Overview and Initiating the Environmental Impact Analysis and Assessment - Environmental Impact Analysis: Process and Methods - page 159

of impacts among alternatives. Thus the final comparison cannot commence
until the impacts are fully assessed and evaluated in combination with the
other critical aspects of the project, plan, or program such as economic via-
bility, engineering or technical feasibility, implementability, and stakeholder
input. Once all of these considerations have been developed, the alternatives
can be compared and an informed decision rendered.
The comparison of alternatives can take many forms, but in many cases it is a
simple extension of the alternative screening process. Generally the same con-
siderations, such as criteria measuring achievement of purpose and need, are
used in the comparison. The final comparison of alternatives does differ from
the screening in several important ways. First there is much more detailed
information available on all aspects of the alternatives including impacts,
costs, permit requirements, engineering details for projects, and similar detail
for plans and policies. Thus the final analysis can be much more detailed than
screening where the differences in impact intensity among alternatives and
environmental resources can be quantified as opposed to the typical binomial
yes or no or retain or discard conclusions in screening.
The final analysis can also incorporate impact significant criteria (see Section
5.3.3) into the comparison, and these are typically not available at the alternative
screening level. These criteria are developed for each environmental resource
to determine whether the effect on the resource from an alternative is signifi-
cant, and frequently there are multiple criteria for each resource so a consistent
level of impact (e.g., no impact, minor impact, moderate impact, or significant
impact) among resources can be expressed. This facilitates comparing alter-
natives with impacts on different environmental resources because from an
environmental perspective, an alternative with significant impacts on multiple
resources would be inferior to one with only minor impacts on any resource.
Alternative comparison employing an impact intensity scale can be fur-
ther enhanced by applying the relative importance of each resource. This can
be included in the final comparison with the benefit of extensive stakeholder
input identifying the relative importance of various factors to the people
directly affected. Thus those aspects of greater concern to stakeholders can
be given greater weight in the comparison of alternatives (see Section 4.3.1
and Table 4.1) where the importance to stakeholders was quantified and
input into the comparison using a decision science approach.
Decision science is a tool first developed for business-oriented decisions
that incorporates many factors to assist in an objective approach to selecting
from among many options (Tillman and Cassone 2012). The approach has been
adapted to environmental decisions (Gregory et al. 2012) and can be very suc-
cessful for a large, complex alternative selection in an environmental impact
analysis. One of the basic methods applied to alternative selection combines the
relative importance of each decision criterion with a measure of the intensity
of impact to produce a total score for the alternative, relative to environmen-
tal concerns. Complex algorithms can be incorporated to include uncertainty,
relative bias, and balance of unequal quantification, but the basic approach is