39 CFR 775.8 - Environmental evaluation guidelines.
(a) Approach. When dealing with proposals which may have an impact on the human environment, environmental coordinators, planners, decision makers, and other officials responsible for actions, will, as appropriate:
(1) Use a systematic approach that integrates natural and social sciences and environmental design in planning and making decisions.
(2) Identify environmental effects and values in detail, and appraise them in conjunction with economic and technical analyses.
(3) Consider environmental documents at all decision points at which other planning documents are considered. (Plans and decisions are to reflect environmental values. Proposed actions should be assessed as soon as their effects can be meaningfully evaluated, to provide the bases for early decision on whether detailed environmental impact statements must be prepared.)
(4) Study, develop, describe, and evaluate at all decision points, reasonable alternatives to recommended actions which may have a significant effect on the environment.
(b) Proposal requirements. When an environmental impact statement has been prepared, it must accompany the proposal through and be used in the decision-making process. Any other proposal must refer to applicable environmental documents (e.g., determination of categorical exclusion; finding of no significant impact; notice of intent to prepare an impact statement), and relevant comments and responses.
(c) Lead agency arrangements. If the Postal Service and another Federal agency become involved in a lead agency arrangement for the preparation of an environmental impact statement, the Service will cooperate fully.