Ozone Redesignation Request and 

Maintenance Plan

Clark County, Nevada 

March 2011 
Ozone Request for Redesignation and Maintenance Plan 

March 2011 ii

ACKNOWLEDGMENTS 

CLARK COUNTY BOARD OF COMMISSIONERS 

Susan Brager, Chair 

Steve Sisolak, Vice-Chair 

Larry Brown 

Tom Collins 

Chris Giunchigliani 

Mary Beth Scow 

Lawrence Weekly 

OFFICE OF THE COUNTY MANAGER 

Don Burnette, County Manager 

Edward Finger, Assistant County Manager 

Randy Tarr, 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 

Stephen Deyo, Assistant Planning Manager 

Robert Tekniepe, Principal Management Analyst 

Zheng Li, Sr. Air Quality Modeler 

Will Cates, Principal Planner 

Jean Paul Huys, Air Quality Specialist II 

Melissa Hamner, Technical Writer 

 
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March 2011 iii

EXECUTIVE SUMMARY 

This Ozone Redesignation Request and Maintenance Plan is a formal request by Clark County to 

the U.S. Environmental Protection Agency (EPA) to redesignate the Clark County ozone 

nonattainment area to attainment for the 1997 8-hour ozone National Ambient Air Quality 

Standard (NAAQS). The plan summarizes the progress in attaining the ozone standard, 

demonstrates that all Clean Air Act (CAA) as amended requirements for attainment have been 

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

Clark County was designated nonattainment of the 8-hour ozone NAAQS in April 2004. The 

Phase 1 Implementation Rule issued by EPA on June 15, 2004 classified Clark County as a 

“basic” nonattainment area under Subpart 1 of the Clean Air Act. Following the April 2004 

designation, the state of Nevada submitted to EPA a request to reconsider the boundaries of the 

nonattainment designation for Clark County. EPA accepted the Nevada recommendations and 

issued a final rule in September 2004 delineating those boundaries. 

On December 22, 2006, the United States Court of Appeals for the District of Columbia Circuit 

vacated the Phase 1 Implementation Rule. EPA and other entities petitioned for a rehearing. On 

June 8, 2007, the court reviewed its decision and decided to vacate only certain portions of the 

rule, including the classification determinations for areas designated under Subpart 1 of the 

CAA. Following the court’s decision, EPA issued a memorandum (dated 6/15/2007) stating that 

nonattainment areas classified under “Subpart 1 are not currently subject to the June 15, 2007 

submission date for their attainment demonstrations” and established a transportation conformity 

rule allowing states in nonattainment to submit an Early Progress Plan (EPP). The EPP was to 

allow nonattainment areas to establish motor vehicle emission budgets (MVEB) that address the 

ozone NAAQS in advance of a complete attainment demonstration. These actions obligated 

Clark County to develop the Eight Hour Early Progress Plan for Clark County.. The Board of 

County Commissioners adopted and approved the Plan on June 17, 2008 which was 

subsequently submitted to the EPA. In May 2009, EPA formally approved the Plan. 

This plan provides an ozone attainment demonstration that makes use of the most recently 

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

approved by the designated Metropolitan Planning Organization for the Las Vegas urban area, 

(i.e., the Regional Transportation Commission of Southern Nevada). The plan also provides, 

among other things, revised emission inventories and updated MVEBs. 

After EPA approval, the plan will become a federally enforceable plan that identifies how Clark 

County will maintain the 1997 ozone NAAQS through 2022. Once approved, the MVEBs 

contained in the plan will become the projected budgets that the Regional Transportation 

Commission will use for transportation conformity determinations in future regional 

transportation plans. 
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TABLE OF CONTENTS 

1.0 PLAN OVERVIEW ....................................................................................................... 1-1

1.1 Introduction .......................................................................................................... 1-1

1.2 Characteristics and Health Effects of Ozone ....................................................... 1-1

1.3 National Ambient Air Quality Standards for Ozone ............................................ 1-2

1.4 History of the Clark County Nonattainment Area ............................................... 1-2

1.5 Required Components of a Redesignation Request ............................................. 1-5

1.5.1 Attainment of the Standard ...................................................................... 1-5

1.5.2 Approved Implementation Plan under Section 110(k) ............................ 1-5

1.5.3 Permanent and Enforceable Improvements in Air Quality ...................... 1-5

1.5.4 Requirements under Section 110 and Part D ........................................... 1-5

1.5.5 Approvable Maintenance Plan under Section 175(a) .............................. 1-5

2.0 ATTAINMENT OF THE OZONE STANDARD ....................................................... 2-1

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

2.2 Monitoring Network ............................................................................................ 2-1

2.3 Monitoring Results and Attainment Demonstration ............................................ 2-3

2.4 Quality Assurance Program ................................................................................. 2-4

3.0 STATE IMPLEMENTATION PLAN APPROVAL .................................................. 3-1

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

3.2 Previous Ozone State Implementation Plan Approvals ....................................... 3-1

4.0 PERMANENT AND ENFORCEABLE IMPROVEMENT IN AIR QUALITY ..... 4-1

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

4.2 Economic Conditions ........................................................................................... 4-1

4.2.1 Development Patterns .............................................................................. 4-1

4.2.2 Population Trends .................................................................................... 4-1

4.3 Meteorological Conditions................................................................................... 4-2

4.4 Attainment and Maintenance Control Measures .................................................. 4-3

4.4.1 Permanent and Enforceable Emission Reduction Control Measures ...... 4-4

4.4.1.1 Federal Tier 2 Vehicle Emission Standards ........................... 4-4

4.4.1.2 Federal Highway Diesel Rule ................................................ 4-4

4.4.1.3 Federal Large Nonroad Diesel Engines Rule ......................... 4-4

4.4.1.4 Federal Nonroad Spark-Ignition Engines and Recreational 

Engines Standards .................................................................. 4-5

4.4.1.5 Federal Nonroad Spark-Ignition Engines and Equipment 

Standard ................................................................................. 4-5

4.4.1.6 State Vehicle Inspection and Maintenance Program ............. 4-5

4.4.1.7 Clark County Stationary Point and Nonpoint Source 

Regulations ............................................................................ 4-6

4.4.2 Additional Emission Reduction Control Measures .................................. 4-6

4.4.2.1 Regional Haze Rule ............................................................... 4-6

4.4.2.2 Actions by California Local Air Agencies ............................. 4-6

4.4.2.3 Alternative Fuels for Government Fleets Program ................ 4-6
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4.4.2.4 Transportation Control Measures/Transportation Demand 

Management Program ............................................................ 4-7

4.4.2.5 Ozone Action Days ................................................................ 4-7

4.4.2.6 Transportation Conformity .................................................... 4-7

4.5 Air Quality Trend Analysis: Weight of Evidence ................................................ 4-7

5.0 REQUIREMENTS FROM SECTION 110 AND PART D OF THE CLEAN AIR 

ACT AMENDMENTS ................................................................................................... 5-1

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

5.2 Section 110 Requirements ................................................................................... 5-1

5.2.1 Section 110(a)(2) ..................................................................................... 5-1

5.2.2 Section 110(l) ........................................................................................... 5-2

5.3 Part D Requirements ............................................................................................ 5-2

5.3.1 Section 172(c) .......................................................................................... 5-2

5.3.2 Section 176(c) .......................................................................................... 5-2

6.0 MAINTENANCE PLAN ............................................................................................... 6-1

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

6.2 Transporation Input Data ..................................................................................... 6-1

6.3 efficiency and Effectiveness Factors ................................................................... 6-1

6.4 Emission Inventory Type Categories ................................................................... 6-2

6.4.1 Point Sources ........................................................................................... 6-2

6.4.2 Nonpoint Sources ..................................................................................... 6-2

6.4.3 Private and Commercial Aviation ............................................................ 6-3

6.4.4 Federal Aviation....................................................................................... 6-3

6.4.5 Railway .................................................................................................... 6-3

6.4.6 On-Road Mobile ...................................................................................... 6-3

6.4.7 Nonroad Mobile ....................................................................................... 6-4

6.4.8 Biogenic ................................................................................................... 6-4

6.4.9 Banked Emission Reduction Credits ....................................................... 6-4

6.5 Summary of Emission Inventories ....................................................................... 6-5

6.6 Maintenance Demonstration ................................................................................ 6-9

6.7 Monitoring Network AND Verification of Continued Attainment ................... 6-11

6.8 Contingency Plan ............................................................................................... 6-11

6.8.1 Potential Contingency Measures ............................................................ 6-12

6.8.1.1 Reid Vapor Pressure Reduction ........................................... 6-12

6.8.1.2 Inspection/Maintenance Program Changes and Additions .. 6-12

6.8.1.3 Consumer and Commercial Products................................... 6-12

6.8.1.4 Architectural Surface Coatings ............................................ 6-12

6.8.1.5 Lawn and Garden Equipment Use ....................................... 6-12

6.8.1.6 Establish/Enhance Trip Reduction Programs ...................... 6-12

6.8.2 Tracking and Triggering Mechanisms ................................................... 6-13

6.8.3 Action Resulting from Trigger Activation ............................................. 6-13

6.9 Subsequent Maintenance Plan Revisions ........................................................... 6-13

7.0 MOTOR VEHICLE EMISSIONS BUDGETS ........................................................... 7-1
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8.0 REFERENCES ............................................................................................................... 8-1

APPENDICES 

APPENDIX A: Clark County Ozone Redesignation Request and Maintenance Plan Technical 

Support Document, December 2010 ................................................................ A-1 

APPENDIX B: EPA Air Quality System, Design Value Report, 2006-2009 ............................B-1 

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

Figure 1-1. Areas in Clark County Designated Nonattainment for the 8-hour Ozone NAAQS 1-4

Figure 2-1. Clark County Ozone Monitoring Stations ................................................................ 2-2

Figure 4-1. Actual and Linear (OLS) Ozone Trends .................................................................. 4-8

Figure 6-1. VOC Emission Inventory for 2008 .......................................................................... 6-6

Figure 6-2. VOC Emission Inventory for 2015 .......................................................................... 6-6

Figure 6-3. VOC Emission Inventory for 2022 .......................................................................... 6-7

Figure 6-4. NOx Emission Inventory for 2008............................................................................ 6-8

Figure 6-5. NOx Emission Inventory for 2015............................................................................ 6-8

Figure 6-6. NOx Emission Inventory for 2022............................................................................ 6-9

