; (4) the proposed agency action is, in whole or in part, a nondiscretionary action with respect to which such agency does not have authority to take environmental factors into consideration in determining whether to take the proposed action; or (5) the proposed agency action is an action for which such agency’s compliance with another statute’s requirements serve the same function as the requirements of this Act with respect to such action. (b) Levels of review (1) Environmental impact statement An agency shall issue an environmental impact statement with respect to a proposed agency action that has a significant effect on the quality of the human environment. (2) Environmental assessment An agency shall issue an environmental assessment with respect to a proposed agency action that is not likely to have a significant effect on the quality of the human environment, or if the significance of such effect is unknown. Such environmental assessment shall be a concise public document prepared by a Federal agency to provide notice to the public for the basis of such agency’s finding of no significant impact. (3) Sources of information In making a determination under this subsection, an agency— (A) may make use of any reliable data source