# Marshall Steam Station

2006-2007 Impingement Study and Assessment of Adverse Environmental Impact

Final Report, 2009

Cosponsor(s)
Duke Power
P.O. Box 1006 Charlotte, NC 28201-1006

Project Manager David E. Bailey

EPRI Project Manager D. Bailey

EPRI • 3412 Hillview Avenue, Palo Alto, California 94304 • PO Box 10412, Palo Alto, California 94303 • USA

800.313.3774 • 650.855.2121 • askepri@epri.com • www.epri.comiiiii 

## CITATIONS

This technical report was prepared by

ASA Analysis & Communication, Inc. 5 Fairlawn Drive, Suite 205

P.O. Box 57 Washingtonville, NY 10992

Principal Investigators

W. Dey

J. McLaren ASA Analysis & Communication, Inc.

This Technical Report describes research spons ored by EPRI and Duke Energy Corporation.

The Technical Report is a corporate document that should be cited in th e literature in the following manner:

Marshall Steam Station: 2006-2007 Impingeme nt Study and Assessment of Adverse Environmental Impact , EPRI, Palo Alto, CA, 2009.v 

## REPORT SUMMARY

This report has been prepared for Duke Energy’ s Marshall Steam Station to support Clean Water Act Section 316(b) requirements. It presents the results of sampling conducted during 2006- 2007 to document current levels of impingement of fish and other aquatic organisms at the facility’s cooling water intake. Sampling results are interpreted in terms of the status of Lake Norman, from which the cooling water is wit hdrawn, and its fish community. Impingement losses are interpreted as to whether they constitu te adverse impact to the fish community of Lake

Norman.

Background

Marshall Steam Station (MSS) is a 2,090-MW co al-fired steam-electric generating facility located on Lake Norman approximately 48 km (30 miles) north of the C ity of Charlotte, North Carolina. MSS consists of four operating un its and uses once-through cooling for its steam condensers. Units 1 and 2 began commercial operation in 1965 and 1966, respectively. Units 3 and 4 began operation in 1969 and 1970, respec tively. During 2002-2007, the average annual capacity factor, based on Maximum Net Dependa ble Capacity, was 79 percent and average annual intake flow during 2002-2006 was 73 percent of the maximum design capacity, which is 1,463 MGD.

Impingement sampling was conducted weekly from 6 April 2006 until 30 March 2007. MSS has 16 intake bays and fixed screens, with each fi xed screen consisting of an upper and a lower removable panel. To conduct impingement samp ling, a crane operator lifte d the upper and lower screen panels, which were pressure-washed, and th e cleaned panels were placed behind the next screen to be sampled to act as a back-up scr een. Because this process was time-consuming, only four screens could be washed and sampled durin g each sampling event. Therefore, the sampling design had to incorporate a random selection pro cess to determine which screens were to be washed and sampled weekly. Sampling and data r ecording adhered to stri ct Standard Operating Procedures prepared specifically for this study and facility.

Impingement Sampling Results

During impingement sampling, a total of 6,219 fish weighing a total of 30.2 kg was collected. Ten fish species were found in the impingement collections. No state or federally-listed threatened or endangered species were impinge d. Threadfin shad and alewife dominated the collections, comprising 80.8 percent and 12.6 percent of the fish collected, respectively. For the 12-month period from 1 April 2006 to 31 Marc h 2007, an estimated 188,419 fish and 1,036 kg of fish biomass were impinged at MSS. This es timate was derived from the density of fish collected during each sampling event, expres sed as number per volume of cooling water withdrawn at each of the four generating units, extrapolated over the full 12-month period.vi Results from a year-long impingement sampling program including all intake bays, directly comparable to the 2006-2007 program, are not ava ilable from previous years for comparison. However, biweekly impingement sampling at one sc reen per unit (four scr eens total) from April 1974 to May 1975 yielded a total of 1,050,505 fish colle cted. Of those iden tified to species in 1974-1975, threadfin shad were the most nume rous, comprising 61.9 percent of the total collections. When combined with gizzard shad, sh ad unidentifiable to species, and unidentified clupeid species, these four ta xa comprised 99.8 percent of the total impingement. While not directly comparable to the 2006- 2007 data, the sampling results i ndicate a dramatic reduction in impingement rates at MSS from 1974-1975 to th e present. Reductions in impingement of clupeid species (threadfin shad, alewife, and gi zzard shad) appear to be the primary reason for this decline in impingement at MSS.

During the 2006-2007 monitoring program, impingeme nt rates were lowest during the spring, April-June, and highest in the late summer a nd early fall (August-October) or mid-winter (February). This seasonal pattern reflected the impingement of the two dominant species, threafin shad and alewife. Alewife primarily were impinged in late summer whereas threadfin shad were impinged throughout the fall and wint er months, September-March. Impingement rates may have been influenced by water temperat ures, lake levels, or DO concentrations. Peak impingement of threadfin shad occurred wh en daily mean water temperatures were approximately 6.7-7.8 ° C (44-46°F) in February and early Ma rch, and the lake level was low. Peak alewife impingement occurred in August when DO concentrations were well below 4 mg/L. Stress related to cold temperatures or low DO may have increased impingement rates for these two species.

AEI Assessment Results

The potential for the estimated levels of im pingement at MSS to be considered “adverse environmental impact” under §316(b) of th e Clean Water Act was assessed. Adverse environmental impact was defined as an unacceptable reduction in:



###  biological integrity as meas ured in terms of aquatic community species composition, diversity, and functional organi zation in Lake Norman; or,



###  human use of the aquatic resources of Lake Norman, especially fishing opportunity or catch quantity or quality.

The assessment used the U.S. Environmental Pr otection Agency’s well-established Framework for Ecological Risk Assessment. Potential adverse effects were addressed from two perspectives: prospective (predict ed future risks) and retrospe ctive (effects linked to present operation). The results were used in a “weight -of-evidence” approach to determine the overall risk of adverse environmental impact from opera tion of the MSS cooling water intake structure

on Lake Norman.

There was no evidence that impingement at M SS is causing adverse environmental impact in

Lake Norman. This conclusion is based on a care ful evaluation of all rele vant lines of evidence including the following:vii 1. Numbers of fish lost as a re sult of impingement are exceedingly small compared to likely sizes of fish populations in La ke Norman. For all but three species, removal rates amounted to less than 10 fish per day. For blue catfis h, removal rates were le ss than 22 young juveniles per day. These young juveniles could be expected to yield only a single harvestable adult, on average. As with the other species, it is ha rd to imagine that such a removal rate would constitute an adverse environmental impact on Lake Norman.

2. Total number impinged each year for the two mo st frequently impinged species, threadfin shad and alewife, amounted to less than 0.3 percent of the pop ulation in the lake. Both species are highly prolific spawne rs with high growth rates and short life spans. This high reproductive potential can easily compensate fo r the relatively small losses at MSS with no long-term effects.

3. The aquatic community of Lake Norman has been relatively stable in terms of fish abundance and trophic structure, pa rticularly in recent years. Fish abundance in pelagic areas

has stabilized since 1997. There also has been no sustained tre nd in the size of the littoral zone catch since 1993, while spec ies richness has increased with the addition of several new species.

4. Intensive recreational fishery management a nd species introductions likely have been responsible for changes in the fish community e xperienced in the past. However, there is no evidence of changes related to operation of th e MSS cooling water intake and impingement

losses.

5. Estimates of total fishery catch that could re sult from the fish impinged at MSS, had they survived, amount to only 254 lb (115 kg) per ye ar, most of which was blue catfish. That amount translates to less than 1 lb (0.5 kg) pe r day. This level of ha rvest is less than what would be expected from a small number of anglers.

6. Estimates of the total production foregone as a result of fish impinged at MSS amounted to just over 5,100 lb (2,313 kg) per year of biomass. Almost all of this was a result of threadfin shad and alewife, both of which are highly abun dant species in Lake Norman. That biomass translates to less than 3 ounces per surface acre (210 g/ha) across the entire reservoir.

7. The best estimate of the total economic valu e of fish impinged at MSS was $577 per year. Even considering the uncertainty in these esti mates, it is highly un likely that the economic value exceeds $800 per year. These values must be considered trivial compared to the likely

total economic value of the recrea tional fishery in Lake Norman.

Keywords Clean Water Act §316(b)

Economics Cooling water intake structures

Fisheries Environmental impact assessmentix 

## CONTENTS

INTRODUCTION .................................................................................................................. .......... 1-1

Background .................................................................................................................... ............ 1-1

Report Organization ........................................................................................................... ........ 1-2

PLANT AND SOURCE WATERBOD Y DESCRIPTIONS .............................................................. 2-1

Marshall Steam Station ........................................................................................................ ...... 2-1

Cooling Water Intake Structure ............................................................................................. 2- 1

Plant Operation and Water Withdrawal ................................................................................. 2-1

Lake Norman ................................................................................................................... ........... 2-2

Geomorphology and Aquatic Habitat ..................................................................................... 2-2

Water Quality ................................................................................................................. ........ 2-3

FISH COMMUNITY DESCRIPTION ............................................................................................... 3-1

Description of Available Information .......................................................................................... . 3-1

Species Composition............................................................................................................ ...... 3-2

Protected Species ............................................................................................................. ......... 3-3

Target Species ................................................................................................................ ........... 3-4

Threadfin Shad ................................................................................................................ ...... 3-4

Alewife ....................................................................................................................... ............ 3-5

Blue Catfish .................................................................................................................. ......... 3-6

White Perch ................................................................................................................... ........ 3-7

Channel Catfish ............................................................................................................... ...... 3-8

IMPINGEMENT MORTALITY ......................................................................................................... 4-1

Impingement Monitoring Programs ............................................................................................ 4- 1

Current Impingement Sampling Program Results ...................................................................... 4-2

Species Composition ........................................................................................................... .. 4-3

Seasonal Patterns ............................................................................................................. .... 4-4

Variables Affecting Impingement Rates ................................................................................ 4-5

Environmental Variables ................................................................................................... 4-5

Species-Specific Abundance and Spatial Distribution ...................................................... 4-6x Annual Losses ................................................................................................................. ........... 4-7

Annual Variability ............................................................................................................ ....... 4-8

Intake Operation .............................................................................................................. . 4-8

Environmental Variables ................................................................................................... 4-8

Fish Abundance ................................................................................................................ 4-8

Comparison of Annual Monitoring Programs .................................................................... 4-9

ASSESSMENT OF ADVERSE ENVI RONMENTAL IMPACT ........................................................ 5-1

Introduction .................................................................................................................. .............. 5-1

Assessment of Ecosystem Effects ............................................................................................. 5 -3

Prospective Approach .......................................................................................................... . 5-3

Retrospective Approach ........................................................................................................ 5-4

Fish Abundance ................................................................................................................ 5-5

Species Richness ............................................................................................................. 5-6

Trophic Structure ............................................................................................................. . 5-6

Retrospective Summary.................................................................................................... 5-7

Effects on Human Uses.......................................................................................................... .... 5-8

Equivalent Loss Measures .................................................................................................... 5 -8

Economic Value ..................................................................................................................... 5-9

Uncertainty in Economic Value .............................................................................................. 5-10

Conclusions ................................................................................................................... ............. 5-10

REFERENCES CITED .............................................................................................................. ...... 6-1

APPENDIX A: METHODS TO ESTIMATE EQUIVALENT LOSS AND ECONOMIC
VALUE OF FISH IMPINGED AT MARSHALL ............................................................................... A-1

Introduction .................................................................................................................. .............. A-1

Estimates of Target Species Equivalent Losses ........................................................................ A-1

Assignment of Age Categories for Impinged Individuals ....................................................... A-3

Life Table Information ........................................................................................................ .... A-3

Life Stage Durations .......................................................................................................... .... A-4

Natural Mortality Rates ....................................................................................................... ... A-4

Fishing Mortality Rates ....................................................................................................... ... A-5

Fishing Vulnerability Rates ................................................................................................... . A-5

Weight at Beginning of Age ................................................................................................... A-6

Economic Valuation Methods .................................................................................................... . A-7xi Direct Use Values ............................................................................................................. ..... A-7

Market Values (Commercial Fishing) .................................................................................... A-7

Non-Market Direct Use Values (Recreational Fishing) .......................................................... A-8

Indirect Use Benefits ......................................................................................................... .... A-9

Non-Use Benefits .............................................................................................................. .... A-12

Adjustment for Other Species ................................................................................................ A-12

Uncertainty Analysis .......................................................................................................... ......... A-13

Inputs to Direct and Indirect Use Benefits ............................................................................. A-14

Sensitivity Analysis .......................................................................................................... ...... A-15

Monte Carlo Analysis ............................................................................................................. A-15xii 

## LIST OF FIGURES

Figure 2-1 Location of MSS ................................................................................................... ... 2-5
Figure 2-2 Aerial View of MSS ................................................................................................ .. 2-6
Figure 3-1 Sampling Zones and Locations for Lake Norman ................................................. 3-10
Figure 4-1 Seasonal Pattern of Impingement Rates for All Species Combined ...................... 4-11
Figure 4-2 Seasonal Impingement Pattern and Length Frequency of Impinged Alewife ........ 4-12
Figure 4-3 Seasonal Impingement Pattern and Length Frequency of Impinged Threadfin
Shad .......................................................................................................................... ....... 4-13
Figure 4-4 Seasonal Impingement Pattern and Length Frequency of Impinged Blue
Catfish ....................................................................................................................... ....... 4-14
Figure 4-5 Seasonal Impingement Pattern and Length Frequency of Impinged Channel
Catfish ....................................................................................................................... ....... 4-15
Figure 4-6 Seasonal Impingement Pattern and Length Frequency of Impinged White
Perch ......................................................................................................................... ....... 4-16
Figure 4-7 Daily Lake Level, Dissolved O xygen Concentration, and Intake Water Temperature vs. Impingement Rate for All Species Combined, April 2006-March

2007 .......................................................................................................................... ....... 4-17
Figure 4-8 Daily Lake Level, Dissolved O xygen Concentration, and Intake Water Temperature vs. Impingement Rate for Young-of-Year (YOY) and Yearling and Older (YAO) Threadfin Shad, April 2006-March 2007...................................................... 4-18
Figure 4-9 Daily Lake Level, Dissolved O xygen Concentration, and Intake Water Temperature vs. Impingement Rate for Young-of-Year (YOY) and Yearling and Older (YAO) Alewife, April 2006-March 2007................................................................... 4-19

Figure 5-1 Annual Population Estimates of Pelagic Fish in Lake Norman Using Hydroacoustic Sampling, 1993-2006 ............................................................................... 5-12
Figure 5-2 Total Annual Electrofishing Catch for Bluegill, Redbreast Sunfish, Largemouth Bass, and All Species Combined at 30 100-m Transects in Lake Norman, 1993-1997 and 1999-2007 ................................................................................ 5-13
Figure 5-3 Total Annual Electrofishing Catch for Blue Catfish, Alewife, and Threadfin Shad at 30 100-m Transects in Lake Norman, 1993-1997 and 1999-2007 ..................... 5-14
Figure 5-4 Total Annual Electrofishing Catch for Channel Catfish and White Perch at 30 100-m Transects in Lake Norman, 1993-1997 and 1999-2007 ....................................... 5-15
Figure 5-5 Species Composition in the Littoral Zone of Lake Norman as Determined by Electrofishing in 1993-1997 and 1999-2007 (Shading Denotes Species Presence) ........ 5-16
Figure 5-6 Percent Composition of Fish Trophic Guilds in the Littoral Zone of Lake Norman Based on Electrofishing Results of 1993-1997 and 1999-2007 ......................... 5-18

Figure 5-7 Estimates of the Range of Effects of Uncertainty in Each Input Parameter on
Estimates of Annual Economic Benefit at MSS ............................................................... 5-19
Figure 5-8 Results of Monte Carlo Analysis of Uncertainty in Key Input Parameters on
Estimates of Annual Economic Benefits at MSS .............................................................. 5-20xiii 

## LIST OF TABLES

Table 2-1 Monthly Mean Cooling Water Flow Rate (MGD) and Percentage of Maximum Design Generation and Flow Rate at Marshall Steam Station, 2002-2007 ........................ 2-7
Table 3-1 Fish Species Collected in Lake Norman Fishery Surveys (Siler et al. 1981; Duke 2004a, 2004b, 2006, 2007) ..................................................................................... 3-11
Table 4-1 Fixed Screens Sampled for Impingement (Marked as “1”) by Unit and Sampling Date, 2006-2007 .............................................................................................. 4-20
Table 4-2 Estimated Total Number and Biomass of Fish Impinged at Marshall Steam Station, 1 April 2006 – 31 March 2007 ............................................................................. 4-22

Table 4-3 Total Number and Percent Composition of Fish Collected at Marshall SS, 6 April 2006 – 30 March 2007 ............................................................................................. 4-23
Table 4-4 Total Biomass and Percent Composition of Fish Collected at Marshall SS, 6 April 2006 – 30 March 2007 ............................................................................................. 4-23
Table 4-5 Number of Impinged Fish Collected* at Marshall Steam Station, 30 April 1974 – May 1975 .................................................................................................................... .. 4-24
Table 4-6 Number and Percent Composition of Taxa Other Than Fish at MSS, 6 April
2006 – 30 March 2007 ..................................................................................................... 4-25
Table 4-7 Estimated Total Number and Biomass of Fish Impinged Monthly at all Units of MSS, 1 April 2006 - 31 March 2007 ................................................................................. 4-26
Table 4-8 Maximum Total Length (mm) Used to Distinguish Young-of-Year from Yearling Fish by Month .................................................................................................... 4-2 8
Table 4-9 Estimated Annual Impingement of Fish by Age Group at all Units of MSS, 1 April 2006 - 31 March 2007 .............................................................................................. 4-29
Table 4-10 Comparison of Relative Abundance of Fish Species in the March-April 2006 Littoral Zone Electrofishing Surv eys and the 2006-2007 MSS Impingement
Collections ................................................................................................................... ..... 4-30
Table 4-11 Estimated Total Number and Biomass of Fish Impinged Monthly at all Units of MSS for Full Flow Operations, 1 April 2006 - 31 March 2007 ...................................... 4-31

Table 5-1 Species Composition of the Purse Seine Catch in Lake Norman, 1993-2006 ....... 5-21
Table 5-2 Trophic Guild Assignments for Fish Species in Lake Norman ................................ 5-22

Table 5-3 Estimates of Potential Total Annual Equivalent Fishery Yield (lb) from Individuals Impinged for Each Target Species at MSS .................................................... 5-23
Table 5-4 Estimates of Potential Total Annual Production Foregone (lb) from Individuals Impinged for Each Target Species at MSS ...................................................................... 5-23
Table 5-5 Estimates of Economic Value of Fish Impinged at MSS ......................................... 5-241-1 

# 1

INTRODUCTION

Background

ASA Analysis & Communication, In c. has prepared this repor t for Duke Energy’s Marshall Steam Station (MSS) as part of the applica tion process for a National Pollution Discharge Elimination System (NPDES) permit from the No rth Carolina Department of Environment and Natural Resources (NCDENR). Under the Clean Water Act §316(b), an NPDES permit applicant must demonstrate that the location, de sign, construction and cap acity of its cooling water intake structure represents Best Tec hnology Available (BTA) for minimizing adverse environmental impact. The primary impacts of concern under §316(b) are entrainment of smaller aquatic organisms into the cooling wate r system and impingement of larger organisms onto traveling screens in the cooling water intake.

In an effort to establish and enforce consis tent national standards under CWA §316(b), the U.S. Environmental Protection Agency (EPA) publishe d a Phase II Rule [69 Fed. Reg. 41576 (9 July 2004)]. The Rule applied to existing electric generating facilities that operate cooling water intake structures (CWIS) with a minimum de sign capacity of 50 million gallons per day (MGD), withdraw water from waters of the U.S., and us e 25 percent or more of the water withdrawn for cooling purposes. MSS fits this definition for a Phase II facility. Compliance with the Phase II Rule was based on achieving performance standards for reduction of impingement mortality and entrainment set by the EPA on the basis of facilit y location. The Rule required that impingement mortality be reduced by 80 to 95 percent and entrainment be reduced by 60 to 90 percent, compared to a baseline level (i.e., the calcula tion baseline) specifica lly determined for the facility. Adhering to the Phas e II Rule guidelines, MSS would not be subject to entrainment reduction performance standards because it is lo cated on a reservoir that has a retention time exceeding seven days.

In 2006, the Phase II Rule was challenged in the U. S. Court of Appeals for the Second Circuit, which reached a decision on 25 January 2007. The decision remanded several provisions of the Phase II Rule, including BTA determination, perfor mance standards, cost-cost and cost-benefit analysis, compliance according to the Technology In stallation and Opera tion Plan (TIOP), restoration as a compliance alternative, and “inde pendent supplier” provisions. In response to this decision, EPA suspended the Phase II Rule [72 Fed. Reg. 37107 (9 July 2007)] and directed that permit requirements for cooling water intake structures at Phase II facilities be established on a case-by-case best professiona l judgment (BPJ) basis. Ho wever, the requirement that permitting agencies develop BPJ controls for cooling water intake structures that reflect BTA for minimizing adverse environmental impact (AEI) wa s retained. Recently th e U.S. Supreme Court agreed to review the Second Circ uit Court’s decision relative to the remand of the cost-benefit component of the original Phase II Rule. The Supreme Court decision is expected in 2009.Introduction

1-2 To comply with the regulations, Duke Energy prepared a Proposal for Information Collection (PIC) for MSS that included the study design for impingement sampling and submitted the PIC to the NCDENR for review. The results of the imp ingement study are the subj ect of this report.