Figure 6-7. Comparison of 2008, 2015, and 2022 NOx Emissions .......................................... 6-10

Figure 6-8. Comparison of 2008, 2015, and 2022 VOC Emissions ......................................... 6-11

LIST OF TABLES 

Table 2-1. Clark County Ozone Monitoring Sites ...................................................................... 2-1

Table 2-2. Three Year Average (ppm) of the 4th Highest Ozone Concentrations (2006-2008) . 2-3

Table 2-3. Three Year Average (ppm) of the 4th Highest Ozone Concentrations (2007-2009) . 2-3

Table 4-1. Clark County Population History (1990-2009) .......................................................... 4-2

Table 4-2. Monthly Averages for Temperature and Rainfall (1937 to 2009) .............................. 4-3

Table 6-1. Demographic Data Used to Develop Emission Inventories ....................................... 6-1

Table 6-2. Summary of Total Daily VOC Emissions (tpd) ......................................................... 6-5

Table 6-3. Summary of Total Daily NOx Emissions (tpd) ........................................................... 6-7

Table 7-1. VOC and NOx MVEBs for Clark County .................................................................. 7-1
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ACRONYMS AND ABBREVIATIONS 

Acronyms

AQR Clark County Air Quality Regulation 

BCC Clark County Board of County Commissioners 

CAA Clean Air Act 

CFR Code of Federal Regulations 

DAQEM Clark County Department of Air Quality & Environmental Management 

DRI Desert Research Institute 

EI Emission Inventory 

EPA U.S. Environmental Protection Agency 

EQM Environmental Quality Management, Inc 

ERC Emission Reduction Credit 

HPMS Highway Performance Monitoring System 

I/M Nevada Vehicle Inspection and Maintenance Program 

MVEB Motor Vehicle Emission Budget 

NAAQS National Ambient Air Quality Standards 

NAC Nevada Administrative Code 

NDEP Nevada Division of Environmental Protection 

NRS Nevada Revised Statues 

RTC Regional Transportation Commission of Southern Nevada 

SIP state implementation plan 

SLAMS State and Local Air Monitoring System 

TDM Transportation Demand Model 

TSD Technical Support Document 

VMT vehicle miles traveled 

Abbreviations

CO carbon monoxide 

NOx nitrogen oxides 

PM particulate matter 

ppm parts per million 

tpd tons per day 

tpy tons per year 

VOCs volatile organic compounds 
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1.0 PLAN OVERVIEW

1.1 INTRODUCTION 

Clark County, in conjunction with the Nevada Division of Environmental Protection (NDEP), 

requests that the U.S. Environmental Protection Agency (EPA) redesignate the Clark County 

ozone nonattainment area to attainment status for the 1997 8-hour National Ambient Air Quality 

Standards (NAAQS) for ozone. 

To comply with EPA guidance, Clark County inventoried emissions of volatile organic 

compounds (VOCs) and nitrogen oxides (NOx) for the 2008 attainment year and projected those 

emissions outward to 2015 and 2022. The inventories were then adjusted to reflect federal, state, 

and local rules on VOC and NOx emissions already adopted or implemented; these controls were 

shown to reduce overall ozone emissions through 2022, the maintenance year. 

1.2 CHARACTERISTICS AND HEALTH EFFECTS OF OZONE 

Ozone is a gas composed of three oxygen atoms that occurs both in Earth’s upper atmosphere 

(stratosphere) and at ground level (troposphere). Ozone in the stratosphere, which extends 

upward from 6 to 30 miles, occurs naturally and protects life from harmful ultraviolet rays. In the 

troposphere, ozone is a pollutant that poses a significant health risk, especially for children, the 

elderly, and people with chronic illnesses. It may also damage crops, trees, and other vegetation. 

Ground-level ozone is not usually emitted directly into the air, but formed through chemical 

reactions between NOx and VOCs in the presence of sunlight. Vehicle exhaust, emissions from 

commercial and industrial sources, gasoline vapors, chemical solvents, and natural sources emit 

NOx and VOCs. Since sunlight is an important formative factor, ozone pollution is usually a 

summertime problem. 

Ozone can irritate lung airways and cause an inflammation that resembles sunburn. Symptoms 

include wheezing, coughing, pain when taking a deep breath, and difficulty breathing during 

exercise or outdoor activities. Children and those with respiratory problems are particularly 

susceptible, but even healthy people who are active outdoors can be affected. Repeated exposure 

to ozone pollution over many months may cause permanent lung damage. Even when 

concentrations are low, ozone pollution may aggravate asthma, reduce lung capacity, and 

increase susceptibility to respiratory illnesses like pneumonia and bronchitis. 

Ground-level ozone may also affect plants and ecosystems. It interferes with the ability of plants 

to produce and store food, which makes them more susceptible to disease, insects, harsh weather, 

and other pollutants. This in turn can impact crop and forest yields. In addition, ozone can 

damage the leaves of trees and other plants. 

Ozone and its precursor pollutants may be transported hundreds of miles downwind from their 

original sources. Transport of pollutants from California into southern Nevada contributes to 

ozone concentrations in Clark County during the summer months. 
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1.3 NATIONAL AMBIENT AIR QUALITY STANDARDS FOR OZONE 

There are two federal standards for ozone: a primary standard that establishes limits to protect 

public health, including the health of sensitive populations such as asthmatics, children, and the 

elderly, and a secondary standard that sets limits to protect public welfare, including protection 

against decreased visibility and damage to animals, crops, vegetation, and buildings. Both 

standards are identical for the 1997 ozone NAAQS: 0.08 parts per million (ppm). 

1.4 HISTORY OF THE CLARK COUNTY NONATTAINMENT AREA 

On March 3, 1978, EPA designated the Las Vegas Valley a nonattainment area for the ozone 

NAAQS in volume 43, page 8962 of the Federal Register (43 FR 8962). Air quality monitoring 

data for calendar years 1975 through 1977 show violations of the 1-hour ozone NAAQS in effect 

at the time. That same month, Nevada’s governor designated the Clark County Board of County 

Commissioners (BCC) the responsible entity for preparing State Implementation Plans (SIPs) for 

Clark County; the BCC then delegated that responsibility to the agency that is now DAQEM. 

On February 8, 1979, the EPA established a primary 1-hour ozone NAAQS of 0.12 ppm (44 FR 

8220). After EPA determined the Las Vegas Valley was a nonattainment area for ozone, the 

county began requiring targeted industries to implement improved control technologies that 

curbed precursor pollutants because research had shown that industrial processes within Clark 

County were contributing to elevated ozone levels. By the end of 1984, control technologies had 

been fully implemented and Clark County had completed a SIP demonstrating attainment of the 

ozone NAAQS. 

In January 1985, the Nevada governor submitted the Clark County ozone SIP to EPA for review 

and approval. This SIP demonstrated attainment of the 1-hour ozone NAAQS, in accordance 

with EPA requirements and federal law. In April 1986, the state of Nevada requested that EPA 

redesignate the Las Vegas Valley as an attainment area, providing documentation that showed 

how control measures and technologies had resulted in improved air quality and compliance with 

the ozone NAAQS. EPA approved the SIP in August 1986, and on November 19, 1986, it 

redesignated the Las Vegas Valley as an attainment area for the 1-hour ozone NAAQS effective 

January 20, 1987 (51 FR 41788). 

On July 18, 1997, EPA revised the ozone NAAQS (62 FR 38856), replacing the 1-hour 0.12-

ppm primary standard with an 8-hour 0.08 ppm standard that was based on the three-year 

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

measured at each monitor within a given area. This rule became effective September 16, 1997. 

On June 27, 2003, Clark County submitted a recommendation to NDEP on the designation of 

Clark County under the 1997 8-hour ozone NAAQS. At the time, the data for the past three years 

(2000, 2001, and 2002) indicated that Clark County was in compliance with the 8-hour standard. 

On July 10, 2003, pursuant to Section 107(d) of the 1990 CAA, the state of Nevada submitted 

the recommended designations to EPA’s Region 9 office. 
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In its response to the governor on December 3, 2003, EPA agreed with the state’s 

recommendation but noted that it was tracking 2003 ozone monitoring data. That data indicated 

that the standard was exceeded, if barely, at one location. Basing its final designation on 2001, 

2002, and 2003 monitoring data, EPA designated Clark County in nonattainment of the 8-hour 

ozone NAAQS on April 15, 2004 (69 FR 23858) under the Title 1, Part D, Subpart 1 of the 

Clean Air Act (CAA). 

On May 21, 2004, the Nevada governor requested that EPA delay the effective date of its 

nonattainment designation for Clark County until October 15, 2004, and on June 18, EPA 

promulgated a final rule deferring the effective date to September 13, 2004 (69 FR 34076). The 

agency agreed that relevant factors for defining a nonattainment area might support a different 

recommendation than the one the state had submitted on April 12, 2004. On August 2, 2004, the 

state submitted a revised recommendation that encompassed the following areas in Clark 

County: 

 Ivanpah Valley (Hydrographic Areas 164A, 164B, 165, and 166). 

 Eldorado Valley (Hydrographic Area 167). 

 Las Vegas Valley (Hydrographic Area 212). 

 Colorado River Valley (Hydrographic Area 213). 

 Paiute Valley (Hydrographic Area 214). 

 Apex Valley (Hydrographic Areas 216 and 217). 

 A portion of Moapa Valley (Hydrographic Area 218). 

Figure 1-1 shows the areas within Clark County designated as basic nonattainment for the 8-hour 

ozone standard. EPA accepted the state’s recommendations and issued a final rule in September 

2004 delineating the revised boundaries. 

On December 22, 2006, a three-judge panel from the U.S Court of Appeals for the District of 

Columbia Circuit vacated the Phase 1 Implementation Rule (472 F. 3d 882 (D.C. Cir. 2006)).

EPA and other organizations filed petitions for a rehearing. On June 8, 2007, the entire court 

reviewed the decision to vacate the rule and decided to vacate only certain portions, including the 

classification determinations for areas designated under Title I, Part D, Subpart 1 of the CAA. 

