2008 PM2.5 Plan 

This appendix has been provided by the California Air Resources Board 

(ARB). For information on the District’s Weight of Evidence work, please 

refer to Section 3.2.4 (Chapter 3), Appendix E, and Appendix F. 

Appendix H 

 

Weight of Evidence 
2008 PM2.5 Plan 

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San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-1 

Appendix H: Weight of Evidence

1. INTRODUCTION: SAN JOAQUIN VALLEY PM2.5 SUPPLEMENTAL ANALYSIS 

The State Implementation Plan or SIP serves as a demonstration of attainment for the 

national ambient air quality standards (NAAQS or federal standards). The attainment 

demonstration comprises analyses used to determine the set of control measures 

needed to meet the NAAQS by the attainment year. These analyses typically include 

air quality modeling, which generally guides the selection of the most effective pollutants 

to control and the magnitude of needed emissions reductions. The Weight of Evidence 

(WOE) analysis provides a set of complementary analyses that supplement the 

SIP-required modeling. These analyses can include consideration of measured air 

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

and additional air quality modeling. 

A WOE approach looks at the entirety of the information at hand to provide a more 

informed basis for the attainment strategy. Because all methods have inherent 

strengths and weaknesses, examining an air quality problem in a variety of ways offsets 

the limitations and uncertainty that are inherent in air quality modeling. This approach 

also provides a better understanding of the overall problem and the level and mix of 

emissions controls needed for attainment. 

The United States Environmental Protection Agency (U.S. EPA) recognizes the 

importance of a comprehensive assessment of air quality data and modeling and 

encourages this type of broad assessment for all attainment demonstrations. In their 

modeling guidance, they further note that the results of supplementary analyses may be 

used in a WOE determination to show that attainment is likely despite modeled results 

which may be inconclusive (U.S. EPA 2007). Under the U.S. EPA guidance, future year 

modeled annual average design values that fall between 14.5 and 15.5 ug/m3

 should be 

accompanied by a WOE demonstration to determine whether attainment will occur. 

This range in modeled design values reflects the uncertainty in predicting absolute 

PM2.5 concentrations that is inherent in air quality modeling, and therefore recognizes 

that an improved assessment of attainment can be derived from examining a broader 

set of analyses. 

U.S. EPA recommends that three basic types of analyses be included to supplement 

the primary modeling analysis in the WOE approach: 

 

1) analyses of trends in ambient air quality and emissions, 

2) observational models and diagnostic analyses, and 

3) additional modeling. 

Each analysis is weighted based on its ability to quantitatively assess the ability of the 

proposed control measures to yield attainment. The scope of the WOE analysis is 

different for each nonattainment area. The level of detail appropriate for each area 

depends upon the complexity of the air quality problem, how far into the future the 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-2 

attainment deadline is, and the amount of data and modeling available. For example, 

less analysis is needed for an area that is projecting attainment near-term and by a wide 

margin, and for which recent air quality trends have demonstrated significant progress, 

than for areas with more severe air quality challenges. The following sections present 

the WOE assessment for PM2.5 in the San Joaquin Valley Air Basin for each of the 

areas outlined in the U.S. EPA guidance. 

2. ASSESSMENT OF RECENT AIR QUALITY AND EMISSION TRENDS 

a. Current Air Quality

According to U.S. EPA’s guidance, even though air quality models are regarded as the 

most appropriate tool to assess impacts in emission changes, it is also possible to 

extrapolate future trends in PM2.5 based on measured historical trends of air quality 

and emissions. Strength of the evidence produced by emissions and air quality trends 

is increased if an extensive monitoring network exists and if there is good correlation 

between past emission reductions and current trends. 

Along with the South Coast, the San Joaquin Valley Air Basin has one of the most 

severe PM2.5 problems in the nation and represents a considerable challenge in 

attaining the federal PM2.5 standards. These standards consist of both a 24-hour 

standard of 65 ug/m3

, and an annual average standard of 15 ug/m3. While the majority 

of monitors with complete data in the San Joaquin Valley still exceed the annual PM2.5 

standard, PM2.5 air quality has shown considerable improvement since 1999 when 

monitoring data for assessing compliance with the federal PM2.5 standard began. 

When the San Joaquin Valley was first designated nonattainment for the federal PM2.5 

standards, the basin exceeded both the annual and the 24-hour PM2.5 standards. 

However, based on 2004-2006 data, the San Joaquin Valley meets the federal 24-hour 

PM2.5 standard of 65 ug/m3 throughout the basin. Thus attaining the annual standard 

is the primary challenge in this State Implementation Plan. 

The San Joaquin Valley Air Basin is a lowland area bordered by mountains to the east, 

west, and south. The mountains act as air flow barriers, with the resulting stagnant 

conditions favoring the accumulation of emissions and pollutants. To the north, the 

Valley borders the Sacramento Valley and Delta lowland, which allows for some level of 

pollutant dispersion. As a result, PM2.5 concentrations are higher in the southern and 

central portions of the Valley, where geography, emissions, and climate pose significant 

challenges to air quality progress. Chapter 3 and Appendix E of the District Plan 

provide detailed information on the conceptual model of PM2.5 formation in the Valley. 

Currently, eleven sites routinely monitor PM2.5 in the Air Basin. Table H-1 provides the 

2006 annual standard design values and the annual average values for 2004, 2005, and 

2006 for each monitoring site with complete data. The design value is a statistic that is 

used to describe the air quality status of a given area relative to the level of the federal 

standard. The annual design values represent the average of the mean annual PM2.5 

concentrations measured during the three year period. Table H-2 provides the 24-hour 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-3 

standard design value for each monitoring site with complete data and the yearly 98th

percentile value of the 24-hour concentrations measured in 2004, 2005, and 2006. The 

24-hour design value represents the average of the yearly 98th percentile of the 24-hour 

concentrations measured during the three year period. Attainment is reached when the 

design value is at or below the corresponding federal standard. 

