MDAQMD 

Federal 8-Hour Ozone Attainment Plan 

(Western Mojave Desert 

Non-attainment Area) 

Adopted on: 

June 9, 2008 

Mojave Desert Air Quality Management District 

14306 Park Avenue 

Victorville, CA 92392-2310 
2

This document was prepared by the MDAQMD Planning, Rule-making and Grants section, with 

input from the entire MDAQMD staff. Significant portions of this document were prepared by, 

or are based on work done by, the California Air Resources Board and the South Coast Air 

Quality Management District staffs. The MDAQMD staff greatly appreciates the assistance of 

those agencies in the preparation of this document. 
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

i

Table of Contents

List of Tables........................................................................................................................... ii

List of Figures......................................................................................................................... ii

Abbreviations and Acronyms ................................................................................................. iii

Executive Summary...................................................................................................................... 1

CHAPTER 1 – Introduction and Background........................................................................... 3

Introduction................................................................................................................................. 5 

Purpose ....................................................................................................................................5

Background................................................................................................................................. 5 

Regulatory History...................................................................................................................5

Regional Ozone Planning Chronology ....................................................................................6

Statement of Issues...................................................................................................................6

Federal Legal Requirements....................................................................................................6

Pollutant Description and Health Effects................................................................................7

Setting ......................................................................................................................................8

Ozone Trend.............................................................................................................................8

CHAPTER 2 – Emission Inventories ........................................................................................ 11

General ..................................................................................................................................13

Modeled Emission Inventory and Sub-Region Inventory.......................................................13

Federal Ozone Non-Attainment Area Base Year Emission Inventory...................................14

Future Year Emission Inventories .........................................................................................14

CHAPTER 3 – Control and Contingency Measures ............................................................... 17

Existing Control Measures ....................................................................................................19

Proposed Control Measures ..................................................................................................19

State Control Measures..........................................................................................................19

Local Rule Adoption Schedule...............................................................................................23

Contingency Measures...........................................................................................................24

Required Progress .................................................................................................................24

Controlled Emission Inventories............................................................................................25

Conformity Budgets ...............................................................................................................25

CHAPTER 4 – Attainment Demonstration.............................................................................. 27

Attainment Demonstration........................................................................................................ 29 

Modeling Approach Overview ...............................................................................................29

Modeling Domain ..................................................................................................................30

Model Inputs ..........................................................................................................................30

Modeling Results....................................................................................................................30

ARB Weight of Evidence Assessment.....................................................................................31

Appendices................................................................................................................................... 33

Appendix A - Base Year Emission Inventory....................................................................... A - 1 

Appendix B - Future Year Emission Inventories.................................................................. B - 1 

Appendix C –Transportation Conformity Budgets............................................................... C - 1 

Appendix D - Annual Ambient Monitoring Data Summary ................................................ D - 1 
ii MDAQMD Federal 8-hour Ozone Attainment Plan 

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Appendix E – ARB Weight of Evidence Assessment ...........................................................E - 1 

List of Tables 

Table 1 – 2002 Base Year Summary ............................................................................................ 14 

Table 2 – Expected Emission Reductions from Proposed New SIP Measures ............................ 23 

Table 3 - Reasonable Further Progress for the WMDONA.......................................................... 25 

Table 4 - Transportation Conformity Budget (FONA)................................................................. 26 

Table 5 - 2020 Federal Ozone Attainment Demonstration........................................................... 31 

List of Figures 

Figure 1 - Federal 8-Hour Ozone Design Value Trend .................................................................. 9 

Figure 2 - 2002 Base Year Pie Charts (FONA) ............................................................................ 14 

Figure 3 - Forecasted VOC Emission Inventories (FONA).......................................................... 15 

Figure 4 - Forecasted NOx Emission Inventories (FONA)........................................................... 16 
MDAQMD Federal 8-hour Ozone Attainment Plan 

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Abbreviations and Acronyms 

AQAP................. Air Quality Attainment Plan 

AQMA ............... Air Quality Management Area 

AQMP................ Air Quality Management Plan 

CALGRID.......... California Photochemical Grid Model 

CARB................. California Air Resources Board 

CCAA ................ California Clean Air Act 

CO...................... Carbon Monoxide 

ERC.................... Emission Reduction Credit 

FCAA................. Federal Clean Air Act 

FMVCP.............. Federal Motor Vehicle Control Program 

FONA................. Federal Ozone Non-attainment Area 

MDAQMD......... Mojave Desert Air Quality Management District 

MPR ................... Model Performance Ratio 

NAAQS.............. National Ambient Air Quality Standard 

NOX.................... Oxides of Nitrogen 

NSR.................... New Source Review 

O3 ....................... Ozone 

RACT................. Reasonably Available Control Technology 

ROG ................... Reactive Organic Gases 

ROP.................... Rate of Progress 

RRF.................... Relative Reduction Factor 

SAAQS .............. State Ambient Air Quality Standard 

SBCAPCD ......... San Bernardino County Air Pollution Control District 

SCAB ................. South Coast Air Basin 

SCAG................. Southern California Association of Governments 

SCAQMD .......... South Coast Air Quality Management District 

SCAQS87........... 1987 Southern California Air Quality Study 

SCOS97.............. 1997 Southern California Ozone Study 

SDMAQMA....... Southeast Desert Modified Air Quality Management Area 

SSAB.................. Salton Sea Air Basin 

tpaad................... Tons per Annual Average Day 

tposd................... Tons per Ozone Seasonal Day 

UAM .................. Urban Airshed Model 

USEPA............... United States Environmental Protection Agency 

VMT................... Vehicle Miles Traveled 

VOC ................... Volatile Organic Compounds 

WMDONA......... Western Mojave Desert Ozone Non-attainment Area 
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Executive Summary 

The United States Environmental Protection Agency (USEPA) designated the Western Mojave 

Desert non-attainment area as non-attainment for the 8-hour ozone National Ambient Air Quality 

Standard (NAAQS) pursuant to the provisions of the Federal Clean Air Act (FCAA). A portion 

of the Mojave Desert Air Quality Management District (MDAQMD) is included in the Western 

Mojave Desert non-attainment area. The MDAQMD has adopted State and Federal attainment 

plans for the region within its jurisdiction. The most recent such plan that was approved by 

USEPA is the MDAQMD 2004 Ozone Attainment Plan adopted in 2004. The most recently 

adopted State plan is the 1996 Triennial Revision to the 1991 Air Quality Attainment Plan. 

The MDAQMD has reviewed and updated all elements of the ozone plan. The portion of the 

MDAQMD designated as a Federal 8-hour ozone non-attainment area (FONA) will be in 

attainment of the 8-hour NAAQS for ozone by 2021. 

This document includes the latest planning assumptions regarding population, vehicle activity 

and industrial activity. This document addresses all existing and forecast ozone precursorproducing activities within the MDAQMD through the year 2020. This document includes all 

necessary information to allow general and transportation conformity findings to be made within 

the MDAQMD. 
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CHAPTER 1 – Introduction and Background 

Purpose 

Regulatory History 

Statement of Issues 

Federal Legal Requirements 

State Legal Requirements 

Pollutant Descriptions 

Health Effects 

Setting 

Ozone Trend 
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INTRODUCTION 

Purpose 

The Western Mojave Desert non-attainment area (as defined in 40 CFR 81.305) was designated 

non-attainment for the NAAQS for ozone by USEPA on April 15, 2004. The Western Mojave 

Desert Ozone Non-attainment Area (WMDONA) includes part of the San Bernardino County 

portion of the MDAQMD, as well as the Antelope Valley portion of Los Angeles County. The 

MDAQMD has experienced ambient ozone concentrations in excess of the 8-hour ozone 

NAAQS. This document: (1) demonstrates that the MDAQMD will meet the primary required 

Federal ozone planning milestones, attainment of the 8-hour ozone NAAQS by June 2021; (2) 

presents the progress the MDAQMD will make towards meeting all required ozone planning 

milestones; and (3) discusses the newest 0.075 part per million 8-hour ozone NAAQS, 

preparatory to an expected non-attainment designation for the new NAAQS. This document 

satisfies 42 U.S.C. §§7410, 7502, 7504 and 7511a (FCAA §§110, 172, 174, and 182) regarding 

implementation plans, non-attainment plan provisions, planning procedures, and ozone plan 

submissions and requirements for the 8-hour NAAQS. 

BACKGROUND 

Regulatory History 

The USEPA designated a portion of the southwestern desert part of San Bernardino County as 

non-attainment and classified it as Moderate for the 8-hour standard. This area was classified 

based on an ozone design value calculated from 2001 through 2003 concentrations in the region. 

The Moderate classification requires attainment of the 8-hour ozone NAAQS by June 2010, six 

years after the date of designation. 

The MDAQMD was established on July 1, 1993, pursuant to H&SC §41200 et seq (Statutes 

1992 ch. 642). The MDAQMD was a successor agency to the San Bernardino County Air 

Pollution Control District (SBCAPCD), which had jurisdiction over the desert portions of San 

Bernardino County commencing in February 1977 through the formation of the MDAQMD. 

The Palo Verde Valley portion of eastern Riverside County was annexed by the MDAQMD from 

the South Coast Air Quality Management District (SCAQMD) effective July 1, 1994, pursuant to 

provisions of H&SC 41210(c) and MDAQMD Resolution 94-03. 

Initial air quality planning for the region was the 1991 Air Quality Attainment Plan (AQAP) 

which was adopted by the SBCAPCD on August 26, 1991 in response to the State of California 

ozone planning requirements. Additional ozone plans were adopted by the MDAQMD to 

address Federal ozone planning requirements, most recently the MDAQMD 2004 Ozone 

Attainment Plan adopted on April 26, 2004. This document replaces or updates all previously 

submitted federal ozone plans. 
6 MDAQMD Federal 8-hour Ozone Attainment Plan 

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Regional Ozone Planning Chronology 

1989 - CARB designates SEDAB as non-attainment for ozone SAAQS 

1990 - CARB classifies the SEDAB as moderate ozone non-attainment 

November, 1990 - Adoption of Federal Clean Air Act Amendments 

August 26, 1991 - Adoption of the 1991 Air Quality Attainment Plan (State) by SBCAPCD 

July 1, 1993 - Formation of Mojave Desert Air Quality Management District 

July 1, 1994 - Annexation of Palo Verde Valley portion of Riverside County 

March 24, 1994 - Adoption of Rate-Of-Progress Plan (Federal) by MDAQMD 

October 26, 1994 - Adoption of Attainment Demonstration Plan (Federal) by MDAQMD 

1996 - SEDAB is subdivided into the Mojave Desert Air Basin (MDAB) and the Salton Sea Air 

Basin (SSAB) 

January 22, 1996 - Adoption of Triennial Revision to 1991 AQAP (State) by MDAQMD 

April 26, 2004 - Adoption of MDAQMD 2004 Ozone Attainment Plan 

Statement of Issues 

The MDAQMD is downwind of the Los Angeles basin, and to a lesser extent, is downwind of 

the San Joaquin Valley. Prevailing winds transport ozone and ozone precursors from both 

regions into and through the MDAB during the summer ozone season. These transport couplings 

have been officially recognized by CARB.1 Local MDAQMD emissions contribute to 

exceedances of both the NAAQS and SAAQS for ozone, but photochemical ozone modeling 

conducted by the SCAQMD and CARB indicates that the MDAB would be in attainment of both 

standards without the influence of this transported air pollution from upwind regions. 

Federal Legal Requirements 

The MDAQMD must adopt a plan that provides for the implementation, maintenance and 

enforcement of the NAAQS within three years after promulgation of the NAAQS. The plan is to 

include enforceable emission limitations, provide for a monitoring program, provide for a permit 

program (including a new source review program), contingency measures, and air quality 

modeling (42 U.S.C. §7410(a); FCAA §110(a)). The MDAQMD most recently met this 

requirement with the MDAQMD 2004 Ozone Attainment Plan. This document represents an 

update to that plan. The MDAQMD has adopted enforceable emission limitations, has a 

monitoring system in place throughout the populated portions of the Federal Ozone NonAttainment Area (FONA), maintains a permit program (including a New Source Review 

program with an ambient air quality modeling requirement), and has performed an attainment 

demonstration using air quality modeling. This document identifies a contingency measure – see 

chapter 3. 

This document incorporates all reasonably available control measures (all such measures have 

already been adopted for the FONA or are being committed to adoption in this plan). This 

 

1

 “Ozone Transport: 2001 Review,” April 2001, CARB identifies the South Coast Air Basin as having an 

overwhelming and significant impact on the Mojave Desert Air Basin (which includes the Mojave Desert) and the 

San Joaquin Valley as having an overwhelming impact on the MDAB. 
MDAQMD Federal 8-hour Ozone Attainment Plan 

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7

document includes a comprehensive, accurate and current inventory of actual emissions (42 

U.S.C. §7502(c)(3), 7511a(a)(1); FCAA §§172(c)(3), 182(a)(1)). 

This document discusses reasonable further progress (42 U.S.C. §§7502(c)(2), 7511a(b)(1); 

FCAA §§172(c)(2), 182(b)(1)) for the applicable periodic milestone dates (2008, 2011, 2014, 

2017 and 2020) (42 U.S.C. §7511a(g); FCAA §182(g)). The FONA is not capable of meeting 

the reasonable further progress milestones on its own; the target levels would require reductions 

in source categories that are not under the jurisdiction of the MDAQMD (specifically mobile 

sources). 

This document has been coordinated with the transportation planning process (42 U.S.C. §7504; 

FCAA §174). The document includes an emission budget for the FONA, and also includes the 

on-road mobile source emission budget for the Western Mojave Desert non-attainment area as an 

appendix. 

This document updates the MDAQMD emissions inventory (42 U.S.C. 7511a(a)(1); FCAA 

§182(a)(1)). 

