. 6-2 

6.2.2.1 Ozone ........................................................................................... 6-2 

6.2.2.2 Particulate Matter......................................................................... 6-3 

6.3 Part D Requirements.................................................................................................. 6-4 

7.0 MAINTENANCE PLAN..................................................................................................... 7-1

7.1 Introduction................................................................................................................ 7-1 

7.2 Maintenance Plan Control Measures ......................................................................... 7-1 

7.3 Emission Inventory Summary.................................................................................... 7-2 

7.3.1 Demographic and Transportation Data.......................................................... 7-3 

7.3.2 Summary of Emission Inventories................................................................. 7-3 

7.4 Maintenance Demonstration ...................................................................................... 7-6 

7.4.1 Urban Airshed Model Analysis ..................................................................... 7-7 

7.4.2 Microscale Modeling ................................................................................... 7-12 

7.4.2.1 CAL3QHC Intersection Modeling............................................. 7-12 

7.4.2.2 Airport Modeling Using the Emissions and Dispersion Modeling 

System........................................................................................ 7-13 

7.4.3 Air Quality Trend Analysis—Weight of Evidence Approach..................... 7-13 

7.5 Motor Vehicle Emissions Budget ............................................................................ 7-14 

7.6 Monitoring Network/Verification of Continued Attainment................................... 7-15 

7.7 Contingency Plan..................................................................................................... 7-15 

7.8 Subsequent Maintenance Plan Revisions................................................................. 7-17 

8.0 REFERENCES..................................................................................................................... 8-1

APPENDICES

APPENDIX A: Clark County Wintertime Gasoline Fuel Specifications Study, 

October 2007.................................................................................................... A-1 

APPENDIX B: Clark County Carbon Monoxide Redesignation Request and Maintenance Plan 

Technical Support Document, May 2008 .........................................................B-1 

APPENDIX C: Documentation of the Public Review Process..................................................C-1 

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Carbon Monoxide Redesignation Request and Maintenance Plan

LIST OF FIGURES 

Figure 3-1. Las Vegas Valley CO Air Quality Trends: Number of Exceedances from 1981-

2007. ....................................................................................................................... 3-1 

Figure 3-2. Las Vegas Valley CO Monitoring Sites, 2008. ......................................................3-2 

Figure 3-3. Las Vegas Valley CO Air Quality Trends: Annual Peak 1-Hour Concentrations of 

Continuously Active Monitoring Sites. 1998-2007................................................ 3-4 

Figure 3-4. Las Vegas Valley CO Air Quality Trends: Annual Peak 8-Hour Concentrations of 

Continuously Active Monitoring Sites (1998-2007). ............................................. 3-5 

Figure 3-5. Las Vegas Valley CO Air Quality Trends: Annual Peak 1-Hour Concentrations of 

Periodically Active Monitoring Sites (1998-2006). ............................................... 3-5 

Figure 3-6. Las Vegas Valley CO Air Quality Trends: Annual Peak 8-Hour Concentrations of 

Periodically Active Monitoring Sites (1998-2006). ............................................... 3-6 

Figure 5-1. Clark County Population Growth Rate, 1990-2007................................................ 5-1 

Figure 5-2. Clark County Economic Growth Rate, 1990-2007.................................................5-2 

Figure 5-3. Clark County VMT Growth Rate from 1990-2007. ............................................... 5-3 

Figure 7-1. 1996 Emission Inventory for the Las Vegas Valley CO Modeling Domain.......... 7-4 

Figure 7-2. 2008 Emission Inventory for the Las Vegas Valley CO Modeling Domain.......... 7-5 

Figure 7-3. 2010 Emission Inventory for the Las Vegas Valley CO Modeling Domain.......... 7-5 

Figure 7-4. 2020 Emission Inventory for the Las Vegas Valley CO Modeling Domain.......... 7-6 

Figure 7-5. Spatial Distribution of UAM predicted 8-Hour Maximum CO Concentrations (ppm) 

for the December 8-9, 1996 Episode Using Emission Forecasts for 2008 (Air 

Version of MOBILE6)............................................................................................ 7-8 

Figure 7-6. Spatial Distribution of UAM predicted 8-Hour Maximum CO Concentrations (ppm) 

for the December 8-9, 1996 Episode Using Emission Forecasts for 2010 (Air 

Version of MOBILE6)............................................................................................ 7-9 

Figure 7-7. Spatial Distribution of UAM predicted 8-Hour Maximum CO Concentrations (ppm) 

for the December 8-9, 1996, Episode Using Emission Forecasts for 2020 (Air 

Version of MOBILE6).......................................................................................... 7-10 

Figure 7-8. Boundaries of the Outer Domain and Subdomains. ............................................. 7-11 

Figure 7-9. CAL3QHC Intersection Location Diagram (Five Points Area). .......................... 7-12 

Figure 7-10. Sunrise Monitoring Site: Actual, Predicted, and Normalized CO Trends............ 7-14 

September 2008 vi
Carbon Monoxide Redesignation Request and Maintenance Plan

LIST OF TABLES 

Table 2-1. Control Measures Adopted for Clark County CO SIPs.......................................... 2-1 

Table 2-2. Complex Model Inputs for Clark County—Winter 2006 Gasoline........................ 2-2 

Table 3-1. Las Vegas Valley CO Monitoring Site Locations and Descriptions ...................... 3-2 

Table 3-2. 2004 CO Monitoring Data Summary for the Las Vegas Valley Nonattainment 

Area......................................................................................................................... 3-3 

Table 3-3. 2005 CO Monitoring Data Summary for the Las Vegas Valley Nonattainment 

Area......................................................................................................................... 3-3 

Table 3-4. 2006 CO Monitoring Data Summary for the Las Vegas Valley Nonattainment 

Area......................................................................................................................... 3-3 

Table 3-5. 2007 CO Monitoring Data Summary for the Las Vegas Valley Nonattainment 

Area......................................................................................................................... 3-4 

Table 5-1. 10-Year Monthly Climate Data for Las Vegas for January....................................5-3 

Table 5-2. 10-Year Monthly Climate Data for Las Vegas for November ............................... 5-4 

Table 5-3. 10-Year Monthly Climate Data for Las Vegas for December................................ 5-4 

Table 6-1. Total PM10 Mobile Source Emissions for 2006...................................................... 6-3 

Table 6-2. 2006 24-Hour Controlled PM10 Emissions............................................................. 6-4 

Table 7-1. Summary of Control Measures Used in CO Maintenance SIP and CO 

Attainment/Revision SIPs....................................................................................... 7-2 

Table 7-2. Demographic Data Used to Develop Emission Inventories ................................... 7-3 

Table 7-3. Summary of Total Daily CO Emissions for the Inventory/Modeling Domain.......7-3 

Table 7-4. Peak UAM 8-Hour Average CO Concentrations Predicted for Modeled Years .... 7-7 

Table 7-5. Grid Definition of the Central Urban Subdomain ................................................ 7-11 

Table 7-6. Weekday On-Road Emissions Increases, UAM-Predicted Peak CO, and Resulting 

Emissions Budget for Each Future Year............................................................... 7-12 

Table 7-7. Peak UAM + CAL3QHC 8-Hour Average CO Concentrations Predicted for 

Modeled Years and Each Intersection ..................................................................7-13 

Table 7-8. Peak Total UAM + EDMS 8-Hour CO Concentrations at Las Vegas Airports for 

2008, 2010, and 2020............................................................................................ 7-13 

Table 7-9. Peak 8-Hour CO Concentrations and MVEBs in the Las Vegas Valley..............7-15 

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Carbon Monoxide Redesignation Request and Maintenance Plan

ACRONYMS AND ABBREVIATIONS 

Acronyms 

ASTM American Society for Testing and Materials 

ATE Advanced Truck Stop Electrification 

BCC Clark County Board of County Commissioners 

CAA 1970 Clean Air Act 

CAAA 1990 Clean Air Act Amendments 

CAL3QHC Hot Spot Emissions and Dispersion Modeling System 

CBG cleaner burning gasoline 

CCSD Clark County School District 

CFR Code of Federal Regulations 

CO carbon monoxide 

DAQEM Clark County Department of Air Quality and Environmental 

Management 

DMV Department of Motor Vehicles 

EDMS Airport Emissions and Dispersion Modeling System 

EPA U.S. Environmental Protection Agency 

FMVECP Federal Motor Vehicle Emissions Control Program 

FY fiscal year 

GVWR Gross Vehicle Weight Rating 

I/M Motor Vehicle Inspection and Maintenance (program) 

MVEB motor vehicle emissions budget 

NAAQS National Ambient Air Quality Standards 

NAMS National Air Monitoring Station 

NAC Nevada Administrative Code 

NOx nitrogen oxides 

NDEP Nevada Division of Environmental Protection 

NRS Nevada Revised Statutes 

PM10 particulate matter with an aerodynamic diameter of 10 microns or less 

RTC Regional Transportation Commission of Southern Nevada 

RVP Reid Vapor Pressure 

SIP state implementation plan 

SLAMS State and Local Air Monitoring Station 

TCM Voluntary Transportation Control Measures 

TDM Transportation Demand Management 

UAM Urban Airshed Model 

VMT vehicle miles traveled 

VOC volatile organic compounds 

VVRP Clark County Voluntary Vehicle Repair Program 

Abbreviations 

g/mi grams per mile 

ppm parts per million 

ppmw parts per million by weight 

psi pounds per square inch 

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tpd tons per day 

September 2008 ix
Carbon Monoxide Redesignation Request and Maintenance Plan 

1.0 INTRODUCTION 

The Clark County Department of Air Quality and Environmental Management (DAQEM), in 

coordination with the Nevada Division of Environmental Protection (NDEP), requests that the 

U.S. Environmental Protection Agency (EPA) redesignate the Las Vegas Valley nonattainment 

area to attainment status for the National Ambient Air Quality Standards (NAAQS) for carbon 

monoxide (CO). 

In the past several years, the valley has experienced substantial improvement in air quality: no 8-

hour CO standard violations have been recorded since 1998. The intensity of CO concentrations 

has also been reduced. In June 2005, EPA determined the Las Vegas Valley had attained the 

NAAQS for CO by the applicable date of December 31, 2000, and was eligible for redesignation. 

1.1 CHARACTERISTICS AND HEALTH EFFECTS OF CARBON MONOXIDE 

CO is a colorless, odorless, tasteless gas that enters the body through the lungs, where it is 

absorbed by hemoglobin in the body’s red blood cells. Hemoglobin normally picks up oxygen 

from the lungs and carries it to the body’s tissues. By displacing oxygen in the hemoglobin, CO 

reduces the flow of oxygen to organs, tissues, and the central nervous system. Children, pregnant 

women, and those with cardiovascular or pulmonary disease are most susceptible to risk from 

prolonged exposure to CO at high concentrations. Common symptoms of CO poisoning include 

dizziness, headaches, fatigue, visual impairment, and disorientation. 

CO is principally produced by the incomplete combustion of carbon contained in fossil fuels. 

Most CO in the Las Vegas Valley is emitted from motor vehicles, with peak concentrations 

normally occurring along roadways and near intersections with high traffic levels. Calm winds 

during the late fall and winter, coupled with night and early morning ground-based temperature 

inversions and low precipitation, generally precipitate the buildup of CO concentrations in the 

Las Vegas Valley. 

1.2 NATIONAL AMBIENT AIR QUALITY STANDARDS FOR CARBON 

MONOXIDE 

There are two federal standards for CO: an 8-hour standard of 9 parts per million (ppm) and a 1-

hour standard of 35 ppm. An exceedance is a monitored value equal to or greater than 9.5 ppm 

for an 8-hour average and 35.5 ppm for a 1-hour average. The standard allows for no more than 

one exceedance of either standard in each calendar year; a violation occurs when two or more 

exceedances are recorded at the same monitoring site in the same year. 

1.3 HISTORY OF THE LASVEGAS VALLEY NONATTAINMENT AREA 

In the mid-1980s, parts of the Las Vegas Valley exceeded the CO NAAQS during the winter 

months. Although the valley never exceeded the 1-hour standard, it exceeded the 8-hour standard 

at least once each year. The number and severity of these violations caused EPA to designate the 

valley a “moderate” nonattainment area upon the enactment of the 1990 Clean Air Act 

Amendments (CAAA). The 1970 Clean Air Act (CAA) and its amendments required that 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

moderate nonattainment areas implement the following emission control measures as 

expeditiously as practicable to attain the CO NAAQS by December 31, 1995: 

1. An Oxygenated Gasoline Program during the winter months requiring gasoline to contain no 

less than 3.5 percent oxygen by weight. 

2. An enhanced Motor Vehicle Inspection and Maintenance (I/M) Program meeting CAA 

criteria. 

