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Federal Register / Vol. 86, No. 122 / Tuesday, June 29, 2021 / Proposed Rules
lotter on DSK11XQN23PROD with PROPOSALS1

or below the NAAQS.5 Additionally, the EPA stated in the Proposed Error Correction that while individually these deficiencies are not dispositive, collectively they are a sufficient basis for the EPA to propose that we erred in relying on the Sierra Club modeling in making the initial nonattainment designations for the three Texas areas.
The EPA received several comments on the Proposed Error Correction. Sierra Club submitted a comment on the Proposed Error Correction that included updated modeling September 2019
modeling. Sierra Clubs updated September 2019 modeling addressed all aspects of the March 2016 modeling that the EPA had identified in the Proposed Error Correction as a limitation or uncertainty. The September 2019
modeling purported to demonstrate that the Martin Lake Electrical Station area did not meet the 2010 SO2 NAAQS at the time of designation in the Round 2
Supplement i.e., December 2016, and also currently does not meet the 2010
SO2 NAAQS based on more recent data.
Sierra Club did not submit updated modeling for the Big Brown and Monticello areas as part of its September 2019 comment submission, but rather asserted that the EPAs previously identified limitations individually or collectively have no material effect on the model results for those areas in the same way as they demonstrated with the Martin Lake areas modeling.
The EPA also notes, upon re-review of the Proposed Error Correction and Round 2 Supplement, that we did not acknowledge in the Proposed Error Correction that we actually considered the collective impact of all these same aspects of the modeling in the record for the Round 2 Supplement to the extent those aspects remained in the March 2016 modeling relied on in the Round 2 Supplement.6 In the Proposed Error Correction, we also did not explain any change in our thinking from our assessment of the collective impact in the Round 2 Supplements record.
As explained further in the technical support document for this withdrawal, the EPA has assessed Sierra Clubs September 2019 modeling submitted during the Proposed Error Correction 5 As explained in the EPAs final designations Technical Support Document TSD, the modeled 99th percentile daily maximum 1-hour SO2
concentrations for the Martin Lake and Monticello facilities are 14 percent and 8 percent above the 2010 SO2 NAAQS, respectively.
6 See pages 2729, 4850, and 7577 of the EPAs final designations TSD, available in the public docket and at https www.epa.gov/sites/
production/files/2016-11/documents/texas_4_
deferred_luminant_tsd_final_docket.pdf.

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public comment period.7 This assessment supports the EPAs previous reliance on the March 2016 modeling as the basis for its final nonattainment designation for the Martin Lake area in the Round 2 Supplement. Based on consideration of that information submitted by commenters and on further consideration of the entirety of our record for the Round 2 Supplement, the EPA now has concerns with the accuracy of the Proposed Error Corrections characterization of the March 2016 modeling and no longer believes that this proposed basis supports the proposed conclusion that an error correction is appropriate or that reliance on such information for the nonattainment designation was in error.
The refined modeling submitted on the Proposed Error Correction demonstrates that the EPAs Round 2 Supplement assessment of the impact of further refining the March 2016 modeling was reasonable and correct, that such refinement would not alter the conclusion that the Martin Lake area was not attaining the NAAQS at the time of the Round 2 Supplement.
Overall, the EPAs assessment of the information and of our record for the Round 2 Supplement for all three areas is that refinement of the aspects of the modeling the EPA identified in the Proposed Error Correction would not alter the EPAs nonattainment designations for any of the three nonattainment area designations in the Round 2 Supplement, and that the submitted information further confirms our Round 2 Supplement analysis of then-available data.
B. Comments on Texass Monitoring Preference In the Proposed Error Correction, the EPA also proposed that when we considered all available information at the time of designation, we erred in failing to give greater weight to the State of Texas preference to use ambient air monitors to characterize SO2
air quality in their state for purposes of the designation. We proposed this despite also acknowledging in the proposal that because these areas around certain SO2 emissions sources were subject to the Round 2 deadline of July 2, 2016, these areas were required to be designated at that time based on the EPAs assessment of available information even though the State of Texas stated a preference to later characterize the areas based on future monitoring data and its intention to install monitors for these areas.
7 See https www.regulations.gov under Docket ID No. EPAHQOAR20140464.

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In addition to the modeling submitted during the public comment period for the Proposed Error Correction, the Sierra Club also commented that the EPA was required to designate the three areas in Texas by the court-ordered deadline based on the information available at that time i.e., Sierra Clubs December 2015 and March 2016
modeling. Because monitoring information was not available in 2016
for the Martin Lake, Big Brown, or Monticello areas, the Sierra Club stated that monitoring data consequently could not inform the EPAs designations decisions. The Environmental Protection Network EPN submitted a similar comment claiming that the EPA
did not have the discretion to delay designations for these three areas in Texas under the applicable courtordered deadline and that the EPA was required to designate the areas based on the best available data at the time of the designations. Additionally, EPN
asserted that Texass preference for future air quality monitoring did not undermine the available modeling data demonstrating that the areas were violating the 2010 SO2 NAAQS.
In light of the comments submitted on the Proposed Error Correction, and the absence of a clearly identified error in the Round 2 Supplement, the EPA no longer believes that this proposed basis supports the proposed conclusion that an error correction is appropriate and no longer believes that we failed to give the appropriate weight to the States preference for future monitoring information when we considered all available information at the time of the Round 2 Supplement. For the reasons discussed below, the EPA has concerns with the prior proposed assertion that the EPA was in error for not giving greater weight to the states preference for future monitoring information in the absence of any available monitoring data at that time, let alone over reliance on then-available air quality modeling to assess SO2 air quality. Given that the Proposed Error Corrections basis was predicated on the EPA relying on or weighing more heavily a preference for information that was not available at the time the EPA was required to finalize the Round 2 Supplement, the EPA no longer believes such a basis provides substantial support for the argument that the Round 2 Supplement should be revised.
CAA section 107d specifies that the EPA make designations based on the air quality at the time of final designations i.e., determining at the time of signature whether the area meets the NAAQS and consider all available information on air quality at that time. In other words, the
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