-- 

## BiologicalServicesProgram 

# 'Flsulsi"~6 FWS/

## 0BS

# -76120.9 Topical Briefs: FishandWildlife 

### 8 

### July 

### 1980 andElectricPower 

# CoolingWater IntakeScreening DevicesUsedto Reduce Entrainmentand Impingement 

# v

FishandWildlifeService 

## US.

## DepartmentoftheInterior

#.Biological Services Program FWS/OBS-76/20.9 Topical Briefs: Fish and Wildlife Resources July 1980 and Electric Power Generation, no. 9



## COOLING WATER INTAKE SCREENING DEVICES USED TO 

# REDUCE ENTF?AINI\IENT AND 

## IMPINEEKENT

Eugene S. 

### Fritz

National Power Plant Team 2929 Plymouth Road, Room 206



### Ann Arbor, Michigan 48105

Power P1ant Project Office ofBiological Services Fish and Wildlife Service U.S. Department of the Interior

Fish and Wildlife Service U.S. Department of the InteriorPreface The series Topical Briefs: Fish and Wildlife Resources and Electric Power Generationys published by the National Power Plant Team of the Power Plant Project 

### toprovide 

### a set ofconcise summaries 

### on topics related 

### toelectric power generation and transmission and their effects 

### on fish and wildlife resources. The briefs are written for fish and wild1ife biologists 

### who review andmake recommendations regarding electricpower projects. Each brief contains background information 

### on and 

### a discussion 

### of the particular topic, 

### a selected bibliography of additional information sources, and, in some cases, 

### a strategy 

### to address the problem. This series 

### is designed 

### toprovide synthesized technical information in 

### a convenient format. 

### Itis, of course, possible 

### to treat only the basic aspects of each topic within this abridged format. Also, the reader should note that this series addresses solely the technical issues concerning electric power generation and transmission. There may be additional informaton sources and considerations, 

### not covered by this series, which should be incorporated into electric power development decisions, We solicitopen discussion and comment 

### on the topic addressed. Documentation of differing points of view would be appreciated. We request that any suggestions 

### orquestions regarding Topical Briefs be directed 

### to: Information Transfer Specialist National Power Plant Team 2929 Plymouth Road, 

### Room 206 

### Ann Arbor, Michigan 48105 (313) 668-2365 FTS: 378-2365COOLINGWATER INTAKE SCREENINGDEVICES USED TO REDUCE ENTRAINMENTAND IMPINGEMENT
ABSTRACT Cooling water intake screening devices that Fish and Wildlife Service personnel may be expected 

### toassess are identified and described. The devices included aremodified vertical traveling screens

### ,singleentrance double-exi

### t screens, horizontal traveling screens

### ,passive intake screens, radial wells, artificial filterbeds, and porous dikes. For each device the location, limitations or restrictions, evidence for reducing entrainment and impingement, and 

### major unresolved problems are also discussed.
INTRODUCTION Section 316(b) of the Clean Water Act requires that 'I

# ... the location, design, construction, and capacity 

### of cooling water intake structures reflect the best available technology available forminimizing adverse environmental impact." The best available technology, exclusive of cost, 

### is most often represented by closed-cycle cooling systems (e.g. 

### , cooling towers, ponds, canals) that reduce the volume of water that

### must be withdrawn from the source of the cooling water. The reduction inthe volume of water results in

### a subsequent decline inthe number of organisms drawn toward 

### or intothe cooling system, 

### or both. Due to the expense of some closed-cycle cooling systems and their potential environmental impacts (e.9-

### ,salt drift, icing, unproductive land use), substantial effort has been expended to identify 

### ordevelop alternative intake systems and devices

# . The purposes of this Topical Brief are 

### to identify and 

### todescribe some of the screening devices 

### that Fish and Wildlife Service biologists may be expected 

### toassess, and 

### todiscuss the major problems associated with each. The information presented can be used in assessing any type of water intake system including those used in irrigation, industrial, and municipal withdrawals. Most screening devices 

### or systems presently available can be included within seven general categories. These are: modified vertical traveling screens, single-entrance double-exit screens

### ,horizontal traveling screens, passive intake screens, radial wells, artificial filterbeds, and porous dikes. ThisTopical Brief focuses on each of the categories rather 

