Text

Forwards Annual Lake Norman Environ Summary Rept for 1993
	ML20078A157
Person / Time
Site:	Mcguire, McGuire
Issue date:	01/18/1995
From:	Mcmeekin T; DUKE POWER CO.
To:	; NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
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	NUDOCS 9501240298
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' DukeIbwCompany .

McGuire Nuclear Generation Depanment V l T. C McMam

^ Vicehesident r 12700Hagers FenyRoad(MG01YP) (704)8754800

'- Huntenodle,NC28078M (104)8754809 Fax DUKEPOWER January 18, 1995 U. S. Nuclear Regulatory Commission ,

Document Control Desk Washington, D.C. 20555 i

Subject:

McGuire Nuclear Station Docket Nos. 50-369, 50-370 Pursuant to McGuire Technical Specifications, Appendix B, Section 3.2,.

please find attached the annual Lake Norman Environmental Summary Report for 1993 as required by NPDES permit NC0024392.

Questions concerning this report should be directed to Kay Crane, McGuire Regulatory Compliance at (704) 875-4306.

Very truly yourr, f(Dud '

T. C. McMeekin, Vice President McGuire Nuclear Station cc 'Mr. Victor Nerses, Project Manager Office of Nuclear' Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. S. D. Ebneter, Regional Administrator U. S. Nuclear Regulatory Commission

-Region II 101 Marietta Street - Suite 2900 Atlanta, Georgia 30323 Mr. George Maxwell Senior Resident Inspector g

McGuire Nuclear Station e

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9501240298 950118 PDR ADOCK 05000369 /

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i LAKE NORMAN: 1993

SUMMARY

l MAINTENANCE MONITORING PROGRAM McGUIRE NUCLEAR STATION: NPDES No. NC0024392 1

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DUKE POWER COMPANY 13339 IIAGERS FERRY ROAD HUNTERSVILLE, NORTII CAROLINA 28078 DECEMBER 1994 e

t TABLE OF CONTENTS i Page EXECUTIVE

SUMMARY

i LIST OF TABLES v l LIST OF FIGURES vi l I

CHAPTER 1: McGUIRE OPERATIONAL DATA 1-1 Introduction 1-1 Operational data for 1993 1-1 Thermal Modeling 1-1 j Results and Discussion 1-2 Summary 1-4 Literature Cited 1-5 CHAPTER 2: WATER CHEMISTRY 2-1 ;

Introduction 2-1 !

Methods and Materials 2-1 Results and Discussion 2-2 i Future Water Chemistry Studies 2-8 !

Summary 2-9 Literature Cited 2-9 (qj CHAPTER 3: PHYTOPLANKTON Introduction 3-1 3-1 Methods and Materials 3-1 Results and Discussion 3-2

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Future Phytoplankton Studies 3-6 Summary 3-6 Literature Cited 3-7 CHAPTER 4: ZOOPLANKTON 4-1 Introduction 4-1 Methods and Materials 4-1 Results and Discussion 4-2 Future Zooplankton Studies 4-5 Summary 4-5 Literature Cited 4-6 CHAPTER 5: FISHERIES 5-1 Introduction 5-1 Methods and Materials 5-2 Results and Discussion 5-2 Future Fisheries Studies 5-3 Literature Cited 5-3 APPENDIX. Progress report on summer habitat selection of striped bass in Lake Norman (Federal Aid in Fish Restoration Project F23-17) A-1

CN Q EXECUTIVE

SUMMARY

OPERATIONAL DATA Both units were operational during July, August, and September, when conservation of cool water and discharge temperatures are most critical. The average monthly discharge temperature was below the permit limit for all months and use of low level intake water was not necessary for compliance with the thermal limit for McGuire Nuclear Station (MNS). l This helped to conserve habitat for cool water fish in Lake Norman.

THERMAL MODELING As in the previously submitted 316(a) demonstration report for MNS in 1985, the meteorology for 1953 still provides a worst case scenario for MNS and Marshall Steam Station (MSS) discharge temperatures. The predicted lake surface area affected by the thermal plumes from both MNS and MSS (at 100% load June-August,90% load the rest of the year) are less than the limit established by these stations' NPDES permits (i.e., 3500 acres). This is true for both the 90*F (32.2*C) isotherm and the 5 F (2.8 C) above i background temperature isotherm.

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1 Use of the Low Level Intake (LLI) pumps has not been necessary to maintain compliance l with the permitted thermal limits. In the event that LLI pumps have to be used, the predicted thermal profiles indicate that the primary temperature change would occur in the hypolimnion only during August, when these waters are usually anoxic and consequently have very low fish densities. l l

WATER CHEMISTRY DATA Temporal and spatial trends in water temperatur and DO data colic,' . monthly in 1993 were similar to those observed historically. Reservoir-wide isotherm and isopleth information for 1993, coupled with heat content and hypolimnetic oxygen data, illustrated that Lake Norman exhibited thermal and oxygen dynamics characteristic of historic i

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I conditions and similar to other Southeastern reservoirs of comparable size, depth, flow '

conditions, and trophic status.

I Availability of suitable pelagic habitat for adult striped bass in Lake Norman in 1993 was generally similar to historic conditions. Reservoir-wide habitat elimination was observed to .

persist for approximately 2 months in the 1993 summer. This is somewhat longer than the a- duration of complete habitat elimination observed in the summer of 1992, but similar to ,

earlier summers.

All chemical parameters measured in 1993 were within the concentration ranges previously reported for the lake during both MNS preoperational and operational years.

Pj D LOPLANKTON DATA Chlorophyll a concentrations at all locations during 1993 were within historical ranges and in the mesotrophic range. They were generally higher than those observed during 1987 through j 1990 but were similar to those observed in 1991 and 1992.

