CHAPTER 5

FUTURE AIR QUALITY

Introduction

Background

Modeling Approach

Future Air Quality

Additional Modeling Analyses

Summary and Conclusions
Draft 2012 AQMP

5-1

INTRODUCTION

Air quality modeling is an integral part of the planning process to achieve clean air. The 

attainment demonstrations provided in this Draft 2012 AQMP reflect the updated 

baseline emissions estimates, new technical information, enhanced air quality modeling 

techniques, and the control strategy provided in Chapter 4 for 24-hour PM2.5. 

Projections for progress towards meeting the annual PM2.5 standard by 2014 and the 

1997 8-hour ozone standard by 2023 are also presented in this chapter. These latter two 

requirements are addressed in the 2007 AQMP.

The Basin is currently designated nonattainment for PM2.5, and extreme nonattainment 

for ozone. The District’s goal is to develop an integrated control strategy which: 1) 

ensures that ambient air quality standards for all criteria pollutants are met by the 

established deadlines in the federal Clean Air Act (CAA); and 2) achieves an expeditious

rate of progress towards attaining the state air quality standards. The overall control 

strategy is designed so that efforts to achieve the standard for one criteria pollutant do 

not cause unnecessary deterioration of another. A two-step modeling process which is 

consistent with the approach used in the 2007 AQMP has been conducted for the Draft 

2012 AQMP. First, future year 24-hour PM2.5 levels are simulated for 2014 and 2019 to 

determine the earliest possible date of attainment. If attainment cannot be demonstrated 

by 2014, U.S. EPA can grant up to an additional five years to demonstrate attainment of 

the 24-hour standard. However, the length of the extension is contingent upon the 

earliest year beyond 2014 that the 24-hour average PM2.5 standard can be achieved 

implementing all feasible control measures. 

BACKGROUND

During the development of the 2007 AQMP, the District convened a panel of seven 

experts to independently review the regional air quality modeling. The consensus of the 

panel was for the District to move to the more current state-of-the-art dispersion 

platforms and chemistry modules. In keeping with the recommendations of the expert 

panel as well as the Scientific Technical Modeling Peer Review Committee, the Draft 

2012 AQMP has continued to move forward to incorporate the current state-of-the-art 

modeling platforms to conduct regional modeling analyses in support of the PM2.5 

attainment demonstrations and ozone update. The Draft 2012 AQMP PM2.5 attainment 

demonstration has been developed using the U.S. EPA supported Community Multiscale 

Air Quality (CMAQ) (version 4.7) modeling platform with SAPRC99 chemistry, and the 

Weather Research and Forecasting Model (WRF) (version 3.3) meteorological fields. 

Supporting PM2.5 and ozone simulations were also conducted using the most current
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and publicly available version of CAMx (version 5.3), which also used SAPRC99 

chemistry and WRF meteorology, to ensure smooth transition from the CAMx platform 

used in the 2007 AQMP to CMAQ. The model analyses were conducted on an expanded 

domain, with increased resolution in the vertical structure, and a finer 4 km grid size.

Detailed information on the modeling approach, data gathering, model development and 

enhancement, model application, and interpretation of results is presented in Appendix 

V. The following sections summarize the results of the 24-hour PM2.5 attainment 

demonstration modeling effort and provide an update to the annual PM2.5 and future 

projected Basin ozone levels given new emissions, design values and modeling tools. 

MODELING APPROACH

Design Values and Relative Response Factors (RRF)

As first employed in the 2007 AQMP, the Draft 2012 AQMP modeling approach to 

demonstrate attainment of the air quality standards relies heavily on the use of design 

values and relative response factors (RRF) to translate regional modeling simulation 

output to the form of the air quality standard. Both PM2.5 and ozone have standards that 

require three consecutive years of monitored data, averaged according to the form of the 

standard to derive a design value, to assess compliance. The 24-hour PM2.5 design 

value is determined from the three-year average of the 98th percentile of all 24-hour 

concentrations sampled at a monitoring site. The annual PM2.5 design value is based on

quarterly average PM2.5 concentrations, averaged by year, for a three-year period. In the 

case of ozone, compliance with the standard is determined from a three-year average of 

the 4th highest daily ozone 8-hour average concentration. 

Design Value Selection

U.S. EPA guidance recommends the use of multiple year averages of design values, 

where appropriate, to dampen the effects of single year anomalies to the air quality trend 

due to factors such as adverse or favorable meteorology or radical changes in the local 

emissions profile. The trend in the Basin 24-hour PM2.5 design values, determined from 

routinely monitored Federal Reference Monitoring (FRM), from 2001 through 2011 

(Figure 5-1) depicts sharp reductions in concentrations over the period. The 24-hour 

PM2.5 design value for 2001 was 76 μg/m3 while the 2008 design value (based on data 

from 2006, 2007 and 2008) is 53 μg/m3. Furthermore, the most current design value 

computed for 2011 has been reduced to 38 μg/m3. The annual PM2.5 design value has 

demonstrated a reduction of 13.6 μg/m3over the 10-year period from 2001 through 

2011. In each case, the trend in PM2.5 is steadily moving in the direction of air quality 
Draft 2012 AQMP

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improvement. The trend of Basin ozone design values is presented in Figure 5-2. The 

design values have averaged a reduction of approximately three parts per billion over the 

14-year period; however the most recent design value (107 ppb) continues to exceed the 

1997 8-hour ozone standard (80 ppb) by 34 percent and the 2006 ozone standard by 43 

percent (75 ppb).

