Docket OW-2002-0049 DCN#: 6-5046H 

Johiiron, I and S Mom, JEA 

Flsh Return System Efficacy and Impingement 

Monitoring Studles for JEA’s Northslde Geneiating 

Station 

FISH WTUW SYSTEM EFFICACY AND IMPINGEMENT MONITORING 

STUDIES FOR JEA’S NORTHSIDE GENERATING STATION 

Isabel C. Johnson 

Golder Associates Inc. 

Gainesville, Florida 

and 

Steve Moser 

JEA 

Jacksonville, Florida 

Abstract 

The JEA Northside Generating Station (Station) is located north of Jacksonville, Florida, and is adjacent to 

San Carlos Creek, a tributary to the St. Johns River. The plant is approximately 10river miles from the 

Atlantic Ocean, and the plant’s once-through cooling water intake flume draws water from a tidal river, the 

St. Johns River; the Station discharges its cooling water back to the St. Johns River. The intake structures at 

the plant consist of: concrete-lined bays approximately 30 feet deep; a set of continuous-belt traveling 

screens; and electrically driven impeller pumps for circulating the cooling water. 

The Station’s fish return system (FRS) is an array of trays, wash sprays, and sluice channels (troughs) 

designed to remove impinged organisms from the traveling screens and return them to the aquatic system. 

Each FRS has a rotating traveling screen (0.5-inch mesh) with collection pans attached approximately every 

four feet. As the traveling screens rotate, low pressure sprays rinse the biota fi-om the screens into the fish 

trays; the biota are then flushed with the water over a rubber lip into the fish return troughs. Troughsjoin 

two main channels that return impinged biota to the San Carlos Creek at two locations. The traveling 

screens are then back-flushed with a high pressure spray wash to remove debris. 

Several impingement monitoring studies have been conducted by JEA to evaluate the efficacy of its FRS 

since the mid 70s. These studies have included monitoring studies for routine operation as well as 

evaluations of alternative schedules for operation. Alternative schedules were evaluated in order to 

optimize the operation and maintenance of the FRS, while maintaining the efficiency of return and survival 

of aquatic organisms impinged upon the screens. This paper summarizes the results of these studies, as well 

as the outcome of the optimization assessment for the FRS. 

Introduction 

The water used at the Northside Generating Station (Station) for condenser cooling is withdrawn fi-om the 

Blount Island Channel of the St. Johns River, north of Jacksonville, Florida. The Blount Island Channel, the 

original channel of the St. Johns River until 1947 when the Fulton Dame Point was constructed, conveys 

approximately 30 to 50 percent ofthe total river flow. This region of the St. Johns River is tidal, and the 

salinity in the Blount Island Channel varies from 12 to 35 ppt. The plant’s NPDES permit allows for 827 

million gallons per day to be withdrawal from the St. Johns River. 

31d(b) Demonstration 

In 1976 JEA completed its 316(b) demonstration for the Station, and this included extensive physical, 

chemical and biological studies (including a 1-year impingement study) [Reynolds, Smith and Hills 

1 
(RS&H), 19761. These studies were conducted to determine, among other factors, the effect of the Station 

upon the aquatic environment, the nature of the aquatic environment of the St. Johns River system, the 

alternative cooling water systems and impingement technologies which would meet the requirements of 

Section 3 16(a) and (b) of the Clean Water Act. Section 3 16 (b) required that the cooling water intake 

structure of the Station reflect the best technology available for minimizing adverse environmental impact. 

The 1976 demonstration concluded that the Blount Island Channel was not a primary spawning ground for 

any species of importance to the St. Johns River ecosystem and that the proposed fish return system (FRS) 

would significantlyreduce the mortality of impinged fish and shellfish. The report concluded that the FRS 

would minimize the adverse environmental impact of the once-through cooling system and would represent 

the best technology in this application, thus satisfyrng Section 3 16(b) of the Clean Water Act. Each FRS 

was scheduled to run continuously when the associated power plant Unit was operating. 

Efficacy of FRS 

In 1984-1985, JEA conducted an assessment of the FRS during the summer and winter conditions as part of 

the Station’s National Pollutant Discharge Elimination System (NPDES) permit requirements (ESE, 1985). 

The purpose of this assessment was to determine the effectiveness of the FRS; that is to define what types of 

organisms were impinged as well as their physical condition after passing through the FRS. 

