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Tennessee Environmental Procedures Manual

Chapter 5: Impact Analysis

5.0 Overview

For all NEPA (and TEER) documents, some level of data collection/records review, technical studies and impact analysis is required. The chapter begins by defining the types of impacts (direct, indirect and cumulative) that may result from a project. Next the chapter describes the process for a records check that should be completed early in project planning to assist in identifying important environmental issues that warrant consideration in the highway location phase. The bulk of this chapter discusses the individual technical studies and analyses that are required for the environmental documentation of a project, including analyses to meet the requirements of Section 106 of the National Historic Preservation Act, Section 4(f) of the Department of Transportation Act and Section 6(f) of the Land and Water Conservation Fund Act.

The timing for undertaking the analyses and technical studies outlined in this chapter may differ from project to project. It is, however, TDOT's intention to start "environmental screening" at the earliest phases, once the preliminary purpose and need and study area are defined, before the EA, EIS or TEER document is initiated. (see Figures 1-3, 1-4 and 1-6 in Chapter 1). Under the Context Sensitive Solutions (CSS), Needs Assessment, and the Transportation Planning Report (TPR) processes, environmental screening occurs early in project planning to identify issues that must be considered in establishing the project location. Initially the screening may be conducted as a desktop records check supplemented by a windshield survey or field reconnaissance by knowledgeable technical staff. The screening process helps with early identification of important resources that must or should be avoided by the project. By laying out on a constraints map the information gathered in the screening process, roadway designers and the public can see the environmental factors that must be considered in defining alternatives or options to address the transportation needs. The full scope of field work for technical areas occurs once project alternatives or options have been identified.

The timing of the tasks discussed in this chapter may also be influenced by any critical issues that are identified early in project planning. These issues may be known by project planners or may have been brought to the attention of planners by local government or the public. Sometimes these issues will require early, in-depth studies or agency coordination to enable TDOT to proceed with identifying the location for a project. Examples of such issues are former dump sites, a National Historic Landmark, and parklands.

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