UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION IX
 

75 Hawthorne Street
 

San Francisco CA 94105
 

July 20, 2011 

Mr. James Goldstene 

Executive Officer 

California Air Resources Board 

1001 I Street 

Sacramento, California 95814 

Re:	 EPA Comments on Proposed Revisions to the State Implementation Plan for San Joaquin Valley 

8-hour 0 one 

EPA has reviewed the Air Resources Board (ARB) staffs proposed revisions to the 2007 8-hour Ozone 

Plan for the San Joaquin Valley. These revisions are in part the result of efforts by ARB and the San 

Joaquin Valley Air Pollution Control District to improve the emissions inventories. We applaud these 

efforts and have evaluated the potential implications of these recent inventory revisions on the Plan's 

attainment demonstration. We understand that ARB is committed to achieving the reductions necessary 

to attain the 1997 8-hour ozone standard. 

The SJV Ozone Plan, as adopted in 2007, includes modeling that indicates a need to reduce NOx 

emissions by 75 percent from the 2002 base year level to 160 tons per day (tpd) in order to attain the 

1997 8-hour ozone national ambient air quality standard. In the proposed revisions to the Plan, NOx 

emissions for the 2002 base year are revised downward by 12 percent to more accurately reflect the 

emissions in the base year, but the Plan's attainment target of 160 tpd remains unchanged. The extent of 

the base year emissions changes adds to the uncertainty inherent in determining the exact emissions level 

needed for attainment. 

To address this uncertainty, EPA recommends that the ARB commit to achieve a 75 percent reduction in 

NOx from the revised 2002 base year levels by 2023. A 75 percent reduction from the revised 2002 base 

year inventory equates to an attainment target level of 141 tpd of NOx emissions. We believe that the 75 

percent reduction from the existing modeling provides the best available estimate of the NOx reductions 

needed to reach attainment. This rests on the reasonable assumption that the ozone decrease expected 

from a given relative emission decrease would be approximately the same were the base case to be 

remodeled, since the underlying chemical and atmospheric processes for the modeled episodes would 

remain unchanged. However, given that the actual emissions reductions needed for attainment could be 

different based on new modeling, we note this commitment could later be revised if you submit, and we 

approve through notice and corriment rulemaking, a revision to the Plan based on a new modeling 

analysis demonstrating attainment of the 1997 8-hour ozone standard as expeditiously as practicable. 

Based on our conversations with your staff, we agree that the preferred approach to reevaluating the 

attainment demonstration in light of the revised emissions estimates would be to perform new air quality 

modeling. We also recognize the time and effort involved in such modeling and appreciate ARB's 

commitment to complete new modeling within the next few years. 
Therefore, EPA recommends that the ARB commit to submit, by a specific date, a revised attainment 

demonstration including the attainment target for the 1997 8-hour ozone standard for the San Joaquin 

Valley. This revised attainment demonstration should be based on new air quality modeling using the 

most recent emissions estimates. 

EPA believes that these recommendations are consistent with ARB's continuing aggressive 

commitments and efforts to achieve the emission reductions needed for attainment of the air quality 

standards in the San Joaquin Valley and the rest of California. Should you or ARB staff wish to discuss 

this issue further, please call me or Matthew Lakin of my staff at 415-972-3851. 

Sincerely, 

e all Jordan 

Director, Air Division 

cc:	 Mr. Seyed Sadredin 

Air Pollution Control Officer, San Joaquin Valley Air Pollution Control District 

Ms. Lynn Terry 

Deputy Executive Officer, California Air Resources Board 

Ms. Karen Magliano 

Chief, Air Quality Data Branch, California Air Resources Board