# Carbon Monoxide State Implementation Plan Revision

Las Vegas Valley Nonattainment Area
Clark County, Nevada

October 2005

Clark County Department of Air Quality and Environmental ManagementCarbon Monoxide State Implementation Plan Revision

ACKNOWLEDGMENTS

CLARK COUNTY BOARD OF COMMISSIONERS Rory Reid, Chair Myrna Williams, Vice-Chair Tom Collins Yvonne Atkinson Gates Chip Maxfield Lynette Boggs McDonald Bruce Woodbury

OFFICE OF THE COUNTY MANAGER Thom Reilly, County Manager Darryl Martin, Assist ant County Manager Elizabeth Macias Quillin, Assistant County Manager Virginia Valentine, Assistant County Manager

DEPARTMENT OF AIR QUALITY AND ENVIRONMENTAL MANAGEMENT Christine Robinson, Director Lewis Wallenmeyer, Assistant Director Alan Pinkerton, Deputy Director Dennis Ransel, Planning Manager Cheng Shih, Assistant Planning Manager John Koswan, Assistant Planning Manager Zheng Li, Modeler Ebrahim Juma, Senior Air Quality Specialist Melissa Hamner, Technical Writer

REGIONAL TRANSPO RTATION COMMISSION Bruce Turner, Planning Manager Jerry Duke, Assistant Planning Manager Brian Hoeft, Principal Planner

Sarah Sun, Principal Planner

iiCarbon Monoxide State Implementation Plan Revision

EXECUTIVE SUMMARY

This document is a re vision of the August 2000 Carbon Monoxide State Implementation Plan, Las Vegas Valley Nonattainment Area, Clark County, Nevada (2000 CO SIP). Its purpose is to update carbon monoxide motor vehicle emissions budgets using MOBILE6, the latest model approved by the U.S. Environmental Protecti on Agency (EPA) for use in transportation conformity determinations.

In the mid-1980s, portions of the Las Vegas Vall ey began violating the carbon monoxide (CO) National Ambient Air Quality Standards (NAAQS) during the winter months. The number and severity of these violations caused EPA to de signate the valley as a “moderate” nonattainment area upon enactment of the Clean Air Act Amendm ents in November 1990. When Clark County did not attain the CO standards after a one-year extension to the required attainment date, EPA reclassified the valley as a “serious” CO nonatta inment area. The county began development of a state implementation plan (SIP) to establish meas ures for attaining the standards by the end of 2000, and in August 2000 the Clar k County Board of County Commi ssioners adopted the plan. EPA issued a final approval of the 2000 CO SIP in September 2004, and in June 2005 EPA found that the Las Vegas Valley had attained the standards by the applicab le date of December 31, 2000.

During the past several years, th e valley has experienced substantia l improvement in air quality: no violations of the 8-hour CO standard have be en recorded since 1998. There has been a similar reduction in the intensity of CO concentrations. CO exceedances (but not necessarily violations) often totaled 40 or more per year in the 1980s. During 1997 and 1998, the valley experienced only four unhealthful and three exceedance days. Exceedances and violations of the 8-hour CO standard eased by 1999, and there have been no recorded exceedances since then.

The greatest modeling effort in this CO SIP revision centered on updati ng the on-road mobile source inventory estimates. This revision focused on recalculating the emissions for on-road and non-road sources using the newer MOBILE6.2 and NONROAD2004 models, respec tively, then running the Urban Airshed Mode l and the CAL3QHC model to determine if the Las Vegas Valley will continue to maintain the CO standards through 2030. The results, as Sections 5 and 6 describe, confirm continued maintenance: model runs for maximu m CO levels using MOBILE6.2 do not show any violations through 2030.

DAQEM updated its CO modeling and conformity an alysis for this 2005 CO SIP revision using the latest tools, data res ources, and methodologies availabl e. The 2000 CO SIP was based on computer modeling of the single best performing episode of the three originally modeled: the night of December 8-9 (Sunday-Monday), 1996. The EPA regional office approved this selection, along with a sca ling factor that resulted in a ma ximum predicted concentration of 11.2 ppm. This SIP revision continues to rely on th e December 8-9, 1996 episode as a base case, but uses new data on population and travel projectio ns for conducting the MOBILE6.2 analysis. For the 1996 base year, the original TRANPLAN output was used to define traffic volume-related parameters. For all future years modeled, the Regional Transportation Commission of Southern Nevada provided output from the new TransC AD transportation demand model. Population

iiiCarbon Monoxide State Implementation Plan Revision

projections (and actual population for 2000) were modi fied to reflect higher growth rates in the county.

EPA requires that SIPs also provide for maintaini ng health standards after attainment. This plan revision assures the public that implementa tion of the programs in the 2000 CO SIP and maintenance of the CO health standards will continue through 2030. Since Clark County has now reached attainment, and the primary source of CO is the on-road mobile sources category, projections for a 30-year horizon past the demonstration date ha ve been forecast. With new planning tools and better predic tive capabilities (such as MOBI LE6) available, Clark County will continue to reanalyze and conf irm long-term maintenance of the CO health standards.

Since additional modeling will likely be required for maintenance plan submittals from areas seeking redesignation, this SIP revision updates the mobile emission model analysis to provide a basis for development of a formal CO maintenan ce plan and a redesignation request in the near future. The Las Vegas Valley air quality implementation plan will remain in effect until superseded by an approved CO maintenance plan.

ivCarbon Monoxide State Implementation Plan Revision

TABLE OF CONTENTS

1. INTRODUCTION ................................................................................................................ 1-1 1.1. Problem Statement ..................................................................................................... 1-2 1.2. Physical Description .................................................................................................. 1-2 1.3. Climatological Setting ............................................................................................... 1-3 1.4. Organization of this Revision .................................................................................... 1-3

2. MONITORING NETWORK AND TRENDS IN AIR QUALITY ................................. 2-1 2.1. Introduction ................................................................................................................ 2-1 2.2. Background ................................................................................................................ 2-1 2.3. Monitoring Network .................................................................................................. 2-1 2.4. Trends in Carbon Monoxide Air Quality ................................................................... 2-3 2.5. Carbon Monoxide Saturation Study ........................................................................... 2-6

3. EMISSION INVENTORY SUMMARY ............................................................................ 3-1 3.1. Introduction ................................................................................................................ 3-1 3.2. Emissions Summary by Category .............................................................................. 3-2 3.2.1. On-Road Mobile Emissions ........................................................................... 3-3 3.2.2. Non-Road Mobile Emissions ......................................................................... 3-8 3.2.3. Point Sources ............................................................................................... 3-10 3.2.4. Area Sources ................................................................................................ 3-11 3.3. Total Annual Emissions ........................................................................................... 3-11

4. CONTROL MEASURES .................................................................................................... 4-1 4.1. Introduction ................................................................................................................ 4-1 4.2. Carbon Monoxide Control Measures ......................................................................... 4-1

5. BASE CASE MODELING .................................................................................................. 5-1 5.1. Introduction ................................................................................................................ 5-1 5.2. Base Case Scenario Modeling ................................................................................... 5-1

6. DEMONSTRATION OF ATTAINMENT ........................................................................ 6-1 6.1. Introduction ................................................................................................................ 6-1 6.2. Urban Airshed Model Attainment Demonstration ..................................................... 6-1 6.3. Microscale Modeling ................................................................................................. 6-6 6.3.1. CAL3QHC Intersection Modeling ................................................................. 6-7 6.3.2. Airport Modeling Using the Emissi ons and Dispersion Modeling System ... 6-8

7. IMPLEMENTATION AND STATE IMPL EMENTATION PLAN COMMITMENTS 7-1 7.1. Implementation, Monitoring, and Reporting ............................................................. 7-1 7.2. Maintenance............................................................................................................... 7-1 7.3. Mobile Source Emissions Budget .............................................................................. 7-2

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

vCarbon Monoxide State Implementation Plan Revision

TABLE OF CONTENTS (continued)

APPENDICES

APPENDIX A: Technical Support Document............................................................................ A-1 APPENDIX B: Carbon Saturation Study ....................................................................................B-1 APPENDIX C: Effectiveness of the In spection and Maintenance Program ...............................C-1 APPENDIX D: Airport Modeling Studies.................................................................................. D-1 APPENDIX E: RTC Support Letter ............................................................................................E-1 APPENDIX F: Documentation of th e Public Review Process....................................................F-1

viCarbon Monoxide State Implementation Plan Revision

LIST OF FIGURES

Figure 2-1. Las Vegas Valley CO Monitoring Sites – 2005. .................................................. 2-2

Figure 2-2. Las Vegas Valley CO Air Qual ity Trends, Number of Exceedances – 1981-2004. ........................................................................................................... 2-4

Figure 2-3. Las Vegas Valley CO Air Qualit y Trends, Annual Peak Concentrations by Station – 1981-2004. ............................................................................................ 2-5

Figure 3-1. Spatial Distribution of Tota l CO Emissions for the 1996 Base Case. ............... 3-14

Figure 3-2. Spatial Distribution of Total Su rface Gridded CO Emissions for the 2030 Future Year. ................................................................................................................... 3-15

Figure 5-1. Spatial Distribution of UAM Pred icted 8-Hour Maximum CO Concentrations(ppm) for the December 8-9, 1996 Base Case with Updated On-Road and NonRoad Mobile Emissions. ...................................................................................... 5-3

Figure 6-1. Spatial Distribution of UAM-Predicted 8-Hour Maximum CO Concentrations (ppm) for the December 8-9, 1996 Episode Using Emissions Forecasts for 2006. ............................................................................................................... 6-3

Figure 6-2. Spatial Distribution of UAM-Predicted 8-Hour Maximum CO Concentrations (ppm) for the December 8-9, 1996 Episode Using Emissions Forecasts for 2030. ............................................................................................................... 6-4

Figure 6-3. Boundaries of the Outer Domain and Subdomains. ............................................. 6-5

Figure 6-4. CAL3QHC Inte rsection Location Diagram. ........................................................ 6-7

viiCarbon Monoxide State Implementation Plan Revision

LIST OF TABLES

Table 2-1. Las Vegas Valley CO Monito ring Site Locations and Descriptions ................... 2-2

Table 3-1. Demographic Data Used in Deve loping Emission Invent ories and to Project Activity in the 2000 CO SIP ................................................................................ 3-1

Table 3-2. Demographic Data Used in Devel oping Emission Inventories and to Project Activity in the 2005 CO SIP Revision ................................................................. 3-2

Table 3-3. Cross-Reference Between RTC and MOBILE6.2 Facility Types ....................... 3-4

Table 3-4. 1996 VMT by Facility Type ................................................................................ 3-5

Table 3-5. Component and Total On-Road Mobile Source CO Emissions (TPD) for the 1996 Base Year ............................................................................................................. 3-6

Table 3-6. Component and Total On-Road S unday Mobile Source CO Emissions (TPD) for All Future Years ................................................................................................... 3-8

Table 3-7. Component and Total On-Road M onday Mobile Source Co Emissions (TPD) for All Future Years ................................................................................................... 3-8

Table 3-8. Annual Airport CO Emission Estim ates (TPY) for the 1996 Base Year and for Future Years 2010, 2015, and 2020 (2006 and 2030 Estimated) ......................... 3-9

Table 3-9. Clark County CO NONROA D Gridded Emission Estimates (TPD) ................. 3-10

Table 3-10. Clark County CO Area Source Grid ded Emissions Estimates (TPD) After Season and Day-of-Week Adjustments .......................................................................... 3-11

Table 3-11. Percent Daily Emi ssions by Source Category and Year .................................... 3-12

Table 3-12. Summary of To tal Daily CO Emissions (TPD) in the UAM CO SIP Revision ............................................................................................................. 3-13

Table 4-1. Adopted CO Control Measures to Reduce On-Road Mobile Source Emissions ............................................................................................................. 4-2

