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ENCLOSURE 1

Revised Recommended California Nonattainment Areas

for the Federal 8-Hour Ozone Standard Based on 2008-2010 Ozone Air Quality Data

Nonattainment Area

Design 

Value1

(ppm)

Area Included

Antelope Valley 0.091 Portion of Los Angeles County in Mojave Desert 

Air Basin

Butte County 0.079 Butte County

Calaveras County 0.083 Calaveras County

Coachella Valley 0.095 Coachella Valley portion of Riverside County

Eastern Kern County 0.083 Mojave Desert Air Basin portion of Kern County, 

excluding Indian Wells Valley

Eastern San Luis Obispo County 0.084 Eastern San Luis Obispo County

Imperial County 0.078 Imperial County

Mariposa County 0.083 Mariposa County 

Sacramento Metro Area 0.102

Sacramento, Yolo, eastern Solano, southern 

Sutter, and western portions of El Dorado and 

Placer counties

San Diego County 0.088 San Diego County

San Francisco Bay Area 0.080

Marin, southern Sonoma, Napa, western Solano, 

Contra Costa, Alameda, Santa Clara, San 

Francisco, and San Mateo counties

San Joaquin Valley 0.104 San Joaquin, Stanislaus, Merced, Madera, 

Fresno, Kings, Tulare, and western Kern counties

South Coast Air Basin 0.112

Western Los Angeles (including Catalina and 

San Clemente Islands), Orange, southwestern 

San Bernardino, and western Riverside counties

Tuscan Buttes 0.080 Tuscan Buttes in Tehama County above 1800’

Ventura County 0.086 Mainland portion of Ventura County (excludes 

Anacapa and San Nicolas islands)

Western Mojave Desert 0.099 Central San Bernardino County

Western Nevada County 0.084 Portion of Nevada County west of the crest of the 

Sierra Nevada

1

The design value is the 3-year average of the annual fourth highest 8-hour ozone concentration 

for the highest monitor in the area (if greater than 0.075 ppm = nonattainment; if less than or 

equal to 0.075 = attainment).
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Revised Recommended California Attainment Areas

for the Federal 8-Hour Ozone Standard

Attainment Area

Design 

Value1

(ppm)

Design 

Value 

Period

Area Included

Amador County 0.071 2009-2011 Amador County

Colusa County 0.066 2008-2010 Colusa County

Glenn County 0.066 2008-2010 Glenn County

Lake County 0.061 2008-2010 Lake County

North Central Coast Air 

Basin 0.069 2009-2011 Monterey, San Benito, and Santa Cruz counties

North Coast Air Basin 0.053 2008-2010

Del Norte, Humboldt, Mendocino, and Trinity 

counties and the North Coast Air Basin 

portion of Sonoma County

Northeast Plateau Air 

Basin 0.060 2008-2010 Lassen, Modoc, and Siskiyou counties 

Northeast 

San Bernardino and 

Eastern Riverside 

Counties

0.075 2008-2010

Mojave Desert portion of San Bernardino 

County outside the Western Mojave Desert 

ozone nonattainment area and Mojave Desert 

portion of Riverside County

Shasta County 0.075 2008-2010 Shasta County

Southern Inyo County 0.072 2008-2010

Inyo County portions of federal hydrologic 

units 16060015, 18090202, 18090203, 

18090204, and 18090205

Sutter and Yuba 

Counties 0.0762

2008-2010

Yuba County and portion of Sutter County 

outside Sacramento Metro Area (including 

Sutter Buttes area) 

Tehama County 0.074 2008-2010 Portion of Tehama County outside Tuscan 

Buttes area 

Tuolumne County 0.074 2009-2011 Tuolumne County

Santa Barbara County 0.073 2009-2011

Mainland portion of Santa Barbara County 

(excludes San Miguel, Santa Barbara, Santa 

Cruz, and Santa Rosa islands) 

Western San Luis 

Obispo County 0.065 2008-2010 Portion of County west of Eastern San Luis Obispo area

1

The design value is the 3-year average of the annual fourth highest 8-hour ozone concentration 

for the highest monitor in the area (if greater than 0.075 ppm = nonattainment; if less than or 

equal to 0.075 = attainment). 2011 data are preliminary.

2 2011 data not yet available, but will likely show attainment.
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Recommended California Unclassifiable Areas 

for the Federal 8-Hour Ozone Standard

Unclassifiable Area Area Included

Eastern Nevada County Portion of Nevada County east of the crest of the 

Sierra Nevada mountains

Great Basin Valleys Alpine County, Mono County, portion of Inyo County 

outside Southern Inyo County attainment area

Indian Wells Valley Existing Indian Wells Valley area in Eastern Kern 

County

Lake Tahoe Air Basin Lake Tahoe Air Basin portions of El Dorado and 

Placer counties

Northern Channel Islands

The islands located in the South Central Coast Air 

Basin, including Anacapa, San Miguel, San Nicolas, 

Santa Barbara, Santa Cruz, and Santa Rosa

Northern Mountain Counties Plumas and Sierra counties 
ENCLOSURE 2

STATE OF CALIFORNIA BOUNDARY DESCRIPTIONS 

FOR NEW RECOMMENDED DESIGNATION AREAS

UNDER THE 2008 FEDERAL 8-HOUR OZONE STANDARD

 

AMADOR COUNTY

All of Amador County.

EASTERN SAN LUIS OBISPO COUNTY

That portion of San Luis Obispo County that lies east of a line described as 

follows: Beginning at the San Luis Obispo County / Santa Barbara County 

boundary and running north along 120 degrees 24 minutes longitude to the 

intersection with 35 degrees 27 minutes latitude; east along 35 degrees 

27 minutes latitude to the intersection with 120 degrees 18 minutes longitude; 

then north along 120 degrees 18 minutes longitude to the San Luis Obispo 

County / Monterey County boundary. 

INDIAN WELLS VALLEY

That portion of Kern County that coincides with the Kern County portion of 

Hydrologic Unit #18090205.

SOUTHERN INYO COUNTY

That portion of Inyo County that lies within the bounds of Hydrologic Unit

Number 16060015, 18090202, 18090203, 18090204, and 18090205.

TUOLUMNE COUNTY

All of Tuolumne County.

TUSCAN BUTTES (TEHAMA COUNTY)

That portion of the immediate Tuscan Buttes area at or above 1,800 feet in 

elevation.