' atal phytoplankton densities and biovolumes remained similar to those observed in previous ,

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years. Phytoplankton taxonomic composition during 1993 was similar to that observed ;

during the same months of 1992. Diatoms, green algae and cryptophytes were the most numerically abundant classes of algae observed. Diatoms and cryptophytes generally !

dominated the phytoplankton biovolumes in all months except August when the l phytoplankton community consisted of a diverse assemblage dominated by small green ;

algae. Dinoflagellates were sporadically dominant in terms of biovolume at some locations during all months except November. Blue-green algae were never a dominant at any location ;

or time in 1993. :

I ZOOPLANKTON DATA Total zooplankton standing crops were generally highest in May and lowest in November :

during 1993. Zooplankton densities, in general, were slightly higher in eplimnetic samples ,

thrai in whole column samples. Total zooplankton densities at Mixing Zone locr.tions were not significantly different from background locations during any quarter in 1993. The typical i

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(O)- trend of increasing zooplankton densities from downlake to uptake was observed only in November in 1993. The range of total zooplankton densities observed during 1993 was

. similar to the ranges observed since 1987. !

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. Overall, rotifers dominated zooplankton standing crops in 1993, as they did in 1992, I followed closely in importance by copepods. Cladocerans were dominant numerically on only one occasion in 1993. Major rotifer taxa observed in 1993 were Keratella, Polyarthra l t

and Synchacta. Copepod populations were dominated by immature forms (nauplii and !

cyclopoid copepodids). As in previous years, Bosmina was the most abundant cladoceran ,

taxa observed at all locations. Overall, zooplankton taxonomic composition in 1993 was l similar to that observed in previous years. f I

FISHERIES DATA j Hydroacoustic density estimates of limnetic fish in lower Lake Norman were similar to' ;

ranges observed in other areas of the reservoir. Densities were lower in the heated water i

( plume on August 4,1993, than in the surrounding areas,. A clumped distribution pattern is evident, with densities ranging from less than 10,000 to greater than 90,000/ha in the MNS l.

mixing zone and in areas of the reservoir with ambient water temperatures. Surface water :

temperatures in the discharge area during August were 35*C. This is higher than the preferred temperatures of threadfin shad, the predominant species in the limnetic area of the reservoir (Duke Power Company 1993). ;

r Nearly all (99.6%) of the fish collected in the purse seine in August were threadfin shad.

The only other species sampled with the purse seine in lower Lake Norman was black crappie.

Dead and dying striped bass were observed during the last 2 weeks in July 1993 in the MNS mixing zone. On July 23, fourteen dead striped bass were count'ed in the main channel from i the dam to Marker 7, approxirnately 6 miles above the dam and 2 miles above the confluence ;

of Davidson Creek and the main channel. On July 30, eleven dead striped bass were counted :

from the dam to Marker IA, approximately 1.5 mi'es above the dam. Only two of the 25 dead striped bass observed were larger than 5 pounds. Anglers fishing the area for striped !

bass were catching large numbers of fish less than the 20 inch size limit and retuming them [

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to the lake. This likely contributed to the large number of dead small fish observed. Striped l f

bass less than 5 pounds have not been reported in the literature as stressed by high summer ,

water temperatures; however, recent research in Tennessee has shown angling mortalities of ,

greater than 60% for striped bass caught in the summer (Phil Bettoli, personal !

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O LIST OF TABLES Page

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Table 1-1 McGuire Nuclear Station (MNS) 1991 capacity factors 1-6 ,

Table 1-2 Predicted MNS discharge temperatures 1-7 l Table 1-3 MNS and Marshall Steam Station (MSS) operating conditions 1-8 l Table 1-4 Hydrological and Meteorological parameters for 1953 1-8

! Table 1-5 90 F(32.2*C) isotherms for MNS and MSS 1-9 ,

Table 1-6 ' 5 F(2.8*C) above background isotherms for MNS and MSS 1-9 Table 2-1 Water chemistry monitoring program schedule 2-12 Table 2-2 Water chemistry methods and detection limits 2-13 Table 2-3 Heat content calculations for Lake Norman in 1993 2-14 Table 2-4 Comparison of Lake Norman with TVA reservoirs 2-15 ;

Table 2-5 Water chemistry data for 1991 for Lake Norman 2-16 Table 3-1 Mean chlorophyll a concentrations in Lake Nonnan 3-9 i Table 3-2 Duncan's multiple range test for Chlorophyll a 3-10 Table 3-3 Total phytoplankton densities from Lake Norman 3-11 Table 3-4 Duncan's multiple range test for phytoplankton densities 3-12 ]

Table 3-5 Duncan's multiple range test for seston in Lake Norman 3-13 Table 4-1 Total zooplankton densities and composition 4-7

) Table 4-2 Duncan's multiple range test for zooplankton densities 4-9 Table 4-3 Zooplankton taxa identified in Lake Norman 1993 4-10 l

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LIST OF FIGURES Page Figure 1-1 Predicted average temperature profiles for Lake Norman 1-10 Figure 2-1 Map of sampling locations on Lake Norman 2-19 Figure 2-2 Monthly precipitation near McGuire Nuclear Station 2-20 Figure 2-3 Monthly mean temperature profiles in background zone 2-21 Figure 2-4 Monthly mean temperature profiles in mixing zone 2-23 Figure 2-5 Monthly temperature and dissolved oxygen data 2-25 Figure 2-6 Monthly mean dissolved oxygen profiles mixing zone 2-26 Figure 2-7 Monthly mean dissolved oxygen in background zone 2-28 Figure 2-8 Monthly isotherms for Lake Norman 2-30 Figure 2-9 Monthly dissolved oxygen isopleths for Lake Norman 2-33 Figure 2-10 Striped bass habitat in Lake Norman 2-36 Figure 3-1 Chlorophyll a measurements of Lake Norman 3-14 Figure 3-2 Phytoplankton chlorophyll a euphotic zone 3-15 Figure 3-3 Total phytoplankton densities and biovolumes 3-16 Figure 3-4 Class composition in euphotic zone 3-17 Figure 4-1 Zooplankton density by sample location in Lake Norman 4-11 Figure 4-2 Lake Norman zooplankton densities among years 4-12 i 4-13 Figure 4-3 Lake Norman zooplankton composition in 1993 Figure 4-4 Lake Norman zooplankton density by group 4-14 Figure 5-1 Fish densities in lower Lake Norman August 4,1993 5-4 vi

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CHAPTER 1 McGUIRE NUCLEAR STATION OPERATIONAL DATA INTRODUCTION In addition to operational data for 1993, results of thermal modeling runs ns requested per the NPDES permit are included in this years annual environmental summary report. This ;

modeling was done to assess the impact of 100% load factor during the months of June, July, and August and 90% the remainder of the year.

