JOCASSEE FOREBAY AND TAILWATER WATER QUALITY REPORT KEOWEE-TOXAWAY PROJECT (FERC PROJECT NO. 2503)

JOCASSEE FOREBAY AND TAILWATER WATER QUALITY REPORT KEOWEE-TOXAWAY PROJECT (FERC PROJECT NO. 2503) Prepared for: Prepared by: DUKE ENERGY CAROLINAS, LLC CHARLOTTE, NC RESERVOIR ENVIRONMENTAL MANAGEMENT, INC. CHATTANOOGA, TN FEBRUARY 2013

TABLE OF CONTENTS 1.0 INTRODUCTION... 1 2.0 BACKGROUND... 2 3.0 OBJECTIVES... 4 4.0 METHODS... 5 4.1 Monitor Locations... 5 4.2 Data Collection... 8 4.3 Laboratory Calibration Procedure... 8 4.4 In-Field Calibration... 9 5.0 RESULTS AND DISCUSSION... 9 6.0 SUMMARY AND CONCLUSIONS... 16 7.0 REFERENCES... 17 Appendix A Appendix B Appendix C 2012 Monthly Plots of Jocassee Tailwater and Forebay Continuous Monitoring Data... A-1 Investigation of Erratic Readings of the Dissolved Oxygen Monitor on Jocassee Intake A (Units 1 and 2)... B-1 Comparison of Jocassee Tailwater Water Quality Data with Lake Jocassee Profile Data Collected at the Depths of the Intake Structure... C-1 ii

LIST OF FIGURES Figure 1. Schematic of Lake Jocassee and Elevation (meters) of Engineering Structures Associated with JPSS... 3 Figure 2. Location of Jocassee Tailwater Water Quality Monitor... 6 Figure 3. Jocassee Tailwater Water Quality Monitor Mounted on Wingwall... 6 Figure 4. Jocassee Forebay Water Quality Monitor Mounted on Intake Structure (B)... 7 Figure 5. Elevation of Jocassee Forebay Water Quality Monitor Sensor End... 7 Figure 6. Jocassee August 2012 Tailwater and Forebay (Intake A and B) 5-minute Water Quality Monitoring Data... 10 Figure 7. Jocassee 2010 Tailwater Hourly Average Water Quality Monitoring Data... 12 Figure 8. Jocassee 2011 Tailwater Hourly Average Water Quality Monitoring Data... 13 Figure 9. Jocassee 2012 Tailwater and Forebay (Intake A) Hourly Average Water Quality Monitoring Data... 14 Table 1. LIST OF TABLES Statistics for the Jocassee Forebay and Tailwater Temperature and Dissolved Oxygen Continuous Monitoring Data... 15 iii

1.0 INTRODUCTION The existing license for the Keowee-Toxaway Project (Project) was issued in 1966 and will expire on August 31, 2016. Duke Energy is using the Federal Energy Regulatory Commission (FERC) Integrated Licensing Process (ILP) to relicense the Project. As part of this process, Duke Energy formed a Water Quality Resource Committee (WQRC) comprising federal and state resource agency representatives along with local and regional stakeholders. This WQRC is responsible for identifying studies within its resource area, providing technical input, drafting study plans, identifying participants for the Study Teams, and synthesizing the findings of the Study Teams for review and consideration by the Stakeholder Team. The WQRC identified two studies necessary to evaluate the effects of project operations on the water quality of the Keowee-Toxaway Project. The results of these studies will be provided to the Stakeholder Team for review and consideration in the development of the Comprehensive Relicensing Agreement as well as to the FERC for the development of the conditions of the new license. In addition, under section 401(a)(1) of the Clean Water Act (CWA), Duke Energy must obtain 401 Water Quality Certification (WQC), or waiver of the WQC, from the responsible regulatory agency, which in this case is the South Carolina Department of Health and Environmental Control (SCDHEC). SCDHEC is responsible for protecting the quality of South Carolina s waters in accordance with the CWA, as amended. The CWA requires that states water quality standards protect the surface waters of the United States for beneficial uses such as recreation, agriculture, domestic and industrial use, and habitat for aquatic life. In order to obtain this certification, Duke Energy must provide reasonable assurance that proposed project releases would meet SCDHEC s State Water Quality Standards. Because SCDHEC has mandatory conditioning authority, FERC will incorporate the requirements of the 401 WQC into the New License. The results of the Jocassee Forebay and Tailwater Water Quality Study will provide information necessary to determine the effects of recent Project modifications at the Jocassee Pumped Storage Project (JPSS) on the water quality of the releases to the tailwater and pumpback water to the forebay. This information will also assist Duke Energy and SCDHEC in the development and evaluation of the 401 WQC.