The MDAQMD has an enhanced non-attainment pollutant monitoring program, requires 

reasonably available control technology (RACT) within the FONA, has a vehicle inspection and 

maintenance program, a De Minimis rule, and a gasoline vapor recovery rule. The District 

participates in the State’s Clean-Fuel Vehicle Program, and performs periodic transportation 

activity consistency demonstrations (including a review of vehicle miles traveled growth) in 

conjunction with the Southern California Association of Governments (SCAG). The MDAQMD 

controls oxides of nitrogen (NOx) in addition to Volatile Organic Compounds (VOC) within the 

FONA, and is addressing both pollutants in this document. The MDAQMD New Source Review 

(NSR) program defines sources emitting 25 tons per year or more as major and requires offsets at 

a 1.3 to 1 ratio (42 U.S.C. §§7511a(d), 7511a(d)(2); FCAA §§182(d) 182(d)(2)). Employer trip 

rules (42 U.S.C. §7511a(d)(1); FCAA §182(d)(1)) have been shown to be not cost-effective for 

the FONA due to low population density. 

Pollutant Description and Health Effects 

Ozone (or O3) is a colorless gas that is a highly reactive form of oxygen. It has a strong odor 

when highly concentrated. Ozone can occur naturally but can also be formed from other 

compounds through photochemistry, a complex system of reactions with hydrocarbons and 

oxides of nitrogen in the presence of sunlight (ultraviolet). The MDAB experiences ozone 

concentrations in excess of the State and Federal ambient air quality standards.

Ozone can cause respiratory irritation and discomfort, making breathing more difficult during 

exercise. Ozone can reduce the respiratory system’s ability to remove inhaled particles, increase 

pulse rate, decrease blood pressure and reduce the body’s ability to fight infection. After six 

hours of exposure a healthy person can have significant reduction of lung function. It is an 

irritant towards the skin, eyes, upper respiratory system, and mucous membranes, although 

symptoms disappear after exposure. It may also be a carcinogen. 
8 MDAQMD Federal 8-hour Ozone Attainment Plan 

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Setting 

The MDAQMD includes the desert portion of San Bernardino County and a portion of eastern 

Riverside County commonly known as the Palo Verde Valley. A portion of the MDAQMD 

(herein referred to as the FONA) has been designated non-attainment for the 8-hour ozone 

NAAQS by USEPA as a portion of the Western Mojave Desert non-attainment area in 40 CFR 

81.305. The ozone design value classifies the area as a Moderate non-attainment area with 2010 

as the required attainment year (42 U.S.C. 7511(a)(2); FCAA §181(a)(2)). The FONA includes 

the communities of Phelan, Hesperia, Adelanto, Victorville, Apple Valley, Barstow, Joshua Tree, 

Yucca Valley and Twentynine Palms (the southwestern portion of the MDAQMD). 

The MDAQMD covers more than 20,000 square miles and included 359,551 persons as of the 

1990 census (approximately 445,000 in 2002). The region is characterized by hot, dry summers 

and cool winters, with little precipitation. The National Training Center at Fort Irwin, the 

Marine Corps Air Ground Combat Center, and portions of Edwards Air Force Base and the 

China Lake Naval Air Weapons Station are in the MDAQMD. The MDAQMD also includes the 

Mojave National Preserve and portions of Death Valley National Park and Joshua Tree National 

Park 

The primary roadways in the MDAQMD are Interstate 15, Interstate 40, State Route 58 and 

United States Route 395. All of these highways carry a significant amount of transiting heavy 

duty truck traffic, and Interstate 15 carries a substantial amount of commute traffic into the 

greater Los Angeles Basin. 

The MDAQMD includes railroad track connecting the Ports of Los Angeles and Long Beach 

with the rest of the continental United States, as well as large diameter high pressure natural gas 

transmission pipelines delivering the majority of the natural gas consumed within the State of 

California. 

The MDAQMD is a growing bedroom community, but does have significant mining and military 

activity. 

Ozone Trend 

The MDAQMD has experienced a substantial reduction in maximum 8-hour ozone 

concentrations, as displayed in Figure 1 (Trona is not within the FONA but is shown for 

comparison). Note that the three stations closest to the South Coast Air Basin (the source of the 

majority of transported ozone and ozone precursors) have the highest historical ozone 

concentrations: Phelan, Hesperia and Victorville. The more distant or isolated stations (Barstow 

and Twentynine Palms) have much lower concentrations, and are in fact recently experiencing 

concentrations in attainment of the NAAQS. 
MDAQMD Federal 8-hour Ozone Attainment Plan 

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9

Figure 1 - Federal 8-Hour Ozone Design Value Trend 

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180

1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

8-Hour Averages (3 Year Average 4th Highest)

Barstow

Hesperia

Phelan

Trona

Twentynine Palms

84 ppb Victorville

(NAAQS)
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CHAPTER 2 – Emission Inventories 

General 

Modeled Emission Inventory and Sub-Region Inventory 

Base Year 

Future Years 
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MDAQMD Federal 8-hour Ozone Attainment Plan 

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General 

Ozone planning requirements call for the use of seasonal inventories representing emissions 

during a typical summer day (since ozone concentrations are typically highest under summer 

weather conditions). This document includes ozone seasonal day inventories, in units of tons per 

ozone seasonal day (or tons per os day, or tposd), unless otherwise indicated. All emissions 

presented in this document have been adjusted or calculated in terms of ozone seasonal day 

emissions. 

Federal ozone planning requirements call for emissions in terms of Volatile Organic Compounds 

(VOC), while State ozone planning requirements call for emissions in terms of Reactive Organic 

Gases (ROG). Due to changes in each definition, there is no effective difference between the 

two terms (for example, ethane is now excluded from both definitions). For purposes of this 

document and attainment planning, the District considers these terms interchangeable. 

Modeled Emission Inventory and Sub-Region Inventory 

The emission inventory for the FONA sub-region of the MDAQMD is provided in Appendix A 

of this document. Complete documentation for San Bernardino Country emissions, including 

emission inventory calculation methodologies, are available from the following web address: 

http://www.arb.ca.gov/ei/maps/basins/abmdmap.htm 

ARB developed a list of the stationary source facilities in the 2002 CEIDARS inventory for San 

Bernardino County and submitted the list to MDAQMD staff for review to determine whether 

the facilities are located in the FONA. MDAQMD made this assessment and submitted the 

FONA facility list to ARB. 

Stationary aggregated, areawide, on-road and other mobile sources emission sector types are all 

treated like area sources when assessing emissions in the FONA portion of San Bernardino 

County. MDAQMD evaluated the San Bernardino County area source inventory to determine 

the relative fractions that should be assigned to the San Bernardino FONA for these sectors. In 

most cases, the fractions span major emission category groups (as defined by EIC Summary 

Code). For a few categories, the fractions are specific to the Emission Inventory Code (EIC). 

The California Emission Forecasting System (CEFS) was used to generate future year emission 

estimates for Stationary Point, Stationary Aggregated, and Areawide category sectors. These 

future year estimates are based on anticipated socioeconomic growth rates, and control factors 

that estimate the impacts of local and state control regulations. For stationary point sources, 

CEFS projections were run based on the 2002 emission inventory only for the facilities located 

in the FONA as previously determined. For Stationary Aggregated and Areawide sources, the 

fractions described above were applied to the San Bernardino County inventory developed for 

CEFSv1.06 and saved as part of the FONA inventory. 

Emissions for On-Road sources (for all calendar years) were imported to CEFS directly from 

EMFAC2007v2.3. Emissions for off-road mobile sources (for all calendar years) were imported 

to CEFS directly from OFFROAD2007. To calculate the FONA portion, the appropriate 
14 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

fractions were applied to CEFSv1.06 and saved as part of the FONA inventory as described 

above. 

Federal Ozone Non-Attainment Area Base Year Emission Inventory 

The initial Federal base year for emission inventory purposes is 2002. 2002 is used as the base 

year inventory for all growth scenarios in this document. The base year emission inventory is 

presented in Appendix A; a summary is presented in Table 1 below. Figure 2 presents the base 

year source category contributions in basic pie chart format (VOC on the left, NOx on the right). 

Mobile sources were the primary emitters in the FONA in 2002. 

Table 1 – 2002 Base Year Summary 

2002 VOC 2002 NOx

Point 5.97 42.18

Area 6.55 0.62

Other mobile 15.98 35.15

On-Road Mobile 18.20 74.24

Totals: 46.69 152.19

(tons per ozone seasonal day)

Figure 2 - 2002 Base Year Pie Charts (FONA) 

Point VOC

13%

Area VOC

14%

Other Mobile VOC

34%

On-Road Mobile 

VOC

39%

Point NOx

28%

Area NOx

0%

Other Mobile NOx

23%

On-Road Mobile 

NOx

49%

Future Year Emission Inventories 

Future year or forecasted emission inventories are estimated by multiplying a base year value for 

each category by a ‘growth code’ for a given future year. The ‘growth code’ is indexed to the 

base year (2002 for this document), so that its value for the base year is 1.00. This allows the 

growth code to estimate future activity in terms of emissions; if the growth code for the year 

2007 is 1.50, activity in that category (and resulting emissions) is expected to be 50 percent 

greater than in 2002. The growth codes used to forecast point sources are available from CARB. 

Forecasted FONA VOC and NOx inventory summaries for each year of interest are presented in 

Figures 3 and 4 respectively (the base year is included in each figure for reference). Future year 

emission inventories are presented in Appendix B. 
MDAQMD Federal 8-hour Ozone Attainment Plan 

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Figure 3 - Forecasted VOC Emission Inventories (FONA) 

0.00

10.00

20.00

30.00

40.00

50.00

60.00

2002 2008 2011 2014 2017 2020

Tons per Ozone Seasonal Day

Point VOC

Area VOC

Other Mobile VOC

On-Road Mobile VOC

FONA VOC
16 MDAQMD Federal 8-hour Ozone Attainment Plan 

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Figure 4 - Forecasted NOx Emission Inventories (FONA) 

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

160.00

2002 2008 2011 2014 2017 2020

Tons per Ozone Seasonal Day

Point NOx

Area NOx

Other Mobile NOx

On-Road NOx

FONA NOx
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CHAPTER 3 – Control and Contingency Measures 

Existing Control Measures 

Proposed Control Measures 

Rule Adoption Schedule 

Contingency Measures 

Required Progress 

Controlled Emission Inventories 

Conformity Budgets 
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Existing Control Measures 

The current MDAQMD set of rules and regulations represents a broad set of control measures 

for MDAQMD sources. The MDAQMD has in place Reasonably Available Control Technology 

(RACT) requirements for the majority of sources (including gasoline dispensing vapor control), 

as well as an NSR program with a 25 ton per year major source level and a 1.3:1 offset ratio 

requirement. In 2006, the MDAQMD committed to taking action on several Federal RACT 

categories.2 The MDAQMD has recently adopted Federal RACT rules for ship surface coating,3

glass manufacturing4 and polyester resin operations.5 The MDAQMD had committed to 

adopting three additional RACT rules by the end of 2007 – the MDAQMD will update the 

adoption schedule for these actions. 

Proposed Control Measures 

The MDAQMD is not proposing to adopt any additional control measures for direct ozone 

precursor reduction purposes. However, the MDAQMD is committed to having all applicable 

Federal RACT rules, and is currently performing analyses on the feasibility of adopting 

additional rules under the State of California “all feasible measures” mandate. In addition, the 

MDAQMD will experience additional future emission reductions resulting from existing and 

proposed Federal and State control measures affecting mobile and area sources (see below). 

State Control Measures 

The California Air Resources Board (CARB or ARB) is the State agency responsible for 

ensuring clean air in California. Under State law, ARB has the responsibility to develop SIP 

strategies for mobile sources and consumer products, to coordinate SIP strategies with the 

Bureau of Automotive Repair (BAR) and Department of Pesticide Regulation (DPR), and to 

review local plans for attaining the State and Federal ambient air quality standards. 

ARB adopted a State Strategy for California’s 2007 SIP in September, 2007. The State Strategy 

is comprehensive; it is designed to enable local districts attain federal air quality standards 

through a combination of technologically feasible, cost-effective, and far reaching measures for 

motor vehicles and other statewide sources. The 2007 State Strategy is also the first to address 

the federal 8-hour ozone standard – it represents a transition from the less stringent 1-hour 

standard that was the benchmark for previous SIPs. The State Strategy also includes measures 

that will contribute to attainment of the federal standard for fine particulates (PM2.5) by the 2014 

PM2.5 deadline. The South Coast Air Basin (SCAB) and the San Joaquin Valley are designated 

nonattainment for the federal PM2.5 standard. 

California first enacted passenger car exhaust standards in 1973. Today the State’s mobile 

source control program addresses a wide variety of on- and off-road vehicles and engines, 

 

2

 “8-Hour Reasonably Available Control Technology – State Implementation Plan Analysis (RACT SIP Analysis),” 

August, 2006 

3

 “Rule 1106 – Marine Coating Operations,” amended October 23, 2006 4

 “Rule 1165 – Glass Melting Furnaces,” amended January 28, 2008 5

 “Rule 1162 – Polyester Resin Operations,” adopted August 27, 2007 
20 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

gasoline and diesel fuel standards, and engine maintenance requirements. The existing program 

is projected to reduce emissions from passenger vehicles and heavy-duty trucks by 

approximately 1/3 between 2006 and 2014. The State Strategy ARB adopted in 2007 will result 

in a greater than 50 percent reduction in emissions from all mobile sources in the South Coast 

Air Basin by 2014. Most of the controls in the State Strategy will be implemented statewide, and 

directly benefit the entire state. Some will uniquely target the South Coast and San Joaquin 

Valley Air Basins, directly reducing emissions in the State’s most polluted areas, and indirectly 

improving air quality in downwind areas including Ventura, Antelope Valley, the Mojave Desert 

area, and the Coachella Valley. 