3. Forecasts of vehicle miles traveled (VMT) in the region, procedures for annual updates and 

reports attesting to the accuracy of the forecasts, and actual VMT estimates based on traffic 

counts on area roadways. 

4. Contingency measures that must be implemented if actual VMT exceeds forecasted VMT or 

if the area fails to attain the standard by the applicable date. 

5. Transportation control measures necessary to demonstrate attainment of the NAAQS (Clean 

Air Act Section 187(b)(2)). 

6. Implementation of all Reasonably Available Control Measures as quickly as practicable. 

Clark County implemented these controls and made significant progress toward attaining the CO 

NAAQS, but fell short of meeting the standard by the applicable date. However, EPA granted 

Clark County a one-year extension because of improved CO levels. When the county did not 

succeed in demonstrating compliance according to CAAA requirements in that year, EPA 

reclassified the Las Vegas Valley as a “serious” CO nonattainment area. 

EPA published the notice of violation reclassifying the area in the Federal Register on October 

2, 1997. The agency set a May 1999 deadline (18 months from the notice publication date) for 

submitting an implementation plan that would demonstrate CO NAAQS attainment by 

December 31, 2000. The CAAA requires that serious nonattainment areas implement all the 

measures for moderate areas listed previously, along with the following: 

1. Gasoline sold during the winter months must contain the level of oxygen necessary to attain 

the standard, in combination with other measures. 

2. Employers of 100 or more people must implement a mandatory travel reduction program that 

requires each company to increase average vehicle occupancy for commutes by at least 25 

percent over the regional average. This requirement can be avoided if the area can show that 

such a program is not needed to demonstrate attainment of the standard or that a comparable 

emission reduction can be achieved by other measures. Congress has since eliminated this 

requirement from the CAAA. 

Areas could also implement an economic incentive program containing fees and marketable 

permits if emission reduction milestones were not met by December 31, 2000. 

Clark County developed a state implementation plan (SIP) to establish measures for attaining CO 

standards by the end of 2000, and in August 2000, the Clark County Board of County 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

Commissioners adopted the plan. In September 2004, EPA issued final approval of the August 

2000 Carbon Monoxide State Implementation Plan, Las Vegas Valley Nonattainment Area, 

Clark County, Nevada (2000 CO SIP). In October 2005, the county commissioners adopted a 

revision to the 2000 CO SIP that updated CO motor vehicle emissions budgets (MVEBs) using 

MOBILE6.2, the latest EPA-approved model for transportation conformity determinations. EPA 

approved the October 2005 Carbon Monoxide State Implementation Plan Revision, Las Vegas 

Valley Nonattainment Area, Clark County, Nevada (2005 CO SIP Revision) in August 2006. 

In June 2005, EPA determined that the Las Vegas Valley had attained the CO NAAQS by the 

applicable date of December 31, 2000, making the area eligible to submit a request for 

redesignation to attainment status for CO. 

1.4 REQUIRED COMPONENTS OF A REDESIGNATION REQUEST 

CAA Sections 107(d)(3)(D) and (E) define the criteria that an area must meet before being 

redesignated to attainment/maintenance status. With the submittal of this redesignation request 

and maintenance plan, the Las Vegas Valley nonattainment area meets the following five 

required criteria: 

1. Attainment of the Standard: Clark County must show that the nonattainment area has attained 

the NAAQS for CO (Section 3). 

2. SIP Approval: The nonattainment area must have a fully approved CO SIP (Section 4). 

3. Improvement in Air Quality due to Permanent and Enforceable Emission Reductions: Clark 

County must demonstrate that the improvement in air quality leading to attainment of the 

standard is due to permanent and federally enforceable emissions reductions (Section 5). 

4. CAA Section 110 and Part D Requirements: Clark County must meet all CAA Section 110 

and Part D requirements. Section 110 describes general requirements for SIPs, and Part D 

contains general requirements applicable to all nonattainment areas (Section 6). 

5. Maintenance Plan: The area must have a fully approved CO maintenance plan that meets 

CAA Section 175a requirements, including a demonstration that the area will maintain the 

standard for at least 10 years following EPA redesignation. The plan must also contain 

contingency measures that could be implemented if the standard is violated at any time 

during the maintenance period (Section 7). 

1.5 USE OF MOBILE6.2 EMISSIONS FACTOR MODEL 

To complete this redesignation request, Clark County used EPA’s current mobile source 

emissions factor model—MOBILE6.2—in concert with updated TransCAD vehicle volume data 

and the Urban Airshed Model (UAM) to estimate CO emissions and to calculate the peak CO 

concentrations for 2008, 2010 and 2020. 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

2.0 PRELIMINARY ANALYSIS OF PROPOSED MODIFICATIONS TO 

EXISTING CONTROL MEASURES IN THE NONATTAINMENT 

AREA 

2.1 INTRODUCTION 

In October 2006, DAQEM commissioned an independent analysis of the current wintertime 

gasoline specifications that apply in the Las Vegas Valley, as well as an evaluation of possible 

changes to those specifications (Appendix A of the Clark County Wintertime Gasoline Fuel 

Specifications Study, October 2007). In the analysis, on-road mobile source CO emission totals 

were estimated and future year CO concentration peaks were assessed using the UAM for 

various control measure modifications in a manner consistent with the 2005 CO SIP Revision. 

The analysis was intended to provide DAQEM with the necessary guidance to develop a set of 

control measures to be used in the development of this redesignation request and maintenance 

plan. 

The analysis began by focusing on discontinuing the CO SIP credits taken from the Cleaner 

Burning Gasoline (CBG) Wintertime Fuels Program and relaxing the Reid Vapor Pressure 

(RVP) wintertime gasoline requirements. Proposing these programs’ discontinuation or 

modification is appropriate at this time because it would reduce the cost of compliance for 

consumers and businesses, and facilitate increased motor fuel supplies to the Las Vegas Valley, 

without jeopardizing compliance with the CO standard. 

The analysis also evaluated discontinuing the CO SIP credits taken from the Voluntary 

Transportation Control Measures/Transportation Demand Management (TCM/TDM) Program 

and the Alternative Fuels for Government Fleets Program. These evaluations were performed 

because of the limited reductions in CO emissions attributable to both measures. 

Table 2-1 provides the current adoption and implementation dates for the control measures in the 

1995 and 2000 CO SIPs and the 2005 CO SIP Revision. 

Table 2-1. Control Measures Adopted for Clark County CO SIPs 

Control Measure Adoption Date 

Oxygenated Gasoline Program 1991/1995 

CBG Wintertime Fuels Program 1999 

Reduced RVP Gasoline Program 1995 

Motor Vehicle I/M Program 1978 

TCM/TDM Program 1999 

Alternative Fuels for Government Fleets Program 1991 

2.2 CLEANER BURNING GASOLINE: WINTERTIME PROGRAM 

Section 54 of the Clark County Air Quality Regulations sets forth the CBG Wintertime Fuels 

Program for Clark County, which requires a low sulfur and aromatic content in gasoline sold 

between November 1 and March 31. As outlined in Section 54, the maximum sulfur content for 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

wintertime fuels sold in Clark County is currently established at 80 parts per million by weight 

(ppmw), with an optional flat sulfur standard for producers and importers not to exceed 40 

ppmw. Similarly, the maximum aromatic content of wintertime fuels sold in Clark County is 

established at 30 percent by volume, with an optional flat aromatic hydrocarbon standard for 

producers and importers not to exceed 25 percent by volume. 

DAQEM evaluated discontinuing the CO SIP credits taken from the CBG Wintertime Fuels 

Program as part of this redesignation request and maintenance plan because wintertime sulfur 

contents of CBG became redundant when federal Tier 2 gasoline sulfur limits of 30 ppm 

average, with a maximum cap of 80 ppm, were fully implemented in 2006. 

The analysis included 2006 winter fuel properties for Clark County and a CO effects estimate 

caused by a revision to the aromatics content (as reflected in the 2006 nationwide average). 

Winter gasoline fuel properties for Clark County and the nationwide average aromatic level were 

taken from the Alliance of Automobile Manufacturers’ winter 2006 fuel survey data. Table 2-2 

shows Clark County gasoline properties. 

Table 2-2. Inputs for Clark County—Winter 2006 Gasoline 

Fuel Property Clark County Gasoline 

MTBE (wt% oxygen) 0 

ETBE (wt% oxygen) 0 

Ethanol (wt% oxygen) 3.47 

TAME (wt% oxygen) 0 

Sulfur (ppm) 31 

RVP (psi) 8.8 

E200 (%) 46.4 

E300 (%) 78.7 

Aromatics (vol%) 20.2 

Olefins (vol%) 6.7 

Benzene (vol%) 0.60 

Source: Winter fuel survey data (Alliance of Automobile Manufacturers’ Winter 2006 Fuel Survey Data). 

The evaluation concluded that very little impact on future CO emissions occurred when the CO 

SIP credits taken from the CBG Wintertime Fuels Program were discontinued (Appendix A). As 

previously mentioned, this is because Clark County wintertime fuel sulfur content requirements 

became redundant when federal Tier 2 gasoline rules were implemented. Additionally, the 

aromatic content requirements of wintertime fuels do not appear to impose any significant 

burden on fuel suppliers, negating any issue with regards to the supply of gasoline to Clark 

County. 

2.3 VAPOR PRESSURE LIMITATIONS 

Chapter 590 of the Nevada Revised Statutes (NRS) and Chapter 590 of the Nevada 

Administrative Code (NAC) set forth the reduced RVP gasoline requirements for wintertime 

fuels sold in Clark County (October 1 through March 31). Adopted by the Nevada Department of 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

Agriculture, these regulations set a maximum RVP of 9 pounds per square inch [psi] for gasoline 

sold in Clark County. 

DAQEM evaluated relaxing the RVP for wintertime fuels sold in Clark County from 9 to 13.5 

psi to coincide with the specification guides in Volume 05.02, “Petroleum Products and 

Lubricants,” of D4814-01a, “Standard Specification for Automotive Spark-Ignition Engine 

Fuel,” in the American Society for Testing and Materials’ (ASTM) 2002 Annual Book of ASTM 

Standards. 

Regionally, only Clark County, Nevada, and Phoenix, Arizona, require a reduced wintertime 

RVP fuel specification as part of their overall CO control strategy. The reduced RVP 

requirement in Clark County contributes to reduced motor vehicle fuel supplies in the Las Vegas 

Valley because it precludes the distribution and sale of conventional and reformulated gasoline, 

which is sold throughout the rest of the southwestern United States during the winter season. 

Additionally, the proposed relaxation of the RVP for wintertime fuels in Clark County is likely 

to have a positive impact on gasoline supplies in Clark County without causing or contributing to 

future CO NAAQS exceedances. 

An analysis using the standard EPA version of MOBILE6 concluded that the largest single 

impact on CO emissions is associated with relaxing the RVP requirement. It should be noted, 

however, that the MOBILE6 algorithm for modeling RVP impacts on CO emissions is quite 

dated and has been shown to be of questionable validity for the later model-year vehicles that 

dominated this analysis (Sierra Research 2005). Therefore, the impact of relaxing the RVP 

requirement for wintertime fuels sold in Clark County on CO emissions based on the standard 

EPA version of MOBILE6 is likely to be considerably overstated. 

The overall analysis concluded that while relaxing the RVP wintertime fuel requirement 

continues to have the largest single impact on future CO emissions, the proposed change to RVP 

requirements would not jeopardize compliance with the CO standard (see Appendix A). 

2.4 TRANSPORTATION CONTROL MEASURES/TRANSPORTATION DEMAND 

MANAGEMENT 

When EPA reclassified the Las Vegas Valley as a “serious” CO nonattainment area in October 

1997, Clark County was required to evaluate and implement TCMs to further reduce CO 

emissions. In 1999, the Transportation Demand Management Division of the Regional 

Transportation Commission of Southern Nevada (RTC), through the adoption of the fiscal year 

(FY) 1998-2000 Transportation Improvement Plan, implemented the Club Ride commuter 

services program (formally known as CAT MATCH). It included employer based commuter 

incentive programs, telecommuting incentives, and area-wide ridesharing programs. 

DAQEM evaluated discontinuing the CO SIP credits taken from the TCM/TDM Program control 

measure. Although this measure still assists in Clark County’s air quality improvement efforts, 

the limited reductions in CO emissions attributed to the measure suggests that the SIP credits 

taken from this measure could be discontinued without impeding Clark County’s ability to 

maintain the CO NAAQS (Appendix A). 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

2.5 ALTERNATIVE FUELS FOR GOVERNMENT FLEETS PROGRAM 

NRS and NAC 486A set forth the Alternative Fuels for Government Fleets Program regulations. 