2.0 BACKGROUND Temperature and dissolved oxygen (DO) data were collected in both the forebay and tailwaters of the JPSS from April through October 2012 to meet the objectives of this study. Additionally, continuous temperature and DO data have been collected in the tailwaters of the JPSS since August 2008. Temperature and DO vertical profile data have also been collected in Lake Jocassee for more than 30 years (on a monthly basis) in support of the Keowee-Toxaway Fisheries Resources Memorandum of Understanding (MOU). During generation, the JPSS releases flows directly into Lake Keowee, which is designated as a Freshwater (FW) No Discharge Zone (NDZ). The JPSS also has the capability to pump water from Lake Keowee into Lake Jocassee as a means of storing water for generation during another timeperiod. Lake Jocassee is designated as a Trout-Put, Grow, and Take (TPGT) water body. The DO standards for Lake Keowee are a minimum surface (1-foot) reading of 4.0 milligrams per liter (mg/l) instantaneous and 5.0 mg/l daily average. For Lake Jocassee, a TPGT reservoir, the DO standard is a surface (1-foot) value of not less than 6.0 mg/l (SCDHEC, 2006). Because the JPSS does not release a heated effluent, compliance with a temperature standard is not required. A schematic of Lake Jocassee (Figure 1) shows the withdrawal (intake) structure relative to full pool and Lake Keowee (below Jocassee). The depth of the top of the openings in the intake structure for the JPSS is approximately 44 feet below the surface at full pond elevation of 1,110 feet above mean sea level (AMSL). This allows the JPSS to pull water from the epilimnion as opposed to a deep withdrawal. 2

Figure 1. Schematic of Lake Jocassee and Elevation (ft AMSL) of Engineering Structures Associated with JPSS Duke Energy has collected water quality data in Lake Jocassee since 1974 and in Lake Keowee since 1971. The sampling programs have consisted of different combinations of parameters such as temperature, DO, conductivity, ph, nutrients, algae, and cations and anions. Monthly and/or quarterly 3

sampling of the lakes has continued since initial data collection began. Historical water quality data have been summarized in Section 6.2 of the Pre-Application Document (Duke Energy, 2011a). The DO data collected in the surface waters of both reservoirs have been well within South Carolina State Water Quality Standards. In 2007-2008, the JPSS Unit 3 and 4 runners were replaced with more efficient turbines. Continuous monitoring for DO and temperature of the releases into Lake Keowee (Jocassee tailwater) began in 2008 to assess the impact of these runner upgrades on DO in the Jocassee tailwaters. Duke Energy (2011a) reported in the Pre-Application Document that DO water quality standards were met from 2008 through 2009. The lowest hourly minimum DO recorded in the Jocassee tailwater was 5.80 mg/l. Additional runner replacements for JPSS Units 1 and 2 were conducted in 2010 and 2011. Jocassee tailwater monitoring was continued through 2011 and 2012 to document the water quality resulting from the releases associated with the new runners. Water quality monitors were installed in the Jocassee forebay to document the influence of the new runners on forebay water quality during pump back operations. In addition to measurements of DO concentrations in the Jocassee tailwaters and forebay to assess compliance with South Carolina State Water Quality Standards, Duke Energy (2011b)has developed a water quality model, CE-QUAL-W2, to evaluate proposed changes in project operations on the water quality of Lake Keowee and the tailrace of the Keowee Development. Since JPSS operations and tailwater water quality are input variables to the CE-QUAL-W2 model, the Jocassee tailwater monitoring data were also used for the initial calibration and subsequent use of the model. 3.0 OBJECTIVES The objectives of the Jocassee Forebay and Tailwater Water Quality Study were defined in the Study Plan as follows: Collect DO and temperature data from the JPSS forebay and tailwater (Lake Keowee); Compare data collected to applicable state water quality standards; and Evaluate the need for modifications to project operations if DO standards are not met. 4

