NC0004979_Assessment of Balanced & Indigneous populations_20091101

ASSESSMENT OF BALANCED AND INDIGENOUS POPULATIONS
IN LAKE WYLIE NEAR ALLEN STEAM STATION
NPDES Permit No. NC0004979
Principal Investigators:
Michael A. Abney
John E. Derwort
Keith A. Finley
DUKE ENERGY
Corporate EHS Services
McGuire Environmental Center
13339 Hagers Ferry Road
Huntersville, NC 28078
November 2009

EXECUTIVE SUMMARY
Pursuant to an agreement with the North Carolina Department of Environment and Natural
Resources, annual monitoring of macroinvertebrates and fish continued at selected Lake
Wylie locations in the vicinity of Allen Steam Station (AS). The objective of this ongoing
monitoring program is to assess macroinvertebrate and fish populations with respect to
operation of AS and evaluate the renewal of thermal limits in the AS National Pollutant
Discharge Elimination System (NPDES) permit (NC0004979).
During 2004 — 2008, AS continued to operate as a base load generation facility and produced
electricity 99.2% of the available days from January 2004 — December 2008. For the entire
five-year period, AS operated at an average of about 64.8% of capacity. The average monthly
CCW discharge water temperature ranged from 16.7 °C (62 °F) in January 2006, to the upper
permitted limit, 38.9 °C (102 °F), in August 2005, August 2007, June 2008, and July 2008.
Discharge temperatures followed a regular seasonal pattern and were similar to previously
reported CCW discharge data for this facility. The thermal limits of the NPDES permit of AS
were not exceeded during the 2004 — 2008 period.
In August, 2008, lake -wide in situ thermal and dissolved oxygen (DO) profiles were obtained
to evaluate potential water quality influences from operation of a temporary condenser
cooling water (CCW) bypass system installed at AS to moderate discharge temperatures. The
relatively brief period of temporary CCW bypass pumping during August 2008 did not
appear to appreciably affect Lake Wylie water quality. Thermal profiles at each of the six
Lake Wylie locations sampled from surface to bottom indicated temperatures were generally
representative of seasonal conditions seen in recent years. Lake Wylie DO profiles were
consistent with recent historical trends, except that near -surface concentrations tended to be
similar to or slightly lower than recent historical minima.
Generally, the macroinvertebrate data from 2004 — 2008 exhibited similar densities and taxa
abundance as seen during previous report periods. The highest overall mean
macroinvertebrate density was collected a the South Fork and Catawba River confluence
monitoring location, followed by Locations at the AS CCW discharge area and the upstream
reference area, respectively. Spatial variations in taxa abundance at the three locations were
consistent with historical data and did not indicate any impact related to the AS thermal
effluent.
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Summer electrofishing surveys during both 2000 — 2003 and 2004 — 2008 were dominated by
centrarchids. Clupeids comprised less of the catch in 2004 — 2008, and mosquitofish were
collected for the first time since sampling began in 1991. Pollution tolerant fish species
decreased slightly in summer 2004 — 2008. The AS discharge canal generally had the lowest
number of individuals and lowest number of species, likely due to elevated water
temperature. Summer electrofishing data is consistent with previously reported data.
Spring electrofishing surveys from the AS area during 2004 — 2008 documented greater
numbers of individuals, biomass, and number of species than at the reference area. This was
also documented in previous reports. Pollution -tolerant species represented similar portions
of the spring electrofishing surveys in both 2000 — 2003 and 2004 — 2008. Spring surveys
were dominated by centrarchids, with lesser contributions from clupeids, similar to 2000-
2003.
Threadfm shad continue to dominate the Lake Wylie forage fish community in 2004 — 2008
fall purse seine surveys. Alewives declined and were absent in the 2007 and 2008 surveys.
Based on the diversity and numbers of individuals in the lake Wylie littoral fish community
during spring and summer, the range of trophic groups represented, and the regular
availability of forage fish to limnetic predators, the operation of AS has not impaired the
Lake Wylie fish community.
Water quality data reported by other researchers, as well as 2008 results associated with the
AS CCW bypass operation, serve to confirm that Lake Wylie in the vicinity of AS, and as a
whole, is capable of sustaining a balanced and indigenous aquatic community. Additionally,
comparison of,AS operation and environmental monitoring data indicate that balanced and
indigenous populations of macroinvertebrates and fish continue to exist in Lake Wylie near
AS. These data support a conclusion that the present thermal limits are appropriately
protective and should be maintained when the Station NPDES permit is renewed.
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