OPERATIONAL DATA FOR 1993 Both units were operational during July, August, and September, when conservation of cool water and discharge temperatures are most critical (Table 1-1). During these months th:

[3 thermal limit for MNS increases from a monthly average of 95 F to 99 F. The average !

monthly discharge temperature was 94.1 F (34.5 C) for July,91.9 F (33.3 C) for August, and 83.8 F (28.8 C) for September 1993. Use oflow level intake water was not necessary for compliance with the thermal limit for MNS. This helped to conserve habitat for cool water fish in Lake Norman. The volume of cool water in Lake Norman is tracked throughout the year to ensure that an adequate volume is available to comply with both the Nuclear Regulatory Commission Technical Specification requirements and the NPDES monthly i

discharge water temperature limit. ,

THERMAL MODELING RESULTS Based on a request made by the North Carolina Department of Environmental Management (NCDEM), Duke Power has completed additional modeling analyses of the thermal regime in Lake Norman resulting from operations at McGuire Nuclear Station (MNS) and Marshall i

Steam Station (MSS). Specifically, NCDEM requested that Duke "remodel and assess the impact of 100% load factor during the months of June-August and 90% for the remainder of 3 the year."

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O The model set-up for this additional analysis is basically the same as it was for the June 1985 316(a) demonstration report (Duke Power Company 1985). Please refer to that report for a description of the model, the assumptions made, validation of the model, and' predictive results assuming a year-round 90% load factor for both MNS and MSS.

Meteorology

. In order to demonstrate worst case conditions, it was necessary to determine which year produced meteorological conditions such that maximum discharge temperatures at MNS and MSS would result. Meteorological records from the Charlotte Airport (approximately 17 miles from MNS and 25 miles from MSS) were obtained for years 1951 through 1993. By running this entire period of meteorological data through the thennal model (set in predictive

) mode),1953 produced the highest June-August discharge temperatures, as shown in Table 1-

2. (Note that this was also the case for the 316(a) demonstration report submitted in 1985.)

I Therefore,1953 meteorological data was used to obtain the model results discussed in the following section.

Results and Disemion For the 1953 predictive model run, the load (or capacity) factor was 100% for June-August and 90% the remainder of the year. Tables 1-3 through 1-6 provide the model results for both MNS and MSS for the June-August period when both stations were operating at 100%.

Note that results for the months having a capacity factor of 90% are given in the 316(a) demonstration report (Duke Power Company 1985).

Table 1-3 provides Condenser Cooling Water (CCW) data for both MNS and MSS.

Although this data is fairly self-explanatory, the discharge temperature and CCW usage at 1-2

O MNS warrant further discussion. The thermal model (when run in a predictive mode) will not let monthly average discharge temperatures at MNS exceed 37.2*C (99.0*F). To accomplish this, the Low Level Intake pumps (LLI) at MNS are judiciously used to bring cool water from the bottom of Lake Norman to the surface so it can be mixed with the warmer water brought in by the Upper Level Intake pumps (ULI) located near the surface of Lake Norman. In doing this, the overall temperature of the intake water at MNS is reduced enough to keep the station's discharge temperature in compliance with its 37.2*C (99.0*F) monthly average discharge limit during the summer months. Refer to the MNS 316(a) demonstration report (Duke Power Company 1985) for a description and drawings of the LLI and ULI pumping structures.

t For the June-August period, LLI water requirements for the 1953 predictive run were 0 cfs,

- 108 cfs, and 173 cfs, respectively (Table 1-3). This amount of flow is very small when compared to the overall station CCW requirements of 4580 cfs. Thus, the majority of CCW water used for the 1953 worst case scenario comes from the surface waters of Lake Norman

) and only a small amount from the cooler bottom layers. This is reflected in the predicted thermal profiles for June, July, and August (Figure 1-1). For the vast majority of years, the model predicts that the LLI pumps will not have to operate to comply with the stations NPDES discharge temperature limit, even with capacity factors of 100% during the summer months. This has also been the experience of station personnel since the 37.2*C (99.0*F) monthly average discharge limit was granted. Use of the LLI pumps has not been necessary to maintain compliance with the permitted thermal limits. In the event that LLI pumps have to be used, the predicted thermal profiles indicate that the primary temperature change would occur in the hypolimnion during only August, when these waters are usually anoxic and ,

consequently have very low fish densities (See Chapters 2 and 5) ;

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i Table 1-4 provides the hydrological and meteorological parameters used for the 1953 predictive model run. Note that the river flow values are simulated Cowans Ford Ilydro !

discharge flow rates. Also, the meteorological data was obtained from the Churlotte Airport.

l The lake surface area and shore-line affected by the 90'F (32.2*C) isotherm resulting from predicted thermal discharges from MNS and MSS are given in Table 1-5. The largest 90 F (32.2*C) isotherm from MNS ~. curred during July (1897 acres, or approximately 7% of :

l Lake Norman's total surfere area). For MSS, the largest 90'F (32.2*C) isotherm occurred j during August (336 acres, or approximately 1% of Lake Norman's total surface area). Note that neither of these isotherm acreages are greater than the limits established in these stations' ;

NPDES permits (i.e., 3500 acres). Maximum shore-line aff ,ted by the 90*F (32.2 C) isotherm is 25 km (16 mi), or 3% of the total shore-line for MNS and 3 km (2 mi), or approximately 0.05% of the total shore-line for MSS. l l

The lake surface area and shore-line affected by the 5'F (2.8'C) above background temperature isotherm resulting from predicted thermal discharges from MNS and MSS are given in Table 1-6. The largest area affected by MNS occurred during August (2100 acres, or approximately 7% of Lake Norman's total surface area). For MSS, the largest area also )

i occurred during August (579 acres, or approximately 2% of Lake Norman's total surface area). Note that neither of these isotherm acreages are greater than the limits established in these stations' NPDES permits (i.e.,3500 acres). Maximum shore-line affected by the 5'F (2.8'C) above background isotherm is 27 km (17 mi),or 3% of the total shore-line for MNS and 9 km (6 mi), or approximately 1% of the total shore-line for MSS.