FIGURE 5-1

South Coast Air Basin 24-Hour Average and Annual PM2.5 Design Values

Note: Each value represents the 3-year average of the highest annual average PM2.5 concentration

FIGURE 5-2

South Coast Air Basin 8-Hour Average Ozone Design Values

Note: Each value represents the 3-year average of the 4

th highest 8-Hour Average Ozone concentration

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Chapter 5 Future Air Quality

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The Draft 2012 AQMP relies on a set of five years of particulate data centered on 2008, 

the base year selected for the emissions inventory development and the anchor year for 

the future year PM2.5 projections. In July, 2010, U.S. EPA proposed revisions to the 24-

hour PM2.5 modeling attainment demonstration guidance. The new guidance suggests 

using five years of data, but instead of directly using quarterly calculated design values, 

the procedure requires the top 8 daily PM2.5 concentrations days in each quarter to 

reconstruct the annual 98th percentile. The logic in the analysis is twofold: by selecting 

the top 8 values in each quarter the 98th percentile concentration is guaranteed to be 

included in the calculation. Second, the analysis projects future year concentrations for 

each of the 32 days in a year (160 days over five years) to test the response of future year 

24-hour PM2.5 to the proposed control strategy. Since the 32 days in each year include 

different meteorological conditions and particulate species profiles it is expected those 

individual days will respond independently to the projected future year emissions profile 

and that a new distribution of PM2.5 concentrations will result. Overall, the process is 

more robust in that the analysis is examining the impact of the control strategy 

implementation for a total of 160 days, covering a wide variety of potential meteorology 

and emissions combinations. 

Table 5-1 provides the weighted 2008 annual and 24-hour average PM2.5 design values 

for the Basin. 

TABLE 5-1

2008 Weighted 24-Hour PM2.5 Design Values (μg/m3)

MONITORING SITE 24-HOURS

Anaheim 35.0

Los Angeles 40.1

Fontana 45.6

North Long Beach 34.4

South Long Beach 33.4

Mira Loma 47.9

Rubidoux 44.1

Relative Response Factors and Future Year Design Values

To bridge the gap between air quality model output evaluation and applicability to the 

health-based air quality standards, U.S. EPA guidance has proposed the use of relative 

response factors (RRF). The RRF concept was first used in the 2007 AQMP modeling

attainment demonstrations. The RRF is simply a ratio of future year predicted air quality 
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with the control strategy fully implemented to the simulated air quality in the base year. 

The mechanics of the attainment demonstration are pollutant and averaging period 

specific. For 24-hour PM2.5, the top 10 percentile of modeled concentrations in each 

quarter of the simulation year are used to determine the quarterly RRFs. For the annual 

average PM2.5, the quarterly average RRFs are used for the future year projections. For 

the 8-hour average ozone simulations, the aggregated response of multiple episode days 

to the implementation of the control strategy is used to develop an averaged RRF for 

projecting a future year design value. Simply stated, the future year design value is 

estimated by multiplying the non-dimensional RRF by the base year design value. Thus, 

the simulated improvement in air quality, based on multiple meteorological episodes, is

translated as a metric that directly determines compliance in the form of the standard. 

The modeling analyses described in this chapter use the RRF and design value approach 

to demonstrate future year attainment of the standards. 

PM2.5 Modeling

Within the Basin, PM2.5 particles are either directly emitted into the atmosphere 

(primary particles), or are formed through atmospheric chemical reactions from 

precursor gases (secondary particles). Primary PM2.5 includes road dust, diesel soot, 

combustion products, and other sources of fine particles. Secondary products, such as 

sulfates, nitrates, and complex carbon compounds are formed from reactions with oxides 

of sulfur, oxides of nitrogen, VOCs, and ammonia.

The Draft 2012 AQMP employs the CMAQ air quality modeling platform with 

SAPRC99 chemistry and WRF meteorology as the primary tool used to demonstrate 

future year attainment of the 24-hour average PM2.5 standard. A detailed discussion of 

the features of the CMAQ approach is presented in Appendix V. The analysis was also 

conducted using the CAMx modeling platform using the “one atmosphere” approach 

comprised of the SAPRC99 gas phased chemistry and a static two-mode particle size 

aerosol module as the particulate modeling platform. Parallel testing was conducted to 

evaluate the CMAQ performance against CAMx and the results indicated that the two 

model/chemistry packages had similar performance. The CAMx results are provided in 

Appendix V as a component of the weight of evidence discussion.

The Draft 2012 modeling attainment demonstrations using the CMAQ (and CAMx) 

platform were conducted in a vastly expanded modeling domain compared with the 

analysis conducted for the 2007 AQMP modeling attainment demonstration. In this 

analysis, the PM2.5 and ozone base and future simulations were modeled 

simultaneously. The simulations were conducted using a Lambert Conformal grid 
Chapter 5 Future Air Quality

5-6

projection where the western boundary of the domain was extended to 084 UTM, over

100 miles west of the ports of Los Angeles and Long Beach. The eastern boundary 

extended beyond the Colorado river while the northern and southern boundaries of the 

domain extend to the San Joaquin Valley and the Northern portions of Mexico (3543

UTM). The grid size has been reduced from 5 kilometers squared to 4 kilometers 

squared and the vertical resolution has been increased from 11 to 18 layers. 

