Quiero saber acerca de...

jbell on DSKJLSW7X2PROD with RULES

15114

Federal Register / Vol. 86, No. 53 / Monday, March 22, 2021 / Rules and Regulations
the States analysis. Taken as a whole, the record supports approval of the States determination that the BART
alternative achieves greater reasonable progress than BART under the clear weight of evidence pursuant to 40 CFR
51.308e2iE.
Comment A.4: EPA fails to provide a basis to rely on a comparison of emissions. EPA merely presents the emission reductions under BART and the alternative, but fails to explain the strengths and weaknesses of this information and does not assign any weight to the emission comparison. A
comparison of multiple pollutant species emission levels alone is not informative without visibility modeling.
The pollutants differing visibility impacts and complex interactions between them and in the atmosphere make it extremely difficult to discern their collective impacts without visibility modeling. EPA has consistently relied on modeling to assess the visibility impacts under these circumstances.
Response: We disagree with the commenters assertion that EPA merely presents the emission reductions under BART and the alternative. In our proposed action,68 our basis for presenting the emission reduction information laid the foundation for describing the differences in visibility outcomes achieved between the FIP and the BART alternative, leading EPA to agree with the State that there was a need to support the BART alternative with visibility modeling. The State first showed reduced emissions from the baseline and then used the modeling to support a conclusion that the emission reduction differences between the FIP
BART benchmark and BART alternative were acceptable because NOX precursor emissions are the main driver contributing to the visibility impacts from this source. Thus, the State proceeded to conduct precisely the modeling analysis the commenter seems to assert is required, using CALPUFF.
Indeed, recognizing the potential interaction between multiple species of visibility pollutants, the State used Method 2 in evaluating the visibility consequences of the BART alternative compared to the BART benchmark. EPA
has relied on the modeling submitted by the State in reaching a conclusion that the SIP submittal is approvable. While EPA does not concede that modeling is required in all cases to conduct an approvable clear weight of evidence analysis under 51.308e2iE, modeling was in fact done in this instance to support the analysis. This 68 85

FR 14847, 14857.

VerDate Sep<11>2014

16:10 Mar 19, 2021

comment is thus premised on a misunderstanding of the record.
To the extent the commenter is asserting that the emissions comparisons alone cannot be used as even one part of a weight of evidence demonstration, the commenter is mistaken in how a weight of evidence analysis is conducted. The term weight connotes that multiple pieces of evidence are brought together and analyzed as a whole.69 Comparative emissions data is obviously a critical piece of that evidentiary record, and provides a foundation on which further analysis, such as modeling, may be conducted. To assert that EPA must ignore emissions comparisonsor any single piece of evidencebecause it does not provide, on its own, a sufficient basis to make a weight of evidence determination is both illogical and a misreading of EPAs regulations. We also note that the regulations require an analysis of emission reductions under BART and the alternative, see 40 CFR
51.308e2iC and D.
Comment A.5: EPA should not provide weight to modeling data of insufficient quality, which fails to meet the requirements of the regulations. It is disingenuous for EPA to suggest that the CALPUFF model is a modified version of the two-part modeling test.
EPA has consistently interpreted the two-part dispersion modeling test under 40 CFR 51.308e3 to mean the Comprehensive Air Quality Model with Extensions CAMx model, and not CALPUFF. EPA and states have consistently used CAMx to assess whether a BART alternative would result in greater reasonable progress under the two-prong test. CAMx and CALPUFF are vastly different models and 40 CFR 51.308e3 requires a specific type of dispersion modeling.
EPAs suggestion that use of CALPUFF
is acceptable because it is consistent with the approach recommended by the BART guidelines for comparing different control options at a single source when developing BART
determinations relying on the 98th percentile visibility impact as the key metric also fails. A comparison of control options at a single source compares changes in the emission reductions in one pollutant, but does not compare the complexities involved in analyzing interactions between multiple pollutants. It is also irrelevant that only the BART sources at Domtar are under consideration. While the FIP
considered each pollutant separately, the alternative attempts to analyze and 69 See
Jkt 253001

PO 00000

71 FR 60612, 60622 October 13, 2006.

Frm 00046

Fmt 4700

Sfmt 4700

take credit for combined emission reductions from three pollutants as it fails to actually assess the effect of the alternative on visibility as compared to BART.
Response: We disagree with the comment that CAMx must be used for the two-part test under 40 CFR
51.308e3 or that CALPUFF cannot be used to support the determination here, which is not under 40 CFR 51.308e3
in any case. The first point is irrelevant because the State is not proceeding under 40 CFR 51.308e3; however, it is worth noting that the regulatory text does not require the use of CAMx.
CALPUFF is also an air dispersion model, and one that the Agency has recognized as available for use for BART
alternatives under 40 CFR
51.308e3.70
Regarding the use of CALPUFF, we did not suggest that CALPUFF was replacing CAMx under 40 CFR
51.308e3. We logically examined the two-part analysis under 40 CFR
51.308e3 in the proposed action to show how the State arrived at classifying the approach as a weight of evidence approach. Our choice of using the term modified to describe the relationship of this analysis to the twopart test under 40 CFR 51.308e3 was intended to describe how the States approach was similar to 40
CFR51.308e3 in considering distribution of emissions and visibility improvements using modeling, but different from 40 CFR 51.308e3
because the analysis based on the CALPUFF modeling focused on the 98th percentile visibility impacts instead of the twenty percent best and worst days required by 40 CFR 51.308e3.
Therefore, the States weight of evidence analysis is acceptable under 40 CFR
51.308e2iE and should not be judged according to 40 CFR 51.308e3.
The commenters objection to 40 CFR
51.308e3 not being met is immaterial since the weight of evidence approach followed in the SIP submittal does not fall under 40 CFR 51.308e3 but under 40 CFR 51.308e2iE.
The commenter states that EPA is wrong to consider CALPUFF as acceptable just because it is consistent with the approach recommended by the BART guidelines for comparing different control options at a single source when developing BART
determinations relying on the 98th percentile visibility impact as the key metric. The commenter points out that a comparison of control options at a single source compares changes in the emission reductions in one pollutant, 70 See
E:FRFM22MRR1.SGM

71 FR 60612, 60616.

22MRR1