The State Strategy addresses three key mobile source issues: the need to clean up the legacy 

diesel fleets, the national and international nature of many diesel fleets, and limitations on SIP 

credit for unsecured funding. 

The total emission reductions and the obligation to propose specific measures for Board 

consideration would become enforceable upon approval by U.S. EPA of the State Strategy and 

each district’s attainment plan. While the State Strategy includes estimates of the emission 

reductions from each of the individual new measures, it is important to note that the State’s 

commitment is to achieve the aggregate emission reductions identified for the adopted State 

Strategy, from the baseline emissions identified in the SIP. Therefore, if a particular measure 

does not achieve its expected emission reductions, the State still commits to achieving the total 

aggregate emission reductions, whether this is realized through additional reductions from the 

new measures, or from alternative control measures or incentive programs. If actual emission 

decreases occur that exceed the projections reflected in the emission inventories and the State 

Strategy, the actual emission decreases may be counted toward meeting ARB’s total emission 

reduction commitments. 

ARB’s emission reduction commitments may be achieved through a combination of actions 

including but not limited to the implementation of control measures; the expenditure of local, 

state or federal incentive funds; or through other enforceable measures. 

Because ARB scientists determined that reducing emissions of one pollutant, oxides of nitrogen 

(NOx), is the most beneficial in reducing levels of both ozone and PM2.5, the state plan focuses 

on curbing pollution from the sources that produce nearly 90 percent of the state's NOx. These 

sources include cars, heavy duty trucks, large off-road equipment, ships and locomotives. The 

baseline emission inventories used to develop the 2007 and 2008 federal plans throughout the 

state incorporate reductions from control measures adopted through 2006. The State Strategy 

identifies new measures to be adopted through 2014; ARB has already acted on some of these 

measures. 

The 2007 State Strategy includes the control measures identified below. Table 2 identifies the 

timeframes for adoption and implementation of these programs. 

Smog Check Improvements The following changes are being developed to improve the 

effectiveness of the smog check program: 
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

21

o A new low pressure evaporative test to examine passenger vehicles for leaks in fuel tanks 

and vapor lines that cause smog-forming emissions; 

o More stringent inspection standards (cutpoints), which are used to determine if a vehicle 

passes or fails; 

o Annual inspections for older and high use vehicles to shorten the time they are emitting 

excess emissions prior to being repaired; 

o The addition of a visible smoke test; and, 

o The addition of inspection requirements for diesel passenger cars and trucks and 

motorcycles, which are currently exempt from Smog Check. 

Expanded Passenger Vehicle Retirement Incentives and other programs retire more highemitting passenger vehicles, especially “off-cycle” vehicles – cars and light trucks that are 

between smog checks inspections. 

Reformulated Gasoline Modifications Modifications to California’s reformulated gasoline 

program will eliminate or offset permeation emissions resulting from the addition of ethanol to 

gasoline blends. 

Cleaner In-Use Heavy-Duty Trucks Modernize diesel trucks and reduce emissions by requiring 

replacement or cleanup of the dirtiest trucks on the road. This critical regulation, which is 

expected to be considered for adoption in 2008, will also include a program for out-of-state 

trucks doing business in California. 

Goods Movement Sources The 2007 State Strategy takes aim at emissions from ships, trucks, 

harbor craft and other sources associated with the growing goods movement sector. ARB has 

already adopted several goods movement emission reduction controls. 

o Harborcraft In November 2007 ARB approved a measure that requires owners of 

commercial harbor craft to either replace old engines with newer, cleaner versions or add 

control technologies to clean up exhaust. 

o Cold Ironing In December 2007, ARB approved a regulation to provide alternative power 

supplies at ports so that ships can use clean fuels, including electricity, instead of dieselfueled auxiliary engines while at dock. 

o Port Trucks In December 2007 ARB approved a measure requiring retrofit or replacement of 

older heavy-duty diesel trucks that service ports or deliver containers from ports to nearby 

transfer facilities. 

o Ship Engines ARB staff is developing a regulation that would require ocean-going vessels to 

use cleaner fuels in ship main and auxiliary engines when they are operating near the 

California coast. 

o Locomotives The State Strategy also calls for reducing emissions from line-haul 

locomotives by replacing and rebuilding existing engines beginning in 2012. This measure 

relies in part on U.S. EPA action to ensure that clean engines are available to meet this 

schedule. 

Construction and Mining Equipment In July 2007, the Board approved a measure which 

regulates existing construction and other industrial equipment. The regulation establishes fleet 

average emission limits and requires older, dirtier engines to be replaced by current models or 

retrofitted with emission control devices. Accelerated clean-up provisions are available to local 
22 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

districts that provide financial assistance to sources that would be subject to the more stringent 

requirements. 

Agricultural Equipment ARB staff is evaluating the options for modernizing and reducing 

emissions from agricultural equipment, and ARB is expected to consider a regulation in 2009. 

Recreational Boats Existing ARB regulations establish new emission limits for recreational 

boats beginning in 2009. The 2007 State Strategy calls for a more stringent, catalyst-based 

exhaust standard to be phased in by 2013. 

Off-Road Recreational Vehicles The State Strategy includes expanded emission standards for 

off-road recreational vehicles that would reduce exhaust emissions from new vehicles by 50 

percent beginning in 2012, using proven automotive and on-road motorcycle exhaust emission 

reduction technologies. 

Fuel Storage ARB adopted enhanced vapor recovery for above ground storage tanks in June 

2007. Additional evaporative emission standards are proposed for portable outboard marine tank 

engines and refueling gasoline tanks that are usually mounted on a vehicle and used to refuel 

other vehicles. 

Consumer Products ARB staff will consider new approaches such as alternative, market-based 

mechanisms, multi-media labeling programs, and public education as it develops ways to meet 

the State Strategy commitment to further reduce ROG emissions from consumer products. 

Greenhouse Gas Reduction Co-Benefits The California Global Warming Solutions Act of 2006 

(AB 32) requires the adoption of a comprehensive program to reduce greenhouse gas emissions. 

ARB has already started to adopt regulations in response to this requirement. Although the AB 

32 regulations will not directly reduce ozone precursors, many of these regulations are expected 

to have criteria pollutant “co-benefits.” 

Pesticides The Department of Pesticide Regulation’s 2008 Pesticide Plan includes strategies to 

reduce ROG emissions from pesticides through regulation of fumigant pesticide use, regulatory 

standards for registration of liquid pesticides, and strategic partnership agreements implementing 

pest management practices and technologies that use less pesticide product. 
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

23

Table 2 – Expected Emission Reductions from Proposed New SIP Measures 

Mojave Desert Non Attainment Area -- 2020

Direct

PM2.5

Passenger Vehicles 0.5 0.5 0 --

 Smog Check Improvements (BAR) 0.4 0.3 0 --

 Expanded Vehicle Retirement 0.1 0 0 --

 Modifications to Reformulated Gasoline Program -- 0.2 -- --

Heavy-Duty Trucks 6.0 0.9 0.6 --

 Cleaner In-Use Heavy-Duty Trucks 6.0 0.9 0.6 --

Goods Movement Sources 16.6 2.1 0.6 --

 Auxiliary Ship Engine Cold Ironing & Clean Technology -- -- -- --

 Cleaner Main Ship Engines and Fuel -- -- -- --

 Port Truck Modernization -- -- -- --

 Accelerated Intro. of Cleaner Line-Haul Locomotives 16.6 2.1 0.6 --

 Clean Up Existing Harbor Craft -- -- -- --

Off-Road Equipment 0.5 0.1 0 --

 Cleaner In-Use Off-Road Equipment (over 25hp) 0.5 0.1 0 --

 Cleaner In-Use Agricultural Equipment NYQ NYQ NYQ --

Other Off-Road Sources 0 10.6 -- --

 New Emission Standards for Recreational Boats 0 0.1 -- --

 Expanded Off-Road Rec. Vehicle Emission Standards -- 10.5 -- --

 Additional Evaporative Emission Standards -- NYQ -- --

 Vapor Recovery for Above Ground Storage Tanks -- NYQ -- --

Areaswide Sources -- 0.5 -- --

 Consumer Products Program -- 0.5 -- --

 Pesticides: DPR 2008 Pesticide Plan -- NYQ -- --

Emission Reductions from Proposed New Measures 23.6 14.7 1.2 --

NYQ = Not Yet Quantified. BAR = Bureau of Automotive Repair. DPR = Dept. of Pesticide Regulation

Locomotives measure relies on U.S. EPA rulemaking and industry agreement to accelerate fleet turnover.

Note: Emission reductions reflect the combination impact of regulations and supportive incentive programs.

(tons per day)

Proposed New SIP Measures NOx ROG SOx

Local Rule Adoption Schedule 

The rule actions identified in Table 3 below are expected to have some (currently unquantified) 

positive effect on ozone precursor emissions. The State all feasible measures actions are 

analyses that may result in a rule adoption action depending on the outcome of the feasibility 

analysis – the specified date is for completion of the feasibility analysis. 

Table 3 – MDAQMD Rule Adoption Schedule 

Rule Title Rule Nature Adoption Date

Residential Space Heaters Federal RACT 1/2009 

Publicly Owned Treatment Works Federal RACT 3/2009 

Graphic Arts Amendment Federal RACT 9/22/2008 

Solvent Cleaning and Degreasing State All Feasible Measures 10/27/2008 

Gas Turbines State All Feasible Measures 10/27/2008 

Boilers, Generators and Process Heaters State All Feasible Measures 10/27/2008 

Internal Combustion Engines State All Feasible Measures 10/27/2008 

Cement Kilns State All Feasible Measures 10/27/2008 

Commercial Charbroilers State All Feasible Measures 10/27/2008 

Residential Gas Furnaces State All Feasible Measures 10/27/2008 
24 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

Rule Title Rule Nature Adoption Date

Residential Water Heaters State All Feasible Measures 10/27/2008 

Soil Decontamination State All Feasible Measures 10/27/2008 

Landfill Gas State All Feasible Measures 10/27/2008 

Adhesives and Sealants State All Feasible Measures 10/27/2008 

Woodworking Operations State All Feasible Measures 10/27/2008 

Lawnmower Buyback State All Feasible Measures 10/27/2008 

Metal Parts and Products Coating State All Feasible Measures 10/27/2008 

Spray Booths State All Feasible Measures 10/27/2008 

Wood Flat Stock Coating State All Feasible Measures 10/27/2008 

Composting Operations State All Feasible Measures 10/27/2008 

Residential Wood Burning State All Feasible Measures 10/27/2008 

Contingency Measures 

The MDAQMD reaffirms the use of the State Enhanced Inspection and Maintenance Program as 

a contingency measure. The MDAQMD would implement the State of California’s version of 

Enhanced I&M should a contingency measure be triggered by failure to attain the Federal 8-hour 

standard. 

Required Progress 

Federal law specifies that each ozone non-attainment area must demonstrate ongoing emission 

reductions relative to the base year (2002). Federal law requires a three percent (3%) per year 

reduction in VOC emissions, and does not allow credit to be taken for certain federal motor 

vehicle control programs (FMVCP). Where both VOC and NOx emissions have been shown to 

contribute to high ozone levels, the Clean Air Act allows NOx emission reductions to be used to 

augment VOC emission reductions in order to demonstrate reasonable further progress. In nonattainment areas that are impacted by transport from other regions, the Federal Clear Air Act also 

allows emissions and emission reduction from those regions to be taken into account when 

assessing reasonable further progress. Air quality modeling, described in Chapter 4, 

demonstrates that emissions from the SCAB contribute to violations of the NAAQS in both the 

Antelope Valley and Mojave Desert portions of the federal non-attainment area (the WMDONA) 

Table 4 demonstrates that the rate of progress projected for the WMDONA meets Federal Clean 

Air Act requirements. The required rate of progress is met in part by substituting NOx reductions 

for VOC reductions at the rate of 1.6 tons of NOx per ton of VOC shortfall. The WMDONA 

consists of the Antelope Valley in Los Angeles County and the Mojave and Victor Valley 

portions of San Bernardino County. The reasonable further progress assessment takes into 

account projected emissions for upwind areas within 100 kilometers of the WMDONA 

(specifically Orange County and the SCAB portions of Los Angeles and San Bernardino 

Counties) as allowed by USEPA guidance. 
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

25

Table 4 - Reasonable Further Progress for the WMDONA 

2002 2008 2011 2014 2017 2020

Baseline ROG 882.5 651.1 601.9 570.3 551.9 543.5

CA MVCP/RVP Adjustment 0.0 54.4 71.0 84.5 91.5 96.0

RACT Corrections 000000

Adjusted 2002 Baseline ROG in milestone year 882.5 828.1 811.4 798.0 791.0 786.5

RFP commitment for ROG reductions from new measures 00000

Required % change since previous milestone year (ROG or 

NOx) compared to 2002

15% 9% 9% 9% 9%

Required % change since 2002 (ROG or NOx)1 15% 24% 33% 42% 51%

Target ROG levels 703.9 616.7 534.6 458.8 385.4

Apparent shortfall in ROG -52.78 -14.73 35.68 93.17 158.17

Apparent shortfall in ROG, % -6.4% -1.8% 4.5% 11.8% 20.1%

ROG shortfall previously provided by NOx substitution, % 0.0% 0.0% 0.0% 4.5% 11.8%

Actual ROG shortfall, % -6.4% -1.8% 4.5% 7.3% 8.3%

Baseline NOx 1123.7 905.0 789.0 696.9 622.9 574.2

CA MVCP Adjustment 0.0 64.8 80.8 93.2 98.7 102.8

Adjusted 2002 Baseline NOx in milestone year 1123.7 1058.8 1042.9 1030.4 1025.0 1020.8

RFP commitment for NOx reductions from new measures 000000

Change in NOx since 2002 153.8 253.8 333.6 402.1 446.6

Change in NOx since 2002, % 14.5% 24.3% 32.4% 39.2% 43.8%

NOx reductions since 2002 already used for RFP substitution 

and contingency through last milestone year, % 0.0% 3.0% 3.0% 7.5% 14.8%

NOx reductions since 2002 available for RFP substitution and 

contingency in this milestone year, %

14.5% 21.3% 29.4% 31.8% 29.0%

Change in NOx since 2002 used for ROG substitution in this 

milestone year, % 0.0% 0.0% 4.5% 7.3% 8.3%

Change in NOx since 2002 available for contingency in this 

milestone year, % 3.0% 3.0% 3.0% 3.0% 3.0%

Change in NOx since 2002 surplus after meeting substitution 

and contingency needs in this milestone year, %

11.5% 21.3% 24.9% 24.4% 20.6%

RFP shortfall, if any 0.0% 0.0% 0.0% 0.0% 0.0%

RFP Met? YES YES YES YES YES

Contingency Met? YES YES YES YES YES

1 15% ROG only reduction required from 2002-2008

Western Mojave Desert & Antelope Valley (with transport from Orange, San Bernardino-SCAB and LA-SCAB), summer 

planning, tons per day

Controlled Emission Inventories 

As the MDAQMD is not proposing any additional local control measures with quantified 

emission reductions, the controlled emission inventory is identical to the forecasted emission 

inventory. 

