33 CFR § 230.6 - Actions normally requiring an EIS.
Actions normally requiring an EIS are:
(a) Feasibility reports for authorization and construction of major projects;
(b) Proposed changes in projects which increase size substantially or add additional purposes; and
(c) Proposed major changes in the operation and/or maintenance of completed projects.
District commanders may consider the use of an environmental assessment (EA) on these types of actions if early studies and coordination show that a particular action is not likely to have a significant impact on the quality of the human environment.