Environmental Compliance

Incomplete or Unavailable Information

In the preparation of an environmental impact statement (EIS), in which an agency is evaluating reasonably foreseeable significant adverse effects (those which have catastrophic consequences, even if their probability is low), an agency may find that information is incomplete or unavailable (40 CFR • 1502.22).

If the missing information is essential to a reasoned choice among the alternatives and the costs of acquiring it are not exorbitant, the agency must obtain the information and include it in the EIS (40 CFR• 1502.22).

If the missing information cannot be obtained because the costs of obtaining it are exorbitant or the means to obtain it are not known, the agency shall include within the EIS: (1) a statement that such information is incomplete or unavailable; (2) a statement of the information's relevance to evaluating reasonably significant adverse impacts on the human environment; (3) a summary of existing credible scientific evidence relevant to evaluating reasonably significant adverse impacts on the human environment; and (4) the agency's evaluation of such impacts based upon scientifically accepted theoretical approaches or research methods (40 CFR• 1502.22).

Legal challenges to the adequacy of environmental documents often make claims that information is incomplete or unavailable, especially if the documents analyze risks for which the scientific evidence is equivocal. When the information is equivocal and is not incomplete or unavailable, agencies have the option of presenting the prevailing scientific opinion or presenting both perspectives. An appropriate procedure is to state within the document that the information is equivocal and remove any doubt that both perspectives were considered or that vital information was missed.