Document ID: ./input/supremecourt_opinions/opinions/23pdf/23a349_0813.pdf
Page Number: 37

Cite as:  603 U. S. ____ (2024) 

15 

BARRETT, J., dissenting 

  In fact, some commenters criticized EPA’s reliance on a 
“nationwide data set” to calculate emissions limits, arguing 
that EPA should “limit the dataset to . . . just the covered 
states”—an  approach  that  would  have  made  the  cost- 
effectiveness thresholds depend on which States were cov-
ered.    Id.,  at  36723.    But  EPA  expressly  defended  its  ap-
proach based on its “intention to identify a technology-specific 
representative emissions rate” and its interest in “the per-
formance  potential  of  a  technology”—which  were  best 
served  by  the  “largest  dataset  possible  (i.e.,  nationwide).”  
Id., at 36723–36724 (emphasis added).  EPA explained that 
it  used  the  same  approach  it  had  successfully  applied  in 
previous rulemakings: It “derive[d] technology performance 
averages” based on nationwide data.  Id., at 36724.  Then it 
applied the relevant industry standard “on a uniform basis” 
to each emitter across the covered States.  Id., at 36817.8 

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than $11,000 per ton.  Ozone Transport Policy Analysis Final Rule TSD 
5 (EPA–HQ–OAR–2021–0668–1080, Mar. 2023) (Final Ozone Analysis).  
EPA then calculated each State’s emissions budget based on the assump-
tion  that  the  State’s  EGUs  would  implement  the  emissions-reductions 
strategies that cost less than the chosen thresholds.  See n. 6, supra; 88 
Fed. Reg. 36762; Final Ozone Analysis 6, 9.  Given the likelihood that 
EPA  selected  cost  thresholds  based  on  nationwide  data,  each  State’s 
budget would be the same even if the FIP covered different States.    

8 While  EPA’s  methodology  with  respect  to  other  industrial  sources 
(non-EGUs)  was  more  complicated, it  also  seems  to  have  relied  on  na-
tionwide data.  EPA chose a “$7,500 marginal cost-per-ton threshold,” 88 
Fed. Reg. 36740, which corresponded to the point of diminishing returns 
(the  “knee  in  the  curve”)  when  EPA  assessed  the  impact  of  emissions 
controls in the highest impact industries and in “all industries” on the 
total “ozone season NOx reduction potential,” Technical Memorandum, 
Screening  Assessment  of  Potential  Emissions  Reductions,  Air  Quality 
Impacts,  and  Costs  From  Non-EGU  Emissions  Units  for  2026,  p.  4, 
(EPA–HQ–OAR–2021–0668–150,  Feb.  2022)  (boldface  omitted).    This 
figure thus appears to have been determined based on industry-wide cost 
and emissions data rather than state-specific calculations.  So too with 
the specific emissions limits EPA decided could be implemented for less 
than that cost.  See, e.g., 88 Fed. Reg. 36825 (“EPA based the proposed