### than 

### on the variation found within each. BACKGROUNO Thermal electric power plants require water tocool steam intheir condensers. This water iswithdrawn from 

### an external water source (Figure 1

### 1. Power plants witha once-through cooling system 

### must withdraw water continuously during plant operation. Among power plants with closed--- 2 Screening Devices
cycle cooling systems, make-up 

### water must be withdrawn periodically 

### to replenish that lost by evaporation, blow-down, and other consumptive uses.

POWER PLANT 

# IS 

# 11

II WASTES 7 /I

Figure 1. The cooling water system of 

### a thermal electric power plant (Shoreham Nuclear Power Station). The stresses that aquatic 

### organisms encounter in each portion of the cooling system are identified 

### (Coutant 1974.). Cooling water iswithdrawn 

### atsome type ofintake structure, the offshore intake, the shoreline intake, 

### or the approach channel intake (Cada et al. 1979). Somewhere between the point 

### that water enters the intake structure and before itenters the power plant it

### must pass through 

### a screening device (Figure 1). The original function of the screening device was to exclude debris inthe water from entering 

### and clogging the condenser tubes. Inspection of these screening devices showed that many fish and shellfish were held against the screening material (impinged) and many of these organisms died. Further investigation demonstrated that water passing 

### through the screens contained many of the younger and smaller stages of aquatic organisms (entrained). Many of the entrained organisms were killed or made more susceptible 

### tonatural mortality as a result of plant passage. VERTICAL TRAVELING SCREEN The most common screening device presently being used 

### atpower plants, and the device 

### most commonly associated with the impacts resultingi Screening Devices 3



### from entra nment and impingement, isthe Vertical Traveli

### ng Screen (VTS).

u i I
SCREEN BASKETS 

# i

LOR “TRAYS”)

WATER FLOW 

# -
f CLEAN
a 

# I [FLCOR OF SCREEN STWCTURE

Figure 2. A conventional vertical traveling screen (from U.S. Environmental Protection Agency 1976). CHAR

spec ?TERISTICS Conventional 

### VTS’s (Figure 2) may be modified slightly

### to suit a fic site, but the following characteristics are common 

### to all.

O They are installed inconcrete structures 

### that act as the screen arid circulating-water pump well.

O 

### Trash bar racks are located ahead ofthe screen to remove large debris.

O They consist of 

### a chain belt with individual screen pane1 attached.

O Screens revolve inthe vertical plane between 

### a set of two sprockets

# . J

O Screen panels are slightly inclined 

### toretain debris,-- 

### -- 4 Screening Devices

O Generally the screen panels are comprised of 9.5-m woven mesh

# .

O Screens are rotated either 

### atpredetermined intervals 

### or with predetermined differential pressure across the screen.

O Debris iswashed off screens with 

### a high pressure spray. MODIFIED VERTICAL TRAVELING SCREEN Modified vertical traveling screens (Figure 3) are conventional vertical traveling screens fittedwitha collection "bucket" 

### or ''pan" beneath the screen panel. The most commonly encountered synonyms for this type of screening device are "the bucket screen," "Ristroph screen," 

### or the "Surry type screen." The lattername arises 

### from the fact 

### that Virginia Electric Power Company's Surry Power Station was one of the original sites that this type of screen was used.

LOWPRESSURE FISHWASHING

CONVENTIONAL

.SIDE ELEVATION FISHSCREEN

Figure 3. The fish-bucket traveling screens 

### atthe Surry Power Station (White and Brehmer 1976). CHARACTERISTICS Although there aremany variations of the modif'ied VTS's they all have the following characteristics:

### -- Screening Devices 5

O They are structural y simi 

### artoconventional VTS's.

O They utilize screen panels that are fittedwith

### a basket capable 

### of retaining'water.

O Impinged fish are washed 

### into the basket with 

### a low pressure spray, thus reducing desiccation.

O They typically have 

### a high pressure 

### spray 

### to clean debris.

O They must be operated continuously 

### when fish are present 

### to attain

### maximum effectiveness (typically3-6 m/min).

O They must be fitted with fine mesh screen 

### (1

### mm or less) 

### to reduce entrainment, this increases impingement.

O They 

### must have 

### a through screen velocity sufficiently 

### low 

### to minimize impingement stress. LOCATION LIMITATIONS OR RESTRICTIONS Modified VTS's can be utilized 

### inany location within design limitations of VTS's because the 

### two are structurally 

### almost identical. EVIDENCE FOR SUCCESSFUL REDUCTION OF ENTRAINMENTAND IMPINGEMENT A number of in situ impingement studies have been conducted 

