2007 Ozone Plan 

Chapter 1 

 

Progress and Current Air Quality 
2007 Ozone Plan 

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San Joaquin Valley Unified Air Pollution Control District April 30, 2007

Chapter 1: Progress and Current Air Quality 

2007 Ozone Plan 

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Chapter 1: Progress and Current Air Quality

1.1 INTRODUCTION 

This chapter presents an overview of the progress that has been made and the current 

state of the San Joaquin Valley’s air quality. Over the past 20 years, the hard work and 

financial and personal investments by industries, individuals, and agencies are 

producing real and tangible results that show a substantial improvement in air quality. 

1.2 ADOPTED RULES 

Since its forming in 1992, the San Joaquin Valley Air Pollution Control District (District) 

has adopted about 500 rules and rule amendments. The District was the nation’s first to 

adopt a progressive Indirect Source Review (ISR) program, which reduces emissions 

from new indirect sources Valley-wide, such as commercial, industrial, and residential 

developments. The District was also the first in the nation to adopt a rule to control 

volatile organic compounds (VOC) emissions from wine production and storage. This 

rule contains groundbreaking compliance options that offer flexibility to operators 

without sacrificing emission reductions. 

The District was the first in the state to regulate emissions from on-field agricultural 

operations. To date, through the Conservation Management Practices (CMP) rule, the 

District has received 6,400 CMP plans from Valley farmers that reduce particulate 

matter emissions from 3.2 million acres of productive agricultural land. The District was 

also the first major air district in the state to regulate the use of residential fireplaces. 

Now, other major districts in the state are using the District’s regulation as the 

benchmark. In addition, the District leads the nation with its stringent emission limits on 

engines, boilers, turbines, and glass-melting furnaces. Air quality improvements 

evidence the success of the District’s innovative rules, as discussed in the next section. 

1.3 CURRENT AIR QUALITY 

The two major indicators of air quality are emissions inventories and ambient air quality 

data. Emissions inventories are estimates indicating how much direct pollution is 

going into the air as a result of various activities. Ambient air quality data, which is 

measured by monitors, tells us how much pollution is in the air we breathe. Together, 

these data show progress made in improving air quality as well as the great challenge 

we face in meeting future standards. 
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1.3.1 Emissions 

An emissions inventory is a tabulation of pollutant emissions into the atmosphere. The 

District uses comprehensive emissions inventories to develop control strategies, 

determine the effectiveness of permitting and control programs, provide input into 

ambient dispersion models, fulfill reasonable further progress requirements, and screen 

sources for compliance investigations. Emissions inventory data, like ambient 

monitoring data, are also used as indicators for trends in air pollution. 

 

Ozone is not directly emitted into the atmosphere, but produced by a photochemical 

reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the 

presence of sunlight (see Figure 1-1). Since there are no ozone emissions, there is no 

emissions inventory for ozone. Therefore, an effective ozone control strategy requires 

emissions inventories for NOx and VOC. 

Figure 1-1 Ozone Formation 

Source: AirNow, <http://airnow.gov/index.cfm?action=jump.jump_ozone>

Typically, an emissions inventory is also organized by emission source category. 

Source categories consist of several broad groups: 

! Mobile sources – motorized vehicles 

o On-road sources include automobiles, motorcycles, buses, and trucks 

o Other, or off-road, sources include farm and construction equipment, lawn 

and garden equipment, forklifts, locomotives, boats, aircraft, and 

recreational vehicles. 
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! Stationary sources – fixed sources of air pollution 

o Power plants, refineries, and manufacturing facilities 

o Aggregated point sources - facilities (such as gas stations and dry 

cleaners) that are not inventoried individually but are estimated as a group 

and reported as a single source category. 

! Area sources –human activity that takes place over a wide geographic area 

o Includes consumer products, fireplaces, tilling, and unpaved road dust. 

! Natural sources – non-anthropogenic, naturally occurring emissions 

o Geogenic sources, such as petroleum seeps 

o Biogenic sources, such as emissions from plants 

The District has made significant progress in reducing ozone precursor emissions. 

These reductions are a result of the many rules and programs put in place by the 

District and the ARB. These reductions represent an impressive accomplishment, 

especially in light of the 37% increase in population in the San Joaquin Valley over the 

same time period. 

Figure 1-2 Ozone Precursor Emissions Reductions 

(Summer Averages), 1990-2005 

(2006 Almanac (base year 2005)) 

Appendix B contains detailed tables showing the emissions inventories for NOx and 

VOC (as well as total organic gases [TOG], particulate matter 10 microns or less in 

diameter [PM10], particulate matter 2.5 microns or less in diameter [PM2.5], total 

suspended particles [TSP], carbon monoxide [CO], and oxides of sulfur [SOx], which 

0

100

200

300

400

500

600

700

800

900

1990 2005

tons per day, summer

NOx

VOC
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are all included to satisfy federal requirements). This appendix also contains more 

information on emissions inventory maintenance. Motor vehicle conformity budgets, 

which are required in state implementation plans (SIPs) and are based on motor vehicle 

emissions inventories, will be available in Appendix C (though not in this draft because 

ARB has not yet released the necessary mobile source emissions model (EMFAC 

2007)). Emission reduction credits (ERC) are presented in Appendix D. 