The final WRF meteorological fields were generated for the identical domain, layer 

structure and grid size. The WRF simulations were initialized from National Centers for 

Environmental Prediction (NCEP) analyses and run for 3-day increments with the option 

for four dimensional data assimilation (FDDA). Horizontal and vertical boundary 

conditions were designated using a “U.S. EPA clean boundary profile.” 

PM2.5 data measured as individual species at six-sites in the AQMD air monitoring 

network during 2008 provided the characterization for evaluation and validation of the 

CMAQ annual and episodic modeling. The six sites include the historical PM2.5 

maximum location (Riverside- Rubidoux), the stations experiencing many of the highest

county concentrations (among the 4-county jurisdiction including Fontana, North Long 

Beach and Anaheim) and source oriented key monitoring sites addressing goods 

movement (South Long Beach) and mobile source impacts (Central Los Angeles). It is 

important to note that the close proximity of Mira Loma to Rubidoux and the common 

in-Basin air flow and transport patterns enable the use of the Rubidoux speciated data as 

representative of the particulate speciation at Mira Loma. Both sites are directly 

downwind of the dairy production areas in Chino and the warehouse distribution centers 

located in the northwestern corner of Riverside County. Speciated data monitored at the 

selected sites for 2006-2007 and 2009-2010 were analyzed to corroborate the 

applicability of using the 2008 profiles.

Day-specific point source emissions were extracted from the District stationary source 

and RECLAIM inventories. Mobile source emissions included weekday, Saturday and 

Sunday profiles based on CARB’s EMFAC2011 emissions model, CALTRANS weighin-motion profiles, and vehicle population data and transportation analysis zone (TAZ) 

data provided by SCAG. The mobile source data and selected area source data were 

subjected to daily temperature corrections to account for enhanced evaporative emissions 

on warmer days. Gridded daily biogenic VOC emissions were provided by CARB using 

BEIGIS biogenic emissions model. The simulations benefited from enhancements made 

to the emissions inventory including an updated ammonia inventory, improved 

emissions characterization that split organic compounds into coarse, fine and primary 
Draft 2012 AQMP

5-7

particulate categories, and updated spatial allocation of primary paved road dust 

emissions. 

Model performance was evaluated against speciated particulate PM2.5 air quality data

for ammonium, nitrates, sulfates, secondary organic matter, elemental carbon, primary 

and total particulate mass for the six monitoring sites (Rubidoux, Central Los Angeles, 

Anaheim, South Long Beach, Long Beach, and Fontana). 

The following section summarizes the PM2.5 modeling approach conducted in 

preparation for this Plan. Details of the PM2.5 modeling are presented in Appendix V. 

24-Hour PM2.5 Modeling Approach

CMAQ simulations were conducted for each day in 2008. The simulations included 

8784 consecutive hours from which daily 24-hour average PM2.5 concentrations (0000-

2300 hours) were calculated. A set of RRFs were generated for each future year 

simulation. RRFs were generated for the ammonium ion (NH4), nitrate ion (NO3), 

sulfate ion (SO4), organic carbon (OC), elemental carbon (EC) and a combined grouping 

of crustal, sea salts and metals (Others). A total of 24 RRFs were generated for each 

future year simulation (4 seasons and 6 monitoring sites).

Future year concentrations of the six component species were calculated by applying the 

model generated quarterly RRFs to the speciated 24-hour PM2.5 (FRM) data, sorted by 

quarter, for each of the five years used in the design value calculation. The 32 days in 

each year were then re-ranked to establish a new 98thpercentile concentration. The 

resulting future year 98th percentile concentrations for the five years were subjected to 

weighted averaging for the attainment demonstration.

In this chapter, future year PM2.5 24-hour average design values are presented for 2014,

and 2019 to (1) demonstrate the future baseline concentrations if no further controls are 

implemented; (2) identify the amount of air quality improvement needed to advance the 

attainment date to 2014; and (3) confirm the attainment demonstration given the

proposed PM2.5 control strategy. In addition, Appendix V will include a discussion and

demonstration that attainment will be satisfied for the entire modeling domain. 

Weight of Evidence

PM2.5 modeling guidance strongly recommends the use of corroborating evidence to 

support the future year attainment demonstration. The weight of evidence demonstration 

for the Draft 2012 AQMP includes brief discussions of the observed 24-hour PM2.5, 
Chapter 5 Future Air Quality

5-8

emissions trends, and future year PM2.5 predictions. Detailed discussions of all model 

results and the weight of evidence demonstration are provided in Appendix V.

FUTURE AIR QUALITY

Under the federal Clean Air Act, the Basin must comply with the federal PM2.5 air 

quality standards by December, 2014 [Section 172(a)(2)(A)]. An extension of up-to five 

years (until 2019) could be granted if attainment cannot be demonstrated any earlier with 

all feasible control measures incorporated. 

24-Hour PM2.5

A simulation of 2014 baseline emissions was conducted to substantiate the severity of 

the 24-hour PM2.5 problem in the Basin. The simulation used the projected emissions 

for 2014 which included all adopted control measures that will be implemented prior to 

and during 2014. The resulting 2014 future-year Basin design value (37.3 μg/m3) failed 

to meet the federal standard. As a consequence additional controls are needed. 

