To achieve the purposes set forth in § 1502.1, agencies shall prepare environmental impact statements in the following manner:

(a) Environmental impact statements shall not be encyclopedic.

(b) Environmental impact statements shall discuss effects in proportion to their significance. There shall be only brief discussion of other than important issues. As in an environmental assessment and 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 analytical, 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 the scope and complexity of the action.

(d) Environmental impact statements shall state how alternatives considered in them and decisions based on them will or will not achieve the requirements of sections 101 and 102(1) of NEPA, 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 the selection of alternatives before making a decision (see also § 1506.1 of this subchapter).

(g) Environmental impact statements shall serve as the means of assessing the environmental impact of proposed agency actions, rather than justifying decisions already made.