The Secretary went on to explain the significance of the dam to the habitat of the snail darter:

"[T]he snail darter occurs only in the swifter portions of shoals over clean gravel substrate in cool, low-turbidity water. Food of the snail darter is almost exclusively snails which require a clean gravel substrate for their survival. The proposed impoundment of water behind the proposed Tellico Dam would result in total destruction of the snail darter's habitat." Ibid. (emphasis added).

Subsequent to this determination, the Secretary declared the area of the Little Tennessee which would be affected by the Tellico Dam to be the "critical habitat" of the snail darter. 41 Fed. Reg. 13926-13928 (1976) (to be codified as 50 CFR § 17.81). Using these determinations as a predicate, and notwithstanding the near completion of the dam, the Secretary declared that pursuant to § 7 of the Act, "all Federal agencies must take such action as is necessary to insure that actions authorized, funded, or carried out by them do not result in the destruction or modification of this critical habitat area." 41 Fed. Reg. 13928 (1976) (to be codified as 50 CFR § 17.81 (b)). This notice, of course, was pointedly directed at TVA and clearly aimed at halting completion or operation of the dam.

During the pendency of these administrative actions, other developments of relevance to the snail darter issue were transpiring. Communication was occurring between the Department of the Interior's Fish and Wildlife Service and TVA with a view toward settling the issue informally. These negotiations were to no avail, however, since TVA consistently took the position that the only available alternative was to attempt relocating the snail darter population to another suitable location. To this end, TVA conducted a search of alternative sites which might sustain the fish, culminating in the experimental transplantation of a number of snail darters to the nearby Hiwassee River. However, the Secretary of the Interior was

not satisfied with the results of these efforts, finding that TVA had presented "little evidence that they have carefully studied the Hiwassee to determine whether or not" there were "biological and other factors in this river that [would] negate a successful transplant." 13 40 Fed. Reg. 47506 (1975).

Meanwhile, Congress had also become involved in the fate of the snail darter. Appearing before a Subcommittee of the House Committee on Appropriations in April 1975-some seven months before the snail darter was listed as endangered-TVA representatives described the discovery of the fish and the relevance of the Endangered Species Act to the Tellico Project. Hearings on Public Works for Water and Power Development and Energy Research Appropriation Bill, 1976, before a Subcommittee of the House Committee on Appropriations, 94th Cong., 1st Sess., pt. 7, pp. 466-467 (1975); Hearings on H. R. 8122, Public Works for Water and Power Development and Energy Research Appropriations for Fiscal Year 1976, before a Subcommittee of the Senate Committee on Appropriations, 94th Cong., 1st Sess., pt. 4, pp. 3775-3777 (1975). At that time TVA presented a position which it would advance in successive forums thereafter, namely, that the Act did not prohibit the completion of a project authorized, funded, and substantially constructed before the Act was passed. TVA also described its efforts to transplant the snail darter, but contended that the dam should be finished regardless of the

13 The Fish and Wildlife Service and Dr. Etnier have stated that it may take from 5 to 15 years for scientists to determine whether the snail darter can successfully survive and reproduce in this new environment. See General Accounting Office, The Tennessee Valley Authority's Tellico Dam Project-Costs, Alternatives, and Benefits 4 (Oct. 14, 1977). In expressing doubt over the long-term future of the Hiwassee transplant, the Secretary noted: "That the snail darter does not already inhabit the Hiwassee River, despite the fact that the fish has had access to it in the past, is a strong indication that there may be biological and other factors in this river that negate a successful transplant." 40 Fed. Reg. 47506 (1975).

experiment's success. Thereafter, the House Committee on Appropriations, in its June 20, 1975, Report, stated the following in the course of recommending that an additional $29 million be appropriated for Tellico :

"The Committee directs that the project, for which an environmental impact statement has been completed and provided the Committee, should be completed as promptly as possible . . . ." H. R. Rep. No. 94–319, p. 76 (1975). (Emphasis added.)

Congress then approved the TVA general budget, which contained funds for continued construction of the Tellico Project." In December 1975, one month after the snail darter was declared an endangered species, the President signed the bill into law. Public Works for Water and Power Development and Energy Research Appropriation Act, 1976, 89 Stat. 1035, 1047.