Simulation of the 2019 baseline emissions indicates that the Basin PM2.5 will attain the 

federal 24-hour PM2.5 standard in 2019 without additional controls. With the control 

program in place, the 24-hour PM2.5 simulations project that the 2014 design value will 

be 34.0 μg/m3and that the attainment date will advance from 2019 to 2014.

Figure 5-3 depicts future 24-hour PM2.5 air quality projections at the Basin design site 

(Mira Loma) and six PM2.5 monitoring sites having comprehensive particulate species 

characterization. Shown in the figure, are the base year design values for 2008 along 

with projections for 2014 with and without control measures in place. All of the sites 

with the exception of Mira Loma will meet the 24-hour PM2.5 standard by 2014 without 

additional controls. With implementation of the control measures, all sites in the Basin

demonstrate attainment.
Draft 2012 AQMP

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*No such state standard.

FIGURE 5-3

Maximum 24-Hour Average PM2.5 Design Concentrations:

2008 Baseline, 2014 and 2014 Controlled

Spatial Projections of PM2.5 Design Values

Figure 5-4 provides a perspective of the Basin-wide spatial extent of 24-hour PM2.5 

impacts in the base year 2008, with all adopted rules and measures implemented. 

Figures 5-5 and 5-6 provide a Basin-wide perspective of the spatial extent of 24-hour 

PM2.5 future impacts for baseline 2014 emissions and 2014 with the proposed control 

program in place. With no additional controls, several areas around the northwestern 

portion of Riverside and southwestern portion of San Bernardino Counties depict grid

cells with weighted PM2.5 24-hour design values exceeding 35 μg/m3. By 2014, the

number of grid cells with concentrations exceeding the federal standard is restricted to a 

small region surrounding the Mira Loma monitoring station in northwestern Riverside 

County. With the control program fully implemented in 2014, the Basin does not exhibit 

any grid cells exceeding the federal standard. 

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2008 2014 2014 Controlled

Federal Std.*
Chapter 5 Future Air Quality

5-10

FIGURE 5-4

2008 Baseline 24-Hour PM2.5 Design Concentrations (μg/m3)

FIGURE 5-5

2014 Baseline 24-Hour PM2.5 Design Concentrations (μg/m3)
Draft 2012 AQMP

5-11

FIGURE 5-6

2014 Controlled 24-Hour PM2.5 Design Concentrations (μg/m3)

Weight of Evidence Discussion

The weight of evidence discussion focuses on the trends of 24-hour PM2.5 and key 

precursor emissions to provide justification and confidence that the Basin will meet the 

federal standard by 2014. 

Figure 5-7 depicts the long term trend of observed Basin 24-hour average PM2.5 design 

values with the CMAQ projected design value for 2014. Also superimposed on the 

graph is the linear best-fit trend line for the observed 24-hour average PM2.5 design 

values. The observed trend depicts a steady 49 percent decrease in observed design

value concentrations between 2001 and 2011. The rate of improvement is just under 4 

μg/m3per year. If the trend is extended beyond 2011, the projection suggests attainment

of the PM2.5 24-hour standard in 2013, one year earlier than determined by the 

attainment demonstration. While the straight-line future year approximation is 

aggressive in its projection, it offers insight to the effectiveness of the ongoing control

program and is consistent with the attainment demonstration.

Figures 5-8 depicts the long term trend of Basin NOx emissions for the same period. 

Figure 5-9 provides the corresponding emissions trend for directly emitted PM2.5. Base 
Chapter 5 Future Air Quality

5-12

year NOx inventories between 2002 (from the 2007 AQMP) and 2008 experienced a 31 

percent reduction while directly emitted PM2.5 experienced a 19 percent reduction over 

the 6-year period. The Basin 24-hour average PM2.5 design value experienced a 

concurrent 27 percent reduction between 2002 and 2008. The projected trend of NOx 

emissions indicates that the PM2.5 precursor associated with the formation of nitrate will 

continue to be reduced though 2019 by an additional 48 percent. Similarly, the projected 

trend of directly emitted PM2.5 projects a more moderate reduction of 13 percent 

through 2019. However, as discussed in the 2007 AQMP and in a later section of this 

chapter, directly emitted PM2.5 is a more effective contributor to the formation of

ambient PM2.5 compared to NOx. While the projected NOx and direct PM2.5 

emissions trends decrease at a reduced rate between 2012 and 2019, it is clearly evident 

that the overall significant reductions will continue to result in lower nitrate, elemental 

carbon and direct particulate contributions to 24-hour PM2.5 design values.

FIGURE 5-7

Basin Observed and CMAQ Projected 

Future Year PM2.5 Design Concentrations (μg/m3)

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FIGURE 5-8

Trend of Basin NOx Emissions (Controlled)

FIGURE 5-9

Trend of Basin PM2.5 Emissions (Controlled)

Control Strategy Choices

PM2.5 has five major precursors that contribute to the development of the ambient 

aerosol including ammonia, NOx, SOx, VOC, and directly emitted PM2.5. Various 

combinations of reductions in these pollutants could all provide a path to clean air. The

24-hour PM2.5 attainment strategy presented in this Draft 2012 AQMP relies on a dual 

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Chapter 5 Future Air Quality

5-14

approach to first demonstrate attainment of the federal standard by 2019 and then

focuses on controls that will be most effective in reducing PM2.5 to accelerate 

attainment to the earliest extent. The 2007 AQMP control measures since implemented 

will result in substantial reductions of SOx, direct PM2.5, VOC and NOx emissions. 

