Air Quality Monitoring & Modeling
| Date | Title | EPA Office | Author | Issues Addressed |
|---|---|---|---|---|
| 11/20/2024 | Guidance on Developing Background Concentrations for Use in Modeling Demonstrations (pdf) (1,974 KB) | OAQPS | Wayland, Richard | EPA-recommended framework of stepwise considerations to assist the regulatory air quality modeling community and regulatory agencies in characterizing a credible and appropriately representative background concentration for cumulative impact analyses. |
| 07/29/2022 | Guidance for Ozone and Fine Particulate Matter Permit Modeling (pdf) (4 MB) | OAQPS | Wayland, Richard and Mathias, Scott | Recommendations for how a stationary source seeking a PSD permit may demonstrate that it will not cause or contribute to a violation of the National Ambient Air Quality Standards for ozone (O3) and fine particulate matter (PM2.5) and PSD increments for PM2.5, as required under Section 165(a)(3) of the Clean Air Act and 40 CFR sections 51.166(k) and 52.21(k). |
| Interim Policy on Stack Height Regulatory Actions (pdf) (25.8 KB) | OAR | Potter, J. Craig | Interim policy on the following stack height regulatory actions: (1) Grandfathering pre-October 11, 1983 within-formula stack height increases from demonstration requirements [40 CFR 51.100(kk)(2)]; (2) Dispersion credit for sources originally designed and constructed with merged or multiflue stacks [40 CFR 51.100(hh)(2)(ii)(A)]; and (3) Grandfathering of pre-1979 use of the refined H + 1.5L formula [40 CFR 51.100(ii)(2)]. | |
| 04/25/1990 | Issuance of PSD Permits in Attainment Areas Where Violations have been Modeled (pdf) (17.9 KB) | Region 3 | Spink, Marcia | Outlines the procedures that must be followed when issuing PSD permits in attainment areas where violations have been modeled. |
| 05/1987 | Ambient Monitoring Guidelines for Prevention of Significant Deterioration (pdf) (3.7 MB) | OAQPS | Ambient monitoring guidelines for PSD. | |
| 03/23/2010 | Modeling Procedures for Demonstrating Compliance with PM2.5 NAAQS (pdf) (751 KB) | OAQPS | Page, Stephen | Guidance on modeling procedures for demonstrating compliance with particulate matter (PM2.5) National Ambient Air Quality Standards (NAAQS). |
| 06/04/1990 | Definition of Post approval Monitoring (pdf) (11.5 KB) | OAQPS | Lillis, Ed | Clarifies the definition of “post approval monitoring” as the term is used in the PSD regulations at 40 CFR 51.166(m)(v). |
| 05/20/2014 | Guidance for PM2.5 Permit Modeling (pdf) (2.6 MB) | OAQPS | Page, Stephen | Provides guidance on demonstrating compliance with the fine particulate matter (PM2.5) National Ambient Air Quality Standards (NAAQS) and Prevention of Significant Deterioration (PSD) increments, especially with regards to considerations of secondarily formed component PM2.5. |
| 02/29/2012 | Concurrence with Region 2's Assessment of the Appropriate Method for Compliance Demonstration Modeling of Emissions Associated with Horizontal Drilling and High-Volume Hydraulic Fracturing of the Marcellus Shale in New York State (pdf) (10.6 MB) | OAQPS | Fox, Tyler | Whether emissions resulting from the predictable and continuous operation of a horizontal drilling and high-volume hydraulic fracturing source at a specified location for upwards of 4 months should be considered intermittent emissions. |
| 10/23/1997 | Interim Implementation of NSR Requirements for PM2.5 (pdf) (16.9 KB) | OAQPS | Seitz, John | Addresses the interim use of PM10 as a surrogate for PM2.5 in meeting new source review (NSR) requirements under the Clean Air Act, including the permit programs for PSD. |
| 10/10/1985 | Q & A on Implementing the Revised Stack Height Regulation (pdf) (42.8 KB) | OAQPS | Helms, G. Tom | Answers several questions related to implementing revised stack height regulations including (1) what criteria should be used to determine when a stack was “in existence” with respect to various grandfathering dates in the regulation; (2) what “source” definition should be used in determining whether tie-ins to grandfathered stacks should be permitted; (3) what is meant by “facility;” (4) whether good engineering practice (GEP) stack height should be established separately for each pollutant; (5) how “reliance” on the 2.5H formula should be determined; and (6) whether OAQPS will be specifying structures not well represented by the formula other than those specifically addressed in the preamble; among other questions. |