As shown in Table H-1, current 2006 annual average design values (reflecting the 2004 

through 2006 period) range from 12.9 ug/m3 to 18.9 ug/m3. The San Joaquin Valley 

monitoring sites with the highest PM2.5 annual design values are located in the 

southern and central portions of the basin, including Bakersfield and Visalia. Monitors 

located in the northern portion of the Valley, including Stockton, Modesto, and Merced 

have lower annual PM2.5 design values and attain the annual PM2.5 standard. As 

shown in bold in the table, the high site for the region is the Bakersfield–Planz monitor 

with a PM2.5 design value of 18.9 ug/m3. 

Table H-1. PM2.5 Annual Average Values 

 Annual Average 

(ug/m3) 

Monitor 2004 2005 2006 

2006 

3-year Annual Average 

Design Value (ug/m3) 

Clovis-N Villa Avenue 15.8 16.0 16.8 16.2 

Bakersfield-410 E Planz Road 17.4 19.9 19.3 18.9 

Bakersfield-5558 California Avenue 19.0 17.9 18.7 18.5 

Bakersfield-Golden State Highway 18.1 18.9 18.6 18.5 

Corcoran-Patterson Avenue 17.3 17.6 16.7 17.2 

Fresno-1st Street 16.4 16.9 16.8 16.7 

Fresno-Hamilton and Winery 17.0 16.9 17.6 17.2 

Merced-2334 M Street 15.3 14.1 14.8 14.7 

Modesto-14th Street 13.6 13.9 14.8 14.1 

Stockton-Hazelton Street 13.2 12.5 13.1 12.9 

Visalia-N Church Street 17.0 18.8 18.8 18.2 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-4 

Table H-2. PM2.5 98th Percentile 24-hour Values 

 Annual 98th Percentile 

(ug/m3

) 

Monitor 2004 2005 2006 

2006 

3-year Average of 

98th Percentile 

Design Value (ug/m3) 

Clovis-N Villa Avenue 42.4 77.0 51.3 57 

Bakersfield-410 E Planz Road 78.6 66.4 50.6 65* 

Bakersfield-5558 California Avenue 59.3 63.6 60.5 62 

Bakersfield-Golden State Highway 53.8 74.9 64.4 64 

Corcoran-Patterson Avenue 49.4 74.5 50.1 58 

Fresno-1st Street 52.0 71.0 51.0 58 

Fresno-Hamilton and Winery 49.4 71.2 55.0 59 

Merced-2334 M Street 43.0 48.3 43.8 45 

Modesto-14th Street 45.0 55.0 52.0 51 

Stockton-Hazelton Street 36.0 44.0 42.0 41 

Visalia-N Church Street 54.0 65.0 50.0 56 

*The 24-hour standard is exceeded when the design value is over 65 ug/m3 

As previously mentioned, all monitors in the San Joaquin Valley currently attain the 

federal 24-hour PM2.5 standard. As shown on Table 2, 2006 24-hour PM2.5 design 

values (reflecting the 2004 through 2006 period) range from 41 ug/m3 to 65 ug/m3. 

Monitoring sites with the highest 24-hour PM2.5 design values are located in the 

southern portion of the Valley, around Bakersfield. As shown in bold on the table, the 

high site for the region is Bakersfield-Planz with a 24-hour PM2.5 design value of 

65 ug/m3

. 

b. Recent PM2.5 Mass Trends

Trends observed in the San Joaquin Valley show that considerable progress has 

occurred in the San Joaquin Valley over the last five years due to the ongoing 

emissions control program. As shown in Figure H-1, 24-hour design values have 

decreased approximately 40 percent and, as discussed above, based on the 2004 

through 2006 data, attain the federal standard at all sites in the Basin. 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-5 

Figure H-1: Comparison of 2006 to 2001 PM2.5 24-hour Design Values 

PM2.5 24-hour Design Value

0

20

40

60

80

100

120

Modesto-14th

Street

Fresno-1st

Street

Visalia BakersfieldGolden

Concentrations (ug/m3)

2001

2006

All San Joaquin Valley monitors with complete data also show a significant decrease in 

annual average design values (Figure H-2). In 2001, all monitoring sites in the Basin 

had annual design values greater than 16 ug/m3, with the Visalia site at approximately 

one and a half times the level of the standard. By 2006, design values decreased 

throughout the basin, and only those sites in the southern and central portions of the 

Valley are still greater than 16 ug/m3. Bakersfield–Planz is the current high site, with a 

design value which is 26 percent above the standard. The greatest rate of progress has 

occurred in the northern and central basin. From 2001 through 2006, the Modesto site 

design value dropped 28 percent, from 19.7 ug/m3 to 14.1 ug/m3, while the Visalia site 

design value dropped 26 percent from 24.7 ug/m3

 to 18.2 ug/m3. As a result, all 

monitoring sites in the northern portion of the Valley now attain the annual PM2.5 

standard of 15 ug/m3

. In contrast, the Bakersfield-Golden site dropped 22 percent from 

23.6 ug/m3

 to 18.5 ug/m3 and the Bakersfield-California site dropped 21 percent from 

23.3 ug/m3

 to 18.5 ug/m3. This trend is further illustrated in Figure H-3 which depicts 

maps of the spatial variations in annual average concentrations in 2001 as compared to 

2006. 

Trends in 24-hour and annual average design values were further evaluated using the 

nonparametric statistical analysis test, known as the Theil test, that U. S. EPA uses in 

national air quality trend analysis1

. This method tests for whether upward or downward 

trends are real (significant) or a chance product of year-to-year variation (not 

significant). Theil test results indicate the 2001 to 2006 downward trends in 24-hour 

and three-year annual average PM2.5 concentrations are statistically significant. 

