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 WTUWSYSTEM 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-linedbays approximately30 feet deep; a set 

### of continuous-belttraveling screens; and electrically driven impellerpumps for circulatingthe cooling water.
The Station’s fish return system (FRS) is an array oftrays, 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 collectionpans attached approximatelyevery four feet. As the traveling screens rotate, low pressure sprays rinse the biota fi-omthe 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 impingedbiota to the San Carlos Creek at two locations. The traveling
screens are then back-flushed with a high pressure spray wash to remove debris.

Severalimpingementmonitoring studieshave been conductedby JEA to evaluate the efficacyof its FRS since the mid 70s. These studieshave included monitoring studies for routine operation as well as evaluations of alternative schedules for operation. Alternative schedules were evaluated in order to optimizethe operation and maintenance ofthe FRS, while maintainingthe efficiency ofreturn and survival of aquatic organisms impinged upon the screens. Thispaper summarizesthe results of these studies, as well
as the outcome ofthe optimization assessment for the FRS.


### Introduction The water used at the Northside Generating Station (Station) for condenser coolingis withdrawn fi-omthe Blount Island Channel of the St. Johns River, north of Jacksonville,Florida.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 1947when 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 salinityin the Blount Island Channel varies from 12to 

### 35 ppt. The plant’s NPDES permit allows for 827 million gallons per day to be withdrawal from the St. Johns River.


### 31

### d(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 studieswere conducted to determine, among other factors, the effect ofthe Station upon the aquatic environment,the nature ofthe aquatic environmentofthe St. Johns River system, the alternative coolingwater systems and impingementtechnologieswhich 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 Stationreflect 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 importanceto 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 environmentalimpact of the once-through cooling system and would represent the best technologyin this application, thus satisfyrng Section 3 16(b) of the Clean Water Act. Each FRS
was scheduledto 

### run continuously when the associatedpower plant Unit was operating. 

### Efficacy of 

### FRS In 1984-1985, JEA conducted 

### an assessmentofthe 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 ofthis assessmentwas to determinethe effectiveness

### of the FRS; that is to define what types of organismswere impinged as well as their physical condition afterpassing 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 screenshave a square mesh size of 0.5 inches (in) with fish pans attached approximatelyevery 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-pressurewash 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)

2Thehigh pressure wash system is the final phase of the FRS and serves to clean the traveling screens of any debris not previously clearedby the low-pressurewash system. Organisms and debris cleared by the highpressure wash system are discharged via the debris trough to the discharge canal. The Stationhas three FRS units (Figure 

### 2). Units I and 

### I1 have 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 organismsto the San Carlos Creek.

Figure2. Diagramatic representationof FRS at JEAs Northside Generating Station (ESE, 1985)
Unit 111was used for the summer studies and Units 1 and 

### 11during the winter studies; all three FRS units are comparable. Standard

### EPA guidance documents were not available for the evaluation ofthe efficacy ofthe FRS, therefore a plan of studywas developed and submitted to EPA for approval. These studies consisted of assessments ofpercentage of animals returned and their longerterm survivability afterpassage through the 

### FRS. 

### Optimization Study A quarterly studywas conducted at the Station in 1998 and 1999to determine if immediate survival, longerterm survival, and retux-n rate efficiency was significantlyaltered as a result ofreducing the operational time of the FRS units (Golder, 1999). The objective ofthese quarterly studies was to comparethe continuous operation of the FRS to two alternative schedules: 1.5hours off : 0.5 hour on, and 3.5 hours off : 0.5 hour

3on. Monitoringwas 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 organismsimmediately afterpassing through the FRS; longer-term survival was assessed by holding groups of organismsin aquaria for 3 

### to 4 days following collection from the FRS. All impinged organismswere identifiedto 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 quantifiedby collecting all organismsfrom the FRS troughs as well as the debris troughs for a pre-determined period oftime).


