Illustration of Methodology for Exceptional Event (EE) Flagging

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Illustration of Methodology for Exceptional
Event (EE) Flagging

• Air quality exceedances due to natural events
  can be flagged for waivers
• The Rule requires States to quantify the
  exceptional event contribution
• Based on the States evidence, EPA decides if
  the EE flag is justified

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May 2007 Sweat Farm Fire Event

• Five-Step Methodology for documenting EE Flags
• Establish potential violation
• Show Exceptional Event cause
• Establish causality between Exceptional Event and
  exceedance
• Demonstrate excess above normal
• Exceedance but for the Exceptional Event

Sweat Farm Fire
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1. Is there a likely exceedance?
Red circles are potential exceedances
Circles show monitoring sites and the magnitude
of the surface concentration
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1. Is there a likely exceedance?
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2. Not Reasonably Controllable or Preventable
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2. Not Reasonably Controllable or Preventable
Online Picture Sharing 215 Photos
2000 Blogs on Florida Smoke
Smoke
Online Video Sharing 100 videos
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3. Causal Relationship between the Data and the
Event Trajectory Analysis
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3. Causal Relationship between the Data and the
Event Chemical Data
PM2.5 Organics
PM2.5 Sulfate
SO2 Emission
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3. Causal Relationship between the Data and the
Event Trajectory Analysis
Not impacted by GA Smoke
Incoming Air
Outgoing Air
GA Smoke Source Region
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3. Causal Relationship between the Data and the
Event Trajectory Analysis
GA Smoke Source Region
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4. The Event is in Excess of the "Normal" Values
/- 15 day Median around May 24
Excess Concentration for May 24
Measured PM 2.5 May 24, 2007
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5. The Exceedance or Violation would not Occur,
But For the Exceptional Event

• The leftmost figure shows a a valid EE to be
  flagged.
• In middle case, is not a 'but for' case and
  should not be flagged.
• In the third case, there is no exceedance.

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Conclusion
Not Exceptional Event Exceedances
Exceptional Event Exceedances
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