Conformity Budgets 

The forecasted emission inventories presented in this document are the emission budgets for 

general conformity purposes, as no additional control measures with quantified emission 

reductions are proposed. A project subject to the general conformity test must be demonstrated 

to conform with the applicable portion of the forecasted emission inventory. For a project that 

falls between forecasted years, a linearly interpolated inventory may be calculated. For a project 

that falls after 2020, use 2020. 

The forecasted on-road mobile source inventory represents the emission budget for 

transportation conformity purposes, as no transportation control measures are proposed. A 
26 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

project subject to the transportation conformity test must be demonstrated to conform with the 

forecasted on-road mobile source inventory. The FONA on-road mobile source inventory is 

presented below, in addition to the appendices. The portion presented in Table 5 is for 

information only - the MDAQMD is officially adopting the transportation budget for the entire 

Western Mojave Desert ozone non-attainment area as presented in Appendix C. 

Table 5 - Transportation Conformity Budget (FONA) 

(tons per ozone seasonal day) 

2002 2008 2011 2014 2017 2020

On-Road Mobile VOC 18.20 14.67 12.42 10.18 8.70 7.75

On-Road NOx 74.24 66.88 56.86 43.37 33.12 26.57
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27

CHAPTER 4 – Attainment Demonstration 

Modeling Approach Overview 

Modeling Domain 

Model Inputs 

Modeling Results 

ARB Weight of Evidence Assessment 
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29

ATTAINMENT DEMONSTRATION 

This chapter paraphrases and reiterates information from the most recent SCAQMD/CARB 

ozone model runs, the runs performed for the 2007 SCAQMD AQMP. For further information, 

please refer to Appendix V of that document.6

The Federal Clean Air Act (FCAA) required the use of photochemical air quality modeling to 

evaluate whether a proposed control strategy will result in attainment of the applicable ozone 

standard. Recognizing the uncertainty inherent in large-scale air quality models, recent federal 

guidance has also required an evaluation of supplementary data, known as a weight of evidence 

analysis. A weight of evidence analysis can also be used to support an attainment demonstration 

if photochemical modeling indicates that the control strategy will result in future ozone 

concentration that will approach but not quite reach the standard. 

Modeling Approach Overview 

The Western Mojave Desert ozone non-attainment area, which includes the MDAQMD, is a 

small portion of the complex greater Southern California airshed. Ozone and ozone precursors 

are known to flow (or be transported), under the influence of winds, throughout Southern 

California. The most technically accurate method of evaluating ozone concentrations, ozone 

emissions, and future ozone behavior is through a large modeling project that includes all of the 

affected areas in Southern California (and a portion of northern Mexico). The modeling effort 

has been performed as a joint project by all of the air districts in the region and CARB, with 

SCAQMD and CARB staff and resources doing the primary work. This regional modeling effort 

has allowed the most accurate understanding and prediction of future ozone concentrations for 

Southern California. 

The modeled attainment demonstration in this plan was prepared using photochemical dispersion 

and meteorological tools developed in response to USEPA modeling guidelines, and 

recommendations from air quality modeling experts. The Urban Airshed Model (UAM) is the 

regional modeling system preferred by USEPA and CARB for analyzing ozone non-attainment 

areas. The UAM predicts future ambient ozone concentrations under historical conditions that 

led to high ambient ozone concentrations. These conditions are typically multi-day ‘episodes’ in 

which the State and Federal ozone standards were exceeded. The UAM also evaluates ozone 

precursor emissions, local and regional meteorology, and regional topography to calculate ozone 

concentrations. These calculations are performed on an hourly basis throughout the modeled 

episode, thus allowing the UAM to stimulate changing conditions (i.e. night, day and wind). 

Meteorological fields were generated using the MM5 prognostic meteorological model, and the 

required modeling emissions inventories were developed by CARB and SCAQMD staff. The 

ozone air quality modeling utilized the Comprehensive Air Quality Model with Extensions 

(CAMx) model, with initial and boundary conditions based on estimates of clean-air 

concentrations. Analysis of the model outputs included the estimation of 1-hour and 8-hour 

ozone concentrations for each ozone monitoring site within the domain, as well as statistical 

 

6

 “Final 2007 Appendix V - Modeling and Attainment Demonstrations,” SCAQMD, June 2007 
30 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

measures comparing observed and stimulated ozone concentrations. These analyses were used 

to evaluate model performance by sub-region within the domain. 

Modeling Domain 

The modeling domain is based on the domain defined for the 1997 Southern California Ozone 

Study and includes the South Coast Air Basin and the surrounding coastal, desert and mountain 

areas, including the MDAQMD. This model domain includes the upwind sources within 

SCAQMD, which are responsible for the overwhelming ozone transport into the MDAQMD. 

The northern boundary of the model extends into Santa Barbara and Kern counties, while the 

southern boundary extends in Mexico. The eastern boundary of the modeling domain extends 

into the desert portions of San Bernardino and Riverside counties, while the western boundary 

extends into the Pacific Ocean. The domain horizontal grid is 116 by 80 cells, with a cell 

resolution of five kilometers. 

Model Inputs 

SCAQMD performed the UAM attainment demonstration using data maintained by CARB and 

MDAQMD. The emissions inventory used for the UAM is consistent with the emissions 

inventory presented in the appendices to this document. 

Modeling Results 

Future years are simulated twice using the UAM: first, using the uncontrolled emissions 

inventory; and second, using a reduced emissions inventory controlled by the proposed ozone 

control strategy. Comparing the uncontrolled and controlled ambient ozone concentrations 

identifies the effectiveness of the proposed ozone control strategy. Attainment year ambient 

ozone concentrations using the reduced emissions inventory controlled by the proposed ozone 

control strategy should achieve the ozone standard. 

As required by federal guidance, a relative reduction factor (RRF) approach was used in 

projecting future design values. The RRF reflects the ratio between the future year model 

prediction (in this case the end of 2020) and the reference year model prediction (in this case 

2002). A reference or base year design value is then multiplied by the RRF to project a future 

year design value. The modeling satisfies the minimum five episode requirement for use in 

developing a site-specific RRF for most sites, as recommended by the USEPA guidance for 

modeling 8-hour ozone design values. 

Table 6 presents the photochemical ozone modeling results for the FONA, including sites within 

the MDAQMD. 
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

31

Table 6 - 2020 Federal Ozone Attainment Demonstration 

Baseline (2001-2003) 2012 2017 2020

Lancaster 100.7 86.5 79.7 74.0

Phelan 104.7 92.6 86.7 80.5

Victorville 98.3 88.0 77.0 74.4

Hesperia 106.3 95.7 88.7 76.5

Barstow 87.6 79.7 73.2 79.5

Twentynine Palms 86.7 77.3 65.8 82.2

Modeled

(all values ozone in ppb)

The modeling results show that the MDAQMD will not attain the 8-hour ozone NAAQS (84 

ppb) by the 2012 attainment deadline for Serious ozone non-attainment areas, or the 2017 

deadline for Severe-15 non-attainment areas, but that the MDAQMD will attain by the 2020 

deadline for Severe-17 non-attainment areas. 

ARB Weight of Evidence Assessment 

Federal modeling guidelines also require non-attainment areas to determine whether other 

evidence, such as evaluations of air quality and emission trends, support the modeled attainment 

demonstration. USEPA’s ozone modeling guidance also indicates that when photochemical 

modeling projects attainment year concentrations of between 0.082 and 0.087 ppm, the State 

may conduct further analyses of the model outcomes and consider other evidence such as 

emissions and air quality trends data. If the weight of this evidence supports a finding that the 

proposed control program will result in attainment by the statutory deadline, the State may 

consider this evidence in determining whether the proposed control program will result in 

attainment. 

CARB has performed a detailed weight of evidence assessment for the attainment demonstration 

of the MDAQMD portion of the Western Mojave Desert federal ozone nonattainment area. This 

analysis supports the determination that the MDAQMD portion will attain the Federal 8-hour 

ozone standard by the 2020 deadline for Severe-17 areas on the basis of reduced transported air 

pollution from upwind areas. Because the photochemical modeling projected a high value of 

88.7 ppm in 2017, the weight of evidence analysis cannot be used to support a projection of 

attainment by 2017. The ARB Weight of Evidence assessment is presented in Appendix F. 
32 MDAQMD Federal 8-hour Ozone Attainment Plan 

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MDAQMD Federal 8-hour Ozone Attainment Plan 

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33

Appendices 

A - Base Year Emission Inventory 

B - Future Year Emission Inventories 

C - Transportation Conformity Budgets 

D - Annual Ambient Monitoring Data Summary 

E - ARB Weight of Evidence Assessment 
34 MDAQMD Federal 8-hour Ozone Attainment Plan 

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MDAQMD Federal 8-hour Ozone Attainment Plan 

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A-1

APPENDIX A - BASE YEAR EMISSION INVENTORY 

All emissions are presented in tons per ozone seasonal day (except where noted) for the 2002 

base year 

NOx VOC

Stationary

ELECTRIC UTILITIES 4.65 0.14

COGENERATION 0.10 0.00

MANUFACTURING AND INDUSTRIAL 2.49 0.15

SERVICE AND COMMERCIAL 2.56 0.21

OTHER (FUEL COMBUSTION) 0.22 0.02

SEWAGE TREATMENT 0.00 0.00

LANDFILLS 0.00 0.11

INCINERATORS 0.06 0.00

OTHER (WASTE DISPOSAL) 0.00 0.02

LAUNDERING 0.00 0.00

DEGREASING 0.00 1.00

COATINGS AND RELATED PROCESS SOLVENTS 0.00 0.57

PRINTING 0.00 0.01

ADHESIVES AND SEALANTS 0.00 0.03

OTHER (CLEANING AND SURFACE COATINGS) 0.00 0.00

PETROLEUM MARKETING 0.02 2.34

CHEMICAL 0.00 0.21

FOOD AND AGRICULTURE 0.00 0.00

MINERAL PROCESSES 29.95 0.95

METAL PROCESSES 0.50 0.00

WOOD AND PAPER 0.00 0.00

GLASS AND RELATED PRODUCTS 1.58 0.00

OTHER (INDUSTRIAL PROCESSES) 0.06 0.21

Stationary Subtotal 42.18 5.97

Area-Wide

CONSUMER PRODUCTS 0.00 2.78

ARCHITECTURAL COATINGS AND RELATED PROCESS SO 0.00 1.53

PESTICIDES/FERTILIZERS 0.00 0.02

ASPHALT PAVING / ROOFING 0.00 0.31

RESIDENTIAL FUEL COMBUSTION 0.45 0.15

FARMING OPERATIONS 0.00 0.72

CONSTRUCTION AND DEMOLITION 0.00 0.00

PAVED ROAD DUST 0.00 0.00

UNPAVED ROAD DUST 0.00 0.00

FUGITIVE WINDBLOWN DUST 0.00 0.00

FIRES 0.00 0.01

MANAGED BURNING AND DISPOSAL 0.17 0.42

COOKING 0.00 0.61

Area-Wide Subtotal 0.62 6.55

On-Road Mobile

LIGHT DUTY PASSENGER (LDA) 6.28 6.11

LIGHT DUTY TRUCKS - 1 (LDT1) 4.12 3.31

LIGHT DUTY TRUCKS - 2 (LDT2) 4.20 2.35

MEDIUM DUTY TRUCKS (MDV) 1.60 0.80

LIGHT HEAVY DUTY GAS TRUCKS - 1 (LHDV1) 0.34 0.25

LIGHT HEAVY DUTY GAS TRUCKS - 2 (LHDV2) 0.21 0.16

MEDIUM HEAVY DUTY GAS TRUCKS (MHDV) 0.20 0.23

HEAVY HEAVY DUTY GAS TRUCKS (HHDV) 0.53 0.14

LIGHT HEAVY DUTY DIESEL TRUCKS - 1 (LHDV1) 0.02 0.00

LIGHT HEAVY DUTY DIESEL TRUCKS - 2 (LHDV2) 0.46 0.01

MEDIUM HEAVY DUTY DIESEL TRUCKS (MHDV) 1.58 0.02

HEAVY HEAVY DUTY DIESEL TRUCKS (HHDV) 53.57 3.75

MOTORCYCLES (MCY) 0.19 0.93

HEAVY DUTY DIESEL URBAN BUSES (UB) 0.07 0.00

HEAVY DUTY GAS URBAN BUSES (UB) 0.05 0.02

SCHOOL BUSES (SB) 0.41 0.03

OTHER BUSES (OB) 0.12 0.02

MOTOR HOMES (MH) 0.29 0.07

On-Road Subtotal 74.24 18.20

Other Mobile

AIRCRAFT 0.16 0.13

TRAINS 29.20 2.19

RECREATIONAL BOATS 0.07 0.46

OFF-ROAD RECREATIONAL VEHICLES 0.23 10.61

OFF-ROAD EQUIPMENT 5.02 1.90

FARM EQUIPMENT 0.48 0.10

FUEL STORAGE AND HANDLING 0.00 0.58

Other Mobile Subtotal 35.15 15.98

FONA Totals: 152.19 46.69
A-2 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

