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Federal Register / Vol. 86, No. 53 / Monday, March 22, 2021 / Rules and Regulations
the States analysis based on the 98th percentile day, which was selected as representative of the highest impact the 8th highest day. The average results across the top ten highest impacted days also supported our position that it is appropriate to give greater weight to Caney Creek impacts 0.9819 dv baseline impairment in our consideration of whether the BART
alternative achieves greater reasonable progress than BART since they are much larger than impacts at the other Class I areas. The BART alternative resulted in more visibility improvement at Caney Creek and slightly less at the other Class I areas when compared to the BART limits, but the visibility improvement at Caney Creek outweighed the difference in visibility benefit at the other three Class I areas altogether. On average, the BART
alternative controls achieved greater overall visibility improvement from the baseline compared to BART for the ten highest impacted days 0.439 Ddv for the alternative versus 0.423 Ddv for BART. Our analysis of the ten highest impacted days similarly supported the conclusion that the BART alternative provides for greater reasonable progress than BART. Finally, we complemented the States analysis by evaluating the modeled number of days impacted by Domtar over 1.0 dv and 0.5 dv for each scenario at each Class I area. This compared the frequency and duration of higher visibility impacts between the two control scenarios. The BART FIP
limits and the BART alternative both reduce the total modeled number of days with visibility impacts over 1.0 dv from fifteen days in the baseline to four days for each scenario. For the metric of days with modeled visibility impacts over 0.5 dv, the FIP limits and the BART
alternative showed nearly identical reduction in the number of days, but very slightly favored the FIP limits over the BART alternative from 82 to 36
days for the FIP limits compared to 37
days for the BART alternative. This single metric, however, on which BART
performed slightly better than the BART
alternative days impacted over 0.5 dv is not sufficient to outweigh the substantial evidence presented using the other metrics as to the relatively greater benefits of the BART alternative over BART. These different metrics reinforce the States analysis in the SIP that greater reasonable progress was achieved by the BART alternative.58
The States weight of evidence analysis of emission reductions and 58 See discussion regarding the different metrics in the March 16, 2020 proposed approval 85 FR
14847, 1485914860.

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visibility improvement using the 98th percentile metric as complemented by our analysis of different metrics, justify our approval of the States determination that the BART alternative achieves greater reasonable progress than BART under 40 CFR
51.308e2iE. The State followed the prescribed process for determining the level of control required for the BART
alternative for the Domtar Ashdown Mill and adequately supported its determination with analysis that meets the requirements under section 40 CFR
51.308e2.
Comment A.2: EPA proposes approving the Arkansas Regional Haze Phase III SIP and relaxing the BART
emission limitations established in its 2016 FIP. The proposed facility-wide emission limitation would allow for fewer emission reductions from the Domtar Ashdown Mill. EPAs proposal reverses course on its FIP, failing to make reasonable progress on reducing visibility impairment in Class I areas in accordance with the CAA mandates and requirements.
Response: The BART alternative establishes pollutant-specific limits at each of the two BART sources at the Ashdown Mill. There is no facilitywide emission limitation as stated by the commenter. In addition, we disagree with the commenter that the EPA is reversing course on its FIP by relaxing BART limitations established in the FIP, and thus failing to make reasonable progress and reduce visibility impairment in Class I areas in accordance with the CAA and its mandates.
The BART alternative results in larger reductions in NOX and PM emissions than required by the FIP, while SO2
emissions are not reduced to the same extent as would be required under the FIP. As explained in our response to comment A.1 of this final action and also in section IV of our proposed action, our analysis of the States weight of evidence conclusion as complemented by EPAs analysis, demonstrate that the State has met the BART and reasonable progress requirements for regional haze under the applicable provisions of the CAA
and the Regional Haze Rule. Thus, the proposed withdrawal of the BART
provisions in the FIP and replacement with the BART alternative requirements in the SIP will not result in a failure to meet the applicable requirements.
The Arkansas Regional Haze Phase III
SIP revision and concurrent withdrawal of the corresponding parts of the FIP
pertaining to Domtar will also not reverse course from the prior FIP with respect to the separate reasonable
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progress requirements for Arkansas. As mentioned in section IV of our proposed action, we determined in our September 27, 2019 Arkansas Regional Haze SO2
and PM SIP revision that Arkansas had fully addressed the reasonable progress requirements under 40 CFR 51.308d1
for the first implementation period in that final action. In that action, we also noted that the 2016 FIP BART
determination requirements for Domtar were still in place but we agreed with the State that as long as those requirements continued to be addressed by the measures in the FIP, nothing further is needed to satisfy the reasonable progress requirements for the first implementation period. In the Arkansas Regional Haze Phase III SIP
submittal, the State assessed whether changes would be needed with respect to the reasonable progress analysis, based on any differences between the SIP and FIP-based measures for Domtar.
The BART alternative analysis performed for the Domtar power boilers was based, in part, on an assessment of the same factors that must be addressed in the reasonable progress analysis. The FIP BART determination analysis was compared to the proposed BART
alternative controls in the Arkansas Regional Haze Phase III SIP submittal.
The BART alternative measures for Domtar resulted in greater overall visibility improvement than the BART
requirements in the FIP and the previously approved BART PM10 limit for Power Boiler No. 1. As a result, nothing further is needed to satisfy the reasonable progress requirements for the first implementation period. For these reasons, approval of the Arkansas Regional Haze Phase III SIP revision and concurrent withdrawal of the corresponding parts of the FIP do not interfere or reverse course from the FIP
with respect to the CAA requirements pertaining to BART or reasonable progress under 40 CFR 51.308d or e.
Comment A.3: EPAs proposal cobbles together two pieces of information a comparison of emission reductions and a modeling analysis and fails to demonstrate that the BART alternative is clearly better than BART. The Regional Haze Rule provides different regulatory tests for a state to use to demonstrate that a BART alternative is better than BART. Arkansas claims that it used the clear weight of evidence test, but the information it provides falls under 40 CFR 51.308e: An emission reduction comparison and modeling. The information Arkansas provides fails to meet the requirements in 40 CFR 51.308e. Therefore, it is
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