32 C.F.R. § 651.21
A Finding of No Significant Impact (FNSI) is a document that briefly states why an action (not otherwise excluded) will not significantly affect the environment, and, therefore, that an EIS will not be prepared. The FNSI includes a summary of the EA and notes any related NEPA documentation. If the EA is attached, the FNSI need not repeat any of the EA discussion, but may incorporate it by reference. The draft FNSI will be made available to the public for review and comment for 30 days prior to the initiation of an action, except in special circumstances when the public comment period is reduced to 15 days, as discussed in § 651.14(b)(2)(iii) . Following the comment period and review of public comments, the proponent forwards a decision package that includes a comparison of environmental impacts associated with reasonable alternatives, summary of public concerns, revised FNSI (if necessary), and recommendations for the decision maker. The decision maker reviews the package, makes a decision, and signs the FNSI or the NOI (if the FNSI no longer applies). If a FNSI is signed by the decision maker, the action can proceed immediately.
32 C.F.R. §651.21