### Methods 31

### 6(b)Demonstration The RS&H (1996) 3 16(b) demonstrationincluded a one year monthly impingement study at the Station. The impingement studywas conductedby Battelle (1975); the original report for the impingement study
was not available, 

### so the methodologywas not reviewed. From the 3 16(b)demonstrationreport it appears that impinged Organisms were collected from the rotating screens at the intake of the Units, enumerated and identifiedto 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’s

### NPDES permit required an efficacy evaluationto be conducted during summer and winter conditions. Ninety-six-hour survivability studies and impingementrate studieswere conductedto evaluate the FRS. These studies were conducted during the anticipatedperiods ofpeak impingementidentified in the Battelle (1975)report. All impinged organismswere taxonomicallyidentified by scientists from the University ofFlorida’s Museum ofNatural History. Survivability Studies These studies were designed to assess the effectiveness 

### ofthe FRS by determining the survivalrates 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 ecosystemby 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 (Leiostomusxanthurus),mullet (Mugil cephalus), and star drum (Stellifer lanceolatus). 3. Tolerant or hardy species that are likelyto pass through the FRS unharmed, such as commercial shrimp (Penaeusspp), blue crab (Callinectessapidus),hogchoker (Trinectes maculates), and heardhead catfish (Ariusfelis).

Onerepresentativegenus or species 

### of fish or invertebratewas selected 

### from each of the three categories for survival evaluation. Species selection depended on their availabilityfrom the FRS, as well as impingement rates.

Test organism collection was accomplishedby using a net at the point of convergence ofthe fish return troughs (Figure2). A minimum of 19individuals 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 organismswere collectedby seining in San Carlos Creek and the St. Johns River. Mortality

4and 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 comparethe total number of organisms impinged with the number of organismsreturned to San Carlos Creek via the FRS. Organisms were collected over 

### two 4-hour periods;
one collectionperiod startingprior to high tide and the otherprior to low tide. Data collected included: total number 

### of organismsreturned via the FRS, species or genus of species returned, and number of organismsreturned 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 powerplant 

### Unit associatedwith 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 ofthe FRS. All impinged organismswere taxonomically identified by scientistsfrom the University ofFlorida’sMuseum ofNatural History.

The Station’sUnit I11 FRS has four rotating screen assembliesreferred to 

### as A, B, C and D (Figure 2). These screen assemblies are grouped into 2 banks (A&B and C&D) and are separatedby a distance of approximately40 feet. For these studies the bank containing screen assembliesA&B was operated continuously,while the other bank (C&D) was operatedunder the alternative operating schedules. The 

### FRS operating schedules were then reversed for the second half ofthe samplingperiod in order to reduce variability in the data. Both screen assemblieswithin the samebank were operated under the same schedule (i.e.,both off or on at the sametime).

As previously stated, these studies were designed to comparethe continuous operation ofthe FRS to 

### two alternative schedules: 1.5hours off :

### 0.5 hour on, and 3.5 hours off : 0.5 hour on. Monitoring ofthe FRS
was conducted during the day and night. Following the first quarterly study, the 3.5 hours off : 0.5 hour on schedulewas discontinued due to significantreduction in the survival of impinged organismspassing through the FRS.

The finalFRS operating schedules evaluatedwere: 1. continuous operation ofthe FRS (current schedule, used 

### as Control), and 2. intermittent operation ofthe FRS: off for 

### 1.5 hours, followedby 0.5 hour of operation (alternate schedule).

The Control FRS (continuously operating screens) was sampled for approximately 16hours over two days. Half ofthe samplingwas conducted during daytime and half during nighttime. For the FRS operatingunder the alternate schedule (1.5 hours off : 0.5 hour on), the collectionperiod was for the 0.5 hour that the FRS operated. Four sampling eventsper quarterly assessmentwere conducted,two during the day and two at night (within a 24-how period) concurrentwith the continuously operating screens. Survivability Studies

5Aquatic organisms impinged on the screens and returned by the 

### FRS were evaluated for the two operating schedulesby collecting organisms from the fish return troughs and determiningtheir survivability. This was done 

### in two ways: 1. Irnmediate survivability

- Impinged organisms were collected over a pre-determinedperiod of time, counted and categorized as dead or alive. 2. Longer term survivability

- Three species,representingthree 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 evaluatelonger term survivability. Impinged organisms were collectedby placing nets in the fish return troughs. The nets were replaced every fiveto seven minutes, immediate survivability and taxonomic identification of each organism was determined. Nets were also placed in the debris troughs and were replaced everyhalfhour. All organisms collected were classified to the lowest taxonomiclevel possible.



