APPENDIX A 

TECHNICAL SUPPORT DOCUMENT 
 International Corporation Air Sciences

Technical Support Document 

CLARK COUNTY CARBON MONOXIDE 

MODELING AND SIP UPDATE 

Prepared for 

Clark County 

Department of Air Quality and Environmental Management 

500 S. Grand Central Parkway 

PO Box 551776 

Las Vegas, NV 89155-1776 

Prepared by 

Chris Emery 

Stella Shepard 

Michele Jimenez 

Gary Wilson 

Alison Pollack 

Sunja Rao 

Chris Lindhjem 

ENVIRON International Corporation 

101 Rowland Way, Suite 220 

Novato, CA 94945 

August 29, 2005 

 101 Rowland Way, Suite 220, Novato, CA 94945 415.899.0700 
August 2005 

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TABLE OF CONTENTS 

Page 

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

1.1 Background...................................................................................................................... 1-1 

 1.1.1 CO Regulatory History ........................................................................................ 1-1 

 1.1.2 Previous CO Modeling ........................................................................................ 1-2 

1.2 Modeling Updates............................................................................................................ 1-2 

 1.2.1 On-Road Emission Estimates .............................................................................. 1-3 

 1.2.2 Other Emission Sources....................................................................................... 1-4 

 1.2.2.1 Airports ......................................................................................................... 1-4

 1.2.2.2 Non-Road and Locomotive........................................................................... 1-4 

 1.2.2.3 Point Sources ................................................................................................ 1-5 

 1.2.3 Model Application ............................................................................................... 1-5 

2. ON-ROAD MOBILE EMISSIONS.................................................................................... 2-1 

2.1 Overview of Approach..................................................................................................... 2-1 

2.2 Base Year Estimates ........................................................................................................ 2-2 

 2.2.1 Base Year MOBILE6 Inputs................................................................................ 2-2 

 2.2.2 Base Year TRANPLAN Link Activity Adjustments........................................... 2-5 

 2.2.2.1 Month/Season, Day of Week ........................................................................ 2-5 

 2.2.2.2 Hourly Temporal Adjustments ..................................................................... 2-5 

 2.2.2.3 Speed Adjustments........................................................................................ 2-6 

 2.2.2.4 Transit Adjustments...................................................................................... 2-6 

 2.2.3 Base Year Link-Level Running Exhaust Emissions............................................ 2-6 

 2.2.4 Base Year Start Emissions................................................................................. 2-10 

 2.2.5 Base Year Intrazonal Activity............................................................................ 2-10 

 2.2.6 Base Year Total Emissions ................................................................................ 2-12 

2.3 Future Year Estimates.................................................................................................... 2-12 

 2.3.1 Future Year MOBILE6 Inputs........................................................................... 2-12 

 2.3.2 Future Year TransCAD Link Activity Adjustments.......................................... 2-16 

 2.3.2.1 Month/Season, Day of Week ...................................................................... 2-16 

 2.3.2.2 Link Volume Adjustments.......................................................................... 2-17 

 2.3.2.3 Hourly Temporal Adjustments ................................................................... 2-18 

 2.3.2.4 Speed Adjustments...................................................................................... 2-18 

 2.3.2.5 Transit Adjustments.................................................................................... 2-19 

 2.3.3 Future Year Link-Level Running Emissions ..................................................... 2-19 

 2.3.4 Future Year Start Emissions .............................................................................. 2-19 

 2.3.5 Future Year Intrazonal Activity......................................................................... 2-25 

 2.3.6 Future Year Total Emissions ............................................................................. 2-26 

3. OTHER EMISSION CATEGORIES ................................................................................ 3-1 

3.1 Non-Road Categories....................................................................................................... 3-1 

 3.1.1 Airports ................................................................................................................ 3-1 
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 3.1.1.1 Temporal and Spatial Allocation .................................................................. 3-1 

 3.1.2 Locomotive .......................................................................................................... 3-4 

 3.1.2.1 Locomotive Projections ................................................................................ 3-5 

 3.1.3 Other Non-Road Categories................................................................................. 3-7 

 3.1.3.1 NONROAD Model Equipment Estimates.................................................... 3-7 

 3.1.3.2 Base Year Gridding Surrogates .................................................................... 3-9 

 3.1.3.3 Future Year Gridding Surrogates.................................................................. 3-9 

 3.1.3.4 Temporal Allocation ................................................................................... 3-14 

3.2 Point Sources ................................................................................................................. 3-14 

3.3 Area Sources .................................................................................................................. 3-15 

 3.3.1 Area Source Gridding Surrogates ...................................................................... 3-16 

3.4 Summary of Total Emissions......................................................................................... 3-16 

4. URBAN AIRSHED MODELING ...................................................................................... 4-1 

4.1 Base Case Simulation ...................................................................................................... 4-2 

 4.1.1 UAM Results from Revised On-Road Emissions................................................ 4-2 

 4.1.2 UAM Results from Revised On-Road and Non-Road Emissions ..................... 4-14 

4.2 Future Year Simulations ................................................................................................ 4-16

4.3 Microscale Modeling ..................................................................................................... 4-29 

 4.3.1 CAL3QHC Intersection Modeling..................................................................... 4-29 

 4.3.2 EDMS Airport Modeling ................................................................................... 4-29 

 4.4 Estimating On-Road Emission Budgets......................................................................... 4-30 

 4.4.1 Impacts of Emissions from the Outer Domain .................................................. 4-30 

 4.4.2 Emission Budgets from Scaling On-Road Emissions........................................ 4-32 

5. SUMMARY .......................................................................................................................... 5-1 

5.1 Emission Updates............................................................................................................. 5-1 

5.2 Model Application ........................................................................................................... 5-2 

 5.2.1 Base Case Simulations......................................................................................... 5-3 

 5.2.2 Future Year Simulations ...................................................................................... 5-4 

 5.2.2.1 Micro-scale Modeling................................................................................... 5-4 

 5.2.2.2 Estimating On-Road Emission Budgets........................................................ 5-5 

REFERENCES.......................................................................................................................... R-1 

TABLES 

Table 2-1. 1996 Base Year Las Vegas MOBILE6.2 input parameters ................................. 2-3 

Table 2-2. MOBILE6 28 vehicle classes and their relative fraction 

 of the overall fleet. ............................................................................................... 2-7 

Table 2-3. Cross-reference between RTC and MOBILE6.2 facility types. .......................... 2-8 

Table 2-4. 1996 VMT by facility type. Totals are shown as output by 

 TRANPLAN, and after seasonal, day-of-week, and public 

 transit adjustments ............................................................................................... 2-8 

Table 2-5. Component and total on-road mobile source CO emissions 

 (TPD) for the 1996 base year............................................................................. 2-12 
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Table 2-6. MOBILE6.2 input parameters for future year Las Vegas runs.......................... 2-14 

Table 2-7. Volume scaling factors by day of week............................................................. 2-17 

Table 2-8. Adjustment factors to observed traffic counts by facility type.......................... 2-18 

Table 2-9. Adjustment factor to scale link-level emissions to 

 account for mass transit ..................................................................................... 2-19 

Table 2-10. 2006 VMT by facility type. Totals are shown as output by 

 TransCAD, and after seasonal, day-of-week, and public 

 transit adjustments ............................................................................................. 2-20 

Table 2-11. 2010 VMT by facility type. Totals are shown as output by 

 TransCAD, and after seasonal, day-of-week, and public 

 transit adjustments ............................................................................................. 2-21 

Table 2-12. 2015 VMT by facility type. Totals are shown as output by 

 TransCAD, and after seasonal, day-of-week, and public 

 transit adjustments ............................................................................................. 2-22 

Table 2-13. 2020 VMT by facility type. Totals are shown as output by 

 TransCAD, and after seasonal, day-of-week, and public 

 transit adjustments ............................................................................................. 2-23 

Table 2-14. 2030 VMT by facility type. Totals are shown as output by 

 TransCAD, and after seasonal, day-of-week, and public 

 transit adjustments ............................................................................................. 2-24 

Table 2-15. Component and total on-road mobile source CO emissions 

 (TPD) for all future years................................................................................... 2-26 

Table 3-1. Annual airport CO emission estimates (tons per year) 

 reported by Ricondo (1999) for the 1996 base year, and 

 by Ricondo (2003) for future years 2010, 2015, and 2020 

 (2006 and 2030 estimated as described in the text). ............................................ 3-2 

Table 3-2. Monthly factors used to disaggregate annual airport CO 

 emissions to monthly totals. The factors for December were 

 used in this study.................................................................................................. 3-2 

Table 3-3. Locomotive emission reductions due to EPA regulations (EPA, 1997).............. 3-6 

Table 3-4. Locomotive emissions relative to 1996 ............................................................... 3-7 

Table 3-5. Summary of inputs used for NONROAD modeling for 1996 ............................. 3-8 

Table 3-6. Summary of inputs used for NONROAD modeling future years........................ 3-8 

Table 3-7. Clark County CO NONROAD gridded emission estimates (TPD)..................... 3-9 

Table 3-8. Base year non-road surrogate categories ........................................................... 3-10 

Table 3-9. Land use category to surrogate code mapping................................................... 3-11 

Table 3-10. Source category cross references to gridded surrogates 

 for NONROAD sources with county-to-modeling grid 

 adjustment factors .............................................................................................. 3-11 

Table 3-11. Land use categories available in the Clark County GIS 

 data coverages for 2003 ..................................................................................... 3-12 

Table 3-12. Landuse category aggregation used for developing 

 spatial allocation surrogates for non-road categories......................................... 3-14 

Table 3-13. Comparison of domain-wide land use percentages for 

 future year spatial allocation.............................................................................. 3-14 

Table 3-14. Clark County CO future year Potential To Emit (PTE) 

 estimates + 70 TPY by facility .......................................................................... 3-15 

Table 3-15. Modeling CO point source emission estimates (TPD) ...................................... 3-15 

Table 3-16. Future year growth/projection factors for area sources. .................................... 3-16 
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Table 3-17. Clark County CO area source gridded emission estimates (TPD)..................... 3-17 

Table 3-18. Summary of total daily CO emissions (TPD) in the 

 UAM CO SIP revision....................................................................................... 3-18 

Table 4-1. Summary performance statistics for the December 8-9, 1996 Base 

 Case with updated on-road mobile source emissions. Bold/colored 

 metrics denote EPA criteria statistics; green (red) indicates within 

 (outside) acceptance criteria ................................................................................ 4-4 

Table 4-2. Names and coordinates of all monitoring sites operating 

 during the Phase II field study over the winter of 1996/97 

 (Egami et al., 1998). The first 14 sites are the standard 

 Clark County sites................................................................................................ 4-6 

Table 4-3. Summary performance statistics for the December 8-9, 

 1996 Base Case with updated on-road and non-road mobile 

 source emissions. Bold/colored metrics denote 

 EPA criteria statistics; green (red) indicates within 

 (outside) acceptance criteria. ............................................................................. 4-16 

Table 4-4. Peak UAM + CAL3QHC 8-hour average CO concentrations 

 (ppm) predicted for each future year and for each intersection......................... 4-29 

Table 4-5. Peak total UAM + EDMS 8-hour CO concentrations (ppm) at 

 all three airports and for all future years evaluated. Values shown 

 for McCarran airport occur at the peak publicly accessible receptor ................ 4-30 

Table 4-6. Grid definition of the central urban sub-domain................................................ 4-30 

Table 4-7. Change in peak 8-hour CO from doubling the total CO emissions 

 inventory outside of the central urban sub-domain............................................ 4-32 

Table 4-8. Weekday domain-wide on-road emission increase, net on-road 

 emission increase that includes an additional 70% increase outside 

 the central urban sub-domain, resulting UAM predicted peak CO, 

 and resulting total and sub-domain on-road emission budgets for 

 each future year.................................................................................................. 4-32 

Table 4-9. Peak UAM + CAL3QHC 8-hour average CO concentrations (ppm) 

 predicted for each future year and for each intersection. UAM 

 results from the on-road sensitivity scaling tests. .............................................. 4-37 

Table 4-10. Peak total UAM + EDMS 8-hour CO concentrations (ppm) at all 

 three airports and for all future years evaluated. Values shown for 

 McCarran airport occur at the peak publicly accessible receptor. 

 UAM results from the on-road sensitivity scaling tests..................................... 4-37 

Table 5-1. Summary of total daily CO emissions (TPD) in the 

 UAM CO SIP revision......................................................................................... 5-3 

Table 5-2. Peak UAM + CAL3QHC 8-hour average CO concentrations 

 (ppm) predicted for each future year and for each intersection........................... 5-5 

Table 5-3. Peak total UAM + EDMS 8-hour CO concentrations (ppm) 

 at all three airports and for all three future years evaluated. 

 Values shown for McCarran airport occur at the peak 

 publicly accessible receptor ................................................................................. 5-5 

Table 5-4. Change in peak 8-hour CO from doubling the total CO 

 emissions inventory outside of the central urban sub-domain............................. 5-5 
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Table 5-5. Weekday domain-wide on-road emission increase, net on-road 

 emission increase that includes an additional 70% increase 

 outside the central urban sub-domain, resulting UAM predicted 

 peak CO, and resulting total and sub-domain on-road emission 

 budgets for each future year................................................................................. 5-6 

Table 5-6. Peak UAM + CAL3QHC 8-hour average CO concentrations 

 (ppm) predicted for each future year and for each intersection. 

 UAM results from the on-road sensitivity scaling tests....................................... 5-6 

Table 5-7. Peak total UAM + EDMS 8-hour CO concentrations (ppm) 

 at all three airports and for all three future years evaluated. 

 Values shown for McCarran airport occur at the peak publicly 

 accessible receptor. UAM results from the on-road 

 sensitivity scaling tests......................................................................................... 5-7 

FIGURES 

Figure 2-1. Hourly weekend and weekday start distributions (fraction) 

 provided by Clark County, used to temporally allocate emissions 

 derived from TRANPLAN and TransCAD ......................................................... 2-4 

Figure 2-2. Fraction of original weekday start distribution and start 

 distributions in all future years for the Las Vegas Boulevard 

 area calculated from the TransCAD origin trips by TAZ.................................... 2-4 

Figure 2-3. Weekday and Sunday hourly VMT distribution.................................................. 2-5 

Figure 2-4. Spatial distribution of on-road mobile source running exhaust 

 CO emissions for the 1996 Base Case ................................................................. 2-9 

Figure 2-5. Spatial distribution of on-road mobile source start exhaust 

 CO emissions for the 1996 Base Case ............................................................... 2-11 

Figure 2-6. Spatial distribution of total on-road mobile source 

 CO emissions for the 1996 Base Case ............................................................... 2-13 

Figure 2-7. Hourly start emission factors from the 2006 MOBILE6 run: 

 “Sun EF” is the Sunday profile used for all start emissions; 

 “Mon EF” is the Monday profile used for start emissions outside 

 of the LVB area; and “LVB Mon EF” is the Monday profile 

 used for start emissions within the LVB area .................................................... 2-17 

Figure 2-8. 2006 hourly vehicle miles traveled (VMT) for Sunday and Monday................ 2-25 

Figure 2-9. Spatial distribution of total on-road mobile source CO 

 emissions for the 2006 future year..................................................................... 2-27 

Figure 2-10. Spatial distribution of total on-road mobile source CO 

 emissions for the 2010 future year..................................................................... 2-28 

Figure 2-11. Spatial distribution of total on-road mobile source CO 

 emissions for the 2015 future year..................................................................... 2-29 

Figure 2-12. Spatial distribution of total on-road mobile source CO 

 emissions for the 2020 future year..................................................................... 2-30 

Figure 2-13. Spatial distribution of total on-road mobile source CO 

 emissions for the 2030 future year..................................................................... 2-31 

Figure 3-1. Hourly activity at McCarran airport used to temporally 

 allocate daily emissions for all years modeled .................................................... 3-3 
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Figure 3-2. Hourly activity at Henderson and North Las Vegas airports 

 used to temporally allocate daily emissions for all years modeled...................... 3-3 

Figure 3-3. Arial photograph of McCarran airport with UAM grid cells overlaid................. 3-4 

Figure 3-4. Available locomotive fuel consumption trends. .................................................. 3-6 

Figure 3-5. 2003 land use data for the Las Vegas area of Clark County.............................. 3-13 

Figure 3-6. Hourly activity profile used to temporally allocate 

 non-road emissions ............................................................................................ 3-15 

Figure 3-7. Spatial distribution of airport and locomotive 

 CO emissions for the 1996 Base Case. .............................................................. 3-19 

Figure 3-8. Spatial distribution of non-road and area source 

 CO emissions for the 1996 Base Case. .............................................................. 3-20 

Figure 3-9. Spatial distribution of total surface gridded CO emissions 

 for the 1996 Base Case. ..................................................................................... 3-21 

Figure 3-10. Spatial distribution of total surface gridded CO emissions 

 for the 2006 future year...................................................................................... 3-22 

Figure 3-11. Spatial distribution of total surface gridded CO emissions 

 for the 2010 future year...................................................................................... 3-23 

Figure 3-12. Spatial distribution of total surface gridded CO emissions 

 for the 2015 future year...................................................................................... 3-24 

Figure 3-13. Spatial distribution of total surface gridded CO emissions 

 for the 2020 future year...................................................................................... 3-25 

Figure 3-14. Spatial distribution of total surface gridded CO emissions 

 for the 2030 future year...................................................................................... 3-26 

Figure 4-1. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 Base 

 Case with updated on-road mobile emissions ..................................................... 4-3 

Figure 4-2. Locations of all Phase II monitoring sites operating during 

 the Phase II field study over the winter of 1996/97 (Emery et al., 1998)............ 4-5 

Figure 4-3. Time series of hourly CO measurements (dots) and 

 UAM predictions (line) at Phase II field study monitoring sites. 

 Plots cover the period 1500 LST December 8 to 1100 LST 

 December 9, 1996. Gray shading indicates the range of minimum 

 to maximum predicted CO concentrations in the nine cells 

 surrounding each site. .......................................................................................... 4-7 

Figure 4-4. Scatter diagram of UAM predictions vs. observations for the 1996 

 Base Case. The linear regression equation is given as the bold line................. 4-14 

Figure 4-5. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 Base 

 Case with updated on-road and non-road mobile emissions ............................. 4-15 

Figure 4-6. Time series of hourly CO measurements (dots) and 

 UAM predictions (black line = revised on-road emissions, 

 red line = revised on-road and non-road emissions) at Phase 

 II field study monitoring sites. Plots cover the period 1500 

 LST December 8 to 1100 LST December 9, 1996 ............................................ 4-17 

Figure 4-7. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 episode 

 using emission forecasts for 2006...................................................................... 4-24 
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Figure 4-8. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 episode 

 using emission forecasts for 2010...................................................................... 4-25 

Figure 4-9. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 episode 

 using emission forecasts for 2015...................................................................... 4-26 

Figure 4-10. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 episode 

 using emission forecasts for 2020...................................................................... 4-27 

Figure 4-11. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 episode 

 using emission forecasts for 2030...................................................................... 4-28 

Figure 4-12. Weekday domain-wide on-road emission increase, net on-road emission 

 increase that includes an additional 70% increase outside the central 

 urban sub-domain, resulting UAM predicted peak CO, and resulting 

 total and sub-domain on-road emission budgets for each future year. .............. 4-31 

Figure 4-13. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 episode 

 using emission forecasts for 2006 with increased on-road 

 mobile source emissions to reach peak CO just under 9.0 ppm. ....................... 4-33 

Figure 4-14. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 episode 

 using emission forecasts for 2010 with increased on-road 

 mobile source emissions to reach peak CO just under 9.0 ppm. ....................... 4-34 

Figure 4-15. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 episode 

 using emission forecasts for 2015 with increased on-road 

 mobile source emissions to reach peak CO just under 9.0 ppm. ....................... 4-35 

Figure 4-16. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 episode 

 using emission forecasts for 2020 with increased on-road 

 mobile source emissions to reach peak CO just under 9.0 ppm ........................ 4-36 

Figure 4-17. Spatial distribution of UAM predicted 8-hour maximum 

 CO concentrations (ppm) for the December 8-9, 1996 episode 

 using emission forecasts for 2030 with increased on-road 

 mobile source emissions to reach peak CO just under 9.0 ppm ........................ 4-37 
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1. INTRODUCTION 

1.1 BACKGROUND 

The Las Vegas Valley is a large desert basin at about 2000 feet elevation, surrounded by 

mountain ranges up to 11,900 feet, making it quite susceptible to air pollution problems. This 

area includes the City of Las Vegas, the City of North Las Vegas, and the City of Henderson. 