### ata number of power pznWCadaeta1

# . 1979). Most of these studies showed 

### a relatively high initial survival rate for impinged fish (as high 

### as 93.3%

### atSalem Nuclear Generating Station in New Jersey). However, littleinformation has been obtained 

### on long-term 

### or latent survival. One of the few studies that did provide evidence for latent survival 

### was conducted 

### atthe tlanford Generating Plant 

### on the Columbia River (Page et al. 1975). In this study 79-95%

### of the chinook salmon fry, that were released and collected 

### on the screens, survived for over 96 hrs. In situ studies have 

### not yet been conducted 

### on impingement 

### of larval fishes 

### on finemesh bucket screens. PROBLEMS Evidence from impingement studies suggests thatjuvenile fishes are less affected by modified vertical traveling screens than by conventional screens. Survival rate, however, appears 

### to be dependent 

### on the physiological characteristics of the 

### organism and hydrological characteristics of the site (e.g., if water 

### isrecirculated survival could be reduced by reimpingement or long-term exposure tothermal stress). The physical shape of impinged organism also appears 

### toinfluence survival rate. 

### For example, filiform larvae tend tobecome entangled infine screen mesh (Joseph Johnson, personal communication).61 Screening Devices
Benefits derived from 

### uti1 izingmodified vertical traveling screens appear 

### tobe site specific and dependent 

### on the physiological capacity of 

### a fish 

### tosurvive impingement force (pinned 

### tothe screen) 

### for a certain duration. 

### In order 

### toreduce the 

### duration of impingement, the screens 

### must be continuously operated. Operation 

### inthis manner 

### is energy expensive and reduces re1iabilitydue 

### tobreakdowns resulting from wear of the 

### moving parts. The use of finemesh screen panels, and 

### a reduction of the clearance between buckets, shows promise 

### for a reduction inentrainment of fish eggs and larvae. However, reduction of entrainment suggests 

### an increase in larval impingements, the consequences of which are species and lifestpagedependent. SINGLE-ENTRANCE DOUBLE-EXIT VERTICAL TRAVELING SCREENS 

### In single-entrance double-exi

### t vertical traveling screens (Figure 4) water enters the center of the screen and passes 

### from the inside 

### to thle outside of the screening surface. 

### Thus debris arid biota are impinged 

### on the inner surface of the screen. The most common device isthe pearshaped Passavant Screen which has been used inEurope 

### for over 30 years.

SPROCKET WHEEL

DEBRIS TROUGH



# -SEMlCYLlNDRlCAL SCREEN PANEL
F,igure4. 

### A single-entrance double-exit screen (Mag1iente et al. 1

### Y78). CHARACTERISTICS The 

### major characteristics ofsingle-entrance double-exit screens are:

O The screen surface 

### is theoretically double that of a comparable conventional VTS

# .

## -- 

# . ' Screening Devices 7

0 Various shapes of screen panels can be utilized but the semicircular screen basket fitted with 

### a water proof membrane and water retaining lip (Figure 5) appears 

### most promising 

### for impact reduction (Mag1iente eta1

# . 1978).

0 Screen baskets 

### can be constructed 

### of any mesh size, however, 0.5-mm fine mesh 

### or smaller isthe most effective for reducing entrainment impacts on larval fish and eggs. The system has 

### a low pressure wash 

### to flush eggs and larvae into 

### the water retaining portion of the bucket. 

### The 

### top of the system 

### has a high pressure spray wash which directs debris, fish eggs, larvae, and post larval stages 

### of fish 

### to

### a collecting 

### trough which returns them to the receiving water.

Figure 5. Semi-circular screen basket used in single-entrance doubleexjt screen systems (Magliente etal. 1978). LOCATION LIMITATIONS OR RESTRICTIONS Based upon manufacturers

### ' claims, sing1e-entrance doluhle-exit Screens can be used in any site

### thatwill accommodate 

### a conventional VTS. EVIDENCE FOR SUCCESSFUL REDUCTION OF ENTRAINMENT AND IMPINGEMENT Only one 

## - in situ study 

### has been completed (Barney M. Davis Generating Station, 

### Corpus Christi, Texas) which evaluated the effectiveness 

### of single-entrance double-exi

### t screens; 86%of the impinged organisms survived. Although survival appears high, one must realize that all observations were made 10-15 min after collection. 

