In Aluminum Co. of America v. Central Lincoln Peoples' Utility Dist., 467 U.S. 380, 389, 104 S.Ct. 2472, 2479, 81 L.Ed.2d 301 (1984), the Supreme Court established a highly deferential scope of review for courts considering the Bonneville Power Administration ("BPA") interpretations of the Regional Act: Under established administrative law principles, it is clear that the Administrator's interpretation of the Regional Act is to be given great weight. "We have often noted that the interpretation of an agency charged with the administration of a statute is entitled to substantial deference." Blum v. Bacon, 457 U.S. 132, 141 102 S.Ct. 2355, 2361, 72 L.Ed.2d 728 (1982). "To uphold the agency's interpretation 'we need not find that its construction is the only reasonable one, or even that it is the result we would have reached had the question arisen in the first instance in judicial proceedings.' ... We need only conclude that it is a reasonable interpretation of the relevant provisions." (467 U.S. at 389, 104 S.Ct. at 2479.)