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Last Updated: Monday, May 5, 2008 2:53 PM

Particulate Matter Hot Spot Analysis

Hot spot analysis for particulate matter (PM) is required under the US Environmental Protection Agency (EPA) Transportation Conformity regulations for projects that are not either "Table 2" exempt projects (40 CFR 93.126 ) or Signal Synchronization Projects (40 CFR 93.128 ) in Federal nonattainment or maintenance areas for PM10 or PM2.5. In all areas, as with carbon monoxide (CO), hot spot evaluation of projects is needed for environmental review (NEPA and CEQA) purposes. The hot spot analysis process for conformity provides a good framework for PM analysis in general at the project level.

The Federal Highway Administration (FHWA) and the EPA provide guidance for qualitative PM10 and PM2.5 hot spot analysis. The current guidance document was released on March 29, 2006. The guidance is available from the FHWA Conformity Web Site and the EPA Conformity Web Site.

Previous PM10 qualitative analysis guidance documents, including the 2000 Caltrans Interim Guidance, the 2001 FHWA Qualitative PM10 Hot Spot Analysis Guidance, and the 2005 Caltrans/UCD/FHWA guidance, are superseded by the March 29 guidance, and shall not be used for project-level hot spot studies started after March 29, 2006 where projects are subject to conformity analysis requirements.

Quantitative hot spot analysis (using dispersion modeling to determine concentrations at receptor locations) is not required, under the conformity rule, until EPA specifies the models and procedures to be used for conformity purposes. EPA has not yet specified those models and procedures. Therefore, for projects of concern as described in the conformity rule, only a "qualitative" hot spot analysis is required for PM, which differs from the approach generally used for carbon monoxide.

Qualitative project-level hot spot analysis has been required for project-level conformity determinations in PM2.5 nonattainment areas since April 5, 2006. The new analysis procedures in the EPA Guidance of March 29, 2006 also apply to PM10 hot spot studies that started after that date. If a project in a PM10 area is considered a Project of Concern, the hot spot analysis must have both a qualitative exhaust emission analysis and re-entrained road dust emission analysis.

EPA's Final Rule of March 10, 2006 and Guidance of March 29, 2006 describe requirements for project-level conformity and what types of projects are of concern. Further guidance can be found in the Frequently Asked Questions document released in May 2006 at the FHWA web site.

Interagency Consultation concurrence is required in determinations that a non-exempt project is not a "Project of Air Quality Concern" (POAQC) under the March 10, 2006 conformity rule revision, and in various aspects of qualitative PM10 and PM2.5 hot spot analyses. The Metropolitan Planning Organization's ( MPO's) Interagency Consultation group should be contacted regarding scheduling and information requirements. See Nonattainment Areas Table for MPO web site links.

Guidance and References

• EPA March 10 Final Rule
• EPA Guidance (PDF file)
• FHWA Q&A Document
• California Air Resource Board Re-Entrained Road Dust Methodologies (PDF files)
  • Basic methodology (1997) - includes county-specific silt loadings
    
  • For San Joaquin Valley (2003)
  • For Bay Area (non-SIP, 2001)
• Map of Federal PM10 and PM2.5 Nonattainment and Maintenance Areas in California
  • Display version (GIF format)
  • Print version (PDF format)

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