Belews Creek Steam Station 

2006-2007 IMPINGEMENT STUDY AND 

ASSESSMENT OF ADVERSE ENVIRONMENTAL 

IMPACT 

Final Report, 2009 

Duke Energy 

P.O. Box 1006 

Charlotte, NC 28201-1006 
ii 
iii 

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 sponsored by EPRI and Duke Energy. 

The Technical Report is a corporate document that should be cited in the literature in the 

following manner: 

Belews Creek Steam Station: 2006-2007 Impingement Study and Assessment of Adverse 

Environmental Impact, EPRI, Palo Alto, CA, 2009. 

v 

REPORT SUMMARY 

This report has been prepared for Duke Energy’s Belews Creek 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 Belews 

Lake, from which the cooling water is withdrawn, and its fish community. Impingement losses 

are interpreted as to whether they constitute adverse impact to the fish community of Belews 

Lake. 

Background 

Belews Creek Steam Station (BCSS) is a 2,240-MW coal-fired steam-electric generating station 

located on Belews Lake in Stokes County, North Carolina approximately 27 km northeast of 

Winston-Salem, North Carolina. It has two generating units, each capable of producing 1,120 

MW. The station uses once-through cooling for both of its units. Together, the two units have a 

design cooling water capacity of 1,454 MGD. Unit 1 began operation in August 1974 and Unit 2 

began in December 1975. BCSS operates primarily as a baseload facility. During 2002 through 

2007, the average annual capacity factor for BCSS was 74 percent, and the average total annual 

flow rate for the cooling water intake was 79 percent of the maximum design capacity. 

Impingement sampling was conducted biweekly (every other week) from 25 April 2006 through 

11 April 2007. BCSS has eight intake bays, each having a single 3/8-in. (9.5-mm) mesh panel 

screen fixed screen, with four fixed screens per unit. To sample each screen, a crane operator 

had to place a back-up screen behind the fixed screen, then lift the fixed screen panel over a 

screen wash trough that led to a collection basin before proceeding to the next fixed screen to be 

washed or sampled. In this manner, all screens associated with operating cooling water pumps 

were pressure-washed and sampled sequentially during each sampling event. 

Impingement Sampling Results 

During 26 sampling events, a total of 706 fish weighing a total of 4,247 g was collected. Eleven 

fish species were found in the impingement collections. No state or federally-listed threatened or 

endangered species were impinged. Bluegill and threadfin shad dominated the collections, 

comprising 77.2 percent and 16.9 percent of the fish collected, respectively. For the 12-month 

period from 19 April 2006 to 18 April 2007, an estimated 9,638 fish and 57.75 kg of fish 

biomass were impinged at BCSS. This estimate was derived from the density of fish collected 

during each sampling event, expressed as number per volume of cooling water withdrawn at 

each of the two generating units, extrapolated over the full 12-month period. 

Impingement rates were highest from late fall through the spring, November to early June, and 

lowest in summer and early fall, mid-June through October. This seasonal impingement pattern 

largely reflected the impingement rates for bluegill because of its dominance in the impingement 
vi 

collections. The peak impingement rate for all species combined occurred on 2-3 January 2007 

at 23.0 fish per 1,000 m3

 of water withdrawn. Bluegill accounted for 96 percent of this peak 

impingement event. Impingement rates during 2006-2007 did not appear to be influenced by 

water temperatures, lake levels, or dissolved oxygen (DO) concentrations. 

AEI Assessment Results 

The potential for the estimated levels of impingement levels at BCSS to be considered “adverse 

environmental impact” under §316(b) of the Clean Water Act was assessed. Adverse 

environmental impact was defined as an unacceptable reduction in: 

 biological integrity as measured in terms of aquatic community species composition, 

diversity, and functional organization in Belews Lake; or, 

 human use of the aquatic resources of Belews Lake, especially fishing opportunity or catch 

quantity or quality. 

The assessment used the US Environmental Protection Agency’s well-established Framework for 

Ecological Risk Assessment. Potential adverse effects were addressed from two perspectives: 

prospective (predicted future risks) and retrospective (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 operation of the BCSS cooling water intake structure on Belews 

Lake. 

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

Belews Lake. This conclusion is based on a careful evaluation of all relevant lines of evidence 

including the following: 

1. Numbers of fish lost as a result of impingement are exceedingly small compare to likely 

sizes of fish populations in Belews Lake. For all but two species, removal rates 

amounted to less than one fish every other day. For bluegill, removal rates were 

equivalent to five adults per day, likely less than or similar to the daily harvest by a single 

angler. 

2. Total number impinged each year for threadfin shad amounted to a biomass removal rate 

of less than 2 grams per surface acre of Belews Lake per year. This species is a highly 

prolific spawner with high growth rate and short life span. This high reproductive 

potential can easily compensate for the relatively small losses at BCSS with no long term 

effects. 

3. The fish community since the mid-1980s has been recovering from the historic effects of 

selenium contamination. Recent data appear to show the continuation of this recovery, 

despite any impacts potentially resulting from impingement losses at BCSS. 

4. Estimates of total fishery catch that could result from the fish impinged at BCSS had they 

survived amount to only 108 lb (49 kg) per year, most of which was bluegill. This level 

of harvest is less than what would be expected annually from a few anglers. 
vii 

5. Estimates of the total production foregone as a result of fish impinged at BCSS amounted 

to less than 730 lb (331 kg) per year of biomass. Most of this was a result of bluegill, an 

abundant species in Belews Lake. 

6. The best estimate of the total economic value of fish impinged at BCSS was $883 per 

year. Even considering the uncertainty in these estimates, it is highly unlikely that the 

economic value exceeds $1,700 per year. These values must be considered insignificant 

compared to the total economic value of the recreational fishery in Belews Lake. 

Keywords 

Clean Water Act §316(b) 

Economics 

Cooling water intake structures 

Fisheries 

Environmental impact assessment 
viii 
ix 

CONTENTS 

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

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

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

PLANT AND SOURCE WATERBODY DESCRIPTIONS .............................................................. 2-1

Belews Creek Steam Station...................................................................................................... 2-1

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

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

Belews Lake ............................................................................................................................... 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.................................................................................................................. 3-1

Community Structure.................................................................................................................. 3-3

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

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

Bluegill ................................................................................................................................... 3-4

Threadfin shad ....................................................................................................................... 3-5

Largemouth Bass .................................................................................................................. 3-5

Channel catfish ...................................................................................................................... 3-6

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

Impingement Sampling Methods ................................................................................................ 4-1

Impingement Sampling Results .................................................................................................. 4-2

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

Seasonal Patterns and Fish Size .......................................................................................... 4-4

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

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

Species-Specific Abundance and Spatial Distribution ...................................................... 4-6
x 

Annual Losses ............................................................................................................................ 4-6

Annual Variability ................................................................................................................... 4-7

Intake Operation ............................................................................................................... 4-7

Environmental Variables ................................................................................................... 4-7

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

Comparison of Annual Monitoring Programs .................................................................... 4-8

ASSESSMENT OF ADVERSE ENVIRONMENTAL 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.................................................................................................... 5-6

Effects on Human Uses.............................................................................................................. 5-7

Equivalent Loss Measures .................................................................................................... 5-7

Economic Value ..................................................................................................................... 5-8

Uncertainty in Economic Value .............................................................................................. 5-9

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

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

APPENDIX A: METHODS TO ESTIMATE EQUIVALENT LOSS AND ECONOMIC 

VALUE OF FISH IMPINGED AT BELEWS CREEK STEAM STATION ........................................ A-1

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

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

Assignment of Age Categories for Impinged Individuals ....................................................... A-4

Life Table Information ............................................................................................................ A-4

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

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

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

Fishing Capture Rates ........................................................................................................... A-6

Fishing Vulnerability Rates .................................................................................................... A-7

Weight at Beginning of Age ................................................................................................... A-7
xi 

Economic Valuation Methods ..................................................................................................... A-8

Direct Use Values .................................................................................................................. A-8

Market Values (Commercial Fishing) .................................................................................... A-8

Non-Market Direct Use Values (Recreational Fishing) .......................................................... A-9

Indirect Use Benefits ............................................................................................................. A-10

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

Adjustment for Other Species ................................................................................................ A-13

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

Inputs to Direct and Indirect Use Benefits ............................................................................. A-15

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

Monte Carlo Analysis ............................................................................................................. A-16
xii 

LIST OF FIGURES 

Figure 2-1 Location of the Belews Creek Steam Station .......................................................... 2-4

Figure 2-2 Aerial View of the Belews Creek Steam Station ...................................................... 2-5

Figure 4-1 Seasonal Pattern of Impingement Rates for All Species Combined ........................ 4-9

Figure 4-2 Seasonal Impingement Pattern and Length Frequency of Impinged Bluegill ........ 4-10

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

Shad ................................................................................................................................. 4-11

Figure 4-4 Seasonal Impingement Pattern and Length Frequency of Impinged 

Largemouth Bass ............................................................................................................. 4-12

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

Catfish .............................................................................................................................. 4-13

Figure 4-6 Daily Lake Level, Dissolved Oxygen Concentration, and Intake Water 

Temperature vs. Impingement Rate for All Species Combined, April 2006-April 

2007 ................................................................................................................................. 4-14

Figure 4-7 Daily Lake Level, Dissolved Oxygen Concentration, and Intake Water 

Temperature vs. Impingement Rate for Young-of-Year (YOY) and Yearling and 

Older (YAO) Bluegill, April 2006 – April 2007................................................................... 4-15

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 – April 2007...................................................... 4-16

Figure 5-1 Total Annual Catch of Fish in Belews Lake, 1996-2005 ........................................ 5-11

Figure 5-2 Mean Annual Catch of Bluegill, Largemouth Bass, Threadfin shad and 

Channel Catfish in Belews Lake Using Boat Electrofishing Sampling, 1996-2005 .......... 5-12

Figure 5-3 Total Number of Fish Species Found in Annual Electrofishing Surveys of 

Belews Lake, 1996-2005 .................................................................................................. 5-13

Figure 5-4 Species Composition in Belews Lake, 1996-2005 ................................................ 5-14

Figure 5-5 Percent Composition of Fish Trophic Guilds in Belews Lake, 1996-2005 ............. 5-15

Figure 5-6 Estimates of the Range of Effects of Uncertainty in Each Input Parameter on 

Estimates of Annual Economic Benefit at BCSS ............................................................. 5-16

Figure 5-7 Results of Monte Carlo Analysis of Uncertainty in Key Input Parameters on 

Estimates of Annual Economic Benefits at BCSS ............................................................ 5-17
xiii 

LIST OF TABLES 

Table 2-1 Monthly Mean Cooling Water Flow Rate (MGD) and Percentage of Maximum 

Flow Rate and Net Capacity Generation at BCSS, 2002-2007 .......................................... 2-6

Table 3-1 Common and Scientific Names of Fish Species Reported from Duke's 

Electrofishing of Belews Lake during 1994-2005 ............................................................... 3-8

Table 3-2 Number of Fish Caught Annually by Electrofishing at 20 300-m Shoreline 

Transects in Belews Lake and Percent Composition, 1996-2005 ...................................... 3-9

Table 3-3 Number of Fish Caught Annually by Electrofishing at 10 300-m Shoreline 

Transects in the Upper and Middle Regions of Belews Lake and Percent 

Composition, 1996-2005 .................................................................................................. 3-10

Table 3-4 Number of Fish Caught Annually by Electrofishing at 10 300-m Shoreline 

Transects in the Lower Region of Belews Lake and Percent Composition, 1996-

2005 ................................................................................................................................. 3-11

Table 3-5 Fish Species Occurring within the Dan River System and Listed by the North 

Carolina Natural Heritage Program as Endangered, Threatened, Of Concern, or 

Rare ................................................................................................................................. 3-12

Table 4-1 Impingement Sampling Dates and Time at BCSS during 2006-2007 ...................... 4-17

Table 4-2 Fixed Screens Sampled for Impingement, by Unit and Sampling Date, 2006-

2007 ................................................................................................................................. 4-18

Table 4-3 Estimated Total Number and Biomass of Fish Impinged at BCSS, 19 April 

2006 – 18 April 2007 ........................................................................................................ 4-19

Table 4-4 Total Number and Percent Composition of Fish Collected at BCSS, 25 April 

2006 – 11 April 2007 ........................................................................................................ 4-20

Table 4-5 Total Biomass and Percent Composition of Fish Collected at BCSS, 25 April 

2006 – 11 April 2007 ........................................................................................................ 4-20

Table 4-6 Number and Percent Composition of Taxa Other Than Fish at BCSS, 25 April 

2006 – 11 April 2007 ........................................................................................................ 4-21

Table 4-7 Estimated Total Number and Biomass of Fish Impinged Monthly at both Units 

of BCSS, 19 April 2006 – 18 April 2007 ........................................................................... 4-22

Table 4-8 Maximum Total Length (mm) Used to Distinguish Young-of-Year from 

Yearling Fish by Month .................................................................................................... 4-25

Table 4-9 Estimated Annual Impingement of Fish by Age Group at both Units of BCSS, 

19 April 2006 – 18 April 2007 ........................................................................................... 4-26

Table 4-10 Comparison of Relative Abundance of Fish Species in the 1996-2005 

Electrofishing Surveys for all Sampling Transects Combined in Belews Lake and 

the 2006-2007 BCSS Impingement Collections ............................................................... 4-27

Table 4-11 Estimated Total Number and Biomass of Fish Impinged Monthly at both 

Units of BCSS for Full Flow Operations, 19 April 2006 – 18 April 2007 ........................... 4-28

Table 5-1 Trophic Guild Assignments for Fish Species in Belews Lake ................................. 5-18
xiv

Table 5-2 Estimates of Potential Total Annual Equivalent Fishery Yield (lb) from 

Individuals Impinged for Each Target Species at BCSS .................................................. 5-19

Table 5-3 Estimates of Potential Total Annual Production Foregone (lb) from Individuals 

Impinged for Each Target Species at BCSS .................................................................... 5-19

Table 5-4 Estimates of Economic Value of Fish Impinged at BCSS ....................................... 5-20
1-1 

1 

INTRODUCTION 

Background 

ASA Analysis & Communication, Inc. has prepared this report for Duke Energy’s Belews Creek 

Steam Station (BCSS) as part of the application process for a National Pollution Discharge 

Elimination System (NPDES) permit from the North Carolina Department of Environment and 

Natural Resources (NCDENR). Under the Clean Water Act §316(b), an NPDES permit 

applicant must demonstrate that the location, design, construction and capacity of its cooling 

water intake structure represents Best Technology Available (BTA) for minimizing adverse 

environmental impact. The primary impacts of concern under §316(b) are entrainment of 

smaller aquatic organisms into the cooling water system or impingement of larger organisms 

onto traveling screens in the cooling water intake. 

In an effort to establish and enforce consistent national standards under CWA §316(b), the U.S. 

Environmental Protection Agency (EPA) published 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 design capacity of 50 million gallons per day (MGD), 

withdraw water from waters of the U.S., and use 25 percent or more of the water withdrawn for 

cooling purposes. BCSS 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 facility location. The Rule required that impingement 

mortality be reduced by 80 to 95 percent and entrainment be reduced by 60 to 80 percent, 

compared to a baseline level (i.e., the calculation baseline) specifically determined for the 

facility. Adhering to the Phase II Rule guidelines, BCSS would not be subject to entrainment 

reduction performance standards because it is located on a reservoir that has a retention time of 

1,236 days at mean annual volume (Alden 2004). This retention time exceeds the criterion of 

seven days set by the Rule as the minimum retention time for a reservoir to not be considered as 

a riverine environment. 

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, performance standards, cost-cost and cost-benefit 
Introduction 

1-2

analysis1

, compliance according to the Technology Installation and Operation Plan (TIOP), 

restoration as a compliance alternative, and “independent 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 professional judgment (BPJ) basis. However, the requirement that 

permitting agencies develop BPJ controls for cooling water intake structures that reflect BTA for 

minimizing adverse environmental impact (AEI) was retained. 

To comply with the regulations, Duke Energy prepared a Proposal for Information Collection 

(PIC) for BCSS that included the study design for impingement sampling and submitted the PIC 

to the NCDENR for review. The results of the impingement study are the subject of this report. 

Since the Phase II Rule was remanded after the PIC preparation and §316(b) is now being 

administered under BPJ, the analytical approach described in the PIC has been modified to be 

appropriate for a BPJ approach rather than for conformance to the remanded Phase II Rule. This 

report presents the results of sampling conducted at BCSS 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 Belews Lake, from which the cooling water is withdrawn, 

and its fish community. 

Report Organization 

Section 2 provides pertinent information on the structure and operation of the station’s cooling 

water intake structure, as well as a brief description of the geomorphology and aquatic habitat of 

Belews Lake. Section 3 describes the river’s fish community composition and structure, 

particularly as related to susceptibility to impingement at the BCSS intake. Section 4 presents 

the results of the 2006-2007 impingement sampling program, describes the seasonality and size 

distribution of impinged fish, and analyzes the possible influence of environmental factors and 

changes in the fish community on impingement rates. This information is used to characterize 

current levels of impingement at BCSS. Section 5 discusses the observed level of impingement 

mortality in terms of whether it constitutes adverse impact on the fish community of Belews 

Lake, using both a predictive approach and a retrospective approach. The predictive approach 

uses modeling to express impingement losses in terms of equivalent reductions in yield to the 

lake fishery and to estimate the economic value of the losses. The retrospective approach 

evaluates the composition of the current fish community to determine whether there is evidence 

of trends that could indicate impairments or instability related to impingement losses. 

 

1

 The Supreme Court has reviewed the Second Circuit Court Decision on the extent to which the cost of compliance 

can be considered relative to the benefits. Their decision was issued on 1 April 2009. The Supreme Court upheld 

EPA’s use of the Cost-Benefit Test in the Phase II Rule. This provision of the Rule allowed facilities to compare the 

cost of technologies to meet performance standards to the benefit that would be achieved. Facilities were not 

required to install technologies that had a cost significantly greater than the benefit. 
2-1 

2 

PLANT AND SOURCE WATERBODY DESCRIPTIONS 

This section describes the cooling water intake structure of the Belews Creek Steam Station 

(BCSS), its operation, and its cooling water source, Belews Lake. 

Belews Creek Steam Station 

BCSS is located on Belews Lake in Stokes County, North Carolina approximately 27 km 

northeast of Winston-Salem, North Carolina (Figure 2-1). It has two coal-fired steam electric 

generating units, each capable of producing 1,120 MW. The station uses once-through cooling 

for both of its units. Together, the two units have a design cooling water capacity of 1,454 

MGD. Unit 1 began operation in August 1974 and Unit 2 began in December 1975. 