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SUMMARY

l. The meteorology for 1953 still provides a worst case scenario for MNS and MSS discharge temperaturcs. Note that 1953 meteorological data was also used to. predict worst case conditions in the 1985 MNS 316(a) demonstration report.

2. Use of the LLI pumps have not been necessary to maintain compliance with the current permitted thermal limits. In the event that LLI pumps has to be used, the predicted thermal profiles indicate that the primary temperature change would occur in the hypolimnion only during August, when these waters are usually anoxic and consequently i

have very low fish densities.

3. The predicted lake surface area affected by the thermal plumes from both MNS and MSS (at 100% load June-August, 90% load the rest of the year) are less than the limit established by these stations' NPDES permits (i.e.,3500 acres). This is true for both the O) y 90*F (32.2*C) isotherm and the 5'F (2.8"C) above background temperature isotherm.

2 LITERATURE CITED Duke Power Company.1985. McGuire Nuclear Station,316(a) Demonstration. Duke Power Company, Charlotte, NC. .

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jr3 u Table 1-1. Average monthly capacity factors (%) calculated from daily unit capacity factors [ Net Generation (Mwe per unit day) x 100 / 24 h l per day x 1129 mw per unit] and monthly average discharge water l temperatures for McGuire Nuclear Station during 1993 l CAPACITY FACTOR (%) TEMPERATURE Month Unit 1 Unit 2 Station Monthly Average Average Average Average OF OC January 101.0 101.9 101.4 67.0 19.4 February 101.90 89.0 95.4 65.1 18.4 ,

March 35.2 94.9 65.1 61.3 16.3 April 0 101.8 50.7 69.3 20.7 May 0 98.1 48.7 75.0 23.9 June 38.2 78.0 58.1 84.0 28.9 July 96.6 0 47.9 94.1 34.5 August 65.2 0 32.0 91.9 33.3 September 0 34.2 16.5 83.8 28.8 October 40.3 49.2 44.8 76.8 24.9 d November 95.3 100.1 97.7 91.7 75.5 69.6 24.2 20.9 December 100.6 82.8

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t Table 1-2: Predicted MNS discharge temperatures (MNS and MSS capacity factors = 100% June, July,

( and August; 90% the remainder of the year).

JUN-AUG YR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC AVO 1951 72.5 71.5 74.8 77.4 84.1 91.2 98.0 99.0 94.1 86.9 77.3 73.7 96.1 i 1952 73.9 74.5 74.9 77.7 83.7 96.0 99.0 98.7 92.1 84.2 76.7 74.4 97.9 1953 73.7 74.2 74.9 78.7 86.7 97.0 98.9 98.6 93.4 36.1 7f ! 73.5 98.2 1954 71.1 73.9 75.7 79.3 82.7 90.9 98.1 99.0 94.1 86.5 75.9 71.4 96.0 1955 71.2 71.2 75.1 30.1 F5.8 91.3 983 97.8 92.0 84.4 76.4 71.7 95.8 1956 683 74.4 74.9 77.1 84.0 91.7 98.0 983 91.1 82.2 R4 74.8 96.0 j 1957 73.2 74.4 74.8 77.9 85.1 92.9 983 96.5 92.3 80.9 73.6 74.7 95.9 1958 68.3 69.2 74.1 77.1 83.2 92.6 97.5- 98.5 91.6 83.5 77.2 713 963 1959 69.7 73 3 74.3 78.9 86.0 92.4 963 98.5 91.5 85.9 76.8 73.6 95.7 1960 72.2 71.6 68.6 77.9 82.6 93.0 973 96.8 91.8 85.5 75.7 71.9 95.7 1961 70.2 70.6 73.1 75.2 81.8 90.8 96.1 96.5 92.2 843 79.2 74.3 94.5 1%2 70.2 72.6 74.3 77.5 86.7 93.4 95.7 95.3 91.2 84.8 74.8 69.7 94.8 1%3 68.6 67.9 74.1 30.4 83.7 91.2 95.0 97.1 90.6 83.7 76.7 70.8 94.4 1964 69.0 70.0 73 3 77.8 84.1 92.7 953 95.4 90.5 81.5 75.0 74.8 94.5 1965 72.2 72.6 73.7 78.7 87.7 92.8 96.0 %.8 92.5 83.2 76.4 74.2 95.2 1966 70.1 69.8 74.0 77.1 84.0 91.4 97.1 96.0 91.6 83.1 RO 72.7 94.8 1967 70.7 71.0 74.3 80.4 81.5 89.5 953 96.0 88.8 83.1 76.2 74.8 93.6 79.4 97.2 98.5 90.8 84.8 76.8 71.9 95.5 l 1968 683 70.0 73.5 83.5 90.9 1969 68.7 713 72.1 79.0 84.6 92.7 98.5 96.4 903 83.6 76.0 70.4 95.9 1970 67.0 713 75.2 78.2 85.5 91.8 95.8 95.6 93.1 84 3 77.4 74.4 94.4 1971 69.8 68.9 74.5 77.4 82.7 91.4 953 95.1 92.4 36.1 78.8 74.7 94.1 1972 74.5 70.1 75.5 E6 82.1 883 94.8 95.1 90.5 81.5 R0 73.6 92.7 h

1973 70.7 69.4 74.6 76.4 81.3 92.0 96.6 963 92.9 84.9 75.9 72.8 95.0 1974 74.8 74.6 75.5 77.8 83.7 90.9 94.5 94.5 89.0 81.0 76.9 71.2 933 1

