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Section 404 of the Clean Water Act

Types of Mitigation under CWA Section 404: Avoidance, Minimization and Compensatory Mitigation


The White House Council on Environmental Quality (CEQ) has defined mitigation in its implementing regulations for the National Environmental Policy Act to include avoiding, minimizing, rectifying, reducing over time, and compensating for impacts.  The Clean Water Act Section 404(b)(1) Guidelines, developed by EPA in coordination with the U.S. Army Corps of Engineers and issued in 1980, establish substantive environmental criteria which must be met for activities to be permitted under Clean Water Act Section 404.  The types of mitigation enumerated by CEQ are compatible with the requirements of the Guidelines; however, as a practical matter, they can be combined to form three general types of mitigation: avoidance, minimization, and compensatory mitigation. 

As discussed in their 1990 Memorandum of Agreement on the mitigation requirements of the Guidelines, the Department of the Army and EPA agree that these mitigation types are generally applied sequentially in the following order:

  1. Avoidance means mitigating an aquatic resource impact by selecting the least-damaging project type, spatial location and extent compatible with achieving the purpose of the project.  Avoidance is achieved through an analysis of appropriate and practicable alternatives and a consideration of impact footprint.
  2. Minimization means mitigating an aquatic resource impact by managing the severity of a project's impact on resources at the selected site.  Minimization is achieved through the incorporation of appropriate and practicable design and risk avoidance measures.
  3. Compensatory Mitigation means mitigating an aquatic resource impact by replacing or providing substitute aquatic resources for impacts that remain after avoidance and minimization measures have been applied, and is achieved through appropriate and practicable restoration, establishment, enhancement, and/or preservation of aquatic resource functions and services.

A 2015 Presidential Memorandum underscores the importance of effectively mitigating adverse impacts to land, water, wildlife, and other ecological resources and having clear and consistent approaches to impact avoidance, minimization, and compensatory mitigation.

Avoidance and Minimization Evaluations and Reports

Compensatory Mitigation Evaluations and Reports

View Compensatory Mitigation Evaluations and Reports.