Cooling Water Intake Structure 

As its cooling water source, BCSS uses Belews Lake, an impoundment of Belews Creek near its 

confluence with the Dan River in the northwestern Piedmont area of North Carolina. The 

cooling water intake for BCSS is located on the western end of a natural cove near mid-lake, and 

the cooling water is discharged through two outfalls to the south of the intake structure (Figure 2-

2). There are eight circulating pumps, four per unit. Each pump has a design capacity of 292.4 

cfs (131,250 gpm). 

The cooling water intake has eight bays, each one devoted to a circulating pump. Each bay 

contains an 18.5-ft (5.6-m) wide fixed screen having 3/8-in. (9.5-mm) mesh. Upstream from the 

fixed screens are trash racks made of steel bars with 2.5-in. (6.4-cm) clear spacing. An alarm 

sounds when the head differential at the fixed screens reaches 10 in (25 cm). The screens are 

cleaned by a high pressure spray when in a raised position. At full pond level and maximum 

design flow, the flow velocity approaching the fixed screens is 0.8 fps (2 cm/s). There are no 

accommodations for returning impinged fish to the lake. 

Plant Operation and Water Withdrawal 

BCSS operates primarily as a baseload facility. During 2002 through 2007, the average annual 

capacity factor for BCSS, based on Maximum Net Dependable Capacity, was 74 percent (Table 

2-1). The average total annual intake flow rate for 2002 through May 2007 was 79 percent of the 

maximum design capacity, 1,459 MGD (Table 2-1). Annual flows during this period ranged 

from 53 percent (2003) to 89 percent (2006) of the maximum design capacity. Intakes flows 
Plant and Source Waterbody Descriptions 

2-2

generally are highest during the warmer months, May-October, and lower during cooler or colder 

months, especially November - April. 

The water velocity approaching the fixed panel screens is 1.0 fps (0.3 m/s) at maximum 

drawdown lake levels with the plant operating at plant design flow (Alden 2004). At full pond 

levels and with the plant operating at plant design flow capacity, the velocity approaching the 

fixed panel screens is 0.8 ft/sec. 

Belews Lake 

Geomorphology and Aquatic Habitat 

Belews Lake was formed in 1970 as a cooling water reservoir for BCSS by impounding Belews 

Creek, East Belews Creek, and West Belews Creek in Stokes and Rockingham counties. Belews 

Lake is located within the Dan River drainage basin. The Dan River basin is the more southern 

of two major parts of the Roanoke River drainage basin, the other part being the Roanoke River 

in Virginia. The Roanoke River runs approximately 400 miles (644 km) from the Blue Ridge 

Mountains in northwestern Virginia to the Albemarle Sound on the Atlantic coast of North 

Carolina. Land use in Roanoke River subbasin 03-02-01, in which Belews Lake is located, 

consists of 73 percent forested land and 25 percent cropland and pasture, with the remaining land 

use being urban or water (NCDWQ 2001). Belews Lake drains a 119- km2

 watershed 

(NCDENR 2000). 

Belews Lake reached full pond in April 1973 at a surface elevation of 725 ft (221 m) above mean 

sea level. It has a surface area of 1,563 ha at mean water level, a mean depth of 14.9 m, a 

maximum depth of 44 m, and 141 km of shoreline (NCDENR 2000). Water surface elevation 

varies a maximum of 1.5 m. The lake stratifies during warm months and experiences a complete 

winter turnover. 

The lake is stratified from February or March until September, or sometimes as late as 

December. When the lake is stratified, maximum temperatures (e.g., in August) can reach 30-

32oC, while bottom temperatures are 10-13oC. Winter water temperatures range from 8oC to 16 o

C. Dissolved oxygen (DO) concentrations in the epilimnion exceed the water quality standard 

(5 mg/L) year-round, but DO depletion in the hypolimnion (e.g., 0-5 mg/l levels) varies annually 

(Duke 2001). 

In 1985 an air injection system was installed in the lake at a depth of 17 m to provide cool water 

to the BCSS intake by means of an upwelling of hypolimnetic water (Duke 2001). The effect of 

the system has been to deepen the late summer thermocline by 7 to 8 m. This phenomenon has 

been reported for other stratified lakes in the southeastern U.S. During recent summers, 

operation of the air injection system has been reduced to allow a greater reserve of cool water for 

a more extended period (Coughlan et al. 2006). In mid-summer, sometimes there is a 

metalimnetic DO depression that may be caused by settling of oxygen-reducing material at the 

density gradient at that depth. 
2-3

Water Quality 

Belews Lake is oligotrophic as indicated by consistently low concentrations of nutrients and 

chlorophyll a, especially in the lower portion of the lake downstream from the Route 65 

causeway (Duke 2001, NCDWQ 2001, Hining 2003, NCDENR 2006a). It has the lowest 

productivity of the Roanoke River basin lakes in North Carolina (NCDENR 2000). Water 

quality analysis has shown differences between uplake and downlake locations (upstream and 

downstream from the NC65 causeway), indicating higher productivity uplake, as well as higher 

turbidity, and iron, aluminum, total organic carbon and total suspended solid concentrations. 

Belews Lake is classified as B/C, signifying best uses for primary recreation, secondary 

recreation, and aquatic life propagation. Its WS-IV classification provides the fourth lowest 

level of watershed protection. In its 2001 and 2006 Water Quality Plans, the NCDENR Division 

of Water Quality states that Belews Lake is oligotrophic and has no indications of water quality 

problems (NCDENR 2001, 2006a). 

In the past, water quality in Belews Lake has been an issue due to the discharge of ash residue 

effluent into the lake from BCSS from 1976 until 1985. In 1978 it was determined that this 

effluent was causing a bioaccumulation of selenium in fish tissues, resulting in severe tissue 

pathology and reproductive impairment of the fish community (Lemly 1993, 2002; Duke 2001). 

In 1984, dry fly-ash collection was used to eliminate input of most selenium and other trace 

elements, and in 1985 the ash basin discharge was rerouted from the lake to the Dan River. 

Recently, water quality has been sampled semi-annually and sediment has been sampled 

annually, as required by the station’s NPDES permit. Prior to 2001, the sampling frequency was 

quarterly for water quality and semiannually for sediment quality. Recent sampling has shown 

that concentrations of selenium and arsenic in the water column have declined to non-detectable 

levels (Duke 2001, Coughlan et al. 2006). The termination of ash basin effluent discharge to 

Belews Lake also has resulted in decreasing levels of alkalinity, calcium, sulfates and specific 

conductance, especially near the former discharge area. In sediment samples taken during 1996-

2000, concentrations of selenium and arsenic have been reduced in the lake overall and have 

become less variable spatially, with some relocation to deeper areas in the lake. Arsenic and 

selenium concentrations in sediments are still elevated relative to non-impacted sites. Tissue 

analysis for selenium has been conducted on selected fish species, such as common carp, redear 

sunfish, white crappie, and black crappie. Selenium concentrations in fish from 2001 through 

2005 were less than the 5.0 μg/g standard and did not exceed 4.3 μg/g (Coughlan et al. 2006). In 

August 2000, NCDENR removed Belews Lake from a fish consumption advisory and its §303(d) 

list of impaired waters (NCDENR 2006a). 
2-4 

 Figure 2-1 Location of the Belews Creek Steam Station
 Figure 2-2 Aerial View of the Belews Creek Steam Station 
Plant and Source Waterbody Descriptions 

2-6Table 2-1 Monthly Mean Cooling Water Flow Rate (MGD) and Percentage of Maximum Flow Rate and Net Capacity 

2002-2007 

Capacity Factors 

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov D

2002 89% 85% 95% 67% 71% 84% 93% 86% 91% 77% 94% 92003 39% 49% 31% 19% 44% 51% 51% 87% 83% 49% 50% 52004 70% 94% 98% 67% 55% 49% 90% 64% 59% 88% 82% 82005 80% 91% 55% 50% 61% 88% 87% 96% 95% 78% 80% 72006 87% 68% 63% 53% 95% 84% 74% 93% 88% 77% 71% 82007 86% 90% 77% 64% 93% 83% 88% 92% 80% 64% 48% 4

Average 75% 80% 70% 53% 70% 73% 81% 87% 83% 72% 71% 7

Actual Plant Flow Rate (MGD) 

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov D

2002 1,294 1,277 1,277 982 1,323 1,431 1,424 1,418 1,409 1,119 1,245 1,2003 518 636 475 309 638 881 1,131 1,451 1,371 692 582 2004 639 398 1,002 977 997 777 1,374 1,114 1,045 1,429 1,300 1,2005 941 1,006 906 770 1,296 1,458 1,455 1,459 1,459 1,442 1,333 1,2006 1,277 1,231 1,136 992 1,432 1,375 1,459 1,459 1,455 1,326 1,112 1,2007 1,303 1,335 1,169 1,191 1,334 

Percentage of Maximum Flow Rate (2,339 CFS or 1,459 MGD) 

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov D

2002 89% 88% 88% 67% 91% 98% 98% 97% 97% 77% 85% 82003 35% 44% 33% 21% 44% 60% 78% 99% 94% 47% 40% 42004 44% 27% 69% 67% 68% 53% 94% 76% 72% 98% 89% 82005 65% 69% 62% 53% 89% 100% 100% 100% 100% 99% 91% 82006 88% 84% 78% 68% 98% 94% 100% 100% 100% 91% 76% 92007 89% 92% 80% 82% 91% N/A N/A N/A N/A N/A N/A N

Average 68% 67% 68% 60% 80% 81% 94% 95% 92% 82% 76% 7
3-1 

3 

FISH COMMUNITY DESCRIPTION 

This section describes the fish community in Belews Lake. 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 commonly found in impingement sampling at Belews Creek Steam Station 

(BCSS) are discussed as background information that might provide insights on annual or 

seasonal susceptibility to impingement. 

Description of Available Information 

The North Carolina Wildlife Resources Commission (NCWRC) and Duke Energy have 

monitored the fish community of Belews Lake since 1972 (Duke 2001, Coughlan et al. 2006). 

From 1972 through 1994 the monitoring consisted of rotenone sampling of selected coves in the 

lake. In 1994 a spring electrofishing survey was added to the rotenone survey, and after 1994 the 

spring electrofishing surveys replaced the rotenone surveys. The electrofishing surveys are 

designed with the objective of management of the developing sport fishery in the lake and to 

monitor the recovery of the fish community after its decline from the effects of selenium 

contamination in the 1970‘s caused by diversion of ash basin discharge to the lake. 

The spring electrofishing surveys are conducted annually using a boat-mounted electrofisher 

during daylight when water temperatures were between 15oC and 20oC. Twenty 300-m shoreline 

transects (five up-lake, five mid-lake, and 10 down-lake) were selected to represent existing 

habitat types. All collected fish are identified to taxon, counted, and weighed in aggregate. 

Total numbers and biomass are reported as the sum of the transect results in the uplake and 

downlake regions. Most importantly, the electrofishing data from 1996 to 2005 provide 

information on the species composition, diversity and relative abundance within the current fish 

community. 

Species Composition 

Duke’s spring electrofishing program during 1994-2005 has identified 27 distinct fish species 

(plus sunfish hybrid) and eight families in Belews Lake (Coughlan et al. 2006 and Table 3-1). 

Sportfish species include largemouth bass, white crappie, black crappie, bluegill, channel catfish, 

yellow perch, and flathead catfish. The dominant fish species are bluegill and threadfin shad, 

representing 46 percent and 18 percent of the total electrofishing catch from 1996 through 2005 

(Table 3-2). 
Fish Community Description 

3-2

There is considerable spatial heterogeneity in the fish community, as indicated by the 

electrofishing catch. For example, 25 fish species were caught in the middle and upper portions 

of the lake over the 10-year (1996-2005) period, compared to 17 species in the lower portion of 

the lake (Tables 3-3 and 3-4). Species notably absent from the lower regions of the lake included 

all catostomids (white sucker, golden redhorse, and notchlip redhorse), several of the ictalurids 

(white catfish, snail bullhead, and brown bullhead), and white perch. Other species that are 

much reduced in abundance in the lower lake include shad (gizzard and threadfin), common 

carp, shiners (satinfin and golden), crappie (white and black), and yellow perch. In contrast, 

centrarchids (largemouth bass and sunfish) are nearly equally abundant in the lower and upper 

portions of the lake. 

The differences in the number of species uplake and downlake appear to be related to water 

quality and productivity differences between the two areas. Fish biomass in the uppermost 

portion of the lake (five uplake transects) consistently has exceeded other lake regions and has 

averaged 164.6 kg/1,500 m from 1994 to 2005 (Coughlan et al. 2006). At the five midlake 

sampling transects, the electrofishing catch biomass has averaged 72.9 kg/1,500 m. Downlake, 

the biomass has averaged 16.6-25.4 kg/1,500 m since 1994. At uplake locations, there is higher 

turbidity and concentrations of iron, aluminum, total organic carbon, and total suspended solids. 

Whereas the lower portions of the lake are characterized as being oligotrophic, and middle and 

upper portions may be more mesotrophic. Also, selenium contamination has been progressively 

less at sampling locations further uplake (Barwick and Harrell 1997, Coughlan et al. 2006). 

Since Belews Lake was created in 1970, the fish community has undergone a transformation 

from its initial establishment as a lentic community, through its “collapse” in the late 1970s and 

early 1980s caused by fly and bottom ash pond overflow and selenium contamination, and 

during its subsequent recovery from the late 1980s to the present. Cove rotenone surveys in the 

lake provide data on this transformation from 1972 through 1994 (Barwick and Harrell 1997), 

and electrofishing surveys continue the data base from 1994 to present (Duke 2001, Coughlan et 

al. 2006). 

Prior to 1975-1976, the community was relatively diverse and dominated by bluegill, common 

carp, largemouth bass, and several other sunfish species (Barwick and Harrell 1997). Seleniumcontaminated water began to be discharged into the lake in the fall of 1975 and continued until 

its containment and diversion was completed in 1985. During 1976- 1981, several fish species 

progressively disappeared from the annual survey catches, leaving only seven of over two dozen 

species that were formerly there (Barwick and Harrell 1997). The total standing crop in the 

sampled lake coves was reduced from 86.7-115.4 kg/ha in 1972-1975 to only 5.7-15.0 kg/ha in 

1980-1981. At its lowest point, the fish community was dominated by fathead minnow and 

eastern mosquitofish, the latter species known to be tolerant of elevated levels of selenium 

(Lemly 2002). Other species were rendered effectively sterile due to teratogenesis and 

reproductive impairment caused by selenium contamination of tissues (Lemly 1993, 2002). 

Several species began to reappear or increase in abundance in 1984 (Barwick and Harrell 1997). 

Although present in 1976-1981, common carp and green sunfish began to dominate the catch in 

1984, and fathead minnow and eastern mosquitofish declined in abundance. After 1986, a 

stocking program was instituted to re-establish sport fish in the fish community, such as 
 

3-3

largemouth bass and bluegill. By 1990-1991, the dominance of common carp and green sunfish 

had evaporated, and species such as bluegill, largemouth bass, channel catfish, and gizzard shad 

became the dominant species. 

Community Structure 

The current fish community structure can be described in several ways. It is useful to group 

species according to their resource requirements, such as functional guilds (e.g., feeding or 

reproductive guilds) and structural guilds (e.g., habitat guilds). Feeding guilds provide 

information on probable trophic dynamics in the community, and are especially helpful for 

making management decisions if food is a limiting resource (Austen et al. 1994). 

Species caught since 1994 may best represent the current fish community structure in the lake, 

and can be assigned to primary trophic guilds (NCDENR 2006b) as follows: 

 Piscivores—largemouth bass, black crappie, white crappie, white perch, yellow perch, and 

flathead catfish 

 Insectivores—bluegill, green sunfish, redbreast sunfish, redear sunfish, hybrid sunfish, 

pumpkinseed, warmouth, satinfin shiner, golden redhorse, notchlip redhorse, white catfish, 

snail bullhead, flat bullhead, and eastern mosquitofish 

 Omnivores—gizzard shad, threadfin shad, golden shiner, fathead minnow, white sucker, 

white catfish, brown bullhead, channel catfish, and common carp 

Piscivores feed primarily on other fish as adults. Insectivores feed primarily on insects, and 

omnivores feed on anything available, including invertebrates, eggs, plant material, and detritus. 

There is a diversity of species within each trophic guild in Belews Lake. Gizzard shad and 

threadfin shad, along with the young of other species, particularly sunfish, provide the food base 

for the lake’s piscivorous predators, such as largemouth bass and crappie. 

Protected Species 

There are 10 fish species listed by the North Carolina Natural Heritage Program (LeGrande et al. 

2008) that have been reported to occur in the Dan River drainage system (Table 3-5). Three are 

classified as endangered, one as threatened, three as species of special concern, and three as 

significantly rare. None has been caught in Belews Lake during Duke’s electrofishing surveys or 

has been impinged at BCSS. 

The bigeye jumprock is a threatened species that is restricted primarily to the part of the Dan 

River running through Upper Precambrian-Paleozoic rocks, where it is associated with boulder 

substrate and undercut banks (Rohde et al. 1994, Rohde et al. 2003). The riverweed darter is a 

species of special concern that is endemic to the upper and middle Roanoke River drainage 

basin, but the only extension of its range into North Carolina occurs in the Dan River. It prefers 

rock riffle areas (Rohde et al. 1994). The Roanoke bass, Roanoke hog sucker, and quillback are 

not protected species, but are considered to be significantly rare by the NCNHP, which has 

determined that they need to be monitored due to their limited abundance in the state. 
Fish Community Description 

3-4

The remaining five species are the cutlip minnow Exoglossum maxillingua (state species of 

special concern), orangefin madtom Notorus gilberti (state endangered and federal species of 

concern), Roanoke logperch Percina rex (state and federal endangered), rustyside sucker 

Thoburnia hamiltoni (state endangered and federal species of concern), and Blue Ridge sculpin 

Cottus caeruleonmentum. All but the Roanoke logperch have been found in the Dan River in the 

Mountain, Gorge, or Piedmont regions (Rohde et al. 2001, 2003). The Roanoke logperch in the 

Roanoke River system is limited to the upper Roanoke, Pigg, and Smith rivers of Virginia 

(Rosenberger and Angermeier 2002), and thus possibly the Dan River drainage (Smith River) in 

Rockingham County (LeGrande et al. 2008). 