4.0 METHODS The methods for achieving the goals and objectives of the Jocassee Forebay and Tailwater Water Quality Study (as described above) are consistent with the FERC approved Study Plan and are also based upon the SCDHEC approved Quality Assurance Project Plan (QAPP) (Duke Energy, 2009) used as part of the Catawba-Wateree Hydroelectric Project (FERC No. 2232) relicensing process. 4.1 Monitor Locations In 2008, a 6-inch plastic standpipes that served to house and protect the water quality monitor was mounted to the wingwall structure in the JPSS tailwater (Figures 2 and 3). Originally, electrical power for the tailrace monitor was supplied by an AC (110-volt) source from the JPSS, but was replaced in 2010 with a 12-volt battery, which in turn, was connected to a solar panel to maintain battery voltage. The sensor end (bottom) of the monitor standpipe was located approximately 9 feet below the Lake Keowee full pond elevation and had numerous perforations to allow for adequate water exchange within the enclosure. In the spring of 2012, a single 6-inch plastic standpipe was mounted on each of the two Jocassee forebay intake structures (Figure 4). Intake A provides flows to Units 1 and 2, and Intake B provides flows to Units 3 and 4. The sensor end of each of the forebay standpipes was located at the 1,055-foot AMSL elevation, which corresponded to the center-line of the intake openings (Figure 5). These standpipes also contained numerous perforations on the sensor end to allow for adequate water exchange. 5

Figure 2. Location of Jocassee Tailwater Water Quality Monitor Figure 3. Jocassee Tailwater Water Quality Monitor Mounted on Wingwall 6

Figure 4. Jocassee Forebay Water Quality Monitor Mounted on Intake Structure (B) Figure 5. Elevation of Jocassee Forebay Water Quality Monitor Sensor End 7

4.2 Data Collection The location of each of the monitors in the tailwater and forebay was selected to provide a safe and direct pathway for monitor access and maintenance. Because all of JPSS units are identical and release water from the same elevations in the forebay and pump water back into the reservoir from the same structure in the tailwater, the horizontal variation in tailwater water quality was hypothesized to be minimal based upon the amount of water moved relative to the cross-sectional area of either structure, regardless of which hydro unit or combination of hydro units were operating. Lake Jocassee forebay data collected over the past 25 to 30 years, coupled with similar water quality data in upper Lake Keowee, indicate that most of the spatial variability occurred in the vertical (depth) distribution of temperature and DO and not the horizontal distribution. Continuous water quality data collection began in the Jocassee tailwater in August 2008, and continued through October 2012. Jocassee forebay monitoring was conducted from April through October 2012. Initially, a single calibrated Hydrolab DS4 minisonde was deployed in the tailwater standpipe. The Hydrolab in the standpipe was typically inspected every three weeks (monthly thereafter) and replaced as necessary with a calibrated Hydrolab. The Hydrolab was programmed to store temperature and DO data at 5-minute intervals, and data were downloaded during each site visit. Beginning in 2011, two Hydrolabs were placed in the tailwater standpipe to minimize the loss of data. Also at that time, a Nexens data logger was employed to record the data as well as download the data via a computer modem. This capability greatly increased the reliability of the data collection by allowing for the comparison of data from the two Hydrolabs. The modem also enabled real time problem detection and rapid corrective action. A similar Nexens data logger was installed on each forebay intake structures with one Hydrolab in each standpipe. This pair of Hydrolabs was to be used for comparison of data collected in the forebay and this was considered adequate due to the close proximity of the forebay intake structures. 4.3 Laboratory Calibration Procedure Prior to the deployment of a monitor, the water quality sensors were calibrated in the laboratory according to the Duke Energy Laboratory s (SCDHEC Certification Number 99046004) Water Quality Procedures. Employing a water bath maintained at room temperatures, temperature readings from the monitor were compared to readings from a NIST traceable thermometer inserted adjacent to the temperature probe and documented. Similarly, the DO sensor was calibrated against a water sample of 8