Each FRS (Figure 1) consists of five major components: a traveling screen, a low-pressure wash system, a 

fish return trough, a high pressure was system, and a debris return trough. The traveling screens have a 

square mesh size of 0.5 inches (in) with fish pans attached approximately every four feet. As the screen 

rotates, impinged organisms are lifted from the intake canal by the screens and fish pans, which in turn are 

flushed by the low-pressure wash system into the fish return troughs. - The troughs serve as conduits to

return impinged organisms to an Carlos Creek. . 

Figure I.Fish Return System (FRS) Traveling Screen and Wash System (ESE, 1985) 

2 
The high pressure wash system is the final phase of the FRS and serves to clean the traveling screens of any 

debris not previously cleared by the low-pressure wash system. Organisms and debris cleared by the highpressure wash system are discharged via the debris trough to the discharge canal. The Station has three FRS 

units (Figure 2). Units I and I1have two traveling screens each, and utilize the same fish return trough 

system. Unit 111has four traveling screens and its own fish return trough system. Both trough systems 

return the impinged organisms to the San Carlos Creek. 

Figure 2. Diagramatic representationof FRS at JEAs Northside Generating Station (ESE, 1985) 

Unit 111was used for the summer studies and Units 1and 11during the winter studies; all three FRS units are 

comparable. Standard EPA guidance documents were not available for the evaluation of the efficacy of the 

FRS, therefore a plan of study was developed and submitted to EPA for approval. These studies consisted 

of assessments of percentage of animals returned and their longer term survivability after passage through 

the FRS. 

Optimization Study 

A quarterly study was conducted at the Station in 1998 and 1999 to determine if immediate survival, longerterm survival, and retux-n rate efficiency was significantly altered as a result of reducing the operational time 

of the FRS units (Golder, 1999). The objective ofthese quarterly studies was to compare the continuous 

operation of the FRS to two alternative schedules: 1.5 hours off : 0.5 hour on, and 3.5 hours off : 0.5 hour 

3 
on. Monitoring was conducted during the day and night. Following the first quarterly study, the 3.5 hour 

off: 0.5 hour on schedule was discontinued due to significantreduction in the survival of impinged 

organisms passing through the FRS. 

Immediate survival was quantified for impinged organisms immediately after passing through the FRS; 

longer-term survival was assessed by holding groups of organisms in aquaria for 3 to 4 days following 

collection from the FRS. All impinged organisms were identified to the lowest taxonomic level possible. 

The return rate efficiency was defined as the number of organisms returned to the San Carlos Creek divided 

by the total number of organisms impinged (total number impinged was quantified by collecting all 

organisms from the FRS troughs as well as the debris troughs for a pre-determined period of time). 

Methods 

316(b)Demonstration 

The RS&H (1996) 316(b) demonstration included a one year monthly impingement study at the Station. 

The impingement study was conducted by Battelle (1975); the original report for the impingement study 

was not available, so the methodology was not reviewed. From the 316(b) demonstration report it appears 

that impinged Organisms were collected from the rotating screens at the intake of the Units, enumerated and 

identified to the lowest taxonomic level. The length of each sampling event was not specified,but it appears 

to be 24 hours. 

Efficacy of FRS 

The Station’sNPDES permit required an efficacy evaluation to be conducted during summer and winter 

conditions. Ninety-six-hour survivability studies and impingement rate studies were conducted to evaluate 

the FRS. These studies were conducted during the anticipatedperiods of peak impingement identified in the 

Battelle (1975) report. All impinged organisms were taxonomicallyidentified by scientists from the 

University of Florida’s Museum of Natural History. 

Survivability Studies 

These studies were designed to assess the effectiveness of the FRS by determining the survival rates of 

various impinged organisms. The organisms studied were divided into three categories: 

1. Vulnerable or sensitive species that are likely to be harmed or die after entrapment, impingement, 

and return to the natural ecosystem by the FRS, such as spotted seatrout (Cynoscionspp), anchovy 

(Anchoa spp), silversides (Menidia spp), and menhaden (Brevoortia spp). 

2. Species of intermediate tolerance, such as Atlantic croaker (Micropogonias undulatus), spot 

(Leiostomus xanthurus), mullet (Mugil cephalus), and star drum (Stellifer lanceolatus). 