Table 4-2. Control Measures Adopted for the 1995 CO SIP and Included as Part of the 2000 CO SIP and 2005 CO SIP Revision ..................................................................... 4-3

Table 5-1. Summary Performance Statistics for the December 8-9, 1996 Base Case with Updated On-Road and Non-Road Mobile Source Emissions .............................. 5-2

viiiCarbon Monoxide State Implementation Plan Revision

LIST OF TABLES (continued)

Table 6-1. Peak 8-Hour CO C oncentrations in Future Years ................................................ 6-2

Table 6-2. Grid Definition of the Central Urban Subdomain ................................................ 6-2

Table 6-3. Change in Peak 8-Hour CO from Doubling the Total CO Emissions Inventory Outside the Central Urban Subdomain ................................................................ 6-6

Table 6-4. Weekday On-Road Emissions Increa ses, UAM-Predicted Peak CO, and Resulting Emissions Budget for Each Future Year .............................................................. 6-6

Table 6-5. Peak UAM + CAL3QHC 8-Hour Av erage CO Concentrations (ppm) Predicted for Each Future Year and for Each Intersection .................................................. 6-7

Table 6-6. Peak Total UAM + EDMS 8-Hour CO Concentrations (ppm) at All Three Airports and for All Three Future Years Evaluated ............................................. 6-8

Table 7-1. 2006 – 2030 MVEB in the Las Vegas Valley ...................................................... 7-2

ixCarbon Monoxide State Implementation Plan Revision

ACRONYMS AND ABBREVIATIONS

Acronyms

CAAA 1990 Clean Air Act Amendments CO carbon monoxide DAQEM Clark County Department of Air Qu ality and Environmental Management EDMS Emissions and Dispersion Modeling System EPA U.S. Environmental Protection Agency EPS3 Emission Processing System, version 3 I/M inspection and maintenance (program) MVEB motor vehicle emission budget NAAQS National Ambient Air Quality Standards NAMS National Air Monitoring Station RTC Regional Transportation Comm ission of Southern Nevada RTP regional transportation plan RVP Reid Vapor Pressure SIP state implementation plan SLAMS State and Local Air Monitoring Station TAZ traffic analysis zone TDM transportation demand management TSD Technical Support Document (Appendix A) UAM Urban Airshed Model VMT vehicle miles traveled

Abbreviations

ppm parts per million TPD tons per day TPY tons per year

xCarbon Monoxide State Implementation Plan Revision



### 1. INTRODUCTION

The 1990 Clean Air Act Amendments (CAAA) rede fined the national air pollution abatement framework and established ambitious policies to carry out air quality planning and control activities. Two National Ambient Air Quality St andards (NAAQS) were established for carbon monoxide (CO): the 1-hour standard has a maxi mum allowable concentration of 35 parts per million (ppm), and the 8-hour standard has a maximum average of 9 ppm over an 8-hour period. Areas that violate one or both of the NAAQS more than two times in a two-year period are classified as CO nonattainment areas.

In the mid-1980s, portions of the Las Vegas Vall ey began violating the CO NAAQS during the winter months. Although the valley never exceeded the 1-hour standard, it exceeded the 8-hour standard at least once each year on a seasonal basis: in winter, lo cal inversions would stagnate air masses and trap pollutants. The overnight buildup of pollutants cau sed violations of the 8-hour standard in a limited ar ea surrounding the East Charleston (now Sunrise Acres) monitoring station.

The number and severity of these violations ca used the U.S. Environmental Protection Agency (EPA) to automatically designa te the valley as a “moderat e” nonattainment area upon CAAA enactment in November 1990. The Clean Air Act and its amendments re quired that moderate nonattainment areas implement the following emi ssion control measures as expeditiously as practicable to attain the CO NAAQS by December 31, 1995:

1. An oxygenated gasoline program during the winter months that requires gasoline to contain no less than 2.7 percent oxygen by weight. 2. An enhanced vehicle inspect ion and maintenance (I/M) pr ogram meeting Clean Air Act criteria. 3. Forecasts of vehicle miles traveled (VMT) in the region, procedures for annual updates and reports attesting to the accuracy of the for ecasts, and estimates of actual VMT based on traffic counts on area roadways. 4. Contingency measures that must be impleme nted if actual VMT exceeds forecasted VMT or if the area fails to attain the standard by the applicable date. 5. Transportation control measures necessary to demonstrate attainment of the NAAQS (Clean Air Act Section 187(b)(2)). 6. Implementation of all Reasonably Available C ontrol Measures as quickly as practicable.

Clark County implemented these co ntrols and made significant pr ogress towards attaining the CO NAAQS, but fell short of meeting the standa rd by the applicable date due to phenomenal population growth. Because of improved CO le vels from the implementation of control measures, EPA granted Clark County a one-year ex tension to demonstrate compliance. However, the county did not succeed a nd, according to CAAA requiremen ts, EPA reclassified the Las Vegas Valley as a “serious” CO nonattainment area.

October 2005 1-1Carbon Monoxide State Implementation Plan Revision

EPA published the notice of violati on reclassifying the area in the Federal Register on October 2, 1997. The agency set a deadline of May 1999 (18 months from the notice publication date) for submittal of an implementation plan that woul d demonstrate attainment of the CO NAAQS by December 31, 2000 (i.e., the Carbon Monoxide State Implementation Plan, Las Vegas Valley Nonattainment Area, Clark County, Nevada, approved in August 2000 [2000 CO SIP]). The CAAA requires that serious nonattainment areas meet all the requirements for moderate areas listed previously, in addition to implementing the following measures:

1. Gasoline sold during the winter months must contain the level of oxygen necessary to attain the standard, in combination with other measures.

2. Employers of 100 or more people must implemen t a mandatory travel re duction program that requires each company to increase average vehi cle occupancy for commute trips by at least 25 percent over the regional average. This requirement can be avoided if the area can show that such a program is not needed to demons trate attainment of the standard or that a comparable emission reduction can be achie ved by other measures. Congress has since eliminated this requirement from the CAAA.

3. Areas can implement an economic incentive pr ogram containing fees and marketable permits if emission reduction milestones are not met by December 31, 2000.

Beginning in 1997, regional trans portation plans (RTPs) had to specifically describe the transportation system for future horizon years. This requires the Regional Transportation Commission of Southern Nevada (RTC) to a pprove specific projects and programs for 2000, 2010, and 2020 (and for 2030 in the 2005 CO SIP revision).

1.1. PROBLEM STATEMENT

Federal transportation conf ormity regulations require use of the latest planning assumptions and EPA-approved emissions models each time a regiona l emissions analysis is conducted (after a one-year grace period from the time of final EPA approval). The RTC must conduct a new regional emissions analysis to upda te its conformity determinations as part of a new RTP. These conformity determinations must be based on budgets from the latest EPA-approved model (i.e., MOBILE6.2), and EPA must appr ove a revised motor vehicle em issions budget (MVEB) before the RTC submits the new RTP.

Section 1.2 of the 2000 CO SIP discusses the reas ons for and requirements of the SIP at that time. This revision will not repeat this info rmation, but simply reference the 2000 CO SIP.

1.2. PHYSICAL DESCRIPTION

The 2000 CO SIP provides a detailed physical desc ription of the Las Vegas nonattainment area.

October 2005 1-2Carbon Monoxide State Implementation Plan Revision

1.3. CLIMATOLOGICAL SETTING

The 2000 CO SIP provides a detailed description of the climatological setting of the Las Vegas Valley.

1.4. ORGANIZATION OF THIS REVISION

Each of the following seven sections addresse s a specific topic. These generally follow the format of the 2000 CO SIP, with one excep tion: Section 7 of th e 2000 SIP, “Additional Requirements of the CAAA,” related to contingency measures needed if the valley did not attain the CO standard by the December 2000 deadline. B ecause the valley attained the standard, EPA stated in its June 2005 notice that contingency measures and the five percent per year reduction in CO emissions were no longer required; therefore, the discussion in Section 7 of the 2000 CO SIP is no longer necessary. The re mainder of that section, a disc ussion of VMT projections and other control measures, is addressed in Section 7 of this SIP revision.

Section 2, “Carbon Monoxide Monitoring Network a nd Trends in Air Quality,” provides updated information on the monitoring network and CO air quality trends.

Section 3, “Emission Inventory Summary,” presents the 1996 base year emissions inventory for stationary, area, and mobile s ources (on- and off-road), as re quired under the 1990 CAAA. This section was greatly expanded from the 2000 CO SIP to provide the reader with a better understanding of the change s required in the mobile source emissions inventory because of the MOBILE6.2 program. The section pr esents future year on-road mobile emissions estimates using MOBILE6.2 inputs, which are based on the tr ansportation network defined in the RTC TransCAD transportation demand model (TDM).

Section 4, “Control Measures,” briefly describes th e control strategies that reduced CO emissions and led to attainment status.

Section 5, “Base Case Modeling,” describes the modeling process for the base case simulations using the Urban Airshed Mode l (UAM), including the prepar ation of inputs and model performance.

Section 6, “Demonstration of Attainment,” desc ribes the modeling analysis demonstrating the continued attainment of the NAAQS and summar izes CO concentrations with implemented control measures. It also explains the use of MOBILE6.2 for conformity and other purposes.

Section 7, “SIP Commitments/Implementation,” discusses the implementation of control measures, monitoring progress, emission budgets, and maintenance of CO attainment. It contains an additional discussion of conf ormity and mobile source emissi on budgets, including the use of new data.

Section 8, “References,” identifies the reports and studies supporting th e 2005 CO SIP revision.

October 2005 1-3Carbon Monoxide State Implementation Plan Revision

Appendices contain the Technica l Support Document (TSD) for the 2005 CO SIP revision and other supporting studies.

October 2005 1-4Carbon Monoxide State Implementation Plan Revision



### 2. MONITORING NETWORK AND TRENDS IN AIR QUALITY

2.1. INTRODUCTION

This section provides a brief summary of the Las Vegas Valley CO monitoring network as of July 2005 and a discussion of the trends in air qual ity for CO over the past several years. The CO monitoring program demonstrates that air qualit y is improving, and the reasons for this positive development are briefly considered.

2.2. BACKGROUND

CO occurs in the atmosphere as the result of inco mplete combustion of fuels. In Las Vegas, as in other urban areas, motor vehicles are the ma jor source of CO emissions, comprising approximately 76 percent of total daily emissions in the base year. Stations usually record exceedances of the standard in the late aftern oon and evening hours. For more details on the sources of CO emissions and a breakdown of contribution by category, see Table 3-11. EPA established specific standards for CO in 1971 to pr otect public health a nd the environment. The most stringent standard of 9 ppm is averag ed over a rolling 8-hour period; the maximum allowable hourly concentration is 35 ppm. The Clean Air Act requires that EPA review the CO standard every five years. EPA has made no changes to the current standards.

2.3. MONITORING NETWORK

EPA has established ambient air quality monito ring requirements and standards for State and Local Air Monitoring Stations (SLAMS) and Nati onal Air Monitoring St ations (NAMS). These provide for operating schedules, data quality assu rance, and design and siting of CO samplers. Although EPA monitoring guidelines require only three CO monito rs for areas such as Clark County, there were eight CO monitors at the be ginning of 2005. Table 2-1 provides details about the monitoring sites. The monitoring schedule is continuous, and each monitoring station uses the Gas Filter Correlation technique.

By 1999, the CO monitoring network in the Las Ve gas Valley had evolved into a system of 15 monitoring sites. Eight of these were SLAMS si tes, and two were NAMS/SLAMS sites. By the beginning of 2005, this network had been reduced to eight sites (Table 2-1). The Clark County Department of Air Quality and Environmental Management (DAQEM) oper ates and administers the air monitoring system, which is governed by a set of quality assurance and quality control procedures approved by EPA a nd subject to periodic EPA pe rformance audits. Air quality monitoring reports are prepared quarterly and submitted to EPA. All sites except the maximum concentration Sunrise Acres monitor have population exposure as thei r objective. Figure 2-1 shows the current CO monitoring locations.