Target Species 

Among all fish species found in Belews Lake, a subset of species was selected for a detailed 

evaluation of impingement mortality presently occurring at the BCSS cooling water intake. 

These species either are most frequently observed in impingement collections, or are important 

because of their economic value or value to the ecosystem. 

The most abundant species in impingement collections at BCSS is the bluegill (Section 4). The 

bluegill is both an important prey species for larger predators and an important panfish species in 

the recreational fishery. As a target species, it also can act as a surrogate for other impinged 

sunfish species such as green sunfish, warmouth, redbreast sunfish, pumpkinseed, and redear 

sunfish. The second-most frequently impinged species is the threadfin shad. It is an important 

forage species in Belews Lake and prey for game species including largemouth bass, channel 

catfish, white crappie, black crappie, and white perch. The last two species selected as target 

species are the largemouth bass and channel catfish. Both support important recreational 

fisheries in the lake and are among the six most frequently impinged species. 

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

Bluegill 

Bluegill is the most abundant species in Belews Lake, comprising 48.7 percent of all fish caught 

during Duke electrofishing surveys of 1996-2005 (Table 3-2). It also was the species found most 

frequently in the 2006-2007 impingement collections, comprising 77.2 percent of the fish 

collected (Section 4). 

The bluegill is native to much of the eastern and central U.S. and occurs in warm, slow or still 

water, usually associated with aquatic vegetation and woody debris (Rohde et al. 1994). It has 

been stocked widely in the mid-Atlantic region and, in fact, was restocked into Belews Lake 

following the collapse of the fish community caused by selenium contamination (discussed 

above) to help restore the sport fishery of the lake. Previously, bluegill also had been the 

dominant species in the lake (Barwick and Harrell 1997). Individual movements tend to be 

highly localized. Their diet consists mostly of invertebrates, but larger bluegills may become 

piscivorous. 
 

3-5

In the Middle Atlantic region, bluegill spawn during May and June when water temperatures 

reach 70o

F (21oC) (Rohde et al. 1994). The spawning season can be protracted over several 

months. Bluegill are colonial breeders in the sense that spawning fish build nests that are usually 

in close proximity to each other. Males construct nests that are about 0.3 m in diameter in 

shallow water (depths of 0.3-0.9 m). The eggs from several females can be fertilized and 

deposited in the nest, which is then defended by the male until the eggs have hatched. Because 

the nests are located in shallow depths, water level fluctuations can severely impact successful 

reproduction. Nests and young can be stranded by a lowering water level or disrupted by severe 

wave action (Heman et al. 1969), or survival of the young may be reduced by increased 

ultraviolet light radiation in highly transparent water (Olson et al. 2008). 

Bluegill in the southeastern U.S. commonly begin to mature by at age 1 or 75-125 mm for both 

sexes (Spotte 2007) and can live up to 11 years. Most adults do not exceed 0.5-0.75 lb (227-340 

g) (Rohde et al 1994). 

Threadfin shad 

Threadfin shad is an excellent forage species because of its size, which seldom will exceed 150 

mm, and its great productivity. Although present in Belews Lake as early as 1974, it did not 

become a major component of the fish community until the late 1980s (Barwick and Harrell 

1997). Threadfin shad is now the second-most abundant fish species, representing 13.2 percent 

of the electrofishing catch during 1996-2005 (Table 3-2). 

The threadfin shad is a planktivore, relying on filter feeding through its gill rakers. As 

planktivores, the young and adults are food competitors for other forage species, such as bluegill 

and the young of several other species. For habitat, threadfin shad prefer open water over sand, 

mud or debris. They tend to school at shallow depths during the day and widely distribute near 

the surface at night. It is primarily a warmwater species, surviving best when winter 

temperatures exceed 10o

C (Ruelle et al. 1977). 

Threadfin shad spawn when water temperatures reach 65-70o

F (18.3-21.1oC) and can have 

multiple spawning peaks through the spring, summer and early fall (Pflieger 1997, Smith 2002). 

Spawning primarily occurs from dawn to shortly after sunrise as spawning schools gather along 

the shoreline. Their adhesive eggs are broadcast over submerged objects and hatch within three 

days. Young threadfin shad grow very rapidly (up to 25 mm. per month), with many reaching 

maturity and spawning by the end of their first summer at approximately 65 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. 

Largemouth Bass 

Largemouth bass is one of the most sought after sport fishes in the state. Originally, its 

distribution within the mid-Atlantic region was limited to South Carolina (Rohde et al. 1994). 

Through stocking it is now found throughout the region, where it can reach sizes in excess of 4.5 
Fish Community Description 

3-6

kg (10 lb) and can live up to 13 years. It is one of the most abundant predator species in Belews 

Lake and comprised 4.6 percent of the electrofishing catch during 1996-2005 (Table 3-2). 

Largemouth bass spawn when water temperatures reach 15.6-23.9oC (60-75°F) (Heidinger 

1975). In Belews Lake, water temperatures of 60-75°F would occur during April to mid-May, 

based on temperatures recorded during impingement sampling at BCSS during 2006-2007. The 

male builds a nest in substrate that typically is rocky, sand or gravel and cleared of organic debris 

and silt (Emig 1966, Rohde et al. 1994, Pflieger 1997). The nests are 0.6-1 m in diameter and 

usually widely spaced (e.g., 9.1 m apart) unless the available nesting area is limited. Nests are 

built in areas of no current or wave action (Pflieger 1997) at depths of 0.3 to 4.6 m. 

Males remain at the nest to fan the eggs to keep them silt-free and to protect the young for up to 

two weeks (Pflieger 1997). Eggs hatch in 2-5 days (Emig 1966) and the fry form tight schools 

over the nest and begin to feed in 5-8 days. The schools break up approximately one month after 

hatching when the young bass are approximately 25 mm long. Growth rates are variable and 

depend on the lake productivity and food availability. Largemouth bass typically mature at 

about ages 1 to 2 in the region (Carlander 1977, Rohde et al. 1994), or about 250 mm long (Pitlo 

et al. 2004a). 

Channel catfish 

The channel catfish is a very important and highly desirable commercial and recreational fish 

species throughout its geographic distribution and in North Carolina. The channel catfish is 

native to the central part of North America (Smith 1985), but it has been stocked in rivers and 

reservoirs throughout the southeast region. Its inclusion as a target species is based primarily on 

its importance as a recreational species. Except for the brief period of 1980-1984 (Barwick and 

Harrell 1997), it has been a resident of Belews Lake at relatively consistent levels, numerically 

averaging 0.6 percent of the electrofishing catch during 1996-2005 (Table 3-2). 

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. 2004b). Spawning generally occurs 

over a range from 21°C (69.8°F) to 29°C (84.2°F), with an optimal temperature of 27°C (80.6°F) 

(Hubert 1999). Several weeks prior to spawning, males select and clear suitable nest sites, 

usually consisting of secluded, dark areas such as hollow logs, drift piles, 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 lasts 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 existing conditions (Pitlo et al. 2004b). 

Adults may be found in many habitats including channels and large open areas, but prefer habitat 

with woody debris, bank cavities and moderate currents (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 benthic arthropods, but at 

100 mm length become omnivorous with fish making up a large part of their diet (Smith 1985). 
 

3-7

Maturity begins at age 4 and approximately 305 mm in length (Rohde et al. 1994, Pitlo et al. 

2004b). The average fecundity is 6,088 eggs per lb of body weight. 
Table 3-1 Common and Scientific Names of Fish Species Reported from Duke's Electrofishing of Belews Lake dur

Family Scientific Name Common Name 

Clupeidae-Herring Dorosoma cepedianum Gizzard shad 

Dorosoma petenense Threadfin shad 

Cyprinidae- Minnows and Carp Cyprinella analostana Satinfin shiner 

Cyprinus carpio Common carp Notemigonus crysoleucas Golden shiner Pimephales notatus Fathead minnow 

Catostomidae-Suckers Catostomus commersoni White sucker 

Moxostoma erythrurum Golden redhorse Moxostoma pappillosum Notchlip redhorse 

Ictaluridae-Bullhead catfishes Ameiurus brunneus Snail bullhead 

Ameiurus catus White catfish Ameirus nebulosus Brown bullhead Ameiurus platycephalus Flat bullhead Ictalurus punctatus Channel catfish Pylodictis olivaris Flathead catfish 

Poecilidae-Livebearers Gambusia holbrooki Eastern mosquitofish Percicthyidae-Temperate basses Morone americana White perch Centrarchidae-Sunfishes Lepomis auritus Redbreast sunfish 

Lepomis cyanellus Green sunfish Lepomis gibbosus Pumpkinseed Lepomis gulosus Warmouth Lepomis macrochirus Bluegill Lepomis microlophus Redear sunfish Lepomis sp. Hybrid sunfish Micropterus salmoides Largemouth bass Pomoxis annularis White crappie Pomoxis nigromaculatus Black crappie 

Percidae-Perches Perca flascens Yellow perch 
Table 3-2 Number of Fish Caught Annually by Electrofishing at 20 300-m Shoreline Transects in Belews Lake and Composition, 1996-2005

Species 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 TGizzard shad 24 45 50 14 24 30 11 35 92 15 

 

Threadfin shad 39 131 413 304 401 202 1,000 196 1,863 3 4

 

Satinfin shiner 18 41 8 73 109 21 143 48 13 43 

 

Common carp 105 122 65 30 29 62 30 42 60 110 

 

Golden shiner 3 8 1 - 3 2 3 12 18 3 

 

Fathead minnow - - - - 2 - - - - - 

 

White sucker - 1 1 - 1 - 1 1 2 - 

 

Golden redhorse 1 - - - - - - - - - 

 

Notchlip redhorse 2 - - - - 1 - - - - 

 

Snail bullhead 1 - - - - - - - - - 

 

White catfish - - - - 1 1 2 5 1 5 

 

Brown bullhead - - - - - - - 4 - - 

 

Flat bullhead 3 3 4 1 - - 4 - - - 

 

Channel catfish 25 18 36 7 2 16 7 34 34 34 

 

Flathead catfish - - - - - - - - 1 2 

 

Eastern mosquitofish - - - - - - - 1 - - 

 

White perch 64 31 71 33 30 172 35 157 208 102 

 

Redbreast sunfish 303 418 565 486 351 366 388 306 308 256 3

 

Green sunfish 27 39 20 11 22 6 26 24 50 54 

 

Pumpkinseed 13 - 1 - - - - 1 - - 

 

Warmouth 9 6 7 5 4 15 15 12 20 32 

 

Bluegill 858 836 997 1,437 1,132 2,104 2,204 1,599 2,553 3,111 16

 

Redear sunfish 156 75 105 194 175 195 135 183 150 208 1

 

Hybrid sunfish 15 28 38 57 72 60 73 27 71 89 

 

Largemouth bass 167 131 174 161 142 172 133 117 226 171 1

 

White crappie 193 36 48 42 39 116 30 48 201 82 

 

Black crappie 27 19 25 42 35 39 - 16 53 23 

 

Yellow perch 343 112 106 67 92 88 133 150 223 130 1

 

Total 2,396 2,100 2,735 2,964 2,666 3,668 4,373 3,018 6,147 4,473 34

 
Fish Community Description 

3-10Table 3-3 Number of Fish Caught Annually by Electrofishing at 10 300-m Shoreline Transects in the Upper and MidBelews Lake and Percent Composition, 1996-2005 

Species 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Gizzard shad 24 44 49 12 24 30 11 34 88 15 

 

Threadfin shad 39 131 413 304 401 137 1,000 196 1,863 3 4

 

Satinfin shiner 18 9 7 68 68 19 120 43 13 15 

 

Common carp 95 96 59 26 29 62 29 39 58 110 

 

Golden shiner 3 8 1 - 2 2 2 8 18 3 

 

Fathead minnow - - - - 2 - - - - - 

 

White sucker - 1 1 - 1 - 1 1 2 - 

 

Golden redhorse 1 - - - - - - - - - 

 

Notchlip redhorse 2 - - - - 1 - - - - 

 

Snail bullhead 1 - - - - - - - - - 

 

White catfish - - - - 1 1 2 5 1 5 

 

Brown bullhead - - - - - - - 4 - - 

 

Flat bullhead 3 2 1 1 - - 3 - - - 

 

Channel catfish 22 10 31 5 1 13 4 30 21 33 

 

Flathead catfish - - - - - - - - - - 

 

Eastern mosquitofish - - - - - - - - - - 

 

White perch 64 31 71 33 30 172 35 157 208 102 

 

Redbreast sunfish 201 292 295 256 170 89 60 38 87 82 1

 

Green sunfish 27 39 15 11 22 4 12 24 48 48 

 

Pumpkinseed 13 - 1 - - - - 1 - - 

 

Warmouth 7 5 1 5 3 2 2 7 12 13 

 

Bluegill 548 671 696 1,034 802 1,001 1,542 819 1,999 2,249 11

 

Redear sunfish 99 38 52 154 128 85 63 109 97 174 

 

Hybrid sunfish 11 22 21 24 27 9 3 2 25 15 

 

Largemouth bass 97 75 96 92 77 76 85 62 140 106 

 

White crappie 193 36 48 42 39 116 30 48 201 82 

 

Black crappie 26 19 25 42 35 39 - 16 46 23 

 

Yellow perch 343 112 106 67 92 88 133 150 214 130 1

 

Total 1,837 1,641 1,989 2,176 1,954 1,946 3,137 1,793 5,141 3,208 24

 
Table 3-4 Number of Fish Caught Annually by Electrofishing at 10 300-m Shoreline Transects in the Lower Region Percent Composition, 1996-2005 

Species 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 TGizzard shad - 1 1 2 - - - 1 4 - 

 

Threadfin shad - - - - - 65 - - - - 

 

Satinfin shiner - 32 1 5 41 2 23 5 - 28 

 

Common carp 10 26 6 4 - - 1 3 2 - 

 

Golden shiner - - - - 1 - 1 4 - - 

 

Fathead minnow - - - - - - - - - - 

 

White sucker - - - - - - - - - - 

 

Golden redhorse - - - - - - - - - - 

 

Notchlip redhorse - - - - - - - - - - 

 

Snail bullhead - - - - - - - - - - 

 

White catfish - - - - - - - - - - 

 

Brown bullhead - - - - - - - - - - 

 

Flat bullhead - 1 3 - - - 1 - - - 

 

Channel catfish 3 8 5 2 1 3 3 4 13 1 

 

Flathead catfish - - - - - - - - 1 2 

 

Eastern mosquitofish - - - - - - - 1 - - 

 

White perch - - - - - - - - - - 

 

Redbreast sunfish 102 126 270 230 181 277 328 268 221 174 2

 

Green sunfish - - 5 - - 2 14 - 2 6 

 

Pumpkinseed - - - - - - - - - - 

 

Warmouth 2 1 6 - 1 13 13 5 8 19 

 

Bluegill 310 165 301 403 330 1,103 662 780 554 862 5

 

Redear sunfish 57 37 53 40 47 110 72 74 53 34 

 

Hybrid sunfish 4 6 17 33 45 51 70 25 46 74 

 

Largemouth bass 70 56 78 69 65 96 48 55 86 65 

 

White crappie - - - - - - - - - - 

 

Black crappie 1 - - - - - - - 7 - 

 

Yellow perch - - - - - - - - 9 - 

 

Total 559 459 746 788 712 1,722 1,236 1,225 1,006 1,265 9

 
Fish Community Description 

3-12

Table 3-5 Fish Species Occurring within the Dan River System and Listed by the North Carolina 

Natural Heritage Program as Endangered, Threatened, Of Concern, or Rare 

Species Status* Rank** 

Blue Ridge sculpin SC S1 

Bigeye jumprock T S1 

Cutlip minnow SC S1 

Orangefin madtom E S1 

Quillback SR S1 

Riverweed darter SC S3 

Roanoke bass SR S2 

Roanoke hog sucker SR S3 

Roanoke logperch E S1 

Rustyside sucker E S1 

*E= endangered, T = threatened, SC = special concern, SR = significantly rare 

**S1 = critically imperiled in North Carolina due to extreme rarity or some factor(s) making it especially vulnerable to 

extirpation (local extinction) 

 S2 = imperiled in North Carolina due to rarity or some factor(s) making it very vulnerable to extirpation 

 S3 = vulnerable to extinction in North Carolina either because rare or uncommon, or found only in a restricted 

range (even if abundant in some locations), or due to other factors making it vulnerable to extirpation 
 

4-1

4 

IMPINGEMENT MORTALITY 

This section presents the methods and results of an impingement monitoring program 

conducted at BCSS during 2006-2007. The observed effects of seasonality and 

environmental variables, including lake level, dissolved oxygen (DO) concentration and 

water temperature, on impingement rates are discussed for dominant fish species in the 

2006-2007 collections. The potential for inter-annual variability in impingement losses at 

BCSS also is discussed. 

Impingement Sampling Methods 

Current impingement at BCSS was evaluated by a monitoring program conducted during 

2006-2007 by MACTEC Engineering and Consulting, Inc. 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 Quality Assurance/Quality Control (QA/QC) procedures. 

BCSS has eight intake bays, each of which has a fixed 3/8-in. (9.5-mm) mesh panel 

screen (Section 2). To sample impingement on each screen, a crane operator had to place 

a back-up screen behind the fixed screen to be sampled, then lift the fixed screen panel 

over a screen wash trough that led to a collection basin. A 1/4-in. (6.4-mm) mesh net was 

inserted into the collection basin to recover the impinged fish sample from each washed 

fixed screen. The screen panels then were pressure-washed, after which the back-up 

screen was placed behind the next screen to be sampled. In this manner, all screens 

associated with operating cooling water pumps were washed and sampled sequentially 

during each sampling event. Units that operated on each sampling date and associated 

screens sampled are shown in Table 4-1. 

Sampling during the 2006-2007 impingement monitoring program was conducted 

biweekly (every other week) starting on 25 April 2006 and continuing until 11 April 2007 

(Table 4-2). Prior to sampling, the fixed panel screens were raised and cleaned, then 

replaced and allowed to accumulate impinged fish for approximately 24 h. 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 also was examined 

for any impinged fish that might have washed off the screen that had been lifted.2

 

 

2 Only partially decomposed fish were observed, indicating they had been previously dead.
Impingement Mortality 

4-2

Impinged specimens recovered from the collection basin net were processed in 

accordance with Standard Operating Procedures (SOP) prepared specifically for this 

facility prior to the start of data collection. Individual fish counts by species and length 

and weight measurements were recorded. 