known oxygen concentration using the ASTM (2005) method, and adjusted if appropriate. All calibration records were retained as a portion of the Duke Energy Laboratory Quality Assurance/Quality Control procedures. 4.4 In-Field Calibration An independent laboratory-calibrated water quality monitor was used to check the calibration of each in-field monitor. Prior to removal of the deployed Hydrolab from the standpipe, a laboratory calibrated unit was lowered into the standpipe and suspended adjacent to the existing unit. The recording interval of both units was changed remotely to 1-minute intervals and side-by-side comparison readings were recorded for 10 minutes. These side-by-side readings were used to document the accuracy of the deployed instrument, and the information was captured and stored for future reference. The in-field monitors were replaced with a laboratory-calibrated instrument and transported back to the Duke Energy Laboratory for post-deployment evaluation and any necessary maintenance. The maximum memory available internal to the monitors requires monthly data downloads. The monitors were serviced at least on a monthly basis. 5.0 RESULTS AND DISCUSSION Preliminary results of the water quality monitoring of the Jocassee tailwaters were previously presented in the Pre-Application Document (Duke Energy, 2011a). In accordance with the Revised Study Plan filed with FERC in 2011 (Duke Energy, 2011b), Duke Energy continued monitoring the Jocassee tailwaters but added a continuous monitoring system on Intake B in March 2012, and a second system on Intake A in May 2012. From the date of installation, except when the standpipe on Intake B was out of service, the 5-minute water quality data recorded from the monitor on Intake B were similar to the data collected from both monitors in the tailrace (Appendix A). Throughout 2012, DO from the forebay and tailwater monitors were very similar with DO differences rarely exceeding 0.2 mg/l, and both locations exhibited DO values significantly higher than state water quality standards. As with DO, temperature values from both locations were generally very similar with very slight differences in the timing of the temperature. From the beginning of data recording in the forebay on Intake A, the temperature data from both forebay monitors were very similar; however, at times the DO concentrations between the two monitors deviated significantly, as illustrated in the August 2012, data (Figure 6). Appendix B describes the troubleshooting steps and the final resolution of the erratic readings from the monitor on 9

Intake A. Because of the sediment build-up in the Intake A standpipe, the DO readings from the monitor on Intake A were removed from the 2012 data analysis (i.e., the values were not plotted nor used in the statistical summary of the Jocassee monitoring data). Figure 6. Jocassee August 2012 Tailwater and Forebay (Intake A and B) 5-minute Water Quality Monitoring Data Preliminary water quality monitoring data collected at the Jocassee tailwaters (Duke Energy, 2011a) demonstrated that the minimum hourly DO concentration observed in 2008 and 2009 was 5.80 mg/l, which is above the state water quality standard of 5.0 mg/l, expressed as a daily average, and 4.0 mg/l, expressed as an instantaneous measurement. The continual monitoring of the Jocassee tailwater in 2010, 2011, and 2012 (Figures 7, 8, and 9, respectively) also demonstrated that, throughout the years, the DO concentrations were consistently well above state standards, with the lowest hourly average DO of 6.55 mg/l observed in 2012. The 2012 tailwater monitoring results for both temperature and DO exhibited a seasonal pattern which paralleled temporal trends in these parameters measured at Intake A in Lake Jocassee (Figure 9). The 10

