(a) Attainment determination. EPA has determined that the Ventura County severe 1-hour ozone nonattainment area attained the 1-hour ozone NAAQS by the applicable attainment date of November 15, 2005. EPA also has determined that the Ventura County severe 1-hour ozone nonattainment area is not subject to the requirements of section 185 of the Clean Air Act (CAA) for the 1-hour standard and that the State is not required to submit a SIP under Section 182(d)(3) of the CAA to implement a section 185 program for the 1-hour standard in this area. In addition, the requirements of section 172(c)(9) (contingency measures) for the 1-hour standard do not apply to the area.

(b) Approval. On December 19, 2007, the California Air Resources Board submitted a maintenance plan for the 1997 8-hour ozone NAAQS for the Monterey Bay Area as required by section 110(a)(1) of the Clean Air Act, as amended in 1990, and 40 CFR 51.905(a)(4). Elements of the section 110(a)(1) maintenance plan for ozone include a base year (2002) attainment emissions inventory for ozone, a demonstration of maintenance of the ozone NAAQS with projected emissions inventories through the year 2014 for ozone, a plan to verify continued attainment, and a contingency plan. The maintenance plan meets the Federal requirements of Clean Air Act section 110(a)(1) and 40 CFR 51.905(a)(4) and is approved as a revision to the California State Implementation Plan for the above mentioned area.

(c) Determination of attainment. Effective January 4, 2010, EPA is determining that the Imperial County, California 8-hour ozone nonattainment area has attained the 1997 8-hour ozone standard. Under the provisions of EPA's ozone implementation rule (see 40 CFR 51.918), this determination suspends the reasonable further progress and attainment demonstration requirements of section 182(b)(1) and related requirements of section 172(c)(9) of the Clean Air Act for as long as the area does not monitor any violations of the 8-hour ozone standard. If a violation of the 1997 ozone NAAQS is monitored in the Imperial County, California 8-hour ozone nonattainment area, this determination shall no longer apply.

(d) Determinations that Certain Areas Did Not Attain the 1-Hour Ozone NAAQS. EPA has determined that the Los Angeles-South Coast Air Basin Area and the San Joaquin Valley Area extreme 1-hour ozone nonattainment areas did not attain the 1-hour ozone NAAQS by the applicable attainment date of November 15, 2010 and that the Southeast Desert Modified Air Quality Maintenance Area severe-17 1-hour ozone nonattainment area did not attain the 1-hour ozone NAAQS by the applicable attainment date of November 15, 2007. These determinations bear on the areas' obligations with respect to the one-hour ozone standard anti-backsliding requirements whose implementation is triggered by a determination of failure to attain by the applicable attainment date: section 172(c)(9) contingency measures for failure to attain and sections 182(d)(3) and 185 major stationary source fee programs.

(e) Determinations of attainment. Effective June 3, 2016.

(f) Determination of attainment. EPA has determined that, as of November 19, 2012, the Sacramento Metro 1-hour ozone nonattainment area has attained the 1-hour ozone standard, based upon complete, quality-assured and certified ambient air quality monitoring data for 2007-2009.

(g) Determination of attainment. EPA has determined that, as of May 15, 2015, the Southeast Desert 1-hour ozone nonattainment area has attained the 1-hour ozone standard, based upon complete, quality-assured and certified ambient air quality monitoring data for 2011-2013.

(h) Determination of attainment. EPA has determined that, as of August 17, 2016, the San Joaquin Valley 1-hour ozone nonattainment area has attained the 1-hour ozone standard, based upon sufficient, quality-assured and certified ambient air quality monitoring data for 2012-2014.

(i) Determination of attainment. The EPA has determined that, as of January 20, 2017, the San Luis Obispo (Eastern San Luis Obispo) 2008 8-hour ozone nonattainment area in California has attained the 2008 ozone standard by the July 20, 2016 applicable attainment date, based upon complete, quality-assured and certified data for 2013-2015. Therefore, the EPA has met its obligation pursuant to CAA section 181(b)(2)(A) to determine, based on the area's air quality data as of the attainment date, whether the area attained the standard. As a result of this determination, the San Luis Obispo (Eastern San Luis Obispo) 2008 ozone nonattainment area in California will not be reclassified for failure to attain by the July 20, 2016 applicable attainment date under section 181(b)(2)(A).

(j) Determination of attainment. The EPA has determined that, as of February 21, 2017, the Mariposa County 2008 8-hour ozone nonattainment area in California has attained the 2008 ozone standard, based upon complete, quality-assured and certified data for 2013-2015. Under the provisions of the EPA's ozone implementation rule (see 40 CFR 51.1118), this determination suspends the requirements for the area to submit attainment demonstrations and associated reasonably available control measures, reasonable further progress plans, contingency measures for failure to attain or make reasonable further progress and other planning SIPs related to attainment of the 2008 ozone standard for as long as the area continues to attain the 2008 ozone standard. If the EPA determines, after notice-and-comment rulemaking, that the Mariposa County ozone nonattainment area no longer meets the 2008 ozone standard, the corresponding determination of attainment for this area shall be withdrawn.

(k) Determination of attainment by the attainment date. Effective September 23, 2019. The EPA has determined that the Mariposa County Moderate nonattainment area in California attained the 2008 8-hour ozone National Ambient Air Quality Standards (NAAQS) by the applicable attainment date of July 20, 2018, based upon complete quality-assured and certified data for the calendar years 2015-2017.

(l) Determination of attainment by the attainment date. Effective August 30, 2021. On February 21, 2019, the EPA determined that San Francisco Bay Area, CA, attained the revoked 1997 8-hour ozone National Ambient Air Quality Standards (NAAQS) by the applicable attainment date of June 15, 2007. The determination was based upon complete quality-assured and certified data for the 3 calendar years 2004-2006. Further, the EPA determined that the Ventura County, CA, area attained the standards for the revoked 1997 8-hour NAAQS by the applicable attainment date of June 15, 2013. The determination was based upon complete quality-assured and certified data for the 3 calendar years 2010-2012.