### No results were available for latentmortality 

### orfor survival rates of larvae.8 Screening Devices



### PROBLEMS Results of the study conducted 

### atthe Barney Davis Generating Station (Murray and Jinnette 1978) do 

### not indicate that the singleentrance double-exit screen is any more effective inreducing impingement mortality 

### than is'themodified VTS. The use offinemesh screen (0.5-mm slot size) should reduce entrainment, but cause simultaneous increase in impingement of fish eggs and larvae. Any fish impinged 

### on the downtravel side ofthe screen would also remain impinged for 

### a longer period than those on the up-travel side. Although results ofthe Barney 

### Davis study suggest increased survival rates among fishes (juveniles and larger), 

### no field data have been obtained which demonstrates 

### that larval impingement survival rates are greater than entrainment survival rates. The keyhole shape ofthe Passavant Screen can itself contribute 

### to higher incidence ofimpingement because the required screen well can act 

### as

### an entrapment device. HORIZONTALTRAVELING SCREENS Horizontal traveling screens (Figure 6) are continuously 

### moving screens that traverse the water source being screened. Although much discussion has surrounded the use ofthe latter screening device, such screens have not been successfully operated 

### atpower plants.

-BAR RACK

WATER FLOW

TRASH REMOVAL S 

# \ DEBRIS 5LUICEWAY

Figure 6. Vertical view 

### of the original design concept for horizontal tlravelina screens in steam-electric power plant intakes (Chezar 1976).SPRAY HEADER TRASH REMOVAL



## 4 CIRCULATING WATER PUMPS Screening Devices 9

CHARACTERISTICS Although many designs have been developed forhorizontal traveling screens, they all have the following incomon:

O The screening surface remains submerged thoughout each cycle.

O The screen 

### is usually oriented atsome angle (usually between 20" and 30') to.theflow.

O Fish and shellfish impinged on 

### or approaching the screen are carried 

### ordirected 

### to

### a return 

### or bypass system.

O Screens can be fittedwithfinemesh to reduce larval entrainment. LOCATION LIMITATIONS OR RESTRICTIONS Horizontal screens have the potential forbeing utilized 

### atany location that can accomodate conventional vertical travel.ino screens. 

### P number ofdesigns have been developed that can be used with a very short canal althoughmost horizontal traveling screen pl-ototypes indicate the need fora relatively long intake canal (Figure 

### 7). 

# r -TRASH BARS
SPRAY HEADER TRASH REMOVAL



## 4 CIRCULATING WATER PUMPS

Figure 

### 7. 

### A screenwell withflushmounted horizontal traveling screen (U.S. Environmental Protection Agency 1976).I



### I 10 Screening Devices I EVIDENCE FOR SUCCESSFUL REDUCTION OF ENTRAINMENT AND IMPINGEMENT The evidence forreduced impingement mortality comes from experiments with prototypes (Cada eta1

# . 1979). These experiments yielded results that showed over 90%diversion efficiency and survival rates 

### of impinged fr.y and fingerlings between 39%and 100%(the experiments utilized chinook salmon, Oncorhynchus tschawt scha, fry and fingerlings). Little evidence has been developed for iological effectiveness of ful1-scale 

# -+-

screens. PROBLEMS The results of experiments with prototypes are insufficient 

### to evaluate the effectiveness of the horizontal screens 

### to reduce the impact of entrainment and impingement. One of the major problems that has not yet been solved, particularly in areas withfluctuating high and low water levels, ismechanical re'liability. The screens 

### mustmove continuously 

### to operate appropriately and effectively. Most of the prototype systems have had problems with excessivemechanical wear. PASSIVE INTAKE SCREENS Passive intake screens (Figure 8) are a generic name given 

### to those devices which screen-out debris and biota with little

### or no mechanical activity required. The 

### most commonly discussed passive screening systems arethose manufactured by the Johnson Division, UOP Imc. (theJohnson Screen). Other devices include the Ranney Surface Water Intake, Ranney Co. and the large 

### number of perforated 

### or screened pipe intakes. CHARACTER1ST

### ICs

O The screening 

### unitsare self supporting.

0 The screening 

### units can be cylindrical, drum shaPed, or Danels.

O Screens aremostly finemesh 

### or with very small perforations (0.5 

## - 2 

### mm). Slots may be as large 

### as 9.5 

### mm.

O Screening material 

### is typically wedge wire (Figure 9), "Smoothtex" 

### or perforated pipe.

O Systems may be self-cleaning inlocations where flowing water passes by the screens, but

### most utilize back-up backflushing components.a.

b. if 4

a ---3 Screening Devices 11



# 7
_----

NOT SHOWN)

C.

