California and the federal governments have established ambient air quality standards for fine particulate matter (PM) less than or equal to 2.5 microns in diameter (PM 2.5).  As a result, there was a need to establish a methodology for calculating PM 2.5 and appropriate PM 2.5 significance thresholds for the purpose of analyzing local and regional PM 2.5 air quality impacts in CEQA or NEPA air quality analyses.  A Working Group was established, which included representatives from various stakeholder groups (XLS, 19kb), to provide input in the development of PM 2.5 significance thresholds and calculation methodology. On October 6, 2006, the SCAQMD Governing Board unanimously adopted the following  methodology to calculate PM2.5 and PM2.5 significance thresholds.  As part of AQMD intergovernmental review (IGR) commenting responsibilities, AQMD staff began submitting comments relative to the PM2.5 proposal on CEQA documents beginning January 2007.

Final Documents

• Final Methodology to Calculate PM2.5 and PM2.5 Significance Thresholds (October 2006)       (PDF, 124KB) (Includes Appendix A- Updated CEIDARS Table with PM2.5 Fractions and   Appendix B- PM2.5 Localized Significance Threshold Look-Up Tables)

Past Meeting Information

Public Hearing for Governing Board to Consider Implementing Methodology to Calculate PM2.5 and PM2.5 Significance Thresholds - October 6, 2006

Governing Board Public Hearing Agenda Item #36

PM 2.5 Working Group Meeting #3 - August 22, 2006

Agenda (DOC, 908kb)

• Overhead Presentation (PPT, 102kb)

• Draft Methodology to Calculate Particulate Matter (PM) 2.5 and PM 2.5 CEQA Significance Thresholds (August 2006) (DOC, 116kb)

• Meeting Minutes (DOC, 914kb)

PM 2.5 Public Workshop - August 9, 2006

• Overhead Presentation (PPT, 519kb)

PM 2.5 Working Group Meeting #2 - July 11, 2006

Agenda (DOC, 907kb)

• Overhead Presentation (PPT, 106kb)

• Example - 2007 Annual Emission Inventory (from 2003 AQMP) (PDF, 318kb)

• Handout #1 - Construction Scenarios (DOC, 900kb) Summary Results (XLS, 883kb)

• Handout #2 - Construction Mitigation Measures (DOC, 925kb)

• Meeting Minutes (DOC, 915kb)

PM 2.5 Working Group Meeting #1 - June 8, 2006

Agenda (DOC, 906kb)

• Overhead Presentation (PPT, 562kb)

• Draft Methodology to Calculate Particulate Matter (PM) 2.5 and PM 2.5 CEQA Significance Thresholds (May 2006) (DOC, 94kb)

• California Emission Inventory Data and Reporting System (CEIDARS) PM Profile (superseded by Appendix A in the above final document)

• Meeting Minutes (DOC, 916kb)