October 2005 2-1Carbon Monoxide State Implementation Plan Revision

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

Site Name Address Type Predominant Wind Direction
City Center 559 N. 7th Stre et NAMS/SLAMS Southwest

East Sahara 4001 E. Sahara Ave. SLAMS Southwest

Orr School Maryland Pkwy. & Flamingo Road SLAMS Southwest

Winterwood 5483 Club House Dr. SLAMS Southeast
S. Las Vegas Blvd. 3799 South Las Vegas Blvd. SLAMS N.A.

Sunrise Acres 2501 S. Sunrise Ave. SLAMS Southwest

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

Freedom Park 1 650 N. Mojave Rd. SLAMS Northwest

1 Ceased operation April 30, 2005.

Figure 2-1. Las Vegas Valley CO Monitoring Sites – 2005.

October 2005 2-2Carbon Monoxide State Implementation Plan Revision

2.4. TRENDS IN CARBON MONOXIDE AIR QUALITY

No site has ever recorded a violation of th e 1-hour CO NAAQS (35 ppm) in the Las Vegas Valley; exceedance events are limited to the 8-hour national st andard of 9 ppm. The East Charleston monitoring station recorded 10 vi olations during the 1991-1992 winter season, but the number of violations dec lined to one in 1995, three in 1996, one in 1997, and two in 1998. There were no violations from 1999 through 2004, th e most recent data year. This downtrend is the direct result of implemen ting CO control measures. The Ea st Charleston monitoring site (relocated and renamed Sunrise Acres in 2000) is adjacent to a junction of major transportation corridors where three state highways intersect, known as the Five Points area. The site also sits in a topographic bowl where air pollution collects. The highest 8-hour average CO concentration, measured at 10.2 ppm, occurred in the Five Points area during the 1996 season. The second highest 8-hour concentrations since that time have been 8.2 ppm in 1999, 7.1 ppm in 2000, 6.3 ppm in 2001, 5.8 ppm in 2002, 5.3 ppm in 2003, and 5.1 ppm in 2004.

During the past several years, the Las Vegas Va lley has experienced substantial improvement in air quality: no violations of the 8-hour CO st andard have been recorded since 1998. There has been a similar reduction in the intensity of CO concentrations. Figures 2- 2 and 2-3 illustrate this improved CO air quality.

Apart from recent winter seasons with fewer in versions, annual reductions in the number of events and in CO concentrations can be attributed to the following factors:

1. Improved motor vehicle emissions control technology and the continued replacement of older, poorly maintained vehicles with newer, cleaner vehicles. 2. The wintertime oxygenated, cleaner-burning gasoline program. 3. Reduced gasoline Reid Vapor Pressure (RVP). 4. Requirements for annual smog tests for moto r vehicles, including medium- and heavy-duty gasoline vehicles. 5. A computerized traffic signal management program. 6. Use of the east leg (I-515) freeway and other roadway improvements. 7. Alternative fuel vehicle programs. 8. Voluntary rideshare programs.

CO exceedances (but not necessarily violations) of the NAAQS frequently totaled 40 or more per year in the 1980s. During 1997 and 1998, the La s Vegas Valley experienced only four unhealthful and three exceedance days, all recorded at the Sunrise Acres station. Exceedances and violations of the 8-hour CO standard eased by 1999, and there have been no recorded exceedances of the CO standard since then.

October 2005 2-3Carbon Monoxide State Implementation Plan Revision273233244132182227136234131200000005101520253035404550 19 8 1 19 8 2 19 8 3 19 8 4 19 8 5 19 8 6 19 8 7 19 8 8 19 8 9 19 9 0 19 9 1 19 9 2 19 9 3 19 9 4 19 9 5 19 9 6 19 9 7 19 9 8 19 9 9 20 0 0 20 0 1 20 0 2 20 0 3 20 0 4YEAR

DAYSExceedances of the EPAStandard for COFigure 2-2. Las Vegas Valley CO Air Quality Trends, Number of Exceedances – 1981-2004.October 20052-4Carbon Monoxide State Implementation Plan Revision0369121519951996 1997 1998 1999 2000 20012002 2003 2004Year

High 8-Hour Average Concentration (ppm)Boulder City*City CenterCraig Road*E. Flamingo / OrrE. SaharaFreedom ParkGreen Valley*Henderson*J.D. SmithPaul Meyer Park*S. Las Vegas BlvdSunrise Acres / E. CharlestonWinterwoodEPA 8-Hour Standard* - Site was discontinued June 30, 2003Figure 2-3. Las Vegas Valley CO Air Quality Trends, Annual Peak Concentrations by Station – 1981-2004.October 20052-5Carbon Monoxide State Implementation Plan Revision

2.5. CARBON MONOXIDE SATURATION STUDY

From November 2001 through January 2002, DAQEM co nducted an intensive saturation study throughout the Las Vegas Valley to measure CO dur ing its historical peak level period (see Appendix B). The purpose was to le arn about CO concentrations in the valley on a much larger geographical basis, to evaluate whether current CO monitors were representing the highest CO concentrations, and to better understand the relationship between land use, meteorology, and ambient CO concentrations. Beginning with an initial network of 32 continuous CO samplers, the program was expanded during the study to 63 st ations. Staff operated a mobile van with a CO analyzer and positional recording systems during two intensive monitoring periods.

The study found that DAQEM monitoring sites ge nerally represented th e high concentration locations for CO in the Las Vegas Valley. N early all of the highest 8-hour average CO concentrations occurred near the Sunrise Acres site , in an area east of do wntown Las Vegas. The highest averages were in the 6 ppm range, fa r below the 9 ppm 8-hour NAAQS for CO. The study confirmed that meteorological conditions (e .g., cold winter nights with poor atmospheric dispersion) led to the accumula tion of CO within 100 feet of the ground in the area around Sunrise Acres. At the same time, areas with si milar emission sources di d not experience high CO levels, further confirming the pooling of pollu tants in the Sunrise Acres area. A special microscale saturation study site ne ar the Fremont Street casino a nd parking garage area recorded the highest one-hour CO level of 18.3 ppm, which is only half the one-hour NAAQS.

This saturation study confirmed the proper locations for CO monitors in the valley, assisted staff in evaluating the results of the modeling work constituting part of this SIP revision, and supported decisions about which CO monitors c ould be safely removed from the Clark County air monitoring network in subsequent years.

October 2005 2-6Carbon Monoxide State Implementation Plan Revision



### 3. EMISSION INVENTORY SUMMARY

3.1. INTRODUCTION

The CAAA requires that all nonattainment areas prepare a base year inventory that is comprehensive, accurate, and curre nt with respect to actual emissions in the area (Section 182(a)(1)). The peak season and modeling CO i nventories are based on this inventory. This section summarizes the 1996 base year CO inve ntory for the Las Vegas Valley nonattainment area, which addresses CO emissions from four ma jor type categories: stat ionary poin t sources, area sources, on-road mobile sour ces, and non-road mobile sources. This section provides a brief overview of the source categories and the met hodologies employed to es timate emissions. For the mobile sources, it includes a discussion of changes from the 2000 CO SIP modeling effort that used MOBILE5b, which was replaced by MOBILE6.2.03. During the development of the 2000 CO SIP, CO emissions from on-road mobile sources (by far the larg est contributor to the overall emission inventory for Las Vegas) were estimated using a combination of MOBILE5b, the Direct Travel Impact Model, and volume/ro adway link information provided by the RTC in its TRANPLAN model. Appendix A provides more detailed information pertaining to this inventory.

The Clark County Health District was the agency or iginally responsible for preparing and submitting the Las Vegas Valley nonattainment area 1996 base year CO emissions inventory. Several other local agencies contributed in formation necessary for preparing emissions estimates, including the RTC, the Clark County Department of Aviation, and the Clark County Fire Department. The Nevada Department of Transportation, the U.S. Forest Service, and Southwest Gas Corporation also provid ed information for these estimates.

The 1996 point source inventory was prepared primarily from a mail survey by the Health District. Survey results were supplemented by information obtained through personal contacts during compliance inspections, and the RTC provide d VMT data necessary to calculate on-road mobile source emissions. The MOBILE5b model wa s run to determine vehicle emission factors from on-road mobile sources. Table 3-1 contai ns the Clark County demographic information used in the 2000 CO SIP.

Table 3-1. Demographic Data Used in Developing Emission Inventories and to Project Activity in the 2000 CO SIP 1

January Population Employment VMT

1996 1,037,844 493, 213 22,469,020
2000 1,269,600 609, 400 24,929,485
2010 1,790,700 859, 500 38,022,330
2020 2,406,500 1,115, 100 57,492,333

1 Data is based on RTC 1997 estimates and projections.

The 2000 CO SIP was based on computer modeling (using UAM) of the singl e best performing episode of the three originally modeled: th e night of December 8-9 (Sunday-Monday), 1996. The

October 2005 3-1Carbon Monoxide State Implementation Plan Revision

2000 CO SIP and its appendices provide technical documentation for the models, application methodologies, performance evaluations, and fu ture year modeling assessments. This SIP revision continues to rely on the December 8-9, 1996 episode.

This 2005 CO SIP revision uses new data on population and VMT projections, especially for conducting the MOBILE6.2 analysis. For the 1996 base year, the RTC’s original TRANPLAN output was used to define link-based volume (in VMT) and other traffic volume-related parameters. No trip tables were available, which allow for the separate estimation of start versus running emissions, so 1996 start emissions were spatially allocated using 2000 TransCAD trip data, as described later in this section. All orig inal ancillary information, including vehicle fleet mix, seasonal/day-of-week adjustment factors, and hourly activity profiles, remained the same as in the original model.

For all future years modeled in this update, the RTC provided output from the new TransCAD TDM, which includes link volumes and trip tabl es for each year. Population projections (and actual population for 2000) were modi fied to reflect higher growth rates in the c ounty. Table 3-2 contains this new data, incl uding the revised 1996 daily VMT.

Table 3-2. Demographic Data Used in Developing Emission Inventories and to Project Activity in the 2005 CO SIP Revision

January Population 1 Modeled DVMT 2

1996 1,037,844 22,395,251
2006 1,923,420 37,076,414
2010 2,281,380 47,170,180
2015 2,687,055 53,973,132
2020 2,999,953 58,181,118
2030 3,410,332 65,586,340

1 Data obtained from the UNLV Center for Busi ness and Economic Research in July 2005.
2 RTC 2005 TransCAD TDM.

3.2. EMISSIONS SUMMARY BY CATEGORY

This section is greatly expanded from the origin al 2000 CO SIP to provide a better understanding of the changes required to develop the mobile source emissions inventory. The 1996 base year and future year inventories for the point source and area source categories remain essentially the same as those reported in the 2000 CO SIP, although direct comparis on with Table 3-2 is difficult because the 2000 CO SIP tables used av erage daily CO season emissions and this SIP revision contains daily emissions for the two episode days of Sunday and Monday. The non-road and on-road mobile source inventories have been greatly revised to reflect new, updated data inputs, new models, and a format to accommo date the MOBILE6.2.03 modeling requirements. Appendix A provides an expanded explanation of the methodology and results of the mobile source inventory changes.

October 2005 3-2Carbon Monoxide State Implementation Plan Revision

3.2.1. On-Road Mobile Emissions

The greatest effort in this CO modeling upda te has focused on the on -road mobile source inventory estimates. The model used in the 2000 CO SIP effort (MOBILE5b) was replaced by the latest version of the model (MOBILE6.2.03) . This version updates CO emission rates for low-emission and Tier 2 vehicles, along with many other changes. The Air Improvement Resource, Inc. version of this model was used because it provides the capability to create a condensed database of composite emission factor s. This is important for applications where numerous MOBILE6 scenarios must be run to generate lookup f actors for link-level emissions estimates, such as this one.