3. Tolerant or hardy species that are likely to pass through the FRS unharmed, such as commercial 

shrimp (Penaeus spp), blue crab (Callinectessapidus), hogchoker (Trinectes maculates), and 

heardhead catfish (Ariusfelis). 

One representative genus or species of fish or invertebratewas selected from each of the three categories for 

survival evaluation. Species selection depended on their availability from the FRS, as well as impingement 

rates. 

Test organism collection was accomplished by using a net at the point of convergence of the fish return 

troughs (Figure 2). A minimum of 19 individuals of each genera, from each sensitivitycategory, were 

monitored for survival using flow-through San Carlos Creek water in 20-gallon aquaria over a 96-hour 

period. Control organisms were collected by seining in San Carlos Creek and the St. Johns River. Mortality 

4 
and physical parameters were monitored at collection and every 24 hours thereafter. Average weight and 

lengths of all animals tested were also recorded. Percent survival for each category was estimated following 

passage through the FRS. 

Impingement Return Rate Assessment 

These studies were designed to compare the total number of organisms impinged with the number of 

organisms returned to San Carlos Creek via the FRS. Organisms were collected over two 4-hour periods; 

one collection period starting prior to high tide and the other prior to low tide. Data collected included: 

total number of organisms returned via the FRS, species or genus of species returned, and number of 

organisms returned via the debris system. From these data the total number of organisms impinged and the 

percent returned to the San Carlos Creek were calculated. 

Optimization Study 

The standard operating procedure at the Station was to operate the FRS continuously, unless the power plant 

Unit associated with the FRS was not being used. These quarterly studies were conducted to evaluate 

different operating schedules, and their impact on the survival of impinged organisms and the return rate 

efficiency of the FRS. All impinged organisms were taxonomically identified by scientists from the 

University of Florida’s Museum of Natural History. 

The Station’sUnit I11FRS has four rotating screen assemblies referred to as A, B, C and D (Figure 2). 

These screen assemblies are grouped into 2 banks (A&B and C&D) and are separated by a distance of 

approximately 40 feet. For these studies the bank containing screen assemblies A&B was operated 

continuously, while the other bank (C&D) was operated under the alternative operating schedules. The FRS 

operating schedules were then reversed for the second half of the sampling period in order to reduce 

variability in the data. Both screen assemblies within the same bank were operated under the same schedule 

(i.e.,both off or on at the same time). 

As previously stated, these studies were designed to compare the continuous operation of the FRS to two 

alternative schedules: 1.5 hours off : 0.5 hour on, and 3.5 hours off :0.5 hour on. Monitoring of the FRS 

was conducted during the day and night. Following the first quarterly study, the 3.5 hours off :0.5 hour on 

schedule was discontinued due to significant reduction in the survival of impinged organisms passing 

through the FRS. 

The final FRS operating schedules evaluated were: 

1. continuous operation of the FRS (current schedule, used as Control), and 

2. intermittent operation of the FRS: off for 1.5 hours, followed by 0.5 hour of operation (alternate 

schedule). 

The Control FRS (continuously operating screens) was sampled for approximately 16 hours over two days. 

Half of the sampling was conducted during daytime and half during nighttime. For the FRS operating under 

the alternate schedule (1.5 hours off :0.5 hour on), the collection period was for the 0.5 hour that the FRS 

operated. Four sampling events per quarterly assessment were conducted, two during the day and two at 

night (within a 24-how period) concurrent with the continuously operating screens. 

Survivability Studies 

5 
Aquatic organisms impinged on the screens and returned by the FRS were evaluated for the two operating 

schedules by collecting organisms from the fish return troughs and determining their survivability. This was 

done in two ways: 

1. Irnmediate survivability-Impinged organisms were collected over a pre-determined period of time, 

counted and categorized as dead or alive. 

2. Longer term survivability-Three species, representing three sensitivity categories (as defined in the 

FRS efficacy study), were collected from the fish return troughs and maintained under flow-through 

conditions for 72 to 96 hours to evaluate longer term survivability. 

Impinged organisms were collected by placing nets in the fish return troughs. The nets were replaced every 

five to seven minutes, immediate survivability and taxonomic identification of each organism was 

determined. Nets were also placed in the debris troughs and were replaced every half hour. All organisms 

collected were classified to the lowest taxonomic level possible. 

