ABSTRACT 

Fish impingement data were collected at four generating 

facilities representing river intake, epilimnetic reservoir 

intake, and hypolimnetic reservoir (skimmer-wall) intake 

designs. The study sites included both traveliig and 

stationary intake-screen systems. At all sites fewer species 

were represented in impingement samples than were collected during concurrent field investigations in the study 

areas. Significant differences in impingement rates among 

seasons were established and were caused primarily by large 

numbers of threadfin shad impinged during the coldest 

months. Intake velocities did not determine relative rates of 

impingement at the sites studied. Certain characteristics of 

intake design appeared to influence impingement rates 

significantly, however. Skimmer walls, present at two sites, 

did not provide a deterrent to fuh impingement. 

'A continuous supply of condenser cooling water is required 

in the operation of steam electric stations using oncethrough coding systems. Losses due to impingement 

represent a potentially significant impact on existing 

fisheries, depending on the number of fish involved and the 

species affected. The impingement of fuh on the intake 

screens of power stations presents problems in terms of 

operating efficiency as well as from a biological standpoint 

(Edsall and Yocom, 1972). Losses due to impingement do 

not necessarily represent significant losses to resident fish 

populations, however (Landry and Strawn, 1974). 

Our study, initiated in the spring of 1974,was designed 

to monitor impingement rates. Data were analyzed in an 

effort to explain some of the causative factors involved in 

the impingement of fish and to provide an indication of 

overall effects on resident fBheries. Fish-impingement data 

were collected at four generating facilities operated by 

Duke Power Company. The sites include an epilimnetic 

reservoir intake design (Men Steam Station), two hypelimnetic reservoir (skimmer-wall) intake designs (Marshal1 

Steam Station and Oconee Nuclear Station), and a river 

intake design (Buck Steam Station). Condenser cooling at 

each of these sites is accomplished with a once-through 

open-loop system. 

DESCRIPTION OF STUDY AREAS 

Allen Steam Station 

Allen Steam Station, an epilimnetic reservoir intake 

design located in Gaston County, N. C., draws condensercooling water from the northern end of Lake Wylie, a 

5040-ha impoundment. This five-unit coal-burning facility 

began operating in 1957 and has a total capacity of 

1140 Mw(e). The intake structure, comprised of 10 pumps 

with a maximum total flow of 35 m3/sec, is located at the 

back of a small cove of -1.5 ha. Intake velocities are 

indicated in Table 1. 

An extensive study of the Lake Wylie fishery was 

conducted from September 1973 to August 1974 (Industrial Bio-Test Laboratories, Inc., 1974). A total of 40 

species of fishes representing 10 families were collected 

with gd nets and electrofishing gear. Collections were 

comprised primarily of the families Clupeidae, Cyprinidae, 

Catostomidae, Ictaluridae, and Centrarchidae. Important 

forage species include gizzard and threadfin shad and 

several cyprinids. Creel census data indicate that Lake Wylie 

supports a better-than-average sport fuhery ;major species 

were crappie, bluegill, largemouth bass, and catfish (Industrial Bio-Test Laboratories, Inc., 1974). 

Marshall Steam Station and 

Oconee Nuclear Station 

Marshall Steam Station is located on Lake Norman in 

Catawba County, N. C.; Oconee Nuclear Station is located 

on Lake Keowee in Oconee County, S.C. Each is a 

hypolimnetic reservoir (skimmer-wall) intake design. At 

both sites condenser cooling water is drawn from an intake 

Edwards, Hunt, Miller, and Srvic: Duke Power Company, Environmental Sciences Unit, Charlotte, North Carolina. 

I 

I 3 73 
TABLE 1 Intake Velocities (cmlsec) 