Newly proposed short-term measures, discussed in Chapter 4, will provide additional 

regional emissions reductions targeting directly emitted PM2.5 and NOx. 

It is useful to weigh the value of the precursor emissions reductions (on a per ton basis) 

to microgram per cubic meter improvements in ambient PM2.5 levels. As presented in 

the weight of evidence discussion, trends of PM2.5 and NOx emissions suggest a direct 

response between lower emissions and improving air quality. The Final 2007 AQMP 

established a set of factors to relate regional per ton precursor emissions reductions to 

PM2.5 air quality improvements based on the annual average concentration. The Draft 

2012 AQMP CMAQ simulations provided a similar set of factors, but this time directed 

at 24-hour PM2.5. The analysis determined that VOC emissions reductions have the 

lowest return in terms of micrograms reduced per ton reduction, one half of the benefit 

of NOx reductions. SOx emissions were about six times more effective than NOx

reductions. However, directly emitted PM2.5 reductions were approximately 14 times 

more effective than NOx reductions. It is important to note that the contribution of 

ammonia emissions is embedded as a component of the SOx and NOx factors since 

ammonium nitrate and ammonium sulfate are the resultant particulates formed in the 

ambient chemical process. Table 5-2 summarizes the relative importance of precursor 

emissions reductions to 24-hour PM2.5 air quality improvements based on the analysis. 

Emission reductions due to existing programs and implementation of the 2012 AQMP 

control measures will result in projected 24-hour PM2.5 concentrations throughout the 

Basin that meet the standard by 2014 at all locations. Basin-wide curtailment of wood 

burning and open burning when the PM2.5 air quality is projected to exceed 30 μg/m3in

Mira Loma will effectively accelerate attainment at Mira Loma from 2019 to 2014. 

Table 5-3 lists the mix of the four primary precursor’s emissions reductions targeted for 

the staged control measure implementation approach. 
Draft 2012 AQMP

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TABLE 5-2

Relative Contributions of Precursor Emissions Reductions to Simulated Controlled 

Future-Year 24-hour PM2.5 Concentrations

PRECURSOR PM2.5 COMPONENT (μg/m3)

STANDARDIZED 

CONTRIBUTION TO 

AMBIENT PM2.5 MASS

VOC Organic Carbon Factor of 0.5

NOx Nitrate Factor of 1

SOx Sulfate Factor of 6

PM2.5 Elemental Carbon & Others Factor of 14

TABLE 5-3

Draft 2012 AQMP 

24-hour PM2.5 Attainment Strategy 

Allowable Emissions (TPD)

YEAR SCENARIO VOC NOx SOx PM2.5

2014 Baseline 451 500 18 70

2014 Controlled 451 498 18 58*

*Winter episodic day emissions

ADDITIONAL MODELING ANALYSES

As a component of the Draft 2012 AQMP, concurrent simulations were also conducted 

to update and assess the impacts to annual average PM2.5 and 8-hour ozone given the 

new modeling platform and emissions inventory. This update provides a confirmation 

that the control strategy will continue to move air quality expeditiously towards 

attainment of the relevant standards.

Annual PM2.5

Annual PM2.5 Modeling Approach

The Draft 2012 AQMP annual PM2.5 modeling employs the same approach to 

estimating the future year annual PM2.5 as was described in the 2007 AQMP attainment 

demonstrations. Future year PM2.5 annual average air quality is determined using site 
Chapter 5 Future Air Quality

5-16

and species specific quarterly averaged RRFs applied to the weighted quarterly average 

2008 PM2.5 design values per U.S. EPA guidance documents. 

In this application, CMAQ and WRF were used to simulate 2008 meteorological and air 

quality to determine Basin annual average PM2.5 concentrations. The future year 

attainment demonstration was analyzed for 2015, the target set by the federal CAA. The 

2014 simulation relies on implementation of all adopted rules and measures through

2014. This enables a full year-long demonstration based on a control strategy that would 

be fully implemented by January 1, 2015. It is important to note that the use of the 

quarterly design values for a 5-year period centered around 2008 (listed in Table 5-4)

continue to be used in the projection of the future year annual average PM2.5 

concentrations. The future year design reflects the weighted quarterly average 

concentration calculated from the projections over five years (20 quarters). 

TABLE 5-4

2008 Weighted Annual PM2.5 Design Values*(μg/m3)

MONITORING SITE ANNUAL*

Anaheim 13.1

Los Angeles 15.4

Fontana 15.7

North Long Beach 13.6

South Long Beach 13.2

Mira Loma 18.6

Rubidoux 16.7

* Calculated based on quarterly observed data between 2006 – 2010

Future Annual PM2.5 Air Quality

The projections for the annual state and federal standards are shown in Figure 5-10. All 

areas will be in attainment of the federal annual standard (15.0 μg/m3) by 2014. The 

2014 design value is projected to be 9 percent below the federal standard. However, as 

shown in Figure 5-10, the Draft 2012 AQMP does not achieve the California standard of 

12 μg/m3by 2014. Additional controls would be needed to meet the California annual 

PM2.5 standard. 
Draft 2012 AQMP

5-17

FIGURE 5-10

Annual Average PM2.5 Design Concentrations:

2008 and 2014 Controlled

Ozone Modeling

The 2007 AQMP provided a comprehensive 8-hour ozone analysis that demonstrated 

future year attainment of the 1997 federal ozone standard (80 ppb) by 2023 with 

implementation of short-term measures and CAA Section 182(e)(5) long term emissions 

reductions. The analysis concluded that NOx emissions needed to be reduced 

approximately 76 percent and VOC 22 percent from the 2023 baseline in order to 

demonstrate attainment. The 2023 base year VOC and NOx summer planning emissions 

inventories included 536 and 506 TPD, respectively. 

