FEDERAL ENERGY REGULATORY COMMISSION Project No. 405 ...

20100204-3055 FERC PDF (Unofficial) 02/04/2010
Project No. 405-087 19
mussels are expected which would be quantitatively surveyed using quadrats, surface
collection, and excavation of sub-surface mussels. It is not clear whether Exelon would
consider employing quantitative survey methods on more than 3 concentrations, if they
were discovered, or if Exelon is limiting their potential level of effort by suggesting that 3
areas is the maximum at which they will use the quantitative methods. In any case, the
objectives of the study are to characterize the mussel community and determine if project
operations affect the community. Even if there is a maximum of 3 locations where
quantitative survey methods are employed, this should not reduce the value of the study
for achieving the stated goals. Therefore, staff do not recommend this modification.
Modification (8) appears to require only a minor clarification. Exelon states that
the semi-quantitative methods will be conducted at minimum flow conditions and under
Task 4 Exelon states that river flow will be recorded during each of the quantitative
surveys. Even though Exelon seems to have already proposed recording river flow
during each mussel search, staff suggest that this clarification be included in the study
plan.
Modification (9) would require Exelon to deposit the voucher specimens collected
into a state or regional natural history museum. This modification is consistent with
accepted scientific procedures as well as requirements for mussel surveys conducted at
other Commission relicensing proceedings and therefore staff recommend this
modification.
3.20 Salinity and Salt Wedge Encroachment
In their comments on the revised study plan, the Maryland DNR, Fish & Boat
Commission, and the SRBC request a revision to Task 1 of the study plan to require
collection of additional 15-minute salinity data in 2010 to augment the post 2007 data, if
needed. Because the data supplied for this analysis are provided from external sources,
all available data should be used in the frequency and duration analysis. If subsequent
statistical analyses of the available data set show that the data set is too small, additional
data collection could be required in a second season of studies (2011).
Salinity threshold
In Task 1 of the study plan, Exelon proposes to use a critical salinity threshold of
0.3 parts per thousand (ppt) in the frequency and duration analysis for the salinity data.
In their comments on the revised study plan, Maryland DNR, Fish & Boat Commission,
and the SRBC request that Task 1 of the study plan be modified to use the current
Environmental Protection Agency (EPA) standard for drinking water of 0.25 ppt for a
critical salinity threshold. A goal of the study is to evaluate the project’s operational
effect on salinity levels at freshwater intakes at the City of Havre de Grace, Maryland.