Since the Phase II Rule was remanded after PI C and §316 is now being ad ministered under BPJ, the analytical approach describe d in the PIC has been modified to be appropriate for a BPJ approach rather than for conformance to the re manded Phase II Rule. This report presents the results of sampling conducted at MSS during 2006- 2007 in order to document current levels of impingement at the facility’s cooling water intake . Sampling results are interpreted in terms of the status of Lake Norman, the impoundment from which the cooling water is withdrawn, and its fish community.



### Report Organization

Section 2 provides pertinent information on the st ructure and operation of the station’s cooling water intake structure, as well as a brief desc ription of the geomorphol ogy of Lake Norman and the aquatic habitat it provides. Section 3 describes the lake’s fish community composition and structure, particularly as relate d to susceptibility to impingement at the MSS intake. Section 4 presents the results of the 2006-2007 impingement sampling program, compares these results to data collected during sampling programs conduc ted during 1974-1975, descri bes the seasonality and size distribution of impinged fish, and anal yzes the possible influence of environmental factors and changes in the fish community on impi ngement rates. This information is used to characterize current baseline levels of impingeme nt at MSS. Section 5 discusses the observed level of impingement mortality in terms of whether it constitutes adverse impact on the fish community of Lake Norman, using both a predictiv e approach and a retros pective approach. The predictive approach uses modeling to express impingement losses in terms of equivalent reductions in yield to the Lake Norman fishery a nd to estimate the economic value of the losses. The retrospective approach evalua tes the composition of the current fish community to determine

whether there is evidence of trends that coul d indicate impairments or instability related to annual impingement losses.2-1 

# 2

PLANT AND SOURCE WATERBODY DESCRIPTIONS

This section describes the coo ling water intake structure of the Marshall Steam Station, its operation, and its cooling wate r source, Lake Norman.



### Marshall Steam Station

Marshall Steam Station (MSS) is a coal-fired steam-electric genera ting facility located approximately 48 km north of the City of Char lotte, North Carolina in Catawba County on Lake Norman, a reservoir on the Catawba River (Figure 2-1) . MSS consists of four coal-fired electric generating units rated at a combined net outpu t of 2,090 MW. Units 1 and 2, rated at 385 MW net each, began operation in 1965 an d 1966, respectively. Units 3 a nd 4, rated at 660 MW net each, began operation in 1969 and 1970, respectivel y. MSS uses once-through cooling for its

condensers.

Cooling Water Intake Structure

MSS has a cooling water intake lo cated at the end of a 2.1-km long, 81-ha cove (Figure 2-2). At

the mouth of the cove is a skimmer wall that is 18.3-m deep at full pond and has a 3-m by 82-m opening for withdrawing cool, hypolimnetic water when the lake is thermally stratified. On the face of the intake are trash racks with 3-in. (76- mm) on-center spacing for the steel bars. Units 1 and 2 each have three intake bays and two circulating pumps, and Units 3 and 4 each have five intake bays and three circulating pumps, for a to tal of 16 intake bays a nd 10 circulating pumps. Heated water is discharged into a 1.6-km long cove that is down lake from the intake cove and

has a surface area of 30 ha.

There are 16 sets (front and back) of fixed sc reens, with each screen consisting of upper and lower removable panels and with one screen set per intake bay. The screens have 3/8-in. (9.5- mm) woven wire mesh. They ar e cleaned individually by removi ng them by crane, placing them horizontally over a steel debris collection pit that can be li fted by crane and emptied, and washing them with a high-pressure spray wash. Normally the screens are washed on an asneeded basis, but the screen washing proce ss can be continuous during periods of heavy debris/fish loading.

Plant Operation and Water Withdrawal

Total generation and condenser cooling water pu mping data are presented in Table 2-1 for 2002 through 2007. Over this period, the average annual capacity factor, based on Maximum NetPlant and Source Waterbody Descriptions

2-2 Dependable Capacity, was 79 percent. The averag e total annual intake flow rate for January 2002 through December 2006 was approximately 73 percent of the maximum design capacity, 2,264cfs or 1,463 MGD (Table 2-1). Annual flows ranged from 69 percent (2006) to 76 percent (2005) of the maximum design capac ity. Typically, one cooling wa ter circulating pump per unit is operated during winter months or during redu ced plant loading, but al l pumps are run during warm months (July-September) a nd periods of peak demand.

Mean approach velocity at the fixed screens is 0.7 ft/s (0.21 m/ s) at maximum drawdown lake level (El. 745.0 ft or 227.0 m) and maximum design flow for Units 1-4 (2,264 cfs or 1,463 MGD). At full pond levels (El. 231.6 ft) and ma ximum design flow for Units 1-4, the velocity approaching the screens is 0.4 ft/s (0.12 m/s) (Alden and EPRI 2005).



### Lake Norman

Geomorphology and Aquatic Habitat

Lake Norman is an impoundment of the Catawba River formed by the Cowans Ford Dam (Figure 2-1). The Catawba River Basin lies in the south-central por tion of western North

Carolina and has its source in th e eastern slopes of the Blue Ridge Mountains in Old Ford, McDowell County, North Carolina. From its sour ce, the Catawba River flows eastward, then southward toward the City of Charlotte. The Catawba River Basin and the Broad River Basin join to form the headwaters of the Santee-Cooper River system.

Lake Norman is located in the portion of th e Catawba River Basin designated as the Middle Catawba River Subbasin 32, which lies within the North Carolina Piedmont physiographic region (Hogan 1981) and the Northern Inner Pied mont and Southern Outer Piedmont ecoregions (NCDENR 2003). The underlying rock in the Pi edmont geologic province predominantly

includes the Inner Piedmont and Charlotte be lts. Rocks of the Inner Piedmont belt are metamorphic in origin and consist almost enti rely of mica gneisses a nd schists, with lesser amounts of hornblende gneiss and granite (Hogan 1981). Rocks of the Ch arlotte belt are of plutonic and metamorphic origin a nd consist largely of granites, di orites, and gabbros. Soils are acidic, highly leached, and weathe red clay subsoils, with slow percolation rates (Hogan 1981).

Lake Norman and the Cowans Ford Dam are part of a system known as the Catawba Chain of Lakes formed by seven Duke Energy hydroelectri c dams. The seven lakes consist of Lake James, Rhodkiss Lake, Lake Hickory, Lookout Shoals Lake, Lake Norman, Mountain Island Lake, and Lake Wylie. The lakes were created between 1904 and 1928, except for Lake Norman, which was created in 1963. Lake Norman is the largest reservoir in the Chain of Lakes and lies between Lookout Shoals Lake upstrea m to the north and Mountain Island Lake

downstream to the south.

The surface area of Lake Norman is 13,156 ha, it s mean depth is 10 m, and it drains a 4,636-km 2
watershed (NCDENR 2003). Lake Norman is 54 miles long from the tailrace of Lookout Shoals Lake downstream to Cowans Ford Dam (NCDEN R and NCWRC 2001). M SS is approximately2-3 in the middle of this distance on what would be the west bank of the river. Major tributaries to Lake Norman are Lyle Creek and Buffalo Shoals Creek.

Land use in Subbasin 32 is 54 percent forested, 31 percent pasture, 9 percent water, and 3 percent each for urban and cultivated cropland. Th e primary use of Lake Norman is for cooling

water at MSS and McGuire Nuclear Station and for hydroelectric ge neration at the Cowens Ford Dam. The secondary use is public recreation.

Lake Norman provides an important recreational fishery for the region, particularly for striped bass, largemouth bass, and black crappie. Striped bass do not repr oduce naturally in the reservoir and have been stocked annually (Van Horn 2001). The lake is managed for these game species and the forage species upon which they are dependent, such as shad species. Other game species include blue catfish, ch annel catfish, flathead catfish, white bass, white perch, yellow perch, white crappie, spotted bass, and several sunfish species such as bluegill. Several fishing tournaments are held on the lake for striped bass, largemouth bass, and catfish (e.g., blue catfish) by local and national organizations.

Water Quality

Lake Norman is characterized as being oligot rophic with low nutrien t values and low algal production, and is classified as a water suppl y, WS-IV (NCDENR 2003, 2008). On the basis of long-term mean phytoplankton concen tration, the lake might be clas sified as oligo-mesotrophic (Duke 2006). Water quality sampling by the NCDE NR Division of Water Quality during MaySeptember 2007 recorded Secchi disc readings of 1.8-2.6 m, low total phosphorus concentrations (usually below detection limits), low to moderate ch lorophyll a concentrati ons, and low ammonia and total organic nitrogen concentrations (N CDENR 2008). However, nitrite plus nitrate

concentrations were elevated.

Mean ambient surface water temperatures range from <7 ° C (44.6 ° F) in January to 30-32 ° C (86-

89.6 ° F) in August (Duke 2004a). The lake thermally begins to stratify in April or May, and fall turnover occurs by November. In the summer, the thermocline is approximately at 15-20 m depth. Surface DO concentration typically ra nges from 6 to 11 mg/L, but hypolimnetic DO concentrations usually are <5 mg/L from June to November and are near 0 mg/L in August to October (Duke 2004a). Anoxic conditions in the hypolimnion are more prevalent during particularly warm summers. Since the skimmer wall on MSS’s intake cove draws from depths below approximately 18.3 m, cool water with a de pressed DO concentration is withdrawn from the hypolimnion during warm weather months.

Water quality monitoring by Duke has shown pH ranging from 6.2 to 7.4, low surface turbidity (1.02-5.05 NTU), low conductivity (69-110 mhos/cm), and heavy metal concentrations that do not exceed state water quality standards, alt hough iron and manganese can be released from bottom sediments during anoxic conditions (Duke 2004a). Surface DO concentrations uplake can exceed 110 percent saturation, as in 2002 (N CDENR 2003). Nutrients and chlorophyll a

concentrations in Lake Norman remain low or less than detection limits. The biggest water quality hazard for the lake is the infestation of the exotic macrophytes Hydrilla and Myriophyllum , which can decrease fish habitat an d impact recreation (NCDENR 2003).Plant and Source Waterbody Descriptions

2-4 Macrophyte control using herbicides and triploid grass carp ( Ctenopharyngodon idella ) stocking has been conducted in 2006-2007 through a joint effort by Duke, the Lake Norman Marine Commission, and the N.C. Divisi on of Water Resources (NCDEN R 2008). There are no fish consumption advisories except for the stat ewide advisory for bowfin due to mercury

contamination.

The Catawba River Basin is the most densely pop ulated river basin in North Carolina, with a population exceeding 1 million persons, inclusive of the City of Ch arlotte (NCDENR and NCWRC 2001). Because the river basin faces unus ually high development pressures, a Catawba

River Basin Natural Resources Plan has been prepared by the NCDENR and the North Carolina Wildlife Resources Commission (NCWRC), with input from multiple plan participants including Duke, for the protection and enhancement of the basin’s natural re sources (NCDENR and NCWRC 2001). This Natural Resources Plan complements the Catawba River Basinwide Management Plan and assigns priorities for sp ecific resources or issues. The upper portion of Lake Norman has been assigned the top priority (I) due to its lower level of development and

more natural riverine environment and resour ces (e.g., shoreline and wetland habitats). The lower portion of Lake Norman has been assigned medium priority (II), with emphasis on its high

recreational demand. Fish and wildlife habitat ar e to be protected and enhanced in both areas.2-5 Figure 2-1 Location of MSSPlant and Source Waterbody Descriptions2-6Figure 2-2 Aerial View of MSS2-7Table 2-1 Monthly Mean Cooling Water Flow Rate (MGD) and Percentage of Maximum Design Generation and Flow Rate at MarshallSteam Station, 2002-2007Percent Net Capacity GenerationYear Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual2002 79% 80% 76% 79% 65% 83% 86% 85% 78% 85% 66% 76% 78%2003 95% 91% 78% 52% 75% 82% 85% 86% 91% 80% 83% 97% 83%2004 94% 83% 82% 74% 71% 88% 85% 86% 77% 72% 74% 84% 81%2005 92% 89% 87% 83% 77% 85% 85% 91% 84% 77% 77% 79% 84%2006 88% 90% 60% 49% 71% 80% 82% 85% 72% 48% 46% 72% 70%2007 75% 94% 80% 76% 77% 85% 68% 86% 66% 86% 86% 87% 81%Average87% 88% 77% 69% 73% 84% 82% 87% 78% 75% 72% 83% 79%Actual Plant Flow Rate (MGD)Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual2002 1,066 1,078 990 965 988 1,094 1,106 1,461 1,431 1,383 937 1,042 1,1282003 1,073 912 840 641 1,014 1,092 1,1021,253 1,463 1,2001,028 1,084 1,0592004 1,092 829 876 911 862 1,095 1,1031,365 1,365 1,0161,086 1,177 1,0652005 843 851 1,002 1,028 1,004 1,093 1,146 1,363 1,444 1,2871,219 1,072 1,1132006 1,083 1,042 758 689 963 1,0621,111 1,463 1,423 853 728 979 1,0132007 1,016 1,082 968 990 N/A N/A N/A N/A N/A N/A N/A N/A 1,014Percentage of Maximum Flow Rate (2,264 CFS or 1,463 MGD)Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual2002 73% 74% 68% 66% 68% 75% 76% 100% 98% 95% 64% 71% 77%2003 73% 62% 57% 44% 69% 75% 75% 86% 100% 82% 70% 74% 72%2004 75% 57% 60% 62% 59% 75% 75% 93% 93% 69% 74% 80% 73%2005 58% 58% 68% 70% 69% 75% 78% 93% 99% 88% 83% 73% 76%2006 74% 71% 52% 47% 66% 73% 76% 100% 97% 58% 50% 67% 69%2007 69% 74% 66% 68% N/A N/AN/A N/A N/A N/A N/A N/A 69%Average*70% 64% 61% 58% 66% 74% 76% 94% 97% 78% 68% 73% 73%*2002-20063-1 

# 3

FISH COMMUNITY DESCRIPTION

This section describes the fish community in La ke Norman. The sources and types of available historical and recent information on the fish community are described first. The species composition and structure of the fish community then are discussed. Finally, the general life history of fish species commonl y found in impingement sampling at Marshall Steam Station is discussed as background information that mi ght provide insights on annual or seasonal susceptibility to impingement.



### Description of Available Information

Duke conducted extensive ecological investigat ions of Lake Norman during 1973-1980 (Hogan and Adair 1981). These investigations, and pa rticularly the fisherie s studies, provide a description of the aquatic habitat and fish co mmunity of Lake Norman during a portion of its

transformation from a riverine to lacustrine e nvironment, which began when the Catawba River was impounded in 1963 to form Lake Norman. Fish eries surveys were conducted by Siler et al. (1981) from August 1973 through December 1980.

Sampling methods included boat electrofishing, 27-m long variable-mesh (2.5 to 5.1-cm mesh) gill nets, rotenone for cove sampling, 2-m by 3-m or 1.5-m by 2-m mid-water Tucker trawls, and a 0.91-m diameter conical ichthyoplankton net (Sile r et al. 1981). Boat electrofishing was quarterly at four to five lo cations in Lake Norman during 1974 through 1979 and monthly during June 1978 through May 1979. Gill netting was quarte rly at three or four locations during 1974 through 1979 and monthly at five locations during June 1978 through May 1979. Rotenone sampling in lake coves was conducted annually in la te June or early August at three locations. Mid-water trawling at four lo cations was conducted monthly from July 1978 through April 1979 and quarterly from April 1979 through Apr il 1980. Ichthyoplantkon sampling was either biweekly or weekly at up to five locations . A special study was conducted on February 21, 1975 to investigate the relative abundance of fish sp ecies within the intake cove by using boat electrofishing.

Under an agreement with the NCDENR, D uke has performed annual physicochemical, macroinvertebrate, and fish community monitoring of Lake Norman since 1993 (Duke 2001, 2003, 2004a, 2004c, 2005, 2006, 2007). The fish community is monitored using boat electrofishing and a combination of hydroacousti cs, purse seining, and sometimes gill netting. For these fisheries assessments, Lake Norman is di vided into five zones. Marshall Steam Station (MSS) is located in Zone 4 (Figure 3-1). Sp ecial sampling programs also have been conducted to monitor striped bass summer mortalities; age, species and size compositi on of forage fish; and cooperatively with North Carolina Wildlife Re sources Commission (NCWRC) to monitor age,Fish Community Description

3-2 growth and condition of striped bass by gill net samp ling; and age and growth of crappies by trap net sampling.

The spring electrofishing program samples three lo cations in late March and early April: near MSS in Zone 4, a reference area in Zone 3, a nd near the McGuire Nuclear Station (MNS) in Zone 1 (Figure 3-1). At each location, ten 300-m shoreline transects are sampled. These transects were found to be representative of habi tat types found in Lake Norman, and have been sampled consistently since 1993. Electrofishi ng is conducted during daylight when water temperatures are expected to be 15-20 ° C.

Hydroacoustics sampling techniqu es and purse seining are used to assess the forage fish populations throughout the entire la ke and its tributaries, and da ta are available for the period 1993-2006 (Duke 2004b, 2007). Sampling is conducted at night during July, September, or November. For the hydroacoustics surveys, all six zones in Figure 3-1 are included. The hydroacoustics gear consists of a multiplexing 200- kHz digital transducer system with side-scan split-beam and down-looking dual-beam transducers. The side-scan transducer samples the top 2 m of the water column, and the down-looking tran sducer samples the remainder of the water

column 1 . The output is integrated to estimate fish densities at 0.25-km intervals along sampling transects, and the estimated zonal densities are summed to estimate total lake standing crops. Species and size composition data are provided by purse seining at night using a 400-ft (121.9- m) by 30-ft (9.1-m) purse seine with 3/16-in. (4.8-mm) mesh.

Duke conducts an electrofishing survey in July in the vicinity of MSS in addition to the lakewide spring electrofishing survey described above. This summer electrofishing program samples

five stations located in coves of Lake Norman in July during daylight hours (Duke 2004b). One sampling station is uplake from the MSS intake in Zone 4 and is used as reference data, two stations are near the MSS discharge in Zone 4, and two are downlake near the middle of Lake Norman in Zones 3 and 4. Shoreline segments that are 100-m in length are sampled on the right

and left banks of each cove.



### Species Composition

A composite of records of fish species collected during fisheries surveys of Lake Norman from 1974 to 2006 indicate that 58 species and two hybrid varieties have been found in the reservoir since 1974 (Table 3-1). The total number of re ported species decreased from 48 to 32 during the

interval from 1974-1980 to 2004-2007. This decrease in species richne ss could be an artifact of differences in sampling methodology, but more likely is the result of the e volution of the fish community from a riverine community to a l acustrine community following the impoundment of the Catawba River. Examples of typically lotic species (Rohde et al. 1994, Pflieger 1997) that have not appeared recently in survey catches incl ude cyprinids such as whitetail shiner and creek chub; catostomids such as white sucker, silver redhorse, V-lip redhorse, br assy jumprock, striped jumprock, and creek chubsucker; and ictalurids such as snail bullhead. Other species not found

1 Prior to 1996, only the down-looking transducer was used.3-3 since 1980 include the river ca rpsucker, smallmouth buffalo, yellow bullhead, and western mosquitofish.

Recently, electrofishing has indicated that the nu merically dominant shore-zone species in the sampled coves are bluegill and redbreast sunf ish (Duke 2007). In terms of biomass, the dominant species are the spotte d bass, largemouth bass, and common carp. Some species have only recently appeared in survey catches, such as alewife, white perch, goldfish, striped mullet, and spotted bass (Table 3-1). These species have not been st ocked by the NCWRC and probably were introduced accidentally or intentionally by anglers. The spotted bass and white perch, in particular, have become established and support ac tive recreational fisherie s. White perch first appeared in 1998 and spotted bass in 2001. There is concern that spotte d bass and white perch may be competing with largemouth bass and white bass, and could be resp onsible for declining populations of these latter two species (Duke 2007, NCWF 2008).

The introduction of alewife to the lake in 1999 ha s affected the composition of the pelagic forage fish community in the lake in re cent years. Prior to the year 2 000, over 99 percent of the forage fish caught by purse seine duri ng the hydroacoustic surveys were threadfin shad (Duke 2007). The percentage of the forage fish catch cons isting of alewife increa sed to 25 percent in 2002, then began to decline again until it was appr oximately 2-5 percent in 2005 and 2006. Gizzard shad have constituted less than 0.5 per cent of the forage base since 1993.



### Protected Species

No fish species currently listed as federal or st ate endangered or threaten ed species have been

collected in Lake Norman. Ther e are, however, two fish species listed by the North Carolina Natural Heritage Program (NCNHP) for Catawb a County as species of concern. These are highfin carpsucker ( Carpoides velifer ) and the Piedmont population of the Santee chub, ( Cyprinella zanema pop 1). The highfin carpsucker is cu rrently listed by NCNHP as a state species of concern with a global ranking of G4G5 2 and a state ranking of S2 3 . The Piedmont population of the Santee chub is cu rrently listed by NCNHP as a sign ificantly rare species with a global ranking of G4T3Q 4 and a state ranking of S3 5 . It is unlikely that either species would occur in Lake Norman since both species pref er lotic environments (Rohde et al. 1994).

