NEPA provides for each agency to develop a list of categories of actions that are determined through agency experience to typically have no significant environmental impact, and thus may generally be excluded from detailed documentation (EA or EIS). Review and documentation for actions that qualify for one or more of these categories is generally minimal but should address any extraordinary circumstances and any requirements of other environmental laws or executive orders. Though detailed NEPA documentation does not apply, requirements of other laws must be documented as appropriate.
FEMA’s list of Categorical Exclusions have been codified at 44 C.F.R. 10.8(d)(2). The agency’s list of Extraordinary Circumstances that should be taken into consideration to determine if a Categorical Exclusion applies include whether the action involves:
(i) Greater scope or size than normally experienced for a particular category of action;
(ii) Actions with a high level of public controversy;
(iii) Potential for degradation, even though slight, of already existing poor environmental conditions;
(iv) Employment of unproven technology with potential adverse effects or actions involving unique or unknown environmental risks;
(v) Presence of endangered or threatened species or their critical habitat, or archaeological, cultural, historical or other protected resources;
(vi) Presence of hazardous or toxic substances at levels which exceed Federal, state or local regulations or standards requiring action or attention;
(vii) Actions with the potential to affect special status areas adversely or other critical resources such as wetlands, coastal zones, wildlife refuge and wilderness areas, wild and scenic rivers, sole or principal drinking water aquifers;
(viii) Potential for adverse effects on health or safety; and
(ix) Potential to violate a Federal, State, local or tribal law or requirement imposed for the protection of the environment.
(x) Potential for significant cumulative impact when the proposed action is combined with other past, present and reasonably foreseeable future actions, even though the impacts of the proposed action may not be significant by themselves.