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Federal Register / Vol. 86, No. 5 / Friday, January 8, 2021 / Proposed Rules
tkelley on DSKBCP9HB2PROD with PROPOSALS

as part of the states nonattainment plan SIP submission for the area.
The EPA has provided guidance interpreting the RACM requirement in the General Preamble for the Implementation of the Clean Air Act Amendments of 1990 General Preamble. This guidance includes the following elements and concepts: A
recommended list of potential PM10
measures for states to consider; 36 an emphasis on a states evaluation of the technological and economic feasibility of potential control measures to determine if such measures are reasonably available for implementation in a given nonattainment area; an expectation that the state will provide a reasoned explanation for a decision not to adopt a given control measure, including a review of any control measures recommended to the state during public comment or public hearing; and, a discussion that in some cases partial implementation of an emissions reduction program may be considered RACM when full implementation would be infeasible within the given Moderate area timeframe.37
2. Summary of the States Submission For the West Pinal County PM10 Plan, ADEQ worked through a process to identify and evaluate potential RACM/
RACT that could contribute to expeditious attainment of the PM10
NAAQS in the West Pinal County nonattainment area. Chapter 6 of the West Pinal County PM10 Plan provides an overview and description of the Plans constituent control measures.
ADEQs RACM/RACT analysis for the PM10 standard is described in Appendix FRACM Analysis for the West Pinal County PM10 Nonattainment Area Appendix F. Appendix F contains summary analyses of potential control measures for emissions reduction opportunities, as well as the economic and technological feasibility and comparability with control requirements in other states and localities.
As a first step in the RACM/RACT
analysis, ADEQ prepared a detailed inventory of direct PM10 emissions sources to identify source categories from which emissions reductions would contribute to attaining the PM10
standard.38 In this analysis, ADEQ
identified point sources, unpaved roads and agriculture on tribal land, dairy operations, nonroad vehicles, residential fuel combustion, and open burning as insignificant sources of 36 57

FR 18070.
FR 13540, 13541.
38 Appendix F, Chapters 2 and 3.
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emissions in the area.39 Then, ADEQ
identified agricultural operations, confined animal feeding operations, fugitive dust from cleared area and unpaved parking lots, construction fugitive dust, and re-entrained dust from paved and unpaved roads as significant sources in the nonattainment area and determined a list of available control measures. ADEQ determined that a source category was significant if those sources contributed more than 5 mg/m3
on a 24-hour basis on a given design day. Conversely, ADEQ determined that source categories contributing less than the 5 mg/m3 threshold were insignificant; furthermore, ADEQ
determined these insignificant sources would not advance attainment of the NAAQS, given their small collective contribution to nonattainment.40
Finally, ADEQ evaluated the efficacy, cost, and technical feasibility of these identified control measures within the nonattainment area.41 As part of this review, ADEQ also compared the control requirements of its proposed rules with those requirements in other PM10 nonattainment areas or similar state and local provisions.42 ADEQ did not identify sources or analyze potential RACM/RACT for PM10 precursors because it concluded that such precursors did not contribute significantly to a violation of the NAAQS.
With this process, ADEQ attempted to evaluate and analyze the universe of potential RACM/RACT level controls for sources of direct PM10 emissions and identify the subset of control measures that were available to include within the West Pinal County PM10 Plan. ADEQ
identified a set of control measures that it determined would be sufficient to enable the area to attain by December 31, 2018, and additional controls that it determined were not necessary for attainment or RFP to serve as contingency measures.43 ADEQ based this conclusion on: 1 The practical feasibility of adopting control measures over the latter half of 2015 with the States desired implementation date of no later than January 1, 2016; and 2
the ability of these control measures to produce immediate emissions reductions and contribute to attainment of the PM10 NAAQS by 2018.44 As 39 Appendix
F, 412.
F, Chapter 2 and Table 1.
41 Appendix F, Chapters 24.
42 Appendix F, Chapter 4; Exhibit FI, Available Measures; Exhibit FII, Construction Comparison;
Exhibit FIII, Agricultural Comparison; and, Exhibit FIV, Fugitive Dust Comparison.
43 West Pinal County PM
10 Plan, Chapter 7; Table 74; Appendix D, Table D51.
44 Appendix F, 29, 47, 51.

discussed earlier, the State submitted the following control measures with the West Pinal County PM10 Plan: The AgBMP Rules for Pinal County, the Pinal County Fugitive Dust Rule, and the Pinal County Construction Dust Rule. ADEQ relied only on the following portions of the AgBMP Rules for Pinal County to meet the RACM/RACT
requirements and demonstrate attainment of the PM10 standard:
AgBMP rule R182610 and 610.03, commercial farms; AgBMP rule R182
611 and 611.03, commercial animal operations except for dairy operations;
and R182612 and 612.01, irrigation districts.45
ADEQ did not provide a complete or systematic analysis of whether the control measures it did not adopt based on concerns about a lack of immediate emission reduction effect, if taken together, would advance the areas attainment date. Nonetheless, ADEQ did adopt those control measures, implemented them over the 20162018
timeframe, and allocated them to serve as contingency measures in the Plan.
ADEQ designated the portion of the AgBMP Rules for Pinal County applicable to dairy operations R182
611 and 611.03, along with the Pinal County Fugitive Dust Rule and the Pinal County Construction Dust Rule, as contingency measures because these rules provided additional emissions reductions not relied upon within the Plans attainment demonstration.46
3. The EPAs Review of the States Submission As described above, ADEQ evaluated a wide range of potentially available measures for the West Pinal County PM10 Plan. ADEQ identified portions of the AgBMP Rules for Pinal County as RACM/RACT and the State adopted them to provide for attainment of the PM10 standard.47 The remaining adopted control measures, some of which were identified as significant sources and potential RACM/RACT, were assigned to provide for contingency measures within the Plan.48 In sum, all source categories identified as significant were covered by controls either as a control measure for attainment, or as contingency measures, and implemented over the 20162018
timeframe. As has been confirmed by subsequent monitoring data, however,
40 Appendix
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45 West
Pinal County PM10 Plan, Chapters 6 and
7.
46 West Pinal County PM
10 Plan, Chapter 6;
Chapter 7, Table 74.
47 West Pinal County PM
10 Plan, Chapters 6 and 7.
48 West Pinal County PM
10 Plan, Chapter 6;
Chapter 7, Table 74.

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