For the 1996 base year, the RTC’s original TRANP LAN output was used to define link-based volume (in VMT) and other traffic volume-related pa rameters. All original ancillary information, including vehicle fleet mix, seasonal/day-of-week adjustment factors, and hourly activity profiles, remained the same as in the original model.

Since the output data and formats for MOBILE6 are significantly different from those of its predecessor, the original program used to estim ate link-level CO emissions (i.e., the Direct Travel Impact Model) was replaced by two new programs. The firs t processes link-based emissions, and the second processes emissions ba sed on traffic analysis zones (TAZs). Both programs produce inputs for the Emission Processi ng System, version 3 (EPS3). EPS3 is the latest version of the EPS program suite used in the original CO SIP model to generate gridded, time-resolved, UAM-ready CO emission input files.

For all future years modeled in this SIP revision, the RTC provide d output from the new TransCAD TDM, which includes link volumes and trip tables for each year. Base year TRANPLAN intrazonal data were provided as volumes by TAZ w ith a trip length from which VMT was calculated. Future year TransCAD intrazonal data were provided as trips by TAZ only. The intrazonal trips were assumed to have a trip length of 1 mile, from which VMT was calculated. VMT was multiplied by the running e xhaust emission factors, then spatially distributed using gridded surroga tes developed from the definition of the future year TransCAD TAZs.

For both the base and future year link-leve l emissions, VMT was calculated from the transportation model output (link volume multiplie d by link length) for each period of the day and allocated to each hour using an hourly distribution for each day of the episode. VMT was then multiplied by the hourly running exhaust emission factors (in grams per mile) from MOBILE6.2, and the total hourly emissions by link were spatially distributed according to the link endpoint coordinates.

Start emissions were calculated by multiplyi ng hourly estimates of link-level VMT by hourly MOBILE6.2 start emission factors in grams per m ile. The link-level start emissions were then totaled over the entire network and spatially dist ributed using the period -specific transportation model trip origin data by TAZ. Since no TRAN PLAN trip data by TAZ were available for the 1996 base year, 1996 start emissions were spatia lly allocated using 2000 TransCAD trip data.

October 2005 3-3Carbon Monoxide State Implementation Plan Revision

3.2.1.1. Base Year Estimates

Section 2.2 of Appendix A describes the methodol ogy to develop on-road mobile emissions in detail. Total on-road mobile source emissions consist of link-level running exhaust emissions, start emissions, and emissions from intrazona l trips. The following subsections briefly summarize how these emissions were estimated.

3.2.1.1.1. MOBILE6 Modeling

Two sets of MOBILE6 runs were performed. The first used start distribution emission factors applied to the entire domain, with the ex ception of a small area along South Las Vegas Boulevard. To better unde rstand specific weekday start em ission factors along the boulevard, a second set of MOBILE6 runs was conducted. Star t activity in this regi on is not typical of commute activity profiles, since trips start in casino/ resort parking lots rather than in residential areas. Based on the two runs, it was decided to apply the modified start distribution for the fraction of the 2000 TransCAD origin trips that occur in the TAZs along South Las Vegas Boulevard for the base year and all future year s. Figure 2-2 in Appendix A shows the results of these runs.

The effectiveness of the Clark County I/M pr ogram was set to 100 pe rcent in the MOBILE6 emission runs. Appendix C justifies this assumption.

3.2.1.1.2. Link-Level Running Exhaust Emissions

The 1996 TRANPLAN activity data we re adjusted for season, day, hour, and transit activity to provide the data for the link-le vel emissions. The TRANPLAN link activity data consisted of the annual daily average volume for each link in the ne twork classified by RTC facility type code. Table 3-3 cross-references RTC facility type codes and MOBILE6.2 roadway types.

Table 3-3. Cross-Refe rence Between RTC and MO BILE6.2 Facility Types

RTC Facility Code Descripti on MOBILE6.2 Roadway Type

0 Externals Freeway

1 System Ramps Ramp

2 Minor Arterials Arterial

3 Major Arterials Arterial

4 Freeway Ramps Ramp

5 Interstates Freeway

6 Freeways Freeway

7 Expressways Freeway

8 Collectors Arterial

9 Centroid Connectors 1 Local

10 Intrazonal Local

1 Centroid connectors were treated as local roads; VMT on the centroid connectors was multiplied by MOBILE6 local road emission factors.

October 2005 3-4Carbon Monoxide State Implementation Plan Revision

Running exhaust emissions for the base year were generated using the Air Improvement Resource, Inc. version of MOBILE6. This versio n takes the standard MOBILE6 database output and condenses it across model y ears for each vehicle class.

In summary, the link-level running e xhaust emissions processing steps were:

1. Adjust daily volumes to hourly volumes usi ng the profiles in Figure 2-3 of Appendix A. 2. Adjust link speeds using the hourly volume to cap acity ratio in the Bureau of Public Roads curve (see Section 2.2.2.3 of Appendix A for details). 3. Calculate the hourly link VMT as the hour ly volume multiplied by the link length.

4. Calculate the link emissions as the li nk VMT multiplied by the MOBILE6.2 composite emission factor for the link roadway type, hour, and adjusted link speed. 5. Spatially allocate the link emissions to the modeling grid. 6. Use EPS3 to adjust emissions to an aver age December day, to Sunday or Monday, and for transit activity.

Table 3-4 shows the tabulations of 1996 VMT by facility type, as reported by TRANPLAN and after adjustment.

Table 3-4. 1996 VMT by Facility Type

Group Code Facility Type Modeled 1996 DVMT DVMT Adjusted to December DVMT Adjusted for Transit Sunday DVMT Monday DVMT

0 External Connector 640,6 05 654,058 655,988 507,734 670,419

1 System Ramp 69,247 70, 701 70,910 54,884 72,470

2 Minor Arterial 7,469,952 7,626, 821 7,649,320 5, 920,574 7,817,605

3 Major Arterial 3,655,890 3,732, 664 3,743,675 2, 897,605 3,826,036

4 Freeway On- or Off-Ramp 267,725 273,348 274,1 54 212,195 280,185

5 Interstate 3,825,715 3,906,0 55 3,917,578 3,032, 205 4,003,764

6 Freeway 1,202,253 1,227,5 01 1,231,122 952, 888 1,258,207

7 Expressway 214,096 218, 592 219,237 169,690 224,060

8 Collector 2,776,772 2,835,0 84 2,843,448 2,200, 828 2,906,003

9 Centroid Connector 2,185,691 2, 231,591 2,238,174 1, 732,347 2,287,414
Intrazonal 87,303 89,13 6 89,399 69,195 91,366 Daily Total 1 22,395,251 22,776,41 4 22,843,605 17,68 0,950 23,346,164
Transit Adjustment 1.00295
December Adjustment 1.021 Sunday Adjustment 0.774 Monday Adjustment 1.022

1 Totals are shown as output by TRANPLAN and after seasonal, day-of-week, and pub lic transit adjustments.

October 2005 3-5Carbon Monoxide State Implementation Plan Revision

3.2.1.1.3. Base Year Start Emissions

The daily link-level VMT from TRANPLAN was allocated to hourly values using the dayspecific hourly VMT profile shown in Figure 2-3 of Appendix A. The base year start emissions were calculated from the product of hourly link VMT and hourly MOBILE6.2 start emission factors. To remain consistent with how future y ear start emissions would be developed, base year start emissions were translated from link-level to TAZ level. A month/se ason adjustment factor of 1.021 was applied to the start emissions to adju st from an average annual day to an average December day.

Day-of-week adjustment factors were applied to adjust from an average annual day to Sunday and Monday. The factors used were 0.774 for Sunday and 1.022 for Monday, the same factors used in the 2000 CO SIP. The hour ly TAZ start emissions were spa tially alloca ted to the grid cell containing the TAZ centroid and th e 24 surrounding cells in a “wedding cake” fashion: the grid cell containing a TAZ centroid received 25 percent of the start emissions from that TAZ, the surrounding 8 grid cells received 60 percent of the start emissions (7.5 percent per cell), and the outside 16 grid cells received 15 percent of the start emissions ( 0.9375 percent per ce ll). Both the EPA Region 9 office and the Office of Transporta tion and Air Quality revi ewed this approach (EPA 2005). Figure 2-5 in Appendix A shows the spatial distributi on of start exhaust emissions for the 1996 base case.

3.2.1.1.4. Base Year Total Emissions

Table 3-5 lists the component an d total on-road mobile source em issions for the 1996 base year. Figure 2-6 of Appendix A presents the spatial distribution of th e total on-road mobile source emissions for December 9, 1996.

Table 3-5. Component and Total On-Road Mobile Source CO Emissions (TPD 1 ) for the 1996 Base Year

Links - Running Starts Intrazonal Total Sunday 12/8 202.75 126.42 0.78 329.95 Monday 12/9 269.31 241.21 1.03 511.55

1 Tons per day.

3.2.1.2. Future Year Estimates

The RTC provided TransCAD model output for each of the future years (2006, 2010, 2015, 2020, and 2030). The TransCAD model output pr ovided link-level volumes (number of vehicles), along with trip origins and destinations, for the following seven time periods: midnight to 7 a.m., 7 a.m. to 9 a.m., 9 a.m. to 2 p.m., 2 p.m. to 4 p.m., 4 p.m. to 6 p.m., 6 p.m. to 8 p.m., and 8 p.m. to midnight. The following subs ections briefly summarize how future year emissions were estimated.

October 2005 3-6Carbon Monoxide State Implementation Plan Revision

3.2.1.2.1. Future Year MOBILE6 Inputs

Table 2-6 of Appendix A details how external file s were used. Eight input files were created for each future year (2006, 2010, 2015, 2020, and 2030), one for weekdays and one for weekends for each of the four roadway types: freeway, arte rial, local, and ramp. Values from a 2002 Clark County traffic study yielded VMT fo r five vehicle types, which were further broken down into sixteen vehicle types based on the MOBILE6 de fault VMT mix for 2002. Because Clark County does not have future year forecasts for vehicl e VMT mix, seasonal/day-of-week adjustments, or hourly activity profiles, the base year informati on for these variables was used for all future
years.

3.2.1.2.2. Link-Level Running Exhaust Emissions

Link volumes were first adjusted to observed traffic counts by facility type, then adjustments were made for month/season and day of the w eek. TransCAD volume data is for an average weekday, so Sunday activities we re adjusted by a 0.774 day-of-w eek factor. Monday was not adjusted because the TransCAD data repres ent an average weekday. Hourly and speed adjustments were made as in the base year approach.

3.2.1.2.3. Future Year Start Emissions

Future year start emissions were calculated the same way as base year start emissions. For Monday, the hourly VMT was estimated by disa ggregating the period VMT to hourly VMT using the day-specific hourly VM T profile shown in Figure 2-3 of Appendix A. Tables 2-10 through 2-14 of Appendix A show the resu lting VMT by facility type for 2006, 2010, 2015, 2020, and 2030. Start emissions were calculated by multiplying the hourly VMT by the hourly MOBILE6 start emission factors.

3.2.1.2.4. Future Year Intrazonal Activity

Intrazonal VMT was calculated assuming a default le ngth of 1 mile for each intrazonal trip, as described in Chapter 5 of the fiscal year 2004-2005 RTP documentation (RTC 2004).

3.2.1.2.5. Future Year Total Emissions

Table 3-6 lists the component and total on-road mobile source emissions for all future years on the second Sunday of December.

October 2005 3-7Carbon Monoxide State Implementation Plan Revision

Table 3-6. Component and Total On-Road Sunday Mobile Source CO Emissions (TPD) for All Future Years

Sunday 2006 2010 2015 2020 2030 Links - Running 149.64 150.26 137.32 133.15 142.66
Starts 125.10 135.93 138.46 139.23 152.54
Intrazonal 0.57 0. 82 0.66 0.71 0.70
Total 275.30 287.01 276.44 273.09 295.90

Table 3-7 lists the component and total on-road mobile source emissions for all future years on the second Monday of December.