Following the court’s decision, EPA issued a memorandum (dated 6/15/2007) stating that 

nonattainment areas classified under “Subpart 1 are not currently subject to the June 15, 2007 

submission date for their attainment demonstrations.” These actions obligated Clark County to 

develop and submit to EPA in 2008 the 8-Hour Ozone Early Progress Plan for Clark County, 

Nevada (DAQEM 2008a) to establish motor vehicle emission budgets (MVEBs) for maintaining 

transportation conformity. The Board of County Commissioners adopted and approved the EPP 

on June 17, 2008. EPA formally approved these MVEBs on May 14, 2009 (74 FR 22738).
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Figure 1-1. Areas in Clark County Designated Nonattainment for the 8-hour Ozone NAAQS 

 
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1.5 REQUIRED COMPONENTS OF A REDESIGNATION REQUEST 

CAA Section 107(d)(3)(E) defines the five conditions that must be met before EPA can 

redesignate a nonattainment area to attainment. With the submittal of this plan, Clark County 

meets these five conditions. 

1.5.1 Attainment of the Standard 

Clark County must show that the area is attaining the applicable NAAQS. Redesignation of 

ozone nonattainment areas to attainment is based solely on ambient air quality data. Section 2 

presents the data that demonstrate Clark County’s attainment of the 1997 ozone NAAQS. 

1.5.2 Approved Implementation Plan under Section 110(k) 

Clark County must have a SIP fully approved under CAA Section 110(k) and must satisfy all 

requirements that apply to the nonattainment area. Section 3 discusses Clark County’s ozone SIP 

development. 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 Clean Air Act 

requirements. 

1.5.3 Permanent and Enforceable Improvements in Air Quality 

Clark County must be able to reasonably attribute the improvement in air quality to emission 

reductions that are permanent and federally enforceable. Section 4 shows that improved air 

quality in the Clark County area is the result of permanent and enforceable emission reduction 

control measures, as opposed to adverse economic or meteorological conditions. 

1.5.4 Requirements under Section 110 and Part D 

Clark County must meet all requirements of CAA Section 110 and Part D that applied before the 

submittal of the redesignation request. Section 5 describes how this SIP does not interfere with 

any requirements for attainment of the ozone NAAQS, reasonable further progress towards 

attainment of all other criteria pollutant NAAQS, or any other applicable CAA requirement. 

1.5.5 Approvable Maintenance Plan under Section 175(a) 

CAA Section 107(d)(3)(E) stipulates that EPA must fully approve a maintenance plan that meets 

the requirements of Section 175(a) before it can redesignate an area to attainment. Section 6 

provides a plan to maintain compliance with the ozone NAAQS for at least ten years after 

redesignation. 
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2.0 ATTAINMENT OF THE OZONE STANDARD 

2.1 INTRODUCTION 

The first required component of an area’s redesignation request is a demonstration that it has 

attained the NAAQS. Attainment of the 1997 ozone standard is demonstrated through the 

establishment of a design value, which is based on the three-year average of the annual fourthhighest daily maximum 8-hour average ozone concentrations measured at each monitor. The 

fourth-highest daily maximum 8-hour average ozone concentration may not exceed 0.084 ppm. 

This section demonstrates, as required by CAA Section 107(d)(3)(E), that Clark County has 

attained the 1997 ozone NAAQS. The attainment demonstration is based on quality-assured 

monitoring data representative of the Clark County ozone nonattainment area. 

2.2 MONITORING NETWORK 

Title 40, Part 58 of the Code of Federal Regulations (40 CFR 58) defines the requirements for 

the ambient air quality monitoring programs mandated by the CAA. The current Clark County 

ozone monitoring network consists of 8 State and Local Air Monitoring Stations (SLAMS). As 

Table 2-1 shows, the monitoring objective of most sites is “population exposure.” The 

exceptions are Jean, which monitors regional transportation, and Joe Neal, whose monitoring 

objective is “highest concentration.” Clark County’s monitoring system is governed by quality 

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

performance audits. 

Table 2-1. Clark County Ozone Monitoring Sites 

Site Name Site Code Address Monitoring Objective 

Paul Meyer 32-002-0043 4525 New Forest Dr., Las Vegas 89147 Population exposure 

Walter Johnson 32-002-0071 7701 Ducharme Ave., Las Vegas 89145 Population exposure 

Palo Verde 32-003-0073 333 Pavilion Center Dr., Las Vegas 89144 Population exposure 

Joe Neal 32-003-0075 6651 Azure Way, Las Vegas 89130 Highest concentration 

Winterwood 32-0030-538 5483 Club House Dr., Las Vegas 89142 Population exposure 

Boulder City 32-003-0601 1005 Industrial, Boulder City 89005 Population exposure 

Jean 32-003-1019 1965 State Highway 161, Jean 89019 Regional transportation 

J.D. Smith 32-003-2002 1301B Tonopah Ave., North Las Vegas 89030 Population exposure 

Figure 2-1 shows the locations of Clark County ozone monitoring stations. Tables 2-2 and 2-3 

show the three-year averages of the fourth-highest ozone concentrations measured at these 

stations during 2006–2008 and 2007–2009, respectively. 
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Figure 2-1. Clark County Ozone Monitoring Stations 
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Thirteen ozone monitoring stations were in operation during the time period 2006-2009. 

Monitoring data from 2006-2008 and 2007-2009 is used to show that Clark County is in 

attainment of the 1997 ozone NAAQS. 

Table 2-2. Three Year Average (ppm) of the 4th Highest Ozone Concentrations (2006-2008) 

Site Name Site Code 2006 2007 2008 Design Value

2006-2008 

Craig Road 32-003-0020 0.079 0.075 0.071 0.075 

Apex 32-003-0022 0.079 0.081 0.071 0.077 

Mesquite 32-003-0023 0.069 0.065 0.069 0.067 

Paul Meyer 32-002-0043 0.083 0.083 0.077 0.081 

Walter Johnson 32-002-0071 0.085 0.085 0.076 0.082 

Lone Mountain 32-003-0072 0.085 0.080 0.078 0.081 

Palo Verde 32-003-0073 0.084 0.081 0.074 0.079 

Joe Neal 32-003-0075 0.083 0.081 0.080 0.081 

Winterwood 32-0030-538 0.078 0.076 0.071 0.075 

Boulder City 32-003-0601 0.074 0.076 0.071 0.073 

Jean 32-003-1019 0.079 0.083 0.074 0.078 

Orr 32-003-1021 0.085 0.077 0.074 0.078 

J.D. Smith 32-003-2002 0.081 0.080 0.068 0.076 

Source: EPA Air Quality System, 2006-2008 (Appendix B). 

Table 2-3. Three Year Average (ppm) of the 4th Highest Ozone Concentrations (2007-2009) 

Site Name Site Code 2007 2008 2009 Design Value

2007-2009 

Craig Road 32-003-0020 0.075 0.071 0.072 0.072 

Apex 32-003-0022 0.081 0.071 0.070 0.074 

Mesquite 32-003-0023 0.065 0.069 0.062 0.065 

Paul Meyer 32-002-0043 0.083 0.077 0.071 0.077 

Walter Johnson 32-002-0071 0.085 0.076 0.074 0.078 

Lone Mountain 32-003-0072 0.080 0.078 0.072 0.076 

Palo Verde 32-003-0073 0.081 0.074 0.072 0.075 

Joe Neal 32-003-0075 0.081 0.080 0.074 0.078 

Winterwood 32-0030-538 0.076 0.071 0.070 0.072 

Boulder City 32-003-0601 0.076 0.071 0.071 0.072 

Jean 32-003-1019 0.083 0.074 0.072 0.076 

Orr 32-003-1021 0.077 0.074 0.071 0.074 

J.D. Smith 32-003-2002 0.080 0.068 0.072 0.073 

Source: EPA Air Quality System, 2007–2009 (Appendix C). 

2.3 MONITORING RESULTS AND ATTAINMENT DEMONSTRATION 

The monitoring data presented in Tables 2-2 and 2-3 verify that the Clark County nonattainment 

area has been in attainment with the ozone NAAQS since 2008, including the most recent threeyear period of 2007–2009, in accordance with the federal requirements of 40 CFR 58. The data 

also depict a downward trend in ozone concentrations in the Clark County nonattainment area. 
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2.4 QUALITY ASSURANCE PROGRAM 

Ozone data have been collected and verified in accordance with 40 CFR 58, Appendix A, 

“Quality Assurance Handbook for Air Pollution Measurement Systems, Volume II: Ambient Air 

Monitoring Program,” and the DAQEM Quality Control and Assurance System for Criteria 

Gaseous Pollutants (DAQEM 2008b).

Ozone data are submitted to EPA’s Air Quality System database and are available for public 

review in the annual network plan Clark County submits to EPA. The data are also posted on the 

Air Quality Index page of Clark County’s Web site and are reported in local media. 
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3.0 STATE IMPLEMENTATION PLAN APPROVAL 

3.1 INTRODUCTION 

The second required component of an area’s redesignation request is a fully approved SIP 

satisfying all the requirements that apply to the nonattainment area under CAA Section 110(k), 

which addresses completeness findings, deadlines for EPA actions, types of EPA actions, and 

sanctions that may be applied to areas failing to meet CAA requirements. 

3.2 PREVIOUS OZONE STATE IMPLEMENTATION PLAN APPROVALS 

The Phase 1 Implementation Rule issued by EPA in April 30, 2004, classified Clark County as a 

“basic” nonattainment area under Subpart 1 of the CAA, effective June 15, 2004 (69 FR 23858). 

Following this designation, the state of Nevada submitted to EPA a request to reconsider the 

boundaries of the Clark County nonattainment area. EPA accepted the Nevada recommendations 

and issued a final rule in September 2004 delineating those boundaries (Section 1.3). 

In December 2006, the U. S. Court of Appeals for the District of Columbia Circuit (D.C. Circuit) 

vacated the Phase 1 Implementation Rule. EPA issued a memorandum in June 2007 stating that 

nonattainment areas previously classified under Subpart 1 were no longer subject to the June 

2007 submittal date for their attainment demonstrations. EPA then established a transportation 

conformity rule allowing nonattainment areas to submit early progress plans containing early 

MVEBs that addressed the ozone NAAQS before submitting a complete attainment 

demonstration. Clark County developed the 8-Hour Ozone Early Progress Plan for Clark 

County, Nevada (DAQEM 2008a) and submitted it to EPA in June 2008 to establish MVEBs, 

and EPA formally approved the MVEBs on May 14, 2009 (74 FR 22738). 

In nonattainment areas where monitored data demonstrate the NAAQS have already been 

achieved, EPA has determined that certain requirements of Part D, Subparts 1 and 2 of the CAA 

do not apply. Therefore, Clark County does not require certain submissions for an area that has 

attained the NAAQS. These include reasonable further progress (RFP) requirements, attainment 

demonstrations, reasonably available control measures (RACM), and contingency measures, 

because these provisions have the purpose of helping achieve attainment of the NAAQS. 