As presented in Chapter 3, the Draft 2012 AQMP controlled 2023 emissions of both 

precursor pollutants are estimated to be lower than the 2023 baseline established in the 

2007 AQMP. The 2023 baseline VOC and NOx emission summer planning emissions 

have been revised to 434 and 313 TPD, respectively. The emissions revision 

incorporated changes made to the on-road truck and off-road equipment categories that 

resulted from CARB rulemaking. The new emissions inventory also reflects the impact 

of the economic slowdown and revisions to regional growth estimates. As a 

consequence, it is important to revisit the projections of 2023 baseline ozone to 

investigate the impact of the inventory revision on the attainment demonstration and 

equally important, what is the impact on the size of the proposed long term NOx

emissions reduction commitment.

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California Std.
Chapter 5 Future Air Quality

5-18

Ozone Representativeness

As a component of the PM2.5 attainment demonstration, the CMAQ modeling provided 

Basin-wide ozone air quality simulations for each hour in 2008. Past ozone attainment 

demonstrations evaluated a set of days characterized by restrictive meteorology or

episodes occurring during concurrent intensive field monitoring programs. Of great 

importance, these episodic periods needed to be rated in terms of how representative 

they were in reference to the ozone standard being evaluated. For the now revoked 1-

hour ozone standard, the attainment demonstration focused on a limited number of days 

closely matching the annual design value. Typically, the analysis addressed fewer than 

5 days of simulations. The 2007 AQMP was the first to address the 8-hour ozone 

standard and the use of the RRFs in the future year ozone projection. To provide a 

robust characterization of the RRFs for use in the attainment demonstration, the analysis 

simulated 36 days. The ozone modeling guidance recommends that a minimum of 5-

days of simulations meeting modeling acceptance criteria be used in a future year RRF 

calculation, but recommends incorporating as many days as possible to fully capture 

both the meteorological variations in the ozone season and the response of ozone 

formation for different daily emissions profiles.

This update to the future year ozone projection focuses on 91 days of ozone air quality 

observed during June through August 2008. During this period, seven well defined 

multiday ozone episodes occurred in the Basin with 75 total days having daily Basinwide maximum concentrations of 80 ppb or higher. More importantly, when adjusted by 

a normalized meteorological potential using a regression based weighting covering 30-

years of data (1998-2010), summarized in the 2003 AQMP, 8 days during the 2008 

period were ranked above the 95th percentile in the long term distribution and another 19 

were ranked between the 90th and 94th percentile. 

Figure 5-11 depicts the time series of the daily Basin 8-hour maximum and Crestline

(the Basin design station) daily maximum 8-hour ozone air quality during the three 

month period in 2008. The seven primary meteorological episodes which occur 

primarily between mid June and August are highlighted in the figure. It is important to 

note that the analysis not only focused on the seven periods or Crestline specifically. All 

station days meeting the acceptance criteria for calculating a daily RRF were included in 

the analysis. Several locations in the San Bernardino and Riverside Valleys exhibit 

similar transport and daily patterns of ozone formation as Crestline. The peak Basin 

2008 8-hour average ozone concentration was observed at Santa Clarita on August 2nd at 

a value of 131 ppb, along a distinctly different transport route. 
Draft 2012 AQMP

5-19

FIGURE 5-11

Observed Basin and Crestline Daily Maximum 8-Hr Average Ozone Concentrations

(Shaded areas indicate multiple day regional ozone episodes)

Overall, the 91-day period provides a robust description of the 2008 ozonemeteorological season. Table 5-4 lists the number of days each Basin station exceeded 

the 8-hour ozone standard during the June through August 2008 period. Also listed in 

Table 5-4 are the 2008, 5-year weighted design values used in the future year ozone 

projections. 

40

50

60

70

80

90

100

110

120

130

140

601604607610613616619622625628701704707710713716719722725728731803806809812815818821824827830

PPB

Basin Maximum Crestline
Chapter 5 Future Air Quality

5-20

TABLE 5-4

2008 Basin Weighted Design Values* and Number of Days Daily Maximum 

Concentrations Exceeded 80 ppb

STATION

2008 5-YEAR 

WEIGHTED 

DESIGN (PPB)

NUMBER OF DAYS IN 2008 

WITH OBSERVED 8-HR 

AVERAGE MAXIMUM 

OZONE > 80 PPB

Azusa 94 16

Burbank 88 10

Reseda 94 16

Pomona 97 19

Pasadena 90 7

Santa Clarita 101 41

Glendora 106 26

Rubidoux 101 39

Perris 104 47

Lake Elsinore 99 39

Banning Airport 102 49

Upland 106 31

Crestline 116 66

Fontana 107 36

San Bernardino 109 46

Redlands 109 50

*Stations having design values greater than 80 ppb

Ozone Modeling Approach

The ozone modeling approach used in this update follows the same criteria employed for 

the 2007 AQMP attainment demonstration. Briefly, the set of 91 days from June 1 

through August 30, 2008, simulated as a subset of the annual PM2.5 simulations, were 

analyzed to determine daily 8-hour average maximum ozone for the 2008 and 2023 

emissions inventories. A separate 2023 simulation was conducted to assess future year 

ozone with VOC and NOx emissions specified at the levels defined by the 2007 AQMP 

attainment demonstration carrying capacity (420 TPD VOC and 114 TPD NOx). 

