Overview and Initiating the Environmental Impact Analysis and Assessment - Environmental Impact Analysis: Process and Methods - page 108

Area of impacts

Alternative
action

Existing
conditions

FIGURE 4.1
Simplicity of an environmental impact prediction.

This concept is expanded in the following presentations of the components
of environmental impact analysis.

4.2 Need for Environmental Impact Analysis

A first step in the environmental analysis is to determine the need for and
general extent of the analysis. Some authors (Morgan 2001) have termed this
process “screening,” but in this topic the term screening is applied to an
initial selection of alternatives (Section 4.5.3) and is not used here to avoid
confusion. The need for analysis can be determined based on several factors
including magnitude and type of proposed action, environmental setting,
environmental resource potentially at risk, and preliminary assessment.
Each of these is discussed subsequently.

4.2.1 Magnitude and Type of the Proposed Action

The size and breadth of the proposed action, be it a project, plan, or policy, are
the most obvious and common factors that determine the need for environmen-
tal analysis. Many organizations have established threshold criteria defining
the need for environmental analysis, and in some cases there are additional
criteria to define the level of analysis required. The presence of significant
impact used to determine the need for a full environmental impact statement
(EIS) as opposed to an environmental assessment (EA) and the listing of actions
for categorical exclusion (CATEX) (as discussed in Chapter 3) are examples of
threshold criteria. There are other examples in state and international programs
as described in Chapter 8. Also individual organizations, such as the World
Bank and many U.S. federal agencies have established lists of actions commonly