This interpretation of the CAA is known as the Clean Data Policy and is the subject of two EPA 

memoranda. EPA also finalized the statutory interpretation set forth in the policy in its final rule, 

40 CFR 51.918, as part of its “Final Rule to Implement the 8-hour Ozone NAAQS—Phase 2” 

(Phase 2 Final Rule) – see discussion in the preamble to the rule at 70 FR 71612, 71645-46 

(November 29, 2005). The D.C. Circuit (2009) upheld this Clean Data regulation as a valid 

interpretation of the CAA in NRDC v. EPA, 571 F. 3d 1245. EPA also finalized its interpretation 

in a regulation that was part of its Implementation Rulemaking for the PM2.5 NAAQS (40 CFR 

51.1004(c)). Thus, EPA has codified the policy when it established final rules governing 

implementation of new or revised NAAQS for the pollutants (70 FR 71612, 71644-46 

(November 29, 2005) (ozone); 72 FR 20585, 20665 (April 25, 2007) (PM2.5)). Otherwise, it 

applies the policy in individual rulemakings related to specific nonattainment areas, (i.e., 75 FR 

6571 (February 10, 2010)). EPA believes that the legal bases set forth in detail in EPA’s Phase 2 
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March 2011 3-2 

Final rule, (i.e., May 10, 1995 memorandum from John S. Seitz, entitled “Reasonable Further 

Progress, Attainment Demonstration, and Related Requirements for Ozone Nonattainment Areas 

Meeting the Ozone National Ambient Air Quality Standard,” the PM2.5 implementation rule, and 

the December 14, 2004 memorandum from Stephen D. Page entitled “Clean Data Policy for the 

Fine Particle National Ambient Air Quality Standards”), are equally pertinent to the 

interpretation of provisions of Subparts 1 and 4 applicable to PM10. Our interpretation that an 

area that is attaining the standards is relieved of obligations to demonstrate RFP and to provide 

an attainment demonstration, RACM and contingency measures pursuant to Part D of the CAA, 

pertains whether the standard is PM10, ozone or PM2.5. 

The monitoring data presented in Tables 2-2 and 2-3 of Section 2.2 verify the Clark County 

nonattainment area has been in attainment with the ozone NAAQS since 2008, including the 

most recent three-year period of 2007–2009. 
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4.0 PERMANENT AND ENFORCEABLE IMPROVEMENT IN AIR 

QUALITY 

4.1 INTRODUCTION 

The third required component of an area’s redesignation request is a demonstration that the 

improvement in air quality is reasonably attributed to emission reductions that are permanent and 

federally enforceable. This section demonstrates that improved air quality in the Clark County 

ozone nonattainment area is the result of permanent and enforceable emission reduction control 

measures, as opposed to adverse economic or meteorological conditions. 

4.2 ECONOMIC CONDITIONS 

Clark County, formed in 1909, totals more than 8,000 square miles in area and is located at the 

southern tip of the state. Most residents live in the Las Vegas Valley, a 600-square-mile basin in 

the middle of the county. In addition to hosting up to 40 million visitors a year, Las Vegas has 

been one of the fastest growing cities in the nation for 25 years. This rapid population growth 

and accompanying development led to increased emissions of pollutants and, beginning in 2001, 

ozone concentrations in Clark County approached (and sometimes exceeded) the 8-hour ozone 

NAAQS. 

4.2.1 Development Patterns 

More than 90 percent of the land in Clark County is owned by federal agencies and restricted 

from public use. The U.S. Bureau of Land Management (BLM) has the largest holdings, 

including the Red Rock National Conservation Area west of Las Vegas. Most of the Spring 

Mountain Range, including Mt. Charleston, is administered by the U.S. Forest Service as part of 

the Toiyabe National Forest. 

Urbanized land is concentrated in the Las Vegas Valley and includes the cities of Las Vegas, 

Henderson, and North Las Vegas, as well as unincorporated areas of Clark County. These 

communities contain the highest population densities and corresponding roadway networks. 

Traffic volumes are increasing every year because of population growth and development. 

Although emissions from mobile and nonpoint sources in Clark County originate primarily in the 

Las Vegas Valley, nearby areas contain significant industrial sources of pollution. The Apex 

Industrial Park, 20 miles northeast of Las Vegas, is home to many sources of NOx. Power plants 

such as the Reid Gardner facility near Moapa are a significant source of NOx. 

4.2.2 Population Trends 

More than 95 percent of Clark County’s population resides in the Las Vegas Valley. But 

communities outside the valley have also experienced significant growth in the past 20 years, 

including Mesquite, on the county’s northeastern edge, and Laughlin, at the county’s southern 

end. Table 4-1 provides population data in Clark County from 1990 to 2009, and Appendix A 

contains Clark County population projections for future years. Clark County experienced a 
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population decrease of less than one percent between 2008 and 2009, but this likely has not had 

an effect on overall ozone concentrations in the county. 

Table 4-1. Clark County Population History (1990-2009) 

Year Population Annual Population Change Annual Percent Increase 

1990 770,280 — — 

1991 835,080 64,800 8% 

1992 873,730 38,650 5% 

1993 916,837 43,107 5% 

1994 990,564 73,727 8% 

1995 1,055,435 64,871 7% 

1996 1,119,052 63,617 6% 

1997 1,193,388 74,336 7% 

1998 1,261,150 67,762 6% 

1999 1,327,145 65,995 5% 

2000 1,394,440 67,295 5% 

2001 1,485,855 91,415 7% 

2002 1,549,657 63,802 4% 

2003 1,620,748 71,091 5% 

2004 1,715,337 94,589 6% 

2005 1,796,380 81,043 5% 

2006 1,874,837 78,457 4% 

2007 1,954,319 79,482 4% 

2008 1,967,716 13,397 <1% 

2009 1,952,040 -15,676 - <1% 

Source: Center for Business and Economic Research, UNLV (2010). 

4.3 METEOROLOGICAL CONDITIONS 

Located in the Mojave Desert, Clark County has four well-defined seasons. Summers display the 

classic characteristics of the desert Southwest: daily high temperatures in the lower elevations 

often exceed 100oF, with lows in the 70s. There has been no change in weather patterns over the 

last decade. 

The summer heat is usually tempered by low relative humidity, which may increase for several 

weeks during July and August in association with moist monsoonal wind flows from the south. 

This is the most common period for thunderstorms in the valley, which can result in flash 

flooding. Temperatures during the spring and fall are generally moderate. Strong winds are the 

most persistent weather hazard: although winds higher than 50 miles per hour are infrequent, 

they often happen during vigorous storms. 

Winters are generally mild and pleasant. Afternoon temperatures average 60oF, and the sky is 

normally clear and sunny. Snow accumulation on valley floors is rare; however, higher 

elevations, such as the Spring Mountains, typically receive 5–10 feet of snowfall annually. Based 

on measurements from McCarran International Airport over the past thirty years, temperatures 

fall below 32oF an average of 24 days a year. 
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Average annual rainfall in the valley, measured at McCarran International Airport, is 

approximately 4.16 inches. Table 4-2 lists temperature and rainfall averages in Clark County 

over the last seven decades. 

Table 4-2. Monthly Averages for Temperature and Rainfall (1937 to 2009) 

Month Maximum (F) Minimum (F) Average (F) Rainfall (inches) 

January 57.1 34.5 47.0 0.52 

February 62.5 38.9 52.2 0.58 

March 69.5 44.3 58.3 0.45 

April 78.2 51.7 66.0 0.20 

May 88.5 61.1 75.4 0.15 

June 98.6 69.9 85.6 0.07 

July 104.6 76.5 91.2 0.43 

August 102.2 74.8 89.3 0.44 

September 94.7 66.6 81.3 0.32 

October 81.3 54.3 68.7 0.25 

November 66.5 42.0 55.0 0.36 

December 57.2 34.7 47.0 0.40 

Annual Average 80.1 54.1 68.1 4.16

Source: Western Regional Climate Center (2010). 

Local meteorology and general weather patterns in the Southwest have a significant effect on the 

valley’s air quality. Stagnant conditions and low wind speeds can build up concentrations of 

ozone and precursor pollutants in the valley; winds from the southwest or west can transport 

ozone and other pollutants into Clark County. Wind speed and direction affect ozone levels in 

different areas at different times, and complex terrain features influence local flows within, into, 

and out of neighboring basins. Ozone concentrations in the Las Vegas Valley can therefore differ 

significantly, depending on location and time of day. 

4.4 ATTAINMENT AND MAINTENANCE CONTROL MEASURES 

This plan demonstrates maintenance of the 1997 ozone NAAQS through 2022 using seven 

permanent and enforceable emissions reduction control measures: 

1. Federal Tier 2 vehicle emissions standards (65 FR 6822). 

2. Federal highway diesel rule (66 FR 5001). 

3. Federal large nonroad diesel engines rule (69 FR 38958). 

4. Nonroad spark-ignition engines and recreational engines standards (65 FR 76789). 

5. Federal nonroad spark-ignition engines and equipment standards (73 FR 59034). 

6. Nevada vehicle inspection and maintenance (I/M) program (Nevada Revised Statutes 

(NRS) 445B and Nevada Administrative Code (NAC) 445B). 
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7. Clark County stationary point and nonpoint source air quality regulations (AQRs). 

Section 4.4.1 discusses each of these seven measures. Section 4.4.2 describes additional emission 

reduction control measures that provide further ozone reductions, but are not quantified in the 

emission inventories (EIs). 

4.4.1 Permanent and Enforceable Emission Reduction Control Measures 

The seven emission reduction control measures used for quantitative emission reductions in the 

ozone maintenance plan are described below. These measures, which are permanent and 

enforceable, will remain in place through the maintenance year of 2022 and will ensure 

continued ozone emission reductions throughout the nonattainment area, as demonstrated in 

Section 6.6. 

 

4.4.1.1 Federal Tier 2 Vehicle Emission Standards

The Tier 2 standards require all passenger vehicles in a manufacturer’s fleet, including light-duty 

trucks and sport utility vehicles, to meet an average standard of 0.07 grams of NOx per mile. 

Implementation of Tier 2 standards began in 2004, and most vehicles had been phased in by 

2007. Federal Tier 2 standards also cover passenger vehicles over 8,500 pounds gross vehicle 

weight rating (e.g., large pickup trucks, sport utility vehicles), which were not covered by the 

previous Tier 1 regulations. Phase-in for these vehicles began in 2008, with full compliance 

achieved in 2009. 