 

1

 U.S. EPA , National Air Quality and Emissions Trends Report, Publication No. EPA 454/R-03-005, Office of Air 

Quality and Standards, Air Quality Strategies and Standards Division, Research Triangle Park, North Carolina. 2003. 

http://www.epa.gov/air/airtrends/aqtrnd03/
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-6 

Figure H-2: Trends in Annual Average PM2.5 Design Values 

Figure H-3: 2001 and 2006 Annual Average Values 

PM2.5 (ug/m3) 

San Joaquin Valley Air Basin

National PM2.5 Annual Average 

(2001) 

Stockton 

Modesto 

Merced 

Clovis Fresno-1st 

Fresno-Hamilton 

Visalia 

Corcoran 

Bakersfield-Golden 

Bakersfield-California 

Bakersfield-Planz 

Three Year Annual Average PM2.5 Design Values

0

5

10

15

20

25

30

2001 2002 2003 2004 2005 2006

Year

Concentrations (ug/m3)

Bakersfield-410 E Planz

Bakersfield-5558 California

Bakersfield-Golden

Modesto-14th Street

Stockton-Hazelton

Visalia-N Church

Fresno-1st Street
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-7 

The progress observed in both the annual and the 24-hour PM2.5 standards reflects the 

linkage between the two standards. The annual average is comprised of individual 24-

hour samples which vary throughout the year. In the San Joaquin Valley, PM2.5 

concentrations exhibit a pronounced seasonal variation, with significantly higher 

monthly average concentrations during the late fall and winter (November through 

January). PM2.5 concentrations from April through September are generally below 

15 ug/m3

. Therefore 24-hour PM2.5 concentrations during the fall and winter seasons 

strongly drive the annual average concentrations. During the late fall and winter, 

stagnant air, cool temperatures, and high humidity can lead to a build-up of PM2.5 over 

a period of several days to weeks. 

Analyses of the changes in the distribution of the 24-hour concentrations between 2001-

2003 and 2004-2006 indicate that the decrease in both 24-hour and annual average 

concentrations is the result of the downward shift in the distribution of daily PM2.5 

concentrations during the fall/winter period. This can be seen in the decrease in the 

monthly average concentrations during the fall/winter months between 2001 and 2006 

at Bakersfield-California and Fresno (Figures H-4 and H-5). 

Figure H-4: Changes in Seasonal Pattern at the Bakersfield-California Monitoring 

Site 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-8 

Figure H-5: Changes in Seasonal Pattern at the Fresno Monitoring Site 

A comparison of the changes in the frequency distribution of 24-hour concentrations 

over the last few years provides another means of understanding progress. Data 

collected from 24-hour samples during 1999-2001 at the Bakersfield site indicate that 6 

percent of the samples had concentrations greater than 65 ug/m3 (Figure H-6). In 

comparison, during the 2004-2006 period, the number of samples with PM2.5 

concentrations greater than 65 ug/m3 fell to 1 percent. During both periods, 45 percent 

of the samples had concentrations above the level of the annual PM2.5 standard of 15 

ug/m3. 

At the Fresno site data collected during the 1999–2001 period indicate that 

approximately 8 percent of the samples had concentrations greater than 65 ug/m3

(Figure H-7), while during the 2004-2006 period, only 1 percent of the samples had 

concentrations greater than 65 ug/m3. In addition, during 1999-2001, 46 percent of the 

samples had concentrations above the level of the annual PM2.5 standard of 15 ug/m3

, 

while during the 2004-2006 period, the number of samples with concentrations greater 

than 15 ug/m3

 fell to 34 percent. This analysis, together with the analysis of monthly 

average PM2.5 trends, further illustrate that progress to date in the annual average is 

primarily linked to reductions in peak concentrations from October through March. 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-9 

Figure H-6: PM2.5 Concentrations at Bakersfield-California 1999-2001 versus 

2004-2006 

Figure H-7: PM2.5 Concentrations at Fresno 1999-2001 versus 2004-2006 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-10 

c. Historical PM2.5 Mass Trends

The PM2.5 Federal Reference Method (FRM) network that is used for comparison to 

the federal standard was deployed in 1998 and 1999. However, PM2.5 data have been 

routinely collected in the San Joaquin Valley Air Basin since the late 1980s using 

dichotomous samplers that were operated for research purposes. The PM2.5 

dichotomous data correlate very well with the FRM data (r=0.98), but are biased lower 

than the FRM by 12 percent, therefore an absolute comparison to the FRM can not be 

made. However, the relative changes in the dichotomous data do provide a longer-term 

context for assessing progress. Figure H-8 depicts PM2.5 concentrations at four sites. 

At all of these sites, the 3-year average concentrations decreased until 1998, then 

increased until 2000. At two of the three highest sites, Bakersfield and Visalia, the Hyear average concentrations decreased about 40 percent from 1990 to 1998 (the 

Bakersfield site trend has a gap from 1994 to 1996). PM2.5 concentrations at 

Bakersfield then increased 19 percent from 1998 to 2000. The dichotomous data 

record at the third high site, Fresno, started in 1992. From 1992 to 1998, PM2.5 

concentrations decreased 21 percent, followed by a 12 percent increase from 1998 to 

2000. PM2.5 concentrations at the low site, Stockton, decreased 40 percent from 1991 

to 1998, followed by a 20 percent increase from 1998 to 2000. The period between 

1999 and 2001 included a number of adverse winter episodes which likely lead to 

higher annual averages during this period. However, overall concentrations declined 20 

to 30 percent over the period from 1990 through 2001. Looking at dichotomous data 

and FRM data together therefore illustrates an overall long-term improvement in PM2.5. 

Figure H-8: Trends in Three-Year Average PM2.5 Concentrations Measured with 

Dichotomous Samplers 

PM2.5 Dichot Three-Year Average Trend

0

5

10

15

20

25

30

35

199019911992199319941995199619971998199920002001

Concentrations (ug/m3)

Bakersfield*

Fresno-1st Street

Stockton

Visalia
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-11 

d. Chemical Composition and Emissions Trends

Current Chemical Composition 

Particulate matter (PM) consists of many different chemical components. Investigating 

these different components and how they vary by site and season provides us with a 

better understanding of their complexity and responses to the emission control program. 

This mix of chemical components consists of both directly emitted PM such as 

geological material and elemental carbon (soot), known as primary PM, as well as PM 

formed in the atmosphere from the reactions of precursor gases, known as secondary 

PM. These precursor pollutants include nitrogen oxides (NOx), sulfur oxides (SOx), 

reactive organic gases (ROG), and ammonia. NOx, SOx, and ammonia combine to 

form secondary ammonium nitrate and sulfate. ROG can form secondary organic 

carbon, as well as participate in the production of secondary ammonium nitrate. 

