As defined by CEQ regulations (40 CFR 1508.11) and section 102(2)(C) of NEPA, an EIS should be a clear, concise, and detailed written statement describing:
The environmental impacts of a proposed action;
Any adverse effects that cannot be avoided if the action is implemented;
Alternatives to the action;
The relationship between local short-term uses of the environment and the maintenance and enhancement of long-term productivity; and
Any irreversible and irretrievable commitments of resources that would be involved in the proposed action should it be implemented.
The CEQ regulations (40 CFR 1501.7 and part 1502) describe the process for determining the scope of an EIS and provide detailed requirements for the preparation of draft and final EIS's. CEQ format and procedures for preparing EIS shall be followed.
Under the conditions prescribed in 40 CFR 1502.9, the agency will prepare a supplement for a draft or final EIS and introduce the supplement into the administrative record.