Impingement Sampling Results 

For the 12-month period from 19 April 2006 to 18 April 2007, an estimated 9,638 fish 

and 57.75 kg of fish biomass were impinged at BCSS (Table 4-3), based on the collection 

of 706 impinged fish (Table 4-4) and 4,247 g of fish biomass (Table 4-5). This estimate 

was derived from the density of fish collected during each sampling event, expressed as 

number per volume of cooling water withdrawn at each of the two generating units, 

extrapolated over the full 12-month period. To estimate the density at each unit for each 

sampling event, the collection totals for all screens at that unit were combined and 

divided by the total flow volume for the unit during the 24-h sampling period. Total 

daily cooling water intake flow volumes for sampling days were obtained from plant 

operation records. 

Impingement density values for non-sampled days were estimated by interpolating 

between density values for the sampling days 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

1 2

1

   

  

i

s s uj

n

j

Np DsiFsi D D F 

Where 

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

bordering the period 

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

Fsi = 24-hour cooling water flow volume on sampling day i in period p 

Fuj = 24-hour cooling water flow volume 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 

two units. 
 

4-3

Species Composition 

A total of 11 distinct fish species were found in the impingement collections (Tables 4-4 

and 4-5). In addition, fish identified only to family Clupeidae (herring/shad), 

Centrarchidae (sunfish), and Cyprinidae (minnows/shiners/carp) or to genus Lepomis

were collected; identification of these fish to species was not possible due to the capture 

of incomplete specimens or physical damage. 

Bluegill and threadfin shad dominated the collections, comprising 77.2 percent and 16.9 

percent of the fish collected, respectively (Table 4-4). Together these two species 

accounted for 94.0 percent of the estimated total annual impingement in terms of 

numbers (Table 4-3) and 76.5 percent of the estimated total impinged biomass. When 

included with largemouth bass and channel catfish, these four target fish species 

(described in Section 3) accounted for 95.7 percent of the estimated numbers impinged 

and 82.0 percent of the fish biomass impinged during the 12-month period. 

Centrarchids were by far the most dominant fish, accounting for 80.9 percent of the 

estimated total annual impingement, followed by clupeids with 18.1 percent. Besides 

bluegill, the centrarchid species included green sunfish, hybrid sunfish, redbreast sunfish, 

redear sunfish, largemouth bass, and spotted bass (Table 4-3). Besides threadfin shad, 

the clupeid species included gizzard shad and alewife. The remaining 1 percent of the 

estimated total annual impingement consisted of channel catfish (0.7 percent), 

unidentified cyprinind species (0.1 percent), and white perch (0.1 percent). 

Two species identified in impingement collections—alewife and spotted bass—have not 

been found by electrofishing in Belews Lake during 1994-2005 (Tables 3-1 through 3-4). 

Alewives were present in the lake soon after its creation, as documented by cove 

rotenone sampling in 1972 and 1973 (Barwick and Harrell 1997), and occur in Kerr 

Reservoir and occasionally in the Dan River downstream from Belews Lake (Rohde et al. 

2003). However, the taxonomic identification of alewife collected during impingement 

sampling was not verified. In 2007, Duke researchers captured blueback herring, a 

species previously not found in the lake. It is possible that the fish identified as alewives 

may have been blueback herring, due to the morphological similarity of the two species. 

Spotted bass have never been identified as occurring in Belews Lake, either by Duke 

Energy or NCWRC. The single 140-mm specimen collected during impingement 

sampling was not retained for taxonomic verification. It may have been a largemouth 

bass that was misidentified because of its damaged condition. 

No federally or state-listed species were impinged. In addition to fish, the invertebrate 

Asiatic clam (Corbicula), crayfish, and a freshwater mussel were found in impingement 

collections (Table 4-6). 
Impingement Mortality 

4-4

Seasonal Patterns and Fish Size 

Impingement rates were highest from late fall through the spring, November to early 

June, and lowest in summer and early fall, mid-June through October (Figure 4-1 and 

Table 4-7). This seasonal impingement pattern reflected the impingement rates for 

bluegill (Figure 4-2) because of its dominance in the impingement collections. The peak 

impingement rate for all species combined occurred on 2 January 2007 at 23.0 fish per 

1,000 m3

 of water withdrawn. Bluegill accounted for 96 percent of this peak 

impingement event. 

Impinged bluegill ranged in size from 48 to 139 mm total length (TL). Based on their 

observed length frequency distribution and literature values on age-length relationships 

for bluegill (Table 4-8), more than two-thirds of the impinged bluegills were yearling or 

older fish (Table 4-9). Yearling or older fish comprised the majority of bluegills 

impinged from November through March, while young-of-year (YOY) fish from the 

2005 year class were more common in the spring collections, April-June (Figure 4-2). 

Threadfin shad were impinged throughout the year, but peak impingement occurred in 

February-March and early August (Figure 4-3). These periods of peak impingement 

involved both YOY and yearling or older fish; overall, nearly half of the impinged 

threadfin shad were estimated to be yearling or older fish, but the probable age of 

approximately 12 percent of those collected could not be determined due to physical 

damage (Table 4-9). Impinged threadfin shad ranged in length from 33 to 120 mm TL 

(Figure 4-3). 

Seven largemouth bass appeared in the impingement collections and ranged in size from 

48 mm TL and 1.2 g to 237 mm TL and 124 g. They were impinged during the summer 

and fall (Figure 4-4). The majority (six fish or 86 percent) were considered to be YOY 

fish (Table 4-9). 

Five impinged channel catfish were collected, ranging in size from 100 mm TL and 7.4 g 

to 190 mm TL and 64 g. One fish was collected per month during the months of May, 

July, November, December, and February (Figure 4-5). All were considered to be 

yearling or older fish (Table 4-9). 

There was an unusually high frequency (269 of 975 collected fish or 27.6 percent) of fish 

collected that were judged to have died previous to the 24-h impingement collection 

period based upon their decomposed state and extensive fungal growth. The great 

majority (75 percent) were bluegill, but other species included alewife, channel catfish, 

largemouth bass, redbreast sunfish, threadfin shad, and white perch. Some could not be 

identified beyond genus (Lepomis) or family (herring), or were totally unidentified 

because of their extremely poor condition. These previously dead fish may have 

remained on the fixed screen panels during the washing prior to the start of the 24-h 

collection or have been near the screens prior to the collection period. They were not 

included in the analysis or impingement estimates. 
 

4-5

The seasonality of impingement for species other than the four species discussed above 

can be summarized as follows (Table 4-7): 

Gizzard shad—November 

Redbreast sunfish—year-round 

Redear sunfish—September 

Redeye bass—April-May and August 

Spotted bass—March-April 

White perch—September-October 

Variables Affecting Impingement Rates 

Three categories of variables potentially affecting impingement rates are discussed: 

environmental variables, species-specific abundance, and spatial distribution. 

Environmental Variables 

Three potentially important environmental variables that could affect impingement rates 

are water temperature, dissolved oxygen concentration (DO), and lake level or elevation. 

Mean daily water temperature records from the BCSS intake and daily lake level data 

were available for the sampling period from 25 April 2006 to 11 April 2007. DO 

readings were made by MACTEC sampling crews at the intake on the day of 

impingement sampling, generally in the morning between 0900 h and 1100 h. 

The mean daily intake temperature varied seasonally from a low of 53.2o

F on 19 

February 2007 to a high of 92.7oF on 5 August 2006 (Figure 4-6). The lake level varied 

only 1 ft (0.3 m) during the 12-month sampling interval, with a maximum elevation of 

724.8 ft above mean sea level and a minimum elevation of 723.8 ft above mean sea level 

(amsl). What little change in elevation did occur was primarily limited to summer 

months, June-September (Figure 4-6). Full pond is 725 ft amsl. DO readings on 

impingement sampling days also showed little seasonal variation, ranging from 5.98 

mg/L on 10 May 2006 to 10.73 mg/L on 24 May 2006 (Figure 4-6). 

Peak impingement rates for all species combined occurred on 2-3 January 2007 (Figure 

4-6). This was a period of declining water temperatures prior to the minimum 

temperature being reached in mid-February. On 2 January 2007, the mean daily water 

temperature at the intake was 60 oF and the DO concentration was 7.4 mg/L (Figure 4-6). 

Neither of these readings would indicate stressful conditions. The lake level on this date 

was 724.7 ft, which was typical for this period and near full pond (Figure 4-6). 

The peak impingement on 2-3 January 2007 almost exclusively consisted of bluegill of 

various ages and sizes (Figure 4-7). While most impingement of yearling and older 

bluegill occurred from November through March, the temperature, DO, and lake level on 

2 January did not appear to be the immediate cause for the impingement spike. Youngof-year bluegill (YOY) impingement also was higher on this date, but for this age group 
Impingement Mortality 

4-6

there was another period of peak impingement in May and early June when temperatures 

were rising (up to 72-82o

F) and DO levels were fluctuating from 6.0 to 10.7 mg/L (Figure 

4-7). It would appear that the increased impingement rates for bluegill observed on these 

dates were related to factors other than temperature, DO level, and lake level. 

Threadfin shad, the other species dominating impingement collections, experienced peak 

impingement on 27-28 February 2007 (YOY fish) and 27-28 March 2007 (yearling and 

older fish). On these dates, water temperatures were beginning to rise from the winter 

minimum, but DO and lake levels were stable (Figure 4-8). Mean daily water 

temperature was 60.2 oF on 27-28 February and 56.1 oF on 27-28 March. DO 

concentration was 7.4 mg/L on 27-28 February and 8.2 mg/L on 27-28 March. The lake 

level was 724.6-724.7 ft amsl on these dates, i.e., near full pond. As with bluegill, the 

peak impingement events for threadfin shad were not obviously related to water 

temperature, DO, or lake level as potentially controlling or stressful factors. 

Species-Specific Abundance and Spatial Distribution 

The electrofishing surveys conducted by Duke during 1996-2005 provide data on the 

relative abundance of fish species in Belews Lake, which can be compared to the 2006-

2007 impingement data to provide insight into the role of species-specific abundance and 

spatial distribution on the susceptibility of species to impingement at BCSS. Based on 

this comparison, it appears that the abundance of an individual species influences its 

susceptibility to impingement. Impingement at BCSS was totally dominated by two 

species—bluegill and threadfin shad. These two species accounted for 94 percent of the 

impinged fish collected in 2006-2007 and also were the two most abundant species in the 

1996-2005 electrofishing catches for the entire lake (Table 4-10). While impingement of 

other species was very limited (<11 specimens per taxon collected), the third and fourth 

most frequently impinged species, redbreast sunfish and largemouth bass, were also 

ranked third and fourth in relative abundance among species captured by electrofishing. 

Two relatively common fish species, yellow perch and white crappie (ranked sixth and 

eighth in the lake), were not found in impingement collections (Table 4-10). Their 

absence may be related to their spatial distribution in the lake, indicated by their reduced 

catch in the lower lake than in upper and middle regions (see Section 3). Overall low 

impingement levels during 2006-2007 may be responsible for the absence of several less 

abundant species, simply by chance. 

Annual Losses 

Impingement sampling during 2006-2007 provides a single year’s estimate of seasonal 

and annual impingement at the BCSS intake, and the best available estimate of current 

impingement for several reasons. Data collected by the 2006-2007 monitoring program 

and ongoing electrofishing sampling are representative of the current relative abundance 

of fish species near the intake and their susceptibility to impingement. In 2006-2007, 

station operation was consistent with its forecasted use as a baseload facility, with 
 

4-7

cooling water flow rates of approximately 90 percent capacity. The monitoring program 

design encompassed complete diel and seasonal cycles of impingement, and the program 

was conducted with strict adherence to Standard Operating Procedures. 

Two alternative approaches to estimating the current levels of impingement are: (1) 

“Normal Operations” representing recent historical and projected operation of the 

facility, and (2) “Full Operations” representing the full design capacity for water 

withdrawals by the facility. Normal Operations would be an estimated annual total of 

9,638 impinged fish weighing 57.8 kg (Table 4-3 in Section 4). An estimate for Full 

Operations can be derived by substituting the design capacity for cooling water flow rates 

(1,454 MGD) rather than actual mean daily flow rates recorded during the 12-month 

sampling interval. Impingement losses under full operation are estimated to total 10,924 

fish weighing 65.3 kg (Table 4-11). These totals represent a 13 percent increase in the 

numbers and biomass of impinged fish over Normal Operations. 

Annual Variability 

Data collected by the 2006-2007 monitoring program are representative of current 

conditions, especially the relative abundance of fish species in the vicinity of the intake 

and their susceptibility to impingement. The data can be interpreted in the context of the 

existing conditions. Seasonal and annual variability in impingement mortality could 

occur if cooling water intake operation, lake level, water temperatures, DO concentration, 

or fish abundance varied to a significant degree. 

Intake Operation 

BCSS is operated as a baseload facility, with an average annual capacity factor of 74 

percent during 2002-2007 (Section 2). The average annual intake flow rate over this 

period was 79 percent of the maximum design capacity. BCSS is expected to continue to 

operate as a baseload facility, so the influence of cooling water flow rates on the 

variability of annual impingement rates should be minimal. 

Intakes flows generally were highest during May-October (Table 2-1), coinciding with 

the period of highest electricity demand. With the exception of May and early June when 

YOY threadfin shad were impinged, impinged fish densities were the lowest recorded 

during 2006-2007 at BCSS (Figure 4-6). This inverse relationship between intake flow 

rates and observed impingement densities helps to reduce annual impingement. 

Environmental Variables 

Impingement rates during 2006-2007 did not appear to be influenced by water 

temperatures, lake levels, or DO concentrations. However, these variables might 

influence impingement rates in future years. 
Impingement Mortality 

4-8

Fish Abundance 

The abundance, species composition, and size composition of fishes in Belews Lake and 

near the BCSS cooling water intake may vary annually as the result of changing habitat 

suitability, trophic dynamics, reproductive success, interspecific competition, or several 

other factors. These changes could affect impingement rates at the intake, particularly if 

the majority of impinged fish are YOY and the strength of successive year classes of 

YOY fish typically are volatile. Some annual variability would appear random while 

some may reflect long-term trends in the abundance of individual species. 

Comparison of Annual Monitoring Programs 

The results of two or more annual monitoring programs conducted at the facility can be 

compared to evaluate inter-annual variability. However, impingement at BCSS has not 

been studied in the past, so no historical information is available. 
 

4-9

Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

0

5

10

15

20

25

Weekly Impingement Rates for All Species Combined

2006 - 2007

Impingement Rate per 106 m3

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

4-10

0 5 10 15 20 25 30 35 40 45

0

10

20

30

40

50

Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

0

5

10

15

20

Impingement Rates by Age

 Young-of-Year

 Yearling & Older

 Undetermined

Bluegill

2006 - 2007

Impingement Rate per 106 m3

Length Frequency

 Percent in Length Interval

 Midpoint of Length Interval (cm)

Figure 4-2 Seasonal Impingement Pattern and Length Frequency of Impinged Bluegill 
 

4-11

0 5 10 15 20 25 30 35 40 45

0

10

20

30

40

50

60

Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

0

1

2

3

4

5

Impingement Rates by Age

 Young-of-Year

 Yearling & Older

 Undetermined

Threadfin shad

2006 - 2007

Impingement Rate per 106 m3

Length Frequency

 Percent in Length Interval

 Midpoint of Length Interval (cm)

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

Shad 
Impingement Mortality 

4-12

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 Apr

0

1

2

3

4

5

Impingement Rates by Age Young-of-Year

 Yearling & Older

 Undetermined

Largemouth bass

2006 - 2007

Impingement Rate per 106 m3

Length Frequency

 Percent in Length Interval

 Midpoint of Length Interval (cm)

Figure 4-4 Seasonal Impingement Pattern and Length Frequency of Impinged 

Largemouth Bass 
 

4-13

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 Apr

0

1

2

3

4

5

Impingement Rates by Age Young-of-Year

 Yearling & Older

 Undetermined

Channel catfish

2006 - 2007

Impingement Rate per 106 m3

Length Frequency

 Percent in Length Interval

 Midpoint of Length Interval (cm)

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

Catfish 
Impingement Mortality 

4-14

722

723

724

725

726

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

0

5

10

15

20

25

Date

Impingement Rate per 106

m3

40

50

60

70

80

90

100

Mean Intake Temp. (

OF)

0

2

4

6

8

10

12

14

16

 Dissolved Oxygen)

Dissolved Oxygen (mgL-1

)

 Elevation

 Elevation (ft-msl)

Figure 4-6 Daily Lake Level, Dissolved Oxygen Concentration, and Intake Water 

Temperature vs. Impingement Rate for All Species Combined, April 2006-April 2007 
 

4-15

722

723

724

725

726

0

2

4

6

8

10

12

14

16

18

20

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

0

1

2

3

4

5

6

7

8

9

10

 YOY

YAO Impingement Rate per 106

m3

Date

YOY Impingement Rate per 106

m3

40

50

60

70

80

90

100

Mean Intake Temp. (OF)

0

2

4

6

8

10

12

14

16

Dissolved Oxygen

Dissolved Oxygen (mgL-1)

Elevation

Elevation (ft-msl)

 YAO

Figure 4-7 Daily Lake Level, Dissolved Oxygen Concentration, and Intake Water 

Temperature vs. Impingement Rate for Young-of-Year (YOY) and Yearling and Older (YAO) 

Bluegill, April 2006 – April 2007 
Impingement Mortality 

4-16

722

723

724

725

726

0

1

2

3

4

5

6

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

0

1

2

3

4

 YOY

YAO Impingement Rate per 106

m3

Date

YOY Impingement Rate per 106

m3

40

50

60

70

80

90

100

Mean Intake Temp. (OF)

0

2

4

6

8

10

12

14

16

Dissolved Oxygen

Dissolved Oxygen (mgL-1)

Elevation

Elevation (ft-msl)

 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 – April 2007
 

4-17

Table 4-1 Impingement Sampling Dates and Time at BCSS during 2006-2007 

Sampling Dates Sampling Interval (24-h) 