23rn PERFORATED 

# I

C

Figure 8. Passive intake screens: (a)design concept for cylindrical wedge-wire screens atpower plant cooling-water intakes (Pagan0 and Smith 1979), (b) 

### a Ranney surfacewater intake (Mickels and Bennett 1978), 

### (c)a perforated pike intake system (Richards and Hronich 1976).

# "7 MATERIAL STAINLESS STEEL SLOTWIDTHS: 1.0-2.5mm 

# kLOT

w,OTH OPENAREA: 22.3

### -39.5 7.

FLOW ___c 

# i 4

4! kr.0 I SECTIONA-A A d DIMENSIONS (mmj SECTION 8-8 Figure 9. Flat wedge-wire screen panels used inthe TVA hydraulic test (Vigander 1978). LOCATION LIMITATIONS OR RESTRICTIONS Passive intake systems can be designed for use in virtually any type of water body; hiowever, their self cleaning characteristic depends upon the bypass velocity 

### of the source water. The physical size of the screening devices is limiting in most passive systems, thus, necessitating the clustering of 

### a number of screening units. Perforated pipes, Ranney Intakes, and large Johnson Screen intakes cannot be utilized in areas where their presence would affect navigation. Siltation, biofouling, and frazzle ice also limit areas where passive screens can be utilized. Most manufacturers claim that these problems can be overcome through engineering (e.g. 

### ,raising the units above sediments), withbackflushing systems, and, in the instance of biofouling, by using antifouling copper alloys. However, site-specific demonstrations are needed. EVIDENCE FOR SUCCESSFUL REDUCTION OF ENTRAINMENT AND IMPINGEMENT Laboratory studies have indicated 

### that passive intake wedge wire screens are effective in reducing larval entrainment 

### (Hanson et al. 1978, Heuer and Tom1janovich 1978). In experimental studies using 1

### .Olmm mesh, Hanson etal. (1978) noted that striped bass less 

### than 40 

### fork length (FL) showed 

### no impingement stress 

### atintake velocities of 15.24 cm/s. Field studies conducted in the St. Johns River, Florida with prototype screens (Lifton 1980) demonstrated very 1ittleentrainment 

### of fish and larvae, minimal impingement of larvae, and no impingement 

### of small fishes. Similar types of studies have not yet been reported for other types of passive screening systems.Screening Devices 13

PROBLEMS There 

### is

### no evidence that 

### a full-scale passive intake system will significantlyreduce entrainment and impingement. The wedge wire screens that have been tested under fieldconditions aremuch smaller than the type thatmay be eventually employed (e.g., 0.6-m long by 0.3-m diameter screens have been used as prototypes for 6-m long by 3-m diameter screens). The difference inscalemakes evaluating the effectiveness of the screens difficult.

+.. i The size and configuration of offshore passive intakes are such i that they could potentially act as artificial reefs. Such a phenomenon, could attract organisms 

### tothe intake, thus, increasing their vulnerability toimpacts. As stated previously, the utilization of passive intake systems in water with high concentrations of suspended particles, high potential 

### for frazzle ice formation, orhigh biofouling potential may pose a number of maintenance problems. The solution of these problems requires 

### information that can only be obtained atfacilitiesusing passive intake systems. RADIAL WELLS Radial we11s (Figure 10)are subsurface collectors located in highly permeable alluvial aquifers where the water table ishigh and in direct contact with a surface stream 

### or lake (recharge source). The 

### most popular brand3name is the Ranney Collector. Yields of radial wells range up 

### to0.93 

### m /s (Mikels and Bennett 1978).

. .' SAND & GRAVEL
.