at Four Duke Power Company 

Generating Facilities 

Pumping Maximum 

mode Full pond drawdown 

Allen Steam Station 

Units 1and 2 

1 Pump 4.57 7.62 

2 pumps 7.62 12.50 

Units 3,4, 

and 5 

1Pump 6.70 11.28 

2 pumps 11.28 18.90 

Marshall Steam Statioh 

Units 1and 2 

1 Pump 7.32 13.41 

2 pumps 10.67 18.90 

Units 3 and 4 

1Pump 5.49 9.75 

2 pumps 9.14 16.15 

3 pumps 11.89 21.03 

Buck Steam Station 

Units 1 and 2 

1 Pump 79.25 79.25 

2 pumps 73.7 6 73.76 

Units 3,4,5, 

and 6 

1 Pump 50.60 82.90 

2 pumps 38.10 61.57 

Oconee Nuclear Station 

Units 1,2, 

and 3 

2 pumps 36.27 51.51 

3 pumps 31.70 45.11 

4 pumps 26.80 38.05 

cove separated from the main body of the lake by a 

skimmer wall, which is a solid concrete structure extending 

from the surface to a depth of 20 m, well below the depth 

of the summer thermocline. During the summer, lowtemperature hypolimnetic water is drawn into the cove and 

provides efficient condenser cooling. At both Marshall and 

Oconee, intake structures are located at the extreme back 

of the intake coves; water flow is from the skimmer waII to 

the intake structure. 

Marshall Steam Station is a four-unit cod-burning 

facility with an output capacity of 2025 Mw(e). The total 

capacity of the 10intake pumps is 65 m3/sec. The Marshall 

intake includes 16 stationary intake screens, and the 

skimmer wall separates the intake cove (-81 ha) from the 

main body of Lake Norman (Fig 1). 

The fishery of Lake Norman has been investigated by 

the North Carolina Wildlife Resources Commission (Miller 

and DeMont, 1974) and the Environmental Sciences Unit at 

Duke Power Company (Duke Power Company, 1974). 

Forty species of fishes representing 10 fadies were 

reported in these two studies. Lake Norman supports 

several species of Cyprinidae, Catostomidae, Ictaluridae, 

374 Edwards, Hunt, Niller, und Sevic 

t

E 

YADKIN RIVER 

0

2 FLOW ____) 

1 - -

123456 

BUCK 

STEAM STATtON 

LAKE WYLIE. CATAWBA RIVER t

1 FLOW +

E T

12345 

FIG. 1 Intake structure locations at three power-plant sites. 

{a) river intake design. (b) epilimnetic reservoir intake design. 

(c) hypolirnnetic reservoir (skimmer-wall)intake design. 

and Centrarchidae. Valued sport species are sunfish, 

crappie, largemouth bass, white bass, and striped bass. 

Threadfin shad have been introduced and have become well 

established as a forage species. Cove rotenone data collected 

during the summers of 1973 and 1974 provided a mean 

biomass estimate of -123 kg/ha. 

Oconee Nuclear Station has three generating units with 

a total output capacity of 2625 Mw(ej. The intake structure includes 24 stationary intake screens and 12 intake 

pumps with a total capacity of 128 m3/sec. The intake cove 

at Oconee (-25 ha) is similar to the Marshall intake cove 

shown in Fig. 1. 

Since June 1972, the Southeast Reservoir Investigations, Bureau of Sport Fisheries and Wildlife, has been 

investigating the fishery of Lake Keowee in connection 

with the operation of Oconee Nuclear Station (Southeast 

Reservoir Investigations, 1972). Electrofishing and $&net 

I 

I 

I 
data have accounted for 41 species representing 9 families. 

Centrarchidae, Ictaluridae, and Catostomidae made up the 

majority of the total catch. A creel census conducted 

between July and September 1973 indicated that largemouth bass, bluegdl, and crappie are important sport fBhes. 

Yearly estimates of fish biomass from cove rotenone data 

from 1972 to 1974 have averaged -67.4 kg/ha. Threadfin 

shad were stocked in February of 1974 and apparently have 

become established as a forage fish. 

Buck Steam Station 

Buck Steam Station, a river intake design located in 

Rowan County, N. C., draws condensercooling water from 

the Yadkin River near its mouth at High Rock Lake. A 

six-unit coal-burning facility, Buck began operation in 1926 

and has a total capacity of 488 Mw(e). 

The intake structure, which is made up of 10 pumps 

capable of drawing water at a maximum rate of 21 m3/sec, 

is located on the shoreline of the river and parallel to the 

river flow (Fig. 1). Intake velocities at Buck are shown in 

Table 1. 

An environmental investigation of the Yadkin River, 

including a field study of the river's fishery, has been 

conducted by Duke Power Company (1975). Forty species 

representing 11 families were collected from October 1973 

to September 1974. Collections from all stations sampled 

were composed primarily of the families Cyprinidae, 

Ictaluridae, Centrarchidae, and Clupeidae. Important sport 

fishes in the area include several species of centrarchids, as 

well as white and channel catfish. Abundant forage species 

are gizzard shad, satinfii shiner, and whitefin shiner. In 

contrast to other sites, threadfin shad are not abundant in 

the area. 

