Environmental Compliance

Determination of "Significance" for Environmental Impacts

The National Environmental Policy Act (NEPA) requires that an environmental impact statement (EIS) be prepared for any major Federal action that significantly affects the quality of the human environment (42 U.S.C. 4332). Any potentially significant adverse effects on ecological, aesthetic, historic, cultural, economic, social, or health resources associated with the action or its range of alternatives must be identified in the EIS. Direct, indirect, and cumulative effects must be considered. The significance of these adverse effects must be determined with respect to both context and intensity (40 CFR• 1508).

Context can refer to several different aspects or dimensions of the human environment. Effects from the action, or its range of alternatives, must be evaluated with respect to all relevant contexts, whether broadly or narrowly defined. Context can be defined by geographic boundaries, such as an affected watershed; political boundaries, such as an affected county; economic boundaries, such as an affected regional economy; or demographic boundaries, such as an affected cultural group. Context can be as broadly defined as society in general.

Intensity refers to the severity of the effect. The NEPA provides a set of issues to consider when evaluating intensity. Adverse impacts must be identified, even if the overall impact of an action is beneficial in the judgment of the agency. The degree to which the action affects public health or safety must be determined. Violations of any Federal, state, or local law or requirements imposed for the protection of the environment must also be identified. Unique ecological, cultural, historic, or social characteristics of the potentially affected area must be noted, as well as the degree to which they are affected by the proposed action. Of special concern is the degree to which the action affects sites registered on the National Register of Historic Places and effects on or threats to endangered or threatened species or critical habitat listed under the Endangered Species Act of 1973. The degree of controversy surrounding the effects must be determined. Uncertainty and unknown risks associated with the effects must be disclosed. The relationship of this action to other actions must be determined, that while individually insignificant, contribute to the cumulative significance of an adverse effect.

Establishing the significance of an adverse effect requires a qualitative determination of both the context in which the effects are considered and the intensity of those effects. There is no quantitative test for significance. Generally the degree of significance of an effect is not determined. The effect is either significant or it is not.