Federal Agency Treatment of Uncertainty in Environmental Impact Statements Under the CEQ’s Amended NEPA Regulation § 1502.22: Worst Case Analysis or Risk Threshold

This Note traces the judicial and administrative treatment of uncertainty under NEPA and supports the CEQ’s replacement of worst case analysis with a qualitative probability threshold. Part I discusses the development of reasonableness standards in NEPA common law to define agency obligations prior to promulgation of the worst case analysis regulation. Part II reviews the worst case analysis regulation and its judicial construction. Finally, Part III outlines the amended regulation, which replaces worst case analysis with a probability threshold employing the rule of reason to limit EIS discussion to environmental effects shown through credible scientific evidence to be reasonably foreseeable. This Part next discusses judicial responses to the CEQ amendment and suggests an interpretation of the new regulation that comports more closely with the amendment than that of the courts. The Note concludes that both the CEQ’s intention and more effective use of the EIS process require major practical alterations in substantive EIS preparation which the amendment, by itself, is unlikely to generate.