1975 73.2 74.7 74.5 77.1 85.9 92,1 94.6 98.1 92.2 84.9 79.0 73.6 94.9 I

1976 68.9 74.0 75.4 78.7 82.3 89.1 94.7 94.7 88.9 82.6 74.7 70.8 92.8 1977 65.0 683 75.5 79.5 83.8 91.8 98.5 97.4 93.9 82.6 77.3 73.2 95.9 l 1978 68.1 66.8 72.2 79.6 82.1 94.0 98.2 98.9 95.0 83.1 79.0 74.2 97.0 1979 68.2 67.0 75.0 79.9 843 90.6 94.4 96.9 91.2 82.1 77.5 73.8 94.0 ;

1980 70.7 69.4 73.1 78.9 82.9 92.1 973 98.5 95.5 83.4 76.4 72.5 96.2 1981 66.6 70.6 74.7 79.2 82.1 94.2 97.0 94.9 90.9 81.4 75.7 70.9 95.4 1982 67.2 72.4 74.7 77.4 843 93.6 98.8 98.2 903 83.9 76.7 743 963-1983 693 72.0 75.2 76.5 32.3 89.4 96.8 98.1 93.6 83.0 76.0 72.9 94.8 1984 67.4 72.4 73.6 76.1 81.7 90.6 95.4 95.9 90.5 84 3 78.3 74.8 94.0 1985 69.6 69.0 75.2 78.8 85.6 93.3 96.6 963 92.0 85.7 79.8 73.7 95.4 l 1986 63.3 71.8 74.2 79.8 84.9 94.6 99.0 98.0 91.7 87.0 78.4 74.6 97.2 1987 70.4 70.9 74.0 77.2 83.0 92.6 98.9 98.9 93.8 81.8 76.0 74.1 96.8 1988 67.7 4 71.5 75.2 79.4 83.9 913 963 98.7 903 81.8 75.2 733 95.4 )

1989 73.7 74.2 74.9 78.0 823 92.8 96.7 96.1 91.6 83.5 78.1 69.6 93.2 1990 71.9 75.9 73.2 77.8 84.9 92.7 97.7 98.0 94.2 86.2 77.7 75.0 %.1 l iP9: 73.5 R8 76.4 30.i 85.6 92.8 983 97.i 93.6 84.3 76.6 74.7 96.i !

1992 72.1 74.1 76.1 78.7 80.4 86.9 97.0 95.4 92.8 81.9 77.6 73.4 93.1 l 1993 73.0 71.9 73.1 77.0 82.5 93.0 99.0 98.2 94.7 83 3 763 73.1 %.7 l 1

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Table 1-3: MNS and MSS Operating Conditions for 1953 Predictive Run.

McGUIRE NUCLEAR STATION MARSHALL STEAM STATION Total LLI CCW Capacit Intake Discharge CCW- CCW Capacity Intake Discharge MO/YR CCW CCW AT y Factor Temp Temp Flow AT Factor Temp Temp efs efs *C cF) (%) *C PF) *C OF) cms (cfs) *C PF) (%) *C PF) *C PF)

JunI 1953 4580 0 9.0 (16.2) 100 27.0 (80.6) 36.0 (96.8) 51 (1784) 11.2 (20.1) 100 17.7 (63.9) 28.9 (84.0)

Jul/1953 4580- 108 9.1 (16.3) 100 28.2 (82.7) 37.2 (99.0) 59 (2068) 9.6 (17.3) 100 22.9 (73.3) 32.6 (90.6)

Aug/1953 4580 173 9.1 (16.4) 100 27.8 (82.1) 36.9 (98.5) 64 (2264) 8.8 (15.81 100 26.4 U9.6) 35.2 (95.4)

Table 1-4: Hydrological and Meteorological Parameters for 1953 Predictive Run.

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HYDROLOGICAL METEOROLOGICAL Background Water Surface River Dry Dew Cloud Solar Wind Speed at

f. MO/YR Temp Elevation Flow Bulb Point Cover Radiation height = 26 m

'C PF) m (ft) ems (cfs) *C PF) *C PF) (%) LY/ Day m/s (mph)

Jun /1953 28.2 (82.8) 230.1 G55.0) 42 (1472) 24.6 G6.3) 18.6 (65.5) 60 511.0 2.19 (4.9)

Jul/1953 29.6 (85.2) 229.4 G52.5) 36 (1256) 26.3 G9.4) 19.1 (66.4) 60 513.2 2.15 (4.8)

Aug/1953 29.2 (84.5) 230.1 (755.0) 36 (1274) 25.2 (77.3) 18.1 (64.5) 40 486 1 1.83 (4.1) 1 i

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Table 1-5: 90 F (32.2 C) Isotherms for MNS and MSS for 1953 Predictive Run. .

90*F (32.2*C) ISOTHERM McGUIRE NUCLEAR STATION MARSHALL STEAM STATION TOTAL OF BOTH PLANTS '

Surface Laket Shore. Lake 2 Surface Laket Shore- Lake 2 Surface laket Shore- Lake 2

[ MO/YR Area Surface line Shore Area Surface 1me Shore Area Surface line Shore Ha (ac) % km (mi) % Ha (ac) % km (mi) % Ha (ac) % km (mi) %

Jun/ 400 (990) 3 17 (11) 2 0 (0) 0 0 (0) 0 400 (990) 3 17 (11) 2 1953 Jul/1953 768 (1897) 7 25 (16) 3 6 (14) 0 0 (0) 0 774 (1911) 7 25 (16) 3 Au/1953 625 (1545) 5 22 (14) 3 136 (336) 1 3 (2) 0 761 (1881) 6 25 (16) 3 Table 1-6: 5*F (2.8 C) Above Background Temperature Isotherm for MNS and MSS 1953 Predictive Run.

