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Federal Register / Vol. 86, No. 103 / Tuesday, June 1, 2021 / Proposed Rules
upon enactment of the 1990 CAA
Amendments.9
The Yuma PM10 nonattainment area Yuma NAA was one of the areas specified by Congress and designated by the 1990 CAA Amendments.
Specifically, the Yuma NAA was designated nonattainment by section 107d4Bi of the Act and classified as Moderate because it had been previously categorized as a Group I
area.10 The EPA announced the Yuma NAA designation, as required by section 107d2 of the Act, on March 15, 1991.11 In accordance with CAA section 189a2, Arizona was required to submit a SIP revision meeting applicable nonattainment plan requirements by November 15, 1991, demonstrating attainment of the 1987
p.m.10 NAAQS in the Yuma NAA by December 31, 1994.12
C. The Clean Data Policy and the 2006
Clean Data Determination In nonattainment areas where monitored data demonstrate that the NAAQS has been attained, the EPA
interprets certain requirements of the Act as no longer being applicable for so long as air quality continues to meet the NAAQS in the area. This interpretation is known as the clean data policy, and EPA findings issued under this policy are known as clean data determinations. On March 14, 2006, the EPA issued a clean data determination for the Yuma NAA for the 1987 24-hour PM10 NAAQS, based on complete, quality-assured and certified PM10 monitoring data for 20022004.13
Because the data from 20022004 were complete and showed no exceedances of the relevant NAAQS, and because preliminary data for 2005 also indicated no such exceedances, the EPA
concluded that the Yuma NAA was in attainment for the 1987 24-hour PM10
NAAQS.14 Based on this finding, the EPA determined that certain nonattainment plan requirements in the Yuma NAA were not applicable for so long as the Yuma NAA continued to 9 See
CAA section 107d4Biii.
FR 29383 August 7, 1987.
11 56 FR 11101.
12 Arizona submitted a Moderate area plan for the Yuma NAA on November 14, 1991. The EPA found this plan to be incomplete on May 14, 1992.
Arizona submitted a revised plan for the Yuma NAA on July 12, 1994, but withdrew this plan in 2006, following the EPAs issuance of a clean data determination for the Yuma NAA.
13 71 FR 13021 March 14, 2006.
14 The clean data determination also applied to the annual PM10 NAAQS, but that NAAQS was revoked later that year. See 71 FR 61144 October 17, 2006.

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monitor attainment of the 1987 24-hour PM10 and annual NAAQS.15
II. Current Monitoring Data In accordance with 40 CFR part 50, appendices J and K, a finding of whether an area has attained or is currently attaining the 1987 24-hour PM10 NAAQS must generally be based upon certified, complete, qualityassured data gathered at monitoring sites in the nonattainment area and entered into the EPAs Air Quality System AQS database. For the 1987
24-hour PM10 NAAQS, appendix K
provides that all data produced by state and local air monitoring sites SLAMS
and other sites submitted to the EPA in accordance with the part 58
requirements be used for evaluating attainment.16
In order to assess whether an area is currently attaining the NAAQS, the PM10 ambient air quality monitoring data collected by the state within the area for the three-year period must meet data completeness criteria, or otherwise unambiguously establish nonattainment according to 40 CFR part 50, appendix K, section 2.3. The ambient air quality monitoring data completeness requirements are met when quarterly data capture rates for all four quarters in a calendar year over a three-year period are at least 75 percent. For purposes of this proposal, we reviewed the data for the 20172019 period for completeness and determined that the PM10 data met the completeness criterion for all 12
quarters at the Yuma Supersite PM10
monitoring site in the Yuma NAA.17
The Arizona Department of Environmental Quality ADEQ is the governmental agency with the authority and responsibilities under the States laws for collecting ambient air quality data for the Yuma NAA. ADEQ submits annual monitoring network plans to the EPA.18 These plans discuss the status of the ambient air monitoring network, as required under 40 CFR part 58. The EPA
reviews these annual network plans for compliance with the applicable reporting requirements in 40 CFR 58.10.
With respect to PM10, the EPA has 15 In the same Federal Register document, the EPA also determined pursuant to CAA sections 179c1 and 188b2 that the Yuma NAA had attained the NAAQS by the Moderate area attainment date of December 31, 1994. Because that determination was tied to that specific attainment date, it would not be affected by the rescission of the clean data determination proposed in this action.
16 40 CFR part 50, appendix K, section 2.3a.
17 EPA, AQS Design Value Report, dated March 31, 2021. This report is included in the docket.
18 See, e.g., State of Arizona Air Monitoring Network Plan for the Year 2020. Copies of Arizonas Annual Network Plans for 20182020 are included in the docket.

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found that the 20182020 annual network plans submitted by ADEQ, which reflect the network during the 20172019 design value period, met the applicable requirements under 40 CFR
part 58.19 Furthermore, we concluded from our 2018 technical systems audit of ADEQs ambient air quality monitoring program that the ambient air monitoring network currently meets or exceeds the requirements for the minimum number of monitoring sites designated as SLAMS for PM10 in the Yuma NAA.20 ADEQ certifies annually that the data it submits to AQS are quality-assured and has done so for each year relevant to our proposed action, 20172019.21
Table 1 provides the 2019 p.m.10
design value for the Yuma Supersite, the sole regulatory monitoring site measuring ambient PM10 within the Yuma NAA, expressed as a single value representing the average expected annual exceedances over the three-year period, 20172019. The PM10 data show that the design value is greater than 1.0
estimated annual average exceedances of the 1987 24-hour PM10 NAAQS.
Consequently, the EPA proposes to determine, based upon three years of complete, quality-assured and certified data from 20172019, that the Yuma NAA is no longer attaining the 1987 24hour PM10 NAAQS.

TABLE 120172019 DESIGN VALUE
FOR THE 1987 24-HOUR PM10
NAAQS FOR THE YUMA NAA
Monitoring site
AQS
identification No.

Design value
Yuma Supersite

040278011

5.7

Source: EPA, AQS Design Value Report, dated March 31, 2021, 15.

We have also reviewed preliminary 2020 data, which indicate that the Yuma NAA had a 20182020 design value of 5.4.22 This preliminary design value 19 See, e.g., letter dated November 8, 2019, from Gwen Yoshimura, Manager, EPA Region IX, Air Quality Analysis Office, to Daniel Czecholinksi, Acting Director, Air Quality Division, ADEQ.
Copies of EPA letters responding to Arizonas Annual Network Plans for 20182020 are included in the docket.
20 Letter dated April 25, 2019, from Elizabeth Adams, Director, EPA Region 9 Air Division to Timothy Franquist, Director, Air Quality Division, ADEQ, enclosure titled Technical Systems Audit of the Ambient Air Monitoring Program: Arizona Department of Environmental Quality, April 2
April 6, 2018, Network Requirements section, 8.
21 See, e.g., letter dated April 13, 2020, from Daniel Czecholinksi, Director, Air Quality Division, ADEQ, to Gwen Yoshimura, Manager, EPA Region IX, Air Quality Analysis Office. Copies of ADEQ
certifications and their respective transmittal letters for years 20172019 are included in the docket.
22 EPA, AQS Design Value Report, dated March 3, 2021.

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