The remainder constitutes unincorporated areas of Clark County. Clark County has been the 

fastest growing areas of the United States over the past 50 years, with a current population of 

about 1,750,000. During the winter months, cold air masses stagnate over the region, and nightly 

temperature inversions trap pollutants within the valley. The overnight buildup of pollutants has 

historically caused violations of the national carbon monoxide standard in a limited area 

surrounding the East Charleston (Sunrise Acres) monitoring station. The East Charleston 

monitoring site in the vicinity of converging major transportation corridors named the “Five 

Points,” where three state highways intersect. Additionally, the site is located within a local 

depression where air pollution often collects. 

The 1990 Clean Air Act Amendments (CAAA) established two National Ambient Air Quality 

Standards (NAAQS) for carbon monoxide (CO). The first sets a maximum allowable 

concentration of 35 parts per million (ppm) averaged over 1 hour, and the second sets a 

maximum concentration of 9 ppm averaged over 8 hours. Areas that exceed one or both of the 

ambient standards more than two times in a two-year period are in violation and are thus 

classified as non-attainment areas for carbon monoxide. 

Although the Las Vegas Valley has never exceeded the 1 hour CO NAAQS, it has previously 

exceeded the 8 hour standard at least once per year on a seasonal basis. The last violation of the 

8-hour standard occurred in January 1996 in the Five Points area and measured 10.2 ppm; this 

became the valley’s last CO Design Value. There have been no CO exceedances from 1999 

through the most recent data year, 2004. This downtrend is the direct result of the 

implementation of local CO control measures and the tighter federal motor vehicle emission 

standards. 

1.1.1 CO Regulatory History 

The number and severity of 8-hour CO violations caused the U.S. Environmental Protection 

Agency (EPA) to automatically designate the Valley as a Moderate nonattainment area upon 

enactment of the 1990 CAAA on November 15, 1990. Moderate nonattainment areas were 

required to implement emission control measures as “expeditiously as practicable” in order to 

attain the CO NAAQS by December 31, 1995. Clark County implemented the set of controls 

required by the Clean Air Act for CO nonattainment areas, and made great strides towards 

attaining the NAAQS for carbon monoxide. However, due to phenomenal growth within the Las 

Vegas Valley, it fell short of meeting the NAAQS by the applicable date of December 31, 1995. 

 

Based upon improved CO levels, which were attributed to the implementation of the 

aforementioned control measures, EPA granted Clark County a one year extension to 

demonstrate compliance with the NAAQS. However, the Las Vegas Valley was not successful 

in achieving compliance by December 31, 1996. According to CAAA requirements, the EPA 
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reclassified the Las Vegas Valley as a “serious” nonattainment area for carbon monoxide on 

October 2, 1997. A deadline of May 1999 (18 months from the notice publication date) was set 

for submission of a State Implementation Plan (SIP) that demonstrates attainment by December 

31, 2000. 

On September 21, 1999, the Clark County Board of Commissioners adopted the Las Vegas 

Valley Non-attainment Area Carbon Monoxide Air Quality Implementation Plan. However, 

EPA Region IX found that the Plan’s emissions budget was inadequate, and raised other issues 

that affected the Plan’s approval. On August 1, 2000, the Clark County Board of Commissioners 

adopted a revised plan, and submitted supplemental CO SIP materials on January 30, 2002, and 

June 4, 2002 that addressed recently adopted vehicle inspection and wintertime fuel regulations. 

On January 28, 2003, EPA proposed to approve the CO SIP with the exception of two individual 

contingency measures. EPA gave final approval to the CO SIP revision on September 21, 2004, 

but did not take any action on the contingency measures. Finally, on June 1, 2005, EPA made a 

finding that the Las Vegas Valley had attained the CO NAAQS by the applicable date of 

December 31, 2000. This action removes the requirement for contingency measures and 

obligation under 187(g) of the CAAA to submit a SIP revision to assure a 5% per year reduction 

of CO emissions until attainment of the NAAQS. 

1.1.2 Previous CO Modeling 

Between 1996-2000, the Clark County Department of Comprehensive Planning developed 

computer models for valley-wide carbon monoxide to provide technical support for the control 

measures being evaluated for their CO SIP. This modeling was developed and conducted 

according to CAAA requirements and followed EPA modeling guidance specific to 8-hour CO 

SIP demonstrations. Modeling was conducted for three historical CO episodes in 1995-96 using 

a combination of numerical models, each focusing upon a specific scale and issue. The Urban 

Airshed Model (UAM) was used to simulate episodic urban-scale CO patterns on a grid with 1-

km spacing over the entire developed portion of the Las Vegas Valley; the CAL3QHC 

intersection model was used to simulate micro-scale CO patterns at the “Five Points” 

intersections; and the EDMS airport model was used to simulate fine-scale emissions and CO 

concentration patterns at the three civil airports in the area, including McCarran International 

Airport. At the time, CO emissions from on-road mobile sources (by far the largest contributor 

to the overall emission inventory for Las Vegas) were estimated using a combination of 

MOBILE5b, DTIM, and volume/roadway link information provided by the Regional 

Transportation Commission (RTC) via their TRANPLAN transportation demand model (TDM). 

In August 2000, Clark County submitted their revised CO SIP for Las Vegas to EPA Region IX. 

The CO plan was based on UAM/CAL3QHC/EDMS modeling for the single best performing 

episode of the three: the night of December 8-9 (Sunday-Monday), 1996. Technical 

documentation for the models, application methodologies, performance evaluation, and future 

year modeling assessments are provided in the 2000 CO SIP and its appendices. 

1.2 MODELING UPDATES 

The Clark County Department of Air Quality and Environmental Management has updated their 

UAM CO modeling and conformity analysis using the latest tools, data resources, and 
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methodologies available to estimate CO emissions. From the revised modeling results, Clark 

County is submitting a revised CO SIP document. This section outlines the approach to 

incorporate emission updates into the UAM dataset, and to perform revised UAM urban-scale 

and CAL3QHC intersection modeling. Details for each component are provided in the following 

Sections. 

Clark County has based their revised modeling upon the previous UAM/CAL3QHC/EDMS 

modeling datasets developed for the December 8-9, 1996 episode. Specific updates to the 

emission inventories are briefly listed below; they include modifications to on-road mobile, nonroad mobile, civil airports, railroads and point sources. Emission estimates for all remaining 

categories (mainly stationary area sources and Nellis Air Force Base) were taken from the 

previous modeling detailed in the 2000 CO SIP submittal, although new spatial distributions 

were developed for area sources from updated land use projections. The future years modeled in 

this update include: 2006, 2010, 2015, 2020, and 2030. 

1.2.1 On-Road Emission Estimates 

The greatest effort in the CO modeling update has focused on the on-road mobile source 

inventory estimates. Section 2 details the specific methodologies employed to update the onroad emissions for the base and all future years. The original EPA vehicle emission factor model 

that was used in the previous SIP effort (MOBILE5b) was replaced by the latest version of the 

model, MOBILE6.2.03. This version has updated CO emission rates for LEV and Tier 2 

vehicles from the previous version of MOBILE6.2. However, the Air Improvement Resource 

(AIR) version of this model was used because it provides the capability to create a condensed 

database of composite emission factors. This is important for applications such as this one where 

many MOBILE6 scenarios must be run to generate lookup factors for link-level emissions 

estimates. 

For the 1996 base year, the RTC’s original TRANPLAN output was used to define link-based 

volume (vehicle miles traveled, or VMT) and other traffic volume-related parameters. However, 

no trip tables were available, which allow for the separate estimation of start versus running 

emissions. Therefore, it was necessary to process base year start emissions differently than the 

future years by utilizing trip data from TransCAD TDM output from the year 2000 (as described 

in Section 2). All original ancillary information, including vehicle fleet mix, seasonal/day-ofweek adjustment factors, and hourly activity profiles remain the same as in the original 

modeling. 

Since output data and formats for MOBILE6 are significantly different from its predecessor, the 

original utility that was used to estimate link-level CO emissions (DTIM) was replaced by two 

new programs. The first processes the link-based emissions, and the other processes the 

emissions based on traffic analysis zones (TAZ). Both of the new programs produce inputs for 

the Emission Processing System, version 3 (EPS3). The EPS3 is the latest version of the EPS 

program suite used in the original CO SIP modeling to generate gridded, time-resolved, UAMready CO emission input files. 

For all future years modeled in this update, the RTC provided output from their new TransCAD 

TDM, which includes link volumes and trip tables for each year. For the link-based data, the 

same program written for the base year was used to produce the link-based emissions for EPS3. 
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For the TAZ data, most of the same type of MOBILE6 output was used in the program 

developed for the base year; but start emissions were handled in a special way (see Section 2). 

1.2.2 Other Emission Sources 

Emission updates were also made to airports, railroad, non-road, and point source categories. 

Specific details are provided in Section 3. 

1.2.2.1 Airports

In 1999, Clark County developed a detailed emissions inventory for the three county airports 

(McCarran, North Las Vegas, and Henderson), and performed airport-scale dispersion modeling, 

using the Federal Aviation Administration’s EDMS model. At the time, EDMS had Mobile5a 

embedded as the source of on-road mobile emissions generation, and used PAL2 and CALINE3 

for dispersion calculations. EDMS was run for the 1996 base year, along with the future years of 

2000, 2010, and 2020. However, airport emission estimates within the UAM were never updated 

to reflect the EDMS estimates, and instead relied on much older airport estimates from a 1992 

study. 

In 2003, Clark County sponsored an updated EDMS project for the three county airports. The 

latest version of EDMS was used, which introduced the AERMOD dispersion model. On-road 

mobile sources were estimated using Clark County runs of Mobile6.2. EDMS was run for 2000, 

2005, 2010, 2015 and 2020 (the 1996 base year was skipped). Again, UAM airport emissions 

were not updated. 

In this CO modeling update, the latest 2003 EDMS airport emission estimates have been 

included into the UAM emissions inventory. Details of emissions by projection year, and their 

spatial/temporal allocation to the UAM grid, are described in Section 3. The issue of doublecounting airport emissions within the UAM and EDMS+UAM modeling results were carefully 

considered. 

1.2.2.2 Non-Road and Locomotive

In the previous modeling, non-road emissions were taken from NEVES estimates, and included 

only a few categories. Clark County has updated their railroad emissions estimates for 2001 

based on a recent non-road study (Mactec, 2003), which include contributions from both line 

haul and switching. These have been incorporated into the updated UAM inventory. 

EPA’s NONROAD2004 model, run with Clark County input data, estimates much higher nonroad emission than the NEVES-based estimates used in the 2000 CO SIP. In this modeling 

update, the NONROAD model was used to generate emission inputs to EPS3 for each simulated 

future year. New spatial and temporal allocation factors were developed based on the latest land 

use projections from Clark County. Airport ground support equipment (GSE) were removed 

from the NONROAD estimates because they were included in the EDMS estimates; railroad 

maintenance emissions were left in since the Mactec emissions were estimated for locomotives 

only. 
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1.2.2.3 Point Sources

Clark County incorporated an updated point source emission inventory, which included revised 

stack parameters, and which defined Potential To Emit (PTE) levels for seven specific facilities. 

The UAM future year inventories included the PTE levels plus an additional 70 ton buffer 

(referred to as “PTE+70”) for these sources. The original point source inventory was used, 

unchanged, for the 1996 base year simulation. 

1.2.3 Model Application 

UAM was provided the updated emission inventories for point, on-road mobile, and non-road 

mobile sources, and run for the December 8-9, 1996 historical CO event. All other 

environmental parameters were taken from the original modeling as documented in the 2000 CO 

SIP. A base-year model performance evaluation was conducted similarly. The UAM was then 

used with the updated future year inventories for 2006, 2010, 2015, 2020 and 2030 to determine 

peak 8-hour CO levels in the basin for the same December 8-9, 1996 conditions. UAM results, 

without airport emissions included in the inventory, were added to EDMS receptor 

concentrations from the 2003 updated airport modeling. 

For hotspot modeling, the CAL3QHC model was used to model three intersections: 

Charleston/Eastern, Charleston/Fremont and Eastern/Fremont. EPA (1992, 1995) guidance for 

screening level modeling of these three intersections was followed. The ambient temperature for 

each hour of the episode (needed to estimate emissions with the MOBILE6 model), and the wind 

direction and speed (needed for the CAL3QHC estimates) were taken from the original 

UAM/CAL3QHC modeling. The CAL3QHC model output was added to the background UAM 

levels to estimate 8-hour CO concentrations for the duration of the episode. 

All modeling results are detailed in Section 4. 
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2. ON-ROAD MOBILE EMISSIONS

2.1 OVERVIEW OF APPROACH 

The greatest effort of the update to the CO modeling system focused on the on-road mobile 

source inventory estimates. The original vehicle emission factor model that was used in the 

previous SIP effort (MOBILE5b) was replaced by the EPA’s latest version of the model, 

MOBILE6.2.03. This version has updated CO emission rates for LEV and Tier 2 vehicles from 

the previous version of MOBILE6.2. In addition, since output data and formats for MOBILE6 

are significantly different from its predecessor, the original utility that was used to estimate linklevel CO emissions (DTIM) was replaced by new programs written by ENVIRON. 

For the 1996 base year, the original TRANPLAN transportation demand model (TDM) output 

provided daily total link-based volumes (number of vehicles on each link), link lengths, and 

other link-related parameters by traffic analysis zone (TAZ). The vehicle miles traveled (VMT) 

was calculated from the product of link volume and link length. The County provided the loaded 

network files, but no trip tables were available to process start emissions separately from running 

emissions. Therefore, trip data from the newer 2000 TransCAD TDM was used as a means to 

spatially allocate the 1996 start emissions for each period available in the daily TransCAD 

output. All other original ancillary information, including vehicle fleet mix, seasonal/day-ofweek adjustment factors, and hourly activity profiles were the same as in the original modeling. 

For the future years (2006, 2010, 2015, 2020, and 2030), the latest TransCAD TDM output was 

provided by the Regional Transportation Commission of Southern Nevada (RTC). The 

TransCAD output included link level activity, intrazonal trips, and origin/ destination trips by 

TAZ for several periods of the day (note that the number and distribution of TAZs, and the 

periods for which TransCAD was run, differed substantially from the original TRANPLAN 

configuration). Three separate programs were written for each of these to generate inputs to the 

Emission Processing System, version 3 (EPS3) 1. The EPS3 is the latest version of the EPS 

program suite used in the original CO SIP modeling. 

For both the base and future year link-level emissions, VMT was calculated from the 

transportation model output (link volume times 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 hourly running exhaust emission factors (gram per mile) from MOBILE6.2. The 

total hourly emissions by link were spatially distributed according to the link end point 

coordinates using LBASE, a component of EPS3. 

For both the base and future years, the start emissions were calculated by multiplying hourly 

estimates of link-level VMT by hourly MOBILE6.2 start emission factors (gram per mile). The 

link-level start emissions were then totaled over the entire network and spatially distributed using 

the period-specific transportation model trip origin data by TAZ. Note that for the 1996 base 

year there were no TRANPLAN trip data by TAZ available. Instead, the 1996 start emissions 

were spatially allocated using 2000 TransCAD trip data. 

 

1

 Note that we used hourly emission factors from the MOBILE6 database output, and M6LINC was not applicable 

for this work because it does not handle hourly emission factors. 
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The base year TRANPLAN intrazonal data were provided as volumes by TAZ with a trip length, 

from which VMT was calculated. The intrazonal running and start emissions were calculated as 

VMT times the MOBILE6.2 start and running emission factors, and then spatially allocated 

according to the centroid of each TAZ. 

The 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. The VMT 

was then multiplied by the running emission factors, and then spatially distributed using gridded 

surrogates developed from the definition of the future year TransCAD TAZs. 

2.2 BASE YEAR ESTIMATES 

2.2.1 Base Year MOBILE6 Inputs 

Base Year MOBILE6 inputs were compiled based on sample MOBILE6 input files for 1996 

provided by Clark County. External files were also provided, and these were used as detailed in 

the Table 2-1 below. Eight input files were created, for each of the four roadway types (freeway, 

arterial, local, and ramp) and for weekday and weekend. For Freeway and Arterial, the model 

was run for speeds between 5 and 65 mph for every 1 mph increment. The Local roadway type 

was set at 12.9 mph, and the Ramp roadway type was set to 34.6 mph by MOBILE6 itself. 

A first set of MOBILE6 runs was conducted using the start distribution contained in the 

“sdist.lv” file shown in Figure 2-1. These emission factors were applied to the whole 

domain except a small region around Las Vegas Boulevard. 

A second set of MOBILE6 runs was conducted to better characterize the specific weekday start 

emission factors along the Las Vegas Boulevard (LVB), where the start activity is not centered 

around residential areas, but rather parking lots near casinos (and thus are not characteristic of 

typical commute activity profiles). A more representative start distribution was calculated as the 

fraction of 2000 TransCAD origin trips occurring over all the TAZs along the boulevard from all 

periods available in the 2000 TransCAD output. Figure 2-2 displays the original weekday start 

distributions (based on the distribution shown in Figure 2-1) against the LVB weekday start 

distributions for all future years. Given the similarity of the future year start distributions, we 

elected to apply the 2000 modified start distribution to the base year and all future years for the 

region around the Las Vegas Boulevard. 

Note that MOBILE6 I/M effectiveness was set to 100%. Clark County has developed a white 

paper to justify this value for Las Vegas (Clark County, 2005), and this is included in Appendix 

C to the 2005 CO SIP revision.
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Table 2-1. 1996 Base Year Las Vegas MOBILE6.2 input parameters. 