Adopted in 1991 and administered by NDEP, these regulations establish procedures for 

accelerating the acquisition and use of alternative fueled vehicles in government fleets. 

DAQEM evaluated discontinuing the CO SIP credits taken from the Alternative Fuels for 

Government Fleets Program. Although the program still assists in Clark County’s air quality 

improvement efforts, the limited reductions in CO emissions attributed to the program suggest 

that the SIP credits taken from this program could be discontinued without impeding Clark 

County’s ability to maintain the CO NAAQS (Appendix A). 

2.6 SUMMARY OF PRELIMINARY CONTROL MEASURE ANALYSIS 

During the past several years, the Las Vegas Valley has experienced substantial improvements in 

air quality; no 8-hour CO standard violations have been recorded since 1998, and the intensity of 

CO concentrations has fallen. Because of this, DAQEM evaluated the impact of relaxing the 

RVP gasoline requirements, and discontinuing the CO SIP credits taken from the CBG 

Wintertime Fuels Program, the TCM/TDM Program and the Alternative Fuels for Government 

Fleets Program. This section provided the initial analysis of the proposed changes. 

As previously discussed, this analysis was only intended to provide necessary guidance to 

develop a set of control measures to be used in the development of the redesignation request and 

maintenance plan. The analysis was not intended to demonstrate maintenance of the CO NAAQS 

or establish future year MVEBs. 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

3.0 ATTAINMENT OF CARBON MONOXIDE STANDARD 

3.1 INTRODUCTION 

The first required component of an area’s redesignation/maintenance request is a demonstration 

that it has attained the CO NAAQS. Attainment is demonstrated when two consecutive years of 

monitoring data for each site show no more than one exceedance per year of either the 8-hour (9 

ppm) or 1-hour (35.0 ppm) standard. The information contained in this section demonstrates, as 

required by CAA Section 107(d)(3)(E), that the Las Vegas Valley nonattainment area has 

attained the CO NAAQS. This is based on quality-assured monitoring data representative of the 

location of expected CO maximum concentrations in the nonattainment area. 

3.2 HISTORICAL PERSPECTIVE 

Prior to 1998, the Las Vegas Valley regularly exceeded the national standards for CO in the 

wintertime. With the implementation of several control programs, CO concentrations began to 

decrease substantially. Data from the regional monitoring network indicate that the Las Vegas 

Valley nonattainment area has not violated the 8-hour standard for CO since 1998. An 

exceedance of the 1-hour CO national standard has never been recorded. In addition, the 

magnitude of observed CO concentrations has declined dramatically since monitoring began. 

Figure 3-1 illustrates the improvement in CO air quality since 1981. 

24

6

4

1 1 000000000

27

41

32

22

27

2 3 3 2

13

18

32

33

0

5

10

15

20

25

30

35

40

45

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

Year

Days

Figure 3-1. Las Vegas Valley CO Air Quality Trends: Number of Exceedances from 1981-2007. 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

3.3 MONITORING NETWORK 

The current CO ambient air monitoring network in the Las Vegas Valley consists of four State 

and Local Air Monitoring Stations (SLAMS) and one National Air Monitoring Station 

(NAMS)/SLAMS (Table 3-1). DAQEM operates the monitoring system, which is governed by a 

set of quality assurance and quality control procedures approved by EPA and subject to periodic 

EPA performance audits. All sites have population exposure as their monitoring objective except 

Sunrise Acres, which has highest concentration as its monitoring objective. 

Table 3-1. Las Vegas Valley CO Monitoring Site Locations and Descriptions 

Site Name Address Type Predominant Wind 

Direction 

East Sahara 4001 E. Sahara Ave. SLAMS Southwest 

Orr School Maryland Pkwy. & Flamingo Road SLAMS Southwest 

Winterwood 5483 Club House Dr. SLAMS Southeast 

Sunrise Acres 2501 S. Sunrise Ave. SLAMS Southwest 

J.D. Smith 1301B E. Tonopah NAMS/SLAMS Northwest 

Source: 2000 CO SIP. 

Figure 3-2 shows the current CO monitoring locations. Tables 3-2 through 3-5 contain summary 

data for all active and inactive sites in operation from 2004 through 2007. 

Figure 3-2. Las Vegas Valley CO Monitoring Sites, 2008. 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

Table 3-2. 2004 CO Monitoring Data Summary for the Las Vegas Valley Nonattainment Area1

1-Hour 8-Hour Site Name 

Max ppm 2nd Max ppm Max ppm 2nd Max ppm 

City Center 7.2 5.8 3.7 3.5 

East Sahara 5.6 5.5 5.2 4.7 

Orr School 4.9 4.7 4.1 3.7 

Winterwood 4.5 4.2 3.3 3.3 

South Las Vegas Blvd. 5.2 4.0 2.9 2.6 

Sunrise Acres 7.0 6.5 5.8 5.1 

J.D. Smith 5.8 5.7 3.8 3.7 

Freedom Park 6.7 6.5 4.9 4.8 1

1-hr standard = 35 ppm; 8-hr standard = 9 ppm. Due to mathematical rounding, values ≥ 35.5 and 9.9 ppm are necessary to exceed the 

national standard. 

Table 3-3. 2005 CO Monitoring Data Summary for the Las Vegas Valley Nonattainment Area1

1-Hour 8-Hour Site Name 

Max ppm 2nd Max ppm Max ppm 2nd Max ppm 

City Center 5.1 5.1 3.7 3.4 

East Sahara 5.1 5.1 4.6 4.5 

Orr School 5.1 5.0 4.2 3.8 

Winterwood 4.7 4.5 3.7 3.5 

South Las Vegas Blvd. 4.2 4.2 2.3 2.3 

Sunrise Acres 6.4 6.3 5.3 5.2 

J.D. Smith 5.6 5.4 4.1 3.9 

Freedom Park 5.7 5.4 4.6 4.1 1

1-hr standard = 35 ppm; 8-hr standard = 9 ppm. Due to mathematical rounding, values ≥ 35.5 and 9.9 ppm are necessary to exceed the 

national standard. 

Table 3-4. 2006 CO Monitoring Data Summary for the Las Vegas Valley Nonattainment Area1

1-Hour 8-Hour Site Name 

Max ppm 2nd Max ppm Max ppm 2nd Max ppm 

City Center2 4.8 4.5 2.9 2.9 

East Sahara 5.5 5.2 4.5 4.2 

Orr School 4.8 4.7 3.9 3.7 

Winterwood 4.2 4.0 3.4 3.4 

South Las Vegas Blvd.3 4.3 4.2 2.7 2.5 

Sunrise Acres 6.6 6.3 5.3 5.0 

J.D. Smith 5.3 4.8 3.8 3.7 

Freedom Park4 --- --- --- --- 1

1-hr standard = 35 ppm; 8-hr standard = 9 ppm. Due to mathematical rounding, values ≥ 35.5 and 9.9 ppm are necessary to exceed the 

national standard. 

2

Ceased operation on April 30, 2006. 

3

Ceased operation on April 3, 2007. 

4

Ceased operation on April 30, 2005. 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

Table 3-5. 2007 CO Monitoring Data Summary for the Las Vegas Valley Nonattainment Area1

1-Hour 8-Hour Site Name 

Max ppm 2nd Max ppm Max ppm 2nd Max ppm 

East Sahara 4.3 4.2 4.0 3.7

Orr School 4.5 4.1 3.4 2.9

Winterwood 3.9 3.8 3.4 2.9

South Las Vegas Blvd.2 2.8 2.8 2.0 1.9

Sunrise Acres 4.7 4.6 4.1 3.8

J.D. Smith 5.0 4.5 3.0 2.8 1

1-hr standard = 35 ppm; 8-hr standard = 9 ppm. Due to mathematical rounding, values ≥ 35.5 and 9.9 ppm are necessary to exceed the 

national standard. 

2

Ceased operation on April 30, 2007. 

Figures 3-3 and 3-4 show the continuous downward long-term trend in 1-hour and 8-hour firsthighest CO concentrations for all continuously active monitoring sites from 1998 through 2007. 

0

2

4

6

8

10

12

14

16

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Year

Concentration (ppm) High 1-Hour 

Average

East Flamingo/Orr East Sahara J.D. Smith

S. Las Vegas Blvd. Sunrise Acres Winterw ood

Figure 3-3. Las Vegas Valley CO Air Quality Trends: Annual Peak 1-Hour Concentrations of 

Continuously Active Monitoring Sites. 1998-2007. 

September 2008 3-4
Carbon Monoxide Redesignation Request and Maintenance Plan 

0

2

4

6

8

10

12

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Year

Concentration (ppm) High 8-Hour Average

East Flamingo/Orr East Sahara J.D. Smith S. Las Vegas Blvd.

Sunrise Acres Winterwood EPA 8-Hour Standard

Figure 3-4. Las Vegas Valley CO Air Quality Trends: Annual Peak 8-Hour Concentrations of 

Continuously Active Monitoring Sites (1998-2007). 

Figures 3-5 and 3-6 show the continuous downward long-term trend in 1-hour and 8-hour firsthighest CO concentrations for all periodically active monitoring sites from 1998 through 2006. 

0

2

4

6

8

10

12

1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Concentration (ppm) High 1-Hour Average

Boulder City Boulder Highw ay City Center Craig Road Freedom Park

Green Valley Henderson Paul Meyer Pauline Way

Figure 3-5. Las Vegas Valley CO Air Quality Trends: Annual Peak 1-Hour Concentrations of 

Periodically Active Monitoring Sites (1998-2006). 

September 2008 3-5
Carbon Monoxide Redesignation Request and Maintenance Plan 

0

1

2

3

4

5

6

7

8

9

10

1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Concentration (ppm) High 8-Hour 

Average

Boulder City Boulder Highw ay City Center Craig Road

Freedom Park Green Valley Henderson Paul Meyer

Pauline Way EPA 8-Hour Standard

Figure 3-6. Las Vegas Valley CO Air Quality Trends: Annual Peak 8-Hour Concentrations of 

Periodically Active Monitoring Sites (1998-2006). 

3.4 MONITORING RESULTS AND ATTAINMENT DEMONSTRATION 

The monitoring data presented in Tables 3-2 through 3-5 and Figures 3-3 through 3-6 verify that 

the Las Vegas Valley nonattainment area has been in attainment with the CO NAAQS since 

1999, including the most recent two-year period (2006-2007), in accordance with the federal 

requirements of Title 40, Part 58 of the Code of Federal Regulations (40 CFR 58). The data also 

illustrate the downward trend in CO concentrations in the Las Vegas Valley. 

Data recovery rates for the monitors exceed the 75 percent completeness requirement for all 

years in accordance with all state and federal quality assurance procedures. 

3.5 QUALITY ASSURANCE PROGRAM 

CO data for the Las Vegas Valley nonattainment area have been collected and quality-assured in 

accordance with 40 CFR Part 58, Appendix A (EPA’s “Quality Assurance Handbook for Air 

Pollution Measurement Systems, Volume II: Ambient Air Specific Methods”) and the DAQEM 

Quality Assurance Project Plan for Gaseous Criteria Pollutant Monitoring (DAQEM 2006). 

CO data are recorded in the EPA Aerometric Information Retrieval System and available for 

public review in air quality monitoring reports that DAQEM produces annually. The data are 

also available to the public in the Air Quality Index report on the DAQEM Monitoring Section 

Web page and are reported in local media. 

September 2008 3-6
Carbon Monoxide Redesignation Request and Maintenance Plan 

4.0 STATE IMPLEMENTATION PLAN APPROVAL 

4.1 INTRODUCTION 

The second required component of an area’s redesignation/maintenance request, per CAA 

Section 110(k), is a fully approved SIP. Section 110(k) addresses completeness findings, 

deadlines for EPA actions, types of EPA actions, and sanctions that may be applied to areas 

failing to meet CAAA requirements. The information in this section demonstrates, as required by 

Section 110(k), that the state of Nevada has an approved CO SIP for the Las Vegas Valley 

nonattainment area. 

4.2 SUMMARY OF PREVIOUS STATE IMPLEMENTATION PLAN APPROVALS 

In accordance with the CAAA, the Las Vegas Valley nonattainment area was initially classified 

as “moderate” for CO. When Clark County did not attain the CO standards after a one-year 

extension to the required attainment date, EPA reclassified the area as “serious” for CO. In order 

to meet the “serious” nonattainment area requirements, DAQEM submitted a CO SIP to EPA in 

August 2000. EPA issued a final approval of the 2000 CO SIP in September 2004, and in June 

2005 found that the Las Vegas Valley had attained the standards by the applicable date of 

December 31, 2000. 