Finally, a set of simulations with incremental VOC and NOx emissions reductions from 

2023 baseline emissions was generated to create ozone isopleths for each station in the 

Basin. The ozone isopleths provide updated guidance to the determination of the future 
Draft 2012 AQMP

5-21

control strategy, particularly in light of the challenge in meeting the current 75 ppb

standard which will require an attainment demonstration to be submitted to U.S. EPA in 

2015.

The ozone RRFs were calculated using the ratio methodology described for the PM2.5 

modeling. Individual station day inclusion in the analysis was determined by three basic 

criteria: (1) the observed ozone concentration had to be ± 30 percent of the station’s 

weighted design value; (2) the absolute prediction accuracy of the base 2008 simulation 

for that day was required to be within 20 percent; and (3) the observed daily maximum 

concentration needed to be greater than 84 ppb. The criteria were designed to eliminate 

extreme values from entering the analysis and to only focus on station days where model

performance met the long-standing criteria for acceptance used in previous attainment 

demonstrations. Finally, only station days where ozone exceeded the 84 ppb threshold 

established to demonstrate attainment of the 1997 ozone standard, as specified in the 

U.S. EPA Modeling Attainment Guidance Document, were included in the analysis. 

Future Ozone Air Quality

Table 5-5 summarizes the results of the updated ozone simulations. Included for general 

comparison are the 2023 ozone baseline and 2023 controlled ozone projections from the 

2007 AQMP ozone attainment demonstration modeling analysis approved by U.S. EPA 

as part of the SIP The Draft 2012 AQMP baseline ozone simulations reflect the 

changes made to the 2023 baseline inventory. The Draft 2012 summer planning 

inventory has a higher ratio between VOC and NOX emissions, 1.39 vs. 1.05, although

total tonnages of both precursor emissions are lower than presented in the 2007 AQMP. 

The higher VOC to NOx ratio is indicative of a more reactive pollutant mix with average 

projected ozone design concentrations 9 percent higher than previously projected. One 

implication of this simulation is that moderate VOC emissions reductions in the years 

between 2014 and 2023 will benefit regional ozone concentrations. Yet, the projected 

2023 baseline design value of 108 ppb continues to exceed the federal standard by 35 

percent. With the implementation of the Draft 2012 AQMP short term control measures 

and the Section 185(e)(5) long-term control measures, (defined in this update as the 

difference between the Draft 2012 AQMP 2023 base year VOC and NOx emissions and 

the corresponding Basin 2007 AQMP ozone attainment demonstration carrying 

capacity), projected regional ozone design values closely match those defined in the 

2007 AQMP ozone attainment demonstration. Regardless, it will still require a 64 

percent reduction in NOx emissions and an additional 3 percent reduction in VOC 

emissions to attain the 1997 ozone standard.
Chapter 5 Future Air Quality

5-22

With controls in place, the updated analysis corroborates the approved 2007 AQMP 

ozone attainment demonstration in that it is expected that all stations in the Basin will 

meet the federal 8-hour ozone standard. The east Basin stations in the San Bernardino 

Valley continue to have among the highest projected 8-hour controlled design values for 

this update. The 2023 controlled ozone design value at Glendora is also projected to 

exceed 80 ppb, but all stations show attainment with the federal 8-hour ozone standard 

(<84ppb). Glendora, Upland, Fontana and San Bernardino are downwind receptors 

along the primary wind transport route that moves precursor emissions and developing 

ozone eastward by the daily sea breeze. The higher projected design value at Glendora 

reflects the higher VOC to NOx ratio observed in the baseline inventory relative to the 

2007 AQMP 2023 baseline inventory. The 2023 controlled design value at Glendora for 

the Draft 2012 AQMP actually represents a greater response to emissions reductions 

than in the 2007 AQMP attainment demonstration. Future year projections of ozone for 

this update along the northerly transport route through the San Fernando Valley indicate 

that the ozone design value in the Santa Clarita Valley will be approximately 15 percent 

below the standard. 