In order to determine longer term survivability, three species selected representing three sensitivity 

categories were held for 72 to 96 hours in 30-gallon flow-through chambers. If an insufficient number of 

organisms from one of the sensitivity categorieswere collected, a mixture of two species from the same 

category were used. Survival was determined in each chamber daily and at the end of the holding period. 

Water quality was monitored in each chamber every 24 hours. Weight and length of each surviving animal 

in the holding chambers were measured at holding period termination. 

Impingement Return Rate Assessment 

The FRS was also evaluated by comparing the total number of organisms impinged with the number of 

organisms returned to the San Carlos Creek via the FRS. This was done by counting the total number of 

organism returned via the FRS and the total number disposed by the debris system. 

Results 

316(b) Demonstration 

Table 1 summarizes the total number of fish impinged, and the distribution of the seven most abundant fish 

species. 

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Table 1. Monthly counts of total fish impinged on the screens at JEA's Northside Generating Station (August 1973 to 

August 1974). Seven most abundant fish species listed. Species key: I.Micropogon undulatus,2. Stellifer 

lanceolatus, 3. Cynoscion regalis,4. Anchoa mitchilli, 5. Cynoscionnothus, 6. Symphurusplagiusa, 7. Opistonema 

oglinum. 

During the one-year impingement study at the Station, 78 species of fish were impinged on the rotating 

screens (RS&H, 1976). Seven species accounted for over 85 percent of all impinged fish. Listed in order of 

decreasing abundance they were: Atlantic croaker (Micmpogon undulatus), star drum (Stellifer 

lanceolatus), weakfish (Cynoscion regalis), silver seatrout (Cynoscionnothus), Atlantic thread herring 

(Opistonema oglinum), bay anchovy (Anchoa mitchilli), and (Symphurusplaqiasa). Of the seven fish 

species, M. undulatus accounted for 43.5 percent. 

Twenty-two species of invertebrates were impinged during the one-year impingement study. Of the 22 

species, four were considered of commercial or sport fishery importance: three commercial shrimp species 

(Panaeus setiferus, Panaeus aztecus and Penaeus duorarum) and the blue crab (Callinectes sapidus). Table 

2 summarizesthe distribution of these four species over the monthly impingement study conducted during 

1973-1974. 

Month P. setiferus P. aztecus P. durarum 

August 393 0 0 

October 425 129 0 

November 32 21 0 

December 14 16 0 

January 43 9 0 

February 26 11 0 

March 3 3 2 

March 0 6 2 

April 18 9 0 

May 55 ~ 

87 1 

June 30 165 0 

Julv 666 670 0 

August 1,642 50 13 

Total 3,347 1,176 18 

Efficacy of FRS 

Total Number of C. sapidus 

Shrimp Collected 

393 77 

554 115 

53 26 

30 31 

52 108 

37 64 

8 4 

8 28 

27 61 

143 61 

195 106 

1.336 176 

1,705 163 

4,541 1,020 

As required by the Station's NPDES permit, the survivability and impingement rates were assessed for the 

continuously operating FRS. These studies were conducted during August and September 1984 and January 

1985 (ESE, 1985). 

Survivability Studies 

The summer survivability study was initially attempted by collecting all organisms impinged over an 8-how 

period in August 1984. Due to the low impingement rates (total of 77 fish and invertebrates), only the 

survivability of the sensitive species (seatrout, Cynoscion nebulosus) was assessed. All of these fish died 

within the first hour after passage through the FRS. 

7 

7 
Based on the Battelle (1975) study and personal observations by JEA Station personnel, higher 

impingement rates were anticipated during the night. Collectionwas again initiated during September 1984. 

Species collected and tested for survivability were fiom the intermediate and tolerant sensitivity ranges; no 

sensitive species were impinged during this collection period. The following species were tested: 

1. intermediate tolerance species: spot (L. xanthurus), Atlantic croaker (M. undulatus), and star drum 

(S. lanceolatus), and 

2. tolerant species: commercial shrimp (Penaeus spp). 

Organisms collected fiom the estuary near the plant, were used as controls. The control organisms used 

were: 

1. sensitive species: menhaden (Brevoortia spp), only sensitive category species collected 

2. intermediatetolerance species: spot (L. xanthurus) and Atlantic croaker (M. undulatus), and 

3. tolerant species: commercial shrimp (Penaeus spp). 

