Air Quality Modeling Guidance for Permits

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Current air quality permit modeling guidance for estimating impacts from stationary sources of air pollution.

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    General Permitting Questions

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    Colorado Modeling Guidance for Air Quality Permits

    • Colorado Modeling Guideline for Air Quality Permits (May 2022)
    • Meteorological Determinations and Application of Dispersion Models 
    • Permit Modeling Unit (PMU) Determinations.
      • Traditional Construction Permits
        • If an applicant is unsure if modeling will be required to conduct a required NAAQS analysis, the APCD-114 Form should be filled out to obtain a decision prior to submitting a permit application or a Modeling Analysis to the Air Pollution Control Division (Division). Form Instructions are provided here. Additional clarification can be found here.
        • Once a determination is made, the applicant will be provided documentation of the PMU Determination by Division. The APCD-114 Form and PMU Determination must be included in the permit application and will be part of the source or modification's permit application record. If a determination of "Modeling Required" is made, the applicant must submit a Modeling Analysis demonstrating compliance with the NAAQS with the permit application. If a determination of “Modeling Not Required” is made, the completed APCD-114 Form and PMU Determination, which demonstrates NAAQS compliance, will be included as part of the source or modification’s permit application record and no further analysis will be required. 
      • New General Permit Registrations: GP01, GP02, GP05, GP06, GP07, GP08, GP09, GP10 and GP11
        •  In order to evaluate if modeling will be required to conduct a required NAAQS analysis pursuant to the Interim Modeling Guidelines (October 2021), the APCD-114 Form should be filled out to obtain a decision prior to submitting a general permit registration  or a Modeling Analysis to the Air Pollution Control Division (Division). Form Instructions are provided here Additional clarification can be found here.
        • Once a determination is made, the applicant will be provided documentation of the PMU Determination by the Division. The APCD-114 Form and PMU Determination must be included in the general permit registration and will be part of the source’s permit application record. If a determination of “Modeling Not Required” is made, the completed APCD-114 Form and PMU Determination will be included as part of the source or modification’s permit application record and no further analysis will be required. If a determination of "Modeling Required" is made, the applicant must submit a Modeling Analysis demonstrating compliance with the NAAQS to the Division and obtain a Modeling Review Report, which is written approval of the Modeling Analysis, prior to submitting a general permit registration. The Modeling Review Report or determination of “Modeling Not Required” must be submitted with the General Permit registration for the registration to be complete.
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    Call to Action for Outstanding Applications

    Summary

    If you have not submitted a Modeling Requirements Determination (APCD-114 Form) with your application, please do so as soon as possible, preferably within the next 2 weeks. Completing this form will help us expedite the processing of your application. When your application is assigned to a permit engineer, the engineer will ask for an APCD-114 for that submittal. Please submit this form within 14 days of the engineer's request since this form is required before the permit can be issued. Therefore, you can expedite the processing of your application by submitting this form prior to permit assignment. You can complete Form APCD-114 now by following the instructions provided here. Timely submittal of this form will not impact your place in line, applications will be assigned based on the day that they were received. Please see more information on this requirement below. 

    Background

    In every permitting action, the Air Pollution Control Division (Division) must conduct an evaluation regarding whether the proposed source or activity which is the basis for the permit action will cause an exceedance of the National Ambient Air Quality Standards (NAAQS). See Regulation Number 3, Part B, Section III.D.1.c. The information requested in APCD-Form 114 will enable the Division to properly conduct its evaluation regarding NAAQS compliance. Therefore, sources must submit a completed APCD-Form 114 for the Division to make its final determination regarding NAAQS compliance. If the Division does not have the required information to ensure the proposed source or activity is compliant with the NAAQS, as required by Section III.D.1.c., it will be forced to deny the permit. See Regulation Number 3, Part B, Section III.F.1. For this reason, the requirement to submit a completed APCD-Form 114 applies both to applications already received by the Division as well as those applications that have not yet been submitted. For applications already assigned, the permit writer will contact the applicant to request the APCD-Form 114. 

    Currently, depending on several factors found in the “Colorado Modeling Guideline for air Quality Permits” dated May 2022, modeling may be required to conduct this required NAAQS analysis. Thus, the Division is requiring that applicants obtain a Modeling Requirements Determination from the Permit Modeling Unit (PMU) prior to submitting a permit application and permit issuance. Form Instructions are provided here.

    Once a Modeling Requirements Determination is made, the applicant will be provided documentation of the Modeling Determination by the Division. The APCD-114 Form and Modeling Determination will be part of the source or modification's permit application record. If a determination of "Modeling Required" is made, the applicant must submit a modeling analysis demonstrating compliance with the NAAQS with the permit application. If an application has already been submitted, the applicant must submit a modeling analysis demonstrating compliance with the NAAQS prior to permit issuance. If a determination of “Modeling Not Required” is made, no further analysis will be required.

    More information can be found in the following link:

    https://cdphe.colorado.gov/air-emissions/air-quality-modeling-guidance-for-permits

     

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    Supplemental Modeling Guidance, Forms, and Information

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    Meteorological & Geophysical Data for Air Quality Permit Modeling

    • The Technical Services Program of the Air Pollution Control Division has data from current and historic meteorological towers in Colorado that are suitable for use in regulatory models. Contact the Division at cdphe_apcd_modeling_files@state.co.us for data. Division approval should be obtained on a case-by-case basis before meteorological datasets are used for regulatory (e.g., air permit) modeling.
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    Federal Modeling Support