Table 3-7. Component and Total On-Road Monday Mobile Source Co Emissions (TPD) for All Future Years

Monday 2006 2010 2015 2020 2030 Links - Running 204.62 205.29 187.70 182.00 194.67
Starts 235.73 257.33 262.53 264.10 289.81
Intrazonal 0.88 1. 33 1.07 1.14 1.13
Total 441.23 463.95 451.30 447.24 485.61

3.2.2. Non-Road Mobile Emissions

3.2.2.1. Airports

The Las Vegas Valley contains three major civil airports (McCarran International, North Las Vegas, and Henderson) and one large military ai rport (Nellis Air Force Base). In 1999, Clark County sponsored an Emissions and Dispersion Modeling System (EDMS) project for the three civil airports. The year s modeled included the 1996 base ye ar and the future years of 2000, 2010, and 2020. UAM results were added to the EDMS recep tor concentrations to provide an estimate of background concentrations. In 2003, Clark Count y sponsored an updated modeling project for the three civil airports using the latest version of EDMS. On-road mobile sources were estimated using Clark County runs of MOBILE6.2. ED MS was run for 2000, 2005, 2010, 2015, and 2020, but UAM results were not added to the EDMS receptor results. The 1996 base year was not included in this revision because the EDMS cont ributions to the UAM for the 1996 base year are zero: the 10 EDMS receptors used in this anal ysis showed that no emissions from McCarran were dispersed and that McCarra n was isolated from the main Las Vegas CO cloud that existed well to the north. The revised modeling resulted in predictions above the 8-hour CO standard at several receptors in all years; however, these were located in areas not generally accessible to the public, primarily aircraft docking areas, the aircra ft apron, etc. EPA has indicated it will accept the removal of receptors in non-public access areas from consideration, since the sites do not fall under the Clean Air Act definition of “public access.”

To properly account for the contribu tions of airports to the valley -wide distribution of CO during the December 8-9 episode, UAM had to include the updated EDMS airport emissions within the gridded inventory. Airport emissions for 1996 were taken from the original EDMS estimates,

October 2005 3-8Carbon Monoxide State Implementation Plan Revision

and emissions for the 2010, 2015, and 2020 future years were taken from the 2003 updated EDMS estimates. Table 3-8 shows the annual airport emissions. Values for 2006 were interpolated from 2005 and 2010 EDMS estimates; values for 2030 were extrapolated from the rate of growth in the 2015 to 2020 EDMS estimates. The or iginal 2000 CO SIP emission estimates for Nellis Air Force Base were retain ed in the UAM modeling. All these estimates, in tons per year (TPY), had to be disaggregat ed to December, Sunday and Monday, and each hour of the day. Clark County provided activity data for the civil airports on which to base the disaggregation from annual to hourly emission rates, listed in Table 3-2 of Appendix A.

Table 3-8. Annual Airport CO Emissi on Estimates (TPY) for the 1996 Base Year 1 and for Future Years 2010, 2015, and 2020 2 (2006 and 2030 Estimated)

Year McCarran Henderson North Las Vegas

1996 10,022 536 2,727

2006 11,600 646 1,848

2010 13,494 762 1,880

2015 15,482 949 1,924

2020 17,553 1,220 1,971

2030 21,695 1,762 2,063

1 Ricondo 1999.
2 Ricondo 2003.

Airport emissions were placed evenly across the gr id cells in which the airports reside. Figures 3-1 and 3-2 in Appendix A illustrate details on hourly activity for the three civil airports.

3.2.2.2. Locomotives

In Clark County, only Union Paci fic operates locomotives. Two switching facilities are located in the county, the downtown (Civic Center) ya rd and a yard at the Boulder Junction Wye. Updated railroad emissions for 2001 based on a recent non-road study (MACTEC 2003) were incorporated into this SIP revi sion. The base year emissions es timates were taken from the 2000 CO SIP. Locomotive emissions from the non-road study included both lin e haul and switching; for switching, emissions were placed at th e same two facilities previously modeled.

The locomotive activity unit most useful for emission ev aluation is fuel consumption. Projected fuel consumption from locomotive use is difficu lt to estimate, especially for a given track segment like the one through Clark County. Fuel c onsumption depends on factors not restricted exclusively to number of trains, tons of freight , or business indicators because of efficiency improvements to trains or operations.

To project locomotive activity increases due to growth in business, a time series plot of available data on fuel consumption was used. Emission fact ors were projected using EPA estimates of the effect of fleet turnover. Tabl e 3-3 in Appendix A shows the pe rcent reduction in emissions for line-haul and switching engines. Locomotive emissi ons for future years were based on projected growth in fuel consumption and reduced by e xpected emission reductions from new engine controls.

October 2005 3-9Carbon Monoxide State Implementation Plan Revision

3.2.2.3. Other Non-Road Categories

Equipment emission estimates for non-road categorie s other than aircraft and locomotives during weekdays and weekends were performed usi ng EPA’s NONROAD model. For the Clark County base year inventory, the period t ype was set to the winter season and emissions were reported as tons per day. Airport ground support equipmen t was removed from the NONROAD emissions estimates because it was estimated separate ly using EDMS, as described previously. Recreational marine estimates were also remove d because the major water areas in Clark County lie outside the modeling domain. Railroad mainte nance emissions for the 1996 base case were extracted from the NONROAD output and processed with locomotive emissions.

Table 3-9 summarizes NONROAD model equipment CO emissions estimates for the base year and all future years evaluated in the 2005 CO SIP modeling. The em issions shown in this table are for the modeling domain only.

Table 3-9. Clark County CO NONR OAD Gridded Emission Estimates (TPD)

Second Sunday in December Base 2006 2010 2015 2020 2030

Recreational 2.47 2. 40 2.44 2.52 2.58 2.72 Construction and Mining 17. 47 1.28 0.99 0.80 0.68 0.59

Industrial 1.80 1.34 0.95 0.41 0.25 0.24

Lawn and Garden 33.56 32.61 36.28 39.97 43.58 50.70 Agriculture 0.00 0. 00 0.00 0.00 0.00 0.00

Commercial 10.82 12.91 14.86 16.98 19.12 23.23

Total 66.13 50.53 55. 52 60.68 66.22 77.48

Second Monday in December Base 2006 2010 2015 2020 2030

Recreational 1.24 1. 20 1.22 1.26 1.29 1.36 Construction and Mining 34. 94 2.56 1.98 1.60 1.36 1.18

Industrial 3.36 2.54 1.74 0.69 0.46 0.43

Lawn and Garden 42.22 42.24 46.32 51.03 55.66 64.78 Agriculture 0.00 0. 00 0.00 0.00 0.00 0.00

Commercial 21.64 25.82 29.72 33.97 38.24 46.45

Total 103.40 74.36 80. 98 88.55 97.02 114.20

Sections 3.1.3.2 and 3.1.3.3 of the TSD (Appendix A) provide additional information on base and future year gridding surrogate s used for these non-road sources.

3.2.3. Point Sources

This SIP revision used the 1996 base year point s ource inventory from the original 2000 CO SIP. Clark County provided an updated point source emi ssion inventory for future years that included updated stack parameters and emissions based on potential-to-emit levels for seven specific

October 2005 3-10Carbon Monoxide State Implementation Plan Revision

facilities. UAM future year inventories include d potential-to-emit levels plus a 70-TPY buffer for these sources. All future year modeling used the same future ye ar point source data. Tables 3- 14 and 3-15 of Appendix A provide future year emissions of these seven facilities and the modeled CO point source emission estimates.

3.2.4. Area Sources

The 1996 base year area source estimates were taken from the 2000 CO SIP with no changes. Base year emissions were projec ted by growth factors to determin e future year emissions for the major area source categories. Table 3-10 summarizes episode-specific area source CO emissions for the base and project years by eleven subcat egories. Table 3-2 of the 2000 CO SIP contains information on these subcategories, but only on an average daily CO season emission basis. The data in Table 3-10 are for the peak episode in th e 1996 base year, so are not directly comparable.

3.3. TOTAL ANNUAL EMISSIONS

Table 3-11 summarizes the percen t contribution to total episodic daily emissions of the four major emission categories for the base year ( 1996) and a future year (2030), based on the modeling performed in this SIP revision.

Table 3-12 summarizes total daily CO emissions by source category for the 1996 base year and all future years.

Figure 3-1 shows the spatial dist ribution of total CO emissions for the 1996 base case. Figure 3-2 shows a similar spatial distribut ion for the 2030 projection year.

Table 3-10. Clark County CO Area Source Grid ded Emissions Estimates (TPD) After Season and Day-of-Week Adjustments

Second Sunday in December Ba se 2006 2010 2015 2020 2030
Electric Utility Generation 0.558 0.687 0.734 0.787 0.840 0.946 Small Stationary 2.701 3.412 3.680 3. 981 4.283 4.885

Boiler Emissions 0.385 0.486 0.524 0. 567 0.610 0.696

Industrial Natural Gas 0. 148 0.186 0.201 0. 218 0.234 0.267

Commercial Natural Gas 0. 041 0.051 0.055 0. 059 0.063 0.070

Residential Natural Gas 0.308 0.360 0.380 0.398 0.416 0.452 Fireplaces 3.033 4. 556 5.233 6.133 7.033 8.832

Brush Fires 1.262 1. 896 2.178 2.552 2.927 3.675 Cigarette Smoking 0.044 0.066 0.076 0. 089 0.102 0.128

Structural Fires 0.646 0.971 1.115 1. 307 1.499 1.882

Vehicular Fires 0.054 0.081 0.093 0. 110 0.126 0.158

Total 9.181 12.753 14.27 0 16.200 18.131 21.991

October 2005 3-11Carbon Monoxide State Implementation Plan Revision

Table 3-10. Clark County CO Area Source Grid ded Emissions Estimates (TPD) After Season and Day-of-Week Adjustments (continued)

Second Monday in December Ba se 2006 2010 2015 2020 2030
Electric Utility Generation 0.558 0.687 0.734 0.787 0.840 0.946 Small Stationary 2.701 3.412 3.680 3. 981 4.283 4.885

Boiler Emissions 0.385 0.486 0.524 0. 567 0.610 0.696

Industrial Natural Gas 0. 369 0.466 0.503 0. 544 0.585 0.667

Commercial Natural Gas 0. 103 0.127 0.138 0. 148 0.157 0.176

Residential Natural Gas 0.308 0.360 0.380 0.398 0.416 0.452 Fireplaces 3.033 4. 556 5.233 6.133 7.033 8.832

Brush Fires 1.262 1. 896 2.178 2.552 2.927 3.675 Cigarette Smoking 0.044 0.066 0.076 0. 089 0.102 0.128

Structural Fires 0.646 0.971 1.115 1. 307 1.499 1.882

Vehicular Fires 0.054 0.081 0.093 0. 110 0.126 0.158

Total 9.464 13.109 14.65 4 16.615 18.576 22.497

Table 3-11. Percent Daily Emissions by Source Category and Year

Base Year – 1996 Future Year - 2030 Source Category Sunday Monday Sunday Monday
On-Road 74 76 62 68
Non-Road 23 21 30 26
Point <1 <1 3 3
Area 2 1 4 2

October 2005 3-12Carbon Monoxide State Implementation Plan Revision

Table 3-12. Summary of Total Daily CO Em issions (TPD) in the UAM CO SIP Revision

Second Sunday in December Ba se 2006 2010 2015 2020 2030
On-Road Running (Links) 202.75 149. 40 150.18 137.31 133.18 142.80