1.3.2 Air Monitoring Data 

The District operates an extensive air monitoring network to measure progress towards 

compliance with the National Ambient Air Quality Standards (NAAQS). Ozone 

monitoring networks are designed to monitor areas with high population densities, areas 

with high pollutant concentrations, areas impacted by major pollutant sources, and 

areas representative of background concentrations. Together, the District, the 

California Air Resources Board (ARB), and the National Park Service operate 22 ozone 

monitoring sites throughout the San Joaquin Valley, as shown in Figure 1-3. Fifteen of 

the 22 currently operating monitors are in locations suitable to measure representative 

concentrations in areas of high population density. The other seven monitors (Oildale, 

Parlier, Clovis, Edison, Maricopa, Merced, and Fresno-Drummond) are sited specifically 

in areas that experience high ozone concentrations. 

Figure 1-3 Ozone Monitoring Sites within the San Joaquin Valley Air Basin 

The ozone monitors yield hourly average concentrations of ozone, reported in parts per 

million (ppm) to three decimal places. As illustrated in Figure 1-4 and Figure 1-5, the 

San Joaquin Valley Air Basin has shown progress in attaining the 1-hour ozone 

standard, which was revoked by EPA on June 15, 2005 (a discussion of federal air 

quality standards can be found in Chapter 2). The District is now continuing to 
San Joaquin Valley Unified Air Pollution Control District April 30, 2007

Chapter 1: Progress and Current Air Quality 

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implement emission control measures contained in its most recent plan for attaining the 

now-revoked 1-hour ozone standard (the Extreme Ozone Attainment Demonstration 

Plan, adopted October 8, 2004). 

Figure 1-4 Improvement in 8-hour Ozone Levels, 1995-2005 
San Joaquin Valley Unified Air Pollution Control District April 30, 2007

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Figure 1-5 Days Over the 1-hour Ozone Standard 

0

10

20

30

40

50

60

1990199119921993199419951996199719981999200020012002200320042005

Year

Number of Days

This plan for the 8-hour ozone standard extends the District’s ozone air pollution control 

strategy to attain the more stringent standards. The one-hour ozone measurements 

collected by air quality monitors are also used to calculate 8-hour averages. At any 

given monitor, the highest of the 24 possible 8-hour average concentrations for a given 

calendar day is recorded as the 8-hour value for that day. For a given year, the fourth 

highest value is selected from the daily 8-hour maxima (as such, the highest three daily 

maximum 8-hour average ozone values each year do not count towards the attainment 

determination) and then averaged with corresponding values for the previous two years 

to determine attainment. The result is the three-year average of the annual fourthhighest daily maximum 8-hour ozone concentration, which is also called the “design 

value” for 8-hour ozone and is also the form of the standard. Table 1-1 illustrates a 

sample calculation. The 8-hour ozone NAAQS is met at a given monitor when the 

design value is less than or equal to 0.08 ppm rounded to the nearest hundredth (so 

concentrations less than 0.085 ppm are considered to be in attainment). 
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Table 1-1 Sample Design Value Calculation 

(Fresno-Sierra Sky Park, 2005) 

Highest Daily Maximum Concentrations (ppm) Year 1st Highest 2nd Highest 3rd Highest 4th Highest 

2003 0.112 0.106 0.103 0.102 

2004 0.095 0.094 0.094 0.091 

2005 0.103 0.102 0.102 0.101 

3 - Year Average: 0.098 

 

Figure 1-6 shows design values by monitoring site for 2003-2005. As you can see from 

the figure, in spite of recent progress, the new 8-hour average standard is still exceeded 

by a significant amount at almost every site, and bringing all sites into attainment will 

represent a significant challenge. 

Figure 1-7 shows the number of days over the numeric value of the 8-hour standard by 

site for 2003, 2004, and 2005; although this is not used for attainment determinations, it 

shows that all sites of the Valley are experiencing fewer days over the standard than a 

couple of years ago, but that significant additional efforts will be needed to bring all sites 

into attainment. More 8-hour ozone data and analysis are available in Appendix A. 
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Figure 1-6 Eight-hour Ozone Design Values, 2003-20051

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Stockton

Modesto

Turlock

Merced

Madera

Clovis

Fresno- Drummond

Fresno- First

Fresno- SSP

Parlier

Lower Kaweah

Ash Mtn.

Visalia

Hanford

Shafter

Oildale

Bakersfield- California 

Bakersfield- Golden 

Edison

Arvin

Maricopa

Concentration (ppm)

2003

2004

2005

 

1

 One of the District’s 22 ozone monitoring sites, the Tracey-Airport site, has not been operating long enough to yield 

design values at this time. 

Federal 8-hour ozone 

standard = 0.084 ppm
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Figure 1-7 Days Over the Level of the Federal 8-hour Ozone Standard 

0 20 40 60 80 100 120

Stockton

Modesto

Turlock

Merced

Madera

Clovis

Fresno- Drummond

Fresno- First

Fresno- SSP

Parlier

Lower Kaweah

Ash Mtn.

Visalia

Hanford

Shafter

Oildale

Bakersfield- California 

Bakersfield- Golden 

Edison

Arvin

Maricopa

2003

2004

2005
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