25-26 April 2006 1004-1334 

9-10 May 2006 1000-1404 

23-24 May 2006 1000-1412 

7-8 June 2006 0857-1345 

20-21 June 2006 1030-1350 

4-5 July 2006 0800-1330 

18-19 July 2006 0827-1335 

1-2 August 2006 0815-1325 

15-16 August 2006 0810-1325 

29-30 August 2006 0815-1320 

12-13 September 2006 0830-1315 

26-27 September 2006 0835-1320 

10-11 September 2006 0820-1315 

24-25 September 2006 0820-1305 

7-8 November 2006 1030-1340 

21-22 November 2006 0805-1135 

5-6 December 2006 0820-1305 

19-20 December 2006 0815-1100 

2-3 January 2007 0820-1305 

16-17 January 2007 0815-1305 

30-31 January 2007 0815-1320 

13-14 February 2007 0810-1100 

27-28 February 2007 0815-1245 

13-14 March 2007 0830-1310 

27-28 March 2007 0815-1010 

10-11 April 2007 0810-1045 
Impingement Mortality 

4-18

Table 4-2 Fixed Screens Sampled for Impingement, by Unit and Sampling Date, 2006-2007 

 Unit 1 Unit 2 

Screen 1A 1B 1C 1D 2A 2B 2C 2D 

Date Sampled 

25-Apr-06 1 1 1 1 1 1 

9-May-06 1 1 1 1 1 1 1 1 

23-May-06 1 1 1 1 1 1 1 1 

7-Jun-06 1 1 1 1 1 1 1 

20-Jun-06 1 1 1 1 1 1 1 1 

4-Jul-06 1 1 1 1 1 1 1 1 

18-Jul-06 1 1 1 1 1 1 1 1 

1-Aug-06 1 1 1 1 1 1 1 1 

15-Aug-06 1 1 1 1 1 1 1 1 

29-Aug-06 1 1 1 1 1 1 1 1 

12-Sep-06 1 1 1 1 1 1 1 1 

26-Sep-06 1 1 1 1 1 1 1 1 

10-Oct-06 1 1 1 1 1 1 1 1 

24-Oct-06 1 1 1 1 1 1 1 

7-Nov-06 1 1 1 

21-Nov-06 1 1 1 1 1 1 1 1 

5-Dec-06 1 1 1 1 1 1 1 1 

19-Dec-06 1 1 1 1 1 1 

2-Jan-07 1 1 1 1 1 1 1 1 

16-Jan-07 1 1 1 1 1 1 1 1 

30-Jan-07 1 1 1 1 1 1 1 1 

13-Feb-07 1 1 1 1 1 1 1 1 

27-Feb-07 1 1 1 1 1 1 1 1 

13-Mar-07 1 1 1 1 1 1 1 1 

27-Mar-07 1 1 1 1 

10-Apr-07 1 1 1 1 1 1 1 1 

Times Sampled: 23 24 25 25 25 25 22 24 

Samples per Unit 97 96 

Sampled/Analyzed 1 

pumps off 

 
 

4-19

Table 4-3 Estimated Total Number and Biomass of Fish Impinged at BCSS, 19 April 2006 – 

18 April 2007 

Unit 1 Unit 2 Total 

Species No. Wt. (g) No. Wt. (g) No. Wt. (g) 

Alewife 32 141 64 536 96 676

Gizzard shad 12 3,613 0 0 12 3,613

Threadfin shad 592 2,859 1,037 3,080 1,628 5,939

Unidentified clupeid 0 0 13 110 13 110

Unidentified cyprinid 0 0 14 11 14 11

Channel catfish 26 261 40 1,007 67 1,268

White perch 0 0 13 125 13 125

Redbreast sunfish 43 911 106 1,876 149 2,786

Green sunfish 14 113 13 84 27 197

Bluegill 2,708 14,016 4,728 24,251 7,436 38,268

Redear sunfish 0 0 14 2,286 14 2,286

Hybrid sunfish 14 25 14 36 28 61

Sunfishes 14 0 0 0 14 0

Lepomis sp. 0 0 14 0 14 0

Largemouth bass 27 77 69 1,817 96 1,894

Spotted bass 12 359 5 156 18 516

Total 3,494 22,375 6,145 35,376 9,638 57,751
Impingement Mortality 

4-20

Table 4-4 Total Number and Percent Composition of Fish Collected at BCSS, 25 April 

2006 – 11 April 2007 

Unit 1 Unit 2 Total 

Species No. % No. % No. % 

Alewife 2 0.79 5 1.10 7 0.99 

Gizzard shad 1 0.40 - - 1 0.14 

Threadfin shad 44 17.46 75 16.52 119 16.86 

Unidentified clupeid - - 1 0.22 1 0.14 

Unidentified cyprinid - - 1 0.22 1 0.14 

Channel catfish 2 0.79 3 0.66 5 0.71 

White perch - - 1 0.22 1 0.14 

Redbreast sunfish 3 1.19 8 1.76 11 1.56 

Green sunfish 1 0.40 1 0.22 2 0.28 

Bluegill 194 76.98 351 77.31 545 77.20 

Redear sunfish - - 1 0.22 1 0.14 

Hybrid sunfish 1 0.40 1 0.22 2 0.28 

Lepomis sp. - - 1 0.22 1 0.14 

Sunfishes 1 0.40 - - 1 0.14 

Largemouth bass 2 0.79 5 1.10 7 0.99 

Spotted bass 1 0.40 - - 1 0.14 

Total 252 100.00 454 100.00 706 100.00 

Table 4-5 Total Biomass and Percent Composition of Fish Collected at BCSS, 25 April 

2006 – 11 April 2007

Unit 1 Unit 2 Total 

Species Wt. (g) % Wt. (g) % Wt. (g) % 

Alewife 10 0.59 43 1.64 52 1.23 

Gizzard shad 293 17.76 - - 293 6.90 

Threadfin shad 214 12.95 205 7.90 419 9.86 

Unidentified clupeid - - 8 0.32 8 0.20 

Unidentified cyprinid - - 1 0.03 1 0.02 

Channel catfish 20 1.19 72 2.79 92 2.17 

White perch - - 10 0.37 10 0.22 

Redbreast sunfish 65 3.94 142 5.45 207 4.87 

Green sunfish 8 0 6 0.25 15 0.34 

Bluegill 1,004 60.87 1,810 69.68 2,814 66.26 

Redear sunfish - - 163 6.29 163 3.85 

Hybrid sunfish 2 0.11 3 0.10 4 0.10 

Lepomis sp. - - - - - - 

Sunfishes - - - - - - 

Largemouth bass 6 0.34 135 5.19 140 3.30 

Spotted bass 29 1.75 - - 29 0.68 

Total 1,649 100 2,597 100.00 4,247 100.00 
 

4-21

Table 4-6 Number and Percent Composition of Taxa Other Than Fish at BCSS, 25 April 

2006 – 11 April 2007

Taxon Count Percent 

Biomass 

(g) Percent 

Corbicula 341 98.55 747 89.88 

Crayfish 4 1 80 9.58 

Freshwater mussel 1 0 5 0.54 

Total 346 100 831 100 
Impingement Mortality 

4-22Table 4-7 Estimated Total Number and Biomass of Fish Impinged Monthly at both Units of BCSS, 19 April 2006 – 1

January February March April May 

Species Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Co

Alewife 20 182 15 131 9 82 0 0 0 0 Gizzard shad 0 0 0 0 0 0 0 0 0 0 Threadfin shad 116 528 306 718 366 1,655 155 1,089 39 257 Unidentified clupeid 0 1 13 110 0 0 0 0 0 0 Unidentified cyprinid 0 0 0 0 0 0 0 0 2 2 Channel catfish 0 0 13 72 0 0 1 12 13 158 White perch 0 0 0 0 0 0 0 0 0 0 Redbreast sunfish 8 128 5 86 25 494 12 12 5 9 Green sunfish 0 0 0 0 0 0 0 0 0 0 Bluegill 1,487 7,401 500 3,729 377 1,918 470 1,917 1,362 6,032 5Redear sunfish 0 0 0 0 0 0 0 0 0 0 Hybrid sunfish 0 0 0 0 0 0 2 4 26 57 Lepomis sp. 0 0 0 0 0 0 0 0 0 0 Sunfishes 0 0 0 0 0 0 0 0 2 0 Largemouth bass 0 0 0 0 0 0 0 0 0 0 Spotted bass 0 0 0 0 14 415 3 100 0 0 Total 1,630 8,240 852 4,845 792 4,564 642 3,134 1,449 6,515 6
Table 4-7 continued 

July August September October November 

Species Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Co

Alewife 10 11 0 0 0 0 3 9 30 213 Gizzard shad 0 0 0 0 0 0 0 0 12 3,430 Threadfin shad 171 433 256 479 53 74 54 322 23 103 Unidentified clupeid 0 0 0 0 0 0 0 0 0 0 Unidentified cyprinid 0 0 0 0 0 0 0 0 0 0 Channel catfish 14 902 0 0 0 0 0 0 15 94 White perch 0 0 0 0 1 7 12 118 0 0 Redbreast sunfish 35 663 14 806 0 0 12 224 1 25 Green sunfish 0 0 0 0 1 10 26 187 0 0 Bluegill 175 942 113 650 197 1,174 327 1,754 859 5,077 1,0Redear sunfish 0 0 0 35 14 2,251 0 0 0 0 Hybrid sunfish 0 0 0 0 0 0 0 0 0 0 Lepomis sp. 0 0 9 0 5 0 0 0 0 0 Sunfishes 0 0 0 0 0 0 0 0 0 0 Largemouth bass 38 58 28 90 11 1,342 3 335 12 61 Spotted bass 0 0 0 0 0 0 0 0 0 0 Total 442 3,009 420 2,059 281 4,858 437 2,949 951 9,003 1,
Impingement Mortality 

4-24Table 4-7 continued 

All 

Species Count 

Biomass 

(g) 

Alewife 96 676 Gizzard shad 12 3,613 Threadfin shad 1,628 5,939 Unidentified clupeid 13 110 Unidentified cyprinid 14 11 Channel catfish 67 1,268 White perch 13 125 Redbreast sunfish 149 2,786 Green sunfish 27 197 Bluegill 7,436 38,268 Redear sunfish 14 2,286 Hybrid sunfish 28 61 Lepomis sp. 14 0 Sunfishes 14 0 Largemouth bass 96 1,894 Spotted bass 18 516 Total 9,638 57,751 
Table 4-8 Maximum Total Length (mm) Used to Distinguish Young-of-Year from Yearling Fish by Month

Species Age Jan Feb Mar Apr May Jun Jul Aug Sep Oct NThreadfin shad 0 75 75 75 75 80 50 55 60 65 70  1 95 95 95 95 100 85 85 90 95 95 Channel catfish 0 80 80 80 90 100 110 50 60 70 80  1 180 180 180 185 190 195 125 145 165 180 Bluegill 0 65 65 65 65 70 75 30 45 60 65  1 110 110 110 110 120 130 85 95 105 110 Largemouth bass 0 165 165 165 180 205 80 110 135 155 165  1 265 265 265 270 280 230 235 245 255 265 Note: shaded month indicates appearance of new year class Sources: Cornish and Welke (2004), Pierce et al. (2003), Carlander (1977), Johnson (1970) 
Impingement Mortality 

4-26

Table 4-9 Estimated Annual Impingement of Fish by Age Group at both Units of BCSS, 19 

April 2006 – 18 April 2007

Young-of-Year Yearling & Older Undetermined 

Species Count Percent Count Percent Count Percent 

Alewife 0 0 0 0 96 100 

Gizzard shad 0 0 0 0 12 100 

Threadfin shad 599 36.77 837 51.42 192 11.81 

Unidentified clupeid 0 0 0 0 13 100 

Unidentified cyprinid 0 0 0 0 14 100 

Channel catfish 0 0 67 100 0 0 

White perch 0 0 0 0 13 100 

Redbreast sunfish 0 0 0 0 149 100 

Green sunfish 0 0 0 0 27 100 

Bluegill 2,235 30.06 5,138 69.1 63 0.84 

Redear sunfish 0 0 0 0 14 100 

Hybrid sunfish 0 0 0 0 28 100 

Lepomis sp. 0 0 0 0 14 100 

Unidentified sunfishes 0 0 0 0 14 100 

Largemouth bass 82 85.92 13 14.08 0 0 

Spotted bass 0 0 0 0 18 100 

Total 2,916 30.25 6,056 62.83 667 6.92 
 

4-27

Table 4-10 Comparison of Relative Abundance of Fish Species in the 1996-2005 

Electrofishing Surveys for all Sampling Transects Combined in Belews Lake and the 

2006-2007 BCSS Impingement Collections

 Electrofishing 2006-2007 Impingement 

Species Total No. % Rank Total No. % Rank 

Bluegill 16,831 48.729 1 545 77.195 1 

Threadfin shad 4,552 13.179 2 119 16.856 2 

Redbreast sunfish 3,747 10.848 3 11 1.558 3 

Largemouth bass 1,594 4.615 4 7 0.992 4 

Redear sunfish 1,576 4.563 5 1 0.142 9 tie 

Yellow perch 1,444 4.181 6 

White perch 903 2.614 7 1 0.142 9 tie 

White crappie 835 2.417 8 

Common carp 655 1.896 9 

Hybrid sunfish 530 1.534 10 2 0.283 7 tie 

Satinfin shiner 517 1.497 11 

Gizzard shad 340 0.984 12 1 0.142 9 tie 

Green sunfish 279 0.808 13 tie 2 0.283 7 tie 

Black crappie 279 0.808 13 tie 

Channel catfish 213 0.617 15 5 0.708 6 

Warmouth 125 0.362 16 

Golden shiner 53 0.153 17 

White catfish 15 0.043 18 tie 

Flat bullhead 15 0.043 18 tie 

Pumpkinseed 15 0.043 18 tie 

White sucker 7 0.020 21 

Brown bullhead 4 0.012 22 

Notchlip redhorse 3 0.009 23 tie 

Flathead catfish 3 0.009 23 tie 

Fathead minnow 2 0.006 25 

Golden redhorse 1 0.003 26 tie 

Snail bullhead 1 0.003 26 tie 

Eastern mosquitofish 1 0.003 26 tie 

Alewife - 7 0.992 5 

Cyprinidae - 1 0.142 9 tie 

Clupeidae - 1 0.142 9 tie 

Lepomis sp. - 1 0.142 9 tie 

Spotted bass - 1 0.142 9 tie 

Unidentified sunfishes - 1 0.142 9 tie 

Total 34,540 100.00 706 100.000 
Impingement Mortality 

4-28Table 4-11 Estimated Total Number and Biomass of Fish Impinged Monthly at both Units of BCSS for Full Flow Op2006 – 18 April 2007 

January February March April May 

Species Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Co

Alewife 22 204 16 142 11 94 0 0 0 0 Gizzard shad 0 0 0 0 0 0 0 0 0 0 Threadfin shad 130 592 332 779 485 2,303 208 1,441 41 267 Herring/shad 0 1 14 118 0 0 0 0 0 0 Cyprinidae 0 0 0 0 0 0 0 0 3 2 Channel catfish 0 0 14 78 0 0 1 13 13 159 White perch 0 0 0 0 0 0 0 0 0 0 Redbreast sunfish 8 143 6 98 28 555 13 13 6 10 Green sunfish 0 0 0 0 0 0 0 0 0 0 Bluegill 1,665 8,285 547 4,065 512 2,561 580 2,387 1,393 6,166 Redear sunfish 0 0 0 0 0 0 0 0 0 0 Hybrid sunfish 0 0 0 0 0 0 2 5 26 57 Lepomis sp. 0 0 0 0 0 0 0 0 0 0 Largemouth bass 0 0 0 0 0 0 0 0 0 0 Spotted bass 0 0 0 0 22 623 6 186 0 0 Unidentified sunfishes 0 0 0 0 0 0 0 0 2 0 Total 1,825 9,226 929 5,280 1,057 6,137 812 4,045 1,483 6,661 
Table 4-11 continued 

July August September October November 

Species Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Count 

Biomass 

(g) Co

Alewife 10 11 0 0 0 0 5 13 41 260 Gizzard shad 0 0 0 0 0 0 0 0 13 3,891 Threadfin shad 171 433 256 479 53 75 60 364 35 169 Herring/shad 0 0 0 0 0 0 0 0 0 0 Cyprinidae 0 0 0 0 0 0 0 0 0 0 Channel catfish 14 902 0 0 0 0 0 0 17 106 White perch 0 0 0 0 1 7 13 126 0 0 Redbreast sunfish 35 663 14 806 0 0 12 241 1 29 Green sunfish 0 0 0 0 1 10 27 193 0 0 Bluegill 175 942 113 650 197 1,176 375 2,029 1,131 6,651 1,Redear sunfish 0 0 0 35 14 2,251 0 0 0 0 Hybrid sunfish 0 0 0 0 0 0 0 0 0 0 Lepomis sp. 0 0 9 0 5 0 0 0 0 0 Largemouth bass 38 58 28 90 11 1,342 3 400 14 68 Spotted bass 0 0 0 0 0 0 0 0 0 0 Unidentified sunfishes 0 0 0 0 0 0 0 0 0 0 Total 442 3,009 420 2,059 281 4,861 495 3,366 1,253 11,175 1,
Impingement Mortality 

4-30Table 4-11 continued 

All 

Species Count 

Biomass 

(g) 

Alewife 115 779 Gizzard shad 14 4,101 Threadfin shad 1,871 7,213 Unidentified clupeid 14 119 Unidentified cyprinid 16 13 Channel catfish 70 1,290 White perch 14 133 Redbreast sunfish 158 2,902 Green sunfish 28 203 Bluegill 8,427 43,425 Redear sunfish 14 2,286 Hybrid sunfish 28 62 Lepomis sp. 14 0 Largemouth bass 99 1,967 Spotted bass 28 809 Unidentified sunfishes 14 0 Total 10,924 65,303 
5-1 

5 

ASSESSMENT OF ADVERSE ENVIRONMENTAL 

IMPACT 

Introduction 

Section 316(b) of the Clean Water 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 existing 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 for the Second Circuit reviewed the Rule and 

remanded several key provisions on 25 January 2007 (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 professional judgment (BPJ) basis.” 

Prior to the Phase II Rule, BPJ compliance with §316(b) was based on a determination of 

whether or not the cooling water intake structure was resulting in adverse environmental 

impact (AEI). With the remand of the Phase II Rule, this approach continues to be 

appropriate in BPJ determinations. Unfortunately, neither the Act nor subsequent 

guidance provided by the EPA provides any definition of the term “adverse 

environmental impact (AEI)” for use by permit writers in making their BPJ 

determinations. Consequently, it is left up to the permitting 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 adverse impact of the 

BCSS cooling water intake structure as a result of an unacceptable reduction in: 

 biological integrity as measured in terms of aquatic community species composition, 

diversity, and functional 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 consistent with both EPA’s original draft 316(b) 

guidance (EPA 1977) as well as historical practice (Dey et al. 2000). 