MATERIALS AND METHODS 

Duke Power Company steam stations have two basic 

types of intake structures. Marshall Steam Station and 

Oconee Nuclear Station have stationary intake screens, 

which must be removed with a crane for each inspection. 

Allen and Buck Steam Stations have traveIing screens made 

up of several panels' mounted on a vertical conveyor-belt 

arrangement. Both traveling and stationary intake screens 

have 1-crn mesh and are located behind vertical trash racks 

with bars at 7.6-cm intervals. 

At sites having stationary intake screens, because of the 

difficulty and time involved, one screen from each unit 

(25% of the total screen area) was removed and inspected at 

2-week intervals. After each inspection screens were cleaned 

thoroughly and replaced; each inspection represented the 

total impingement per screen occurring over a 2-week 

period. Fishes were identified, measured, and counted. 

When exceptionally large numbers of fishes were collected, 

total numbers were estimated from a subsample. 

At traveling screen sites, one screen associated with 

each generating unit was inspected regularly twice each 

week. During the normal screen-washing procedure, water 

jets are directed at screens as they are rotated. Debris and 

impinged fishes are washed off into a sluiceway that flows 

into the river or reservoir. For our inspechon screens were 

rotated, washed, and left in place for 24 hr. They were then 

rotated and washed again, and fishes and debris were 

collected in a wire-mesh catch basket placed in the 

sluiceway. Fishes collected were preserved in 10%formalin ' 

and brought back to the laboratory, where they were 

identified, measured, and counted. 

At Allen Steam Station impingement studies were 

conducted for 1 year by Industrial Bio-Test Laboratories, 

Inc. (Krueger, Rice, and Otto, 1974). Three 8-hr subsamples were taken over a 24-hr sample period every 2 

weeks. All screens were sampled on each sample date. 

At some steam stations, when river conditions and 

heavy accumulation of debris have necessitated early 

cleaning of intake screens, total sample periods have been 

less than 24 hr. An effort was made at all stations to be as 

consistent as possible in the actual screen sampling and the 

total time screens were left stationary. Occasionally alternate screens were sampled because of operating difficulties 

or required repairs. 

Fish impingement has been expressed as total seasonal 

impingement by species (fish per screen per day) and 

es+mated impingement rates (total daily impingement). 

Estimated rates were derived by extrapolating collected 

data (fish per representative intake screen per sample 

period). Fishes that were unidentifiable because of decomposition were listed as such; otherwise, identifications were 

made to lowest possible taxon. 

Intake-approach velocities were calculated from total 

pump flow and actual area of intake-screen openings. 

Intake temperatures were monitored hourly at each station 

with a thermocouple or a resistance temperature device. 

To satisfy required assumptions of analysis of variance, 

we transformed raw data collected at Marshall Steam Station 

using common logarithms. A two-way analysis of variance 

(ANOVA) (Sokal and Rohlf, 1969) was then used to test 

for differences in impingement rates between units and 

seasons. Duncan's multiple range test was used to determine 

relative differences between units (SteeI and Torrie, 1960). 

RESULTS 

Allen Steam Station 

At Allen Steam Station, 55,762 fishes representing 19 

taxonomic groups (18 species plus 1 genus) were collected 

from October 1973 through September 1974 (Table 2). 

Gizzard shad, threadfin shad, channel catfish, and bluegill 

were collected most consistently and were present in 

samples during each month of the study. Threadfm shad 

accounted for the majority of fishes collected (54,971) and 

comprised 98.6% of the total catch. Of these, 91.8% were 

collected from November 1973 through January 1974. 