In October 2005, DAQEM submitted a revision to the 2000 CO SIP to reflect updated CO 

MVEBs using MOBILE6.2, the latest EPA-approved model for transportation conformity 

determinations. The CO SIP Revision focused on recalculating the emissions for on-road and 

non-road sources using the newer MOBILE6.2 and NONROAD2004 models. 

In August 2006, the EPA approved the 2005 CO SIP revision. The state of Nevada thus has an 

approved CO SIP for the Las Vegas Valley nonattainment area, as required by CAA Section 

110(k). 

September 2008 4-1
Carbon Monoxide Redesignation Request and Maintenance Plan 

5.0 PERMANENT AND ENFORCEABLE IMPROVEMENT IN AIR 

QUALITY 

5.1 INTRODUCTION 

The third required component of an area’s redesignation/maintenance request is a demonstration 

that improved air quality is due to permanent and enforceable emission reductions from the 

implementation of an applicable SIP. This section shows that the improved air quality in the Las 

Vegas Valley is the result of permanent and enforceable emission reduction control measures, as 

opposed to adverse economic or meteorological conditions. 

5.2 ECONOMIC CONDITIONS 

Between 1990 and 2007, the Las Vegas Valley has experienced strong economic growth while 

continuously reducing ambient CO levels. Based on these trends, it is reasonable to conclude that 

improvements in CO concentrations in the valley are attributable to emission reduction control 

measures that are permanent and enforceable, as opposed to a downturn in the valley’s economy. 

5.2.1 Population Trends 

Clark County is one of the fastest-growing counties in the nation. Its population increased by 

1,125,949 residents between 1990 and 2007, raising the total population to 1,996,542—an 

increase of 177 percent since 1990 (Clark County Department of Comprehensive Planning 

2007). Figure 5-1 illustrates population growth from 1990 to 2007. 

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

Year

Population

 Source: Clark County Department of Comprehensive Planning (2007). 

Figure 5-1. Clark County Population Growth Rate, 1990-2007. 

September 2008 5-1
Carbon Monoxide Redesignation Request and Maintenance Plan 

5.2.2 Total Full-Time Employment Growth 

The Las Vegas Valley has consistently led the nation in job growth since 1990, with most of 

those jobs created by the resort industry. From 1990 to 2007, total full-time employment in the 

valley grew from 374,642 to 926,783, an increase of 247 percent (UNLV Center for Business 

and Economic Research 2008). Figure 5-2 illustrates Las Vegas job growth from 1990 to 2007. 

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

900,000

1,000,000

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

Year

Population

 Source: UNLV Center for Business and Economic Research (2008). 

Figure 5-2. Clark County Economic Growth Rate, 1990-2007. 

5.2.3 Vehicle Miles Traveled 

With the rapid population growth in Clark County, VMT has similarly increased. The Las Vegas 

Valley’s VMT increased by 29,786,606 from 1990 to 2007, raising total VMT to 42,733,565—a 

330 percent increase since 1990 (RTC 2007). Figure 5-3 illustrates the valley’s VMT growth 

from 1990 to 2007. 

5.3 METEOROLOGICAL CONDITIONS 

Las Vegas sits in a broad desert valley that runs about 600 miles from northwest to southeast. 

The mountains surrounding the valley extend from 2,000 to 10,000 feet above sea level. A 

general wintertime climatic summary shows that winters are mild and pleasant. Skies are mostly 

clear, and afternoon temperatures usually approach 60 degrees. Pacific storms occasionally bring 

rain to the valley; however, the Sierra Nevada and Spring Mountains generally block Pacific 

moisture. Nighttime temperatures fall below freezing, on average, 24 days per year. Snow 

accumulation is rare, perhaps an inch or more every four to five years. 

September 2008 5-2
Carbon Monoxide Redesignation Request and Maintenance Plan 

0.00

5,000,000.00

10,000,000.00

15,000,000.00

20,000,000.00

25,000,000.00

30,000,000.00

35,000,000.00

40,000,000.00

45,000,000.00

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

Year

Vehicle Miles Traveled

 Source: Regional Transportation Commission of Southern Nevada (2008) 

Figure 5-3. Clark County VMT Growth Rate from 1990-2007. 

Cooler nights, combined with the local mountain topography, can create temperature inversions 

where a layer of cold air is contained in the valley. Warm air then hovers above, trapping CO 

pollutants. Such weather happens regularly and is characterized by stable atmospheric 

conditions, light winds, sunny days, and clear, cold nights. Weather conditions unfavorable for 

CO development include periods of unstable atmospheric conditions: clouds, precipitation, 

milder temperatures, wind, and good dispersion all impede CO development. 

Tables 5-1, 5-2, and 5-3 summarize temperature and precipitation data (as well as departures 

from normal) recorded at McCarran International Airport from 1998 to 2007 during January, 

November, and December, respectively. A column in each table shows years in which favorable 

meteorological conditions, such as increased precipitation combined with increased 

temperatures, led to low CO concentrations. 

Table 5-1. 10-Year Monthly Climate Data for Las Vegas for January 

Year Temperature in 

Celsius 

Departure from 

Normal 

Precipitation 

(0.01 inches or 

greater) 

Departure from 

Normal 

Favorable 

Meteorology 

2007 7.9 .4 2 -9 

2006 10.1 2.6 0 -12 

2005 10.8 3.3 8 41 X 

2004 8.7 1.2 0 -12 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

Table 5-1. 10-Year Monthly Climate Data for Las Vegas for January (cont.) 

Year Temperature in 

Celsius 

Departure from 

Normal 

Precipitation 

(0.01 inches or 

greater) 

Departure from 

Normal 

Favorable 

Meteorology 

2003 12.4 4.9 0 -12 

2002 8.0 .5 0 -12 

2001 8.0 .5 5 10 X 

2000 10.8 3.3 0 -12 

1999 10.1 2.6 0 -12 

1998 9.4 1.9 2 -8 

Source: Monthly Climatic Data for the World as prepared by the National Oceanic and Atmospheric Administration, Asheville, NC.

Table 5-2. 10-Year Monthly Climate Data for Las Vegas for November 

Year Temperature in 

Celsius 

Departure from 

Normal 

Precipitation Departure from 

Normal 

Favorable 

Meteorology 

2007 16.1 3.3 2 6 X 

2006 14.7 1.9 0 -10 

2005 14.3 2.3 0 -10 

2004 12.1 -.7 4 33 X 

2003 11.6 -1.2 2 6 X 

2002 13.9 1.1 3 -7 

2001 14.9 2.1 1 -8 

2000 10.1 -2.7 0 -10 

1999 15.0 2.2 0 -10 

1998 12.5 -.3 2 -2 

Source: Monthly Climatic Data for the World as prepared by the National Oceanic and Atmospheric Administration, Asheville, NC.

Table 5-3. 10-Year Monthly Climate Data for Las Vegas for December 

Year Temperature in 

Celsius 

Departure from 

Normal 

Precipitation Departure from 

Normal 

Favorable 

Meteorology 

2007 7.5 -.1 1 -7 

2006 8.7 1.1 2 -4 

2005 10.1 2.5 0 -9 

2004 9.6 2.0 2 44 X 

2003 8.9 1.3 3 15 X 

2002 8.7 1.1 2 -7 

2001 7.6 .0 0 -9 

2000 9.7 2.1 1 -8 

1999 9.4 1.8 0 -9 

1998 8.7 1.1 1 -8 

Source: Monthly Climatic Data for the World as prepared by the National Oceanic and Atmospheric Administration, Asheville, NC.

Wintertime data indicates that over a ten-year period, January had two favorable months, 

November three, and December two. Because so few months were considered favorable to low 

CO concentrations, it is reasonable to conclude that improvements in CO concentrations are 

September 2008 5-4
Carbon Monoxide Redesignation Request and Maintenance Plan 

attributable to emission reduction control measures that are permanent and enforceable, rather 

than weather conditions favorable to low CO concentrations. 

5.4 ATTAINMENT AND MAINTENANCE CONTROL MEASURES 

This plan demonstrates maintenance of the CO NAAQS in 2020 with the following permanent 

and enforceable emissions reduction control measures: (1) the Federal Motor Vehicle Emissions 

Control Program (FMVECP), (2) the state I/M Program, (3) the Oxygenated Gasoline Program, 

(4) a relaxed RVP gasoline standard (as modified in Section 2), and (5) the state Technician 

Training and Certification Program. Other emissions reduction control measures providing 

further CO reductions, but not used for emission reduction credit in this plan, are discussed, 

along with a brief summary of current stationary point and area source programs. 

5.4.1 Permanent and Enforceable Emissions Reduction Control Measures 

The five control measures used for numeric emission reduction credit in this CO maintenance 

plan are described below. These measures, which are permanent and enforceable, will be in place 

through the maintenance year of 2020 and will ensure continued CO emissions reductions in the 

nonattainment area, as demonstrated in Section 7.4. 

1. FMVECP

The first control measure is the FMVECP. This program, originally established in 1968, has 

dramatically reduced CO emissions by continually requiring automobile manufacturers to 

produce new vehicles that meet increasingly tighter emission standards. These requirements 

include the federal Tier 2 emission standards for new light- and medium-duty cars and trucks, as 

well as standards for heavy-duty on-road and non-road vehicles. 

Before CO emissions were regulated, a typical 1950s car emitted approximately 87 grams per 

mile (g/mi) of CO. Federal rules have since lowered CO emissions to the point where today’s 

requirements limit cars to no more than 3.4 g/mi of CO, a 95 percent reduction (EPA 2007). 

DAQEM will continue to rely on the FMVECP as a primary control measure for maintaining the 

CO NAAQS. Emission reductions mandated by the FMVECP have been primarily responsible 

for the large decrease in CO concentrations in the Las Vegas Valley. As newer, cleaner vehicles 

replace older, dirtier ones, CO emissions will continue to decline. 

2. State Vehicle I/M Program

The second control measure is the state’s I/M Program. NRS and NAC 445B set forth the 

regulations governing motor vehicles in Clark County. Adopted in 1978 and administered by the 

Nevada Department of Motor Vehicles (DMV), these regulations establish annual testing 

procedures for 1968 or newer gasoline-powered vehicles, regardless of size, and for dieselpowered vehicles with a manufacturer’s gross vehicle weight rating (GVWR) of up to 10,000 

pounds. The I/M Program also allows for exemptions from emissions testing for new vehicles on 

their first and second registration, new hybrid-electric vehicles for the first five model years, 

September 2008 5-5
Carbon Monoxide Redesignation Request and Maintenance Plan 

alternative fuel vehicles, vehicles registered as Classic Rods or Classic Vehicles and driven 

2,500 miles or less per year, and vehicles registered as Replica Vehicles. 

Nevada uses on-board diagnostic testing procedures for 1996 and newer vehicles, while older 

vehicles are tested with a two-speed idle test. The program also includes waiver provisions for 

motorists who spend $450 on emission-related repairs. No waivers are allowed for vehicles that 

emit visible smoke. 

As part of this CO redesignation request and maintenance plan, DAQEM will continue to rely on 

the I/M Program as a primary control measure for maintaining the CO NAAQS. Emission 

reductions since the program’s inception have been central to decreasing CO concentrations in 

the Las Vegas Valley. 

3. Oxygenated Gasoline Program

The third control measure is the Oxygenated Gasoline Program. The current program, set forth in 

Section 53 of the Clark County Air Quality Regulations, requires that all fuel during the winter 

season (October 1 to March 31) contain 3.5 percent oxygenate by weight. The area of 

applicability covers the hydrographic basins containing the Las Vegas, Eldorado, and Ivanpah 

Valleys, the Boulder City limits, and any area within three miles of these hydrographic basins 

that is within Clark County. 

The use of oxygenated gasoline was originally mandated under the CAAA, which required 

gasoline sold in areas that did not meet the CO NAAQS to contain 2.7 percent oxygen content by 

weight. Clark County’s program is considerably more stringent than that minimum (i.e., 3.5 

percent oxygen content by weight or 10 percent by volume). Ethanol is the principal oxygenate 

used in Clark County. 

As part of this CO redesignation request and maintenance plan, DAQEM will depend on the 

current Oxygenated Gasoline Program as a primary control measure for maintaining the CO 

NAAQS. 

4. Relaxed RVP Gasoline Standard

The fourth control measure is a relaxed RVP standard. NRS and NAC 590 currently set a 

maximum RVP of 9 psi for gasoline sold in Clark County. 

