Confronting Uncertainty under NEPA

31 Pages Posted: 13 May 2009 Last revised: 26 May 2009

See all articles by Daniel A. Farber

Daniel A. Farber

University of California, Berkeley - School of Law


Quantifying risks with confidence is often difficult. For the past thirty years, agencies and courts have struggled with the treatment of uncertainty in environmental impact statements. As we will see, the results have been an unsatisfactory muddle. We should be able to do better. This problem is all the more important today. Climate change will require innovative solutions - new energy technologies, new adaptation strategies. These innovations will inevitably pose risks, often in the form of possible harm to human welfare or the environment. Climate change itself involves uncertainties. Evaluating these risks and informing decision makers and members of the public will be challenging.

Part I of this article provides background on the National Environmental Policy Act (NEPA) for the uninitiated. It will then use the example of dam failure to illuminate the problem of risk assessment in impact statements. Part II uses nuclear power as the basis for a detailed case study. It is hard to resist the impression that the regulatory agency has shied away from discussing risks whenever allowed to do so by the courts. In Part III, the focus turns to the effort of the Council on Environmental Quality to guide agency consideration of uncertainty. Finally, Part IV provides some suggestions for improvements in current practice, and Part V offers a brief conclusion.

Keywords: NEPA, uncertainty, model uncertainty, environmental assessment, nuclear power

Suggested Citation

Farber, Daniel A., Confronting Uncertainty under NEPA. UC Berkeley Public Law Research Paper No. 1403723. Available at SSRN: or

Daniel A. Farber (Contact Author)

University of California, Berkeley - School of Law ( email )

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Room 894
Berkeley, CA 94720-7200
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