# ir Resources Board Mary D. Nichols, Chairman

1001 IStreet· P.O. Box 2815 Linda S. Adams Sacramento, California 95812·www.arb.ca.gov Arnold Schwarzenegger

Secretaryfor Governor EnvironmentalProtection

March 23, 2010

Mr. Jared Blumenfeld Regional Administrator U.S. Environmental Protection Agency Region 9 75 Hawthorne Street San Francisco, California 94105 Dear Mr. Blumenfeld:
TheAir Resources Board (ARB) requests thatthe U.S. Environmental Protection Agency (U.S. EPA) grantthe Southern Mountain Counties 8-hour ozone nonattainment area a one-year extension ofthe 1997 8-hour ozone national ambient airquality standard (standard) attainmentdate. On April 15, 2004, Southern Mountain Counties were designated nonattainmentforthe federal 8-hour ozone standard and classified as a basic area. On January 16, 2009, U.S. EPA proposed to reclassify the Southern Mountain Counties under subpart 2 as a "Moderate nonattainment area" with an attainment date ofJune 15, 2010 (74 CFR 2936). U.S. EPA has yet to finalize this ruling, and has, therefore, not officially set an attainment date forthis area. However, ARB believes that U.S. EPA could propose to grant a one-year extension now, pending final action to classify the Southern Mountain Counties as a moderate area with an attainment date ofJune 15, 2010. U.S. EPA guidance specifies that the design vaiue forthis standard is the three-year average ofthe fourth-highest daily maximum 8-hour average ozone concentrations measured at each monitoring station. Since three full years ofair quality data are needed to demonstrate attainment, the date ofJune 15, 2010 is based on ozone levels from 2007-2009. Data recorded atthe Southern Mountain Counties air quality monitoring sites indicatesthat airquality in the Southern Mountain Counties is improving to the point thatthe fourth highestdaily average at all sites is well belowthe standard in 2009. However, the 2009 design value for the Southern Mountain Counties still exceeds the standard as illustrated by Table 1 in the enclosure. The 8-hour ozone implementation rule gives U.S. EPAthe discretion to grant upto two one-year extensions ofthe attainment date upon application by a state if: 1) the state has complied with all requirements and commitments pertaining to the area in the

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Printedon RecycledPaperMr. Jared Blumenfeld March 23, 2010 Page 2
applicable SIP; and, 2) air quality data showthatforthe first one-year extension, the area's fourth highestdaily 8-hour average in the attainmentyear is 0.084 parts per million (ppm) or less, and for the second year, the area's fourth highest daily 8-hour value averaged overthe original attainmentyear and the first extension year, is 0.084 ppm or less. We believe thatthe Southern Mountain Counties, as aformer Subpart 1 area, has met both ofthese criteria and it is appropriate for U.S. EPA to grantthe first one-year extension. The supporting documentation for our request is described below and contained in the enclosure. Table 1demonstratesthatthe Southern Mountain Counties fourth highest 8-hour ozone averagefor 2009 is belowthe standard and qualifies the Southern Mountain Counties for a one-year extension oftheir 8-hour ozone attainment date. Table 2 demonstrates thatthe Southern Mountain Counties was on trackto attain the 8-hour ozone standard by its original attainment date under Subpart 1 ofJune 15, 2009. However, in 2008, the Southern Mountain Counties recorded multiple air quality exceedances at a time when numerous wildfires were burning throughout Northern California, and consequently did not meet its attainment date. Ifthe 2008 exceptional events requests submitted to U.S. EPA on March 12, 2009 are approved, the Southern Mountain Countieswill have attained the 1997 8-hour ozone standard. We believe the Southern Mountain Counties have clearly metthe criteria for a one-year extension ofthe attainment date and that emissions are continuing to decline. We look forward to U.S. EPA approval ofthis request for an extension ofthe attainment date. If you have any questions, please call Ms. Lynn Terry, Deputy Executive Officer, at (916) 322-2739, or have your staff contact Ms. Karen Magliano, Chief, Air Quality Data Branch at (916) 322-7137. Sincerely,

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### c: Executive Officer Enclosure

cc: Ms. Debbie Jordan, Director U.S. Environmental Protection Agency Air Division

- Region 9 75 Hawthorne Street San Francisco, California 94105

Continued next page.

### Mr. Jared Blumenfeld March 23, 2010 Page 3

Charles Mosher Air Pollution Control Officer Mariposa County P.O. Box 2039 (5101 Jones St:) 

### Mariposa, California 95338 Vicki Helmar Air Pollution Control Officer Tuolumne County 2 South Green Street Sonora, California 95370 Lynn Terry Deputy Executive Officer Executive Office Karen Magliano, Chief

.Air Quality Data BranchEnclosure

Table 1 Fourth Highest8-hour Ozone Daily Maximums for 2006 to 2009 and 2009 Design Value for Southern Mountain Counties (parts per million)

Monitoring Site Fourth-Highest 8-hour Ozone Concentration Design Value 2006 2007 2008 2009 2009 Yosemite Natl Park-Turtleback 0.084­ 0.087 0.094 0.079 0.086 Jerseydale 0.08 0.083 0.089 0.077 0.083 Sonora 0.079 0.084 0.098 0.077 0.086

Table 2 Southern Mountain Counties 8-hour Ozone Design Values from 2001 to 2009 (parts per million)

Design Value 2001 2002 2003 2004 2005 2006 2007 2008 2009 Southern Mtn. Counties 0.092 0.091 0.091 0.09 0.088 0.086 0.085 0.087 0.086

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