Cite as: 540 U. S. 461 (2004)
Opinion of the Court
trary, capricious, an abuse of discretion, or otherwise not in accordance with law." Even when an agency explains its decision with "less than ideal clarity," a reviewing court will not upset the decision on that account "if the agency's path may reasonably be discerned." Bowman Transp., Inc. v. Arkansas-Best Freight System, Inc., 419 U. S. 281, 286 (1974). EPA's three skeletal orders to ADEC and Cominco surely are not composed with ideal clarity. These orders, however, are properly read together with accompanying explanatory correspondence from EPA; so read, the Agency's comments and orders adequately ground the determination that ADEC's acceptance of Low NOx for MG-17 was unreasonable given the facts ADEC found.
In the two draft permits and the final permit, ADEC formally followed the EPA-recommended top-down methodology to determine BACT, as Cominco had done in its application. App. 61, 109, 175; see supra, at 475-476. Employing that methodology in the May 1999 draft permit, ADEC first concluded that SCR was the most stringent emission-control technology that was both "technically and economically feasible." App. 65; see supra, at 476. That technology should have been designated BACT absent "technical considerations, or energy, environmental, or economic impacts justif[ying] a conclusion that [SCR was] not 'achievable' in [this] case." New Source Review Manual, p. B.2; App. 61-62. ADEC nevertheless selected Low NOx as BACT; ADEC did so in May 1999 based on Cominco's suggestion that fitting all Red Dog Mine generators with Low NOx would reduce aggregate emissions. Id., at 87, 111-112; see supra, at 476-477.
In September and December 1999, ADEC again rejected SCR as BACT but no longer relied on Cominco's suggestion that it could reduce aggregate emissions by equipping all generators with Low NOx. See supra, at 478-480. ADEC candidly stated that it aimed "[t]o support Cominco's Red Dog Mine Production Rate Increase Project, and its contri-
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