The opinion
SENTELLE, Circuit Judge,
concurring:
I write separately not because I disagree with the majority’s conclusion that the EPA’s interpretation of 42 U.S.C. § 7651c(d)(4)(A) is a reasonable one, but rather because I agree with the majority’s conclusion more firmly than the majority itself does. That is, I would hold that the EPA’s interpretation is not merely a reasonable construction, but the only reasonable construction. I do not agree *648 that Congress was silent on the question of whether the EPA should “mechanically calculate a utility unit’s average annual emission by dividing the total emission during calendar years 1988 and 1989 by two.” Maj. op. at 646. Rather, I do not see how Congress could have said any more explicitly than it did that this is precisely what it was mandating. We have observed in the past that “some will find ambiguity even in a ‘No Smoking’ sign_” International Union, United Auto. Aerospace & Agric. Implement Workers of America v. General Dynamics Land Sys. Din, 815 F.2d 1570 , 1575 (D.C.Cir.1987). I see little more ambiguity in the present statute on the question before the EPA than in such a sign. I would therefore reach the same conclusion as the majority, but I would reach it under the first step of the Chevron analysis without proceeding to the second.