Conducting the Environmental Impact Analysis and Assessment - Environmental Impact Analysis: Process and Methods - page 194

significant criteria for wetland impacts are based on the square meters of fill
identified in Section 404 of the Clean Water Act permit requirements:

r No wetlands within the facility foot print—no impact
r Allowed by permit— de minimis impact
r Allowed if there is two for one replication—insignificant impact
r Not allowable—significant impact

Another example is air quality permitting under the Clean Air Act, which
differentiates areas as either compliant or noncompliant areas, and the allow-
able activities are different in each. An alternative in a compliant area could
have a low level of significance with similar activities in noncompliant areas
having different levels of significance. An activity which creates a new non-
compliance area could have an even greater level of significance.
There are many advantages in using standards and criteria to define lev-
els of impact significance. Environmental analysis team members should be
familiar with such criteria within their area of expertise, and they can effi-
ciently define and adapt them to specific conditions for use in the environ-
mental analysis. Also using such criteria all but guarantees acceptance by
stakeholders and provides a level of confidence in decisions made based on
established standards and regulations as significance criteria.

5.3.3.2 Significance Criteria for Specific Environmental Impact Analyses

Unfortunately, standards are not available for all environmental resources
and types of impacts. In these cases the expertise, experience, and creativ-
ity of the environmental analysis team and stakeholders come into play.
Frequently, there are research techniques that are familiar to the discipline
experts on the team that can be useful in establishing significance criteria,
such as grading the level of service or wait times at intersections for traf-
fic impacts. Also, similar or comparable criteria used in other environmen-
tal analyses involving similar actions can be considered. Stakeholder input
and polling is another method that has been used successfully to determine
the level of impact in specific cases. The DCR EIS (U.S. Coast Guard 2008)
applied various techniques to develop significance criteria (Table 5.2) for
each type of impact identified during scoping and through the impact pre-
diction conceptual model (see Section 10.2 for a description of the EIS and
background information). Use of significance criteria also facilitates presen-
tation of predicted impacts in a simple and usable comparative form for a
variety of projects, such as a hypothetical highway bypass (Figure 5.12).
Original research as part of a specific environmental impact analysis
can also be used to develop significance criteria. The USCG DCR exam-
ple (Table 5.2) and impact significance criteria related to invasive mussels