Particulate Matter (PM) 2.5 Significance Thresholds and Calculation Methodology

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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, 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) (119 KB, doc file)

  • Appendix A - Updated CEIDARS Table with PM2.5 Fractions (139 KB, doc file)

  • Appendix B - PM2.5 Localized Significance Threshold Look-Up Tables (414 KB, doc file)

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 (908 KB, doc file)

• Overhead Presentation (102 KB, ppt file)

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

• Meeting Minutes (914 KB, doc file)

PM 2.5 Public Workshop - August 9, 2006

• Overhead Presentation (519 KB, ppt file)

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

Agenda (907 KB, doc file)

• Overhead Presentation (106 KB, ppt file)

• Example - 2007 Annual Emission Inventory (from 2003 AQMP)
  (318 KB, pdf file)

• Handout #1 - Construction Scenarios (900 KB, doc file)

  Summary Results (883 KB, xls file)

• Handout #2 - Construction Mitigation Measures (925 KB, doc file)

• Meeting Minutes (915 KB, doc file)

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

Agenda (906 KB, doc file)

• Overhead Presentation (562 KB, ppt file)

• Draft Methodology to Calculate Particulate Matter (PM) 2.5 and PM 2.5 CEQA Significance Thresholds (May 2006) (94 KB, doc file)

  • California Emission Inventory Data and Reporting System (CEIDARS) PM Profile (superseded by Appendix A in the above final document)

• Meeting Minutes (916 KB, doc file)