&, the data in Table 2 indicate, rates of fish irnpingemcnt at Allen were lowest in spring and summer and 

highest in fall and winter. The estimated number of fish 

impinged per screen per day, calculated on a seasonal basis, 

ranged from 13 in spring 1974 to 349 in fall 1973. This 
TABLE 2 Seasonal Summary of Fish Impingement at Allen Steam Station* 

Common name Scientificname Oct.--Dec. 1973 Jan.-Mar. 1974 Apr.-June 1974 Jd.-Sept. 1974 

Gizzard shad 

Threadfin shad 

Channel catfish 

Bluegill 

Miscellaneoust 

Dorosoma cepedianum 59 26 43 70 

Dorosoma petenense 31,295 20,219 836 2621 

Ictalurus punctatus 7 45 20 12 

Lepomis macrochirus 31 24 168 89 

20 34 71 72 

Total number of fish collected 31,412 20,348 1138 2864 

Estimated fishlscreenlday 349 226 13 32 

Estimated total fish/day 5,235 3,390 195 480 

*Fish per screen per day and total fEh per day were determined from the number of fish impinged on all intake screens. All 

screens were sampled from October 1973 to August 1974 by Industrial Bio-Test Laboratories, Inc. Total impingement in September 

1974 was estimated from samples collected from five representativescreens by Duke Power Company, Environmental Sciences Unit 

(total number of screens at AIlen is 15). 

tMiscellaneous fish, listed from most to least frequently impinged, are: white catfish, Ictalurw catus; yellow perch, Perca 

flmescens; pumpkinseed, Lepomis gibbosus; warmouth, Lepomis gulosus; redbreast, Lepomis auritus; catfish, Ictalurus sp.; redear, 

Lepomis micsolophw; silvery minnow, Hy bognathus nuchalis; brown bullhead, Ictalurus nebulosus; golden shiner, Notemjgonus 

cryzo&ucar; mosquitofish, Gambusia affinis; white bass, Morone Chrysops; satinfin shiner, Notropis andostunus; black crappie, 

Pornoxis nigromaculatus; and largemouth bass, Micropterus salrnoides. 

corresponds to a range in total daily impingement of 195 to 

5235 fEhes for spring and fall, respectively. An estimated 

898,911 fishes were impinged at Allen throughout the 

study period. 

Oconee Nuclear Station 

At Oconee Nuclear Station, .241,697 fishes, including 

12 taxonomic groups (9 species and 3 genera), were 

collected on representative screens from July 1974 through 

May 1975 (Table 3). Threadfin shad, stocked in February 

1974, were not represented in the samples to any extent 

until November 1974. Prior to this, yellow perch and 

blue$ comprised the majority of identifiable fish (22.2% 

and 72.6%, respectively). By December threadfin shad had 

become the dominant species collected and remained so 

through winter 1975. Overall, threadfin shad accounted for 

49.3% of the total identifiable fish collected. Yellow perch, 

blue*, and threadfin (4 to 6 cm long and weighing -2.1 g 

each) were the most commonly impinged fishes at Oconee. 

Impingement rates were lower in spring and summer 

than in fall and winter. The estimated number of fish 

impinged per screen per day ranged from 15 in summer 

1974 to 393 in winter 1975. This represents an estimated 

total daily impingement rate of 372 in summer 1974 and 

9425 in winter 1975. An estimated total of 1,064,262 

fishes were impinged at Oconee throughout the study 

period. 

Marshall Steam Station 

Impingement data collected at Marsh& Steam Station 

from April 1974 through March 1975 are presented in 

Table 4. Fishes collected at Marshall have been categorized 

into 14 ~OUPS,including 10 species and 4 genera. A total 

of 974,896 fBhes were collected on representative screens 

throughout the study period. Impingement rates at Marshall 

376 Edwards, Hunt, Miller, and Sevic 

were highest in fall 1974 and winter 1975 (1518 and 1108 

fEh/screen/day, respectively). An estimated 54 fuhlscreenl 

day were collected in spring 1974, and 6 fish/screen/day 

were collected in summer 1974. Total fish impinged per 

day ranged from 96 in summer 1974 to 24,090 in fall 1974. 

An estimated 3,769,300 fishes were impinged at Marshall 

throughout the study period. Approximately 9vo of this 

total was made up of threadfin shad and Dorosoma sp- The 

size range of the Dorosorna suggests that they also were 

threadfm shad. The majority of the shad were collected in 

November and December 1974 and January 1975. 

Analysis of variance indicated that significant differences existed in the number of fishes collected among 

units (P<O.O1) and among winter, spring, and summer' 

seasons (P <0.01). Fall data were not included in statistical 

analyses because unit 3 intake pumps did not operate for 

several days. Duncan's multiple range test has shown that 

the mean number of fishes collected at each unit is 

significandy different from means at all other units. 