M6.2 Input Command Weekday Parameters Weekend Parameters 

HOURLY TEMPERATURES 

42.0 44.0 49.0 51.0 55.0 58.0 

64.0 66.0 66.0 66.0 62.0 58.0 

55.0 53.0 51.0 50.0 48.0 47.0 

45.0 44.0 44.0 43.0 42.0 42.0 

42.0 44.0 49.0 51.0 55.0 58.0 

64.0 66.0 66.0 66.0 62.0 58.0 

55.0 53.0 51.0 50.0 48.0 47.0 

45.0 44.0 44.0 43.0 42.0 42.0 

REG DIST LV_reg02.RDT LV_reg02.RDT 

VMT FRACTIONS 

0.5067 0.0770 0.2562 0.0790 

0.0363 0.0111 0.0011 0.0009 

0.0006 0.0024 0.0029 0.0032 

0.0113 0.0028 0.0013 0.0072 

0.5067 0.0770 0.2562 0.0790 

0.0363 0.0111 0.0011 0.0009 

0.0006 0.0024 0.0029 0.0032 

0.0113 0.0028 0.0013 0.0072 

VMT BY HOUR Hvmt_lv.wek Hvmt_lv.wnd 

START DIST sdist.lv sdist.lv 

OXYGENATED FUELS .240 .760 .027 .035 1 .240 .760 .027 .035 1 

ANTI-TAMP PROG 83 81 50 22222 22222222 2 11 

090. 22212112 

83 81 50 22222 22222222 2 11 

090. 22212112 

 

Exhaust I/M program #1 same as weekday 

I/M PROGRAM 1 1983 2050 1 TRC 2500/IDLE 

I/M MODEL YEARS 1 1968 2050 

I/M VEHICLES 1 22222 22222222 2 

I/M STRINGENCY 1 22 

I/M COMPLIANCE 1 90 

I/M WAIVER RATES 1 0.1 0.1 

I/M EFFECTIVENESS 1.00 1.00 1.00 

I/M GRACE PERIOD 1 2 

NO I/M TTC CREDITS 1 

 

CALENDAR YEAR * 1997 1997 

EVALUATION MONTH * 1 1 

FUEL RVP 9 9 

FUEL PROGRAM 1 1 

* Since MOBILE6.2 models January and July periods, January 1997 was chosen because it is closest to the 

December 1996 episode. 
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Figure 2-1. Hourly weekend and weekday start distributions (fraction) provided by Clark 

County, used to temporally allocate emissions derived from TRANPLAN and TransCAD. 

Figure 2-2. Fraction of original weekday start distribution and start distributions in all future 

years for the Las Vegas Boulevard area calculated from the TransCAD origin trips by TAZ. 

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 4 8 12 16 20 24

Hour beginning

Fraction of Daily Total

Weekday

Weekend

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour

Fraction of Daily Total

Original Starts

2000

2006

2010

2015

2020

2030
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2.2.2 Base Year TRANPLAN Link Activity Adjustments 

The 1996 TRANPLAN activity data is representative of an average annual day. The following 

episode-specific adjustments were applied to the data, where the two-day episode modeled was 

Sunday, December 8 through Monday, December 9, 1996. 

2.2.2.1 Month/Season, Day of Week

A factor of 1.021 was applied to adjust from average annual day to a typical December day. This 

adjustment factor was applied to all the running, start, and intrazonal emissions for both days of 

the episode. This value is the same as was used in the previous SIP modeling effort. 

A factor of 0.774 and 1.022 were applied to adjust from a typical day to Sunday and Monday, 

respectively. These are the same factors as used in the 2000 SIP. 

2.2.2.2 Hourly Temporal Adjustments

The same day-specific hourly VMT distribution factors used to generate hourly MOBILE6 

emission factors were used to scale daily VMT from TRANPLAN to each hour of the episode, 

presented in Figure 2-3. 

On-Road Hourly VMT Distribution

0

1

2

3

4

5

6

7

8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour

Percent

Dec. 8 Dec. 9

Figure 2-3. Weekday and Sunday hourly VMT distribution. 
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2.2.2.3 Speed Adjustments

After the link data were temporally allocated to hourly values, the TRANPLAN hourly speed 

was calculated using the following Bureau of Public Roads (BPR) curve, where the volume to 

capacity ratio was capped at 1.25: 

( ) ⎥⎦

⎤ ⎢⎣⎡ +

= B

ff

a

C A V

S

S

1 *

where: 

Sa = adjusted link speed (mph) 

Sff = reported link free flow speed (mph) 

V = total link volume (vehicles OR vehicles per hour) 

C = total link capacity (vehicles OR vehicles per hour) 

For freeways, interstates, system ramps, and expressways, 

 A = 0.66 B = 7.2 

For major arterials, minor arterials, collectors, ramps, and other, 

 A = 0.76 B = 5.9 

However, the resulting adjustment to the speeds using the BPR curve had no impact on the total 

base year emissions. 

2.2.2.4 Transit Adjustments

The link-level emissions were adjusted upward by a factor of 1.00295 to include the contribution 

from public transit activity, which were not included in the TRANPLAN calculations. 

2.2.3 Base Year Link-Level Running Exhaust Emissions 

Emission factors were generated using the Air Improvement Resource, Inc. (AIR) version of 

MOBILE6, outputting hourly emission factors for 28 vehicle classes. A vehicle composite 

emission factor was calculated across all 28 classes using the vehicle class distribution shown in 

Table 2-2. 

The TRANPLAN link activity data consisted of the annual daily average volume for each link in 

the network. The links were classified by the RTC facility type code. The cross-reference 

between the RTC facility type code and the MOBILE6.2 roadway types used is displayed in 

Table 2-3. 

In summary, the link-level running exhaust emissions processing steps were as follows: 

1) Adjust the daily volumes to hourly volumes (using profiles shown Figure 2-3); 

2) Adjust the link speeds using the hourly volume to capacity ratio in the BPR curve; 

3) Calculate the hourly link VMT as the hourly volume times the link length; 
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Table 2-2. MOBILE6 28 vehicle classes and their relative fraction of the overall fleet. 

Class 

Number Class Description Fraction 

1 LDGV Light-Duty Gasoline Vehicles (Passenger Cars) 0.504287

2 LDGT1 Light-Duty Gasoline Trucks 1 (0-6,000 lbs. GVWR, 0-3750 lbs. LVW) 0.076726

3 LDGT2 Light-Duty Gasoline Trucks 2 (0-6,000 lbs. GVWR, 3751-5750 lbs. 

LVW) 0.25529

4 LDGT3 Light-Duty Gasoline Trucks 3 (6,001-8,500 lbs. GVWR, 0-5750 lbs. 

ALVW) 0.077912

5 LDGT4 Light-Duty Gasoline Trucks 4 (6,001-8,500 lbs. GVWR, 5751 lbs. 

and greater ALVW) 0.0358

6 HDGV2B Class 2b Heavy-Duty Gasoline Vehicles (8501-10,000 lbs. GVWR) 0.008055

7 HDGV3 Class 3 Heavy-Duty Gasoline Vehicles (10,001-14,000 lbs. GVWR) 0.000261

8 HDGV4 Class 4 Heavy-Duty Gasoline Vehicles (14,001-16,000 lbs. GVWR) 0.000197

9 HDGV5 Class 5 Heavy-Duty Gasoline Vehicles (16,001-19,500 lbs. GVWR) 0.000348

10 HDGV6 Class 6 Heavy-Duty Gasoline Vehicles (19,501-26,000 lbs. GVWR) 0.000773

11 HDGV7 Class 7 Heavy-Duty Gasoline Vehicles (26,001-33,000 lbs. GVWR) 0.000373

12 HDGV8A Class 8a Heavy-Duty Gasoline Vehicles (33,001-60,000 lbs. GVWR) 0.000002

13 HDGV8B Class 8b Heavy-Duty Gasoline Vehicles (>60,000 lbs. GVWR) 0

14 LDDV Light-Duty Diesel Vehicles (Passenger Cars) 0.002413

15 LDDT12 Light-Duty Diesel Trucks 1 and 2 (0-6,000 lbs. GVWR) 0.001184

16 HDDV2B Class 2b Heavy-Duty Diesel Vehicles (8501-10,000 lbs. GVWR) 0.003045

17 HDDV3 Class 3 Heavy-Duty Diesel Vehicles (10,001-14,000 lbs. GVWR) 0.000839

18 HDDV4 Class 4 Heavy-Duty Diesel Vehicles (14,001-16,000 lbs. GVWR) 0.000703

19 HDDV5 Class 5 Heavy-Duty Diesel Vehicles (16,001-19,500 lbs. GVWR) 0.000252

20 HDDV6 Class 6 Heavy-Duty Diesel Vehicles (19,501-26,000 lbs. GVWR) 0.001627

21 HDDV7 Class 7 Heavy-Duty Diesel Vehicles (26,001-33,000 lbs. GVWR) 0.002527

22 HDDV8A Class 8a Heavy-Duty Diesel Vehicles (33,001-60,000 lbs. GVWR) 0.003198

23 HDDV8B Class 8b Heavy-Duty Diesel Vehicles (>60,000 lbs. GVWR) 0.0113

24 MC Motorcycles (Gasoline) 0.0072

25 HDGB Gasoline Buses (School, Transit and Urban) 0.000832

26 HDDBT Diesel Transit and Urban Buses 0.0013

27 HDDBS Diesel School Buses 0.001968

28 LDDT34 Light-Duty Diesel Trucks 3 and 4 (6,001-8,500 lbs. GVWR) 0.001588 

4) Calculate the link emissions as the link VMT times the MOBILE6.2 composite emission 

factor for the link roadway type, hour, and adjusted link speed; 

5) Spatially allocate the link emissions using LBASE; and 

6) Adjust the emissions to average December day, Sunday or Monday, and for transit 

activity, in EPS3. 

Table 2-4 presents tabulations of 1996 VMT by facility type, directly reported by TRANPLAN, 

and after various adjustments described above. 

Figure 2-4 shows the spatial distribution of link-level running exhaust emissions for the 1996 

base case. 
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Table 2-3. Cross-reference between RTC and MOBILE6.2 facility types. 

RTC Facility Code Description 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 Local 

10 Intrazonal Local 

 

Table 2-4. 1996 VMT by facility type. Totals are shown as output by TRANPLAN, and after 

seasonal, day-of-week, and public transit adjustments. 

Group 

Code Facility Type 

Modeled 

1996 

DVMT 

DVMT 

Adjusted to 

December

DVMT 

Adjusted 

for Transit

Sunday 

DVMT 

Monday 

DVMT 

0 External Connctor 640,605 654,058 655,988 507,734 670,419

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 267,725 273,348 274,154 212,195 280,185

5 Interstate 3,825,715 3,906,055 3,917,578 3,032,205 4,003,764

6 Freeway 1,202,253 1,227,501 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 2,835,084 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 89,136 89,399 69,195 91,366

Daily 

Total 22,395,251 22,776,414 22,843,605 17,680,950 23,346,164

Transit adjustment 1.00295 

December adjustment 1.021

Sunday adjustment 0.774

Monday adjustment 1.022
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Figure 2-4. Spatial distribution of on-road mobile source running exhaust CO emissions for the 

1996 Base Case. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.00

0.30

0.60

0.90

1.20

1.50

1.80

2.10

2.40

2.70

Onroad Running Emissions

Base Year - Dec 9, 1996

CO (tons per day)
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2.2.4 Base Year Start Emissions 

The daily link-level VMT from TRANPLAN was allocated to hourly values using the dayspecific hourly VMT profiles shown in Figure 2-3. The base year start emissions were 

calculated from the product of hourly link VMT and the hourly MOBILE6.2 start emission 

factors. To remain consistent with how the future year start emissions were to be developed, the 

base year start emissions were translated from link-level to TAZ level. Note that for the 1996 

base year there were no TRANPLAN trip data by TAZ available. Instead, the 1996 start 

emissions were spatially allocated to TAZs using 2000 TransCAD trip data. For Monday, the 

hourly link start emissions were totaled over the entire network and redistributed to 2000 

TransCAD TAZs based on the fraction of period-specific trip origins for each TAZ over the total 

number of trip origins over all TAZs. For Sunday, the TransCAD start activity is not 

representative of a typical weekday profile, so the start emissions for all hours were spatially 

distributed to each TAZ using a single ratio of the daily total TAZ trip origins to the daily total of 

all trip origins over the domain. 

A month/season adjustment factor of 1.021 was applied to the start emissions. This adjustment 

is from average annual day to average December day. This adjustment factor was applied to all 

the running, start, and intrazonal emissions for both days of the episode. It is the same as was 

used in the previous SIP modeling effort. 

The day of week adjustments are from average annual day to Sunday and Monday. The factors 

used were 0.774 for Sunday and 1.022 for Monday. These are the same factors as used in the 

2000 SIP. 

The hourly TAZ start emissions were spatially allocated to the grid cell containing the TAZ 

centroid and the 24 surrounding cells in a “wedding cake” fashion: the grid cell containing a 

TAZ centroid receives 25% of the start emissions from that TAZ, the surrounding 8 grid cells 

receive 60% of the start emissions (7.5% per cell), and the outside 16 grid cells receive 15% of 

the start emissions (0.9375% per cell). The wedding cake approach is based on the duration of 

start emissions as defined from EPA’s vehicle testing cycle, which reports emissions during the 

first 505 seconds (Bag 1) of operation after a cold engine start. Emissions are highest during the 

first few minutes after a vehicle is started. As the vehicle travels from the start location, its 

catalytic converter warms and the emissions decrease. With the wedding cake approach, all 

engine starts occur within a given TAZ, so the grid cell containing that TAZ receives the highest 

fraction of those start emissions. Grid cells surrounding that TAZ receive progressively smaller 

fractions of emissions as engines warm and vehicles travel from the TAZ. Clark County believes 

that this is a very conservative method for allocating start emissions. Given the lack of any 

research data to improve upon this methodology, Clark County requested EPA Region IX and 

the Office of Transportation and Air Quality to review the wedding cake approach; both verbally 

agreed to allow its use for this modeling analysis (EPA Region IX, personal communication). 

Figure 2-5 shows the spatial distribution of start exhaust emissions for the 1996 base case. 

2.2.5 Base Year Intrazonal Activity 

Intrazonal VMT was included in the previous modeling by locating their contribution at the 

centroid coordinates of each TAZ. The TAZ boundary information for the 1996 base year was 
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Figure 2-5. Spatial distribution of on-road mobile source start exhaust CO emissions for the 

1996 Base Case. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.00

0.08

0.16

0.24

0.32

0.40

0.48

0.56

0.64

0.72

Onroad START Emissions

Base Year - Dec 9, 1996

CO (tons per day)
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not available, so these were allocated to the grid cells corresponding to each centroid coordinate 

as was performed in the previous modeling for the 2000 SIP submittal. 

2.2.6 Base Year Total Emissions 

Table 2-5 lists the component and total on-road mobile source emissions for the 1996 base year. 

Figure 2-6 presents the spatial distribution of the total on-road mobile source emissions for 

December 9, 1996. 

Table 2-5. Component and total on-road mobile source CO emissions (TPD) for the 1996 base 

year. 

Links - 

Running Starts Intrazonals Total 

Sunday 12/8 202.75 126.42 0.78 329.95 

Monday 12/9 269.31 241.09 1.03 511.43 

2.3 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 provided link-level volumes (number of vehicles) 

and trip origins and destinations for the following seven diurnal periods: midnight – 7 AM, 7 

AM – 9 AM, 9 AM – 2 PM, 2 PM – 4 PM, 4 PM – 6 PM, 6 PM – 8 PM, 8 PM – midnight. 

When modeling Sunday, the period data were first summed together over all seven periods and 

then redistributed to hourly values using a weekend temporal distribution. When modeling 

Monday, the period totals were maintained as output by TransCAD. They were further 

disaggregated into hourly values by applying the fraction of each hour within each period from 

the weekday distribution. 

2.3.1 Future Year MOBILE6 Inputs 

Future year MOBILE6 inputs were compiled based on sample MOBILE6 input files for 2010 

provided by Clark County. External files were also provided, and these were used (as detailed in 

Table 2-6). For each future year (2006, 2010, 2015, 2020, 2030), eight input files were created, 

for each of the four roadway types (freeway, arterial, local, and ramp) both for weekday and 

weekend. For Freeway and Arterial, the model was run for speeds between 5 and 65 mph for 

every 1 mph increment. The Local roadway type was set at 12.9 mph, and the Ramp roadway 

type was set to 34.6 mph by MOBILE6 itself. 

For the Natural Gas Vehicles Fractions external files, the following assumptions were made (by 

Clark County) in creating the files. CNG vehicles start with model year 1998, and are assumed 

to be a very small fraction of the fleet and comprised of government vehicles only. It is also 

assumed that the vehicles last seven years, and then are removed from service or sold to a 

consumer, who fuels them with gasoline. 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-13

Figure 2-6. Spatial distribution of total on-road mobile source CO emissions for the 1996 Base 

Case. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.00

0.30

0.60

0.90

1.20

1.50

1.80

2.10

2.40

2.70

ONROAD Emissions

Base Year - Dec 9, 1996

CO (tons per day)
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-14

Table 2-6. MOBILE6.2 input parameters for future year Las Vegas runs. 

M6 Input Parameter Weekday Parameters Weekend Parameters Source 

HOURLY TEMPERATURES 

42.0 44.0 49.0 51.0 55.0 

58.0 64.0 66.0 66.0 66.0 

62.0 58.0 55.0 53.0 51.0 

50.0 48.0 47.0 45.0 44.0 

44.0 43.0 42.0 42.0 

42.0 44.0 49.0 51.0 55.0 

58.0 64.0 66.0 66.0 66.0 

62.0 58.0 55.0 53.0 51.0 

50.0 48.0 47.0 45.0 44.0 

44.0 43.0 42.0 42.0 

same 

temperatures 

used as in 

previous work 

REG DIST LV_reg02.RDT LV_reg02.RDT provided by 

Clark County 

VMT FRACTIONS 

0.5067 0.0770 0.2562 

0.0790 0.0363 0.0111 

0.0011 0.0009 0.0006 

0.0024 0.0029 0.0032 

0.0113 0.0028 0.0013 

0.0072 

0.5067 0.0770 0.2562 

0.0790 0.0363 0.0111 

0.0011 0.0009 0.0006 

0.0024 0.0029 0.0032 

0.0113 0.0028 0.0013 

0.0072 

provided by 

Clark County 

VMT BY HOUR Hvmt_lv.wek Hvmt_lv.wnd provided by 

Clark County 

START DIST sdist.lv sdist.lv provided by 

Clark County 

NGV FRACTION 

ngvfr06.lv, ngvfr10.lv, 

ngvfr15.lv, ngvfr20.lv, 

ngvfr30.lv 

ngvfr06.lv, ngvfr10.lv, 

ngvfr15.lv, ngvfr20.lv, 

ngvfr30.lv 

provided by 

Clark County 

OXYGENATED FUELS .001 .999 0.027 0.035 1 .001 .999 0.027 0.035 1 provided by 

Clark County 

ANTI-TAMP PROG 

83 81 50 22222 

22222222 2 11 090. 

22212112 

83 81 50 22222 

22222222 2 11 090. 

22212112 

provided by 

Clark County 

 

> Exhaust I/M program #1 provided by 

Clark County 

I/M PROGRAM 1 1983 2050 1 TRC 

2500/IDLE 

 1 1983 2050 1 TRC 

2500/IDLE 

I/M MODEL YEARS 1 1968 1995 1 1968 1995 

I/M VEHICLES 1 22222 22222222 2 1 22222 22222222 2 

I/M STRINGENCY 1 22 1 22 

I/M COMPLIANCE 1 90 1 90 

I/M WAIVER RATES 1 0.1 0.1 1 0.1 0.1 

I/M EFFECTIVENESS 1.00 1.00 1.00 1.00 1.00 1.00 

I/M GRACE PERIOD 1 2 1 2 

I/M CREDIT FILE tech12.d tech12.d 

 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-15

Table 2-6 (continued). 

