here are the regulations for a waiver under NEPA in "emergency" situations.
Sec. 1506.11 Emergencies.
"Where emergency circumstances make it necessary to take an action with significant environmental impact without observing the provisions of these regulations, the Federal agency taking the action should consult with the Council about alternative arrangements. Agencies and the Council will limit such arrangements to actions necessary to control the immediate impacts of the emergency. Other actions remain subject to NEPA review. "
The "Council" mentioned in the regulations is the Council on Environmental Quality which is an office of the president.
there may be subsequent laws that have been passed that exempt certain activities since NEPA. here is an article that names a few. Again, it may be a situation that comes down to the interpretation of "emergency" to be decided by litigation.
http://www.grist.org/news/muck/2004/08/12/griscom-defen... /
"Last year, President Bush pushed through legislation that exempts military training bases from cornerstone environmental protections mandated by the Endangered Species Act and Marine Mammal Protection Act, in the name of "military readiness."