Buck Steam Station 

Impingement rates were low at Buck Steam Station 

(Table 5) despite relatively high intake velocities (Table 1). 

A total of 467 fishes was collected from representative 

screens from Jdy ,1974 through June 1975. Fishes impinged at Buck, identified tolowest possible ma, comprise 

7 species and 2 genera groups. 

Estimated total daily impingement at Buck was less 

than 1 fish/day in both fall and winter 1974. The estimated 

total fish collected per day was highest in summer 1974 

(42.5 fish/day) and intermediate in spring 1975 (1.3 

f&h/day). Fish mortalities occurring upstream are the 

suspected cause of relatively high numbers of fish collected 

during the summer period. 

I 

I 

i 
TABLE 3 Seasonal Summary of Fish Impingement at Oconee Nuclear Station* 

Common name Scientific name JulySept. 1974 0ct.-Dec. 1974 Jan.-Mar. 1975 Apr.-May 1975 

Threadfm shad Dorosoma petenense 0 9,949 107365 1426 

Bluegill Lepomis macrochirus 2749 183 365 82 

Yellow perch Perca frauescens 757 182 4,164 874 

Unidentifiable 5005 3,157 99,653 5215 

Misceilaneoust 24 26 14 7 

Total number of fish collected 8535 13,497 212,061 7604 

Estimated fishlscreen/day 15 24 393 28 

Estimated total fishlday 372 587 9,425 676 ~ ~~ 

+Fish per screen per day and total fish per day were estimated from the number of fish impinged on six representative intake 

screens; total number of screens at Oconee is 24. 

t Miscellaneous fish, listed from most to least frequently impinged, are: gizzard shad, Dorosoma cepedianum; crappie, 

Pomoxis cpi.; white crappie, Pomoxis annulark; catfish, IctaIunrs sp.; pumpkinseed, Lepomis gibbosus; warmouth, Lepomis gulosus; 

carp, Cyprt:us carpio; largemouth bass, Micropterus salmoides; and trout, Sdmo sp. 

TABLE 4 Seasonal Summary of Fish Impingement at Marshall Steam Station* 

Common name Scientific name Apr.-June 1974 July-Sept. 1974 0ct.-Dec. 1974 Jan.-Mar. 1975 

~~ 

Gizzard shad Dorosoma cepedianum 1,108 49 69 40 

Threadfm shad Dorosoma petenense 1,995 1879 181,109 393,623 

Shad Dorosoma sp. 6,780 70 377,419 0 

Catfish Ictalurn sp. 4 99 22 0 

Yellow perch Perca jlavescens 722 19 42 10 

Unidentifiable 4,414 22 . 17 5,356 

Miscellaneoust 17 6 3 2 

Total number of fish collected 15,040 2144 558,681 399,031 

Estimated fish/screen/day 54 6 1,518 1,108 

Estimated total fish/day 864 96 24,090 17,728 

*Fish per screen per day and total fish per day were estimated from the number of fish impinged on four representative intake 

screens; total number of screens at Marshall is 16. 

tMiscellaneous fish, listed from most to least frequently impinged, are: minnows, Nohopissp.; black crappie, Pomoris 

nigromacukztus; white crappie, Pomoxis annularis; largemouth bass, Microptern salmoides; bluegill, Lepomis macrochirus; sunfish, 

Lepomis sp.; striped bass, Morone saxatilis; carp, Cyprinus cmpio;and golden shiner, Notemigonus crysoleucar. 

TABLE 5 Seasonal Summary of Fish Impingement at Buck Steam Station* 

Common name Scientific name JutySept. 1974 0ct.-Dec. 1974 Jan.-Mar. 1975 Apr.-June 1975 

Gizard shad Dorosoma cepedianum 391 0 1 0 

Threadfm shad Dorosoma petenme 1 0 0 10 

Shad Dorosoma sp. 33 0 0 2 

Miscellaneoust 14 0 1 14 

Total number of fish collected 439 0 2 26 

Estimated fish/screen/day 4.25 0 <0.1 0.13 

Estimated total fishlday 42.5 0 <0.1 1.3 ~~ ~ ~~ 

*Fish per screen per day and total fish per day were estimated from the number of fish impinged on four representative intake 

screens; total number of screens at Buck is 14. 

tMiscellaneous fish, listed from most to least frequently impinged, are: white catfish, Ictalurus catus; bluegill, hpomis 

macrochirus; catfish, Ictalurus sp.; channel catfish, IctaIurn punctatus; brown bullhead, Ictalurus nebuZosus; and black crappie, 

Pomoxisnigromacuhtus. 