2 G4G5=Apparently or demonstrably secure globally, although it might be quite rare in parts of its range (especially at the periphery).

3 S2=Imperiled in North Carolina because of its rarity or otherwise vulnerable to extirpation in the state.

4 G4T3Q=Species is apparently secure globally, but subspecies or variety is either very rare and local or found locally in a restricted area; ta xonomic status is questionable.

5 S3=Rare or uncommon in North Carolina.Fish Community Description

3-4 

### Target Species

Among all fish species found in Lake Norman, a s ubset of species was selected for a detailed evaluation of impingement mortality presently oc curring at the MSS cooling water intake. These species are most frequently observed in impinge ment collections, or are important because of their economic value or value to the ecosystem.

The threadfin shad dominates the pelagic fish community in Lake Norman as well as impingement collections at the MSS intake (Section 4). Although much less abundant, the alewife, like the threadfin sha d, is an important component of the forage base for the recreationally important fish species in Lake No rman. For these reasons, both threadfin shad and alewife were selected as target species for detail ed evaluation. Other selected species include the blue catfish, white perch, and channel catfish. Blue catfish and channel catfish are traditionally important game species in Lake Norman, while the newcomer, white perch, had been added to the list of recreational species. These three species ranked third, fourth, and fifth in relative abundance in the 2006-2007 impingement collecti ons at MSS (Section 4), and thus deserve

further consideration.

This section presents background information on the life history of these five species.

Threadfin Shad

Historically, the threadfin shad has been the mo st abundant pelagic species in Lake Norman and most abundant in impingement collections at MSS. Threadfin shad is an important forage base for several predator species that provide the re creational fishery of Lake Norman, including the striped bass, largemouth bass, spotted bass, catfish species, and crappie. Threadfin shad is an excellent forage species because of its size, which seldom will exceed 150 mm, and its great productivity. It is a planktivore, relying on filte r feeding through its gill ra kers. Threadfin shad

were introduced into Lake Norman afte r its impoundment (S iler et al. 1981).

Threadfin shad spawn when water temperatures reach 65-70 ° F (18.3-21.1 ° C) and can have multiple spawning peaks through the spring, summe r and early fall (Pflieger 1997, Smith 2002). In the late 1970s, clupeid larvae, which included threadfin shad and gizzar d shad, were caught in ichthyoplankton samples in Lake Norman from Ap ril through August, peaking in May and June (Siler et al. 1981). Spawning prim arily occurs from dawn to s hortly after sunrise as spawning schools gather along the shoreline. The adhesive eggs are broa dcast over submerged objects and hatch within three days. Young th readfin shad grow very rapidly (up to 25 mm per month), with many reaching maturity and spawning by the end of their first summer at 64 mm in length. Females generally grow larger and live longer than males, with a maximum age of about four years for females and three years for males.

For habitat, threadfin shad prefer open water ove r sand, mud or debris. Threadfin shad tend to be more abundant in the upper portions of the lake rather than the lower portions, possibly due to differences in habitat or nutrient levels and pr oductivity among in lake zones (Siler et al. 1981, Duke 2004b). The continued existence and rela tive abundance of threadfin shad, which is intolerant of water temperatures below 10 ° C (Ruelle et al. 1977, Griff ith 1978), in Lake Norman3-5 may be dependent upon the thermal input from MSS and McGuire Nuclear Station and the thermal refuges they provide during the winter.

Alewife

The alewife is a re lative newcomer to the Lake Norman fi sh community, first appearing in 1999. Its introduction probably originated from angler releases, since it was not stocked by NCWRC. At the time of its appearance, th readfin shad dominated the forage fish base in Lake Norman. Threadfin shad continues to dominate pelagic fo rage species, but at its most recent peak abundance in 2002, alewife may have comprised nu merically as much as 25 percent of this pelagic forage fish base. Alewife was the seco nd-most frequently impinged species at the MSS intake in 2006-2007, behind th readfin shad (Section 4).

The alewife is an anad romous clupeid that is indigenous to the Atlantic Coast from

Newfoundland to South Carolina an d spawns in coastal freshwat er or brackish rivers and tributaries (Pardue 1983). Landloc ked populations have long been established in the Great Lakes and several northern inland lakes such as the Finger Lakes of New York. Rarely has this species

been introduced to southern lakes or reservoirs but Claytor Lake in Virginia is such an example. Studies at Claytor Lake, a mesothermal lake with temperatures ranging from 2 ° C to 27 ° C (Kohler and Ney 1981, Nigro and Ney 1982), may provide insi ghts into the general life history of the

alewife in a southern reser voir such as Lake Norman.

Nigro and Ney (1982) found alewives in Claytor La ke to be shorter-lived than alewives in northern landlocked populations, while achieving maturity earlie r and having higher absolute and relative fecundity. They attributed these differe nces to a longer grow ing season in the south, rather than accelerated growth rates. Maturity was reached at approximately the same size as their northern counterparts. Eight y-six percent of age-1 females we re mature at a median length of 160 mm total length (TL) while all age 2 and ag e 3 females were mature. Maximum first year growth was 130-160 mm.

In Claytor Lake, as may happen in Lake Norman, alewives move inshore in large concentrations to spawn in the spring and early summer. Ripe ma les were first seen in the littoral zone when water temperatures were 13 ° C, and spawning was first obs erved in early May at 16-18 ° C (Nigro and Ney 1982). Peak egg densities occurr ed in the third week of May at 21-23 ° C, then declined during June through July. This extended spawni ng season was interpreted as possibly indicating fractional spawning, i.e., repeated egg deposition by individual females.

Alewife eggs initially are demers al and adhesive, but when water-hardened they become pelagic and lose their adhesive propert ies (Pardue 1983). Egg incubation lasts from 36 hours to 6 days, depending on water temperature (Carlander 1969, Au er 1982). The yolk-sac is absorbed in 2-5 days at a length of 5.1 mm (Pardue 1983) and larv ae transform to the juvenile stage at 20 mm. Early life stages are positively phototaxic and pe lagic. The principal food items are diatoms, copepods, and ostracods (Carland er 1969). Adults are size-sel ective planktivores feeding on cyclopoid copepods, and occasionally are pisc ivorous (Kohler and Ney 1981, Nigro and Ney 1982).Fish Community Description

3-6 Blue Catfish

Blue catfish was the third-most frequently impinged species at MSS in 2006-2007 (Section 4). The blue catfish is native to the Mississippi, Miss ouri, and Ohio river basins and is considered a big river species (Graham 1999). It is the largest catfish in the United States. The largest recorded blue catfish weighed 315 lb (142.9 kg) and was caught in the Missouri River just below Portland, Missouri in 1866 (Graham 1999). Duri ng the mid-1800s, it was common to catch blue catfish weighing 125-200 lb (45.4-90.7 kg). The North Carolina record was caught in Lake Norman in 2004; it was 51.25 in. (1,302 cm) in length and weighed 85 lb (38.6 kg). Maximum age is 18 years.

The blue catfish is an introduced species in Lake Norman, apparently being stocked by the NCWRC when Lake Norman was impounded. It was not detected until 1983, but its population has been growing rapidly ever si nce (Grist 2002). During this peri od, there has been a decline in

the white catfish and snail bullhead populations. An active fishery has developed for blue catfish in Lake Norman, including tournaments specifically for this and other ca tfish species. Blue

catfish dominate the catch and harvest of catfish species in Lake Norman, with 70 percent of the numbers caught and 77 percent of the biomass harv ested (Grist 2002). Nort h Carolina treats the blue catfish as a non-game species for which ther e is no catch limit, and the catch can be sold commercially.

There are few technical reports on the life history of blue catfish. Adult blue catfish in the lower

reaches of Lake Norman have been shown to move up to 34 km or more to the upper, more riverine portion of the lake in the spring, possibly to spawn, then re turn in the fall and winter to the lower lake (Grist 2002). Mi gratory movements in rivers can span several hundred kilometers with movement upstream in the spring and dow nstream in the fall in response to water temperature (Lagler 1961, Pflieger 1997). Spawning in the Ohio River has been reported to occur at water temperatures ranging from 68 ° F to 86°F (20-30 ° C), with optimum temperatures of 72-82°F (22.2-27.8 ° C) (Simon and Wallus 2003). In Lake Norman, water temperatures of 72-

82 ° F would occur in June and July.

Their spawning habits are believed to be simila r to channel catfish (Pflieger 1997, Hubert 1999). Blue catfish are cavity nesters and deposit eggs in protected ar eas behind rocks, root-wads, depressions, undercut streambanks, or other areas with minimal cu rrents. The male guards the eggs and fry. Egg diameters are between 3.0 and 3.3 mm, and fecundity ranges from 900 to 1350 eggs/kg of body weight (Graham 1999). Egg incubation lasts 168 to 240 hours at 75 to

79 ° F (23.9-26.1 ° C) in the Ohio River (Simon and Wallus 2003). Eggs hatch in 7-8 days at temperatures between 21 to 24 ° C (Graham 1999; Pflieger 1997). Bl ue catfish yolk-sac larvae are 4.1 to 8.9 mm long when they hatch (Simon an d Wallus 2003), and youn g may grow slower during their first year than channel catfish (T idwell and Mims 1990). In Lake Norman, early growth rates and body condition are lower than in other impoundments (G rist 2002) but improve as the fish grow older and become more piscivorous.

Graham and DeiSanti (1999) aged 2,389 blue ca tfish collected from 1988-1995 at the Truman Dam Tailwater, Osage River, Missouri. The m ean back-calculated total lengths at annulus formation for the first eight years of life were as follows: 105 mm at age 1, 178 mm at age 2, 2433-7 mm at age 3, 309 mm at age 4, 371 mm at age 5, 371 mm at age 6, 426 mm at age 7, and 484 mm at age 8. Blue catfish become sexually matu re at about 381 mm in the Mississippi River near St. Louis (Graham 1999) and between 420-480 mm (about 6-7 years) in Lake of the Ozarks, Missouri (Graham and DeiSanti 1999).

Blue catfish prefer open waters of large reservoirs and main channels, backwaters, and embayments of large flowing rivers where water is normally turbid and substrate varies from gravel-sand to silt-mud (Graham 1999). In Lake Norman, they are found at greater depths (e.g., >5 m) than channel catfish and prefer more open water (Grist 2002) . Clupeids such as threadfin shad and alewife are their primary food, but they also feed on mollusks such as the Asiatic clam

Corbicula and on stonewort Chara (Grist 2002). They likely compete with the stocked striped bass in Lake Norman for clupeids.

White Perch

White perch was the fourth-most frequently impinged fish species at MSS during 2006-2007 (Section 4). Like severa l other species, it is not native to La ke Norman. It likely was introduced to Lake Norman by anglers, and first appeared in 1998. Since then, it s population has grown rapidly, and it now supports a recr eational fishery in Lake Norman. There is, however, the fear

that its establishment has affected or will affect the fishery for other species, such as white bass, crappie, largemouth bass, and striped bass. While the white perch popul ation has expanded, the white bass population has become decimated, possibl y due to predation on the eggs or fry of white bass ( http://www.ncwildlifederation.or g/home/lakenormanfishery.htm ) or through competition for food. There is also the fear that eventually white perch will become overpopulated and stunted. Most adult white perch in Lake Norman are 150-305 mm long and <0.5 lb (227 g).

White perch is distributed ge ographically along the Atlantic coast from Canada to South Carolina. In coastal areas, it is semi-anadromous, leaving brackish water to spawn in freshwater. It has become established in inland lakes, incl uding the Great Lakes, either naturally or through stocking in several states in the eastern and central US (Rohde et al . 1994,). It also recently has invaded the Mississippi Rive r system (Irons et al. 2002) and the Arkansas River system as far as Oklahoma (Harris 2006). In the southeast, whit e perch has established populations in the Kerr Reservoir in Virginia and North Carolina, and th e B. Everett Jordan Reservoir in North Carolina (Harris 2006).

There is little or no information on the life hist ory of white perch in Lake Norman. Based on studies elsewhere, spawning in freshwater lake s occurs in April and May (Stanley and Danie 1983). In the Hudson River, peak spawning occurred at water temperatures of 16-20 ° C (Klauda et al. 1988). Eggs are broadcast at depths of <12 ft (3.7 m). The demersal and adhesive eggs attach to vegetation and other firm substrates, an d no parental care is given to the eggs or young. The eggs hatch in 30 hours at water temperatures of 20 ° C, or may take as long as 96-108 hours at

15 ° C. The yolk-sac life stage lasts 3-5 days until a length of 3.5-4 mm is reached (Klauda et al. 1988). Juveniles tend to be demersal in depths of 8-12 ft (2.4-2.7 m) (Stanley and Davie 1983).Fish Community Description

3-8 In daylight, white perch school in open water, of ten over shoals or brush piles, and at night go inshore. Young white perch feed on zooplankton such as copepods, cladocerans, and ostracods (Prout et al. 1990). Adults cons ume benthic invertebrates and fish eggs, and when larger than 80-150 mm are primarily pisciv orous (Harris 2006).

Males mature slightly earlier than females, beginning at age 2 when males are 100-110 mm TL and females are 110-120 mm TL (Klauda et al. 19 88, Rohde et al. 1994). Most are mature by age 3-4. Maximum age is approximately 17 year s but few are older than age 7. Fecundity ranges from approximately 5,000 to 300,000 eggs de pending on female size (Stanley and Davie 1983). In Kerr Reservoir, North Carolina, whit e perch reach a mean length of 104 mm at age 1, 175 mm at age 3, 239 mm at age 5, 264 mm at ag e 7, and 303 mm at age 9 (Harris 2006). Angler exploitation of white perch on Kerr Re servoir begins at lengths of 150-200 mm TL.

Channel Catfish

A total of 57 channel catfish were collected during impingeme nt sampling at MSS in 2006-2007, making them the fifth-most frequently impinged sp ecies (Section 4). Cha nnel catfish is a longterm resident of Lake Norman and historically has supported commercial or recreational fisheries on the lake (Siler et al. 1981).

The channel catfish is a very important and hi ghly desirable commercia l and recreational fish species throughout its geographic dist ribution and in North Carolina. It is native to the central part of North America (Smith 1985), but it has b een stocked in rivers and reservoirs throughout the southeast region. It occurs in a variety of habitats and is esp ecially characteri stic of large,

turbid streams and rivers that have a low or moderate gradient. In Lake Moultrie, South Carolina, channel catfish can reach up to 58 lb (26 kg) in size (Rohde et al. 1994).

Channel catfish spawn in late spring and early summer when water temperatures reach 65°F (18.3°C) or more (McMahon and Terrell 1982, Pitlo et al. 2004). Spawning generally occurs over a range from 21°C to 29°C, with an optimal temperature of 27°C (H ubert 1999). Sustained temperatures in this range (21°C to 29°C) in Lake Norman would correspond to June and July.

Several weeks prior to spawning, males select and clear suitable nest sites, usually consisting of secluded, dark areas such as hollow logs, drift pi les, undercut banks, muskrat or beaver burrows, or rip rap. A single male often will spawn with several females (Rohde et al. 1994). Eggs are deposited in a gelatinous mass. Incubation la sts for 5.5 to 10 days at 75-82°F (23.9-27.8°C) (Holland-Bartels and Duval 1988). The male tends the nest while eggs hatch and stays there for about one week after hatching to guard the fry. Early growth is variable among year classes and apparently is dependent upon existi ng conditions (Pitlo et al. 2004).

Adults may be found in many habitats including cha nnels and large open area s, but prefer habitat with woody debris, bank cavities and moderate curre nts (Koel et al. 1998). In daylight they seek depths with cover and current. At night or in rising water levels they feed near or on the bottom in shallower depths. Young feed largely on aquatic insects and other bent hic arthropods, but at 100 mm length become omnivorous with fish maki ng up a large part of their diet (Smith 1985).3-9 Channel catfish begin to mature at age 4 a nd 305 mm in length, and 75 percent of females are mature by age 6 (Pitlo et al. 2004). The averag e fecundity is 6,088 eggs per lb of body weight.Fish Community Description

3-10 Figure 3-1 Sampling Zones and Locations for Lake Norman

.3-11Table 3-1 Fish Species Collected in Lake Norman Fishery Surveys (Siler et al. 1981; Duke 2004a, 2004b, 2006, 2007)Family Scientific Name Common Name 1974-1980 1993-1999 2000-2003 2004-2007LepistosteidaeLepistosteus osseusLongnose gar X X XAmiidaeAmia calvaBowfin XClupeidaeDorosoma cepedianumGizzard shad X X X XDorosoma petenseThreadin shad X X X XAlosa pseudoharengusAlewife X XAlosa aestivalisBlueback herring* XSalmonidaeOncorhynchus mykissRainbow trout XCyprinidaeCyprinus carpioCommon carp X X X XCarassius auratusGoldfish XHypognathus regiusEastern silvery minnow X XNocomis leptocephalusBluehead chub X XNotemigonus crysoleucasGolden shiner X X XCyprinella analostanaSatinfin shiner ?Cyprinella chloristiaGreenfin shiner X X X XCyprinella galacturaWhitetail shiner XNotropis hudsoniusSpottail shiner X X X XCyprinella niveaWhitefin shiner X X X XSemotilus atromaculatusCreek chub XNotropis procneSwallowtail shiner X XPimephales promelasFathead minnow XCatostomidaeCarpoides carpioRiver carpsucker XCarpoides cyprinusQuillback X X X XCatostomus commersoniWhite sucker XErimyzon oblongusCreek chubsucker XIctiobus bubalusSmallmouth buffalo XMoxostoma anisurumSilver redhorse XMoxostoma macrolepidotumShorthead redhorse X X X XMoxostoma pappilosumV-lip redhorse XScartomyzonsp.Brassy jumprock XScartomyzon rupiscartesStriped jumprock XFish Community Description3-12Table 3-1 continuedFamily Scientific Name Common Name 1974-1980 1993-1999 2000-2003 2004-2007IctaluridaeAmeirus brunneusSnail bullhead XAmeirus catusWhite catfish X XIctalurus furcatusBlue catfish X X XAmeirus melasBlack bullhead XAmeirus natalisYellow bullhead XAmeirus nebulosusBrown bullhead XAmeirus platycephalusFlathead bullhead XPylodictis olivarisFlathead catfish X X X XIctalurus punctatusChannel catfish X X X XMugilidaeMugil cephalusStriped mullet XPoecilidaeGambusia affinisWestern mosquitofish XMoronidaeMorone chrysopsWhite bass X X XMorone saxatilisStriped bass X X X XMorone americanaWhite perch X X XCentrarchidaeLepomis auritusRedbreast sunfish X X X XLepomis gibbosusPumpkinseed X XLepomis gulosusWarmouth X X X XLepomis macrochirusBluegill X X X XLepomis microlophusRedear sunfish X X X XLepomis cyanellusGreen sunfish XMicropterus salmoidesLargemouth bass X X X XPomoxis annularisWhite crappie X X XPomoxis nigromaculatusBlack crappie X X X XLepomishybridSunfish hybrid X X XMicropterus punctulatusSpotted bass X XMicropoterushybridBlack bass hybrid XPercidaeEtheostoma fusiformeSwamp darter X XEtheostoma nigrumJohnny darter ?Etheostoma olmstediTessellated darter X X X XPerca flavescensYellow perch X X X XTotal species 48 26 29 32Total hybrids 0 1 1 24-1 

# 4

IMPINGEMENT MORTALITY

This section presents the results of a one-year impingement monitoring program conducted at Marshall Steam Station (M SS) during 2006-2007 and earlier efforts to describe impingement in 1974-1975. The effects of seasonality and environmental variables, including lake level, dissolved oxygen (DO) concentration and water temperature, on impingement rates are discusse d in the context of dominant fish species in the 2006-2007 impingement collections.



### Impingement Monitoring Programs

Current impingement rates at MSS were evaluated by a monitoring program conducted during 2006-2007 by MACTEC Engineering and Consulting, Inc. (MACTEC). Complying with the requirements of the §316( b) Phase II Rule, Duke Energy submitted a Proposal for Information Collection (PIC) to North Carolina Department of Environment and Natural Resources (NCDENR) outlining a proposed plan for impingement data collection and analysis, and associated Qu ality Assurance/Quality Control (QA/QC) procedures (EPRI Solutions, Inc. 2006). De tailed descriptions of the sampling and QA/QC procedures used dur ing the 2006-2007 monitoring program are presented in Standard Operating Procedures (SOP) prepared prior to the start of data collection.

MSS has 16 intake bays and each of the 16 intake bays has a fixed screen consisting of an upper and a lower removable panel (Section 2). To clean or sample each screen, a crane operator had to lift the upper and lower screen panels and place them over a collection pit

on the intake structure deck. The screen panels then were pressure-washed and the cleaned panels were placed behind the next screen to be sampled to act as a back-up screen. Because this process was time-cons uming, only four screens could be washed and sampled during each sampling event. Therefore, the sampling design had to incorporate a random selection process to de termine which screens were to be washed and sampled weekly. Fish impingement for all operating units had to be estimated by expansion of numbers collected from the samp led screens to all screens associated with operating units.

Impingement sampling began on 6 April 2006 and continued week ly through 30 March 2007. Prior to each sampling event, four fixe d screens were chosen randomly from all screens associated with one or more operati ng cooling water circul ating pumps (Table 4-Impingement Mortality

4-2 1). In a few cases 6 , pumps at a particular unit only ope rated for a portion of the sampling day and estimated densities of impinged fi sh were based on the shortened time period

rather than a full 24 hours. Individual scre ens were sampled from five to 19 times over the entire sampling program, and individua l units were sampled from 39 to 61 times (Table 4-1).