 

As part of this CO redesignation request and maintenance plan, DAQEM proposes relaxing the 

RVP for wintertime fuels sold in Clark County from 9 to 13.5 psi to coincide with the 

specification guides for gasoline contained in Standard D4814-01a, Volume 05.02, of the 2002 

Annual Book of ASTM Standards (ASTM 2006). The proposed relaxation of the RVP for 

wintertime fuels will have a positive impact on gasoline supplies to the Las Vegas Valley 

because it will no longer preclude the distribution and sale of conventional and reformulated 

gasoline, which is sold throughout the rest of the southwestern United States during the winter 

season. 

September 2008 5-6
Carbon Monoxide Redesignation Request and Maintenance Plan 

5. State Technician Training and Certification Program

The fifth control measure is the state’s Technician Training and Certification Program. 40 CFR 

51.367 requires that state I/M inspectors be trained and certified; NRS and NAC 445B set forth 

the regulations governing technician training and certification. The Nevada DMV is responsible 

for administering these regulations. 

The general requirements to become a class 1 approved inspector include submittal of a 

certificate of competence from an exhaust gas analyzer manufacturer, successful completion of a 

training course and written exam, and a practical demonstration of the procedures for testing 

motor vehicles prescribed by the DMV. Requirements for becoming a class 2 approved inspector 

include establishment of proper qualifications; demonstration of the ability to test motor vehicles 

and to diagnose, repair, and service a device for controlling exhaust emissions; successful 

completion of a written test; and submittal of a current certification from the National Institute 

for Automotive Service Excellence as an advanced engine performance specialist. 

DAQEM will continue to rely on the Technician Training and Certification Program as a primary 

control measure for maintaining the CO NAAQS. 

5.4.2 Other Carbon Monoxide Control Programs 

The Las Vegas Valley also benefits from the other CO control programs listed below. Although 

these programs are not used for numeric emission reduction credit in the CO maintenance plan, 

they play an important role in assisting Clark County’s air quality improvement efforts. 

5.4.2.1 Contingency Measure Programs

1. TCM/TDM Program

As noted in Section 2.4, EPA required Clark County to evaluate and implement TCMs to further 

reduce CO emissions. In 1999, the RTC’s Transportation Demand Management Division, 

through the adoption of the Transportation Improvement Plan (FY 1998-2000), implemented the 

Club Ride commuter services program. The program included employer based commuter 

incentive programs, telecommuting incentives, and area-wide ridesharing programs. This 

program is referenced in both the 2000 CO SIP and the 2005 CO SIP Revision. 

Major components of the Club Ride commuter services program include employer/community 

outreach and marketing efforts, employer rideshare program incentives, preferential parking for 

carpoolers and vanpoolers, emergency rides home for Club Ride members, travel assistance 

information on the Internet and at public kiosks, transit passes to subsidize employees’ transit 

expenses, and partnerships with vanpool leasing companies. 

These voluntary TCM/TDM programs, while no longer used for numeric emission reduction 

credit, continue to play an important role in Clark County’s efforts to improve air quality and 

serves as a contingency measure, as described in Section 7.7. They are expected to reduce mobile 

source emissions by approximately 2.3 tpd in 2020 (2000 CO SIP). 

September 2008 5-7
Carbon Monoxide Redesignation Request and Maintenance Plan 

2. Alternative Fuels for Government Fleets Program

As noted in Section 2.5, NRS and NAC 486A set forth regulations for the Alternative Fuels for 

Government Fleets Program. Adopted in 1991 and administered by NDEP, these regulations 

establish procedures for accelerating the acquisition/conversion and use of alternative fueled 

vehicles in government fleets. This program is referenced in both the 2000 CO SIP and the 2005 

CO SIP Revision. 

The Alternative Fuels for Government Fleets Program regulates state and local government fleets 

based in Clark County and operating 10 or more vehicles. Alternative fuels accepted by the 

program include methanol, ethanol or other alcohol 85 percent or greater by volume (E-85), 

compressed natural gas, liquefied petroleum gas, hydrogen, federal reformulated gasoline or its 

equivalent, ultra-low sulfur diesel, electricity, certain ethanol-diesel blends (e.g., O2DieselTM), 

and biodiesel from B5 to B100. Hybrid electric vehicles are considered alternative fuel vehicles 

if the electric motor is used as a propulsion device during parts of the vehicle’s drive cycle. As of 

FY 2000, government fleet operators had to ensure that 90 percent of new vehicle purchases 

were alternative fueled vehicles. 

While no longer used for numeric emission reduction credit, this program continues to assist in 

Clark County’s efforts to improve air quality and serves as a contingency measure, as described 

in Section 7.7. It is expected to reduce mobile source emissions by approximately 1.37 tpd in 

2020 (2000 CO SIP). 

3. CBG Wintertime Fuels Program

As noted in Section 2.2, the CBG Wintertime Fuels Program for Clark County requires a low 

sulfur and aromatic content in gasoline sold between November 1 and March 31. The maximum 

sulfur content for wintertime fuels sold in Clark County is currently established at 80 ppmw, 

with an optional flat sulfur standard for producers and importers not to exceed 40 ppmw. 

Similarly, the maximum aromatic content of wintertime fuels sold in Clark County is established 

at 30 percent by volume, with an optional flat aromatic hydrocarbon standard for producers and 

importers not to exceed 25 percent by volume. 

Clark County wintertime fuel sulfur content requirements became redundant when federal Tier 2 

gasoline rules were implemented. Additionally, the aromatic content requirements of wintertime 

fuels do not appear to impose any significant burden on fuel suppliers, negating any issue with 

regards to the supply of gasoline to Clark County. While no longer used for numeric emission 

reduction credit, this program continues to assist in Clark County’s efforts to improve air quality 

and serves as a contingency measure, as described in Section 7.7. 

4. Reduced RVP Gasoline Program

As noted in Section 2.3, NRS and NAC 590 set a maximum RVP of 9 psi for gasoline sold in 

Clark County. Tightening the RVP standard back to 9.0 psi will act as a contingency measure if 

future CO exceedances occur, as described in Section 7.7. 

September 2008 5-8
Carbon Monoxide Redesignation Request and Maintenance Plan 

5.4.2.2 State Mandated and Voluntary Emission Reduction Programs

1. Heavy-Duty Vehicle Program

NRS and NAC 445B set forth the Heavy-Duty Vehicle Program regulations. Adopted in 1991 

and administered by the DMV, these regulations establish procedures for reducing motor vehicle 

emissions by limiting excessive tailpipe or smokestack smoke from any vehicle, diesel or 

gasoline, with a manufacturer’s GVWR of 8,500 pounds or more. 

The program incorporates random roadside testing of heavy-duty vehicles to determine if their 

exhaust exceeds state opacity (or smoke) standards. Violators are notified and must repair and 

retest the vehicle within 30 days. Government and private fleet operators may request opacity 

testing of their fleet vehicles as well; if violations are found, fleet managers are notified and 

vehicles are voluntarily repaired and retested. 

2. Smoking Vehicle Program

The Smoking Vehicle Program was developed in 1996 by the DMV in accordance with CAAA 

Titles I and II and NRS Sections 445B.100 and 445B.845. The program allows Nevada residents 

to voluntarily participate in improving the region’s air quality by reporting motor vehicles with 

visible exhaust emissions. The program also educates the public on the causes of exhaust 

emissions and the benefits of keeping vehicles in good running order. 

Once a smoking vehicle is reported, the DMV sends a courtesy notice to the registered owner of 

the vehicle asking the owner to repair it. If multiple reports are received on the same vehicle, or 

if law enforcement or DMV staff make the report, the notice will require the owner to bring the 

vehicle to a DMV emissions lab for testing. Failure to comply can result in a hold or suspension 

of the vehicle’s registration, in accordance with state law. 

3. Voluntary Vehicle Repair Program

DAQEM implemented the Voluntary Vehicle Repair Program (VVRP) in 2006. Funded through 

a grant from the DMV Emissions Control Program, the VVRP helps eligible residents fix highemitting vehicles and light-duty trucks that have failed a smog check. 

The program provides eligible recipients up to $650 toward the repair of a vehicle. An individual 

may be eligible to receive VVRP assistance if a vehicle is currently registered and operating in 

Clark County, the vehicle to be repaired is registered to the owner/participant, the needed repairs 

are not covered by a manufacturer’s warranty, the estimated repairs do not exceed the fair market 

value of the vehicle, and the owner/participant meets income eligibility requirements. 

In addition to reducing CO emissions, the VVRP results in better vehicle performance, extended 

vehicle life, and improved fuel efficiency. 

September 2008 5-9
Carbon Monoxide Redesignation Request and Maintenance Plan 

4. Advanced Truck Stop Electrification Program

DAQEM received almost $2 million in Congestion Mitigation and Air Quality (CMAQ) funds to 

install Advanced Truck Stop Electrification (ATE) systems in Clark County between 2007 and 

2010. DAQEM plans to equip 150 truck parking spaces in the valley with an ATE system. 

CMAQ will fund 100 percent of the project. 

ATE facilities remove 100 percent of emissions associated with extended diesel idling, including 

nitrogen oxides, particulate matter, volatile organic compounds, CO, and carbon dioxide. The 

system reduces criteria pollutants by 98 percent, even after accounting for the electricity from the 

grid used to power the system. 

DAQEM will continue to explore funding additional ATE projects through CMAQ and/or local 

funding sources. 

5. Diesel Engine Retrofit Program

Using almost $1 million in CMAQ funds, DAQEM plans to retrofit 69 non-road diesel engines 

with diesel oxidation catalysts, diesel particulate filters, and closed crankcase filter systems 

between 2007 and 2010. The retrofit is expected to reduce CO emissions from these engines by 

52 percent each year. 

DAQEM will continue to explore funding an expanded diesel-engine retrofit program to include 

on-road diesel engines. 

6. Clark County School District Bus Retrofit Program

The Clark County School District (CCSD) received $1 million in Federal Highway 

Administration funds from the U.S. 95 widening project settlement to retrofit diesel-powered 

school buses. CCSD plans to retrofit 400-500 buses with diesel oxidation catalysts and closed 

crankcase filter systems at an estimated cost of $2,000 per vehicle. CCSD will begin with the 

newest buses that do not have after-market emission reduction equipment: those from the 2003 

model year. The CCSD anticipates that the EPA-verified retrofit technologies will reduce CO by 

50 percent after it begins the project in January 2008. 

The CCSD is seeking additional funding sources, including EPA grants, to further retrofit the 

school bus fleet. 

5.4.3 Stationary Point and Area Source Programs 

Clark County estimates that stationary point and area sources account for about 3 percent of total 

CO emissions in the Las Vegas Valley. This plan suggests no controls other than the minimum 

federal requirements. 

September 2008 5-10
Carbon Monoxide Redesignation Request and Maintenance Plan 

6.0 SECTION 110 AND PART D REQUIREMENTS 

6.1 INTRODUCTION 

The fourth required component of an area’s redesignation/maintenance request is proof that it 

meets CAAA Section 110 and Part D requirements. This section addresses those requirements. 

6.2 SECTION 110 REQUIREMENTS 

Before EPA can redesignate the Las Vegas Valley nonattainment area to attainment, based on 

the proposed changes contained in this plan, the provisions of Section 110(a)(2) and Section 

110(l) must be satisfied. Section 110(a)(2) addresses the general requirements for SIPs. Section 

110(l) prevents approval of SIP revisions if the revision would interfere with any applicable 

requirement concerning attainment and reasonable further progress towards attainment of a 

NAAQS or any other applicable requirement of the CAAA. 

6.2.1 Section 110(a)(2) Analysis 

In general, the requirements for SIPs contained in Section 110(a)(2) are: 

1. The establishment and implementation of enforceable emission limitations. 

2. The monitoring, compilation, and analysis of ambient air quality data. 

3. Pre-construction reviews and permitting of new and modified major stationary sources. 

4. Consultation with, and provisions for the participation of, affected local governments. 

5. Assurance that the state has adequate funds and authority to enforce the SIP element and 

associated regulations. 

6. The establishment of permit fees for stationary sources. 

NRS 445B.500 addresses the establishment, administration, and enforcement of programs for 

controlling air pollution. In Clark County, these programs are administered and enforced by 

DAQEM. The department has nearly 150 staff members and an annual budget of approximately 

$24 million to implement and enforce the air quality plans and regulations applicable to the Las 

Vegas Valley CO nonattainment area. 

Furthermore, the 2000 CO SIP and 2005 CO SIP Revision include the provisions required by 

Section 110(a)(2). In approving the Clark County 2000 CO SIP and 2005 CO SIP Revision in 

January 2003 and August 2006, respectively, EPA determined that DAQEM met Section 

110(a)(2) requirements. 