On-Road Starts 126.42 125.10 135.93 138.46 139.23 152.54

On-Road Intrazonal 0.78 0.57 0.82 0.66 0.71 0.70
Henderson Airport 1.12 1.35 1.59 1.99 2.55 3.69
McCarran Airport 24.69 28.57 33.24 38. 14 43.24 53.44

Nellis Air Force Base 2.86 2.86 2.86 2.86 2.86 2.86
North Las Vegas Airport 7.58 5.13 5.22 5.35 5.48 5.73

Area Sources 9.18 12. 75 14.27 16.20 18.13 21.99

Non-road - NONROAD 66.13 50.49 55.50 60. 66 66.21 77.44

Point Sources 3.13 15. 82 15.82 15.82 15.82 15.82
Railway - Line Haul 0. 14 0.17 0.19 0.20 0.22 0.27
Railway - Maintenance 0. 03 0.04 0.04 0.04 0.05 0.06

Total 444.81 392.49 415.73 417.71 427.65 477.19

Second Monday in December Ba se 2006 2010 2015 2020 2030
On-Road Running (Links) 269.31 204. 62 205.29 187.70 182.00 194.67

On-Road Starts 241.09 235.73 257.33 262.53 264.10 289.81

On-Road Intrazonal 1.03 0.88 1.33 1.07 1.14 1.13
Henderson Airport 0.88 1.07 1.26 1.57 2.01 2.91
McCarran Airport 24.69 28.57 33.24 38. 14 43.24 53.44

Nellis Air Force Base 2.86 2.86 2.86 2.86 2.86 2.86
North Las Vegas Airport 5.98 4.05 4.12 4.22 4.32 4.52

Area Sources 9.46 13. 11 14.65 16.62 18.58 22.50

Non-road - NONROAD 103.40 74.30 80.94 88.52 96.99 114.17

Point Sources 3.13 15. 82 15.82 15.82 15.82 15.82
Railway - Line Haul 0. 14 0.17 0.19 0.20 0.22 0.27
Railway - Maintenance 0. 11 0.14 0.15 0.16 0.18 0.21

Total 662.08 581.31 617.17 619.41 631.46 702.31

October 2005 3-13Carbon Monoxide State Implementation Plan Revision

642 652 662 672 682 692 UTM Easting (km) 3973 3983 3993 4003 4013 4023UTM Northing (km)

0.0 0.6 1.2 1.8 2.4 3.0 3.6 4.2 4.8 5.4



### Total Surface Emissions Base Year - Dec 9, 1996 CO (tons per day)

Figure 3-1. Spatial Distribution of To tal CO Emissions for the 1996 Base Case.

October 2005 3-14Carbon Monoxide State Implementation Plan Revision

642 652 662 672 682 692 UTM Easting (km) 3973 3983 3993 4003 4013 4023UTM Northing (km)

0.0 0.6 1.2 1.8 2.4 3.0 3.6 4.2 4.8 5.4



### Total Surface Emissions Future Year - Dec 9, 2030 CO (tons per day)

Figure 3-2. Spatial Distribution of Total Surf ace Gridded CO Emissions for the 2030 Future Year.

October 2005 3-15Carbon Monoxide State Implementation Plan Revision

THIS PAGE INTE NTIONALLY BLANK

October 2005 3-16Carbon Monoxide State Implementation Plan Revision



### 4. CONTROL MEASURES

4.1. INTRODUCTION

This SIP revision focused on recalculating the emissions for on-road and non-road sources using the newer MOBILE6.2 and NO NROAD2004 models, respectivel y, and then running the UAM to determine if the Las Vegas Valley will conti nue to maintain the CO standards through 2030. The results, as Sections 5 and 6 describe in detail, confirm con tinued maintenance. Accordingly, no new control measures are required in this SI P revision, so this secti on primarily references relevant portions of Section 4 of the 2000 CO SIP with some summary information. The impacts of the four CO control measures in the 2000 CO SIP were not recalculated in this revision.

The 2000 CO SIP noted that about 86 percent of the CO emissions in the Las Vegas Valley in 1996 were produced by on-road motor vehicles. Non-road mobile sources contributed about 11 percent, and stationary point and area source s accounted for the remaining 3 percent. The proportions have changed slightly in this SIP revision due to the new models employed and a focus on emissions for a December Sunday-M onday peak episode rather than on average seasonal CO emissions. The 1996 base year propor tions under the new m odeling analysis are about 75 percent from on-road sources, 22 percent from non-ro ad mobile sources, and the remaining 3 percent from stationary area and poi nt sources. On-road source proportions are less in 2030 due to improved vehicle emission controls: they only make up about 65 percent of CO emissions. Non-road emissions increase to 28 pe rcent, point sources to 3 percent, and area sources to about 4 percent. These data can be examined in detail in Tables 3-11 and 3-12.

In developing the 2000 CO SIP, Clark County ex amined the potential for additional control measures on each of the four major source ca tegories. After reviewing the impacts on CO attainment from each category and the additional measures available to further reduce CO, the county decided to focus new control measures on the major on-road cate gory of the emissions inventory. Four new control measures were adopted and implemented. Several additional CO control measures adopted in the 1967 to 1995 time frame continue to support achievement of the CO standards.

4.2. CARBON MONOXIDE CONTROL MEASURES

Regulations and resolutions in support of the control measures necessary for CO attainment were adopted prior to submittal of the 2000 CO SIP and became effective at the end of 1999. Control measures and programs from previous plans, listed in Tables 4-1 a nd 4-2, served as the foundation to which the four new measures were added to achieve attainment of the standard. When fully implemented, the four control measur es proposed in the 2000 CO SIP, along with all the control measures previously implemented , reduced CO emissions from on-road motor vehicles by over 22 percent between 1996 and 2000. These measures were a major reason Clark County could offset extraordinary population growth and vehicle us age during the 1990s and attain the standards by 2001. Sec tion 4.2.1 of the 2000 CO SIP desc ribes in detail the four onroad mobile source control measures. Since the control measures have not changed and 2000 emission reductions remain as projected by MOBILE5b, Table 4-1 simply summarizes the

October 2005 4-1Carbon Monoxide State Implementation Plan Revision

control measures. Descriptions of the contro l measures, legislative history, and acceptance criteria are provided in Chapter 4 of the 2000 CO SIP.

Table 4-1. Adopted CO Control Measures to Reduce On-Road Mobile Source Emissions

Control Measure Year 2000 Emission Reduction % Daily CO Benefit (TPD) Adoption Date Implementing Agency

Cleaner Burning Gasoline Program 9.80% 31.9 1999 DAQEM Voluntary TDM and Transportation Control Measures 0.08% 0.3 1999/Ongoing RTC

I/M Technician Training 2.95% 10.4 1996 (enhanced) NV Department of Motor Vehicles & Public Safety
Alternative Fuels for Government Fleets 0.12% 0.4 1995-2001 NV Division of Environmental Protection

Combined Effect of Controls 12.2% 43.1

None of the four control measures were rerun individually as part of the MOBILE6.2 analysis. It was unnecessary because the measures have been approved and adopted as part of the 2000 CO SIP, and UAM runs for maximum CO levels using MOBILE6.2 do not show any violations through 2030.

Section 4.3 of the 2000 CO SIP desc ribes controls on off-road m obile sources. It identifies the only direct proactive controls affecting off-road sources, m obile and otherwise, as the Wintertime Cleaner Burning Gasoline and Oxyge nated Fuel programs. Since this category contributes only about 11 percent of the total CO emissions for the Las Vegas Valley, the 2000 SIP determined that further controlling these emi ssions would not be cost-effective or practical.

Section 4.4 of the 2000 CO SIP notes that only 3 percent of CO emi ssions in the area come from stationary point and area sources. Except for permit-related controls resulting from New Source Review and New Source Performance standards, no new controls on point and area sources were included in the 2000 CO SIP or in this SIP revision.

Section 4.5 of the 2000 CO SIP discusses previous ly adopted control m easures from the 1995 CO SIP and how they continue to assist in air quality improvement efforts. Fleet turnover, partly from high annual increases in vehi cle registrations and new model y ear vehicles, continues to be a major factor in reducing m obile source CO emissions. In 1997, Clark County increased the oxygenated fuels weight control re gulation from the 2.7 percent credited in the 1995 CO SIP to 3.5 percent. The I/M program for motor vehicles, in effect since 1978, continues to provide a major reduction in CO emissions. As Appendix C points out, the Nevada Legislature modified that program slightly in 2005. Table 4-2 lists pr eviously adopted and en forceable CO control

measures.

October 2005 4-2Carbon Monoxide State Implementation Plan Revision

Table 4-2. Control Measures Adopted for the 1995 CO SIP and Included as Part of the 2000 CO SIP and 2005 CO SIP Revision

Control Measure Adoption Date Oxygenated Fuels 1991/1995 Reduced RVP Gasoline 1995 Motor Vehicle I/M Program 1978 Fleet Turnover 1967

In summary, the primary control measures in th e 1995 and 2000 CO SIPs ha ve been adopted and implemented. This 2005 CO SIP revision suggests no new measures, since the area attained the CO standards and EPA approved the 2000 CO SIP. Furthermore, the modeling conducted as part of this revision demonstrates continued attain ment of CO standards through at least 2030.

October 2005 4-3Carbon Monoxide State Implementation Plan Revision

THIS PAGE INTE NTIONALLY BLANK

October 2005 4-4Carbon Monoxide State Implementation Plan Revision



### 5. BASE CASE MODELING

5.1. INTRODUCTION

This section summarizes the modeling performed to establish that current CO emission inventory projections result in continue d maintenance of the 8-hour average NAAQS for CO in the Las Vegas nonattainment area. Appendix A provides deta iled technical documentation of the models used for this 2005 CO SIP revision.

The CAAA requires that serious CO nonattainmen t areas like the Las Vegas Valley use EPAapproved models to demonstrate attainment. The current models of choice for CO attainment demonstrations are (1) the UAM, an urban-scal e, three-dimensional, grid-type, numerical simulation model; and (2) CAL3QHC, a microscale roadway intersection (i.e., “hot spot”) plume model. Since EPA has identified the UAM an d CAL3QHC as effective tools for evaluating emission control programs, they were selected to demonstrate attainment in the 2000 CO SIP.

DAQEM updated its UAM CO modeling for this 2005 CO SIP revision using the latest tools, data resources, and methodologies available. It based the revised models on the modeling data sets developed in the 2000 CO SIP for the D ecember 8-9, 1996 historical event. Section 3 describes specific updates to the emissions invent ories, which include modifications to on-road mobile sources, non-road mobile s ources, civil airports, railroads, and point sources. Emissions estimates for all remaining categories (mainly area sources and Nellis Air Force Base) were taken from the previous modeling detailed in the 2000 CO SIP, although new spatial distributions were developed for area s ources from updated land use projections.

5.2. BASE CASE SCENARIO MODELING

The December 1996 base case in the 2000 CO SIP included in its emissions inventory the existing I/M program, the 3.5 percent oxygenated fuel program, low RVP gasoline (9 pounds per square inch), and other control measures in place or mandated by the CAAA. For the 2005 CO SIP revision base case, the UAM was used to simulate the emission and transport of CO throughout the Las Vegas Valley during the ni ght of December 8-9, 1996 (Sunday-Monday). Specifically, the UAM was run from 1500 local standard time on December 8 to 1100 local standard time on December 9 to cover the cold est, most stagnant and stable portion of the episode during which CO was observed to build up. Two base case simu lations were run:

A. With revised on-road emission estimates, keeping all the point, area, and non-road emissions the same as the 2000 CO SI P model (see Section 4.1.1 of the TSD).

B. With both revised on-road and non-road em ission estimates, keeping all point and area emissions the same as the 2000 CO SI P model (see Section 4.1.2 of the TSD).

In both cases, estimated 1996 airport emissions from Ricondo (1999) were included in the emissions inventory.

