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Tennessee Environmental Procedures Manual

Chapter 9: Environmental Commitments and Coordination With Design and Construction Activities

9.1 Types of Commitments

When adverse or negative impacts are identified in project planning, numerous methods are available to address them. Three basic types of environmental commitments are made in the NEPA and permitting processes:

  • Avoidance;
  • Minimization; and
  • Mitigation.

These types of commitments, described in more detail below, can respond to a variety of impacts to natural or manmade resources.

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9.1.1 Avoidance

During project planning, potential impacts to sensitive resources are identified. Where feasible, alternatives can be changed during the planning or design phase to avoid impact to these areas. Avoidance can involve alignment shifts (or selection of an entirely new alignment) as well as grade changes to go over or under a sensitive area. Examples include:

  • In the planning stages, a family cemetery is located adjacent to the proposed alignment. Planners are unsure of whether it will be affected by the project. They inform project designers who determine that the cemetery does fall within a cut area. The alignment can be shifted slightly in this area to avoid the cemetery.
  • A significant archaeological site is identified that warrants preservation in place. During project design, it is determined that the site can be completely bridged, thus avoiding impacts to the site and preserving it in place.
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9.1.2 Minimization

Minimization involves the creation and implementation of measures to reduce the potential impact to a resource. Minimization measures can include:

  • Shifting alignment(s);
  • Committing to off-season construction in order to avoid the habitat of an endangered species during the breeding season;
  • Incorporating drainage structures into the highway to prevent or control release of storm water into protected water resources;
  • Constructing noise walls or depressing a section of road to reduce noise impacts;
  • Including landscaping to serve as a visual screen; or
  • Limiting the number of interchanges on a full access control facility to minimize incompatible development.
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9.1.3 Mitigation

Mitigation includes compensation and enhancement. Compensation makes an effort to offset damages to or displacements of the affected features. Examples of compensation include:

  • Adding land and/or amenities to a public park and recreation area to replace lost facilities; and
  • Providing off-site compensation for loss of wetlands.

Enhancements add desirable features to the project to allow it to blend more harmoniously with the surrounding environment. Enhancements can occur when a project's impacts cannot be avoided or minimized. Examples include:

  • Developing bicycle trails or paths adjacent to roadways;
  • Creating a landscaped gateway into a community;
  • Including public art on an overpass that requires widening;
  • Providing signage to recognize specific cultural or historical resources; and
  • Creating wildlife passageways.
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