Prior to sampling, the selected screens we re raised and cleaned, then replaced and allowed to accumulate impinged fish for approximately 24 hours. On the second day (after the 24-h accumulation), impinged fish were washed from the raised screens and collected. The back-up screen behind the cleaned screen was examined for any impinged fish that might have washed off the screen that had been lifted. 7 During backwash cleaning, the screen panels were placed over a collection pit on the intake decking, fitted with a sampling net and tarp collection syst em. Impinged specimens collected from the net were processed for species identificati on and length and weight measurements in

accordance with the SOP.

Earlier impingement monitoring had been conducted at MSS from 30 April 1974 to 27 May 1975. Sampling was biweekly (once ever y two weeks). Afte r clearing fish and debris, one screen per unit (four screens total) was allowed to accumulate fish and debris over a two-week period, then was raised and inspected for impinged fish. Impinged fish were identified to species (if possible), measured, and counted, and the degree of decomposition was noted. In cases of large numbe rs of fish for individual species such as threadfin shad, total numbers of that sp ecies were estimated from subsamples.



### Current Impingement Sampling Program Results

For the 12-month period from 1 April 2006 to 31 March 2007, an estimated 188,419 fish and 1,036 kg of fish biomass were impinged at MSS (Table 4-2), based on the collection of 6,219 impinged fish (Table 4-3) and 30,229 g of fish biomass (Table 4-4). This estimate was derived from the density of fish collected during each sampling event, expressed as number per volume of cooli ng water withdrawn at each of the four generating units, extrapolated over the full 12-month period. To estimate the density at each unit on a particular sampling event, the collection totals were scaled up from the number of sampled screens to the total number of screens for the unit 8 . The scaled-up collection total was divided by the total flow volume for that unit during the 24-h sampling period to estimate the impingement density for that unit and period. If no screens were sampled at a unit on a particul ar date when it was operating, the impinged fish density for that unit was estimated as th e average of the sample d units on that date.

6 8 June 2006 at Unit 1, 25 January 2007 at Unit 4, and 29 March 2007 at Unit 2

7 Only partially decomposed fish were observed, indicating they had been previously dead and thus were not

counted.

8 For example, if three screens at Unit 3 were samp led on a particular date, the collection total was multiplied by 5/3 or 1.67, assuming that the randomly selected screens represented the average density of fish per screen.4-3 Total daily cooling water intake flow volum es for sampling days were obtained from plant operation records.

Impingement density values for non-sample d days were estimated by interpolating between density values for the sampling da ys that were immediately previous and subsequent to the unsampled time interval, then multiplying the interpolated density by each total daily intake flow reported for the non-sampled days and summing the estimated impingement counts across the time interval:

) )( 2 / ( 2

1 2 1

1 

##  

    

i uj s s n

j i s si p F D D F D N

where

N

p = estimated total impingement during non-sampled period p and the sampled days bordering the period

D si = organism density of sampling day i (1 = start, 2 = end) of period p

F

si = 24-hour cooling water flow vol ume on sampling day in period p

F

uj = 24-hour cooling water flow volum e on non-sampling day j in period p

n = number of non-sampled days during period p

Total annual impingement then was estimated by summing the estimated impingement during sampled days and non-sampled periods for each unit, then summing across the

four units.

Species Composition

A total of 10 fish species were found in the impingement collections (Table 4-3).

Threadfin shad and alewife dominated the collections, comprising 80.8 percent and 12.6 percent of the fish collecte d, respectively. Together thes e two species accounted for 92.0 percent of the estimated total annual impinge ment in terms of numbers (Table 4-2) and 79.4 percent of the estimated total impinged biomass 9 . When included with blue catfish, white perch, and channel catfish, these five fish species (described in Section 3) accounted for 99.3 percent of the estimated numbers impinged and 99.6 percent of the fish biomass impinged during the 12-month period. Threadfin shad was the most

9 Note that the percentages of estima ted total annual impingement for each species differ slightly from the percentages of all impinged fish collected because of the time- and flow-based extrapolation used to estimate total annual impingement.Impingement Mortality

4-4 commonly impinged species during the 1974-1975 monitoring program at MSS (Table 4- 5).

The remaining seven impinged species (Table 4-3) included gizzard shad and four centrarchids (redbreast sunfish, bluegill, pumpkinseed, and white crappie), which combined represented <1 percent of the estim ated total annual impingement. No federal or state-listed species were impinged. In addi tion to fish, the invert ebrate Asiatic clam ( Corbicula ) and crayfish were found in impi ngement collections (Table 4-6).

Seasonal Patterns

Impingement rates for all fish species comb ined were lowest during the spring, AprilJune, and highest in the late summer and early fall (August-October) or mid-winter (February) (Figure 4-1 and Table 4-7), reflec ting the seasonal impingement patterns of the two dominant species, threadfin shad and alewife. Alewife primarily were impinged in late summer (Figure 4-2) whereas thread fin shad were impinged throughout the fall and winter months, Septembe r-March (Figure 4-3).

Impinged alewives were larger than impinge d threadfin shad. The length frequency for alewives was bimodal, with modes at a pproximately 80 mm and 150 mm (Figure 4-2), as opposed to the unimodal distribution for th readfin shad with a modal length of approximately 60 mm (Figure 4-3). Based on th ese length frequency data and literature sources on length at age (Table 4-8), most impinged alewiv es were yearling and older fish, whereas approximately half of the impinged threadfin shad were young-of-year (YOY) fish (Table 4-9).

Blue catfish were impinged primarily in the summer, July-August (Figure 4-4). The

smallest blue catfish was 51 mm TL and the largest was 250 mm TL and weighed 101 g. The great majority of impinged blue catfish we re yearling and older fi sh (Table 4-9), but YOY began to be impinged after mid-November.

Channel catfish primarily were impinged during the spring and summer, from March through mid-August (Figure 4-5). They ranged in length from 52 to 114 mm TL and most appeared to belong to the 2005 year class and were classified as YOY until July 2006, when they became yearling fish (channel catfish were considered to become one year old as of 1 July following the year of spawning; Table 4-8). Peak impingement rates were recorded in July and August (Figure 4-5).

White perch primarily were impinged during the late summer, August-September, as yearling and older fish (Figur e 4-6). The median length was 147 mm TL and the length range was from 58 to 199 mm. Ba sed on literature values for white perch in an estuarine enviroment, almost all of these fish would be yearling or older fish (Table 4-9); growth rate information for white perch in Lake Norman currently is not available.

The seasonality of impingement for other species can be summarized as follows (Table 4- 7):4-5 Bluegill—primarily winter, January-February Gizzard shad—September-October Pumpkinseed—June Redbreast sunfish—spring and fall White crappie—September

Variables Affecting Impingement Rates

Three categories of variables potentially affecting impingement rates are discussed: environmental variables, species-specifi c abundance, and spatial distribution.

Environmental Variables

Three potentially important environmental vari ables that could affect impingement rates are water temperature, dissolved oxygen concen tration (DO), and lake level or elevation. Mean daily water temperature records from the MSS intake and daily lake level data were available for the sampling period from April 2006 through March 2007. DO readings were made by MACTEC sampling crews at the intake on the day of impingement sampling, usually in the morning between 0700 h and 1100 h.

The mean daily intake temperature varied s easonally from a low of 44.3°F (6.8°C) on 13- 14 February 2007 to a high of 80.6°F (27°C) on 30 August 2006 (Figure 4-7). The lake level varied 4.5 ft (1.37 m) during the 12-m onth sampling interval from 1 April 2006 to 31 March 2007, with a maximum elevation (759. 0 ft or 231.3 m above mean sea level) on 8 January 2007 and a minimum elevation (754.5 ft or 230.0 m amsl) on 19-20 February 2007. Full pond is 760 ft (231.6 m) amsl. DO readings on impingement sampling days ranged from 0.4 mg/L on 11 August 2006 to 11.0 mg/L on 15 February 2007 (Figure 4- 7).

The peak impingement rate for all species combined occurred on 15 February 2007, when the lake’s surface elevation and water temperat ures were near their minimum levels for the year (Figure 4-7). Impingement on this da te consisted primarily of yearling and older threadfin shad, but also included YOY thread fin shad and YOY alewife (Figures 4-8 and 4-9). No other species were impinged on this date. DO levels at this time were near

saturation.

Minor peaks in impingement rates for YOY threadfin shad occurred on 19 October 2006, 8 February 2007, and 1 March 2007 (Figure 4-8) . The October peak coincided with the period of declining temperatures, but the water temperature was still moderate at approximately 70°F (21.1°C). The other two pe aks occurred at winter low temperatures (approximately 46°F or 7.8°C) and reduced lake levels. Threadfin shad are stressed at water temperatures less than 10 o C (50 o F) and suffer complete mortality at 4°C (39.2°F) (Griffith 1978).Impingement Mortality

4-6 Most alewife impingement was experienced in one of two periods: mid-summer or midwinter (Figure 4-9). The mid-summer impi ngement involved yearli ng and older fish, as well as YOY, while the mid-winter impingeme nt involved the 2006 y ear class (YOY). A prominent peak in impingement of yearli ng and older alewife occurred on 10 August 2006 when water temperatures were near 73° F (22.8°C), but DO concentrations at the intake were nearly anaerobic (0.39 mg/L).

Stress related to low DO concentrations may have increased impingement rates during July and August. DO concentrations at th e intake on impingement sampling days were <4 mg/L from 22 June until 14 September, with the lowest concentrations occurring on 4 August (0.70 mg/L) and 10 A ugust (0.39 mg/L). Cooling water for MSS is drawn

beneath a skimmer wall at the entrance to the intake canal, thus drawing water with low DO concentrations from the lake’s hypolimnion. Fish occupying the canal at this time may succumb to the lowered DO levels and become impinged at the intake. Besides alewife and threadfin shad, fish species that showed increased impingement rates at this time included blue catfish (July-August, Figure 4-4), channel catfish (July-August, Figure 4-5), and white perch (August- September, Figure 4-6).

During the 1974-1975 monitoring programs at MSS, summer impingement rates were considerably lower than during the remainder of the year, part icularly the winter (Table 4-5). In that earlier stud y, cold water temperatures, particularly during DecemberFebruary, appeared to have had an influe nce on impingement rates, especially for

threadfin shad.

Species-Specific Abundance and Spatial Distribution

Data on the relative abundan ce of individual species and their distribution in Lake

Norman are available from recent annual electro fishing surveys of the littoral zone and hydroacoustic/purse seine survey s of the pelagic zone (Section 3). A comparison of the results of these surveys and the species composition of the 2006-2007 impingement collections provides insight into the role of species-specific abundance and spatial distribution on the susceptibility of species to impingement at MSS.

As is typical for many deep reservoirs, th e fish community of Lake Norman may be partitioned into at least two components: the near-shore, littoral zone community and the open water, pelagic community. The annual fi sheries surveys target these two sometimes distinct communities, but relating the relative abundance of individual littoral vs. pelagic species becomes difficult because of the differe nces in sampling gear efficiencies in the

two zones.

Four clupeids have been identified in Lake Norman and are associated with the pelagic zone: threadfin shad, alewife, gizzard sha d, and blueback herring. In 2006, threadfin shad appeared to be the dominant species in the pelagic zone, co mprising 94.9 percent of the purse seine catch (Duke 2007). Alewif e comprised the remaining 5.1 percent. Gizzard shad, once more common than now, did not occur in the 2006 purse seine catch. Blueback herring are rare and were reported in the gill net surv ey of 2004 (Duke 2004c).4-7 Threadfin shad and alewife, the principal com ponents of the pelagic fish community, also dominated the 2006-2007 impingement collectio ns at MSS, indicating that pelagic species are more vulnerable to impingement than littoral species. Together, they comprised 92.0 percent of the estimated a nnual impingement. In the collections, threadfin shad outnumbered alewife by over six to one, which was a lower ratio than the approximately 19:1 ratio in the purse seine catch of 2006. Thus, it would appear that alewife were more susceptible to impingement than threadfin shad, possibly reflective of the spatial distribution of the two species a nd increased impingement of alewife in late summer, August-September 2006 (Figure 4-2). While not caught by the 2006 purse seine surveys, gizzard shad appeared in li mited numbers (two fish) in the 2006-2007 impingement collections.

Seven additional species were impinged at MSS during 2006-2007: blue catfish, white perch, channel catfish, bluegill, redbreast sunf ish, pumpkinseed, and white crappie (Table 4-10). Together, these seven species comp rised only 6.6 percent of the total annual impingement collections. Two of the seven sp ecies, bluegill and redbreast sunfish, were the two most frequently caught species during the March-April 2006 electrofishing surveys of the littoral zone of Lake Norman (Table 4-10). Bluegill and redbreast sunfish are residents of the littoral zone, along w ith pumpkinseed; however pumpkinseed, while impinged (two fish collected), were not ca ught during the 2006 elec trofishing surveys.

Four impinged species—blue catfish, channe l catfish, white perch, and white crappie— are often associated with open water, and thus might be expected to be less common in the electrofishing survey results. Thes e four species were not abundant in the impingement collections in terms of numbers (Table 4-10), but th eir presence in the impingement collections further indicates that pelagic or open water species could be more susceptible to impingement than strictly littoral zone species. It is possible that pelagic species would more likely encounter a nd enter the intake cove , while littoral zone species would be excluded by the 60-ft deep skimmer wall at its entrance unless they already resided in the intake cove.



### Annual Losses

Impingement sampling during 2006-2007 has provided a single year’s estimate of seasonal and annual impingement rates occu rring at the MSS intake, and the best available estimate of current impingement fo r several reasons. Data collected by the 2006-2007 monitoring program are representative of the cu rrent relative abundance of fish species in the vicinity of the intake and their susceptibility to impingement. In 2006- 2007, station operation was consistent with its fo recasted use as a base load facility, with cooling water flow rates of approximately 73 percent capacity. The monitoring program design encompassed complete diel and seasona l cycles of impingement, and the program

was conducted with strict adherence to Standard Operating Procedures.

Two alternative approaches to estimating th e current levels of impingement are: (1) “Normal Operations” representing recent hi storical and projected operation of the facility, and (2) “Full Oper ations” representing the full design capacity for water withdrawals by the facility. Normal Operati ons would be an estimated annual total ofImpingement Mortality

4-8 188,419 impinged fish weighing 1,036 kg (Table 4- 2). An estimate for Full Operations can be derived by substituting the design capacity for cooling water flow rates ( 2,264 CFS or 1,463 MGD) rather than actual mean daily flow rates recorded during the 12- month sampling interval. Impingement losses under full operation are estimated to total 246,549 fish weighing 1,168 kg (Table 4-11). These totals repr esent a 31 percent increase in the numbers and a 13 percent in crease in biomass of impinged fish over Normal Operations

.

Annual Variability

Data collected by the 2006-2007 monitoring pr ogram are representative of current conditions, especially the relative abundance of fish species and th eir susceptibility to impingement. The data must be interpreted in the context of th e existing conditions. Seasonal and annual variability in impingement mortality could occur if cooling water intake operation, lake level, water temperatures, DO con centration, or fish abundance varied to a significant degree.

Intake Operation

MSS is operated generally as a baseload facili ty, with an average a nnual capacity factor of 79 percent during 2002-2007 (Section 2). Th e average annual intake flow rate for most of this period (2002-2006) was 73 percent of the maxi mum design capacity. MSS is expected to continue to operate as a baseload facility, so the influence of cooling water flow rates on the variability of annual im pingement rates should be minimal.

Environmental Variables

Impingement rates during 2006-2007 appeared to be influenced by water temperatures, lake levels, or DO concentrations. Peak im pingement of threadfin shad occurred when daily mean water temperatures were approxi mately 44-46°F (6.7-7.8°C) in February and early March, and the lake level was low. Peak alewife impingement occurred in August when DO concentrations were well below 4 mg/L . Stress related to cold temperatures or low DO may have increased impingement rate s for these two species. These variables might influence impingement rates in future years, as also indicated by higher impingement rates durin g winter in 1974-1975.

Fish Abundance

The abundance, species composition, and size composition of fishes in Lake Norman could vary annually as the result of ch anging habitat suitability, trophic dynamics, reproductive success, interspecific competition, or several other factors. These changes also could affect impingement rates at the in take. Some annual vari ability would appear random while some may reflect long-term trends in the abundance of individual species.4-9 Future changes in annual impingement totals might be expected if impingement is a

function of fish abundance. If the results of annual hydroacous tic and electrofishing surveys are indicative of the annual abundance of fish in Lake Norman, up to a two or three-fold variation in total impingement r easonably might be expected annually. Whole lake populations of threadfin shad and alewif e, which contribute the greatest number of fish to impingement counts at MSS, combined have varied from a low of 41 to 91 million fish since 1997 (see Section 5), an approxi mately two-fold difference. While not contributing as greatly to impingement to tals as pelagic populations, the total electrofishing catch for littoral zone fish va ried approximately two to three-fold since 2000, from 2,753 fish in 2006 to 8,266 fish in 2003.

Threadfin shad and alewife dominate impinge ment collections, so annual variations in their relative abundance would have the greate st influence on annual impingement totals. A third species, white perch, also appears to be especially susceptible to impingement at MSS because of its open water distribution, as also shown elsewhere, particularly in estuarine environments (Klauda et al. 1988, J acobsen et al. 2004). White perch is a newcomer to the fish community of Lake No rman (Section 3) and has the potential to expand its population rapidly in the reservoir, as it ha s in the Kerr Reservoir, Virginia/North Carolina and ot her southeastern reservoirs (Harris 2006). In time, white perch may be added to impingement collectio ns as a dominant species, thus possibly increasing annual impingement totals at MSS.

Comparison of Annual Monitoring Programs

The results of two or more annual monitoring programs can be compared to evaluate inter-annual variability impinge ment at MSS. The impingement monitoring program in 1974-1975 collected an estimated 1,050,505 impinged fish (Table 4-5). This estimate was based on biweekly collections at one screen per unit (four screens total). The sampled screens were allowed to accumul ate fish over the 14-day period between collections. Decomposition and predation/s cavenging may have reduced the number of impinged fish recovered. While only represen ting four of the 16 fixed screens at MSS and not including fish lost to decompositi on or predation or scavenging, the 1974-1975 total of 1,050,505 fish was more than five tim es greater than the 2006-2007 impingement estimate (188,419 fish) for all 16 screens combined.

In 1974-1975, a high percentage ( 38 percent) of fish could no t be identified to species due to decomposition. Of those identified, threadfin shad were the most numerous, comprising 61.9 percent of the total collections . When combined with gizzard shad, shad unidentifiable to species, and unidentified clupeid species, th ese four taxa comprised 99.8 percent of the total impingement. This dom inance by clupeid species was similar to the 2006-2007 results, where threadfin shad and alew ife comprised 92 percent of the annual impingement. Seasonal patterns in impingeme nt rates also were similar for the two monitoring programs. In 1974-1975, impingement was greatest during the late fall and winter months of November through Febr uary, while in 2006-2007 impingement rates were greatest in late summer and mi d-winter, especially February.Impingement Mortality

4-10 Reductions in impingement of clupeid speci es was the primary reason why impingement

totals declined drama tically between 1974-1975 and 2006-2007. In 1974-1975 over 1 million impinged clupeids were collected from four screens, compared to an estimated 173,462 clupeids (threadfin shad, alewife, and gizzard shad; Table 4-2) impinged on all 16 screens in 2006-2007. Thus, there appeared to be a reduction of more than an order of magnitude in clupeid impingement betw een the early and current studies.