In the San Joaquin Valley, chemical components are routinely measured at four sites, 

Bakersfield, Fresno, Visalia, and Modesto. These sites represent urban areas in 

different portions in the air basin. The chemical composition of PM2.5, seasonal 

variability, and trends in these components at two of these sites, Fresno and Bakersfield 

are discussed below to provide further insight into the linkage between observed 

progress and ongoing emission reductions. 

The annual average PM2.5 chemical composition for Bakersfield and Fresno is shown 

in Figure H-9. Ammonium nitrate and organic carbon are the major constituents at both 

sites. However, at Bakersfield, ammonium nitrate constitutes a higher percentage (39 

percent) of PM2.5 than organic carbon (35 percent), while the reverse (37 percent 

ammonium nitrate and 41 percent organic carbon) occurs in Fresno. Ammonium nitrate 

is formed in the atmosphere from chemical reactions of NOx emitted from motor 

vehicles and stationary combustion sources. Stagnant, cold, and damp conditions in 

the winter promote the formation and accumulation of ammonium nitrate. Burning 

activities, such as residential wood combustion, cooking, and direct tailpipe emissions 

from mobile sources are major sources of organic carbon. Ammonium sulfate is also 

formed in the atmosphere from chemical reactions of SOx emitted from combustion 

sources. Ammonium sulfate constitutes about one tenth of ambient PM2.5 at both sites. 

Elemental carbon resulting from mobile and stationary combustion sources, and 

geological material from roads and other dust producing activities also contribute to 

PM2.5 at both sites, but to a lesser extent. 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-12 

Figure H-9: 2004-2006 Average Chemical Composition of PM2.5 at Bakersfield 

and Fresno 

Figures H-10 and H-11 illustrate the seasonal variability in chemical components that 

make up PM2.5 for the Bakersfield and Fresno sites averaged over 2004 through 2006. 

As discussed previously, PM2.5 concentrations are highest during the fall and winter. 

These higher concentrations are driven by increases in ammonium nitrate and carbon. 

At the Bakersfield site (Figure H-10), ammonium nitrate is highest during the fall and 

winter months (November through January) and lowest from April through September. 

Ammonium nitrate concentrations at Fresno follow the same trend. Cold and humid 

conditions during the fall and winter favor the formation of ammonium nitrate in the 

atmosphere from chemical reactions of nitrogen oxides emitted from mobile and 

stationary combustion sources. At the Fresno site (Figure H-11), organic carbon has a 

similar trend as that of ammonium nitrate. At the Bakersfield site, organic carbon is also 

highest during the fall and winter months, but at this site organic carbon levels start high 

in January, decrease until April and then increase almost linearly until reaching a 

maximum in December. Increased activity in residential wood combustion during the 

fall/winter period is one cause of higher organic carbon concentrations. At both 

locations, elemental carbon component remains fairly constant throughout the year, 

while the ammonium sulfate component is more prevalent from May through 

September, and the geological components from April through October. 

2004-2006 Average Composition

Bakersfield

AmmNitrate

39%

AmmSulfate

13%

OC

35%

Geological

6%

EC

5%

Elements

2%

2004-2006 Average Composition

Fresno

AmmNitrate

37%

AmmSulfate

11%

OC

41%

Geological

4% EC

5%

Elements

2%
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-13 

Figure H-10: Seasonal Variation in PM2.5 Chemical Components at Bakersfield 

Figure H-11: Seasonal Variation in PM2.5 Chemical Components at Fresno 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-14 

Chemical Composition and Precursors Trends 

As discussed previously, monitoring sites in the San Joaquin Valley have shown PM2.5 

concentrations decreasing from 2001 to 2006. Trends in individual chemical 

components and precursor concentrations, as well as emissions inventory trends were 

evaluated to understand the main chemical components responsible for this progress 

and to evaluate the response to our ongoing control program. Figures H-12 and H-13 

illustrate recent trends in PM2.5 concentrations and its individual chemical components 

at Fresno and Bakersfield. Improvements in PM2.5 in the San Joaquin Valley can be 

mostly attributed to reductions in carbonaceous aerosols and ammonium nitrate. In 

Fresno, carbonaceous aerosols have dropped 37 percent, and ammonium nitrate 

concentrations have dropped 24 percent. The overall improvement in PM2.5 mass 

observed in Fresno is therefore due in most part to reductions in carbonaceous aerosols 

(63 percent), with a smaller portion of the remaining PM2.5 improvement due to 

reductions in ammonium nitrate (24 percent). In Bakersfield, carbonaceous aerosols 

have dropped by 16 percent and ammonium nitrate concentrations dropped by 

23 percent since 2002. Therefore 41 percent of the overall reduction in PM2.5 mass is 

due to reductions in carbonaceous aerosols, while 59 percent is due to reductions in 

ammonium nitrate. Understanding the role of carbonaceous compounds in PM2.5 

pollution, the San Joaquin Valley Air Pollution Control District made the Valley’s 

Residential Wood Combustion Rule more stringent in 2003, which may have contributed 

to the observed decrease in carbonaceous aerosols. 

Figure H-12: Trends in PM2.5 Mass and Chemical Components at Fresno 

* The three-year design value is not considered valid. 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-15 

Figure H-13: Trends in PM2.5 Mass and Chemical Components at BakersfieldCalifornia 

Concentrations in ambient NOx, a precursor to nitric acid and ammonium nitrate 

decreased steadily from 2001 through 2006. Figures H-14 and H-15 illustrate the shortterm trends in the Basin average NOx compared to ammonium nitrate concentrations in 

Fresno and Bakersfield. Ambient NOx concentrations in the Valley have shown a 

modest decrease of 15 percent. Ammonium nitrate concentrations were highest in 

2002 at both sites, with a small decrease between 2001 and 2006 at Fresno of 

7 percent. 

