(a) Once a conformity determination is completed by a Federal agency, that determination is not required to be re-evaluated if the agency has maintained a continuous program to implement the action; the determination has not lapsed as specified in paragraph (b) of this section; or any modification to the action does not result in an increase in emissions above the levels specified in Sec. 93.153(b). If a conformity determination is not required for the action at the time NEPA analysis is completed, the date of the finding of no significant impact (FONSI) for an Environmental Assessment, a record of decision (ROD) for an Environmental Impact Statement, or a categorical exclusion determination can be used as a substitute date for the conformity determination date.
(b) The conformity status of a Federal action automatically lapses 5 years from the date a final conformity determination is reported under Sec. 93.155, unless the Federal action has been completed or a continuous program to implement the Federal action has commenced.
(c) Ongoing Federal activities at a given site showing continuous progress are not new actions and do not require periodic re-determinations so long as such activities are within the scope of the final conformity determination reported under Sec. 93.155.
(d) If the Federal agency originally determined through the applicability analysis that a conformity determination was not necessary because the emissions for the action were below the limits in Sec. 93.153(b) and changes to the action would result in the total emissions from the action being above the limits in Sec. 93.153(b), then the Federal agency must make a conformity determination. [75 FR 17276, Apr. 5, 2010]