Sampling methods differed between the 1974-1975 and 2006-2007 mon itoring programs in terms of the number of screens sampled per event, the selection of screens for sampling, and the period of time the screens we re allowed to accumulate fish before screen impinged fish recovery (14 days in 1974-1975 and one day in 2006-2007). The degree to which the difference in sampling me thods is responsible for the difference in

results is not clear.4-11 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar 0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200 1,300 1,400 1,500 Weekly Impingement Rates for All Species Combined

2006 - 2007Impingement Rate per 106m3

Figure 4-1 Seasonal Pattern of Impingement Rates for All Species CombinedImpingement Mortality

4-12 0 5 10 15 20 25 30 35 40 45 0 10 20 30 40 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar

0 50 100 150 200 250 300 Impingement Rates by Age Young-of-Year Yearling & Older

Undetermined 

### Alewife

2006 - 2007Impingement Rate per 106m3

Length FrequencyPercent in Length Interval

Midpoint of Length Interval (cm)

Figure 4-2 Seasonal Impingement Pattern and Length Frequency of Impinged Alewife4-13 0 5 10 15 20 25 30 35 40 45 0 5 10 15 20 25 30 35 40 45 50 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar

0 500 1000 1500 Impingement Rates by Age

Young-of-Year Yearling & Older

Undetermined 

### Threadfin Shad

2006 - 2007Impingement Rate per 106m3

Length FrequencyPercent in Length Interval

Midpoint of Length Interval (cm)

Figure 4-3 Seasonal Impingement Pattern and Length Frequency of Impinged Threadfin
ShadImpingement Mortality

4-14 0 5 10 15 20 25 30 35 40 45 0 5 10 15 20 25 30 35 40 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar 0 50 100 150 Impingement Rates by Age Young-of-Year Yearling & Older

Undetermined 

### Blue catfish

2006 - 2007Impingement Rate per 106m3

Length FrequencyPercent in Length Interval

Midpoint of Length Interval (cm)

Figure 4-4 Seasonal Impingement Pattern and Length Frequency of Impinged Blue
Catfish4-15 0 5 10 15 20 25 30 35 40 45 0 5 10 15 20 25 30 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar

0 5 10 15 20 Impingement Rates by Age Young-of-Year Yearling & Older

Undetermined 

### Channel catfish

2006 - 2007Impingement Rate per 106m3

Length FrequencyPercent in Length Interval

Midpoint of Length Interval (cm)

Figure 4-5 Seasonal Impingement Pattern and Length Frequency of Impinged Channel
CatfishImpingement Mortality

4-16 0 10 20 30 40 50 60 70 80 90 0 5 10 15 20 25 30 35 40 45 50 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar

0 5 10 15 20 25 Impingement Rates by Age

Young-of-Year Yearling & Older

Undetermined 

### White perch

2006 - 2007Impingement Rate per 106m3

Length FrequencyPercent in Length Interval

Midpoint of Length Interval (cm)

Figure 4-6 Seasonal Impingement Pattern and Length Frequency of Impinged White
Perch4-17 

### 754 755 756 757 758 759 760

4/1/2006 6/1/2006 8/1/2006 10/1/2006 12/1/2006 2/1/2007 

### 0 200 400 600 800 1,000 1,200 1,400

DateImpingement Rate per 106m3 

### 40 50 60 70 80 90Mean Intake Temp. (OF) 

### 0

1 2 3 4 5 6 7 8 9 10 11 12

Dissolved OxygenDissolved Oxygen (mgL-1) ElevationElevation (ft)

Figure 4-7 Daily Lake Level, Dissolved Oxygen Concentration, and Intake Water Temperature vs. Impingement Rate for All Species Combined, April 2006-March 2007Impingement Mortality

4-18 

### 754 755 756 757 758 759 760

0 200 400 600 800 1,000 1,200 1,400

4/1/2006 6/1/2006 8/1/2006 10/1/2006 12/1/2006 2/1/2007 

### 0 100 200 300 400 500

YOY



### DateYOY Impingement Rate per 106m3 

### 40 50 60 70 80 90Mean Intake Temp. (OF) 

### 0 1 2 3 4 5 6 7 8 9 10 11 12

Dissolved OxygenDissolved Oxygen (mgL-1) ElevationElevation (ft)YAO Impingement Rate per 106m3

YAO

Figure 4-8 Daily Lake Level, Dissolved Oxygen Concentration, and Intake Water Temperature vs. Impingement Rate for Young-of-Year (YOY) and Yearling and Older (YAO) Threadfin Shad, April 2006-March 20074-19 

### 754 755 756 757 758 759 760

0 50 100 150 200 250 300 350 400

4/1/2006 6/1/2006 8/1/2006 10/1/2006 12/1/2006 2/1/2007 

### 0 5 10 15 20 25 30 35 40

YOY



### DateYOY Impingement Rate per 106m3 

### 40 50 60 70 80 90Mean Intake Temp. (OF) 

### 0 1 2 3 4 5 6 7 8 9 10 11 12

Dissolved OxygenDissolved Oxygen (mgL-1) ElevationElevation (ft)YAO Impingement Rate per 106m3

YAO

Figure 4-9 Daily Lake Level, Dissolved Oxygen Concentration, and Intake Water Temperature vs. Impingement Rate for Young-of-Year (YOY) and Yearling and Older (YAO) Alewife, April 2006-March 2007Impingement Mortality

4-20 Table 4-1 Fixed Screens Sampled for Impingement (Marked as “1”) by Unit and Sampling Date, 2006-2007

Unit 1 Unit 2 Unit 3 Unit 4

Screen A AB B A AB B A AB B BC C A AB B BC CDate Sampled 4/6/2006 1 1 1 1

4/12/2006 1 1 1 1

4/20/2006 1 1 1 1

4/27/2006 1 1 1 1

5/4/2006 1 1 1 1

5/11/2006 1 1 1 1

5/18/2006 1 1 1 1

5/25/2006 1 1 1 1

6/1/2006 1 1 1 1

6/8/2006 1 1 1 1

6/15/2006 1 1 1 1

6/22/2006 1 1 1 1

6/29/2006 1 1 1 1

7/6/2006 1 1 1 1

7/13/2006 1 1 1 1

7/20/2006 1 1 1 1

7/27/2006 1 1 1 1

8/3/2006 1 1 1 1

8/10/2006 1 1 1 1

8/17/2006 1 1 1 1

8/24/2006 1 1 1 1

8/31/2006 1 1 1 1

9/7/2006 1 1 1 1

9/14/2006 1 1 1 1

9/21/2006 1 1 1 1

9/28/2006 1 1 1 1

10/5/2006 1 1 1 1

10/12/2006 1 1 1 1

10/19/2006 1

10/26/2006 1 1 1 1

11/2/2006 1 1 1 1

11/9/2006 1 1 1 1

11/16/2006 1 1 1 1

11/21/2006 1 1 1 1

11/30/2006 1 1 1 1

12/7/2006 1 1 1 1

12/14/2006 1 1 1 1

12/21/2006 1 1 1 1

12/28/2006 1 1 1 1

1/4/2007 1 1 1 14-21 Table 4-1 continued

Unit 1 Unit 2 Unit 3 Unit 4

Screen A AB B A AB B A AB B BC C A AB B BC C

1/11/2007 1 1 1 1

1/18/2007 1 1 1 1

1/25/2007 1 1 1 1

2/8/2007 1 1 1 1

2/15/2007 1 1 1 1

2/22/2007 1 1 1 1

3/1/2007 1 1 1 1

3/8/2007 1 1 1 1

3/15/2007 1 1 1 1

3/22/2007 1 1 1 1

3/29/2007 1 1 1 1 Total Samples per
Screen 10 17 12 12 19 12 15 14 13 11 5 11 13 7 19 11

Total Samples per Unit 39 43 58 61

All Unit Pumps OffImpingement Mortality4-22Table 4-2 Estimated Total Number and Biomass of Fish Impinged at Marshall Steam Station, 1 April 2006 – 31 March 2007Unit 1 Unit 2 Unit3 Unit 4 TotalSpecies No. Wt. (g) No. Wt. (g) No. Wt. (g) No. Wt. (g) No. Wt. (g)Alewife 1,023 20,674 1,317 21,294 7,129 140,671 18,681 372,896 28,150 555,535Gizzard shad 20 6,448 0 0 0 0 32 8,899 52 15,348Threadfin shad 16,424 28,141 14,745 24,98555,952 91,985 58,139 121,752 145,260 266,862Blue catfish 224 1,078 1,579 5,976 222 2,296 5,927 23,087 7,952 32,437Channel catfish 127 249 296 987 304 1,037 1,223 5,227 1,950 7,501White perch 321 14,291 320 12,766591 20,544 2,490 91,424 3,722 139,025Bluegill 37 503 180 1,604 74 930 919 10,248 1,210 13,286Pumpkinseed 0 0 0 0 37 140 18 69 55 209Redbreast sunfish 21 231 11 122 9 98 4 50 45 501White crappie 0 0 0 0 6 1,357 18 4,071 23 5,427Total 18,196 71,614 18,447 67,733 64,324 259,059 87,452 637,723 188,419 1,036,1304-23Table 4-3 Total Number and Percent Composition of Fish Collected at Marshall SS, 6 April 2006 – 30 March 2007Unit 1 Unit 2 Unit3 Unit 4 TotalSpecies No. % No. % No. % No. % No. %Alewife 13 10.00 20 3.89 114 4.72 643 20.35 783 12.59Gizzard shad - - - - - - 1 0.03 2 0.03Threadfin shad 98 75.38 467 90.862,262 93.66 2,199 69.59 5,026 80.82Blue catfish 8 6.15 13 2.53 22 0.91 178 5.63 212 3.41Channel catfish 3 2.31 5 0.97 6 0.25 38 1.20 57 0.92White perch 5 3.85 7 1.36 7 0.29 84 2.66 114 1.83Bluegill 2 1.54 1 0.19 2 0.08 16 0.51 19 0.31Redbreast sunfish 1 0.77 1 0.19 2 0.08 1 0.03 3 0.05Pumpkinseed - - - - - - - - 2 0.03White crappie - - - - - - - - 1 0.02Total 130 100.00 514 100.00 2,415100.00 3,160 100.00 6,219 100.00Table 4-4 Total Biomass and Percent Composition of FishCollected at Marshall SS, 6 April 2006 – 30 March 2007Unit 1 Unit 2 Unit3 Unit 4 TotalSpeciesWeight(g) %Weight(g) %Weight(g) %Weight(g) %Weight(g) %Alewife 321 29.63 73 5.53 1,85328.60 12,221 57.26 14,652 48.47Gizzard shad - - - - - - 233 1.09 606 2.01Threadfin shad 180 16.64 769 58.133,676 56.74 4,517 21.16 9,142 30.24Blue catfish 19 1.74 257 19.45 802 12.37 690 3.23 893 2.96Channel catfish 208 19.15 185 14.00 111 1.72 164 0.77 206 0.68White perch 5 0.47 18 1.34 19 0.30 3,020 14.15 4,214 13.94Bluegill 22 2.03 9 0.68 10 0.16 222 1.04 241 0.80Pumpkinseed - - - - - - - - 8 0.03Redbreast sunfish 329 30.35 12 0.88 8 0.12 278 1.30 34 0.11White crappie - - - - - - - - 233 0.77Total 1,084 100.00 1,322 100.00 6,479 100.00 21,344 100.00 30,229 100.00Impingement Mortality4-24Table 4-5 Number of Impinged Fish Collected*at Marshall Steam Station, 30 April 1974 – May 1975Species Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Total % TotalGizzard shad 328182452123346292019150-1,3160.125Threadfin shad 1,6883227514391,826505316180,288211,264166,11316,24661,02910,445650,08061.883Shad -6,780-691--49,032328,387-----384,26936.579Common carp -----1------1130.000Golden shiner ---1----------10.000Shiner 421-------1--4120.001Catfish/bullhead ---44-111-----1480.005Flat bullhead ---4--------1-50.000White catfish 2-237103911------740.007Striped bass ---1----------10.000Black crappie 11111-1----1--70.001Bluegill -1----1-----1-30.000Largemouth bass -1------1-----20.000Sunfish ---1----------10.000White crappie 41-----------160.001Yellow perch 7084106310231273-731118350.079Unidentifiable 1,2737082,4336881043--5,356-4,03313,8421.318Total* 3,6837,8113,546189831,87258449,382508,715211,287166,13321,61161,11314,4961,050,505*based on collections from one screen from each of four units4-25Table 4-6 Number and Percent Composition of Taxa Other Than Fish at MSS, 6 April 2006 – 30 March 2007Unit 1 Unit 2 Unit3 Unit 4 TotalTaxon No. % No. % No. % No. % No. %Corbicula10 76.92 55 98.21 4 100 1 9.09 70 83.33Crayfish 3 23.08 1 1.79 - - 10 90.91 14 16.67Total 13 100 56 100 4 100 11 100 84 100Impingement Mortality4-26Table 4-7 Estimated Total Number and Biomass of Fish Impinged Monthly at all Units of MSS, 1 April 2006 - 31 March 2007January February March April May JuneSpecies CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g)Alewife 2,570 17,304 1,978 10,560 1641,018 56 471 105 1,639 126 2,371Gizzard shad 0 0 0 0 0 0 0 0 0 0 0 0Threadfin shad 13,714 30,119 72,941 118,13311,977 21,811 2,079 3,606 439 787 131 336Blue catfish 33 108 23 28 90 148 0 0 18 18 150 239Channel catfish 34 162 0 0 63 208 61 84 142 296 46 80White perch 54 5,830 8 997 0 0 0 0 0 0 0 0Bluegill 615 6,057 222 1,914 139 2,196 0 0 35 180 39 296Pumpkinseed 0 0 0 0 0 0 0 0 0 0 55 209Redbreast sunfish 0 0 0 0 0 0 25 275 5 53 0 0White crappie 0 0 0 0 0 0 0 0 0 0 0 0Total 17,021 59,580 75,173 131,631 12,43425,382 2,221 4,436744 2,973 548 3,530July August September October November DecemberSpecies CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g)Alewife 521 12,799 17,394 425,432 4,60973,721 525 9,496 19 127 83 597Gizzard shad 0 0 0 0 41 12,213 11 3,135 0 0 0 0Threadfin shad 42 202 1,286 4,572 16,755 39,074 12,692 23,825 6,53310,388 6,670 14,010Blue catfish 7,048 24,686 446 2,918 86 3,674 13 565 43 53 0 0Channel catfish 729 2,808 874 3,863 0 0 0 0 0 0 0 0White perch 0 0 1,126 39,307 2,17978,773 283 9,811 21 844 52 3,463Bluegill 37 309 47 980 26 495 7 127 0 0 43 732Pumpkinseed 0 0 0 0 0 0 0 0 0 0 0 0Redbreast sunfish 0 0 0 0 0 0 14 168 0 4 0 0White crappie 0 0 0 0 23 5,427 0 0 0 0 0 0Total 8,377 40,803 21,174 477,073 23,719 213,377 13,545 47,127 6,616 11,416 6,848 18,8024-27Table 4-7 continuedAllSpecies CountBiomass(g)Alewife 28,150 555,535Gizzard shad 52 15,348Threadfin shad 145,260 266,862Blue catfish 7,952 32,437Channel catfish 1,950 7,501White perch 3,722 139,025Bluegill 1,210 13,286Pumpkinseed 55 209Redbreast sunfish 45 501White crappie 23 5,427Total 188,419 1,036,130Impingement Mortality4-28Table 4-8 Maximum Total Length (mm) Used to Distinguish Young-of-Year from Yearling Fish by MonthSpecies Age Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Decthreadfin shad 0 65 68 72 75 7845 50 55 60 65 65 651 89 89 90 94 9980 82 84 86 87 88 88alewife 0 130 130 130 140 15050 70 90 115 130 130 1301 200 200 200 205 210160 175 190 200 200 200 200blue catfish 0 100 100 100 110 120 13050 60 80 100 100 1001 180 180 180 185 190 195145 160 175 180 180 180white perch 0 105 105 105 110 11535 65 85 90 105 105 1051 150 150 150 155 160125 135 145 150 150 150 150channel catfish 0 80 80 80 90 100 11050 60 70 80 80 801 180 180 180 185 190 195125 145 165 180 180 180Note: shaded month indicated appearance of new year classSources: Klauda et al. (1988), Grist (2002), Graham (1999), Nigro and Ney (1982), Pierce (2003)4-29Table 4-9 Estimated Annual Impingement of Fish byAge Group at all Units of MSS, 1 April 2006 - 31 March 2007Young-of-Year Yearling & Older UndeterminedSpecies Count Percent Count Percent Count PercentAlewife 6,793 24.13 21,268 75.55 89 0.32Gizzard shad 0 0 0 0 52 100Threadfin shad 77,722 53.51 67,226 46.28 312 0.21Blue catfish 379 4.77 7,572 95.23 0 0Channel catfish 263 13.46 1,648 84.52 39 2.02White perch 28 0.75 3,694 99.25 0 0Bluegill 0 0 0 0 1,210 100Pumpkinseed 0 0 0 0 55 100Redbreast sunfish 0 0 0 0 45 100White crappie 0 0 0 0 23 100Total 85,186 45.21 101,408 53.82 1,825 0.97Impingement Mortality

4-30 Table 4-10 Comparison of Relative Abundance of Fish Species in the March-April 2006 Littoral Zone Electrofishing Surveys and the 2006-2007 MSS Impingement Collections

2006 Electrofishing 2006-2007 Impingement Species Total No. % Rank Total No. % Rank
Bluegill 1,166 42.35 1 19 0.31 6

Redbreast sunfish 724 26.30 2 3 0.05 7
Threadfin shad 218 7.92 3 5,026 80.82 1

Redear sunfish 162 5.88 4 - Spotted bass 137 4.98 5 - Largemouth bass 97 3.52 6 - Hybrid sunfish 83 3.01 7 -

Warmouth 53 1.93 8 -

Whitefin shiner 28 1.02 9 - Commom carp 19 0.69 10 - Spottail shiner 17 0.62 11 -

Green sunfish 13 0.47 12 -

Channel catfish 10 0.36 13 57 0.92 5

Flathead catfish 6 0.22 14 - Hybrid black bass 4 0.15 15 tie -

Shorthead redhorse 4 0.15 15 tie -

Gizzard shad 3 0.11 17 tie 2 0.03 8 tie

Quillback 3 0.11 17 tie - Black crappie 2 0.07 19 -

Golden shiner 1 0.04 20 tie - Striped bass 1 0.04 20 tie -

Tesselated darter 1 0.04 20 tie - Yellow perch 1 0.04 20 tie -

Alewife - - 783 12.59 2

Blue catfish - - 212 3.41 3 Pumpkinseed - - 2 0.03 8 tie White crappie - - 1 0.02 10 White perch - - 114 1.83 4
Total 2,753 100.00 6,219 100.004-31Table 4-11 Estimated Total Number and Biomass of Fish Impinged Monthly at all Units ofMSS for Full Flow Operations, 1 April 2006 -31 March 2007January February March April May JuneSpecies CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g)Alewife 3,313 22,278 2,558 13,646242 1,510 79 695 160 2,523 170 3,243Gizzard shad 0 0 0 0 0 0 0 0 0 0 0 0Threadfin shad 18,509 40,655 94,959 153,801 17,198 31,313 3,340 5,791 621 1,124 165 419Blue catfish 44 144 30 35 159 259 0 0 21 21 190 303Channel catfish 43 203 0 0 89 293 155 198 229 448 65 109White perch 80 8,685 12 1,502 0 0 0 0 0 0 0 0Bluegill 1,087 10,587 288 2,476 199 3,150 0 0 48 215 51 386Pumpkinseed 0 0 0 0 0 0 0 0 0 0 91 346Redbreast sunfish 0 0 0 0 0 0 74 816 10 114 0 0White crappie 0 0 0 0 0 0 0 0 0 0 0 0Total 23,075 82,553 97,847 171,461 17,88636,525 3,648 7,500 1,088 4,446 731 4,807July August September October November DecemberSpecies CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g) CountBiomass(g)Alewife 647 15,828 17,405 425,692 4,615 73,831 708 12,492 38 254 114 826Gizzard shad 0 0 0 0 41 12,226 11 3,135 0 0 0 0Threadfin shad 53 253 1,287 4,574 16,981 39,330 22,964 41,138 12,682 20,387 9,460 19,923Blue catfish 8,819 30,755 447 2,919 86 3,680 13 566 131 163 0 0Channel catfish 889 3,445 875 3,865 0 0 0 0 0 0 0 0White perch 0 0 1,126 39,323 2,185 78,998 350 12,424 36 1,467 71 4,706Bluegill 55 460 47 981 26 496 7 127 0 0 56 946Pumpkinseed 0 0 0 0 0 0 0 0 0 0 0 0Redbreast sunfish 0 0 0 0 0 0 28 319 1 7 0 0White crappie 0 0 0 0 23 5,431 0 0 0 0 0 0Total 10,462 50,742 21,186 477,355 23,957 213,991 24,079 70,201 12,886 22,278 9,702 26,401Impingement Mortality4-32Table 4-11 continuedTotalSpecies CountBiomass(g)Alewife 30,048 572,819Gizzard shad 52 15,361Threadfin shad 198,218 358,709Blue catfish 9,939 38,844Channel catfish 2,344 8,562White perch 3,860 147,105Bluegill 1,862 19,824Pumpkinseed 91 346Redbreast sunfish 113 1,256White crappie 23 5,431Total 246,549 1,168,2585-1 

# 5

ASSESSMENT OF ADVERSE ENVIRONMENTAL
IMPACT

Introduction

Section 316(b) of the Clean Wa ter Act calls for use of the “...best technology available to minimize adverse environmental impact.” In 2004, EPA issued the Phase II Rule which addressed implementation of §316(b) for existi ng cooling water intake structures that have a design flow of more than 50 MGD. As a result of challenges to this Rule by several groups, the U.S. Court of Appeals fo r the Second Circuit reviewed the Rule and remanded several key provisions on 25 January 2 007 (see Section 1). As a result of this remand, EPA issued a suspension of the Phase II Rule on 9 July 2007 and directed that “Permit requirements for cooling water intake structures at Phase II facilities should be established on a case-by-case best pr ofessional judgment (BPJ) basis”.

Prior to the Phase II Rule, BPJ compliance w ith §316(b) was based on a determination of whether or not the cooling water intake stru cture was resulting in adverse environmental impact (AEI). With the remand of the Phas e II Rule, this approach continues to be appropriate in BPJ determinations. Unfo rtunately, neither the Act nor subsequent guidance provided by the EPA provides any definition of the term “adverse environmental impact” for use by permit writers in making their BPJ determinations. Consequently, it is left up to the permitti ng authority to determine what constitutes adverse environmental impact to be minimized under §316(b).