' APUIFER

Figure 10. A radial well intake system (Ray etal. 1976).The fundamenta.1 characteristics of

### the radial well intake are:

O A submerged concrete caisson 

### sunk into the base of an aquifer adjacent 

### toa recharge source.

O A number of perforated pipes that radiatefrom the base of 

### the caisson into the aquifer.

O A pump tomove water from 

### the well tothe plant. LOCATION LIMITATIOMS AND RESTRICTIONS 

# I to’provide

### a reliable-source ofwater, the recharge source

### must be ata higher level than 

### the aquifer. 

# I Water is obtained directly from the aquifer, thus, aquatic resources arenot affected 

### unless the recharge source is reduced toa level that

The major problem associated with radial wells is 

### the necessity to locate them ina sand orgravel aquifer. The volume of water that can beobtained 

### is limited by the aquifer and the recharge source. These problems limit

### the application of radial wells to relatively specific areas. ARTIFICIAL FILTER BEDS Artificial filterbeds (Figure 11) areman-made filteringfacilities designed toreduce the impact Of Waterwithdrawals on aauaticoraqnisrns. The s.$ate-of-the-art artificial filterbed may be capable of providing 3.1 

### m /s atmaximum performance (Richards 1978).Screening Devices 15

PUMP 

### WATER BACKWASH 

### PIPE



# A PERFORATED COLLECTOR 

### AIR BACKWASH 

### PIPE PIPE
Figure 71. An infiltration barrier intake (Richards 1978). CHARACTERISTICS

O A large excavated area filled with suitable filtermaterial.

O A perforated pipe 

### or series of pipes imbedded in the filter material.

O A pumping facility.

O A backflush system. I-OCATION LIMITATIONS OR RESTRICTIONS Artificial filterbeds can only be sited 

### on water bodies that have 11ow concentrations of suspended particles and where the potential for biofouling islow. EVIDENCE FOR SUCCESSFUL REDUCTION OF ENTRAINMENTAND IMPINGEMENT Filtration waters as high as 407.3 1/ rnin/rn' (0.61 cm/s filter velocity) have been evaluated and do 

### not appear 

### to affectjuvenile fish (Stober 1978). Although filters are 

### not presently operational 

### at

### a

# --

16 Screening Devices

power plant site, some engineers believe that filters can eventually be designed to effectively eliminate entrainment and impingement of fish eggs and larvae. PROBLEM 

### Most authorities believe thattechnology is

### not sufficiently advanced 

### to permit the construction and operation of 

### a reliable filter. The 

### major problems are clogging and biofouling. POROUS DIKES 

### Porous dikes (Figure 12) are fi

### 1ters resembling 

### a breakwater surrounding a cooling water intake. The core of

### the dike consists of cobble 

### or gravel which permits free passage of water. The dike acts both as 

### a physical and behavioral barrier 

### to aquatic organisms.

A POROUS DIKE 

# k

SECTION OF POROUS DIKE 

# Y@

Figure 

### 12. A Gabion dam (Schrader and Ketschke 1978). CHARACTERISTICS The 

### main characteristics of porous dikes are: 

### ' The filtering mechanism includes 

### a breakwater 

### or some other type ofbarrier and the filtering core. Both components 

### can be built ofthe same type and size material.

O Filtering material 

### must be a size thatpermits free passage of water but still prevents entrainment and impingement.Screening Devices 17

LOCATION LIMITATIONS OR RESTRICTIONS Porous dikes c'an be utilized inlarge lakes and coastal areas. However, this type of screening device may have limited application 

### in lareaswith high conlcentration of suspended particles and biofouling ipotential. EVIDENCE FOR SUCCESSFUL REDUCTION 

### OF ENTRAINMENT AND IMPINGEMENT Controlled studies inthe laboratory and under field conditions 'indicate thatfilteringmaterial 

### of the dike and behavioral responses to the dike can effectively exclude fish larvae and juveniles. Schrader iind Ketschke (1978) studied the porous dike atWisconsin Electric Service Company's Lakeside Plant 

### on Lake Michigan and found that numerous fish penetrated large void spaces but formost fish accessability was 1imited PROBLEMS The technology for

### porous dikes 

### is presently bein developed and rriuch evidence, from operating facilities, isneeded be

# 9 ore they can be thoroughly evaluated. Dikes have the potential problems of being clogged by settling suspended particulates and biofouling. These problems could reduce reliability, thus necessitating costly maintenance (e.g. 