M6 Input Parameter Weekday Parameters Weekend Parameters Source 

> Exhaust I/M program #2 

I/M PROGRAM 2 1983 2050 1 TRC 

OBD I/M 

 2 1983 2050 1 TRC 

OBD I/M 

I/M MODEL YEARS 2 1996 2050 2 1996 2050 

I/M VEHICLES 2 22222 22222222 2 2 22222 22222222 2 

I/M STRINGENCY 2 22 2 22 

I/M COMPLIANCE 2 90 2 90 

I/M WAIVER RATES 2 0.1 0.1 2 0.1 0.1 

I/M GRACE PERIOD 2 2 2 2 

 

> Evap I/M program #3 

I/M PROGRAM 3 1983 2050 1 TRC 

EVAP OBD 

 3 1983 2050 1 TRC 

EVAP OBD 

I/M MODEL YEARS 3 1996 2050 3 1996 2050 

I/M VEHICLES 3 22222 11111111 1 3 22222 11111111 1 

I/M COMPLIANCE 3 90 3 90 

I/M WAIVER RATES 3 0.1 0.1 3 0.1 0.1 

I/M GRACE PERIOD 3 2 3 2 

 

CALENDAR YEAR 2007, 2011, 2016, 2021, 

2031 

2007, 2011, 2016, 2021, 

2031 

EVALUATION MONTH 1 1 

WE VEH US no yes 

FUEL RVP 9 9 provided by Clark 

County 

FUEL PROGRAM 4 4 provided by Clark 

County 

 Average Gasoline Fuel 

Sulfur Content = 30 ppm 

Average Gasoline Fuel 

Sulfur Content = 30 ppm 

 Maximum Gasoline Fuel 

Sulfur Content = 80 ppm 

Maximum Gasoline Fuel 

Sulfur Content = 80 ppm 

DIESEL SULFUR 250,15,15,15,15 250,15,15,15,15 provided by Clark 

County 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-16

Note that MOBILE6 I/M effectiveness was set to 100%. Clark County has developed a white 

paper to justify this value for Las Vegas (Clark County, 2005), and this is included in Appendix 

C to the 2005 CO SIP revision. 

For the VMT mix, values generated from a 2002 traffic study conducted by RTC in Las Vegas 

(Orth-Rodgers and Associates, 2003) were used, which yielded VMT for 5 vehicle types that 

were further broken down into 16 vehicle types based on MOBILE6 default VMT mix for 2002. 

Clark County does not have future year forecasts for vehicle VMT mix, seasonal/day-of-week 

adjustments, or hourly activity profiles, so the 2002 vehicle VMT mix and other information 

from the base year were used for all future years. 

A first set of MOBILE6 runs was conducted using the start distribution contained in the sdist.lv 

file (shown in Figure 2-1). These emission factors were applied to the whole domain except for 

a small region around Las Vegas Boulevard. 

A second set of MOBILE6 runs was conducted to better estimate the specific weekday start 

emission factors along the Las Vegas Boulevard (LVB), where the start activity is not centered 

around residential areas, but rather parking lots near casinos (and thus are not characteristic of 

typical commute activity profiles). A more representative start distribution was calculated as the 

fraction of TransCAD origin trips occurring over all TAZs along the boulevard from all periods 

available in the TransCAD output. Figure 2-2 above shows the weekday start distributions for 

all future years along the Las Vegas Boulevard. Given the similarity of the future year start 

distributions, we elected to apply the 2000 modified start distribution to the base year and all 

future years for the region around the Las Vegas Boulevard. Figure 2-7 compares the hourly 

2006 MOBILE6 start emission factor profiles for Sunday (entire domain), Monday (LVB area), 

and Monday (remainder of the domain). 

2.3.2 Future Year TransCAD Link Activity Adjustments 

2.3.2.1 Month/Season, Day of Week

The link-level activity was adjusted from annual average to December by a factor of 1.021, as 

was done for the base year. 

The TransCAD volume data is representative of an average weekday. The data were scaled to 

Sunday estimates by weighting the Sunday day-of-week factor by the average weekday factor. 

The day of week factors are shown in Table 2-7. 

The Sunday adjustment was therefore calculated as: 

Sunday Adjustment = 0.774/[(1.022 + 1.047 + 1.060 + 1.062 + 1.109)/5] = 0.73 

Monday was not adjusted. 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-17

Table 2-7. Volume scaling factors by day of week. 

Day of Week Day of Week Factors 

Sunday 0.774 

Monday 1.022 

Tuesday 1.047 

Wednesday 1.060 

Thursday 1.062 

Friday 1.109 

Saturday 0.925 

Figure 2-7. Hourly start emission factors from the 2006 MOBILE6 run: “Sun EF” is the Sunday 

profile used for all start emissions; “Mon EF” is the Monday profile used for start emissions 

outside of the LVB area; and “LVB Mon EF” is the Monday profile used for start emissions within 

the LVB area. 

2.3.2.2 Link Volume Adjustments

Prior to calculating the link-based emissions, the link volumes were first adjusted to observed 

traffic counts by facility type. Then, the adjusted link volumes were adjusted to bring the total 

volume into agreement with the VMT reported through the Highway Performance Monitoring 

System (HPMS). Table 2-8 shows the adjustment factors to observed traffic counts by facility 

type. 

The overall HPMS adjustment was a single factor multiplied uniformly to the volumes to bring 

the total into agreement with HPMS. The HPMS adjustment factor used was 1.0145. 

0

0.002

0.004

0.006

0.008

0.01

0.012

123456789

101112131415161718192021222324

Hour

g/mile

Mon EF Sun EF LVB Mon EF
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-18

Table 2-8. Adjustment factors to observed traffic counts by facility type. 

Facility Type Count Correction Factor 

external connector 0.9880 

system ramp 0.9880 

minor arterial 1.0917 

major arterial 1.0917 

service ramp 0.9880 

interstate 0.9880 

freeway 0.9880 

beltway 0.9880 

collector 1.0917 

centroid 1.0917 

2.3.2.3 Hourly Temporal Adjustments

The TransCAD volume data is representative of an average weekday. Within each of the seven 

periods, the data were further disaggregated using the default weekday (Dec. 9) distribution for 

Monday. For Sunday, the data were summed to obtain the daily total before re-distributing into 

the hours using the default weekend (Dec. 8) distribution. The same VMT distributions that were 

used for the 1996 base year were used for the future years, as illustrated in Figure 2-3. 

2.3.2.4 Speed Adjustments

After the link data were temporally allocated to hourly values, the hourly speeds were adjusted 

using the following Bureau of Public Roads (BPR) curve, where the volume to capacity ratio was 

capped at 1.25: 

( ) ⎥⎦

⎤ ⎢⎣⎡ +

= B

ff

a

C A V

S

S

1 *

where: 

Sa = adjusted link speed (mph) 

Sff = reported link free flow speed (mph) 

V = total link volume (vehicles OR vehicles per hour) 

C = total link capacity (vehicles OR vehicles per hour) 

For freeways, interstates, system ramps, and expressways, 

 A = 0.66 B = 7.2 

For major arterials, minor arterials, collectors, ramps, and other, 

 A = 0.76 B = 5.9 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-19

2.3.2.5 Transit Adjustments

The link-level emissions were adjusted upward by the factors shown in Table 2-9 to capture 

transit activity (interpolated to the model years from transit fractions from the RTP-TIP). The 

link-level emissions were also adjusted slightly downward as shown in Table 2-9 to capture 

impacts from TCMs. 

Table 2-9. Adjustment factor to scale link-level emissions to account for mass transit. 

Year Transit Adjustment Factor TCM Adjustment Factor 

2006 1.004962 0.9996 

2010 1.003913 0.9996 

2015 1.003553 0.9995 

2020 1.003192 0.9995 

2030 1.002471 0.9995 

2.3.3 Future Year Link-Level Running Emissions 

The TransCAD link level volumes were first adjusted by the count correction factor and the 

HPMS adjustment. Then, they were disaggregated to hourly volumes. The speed was adjusted 

using the hourly volume to capacity ratio in the BPR curve. The MOBILE6 emission factor for 

that hour and adjusted speed was multiplied by the hourly link volume to get hourly emissions. 

The hourly emissions were further adjusted to December, day of week, transit activity, and 

TCM’s in CNTLEM within the EPS3 processing. Figure 2-8 shows the resulting hourly 2006 

VMT. 

Tables 2-10 through 2-14 present tabulations of VMT by facility type for each future year, as 

directly reported by TransCAD, and after the adjustments described above. 

2.3.4 Future Year Start Emissions 

The start emissions were calculated in the same manner as was done for the base year. For 

Monday, the hourly VMT was estimated by disaggregating the period VMT to hourly VMT 

using the weekday VMT distribution show in Figure 2-3. The start emissions were calculated by 

multiplying the hourly VMT by the hourly MOBILE6 start emission factors. The hourly link 

start emissions were then totaled over the entire network and redistributed to TAZ, based on the 

fraction of period-specific trip origins for each TAZ over the total number of trip origins over all 

TAZs. For Sunday, the TransCAD data is not representative of a typical weekend profile, so the 

hourly VMT was estimated by first totaling all the period VMT to a daily value, then it was 

distributed to hourly values using the weekend profile in Figure 2-3. The Sunday start emissions 

were then calculated by multiplying the hourly VMT by the MOBILE6 hourly emission factors 

for all hours. The emissions were totaled over the entire network and then spatially distributed to 

each TAZ using a single ratio of the daily total TAZ trip origins to the daily total of all trip 

origins over the domain. 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-20Table 2-10. 2006 VMT by facility type. Totals are shown as output by TransCAD, and after seasonal, day-of-week, and public 

transit adjustments.

Group Code Facility Type 

Modeled 

2006 

DVMT 

DVMT 

Corrected to 

Count 

DVMT 

Corrected to 

HPMS 

DVMT 

Adjusted to 

December 

DVMT 

Adjusted for 

Transit 

Sunday 

 DVMT 

Monday 

 DVMT 

0 External Connector 621,151 613,697 622,596 635,671 637,546 465,408 637,546 1 System Ramp 288,128 284,671 288,798 294,863 295,733 215,885 295,733 2 Minor Arterial 2,777,828 3,032,555 3,076,527 3,141,134 3,150,401 2,299,793 3,150,401 3 Major Arterial 16,612,275 18,135,621 18,398,587 18,784,958 18,840,373 13,753,473 18,840,373 4 Freeway on- or offramp 962,346 950,798 964,585 984,841 987,746 721,055 987,746 5 Interstate 8,341,200 8,241,106 8,360,602 8,536,174 8,561,356 6,249,790 8,561,356 6 Freeway 3,088,561 3,051,499 3,095,745 3,160,756 3,170,080 2,314,159 3,170,080 7 Expressway 142,816 141,103 143,149 146,155 146,586 107,008 146,586 8 Collector 1,416,105 1,545,961 1,568,378 1,601,314 1,606,038 1,172,407 1,606,038 9 Centroid Connector 2,738,699 2,989,838 3,033,191 3,096,888 3,106,024 2,267,397 3,106,024 

 Intrazonal 87,303 87,303 88,569 90,429 90,696 66,208 90,696 Daily Total 37,076,414 39,074,152 39,640,727 40,382,753 40,501,883 29,566,374 40,501,883 Transit adjustment 1.004962 HPMS adjustment 1.0145 December adjustment 1.021 Sunday adjustment 0.73 Monday adjustment 1 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-21Table 2-11. 2010 VMT by facility type. Totals are shown as output by TransCAD, and after seasonal, day-of-week, and public 

transit adjustments. 

Group Code Facility Type 

Modeled 

2010 

DVMT 

DVMT 

Corrected to 

Count 

DVMT 

Corrected to 

HPMS 

DVMT 

Adjusted to 

December 

DVMT 

Adjusted for 

Transit 

Sunday 

DVMT 

Monday 

DVMT 

0 External Connector 611,100 603,767 612,521 625,384 627,229 457,877 627,229 1 System Ramp 427,211 422,084 428,204 437,197 438,486 320,095 438,486 2 Minor Arterial 3,472,785 3,791,239 3,846,212 3,926,982 3,938,567 2,875,154 3,938,567 3 Major Arterial 19,347,711 21,121,896 21,428,164 21,878,155 21,942,696 16,018,168 21,942,696 4 Freeway on- or off-ramp 1,264,307 1,249,136 1,267,248 1,293,860 1,297,677 947,304 1,297,677 5 Interstate 10,176,081 10,053,968 10,199,750 10,413,945 10,444,666 7,624,606 10,444,666 6 Freeway 5,650,830 5,583,020 5,663,974 5,782,917 5,799,977 4,233,983 5,799,977 7 Expressway 525,996 519,684 527,219 538,291 539,879 394,111 539,879 8 Collector 2,013,021 2,197,615 2,229,481 2,276,300 2,283,015 1,666,601 2,283,015 9 Centroid Connector 3,525,078 3,848,327 3,904,128 3,986,115 3,997,874 2,918,448 3,997,874 

 Intrazonal 156,061 156,061 158,324 161,649 162,126 118,352 162,126 Daily Total 47,170,180 49,546,797 50,265,226 51,159,147 51,310,066 37,456,348 51,310,066 Transit adjustment 1.003913 HPMS adjustment 1.0145 December adjustment 1.021 Sunday adjustment 0.73 Monday adjustment 1 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-22Table 2-12. 2015 VMT by facility type. Totals are shown as output by TransCAD, and after seasonal, day-of-week, and public 

transit adjustments. 

Group Code Facility Type 

Modeled 

2015 

DVMT 

DVMT 

Corrected to 

Count 

DVMT 

Corrected to 

HPMS 

DVMT 

Adjusted to 

December 

DVMT 

Adjusted for 

Transit 

Sunday 

DVMT 

Monday 

DVMT 

0 External Connector 621,151 613,697 622,596 635,671 637,546 465,408 637,546 1 System Ramp 476,926 471,203 478,035 488,074 489,514 357,345 489,514 2 Minor Arterial 3,964,841 4,328,417 4,391,179 4,483,394 4,496,620 3,282,532 4,496,620 3 Major Arterial 21,843,415 23,846,456 24,192,229 24,700,266 24,773,132 18,084,386 24,773,132 4 Freeway on- or off-ramp 1,313,314 1,297,554 1,316,369 1,344,013 1,347,978 984,024 1,347,978 5 Interstate 11,023,875 10,891,588 11,049,516 11,281,556 11,314,837 8,259,831 11,314,837 6 Freeway 6,542,175 6,463,669 6,557,392 6,695,097 6,714,848 4,901,839 6,714,848 7 Expressway 1,599,742 1,580,545 1,603,463 1,637,136 1,641,966 1,198,635 1,641,966 8 Collector 2,354,214 2,570,095 2,607,361 2,662,116 2,669,969 1,949,077 2,669,969 9 Centroid Connector 4,088,071 4,462,947 4,527,660 4,622,740 4,636,377 3,384,556 4,636,377 

 Intrazonal 145,409 145,409 147,517 150,615 151,060 110,274 151,060 Daily Total 53,973,132 56,671,581 57,493,319 58,550,063 58,722,786 42,867,634 58,722,786 Transit adjustment 1.003553 HPMS adjustment 1.0145 December adjustment 1.021 Sunday adjustment 0.73 Monday adjustment 1 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-23Table 2-13. 2020 VMT by facility type. Totals are shown as output by TransCAD, and after seasonal, day-of-week, and public 

transit adjustments. 

Group Code Facility Type 

Modeled 

2020 

DVMT 

DVMT 

Corrected to 

Count 

DVMT 

Corrected to 

HPMS 

DVMT 

Adjusted to 

December 

DVMT 

Adjusted for 

Transit 

 Sunday 

DVMT 

Monday 

DVMT 

0 External Connector 641,546 633,848 643,039 656,542 658,479 480,690 658,479 1 System Ramp 491,767 485,866 492,911 503,262 504,747 368,465 504,747 2 Minor Arterial 4,433,933 4,840,525 4,910,712 5,013,837 5,028,628 3,670,899 5,028,628 3 Major Arterial 23,282,398 25,417,394 25,785,946 26,327,451 26,405,117 19,275,735 26,405,117 4 Freeway on- or off-ramp 1,403,726 1,386,881 1,406,991 1,436,538 1,440,776 1,051,766 1,440,776 5 Interstate 12,148,354 12,002,574 12,176,611 12,432,320 12,468,996 9,102,367 12,468,996 6 Freeway 7,019,517 6,935,283 7,035,844 7,183,597 7,204,789 5,259,496 7,204,789 7 Expressway 1,612,455 1,593,105 1,616,205 1,650,146 1,655,014 1,208,160 1,655,014 8 Collector 2,596,741 2,834,862 2,875,968 2,936,363 2,945,025 2,149,869 2,945,025 9 Centroid Connector 4,383,208 4,785,148 4,854,533 4,956,478 4,971,100 3,628,903 4,971,100 

 Intrazonal 167,472 167,472 169,900 173,468 173,980 127,005 173,980 Daily Total 58,181,118 61,082,958 61,968,661 63,096,535 63,282,670 46,196,349 63,282,670 Transit adjustment 1.003192 HPMS adjustment 1.0145 December adjustment 1.021 Sunday adjustment 0.73 Monday adjustment 1 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-24Table 2-14. 2030 VMT by facility type. Totals are shown as output by TransCAD, and after seasonal, day-of-week, and public 

transit adjustments. 

Group Code Facility Type 

Modeled 

2030 

DVMT 

DVMT 

Corrected to 

Count 

DVMT 

Corrected to 

HPMS 

DVMT 

Adjusted to 

December 

DVMT 

Adjusted for 

Transit 

Sunday 

DVMT 

Monday 

DVMT 

0 External Connector 678,697 670,552 680,275 694,561 696,610 508,525 696,610 1 System Ramp 548,440 541,859 549,716 561,260 562,915 410,928 562,915 2 Minor Arterial 5,394,312 5,888,971 5,974,361 6,099,822 6,117,817 4,466,006 6,117,817 3 Major Arterial 26,825,037 29,284,892 29,709,523 30,333,423 30,422,907 22,208,722 30,422,907 4 Freeway on- or off-ramp 1,580,942 1,561,971 1,584,619 1,617,896 1,622,669 1,184,548 1,622,669 5 Interstate 13,368,302 13,207,882 13,399,396 13,680,784 13,721,142 10,016,434 13,721,142 6 Freeway 8,306,442 8,206,765 8,325,763 8,500,604 8,525,681 6,223,747 8,525,681 7 Expressway 598,066 590,889 599,457 612,046 613,852 448,112 613,852 8 Collector 3,079,919 3,362,348 3,411,102 3,482,735 3,493,009 2,549,897 3,493,009 9 Centroid Connector 5,034,875 5,496,573 5,576,273 5,693,375 5,710,170 4,168,424 5,710,170 

 Intrazonal 171,308 171,308 173,792 177,442 177,965 129,914 177,965 Daily Total 65,586,340 68,984,010 69,984,278 71,276,506 71,486,772 52,185,344 71,486,772 Transit adjustment 1.002471 HPMS adjustment 1.0145 December adjustment 1.021 Sunday adjustment 0.73 Monday adjustment 1 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-25

Figure 2-8. 2006 hourly vehicle miles traveled (VMT) for Sunday and Monday. 