Evaluation ofI&ingernent of Fishes 377 
- 

An estimated 4069 fishes were impinged at Buck 

throughout the study period. Gizzard shad, threadfin shad, 

and Dorosorna sp. made up 93.8% of dl fish collected. 

. DISCUSSION 

Intake Velocity 

Intake. velocities vary considerably among the stations 

at which impingement has been monitored (Table 1). 

Velocities fluctuate with water level and the number of 

intake pumps in operation. Ranges of possible intake 

velocities for Marshall and Allen Steam Stations are similar 

and are the lowest ranges of the four sites. Intake velocities 

at Oconee Nuclear Station are intermediate, and those at 

Buck Steam Station are the highest encountered in the 

study. 

Impingement rates at these sites cannot be explained on 

the basis of intake velocity. Despite the high intake 

velocities at Buck, the rate of fish impingement at this site 

was lowest. 'The highest number of fish were collected at 

Marshall and Allen, where velocities were relatively low. 

Average intake velocities throughout the study period 

were calculated for each of the four generating units at 

Marshall Steam Station, and corresponding impingement 

rates were determined (Fig. 2). Velocities were calculated 

on the basis of the number of pumps in operation; constant 

water level (full pond) was assumed. Although intake 

velocities are similar for each of the four units at Marshall, 

significant differences in rates of impingement occurred. 

i' At Allen the highest numbers of fish were collected at 

units 1 and 5,even though these units represent the lowest 

and highest velocities, respectively, at this station. These !,& data indicate that impingement rates vary significantthat cKk~emces~c~u~&~depemfmnaf intaKe * ' veiocines. * .. 

Intake Structure Design 

The intake design at Buck Steam Station may be a - m a j o L f g to low impinmment ra-t .. 

dsite. The intake structure is parallel to and relatively iiush 

with the river bank (Fig. 1). This design reduces the 

possibility -of eddy currents, which may concentrate fish 

and subsequently trap them in the intake (U. S. Environmental Protection Agency, 1973). 

Impingement of both threadfin shad and all other 

species combined is considerably higher at Marshall than at 

Buck despite Marshall's relatively low intake velocities. It 

has been established that variation in impingement rates 

among units 1 to 4 at Marshall is apparently not related to 

intake velocity. The shape of the intake cove probably 

causes the high impingement- rates at unit 4 and the 

consecutively decreasing rates at units 3,2, and 1 (Fig. 2). 

As shown in Fig. 1, the intake structure at Marsh& is 

located at ehe extreme back of a cove. Currents create 

eddys next to screens associated with unit 4, and fish 

apparently concentrate in these eddy currents and become 

susceptible to impingement. 

Variations in impingement rates among units at Allen 

were also observed. These have been attributed, in part, to 

3 78 Edwards, Hunt, Miller, and Sevic 

v = 8.2 

UNlT 1 UNIT 2 UNIT 3 UNIT 4 

FIG. 2 Impingement rare and mean daily velocity (Y),in cmlsec, 

for the four units at Marshall Steam Station from Apr. 30, 1974, 

through Feb. 4,1975. 

the relative position of intake screens (Fig. I). Consistently 

higher numbers of fEh were collected at units 1 and 5, 

probably because of the extreme upstream and downstream 

position of these units. It is likely that eddy currents on 

either side of the intake structure attract fish, which 

subsequently become impinged on. the nearest intake 

screens (those associated with units 1 and 5). 

Resident Fish Populations 

Field fishery investigations in the vicinities of Allen, 

Buck, and Marshall Steam Stations and Oconee Nuclear 

Station have indicated 

are low, the areas 

all cases, 

conected 

-on intake screens. - .. -- I 

I 
At Allen, 24 species were collected in the area during a 

field study on Lake Wylie; 16 of these were collected from 

the traveling screens at the intake. Silvery minnows and 

mosquito fish, which were collected on intake screens, were 

not represented in field collections, and eight species were 

collected in the field which were absent from screen 

samples. At Lake Keowee, 33 species collected in the field 

were not collected on intake screens at Oconee; all species 

impinged were represented in field samples. Of the 40 

species reported from Lake Norman, only 10 were impinged at Marshall. At Buck, 100-fishes were collected 

immediately above and beIow the intake structure in 

-40min on a single day in February; these included 16 

species representing 7 families. There were no fish impinged 

at Buck in February, however, and only 7 species were 

impinged throughout the entire study. 