Duke proposes to use multiple lines of investigation 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 based on losses to impinged species 

o conducting a retrospective evaluation based on analysis of 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 adverse environmental impact for BCSS? 

Recognizing the need for a consistent and technically sound approach to assessing the 

potential effects of a wide variety of anthropogenic stresses on ecosystems, the EPA 

began an intensive effort to develop an approach for ecological risk assessment during 

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

that used for human health risk assessment 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 Guidelines) was 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 address 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 entrainment and impingement result in the exposure 

of aquatic organisms to physical and chemical stresses, it seems that a logical approach to 

assessing the risk of adverse environmental impact of cooling water withdrawals as 

required by §316(b) would be through the use of an ecological risk assessment 

framework, such as that provided by EPA. 

As noted above, the risk of adverse environmental impact from the continued operation 

of the BCSS cooling water intake system needs to be addressed from two perspectives: 

ecosystem (i.e., biological integrity) 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 to 
 

5-3

determine the overall risk of adverse environmental impact from the BCSS cooling water 

intake structure on Belews Lake.

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 lines are independently assessed using two broad 

categories of methods: prospective and retrospective methods. Prospective methods 

attempt to predict the effects of a stressor, such as cooling water withdrawal, on the 

ecological endpoints selected for the assessment. Retrospective methods, on the other 

hand, evaluate the potential effects of an existing stressor, such as a cooling water intake 

structure, by measuring the actual effects on the ecological endpoints. In this assessment, 

we use a combination of prospective and retrospective methods to determine the potential 

ecosystem effects of cooling water withdrawals at BCSS. 

Prospective Approach 

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

of the future risks of a stressor not yet released into the environment or of future 

conditions resulting from an existing stressor” (EPA 1998). For this assessment, 

prospective methods entail predicting the potential consequences of impingement at 

BCSS on the fish community composition and function and on recreational fishing in 

Belews Lake. 

As described in Section 4, impingement monitoring studies were conducted at BCSS over 

the period April 2006 – April 2007. The results of these studies were used to estimate the 

expected annual impingement at BCSS under normal operations: 

Species 

Total Average 

Weight per 

Count Individual (g) 

Biomass 

(g) 

Bluegill 7,436 38,268 5.1 

Threadfin shad 1,628 5,939 3.6 

Redbreast sunfish 149 2,786 18.7 

Alewife 96 676 7.0 

Largemouth bass 96 1,894 19.7 

Channel catfish 67 1,268 18.9 

Hybrid sunfish 28 61 2.2 

Green sunfish 27 197 7.3 

Spotted bass 18 516 28.7 

Cyprinidae 14 11 0.8 

Lepomis sp. 14 0 0.0 

Redear sunfish 14 2,286 163.3 
Assessment of Adverse Environmental Impact 

5-4

Unidentified sunfishes 14 0 0.0 

Herring 13 110 8.5 

White perch 13 125 9.6 

Gizzard shad 12 3,613 301.1 

Total 9,638 57,751 6.0 

Mean weights per fish suggest that most, if not all, of the fish collected were juveniles 

and most likely were either age 0 or age 1. Only for redear sunfish (14 impinged) and 

gizzard shad (12 impinged) would those individuals impinged be considered adults. 

All but two of the taxa collected had estimates of annual impingement that averaged less 

than one fish every other day. Given that all of these species are common to Belews 

Lake, it is hard to image that the removal of one individual or less of each species every 

other day, most likely juveniles, could be considered an adverse environmental impact 

from Belews Lake, a lake of more than 3,800 acres (1,560 ha). 

Bluegill, the species with the highest estimated annual impingement, is one of the most 

abundant fish found in littoral areas of the lake and is a popular panfish target of anglers. 

The estimated annual impingement of this species represents a removal rate of less than 

twenty individuals per day. Most of these were likely less than 2 years old. Assuming a 

conservative total mortality rate of 50 percent per year, these 20 juveniles would survive 

to be about five average-sized harvestable adult (i.e., 7.5 in. long and 4 years old). 

Hence, the current annual impingement of bluegills is equivalent to the removal of five 

adult bluegill per day. As with the other species, it is hard to imagine that such a removal 

rate would constitute an adverse environmental impact on Belews. 

The other species commonly impinged, threadfin shad, is abundant throughout the 

pelagic areas of Belews Lake. The estimated annual impingement of this species 

represents a removal rate of less than five individuals per day. Most of these were likely 

less than 1 year old. At 3.6 grams each, this removal rate translates to an annual removal 

rate of less than 2 grams of biomass per surface acre of Belews Lake per year. Given the 

rapid growth, short life span, and high reproductive potential of this species, it is hard to 

imagine that such removal rates can have any detectable effects on either population 

persistence for this 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 1998b). For this assessment, the stressor would be the 

loss of fish from the Belews Lake community caused by impingement at the CWIS. The 

retrospective approach evaluated whether effects on individual species populations or the 

community as a whole are apparent by examining trends in the species richness and 
 

5-5

relative abundance of individual species during the time that BCSS has operated. 

Community metrics involving species richness and abundance would be appropriate 

because impingement is equivalent to harvesting 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 recent occurrence of fish species and their 

relative abundance in the littoral zone of Belews Lake from 1996 to 2005, available from 

Duke’s annual spring electrofishing surveys. Trends in species richness and relative 

abundance should be apparent if operation of BCSS has had a discernable, progressive 

effect on the fish community in the lake over this 10-year period. If there are discernable 

effects, are they consistent with the selective loss of individual species to impingement 

that could be interpreted as being causal in nature? 

Hypothetically, selective harvesting 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, species composition, and relative abundance may 

reveal significant, sustained changes in species occurrence and abundance, or a trophic 

imbalance. Also, a persistence or increase in top carnivores (piscivores) might indicate 

stability or improvement in the community, and vice versa. 

Surveys were conducted once per year by Duke in the spring from 1995 to 2005, daylight 

when water temperatures were between 15o

C and 20oC (Coughlan et al. 2006). Twenty 

300-m shoreline transects (five up-lake, five mid-lake, and 10 down-lake) were selected 

to represent existing habitat types. The results of these surveys are discussed in terms of 

fish abundance, species richness, and trophic structure of the fish community as follows. 

Fish Abundance 

In the littoral zone of Belews Lake, there appears to be a trend of increasing fish 

abundance over the period from 1996 to 2005 (Figure 5-1). The total spring 

electrofishing catch should reflect the annual abundance of fish since the sampling 

methodology and intensity has remained constant from year to year (Section 3). The total 

annual catch in 1996-2000 ranged from 2,100 to 2,735 fish, then began to increase in 

2001 to 3,668 fish and peaked at 6,127 fish in 2004 (Figure 5-1). This trend of increasing 

catch or fish abundance was observed in all regions of the lake (see Tables 3-3 and 3-4 in 

Section 3), but particularly so in the lower region (Table 3-4). 

The trend of increasing total catch is mostly a reflection of the increasing abundance of 

bluegill (Figure 5-2), the numerically dominant species in the lake. Threadfin shad, the 

second most common species, was especially abundant in the 2004 catch (Figure 5-2), 

adding to the peak total catch observed in that year (Figure 5-1). Largemouth bass and 

channel catfish, the remaining target species, also were relatively abundant in 2004, but 

showed no overall trend during the 10-year period (Figure5-2). 
Assessment of Adverse Environmental Impact 

5-6

Species Richness 

While the abundance of fish appears to be increasing in recent years, there has been little 

change in species richness in the littoral zone of the whole lake (combined upper, middle, 

and lower regions) from 1996 to 2005. There have been regional differences in species 

composition, however, as noted in Section 3. 

The total number of species caught annually in the entire lake varied between 17 in 1999 

and 21 in 1996 and 2003 (Figure 5-3). Species consistently caught in all annual surveys 

were bluegill, channel catfish, common carp, gizzard shad, green sunfish, largemouth 

bass, redbreast sunfish, redear sunfish, satinfin shiner, threadfin shad, warmouth, and 

white crappie, white perch, and yellow perch (Figure 5-4). In contrast, some species only 

were caught in only a single year, such as brown bullhead and eastern mosquitofish 

(2003), fathead minnow (2000), and golden redhorse (1996), likely due to their relatively 

low abundance or distribution in areas not readily sampled by electrofishing. 

Trophic Structure 

Species were divided into trophic guilds consisting of insectivore, omnivore, and 

piscivore (Table 5-1). Insectivores were dominant in electrofishing surveys, ranging 

from 51.5 to 84.8 percent (Figure 5-5). Omnivores and piscivores alternated annually as 

the second-most abundant trophic guild in the lake. Omnivores comprised 3.8 to 33.7 

percent of the fish community, and piscivores ranged from 7.6 to 33.1 percent of the 

community. There was no consistent trend in the relative abundance of each of the three 

guilds from 1996 through 2005. 

Retrospective Summary 

Recent data (1996-2005) from electrofishing in the littoral zone of Belews Lake do not 

indicate any changes in the fish community that could be linked to the destabilizing 

effects of impingement losses at BCSS. Instead, the data show a sustained increase in 

fish abundance since 1996, particularly for the dominant species, bluegill. Other indices, 

species richness and trophic structure, show a relatively stable fish community in terms of 

its composition and trophic dynamics. 

The fish community of Belews Lake since the mid-1980s has been recovering from the 

effects of selenium contamination (see Section 3). The 1996-2005 electrofishing data 

may be showing the continuation of this recovery, where the fish community composition 

has reached some stability but individual populations continue to expand. This recovery 

is occurring despite the continuing operation of BCSS and any impacts potentially 

resulting from impingement losses. 
 

5-7

Effects on Human Uses 

Belews Lake, from which BCSS withdraws its cooling waters, provides important 

recreational fishing opportunities to people from North Carolina and adjacent states. 

Popular targets of anglers include largemouth, several species of catfish, and a variety of 

panfish species including bluegill, crappie, and yellow perch. In addition, the lake 

supports a healthy community of other water-dependent species that provide passive use 

opportunities such as nature watching. Hence, in addition to potential effects on 

biological integrity, it is reasonable to address the potential effects of impingement of fish 

at BCSS on human uses of Belews Lake, including fishing. 

Two different types of measures of the potential effects of impingement on human uses 

of the aquatic resources in Belews Lake, equivalent loss and economic value, were used 

in this analysis. Estimates of the two types of measures were calculated for each of four 

target species: threadfin shad, largemouth bass, bluegill, and channel catfish. Together, 

these four species comprised more than 95 percent of total impingement at BCSS. The 

methods and parameter values used to develop these two measures are discussed in 

Appendix A. The resulting measures are described below. 

Equivalent Loss Measures 

Since impingement at BCSS involves several species of fish and includes a variety 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 the additional weight of each species that 

could have been harvested by anglers in the absence of any impingement at BCSS. 

 Production foregone provides a measure of the additional biomass production that 

could have resulted from the impinged individuals in the absence of any impingement 

at BCSS. 

Using the methodology and the most probable estimates for each of the input parameters 

described Appendix A, estimates of equivalent fishery yield and production foregone for 

each of the four target species were generated using the monthly impingement estimates 

at BCSS. The monthly estimates were then summed to calculate total annual values. 

Three of the four target species evaluated in this assessment, largemouth bass, bluegill 

and channel catfish, directly support fisheries in Belews Lake. Annual fishery yield that 

could result from the fish impinged at BCSS totaled 108 lb (49.0 kg) under actual cooling 

water flows during the course of the impingement monitoring program and 121 lb (54.9 

kg) under maximum (design) cooling water flows (Table 5-2). Most (> 93 percent) of 

this equivalent yield was through bluegill. 
Assessment of Adverse Environmental Impact 

5-8

Annual production from the target species impinged at BCSS totaled 730 lb (331.1 kg) 

under actual cooling water flows and 887 lb (402.3 kg) under maximum cooling water 

flow (Table 5-3). Most (>91 percent) of this production foregone was through bluegill. 

In the absence of impingement at BCSS, this additional production could support 

additional biomass of fish targeted by fishermen and provide energy to support other 

ecosystem functions. 

Economic Value 

Calculation of economic value takes the estimates of equivalent yield and production 

foregone described above and assigns economic value based 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 weighing 

the estimates of equivalent loss by the relative “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 the Phase II rulemaking (EPA 2004). 

In this assessment, economic values were assigned to each of the four categories of 

benefit values relevant to §316(b) regulations for existing facilities: 

 market direct use benefits; 

 nonmarket direct use benefits; 

 indirect use benefits; and, 

 non-use 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-marketed 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 indirectly the direct 

use values even though the resources themselves are not directly used. Finally, in 

addition to these direct and indirect use-related values, there is a potential for 

environmental changes to increase the welfare of individuals who do not use the resource 

at all. These latter benefits are considered non-use benefits. Methods and input values 

used to calculate economic values for each of these benefits categories are described in 

Appendix A. 

Total annual economic value for all fish impinged at BCSS totaled only $883 under 

actual cooling water flow and only $994 under maximum cooling water flow (Table 5-4). 

Most of this economic value (~62 percent) was as a result of the direct loss of bluegill. 
 

5-9

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 estimates of economic value generated for any 

individual facility. It is for this reason that EPA guidance on conducting such economic 

evaluations recommends that an uncertainty analysis be conducted as part of the 

evaluation (EPA 2000b). The purpose of such an uncertainty analysis is to make 

transparent all the underlying sources of uncertainty in the calculation of economic value 

such that the reader can independently determine whether the results have sufficient 

precision and accuracy to meet regulatory needs. 

In this report, uncertainty was 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 focused 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 illustrated in Figure 5-6. Uncertainty in recreational 

price per pound yielded the greatest range in estimates of annual economic value (-63 to 

+210 percent) while uncertainty in the fishing mortality rate yielded the second greatest 

range (-13 to +88 percent). Uncertainty in these two parameters was clearly the most 

important in determining the total uncertainty in the estimate of annual economic value. 

Uncertainty in the remaining seven input parameters (natural mortality rate, fishing 

vulnerability, weight, release rate, post-release survival, trophic conversion factor, and 

equivalent predatory exploitation rate) had relatively minor effects on estimates of annual 

economic value (< + 40 percent). 

The results of the Monte Carlo analysis are illustrated in Figure 5-7. The frequency 

distribution of the resulting annual estimates appeared generally symmetrical, although 

most of the estimates of economic value resulting from this uncertainty analysis were 

higher than the most probable estimate (Figure 5-7). The median value from the Monte 

Carlo analysis was 78 percent higher than the most probable estimate while the 25th and 

75th percentiles were 39 percent and 131 percent higher, respectively. There was less 

than a 10 percent chance that the true annual economic benefit was more than twice the 

most probable estimate reported in Table 5-4. The fact that most of the estimates of 

economic value were higher than the most probable estimate is likely related to the nonsymmetrical effects of the two key parameters, the recreational price per pound and the 

fishing mortality rate, described above. 
Assessment of Adverse Environmental Impact 

5-10

Conclusions 

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

effects within Belews Lake that rise to a level that could be considered an “adverse 

environmental impact.” This conclusion is based on a careful evaluation of all relevant 

lines of evidence including the following observations: 

1. Numbers of fish lost as a result of impingement are exceedingly small compared 

to likely sizes of fish populations in Belews Lake. For all but two species, 

removal rates amounted to less than one fish every other day. For bluegill, 

removal rates were equivalent to five adults per day; likely less than or similar to 

the daily harvest by a single angler. 

2. Total number impinged each year for threadfin shad amounted to a biomass 

removal rate of less than 2 grams per surface acre of Belews Lake per year. This 

species is a highly prolific spawner with high growth rate and short life span. 

This high reproductive potential can easily compensate for the relatively small 

losses at BCSS with no long-term effects. 

3. Electrofishing data from 1996-2005 do not indicate any changes in the fish 

community that could be linked to the destabilizing effects of impingement losses 

at BCSS. Instead, the data show a sustained increase in fish abundance since 

1996 and a relatively stable fish community in terms of its species richness, 

species composition, and trophic structure. 

4. The fish community since the mid-1980s has been recovering from the historic 

effects of selenium contamination. Recent data appear to show the continuation 

of this recovery, despite the continuing operation of BCSS and any impacts 

potentially resulting from impingement losses. 

5. Estimates of total fishery catch that could result from the fish impinged at BCSS 

had they survived amount to only 108 lb (49 kg) per year, most of which was 

bluegill. This level of harvest is less than what would be expected annually from 

a few anglers. 

6. Estimates of the total production foregone as a result of fish impinged at BCSS 

amounted to less than 730 lb (331 kg) per year of biomass. Most of this was a 

result of bluegill, an abundant species in Belews Lake. 

7. The best estimate of the total economic value of fish impinged at BCSS was $883 

per year. Even considering the uncertainty in these estimates, it is highly unlikely 

that the economic value exceeds $1,700 per year. These values must be 

considered trivial compared to the total economic value of the recreational fishery 

in Belews Lake. 
 