5'F (2.8*C) ABOVE BACKGROUND TEMPERATURE ISOTHERM McGUIRE NUCLEAR STATION MARSHALL STEAM STATION TOTAL OF BOTH PLANTS

- Surface Laket Shore. Lake 8 Surface Laket Shore- . Lake 2 Surface Laken Shore- Lake 2 U MO/YR Area Surface line Shore Area Surface line Shore Area Surface line Shore Ha (ac) % km (mi) % Ha (ac) % km (mi) % Ha (ac) % km (mi) %

Jun/ 797 (1969) 7 25 (16) 3 0 (0) 0 0 (0) 0 797 (1969) 7 25 (16) 3 1953 Jul/1953 768 (1897) 7 25 (16) 3 6 (14) 0 0 (0) 0 774 (1911) 7 25 (16) 3 Au/1953 850 (2100) 7 27 (17) 3 234 (579) 2 9 (6) 1 1084 (2679) 9 36 (22) 4

1. Lake surface areas (based on monthly water surface elevations): June 11780 Ha (29100 ac); July 11030 Ha (27250 ac); August 11780 Ha (29100 ac).

2. Based on total shoreline mileage of 840 km (522 mi).

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i G,G-CHAPTER 2 WATER CHEMISTRY INTRODUCTION The objectives of the water chemistry portion of the McGuire Nuclear Station (MNS) i NPDES Maintenance Monitoring Program are to:

1) maintain continuity in Lake Norman's chemical data base so as to allow i detection of any significant station-induced and/or natural change in the-physicochemical structure of the lake; and .

2) compare, where appropriate, these physicochemical data to similar data in i other hydropower reservoirs and cooling impoundments in the Southeast.

This year's report focuses primarily on 1992 and 1993. Where appropriate, reference to pre-1992 data will be made by citing reports previously submitted to the- North Carolina Department of Environment, Health, and Natural Resources (NCDEHNR).

METHODS AND MATERIALS

)

The complete water chemistry monitoring program, including specific variables, locations, !

depths, and frequencies is outlined in Table 2-1. Sampling locations are identified in Figure f 2-1, whereas specific chemical methodologies, along with the appropriate references are ;

presented in Table 2-2. Data were analyzed using two approaches, both of which were consistent with earlier studies (Duke Power Company 1985,1987,1988a,1989,1990,1991, ;

1992, 1993). The first method involved partitioning the reservoir into mixing, background, i and discharge zones, and making comparisons among zones and years. In this report, the j discharge includes only. Location 4; the mixing zone encompasses Locations 1 and 5; the - ;

background zone includes Locations 8,11, and 15. The second approach emphasized a much l broader lake-wide investigation and encompassed the plotting of monthly isotherms and l isopleths, and summer-time striped bass habitat. Several quantitative calculations were also l

performed. These included the calculation of the areal hypolimnetic oxygen deficit (AHOD),

]

numimum whole-water column and hypolimnion heat content, mean epilimnion and hypolimnion heating rates over the stratified period, and the Birgean heat budget.

2-1 I

b

P V RESULTS AND DISCUSSION 7 Precipitation Amount Precipitation in the vicinit, ?f MNS measured about 46 inches in 1993, compared to 49 inches in 1992 (Figure 2-2.). The wettest month of 1993 was March in which 8.65 inches of precipitation fell.

t Temperature and Dissolved Oxygen Water temperatures measured in 1993 illustrated similar temporal and spatial trends in the background and mixing zones (Figures 2-3,2-4). Water temperatures in the winter and spring of 1993 were generally equal to or cooler throughout the water column as compared to 1992 in both zones (Figure 2-3,2-4). The only exception to this occurred in February when epilimnion temperatures in the mixing zone were 2 to 5'C (3.6 to 9.0'F) warmer than the p background zone. Both zones exhibited slightly warmer epilimnion and metalimnion V temperatures in the summer of 1993 than in 1992 with the greatest between year differences (3 to 5'C or 5.4 to 9.0'F) measured in July and September. Fall temperatures were similar I l throughout the reservoir in 1992 and 1993. Despite some seasonal and spatial variability in temperature data between 1992 and 1993, the 1993 temperatures were well within the historic range (Duke Power Company 1985, 1989, 1991, 1993). Temperature data at the discharge location in 1993 were generally similar to or slightly cooler than measured in 1992 (Figure 2-

5) and historically (Duke Power Company 1985, 1987, 1988a, 1989, 1900, 1991, 1992, 1993). The warmest temperature at the discharge location in 1993 occurred in August and measured 35.3*C (95.5'F), slightly less than the historic maximum of 36.3*C (97.3'F) measured in August,1991 (Duke Power Company 1992).

2-2 l

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V Seasonal and spatial patterns of DO in 1993 were reflective of the patterns exhibited for ten'iperature, i. e., generally similar in both the mixing and background zones (Figures ~ 2-6 and 2-7). Winter and spring DO values generally ranged from about 0.2 to 2.0 mg/l higher throughout the water column in both zones in 1993 than in 1992, and were well within the historic range (Duke Power Company 1985, 1987, 1988a, 1989, 1990, 1991, 1992, 1993). '

- Summer DO values in 1993 were generally lower throughout the water column in both the '

mixing and background zones than observed in 1992, but within the historic range (Duke Power Company 1985,1987,1988a,1989,1990,1991,1992,1993). These lower values in 1993 may be related, at least partially, to the warmer water temperatures in 1993 which would decrease oxygen solubility and increase microbial respiration (Wetzel 1975). Fall DO values were generally similar between the two years. Some differences were observed in November but these data are probably a reflection of meteorological differences influencing i

' the rate of water column cooling and reoxygenation. Interannual differences in DO are common in Southeastern reservoirs, particularly during the stratified period, and can reflect yearly differences in hydrological, meteorological, and limnological forcing variables (Cole

] and Hannon 1985; Petts1984).

[V The seasonal pattern of DO in 1993 at the discharge location was similar to that measured

) historically, with the highest values observed during the winter and lowest observed in the summer and early-fall (Figure 2-5). Generally, DO values in 1993 were either equal to or slightly less than in 1992, but within the historic range (Duke Power Company 1985,1987, 1988a, 1989, 1990, 1991, 1992, 1993). The lowest DO concentration measured at the discharge location in 1993 (4.1 mg/1) occurred in August and was slightly lower than the August,1992, low of 5.0 mg/l (Figure 2-5).

