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Federal Register / Vol. 86, No. 232 / Tuesday, December 7, 2021 / Rules and Regulations
we, us, or our is used, we mean EPA.

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I. Background Information On August 17, 2021 86 FR 45947, EPA proposed to determine that the St.
Clair SO2 nonattainment area St. Clair area has attained the 2010 SO2 NAAQS.
This determination, also known as a Clean Data Determination CDD, would suspend certain planning requirements for the nonattainment area for as long as the area continues to attain the 2010
SO2 NAAQS. EPA also proposed to require the Michigan Department of Environment, Great Lakes, and Energy EGLE to submit annual statements to address whether the St. Clair area has continued to attain the 2010 SO2
NAAQS. A detailed analysis of EPAs proposed decision was provided in the August 17, 2021, notice of proposed rulemaking NPRM and will not be restated here. The public comment period for this NPRM ended on September 16, 2021. EPA received five comment submittals on the proposed action.
II. Response to Comments EPA received two anonymous comments and two comments from citizens, all in support of EPAs action.
EPA acknowledges these supportive comments. EPA also received a detailed comment document from the Sierra Club the commenter, which includes adverse comments on EPAs proposed action. EPA is addressing these comments below. EPA notes that the commenter frequently refers to information given in an EGLE document which was not part of EGLEs July 24, 2020, CDD submittal. The document is entitled Proposed Sulfur Dioxide OneHour National Ambient Air Quality Standard State Implementation Plan SIP for St. Clair County Nonattainment Area, dated October 7, 2019. EPA will refer to this document as the 2019
draft. The commenter claimed that this document was submitted to EPA in 2019 for approval and has requested that if there is a final version of the document, that it be added to the docket for this action, but in fact, neither the 2019 draft nor any final version of the 2019 draft document was submitted to EPA as a SIP revision or as part of EGLEs CDD request. EPA considers the 2019 draft document and its contents to be a draft State product which predated and has limited relevance to EGLEs July 24, 2020, CDD request. EPA
has no final version of the 2019 draft to docket, but will retain the 2019
draft in Docket ID No. EPAR05OAR
20200385 as an exhibit attached to Sierra Clubs comment.

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Comment A: At several places in the Sierra Club comment document, the commenter suggests that certain emission reductions which have been discussed or imposed in the time since the St. Clair area was designated nonattainment should be evaluated for adequacy to provide for full attainment or imposed quickly under a State or Federal plan to provide for healthy air.
The commenter additionally requests that EGLE should perform various new modeling analyses either before the CDD
is finalized, or during the time that the CDD is in place. These requested analyses would be used to show whether further State regulations are needed to bring healthy air into the St.
Clair area. The commenter also states that EPA should not allow delays in achieving healthy air in the St. Clair area.
Response A: In its August 17, 2021, NPRM, EPA presented evidence and proposed to find that the St. Clair area has attained the 1-hour SO2 NAAQS as of 20172020. To the extent that the commenter is asserting that additional measures must be adopted in order for the area to attain the NAAQS, we do not agree. The CDD would cause no delays, as the St. Clair area and surrounding communities have already demonstrated air quality values that meet the healthbased NAAQS. Therefore, Clean Air Act CAA planning requirements for nonattainment areas can be suspended under a CDD, and no further analyses or emission reduction actions are required of EGLE at this time. As stated in the proposal, EGLE will be required to provide demonstrations on an annual basis that the area continues to attain the NAAQS, and if EPA determines in the future that the area is no longer attaining the NAAQS, the CDD would be rescinded.
Comment B: The commenter asserted that EGLEs request for a CDD relied on the assumption that the St. Clair plants expected closure will allow the State to formally demonstrate attainment, despite the emissions from the Belle River plant and a new gas power plant.
The commenter stated that this assumption has not been tested and should be tested before moving ahead with the CDD. The commenter stated that nothing in the CAA allows EPA to suspend immediate action in anticipation of emission reductions accompanying a plant retirement that is still more than a year away.
Response B: The plan to close the St.
Clair plant in 2022 was not a factor which EGLE or EPA relied upon to justify the determination of attainment.
EGLEs CDD request relied on actual emissions and monitoring data, and a
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finding that the area is attaining the NAAQS based on those emissions and monitoring data. In finalizing a CDD, EPA is suspending the CAA obligation to submit attainment planning requirements because the area is currently attaining the standard, regardless of any anticipated future emission reductions, including the planned plant retirement. EPA does not agree that additional modeling analyses are required at this time for EPA to find that this area is currently attaining and to finalize the CDD. Such analyses that the commenter is requesting might instead be expected in a future redesignation request or nonattainment SIP. It is worth noting that although the St. Clair CDD is already fully supported by air quality data, if a coal power plant were to permanently and enforceably close in the St. Clair area, any actual SO2 emission decreases that occur would only help the area stay in attainment under the CDD and help provide a path forward to eventual redesignation of the area to attainment.
Comment C: The commenter stated that EPA should ensure it is not delaying action that may be needed to demonstrate that the area is meeting the NAAQS based not only on actual emissions, which can increase, but on allowable emissions. The commenter stated that EPA should determine if further action will be needed following St. Clairs retirement, and if so, EGLE
should be developing additional measures now, rather than waiting until a monitoring violation occurs and the CDD must be rescinded. Waiting to restart the process of developing needed measures until after rescission of the CDD would cause delays.
Response C: The St. Clair area is currently meeting the 2010 SO2 NAAQS
and therefore, EPA may finalize this CDD. Enforceable allowable emission limits would be expected in a subsequent redesignation request.
Again, however, EPA does not require additional action from EGLE for the St.
Clair area while the CDD is in place and the area continues to attain the standards.
Comment D: The commenter stated that EPAs NPRM does not explicitly address whether the DTE monitors meet the criteria in 40 CFR part 58, appendices A, C, and E; whether EGLE
submitted relevant information for EPA
to make this assessment, and whether relying on this data is consistent with other treatment of third-party monitoring.
Response D: As stated in the NPRM, EPA reviewed monitoring data and evidence that quality assurance activities had been performed. EPA

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