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Treatment of Data Influenced by Exceptional Events


EPA Releases Interim Guidance and Announces Intention to Pursue Exceptional Event Rule Revisions
On Friday, May 10, 2013, EPA issued interim guidance to help state, local and tribal governments manage air quality data recorded during “exceptional events.” EPA also announced our intention to propose and finalize revisions to the 2007 Exceptional Events Rule, which will incorporate into regulation important aspects of the Interim Guidance and further streamline implementation challenges.

Exceptional Events are unusual or naturally occurring events that can affect air quality but are not reasonably controllable using techniques that tribal, state or local air agencies may implement in order to attain and maintain the National Ambient Air Quality Standards.

Contact:      Mark Evangelista
                    (919) 541-2803


The Environmental Protection Agency (EPA) finalized a rule to establish criteria and procedures for use in determining if air quality monitoring data has been influenced by exceptional events. The rule:

In July 2012, EPA issued a Federal Register Notice of Availability announcing the release of draft exceptional events implementation guidance developed to clarify key provisions of the 2007 Exceptional Events Rule (EER), respond to questions and issues that arose after the EER was promulgated, and reduce the burden associated with the demonstration preparation and review process. After considering the feedback received during the public comment period, EPA has decided to resolve a number of commenter-identified issues and needed clarifications in a more formal rulemaking process. Because the notice and comment rulemaking process is expected to take up to two years to conclude, EPA is issuing the interim guidance.

Interim Exceptional Events Guidance Documents (Posted: 05/13/13)

For guidance-related questions, please contact Beth W. Palma at 919-541-5432 or palma.elizabeth@epa.gov

Web-based Quick-Reference Guide for Exceptional Events Demonstrations

This user-friendly, web-based quick reference matrix is intended to direct air agency staff and other interested persons to specific information and guidance related to exceptional events demonstrations. The matrix pairs event and pollutant combinations (x-axis) with current Exceptional Events Rule criteria (y-axis). Each cell contains links that direct the user to specific example analyses or language that may be used in Exceptional Events Demonstrations. EPA expects to update this matrix as additional information (rule revisions, guidance, demonstrations) become available.

Click here to access the Matrix: Exceptional Events Requirements - Reference Guide

Examples of Reviewed Exceptional Event Submissions

This linked table provides examples of air agency-submitted and EPA concurred exceptional events demonstration packages along with the accompanying EPA concurrence letters and supporting analyses. EPA expects to update this table as additional demonstrations become available.

Click here to access the Table: Exceptional Events Submissions Table
Publicly Available Support Information and Tools

EPA provides no endorsement of specific publicly available tools, nor does EPA mandate their use. EPA believes that publicly available tools can provide supporting documentation for one or several of the exceptional event criteria within an air agency exceptional event demonstration, but EPA generally does not believe that links and/or references to these tools constitute a complete demonstration submittal.

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