(a) Activities that require Corps authorization under 33 U.S.C. 1344, 33 U.S.C. 401, 33 U.S.C. 403, and 33 U.S.C. 1413 are reviewed (and when applicable, permitted) on a site-specific basis based upon an application containing a complete description of the proposed activity, and all activities which the applicant plans to undertake which are reasonably related to the same project and for which a Corps permit will be required. See 33 CFR 325.1(d)(1)-(2). However, only for reviews of activities under 33 U.S.C. 408, the District Engineer may prepare tiered environmental documents when conducting multi-phased reviews of proposed alterations or in other appropriate circumstances. Multi-phased reviews under 33 U.S.C. 408 evaluate proposed alterations in multiple successive iterations of progressively greater detail. Each successive review must be accompanied by a NEPA document that considers the potential impacts of the alteration at the level of detail of the given phase of review to help inform the development of the proposed alteration. The analysis in each environmental document will reflect the level of planning in each tier. For example, the first tier may consider the differing impacts of selecting different sites for the alteration, the second tier may consider different project configurations, and the final tier may consider the impacts from different construction methods. Each successive analysis should build off the previous analysis, formally incorporating the prior environmental documents.

(b) After completing a programmatic environmental assessment or environmental impact statement for a review under 33 U.S.C. 408, the District Engineer may rely on that document for 5 years if there are not substantial new circumstances or information about the significance of adverse effects that bear on the analysis. After 5 years, as long as the District Engineer reevaluates the analysis in the programmatic environmental document and any underlying assumption to ensure reliance on the analysis remains valid and briefly documents its reevaluation and explains why the analysis remains valid considering any new and substantial information or circumstances, the District Engineer may continue to rely on the document.

(a) Generally. The District Engineer may rely on an environmental impact statement, environmental assessment, or portion thereof, provided that the statement, assessment, or portion thereof meets the standards for an adequate statement or assessment under these procedures. When relying on an environmental impact statement, environmental assessment, or portion thereof, the District Engineer will cite, briefly describe the content and relevance to the environmental document, and may make modifications that are necessary to render the relied-upon document, or portion thereof, fit for fulfilling NEPA's analytic requirements for the action. If the District Engineer finds that the other agency's environmental impact statement or environmental assessment is inadequate with respect to the Corps permit or permission action, the District Engineer should incorporate the other agency's NEPA document or a portion thereof and prepare an appropriate and adequate NEPA document to address the Corps involvement with the proposed action.

(b) Substantial similarity. (1) If the actions covered by the original environmental impact statement or environmental assessment and the proposed action are substantially the same, the District Engineer will document their reliance on the statement or assessment.

(2) If the actions are not substantially the same, the District Engineer may modify the statement or assessment as necessary to render the statement fit for fulfilling NEPA's analytic requirements for the action at hand, and document the reliance on the statement or assessment, as modified, or may incorporate relevant portions in the District Engineer's own NEPA document. Where appropriate, the District Engineer may solicit comment to the extent that solicitation of comment will assist the District Engineer in expeditiously adapting the relied-upon statement or assessment so that it is fit for the District Engineer's purposes.

The District Engineer may incorporate material, such as planning studies, analyses, or other relevant information, into environmental documents by reference when the effect will be to cut down on bulk without impeding the Corps review of the action. When incorporating material by reference, the District Engineer will cite, briefly describe the content and relevance to the environmental document, and make the materials reasonably available for review by potentially interested parties. The District Engineer will not use incorporation as a means to evade the statutory page limits.

The District Engineer will prepare supplements to environmental documents only if a major Federal action remains to occur, and:

(a) The applicant makes substantial changes to the proposed action that are relevant to environmental concerns; or

(b) The District Engineer decides, in their discretion, that there are substantial significant new circumstances or information about the significance of the adverse effects that bear on the proposed action or its effects.

(a) The District Engineer will not undertake new scientific and technical research to inform their analyses unless that is essential to a reasoned choice among alternatives and the overall costs and time frame of such undertaking are not unreasonable. Rather, the District Engineer will make use of reliable existing data and resources.

(b) When the District Engineer is evaluating an action's reasonably foreseeable effects on the human environment, and there is incomplete or unavailable information that cannot be obtained at a reasonable cost or the means to obtain it are unknown, the District Engineer will make clear in the relevant environmental document that such information is lacking.

(a) To the fullest extent possible, the District Engineer will prepare environmental documents concurrently with and integrated with analyses and related surveys and studies required by other Federal statutes. In appropriate instances, the District Engineer may participate in preparing single environmental assessment, finding of no significant impact, environmental impact statement, and Record of Decision documents.

(b) The District Engineer will combine an environmental document prepared in compliance with NEPA with any other agency document to reduce duplication and paperwork. Thus, the District Engineer may combine an environmental document with related plans, rules, or amendments as a single consolidated document.

(c) If comments on a notice of intent or other aspects of a scoping process identify consultations, permits, or licenses necessary under other environmental laws, the environmental document may contain a section briefly listing the applicable requirements and how the applicant has or will meet them (e.g., permits applied for or received, consultations initiated or concluded).

(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) Joint planning processes;

(2) Joint environmental research and studies;

(3) Joint public hearings (except where otherwise provided by statute); or

(4) Joint environmental documents.

For all environmental documents, the District Engineer will provide a unique identification number for tracking purposes, which the District Engineer will reference on all associated environmental review documents prepared for the proposed agency action and in any database or tracking system for such documents. The District Engineer will coordinate with the CEQ and other Federal agencies to ensure uniformity of such identification numbers across Federal agencies.

In responding to emergency situations to prevent or reduce imminent risk of life, health, property, or severe economic losses, district commanders may proceed without the specific documentation and procedural requirements of other sections of this regulation. District Engineers shall consider the probable environmental consequences in determining appropriate emergency actions and when requesting approval to proceed on emergency actions, will describe proposed NEPA documentation or reasons for exclusion from documentation. NEPA documentation should be accomplished prior to initiation of emergency work if time constraints render this practicable. Such documentation may also be accomplished after the completion of emergency work, if appropriate. When possible, emergency actions considered major in scope with potentially significant environmental impacts shall be referred through the Division Engineers to Headquarters, U.S. Army Corps of Engineers for consultation with CEQ about NEPA alternative arrangements.