FONA Point Sources for 2002 (all emissions in tons per year) 

ROG NOx

Aerochem Inc Aerospace El Mirage 0.9 176.7

Lockheed Martin Aerospace Helendale 0.3 0.2

SCLA Aerospace Victorville 0.0 0.5

Aerospace Totals: 1.2 177.4

Agcon Inc Batch Plant Helendale 0.0 0.0

Blue Diamond Materials Batch Plant Victorville 0.0 0.0

Calmat Vulcan Batch Plant Oro Grande 2.0 6.3

Cornerstone C&M Batch Plant Victorville 0.0 0.0

Dan Copp Crushing Batch Plant Barstow 0.0 1.2

Diversified Materials Batch Plant Hesperia 0.0 0.0

Diversified Materials Batch Plant Lucerne Valley 0.0 0.5

Granite Construction Batch Plant Twentynine Palms 0.0 0.0

Hanson Aggregate Batch Plant Newberry Springs 25.4 168.4

Hi-Grade Materials Batch Plant Hesperia 0.0 0.0

Hi-Grade Materials Batch Plant Lucerne Valley 0.9 13.7

Kinne Limestone Batch Plant Lucerne Valley 0.2 2.6

Robertson's Readymix Batch Plant Adelanto 0.1 0.8

Service Rock Products Batch Plant Barstow 0.0 0.0

Sierra Aggregate Batch Plant Lucerne Valley 0.6 6.9

Batch Plant Totals: 29.2 200.4

Cemex Black Mountain Quarry Cement Manufacturing Apple Valley 63.3 5383.0

Cemex River Plant Cement Manufacturing Victorville 0.0 0.0

Mitsubishi Cement Cement Manufacturing Lucerne Valley 17.1 2244.8

TXI Riverside Cement Cement Manufacturing Oro Grande 77.4 4186.0

Cement Manufacturing Totals: 157.8 11813.8

California Cogeneration Electric Generation Victorville 0.0 5.5

Daggett Leasing Electric Generation Daggett 6.3 13.0

Harper Lake Electric Generation Harper Lake 17.5 23.5

Kramer Junction Electric Generation Boron 15.3 62.0

Reliant Energy Electric Generation Daggett 15.8 909.5

SCE Victorville Electric Generation Victorville 0.0 0.4

US West Financing Electric Generation Oro Grande 0.7 35.8

Electric Generation Totals: 55.6 1049.7

Cabo Yachts Fiberglass Adelanto 18.9 0.0

Hawaiian Fiberglass Fiberglass Adelanto 5.6 0.0

Kormil Industries Fiberglass Hesperia 1.8 0.0

May Manufacturing Fiberglass Victorville 7.1 0.0

Molded Fiber Glass Fiberglass Adelanto 16.1 0.0

Pacific Tank Fiberglass Adelanto 4.0 0.0

Rainbow Fiberglass Fiberglass Adelanto 18.4 0.0

Fiberglass Totals: 71.9 0.0

AFG Industries Glass Manufacturing Victorville 0.1 578.5

Desert Valley Hospital Institution Victorville 0.3 0.7

Hi Desert Medical Institution Joshua Tree 0.0 0.7

St. Mary Hospital Institution Apple Valley 0.3 4.7

Veterans Home of Barstow Institution Barstow 0.1 1.1

Victor Valley Community Hospital Institution Victorville 0.1 3.2

Victor Valley Memorial Institution Victorville 0.1 0.0

Institution Totals: 0.9 10.4
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

A-3

AFFTC Edwards Military Edwards 0.0 0.1

US Army Dagget Airfield Military Daggett 1.1 1.3

USMC Logistics Base Nebo Military Barstow 5.4 11.5

USMC Logistics Base Yermo Military Barstow 20.2 35.3

USMCAGCC Military Twentynine Palms 3.5 17.3

Military Totals: 30.2 65.5

Brubaker-Mann Mining Barstow 0.0 0.0

Calico Rock Mining Barstow 0.0 0.0

OMYA Mining Lucerne Valley 0.1 1.1

Rheox Mining Newberry Springs 0.2 9.1

Specialty Minerals Mining Lucerne Valley 0.1 1.5

Victorville Industrial Minerals Mining Oro Grande 0.0 0.0

Mining Totals: 0.4 11.7

Advance Disposal Misc Coating/Manuf Hesperia 0.3 0.0

Alrayco Misc Coating/Manuf Adelanto 0.0 4.7

Daily Press Misc Coating/Manuf Victorville 1.5 0.0

Ennis Paint Misc Coating/Manuf Adelanto 0.0 0.0

Fast Tops Misc Coating/Manuf Hesperia 15.1 0.0

Induction Technology Misc Coating/Manuf Adelanto 0.4 0.0

Jack B. Kelly Misc Coating/Manuf Adelanto 0.7 0.0

JPM Product Misc Coating/Manuf Hesperia 0.5 0.1

Labelhouse Misc Coating/Manuf Adelanto 2.1 0.0

Lead Masters Misc Coating/Manuf Hesperia 0.0 0.0

McWelco Products Misc Coating/Manuf Hesperia 2.9 0.0

Mobile Pipe Wrap Misc Coating/Manuf Adelanto 14.6 0.2

National Arnold Magnetics Misc Coating/Manuf Adelanto 13.5 0.8

Northwest Pipe & Casing Misc Coating/Manuf Adelanto 11.5 0.0

Sherwin-Williams Misc Coating/Manuf Victorville 32.5 0.0

Simtec Misc Coating/Manuf Hesperia 0.1 0.0

Spede Tool Mfg Misc Coating/Manuf Adelanto 0.9 0.8

Spede Tool Mfg Misc Coating/Manuf Adelanto 4.6 0.0

Technique Design Misc Coating/Manuf Morongo Valley 0.2 0.0

TPS Technologies Misc Coating/Manuf Adelanto 0.2 15.7

World of Leisure Misc Coating/Manuf Adelanto 6.9 0.1

Misc Coating/Manuf Totals: 108.5 22.4

PG&E Hinkley Natural Gas Transmission Hinkley 70.1 578.7

SCG Adelanto Natural Gas Transmission Adelanto 0.5 32.8

SCG Kelso Natural Gas Transmission Kelso 0.5 80.4

SCG Newberry Springs Natural Gas Transmission Newberry Springs 3.0 171.5

SCG Victorville Natural Gas Transmission Victorville 0.1 0.0

Natural Gas Transmission Totals: 74.2 863.4

Accent Auto Body Paint & Body Hesperia 0.6 0.0

Best Auto Body Paint & Body Hesperia 0.1 0.0

Daves Auto Body Paint & Body Lenwood 0.1 0.0

Doman Auto Body Paint & Body Hesperia 0.2 0.0

Mc Geez Auto Body Paint & Body Twentynine Palms 1.4 0.0

Monty's Chevrolet Paint & Body Victorville 1.0 0.0

Pacific Paint Paint & Body Hesperia 0.2 0.0

Rancho Motors Paint & Body Victorville 0.3 0.0

Sonshine Auto Body Paint & Body Victorville 1.0 0.0

Sunland Ford Paint & Body Victorville 0.2 0.0

Sunset Paint and Body Paint & Body Hesperia 1.7 0.0

Yucca Auto Body Paint & Body Yucca Valley 1.0 0.0

Yucca Valley Ford Paint & Body Yucca Valley 0.3 0.0

Paint & Body Totals: 8.1 0.0
A-4 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

Beck Oil Petroleum Pipeline & Terminal Victorville 0.6 0.0

CalNev Bulk Plant Petroleum Pipeline & Terminal Daggett 35.1 0.0

Petroleum Pipeline & Terminal Totals: 35.7 0.0

Barstow Railyard Railroad Switching Barstow 6.4 0.9

City of Barstow Wastewater/Landfill/Water Barstow 0.2 37.8

Lenwood Hinkley Wastewater/Landfill/Water Hinkley 0.1 0.8

Victor Valley Wastewater Treatment Wastewater/Landfill/Water Victorville 0.0 1.5

Wastewater/Landfill/Water Totals: 0.3 40.1

C&M Wood Industries Wood Coating Hesperia 6.9 1.2

Commercial Wood Products Wood Coating Adelanto 7.9 0.0

Hacker Wallsystems Wood Coating Yucca Valley 0.1 0.0

Inland Panel Coatings Wood Coating Adelanto 20.9 0.0

Mueller Turner Wood Coating Morongo Valley 1.3 0.0

Terrell Industries Wood Coating Hesperia 13.3 0.0

Walnut Valley Finishing Wood Coating Adelanto 26.7 1.9

Wood Coating Totals: 77.1 3.1

FONA Totals (tpy): 657.6 14837.3

Totals (tpaad): 1.80 40.65
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

B-1

APPENDIX B - FUTURE YEAR EMISSION INVENTORIES 

(all emissions in tons per ozone seasonal day unless otherwise indicated) 

VOC: 