- That the species collected on intake screens were not 

represented in numbers proportional to the field samples 

suggests further that susceptibility to impingement is, to 

- some degree, species specific. Data collected from the 

intake cove at Marshall provide an example. Electrofishing 

samples were collected in the intake cove on Feb. 21, 1975, 

in an effort tto compare the numbers and species of fishes 

impinged with those present in the intake cove. Samples 

collected in snnalI inlets above the intake structure provided 

182 fishes, representing 12 species and 5 families. Sport 

fishes, including centrarchids, percids, and percichthyids, 

made up 39.5% of the catch. Threadfin shad accounted for 

52.7% of all fish collected; all others were carp. Impingement data collected at Marshall in February indicate a total 

of 166.115 fishes impinged on four representative intake 

screens. Threadfin shad accounted for 99.9% (166,095) of 

the total; others included gizzard shad and one white 

catfish. 

Temperature 

Data collected at Allen and Marshall Steam Stations and 

Oconee Nuclear Station have shown seasonal trends in total 

, numbers of fish impinged. Impingement rates have generally been relatively high in late fall and winter and low 

throughout the rest of the year. This trend resulted from 

the collection of large numbers of threadfin shad when 

temperatures were low. 

The relationship between temperature, the impingement of shad, and the impingement of all other species at 

Marshall is shown in Fig. 3. Threadfin shad were collected 

at relatively high rates beginning in November, when water 

temperatures dropped to -13°C. Threadfin shad are known 

to be susceptible to low temperatures, and mortalities have 

been reported below 9°C (Strawn, 1963). Data presented 

here indicate that threadfin may become stressed at 

temperatures considerably higher than 9°C and are then 

susceptible to impingement because of their inability to 

resist intake currents. At Marshall, the impingement of 

species other than threadfin shad appears to be unrelated to 

temperature. Other species impinged, which have wider 

10' 

25 

1oL 

20 

6103 0 

LL UJ lA E 0 3 rn Ia 

w 5," m W 

I a. 

3102 z z w 

II O 

10' -....... 1. .*e . . . . .I... 

10 

3014281325 9 22 620 317 1152912261123 8217 18 6 18 

APR. MAY JUNE JULYAUG.SEPT. OCT. NOV. OEC. JAN. FEE. MAR. 

1974 1975 

FIG. 3 Fish impingement at Marshall Steam Station, in mean 

number of fish per screen per day, relative to water temperature. 

Shad, -. Other species, - - - -.Temperature,. .... 

ranges of thermal tolerance, are apparently not stressed by 

the ambient winter temperatures of Lake Norman. 

A similar situation existed at Allen Steam Station. Of 

the total number of threadfin shad impinged there (98.8% 

of total fishes collected), 95.4% of the mortalities were 

attributed to low winter temperatures. 

After being introduced into Lake Keowee for the first 

time in February 1974, threadfin shad made up the 

majority of the fishes impinged at Oconee Nuclear Station 

in the winter of 1974-1975. Low winter temperatures are 

suspected as the cause. 

The impingement of threadfin shad at these sites does 

not appear to be a major cause of mortality but is rather an 

indication of natural mortality of the species. *. -.-A 

*.-- Summarizing the major points discussed, we conclude: 

* 1.Threadfin shad made up the majority of fish collected on intake screens. Sport fishes and other valuable 

species were considerably less susceptible to impingement. 

2. In all cases the number of fish species impinged at 

specific sites was fewer than the number collected during 

concurrent field investigations in the study area. 

3. Overall, relatively large numbers of fuh were COIIected on intake screens during late fall or winter, This was 

caused 

temperature. 

by the 

The 

susceptibility 

majority of 

of 

the 

threadfin 

threadfin 

shad 

shad 

to 

were 

low I

apparently stressed or dead before they were collected on 

intake screens. 