In this analysis, Duke Energy will evaluate the potential for an a dverse impact of the MSS cooling water intake structure as a result of an unacceptable reduction in:

 biological integrity as meas ured in terms of aquatic community species composition, diversity, and functiona l organization; or

 human use of the aquatic resources in the source waterbody, especially fishing opportunity or catch quantity or quality.

These two evaluation criteria are consiste nt with the EPA’s original draft §316(b) guidance (EPA 1977) as well as histor ical practice (Dey et al. 2000).

Duke proposes to use multiple lines of i nvestigation to determine the potential for unacceptable adverse impacts by evaluating:Assessment of Adverse Environmental Impact

5-2  potential ecosystem impacts by:

o conducting a prospective evaluation ba sed on losses to impinged species

o conducting a retrospective evaluation based on analysis of a long-term data base, and

 impacts to human use by:

o estimating economic losses from impingement.

How do we go about assessing the risk of a dverse environmental impact for MSS? Recognizing the need for a consistent and technically sound approach to assessing the potential effects of a wide variety of an thropogenic stresses on ecosystems, the EPA began an intensive effort to develop an a pproach for ecological risk assessment during

the late 1980s. The intent of this effort wa s to develop an approach that would parallel

that used for human health risk assessme nt but focus on the non-human ecosystem. These efforts, which were independent of those to re-promulgate §316(b) regulations, resulted in the publication of a “Framework for Ecological Risk Assessment” (ERA) in 1992 (EPA 1992). Following considerable public review, input and debate, “Guidelines for Ecological Risk Assessment” (ERA Guide lines) were finalized in October 1998 (EPA 1998).

These Guidelines replace the earlier framework, describe general principles, and give examples of how ecological risk assessment can be applied to a wide variety of systems, stressors, and spatial and temporal scales. The general principles reflect an effort to promote consistency in assessing ecological risk among EPA’s offices and regions, while at the same time permitting development of site-specific methods to meet local needs. EPA’s ERA approach has been used to a ddress a variety of chemical, physical, and biological stressors, as well as the combined effects of multiple stressors, across many agencies throughout the United States.

EPA defines ecological risk assessment as “... a process that evaluates the likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors” (EPA 1992). Since entrainm ent and impingement result in the exposure of aquatic organisms to physical and chemical st resses, it seems that a logical approach to assessing the risk of adverse environmenta l impact of cooling water withdrawals as required by §316(b) would be through the use of an ecological risk assessment framework, such as th at provided by EPA.

As noted above, the risk of adverse envir onmental impact from the continued operation of the MSS cooling water intake system need s to be addressed from two perspectives: ecosystem (i.e., biological in tegrity) and human (i.e., fishing opportunity). Potential adverse effects from these two perspectives were addressed within the framework of an ecological risk assessment as described in EPRI (2002). The results of these two assessments are then used together as part of a “weight-of-evidence” approach to5-3 determine the overall risk of adverse envir onmental impact from MSS’s cooling water

intake structure on Lake Norman.



### Assessment of Ecosystem Effects

EPA recognized that it is unlikely that risk can be accurately determined through use of a single measure. Therefore, the ecological risk assessment framework calls for careful review of all information relevant to the issue under a “multiple lines of evidence” approach to risk assessment. These line s are independently as sessed using two broad categories of methods: prospective and retr ospective methods. Prospective methods attempt to predict the effects of a stressor, such as cooling water withdrawal, on the ecological endpoints selected for the assessm ent. Retrospective methods, on the other hand, evaluate the potential effects of an exis ting stressor, such as a cooling water intake structure, by measuring the actual effects on th e ecological endpoints. In this assessment, we use a combination of prospective and retr ospective methods to determine the potential ecosystem effects of cooling water withdrawals at MSS.

Prospective Approach

EPA defines use of prospective methods for ecological risk assessment as “an evaluation

of the future risks of a stre ssor not yet released into th e environment or of future conditions resulting from an existing stre ssor” (EPA 1998). For this assessment, prospective methods entail pred icting the potential consequen ces of impingement at MSS on the fish community composition and func tion and on recreational fishing in Lake

Norman.

As described in Section 4, impingement monitoring was conducted at MSS over the period April 2006 – March 2007. The results of these studies were used to estimate the expected annual impingement at MSS under normal operations:

Species Count Biomass (kg) Mean Weight per

fish (g)

Threadfin shad 145,260 266,862 1.8

Alewife 28,150 555,535 19.7

Blue catfish 7,952 32,437 4.1

White perch 3,722 139,025 37.4

Channel catfish 1,950 7,501 3.8

Bluegill 1,210 13,286 11.0

Pumpkinseed 55 209 3.8

Gizzard shad 52 15,348 295.2

Redbreast sunfish 45 501 11.1

White crappie 23 5,427 236.0

Total 188,419 1,036,130 5.5Assessment of Adverse Environmental Impact

5-4 Mean weights per fish suggest that, with th e exception of a small number of adult gizzard shad and white crappie impinged, most of the fish collected were small and most likely either age 0 or age 1 individuals. Two pelagic forage species, threadfin shad and alewife, accounted for 92 percent of the fish and 79 percent of the biomass impinged annually based on the results of this study.

All but three of the species co llected had estimates of annua l impingement that averaged less than ten fish per day. Given that all of these species are co mmon to Lake Norman, it is hard to image that the removal of i ndividuals of each species daily, most likely juveniles, could be considered an adverse environmental impact from Lake Norman, a lake of more than 13,000 ha.

Blue catfish, the species with the third highe st estimated annual impingement, is one of two catfish species that are popul ar target of anglers. The estimated annual impingement of this species represents a removal rate of less than 22 individuals per day. At an average weight of only 4.1 grams each, most of these were likely only a few months old. Assuming a conservative survival rate of 5 pe rcent from the time of impingement to the average age of harvest by anglers, these 22 juveniles result in appr oximately one averagesized harvestable adult (i.e., 5 years old and about 0.5 lb or 227 g). Hence, the current annual impingement of blue catfish is equivale nt to the removal of less than one adult per day that could be caught by an angler. As with the other species, it is hard to imagine

that such a removal rate would constitute an adverse environmental impact on Lake

Norman.

The two most abundant species impinged, th readfin shad and alewife, are abundant throughout the pelagic areas of Lake Norma n. Together, estimated annual impingement of these two species amounted to slightly more than 170,000 individuals weighing 823 kg (1,811 lb). Both species are pelagic and se rve as important forage for a variety of gamefish in Lake Norman. Owing to their importance as forage, pelagic species (predominantly threadfin shad and alewif e) have been the subject of annual hydroacoustic studies designed to determine overall abundance in Lake Norman (Section 3). Based on the results of these studies, the number of pe lagic fish throughout the lake during 2000-2003 has varied from just over 64 m illion to 86 million individuals. At these levels, the removal of these species by impingement at Marshall amounts to 0.2 to 0.3 percent of the population each year. Given th e rapid growth, short life span, and high reproductive potential of both species, it is ha rd to imagine that such removal rates can have any detectable effects on either population persistence for either species or on the

amount of food available to support higher trophic levels.

Retrospective Approach

Within the ecological risk assessment framework, a retrospective assessment of risk is an evaluation of the causal linkages between observed ecological effects and stressors present in the environment (EPA 1998). For this assessment, the stressor would be the loss of fish from the Lake Norman community caused by impingement at the CWIS. The retrospective approach evaluate d whether effects on individual species populations or the5-5 community as a whole are apparent by exam ining trends in the species richness and

relative abundance of individual species during the time that MSS has operated. Community metrics involving species ric hness and abundance would be appropriate because impingement is equivalent to harv esting fish, without adding pollutants or altering the physical habitat of the lake, for which other community metrics might be appropriate.

Fortunately, there exists a database on the occurrence of fish species and their relative abundance in Lake Norman, which includes recent data from 1993 through 2007. Trends in species richness and relative abundance should be apparent if operation of MSS has

had a discernable effect on the Lake Norman fish community. If there are discernable effects, are they consistent with the selec tive loss of individual species to impingement that could be interpreted as being causal in nature?

Hypothetically, selective harv esting of fish species by impingement could result in species or trophic imbalance in the community, or reduced standing crops of fish. If true, metrics involving species richness, relative abundance, and standing crop (absolute abundance) should reveal significant, sust ained changes in species occurrence and abundance, or a trophic imbalance. Also, a persistence or increase in top carnivores (piscivores) might indicate st ability or improvement in th e community, and vice versa.

In the database, the lake is divided into tw o zones (pelagic and lit toral, i.e., open water and near-shore, respectively). From 1993 until the present, the pelagic zone has been sampled by mobile hydroacoustics and purse se ine surveys, resulting in annual estimates of absolute abundance of the primary pelagic species (combined): threadfin shad, alewife, and gizzard shad. The littoral zone was sa mpled annually by boat electrofishing from 1993 through the present (see Section 3 for sampling method descriptions).

The results of these surveys in terms of fi sh abundance, species richness, and trophic structure of the fish community are discussed as follows.

Fish Abundance

The abundance of pelagic clupeid species, acco rding to annual hydroacoustic surveys in September, varied dramatically from 1993 to 1997, then appeared to stabilize after 1997 (Figure 5-1). Acoustic surveys prior to 1996 used only a down-looking transducer. For the 1996-2006 surveys, a multiplexed side-scan transducer was added to include fish residing within 2 m of the water surface. From 1996 on, abundance data should be directly comparable and would reflect the most recent status of the pelagic forage fish populations. Since 1997, population estimates fo r threadfin shad, alewife, and gizzard shad combined have ranged from 47,172,559 fish in 2004 to 91,335,000 fish in 1998.

Although gizzard shad were once a major comp onent of the forage fish community, especially in littoral areas (Siler et al. 1981), in recent ye ars they contribute very few fish compared to threadfin shad and alewife (Table 5-1). After its init ial appearance in LakeAssessment of Adverse Environmental Impact

5-6 Norman in 1999, alewife increased in abundance to make up 12 to 25 percent of the purse seine catch, but was reduced to 5 percent or less in 2005-2007.

In the littoral zone of Lake Norman, elec trofishing surveys during 1993-2007 (Figure 5- 2) have shown a nearly three-fold variati on in the annual total catch for all species combined (2,849 in 1995 to 8,266 fish in 2003). However, there has been no sustained

trend in the overall numeric al abundance of fish.

Bluegill and redbreast sunfish have been th e dominant species in electrofishing surveys since 1993, and were abundant in the earlier 1978- 1979 rotenone surveys (Siler et al. 1981). The annual variation in total electrofishing catch from 1993 to 2007 to some degree reflected the variation in catch of bluegill in partic ular (Figure 5-2). The annual

catch of redbreast sunfish a nd largemouth bass has shown less variation over the 15-year period (Figure 5-2).

The five target species (threadfin shad, alew ife, channel catfish, blue catfish, and white perch) chosen for detailed im pingement analysis in Secti ons 3 and 4, with the exception of threadfin shad, were not as abundant in the 1993-2007 electrofishing catches as bluegill, redbreast sunfish, a nd largemouth bass (Figures 5-3 and 5-4). Threadfin shad and alewife are pelagic species ; therefore, the hydroacoustic data presented in Figure 5-1

should be a more accurate reflection of thei r annual abundance than the littoral zone electrofishing data (Figure 5-3). Channel catf ish, blue catfish, and white perch are caught infrequently by electrofishing but show occas ionally higher annual catch totals that do

not indicate trends in their abundance. White perch had not been caught prior to 1998.

Species Richness

Since 1993 there has been an increase in the number of fish species found during electrofishing surveys, from 20-22 species annually prior to 1998 to as many as 29 species after 1998 (Figure 5-5). Species a dded since 1997 include alewife, bluehead chub, bowfin, fathead minnow, goldfish, green sunfish, rainbow trout, spotted bass, striped mullet, swallowtail shiner, walleye, wh ite catfish, white crappie, and white perch. Of these 14 species, bowfin, bluehead chub , wh ite catfish, and white crappie previously had been reported as occurring in Lake No rman during 1974-1980 (Table 3-1 in Section 3).

Trophic Structure

Species caught by annual spring electrofishi ng surveys were divided into trophic guilds consisting of insectivores, omnivores, herbivores , and piscivores (Table 5-2) according to classifications used by NCDENR (2006). Insectivores dominated the annual electrofishing catch, representing 51 to 93 per cent of all fish caught and a 14-year mean of 78 percent (Figure 5-6). Omnivores and piscivores varied annually but each had a 14- year mean of 11 percent. The eastern s ilvery minnow was the only herbivorous species5-7 and comprised only 01.-0.2 percent of all fish caught in the years when they occurred (1993 and 2000).

Omnivores (primarily threadfin shad) were unusually abundant in 1993-1994 when they comprised 26-36 percent of the total electrofishing catches (Figure 5-6). The abundance

of threadfin shad in 1993 and 1994 also was reflected in the pelagic fish population estimates (Figure 5-1). After 1994 omnivores comprised <15 percent of all fish caught annually.

From 1993 to 1999, piscivores represented 13 to 20 percent of all fi sh caught (Figure 5- 6). After 1999, they decreased to 6-11 per cent of the total catc h. The number of piscivores caught annually decreased from a mean of 623 fish in 1993-1999 to 409 fish in 2000-2007. The decrease in piscivores largel y reflected a decrease in the abundance of largemouth bass, the dominant piscivore. Coincident with this decrease was the introduction and gradual prolifer ation of spotted bass, from six fish in 2001 to 194 fish in

2007.

Retrospective Summary

The fish community of Lake Norman has changed since the commencement of operation of MSS in terms of fish abundance, species richness, species composition, and trophic structure. Initially, the change s were related to the evoluti on of the fish community from a riverine community to a lacustrine community following the impoundment of the Catawba River in the early 1960s. Typical ri verine species were lost and lacustrine species became better established. Recent ch anges (since 1993) are readily tracked by examining the results of standardized a nnual sampling of the fish community using hydroacoustics, net gear, and electrofishing.

Despite long-term changes in the community, there is evidence of stabilization, particularly in this past decade. The fall population size of pelagic forage species stabilized after 1997. Since 1993, there also ha s been no sustained trend in the littoral zone catch size. However, there has been an increase in species richness since 1993, with the addition of 14 new species in the past 10 years. The trophic structure has become more stable after 1994, with insectivores numerically representing approximately 70-90 percent of the littoral zone catch, with th e remainder nearly equally divided between piscivores and omnivores.

Intensive recreational fishery management m easures and species introductions likely will modify the fish community of Lake Norman in the future, and have been largely responsible for changes experien ced in the past. However, th ere is no evidence that any community changes are relate d to operation of the MSS cooling water intake and impingement losses.Assessment of Adverse Environmental Impact

5-8 

### Effects on Human Uses

Lake Norman, from which MSS withdraws its cooling waters, provide s important fishing opportunities to people from North Carolina and adjacent states. Popular targets of anglers include striped, largem outh and spotted bass; several species of catfish; and a variety of panfish species including bluegill, crappie, and perch. In addition, the lake supports a healthy community of other water-dependent species that provide passive use opportunities such as nature watching. He nce, in addition to potential effects on biological integrity, it is reasona ble to address the potential e ffects of impingement of fish at MSS on human uses of Lake Norman, especially fishing.

Two different types of measures of the pot ential effects of impingement on human uses of the aquatic resources in Lake Norman, e quivalent loss and economic value, were used in this analysis. Estimates of the two types of measures were calcula ted for each of five target species: threadfin sha d, alewife, blue catfish, channe l catfish, and white perch. Together, these five species comprised more than 99 percent of total impingement at MSS. The methods and parameter values us ed to develop thes e two measures are discussed in Appendix A. The result ing measures are described below.

Equivalent Loss Measures

Since impingement at MSS involves several spec ies of fish and a vari ety of sizes within each species, equivalent loss calculations provide a means to express these losses in biological terms that are more amenable to interpretation. In this assessment, two different equivalent loss measures were estimated for each target species:

 Equivalent yield provides a measure of th e additional weight of each species that could have been harvested by anglers in the absence of any impingement at MSS.

 Production foregone provides a measure of the additional biomass production that could have resulted from the impinged indi viduals in the absence of any impingement

at MSS.

Using the methodology and the most probable es timates for each of the input parameters described in Appendix A, estimates of equi valent fishery yield and production foregone for each of the five target species were generated using the monthly impingement estimates at MSS. The monthly estimates we re then summed to calculate total annual

values.

Only three of the five target species evaluated in this assessment, blue catfish, channel catfish and white perch, direc tly support fisheries in Lake Norman. Annual fishery yield that could result from the fish impinged at MSS totaled 254 lb (115.2 kg) under actual cooling water flows during the course of the impingement monitoring program and 304 lb (137.9 kg) under maximum (design) cooli ng water flows (Table 5-3). Most (67 percent) of this equivalent yield was through blue catfish.5-9 Annual production from the ta rget species impinged at M SS totaled 5,134 lb (2,329 kg) under actual cooling water flows and 6,037 lb (2,738 kg) under maximum cooling water flow (Table 5-4). Three speci es, alewife, blue catfish a nd threadfin shad, accounted for just over 83 percent of th e total annual production fore gone. In the absence of impingement at MSS, this additional producti on could support additional biomass of fish targeted by anglers and provide energy to support other ecosystem functions.

Economic Value

Calculation of economic value takes the es timates of equivalent yield and production foregone described above and assigns economic value based on estimates of “willingness to pay” for additional resources by the users of that resource. As such, this measure provides another perspective on the issue of adverse environmental impact by weighting the estimates of equivalent loss by the rela tive “importance” of each species assigned by

humans. Calculation of economic value has a long history of use including for the assignment of economic benefits of th e Phase II rulemaking (EPA 2004a, 2004b, 2004c).

In this assessment, economic values were a ssigned to each of the four categories of benefit values relevant to §316(b) re gulations for existing facilities:

 market direct use benefits;

 nonmarket direct use benefits;

 indirect use be nefits; and,

 nonuse benefits.

The value of marketed goods is equivalent to the sum of predicted changes in “consumer and producer surplus.” Producer surplus is the difference between the price obtained for a good (e.g., fish) and the cost of producing that commodity. Consumer surplus is the difference between the perceived value of a good or service to the consumer and the cost of acquiring that good or service. Non-ma rketed goods, such as recreational fishing, normally require using indirect markets, such as travel, to infer their value. In addition, some positive changes in resources such as forage fish might increase the direct use values even though the resources themselves are not directly used. Fi nally, in addition to

these direct and indirect use -related values, there is a poten tial for environmental changes

to increase the welfare of individuals who do not use the resource at all. These latter

benefits are considered nonuse benefits. Me thods and input values used to calculate

economic values for each of these benefits categories are described in Appendix A.

The annual economic value for all fish impi nged at MSS totaled only $577 under actual cooling water flow and only $680 under maximum cooling water flow (Table 5-5). Most of this economic value (~51 percent) was attr ibutable to the loss of threadfin shad and alewife through their combined effects on the equivalent pr edator (striped bass).Assessment of Adverse Environmental Impact

5-10 Uncertainty in Economic Value

Given the large number of parameters needed to calculate economic values, coupled with the difficulty in obtaining precise estimates of the input values for each parameter, there can be considerable uncertainty in the es timates of economic value generated for any individual facility. It is for this reas on that EPA guidance on conducting such economic

evaluations recommends that an uncertaint y analysis be conducted as part of the evaluation (EPA 2000). The purpose of such an uncertainty analysis is to make transparent all the underlying s ources of uncertainty in the calculation of economic value such that the reader can independently de termine whether the results have sufficient precision and accuracy to meet regulatory needs.

In this report, uncertainty wa s addressed using two methods. First, sensitivity analysis was conducted on key input parameters to determine the relative importance of the uncertainty in the values for each parameter to the estimates of economic value. Second, Monte Carlo analysis was used to evaluate the cumulative uncertainty in the estimates in economic benefit, combining the uncertainty in each of the input parameters. For simplicity, this uncertainty analysis focuse d on the estimates of economic benefit based on actual cooling water flows. Uncertainty for the maximum cooling water flow case

should be almost identical. Results for each of the two methods are discussed below.

The results of sensitivity analysis are illust rated in Figure 5-7. Uncertainty in natural mortality rate yielded the greatest range in estimates of annual economic value (-48 to +281 percent) while uncertain ty in the recreational fish ing price yielded the second greatest range (-71 to +112 per cent). Uncertainty in these two parameters was clearly most important in determining the total unc ertainty in the estimate of annual economic value. Uncertainty in the remaining five inpu t parameters (natural mortality rate, fishing vulnerability, weight, trophic conversion factor, and equiva lent predatory exploitation rate) had relatively minor effects on estimates of annual economic value (< + 30 percent).

The results of the Monte Carlo analysis are illustrated in Figure 5-8. The frequency distribution of the resulting annual estimates appeared generally symmetrical, although

most of the estimates of economic value resu lting from this uncertainty analysis were higher than the most probable estimate. The median value from the Monte Carlo analysis was 17 percent higher than the most pr obable estimate while the 25th and 75th percentiles were 0 percent and 34 percent highe r, respectively. There was less than a 10 percent chance that the true annual economic benefit was more than 50 percent greater than the most probable estimate reported in Tabl e 5-5. The fact that most of the estimates of economic value were higher than the most probable estimate is likely related to the non-symmetrical effects of the two key parame ters, the natural mortality rate and the recreational price per pound, described above.



