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Air Dispersion Modeling

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Air quality dispersion modeling is a computer simulation that predicts air quality concentrations from various types of emission sources. For pollutants emitted through a stack, it considers the emission rate, stack height, stack diameter, and stack gas temperature and velocity, as well as the effect of nearby buildings and terrain. Other emission sources like vehicle traffic or wind erosion from storage piles are represented as 2-dimensional area sources or 3-dimensional volume sources.

Air quality dispersion models use meteorological data such as temperature, wind direction, and wind speed to calculate concentrations. Five years of National Weather Service meteorological data is typically used for air quality modeling required by the US Environmental Protection Agency (EPA), Federal Land Managers (FLMs), and Minnesota Pollution Control Agency (MPCA). In some cases one year of onsite meteorological data is used.

Model results are often compared to benchmark levels such as ambient standards to determine if they meet state and federal requirements. Sometimes results are used to help site ambient monitors or they may be input into health risk assessments or ecological risk assessments.

What's New?

Agenda for Informational Session on Draft MPCA Air Dispersion Modeling Guidance is Available! (December 4, 2012)

A detailed agenda for the informational session on the draft Modeling Guidance is now available.

The focus of this information session will be on the “how” of modeling, which relate to sections 3, 4, & 5 of the Draft Guidance. There will be presentations by MPCA staff on the overall guidance, background of technical changes, and demonstrations. There will be a facilitated activity for attendees, followed by discussion.

For a copy of the detailed agenda, please send a request to the MPCA Air Quality Modeling Unit email at airmodeling.pca@state.mn.us.

Draft MPCA Air Dispersion Modeling Guidance and Informational Session (November 9, 2012)

An informational session on the draft guidance will be held on Tuesday December 11, 2012, at the MPCA’s St. Paul office in Meeting Room #6-2 from 1:00pm – 4:00pm CST.  Those wishing to attend the information session should RSVP by Friday December 7, 2012 via the MPCA air quality modeling unit email address at airmodeling.pca@state.mn.us.

A detailed agenda for the informational session will be made available around Tuesday December 4, 2012.

PDF Document Draft MPCA Air Dispersion Modeling Guidance (aq2-58) . NEW! Draft version of the MPCA Guidance for Title V and PSD Air Dispersion Modeling Guidance is available for review and comment. Please note the draft version of this document will be removed from the website for final review on December 14, 2012. Comments may be sent to the MPCA air quality modeling unit email address at airmodeling.pca@state.mn.us.

Update to “Data for AERMOD Applications” subpage (March 6, 2012)

The “Data for AERMOD Applications” subpage has been revised and is now the “Meteorological Data” subpage.  As part of this revision, files processed with AERMET versions 04300 and 06341, as well as Digital Elevation Model (DEM) data for AERMAP, have been removed and are no longer available through our modeling Web pages. 

 Meteorological data processed with AERMET version 11059, as well as AERMINUTE version 11059 and AERSURFACE version 08009, are now available on this updated subpage.  The data sets are for the 5-year period of 2006 – 2010.  For more information and to access the data, please go to the “Meteorological Data” subpage.

Removal of ISC-Type Meteorological Data (November 17, 2011)

The "Air Dispersion Modeling Data: Meteorological Data for ISC-Type Models" page and subsequent PCRAMMET version 99169 processed meteorological data are no longer available through our modeling Web pages. Contact the appropriate MPCA modeling staff member for special-request meteorological data.

New Requirement: Air Dispersion Modeling Protocol Forms (September 27, 2011)

Permit applicants required to conduct air dispersion modeling should complete and submit the Air Quality Dispersion Modeling Protocol form (AQDMP-01 and the Air Quality Dispersion Modeling Protocol Spreadsheet (AQDMPS-01) along with accompanying files to the MPCA.  Applicants should receive MPCA approval of the AQDMP-01 and AQDMPS-01 prior to submitting the Air Quality Dispersion Modeling Report (AQDMR-01) with the permit application.

Applicants should submit two paper copies of the completed Air Quality Dispersion Modeling Protocol form (AQDMP-01), the Air Quality Dispersion Modeling Protocol Spreadsheet (AQDMPS-01), and the accompanying files to:

  • MPCA, Air Quality Permit Document Coordinator, IND/AQPD
    520 Lafayette Road
    St. Paul, MN 55155-4194. 

Applicants may submit an electronic version in addition to the two paper copies.

The AQDMP-01 is a standardized modeling protocol form that combines simple checkboxes, dropdown lists, and text to document a facility’s air dispersion modeling methodologies. All sections of the AQDMP-01 and the AQDMPS-01 must be filled out and reviewed by the MPCA before an applicant receives approval.

Protocol Forms:

Air Dispersion Modeling Report Forms

Permit applicants that have received approval of the AQDMP-01 and AQDMPS-01 should complete an Air Quality Dispersion Modeling Report (AQDMR-01) and submit this with the permit application.

