FEDERAL ENERGY REGULATORY COMMISSION Project No. 405 ...

20100204-3055 FERC PDF (Unofficial) 02/04/2010
Project No. 405-087 16
license term (30 to 50 years) and highlight the effect on the cumulatively affected
resources. The study report should include a sediment management plan that includes
projections of sediment accumulation; benchmarks for potential impacts and actions; and
options to manage, mitigate, and remove accumulated sediment. If, at the completion of
the Sediment Introduction and Transport (Sediment and Nutrient Loading) Study, the
results of the study do not adequately characterize the geographic and temporal
cumulative effects, Exelon may be required to conduct a sediment transport modeling
study during the second field season (2011).
3.16 Instream Flow Habitat Assessment below Conowingo Dam
Exelon proposes to evaluate instream habitat below Conowingo dam over a range
of flows using a combination of literature review, field surveys of bathymetric and
hydraulic data, and hydraulic habitat modeling.
SRBC and The Nature Conservancy recommend that Exelon be required to
develop site-specific habitat suitability curves for the species being evaluated and to
incorporate ecological dynamics into the model. Interior recommends that if Exelon
cannot verify that literature-based habitat suitability curves are representative of
conditions below Conowingo dam, then Exelon should be required to develop sitespecific
curves.
Staff agree that one of the requirements of a successful and meaningful instream
flow habitat assessment is the use of appropriate habitat suitability curves for the species
and life stages of interest. However, it is premature to require Exelon to develop sitespecific
suitability curves prior to conducting a literature review. It is accepted practice
to initially search for appropriate curves that have already been developed and then
consult with stakeholders about the findings of the search and the necessity of sitespecific
curves. This is the procedure Exelon proposes in Task 1 of this study plan.
Therefore, staff do not recommend modification of the revised study plan.
SRBC and The Nature Conservancy did not elaborate on what they mean by
requiring ecological dynamics to be incorporated in the model. Therefore, staff do not
recommend a modification to the study. Exelon’s methodology is consistent with
accepted methodology for instream flow habitat assessments and will be adequate to
evaluate possible operational changes that may be proposed, recommended, or required.
3.18 Characterization of Downstream Aquatic Communities
Exelon proposes to conduct a literature review and produce a report summarizing
and characterizing the fish and macroinvertebrate communities below Conowingo dam.