The NEPA process starts after a proposal is formulated.  In the process, there are three levels of analysis depending on whether or not an undertaking could significantly affect the environment.  The basic levels of NEPA environmental review and documentation process include: 

• Categorical Exclusion (CATEX):  A category of actions that do not have, under normal circumstances, individually or cumulatively, a significant effect on the human environment or that have been previously studied and found to have no significant effect.  Some CATEXs are documented with a Record of Environmental Consideration (REC).
• Environmental Assessment (EA):  documents any proposed actions or activities that possibly have a significant impact on the human environment, or indicates if it is unclear whether or not there are any significant impacts on the environment.  In the event an EA is prepared and there are no significant impacts identified, then the decision is documented as a Finding of No Significant Impact (FONSI).  If there will be significant impacts, then the decision is documented as a Notice of Intent (NOI), and scoping will be conducted to prepare and Environmental Impact Statement.
• Environmental Impact Statement (EIS):  documents proposed actions or activities expected to have a significant impact on the quality of the human environment.  The EIS will describe the proposed action, any alternative actions that were identified, and the environmental impacts associated with the alternative actions.  The decision on which action to implement is documented by a Record of Decision (ROD).

After the decision is made, then the proposed action is implemented with (or without) mitigation measures and monitored. Mitigations avoid or reduce the impact of the action and can include:

• Avoiding the impact by not taking action or not implementing certain parts of the action,
• Minimizing impacts by limiting the degree or magnitude of the action,
• Repairing, rehabilitating, or restoring the affected environment,
• Reducing or eliminating the impact by preservation and maintenance operations during implementation over time, and
• Compensating for the impact by replacing or providing for substitute resources or environments.

>>How the MDA implements NEPA>>