While the short-term trends for ammonium nitrate have been modest, longer-term 

records show concomitant decreases between ambient NOx and ammonium nitrate as 

well as between ambient SO2 and ammonium sulfate. Figure H-16 shows trends in the 

basin three-year average ambient NOx concentrations and the corresponding ambient 

nitrate measurements from the PM10 network extending back to the late 1980s. The 

hills and valleys in the ammonium nitrate concentrations reflect the effects of the varying 

meteorology on ammonium nitrate formation. Since 1987, ambient NOx has decreased 

50 percent while ammonium nitrate decreased by 35 percent. Figure H-17 shows the 

trends from 1987 to 1996 in the basin three-year average ambient SO2 concentrations 

and ammonium sulfate measurements from the PM10 network. During this period SO2 

decreased by 42 percent with a concurrent decrease in PM10 sulfate of 39 percent. 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-16 

Figure H-14: PM2.5 Ammonium Nitrate Compared to NOx – Fresno 

Figure H-15: PM2.5 Ammonium Nitrate Compared to NOx - Bakersfield 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-17 

Figure H-16: Long-Term Trends in Three-Year Average Concentrations of PM10 

Nitrate and NOx in San Joaquin Valley 

Three-year Average Concentrations

of PM10 Nitrate and NOx in San Joaquin Valley

0

1

2

3

4

5

6

7

8

9

10

1987198819891990199119921993199419951996199719981999200020012002200320042005

PM10 Nitrate (ug/m 3

)

0

1

2

3

4

5

NOx (pphm)

NO3-

NOx

Figure H-17: Long-Term Trends in Three-Year Average Concentrations of PM10 

Sulfate and NOx in the San Joaquin Valley 

Three-year Average Concentrations of PM10 Sulfate 

and SO2 in the SJV

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

1987198819891990199119921993199419951996199719981999200020012002200320042005

PM10 Sulfate (ug/m 3

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

SO2 (pphm)

SO4--

SO2

SO2 monitoring discontinued 

in 1997
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-18 

 Emission Trends 

At the same time that ambient concentrations have been declining, the emissions of 

pollutants that contribute to the different components of PM2.5 have been decreasing. 

Figure H-18 illustrates the recent emission trends in the San Joaquin Valley air basin 

from 2001 through 2005. The greatest decrease in emissions occurred in ROG with a 

decrease of 33 tpd or 8 percent. NOx also decreased slightly, with a decline of 28 tpd, 

or 4 percent. Direct PM2.5 emissions showed a decrease of 7 tpd, or 7 percent, while 

SOx emissions did not change. 

The combined downward trends in PM2.5 components, precursor concentrations, and 

emissions all indicate that over both in the short- and long-term the ongoing control 

program has had substantial benefits in improving air quality and that similar emission 

reductions in the future should provide continuing progress towards attaining the federal 

PM2.5 standards. 

Figure H-18: PM2.5 and PM2.5 Precursor Emission Trends in the San Joaquin 

Valley 

Annual Emission Inventory Trends

2001-2005

0

100

200

300

400

500

600

700

2001 2002 2003 2004 2005

Emissions (tpd)

NOx

ROG

SOx

PM2.5
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-19 

3. OBSERVATIONAL MODELS AND DIAGNOSTIC ANALYSES 

Observational models take advantage of monitored data to draw conclusions about the 

relative importance of different types of emissions and precursors as factors contributing 

to observed PM2.5 concentrations. According to U.S. EPA guidance, observational 

models can be used to corroborate the effects of prior control strategies, as well as 

identify the potential effectiveness of proposed control approaches. U.S. EPA 

recommends using both source apportionment (receptor models) and indicator species 

approaches. The two most widely applied receptor modeling approaches are multivariate statistical models such as positive matrix factorization (PMF) and the chemical 

mass balance model (CMB). Receptor models are particularly useful in identifying the 

source contributions to directly emitted PM. This section summarizes results from prior 

source apportionment studies as well as both PMF and CMB applied to recent data. In 

addition, previous work using an indicator species approach to assess the limiting 

precursor in secondary nitrate formation in the San Joaquin Valley is discussed. 

a. Observational Models

 Prior Source Apportionment Studies 

The Chemical Mass Balance (CMB), and the Positive Matrix Factorization (PMF) and 

UNMIX (named for its function, which is to "unmix" the concentrations of chemical 

species measured in the ambient air to identify the contributing sources) multivariate 

receptor models have been applied to PM2.5 data collected in the San Joaquin Valley. 

Chow, et al.2 used the CMB source apportionment model to estimate the contribution of 

sources to PM2.5 in Fresno during high PM2.5 days occurring from December 15, 2000 

through February 3, 2001 illustrated in Figure H-19. Secondary ammonium nitrate is 

the most significant source, contributing 32 percent to the measured PM2.5. 

Residential wood combustion constitutes 30 percent of PM2.5. Vehicle emissions 

account for 13 percent of PM2.5, with similar contributions from gasoline (7 percent) 

and diesel (6 percent) fueled vehicles. Cooking accounts for 12 percent of PM2.5. 

 

2

 J .C. Chow, J. G. Watson, D. H. Lowenthal, L.-W. A. Chen, B. Zelinska, L. R. Rinehart, and K. L. Magliano: 

Evaluation of organic markers for chemical mass balance source apportionment at the Fresno Supersite, 

Atmospheric Chemistry and Physics Discussions, 6, 10341 – 10372, 2006 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-20 

Figure H-19: Source Contribution to PM2.5 Concentrations at Fresno Estimated 

Using the Chemical Mass Balance (CMB) Method 

Chen, et al.3

 applied the PMF and UNMIX models to chemically speciated PM2.5 

measurements from 23 sites operated in the in the San Joaquin Valley during the 

2000/2001 Central California PM Air Quality Study (CRPAQS) to estimate source 

contributions. Figure H-20 illustrates the resulting source contribution throughout the 

Valley, estimated for the period when high PM2.5 concentrations occurred (November 

through January). PMF and UNMIX source contribution estimates are similar. Particles 

formed through chemical reactions in the atmosphere, including ammonium nitrate and 

secondary organic compounds are the major contributors, accounting for 48 percent 

(PMF) and 51 percent (UNMIX) of PM2.5. Residential wood combustion follows, with a 

contribution of 23 percent (PMF) and 24 percent (UNMIX). Particles directly emitted 

from motor vehicles account for 10 percent (PMF) and 15 percent (UNMIX) of PM2.5. 

