Air dispersion modeling may be required for some projects in order to demonstrate compliance with applicable requirements. These projects include those subject to “
New Source Review of Toxic Air Contaminants” (BAAQMD Regulation 2-5), the
California Air Toxics “Hot Spots” Program (AB2588), and Prevention of Significant Deterioration “PSD” BAAQMD Regulation 2-2-304, 40 CFR 51.116). The intent of the modeling analysis is to demonstrate that emissions from a given facility or project do not or will not adversely impact the maintenance of air quality standards in the BAAQMD; be it acceptable levels of toxic air contaminants (TAC), the California or National Ambient Air Quality Standards (AAQS), or applicable PSD increments.
For permit applications involving air toxics, modeling may be required as part of a health risk screening analysis (HRSA). In most cases this modeling is performed by the BAAQMD with input from the applicant. For projects where the applicant is responsible for modeling, in particular for a PSD analysis, the BAAQMD Permit Modeling Guidance document should be followed. This document has been prepared by the Engineering Division of the BAAQMD to give the permit applicant specific assumptions, requirements, conventions, and procedures for the preparation of a modeling analysis. Because this guidance cannot cover every aspect of the analysis needed for a proposed source without becoming unwieldy the applicant should submit a modeling plan (protocol) for BAAQMD comment before beginning the analysis.