5-11

1996 1998 2000 2002 2004

2,000

3,000

4,000

5,000

6,000

7,000

Total Catch

Figure 5-1 Total Annual Catch of Fish in Belews Lake, 1996-2005 
Assessment of Adverse Environmental Impact 

5-12

1996 1998 2000 2002 2004

0

500

1,000

1,500

2,000

2,500

3,000

3,500

Bluegill

0

50

100

150

200

250

Largemouth bass

0

500

1,000

1,500

2,000

Threadfin shad

0

10

20

30

40

Total Catch

Channel catfish

Figure 5-2 Mean Annual Catch of Bluegill, Largemouth Bass, Threadfin shad and Channel 

Catfish in Belews Lake Using Boat Electrofishing Sampling, 1996-2005
 

5-13

1996 1998 2000 2002 2004

0

5

10

15

20

25

30

Total No. of Species

Figure 5-3 Total Number of Fish Species Found in Annual Electrofishing Surveys of 

Belews Lake, 1996-2005
Assessment of Adverse Environmental Impact 

5-14

Species 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Gizzard shad 

Threadfin shad 

Common carp 

Fathead minnow 

Golden shiner 

Satinfin shiner 

Golden redhorse 

Notchlip redhorse 

White sucker 

Brown bullhead 

Channel catfish 

Flat bullhead 

Flathead catfish 

Snail bullhead 

White catfish 

White perch 

Eastern mosquitofish 

Redbreast sunfish 

Green sunfish 

Pumpkinseed 

Bluegill 

Redear sunfish 

Hybrid sunfish 

Warmouth 

Largemouth bass 

Black crappie 

White crappie 

Yellow perch 

Total No. of Species 

 

22 

 

19 

 

20 

 

17 

 

20 

 

19 

 

19 

 

22 

 

20 

 

19 

Figure 5-4 Species Composition in Belews Lake, 1996-2005 
 

5-15

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

0

10

20

30

40

50

60

70

80

90

100

 Percent Trophic Level Composition

 % Insectivore % Omnivore % Piscivore

Figure 5-5 Percent Composition of Fish Trophic Guilds in Belews Lake, 1996-2005
Assessment of Adverse Environmental Impact 

5-16

Recreational Price

Exploitation Rate

Trophic Conversion

Weight

Release Survival

Release rate

Fishing Mortality

Vulnerability

Natural Mortality

-200 -150 -100 -50 0 50 100 150 

Percent Difference

Figure 5-6 Estimates of the Range of Effects of Uncertainty in Each Input Parameter on Estimates of Annual Econ
020406080100

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

05

10152025

Percent Frequency

Percent Difference from Estimate

Figure 5-7 Results of Monte Carlo Analysis of Uncertainty in Key Input Parameters on Estimates of Annual Econo
Assessment of Adverse Environmental Impact 

5-18

Common Name 

Trophic 

Guild 

Gizzard shad O 

Threadfin shad O 

Common carp O 

Fathead minnow O 

Golden shiner O 

Satinfin shiner I 

Golden redhorse I 

Notchlip redhorse I 

White sucker O 

Brown bullhead O 

Channel catfish O 

Flat bullhead I 

Flathead catfish P 

Snail bullhead I 

White catfish O 

White perch P 

Eastern mosquitofish I 

Redbreast sunfish I 

Green sunfish I 

Pumpkinseed I 

Bluegill I 

Redear sunfish I 

Hybrid sunfish I 

Largemouth bass P 

Warmouth I 

Black crappie P 

White crappie P 

Yellow perch P 

Source: NCDENR (2006) 

P = Piscivore 

I = Insectivore/Invertivore 

O = Omnivore 

H = Herbivore 

 Table 5-1 Trophic Guild Assignments for Fish Species in Belews Lake 
 

5-19

Table 5-2 Estimates of Potential Total Annual Equivalent Fishery Yield (lb) from 

Individuals Impinged for Each Target Species at BCSS 

Species 

Annual Fishery Yield (lb) 

Actual Flow Maximum Flow 

Threadfin shad 0 0 

Channel catfish 1 1 

Bluegill 101 115 

Largemouth bass 6 6 

Total 108 121 

Table 5-3 Estimates of Potential Total Annual Production Foregone (lb) from Individuals 

Impinged for Each Target Species at BCSS 

Species 

Annual Production Foregone (lb) 

Actual Flow Maximum Flow 

Threadfin shad 24 27 

Channel catfish 12 13 

Bluegill 671 823 

Largemouth bass 23 24 

Total 730 887 
Assessment of Adverse Environmental Impact 

5-20

 Table 5-4 Estimates of Economic Value of Fish Impinged at BCSS 

Species 

Total Impingement Value (2008$) 

Actual Flow Maximum Flow 

Threadfin shada 0 0 

Channel catfish 0 0 

Bluegill 543 615 

Largemouth bass 34 35 

Equivalent predatorb 267 301 

Non-target speciesc 38 43 

Total 883 994 

a Economic benefits for threadfin shad 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 (largemouth bass). 

c

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

6 

REFERENCES CITED 

Alden Research Laboratory (Alden). 2004. Evaluation of the Belews Creek Steam Station with 

respect to the Environmental Protection Agency’s §316(b) Rule for Existing Facilities. Draft. 

Electric Power Research Institute, October 2004. 

Allen, M.S., C.J. Walters, and R. Myers. 2008. Temporal trends in largemouth bass mortality, 

with fishery implications. North American Journal of Fisheries Management 28: 418-427. 

Austen, D.J., P.B. Bayley, and B.W. Menzel. 1994. Importance of the guild concept to fisheries 

research and management. Fisheries 19(6):12-20. 

Barwick, D.H. and R.D. Harrell. 1997. Recovery of fish populations in Belews Lake following 

selenium contamination. Proceedings of the Annual Conference of Southeastern Fish and 

Wildlife Agencies 51:209-216. 

Carlander, K.D. 1977. Handbook of freshwater fishery biology. Vol. 2. The Iowa State 

University Press, Ames, IA. 431 pp. 

Coble, D.W. 1988. Effects of angling on bluegill populations: management implications. North 

American Journal of Fisheries Management 8:277-283. 

Cornish, M. and K. Welke. 2004. Bluegill (Lepomis macrochirus). In: Pitlo, J.M. Jr. and J.L. 

Rasmussen (eds.). UMRCC Fisheries Compendium. 3rd Edition. Upper Mississippi River 

Conservation Committee. Rock Island, Illinois. January 2004. p. 177-180. 

Coughlan, D.J., K.A. Finley, and J.J. Hall. 2006. Assessment of balanced and indigenous 

populations in Belews Lake, for Belews Creek Steam Station: NPDES No. NC0024406. 

Duke Energy, Huntersville, North Carolina. August 2006. 

Dey, W. P., S.M. Jinks and G.J. Lauer. 2000. The 316(b) assessment process: evolution towards 

a risk-based approach. Environmental Science and Policy (3): S15-S23. 

Dey, W.P. 2002. Use of equivalent loss models under Section 316(b) of the Clean Water Act. 

The Scientific World. 2(S1): 254-270. 

Duke Power (Duke). 2001. Assessment of balanced and indigenous populations in Belews Lake 

for Belews Creek Steam Station: NPDES Np. NC0024406. September 2001. 
References Cited 

6-2 

Electric Power Research Institute (EPRI). 2002. Evaluating the effects of power plant operations 

on aquatic communities: an ecological risk assessment framework for Clean Water Act 

§136(b) determinations. EPRI Report 1005337. 

Electric Power Research Institute (EPRI). 2004. Extrapolating Impingement and Entrainment 

Losses to Equivalent Adults and Production Foregone. EPRI Report 1008471. 

Electric Power Research Institute (EPRI). 2005. Parameter Development for Equivalent Adult 

and Production Foregone Models. EPRI Report 1008832. 

Emig, J.W. 1966. Largemouth bass. In: A. Calhoun (ed.). Inland Fisheries Management. State 

of California, Department of Fish and Game. 

Heidinger, R.C. 1975. Life history and biology of the largemouth bass. Pages 11-20 In: R.H. 

Stroud and H. Clepper (eds.). Black Bass Biology and Management. Sport Fishing Institute, 

Washington, D.C. 

Heidinger, R.C. and J.H. Waddell. 1989. Lower Ohio River Fisheries Study. Illinois Department 

of Conservation. Final report. 1 July 1986 through 30 June 1989. F-59-R. 349 pp. 

Heman, M.L., R.S. Campbell, and L.C. Redmond. 1969. Manipulation of fish populations 

through reservoir drawdown. Transactions of the American Fisheries Society 98(2):293-304. 

Hining, K. 2003. Characteristics of the black and white crappie populations in Belews Lake, 

2001-2002. Final report. Mountain Fisheries Investigations. Federal Aid in Fish Restoration 

Project F-24. North Carolina Wildlife Resources Commission, Division of Inland Fisheries. 

Raleigh, NC. 

Holland-Bartels, L.E. and M.C. Duval. 1988. Variations in abundance of young-of-the-year 

channel catfish in a navigation pool of the Upper Mississippi River. Transactions of the 

American Fisheries Society. 117:202-208. 

Hubert, W.A. 1999. Biology and management of channel catfish. Pages 3-22 In: E.R. Irwin, 

W.A. Hubert, C.F. Rabeni, H.L. Schramm, Jr., and T. Coon (eds.). Catfish 2000:Proceedings 

of the International Ictalurid Symposium. American Fisheries Society, Bethesda, Maryland. 

Koel, T.M., R.M. Sparks, and R.E. Sparks. 1998. Channel catfish populations in the Upper 

Mississippi River System. Illinois Natural History Survey Reports, September-October 1998. 

LeGrande, H.E. Jr., S.E. McRae, S.P. Hall, and J.T. Finnegan. 2008. Natural Heritage Program 

list of the rare animal species of North Carolina. North Carolina Natural Heritage Program, 

N.C. Department of Environment and Natural Resources, Division of Natural Resource 

Planning and Conservation. 

Lemly, A.D. 1993. Teratogenic effects of selenium in natural populations of freshwater fish. 

Ecotoxicology and Environmental Safety 26:181-204. 
 

6-3 

Lemly, A.D. 2002. Symptoms and implications of selenium toxicity in fish: the Belews Lake 

case example. Aquatic Toxicology 57: 39-49. 

McMahon, T.E. and J.W. Terrell. 1982. Habitat suitability index models: channel catfish. 

U.S.D.I. Fish and Wildlife Service. FWS/OBS-82/10.2 29 pp. 

North Carolina Department of Environment and Natural Resources (NCDENR). 2000. 

Basinwide assessment report, Roanoke River Basin. Division of Water Quality, 

Environmental Sciences Section. May 2000. 

North Carolina Department of Environment and Natural Resources (NCDENR). 2001. 

Basinwide Planning Program: 2001 Roanoke River Water Quality Plan. Division of Water 

Quality, Environmental Sciences Section. 

North Carolina Department of Environment and Natural Resources (NCDENR). 2005. 

Basinwide assessment report, Roanoke River Basin. Division of Water Quality, 

Environmental Sciences Section. April 2005. 

North Carolina Department of Environment and Natural Resources (NCDENR). 2006a. 

Roanoke River Basinwide Water Plan, September 2006. Division of Water Quality Basinwide 

Planning Unit. Raleigh, North Carolina. 

North Carolina Department of Environment and Natural Resources (NCDENR). 2006b. 

Standard operating procedure. Biological monitoring. Stream Fish Community Assessment 

Program. Division of Water Quality, Environmental Sciences Section, Biological Assessment 

Unit. 1 August 2006. 

Olson, M.H., T. Adams-Deustch, K.J. Cassels, A.E. Oliver, and D.L. Mitchell. 2008. Patterns of 

ultraviolet radiation exposure in bluegill nests over the course of the spawning season. 

Transactions of the American Fisheries Society 137:1446-1454. 

Paukert, C.P., D.W. Willis, and D.W. Gabelhouse, Jr. 2002. Effect and acceptance of bluegill 

length limits in Nebraska Sandhill lakes. North American Journal of Fisheries Management 

22:1306-1313. 

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. Braaten. 2003. Fish growth, mortality, recruitment, 

condition and size structure. Volume 4. Population structure and habitat use 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., D. Dieterman, and G. Jones. 2004a. Largemouth bass (Micropterus salmoides). In: 

Pitlo, J.M. Jr. and J.L. Rasmussen (eds.). UMRRC Fisheries Compendium. 3rd Edition. Upper 

Mississippi River Conservation Committee. Rock Island, Illinois. January 2004. pp. 169-173. 
References Cited 

6-4 

Pitlo, J., K. Brummet, and M. Endris. 2004b. Channel catfish (Ictalurus punctatus). In: Pitlo, 

J.M. Jr. and J.L. Rasmussen (eds.). UMRRC Fisheries Compendium. 3rd Edition. Upper 

Mississippi River Conservation Committee. Rock Island, Illinois. January 2004. pp. 151-155. 

Ricker, W.E., ed. 1975. Computation and Interpretation of Biological Statistics of Fish 

Populations. Bulletin 191. Department of the Environment, Fisheries and Marine Service, 

Ottawa. 382 pp. 

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. 

Rohde, F.C., R.G. Arndt, and S.M. Smith. 2001. Longitudinal succession of fishes in the Dan 

River in Virginia and north Carolinga (Blue Ridge/Piedmont Provinces). Southeastern Fishes 

Council Proceedings 42:1-13. 

Rohde, F.C., R.G. Arndt, D.J. Coughlan, and S.M. Smith. 2003. An annotated list of the fishes 

known from the Dan River in Virginia and North Carolina (Blue Ridge/Piedmont Provinces). 

Southeastern Fishes Council Proceedings 45:1-10. 

Rosenberger, A.E. and P.L. Angermeier. 2002. Roanoke logperch (Percina rex) population 

structure and habitat use. Virginia Cooperative Fish and Wildlife Research Unit, Virginia 

Tech, Blacksburg, VA. June 2002. 

Rosenberger, R.S. and J.B. Loomis. 2001. Benefit 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, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station. 59p. 

(www.fs.fed.us/rm/pubs/rmrs_gtr72.html). 

Ruelle, R. W. Lorenzen, and J. Oliver. 1977. Population dynamics of young-of-the-year fish in a 

reservoir receiving heated effluent. Proceedings of the Conference on Assessing the Effects of 

Power-Plant Mortality on Fish Populations. Reprinted in Duke 1977. Oconee Nuclear 

Station Environmental Summary Report 1971-1976. Volume 2. Charlotte, North Carolina. 

Simon, T.P. and R. Wallus. 2004. Reproductive biology and early life history of fishes in the 

Ohio River drainage. Volume 3: Ictaluridae-catfishes and madtoms. CRC Press, New York, 

New York. 204 pp. 

Smith, C.L. 1985. The inland fishes of New York State. New York State Department of 

Conservation. 522 pp. 

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

pp. 
 

6-5 

Spotte, S. 2007. Bluegills: biology and behavior. American Fisheries Society, Bethesda, 

Maryland. 214 p. 

Thompson, J.S., J.A. Rice, D.S. Waters, J.C. Taylor, J.E. Hightower, L.A. Davis, and P.S. Rand. 

2005. Energetics of reservoir striped bass populations: Phase I final report. Prepared for 

Division of Inland Fisheries, North Carolina Wildlife Resources Commission by North 

Carolina Cooperative Fish and Wildlife Research Unit, North Carolina State University, 

Raleigh, NC. 

United States Environmental Protection Agency (EPA). 1977. Guidance for Evaluating the 

Adverse Impact of Cooling Water Intake Structures on the Aquatic Environment: Section 

316(b) P.L. 92-500. Draft. 

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

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

United States Environmental Protection Agency (EPA). 1998. Guidelines for Ecological Risk 

Assessment. EPA/630/R-95/002F. 

United States Environmental Protection Agency (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 Establish Requirements for Cooling Water Intake 

Structures at Phase II Existing Facilities. 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. Washington, D.C. Washington, D.C. 

United States Environmental Protection Agency (EPA). 2006. Cooling Water Intake Structures 

– Section 316(b) – Final Rule for Cooling Water Intake Structures at Phase III Existing 

Facilities. Office of Water. EPA-821-F-06-007. June.

A-1 

A 

APPENDIX A: METHODS TO ESTIMATE 

EQUIVALENT LOSS AND ECONOMIC VALUE OF 

FISH IMPINGED AT BELEWS CREEK STEAM 

STATION 

Introduction 

This appendix describes the methods used to develop estimates of annual equivalent loss 

and economic value of fish impinged at the Belews Creek Steam Station (BCSS). For this 

assessment, annual impingement estimates were developed using recent impingement 

monitoring data collected at BCSS over the period 25 April 2006 – 11 April 2007 

(Section 4). 

Estimates of Target Species Equivalent Losses 

In order to calculate economic value, estimates of annual impingement loss at BCSS for 

the four target species (threadfin shad, largemouth bass, bluegill, and channel catfish) 

must be converted to equivalent measures that can be assigned economic value for these 

species. For species of commercial and/or recreational importance, the equivalent 

measure selected was the yield to the fishery 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 selected was the production of biomass available 

as food for higher trophic levels that would have been expected had the individuals not 

been impinged. Methods used in this report 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 defined as the annual total yield (in weight) that 

could have occurred in the commercial or recreational fishery from those individuals lost 

to impingement in the absence of compensatory changes in total mortality. This yield is 

calculated using the Equivalent Yield Model (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-dependent changes in 

mortality or growth rates that often occur in natural populations were not included. 

Using the EYM, fishery yield equivalent to the annual impingement loss at BCSS for 

each target species was estimated as follows: 
Appendix A: Methods to Estimate Equivalent Loss and Economic Value of Impinged Fish At Belews Creek 

SS 

A-2 

where: 

EY = Equivalent yield to fishery 

NLj = Number of each age or life stage category (j) lost annual to impingement 

BCSS 

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

nj = Number of age or life stage categories (j) impinged at BCSS 

Vi = Vulnerability of age (i) to fishing 

Fi = Instantaneous fishing mortality rate for age (i) 

Zi = Instantaneous total mortality rate for age (i) 

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

Wi = 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 defined 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 as it does not support any direct commercial 

or recreational fishing. 

The measure of biomass production that could have resulted from individuals impinged at 

BCSS was calculated using the Production Foregone Model (PFM) (Dey 2002, EPRI 

2004). As with the EYM, this method is also conservative in that potential densitydependent changes in mortality or growth rates that often occur in natural populations 

were not included. Using the PFM, potential biomass production from individuals 

impinged was estimated for each of the target species as follows: 

    

 



 



 

f l n

i i

i i

i i

n

j

j j i Z

V F EY NL S AW

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

Steam STation 

A-3 

 

     

i i

G Z

i i

n

j

j j i L

i

i G Z

NL S G W e

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

P Pi

1

where: 

P = Total production foregone 

Pi = Production foregone for individuals impinged at the BCSS in age category 

(i) 

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

NLj = Number of each age category (j) lost to impingement at BCSS 

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

nj = Number of age categories (j) impinged at BCSS 

Wi = Average weight of individuals in age category (i) 

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

m = Total number of age categories impinged at BCSS. 

L = Final age category. 

The PFM was applied to all target species that as individuals serve as food for other 

aquatic organisms during at least part of their life cycle. 

Both the EYM and PFM are consistent with the benefits calculation procedures used by 

EPA in their regional analysis of the benefits of the Phase II Rule (EPA 2004b). 

Estimation of the biological input parameters for each of the target species is described 

below. 
Appendix A: Methods to Estimate Equivalent Loss and Economic Value of Impinged Fish At Belews Creek 

SS 

A-4 

Assignment of Age Categories for Impinged Individuals 

One of the necessities of equivalent loss calculation 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 estimates 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 Production Foregone and Equivalent Yield models 

include life stage durations, instantaneous natural and fishing mortality rates, and the 

fraction vulnerable to the fishery for each life stage and age, as well as mean weights at 

the beginning of each life stage and age for each target species. Each of these model 

inputs was 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 recognize that fish do not 

become vulnerable to impingement until they are approximately 1 in. 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 BCSS were assigned as follows: 

Species 

Peak Spawning 

Month 

Average Month 

When Individuals 

Reach 1 in. TL 

Threadfin shad Mid-May Mid-July 

Largemouth bass Late April Early June 

Bluegill Early June Late August 

Channel catfish Early Jun Mid-July 

Natural Mortality Rates 

A range (maximum, most probable, and minimum) of instantaneous natural mortality 

rates for each target species was obtained from the following sources: 

Threadfin shad –Daily instantaneous natural mortality rates were obtained from EPRI 

(2005) Table 4-43. For age 0, the most probable value was assumed to be the midpoint 

between the maximum and minimum values listed. For ages 1 and 2, maximum and 
Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Belews CreeK 

Steam STation 

A-5 

minimum values were assumed to be 25 percent higher and 25 percent lower than the 

most probable value, respectively. 