Evaluation of I&in.ernent of Fishes 379 
E 4. Intake velocity was not a determining factor concern­ \ing relative rates of impingement among the sites discussed. 

5. Intake design, specifically the position of the intake r. 

structure relative to the cooling-water source, signiticantly 

affected impingement rates. 

6.The skimmer walls at Marshall Steam Station and 

. Oconee Nuclear Station have not provided a deterrent to L 

the impingement of fish. 

7. In view of the species and numbers of fsh affected, it 

is doubtful that impingement at these sites has had 

significant impact on resident fish populations.

-. 

ACKNOWLEDGMENTS 

This research would not have been possible without the 

cooperation of the superintendents and station personnel at 

Duke Power Company’s Allen, Buck, and Marshall Steam 

Stations and Oconee Nuclear Station. We appreciate the 

constructivle reviews offered by W. D. Adair and L. L. 

Olmsted and the preparation of the final manuscript by 

Stan McCorkle. 

REFERENCES 

Duke Power Company, 1975, Environmental Report, Project 81, 

Perkins Nuclear Station, Volume 1,Charlotte, N. C. 

-, ’ 1974, Environmental Report, McGuire Nuclear Station, 

Units 1 and 2, Operating License Stage, Volume 1, Charlotte, 

N. C. 

Edsall, T. A., and T. G. Yocom, 1972, Review of Recent Technical 

Information Concerning the Adverse Effects of Once-Through 

380 E,dwards, Hunt, Miller, and Sevic 

Cooling on Lake Michigan, U. S. Fish and Wildlife Service, 

Bureau of Sport FisheGes and WiIdlife, Great Lakes Fishery 

Laboratory, Ann Arbor, Mich. 

Industrial Bio-Test Laboratories, Inc., 1974, A Baseline I Predictive 

Environmental Investigation of Lake Wylie, September 

1973-August 1974, Report to Duke Power Company, Charlotte, N. C. 

Krueger, J. F., J. 0. Rice, and R. G. Otto, 1974, Screen Monitoring 

at Allen Station, September 1973-August 1974, Industrial 

Bio-Test Laboratories, Inc., Charlotte, N. C. 

Landry, A. M., Jr., and K. Strawn, 1974, Number of Individuals and 

Injury Rates of Fishes Caught on Revolving Screens at the P. H. 

Robinson Generating Station, in Proceedings of the Second 

Workshop on Entrainment and Intuke Screening, L. D. Jensen 

(Ed.), pp. 263-271, Research Project RP-49. Report No. 15, 

The Johns Hopkins University Press, Baltimore, Md. 

Miller, R. W., and D. J. DeMont, 1974, Fisheries Research, in 

Environmentul Responses to Thermal Discharges from Marshall 

Steam Station, Lake Nomn, North Carolina, L. D. Jensen 

(Ed.), pp. 187-216, Research Project RP-49, Report 11, The 

Johns Hopkins University Press, Baltimore, Md. 

Sokal, R. R., and F. J. Rohlf, 1969, Biometry, W. H. Freemanand 

Company, San Francisco. 

Southeast Reservoir Investigations, 1972, Annual Report, U. S. 

Bureau of Sport Fisheries and Wildlife, Clemson, S. C. 

Steel, R. G. D., and J. H. Tome, 1960, Principles and Procedures of 

Statistics, McGraw-Hill Book Company, Inc., New York. 

Strawn, K., 1963, Resistance of Threadfin Shad to Low Temperatures, Proc. Annu. Conf.Southeast. Assoc. Game Fish Comm., 

17: 290-293. 

U. S. Environmental Protection Agency, 1973, Development 

Document for Proposed Best Technology Available for Minimizing Adverse Environmental Impact of Cooling Water Intake 

Structures, Report No. EPA 44011-741015, Washington, D. C. 
-__I__ 

.-­

d' ti 1 

CONF-750425 

1 

Thermal 

Ecology II 

Proceedings of a symposium held at Augusta, Georgia 

April 2-5,1975 

Sponsored by 

Savannah River Ecology Laboratory 

Institute of Ecology, University of Georgia 

Division of Biomedical and Environmental Research 

Energy Research and Development Administration 

Edited by 

Gerald W. Esch 

Wake Forest University 

Robert W. McFariane 

Savannah River Ecology Laboratory 

1976 

Pubfished by 

Technical Information Center 1 Energy Research and Development Administration I