| 10/28/1985 | Implementation of Stack Height Regulations - Exceptions from Restrictions on Credit for Merged Stacks (pdf) (2,006 KB) | CPDD | Tyler, Darryl | Establishes a procedure that should be used to prepare and to review justifications for merging gas streams for economic or engineering reasons, and to address the presumption that merging was significantly motivated by an intent to gain credit for increased dispersion. |
| 01/02/1990 | Effect of Changing Stack Heights on PSD Modeling and Monitoring (pdf) (16 KB) | OAQPS | Calcagni, John | Whether and when the beneficial air quality impacts that result from an existing stack height at a source can be considered as part of a proposed PSD modification. |
| 01/29/1987 | Implementation of the Revised Modeling Guidance for PSD (pdf) (20.8 KB) | CPDD | Tyler, Darryl | Guidance on the implementation of the revised modeling guidance for PSD. |
| 12/10/2001 | Response to September 7, 2001 Letter on PSD (pdf) (50.2 KB) | OAQPS | Seitz, John | Regards the modeling method used to track increment and the use of continuous emissions monitor (CEM) data to replace calculated emissions values based on permit limits. This memorandum also addresses how the Federal Land Manager (FLM) certifications and variance procedures in the Clean Air Act (CAA) affect increment. |
| 04/08/2014 | Interim Guidance on the Treatment of Condensable Particulate Matter Test Results in the Prevention of Significant Deterioration and Nonattainment New Source Review Permitting Programs (pdf) (4.3 MB) | OAQPS | Page, Stephen | Provides interim guidance on the treatment of condensable particulate matter (CPM) under EPA’s NSR permit programs for particulate matter. |
| 03/31/1989 | Applicability of Building Downwash in PSD Permit Analyses (pdf) (14.3 KB) | OAQPS | Calcagni, John | Whether building downwash modeling should be required for background sources. |
| 08/09/1988 | Model Accuracy and Uncertainty (pdf) (346 KB) | OAQPS | Laxton, William | Summarizes the details of model accuracy and uncertainty. |
| 02/01/1981 | PSD Significance Levels for Monitoring (pdf) (14.6 KB) | CPDD | Tyler, Darryl | Guidance on significance levels of projected ambient impacts for the purpose of determining whether a proposed source or modification would be eligible for an exemption from the requirement for ambient monitoring. |
| 08/25/1989 | Texas Air Control Board Inquiry Regarding Allowable Emissions in PSD NAAQS Analyses (pdf) (32.6 KB) | Region 6 | Hathaway, William | Clarifies the use of Guidelines on Air Quality Models Table 9-1 emissions in PSD NAAQs analyses. |
| 03/15/2002 | Use of the Ambient Ratio Method for Modeling Significant Ambient Impacts of NO2 (pdf) (32.6 KB) | OAQPS | deRoeck, Daniel | Guidance on the use of the ambient ration method for modeling significant ambient impacts of NO2. |
| 07/05/1988 | Air Quality Analysis for PSD (pdf) (24.4 KB) | OAQPS | Emison, Gerald | Resolves inconsistency associated with how to interpret dispersion modeling results to determine whether a source will cause or contribute to a new or existing violation of a national ambient air quality standard (NAAQS) or PSD increment. |
| 03/01/2011 | Additional Clarification of Guidance for Implementation of the 1-hour NO2 NAAQS Under PSD (pdf) (391 KB) | OAQPS | Page, Stephen | Provides additional clarification of guidance for implementation of the 1-hour NO2 NAAQS under PSD. |
| 04/30/2019 | Guidance on the Development of Modeled Emission Rates for Precursors (MERPs) as a Tier 1 Demonstration Tool for Ozone and PM2.5 under the PSD Permitting Program (pdf) (3.2 MB) | Air Quality Assessment Division | Wayland, Richard A. | Guidance on the development of modeled emission rates for precursors (MERPs) as a Tier 1 demonstration tool for ozone and PM2.5 under the PSD permitting program. |
| 04/16/2013 | North Carolina's Implementation of Visibility Impact Assessment Requirements for New Major Stationary Sources and Major Modifications Subject to Clean Air Act Prevention of Significant Deterioration Requirements (pdf) (7.7 MB) | Region 4, OAQPS | Bannister, Beverly and Wood, Anna Marie | Guidance on North Carolina’s implementation of visibility impact assessment requirements for new major stationary sources and major modifications subject to Clean Air Act Prevention of Significant Deterioration (PSD) requirements. |
| 12/13/2000 | Southern LNG, Inc., Elba Island Terminal, Savannah Georgia Draft Air Quality Permit and PSD Preliminary Determination (pdf) (29.7 KB) | Region 4 | Neeley, R. Douglas | Answers numerous questions and provides comments related to a PSD determination including on whether emissions units at the facility should be considered an existing source and not a new source for PSD applicability purposes under EPA’s Reactivation Policy; the vaporizer BACT portion of the permit; the impact area visibility analysis addressing visibility in the “near field region;” emission inventories used in the national ambient air quality standards and PSD compliance monitoring; and ozone ambient conditions. |
