NPS Director's Order 12: Conservation Planning, Environmental Impact Analysis and Decision Making
Table of Contents
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Introduction | Overview of the NEPA Process | Categorical Exclusions | Environmental Impact Statements | Environmental Assessments | Decision Documents | Programmatic Documents and Planning | NPS Review of Non-NPS Documents | Definitions and Acronyms | Appendix 1: Environmental Screening Form | Appendix 2: Categorical Exclusion Form | Contacts | Index
Arlington House, the Robert E. Lee Memorial, VA5.2 Environmental Assessments — When to Prepare an EA
Introduction | When to Prepare an EA | Length of an EA | Format and Content of an EA | Public Involvement | Administrative Process of Review of EAs

An EA should be prepared if:

  • an action is not listed as a CE (i.e., in section 3.3 or 3.4), or if the action is not listed as an action normally requiring an EIS (section 4.4), and a decision to prepare an EIS has not been made.
  • additional analysis and public input is needed to know whether the potential for significant impact exists.
  • preliminary analysis indicates there is no scientific basis to believe significant impacts would occur, but some level of controversy over the use of one or more environmental resources exists.
  • the action is described on the list of actions normally categorically excluded, but one of the exceptional circumstances described in section 3.5 applies.

If a proposal analyzed by an EA is found to have significant impacts, instead of requiring an EIS, CEQ (Q40) allows agencies to employ mitigation to reduce impacts to below significance in case of any of the following:

(a) the mitigation is imposed by statute or regulation.
(b) the proposal is rewritten to include mitigation as an integral part of the description.
(c) the proposal is fundamentally changed to avoid the impact.

The effectiveness and enforceability of the mitigation must be guaranteed, and a new EA analyzing only the impacts of the mitigated or changed proposal must be prepared. CEQ refers to this as a “mitigated EA.”

CEQ warns against trying to avoid an EIS rather than reducing impact through “mitigated EAs.” If you need several mitigation measures to avoid a significant impact, or if the mitigation measures are highly speculative or distant in time, you should carefully consider preparing an EIS instead of a mitigated EA. As an example: Construction of a proposed parking lot would result in a loss of a large number of old growth trees. In order to mitigate the loss, the park proposes planting seedlings and waiting 500 years for the lost tree stand to be replaced. This effort at mitigation is too speculative and distant to adequately lessen the significance of the impact.

Further Links:

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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