In February 1976, pursuant to § 11 (g) of the Endangered Species Act, 87 Stat. 900, 16 U. S. C. § 1540 (g) (1976 ed.),15 respondents filed the case now under review, seeking to enjoin completion of the dam and impoundment of the reservoir on the ground that those actions would violate the Act by directly causing the extinction of the species Percina (Imostoma) tanasi. The District Court denied respondents' request for a preliminary injunction and set the matter for trial. Shortly thereafter the House and Senate held appropriations hearings which would include discussions of the Tellico budget.

14 TVA projects generally are authorized by the Authority itself and are funded-without the need for specific congressional authorization-from lump-sum appropriations provided in yearly budget grants. See 16 U. S. C. §§ 831c (j) and 831z (1976 ed.).

15 Section 11 (g) allows "any person" to commence a civil action in a United States District Court to, inter alia, "enjoin any person, including the United States and any other governmental instrumentality or agency (to the extent permitted by the eleventh amendment to the Constitution), who is alleged to be in violation of any provision" of the Act "or regulation issued under the authority thereof . . . ."

At these hearings, TVA Chairman Wagner reiterated the agency's position that the Act did not apply to a project which was over 50% finished by the time the Act became effective and some 70% to 80% complete when the snail darter was officially listed as endangered. It also notified the Committees of the recently filed lawsuit's status and reported that TVA's efforts to transplant the snail darter had "been very encouraging." Hearings on Public Works for Water and Power Development and Energy Research Appropriation Bill, 1977, before a Subcommittee of the House Committee on Appropriations, 94th Cong., 2d Sess., pt. 5, pp. 261-262 (1976); Hearings on Public Works for Water and Power Development and Energy Research Appropriations for Fiscal Year 1977, before a Subcommittee of the Senate Committee on Appropriations, 94th Cong., 2d Sess., pt. 4, pp. 3096–3099 (1976).

Trial was held in the District Court on April 29 and 30, 1976, and on May 25, 1976, the court entered its memorandum opinion and order denying respondents their requested relief and dismissing the complaint. The District Court found that closure of the dam and the consequent impoundment of the reservoir would "result in the adverse modification, if not complete destruction, of the snail darter's critical habitat," 16

16 The District Court made the following findings with respect to the dam's effect on the ecology of the snail darter:

"The evidence introduced at trial showed that the snail darter requires for its survival a clear, gravel substrate, in a large-to-medium, flowing river. The snail darter has a fairly high requirement for oxygen and since it tends to exist in the bottom of the river, the flowing water provides the necessary oxygen at greater depths. Reservoirs, unlike flowing rivers, tend to have a low oxygen content at greater depths.

"Reservoirs also tend to have more silt on the bottom than flowing rivers, and this factor, combined with the lower oxygen content, would make it highly probable that snail darter eggs would smother in such an environment. Furthermore, the adult snail darters would probably find this type of reservoir environment unsuitable for spawning.

"Another factor that would tend to make a reservoir habitat unsuitable for snail darters is that their primary source of food, snails, probably

making it "highly probable" that "the continued existence of the snail darter" would be "jeopardize [d]." 419 F. Supp. 753, 757 (ED Tenn.). Despite these findings, the District Court declined to embrace the plaintiffs' position on the merits: that once a federal project was shown to jeopardize an endangered species, a court of equity is compelled to issue an injunction restraining violation of the Endangered Species Act..

In reaching this result, the District Court stressed that the entire project was then about 80% complete and, based on available evidence, "there [were] no alternatives to impoundment of the reservoir, short of scrapping the entire project." Id., at 758. The District Court also found that if the Tellico Project was permanently enjoined, "some $53 million would be lost in nonrecoverable obligations," id., at 759, meaning that a large portion of the $78 million already expended would be wasted. The court also noted that the Endangered Species Act of 1973 was passed some seven years after construction on the dam commenced and that Congress had continued appropriations for Tellico, with full awareness of the snail darter problem. Assessing these various factors, the District Court concluded:

"At some point in time a federal project becomes so near completion and so incapable of modification that a court of equity should not apply a statute enacted long after inception of the project to produce an unreasonable result. . . . Where there has been an irreversible and irretrievable commitment of resources by Congress to a project over a span of almost a decade, the Court should proceed with a great deal of circumspection." Id., at 760. To accept the plaintiffs' position, the District Court argued, would inexorably lead to what it characterized as the absurd result of requiring "a court to halt impoundment of water

would not survive in such an environment." 419 F. Supp. 753, 756 (ED Tenn. 1976).