NEPA requires that federal agencies will consider the impacts of actions on the human environment before decisions are made and the before action is taken. It requires that NEPA documents concentrate on issues that are significant to the action in question. The NEPA process is intended to help public officials make better decisions based on an understanding of environmental consequences, and take actions that protect, restore, and enhance the human environment.
Read more about NEPA and the Step by Step developing of an Environmental Impact Statement in the Access Notebook NEPA - National Environmental Policy Act