| 03/16/1989 | Use of Allowable Emissions for NAAQS Impact Analysis Under the Requirements for PSD (pdf) (19.9 KB) | OAQPS | Calcagni, John | Clarifies EPA’s policy concerning the implementation of the PSD air quality impact analysis under 40 CFR 51.166(k). Of specific concern is the question of whether the required analysis for new major sources and major modifications is to be based on actual or allowable emissions from existing background sources. |
| 07/31/1981 | Policy Determinations Regarding PSD Questions (pdf) (27.2 KB) | Region 4 | Devine, Thomas | Addresses multiple PSD questions including those related to maintenance conducted on a shutdown boiler that intends to return to service, the addition of 7 compounds to be of negligible photochemical reactivity whether this impacts what compounds are considered VOCs, whether a major source proposing to build in a nonattainment area is subject to PSD if the area is projected to be attainment before startup of the source, and questions related to PSD baseline and ambient monitoring, among others. |
| 04/01/1982 | Response to Kay Phillips Regarding a Review on the Stack Height Regulations and Accompanying Preamble Language (pdf) (11.3 KB) | CPDD | Tyler, Darryl | Whether flares are to be considered stacks under the regulations and how the ambient air quality modeling of criteria pollutants coming from a flare should be modeled. |
| 12/01/2016 | Use of Models for Assessing the Impacts of Emissions from Single Sources on the Secondarily Formed Pollutants: Ozone and PM2.5 (pdf) (354 KB) | OAQPS | Air Quality Assessment Division | Guidance on the use of models for assessing the impacts of emissions from single sources on the secondarily formed pollutants ozone and PM2.5. |
| 07/06/1979 | EPA Quality Assurance Policy Statement (pdf) (33.1 KB) | Region 4 | Finger, James | Addresses the need for uniform quality assurance activities, agency-wide, in all monitoring activities. |
| 05/29/1987 | UNAMAP 6 Dispersion Modeling with Building Wake Effects (pdf) (23.4 KB) | OAQPS | Tikvart, Joseph | Whether all sources that experience downwash should be modeled utilizing the downwash algorithm and whether it is necessary to perform downwash analyses of an off-site source when evaluating the impact of other sources, among other issues. |
Related Topics: Prevention of Significant Deterioration (PSD) Increments | Significant Impact Levels (SILs) & Cumulative Analyses | Definition/Interpretations of Ambient Air
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The “Relevant Guidance” index includes a collection of documents issued by EPA organized by topic area. These documents include memoranda, letters, orders, and other types of EPA actions that may provide guidance in one or more forms, such as an adjudication, statement of policy, interpretation of statutes or regulations, or technical information. Each collection is intended to be representative of EPA statements on the topic, but it may not be a complete listing of such statements. The collection does not reflect topic-specific statements that have been expressed by EPA though published rule preambles and Title V petition orders, nor does it include EAB decisions. Each document in the collection speaks for itself, and the inclusion or exclusion of a document in the collection is not intended by EPA to communicate anything more than what is expressed within each document. EPA makes no independent representations on this website as to the extent to which any document in the collection reflects EPA’s current views on the topic, is a final action by EPA, or has any legal effect or precedential weight. Readers are advised to review the documents in the collection and conduct their own assessment of such considerations based on the content of each document and other documents in the collection. Some of the information or views included in the documents may be affected by subsequent changes to the referenced statutory or regulatory language or by court decisions. In addition, many of the statements in these documents are based upon the federal regulations which may differ from rules that govern federally-approved programs. Permitting authorities are advised to consult with their EPA Regional Offices if there is a question as to the relevance of a particular statement to their NSR program.