The summer conditions resulted in control survival at 96 hours of 95 percent or higher for all species tested. 

For the species collected fiom the FRS, the survival rates were: spotted seatrout had no surviving organisms 

after 1hour; spot/croaker 80 percent, and star drum 80 percent; and penaeid shrimp 90 percent survival. 

The salinity varied fiom 19 to 31ppt over this 4-day period; this was due to the tides. The water 

temperaturewas 27 2°C 

The winter survivability study was initiated in January 1985, and the following species were tested: 

1. sensitive species: Atlantic menhaden (Brevoortia tyrannus), 

2. intermediate tolerance species: star drum (S. lanceolatus), and 

3. tolerant species: hardhead catfish (Ariusfelis). 

Organisms collected fiom the estuary near the plant, were used as controls. The control organisms used 

were: 

1. sensitive species: inland silverside(Menidia berylha), 

4. intermediate tolerance species: striped mullet (Mugil cephalus), and 

5. tolerant species: hardhead catfish (A.felis). 

The winter conditions resulted in 100 percent control survival at 96 hours for the silversides and mullet; 75 

percent survival in the catfish. For the species collected from the FRS, the survival rates were: menhaden 5 

percent; star drum 10percent; and catfish 90 percent. The salinity varied fkom 17 to 22 ppt over this 4-day 

period. The water temperature range was 9.5 to 12.5 "C. 

Impingement Return Rate Assessment 

Impingement rates at the Stationwere relatively low for the sumrner and winter conditions. During each 

event, sampling was conducted for 4 hours prior to low tide and 4 hours prior to high tide. Table 3 

summarizes these data. 

I (afternoon) I 

8 
1 High 859 9 1 Hardhead catfish I 463 I 

summer and winter conditions (1984-1985). Collection time: 8 hours. 

Table 4 summarizes the number of organisms returned through the debris trough. These organisms are 

discharged through the outfall to the St. Johns River (Blount Island Channel). 

Total Number Total Number of 

Invertebrates Collected 

I (night) 11 Star drum 

Table 4. Impinged organisms disposed through the debris troughs at JEA's Northside Generating Station during 

summer and winter conditions (1984-1985). Collection time: 8 hours. 

During summer conditions, at low tide, night collections from the FRS resulted in 150 organisms being 

impinged over 4 hours, of these, 110were returned to the San Carlos Creek via the FRS. The calculated 

FRS return rate was 73 percent. Commercial shrimp accounted for 76 percent and blue crabs for 14 percent 

of the total impinged. At high tide (night collection) 42 organisms were impinged, again commercial 

shrimp was the primary species collected accounting for 81 percent. The calculated FRS retum rate was 79 

percent. 

During winter conditions, at low tide, afternoon collections fi-omthe FRS resulted in 75 organisms being 

impinged over 4 hours, of these, 37 were returned to the San Carlos Creek via the FRS. The calculated FRS 

return rate was 49 percent. Star drum accounted for 24. percent of the total impinged. At high tide (night 

collection) 1,537 organisms were impinged, hardhead catfish and star drum were the dominant species 

accounting for 48 percent and 47 percent of the organisms impinged, respectively. The calculated FRS 

return rate was 56.5 percent. 

FRS retum rates for this study are summarized in Table 5. 

Season Tide FRS Return Rate (percent) 

Summer Low 73 

(night) I High 79 

(night)

Winter Low 49 

(afternoon) 

9 
56.5 

I f . Y I I 

Table 5. FRS return rate at JEA's Northside Generating Station during summer and winter conditions (I984-1985). 

Optimization Study 

Immediate Survival 

Immediate survival was the most useful end point measured to compare the alternative FRS operating 

schedules. As summarized in Table 6, immediate survival among fish exposed to a 3.5 hour screen 

stoppage was significantly reduced (49.5 percent immediate survival versus 85.8 percent in the continuous 

operation group) during the March 1998 monitoring period. This group was dismissed from further study; 

the remainder of this discussion examines the effect of a 1.5-hour stoppage of the FRS on survival of biota 

in comparison to continually operating the FRS. 