SUBCATEGORY 2002 2008 2011 2014 2017 2020

Stationary

ELECTRIC UTILITIES 0.14 0.20 0.21 0.21 0.23 0.27

COGENERATION 0.00 0.00 0.00 0.00 0.00 0.00

MANUFACTURING AND INDUSTRIAL 0.15 0.16 0.17 0.18 0.19 0.19

SERVICE AND COMMERCIAL 0.21 0.21 0.21 0.21 0.21 0.21

OTHER (FUEL COMBUSTION) 0.02 0.02 0.02 0.02 0.02 0.02

SEWAGE TREATMENT 0.00 0.00 0.00 0.00 0.00 0.00

LANDFILLS 0.11 0.13 0.13 0.14 0.15 0.15

INCINERATORS 0.00 0.00 0.00 0.00 0.01 0.01

OTHER (WASTE DISPOSAL) 0.02 0.02 0.02 0.02 0.03 0.03

LAUNDERING 0.00 0.00 0.00 0.00 0.00 0.00

DEGREASING 1.00 1.00 1.04 1.08 1.11 1.15

COATINGS AND RELATED PROCESS SOLVENTS 0.57 0.62 0.65 0.69 0.72 0.75

PRINTING 0.01 0.01 0.01 0.01 0.01 0.01

ADHESIVES AND SEALANTS 0.03 0.03 0.04 0.04 0.04 0.05

OTHER (CLEANING AND SURFACE COATINGS) 0.00 0.00 0.00 0.00 0.00 0.00

PETROLEUM MARKETING 2.34 2.59 2.72 2.85 2.99 3.13

CHEMICAL 0.21 0.25 0.27 0.29 0.30 0.32

FOOD AND AGRICULTURE 0.00 0.00 0.00 0.00 0.00 0.00

MINERAL PROCESSES 0.95 1.05 1.11 1.17 1.23 1.29

METAL PROCESSES 0.00 0.00 0.00 0.00 0.00 0.00

WOOD AND PAPER 0.00 0.00 0.00 0.00 0.00 0.00

GLASS AND RELATED PRODUCTS 0.00 0.00 0.00 0.00 0.00 0.00

OTHER (INDUSTRIAL PROCESSES) 0.21 0.22 0.25 0.25 0.28 0.31

Stationary Subtotal 5.97 6.53 6.85 7.18 7.52 7.89

Area-Wide

CONSUMER PRODUCTS 2.78 2.80 3.01 3.22 3.43 3.64

ARCHITECTURAL COATINGS AND RELATED PROCES 1.53 1.37 1.41 1.46 1.51 1.57

PESTICIDES/FERTILIZERS 0.02 0.02 0.02 0.02 0.02 0.02

ASPHALT PAVING / ROOFING 0.31 0.32 0.32 0.32 0.33 0.33

RESIDENTIAL FUEL COMBUSTION 0.15 0.16 0.17 0.17 0.18 0.18

FARMING OPERATIONS 0.72 0.72 0.72 0.72 0.72 0.72

CONSTRUCTION AND DEMOLITION 0.00 0.00 0.00 0.00 0.00 0.00

PAVED ROAD DUST 0.00 0.00 0.00 0.00 0.00 0.00

UNPAVED ROAD DUST 0.00 0.00 0.00 0.00 0.00 0.00

FUGITIVE WINDBLOWN DUST 0.00 0.00 0.00 0.00 0.00 0.00

FIRES 0.01 0.01 0.01 0.01 0.01 0.01

MANAGED BURNING AND DISPOSAL 0.42 0.37 0.35 0.33 0.31 0.28

COOKING 0.61 0.68 0.72 0.75 0.79 0.82

Area-Wide Subtotal 6.55 6.46 6.74 7.01 7.30 7.58

On-Road Mobile

LIGHT DUTY PASSENGER (LDA) 6.11 3.75 2.84 2.07 1.63 1.34

LIGHT DUTY TRUCKS - 1 (LDT1) 3.31 2.06 1.68 1.31 1.00 0.79

LIGHT DUTY TRUCKS - 2 (LDT2) 2.35 1.77 1.54 1.29 1.14 1.03

MEDIUM DUTY TRUCKS (MDV) 0.80 0.77 0.69 0.64 0.59 0.56

LIGHT HEAVY DUTY GAS TRUCKS - 1 (LHDV1) 0.25 0.18 0.15 0.13 0.14 0.15

LIGHT HEAVY DUTY GAS TRUCKS - 2 (LHDV2) 0.16 0.10 0.09 0.07 0.07 0.06

MEDIUM HEAVY DUTY GAS TRUCKS (MHDV) 0.23 0.11 0.08 0.06 0.04 0.03

HEAVY HEAVY DUTY GAS TRUCKS (HHDV) 0.14 0.09 0.08 0.07 0.05 0.05

LIGHT HEAVY DUTY DIESEL TRUCKS - 1 (LHDV1) 0.00 0.01 0.01 0.01 0.01 0.01

LIGHT HEAVY DUTY DIESEL TRUCKS - 2 (LHDV2) 0.01 0.01 0.01 0.01 0.01 0.01

MEDIUM HEAVY DUTY DIESEL TRUCKS (MHDV) 0.02 0.02 0.02 0.02 0.02 0.02

HEAVY HEAVY DUTY DIESEL TRUCKS (HHDV) 3.75 3.80 3.28 2.52 1.92 1.54

MOTORCYCLES (MCY) 0.93 1.88 1.84 1.88 1.98 2.08

HEAVY DUTY DIESEL URBAN BUSES (UB) 0.00 0.00 0.00 0.00 0.00 0.00

HEAVY DUTY GAS URBAN BUSES (UB) 0.02 0.02 0.02 0.02 0.02 0.02

SCHOOL BUSES (SB) 0.03 0.03 0.03 0.03 0.03 0.03

OTHER BUSES (OB) 0.02 0.02 0.02 0.02 0.02 0.01

MOTOR HOMES (MH) 0.07 0.05 0.04 0.03 0.02 0.01

On-Road Subtotal 18.20 14.67 12.42 10.18 8.70 7.75

Other Mobile

AIRCRAFT 0.13 0.16 0.17 0.19 0.20 0.21

TRAINS 2.19 2.24 2.29 2.35 2.43 2.52

RECREATIONAL BOATS 0.46 0.39 0.35 0.33 0.31 0.30

OFF-ROAD RECREATIONAL VEHICLES 10.61 15.28 16.82 18.61 20.65 22.94

OFF-ROAD EQUIPMENT 1.90 1.67 1.48 1.32 1.21 1.15

FARM EQUIPMENT 0.10 0.08 0.06 0.05 0.04 0.03

FUEL STORAGE AND HANDLING 0.58 0.40 0.33 0.28 0.24 0.22

Other Mobile Subtotal 15.98 20.23 21.50 23.12 25.07 27.37

Grand Total 46.69 47.89 47.51 47.50 48.60 50.58
B-2 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

NOx: 

SUBCATEGORY 2002 2008 2011 2014 2017 2020

Stationary

ELECTRIC UTILITIES 4.65 6.75 7.00 7.00 7.79 8.98

COGENERATION 0.10 0.10 0.10 0.10 0.10 0.09

MANUFACTURING AND INDUSTRIAL 2.49 2.76 2.88 3.03 3.16 3.28

SERVICE AND COMMERCIAL 2.56 2.59 2.58 2.57 2.54 2.50

OTHER (FUEL COMBUSTION) 0.22 0.24 0.24 0.24 0.24 0.24

SEWAGE TREATMENT 0.00 0.00 0.00 0.00 0.00 0.00

LANDFILLS 0.00 0.00 0.00 0.00 0.00 0.00

INCINERATORS 0.06 0.06 0.07 0.07 0.07 0.08

OTHER (WASTE DISPOSAL) 0.00 0.00 0.00 0.00 0.00 0.00

LAUNDERING 0.00 0.00 0.00 0.00 0.00 0.00

DEGREASING 0.00 0.00 0.00 0.00 0.00 0.00

COATINGS AND RELATED PROCESS SOLVENTS 0.00 0.00 0.00 0.00 0.00 0.00

PRINTING 0.00 0.00 0.00 0.00 0.00 0.00

ADHESIVES AND SEALANTS 0.00 0.00 0.00 0.00 0.00 0.00

OTHER (CLEANING AND SURFACE COATINGS) 0.00 0.00 0.00 0.00 0.00 0.00

PETROLEUM MARKETING 0.02 0.02 0.02 0.02 0.02 0.02

CHEMICAL 0.00 0.00 0.00 0.00 0.00 0.00

FOOD AND AGRICULTURE 0.00 0.00 0.00 0.00 0.00 0.00

MINERAL PROCESSES 29.95 32.74 34.35 36.11 37.78 39.36

METAL PROCESSES 0.50 0.49 0.52 0.55 0.58 0.61

WOOD AND PAPER 0.00 0.00 0.00 0.00 0.00 0.00

GLASS AND RELATED PRODUCTS 1.58 1.72 1.90 2.08 2.19 2.33

OTHER (INDUSTRIAL PROCESSES) 0.06 0.06 0.06 0.06 0.07 0.08

Stationary Subtotal 42.18 47.53 49.72 51.84 54.55 57.56

Area-Wide

CONSUMER PRODUCTS 0.00 0.00 0.00 0.00 0.00 0.00

ARCHITECTURAL COATINGS AND RELATED PROCESS SOLVEN 0.00 0.00 0.00 0.00 0.00 0.00

PESTICIDES/FERTILIZERS 0.00 0.00 0.00 0.00 0.00 0.00

ASPHALT PAVING / ROOFING 0.00 0.00 0.00 0.00 0.00 0.00

RESIDENTIAL FUEL COMBUSTION 0.45 0.48 0.49 0.50 0.52 0.53

FARMING OPERATIONS 0.00 0.00 0.00 0.00 0.00 0.00

CONSTRUCTION AND DEMOLITION 0.00 0.00 0.00 0.00 0.00 0.00

PAVED ROAD DUST 0.00 0.00 0.00 0.00 0.00 0.00

UNPAVED ROAD DUST 0.00 0.00 0.00 0.00 0.00 0.00

FUGITIVE WINDBLOWN DUST 0.00 0.00 0.00 0.00 0.00 0.00

FIRES 0.00 0.00 0.00 0.00 0.00 0.00

MANAGED BURNING AND DISPOSAL 0.17 0.15 0.14 0.14 0.13 0.12

COOKING 0.00 0.00 0.00 0.00 0.00 0.00

Area-Wide Subtotal 0.62 0.63 0.64 0.64 0.65 0.65

On-Road Mobile

LIGHT DUTY PASSENGER (LDA) 6.28 3.81 2.99 2.23 1.76 1.42

LIGHT DUTY TRUCKS - 1 (LDT1) 4.12 2.38 2.00 1.59 1.24 0.97

LIGHT DUTY TRUCKS - 2 (LDT2) 4.20 3.12 2.65 2.15 1.79 1.50

MEDIUM DUTY TRUCKS (MDV) 1.60 1.57 1.35 1.15 0.99 0.84

LIGHT HEAVY DUTY GAS TRUCKS - 1 (LHDV1) 0.34 0.36 0.37 0.36 0.36 0.38

LIGHT HEAVY DUTY GAS TRUCKS - 2 (LHDV2) 0.21 0.13 0.13 0.12 0.12 0.12

MEDIUM HEAVY DUTY GAS TRUCKS (MHDV) 0.20 0.14 0.11 0.09 0.07 0.06

HEAVY HEAVY DUTY GAS TRUCKS (HHDV) 0.53 0.35 0.35 0.34 0.35 0.36

LIGHT HEAVY DUTY DIESEL TRUCKS - 1 (LHDV1) 0.02 0.59 0.46 0.36 0.30 0.26

LIGHT HEAVY DUTY DIESEL TRUCKS - 2 (LHDV2) 0.46 0.57 0.49 0.40 0.32 0.27

MEDIUM HEAVY DUTY DIESEL TRUCKS (MHDV) 1.58 1.92 1.68 1.29 0.99 0.78

HEAVY HEAVY DUTY DIESEL TRUCKS (HHDV) 53.57 50.49 42.82 31.83 23.39 18.22

MOTORCYCLES (MCY) 0.19 0.50 0.51 0.54 0.58 0.62

HEAVY DUTY DIESEL URBAN BUSES (UB) 0.07 0.06 0.05 0.05 0.05 0.05

HEAVY DUTY GAS URBAN BUSES (UB) 0.05 0.04 0.04 0.04 0.04 0.04

SCHOOL BUSES (SB) 0.41 0.44 0.47 0.49 0.49 0.48

OTHER BUSES (OB) 0.12 0.14 0.13 0.11 0.09 0.07

MOTOR HOMES (MH) 0.29 0.28 0.26 0.22 0.18 0.14

On-Road Subtotal 74.24 66.88 56.86 43.37 33.12 26.57

Other Mobile

AIRCRAFT 0.16 0.20 0.21 0.23 0.25 0.26

TRAINS 29.20 22.25 17.07 18.16 19.42 20.85

RECREATIONAL BOATS 0.07 0.10 0.10 0.10 0.11 0.11

OFF-ROAD RECREATIONAL VEHICLES 0.23 0.33 0.37 0.41 0.46 0.51

OFF-ROAD EQUIPMENT 5.02 4.27 3.73 3.18 2.61 2.17

FARM EQUIPMENT 0.48 0.37 0.32 0.26 0.20 0.15

FUEL STORAGE AND HANDLING 0.00 0.00 0.00 0.00 0.00 0.00

Other Mobile Subtotal 35.15 27.52 21.81 22.35 23.04 24.05

Grand Total 152.19 142.56 129.03 118.20 111.35 108.83
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

C-1

APPENDIX C –TRANSPORTATION CONFORMITY BUDGETS 

Antelope Valley - Western Mojave Desert Nonattainment Area

Transportation Conformity Budgets

Summer Planning Emissions in Tons per Day*

2008

ROG NOx

On-Road Emissions from 

EMFAC2007 22.7 82.0

Adjustments to Baseline* 0.0 -4.4

Net Inventory 22.63 77.56

Conformity Budget** 23 78

* Reductions from adopted rules not

 reflected in EMFAC

** Budget is obtained by rounding up

 to the nearest ton.

Antelope Valley - Western Mojave Desert Nonattainment Area

Transportation Conformity Budgets

Summer Planning Emissions in Tons per Day*

2011

ROG NOx

On-Road Emissions from 

EMFAC2007 19.8 70.5

Adjustments to Baseline* -0.1 -4.4

Net Inventory 19.7 66.1

Conformity Budget** 20 67

* Reductions from adopted rules not

 reflected in EMFAC

** Budget is obtained by rounding up from two significant figures

 to the nearest ton.
C-2 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

Antelope Valley - Western Mojave Desert Nonattainment Area

Transportation Conformity Budgets

Summer Planning Emissions in Tons per Day*

2014

ROG NOx

On-Road Emissions from 

EMFAC2007 16.6 54.9

Adjustments to Baseline* -0.1 -4.1

State Strategy Reductions -3.4 -15.3

Net Inventory 13.0 35.5

Conformity Budget** 14 36

* Reductions from adopted rules not

 reflected in EMFAC

** Budget is obtained by rounding up from two significant figures

 to the nearest ton.

Antelope Valley - Western Mojave Desert Nonattainment Area

Transportation Conformity Budgets

Summer Planning Emissions in Tons per Day*

2017

ROG NOx

On-Road Emissions from 

EMFAC2007 14.5 43.1

Adjustments to Baseline* -0.1 -3.9

State Strategy Reductions -2.5 -14.1

Net Inventory 11.9 25.1

Conformity Budget** 12 26

* Reductions from adopted rules not

 reflected in EMFAC

** Budget is obtained by rounding up from two significant figures

 to the nearest ton.
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

C-3

Antelope Valley - Western Mojave Desert Nonattainment Area

Transportation Conformity Budgets

Summer Planning Emissions in Tons per Day*

2020

ROG NOx

On-Road Emissions from 

EMFAC2007 13.2 35.4

Adjustments to Baseline* -0.1 -3.7

State Strategy Reductions -1.7 -7.4

Net Inventory 11.4 24.2

Conformity Budget** 12 25

* Reductions from adopted rules not

 reflected in EMFAC

** Budget is obtained by rounding up from two significant figures

 to the nearest ton.
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D-1

APPENDIX D - ANNUAL AMBIENT MONITORING DATA SUMMARY 

Maximum One Hour Ozone (ppm)

Barstow Hesperia Phelan Trona Twentynine Palms Victorville

1988 0.15 0.27 0.19 0.12 0.15 0.18

1989 0.14 0.21 0.22 0.10 0.13 0.17

1990 0.13 0.27 0.24 0.11 0.14 0.18

1991 0.13 0.19 0.24 0.12 0.14 0.19

1992 0.13 0.23 0.19 0.10 0.12 0.19

1993 0.13 0.17 0.20 0.10 0.13 0.16

1994 0.13 0.18 0.19 0.10 0.12 0.16

1995 0.12 0.17 0.24 0.09 0.11 0.15

1996 0.13 0.17 0.18 0.10 0.12 0.16

1997 0.12 0.18 0.19 0.10 0.12 0.15

1998 0.11 0.16 0.20 0.11 0.12 0.16

1999 0.12 0.13 0.14 0.10 0.11 0.12

2000 0.11 0.16 0.14 0.09 0.11 0.14

2001 0.10 0.12 0.15 0.09 0.12 0.11

2002 0.11 0.15 0.15 0.11 0.10 0.13

2003 0.11 0.16 0.14 0.10 0.10 0.15

2004 0.10 0.14 0.12 0.11 0.10 0.11

2005 0.10 0.14 0.15 0.09 0.11 0.13

2006 0.11 0.15 0.14 0.09 0.14

Maximum 3-Yr Av 4th H

1986 0.225 0.168

1987 0.161 0.163

1988 0.167 0.165

1989 0.161 0.153

1990 0.198 0.151

1991 0.173 0.151

1992 0.165 0.147

1993 0.147 0.139

1994 0.155 0.138

1995 0.170 0.137

1996 0.146 0.131

1997 0.133 0.124

1998 0.144 0.127

1999 0.122 0.118

2000 0.132 0.110

2001 0.117 0.102

2002 0.123 0.106

2003 0.13 0.106

2004 0.119 0.107

2005 0.123 0.105

2006 0.124 0.103

8-Hour Trend (FONA)
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E-1

APPENDIX E – ARB WEIGHT OF EVIDENCE ASSESSMENT 

(prepared by CARB staff) 
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E-3

Western Mojave Desert Weight of Evidence Assessment

Introduction

For ozone planning purposes, the U.S. EPA has combined portions of Los Angeles and 

San Bernardino counties and designated them as the Western Mojave 8-Hour Ozone 

Nonattainment Area. The Nonattainment Area includes the northeast portion of 

Los Angeles County and the southwest portion of San Bernardino County, both of which 

are in the Mojave Desert Air Basin (refer to Figure 1). These two areas are managed by 

two separate jurisdictions. The Antelope Valley Air Quality Management District has 

jurisdiction over the Los Angeles County portion of the Nonattainment Area, while the 

Mojave Desert Air Quality Management District has jurisdiction over the San Bernardino 

County portion of the Nonattainment Area. This Weight of Evidence (WOE) evaluation 

covers the San Bernardino County portion of the Nonattainment Area which is referred 

to as the Western Mojave Desert Planning Area in this document. 