The Tier 2 rule also reduced the sulfur content of gasoline from major refineries to 30 ppm 

starting in January 2006; before then, most summertime gasoline sold in Clark County had a 

sulfur content of about 300 ppm. Emission reductions from the federal Tier 2 standards have 

been primarily responsible for a large decrease in ozone concentrations in Clark County. 

4.4.1.2 Federal Highway Diesel Rule

Beginning with the 2007 model year, this rule reduced emissions from heavy-duty diesel 

vehicles by more than 90 percent. Additionally, the rule led to a 97 percent reduction in the 

sulfur content of highway diesel fuel. Previous levels were between 500 ppm (low sulfur diesel) 

and 15 ppm (ultra-low sulfur diesel). Advanced pollution control technology for cars, trucks, and 

buses allowed engine manufacturers to meet 2007 emission standards. EPA estimated this rule 

would eliminate 2.6 million tons of NOx emissions from heavy-duty vehicles each year once the 

program was fully implemented, equivalent to a 95 percent reduction in NOx emissions when 

compared to older diesel engines using higher-content sulfur diesel. 

4.4.1.3 Federal Large Nonroad Diesel Engines Rule

This rule, promulgated in 2004, applies to large nonroad diesel engines like those used in 

construction, agricultural, and industrial equipment. EPA began phasing in the program in 2008, 

and is scheduled to finish in 2014. The rule reduces the allowable sulfur in nonroad diesel fuel to 

15 ppm by 2010. The combined engine and fuel rules should reduce NOx emissions from large 
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March 2011 4-5 

nonroad diesel engines by over 90 percent when compared to older nonroad engines using 

higher-content sulfur diesel. 

4.4.1.4 Federal Nonroad Spark-Ignition Engines and Recreational Engines Standards

In 2003, this standard began regulating NOx and VOCs for groups of previously unregulated 

nonroad engines, including large spark-ignition engines (e.g., forklifts, airport ground service 

equipment), recreational vehicles (e.g., off-highway motorcycles), and recreational marine diesel 

engines. In Clark County, the standards on large spark-ignition engines and recreational vehicles 

have contributed the most to reducing local ozone concentrations. EPA estimates that by 2020, 

the standard will reduce NOx emissions from these types of equipment by 80 percent and VOC 

emissions by 72 percent. 

4.4.1.5 Federal Nonroad Spark-Ignition Engines and Equipment Standard

In 2011, this standard will start regulating NOx, VOCs, and carbon monoxide (CO) from all new 

land-based spark-ignition engines running at or below 19 kilowatts (e.g., lawn and garden 

equipment, utility vehicles, generators) and from spark-ignition engines used in marine vessels 

(e.g., outboard engines, personal watercraft, stern drive/inboard engines). The standard also 

adopts new evaporative emissions standards to control permeation from these engines. In Clark 

County, the standards on small engines used in lawn and garden equipment, utility vehicles, and 

generators will contribute the most to reducing local ozone concentrations. EPA estimates that by 

2020, the standard will reduce NOx emissions from these types of equipment by 46 percent and 

VOC emissions by 33 percent. 

 

4.4.1.6 State Vehicle Inspection and Maintenance Program

Chapter 445B in the NRS and the NAC set forth the regulations governing motor vehicles in 

Clark County. Adopted in 1978 and administered by the Nevada Department of Motor Vehicles, 

these regulations establish annual testing procedures for 1968 or newer gasoline-powered 

vehicles, regardless of size, and for diesel-powered vehicles with a manufacturer’s gross vehicle 

weight rating of up to 10,000 pounds. The Nevada I/M program allows exemptions from 

emission testing for new vehicles on their first and second registration, new hybrid-electric 

vehicles during their first five model years, 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. 

On-board diagnostic testing procedures are used for 1996 and newer vehicles, while older 

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

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

that emit visible smoke. 

 
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4.4.1.7 Clark County Stationary Point and Nonpoint Source Regulations

Stationary sources in the Clark County nonattainment area are generally industrial, commercial, 

or institutional sources that emit 10 tons per year (tpy) or more of VOCs, 25 tpy of NOx, and 100 

tpy of any other criteria pollutant. Any source that generates, or has the potential to generate, at 

least 10 tpy of any single hazardous air pollutant (HAP) or 25 tpy of aggregate HAPs must report 

emissions. Nonpoint sources are commercial, small-scale industrial and residential sources 

whose emissions fall below point source reporting levels, and which are too numerous or too 

small to identify individually. 

Clark County has numerous regulations in place for stationary and nonpoint sources, notably 

AQR Sections 12.0 through 12.13, and Sections 13, 14, 16, 19 and 21. Clark County also 

regulates nonpoint sources, including gasoline-dispensing facilities, through the Stage II vapor 

recovery requirements in AQR Section 52, “Gasoline Dispensing Facilities.” Clark County 

enforces several federal regulations, such as 40 CFR Part 60, “Standards of Performance for New 

Stationary Sources, 40 CFR Part 61, “National Emission Standards for Hazardous Pollutants,” 

and 40 CFR Part 63, “National Emission Standards for Hazardous Air Pollutants for Source 

Categories,” to control emissions. 

4.4.2 Additional Emission Reduction Control Measures 

The Las Vegas Valley also benefits from the regional, state, and local ozone control programs 

listed below. Although these programs are not quantified in the EIs of this plan, they play an 

important role in reducing ozone levels in Clark County. 

4.4.2.1 Regional Haze Rule

This rule, promulgated in July 1999, mandates emission reductions to achieve natural visibility 

levels in mandatory Class I areas by 2064. Emission reduction control measures principally 

address light-scattering and -absorbing aerosols, such as NOx and VOC emissions. Several 

control measures will be implemented throughout the western states: for example, Best Available 

Retrofit Technologies will be installed on older units to significantly reduce NOx and VOCs. 

These controls will be operating by January 1, 2015, or no later than five years after approval of 

state regional haze SIPs, whichever comes first. Most western states, including Nevada, have 

submitted regional haze SIPs and are awaiting EPA approval. 

4.4.2.2 Actions by California Local Air Agencies 

Several local air agencies in California, such as the South Coast and San Joaquin Air Pollution 

Control Districts, are implementing control measures in conjunction with their SIPs. These 

control measures will likely reduce ozone transport into Clark County. 

4.4.2.3 Alternative Fuels for Government Fleets Program

This program is designed to reduce motor vehicle emissions, including NOx and VOCs, by 

regulating state and local government fleets of more than 24 vehicles based in Clark County. 
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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 fiscal year 2000, government fleets had to ensure that 90 

percent of new vehicle purchases were alternative-fuel vehicles. 

4.4.2.4 Transportation Control Measures/Transportation Demand Management Program

In 1999, after adoption of the Transportation Improvement Plan FY 1998-2000 (RTC 1999), the 

Regional Transportation Commission of Southern Nevada (RTC) created Club Ride, a employerbased commuter services program. Major components 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. Although voluntary, this and other RTC programs 

play an important role in Clark County’s efforts to reduce ozone levels. 

4.4.2.5 Ozone Action Days

This public outreach and education program is a voluntary initiative asking local residents to take 

additional preventive actions when high ozone levels are predicted. Under certain meteorological 

conditions, Clark County meteorologists can forecast when ground-level ozone may exceed 

health standards. On those days, Clark County faxes an air quality message to media outlets, 

government agencies, and other Ozone Action Day participants. The department also makes 

Ozone Action Day messages and daily forecasts available to the public on its Web site. 

Preventive actions to reduce air pollution on these days include refueling vehicles after dusk, 

avoiding excessive driving, using public transportation, and telecommuting. 

4.4.2.6 Transportation Conformity

Clark County will continue to work closely with the RTC to assure that Regional Transportation 

Plans and Transportation Improvement Programs in the Clark County ozone nonattainment area 

are consistent with and conform to Clark County’s air quality program, including the ozone SIP. 

4.5 AIR QUALITY TREND ANALYSIS: WEIGHT OF EVIDENCE 

Forecasting ozone concentrations in future years carries some level of uncertainty, so Clark

County performed an air quality trend analysis for the period between 2003 and 2009 using 

quality-assured data from the EPA Air Quality System database (Figure 4-1). The trend analysis 

would contribute to a weight-of-evidence approach to support the attainment demonstration of 

the ozone NAAQS with future-year VOC and NOx MVEBs. This trend analysis also supports 

Section 4.4.1 – Permanent and Enforceable Emission Reduction Control Measures. Declining 

design values started with the implementation of the first Federal emission standard for engines 

in 2003. The 2007 design value went slightly up due to 3 consecutive intensive wildfire seasons 
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March 2011 4-8 

in 2005, 2006 and 2007. The significant drop of the DV in 2009 can be contributed, in part, to 

the implementation of the Large Nonroad Engine rule; the source apportionment of the nonroad 

emissions category in 2008 was 33% for NOx and 20% for VOC. 

This linear analysis, based on the ordinary least squares, showed a continued downward trend of 

the design values. Clark County is confident that future ozone concentrations will continue to 

trend downward with the maintenance control measures described in Section 4.4 in place. 

Source: EPA Air Quality System, 2003-2010 (Appendix D). 

Figure 4-1. Actual and Linear (OLS) Ozone Trends 

86

85 85

83

86

82

78

y = ‐1.0357x + 87.714

R2 = 0.6042

70

72

74

76

78

80

82

84

86

88

90

2003 2004 2005 2006 2007 2008 2009

Ozone Concentrations (ppb)

Years

Ozone Trend

Design Values Linear (Design Values)

Tier II

Rule

Heavy Duty

Highway Rule

Nonroad Spark

Ingnition &

Recreational

Large

Nonroad Engine

Rule

Ultra Low

Sulfur Diesel

Rule
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5.0 REQUIREMENTS FROM SECTION 110 AND PART D OF THE 

CLEAN AIR ACT AMENDMENTS 

5.1 INTRODUCTION 

The fourth required component of a redesignation request is verification that Clark County meets 

CAA Section 110 and Part D requirements. This section provides that verification. 

5.2 SECTION 110 REQUIREMENTS 

Before EPA can redesignate the Clark County ozone nonattainment area, the provisions of CAA 

Section 110(a)(2) and CAA 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 components 

of the plan would interfere with any applicable requirement concerning attainment, with 

reasonable further progress towards attainment of a NAAQS, or with any other applicable CAA 

requirement. 

