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Last Updated: Friday, January 19, 2018 10:24 AM

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 in Federal nonattainment or maintenance areas for PM10 or PM2.5 that are not either "Table 2" exempt projects (40 CFR 93.126) or Signal Synchronization Projects (40 CFR 93.128). 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 framework for PM analysis in general at the project level.

The Federal Highway Administration (FHWA) and the EPA provide guidance for PM10 and PM2.5 hot spot analysis. The guidance is available from the EPA Conformity Web Site Exit Caltrans website.

Previous PM10 analysis guidance documents, including the 2000 Caltrans Interim Guidance, the 2001 FHWA Qualitative PM10 Hot Spot Analysis Guidance, the 2005 Caltrans/UCD/FHWA guidance, and the 2006 EPA guidance, are superseded by the EPA quantitative analysis guidance announced in the Federal Register on December 20, 2010 and upated in November 2013. NON-EPA GUIDANCE SHALL NOT BE USED for conformity-related project-level hot spot analysis for NEPA action after March 29, 2009.

Project-level PM hot spot conformity analysis that requires detailed analysis, and that starts after December 22, 2010, should consider using the latest EPA guidance. EPA's guidance Exit Caltrans website allowed a grace period of up to 2 years to complete the NEPA process and a project-level conformity determination that has already started using the 2006 guidance. With concurrence by Interagency Consultation, the 2006 EPA guidance may continue to be used for projects starting between December 2010 and December 2012.

All projects requiring detailed analysis - Projects of Localized Air Quality Concern (POAQC) - that start studies after December 22, 2012 must use the Quantitative Analysis Guidance procedures in place at the time studies start.

Quantitative hot spot analysis (using dispersion modeling to determine concentrations at receptor locations) is now required because EPA has specified the models and procedures to be used for conformity purposes. The guidance specifies use of the CAL3QHCR Exit Caltrans website line-source model for simple highway and intersection projects, and the AERMOD Exit Caltrans website dispersion model for complex highway projects and projects involving non-highway (i.e. transit, freight movement) emission sources.

Project-level hot spot analysis has been required for project-level conformity determinations in PM2.5 nonattainment areas since April 5, 2006. The qualitative analysis procedures in the EPA Guidance of March 29, 2006 also applied to PM10 hot spot studies that started after that date. The December 2010/November 2013 quantitative analysis guidance replaces the March 2006 guidance for both PM2.5 and PM10 studies.

If a project in a PM10 area is considered a Project of Concern, the detailed hot spot analysis must include both direct (exhaust, tire wear, and brake wear, usually developed using EMFAC) and re-entrained road dust (developed using EPA's AP-42 method Exit Caltrans website unless a local method is specified in an approved PM10 SIP) emissions. Project analysis for PM2.5 need not include reentrained dust unless an approved SIP says that it's needed; as of January 2014, only the South Coast PM2.5 SIP includes such a finding.

If a project is Not a Project of Concern ('Not a POAQC' in typical jargon) a detailed analysis is not required. Criteria for determining whether a project is a Project of Concern were specified in the 2006 EPA guidance and did not change in the 2010 guidance. Generally, a project is not a Project of Concern unless it changes capacity or alignment of a road with more than 125,000 AADT and 8% trucks, more than 10,000 truck AADT (8% of 125,000), or otherwise may substantially increase or concentrate diesel exhaust emissions (such as bus terminals and transfer points, designated truck routes, and freight intermodal terminals). These criteria are only guidelines, not "bright line" thresholds; projects with localized land use or other issue might be "of concern" at lower traffic or truck volumes, and projects that don't substantially affect mainline traffic might NOT be "of concern" even when they are associated with a freeway that has much higher volumes.

Interagency Consultation concurrence is required for 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 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. Many MPOs use the SCAG project review form Exit Caltrans website to support consultation about whether a project is a POAQC.



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