intake structure opening for the JPSS (forebay monitoring location) is located at elevations within the upper, well oxygenated portion of the water column (epilimnion) of Lake Jocassee (Figure 1). Historical data depicting seasonal trends in temperature and DO in Lake Jocassee (Foris, 1995; 2008) illustrate the highest epilimnion DO levels are usually observed concurrent with or slightly later, than minimum water temperatures, i.e., maximum mixing of Lake Jocassee. As temperatures begin to warm and lake stratification intensifies, DO concentrations begin to decrease throughout the water column, including the epilimnion. This trend continues throughout the stratified period until the advent of fall cooling when the lake begins to convectively mix, thereby increasing DO levels in the epilimnion, and hence the tailwaters. Thus, hydroelectric withdrawals from the well oxygenated epilimnion in the Lake Jocassee forebay, coupled with generally excellent water quality in the reservoir, are the primary reasons releases to the JPSS tailwaters consistently met state water quality DO standards over the 2008 through 2012 study period (see also Appendix C). Also, the monthly historical temperature and DO profile data Duke Energy collected in the forebay of Lake Jocassee since the reservoir was impounded in 1974 suggest that state DO standards at the Jocassee tailwaters have likely been continually met since initial impoundment of the reservoir. Further, no future change from this pattern would be anticipated unless 1) water quality in Lake Jocassee changed dramatically and eventually resulted in a decrease in epilimnetic DO concentrations, or 2) the JPSS intake structure was modified and water for usage in power generation was withdrawn from the deeper, hypoxic part of the water column (the hypolimnion). 11

Figure 7. Jocassee 2010 Tailwater Hourly Average Water Quality Monitoring Data 12

Figure 8. Jocassee 2011 Tailwater Hourly Average Water Quality Monitoring Data 13

Figure 9. Jocassee 2012 Tailwater and Forebay (Intake A) Hourly Average Water Quality Monitoring Data 14

Table 1 provides the minimum, mean, and maximum temperature and DO concentrations measured in 2012 in both the forebay and tailwater locations. The 5-minute, hourly, and daily values were well above the state water quality standards. Table 1. Statistics for the Jocassee Forebay and Tailwater Temperature and Dissolved Oxygen Continuous Monitoring Data 15

6.0 SUMMARY AND CONCLUSIONS The CWA requires SCDHEC to issue 401 WQC prior to the issuance of a new license for the Project. SCDHEC will only issue a 401 WQC if Duke can demonstrate that the Project releases have a reasonable assurance of meeting SCDHEC s State Water Quality Standards. Four years of Jocassee tailwater monitoring have demonstrated that the water released from Lake Jocassee has DO concentrations well above South Carolina State Water Quality Standards. Monthly statistics for 2012 (Table 1) show the same conditions in 2012. At no time did DO concentrations in the tailwater or forebay fall below state standards in the data reviewed for this report. At all times, the 2012 forebay temperature and DO concentrations were similar to that measured in the tailwater, indicating that all of the monitors collected data representative of the water released or pumped back, regardless of the combination of unit operation. DO concentrations in the JPSS tailwaters consistently meet and exceed state water quality standards primarily because flow withdrawals from the forebay of Lake Jocassee during electrical generation at the JPSS originate from the epilimnion or the well-oxygenated portion of the water column. The results of this study indicate that no changes in project operation or other measures would be required to maintain or enhance DO levels in Project discharges. 16

7.0 REFERENCES ASTM (American Society for Testing and Materials). 2005. D888-05 Standard Test Methods for Dissolved Oxygen in Water. ASTM. West Consholocken, PA. Duke Energy. 1995. Oconee Nuclear Station, 316a Demonstration Report. Duke Energy Carolinas, LLC, Charlotte, NC.. 2007. Oconee Nuclear Station, 316a Demonstration Report. Duke Energy Carolinas, LLC, Charlotte, NC.. 2009. Quality Assurance Project Plan for the Catawba-Wateree Tailwater Dissolved Oxygen Monitoring, FERC Project No. 2232. Duke Energy Carolinas, LLC, Charlotte, NC.. 2011a. Pre-Application Document, Volume III, Section 6.2.7 Keowee-Toxaway Hydroelectric Project, FERC No. 2503. Duke Energy Carolinas, LLC, Charlotte, NC.. 2011b. Keowee-Toxaway Relicensing FERC No. 2503 Revised Study Plan. Duke Energy Carolinas, LLC, Charlotte, NC. Foris, W.J. 1995. Jocassee Reservoir Trout Habitat Summary. DPC Rpt. Bad Creek Project. 20pp.. 2008. Jocassee Reservoir Pelagic Trout Habitat-2007. DPC Rpt. Bad Creek Project. 14pp. SCDHEC (South Carolina Department of Health and Environmental Control). 2006. South Carolina Regulation 61-68 Water Classifications and Standards. 59pp. South Carolina Department of Health and Environmental Control. Columbia, SC. 17