Schedule and Immediate Survival (percent) 

1.5 hours oft 3.5 hours ofE 

Quarter Continuous 0.5 hour on 0.5 hour on 

March 85.8 86.3 49.5 

Table 6. Immediatesurvival of organisms returned by the FRS under different operating schedules, JEA's Northside 

GeneratingStation (1998-1999). N/A, not applicable, this schedule was discontinued after the first quarter due to low 

survival. 

During the March 1998 and January 1999 quarterly monitoring periods, the immediate survival of the 1.5 

hours ofE 0.5 hour on group (referred to hereafter as the treatment group) was similar to that of the 

continuously-operating group (referred to hereafter as the control group). The immediate survival values for 

the control and treatment groups were: 85.8 and 86.3 percent (Marck 1998); and 90.6 and 91.9 percent 

(January 1999), respectively. 

During the June and September 1998 quarterly monitoring periods, the immediate survival of the treatment 

group in comparison to the control group was significantly reduced. The immediate survival values were 

93.0 percent versus 72.3 percent (June 1998) and 95.4 percent versus 82.3 percent (September 1998), for the 

control and treatment groups, respectively. These values translate to a treatment mortality rate that is 

approximately 4 times greater than the control mortality rate (Table 6). 

It is important to note that the values presented in the preceding paragraphs include all impinged organisms. 

The drum family (Sciaenidae),which includes spotted and gray seatrout, spot, silver perch, red drum,star 

drum, and Atlantic croaker, was the numerically dominant family of fish collected (70 percent) from the 

FRS during all sampling events. When the data for this family were examined separately, a similar trend in 

immediate survival was observed, but with greater magnitude. The immediate survival in the treatment 

group was again similar to that in the control group for the March period (83.9 percent versus 81.5 percent, 

respectively) and the January period (100 percent survival in both groups). However, the immediate 

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I 
survival values for the control and treatment groups were 95.8 percent versus 66.7 percent, respectively, for 

June and 89.1 percent versus 2 1.7 percent, respectively, for September. These values translate to treatment 

mortality rates that are approximately 7 to 8 times greater than the control mortality rates (Table 7). 

Schedule and Immediate Survival (percent) Total 

Quarter Continuous 1.5 hours off: 0.5 hour on Number 

Collected 

I March I 81.5% I 83.9% I 1,312 I 

June 95.8% 66.7% 497 

September 89.1% 21.7% 257 

January 100% 100% 8 

Immediate survival of crustaceans, which comprised approximately half of the organisms collected, was 

excellent regardless of season. Control group survival ranged from 87.5 percent to 100 percent and 

treatment group survival ranged from 88.0 percent to 97.4 percent. 

Longer-term Survival 

The results of the longer-term were difficult to interpret due to the low numbers of sensitive species 

impinged. When statistical analyses could be employed to analyze the longer term survival data, no 

significant reductions in the treatment group (alternate FRS schedule) survival were detected, as compared 

to the controls (continuous FRS schedule) (Table 8). But, survivability was relatively low for the controls 

and treatments in June and September 1998 for the sensitive and intermediate species. 

Quarter 

March 1998 

June 1998 

September 1998 

January 1999 

I Long-Term Survival hercent) 

Sensitive Intermediate Tolerant 

Control Not available 100 37* 

Treatment Not available 90 100 

Control 

1 Treatment 

25 

11 

53 

39 I 

90 

90 

Control Not available 17 100 

Treatment Not available 7 100 

Control Not available 100 93 

Treatment Not available 75 100 

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Impingement Return Rate Assessment 

During the March sampling event, approximatelytwo-thirds of the impinged organisms collected was 

during the day, while the remainder was collected during the evening hours. For the other three quarterly 

monitoring periods, very few organisms (35 out of 2,402 or 4.5 percent of the total) were collected during 

daytime hours. 

Species composition over the four quarterly monitoring periods revealed a population of impinged 

organisms that was 57 percent fish and 43 percent crustacean. Fish from the family Sciaenidae comprised 

70 percent of impinged fish, which is equivalent to approximately 40 percent of impinged organisms. The 

remaining 30 percent of the fish population was comprised of many families. 

Return rate of the FRS units was very high regardless of FRS operating schedule (Table 9). The return rate 

was 87.9 percent, or higher, and no significant reduction in return rate was detected for any monitoring 

period. Usually, crustaceans rather than fish were found in the debris chute nets, as these organisms have 

the ability to hang on to the mesh screen until dislodged by the high-pressure wash spray. 

