Air Dispersion Modeling and Health Risk Assessment Report Requirements

All criteria pollutant analyses and Health Risk Assessments (HRAs) in support of permit applications require the submittal of an air quality dispersion modeling report that details the assumptions, technical justifications, results, source parameters, and other relevant data used in the modeling analysis.

This includes a discussion of:

• Project description

• Description of the source(s) under review, including operating schedules and existing permit conditions

• Purpose of modeling analysis including applicable South Coast AQMD rules

• Models used and version numbers (ex., AERMOD Version 18081, HARP2 Version 19121, etc.), not the software GUI name and version, i.e. Lakes, Breeze, BEEST, etc.

• Model options utilized

• Averaging times utilized

• Sources modeled and how the sources were characterized in the model

  • Tables containing the source parameters should be included

• Emission rates

• Modeling domain extent

• Receptor grid type and spacing

• Location of nearby sensitive and off-site worker receptors

• Nearby terrain and elevation considerations, such as elevation data sets and the resolution used, coordinate system, datum, complex terrain, etc.

• A description of how the representative meteorological station was selected

• Selection of background concentrations and nearby sources, if applicable

• Contact information (name, email, and phone number) for the applicant and/or modeling contact

• Any other applicable information to the modeling analysis and HRA

South Coast AQMD staff’s responsibility is to review the applicant’s submitted modeling analyses and reports, and contact the applicant if there are any deficiencies in the submittal. If any deficiencies are found by South Coast AQMD staff, it is the responsibility of the applicant to make corrections to the analysis and/or report, and resubmit the revisions to South Coast AQMD for staff final approval.  Please be aware that any deficiencies found will result in delays to the final modeling approval.

Required Electronic Modeling Files

Modeling reports need to include all electronic modeling files generated as part of the analysis, including (in the native format, not Word or PDF documents):

• AERMOD input and output files

• Plot files (*.plt) separated by individual averaging time and source groups

  • Should not be concatenated into one file (such as *.grf files)

• BPIPPRM input and output files

• AERMAP input and output files

• USGS elevation input file (*.tif or *.dem)

• Meteorological files (*.sfc and *.pfl)

• Emission calculation spreadsheets

  • Excel spreadsheets with formulas that include emission rate assumptions

  • For HRAs, please include the annual average emission rate in pounds/year and the maximum 1-hour emission rate in pounds/hour

• All HARP2 generated input and output files and subfolders

• And other files as needed

  • background concetrations

  • hourly ozone files

  • hourly emission files

  • nearby source information

  • spreadsheets with risk calculations if not using HARP2

  • README files for projects with multiple modeling scenarios

Printouts of electronic modeling files within reports are highly discouraged, as the same information is contained in the electronic modeling files that are required for submittal.  Electronic files can be submitted via CD or USB thumb drive with the modeling report.  Due to South Coast AQMD’s internal firewall, transfers of data via FTP sites are not recommended.

Modeling Protocols

All modeling projects that are subject to the Prevention of Significant Deterioration (PSD) program (South Coast AQMD Reg. XVII) are highly encouraged to submit a modeling protocol for South Coast AQMD staff’s review and approval prior to conducting modeling or submitting an air quality modeling report.  In addition, modeling projects that deviate from South Coast AQMD’s modeling recommendations listed above are highly encouraged to submit a modeling protocol for review prior to submitting an air quality modeling analysis.  While a protocol review might add more time to the front end of a project, this will help ensure that the alternative modeling methodology is approved prior to the actual modeling being conducted.  If the modeling does not follow South Coast AQMD’s recommendations below and a protocol is not submitted, this could lead to additional review time by South Coast AQMD staff, as well as re-modeling if South Coast AQMD staff does not agree with the technical justification for the use of the non-recommended options.