The future year start emissions were calculated twice; once using the MOBILE6 emission factors 

generated using the sdist.lv hourly start distribution (Figure 2-1), and once using the MOBILE6 

emission factors generated using the modified start distribution discussed above to reflect the 

activity along the Las Vegas Boulevard. 

The hourly TAZ start emissions were spatially allocated to the grid cell containing the TAZ 

centroid and the 24 surrounding cells in a “wedding cake” fashion: the grid cell containing a 

TAZ centroid receives 25% of the start emissions from that TAZ, the surrounding 8 grid cells 

receive 60% of the start emissions (7.5% per cell), and the outside 16 grid cells receive 15% of 

the start emissions (0.9375% per cell). This approach was reviewed by EPA Region IX and the 

Office of Transportation and Air Quality (EPA Region IX, personal communication). 

2.3.5 Future Year Intrazonal Activity 

The intrazonal VMT was calculated assuming a default length of 1 mile for each intrazonal trip 

(as is described in the 2004-2005 Regional Transportation Plan documentation [FY 2004-2025 

RTP and FY 2004-2006 TIP, Chapter 5, page 5-16]). 

0

500

1000

1500

2000

2500

3000

3500

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour

miles/1000

Mon VMT Sun VMT
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-26

2.3.6 Future Year Total Emissions 

Table 2-15 lists the component and total on-road mobile source emissions for all future years. 

Figures 2-9 through 2-13 present the future year spatial distribution of the total on-road mobile 

source emissions for December 9, 1996. 

Table 2-15. Component and total on-road mobile source CO emissions (TPD) for all future 

years. 

2006 2010 2015 2020 2030 

Sunday 12/8/2005 

Links - Running 149.64 150.26 137.32 133.15 142.66 

Starts 125.10 135.93 138.46 139.23 152.54 

Intrazonals 0.57 0.82 0.66 0.71 0.70 

Total 275.30 287.01 276.44 273.09 295.90 

Monday 12/9/2005 

Links - Running 204.62 205.29 187.70 182.00 194.67 

Starts 235.73 257.33 262.53 264.10 289.81 

Intrazonals 0.88 1.33 1.07 1.14 1.13 

Total 441.23 463.95 451.30 447.24 485.61 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_2_Onroad.doc 2-27

Figure 2-9. Spatial distribution of total on-road mobile source CO emissions for the 2006 future 

year. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

ONROAD Emissions

Future Year - Dec 9, 2006

CO (tons per day)
August 2005 

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Figure 2-10. Spatial distribution of total on-road mobile source CO emissions for the 2010 

future year.

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

ONROAD Emissions

Future Year - Dec 9, 2010

CO (tons per day)
August 2005 

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Figure 2-11. Spatial distribution of total on-road mobile source CO emissions for the 2015 

future year.

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

ONROAD Emissions

Future Year - Dec 9, 2015

CO (tons per day)
August 2005 

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Figure 2-12. Spatial distribution of total on-road mobile source CO emissions for the 2020 

future year.

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

ONROAD Emissions

Future Year - Dec 9, 2020

CO (tons per day)
August 2005 

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Figure 2-13. Spatial distribution of total on-road mobile source CO emissions for the 2030 

future year.

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

ONROAD Emissions

Future Year - Dec 9, 2030

CO (tons per day)
August 2005 

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3. OTHER EMISSION CATEGORIES

3.1 NON-ROAD CATEGORIES 

3.1.1 Airports 

In 1999, Clark County and their contractor Ricondo and Associates developed a detailed 

emissions inventory at the three county civil airports (McCarran, North Las Vegas, and 

Henderson), and performed dispersion modeling using the Federal Aviation Administration’s 

(FAA) EDMS model. At the time, EDMS had MOBILE5a embedded as the source of on-road 

mobile emissions generation, and used PAL2 and CALINE3 for dispersion calculations. EDMS 

was run for the 1996 base year, along with the future years of 2000, 2010, and 2020. UAM 

results were used to provide the larger scale "background" CO levels. The combination of 

UAM-predicted grid cell concentrations from the 2000 SIP submittal, plus EMDS-predicted 

receptor concentrations, were used for the airport microscale analyses. The UAM+EDMS results 

showed no 8-hour CO exceedances at any EDMS receptor (Ricondo, 1999). 

In 2003, Clark County sponsored an updated EDMS project for the three county airports. The 

latest version of EDMS was used, which introduced the AERMOD dispersion model. On-road 

mobile sources were estimated using Clark County runs of MOBILE6.2. EDMS was run for 

2000, 2005, 2010, 2015 and 2020 (the 1996 base year was skipped). UAM results were not 

added to the EDMS receptor results. The revised modeling resulted in predictions above the 8-

hour CO standard at several receptors in all years (Ricondo, 2003); however, these were located 

in "non-public access" areas (primarily aircraft docking areas, apron, etc.), as documented by 

Ricondo (2005). EPA has indicated that it will accept the removal of receptors in non-public 

access areas from consideration. 

To properly account for the contributions of airports toward the valley-wide distribution of CO 

during the December 8-9 episode, UAM needs to include the updated EDMS airport emissions 

within the gridded inventory. Airport emissions for 1996 were taken from the Ricondo (1999) 

estimates, while emissions for the 2010, 2015, and 2020 future years were taken from the 

updated Ricondo (2003) estimates. Emission estimates for 2006 were derived by linearly 

interpolating total airport emissions from 2005 and 2010, while emission estimates for 2030 were 

derived by linearly extrapolating total airport emissions from 2015 and 2020. Annual airport 

emissions are shown in Table 3-1. Note that original 2000 SIP emission estimates for Nellis 

AFB were retained in the UAM modeling. 

3.1.1.1 Temporal and Spatial Allocation

The EDMS CO emission estimates are reported as tons per year. Therefore it was necessary to 

disaggregate these estimates to December, Sunday and Monday, and to each hour of the day. 

Clark County provided activity data for these airports on which to base the disaggregation from 

annual to hourly emission rates. 
August 2005 

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Table 3-1. Annual airport CO emission estimates (tons per year) reported by Ricondo (1999) 

for the 1996 base year, and by Ricondo (2003) for future years 2010, 2015, and 2020 (2006 and 

2030 estimated as described in the text). 

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 

Factors to translate from annual to December emissions are provided in Table 3-2. The same 

day-of-week activity factors were given for Henderson and North Las Vegas airports to translate 

from monthly estimates to specific days: 3.2% for Sunday, and 2.5% for Monday. No dayspecific factors were given for McCarran airport, so a constant day-of-week profile was applied. 

Figure 3-1 shows the hourly distribution applied to McCarran airport, while Figure 3-2 shows the 

hourly distribution applied for both Henderson and North Las Vegas airports. 

Table 3-2. Monthly factors used to disaggregate annual airport CO emissions to monthly totals. 

The factors for December were used in this study. 

Month McCarran Henderson North Las Vegas 

January 7.75% 8.46% 6.25% 

February 7.61% 9.13% 7.27% 

March 8.86% 10.26% 7.20% 

April 8.47% 9.00% 7.13% 

May 8.70% 10.16% 9.35% 

June 8.40% 8.37% 7.82% 

July 8.43% 7.11% 8.32% 

August 8.67% 7.18% 8.53% 

September 8.47% 7.84% 9.49% 

October 9.01% 8.71% 10.40% 

November 8.10% 7.38% 9.76% 

December 7.54% 6.40% 8.48% 

Airport emissions were placed evenly across the grid cells in which the airports reside. Note that 

in this project we expanded the definition of McCarran airport from two cells (as treated in the 

2000 SIP modeling) to twelve cells, based on grid overlays upon aerial photographs of the airport 

layout (Figure 3-3). The single host cell for North Las Vegas airport was shifted one cell east to 

better locate that property relative to the nearby roadways. The location of Henderson was not 

changed from the original location. 
August 2005 

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Figure 3-1. Hourly activity at McCarran airport used to temporally allocate daily emissions for 

all years modeled. 

Figure 3-2. Hourly activity at Henderson and North Las Vegas airports used to temporally 

allocate daily emissions for all years modeled. 

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour

Fraction

0%

2%

4%

6%

8%

10%

12%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour

Fraction
August 2005 

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Figure 3-3. Arial photograph of McCarran airport with UAM grid cells overlaid. 

Airport grid cells are defined as follows: 

 McCarran (i,j) (24,21) (24,22) (24,23),(24,24) 

(25,21) (25,22) (25,23),(25,24) 

(26,21) (26,22) 

(27,21) (27,22) 

 North Las Vegas (i,j) (21,36) 

 Henderson (i,j) (27,10) 

3.1.2 Locomotives 

Clark County has updated railroad emissions for 2001 based on a Mactec non-road study 

(Mactec, 2003). These updated emission estimates were incorporated into this work. The base 

year emissions estimates were taken from Table 3-33 of the Mactec report. Locomotive 

emissions from the Mactec report include both line haul and switching. For switching, emissions 

are placed at the same two facilities as modeled previously. The grid cells for these facilities are: 

Civic Center Yard (i,j) (24,29) (24,30) (25,30) (25,31) (25,32) 

Boulder Junction Wye (i,j) (21,20) (21,21) (21,22) (21,23) 
August 2005 

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These locations are modeled as zero length link sources. For the line haul, the locomotive 

emissions were put into grid cells using coordinates defined from the rail map provided by Clark 

County. Each segment is defined by two node endpoints with the emissions of each segment 

distributed equally along the line between each node. 

3.1.2.1 Locomotive Projections

Projecting locomotive emissions requires two estimates: activity growth and effects of emissions 

control through fleet turnover with EPA engines. Only Union Pacific operates locomotives in 

Clark County, so Union Pacific may have more accurate figures of historic usage for the specific 

rail segments in Clark County. However, conducting a survey of this historic usage was beyond 

the scope of this project. 

The locomotive activity unit most useful for emission evaluation is fuel consumption. Projected 

fuel consumption from locomotive use is difficult to estimate especially for a given track 

segment such as through Clark County. The fuel consumption depends on factors not 

exclusively restricted to the number of trains, tons of freight, or business indicators because of 

efficiency improvements to the trains or operations. 

To project the locomotive activity increases due to the growth in business, a time series plot of 

the available fuel consumption data was used. Three sources of fuel consumption data were 

available: online data purchased from the American Association of Railroads (AAR) for the 

years 1999 and 2002 (AAR, 2004), the AAR ten years trends report for 1990 through 1999 

(AAR, 2000), and estimates from the Energy Information Administration (EIA) of the 

Department of Energy that track fuels consumption by end use (EIA, 2005). As shown in Figure 

3-4, the EIA data does not match at all the AAR figures so these were ignored. The AAR online 

data provides fuel consumption estimates for individual railroads and has a total of the largest 

railroads called Class 1 railroads, of which Union Pacific is the largest. The most recent trend 

between 1999 and 2001 for Union Pacific indicates a 1.9% per year increase in fuel 

consumption. While basing a growth estimate with only two years of data is suspect, the 1.9% 

per year growth rate mirrors the US total growth rate of 2.0% for 1990 through 1999 and 1.5% 

for the period of 1990 through 2002. 

The emissions were projected using the EPA’s estimates of the effect of fleet turnover. Table 3-

3 shows the percent reduction in emissions for Class 1 line-haul and switching engines due to the 

Federal standard (EPA, 1997). Combining the projected growth from fuel consumption 

estimates with the expected emission reductions from engine controls, the emissions relative to 

1996 were calculated and shown in Table 3-4. 

The 1996 railroad maintenance emissions were estimated with EPA’s NONROAD Model, which 

is discussed in detail in the following subsection. These estimates were processed and reported 

separately. The 1996 base case railroad maintenance emissions were projected based on the 

locomotive projections presented in Table 3-4. 
August 2005 

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Figure 3-4. Available locomotive fuel consumption trends.

Table 3-3. Locomotive emission reductions due to EPA regulations (EPA, 1997). 

Year HC CO NOx PM 

Class 1 Line-Haul 

1996 0.0% 0.0% 0.0% 0.0%

2002 0.1% 0.0% 11.8% 0.0%

2006 7.5% 0.0% 37.6% 7.7%

2010 17.8% 0.0% 46.1% 18.7%

2015 24.1% 0.0% 49.7% 25.4%

2020 30.0% 0.0% 53.1% 31.8%

2025 35.4% 0.0% 56.2% 37.6%

Switching Engines 

1996 0.0% 0.0% 0.0% 0.0%

2002 0.0% 0.0% 1.7% 0.0%

2006 1.1% 0.0% 8.9% 1.3%

2010 3.6% 0.0% 16.7% 4.2%

2015 7.3% 0.0% 27.1% 8.3%

2020 11.4% 0.0% 33.3% 13.1%

2025 16.2% 0.0% 38.1% 18.5%

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

1988 1990 1992 1994 1996 1998 2000 2002 2004

Year

Millions of Gallon per Year

AAR Online

AAR 10-Year Trend

DOE - EIA

Union Pacific
August 2005 

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Table 3-4. Locomotive emissions relative to 1996. 

Year HC CO NOx PM 

Class 1 Line-Haul 

1996 1 1 1 1 

2002 1.12 1.12 0.99 1.12 

2006 1.12 1.21 0.75 1.12 

2010 1.07 1.30 0.70 1.06 

2015 1.09 1.43 0.72 1.07 

2020 1.10 1.57 0.74 1.07 

2025 1.12 1.73 0.76 1.08 

Switching Engines 

1996 1 1 1 1 

2002 1.12 1.12 1.10 1.12 

2006 1.19 1.21 1.10 1.19 

2010 1.26 1.30 1.08 1.25 

2015 1.33 1.43 1.04 1.31 

2020 1.39 1.57 1.05 1.37 

2025 1.45 1.73 1.07 1.41 

3.1.3 Other Non-Road Categories 

3.1.3.1 NONROAD Model Equipment Estimates

Weekday and weekend emissions were estimated using EPA’s NONROAD Model (Core Model 

Ver. 2.3c, Apr 2004). For the Clark County base year inventory, the period type was set to 

Winter Season, and emissions were reported as tons per day. 

Table 3-5 summarizes the input parameters specified for the 1996 Clark County base year 

NONROAD Model runs. The temperatures used for the NONROAD modeling were the same as 

the modeling temperatures used for the previous Clark County SIP modeling work. Gasoline 

fuel RVP, oxygen weight %, gasoline sulfur level, and CNG/LPG sulfur levels were those used 

in 1996 modeling for Clark County in work performed by ENVIRON for the Western Regional 

Air Partnership (Pollack et al., 2004). From discussions with Clark County, the non-road diesel 

sulfur level for 1996 was set at 250 ppm for this modeling. In addition, it was agreed that Clark 

County would be modeled as a “Southwest” region instead of the EPA default “Central West” 

region and the NONROAD model seasonality file (containing temporal adjustment data), 

SEASON.DAT, was modified to reflect this decision. 

Similar NONROAD Model (Core Model Ver. 2.3c, Apr 2004) weekday and weekend runs were 

performed for the five future years (2006, 2010, 2015, 2020, 2030) for Clark County. Table 3-6 

summarizes the NONROAD Model input parameters for each future year. Temperature and 

CNG/LPG sulfur level inputs were not changed from the base year. From discussions with Clark 

County, the oxygen weight % was set to 3.5% for all the future years based on local regulations. 

The gasoline sulfur level was set to 30 ppm for all future years and the non-road diesel sulfur 

level was set to 250 ppm for 2006 and 15 ppm for subsequent future years, per federal 

regulation. Similar to the base year, Clark County was modeled as a “Southwest” region instead 

of the default “Central West” region. 
August 2005 

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Table 3-5. Summary of inputs used for NONROAD modeling for 1996. 

1996 

 

 

Weekday 

(tons/day) 

Weekend 

(tons/day) 

Period Type Seasonal Seasonal 

Summation Type Typical Day Typical Day 

Year of Episode 1996 1996 

Season of Year Winter Winter 

Weekend or Weekday Weekday Weekend 

Fuel RVP for gas 9 9 

Oxygen Weight % 3.31 3.31 

Gas sulfur % 0.009 0.009 

Diesel sulfur % 0.025 0.025 

CNG/LPG sulfur % 0.003 0.003 

Minimum temper. (F) 42 42 

Maximum temper. (F) 66 66 

Average temper. (F) 51.875 51.875 

Altitude of region low Low 

Table 3-6. Summary of inputs used for NONROAD modeling future years. 

2006 2010 2015 2020 2030 

 

 Weekday 

(tpd) 

Weekend 

(tpd) 

Weekday 

(tpd) 

Weekend 

(tpd) 

Weekday 

(tpd) 

Weekend 

(tpd) 

Weekday 

(tpd) 

Weekend 

(tpd) 

Weekday 

(tpd) 

Weekend 

(tpd) 

Period Type Monthly Monthly Monthly Monthly Monthly Monthly Monthly Monthly Monthly Monthly 

Summation Type 

Typical 

Day 

Typical 

Day 

Typical 

Day 

Typical 

Day 

Typical 

Day 

Typical 

Day 

Typical 

Day 

Typical 

Day 

Typical 

Day 

Typical 

Day 

Year of Episode 2006 2006 2010 2010 2015 2015 2020 2020 2030 2030 

Month of Year Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. 

Weekend or weekday Weekday Weekend Weekday Weekend Weekday Weekend Weekday Weekend Weekday Weekend

Fuel RVP for gas 9 9 9 9 9 9 9 9 9 9 

Oxygen Weight % 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 

Gas sulfur % 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 

Diesel sulfur % 0.025 0.025 0.0015 0.0015 0.0015 0.0015 0.0015 0.0015 0.0015 0.0015 

CNG/LPG sulfur % 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 

Minimum temper. (F) 42 42 42 42 42 42 42 42 42 42 

Maximum temper. (F) 66 66 66 66 66 66 66 66 66 66 

Average temper. (F) 51.9 51.9 51.9 51.9 51.9 51.9 51.9 51.9 51.9 51.9 

Altitude of region low low low low low low low low low low 

Airport ground support equipment (GSE) was removed from the NONROAD emissions 

estimates because they were handled separately, as described above in Section 3.1.1. 

Recreational marine estimates were also removed since the major water areas in Clark County lie 

outside of the modeling domain. Railroad maintenance emissions for the 1996 base case were 

extracted from the non-road output and processed with locomotive emissions. 

Table 3-7 presents a summary of NONROAD model CO emissions estimates for the base year 

and all future years evaluated in this modeling. The NONROAD model estimates emissions for 

the entirety of Clark County; the emissions shown in Table 3-7 are those for the modeling 

domain only. The gridding approach is described in the next subsection. 
August 2005 

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Table 3-7. Clark County CO NONROAD gridded emission estimates (TPD). 

Base 2006 2010 2015 2020 2030 

Sunday 12/8/2005 

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 & 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 

Monday 12/9/2005 

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 & 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 

3.1.3.2 Base Year Gridding Surrogates

Base year emission estimates were allocated to the modeling grid cells using spatial surrogates 

developed from land use acreage obtained from the Clark County RTC. These surrogate data 

were the same that were used in the 2000 SIP submittal. However, since the NONROAD Model 

generates more source categories than were originally used in the 2000 SIP, additional surrogates 

were developed for this base inventory. Tables 3-8 and 3-9 indicate the categories provided by 

Clark County and the surrogate category mapping used for the base inventory. 