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APPENDIX A 2012 MONTHLY PLOTS OF JOCASSEE TAILWATER AND FOREBAY CONTINUOUS MONITORING DATA

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APPENDIX A 2012 MONTHLY PLOTS OF JOCASSEE TAILWATER AND FOREBAY CONTINUOUS MONITORING DATA This appendix provides the detailed information (5-minute data recordings) for the Forebay and Tailwater Water Quality and Tailwater Depth Data that were collected during 2012 (March through October). The data are plotted on the same monthly charts with the exception of July, to allow illustration of the similarities between the forebay and tailwater concentrations as well as the differences between the monitors on Intake A and B (see Appendix B for details). The July temperature scale was changed to avoid overlay of the data. A-1

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APPENDIX B INVESTIGATION OF ERRATIC READINGS OF THE DISSOLVED OXYGEN MONITOR ON JOCASSEE INTAKE A (UNITS 1 AND 2)

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APPENDIX B INVESTIGATION OF ERRATIC READINGS OF THE DISSOLVED OXYGEN MONITOR ON JOCASSEE INTAKE A (UNITS 1 AND 2) A dissolved oxygen (DO) monitor was installed on Jocassee Forebay Intake Structure B (Units 3 and 4) in March 2012. Several problems were encountered early on (the standpipe was broken off, lightning strike, and a faulty cable), which resulted in intermittent data collected between February and April 2012. Since May, reliable data have been collected at this monitoring location. However, since the installation of the DO monitor on Jocassee Forebay Intake Structure A (Units 1 and 2), erratic DO readings have been observed as well as typically lower readings than those observed on the Intake B monitor. This observation did not make sense because the intakes are less than 100 yards apart. It was originally thought that the monitors used on Intake A were malfunctioning after the calibration because it would take a while for the erratic readings to begin. To investigate this problem, the data logger was tested and comparisons were made with a separate monitoring instrument. Many times during the calibration, the initial readings, before the old monitor was removed indicated lower readings. When a new monitor replaced the old monitor, the calibration instrument read the same as the new monitor. However, within a very short period of time, the monitor would begin the erratic, lower readings. After numerous replacement monitors it was concluded that the monitors did not appear to be the cause of the erratic readings because all of the replacement monitors would eventually exhibit the same pattern. On September 20, 2012, the calibration instrument remained in the pipe to see if the two monitors would behave the same for longer than the calibration period. The two instruments, referred to as SDI 1 (the normal monitor) and SDI 3 (the second instrument usually reserved for the calibration instrument) measured side by side for a one week period. The results (Figure B-1) showed both monitors had the same response with erratic and progressively lower readings than the monitor on Intake B. Therefore, it was suspected that the location of the monitors in the standpipe might be the problem. Prior to the installation of the pipe on Intake A, a picture was taken of the lower end of the standpipe (Figure B-2). There appeared to be plenty of holes in the lower end of the pipe to allow for adequate

