Section 1506.11 of the CEQ regulations provides for alternative arrangements to comply with NEPA when there is insufficient time to prepare an EIS before the Federal agency must make a decision. Alternative Arrangements can be issued by CEQ, in consultation with the agency, when agency action is:
Under such circumstances, the agency should notify CEQ as quickly as practicable to consult in determining the most appropriate alternative arrangements that will take the place of the normal EIS process. Alternative arrangements are limited to activities necessary to address the immediate impacts of the Federal action. Subsequent agency activities undergo NEPA review in accordance with the CEQ Regulations and Agency NEPA procedures.
In 2016 CEQ issued updated guidance on Alternative Arrangements for NEPA compliance in emergency situations.
Here is a comprehensive list of alternative arrangements made by CEQ and the Federal agencies since NEPA's inception.