5.2.1 Section 110(a)(2) 

This CAA section contains the following SIP requirements: 

1. Establishment and implementation of enforceable emission limitations. 

2. Monitoring, compilation, and analysis of ambient air quality data. 

3. Preconstruction review and permitting of new and modified major stationary sources. 

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

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

regulations. 

6. Establishment of permit fees for stationary sources. 

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

controlling air pollution in Nevada. In Clark County, these programs are administered and 

enforced by Clark County. The department has more than 100 staff members and an annual 

budget of approximately $28 million to administer, implement and enforce the CAA, including 

air quality plans and regulations applicable to the Clark County ozone nonattainment area. 

Clark County’s current air program meets all provisions required by CAA Section 110(a)(2). If 

Clark County becomes unable to meet any of the provisions, NRS 445B.520 and 445B.530 allow 

the State Environmental Commission to assume jurisdiction over the local air quality 

management program to ensure that CAA requirements are met. EPA also has authority to 

impose sanctions on a state if it “...finds that any requirement of an approved plan (or approved 

part of a plan) is not being implemented” (CAA, Section 179). 
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5.2.2 Section 110(l) 

CAA Section 110(l) requires that SIP revisions not interfere with requirements for attainment or 

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

requirements. Since this plan proposes no changes to current emission reductions control 

measures, it poses no interference with Clark County’s progress towards continued attainment of 

the CO or particulate matter NAAQS. Nevada is currently designated as 

attainment/unclassifiable for particulate matter less than 2.5 microns in diameter under Section 

107(d) of the CAA. 

5.3 PART D REQUIREMENTS 

Sections 172(c) and 176(c) in Part D of the CAA lay out requirements applicable to all areas 

designated as nonattainment because of a NAAQS violation. Clark County was not classified 

under CAA Part D, so it is only subject to the general provisions of CAA Subpart 1, 

“Nonattainment Areas in General.” 

5.3.1 Section 172(c) 

This section contains general requirements for maintenance plans, including: 

1. Implementation of reasonably available control measures, including reasonably available 

control technologies, for existing sources. 

2. Reasonable further progress for existing sources. 

3. A current EI, and periodic EIs every three years until attainment. 

4. Identification and quantification of allowable emissions for new and modified stationary 

sources. 

5. 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. 

Clark County’s current air program, in conjunction with the components of this plan, meets all 

Section 172(c) provisions. 

5.3.2 Section 176(c) 

This section contains transportation and general conformity provisions applicable in maintenance 

areas. The transportation conformity process ensures transportation plans, programs, and projects 

in maintenance areas do not create new violations of the NAAQS, do not increase the frequency 
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March 2011 5-3 

or severity of NAAQS violations, and do not delay timely attainment of the NAAQS. It does not 

allow federal agencies to engage in, support, or provide financial assistance for licensing, 

permitting, or approving any project unless the project conforms to the SIP. 

In approving the Clark County Transportation Conformity Plan (DAQEM 2008c) and the 

transportation conformity budgets in the 8-Hour Ozone Early Progress Plan for Clark County, 

Nevada (DAQEM 2008a), EPA determined that Clark County met the Section 176(c) 

requirements of the transportation conformity rule, 40 CFR 93, Subpart A (73 FR 66183). 

Additionally, Clark County’s commitment to submit a maintenance plan to EPA that 

incorporates all emissions from a conformity determination for the force beddown of the F-35 

Force Development Evaluation and Weapons School at Nellis Air Force Base is consistent with 

the general conformity requirements of CAA Section 176(c) and 40 CFR 93.158(a)(5)(i)(B). 
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6.0 MAINTENANCE PLAN 

6.1 INTRODUCTION 

The fifth required component of an area’s redesignation request is fulfillment of CAA Section 

107(d)(3)(E) requirements. These specify that for an area to be redesignated to attainment, EPA 

must approve a maintenance plan that meets all the conditions of CAA Section 175(a), including 

a comprehensive and accurate demonstration of continued maintenance of the ozone NAAQS for 

ten years after redesignation. 

Two approaches are acceptable for demonstrating maintenance of the NAAQS (Calcagni, 1992). 

The first, the emissions projections approach, compares a projected EI with an attainment EI. 

The second is a complex analysis using gridded dispersion modeling. Clark County used the 

emissions projection approach, comparing an EI for the attainment year (2008) to an EI for the 

maintenance year (2022). The maintenance year was chosen to allow EPA 18 months after 

receipt of a complete submittal to process Clark County’s redesignation request. 

The attainment EI represents an emission level that would not cause a NAAQS violation. If the 

projected maintenance year EI remains at or below the attainment year EI, continued 

maintenance is demonstrated. In addition, the maintenance demonstration includes a comparison 

between an interim year EI (2015) and the attainment year EI to show definitive maintenance

throughout the 10-year period after redesignation, not just in the maintenance year. 

6.2 TRANSPORATION INPUT DATA 

Table 6-1 summarizes the transportation data (daily VMT) used to develop the EIs in Section 

6.4. The information was obtained from the Regional Transportation Plan 2009-2030, approved 

in November 2008 (RTC 2008). All other input data used in developing the EIs, such as vehicle 

fleet mix, seasonal/day-of-the-week adjustment factors, and hourly activity profiles, has also 

been updated with the most current data available. 

Table 6-1. Demographic Data Used to Develop Emission Inventories 

Year Vehicle Miles Traveled 

2008 - attainment 45,259,209 

2015 - interim 56,903,109 

2022 - maintenance 73,731,008 

6.3 EFFICIENCY AND EFFECTIVENESS FACTORS 

Control efficiency, rule effectiveness and rule penetration factors were applied to the attainment 

emissions of point and nonpoint source categories affected by Clark County AQRs, when 

applicable. The term control efficiency includes capture efficiency for point sources which 

defines the percentage of emissions from a source that is captured by a control device. Rule 

effectiveness reflects the actual capability of a regulatory program to achieve the emission 

reductions required by regulation. Rule penetration, on the other hand, are the assumed 
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March 2011 6-2 

percentage of emissions of the targeted Source Classification Code (SCC) subject to the 

requirements of a rule. 

6.4 EMISSION INVENTORY TYPE CATEGORIES 

The inventories for NOx and VOC emissions for the Clark County nonattainment area was 

derived from estimates developed for nine EI type categories: point sources, nonpoint sources, 

private and commercial aviation, Federal aviation, railway, on-road mobile, nonroad mobile, 

biogenic, and banked emission reduction credits. The following sections provide a brief 

discussion of each category and its estimated emissions; more detailed explanations of EI 

estimates can be found in Appendix A, the Clark County Ozone Redesignation Request and 

Maintenance Plan Technical Support Document (TSD). 

6.4.1 Point Sources 

Point source inventories include all Title V major stationary sources, minor stationary sources 

that emit at least 10 tpy of VOCs or 25 tpy of NOx per year, and clustered minor stationary 

sources that could be considered emission hot spots. The source emissions are tabulated from 

data collected by direct on-site measurements or calculated using emission factors and activities 

data. When a single facility has multiple sources, emission data is collected for each source and 

entered into a database that organizes it and allocates the emissions to a geographic location. To 

calculate projected EIs, point sources are adjusted by growth factors based on Source 

Classification Codes using version 5.0 of EPA’s Economic Growth Analysis System program. 

6.4.2 Nonpoint Sources 

Nonpoint sources of emissions are those that fall below point source reporting levels and are too 

numerous or small to identify individually. Generally, they are small-scale industrial or 

residential operations that use emission-generating materials or processes. Nonpoint sources are 

generally divided into two groups, according to the emission mechanism: (1) hydrocarbon 

evaporative emissions, considered primarily as VOCs, or (2) fuel combustion emissions, 

considered primarily as NOx. Hydrocarbon evaporative emission sources include printing 

presses, industrial coatings, degreasing solvents, house paints, and the filling of underground 

gasoline tanks. Fuel combustion emission sources include stationary source fossil fuel 

combustion at residences and businesses, vehicle/equipment operations, materials burning 

outdoors, and structural fires. 

Nonpoint source emission calculations are estimated as county-wide totals rather than as 

individual source emissions. With some exceptions, these emissions may be calculated by 

multiplying an EPA-approved factor (emissions per unit of activity) by the appropriate activity 

or activity surrogate responsible for generating emissions. When available, actual activity data is 

used; when unavailable, surrogates are used, including county population or employment data by 

industry type (and, when applicable, by growth factors from EPA’s Economic Growth Analysis 

System model). 
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March 2011 6-3 

6.4.3 Private and Commercial Aviation 

Private and commercial aviation in Clark County is overseen by the Clark County Department of 

Aviation and served by five airports: (1) McCarran International Airport; (2) North Las Vegas 

Airport; (3) Henderson Executive Airport; (4) Jean Airport; and (5) Perkins Field Airport. The 

Aviation Department provided Clark County with the 2008 actual and 2022 estimated EIs for 

each of these five facilities, along with emission estimates for the proposed Ivanpah Airport and 

Sloan Heliport (Ricondo and Associates Inc. 2008) in the southern part of the county. Emission 

estimates for 2015 were interpolated using the 2008 and 2022 EIs, minus the estimates for 

Ivanpah and Sloan. The Ivanpah Airport will not be completed until 2020, and the Sloan Heliport 

will not be operational until 2017. 

6.4.4 Federal Aviation 

Federal aviation in Clark County centers around Nellis Air Force Base, a major aircraft training 

facility seven miles northeast of Las Vegas. Although most emissions at Nellis come from 

aircraft operations, the base holds a Title V permit to cover stationary source emissions that also 

permeate the area. Both emission types were included in the overall EIs Nellis provided to Clark 

County for 2008 and 2022. 

The 2022 EI included emissions from the beddown of F-35 aircraft, which will be used to train 

instructor pilots and support the Air Force Weapons School’s mission of testing and evaluation. 

Emission estimates for 2015 were interpolated using the 2008 and 2022 EIs, minus the emissions 

from the F-35 beddown. Once the 2015 EI was calculated, F-35 beddown emissions were added 

back in because Nellis expects the wing to be fully operational between 2012 and 2013. 

6.4.5 Railway 

The sole proprietor of railroad track in Clark County is Union Pacific Railroad; in 2008, it 

operated roughly 148 miles of track in the county and consumed about 3.9 million gallons of 

diesel while hauling approximately 3.2 billion gross tons. Emissions from locomotives are 

assumed to be uniform throughout the year, and are based on activity throughput data in the form 

of gross tonnage hauled and emission factors. 

