Draft EIS/EIR for the San Luis Reservoir SRA Resource ...

5. Environmental Analysis
5.2.3 Assumptions and Methods for Evaluating Impacts
Impact analyses and conclusions are based on interdisciplinary team knowledge
of resources and the Plan Area, reviews of existing literature, and information
provided by experts in Reclamation, CSP, and other agencies. Impacts described
in this section are based on the conceptual Plan as implemented by the proposed
alternatives described in Chapter 4. The information used to establish a baseline
of existing conditions (including applicable laws and regulations for each
resource) is described in Chapter 2. The management alternatives have been
configured to optimize benefits and minimize adverse effects on both ecosystem
function and the human environment. In the absence of quantitative data, best
professional judgment prevails. Protocol surveys for special-status species were
not conducted as part of this programmatic planning effort.
One of the primary differences between NEPA and CEQA is the way significance
is determined and discussed in environmental documents. Under NEPA,
significance is used to determine whether an EIS or some lower level of
documentation will be required. NEPA requires preparation of an EIS when the
proposed federal action (project) as a whole has the potential to “significantly
affect the quality of the human environment.” The determination of significance is
based on context and intensity (40 CFR §1508.27). Some impacts determined to
be significant under CEQA may not be of sufficient magnitude to be determined
significant under NEPA. Under NEPA, once a decision to prepare an EIS is made,
it is the magnitude of the impact that is evaluated, and no judgment of its
significance is deemed important for the text. NEPA does not require that a
determination of significance for individual resources be stated in an
environmental document. Once the proposal itself is considered as a whole to
have significant effects, all of its specific effects on the environment (whether or
not “significant”) must be considered, and mitigation measures must be developed
where it is feasible to do so (40 CFR §1502.14(f), 1502.16(h), 1508.14, and the
Council on Environmental Quality’s [CEQ’s] 40 Most Asked Questions #19a 7 ).
CEQA, on the other hand, does require an identification of each “significant effect
on the environment” resulting from the project and ways to mitigate each
significant effect. A significant effect on any environmental resource triggers the
preparation of an EIR. Each significant effect on the environment must be
disclosed in the EIR and mitigated, if feasible. In addition, the CEQA Guidelines
list a number of mandatory findings of significance that also require the
preparation of an EIR. There are no types of actions under NEPA that parallel the
findings of mandatory significance in CEQA.
According to the CEQA Guidelines Section 15382, a significant impact on the
environment refers to a “substantial, or potentially substantial, adverse change in
any of the physical conditions within the area affected by the project, including
land, air, water, minerals, flora, fauna, ambient noise, and objects of historical or
aesthetic significance.” Environmental impacts may be associated with visitor
7 http://ceq.hss.doe.gov/NEPA/regs/40/40p3.htm.
San Luis Reservoir SRA 5-5
Draft RMP/GP and Draft EIS/EIR