MPCA Internal Review Forms

The following forms are used by MPCA air dispersion modeling staff to review submittals. These are for MPCA internal use only.

Modeling Policy Documents

Standardized Air Modeling (SAM) spreadsheets for regulatory air modeling (>April 7, 2009):

These spreadsheets are works-in-progress. Their use is optional but recommended. We expect they will change/improve over time and we appreciate your patience as we move forward. The 5-digit version numbers resemble EPA model version numbers (i.e. 2-digit year id and 3-digit Julian date) so that “09097” is April 7, 2009, “09098” is April 8, 2009, “09099” is April 9, 2009, etc. Please direct any questions to Dennis Becker at 651-757-2217 or dennis.becker@state.mn.us.

Standardized Air Modeling (SAM) Goals:

  • Better communicate air dispersion modeling information to all persons
  • Better communicate agency expectations to air permit applicants and consultants
  • Standardize and streamline our review of air dispersion modeling submittals
    • Protocols, results, revisions, modeling-related permit conditions, etc.
  • Identify/fix the most common mistakes (e.g. math errors, missing sources, etc.)
  • Identify/fix the most time consuming modeling steps (e.g. fugitive emissions)
  • Use less paper

Modeled Background (April 7, 2009)

In Nov. 2008, MPCA gave a presentation to the Upper Midwest Section – Air & Waste Management Association on modeled background instead of monitored background for PM2.5 NAAQS modeling - sources & background paired in space & time (paired sums) is just a conceptual idea and is not for regulatory purposes at this time. Please direct any questions to Dennis Becker at 651-757-2217 or dennis.becker@state.mn.us.

Modeling Guidance

Listed below are links to EPA modeling guidance for federal purposes and MPCA modeling guidance for state Title V modeling.

Air Disperson Modeling Training from the 2006 Air, Water and Waste Environmental Conference

PSD Minor Source Baseline Dates

Federal Prevention of Significant Deterioration (PSD) rules prescribe modeling requirements for facilities whose emissions and/or ambient impacts of certain pollutants exceed regulatory thresholds. One part of these rules regulates the level of deterioration in air quality allowed for a specified area. Deterioration of air quality is measured against specific "baseline dates" and is tracked at a county level in Minnesota. The amount of additional air pollution allowed after the baseline dates is called the "increment." The "Major Source Baseline Date" is the date after which increases in air pollution from major sources (as defined in PSD rules) "consume" increment. These dates are January 6, 1975 for PM10 and SO2, and February 8, 1988 for NOx. The Major Source Baseline Dates are the same for every county in Minnesota. The "Minor Source Baseline Date" is the date after which increases in air pollution from all sources consume increment. The Minor Source Baseline Dates are pollutant and county specific. Minor Source Baseline dates for Minnesota counties are shown in the files below.

Who to Contact

  • MPCA
    Phone: 651-296-6300 or 800-657-3864
    • MPCA Title V Modeling Policy (call to obtain a copy)
  • Dennis Becker
    Phone: 651-757-2217
    email: dennis.becker@state.mn.us
    • MPCA Standardized Mobile Source (SAMS) spreadsheet
    • PSD modeling and Title V modeling
    • Status of Minnesota Environmental Review Cumulative Effects-Air Modeling
  • Margaret McCourtney
    Phone: 651-757-2558
    email: margaret.mccourtney@state.mn.us
    • Photochemical modeling
    • Title V information submittals (electronic information requests)
    • Modeling for PM-2.5, Ozone, Regional Haze and Toxics
  • Greg Pratt
    Phone: 651-757-2655
    email: gregory.pratt@state.mn.us
    • Toxic air pollutants modeling
    • Deposition modeling
  • Ruth Roberson
    Phone: 651-757-2672
    email: ruth.roberson@state.mn.us
    • Status of Minnesota Environmental Review Cumulative Effects-Air Modeling
    • Toxic air pollutants modeling
    • PSD modeling and Title V modeling
    • GIS-based modeling tools
    • State Implementation Plan modeling
  • Melissa Sheffer
    Phone: 651-757-2718
    email: melissa.sheffer@state.mn.us
    • Pre-processed meterological data (AERMOD)
    • PSD modeling and Title V modeling
    • PSD increment files and nearby sources for PSD modeling
    • PSD minor source baseline dates by county (NOX, SO2, and PM10)
  • Jim Sullivan
    Phone: 651-757-2769
    email: jim.sullivan@state.mn.us
    • MPCA Title V and PSD modeling policy
    • MPCA Title V and PSD modeling guidance
    • PSD modeling and Title V modeling

Please contact any of the above persons if you have general modeling questions.

Additional Resources

Last modified on January 03, 2013 13:22
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