### In order to determinelonger term survivability, three species selectedrepresenting three sensitivity categories were held for 72 to 96 hours in 30-gallon flow-through chambers. 

### If an insufficient number of organisms from one 

### ofthe sensitivity categorieswere collected, a mixture of

### two species from the same category were used. Survivalwas determined in each chamber daily and at the end ofthe holdingperiod. 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 evaluatedby comparingthe total number of organisms impinged with the number of organismsreturned to the San Carlos Creek via the FRS. This was done

### by counting the total number of organismreturned via the FRS and the total number disposed by the debris system.


### Results 

### 31

### 6(b)

### Demonstration Table 

### 1 summarizesthe total number 

### of fish impinged, and the distribution ofthe seven most abundant fish species.

6Table 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 abundancethey were: Atlantic croaker (Micmpogon undulatus), star drum (Stellifer lanceolatus),weakfish (Cynoscion regalis),silver seatrout (Cynoscionnothus),Atlantic thread herring (Opistonema oglinum),bay anchovy (Anchoamitchilli), and (Symphurus 

### plaqiasa). Ofthe 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 (Panaeussetiferus, Panaeus aztecus and Penaeus duorarum) and the blue crab (Callinectessapidus). Table 2 summarizesthe distribution 

### ofthese 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 continuouslyoperating FRS. These studieswere conducted during 

### August and September 1984 and January 1985 

### (ESE, 1985). Survivability Studies The summer survivability studywas initially attemptedby collecting all organismsimpinged over 

### an 8-how period in August 1984. Due to the low impingementrates (total of 77 fish and invertebrates), only the survivability of the sensitive species (seatrout, Cynoscion nebulosus)was assessed. All ofthese fish died within the first hour after passage through the FRS.

7 7Based on the Battelle (1975) study and personal observationsby JEA Stationpersonnel, higher impingementrates were anticipated during the night. Collectionwas again initiated during September 1984. Species collected and tested for survivability were fiom the intermediate and tolerant sensitivityranges; 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 conditionsresulted in control survival at 96 hours 

### of 95percent or higher for all species tested. For the species collected fiom the FRS, the survival rates were: spotted seatrout had no surviving organisms after 1 hour; spot/croaker 80percent, and star drum 80 percent; and penaeid shrimp 90percent survival. The salinityvaried fiom 19to 

### 3 1 ppt over this 4-day period; this was due to the tides. The water temperaturewas 27 2°C

The winter survivability studywas initiated in January 1985, and the following specieswere 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 organismsused
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 conditionsresulted in 100percent control survival at 96 hours for the silversides and mullet; 75 percent survivalin the catfish. For the species collected from the FRS, the survival rates were: menhaden 5 percent; star drum 10percent; and catfish 90 percent. The salinityvaried fkom 

### 17to 22 ppt over this 4-day period. The water temperaturerange was 9.5 to 12.5 "C. ImpingementReturn Rate Assessment Impingementrates 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). Collectiontime: 8 hours.
Table 4 summarizesthe number of organismsreturned through the debris trough. These organisms are dischargedthrough the outfall to the St. 