October 2005 5-1Carbon Monoxide State Implementation Plan Revision

Figure 5-1 shows the UAM-predict ed episode maximum 8-hour CO concentrations (in ppm) from the base case simulation using the revised on-road and non-road emissions summarized in Section 3 and documented in Sections 2 and 3 of the TSD (Appendix A). The two distinct areas of CO maxima in the simulation are located ne ar where U.S. Highway 95 makes a sharp turn southward in northeast Las Ve gas (called the “elbow”) and along South Las Vegas Boulevard near the Spring Mountain Road intersection. The peak in the domain is 11.4 ppm along South Las Vegas Boulevard. According to the RTC Tr ansCAD model, this is due to the high concentration of parking structures in the area. The secondary maximum reaches more than 9 ppm along U.S. 95 during the morning commute hours on Monday, December 9. Overall, the spatial pattern of predicted 8-hour maximum CO agrees with the previous modeling in the 2000 CO SIP and with the distribution of observe d CO for this period. Unlike the modeling documented in the 2000 CO SIP, no external sca ling was applied to the UAM results in these revised runs.

Modeling for the on-road and non-road revisions was performed using standard and EPA criteria model performance statistics; Table 5-1 shows the statistics used fo r this simulation. The statistics are based on pairings of 8-hour CO predictions and observati ons across all available monitoring sites for the period, which include standard EPA-method monitoring conducted by Clark County and special saturation monitori ng performed for the Las Vegas Phase II field monitoring study. The saturation study was conducted during the winter of 1996-97 and supplemented the 14 existing CO sites in the county. These statistics show that UAM performance is quite good and should be considered acceptable.

Table 5-1. Summary Performance Statistics for the December 8-9, 1996 Base Case with Updated On-Road and Non-Road Mobile Source Emissions

Peak 8-hour Observation 9.6 ppm, Marnel Field Unpaired Peak 11.4 ppm
Paired Peak 8.1 ppm
Statistical Measures Unpaired Peak Accuracy 19% 1
Paired Peak Accuracy -15% Peak Timing Error 1 hr Average Peak Bias > 5 ppm -3% Average Peak Error > 5 ppm 13% Average Peak Timing Bias > 5 ppm 2 hr Average Peak Timing Error > 5 ppm 2 hr Overall Bias > 5 ppm -6% Overall Error > 5 ppm 15%

1 Bold/colored metrics denote EPA criteria statistics. Blue indicates a number within the acceptance criteria and red indicates a number outside the acceptance criteria.

Figure 4-6 of Appendix A shows a time seri es of observed and predicted hourly CO concentrations at each of the 28 availabl e monitoring sites during the 1996-97 study period.

October 2005 5-2Carbon Monoxide State Implementation Plan Revision

642 652 662 672 682 692 UTM Easting (km) 3973 3983 3993 4003 4013 4023UTM Northing (km)

5 6 7 8 9 10 11 12

ppm 

### UAM Max 8-hour CO Concentrations 1996 Base Case (96B08)

Peak = 11.4 ppm

Figure 5-1. Spatial Distribution of UAM Predicte d 8-Hour Maximum CO Concentrations (ppm) for the December 8-9, 1996 Base Case with Updated On-Road and Non-Road Mobile Emissions.

October 2005 5-3Carbon Monoxide State Implementation Plan Revision

THIS PAGE INTE NTIONALLY BLANK

October 2005 5-4Carbon Monoxide State Implementation Plan Revision



### 6. DEMONSTRATION OF ATTAINMENT

6.1. INTRODUCTION

Air quality modeling is an integral part of the air quality planning process to attain the NAAQS. Section 6 in the 2000 CO SIP summarized the ap plication of the UAM and CAL3QHC models in demonstrating attainment of the CO NAAQ S by December 31, 2000. The primary purpose for conducting UAM area-wide and CAL3QHC roadway in tersection modeling is to demonstrate the effectiveness of control strategies in atta ining the 8-hour aver age NAAQS for CO. The attainment demonstration consists of four parts:

1. Developing an attainment-year base case emissi on inventory that reflects the net effect of existing required controls and growth projections for all source categories. 2. Developing future-year emission strategies. 3. Performing attainment year model simu lations to assess control strategies. 4. Using results from the UAM and CAL3QHC modeling to demonstrate attainment.

EPA requires the estimated 8-hour average concentrations be be low the 9 ppm standard when using the UAM area-wide model to demonstrate attainment. EP A also recommends that the CAL3QHC model be applied to intersections at potential hot-spot locations. The hot-spot modeling analysis combines concentrations from the UAM with those from the CAL3QHC microscale model.

This section outlines the approach taken to incorporate emissions updates into the UAM data set and perform revised UAM urban-scale modeling for the future years of 2006, 2010, 2015, 2020, and 2030. Additionally, EDMS results from the Ri condo (2003) analyses were combined with revised UAM model predictions for the fu ture years of 2006, 2010, 2015, and 2020 to estimate 8-hour CO concentrations for the duration of th e episode on and around th e three civil airport properties in the valley. The following sections provide details on each of these components.

6.2. URBAN AIRSHED MODEL ATTA INMENT DEMONSTRATION

As described below, the UAM used updated emissi on inventories for point, on-road mobile, and non-road mobile sources for the December 8-9, 1996 historical CO event. All other environmental parameters were taken from th e original modeling documented in the 2000 CO SIP. A similar model performance evaluation was conducted for the base year (Table 5-1). The UAM was then run with the updated future year inventories for 2006, 2010, 2015, 2020, and 2030 to determine peak 8-hour CO levels in th e valley using the same December 8-9, 1996 conditions. Figures 6-1 and 6-2 display predicted 8-hour maximu m CO concentrations in the modeling domain for the years 2006 and 2030, re spectively. Section 4.2 of the TSD (Appendix A) contains similar displays of UAM maximu m 8-hour concentrations for future years 2010, 2015, and 2020. UAM predictions show that the 8- hour CO standard of 9 ppm will not be violated anywhere within the domain. As Table 6-1 shows, peak 8-hour CO decreases in each year until 2015 and then begi ns to increase out to 2030.

October 2005 6-1Carbon Monoxide State Implementation Plan Revision

Table 6-1. Peak 8-Hour CO Concentrations in Future Years

Year Peak 8-hour CO
2006 7.4
2010 7.2
2015 6.5
2020 6.7
2030 8.0

Figures 6-1 and 6-2 show that the contribution of McCarran International Airport to local CO concentrations increases steadily during this pe riod due to the projected growth in airport activities reported by Ricondo (2003). In each successive year through 2020, the contribution from on-road mobile sources diminishes and the peak moves from the U.S. 95 “elbow” in northeast Las Vegas to the north ern boundary of McCarran along Tr opicana Boulevard. As in the 1996 base case, a lower secondary peak occurs in the South Las Vegas Boulevard area near Spring Mountain Road. That area possesses a hi gh concentration of parking structures, which leads to a local maximum in trip starts in the RTC TransCAD model and a local maximum in vehicle start emissions in the modeling emission i nventory. This poses the potential for an actual local emissions hot spot in this area, and Clark County undertook a satu ration study in 2002 to address this possibility (Appe ndix B). Although the TransCAD, E PS3, and UAM models show a potential emissions hot spot at Spring Mount ain Road and South Las Vegas Boulevard, the 2002 saturation study showed no hot s pot at all in that location.

The UAM was then used to undertak e several sensitivity tests to re fine the estimation of future year on-road mobile CO emission budgets for the central, most urbanized portion of the modeling domain. Table 6-2 defines this centra l urban subdomain, and Figure 6-3 outlines the subdomain in relation to the total modeling domain.

Table 6-2. Grid Definition of the Central Urban Subdomain

Column Row UTM 1 East UTM North
Low-Left 11 19 652.000 3991.000 Upper-Right 36 45 678.000 4018.000

1 Universal Transverse Mercator.

The first analysis tested the a ssertion that the emissions inve ntory outside the central urban subdomain has no significant impact on CO con centrations downtown, along South Las Vegas Boulevard, and in traditional hot-spot areas. Emi ssions in the outer grid area were doubled for each future year, and the UAM was run to show the incremental impact on peak CO concentration. As Table 6-3 demonstrates, p eak 8-hour CO concentrations changed by a maximum of only 0.07 ppm. The location of the predicted peak did not change at all.

October 2005 6-2Carbon Monoxide State Implementation Plan Revision

6 4 2 6 5 2 6 6 2 6 7 2 6 8 2 6 9 2 UTM Easting (km) 3973 3983 3993 4003 4013 4023UTM Northing (km)

5 6 7 8 9 10 11 12

ppm 

### UAM Max 8-hour CO Concentrations 2006 Future Year

Peak = 7.37 ppm

Figure 6-1. Spatial Distribution of UAM-Predicte d 8-Hour Maximum CO Concentrations (ppm) for the December 8-9, 1996 Episode Us ing Emissions Forecasts for 2006.

October 2005 6-3Carbon Monoxide State Implementation Plan Revision

6 4 2 6 5 2 6 6 2 6 7 2 6 8 2 6 9 2 UTM Easting (km) 3973 3983 3993 4003 4013 4023UTM Northing (km)

5 6 7 8 9 10 11 12

ppm 

### UAM Max 8-hour CO Concentrations 2030 Future Year

Peak = 7.96 ppm

Figure 6-2. Spatial Distribution of UAM-Predicte d 8-Hour Maximum CO Concentrations (ppm) for the December 8-9, 1996 Episode Us ing Emissions Forecasts for 2030.

October 2005 6-4Carbon Monoxide State Implementation Plan Revision

642 652 662 672 682 692 UTM Easting (km) 3973 3983 3993 4003 4013 4023UTM Northing (km)

Figure 6-3. Boundaries of the Outer Domain and Subdomains.

October 2005 6-5Carbon Monoxide State Implementation Plan Revision

Table 6-3 demonstrates that the model-predicted peak CO is driv en by local emission sources in the central urban subdomain, and is therefore insensitive to large changes in emissions in outer

areas.

Table 6-3. Change in Peak 8-Hour CO from Do ubling the Total CO Emissions Inventory Outside the Central Urban Subdomain

Peak 8-hour CO (ppm) Year From Table 6-1 Doubled Outer Emissions
2006 7.37 7.41
2010 7.17 7.24
2015 6.47 6.54
2020 6.74 6.80
2030 7.96 8.03

In the second analysis, future year on-road mobile source emissions were scaled up across the entire modeling domain to the point at which th e peak 8-hour CO concentration reached 8.9 ppm. The on-road mobile source emissions out side the central urba n subdomain were then increased by an additional 70 percent in each year to reach a maximum peak 8-hour CO concentration of just under 9.0 ppm (Table 6-4). Figures 4-13 through 4-17 of Appendix A show plots of daily maximum CO concentrations for each future year. There was no change in the location of the predicted peak. No additional ho t spots were generated anywhere in the domain by increasing the on-road mobile source emissi ons in the outer portio n of the domain by 70 percent.

Table 6-4. Weekday On-Road Emissions Incr eases, UAM-Predicted Peak CO, and Resulting Emissions Budget for Each Future Year

Eastern/Charleston Eastern/F r emont F r emont/Charleston Year UAM C A L3QHC C A L3QHC+U A M C A L3QHC C A L3QHC+U A M C A L3QHC C A L3QHC+U A M 2006 4.89 1.64 6.14 1.28 5.66 0.71 5.09 2010 4.62 1.33 5.61 1.14 5.32 0.69 4.81 2015 4.19 1.16 4.97 0.96 4.76 0.51 4.31 2020 3.97 1.05 4.67 0.88 4.48 0.49 4.07 2030 4.07 1.03 4.83 0.84 4.58 0.50 4.20
Once EPA approves them, the tota l domain emissions in Table 6-4 will become the MVEBs the RTC uses in future conformity analyses.

