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Federal Register / Vol. 86, No. 7 / Tuesday, January 12, 2021 / Proposed Rules C. CAA and Regulatory Requirements for 2008 Ozone Nonattainment Area SIPs II. The 2018 Western Nevada County Ozone Plan A. Summary of Submission B. Clean Air Act Procedural Requirements for Adoption and Submission of SIP
Revisions III. Evaluation of the 2018 Western Nevada County Ozone Plan A. Emissions Inventories B. Emissions Statements C. Reasonably Available Control Measures Demonstration D. Attainment Demonstration E. Rate of Progress Plan and Reasonable Further Progress Demonstration F. Contingency Measures G. Motor Vehicle Emissions Budgets for Transportation Conformity H. Other Clean Air Act Requirements Applicable to Serious Ozone Nonattainment Areas IV. Proposed Action V. Statutory and Executive Order Reviews
I. Regulatory Context
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A. Ozone Standards, Area Designations, and SIPs Ground-level ozone pollution is formed from the reaction of volatile organic compounds VOC and oxides of nitrogen NOX in the presence of sunlight.1 These two pollutants, referred to as ozone precursors, are emitted by many types of sources, including on-and off-road motor vehicles and engines, power plants and industrial facilities, and smaller area sources such as lawn and garden equipment and paints.
Scientific evidence indicates that adverse public health effects occur following exposure to ozone, particularly in children and adults with lung disease. Breathing air containing ozone can reduce lung function and inflame airways, which can increase respiratory symptoms and aggravate asthma or other lung diseases.2
Under section 109 of the CAA, the EPA promulgates NAAQS for pervasive air pollutants, such as ozone. The NAAQS are concentration levels that, the attainment and maintenance of which, the EPA has determined to be requisite to protect public health and welfare. Section 110 of the CAA
requires states to develop and submit SIPs to implement, maintain, and enforce the NAAQS.
In 1979, the EPA established the 1hour ozone NAAQS of 0.12 parts per 1 The State of California refers to reactive organic gases ROG rather than VOC in some of its ozonerelated SIP submissions. As a practical matter, ROG
and VOC refer to the same set of chemical constituents, and for the sake of simplicity, we refer to this set of gases as VOC in this proposed rule.
2 Fact Sheet2008 Final Revisions to the National Ambient Air Quality Standards for Ozone dated March 2008.

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million ppm referred to herein as the 1-hour ozone NAAQS.3 All of Nevada County was designated Unclassifiable/Attainment for the 1hour standard on November 15, 1990.4
In 1997, the EPA revised the NAAQS
for ozone, setting it at 0.08 ppm averaged over an 8-hour timeframe referred to herein as the 1997 ozone NAAQS to replace the existing 1-hour ozone NAAQS.5 In 2004, the EPA
initially designated and classified Western Nevada County as a Subpart 1 nonattainment area for the 1997
ozone NAAQS.6 In response to a decision of the United States Court of Appeals for the District of Columbia Circuit vacating the EPAs subpart 1
designations, the EPA in 2012 revised the areas classification for the 1997
ozone NAAQS to Moderate, with an outermost attainment date of June 15, 2011.7 In 2011, the design value for the area was 0.079 ppm, and the EPA
published a clean data determination on December 3, 2012, suspending attainment-related planning requirements for the 1997 ozone NAAQS.8
In 2008, the EPA lowered the 8-hour ozone NAAQS to 0.075 ppm referred to herein as the 2008 ozone NAAQS to replace the 1997 ozone NAAQS of 0.08
ppm.9 In 2012, the EPA designated Western Nevada County as nonattainment for the 2008 ozone NAAQS and classified the area as Marginal.10 Areas classified as Marginal must attain the NAAQS within 3 years of the effective date of the nonattainment designation. For Western Nevada County, the applicable Marginal area attainment date was as expeditiously as practicable but no later than July 20, 2015. The area failed to attain the 2008 ozone NAAQS by this date, and the EPA published a reclassification to Moderate on May 4, 2016.11 Upon reclassification, Western Nevada County was required to attain the 2008 ozone NAAQS as 3 44

FR 8202 February 8, 1979.
FR 56694 November 6, 1991.
5 62 FR 38856 July 18, 1997. The 1-hour ozone standard was revoked effective June 15, 2005. See 70 FR 44470 August 3, 2005.
6 69 FR 23857 April 30, 2004.
7 77 FR 28423 May 14, 2012. For more details on the revised classification, see 77 FR 56775, 56776 September 14, 2012.
8 77 FR 71551 December 3, 2012.
9 73 FR 16436 March 27, 2008. The EPA further tightened the 8-hour ozone NAAQS to 0.070 ppm in 2015, but todays proposed action relates to the requirements for the 2008 ozone NAAQS only.
Information on the 2015 ozone NAAQS is available at 80 FR 65292 October 26, 2015.
10 77 FR 30088 May 21, 2012.
11 81 FR 26697 May 4, 2016.
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expeditiously as practicable but no later than July 20, 2018.
In November 2018, pursuant to CAA
section 181b2, the EPA proposed to determine that the Western Nevada County Moderate nonattainment area failed to attain the 2008 ozone NAAQS
by the Moderate area attainment date.12
Additionally, following the EPAs November 2018 proposal, the California Air Resources Board CARB submitted a request under CAA section 181b3
to voluntarily reclassify the Western Nevada County nonattainment area from Moderate to Serious nonattainment for the 2008 ozone standards accompanied by a SIP revision to address planning elements for a Serious area.13
In a final rule dated August 23, 2019, the EPA found that Western Nevada County failed to attain the 2008 ozone NAAQS by the applicable attainment date, and reclassified the area as Serious by operation of law, effective September 23, 2019.14 Once reclassified to Serious, the area is required to attain the standard as expeditiously as practicable, but no later than 9 years after the initial designation as nonattainment, i.e., July 20, 2021.
The SIP revision that is the subject of todays proposed action addresses the Serious nonattainment area requirements that apply to Western Nevada County for the 2008 ozone NAAQS.
B. The Western Nevada County Ozone Nonattainment Area The Western Nevada County nonattainment area for the 2008 ozone NAAQS consists of the portion of Nevada County west of the ridge of the Sierra Nevada mountains. Western Nevada County encompasses an area of approximately 800 square miles. The nonattainment area is bounded on the north by the Middle Yuba River and most of the southern border is defined by the Bear River. The eastern boundary is a line running north/south that generally follows the ridge of the Sierra 12 83

FR 56781 November 14, 2018.
letter dated December 2, 2018, from Richard W. Corey, Executive Officer, CARB, to Michael Stoker, Regional Administrator, EPA
Region IX, and letter dated November 14, 2018 from Gretchen Bennitt, Executive Director, NSAQMD, to Richard W. Corey, Executive Officer, CARB, subject Submittal of the Northern Sierra Air Quality Management District Ozone Attainment Plan for the 2008 Federal 8-hour Ozone Standard.
14 84 FR 44238. The notice for this action acknowledges CARBs request for voluntary reclassification, and notes that the EPAs determination resulted in the same outcome as would occur with an approval of that request.
13 See
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