Quarter 

March 1998 

June 1998 

Smtember 1998 

January 1999 

Total Number Total Number FRS Return Rate 

Impinged Returned by FRS (percent) 

Control 1196 1167 97.6 

Treatment 456 446 97.8 

I I 

Control 497 487 98.0 

Treatment 398 375 94.2 

Control 983 947 96.3 

Treatment 596 524 87.9 

Control 32 32 100 

Treatment I 38 I 37 I 97.4

Table 9. FRS return rates for the 1998-1999 evaluation of continuous (control) and treatment (1.5 hours off : 0.5 hour 

on) operation schedules at JEAs Northside GeneratingStation. Control collection time: 16 hours; treatment 

collectiontime: 8 hours. 

Conclusions 

The 316(b) demonstration concluded that the Station reauired amxoximatelv ten Dercent of the averasre flow 

of the Blount Island Channel, and that the Channel represented less than 50 percent of the river flow. 

Biological field studies documented that the Channel was not a primary spawning ground for any species of 

ecological importance, however, the lower portions of the St. Johns River were found to serve as an access 

route to the upper estuary areas of the St. Johns River. 

During the one-year impingement study, 78 species offish were impinged on the Station's screens, and 

seven species accounted for 85 percent of all impinged fish. These species were: Atlantic croaker 

(Micropogon undulatus), star chum (Stellifer lanceolatus), weakfish (Cynoscion regalis), silver seatrout 

(Cynoscion nothus), Atlantic thread herring (Opistonema oglinum), bay anchovy (Anchoa mitchilli), and 

(Symphurusplaqiasa). Of the seven fish species, M. undulatus accounted for 43.5 percent. July and August 

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data showed the highest fish impingement rates in this study, and December, March and April had the 

lowest impingement rates. 

. 

Twenty-two species of invertebrates were impinged during the one-year impingement study. Of the 22 

species, four were considered of commercial or sport fishery importance: three species of the commercial 

shrimp (Panaeus setifens, Panaeus aztecus and Penaeus duorarum) and the blue crab (Cattinectes 

sapidus). Of the commercial shrimp, P. setqerus was the dominant species, with daily impingement rates 

ranging from 0 in March 1973 to 1,642 in August 1974. ‘Bluecrab daily impingement ranged from 4 per 

day in March 1973 to 176 crabs per day in August 1974. 

The impinged fish and shellfish data developed to support the 3 16(b) demonstration showed that 

impingement rates at the Station were relatively low. The demonstration concluded that these low total 

numbers (12 to 3,199 per 24 hours) in conjunctionwith the fish return system proposed would significantly 

reduce the fatal impingement of fish and shellfish, and would minimize adverse environmental impact and 

represent the best technology in this application. 

The FRS Efficacy study conducted in 1984 and 1985 documented that impingementrates were low at the 

Station during the summer and winter months. The winter impingement numbers, as compared to the 

summer, were found to be higher at night than in the daytime. During the summer, commercial shrimp and 

blue crabs were the primary impinged organisms, representing 76 and 14percent of the impinged 

organisms, with very few fish impinged. During the winter fish were the primary species impinged, with 

hardhead catfish and star drum as the primary species collected and representing 48 and 47 percent of the 

impinged organisms. 

The FRS return rates were evaluated at low tide and high tide and the results were: 73 and 79 percent return 

efficiency in the summer, and 49 and 56.5 return efficiency in the winter. 

The results of the summer longer term survivabilitytests indicated that the sensitive species did not survive 

after passage through the FRS during the summer conditions evaluated; 95 percent control survival was 

observed for the sensitive species. The intermediate and tolerant species had greater than 80 percent 

survival after passage through the FRS. 

The winter evaluation showed low survival of the sensitive and intermediate sensitivity species (menhaden, 

5 percent survival; star drum,10percent survival), as compared to the controls with 100 percent survival for 

these 2 categories. In all cases, the tolerant species (commercial shrimp and catfish) had excellent survival. 

