40 CFR § 1502.9 - Draft, final, and supplemental statements.
(a) Generally. Except for proposals for legislation as provided in § 1506.8 of this chapter, agencies shall prepare environmental impact statements in two stages and, where necessary, supplement them, as provided in paragraph (d)(1) of this section.
(b) Draft environmental impact statements. Agencies shall prepare draft environmental impact statements in accordance with the scope decided upon in the scoping process (§ 1501.9 of this chapter). The lead agency shall work with the cooperating agencies and shall obtain comments as required in part 1503 of this chapter. To the fullest extent practicable, the draft statement must meet the requirements established for final statements in section 102(2)(C) of NEPA as interpreted in the regulations in this subchapter. If a draft statement is so inadequate as to preclude meaningful analysis, the agency shall prepare and publish a supplemental draft of the appropriate portion. At appropriate points in the draft statement, the agency shall discuss all major points of view on the environmental impacts of the alternatives including the proposed action.
(c) Final environmental impact statements. Final environmental impact statements shall address comments as required in part 1503 of this chapter. At appropriate points in the final statement, the agency shall discuss any responsible opposing view that was not adequately discussed in the draft statement and shall indicate the agency's response to the issues raised.
(d) Supplemental environmental impact statements. Agencies:
(1) Shall prepare supplements to either draft or final environmental impact statements if a major Federal action remains to occur, and:
(i) The agency makes substantial changes to the proposed action that are relevant to environmental concerns; or
(ii) There are significant new circumstances or information relevant to environmental concerns and bearing on the proposed action or its impacts.
(2) May also prepare supplements when the agency determines that the purposes of the Act will be furthered by doing so.
(3) Shall prepare, publish, and file a supplement to a statement (exclusive of scoping (§ 1501.9 of this chapter)) as a draft and final statement, as is appropriate to the stage of the statement involved, unless the Council approves alternative procedures (§ 1506.12 of this chapter).
(4) May find that changes to the proposed action or new circumstances or information relevant to environmental concerns are not significant and therefore do not require a supplement. The agency should document the finding consistent with its agency NEPA procedures (§ 1507.3 of this chapter), or, if necessary, in a finding of no significant impact supported by an environmental assessment.