September23, 2013 

## Georgia Departmentof Natural Resources Environmental Protection Division• Air Protection Branch 4244 International Pari<V)Iay • Suite 120• Atlanta• Georgia30354 404/363-7000• Fax: 404/363-7100 Judson H. Turner, Director

Carol Kemker, Acting 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 of PM2.s Maintenance Plan Contingency Requirements Dear Ms. Kemker: In 2012 the Georgia Environmental Division (EPD) submitted to the U.S. Environmental Protection Agency (EPA) redesignation requests and maintenance plans for four Georgia areas that had been designated nonattainment for the 1997 Annual PM2.5 National Ambient Air Quality Standard (NAAQS) for approval and incorporation into Georgia's State Implementation Plan (SIP). The four nonattainment areas, with their submittal dates, are as follows:

• Floyd County • Macon • Atlanta • Chattanooga June 21, 2012 June 21, 2012 August 30, 2012 September 14, 2012 (Georgia counties- CatoosaandWalker) Recently, staff from EPA Region 4 requested that Georgia EPD provide additional clarification on the timing and content of the contingency measures identified in these maintenance plans. Georgia EPD is submitting this letterto provide further clarification of the contingency requirements found in the plans. Note that the contingency measures are identical in each ofthe plans. The plans include Tier Iand Tier II triggers which, if activated, will require EPD to take corrective actions to mitigate in accordance with the trigger. ATier 1trigger is activated when anyone ofthefollowing conditions occurs:Ms. Carol Kemker September 23, 2013 Page Two

• the previous calendaryear's annual average PM2.s concentration exceedsthe standard by 1.5 ug/m3 or more; • the annual average PM2 .s concentration in each of the previous two consecutive calendaryears exceedsthe standard by

### 0.5 ug/m3 or more; • the total maintenance area S02emissions in the most recent NEI exceedsthe corresponding attainment-year inventory by morethan 

### 10.0 percent; and • the total maintenance area PM2.s emissions in the most recent NEI exceeds the corresponding attainment-year inventory by morethan 

### 30.0 percent. ATier II trigger is activated when anyviolation ofthe annual PM2

.5 NAAQS 

### (15.0 ug/m3) atany ofthe monitoring stations is recorded based on quality-assured monitoring data. The purpose of this letter is to confirm that EPD commits to address and correct any violation ofthe 1997 annual PM2

.5 NAAQS as expeditiously as practicable and no later than 

### 24 monthsfrom the trigger activation. Upon activation of aTier I or II trigger, EPD will commence a comprehensive study of all available data to determine the cause of the exceedance or violation of the NAAQS. The study will be completed as expeditiously as practicable, but no laterthan nine months after the trigger is activated. The study includes determining the cause oftriggeractivation or ofthe violation and any emissions control measures that may be necessaryto prevent orcorrect, respectively, a violation of the NAAQS. Emissions reductions from implementation of previously adopted controls, which have notyet been realized and which are not relied upon in the maintenance demonstration, will be implemented within 18 to 

### 24 months. These emissions control measures, which were identified in EPD's maintenance plan, will produce substantial reduction of PM2 .s and PM2.s 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 sufficient to address anyviolation ofthe NAAQS, EPD will adopt additional rules or controls to require further 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 of the 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 the Air Planning Agreement, will consult and seek reviewfrom EPA on the analysisto determine the cause of the violation. EPD commits to develop a plan, then adopt and implement measures to correct the violation within 18 to 

### 24 months of any violation of the NAAQS.Ms. Carol Kemker September23, 2013 Page Three If you have any questions or need more information, please contact JimmyJohnston at (404) 363-7014 orvia email atjimmy.johnston@dnr.state.ga.us. Sincerely,

# ~ Keith Bentley, Chief " Air Protection Branch KB:JK:klc

c: Lynorae Benjamin, EPA Region 4 JimmyJohnston,Air Protection branch