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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

Examples of Reviewed Exceptional Event Submissions

These documents are examples of exceptional event submissions, or the decision documents responding to the demonstrations, for various cases of exceptional events. The purpose of this table is to provide examples of Exceptional Event demonstrations that have been reviewed by EPA. This table is not intended to serve as a database for all Agency actions on exceptional events. These examples may help agencies develop demonstration packages submitted in support of requests for data exclusion due to influence of Exceptional Events; however, they may not contain the minimum level of data or case-specific analyses necessary for any other exceptional event demonstration.

Please note that not all concentrations addressed in the demonstrations in this table may have resulted in EPA concurrences.

Event Agency Location Available Documentation
Summer 2008 Wildfires
(series 2)
California ARB Plumas and Shasta Cos. Shasta-Plumas demonstration series 2 (8/28/09) (ZIP, 463 KB)
EPA response letter (4/02/10) (PDF, 53 KB)
EPA technical support document (3/30/10) (PDF, 1.5 MB)
Summer 2008 Wildfires
(series 1)
California ARB Plumas and Shasta Cos. Shasta-Plumas demonstration series 1 (8/28/09) (ZIP, 900 KB)
EPA response letter (3/11/10) (PDF, 60 KB)
EPA technical support document (3/11/10) (PDF, 1.5 MB)
Summer 2007 Wildfires California ARB Plumas Co. Plumas demonstration (6/17/09) (ZIP, 29 MB)
EPA response letter (3/11/10) (PDF, 60 KB)
EPA technical support document (3/11/10) (PDF, 980 KB)
July 2008 Fireworks Illinois EPA Granite City, IL  Granite City demonstration (6/17/09) (ZIP, 603 KB)
EPA response letter (7/24/09) (PDF, 225 KB)
EPA technical support document (7/24/09) (PDF, 443 KB)
Summer 2007 Wildfires Montana DEQ Multiple locations across Montana

MT DEQ demonstration (12/14/07) (PDF, 43 MB)
EPA response letter (8/18/08) (PDF, 758 KB)
EPA technical support document (8/18/08) (PDF, 272 KB)

July 2007 Wildfire Utah DEQ Lindon, UT Lindon demonstration (12/24/2007) (PDF, 3 MB)
EPA response letter (4/29/08) (PDF, 612 KB)
July 2007 Fireworks Utah DEQ Rose Park, UT
West Valley, UT
Rose Park demonstration (12/24/2007) (PDF, 895 KB)
West Valley demonstration (12/24/2007) (PDF, 877 KB)
EPA response letter (4/29/08) (PDF, 612 KB)
Event Agency Location Available Documentation
July 2011 High Wind Dust Event Arizona DEQ Phoenix, AZ AZ DEQ demonstration (3/8/12) (PDF, 9.6 MB)
EPA response letter and technical support document (9/6/12) (PDF, 801 KB)
August 2007 Wildfires Montana DEQ Silverbow Co., MT MT DEQ demonstration (12/14/07) (PDF, 43 MB)
EPA response letter (8/18/08) (PDF, 758 KB)
EPA technical support document (8/18/08) (PDF, 272 KB)
Event Agency Location Available Documentation
June 2012 Stratospheric Ozone Intrusion Wyoming Department of Environmental Quality Big Piney and Boulder, Wyoming WYDEQ demonstration (PDF, 5.2 MB)
EPA response letter (May 28, 2014) (PDF, 72 KB)
EPA Technical Support Document (PDF, 2 MB)
April 2011 Fires Kansas Department of Health and Environment Kansas City, Wichita, and Topeka areas, KS KDHE demonstration (11/27/12) (PDF, 18.2 MB)
EPA response letter (12/28/12) (PDF, 96 KB)
Summer 2008 Wildfires California ARB Sacramento County, CA CARB demonstration (3/30/11) (ZIP, 80 MB)
EPA response letter (4/13/11) (PDF, 92 KB)
EPA technical support document (4/13/11) (PDF, 238 KB)
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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