40 CFR § 1502.2 - Implementation.
(a) Environmental impact statements shall not be encyclopedic.
(b) Environmental impact statements shall discuss impacts in proportion to their significance. There shall be only brief discussion of other than significant issues. As in a finding of no significant impact, there should be only enough discussion to show why more study is not warranted.
(c) Environmental impact statements shall be analytic, concise, and no longer than necessary to comply with NEPA and with the regulations in this subchapter. Length should be proportional to potential environmental effects and project size.
(d) Environmental impact statements shall state how alternatives considered in it and decisions based on it will or will not achieve the requirements of sections 101 and 102(1) of NEPA as interpreted in the regulations in this subchapter and other environmental laws and policies.
(e) The range of alternatives discussed in environmental impact statements shall encompass those to be considered by the decision maker.
(f) Agencies shall not commit resources prejudicing selection of alternatives before making a final decision (see also § 1506.1 of this chapter).
(g) Environmental impact statements shall serve as the means of assessing the environmental impact of proposed agency actions, rather than justifying decisions already made.