Environmental Review Toolkit
NEPA and Project Development

NEPA and Transportation Decisionmaking

Mitigation of Environment Impacts

The NEPA process is intended to help public officials make decisions that are based on understanding of environmental consequences, and take actions that protect, restore, and enhance the environment.

-- 40 CFR § 1500.1(b): Purpose

Federal agencies shall to the fullest extent possible:

Use all practicable means consistent with the requirements of the Act and other essential considerations of nation policy, to restore and enhance the quality of the human environment and avoid or minimize any possible adverse effects of their actions on the quality of the human environment.

-- 40 CFR 1500.2(f)

The mitigation of impacts must be considered whether or not the impacts are significant. ("Forty Most Asked Questions and Answers on the CEQ Regulations" Number 19a). Agencies are required to identify and include in the action all relevant and reasonable mitigation measures that could improve the action.

The CEQ regulations define mitigation as:

  • Avoiding the impact altogether by not taking a certain action or parts of an action.
  • Minimizing impacts by limiting the degree or magnitude of the action and its implementation.
  • Rectifying the impact by repairing, rehabilitating, or restoring the affected environment.
  • Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action.
  • Compensating for the impact by replacing or providing substitute resources or environments.

-- 40 CFR 1508.20

Mitigation: Avoid --> Minimize --> Repair or Restore --> Reduce over time --> Compensate

This ordered approach to mitigation is known as "sequencing" and involves understanding the affected environment and assessing transportation effects throughout project development. Effective mitigation starts at the beginning of the NEPA process, not at the end. Mitigation must be included as an integral part of the alternatives development and analysis process.

FHWA's mitigation policy states:

Measures necessary to mitigate adverse impacts will be incorporated into the action and are eligible for Federal funding when the Administration determines that:

  1. The impacts for which the mitigation is proposed actually result from the Administration action; and
  2. The proposed mitigation represents a reasonable public expenditure after considering the impacts of the action and the benefits of the proposed mitigation measures. In making this determination, the Administration will consider, among other factors, the extent to which the proposed measures would assist in complying with a Federal statute, Executive Order, or Administration regulation or policy.

-- 23 CFR 771.105(d)

Additional Information

Context Sensitive Solutions
Flexibility in Highway Design
Context Sensitive Design

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