To project activity throughput, Clark County incorporated an average annual growth rate of one 

and a half percent into the 2008 EI, based on average domestic freight demand forecasts from the 

Federal Highway Administration. EIs for 2015 and 2022 included future emissions associated 

with proposed high-speed passenger train service between Las Vegas and southern California, 

for which Clark County obtained estimates from the draft environmental impact statement 

(Federal Railroad Administration 2008). 

6.4.6 On-Road Mobile 

On-road mobile sources consist of cars, trucks, motorcycles, and other motor vehicles traveling 

on public roadways. Combustion-related emissions (NOx and CO) were estimated for vehicle 

engine exhaust; evaporative hydrocarbon emissions (VOCs) were estimated for the fuel tank and 
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March 2011 6-4 

other evaporative leak sources on the vehicle. Clark County then developed emission factors for 

2008, 2015, and 2022 using the CONCEPT MV model; the MOBILE6 emissions factor model; 

Vehicle Miles Travelled (VMT) from the RTC’s transportation demand model (TDM); and 

federal Highway Performance Monitoring System (HPMS) data from the Nevada Department of 

Transportation (NDOT). Every effort was made to use parameters reflective of local conditions. 

Local parameters include vehicle speeds by roadway type, vehicle registration by vehicle type 

and age, percentage of vehicles in cold-start mode, percentage of miles traveled by vehicle type, 

type of I/M program in place, and gasoline vapor pressure. 

6.4.7 Nonroad Mobile 

Nonroad mobile sources consist of a wide variety of equipment types that either move under 

their own power or can be moved from site to site, with the exception of locomotive, aircraft, and 

airport ground support equipment. Nonroad EIs for 2008, 2015, and 2022, which were estimated 

using the EPA’s NONROAD model, included more than 80 basic and 260 specific types of 

nonroad equipment. The model further stratified equipment types into ten categories by 

horsepower rating and fuel type, then incorporated the effects of recent federal regulatory actions 

(i.e., emission standards for nonroad compression ignition engines and ultra-low sulfur diesel). 

The model also accounted for fleet turnover, when older engines are replaced by newer engines 

that comply with stricter federal emission controls. 

6.4.8 Biogenic 

Biogenic sources include agricultural crops; lawn grass; forests that produce isoprene, 

monoterpene, alpha-pinene, and other VOC emissions; and soils that generate trace amounts of 

NOx. Like emissions from man-made sources (anthropogenic emissions), biogenic emissions 

react with oxidants in the atmosphere to produce ozone; they can even dominate anthropogenic 

emissions in some areas. A comparison of biogenic emissions estimates to emissions estimates 

for other categories (e.g., mobile sources) showed that biogenic emissions represent a large 

portion of overall VOC emissions in Clark County. Clark County assumed these emissions 

would remain constant over time because biogenic emissions are beyond the scope of reasonable 

emission reduction measures. The EIs for 2008, 2015, and 2022 were based on the Model of 

Emissions of Gasses and Aerosols from Nature (MEGAN) estimates, measured emission factors, 

and species information from completed surveys. 

6.4.9 Banked Emission Reduction Credits 

Under strict guidelines, Emission Reduction Credits (ERCs) may be granted, if requested, to a 

source that voluntarily reduces emissions beyond required levels of control. ERCs may be sold, 

leased, banked for future use, or traded in accordance with applicable regulations. Both NDEP 

and Clark County have authority to bank ERCs in Clark County. NDEP has jurisdiction over 

permitting, compliance, and ERC banking for plants that burn fossil fuels in a boiler to produce 

steam for the production of electricity (NRS 445B.500) in Clark County; all other emission units 

in Clark County are under the jurisdiction of Clark County. While developing this plan, Clark 

County verified NDEP’s bank of VOCs and NOx and the two facilities from which the related 
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March 2011 6-5 

ERCs originated. At this time, neither Clark County nor NDEP has any pending ERC 

applications. 

Clark County chose to account for all ERCs in the maintenance year 2022 because ERCs can be 

used in nonattainment areas to offset emissions of new major sources and major modifications at 

existing major sources. Therefore, ERC emissions are already accounted for in the point source 

emissions growth estimated for 2022, i.e., point source emissions growth and ERCs largely 

overlap. To be conservative, however, Clark County is not considering the potential overlap of 

these emissions in this plan. 

6.5 SUMMARY OF EMISSION INVENTORIES 

Table 6-2 summarizes the 2008, 2015, and 2022 VOC EIs for nine source type categories in tons 

per day (tpd). Figures 6-1 through 6-3 show the VOC EIs for 5 source categories1

 for each of 

those three years. Detailed information on the methodologies used to estimate EIs can be found 

in the TSD (Appendix A). 

Table 6-2. Summary of Total Daily VOC Emissions (tpd)

Source Category 2008 VOC 2015 VOC 2022 VOC 

Point source 1.32 1.61 1.74

Nonpoint source 57.07 66.21 76.15

Commercial Aviation 2.6 2.83 4.14

Federal Aviation 0.79 0.9 0.95

On-road mobile 65.08 45.32 36.71

Nonroad mobile 42.91 32.29 29.73

Biogenic 132 132 132

ERC 0 0.43 0.43

Total 301.77 281.59 281.85

 

1 Airports are considered point sources; therefore, the commercial and federal aviation emissions are accounted for in the Point 

Source category. Only five source categories are shown in the graphs.

. 
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March 2011 6-6 

Point source

1%

Nonpoint source

19%

Mobile

36%

Biogenic

44%

ERC

0%

2008 VOC

Figure 6-1. VOC Emission Inventory for 2008

Point source

2%

Nonpoint source

23%

Mobile

28%

Biogenic

47%

ERC

0%

2015 VOC

Figure 6-2. VOC Emission Inventory for 2015
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March 2011 6-7 

Point source

2%

Nonpoint source

27%

Mobile

24%

Biogenic

47%

ERC

0%

2022 VOC

Figure 6-3. VOC Emission Inventory for 2022

Table 6-3 summarizes the 2008, 2015, and 2022 NOx EIs for all nine source type categories. 

Figures 6-4 through 6-6 show the NOx EIs for 5 source categories2

 for each of those three years. 

Detailed information on the methodologies used to estimate EIs can be found in the TSD 

(Appendix A). 

Table 6-3. Summary of Total Daily NOx Emissions (tpd)

Source Category 2008 NOx 2015 Nox 2022 Nox

Point source 28.73 31.54 31.73

Nonpoint source 5.41 5.64 5.9

Commercial Aviation 11.41 14.78 28.82

Federal Aviation 1.27 1.87 2.26

On-road mobile 68.46 34.69 23.15

Nonroad mobile 43.28 30.1 19.51

Biogenic 5 5 5

ERC 0 22.23 22.23

Total 163.56 145.85 138.6

 

 

2 Airports are considered point sources; therefore, commercial and federal aviation emissions are accounted for in the Point 

Source category. Only five source categories are shown in the graphs.
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March 2011 6-8 

Point source

25%

Nonpoint source

3%

Mobile

69%

Biogenic

3%

ERC

0%

2008 NOx

Figure 6-4. NOx Emission Inventory for 2008 

Point source

33%

Nonpoint source

4%

Mobile

44%

Biogenic

4%

ERC

15%

2015 NOx

Figure 6-5. NOx Emission Inventory for 2015
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March 2011 6-9 

Point source

45%

Nonpoint source

4%

Mobile

31%

Biogenic

4%

ERC

16%

2022 NOx

Figure 6-6. NOx Emission Inventory for 2022

In summary, total VOC emissions decrease by 19.9 percent between 2008 and 2022 with the 

maintenance control measures described in Section 4.4, or from 301.77 tpd to 281.85 tpd. Total 

NOx emissions follow a similar downtrend, decreasing 24.9 percent between 2008 and 2022, or 

from 163.5 tpd to 138.6 tpd. 

6.6 MAINTENANCE DEMONSTRATION 

CAA Section 175(a) requires each request for redesignation to be accompanied by a SIP revision 

that provides for maintenance of the NAAQS for at least ten years after redesignation. Following 

EPA guidance (Calcagni, 1992), Clark County demonstrated maintenance of the ozone NAAQS 

by comparing projected 2015 and 2022 EIs with the attainment year EI (2008). If the 2015 and 

2022 EIs are less than the 2008 EI, then maintenance of the NAAQS is demonstrated. As 

illustrated in Tables 6-2 and 6-3, projected future year VOC and NOx emissions in the Clark 

County nonattainment area are less than 2008 emissions. Figure 6-7 illustrates the differences in 

the attainment, interim, and maintenance year EIs for VOC and NOx. 
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March 2011 6-10 

Figure 6-7. Comparison of 2008, 2015, and 2022 NOx Emissions 

0

20

40

60

80

100

120

140

160

180

2008 NOx 2015 NOx 2022 NOx

NOx Emissions (tpd)

Point source Nonpoint source Mobile Biogenic ERC

`

Attainment = 163.5 tpd
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March 2011 6-11 

Figure 6-8. Comparison of 2008, 2015, and 2022 VOC Emissions 

The EIs show a downward trend in both VOC and NOx emissions, due mainly to the control 

measures described in Section 4.4. No increases in emissions are expected in the intervening 

years that will threaten the demonstration of attainment because this downward trend, and the 

fact that future EIs in the maintenance year are considerably below the 2008 levels. 

6.7 MONITORING NETWORK AND VERIFICATION OF CONTINUED 

ATTAINMENT 

After EPA redesignates the Clark County nonattainment area to attainment status, Clark County 

will continue to operate the air quality monitoring network to verify the continued attainment of 

the 1977 8-hour ozone NAAQS. Annual review of the SLAMS air quality surveillance system 

will be conducted in accordance with 40 CFR 58.20(d) to determine whether the system 

continues to meet monitoring objectives. 

6.8 CONTINGENCY PLAN 

CAA Section 175A(d) requires that a maintenance plan contain contingency provisions to assure 

prompt correction of any violation of the 8-hour ozone NAAQS. Contingency plans must also 

describe the methods that will be used to ensure the measures in the plan are adopted 

expeditiously once the need is triggered. While EPA guidance states that a contingency plan does 

not have to contain fully adopted contingency measures (Calcagni, 1992), it should at least have 

three primary elements: 

0

50

100

150

200

250

300

350

2008 VOC 2015 VOC 2022 VOC

VOC Emissions (tpd)

Point source Nonpoint source Mobile Biogenic ERC

`

Attainment = 301.8 tpd
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March 2011 6-12 

1. A list of potential contingency measures. 

2. An explanation of the tracking and triggering mechanisms that will determine when 

contingency measures are needed. 