### Conclusions

The results of this assessment provide no evidence that impingement at MSS is causing

effects within Lake Norman that rise to a level that could be considered an “adverse5-11 environmental impact.” This conclusion is based on a careful evalua tion of all relevant lines of evidence, including the following observations:

1. Numbers of fish lost as a result of im pingement are exceedingly small compared to likely sizes of fish populations in La ke Norman. For all but three species,

removal rates amounted to less than 10 fi sh per day. For blue catfish, removal rates were less than 22 young juveniles per day. These young juveniles could be expected to yield only a si ngle harvestable adult, on aver age. As with the other species, it is hard to imagine that such a removal rate would constitute an adverse environmental impact on Lake Norman.

2. Total numbers impinged each year for th e two most abundant species, threadfin shad and alewife, amounted to less than 0.3 percent of th e population in the lake. Both species are highly prolific spawne rs with high growth rates and short life spans. This high reproductive potential can easily compensate for the relatively

small losses at MSS with no long-term effects.

3. After evolving from a riverine to lacust rine community, the aquatic community of Lake Norman appears to have stabilized in terms of fish abundance and trophic structure, particularly in this past decade. Fish abundance in pelagic areas has

stabilized since 1997. There also has been no sustained trend in the littoral zone catch size since 1993, while species richness has increased with the addition of 14 new species in the past 10 years.

4. Intensive recreational fishery management and species introductions likely have been responsible for changes experienced in the past. However, there is no evidence that any community changes are related to operation of the MSS cooling water intake and impingement losses.

5. Estimates of total fishery catch that c ould result from the fish impinged at MSS had they survived amount to only 254 lb (115.2 kg) per year, most of which was

blue catfish. That amount translates to less than 1 lb per day. This level of harvest is less than what would be exp ected from a small number of anglers.

6. Estimates of the total production foregone as a result of fish impinged at MSS amounted to just over 5,100 lb (2,313 kg) per year of biomass. Almost all of this

was a result of threadfin shad and alew ife, both of which are highly abundant species in Lake Norman. That biomass translates to less than 3 ounces per surface acre (210 g/ha) acro ss the entire reservoir.

7. The best estimate of the total economic value of fish impinged at MSS was $577 per year. Even considering the uncertainty in these estimates, it is highly unlikely that the economic value exceeds $800 per year. These values must be considered trivial compared to the likely total economic value of the recreational fishery in

Lake Norman.Assessment of Adverse Environmental Impact

5-12 1992 1994 1996 1998 2000 2002 2004 2006 0 1x10 8 2x10 8 3x10 8 4x10 8 5x10 8 6x10 8 7x10 8Hydroacoustic Population Estimate

Figure 5-1 Annual Population Estimates of Pelagic Fish in Lake Norman Using Hydroacoustic Sampling, 1993-20065-13 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000

Total Bluegill

Redbreast sunfish Largemouth bassElectrofishing Catch

Figure 5-2 Total Annual Elect rofishing Catch for Bluegill, Re dbreast Sunfish, Largemouth

Bass, and All Species Combined at 30 100-m Transects in Lake Norman, 1993-1997 and

1999-2007Assessment of Adverse Environmental Impact

5-14 1994 1996 1998 2000 2002 2004 2006 0 200 400 600 800 1,000Threadfin shadTotal Catch

0 10 20 30 40 50 60Alewife 0

2 4 6 8 10Blue catfish

Figure 5-3 Total Annual Electrofishing Catc h for Blue Catfish, Alewife, and Threadfin Shad at 30 100-m Transects in Lake Norman, 1993-1997 and 1999-20075-15 1994 1996 1998 2000 2002 2004 2006 0 40 80 120 160White perchTotal Catch

0

10 20 30 40 50 60Channel catfish

Figure 5-4 Total Annual Electrofishing Catch for Channel Catfish and White Perch at 30 100-m Transects in Lake Norman, 1993-1997 and 1999-2007Assessment of Adverse Environmental Impact5-16ElectrofishingSpecies19931994199519961997199920002001200220032004200520062007Longnose garBowfinAlewifeGizzard shadThreadfin shadBluehead chubCommom carpEastern silvery minnowFathead minnowGolden shinerGoldfishGreenfin shinerSpottail shinerSwallowtail shinerWhitefin shinerBrassy jumprockQuillbackShorthead redhorseSilver redhorseBlue catfishBrown bullheadChannel catfishFlat bullheadFlathead catfishSnail bullheadFigure 5-5 Species Composition in the Littoral Zone of Lake Norman as Determined by Electrofishing in 1993-1997 and 1999-2007(Shading Denotes Species Presence)5-17Species19931994199519961997199920002001200220032004200520062007White catfishRainbow troutStriped mulletMosquitofishWhite bassWhite perchStriped bassBlack crappieBluegillGreen sunfishHybrid black bassHybrid sunfishLargemouth bassPumpkinseedRedbreast sunfishRedear sunfishSpotted bassWarmouthWhite crappieSwamp darterTessellated darterUnidentified darterWalleyeYellow perchTotal No. of Species20202021222324 28 23 29 25 24 2325Figure 5-5 continuedAssessment of Adverse Environmental Impact

5-18 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 0 10 20 30 40 50 60 70 80 90 100 % Herbivore % Insectivore % Omnivore % PiscivorePercent Trophic Level Composition

Figure 5-6 Percent Composition of Fish Trophic Guilds in the Littoral Zone of Lake Norman Based on Electrofishing Results of 1993-1997 and 1999-20075-19 Vulnerability Fishing Mortality Exploitation Rate Trophic Conversion Weight Recreational Price

Natural Mortality

-300 -250 -200 -150 -100 -50 0 50 100 150 200 250 300

Percent Difference

Figure 5-7 Estimates of the Range of Effects of Uncertainty in Each Input Parameter on
Estimates of Annual Economic Benefit at MSSAssessment of Adverse Environmental Impact

5-20 0 20 40 60 80 100

-100 -80 -60 -40 -20 0 20 40 60 80 100 0 5 10 15 20Percent Frequency

Percent Difference from EstimateCumulative Percent

Figure 5-8 Results of Monte Carlo Analysis of Uncertainty in Key Input Parameters on
Estimates of Annual Economic Benefits at MSS5-21Table 5-1 Species Composition of the Purse Seine Catch in Lake Norman, 1993-2006Species Composition (%)Species19931994199519961997199819992000200120022003200420052006Threadfin shad 100 99.94 99.95 100 99.99 99.95 99.26 87.4 76.47 74.96 82.59 86.55 98.1 94.87Gizzard shad 0 0.06 0.05 0 0.01 0.05 0.26 0.22 0.01 0 0.14 0.24 0 0Alewife 0 0 0 0 0 0 0.48 12.37 23.52 25.04 17.27 13.2 1.9 5.13Assessment of Adverse Environmental Impact

5-22 Table 5-2 Trophic Guild Assignments for Fish Species in Lake Norman

Taxa Trophic
Guild Taxa Trophic
Guild Longnose gar P White catfish I

Bowfin P Rainbow trout P Alewife F Striped mullet O Gizzard shad O Mosquitofish I Threadfin shad O Striped bass P

Bluehead chub O White bass P Commom carp O White perch P Eastern silvery minnow H Black crappie P Fathead minnow O Bluegill I

Goldfish O Green sunfish I Golden shiner O Hybrid black bass P Greenfin shiner I Hybrid sunfish I Spottail shiner I Largemouth bass P Swallowtail shiner I Pumpkinseed I

Whitefin shiner I Redbreast sunfish I Brassy jumprock I Redear sunfish I Quillback O Spotted bass P

Shorthead redhorse I Warmouth P Silver redhorse I Swamp darter I

Blue catfish P Tessellated darter I

Brown bullhead I Unidentified darter I Channel catfish P Walleye P Flat bullhead O White crappie P Flathead catfish P Yellow perch I

Snail bullhead I

Source: NCDENR (2006)

I = Insectivore

P = Piscivore

O = Omnivore

H = Herbivore5-23 Table 5-3 Estimates of Potential Total A nnual Equivalent Fishery Yield (lb) from Individuals Impinged for Each Target Species at MSS

Species Annual Fishery Yield (lb)

Actual Flow Maximum Flow

Threadfin shad 0 0

Alewife 0 0

Blue catfish 170 211

Channel catfish 44 51

White perch 40 42

Total 254 304

Table 5-4 Estimates of Potential Total Annua l Production Foregone (lb) from Individuals Impinged for Each Target Species at MSS

Species Annual Production Foregone (lb)

Actual Flow Maximum Flow

Threadfin shad 1,068 1,433

Alewife 1,654 1,709

Blue catfish 1,561 1,933

Channel catfish 669 775

White perch 181 187

Total 5,134 6,037Assessment of Adverse Environmental Impact

5-24 Table 5-5 Estimates of Economic Value of Fish Impinged at MSS

Species Total Impingement Value (2008$)

Actual Flow Maximum Flow

Threadfin shad a 0 0

Alewife a 0 0

Blue catfish 145 179

Channel catfish 75 87

White perch 61 64

Equivalent predator b 295 347

Non-target species c 2 3

Total 577 680

a Economic benefits for threadfin shad and alewife only occur through forage benefits to the equivalent predator.

b Equivalent biomass production for all Target Species converted to an equivalent biomass of a recreationally important predator (striped bass).

c Economic value associated with all impinged fish s pecies that were not selected as target species.6-1 

# 6

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O’Gorman, R., O.E. Johannsson, and C.P. Schneide r. 1997. Age and growth of alewives in the changing pelagia of Lake Ontario, 1978-1992. Transa ctions of the Ameri can Fisheries Society 126:112-126.Pardue, G.B. 1983. Habitat suitabil ity index models: alewife and blueback herring. U.S. Fish and Wildlife Serv ice, Washington, D.C. FWS/OBS-82/10.58.

Pardue, G.B. 1983. Habitat suitability index mo dels: alewife and blueback herring. Fish and Wildlife Seervice, U.S. Department of th e Interior. Washington, D.C. FWS/OBS-82/10.58. September 1983.

Pflieger, W.L. 1997. The Fishes of Missouri. Missouri Department of Conservation, Jefferson City, MO. 372 pp.

Pierce, C.L., C.S. Guy, M.A. Pegg, and P.J. Braat en. 2003. Fish growth, mortality, recruitment, condition and size structure. Volume 4. Population structure and habitat us e of benthic fishes along the Missouri and Yellowstone rivers. U. S. Geological Survey, Cooperative Research Units, Iowa State University. Science Hall II, Ames, Iowa.

Pitlo, J., K. Brummet, and M. Endris. 2004. Channel catfish ( Ictalurus punctatus ). In: Pitlo, J.M. Jr. and J.L. Rasmussen (eds.). UMRRC Fi sheries Compendium. 3rd Edition. Upper Mississippi River Conservation Committee. Rock Island, Illinois. January 2004. p. 151-155.

Prout, M.W., E.L. Mills, and J.L. Forney. 1990. Diet, growth, and potential competitive interactions between age-0 white perch and yellow perch in Onei da Lake, New York.

Transactions of the American Fisheries Society 119:966-975.

Ricker, W.E., ed. 1975. Computation and Interp retation of Biological Statistics of Fish Populations. Bulletin 191. Department of the Environment, Fisheries and Marine Service, Ottawa. 382 pp.6-5 Rohde, F.C., R.G. Arndt, D.L. Lindquist, and J.F. Parnell. 1994. Freshwater fishes of the Carolinas, Virginia, Maryland, & Delaware. The University of North Carolina Press. Chapel Hill, NC. 222 pp.

Rosenberger, R.S. and J.B. Loomis. 2001. Benef it Transfer of Outdoor Recreation Use Values: A Technical Document Supporting the Forest Service Strategic Plan (2000 Revisions). General Technical Report RMRS-GTR-72. Fort Collins, Colorado: U.S. Department of Agriculture, Forest Service, Ro cky Mountain Research Station. 59p. (www.fs.fed.us/rm/pubs/rmrs_gtr72.html).

Ruelle, R., W. Lorenzen, and J. Oliver. 1977. P opulation dynamics of young-of-the-year fish in a reservoir receiving heated effluent. Proceedi ngs of the Conference on Assessing the Effects of Power-Plant Mortality on Fish Populations . Reprinted in Duke 1977. Oconee Nuclear Station Environmental Summary Report 1971-1 976. Volume 2. Charlotte, North Carolina.

Siler, J.R., R.E. Lewis, B.K. Baker, R.A. Hansen, and G.E. Vaughn. 1981. Chapter 10, Fish. In: Hogan, J.E. and W.D. Adair (eds.). Lake Norman summary. Volumes 1 and 2. Duke Power Company, Environmental Services Section, Hunt ersville, North Carolina. Research Report

EL/81-28.

Simon, T.P. and R. Wallus. 2003. Reproductive biology and early lif e history of fishes in the Ohio River drainage: Ictaluridae – catfish and madtoms, Vol. 3. CRC Press, Boca Raton, Florida. 232 pp.

Smith, C.L. 1985. The inland fishes of New Yo rk State. New York State Department of Conservation. 522 pp.

Smith, P.W. 2002. The Fishes of Illinois. Univer sity of Illinois Press, Urbana and Chicago. 314

pp.

Stanley, J.G. and D.S. Danie. 1983. Species profiles: life histories and environmental requirements of coastal fishes and invertebrate s (North Atlantic). U.S. Department of the Interior, Fish and Wildlife Service, Washington, DC FWS/OBS-82/11.7. October 1983.

Thompson, J.S., J.A. Rice, D.S. Waters, J.C. Tayl or, J.E. Hightower, L.A. Davis, and P.S. Rand. 2005. Energetics of reservoir striped bass popula tions: Phase I final report. Prepared for Division of Inland Fisheries, North Caroli na Wildlife Resources Commission by North Carolina Cooperative Fish and Wildlife Research Unit, North Carolina State University, Raleigh, NC.Tidwell, J.H. and S.D. Mims. 1990. A comparison of second-year growth of blue catfish and channel catfish in Kentucky. Th e Progressive Fish-Culturalist 52:203-204.

Tidwell, J.H. and S.D. Mims. 1990. A comparis on of send-year growth of blue catfish and channel catfish in Kentucky. Progres sive Fish-Culturist 52(3):203-204.References Cited

6-6 United States Environmental Protection Agen cy (EPA). 1977. Guidance for Evaluating the Adverse Impact of Cooling Water Intake St ructures on the Aquatic Envirnment: Section 316(b) P.L. 92-500. Draft. Washington, D.C.

United States Environmental Protection Agency (EPA). 1992. Framework for Ecological Risk

Assessment. Risk Assessment Foru m, EPA/630/R-92/001. Washington, D.C.

United States Environmental Protection Agency (EPA). 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. Washington, D.C.

United States Environmental Protection Agen cy (EPA). 2000. Guidelines for Preparing Economic Analysis. EPA/240/R-00/003. Washington D.C., 227 pp.

United States Environmental Protection Agency (EPA). 2004a. National Pollutant Discharge Elimination System – Final Regulations to Es tablish Requirements for Cooling Water Intake Structures at Phase II Existing Facilit ies. 40 CFR Parts 9, 122, 123, 124, and 125.

United States Environmental Protection Agency (EPA). 2004b. Regional Analysis Document for the Final Section 316(b) Phase II Existing Facilities Rule. Office of Water. EPA/821/R02/003. Feb. 12.

United States Environmental Protection Agency (EPA). 2004c. §316(b) Phase II Final Rule, Regional Studies, Part H: Inland Studies.

Van Horn, S.L. 2001. Lake Norman striped ba ss management: a conf lict between fishery managers and anglers. Proceedings of the Annual Conference of Southeastern Fish and Wildlife Agencies 2001:316-323.A-1 

# A

APPENDIX A: METHODS TO ESTIMATE
EQUIVALENT LOSS AND ECONOMIC VALUE OF
FISH IMPINGED AT MARSHALL

Introduction

This appendix describes the methods used to develop estimates of annual equivalent loss and economic value of fish impinged at the Marshall Steam Station (MSS). For this assessment, annual impingement estimates we re developed using recent impingement monitoring data collected at MSS over the period 6 April 2006 – 30 March 2007 (Section 4).



### Estimates of Target Species Equivalent Losses

In order to calculate economic value, estimates of annual impingement loss at MSS for the five target species (thread fin shad, alewife, blue catf ish, channel catfish and white perch) must be converted to equivalent meas ures that can be assigned economic value for these species. For species of commercial a nd/or recreational importa nce, the equivalent measure selected was the yield to the fisher y that would have been expected had the individuals not been impinged. For species that serve as forage for other, generally larger, aquatic organisms, the measure select ed was the production of biomass available as food for higher trophic levels that would have been expe cted had the individuals not been impinged. Methods used in this re port to calculate these two measures are consistent with those used by EPA in the Phase II rulemaking and are described below.

The measure “yield to the fishery” is define d as the annual total yi eld (in weight) that

could have occurred in the commercial or r ecreational fishery from those individuals lost to impingement in the absence of compensatory changes in to tal mortality. This yield is calculated using the Equivalent Yield Mode l (EYM), which integrates Baranov’s catch equation (Ricker 1975) with estimates of the mean weight by age (Dey 2002, EPRI 2004). This method is conservative in that potential density-dep endent changes in mortality or growth rates th at often occur in natural popul ations were not included. Using the EYM, fishery yield equivalent to the annual impingement loss at MSS for each target species was estimated as follows:



#    

   

###      

 f l n

i i i i

i i n

j i j j 

### Z F V W A S NL EY

1 1Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-2 where:

EY = Equivalent yield to fishery

NL j = Number of each age or life stage category (j) lost annually to impingement

at MSS

S

j → i = Total survival from age or life stage category (j) to age (i)

n

j = Number of age or life stag e categories (j) impinged at MSS

V

i = Vulnerability of age (i) to fishing

F

i = Instantaneous fishing mortality rate for age (i)

Z

i = Instantaneous total mortality rate for age (i)

A i = Total mortality rate for age (i) = 1-e-Zi

W

i = Average weight for individual of age (i) captured in the fishery

nf

= Maximum number of ages (i) vulnerable to fishery.

The EYM results in an estimate of yield define d in the same units used to describe the average weight of the individuals and integrates yield across all ages. In this assessment, the EYM was not applied to threadfin shad or alewife as neither supports any direct commercial or recreational fishing.

The measure of biomass production that could ha ve resulted from individuals impinged at MSS was calculated using the Production Fo regone Model (PFM) (Dey 2002, EPRI 2004). As with the EYM, this method is also conservative in th at potential densitydependent changes in mortality or growth ra tes that often occur in natural populations were not included. Using the PFM, potenti al biomass production from individuals impinged was estimated for each of the target species as follows:



#     

#  

i i Z G

i i n

j i j j L

i i Z G e W G S NL

P i i l

 

 

 

 

##   1

1

1

and the total production foregone (P) can be found by summing over all the age categories that are impinged:



# 

  m

i i P P

1A-3 where:

P

= Total production foregone

P i = Production foregone for individuals impinged at MSS in age category (i)

G i = Instantaneous growth rate in weight for age category (i)

NL j = Number of each age category (j ) lost to impingement at MSS

S

j → i = Total survival from age category (j) to age (i)

n

j = Number of age categories (j) impinged at MSS

W

i = Average weight of indi viduals in age category (i)

Z

i = Average instantaneous mortality rate for age category (i)

m = Total number of age categories impinged at MSS

L = Final age category.

The PFM was applied to all target species th at as individuals serv e as food for other aquatic organisms during at leas t part of their life cycle.

Both the EYM and PFM are consistent with th e benefits calculation procedures used by EPA in their regional analys is of the benefits of th e Phase II Rule (EPA 2004b). Estimation of the biological input parameters for each of the target species is described

below.

Assignment of Age Categories for Impinged Individuals

One of the necessities of equivalent loss cal culation is that the direct measures of impingement mortality must be assigned to individual age categories as defined in the production foregone and equivalent yield models. In this assessment, age was assigned using length information for each target species obtained from the current impingement monitoring together with estim ates of maximum length at age for these same species

obtained from the scientific literature and from an analysis of the length-frequency patterns for each species.

Life Table Information

Biological input parameters for the Producti on Foregone and Equivalent Yield models include life stage durations, in stantaneous natural and fishin g mortality rates, and the fraction vulnerable to the fishery for each life stage and age, as well as mean weights atAppendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-4 the beginning of each life stage and age for each target species. Each of these model inputs were determined as described below.

Life Stage Durations

Estimates of impingement were developed for this assessment on a monthly basis. Consequently, the duration of each month was set as 30.4 days, the average monthly duration across the entire year. However, it is important to rec ognize that fish do not become vulnerable to impingement until they are approximately 25 mm long and typically 1 to 2 months of age. Hence, the number of monthly increments in the first year of life is less than 12. Spawning months and months at which each species first became vulnerable to impingement at M SS were assigned as follows:

Species Peak Spawning
Month Average Month
When Individuals
Reach 25 mm TL

Threadfin shad Jun Jul

Alewife Jun Jul

Blue catfish Jul Aug

Channel catfish Jul Aug

White perch May Jul

Natural Mortality Rates

A range (maximum, most probable, and minimum) of instantaneous natural mortality rates for each target species were ob tained from the following sources:

Threadfin shad – Daily instantaneous natura l mortality rates were obtained from EPRI (2005) Table 4-43. For age 0, the most proba ble value was assumed to be the midpoint between the maximum and minimum values listed. For ages 1 and 2, maximum and minimum values were assumed to be 25 per cent higher and 25 per cent lower than the most probable value, respectively.