Largemouth bass – Most probable daily instantaneous natural mortality rates for Age 0 

individuals were assumed to be the same as for the closely-related species, black crappie, 

obtained from EPRI (2005), Table 4-41. Maximum and minimum values were assumed 

to be 25 percent higher and 25 percent lower than the most probable value, respectively. 

Most probable daily instantaneous natural mortality rates for Ages 1+ were calculated 

from total mortality and exploitation rates obtained from Allen et al. (2008). 

Bluegill – Maximum and minimum daily instantaneous natural mortality rates for Age 0+ 

individuals were assumed to be the same as for the closely related species, black crappie, 

and obtained from EPRI (2005), Table 4-41. Most probable values were assumed to be at 

the mid-point between the maximum and minimum values reported. 

Channel catfish – Daily instantaneous natural mortality rates for Ages 0+, daily 

instantaneous natural mortality rates for all ages were obtained from EPRI (2005), Table 

4-25. 

These 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. 

Fishing Mortality Rates 

A range (maximum, most probable, and minimum) of instantaneous fishing mortality 

rates for the two species that directly support fishing were selected as follows: 

Largemouth bass – Daily instantaneous fishing mortality rates for Ages 2+ were 

calculated from total mortality and exploitation rates obtained from Allen et al. (2008). 

These instantaneous fishing mortality rates accounted for fish that are caught and kept as 

well as those that are caught and released but subsequently die from the stress of capture. 

Bluegill – Most probable and maximum daily instantaneous fishing mortality rates for 

Ages 3+ were from Coble (1988) while the minimum value was from Paukert et al. 

(2002). 

Channel catfish – The maximum, most probable, and minimum daily instantaneous 

fishing mortality rates for Ages 5+ were assumed values based on annual fishing 

mortality rates of 0.15, 0.10, and 0.05 respectively, consistent with a lightly exploited 

stock. 

As with natural mortality, 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. Since there is little or no harvest of threadfin shad in Belews 

Lake, fishing mortality rates for this species were set to 0. 
Appendix A: Methods to Estimate Equivalent Loss and Economic Value of Impinged Fish At Belews Creek 

SS 

A-6 

Fishing Capture Rates 

The instantaneous rate of capture by the fishery (Fc) is a measure of the rate fish are 

being caught. For all species except largemouth bass, all fish captured by anglers that 

were caught by anglers were assumed to have been kept. For those species, the 

instantaneous rate of capture is the same as the instantaneous fishing mortality rate (F). 

For largemouth bass, however, the fishery includes of a high rate of catch and release. 

This purposeful release of live fish after capture demonstrates that for this species, it is 

the capture of the fish by recreational anglers that is valued and not merely the harvest of 

fish for consumption. Therefore for this species, the catch rate was assumed to be higher 

than the fishing mortality rate. In this assessment, estimates of the instantaneous rate of 

capture were calculated based on probabilities of release and probabilities of subsequent 

survival as follows: 

 

 

365

1

ln

365





 





   

 

R RS

e

Fc

F

where: 

F = Daily instantaneous fishing mortality rate determined as described above 

R = Probability that a fish that is caught will be released 

RS = Probability that a fish caught and released will survive. 

A range of values for the probabilities that a fish will be released and that it will 

subsequently survive were selected based on best professional judgment following a 

review of available scientific literature: 

Range of Values 

Probability of 

Release 

Probability of 

Survival 

Following 

Release 

Maximum 0.50 0.30 

Most probable 0.25 0.15 

Minimum 0.18 0.05 
Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Belews CreeK 

Steam STation 

A-7 

Fishing Vulnerability Rates 

Fishing vulnerability rates refer to the fraction of each age at a size vulnerable to be 

harvested by anglers. For the maximum and minimum fishing vulnerability rates 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. The ages of complete vulnerability 

were estimated using best professional judgment based on length at age information from 

the scientific literature. Resulting estimates are as follows: 

Species 

Youngest Age of 

Vulnerability 

Oldest Age of 

Vulnerability 

Largemouth bass 2 4 

Bluegill 3 4 

Channel catfish 5 6 

For the most probable values, it was assumed that half of the population became 

vulnerable at the youngest age while the remaining half became vulnerable at the oldest 

age. These 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. 

Weight at Beginning of Age 

A range (maximum, most probable, and minimum) 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 weight at the time of first impingement (Age 

0) was assumed to be 1 g, while those for subsequent ages were obtained from Thompson 

et al. (2005). The maximum and minimum weights were assumed to be 20 percent 

higher and 20 percent lower than the most probable value, respectively. 

Largemouth bass – The most probable mean weight at the time of first impingement (Age 

0) was assumed to be 1 g. Most probable weights for Ages 1+ were estimates using 

lengths and a length-weight relationship for largemouth bass in North Carolina presented 

in Carlander (1977). Maximum and minimum values for all ages were assumed to be 20 

percent higher and 20 percent lower than the most probable value, respectively. 

Bluegill – The most probable mean weight at the time of first impingement (Age 0) was 

assumed to be 1 g, while the maximum and minimum values were assumed to be 20 

percent higher and 20 percent lower than the most probable value, respectively. 

Maximum, most probable and minimum weights for Ages 1+ were based on maximum, 

most probable and minimum lengths at age from Carlander (1977), Cornish and Welke 

(2004), and Heidinger and Waddell (1989), respectively, coupled with a length-weight 

relationship based on unpublished data. 
Appendix A: Methods to Estimate Equivalent Loss and Economic Value of Impinged Fish At Belews Creek 

SS 

A-8 

Channel catfish – The most probable mean weight at the time of first impingement (Age 

0) was assumed to be 1 g. Maximum and minimum values for this age were assumed to 

be 20 percent higher and 20 percent lower than the most probable value, respectively. 

Maximum weights for Ages 1+ were based on lengths at age from Heidinger and 

Waddell (1989) while the most probable and minimum weights were based on lengths at 

age from Pierce et al. (2003) coupled with a length-weight relationship from 

www.Fishbase.org. 

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 beginning 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 BCSS were calculated for each of the 

benefit categories described using standard economic concepts outlined in EPA (2004b, 

Part A: Evaluation Methods, Chapter A9: Benefit Categories and Valuation). Methods 

used to estimate values associated with each of the four benefit categories (market direct 

use benefits, non-market direct use benefits, indirect use benefits, and non-use benefits) 

are discussed below. 

Direct Use Values 

Direct use values accrue to individuals who directly use the aquatic resources affected, in 

other words, commercial and recreational fishermen. The economic value of this benefit 

category is then equivalent to the economic value of the harvest by fishermen 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 value of the direct use 

benefit category was estimated for each sub-component (market and non-market) 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 structures had the potential to increase stock 

size, and hence commercial harvests, positive market benefits could potentially accrue 

had they not been impinged. At present, commercial fishing on Belews Lake appears to 

be non-existent. Hence for this assessment, the market value of any increase in 

commercial fishing was assumed to be essentially 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 Belews CreeK 

Steam STation 

A-9 

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 individual anglers as well as an 

increase in the number of fishing trips by anglers. 

Unfortunately, benefits from increased recreational use of the resource are not directly 

reflected in the primary market, i.e., the market for recreational fishing. However, EPA 

concluded that there is considerable literature to support valuing this benefit through 

estimation of an angler’s “willingness to pay” 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 benefit per unit change in recreational catch. 

For this assessment, total “willingness to pay” for each target species was calculated by 

multiplying the estimated biological benefits (pounds) of impinged fish by the expected 

value per pound recreational anglers were willing to pay for that increased harvest: 

 RFBS  BBRS  RPS

where: 

RFBS = Economic benefits ($) to recreational fishing for each target species (S) 

BBRS = Biological benefits (lbs) to recreational fishing for each target species (S) 

RPS = Value per pound anglers are willing to pay for the increase in harvest of the 

target species (S). 

The biological benefits to the recreational fishery for each target species estimated for 

BCSS (Table 5-2) are likely to be a very small fraction of the estimated recreational catch 

of comparable species in Belews Lake in recent years. Hence, there is no reason to 

expect that changes in recreational fishing harvest that could result had the fish not been 

impinged at BCSS would be sufficiently large so as to affect the price the anglers are 

willing to pay. Therefore, the values that anglers are currently willing to pay for each 

species should be a reasonable measure of the values they would be willing to pay 

assuming impingement was eliminated. This 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 III Rule (EPA 2006), which were then adjusted to reflect current (2009$). 
Appendix A: Methods to Estimate Equivalent Loss and Economic Value of Impinged Fish At Belews Creek 

SS 

A-10 

Each of the recreationally-caught target species in this assessment falls into EPA’s 

panfish category. Values used in this assessment were: 

 

Species Group

Recreational Value (2009 $/fish) 

Maximum Most Probable3 Minimum 

Bass 14.49 8.48 4.97 

Panfish 1.82 0.99 0.54 

To convert these values to a weight basis to be consistent with the biological benefits 

calculation, each of these recreational values was divided by an estimated average weight 

per harvested fish based on best professional judgment. The resulting average weights 

per fish that directly support recreational fishing are as follows: 

 

Species 

Average Weight per Fish Harvested (lb/fish) 

Maximum Most Probable Minimum 

Largemouth bass 2.0 1.5 1.0 

Bluegill 0.3 0.2 0.1 

Channel catfish 3.0 2.0 1.0 

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

 

Species 

Recreational Value (2009$/lb) 

Maximum Most Probable Minimum 

Largemouth bass 14.49 5.66 2.49 

Bluegill 18.22 5.37 1.79 

Channel catfish 1.82 0.54 0.18 

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. 

Indirect Use Benefits 

This category includes benefits that accrue to humans from the use of the resource 

indirectly. Relative to §316(b) regulations, the indirect benefit 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 higher trophic levels, and 

hence, increase fishing opportunities. Production consumed by higher trophic levels 

 

3

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

Steam STation 

A-11 

results from pelagic forage species, such as threadfin shad, as well as individuals of 

recreationally important species that die of natural causes. 

Unfortunately, there are no generally accepted methods to directly assign a value to this 

benefit. Instead, the value of this benefit is assigned indirectly by quantifying the amount 

of commercially and/or recreationally important species that could be supported by the 

production potentially generated by these impinged organisms, which were subsequently 

harvested by man. Hence, the value of the production equivalent to the fish impinged is 

equal to the value of commercial and/or recreational harvest that could be supported by 

that production. 

The value of the indirect benefits of impinged fish at BCSS using the following three-step 

process. 

Step 1 – Estimation of Total Biomass of Higher Trophic Levels Supportable by the 

Annual Productivity Equivalent to the Impingement. The total biomass of higher trophic 

levels supportable is calculated by using a trophic transfer method as follows: 

 HTB   PFB TTC

S

  S  

4

1

where: 

HTB = Total annual higher trophic level biomass (pounds) supported by production 

foregone attributable to impingement 

PFBS = 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 Section 316(b) Final Phase II Rule 

(EPA 2004b). 

For this assessment, production foregone estimates equivalent to impingement at BCSS 

for each of the target species were calculated 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 BCSS. 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 biomass 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 the uncertainty analysis, a range for the trophic 

transfer coefficient of 5 to 15 percent was assumed. 

Step 2 – Estimation of Equivalent Predator Harvest Supported by Annual Productivity 

Equivalent to the Reduction in Impingement. As previously noted, the value of indirect 
Appendix A: Methods to Estimate Equivalent Loss and Economic Value of Impinged Fish At Belews Creek 

SS 

A-12 

benefits is determined by the value of the commercial and/or recreational harvest 

supported by the increased productivity. Hence, 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 biomass of a popular commercial or recreational 

species and then multiplying the value by the annual fishery exploitation rate for that 

species as follows: 

EPY  HTB  EREP

where: 

EPY = Equivalent predatory yield (pounds) attributable to target fish impinged 

HTB = Higher trophic level biomass (pounds) attributable to target fish impinged 

EREP = Fishery exploitation rate for the selected equivalent predator. 

For this assessment, largemouth bass was selected as the equivalent predator endpoint 

upon which the estimate of indirect value is based. In reality, any potential production 

increase would of course be transferred among many species, including some with little 

or no recreational or commercial importance. However, this species is a common 

predator throughout Belews Lake where it is a popular target of anglers. Hence, this 

species should be a reasonably representative species for assigning recreational 

importance, and hence value, for this assessment. Using the life table information, the 

annual probability of capture for largemouth bass was estimated to be 60 percent, 

assuming a relatively intense fishery. For the uncertainty analysis, a range of 40 to 80 

percent was assumed. We believe that the selection of the largemouth bass as the 

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 addressed in this assessment. 

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

of the increased recreational harvest resulting from increases in forage biomass were 

calculated using the methods previously described for direct-use non-market benefits. 

For this assessment, the value per fish for largemouth bass (the equivalent predator) was 

assumed to be the same as described above. 

Non-Use Benefits 

As previously discussed, this category, also known as passive use values, includes all 

benefits above and beyond any accrued through use of the resource. Most commonly 

cited non-use benefits include bequest and existence values. EPA acknowledges that 

these benefits can be estimated best by using contingent valuation methods on a sitespecific basis. However, they concluded that such studies are unlikely to be conducted 
Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Belews CreeK 

Steam STation 

A-13 

for specific facilities and were clearly beyond the scope and budget of EPA for 

development of the § 316(b) regulations (EPA 2004a). 

In the final rule, EPA provided that "In cases where an impingement mortality and 

entrainment characterization study does not identify substantial harm to a threatened or 

endangered species, to the sustainability of populations of important species of fish, 

shellfish, or wildlife, or to the maintenance of community structure and function in a 

facility's waterbody or watershed, monetization [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 benefits if they are believed to exist. 

The fisheries monitoring studies described in Section 5 provide no evidence that 

impingement at BCSS is causing “substantial harm” to threatened and endangered 

species or to aquatic populations and communities of the Belews Lake. 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 the sum of the annual 

economic benefits for all benefit categories described above. These target species, 

however, do not account for all fish impinged at BCSS but only 95.7 percent. The 

following equation was used to account for the benefits resulting from reductions in 

impingement for the remaining 4.3 percent of fish impinged at BCSS: 



 



 



  

4

1

1

0.957

1

TS

Bennon TS BenTS

where: 

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

BenTS = Economic benefits accruing to four target species and the 

equivalent predator. 

The total annual economic value of fish impinged at BCSS is the sum of the benefits to 

the target species plus the benefit to the equivalent predator and the benefit to non-target 

species. 

Uncertainty Analysis 

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

based on benefits valuation also submit “an analysis of the effects of significant sources 

of uncertainty on the results of the study” [§125.95(b)(6)(iii)(C)]. Uncertainty refers to 

the lack of knowledge about measures and components that go into each element of the 
Appendix A: Methods to Estimate Equivalent Loss and Economic Value of Impinged Fish At Belews Creek 

SS 

A-14 

benefits valuation procedures. Under Phase II, the purpose of the uncertainty analysis is 

to make transparent all the underlying sources of uncertainty in the calculation of 

economic value such that the appropriate regulatory authority can independently 

determine whether the results have sufficient precision and accuracy to meet regulatory 

needs (EPA 2004b) and form sufficient basis for sound regulatory decisions. The 

purpose of this section is to evaluate the effects of uncertainty in key input parameters on 

the estimates of economic value for BCSS. 

Uncertainty is not unique to the calculation of economic value under Phase II §316(b). 

Some uncertainty exists in almost all predictions of future conditions based on past or 

existing information and this is especially true when dealing with environmental science 

and economic issues. In both environmental science and economics, inherent variability 

and limited understanding of underlying processes, coupled with difficulty in making 

accurate measurements of underlying parameters, makes consideration of uncertainty in 

these cases especially important. Uncertainty analysis is becoming an increasingly 

important part of cost-benefit assessments as they play a greater role in the environmental 

regulatory process. 

EPA (2000) identified the following minimum requirements applicable to most 

uncertainty analyses related to environmental regulations: 

 To present the outcomes or conclusions based 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 uncertainty in model parameters. Natural variation 

results from natural differences across elements within a population or in a population 

across time. For example, not all members of the United States population are expected 

to value increased recreational fishing opportunities to the same degree. Alternatively, 

wide year-to-year differences in impingement densities at the same station are common. 

These differences in abundance can result in large differences in the annual economic 

value. Both of these examples can yield uncertainty in the total economic value 

estimated under §316(b). 

Uncertainty related to model structure arises from the lack of knowledge as to what is the 

most appropriate form of the model to accurately describe the process being modeled. 

For example, the form of the relationship between the number of trips and travel cost in a 

simple travel cost model has been assumed to be linear, semi-log, or log by various 

analysts (Rosenberger and Loomis 2001). However, 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. 
Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Belews CreeK 

Steam STation 

A-15 

Finally, uncertainty in model parameters can result 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 economic 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, estimates of the performance of the various 

CWIS alternatives, 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 and magnitude of non-use 

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 Indirect Use Benefits 

Key input parameters addressed in this section include: 

 Natural mortality rate, 

 Fishing mortality rate, 

 Recreational fishing release rate, 

 Post-release survival 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, impingement rates and age composition, were not 

addressed in this uncertainty analysis as reliable information on the uncertainty was 

unavailable from the historical 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 uncertainty in the estimates of annual economic 

value resulting from the current levels of uncertainty. The results of each of these 

analyses are provided below. 

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., maximum and minimum) for each parameter while 
Appendix A: Methods to Estimate Equivalent Loss and Economic Value of Impinged Fish At Belews Creek 

SS 

A-16 

holding all other parameters constant at their most probable values. The purpose of this 

sensitivity analysis was to determine the parameters 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 based 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, wherein the maximum and minimum values for 

the distribution were set to the maximum and minimum values for each parameter 

described earlier and the mode of the distribution 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 and the Monte Carlo analysis was run using 

1,000 iterations to define the resulting frequency distribution in annual estimates of 

equivalent loss measures and economic benefit.