6.3. MICROSCALE MODELING

Future year UAM simulation re sults provided estimates of b ackground ambient CO levels for microscale modeling of the Five Points area hot s pot and the three civil airports in the modeling domain (McCarran, Henderson, and North Las Vegas). UAM concentrations from the appropriate grid cells were simply added to th e concentrations predicted at each microscale receptor to obtain a total (background + microscale) CO concentration.

October 2005 6-6Carbon Monoxide State Implementation Plan Revision

6.3.1. CAL3QHC Intersection Modeling

As previously stated, EPA recommends that a micr oscale hot-spot analysis be conducted as part of the attainment demonstration. Selection criteria for intersections to be analyzed include high traffic volume, poor levels of service, and clos e proximity to the moni toring station recording exceedances. The Five Points area, which meets a ll three criteria, was se lected for modeling to meet the microscale and attainme nt demonstration requirements.

For hot-spot modeling, the CAL3QHC model was us ed to model three in tersections: Charleston and Eastern, Charleston and Fr emont, and Eastern and Fremont (Figure 6-4). EPA (1992, 1995) guidance for screening-level modeling of these three inte rsections was followed. The UAM/CAL3QHC model for the 2000 CO SIP provide d the ambient temperature for each hour of the episode, needed to estimate emissions with the MOBILE6.2 model, and the wind speed and direction needed for the CAL3QHC estimates. The CAL3QHC model output was added to the background UAM levels to estimate 8-hour CO concentrations for the duration of the episode.

Figure 6-4. CAL3QHC Intersection Location Diagram.

Table 6-5 presents the peak UAM + CAL3QHC 8- hour average CO concentr ations predicted in each of the future years fo r each of the three inters ections in the Five Points area. All values are well below the 9 ppm standard.

Table 6-5. Peak UAM + CAL3QHC 8-Hour Average CO Concentrations (ppm) Predicted for Each Future Year and for Each Intersection

Year Eastern/Charleston East ern/Fremont Fremont/Charleston 2006 7.14 6.65 6.12 2010 6.70 6.43 5.94 2015 6.53 6.30 5.88 2020 6.43 6.23 5.83 2030 6.49 6.22 5.85

October 2005 6-7Carbon Monoxide State Implementation Plan Revision

6.3.2. Airport Modeling Using the Emissions and Dispersion Modeling System

For microscale airport modeling, the UAM was run for all future years w ith exactly the same inputs described in Section 4.2 of Appendix A; however, airport emissions for the three civil airports in the domain were removed from th e UAM inventory to avoid double counting. Clark County provided EDMS simulations for thes e airports for 2005, 2010, 2015, and 2020 (Ricondo 2003). All receptors above the 9 ppm standard in al l future years evaluated were located within areas that are not publicly accessible, as defi ned by Ricondo (2005). Disregarding receptors in restricted areas, which EPA has indicated is accep table, removes all exceedance estimates. Table 6-6 lists the peak total 8-hour CO concentrations at all three civil airports for each future year evaluated. Values for McCarran ar e taken from the peak publicly accessible receptor. All peak CO concentrations are below the 9 ppm standard in all years.

Table 6-6. Peak Total UAM + EDMS 8-Hour CO Co ncentrations (ppm) at All Three Airports and for All Three Future Years Evaluated

Airport 2005 2010 2015 2020
McCarran 7.76 7.47 8.09 8.98
Henderson Executiv e 1.28 1.61 2.74 3.96 North Las Vegas 6.07 6.28 6.14 6.08

1 Values shown for McCarran occur at t he peak publicly accessible receptor.

October 2005 6-8Carbon Monoxide State Implementation Plan Revision



### 7. IMPLEMENTATION AND STATE IMPLEMENTATION PLAN COMMITMENTS

The purpose of this 2005 CO SIP revision is to assure the public that implementation of the programs in the 2000 CO SIP and maintenance of th e CO health standards will continue through 2030. As noted earlier, EPA has approved the 2000 CO SIP and determined that it attained its goal of achieving the CO NAAQS by the end of 2000. However, with new planning tools and better predictive capabilit ies (such as MOBILE6) available, Clark County will continue to reanalyze and confirm long-term maintenance of the CO health standards. In addition to the practical aspects of meeting the transportati on conformity regulatory requirements for new emission models, this SIP revision also lays the foundation for development of a formal CO maintenance plan and a redesignation request to EP A. The rest of this section describes how the 2000 CO SIP control measures are being impl emented and tracked, and how the revised emission budget for mobile sources will provide a basi s for the valley to continue to meet federal transportation requirements.

7.1. IMPLEMENTATION, MONI TORING, AND REPORTING

Implementation of the control measures specifie d in Section 4 is necessary for the Las Vegas Valley to continue maintaining the CO NAAQS . The responsibility fo r implementing these control measures lies with DAQEM, the Nevada Division of Environmen tal Protection, and the RTC. Each entity has the personnel, funding, and au thority to implement its respective part of the proposed primary control measures. Table 4-1 provides the adoption and implementation status of each of the four key on -road mobile source control measures.

In addition to continued implementation of control measures, the 1990 CAAA requires continual air quality monitoring. As Section 2 noted, DAQEM currently has eight monitoring sites to observe CO levels and will notify th e state and EPA of any NAAQS violations or exceedances. This coverage is more than adequate for an area and population such as Clark County; EPA requires only three monitoring sites for similar-size areas. This network will continue to operate in accordance with the requirements of 40 CFR 58, and DAQEM will continue to submit quarterly reports to EP A as mandated. DAQEM provided EPA with its 2004 annual NAMS/SLAMS report in May 2005.

7.2. MAINTENANCE

EPA requires that implementation plans also provide for maintaining the standard after attainment. Since Clark County has now reached attainment, and the primary source of CO is the on-road mobile sources category, VMT projections for a 30-year horizon past the demonstration date have been forecast. Since additional modeling will likely be required for maintenance plan submittals from areas seeking redesignation, this 2005 CO SIP revision updated the mobile emission model analysis to provide a basis for development of a formal CO maintenance plan and a redesignation request in the near future. The Las Vegas Valley air quality implementation plan will remain in effect until supers eded by an approved CO maintenance plan.

October 2005 7-1Carbon Monoxide State Implementation Plan Revision

7.3. MOBILE SOURCE EMISSIONS BUDGET

Under Section 176(c) of the Clean Air Act, 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 th e on-road MVEBs specified in th e applicable SIP. 40 CFR 93.118 provides the criteria and procedures for MVEBs.

The MVEB establishes a cap on motor vehicle-re lated 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 subse quent years until a different budget is defined for another year or a SIP revision modifies the budget. Wit hout a clearly indicated intent otherwise expressed in the SIP, the estimate of future transportation network emissions used in the milestone or attainment demonstration acts as the MVEB.

The emissions analysis for confor mity determinations must include emissions from the entire transportation network within the nonattainment area. In th e case of Las Vegas, the nonattainment area encompasses both the air qua lity modeling domain and the transportation planning domain.

The decision on what years to propose for the CO MVEB is a joint policy call between various stakeholders, state and federal transportation agencies, and stat e and local air quality agencies. One choice is to identify motor vehicle emissions in the year of the ne xt conformity finding (2006) and maintain the budget for all subseque nt analysis years (i.e., the interim year conformity analyses, the horizon year, and all years beyond the horizon year). In the case of Las Vegas, that would mean a total domain budget of 623 TPD in the initial 2006-2009 time frame.

Table 7-1 reflects the calculat ed MVEBs based on MOBILE6.2 in this 2005 CO SIP revision. Section 6 and Appendix A of this SIP revisi on provide specific information on how these multiyear budget values were derived; DAQEM dete rmined that it would be more accurate to establish multiyear budgets for modeling. The MVEBs in Table 7-1 are the budgets Clark County proposes for EPA approval and, subse quently, for RTC use in making conformity determinations for the next RTP.

Table 7-1. 2006 – 2020 MVEB in the Las Vegas Valley

Years Peak 8-hr CO (ppm) MVEB (TPD)
2006-2009 8.96 623
2010-2014 8.98 690
2015-2019 8.98 768

2020+ 8.97 817

Amended May 2006 7-2Carbon Monoxide State Implementation Plan Revision



### 8. REFERENCES

AAR (Association of American Railroads) 2000. “Railroad Ten-Year Trends 1990-1999.” Washington, D.C.: Association of American Railroads.

AAR 2004. “Analysis of Class I Railroads 2002 – Data.” Washington, D.C.: Association of American Railroads. Available online at http://www.aar.org/pubstores/listItems.aspx.

Egami, D., J. Bowen, P. Roberts, S. Reyes, T. Dye, C. Emery, and D. Souten 1998. “The Las Vegas Valley Carbon Monoxide Urban Airshed Mode l Update Project – Phase II: Field Data Collection.” Las Vegas, NV: Clark Count y Department of Comprehensive Planning.

EIA (Energy Information Administration) 2005. “Distillate Sales by End Use, Annual Data.” Washington, D.C.: U.S. Department of Energy. Available online at http://www.eia.doe.gov/oil_gas/petroleu m/info_glance/distillate.html.

Emery, C., D. Souten, N. Kumar, F. Lurma n, and P. Roberts 1998. “The Las Vegas Valley Carbon Monoxide Urban Airshed Model Update Project – Phase II: UAM Base Case and Sensitivity Applications.” Las Vegas, NV: Clark County Department of Comprehensive Planning.

EPA (U.S. Environmental Protection Ag ency) 2005. July 2005 phone call from Karina O’Connor, EPA Region 9 Office, San Francisco, CA, to David Calkins, ENVIRON Holdings, Inc., Las Vegas, NV, approving use of “wedding cake” grid system for allocating hourly TAZ start emissions.

EPA 1997. “Final Emissions Standards for Locomotives.” EPA420-F-97-048. Washington, D.C.: U.S. Environmental Protection Agency.

EPA 1995. “User’s Guide to CAL3QHC Version 2.0: A Modeling Methodol ogy for Predicting Pollutant Concentrations Near Roadway In tersections.” EPA-454/R-92-06. Washington, D.C.: U.S. Environmental Protection Agency.

EPA 1992. “Guideline for Modeling Carbon Monoxi de from Roadway Intersections.” EPA454/R-92-005. Washington, D.C.: U.S. Environmental Protection Agency.

MACTEC 2003. “Clark County-Wide Inventory of Non-road Engi nes Project.” Las Vegas, NV: Clark County Department of Air Qual ity and Environmental Management.

October 2005 8-1Carbon Monoxide State Implementation Plan Revision

Orth-Rodgers & Associates, Inc. 2003. "Air Qu ality Vehicle Distribu tion Study and Modeling." Las Vegas, NV: Regional Transportati on Commission of Southern Nevada.

Pollack, A.K., R. Chi, C. Lindhjem, C. Tran, P. Chandraker, P. Heirigs, L. Williams, S.S. Delaney, M.A. Mullen, and K.B. Thesing 20 04. “Development of WRAP Mobile Source Emission Inventories.” Denver, CO: Western Governors’ Association.

RTC (Regional Transportation Commission of Southern Nevada) 2004. Chapter 5 of FY 2004- 2025 Regional Transportation Plan . Las Vegas, NV: Regional Transportation Commission of Southern Nevada.

Ricondo and Associates, Inc. 1999. “Carbon Monoxide Emissions Inventory and Dispersion Modeling.” Las Vegas, NV: Clark County Department of Aviation.

Ricondo and Associates, Inc. 2003. “Carbon Monoxide Emissions Inventory and Dispersion Modeling Study Update 2003.” Las Vegas, NV: Clark County Department of Aviation.

Ricondo and Associates, Inc. 2005. “Addendu m to the 2003 Carbon Monoxide Emissions Inventory and Dispersion Mode ling Study.” Memorandum dated 5/19/05 from Adrian Jones, Ricondo & Associates, San Francisco, CA, to De nnis Mewshaw, Clark County Department of Aviation, Las Vegas, NV.

October 2005 8-2