33 C.F.R. § 333.37 – Elimination of duplication with State, Tribal, and local procedures.

(a) The District Engineer will, where appropriate, cooperate with State, Tribal, and local agencies that are responsible for preparing environmental documents.
(b) To the fullest extent practicable unless specifically prohibited by law, the District Engineer will cooperate with State, Tribal, and local agencies to reduce duplication between NEPA and State, Tribal, and local requirements, including through use of studies, analysis, and decisions developed by State, Tribal, or local agencies. Such cooperation may include:
1. (1) Joint planning processes;
2. (2) Joint environmental research and studies;
3. (3) Joint public hearings (except where otherwise provided by statute); or
4. (4) Joint environmental documents.