An Environmental Impact Statement (EIS) is prepared for major actions that are determined by the agency to have significant impacts on the environment. The EIS provides a full and unbiased discussion of significant environmental impacts and informs the decision makers and the public of the reasonable alternatives that would avoid or minimize adverse impacts or enhance the quality of the human environment. An EIS results in a Record of Decision (ROD). The ROD is a public record of the agency's decision selecting one alternative for implementation from among the alternatives considered in detail, including the "No Action Alternative". Agencies may prepare an Environmental Assessment to help determine if it needs to prepare an EIS.
An Environmental Assessment (EA) is prepared for those actions that are not Categorically Excluded, and when (a) the proposed action is not anticipated to have a significant impact on the environment, or (b) it is uncertain whether the effects of the proposed action will have a significant impact on the environment, or (c) there is reason to believe that the proposed action will be environmentally controversial. An EA will result in either:
- A Finding of No Significant Impact
- A decision to prepare an EIS
- An decision to withdraw the proposed action (Implement the No Action Alternative)
The Council on Environmental Quality (CEQ), established by Section 202 of the NEPA, allows Categorical Exclusions (CATEX) for actions which, under normal circumstances, have been determined to have no significant effect individually or cumulatively on the environment and, therefore for which neither an EA nor an EIS is required. CATEX applies to those actions that do not result in substantial change from the existing environmental conditions at the site of the proposed action.
- CEQ Regulations For Implementing the Procedural Provisions of the National Environmental Policy Act (40 CFR Parts 1500-1508)
- MCO P5090.2A Environmental Compliance and Protection Manual