### ,cleaning 

### or bisciding). The dike can also act as 

### an artifical reef, thereby attracting organisms and increasing the potential for some type of adverse impacts (e.g., increased predation, mortality due 

### tobiocide additions, increased l'i shing pressure).
CONCLUSION C1osed cycle cooling systems reduce the volume of cooling water withdrawn from 

### a water body by atleast 90%of that required for oncethrough cooling systems. In estimating the effectiveness of closed cycle cooling with once 

### through cooling systems fit,tedwith 

### a, VTS, Boreman etal, (1979) concluded that closed cycle cooling minimizes 

### the biological impact by 

### atleast 90%. To be considered an alternative 

### to closed cycle cooling a once-through cooling system with its screening device 

### must be shown 

### toreduce impingement and entrainment mortality by 90%of that evected of 

### a once through system fittedwith

### a VTS. The intake technologies described in this topilcal brief show some promise 

### for reducing the impacts of entrainment and impingement. However, evidence is insufficient 

### todemonstrate that any of these intake systems ailone, 

### or incombination, can afford the protection that 

### is presently attainable by closed cycle cooling. The 

### most effective systems, the radial well and artificial filterbed, can only provide enough water for make up water inclosed cycle systems. The screening devices, both aictive and passive, do 

### notyet have a sufficient data base to demonstrate18, Screening Devices

effectiveness 

### or re1iability. More experience is needed operating and maintaining these devices before they can be considered 

### as a1ternatives 

### to closed cycle cooling forminimizing the adverse impact 

### of cooling waiter intakes. Another subject, thatmust be considered when assessing screening devices which require the impingement of 

### an organism, is the fish bypass 

### or return system. The success 

### of the screening system is greatly dependent 

### on aeturning or bypassing fish, eggs, and larvae 

### tothe source water with 

### a high probability 

### for their survival. Any system that minimizes dannage 

### toorganisms during their capture, but damages 

### or overly stresses them when released, 

### cannot be considered the best technology available. Siniilarly, 

### a system that returns organisms 

### toan area that is unsuitable fortheir survival cannot be considered best technology available. Fish return systems differ greatly 

### atdifferent power plants. These differences have inhibited the evaluation of the return portions 

### of water intake syr;tems

# .

# --

, li Screening Devices 19
REFERENCES 

## I Boreman, J., L. W. Barnthouse, D. S. Vaughan, C. P. Goodyear, and S. W. 

### Christensen. 1979. Entrainment Impact Estimates for Six Fish Populations Inhabiting the Hudson River Estuary. JointTestimony. Prepared forthe U.S. EPA. Kegion 11. no pagination. Cada, G. F., J. B. Cannon, and D. W. Lee. 1979. Alternative Screening Devices atIndian Point 

### Units 2 and 3, Bowline Point, and Roseton Generating Stations. Joint Testimony Prepared for the U.S. EPA Region 11. Oak Ridge National Laboratory, Oak Ridge, Tennessee. 138pp. Chezar, B. 1976. Mutifarious Power Plant Water Intake Structure 

### (MWIS)

## - A Design Concept toR?duce the Environmental Effects of CoolingWater Intake Structures. 

### t4ew York StateEnergy Research and Development Authority, 164 pp. Cloutant, C.C. 1974. Opening remarks atentrainment; and intake screening workshop: "Evaluation of entrainment effect", pp. 1-11. In Proceedings ofthe Second Workshop on Entrainment and Intake ScreeningrEPRI

### , Publ. 74-049-00-5. Hanson, B. M. 

### ,W. H. Bason, B. C. Beitz, and K. E. Charles. 1978. Practicalityof profile-wire screen inreducing entrainment and impingement, pp. 195-233. In Larval Exclusion Systems for Power Plant Cooling Water Intakes. Proceedings of the workshop held 7-8 February, 1978. San Diego, California. Heuer, J. H., and D. A. Tomljanovich. 1978. A study on the protection of fish larvae atwater intakes using wedge-wire screening, pp. 169-194. 