3. A description of the process for recommending and implementing contingency measures, 

with specific timelines for action. 

6.8.1 Potential Contingency Measures 

In addition to the six potential contingency measures outlined below, Clark County may evaluate 

other strategies to address any future ozone NAAQS violations in the most appropriate and 

effective manner possible. 

6.8.1.1 Reid Vapor Pressure Reduction

In conjunction with the Nevada Department of Agriculture, Clark County may consider requiring 

the reduction of gasoline Reid vapor pressure to below 9.0 psi within the nonattainment area 

during the summer ozone season. 

6.8.1.2 Inspection/Maintenance Program Changes and Additions

In conjunction with the Nevada Department of Transportation, Clark County may consider 

changing the cutpoints for VOCs and NOx applicable to pre-1996 vehicles and/or increase the 

I/M waiver repair rate in Clark County. 

6.8.1.3 Consumer and Commercial Products

Clark County may consider regulations to restrict the sale, offer for sale, or manufacture for sale 

of any consumer product, such as personal care products, automotive and industrial maintenance 

products, and pesticides that contain VOCs above specified limits. 

6.8.1.4 Architectural Surface Coatings

Clark County may consider regulations to restrict the sale, supply, offer for sale, or solicitation of 

the application of architectural coatings that contain VOCs above specified limits. 

6.8.1.5 Lawn and Garden Equipment Use

Clark County may consider regulations to restrict the use of gasoline-powered lawn mowers on 

announced ozone action days in the Clark County nonattainment area. 

6.8.1.6 Establish/Enhance Trip Reduction Programs

In conjunction with the RTC, Clark County may establish and/or enhance employer-based 

community outreach and marketing efforts, employer rideshare program incentives, preferential 

parking for carpoolers and vanpoolers, emergency rides home for Club Ride members, travel 
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March 2011 6-13 

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

transit expenses, and partnerships with vanpool leasing companies. 

6.8.2 Tracking and Triggering Mechanisms 

The primary tracking mechanism will be Clark County’s continuous ozone monitoring, as 

described in Section 6.7. Clark County will examine ambient air quality monitoring data within 

30 days of collection to determine if the ozone NAAQS has been exceeded. The RTCs ongoing 

regional transportation planning process will serve as another means of tracking mobile source 

VOC and NOx precursor emissions. RTC revises its transportation improvement plan every three 

years, and these revisions are subject to a transportation conformity finding; that process will 

serve as a periodic check on maintaining the VMT and mobile source emissions projections of 

this plan. 

The primary trigger mechanism will be a confirmed violation of the 1997 8-hour ozone NAAQS, 

or a three-year average of the fourth highest values that is equal to or greater than 0.085 ppm. 

The trigger date will be 60 days from the date Clark County observes a fourth highest value that, 

would result in a design value equal to or greater than 0.085 ppm. 

The triggering of the contingency plan does not automatically require a revision of the Clark 

County ozone SIP, nor would Clark County necessarily be redesignated to nonattainment. 

Instead, Clark County will have a period of time to correct the violation by implementing one or 

more contingency measures. If ozone violations continue after contingency measures have been 

implemented, additional measures will be implemented until the violations are corrected. 

6.8.3 Action Resulting from Trigger Activation 

Within 45 days of the trigger date, Clark County will notify EPA that an internal review process 

will begin to evaluate potential contingency measures. Within 90 days of that notification, Clark 

County will send EPA an information report outlining recommended actions. Clark County will 

then solicit stakeholder involvement through public forums (i.e., ozone working groups) to refine 

the process of implementing the recommended actions. The BCC, Nevada State Board of 

Agriculture, and/or Nevada State Environmental Commission will hold a public hearing(s) to 

consider the recommended contingency measures, along with any other contingency measures 

that may address the confirmed violation. The necessary contingency measures will be adopted 

and implemented within 18 months after submittal of the information report to EPA. 

6.9 SUBSEQUENT MAINTENANCE PLAN REVISIONS 

Section 175A(b) requires that eight years after redesignation of any area to attainment under 

Section 107(d), the state shall submit an additional revision of the applicable SIP that shows how 

the NAAQS will be maintained for 10 years after the expiration of the first 10-year period. Clark 

County commits to the submittal of a revised maintenance plan eight years after Clark County is 

redesignated to attainment. 
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March 2011 7-1 

7.0 MOTOR VEHICLE EMISSIONS BUDGETS 

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 

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. 

Table 7-1 provides 2015 and 2022 VOC and NOx MVEBs for the area of Clark County that 

comprises the 1997 8-hour ozone maintenance area. Upon an EPA affirmative adequacy finding 

and approval of the MVEBs, these budgets will be used for conformity determinations in future 

regional transportation plans. 

Table 7-1. VOC and NOx MVEBs for Clark County 

Year VOC MVEBs (tpd) NOx MVEBs (tpd) 

2008 – attainment 65.08 68.46

2015 – interim 45.32 34.69

2022 – maintenance 36.71 23.15
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March 2011 8-1 

8.0 REFERENCES 

43 FR (Federal Register) 8962.” National Ambient Air Quality Standards: State Attainment 

Status.” 

44 FR 8220. Revision of primary and secondary ozone standards. 

51 FR 41788. “Designations of Areas for Air Quality Planning Purposes; Las Vegas Valley, NV, 

Redesignation for Ozone.” 

62 FR 38856. “National Ambient Air Quality Standards for Ozone; Final Rule.” 

65 FR 6822. “Control of Air Pollution From New Motor Vehicles: Tier 2 Motor Vehicle 

Emissions Standards and Gasoline Sulfur Control Requirements; Final Rule. Part 80—

Regulation of Fuels and Fuel Additives.” 

65 FR 76789. “Control of Emissions from New Nonroad Spark-Ignition Engines Rated Above 

19 Kilowatts and New Land-Based Recreational Spark-Ignition Engines.” 

69 FR 23858. “8-Hour Ozone National Ambient Air Quality Standards; Final Rules. Air Quality 

Designations and Classifications for the 8-Hour Ozone National Ambient Air Quality Standards; 

Early Action Compact Areas with Deferred Effective Dates.” 

69 FR 34076. “Air Quality Designations and Classifications for the 8-Hour Ozone National 

Ambient Air Quality Standards; Deferral of Effective Date.” 

69 FR 38958. “Control of Emissions of Air Pollution from Nonroad Diesel Engines and Fuel; 

Final Rule.” 

70 FR 20665. “Clean Air Fine Particle Implementation Rule.” 

70 FR 71612. “Final Rule To Implement the 8-Hour Ozone National Ambient Air Quality 

Standard-Phase 2; Final Rule To Implement Certain Aspects of the 1990 Amendments Relating 

to New Source Review and Prevention of Significant Deterioration as They Apply in Carbon 

Monoxide, Particulate Matter and Ozone NAAQS; Final Rule for Reformulated Gasoline.” 

73 FR 59034. “Control of Emissions from Nonroad Spark-Ignition Engines and Equipment; 

Final Rule.” 

73 FR 66182. “Approval and Promulgation of Implementation Plans; Revisions to the Nevada 

State Implementation Plan; Clark County.” 

74 FR 22738. “Adequacy Status of Motor Vehicle Emissions Budgets in Submitted Early 

Progress Plan for Clark County 8-hour Ozone for Transportation Conformity Purposes; Nevada.” 
Ozone Redesignation Request and Maintenance Plan 

March 2011 8-2 

75 FR 6571. “Approval and Promulgation of Air Quality Implementation Plans; Louisiana; 

Baton Rouge 1-Hour Ozone Nonattainment Area; Determination of Attainment of the 1-Hour 

Ozone Standard.” 

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. 2010. “Historical Economic Data for Metropolitan 

Las Vegas.” Las Vegas, Nevada: University of Nevada, Las Vegas. 

http://cber.unlv.edu/snoutlk.html. 

DAQEM (Clark County Department of Air Quality and Environmental Management). 2008a. 

Eight Hour Early Progress Plan for Clark County. Las Vegas, Nevada: Clark County 

Department of Air Quality and Environmental Management. 

DAQEM. 2008b. Quality Control and Assurance System for Criteria Gaseous Pollutant. Las 

Vegas, Nevada: Clark County Department of Air Quality and Environmental Management. 

DAQEM. 2008c. Clark County Transportation Conformity Plan. Las Vegas, Nevada: Clark 

County Department of Air Quality and Environmental Management. 

DAQEM. 2010a. Clark County Air Quality Regulation, Section 12. Preconstruction Review for 

New or Modified Stationary Sources. Las Vegas, Nevada: Clark County Department of Air 

Quality and Environmental Management. 

DAQEM. 2010b. Clark County Air Quality Regulation, Section 52. Gasoline Dispensing 

Facilities. Las Vegas, Nevada: Clark County Department of Air Quality and Environmental 

Management. 

Desert Research Institute. 2006. Biogenic Volatile Organic Compound Emission Inventory 

Improvement Project. Prepared for the Clark County Department of Air Quality and 

Environmental Management. 

Environ, Inc. 2007. Clark County Consolidated Emissions Inventory Report. Prepared for Clark 

County Department of Air Quality and Environmental Management. 

Environmental Quality Management, Inc. 2006. Biogenic Emission Inventory for Clark County, 

Nevada. Prepared for Clark County Department of Air Quality and Environmental Management. 

Ricondo & Associates, Inc. 2008. Emission Inventories Clark County Airport System Airports. 

Prepared for Clark County Department of Air Quality and Environmental Management. 

RTC (Regional Transportation Commission of Southern Nevada). 1999. Transportation 

Improvement Plan 1998-2000. Las Vegas, Nevada: Regional Transportation Commission of 

Southern Nevada. 
Ozone Redesignation Request and Maintenance Plan 

March 2011 8-3 

RTC. 2008. Regional Transportation Plan 2006-2030. Las Vegas, Nevada: Regional 

Transportation Commission of Southern Nevada. 

Western Regional Climate Center. 2010. “Western Regional Climate Center / Historical Climate 

Information.” Las Vegas, Nevada: Desert Research Institute. 

www.wrcc.dri.edu/CLIMATEDATA.html.