The original Clark County land use data set covers the UAM modeling domain for the Las Vegas 

urban growth area while the NONROAD emissions estimates are county totals. Therefore, an 

additional set of county-wide landuse data provided by RTC was used to estimate the fraction of 

each category that was allocated to the modeling grid. Table 3-10 lists the surrogates that were 

used to spatially allocate each of the NONROAD source categories to the UAM grid, and the 

fraction of county surrogate within the modeling domain. 

3.1.3.3 Future Year Gridding Surrogates

Future-year emissions estimates were allocated to the modeling grid cells using a different set of 

spatial surrogates that were developed from an updated land use database obtained from the 

Clark County RTC. The updated land use data were developed for the year 2003 and 

characterized the land use in the entire county based on the descriptions given in Table 3-11. 

Figure 3-5 displays a subset of these data for the Las Vegas area as aggregated land use 

categories for clarity. 
August 2005 

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Table 3-8. Base year non-road surrogate categories. 

Category Description 

 Rural 1-2 units per acre 

 Low Density 3-5 units per acre 

 Medium 6-8 units per acre 

 Medium High 9-18 u/ac, single level apts., some trailer, multi-family low

 High Density 7-18 u/ac, multi-level apartments, some trailer parks 

 Neighborhood Retail grocery, convenience, restaurants, service station, etc. 

 Community Retail large shopping centers 

 Regional Retail small shopping malls, factory outlet 

 Resort Casino casinos with table gaming 

 Office office complexes, government, medical, banking, etc. 

 Light Industrial small manufacturing, repair, warehousing, etc. 

 Heavy Industrial cement plants, steel, BMI complex, larger manufacturing

 Government non-office building government (fire, police, bus yard) 

 Education schools and attached parks 

 Hospitals hospitals only 

 Parks and Golf Courses free standing parks (incl. buildings) 

 Public Facilities limited trip generators (landfill, utility facilities) 

 Open Space drainages and other un-developable land 

 Mining gravel pits, excavation projects 

 Religion churches, etc. 

 Special Generators UNLV, McCarran Airport, Nellis AFB, etc. 

 Vacant land that can be developed 

 Agriculture farming 
August 2005 

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Table 3-9. Land use category to surrogate code mapping. 

Surrogate 

Code 

Surrogate 

Description Based on 1995 LULC categories 

1 Housing rural + low density + medium + medium high + high density 

2 Industrial light industrial + heavy industrial 

3 Commercial neighborhood retail + community retail + regional retail 

4 Buildings 

above Housing + above Commercial + above Industrial + 

casinos + office + government + education + hospitals + public 

facilities + religion 

5 Land area land area 

6 Casinos resort and casinos 

7 

Recreational 

Space open space + mining + vacant 

8 

Commercial 

Lawn & Garden 

neighborhood retail + community retail + regional retail + parks 

and golf courses 

9 Golf Courses parks and golf courses 

10 Agriculture agriculture 

11 Vacant Land vacant land 

12 Population density weighted housing 

Table 3-10. Source category cross references to gridded surrogates for NONROAD sources 

with county-to-modeling grid adjustment factors. 

Surrogate 

Code SCC 

Adjustment 

Factor Description Surrogate Description 

1 22xx004xxx 0.950 Lawn & Garden Equipment Housing 

2 22xx003xxx 0.786 Industrial Equipment Industrial 

3 22xx006xxx 0.786 Light Commercial Commercial 

7 22xx001xxx 0.244 Recreational Vehicles Recreational Space 

8 22xx004yyy 0.802 Lawn and Garden Equipment (Commercial) Commercial Lawn & Garden

9 22xx001050 0.802 Recreational Vehicles, Golf Carts Golf Courses 

10 22xx005xxx 0.113 Farm Equipment Agriculture 

11 22xx002xxx 0.958 Construction Equipment Vacant Land 
August 2005 

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Table 3-11. Land use categories available in the Clark County GIS data coverages for 2003.

# LU_TDFM NOTE DENSITY AVG

1 RRes Residential - Rural < 2 2.0

2 LDRes Residential - Low Density >= 2, < 6 5.0

3 MDRes Residential - Mid Density >= 6, < 8 6.0

4 MHDRes Residential - Mid-High Density >= 8, < 13.5 12.0

5 HDRes Residential - High Density >= 13.5 16.0

6 Hotel_R Hotel&Resort

7 Hotel_H Hotel

8 Casino Casino

9 RRet Retail - Regional

10 CRet Retail - Community

11 NRet Retail - Neighborhood

12 CarSale Retail - Auto Dealership

13 ORet Retail - Race Track, etc

14 Office Office

15 Hospital Hospital and Medical Center

16 School School

17 Religiou Religious

18 P_F Police and Fire Station

19 Trans_1 Transportation - Terminal, Depot, etc

20 Warehous Warehouse

21 REC_O Recreational - out door (golf course, race track)

22 REC_I Recreational - indoor

23 REC_RP Recreational - RV Park

24 Parking Parking lot, garage

25 OS Open Space

26 LInd Light Industrial

27 HInd Heavy Industrial

28 AgMining Agriculture, Ranching, Mining

29 ROW Right-Of-Way

30 PHeld Public Land Management Area\Public Held

31 NAFB Nellis AFB

32 MIA MaCarran Int'l Airport

33 UNLV UNLV

34 Vac Vacant
August 2005 

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Figure 3-5. 2003 land use data for the Las Vegas area of Clark County. 

For future-year land use, Clark County provided GIS databases that specify which vacant land 

parcels in the 2003 dataset are to be developed for each of the planning years 2005, 2010, 2015, 

2020, 2025 and 2030, as well as the planned land use for that parcel. The land use planning 

databases included separate GIS coverages for Las Vegas, North Las Vegas, Henderson and the 

rest of Clark County. Land use coverages for each of the future years modeled were developed 

by replacing those vacant land parcels in the land use base-year datasets with the future year 

planned land use category. Each of the future year GIS databases was developed incrementally 

from the previous planning year starting from the 2003 land use base year database. 

The Arc/INFO GIS was used to generate the required spatial surrogate ratios for the development 

of gridding surrogates. Within the GIS, each future year land use coverage was overlayed with 

the modeling grid and the fraction of each land use type in each grid cell was calculated. 

Because the land use categories available in the databases (Table 3-11) are more detailed than 

required for spatial allocation of emission estimates, they were aggregated prior to the 

development of the surrogate ratios. Table 3-12 presents the aggregation scheme used for the 

project. 

Table 3-13 provides a comparison of the domain-wide percentage of primary land use categories 

used for allocation of non-road mobile source emissions for each of the future years modeled. 
August 2005 

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Table 3-12. Landuse category aggregation used for developing spatial allocation surrogates for 

non-road categories. 

Surrogate 

Code 

Surrogate 

Description Based on 1995 LULC categories 

1 Housing 

residential: rural + low + mid + mid-high + high density + single 

family + multi family 

2 Industrial light industrial + heavy industrial + industrial 

3 Commercial 

neighborhood retail + community retail + regional retail + 

racetrack retail + car sale retail 

4 Buildings 

above Housing + above Industrial + above Commercial + 

hotels + casinos + office + government + education + hospitals 

+ public facilities + religion 

5 Land area land area 

6 Casinos hotels + hotels&resort + casinos 

7 

Recreational 

Space recreational outdoor + open space + vacant land 

8 

Commercial 

Lawn & Garden 

neighborhood retail + community retail + regional retail + 

recreational_outdoor + hotel&resort + school + hospital 

9 Golf Courses Recreational – outdoor 

10 Agriculture Agriculture, Ranching and Mining 

11 Vacant Land vacant land 

Table 3-13. Comparison of domain-wide land use percentages for future year spatial allocation. 

Year Housing Industrial Commercial Buildings

Land 

Area Casinos

Rec 

Space

Comm 

L&G GolfCrses Agriculture Vacant

2005 0.812 0.611 0.741 0.775 0.120 0.845 0.091 0.793 0.794 0.140 0.086

2010 0.886 0.672 0.772 0.844 0.120 0.857 0.075 0.816 0.794 0.140 0.069

2015 0.895 0.702 0.788 0.853 0.120 0.870 0.071 0.826 0.794 0.140 0.064

2020 0.898 0.726 0.801 0.860 0.120 0.877 0.068 0.833 0.794 0.140 0.061

2025 0.901 0.736 0.806 0.864 0.120 0.881 0.066 0.837 0.794 0.140 0.059

2030 0.903 0.748 0.811 0.867 0.120 0.885 0.065 0.840 0.794 0.140 0.058

% of county total within modeling domain

3.1.3.4 Temporal Allocation

Figure 3-6 shows the hourly distribution used to temporally allocate non-road sources. 

3.2 POINT SOURCES 

The 1996 base year point source inventory from the original 2000 SIP modeling was used for 

this update. Clark County provided an updated point source emission inventory for future years 

that included updated stack parameters and emissions based on “Potential To Emit” (PTE) levels 

for seven specific facilities. The UAM future year inventories included PTE levels plus a 70 

ton/year buffer for these sources. All future year modeling used the same future year point 

source data. Table 3-14 indicates the future year tons per year estimates by facility provided by 

Clark County. Table 3-15 shows a breakdown by elevated and low-level point sources. 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_3_Other.doc 3-15 

Figure 3-6. Hourly activity profile used to temporally allocate non-road emissions. 

Table 3-14. Clark County CO future year Potential To Emit (PTE) estimates + 70 TPY by 

facility. 

Facility Name 

PTE + 70 

(tons/Year) 

Nevada Power- Clark Station (NDEP) 620.9

Nevada Power- Clark Station (DAQM) 2106.9

Nevada Power - Sunrise Station (NDEP) 392.9

Nevada Power - Sunrise Station (DAQM) 463.5

Titanium Metals 1707.8

USAF - 99 CES/CEV 295.7

James Hardie Gypsum/BPB Gypsum, Inc 184.4

Total 5772.1

Table 3-15. Modeling CO point source emission estimates (TPD). 

 Base Future Years 

Elevated 2.07 15.53

Low Level 1.06 0.28

Total 3.13 15.82

3.3 AREA SOURCES 

The 1996 base year area source estimates were taken from the 2000 SIP modeling with no 

changes. The base year emissions were projected by the factors shown in Table 3-16 to the 

future modeling years. These factors were developed by the Clark County Department of Air 

Quality and Environmental Management. Values were interpolated for those modeling years in 

between reported years. 

0

0.02

0.04

0.06

0.08

0.1

0.12

13579

11131517192123

Hour
August 2005 

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Table 3-16. Future year growth/projection factors for area sources. 

Adjustment Factors Applied to Base Year 

Category Description 2006 2010 2015 2020 2030 

Electric Utility Generation 1.2312 1.3154 1.4101 1.5048 1.6942

Small Stationary 1.2632 1.3623 1.4738 1.5853 1.8083

Boiler Emissions 1.2632 1.3623 1.4738 1.5853 1.8083

Industrial Natural Gas 1.2636 1.3627 1.4743 1.5858 1.8089

Commercial Natural Gas 1.2291 1.3429 1.4331 1.5233 1.7037

Residential Natural Gas 1.1686 1.2329 1.2917 1.3504 1.4679

Fireplaces 1.5022 1.7254 2.0221 2.3187 2.9121

Railroad Equipment 0.9479 0.9341 0.9186 0.9031 0.8722

Brush Fires 1.5022 1.7254 2.0221 2.3187 2.9121

Cigarette Smoking 1.5022 1.7254 2.0221 2.3187 2.9121

Structural Fires 1.5022 1.7254 2.0221 2.3187 2.9121

Vehicular Fires 1.5022 1.7254 2.0221 2.3187 2.9121

3.3.1 Area Source Gridding Surrogates 

The 1996 base year area source emissions were spatially allocated to the modeling domain using 

the same gridding surrogates that were developed for the 2000 SIP. The future year gridding 

surrogates were based upon those developed for the non-road emission categories, as described 

in Section 3.1.3.3. The only change needed for area source categories was to normalize them 

relative to the modeling domain (instead of county total), since the original area source emission 

estimates were wholly contained within the UAM domain. 

A summary of area source emissions by category is provided in Table 3-17 for each future year. 

3.4 SUMMARY OF TOTAL EMISSIONS 

Table 3-18 presents a summary of total daily CO emissions by source category, including onroad emissions, for 1996 base and all future years. Figures 3-7 through 3-9 show the spatial 

distribution of component and total CO emissions for the 1996 base case. Figures 3-10 through 

3-14 show the spatial distribution of total CO emissions for all future years.
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_3_Other.doc 3-17 

Table 3-17. Clark County CO area source gridded emission estimates (TPD) after season, and 

day-of-week adjustments. 

Source Category Base 2006 2010 2015 2020 2030 

Sunday 12/8 

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 14.270 16.200 18.131 21.991

Monday 12/9 

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 14.654 16.615 18.576 22.497
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_3_Other.doc 3-18 

Table 3-18. Summary of total daily CO emissions (TPD) in the UAM CO SIP revision. 

Base 2006 2010 2015 2020 2030 

Sunday 12/8

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 Intrazonals 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 AFB 2.86 2.86 2.86 2.86 2.86 2.86

North LV 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

Monday 12/9 

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 Intrazonals 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 AFB 2.86 2.86 2.86 2.86 2.86 2.86

North LV 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
August 2005 

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Figure 3-7. Spatial distribution of airport and locomotive CO emissions for the 1996 Base 

Case. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Airports and Rail Emissions

Base Year - Dec 8, 1996

CO (tons per day)
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_3_Other.doc 3-20 

Figure 3-8. Spatial distribution of non-road and area source CO emissions for the 1996 Base 

Case. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.00

0.08

0.16

0.24

0.32

0.40

0.48

0.56

0.64

0.72

Area and NONROAD Emissions

Base Year - Dec 9, 1996

CO (tons per day)
August 2005 

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Figure 3-9. Spatial distribution of total surface gridded CO emissions for the 1996 Base Case. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM 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)
August 2005 

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Figure 3-10. Spatial distribution of total surface gridded CO emissions for the 2006 future year. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM 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, 2006

CO (tons per day)
August 2005 

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Figure 3-11. Spatial distribution of total surface gridded CO emissions for the 2010 future year. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM 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, 2010

CO (tons per day)
August 2005 

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Figure 3-12. Spatial distribution of total surface gridded CO emissions for the 2015 future year. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM 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, 2015

CO (tons per day)
August 2005 

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Figure 3-13. Spatial distribution of total surface gridded CO emissions for the 2020 future year. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM 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, 2020

CO (tons per day)
August 2005 

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Figure 3-14. Spatial distribution of total surface gridded CO emissions for the 2030 future year. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM 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)
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-1 

4. URBAN AIRSHED MODELING 

The Urban Airshed Model (UAM) was provided with the updated emission inventories for onroad mobile, non-road mobile, point and area sources, and run for the December 8-9, 1996 

historical CO event. All other environmental parameters were taken from the original modeling 

as documented in the 2000 CO SIP. A base-year CO model performance evaluation was 

similarly conducted. The UAM was then used with the updated future year inventories for 2006, 

2010, 2015, 2020 and 2030 to determine peak 8-hour CO levels in the basin for the same 

December 8-9, 1996 conditions. 

For the future year assessments, we addressed UAM valley-wide CO distributions, intersection 

“hot spot” modeling with CAL3QHC, and the updated EDMS micro-scale results reported by 

Ricondo (2003). With regard to the airports, it was necessary to run UAM twice using two 

different inventories per future year: 

1. Valley-wide CO and micro-scale intersection modeling – including updated EDMS 

emissions in the UAM; 

2. Micro-scale airport CO modeling – removing EDMS airport emissions from the UAM 

inventory in order to avoid double-counting. 

EDMS results from the Ricondo (2003) analyses were combined with the revised UAM model 

predictions for the future years of 2006, 2010, 2015, 2020 to estimate 8-hour CO concentrations 

for the duration of the episode on and around the airport properties. This was not done for the 

1996 base case since the EDMS dispersion results for that year are considered out-dated. Note 

that the 2005 EDMS results were added to the 2006 UAM results, and that 2030 was disregarded 

since it was not considered in the EDMS analysis. 

For hotspot modeling, the CAL3QHC model was used to model three intersections: 

Charleston/Eastern, Charleston/Fremont and Eastern/Fremont, which are referred to collectively 

as the “Five Points” area. EPA (1992, 1995) guidance for screening level modeling of these 

three intersections was followed. The ambient temperature for each hour of the episode (needed 

to estimate emissions with the MOBILE6 model), and the wind direction and speed (needed for 

the CAL3QHC dispersion estimates) were taken from the original UAM/CAL3QHC modeling 

documented in the 2000 SIP. The same MOBILE6 inputs documented for the on-road emissions 

calculations in Section 2 were used to estimate emission inputs for CAL3QHC. The CAL3QHC 

model output was added to the background UAM levels to estimate 8-hour CO concentrations 

for the duration of the episode. 

Following the micro-scale analyses, additional ancillary simulations were run with UAM to 

develop on-road mobile emission budgets, both for the entire modeling domain and just the 

central urban portion, that demonstrate compliance with the 8-hour CO standard. 
August 2005 

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4.1 BASE CASE SIMULATION 

The UAM was used to simulate the emissions and transport of carbon monoxide throughout the 

Las Vegas Valley during the night of December 8-9, 1996 (Sunday-Monday). Specifically, the 

UAM was run from 1500 LST December 8 to 1100 LST December 9 to cover the most cold, 

stagnant and stable portion of the episode during which CO was observed to build up. Two base 

case simulations were run: 

A. With revised on-road emission estimates, keeping all point, area, and non-road 

emissions the same as the 2000 SIP modeling (see Section 4.1.1); 

B. With both revised on-road and non-road emission estimates, keeping all point and 

area emission the same as the 2000 SIP modeling (see Section 4.1.2). 

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

emissions inventory. Model performance was evaluated graphically and statistically relative to 

the observational data that were available during this period. EPA (1992) provides the following 

criteria that must be met in order to consider UAM performance acceptable for CO attainment 

demonstrations: 

1. The unpaired peak prediction accuracy (UPPA; a comparison between the peak 

measurement and the peak prediction anywhere in the domain at any time) must be 

within ±30-35%; 

2. The average gross error among all paired measured and predicted peaks (matched in 

space and time) above 5 ppm must be within 20-25%; 

3. The average gross error in the timing of the predicted peaks among all sites above 5 

ppm must be within 2 hours. 

4.1.1 UAM Results From Revised On-Road Emissions 

Figure 4-1 shows the UAM predicted episode-maximum 8-hour CO concentrations (ppm) from 

the base case simulation using the revised on-road emissions documented in Section 2. Two 

distinct areas of CO maxima occur in the simulation: (1) near the “elbow” of U.S. 95 in northeast 

Las Vegas, and (2) along the Las Vegas Boulevard “strip” near the intersection with Spring 

Mountain Road. The peak in the domain is 10.7 ppm along Las Vegas Boulevard. The 

secondary maximum reaches above 9 ppm along U.S. 95, and this occurs during the morning 

commute hours on Monday, December 9. Overall, the spatial pattern of predicted 8-hour 

maximum CO agrees with the previous modeling performed for the 2000 CO SIP, and with the 

distribution of observed CO for this period. 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-3 

 

Figure 4-1. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) for 

the December 8-9, 1996 Base Case with updated on-road mobile emissions. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

5

6

7

8

9

10

11

12

ppm

UAM Max 8-hour CO Concentrations

 1996 Base Case (96B07)

Peak = 10.7 ppm
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-4 

Standard and EPA criteria model performance statistics are shown in Table 4-1 for this 

simulation. These statistics are based upon pairings of 8-hour CO predictions and observations 

across all available monitoring sites for the period, which include standard EPA-method 

monitoring conducted by Clark County, as well as special saturation monitoring performed for 

the Las Vegas Phase II field monitoring study (Egami et al., 1998; Emery et al., 1998). Figure 

4-2 shows the locations of all monitoring sites operating during the Phase II field study, while 

Table 4-2 lists the site names with their coordinates. Based upon these statistics, UAM 

performance is quite good and should be considered acceptable. 

