Guidance on the consideration of past actions in cumulative effects analysis

This 2005 memo from the White House Council on Environmental Quality instructs federal agencies on how to handle past actions when analyzing cumulative environmental impacts under the National Environmental Policy Act (NEPA). Agencies are not required to exhaustively catalog every past action, but must describe their current combined effects when those effects are relevant to a proposed action's foreseeable environmental impacts. The guidance emphasizes using the scoping process to focus analysis on truly significant cumulative effects rather than accumulating unnecessary background data.

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This CEQ memorandum provides guidance to federal agency heads on the extent to which agencies must analyze the environmental effects of past actions when conducting cumulative effects analysis under NEPA. It clarifies that agencies need only describe the identifiable present effects of past actions to the extent they are relevant and useful in analyzing the proposed action’s effects, and that agencies are not required to exhaustively list or analyze all individual past actions. The memo also offers practical tools for NEPA practitioners, including guidance on scoping and handling incomplete or unavailable information.

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