In addition, the zinc component resulting from the PMF analysis is thought to be related 

to brake and tire wear and contributes 9 percent to PM2.5.

 

3

 L.-W. A. Chen, J. G. Watson, J. C. Chow, and K. L. Magliano: Quantifying PM2.5 Source Contributions for the San 

Joaquin Valley with Multivariate Receptor Models, submitted for publication, 2006. 

PM2.5 Source Contribution (CMB) in Percent 

Fresno - 2000/2001 Winter Average

Wood 

Burning

30%

Ammonium 

Nitrate

32%

Ammonium 

Sulfate

2% Cooking

12%

Vehicle 

Exhaust 

(Gasoline)

7%

Unknown

11% Vehicle 

Exhaust 

(Diesel)

6%
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-21 

Figure H-20: Source Contribution to PM2.5 in the San Joaquin Valley Estimated 

Using the Positive Matrix Factorization (PMF) and the UNMIX Models 

 Recent Studies 

To evaluate the major PM2.5 sources and their contributions in the San Joaquin Valley 

using recent data, two different source apportionment techniques were applied to data 

collected in 2003 through 2006. The Chemical Mass Balance model (CMB) uses 

measured source profiles and chemical speciation data in combination to determine 

source contributions. A fundamental underlying assumption is that the source profiles 

used as input are appropriate and representative for the region. In contrast, PMF does 

not require the input of source profiles, but rather evaluates the covariance of the 

chemical species to determine a set of factors, which are typically interpreted as source 

types. Source contributions are then calculated for each of the factors. Because the 

factors reflect species which vary in time in a similar manner, the factors may reflect the 

impacts of primary sources, as well the secondary species that have condensed on 

these primary particles. Since each technique has strengths and weaknesses, 

combined the two source apportionment techniques provide complementary results. 

Positive Matrix Factorization 

The PMF2 model was applied to chemically speciated PM2.5 data collected at the 

Fresno-First St. and Bakersfield-California Ave. Speciation Trends Network (STN) 

monitoring sites from July 2003 through December 2006. The average source 

contribution estimates illustrated in Figure H-21 show ammonium nitrate is the major 

contributor to PM2.5 at both sites (41 percent at Fresno and 45 percent at Bakersfield). 

Biomass smoke contributes similar percentages at both sites (8 percent at Fresno, 

7 percent at Bakersfield) as does the total aged aerosol (10 percent at Fresno, 

11 percent at Bakersfield). The main differences in source contribution between the two 

sites include particles directly emitted from motor vehicles, which at Fresno account for 

23 percent of PM2.5, the 2nd major component, while at Bakersfield account for 

13 percent. Ammonium sulfate accounts for 10 percent of PM2.5 at Fresno and 

Source Contibution (PMF) in Percent

San Joaquin Valley - 2000/2001 Winter Average 

Motor Vehicle

10%

Residential 

Wood 

Combustion

23%

Zinc

9%

Cooking

3%

Fugitive Dust

5% Ag-Dairy

2%

Ammonium 

Nitrate and 

Secondary 

Organic

48%

Source Contribution (UNMIX) in Percent 

San Joaquin Valley - 2000/2001 Winter Average

Motor Vehicle

15%

Ag-Dairy

2%

Fugitive Dust

3%

Residential 

Wood 

Combustion

24% Ammonium 

Nitrate and 

Secondary 

Organic

51%

Cooking

5%
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-22 

14 percent at Bakersfield. Airborne soil is a minor contributor to PM2.5 at Fresno (3 

percent), with a 9 percent contribution at Bakersfield. 

Figure H-21. Average Source Contributions Estimated Using PMF2 

(2003-2006) 

Chemical Mass Balance Modeling

Annual average source contributions at Bakersfield-5558 California Avenue (BAC) and 

Fresno-1st Street (FSF) were also estimated by applying the Chemical Mass Balance 

(CMB 8.2) model to individual PM2.5 sample concentrations collected between January 

1, 2004 and December 31, 2006 and using source profiles for PM2.5 developed during 

previous studies. Source contribution estimates were calculated based on the 2004-

2006 annual average of the individual samples. Figure H-22 shows the calculated 

contributions to ambient fine particulate matter made by sources included in the model. 

Ammonium nitrate was the most significant source contributing 44% and 39% of the 

PM2.5 mass at Bakersfield and Fresno, respectively. Ammonium sulfate accounted for 

12% at Bakersfield and 10% at Fresno. The motor vehicle exhaust (diesel and gasoline 

combined) contribution was 9% at both sites. Vegetative burning, which included 

residential wood combustion and agricultural and prescribed burning, contributed 9% 

and 14%, respectively, of the PM2.5 mass. The sea salt contribution was negligible at 

both sites. The ‘Other OC’, which represents contributions from secondary organic 

carbon, other unidentified primary sources, and the possible positive sampling artifacts 

of organic carbon, accounted for 20% to 23% of the PM2.5 mass. 

July 2003 - Dec. 2006 Average Source 

Contribution in Fresno-1st Street

Airborne 

soil

3%

Secondary 

nitrate

41%

Aged 

aerosol 

with sea 

salt2

5%

Motor 

vehicle

23%

Industrial

5%

Biomass 

smoke

8%

Aged 

aerosol 

with sea 

salt1

5%

Secondary 

Sulfate

10%

July 2003 - Dec. 2006 Average Source 

Contribution in Bakersfield-California Ave.

Secondary 

nitrate

45%

Airborne 

soil

9%

Industrial

1%

Aged 

aerosol 

with sea 

salt2

7%

Motor 

vehicle

13%

Aged 

aerosol 

with sea 

salt1

4%

Biomass 

smoke

7%

Secondary 

Sulfate

14%
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-23 

Figure H- 22. CMB Model Calculated 2004-2005 Average PM2.5 Source 

Contributions. 

