Environmental impact statement

An environmental impact statement (EIS) is an examination of the effects on the environment that will occur if a particular action is taken. The purpose of the EIS requirement is to ensure that decision-makers consider environmental impacts before deciding whether to proceed.

The EIS system originated in the National Environmental Policy Act (NEPA), enacted in the United States in 1969. Certain actions of federal agencies must be preceded by an EIS. Contrary to a widespread misconception, NEPA does not prohibit the federal government or its licensees/permittees from harming the environment, but merely requires that the prospective impacts be understood and disclosed in advance. The same general pattern has since been followed by several U.S. state governments that have adopted "little NEPA's," i.e., state laws imposing EIS requirements for particular state actions. Many other countries have also enacted laws requiring environmental impact assessment.

Usually, an agency will release a Draft Environmental Impact Statement (DEIS) for comment. Interested parties and the general public have the opportunity to comment on the draft, after which the agency will approve the Final Environmental Impact Statement (FEIS). Occasionally, the agency will later release a Supplemental Environmental Impact Statement (SEIS).

The adequacy of an EIS can be challenged in court. Major proposed projects have been blocked because of an agency's failure to prepare an acceptable EIS. One prominent example was the Westway landfill and highway development in and along the Hudson River in New York City -- see the court decision in Sierra Club v. United States Army Corps of Engineers.