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Federal Register / Vol. 86, No. 139 / Friday, July 23, 2021 / Rules and Regulations
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less than 30 microns in diameter with new standards applying only to particulate matter up to 10 microns in diameter.1 An area attains the 24-hour PM10 standard of 150 micrograms per cubic meter mg/m3 when the expected number of days per calendar year, averaged over a three year period, with a 24-hour concentration exceeding the standard referred to as an exceedance, is equal to or less than one.2 On January 13, 2013, the EPA announced that it was again retaining the 24-hour PM10
NAAQS as a 24-hour standard of 150
mg/m3.3
On October 14, 2009, consistent with Section 107d3A of the CAA, the EPA notified the Governor of Arizona and the leaders of four Tribes with areas of Indian country either entirely or partly within Pinal County that the designation for Pinal County and nearby areas contributing to monitored violations of the PM10 NAAQS should be revised.4 The EPAs initiation of the redesignation process for Pinal County was based upon our review of 2006
2008 ambient PM10 monitoring data from monitoring stations within the county showing widespread, frequent, and, in some cases, severe violations of the PM10 NAAQS.
On May 31, 2012, EPA redesignated part of Pinal County from unclassifiable to nonattainment for the 24-hour PM10
NAAQS, creating the West Pinal County PM10 nonattainment area.5 The EPAs nonattainment redesignation of West Pinal County was based on ambient PM10 data collected from 2007 to 2009.6
Our redesignation of West Pinal County 1 53 FR 24634 July 1, 1987. The 1987 PM
10
standards included a 24-hour 150 micrograms per 3
cubic meter mg/m and an annual standard 50 mg/
m3. In 2006, the EPA revoked the annual standard;
see 71 FR 61144 October 17, 2006 and 40 CFR
50.6.
2 An exceedance is defined as a daily value that is above the level of the 24-hour standard, 150 mg/
m3, after rounding to the nearest 10 mg/m3 i.e., values ending in five or greater are to be rounded up. Consequently, a recorded value of 154 mg/m3
would not be an exceedance because it would be rounded to 150 mg/m3; whereas, a recorded value of 155 mg/m3 would be an exceedance because it would be rounded to 160 mg/m3. See 40 CFR part 50, appendix K, section 1.0.
3 78 FR 3806 January 13, 2013.
4 Letter from Laura Yoshii, Acting Regional Administrator, to Governor of Arizona Jan Brewer dated October 14, 2009. By letters dated December 30, 2009, the EPA notified the tribal leaders of the Ak-Chin Indian Community, Gila River Indian Community, and San Carlos Apache Tribe. The EPA
notified Tohono Oodham Nation by letter dated September 21, 2010.
5 For the boundaries of the West Pinal County PM10 nonattainment area, see 40 CFR 81.303. Also, for a detailed discussion of these boundaries, see our final rule at 77 FR 32024 May 31, 2012 and proposed rule at 75 FR 60680 October 1, 2010. No areas of Indian country are located in the West Pinal PM10 nonattainment area.
6 75 FR 60680 October 1, 2010.

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to nonattainment for the PM10 NAAQS
was effective on July 2, 2012.
Consequently, under section 188c1 of the CAA, Arizona was required to submit an implementation plan providing for West Pinal Countys attainment of the PM10 NAAQS as expeditiously as practicable, but no later than the close of the sixth calendar year after redesignation, or December 31, 2018. As specified in our May 31, 2012
rulemaking, the Moderate area PM10
attainment plan for West Pinal County was due on January 2, 2014, 18 months after the effective date of the redesignation, as required by section 189a2B of the CAA.
On December 21, 2015, Arizona submitted The 2015 West Pinal Moderate PM10 Nonattainment Area SIP Moderate Area Plan with related rules and analyses for West Pinal County.7 The submission included rules regulating PM10 emissions from construction sites, crop operations, animal operations, irrigation districts, and general fugitive dust. On May 1, 2017, the EPA approved the submitted rules regulating PM10 emissions from construction sites, crop operations, irrigation districts, and general fugitive dust, but did not act on the remainder of the submission.8
On June 24, 2020, the EPA
determined that the West Pinal County nonattainment area had not attained the 1987 24-hour PM10 NAAQS by the latest permissible December 31, 2018
attainment date and reclassified the area from Moderate to Serious.9 The EPAs finding of failure to attain the NAAQS
by the required date and concomitant reclassification established an 18-month deadline for Arizona to submit a Serious area attainment plan for the West Pinal County PM10 nonattainment area by January 24, 2022.
On January 8, 2021, the EPA proposed a partial approval and partial disapproval of the Moderate Area Plan, proposing to disapprove all elements of the attainment plan, except the emissions inventories.10 Subsequently, on February 26, 2021, we proposed a limited approval and limited disapproval of statutory provisions and rules that govern particulate matter emissions from agricultural activity that Arizona submitted with the plan.11
On May 17, 2021, ADEQ withdrew all submitted portions of the Moderate Area 7 Letter dated December 21, 2015 from Eric C.
Massey, Director, Air Quality Division, ADEQ to Jared Blumenfeld, Regional Administrator, EPA
Region IX.
8 82 FR 20267 May 1, 2017.
9 85 FR 37756 June 24, 2020.
10 86 FR 1347 January 8, 2021.
11 86 FR 11681 February 26, 2021.

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Plan that the EPA had not approved previously into the SIP.12 In addition to the required attainment plan, Arizonas withdrawal action included the agricultural dust regulations that the EPA had not already approved into the SIP. Because Arizona has withdrawn the submission, the State has failed to meet its obligation to submit an attainment plan for the Moderate area attainment plan requirements for the West Pinal County PM10 nonattainment area, providing the basis for this finding.
B. CAA Moderate PM10 Nonattainment Area Requirements for West Pinal County Areas redesignated as nonattainment are subject to the applicable requirements of part D, title I of the CAA and are classified as Moderate by operation of law, consistent with section 188a of the CAA. Within 18 months of the effective date of the redesignation, i.e., by January 2, 2014, Arizona was required to submit an attainment plan to the EPA providing for how the State will meet the PM10 NAAQS within the West Pinal County nonattainment area no later than December 31, 2018.
Among other things, this Moderate area attainment plan must contain statutorily mandated elements and, according to the CAA and EPA guidance, address the following requirements: 1 An approved permit program for construction of new and modified major stationary sources; 13 2 a demonstration that the plan provides for attainment by no later than the applicable Moderate area attainment date or a demonstration that attainment by that date is impracticable; 14 3
provisions for the implementation of reasonably available control measures RACM and reasonably available control technology RACT; 15 4
quantitative milestones that will be used to evaluate compliance with the requirement to demonstrate reasonable further progress RFP; 16 5 evaluation and regulation of PM10 precursors; 17 6
a description of the expected annual incremental reductions in emissions that will demonstrate RFP; 18 7
emissions inventories, as necessary; 19
8 other control measures besides RACM and RACT as may be needed for 12 Letter from Daniel Czecholinski, Arizona Department of Environmental Quality, to Deborah Jordan, EPA Region IX, dated May 17, 2021.
13 CAA section 189a1A.
14 CAA section 189a1B.
15 CAA section 189a1C.
16 CAA section 189c.
17 CAA section 189e.
18 CAA section 172c2.
19 CAA section 172c3.

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