### Johns River (Blount Island Channel).

TotalNumber TotalNumber 

### of Invertebrates Collected



# I (night) 

# 11 Star drum Table 4. Impinged organisms disposedthrough the debris troughs at JEA's Northside Generating Station during summer and winter conditions (1984-1985). Collectiontime: 8 hours. During summer conditions, at low tide, night collections from the FRS resulted in 150organismsbeing impinged over 4 hours, ofthese, 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 14percent ofthe 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 organismsbeing impinged over 4 hours, ofthese, 37 were returned to the 

### San Carlos Creek via the FRS. The calculatedFRS return rate was 49 percent. Star drum accounted for 24. percent 

### ofthe 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 (I 984-1985). 

### OptimizationStudy 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 85.8percent in the continuous operation group) during the March 1998monitoringperiod. 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 comparisonto continuallyoperating 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. Immediate survival of organisms returned by the FRS under different operating schedules, JEA's Northside Generating Station (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 (referredto hereafter as the control group). The immediate survivalvalues for the control and treatment groups were: 85.8 and 86.3percent (Marck 1998); and 90.6 and 91.9 percent (January 1999),respectively. During the June and September 1998quarterly monitoringperiods, the immediate survival ofthe treatment group in comparisonto the control group was significantlyreduced. The immediate survivalvalues 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 approximately4 times greater than the control mortality rate (Table 6).

It is important to note that the values presented in the precedingparagraphs include all impinged organisms. The drum family (Sciaenidae), which includes spotted and gray seatrout, spot, silverperch, red 

### drum, star drum, and Atlantic croaker, was the numerically dominant family of fish collected (70percent) from the FRS during all sampling events. When the data for this family were examined separately, a similartrend in immediate survivalwas observed, but with greater magnitude. The immediate survival in the treatment group was again similarto 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

10 Isurvival values for the control and treatment groups were 95.8 percent versus 66.7 percent, respectively, for June and 89.1 percent versus 2 1.7percent, 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 1.5hours 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 100percent and treatment group survival ranged 

### from 88.0percent 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 significantreductions in the treatment group (alternate 

### FRS schedule) survival were detected, as compared to the controls (continuous 

### FRS schedule) (Table 8). But, survivabilitywas 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

11Impingement Return Rate Assessment During the March sampling event, approximatelytwo-thirds of the impinged organisms collectedwas during the day, while the remainder was collected during the eveninghours. For the other three quarterly monitoring periods, very few organisms (35 out of 2,402 or 4.5 percent ofthe total) were collected during daytimehours. Species composition over the four quarterly monitoringperiods revealed a population ofimpinged organisms that was 57 percent fish and 43 percent crustacean. Fish from the family Sciaenidaecomprised 70percent of impinged fish, which is equivalentto approximately40 percent of impinged organisms. The remaining 30percent ofthe 

### fish population was comprised ofmany families.

Return rate ofthe FRS units was very high regardless of

### FRS operating schedule (Table 9). The return rate was 87.9 percent, or higher, and no significantreduction in return rate was detected for any monitoring period. Usually, crustaceansrather than fish were found in the debris chute nets, as these organisms have the ability to hang on to the mesh screen until dislodgedby the high-pressurewash 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 38 37 97.4

I I I 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 Generating Station. Control collectiontime: 16 hours; treatment collection time: 8 hours. 

### Conclusions The 3 16(b) demonstration concluded that the Stationreauired amxoximatelvten 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 lowerportions 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). Ofthe seven fish species,M. undulatus accounted for 43.5 percent. July and August

12data showed the highest fish impingementrates in this study, and December, March and April had the lowest impingement rates. .

Twenty-two species of invertebrateswere impinged during the one-yearimpingement study. Ofthe 22 species, four were considered of commercial or sport fishery importance: three species ofthe commercial shrimp (Panaeussetifens, Panaeus aztecus and Penaeus duorarum)and the blue crab (Cattinectes sapidus). Ofthe commercial shrimp, 

### P. setqerus was the dominant species, with daily impingement rates ranging from 

### 0 in March 1973to 1,642 in August 1974. ‘Bluecrab daily impingementranged from 4 per day in March 1973to 176crabs per day in August 1974.

The impinged fish and shellfish data developedto supportthe 

### 3 16(b) demonstration showed that impingementrates at the Stationwere relatively low. The demonstration concludedthat these low total numbers (12 to 3,199per 24 hours) in conjunctionwith the fish return systemproposed would significantly reduce the fatal impingementof fish and shellfish, and would minimize adverse environmentalimpact and represent the best technology in this application.

