36 C.F.R. § 1010.9 – Preparation of an EIS.

(a) Notice of intent. When the Trust decides to prepare an EIS, it shall publish a notice of intent in the Federal Register in accordance with 40 CFR 1501.7 and 1508.22. Where there is a lengthy period between the Trust's decision to prepare an EIS and the time of actual preparation, then at the discretion of the NEPA Compliance Coordinator the notice of intent shall be published at a reasonable time in advance of preparation of the EIS.
(b) Preparation. After having determined that an EIS will be prepared and having published the notice of intent, the Trust will begin to prepare or to direct the preparation of the EIS. The EIS shall be formatted in accordance with 40 CFR 1502.10.
(c) Supplemental environmental impact statements. The Trust may supplement a draft or final EIS at any time. The Trust shall prepare a supplement to either a draft or final EIS when:
1. (1) Substantial changes are proposed to an action analyzed in the draft or final EIS that are relevant to environmental concerns;
2. (2) There are significant new circumstances or information relevant to environmental concerns and bearing on the proposed action or its impacts; or
3. (3) Actions are proposed which relate to or are similar to other actions taken or proposed and that together will have a cumulatively significant impact on the human environment.