Should DAQEM be unable to meet these requirements in the future, NRS 445B.520 and 

445B.530 allow the State Environmental Commission to assume jurisdiction over the local air 

quality management program to ensure that CAAA requirements are satisfied. EPA also has 

September 2008 6-1
Carbon Monoxide Redesignation Request and Maintenance Plan 

authority to impose sanctions on a state where EPA “...finds that any requirement of an 

approved plan (or approved part of a plan) is not being implemented” (CAAA, Section 179). 

6.2.2 Section 110(l) Analysis 

The maintenance plan proposes to relax one federally enforceable control measure—the Reduced 

RVP Gasoline Program—and discontinue the CO SIP credits taken from three other previous 

control measures: the CBG Wintertime Fuels Program, the TCM/TDM Program, and the 

Alternative Fuels for Government Fleets Program. 

CAA Section 110(l) requires that any SIP revision not interfere with requirements for attainment 

or reasonable further progress regarding other criteria pollutants, or with any other CAA 

requirements. The following analysis demonstrates that the control measure changes proposed in 

this CO maintenance plan will not interfere with Clark County’s progress towards attaining the 

8-hour ozone NAAQS, or with continued attainment of the PM10 NAAQS. Nevada is currently 

designated as attainment/unclassifiable for PM2.5 under Section 107(d) of the CAA; therefore, no 

analysis is required on PM2.5 NAAQS impacts.

6.2.2.1 Ozone

1. Relaxed RVP Gasoline and CBG Wintertime Fuels Programs

Relaxation of the RVP for wintertime fuels and discontinuation of the CO SIP credits taken for 

the CBG Wintertime Fuels Program are not expected to interfere with attainment of the 8-hour 

ozone standard because both are wintertime programs. Elevated levels of ozone normally occur 

during the summertime, since heat and sunlight are needed to produce the chemical reaction 

between nitrogen oxides (NOx) and volatile organic compounds (VOC) that forms ground-level 

ozone. 

2. TCM/TDM Program

CAAA Section 187(b)(2) requires areas classified as serious nonattainment to adopt TCMs as 

provided in Section 182(d)(1). The RTC adopted Resolutions No. 177 and No. 186 (2000 CO 

SIP, Appendix D), which indicated support for, and established the guidelines for administering, 

a voluntary employer-based commuter incentive program, currently known as Club Ride. 

DAQEM is evaluating the benefits of this program in conjunction with the development of the 

ozone SIP; discontinuation of CO SIP credits from the TCM/TDM Program is not expected to 

interfere. 

3. Alternative Fuels for Government Fleets Program

The state of Nevada developed the Alternative Fuels for Government Fleets Program as a result 

of the Energy Policy Act of 1992, which required federal, state, and fuel provider fleets to 

acquire alternative fuel vehicles. The law establishing this program is set forth in NRS 486a, 

which authorizes the State Environmental Commission to promulgate implementing regulations. 

September 2008 6-2
Carbon Monoxide Redesignation Request and Maintenance Plan 

NAC 486a sets forth those regulations. 

DAQEM is evaluating the benefits of the Alternative Fuels for Government Fleets Program in 

conjunction with the development of the ozone SIP; discontinuation of CO SIP credits from the 

program is not expected to interfere, since the estimated benefits from this program are small. 

6.2.2.2 Particulate Matter 

Relaxation of the RVP requirement for wintertime fuels and discontinuation of the CO SIP 

credits taken from the CBG Wintertime Fuels Program, TCM/TDMs and Alternative Fuels for 

Government Fleets Program are not expected to interfere with continued attainment of the 24-

hour PM10 standard because DAQEM has demonstrated that motor vehicle exhaust is an 

insignificant source of PM10 in the Las Vegas Valley (PM10 State Implementation Plan for Clark 

County, DAQEM 2001; Milestone Achievement Report for Clark County, DAQEM 2007). 

Additionally, removing fuel controls has no impact on PM10 emissions from vehicle exhaust. 

DAQEM’s determination of source significance was based primarily on the J.D. Smith annual 

inventory and the 24-hour micro-inventories at five representative sites, supplemented by 

reviews of the 1998 valley-wide annual emission inventory and Chemical Mass Balance 

modeling. The emission inventories/projections in the Milestone Achievement Report for Clark 

County (DAQEM 2007) show that motor vehicle exhaust makes an insignificant contribution to 

PM10 concentrations, so additional reductions were not needed to advance the attainment date. 

Table 6-1 shows total PM10 mobile source emissions for the Las Vegas Valley in 2006. The 

contribution of vehicle exhaust to total PM10 mobile source emissions is less than 1 percent. 

Table 6-1. Total PM10 Mobile Source Emissions for 2006 

On-Road Mobile Source Category Tons per Day (tpd) 

Paved road dust (includes construction and unpaved shoulder track-out) 83.53 

Private unpaved roads 9.34 

Highway construction projects activities 1.34 

Highway construction projects - wind erosion 3.13 

Vehicular sulfate PM 0.02 

Vehicle tire wear 0.37 

Vehicle brake wear 0.55 

Vehicle exhaust 0.53 

Total PM10 mobile source emissions 98.81 

Source: PM10 Milestone Achievement Report for Clark County, DAQEM 2007. 

Table 6-2 shows that mobile source emission programs, such as reduced RVP, CBG, 

TCM/TDM, and alternative fuel fleets, have a negligible effect in reducing 24-hour PM10

concentrations in the Las Vegas Valley. 

September 2008 6-3
Carbon Monoxide Redesignation Request and Maintenance Plan 

Table 6-2. 2006 24-Hour Controlled PM10 Emissions 

On-Road Mobile Source Category Uncontrolled PM10

(tpd) 

Controlled PM10 

(tpd) 

Percent 

Reduction 

Paved road dust (includes construction track-out) 83.53 59.31 29.00 

Unpaved road dust 9.34 3.27 65.00 

Highway construction projects activities 1.34 0.43 68.00 

Highway construction projects–wind erosion 3.13 0.91 71.00 

Vehicle sulfate PM 0.02 0.02 0.00 

Vehicle tire wear 0.37 0.37 0.00 

Vehicle brake wear 0.55 0.55 0.00 

Vehicle exhaust 0.53 0.53 0.00 

Total 98.81 65.38 33.83 

Source: PM10 Milestone Achievement Report for Clark County, DAQEM 2007. 

6.3 PART D REQUIREMENTS 

CAAA Part D requires the following items be addressed in nonattainment plan provisions: 

1. The implementation of reasonable available control measures, including reasonably available 

control technologies, for existing sources. 

2. Reasonable further progress for existing sources. 

3. A current emissions inventory and periodic inventories every three years until attainment. 

4. The identification and quantification of allowable emissions for new and modified stationary 

sources. 

5. A stationary source permitting program. 

6. Other measures, including enforceable emission limitations, additional control measures, and 

a schedule for compliance. 

7. Compliance with Section 110 provisions. 

8. Contingency measures. 

The EPA-approved 2000 CO SIP and 2005 CO SIP Revision include the provisions required by 

CAAA Part D. In approving the CO SIP and CO SIP Revision in January 2003 and August 2006, 

respectively, EPA determined that DAQEM met the CAAA Part D requirements. 

Other Part D requirements applicable in nonattainment and maintenance areas include the 

general and transportation conformity provisions of CAAA Section 176(c). These provisions 

ensure that federally funded or approved projects and actions will conform to this CO 

maintenance plan before implementation. In approving the 2000 CO SIP and 2005 CO SIP 

Revision in January 2003 and August 2006, respectively, EPA determined that DAQEM met the 

Section 176(c) requirements and the transportation conformity rule (40 CFR 93, Subpart A). 

September 2008 6-4
Carbon Monoxide Redesignation Request and Maintenance Plan 

7.0 MAINTENANCE PLAN 

7.1 INTRODUCTION 

The fifth required component of an area’s redesignation/maintenance request is fulfillment of 

CAAA Section 107(d)(3)(E) requirements. These specify that for an area to be redesignated as 

attainment, EPA must approve a maintenance plan that meets Section 175(A) requirements. This 

plan provides for maintenance of the CO NAAQS for at least ten years after the redesignation. 

CAAA Section 107(d)(3)(D) allows EPA up to 18 months after submittal to process a 

redesignation/maintenance request. To accommodate the potential review time, this plan covers 

the period from 2008 to 2020. 

This section focuses on the following core elements EPA has established as necessary for 

approval of maintenance plans: 

1. Maintenance plan control measures (Section 7.2). 

2. Emission inventory summary (Section 7.3). 

3. Maintenance demonstration (Section 7.4). 

4. MVEB (Section 7.5). 

5. Approved monitoring networks (Section 7.6). 

6. Verification of continued attainment (Section 7.6). 

7. Contingency plan (Section 7.7). 

8. Subsequent maintenance plan revisions (Section 7.8). 

7.2 MAINTENANCE PLAN CONTROL MEASURES 

DAQEM will rely on the five control measures discussed in Section 5.3.1 to demonstrate 

maintenance of the CO NAAQS through 2020: 

1. The FMVECP, as approved in the 2000 CO SIP and 2005 CO SIP Revision. 

2. The state I/M Program, as approved in the 2000 CO SIP and 2005 CO SIP Revision. 

3. The Oxygenated Gasoline Program, as approved in the 2000 CO SIP and 2005 CO SIP 

Revision. 

4. The state Technician Training and Certification Program, as approved in the 2000 CO SIP 

and 2005 CO SIP Revision. 

5. A Relaxed RVP Gasoline Program, with a maximum RVP of 13.5 psi. 

September 2008 7-1
Carbon Monoxide Redesignation Request and Maintenance Plan 

No other emission reduction credit has been taken in the maintenance demonstration for any 

other state or local control programs. No other programs, strategies, or regulations shall be 

incorporated or deemed enforceable control measures for the maintenance demonstration. 

Four attainment control measures in the CO SIP that will no longer be used for SIP credit will 

remain as contingency measures in the CO maintenance plan. These include the Reduced RVP 

Gasoline Program (a maximum RVP of 9 psi), the TCM/TDM Program, the Alternative Fuels for 

Government Fleets Program, and the CBG Wintertime Fuels Program. 

Table 7-1 lists the maintenance control measures that will be used for numeric credit in the CO 

maintenance plan, along with the attainment control measures approved in the 2000 CO SIP and 

2005 CO SIP Revision that will now be incorporated as contingency measures. 

Table 7-1. Summary of Control Measures Used in CO Maintenance SIP and CO 

Attainment/Revision SIPs 

Control Measure Status in Maintenance Plan Status in Attainment Plan 

and Revision 

FMVECP Maintenance measure Attainment measure 

State I/M Program Maintenance measure Attainment measure 

Oxygenated Gasoline Program Maintenance measure Attainment measure 

Technician Training and Certification 

Program Maintenance measure Attainment measure 

Relaxed RVP Gasoline Program Maintenance measure (with 13.5 psi max RVP) N/A 

Reduced RVP Gasoline Program Contingency measure (with 9 psi max RVP) Attainment measure 

TCM/TDM Program Contingency measure Attainment measure 

Alternative Fuels for Government 

Fleets Program Contingency measure Attainment measure 

CBG Wintertime Fuels Program Contingency measure Attainment measure 

7.3 EMISSION INVENTORY SUMMARY 

EPA requires that all maintenance plans include an emissions inventory that is comprehensive, 

accurate, and current with respect to actual emissions in the area. This section summarizes the 

1996 base year CO inventory for the Las Vegas Valley nonattainment area, which addresses CO 

emissions from four major type categories: on-road mobile, area sources, non-road mobile, and 

point sources. Detailed information on the development of the 1996 base year CO inventory can 

be found in the 2000 CO SIP and the 2005 CO SIP Revision. 

The 2000 CO SIP and 2005 CO SIP Revision were also based on computer modeling (using 

UAM) of the single best performing episode of the three originally modeled: the night of 

December 8-9 (Sunday-Monday), 1996. This maintenance plan continues to rely on that episode. 

For all future years modeled in this plan, DAQEM used the most recently adopted planning 

variables approved by the RTC, which is the designated Metropolitan Planning Organization for 

the Las Vegas urban area. Output provided by the RTC from the 2006 TransCAD TDM includes 

updated link volumes and trip tables, modified population projections reflecting higher growth 

rates in the county, and revised daily VMT. 

September 2008 7-2
Carbon Monoxide Redesignation Request and Maintenance Plan 

All emission inventory estimates are for the Las Vegas Valley CO nonattainment area on a 

typical weekday during the wintertime season (November through February). The inventories 

were developed using EPA-approved emissions modeling methods. 

7.3.1 Demographic and Transportation Data 

Table 7-2 summarizes the demographic data used to develop the emission inventories for the Las 

Vegas Valley CO inventory/modeling domain. The information was obtained from the RTC FY 

2006-2030 Regional Transportation Plan, approved in October 2006. All other information in 

the CO maintenance plan inventory/modeling domain—including vehicle fleet mix, 

seasonal/day-of-week adjustment factors, and hourly activity profiles—has also been updated 

with the most current data available. 

