Decision Analysis: The Core of NEPA

Prediction is Hard. Especially about the future.
decision tree

Decision Tree Climbing

NEPA as implemented has become synonymous with a series of pre-fabricated, mostly mandatory routines.  The Administrative Procedure Act (APA) and 1978 Council on Environmental (CEQ) regulations combine to create the boundaries that form these routines.  The Environmental Impact Statement (EIS), the Environmental Assessment (EA), Finding of No Significant Impact (FONSI) and Categorical Exclusion (CATX) form the principal subdivisions, although the Council on Environmental Quality (CEQ) doesn’t define whatever results from the agency CATX routine as a NEPA document. See 40 C.F.R. § 1508.10.

If we envision the typical NEPA routine (of whatever scope) as a decision tree, the trunk/branch splits would number at least three.  First is the decision whether to prepare a NEPA document at all and, if so, which one.  Next is the decision whether the action as proposed will or may have a “significant” impact on the human environment.  Last is the determination of plausible alternatives and their possible or probable outcomes.  Here things can either be very simple or they can be mind-numbingly complex.

The significance determination in that supposed decision tree will intersect and/or dominate the other two.  Whether to prepare a NEPA document hinges on agency routines and habits, of course, but legally it depends on NEPA § 102’s concept of “significance.”  The plausible alternatives to a proposal will be some reflection of the agency’s preference, jurisdiction, and timing.  But they will also reflect what the agency believes are likely (significant) environmental impacts.  This is the subtle pressure that NEPA was intended to exert on agency decision-makers.


I teach environmental, natural resources, and administrative law at Penn State Law. Before teaching I was an enforcement lawyer at U.S. EPA. Along the way I've done work for environmental nonprofits and written a fair bit about NEPA.
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