The FRS Efficacy study conductedin 1984 and 1985documentedthat impingementrates were low at the Station during the summer and winter months. The winter impingementnumbers, as comparedto 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 ofthe 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 ofthe 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 efficiencyin the winter.

The results of the summerlonger term survivabilitytests indicated that the sensitive species did not survive afterpassage 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 ofthe sensitive and intermediate sensitivity species (menhaden, 

### 5 percent survival; star 

### drum, 10percent survival), as compared to the controls with 100percent survival for these 2 categories. 

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

An Optimization Studywas conducted in 1998and 1999to 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 ofthe low spraywash, water pressure, and water flow in the troughs). Ofthe 2 alternative schedulesoriginallyplanned, only the “1.5 hours off : 0.5 hour 

### on” was assessed for four quarters;the “3.5 hour off: 0.5 hour on” alternativeresulted in high mortalityimmediately followingpassage through the FRS, and was discontinued. The continuous operation schedule was considered the control for comparison.

The return rate efficiencyof the FRS units was high, between 96.3 and 100percent during continuous operation and 87.9 and 97.8 using the alternate schedule. The return rates were not significantly affectedby the alternate operation schedule.

13Immediate survivalwas considered the most useful endpointmeasured to compare the alternate operation schedules. The “1.5 hours off : 0.5 hour on” scheduleresulted in similar survivalto the continuous operation during the March and January monitoringperiods 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 comparedto the control schedulewas significantly reduced (June control immediate survival of 93 percent and alternate schedule immediate survival of 72.3 percent; Septembercontrol immediate survival of 95.4 and alternate schedule immediate survival of 82.3 percent). The family Scianidae comprised the majority of thejuvenile fish impinged on the FRS screens during all sampling events. When the immediate survivability ofthis group was evaluated for the alternate schedule and the continuous schedule, a significantreduction in survival ofthis group 

### of fishwas observedusing the alternate schedule as compared to the controls. Immediate survival of crustaceans was excellentregardless of season or schedule. Control group immediate survivalranged fi-om 87.5 to 100percent and alternate schedule survival fi-om 88 to 97.4 percent.
The longer term (96-hour) survivability assessments were inconclusivedue to the fact that very few sensitive specieswere 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 (continuousoperation) 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 ofthe impinged fish, which is equivalentto 40 percent of the impinged organisms.

The Optimizationreport concludedthat the use of the alternate schedule (I-5hours off :0.5 hour on) during the cool season months in north Florida would not significantlydecrease the FRS return efficiency, the immediate, or the longer-term survivability of impinged fish and crustaceans. The report also stated that during the warmermonths, this alternate schedulecould also be used during the day (due to the low impingementrates observed),but that the FRS would have to 

### runcontinuously during the night. The report suggested that the 

### FRS schedule shouldbe determined by water temperature, and proposed that once water temperature reached 20°C, the warm season schedule could be implemented.

Based on observationsmade during the 

### ESE (1985) study and the Golder (1999) study, sufficient water flow in the fish return troughs and appropriatepressure of the 

### FRS nozzles were of greatest importance in the proper function ofthe 

### FRS and resulted in improved FRS return efficiency and high survival of impinged organisms. Predation by birds fi-omthe fish return troughs was not quantified, but observed duringboth studies. Both studies also recommended that the fish return troughs shouldbe long enough so that during low tide the fish are not dropped into the aquatic system.


### References Battelle Laboratories, 1975. Biological Assessment ofWater and Marsh Areas ofthe St. Johns River. Prepared for Reynolds, Smith and Hills. January 1975.

14ESE, 1985. 

### An Assessment 

### ofthe Fish Return System at the Jacksonville Electric AuthorityNorthside Generating Station, Jacksonville, Florida. Prepared for JacksonvilleElectric 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 16Demonstration. Prepared for JacksonivlleElectric Authority. March 1976.