While the specific contributions vary to some extent, taken together these sources 

apportionment studies highlight the importance of secondary ammonium nitrate 

contributions to both the 24-hour and annual average concentrations. In addition, 

biomass burning and mobile sources were found to be significant contributors to 

primary PM2.5. 

Diagnostic Analyses

 Indicator Species Approach 

As discussed in prior sections, trends in ammonium nitrate concentrations have tracked 

well with concurrent reductions in NOx, suggesting that NOx control is an effective 

approach for ensuring further reductions in ammonium nitrate. An indicator species 

approach provides an additional method to investigate which chemical precursor a 

secondary species such as ammonium nitrate is most responsive to control of. 

Ammonium nitrate is formed in the atmosphere through the reactions of precursor 

nitrogen oxides (NOx), reactive organic gases (ROG), and ammonia (NH3). The 

amount of each precursor in the atmosphere relative to each other determines how 

much ammonium nitrate is formed. The chemistry is complex, but essentially the 

precursor in shortest supply will limit how much ammonium nitrate is produced. 

Reducing emissions of this limiting precursor provides the best opportunity to cut 

ammonium nitrate levels. In simple terms, photochemical reactions of NOx and ROG 

form nitric acid (HNO3). Nitric acid then reacts with ammonia (NH3) to form ammonium 

BAC Modeled 2004-2006 Avg

Ammonium 

Nitrate

45%

Ammonium 

Sulfate

12%

Sea Salt

0%

Biomass 

Burning

9%

Other OC

20%

Airborne 

Soil

4%

Tire/Brake

1%

Motor 

Vehicle

9%

FSF Modeled 2004-2006 Avg

Ammonium 

Nitrate

39%

Ammonium 

Sulfate

10%

Sea Salt

0%

Biomass 

Burning

14%

Other OC

23%

Airborne 

Soil

4%

Motor 

Vehicle

9%

Tire/Brake

1%
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-24 

nitrate. Lurmann, et al.4

 compared ammonia and nitric acid ambient concentrations 

measured in the San Joaquin Valley during the winter of 2000/2001, as part of 

CRPAQS. Figures H-23 and H-24 show the concentrations of nitric acid and ammonia 

measured at the rural Angiola site and at the urban Fresno site. At both sites ammonia 

concentrations are generally at least an order of magnitude higher than the nitric acid 

concentrations. These ammonia-rich conditions throughout the Valley indicate that, 

during the winter, nitric acid is the limiting precursor. 

Figure H-23: Comparison of Ammonia and Nitric Acid Concentrations Measured 

at Angiola during the Winter of 2000/2001 as Part of CRPAQS 

 

4

 F. W. Lurmann, S. G. Brown, M. C. McCarthy, and P. T. Roberts: Processes Influencing Secondary Aerosol 

Formation in the San Joaquin Valley during Winter, Journal of Air and Waste Management Association, 56, 1679-

1693, 2006. 

Comparison of Ammonia and Nitric Acid Concentrations 

Angiola - Winter 2000/2001

-10

0

10

20

30

40

50

60

-2 0 2 4 6 8 10 12 14 16 18

HNO3 Concentration (ug-N/m3)

NH3 Concentration (ug-N/m3)

1:1 Line
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-25 

Figure H-24: Comparison of Ammonia and Nitric Acid Concentrations Measured 

at Fresno during the Winter of 2000/2001 as Part of CRPAQS 

Comparison of Ammonia and Nitric Acid Concentrations 

Fresno - Winter 2000/2001

-4

0

4

8

12

16

20

-2 0 2 4 6 8

HNO3 Concentration (ug-N/m3

)

NH3 Concentration (ug-N/m3)

1:1 Line

4. AIR QUALITY MODELING 

a. Rollback Modeling

In addition to the evaluation of air quality trends and the observational and diagnostic 

analyses, a rollback modeling analysis was conducted by the District to estimate the 

impacts of future emission reductions on resulting air quality. An extensive discussion 

of the rollback methodology and the results are provided in Chapter 3 and associated 

spreadsheets of the District Plan. The rollback modeling showed that Fresno and 

Corcoran would attain the annual PM2.5 standard with baseline emission reductions in 

2014. With the addition of the ARB and District proposed control strategy, both Visalia 

and Bakersfield-Planz would attain in 2014 as well. 

b. Grid-Based Modeling

As stipulated in the EPA Modeling Guidance, a grid-based photochemical model 

is necessary to perform the modeled attainment test for PM2.5 (EPA, 2007). Such 

models offer the best available representation of important atmospheric processes and 

are an essential tool in analyzing the impacts of proposed emissions controls on 

pollutant concentrations. The EPA recommends guidelines for choosing a model for 

use in the attainment test. For example, the model source code should be free or low 

cost, modeling elements should have undergone rigorous scientific peer-review, and it 

should have been shown to perform well in the past for similar applications. 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-26 

The Community Multiscale Air Quality Modeling System (CMAQ) has been 

selected for use in the PM2.5 modeled attainment demonstration for the San Joaquin 

Valley Air Pollution Control District. CMAQ is a state-of-the-science “one-atmosphere” 

system that treats major atmospheric and land processes (e.g., advection, diffusion, gas 

phase chemistry, gas-particle mass transfer, nucleation, coagulation, wet and dry 

deposition, aqueous phase chemistry, etc.) and a range of species (e.g., anthropogenic 

and biogenic, primary and secondary, gaseous and particulate) in a comprehensive 

framework (EPA, 1999; CMAS, 2007). 

CMAQ was run for the year 2000 to provide the basis for the model performance 

evaluation. It was during 2000 that the California Regional PM10/PM2.5 Air Quality Study 

(CRPAQS) took place. The study resulted in a wealth of data with which to evaluate 

model performance. As it is necessary to execute simulations for a model reference 

year and a future year to perform the recommended modeled attainment demonstration, 

2005 and 2014 were also simulated. Simulations for all years were driven by the 

meteorological inputs for 2000, while emissions varied from year to year. 