Table 4-1. Summary performance statistics for the December 8-9, 1996 Base Case, with 

updated on-road mobile source emissions. Bold/colored metrics denote EPA criteria statistics; 

green (red) indicates within (outside) acceptance criteria. 

Peak 8-hour Observation 9.6 ppm, Marnell Field 

Unpaired Peak 10.7 ppm 

Paired Peak 8.1 ppm 

Statistical Measures 

Unpaired Peak Accuracy 12 % 

Paired Peak Accuracy -15 % 

Peak Timing Error 1 hr 

Average Peak Bias > 5 ppm -5 % 

Average Peak Error > 5 ppm 12 % 

Average Peak Timing Bias > 5 ppm 1 hr 

Average Peak Timing Error > 5 ppm 2 hr 

Overall Bias > 5 ppm -7 % 

Overall Error > 5 ppm 14 % 

Figure 4-3 presents hourly time series of observed and predicted CO concentrations at each of 

these monitoring sites. The dots represent the observations at each site, while the solid line 

shows the UAM prediction at that location. The gray shaded area delineates the minimum to 

maximum predicted CO concentrations within the surrounding nine grid cells around each site to 

indicate the extent of predicted spatial gradients. Overall, the trends are reproduced adequately. 

Some notable exceptions include City Center, Shadow Lane, Winterwood, MGM, and Eastern 

and Owens. The MGM site was new in 1995 and measured micro-scale influences near the 

busiest intersections on Las Vegas Boulevard. The general under prediction there is likely due to 

the inability of UAM to resolve the small scale conditions. The Eastern and Owens special study 

site is located about 2.5 km north of U.S. 95 in northeastern Las Vegas; according to Egami et al. 

(1998), this site is situated in a local depression, and a pooling of locally-derived CO may be 

occurring there. The other identified sites are located within or very near high emission density 

grid cells (freeways) and over predictions at these sites might be the result from a “smearing” of 

high CO emissions over the entire 1 km grid cells. In most cases the range of predicted CO 

within one grid cell of each site is sufficient to contain the observed CO each hour. 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-5 

Figure 4-2. Locations of all Phase II monitoring sites operating during the Phase II field study 

over the winter of 1996/97 (Emery et al., 1998). 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-6 

Table 4-2. Names and coordinates of all monitoring sites operating during the Phase II field 

study over the winter of 1996/97 (Egami et al., 1998). The first 14 sites are the standard Clark 

County sites. 

Symbol Site Name 

UTM 

Easting (km)

UTM 

Northing (km) 

BS Craig Road/Bemis 671.439 4012.654 

CC City Center 667.440 4004.817 

CW Crestwood 668.500 4002.500 

EC East Charleston 670.028 4003.124 

FL East Flamingo 665.386 3998.034 

GV Green Valley 675.025 3991.294 

MC Maycliff 672.246 4001.458 

MG MGM 664.600 3996.700 

PL Powerline 680.431 3989.445 

PM Paul Meyer 657.191 3997.118 

PT Pittman 680.390 3991.640 

SA Sunrise Acres 669.675 4003.630 

SL Shadow Lane 665.304 4003.473 

WW Winterwood 675.025 4001.446 

ECB East Charleston DRI 670.028 4003.124 

MAF Marnel Field 669.804 4003.776 

EAB Eastern & Bonanza 669.720 4004.636 

EAO Eastern and Owens 669.722 4006.290 

BAG Bruce and Grayson 668.604 4005.709 

CAR Carson and 17th 668.510 4003.407 

EAT Eastern and Tioga 669.226 3998.931 

SLA St. Louis & Atlantic 669.836 4001.811 

CAP Charleston and Pecos 671.152 4003.252 

CAS Charleston & Sacrame 672.130 4003.142 

PVP Paradise Valley Park 670.171 3996.693 

DRS Del Robison School 673.511 4005.104 

SIL Silver Bowl 679.238 3995.384 

ALC Alhambra & Cordova 667.151 4001.601 
August 2005 

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Figure 4-3. Time series of hourly CO measurements (dots) and UAM predictions (line) at 

Phase II field study monitoring sites. Plots cover the period 1500 LST December 8 to 1100 LST 

December 9, 1996. Gray shading indicates the range of minimum to maximum predicted CO 

concentrations in the nine cells surrounding each site. 

BS: Craig Road/Bemis 671.439 4012.654

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

CC: City Center 667.440 4004.817

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

CW: Crestwood 668.500 4002.500

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

EC: East Charleston 670.028 4003.124

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-8 

Figure 4-3. (continued). 

FL: East Flamingo 665.386 3998.034

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

GV: Green Valley 675.025 3991.294

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

MC: Maycliff 672.246 4001.458

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

MG: MGM 664.600 3996.700

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-9 

Figure 4-3. (continued). 

PL: Powerline 680.431 3989.445

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

PM: Paul Meyer 657.191 3997.118

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

PT: Pittman 680.390 3991.640

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

SA: Sunrise Acres 669.675 4003.630

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-10 

Figure 4-3. (continued). 

SL: Shadow Lane 665.304 4003.473

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

WW: Winterwood 675.025 4001.446

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

ECB: East Charleston DRI 670.028 4003.124

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

MAF: Marnel Field 669.804 4003.776

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-11 

Figure 4-3. (continued). 

EAB: Eastern & Bonanza 669.720 4004.636

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

EAO: Eastern and Owens 669.722 4006.290

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

BAG: Bruce and Grayson 668.604 4005.709

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

CAR: Carson and 17th 668.510 4003.407

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-12 

Figure 4-3. (continued).

EAT: Eastern and Tioga 669.226 3998.931

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

SLA: St. Louis & Atlantic 669.836 4001.811

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

CAP: Charleston and Pecos 671.152 4003.252

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

CAS: Charleston & Sacrame 672.130 4003.142

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-13 

Figure 4-3. (concluded). 

PVP: Paradise Valley Park 670.171 3996.693

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

DRS: Del Robison School 673.511 4005.104

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

SIL: Silver Bowl 679.238 3995.384

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted

ALC: Alhambra & Cordova 667.151 4001.601

0

5

10

15

12/8/1996

Date

CO [ppm]

Minimum to Maximum Range Observed Predicted
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-14 

A scatter diagram of all observations and predictions combined from all monitoring sites is 

provided in Figure 4-4. The slope of the regression line is near 1:1, which indicates that the 

UAM develops only a minor negative bias tendency towards increasing CO concentrations. 

Model performance in this regard is quite good and encouraging. The R2 value (fraction of 

variation explained) provides a quantitative measure that indicates a large degree of scatter (as 

seen in the spread of the observation-prediction pairings). At first glance an R2 value of 0.62 

would appear to be low; however this is a common trait of dispersion modeling and so UAM 

performance in this regard is not particularly problematic when considered in that context. 

Figure 4-4. Scatter diagram of UAM predictions vs. observations for the 1996 Base Case. The 

linear regression equation is given as the bold line. 

4.1.2 UAM Results From Revised On-Road and Non-Road Emissions 

Figure 4-5 shows the UAM predicted episode-maximum 8-hour CO concentrations (ppm) from 

the base case simulation using the revised on-road and non-road emissions documented in 

Sections 2 and 3. Overall the pattern is quite similar to the results described in Section 4.1.1, 

with a slight increase in CO of a few tenths of a ppm. The peak in the domain is 11.4 ppm along 

Las Vegas Boulevard. 

Scatter Plot of Predicted vs. Observed Concentrations

LV Dec 8-9

y = 0.7946x + 1.301

R2

 = 0.6211

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Observed [ppm]

Predicted [ppm]
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-15 

Figure 4-5. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) for 

the December 8-9, 1996 Base Case with updated on-road and non-road mobile emissions. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM 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
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-16 

Standard and EPA criteria model performance statistics are shown in Table 4-3 for this 

simulation. UAM performance is quite similar to the previous run, and should be considered 

acceptable. 

Figure 4-6 presents hourly time series of observed and predicted CO concentrations at each of 

the monitoring sites. The dots represent the observations at each site, while the black solid line 

shows the UAM predictions from Section 4.1.1, and the red solid line shows the UAM 

predictions with the addition of updated non-road emissions. Differences in the model 

predictions only appear in the morning hours, when non-road emissions begin to build up. 

However, these differences are insignificant as they are certainly within model uncertainty, and 

they do not overtly impact model performance.

Table 4-3. Summary performance statistics for the December 8-9, 1996 Base Case with 

updated on-road and non-road mobile source emissions. Bold/colored metrics denote EPA 

criteria statistics; green (red) indicates within (outside) acceptance criteria. 

Peak 8-hour Observation 9.6 ppm, Marnell Field 

Unpaired Peak 11.4 ppm 

Paired Peak 8.1 ppm 

Statistical Measures 

Unpaired Peak Accuracy 19 % 

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 % 

4.2 FUTURE YEAR SIMULATIONS 

Figures 4-7 through 4-11 display predicted 8-hour maximum CO concentrations in the modeling 

domain for the years 2006, 2010, 2015, 2020, and 2030, respectively. UAM predictions show 

that the 8-hour CO standard of 9 ppm will not be violated anywhere within the domain. Peak 8-

hour CO decreases in each year to 2015, then begins to increase out to 2030: 

 Year Peak 8-hour CO

 2006 7.4 

 2010 7.2 

 2015 6.5 

 2020 6.7 

 2030 8.0 

Note that the contribution of McCarran airport to local CO concentrations in that area steadily 

increases over this period. This is due to the projected growth in airport activities as reported by 

Ricondo (2003). In each successive year through 2020, however, the contribution from on-road 

mobile sources diminishes, while the peak moves from the U.S. 95 “elbow” in northeast Las 

Vegas to the northern boundary of McCarran airport along Tropicana Boulevard. Like the 1996 

Base Case, a lower secondary peak occurs in the Las Vegas Boulevard area near Spring 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-17 

Figure 4-6. Time series of hourly CO measurements (dots) and UAM predictions (black line = 

revised on-road emissions, red line = revised on-road and non-road emissions) at Phase II field 

study monitoring sites. Plots cover the period 1500 LST December 8 to 1100 LST December 9, 

1996. 

BS: Craig Road/Bemis 671.439 4012.654

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

CC: City Center 667.440 4004.817

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

CW: Crestwood 668.500 4002.500

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

EC: East Charleston 670.028 4003.124

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-18 

Figure 4-6. (continued). 

FL: East Flamingo 665.386 3998.034

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

GV: Green Valley 675.025 3991.294

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

MC: Maycliff 672.246 4001.458

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

MG: MGM 664.600 3996.700

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-19 

Figure 4-6. (continued). 

PL: Powerline 680.431 3989.445

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

PM: Paul Meyer 657.191 3997.118

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

PT: Pittman 680.390 3991.640

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

SA: Sunrise Acres 669.675 4003.630

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-20 

Figure 4-6. (continued). 

SL: Shadow Lane 665.304 4003.473

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

WW: Winterwood 675.025 4001.446

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

ECB: East Charleston DRI 670.028 4003.124

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

MAF: Marnel Field 669.804 4003.776

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-21 

Figure 4-6. (continued). 

EAB: Eastern & Bonanza 669.720 4004.636

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

EAO: Eastern and Owens 669.722 4006.290

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

BAG: Bruce and Grayson 668.604 4005.709

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

CAR: Carson and 17th 668.510 4003.407

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-22 

Figure 4-6. (continued).

EAT: Eastern and Tioga 669.226 3998.931

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

SLA: St. Louis & Atlantic 669.836 4001.811

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

CAP: Charleston and Pecos 671.152 4003.252

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

CAS: Charleston & Sacrame 672.130 4003.142

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-23 

Figure 4-6. (concluded).

PVP: Paradise Valley Park 670.171 3996.693

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

DRS: Del Robison School 673.511 4005.104

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

SIL: Silver Bowl 679.238 3995.384

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 

ALC: Alhambra & Cordova 667.151 4001.601

0

5

10

15

12/8/1996

Date

CO [ppm]

 Observed New _NR Orig_NR 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-24 

Figure 4-7. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) for 

the December 8-9, 1996 episode using emission forecasts for 2006. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

5

6

7

8

9

10

11

12

ppm

UAM Max 8-hour CO Concentrations

 2006 Future Year

Peak = 7.37 ppm
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-25 

Figure 4-8. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) for 

the December 8-9, 1996 episode using emission forecasts for 2010. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

5

6

7

8

9

10

11

12

ppm

UAM Max 8-hour CO Concentrations

 2010 Future Year

Peak = 7.17 ppm
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-26 

Figure 4-9. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) for 

the December 8-9, 1996 episode using emission forecasts for 2015. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

5

6

7

8

9

10

11

12

ppm

UAM Max 8-hour CO Concentrations

 2015 Future Year

Peak = 6.47 ppm
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-27 

Figure 4-10. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) 

for the December 8-9, 1996 episode using emission forecasts for 2020. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

5

6

7

8

9

10

11

12

ppm

UAM Max 8-hour CO Concentrations

 2020 Future Year

Peak = 6.74 ppm
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-28 

Figure 4-11. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) 

for the December 8-9, 1996 episode using emission forecasts for 2030. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

5

6

7

8

9

10

11

12

ppm

UAM Max 8-hour CO Concentrations

 2030 Future Year

Peak = 7.96 ppm
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-29 

Mountain Road. The Las Vegas Boulevard – Spring Mountain road area possesses a high 

concentration of parking structures, which leads to a local maximum in trip starts in the RTC 

TransCAD transportation demand model, and therefore a local maximum in vehicle “start” 

emissions in the modeling emission inventory. This poses a potential for an actual local 

emissions “hot spot” in this area. However, Clark County recently undertook a saturation study 

in 2002 (T&B Systems and Parsons Engineering Science, 20021) to address this possibility. 

Although the TransCAD, EPS, and UAM modeling show a potential emissions hot spot at Spring 

Mountain Road and Las Vegas Boulevard, the 2002 saturation study showed no hot spot at all in 

that location. 

4.3 MICROSCALE MODELING 

Future year UAM simulation results were used to provide estimates of background ambient CO 

levels for micro-scale modeling performed for the “Five Points” hot spot intersection and for the 

three civil airports in the modeling domain (McCarran, Henderson Executive, and North Las 

Vegas). UAM concentrations from the appropriate grid cells were simply added to the 

concentrations predicted at each micro-scale receptor to obtain a total (background + microscale) CO concentration. Results are presented in the following sub-sections. 

4.3.1 CAL3QHC Intersection Modeling 

Table 4-4 presents the peak UAM + CAL3QHC 8-hour average CO concentrations predicted in 

each of the future years for each of the three intersections in the “Five Points” area. All values 

are well below the 9 ppm standard. 

Table 4-4. Peak UAM + CAL3QHC 8-hour average CO concentrations (ppm) predicted for 

each future year and for each intersection. 

Year Eastern/Charleston Eastern/Fremont Fremont/Charleston 

2006 6.14 5.66 5.09 

2010 5.61 5.32 4.81 

2015 4.97 4.76 4.31 

2020 4.67 4.48 4.07 

2030 4.83 4.58 4.20 

4.3.2 EDMS Airport Modeling 

In consideration of micro-scale airport modeling, the UAM was run for all future years with 

exactly the same inputs as described in Section 4.2; however, airport emissions for the three civil 

airports in the domain were removed from the UAM inventory to avoid double counting. Clark 

County provided EDMS simulations for 2005, 2010, 2015 and 2020, based on the work of 

Ricondo (2003). In each of these years, several receptors at McCarran airport reported total 8-

hour CO concentrations (sum of EDMS and UAM components) above the 8-hour CO standard of 

9 ppm. Note, however, that all receptors above the 9 ppm standard in all future years evaluated 

 

1 Information regarding the 2002 Las Vegas Boulevard Saturation Study can be found at 

http://www.co.clark.nv.us/air_quality/Studies/COSat1-7.pdf. 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-30 

occur within areas that are not publicly accessible, as defined by Ricondo (2005). Disregarding 

any receptors in publicly restricted areas removes all exceedance estimates. 

Table 4-5 presents the peak total 8-hour CO concentration at all three airports for each future 

year evaluated. Values for McCarran are taken from the peak publicly accessible receptor. All 

peak CO concentrations are below the 9 ppm standard in all years. 

Table 4-5. Peak total UAM + EDMS 8-hour CO concentrations (ppm) at all three airports and 

for all future years evaluated. Values shown for McCarran airport occur at the peak publicly 

accessible receptor. 

Airport 2005 2010 2015 2020 

McCarran 7.47 7.14 7.60 8.45 

Henderson Executive 1.12 1.36 1.99 3.05 

North Las Vegas 5.01 5.04 4.46 4.19 

 

4.4 ESTIMATING ON-ROAD EMISSION BUDGETS 

The UAM was used to undertake several sensitivity tests to refine the estimation of future year 

on-road mobile CO emission budgets for the central, most urbanized portion of the modeling 

domain. The definition of the central urban sub-domain is given in Table 4-6 and shown in 

Figure 4-12. The first analysis tested the assertion that the emissions inventory outside of the 

central urban sub-domain has no significant impact on CO concentrations downtown, along the 

Las Vegas Boulevard “strip”, and in traditional “hot spot” areas. Emissions in the outer grid area 

were doubled for each future year, and the UAM was run to show the incremental impact on the 

peak CO concentration. 

In the second analysis, on-road mobile source emissions were scaled up over the entire domain to 

the point at which the peak 8-hour CO concentration reached 8.9 ppm in each of the future years. 

Hence, the resulting daily on-road emission totals for December 9 can be used to establish 

future-year emission budgets for both the entire domain and the central urban sub-domain. 

Table 4-6. Grid definition of the central urban sub-domain. 

 Column Row UTM East UTM North 

Low-left 11 19 652.000 3991.000 

Upper-Right 36 45 678.000 4018.000 

4.4.1 Impacts of Emissions from the Outer Domain 

The total CO emissions inventory in the outer area of the modeling domain was doubled to 

investigate the sensitivity of peak predicted CO in central Las Vegas to outlying emission 

sources. As shown in Table 4-7, peak 8-hour CO concentrations changed by a maximum of only 

0.07 ppm. There was no change in the location of the predicted peak. 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-31 

Figure 4-12. Location of the central urban sub-domain used in the UAM sensitivity tests (heavy 

red line). 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-32 

Table 4-7. Change in peak 8-hour CO from doubling the total CO emissions inventory outside 

of the central urban sub-domain. 

Peak 8-hour CO (ppm) 

Year From Section 4.2 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 

This demonstrates that the model-predicted peak CO is driven by local emission sources in the 

central urban sub-domain, and is therefore insensitive to large changes in emissions in outer 

areas. 