 

Figure 1: Western Mojave Desert Planning Area and Surrounding Region 

 
E-4 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

The Western Mojave Desert Planning Area (Western Mojave Desert or Planning Area) 

is currently classified as a Moderate nonattainment area for the federal 8-hour ozone 

standard and has a nominal attainment deadline of June 15, 2010. However, air quality 

analyses, as well as photochemical modeling completed by the South Coast Air Quality 

Management District (South Coast District), indicate it is unlikely the Desert will attain by 

2010, as required for Moderate areas. Ozone air quality in the Western Mojave Desert 

is impacted by transport from both the South Coast Air Basin (South Coast) and the 

San Joaquin Valley Air Basin (San Joaquin Valley). As a result, attainment projections 

for Western Mojave Desert must consider not only local emissions, but also the impact 

of transported emissions and pollutants. 

Although the proposed South Coast, San Joaquin Valley, and statewide emissions 

reduction strategies will lower ozone concentrations in the Western Mojave Desert over 

the next several years, the expected level of emissions reductions will fall short of those 

needed to attain by 2010. However, the modeling results do show that the Planning 

Area could attain by the 2021 deadline for a Severe-17 nonattainment area. Therefore, 

the Mojave Desert Air Quality Management District has requested a reclassification to 

Severe-17, with an attainment date of June 15, 2021. The following sections describe 

the air quality and emissions analyses needed to justify reclassifying the Western 

Mojave Desert Planning Area as Severe-17 and to support the overall conclusion that 

the Planning Area will attain the federal standard by 2021. 

U.S. EPA Attainment Demonstration Requirements

The attainment demonstration portion of a SIP consists of the analyses used to 

determine whether a proposed control strategy provides the emissions reductions 

needed to meet the federal standard by the attainment year. This attainment 

demonstration includes photochemical modeling which predicts that projected 

emissions controls will result in an 8-hour ozone design value of 0.082 parts per 

million (ppm) by the end of 2020 (note: because the design value is based on a 

three-year average, an area must have a design value that meets the standard at the 

end of the year prior to the attainment year; for example, an area with a June 15, 2021 

attainment date must have a design value that meets the standard at the end of 2020).

Because of the uncertainties inherent in photochemical modeling, the U.S. EPA allows 

states to supplement the modeling results with a “Weight of Evidence” (WOE) 

demonstration when the model predicts ozone levels of 0.082 ppm to 0.087 ppm. 

The WOE assessment may include consideration of measured air quality, emissions, 

and meteorological data, evaluation of other air quality indicators, and additional air 

quality modeling. Because all analysis methods have strengths and weaknesses, 

examining an air quality problem in a variety of ways helps offset the limitations and 

uncertainties that are inherent in each particular method. 

The scope of the WOE analysis is different for each nonattainment area. The level of 

detail appropriate for a particular area depends upon the complexity of the air quality 

problem, how far into the future the attainment deadline is, and the amount of data and 
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

E-5

modeling available. This document summarizes the analyses that comprise the WOE 

assessment for the Western Mojave Desert Planning Area as of March 2008. 

Physical Context

The Western Mojave Desert Planning Area (refer to Figure 1) is located in southwestern 

San Bernardino County, within the Mojave Desert Air Basin and falls under the 

jurisdiction of the Mojave Desert Air Quality Management District. 

Although the Western Mojave Desert Planning Area is the focus of this WOE 

Evaluation, on the federal level, the Western Mojave Desert Planning Area is included 

with the Antelope Valley Planning Area as a single federal 8-hour ozone nonattainment 

area. 

The Western Mojave Desert area extends about 90 miles north to south and 120 miles 

east to west. The Planning Area is classified as high desert with elevations ranging 

from 2,000 to 5,000 feet and annual precipitation averaging 4 to 6 inches. Average 

daily maximum temperatures are highest during July, ranging from 100 to 105 degrees 

Fahrenheit. In contrast, winter daily maximum temperatures average in the low 60s. 

The Western Mojave Desert is a recreational area and given its proximity to the South 

Coast, provides a transportation link to the urbanized area. Major cities in the Planning 

Area include Victorville, Hesperia, Apple Valley, and Twentynine Palms. Overall, the 

Planning Area comprises about 9200 square miles and has a total population of more 

than 350,000 (2006 estimate). The major highways traveling through the Western 

Mojave Desert are Interstate 15, Interstate 40, U.S. Highway 395, and California State 

Highway 58. These roadways carry significant commuter and truck traffic in and out of 

the South Coast region. 

Transport Impacts

As mentioned earlier, ozone concentrations in the Western Mojave Desert are impacted 

by transport from both the South Coast and San Joaquin Valley. Therefore, transport 

must be considered in evaluating the prospects for attainment. Several mountain 

passes provide transport routes into the Western Mojave Desert from the South Coast. 

Soledad Canyon on the eastern edge of the San Gabriel Mountains and Cajon Pass 

between the San Gabriel and San Bernardino mountains are the two major transport 

corridors from the South Coast to the Western Mojave Desert. A third transport corridor 

runs through the Tehachapi Pass in the Tehachapi Mountains and provides an outlet for 

emissions and pollutants from the southern San Joaquin Valley to the Western Mojave 

Desert. 

 

Previous ARB transport assessments concluded that during 1-hour State ozone 

exceedances, the transport contribution from the South Coast to ozone in the Western 

Mojave Desert could be overwhelming. The transport assessments also found there 
E-6 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

could be a shared impact between the South Coast and Western Mojave Desert, 

meaning ozone exceedances could be caused by a combination 

of transport and local emissions (ARB 1990; ARB 1996)7, 8. In addition to the South 

Coast impact, the ARB transport assessments found an overwhelming transport impact 

from the San Joaquin Valley to the Western Mojave Desert. 

Although the impact of transport on ozone air quality in the Western Mojave Desert can 

be overwhelming, the frequency of the impacts has not been determined. However, 

more recent analyses indicate that ozone exceedances in the Western Mojave Desert 

continue to be impacted by transported pollutants. Areas impacted by transport 

generally show ozone concentrations peaking in the late afternoon or evening hours. 

The 24-hour ozone profile for Hesperia, which is located in the southwestern portion of 

the Planning Area, just north of the South Coast (refer to Figure 2), shows this 

characteristic later peak, indicating that transport is an important contributor to high 

ozone concentrations in this area. 

The impact of transport is also seen in the southeastern portion of the Planning Area. 

Figure 3 shows diurnal plots of hourly average ozone concentrations at Banning in the 

South Coast, Palm Springs in the Coachella Valley Planning Area, 

and Joshua Tree in the Western Mojave Desert Planning Area (refer to Figure 1 for 

relative locations). These three sites reflect a general west-to-east transport of 

emissions and pollutants. As shown in Figure 3, the daily peak ozone concentration 

occurs at a progressively later hour with distance downwind of the major South Coast 

emissions source areas. This progressively later peak hour 

with distance suggests that transport is the primary cause of high ozone at the 

downwind locations. Therefore, as emissions are reduced in the upwind source 

areas, ozone air quality in the downwind transport impacted areas should also improve. 

Recent photochemical modeling completed for the Western Mojave Desert also 

evaluated the impact of transported emissions on air quality in the Western Mojave 

Desert. In general, the results showed that without transport, emissions within the 

Western Mojave Desert would likely not be sufficient to generate a violation of the 

federal 8-hour ozone standard in future years. 

 

7 Air Resources Board, 1990: Assessment and Mitigation of the Impacts of Transported Pollutants on 

Ozone Concentrations within California. ARB Staff Report prepared by the Technical Support Division 

and the Office of Air Quality Planning and Liaison, June 1990. 

8 Air Resources Board, 1996: Second Triennial Review of the Assessment of the Impacts of Transported 

Pollutants on Ozone Concentrations in California (Revised). ARB Staff Report prepared by the Technical 

Support Division, November 1996. 
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June 9, 2008 

E-7

Figure 2: Hourly Average Ozone on the Top Ten Days During 2006 

at Hesperia 

 

Hourly Ozone on the Top Ten Days During 2006 at Hesperia

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Hour (PST)

Concentration (ppm)

Figure 3: Hourly Average Ozone on the Top Ten Days During 2006 

at Banning, Palm Springs, and Joshua Tree 

 

Hourly Average Ozone on Top Ten Days During 2006 at Downwind Sites

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Hour (PST)

Concentration (ppm)

Joshua Tree Palm Springs Banning Airport

Ozone Air Quality Trends

The following discussion is based on ozone air quality data collected at sites in the 

Western Mojave Desert from 1995 to the present. During this time period, five 

monitoring sites have complete data: Barstow, Hesperia-Olive Street, Joshua TreeNational Monument, Phelan-Beekley Road & Phelan Road, and Victorville-14306 Park 
E-8 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

Avenue. In addition, a sixth site operated at Twentynine Palms, but data are available 

only through 2005. Of the six long-term sites, Hesperia, Joshua Tree, and Phelan are 

the high sites with respect to ozone. 

Ozone indicator values for the Western Mojave Desert are shown in Figure 4. As seen 

in the figure, all indicators have decreased since 1995, indicating overall improvements 

in the various measures of ozone air quality. As in many other areas of the State, the 

largest drop is seen in the number of exceedance days – an overall decrease of 

35 percent from 1995 to 2006 (from 74 days to 47 days). The value for 2007 is slightly 

less than that for 2006, with 45 exceedance days during the year. 

Figure 4: Western Mojave Desert Planning Area Ozone Trends 1995 to 2006 

 

Western Mojave Desert Planning Area Ozone Statistics

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1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Ozone (ppm)

0

20

40

60

80

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Number of Days

Maximum Concentration Design Value Mean Top 30 Exceedance Days

While not quite as high, the improvement in the other indicators has also been fairly 

substantial. Overall, the maximum concentration and design value decreased 20 and 

25 percent, respectively. The decrease in the mean Top 30 was a bit less, at 

15 percent between 1995 and 2006. Based on complete data, the 2007 maximum 

concentration was lower (0.109 ppm in 2007 compared with 0.124 ppm in 2006), while 

the mean Top 30 concentration was comparable (0.096 ppm in 2007 compared with 

0.095 ppm in 2006). The 2007 design value showed no change from the previous year 

(0.103 ppm in 2007 and 2006). Although the 2007 design value for Western Mojave 

Desert is still more than 20 percent above the federal standard, it compares with a 

design value nearly 60 percent above the standard in 1995 (0.133 ppm). Thus, the area 

has already achieved two-thirds of the progress needed to attain the standard. 

It is interesting to note that the Western Mojave Desert trend lines for all four indicators 

show little or no progress between 2001 and 2006. A similar trend is seen in ozone 

statistics for the South Coast (refer to Figure 5). As discussed earlier in this document, 
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

E-9

emissions and pollutants transported from the South Coast can have an overwhelming 

impact on ozone in the Western Mojave Desert. Therefore, it is not unexpected that the 

shapes of the trend lines for the Western Mojave Desert and the South Coast are 

similar. However, while the South Coast shows a slight decrease from 2001 to 2006, 

the Western Mojave Desert trend is essentially flat, because of the trend at Joshua 

Tree. 

Figure 5: Federal 8-Hour Ozone Design Values for Western Mojave Desert 

 Planning Area and South Coast Air Basin 1995 to 2006 

 

Federal 8-Hour Design Values for Mojave Desert & South Coast

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1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Ozone (ppm)

South Coast Air Basin Western Mojave Desert Planning Area

Looking at the design values for individual sites in the Western Mojave Desert gives 

some insight as to how ozone air quality is changing within the Planning Area and how 

Joshua Tree compares with other sites. Figure 6 shows the trend lines for Hesperia 

and Joshua Tree (note: although not shown, the trend line for Phelan is similar to that 

for Hesperia). The trend line for Hesperia shows an overall reduction in design value, 

although the decrease since 2001 is slight. In contrast, Joshua Tree shows an overall 

increase in design value, with the increase being especially apparent since 2001, 

although the trend has flattened out over the last several years. 

While the Joshua Tree and Phelan trends differ, both the trend and level of the design 

value for Joshua Tree are similar to those for Palm Springs in the Coachella Valley 

Planning Area. As mentioned previously, both of these sites are located downwind of 

the South Coast Air Basin. Previous ARB transport assessments show that Palm 

Springs is overwhelmed by transport from the South Coast. It is likely that Joshua Tree 

is also impacted by transport, although ARB has not completed a formal assessment. 
E-10 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

Given the likelihood of a transport impact, a portion of the increase in the trend at 

Joshua Tree may be attributable to changing emissions in the South Coast. 