Regional air quality modeling only represents a portion of the attainment test. In 

order to perform the EPA-recommended Speciated Modeled Attainment Test, or SMAT, 

the relative response between the modeled reference and future years must be 

considered in conjunction with observations. This approach minimizes the uncertainties 

in predicting future year attainment that result from potential model bias in predicting 

absolute species concentrations. 

Federal Reference Method (FRM) PM2.5 mass measurements provide the basis 

for nonattainment designations. For this reason it is recommended that the FRM data 

also be used to project future air quality and progress towards attainment of the healthbased National Ambient Air Quality Standard (NAAQS) for PM2.5. However, given the 

complex physicochemical nature of PM2.5, it is necessary to consider individual species 

as well. While the FRM measurements give the mass of the bulk sample, a method for 

apportioning this bulk mass to individual PM2.5 components is a first step towards 

determining the best targets for emissions controls in order to reach NAAQS levels in a 

timely manner. Given that (1) attainment status is currently dependent upon FRM 

measurements and (2) concentrations of individual PM2.5 species need to be considered 

in order to understand the nature of and efficient ways to ameliorate the PM2.5 problem 

in a given region, a method has been developed to speciate bulk FRM PM2.5 mass with 

known FRM limitations in mind. This method is referred to as the measured Sulfate, 

Adjusted Nitrate, Derived Water, Inferred Carbonaceous material and estimated aerosol 

acidity (H+) approach or “SANDWICH”. SANDWICH is based on speciated 

measurements from other (often co-located) samplers, such as those from the 

Speciated Trends Network (STN), and the known sampling environment of the FRM. 

The approach serves to provide mass closure, reconciliation between speciated and 

bulk mass concentration measurements, and the basis for a connection between 

observations, modeled PM2.5 concentrations, and the air quality standard. 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-27 

The SMAT procedure was applied to FRM monitors operating in the San Joaquin 

Valley with minimal deviations from U.S. EPA’s recommended procedure. The 2005 

design value was used as a basis from which to project forward to estimated future year 

design values for the year 2014. Speciation data for four STN (speciation) sites was 

used to speciate the FRM mass for all FRM sites. For those sites not collocated with 

STN monitors, “surrogate” speciation sites were determined based on analysis of 

CRPAQS data to determine which sites had similar speciation profiles. The 

composition was assumed to be the same at all three Bakersfield sites (BAC, BGS, and 

BEP). Similarly, the percent composition at the two Fresno sites (FSF and FSH) was 

assumed to be the same. In addition, Stockton (SOH), Clovis (CLO), Corcoran (COP), 

and Modesto (MRM), were assumed to have the same speciation as one of the four 

speciation sites based on CRPAQS data analysis. 

Quarterly average species concentrations were calculated at each STN site 

using the SANDWICH procedure. Modeled concentrations for the reference year 

(2005) and future year (2014) for each component were extracted for the FRM sites as 

a nine-cell average. The relative response factors were calculated for each component 

for each quarter. These calculations were performed using all modeled days, as we 

assumed that the selected FRM measurements provided a stable quarterly average 

value. 

These quarterly species percentages were then multiplied against the base year 

design value for 2006 (the average FRM PM2.5 concentrations for 2004, 2005, and 

2006). The quarterly observed species concentrations were then multiplied by the 

RRFs and summed and averaged to get a future year PM2.5 design value at each FRM 

site. See Table H-3 for the predicted baseline and controlled 2014 PM2.5 design values. 

For the “controlled” 2014 emissions sensitivity scenario described above, future annual 

PM2.5 concentrations at all FRM sites are below the annual PM2.5 NAAQS of 15.0 μg/m3, 

and, therefore, the San Joaquin Valley has passed the speciated modeled attainment 

test for the annual PM2.5 NAAQS. 

A similar procedure to the attainment demonstration for the annual PM2.5

standard was followed for the 24-hour PM2.5 standard attainment demonstration. The 

exception was that only the top 25% of the measured and modeled days for each 

quarter were used instead of all available days. The top 25% of the days are expected 

to be more representative of the 24-hour design value than would all available days for 

a given quarter. 

Table H-4 shows the predicted 2014, 24-hour PM2.5 design values for the top five 

2006 design value sites for the controlled emissions case. As shown, all sites in the 

SJV attained the 24-hour standard in 2006, and further emissions controls do not cause 

any monitors to become non-attainment in 2014. 
San Joaquin Valley Unified Air Pollution Control District April 30, 2008

Appendix H: Weight of Evidence 

2008 PM2.5 Plan 

H-28 

Table H-3. Reference and future year annual design values for SJV FRM sites

Site Code Speciation 2006 

DV 

2014 

Baseline 

DV 

2014 

"Controlled" 

DV 

Bakersfield - 5558 California BAC BAC 18.51 15.40 13.84 

Bakersfield - 410 E Planz 

Road BEP BAC 18.86 15.83 14.30 

Bakersfield - Golden State BGS BAC 18.64 16.32 14.68 

Clovis - N Villa Avenue CLO FSF 16.39 14.83 13.40 

Corcoran - Patterson 

Avenue COP VCS 17.24 14.61 13.12 

Fresno - 1st Street FSF FSF 16.68 14.77 13.32 

Fresno - Hamilton and 

Winery FSH FSF 17.16 15.06 13.59 

Merced - 2334 M Street MRM M14 14.69 13.07 11.96 

Modesto - 14th Street M14 M14 14.10 12.40 11.33 

Stockton - Hazelton Street SOH M14 12.93 11.92 11.01 

Visalia - N. Church Street VCS VCS 18.20 15.88 14.29 

Table H-4. Reference and future year 24-hour design values for SJV FRM sites

Site Code Speciation 2006 

DV 

2014 

"Controlled" 

DV 

Bakersfield - 5558 California BAC BAC 62.4 42.9 

Bakersfield - 410 E Planz 

Road BEP BAC 65.2 41.9 

Bakersfield - Golden State BGS BAC 64.4 44.6 

Fresno - 1st Street FSF FSF 58.0 42.2 

Fresno - Hamilton and 

Winery FSH FSF 58.5 40.3