Voglio sapere a riguardo di…

tkelley on DSKBCP9HB2PROD with PROPOSALS

Federal Register / Vol. 86, No. 5 / Friday, January 8, 2021 / Proposed Rules these adopted control measures were insufficient to attain the PM10 NAAQS
by the applicable attainment date, in part because the State overestimated the effectiveness of the RACM/RACTdesignated adopted controls. As an example, ADEQ assumed high and insufficiently conservative compliance rates for agricultural operations that had either no previous experience implementing control measures, or little to no reliable documented compliance history. We review the States analysis and attainment demonstration in Section III.D and provide detailed discussion in the Technical Support Document TSD.
The Plan described the adopted control measures and concluded that a subset was reasonable and would achieve the NAAQS by the attainment date; therefore, the State concluded that the RACM/RACT-designated subset of adopted control measures constituted the necessary RACM/RACT for the area.49 The State adopted several additional measures beyond the RACM/
RACT measures to serve as contingency measures in the Plan. If the RACM/
RACT-designated adopted controls actually sufficed to achieve attainment, then these control measures could have constituted sufficient RACM, as additional measures beyond those necessary for attainment need not necessarily be considered as RACM/
RACT.50 Because the adopted controls designated as RACM/RACT in the West Pinal County PM10 Plan were insufficient, however, to achieve attainment, due in part to overestimates of the control efficiency of these rules, we find that the State terminated its RACM/RACT analysis prematurely. The control measures reserved for contingency measures that the State did not include as RACM/RACT should have been included and justified as RACM. Furthermore, because the States determination regarding PM10
precursors failed to demonstrate that precursors do not contribute significantly to a violation of the NAAQS, the State remains obligated to demonstrate that additional PM10
precursor control measures are not required RACM/RACT.
Despite the RACM/RACT-designated rules and contingency measures adopted and implemented by the State, we find that the State failed to adopt RACM/RACT sufficient to achieve the PM10 NAAQS, due in part, to overestimating the control effectiveness 49 Appendix
F, Chapter 4.
81 FR 58010, 58035. Although such controls should be evaluated to determine if their adoption could advance attainment.
50 See
VerDate Sep<11>2014

20:05 Jan 07, 2021

Jkt 253001

of these RACM/RACT control measures.
Our conclusion is confirmed by the failure of the Plans adopted and designated measures to result in attainment of the PM10 NAAQS by the applicable attainment date of December 31, 2018. Because the adopted controls were insufficient to meet the PM10
NAAQS by the attainment date, and the State excluded source categories, including sources of precursors, from its RACM/RACT demonstration without sufficient justification, we propose to disapprove the RACM/RACT
demonstration in the West Pinal County PM10 Plan and determine that the Plan does not provide for the implementation of all RACM/RACT as required by CAA
section 172c1 and section 189a1C.
D. Attainment Demonstration 1. Statutory and Regulatory Requirements Section 189a1B of the CAA
requires that a plan for a Moderate PM10
nonattainment area include a demonstration including air quality modeling that the plan will provide for attainment of the PM10 NAAQS by the applicable attainment date. An attainment demonstration consists of several elements including technical analyses, such as base year and future year modeling, to locate and identify sources of emissions that are contributing to violations of the PM10
NAAQS within the nonattainment area i.e., analyses related to the emissions inventory for the nonattainment area and the emissions reductions necessary to attain the standard. Section 188c1
of the CAA requires Moderate areas to meet the PM10 standard as expeditiously as practicable, but no later than the sixth calendar year from the area designation.
In addition to reviewing the attainment demonstration modeling and related analyses, we evaluate the Plans control strategy and the efficacy of the Plans adopted controls to meet the PM10 NAAQS by the applicable date.
2. Summary of the States Submission ADEQ applied a form of proportional roll back and dispersion modeling using a micro-emissions inventory method to model attainment of the PM10 NAAQS.
ADEQ modeled two meteorological scenarios causing ambient air values in excess of the 24-hour PM10 NAAQS of 150 mg/m3, high wind conditions and stagnant or low wind conditions, at a representative subset of the monitoring sites in the nonattainment area.51 Under 51 West
PO 00000

Pinal PM10 Plan County, Section 7.1.

Frm 00053

Fmt 4702

Sfmt 4702

1355

stagnation conditions, wind speeds are typically below 3 mph and particles accumulate in the air without any meteorological reprieve. Under high wind conditions, elevated wind speeds e.g., over 12 mph generate dust from disturbed soil surfaces, elevating PM10
concentrations. Each selected monitoring site in each modeling scenario had design day specific microemissions inventories consistent with the chosen areal modeling domain and application. ADEQ calculated the 2008
Base, 2018 Base, and 2018 Attainment micro-emissions inventories for the given requirements of the modeling application at the respective monitoring site domain and meteorological day scenario.
The States attainment demonstration approach is described in the Plan within the following documents: Chapter 7, Attainment Demonstration and Reasonable Further Progress;
Appendix A, Pinal County PM
Inventory Preparation Plan IPP;
Appendix B, Pinal County PM10
Nonattainment Area Emissions Inventories for 2008 and 2018 Base Years and Design Days Modeling EI; Appendix C, Pinal County PM10
Nonattainment Area Source Apportionment Modeling for 2008 and 2018 Base Scenario Design Days Modeling TSD; and, Appendix D, Pinal County PM10 Nonattainment Area 2018 Attainment Demonstration and Controlled Emissions Inventories.
The West Pinal County PM10 Plan discusses the control strategy within Chapter 6 of the Plan and in more detail within Appendix D of the Plan.
a. Modeling As noted, the West Pinal County PM10
Plans attainment demonstration considers two specific problems contributing to nonattainment of the PM10 standard in West Pinal County: 1
PM10 emissions from windblown dust and human activity on days with elevated wind speeds; and 2 PM10
emissions from human activity, particularly on days with very low wind or stagnant meteorological conditions.
ADEQ developed a high wind day scenario for Cowtown, Maricopa, Pinal County Housing, and Stanfield monitors and surrounding area micro-emissions inventories. Each monitor has its own two domain micro-emissions inventory for modeling: High wind hours/
windblown dust; and, low wind hours/
activity-based emissions. The high wind scenario used a proportional rollback approach that accounts for the timing
E:FRFM08JAP1.SGM

08JAP1