4.4.2 Emission Budgets from Scaling On-Road Emissions 

Future year on-road mobile source emissions were scaled up across the entire modeling domain 

to the point at which the peak 8-hour CO concentration reached 8.9 ppm. Additionally, the onroad mobile source emissions outside the central urban sub-domain were increased by an 

additional 70% in each year to reach a maximum peak 8-hour CO concentration of just under 

9.0ppm. Results from this analysis are presented in Table 4-8. Plots of daily maximum CO 

concentrations for each future year are shown in Figures 4-13 through 4-17. There was no 

change in the location of the predicted peak. No additional hot spots were generated anywhere 

in the domain by increasing the on-road mobile source emissions in the outer portion of the 

domain by 70%. 

Table 4-8. Weekday domain-wide on-road emission increase, net on-road emission increase 

that includes an additional 70% increase outside the central urban sub-domain, resulting UAM 

predicted peak CO, and resulting total and sub-domain on-road emission budgets for each 

future year. 

Year 

Domain-Wide 

On-Road 

Emissions 

Increase 

Net On-Road 

Emissions 

Increase 

Peak 8-hr 

CO (ppm) 

Total Domain 

On-Road 

Emissions 

(TPD) 

Sub-Domain 

On-Road 

Emissions 

(TPD) 

2006 23% 41% 8.96 623 427 

2010 26.5% 49% 8.98 690 438 

2015 41.5% 70% 8.98 768 453 

2020 50% 83% 8.97 817 463 

2030 46% 81% 8.97 881 464 

Table 4-9 presents the peak UAM + CAL3QHC 8-hour average CO concentrations predicted in 

each of the future year sensitivity runs shown in Table 4-8 and for each of the three intersections 

in the “Five Points” area. All values remain well below the 9 ppm standard. 

Table 4-10 presents the peak total UAM + EDMS 8-hour CO concentration from the UAM 

sensitivity runs shown in Table 4-8 (without airports included) at all three airports for each future 

year evaluated. Values for McCarran are taken from the peak publicly accessible receptor. All 

peak CO concentrations are below the 9 ppm standard in all years. 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-33 

Figure 4-13. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) 

for the December 8-9, 1996 episode using emission forecasts for 2006 with increased on-road 

mobile source emissions to reach peak CO just under 9.0 ppm. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

5

6

7

8

9

10

11

12

ppm

UAM Max 8-hour CO Concentrations

 2006 Future Year

Peak = 8.96 ppm
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-34 

Figure 4-14. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) 

for the December 8-9, 1996 episode using emission forecasts for 2010 with increased on-road 

mobile source emissions to reach peak CO just under 9.0 ppm. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

5

6

7

8

9

10

11

12

ppm

UAM Max 8-hour CO Concentrations

 2010 Future Year

Peak = 8.98 ppm
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-35 

Figure 4-15. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) 

for the December 8-9, 1996 episode using emission forecasts for 2015 with increased on-road 

mobile source emissions to reach peak CO just under 9.0 ppm. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

5

6

7

8

9

10

11

12

ppm

UAM Max 8-hour CO Concentrations

 2015 Future Year

Peak = 8.98 ppm
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-36 

Figure 4-16. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) 

for the December 8-9, 1996 episode using emission forecasts for 2020 with increased on-road 

mobile source emissions to reach peak CO just under 9.0 ppm. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

5

6

7

8

9

10

11

12

ppm

UAM Max 8-hour CO Concentrations

 2020 Future Year

Peak = 8.97 ppm
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_4_Modeling.doc 4-37 

Figure 4-17. Spatial distribution of UAM predicted 8-hour maximum CO concentrations (ppm) 

for the December 8-9, 1996 episode using emission forecasts for 2030 with increased on-road 

mobile source emissions to reach peak CO just under 9.0 ppm. 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

5

6

7

8

9

10

11

12

ppm

UAM Max 8-hour CO Concentrations

 2030 Future Year

Peak = 8.97 ppm
August 2005 

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Table 4-9. Peak UAM + CAL3QHC 8-hour average CO concentrations (ppm) predicted for 

each future year and for each intersection. UAM results from the on-road sensitivity scaling 

tests. 

Year Eastern/Charleston Eastern/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 

Table 4-10. Peak total UAM + EDMS 8-hour CO concentrations (ppm) at all three airports and 

for all future years evaluated. Values shown for McCarran airport occur at the peak publicly 

accessible receptor. UAM results from the on-road sensitivity scaling tests. 

Airport 2005 2010 2015 2020 

McCarran 7.76 7.47 8.09 8.98 

Henderson Executive 1.28 1.61 2.74 3.96 

North Las Vegas 6.07 6.28 6.14 6.08 
August 2005 

Y:\Las_Vegas_MSEI\CO SIP Update\Tech Support Doc\Final TSD\Sec_5_Conclusion.doc 5-1

5. SUMMARY 

The Clark County Department of Air Quality and Environmental Management has updated their 

UAM CO modeling and conformity analysis using the latest tools, data resources, and 

methodologies available to estimate CO emissions. From the revised modeling results, Clark 

County is submitting a revised CO SIP document. The revised modeling is based upon the 

previous UAM/CAL3QHC/EDMS modeling datasets developed for the December 8-9, 1996 

episode and reported in the 2000 CO SIP for Clark County. Specific updates to the emission 

inventories include modifications to on-road mobile, non-road mobile, civil airports, railroads 

and point sources. Emission estimates for all remaining categories (mainly stationary area 

sources and Nellis Air Force Base) were taken from the previous modeling detailed in the 2000 

CO SIP submittal, although new spatial distributions were developed for area sources from 

updated land use projections. The future years modeled in this update include: 2006, 2010, 

2015, 2020, and 2030. 

5.1 EMISSION UPDATES 

The greatest effort in the CO modeling update has focused on the on-road mobile source 

inventory estimates. The original EPA vehicle emission factor model that was used in the 

previous SIP effort (MOBILE5b) was replaced by the latest version of the model, 

MOBILE6.2.03. However, the Air Improvement Resource (AIR) version of this model was used 

because it provides the capability to create a condensed database of composite emission factors. 

This is important for applications such as this one where many MOBILE6 scenarios must be run 

to generate lookup factors for link-level emissions estimates. 

Since output data and formats for MOBILE6 are significantly different from its predecessor, the 

original utility that was used to estimate link-level CO emissions (DTIM) was replaced by two 

new programs. The first processes the link-based emissions, and the other processes the 

emissions based on traffic analysis zones (TAZ). Both of the new programs produce inputs for 

the Emission Processing System, version 3 (EPS3). The EPS3 is the latest version of the EPS 

program suite used in the original CO SIP modeling to generate gridded, time-resolved, UAMready CO emission input files. 

For the 1996 base year, the RTC’s original TRANPLAN transportation demand model (TDM) 

output was used to define link-based volume (vehicle miles traveled, or VMT) and other traffic 

volume-related parameters. However, no trip tables were available, which allow for the separate 

processing of start versus running emissions. Therefore, trip data from the newer 2000 

TransCAD TDM was used as a means to spatially allocate the 1996 start emissions for each 

period available in the daily TransCAD output. All other original ancillary information, 

including vehicle fleet mix, seasonal/day-of-week adjustment factors, and hourly activity profiles 

remain the same as in the original modeling. 

For all future years modeled in this update, the RTC provided output from their new TransCAD, 

which includes link volumes and trip tables for each year. For the link-based data, the same 

program written for the base year was used to produce the link-based emissions for EPS3. For 

the TAZ data, most of the same type of MOBILE6 output was used in the program developed for 

the base year; but start emissions were handled in a special way. 
August 2005 

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In this CO modeling update, the latest EDMS airport emission estimates developed in 2003 have 

been included into the UAM emissions inventory. The issue of double-counting airport 

emissions within the UAM and EDMS+UAM modeling results were carefully considered. 

Clark County has updated their railroad emissions estimates for 2001 based on a recent non-road 

study, which include contributions from both line haul and switching. These have been 

incorporated into the updated UAM inventory. 

The EPA’s NONROAD model was used to generate emission inputs to EPS3 for each simulated 

future year. New spatial and temporal allocation factors were developed based on the latest land 

use projections from Clark County. Airport ground support equipment (GSE) were removed 

from the NONROAD estimates because they were included in the EDMS estimates; railroad 

maintenance emissions were left in since the Mactec emissions were estimated for locomotives 

only. 

Clark County incorporated an updated point source emission inventory, which included revised 

stack parameters, and which defined Potential To Emit (PTE) levels for seven specific facilities. 

The UAM future year inventories included the PTE levels plus an additional 70 ton buffer 

(referred to as “PTE+70”) for these sources. The original point source inventory was used, 

unchanged, for the 1996 base year simulation. 

Table 5-1 presents a summary of total daily CO emissions by source category for 1996 base and 

all future years. 

5.2 MODEL APPLICATION 

UAM was provided the updated emission inventories for point, on-road mobile, and non-road 

mobile sources, and run for the December 8-9, 1996 historical CO event. All other 

environmental parameters were taken from the original modeling as documented in the 2000 CO 

SIP. A base-year model performance evaluation was conducted for two base cases: (1) using the 

original NEVES-based non-road emission estimates reported in the 2000 CO SIP; and (2) with 

revised non-road emission estimates developed using EPA’s NONROAD model. The UAM was 

then used with the updated future year inventories for 2006, 2010, 2015, 2020 and 2030 to 

determine peak 8-hour CO levels in the basin for the same December 8-9, 1996 conditions. 

UAM results, without airport emissions included in the inventory, were added to EDMS receptor 

concentrations from the 2003 updated airport modeling. 

For hotspot modeling, the CAL3QHC model was used to model three intersections: 

Charleston/Eastern, Charleston/Fremont and Eastern/Fremont. EPA (1992, 1995) guidance for 

screening level modeling of these three intersections was followed. The ambient temperature for 

each hour of the episode (needed to estimate emissions with the MOBILE6 model), and the wind 

direction and speed (needed for the CAL3QHC estimates) were taken from the original 

UAM/CAL3QHC modeling. The CAL3QHC model output was added to the background UAM 

levels to estimate 8-hour CO concentrations for the duration of the episode. 
August 2005 

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Table 5-1. Summary of total daily CO emissions (TPD) in the UAM CO SIP revision. 

Base 2006 2010 2015 2020 2030 

Sunday 12/8/2005

On-Road Mobile 329.95 275.30 287.01 276.44 273.09 295.90

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 AFB 2.86 2.86 2.86 2.86 2.86 2.86

North LV 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 0.17 0.21 0.23 0.24 0.27 0.33

Total 447.81 395.81 419.81 422.51 433.24 484.39

Monday 12/9/2005 

On-Road Mobile 511.43 441.23 463.95 451.30 447.24 485.61

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 AFB 2.86 2.86 2.86 2.86 2.86 2.86

North LV 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 0.25 0.31 0.34 0.36 0.40 0.48

Total 669.15 591.60 627.67 630.36 643.13 715.87

5.2.1 Base Case Simulations 

The UAM base case results show two distinct areas of CO maxima occur in the simulation: (1) 

near the “elbow” of U.S. 95 in northeast Las Vegas, and (2) along the Las Vegas Boulevard 

“strip” near the intersection with Spring Mountain Road. Both base case simulations show a 

domain peak of 10.7 ppm and 11.4 ppm along Las Vegas Boulevard, respectively. This is 

primarily caused by a large contribution from automobile start emissions during the morning of 

December 9, which is in turn due to the large concentration of parking structures in that area, 

according to TransCAD. The secondary maximum reaches above 9 ppm along U.S. 95, and this 

occurs during the morning commute hours on Monday, December 9. Overall, the spatial pattern 

of predicted 8-hour maximum CO agrees with the previous modeling performed for the 2000 CO 

SIP, and with the distribution of observed CO for this period. 

Performance statistics were calculated based upon pairings of 8-hour CO predictions and 

observations across all available monitoring sites for the period, which include standard EPAmethod monitoring conducted by Clark County, as well as special saturation monitoring 

performed for the Las Vegas Phase II field monitoring study (Egami et al., 1998; Emery et al., 

1998). Statistics were compared to EPA criteria for acceptable model performance, and all 

criteria were met. Based upon the statistics calculated for both base cases, UAM performance is 

quite good and should be considered acceptable. Analysis of time-series of predicted and 

observed hourly CO concentrations at each monitoring sites showed that the diurnal and 

neighborhood CO trends are reproduced adequately. 
August 2005 

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5.2.2 Future Year Simulations 

UAM predictions show that the 8-hour CO standard of 9 ppm will not be violated anywhere 

within the domain. Peak 8-hour CO decreases in each year to 2015, then begins to increase out 

to 2030: 

 Year Peak 8-hour CO

 2006 7.4 

 2010 7.2 

 2015 6.5 

 2020 6.7 

 2030 8.0 

In each successive year through 2020, the contribution from on-road mobile sources diminishes, 

while the peak moves from the U.S. 95 “elbow” in northeast Las Vegas to the northern boundary 

of McCarran airport along Tropicana Boulevard. Like the 1996 Base Case, a lower secondary 

peak occurs in the Las Vegas Boulevard area near Spring Mountain Road. Again, the Las Vegas 

Boulevard – Spring Mountain road area possesses a high concentration of parking structures, 

which leads to a local maximum in trip starts in TransCAD, and therefore a local maximum in 

vehicle “start” emissions in the modeling emission inventory. This poses a potential for an 

actual local emissions “hot spot” in this area. However, Clark County recently undertook a 

saturation study in 2002 (T&B Systems and Parsons Engineering Science, 2002) to address this 

possibility. Although the TransCAD, EPS, and UAM modeling show a potential emissions hot 

spot at Spring Mountain Road and Las Vegas Boulevard, the 2002 saturation study showed no 

hot spot at all in that location. 

5.2.2.1 Micro-scale Modeling

Future year UAM simulation results were used to provide estimates of background ambient CO 

levels for micro-scale modeling performed for the “Five Points” hot spot intersection and for the 

three civil airports in the modeling domain (McCarran, Henderson Executive, and North Las 

Vegas). UAM concentrations from the appropriate grid cells were simply added to the 

concentrations predicted at each micro-scale receptor to obtain a total (background + microscale) CO concentration. 

Table 5-2 presents the peak UAM + CAL3QHC 8-hour average CO concentrations predicted in 

each of the future years for each of the three intersections in the “Five Points” area. All values 

are well below the 9 ppm standard. 
August 2005 

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Table 5-2. Peak UAM + CAL3QHC 8-hour average CO concentrations (ppm) predicted for 

each future year and for each intersection. 

Year Eastern/Charleston Eastern/Fremont Fremont/Charleston 

2006 6.14 5.66 5.09 

2010 5.61 5.32 4.81 

2015 4.97 4.76 4.31 

2020 4.67 4.48 4.07 

2030 4.83 4.58 4.20 

In consideration of micro-scale airport modeling, the UAM was re-run for all future years, but 

airport emissions for the three civil airports in the domain were removed from the UAM 

inventory to avoid double counting. Clark County provided EDMS simulations for 2005, 2010, 

2015 and 2020, based on the work of Ricondo (2003). At McCarran airport, all receptors 

reporting peak 8-hour CO above the 9 ppm standard in all future years evaluated occur within 

areas that are not publicly accessible, as defined by Ricondo (2005). Disregarding any receptors 

in publicly restricted areas removes all exceedance estimates. 

Table 5-3 presents the peak total 8-hour CO concentration at all three airports for each future 

year evaluated. Values for McCarran are taken from the peak publicly accessible receptor. All 

peak CO concentrations are below the 9 ppm standard in all years. 

Table 5-3. Peak total UAM + EDMS 8-hour CO concentrations (ppm) at all three airports and 

for all three future years evaluated. Values shown for McCarran airport occur at the peak 

publicly accessible receptor. 

Airport 2005 2010 2015 2020 

McCarran 7.47 7.14 7.60 8.45 

Henderson Executive 1.12 1.36 1.99 3.05 

North Las Vegas 5.01 5.04 4.46 4.19 

5.2.2.2 Estimating On-Road Emission Budgets

The UAM was used to undertake several sensitivity tests to refine the estimation of future year 

on-road mobile CO emission budgets for the central, most urbanized portion of the modeling 

domain. The first analysis tested the assertion that the emissions inventory outside of the central 

urban sub-domain has no significant impact on CO concentrations downtown, along the Las 

Vegas Boulevard “strip”, and in traditional “hot spot” areas. Emissions in the outer grid area 

were doubled for each future year, and the UAM was run to show the incremental impact on the 

peak CO concentration. As shown in Table 5-4, peak 8-hour CO concentrations changed by a 

maximum of only 0.07 ppm. There was no change in the location of the predicted peak. 

Table 5-4. Change in peak 8-hour CO from doubling the total CO emissions inventory outside 

of the central urban sub-domain. 

Peak 8-hour CO (ppm) 

Year Future Year Peak 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 
August 2005 

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This demonstrates that the model-predicted peak CO is driven by local emission sources in the 

central urban sub-domain, and is therefore insensitive to large changes in emissions in outer 

areas 

In the second analysis, future year on-road mobile source emissions were scaled up across the 

entire modeling domain to the point at which the peak 8-hour CO concentration reached 8.9 

ppm. Additionally, the on-road mobile source emissions outside the central urban sub-domain 

were increased by an additional 70% in each year to reach a maximum peak 8-hour CO 

concentration of just under 9.0 ppm. Hence, the resulting daily on-road emission totals for 

December 9 can be used to establish future-year emission budgets. Results from this analysis are 

presented in Table 5-5. There was no change in the location of the predicted peak. No 

additional hot spots were generated anywhere in the domain by increasing the on-road mobile 

source emissions in the outer portion of the domain by 70%. 

Table 5-5. Weekday domain-wide on-road emission increase, net on-road emission increase 

that includes an additional 70% increase outside the central urban sub-domain, resulting UAM 

predicted peak CO, and resulting total and sub-domain on-road emission budgets for each 

future year. 

Year 

Domain-Wide 

On-Road 

Emissions 

Increase 

Net On-Road 

Emissions 

Increase 

Peak 8-hr 

CO (ppm) 

Total Domain 

On-Road 

Emissions 

(TPD) 

Sub-Domain 

On-Road 

Emissions 

(TPD) 

2006 23% 41% 8.96 623 427 

2010 26.5% 49% 8.98 690 438 

2015 41.5% 70% 8.98 768 453 

2020 50% 83% 8.97 817 463 

2030 46% 81% 8.97 881 464 

Table 5-6 presents the peak UAM + CAL3QHC 8-hour average CO concentrations predicted in 

each of the future year sensitivity runs above and for each of the three intersections in the “Five 

Points” area. All values remain well below the 9 ppm standard. 

Table 5-6. Peak UAM + CAL3QHC 8-hour average CO concentrations (ppm) predicted for 

each future year and for each intersection. UAM results from the on-road sensitivity scaling 

tests. 

Year Eastern/Charleston Eastern/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 

Table 5-7 presents the peak total UAM + EDMS 8-hour CO concentration from the UAM 

sensitivity runs (without airports included) at all three airports for each future year evaluated. 

Values for McCarran are taken from the peak publicly accessible receptor. All peak CO 

concentrations are below the 9 ppm standard in all years. 
August 2005 

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Table 5-7. Peak total UAM + EDMS 8-hour CO concentrations (ppm) at all three airports and 

for all future years evaluated. Values shown for McCarran airport occur at the peak publicly 

accessible receptor. UAM results from the on-road sensitivity scaling tests. 

Airport 2005 2010 2015 2020 

McCarran 7.76 7.47 8.09 8.98 

Henderson Executive 1.28 1.61 2.74 3.96 

North Las Vegas 6.07 6.28 6.14 6.08 
August 2005 

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