Environmental Assessment (EA): A preliminary analysis to determine if an action will significantly affect the environment. If a significant impact is found, an Environmental Impact Statement (EIS) is required.
Environmental Impact Statement (EIS): A comprehensive study of the environmental consequences of the proposed action. If an EIS is not deemed necessary, a Finding of No Significant Impact is made.
Categorical Exclusion: This applies to actions predetermined to not have significant environmental effects. Actions under categorical exclusion do not require an EA or EIS.
These reviews are integral for agencies to consider environmental impacts, alternative actions, and their rationale for choosing a particular approach. The Council of Environmental Quality (CEQ) issues regulations for these processes, offering a framework for agency compliance with flexibility.