Reservoir-wide Temperature and Dissolved Oxygen The monthly reservoir-wide temperature and dissolved oxygen data for 1993 are presented in

. Figures 2-8 and 2-9. For the most part, the temporal and spatial distributional patterns of I both temperature and dissolved oxygen are similar to other cooling impoundments and hydropower reservoirs in the Southeast (Cole and Hannon 1985; Petts 1984). During the winter cooling and mixing period, vertical rather than horizontal homogeneity in temperature I

predominated, with the shallower uplake ' riverine' zone exhibiting slightly cooler s

temperatures than the deeper downlake ' lacustrine' zone (Figure 2-8). These longitudinal :

2-3 h

r differences in temperatures were clearly illustrated in January and February. The principal factors influencing this gradient in Lake Norman are thermal discharges from MSS and MNS, morphometric (depth) differences within the reservoir, and surface watcr inputs from

- the upper reaches of the reservoir.

The heating period in Lake Norman generally begins in March, as more heat is gained at the water's surface than is lost at night. During the initial stages of the heating period, buoyancy

- forces " smooth out" the horizontal differences in temperature, thereby reducing temperature differences between up-reservoir and down-reservoir locations. Due to the vertical instability of the water column during this period, temperature increases are observed at all depths.

These points are illustrated by contrasting the January and February temperature data with the March and April data (Figure 2-8). As solar radiation and air temperatures increase, heating occurs at a greater rate in the upper waters than in the mid or bottom waters due to differential thermal absorption and vertical density differences (Wetzel 1975, Ford 1985 ).

Eventually, differential heating at the surface leads to the formation of the classical epilimnion, metslimnion, and hypolimnion zones. These zones are clearly depicted in the July,1993 data (Figure 2-8).

) In contrast to most natural lakes, but not unlike many reservoirs in the Southeast, a distinct thermocline within the metalimnion was not observed in Lake Norman in 1993 and is consistent with that observed in previous years (Duke Power Company 1992,1993). Rather, the metalimnion was more or less continuous with respect to vertical density differences within the lower water column, and even showed signs of merging with the hypolitnnion, as illustrated in the August data (Figure 2-8).

Cooling of the water column began in early September as illustrated by decreases in surface temperatures compared to August data. Concurrent with decreases in surface temperatures was an increase in the depth of the epilimnion (caused by convective mixing) and a dismption of the horizontal homogeneity in epilimnion temperatures (caused by reservoir-wide differential heating and cooling, and advective inputs from upstream). Continuation of these differential vertical and horizontal processes led to even more pronounced thermal differences within the reservoir. For example, by October the uplake riverine zone had already ' turned over', while the downlake lacustrine zone was still strongly stratified. Not until early November was Lake Norman completely mixed vertically throughout the 2-4

i I .

reservoir. Morphometric, and in particular, depth differences throughout the longitudinal ,

reaches of the reservoir, coupled with seasonal variability in the volume and density of ,

upstream inputs are major contributors to these horizontal gradients of heating and cooling in ,

reservoirs (Ford 1986;Imberger 1987 ; Petts 1984).

Distributional pattems of dissolved oxygen in 1993 were similar to but not identical to temperature (Figure 2-9). Generally, dissolved oxygen concentrations were greatest during the winter cooling and mixing period when biological respiration was at a minimum and atmospheric reacration was at a maximum. The highest reservoir-wide mean concentration ,

of dissolved oxygen (11.6 mg/l) occurred in March when the reservoir exhibited a mean temperature of 8.7"C or 47.7'F (Figure 2-8). Unlike the thermal regime, no major j longitudinal differences existed in dissolved oxygen within the reservoir during the winter.

Not until the lake became stratified, thereby isolating the metalimnion and hypolimnion from atmospheric reaeration and vertical water mass exchanges, were uplake-to-downlake gradients in dissolved oxygen observed. Longitudinal gradients in metalimnetic and ,

hypolimnetic dissolved oxygen in 1993 were first observed in May. Differential dissolved oxygen depletion and eventual anoxia were first observed in the transitional zone (Locations 15 through 62) where hypolimnetic volume is small, water column and sediment organic 0

matter high, and advective mixing minimal. This longitudinal and progressive display of ;

oxygen depletion has been reported for many southem U.S. impoundments (Hannon et. al., j 1979; Cole and Hannon 1985; Petts 1984). By August, the complete hypolimnion l throughout the reservoir below elevation 219 m was anoxic. This represents approximately i 22% of the entire volume of the lake at full pond. Complete hypolimnetic deoxygenation 3 (below the thermocline) in natural lakes is indicative of the net effect of cultural eutrophication (Wetzel 1975). Alternatively, the occurrence of hypoxia in reservoirs is '

influenced by a combination of hydrologic, hydraulic, morphometric and limnological factors (Cole and Hannon 1985; Petts 1984; Ruane 1989).

Reacration of the water column started in September concomitantly with the cooling and

~

mixing of the reservoir. Decreasing air temperatures cooled the surface waters resulting in a convective deepening, aided by wind-induced mixing, of the epilimnion. As the oxygenated epilimnion eroded progressively deeper into the water column, the width of the anoxic zone decreased. Longitudinal differences in reaeration were also observed and apparently were .

I

%/ related to differential mixing caused by MNS and MSS, and upstream advective inputs from l

2-5 N _ _ _ _ _ __ ___ _ _ _ , - _ .

7 (v) Lookout Shoals Hydroelectric Facility. Reaeration of the reservoir was essentially complete by early November, except for the bottom waters in the downlake " lacustrine" zone.

Table 2-3 presents some common quantitative limnological calculations for the thermal environment in Lake Norman. Few comparable calculations exist in the literature for reservoirs, but these data are generally within the "ballpark" of those presented by Hutchinson (1957) for natural lakes at similar latitudes throughout the world.

Table 2-4 presents the 1993 AHOD for Lake Norman compared to similar estimates for 18 TVA reservoirs. The data illustrate that Lake Norman exhibits an AHOD that is similar to other Southeastern reservoirs of comparable depth, chlorophyll a status, and secchi depth.