Figure 6: Federal 8-Hour Ozone Design Values for Hesperia and Joshua Tree 

 1995 to 2006 

 

Federal 8-Hour Design Values for Mojave Desert Sites

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1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Ozone (ppm)

Hesperia Joshua Tree

Over time, emissions reductions in the South Coast have reduced the reactivity of the 

hydrocarbon mix. Because the mix is less reactive now, it takes longer for the 

photochemical reactions that form ozone to occur. With the reduction in reactivity, 

ozone concentrations in areas closer to the major South Coast emissions source areas 

have improved more rapidly than those in downwind areas. Because of the slower rate 

of improvement, it will take these downwind areas longer to reach attainment. 

Photochemical modeling analyses indicate that Palm Springs will reach attainment for 

the federal 8-hour ozone standard by 2018. Because the design value concentrations 

and trends for Palm Springs and the Western Mojave Desert are so similar, it is 

reasonable to assume that the Desert will reach attainment in approximately the same 

timeframe as Palm Springs. Therefore, reclassifying the Western Mojave Desert as 

Severe-17 with a June 15, 2021 attainment date is appropriate. 
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

E-11

Spatial Ozone Trends

Another way to look at the improvement in air quality is to map the change in the 

number of exceedance days. The maps in Figure 7 are based on monitoring data and 

show the reduction in the number of days exceeding the federal 8-hour standard over 

the last decade (1995 to 2005). This approach provides an estimate of the change in 

the spatial extent of the ozone problem. Ten years ago (1995 map, based on 1993 to 

1995 means), about a quarter of the Western Mojave Desert experienced 51 to 100 

exceedance days per year, while most of 

Figure 7: Western Mojave Desert Planning Area Change in Federal 8-Hour 

 Exceedance Days 1995 to 2005 

 

Western Mojave Desert Planning Area

Federal 8-Hour Exceedance Days
E-12 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

the remaining areas experienced 21 to 50 days per year. Today (2005 map, based on 

2003 to 2005 means), about half of the Desert falls into the 21 to 50 days per year 

category, with the other half having 11 to 20 days and 6 to 10 days per year. The 

exceedance day maps clearly illustrate the influence of the South Coast on Western 

Mojave Desert. The highest number of exceedance days is found in the southwestern 

portion of the Planning Area, adjacent to the South Coast Air Basin. However, as 

shown on the maps, air quality in these areas has improved over time, and it should 

continue to improve with implementation of the South Coast and Statewide emissions 

control strategies. 

Additional Air Quality Analyses 

ARB staff conducted additional air quality analyses and also reviewed photochemical 

modeling for the Western Mojave Desert to assess whether the rate of progress 

historically, as well as the more modest progress in recent years, supports a 

2021 attainment date. 

Mean of the Top 30 Analysis 

The mean of the Top 30 represents the mean or average of the 30 highest daily 

maximum 8-hour ozone concentrations measured at a site during each year. Changes 

in this indicator over time reflect the change in the average ozone concentration on the 

30 worst days. Because this indicator is based on a relatively large number of 

observations, it is more robust than other indicators, such as maximum concentration. 

Although the mean of the Top 30 is not directly related to the federal standard, it does 

provide a stable indicator that is not highly influenced by year-to-year changes in 

meteorology. 

Figure 8 shows the trend of the mean of the Top 30 8-hour ozone concentrations for the 

three high sites in Western Mojave Desert. Since 1995, the mean of the Top 30 

declined 10 and 20 percent, respectively, at Hesperia and Phelan. In contrast, the 

mean Top 30 values increased about 5 percent at Joshua Tree. As a way of gaining 

further insight into how the mean of the Top 30 has changed over time, ARB staff 

evaluated the rate of change, relative to the start year (1995) at the same three sites. 

For this evaluation, three-year averages of the annual mean Top 30 values were 

normalized to the start year by calculating the ratio of the averaged Top 30 

concentration for each year to the 1995 averaged Top 30 concentration. The 

normalized rate of progress values are plotted in Figure 9. 

Hesperia and Phelan both show overall progress during the 12-year period. Although 

progress has slowed over the last 5 to 6 years, the recent trend is downward, and the 

2006 values for both sites are slightly lower than the 2001 values. In contrast, the 

Joshua Tree site shows an upward trend since 2001. As mentioned earlier (refer to 

Ozone Air Quality Trends section), the lack of progress at Joshua Tree may be 

attributable to transport from the South Coast. Because emissions reductions in the 
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

E-13

South Coast have reduced the reactivity of the hydrocarbon mix, it now takes longer for 

ozone to form. As a result, ozone air quality has improved faster in the upwind areas 

located closer to South Coast emissions source areas than it has in the downwind 

transport impacted areas. The impact of transport is discussed further in the next 

section. 

Figure 8: Mean of the Top 30 Daily Maximum 8-Hour Ozone Concentrations for 

Phelan, Hesperia, and Joshua Tree 1995 to 2006 

 

Western Mojave Desert Planning Area Sites

Mean of the Top 30 8-Hour Ozone Concentrations

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1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Concentration (ppm)

Phelan Hesperia Joshua Tree

 

Figure 9: Mean of Top 30 8-Hour Ozone Concentrations at Western Mojave 

Desert Sites Normalized to 1995 Start Year 

 

Western Mojave Desert Planning Area Sites

Normalized 3-Year Average Rate of Change of Mean Top 30 8-Hour Ozone Concentrations

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1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Concentration (ppm)

Joshua Tree Phelan Hesperia

Modeling Evaluations and Regression Analyses 
E-14 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

As part of the photochemical modeling analyses, South Coast District staff evaluated 

the impacts of transport on attainment in the Western Mojave Desert. Using a gridded 

domain, South Coast District staff modeled several emissions reduction scenarios using 

the two 2005 modeling episodes. The scenarios included (1) removing emissions from 

the local planning area (Western Mojave Desert and Antelope Valley planning areas); 

(2) removing emissions from Ventura and Santa Barbara counties, and (3) removing 

emissions from the South Coast. The results demonstrated that emissions within the 

Western Mojave Desert Planning Area were not sufficient to generate federal 8-hour 

ozone exceedances and that the impact of South Coast emissions was overwhelming. 

Therefore, emissions reductions in the upwind area are critical to the attainment 

demonstration. Given the results of the modeling evaluations, the current trends at 

Joshua Tree are not expected to delay the 2021 attainment date for Western Mojave 

Desert. 

As additional analyses, ARB staff completed regression analyses of design values for 

the South Coast versus Western Mojave Desert, as well as the San Joaquin Valley 

versus Western Mojave Desert. Although there are a number of uncertainties 

associated with these analyses, the results suggest that the design value for the 

Western Mojave Desert, including the Joshua Tree area, will reach the level of 

attainment before either the South Coast or San Joaquin Valley, both of which have a 

2024 attainment date. This lends further support to the 2021 attainment date for 

Western Mojave Desert. 

 

Emissions Trends

In 2006, ROG emissions in the Western Mojave Desert were dominated by off-road 

recreational vehicles, light duty passenger vehicles, heavy duty diesel trucks, and 

petroleum marketing. The main contributors of NOx emissions were heavy duty diesel 

trucks, mineral processing, trains, and off-road equipment. Statewide and local 

emissions control measures have significantly reduced the amounts of both ROG and 

NOx emitted by various sources throughout California. However, these reductions have 

not resulted in the same rate of decline in emissions in all areas. Furthermore, 

emissions in the Western Mojave Desert continue to be overshadowed by emissions 

from the South Coast and San Joaquin Valley. Figure 10 shows the estimated trend in 

the Western Mojave Desert ozone precursor emissions from 1995 to 2006. The totals 

reflect estimates for the summer season in tons per day and do not include emissions 

from natural biogenic sources. 

ROG emissions show a small decline over the entire period. In contrast, there has been 

a fairly consistent increase in NOx emissions. The overall decrease in ROG emissions 

is about 15 percent from 1995 to 2006, compared with a 5 percent overall increase in 

NOx emissions during the same time period. Despite these changes, the levels of 

emissions in the Western Mojave Desert are less than levels in the upwind areas. For 

comparison, 2005 ROG and NOx emissions in the South Coast were about 10 and 
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

E-15

5 times the level, respectively, of those in the Western Mojave Desert, while ROG and 

NOx emissions in the San Joaquin Valley were both about 5 times the level of those in 

the Desert. As emissions in these upwind areas are reduced, ozone air quality in the 

downwind Western Mojave Desert should also improve. 

Figure 10: Western Mojave Desert Estimated ROG and NOx Emissions 

 1995 to 2006 

 

Western Mojave Desert Planning Area ROG and NOx Emissions

Summer SIP Inventory without Biogenics - Ver 1.06

0

50

100

150

200

250

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Emissions (tons/day)

NOx ROG

Photochemical Modeling Results

The U.S. EPA (2005) provided criteria for calculating future year 8-hour ozone design 

values using air quality simulation results. Among these criteria were recommendations 

for air quality model performance, observed and simulated ozone concentration 

thresholds, and the number of simulated days used to calculate the relative response 

factor (RRF) used to scale reference year design values for future years. To meet 

these criteria, the South Coast District staff evaluated the results from the simulation of 

six high ozone episode periods occurring during the years 2004 and 2005. 

Of the six episodes, the simulation results for the July 15 through 19, 2005 and the 

August 3 through 9, 2005 episode periods showed high concentrations and acceptable 

air quality model performance for ozone monitoring sites in the Western Mojave Desert 

and Antelope Valley planning areas. Therefore, subsequent analysis focused on these 

two periods. To evaluate future year ozone design values, the South Coast District staff 

simulated these episodes using emissions inventories developed for the years 2002 

(the reference year for design values), 2005 (to evaluate ozone model performance), 

2012, 2017 (for an attainment year of 2018), and 2020 (for an attainment year of 2021). 

Emissions totals were based on projections from the South Coast District’s 2007 Air 

Quality Management Plan. 
E-16 MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

Based on the results, Phelan and Hesperia have the highest design values in 2017, but 

do not meet the federal 8-hour standard by then. Therefore, a 2018 attainment date, 

similar to that for the Coachella Valley Planning Area, is not appropriate. However, 

modeling predicted a design value at Phelan of 0.080 ppm by the end of 2020, which 

does show attainment and is consistent with a June 15, 2021 attainment deadline. The 

Joshua Tree site shows a 2020 design value of 0.060 ppm, while Twentynine Palms, 

the highest site in 2020, shows a design value of 0.082 ppm. These sites, as well as all 

others in the Western Mojave Desert and Antelope Valley planning areas, therefore 

show attainment by the end of 2020, as required for a Severe-17 nonattainment area 

and are consistent with a June 15, 2021 attainment deadline. 

Summary

The Weight of Evidence package comprises a set of analyses that provide support for 

the attainment demonstration. Currently, the Western Mojave Desert is classified as 

Moderate with respect to the federal 8-hour ozone standard, with attainment required by 

2010. Because of the transport impact of emissions and pollutants from the South 

Coast and San Joaquin Valley and the expected timing of emissions reductions in these 

upwind areas, the Mojave Desert Air Quality Management District has requested 

reclassification of the Western Mojave Desert Planning Area as Severe-17, with an 

attainment date of June 15, 2021. Based on the air quality and emissions analyses 

completed for the WOE assessment, attainment in the Western Mojave Desert can be 

projected by 2021, based on the following factors: 

• Since 1995, there has been a 35 percent decrease in exceedance 

days, 20 and 25 percent decreases in maximum concentration and 

design value, and a 15 percent decrease in the mean Top 30 value. 

Although progress has slowed over the last five to six years, the ozone 

indicators, taken together, continue to show some improvement, albeit 

at a slower rate. Because of the continued improvement, the design 

value for Western Mojave Desert is now about 20 percent above the 

level of the standard, compared with a design value nearly 60 percent 

above the standard in 1995. 

• Transport and air quality analyses support a link between the South 

Coast and Western Mojave Desert, as well as the San Joaquin Valley 

and Western Mojave Desert, with respect to ozone air quality. ROG 

and NOx emissions in the upwind areas are 5 to 10 times the level of 

those in the Western Mojave Desert. Furthermore, the transport 

impact from the upwind areas is overwhelming on some days. 

Modeling analyses show that attainment in the Western Mojave Desert 

will be dependent on emissions reductions in the upwind areas. 
MDAQMD Federal 8-hour Ozone Attainment Plan 

June 9, 2008 

E-17

• The South Coast, San Joaquin Valley, and statewide emissions control 

strategies are expected to result in massive emissions reductions over 

the next 15 years, with both upwind areas expecting attainment by 

2024. These emissions reductions will help facilitate attainment in 

downwind areas such as the Western Mojave Desert. Because ozone 

levels in the Western Mojave Desert are not as high as levels in the 

South Coast or the San Joaquin Valley, the emissions reductions 

needed for attainment in the Western Mojave Desert are not as high. 

Therefore, attainment is expected earlier than 2024. 

• Although there is a great deal of uncertainty in the regression analyses 

completed for the Western Mojave Desert, they do suggest that the 

Western Mojave Desert will reach attainment before either the South 

Coast or San Joaquin Valley air basins. 

• Photochemical modeling shows the Western Mojave Desert will not 

attain by 2010, or even by 2018. However, results show the area will 

attain by the end of 2020, with all sites having a design value of 

0.082 ppm or less. 

Taken together, the results from all of these analyses indicate the Western Mojave 

Desert Planning Area will not attain the federal 8-hour ozone standard by 2010, the 

area’s a current deadline as a Moderate ozone nonattainment area. However, given the 

recent trends, the transport impact from the South Coast and San Joaquin Valley, and 

the expected level and timing of emissions reductions in these upwind areas, the 

Western Mojave Desert can expect to reach attainment by the end of 2020, consistent 

with the June 15, 2021 attainment deadline for Severe-17 nonattainment areas.