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Air Quality Modeling: Permitting & CEQA

Quick Links

The District no longer accepts analyses performed using the Industrial Source Complex –
Short-Term (ISCST3) model.

All meteorological data have been processed with AERMET, Version 06341.

Meteorological Data (Only for use in the AERMOD model)

All meteorological data sets are draft at this time but should be used for any modeling of sources in the San Joaquin Valley. Please download the latest data sets before modeling. Use the most recent five years of meteorological data. Model all five years. Use all the data available for a site if less than five years of data are available. For a cancer or a chronic non-cancer risk assessment, the average cancer risk of all years modeled should be used. If concatenated data sets are used for an analysis of compliance with ambient air quality standards, the 5-year average concentration obtained by running a concatenated data set shall be multiplied by a factor of 1.5 except for Bakersfield, Hanford, and Modesto. For those three data sets, a factor of 1.75 shall be used. If a violation of an annual average standard is predicted using this approach, the project can be remodeled using each year's data set. Then, the maximum annual average concentration predicted will be compared to annual average standard.

Meteorological data are available from two sources: 1) the National Climatological Data Center (NCDC) and 2) the MM5 Numerical Model. NCDC data were collected at major airports in the Valley. These data can be used for health risk assessments and ambient air quality analyses. The data derived from the MM5 numerical model are for sites where there are no airports. These sites are in the western part of the Valley. MM5- derived data can be used for health risk assessments. They cannot be used for ambient air quality analyses.

National Climatological Data Center


Meteorological Data Derived from MM5 Numerical Modeling

Los Banos
Missouri Triangle

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Ozone Data (Only for use in the AERMOD model)**

To use file click on link and pick Save As to save to your PC


For information about each of these sites please refer to ARB's Quality Assurance Air Monitoring Site Information.

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Nitrogen Dioxide Data (Only for use in performing a Tier IV or paired sums analysis)**

To use file click on link and pick Save As to save to your PC


To download the District’s guidance on developing “EPA’s NO2 Modeling Background Datasets”. Click here.

For information about each of these sites please refer to ARB's Quality Assurance Air Monitoring Site Information.

Contact the District before performing a Tier IV or paired sums analysis!

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Monitoring Background Values

1-Hour NO2

The District has processed the NO2 monitoring data for all sites located within the San Joaquin Valley using the guidance provided in Appendix S of Part 50. A detailed description of the District’s procedure and a summary of the data used can be downloaded here.

County Site Name 3yr Ave. of the 98th percentile of the annual distribution of the daily 1 hour max ppb / ug/m3
Fresno Fresno-Drummond Street 61.00 / 115.10
Fresno Fresno-1st Street 56.67 / 106.92
Fresno Fresno-Sierra Skypark #2 45.67 / 85.31
Fresno Parlier 39.33 / 74.21
Fresno Clovis-N Villa Avenue 58.67 / 110.70
Kern Edison 40.00 / 75.47
Kern Bakersfield-Golden State Highway 60.00 / 113.21
Kern Bakersfield-5558 California Avenue 61.00 / 115.10
Kern Arvin-Bear Mountain Blvd 31.67 / 59.76
Kern Shafter-Walker Street 53.33 / 100.62
Kings Hanford-S Irwin Street 53.00 / 100.00
Madera Madera-Pump Yard 40.33 / 76.10
Merced Merced-S Coffee Avenue 43.33 / 81.76
San Joaquin Stockton-Hazelton Street 57.67 / 108.81
San Joaquin Tracy-Airport 38.67 / 72.96
Stanislaus Turlock-S Minaret Street 48.67 / 91.83
Tulare Visalia-N Church Street 61.33 / 115.72

1-Hour SO2

The District has processed the SO2 monitoring data for all sites located within the San Joaquin Valley using the guidance provided in Appendix T of Part 50.

County Site Name 3yr Ave. of the 99th percentile of the annual distribution of the daily 1 hour max ppb / ug/m3
Fresno Fresno-1st Street 7.33 / 19.20

Other Background Values

All other background values can be downloaded from EPA at http://www.epa.gov/airdata/ad_rep_mon.html.


Date County/City Monitor Comment
8-19-10 Fresno/Fresno 1st Street It was recently noted that CARB incorrectly reported SO2 monitoring data to EPA. In previous submittals the data was submitted as parts per 100 million instead of parts per billion. Data on CARB’s website has been updated and corrections have been submitted to EPA. At the current time data at EPA, using the link under “Other Background Values”, has not yet been updated.
---- Fresno/Fresno 1st Street

On 4 and 5 July 2007, there was an unusual event in Fresno. Because of very stagnant meteorological conditions with high ambient temperatures, this site was unduly affected by emissions from fireworks. The District has filed a report under EPA’s Natural Events Policy to exclude ozone and particulate matter data collected on those dates from use in determining attainment of the federal standards. Therefore the following sulfur dioxide concentrations should be used for background:

1-hr max: 0.13 ppm
3-hr max: 0.075 ppm
24-hr max 0.031 ppm
Annual Average: 0.007 ppm

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Modeling Guidance

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Modeling Resources

AERMOD Modeling System Hot Spots Analysis and Reporting Program (HARP)
EPA Modeling Guidance Health Risk Assessment (HRA) Guidance
CALINE4 CO Protocol
PM10 Protocol  

All health risk assessments must comply with the Office of Environmental Health Hazard Assessment’s (OEHHA’s) guidelines. Any methodology that does not use HARP must be reviewed by ARB and/or OEHHA prior to submission to the District to ensure that OEHHA’s guidelines are fully implemented.

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