Alewife – Most probable daily instantaneous na tural mortality rates were obtained from EPRI (2005) Table 4-24. For all ages, maxi mum and minimum values were assumed to be 25 percent higher and 25 per cent lower than the most probable value, respectively.

Blue catfish – The maximum, most proba ble and minimum estimates of the daily instantaneous natural mortality rates were assu med to be the same as that for the closely

related channel catfis h, discussed below.

Channel catfish – The maximum, most probable and minimum estimates of the daily instantaneous natural mortality rates for all ages were obtained from EPRI (2005) Table

4-25.A-5 White perch – The maximum a nd most probable estimates of the daily instantaneous natural mortality rates for Age 0 were base d on survival rates pr ovided in EPRI (2005)

Table 4-12. The minimum value was assumed to be the same distance less than the most probable value as the maximum was higher. The most probable estimates for all older ages were based on survival rates provide d in EPRI (2005) Table 4-12. The maximum and minimum values were assumed to be 25 percent higher and lower than the most probable value, respectively.

These most probable values were used to provi de the best estimates of equivalent loss, while the maximum and minimum values were considered in the uncertainty analysis.

Fishing Mortality Rates

A range (maximum, most probable, and mini mum) of instantaneous fishing mortality rates for the three species that directly support fishing were selected as follows:

Blue and channel catfish – The maximum, most probable, and minimum estimates of annual fishing mortality were set to 0.15, 0.10, and 0.05, respectively. These annual exploitation rates were then converted to daily instantaneous fi shing mortality rates required for this analysis.

White perch –The maximum, most probable, and minimum estimates of annual fishing mortality were set to 0.20, 0.15, and 0.10, respec tively. These annual exploitation rates were then converted to daily instantaneous fishing mortality rates required for this analysis.

As with natural mortality, the most probabl e values were used to provide the best estimates of equivalent loss, while the maxi mum and minimum values were considered in the uncertainty analysis. Since there is little or no harvest of either threadfin shad or alewife in Lake Norman, fishing mortality rate s for both of these species were set to 0.

Fishing Vulnerability Rates

Fishing vulnerability rates refer to the frac tion of each age at a size vulnerable to be harvested by anglers. For the fishing vulnerability rate s used in this assessment,

individuals were assumed to be not vulnerable (rate = 0) up to a set age and completely vulnerable (rate = 1) above that age. Th e maximum and minimum ages of complete vulnerability were estimated using best pr ofessional judgment based on length at age information from the scientific literature. Resulting estimates are as follows:Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-6 Species Youngest Age of Vulnerability Oldest Age of Vulnerability

Blue catfish 4 5

Channel catfish 5 6

White perch 3 4

For the most probable vulnerability rates, ha lf of the individuals were assumed to be vulnerable at the youngest age while the remain ing half did not become vulnerable until the oldest age.

The most probable values were used to provi de the best estimates of equivalent loss, while the maximum and minimum values were considered in the uncertainty analysis.

Since there is little or no harvest of either threadfin shad or alewife in Lake Norman, fishing vulnerability rates for both of these species were set to 0.

Weight at Beginning of Age

A range (maximum, most probable, and minimu m) of estimated weights at the beginning of each age were obtained for each target species from the following sources:

Threadfin shad – The most probable mean wei ght at the time of first impingement was assumed to be 1 g each while those for subse quent ages were obtained from Thompson et al. (2005). The maximum and minimum weights were assume d to be 20 percent higher and 20 percent lower than the most probable value, respectively.

Alewife – The most probable mean weight at the time of first impingement was assumed to be 1 g each while those for subsequent ag es were based on length-at-age data from O’Gorman et al. (1997) coupled with a lengt h-weight relationship from Thompson et al. (2005). The maximum and mini mum weights were assumed to be 20 percent higher and 20 percent lower than the most probable value, respectively.

Blue catfish – The most probable mean wei ght at the time of first impingement was assumed to be 1 g each and the maximum a nd minimum mean weights were assumed to be 20 percent higher and lower, respectivel y, than the most probable values. The maximum and minimum weights at age for all other ages were based on mean lengths at age for ages < 10 from Grist (2002) and for ages 11 – 18 from Graham (1999). Maximum mean weights were calculated fr om these lengths using a length-weight relationship from Graham (1999) while the mi nimum mean weights were calculated from these lengths using a length-weight relati onship from unpublished data for the Missouri River. The most probable mean weights were assumed to be at the mid-point between

the maximum and minimum values.

Channel catfish – The most probable mean wei ght at the time of first impingement was assumed to be 1 g each while for subsequent ages mean weights were based on mean lengths at age provided by Pi erce et al. (2003) for the Miss ouri River and a length-weightA-7 relationship for Georgia rivers obtained from www.fishbase.org . For all ages, the maximum and minimum mean weights were as sumed to be 20 percent higher and lower, respectively, than the most probable values.

White perch – The most probable mean weight at the time of first impingement was assumed to be 1 g each while those for subs equent ages were obtained from Marcy and Richards (1974). The maximum and minimum weights were assumed to be 20 percent higher and 20 percent lower than the most probable valu e, respectively.

For all species, weights at the beginning of each month within an age were interpolated using an instantaneous growth rate based on the weights at the begi nning and end of that age. The most probable values were used to provide the best estimates of equivalent loss, while the maximum and minimum values were considered in the uncertainty analysis.



### Economic Valuation Methods

The potential economic values of impingement at MSS were calculated for each of the benefit categories described using standard economic con cepts outlined in EPA (2004b, Part A: Evaluation Methods, Chapter A9: Be nefit Categories and Valuation). Methods

used to estimate values associated with each of the four benefit cat egories (market direct use benefits, nonmarket direct use benefits, in direct use benefits, a nd nonuse benefits) are

discussed below.

Direct Use Values

Direct use values accrue to individuals who di rectly use the aquatic resources affected, in other words, recreational anglers. The econom ic value of this bene fit category is then equivalent to the economic value of the harv est by anglers that would have resulted from the fish that were impinged. The biological benefit values were defined in terms of pounds to be consistent with reported fishery economic statistics. Using these estimates of increased fishery harvest, the economic va lue of the direct use benefit category was estimated for each sub-component (m arket and nonmarket) as follows.

Market Values (Commercial Fishing)

Market benefits refer to economic benefits that can be directly measured from data obtained in the marketplace. Changes in the magnitude of commercial fish and shellfish harvests are the principal market benefits relevant to §316(b) regulations. Since impingement losses at cooling water intake st ructures had the potenti al to increase stock size, and hence commercial harvests, positive market benefits could potentially accrue had they not been impinged. At present, co mmercial fishing on Lake Norman appears to be non-existent. Hence for this assessment, the market value of any increase in commercial fishing was assumed to be essent ially non-existent and no further estimation of this category was required.Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-8 Non-Market Direct Use Values (Recreational Fishing)

This category includes benefits derived through use of the resource that are not reflected

in the market for the resource. Relative to §316(b) regulations, the most common benefit that could accrue from impinged fish would be through increases in recreational fishing opportunities. Increased abundance of adult fish that could result had impingement

losses not occurred can lead to increased catch rates for indi vidual anglers as well as an

increase in the number of fishing trips by anglers.

Unfortunately, benefits from increased recreatio nal use of the resour ce are not directly reflected in the primary market, i.e., the ma rket for recreational fishing. However, EPA

concluded that there is considerable liter ature to support valui ng this benefit through estimation of an angler’s “willingness to pa y” for recreational opportunities. Thus, the

non-market direct use value for additional recreational catch can be defined as the increase in the total “willingness to pay” across all anglers resulting from any greater recreational opportunities due to reduction in impingement losses. The recreational values used represent the marginal benef it per unit change in recreational catch.

For this assessment, total “willingness to pa y” for each target species was calculated by multiplying the estimated biological benefits (pounds) of impinged fish by the expected value per pound recreational fishermen were wi lling to pay for that increased harvest:

S S S RP BBR RFB  

where:

RFB S = Economic benefits ($) to recreationa l fishing for each target species (S)

BBR S = Biological benefits (lbs) to recreati onal fishing for each target species (S)

RP S = Value per pound recreational anglers are willing to pay for the increase in harvest of the target species (S).

The biological benefits to the recreational fi shery for each target species estimated for MSS (Table 5-2) are likely to be a very sm all fraction of the estimated recreational catch of comparable species in Lake Norman in re cent years. Hence, there is no reason to expect that changes in recreational fishing ha rvest that could result had the fish not been impinged at MSS would be sufficiently large so as to affect the price the anglers are willing to pay. Therefore, the values that r ecreational anglers are currently willing to pay for each species should be a reasonable measur e of the values they would be willing to pay assuming impingement was eliminated. Th is is the same assumption used by EPA in calculating the national benefits of the Phase II Rule (EPA 2004b).

For this assessment, we used the same recreational values per fish as used by the EPA in the Phase II Rule (EPA 2004c). The EPA valu es (2002$) were then adjusted to reflect current (2008$) yielding:A-9 Species Group Recreational Value (2008 $/fish)

Maximum Most Probable 10 Minimum

Panfish 5.51 2.55 0.77

Perch 0.52 0.46 0.40

Following the EPA approach, values for speci es group “panfish” were assumed to apply

to blue and channel catfish whereas the values for species group “perch” were assumed to apply to white perch.

To convert these values to a weight basis to be consistent with the biological benefits calculation, each of these recreational values were divided by an estimated average weight per harvested fish using the life tabl e information described in Section 3. The resulting average weights per fi sh that directly s upport recreational fishing are as follows:

Species Average Weight per Fish Harvested (lb/fish)

Maximum Most Probable Minimum

Blue catfish 4.00 3.00 2.00

Channel catfish 2.00 1.50 1.00

White perch 0.40 0.30 0.20

The resulting values ($) per pound of fish for each target species are as follows:

Species Recreational Value (2008$/lb)

Maximum Most Probable Minimum

Blue catfish 2.76 0.85 0.19

Channel catfish 5.51 1.70 0.39

White perch 2.60 1.53 1.00

The most probable values were used to provide the best estimates of equivalent loss while

the maximum and minimum values were c onsidered in the uncertainty analysis.

Indirect Use Benefits

This category includes benefits that accrue to humans fr om the use of the resource indirectly. Relative to §316(b) regulations, the indirect bene fit that could result from fish that were not impinged would be through an increased consumption by higher trophic levels of production that result from these organisms. This increased consumption could result in greater growth and survival rates among fish in these hi gher trophic levels, and

10 Used EPA’s mean value as most probable.Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-10 hence, increase fishing opportunities. Pr oduction consumed by higher trophic levels results from pelagic forage species, such as threadfin shad and alewife, as well as individuals of recreationally important sp ecies that die of natural causes.

Unfortunately, there are no generally accepted me thods to assign a value directly to this benefit. Instead, the value of this benefit is assigned indi rectly by quantifying the amount of commercially and/or recr eationally important species th at could be supported by the production potentially generated by these impi nged organisms, which were subsequently harvested by man. Hence, the value of the production equivalent to the fish impinged is equal to the value of commerc ial and/or recreational harves t that could be supported by that production.

The value of the indirect benefits of impinge d fish at MSS uses the following three-step

process.

Step 1 – Estimation of Total Biomass of Higher Trophic Levels Supportable by the Annual Productivity Equivalent to the Impingeme nt. The total biomass of higher trophic levels supportable is calculated by usi ng a trophic transfer method as follows:



#   TTC

PFB HTB

S S 

###   

# 

 5

1

where:

HTB = Total annual higher trophic level biomass (pounds) supported by production foregone attributable to impingement

PFB S = Biomass production foregone for each target species (S) attributable to impingement

TTC = Trophic transfer coefficient.

This approach is identical to that used by EPA in the Sect ion 316(b) Final Phase II Rule (EPA 2004b).

For this assessment, production foregone estima tes equivalent to impingement at MSS for each of the target species were calculat ed using the Production Foregone Model as

described above and listed in Table 5-3. These estimates of production foregone were based on annual impingement estimates from M SS. A trophic transfer coefficient of 10 percent, consistent with EPA (2004b), was then used to convert the total biomass forgone to an amount of higher trophic level biom ass supportable by that production foregone. The coefficient means that an average of 10 percent of the production foregone would have ended up as predator biomass. For th e uncertainty analysis, a range for the trophic transfer coefficient of 5 to 15 percent was assumed.A-11 Step 2 – Estimation of Equivalent Pred ator Harvest Supporte d by Annual Productivity Equivalent to the Reduction in Impingement. As previously noted, the value of indirect benefits is determined by the value of th e commercial and/or recreational harvest supported by the increased productivity. Hen ce, the total higher trophic level biomass estimated under Step 1 needs to be converted to an estimate of actual yield to the fishery expressed as equivalent predator harvest. This is accomplished by assuming that the total higher level biomass is converted to biom ass of a popular commercial or recreational species and then multiplying the value by the annual fishery exploitation rate for that species as follows:

EP ER HTB EPY  

where:

EPY = Equivalent predatory yield (pounds) attributable to impingement compliance

HTB = Higher trophic level biomass (pounds) at tributable to impingement compliance

ER EP = Fishery exploitation rate for th e selected equivalent predator.

For this assessment, striped bass was select ed as the equivalent predator endpoint upon

which the estimate of indirect value is based. In reality, any potential production increase of course would be transferred among many sp ecies, including some with little or no recreational or commercial importance. Howe ver, this species is a popular target of recreational anglers in Lake Norman. He nce, this species should be a reasonably representative species for a ssigning recreational importance, and hence value, for this assessment. Using the life table information, the annual exploitation rate for striped bass was estimated to be 20 percent. For the uncer tainty analysis, a range of 10 to 30 percent

was assumed. We believe that the selection of the striped bass as th e equivalent predator provides a reasonably conservative estimate of indirect-use value, since the “willingness to pay” (WTP) estimates for this species is at the upper boundary of the range of WTP values for other species addr essed in this assessment.

Step 3 – Estimation of Indirect Use Economic Benefit. Estimates of the economic value

of the increased recreational harvest resulti ng from increases in forage biomass were calculated using the methods previously desc ribed for direct-use non-market benefits. For this assessment, the value per fish for striped bass (the equivalent predator) was based on the values per fish assigned to this species in EPA (2004c). These were then converted to a value per pound a ssuming an average weight per harvest striped bass of 5

lb each as follows:

Maximum Most Probable Minimum

Value per fish (EPA 2004c) 19.48 14.33 3.92

Value per pound 3.90 2.87 0.78Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-12 Non-Use Benefits

As previously discussed, this category, al so known as passive use values, includes all benefits above and beyond any accrued through use of the resource. Most commonly

cited non-use benefits incl ude bequest and existence va lues. EPA acknowledges that these benefits can be estimated best by us ing contingent valuation methods on a sitespecific basis. However, they concluded th at such studies are un likely to be conducted for specific facilities and were clearl y beyond the scope and budget of EPA for development of the §316(b) re gulations (EPA 2004a).

In the final rule, EPA provided that "In cases where an impingement mortality and entrainment characterization study does not iden tify substantial harm to a threatened or endangered species, to the sustainability of populations of important species of fish, shellfish, or wildlife, or to the maintenan ce of community structure and function in a facility's waterbody or watershed, monetizati on [of non-use benefits] is not necessary." [69 Fed. Reg. Vol. 131 (9 July 2004) page 41648]. However, they do require a qualitative discussion of these benefi ts if they are believed to exist.

The impingement monitoring studies provide no evidence that impingement at MSS is causing “substantial harm” to threatened and endangered species or to aquatic populations and communities of the Lake Norm an. Therefore, consistent with the EPA approach for the Section 316(b) Phase II Rule, non-use values were not included in this

economic valuation.

Adjustment for Other Species

The total annual economic benefits for the target species is th e sum of the annual economic benefits for all benefit categorie s described above. These target species, however, do not account for all fish impi nged at MSS but only 99.6 percent. The following equation was used to account for th e benefits resulting from reductions in impingement for the remaining 0.4 per cent of fish impinged at MSS:



# 

  

###       

  4

1 

### 1 996

. 0 1

TS TS TS non 

### Ben Ben

where:

Ben

non - TS = Economic benefits accruing to non-target species

Ben TS = Economic benefits accruing to four target species and the equivalent predator.

The total annual economic value of fish impinged at MSS is the sum of the benefits to the target species plus the benef it to the equivalent predator and the benefit to non-target species.A-13 

### Uncertainty Analysis

EPA’s Phase II §316(b) Rule requires that a faci lity seeking a site-specific determination

based on benefits valuation also submit “an an alysis of the effects of significant sources of uncertainty on the results of the study” [ §125.95(b)(6)(iii)(C)]. Un certainty refers to the lack of knowledge about measures and comp onents that go into each element of the benefits valuation procedures. Under Phase II , the purpose of the uncertainty analysis is to make transparent all the underlying sour ces of uncertainty in the calculation of economic value such that the appropriat e regulatory authority can independently

determine whether the results have sufficient precision and accuracy to meet regulatory needs (EPA 2004b) and form sufficient basi s for sound regulatory decisions. The purpose of this section is to evaluate the eff ects of uncertainty in key input parameters on

the estimates of economic value for MSS.

Uncertainty is not unique to the calculati on of economic value under Phase II §316(b). Some uncertainty exists in almost all predic tions of future conditions based on past or existing information and this is especially tr ue when dealing with environmental science

and economic issues. In both environmental scien ce and economics, inhe rent variability and limited understanding of underlying proce sses, coupled with difficulty in making accurate measurements of underlying paramete rs, makes consideration of uncertainty in these cases especially important. Uncertain ty analysis is beco ming an increasingly important part of cost-benefit assessments as th ey play a greater role in the environmental regulatory process.

EPA (2000) identified the following mini mum requirements applicable to most uncertainty analyses related to environmental regulations:

 To present the outcomes or conclusions base d on expected or most plausible values;

 To provide descriptions of all known key assumptions, biases, and omissions;

 To perform sensitivity analysis on key assumptions; and

 To justify the assumptions used in the sensitivity analysis.

Uncertainty arises in assessments from three general sources: natural variation, uncertainty in model structure, and uncertain ty in model parameters. Natural variation

results from natural differences across elem ents within a populat ion or in a population across time. For example, not all members of the United States population are expected

to value increased recreationa l fishing opportunities to the same degree. Alternatively, wide year-to-year differences in entrainm ent and impingement densities at the same

station are common. These differences in abund ance can result in large differences in the

annual economic value. Both of these exam ples can yield uncertainty in the total economic value estimated under §316(b).

Uncertainty related to model stru cture arises from the lack of knowledge as to what is the most appropriate form of the model to accura tely describe the process being modeled. For example, the form of the relationship betw een the number of trips and travel cost in aAppendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-14 simple travel cost model has been assumed to be linear, semi-log, or log by various analysts (Rosenberger and Loomis 2001). Howe ver, the most appropriate form is still a matter of debate. Likewise, alternatives that reduce total cooling water flow can result in reduced impingement. Most commonly, an assumption of a linear relationship with cooling water volume is made. However, this assumption also remains an area of debate.

Finally, uncertainty in model parameters can re sult from difficulty in measurement or in inherent variability in the model parameter. This is likely to be the most frequently encountered source of uncertainty in econom ic valuation under the Phase II Rule. Examples of this source of uncertainty include estimates of life stage-specific life table parameters for equivalent loss estimation and measurements of angler’s “willingness to pay” obtained from surveys.

In this section we address three broad areas of uncertainty: parameters used to estimate direct and indirect use benefits, questions regarding the use an d magnitude of nonuse benefits, and the economic factors used to estimate the lifetime benefits, focusing primarily on uncertainty in model parameters. Each of these areas is discussed below.

Inputs to Direct and I ndirect Use Benefits

Key input parameters addresse d in this section include:

 Natural mortality rate,

 Fishing mortality rate,

 Age of recruitment to the fishery,

 Mean weight at beginning of each stage,

 Trophic conversion factor,

 Exploitation rate for equivalent predator, and

 Recreational value per pound.

Two other key input parameters, impingeme nt rates and age composition, were not addressed in this uncertainty analysis as reliable information on the uncertainty was

unavailable from the hi storical studies.

Uncertainty for this assessment was addressed by two means. First, a sensitivity analysis was conducted on individual input parameters . Second, a Monte Carlo analysis was conducted to determine the likely overall uncer tainty in the estimates of annual economic value resulting from the current levels of uncertainty. The results of each of these analyses are provided below.A-15 Sensitivity Analysis

A sensitivity analysis was conducted individually on each of the seven input parameters listed above. Multiple calculations of annual equivalent loss and economic value were made using the extreme values (i.e., maxi mum and minimum) for each parameter while holding all other parameters constant at their most probable values. The purpose of this sensitivity analysis was to determine the pa rameters for which the current levels of uncertainty have the greatest effect on each of the estimates.

Monte Carlo Analysis

Monte Carlo analysis was used to assess the overall uncertainty in the estimates of total annual equivalent loss and economic benefits ba sed on the current levels of uncertainty in each of the seven input parameters. For each of these parameters, random values were selected from a triangular distribution, wh erein the maximum and minimum values for

the distribution were set to the maximu m and minimum values for each parameter

described earlier and the mode of the distri bution was set to the mid-point used as the best estimate for each parameter. Values for each parameter were randomly selected separately for each species and life stage a nd the Monte Carlo analysis was run using 1,000 iterations to define the resulting fre quency distribution in annual estimates of equivalent loss measures and economic benefit.