### - In Larval Exclusion Systems for Power Plant Cooling Water Intakes. Proceedings of the Workshop held 7-8 February, 1978. San Diego, California. Lifton, W. S. 1980. Biological 

### Aspects of Screen 'resting on 

### the St. Johns 

### River, Palatka, Florida. Dames and Moore, Cincinnati

### ,Ohio. 14 PPVlagliente, S. H., D. A. Tomljanovich, J. H. 

### Heuer, S. Vigander, and M. N. Smith. 1978. Investigations on the protection of fish larvae atwater intakes using fine-mesh screening. Impingement release concept: Laboratory study of single-entrance double-exit, vertical traveling screen concept, pp. 69-77. 

### &Larval Exclusion Systems forPower Plant Cooling Water Intakes. Proceeding of

### theworkshop held 7-8 February, 1978. San Diego, California. Mikels, F. C., and T. W. 

### Bennett. 1978. Cooling water intakes utilizing Ranney Collectors and Ranney Intakes, pp. 15-25. In Larval Exclusion Systems forPower Plant Cooling Water Intakes. Proceedings of the Workshop held 7-8 February, 1978. San Diego, California.20 Screening Devices Murray, L. S., and 7. S. Jinnette. 1978. Survival of dominant estuarine organisms impinged on fine-mesh traveling screens atthe Barney M. Davis 

### Power Station, pp. 79-87. In Larval Exclusion Systems for 

### Power Plant Cooling Water Intakes. Proceedings of the Workshop held 7-8 February, 1978. San Diego, California. Pagano, R. and H. B. Smith. 1977. Recent developments intechniques 

### to Protect aquatic.Organisms atthe Water Intake Stearn-electric power plants. 

### Report 7671.

.Prepared for

### the MITRE Corporation, Milean, Virginia. 74 pp. P'age, T. L., R. H. Gray, and 

### E. G. Wolf. 1975. Report 

### on Impingement Studies 

### Conducted at

### the Hanford Generating Project

## - March and April 1976. Report toWashington Public 

### Power Supply System. Battelle

# - Northwest, Richland, Washington. 9 

### pp. R,ay, S. S., R. L. Snipes, and D. A. Tomljanovich. 1976. A State-of-the 

### Art Report 

### on Intake Technologies. Report PRS-16, EPA-600,' 7-76­ 020. Prepared by 

### the TVA 

### for the U.S. EPA, Washington, D.C. 82 pp. Richards, R. T. 1973. Engineering constraints in

### the 

### use of artificial filterbeds, pp 5-12. Larval Exclusion Systems for Power Plant Cooling Water Intakes. Proceedings ofthe Workshop held 7-8 February, 1978. San Diego, California. Richards, R. T. and M. J. Hronich. 1976. Perforated-pipe water intake 

### for fish protections. J. Hydra. Div. Proc. Am. SOC. Civ. Eng. 102 

### (HY2): 139-147. Schrader, 

### B. P., and B. A. Ketschke. 1978. Biological aspects of Porous-dike intake structures, pp 51-63. In Larval Exclusion Systems for Power Plant Cooling Water Intakes. 

### Proceedings of the workshop held 7,-8February, 1978. San Diego, California. 

### Stober, 

### Q.J. 1978. High-capacity filters

### for power plant cooling water intakes, pp. 13-14. In Larval Exclusion Systems for Power Plant Cooling Water IntakesTProceeding of 

### the workshop held 7-8 February, 1978. San Diego, California. U.S. Environmental Protection Agency. 1976.


## . Development Document for 

### Best Technology Available 

### for the Location, 

### Design, Construction, and Capacity of Cooling Water Intake Structures 

### for Minimizing 

### Adverse Environmental Impact. Report EPA 440 1-76 015-a. Washington, D.C. 263 pp. Vigander, S. 1978. Current TVA 

### work on the fluid mechanics of screens with very small openings for the exclusion of larvae atpower plant cooling water intakes, pp 91-105. Larval Exclusion System for Power Plant Cooling Water Intakes. Proceedings, ofthe wvkshop held 7-8 February, 1978. San Diego, California.Screening Devices 21
White, J. C., and M. L. Brehmer. 1976. Eighteenth-month evaluation of the Ristroph Traveling fish screens, pp 376-380. In Proceedings of the Third National Wordshop on Entrainment and Impxgement: Section 316 (b)

## - Research and Compliance. E. A. Commui:ications. Melville, New 

### York.

Stock NO. 024-010-00553-0 

# * U.S. GOVERNMENT PRINTING OFFICE: 1980-654-500 

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