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Support Center for Regulatory Atmospheric Modeling (SCRAM)

State Implementation Plan (SIP) Attainment Demonstration Guidance

The EPA’s Air Quality Modeling Group (AQMG) provides guidance documents to EPA Regional, State, and Tribal air quality management authorities and the general public on how to prepare attainment demonstrations for National Ambient Air Quality Standards (NAAQS) and the Regional Haze Rule using air quality modeling and other relevant technical analyses. These guidance documents are primarily directed at modeling applications in nonattainment areas but are also useful for modeling in maintenance areas or to support other rules or sections of the Clean Air Act. These guidance documents recommend procedures for estimating if a control strategy to reduce pollutant emissions (e.g., ozone precursors) will lead to attainment of the appropriate NAAQS. They also describe how to apply air quality models to generate the predictions later used to see if attainment is shown. This section of guidance is divided into three components: 8-hour Ozone/Particulate Matter (PM2.5)/Regional Haze Guidance, PM10 Guidance, and Carbon Monoxide Guidance.

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8-hour Ozone/PM2.5/Regional Haze Modeling Guidance
Draft Modeling Guidance for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze (PDF)(214 pp, 3.25 M) - December 2014 - Draft version of the updated Ozone, PM2.5, and Regional Haze modeling guidance document.

Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze (PDF)(262 pp, 1 M) - April 2007 - Final version of the Ozone, PM2.5, and Regional Haze modeling guidance document.

Update to the 24 Hour PM2.5 NAAQS Modeled Attainment Test (PDF)(8 pp, 385 K) - Updated version of the 24-hour PM2.5 attainment test. This new version replaces section 5.2 of the 2007 PM2.5 modeling guidance (PDF)(262 pp, 1 M).

The Modeled Attainment Test Software (MATS) Tool is now available.
Supporting Documents - Ozone/PM2.5/Regional Haze
Draft Criteria For Assessing Whether an Ozone Nonattainment Area is Affected by Overwhelming Transport (PDF)(8 pp, 29 K) and the Errata Sheet for Draft Criteria: March 28, 2006 (PDF)(1 pg, 10 K)

Frequently Asked Questions on Implementing the DRAFT 8-Hour Ozone Modeling Guidance to Support Attainment Demonstrations for Early Action Compact (EAC) (PDF)(9 pp, 29 K) -  Updated February 23, 2004

Guidance for the 1-hour Ozone Nonattainment Areas that Rely on Weight-of-Evidence for Attainment Demonstrations (PDF)(31 pp, 66 K) - Mid-Course Review Guidance April 4, 2002

Guidance for Improving Weight-of-Evidence Through Identification of Additional Emission Reduction Not Modeled (WPD)(56 K) - November 1999

Guidance on Use of Modeled Results to Demonstrate Attainment of 1-hr Ozone NAAQS (ZIP)(637 K) - June 1996

Guideline for Regulatory Application of the Urban Airshed Model (PDF)(83 pp, 127 K) - July 1991

Note: Information on air quality modeling of individual sources for visibility assessments can be found at:

Phase I Guidance:

Phase II Guidance:

PM10 Guidance
Fugitive Dust Guidelines (ZIP)(692 K) - Guidance for modeling fugitive dust: Phase I, II & III, December 9, 1996
Carbon Monoxide Guidance
Guideline for Modeling Carbon Monoxide from Roadway Intersections (PDF)(64 pp, 532 K) - Applicable for roadway intersections, July 19, 1993