An Optimization Study was conducted in 1998 and 1999 to evaluate the FRS and to assess alternative 

operating schedules. Prior to the initiation of the optimization study, each FRS was evaluated and the 

system optimized in its operation (such as direction of the low spray wash, water pressure, and water flow in 

the troughs). Of the 2 alternative schedules originallyplanned, only the “1.5 hours off :0.5 hour on” was 

assessed for four quarters; the “3.5 hour off: 0.5 hour on” alternative resulted in high mortality immediately 

following passage through the FRS, and was discontinued. The continuous operation schedule was 

considered the control for comparison. 

The return rate efficiency of the FRS units was high, between 96.3 and 100 percent during continuous 

operation and 87.9 and 97.8 using the alternate schedule. The return rates were not significantly affected by 

the alternate operation schedule. 

13 
Immediate survival was considered the most useful endpoint measured to compare the alternate operation 

schedules. The “1.5 hours off :0.5 hour on” schedule resulted in similar survival to the continuous 

operation during the March and January monitoring periods march control immediate survival of 85.8 

percent and alternate schedule immediate survival of 86.3 percent; January control immediate survival of 

90.6 percent and alternate immediate survival of 91.O percent). 

During the wmer months (June and September), the immediate survival under the alternate schedule as 

compared to the control schedule was significantly reduced (June control immediate survival of 93 percent 

and alternate schedule immediate survival of 72.3 percent; September control immediate survival of 95.4 

and alternate schedule immediate survival of 82.3 percent). The family Scianidae comprised the majority of 

the juvenile fish impinged on the FRS screens during all sampling events. When the immediate 

survivability of this group was evaluated for the alternate schedule and the continuous schedule, a 

significant reduction in survival of this group of fish was observed using the alternate schedule as compared 

to the controls. Immediate survival of crustaceans was excellent regardless of season or schedule. Control 

group immediate survival ranged fi-om 87.5 to 100 percent and alternate schedule survival fi-om 88 to 97.4 

percent. 

The longer term (96-hour) survivability assessments were inconclusive due to the fact that very few 

sensitive species were impinged during the sampling events, and both the control and alternate schedule 

assessments showed low survival for the intermediate species during the wanner months. The tolerant 

species showed excellent survival (>93 percent) regardless of season, with one exception, the commercial 

shnmp control (continuous operation) during March showed low survival (37 percent) and the alternative 

schedule had 100percent survival. 

Species composition over the four quarterly monitoring periods showed a population of impinged organisms 

that was 57 percent fish and 43 percent crustaceans. Fish from the family Scianidae comprised 70 percent 

of the impinged fish, which is equivalent to 40 percent of the impinged organisms. 

The Optimization report concluded that the use of the alternate schedule (I -5hours off : 0.5 hour on) during 

the cool season months in north Florida would not significantly decrease the FRS return efficiency, the 

immediate, or the longer-term survivability of impinged fish and crustaceans. The report also stated that 

during the warmer months, this alternate schedule could also be used during the day (due to the low 

impingement rates observed), but that the FRS would have to runcontinuously during the night. The report 

suggested that the FRS schedule should be determined by water temperature, and proposed that once water 

temperature reached 20°C, the warm season schedule could be implemented. 

Based on observations made during the ESE (1985) study and the Golder (1999) study, sufficient water flow 

in the fish return troughs and appropriate pressure of the FRS nozzles were of greatest importance in the 

proper function of the FRS and resulted in improved FRS return efficiency and high survival of impinged 

organisms. Predation by birds fi-om the fish return troughs was not quantified, but observed during both 

studies. Both studies also recommended that the fish return troughs should be long enough so that during 

low tide the fish are not dropped into the aquatic system. 

References 

Battelle Laboratories, 1975. Biological Assessment of Water and Marsh Areas of the St. Johns River. 

Prepared for Reynolds, Smith and Hills. January 1975. 

14 
ESE, 1985. An Assessment of the Fish Return System at the Jacksonville Electric Authority Northside 

Generating Station, Jacksonville, Florida. Prepared for Jacksonville Electric Authority. April 1985. 

Golder Associates Inc., 1999. Fish Return System Optimization,Study: Summary of Results and 

Discussion, Considerations, and Recommendations. Prepared for Jacksonville Electric Authority, October 

1999. 

Reynolds, Smith and Hills, 1976. Northside Generating Station 3 16 Demonstration. Prepared for 

Jacksonivlle Electric Authority. March 1976.