(a) General. Prior to initiating an environmental impact statement, the District Engineer must determine the proposed activity is likely to have reasonably foreseeable significant effects on the quality of the human environment, after consideration of any mitigation the Corps may require. As described in § 333.12(a)(5)(i) and § 333.15 of this part, this determination can be made following the completion of an environmental assessment in cases where that environmental assessment cannot conclude in a finding of no significant impact; in other situations, it can be made without first preparing an environmental assessment in instances where initial consideration as to the appropriate level of review as described indicates that the proposed activity is likely to have reasonably foreseeable significant effects. In cases where it is obvious that the proposed activity is likely to result in reasonably foreseeable significant effects and an environmental assessment terminating in a finding of no significant impact is therefore not prepared, the District Engineer must make a determination that an environmental impact statement is required due to the likely significant effects of the activity. This determination will be made in accordance with § 333.12(b) and documented. Whether an impact rises to the level of significant is a matter of the District Engineer's expert judgment.

(b) Timing. The determination to prepare an environmental impact statement should be made as soon as the Corps has sufficient information to consider on whether the project would result in significant effects on the human environment, after consideration of any mitigation the Corps would require. In many cases this is soon after the receipt of a complete DA permit application or request for permission, although in some cases a determination may not be made until after an environmental assessment has been prepared. After a determination has been made to prepare an environmental impact statement as the lead agency, the Corps will notify the applicant in writing as soon as practicable.