Table 7-2. Demographic Data Used to Develop Emission Inventories 

January Population of Las Vegas Valley Modeled VMT (Monday)

1996 Base1 1,037,844 22,395,251 

20082 2,102,216 49,439,086 

20102 2,281,340 54,375,446 

20202 2,999,953 70,240,128 1

2000 CO SIP and 2005 CO SIP Revision. 

2

RTC FY2006-2030 RTP, adopted October 2006. 

7.3.2 Summary of Emission Inventories 

The 1996 base year emissions inventory incorporates the nonattainment control measures 

described in the 2000 CO SIP. Inventories for the 2008 and 2010 interim years, and the 2020 

maintenance year, incorporate the maintenance plan control measures described in Section 7.2. 

All inventories include on-road mobile, aviation (including McCarran International, North Las 

Vegas, Henderson, and Nellis Air Force Base), area, non-road mobile, railway, and point 

sources. 

Table 7-3 summarizes the emission inventories by source category for all years, also with the 

control measures described in Section 7.2. Figures 7-1 through 7-4 show the emission 

inventories for each individual year; detailed information on the methodologies used to estimate 

future year emissions can be found in the 2005 CO SIP Revision. 

In all four years, on-road mobile source emissions represent the largest source of CO in the 

modeling domain: about 77 percent in the base year, 82 percent in the interim years, and 79 

percent in the maintenance year. The modeling domain shows that with the implementation of 

the maintenance control measures in Section 7.2, in conjunction with stricter federal controls on 

vehicles and fuels, on-road mobile emissions change by less than 1 percent between 2008 and 

2020, or from 579.3 tpd to 574.4 tpd. 

Table 7-3. Summary of Total Daily CO Emissions for the Inventory/Modeling Domain (tpd)

Source Category 1996-Base2 20083 20103 20203

September 2008 7-3
Carbon Monoxide Redesignation Request and Maintenance Plan 

On-road mobile1 511.4 579.3 579.7 574.4 

Aviation 34.4 39.7 42.2 53.5 

Area sources 9.5 13.9 14.7 18.6 

Non-road mobile 103.4 57.7 60.8 71.2 

Railway 0.3 0.3 0.3 0.4 

Point sources 3.1 15.8 15.8 15.8 

Total 662.1 706.7 713.5 733.9 1

Based on the second Monday in December (12/9/2006). 2

2000 CO SIP and 2005 CO SIP Revision. 

3

Clark County Carbon Monoxide Redesignation Request and Maintenance Plan Technical Support Document, DAQEM 2008. 

On-Road 

Mobile

77.24%

Aviation

5.20%

Area Sources

1.43%

Non-Road 

Mobile

15.62%

Railway

0.05% Point 

Sources

0.47%

Figure 7-1. 1996 Emission Inventory for the Las Vegas Valley CO Modeling Domain. 

September 2008 7-4
Carbon Monoxide Redesignation Request and Maintenance Plan 

On-Road 

Mobile

82.16%

Aviation

5.49%

Area Sources

1.96%

Non-Road 

Mobile

8.13%

Railway

0.04%

Point Sources

2.23%

Figure 7-2. 2008 Emission Inventory for the Las Vegas Valley CO Modeling Domain. 

Non-Road 

Mobile

8.39%

Area Sources

2.03%

Aviation

5.71%

On-Road 

Mobile

81.65%

Railway

0.04% Point Sources

2.18%

Figure 7-3. 2010 Emission Inventory for the Las Vegas Valley CO Modeling Domain. 

September 2008 7-5
Carbon Monoxide Redesignation Request and Maintenance Plan 

On-Road 

Mobile

78.70%

Area Sources

2.50%

Aviation

7.07%

Non-Road 

Mobile

9.56%

Railway

0.05% Point Sources

2.12%

Figure 7-4. 2020 Emission Inventory for the Las Vegas Valley CO Modeling Domain. 

Non-road mobile source emissions represent the second largest source of CO in the modeling 

domain: about 16 percent in the base year, 8 percent in the interim years, and 9 percent in the 

maintenance year. Non-road mobile source emissions increase by about 19 percent between 2008 

and 2020, or from 57.7 tpd to 71.2 tpd. The increase comes mainly because maintenance control 

measures do not fully offset growth in the number of non-road engines.

Aviation CO emissions rank third in the modeling domain at about 5 percent in the base year, 5-6 

percent in the interim years, and 7 percent in the maintenance year. Aviation CO emissions 

increase steadily during the maintenance period due to projected growth in airport activities. 

Area, railway, and point source CO emissions combined contribute less than 2 percent to the 

base year modeling domain, increasing to 4 percent in the interim years and 5 percent in the 

maintenance year due to anticipated regional population growth. 

In summary, total emissions increase by only 5 percent between 2008 and 2020 with the 

implementation of the maintenance control measures described in Section 7.2, or from 706.7 tpd 

to 733.9 tpd. 

7.4 MAINTENANCE DEMONSTRATION 

As required by CAAA Section 175(a), each request for redesignation must include a SIP revision 

that provides for maintenance of the NAAQS for at least 10 years after redesignation. Per EPA 

September 2008 7-6
Carbon Monoxide Redesignation Request and Maintenance Plan 

guidance and policy, maintenance plans require the same level of modeling performed for the 

attainment demonstration (Calcagni 1992). 

This section summarizes the application of the UAM and CAL3QHC models in demonstrating 

maintenance of the CO NAAQS through December 31, 2020. The primary purpose for 

conducting UAM area-wide and CAL3QHC roadway intersection modeling is to demonstrate the 

effectiveness of the control measures described in Section 7.2 in maintaining the 8-hour average 

CO NAAQS. 

EPA requires estimated 8-hour average concentrations to be lower than the 9 ppm standard when 

using the UAM area-wide model to demonstrate continued attainment. EPA also recommends 

that the CAL3QHC model be applied to intersections at potential hot-spot locations. The hot-spot 

modeling analysis combines concentrations from the UAM with those from the CAL3QHC 

microscale model. 

To further support the maintenance demonstration, Emissions and Dispersion Modeling System 

(EDMS) results from the Ricondo (2003) analyses were combined with revised UAM model 

predictions for all future years to estimate 8-hour CO concentrations for the duration of an 

episode on and around the three civil airport properties in the valley. The following sections 

provide details on each of these components. 

7.4.1 Urban Airshed Model Analysis 

The UAM analysis used updated emission inventories for point, on-road mobile, and non-road 

mobile sources for the December 8-9, 1996, historical CO event. All other environmental 

parameters were taken from the original modeling documented in the 2000 CO SIP. The UAM 

was then run with the updated future year inventories for 2008, 2010, and 2020 to determine 

peak 8-hour CO levels in the valley using the same December 8-9, 1996, conditions. Figures 7-5 

through 7-7 display predicted 8-hour maximum CO concentrations in the modeling domain for 

the 2008 and 2010 interim years and the 2020 maintenance year, respectively. UAM predictions 

show that the 8-hour CO standard of 9 ppm will not be violated anywhere within the domain. As 

Table 7-4 shows, peak 8-hour CO concentrations continue to decrease in each of the future years. 

Table 7-4. Peak UAM 8-Hour Average CO Concentrations Predicted for Modeled Years 

Year Maximum 8-Hour CO Concentration (ppm) 

2008 8.8 

2010 8.5 

2020 7.7 

Figures 7-1 through 7-4 showed that the contribution of McCarran International Airport to local 

CO concentrations increases only slightly during this period, due to the projected growth in 

airport activities reported by Ricondo (2003). 

September 2008 7-7
Carbon Monoxide Redesignation Request and Maintenance Plan 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

ppm

UAM Max 8-hour CO Concentrations

 2008 Future Year (EPA M6)

Peak = 8.8 ppm

5

6

7

8

9

10

11

12

Figure 7-5. Spatial Distribution of UAM predicted 8-Hour Maximum CO Concentrations (ppm) for 

the December 8-9, 1996 Episode Using Emission Forecasts for 2008 (Air Version of 

MOBILE6). 

September 2008 7-8
Carbon Monoxide Redesignation Request and Maintenance Plan 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

ppm

UAM Max 8-hour CO Concentrations

 2010 Future Year (EPA M6)

Peak = 8.5 ppm

5

6

7

8

9

10

11

12

Figure 7-6. Spatial Distribution of UAM predicted 8-Hour Maximum CO Concentrations (ppm) for 

the December 8-9, 1996 Episode Using Emission Forecasts for 2010 (Air Version of 

MOBILE6). 

September 2008 7-9
Carbon Monoxide Redesignation Request and Maintenance Plan 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

ppm

UAM Max 8-hour CO Concentrations

 2020 Future Year (EPA M6)

Peak = 7.7 ppm

5

6

7

8

9

10

11

12

Figure 7-7. Spatial Distribution of UAM predicted 8-Hour Maximum CO Concentrations (ppm) for 

the December 8-9, 1996, Episode Using Emission Forecasts for 2020 (Air Version of 

MOBILE6). 

The UAM was used to refine the estimation of future year on-road mobile CO emission budgets 

for the central, most urbanized portion of the modeling domain. Table 7-5 defines this central 

urban subdomain, and Figure 7-8 outlines the subdomain in relation to the total modeling 

domain. 

September 2008 7-10
Carbon Monoxide Redesignation Request and Maintenance Plan 

Table 7-5. Grid Definition of the Central Urban Subdomain 

Column Row UTM East1 UTM North

Low-Left 11 19 652.000 3991.000 

Upper-Right 36 45 678.000 4018.000 

1

Universal Transverse Mercator. 

Figure 7-8. Boundaries of the Outer Domain and Subdomains. 

In the analysis, future year on-road mobile source emissions were scaled up across the entire 

modeling domain to the point at which the peak 8-hour CO concentrations reached 8.9 ppm. 

Next, on-road mobile source emissions outside the central urban subdomain were increased in 

each year by an additional 60 percent to reach a maximum peak 8-hour CO concentration of just 

under 9 ppm. Hence, the resulting daily on-road emission totals for December 9 can be used to 

establish future-year emission budgets. Table 7-6 presents the results of this analysis. 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

Table 7-6. Weekday On-Road Emissions Increases, UAM-Predicted Peak CO, and Resulting 

Emissions Budget for Each Future Year 

Year 

Domain-Wide OnRoad Emissions 

Increase 

Net On-Road 

Emissions 

Increase1 

Peak 8-Hour CO 

(ppm) 

Total Domain OnRoad Emissions 

(tpd) 

Subdomain OnRoad Emissions 

(tpd) 

2008 0.05% 13% 8.87 658 457 

2010 4.0% 18% 8.88 686 464 

2020 5.0% 23% 8.12 704 435 1

Includes an additional 60 percent increase outside the central urban subdomain. 

There was no change in the location of the predicted peak. Furthermore, no additional hot spots 

were generated anywhere in the domain by increasing the on-road mobile source emissions in the 

outer portion of the domain by 60 percent. 

7.4.2 Microscale Modeling 

Future year UAM simulation results provided estimates of background ambient CO levels for 

microscale modeling of the Five Points area hot spot and the three civil airports in the modeling 

domain: McCarran, Henderson, and North Las Vegas. UAM concentrations from the appropriate 

grid cells were simply added to the concentrations predicted at each microscale receptor to obtain 

a total (background + microscale) CO concentration. 

7.4.2.1 CAL3QHC Intersection Modeling

Consistency with the 2005 CO SIP Revision was imperative for hot-spot modeling, so the 

following three intersections were used: Charleston and Eastern, Charleston and Fremont, and 

Eastern and Fremont (Figure 7-9). DAQEM followed EPA guidance for screening-level 

modeling of these three intersections (EPA 1992, 1995). The UAM + CAL3QHC model for the 

2000 CO SIP provided the ambient temperature for each hour of the episode—which was needed 

to estimate emissions with the MOBILE6.2 model—and the wind speed and direction needed for 

the CAL3QHC estimates. The CAL3QHC model output was added to the background UAM 

levels to estimate 8-hour CO concentrations for the duration of the episode. 

Figure 7-9. CAL3QHC Intersection Location Diagram (Five Points Area). 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

Table 7-7 presents the peak UAM + CAL3QHC 8-hour average CO concentrations predicted in 

each of the future years for each of the three intersections in the Five Points area. Modeling for 

the intersections showed no violations of the 8-hour maximum CO NAAQS. Further, all values 

are well below the 9 ppm standard. 

