NPS Director's Order 12: Conservation Planning, Environmental Impact Analysis and Decision Making
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Congaree Swamp National Monument, SC4.2 Environmental Impact Statements — Criteria for Significant Impact

If something your park is proposing might have a significant impact on the human environment, you must prepare an EIS. It is important, then, to understand how the significance of an impact is gauged. Although significance may often be a subjective judgment, to the maximum extent possible it must be based on the scientific evidence and public input that NEPA provides. Section 4-2 (B) contains the CEQ criteria you should use in deciding whether an EIS may be required. CEQ requires you to evaluate the severity of impacts in several different contexts, if two or more apply.

A. Context

Evaluating impacts in particular contexts gives valuable comparative information. Context may be temporal (i.e., short-term impacts vs. long-term), but it is most often geographical. For instance, the temporary closure of a 1,000-acre recreation area may have only minor impacts on the nation's recreation users but severe impacts on local residents who depend on the area as the sole source of outdoor recreation for many miles around. Or, building 30 homes in Denver may not have a major impact, whereas building them in Denali National Park could.


Are these special resources affected:

  • Public safety or health?
  • Wetlands, floodplains, or ecologically sensitive areas?
  • Important scientific, cultural, or historic resources?
  • Threatened or endangered species or their habitat?

Is the proposal:

  • Likely to be highly controversial or its impact analysis highly debated?
  • Likely to involve highly uncertain impacts or unique or unknown risks?
  • Likely to pave the way for future actions?
  • Part of a larger proposal?
  • Likely to violate any law or requirement imposed to protect the environment?

If so, consider an EIS rather than an EA or a CE.


B. Criteria

Your team or park decision-maker must consider the following criteria when determining whether an impact may be significant in helping to determine if an EIS is appropriate (1508.27):

  1. Impacts that may have both beneficial and adverse aspects and which on balance may be beneficial, but that may still have significant adverse impacts which require analysis in an EIS.
  2. The degree to which public health and safety are affected.
  3. Any unique characteristics of the area (proximity to historic or cultural resources, wild and scenic rivers, ecologically critical areas, wetlands or floodplains, and so forth).
  4. The degree to which impacts are likely to be highly controversial.
  5. The degree to which the potential impacts are highly uncertain or involve unique or unknown risks.
  6. Whether the action may establish a precedent for future actions with significant effects, or represents a decision in principle about a future consideration.Consider historic properties as part of the criteria
    Whether the action is related to other actions that may have individual insignificant impacts but cumulatively significant effects. Significance cannot be avoided by terming an action temporary or breaking it down into small component parts.
  7. The degree to which the action may adversely affect historic properties in or eligible for listing in the National Register of Historic Places, or other significant scientific, archeological, or cultural resources.
  8. The degree to which an action may adversely affect an endangered or threatened species or its habitat.
  9. Whether the action threatens a violation of federal, state, or local law or requirements imposed for the protection of the environment.

Further Links:

Important NEPA Facts
DO 28 Cultural Resources Management
DO 28B Management of Archaeological Resources
DO 41 Wilderness Preservation and Management
DO 77 Wet Land Protection

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