TABLE 5-5

Model-Predicted 8-Hour Ozone Concentrations 

LOCATION

2007 OZONE 

SIP-2023 

BASELINE 

DESIGN (PPB)

2007 OZONE 

SIP-2023

CONTROLLED 

DESIGN (PPB)

DRAFT 2012 

AQMP-UPDATED 

2023* BASELINE 

DESIGN (PPB)

DRAFT 2012 

AQMP- UPDATED* 

2023*CONTROLLED 

DESIGN (PPB)

Azusa 82 80** 95 77

Burbank 86 70** 88 72

Reseda 86 68 90 73

Pomona 85 75 100 80

Pasadena 78 74** 92 76

Santa Clarita 95 74 94 73

Glendora 91 79 107 84

Riverside 92 78 100 77

Perris 94 78*** 88 66

Lake Elsinore 80 64 85 66

Banning 88 70 94 73

Upland 92 78 106 83

Crestline 100 83 107 81

Fontana 97 81 104 81

San 

Bernardino 92 78 108 83
Draft 2012 AQMP

5-23

TABLE 5-5 (concluded)

Model-Predicted 8-Hour Ozone Concentrations 

LOCATION

2007 OZONE 

SIP-2023 

BASELINE 

DESIGN (PPB)

2007 OZONE 

SIP-2023

CONTROLLED 

DESIGN (PPB)

DRAFT 2012 

AQMP-UPDATED 

2023* BASELINE 

DESIGN (PPB)

DRAFT 2012 

AQMP- UPDATED* 

2023*CONTROLLED 

DESIGN (PPB)

Redlands 98 81 103 77

* Informational purpose only based on draft emissions inventories and across-the-board reductions. 

** Based on the city-station specific RRF’s determined from the 19 episode day average.

*** Based on the average of the RRF’s determined from the stations meeting the criteria having more than 5 

episode days.

Note: Attainment with the 1997 Federal 8-hour ozone standard requires 84 ppb or less

Spatial Projections of 8-Hour Ozone Design Values

The spatial distribution of ozone design values for the 2008 base year is shown in Figure 

5-12. Future year ozone air quality projections for 2024 with and without 

implementation of all control measures are presented in Figures 5-13 and 5-14. The 

predicted ozone concentrations will be significantly reduced in the future years in all 

parts of the Basin with the implementation of proposed control measures in the South 

Coast Air Basin.

Appendix V provides base year model performance statistics, grid level spatial plots of 

simulated ozone (base cases and future year controlled) as well as weight of evidence 

discussions to support the modeling attainment demonstration. 
Chapter 5 Future Air Quality

5-24

FIGURE 5-12

2008 Baseline 8-Hour Ozone Design Concentrations (ppb)

FIGURE 5-13

Model-Predicted 2023 Baseline 8-Hour Ozone Design Concentrations (ppb)
Draft 2012 AQMP

5-25

FIGURE 5-14

Model-Predicted 2023 Controlled 8-Hour Ozone Design Concentrations (ppb)

A First Look at Attaining the 2006 8-Hour Ozone Standard

In 2006, the U.S. EPA lowered the federal 8-hour ozone standard to 75 ppb. Recent 8-

hour ozone rule implementation guidance requires that a SIP revision with an updated 

attainment demonstration and control strategy be submitted to U.S. EPA no later than 

December 2015. The Basin has been designated as an extreme non-attainment area for 

the new standard, consistent with the classification of the 80 ppb standard. Thus, the 

deadline for attainment of the 75 ppb standard is 2032, 8-years after the attainment date 

for the previous 80 ppb federal standard in 2024. It is critical to conduct preliminary 

analyses to assess the need for potential adjustments to the overall control strategy 

considering this new standard and deadline 

The preliminary projections, based upon a modeling evaluation of how VOC and NOx 

reductions affect the Basin’s ozone levels (ozone “isopleths”) indicates that that a 75 

percent reduction in NOX emissions beyond the 2023 baseline is needed to meet the 75 

ppb level in 2032. The resulting 2032 Basin NOx carrying capacity could be as low as 

to 85 tpd. Further discussion of the ozone isopleths and a glance at the potential impact 

to the control strategy and carrying capacity for potential future revisions to the 8-hour 

ozone standard is presented in Chapter 8.
Chapter 5 Future Air Quality

5-26

SUMMARY AND CONCLUSIONS

Figure 5-15 shows the 2008 observed and model-predicted regional peak concentrations 

for 24-hour average and annual PM2.5 as percentages of the most stringent federal 

standard, for 2014. The federal 24-hour and annual PM2.5 standards are predicted to be 

met in 2014 with implementation of the Draft 2012 AQMP control strategy. The 

California annual PM2.5 standard will not be attained before 2019. (See Figure 5-16).

Given the changes made to the modeling platform, the number of episodes evaluated,

and the distinct changes in the projected Draft 2012 AQMP 2023 baseline inventory, 

projected 8-hour ozone design values with implementation of the short- and long-term 

controls are very consistent with those presented in the 2007 AQMP attainment 

demonstration. Again, an approximate 65 percent reduction in NOx emissions in 2023 

will be required to meet the 1997 80 ppb standard by 2024.

The challenges of meeting potential future standards for 8-hour ozone and a proposed

federal annual PM2.5 standard between 12 and 13 μg/m

3

are discussed in Chapter 8 of 

this document.

The challenge of future year attainment of proposed revisions to the federal annual 

PM2.5 standard at a value between 12 and 13 μg/m

3

are discussed in Chapter 8 of the 

Draft 2012 AQMP. 

FIGURE 5-15

Projection of Future Air Quality in the Basin in Comparison 

with the Federal Standards. 

0

20

40

60

80

100

120

140

160

2008 Observed 2014 Baseline 2014 Controlled

24-Hr Average Annual

Federal Standard

Percent of Fed. Std.
Draft 2012 AQMP

5-27

FIGURE 5-16

Projection of Future PM2.5 in the Basin in Comparison with

California State Standard

0

20

40

60

80

100

120

140

160

180

2008 Observed 2014 Predicted 2019 Predicted

Percent of California Standard

California

Standard