Table 7-7. Peak UAM + CAL3QHC 8-Hour Average CO Concentrations Predicted for Modeled Years 

and Each Intersection 

Year Charleston/Eastern Fremont/Eastern Fremont/Charleston 

2008 8.2 7.8 7.0 

2010 8.0 7.7 7.0 

2020 7.2 7.0 6.3 

7.4.2.2 Airport Modeling Using the Emissions and Dispersion Modeling System

For microscale airport modeling, peak total UAM + EDMS 8-hour CO concentrations at all three 

Las Vegas civil airports were evaluated. The UAM + EDMS model runs for 2008, 2010, and 

2020 incorporated the maintenance plan control measures proposed in Section 7.2. To minimize 

double-counting, emissions for the three airports were removed from the UAM inventory. 

It is important to note that traffic volumes on the major roadways within the McCarran airport 

property are included in both EDMS and TransCAD. As a result, the EDMS + UAM CO 

concentration results for McCarran reflect a double-counting of portions of the on-road mobile 

source emissions on that property; therefore, the CO concentrations reported for McCarran are 

conservative (i.e., high) estimates. 

Table 7-8 lists the peak total 8-hour CO concentrations at all three airports for each of the 

modeled years. Values for McCarran are taken from the peak publicly accessible receptor. As the 

table shows, all peak CO concentrations are below the 9 ppm standard in all modeled years. 

Table 7-8. Peak Total UAM + EDMS 8-Hour CO Concentrations at Las Vegas Airports 

for 2008, 2010, and 2020 

Airport 2008 2010 2020 

McCarran1 7.88 7.77 8.98 

Henderson Executive 1.38 1.50 3.38 

North Las Vegas 3.53 3.51 3.10 

1

Values shown for McCarran occur at the peak publicly accessible receptor. 

7.4.3 Air Quality Trend Analysis—Weight of Evidence Approach 

Modeling for CO concentrations in future years carries some level of uncertainty, so DAQEM 

performed an air quality trend analysis for the ten-year period from 1996 to 2005 using data from 

the Sunrise Acres monitoring site (2005 CO SIP Revision, Appendix D). The purpose was to use 

a weight-of-evidence approach to support the attainment demonstration of the CO NAAQS with 

future-year CO emissions budgets. 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

Recognizing that meteorological conditions may affect CO concentrations, the trend analysis 

incorporated a normalization approach to account for temperature variations and wind velocity. 

The meteorological data set used for statistical analysis consisted of hourly temperature and wind 

velocity readings (6 p.m. to 6 a.m.) collected at the Sunrise Acres monitoring site for each day 

between November 1 and January 31 (typically considered the CO season) from 1996 to 2005. 

The normalized analysis showed a continued downward trend of maximum CO concentrations in 

future years (Figure 7-10). It also indicated that year-to-year variations in temperature and wind 

velocity did not substantially influence the downward trend in observed 8-hour maximum CO 

concentrations at the site. 

Based on this analysis, DAQEM is confident that future 8-hour maximum CO concentrations in 

the Las Vegas Valley will continue to trend downward, even with the control measure 

modifications and discontinuation of the credits proposed in Section 2. This trend analysis also 

supports the MVEBs developed from the modeling conducted for this maintenance plan. Even 

with the forecasted increases in future CO emissions resulting from the proposed maintenance 

plan control measures in Section 7.2, DAQEM is confident that future CO concentrations will be 

well below the CO NAAQS. 

0

2

4

6

8

10

12

1996 1998 2000 2002 2004 2006 2008

year

CO, ppm (or low u, m/s)

Monitored CO Predicted CO Normalized CO

Figure 7-10. Sunrise Monitoring Site: Actual, Predicted, and Normalized CO Trends. 

7.5 MOTOR VEHICLE EMISSIONS BUDGET 

Under CAA Section 176(c), transportation plans, programs, and projects in maintenance areas 

that are funded or approved under Title 23 of the U.S. Code or the Federal Transit Act must 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

conform to the on-road MVEBs specified in the applicable SIP. In this case, 40 CFR 93.118 

provides the criteria and procedures for MVEBs. 

The MVEB establishes a cap on motor vehicle-related emissions that cannot be exceeded by 

predicted transportation system emissions. The emissions budget applies as a ceiling on 

emissions in the year for which it is defined, and for all subsequent years until a different budget 

is defined for another year or a SIP revision modifies the budget. Unless the SIP clearly indicates 

otherwise, the estimate of future transportation network emissions used in the milestone or 

attainment demonstration acts as the MVEB. 

The emissions analysis for conformity determinations must include emissions from the entire 

transportation network within the nonattainment area. In the case of Las Vegas, the 

nonattainment area encompasses both the air quality modeling domain and the transportation 

planning domain. 

Table 7-9 reflects the calculated peak 8-hour CO concentrations and MVEBs for the 2008 and 

2010 interim years, and the 2020 maintenance year, based on MOBILE6.2. 

Table 7-9. Peak 8-Hour CO Concentrations and MVEBs in the Las Vegas Valley 

Year Peak 8-Hour CO (ppm) MVEB (tpd) 

2008 8.871 658 

2010 8.881 686 

2020 8.982 704 

Note: Values include impacts of microscale modeling concentrations predicted at peak microscale receptor. 1

Values shown for UAM-predicted peak CO. 

2 Value shown for UAM + EDMS predicted peak CO for McCarran publicly accessible receptor.

Based on the analysis in this plan, future motor vehicle emissions nearing the MVEB will not 

lead to an exceedance or violation of the CO NAAQS. Once approved by EPA, the MVEBs 

listed in Table 7-9 will become the budgets that the RTC will use for conformity determinations 

in future regional transportation plans. 

 

7.6 MONITORING NETWORK/VERIFICATION OF CONTINUED ATTAINMENT 

After EPA redesignates the Las Vegas Valley CO nonattainment area to attainment status, 

DAQEM will continue to operate a monitoring network in accordance with 40 CFR 58 to verify 

continued attainment of the CO NAAQS. If measured mobile source parameters (e.g., VMT, 

fleet mix) change over time, DAQEM will conduct studies to determine whether additional or resited monitors are necessary. Additionally, the air quality monitoring system will be reviewed 

annually in accordance with 40 CFR 58.10 to determine whether the system continues to meet 

the monitoring objectives in 40 CFR 58, Appendix D. 

7.7 CONTINGENCY PLAN 

CAAA Section 175A(d) requires that the maintenance plan contain contingency provisions. The 

inclusion of contingency provisions in maintenance plans is to assure prompt correction of any 

violation of the CO NAAQS. Additionally, such provisions shall include a requirement that the 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

state will implement all measures that were contained in the SIP before the area was redesignated 

to attainment. 

While EPA guidance states that a contingency plan does not need to contain fully adopted 

contingency measures (EPA memorandum, 09/04/92), it should contain: 

1. Clearly identified contingency measures. 

2. Tracking and triggering mechanisms to determine when contingency measures are needed. 

3. A description of the process for recommending and implementing contingency measures. 

4. A specific time limit for action. 

Consistent with the EPA guidance memorandum titled, “Early Implementation of Contingency 

Measures for Ozone and Carbon Monoxide (CO) Nonattainment Areas” (08/13/93), the 

contingency plan described in this maintenance plan is comprised of committed control 

measures. The four contingency measures set forth by Clark County are the Reduced RVP 

Gasoline Program, the TCM/TDM Program, the Alternative Fuels for Government Fleets 

Program, and the CBG Wintertime Fuels Program. 

DAQEM’s primary tracking mechanism is continuous monitoring of CO levels, and the 

department will continue to maintain CO monitors (Section 3.3). To ensure that future violations 

of the CO NAAQS do not occur, ambient air quality monitoring data will be examined to 

determine if additional contingency measures are needed. A NAAQS violation occurs when the 

second-highest reading at the same monitoring site over two consecutive years is greater than or 

equal to 9.5 ppm. Any verified exceedance over 9 ppm during the CO season (October 1 through 

March 31) will trigger an automatic review to determine which contingency measure(s) should 

be adopted if another exceedance occurs at the same monitor. 

DAQEM must review and verify monitoring data within three months of an exceedance, and 

recommend contingency measures within six months. DAQEM may recommend local, voluntary 

measures to prevent a second exceedance; however, such action is voluntary. The only federallyenforceable trigger for mandatory implementation of contingency measures shall be a violation 

of the 8-hour CO NAAQS. 

If a second exceedance occurs at the same monitoring site within a consecutive two-year period, 

DAQEM will recommend contingency measures to the Clark County Board of County 

Commissioners (BCC). If the contingency measures in Sections 5.3.1.(4), 5.3.2.(1), 5.3.2.(2), and 

2.2 are not adequate to prevent future exceedances, DAQEM will recommend more stringent 

contingency measures and/or additional CO reduction measures. Within three months of the 

second exceedance, DAQEM will verify and evaluate the monitoring data; within six months, 

the department will determine what contingency measures should be implemented and make 

recommendations to the BCC. The contingency control measures will be implemented six to 

twelve months after BCC approval, depending on the time needed to put the measures in place. 

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Carbon Monoxide Redesignation Request and Maintenance Plan 

7.8 SUBSEQUENT MAINTENANCE PLAN REVISIONS 

A maintenance plan revision must be submitted to EPA eight years after the original 

redesignation request/maintenance plan is approved. The revision should provide for 

maintenance of the NAAQS for an additional ten years following the first ten-year period. As the 

designated air pollution control agency for Clark County—specifically, the Las Vegas Valley 

CO nonattainment area—DAQEM intends to prepare a revised maintenance plan eight years 

after redesignation to attainment, as required by the CAAA and EPA. 

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8.0 REFERENCES 

Alliance of Automobile Manufacturers 2006. “Alliance of Automobile Manufacturers North 

American Fuel Survey Motor Gasoline.” Winter 2006. Washington, D.C.: Alliance of 

Automobile Manufacturers. 

American Society for Testing and Materials 2006. 2002 Annual Book of ASTM Standards, 

D4814-01a, “Standard Specification for Automotive Spark-Ignition Engine Fuel,” Volume 

05.02, “Petroleum Products and Lubricants.” Philadelphia, Pennsylvania: American Society for 

Testing and Materials. 

Calcagni, J. 1992. “Procedures for Processing Requests to Redesignate Areas to Attainment.” 

Memorandum from John Calcagni, Air Quality Management Division Director, to EPA Regional 

Division Directors, dated 9/4/1992. 

Center for Business and Economic Research 2008. “Historical Economic Data for Metropolitan 

Las Vegas.” Las Vegas, Nevada: University of Nevada, Las Vegas. 

http://cber.unlv.edu/snoutlk.html. 

Clark County Department of Air Quality and Environmental Management (DAQEM) 2000. 

Carbon Monoxide State Implementation Plan, Las Vegas Valley Nonattainment Area, Clark 

County, Nevada. Las Vegas: DAQEM. 

Clark County Department of Air Quality and Environmental Management 2001. PM10 State 

Implementation Plan for Clark County. Las Vegas: DAQEM. 

Clark County Department of Air Quality and Environmental Management 2005. Carbon 

Monoxide State Implementation Plan Revision, Las Vegas Valley Nonattainment Area, Clark 

County, Nevada. Las Vegas: DAQEM. 

Clark County Department of Air Quality and Environmental Management 2007. PM10 State 

Implementation Plan Milestone Achievement Report. Las Vegas: DAQEM.

Clark County Department of Comprehensive Planning 2008. http://www.co.clark.nv.us/ 

comprehensive_planning/Advanced/Demographics/HistoricalPopulationData/CCHistoricalPop 

Summary1990toPresent.pdf. Las Vegas, Nevada: Clark County Department of Comprehensive 

Planning. 

Environ International Corporation 2007. “Clark County Wintertime Gasoline Fuel Specifications 

Study.” Las Vegas, Nevada: Clark County Department of Air Quality and Environmental 

Management. 

Regional Transportation Commission of Southern Nevada . FY 1998-2000 Transportation 

Improvement Plan. Las Vegas: RTC. 

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Sierra Research 2003. “Review of Current and Future CO Emissions from On-Road Vehicles in 

Selected Western Areas.” Prepared for Western States Petroleum Association, by Sierra 

Research, Inc., Report No. SR03-01-01 (January 28, 2003) 

Sierra Research 2005. “Impacts of Eliminating Maricopa County Wintertime Gasoline Standards 

on Emissions and Ambient Concentrations of CO in February and March.” Prepared for the 

Arizona Department of Environmental Quality by Sierra Research\, Inc. (January 24, 2005). 

U.S. Environmental Protection Agency 2007. “Milestones in Auto Emissions Control.” Seattle, 

Washington: EPA Region 10. http://yosemite.epa.gov/R10/airpage.nsf/webpage/ 

Milestones+in+Auto+Emissions+Control. 

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