Environmental Impact Statement

An environmental impact statement (EIS), under United States environmental law, is a document required by the National Environmental Policy Act (NEPA) for certain actions "significantly affecting the quality of the human environment". An EIS is a tool for decision making. It describes the positive and negative environmental effects of a proposed action, and it usually also lists one or more alternative actions that may be chosen instead of the action described in the EIS. Several U.S. state governments require that a document similar to an EIS be submitted to the state for certain actions. For example, in California, an Environmental Impact Report (EIR) must be submitted to the state for certain actions, as described in the California Environmental Quality Act (CEQA). One of the primary authors of the act is Lynton K. Caldwell.

The purpose of the NEPA is to promote informed decision-making by federal agencies by making "detailed information concerning significant environmental impacts" available to both agency leaders and the public. The NEPA was the first piece of legislation that created a comprehensive method to assess potential and existing environmental risks at once. It also encourages communication and cooperation between all the actors involved in environmental decisions, including government officials, private businesses, and citizens.

In particular, an EIS acts as an enforcement mechanism to ensure that the federal government adheres to the goals and policies outlined in the NEPA. An EIS should be created in a timely manner as soon as the agency is planning development or is presented with a proposal for development. The statement should use an interdisciplinary approach so that it accurately assesses both the physical and social impacts of the proposed development. In many instances an action may be deemed subject to NEPA’s EIS requirement even though the action is not specifically sponsored by a federal agency. Eccleston identifies instances that may ‘federalize’ such actions for the purposes of NEPA. These factors may include actions that receive federal funding, federal licensing or authorization, or that are subject to federal control.

Not all federal actions require a full EIS. If the action may or may not cause a significant impact the agency can first prepare a smaller, shorter document called an Environmental Assessment (EA). The finding of the EA determines whether an EIS is required. If the EA indicates that no significant impact is likely, then the agency can release a finding of no significant impact (FONSI) and carry on with the proposed action. Otherwise, the agency must then conduct a full-scale EIS. Most EAs result in a FONSI. A limited number of federal actions may avoid the EA and EIS requirements under NEPA if they meet the criteria for a categorical exclusion (CATEX). A CATEX is usually permitted when a course of action is identical or very similar to a past course of action and the impacts on the environment from the previous action can be assumed for the proposed action, or for building a structure within the footprint of an existing, larger facility or complex. For example, two proposed sections of Interstate 69 in Kentucky were granted a CATEX from NEPA requirements as these portions of I-69 will be routed over existing freeways requiring little more than minor spot improvements and a change of highway signage. Additionally, a CATEX can be issued during an emergency when time does not permit the preparation of an EA or EIS. An example of the latter is when the Federal Highway Administration issued a CATEX to construct the replacement bridge in the wake of the I-35W Mississippi River Bridge Collapse.

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