National Environmental Policy Act of 1969

Established when signed into law by president Nixon, the NEPA requires all major federal actions that  affect the environment to be accompanied by an environmental impact statement, identifying any environmental hazards or effects the action will create.  NEPA is a procedural statute with two main goals:
1) It obligates federal agencies to consider all environmental repercussions before proceeding.
2) It ensures that these agencies will inform the public as to what the action is and the effects it will have on the environment.

There are three different classes of action that determine the documentation NEPA requires to properly review a federal action:

Class I: Environmental Impact Statement (EIS)- Reserved for actions with a significant effect on the environment.

Class II: Categorical Exclusion- Required when actions do not have a signifiant effect, cumulatively or individually, on the environment.

Class III: Environmental Assessment- For actions that have an unclear or loosely established effect on the environment.

Every NEPA planning process takes steps to look at the following aspects:

-Purpose and need: Establishes what the project's for and why it's necessary.

-Affected Environments and Constraints: Describes the project area, location, and specifications.

-Alternatives: All alternatives are considered.

-Public Involvement: Involving the public in some way.

-Mitigation: Developing mitigation strategies (if applicable).

Links:

http://www.fta.dot.gov/documents/Unit1_01CRSReport.pdf

http://www.coloradodot.info/programs/environmental/planning-env-link-program/background/what-is-nepa.html