The National Environmental Policy Act was signed into law by President Nixon in 1969. The Act declares a national policy to "encourage productive and enjoyable harmony between man and his environment; to promote efforts which will prevent or eliminate damage to the environment and biosphere and stimulate the health and welfare of man; [and] to enrich the understanding of the ecological systems and natural resources important to the Nation...".
NEPA imposes no requirements on the public. Rather, it directs Federal agencies to "utilize a systematic, interdisciplinary approach ... in planning and decision making which may have an impact on man's environment", to insure that "environmental amenities and values ... be given appropriate consideration in decision making along with economic and technical considerations", and to "study, develop, and describe appropriate alternatives to recommended courses of action...". This mandate applies to all "Federal actions". As a result, NEPA affects virtually all decisions regarding the use of the public lands.
NEPA further requires that agencies prepare a "detailed statement" describing impacts, alternatives, adverse environmental effects, the relationship between short-term effects and long-term productivity, and any irreversible and irretrievable commitments, for any "major Federal action significantly affecting the quality of the human environment...". In this language arises the requirement for the "Environmental Impact Statement" (EIS).
The preparation of an EIS follows a highly formalized process , consisting of eight major steps:
Issue the Notice of Intent to prepare an EIS;
Conduct public and agency scoping of the issues and alternatives;
Prepare the interdisciplinary analysis of the issues and alternatives;
Issue the Draft EIS;
Conduct the public review and comment period;
Issue the Final EIS, which includes responses to comments;
Conduct another public review and comment period;
Issue the Record of Decision.
The public review and comment periods have mandated minimum lengths (which can be extended at the discretion of the official responsible for preparation of the EIS.) Additionally, the Federal agency cannot take action until at least 30 days after the publication of the Final EIS. Because of this, an EIS generally takes at least eight to twelve months to complete, and depending on the complexity of the issues and the analysis, may take considerably longer.
Some actions are almost always considered "significant" and the agency will generally proceed directly with the preparation of an EIS. However, in most cases the agency will prepare an Environmental Assessment (EA) to determine whether the proposed action may result in direct or indirect effects which could cause significant impacts, either considered individually or cumulatively with other actions which may be occurring in the area. There is no specified process for preparation of an EA, and the EA may be prepared in any format that is useful to the decision-maker, but must include a discussion of need for the action, alternatives, impacts of the proposed action and the alternatives, and a list of agencies and persons consulted. The need for formal public scoping and review is at the discretion of the responsible official, but the finished document must be made available to the public. If the results of the analysis in the EA indicate that the potential impacts of implementing the action could be "significant", an EIS must be prepared before the action may be authorized. If, in the judgment of the decision-maker, the action would not result in significant impacts, a Decision Record is issued, along with a Finding of No Significant Impact (FONSI).
Certain categories of actions may be determined by an agency (through a formal procedure) to have no significant impact on the human environment, either individually or cumulatively. These actions are said to be "Categorically Excluded" from the requirements of NEPA, and no EIS or EA is required. The decision-maker must still review the proposed action against certain tests of significance to ensure that it does not represent an exception to the category. In BLM, the results are recorded in a document known as a Categorical Exclusion Review (CX).
If a proposed action has been completely covered in a previous NEPA document, and there are no changed circumstances, the agency may rely on the previous document for NEPA compliance. In BLM, the decision that a previous NEPA document completely covers a proposed action is recorded in the Documentation of NEPA Adequacy (DNA).
The above information is taken from Title 43, Part 1500 of the Code of Federal Regulations and the Council on Environmental Quality's publication, "40 Most Asked Questions."