Je veux savoir à propos de…

1357

Federal Register / Vol. 86, No. 5 / Friday, January 8, 2021 / Proposed Rules The State adopted and preimplemented control measures to meet the contingency measures requirement within the Plan: 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.54 We address the contingency measures requirement of the Act more completely in Section III.F, where we point out that pre-implemented contingency measures are not approvable under CAA section 172c9. Here, we mention the control measures, adopted and subsequently implemented as contingency measures, to emphasize two points: 1 Given the shortfall in attaining the PM10 NAAQS, these control measures designated for contingency should have been evaluated and designated RACM/RACT, as we discussed in Section III.C; and 2
despite implementing the RACM/RACT
control measures for attainment and the designated contingency measures, the West Pinal County area still failed to attain the PM10 NAAQS, by a large margin.

3. The EPAs Review of the States Submission As previously discussed, the EPA
issued a finding that the West Pinal County area failed to attain the PM10
NAAQS by the outermost statutory attainment date of December 31, 2018.55
In addition to our previous regulatory review of the air monitoring data from 20162018, detailed in our June 24, 2020 notice, we reviewed ambient air monitoring data collected from 2006
2018 to examine PM10 values over time and recent trends over the 20162018
control strategy period of Plan implementation. Our detailed review of PM10 data is included in our TSD
provided in the docket for this proposal.
We provide two general conclusions from our data review.
First, when considering the number of exceedances of the PM10 standard, the data show that the West Pinal County monitoring sites have consistently measured many exceedances in every year between the start of the base year period, 20062008, and in 2018, the attainment year. While the number of exceedances each year has generally and gradually decreased over time, there is no clear evidence of a sustained decrease in recent years as ADEQ

implemented control measures. For example, over the 2016 through 2018
period that would have been relevant to attainment by December 31, 2018, the annual number of exceedances of the 24-hour PM10 NAAQS ranged from 29 to 38.56 The form of the NAAQS allows for no more than one exceedance per year, averaged over a three year period.
Furthermore, all eight monitors in the West Pinal County nonattainment area showed violations of the PM10 NAAQS
as determined by their 2018 design values.57
Second, design value trends show that the number of expected exceedances remain well above the PM10 NAAQS of one exceedance per year. The high concentrations and number of exceedances clearly show that PM10
concentrations well above the level of the NAAQS 150 mg/m3 continue to be a major air quality problem in the West Pinal County nonattainment area despite the implementation of control measures meant to reduce PM10 levels.
For example, the design concentration for 20162018, the period in which values should be at or under 150 mg/m3
to show attainment by 2018, is 403 mg/
m3, or 269 percent of the standard.58

TABLE 5THREE-YEAR PM10 MONITORING DATA STATISTICS FOR THE COWTOWN AND HIDDEN VALLEY MONITORING
SITES a 3-Year period
2006
2008

Design Concentration g/m3
3-year Design Value

2007
2009

916
201.2

2008
2010

653
139.8

2009
2011

539
86.1

1064
60.7

2010
2012
1064
63

2011
2013

2012
2014

1064
75.7

521
64

2013
2015
510
50.5

2014
2016

2015
2017

b 357

b 303

b 38.3

b 29.8

2016
2018
403
32.8

tkelley on DSKBCP9HB2PROD with PROPOSALS

Sources: EPA AQS Quick Look Report, December 10, 2020, and EPA AQS Design Value Report, December 10, 2020. The design concentration for these sites is the 4th highest 24-hour concentration measured over each three-year period, as detailed in Section 6.3.1 of the PM10 SIP Development Guideline, EPA450/286
001 June 1987.
a Data collected prior to 2016 were collected from the Cowtown monitoring site; data since 2016 were collected at the Hidden Valley monitoring site, as described in our TSD, page 6, within the docket for this rulemaking.
b The EPAs relocation approval letter stated that the data from Cowtown and Hidden Valley would be combined to form one continuous data record for design value calculations. Consequently, the 20142016 and 20152017 design values are each a composite data record consisting of 2014 and/or 2015 data from the Cowtown monitoring site, and 2016 and/or 2017 data from the Hidden Valley monitoring site, as applicable.

The West Pinal County 2015 PM10
design value was 50.5 exceedances. For the area to meet the PM10 standard by 2018, it could not have more than three exceedances of the PM10 NAAQS across the three years, 20162018, to show a design value of 1.0 exceedances, averaged over three years. Instead, the Plans control strategy resulted in the following number of primary exceedances: 30 in 2016; 38 in 2017;
and 29 in 2018.59 Not only did the Plans control strategy fail to produce the effect intended in 2016, the designated control strategy rules and pre-implemented contingency measures 54 West Pinal County PM
10 Plan, Chapter 6;
Chapter 7, Table 74.
55 85 FR 37756.
56 See Table 2 in the TSD.

VerDate Sep<11>2014

20:05 Jan 07, 2021

Jkt 253001

failed to reduce PM10 exceedances to a level needed to attain the PM10 standard by December 31, 2018.
Given the ambient monitoring data unequivocally indicate that the Plan was insufficient to achieve attainment by the 2018 attainment date, we do not provide an exhaustive evaluation of the attainment demonstration analyses in the West Pinal County PM10 Plan.
Instead, we focused our review on two major deficiencies that preclude our approval of this Plan element. Our review of these two deficiencies is illustrative of the insufficiently conservative analyses or assumptions 57 See
Table 1 in the TSD.
Table 3 and further discussion in Section II.B of the TSD.
58 See
PO 00000

Frm 00055

Fmt 4702

Sfmt 4702

underlying the Plans failed attainment demonstration. Specifically, we evaluated the design days ADEQ
selected to conduct the modeling exercises and the specific design day micro-emissions inventories and rule control effectiveness assumptions ADEQ
made to model the Plans control strategy within the 2018 attainment modeling analyses. Next, we provide a short summary of our review. We also provide a more detailed review in our TSD.
First, we find the design days that ADEQ selected for modeling the Cowtown monitor under stagnation 59 TSD, Table 2; EPA AQS Quick Look Report, December 10, 2020, in the docket for this rulemaking action.

E:FRFM08JAP1.SGM

08JAP1