water circulation; however, the one small hole on the bottom of the pipe cap suggested sediment may be accumulating in the pipe cap. The instruments are lowered so they rest on the cap at the bottom of the standpipe which relieves the strain on the cable. This being the case, the sensors would be in or slightly above any accumulated sediment. To test this hypothesis, the monitor connected to SDI 1 was raised one foot above the bottom of the pipe cap; the SDI 3 instrument was left resting on the pipe cap (normal procedure). The instrument one foot above the pipe cap (SDI 1) had consistent readings with very similar patterns to the monitor on Intake B. The instrument resting on the pipe cap (SDI 3) continued to exhibit erratic readings, lower than the monitor on Intake B and lower than the instrument one foot higher. Comparison of the recordings (Figure B-3) supported the hypothesis of sediment accumulation. In summary, Duke Energy s protocol will change where instruments in the pipes will be raised 1-1½ feet above the pipe cap to eliminate interference from accumulated sediment. Future pipe installations should have plenty of holes in the pipe cap to prevent sediment accumulation. Figure B-1. Calibration Monitor remained in the standpipe of Intake A Both SDI 1 and SDI 3: Intake A on Pipe Cap 9 SDI 1 - Intake A SDI 3 - Intake A Intake B 8 Dissolved Oxygen (mg/l) 7 6 5 20-Sep 22-Sep 24-Sep 26-Sep 28-Sep 30-Sep 2-Oct 4-Oct B-2

Figure B-2. Picture of Standpipe Mounted on Intake A Figure B-3. Results of Instrument raised off the bottom of the standpipe After SDI 1: Intake A Raised One Foot (SDI 3 remained on pipe cap) 9 SDI 1 - Intake A SDI 3 - Intake A Intake B 8 Dissolved Oxygen (mg/l) 7 6 5 10-Oct 12-Oct 14-Oct 16-Oct 18-Oct B-3

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APPENDIX C COMPARISON OF JOCASSEE TAILWATER WATER QUALITY DATA WITH LAKE JOCASSEE PROFILE DATA COLLECTED AT THE DEPTHS OF THE INTAKE STRUCTURE

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APPENDIX C Comparison of Jocassee Tailwater Water Quality Data with Lake Jocassee Profile Data Collected at the Depths of the Intake Structure The Jocassee forebay continuous temperature and DO data collected on Intake B was similar to the data collected in the tailwater from March through October, 2012. Because the forebay continuous monitoring data were not collected prior to 2012, comparisons of the of the mean hourly tailwater data to data collected from the monthly lake profiles for the fisheries resource MOU in 2009-2012 would provide an additional check on the accuracy of the continuous tailwater monitoring. Temperature and DO data from the monthly forebay profiles for each sampling day were taken from the elevations corresponding to the top, middle, and bottom of the intake opening (Figures 1 and 5). Differences in the temperature from the three intake depths were indicative of the temperature stratification in the upper water column of Lake Jocassee (Figures C-1, C-2, C-3 and C-4). When the profile temperature differences were minimal, the upper epilimnetic layer was well mixed. The temperatures collected in the tailwaters during these well mixed periods followed the epilimnetic temperatures measured in Lake Jocassee. When the Lake Jocassee exhibited some stratification, the water temperature in the tailrace followed the temperatures from the upper portion of the JPSS forebay intake openings, indicating selective withdrawal from the upper intake opening. Regardless of the temperature stratification, the epilimnion DO was always at or near saturation. As expected, the DO comparisons (Figures C-1, C-2, C-3, and C-4) revealed the DO concentrations measured in the Jocassee tailwaters followed the conditions measured from the JPSS epilimnetic intake openings. Not only do these comparisons confirm the accuracy of the continuous monitors in both the tailwater and the forebay, but also serves to illustrate state water quality standards have been met for many years based upon 30-year, high DO concentrations observed in the historical epilimnetic records reported by Duke Energy (Foris, 1995 and 2008). C-1

Figure C-1. Comparison of 2009 Jocassee Tailwater Hourly Mean Dissolved Oxygen and Temperature Data to Lake Profile Data Collected at the Depths of the Jocassee Intake C-2

Figure C-2. Comparison of 2010 Jocassee Tailwater Hourly Mean Dissolved Oxygen and Temperature Data to Lake Profile Data Collected at the Depths of the Jocassee Intake C-3

Figure C-3. Comparison of 2011 Jocassee Tailwater Hourly Mean Dissolved Oxygen and Temperature Data to Lake Profile Data Collected at the Depths of the Jocassee Intake C-4

Figure C-3. Comparison of 2012 Jocassee Tailwater Hourly Mean Dissolved Oxygen and Temperature Data to Lake Profile Data Collected at the Depths of the Jocassee Intake C-5