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Last Updated: Tuesday, September 10, 2013 3:35 PM
Emission factors that represent the vehicle fleet, speeds, and environmental conditions associated with a project are needed to perform project-level air quality modeling.The EMFAC model issued by the California Air Resources Board is used for this process in California. For more details regarding project-level "hot spot"modeling, please refer to the CO Protocol, Appendix B and the U.S. EPA's latest guidance for particulate matter hot spot analysis.
EMFAC 2011 was released by ARB on September 30, 2011. It was made available for conformity use by U.S. EPA on March 6, 2013 (Federal Register notice (PDF) ). All new air quality analysis must use the new version, except that for conformity purposes a transition period of 6 months, until September 6, 2013, is allowed for starting new studies.
Do not use EMFAC 2007 for new studies. Conformity studies begun with EMFAC 2007 may be completed with it as long as, in general, studies are completed within 3 years of starting work. For project-level conformity purposes, EPA will generally accept a project-level conformity determination if the Final NEPA document is completed and the project approved within 3 years of circulating the Draft NEPA document based on the older model version.
EMFAC software should be obtained from the ARB web http://www.arb.ca.gov/msei/msei.htm .
The EMFAC model and all supporting data are provided and supported by the California Air Resources Board .
Caltrans and UC Davis interpreted the EMFAC 2007 model to provide a simplified user interface for project-level emission analysis, including emission factors and emission burden of criteria pollutants typically analyzed and Mobile Source Air Toxics (based on ARB's speciation factors for Total Organic Gases - TOG). For more information and to download the software package, see the CT-EMFAC page.
CT-EMFAC 4.1 is based on EMFAC 2007, and should not be used for NEW environmental studies started after October 1, 2011. However, it may still be used for conformity-related studies started before September 6, 2013, with interagency consultation concurrence in the case of particulate matter studies. The web-interface and (new in January 2013) EMFAC 2011-PL versions of EMFAC 2011 can be used for project-level analysis pending availability of CT-EMFAC 5 for conformity use. CT-EMFAC 5 (based on EMFAC 2011) may, however, be used for environmental studies other than the conformity process.