The Federal law known as the National Environmental Policy Act (NEPA) requires the federal government to evaluate the effects of its actions on the environment, to consider alternative courses of action, and to obtain public input on proposed actions. An Environmental Impact Statement is a document that describes the expected effects of proposed activities on the environment. In this case, "environment" is defined as the natural and physical environment and the relationship of people with that environment. An EIS will thus describe potential impacts of a proposed activity as well as alternative activities on the physical environment (air, water, soil), the biological environment (fish, wildlife, vegetation), and the human environment (socio-economics, recreation, or cultural activities). An EIS also compares the potential effects of the action being proposed to doing nothing (the "no action alternative").

The Trustees are preparing an EIS for the Coeur d'Alene Basin Draft Restoration plan to fulfill the federal agencies' obligation under the NEPA to evaluate the effects of the Draft Restoration Plan and alternatives on the environment, and to obtain public input on the plan. The EIS process is also intended to satisfy CERCLA's requirement that the Trustees develop a restoration plan through a process that involves public participation.