Striped Bass Habitat Suitable pelagic habitat for adult striped bass, defimed as that layer of water with Q temperatures s 26 C and DO levels 2: 10 mg/1, was found lake-wide from October 1992 through June 1993. Beginning in late June, habitat reduction proceeded rapidly throughout the reservoir both as a result of deepening of the 26*C isotherm and metalimnetic and

) hypolimnetic deoxygenation (Figure 2-10). Complete habitat elimination occurred sometime in mid-July and persisted until mid-September, or about 2 months. Refugia for adult striped bass were recorded during this period but these areas were oflimited size and restricted to the uplake, riverine sections of the reservoir just below the Lookout Shoals Hydroelectric facility. Physicochemical habitat was observed to expand appreciably in late September, primarily as a result of epilimnion cooling, and in response to changing meteorological conditions The temporal and spatial pattem of striped bass habitat expansion and reduction observed in 1993 was similar to that previously reported in Lake Norman and many other Southeastern reservoirs (Coutant 1985, Matthews 1985; DPC 1992, DPC 1993). The duration of complete habitat elimination in 1993 was greater than observed in 1992 but well within the historic range.

2-6 L

I a V

Turbidity and Specific Conductance ;

Surface turbidity values were low at the MNS discharge, mixing zone, and mid-lake background locations during 1992 and 1993, ranging from 2-6 NTUs (Table 2-5). Bottom turbidity values were also low over the two-year period, ranging form 1-10 NYUs (Table 2-5). These values were well within the range (Duke Power Company 1989, 1990, 1991, 1992).

Specific conductance in Lake Norman in 1993 ranged from 51 to 88 umho/cm and was similar to that observed in 1992 (Table 2-5) and historically (Duke Power Company 1989,1992). Specific conductance in surface and bottom waters was generally similar throughout the year except in late fall at several of the deeper locations when bottom waters averaged about 20-40 umhos/cm higher than surface values. These increases in conductance were undoubtedly related te the release of soluble iron and manganese from the lake bottom under anoxic conditions (Table 2-5).

CN pH and Alkalinity t

During 1993, pH and alkalinity values were similar among MNS discharge, mixing, and mid-take-lake background zones (Table 2-5); they were also similar to values measured in 1992 (Table 2-5) and historically (DPC 1989,1992). Individual pH values in 1993 ranged from 6.1 to 6.9, whereas alkalinity ranged from 10.6 to 23.8 mg-CACO3 /l.

Major Cations and Anions The concentrations (mg/l) of major ionic species in the MNS discharge, mixing, and mid-lake background zones are provided in Table 2-5. The overall ionic composition of Lake Norman during 1993 was similar to that reported for 1992 (Table 2-5) and previously (Duke Power Company 1989,1992). Lake-wide, the major cations were sodium, calcium, magnesium, and potassium; major anions were bicarbonate, sulfate, and chloride.

2-7

0 Nutrients Nutrient concentrations in the discharge, mixing, and mid-lake background zones of Lake Norman are provided in Table 2-5. Overall, nitrogen and phosphorus levels in 1993 were similar to those measured in 1992 and historically (Duke Power Company 1989,1990,1991, 1992); they are also characteristic of the lake's oligo-mesotrophic status (Rodriguez 1982).

Ammonia nitrogen concentrations increased in bottom waters in each of the three zones during the summer and fall, concurrent with the development of anoxic conditions. Total and soluble phosphorus concentrations in 1993 were similar to values recorded in 1992 and historically (Duke Power Company 1989,1990,1991,1992,1993).

Metals Metal concentrations in the discharge, mixing, and mid-lake background zones of Lake ,

Norman for 1993 were similar to that measured in 1992 (Table 2-5) and historically (DPC 1989, 1990, 1991, 1992, 1993). Iron concentrations near the surface were generally low (s 0.1 mg/1) during 1992 and 1993, whereas iron levels near the bottom were slightly higher during the stratified period, particularly in early fall. Similarly, manganese concentrations in the surface and bottom waters were generally low ($ 0.1 mg/1) in both 1992 and 1993, except during the summer and fall when bottom waters approached or became anoxic (Table 2-5).

Manganese concentrations near the bottom rose above the NC water quality standard (0.5 mg/l) at various locations throughout the lake in summer and fall of both years, and is characteristic of historic conditions (Duke Power Company 1989,1990,1991, 1992, 1993). -

Heavy metal concentrations in Lake Norman never approached NC water quality standards, and there were no consistent appreciable differences between 1992 and 1993.

FUTURE STUDIES ,

No changes are planned for the Water Chemistry portion of the Lake Norman maintenance ,

monitoring program during 1994.

l ,

6 2-8 I

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. (/'% .

SUMMARY

Temporal and spatial trends in water temperature and DO data collected monthly in 1993 ~

were similar to those observed historically. Temperature and DO data collected in 1993 were within the range of previously measured values.

Reservoir-wide isotherm and isopleth information for 1993, coupled with heat content and hypolimnetic oxygen data, illustrated that Lake Norman exhibited thermal and oxygen dynamics characteristic of historic conditions and similar to other Southeastern reservoirs of comparable size, depth, flow conditions, and trophic status.

Availability of suitable pelagic habitat for adult striped bass in Lake Norman in 1993 was l

generally similar to historic conditions. Reservoir-wide habitat elimination was observed to persist for approximately 2 months in 1993. This is somewhat longer than the duration of complete habitat elimination observed in 1992, but similar to that in earlier years.

All chemical parameters measured in 1993 were within the concentration ranges previously reported for the lake during both MNS preoperational and operational years. As has been observed historically, manganese concentrations in the bottom waters in the summer and fall of 1993 often exceeded the NC water quality standard.

LITERATURE CITED Coutant, C. C.1985. Striped bass, temperature, and dissolved oxygen: a speculative hypothesis for environmental risk. Trans. Amer. Fisher. Soc. I14:31-61.

Duke Power Company.1985. McGuire Nuclear Station,316(a) Demonstration. Duke Power Company, Charlotte, NC.

Duke Power Company.1987. Lake Norman maintenance monitoring program: 1986 summary.