September20, 2013

Carol Kemker, Acting Director 

## Georgia DepartmentofNatural Resources Environmental Protection Division• Air Protection Branch 4244 International Parkway• Suite 120• Atlanta• Georgia30354 404/363-7000• Fax: 404/363-7100 Judson H. Turner, Director

Air Pesticides and Toxics Management Division U.S. EPA, Region 4 Atlanta Federal Center 61 Forsyth Street, S.W. Atlanta, Georgia 30303
Re: Clarification ofMaintenance Plan Contingency Requirements
Dear Ms. Kemker: On April 4, 2012, the Georgia Environmental Division (EPD) submitted to the U.S. Environmental Protection Agency (EPA) a redesignation request and maintenance plan for the Atlanta nonattainment area for the 1997 8-hour ozone National Ambient Air Quality Standard (NMOS) for approval and incorporation into Georgia's State Implementation Plan (SIP). Recently, staff from EPA Region 4 requested that Georgia EPD provide additional clarification on the timing and content of the contingency measures identified in the maintenance plan for the Atlanta area. Georgia EPD is submitting this letterto provide furtherclarification ofthe contingency requirementsfound in the plan.
The Atlanta maintenance plan includes Tier Iand Tier II triggers which, ifactivated, will require EPD to take corrective actions to mitigate in accordancewith the trigger. A Tier I trigger is activated when any quality-assured, 8-hour ozone monitoring reading exceeds 0.084 parts per million (ppm) or if the periodic emission inventory updates reveal excessive or unanticipated growth greaterthan 10 percent in emissions ofeither ozone precursor. A Tier II trigger is activated when any violation ofthe 8-hour ozone NMOS at any of the monitoring stations is recorded based on quality-assured monitoring data.
The purpose ofthis Jetter is to confirm that EPD commits to address and correct any violation ofthe 1997 8-hour ozone NMOSas expeditiously as practicable and no later than 24 monthsfrom the trigger activation. Upon activation ofa Tier Ior II trigger, EPD will commence a comprehensive study ofall available data to determine the cause of the exceedance or violation of the ozone NMOS. The study will be completed as expeditiously as practicable, but no laterthan nine months afterthe trigger is activated. The study includes determining the cause of the monitor reading in excess of 0.084 ppm or ofthe violation and any emissions control measures that may be necessary to prevent orcorrect, respectively, aviolation ofthe NMOS. EmissionsfromMs. Carol Kemker September20,2013 PageTwo implementation of previously adopted controls, which have not yet been realized and .which are not relied upon in the maintenancedemonstration, will be implementedwithin 18 to 24 months. These emissions control measures, which were identified in EPD's maintenance plan, will produce substantial reduction of ozone precursors in excess of what was relied upon in the maintenance demonstration. These controls include Georgia's Multipollutant Rule and diesel engine retrofit, replacement and repowering programs. In the event that EPD's review and analysis concludes that the previously adopted emission control programs identified above and in the plan are not sufficientto address anyviolation ofthe NAAQS, EPD will adopt additional rules orcontrols to requirefurther emissions reductions as identified in the plan. Any additional rules or controls to address a violation would be adopted and implemented within 18

- 24 months ofthe activation of a trigger. Any new rule will be submitted to EPA for approval into the State's SIP.
In any event, ifaTier II trigger is activated, EPD, consistentwith its commitmentto EPA in theAir Planning Agreement, will consult and seek reviewfrom EPA on the analysisto determine the cause ofthe violation. EPD commits to develop a plan, then adopt and implement measures to correct the violation within 18 to 24 months ofany violation of the NAAQS.
Ifyou have any questions or need more information, please contact Jimmy Johnston at (404) 363-7014 orvia email atjimmy.johnston@dnr.state.ga.us. Sincerely,

# ~~~Z1 

# - Keith

# Bentley,~ Air Protection Branch
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c: Lynorae Benjamin, EPA Region 4 JimmyJohnston, Air Protection branch