The following apply to the design and preparation of EISs:

(1) The agency shall prepare EISs that are analytic rather than encyclopedic.

(2) The agency shall discuss the impacts of a proposed action in a level of detail that is proportionate to their significance. For other than significant issues, an EIS need only include enough discussion to show why more study is not warranted.

(3) The agency shall prepare with each draft and final EIS a brief summary that is available for distribution separate from the EIS. The summary must describe:

(a) the proposed action being evaluated by the EIS, the impacts, and the alternatives;

(b) areas of controversy and major conclusions;

(c) the tradeoffs among the alternatives; and

(d) the agency's preferred alternative, if any.