Attachment B

Attainment of Annual PM2.5 Standard by 2020 at Madera City Monitoring Site

Monitoring for PM2.5 began in Madera with deployment of a Federal Equivalence 

Method Beta Attenuation Monitor (FEM BAM) in July, 2010. The monitor was installed

at the Madera City monitoring site with operation and maintenance under the control of 

the San Joaquin Valley Air Pollution Control District. Established north-south PM2.5 

concentration gradients within the San Joaquin Valley indicate that average PM2.5 

concentrations in Madera are expected to be similar or slightly higher than 

measurements in Merced, but lower than those measured in Fresno. However, 

comparison of 2011 PM2.5 concentrations measured at Madera and Fresno revealed 

that on an annual basis, Madera concentrations were 30 percent higher compared to

measurements in Fresno.

The weight of evidence analysis for the 2015 PM2.5 Plan includes a comprehensive 

assessment of the representativeness of measurements made with the FEM BAM at the 

Madera monitoring site during 2011 (see Appendix A2 of the 2015 PM2.5 Plan). Per 

this assessment, the 2011 Madera FEM BAM data used in the attainment 

demonstration appear to be biased high. These anomalous PM2.5 results were likely

due to initial calibration issues associated with operation of the FEM BAM and are 

therefore not considered representative of air quality in the surrounding region. 

The 2011 data were nevertheless included in the 2015 PM2.5 Plan attainment 

demonstration, and the site showed attainment by 2020 with a design value of 

15.0 ug/m3. However, ARB staff recently identified a technical error in the annual 

average and 24-hour PM2.5 design value calculations. Correction of this error resulted 

in a small increase in 24-hour and annual average design values at most sites. All sites 

continue to have design values below the annual PM2.5 standard in 2020 with the 

exception of the Madera site with a corrected PM2.5 design value in 2020 of 

16.2 μg/m3

. ARB staff therefore conducted additional analysis that indicates 

development of a more representative design value supports a finding that Madera 

would demonstrate attainment by 2020.

PM2.5 Air Quality at Madera and Merced Monitoring Sites

Table 1 on the next page shows the PM2.5 annual averages and design values for the 

Madera monitor for 2011 through 2014. Despite continued drought-related conditions, 

recent data indicates that the annual average concentrations at Madera are improving. 

In 2014, the annual average decreased by 4.1 μg/m3, resulting in a 2.3 μg/m3 decrease 

in the 2014 design value. Thus the most recent measured design value is already 

below what is predicted in the corrected attainment analysis for 2020.

Table 1. PM2.5 Annual Average and Design Values at Madera

Annual Average (μg/m3) Annual DV (μg/m3)

2011 2012 2013 2014 2013 2014

20.4 16 17.6 13.5 18.1 15.8

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ARB staff also compared recent data from the Madera monitor to measurements 

collected in Merced, about 30 miles to the north. Given the regional nature of PM2.5 

concentrations in the Valley, the PM2.5 FEM BAM monitors at Madera and MercedCoffee Road are expected to record similar values. They are located relatively close to 

one another in cities with similar year-round populations and surrounding emission 

sources. Review of the data from PM2.5 monitoring conducted at the Madera and 

Merced-Coffee Road sites from July 1, 2014, through June 30, 2015, indicate that 

PM2.5 concentrations at both sites track each other closely, with the Madera site 

recording values about three percent higher than the Merced-Coffee site on average 

(Figure 1 & 2). This is consistent with the established concentration gradient in the 

Valley. 

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7/1/14 8/1/14 9/1/14 10/1/14 11/1/1412/1/14 1/1/15 2/1/15 3/1/15 4/1/15 5/1/15 6/1/15

PM2.5 Concentration (

μg/m3)

Figure 1. Comparison of PM2.5 Concentrations 

at Madera and Merced-Coffee Street Sites 

Madera-28261 Avenue 14 Merced-S. Coffee Street

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Based on data from July 1, 2014 through June 30, 2015

Attainment Demonstration Using Alternative Base Year Scenarios

Based on the information discussed above, the annual average attainment 

demonstration for 2020 at the Madera site was run using two alternative scenarios to 

develop a more representative base year design value. Each indicates attainment at 

the Madera site by 2020. 

Scenario 1:

The Madera City 2014 design value of 15.8 μg/m3 - estimated using 2012 through 2014 

BAM data was used as a replacement for the 2013 base year design value. The 

attainment demonstration analysis then results in a 2020 PM2.5 design value of 

14.1 μg/m3. 

Scenario 2:

The 2013 base year design value was estimated using 2011 through 2013 FEM BAM 

monitoring data, where 2011 Merced-Coffee Road data replaced the 2011 Madera data. 

Because the Madera PM2.5 monitoring values are slightly higher on average than 

Merced, the 2011 Merced data were adjusted upward to compensate for the observed 

difference between the two sites. Quarterly average values for 2011 for Merced-Coffee 

were therefore multiplied by 1.03 to obtain 2011 substitute quarterly average values for 

Madera. This substitution resulted in a 2013 design value at Madera of 16.7 μg/m3

. 

The attainment demonstration analysis then results in a 2020 design value of 

14.9 μg/m3.

The results of the two scenarios are summarized in Table 2. 

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PM2.5 Concentrations (ug/m3)

Figure 2. Comparison of Monthly Average PM2.5 Concentrations1

at Madera and Merced-Coffee Street Sites 

Madera-28261 Avenue 14 Merced-S. Coffee Street

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Table 2. Alternative Attainment Demonstration Scenarios for Madera

Scenario Base Year Annual DV 

(μg/m3)

2020 Annual DV

(μg/m3)

Madera (using 2014 data) 15.8 14.1

Madera (using 2012, 2013, and 

2011 Merced-Coffee data) 16.7 14.9

Conclusion

As documented in the 2015 PM2.5 Plan weight of evidence analysis, ARB staff 

concluded that 2011 Madera data collected with a continuous federal equivalent method 

(FEM) monitor were not representative of PM2.5 air quality in the region due to 

calibration issues. Inclusion of 2011 data in the attainment demonstration analysis for 

Madera resulted in a design value that was substantially higher than other locations in 

the Valley. Procedures for operation and maintenance of the Madera monitor have 

since been improved, and PM2.5 measurements from the FEM are now consistent with 

a new filter-based federal reference method monitor installed at the site in mid-2014, as 

well as with similar sites in the central portion of the Valley. 

The analysis presented above to develop a more representative base year design value 

for use in the attainment demonstration along with 2015 PM2.5 Plan weight of evidence 

supports the conclusion that the Madera monitoring site will reach attainment of the 

annual PM2.5 standard of 15 μg/m3 by 2020.

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